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"*^ DESCRIPTION
OPTICAL INFORMATION RECORDING MEDIUM, AND METHOD OF
MANUFACTURING THE SAME
5
TECHNICAL FIELD
[0001]
The present invention relates to an optical
information recording medium and a method of
10 manufacturing the optical information recording medium.
More particularly, the present invention relates to an
optical information recording medium which has an
antireflection function on a surface.
15 BACKGROUND ART
[0002]
Optical disks have advantages of convenience to
handle, easiness of mass production and low manufacturing
cost, and therefore are widespread as recording media for
20 recording video images and music. Although an optical
disk is a recording medium for recording and playing back
an information signal by way of radiation and reflection
of light by using an optical drive device, (1) a problem
of a drive device side and (2) a problem of an optical
25 disk side are conventionally pointed out as described
below.
[0003]
1. Problem of Drive (Player) Optical Pickup Side
A surface reflectivity of an optical resin material
3 0 such as polycarbonate which is generally used for optical
disks is about 5% over the entire visible light. Hence,
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when a disk is placed on a drive (player), the amount of
light emitted from a light source laser (CD (Compact
! Disc) 780 nm, DVD (Digital Versatile Disc) 650 nm or BD
(Blu-ray Disc (registered trademark)) 405 nm) of an
5 optical pickup for reading a disk signal attenuates by
about 5% upon incidence on a disk substrate. Further,
when transmitting light is reflected on a reflection
layer of a signal surface and returns to a pickup side,
the amount of light attenuates by about 5% again when the
10 light passes a disk substrate surface. Then, the amount
of light in the total amount of the amount of playback
i
signal attenuates by about 10%, and therefore a pickup
light source laser requires excessive emission power and
has a corresponding load, and therefore causes a negative
15 influence such as short longevity of a laser.
[0004]
Although a recording laser requires greater power
than the playback system in case of a recording disk, the
recording laser requires power which is about 5% more
2 0 excessive than originally required power due to surface
reflection and has a corresponding load, and therefore
causes a negative influence such as a short longevity of
a laser. Further, the amount of reflected light which is
a disk playback signal from a disk reflection film
25 surface attenuates by about 5% likewise as the time of
incidence when the light is emitted from the disk
substrate surface, and therefore signal quality is
deteriorated.
[0005]
30 Further, although, when an optical disk is placed
on a drive (player), an optical pickup first applies a
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servo focus to a disk signal reflection film surface
(from a film closer to a surface in case of a multi-layer
film), if the reflectivity of the disk surface is high in
this case, there is a problem that this surface is
5 erroneously recognized as the signal reflection film
i surface, and disk information cannot be read and played
back. This problem became obvious after a film of a low
reflectivity is adopted for a two-layer structure disk of
a DVD-DL specification, the reflectivity of a reflection
10 film close to the surface in 25 GB/layer x 8 layers: 200
G structure which is a future capacity expanded
specification of BD described below is also likely to be
about 2% or less, and is likely to cause a significant
problem.
15 [0006]
Further, although an optical pickup for an octospeed
recording/playback technique is studied for BD (see,
for example, Non-Patent Document 1), surface reflection
of a disk causes loss resulting from high power required
2 0 for high-speed recording and loss of the amount of
playback signal upon high-speed playback which are
significant failure.
[0007]
2. Problem of Optical Disk Side
25 The reflectivity as the amount of playback signal
is clearly defined per standard. For example, under
conditions of use of a polarization optical pickup, the
reflectivity is, for example, CD: 58% < (780 nm) and 35%
< (650 nm), DVD-SL: 45 to 85% and DL 18 to 30% (650 nm),
30 and BD-SL: high reflectivity 35 to 70% and DL (including
SL low reflectivity) 12 to 28% (405 nm) . To satisfy
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these reflectivity standards, it is necessary to set a
higher original reflectivity in advance and secure the
amount of reflected light taking into account that the
amount of signal reflected light from a disk reflection
5 film attenuates by about 5% when the light is emitted
from the disk substrate surface.
[0008]
Particularly, in case of two-layer structure disks
such as a DVD and a BD, precise film thickness control
10 for keeping the balance of securing the amount of
reflected light in a semi-transmission layer close to a
substrate surface side and also securing the amount of
transmitted light for a reflection layer in the depth
side is required, and causes a significant trouble upon
15 manufacturing. Although multi-layer structure disks such
as 25 GB/layer:x 8 layer 2 00 G and 25 GB/layer x 16 layer
400 G for future expansion of capacity of BD are released
and actively studied, the reflectivity of each layer in a
greater number of layers naturally becomes lower and the
20 amount of signal light also becomes little, and therefore
there is a significant problem that the amount of light
attenuates by about 5% on a disk surface. This decrease
in the amount of signal light causes that a signal is
weakened by electric noise in an optical pickup playback
25 signal detector mentioned above and a reading error
occurs.
[0009]
To solve the above problem, a technique of
providing an antireflection film on an optical disk
3 0 surface is proposed (see, for example, Patent Document 1
and Patent Document 2) . However, as the density of an
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optical disk becomes higher in recent years, a better
antireflection function is desired.
CITATION LIST
5 PATENT DOCUMENTS
[0010]
Patent Document 1: Japanese Patent Application Laid-Open
No. 6-28716
Patent Document 2: Japanese Patent Application Laid-Open
10 No. 2003-208733
NON-PATENT DOCUMENT
Non-Patent Document 1: CX-PAL, Semiconductor & Component
News, Sony Corporation, October 2 007, vol. 74
15 SUMMARY OF THE INVENTION
PROBLEMS TO BE SOLVED BY THE INVENTION
[0011]
It is therefore an object of the present invention
to provide an optical information recording medium which
20 has a good antireflection function, and a method of
manufacturing the optical information recording medium.
SOLUTIONS TO PROBLEMS
[0012]
25 To solve the above problem, a first invention is an
optical information recording medium which has: a
substrate; one, two or more information signal layer
which is formed on the substrate; and a protective layer
which is formed on the one, two or more information
3 0 signal layer, and in which the surface of the protective
layer is a reading surface on which light for recording
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or playing back an information signal in the information
signal layer is radiated, and, in the reading surface, a
plurality of subwavelength structures is formed.
[0013]
5 A second invention is an optical information
recording medium which has: a first substrate; one, two
or more information signal layer which is formed on the
first substrate; and a second substrate which is formed
on the one, two or more information signal layer, and in
10 which a surface of the second substrate is a reading
surface on which light for recording or playing back an
information signal in the information signal layer is
radiated and, in the reading surface, a plurality of
subwavelength structures is formed.
15 [0014]
A third invention is an optical information
recording medium which has: a substrate; one, two or more
information signal layer which is formed on the
substrate; and a protective layer which is formed on the
20 one, two or more information signal layer, and in which a
surface of the substrate is a reading surface on which
light for recording or playing back an information signal
in the information signal layer is radiated and, in the
reading surface, a plurality of subwavelength structures
25 is formed.
[0015]
A fourth invention is an optical information
recording medium which has: a reading surface on which
light for recording or playing back an information signal
30 is radiated, and in which, in the reading surface, a
plurality of subwavelength structures is formed.
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[0016]
A fifth invention is a method of manufacturing an
optical information recording medium which includes:
transferring a shape of a reading surface forming master
5 to a resin material, and forming a substrate or a
protective layer on a surface of which a plurality of
i subwavelength structures is formed, and in which a
surface of the substrate or the protective layer is a
reading surface on which light for recording or playing
10 back an information signal in the information signal
layer is radiated.
[0017]
In the present invention, the subwavelength
structure refers to a structure which is formed to have
15 the dimension shorter than a visible light wavelength
region, and, more specifically, refers to a structure in
which a bottom surface having a circular or elliptic
shape has the substantially fixed diameter or long
diameter and short diameter in a range of 150 nm to 480
2 0 nm, and has a conical shape or a circular truncated
conical shape the top of which is almost planar which has
the height in a range of 100 nm to 28 0 nm.
[0018]
In the present invention, the subwavelength
25 structures are formed on the reading surface, so that it
is possible to reduce reflection of recording light or
playback light incident on the reading surface.
Consequently, it is possible to reduce loss of recording
light or playback light on the reading surface.
30
EFFECTS OF THE INVENTION
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[0019]
As described above, the present invention has a
subwavelength structures formed on a reading surface on
which light for recording or playing back an information
5 signal is radiated, and consequently can realize a good
antireflection function.
BRIEF DESCRIPTION OF DRAWINGS
[0020]
10 Fig. 1 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to a first embodiment of the
present invention.
Fig. 2A is a schematic plan view illustrating an
15 example of a configuration of a reading surface of the
optical information recording medium according to the
first embodiment of the present invention.
Fig. 2B is a plan view enlarging part of the
reading surface of the optical information recording
20 medium illustrated in Fig. 2A.
Fig. 2C is a cross sectional view in tracks Tl, T3
and ... in Fig. 2B.
i
Fig. 2D is a cross sectional view in tracks T2, T4
and ... in Fig. 2B.
25 Fig. 2E is a schematic diagram illustrating a
modulated waveform of laser light used to form latent
images corresponding to the tracks Tl, T3 and ... in Fig.
2B.
Fig. 2F is a schematic diagram illustrating a
3 0 modulated waveform of laser light used to form latent
images corresponding to tracks T2, T4 and ... in Fig. 2B.
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Fig. 3A is a cross sectional view of the reading
surface illustrated in Fig. 2B in a track extending
direction.
Fig. 3B is a cross sectional view of the reading
5 surface illustrated in Fig. 2A in a 0 direction.
Figs. 4A and 4B are perspective views enlarging
part of the reading surface of the optical information
recording medium illustrated in Fig. 2A.
Figs. 5A and 5B are perspective views enlarging
10 part of the reading surface of the optical information
recording medium illustrated in Fig. 2A.
Fig. 6A is a schematic diagram illustrating an
example of an arrangement of structures having conical
shapes or circular truncated conical shapes.
15 Fig. 6B is a schematic diagram illustrating an
example of an arrangement of structures of elliptic
conical shapes or elliptic truncated conical shapes.
Fig. 7A is a schematic plan view illustrating an
example of a configuration of a molding surface of a
2 0 reading surface forming master for forming structures on
a reading surface.
Fig. 7B is a plan view enlarging part of the
molding surface of the reading surface forming master
illustrated in Fig. 7A.
25 Fig. 8 is a schematic diagram for explaining a
configuration of a master exposure device used in
procedure of exposing a moth-eye pattern.
Figs. 9A to 9E are procedure diagrams for
explaining an example of a method of manufacturing the
3 0 optical information recording medium according to the
first embodiment of the present invention.
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Figs. 10A to 10F are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to the
first embodiment of the present invention.
5 Figs. 11A to 111 are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to a
second embodiment of the present invention.
Fig. 12 is a cross sectional view illustrating an
10 example of a configuration of an optical information
recording medium according to a third embodiment of the
present invention.
Figs. 13A to 131 are procedure diagrams for
explaining an example of a method of manufacturing the
15 optical information recording medium according to the
third embodiment of the present invention.
Fig. 14 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to a fourth embodiment of the
2 0 present invention.
Figs. 15A to 15J are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to the
fourth embodiment of the present invention.
25 Fig. 16 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to a fifth embodiment of the
present invention.
Figs. 17A to 17J are procedure diagrams for
3 0 explaining an example of a method of manufacturing the
optical information recording medium according to the
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fifth embodiment of the present invention.
Figs. 18A to 18D are procedure diagrams for
explaining an example of a method of manufacturing an
optical information recording medium according to a sixth
5 embodiment of the present invention.
Figs. 19A to 19E are procedure diagrams for
explaining an example of a method of manufacturing an
optical information recording medium according to a
seventh embodiment of the present invention.
10 Fig. 20 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to an eighth embodiment of the
present invention.
Figs. 21A to 21G are procedure diagrams for
15 explaining an example of a method of manufacturing the
optical information recording medium according to the
eighth embodiment of the present invention.
Figs. 22A to 22H are procedure diagrams for
explaining an example of a method of manufacturing the
20 optical information recording medium according to a ninth
embodiment of the present invention.
Fig. 23A is a schematic plan view illustrating an
example of a configuration of a reading surface of an
optical information recording medium according to a tenth
25 embodiment of the present invention.
Fig. 23B is a plan view enlarging part of the
reading surface of the optical information recording
medium illustrated in Fig. 23A.
Fig. 23C is a cross sectional view in tracks Tl, T3
3 0 and ... in Fig. 23B.
Fig. 23D is a cross sectional view in tracks T2, T4
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and ... in Fig. 23B.
Fig. 23E is a schematic diagram illustrating a
modulated waveform of laser light used to form latent
images corresponding to the tracks Tl, T3 and ... in Fig.
5 23B.
Fig. 23F is a schematic diagram illustrating a
modulated waveform of laser light used to form latent
images corresponding to tracks T2, T4 and ... in Fig. 23B.
Fig. 24A is a schematic plan view illustrating an
10 example of a configuration of a reading surface of an
optical information recording medium according to an
eleventh embodiment of the present invention.
Fig. 24B is a plan view enlarging part of a reading
surface of the optical information recording medium
15 illustrated in Fig. 24A.
Fig. 24C is a cross sectional view in tracks Tl, T3
and ... in Fig. 24B.
Fig. 24D is a cross sectional view in tracks T2, T4
and ... in Fig. 24B.
20 Fig. 24E is a schematic diagram illustrating a
modulated waveform of laser light used to form latent
images corresponding to the tracks Tl, T3 and ... in Fig.
24B.
Fig. 24F is a schematic diagram illustrating a
25 modulated waveform of laser light used to form latent
images corresponding to tracks T2, T4 and ... in Fig. 24B.
Fig. 25A is a schematic perspective view
illustrating an example of a configuration of a molding
surface of a reading surface forming master for forming
3 0 structures on a reading surface.
Fig. 25B is a plan view enlarging part of the
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molding surface of the reading surface forming master
illustrated in Fig. 25A.
Fig. 26 is a schematic diagram for explaining a
configuration of a roll master exposure device used in
5 procedure of exposing a moth-eye pattern.
Fig. 27A is a schematic plan view illustrating part
of a reading surface of an optical information recording
medium according to a twelfth embodiment of the present
invention.
10 Fig. 27B is a plan view enlarging part of the
reading surface of the optical information recording
medium illustrated in Fig. 2 7A.
Fig. 28A is a schematic plan view illustrating an
example of a configuration of an optical information
15 recording medium according to a thirteenth embodiment of
the present invention.
Fig. 28B is a plan view enlarging part of the
optical information recording medium illustrated in Fig.
28A.
20 Fig. 28C is a cross sectional view in tracks Tl, T3
and ... in Fig. 28B.
Fig. 28D is a cross sectional view in tracks T2, T4
and ... in Fig. 28B.
Fig. 29 is a perspective view enlarging part of the
25 optical information recording medium illustrated in Fig.
28B.
Fig. 3 0 is a graph illustrating simulation results
of Test Examples 1 to 3.
Figs. 31A to 31C are graphs illustrating simulation
30 results of Test Example 4.
Figs. 32A to 32C are graphs illustrating simulation
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results of Test Example 5.
Figs. 33A and 33B are graphs illustrating
simulation results of Test Example 6.
Figs. 34A to 34C are graphs illustrating simulation
5 results of Test Example 7.
Figs. 35A to 35C are graphs illustrating simulation
results of Test Example 8.
Figs. 36A and 36B are graphs illustrating
simulation results of Test Example 9.
10 Figs. 37A to 37C are graphs illustrating simulation
results of Test Example 10.
Figs. 38A to 38C are graphs illustrating simulation
results of Test Example 11.
Figs. 3 9A and 3 9B are graphs illustrating
15 simulation results of Test Example 12.
Fig. 40A is a graph illustrating simulation results
of Test Example 13.
Fig. 40B is a graph illustrating simulation results
of Test Example 14.
20 Fig. 40C is a graph illustrating simulation results
of Test Example 15.
MODES FOR CARRYING OUT THE INVENTION
[0021]
25 Embodiments of the present invention will be
described in the following order with reference to the
drawings.
[0022]
1. First Embodiment (First Example of Optical
3 0 Information Recording Medium in which Substrate Side is
Reading Surface)
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2. Second Embodiment (Second Example of Optical
Information Recording Medium in which Substrate Side is
Reading Surface)
3. Third Embodiment (Example of Optical Information
5 Recording Medium of Lamination Type)
4. Fourth Embodiment (First Example of Optical
Information Recording Medium having Two Information
Signal Layers)
5. Fifth Embodiment (Second Example of Optical
10 Information Recording Medium having Two Information
Signal Layers)
6. Sixth Embodiment (First Example that Structures
are formed in Reading Surface of Optical Information
Recording Medium)
15 7. Seventh Embodiment (Second Example that
Structures are formed in Reading Surface of Optical
Information Recording Medium)
8. Eighth Embodiment (First Example of Optical
Information Recording Medium in which Protective Layer
20 Side is Reading Surface)
9. Ninth Embodiment (Second Example of Optical
Information Recording Medium in which Protective Layer
Side is Reading Surface)
10. Tenth Embodiment (Example that Structures are
25 aligned in Square Lattice Pattern)
11. Eleventh Embodiment (Example that Structures
are linearly aligned)
12. Twelfth Embodiment (Example that Structures are
aligned in Wobbling Pattern)
30 13. Thirteenth Embodiment (Example that Structures
of Concave Shapes are arranged)
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[0023]
<1. First Embodiment>
[Configuration of Optical Information Recording Medium]
Fig. 1 is a cross sectional view illustrating an
5 example of a configuration of an optical information
recording medium according to a first embodiment of the
present invention. This optical information recording
medium has a substrate 1, an information signal layer 2
formed on the substrate 1 and a protective layer 3 formed
10 on the information signal layer 2. In a reading surface
of the optical information recording medium on which
laser light is radiated, a plurality of subwavelength
structures (also referred to simply as "structures"
below) 11 having convex shapes is formed. Meanwhile, the
15 reading surface means a surface on which an information
signal is recorded and/or played back by being radiated
by laser light.
[0024]
In this optical information recording medium
2 0 according to the first embodiment, an information signal
is recorded or played back by radiating laser light on
the information signal layer 2 from a substrate 1 side.
For example, an objective lens having the numerical
aperture of 0.45 or more and 0.50 or less condenses laser
25 light having the wavelength of 780 nm or more and 790 nm
or less, and radiates the laser light on the information
signal layer 2 from the substrate 1 side, so that an
information signal is recorded and/or played back. Such
an optical information recording medium is, for example,
3 0 a CD (Compact Disc).
[0025]
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When an optical information recording medium is
compliant with a CD standard, an arrangement pitch of the
structures 11 is preferably 900 nm or less, is more
preferably 200 nm or more and 480 nm or less, and is
5 still more preferably 240 nm or more and 400 nm or less.
When the arrangement pitch exceeds 90 0 nm, about 78 0 nm
which is a value obtained by multiplying 90 0 with V3/2
corresponds to a dimension value which is the nearest
effective diffraction grating interval in case of a
10 hexagonal lattice arrangement, and a rapid rise in the
reflectivity in a region having this wavelength or less
is observed and the reflectivity exceeds 1%, and
therefore the antireflection effect becomes insufficient.
[0026]
15 The height of the structures 11 is preferably 100
nm or more and 300 nm or less, is more preferably 170 nm
or more and 280 nm or less, and is still more preferably
190 nm or more and 240 nm or less. When the height is
less than 100 nm, the reflectivity exceeds 1%, and the
20 antireflection effect becomes insufficient. Meanwhile,
when the height exceeds 3 00 nm, while antireflection
performance is still sufficient, the height of the
structures itself increases, and therefore it is
difficult to make the structures.
25 [0027]
A flat portion diameter of a top of the structures
11 is preferably 0 fold or more and 0.8 folds or less of
an arrangement pitch or greater than 0 fold and 0.8 folds
or less of the arrangement pitch, is more preferably 0.4
3 0 folds or more and 0.6 folds or less of the arrangement
pitch and is the most preferably 0.5 folds. When the
1
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flat portion diameter exceeds 0.8 folds, the reflectivityexceeds
1%, and the antireflection effect becomes
insufficient.
[0028]
5 The ratio (X/H) of a wavelength X of light for
recording or playing back an information signal to a
height H of the structures 11 is preferably 2 or more and
6 or less. When the ratio is less than 2, while the
antireflection performance is still sufficient, the
10 heights of the structures 11 increase, and therefore it
is difficult to make the structures. Meanwhile, when the
ratio exceeds 6, the reflectivity exceeds 1%, and the
antireflection effect becomes insufficient.
[0029]
15 (Substrate)
The substrate 1 has, for example, an annular shape
in which an opening (referred to as a "center hole"
below) is formed in the center. The substrate 1 has a
first principal surface and a second principal surface.
2 0 A reading surface which is the first principal surface of
the substrate 1 is a fine concave-convex surface in which
the structures 11 are formed as described above.
Meanwhile, the signal surface which is the second
principal surface of the substrate 1 is, for example, a
25 concave-convex surface in which concave-convex portions
12 are formed, and the information signal layer 3 is
formed in this concave-convex surface. Meanwhile, the
signal surface means a surface in which the information
signal layer 3 is formed. The shape of these concave-
3 0 convex portions 12 may take various shapes such as a
spiral shape, a concentric shape or a pit array. Further,
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1 to add address information, these concave-convex portions
i 12 may be wobbled.
[0030]
The diameter of the substrate 1 is, for example,
5 selected to be 12 0 mm. The thickness of the substrate 1
is selected taking rigidity into account, and is
preferably 0.3 mm to 1.3 mm, is more preferably 0.6 mm to
1.3 mm and is, for example, selected to be 1.1 mm.
Further, the diameter of the center hole is, for example,
10 selected to be 15 mm.
[0031]
For example, a plastic material or glass can be
used for a material of the substrate 1, and a plastic
material is preferably used from a view point of cost.
15 For example, a polycarbonate resin, a polyolefin resin or
an acrylic resin can be used for the plastic material.
[0032]
(Information Signal Layer)
The information signal layer 2 is formed to be
2 0 capable of recording and/or playing back an information
signal. This configuration is adequately selected
depending on, for example, whether a desired optical
information recording medium is one of a playback
dedicated type, a recordable type and a rewritable type.
25 [0033]
When the desired optical information recording
medium is the playback dedicated type, the information
signal layer 2 is, for example, a reflection film. A
material of this reflection film is, for example, a
30 metallic element, a metalloid element or a compound or a
mixture of these. More specifically, the material is a
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simple substance such as aluminum (Al), silver (Ag), gold
(Au), nickel (Ni), chrome (Cr), titanium (Ti), palladium
(Pd), cobalt (Co), silicon (Si), tantalum (Ta), tungsten
(W), molybdenum (Mo) or germanium (Ge) or an alloy which
5 includes these simple substances as main components.
Further, when practicality is taken into account, an Al,
Ag, Au, Si or Ge material of these elements is preferably
used.
[0034]
10 When a desired optical information recording medium
is a recordable type, the information signal layer 2 is,
for example, a recordable recording layer, and, for this
recording layer, a recording layer which can be generally
used in a conventionally known recordable optical
15 information recording medium can be used. More
specifically, the recordable recording layer is, for
example, a laminated film obtained by sequentially
laminating on the optical disk substrate 1 a reflection
film, an organic dye film or an inorganic recording film.
20 [0035]
When a desired optical information recording medium
is a rewritable type, the information signal layer 2 is,
for example, a rewritable recording layer and, for this
recording layer, a recording layer which can be generally
25 used in a conventionally known rewritable optical
information recording medium can be used. More
specifically, the rewritable recording layer is, for
example, a laminated film obtained by sequentially
laminating on the substrate 1 a reflection film, a lower
3 0 dielectric layer, a phase-change recording layer and an
upper dielectric layer.
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[0036]
i
(Protective Layer)
The protective layer 3 is formed by solidifying a
photosensitive resin such as an ultraviolet curable resin
5 (UV resin) . A material of the protective layer 3 is, for
example, an acrylic resin of an ultraviolet curable type.
[0037]
[Subwavelength Structure]
Fig. 2A is a schematic plan view illustrating an
10 example of a configuration of a reading surface of the
optical information recording medium according to the
first embodiment of the present invention. Fig. 2B is a
plan view enlarging part of the reading surface of the
optical information recording medium illustrated in Fig.
15 2A. Fig. 2C is a cross sectional view in tracks Tl, T3
and ... in Fig. 2B. Fig. 2D is a cross sectional view in
tracks T2, T4 and ... in Fig. 2B. Fig. 2E is a schematic
diagram illustrating a modulated waveform of laser light
used to form latent images corresponding to the tracks Tl,
20 T3 and ... in Fig. 2B. Fig. 2F is a schematic diagram
illustrating a modulated waveform of laser light used to
form latent images corresponding to tracks T2, T4 and ...
in Fig. 2B. Fig. 3A is a cross sectional view of the
reading surface illustrated in Fig. 2B in a track
25 extending direction (an X direction (also referred to as
a "track direction")). Fig. 3B is a cross sectional view
of the reading surface illustrated in Fig. 2A in a 0
direction. Figs. 4A and 5B are perspective views
enlarging part of the reading surface of the optical
30 information recording medium illustrated in Fig. 2A.
[0038]
1 22
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3 •
A plurality of structures 11 formed in the reading
surface is, for example, concentrically aligned. A
plurality of structures 11 formed in the reading surface
is preferably provided in two-dimensional alignment on j
5 one principal surface at an arrangement pitch equal to or
less than a wavelength of laser light which is targeted
to reduce reflection. Meanwhile, the arrangement pitch
means an arrangement pitch PI or an arrangement pitch P2.
[0039]
10 The structures 11 have an arrangement mode which
forms a plurality of arrays of tracks Tl, T2, T3 and ...
(also referred to as "tracks T" collectively below) in
the reading surface of the optical information recording
medium. Meanwhile, the track refers to a portion of the
15 reading surface of the optical information recording
medium at which the structures 11 are formed. The track
T is preferably concentric or spiral.
[0040]
The structures 11 are arranged at positions which
2 0 are half a pitch displaced between two neighboring tracks
T. More specifically, between the two neighboring tracks
T and at intermediate positions (positions which are
displaced half a pitch) of the structures 11 aligned in
one track (for example, Tl), the structures 11 in another
25 track (for example, T2) are arranged. As a result, as
illustrated in Fig. 2B, the structures 11 are arranged
such that the hexagonal lattice pattern or the semihexagonal
lattice pattern in which the centers of the
structures 11 are positioned at respective point of al to
3 0 a7 between three arrays of neighboring tracks (Tl to T3)
is formed.
1 23
SP262786WO00
[0041]
When the structures 11 are arranged to form the
semi-hexagonal lattice pattern, as illustrated in Fig. 2B,
the arrangement pitch PI (the distance between al and a2)
5 of the structures 11 in the same track (for example, Tl)
is preferably longer than an arrangement pitch of the I
structures 11 between two neighboring tracks (for example,
Tl and T2), that is, the arrangement pitch P2 (for
example, the distances between al and a7, and a2 and a7)
10 of the structures 11 in ±0 directions in the track
extending direction. By arranging the structures 11 in
this way, it is possible to improve a packing density of
the structures 11.
[0042]
15 From the view point of easiness of molding, the
structures 11 preferably have cone shapes or cone shapes
obtained by stretching or contracting the cone shapes in
the track direction. The structures 11 preferably have
axially symmetrical cone shapes or cone shapes obtained
20 by stretching or contracting the cone shapes in the track
direction. When the neighboring structures 11 are
jointed, the structures 11 preferably have axially
symmetrical cone shapes except lower portions jointed to
the neighboring structures 11 or cone shapes obtained by
25 stretching or contracting the cone shapes in the track
direction. Further, a conical surface of the cone shape
may be curved in a concave shape or a convex shape. The
cone shape is, for example, a conical shape, a circular
truncated conical shape, an elliptic conical shape, an
3 0 elliptic truncated conical shape, a pyramidal shape (such
as a triangular pyramidal shape, a quadrangular pyramidal
24
I SP262786WO00
i
shape or a pentagonal pyramidal shape) or a truncated
pyramidal shape. Meanwhile, as described above, the cone
shape refers to an idea including the circular truncated
conical shape, the truncated pyramidal shape, the j
i
5 elliptic conical shape and the elliptic truncated conical
shape in addition to the conical shape and the pyramidal
shape. Further, the circular truncated conical shape
refers to a shape obtained by cutting the top of the
conical shape, the elliptic truncated conical shape
10 refers to a shape obtained by cutting the top of the
elliptic cone and the truncated pyramidal shape refers to
a shape obtained by cutting the top of a pyramid.
[0043]
As illustrated in Figs. 4A and 4B, the structures
15 11 are preferably elliptic, oval or egg-shaped cone
structures which have bottom surfaces having long axes
and short axes, and elliptic conical shapes having curved
tops. Alternatively, as illustrated in Fig. 5B, the
structure preferably has a bottom surface of an elliptic,
2 0 oval or egg-shaped cone structure which has the long axis
and the short axis, and a flat top of a circular
truncated conical shape. By forming this shape, it is
possible to improve a packing rate in an array direction.
[0044]
25 From a view point of improvement of a reflection
property, a cone shape (see Fig. 4A) having a moderate
inclination at the top and an increasingly steep
inclination from the center portion to the bottom portion
is preferable. Further, from a view point of improvement
3 0 of the reflection property and the transmission property,
a cone shape (see Fig. 4B) which has a steeper
1 25
SP262786WO00
inclination at the center portion than those at the
bottom portion and the top or a cone shape (see Fig. 5A)
which has a flat top is preferable. When the structures
11 have elliptic conical shapes or elliptic truncated
5 conical shapes, the long axis direction of a bottom
surface of these shapes is preferably parallel to the
track extending direction. Although each of the I
structures 11 has the same shape in Figs. 4A to 5B, the I
shapes of the structures 11 are not limited to this, and
10 structures 11 with two or more types of shapes may be
formed on a base surface. Further, the structures 11 may
be formed integrally with a base 2.
[0045]
Further, as illustrated in Figs. 4A to 5B, a
15 projecting portion lib is preferably provided in part or
entirety of the periphery of the structures 11. By so
doing, even when the packing rate of the structures 11 is
low, it is possible to make the reflectivity low. More
specifically, as illustrated in Figs. 4A to 5A, the
20 projecting portion lib is provided between the
neighboring structures 11. Further, as illustrated in
Fig. 5B, a long and thin projecting portion lib may be
provided in part or entirety of the periphery of the
structures 11. This long and thin projecting portion lib
25 extends, for example, in a direction from the top of the
structures 11 to the lower portion. Although the shape
of the projecting portion lib includes, for example, a
triangular cross section or a quadrangular cross section,
the shape is not limited to these shapes in particular,
3 0 and can be selected by taking into account easiness of
molding. Further, the surface of part or entirety of the
1 26
SP262786WO00
periphery of the structures 11 may be roughened to form
fine concavities and convexities. More specifically, a
surface between the neighboring structures 11 may be
roughened to form fine concavities and convexities.
5 Further, a fine hole may be formed in a surface of the
structures 11, for example, the top.
[0046]
The structures 11 are not limited to the
illustrated convex shapes, and may be formed with a
i
10 concave portion formed in the surface of the base 2. The j
height of the structures 11 is not limited in particular,
and is, for example, about 420 nm and, more specifically,
is 415 nm to 421 nm. In addition, when the structures 11 I
are formed in the concave shapes, the height corresponds
15 to the depth of the structures 11.
[0047]
The height HI of the structures 11 in the track
extending direction is preferably smaller than the height
H2 of the structures 11 in an array direction. That is,
20 the heights HI and H2 of the structures 11 preferably
satisfy the relationship of HI < H2. When the structures
11 are aligned to satisfy the relationship of HI ^ H2, it
is necessary to make the arrangement pitch PI in the
track extending direction longer, and therefore the
25 packing rate of the structures 11 in the track extending
direction decreases. When the packing rate decreases in
this way, a decrease in the reflection property occurs.
[0048]
In addition, the aspect ratios of the structures 11
3 0 are not limited to the same aspect ratio, each of the
structures 11 may have a given height distribution (for
1 27
SP262786WO00
example, in the range of about 0.83 to 1.4 6 of the aspect
ratios). By providing the structures 11 having the
height distributions, it is possible to reduce wavelength
dependency of the reflection property. Consequently, it
5 is possible to realize an optical information recording
medium which has a good antireflection property.
[0049]
Meanwhile, the height distribution means that the
structures 11 having height (depth) of two or more types
10 are provided on the surface of the base 2. That is,
structures 11 which have reference height and structures
11 which have height different from these structures 11
are provided on the surface of the base 2. For example,
i
the structures 11 which have the height different from j
15 the reference are cyclically or non-cyclically (at
random) provided on the surface of the base 2. A
direction of this cycle is, for example, the track
extending direction or the array direction.
[0050]
2 0 A skirt portion 11a is preferably provided to a
periphery portion of the structures 11 because it is
possible to easily separate the optical information
recording medium from a mold or the like in procedure of
manufacturing the optical information recording medium.
25 Meanwhile, the skirt portion 11a means a projecting
portion provided to the periphery portion of the bottom
portion of the structures 11. From the view point of the
above separation property, this skirt portion 11a
preferably has a curved surface the height of which
3 0 moderately decreases in the direction from the tops of
the structures 11 to the lower portion. In addition,
1 28
SP262786WO00
although the skirt portion 11a may be provided only to
part of the periphery portion of the structures 11, the
skirt portion is preferably provided to entirety of the
periphery portion of the structures 11 from the view
5 point of improvement of the separation property. Further,
when the structures 11 are concave portions, the skirt
portion is a curved surface provided to an opening
periphery of the concave portions which are the
structures 11.
10 [0051]
The aspect ratio in the present invention is j
defined by the following equation (1). ]
[0052] I
Aspect ratio = H/P ... (1)
15 where H: a height of a structure, and P: an average
arrangement pitch (average cycle)
Meanwhile, the average arrangement pitch P is
defined by the following equation (2).
[0053]
20 Average arrangement pitch P = (PI + P2 + P2)/3 ...
(2)
where PI: an arrangement pitch (track extending
direction cycle) in a track extending direction, P2:
arrangement pitches (0 direction cycle) of ±0 directions
25 (where 0 = 60° - 5, and 5 is preferably 0° < 5 < 11° and
is more preferably 3° < 8 < 6°)
[0054]
Further, the height H of the structures 11 is the
height of the structures 11 in the array direction. The
30 height of the structures 11 in the track extending
direction (X direction) is lower than the height in the
29
SP262786WO00
1
array direction (Y direction), and the height of a
portion of the structures 11 other than in the track
extending direction is substantially the same as the
height in the array direction, so that the height of the
5 subwavelength structures is represented by the height in
the array direction. Meanwhile, when the structures 11
are concave portions, the height H of the structures in
above equation (1) is the depth H of the structures.
[0055]
10 When an arrangement pitch of the structures 11 in
the same track is PI and an arrangement pitch of the
structures 11 between two neighboring tracks is P2, a
ratio P1/P2 preferably satisfies a relationship of 1.00 <
P1/P2 < 1.1 or 1.00 < P1/P2 < 1.1. By setting this
15 numerical value range, it is possible to improve the
packing rate of the structures 11 having elliptic conical
shapes or elliptic truncated conical shapes and,
consequently, improve the antireflection property.
[0056]
20 The packing rate of the structures 11 on the base
surface has an upper limit of 100%, and is in a range of
65% or more, preferably 73% or more and more preferably
86% or more. By setting this range of the packing rate,
it is possible to improve the antireflection property.
25 To improve the packing rate, it is preferably to joint
the lower portions of the neighboring structures 11 or
adjust the ellipticity of structure bottom surfaces to
apply distortions to the structures 11.
[0057]
3 0 Meanwhile, the packing rate (average packing rate)
of the structures 11 is a value calculated as follows.
• ' 30
J SP262786WO00
I [0058]
First, an image of the surface of the optical
information recording medium is captured from a top view
using a scanning electron microscope (SEM). Next, a unit
5 cell Uc is selected at random from the captured SEM
picture to measure the arrangement pitch PI of the unit
cell Uc and the track pitch Tp (see Fig. 4B). Further,
an area S of the bottom surface of the structure 11 which
is positioned in the center of this unit cell Uc is
10 measured by image processing. Next, the packing rate is
calculated according to the following equation (3) using
the measured arrangement pitch PI, track pitch Tp and
bottom surface area S.
[0059]
15 Packing rate = (S(hex.)/S(unit)) x 100 ... (3)
Unit cell area: S(unit) = Plx2Tp
Area of bottom surface of structure existing in
unit cell: S(hex.) = 2S
[0060]
2 0 The above processing of calculating the packing
rate is performed for ten unit cells selected at random
from the captured SEM picture. Further, by simply
averaging (taking an arithmetic average of) measurement
values, the average rate of the packing rates is
25 calculated as the packing rate of the structures 11 on
the base surface.
[0061]
When the structures 11 overlap or there are
substructures such as the projecting portion lib between
3 0 the structures 11, it is possible to calculate the
packing rate according to a method of deciding an area
!
31
SP262786WO00
ratio to the height of the structures 11 by using a
portion corresponding to 5% of the height as a threshold.
[0062]
When the structures 11 form the semi-hexagonal
5 lattice pattern, an ellipticity e of a structure bottom
surface is preferably 100% < e < 150% or less. This is
because, by setting this range, it is possible to improve
the packing rate of the structures 11 and obtain the good
antireflection property.
10 [0063]
Meanwhile, the ellipticity e is defined by (a/b) x
100 when the diameter of the structure bottom surface in j
the track direction (X direction) is a and the diameter
in the array direction (Y direction) orthogonal to the
15 diameter a is b. In addition, the diameters a and b of
the structures 11 are values calculated as follows.
First, an image of the surface of the optical information
recording medium is captured from a top view using a
scanning electron microscope (SEM) to extract the ten
20 structures 11 at random from the captured SEM picture.
Next, the diameters a and b of each of the extracted
structures 11 are measured. Further, by simply averaging
(taking an arithmetic average of) measurement values,
average values of the diameters a and b of the structures
25 11 are calculated as the diameters a and b of the
structures 11.
[0064]
Fig. 6A illustrates an example of an arrangement of
the structures 11 having conical shapes or circular
30 truncated conical shapes. Fig. 6B illustrates an example
of an arrangement of the structures 11 of elliptic
!
32
SP262786WO00
conical shapes or elliptic truncated conical shapes. As
illustrated in Figs. 6A and 6B, the structures 11 are
preferably jointed such that lower portions overlap each
other. More specifically, the lower portions of the
5 structures 11 are preferably jointed to a partial or
entire lower portions of the neighboring structures 11.
More specifically, in the track direction, in the 0
direction or in both directions, the lower portions of
the structures 11 are preferably jointed. More
10 specifically, in the track direction, in the 0 direction
or in both directions, the lower portions of the !
structures 11 are preferably jointed. Figs. 6A and 6B j
illustrate examples that entire lower portions of the
neighboring structures 11 are jointed. By jointing the
15 structures 11 in this way, it is possible to improve the
packing rate of the structures 11. The structures are
preferably jointed at portions which are the one fourth
of the maximum value of a wavelength band of light under
use environment in an optical path which takes the
20 reflectivity into account. By this means, it is possible
to obtain the good antireflection property.
[0065]
As illustrated in Fig. 6B, when the lower portions
of the structures 11 having the elliptic conical shapes
25 or the elliptic truncated conical shapes are jointed, the
heights of joint portions become lower in order of the
joint portions a, b and c.
[0066]
The ratio ((2r/Pl) x 100) of a diameter 2r to the
30 arrangement pitch PI is 85% or more, is preferably 90% or
more and is more preferably 95% or more. By setting this
1 33
SP262786WO00
•: W
range, it is possible to improve the packing rate of the
structures 11 and improve the antireflection property.
When the ratio ((2r/Pl)xlOO) becomes large and the degree
of overlapping of the structures 11 is higher, the
5 antireflection property tends to decrease. Hence, an
upper limit value of the ratio ((2r/Pl)xlOO) is
preferably set such that the structures are jointed at
portions which are the one fourth of the maximum value of
a wavelength band of light under use environment in an
10 optical path which takes the reflectivity into account.
Meanwhile, the arrangement pitch PI is an arrangement
pitch of the structures 11 in the track direction, and
the diameter 2r is the diameter of a structure bottom
surface in the track direction. In addition, when the
15 structure bottom surface is circular, the diameter 2r is
the diameter, and, when the structure bottom surface is
elliptic, the diameter 2r is the long diameter.
[0067]
[Configuration of Reading Surface Forming Master]
20 Fig. 7A is a schematic plan view illustrating an
example of a configuration of a molding surface of a
reading surface forming master for forming above
structures on a reading surface. Fig. 7B is a plan view
enlarging part of the molding surface of the reading
25 surface forming master illustrated in Fig. 7A. A reading
surface forming master 201 has a circular disk shape, and
a plurality of structures 202 having concave shapes is
aligned on the surface of the reading surface forming
master. The structures 202 are arranged on, for example,
3 0 a concentric or spiral track. Although, for example,
glass can be used for a material of the reading surface
34
I SP262786WO00
forming master 201, this material is not limited in
particular. By spatially linking two dimensional
patterns using a roll master exposure device described
below, synchronizing a polarity inversion formatter
5 signal and a rotation controller of a recording device
per one track, generating a signal and performing
patterning at an adequate feed pitch using CAV, it is
possible to record a hexagonal lattice pattern or a semihexagonal
lattice pattern. By adequately setting the
10 frequency of the polarity inversion formatter signal and
the number of rotations of roll, it is possible to form a
lattice pattern of a uniform spatial frequency in a
desired recording region.
[0068]
15 [Configuration of Exposure Device]
First, a configuration of the master exposure
device used for procedure of exposing a moth-eye pattern
will be described with reference to Fig. 8. This master
exposure device is formed based on an optical disk
2 0 recording device.
[0069]
A laser light source 21 is a light source which
exposes a resist layer deposited on a surface of a master
211 as a recording medium, and oscillates recording laser
25 light 15 of, for example, a wavelength X = 266 nm. The
laser light 15 emitted from the laser light source 21
travels straightforward as a parallel beam, and is
incident on an electro optical modulator (EOM) 22. The
laser light 15 having transmitted through the electro
30 optical modulator 22 is reflected by a mirror 23, and is
guided to a modulating optical system 25.
35
SP262786WO00
[0070]
The mirror 23 is formed with a polarized beam
splitter, and has a function of reflecting one
polarization component and allowing transmission of the
5 other polarization component. The polarization component
having transmitted through the mirror 23 is received by a
photodiode 24, and the electro optical modulator 22 is
controlled based on this received light signal to
modulate the phase of the laser light 15.
10 [0071]
In the modulating optical system 25, the laser
light 15 is condensed on an acousto-optic modulator (AOM)
27 made of glass (Si02) or the like by a condenser lens
26. The intensity of the laser light 15 is modulated by
15 the acousto-optic modulator 27, and the laser light is
spread and converted into a parallel beam by a lens 28.
The laser light 15 emitted from the modulating optical
system 25 is reflected by a mirror 31, and is guided
horizontally and in parallel on a moving optical table 32.
20 [0072]
The moving optical table 32 has a beam expander 33
and an objective lens 34. The laser light 15 guided to
the moving optical table 32 is shaped into a desired beam
shape by the beam expander 33, and then is radiated on
25 the resist layer on the master 12 through a mirror 3 8 and
the objective lens 34. The master 12 is set on a turn
table 36 connected to a spindle motor 35. Further, by
rotating the master 211, guiding the laser light 15 in a
radial direction of the master 211 and intermittently
30 radiating the laser light 15 on the resist layer,
procedure of exposing the resist layer is performed. A
5,
36
SP262786WO00
formed latent image has a virtually elliptic shape which
has a long axis in a circumferential direction. The
laser light 15 is moved by moving the moving optical
table 32 in an arrow R direction.
5 [0073]
The exposure device has a control mechanism 3 7
which forms on the resist layer a latent image
corresponding to a two dimensional pattern of a hexagonal
lattice or a semi-hexagonal lattice. The control
10 mechanism 37 has a formatter 29 and a driver 30. The
formatter 29 has a polarity inverting unit, and this
polarity inverting unit controls timing to radiate the
laser light 15 on the resist layer. The driver 3 0
receives an output from the polarity inverting unit, and
15 controls the acousto-optic modulator 27.
[0074]
This roll master exposure device generates a signal
by synchronizing a polarity inversion formatter signal
and the rotation controller of the recording device per
2 0 one track such that two dimensional patterns are
spatially linked, and the acousto-optic modulator 2 7
modulates the intensity. By performing patterning at a
constant angular velocity (CAV), at an adequate
modulation frequency, at an adequate feed pitch and with
25 the adequate number of rotations, it is possible to
record a hexagonal lattice or semi-hexagonal lattice
pattern. For example, the feed pitch only needs to be
set to 251 nm to set a cycle in the circumferential
direction to 315 nm and set the cycle in an about 6 0
30 degree direction (about -60 degree direction) with
respect to the circumferential direction to 300 nm (the
1 37
SP262786WO00
Pythagorean theorem). The frequency of the polarity
inversion formatter signal is changed by the number of
rotations of roll (1800 rpm, 900 rpm and 450 rpm). The
semi-hexagonal lattice pattern in which the spatial
5 frequency (a circle 315 ran cycle, and a circumferential
direction about 60 degree direction (about -60 degree
direction) 300 nm cycle) in a desired recording region is
uniform is obtained by expanding far ultraviolet laser
light to a five-fold beam diameter by the beam expander
10 (BEX) 33 on the moving optical table 32, radiating the
laser light on the resist layer on the master 12 through
the objective lens 34 of a numerical aperture (NA) 0.9
and forming a fine latent image.
[0075]
15 [Method of Manufacturing Optical Information Recording
Medium]
Figs. 9A to 10F are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to the
2 0 first embodiment of the present invention.
[0076]
(Resist Film Forming Procedure)
First, as illustrated in Fig. 9A, a master 211 of a
circular disk shape is prepared. Next, as illustrated in
25 Fig. 9B, the resist layer 212 is formed on the surface of
the master 211. As a material of the resist layer 212,
for example, one of an organic resist and an inorganic
resist may be used. As the organic resist, for example,
a novolac resist or a chemically-amplified resist can be
3 0 used. Further, as the inorganic resist, for example, a
metal compound including transition metals of one, two or
i.
1 38
SP262786WO00
more types can be used.
[0077]
(Exposure Procedure)
Next, as illustrated in Fig. 9C, the master 211 is
5 rotated using the above master exposure device, and the
laser light 213 which is an exposure beam is radiated on
the resist layer 212. In this case, by intermittently
radiating the laser light 213 while moving the laser
light 213 in the radial direction of the master 211, the
10 entire surface of the resist layer 212 is exposed. By j
this means, a latent image 214 matching a trajectory of
the laser light 213 is formed on the entire surface of
the resist layer 212.
[0078]
15 For example, the latent image 214 is arranged to
form a plurality of arrays of tracks on a master surface,
and forms a hexagonal lattice pattern or a semi-hexagonal
lattice pattern. The latent image 212 has, for example,
an elliptic shape having a long axis direction in the
20 track extending direction.
[0079]
(Developing Procedure)
Next, a developer is dropped on the resist layer
212 while rotating the master 211 to develop the resist
25 layer 212 as illustrated in Fig. 9D. As illustrated,
when the resist layer 212 is formed with a positive
resist, a solution rate of an exposed portion exposed by
the laser light 213 with respect to the developer
increases compared to a non-exposed portion, and a
3 0 pattern matching the latent image (exposed portion) 214
is formed on the resist layer 212.
39
SP262786WO00
[0080]
(Etching Procedure)
Next, the surface of the master 211 is etched using
the pattern (resist pattern) of the resist layer 212
5 formed on the master 211 as a mask. By this means, as
illustrated in Fig. 9E, concave portions of elliptic
conical shapes or elliptic truncated conical shapes ;
having the long axis direction in the track extending
direction, that is, the structures 202 are obtained. An
10 etching method is performed by, for example, dry etching.
In this case, by alternately performing etching
processing and ashing processing, it is possible to form,
for example, a pattern of the structures 2 02 of cone
shapes. Further, it is possible to make a glass master
15 having a three-fold depth (selectivity 3 or more) or more
compared to the resist layer 212, and make the aspect
ratio of the structures 202 higher. Thus, as illustrated
in Fig. 10A, the reading surface forming master 201
having, for example, the hexagonal lattice pattern or the
20 semi-hexagonal lattice pattern is obtained.
[0081]
(Transferring Procedure)
Next, as illustrated in Fig. 10B, the signal
surface forming master 221 on which concavities and
25 convexities for forming the signal surface on the surface
is prepared. For this signal surface forming master 221,
a known stamper (generally referred to as a "mold" or a
"template" for use of nanoimprint) upon manufacturing of
optical disks such as conventional CDs can be used. Such
3 0 a stamper is, for example, a nickel stamper.
[0082]
I
40
SP262786WO00
Next, as illustrated in Fig. IOC, according to, for
example, an injection molding method, shapes of the
reading surface forming master 201 and the signal surface
forming master 221 are transferred to the resin material
5 13. By this means, as illustrated in Fig. 10D, the
substrate 1 on both surfaces of which the shapes are
transferred is obtained. More specifically, for example,
the substrate 1 is formed as follows. First, the reading
surface forming master 201 is arranged on a mirror
10 surface of one mold of an injection molding device, and
the signal surface forming master 221 is arranged on a
mirror surface of the other mold of the injection molding
device. Next, for example, a cavity is formed by making
both molds butt, a resin material melted in this cavity
15 is supplied and solidified, and both molds are separated.
By this means, the substrate 1 in which the concaveconvex
portions 12 are formed in the signal surface, and
a plurality of structures 11 is formed in the reading
surface.
20 [0083]
(Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 10E, the information
signal layer 2 is formed on the concave-convex portions
12 of the substrate 1 using, for example, a spattering
25 method or a spin coat method.
[0084]
(Protective Layer Forming Procedure)
Next, as illustrated in Fig. 10F, a photosensitive
resin such as an ultraviolet curable resin is applied to
3 0 the information signal layer 2 according to, for example,
the spin coat method, and the layer is radiated with
i
1 41
SP262786WO00
light such as an ultraviolet ray and is solidified to
form the protective layer 3.
[0085]
According to the above procedure, a target optical
5 information recording medium is obtained.
[0086]
According to the first embodiment, a plurality of
structures 11 is formed on the reading surface of the
optical information recording medium, so that it is
10 possible to reduce reflection of recording light or
playback light on the reading surface.
[0087]
By, for example, decreasing the surface
reflectivity of an optical disk by about 4 to 5%, it is
15 not necessary to input excessive power of playback and
recording laser using an optical pickup of a player
(drive) and, consequently, it is possible to reduce a
load on the laser and increase the longevity of the laser.
Particularly, this is effective for use in recording
2 0 which requires high power such as high speed rotation
(for example, 6X or 8X) recording of a DVD or a BD.
[0088]
By, for example, suppressing about 4% to 5%
corresponding to a decrease in the signal reflectivity
25 from a disk upon disk playback, it is possible to prevent
a decrease in the amount of signal and deterioration of
signal quality such as deterioration of the S/N ratio.
Further, it is also possible to reduce a load on the
playback system on the player (drive) side and play back
30 signals well. The amount of playback signal decreases
upon high speed rotation (for example, 6X or 8X) playback
1 42
SP262786WO00
of a DVD or a BD in particular, and therefore preventing
loss of the amount of playback signal and deterioration
of S/N is effective.
[0089]
5 As antireflection film specifications of the low
reflectivity such as a DVD-DL specification, a BD-DL
specification and a future BD multi-layer structure
specification increase, it is possible to prevent the
reflectivity of a disk surface from being erroneously
10 recognized as a reflection layer by the player (drive).
[0090]
For example, it is possible to suppress about 4 to
5% at which a signal returning form the disk reflection
film decreases due to reflection on the disk surface, so
15 that a setting which is required to set a higher
reflectivity taking this loss of this standard into
account is not required. Consequently, a process margin
of setting a thin reflection film and material cost
become more advantageous.
20 [0091]
Particularly, in case of the multi-player structure
disk, when the original reflectivity is maintained as a
result of improvement of the reflectivity of a reflection
film, it is possible to provide advantages of, for
25 example, improving the entire balance and increase the
number of reflection films by making the reflection film
thinner and improving the transmittance.
[0092]
For example, the subwavelength structures can
30 reduce the reflectivity to 0.2% or less in the entire
visible light region of 400 to 850 nm, so that single
43
SP262786WO00
structures can provide an effect of reducing the
reflectivity for CD 780 nm, DVD 650 nm and BD 405 nm
pickup lasers to the same degree.
[0093]
5 In addition to improvement of the optical disk
optical property, forming the subwavelength structures on
the disk reading surface provides a water repellent
function like a lotus leaf structure and can provide a
function of preventing contamination.
10 [0094]
<2. Second Embodiment>
Fig. 11 is a procedure diagram for explaining an
example of a method of manufacturing the optical
information recording medium according to a second
15 embodiment of the present invention. The second
embodiment of the present invention differs from the
first embodiment in forming a substrate 1 by laminating a
first compact la and a second compact lb. In addition,
portions of the second embodiment corresponding to those
2 0 of the first embodiment will be assigned the same
reference numerals.
[0095]
(Transferring Procedure)
First, as illustrated in Fig. 11A, a reading
25 surface forming master 201 is prepared. Next, as
illustrated in Fig. 11B, according to, for example, an
injection molding method, the shape of the reading
surface forming master 201 is transferred to a resin
material 13. By this means, as illustrated in Fig. lie,
30 a first compact la in which a plurality of structures 11
is formed in one principal surface and a flat surface is
44
SP262786WO00
formed in the other principal surface is obtained. The
first compact la has, for example, a sheet shape or a
flat shape and is preferably flat from the view point of
easiness to handle.
5 [0096]
Next, as illustrated in Fig. 11D, the signal
surface forming master 221 is prepared. Next, as
illustrated in Fig. HE, according to, for example, an
injection molding method, the shape of the signal surface
10 forming master 201 is transferred to the resin material
13. By this means, as illustrated in Fig. 11F, the
second compact lb in which concave-convex portions 12 are
formed in one principal surface and a flat surface is
formed in the other principal surface is obtained. The
15 second compact lb has, for example, a sheet shape or a
flat shape and is preferably flat from the view point of
easiness to handle.
[0097]
(Laminating Procedure)
20 Next, as illustrated in Fig. 11G, a substrate 1 is
obtained by laminating the flat surfaces of the first
compact la and the second compact lb across a laminating
layer 14. For a material of the laminating layer 14, a
material which includes main components such as an
25 ultraviolet curable resin and a pressure sensitive
adhesive (PSA) can be used. When the laminating layer 14
includes the pressure sensitive adhesive as the main
component, the laminating layer 14 may be formed in
advance on one flat surface of the first compact la and
3 0 the second compact lb.
[0098]
1
45
SP262786WO00
, (Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 11H, the information
signal layer 2 is formed on the concave-convex portions
12 of the substrate 1 using, for example, a spattering
5 method or a spin coat method.
[0099]
(Protective Layer Forming Procedure)
Next, as illustrated in Fig. Ill, a photosensitive
resin such as an ultraviolet curable resin is applied to j
10 the information signal layer 2 according to, for example,
the spin coat method, and the layer is radiated with
light such as an ultraviolet ray and is solidified to
form the protective layer 3.
[0100]
15 According to the above procedure, a target optical
information recording medium is obtained.
[0101]
<3. Third Embodiment>
Fig. 12 is a cross sectional view illustrating an
2 0 example of a configuration of an optical information
recording medium according to a third embodiment of the
present invention. This optical information recording
medium has a first substrate 41, an information signal
layer 2 formed on the first substrate 41 and a second
25 substrate 42 formed on the information signal layer 2.
In the surface of the second substrate 42, a plurality of
structures 11 having convex shapes is formed. The same
portions of the third embodiment as those of the first
embodiment will be assigned the same reference numerals,
3 0 and will not be described.
[0102]
46
SP262786WO00
In this optical information recording medium, an
information signal is recorded and/or played back byradiating
laser light on the information signal layer 2
from a second substrate 42 side. For example, an
5 objective lens having the numerical aperture of 0.64 or
more and 0.66 or less condenses laser light having the
wavelength of 650 nm or more and 665 nm or less, and
radiates the laser light on the information signal layer
2 from the second substrate 41 side, so that an
10 information signal is recorded and/or played back. Such
an optical information recording medium is, for example,
a DVD (Digital Versatile Disc).
[0103]
When an optical information recording medium is
15 compliant with a DVD standard, an arrangement pitch of
the structures 11 is preferably 750 nm or less, is more
preferably 150 nm or more and 4 50 nm or less, and is
still more preferably 240 nm or more and 400 nm or less.
When the arrangement pitch exceeds 7 50 nm, about 650 nm
20 which is a value obtained by multiplying 750 with V3/2
corresponds to a dimension value which is the nearest
effective diffraction grating interval in case of a
hexagonal lattice arrangement, and a rapid rise in the
reflectivity in a region having this wavelength or less
25 is observed and the reflectivity exceeds 1%, and
therefore the antireflection effect becomes insufficient.
[0104]
The height of the structures 11 is preferably 8 0 nm
or more and 24 0 nm or less, is more preferably 14 0 nm or
30 more and 200 nm or less, and is still more preferably 160
nm or more and 180 nm or less. When the height is less
f.
i
I
1 ' 47
j SP262786WO00
\ than 8 0 nm, the reflectivity exceeds 1%, and the
antireflection effect becomes insufficient. Meanwhile,
when the height exceeds 240 nm, while antireflection
performance is still sufficient, the height of the
5 structures 11 increases, and therefore it is difficult to
make the structures.
[0105]
A flat portion diameter of a top of the structures
11 is preferably 0 fold or more and 0.7 folds or less of
10 an arrangement pitch or greater than 0 fold and 0.7 folds
or less of the arrangement pitch, is more preferably 0.4
folds or more and 0.6 folds or less of the arrangement
pitch and is the most preferably 0.5 folds. When the
flat portion diameter exceeds 0.7 folds, the reflectivity
15 exceeds 1%, and the antireflection effect becomes
insufficient.
[0106]
The ratio (X/E) of a wavelength X of light for
recording or playing back an information signal to a
20 height H of the structures 11 is preferably 2 or more and
6 or less. When the ratio is less than 2, while the
antireflection performance is still sufficient, the
heights of the structures 11 increase, and therefore it
is difficult to make the structures. Meanwhile, when the
25 ratio exceeds 6, the reflectivity exceeds 1%, and the
antireflection effect becomes insufficient.
[0107]
The first substrate 41 and the second substrate 42
have annular shapes in which center holes (not
3 0 illustrated) are formed in the centers, and the
thicknesses are, for example, selected to be 0.6 mm. A
48
SP262786WO00
plurality of structures 11 is formed in one principal
surface of the second substrate 42, and concave-convex
portions 11 are formed in the other principal surface.
For materials of the first substrate 41 and the second
5 substrate 42, the same material as a substrate 1 in the
first embodiment can be used.
[0108]
Figs. 13A to 131 are procedure diagrams for
explaining an example of a method of manufacturing the
10 optical information recording medium according to the
third embodiment of the present invention.
[0109]
(Transferring Procedure)
First, as illustrated in Figs. 13A and 13B, a
15 reading surface molding master 201 and a signal surface
forming master 221 are prepared. Next, as illustrated in
Fig. 13C, according to, for example, an injection molding
method, the shapes of the reading surface molding master
201 and the signal surface forming master 221 are
20 transferred to a resin material 13. By this means, as
illustrated in Fig. 13D, the second substrate 42 in which
a plurality of structures 11 is formed in one principal
surface and the concave-convex portions 12 are formed in
the other principal surface is obtained.
25 [0110]
(Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 13E, the information
signal layer 2 is formed on the concave-convex portions
12 of the second substrate 42 using, for example, a
3 0 spattering method or a spin coat method.
[0111]
49
SP262786WO00
i
(Transferring Procedure)
Next, as illustrated in Fig. 13F, for example, a
master 231 or a mold which has a smooth molding surface
is prepared. Next, as illustrated in Fig. 13G, according
5 to, for example, an injection molding method, the shape
of the smooth molding surface of the master 231 or the
mold is transferred to the resin material 13. By this
means, as illustrated in Fig. 13H, the first substrate 41
which has smooth surfaces on both principal surfaces is
10 formed.
[0112]
| (Laminating Procedure)
Next, as illustrated in Fig. 131, the smooth
surface of the first substrate 41 and the information
15 signal layer forming surface of the second substrate 42
are laminated by a laminating layer 14.
[0113]
According to the above procedure, a target optical
information recording medium is obtained.
20 [0114]
<4. Fourth Embodiment>
(Configuration of Optical Information Recording
Medium)
Fig. 14 is a cross sectional view illustrating an -
25 example of a configuration of an optical information [
recording medium according to a fourth embodiment of the
present invention. The optical information recording l
medium has a configuration in which a first substrate 41,
a first information signal layer (referred to as a "L0
30 layer") 43, an intermediate layer 44, a second
information signal layer (referred to as a "LI layer") 45 r
50
SP262786WO00
m
and a second substrate 42 sequentially are laminated in
this order. The same portions of the fourth embodiment
as those of the third embodiment will be assigned the same reference numerals, and will not be described. [
5 [0115]
The first information signal layer 43 and the
second information signal layer 4 5 are formed to be
capable of recording and/or playing back an information
signal. This configuration is adequately selected
10 depending on, for example, whether a desired optical
information recording medium is one of a playback
dedicated type, a recordable type and a rewritable type.
The second information signal layer 45 differs from the
first information signal layer 43 in a semi-transmission
15 layer which is formed to reflect laser light and allows
transmission of laser light.
[0116]
The intermediate layer 44 is made of a resin
material which has transparency with respect to laser
20 light for recording and/or playing back an information
signal, and, for example, a plastic material such as a
polycarbonate resin, a polyolefin resin or an acrylic
resin can be used as such a material.
: [0117]
25 (Method of Manufacturing Optical Information
i Recording Medium)
Figs. 15A to 15J are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to the
i
3 0 fourth embodiment of the present invention.
] [0118]
51
SP262786WO00 :
(Transferring Procedure) [
i
First, as illustrated in Figs. 15A and 15B, a I
reading surface molding master 201 and a first signal
i
surface forming master 241 are prepared. Next, as 5 illustrated in Fig. 15C, according to, for example, an )
.
injection molding method, the shapes of the reading I
i
surface molding master 201 and the first signal surface
forming master 241 are transferred to a resin material 13.
By this means, as illustrated in Fig. 15D, the second
10 substrate 42 in which a plurality of structures 11 is
formed in one principal surface and the concave-convex
portions 12 are formed in the other principal surface is
obtained.
[0119]
15 (Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 15E, the information
signal layer 45 is formed on the concave-convex portions
12 of the second substrate 42 using, for example, a |
spattering method or a spin coat method.
20 [0120]
(Transferring Procedure)
Next, as illustrated in Fig. 15F, a second signal
surface forming master 242 is prepared. Next, as
illustrated in Fig. 15G, according to, for example, an
25 injection molding method, the shape of the second signal
\ surface forming master 242 is transferred to the resin
material 13. By this means, as illustrated in Fig. 15H,
i the first substrate 41 in which concave-convex portions
12 are formed in one principal surface and a smooth
3 0 surface is formed in the other principal surface is
obtained.
•
L
i
i
SP262786WO00 !
[0121]
(Information Signal Layer Forming Procedure) t
Next, as illustrated in Fig. 151, the information •
signal layer 43 is formed on the concave-convex portions 5 12 of the first substrate 41 using, for example, a
spattering method or a spin coat method.
[0122]
(Laminating Procedure)
Next, as illustrated in Fig. 15J, the first
10 information signal layer forming surface of the first
substrate 41 and the second information signal layer
forming surface of the second substrate 42 are laminated
by the intermediate layer 44.
[0123]
15 According to the above procedure, a target optical
information recording medium is obtained.
[0124] |
<5. Fifth Embodiment>
(Configuration of Optical Information Recording
2 0 Medium)
Fig. 16 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to a fifth embodiment of the
present invention. The optical information recording
25 medium has a first substrate 51, a first information
signal layer 52, a second substrate 53, a second
information signal layer 54 and a protective layer 3
; sequentially laminated in this order. The same portions
of the fifth embodiment as those of the first embodiment
30 will be assigned the same reference numerals, and will
not be described.
•
.
;
>
53 I
SP262786WO00 '<•
f
[0125] •
r <-
The first substrate 51 and the second substrate 53
have annular shapes in which center holes (not
illustrated) are formed in the centers, and the :
5 thicknesses are, for example, selected to be 0.6 mm. A
plurality of structures 11 is formed in one principal
surface of the first substrate 51, and concave-convex
portions 12 are formed in the other principal surface.
The concave-convex portions 12 are formed in one
10 principal surface of the second substrate 53. For
materials of the first substrate 51 and the second
substrate 53, the same material as that of a substrate 1
in the first embodiment can be used. The first
information signal layer 52 is a semi-transmission layer
15 which has a configuration which reflects laser light and
allows transmission of laser light. The first i
information signal layer 52 employs a configuration which
enables, for example, high density recording compared to
the second information signal layer 54.
20 [0126]
(Method of Manufacturing Optical Information
Recording Medium)
Figs. 17A to 17J are procedure diagrams for
explaining an example of a method of manufacturing the
25 optical information recording medium according to the
fifth embodiment of the present invention.
} [0127]
• (Transferring Procedure)
First, as illustrated in Figs. 17A and 17B, a
3 0 reading surface molding master 2 01 and a first signal
• surface forming master 251 are prepared. Next, as
•
* 54
SP262786WO00 illustrated in Fig. 17C, according to, for example, an
injection molding method, the shapes of the reading
surface molding master 201 and the first signal surface
forming master 251 are transferred to a resin material 13.
5 By this means, as illustrated in Fig. 17D, the first
substrate 51 in which a plurality of structures 11 is
: formed in one principal surface and the concave-convex
portions 12 are formed in the other principal surface is
obtained.
10 [0128]
(Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 17E, the first
information signal layer 52 is formed on the concaveconvex
portions 12 of the first substrate 51 using, for
15 example, a spattering method or a spin coat method.
[0129]
(Transferring Procedure)
Next, as illustrated in Fig. 17F, a second signal
surface forming master 252 is prepared. Next, as
20 illustrated in Fig. 17G, according to, for example, an
injection molding method, the shape of the second signal
; surface forming master 252 is transferred to the resin
material 13. By this means, as illustrated in Fig. 17H,
the second substrate 53 in which the concave-convex
25 portions 12 are formed in one principal surface and a
i smooth surface is formed in the other principal surface
is obtained.
[0130]
(Information Signal Layer Forming Procedure)
3 0 Next, as illustrated in Fig. 171, the second
information signal layer 54 is formed on the concave55
SP262786WO00
convex portions 12 of the second substrate 53 using, for
example, a spattering method or a spin coat method.
[0131]
(Protective Layer Forming Procedure)
5 Next, as illustrated in Fig. 171, a photosensitive
resin such as an ultraviolet curable resin is applied to
the second information signal layer 2 according to, for
example, the spin coat method, and the layer is radiated
with light such as an ultraviolet ray and is solidified
10 to form the protective layer 3.
[0132]
(Laminating Procedure)
Next, as illustrated in Fig. 17J, the signal
surface of the first substrate 51 and the smooth surface
15 of the second substrate 42 are laminated by a laminating
layer 14.
[0133]
According to the above procedure, a target optical
information recording medium is obtained.
20 [0134]
<6. Sixth Embodiment>
Figs. 18A to 18D are procedure diagrams for
explaining an example of a method of manufacturing an
optical information recording medium according to a sixth
25 embodiment of the present invention. The sixth
embodiment of the present invention differs from the
; fourth embodiment in forming a plurality of structures 11
l in a reading surface of an optical information recording
medium in final procedure. In addition, the same
3 0 portions of the sixth embodiment as those of the first
embodiment will be assigned the same reference numerals.
i
;
f
i
> ?~.
56
SP262786WO00
[0135]
First, as illustrated in Fig. 18A, a reading
surface forming master 201 is prepared. Next, as
illustrated in Fig. 18B, an optical information recording
5 medium in which a first substrate 41, a second
information signal layer 43, an intermediate layer 44, a
second information signal layer 45 and a second substrate
42a are laminated in this order is prepared. The second
substrate 42a is the same as a second substrate 42 in the
10 fourth embodiment except that the structures 11 are not
formed in one principal surface and a smooth surface is
formed therein.
[0136] J
Next, as illustrated in Fig. 18C, a photosensitive
15 resin such as an ultraviolet curable resin is applied to
the reading surface of the optical information recording
medium according to, for example, the spin coat method.
Next, the reading surface forming master 201 is pressed
against the ultraviolet curable resin to radiate with
20 light such as an ultraviolet ray and solidify. By this
means, as illustrated in Fig. 18D, a plurality of
structures 11 is formed in the reading surface of the
optical information recording medium.
[0137]
25 According to the above procedure, a target optical
{ information recording medium is obtained.
i
[0138]
According to the sixth embodiment, in final
procedure of the procedure of manufacturing the optical
30 information recording medium, a plurality of structures
11 is formed in the reading surface, so that it is
!
'
1
1
57
SP262786WO00
possible to make an optical information recording medium
which has a good antireflection property without
substantially changing a manufacturing line of
conventional optical information recording media.
5 [0139]
<7. Seventh Embodiment>
Figs. 19A to 19E are procedure diagrams for
explaining an example of a method of manufacturing an
optical information recording medium according to a
10 seventh embodiment of the present invention. The seventh
embodiment of the present invention differs from the
sixth embodiment in forming a plurality of structures 11
in a reading surface by laminating a compact 15 in which
a plurality of structures 11 is formed, on the reading
15 surface of the optical information recording medium. In
addition, the same portions of the seventh embodiment as
those of the sixth embodiment will be assigned the same
reference numerals.
[0140]
20 First, as illustrated in Fig. 19A, a reading
surface forming master 201 is prepared. Next, as
illustrated in Fig. 19B, the reading surface forming
master 201 is pressed against a resin material 13 to
transfer the shape of the reading surface forming master
25 201 to the resin material 13. For a transferring method,
for example, optical transfer such as UV transfer or
thermal transfer can be used. By this means, as
illustrated in Fig. 19C, the compact 15 in which the
structures 11 are formed in one principal surface is
j
3 0 obtained. The shape of the compact 15 is, for example, a
• sheet shape or a flat shape. The resin material 13 is,
1
;
:
58
SP262786WO00 |
for example, an ultraviolet curable resin, a
thermosetting resin or a thermoplastic resin.
[0141]
Next, as illustrated in Fig. 19D, an optical
5 information recording medium in which a first substrate
41, a second information signal layer 43, an intermediate
layer 44, a second information signal layer 45 and a
second substrate 42a are laminated in this order is
prepared. Next, as illustrated in Fig. 19E, the compact
10 15 is laminated to the reading surface of the optical
information recording medium across a laminating layer 14.
[0142]
According to the above procedure, a target optical
i
information recording medium is obtained.
15 [0143]
According to the seventh embodiment, in final
procedure of the procedure of manufacturing the optical
information recording medium, a plurality of structures
11 is formed in the reading surface, so that it is
20 possible to provide the same effect as that of the sixth
embodiment.
[0144]
<8. Eighth Embodiment>
(Configuration of Optical Information Recording
25 Medium)
Fig. 20 is a cross sectional view illustrating an
example of a configuration of an optical information
recording medium according to an eighth embodiment of the
present invention. The optical information recording
3 0 medium has a substrate 1, an information signal layer 2
•
formed on the substrate 1 and a protective layer 61
I
%
59 t
SP262786WO00 1
formed on the information signal layer 2. In the surface
of the protective layer 61, a plurality of structures 11
having convex shapes is formed. The same portions of the
eighth embodiment as those of the first embodiment will
5 be assigned the same reference numerals, and will not be
described.
[0145]
In this optical information recording medium, an
information signal is recorded or played back by
10 radiating laser light on the information signal layer 2
from a protective layer 61 side which is an optical
transmission layer. For example, an objective lens
having the numerical aperture of 0.84 or more and 0.86 or
less condenses laser light having the wavelength of 400
15 nm or more and 410 nm or less, and radiates the laser
light on the information signal layer 2 from the
protective layer 61 side, so that an information signal
; is recorded or played back. Such an optical information
recording medium is, for example, a BD (Blu-ray Disc
; 20 (registered trademark)).
[0146]
When an optical information recording medium is
compliant with a BD standard, an arrangement pitch of the
structures 11 is preferably 470 nm or less, is more
; 25 preferably 150 nm or more and 350 nm or less, and is
I still more preferably 200 nm or more and 315 nm or less.
When the arrangement pitch exceeds 470 nm, about 407 nm
which is a value obtained by multiplying 470 with V3/2
corresponds to a dimension value which is the nearest
30 effective diffraction grating interval in case of a
hexagonal lattice arrangement, and a rapid rise in the
60
SP262786WO00
reflectivity in a region having this wavelength or less
is observed and the reflectivity exceeds 1%, and
therefore the antireflection effect becomes insufficient.
[0147]
5 The height of the structures 11 is preferably 8 0 nm
i
or more and 200 nm or less, is more preferably 100 nm or
more and 16 0 nm or less, and is still 110 nm or more and
145 nm or less. When the height is less than 80 nm, the
reflectivity exceeds 1%, and the antireflection effect
10 becomes insufficient. Meanwhile, when the height exceeds
200 nm, while antireflection performance is still
sufficient, the height of the structures 11 increases,
and therefore it is difficult to make the structures.
[0148]
15 A flat portion diameter of a top of the structures
11 is preferably 0 fold or more and 0.7 folds or less of
an arrangement pitch or greater than 0 fold and 0.7 folds
1 or less of the arrangement pitch, is more preferably 0.2
• folds or more and 0.5 folds or less of the arrangement
! 20 pitch and is still more preferably 0.3 folds or more and
0.4 folds or less. When the flat portion diameter
exceeds 0.7 folds, the reflectivity exceeds 1%, and the
antireflection effect becomes insufficient.
[0149]
] 25 The ratio (X/U) of a wavelength X of light for
: recording or playing back an information signal to a
height H of the structures 11 is preferably 2 or more and
6 or less. When the ratio is less than 2, while the
antireflection performance is still sufficient, the 1 30 heights of the structures 11 increase, and therefore it
is difficult to make the structures. Meanwhile, when the
61
SP262786WO00
ratio exceeds 6, the reflectivity exceeds 1%, and the
antireflection effect becomes insufficient.
[0150]
The protective layer 61 which is an optical
5 transmission layer is formed with, for example, an
optical transmission sheet which has an annular shape and
an adhesive layer which laminates this optical
transmission sheet to the substrate 1. The optical
transmission sheet is preferably made of a material of
10 low absorption capacity with respect to laser light used
for recording and/or playback, and, more specifically, is
preferably made of a material of 90% or more of the
transmittance. The material of the optical transmission
sheet is, for example, a polycarbonate resin material or
15 a polyolefin resin (for example, ZEONEX (registered
trademark)). The thickness of the optical transmission
sheet is preferably selected to be 0.3 mm or less and is
i more preferably selected to be in a range of 3 urn to 177
j^m. The adhesive layer is made of, for example, an
20 ultraviolet curable resin or a pressure sensitive
<
i adhesive (PSA). Further, the protective layer 61 may be
formed with a resin cover which is formed by solidifying
• a photosensitive resin such as a UV resin. A material of
the resin cover is, for example, an acrylic resin of an
25 ultraviolet curable type.
1 [0151]
The thickness of the protective layer 61 is
preferably selected to be in a range of 10 \xm to 177 um,
and is, for example, selected to be 100 jxm. By combining
J 30 this thin protective layer 61 and the objective lens with
a high numerical aperture of, for example, about 0.85, it
k
f
62 I
SP262786WO00 f
i
is possible to realize high density recording.
[0152]
(Method of Manufacturing Optical Information
Recording Medium)
5 Figs. 21A to 21G are procedure diagrams for
I explaining an example of a method of manufacturing the
optical information recording medium according to the
eighth embodiment of the present invention.
[0153]
10 (Transferring Procedure)
First, as illustrated in Fig. 21A, the signal
surface forming master 221 is prepared. Next, as ':
illustrated in Fig. 2IB, according to, for example, an
injection molding method, the shape of the signal surface
15 forming master 221 is transferred to the resin material
13. By this means, as illustrated in Fig. 21C, the first
substrate 1 in which concave-convex portions 12 are
formed in one principal surface is obtained.
[0154]
i
i
\ 20 (Information Signal Layer Forming Procedure)
Next, as illustrated in Fig. 21D, the information
signal layer 2 is formed on the concave-convex portions
12 of the substrate 1 using, for example, a spattering
method or a spin coat method.
j 25 [0155]
1 (Transferring Procedure)
i
Next, as illustrated in Fig. 2IE, a reading surface
forming master 201 is prepared. Next, as illustrated in
Fig. 21F, the resin material 13 such as an ultraviolet
3 0 curable resin is applied to the information signal layer
2 of the substrate 1 according to, for example, a spin
:
'•
;
63 I
SP262786WO00 coat method. Next, the reading surface forming master
201 is pressed against this resin material 13 and an
ultraviolet ray or the like is radiated on the resin
material 13 to solidify. By. this means, as illustrated
5 in Fig. 21G, an optical information recording medium in
which a plurality of structures 11 is formed in the
reading surface is obtained.
[0156]
<9. Ninth Embodiment>
10 Figs. 22A to 22H are procedure diagrams for
explaining an example of a method of manufacturing the
optical information recording medium according to a ninth
embodiment of the present invention.
[0157]
15 First, as illustrated in Figs. 22A to 22D, a
substrate 1 in which an information signal layer 2 is
formed on concave-convex portions 12 is made similar to
the eighth embodiment. Next, as illustrated in Fig. 22E,
a reading surface forming master 201 is prepared. Next,
20 a resin material 13 such as an ultraviolet curable resin
is applied on a base 61a according to, for example, a
spin coat method. The shape of the base 61a is, for
\ example, a sheet shape. Next, as illustrated in Fig. 22F,
\ the reading surface forming master 201 is pressed against
25 this resin material 13 and an ultraviolet ray or the like
is radiated on the resin material 13 to solidify. By
j this means, as illustrated in Fig. 22G, an antireflection
layer 61b which has multiple structures 11 on one
principal surface of the base 61a is formed. Next, as
30 illustrated in Fig. 22H, a smooth surface of the base 61a
and a signal surface of the substrate 1 are laminated
-
64 I
SP262786WO00
across a laminating layer 14. By this means, an optical
information recording medium in which a plurality of
structures 11 is formed in the reading surface is
obtained.
5 [0158]
<10. Tenth Embodiment>
Fig. 23A is a schematic plan view illustrating an
example of a configuration of a reading surface of an
optical information recording medium according to a tenth
10 embodiment of the present invention. Fig. 23B is a plan
view enlarging part of the reading surface of the optical
information recording medium illustrated in Fig. 23A.
Fig. 23C is a cross sectional view in tracks Tl, T3
and ... in Fig. 23B. Fig. 23D is a cross sectional view
15 in tracks T2, T4 and ... in Fig. 23B. Fig. 23E is a
schematic diagram illustrating a modulated waveform of
laser light used to form latent images corresponding to
the tracks Tl, T3 and ... in Fig. 23B. Fig. 23F is a
schematic diagram illustrating a modulated waveform of
20 laser light used to form latent images corresponding to
tracks T2, T4 and ... in Fig. 23B.
[0159]
An optical information recording medium according
to the fourth embodiment differs from that of the first
'
I 25 embodiment in that each of the structures 11 forms a
square lattice pattern or a semi-square lattice pattern
between three neighboring arrays of tracks.
[0160]
An arrangement pitch PI of the structures 11 in the
\ 3 0 same track is preferably longer than an arrangement pitch
P2 of the structures 11 between two neighboring tracks.
'.
1
65
SP262786WO00
i J
When an arrangement pitch of the structures 11 in the
same track is PI and an arrangement pitch of the
structures 11 between two neighboring tracks is P2, P1/P2
preferably satisfies a relationship of 1.4 < P1/P2 < 1.5.
5 By setting this numerical value range, it is possible to
improve the packing rate of the structures 11 having the
elliptic conical shapes or elliptic truncated conical
shapes and, consequently, improve the antireflection
property. Further, the height or the depth of the
10 structures 11 in a 45 degree direction or an about 45
degree direction with respect to the tracks is preferably
smaller than the height or the depth of the structures 11
in a track extending direction.
[0161]
15 A height H2 of the structures 11 in an alignment
direction (9 direction) which is oblique with respect to
the track extending direction is preferably smaller than
a height HI of the structures 11 in the track extending
direction. That is, the heights HI and H2 of the
20 structures 11 preferably satisfy the relationship of HI >
H2.
[0162]
I When the structures 11 form the square lattice or
j semi-square lattice pattern, an ellipticity e of a
! 25 structure bottom surface is preferably 150% < e < 180%.
• This is because, by setting this range, it is possible to
i
improve the packing rate of the structures 11 and obtain
the good antireflection property.
[0163]
3 0 The packing rate of the structures 11 on the base
l surface has an upper limit of 100%, and is in a range of
i
i
66
SP262786WO00
65% or more, preferably 73% or more and more preferably
86% or more. By setting this range of the packing rate,
it is possible to improve the antireflection property.
[0164]
5 Meanwhile, the packing rate (average packing rate)
of the structures 11 is a value calculated as follows.
[0165]
First, an image of the surface of the optical
information recording medium is captured from a top view
10 using a scanning electron microscope (SEM). Next, a unit
cell Uc is selected at random from the captured SEM
picture to measure the arrangement pitch PI of the unit !
cell Uc and the track pitch Tp (see Fig. 23B) . Further,
an area S of the bottom surface of one of the four
15 structures 11 included in this unit cell Uc is measured
by image processing. Next, the packing rate is
calculated according to the following equation (2) using
the measured arrangement pitch PI, the track pitch Tp and
the bottom surface area S.
20 [0166]
Packing rate = (S(tetra)/S(unit)) x 100 ... (2)
Unit cell area: S(unit) = 2x((PlxTp)x(1/2)) = PlxTp
i Area of bottom surface of structure existing in
unit cell: S(tetra) = S
25 [0167]
The above processing of calculating the packing
rate is performed for ten unit cells selected at random
from the captured SEM picture. Further, by simply
averaging (taking an arithmetic average of) measurement
1
3 0 values, the average rate of the packing rates is
• calculated as the packing rate of the structures 11 on
-
.
67 I
SP262786WO00 I
the base surface.
[0168]
The ratio ((2 x 2r)/PI x 100) which is two times as
a diameter 2r to the arrangement pitch PI is 127% or more,
5 is preferably 137% or more and is more preferably 146% or
more. By setting this range, it is possible to improve
the packing rate of the structures 11 and improve the
antireflection property. Meanwhile, the arrangement
pitch PI is an arrangement pitch of the structures 11 in
10 the track direction, and the diameter 2r is the diameter
of a structure bottom surface in the track direction. In
addition, when the structure bottom surface is circular,
the diameter 2r is the diameter, and, when the structure
bottom surface is elliptic, the diameter 2r is the long
15 diameter.
[0169]
<11. Eleventh Embodiment>
[Configuration of Optical Information Recording Medium]
Fig. 24A is a schematic plan view illustrating an
2 0 example of a configuration of a reading surface of an
optical information recording medium according to an
eleventh embodiment of the present invention. Fig. 24B
is a plan view enlarging part of a reading surface of the
optical information recording medium illustrated in Fig.
: 25 24A. Fig. 24C is a cross sectional view in tracks Tl, T3
•
; and ... in Fig. 24B. Fig. 24D is a cross sectional view
in tracks T2, T4 and ... in Fig. 24B. Fig. 24E is a
schematic diagram illustrating a modulated waveform of
laser light used to form latent images corresponding to
30 the tracks Tl, T3 and ... in Fig. 24B. Fig. 24F is a
"'- schematic diagram illustrating a modulated waveform of
68
SP262786WO00
|
laser light used to form latent images corresponding to
tracks T2, T4 and ... in Fig. 24B.
[0170]
The optical information recording medium according
5 to the eleventh embodiment differs from that of the first
embodiment in linearly aligning structures 11 to form a
plurality of tracks.
[0171]
[Configuration of Reading Surface Forming Master]
10 Fig. 25A is a schematic perspective view
illustrating an example of a configuration of a molding
surface of a reading surface forming master for forming
above mentioned structures on a reading surface. Fig.
25B is a plan view enlarging part of the molding surface
15 of the reading surface forming master illustrated in Fig.
25A. The reading surface forming master 2 01 has a
configuration in which multiple structures 202 which are
concave portions are arranged on the surface of the
reading surface forming master. The reading surface
20 forming master 201 has a columnar or cylindrical shape.
Although, for example, glass can be used for a material
of the reading surface forming master 201, this material
is not limited in particular. By spatially linking two
dimensional patterns using a roll master exposure device
25 described below, synchronizing a polarity inversion
formatter signal and a rotation controller of a recording
device per one track, generating a signal and performing
patterning at an adequate feed pitch using CAV, it is
possible to record a hexagonal lattice pattern or a semi-
3 0 hexagonal lattice pattern. By adequately setting the
frequency of the polarity inversion formatter signal and
69
SP262786WO00
the number of rotations of roll, it is possible to form a
lattice pattern of a uniform spatial frequency in a
desired recording region.
[0172]
5 [Configuration of Exposure Device]
A configuration of the master exposure device used
for procedure of exposing a moth-eye pattern will be
described with reference to Fig. 26. This master
exposure device is formed based on an optical disk
10 recording device.
j [0173]
A laser light source 21 is a light source which
exposes a resist deposited on a surface of a master 201
as a recording medium, and oscillates recording laser
15 light 15 of, for example, a wavelength X = 266 nm. The
laser light 15 emitted from the laser light source 21
travels straightforward as a parallel beam, and is
incident on an electro optical modulator (EOM) 22. The
laser light 15 having transmitted through the electro
20 optical modulator 22 is reflected by a mirror 23, and is
guided to a modulating optical system 25.
[0174]
The mirror 23 is formed with a polarized beam
splitter, and has a function of reflecting one !
25 polarization component and allowing transmission of the
other polarization component. The polarization component
having transmitted through the mirror 23 is received by a
photodiode 24, and the electro optical modulator 22 is
controlled based on this received light signal to
30 modulate the phase of the laser light 15.
[0175]
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SP262786WO00
In the modulating optical system 25, the laser
light 15 is condensed on an acousto-optic modulator (AOM)
27 made of glass (Si02) or the like by a condenser lens
26. The intensity of the laser light 15 is modulated by
5 the acousto-optic modulator 27, and the laser light is
spread and converted into a parallel beam by a lens 28.
The laser light 15 emitted from the modulating optical
system 25 is reflected by a mirror 31, and is guided
horizontally and in parallel on a moving optical table 32.
10 [0176]
The moving optical table 32 has a beam expander 3 3
and an objective lens 34. The laser light 15 guided to
the moving optical table 32 is shaped into a desired beam
shape by the beam expander 33, and then is radiated on
15 the resist layer on the master 12 through the objective
lens 34. The master 12 is set on a turn table 36
connected to a spindle motor 35. Further, by rotating
the master 12, guiding the laser light 15 in a height
direction of the master 12 and intermittently radiating
2 0 the laser light 15 on the resist layer, procedure of
exposing the resist layer is performed. A formed latent
image has a virtually elliptic shape which has a long
axis in a circumferential direction. The laser light 15
is moved by moving the moving optical table 32 in an
25 arrow R direction.
[0177]
The exposure device has a control mechanism 3 7
which forms on the resist layer a latent image
corresponding to a two dimensional pattern of a hexagonal
3 0 lattice or a semi-hexagonal lattice. The control
mechanism 37 has a formatter 29 and a driver 30. The
71
SP262786WO00
formatter 2 9 has a polarity inverting unit, and this
polarity inverting unit controls a timing to radiate the
laser light 15 on the resist layer. The driver 3 0
receives an output from the polarity inverting unit, and
5 controls the acousto-optic modulator 27.
[0178]
This roll master exposure device generates a signal
by synchronizing a polarity inversion formatter signal
and the rotation controller of the recording device per
10 one track such that two dimensional patterns are
spatially linked, and the acousto-optic modulator 27
modulates the intensity. By performing patterning at a
constant angular velocity (CAV), at an adequate
modulation frequency, at an adequate feed pitch and with
15 the adequate number of rotations, it is possible to
record a hexagonal lattice or semi-hexagonal lattice
pattern. For example, the feed pitch only needs to be
i
| set to 251 nm to set a cycle in the circumferential
i
| direction to 315 nm and set the cycle in an about 60
I
! 20 degree direction (about -60 degree direction) with
| respect to the circumferential direction to 300 nm (the
Pythagorean theorem). The frequency of the polarity
inversion formatter signal is changed by the number of
rotations of roll (1800 rpm, 900 rpm and 450 rpm). The
25 semi-hexagonal lattice pattern in which the spatial
frequency (a circle 315 nm cycle, and a circumferential
direction about 60 degree direction (about -60 degree
direction) 300 nm cycle) in a desired recording region is
uniform is obtained by expanding far ultraviolet laser
30 light to a five-fold beam diameter by the beam expander
(BEX) 33 on the moving optical table 32, radiating the
*
72
SP262786WO00
laser light on the resist layer on the master 12 through
the objective lens 34 of a numerical aperture (NA) 0.9
and forming a fine latent image.
[0179]
5 [Method of Manufacturing Optical Information Recording
Medium]
An optical information recording medium employing
the above configuration is made, for example, as follows
using the reading surface forming master 201.
10 [0180]
First, a photosensitive resin such as an
ultraviolet curable resin is applied to a sheet. Next,
while the reading surface forming master 201 is rotated,
this molding surface is pressed against the
15 photosensitive resin applied to the sheet, and light such
as an ultraviolet ray is radiated on the photosensitive
resin from the sheet side to solidify the photosensitive
resin. Then, while rotation of the reading surface
forming master 201 is maintained, the molding surface is
20 peeled from the solidified photosensitive resin. By this
means, a plurality of linearly aligning structures 11 is
formed in one principal surface of the sheet. Next, this
sheet is annularly punched, and the punched annular sheet
is laminated on an information signal layer formed on the
25 substrate across the laminating layer made of an
ultraviolet curable resin, a pressure sensitive adhesive
or the like.
[0181]
According to the above procedure, a target optical
3 0 information recording medium is obtained.
[0182]
73
SP262786WO00
<12. Twelfth Embodiment>
Fig. 27A is a schematic plan view illustrating part
of a reading surface of an optical information recording I
medium according to a twelfth embodiment of the present I
5 invention. Fig. 27B is a plan view enlarging part of the 1
reading surface of the optical information recording
medium illustrated in Fig. 27A.
[0183]
The optical information recording medium according
10 to the twelfth embodiment differs from that of the first
embodiment in aligning structures 11 on wobbling tracks
(hereinafter referred to as "wobble tracks"). A wobble
of each track on the base 2 is preferably synchronized.
That is, the wobbles are synchronized wobbles. By
15 synchronizing the wobbles in this way, it is possible to
maintain a unit cell shape of a hexagonal lattice or a
semi-hexagonal lattice, and keep a high packing rate.
The wave shapes of the wobble tracks are, for example,
sine curves or triangular waves. The wave shapes of the
20 wobble tracks are not limited to cyclic wave shapes, and
may be non-cyclic wave shapes. A wobble amplitude of the
wobble track is, for example, selected to about ±10 \xm.
[0184]
This twelfth embodiment is the same as the first
25 embodiment except the above.
[0185]
In the twelfth embodiment, the structures 11 are
aligned on the wobble tracks, so that it is possible to
suppress unevenness of an outlook.
30 [0186]
<13. Thirteenth Embodiment>
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SP262786WO00
Fig. 28A is a schematic plan view illustrating an
example of a configuration of an optical information
recording medium according to a thirteenth embodiment of
the present invention. Fig. 28B is a plan view enlarging
5 part of the optical information recording medium
illustrated in Fig. 28A. Fig. 28C is a cross sectional
view in tracks Tl, T3 and ... in Fig. 28B. Fig. 28D is a
cross sectional view in tracks T2, T4 and ... in Fig. 28B.
Fig. 29 is a perspective view enlarging part of the
10 optical information recording medium illustrated in Fig.
28B.
[0187]
An optical information recording medium 1 according
to the thirteenth embodiment differs from the first
15 embodiment in aligning multiple structures 11 having
concave shapes on a base surface. The shapes of these
structures 11 are concave shapes obtained by inverting
convex shapes of the structures 11 in the first
embodiment. In addition, when the structures 11 are
20 concave portions as described above, an opening portion
(inlet portion of a concave portion) of the structures 11
which is a concave portion is defined as a lower portion,
and a lowermost portion of the substrate 1 in a depth
direction (a depthmost portion of a concave portion) is
25 defined as a top. That is, the structures 11 which are
nonentity space define the top and the lower portion.
I
Further, in the thirteenth embodiment, the structures 11
| are the concave portion, and a height H of the structures
11 in equation (1) is a depth H of the structures 11.
30 [0188]
This thirteenth embodiment is the same as the first
j
!
•'i
75
SP262786WO00
embodiment except the above.
[0189]
In this thirteenth embodiment, the shapes of the
structures 11 having the convex shapes in the first
5 embodiment are inverted to concave shapes, so that it is
possible to provide the same effect as that of the first
embodiment.
[0190]
[Examples]
10 Although the present invention will be specificallydescribed
below based on examples, the present invention
is not limited only to these examples.
[0191]
(Example 1)
15 First, a signal surface forming stamper (nickel
stamper) which records an information signal compliant
with the CD standard, and a reading surface forming
stamper in which the following subwavelength structures
are formed in a region (the radius of 2 0 mm to 59 mm)
2 0 corresponding to a signal region of this signal surface
forming stamper were prepared.
[0192]
Structure pitch (inter-structure center distance)
About 3 00 nm
25 Structure height: About 250 nm
Structure arrangement pattern: Semi-hexagonal
lattice arrangement
Structure shape: Elliptic truncated conical shape
[0193]
3 0 Next, the signal surface forming stamper was
attached to one mold of an injection molding device, the
76
SP262786WO00
reading surface forming stamper was attached to the other
mold and this injection molding device was used to
transfer the shapes of the stampers to a resin material.
By this means, a polycarbonate substrate (referred to as
5 a "PC substrate" below) which had a signal surface on
which a concave-convex pattern was formed and a reading
surface on which subwavelength structure patterns were
formed, and which had the thickness of 1.2 mm was
obtained.
10 [0194]
Next, according to the spattering method, an
aluminum film (reflection film) was formed on the signal
surface of this substrate. Next, by applying and
solidifying an ultraviolet curable resin on the aluminum
15 film according to the spin coat method, a protective film
was formed. By this means, an optical disk which had
desired subwavelength structures in a reading surface and
which was compliant with the CD standard was obtained.
[0195]
2 0 (Example 2)
First, the same signal surface forming stamper and
reading surface forming stamper as those in Example 1
were prepared. Next, the signal surface forming stamper
was attached to one mold of an injection molding device,
25 the other mold was formed as a mirror surface (flat
surface) without being attached a stamper and this
injection molding device was used to transfer the shape
of the stamper to a resin material. By this means, a
first PC substrate which had a signal surface on which a
3 0 concave-convex pattern was formed and a flat surface, and
which had a thickness of 0.6 mm was obtained. Next, the
77
SP262786WO00
I1 reading surface forming stamper was attached to one mold
of an injection molding device, the other mold was formed
as a mirror surface (flat surface) without being attached
a stamper and this injection molding device was used to
5 transfer the shape of the stamper to a resin material.
1
By this means, a second PC substrate which had a reading
surface on which subwavelength structure patterns were
formed and a flat surface, and which had a thickness of
0.6 mm was obtained.
10 [0196]
Next, by laminating the flat surfaces of the first
•
and second substrates by an ultraviolet curable resin, a
substrate which had a signal surface in which the
concave-convex pattern was formed in one principal
15 surface and a reading surface on which a plurality of
subwavelength structure patterns was formed on the other
principal surface was made. Next, according to the
spattering method, an aluminum film (reflection film) was
formed on the signal surface of this substrate. Next, by
20 applying and solidifying an ultraviolet curable resin on
the aluminum film according to the spin coat method, a
protective film was formed. By this means, an optical
disk which had desired subwavelength structures in a
reading surface and which was compliant with the CD
25 standard was obtained.
[0197]
(Example 3)
First, a signal surface forming stamper (nickel
\ stamper) which recorded an information signal compliant
3 0 with the DVD-SL (DVD-Single Layer) standard, and a
I reading surface forming stamper in which the same
; ' 78
SP262786WO00
subwavelength structures as those in Example 1 were
formed in a region (the radius of 2 0 mm to 59 mm)
corresponding to a signal region of this signal surface
forming stamper were prepared.
5 [0198]
Next, the signal surface forming stamper was
attached to one mold of an injection molding device, the
reading surface forming stamper was attached to the other
mold and this injection molding device was used to
10 transfer the shapes of the stampers to a resin material.
By this means, a second PC substrate which had a signal
surface on which a concave-convex pattern was formed and
a reading surface on which subwavelength structure
patterns were formed, and which had a thickness of 0.6 mm
15 was obtained. Next, according to the spattering method,
an aluminum film (reflection film) was formed on the
signal surface of this second substrate.
[0199]
Next, a stamper in which a signal region of the
20 DVD-SL signal surface forming stamper was a flat surface
(mirror) was prepared. Next, this stamper was attached
to one mold of an injection molding device, the other |
mold was formed as a mirror surface (flat surface)
without being attached a stamper and this injection
25 molding device was used to transfer the shape of the
stamper to a resin material. By this means, a first PC
substrate both surfaces of which were flat surfaces was
obtained.
[0200]
3 0 Next, the signal surface of the first substrate and
the flat surface of the second substrate were laminated
79
SP262786WO00
by an ultraviolet curable resin. By this means, an
optical disk which had desired subwavelength structures
; in a reading surface and which was compliant with the
DVD-SL standard was obtained.
5 [0201]
(Example 4)
First, a L0 layer signal surface forming stamper
•
(nickel stamper) which recorded an information signal
compliant with a L0 layer standard of DVD-DL (DVD-Dual
10 Layer), and a reading surface forming stamper in which
the same subwavelength structures as those in Example 1
were formed in a region (the radius of 2 0 mm to 59 mm)
corresponding to a signal region of this signal surface
forming stamper were prepared.
15 [0202]
• Next, the L0 layer signal surface forming stamper
was attached to one mold of an injection molding device,
the reading surface forming stamper was attached to the
other mold and this injection molding device was used to
20 transfer the shapes of the stampers to a resin material.
By this means, a second PC substrate which had a signal
surface on which a concave-convex pattern was formed and
: a reading surface on which subwavelength structure
patterns were formed, and which had a thickness of 0.6 mm
25 was obtained. Next, according to the spattering method,
a silicon film or a silver alloy film (semi-transmission
reflection film) was formed on the signal surface of this
second PC substrate.
[0203]
3 0 Next, a LI layer signal surface forming stamper
(nickel stamper) which recorded an information signal
i
I
80
SP262786WO00
compliant with the LI layer standard of DVD-DL was
prepared. Next, the LI layer signal surface forming
stamper was attached to one mold of an injection molding
] device, the other mold was formed as a mirror surface
j 5 (flat surface) without being attached a stamper and this
injection molding device was used to transfer the shape
of the stamper to a resin material. By this means, a
first PC substrate which had a signal surface on which a
concave-convex pattern was formed and a flat surface, and
10 which had a thickness of 0.6 mm was obtained. Next,
according to the spattering method, an aluminum film or a
silver alloy film (total reflection film) was formed on
the signal surface of this first PC substrate.
[0204]
15 Next, the signal surfaces of the first substrate
and the second substrate were laminated by an ultraviolet
curable resin. By this means, an optical disk which had
desired subwavelength structures in a reading surface and
which was compliant with the DVD-DL standard was obtained.
20 [0205]
(Example 5)
First, a signal surface forming stamper (nickel
stamper) which recorded an information signal compliant
with the SACD-HD (SACD-Hybrid) standard, and a reading
25 surface forming stamper in which the same subwavelength
structures as those in Example 1 were formed in a region
(the radius of 20 mm to 59 mm) corresponding to a signal
region of this signal surface forming stamper were
prepared.
30 [0206]
Next, the SACD layer signal surface forming stamper
i
81
SP262786WO00
, was attached to one mold of an injection molding device,
the other mold was formed as a mirror surface (flat
surface) without being attached a stamper and this
injection molding device was used to transfer the shape
5 of the stamper to a resin material. By this means, a
first PC substrate which had a signal surface on which a
concave-convex pattern was formed and a flat surface, and
which had a thickness of 0.6 mm was obtained. Next,
according to the spattering method, a silicon film or a
10 silver alloy film (semi-transmission reflection film) was
formed on the signal surface of this first PC substrate.
[0207]
Next, a CD layer signal surface forming stamper
(nickel stamper) which recorded an information signal
15 compliant with the CD layer standard of SACD-HD was
prepared. Next, the CD layer signal surface forming
stamper was attached to one mold of an injection molding
device, the other mold was formed as a mirror surface
(flat surface) without being attached a stamper and this
20 injection molding device was used to transfer the shape
of the stamper to a resin material. By this means, a
second PC substrate which had a signal surface on which a
concave-convex pattern was formed and a flat surface, and
which had a thickness of 0.6 mm was obtained. Next,
25 according to the spattering method, an aluminum film or a
silver alloy film (total reflection film) was formed on
the signal surface of this second PC substrate. Next, by
applying and solidifying an ultraviolet curable resin on
the aluminum film according to the spin coat method, a
30 protective film was formed.
[0208] ;
t
i
's
1
i
t-
(
f
82
SP262786WO00
Next, the signal surface of the first PC substrate
I and the flat surface of the second PC substrate were
laminated by an ultraviolet curable resin. By this means,
an optical disk which had desired subwavelength
5 structures in a reading surface and which was compliant
with the SACD-HD standard was obtained.
[0209]
(Example 6)
Next, a L0 layer signal surface forming stamper
10 (nickel stamper) which recorded an information signal
compliant with the L0 layer standard of DVD-DL (DVD-Dual
Layer) was prepared. Next, the L0 layer signal surface
forming stamper was attached to one mold of an injection
molding device, the other mold was formed as a mirror
15 surface (flat surface) without being attached a stamper
and this injection molding device was used to transfer
the shape of the stamper to a resin material. By this
means, a second PC substrate which had a signal surface
on which a concave-convex pattern was formed and a flat
20 surface, and which had a thickness of 0.6 mm was obtained.
[0210]
Next, a reading surface forming stamper in which
the same subwavelength structures as those in Example 1
were formed was prepared. Next, according to the spin
25 coat method, an ultraviolet curable resin corresponding
to the thickness of at least the heights of the
subwavelength structures or more was applied to the flat
surface of the second PC substrate. Next, the reading
surface forming stamper was pressed against this
30 ultraviolet curable resin, the ultraviolet curable resin
was radiated by an ultraviolet ray from the signal
83
SP262786WO00
surface side of the second substrate and was solidified,
; and the stamper was peeled off. By this means, a
plurality of subwavelength structures was formed on the
reading surface side of the second substrate. In
5 subsequent procedure, similar to above Example 4, an
optical disk which had desired subwavelength structures
in a reading surface and which was compliant with the
DVD-DL standard was obtained.
[0211]
10 (Example 7)
First, an optical disk compliant with the DVD-DL
standard was prepared. Next, a reading surface forming
quartz stamper (thickness 0.7 to 1.2 mm) in which the
same subwavelength structures as those in Example 1 ware
15 formed was prepared. Next, according to the spin coat
method, an ultraviolet curable resin corresponding to the
thickness of at least the heights of the subwavelength
structures or more (400 nm or more) was applied to the
reading surface of the optical disk. Next, the reading
2 0 surface forming stamper was pressed against this
ultraviolet curable resin, the ultraviolet curable resin
was radiated with an ultraviolet ray from a back surface
of the quartz stamper and was solidified, and a plurality
of subwavelength structures was formed in the reading
25 surface of the optical disk. By this means, an optical
disk which had desired subwavelength structures in a
reading surface and which was compliant with the DVD-DL
standard was obtained. |
I
[0212] j
3 0 In addition, although a case that the quartz
stamper is used has been described as an example in this
t
I
84
SP262786WO00
Example 7, a transparent substrate made by way of molding
transfer using a nickel stamper may also be used instead
of a quartz stamper. Further, a subwavelength structure
forming method used in this Example 7 is not limited to
5 DVD-DL, and is applicable to optical disks of various
standards such as a CD and a BD.
[0213]
(Example 8)
\ First, an optical disk compliant with the DVD-DL
10 standard was prepared. Next, a reading surface forming
quartz stamper (thickness 0.7 to 1.2 mm) in which the
same subwavelength structures as those in Example 1 were
formed was prepared. Next, an ultraviolet curable resin
corresponding to the thickness of the heights of the
• 15 subwavelength structures or more (400 nm or more) was
applied to a film base of about 0.1 mm made of
polycarbonate, PMMA or PET. Next, the quartz stamper was
pressed against the ultraviolet curable resin, the
ultraviolet curable resin was radiated with an
2 0 ultraviolet ray from the back surface side of the quartz
stamper and solidified and then the quartz stamper was
peeled off from the film base. By this means, the film
base which had desired subwavelength structures in the
surface and had a thickness of about 0.1 mm was obtained.
25 [0214]
Next, an optical disk in which the thickness of a
second substrate was 0.5 mm and was compliant with the
DVD-DL standard was prepared. Next, the film base was
laminated to the reading surface of this second substrate
3 0 across an adhesive. By this means, an optical disk which
had desired subwavelength structures in a reading surface
85
SP262786WO00
and which was compliant with the DVD-DL standard was
obtained.
[0215]
1 A subwavelength structure forming method used in
5 this Example 8 is not limited to DVD-DL, and is
applicable to optical disks of various standards such as
<
a CD and a BD.
[0216]
Next, sizes and shapes of surface antireflection
10 moth-eye patterns of optical disks compliant with BD, DVD
and CD standards were studied using a RCWA simulation
method.
[0217]
The following two conditions were preconditions
15 upon this study.
(1) A setting can be made under current molding
conditions or can be changed under conditions which are
simple to such a degree that manufacturing is not
significantly influenced.
20 (2) A current signal pattern exposure device can
simply form a pattern.
[0218]
Hence, a pattern height was 200 nm or less
regarding a pit height 150 nm of a CD of the highest
25 pattern height as a target value, a pattern pitch was 200
nm or more based on resolving power and a ratio (aspect
ratio) of the height to the pattern pitch was 1 or less
from a view point of easiness of molding, and a circular
truncated conical shape which had an adequate inclination
30 was a target.
[0219]
86
SP262786WO00
• . . ..
Further, the reflectivity which is an indicator of
the antireflection effect was 0.2% or less as a level at
which an effect worked with respect to n = about 1.5 with
a substrate such as polycarbonate, acryl or glass in mind,
5 and 0.1% or less as a target of a desirable level.
[0220]
(Test Example 1)
The reflectivity in case that a plurality of
structures employing the following configurations was
10 formed in a reading surface of an optical disk compliant
with the BD standard was calculated using the RCWA
simulation method. The result is illustrated in Fig. 30.
[0221]
Pattern pitch: 300 nm
15 Pattern height: 120 nm
Flat portion diameter of pattern upper portion: 90
nm
\ Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape
20 [0222]
In the present example, the flat portion diameter
means the diameter of the flat portion.
[0223]
The above simulation result shows that the
25 reflectivity with respect to 405 nm of a BD reading
pickup wavelength is almost 0%. Further, when the
reflectivity was checked at 4 5 degrees of an incident
angle taking 0.85 of a pickup lens NA value into account,
the reflectivity was about 0.5% and provided an
30 antireflection effect although the reflectivity
deteriorated compared to vertical incidence.
87
SP262786WO00
[0224]
(Test Example 2)
* The reflectivity in case that a plurality of
!
structures employing the following configurations was
5 formed in a reading surface of an optical disk compliant
with the DVD standard was calculated using the RCWA
I
simulation method. The result is illustrated in Fig. 30.
[0225]
Pattern pitch: 300 nm,
10 Pattern height: 180 nm,
Flat portion diameter of pattern upper portion: 150
nm
Pattern alignment: Hexagonal lattice pattern
! Pattern shape: Circular truncated conical shape
15 [0226]
The above simulation result shows that the
reflectivity with respect to 650 nm of a DVD reading
pickup wavelength is almost 0%.
[0227]
2 0 (Test Example 3)
The reflectivity in case that a plurality of
structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the CD standard was calculated using the RCWA
25 simulation method. The result is illustrated in Fig. 30.
[0228]
Pattern pitch: 300 nm |
i
Pattern height: 215 nm
Flat portion diameter of pattern upper portion: 150
3 0 nm
Pattern alignment: Hexagonal lattice pattern
88
SP262786WO00
Pattern shape: Circular truncated conical shape
[0229]
\ The above simulation result shows that the
reflectivity with respect to 780 nm of a CD reading
5 pickup wavelength is almost 0%.
[0230]
(Test Example 4)
The reflectivity in case that a plurality of
structures employing the following configurations was
10 formed in a reading surface of an optical disk compliant
with the BD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
31A to 31C.
[0231]
15 Pattern pitch: Change in range of 120 to 450 nm
Pattern height: 120 nm
Flat portion diameter of pattern upper portion: 0.3
folds (circular truncated conical shape) of setting pitch
and 0 (conical shape)
20 Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape,
conical shape
[0232]
Fig. 31A illustrates a graph in case that the flat
25 portion diameter of a pattern upper portion is 0.3 folds
(circular truncated conical shape) of a pitch. Fig. 31B
illustrates a graph in case that the flat portion
diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 31C illustrates a graph in case
30 that the reflectivity at 405 nm of an OP (Optical Pickup)
i
wavelength is associated with a pattern pitch. I
5
'(•
89
SP262786WO00
j [0233]
i
As is clear from Fig. 31C, in case of 405 nm of the
target OP wavelength, under the setting conditions, the
reflectivity is lower when the flat portion diameter of
i 5 the pattern upper portion is 0.3 folds (elliptic conical
j shape) of a pitch than when the flat portion diameter is
0 fold (conical shape) of a pitch. However, even when
the flat portion diameter of the pattern upper portion is
0 fold of the pitch, the reflectivity is 1% or less in
10 the range of 120 to 450 nm of the pitch, so that it is
possible to provide an antireflection effect.
[0234]
Further, as are clear from Figs. 31A and 31B, in
j both cases, when the pitch is 450 nm, a rapid rise in the
15 reflectivity occurs near about 390 nm of the wavelength
or less. This is a value obtained by multiplying 450 nm
of the pitch with V3/2 and corresponds to a dimension
value which is the nearest effective diffraction grating
interval in case of the hexagonal lattice arrangement.
2 0 This is a value of a height of a triangle in case that a
pattern is arranged at each top of a regular triangle
(the length of one side is a pitch dimension).
[0235]
In addition, in case of a square lattice
25 arrangement, the pitch dimension itself is the nearest
effective diffraction grating interval and is 450 nm.
[0236]
Although a pattern density of a hexagonal lattice
arrangement is higher and more advantageous than that of
3 0 the square lattice and therefore the hexagonal lattice
will be mainly described, in case of 450 nm of the pitch,
90
SP262786WO00
i
the reflectivity rises due to an influence of diffraction
: when the wavelength is 3 90 nm or less, and therefore it
shows that the antireflection effect cannot be obtained.
[0237]
5 According to this, when the OP wavelength of a BD
is 405 nm, the pitch dimension which causes an influence
•
of a rise in the reflectivity resulting from this
diffraction grating is 468 nm obtained by dividing 405 nm
by V3/2, and, when the pitch dimension is about 470 nm or
10 less, the antireflection effect can be obtained at 405 nm
of the OP wavelength.
[0238]
Thus, in case of the optical disk compliant with
the BD standard, the pattern pitch is preferably set to a
15 range equal to or less than about 4 70 nm to obtain the
antireflection effect.
[0239]
(Test Example 5)
The reflectivity in case that a plurality of
20 structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the BD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
32A to 32C.
25 [0240]
Pattern pitch: 300 nm
Pattern height: Change in range of 40 to 200 nm
Flat portion diameter of pattern upper portion: 0.3
folds (circular truncated conical shape) of setting pitch
3 0 and 0 (conical shape)
Pattern alignment: Hexagonal lattice pattern
•
i
91
SP262786WO00
Pattern shape-. Circular truncated conical shape,
conical shape
[0241]
; Fig. 32A illustrates a graph in case that the flat
5 portion diameter of a pattern upper portion is 0.3 folds
\ (circular truncated conical shape) of a pitch. Fig. 32B
illustrates a graph in case that the flat portion
•
diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 32C illustrates a graph in case
\ 10 that the reflectivity at 405 nm of an OP wavelength is
associated with a pattern height.
[0242]
As is clear from Fig. 32C, in case of 405 nm of the
target OP wavelength, when the height is 150 nm or less,
15 the reflectivity is lower when the flat portion diameter
of the pattern upper portion is 0.3 folds (elliptic
conical shape) of a pitch than when the flat portion
diameter is 0 fold (conical shape) of a pitch. However,
even when the flat portion diameter of the pattern upper
20 portion is 0 fold of the pitch, the reflectivity is 2% or
less in the range of 80 to 2 00 nm of the height, so that
it is possible to provide an antireflection effect.
[0243]
Further, when the flat portion diameter of the
25 pattern upper portion is 0 fold (conical shape) of the
pitch, as the height becomes higher, the reflectivity
becomes lower and the effect becomes higher, and the
height equal to or more than 16 0 nm is required to obtain
the reflectivity close to 0%. With a broad view, in a
30 range of 80 to 200 nm of the height, the antireflection
effect can be obtained.
SP262786WO00
[0244]
Although a lower height matches the object of the
present invention, the antireflection effect is more
advantageous when the height is higher, and therefore two
5 folds of about 100 nm of the BD pit height is a target of
an upper limit value.
[0245]
(Test Example 6)
The reflectivity in case that a plurality of
10 structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the BD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
33A and 33B.
15 [0246]
Pattern pitch: 300 nm
Pattern height: 120 nm
Flat portion diameter of turn upper portion
Change from 0 to 0.7 folds of pitch
20 Pattern alignment: Hexagonal lattice pattern
j
Pattern shape: Circular truncated conical shape,
conical shape
[0247]
Fig. 33A illustrates a graph in case that the flat
25 portion diameter of a pattern upper portion is changed
from 0 to 0.7 folds of a pitch. Fig. 33B illustrates a
graph in case that the reflectivity at 405 nm of an OP
wavelength is associated with a flat portion diameter of
the pattern upper portion.
30 [0248]
As is clear from Fig. 3 3B, when the target OP
93
SP262786WO00
i wavelength is 405 nm, if the flat portion diameter of the
pattern upper portion is close to 0.3 folds (90 nm) of
the pitch, and the reflectivity becomes the lowest. In
addition, when the flat portion diameter of the pattern
5 upper portion is 0 fold of the pitch which is the
narrowest, the reflectivity is about 0.5% and, when the
flat portion diameter of the pattern upper portion is 0.7
folds (210 nm) of the pitch which is the widest, the
reflectivity is about 1.2%, so that it is possible to
10 obtain an antireflection effect in this range.
[0249]
(Test Example 7)
The reflectivity in case that a plurality of
structures employing the following configurations was
15 formed in a reading surface of an optical disk compliant
with the DVD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
34A to 34C.
[0250]
20 Pattern pitch: Change in range of 120 to 750 nm
Pattern height: 180 nm
Flat portion diameter of pattern upper portion: 0.5
folds (circular truncated conical shape) of setting pitch
and 0 (conical shape)
25 Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape,
conical shape
[0251] ;
Fig. 34A illustrates a graph in case that the flat
3 0 portion diameter of a pattern upper portion is 0.5 folds
(circular truncated conical shape) of a pitch. Fig. 34B
~
*
94
SP262786WO00
illustrates a graph in case that the flat portion
diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 34C illustrates a graph in case
that the reflectivity at 650 nm of an OP wavelength is
5 associated with a pattern pitch.
[0252]
As is clear from Fig. 34C, in case of 650 nm of the
target OP wavelength, under the setting conditions, the
reflectivity is lower when the flat portion diameter of
10 the pattern upper portion is 0.5 folds (elliptic conical
shape) of a pitch than when the flat portion diameter is
0 fold (conical shape) of a pitch. When the flat portion
diameter of the upper portion is 0.5 folds of the pitch,
the reflectivity is almost 0% in the range of 150 to 450
15 nm of the pitch dimension. However, even when the flat
portion diameter of the pattern upper portion is 0 fold
of the pitch, the reflectivity is 2% or less in the range
of 120 to 750 nm of the pitch, so that it is possible to
provide an antireflection effect.
20 [0253]
Further, similar to the optical disk compliant with
the BD standard, as are clear from Figs. 34A and 34B,
when the pitch is increased in both cases, there is a
region in which the reflectivity rapidly changes due to
25 an influence of diffraction.
[0254]
When the pitch is 750 nm in the hexagonal lattice
arrangement, about 650 nm which is a value obtained by
multiplying 750 nm with V3/2 corresponds to a dimension
30 value which is the nearest effective diffraction grating
interval, and then a rapid rise in the reflectivity is
i
95
SP262786WO00
observed in a wavelength region having this dimension or
less.
[0255]
Meanwhile, 650 nm is the OP wavelength of a DVD as-
5 is and, in case of the DVD, it is possible to obtain the
antireflection effect at 750 nm or less of the pitch
dimension. In addition, in case of a square lattice
arrangement, the pitch dimension is the nearest
diffraction grating interval, so that, when the pitch
10 dimension is 650 nm or less, it is possible to obtain the
antireflection effect.
[0256]
Thus, in case of the optical disk compliant with
the DVD standard, the pattern pitch is preferably set to
15 a range equal to or less than about 750 nm to obtain the
antireflection effect.
[0257]
(Test Example 8)
The reflectivity in case that a plurality of
20 structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the DVD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
35A to 35C.
25 [0258]
Pattern pitch: 300 nm
Pattern height: Change in range of 80 to 260 nm
Flat portion diameter of pattern upper portion: 0.5
folds (circular truncated conical shape) of setting pitch !
3 0 and 0 (conical shape) I
Pattern alignment: Hexagonal lattice pattern 1
i
I
96
SP262786WO00
Pattern shape: Circular truncated conical shape,
conical shape
[0259]
Fig. 3 5A illustrates a graph in case that the flat
5 portion diameter of a pattern upper portion is 0.5 folds
(circular truncated conical shape) of a pitch. Fig. 3 5B
illustrates a graph in case that the flat portion
diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 35C illustrates a graph in case
10 that the reflectivity at 650 nm of an OP wavelength is
associated with a pattern height.
[0260]
As is clear from Fig. 35C, in case of 650 nm of the
target OP wavelength, the reflectivity is lower when the j
I
15 flat portion diameter of the pattern upper portion is 0.5 j
folds (elliptic conical shape) of a pitch in the region
having 8 0 to 23 0 nm of the height than when the flat
portion diameter is 0 fold (conical shape) of a pitch.
When the flat portion diameter of the pattern upper
20 portion is 0.5 folds of the pitch, the reflectivity is 2%
or less when the height is 80 nm or more, the
reflectivity is 1% or less when the height is 110 nm or
less and the reflectivity is almost 0% when the height is
around between 160 and 2 00 nm.
25 [0261]
Further, when the flat portion diameter of the
pattern upper portion is 0 fold (conical shape) of the
pitch, as the height becomes higher, the reflectivity
becomes lower and the antireflection effect becomes
3 0 higher, and the height equal to or more than 260 nm is
required to obtain the reflectivity close to 0%.
j
: ' 97
SP262786WO00
i [0262]
With a broad view, in a range of 80 to 2 60 nm of
the height, the antireflection effect can be obtained.
"; [0263]
' 5 Although a lower height matches the object of the
i
present invention, the antireflection effect is more
advantageous when the height is higher, and therefore two
folds of about 13 0 nm of the DVD pit height is a target
of an upper limit value.
10 [0264]
(Test Example 9)
The reflectivity in case that a plurality of
; structures employing the following configurations was
formed in a reading surface of an optical disk compliant
15 with the DVD standard was calculated using the RCWA
simulation method. The results are illustrated in Figs.
36A to 36C.
[0265]
Pattern pitch: 3 00 nm I
20 Pattern height: 180 nm
Flat portion diameter of pattern upper portion:
Change from 0 to 0.7 folds of pitch
Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape,
25 conical shape
[0266]
Fig. 36A illustrates a graph in case that the flat
portion diameter of a pattern upper portion is changed
from 0 to 0.7 folds of a pitch. Fig. 36B illustrates a j
30 graph in case that the reflectivity at 650 nm of an OP j
wavelength is associated with a flat portion diameter of !
98
SP262786WO00
the pattern upper portion.
[0267] |
As is clear from Fig. 3 6B, when the target OP
wavelength is 650 nm, if the flat portion diameter of the
5 pattern upper portion is close to 0.5 folds (150 nm) of
the pitch, and the reflectivity becomes the lowest. In
addition, when the flat portion diameter of the pattern
upper portion is 0 fold of the pitch which is the
narrowest, the reflectivity is about 1.1% and, when the
10 flat portion diameter of the pattern upper portion is 0.7
folds (210 nm) of the pitch which is the widest, the
reflectivity is about 0.5%, so that it is possible to
obtain an antireflection effect in this range.
[0268]
15 (Test Example 10)
The reflectivity in case that a plurality of
structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the CD standard was calculated using the RCWA
2 0 simulation method. The results are illustrated in Figs.
37A to 37C.
[0269]
Pattern pitch: Change in range of 120 to 900 nm
Pattern height: 215 nm
i
25 Flat portion diameter of pattern upper portion: 0.5 |
folds (circular truncated conical shape) of setting pitch
and 0 (conical shape)
Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape,
30 conical shape
[0270]
I
f
J
99
SP262786WO00
!
Fig. 3 7A illustrates a graph in case that the flat
portion diameter of a pattern upper portion is 0.5 folds
(circular truncated conical shape) of a pitch. Fig. 37
illustrates a graph in case that the flat portion
5 diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 37C illustrates a graph in case
that the reflectivity at 78 0 nm of an OP wavelength is
associated with a pattern pitch.
I [0271]
10 As is clear from Fig. 37C, in case of 780 nm of the
target OP wavelength, under the setting conditions, the
reflectivity is lower when the flat portion diameter of
the pattern upper portion is 0.5 folds (circular
truncated conical shape) of a pitch than when the flat
15 portion diameter is 0 fold (conical shape) of a pitch.
When the flat portion diameter of the upper portion is
0.5 folds of the pitch, the reflectivity is almost 0% in
the range of 200 to 550 nm of the pitch dimension.
[0272]
20 Even when the flat portion diameter of the pattern
upper portion is 0 fold of the pitch, the reflectivity is
j
2% or less in the range of 150 to 900 nm of the pitch, so
that it is possible to provide an antireflection effect.
[0273]
25 Further, similar to the above mentioned optical
disks compliant with the BD and DVD standards, as are
clear from Figs. 3 7A and 3 7B, when the pitch is increased
in both cases, there is a region in which the
reflectivity rapidly changes due to an influence of j
3 0 diffraction.
[0274]
f
r
•
1
I
100
SP262786WO00
When the pitch is 900 nm in the hexagonal lattice
arrangement, about 780 nm which is a value obtained bymultiplying
900 nm with V3/2 corresponds to a dimension
value which is the nearest effective diffraction grating
5 interval, and then a rapid rise in the reflectivity is
observed in a wavelength region having this dimension or
less.
[0275]
Meanwhile, 780 nm is the OP wavelength of a CD and,
10 in case of the CD, it is possible to obtain the
antireflection effect at 900 nm or less of the pitch
dimension. In addition, in case of a square lattice
I arrangement, the pitch dimension is the nearest
diffraction grating interval, so that, in a region in
15 which the pitch is 780 nm or less, it is possible to
obtain the antireflection effect.
[0276]
Thus, in case of the optical disk compliant with
the CD standard, the pattern pitch is preferably set to a
20 range equal to or less than about 900 nm to obtain the
antireflection effect.
[0277]
(Test Example 11) j
The reflectivity in case that a plurality of
25 structures employing the following configurations was j
formed in a reading surface of an optical disk compliant j
with the CD standard was calculated using the RCWA j
simulation method. The results are illustrated in Figs.
38A to 38C. 30 [0278]
Pattern pitch: 300 nm
' 101
SP262786WO00
Pattern height: Change in range of 100 to 350 nm
•
Flat portion diameter of pattern upper portion: 0.5
folds (circular truncated conical shape) of setting pitch
I and 0 (conical shape)
5 Pattern alignment: Hexagonal lattice pattern
• Pattern shape: Circular truncated conical shape,
conical shape
[0279]
Fig. 38A illustrates a graph in case that the flat
10 portion diameter of a pattern upper portion is 0.5 folds
(circular truncated conical shape) of a pitch. Fig. 38B
illustrates a graph in case that the flat portion
diameter of a pattern upper portion is 0 fold (conical
shape) of a pitch. Fig. 38C illustrates a graph in case
15 that the reflectivity at 78 0 nm of an OP wavelength is
associated with a pattern height.
[0280]
As is clear from Fig. 38C, in case of 780 nm of the
target OP wavelength, the reflectivity is lower when the
20 flat portion diameter of the pattern upper portion in the
region of 100 to 280 nm of the height is 0.5 folds
(circular truncated conical shape) of a pitch than when
the flat portion diameter is 0 fold (conical shape) of a
pitch. When the flat portion diameter of the pattern
25 upper portion is 0.5 folds of a pitch, the reflectivity
is 2% or less when the height is 100 nm or more, the
reflectivity is 1% or less when the height is 130 nm or
more and the reflectivity is almost 0% when the height is
around between 20 0 and 22 0 nm. !
30 [0281] |
Further, when the flat portion diameter of the
••
',
102
SP262786WO00
pattern upper portion is 0 fold (conical shape) of the
pitch, as the height pattern becomes higher, the
reflectivity becomes lower and the antireflection effect
becomes higher, but the height equal to or more than 350
5 nm is required to obtain the reflectivity close to 0%.
With a broad view, in a range of 100 to 300 nm of the
height, the antireflection effect can be obtained.
[0282]
Although a lower height matches the object of the
10 present invention, the antireflection effect is more
advantageous when the height is higher, and therefore two
folds of about 150 nm of the CD pit height is a target of
an upper limit value.
| [0283]
' 15 (Test Example 12)
The reflectivity in case that a plurality of
structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the CD standard was calculated using the RCWA
20 simulation method. The results are illustrated in Figs.
3 9A and 3 9B.
i
[0284] |
Pattern pitch: 3 00 nm
Pattern height: 215 nm j
25 Flat portion diameter of pattern upper portion: j
Change from 0 to 0.8 folds of pitch j
Pattern alignment: Hexagonal lattice pattern j
Pattern shape: Circular truncated conical shape,
conical shape
30 [0285]
Fig. 3 9A illustrates a graph in case that the flat
r
4
: 103
SP262786WO00
portion diameter of a pattern upper portion is changed
from 0 to 0.8 folds of a pitch. Fig. 39B illustrates a
graph in case that the reflectivity at 780 nm of an OP
\ wavelength is associated with a flat portion diameter of
5 the pattern upper portion.
[0286]
As is clear from Fig. 3 9B, when the target OP
wavelength is 780 nm, if the flat portion diameter of the
pattern upper portion is close to 0.5 folds (150 nm) of
10 the pitch, and the reflectivity becomes the lowest. In
addition, when the flat portion diameter of the pattern
upper portion is 0 fold of the pitch which is the
narrowest, the reflectivity is about 1.2% and, when the
flat portion diameter of the pattern upper portion is 0.8
15 folds (240 nm) of the pitch which is the widest, the
reflectivity is about 1.2%, so that it is possible to
obtain an antireflection effect in this range.
[0287]
(Test Example 13)
20 The reflectivity in case that a plurality of
structures employing the following configurations was
formed in a reading surface of an optical disk compliant
with the BD standard was calculated using the RCWA
simulation method. The result is illustrated in Fig. 40A.
25 [0288]
Pattern pitch: 240 nm
Pattern height: Change in range of 80 to 200 nm i
Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape
30 [0289] (Test Example 14) •
;
* •
104
SP262786WO00
• The reflectivity in case that a plurality of
structures employing the following configurations was
J
formed in a reading surface of an optical disk compliant
with the DVD standard was calculated using the RCWA
5 simulation method. The result is illustrated in Fig. 40B.
[0290]
Pattern pitch: 3 00 nm
Pattern height: Change in range of 100 to 260 nm
Pattern alignment: Hexagonal lattice pattern
10 Pattern shape: Circular truncated conical shape
[0291]
(Test Example 15)
The reflectivity in case that a plurality of
structures employing the following configurations was
15 formed in a reading surface of an optical disk compliant
with the CD standard was calculated using the RCWA
simulation method. The result is illustrated in Fig. 40C.
[0292]
Pattern pitch: 300 nm
20 Pattern height: Change in range of 120 to 350 nm
Pattern alignment: Hexagonal lattice pattern
Pattern shape: Circular truncated conical shape
[0293]
In Figs. 40A to 40C, the horizontal axis indicates
25 the ratio (OP wavelength/height) of an OP wavelength (BD
4 05 nm, DVD 650 nm and CD 78 0 nm) to a structure height.
Further, the vertical axis indicates a ratio (flat
portion diameter of upper portion/pitch) which is the
lowest reflectivity at each structure height, and the
30 lowest reflectivity (%) . In addition, in an optical disk !
compliant with the BD standard, although, when a pattern
105
SP262786WO00
pitch is 300 nm like the optical disks compliant with the
CD standard and the DVD standard, the influence is a
little, the pattern pitch is influenced partially by
interference. Therefore, the pattern pitch is set to 240
5 nm at which no influence is caused.
I [0294]
The following is clear from Figs. 4 0A to 4 0C.
[0295]
In case of any optical disk of the BD, DVD and CD
10 standard, when the ratio (OP wavelength/height)
(horizontal axis) is near about 3.5, a minimum
reflectivity which is almost 0% is obtained. Even when
the ratio is higher than the above value (that is, even
when the structure height is lower) or even when the
15 ratio is lower (that is, even when the structure height
is higher), the reflectivity tends to become high.
[0296]
To obtain the minimum reflectivity at which the
reflectivity is almost 0%, the ratio (OP
20 wavelength/height) is set to about 3.5, and, in case of
an optical disk compliant with the BD standard, the ratio
(flat portion diameter of upper portion/pitch) is
preferably set to 0.3 to 0.4 and, in case of an optical
disk compliant with the DVD or CD standard, the ratio is
25 preferably set to about 0.5.
[0297]
To obtain a good antireflection property equal to
or less than 1% of the reflectivity, the ratio (OP
wavelength/height) is preferably set to about 2 to 6 and
30 the ratio (flat portion diameter of upper portion/pitch)
is preferably set to a range of about 0 to 0.7 commonly
i
}
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between the optical disks compliant with the BD, DVD and
CD.
[0298]
Although the embodiments of the present invention
5 have been specifically described above, the present
invention is by no means limited to the above embodiments,
and can be variously modified based on a technical idea
of the present invention.
[0299]
10 For example, configurations, methods, shapes,
materials and numerical values in the above embodiments
are only exemplary, and different configurations, methods,
shapes, materials and numerical values may be used if
necessary.
15 [0300]
Further, each configuration of the above
embodiments can be combined with one another as long as
the combination does not deviate from the spirit of the
present invention.
20 [0301]
Furthermore, the present invention is not limited
to the optical information recording media according to
the above embodiments, and is applicable to an optical
information recording medium which has a reading surface
25 on which light for recording or playing back an
information signal is radiated. For example, the present
invention is applicable to a next-generation information
recording medium such as a volume information recording
medium (volume hologram).
30 [0302] ;
Further, although cases have been described with
-
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the above embodiments as examples where a plurality of
structures is aligned regularly or cyclically, a
plurality of structures may be aligned at random.
[0303]
5 Furthermore, although cases have been described
i with the above embodiments as examples where a plurality
of structures has the same size, sizes of a plurality of
structures may be changed at random. Still further, the
sizes of a plurality of structures may be changed at
10 random, and a plurality of structures is further arranged
at random.
[0304]
Moreover, although cases have been described with
the above embodiments as examples where the present
15 invention is applied to an optical information recording j
medium which has one or two information signal layer, the
total number of information signal layers is not limited
to this, and the present invention is applicable to an
optical information recording medium which has one, two
20 or more information signal layers.
REFERENCE SIGNS LIST
[0305]
1 Substrate
25 la First compact
lb Second compact
2 Information signal layer
3 Protective layer
11 Structures
3 0 12 Convex-concave portion
13 Resin material
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14 Laminating layer
41 First substrate
42 Second substrate
43 First information signal layer
5 44 Intermediate layer
45 Second information signal layer
51 First substrate
52 First information signal layer
53 Second substrate
10 54 Second information signal layer
61 Substrate
62 Protective layer
[
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CLAIMS
1. An optical information recording medium comprising:
! a substrate;
5 one, two or more information signal layer which is
formed on the substrate; and
a protective layer which is formed on the one, two
or more information signal layer, wherein
a surface of the protective layer is a reading
10 surface on which light for recording or playing back an
information signal in the information signal layer is
radiated, and
in the reading surface, a plurality of
subwavelength structures is formed.
15
2. The optical information recording medium according
to claim 1, wherein
an arrangement pitch of the subwavelength
structures is 470 nm or less, and
2 0 a height of the subwavelength structures is 8 0 nm
or more and 200 nm or less.
1
I
3. An optical information recording medium comprising:
a first substrate;
25 one, two or more information signal layer which is <
formed on the first substrate; and 't
a second substrate which is formed on the one, two
or more information signal layer, wherein !
a surface of the second substrate is a reading 3 0 surface on which light for recording or playing back an
information signal in the information signal layer is
|
/s
4
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radiated, and
in the reading surface, a plurality of
subwavelength structures is formed.
5 4. The optical information recording medium according
to claim 3, wherein
an arrangement pitch of the subwavelength
structures is 750 nm or less, and
a height of the subwavelength structures is 80 nm
10 or more and 240 nm or less.
5. An optical information recording medium comprising:
a substrate;
one, two or more information signal layer which is
15 formed on the substrate; and
a protective layer which is formed on the one, two
or more information signal layer, wherein j
a surface of the substrate is a reading surface on
which light for recording or playing back an information
20 signal in the information signal layer is radiated, and
i in the reading surface, a plurality of j
subwavelength structures is formed. j
6. The optical information recording medium according 25 to claim 5, wherein
an arrangement pitch of the subwavelength
structures is 900 nm or less, and
a height of the subwavelength structures is 100 nm »
or more and 300 nm or less.
30
7. The optical information recording medium according
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SP262786WO00
to any one of claims 1 to 6, wherein
the plurality of subwavelength structures is
arranged to form a plurality of columns of tracks, and
the tracks have concentric shapes, spiral shapes or
5 linear shapes.
8. The optical information recording medium according
; to claim 7, wherein the plurality of subwavelength
; structures forms a hexagonal lattice pattern, a semii
s 10 hexagonal lattice pattern, a square lattice pattern or a
', semi-square lattice pattern.
9. The optical information recording medium according
to claim 7, wherein the tracks are wobbling.
15
' 10. The optical information recording medium according
to claim 1, 3 or 5, wherein a ratio (X/H) of a wavelength
: X of the light for recording or playing back the
information signal to a height H of the subwavelength
' 20 structures is 2 or more and 6 or less.
11. The optical information recording medium according
to claim 1, 3 or 5, wherein a ratio (R/P) of a flat
portion diameter R of an upper portion of the
25 subwavelength structures to an arrangement pitch P of the
subwavelength structures is 0 or more and 0.7 or less.
12. An optical information recording medium comprising:
a reading surface on which light for recording or playing
3 0 back an information signal is radiated,
wherein, in the reading surface, a plurality of
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subwavelength structures is formed.
13 A method of manufacturing an optical information
recording medium comprising: transferring a shape of a
5 reading surface forming master to a resin material, and
forming a substrate or a protective layer on a surface of
which a plurality of subwavelength structures is formed,
wherein a surface of the substrate or the
protective layer is a reading surface on which light for
10 recording or playing back an information signal is
radiated.