Description
APPARATUS FOR ATTACHING AND DETACHING CAP FOR
OPTCIAL DISC SPIN-COATING, APPARATUS FOR OPTCIAL
DISC SPIN-COATING COMPRISING THE SAME, METHOD OF
MANUFACTURING OPTCIAL DISC USING THE APPARATUS
FOR ATTACHING AND DETACHING CAP FOR OPTCIAL
DISC SPIN-COATING
Technical Field
[1 ] The present invention relates to an apparatus for optical disc spin-coating, and more
particularly, to an apparatus for optical disc spin-coating that can easily attach and
detach a cap for covering a central hole of an optical disc by including a permanent
magnet even when contaminated by a photocurable resin, an apparatus for optical disc
spin-coating comprising the same, and a method of manufacturing an optical disc using
the apparatus for attaching and detaching a cap for optical disc spin-coating.
Background Art
(2] Optical discs are used in optical pickup apparatuses for recording/reproducing information.
Examples of optical disc include compact discs (CDs) with a storage
capacity of 600 to 800 MB and digital versatile discs (DVDs) with a storage capacity
of 4 to 10 GB. Recently, to store more data and achieve higher audio and video quality,
blu-ray discs (BDs) or HD-DVDs with a storage capacity of 20 GB or greater have
been developed using a 405 nm blue laser technology.
[3] To increase recording density of optical discs, various methods are used. One
possibility in this regard is to minimize the size of a light spot, which is achieved by
conitollinj', (he wavdengili of a laser and (he number of apertures of a lens according to
the following equations:
[4] D α or 1.22 X / N A . . . ( 1 )
[5] F α NA2 .,.(2)
[6| f α A/2NA ...(3)
[7] where D is the diameter of a spot, X is the wavelength of a laser, NA is the number
of apertures of a lens, F is a focal depth, f is a focal distance, and A is the diameter of a
lens.
[8] As shown in equation 1, when the wavelength of a laser decreases and the number
of the apertures of a lens increases, the size of the spot decreases, the pit of a disc and
the size of a corresponding track decreases, and the record density increases inverseproportionally
to the square of the size of the spot. On the other hand, as shown in the
equations 2 and 3, when the wavelength decreases and the number of the apertures
increases, the focal depth decreases and the focal distance decreases.
[9] That is, the BD has a light spot of a smaller diameter, smaller focal depth, and
smaller focal distance than the DVD, which has a light spot of smaller diameter,
smaller focal depth, and smaller focal distance than the CD. As the focal depth and the
focal distance decreases, the reproducing characteristics become more dependent on
the slate of the light incidence surface of the optical disc. Accordingly, the incidence
surface must be protected from scratches and variance of the thickness of the optical
disc musi be very small.
[10] Meanwhile, in a method of manufacturing an optical disc, a light-transmitting layer,
a protecting layer, a lacquer layer, and the like are formed by spin-coating. The use of
spin-coaling brings about many advantages. For example, a resin that is removed after
the spin-coating can be re-circulated in the apparatus, and by controlling the time for
the spin-coating and the viscosity of the resin the light-transmitting layer and the like
can have various thicknesses.
[ 1 1 ] FIG. i is a graph illustrating the thickness of the light-transmitting layer with
respect to the distance between the center of a substrate and a position at which a pholocurable
resin is discharged onto the substrate. Referring to FIG. 1, the distance varies
from 5 to 25 mm and is increased by 5 mm. Numeral '31' denotes the case where the
distance is 5 mm, numeral '32' denotes the case where the distance is 10 mm, numeral
'33' dcnoies the case where the distance is 15 mm, numeral '34' denotes the case where
the distance is 20 mm, and numeral '35' denotes the case where the distance is 25 mm.
As illustrated in FIG. 1, as the position at which a photocurable resin is discharged
onto the substrate is closer to the inner circumference of the substrate, the variance of
the thickness of the light-transmitting layer decreases. When the discharge position
corresponds to the center of the substrate, theoretically, a light-transmitting layer with
no thickness variance can be obtained.
[12] In a method of manufacturing a CD, a recording layer and a reflecting layer are
formed on a polycarbonate substrate with a thickness of 1.2 mm by sputtering, and
then a thin lacquer layer is formed thereon by spin-coating to protect the recording
layer, ref lecting layer, and the like because the focal distance of a laser is too long.
Since the thickness of the lacquer layer is as small as 3 to 5 um, even when a thickness
variance occurs, the variance is very low. In addition, a recording or reproducing light
enters from (he lower portion of the polycarbonate substrate so that even when the
thickness of the upper most layer, that is, the lacquer layer, varies, no errors occur
during da(a reproducing. Accordingly, there is no need to discharge the photocurable
resin at the center of the optical disc when the lacquer layer is formed by spin-coating.
[ 13] However, in a method of manufacturing a BD with higher integration capacity
using a blue laser, since the focal distance is very short while the integrity of data
increases, a reflecting layer, a recording layer, and the like are formed on a 1.1 mm
thick polycarbonate and then a 0.1 mm thick light-transmitting layer, through which a
reproducing light enters, is formed thereon. Accordingly, the reproduction characteristics
of the BD are very dependent on the state of the surface and thickness variance
of the photo-transmitting layer.
[14] The light-transmitting layer can be formed by attaching a 0.1 mm thick lighttransmitting
sheet made of polycarbonate using a reduced pressure adhesive or an ultraviolet
curable adhesive. In this case, however, a disc is attached to a large sheet and
the remaining part is removed, so that the much of the sheet is wasted, the manufacturing
costs are increased, and the environment load is increased. Due to these
problems, the spin-coating is mainly used for the formation of the light-transmitting
layer.
[15] As described with reference to FIG. 1, when the spin-coating is performed by
discharging the photocurable resin circularly at a predetermined position departing
from the center of the optical disc, the thickness of the resin layer increases from the
center of the optical disc to the outside. When such an increase of the thickness occurs
in the BD, data reproducing errors can occur. In order to prevent this problem, the photocurable
resin must be discharged at the center of the rotating disc. However, since a
conventional optical disc has a hole at its center, another problem occurs, i.e., the photocurable
resin can leak into the hole. As a result, many techniques have been
developed to prevent the leakage of the photocurable resin into the hole.
[ 16] For example, according to Japanese Patent Laid-open Publication No.
1998-289489, a center hole of an optical disc is covered by a cap, and then the cap is
detached using an electromagnet when spin-coating is completed. In this case,
however, the cap is persistently attached to an electromagnet because the electromagnet
is contaminated by a resin doped on the surface of the cap, when the power
source is lurried off
[ 17] According to US Patent No. 6689415, a cap is attached to or detached from the
optical disc using a holding axis formed at its center to cover a center hole of an optical
disc. However, the use of the holding axis is much inefficient compared to the use of
the electromagnet for attaching and detaching operations. In addition, a photocurable
resin cannot be doped at the center of the optical disc because of the holding axis
formed at the center of the cap, so that thickness variance can occur in a coated layer.
Disclosure of Invention
Technical Problem
[18] The present invention provides an apparatus for attaching and detaching a cap for
optical disc spin-coating that prevents the contamination due to a resin and can easily
attach and detach the cap, thus increasing manufacturing efficiency.
[19] The present invention also provides an apparatus for optical disc spin-coating
comprising the apparatus for attaching and detaching a cap for optical disc spincoating.
[20] The present invention also provides a method of manufacturing an optical disc
using the apparatus for attaching and detaching a cap for optical disc spin-coating.
Technical Solution
[21] According to an aspect of the present invention, there is provided an apparatus for
attaching and detaching a cap for optical disc spin coating which is attached to and
detached from the center hole of the optical disc, including: a guide member that can
approach and recede from an upper portion of the cap; and a permanent magnet
member (hat is coupled to the guide member such that the permanent magnet member
can slide from a position where the guide member can be magnetically bonded to the
cap to a position where the guide member can be magnetically separated from the cap.
[ 22] The guide member may be conduit-shaped and forms a space for moving where the
permanent magnet member slides.
[23] The permanent magnet member may include a piston head - shaped permanent
magnet, and a shaft-shaped holding member that has an end bonded to the permanent
magnet and the other end bonded to the outside the guide member.
[24] According to another aspect of the present invention, there is provided an apparatus
for optical disc spin-coating, including a rotary turntable on which an optical disc is
placed; a cap for covering a center hole of the optical disc; and the apparatus for
attaching and detaching the cap for optical disc spin-coating.
[25] According to yet another aspect of the present invention, there is provided a method
of manufacturing an optical disc including: covering a center hole of the optical disc
using a cap; discharging a photocurable resin onto a center of the cap; and spreading
the photocurable resin on the entire surface of the optical disc by rotating the optical
disc to form a protective layer, the method including attaching or detaching the cap
using the apparatus.
Description of Drawings
[26] The above and other features and advantages of the present invention will become
more apparent by describing in detail exemplary embodiments thereof with reference
to the attached drawings in which:
[27] FIG. 1 is a graph illustrating the thickness of a light-transmitting layer with respect
to the distance between the center of a substrate and a position at which a photocurable
resin is discharged ;
[28] FIG. 2 is a schematic view of an apparatus for attaching and detaching a cap for
optical disc spin-coating according to an embodiment of the present invention;
[29] FIG. 3 illustrates exemplary shapes of an end of a guide member according to an
embodiment of the present invention;
[30] FIG. 4 illustrates a method of mounting a cap onto a center hole of an optical disc
substrate according to an embodiment of the present invention;
[31] FIG, 5 illustrates a method of removing an electromagnetic bond by lifting a
permanent magnet member after the cap is covered onto the center hole of the optical
disc substrate according to an embodiment of the present invention;
132] FIG. 6 illustrates a method of separating a guide member from an upper portion of
the cap according to an embodiment of the present invention;
133] FIG. 7 illustrates a method of spin coating a photocurable resin after the cap is
attached according to an embodiment of the present invention; and
[34] FIG. 8 illustrates a method of attaching a cap using an electromagnet according to
Comparative Example.
Best Mode
[35 ] The present invention will now be described more fully with reference to the accompanying
drawings.
[36] An apparatus according to the present invention for attaching and detaching a cap
for optical disc spin-coating which is attached to and detached from the center hole of
the optical disc includes: a guide member that can approach and recede from an upper
portion of the cap; and a permanent magnet member that is coupled to the guide
member such that the permanent magnet member can slide from a position where the
guide member can be magnetically bonded to the cap to a position where the guide
member can be magnetically separated from the cap.
[37] FIG. 2 is a schematic view of an apparatus for attaching and detaching a cap for
optical disc spin-coating according to an embodiment of the present invention. The
permanent magnetic member 21 includes a piston head - shaped permanent magnet 22,
and a shaft-shaped holding member 23 that is bonded to the permanent magnet 22.
However, the shape of the permanent magnetic member 21 is not limited thereto, and
any modification known to those skilled in the art can be made on the permanent
magnetic member 21. For example, the permanent magnetic 22 and the holding me
mber 23 may form a cylindrical structure formed of a permanent magnet. Meanwhile,
an end of the holding element 23 is connected to the outside of a guide member 25, for
example, (he axis of a rotary motor and cam, so that the holding element 23 can slide
upward and downward in the guide member 25.
[38] The guide member 25 that is conduit-shaped has a space for moving therein. The
guide member 25 may have a cross section of a polygon structure, such as triangle,
quadrangle, pentagon, and the like, or a circle. However, the shape of the guide
member 25 is not limited thereto.
[39] When the cap 10 is attached using the apparatus for attaching and detaching a cap
for optical disc spin-coating, first the guide member 25 is placed on an upper portion of
the cap 10, and then the permanent magnet member 21 inside the guide element 25
slides downward so that a lower surface of the permanent magnetic member 21 is magnetically
bonded to an upper surface of the cap 10. The magnetic bonding does not
indicate that the permanent magnet member 21 must physically contact the cap 10.
That is, although the permanent magnet member 21 does not physically contact the cap
10, the cap 10 can be attached to the permanent magnet member 21 by a magnetic
force. The cap 10 is mounted onto a center hole of an optical disc substrate by moving
the apparatus of attaching and detaching a cap for optical disc spin-coating that is magnetically
bonded to the cap 10. Thereafter, the permanent magnetic member 21 inside
the guide member 25 slides upward to a position where the magnetic bonding is
removed, so thai the cap 10 is detached.
140] The end of the guide member 25 may have a shape formed such that the contact
surface between the upper surface of the cap 10 and the guide member 20 is
minimized, as shown in FIG. 3. However, the shape of the end of the guide member 25
is not limited thereto.
[41 ] FIG. 4 illustrates a method of mounting the cap 10 onto a center hole of an optical
disc substrate 11 according to an embodiment of the present invention. The optical disc
substrate 11 is placed on the turntable 20, and then the cap 10 is mounted onto the
center hole of the optical disc substrate 11 using the apparatus for attaching and
detaching a cap, thus covering the center hole of the optical disc substrate 11. In FIG.
5, the apparatus for attaching and detaching a cap is detached from the cap 10. In
detail, after the cap 10 is mounted onto the center hole of the optical disc substrate 11,
the permanent magnetic member 21 inside the guide member 20 slides upward to the
position where the magnetic bonding is removed, so that the cap 10 is detached. In
FIG. 6, the guide member 25 is separated from the upper surface of the cap 10. As a
result, a pre-operation for spin coating is completed.
[42] An apparatus for optical disc spin coating according to an embodiment of the
present invention includes: a rotary turntable on which an optical disc can be mounted;
a cap for covering a center hole of the optical disc; and an apparatus for attaching and
detaching a cap for optical disc spin-coating.
[43] The turntable can be made of any material that is commonly used in the art. The cap
may be formed of a magnetic material, such as metal or the like, so that the cap can be
attached to and detached from the optical disc by a permanent magnet.
[44] After the cap is mounted onto the center hole of the optical disc, the cap and the
optical disc are fixed by providing vacuum pressure therebetween. In this case, the
vacuum pressure must be removed before the cap is detached.
[45] In a method of coating an optical disc according to an embodiment of the present
invention, the center hole of the optical disc is covered by the cap, a photocurable resin
is discharged on the central upper surface of the cap, and then the discharged photocurable
resin is spread on the entire surface of the optical disc by rotating the optical
disc, thus forming a protective layer. In this method, the cap is attached or detached
using the apparatus for attaching and detaching a cap for optical disc sping-coating
according to the present invention.
[46] The apparatus for optical disc spin coating and method of manufacturing an optical
disc according lo the present invention can be used to manufacture a write once read
many (WORM)-type optical disc and an erasable-type optical disc that includes a
recording layer, a read only memory (ROM) optical disc, and any optical disc
including a light-transmitting layer that is formed by spin coaling. The apparatus can
also be used to form, in addition to the light-transmitting layer, a protecting layer, a
middle layer, a lacquer layer, or the like, in order to improve the mechanical characteristics
of the optical disc.
[47] FIG. 7 illustrates a method of spin coating a photocurable resin 40 after the cap 10
is attached according to an embodiment of the present invention. Referring to FIG. 7,
the photocurable resin 40 is discharged to the center of the cap 10 via a nozzle 30, and
then spin coating is performed by rotating the turntable 20 at a rotary speed of about 20
to 100 rpm, which is relatively slow. When the discharging of the photocurable resin
40 is completed, the rotation speed is increased to produce a uniform light transmitting
layer. The rotary speed is closely related to the thickness of the light transmitting layer
to be formed. That is, as the rotary speed increases, the thickness of the light
transmitting layer decreases. Any photocurable resin that is commonly used in the art
can be used in the present invention. For example, an acylate resin is mainly used.
|48] After the photocurable resin 40 is spin coated, the cap 10 must be detached. The
removal of the cap 10 can be performed before or after the photocurable resin has
hardened. However, when the cap 10 is removed after the photocurable resin has
hardened, a boundary surface between the cap 10 and the light-transmitting layer can
be damaged so that a burr can be formed. Accordingly, preferably, the cap 10 is
removed before the photocurable resin has hardened. The apparatus for attaching and
detaching a cap for optical disc spin-coaling is placed on the upper portion of the cap
10 in order to detach the cap 10, while the turntable 20 rotates. However, it is
preferable when the turntable rotates more slowly, or stops.
[49] The present invention will be described in further detail with reference to the
following examples. However, the following examples are for illustrative purposes
without departing from the spirit and scope of the present invention as defined by the
following claims.
Industrial Applicability
[55] By using the apparatus for attaching and detaching a cap for optical disc spincoating,
the cap can be easily attached and detached even when the viscosity of the
photocurable resin is high. In addition the use of the apparatus for optical disc spincoating
and the method of manufacturing an optical disc according to the present
invention results in high manufacturing efficiency.

Claims
[1] An apparatus for attaching and detaching a cap for optical disc spin coating
which is attached to and is detached from the center hole of the optical disc, the
apparatus comprising:
a guide member that can approach and recede from an upper portion of the cap;
and
a permanent magnet member that is coupled to the guide member such that the
permanent magnet member can slide from a position where the guide member
can be magnetically bonded to the cap to a position where the guide member can
be magnetically separated from the cap.
[2] The apparatus of claim 1, wherein the guide member is conduit-shaped and
forms a space for moving where the permanent magnet member slides.
[3] The apparatus of claim 2, wherein the permanent magnet member comprises a
piston head - shaped permanent magnet, and a shaft-shaped holding member that
has an end bonded to the permanent magnet and the other end bonded to the
outside the guide member.
[4] An apparatus for optical disc spin-coating, comprising
a rotary turntable on which an optical disc is placed;
a cap for covering a center hole of the optical disc; and
the apparatus for attaching and detaching the cap for optical disc spin-coating of
any one of claims 1 through 3.
[51 A method of manufacturing an optical disc comprising: covering a center hole of
the optical disc using a cap; discharging a photocurable resin onto a center of the
cap; and spreading the photocurable resin on the entire surface of the optical disc
by rotating the optical disc to form a protective layer, the method comprising
attaching or detaching the cap using the apparatus of any one of claims 1 through
3.