DESCRIPTION
Title of Invention: ILLUMINATION DEVICE AND DISPLAY UNIT
TECHNICAL FIELD
[0001] The-present technology relates to, for example, an illumination
device suitable for an application where a transmissive liquid crystal panel
is illuminated from the back thereof, and a display unit including the
illumination device. In particular, the technology relates to an
illumination device suitable for a backlight of a display unit capable of
performing two-dimensional display (planar display) and three-dimensional
display (stereoscopic display), and a display unit including the illumination
device.
BACKGROUND ART
[0002] Some of the display units capable of three-dimensional display
demand special glasses to be worn, while others do not demand them. In
the latter type of display unit, a lenticular lens or a parallax barrier is used
to allow a stereoscopic image to be viewed by naked eyes. Image
information is split to left and right eyes by such a component, so that
different images are viewed by the two individual eyes. As a result,
three-dimensional display is achieved.
[0003] Use of the parallax barrier gives realistic sensation in
three-dimensional display, but impairs resolution in two-dimensional
display. Thus, PTL 1 discloses a technique for performing
three-dimensional display without impairing resolution in two-dimensional
display. In the technique of PTL 1, the parallax barrier is configured of a
1
SP323000
f
liquid crystal element. When three-dimensional display is performed, the
liquid crystal element is partially made untransmissive and thus acts as the
parallax barrier. When two-dimensional display is performed, the liquid
crystal element as a whole is made transmissive so as not to act as the
parallax barrier, sa that the entire image on a display screen equally enters
the left and right eyes. In the technique described in PTL 1, however, light
is disadvantageously absorbed by the parallax barrier during
three-dimensional display, leading to low display luminance.
[0004] In contrast, for example, PTL 2 discloses a technique where
polymer dispersed liquid crystal (PDLC), which is controllable to be
transparent or diffusive through voltage application, is provided in the
inside of a waveguide. In this technique, strip-like scattering regions are
formed in part of PDLC, so that light propagating within the waveguide is
scattered in each scattering region, resulting in formation of linear light
sources. In this technique, the PDLC as a whole is made into a scattering
region, so that light propagating within the waveguide is scattered in the
scattering region, resulting in formation of a planar light source. This
allows three-dimensional display and two-dimensional display to be
selectively performed without providing the parallax barrier, which
prevents a reduction in display luminance due to the parallax barrier.
Citation List
Patent Literature
[0005] PTL 1: Japanese Unexamined Patent Application Publication No.
3-119889.
PTL 2: Japanese Unexamined Patent Application Publication
2
SP323000
(Published Japanese Translation of PCT Application) No. 2007-514273.
SUMMARY OF THE INVENTION
[0006] In the waveguide described in PTL 2, when part or all of the
PDLC is made into a scattering state, scattered light is emitted not only to a
display panel side but also to a waveguide bottom side. Thus, the
paragraph 0054 of PTL 2 describes that a reflector is provided on the bottom
of the waveguide, and therefore the scattered light emitted to the waveguide
bottom side is reflected toward the display panel side to increase display
luminance.
[0007] When the reflector is simply provided, most reflected light is
emitted to the display panel side through a region (i.e., transmissive region)
different from the scattering region during three-dimensional display. As
a result, light emitted from the scattering region and light emitted from the
transmissive region collectively pass through the display panel, causing
formation of a double image. Consequently, display quality is
disadvantageously degraded.
[0008] It is therefore desirable to provide an illumination device
capable of suppressing formation of a double image in three-dimensional
display, and a display unit including the illumination device.
[0009] According to an embodiment of the presenttechnology, there is
provided an illumination device including an illumination optical system
configured to generate linear illumination light including a plurality of
pieces of linear or dot illumination light arranged two-dimensionally, and a
reflector reflecting the linear illumination light. The reflector is
3
SP323000
9
configured to reflect the linear illumination light onto a plane or the
neighborhood of the plane, the plane running through each of sites that
generate the linear illumination light and being perpendicular to a plane
containing the reflector. According to the present technology, there is
provided a display unit including a display panel having a plurality of
pixels driven based on image signals, and an illumination device configured
to illuminate the display panel. The illumination device included in the
display unit includes the same components as those of the above-described
illumination device.
[0010] In the illumination device and the display unit according to the
above-described respective embodiments of the present technology, the
reflector reflects the linear illumination light so that the linear illumination
light is reflected onto the plane or the neighborhood of the plane, the plane
running through the site that generates the linear illumination light, and
being perpendicular to a plane containing the reflector. This allows front
intensity distribution and angular intensity distribution of the reflected light
to be similar to front intensity distribution and angular intensity distribution
of light, as part of linear illumination light, emitted to a side opposite to the
reflector side.
[0011] In the above-described respective embodiments of the present
technology, the reflector more preferably has a surface shape allowing the
reflected light to be focused directly below the site generating the linear
illumination light. Moreover, in the present technology, the reflector
preferably includes a reflecting surface as part of an inner surface of a
cylinder at a position opposed to the site generating the linear illumination
4
SP323000
light. In the present technology, in the case where the illumination optical
system generates a plurality of pieces of dot illumination light, the reflector
may have a reflecting surface as part of a spherical surface at a position
opposed to each site generating the dot illumination light.
[0012] In the above-described respective embodiments of the present
technology, the illumination optical system may have a first transparent
substrate and a second transparent substrate disposed oppositely to each
other with the sites generating the linear illumination light therebetween,
and an electrode provided on a surface of one or both of the first and second
transparent substrates. Furthermore, the illumination optical system may
have a light source configured to apply light to an end face of the first
transparent substrate, a light modulation layer provided in a clearance
between the first and second transparent substrates, and a drive section
configured to drive the electrode.
[0013] The light modulation layer exhibits a scattering or transparent
property to light from the light source depending on magnitude of an
electric field. For example, the light modulation layer exhibits a
transparent property to light from the light source in the case of a relatively
low electric field, while exhibiting a scattering property to light from the
light source in the case of a relatively high electric field. For example, the
light modulation layer may exhibit a scattering property to light from the
light source in the case of a relatively low electric field, while exhibiting a
transparent property to light from the light source in the case of a relatively
high electric field.
[0014] When the light modulation layer has the former property, the
5
SP323000
drive section drives the electrode to allow the light modulation layer to
have a plurality of first regions each exhibiting a scattering property, so that
the linear illumination light is emitted from each of the first regions. On
the other hand, when the light modulation layer has the latter property, the
drive section does not drive the electrode to allow the light modulation
layer to have a plurality of first regions each exhibiting a scattering
property, so that the linear illumination light is emitted from each of the
first regions.
[0015] When the light modulation layer has the former property, the
drive section may be configured to drive the electrode to allow the entire
light modulation layer to have the first region to allow planar illumination
light to be emitted from the entire light modulation layer. On the other
hand, when the light modulation layer has the latter property, the drive
section may be configured not to drive the electrode to make the entire light
modulation layer into a first region, so that planar illumination light is
emitted from the entire light modulation layer.
[0016] According to the illumination device and the display unit of the
above-described respective embodiments of the present technology, front
intensity distribution and angular intensity distribution of the reflected light
are allowed to be similar to front intensity distribution and angular intensity
distribution of light, as part of linear illumination light, emitted to a side
opposite to the reflector side. This makes it possible to reduce a
proportion of illumination light emitted at a position unnecessary for
three-dimensional display or in an angular direction unnecessary for
three-dimensional display as compared with the case where a top of the
6
SP323000
reflector is configured of a flat surface or a paraboloid generating parallel
light. Consequently, in the case where such an illumination device is used
as a backlight of a display unit for three-dimensional display, it is possible
to suppress formation of a double image in three-dimensional display. As
a result, display quality is improved in three-dimensional display.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] [FIG. 1] FIG. 1 is a cross-sectional view illustrating an
exemplary configuration of an illumination device according to a first
embodiment of the present technology.
[FIG. 2] FIG. 2 is a cross-sectional view illustrating an exemplary
configuration of a light modulation device in FIG. 1.
[FIG. 3] FIG. 3 is a top view illustrating an example of an electrode
structure in FIG. 2.
[FIG. 4] FIG. 4 is a top view illustrating a first Modification of the
electrode structure in FIG. 2.
[FIG. 5] FIG. 5 is a top view illustrating a second Modification of the
electrode structure in FIG. 2.
[FIG. 6] FIG. 6 is a top view illustrating an example of the electrode
structure in FIG. 5.
[FIG. 7] FIG. 7 is a top view illustrating another example of the
electrode structure in FIG. 5.
[FIG. 8] FIG. 8 is a top view illustrating a third Modification of the
electrode structure in FIG. 2.
[FIG. 9] FIG. 9 is a top view illustrating a fourth Modification of the
7
SP323000
electrode structure in FIG. 2.
[FIG. 10] FIG. 10 is a diagram illustrating exemplary optical
characteristics of an ITO film and exemplary place dependence of variation
in chromaticity of a backlight.
[FIG. 11] FIG. 11 is a diagram illustrating exemplary positional
dependence of a light guide spectrum.
[FIG. 12] FIG. 12 is a schematic diagram for explaining an exemplary
function of the light modulation layer in FIG. 2.
[FIG. 13] FIG. 13 is a schematic diagram for explaining another
exemplary function of the light modulation layer in FIG. 2.
[FIG. 14] FIG. 14 is a schematic diagram for explaining an exemplary
function of the illumination device of FIG. 1.
[FIG. 15] FIG. 15 is a diagram illustrating an exemplary streaky
structure of a bulk in FIG. 2.
[FIG. 16] FIG. 16 is a cross-sectional view illustrating an exemplary
configuration of each of the light modulation layer and a reflector in FIG. 1.
[FIG. 17] FIG. 17 is a cross-sectional view illustrating a Modification
of the configuration of each of the light modulation layer and the reflector
in FIG. 1.
[FIG. 18] FIG. 18 is a cross-sectional view illustrating another
Modification of the configuration of each of the light modulation layer and
the reflector in FIG. 1.
[FIG. 19] FIG. 19 is a distribution chart illustrating exemplary front
luminance distribution and angular luminance distribution of light directly
emitted to a top from a light source and of light reflected by the reflector.
8
SP323000
[FIG. 20] FIG. 20 is a cross-sectional view illustrating an exemplary
configuration of a reflector according to a comparative example.
[FIG. 21] FIG. 21 is a distribution chart illustrating exemplary front
luminance distribution and angular luminance distribution of light directly
emitted to a top from the light source in FIG. 20 and of light reflected by the
reflector in FIG. 20.
[FIG. 22] FIG. 22 is a cross-sectional view illustrating an exemplary
configuration of a reflector according to another comparative example.
[FIG. 23] FIG. 23 is a distribution chart illustrating exemplary front
luminance distribution and angular luminance distribution of light directly
emitted to a top from the light source in FIG. 22 and of light reflected by the
reflector in FIG. 22.
[FIG. 24] FIG. 24 is a cross-sectional view illustrating another
exemplary configuration of the reflector in FIG. 1.
[FIG. 25] FIG. 25 is a cross-sectional view for explaining
manufacturing steps of the light modulation device of FIG. 2.
[FIG. 26] FIG. 26 is a cross-sectional view for explaining
manufacturing steps following the steps of FIG. 25.
[FIG. 27] FIG. 27 is a cross-sectional view for explaining
manufacturing steps following the steps of FIG. 26.
[FIG. 28] FIG. 28 is a cross-sectional view illustrating a first
Modification of the configuration of the illumination device of FIG. 1.
[FIG. 29] FIG. 29 is a cross-sectional view illustrating a second
Modification of the configuration of the illumination device of FIG. 1.
[FIG. 30] FIG. 30 is a cross-sectional view illustrating a third
9
SP323000
Modification of the configuration of the illumination device of FIG. 1.
[FIG. 31] FIG. 31 is a top view illustrating a fifth Modification of the
electrode structure in FIG. 2.
[FIG. 32] FIG. 32 is a top view illustrating a sixth Modification of the
electrode structure in FIG. 2.
[FIG. 33] FIG. 33 is a top view illustrating a seventh Modification of
the electrode structure in FIG. 2.
[FIG. 34] FIG. 34 is a top view illustrating an eighth Modification of
the electrode structure in FIG. 2.
[FIG. 35] FIG. 35 is a cross-sectional view illustrating a fourth
Modification of the configuration of the illumination device of FIG. 1.
[FIG. 36] FIG. 36 is a cross-sectional view illustrating an example of a
barrier layer in FIG. 35.
[FIG. 37] FIG. 37 is a cross-sectional view illustrating another example
of the barrier layer in FIG. 35.
[FIG. 38] FIG. 38 is a cross-sectional view illustrating an exemplary
configuration of an illumination device according to a second embodiment
of the present technology.
[FIG. 39] FIG. 39 is a top view illustrating an example of a light source
in FIG. 38.
[FIG. 40] FIG. 40 is a top view illustrating a first Modification of the
light source in FIG. 38.
[FIG. 41] FIG. 41 is a top view illustrating a second Modification of the
light source in FIG. 38.
[FIG. 42] FIG. 42 is a top view illustrating a third Modification of the
10
SP323000
light source in FIG. 38.
[FIG. 43] FIG. 43 is a cross-sectional view illustrating an exemplary
configuration of each of the light source and a reflector in FIG. 38.
[FIG. 44] FIG. 44 is a cross-sectional view illustrating a Modification
of the configuration of each of the light source and the reflector in FIG. 38.
[FIG. 45] FIG. 45 is a cross-sectional view illustrating another
Modification of the configuration of each of the light source and the
reflector in FIG. 38.
[FIG. 46] FIG. 46 is a cross-sectional view illustrating an exemplary
configuration of an illumination device according to a third embodiment of
the present technology.
[FIG. 47] FIG. 47 is a top view illustrating an example of a light guide
plate in FIG. 46.
[FIG. 48] FIG. 48 is a top view illustrating another example of the light
guide plate in FIG. 46.
[FIG. 49] FIG. 49 is a cross-sectional view illustrating an exemplary
configuration of each of the light guide plate and a reflector in FIG. 46.
[FIG. 50] FIG. 50 is a cross-sectional view illustrating a first
Modification of the configuration of each of the light guide plate and the
reflector in FIG. 46.
[FIG. 51] FIG. 51 is a cross-sectional view illustrating a second
Modification of the configuration of each of the light guide plate and the
reflector in FIG. 46.
[FIG. 52] FIG. 52 is a cross-sectional view illustrating a third
Modification of the configuration of each of the light guide plate and the
11
SP323000
reflector in FIG. 46.
[FIG. 53] FIG. 53 is a cross-sectional view illustrating a fourth
Modification of the configuration of each of the light guide plate and the
reflector in FIG. 46.
[FIG. 54] FIG. 54 is a cross-sectional view illustrating a fifth
Modification of the configuration of each of the light guide plate and the
reflector in FIG. 46.
[FIG. 55] FIG. 55 is a cross-sectional view illustrating a first
Modification of the configuration of the reflector in FIG. 1.
[FIG. 56] FIG. 56 is a cross-sectional view illustrating a second
Modification of the configuration of the reflector in FIG. 1.
[FIG. 57] FIG. 57 is a cross-sectional view illustrating a third
Modification of the configuration of the reflector in FIG. 1.
[FIG. 58] FIG. 58 is a cross-sectional view for explaining an exemplary
focal point of the reflector of FIG. 57.
[FIG. 59] FIG. 59 is a cross-sectional view for explaining another
exemplary focal point of the reflector of FIG. 57.
[FIG. 60] FIG. 60 is a cross-sectional view for explaining another
exemplary focal point of the reflector of FIG. 57.
[FIG. 61] FIG. 61 is a cross-sectional view for explaining a function of
the reflector of FIG. 57.
[FIG. 62] FIG. 62 is a cross-sectional view for explaining a function of
the reflector of FIG. 58.
[FIG. 63] FIG. 63 is a cross-sectional view for explaining a function of
the reflector of FIG. 59.
12
SP323000
[FIG. 64] FIG. 64 is a cross-sectional view illustrating a fourth
Modification of the configuration of the reflector in FIG. 1.
[FIG. 65] FIG. 65 is a cross-sectional view illustrating a fifth
Modification of the configuration of the reflector in FIG. 1.
[FIG. 66] FIG. 66 is a diagram illustrating an exemplary
transmitter-receiver system for television broadcast signals according to a
fourth embodiment of the present technology.
[FIG. 67] FIG. 67 is a diagram illustrating an exemplary functional
block of a receiver unit in FIG. 66.
[FIG. 68] FIG. 68 is a cross-sectional view illustrating an exemplary
configuration of a display section of the receiver unit in FIG. 66.
[FIG. 69] FIG. 69 is a perspective view illustrating an exemplary
relationship between a rubbing direction and a transmission axis of a
polarizing plate in the receiver unit in FIG. 66.
[FIG. 70] FIG. 70 is a schematic view for explaining three-dimensional
display by the display section in FIG. 68.
[FIG. 71] FIG. 71 is a schematic view for explaining two-dimensional
display by the display section in FIG. 68.
[FIG. 72] FIG. 72 is a top view illustrating an exemplary electrode
configuration of an illumination device according to an Example.
[FIG. 73] FIG. 73 is a top view illustrating the exemplary electrode
configuration of FIG. 72 in an enlarged manner.
MODE(S) FOR CARRYING OUT THE INVENTION
[0018] Hereinafter, modes for carrying out the invention are described
13
f SP323000
in detail with reference to the accompanying drawings.
It is to be noted that description is made in the following order.
1. First Embodiment (Illumination device).
An example of an illumination device of an edge light type.
An example of an illumination device having a light modulation
device.
2. Modifications of First Embodiment (Illumination device).
3. Second Embodiment (Illumination device).
An example of an illumination device of a directly-below type.
4. Modification of Second Embodiment (Illumination device).
.5. Third Embodiment (Illumination device).
An example of an illumination device of an edge light type.
An example of an illumination device including a light guide plate
having a scattering region.
6. Modifications of Third Embodiment (Illumination device).
7. Fourth Embodiment (Display unit).
An example of a display unit including the illumination device of
any one of the first to third embodiments as a backlight.
8. Examples (Display unit).
[0019] [1. First Embodiment]
FIG. 1 illustrates a sectional configuration of an illumination device 1
according to a first embodiment of the present technology. The
illumination device 1 is applicable as a backlight of a display unit, and, for
example, as illustrated in FIG. 1, includes a light guide plate 10, a light
source 20 disposed on a side face of the light guide plate 10, a light
14
SP323000
modulation device 30 and a reflector 40 disposed behind the light guide
plate 10, and a drive circuit 50 configured to drive the light modulation
device 30.
[0020] The light guide plate 10 corresponds to a specific but not
limitative example of "first transparent substrate" or "second transparent
substrate". The light source 20 corresponds to a specific but not limitative
example of "light source". The reflector 40 corresponds to a specific but
not limitative example of "reflector". The drive circuit 50 corresponds to
a specific but not limitative example of "drive section". An optical system
including the light source 20 and the light modulation device 30
corresponds to a specific but not limitative example of "illumination optical
system".
[0021] The light guide plate 10 guides light from the light source 20
disposed on the side face of the light guide plate 10 to a top side of the light
guide plate 10 (specifically, to a light emission surface 1A of the
illumination device 1). For example, the light guide plate 10 has a shape
corresponding to an irradiation object (for example, a display panel 210
described later) disposed on the top of the light guide plate 10, and, for
example, has a rectangular solid shape enclosed by the top, the bottom, and
the side faces. Hereinafter, among the side faces of the light guide plate
10, a particular side face receiving light from the light source 20, is referred
to as a light-incident surface 10A.
[0022] For example, the light guide plate 10 has a predetermined
patterned shape on one or both of the top and the bottom, and has a function
of scattering and equalizing light entering through the light-incident surface
15
SP323000
•tw*
10A. In the case where luminance is equalized by modulating a voltage to
be applied to the light modulation device 30, it is possible to use an
unpatterned flat light guide plate as the light guide plate 10. For example,
the light guide plate 10 mainly includes transparent thermoplastic resin
such as polycarbonate resin (PC) and acrylic resin (such as polymethyl
methacrylate (PMMA)).
[0023] The light source 20 is a linear light source, examples of which
include a hot cathode fluorescent lamp (HCFL), a cold cathode fluorescent
lamp (CCFL), and a plurality of light emitting diodes (LEDs) arranged in a
line. In the case where the light source 20 includes a plurality of LEDs, all
the LEDs are each preferably a white LED from the viewpoint of efficiency,
thickness reduction, and uniformity. For example, the light source 20 may
include red LEDs, green LEDs, and blue LEDs. The light source 20 may
be provided on only one side face of the light guide plate 10 (see FIG. 1).
Alternatively, the light sources 20 may be provided on two, three, or all of
the side faces of the light guide plate 10.
[0024] In the present embodiment, the light modulation device 30 is in
tight contact with the back (bottom) of the light guide plate 10 with no air
layer therebetween, and, for example, is configured to adhere to the back of
the light guide plate 10 with an adhesive agent (not shown) therebetween.
For example, as illustrated in FIG. 2, the light modulation device 30
includes a transparent substrate 31, a lower electrode 32, an alignment film
33, a light modulation layer 34, an alignment film 35, an upper electrode 36,
and a transparent substrate 37 in order of closeness to the reflector 40.
The lower electrode 32 and the upper electrode 36 each correspond to a
16
SP323000
specific but not limitative example of "electrode".
[0025] The transparent substrates 31 and 37 support the light
modulation layer 34, and are each typically configured of a substrate
transparent to visible light, for example, a glass plate or a plastic film.
The upper electrode 36 is provided on a surface of the transparent substrate
37, the surface being opposed to the transparent substrate 31, and, for
example, includes one solid film formed over the entire surface. On the
other hand, the lower electrode 32 is provided on a surface of the
transparent substrate 31, the surface being opposed to the transparent
substrate 37, and, for example, includes a plurality of partial electrodes 32A
as illustrated in FIG. 3.
[0026] For example, as illustrated in FIG. 3, the plurality of partial
electrodes 32A each have a strip-like shape extending in one direction in a
plane (for example, a direction parallel to the light-incident surface 10A).
A plurality of particular partial electrodes 32A (hereinafter, referred to as
"partial electrodes 32B") among the plurality of partial electrodes 32A are
used for generation of linear illumination light during three-dimensional
display performed by the display unit. The plurality of partial electrodes
32B are arranged at a pitch PI corresponding to a pixel pitch P3 (see FIG.
70) (i.e., at a pitch equal or similar to the pixel pitch P3) during
three-dimensional display performed by the display unit.
[0027] Among the plurality of partial electrodes 32A, a plurality of
partial electrodes 32A (hereinafter, referred to as "partial electrodes 32C")
other than the partial electrodes 32B are used for generation of planar
illumination light together with the partial electrodes 32A during
17
SP323000
two-dimensional display performed by the display unit. Specifically, when
the display unit performs two-dimensional display, all the partial electrodes
32A are used for generation of planar illumination light. The plurality of
partial electrodes 32B and the plurality of partial electrodes 32C are
regularly arranged in a direction orthogonal to the light-incident surface
10A. For example, as illustrated in FIGs. 2 and 3, a plurality of sets of
partial electrode groups, each set including one partial electrode 32B and
two partial electrodes 32C, are arranged in the direction orthogonal to the
light-incident surface 10A. For example, the width of the partial electrode
32B is narrower than that of each pixel of the display unit.
[0028] For example, as illustrated in FIG. 4, the partial electrodes 32A
may be configured such that each partial electrode 32A has a block shape,
and the plurality of partial electrodes 32A are arranged two-dimensionally.
In such a case, when the plurality of partial electrodes 32A are considered
as one linear electrode 32D, each linear electrode 32D may be used as the
partial electrode 32B or 32C described above. For example, among the
plurality of linear electrode 32D, a plurality of particular linear electrodes
32D are used as the partial electrodes 32B. Among the plurality of linear
electrodes 32D, a plurality of linear electrodes 32D, excluding the linear
electrodes 32D used as the partial electrodes 32B, are used as the partial
electrodes 32C.
[0029] In the case where each partial electrode 32A has a block shape,
and the plurality of partial electrodes 32A are arranged two-dimensionally,
the individual partial electrodes 32A may be used for generation of dot
illumination light during three-dimensional display performed by the
18
SP323000
display unit. Moreover, in the case where each partial electrode 32A has a
block shape and the plurality of partial electrodes 32A are arranged
two-dimensionally, and when the display unit performs two-dimensional
display that allows different two-dimensional images to be viewed from two
perspectives, the individual partial electrodes 32A may also be used for
generation of dot illumination light.
[0030] In addition, for example, as illustrated in FIGs. 5 and 6, a partial
electrode 32C having a width larger than that of the partial electrode 32B
may be provided between partial electrodes 32B adjacent to each other. In
this case, for example, as illustrated in FIG. 7, each partial electrode 32B
may be configured of a plurality of partial electrodes 32A, and each partial
electrode 32C may also be configured of a plurality of partial electrodes
32A.
[0031] Moreover, for example, as illustrated in FIG. 8, each partial
electrode 32A may extend in a direction obliquely crossing the
light-incident surface 10A at an angle other than the right angle. Moreover,
in the case where each partial electrode 32A has a block shape and a
plurality of partial electrodes 32A are arranged two-dimensionally, each
linear electrode 32D may extend in a direction obliquely crossing the
light-incident surface 10A at an angle other than the right angle, for
example, as illustrated in FIG. 9. In the case where each partial electrode
32A extends in a direction obliquely crossing the normal to the
light-incident surface 10A, the extending direction of the partial electrode
32A is preferably a direction crossing an arrangement direction of pixels of
the display panel 210 described later. In the case of such a configuration,
19
SP323000
it is possible to reduce a difference between resolution in a direction
parallel to the normal to the light-incident surface 10A and resolution in a
direction parallel to the light-incident surface 10A during three-dimensional
display.
[0032] Each of the lower electrode 32 and the upper electrode 36 is
configured of a transparent conductive film. For example, the transparent
conductive film preferably has properties as represented by the following
expression (see (A) of FIG. 10). For example, the transparent conductive
film is configured of an ITO-containing film (hereinafter, referred to as
"ITO film"). It is to be noted that each of the lower electrode 32 and the
upper electrode 36 may be configured of indium zinc oxide (IZO), metal
nanowire, carbon nanotube, graphene, etc.
[0033] |A1-A2|<2.00
Al: maximum optical absorptance (%) in 450 nm to 650 nm both
inclusive.
A2: minimum optical absorptance (%) in 450 nm to 650 nm both
inclusive.
[0034] Visible light is used as the illuminating light; hence, differences
in optical absorbance of the transparent conductive film are preferably
small within a range of 380 nm to 780 nm both inclusive. A difference
between the maximum value and the minimum value of optical absorptance
is preferably 10.00 or less, and more preferably 7.00 or less within the
range of 380 nm to 780 nm both inclusive. In particular, in the case where
the transparent conductive film is used for the backlight, the difference
between the maximum value and the minimum value of optical absorptance
20
SP323000
is preferably 2.00 or less, and more preferably 1.00 or less within a
wavelength range of a light source to be used. For example, in the case
where typical LED is used as the light source, the difference between the
maximum value and the minimum value of optical absorptance is preferably
2.00 or less, and more preferably 1.00 or less within a range of 450 nm to
650 nm both inclusive. The optical absorptance is measured by V-550
from Jasco Corporation in such a manner that reflectance and transmittance
are measured at an incidence angle of 5° from a normal direction to a
substrate, and the optical absorptance is determined as a value obtained by
subtracting the values of the reflectance and the transmittance from 100%.
[0035] In this way, in the case where the transparent conductive film
has the properties as represented by the above expression, and when light
emitted from the light source 20 repeatedly passes through the transparent
conductive film in the light modulation device 30 during propagation of the
light within the light guide plate 10, wavelength dependence of light
absorption is suppressed. In the case where the transparent conductive
film includes a typical ITO film, a longer wavelength component increases
with an increase in distance from the light source 20, for example, as
illustrated by broken lines in (B) and (C) of FIG. 10 and by an arrow in (A)
of FIG. 11. On the other hand, in the case where the transparent
conductive film includes an ITO film improved in film quality, the ITO film
having the properties as represented by the above expression, a longer
wavelength component increases with an increase in distance from the light
source 20 at a reduced rate, for example, as illustrated by solid lines in (B)
and (C) of FIG. 10 and in (B) of FIG. 11. It is to be noted that AuV shown
21
SP323000
as the vertical scale of each of (B) and (C) of FIG. 10 is an index that
correspondingly indicates an increase in longer wavelength component with
an increase in value of the index.
[0036] For example, in the case where each of the lower electrode 32
and the upper electrode 36 is configured of an ITO film, a certain portion of
an optical path along which light is being guided (for example, one or both
of the light guide plate 10 and the light modulation device 30) preferably
contains a dye or pigment that more absorbs light in a long wavelength
range than light in a short wavelength range. Known dye or pigment
materials may be used as the dye or pigment. In particular, in the case
where an ultraviolet irradiation process is used for formation of the light
modulation layer 34, for example, after formation of the light modulation
device 30, the light guide plate 10 containing the dye or pigment is
preferably bonded to the light modulation device 30, or the portion
containing the dye or pigment is preferably protected from ultraviolet rays
by an ultraviolet absorbing layer. In this way, a certain portion of an
optical path, along which light is being guided, contains the dye or pigment,
and thus when light emitted from the light source 20 repeatedly passes
through the light modulation device 30 during propagation of the light
within the light guide plate 10, light is absorbed by the light modulation
device 30 including the ITO film while wavelength dependence of light
absorption is suppressed.
[0037] When the lower electrode 32 and the upper electrode 36 are
viewed from the normal direction to the light modulation device 30, a
portion of the light modulation device 30, the portion corresponding to a
22
SP323000
region where the lower electrode 32 is opposed to the upper electrode 36,
configures a light modulation cell 30-1 (see FIGs. 2 and 5).
[0038] The light modulation cell 30-1 corresponds to a portion of the
light modulation device 30, the portion corresponding to a region where
each partial electrode 32A is opposed to the upper electrode 36. Among
the plurality of light modulation cells 30-1, cells 30a each including the
partial electrode 32B (see FIGs.2 to 9) are used for generation of linear
illuminating light during three-dimensional display performed by the
display unit. Among the plurality of light modulation cells 30-1, cells 30b
each including the partial electrode 32C (see FIGs.2 to 9) are used for
generation of planar illumination light together with the plurality of cells
30a during two-dimensional display performed by the display unit.
Specifically, when the display unit performs two-dimensional display, all
the light modulation cells 30-1 are used for generation of planar
illumination light.
[0039] The light modulation cells 30-1 are individually drivable by
applying a predetermined voltage between each partial electrode 32A and
the upper electrode 36, and each exhibit a transparent or scattering property
to light from the light source 20 depending on the magnitude of a voltage
value applied between the partial electrode 32A and the upper electrode 36.
It is to be noted that the transparent property and the scattering property are
described in detail in description of the light modulation layer 34.
[0040] For example, the alignment films 33 and 35 are provided to align
the liquid crystal or monomer used for the light modulation layer 34.
Examples of types of the alignment film include a vertical alignment film
23
SP323000
and a horizontal alignment film, and the horizontal alignment film is used
as each of the alignment films 33 and 35 in the present embodiment.
Examples of the horizontal alignment film include an alignment film formed
through rubbing of polyimide, polyamide-imide, polyvinyl alcohol, etc.,
and an alignment film having a groove pattern provided thereon by transfer,
etching, etc. Examples of the horizontal alignment film include an
alignment film formed by obliquely evaporating an inorganic material such
as silicon oxide, a diamond-like carbon alignment film formed by ion beam
irradiation, and an alignment film having electrode pattern slits. In the
case where a plastic film is used for each of the transparent substrates 31
and 37, baking temperature is preferably as low as possible after the
alignment films 33 and 35 are applied onto the respective surfaces of the
transparent substrates 31 and 37 in a manufacturing process; hence,
polyamide-imide, which allows film formation at a temperature of 100°C or
less, is preferably used for the alignment films 33 and 35.
[0041] Each of the vertical and horizontal alignment films may have
only the function of aligning the liquid crystal or the monomer, i.e., may not
have reliability for repeated voltage application demanded for a typical
liquid crystal display. The reason for this is that the reliability for voltage
application after device fabrication is determined by an interface between a
polymerization product of the monomer and the liquid crystal. Even if the
alignment film is not used, the liquid crystal or the monomer used for the
light modulation layer 34 may also be aligned by, for example, applying an
electric or magnetic field between the lower electrode 32 and the upper
electrode 36. Specifically, the light modulation cell is irradiated with
24
SP323000
ultraviolet rays while the electric or magnetic field is applied between the
lower electrode 32 and the upper electrode 36, and thus it is possible to fix
an alignment state of the liquid crystal or the monomer while no voltage is
applied. When voltage is used for formation of the alignment film,
electrodes are separately provided for alignment and drive. Alternatively,
dual-frequency liquid crystal, of which the sign of dielectric constant
anisotropy is inverted depending on frequencies, may be used as a liquid
crystal material. When the magnetic field is used for formation of the
alignment film, a material having large susceptibility anisotropy is
preferably used for the alignment film. For example, a material having
many benzene rings is preferably used.
[0042] The light modulation layer 34 exhibits a scattering or
transparent property to light from the light source 20 depending on
magnitude of an electric field. When the electric field is relatively small,
the light modulation layer 34 exhibits a transparent property to the light
from the light source 20. When the electric field is relatively large, the
light modulation layer 34 exhibits a scattering property to the light from the
light source 20. For example, as illustrated in FIG. 2, the light modulation
layer 34 is configured of a composite layer containing a bulk 34A and a
plurality of fine particles 34B dispersed in the bulk 34A. The bulk 34A
and the fine particle 34B each have optical anisotropy.
[0043] (A) of FIG. 12 schematically illustrates an exemplary alignment
state within each fine particle 34B during no voltage application between
the lower electrode 32 and the upper electrode 36. In (A) of FIG. 12, an
alignment state within the bulk 34A is not illustrated. (B) of FIG. 12
25
SP323000
illustrates exemplary optical indicatrices showing refractive index
anisotropy of each of the bulk 34A and the fine particle 34B during no
voltage application between the lower electrode 32 and the upper electrode
36. The optical indicatrices each include a tensor ellipsoid showing a
refractive index of linear polarization incident from any of various
directions, and allow the refractive index to be geometrically known
through viewing a section of the ellipsoid in a light incidence direction.
(C) of FIG. 12 schematically illustrates an exemplary state where light LI
traveling in the front direction and light L2 traveling in an oblique direction
pass through the light modulation layer 34 during no voltage application
between the lower electrode 32 and the upper electrode 36.
[0044] (A) of FIG. 13 schematically illustrates an exemplary alignment
state within each fine particle 34B during voltage application between the
lower electrode 32 and the upper electrode 36. In (A) of FIG. 13, an
alignment state of the bulk 34Ais not illustrated. (B) of FIG. 13 illustrates
exemplary optical indicatrices showing refractive index anisotropy of each
of the bulk 34A and the fine particle 34B during voltage application
between the lower electrode 32 and the upper electrode 36. (C) of FIG. 13
schematically illustrates an exemplary state where light LI traveling in the
front direction and light L2 traveling in the oblique direction are scattered
by the light modulation layer 34 during voltage application between the
lower electrode 32 and the upper electrode 36.
[0045] For example, as illustrated in (A) and (B) of FIG. 12, the bulk
34A and the fine particles 34B are configured such that while no voltage is
applied between the lower electrode 32 and the upper electrode 36, a
26
SP323000
direction of the optical axis AXl of the bulk 34A is equal (parallel) to a
direction of the optical axis AX2 of the fine particle 34B. It is to be noted
that the optical axes AXl and AX2 each refer to a line parallel to a beam
traveling direction along which a refractive index has one value regardless
of polarization directions. The direction of the optical axis AXl and the
direction of the optical axis AX2 may not constantly be equal to each other,
i.e., may be somewhat different from each other due to manufacturing error,
for example.
[0046] Moreover, for example, the fine particle 34B is configured such
that while no voltage is applied between the lower electrode 32 and the
upper electrode 36, the optical axis AX2 is parallel to the light-incident
surface 10A of the light guide plate 10. Furthermore, for example, the fine
particle 34B is configured such that while no voltage is applied between the
lower electrode 32 and the upper electrode 36, the optical axis AX2
intersects with each of the surfaces of the transparent substrates 31 and 37
at a small angle 81 (see (B) of FIG. 12). The angle 91 is described in detail
in description of materials configuring the fine particle 34B.
[0047] On the other hand, for example, the bulk 34A is configured such
that the optical axis AXl of the bulk 34A is fixed regardless of presence or
absence of voltage application between the lower electrode 32 and the upper
electrode 36. Specifically, for example, as illustrated in (A) and (B) of
FIG. 12 and (A) and (B) of FIG. 13, the bulk 34A is configured such that the
optical axis AXl of the bulk 34A is parallel to the light-incident surface
10A of the light guide plate 10, and intersects with each of the surfaces of
the transparent substrates 31 and 37 at the predetermined angle 81.
27
SP323000
Specifically, the optical axis AX1 of the bulk 34A is parallel to the optical
axis AX2 of the fine particle 34B during no voltage application between the
lower electrode 32 and the upper electrode 36.
[0048] The optical axis AX2 may not constantly be parallel to the
light-incident surface 10A while intersecting with each of the surfaces of
the transparent substrates 31 and 37 at the angle 01, i.e., may intersect with
each of the surfaces of the transparent substrates 31 and 37 at an angle
slightly different from the angle 01 due to manufacturing error, for example.
In addition, each of the optical axes AX1 and AX2 may not constantly be
parallel to the light-incident surface 10A, i.e., may intersect with the
light-incident surface 10A at a small angle due to manufacturing error, for
example.
[0049] It is preferable that the ordinary refractive index of the bulk 34A
is equal to that of the fine particle 34B, and the extraordinary refractive
index of the bulk 34A is equal to that of the fine particle 34B. In such a
case, for example, while no voltage is applied between the lower electrode
32 and the upper electrode 36, as illustrated in (A) of FIG. 12, almost no
difference in refractive index exists between all directions including the
front direction and the oblique direction, leading to high transparency.
Consequently, for example, as illustrated in (C) of FIG. 12, the light LI
traveling in the front direction and the light L2 traveling in the oblique
direction pass through the light modulation layer 34 without being scattered
in the light modulation layer 34. As a result, for example, as illustrated in
(A) and (B) of FIG. 14, light L (light in the oblique direction) from the light
source 20 is totally reflected by any of interfaces (the bottom of the
28
SP323000
transparent substrate 31 and the top of the light guide plate 10) of a
transparent region (transmissive region 30A) in the light modulation layer
34, and thus luminance of the transmissive region 30A (luminance in black
display) is lowered compared with a case where light is uniformly emitted
over the entire area (a dashed-dotted line in (B) of FIG. 14). The profile of
the front luminance in (B) of FIG. 14 is obtained by measuring front
luminance through a diffuser sheet (not shown) provided on the light guide
plate 10.
[0050] When the illumination device 1 is used as the backlight of the
display unit, the top of the light guide plate 10 (light emission surface 1A in
FIG. 14), which is one of the interfaces of the transmissive region 30A, is
preferably in contact with a material having a refractive index lower than
that of the top of the light guide plate 10. Such a material having the low
refractive index typically includes air. When the illumination device 1 is
used as the backlight of the display unit, and in the case where the top of the
light guide plate 10 is bonded to another optical component (for example, a
display panel) within the display unit, the material having the low refractive
index, which is to be in contact with the top of the light guide plate 10, may
be a bonding agent or an adhesive agent.
[0051] For example, as illustrated in (A) and (B) of FIG. 13, the bulk
34A and the fine particles 34B are configured such that while voltage is
applied between the lower electrode 32 and the upper electrode 36, the
direction of the optical axis AX1 is different from (intersect with or is
substantially orthogonal to) the direction of the optical axis AX2.
Furthermore, for example, the fine particle 34B is configured such that
29
SP323000
while voltage is applied between the lower electrode 32 and the upper
electrode 36, the optical axis AX2 of the fine particle 34B is parallel to the
light-incident surface 10A of the light guide plate 10, and intersects with
each of the surfaces of the transparent substrates 31 and 37 at an angle 92
(for example, 90°) larger than the angle 91. The angle 92 is described in
detail in description of the materials configuring the fine particle 34B.
[0052] As a result, while voltage is applied between the lower electrode
32 and the upper electrode 36, a difference in refractive index increases in
all directions including the front direction and the oblique direction in the
light modulation layer 34, leading to a high scattering property of the light
modulation layer 34. Consequently, for example, as illustrated in (C) of
FIG. 13, the light LI traveling in the front direction and the light L2
traveling in the oblique direction are scattered in the light modulation layer
34. As a result, for example, as illustrated in (A) of FIG. 14, the light L
(light in the oblique direction) from the light source 20 passes through an
interface (an interface between the transparent substrate 31 or the light
guide plate 10 and air) of a scattering region 30B, and light transmitted to
the reflector 40 side is reflected by the reflector 40 and passes through the
light modulation device 30. Consequently, luminance of the scattering
region 30B is extremely high compared with the case where light is
uniformly emitted over the entire area (the dashed-dotted line in (B) of FIG.
14), and luminance in partial white display (luminance enhancement)
increases in correspondence to a reduction in luminance of the transmissive
region 30A. The scattering region 30B corresponds to a specific but not
limitative example of "first region" of the present technology.
30
SP323000
[0053] The ordinary refractive index of the bulk 34A and the ordinary
refractive index of the fine particle 34B may be somewhat different from
each other due to manufacturing error, for example. For example, such a
difference is preferably 0.1 or less, and more preferably 0.05 or less. The
extraordinary refractive index of the bulk 34A and the extraordinary
refractive index of the fine particle 34B may also be somewhat different
from each other due to manufacturing error, for example. For example,
such a difference is preferably 0.1 or less, and more preferably 0.05 or less.
[0054] The refractive index difference of the bulk 34A
(Anp=extraordinary refractive index nep-ordinary refractive index nop) and
the refractive index difference of the fine particle 34B (AnL=extraordinary
refractive index neL-ordinary refractive index noL) are each preferably as
large as possible, and are each preferably 0.05 or more, more preferably 0.1
or more, and still more preferably 0.15 or more. The reason for this is that
when the refractive index difference of each of the bulk 34A and the fine
particle 34B is large, the light modulation layer 34 exhibits higher
scattering performance, and thus a light guiding condition is allowed to be
easily broken, and consequently light is easily extracted from the light
guide plate 10.
[0055] The response speed to an electric field of the bulk 34A is
different from that of the fine particle 34B. For example, the bulk 34A has
a streaky structure (see (A) and (B) of FIG. 15), a porous structure, or a
rod-like structure having a response speed slower than that of the fine
particle 34B. (A) and (B) of FIG. 15 show polarization microscope
photographs during application of an electric field to the light modulation
31
SP323000
*
device 30, where each of streaky and bright portions corresponds to the
streaky structure. (A) of FIG. 15 illustrates the streaky structure of the
bulk 34A at a weight ratio of liquid crystal to monomer of 95:5. (B) of FIG.
15 illustrates the streaky structure of the bulk 34A at a weight ratio of liquid
crystal to monomer of 90:10. For example, the bulk 34A is formed of a
polymer material produced through polymerization of low-molecular
monomer. For example, the bulk 34A is formed by polymerizing a material
having alignable and polymerizable properties (for example, monomer) by
one or both of heat and light, the material having been aligned along an
alignment direction of the fine particle 34B or of the alignment film 33 or
35.
[0056] For example, the streaky structure, the porous structure, or the
rod-like structure of the bulk 34A has the major axis in a direction that is
parallel to the light-incident surface 10A of the light guide plate 10, and
intersects with each of the surfaces of the transparent substrates 31 and 37
at a small angle 91. In the case where the bulk 34A has the streaky
structure, average streaky structure size in a minor axis direction is
preferably 0.1 urn to 10 urn both inclusive, and is more preferably in a range
of 0.2 urn to 2.0 |im both inclusive, from the viewpoint of enhancing
scattering of guided light. In the case where the average streaky structure
size in the minor axis direction is 0.1 jim to 10 ^m both inclusive, the
scattering performance in the light modulation device 30 is substantially
even in a visible range of 380 nm to 780 nm both inclusive. This prevents
only light having a particular wavelength component from increasing or
decreasing in a plane, making it possible to achieve good light balance in a
32
SP323000
ft
plane within the visible range. If the average streaky structure size in the
minor axis direction is less than 0.1 um or exceeds 10 um, the light
modulation device 30 exhibits low scattering performance regardless of
wavelengths, and is thus less likely to function as a light modulation device.
[0057] From the viewpoint of reducing wavelength dependence of light
scattering, the average streaky structure size in the minor axis direction is
preferably 0.5 pm to 5 um both inclusive, and is more preferably within a
range of 1 um to 3 |im both inclusive. In the case of such a configuration,
when light emitted from the light source 20 repeatedly passes through the
bulk 34A in the light modulation device 30 during propagation of the light
within the light guide plate 10, wavelength dependence of light scattering in
the bulk 34A is suppressed. The size of the streaky structure is observed
by a polarization microscope, a confocal microscope, an electron
microscope, etc.
[0058] On the other hand, for example, the fine particle 34B mainly
includes a liquid crystal material, and has a sufficiently fast response speed
compared with the response speed of the bulk 34A. Examples of the liquid
crystal material (liquid crystal molecules) contained in the fine particle 34B
include rod-like molecules. A liquid crystal molecule having positive
dielectric constant anisotropy (so-called positive liquid crystal) is
preferably used as the liquid crystal molecule contained in the fine particle
34B.
[0059] While no voltage is applied between the lower electrode 32 and
the upper electrode 36, the major axis direction of each liquid crystal
molecule is parallel to the optical axis AX1 in the fine particle 34B. Here,
33
SP323000
the major axis of each liquid crystal molecule in the fine particle 34B is
parallel to the light-incident surface 10A of the light guide plate 10, and
intersects with each of the surfaces of the transparent substrates 31 and 37
at a small angle 01. Specifically, while no voltage is applied between the
lower electrode 32 and the upper electrode 36, the liquid crystal molecules
in the fine particle 34B are aligned while being tilted by the angle 91 in a
plane parallel to the light-incident surface 10A of the light guide plate 10.
The angle 01, which is referred to as pretilt angle, is preferably within a
range of 0.1° to 30° both inclusive, for example. The angle 01 is more
preferably within a range of 0.5° to 10° both inclusive, and still more
preferably within a range of 0.7° to 2° both inclusive. When the angle 01
is increased, scattering efficiency tends to be reduced due to the reason as
described later. In addition, an excessively decreased angle 01 causes a
variation in azimuth angle at which liquid crystal rises upon voltage
application. For example, rising of liquid crystal may occur in 180
degrees opposite orientation (i.e., reverse tilt may occur). This prevents
effective use of the difference in refractive index between the fine particle
34B and the bulk 34A, leading to a reduction in scattering efficiency, and
consequently luminance tends to be reduced.
[0060] While voltage is applied between the lower electrode 32 and the
upper electrode 36, the major axis direction of each liquid crystal molecule
intersects with (or is orthogonal to) the optical axis AX1 in the fine particle
34B. Here, the major axis of each liquid crystal molecule in the fine
particle 34B is parallel to the light-incident surface 10A of the light guide
plate 10, and intersects with each of the surfaces of the transparent
34
SP323000
substrates 31 and 37 at an angle 92 (for example, 90°) larger than the angle
91. Specifically, while voltage is applied between the lower electrode 32
and the upper electrode 36, each liquid crystal molecule in the fine particle
34B is aligned while being tilted by the angle 92 in a plane parallel to the
light-incident surface 10A of the light guide plate 10 or while straightly
standing at the angle 92 (=90°).
[0061] Although any material, which is optically anisotropic and
compoundable with liquid crystal, may be used as the above-described
monomer having alignable and polymerizable properties, low-molecular
monomer, which is curable with ultraviolet rays, is preferably used in the
present embodiment. During no voltage application, the direction of
optical anisotropy of the liquid crystal is preferably equal to that of a
polymerization product of the low-molecular monomer (a polymer material).
Hence, the liquid crystal and the low-molecular monomer are preferably
aligned in the same direction before ultraviolet curing. In the case where
liquid crystal is used as the fine particle 34B, and when the liquid crystal
includes rod-like molecules, the monomer material to be used also
preferably has a rod-like shape. Consequently, a material having both
polymerizable and liquid-crystalline properties is preferably used as the
monomer material. Preferred examples of the monomer material include a
material having, as a polymerizable functional group, one or more
functional group selected from a group configured of an acrylate group, a
methacrylate group, an acryloyloxy group, a methacryloyloxy group, a vinyl
ether group, and an epoxy group. Such functional groups are each
polymerizable through irradiation of ultraviolet rays, infrared rays, or
35
SP323000
electron beams, or through heating. A polyfunctionalized
liquid-crystalline material may be added in order to suppress a reduction in
degree of alignment during ultraviolet irradiation. In the case where the
bulk 34A has the above-described streaky structure, a bifunctional
liquid-crystalline monomer is preferably used as a material for the bulk 34A.
A monofunctional monomer may be added to the material for the bulk 34A
in order to adjust the temperature indicating a liquid crystallinity, or tri or
more functional monomer may be added thereto in order to increase
crosslink density.
[0062] For example, the drive circuit 50 controls the magnitude of a
voltage applied to the pair of electrodes (the partial electrode 32A and the
upper electrode 36) of each light modulation cell 30-1 such that the optical
axis AX2 of the fine particle 34B is parallel or substantially parallel to the
optical axis AX1 of the bulk 34A in one light modulation cell 30-1, while
the optical axis AX2 of the fine particle 34B intersects with or is orthogonal
to the optical axis AX1 of the bulk 34A in another light modulation cell
30-2. Specifically, the drive circuit 50 allows, through control of an
electric field, the respective optical axes AX1 and AX2 of the bulk 34A and
the fine particle 34B to be equal (or substantially equal) to each other, or to
be different from (or orthogonal to) each other.
[0063] When the drive circuit 50 receives a signal designating
three-dimensional display as a control signal 20A, the drive circuit 50
allows the light modulation device 30 to output a plurality of pieces of
linear illumination light. Specifically, the drive circuit 50 applies a
voltage causing the light modulation layer 34 to exhibit a scattering
36
SP323000
property to a plurality of particular partial electrodes 32B among the
plurality of partial electrodes 32A, while applying a voltage causing the
light modulation layer 34 to exhibit a transparent property to a plurality of
partial electrodes 32C other than the plurality of partial electrodes 32B
among the plurality of partial electrodes 32A. In other words, the drive
circuit 50 controls the magnitude of a voltage applied to the pair of
electrodes (the partial electrode 32A and the upper electrode 36) of each
light modulation cell 30-1 such that the optical axis AX2 of the fine particle
34B intersects with the optical axis AX1 of the bulk 34A in each cell 30a in
the light modulation device 30, while the optical axis AX2 of the fine
particle 34B is parallel to the optical axis AX1 of the bulk 34A in the cell
30b in the light modulation device 30. Consequently, the drive circuit 50
allows the scattering region 30B to be formed in the cell 30a including the
partial electrode 32B while allowing the transmissive region 30A to be
formed in the cell 30b including the partial electrode 32C so that linear
illumination light is output from the scattering region 30B.
[0064] When the drive circuit 50 receives a signal designating
two-dimensional display as the control signal 20A, the drive circuit 50
allows the light modulation device 30 to output planar illumination light.
Specifically, the drive circuit 50 applies a voltage causing the light
modulation layer 34 to exhibit a scattering property to each partial electrode
32A. In other words, the drive circuit 50 controls the magnitude of a
voltage applied to the pair of electrodes (the partial electrode 32A and the
upper electrode 36) of each light modulation cell 30-1 such that the optical
axis AX2 of the fine particle 34B intersects with or is orthogonal (or
37
SP323000
substantially orthogonal) to the optical axis AXl of the bulk 34A in any of
the light modulation cells 30-1 contained in the light modulation device 30.
Consequently, the drive circuit 50 allows the scattering regions 30B to be
formed in each light modulation cell 30-1 so that planar illumination light is
output from the scattering region 30B.
[0065] When the drive circuit 50 receives a signal on image data in
addition to a signal designating two-dimensional display as the control
signal 20A, the drive circuit 50 may allow the light modulation device 30 to
output planar illumination light having luminance distribution
corresponding to the image data (for example, planar illumination light
partially having a dark portion in a plane). In such a case, however, the
lower electrodes 32 are preferably in a layout corresponding to the pixel
layout of the display panel. In the case where the lower electrodes 32 are
in a layout corresponding to the layout of display pixels, the drive circuit 50,
depending on the image data, applies a voltage causing the light modulation
layer 34 to exhibit a scattering property to part of the plurality of partial
electrodes 32A, and applies a voltage causing the light modulation layer 34
to exhibit a transparent property to one or a plurality of partial electrodes
32A, to which the voltage causing the light modulation layer 34 to exhibit a
scattering property is not applied, among the plurality of partial electrodes
32A.
[0066] The reflector 40 returns leakage light, which comes from the
back of the light guide plate 10 through the light modulation device 30, to a
light guide plate 10 side. For example, the reflector 40 has functions of
reflection, diffusion, and scattering of light. This allows light emitted
38
SP323000
from the light source 20 to be efficiently used, and helps to increase front
luminance. The fine pattern surface of the reflector 40 is preferably a
mirror surface. In such a case, light emitted from the light modulation
layer 40 is allowed to be regularly reflected (mirror-reflected), and is thus
allowed to be efficiently reflected to a focal point C (described later). For
example, the reflector 40 is configured of foamed PET (polyethylene
terephthalate), a silver-evaporated film, a multilayer reflection film, white
PET, etc. In the case where the reflector 40 is allowed to have a function
of regular reflection (mirror reflection), the reflector 40 is preferably
configured of the silver-evaporated film, the multilayer reflection film, and
an aluminum-evaporated film, for example. In the case where the reflector
40 has a fine pattern thereon, the reflector 40 may be formed integrally with
the fine pattern by a process such as heat press molding or melt extrusion
molding using thermoplastic resin, or may be formed in the following way:
energy-ray (for example, ultraviolet-ray) curable resin is applied onto a
substrate including PET, etc., and then the pattern is transferred onto the
energy-ray curable resin to complete the reflector 40. Examples of the
thermoplastic resin include polycarbonate resin, acrylic resin such as
PMMA (polymethylmethacrylate), polyester resin such as polyethylene
terephthalate, amorphous copolymeric polyester resin such as MS
(copolymer of methylmethacrylate and styrene), polystyrene resin, and
polyvinyl chloride resin. In the case where the pattern is transferred onto
the energy-ray (for example, ultraviolet-ray) curable resin, the substrate
may include glass. In the case where the reflector 40 is importantly
aligned with the light modulation device 30, the reflector 40, the light guide
39
SP323000
plate 10, the transparent substrate 31, and the transparent substrate 37
preferably include the same material, or preferably have linear expansion
coefficients similar to one another. The reason for this is to prevent
displacement therebetween due to variation in outside temperature or heat.
[0067] For example, as illustrated in FIG. 16, the reflector 40 is
disposed at a distance HI from the bottom of the light modulation layer 34,
and has a reflecting surface 40A on a side close to the light modulation
layer 34. The reflecting surface 40A reflects part of light emitted from the
light source 20 toward the light emission surface 1A. Specifically, when
the display unit performs three-dimensional display, the reflector 40 reflects
linear illumination light generated in the scattering region 30B to generate
reflected light to be focused.
[0068] When the display unit performs three-dimensional display, the
reflector 40 may reflect linear illumination light, as an aggregation of a
plurality of pieces of dot illumination light generated in the scattering
region 30B, to generate reflected light to be focused. Moreover, when the
display unit performs two-dimensional display that allows different
two-dimensional images to be viewed from two perspectives, the reflector
40 may reflect dot illumination light generated in the scattering region 30B
to generate reflected light to be focused.
[0069] The reflector 40 reflects light toward a plane or the
neighborhood of the plane, the plane running through each of sites (the
scattering regions 30B) that generate the linear illumination light, and being
perpendicular to a plane containing the reflector 40. Specifically, when
the linear illumination light is assumed to have a light component that is
40
SP323000
parallel to a plane perpendicular to the site (the scattering regions 30B)
generating the linear illumination light, the reflector 40 has a
concave-convex shape causing generation of reflected light to be focused on
a segment or the neighborhood of the segment, the segment running through
the site (the scattering region 30B) that generates the linear illumination
light and being parallel to the normal to a plane containing the reflector 40.
Furthermore, when the linear illumination light is assumed to have a light
component that intersects with the plane perpendicular to the site (the
scattering regions 30B) generating the linear illumination light, the
reflector 40 has a concave-convex shape so as to reflect light from the linear
illumination light to the site (the scattering regions 30B) generating the
linear illumination light or to the neighborhood of the site. When the
reflecting surface 40A is configured to reflect generated light to a
generation site of the light, such light reflection is represented by the
following expressions, for example. Specifically, the reflector 40 has a
property of two-dimensionally recursive reflection.
Vector V of light before reflection=(Vx, Vy, Vz)
Vector V of light after reflection=(Vx, -Vy, -Vz)
[0070] For example, as illustrated in FIG. 16, when a light component is
assumed to exist, the light component being parallel to the plane
perpendicular to the site (the scattering regions 30B) generating the linear
illumination light, the reflector 40 has a concave-convex shape that allows
reflected light to be concentrated on a focal point C on a segment AX3 or
the neighborhood of the segment AX3 and directly below the scattering
region 30B. At this time, a distance H2 between the position of the focal
41
SP323000
point C and the top of the reflector 40 is shorter than the distance HI, and is
preferably equal to or more than (Hl/nl-Wl) and less than HI. The top of
the reflector 40 refers to a plane containing a plurality of apexes provided
in the top of the reflector 40. It is to be noted that Wl denotes a width of
the site (the scattering regions 3OB) generating the linear illumination light.
In addition, nl denotes the refractive index of a region between the top of
the reflector 40 and the position of the focal point C, and corresponds to the
refractive index of the transparent substrate 31 in the present embodiment.
The segment AX3 is a segment that runs through the site (the scattering
regions 30B) generating the linear illumination light and is parallel to the
normal to the plane containing the reflector 40.
[0071] For example, as illustrated in FIG. 17, when a light component is
assumed to exist, the light component being parallel to the plane
perpendicular to the site (the scattering regions 30B) generating the linear
illumination light, the reflector 40 may have a concave-convex shape that
allows reflected light to be concentrated on the focal point C on the segment
AX3 or the neighborhood of the segment AX3 and directly above the
scattering region 30B. In this case, the distance H2 is longer than the
distance HI, and is preferably larger than HI and equal to or less than
(Hl/nl+Wl). For example, as illustrated in FIG. 18, the reflector 40 may
have a concave-convex shape that allows reflected light to be concentrated
on the focal point C on the segment AX3 or the neighborhood of the
segment AX3 and within the scattering region 30B. In this case, the
distance H2 is roughly equal to the distance HI.
[0072] The reflector 40 has the reflecting surface 40A as part of an
42
SP323000
inner surface of a cylinder, having a central axis running through the focal
point C, at a position opposed to each of the sites (the scattering regions
30B) generating the linear illumination light. The reflecting surface 40A
preferably has a maximum depth at the position opposed to the scattering
region 30B.
[0073] When positions of the focal point C in FIGs. 16, 17, and 18 are
compared with one another, the position shown in FIG. 16 (a position
directly below the scattering region 30B) is most preferable. Here, the
position of the focal point C most preferably satisfies H2=Hl/nl. A pitch
P2 of a three-dimensional shape of the reflecting surface 40A of the
reflector 40 is most preferably equal or substantially equal to a pitch PI
between the scattering regions 3OB (the sites generating the linear
illumination light) in the light modulation layer 34. Furthermore, in this
case, a portion, which corresponds to the part of the inner surface of thecylinder,
of the reflecting surface 40A most preferably has a radius of
(H22+(P1/2)2)1/2. In the case of such a configuration, light reflected by the
reflecting surface 40A travels toward the focal point C, and is refracted by
the bottom of the transparent substrate 31, and recursively arrives at the
scattering region 30B.
[0074] Description is now made on front luminance distribution and
angular luminance distribution of reflected light generated by the reflector
40. (A) of FIG. 19 illustrates exemplary front luminance distribution and
angular luminance distribution of light LI3, which is emitted to a light
emission surface 1A side, as a part of light output from the scattering
regions 30B of the light modulation layer 34. (B) of FIG. 19 illustrates
43
SP323000
exemplary front luminance distribution and angular luminance distribution
of light L12, which is emitted to a side opposite to the light emission
surface 1A side and is reflected by the reflector 40, as another part of the
light output from the scattering regions 30B of the light modulation layer 34.
(A) and (B) of FIG. 19 illustrate results obtained assuming that the
refractive index n of the transparent substrate 41 is 1.515, HI is 700 jxm, H2
is 462 urn (=Hl/n), the distance (radius R) between the focal point C and the
reflecting surface 40A is 526 jj,m, PI and P2 are each 504 um, Wl is 63 um,
and the focal point C is directly below the scattering region 30B.
[0075] In each of (A) and (B) of FIG. 19, the left graph illustrates the
front luminance distribution, and the right graph illustrates the angular
luminance distribution. The front luminance distribution refers to in-plane
luminance distribution of light emitted in the normal direction to the light
modulation layer 34, in which an origin on the horizontal scale corresponds
to a position directly above the scattering region 30B. The angular
luminance distribution refers to angular distribution of luminance
distribution of light, which is diverged in the normal direction to the light
modulation layer 34, as part of light passing through an in-plane central
point in the scattering regions 30B, in which the origin in the horizontal
scale corresponds to the normal direction to the light modulation layer 34.
[0076] (A) and (B) of FIG. 19 teach that the front luminance
distribution and the angular luminance distribution of the light LI2 are
equal or substantially equal to the front luminance distribution and the
angular luminance distribution of the light L13. Specifically, the reflector
40 returns the light LI3 to the scattering regions 30B with almost no
44
SP323000
variation in front luminance distribution and in angular luminance
distribution of light output from the scattering regions 30B to the light
emission surface 1A side. This means that the reflector 40 has not only an
effect of reducing a proportion of the reflected light that enters the
transmissive region 30A of the light modulation device 34, but also an
effect of preventing increase of light emitted in an angular direction
unnecessary for three-dimensional display.
[0077] FIG. 20 schematically illustrates a reflector 41 according to a
comparative example together with a light source 21. The reflector 41 has
a paraboloid that reflects light from the light source 21 to generate parallel
light. In FIG. 20, light LI6 is directly emitted upward from the light
source 21, light L14 is emitted to the reflector 41 from the light source 21,
and part of the light L14, i.e., light L15, is reflected by the reflector 41.
(A) of FIG. 21 illustrates exemplary front luminance distribution and
angular luminance distribution of the light L16. (B) of FIG. 21 illustrates
exemplary front luminance distribution and angular luminance distribution
of the light LI5. In each of (A) and (B) of FIG. 21, the left graph
illustrates the front luminance distribution, and the right graph illustrates
the angular luminance distribution.
[0078] (A) and (B) of FIG. 21 teach that the front luminance
distribution and the angular luminance distribution of the light LI5 are
significantly different from the front luminance distribution and the angular
luminance distribution of the light L16. The front luminance distribution
of the light LI5 is roughly uniform regardless of places in a plane, and a
considerable proportion of light LI5 enters the transmissive region 30A of
45
SP323000
the light modulation device 34. Moreover, the angular luminance
distribution of the light LI 5 is extremely dense in the front direction, which
may disadvantageously reduce display quality in three-dimensional display.
[0079] FIG. 22 schematically illustrates a reflector 42 according to
another comparative example together with a light source 21. The
reflector 42 has a flat surface that regularly reflects light from the light
source 21. In FIG. 22, light LI6 is directly emitted upward from the light
source 21, and part of light emitted to the reflector 42 from the light source
21, i.e., light LI 7, is regularly reflected by the reflector 42. (A) of FIG. 23
illustrates exemplary front luminance distribution and angular luminance
distribution of the light LI6. (B) of FIG. 23 illustrates exemplary front
luminance distribution and angular luminance distribution of the light LI7.
In each of (A) and (B) of FIG. 23, the left graph illustrates the front
luminance distribution, and the right graph illustrates the angular luminance
distribution.
[0080] (A) and (B) of FIG. 23 teach that the front luminance
distribution and the angular luminance distribution of the light LI7 are
significantly different from the front luminance distribution and the angular
luminance distribution of the light LI6. The front luminance distribution
of the light LI7 has a peak in the front direction, but also has large
components in other directions, showing that a considerable proportion of
light LI 7 enters the transmissive region 30A of the light modulation device
34. Moreover, the angular luminance distribution of the light LI7 is
uniform regardless of angles, which may disadvantageously reduce display
quality in three-dimensional display.
46
SP323000
[0081] In the present embodiment, the reflector 40 may be bonded to
the transparent substrate 31. Possible types of bonding of the reflector 40
to the transparent substrate 31 include whole-surface bonding, peripheral
bonding (bonding over the annular portion other than the display region),
and point bonding (bonding at points in the portion other than the display
region). In the case of the whole-surface bonding of the reflector 40 to the
transparent substrate 31, the apex portions of the reflector 40 are possibly
bonded to the transparent substrate 31. In such a case, each of the apex
portions of the reflector 40 may be formed as a slightly flat surface.
[0082] In the present embodiment, for example, as illustrated in FIG. 24,
the reflector 40 may have a black 43 on each of sites to be in contact with
the transparent substrate 31. For example, the black 43 may be a mixture
of a black pigment with an adhesive agent for fixation of the reflector 40 to
the back of the transparent substrate 31.
[0083] A method of manufacturing the illumination device 1 of the
present embodiment is now described with reference to (A) to (C) of FIG. 25
to (A) to (C) of FIG. 27.
[0084] First, a transparent conductive film 32E such as an ITO film is
formed on the transparent substrate 31 including a glass substrate or a
plastic film substrate ((A) of FIG. 25). Subsequently, a resist layer is
formed over the entire surface, and an electrode pattern is then formed in
the resist layer by patterning. Subsequently, the lower electrode 32 is
formed through exposure and development, and then the resist layer is
removed ((B) of FIG. 25).
[0085] Examples of usable patterning processes include a
47
SP323000
photolithography process, laser processing, a pattern printing process, and a
screen printing process. In addition, for example, the resist layer may be
patterned by screen printing using a "Hyper-Etch" material from Merck Ltd.
followed by predetermined heating and rinsing. The electrode pattern is
determined based on a drive method and a division number of partial drive.
For example, the electrode pattern is formed at a pitch equal or similar to a
pixel pitch of a display unit to be used. The width of the formed electrode,
which is also determined depending on formation processes, is preferably as
narrow as possible from the viewpoint of extraction efficiency of light.
For example, the width of the formed electrode is 50 um or less, preferably
20 |a.m or less, and more preferably 5 (xm or less. In addition, the electrode
pattern may be formed by pattern printing of ITO nanoparticles followed by
baking of the printed pattern.
[0086] Subsequently, the alignment film 33 is applied onto the entire
surface, and then the alignment film 33 is dried and baked ((C) of FIG. 25).
In the case where a polyimide series material is used for the alignment film
33, NMP (N-methyl-2-pyrolidone) is often used as a solvent. In such a
case, a temperature of about 200°C is necessary in the air. In such a case,
when a plastic substrate is used as the transparent substrate 31, the
alignment film 33 may be vacuum-dried and baked at 100°C. Subsequently,
the alignment film 33 is subjected to rubbing treatment. This allows the
alignment film 33 to serve as an alignment film for horizontal alignment,
and allows pretilt to be formed in the rubbing direction of the alignment
film 33.
[0087] Similarly, a transparent conductive film such as an ITO film is
48
SP323000
formed on the transparent substrate 37 including a glass substrate or a
plastic film substrate. Subsequently, a resist layer is formed over the
entire surface, and an electrode pattern is formed in the resist layer by
patterning. Subsequently, the upper electrode 36 is formed through
exposure and development, and then the resist layer is removed.
Subsequently, the alignment film 35 is applied onto the entire surface, and
is then dried and baked. Subsequently, the alignment film 35 is subjected
to rubbing treatment. This allows the alignment film 35 to serve as an
alignment film for horizontal alignment, and allows pretilt to be formed in
the rubbing direction of the alignment film 35.
[0088] Subsequently, spacers 38 for forming a cell gap are dispersed on
the alignment film 33 by a dry or wet process ((A) of FIG. 26). In the case
where the light modulation cell 30-1 is formed by a one drop fill process,
the spacers 38 may be beforehand mixed in a mixture to be dropped.
Columnar spacers may be formed by a photolithography process in place of
the spacers 38. Substantially, a seal agent pattern 39 for bonding and
prevention of leakage of liquid crystal is applied onto the alignment film 35
in, for example, a frame pattern ((B) of FIG. 26). The seal agent pattern 39
is formed by a dispenser process or a screen printing process.
[0089] Although the one drop fill process (ODF process) is described
below, the light modulation cell 30-1 may be formed-by a vacuum injection
process or a roll bonding process.
[0090] First, a mixture 44 of liquid crystal and monomer is uniformly
dropped in a plane in amount corresponding to a volume determined based
on a cell gap, a cell area, etc. ((C) of FIG. 26). The mixture 44 is
49
SP323000
preferably dropped using a precision dispenser of a linear guide type, but
may be dropped by a die coater using the seal agent pattern 39 as a bank.
[0091] While the liquid crystal and the monomer may each include the
above-described materials, the weight ratio of the liquid crystal to the
monomer is 98:2 to 50:50 both inclusive, preferably 95:5 to 75:25 both
inclusive, and more preferably 92:8 to 85:15 both inclusive. Drive voltage
may be reduced by increasing a proportion of the liquid crystal. When the
liquid crystal is excessively increased, however, whiteness is reduced
during voltage application, or response speed is reduced after turning off
the voltage, and thus the cell is less likely to return to a transparent state.
[0092] A polymerization initiator is added to the mixture 44 in addition
to the liquid crystal and the monomer. A ratio of the polymerization
initiator to be added to the monomer is adjusted within a range of 0.1 to 10
wt% both inclusive depending on wavelengths of ultraviolet rays to be used.
In addition, a polymerization inhibitor, a plasticizer, and a viscosity
modifier may be added to the mixture 44 as necessary. In the case where
the monomer is a solid or gelatinous material at room temperature, a cap, a
syringe, and a substrate are preferably warmed.
[0093] The transparent substrate 31 and the transparent substrate 37 are
placed in one drop fill equipment (not shown), and are then subjected to
evacuation for bonding ((A) of FIG. 27). Subsequently, the bonded
substrates are released to the air, and the cell gaps are made even by
uniform pressurization under atmospheric pressure. While the cell gap is
appropriately selected based on a relationship between white luminance
(whiteness) and drive voltage, the cell gap is 5 to 40 nm both inclusive,
50
SP323000
preferably 6 to 20 urn both inclusive, and more preferably 7 to 10 um both
inclusive.
[0094] After the bonding, alignment treatment (not shown) is
preferably performed as necessary. When the resultant cells are inserted
between crossed-Nicol polarizing plates, and if light leakage occurs, the
cell is heated or left at room temperature for certain time for alignment.
Subsequently, the cell is irradiated with ultraviolet rays L3 so that the
monomer is polymerized into polymer ((B) of FIG. 27). In this way, the
light modulation device 30 is manufactured.
[0095] The temperature of the cell is preferably not varied during
ultraviolet irradiation. Thus, an infrared cut filter or UV-LED as a light
source is preferably used. The illuminance of the ultraviolet rays affects a
structure of a composite material. It is therefore preferable that the
illuminance is appropriately adjusted based on a liquid .crystal material and
a monomer material to be used, and compositions thereof. The
illuminance is preferably within a range of 0.1- to 500 mW/cm both
inclusive, and more preferably within a range of 0.5 to 30 mW/cm both
inclusive. The drive voltage tends to be lowered with a decrease in
illuminance of the ultraviolet rays. Illuminance of the ultraviolet rays is
therefore preferably selected in light of both productivity and properties.
[0096] Subsequently, the light modulation device 30 is bonded to the
light guide plate 10 ((C) of FIG. 27). While the bonding may be performed
by either of gluing and adhesion, the gluing or adhesion is preferably
performed using a material having a refractive index that is as close as
possible to. the refractive index of the light guide plate 10 and to the
51
SP323000
refractive index of the substrate materialfor the light modulation device 30.
Finally, a lead (not shown) is attached to each of the lower electrode 32 and
the upper electrode 36. In this way, the illumination device 1 of the
present embodiment is manufactured.
[0097] In this way, description has been made on a process where the
light modulation device 30 is first fabricated, and finally the light
modulation device 30 is bonded to the light guide plate 10. However, the
transparent substrate 37 having the alignment film 35 thereon may be
beforehand bonded to the surface of the light guide plate 10 before
fabrication of the illumination device 1. The illumination device 1 may be
fabricated in either of a sheet-feeding manner and a roll-to-roll manner.
[0098] Functions and effects of the illumination device 1 of the present
embodiment are now described.
[0099] In the illumination device 1 of the present embodiment, during
three-dimensional display, a voltage is applied to the pair of electrodes (the
partial electrode 32A and the upper electrode 36) of each light modulation
cell 30-1 such that the optical axis AX2 of the fine particle 34B intersects
with or is orthogonal to the optical axis AX1 of the bulk 34A in each cell
30a, while the optical axis AX2 of the fine particle 34B is parallel or
substantially parallel to the optical axis AX1 of the bulk 34A in each cell
30b. Consequently, in the light modulation device 30, each cell 30a
becomes the scattering region 30B, while each cell 30b becomes the
transmissive region 30A. As a result, light, which is emitted from the light
source 20 and enters the light guide plate 10, passes through each
transmissive region 30A in the light modulation device 30, and is scattered
52
SP323000
in each scattering region 30B in the light modulation device 30 (FIG. 14).
A part of the scattered light passes through the bottom of the scattering
regions 30B, and is reflected by the reflector 40 so as to be returned into the
light guide plate 10, and is then emitted from the top of the illumination
device 1. Another part of the scattered light travels toward the top of the
scattering region 30B and passes through the light guide plate 10, and is
then emitted from the top of the illumination device 1. In this way, during
three-dimensional display, light is substantially not emitted from the top of
the transmissive region 30A, but is emitted from the top of the scattering
region 30B. In this way, for example, as illustrated in FIG. 14, linear
illumination light is output in the front direction.
[0100] In the illumination device 1 of the present embodiment, during
two-dimensional display, for example, a voltage is applied to the pair of
electrodes (the partial electrode 32A and the upper electrode 36) of each
light modulation cell 30-1 such that the optical axis AX2 of the fine particle
34B intersects with or is orthogonal to the optical axis AXl of the bulk 34A
in each light modulation cell 30-1. Consequently, light is emitted from the
light source 20, enters the light guide plate 10, and is scattered by the
scattering region 30B formed in the entire light modulation device 30. A
part of the scattered light passes through the bottom of the scattering
regions 30B, and is reflected by the reflector 40 so as to be returned into the
light guide plate 10, and is then emitted from the top of the illumination
device 1. Another part of the scattered light travels toward the top of the
scattering region 30B and passes through the light guide plate 10, and is
then emitted from the top of the illumination device 1. In this way, during
53
«
SP323000
two-dimensional display, for example, light is emitted from the entire area
of the top of the light modulation device 30, and planar illumination light is
emitted in the front direction.
[0101] In the present embodiment, no parallax barrier is necessary for
three-dimensional display. Even if a parallax barrier is provided on a light
emission side of the illumination device 1, part of the light modulation layer
34 is formed to be the scattering regions 30B such that the scattering
regions 30B correspond to light-transmissive regions of the parallax barrier,
making it possible to extremely reduce a proportion of light that is output
from the light modulation layer 34 and absorbed by the parallax barrier.
Moreover, in the present embodiment, no cylindrical lens is necessary for
three-dimensional display; hence, disadvantageous aberration due to the
cylindrical lens does not occur.
[0102] In the present embodiment, a part of linear illumination light is
emitted to the reflector 40 side and is reflected by the reflector 40, and
therefore reflected light LI2 to be focused is generated. This allows front
intensity distribution and angular intensity distribution of the reflected light
LI2 to be similar to front intensity distribution and angular intensity
distribution of the light LI3, as another part of linear illumination light,
emitted to a side opposite to the reflector 40 side. As a result, it is
possible to reduce a proportion of the reflected light L13 emitted from the
top of the reflector through a region (i.e., the transmissive region 30A)
different from the scattering region 30B during three-dimensional display
compared with a case where the top of the reflector is configured of a flat
surface (see FIG. 22) or is configured of a paraboloid generating parallel
54
SP323000
light (see FIG. 20). Furthermore, it is possible to reduce a proportion of
the reflected light L12 emitted in an angular direction unnecessary for
three-dimensional display. As a result, in the case where such an
illumination device 1 is used as the backlight of the display unit for
three-dimensional display, it is possible to suppress formation of a double
image in three-dimensional display. Consequently, display quality is
improved in three-dimensional display.
[0103] Other effects of the illumination device 1 of the present
embodiment are now described.
[0104] In general, PDLC is formed by a process where the liquid crystal
material is mixed with an isotropic low-molecular material, and then phase
separation is induced in such a mixture through ultraviolet irradiation or
drying of a solvent, and thus includes a composite layer in which fine
particles of the liquid crystal material are dispersed in the polymer material.
During no voltage application, the liquid crystal material in the composite
layer is randomly oriented; hence, the PDLC exhibits a scattering property.
During voltage application, the liquid crystal material is aligned in an
electric field direction; hence, when the ordinary refractive index of the
liquid crystal material is equal to the refractive index of the polymer
material, the PDLC exhibits a highly transparent property in a front
direction (the normal direction to the PDLC). In the case of such a liquid
crystal material, however, the extraordinary refractive index of the liquid
crystal material is significantly different from the refractive index of the
polymer material in an oblique direction, and therefore the PDLC exhibits a
scattering property in the oblique direction though the PDLC is transparent
55
• SP323000
in the front direction.
[0105] In general, a light modulation device using PDLC often has a
structure where the PDLC is sandwiched between two glass plates each
having a transparent conductive film on its surface. In the case where
light obliquely enters, from air, the light modulation device having the
structure as described above, such obliquely incident light is refracted due
to a difference in refractive index between air and the glass plate, and thus
enters the PDLC at a smaller angle. As a result, significant scattering does
not occur in such a light modulation device. For example, when light
enters the light modulation device from air at an angle of 80°, the incidence
angle of the light on the PDLC is decreased to about 40° due to refraction at
an interface of glass.
[0106] In an edge-light-type illumination device using a light guide
plate, however, since light is incident through the light guide plate, the light
crosses the PDLC at a large angle of about 80°. As a result, the
extraordinary refractive index of the liquid crystal material greatly differs
from the refractive index of the polymer material. Furthermore, light
crosses the PDLC at a further large angle, and thus an optical path along
which the light is scattered is lengthened. For example, in the case where
fine particles of a liquid crystal material having an ordinary refractive index
of 1.5 and an extraordinary refractive index of 1.65 are dispersed in a
polymer material having a refractive index of 1.5, no difference in
refractive index exists in a front direction (the normal direction to PDLC),
but a large difference in refractive index exists in an oblique direction.
This prevents a reduction in scattering in the oblique direction, leading to
56
SP323000
bad viewing angle characteristics. Furthermore, in the case where an
optical film such as a diffuser film is provided on the light guide plate,
oblique leakage light is also diffused in the front direction by the diffuser
film, resulting in an increase in light leakage in the front direction and in
turn a reduction in modulation ratio in the front direction.
[0107] In contrast, in the present embodiment, the bulk 34A and the
fine particle 34B each mainly include an optically anisotropic material;
hence, scattering performance is reduced in the oblique direction, making it
possible to improve transparency. For example, when the bulk 34A and the
fine particle 34B mainly include the optically anisotropic materials, of
which the ordinary refractive indexes are equal to each other and the
extraordinary refractive indexes are also equal to each other, the optical
axis directions of them are equal or substantially equal to each other in a
region where no voltage is applied between the lower electrode 32 and the
upper electrode 36. Consequently, a difference in refractive index is
reduced or eliminated in any of directions including the front direction
(normal direction to the light modulation device 30) and the oblique
direction, leading to high transparency. As a result, light leakage is
reduced or almost eliminated in a wide viewing angle range, making it
possible to improve viewing angle characteristics.
[0108] For example, when a liquid crystal having an ordinary refractive
index of 1.5 and an extraordinary refractive index of 1.65 is mixed with a
liquid crystalline monomer having an ordinary refractive index of 1.5 and
an extraordinary refractive index of 1.65, and when the liquid crystalline
monomer is polymerized while the liquid crystal and the liquid crystalline
57
SP323000
monomer are aligned by an alignment film or an electric filed, the optical
axis of the liquid crystal corresponds to the optical axis of the polymer
formed through polymerization of the liquid crystalline monomer. This
allows the refractive indexes of them to be equal to each other in any of
various directions. In the case of such a configuration, a high transparent
state is thus achieved, leading to further improvement in viewing angle
characteristics.
[0109] In the present embodiment, for example, as illustrated in (A) and
(B) of FIG. 14, luminance of the transmissive region 30A (luminance in
black display) is lower than that in the case where light is uniformly emitted
over the entire area (the dashed-dotted line in (B) of FIG. 14). On the
other hand, luminance of the scattering region 30B is extremely high
compared with the case where light is uniformly emitted over the entire area
(the dashed-dotted line in (B) of FIG. 14), and luminance in partial white
display (luminance enhancement) increases in correspondence to a
reduction in luminance of the transmissive region 30A.
[0110] The luminance enhancement refers to a technique that increases
luminance in partial white display compared with luminance in the case
where white display is performed over the entire area. This is a common
technique used in CRT, PDP, etc. In the liquid crystal display, however,
the backlight uniformly emits light over the entire area regardless of
images; hence, partial increase in luminance is not allowed. In the case
where the backlight is configured of an LED backlight in which a plurality
of LEDs are two-dimensionally arranged, the LEDs may be partially turned
off. In the case of such a configuration, however, no diffused light is
58
SP323000
supplied from a dark region in which each LED is turned off, leading to a
reduction in luminance compared with a case where all the LEDs are turned
on. It is possible to increase luminance by increasing a current flowing
through each of LEDs being partially turned on. In the case of such a
configuration, however, a large amount of current flows in an extremely
short time, thereby leading to problems in circuit load and reliability.
[0111] In contrast, in the present embodiment, since the bulk 34A and
the fine particle 34B each mainly include an optically anisotropic material,
scattering is suppressed in the oblique direction, and thus small quantity of
leakage light comes from the light guide plate in a dark state.
Consequently, light is guided from a partially dark portion to a partially
light portion; hence, luminance enhancement is achievable without
increasing input power to the illumination device 1.
[0112] In the present embodiment, in a region where no voltage is
applied between the lower electrode 32 and the upper electrode 36, the
optical axis AX2 of the fine particle 34B is parallel to the light-incident
surface 10A of the light guide plate 10, and intersects with each of the
surfaces of the transparent substrates 31 and 37 at a small angle 61.
Specifically, the liquid crystal molecules contained in the fine particle 34B
are aligned while being tilted by the angle 91 in a plane parallel to the
light-incident surface 10A (aligned with a pretilt angle). As a result, when
voltage is applied between the lower electrode 32 and the upper electrode
36, the liquid crystal material contained in the fine particle 34B does not
rise in random orientation, but rises in a plane parallel to the light-incident
surface 10A. At this time, the optical axis AX1 of the bulk 34A intersects
59
SP323000
with or is orthogonal to the optical axis AX2 of the fine particle 34B in the
plane parallel to the light-incident surface 10A. Here, light enters the
light guide plate 10 from the light-incident surface 10A, and part of the
light, which oscillates perpendicularly to the transparent substrate 31, is
influenced by a difference between the extraordinary refractive index of the
fine particle 34B and the ordinary refractive index of the bulk 34A. In this
case, a large difference exists between the extraordinary refractive index of
the fine particle 34B and the ordinary refractive index of the bulk 34A,
thereby leading to high scattering efficiency for light oscillating
perpendicularly to the transparent substrate 31. On the other hand, another
part of the light, which oscillates parallel to the transparent substrate 31, is
influenced by a difference between the ordinary refractive index of the fine
particle 34B and the extraordinary refractive index of the bulk 34A. In
this case, a large difference also exists between the ordinary refractive
index of the fine particle 34B and the extraordinary refractive index of the
bulk 34A, thereby leading to high scattering efficiency for light oscillating
parallel to the transparent substrate 31. Hence, light propagating through
a region where a voltage is applied between the lower electrode 32 and the
upper electrode 36 contains a large amount of oblique components. For
example, in the case where an acryl light guide plate is used as the light
guide plate 10, light propagates at an angle of 41.8° or more within the
region where a voltage is applied between the lower electrode 32 and the
upper electrode 36. This results in an increase in difference in refractive
index in any of various directions including the oblique direction, and thus
high scattering performance is achieved, thereby making it possible to
60
SP323000
increase display luminance. Moreover, it is possible to further increase
display luminance by the effect of the above-described luminance
enhancement.
[0113] For example, in the case where the optical axis AX1 of the bulk
34A and the optical axis AX2 of each fine particle 34B are disposed
perpendicularly to the light-incident surface 10A of the light guide plate 10
during no voltage application, and when the liquid crystal material
contained in the fine particle 34B rises in a plane perpendicular to the
light-incident surface 10A upon application of a voltage between the lower
electrode 32 and the upper electrode 36, light oscillating perpendicularly to
the transparent substrate 31 is influenced by the difference between the
extraordinary refractive index of the fine particle 34B and the ordinary
refractive index of the bulk 34A as with the case described above, but light
oscillating parallel to the transparent substrate 31 is influenced by the
difference between the ordinary refractive index of the fine particle 34B and
the ordinary refractive index of the bulk 34A. Here, no difference or
almost no difference exists between the ordinary refractive index of the fine
particle 34B and the ordinary refractive index of the bulk 34A. Hence, in
the light entering from the light-incident surface 10A, the light oscillating
perpendicularly to the transparent substrate 31 is influenced by the large
difference in refractive index as with the case described above, but the light
oscillating parallel to the transparent substrate 31 is not influenced or
almost not influenced by a difference in refractive index. As a result,
although scattering efficiency is high for the light oscillating
perpendicularly to the transparent substrate 31, the scattering efficiency is
61
SP323000
low or zero for the light oscillating parallel to the transparent substrate 31.
Consequently, in the case where the optical axis AXl and the optical axis
AX2 are disposed perpendicularly to the light-incident surface 10A, the
scattering efficiency is low compared with a case where the optical axis
AXl and the optical axis AX2 are disposed parallel to the light-incident
surface 10A; hence, lower luminance is extracted from the light guide plate
10 than that in the case of the light modulation device 30 in the present
embodiment.
[0114] As described above, the present embodiment achieves an
increase in display luminance while light leakage is reduced or almost
eliminated in a wide viewing angle range. As a result, it is possible to
increase a modulation ratio in the front direction.
[0115] [2. Modifications of First Embodiment]
Modifications of the first embodiment are now described. Any of
combinations of the following Modifications may be applied to the display
unit 1 according to the first embodiment within the scope without any
inconsistency therebetween.
(First Modification)
In the above-described embodiment, the light modulation device 30 has
been bonded to the back (bottom) of the light guide plate 10 in a tight
contact manner with no air layer therebetween, but, for example, as
illustrated in FIG. 28, the light modulation device 30 may be bonded to the
top of the light guide plate 10 in a tight contact manner with no air layer
therebetween. For example, as illustrated in FIG. 29, the light modulation
device 30 may be provided within the light guide plate 10. In such a case,
62
SP323000
EL
it is also necessary for the light modulation device 30 to be bonded to the
light guide plate 10 in a tight contact manner with no air layer
therebetween.
[0116] (Second Modification)
Although no component has been provided on the light guide plate 10
in the above-described embodiment and the above-described Modification
thereof, an optical sheet 90 (for example, a diffuser plate, a diffuser sheet, a
lens film, and a polarization separation sheet) may be provided thereon, for
example, as illustrated in FIG. 30. In the case of such a configuration, part
of light, which is obliquely emitted from the light guide plate 10, rises in
the front direction, thereby allowing an effective increase in front
luminance.
[0117] (Third Modification)
Although the upper electrode 36 has been a solid film formed over the
entire surface, and the lower electrode 32 has been configured of a plurality
of strip-like partial electrodes 32A in the above-described embodiment and
the above-described Modifications thereof, for example, the upper electrode
36 may be configured of a plurality of strip-like partial electrodes 32A, and
the lower electrode 32 may be a solid film formed over the entire surface.
Alternatively, for example, the lower electrode 32 may be configured of a
plurality of strip-like partial electrodes 32A, and the upper electrode 36
may be also configured of a plurality of strip-like partial electrodes 32A.
[0118] (Fourth Modification)
In the case where the lower electrode 32 is configured of a plurality of
block-like partial electrodes 32A arranged in a matrix in the
63
SP323000
above-described embodiment and the above-described Modifications
thereof, one of a source and a drain of TFT may be connected to each partial
electrode 32A, a scan line may be connected to a gate of the TFT, and the
other of the source and the drain of the TFT, which is not connected to the
partial electrode 32A, may be connected to a data line. In this case, the
drive circuit 50 may be configured to sequentially select a plurality of scan
lines, and apply a signal voltage corresponding to an image signal to each
data line. In other words, the drive circuit 50 may be configured to
perform active matrix drive on each partial electrode 32A.
[0119] (Fifth Modification)
In the above-described embodiment and the above-described
Modifications thereof, the drive circuit 50 may apply the same voltage to
the individual partial electrodes 32A regardless of distances from the light
source 20, or may apply voltages corresponding to the distances from the
light source 20 to the individual partial electrodes 32A. In the case of
such a configuration, when illumination light is output such that only a
particular portion of the top of the illumination device 1 shows white
luminance, it is possible to reduce possibility of occurrence of a difference
in white luminance level between a case where the portion showing white
luminance is close to the light source 20 and a case where the portion is far
from the light source 20.
[0120] (Sixth Modification)

SP323000
I 47^13'
0 1 NOV 2013
[Claim 1]
An illumination device, comprising:
an illumination optical system configured to generate linear
illumination light including a plurality of pieces of linear or dot
illumination light arranged two-dimensionally; and
a reflector reflecting the linear illumination light, the reflector being
configured to reflect the linear illumination light onto a plane or the
neighborhood of the plane, the plane running through each of sites that
generate the linear illumination light and being perpendicular to a plane
containing the reflector.
[Claim 2]
The illumination device according to claim 1, wherein
when the linear illumination light is assumed to have a light
component that is parallel to a plane perpendicular to the site generating the
linear illumination light, the reflector generates reflected light to be
focused on a segment or the neighborhood of the segment, the segment
running through the site generating the linear illumination light and being
parallel to the normal to the plane containing the reflector.
[Claim 3]
The illumination device according to claim 2, wherein
117
OpT^NAL
CLAIMS
A SP323000
^ ORIGINAL , . , 9 i 47«*13.
the reflector has a surface shape allowing the reflected light to be
focused directly below the site generating the linear illumination light.
0 1 NOV 2013
[Claim 4]
The illumination device according to claim 2, wherein
the reflector has a surface shape allowing the reflected light to be
focused on a position satisfying the following expression,
Hl/nl-Wl - SP323000
\ 4 47^13 the reflector is bonded to the light guide pwfe. ~J
[Cairn ,4] ° 1 NOV 2013
The illumination device according to claim 1, wherein
the illumination optical system includes
a first transparent substrate and a second transparent substrate
disposed oppositely to each other with the sites generating the linear
illumination light therebetween,
an electrode provided on a surface of one or both of the first
transparent substrate and the second transparent substrate,
a light source configured to apply light to an end face of the first
transparent substrate,
a light modulation layer that is provided in a clearance between the
first transparent substrate and the second transparent substrate, and is
configured to exhibit a scattering or transparent property to light from the
light source depending on magnitude of an electric field, and
a drive section configured to drive the electrode,
the light modulation layer exhibits the transparent property to light
from the light source in the case of a relatively low ele-ctric field, while
exhibiting the scattering property to light from the light source in the case
of a relatively high electric field, and
the drive section drives the electrode to allow the light modulation
layer to have a plurality of first regions each exhibiting the scattering
property to allow the linear illumination light to be emitted from each of the
first regions.
122
M ORIGINAL SP323000
0 1 NOV 22001133
[Claim 15]
The illumination device according to claim 14, wherein
the drive section drives the electrode to allow the entire light
modulation layer to have the first region to allow planar illumination light
to be emitted from the entire light modulation layer.
[Claim 16]
A display unit, comprising:
a display panel including a plurality of pixels to be driven based on
image signals; and
an illumination device configured to illuminate the display panel,
wherein the illumination device includes
an illumination optical system configured to generate linear
illumination light including a plurality of pieces of linear or dot
illumination light arranged two-dimensionally, and
a reflector reflecting the linear illumination light, the reflector being
configured to reflect the linear illumination light onto a plane or the
neighborhood of the plane, the plane running through each of sites that
generate the linear illumination light and being perpendicular to a plane
containing the reflector.
[Claim 17]
The display unit according to claim 16, wherein
the illumination device includes
123
* r \ M M mm SP323000 ORIGINAL - ^ .
a first transparent substrate and a second transparent substrate
disposed oppositely to each other with the sites generating the linear
illumination light therebetween,
an electrode provided on a surface of one or both of the first
transparent substrate and the second transparent substrate,
a light source configured to apply light to an end face of the first
transparent substrate,
a light modulation layer that is provided in a clearance between the
first transparent substrate and the second transparent substrate, and is
configured to exhibit a scattering or transparent property to light from the
light source depending on magnitude of an electric field, and
a drive section configured to drive the electrode based on image
signals,
the light modulation layer exhibits a transparent property to light
from the light source in the case of a relatively low electric field, while
exhibiting a scattering property to light from the light source in the case of
a relatively high electric field, and
the drive section drives the electrode into a three-dimensional
display mode to allow the light modulation layer to have a plurality of first
regions exhibiting the scattering property to allow the linear illumination
light to be emitted from each of the first regions.
[Claim 18]
The display unit according to claim 17, wherein
the display unit further includes a pair of polarizing plates opposed
124
* ORIGINAL SP323000
0 1 NOV 2013
to each other with the display panel therebetwteenV 4 47^13
the light modulation layer includes a first optically anisotropic
region having relatively high responsivity to an electric field, and a second
optically anisotropic region having relatively low responsivity to an electric
field,
when the light modulation layer exhibits the transparent property,
each of the first region and the second region mainly has an optical axis
component in a direction parallel to a transmission axis of the polarizing
plate on a side close to the illumination device between the pair of the
polarizing plates, and
when the light modulation layer exhibits the scattering property, the
second region mainly has an optical axis component in the direction parallel
to the transmission axis of the polarizing plate on the side close to the
illumination device between the pair of the polarizing plates, and the first
region has an optical axis in a direction that intersects with or is orthogonal
to the optical axis of the second region, and intersects with or is orthogonal
to the first transparent substrate.