DESCRIPTION
Title of Invention
LIGHTING UNIT, DISPLAY, AND THREE-DIMENSIONAL DISPLAY
Technical Field
[0001] The invention relates to a lighting unit provided with a light modulation device
that exhibits scattering property or transparency to light. Moreover, the invention
relates to a display and a three-dimensional display that include the above-described
lighting unit.
Background Art
[0002] In recent years, a backlight of a scan system is used to improve moving picture
responsiveness of a liquid crystal television. Further, recently, the scan system attracts
attention to suppress crosstalk of 3D display using a shutter eyeglasses system.
Moreover, particularly in a large television, a combination of an edge light and a light
guide plate is a main stream to meet request of thickness reduction, and a backlight
capable of being scan driven in a light guide plate system is desired (see PTLs 1 and 2).
Citation list
Patent Literature
[0003] PTL 1: Japanese Unexamined Patent Application Publication No. H1 -082019
PTL2: U.S. Patent Application Publication No. 2005/00075616 specification
PTL 3: Japanese Unexamined Patent Application Publication No. 2001-92370
PTL 4: Japanese Unexamined Patent Application Publication No. 2009-283383
Summary of Invention
[0004] Incidentally, the backlight in such a scan system has an issue of display
luminance being dark. For example, when a screen is segmented into eight sections, if
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power enough to obtain eight times luminance can be supplied to a light source in a
display of segmented one section, the display luminance is equivalent in principle to
luminance when scan is not performed. However, power corresponding to about two
times luminance is only supplied actually, and thus the display luminance is lowered.
In addition, it is not preferable that a large power be applied to a light source in such an
extremely short time in terms of light use efficiency and low power consumption.
Further, reliability of the circuit board is necessarily secured in consideration of inrush
power (specifically, large power temporality flows through the light source upon power
supply), and thus it is unfit for cost reduction.
[0005] Moreover, in a large television, employment of an edge light guide plate is
progressing in order to meet request of thickness reduction of a backlight, similarly to
medium and small-sized liquid crystal displays. For example, PTL 3 discloses that, in
an edge light guide plate system, a light guide plate is configured of a plurality of blocks,
a reflector is provided between the blocks to achieve scan of strip-shaped illumination
light. In addition, for example, PTL 4 discloses that, instead of dividing a light guide
plate, a prism structure is formed on a main surface of a light guide plate to achieve scan
of strip-shaped illumination light. However, issues occur in all of display luminance,
consumed power, and reliability of a circuit board even by using the methods described
in these literatures.
[0006] In view of the above circumstances, it is a first object of the invention to
provide a lighting unit having all of high luminance, low power consumption, and high
reliability of a circuit board in a scan system. In addition, it is a second object of the
invention to provide a display and a three-dimensional display that include such a
lighting unit.
[0007] A lighting unit according to the invention includes a light guide plate, a light
source disposed on a side surface of the light guide plate, and a light modulation device
disposed on a surface or in an inside of the light guide plate and bonded to the light
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guide plate. The light modulation device includes a pair of transparent substrates
disposed opposite to each other with a distance in between, a pair of electrodes disposed
on respective surfaces of the pair of transparent substrates, and a light modulation layer
provided in a gap between the pair of transparent substrates. Here, one or both of the
pair of electrodes have a plurality of partial electrodes arranged in a direction
orthogonal to a light incident surface of side surfaces of the light guide plate, the light
incident surface receiving light from the light source. The light modulation layer
totally or partially exhibits scattering property or transparency to the light from the light
source depending on a magnitude of an electric field generated by the electrodes. A
drive circuit sequentially drives the plurality of partial electrodes on a predetermined
unit basis to scan a region exhibiting the scattering property of the light modulation
layer in the direction orthogonal to the light incident surface.
[0008] A display according to the invention includes: a lighting unit outputting
illumination light; a display panel modulating the illumination light to output a picture;
and a drive circuit driving the lighting unit and the display panel. The lighting unit
included in the display includes the same components as those of the lighting unit
described in the previous paragraph.
[0009] A three-dimensional display according to the invention includes a display
outputting a picture and a control signal; and shutter glasses having a right-eye shutter
and a left-eye shutter, the right-eye shutter and the left-eye shutter performing
I transmission and blocking of the picture based on the control signal. The display
included in the three-dimensional display includes a lighting unit outputting
illumination light, a display panel modulating the illumination light to output the picture,
an output circuit outputting the control signal, and a drive circuit driving the lighting
unit, the display panel, and the output circuit. In this case, the lighting unit includes
the same components as those in the lighting unit described in the paragraph before the
previous paragraph.
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[0010] In the lighting unit, the display, and the three-dimensional display of the
invention, the plurality of partial electrodes arranged in the direction orthogonal to the
light incident surface are sequentially driven on a predetermined unit basis.
Accordingly, the region exhibiting the scattering property (hereinafter, referred to as
"scattering region") of the light modulation layer is scanned in the direction orthogonal
to the light incident surface during the process in which the light emitted from the light
source propagates through the light guide plate. As a result, the light that is scattered
in the scattering region and is to be emitted from the upper surface of the lighting unit to
the outside is scanned in the direction orthogonal to the light incident surface. At this
time, the light emitted from the light source is scarcely scattered in the region exhibiting
the transparency (hereinafter, referred to as "transparent region") of the light modulation
layer, and thus light is scarcely leaked from the transparent region. Therefore, the light
emitted from the light source is guided from the transparent region to the scattering
region, and thus luminance higher than that in an existing system driving the light
source is obtainable. Further, since scan driving of the light source is not performed,
high luminance is obtainable without increasing power supplied to the lighting unit. In
addition, in the invention, as described above, since the scan driving of the light source
is not performed, inrush power that occurs in the case where large power is supplied to
the light source in an extremely short time to perform the scan driving is not necessarily
considered, and reliability of the circuit board is not impaired.
[0011] According to the lighting unit, the display, and the three-dimensional display
of the invention, the light that is to be emitted from the upper surface of the lighting unit
to the outside is scanned by scanning the scattering region of the light modulation layer
instead of the scan driving of the light source, and therefore in the scan system, all of
high luminance, low power consumption, high reliability of the circuit board are
achievable at a time.
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Brief Description of Drawings
[0012] [FIG. 1] FIG. 1 is a sectional diagram illustrating an example of a
configuration of a backlight according to a first embodiment of the invention.
[FIG. 2] FIG. 2 is a perspective view illustrating an example of a configuration of a
light source of FIG. 1.
[FIG. 3] FIG. 3 is a perspective view illustrating another example of the configuration
of the light source of FIG. 1.
[FIG. 4] FIG. 4 is a perspective view illustrating an example of a configuration of
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electrodes of FIG. 1.
[FIG. 5] FIG. 5 is a sectional diagram illustrating another example of the
configuration of the backlight of FIG. 1.
[FIG. 6] FIG. 6 is a schematic diagram for explaining a configuration when a voltage
is not applied to a light modulation device of FIG. 1.
[FIG. 7] FIG. 7 is a schematic diagram for explaining a configuration when a voltage
is applied to the light modulation device of FIG. 1.
[FIG. 8] FIG. 8 is a schematic diagram for explaining a function of the backlight of
FIG. 1.
[FIG. 9] FIG. 9 is a schematic diagram for explaining scanning in a scattering region
in the light modulation device.
[FIG. 10] FIG. 10 is a schematic diagram for explaining scanning in the scattering
region in the light modulation device.
[FIG. 11] FIG. 11 is a schematic diagram for explaining scanning in the scattering
region in the light modulation device.
[FIG. 12] FIG. 12 is a schematic diagram for explaining scanning in the scattering
region in the light modulation device.
[FIG. 13] FIG. 13 is a sectional diagram for explaining processes of manufacturing
1 the backlight of FIG. 1.
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[FIG. 14] FIG. 14 is a sectional diagram for explaining manufacturing processes
following the processes of FIG. 13.
[FIG. 15] FIG. 15 is a sectional diagram for explaining manufacturing processes
following the processes of FIG. 14.
[FIG. 16] FIG. 16 is a sectional diagram illustrating an example of a configuration of
a backlight according to a second embodiment of the invention.
[FIG. 17] FIG. 17 is a schematic diagram for explaining a configuration when a
voltage is not applied to a light modulation device of FIG. 16.
[FIG. 18] FIG. 18 is a schematic diagram for explaining a configuration when a
voltage is applied to the light modulation device of FIG. 16.
[FIG. 19] FIG. 19 is a schematic diagram for explaining an example of relationship
between scan timing of partial electrodes and blinking timing of the light source.
[FIG. 20] FIG. 20 is a schematic diagram for explaining another example of the
relationship between the scan timing of the partial electrodes and the blinking timing of
the light source.
[FIG. 21] FIG. 21 is a plan view illustrating a first modification of the configuration
of the electrode of FIG. 1.
[FIG. 22] FIG. 22 is a plan view illustrating a second modification of the
configuration of the electrode of FIG. 1.
[FIG. 23] FIG. 23 is a plan view illustrating an example of a voltage applied to each
thin wire electrode of FIG. 22.
[FIG. 24] FIG. 24 is a plan view illustrating a third modification of the configuration
of the electrode of FIG. 1.
[FIG. 25] FIG. 25 is a sectional diagram illustrating a first modification of the
configuration of the backlight of FIG. 1 or FIG. 16.
[FIG. 26] FIG. 26 is a sectional diagram illustrating a second modification of the
configuration of the backlight of FIG. 1 or FIG. 16.
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[FIG. 27] FIG. 27 is a sectional diagram illustrating a third modification of the
configuration of the backlight of FIG. 1 or FIG. 16.
[FIG. 28] FIG. 28 is a sectional diagram illustrating an example of a display according
to an application example.
[FIG. 29] FIG. 29 is a schematic diagram for explaining an example of relationship
between scan timing of pixels of a display panel and scan timing of partial electrodes in
the display of FIG. 28.
[FIG. 30] FIG. 30 is a perspective view illustrating an example of a three-dimensional
display according to another application example.
Description of Embodiments
[0013] Hereinafter, embodiments for carrying out the invention will be described in
detail with reference to drawings. Note that description will be given in the following
order.
1. First embodiment (FIG. 1 to FIG. 15)
An example in which a horizontal alignment inversion PDLC is provided in a
backlight
2. Second embodiment (FIG. 16 to FIG. 18)
An example in which a vertical alignment inversion PDLC is provided in a backlight
3. Modifications (FIG. 19 to FIG. 27)
4. Application examples (FIG. 28 to FIG. 30)
An example in which a backlight is used as a light source of a display
[0014] <1. First Embodiment
FIG. 1(A) is a sectional diagram illustrating an example of a schematic
configuration of a backlight 1 according to a first embodiment of the invention. The
backlight 1 corresponds to a specific example of a lighting unit of the invention. FIG.
1(B) is a sectional diagram illustrating an example of a schematic configuration of a
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light modulation device in the backlight 1 of FIG. 1 (A). Note that FIGs. 1 (A) and 1 (B)
are schematic illustration, and the illustration may not be the same as actual dimensions
and shapes. The backlight 1 emits illumination light from an upper surface thereof,
and for example, is used for illuminating a liquid crystal display panel and the like from
behind. The backlight 1 includes, for example, a light guide plate 10, a light source 20
disposed on a side surface of the light guide plate 10, a light modulation device 30 and a
reflector 40 disposed on a back of the light guide plate 10, and a drive circuit 50 driving
the light source 20 and the light modulation device 30.
[0015] The light guide plate 10 guides light from the light source 20 that is disposed
on the side surface of the light guide plate 10 to an upper surface of the light guide plate
10. The light guide plate 10 has a shape corresponding to a display panel (not
illustrated) disposed on the upper surface of the light guide plate 10, for example, a
rectangular parallelepiped shape surrounded by the upper surface, a lower surface, and
side surfaces. Note that, in the following description, the side surface that receives the
light from the light source 20, of the side surfaces of the light guide plate 10 is referred
to as a light incident surface 10A. For example, the light guide plate 10 has a
predetermined-patterned shape on one or both of the upper surface and the lower
surface, and has a function to scatter and uniformize the light entering from the light
incident surface 10A. Note that, when a voltage applied to the backlight 1 is
modulated to uniformize luminance, a flat light guide plate not patterned may be used as
the light guide plate 10. For example, the light guide plate 10 functions as a support
body supporting an optical sheet (for example, a diffuser panel, a diffuser sheet, a lens
film, or a polarization separation sheet) disposed between the display panel and the
backlight 1. The light guide plate 10 is formed to contain a transparent thermoplastic
resin such as polycarbonate resin (PC) and acrylic resin (polymethyl methacrylate
(PMMA).
[0016] For example, as illustrated in FIG. 2(A), the light source 20 includes a linear
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light source 21 and a reflective mirror 22. The linear light source 21 is formed of, for
example, a hot cathode fluorescent lamp (HCFL) or a cold cathode fluorescent lamp
(CCFL). The reflective mirror 22 reflects, to the light incident surface 10A side, light
toward a direction not directly entering the light incident surface 10A out of light
emitted from the linear light source 21. For example as illustrated in FIG. 2(B) or 2(C),
the light source 20 may be configured by arranging a plurality of point light sources 23
in line. Each of the point light sources 23 emits light toward the light incident surface
10A, and is configured of, for example, a light emitting device having an emission spot
on a surface facing the light incident surface 10A. Examples of such a light emitting
device include an LED and a laser diode (LD).
[0017] For example, as illustrated in FIG. 2(B) or 2(C), the plurality of point light
sources 23 may be provided by two or more point light sources 23 on common
substrates 24. In this case, a light source block 25 is configured of one substrate 24
and two or more point light sources 23 provided on the substrate 24. For example, the
substrate 24 is a circuit board formed with a wiring that electrically connects the point
light sources 23 to the drive circuit 50, and each of the point light sources 23 is mounted
on the circuit board. The point light sources 23 provided on the common substrate 24
(the point light sources 23 in the light source block 25) are collectively
(non-independently) driven by the drive circuit 50, and for example, although not
illustrated, are connected to one another in parallel or in series. In addition, the point
light sources 23 provided on different substrates 24 (the point light sources 23 in the
respective light source blocks 25) are collectively (non-independently) driven by, for
example, the drive circuit 50, and as illustrated in FIG. 2(B) for example, are connected
to one another in parallel or, for example although not illustrated, are connected to one
another in series. The point light sources 23 provided on the different substrates 24
(the point light sources 23 in the respective light source blocks 25) may be driven
independently by, for example, the drive circuit 50. In this case, for example, as
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illustrated in FIG. 2(C), the point light sources 23 provided on the different substrates
24 are connected to different current paths.
[0018] As illustrated in FIGs. 2(A) to 2(C), the light source 20 may be provided on
one side surface of the light guide plate 10, or as illustrated in FIG. 3, may be provided
on two side surfaces (for example, two side surfaces opposing to each other) of the light
guide plate 10.
[0019] The reflector 40 returns, to the light guide plate 10 side, light leaked from the
back of the light guide plate 10 through the light modulation device 30, and for example,
has a function of reflection, diffusion, scattering, and the like. This allows efficient
use of light emitted from the light source 20, and also helps improvement of front
luminance. The reflector 40 is formed of, for example, foamed PET (polyethylene
terephthalate), an evaporated silver film, a multilayer reflective film, and white PET.
[0020] In the present embodiment, the light modulation device 30 is tightly adhered to
the back (the lower surface) of the light guide plate 10 without an air layer in between,
and is adhered to the back of the light guide plate 10 with, for example, an adhesive
agent (not illustrated) in between. For example, as illustrated in FIG. 1(B), the light
modulation device 30 is configured by arranging 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 from a back surface side (for
example, the reflector 40 side) of the backlight 1.
[0021] The transparent substrates 31 and 37 support the light modulation layer 34, and
are each typically formed of a substrate transparent to visible light, for example, a glass
plate or a plastic film. The lower electrode 32 is provided on a surface on the light
modulation layer 34 side of the transparent substrate 31, and as illustrated in FIGs. 4(A)
and 4(B), is formed by arranging a plurality of strip-shaped partial electrodes 32A in
parallel to one another. Each of the partial electrodes 32A extends in a direction
parallel to the light incident surface 10A of the light guide plate 10 as found from the
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direction of the XYZ coordinate axes in FIGs. 2(A) to 2(C), FIG. 3, and FIGs. 4(A) and
4(B). On the other hand, the upper electrode 36 is provided on a surface on the light
modulation layer 34 side of the transparent substrate 37, and for example, as illustrated
in FIG. 4(A), is a single sheet electrode formed over the entire plane.
[0022] Note that, for example, as illustrated in FIG. 4(B), the upper electrode 36 may
be formed by arranging in parallel a plurality of strip-shaped partial electrodes 36A that
extend in a direction intersecting (or orthogonal to) the extending direction of the partial
electrodes 32A. In addition, for example, although not illustrated, the upper electrode
36 may be configured by arranging in parallel the plurality of strip-shaped partial
electrodes 36A that extend in a direction parallel to the extending direction of the partial
electrodes 32A to face the partial electrodes 32A. Incidentally, in the case where the
upper electrode 36 is divided into the plurality of partial electrodes 3 6A, the partial
electrodes 36A may be electrically connected to one another or may be electrically
separated from one another.
[0023] The lower electrode 32 and the upper electrode 36 is each formed of, for
example, a transparent conductive material such as indium tin oxide (ITO). The
transparent conductive material is preferably a material that absorbs visible light as little
as possible. However, the lower electrode 32 may not be a transparent material, and
for example, may be formed of a metal. Incidentally, in the case where the lower
electrode 32 is formed of a metal, the lower electrode 32 also has a function to reflect
light. Accordingly, in this case, for example as illustrated in FIG. 5, the reflector 40
may be omitted.
[0024] When the light modulation device 30 is viewed from a normal direction of the
light modulation device 30, a region of the light modulation device 30 facing the partial
electrode 32A configures a light modulation cell 30-1. For example, a region
illustrated by a dashed line in FIG. 1(B) corresponds to the light modulation cell 30-1.
The plurality of light modulation cells 30-1 extend in a direction parallel to the light
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incident surface 10A, similarly to the plurality of partial electrodes 3 2 A, and are
arranged in a direction orthogonal to the light incident surface 10 A. Each of the light
modulation cells 30-1 is a region capable of being independently driven by application
of a predetermined voltage to the partial electrode 32A and the upper electrode 36, and
exhibits transparency or scattering property to light from the light source 20 depending
on a magnitude of a voltage value applied to the partial electrode 32A and the upper
electrode 36. Note that the transparency and the scattering property will be described
in detail when the light modulation layer 34 is described.
[0025] For example, the alignment films 33 and 35 align a liquid crystal and a
monomer used for the light modulation layer 34. For example, kinds of the alignment
films include a vertical alignment film and a horizontal alignment film; however in the
present embodiment, the horizontal alignment film is used for the alignment films 33
and 35. Examples of the horizontal alignment film include an alignment film formed
by performing rubbing treatment on polyimide, polyamide-imide, poly vinyl alcohol, or
the like, and an alignment film provided with a groove by transfer or etching.
Moreover, examples of the horizontal alignment film include an alignment film formed
by oblique evaporation of an inorganic material such as silicon oxide, a diamond-like
carbon alignment film formed by ion beam irradiation, and an alignment film formed
with an electrode pattern slit. In the case where a plastic film is used as the transparent
substrates 31 and 37, polyamide-imide capable of being formed at a temperature of
100°C or lower is preferably used as the alignment films 33 and 35 because a firing
temperature after the alignment films 33 and 35 are applied to the surface of the
transparent substrates 31 and 37, respectively, is preferably as low as possible in
manufacturing process.
[0026] Note that a horizontal alignment film that has a function to provide pretilt to a
liquid crystal molecule adjacent to the horizontal alignment film is preferably used.
For example, rubbing may be used as a method of developing a pretilt function of the
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horizontal alignment film. The pretilt is referred to as intersecting the longitudinal
axis of a liquid crystal molecule adjacent to an alignment film to "a surface parallel to
the surface of the alignment film" or "a normal of the alignment film" at a slight angle.
For example, the above-described horizontal alignment film preferably has a function to
allow the longitudinal axis of the liquid crystal molecule adjacent to the horizontal
alignment film to intersect with the surface of the horizontal alignment film at slight
angle in the plane parallel to the light incident surface 10A. The horizontal alignment
film having such a function is achievable by, for example, making the rubbing direction
parallel to the light incident surface 10A.
[0027] Moreover, it is sufficient for both of the vertical and horizontal alignment films
to have a function to align the liquid crystal and the monomer, and reliability in repeat
application of a voltage requested for a typical liquid crystal display is unnecessary.
This is because the reliability in the voltage application after device fabrication is
determined by an interface between polymerized monomer and the liquid crystal. In
addition, the liquid crystal and the monomer used for the light modulation layer 34 are
allowed to be aligned by, for example, application of an electric field or a magnetic field
between the lower electrode 32 and the upper electrode 36, without using the alignment
films 33 and 35. In other words, alignment state of the liquid crystal and the monomer
in a voltage applied state is allowed to be fixed by irradiation of ultraviolet ray while the
electric field or the magnetic field is applied between the lower electrode 32 and the
upper electrode 36. In the case where a voltage is used for formation of the alignment
films 33 and 35, electrodes are differently formed for alignment and for drive, or a
dual-frequency liquid crystal in which sign of dielectric constant anisotropy is inverted
by the frequency may be used for a liquid crystal material. In addition, in the case
where the magnetic field is used for formation of the alignment films 33 and 35, it is
preferable to use a material having large magnetic susceptibility anisotropy for the
alignment films 33 and 35, and for example, it is preferable to use a material having a
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large number of benzene rings.
[0028] The light modulation layer 34 totally or partially exhibits scattering property or
transparency to the light from the light source 20 depending on the magnitude of the
electric field. Specifically, when the voltage is not applied to the partial electrodes
32A and the upper electrode 36, the light modulation layer 34 exhibits the transparency
to the light from the light source 20, and when the voltage is applied to the partial
electrodes 32A and the upper electrode 36, exhibits the scattering property to the light
from the light source 20. For example, as illustrated in FIG. 1(B), the light modulation
layer 34 is a composite layer including a bulk 34A and a plurality of microparticles 34B
dispersed into the bulk 34A. The bulk 34A and the microparticles 34B have optical
anisotropy.
[0029] FIG. 6 schematically illustrates an example of an alignment state in the bulk
34A and the microparticles 34B when a voltage is not applied between the partial
electrodes 32A and the upper electrode 36. An ellipsoid 134A in FIG. 6 illustrates an
example of an index ellipsoid exhibiting refractive index anisotropy of the bulk 34A
when a voltage is not applied between the partial electrodes 32A and the upper electrode
36. An ellipsoid 134B in FIG. 6 illustrates an example of an index ellipsoid exhibiting
refractive index anisotropy of the microparticle 34B when a voltage is not applied
between the partial electrodes 32A and the upper electrode 36. The index ellipsoid
indicates a refractive index of linear polarized light entering from various directions by
a tensor ellipsoid, and geometrically indicates a refractive index through viewing of a
cross-sectional surface of the ellipsoid from an entering direction of the light.
[0030] FIG. 7 schematically illustrates an example of an alignment state in the bulk
34A and the microparticles 34B when a voltage is applied between the partial electrodes
32A and the upper electrode 36. The ellipsoid 134A in FIG. 7 illustrates an example
of an index ellipsoid exhibiting refractive index anisotropy of the bulk 34A when a
voltage is applied between the partial electrodes 32A and the upper electrode 36. The
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ellipsoid 134B in FIG. 7 illustrates an example of an index ellipsoid exhibiting
refractive index anisotropy of the microparticle 34B when a voltage is applied between
the partial electrodes 32A and the upper electrode 36.
[0031] For example, as illustrated in FIG. 6, the bulk 34A and the microparticle 34B
have configuration in which a direction of an optical axis AX1 of the bulk 34A
(specifically, a longitudinal axis of the ellipsoid 134A) and a direction of an optical axis
AX2 of the microparticle 34B (specifically, a longitudinal axis of the ellipsoid 134B)
coincide with (are parallel to) each other. Incidentally, the optical axes AX1 and AX2
each indicate a line parallel to a traveling direction of light ray having a fixed refractive
index irrespective of polarization direction. In addition, it is unnecessary for the
direction of the optical axis AX1 and the direction of the optical axis AX2 to constantly
coincide with each other when a voltage is not applied between the lower electrode 32
and the upper electrode 36, and the direction of the optical axis AX1 may be deviated in
some degree from the direction of the optical axis AX2 due to, for example,
manufacturing error.
[0032] Moreover, when a voltage is not applied between the partial electrodes 32A
and the upper electrode 36, the optical axis AX2 is parallel (or substantially parallel) to
the light incident surface 10A of the light guide plate 10 and is parallel (or substantially
parallel) to the surface of the transparent substrate 31. In other words, when a voltage
is not applied between the partial electrodes 32A and the upper electrode 36, the optical
axis AX2 is parallel (or substantially parallel) to a surface including the partial
electrodes 32A or the upper electrode 36, and is parallel (or substantially parallel) to the
extending direction of the partial electrodes 3 2 A.
[0033] Note that, in the case where the horizontal alignment film has the
above-described pretilt function, when a voltage is not applied between the partial
electrodes 32A and the upper electrode 3'6, the optical axis AX2 is parallel (or t
substantially parallel) to the light incident surface 10A of the light guide plate 10, and
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intersects the surface of the transparent substrate 31 at a predetermined pretilt angle.
[0034] On the other hand, the bulk 34A has a configuration in which the optical axis
AX1 is fixed irrespective of presence or absence of voltage application between the
partial electrodes 32A and the upper electrode 36. Specifically, the optical axis AX1 is
parallel (or substantially parallel) to the light incident surface 10A of the light guide
plate 10, and is parallel (or substantially parallel) to the surface of the transparent
substrate 31. In other words, when a voltage is not applied between the partial
electrodes 32A and the upper electrode 36, the optical axis AX1 is parallel (or
substantially parallel) to the optical axis AX2.
[0035] Note that, in the case where the horizontal alignment film has the
above-described pretilt function, the optical axis AX1 is parallel (or substantially
parallel) to the light incident surface 10A of the light guide plate 10, and intersects the
surface of the transparent substrate 31 at a predetermined pretilt angle. In other words,
also in this case, when a voltage is not applied between the partial electrodes 32A and
the upper electrode 36, the optical axis AX1 is parallel (or substantially parallel) to the
optical axis AX2.
[0036] Here, it is preferable that an ordinary refractive index of the bulk 34A be equal
to that of the microparticle 34B, and an extraordinary refractive index of the bulk 34A
be equal to that of the microparticle 34B. In this case, for example, when a voltage is
not applied between the partial electrodes 32A and the upper electrode 36, difference in
refractive index is hardly generated in all directions including a front direction and an
oblique direction, and high transparency is obtainable. Accordingly, for example, light
toward the front direction and light toward the oblique direction are not scattered in the
light modulation layer 34 and pass through the light modulation layer 34. As a result,
for example, as illustrated in (A) and (B) of FIG. 8, light Li from the light source 20
(light from the oblique direction) is totally reflected by an interface (an interface
between air and the transparent substrate 31 or the light guide plate 10) in a transparent
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region (a transmissive region 30A) in the light modulation device 30, and luminance of
the transmissive region 30A (luminance of black display) is decreased as compared with
the case where the light modulation device 30 is not provided (alternate long and short
dash line in (B) of FIG. 8). Note that a graph in (B) of FIG. 8 illustrates front
luminance measured in a state where a diffuser sheet 41 is provided on the light guide
plate 10 as illustrated in (A) of FIG. 8.
[0037] Moreover, for example, when a voltage is applied between the partial
electrodes 32A and the upper electrode 36, the bulk 34A and the microparticle 34B have
a configuration in which the direction of the optical axis AX1 is different from
(intersects or is orthogonal to) that of the optical axis AX2 as illustrated in FIG. 7. In
addition, for example, when a voltage is applied between the partial electrodes 32A and
the upper electrode 36, the microparticle 34B has a configuration in which the optical
axis AX2 is parallel (or substantially parallel) to the light incident surface 10A of the
light guide plate 10 and is parallel to (or substantially parallel) to the normal of the
transparent substrate 31. In other words, when a voltage is applied between the partial
electrodes 32A and the upper electrode 36, the optical axis AX2 is orthogonal (or
substantially orthogonal) to a surface including the partial electrodes 32A or the upper
electrode 36.
[0038] Accordingly, when a voltage is applied between the partial electrodes 32A and
the upper electrode 36, in the light modulation layer 34, difference in refractive index is
increased in all directions in a plane parallel to the light incident surface 10A, and high
scattering property is obtainable. Therefore, for example, the light toward the front
direction and the light toward the oblique direction are scattered in the light modulation
layer 34. As a result, for example, as illustrated in (A) and (B) of FIG. 8, the light Li
from the light source 20 (the light from the oblique direction) passes through the
interface (the interface between air and the transparent substrate 31 or the light guide
plate 10) in a region (a scattering region 3 0B) in a scattering state in the light
;
!
17
SP312411
*
modulation device 30, and the light that has passed to the reflector 40 side is reflected
by the reflector 40 and passes through the light modulation device 30. Therefore,
luminance of the scattering region 3 OB is extremely high as compared with the case
where the light modulation device 30 is not provided (an alternate long and short dash
line in (B) of FIG. 8), and luminance of partial white display (luminance enhancement)
is increased by a decreased amount of luminance of the transmissive region 30 A.
[0039] Note that the ordinary refractive index of the bulk 34A may be slightly
different from that of the microparticle 34B due to, for example, manufacturing error,
and the difference therebetween is preferably 0.1 or less, and is more preferably 0.05 or
less. In addition, the extraordinary refractive index of the bulk 34A may also be
slightly different from that of the microparticle 34B due to, for example, manufacturing
error, and the difference therebetween is preferably 0.1 or less, and is more preferably
0.05 or less.
[0040] In addition, the difference in refractive index (= the extraordinary refractive
index - the ordinary refractive index) of the bulk 34A and the difference in refractive
index (= the extraordinary refractive index - the ordinary refractive index) of the
microparticle 34B are preferably as large as possible, are preferably 0.05 or more, and
are more preferably 0.1 or more, and are still more preferably 0.15 or more. This is
because when the difference in the refractive index of each of the bulk 34A and the
microparticle 34B is large, the scattering power of the light modulation layer 34 is
increased to easily disrupt light guiding condition, and the light from the light guide
plate 10 is easily extracted.
[0041] Moreover, a response speed to the electric field of the bulk 34A is different
from that of the microparticle 34B. The bulk 34A has, for example, a streaky structure
or a porous structure that does not respond to the electric field, or has a rod-like
structure having a response speed lower than that of the microparticle 34B. For
example, the bulk 34A is formed of a polymer material obtained by polymerization of a
18
SP312411
*
low-molecular monomer. For example, the bulk 34A is formed by polymerizing a
material (for example, monomer) that is aligned along the alignment direction of the
microparticle 34B or the alignment direction of the alignment films 33 and 35 and has
alignment property and polymerizability, by heat or light or both.
[0042] On the other hand, for example, the microparticle 34B is configured to contain
a liquid crystal material mainly, and has a response speed higher than that of the bulk
3 4A. The liquid crystal material (liquid crystal molecule) contained in the
microparticle 34B is, for example, a rod-like molecule. As the liquid crystal molecule
contained in the microparticle 34B, a liquid crystal molecule having positive dielectric
constant anisotropy (so-called positive liquid crystal) is preferably used.
[0043] Here, when a voltage is not applied between the partial electrodes 32A and the
upper electrode 36, the longitudinal direction of the liquid crystal molecule is parallel to
the optical axis AX1 in the microparticle 34B. At this time, the longitudinal axis of
the liquid crystal molecule in the microparticle 34B is parallel (or substantially parallel)
to the light incident surface 10A of the light guide plate 10 and is parallel (or
substantially parallel) to the surface of the transparent substrate 31. In addition, when
a voltage is applied between the partial electrodes 32A and the upper electrode 36, the
longitudinal direction of the liquid crystal molecule intersects (or is orthogonal to) the
optical axis AX1 in the microparticle 34B. At this time, the longitudinal axis of the
liquid crystal molecule in the microparticle 34B is parallel (or substantially parallel) to
the light incident surface 10A of the light guide plate 10 and is parallel (or substantially
parallel) to the normal of the transparent substrate 31.
[0044] As the above-described monomer having the alignment property and the
polymerizability, although a material that has optical anisotropy and is combined with a
liquid crystal is sufficient, in the present embodiment, a low-molecular monomer to be
cured by ultraviolet ray is preferable. Since it is preferable that the direction of optical
anisotropy of the liquid crystal coincide with the direction of the optical anisotropy of
19
SP312411
•
the material (polymer material) formed by polymerization of the low-molecular
monomer in the state of no-voltage application, the liquid crystal and the low-molecular
monomer are preferably aligned in the same direction before ultraviolet curing. In the
case where a liquid crystal is used as the microparticle 34B, when the liquid crystal is a
rod-like molecule, it is preferable that the shape of the monomer material to be used also
have a rod-like shape. As described above, it is preferable to use a material having
both of polymerizability and liquid crystallinity as a monomer material, and the material
preferably contains, as the polymerizable functional group, one or more functional
groups selected from the group consisting of acrylate group, methacrylate group,
acryloyloxy group, methacryloyloxy group, vinyl ether group, and epoxy group.
These functional groups may be polymerized by irradiation of ultraviolet ray, infrared
ray, or an electron beam, or heating. To suppress deterioration in alignment property
at the time of ultraviolet ray irradiation, a polyfunctionalized liquid crystal material may
be added. When the bulk 34A has the above-described streaky structure, bifunctional
liquid-crystalline monomer is preferably used as a material of the bulk 34A. Moreover,
monofunctional monomer may be added in order to adjust temperature exhibiting liquid
crystalinity or trifunctional monomer may be added in order to improve crosslink
density, to the material of the bulk 34A.
[0045] For example, the drive circuit 50 controls the magnitude of the voltage applied
to a pair of electrodes (the partial electrode 32A and the upper electrode 36) of each of
the light modulation cells 30-1 so that the optical axis AX2 of the microparticle 34B is
parallel or substantially parallel to the optical axis AX1 of the bulk 34A in a certain
light modulation cell 30-1 and the optical axis AX2 of the microparticle 34B intersects
or is orthogonal to the optical axis AX1 of the bulk 34A in the other light modulation
cells 30-1. In other words, the drive circuit 50 allows the directions of the optical axes
AX1 and AX2 of the bulk 34A and the microparticle 34B to coincide (or substantially
coincide) with each other or to be different from each other (or be orthogonal to each
20
SP312411
other) through electric field control.
[0046] Further, the drive circuit 50 sequentially drives the plurality of partial
electrodes 32A by a predetermine unit to scan the region exhibiting scattering property
(the scattering region 3 OB) of the light modulation layer 34 in a direction orthogonal to
the light incident surface 10A. Accordingly, the drive circuit 50 scans the light that is
scattered by the scattering region 3 0B and emitted from the upper surface of the
backlight 1 to the outside, in a direction orthogonal to the light incident surface 10A
during a process in which light emitted from the light source 20 propagates through the
light guide plate.
[0047] FIGs. 9(A) and 9(B) to FIGs. 12(A) and 12(B) schematically illustrate a state
in which the scattering region 3 0B is scanned in a direction orthogonal to the light
incident surface 10A. For example, as illustrated in FIGs. 9(A) and 9(B) and FIGs.
10(A) and 10(B), the drive circuit 50 sequentially drives the plurality of partial
electrodes 32A on a predetermined unit basis to scan the scattering region 30B (the light
emission region) in the direction orthogonal to the light incident surface 10A in a state
where all of the light sources 20 in the backlight 1 are turned on. Incidentally, FIGs.
9(A) and 9(B) and FIGs. 10(A) and 10(B) illustrate a case where the plurality of partial
electrodes 32 A are sequentially driven line by line in a positive direction of the X axis.
[0048] When one light source 20 is provided in each of the two side surfaces of the
light guide plate 10, the drive circuit 50 may turn off or darken one of the light sources
20 depending on a distance of the partial electrode 32A to be driven from the light
source 20. For example, the drive circuit 50 may make the light source 20 closer to the
partial electrode 32A to be driven of the two light sources 20 brighter than the light
source 20 farther from the partial electrode 32A to be driven of the two light sources 20,
and may make the light source 20 farther.from the partial electrode 32A to be driven of
the two light sources 20 darker than the light source 20 closer to the partial electrode
32A to be driven of the two light sources 20.
21
_ SP312411 •
[0049] For example, as illustrated in FIGs. 11(A) and 11(B) and FIGs. 12(A) and
12(B), the drive circuit 50 may turn on the light source 20 closer to the partial electrode I
32 A to be driven of the two light sources 20, and may turn off the light source 20 farther f
from the partial electrode 32A to be driven of the two light sources 20, while
sequentially driving the plurality of partial electrodes 32A on the predetermined unit
basis. In other words, when the partial electrode 32A to be driven is located closer to t
T
one (for convenience, referred to as a light source A) of the light sources 20, the drive I
circuit 50 may turn on only the light source A, and when the partial electrode 32A to be
driven is located closer to the other (for convenience, referred to as a light source B) of '
the light sources 20, the drive circuit 50 may turn on only the light source B. In such a
case, an amount of light propagating through the region exhibiting the transparency (the
transmissive region 30A) of the light modulation layer 34 is decreased so that black
luminance is allowed to be decreased.
[0050] In addition, for example, although not illustrated, the drive circuit 50 may turn
l
on the light source 20 farther from the partial electrode 32A to be driven of the two light
sources 20 darker than the light source 20 closer to the partial electrode 32A to be
driven of the two light sources 20, after turning on both of the two light sources 20.
Also in this case, the amount of the light propagating through the region exhibiting the
transparency (the transmissive region 30 A) of the light modulation layer 34 is decreased
by the decreased light amount of one of the light sources 20 so that the black luminance
is allowed to be decreased.
[0051] Hereinafter, a method of manufacturing the backlight 1 of the embodiment will
be described with reference to FIGs. 13(A) to 13(C) to FIGs. 15(A) to 15(C).
[0052] At first, a transparent conductive film 32D made of, for example, ITO is
formed on the transparent substrate 31 configured of a glass substrate or a plastic film
substrate (FIG. 13(A)). Then, after a patterned resist layer (not illustrated) is formed on the transparent conductive film 32D, the transparent conductive film 32D is
22
SP312411
selectively etched with use of the resist layer as a mask. As a result, the lower
electrode 32 is formed (FIG. 13(B)).
[0053] Next, the alignment film 33 is applied on the entire surface, followed by drying
and firing (FIG. 13(C)). When a polyimide-based material is used as the alignment
film 33, NMP (N-methyl-2-pyrroridone) is frequently used as a solvent, and at this time,
a temperature of about 200°C is necessary in the atmosphere. Note that, in this case,
when a plastic substrate is used as the transparent substrates 31 and 37, the alignment
film 33 may be dried in a vacuum at 100°C and fired. After that, rubbing treatment is
performed on the alignment film 33. As a result, the alignment film 33 can function as
an alignment film for horizontal alignment.
[0054] Next, spacers 38 for forming a cell gap are spread on the alignment film 33 by
a dry method or a wet method (FIG. 14(A)). Note that, when the light modulation cell
30-1 is formed by vacuum bonding method, the spacers 38 may be mixed into a mixture
to be dropped. In addition, instead of the spacers 38, column spacers may be formed
by photolithography.
[0055] Subsequently, a seal agent pattern 39 for bonding and for preventing leakage
of liquid crystal is applied, for example, in a frame shape on the alignment film 35 that
has been fabricated by a method similar to that described above (FIG. 14(B)). The seal
agent pattern 39 is formed by a dispenser method or a screen printing method.
[0056] Although the vacuum bonding method (one drop fill method, ODF method)
will be described below, the light modulation cell 30-1 may be formed by a vacuum
injection method or a roll bonding system.
[0057] First, a mixture 42 of liquid crystal and monomer corresponding to a volume
that is determined from the cell gap, a cell area, and the like is dropped uniformly in a
plane (FIG. 14(C)). Although a precise dispenser of linear guide system is preferably
used for dropping the mixture 42, the seal agent pattern 39 may be used as a bank and a
dye coater or the like may be used.
23
SP312411
[0058] The above-described material may be used for the liquid crystal and the
monomer, and the weight ratio of the liquid crystal and the monomer is 98: 2 to 50:50,
is preferably 95:5 to 75:25, and is more preferably 92:8 to 85:15. The drive voltage is
allowed to be decreased by increasing the rate of the liquid crystal, however, if the
liquid crystal is excessively increased, whiteness tends to be lowered at the time of
voltage application, or transparency is tends to be deteriorated due to lowering of
response speed after voltage off.
[0059] The mixture 42 is added with a polymerization initiator, in addition to the
liquid crystal and the monomer. The monomer ratio of the polymerization initiator to
be added is adjusted within a range of 0.1 to 10 wt% depending on the wavelength of
ultraviolet ray to be used. The mixture 42 may be added with a polymerization
inhibitor, a plasticizer, a viscosity modifier, and the like, in addition thereto. When the
monomer is in a solid or a gel at room temperature, a metal cap, a syringe, and a
substrate are preferably warmed.
[0060] After the transparent substrate 31 and the transparent substrate 37 are placed
on a vacuum bonding machine (not illustrated), evacuation and bonding are performed
(FIG. 15(A)). After that the bonded body is released in the air, and the cell gap is
uniformized by uniform pressurization at atmosphere pressure. The cell gap is
arbitrarily selectable based on relationship between white luminance (whiteness) and the
drive voltage, and is 5 to 40 urn, is preferably 6 to 20 urn, and is more preferably 7 to 10
um.
[0061] After bonding, it is preferable to perform alignment treatment if necessary (not
illustrated). When light leakage occurs at the time of inserting the bonded cell
between crossed-Nicols polarizers, the cell is subjected to heat treatment for a certain
time or is left at room temperature to be aligned. After that, ultraviolet ray L3 is
irradiated to polymerize the monomer, and thus polymer is formed (FIG. 15(B)). In
this way, the light modulation device 30 is manufactured.
24
SP312411
*
[0062] It is preferable that the temperature of the cell be prevented from being varied
during irradiation of the ultraviolet ray. It is preferable to use an infrared cut filter, and
use a UV*LED or the like as a light source. The illuminance of the ultraviolet ray
affects the structure of the composite material, and thus the illuminance is preferably
adjusted based on the liquid crystal material to be used, the monomer material to be
used, and the compositions thereof, is preferably within a range of 0.1 to 500 mW/cm ,
and is more preferably within a range of 0.5 to 30 mW/cm . There is a tendency that
the drive voltage is decreased as the illuminance of the ultraviolet ray is decreased and
preferable illuminance of the ultraviolet ray is selectable in terms of both of productivity
and characteristics.
[0063] Then, the light modulation device 30 is bonded to the light guide plate 10 (FIG.
15(C)). Although the bonding may be performed through adhesion or bonding, the
adhesion or the bonding is preferably performed with use of a material that has a
refractive index as close to that of the light guide plate 10 and that of the substrate
material of light modulation device 30 as possible. Finally, lead wire (not illustrated)
is attached to the lower electrode 32 and the upper electrode 36. In this way, the
backlight 1 of the present embodiment is manufactured.
[0064] As described above, the process in which the light modulation device 30 is
fabricated and the light modulation device 30 is finally bonded to the light guide plate
10 has been described, however, the transparent substrate 37 formed with the alignment
film 35 may be previously bonded to the surface of the light guide plate 10 and then the
backlight 1 may be fabricated. Moreover, the backlight 1 may be fabricated by a
single wafer system or a roll to roll system.
[0065] Next, functions and effects of the backlight 1 of the present embodiment will
be described.
[0066] In the backlight 1 of the present embodiment, the voltage is applied between
the partial electrode 32A of each of the light modulation cells 30-1 and the upper
25
SP312411
*
electrode 36 so that the optical axis AX2 of the microparticle 34B is parallel or
substantially parallel to the optical axis AX1 of the bulk 34A in a certain light
modulation cell 30-1 and the optical axis AX2 of the microparticle 34B intersects or is
orthogonal to the optical axis AX1 of the bulk 34A in the other light modulation cell
30-1. As a result, the light that has been emitted from the light source 20 and has
entered the light guide plate 10 passes through the transmissive region 30A of the light
modulation device 30 where the optical axis AX1 is parallel or substantially parallel to
the optical axis AX2. In addition, the light that has been emitted form the light source
20 and has entered the light guide plate 10 is scattered in the scattering region 3 0B of
the light modulation device 30 where the optical axis AX1 intersects or is orthogonal to
the optical axis AX2. Light that has passed through the lower surface of the scattering
region 3 0B of the scattered light is reflected by the reflector 40 to return to the light
guide plate 10 again, and then is emitted from the upper surface of the backlight 1. In
addition, light toward the upper surface of the scattering region 3 0B of the scattered
light passes through the light guide plate 10, and then is emitted from the upper surface
of the backlight 1. As described above, in the present embodiment, light is scarcely
emitted from the upper surface of the transmissive region 30A and the light is emitted
from the upper surface of the scattering region 30B. In this way, the modulation ratio
in the front direction is increased.
[0067] Typically, the PDLC is formed by mixing a liquid crystal material and an
isotropic low-molecular material and causing phase separation by ultraviolet irradiation,
drying of a solvent, etc., and has a composite layer in which microparticles of the liquid
crystal material are dispersed in a polymer material. The liquid crystal material in the
composite layer exhibits scattering property because the liquid crystal material directs in
random directions at the time of no-voltage application; however the liquid crystal
material aligns in an electric field direction at the time of voltage application.
Accordingly, the liquid crystal material exhibits high transparency in the front direction
26
SP312411
«
(in the normal direction of the PDLC) when the ordinary refractive index of the liquid
crystal material is equal to the refractive index of the polymer material. However, in
the liquid crystal material, in the oblique direction, difference between the extraordinary
refractive index of the liquid crystal and the polymer material is remarkable, and this
results in expression of scattering property in the oblique direction even when
transparency is expressed in the front direction.
[0068] Usually, a light modulation device using the PDLC frequently has a structure
in which the PDLC is sandwiched between two glass plates that have a front surface
formed with a transparent conductive film. When light obliquely enters, from the air,
the light modulation device having the above-described structure, the light that has
entered the light modulation device in the oblique direction is refracted by difference in
refractive index between the air and the glass plate, and enters the PDLC at a smaller
angle. Therefore, in such a light modulation device, large scattering does not occur.
For example, when light enters the light modulation device from the air at an angle of
80 degrees, the entering angle of the light to the PDLC is decreased to about 40 degrees
by refraction at the glass interface.
[0069] However, in an edge light system using a light guide plate, since light enters
through the light guide plate, the light passes through the PDLC at a large angle of
about 80 degrees. Therefore, difference between the extraordinary refractive index of
the liquid crystal material and the refractive index of the polymer material is large, and
further the light passes through the PDLC at larger angle, and optical path subjected to
scattering is also increased accordingly. For example, when microparticles of a liquid
crystal material that has an ordinary refractive index of 1.5 and an extraordinary
refractive index of 1.65 are dispersed into a polymer material having a refractive index
of 1.5, difference in refractive index is not generated in the front direction (the normal
direction of the PDLC); however the difference in refractive index is increased in the
oblique direction. Therefore, scattering property in the oblique direction cannot be
27
SP312411
•
decreased so that viewing angle characteristics are deteriorated. Further, when an
optical film such as a diffuser film is provided on the light guide plate, obliquely-leaked
light is diffused also in the front direction by the diffuser film or the like. Therefore,
light leakage in the front direction is increased and the modulation ratio in the front
direction is lowered.
[0070] Moreover, it is conceivable that a holographic PDLC (H-PDLC) is used
instead of the above-described PDLC. In the H-PDLC, when a voltage is applied to
some regions of the H-PDLC, the direction of liquid molecules existing in that regions
is changed. A region (non-transition region) where a voltage is not applied and the
direction of the liquid molecules is not changed is present around the region (transition
region) where the direction of the liquid crystal molecules is changed in such a way, and
a boundary between the two kinds of regions configures a diffraction grating. The
diffraction grating diffracts a p-polarized wave and allows an s-polarized wave to pass
therethrough. Therefore, a p-polarized wave of the light that has propagated through
the light guide plate is diffracted by the diffraction grating and the diffracted light is
then extracted to the outside, however an s-polarized wave of the light that has
propagated through the light guide plate passes through the diffraction grating.
Accordingly, in the H-PDLC, the modulation ratio in the front direction is low in
principle.
[0071] On the other hand, in the present embodiment, since the bulk 34A and the
microparticle 34B are formed to mainly contain respective optical anisotropic materials
in the light modulation device 30, the scattering property is decreased and the
transparency is improved in the oblique direction. For example, in a region where the
bulk 34A and the microparticle 34B mainly contain respective optical anisotropic
materials whose ordinary refractive indices are equal to each other and whose
extraordinary refractive indices are also equal to each other and a voltage is not applied
between the partial electrodes 32A and the upper electrode 36, the directions of the
28
SP312411
optical axes thereof coincide or substantially coincide with each other. Therefore,
difference in refractive index is decreased or eliminated in all directions including the
front direction (the normal direction of the light modulation device 30) and the oblique
direction, and higher transparency is obtainable. As a result, light leakage in a region
where a viewing angle is large is decreased or substantially eliminated, and viewing
angle characteristics are improved.
[0072] For example, when a liquid crystal that has an ordinary refractive index of 1.5
and an extraordinary refractive index of 1.65 and a liquid crystalline monomer that has
an ordinary refractive index of 1.5 and an extraordinary refractive index of 1.65 are
mixed and the liquid crystalline monomer is polymerized in a state where the liquid
crystal and the liquid crystalline monomer are aligned by the alignment film or an
electric field, the optical axis of the liquid crystal coincides with the optical axis of a
polymer formed by polymerization of the liquid crystalline monomer. As a result,
since the refractive indices are coincident with each other in all directions, in such a
case, a state with higher transparency is achievable and the viewing angle characteristics
are further improved.
[0073] In addition, in the present embodiment, for example, as illustrated in (A) and
(B) of FIG. 8, the luminance of the transmissive region 30A (the luminance of black
display) is lower than that in the case where the light modulation device 30 is not
provided (alternate long and short dash line in (B) of FIG. 8). On the other hand, the
luminance of the scattering region 3 0B is extremely higher than that in the case where
the light modulation device 30 is not provided (alternate long and short dash line in (B)
of FIG. 8), and the luminance of partial white display (luminance enhancement) is
increased by a decreased amount of the luminance of the transmissive region 30 A.
[0074] Incidentally, the luminance enhancement is a technique to enhance luminance
when partial white display is performed, as compared with the case of entire white
display. This is a technique generally used for CRT, PDP, and the like. In a liquid
29
SP312411
*
crystal display, however, a backlight uniformly emits light as a whole irrespective of an
image so that partial enhancement of luminance is difficult. Incidentally, when the
backlight is configured as an LED backlight in which a plurality of LEDs are
two-dimensionally arranged, the LEDs are allowed to be partially turned off. However,
in such a case, diffusion light from a dark region where the LEDs are turned off is
absent, and thus the luminance is lowered as compared with the case where all of the
LEDs are turned on. In addition, although it is possible to increase the luminance by
increasing a current flowing through the LEDs partially turned on, in such a case, large
current flows through the LEDs in an extremely short time, and thus issues are remained
in terms of load of circuits and reliability.
[0075] On the other hand, in the present embodiment, since the bulk 34A and the
microparticle 34B are formed to mainly contain respective optical anisotropic materials
in the light modulation device 30, the scattering property in the oblique direction is
suppressed and leakage of light from the light guide plate in a dark state is suppressed.
Therefore, the light propagating through the light guide plate 10 propagates from a
partial dark region to a partial bright region with slight optical loss so that luminance
enhancement is achievable without increasing power supplied to the backlight 1. As a
result, high luminance is achievable.
[0076] Moreover, in the present embodiment, when the horizontal alignment film has
the above-described pretilt function, in a region where a voltage is not applied between
the partial electrodes 32A and the upper electrode 36, the optical axis AX2 of the
microparticle 34B is parallel (or substantially parallel) to the light incident surface 10A
of the light guide plate 10, and intersects the surface of the transparent substrate 31 at a
predetermined pretilt angle. Specifically, the liquid crystal molecule contained in the
microparticle 34B is aligned in a state of being inclined at the predetermined pretilt
angle in a plane parallel to the light incident surface 10A. Therefore, when a voltage is
applied between the partial electrodes 32A and the upper electrode 36, the liquid crystal
30
SP312411
molecule contained in the microparticle 34B does not stand up in a random direction,
and stands up in the plane parallel to the light incident surface 10A. At this time, the
optical axis AX1 of the bulk 34A intersects or is orthogonal to the optical axis AX2 of
the microparticle 34B in the plane parallel to the light incident surface 10A.
Accordingly, in the region where a voltage is applied between the partial electrodes 32A
and the upper electrode 36, difference in refractive index is increased in all directions
including the front direction (the normal direction of the light modulation device 30)
and the oblique direction, and high scattering property is obtainable. As a result,
display luminance is allowed to be improved. In addition, luminance is allowed to be
further improved by the effect of the above-described luminance enhancement.
[0077] Moreover, in the present embodiment, the plurality of partial electrodes 32A
arranged in the direction orthogonal to the light incident surface 10A are sequentially
driven on the predetermined unit basis. Accordingly, during the process in which the
light emitted from the light source 20 propagates through the light guide plate 10, the
region exhibiting the scattering property (the scattering region 3 0B) of the light
modulation layer 34 is scanned in the direction orthogonal to the light incident surface
10A. As a result, the light that is scattered in the scattering region 3 0B and is to be
emitted from the upper surface of the backlight 1 to the outside is scanned in the
direction orthogonal to the light incident surface 10A. At this time, since scan driving
of the light source 20 is not performed, luminance higher than that in the existing
method in which scan driving of a light source is performed is obtainable by the effect
of the above-described luminance enhancement. In addition, in the present
embodiment, as described above, since the scan driving of the light source 20 is not
performed, it is rarely necessary to consider inrush power generated when a large power
is supplied to the light source in an extremely short time to perform the scan driving,
and reliability of the circuit board is not impaired.
[0078] As described above, in the present embodiment, the light emitted from the
31
SP312411 •
upper surface of the backlight 1 is scanned by scanning the scattering region 3 OB of the
light modulation layer 34 instead of the scan driving of the light source 20, and thus
high luminance, low power consumption, high reliability of the circuit board are all
achievable at a time in scan system.
[0079] <2. Second Embodiment
FIG. 16(A) is a sectional diagram illustrating an example of a schematic
configuration of a backlight 2 according to a second embodiment of the invention.
The backlight 2 corresponds to a specific example of a lighting unit of the invention.
FIG. 16(B) is a sectional diagram illustrating an example of a schematic configuration
of a light modulation device 60 included in the backlight 2 of FIG. 16(A). Note that
FIGs. 16(A) and 16(B) are schematic illustration, and the illustration may not be the
same as actual dimensions and shapes.
[0080] The configuration of the backlight 2 of the present embodiment is different
from the configuration of the backlight 1 according to the first embodiment in terms of
being provided with the light modulation device 60 instead of the light modulation
device 30. Thus, hereinafter, differences with the above-described embodiment will be
described mainly, and the description for common points to the above-described
embodiment will be arbitrarily omitted.
[0081] In the present embodiment, the light modulation device 60 is tightly adhered to
the back (the lower surface) of the light guide plate 10 without an air layer in between,
and is adhered to the back of the light guide plate 10 with, for example, an adhesive
agent (not illustrated) in between. For example, as illustrated in FIG. 16(B), the light
modulation device 60 is configured by arranging the transparent substrate 31, the lower
electrode 32, an alignment film 63, a light modulation layer 64, an alignment film 65,
the upper electrode 36, and the transparent substrate 37 in order from the reflector 40
side.
[0082] For example, the alignment films 63 and 65 align a liquid crystal and a
32
' • i . <
SP312411
#
monomer used for the light modulation layer 64. For example, kinds of the alignment
films include a vertical alignment film and a horizontal alignment film; however in the
present embodiment, the vertical alignment film is used for the alignment films 63 and
65. As the vertical alignment film, a silane coupling material, polyvinyl alcohol
(PVA), a polyimide-based material, a surfactant, and the like may be used. In addition,
when a plastic film is used as the transparent substrates 31 and 37, a silane coupling
material capable of being used with an alcohol-based solvent as the alignment films 63
and 65 is preferably used because firing temperature after the alignment films 63 and 65
are applied to the surface of the transparent substrates 31 and 37, respectively, is
preferably as low as possible in manufacturing process.
[0083] Note that a vertical alignment film that has a function to provide pretilt to a
liquid crystal molecule adjacent to the vertical alignment film is preferably used. For
example, rubbing may be used as a method of developing a pretilt function of the
vertical alignment film. For example, the above-described vertical alignment film
preferably has a function to allow the longitudinal axis of the liquid crystal molecule
adjacent to the vertical alignment film to intersect with the normal of the vertical
alignment film at a slight angle in a plane parallel to the light incident surface 10A.
The vertical alignment film having such a function is achievable by, for example,
making the rubbing direction parallel to the light incident surface 10A.
[0084] However, when the vertical alignment film is used as the alignment films 63
and 65, as a liquid crystal molecule contained in a microparticle 64B described later, a
liquid crystal molecule having negative dielectric constant anisotropy (so-called
negative liquid crystal) is preferably used.
[0085] Next, the light modulation layer 64 of the present embodiment is described.
For example, as illustrated in FIG. 16(B), the light modulation layer 64 is a composite
layer including a bulk 64A and a plurality of microparticles 64B dispersed into the bulk
64A. The bulk 64A and the microparticles 64B have optical anisotropy.
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[0086] FIG. 17 schematically illustrates an example of an alignment state in the bulk
64A and the microparticles 64B when a voltage is not applied between the partial
electrodes 32A and the upper electrode 36. An ellipsoid 164A in FIG. 17 illustrates an
example of an index ellipsoid exhibiting refractive index anisotropy of the bulk 64A
when a voltage is not applied between the partial electrodes 32A and the upper electrode
36. An ellipsoid 164B in FIG. 17 illustrates an example of an index ellipsoid
exhibiting refractive index anisotropy of the microparticle 64B when a voltage is not
applied between the partial electrodes 32A and the upper electrode 36.
[0087] FIG. 18 schematically illustrates an example of an alignment state in the bulk
64 A and the microparticles 64B when a voltage is applied between the partial electrodes
32A and the upper electrode 36. The ellipsoid 164A in FIG. 18 illustrates an example
of an index ellipsoid exhibiting refractive index anisotropy of the bulk 64A when a
voltage is applied between the partial electrodes 32A and the upper electrode 36. The
ellipsoid 164B in FIG. 18 illustrates an example of an index ellipsoid exhibiting
refractive index anisotropy of the microparticle 64B when a voltage is applied between
the partial electrodes 32A and the upper electrode 36.
[0088] For example, as illustrated in FIG. 17, the bulk 64A and the microparticle 64B
have configuration in which a direction of an optical axis AX3 of the bulk 64A
(specifically, a longitudinal axis of the ellipsoid 164A) and a direction of an optical axis
AX4 of the microparticle 64B (specifically, a longitudinal axis of the ellipsoid 164B)
coincide with (are parallel to) each other. Incidentally, the optical axes AX3 and AX4
each indicate a line parallel to a traveling direction of light ray, the line defining a
refractive index as one value irrespective of polarization direction. In addition, it is
unnecessary for the direction of the optical axis AX3 and the direction of the optical
axis AX4 to constantly coincide with each other when a voltage is not applied between
the partial electrodes 32A and the upper electrode 36, and the direction of the optical
axis AX3 may be deviated in some degree from the direction of the optical axis AX4
34
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due to, for example, manufacturing error.
[0089] Moreover, when a voltage is not applied between the partial electrodes 32A
and the upper electrode 36, the optical axis AX4 is parallel (or substantially parallel) to
the light incident surface 10A of the light guide plate 10 and is parallel (or substantially
parallel) to the normal of the surface of the transparent substrate 31. In other words,
when a voltage is not applied between the lower electrode 32 and the upper electrode 36,
the optical axis AX4 is orthogonal (or substantially orthogonal) to a surface including
the lower electrode 32 or the upper electrode 36.
[0090] Note that, in the case where the vertical alignment film has the
above-described pretilt function, when a voltage is not applied between the partial
electrodes 32A and the upper electrode 36, the optical axis AX4 is parallel (or
substantially parallel) to the light incident surface 10A of the light guide plate 10, and
intersects the normal of the transparent substrate 31 at a predetermined pretilt angle.
[0091] On the other hand, the bulk 64A has a configuration in which the optical axis
AX3 is fixed irrespective of presence or absence of voltage application between the
partial electrodes 32A and the upper electrode 36. Specifically, the optical axis AX3 is
parallel (or substantially parallel) to the light incident surface 10A of the light guide
plate 10, and is parallel (or substantially parallel) to the normal of the surface of the
transparent substrate 31. In other words, when a voltage is not applied between the
partial electrodes 32A and the upper electrode 36, the optical axis AX3 is parallel (or
substantially parallel) to the optical axis AX4.
[0092] Note that, in the case where the vertical alignment film has the
above-described pretilt function, the optical axis AX3 is parallel (or substantially
parallel) to the light incident surface 10A of the light guide plate 10, and intersects the
normal of the transparent substrate 31 at a predetermined pretilt angle. In other words,
also in this case, when a voltage is not applied between the partial electrodes 32A and
the upper electrode 36, the optical axis AX3 is parallel (or substantially parallel) to the
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optical axis AX4.
[0093] Here, it is preferable that an ordinary refractive index of the bulk 64A be equal
to that of the microparticle 64B, and an extraordinary refractive index of the bulk 64A
be equal to that of the microparticle 64B. In this case, for example, when a voltage is
not applied between the partial electrodes 32A and the upper electrode 36, difference in
refractive index is not generated in all directions including a front direction and an
oblique direction, and high transparency is obtainable. Accordingly, for example, light
toward the front direction and light toward the oblique direction are not scattered in the
light modulation layer 64 and pass through the light modulation layer 64. As a result,
for example, light from the light source 20 (light from the oblique direction) is totally
reflected by an interface (an interface between air and the transparent substrate 31 or the
light guide plate 10) in a transparent region (the transmissive region 30A) in the light
modulation device 60, and luminance of the transmissive region 30A (luminance of
black display) is decreased as compared with the case where the light modulation device
60 is not provided (see (A) and (B) of FIG. 8).
[0094] Moreover, for example when a voltage is applied between the partial
electrodes 32A and the upper electrode 36, the bulk 64A and the microparticle 64B have
a configuration in which the direction of the optical axis AX3 is different from
(intersects or is orthogonal to) that of the optical axis AX4 as illustrated in FIG. 18. In
addition, for example, when a voltage is applied between the partial electrodes 32A and
the upper electrode 36, the microparticle 64B has a configuration in which the optical
axis AX4 is parallel (or substantially parallel) to the light incident surface 10A of the
light guide plate 10 and is parallel (or substantially parallel) to the surface of the
transparent substrate 31. In other words, when a voltage is applied between the partial
electrodes 32A and the upper electrode 36, the optical axis AX4 is parallel (or
substantially parallel) to a surface including the partial electrodes 32A or the upper
electrode 36, and is parallel (or substantially parallel) to the extending direction of the
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partial electrodes 32A.
[0095] Accordingly, when a voltage is applied between the partial electrodes 32A and
the upper electrode 36, in the light modulation layer 64, difference in refractive index is
increased in all directions in a plane that is parallel to the light incident surface 10A and
is orthogonal to the surface of the transparent substrate 31, and high scattering property
is obtainable. Therefore, for example, the light toward the front direction and the light
toward the oblique direction are scattered in the light modulation layer 64. As a result,
for example, the light L from the light source 20 (the light from the oblique direction)
passes through the interface (the interface between air and the transparent substrate 31
or the light guide plate 10) of the scattering region 3 OB, and the light that has passed to
the reflector 40 side is reflected by the reflector 40 and passes through the light
modulation device 60. Therefore, luminance of the scattering region 30B is extremely
high as compared with the case where the light modulation device 60 is not provided,
and luminance of partial white display (luminance enhancement) is increased by a
decreased amount of luminance of the transmissive region 30 A.
[0096] Note that the ordinary refractive index of the bulk 64A may be slightly
different from that of the microparticle 64B due to, for example, manufacturing error,
and the difference therebetween is preferably 0.1 or less, and is more preferably 0.05 or
less. In addition, the extraordinary refractive index of the bulk 64A may also be
slightly different from that of the microparticle 64B due to, for example, manufacturing
error, and the difference therebetween is preferably 0.1 or less, and is more preferably
0.05 or less.
[0097] In addition, the difference in refractive index (= the extraordinary refractive
index - the ordinary refractive index) of the bulk 64A and the difference in refractive
index (= the extraordinary refractive index - the ordinary refractive index) of the
microparticle 64B are preferably as large as possible, are preferably 0.05 or more, and
are more preferably 0.1 or more, and are still more preferably 0.15 or more. This is
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^*
because when the difference in the refractive index of each of the bulk 64A and the
microparticle 64B is large, the scattering power of the light modulation layer 64 is
increased to easily disrupt light guiding condition, and the light from the light guide
plate 10 is easily extracted.
[0098] Moreover, a response speed to the electric field of the bulk 64A is different
from that of the microparticle 64B. The bulk 64 A has, for example, a streaky structure
or a porous structure that does not respond to the electric field, or has a rod-like
structure having a response speed lower than that of the microparticle 64B. For
example, the bulk 64A is formed of a polymer material obtained by polymerization of a
low-molecular monomer. For example, the bulk 64A is formed by polymerizing
material that is aligned along the alignment direction of the microparticle 64B or the
alignment direction of the alignment films 63 and 65 and has an alignment property and
polymerizability, by heat or light or both. On the other hand, for example, the
microparticle 64B is configured to contain a liquid crystal material mainly, and has a
response speed sufficiently higher than that of the bulk 64A. The liquid crystal
material (liquid crystal molecule) contained in the microparticle 64B is, for example, a
rod-like molecule.
[0099] Here, when a voltage is not applied between the partial electrodes 32A and the
upper electrode 36, the longitudinal direction of the liquid crystal molecule is parallel to
the optical axis AX3 in the microparticle 64B. At this time, the longitudinal axis of
the liquid crystal molecule in the microparticle 64B is parallel (or substantially parallel)
to the light incident surface 10A of the light guide plate 10 and is parallel (or
substantially parallel) to the surface of the transparent substrate 31. In addition, when
a voltage is applied between the partial electrodes 32A and the upper electrode 36, the
longitudinal direction of the liquid crystal molecule intersects (or is orthogonal to) the
optical axis AX3 in the microparticle 64B. At this time, the longitudinal axis of the
liquid crystal molecule in the microparticle 64B is parallel (or substantially parallel) to
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the light incident surface 10A of the light guide plate 10 and is parallel (or substantially
parallel) to the surface of the transparent substrate 31.
[0100] As the above-described monomer having the alignment property and the
polymerizability, although a material that has optical anisotropy and is combined with a
liquid crystal is sufficient, in the present embodiment, a low-molecular monomer to be
cured by ultraviolet ray is preferable. Since it is preferable that the direction of optical
anisotropy of the liquid crystal coincide with the direction of the optical anisotropy of
the material (polymer material) formed by polymerization of the low-molecular
monomer in the state of no-voltage application, the liquid crystal and the low-molecular
monomer are preferably aligned in the same direction before ultraviolet curing. In the
case where a liquid crystal is used as the microparticle 64B, when the liquid crystal is a
rod-like molecule, it is preferable that the shape of the monomer material to be used also
have a rod-like shape. As described above, it is preferable to use a material having
both of polymerizability and liquid crystalinity as a monomer material, and the
monomer material preferably contains, as a polymerizable functional group, one or
more functional groups selected from the group consisting of acrylate group,
methacrylate group, acryloyloxy group, methacryloyloxy group, vinyl ether group, and
epoxy group. These functional groups may be polymerized by irradiation of
ultraviolet ray, infrared ray, or an electron beam, or heating. To suppress deterioration
in alignment property at the time of ultraviolet ray irradiation, a polyfunctionalized
liquid crystal material may be added. When the bulk 64A has the above-described
streaky structure, bifunctional liquid-crystalline monomer is preferably used as a
material of the bulk 64A. Moreover, monofunctional monomer may be added in order
to adjust temperature exhibiting liquid crystalinity or trifunctional monomer may be
added in order to improve crosslink density, to the material of the bulk 64 A.
[0101] For example, the drive circuit 50 controls the magnitude of the voltage applied
to a pair of electrodes (the partial electrode 32A and the upper electrode 36) of each of
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the light modulation cells 30-1 so that the optical axis AX4 of the microparticle 64B is
parallel or substantially parallel to the optical axis AX3 of the bulk 64A in a certain
light modulation cell 30-1 and the optical axis AX4 of the microparticle 64B intersects
or is orthogonal to the optical axis AX3 of the bulk 64A in the other light modulation
cell 30-1. In other words, the drive circuit 50 allows the directions of the optical axes
AX3 and AX4 of the bulk 64A and the microparticle 64B to coincide (or substantially
coincide) with each other or to be different from each other (or be orthogonal to each
other) through electric field control.
[0102] Further, the drive circuit 50 sequentially drives the plurality of partial
electrodes 32A by a predetermine unit to scan the region exhibiting the scattering
property (the scattering region 3 0B) of the light modulation layer 64 in a direction
orthogonal to the light incident surface 10A. Accordingly, the drive circuit 50 scans
the light that is scattered by the scattering region 3 0B and emitted from the upper
surface of the backlight 2 to the outside, in the direction orthogonal to the light incident
surface 10A during the process in which the light emitted from the light source 20
propagates through the light guide plate.
[0103] Next, functions and effects of the backlight 2 of the present embodiment will
be described.
[0104] In the backlight 2 of the present embodiment, a voltage is applied between the
partial electrode 32A of each of the light modulation cells 30-1 and the upper electrode
36 so that the optical axis AX4 of the microparticle 64B is parallel or substantially
parallel to the optical axis AX3 of the bulk 64 A in a certain light modulation cell 30-1
and the optical axis AX4 of the microparticle 64B intersects or is orthogonal to the
optical axis AX3 of the bulk 64A in the other light modulation cell 30-1. As a result,
the light that has been emitted from the light source 20 and has entered the light guide
plate 10 passes through the transmissive region 30A of the light modulation device 60
where the optical axis AX3 is parallel or substantially parallel to the optical axis AX4.
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In addition, the light that has been emitted form the light source 20 and has entered the
light guide plate 10 is scattered in the scattering region 3 OB of the light modulation
device 60 where the optical axis AX3 intersects or is orthogonal to the optical axis AX4.
Light that has passed through the lower surface of the scattering region 3 OB of the
scattered light is reflected by the reflector 40 to return to the light guide plate 10 again,
and then is emitted from the upper surface of the backlight 2. In addition, light toward
the upper surface of the scattering region 3 OB of the scattered light passes through the
light guide plate 10, and then is emitted from the upper surface of the backlight 2. As
described above, in the present embodiment, light is scarcely emitted from the upper
surface of the transmissive region 30A and the light is emitted from the upper surface of
the scattering region 30B. In this way, the modulation ratio in the front direction is
increased.
[0105] Incidentally, in the present embodiment, since the bulk 64A and the
microparticle 64B are formed to mainly contain respective optical anisotropic materials,
the scattering property is decreased and the transparency is improved in the oblique
direction. For example, in a region where the bulk 64A and the microparticle 64B
mainly contain respective optical anisotropy materials whose ordinary refractive indices
are equal to each other and whose extraordinary refractive indices are also equal to each
other and a voltage is not applied between the partial electrodes 32A and the upper
electrode 36, the directions of the optical axes thereof coincide or substantially coincide
with each other. Therefore, difference in refractive index is decreased or eliminated in
all directions including the front direction (the normal direction of the light modulation
device 60) and the oblique direction, and higher transparency is obtainable. As a result,
1
light leakage in a region where a viewing angle is large is decreased or substantially
eliminated, and viewing angle characteristics are improved.
[0106] For example, when a liquid crystal that has an ordinary refractive index of 1.5
and an extraordinary refractive index of 1.65 and a liquid crystalline monomer that has
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an ordinary refractive index of 1.5 and an extraordinary refractive index of 1.65 are
mixed and the liquid crystalline monomer is polymerized in a state where the liquid
crystal and the liquid crystalline monomer are aligned by the alignment film or an
electric field, the optical axis of the liquid crystal coincides with the optical axis of a
polymer formed by polymerization of the liquid crystalline monomer. As a result,
since the refractive indices are coincident with each other in all directions, in such a
case, a state with higher transparency is achievable and the viewing angle characteristics
are further improved.
[0107] In addition, in the present embodiment, for example, the luminance of the
transmissive region 30A (the luminance of black display) is lower than that in the case
where the light modulation device 60 is not provided. On the other hand, the
luminance of the scattering region 3 OB is extremely higher than that in the case where r
the light modulation device 60 is not provided, and further, the luminance of partial
white display (luminance enhancement) is increased by a decreased amount of the
luminance of the transmissive region 30A. This is because the bulk 64A and the
microparticle 64B are formed to mainly contain respective optical anisotropic materials,
scattering property in the oblique direction is suppressed and leakage of light form the
light guide plate in a dark state is suppressed. Therefore, the light is guided from the
partial dark region to the partial bright region so that luminance enhancement is
achievable without increasing power supplied to the backlight 2.
[0108] Moreover, in the present embodiment, when the vertical alignment film has the
above-described pretilt function, in a region where a voltage is not applied between the l
partial electrodes 32A and the upper electrode 36, the optical axis AX4 of the
microparticle 64B is parallel (or substantially parallel) to the light incident surface 10A
of the light guide plate 10, and intersects the normal of the transparent substrate 31 at a
predetermined pretilt angle. Specifically, the liquid crystal molecule contained in the
microparticle 64B is aligned in a state of being inclined at the predetermined pretilt
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angle in a plane parallel to the light incident surface 10A. Therefore, when a voltage is
applied between the partial electrodes 32A and the upper electrode 36, the liquid crystal
molecule contained in the microparticle 64B does not stand up in a random direction,
and stands up in the plane parallel to the light incident surface 10A. At this time, the
optical axis AX3 of the bulk 64A intersects or is orthogonal to the optical axis AX4 of
the microparticle 64B in the plane parallel to the light incident surface 10A.
Accordingly, in the region where a voltage is applied between the partial electrodes 32A
and the upper electrode 36, difference in refractive index is increased in all directions
including the front direction (the normal direction of the light modulation device 60)
and the oblique direction, and high scattering property is obtainable. As a result,
display luminance is allowed to be improved. In addition, luminance is allowed to be
further improved by the effect of the above-described luminance enhancement.
[0109] Moreover, also in the present embodiment, the plurality of partial electrodes
32A arranged in the direction orthogonal to the light incident surface 10A are
sequentially driven on the predetermined unit basis. Accordingly, during the process
in which the light emitted from the light source 20 propagates through the light guide
plate 10, the region exhibiting the scattering property (the scattering region 3 0B) of the
light modulation layer 64 is scanned in the direction orthogonal to the light incident
surface 10A. As a result, the light that is scattered in the scattering region 3 0B and is
to be emitted from the upper surface of the backlight 2 to the outside is scanned in the
direction orthogonal to the light incident surface 10A. At this time, since the scan
driving of the light source 20 is not performed, luminance higher than that in the
existing method in which scan driving of a light source is performed is obtainable by the
effect of the above-described luminance enhancement. In addition, in the present
embodiment, as described above, since the scan driving of the light source 20 is not
performed, it is rarely necessary to consider inrush power generated when a large power
is supplied to the light source in an extremely short time to perform the scan driving,
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and reliability of the circuit board is not impaired.
[0110] As described above, also in the present embodiment, light emitted from the
upper surface of the backlight 2 is scanned by scanning the scattering region 3 OB of the
light modulation layer 64 instead of the scan driving of the light source 20, and thus
high luminance, low power consumption, high reliability of the circuit board are all
achievable at a time in scan system.
[0111] <3. Modifications>
[First Modification]
In each of the above-described embodiments, during the process in which the
plurality of partial electrodes 32A are sequentially driven on the predetermined unit
basis, the drive circuit 50 may turn on the light source 20 constantly. For example, as
illustrated in (A) and (B) of FIG. 19, when one or the plurality of partial electrodes 32 A
are regarded as one block, the drive circuit 50 may turn on the light source 20 in
synchronization with drive of a first block, and may continuously turn on the light
source 20 until completion of scanning of all blocks during the process in which the
plurality of partial electrodes 32A are sequentially driven on a block basis.
[0112] Note that (A) of FIG. 19 conceptually illustrates an example of timings of
voltage application to the partial electrodes 3 2A, and (B) of FIG. 19 schematically
illustrates an example of a waveform of a voltage applied to the light source 20. In (A)
and (B) of FIG. 19, the case where the drive circuit 50 turns on the light source 20 at the
same time as driving of the first block is started is exemplified, however, the drive
circuit 50 may turn on the light source 20 before driving of the first block is started. In
addition, in consideration of a property in which a liquid crystal responds to the voltage
application with a time lag, the drive circuit 50 may turn on the light source 20
immediately after the driving of the first block is started.
[0113] [Second Modification]
Moreover, in each of the above-described embodiments, the drive circuit 50
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may blink the light source 20 in synchronization with the drive timings of the partial
electrodes 32A during the process in which the plurality of partial electrodes 32A are
sequentially driven on the predetermined unit basis. For example, as illustrated in (A)
and (B) of FIG. 20, the drive circuit 50 may turn on the light source 20 only in a period
where a voltage is applied to the partial electrodes 32A during the process in which the
plurality of partial electrodes 32A are sequentially driven on the predetermined unit
basis.
[0114] Note that (A) of FIG. 20 conceptually illustrates an example of timings of
voltage application to the partial electrodes 32A, and (B) of FIG. 20 schematically
illustrates an example of a waveform of a voltage applied to the light source 20. In (A)
and (B) of FIG. 20, the case where the drive circuit 50 turns on the light source 20 at the
same time as driving of each block is started is exemplified, however, the drive circuit
50 may turn on the light source 20 before the driving of each block is started. In
addition, in consideration of the property in which the liquid crystal responds to the
voltage application with a time lag, the drive circuit 50 may turn on the light source 20
immediately after the driving of each block is started.
[0115] In the present modification, it may be said that the drive circuit 50 turns on the
light source 20 when the light modulation layer 34 exhibits the scattering property in
some regions thereof, and turns off the light source 20 when the light modulation layer
34 exhibits transparency over the entire region thereof.
[0116] Incidentally, in each of the above-described embodiments, when the scan
driving is performed at high speed (for example, at several hundreds Hz), a waveform of
the voltage applied to the partial electrode 32A may be distorted by a time constant
determined by wiring resistance of the partial electrode 32A and an electrostatic
capacitance of the light modulation layer 34 (or the light modulation layer 64), and thus
the applied waveform may be delayed at an end of the partial electrode 32A. In this
case, in the light emitted from the backlight 1 (or the backlight 2), defects in image
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quality such as difference in brightness in a direction corresponding to the extending
direction of the partial electrode 32A and interference of adjacent scan region may
occur. Therefore, for example, as illustrated in (A) and (B) of FIG. 20, when such
defects occur, it is preferable to blink the light source 20 in synchronization with the
drive timings of the partial electrodes 32A during the process in which the plurality of
partial electrodes 32A are sequentially driven on the predetermined unit basis. In this
way, image quality at the time of high speed scan driving is allowed to be improved.
[0117] [Third Modification]
In addition, in each of the above-described embodiments and the modification
thereof (hereinafter, simply referred to as "each of the above-described embodiments
and the like"), for example, as illustrated in FIG. 21, a metal wiring 43 extending in the
extending direction of the partial electrodes 32A may be provided to be in contact with
each of the partial electrodes 3 2 A. The metal wiring 43 is preferably formed of a
material that has a surface to be a mirror as much as possible and has wiring resistance
as low as possible. Examples of such a material include Al (aluminum), Ag (silver),
Au (gold), Cu (copper), Mo (molybdenum), and Ta (tantalum). The metal wiring 43
preferably has a width to the extent where the metal wiring 43 does not become a dark
line for the backlight 1 or 2, and the width is preferably 500 um or less, is more
preferably 300 urn or less, and is still more preferably 150 urn or less.
[0118] [Fourth Modification]
In addition, in each of the above-described embodiments and the like, the drive
circuit 50 may adjust the light amount of the light source 20 depending on the distance
of the partial electrode 32A to be driven from the light source 20. For example, the
drive circuit 50 may increase the light amount of the light source 20 with increasing the
distance of the partial electrode 32 A to be driven from the light source 20.
[0119] [Fifth Modification]
Moreover, in each of the above-described embodiments and the like, as
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illustrated in FIG. 22, each of the partial electrodes 32A may be configured of a
plurality of thin wire electrodes 32B. Note that, the thin wire electrode 32B
corresponds to a specific example of "partial electrode" of the invention in some cases.
Incidentally, in the present modification, the drive circuit 50 may apply a voltage that is
modulated depending on the distance from the light source 20, to the plurality of thin
wire electrodes 32B included in the partial electrode 32A to be driven during the
process in which the plurality of partial electrodes 32A are sequentially driven on the
predetermined unit basis. For example, as illustrated in FIG. 23, the drive circuit 50
may apply, to the plurality of thin wire electrodes 32B included in the partial electrode
32A to be driven, a voltage whose crest value is increased with increasing the distance
from the light source 20 during the process in which the plurality of partial electrodes
32A are sequentially driven on the predetermined unit basis. In addition, the drive
circuit 50 may sequentially drive the plurality of thin wire electrodes 32B on a
predetermined unit basis (for example, for each partial electrode 32A), or may
sequentially drive the plurality of thin wire electrodes 32B one by one.
[0120] [Sixth Modification]
In addition, in each of the above-described embodiments and the like, each of
the partial electrodes 32A may be patterned. For example, as illustrated in FIGs.
24(A) and 24(B), each of the partial electrodes 32A may have a plurality of openings
32C. The opening 32C has, for example, a circular shape, an ellipsoidal shape, or a
multangular shape. At this time, density of the plurality of openings 32C (occupancy
of the openings 32B per unit area) provided in each of the partial electrodes 32A is
varied depending on the distance from the light source 20. For example, as illustrated
in FIG. 24(A), the number of the openings 32C per unit area may be fixed irrespective
of the distance from the light source 20, and the diameter of the opening 32C may be
decreased with increasing the distance from the light source 20. In addition, for
example, as illustrated in FIG. 24(B), the diameter of the opening 32C may be fixed
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irrespective of the distance from the light source 20, and the number of the openings
32C per unit area may be decreased with increasing the distance from the light source
20. Therefore, in both of the above-described examples, the density of the openings
32C becomes sparse (is decreased) with increasing the distance from the light source 20.
In other words, the pattern density of the partial electrode 32A (occupancy of a region
other than the openings 32C in the partial electrode 32A per unit area) becomes dense
(is increased) with increasing the distance from the light source 20.
[0121] As described above, varying the pattern density of the partial electrode 32A
depending on the distance from the light source 20 provides a desired density
distribution of the transparent region 30A and the scattering region 30B in the light
emission region of the backlight 1 or 2. Therefore, the luminance on a side closer to
the light source 20 in the light emission region of the backlight 1 or 2 is suppressed as
compared with the case where the light modulation device 30 or 60 is not provided, and
the luminance on a side farther from the light source 20 in the light emission region of
the backlight 1 or 2 is allowed to be higher than that in the case where the light
modulation device 30 or 60 is not provided. As a result, for example, in addition to the
case where the entire light emission region of the backlight 1 or 2 is in a dark state, also
in the case where the entire light emission region of the backlight 1 or 2 is in a bright
state, in-plane luminance is allowed to be uniform. Accordingly, for example, when
white display is performed in a region closer to the light source 20 and in a region
farther from the light source 20, white luminance in both regions are allowed to be
equivalent to each other. Moreover, for example, when a black display is performed in
the region closer to the light source 20 and in the region farther from the light source 20,
black luminance in both regions are allowed to be equivalent to each other. As
described above, in the present modification, the modulation ratio is allowed to be
increased while in-plane luminance is uniform.
[0122] [Seventh Modification]
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#
Moreover, in each of the above-described embodiments and the like, the light
modulation device 30 or 60 is tightly adhered to the back (the lower surface) of the light
guide plate 10 without an air layer in between, however, for example, as illustrated in
FIG. 25, the light modulation device 30 or 60 may be tightly adhered to the upper
surface of the light guide plate 10 without an air layer in between. In addition, for
example, as illustrated in FIG. 26, the light modulation device 30 or 60 may be provided
inside the light guide plate 10. However, also in this case, it is necessary for the light
modulation device 30 or 60 to be tightly adhered to the light guide plate 10 without an
air layer in between.
[0123] [Eighth Modification]
In addition, in the above-described embodiments and the like, nothing is
provided particularly on the light guide plate 10, however, for example as illustrated in
FIG. 27, an optical sheet 70 (for example, a diffuser plate, a diffuser sheet, a lens film,
or a polarization separation sheet) may be provided. In such a case, part of the light
emitted from the light guide plate 10 in the oblique direction stands up in the front
direction, and thus the modulation ratio is effectively improved.
[0124]
[First Application Example]
Next, an application example of the backlights 1 and 2 of the above-described
embodiments and the like will be described.
[0125] FIG. 28 illustrates an example of a schematic configuration of a display 3
according to the present application example. The display 3 includes a display panel
80 and the backlight 1 or 2 provided behind the display panel 80.
[0126] The display panel 80 displays a picture. The display panel 80 includes a
plurality of pixels two-dimensionally arranged, and the plurality of pixels are driven
based on a picture signal to allow the display panel 80 to display a picture. The
display panel 80 is, for example, a transmissive liquid crystal display panel, and has a
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structure in which a liquid crystal layer is sandwiched between a pair of transparent
substrates. The display panel 80 includes, for example, although not illustrated, a
polarizer, a transparent substrate, pixel electrodes, an alignment film, a liquid crystal
layer, an alignment film, a common electrode, a color filter, a transparent substrate, and
a polarizer in order from the backlight 1 or 2 side.
[0127] The transparent substrate is formed of a substrate transparent to visible light,
for example, a plate glass. Incidentally, although not illustrated, a TFT (thin film
transistor) electrically connected to the pixel electrodes and an active drive circuit
including wirings and the like are formed on the transparent substrate on the backlight 1
or 2 side. The pixel electrodes and the common electrode are each formed of, for
example, ITO. The pixel electrodes are arranged regularly, for example, in lattice
arrangement or delta arrangement, on the transparent substrate. The pixel electrode
functions as an electrode for each pixel. On the other hand, the common electrode is
formed on the entire surface of the color filter. The common electrode functions as a
common electrode opposing to the pixel electrodes. The alignment film is formed of a
polymer material such as polyimide, and performs alignment treatment on the liquid
crystal. The liquid crystal layer is formed of a liquid crystal of, for example, VA
(Vertical Alignment) mode, TN (Twisted Nematic) mode, or STN (Super Twisted
Nematic) mode, and has a function of changing the direction of the polarizing axis of
the light emitted from the backlight 1 or 2 for each pixel, in response to a voltage
applied from the drive circuit (not illustrated). Incidentally, the direction of the
transmission axis for each pixel is adjusted at multiple levels by changing the
arrangement of the liquid crystal at multiple levels. The color filter is configured by
arranging, corresponding to the arrangement of the pixel electrodes, color filters that
separates light that has passed through the liquid crystal layer, into three primary colors
of red (R), green (G), and blue (B), for example, or into four colors of R, G, B, and
white (W). Examples of the filter arrangement (pixel arrangement) include, typically,
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#
stripe arrangement, diagonal arrangement, delta arrangement, and rectangle
arrangement.
[0128] The polarizer is a kind of an optical shutter, and allows light (polarized light)
that oscillates in a certain direction to pass therethrough. Note that the polarizer may
be an absorption type polarizing device absorbing light (polarized light) that oscillates
in a direction other than the transmission axis, however, the polarizer is preferably a
reflection type polarizing device reflecting the light toward the backlight 1 or 2 side in
terms of luminance improvement. The polarizers are disposed so that the polarizing
axes are different by 90 degrees from each other, and this allows the light emitted from
the backlight 1 or 2 to pass therethrough through the liquid crystal layer or to be
blocked.
[0129] In the backlight 1 or 2, the plurality of partial electrodes 32A are arranged in a
direction parallel to one arrangement direction (for example, a vertical direction) of the
plurality of pixels (or pixel electrodes) of the display panel 80. Incidentally, when the
plurality of pixels (or pixel electrodes) are arranged also in a horizontal direction, the
plurality of partial electrodes 32A preferably extend in the horizontal direction. The
width of each of the partial electrodes 32A may be equal to, however, is preferably
wider than the width of each pixel of the display panel 80. This is because the
scanning of each scattering region 3 0B of the backlight 1 or 2 is not necessarily precise
unlike the scanning of the pixels of the display panel 80. Note that, in the following, it
is assumed that the width of each of the partial electrodes 32 A is wider than the width of
each pixel of the display panel 80.
[0130] In the present application example, the drive circuit 50 sequentially drives the
plurality of pixels (or pixel electrodes) of the display panel 80 for each line to modulate
the light emitted from the backlight 1 or 2 by the display panel 80. Therefore, the
drive circuit 50 displays a picture on the display panel 80. In addition, the drive circuit
50 sequentially drives the plurality of partial electrodes 32A of the backlight 1 or 2 on
51
^ SP312411
#
the predetermined unit basis to scan the region exhibiting the scattering property (the
scattering region 3 OB) of the light modulation layer 34 or 64 in the direction orthogonal
to the light incident surface 10A. Accordingly, the drive circuit 50 scans the light that
is scattered in the scattering region 3 OB and is to be emitted from the upper surface of
the backlight 1 or 2 to the back surface of the display panel 80, in the direction
orthogonal to the light incident surface 10A during the process in which the light
emitted from the light source 20 propagates through the light guide plate.
[0131] Further, the drive circuit 50 drives the plurality of partial electrodes 32A in
synchronization with driving of the plurality of pixels of the display panel 80. For
example, as illustrated in (A) and (B) of FIG. 29, when the plurality of pixels
corresponding to a plurality of lines (in the drawing, 135 lines) are regarded as one
block and one or the plurality of partial electrodes 32A corresponding to the block are
regarded as one block, the drive circuit 50 drives one or the plurality of partial
electrodes 32A included in a block corresponding to a block that includes a pixel to be
driven, out of the plurality of partial electrodes 3 2A, during the process in which the
plurality of pixels of the display panel 80 are sequentially driven on a line basis. Note
that (A) of FIG. 29 conceptually illustrates an example of timings of voltage application
to the plurality of pixels of the display panel 80, and (B) of FIG. 29 conceptually
illustrates an example of timings of voltage application to the partial electrodes 3 2 A.
[0132] In (A) and (B) of FIG. 29, the case where the drive circuit 50 starts to drive the
partial electrodes 32A at the same time as driving of the pixels of the display panel 80 is
started is exemplified, however, the drive circuit 50 may start to drive the partial
electrodes 32A before the driving of the pixels of the display panel 80 is started. In
addition, in consideration of property in which the liquid crystal responds to voltage
application with a time lag, the drive circuit 50 may start to drive the partial electrodes
32A immediately after the driving of the pixels of the display panel 80 is started.
[0133] In addition, the drive circuit 50 may drive one or a plurality of partial
52
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*
electrodes 32A included in a block corresponding to a block that includes a pixel to be
driven, out of the plurality of partial electrodes 3 2A, and may blink the light source 20
in synchronization with the drive timing of the partial electrode 32A, during the process
in which the plurality of pixels of the display panel 80 are sequentially driven on a line
basis. For example, the drive circuit 50 may turn on the light source 20 as described in
the above-described second modification. In such a case, display with high luminance
and suppressed blur of moving picture responsiveness becomes possible.
[0134] In the present application example, as the light source illuminating the display
panel 80, the backlight 1 or 2 of the above-described embodiments is used. Therefore,
in the scan system, an image with high contrast and high display luminance is allowed
to be displayed with low power consumption. Moreover, in the present application
example, when the plurality of partial electrodes 32A are driven in synchronization with
the driving of the plurality of pixels of the display panel 80 and the light source 20 is
blinked in synchronization with sequential driving of the partial electrodes 32A on the
predetermined unit basis, display with high luminance and suppressed blur of moving
picture responsiveness becomes possible.
[0135] [Second Application Example]
Next, other application example of the backlights 1 and 2 of the
above-described embodiments and the like will be described.
[0136] FIG. 30 illustrates an example of a schematic configuration of a
three-dimensional display 4 according to the present application example. The
three-dimensional display 4 allows observation of a stereoscopic image by time-division
system, and includes, for example, a display 3 and shutter glasses 5. The display 3 is a
display (3D display) allowing a viewer to perceive a stereoscopic picture when the
viewer views the image display surface 3 A of the display 3 through the shutter glasses
5.
[0137] In the display 3, although not illustrated, for example, the drive circuit 50
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includes a picture signal processing circuit, a timing generation circuit, a signal line
drive circuit, and a scan line drive circuit. The picture signal processing circuit
performs a predetermined correction on a digital picture signal input from the outside,
and outputs a corrected picture signal to the signal line drive circuit. Examples of a
kind of the picture signal include a picture signal for right-eye image, a picture signal
for left-eye image, and a picture signal for black image. Moreover, examples of the
predetermined correction includes gamma correction and overdrive correction.
[0138] The timing generation circuit controls the signal line drive circuit, the scan line
drive circuit, and the shutter glasses 5 to operate in conjunction with one another. For
example, the timing generation circuit outputs a- control signal to these circuits and the
like in response to (in synchronization with) a synchronization signal input from the
outside.
[0139] The signal line drive circuit applies an analog picture signal corresponding to
the picture signal input from the picture signal processing circuit to each signal line (not
illustrated) in the display panel 80 in response to (in synchronization with) the input of
the above-described control signal, and writes the analog picture signal or a signal
corresponding thereto in a pixel to be selected. For example, the signal line drive
circuit applies, for each frame period, a signal voltage corresponding to the picture
signal for black image, a signal voltage corresponding to the picture signal for right-eye
image, the signal voltage corresponding to the picture signal for black image, and a
signal voltage corresponding to the picture signal for left-eye image in this order to each
signal line, and writes the signal to a pixel to be selected.
[0140] The scan line drive circuit sequentially applies a selection pulse to a plurality
of scan lines (not illustrated) in the display panel 80 in response to (in synchronization
with) the input of the above-described control signal, and sequentially selects the
plurality of pixels for each line.
[0141] The shutter glasses 5 are worn in front of eyes of a viewer (not illustrated), and
54
SP312411
are used by the viewer when the viewer views an image displayed on the image display
surface 3 A of the display 3. The shutter glasses 5 includes, for example, a right-eye
shutter 51, a left-eye shutter 52, and a control line (not illustrated) applying a control
signal for controlling open and close of the right-eye shutter 51 and open and close of
the left-eye shutter 52. The control line for shutter control may be directly connected
to the drive circuit 50 of the display 3, or may be connected to a wireless unit (not
illustrated) capable of communicating with the drive circuit 50 of the display 3. The
right-eye shutter 51 and the left-eye shutter 52 performs transmission and blocking of an
image output from the image display surface 3A based on the control signal. The
right-eye shutter 51 is opened when a right-eye image is output from the image display
surface 3 A. On the other hand, the left-eye shutter 52 is opened when a left-eye image
is output from the image display surface 3 A.
[0142] In the following, a period during which at least a part of the right-eye image is
displayed on the image display surface 3A is referred to as a period for displaying a
right-eye image (right-eye image display period). Likewise, a period during which at
least a part of the left-eye image is displayed on the image display surface 3 A is referred
to as a period for displaying a left-eye image (left-eye image display period). In
addition, a period during which a black image is displayed on the entire image display
surface 3A is referred to as a period for displaying a black image (black image display
period).
[0143] For example, the drive circuit 50 repeats the black image display period, the
right-eye image display period, the black image display period, and the left-eye image
display period, for each frame period. At this time, the viewer wears the shutter
glasses 5 to perceive the left-eye image only by his left eye and to perceive the right-eye
image only by his right eye. For example, the drive circuit 50 outputs a control signal
for opening the left-eye shutter 52 (for allowing the left-eye glass to be in a transmissive
state) during the left-eye image display period, and outputs a control signal for closing
55
SP312411
the left-eye shutter 52 (for allowing the left-eye glass to be in a non-transmissive state)
during the other periods. In addition, the drive circuit 50 outputs a control signal for
opening the right-eye shutter (for allowing the right-eye glass to be in a transmissive
state) during the right-eye image display period, and outputs a control signal for closing
the right-eye shutter (for allowing the right-eye glass to be in a non-transmissive state)
during the other periods. Accordingly, the left-eye image is perceived only by the left
eye and the right-eye image is perceived only by the right eye, and therefore the left-eye
image and the right-eye image are imaged on the retina of the viewer. As a result, the
>
viewer can view a stereoscopic picture.
[0144] The drive circuit 50 sequentially drives the plurality of partial electrodes 32A
on the predetermined unit basis to scan the region exhibiting the scattering property (the
scattering region 3 OB) of the light modulation layer 34 or 64 in the direction orthogonal
to the light incident surface 10A. Therefore, the drive circuit 50 scans the light that is
scattered in the scattering region 3 OB and is to be emitted from the upper surface of the
backlight 1 or 2 to the outside in the direction orthogonal to the light incident surface
10A, during the process in which the light emitted from the light source 20 propagates
through the light guide plate. Similarly to the above-described first application
example, the drive circuit 50 drives the plurality of partial electrodes 32A in
synchronization with the drive of the plurality of pixels of the display panel 80.
Further, similarly to the above-described first application example, the drive circuit 50
may drive the plurality of partial electrodes 32 A in synchronization with the drive of the
plurality of pixels of the display panel 80 as well as may blink the light source 20 in
synchronization with the sequential drive of the partial electrodes 32A on the
predetermined unit basis.
[0145] In the present application example, the backlight 1 or 2 of the above-described
embodiments is used as the light source illuminating the display panel 80. Therefore,
in the scan system, an image with high contrast and high display luminance is displayed
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with low power consumption. In addition, in the present application example, when
the plurality of partial electrodes 32 A are driven in synchronization with the drive of the
plurality of pixels of the display panel 80 as well as the light source 20 is blinked in
synchronization with the sequential drive of the partial electrodes 32A, display with
high luminance and suppressed blur of moving picture responsiveness becomes possible
and occurrence of crosstalk between the left-eye image and the right-eye image is
allowed to be suppressed.
V:
f
:
:
'<
(
5 7

SP312411
*
CLAIMS
L A display comprising:
a lighting unit outputting illumination light;
a display panel modulating the illumination light to output a picture; and
a drive circuit driving the lighting unit and the display panel, wherein
the lighting unit includes
a light guide plate,
a light source disposed on a side surface of the light guide plate, and
a light modulation device disposed on a surface or in an inside of the
light guide plate and bonded to the light guide plate,
the light modulation device includes
a pair of transparent substrates disposed opposite to each other with a
distance in between,
a pair of electrodes disposed on respective surfaces of the pair of
transparent substrates, and
a light modulation layer provided in a gap between the pair of
transparent substrates,
one or both of the pair of electrodes have a plurality of partial electrodes
arranged in a direction orthogonal to a light incident surface of side surfaces of the light
guide plate, the light incident surface receiving light from the light source,
the light modulation layer totally or partially exhibits scattering property or
transparency to the light from the light source depending on a magnitude of an electric
field generated by the electrodes, and
the drive circuit sequentially drives the plurality of partial electrodes on a
predetermined unit basis to scan a region exhibiting the scattering property of the light
modulation layer in the direction orthogonal to the light incident surface.
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2. The display according to claim 1, wherein
the display panel includes a plurality of pixels two-dimensionally arranged,
the plurality of partial electrodes are arranged in a first direction parallel to one
arrangement direction of the plurality of pixels, and
the drive circuit sequentially drives the plurality of pixels on the predetermined
unit basis in the first direction and drives the plurality of partial electrodes in
synchronization with the drive of the plurality of pixels.
3. The display according to claim 2, wherein the light modulation layer
exhibits transparency when a voltage is not applied to the electrodes, and exhibits
scattering property when a voltage is applied to the electrodes.
4. The display according to claim 3, wherein the light modulation layer
includes a liquid crystal molecule and a polymer, the liquid crystal molecule responding
to the electric field generated by the electrodes at a relatively high speed, and the
polymer responding to the electrode field generated by the electrodes at a relatively low
speed.
5. The display according to claim 4, wherein the liquid crystal molecule and
the polymer are aligned in a direction parallel to or substantially parallel to the light
incident surface and the transparent substrates when a voltage is not applied to the
electrodes.
6. The display according to any one of claims 1 to 5, wherein the drive circuit
constantly turns on the light source.
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«r
7. The display according to any one of claims 1 to 5, wherein the drive circuit
turns on the light source when the light modulation layer exhibits scattering property,
and turns off the light source when the light modulation layer totally exhibits
transparency.
8. The display according to any one of claims 1 to 5, wherein
the light source is disposed on a first side surface and a second side surface of
side surfaces of the light guide plate, the first side surface and the second side surface
facing each other, and
the drive circuit sequentially drives the plurality of partial electrodes on the
predetermined unit basis, makes the light source disposed on the first side surface
blighter than the light source disposed on the second side surface when the partial
electrode to be driven is located closer to the first side surface, and makes the light
source disposed on the second side surface brighter than the light source disposed on the
first side surface when the partial electrode to be driven is located closer to the second
side surface.
9. The display according to any one of claims 1 to 5, wherein the drive circuit
adjusts a light amount of the light source depending on a distance of the partial
electrode to be driven of the plurality of partial electrodes from the light source.
10. The display according to any one of claims 1 to 5, wherein
each of the partial electrodes is formed of a plurality of thin wire electrodes,
and
the drive circuit applies a voltage to the plurality of thin wire electrodes
included in the partial electrode to be driven when sequentially driving the plurality of
partial electrodes on the predetermined unit basis, the voltage being modulated
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*
depending on the distance from the light source.
11. The display according to any one of claims 1 to 5, wherein
each of the partial electrodes is patterned, and
a pattern density of each of the partial electrodes is varied depending on the
distance from the light source.
12. The display according to claim 11, wherein
each of the partial electrodes has a plurality of openings,
each of the openings has a fixed diameter irrespective of the distance from the
light source, and
a density of the openings is varied depending on the distance from the light
source.
13. The display according to claim 11, wherein
each of the partial electrodes has a plurality of openings,
each of the openings has a different diameter depending on the distance from
the light source, and
a density of the openings is varied depending on the distance from the light
source.
14. The display according to any one of claims 1 to 5, wherein
each of the partial electrodes has a strip shape extending in a direction parallel
to the light incident surface, and
i
the light modulation device extends in the direction parallel to the light incident
surface and has a plurality of metal wires electrically connected to the respective partial
electrodes.
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15. A three-dimensional display comprising:
a display outputting a picture and a control signal; and
shutter glasses having a right-eye shutter and a left-eye shutter, the right-eye
shutter and the left-eye shutter performing transmission and blocking of the picture
based on the control signal, wherein
the display includes
a lighting unit outputting illumination light,
a display panel modulating the illumination light to output the picture,
an output circuit outputting the control signal, and
a drive circuit driving the lighting unit, the display panel, and the
output circuit,
the lighting unit includes
a light guide plate,
a light source disposed on a side surface of the light guide plate, and
a light modulation device disposed on a surface or in an inside of the
light guide plate and bonded to the light guide plate,
the light modulation device includes
a pair of transparent substrates disposed opposite to each other with a
distance in between,
a pair of electrodes disposed on respective surfaces of the pair of
transparent substrates, and
a light modulation layer provided in a gap between the pair of
transparent substrates,
one or both of the pair of electrodes have a plurality of partial electrodes
arranged in a direction orthogonal to a light incident surface of side surfaces of the light
guide plate, the light incident surface receiving light from the light source,
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the light modulation layer totally or partially exhibits scattering property or
transparency to the light from the light source depending on a magnitude of an electric
field generated by the electrodes, and
the drive circuit sequentially drives the plurality of partial electrodes on a
predetermined unit basis to scan a region exhibiting the scattering property of the light
modulation layer in the direction orthogonal to the light incident surface.
16. A lighting unit comprising:
a light guide plate;
a light source disposed on a side surface of the light guide plate;
a light modulation device disposed on a surface or in an inside of the light
guide plate and bonded to the light guide plate; and
a drive circuit driving the light source and the light modulation device, wherein
the light modulation device includes
a pair of transparent substrates disposed opposite to each other with a
distance in between,
a pair of electrodes disposed on respective surfaces of the pair of
transparent substrates, and
a light modulation layer provided in a gap between the pair of
transparent substrates,
one or both of the pair of electrodes have a plurality of partial electrodes
arranged in a direction orthogonal to a light incident surface of side surfaces of the light
guide plate, the light incident surface receiving light from the light source,
the light modulation layer totally or partially exhibits scattering property or
transparency to the light from the light source depending on a magnitude of an electric
field generated by the electrodes, and
the drive circuit sequentially drives the plurality of partial electrodes on a
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predetermined unit basis to scan a region exhibiting the scattering property of the light
modulation layer in the direction orthogonal to the light incident surface.