U.S. patent application number 12/232366 was filed with the patent office on 2009-01-29 for liquid crystal display device having a prism sheet between first and second light diffusion.
This patent application is currently assigned to Hitachi Displays, Ltd.. Invention is credited to Kouichi Fukuda, Tetsuya Nagata.
Application Number | 20090027593 12/232366 |
Document ID | / |
Family ID | 32321594 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090027593 |
Kind Code |
A1 |
Fukuda; Kouichi ; et
al. |
January 29, 2009 |
Liquid crystal display device having a prism sheet between first
and second light diffusion
Abstract
In a liquid crystal display device capable of performing as both
a transmissive display and a reflective display using a
transmissive type liquid crystal display panel, the influence
attributed to a shade as viewed from the oblique direction can be
reduced so that favorable visibility can be ensured. In a liquid
crystal display device including a transmissive type liquid crystal
display panel which sandwiches a liquid crystal layer between a
pair of substrates and a backlight which is arranged at a back face
of the liquid crystal display panel and has a light source and a
reflector, wherein the device is capable of performing as a
transmissive display using light from the light source and as a
reflective display using external light incident from a front face
side of the liquid crystal display panel by reflecting the external
light on the reflector, at least two or more light diffusion layers
are arranged between the back-face-side substrate out of the pair
of substrates and the reflector of the backlight.
Inventors: |
Fukuda; Kouichi; (Mobara,
JP) ; Nagata; Tetsuya; (Mobara, JP) |
Correspondence
Address: |
Stanley P. Fisher;Reed Smith LLP
Suite 1400, 3110 Fairview Park Drive,
Falls Church
VA
22042-4503
US
|
Assignee: |
Hitachi Displays, Ltd.
|
Family ID: |
32321594 |
Appl. No.: |
12/232366 |
Filed: |
September 16, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10662405 |
Sep 16, 2003 |
7443461 |
|
|
12232366 |
|
|
|
|
Current U.S.
Class: |
349/64 |
Current CPC
Class: |
G02B 6/0056 20130101;
G02F 1/133626 20210101; G02B 6/0051 20130101 |
Class at
Publication: |
349/64 |
International
Class: |
G02F 1/13357 20060101
G02F001/13357 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 28, 2002 |
JP |
2002-312032 |
Claims
1. A liquid crystal display device comprising: a transmissive type
liquid crystal display panel which sandwiches a liquid crystal
layer between a pair of substrates; a light source; a light guide
body which is arranged at a back face side of the liquid crystal
display panel and on which light from the light source is incident;
and a reflector which is arranged at a back face of the light guide
body, wherein the liquid crystal display device is configured to
simultaneously perform as a transmissive display which transmits
the light form the light source therethrough and as a reflective
display which reflects external light incident from a front face
side of the liquid crystal display panel by the reflector, a first
polarizer is arranged between the back-face-side substrate of the
pair of substrates and the light guide body, the first polarizer is
formed to absorb polarized light having a predetermined
polarization direction, a first light diffusion layer and a second
light diffusion layer are arranged between the back-face-side
substrate of the pair of substrates and the light guide body, a
prism sheet and a second polarizer are arranged between the first
light diffusion layer and the second light diffusion layer, the
first polarizer is provided with an antiglare layer as the first
light diffusion layer, and the second polarizer is a reflection
polarizer.
2. A liquid crystal display device according to claim 1, wherein
the first light diffusion layer and the second light diffusion
layer diffuse the external light and make a shade hardly apparent
when viewed from an oblique direction.
3. A liquid crystal display device according to claim 1, wherein
the second light diffusion layer is a diffusion film.
4. A liquid crystal display device according to claim 1, wherein
the second light diffusion layer is a diffusion sheet.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Continuation from U.S. application
Ser. No. 10/662,405 filed on Sep. 16, 2003. Priority is claimed
based on U.S. application Ser. No. 10/662,405 filed on Sep. 16,
2003, which claims priority from Japanese Patent Application No.
2002-312032 filed on Oct. 28, 2002, the content of which is hereby
incorporated by reference into this application.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a liquid crystal display
device, and more particularly to a liquid crystal display device
which is capable of performing both of a transmissive display and a
reflective display using a transmissive-type liquid crystal display
panel.
[0003] For example, with respect to a liquid crystal display device
which is served for a mobile telephone or the like, there has been
known a liquid crystal display device which can perform both of a
transmissive display and a reflective display such that the
transmissive display is performed using light from a backlight
under a dark environment and the reflective display is performed
using an external light under a bright atmosphere.
[0004] The liquid crystal display device which is capable of
performing both of the transmissive display and the reflective
display is roughly classified into two types of systems.
[0005] The first type of system is a system which combines a liquid
crystal display panel of a semi-transmissive type (also referred to
as a partial transmissive type) which incorporates a
semi-transparent reflective film such as a half mirror or a
reflection film having an opening for allowing light from a
backlight to pass therethrough in the inside of the liquid crystal
display panel and the backlight.
[0006] The second type of system is a system in which a liquid
crystal display panel per se uses a transmissive type liquid
crystal display panel and enables a transmissive display using
light from a light source such as a backlight and a reflective
display which uses an external light incident from a front face
side of the liquid crystal display panel in such a manner that the
external light is reflected on a reflector of the backlight (see
following patent literatures 1, 2 and 3).
[0007] FIG. 9 is a cross-sectional view for explaining an example
of a conventional second-type liquid crystal display device. This
drawing depicts a content described in the patent literature 1 in a
simplified form.
[0008] As shown in FIG. 9, a backlight is arranged at a back face
of a transmissive type liquid crystal display panel (liquid crystal
display element).
[0009] The liquid crystal display panel is constituted such that a
liquid crystal layer 3 is sandwiched between a pair of substrates
(first substrate 1 and second substrate 2) which are laminated to
each other using a sealing material 4, a polarizer 5 is laminated
to a back face of the first substrate 1 which is positioned at a
back face side, and a polarizer 6 is laminated to a front face of
the second substrate 2 which is positioned at a front face side.
Here, electrodes, orientation films, color filters and the like are
omitted from the drawing.
[0010] The backlight is constituted of a light source 9, a light
guide body 7 on which light from the light source 9 is incident and
a reflector 8 which is arranged on the back face of the light guide
body 7. Here, although the light guide body 7 includes a prism
portion, the prism portion is omitted from the drawing. Further,
although the backlight may be provided with a prism sheet, the
prism sheet is omitted from the drawing.
[0011] Here, the liquid crystal display panel is of a transmissive
type liquid crystal display panel and performs a transmissive
display using light 20 from the light source 9. Further, the liquid
crystal display panel is capable of performing a reflective display
using a reflection light 22 obtained by reflecting an external
light 21 from the front face side of the liquid crystal display
panel on the reflector 8 of the backlight.
[0012] Further, in this liquid crystal display device, for the
purpose of obtaining a display with no luminance irregularities, a
light diffusion plate 10 is arranged between the liquid crystal
display panel and the backlight whereby light 20 from the light
source 9, the external light 21 and the reflection light 22 are
diffused.
[0013] Further, in the patent literature 2, there is disclosed a
liquid crystal display panel in which in place of the light
diffusion plate 10, a resin film in which scattering fillers are
dispersed is laminated to a lower face of the polarizer 5 at the
back face side. With respect to the position of the resin film,
there is a description that the resin film is arranged at an
arbitrary position so long as the resin film is disposed between
the reflector 8 of the backlight and the front-face-side polarizer
6. Further, there is also a description that using a diffusion
layer formed of a tacky adhesive material in which scattering
fillers are dispersed, members which are arranged in front of and
behind the diffusion layer (for example, a reflection polarizer and
a .lamda./4 phase plate or a twisted phase plate) may be laminated
to each other. This diffusion layer is also provided for obtaining
a display having no luminance irregularities.
[0014] Further, in the patent literature 3, there is disclosed a
liquid crystal display panel in which, in place of the light
diffusion plate 10 of the patent literature 1, a filler mixed type
diffusion plate or a diffusion plate formed of a micro lens sheet
is arranged between the front-face-side second substrate 2 and the
polarizer 6. Further, by imparting the backscattering property to
the diffusion plate, a portion of the external light 21 incident
from the front face side is made to directly return to the front
face side due to reflection without making the portion to pass
through the liquid crystal layer 3 whereby the luminance of a
screen is enhanced.
[0015] Here, the patent literature 3 discloses, as a modification
of the invention described therein, an example in which a diffusion
plate is arranged between the back-face-side first substrate 1 and
the polarizer 5 or an example in which diffusion plates are
arranged between the front-face-side second substrate 2 and the
polarizer 6 as well as between the back-face-side first substrate 1
and the polarizer 5. However, in the patent literature 3, there is
a description that when the diffusion plate is arranged at the back
face side, light for enhancing the luminance of screen passes
through the liquid crystal layer 3 and hence, a quantity of light
which is irradiated to the front face side is changed in response
to an image to be displayed whereby it is preferable to arrange the
diffusion plate at the front face side.
[0016] Patent literature 1: Japanese Unexamined Patent Publication
2002-98960 (paragraphs 0033 to 0043, FIG. 1 to FIG. 5)
[0017] Patent literature 2: Japanese Unexamined Patent Publication
2002-98963 (paragraphs 0044, 0060, 0130 to 0132, FIG. 1, FIG. 3 and
FIG. 5)
[0018] Patent literature 3: Japanese Unexamined Patent Publication
2001-91943 (paragraphs 0037, 0073 to 0076, 0087 to 0089, FIG. 1 to
FIG. 5)
SUMMARY OF THE INVENTION
[0019] However, inventors of the present application have found out
that the conventional liquid crystal display devices have following
drawbacks.
[0020] FIG. 10 is a perspective view for explaining the drawback
when a screen of the conventional second-system liquid crystal
display device is viewed from an oblique direction.
[0021] In the conventional first system, in performing the
transmissive display which uses the light source of the backlight,
the use efficiency of light is lowered and hence, it is
advantageous to adopt the second system when the transmissivity is
emphasized.
[0022] However, in case the second system is adopted, at the time
of performing the reflective display using an external light, when
black is displayed at a portion of the display region 30 and a
viewer observes the screen from the oblique direction, it has been
found that a thin shade 32 appears behind or in the depths of an
original black display region 31.
[0023] This phenomenon is considered to occur due to a following
reason.
[0024] FIG. 11 is a cross-sectional view for explaining the reason
why the shade shown in FIG. 10 is generated.
[0025] Here considered is a case in which an eye 40 of a viewer
observes the screen from the oblique direction in the conventional
structure explained in conjunction with FIG. 9. An external light
23 which is incident from a front face advances via a region of the
liquid crystal layer 3 which performs a white display and hence,
the external light 23 directly passes through the liquid crystal
display panel, is diffused by the light diffusion plate 10 and,
thereafter, is reflected on a reflector 8 thus being turned into a
reflection light 25. The reflection light 25 is diffused by the
light diffusion plate 10 and, thereafter, is turned into a linearly
polarized light by the polarizer 5 at the back-face side of the
liquid crystal display panel. The linearly polarized light passes
through a region 34 of the liquid crystal layer 3 which performs a
black display and, thereafter, is absorbed in the front-face-side
polarizer 6. Accordingly, as indicated by a dotted line in the
drawing, the reflection light 25 does not reach the eye 40 of the
viewer and hence, the original black display region 31 is
displayed.
[0026] On the other hand, an external light 24 which is incident
from the front face side passes through a region 34 of the liquid
crystal layer 3 which performs a black display and hence, the
external light 24 is absorbed by the polarizer 5 at the back face
side and a black display region 33 is also formed at the back side
of the liquid crystal display panel. Here, the external light 24
does not reach the reflector 8 as indicated by a dotted line in the
drawing and hence, a reflection light 26 does not return to the eye
40 of the viewer. Here, to consider the observation from the eye 40
of the viewer, the black display region 33 in the back side is
reflected on the reflector 8 and hence, the external light 24
appears as the shade 32. Although the shade 32 has an end portion
thereof more or less blurred by the light diffusion plate 10, the
shade 32 has not yet reached a state in which the shade 32 is
completely erased.
[0027] Further, although not shown in the drawing, it is also
considered that the shade 32 is reflected on the light diffusion
plate 10 as well as the reflector 8.
[0028] Here, the conventional first system uses the
semi-transmissive reflective type liquid crystal display panel and
hence, it is considered that the shade is formed more or less based
on the same principle. However, the reflection display by the
built-in reflection film which is performed before the external
light reaches the polarizer at the back side is dominant and hence,
the shade is hardly apparent.
[0029] Although the above-mentioned explanation is made by taking
the structure disclosed in the patent literature 1 into
consideration, even when the diffusion layer disclosed in the
patent literature 2 is used, the complete erasing of the shade 32
cannot be realized.
[0030] Further, although the patent literature 3 uses the diffusion
layer which generates the backscattering to enhance the luminance
of the screen, while the enhancement of the luminance is obtained,
there arises a drawback that the contrast is lowered. Further,
there also exists a drawback that when the diffusion layer is
arranged at the front side and the high definition is advanced, the
image is blurred.
[0031] In this manner, conventionally, none of the patent
literatures 1 to 3 recognize the drawbacks with respect to the
shade 32 and hence, the drawbacks have not been studied.
[0032] The present invention has been made in view of such
circumstances and it is an advantageous effect of the present
invention that a liquid crystal display device which ensures the
favorable visibility can be obtained.
[0033] Other tasks and advantages of the present invention will
become apparent in view of the description of the whole
specification.
[0034] Accordingly, in the present invention, at least two or more
light diffusion layers are provided between the first substrate 1
at a back face side of the liquid crystal display panel to the
reflector 8 of the backlight.
[0035] To enumerate one example of typical constitutions of the
present invention, they are as follows.
[0036] (1) In a liquid crystal display device which includes
[0037] a transmissive type liquid crystal display panel which
sandwiches a liquid crystal layer between a pair of substrates
and
[0038] a backlight which is arranged at a back face of the liquid
crystal display panel and has a light source and a reflector
and
[0039] is capable of performing a transmissive display which uses
light from the light source and a reflective display which uses an
external light incident from a front face side of the liquid
crystal display panel by reflecting the external light on the
reflector,
[0040] the improvement is characterized in that at least two or
more light diffusion layers are arranged between the back-face-side
substrate out of the pair of substrates and the reflector of the
backlight.
[0041] (2) In the above-mentioned constitution (1), at least one of
the light diffusion layers is constituted of a diffusion plate or a
diffusion sheet.
[0042] (3) In the above-mentioned constitution (1) or (2), at least
one of the light diffusion layers is constituted of a diffusion
tacky adhesive material.
[0043] (4) In any one of the above-mentioned constitutions (1) to
(3), at least one of the light diffusion layers is constituted of a
diffusion film.
[0044] (5) In a liquid crystal display device which includes
[0045] a transmissive type liquid crystal display panel which
sandwiches a liquid crystal layer between a pair of substrates,
[0046] a light source,
[0047] a light guide body which is arranged at a back face side of
the liquid crystal display panel and on which light from the light
source is incident, and
[0048] a reflector which is arranged at a back face of the light
guide body, and
[0049] is capable of performing a transmissive display which uses
light from the light source and a reflective display which uses an
external light incident from a front face side of the liquid
crystal display panel by reflecting the external light on the
reflector,
[0050] the improvement is characterized in that at least two or
more light diffusion layers are arranged between the back-face-side
substrate out of the pair of substrates and the light guide
body.
[0051] (6) In the constitution (5), the liquid crystal display
device includes
[0052] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide body
and
[0053] the light diffusion layer which is arranged between the
back-face-side substrate and the polarizer.
[0054] (7) In the constitution (5), the liquid crystal display
device includes
[0055] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide body
and
[0056] a diffusion tacky adhesive material which is arranged
between the back-face-side substrate and the polarizer and acts as
the light diffusion layer.
[0057] (8) In the constitution (5), the liquid crystal display
device includes
[0058] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide body
and
[0059] the light diffusion layer which is arranged on a surface of
the polarizer at a side where the light guide body is
positioned.
[0060] (9) In the constitution (5), the liquid crystal display
device includes a polarizer provided with an antiglare layer which
is arranged between the back-face-side substrate out of the pair of
substrates and the light guide body and acts as the light diffusion
layer.
[0061] (10) In the constitution (5), the liquid crystal display
device includes
[0062] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide
body,
[0063] a reflection polarizer which is arranged between the
polarizer and the light guide body, and
[0064] the light diffusion layer which is arranged between the
polarizer and the reflection polarizer.
[0065] (11) In the constitution (5), the liquid crystal display
device includes
[0066] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide
body,
[0067] a reflection polarizer which is arranged between the
polarizer and the light guide body, and
[0068] a diffusion tacky adhesive material which is arranged
between the polarizer and the reflection polarizer and acts as the
light diffusion layer.
[0069] (12) In the constitution (5), the liquid crystal display
device includes
[0070] a polarizer which is arranged between the back-face-side
substrate out of the pair of substrates and the light guide
body,
[0071] a reflection polarizer which is arranged between the
polarizer and the light guide body,
[0072] the light diffusion layer which is arranged between the
back-face-side substrate and the polarizer, and
[0073] the light diffusion layer which is arranged between the
polarizer and the reflection polarizer.
[0074] (13) In any one of the constitutions (5) to (12), the liquid
crystal display device includes a diffusion plate or a diffusion
sheet which acts as one of the light diffusion layers and the
diffusion plate or the diffusion sheet is arranged at a position
closest to the light guide body among at least two or more light
diffusion layers.
[0075] The present invention is not limited to the above-enumerated
constitutions and various modifications can be conceivable without
departing from the technical concept of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0076] FIG. 1 is a cross-sectional view for explaining the first
embodiment of the present invention.
[0077] FIG. 2 is a cross-sectional view for explaining a reason
that a shade can be reduced by the embodiment shown in FIG. 1.
[0078] FIG. 3 is a cross-sectional view for explaining the second
embodiment of the present invention.
[0079] FIG. 4 is a cross-sectional view for explaining the third
embodiment of the present invention.
[0080] FIG. 5 is a cross-sectional view for explaining the fourth
embodiment of the present invention.
[0081] FIG. 6 is a cross-sectional view for explaining the fifth
embodiment of the present invention.
[0082] FIG. 7 is a cross-sectional view for explaining the sixth
embodiment of the present invention.
[0083] FIG. 8 is a cross-sectional view for explaining the seventh
embodiment of the present invention.
[0084] FIG. 9 is a cross-sectional view for explaining an example
of a conventional second type liquid crystal display device.
[0085] FIG. 10 is a perspective view for explaining drawbacks when
a screen of the conventional second type liquid crystal display
device is observed in the oblique direction.
[0086] FIG. 11 is a cross-sectional view for explaining a reason
that a shade shown in FIG. 10 is generated.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0087] Embodiments of the present invention are explained in detail
hereinafter in conjunction with drawings.
First Embodiment
[0088] FIG. 1 is a cross-sectional view for explaining the first
embodiment of the present invention.
[0089] In a liquid crystal display panel according to this
embodiment, a liquid crystal layer 3 is sandwiched between a pair
of substrates (first substrate 1 and second substrate 2) which are
laminated to each other by a sealing material 4, a polarizer 5 is
formed on a back face of the first substrate 1 which is positioned
at a back face side of the liquid crystal display panel, and a
polarizer 6 is formed on a front face of the second substrate 2
which is positioned at a front face side of the liquid crystal
display panel.
[0090] The liquid crystal display panel may adopt any one of, for
example, an STN method, a TN method, a vertical electric field
method, a lateral electric field method and the like. Here, on an
inner surface of at least one of the first substrate 1 and the
second substrate 2, electrodes not shown in the drawing which are
served for driving the liquid crystal layer 3 are formed. Further,
although various parts including orientation films which determine
the initial orientation directions of the liquid crystal layer 3,
color filters for performing a color display and the like are
provided depending on necessity, they are omitted from the drawing.
Further, phase difference plates, a touch panel and the like may be
arranged on the outsides of a pair of substrates.
[0091] On a back face (opposite to a viewer) of the liquid crystal
display panel, a backlight is arranged. In this embodiment, as an
example, the backlight is constituted of a light source 9, a light
guide body 7 on which light from the light source 9 is incident and
a reflector 8 which is arranged on a back face of the light guide
body 7. Here, a shape of the light guide body 7 is not specifically
limited and grooves or the like which perform a function of a prism
may be formed in the light guide body 7, for example. A metal plate
or a resin-made sheet having a metallic color or a white color, for
example, can be used as the reflector 8. Further, in this
specification, a part which forms a metal film on the back side of
the light guide body 7 by vapor deposition may be also included in
the concept of the reflector 8. As the light source 9, for example,
light emitting diodes (LED) or a cold cathode fluorescent tube can
be used.
[0092] Here, as functions which the backlight according to the
present invention must satisfy, at least two functions, that is, a
function as a light source which is used at the time of performing
a transmissive display and a function for reflection which is used
at the time of performing a reflective display are necessary.
Accordingly, the backlight includes the light source 9 and the
reflector 8. Provided that the backlight has these two functions,
any type of backlight can be used. For example, the backlight may
be constituted of a combination of a light source such as an EL
(electroluminescence) and the reflection function.
[0093] Due to such a constitution, it is possible to perform not
only the transmissive display using light 20 from the light source
9 but also the reflective display using a reflection light 22 by
reflecting an external light 21 from a front face side of the
liquid crystal display panel on the reflector 8 of the backlight.
Here, to enhance the use efficiency of light, it is desirable to
enhance the optical transmissivity of the liquid crystal display
panel. For example, it is desirable to provide ideas to ensure the
sufficient visibility also in the reflective display by increasing
a numerical aperture or by decreasing a thickness of color filters
and the like.
[0094] Further, according to this embodiment, while a light
diffusion layer 10 is arranged between the light guide body 7 of
the backlight and the polarizer 5 at a back face side of the liquid
crystal display panel, a light diffusion layer 11 is also arranged
between the polarizer 5 at the back face side and the first
substrate 1 at the back face side. That is, two light diffusing
layers 10, 11 are arranged between the back-face-side first
substrate 1 and the reflector 8.
[0095] As the light diffusion layer 10, for example, a light
diffusion plate, a light diffusion sheet or the like can be used.
Further, as the light diffusion layer 11, for example, a diffusion
tacky adhesive material can be used. In this case, the light
diffusion layer 11 can also have a function of laminating the
polarizer 5 to the first substrate 1 and hence, the number of parts
can be reduced. Here, as the light diffusion layer 11, it is
possible to use other member such as a light diffusion plate, a
light diffusion sheet or a light diffusion film, for example,
without using the diffusion tacky adhesive material.
[0096] With the provision of these light diffusion layers 10, 11,
it is possible not only to obtain the display having no luminance
irregularities but also to reduce the influence of a shade 32 as
viewed from the oblique direction as explained in conjunction with
FIG. 10.
[0097] FIG. 2 is a cross-sectional view for explaining a reason why
the shade can be reduced according to the embodiment shown in FIG.
1.
[0098] Also in this embodiment, considered is a case in which an
eye 40 of a viewer observes the screen in the oblique direction as
has been explained in conjunction with FIG. 10 and FIG. 11. The
external light 23 which is incident from the front face advances
via the region of the liquid crystal layer 3 which performs a white
display and hence, the external light 23 directly passes through
the liquid crystal display panel. Thereafter, the external light 23
is reflected on the reflector 8 and is turned into the reflection
light 25. The reflection light 25 is turned into a linearly
polarized light due to the polarizer 5 at the back face side. The
linearly polarized light passes through a region 34 of the liquid
crystal layer 3 where the black display is performed and,
thereafter, is absorbed by the polarizer 6 at the front face side.
Accordingly, as indicated by a dotted line in the drawing, the
reflection light 25 does not reach the eye 40 of the viewer and
hence, the original black display region 31 is displayed.
[0099] On the other hand, the external light 24 which is incident
from the front face side passes through the region 34 of the liquid
crystal layer 3 which performs the black display and hence, the
external light 24 is absorbed by the back-face-side polarizer 5
whereby the black display region 33 is formed also on the back side
of the liquid crystal display panel.
[0100] However, according to this embodiment, different from the
case explained in conjunction with FIG. 11, the light diffusion
layers 10, 11 are arranged at two positions. Accordingly, after the
external light 23 is scattered by the light diffusion layer 11,
both of the light which advances straightly without being scattered
and the scattered external light are further scattered by the light
diffusion layer 10 and hence, when the scattered light reaches the
reflector 8, the scattered light reaches, in a sufficiently
diffused manner, locations where the scattered light cannot reach
when only either one of the light diffusion layer 10 or the light
diffusion layer 11 is provided. Then the scattered light is
reflected and is turned into the reflection light 27. Then, the
reflection light 27 is again scattered by the light diffusion
layers 10, 11 arranged at two positions so that the light which has
not reached conventionally reaches the eye 40 of the viewer.
[0101] Further, an external light 28 which is incident from a
separate locations is also sufficiently diffused by two light
diffusion layers 10, 11 and hence, the external light 28 is
sufficiently diffused to a range which the external light 28 cannot
reach with only either one of the light diffusion layer 10 or the
light diffusion layer 11 whereby the external light 28 reaches the
eye 40 of the viewer as the reflection light.
[0102] By sufficiently diffusing the external light 28 using two
light diffusion layers 10, 11 in this manner, it is possible to
make the shade 32 hardly apparent.
[0103] Further, even when the shade is reflected on the light
diffusion layer 10 instead of the reflector 8, since the sufficient
diffusion is ensured, the visibility is not adversely affected.
[0104] To ensure the sufficient diffusion of light, it is effective
to make the light diffusion layers 10, 11 and the reflector 8
sufficiently spaced apart from each other. Accordingly, in this
embodiment, by arranging the light diffusion layer 11 between the
first substrate 1 and the polarizer 5, the distance between the
light diffusion layer 11 and the light diffusion layer 10 is
increased. Further, also due to the presence of the light guide
body 7 between the light diffusion layer 10 and the reflector 8,
the distance between both of them can be increased.
[0105] Further, in this embodiment, it is desirable to provide at
least two or more light diffusion layers 10, 11 at the back face
side of the liquid crystal display panel, while it is not desirable
to provide them at the front face side of the liquid crystal
display panel. The reason is that when the light diffusion layers
are provided at the front face side of the liquid crystal display
panel, along with the progress of the high definition, images are
blurred and hence, the visibility is lowered. In one example of
high definition, for example, the size of one sub pixel is not more
than 200 .mu.m in the longitudinal direction and not more than
200/3 .mu.m in the lateral direction. However, provided that the
viewer does not care the blur of images, the light diffusion layers
may be provided at the front face side of the liquid crystal
display panel.
[0106] Further, since this embodiment has the advantageous effect
that the shade when viewed in the oblique direction becomes less
apparent, this advantageous effect is large in the liquid crystal
display device adopting a lateral electric field type, for example,
having a wide viewing angle (for example, the viewing angle being
not less than 150 degrees).
Second Embodiment
[0107] FIG. 3 is a cross-sectional view for explaining the second
embodiment of the present invention.
[0108] In this embodiment, the explanation of the points which
overlap the corresponding points of the first embodiment described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the first embodiment shown in FIG. 1
lies in that in place of arranging the light diffusion layer 11
between the first substrate 1 and the polarizers, a light diffusion
layer 12 is arranged on a surface of the back face side (side at
which the light guide body 7 is positioned) of the polarizer 5.
[0109] By using a polarizer having an antiglare layer which
functions as a light diffusion layer, for example, as the light
diffusion layer 12, the number of parts can be reduced. The light
diffusion layer 12 is not limited to the polarizer having an
antiglare layer and may be formed of a diffusion tacky adhesive
material, a diffusion plate, a diffusion sheet, a diffusion film or
the like.
Third Embodiment
[0110] FIG. 4 is a cross-sectional view for explaining the third
embodiment of the present invention.
[0111] In this embodiment, the explanation of the points which
overlap the corresponding points of other embodiments described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the first embodiment shown in FIG. 1
lies in that a prism sheet 13 is added.
[0112] Although the position of the prism sheet 13 is arranged
between the polarizer 5 and the light diffusion layer 10 in FIG. 4,
the position of the prism sheet 13 is not limited to such an
arrangement. That is, the prism sheet 13 may be arranged between
the light diffusion layer 10 and the light guide body 7 or between
the light guide body 7 and the reflector 8. The number of the prism
sheets 13 may be one, two or more.
Fourth Embodiment
[0113] FIG. 5 is a cross-sectional view for explaining the fourth
embodiment of the present invention.
[0114] In this embodiment, the explanation of the points which
overlap the corresponding points of other embodiments described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the first embodiment shown in FIG. 1
lies in that a reflection polarizer 14 is added at the back face
side of the polarizer 5.
Fifth Embodiment
[0115] FIG. 6 is a cross-sectional view for explaining the fifth
embodiment of the present invention.
[0116] In this embodiment, the explanation of the points which
overlap the corresponding points of other embodiments described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the fourth embodiment shown in FIG.
5 lies in the position of the light diffusion layer 15. That is, in
place of the light diffusion layer 11 which is arranged between the
first substrate 1 and the polarizer 5, the light diffusion layer 15
is arranged between the polarizer 5 and the reflection polarizer
14.
[0117] By using, for example, a diffusion tacky adhesive material
which functions as a light diffusion layer as the light diffusion
layer 15 and by laminating the polarizer 5 and the reflection
polarizer 14 to each other, the number of parts can be reduced.
This embodiment is not limited to such a constitution and other
part which function as a light diffusion layer may be used.
Sixth Embodiment
[0118] FIG. 7 is a cross-sectional view for explaining the sixth
embodiment of the present invention.
[0119] In this embodiment, the explanation of the points which
overlap the corresponding points of other embodiments described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the fourth embodiment shown in FIG.
5 lies in that in addition to the light diffusion layer 10 and the
light diffusion layer 11 which is arranged between the first
substrate 1 and the polarizer 5, a light diffusion layer 15 is also
arranged between the polarizer 5 and the reflection polarizer
14.
[0120] By using, for example, a diffusion tacky adhesive material
which functions as a light diffusion layer as the light diffusing
layers 11, 15, the number of parts can be reduced. This embodiment
is not limited to such a constitution and other part which
functions as a light diffusion layer may be used.
[0121] The constitution which makes this embodiment different from
other embodiments which have been explained heretofore lies in that
the number of light diffusion layers which are arranged between the
first substrate 1 and the reflector 8 is three. The number of light
diffusion layers is not limited to three and may be four or more.
The larger the number of the light diffusion layers, the diffusion
effect can be increased. However, from a viewpoint of loss of
light, it is desirable to reduce the number of the light diffusion
layers.
Seventh Embodiment
[0122] FIG. 8 is a cross-sectional view for explaining the seventh
embodiment of the present invention.
[0123] In this embodiment, the explanation of the points which
overlap the corresponding points of other embodiments described
above is omitted. In this embodiment, the constitution which makes
this embodiment different from the sixth embodiment shown in FIG. 7
lies in that the light diffusion layer 10 is omitted.
[Other Modifications]
[0124] With respect to the embodiments explained heretofore, two or
more embodiments can be combined to each other provided that they
do not conflict each other. For example, the prism sheet 13 which
is explained in the third embodiment shown in FIG. 4 is applicable
to the fourth embodiment shown in FIG. 5.
[0125] According to the embodiments and modifications described
heretofore, it is possible to obtain the liquid crystal display
device which ensure the favorable visibility.
* * * * *