U.S. patent application number 10/531392 was filed with the patent office on 2006-01-19 for liquid crystal display device viewable from both surfaces and portable apparatus using same.
This patent application is currently assigned to Casio Computer Co., Ltd.. Invention is credited to Norihiro Arai, Kunpei Kobayashi, Toshiharu Nishino.
Application Number | 20060012736 10/531392 |
Document ID | / |
Family ID | 32211613 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060012736 |
Kind Code |
A1 |
Nishino; Toshiharu ; et
al. |
January 19, 2006 |
Liquid crystal display device viewable from both surfaces and
portable apparatus using same
Abstract
In front of a liquid crystal display element (1), a surface
light source (25) is arranged which emits a light toward the liquid
crystal display element (1) and lets lights coming from its front
and its back permeate therethrough. The liquid crystal display
element (1) has reflection/permeation means (10) which is provided
behind a liquid crystal cell (2) and a liquid crystal layer (5),
and which reflects a part of a light that comes to each of a
plurality of pixels (80) from the front of the liquid crystal cell
(2), and lets the other part of the light permeate the
reflection/permeation means (10).
Inventors: |
Nishino; Toshiharu; (Tokyo,
JP) ; Arai; Norihiro; (Tokyo, JP) ; Kobayashi;
Kunpei; (Tokyo, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
220 5TH AVE FL 16
NEW YORK
NY
10001-7708
US
|
Assignee: |
Casio Computer Co., Ltd.
6-2, Hon-machi 1-chome, Shibuya-ku
Tokyo
JP
151-8543
|
Family ID: |
32211613 |
Appl. No.: |
10/531392 |
Filed: |
October 24, 2003 |
PCT Filed: |
October 24, 2003 |
PCT NO: |
PCT/JP03/13663 |
371 Date: |
April 14, 2005 |
Current U.S.
Class: |
349/114 ;
349/63 |
Current CPC
Class: |
G02F 2203/09 20130101;
G02F 1/133555 20130101; H04M 1/0214 20130101; G02F 1/133342
20210101; G02F 1/133536 20130101; G02F 1/133616 20210101; H04M
2250/16 20130101 |
Class at
Publication: |
349/114 ;
349/063 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2002 |
JP |
2002-314388 |
Claims
1. A liquid crystal display device comprising: a first substrate
(3) and a second substrate (4) which are arranged so as to oppose
to each other; at least one first electrode (6) which is formed on
one of opposing internal surfaces of said first substrate (3) and
said second substrate (4); a plurality of second electrodes (7)
which are formed on the other of the opposing internal surfaces of
said first substrate (3) and said second substrate (4), and which
form a plurality of pixels (80) arranged in a matrix in an area
opposing to said first electrode (6) on the one internal surface; a
liquid crystal layer (5) which is sealed in a predetermined gap
between said first substrate (3) and said second substrate (4); a
pair of polarizing plates (16, 17) which are arranged so as to
sandwich said first substrate (3) and said second substrate (4);
reflection/permeation means (10,14,15) which is provided between
said liquid crystal layer (5) and one of said pair of polarizing
plates (16, 17), and which reflects a part of a light coming to
each of said plurality of pixels (80) and lets the other part of
the light permeate said reflection/permeation means; and a surface
light source (25) which is arranged so as to oppose to the other of
said pair of polarizing plates (16, 17), and which emits a light
toward said opposing other polarizing plate (16), and lets lights
coming to said surface light source (25) from a side of the
opposing other polarizing plate (16) and from a side opposing to
this side permeate said surface light source (25).
2. The liquid crystal display device according to claim 1, wherein
said reflection/permeation means (10,14,15) is constituted by a
half-transparent and half-reflection film (10) which reflects and
allows permeation of, an incident light with a predetermined
reflection ratio and a predetermined permeation ratio.
3. The liquid crystal display device according to claim 1, wherein
said reflection/permeation means (10,14,15) is arranged on the
internal surface of said first substrate (3) or said second
substrate (4) on a side of said one polarizing plate (17).
4. The liquid crystal display device according to claim 1, wherein
said reflection/permeation means (10,14,15) is constituted by a
reflection film (14) having an open portion (14a) and a reflection
portion (14b) formed for each of said pixels (80) to constitute a
partial reflection/permeation layer (14) which reflects, of a light
coming to each of said pixels (80), a light that comes to said
reflection portion (14b), and lets a light that comes to said open
portion (14a) permeate said reflection/permeation means.
5. The liquid crystal display device according to claim 4, wherein
said partial reflection/permeation layer (14) is arranged on the
internal surface of said first substrate (3) or said second
substrate (4) on a side of said one polarizing plate (17).
6. The liquid crystal display device according to claim 4, wherein
said partial reflection/permeation layer (14) is constituted by a
metal reflection film in which an opening having a predetermined
size is formed for each of said plurality of pixels (80).
7. The liquid crystal display device according to claim 1, wherein
said reflection/permeation means (10,14,15) is constituted by a
polarized light separating element (15) which reflects, of two
different polarized components of an incident light, one polarized
component, and lets the other polarized component permeate said
reflection/permeation means (10,14,15).
8. The liquid crystal display device according to claim 1, wherein
said reflection/permeation means (10,14,15) is constituted by a
reflecting/polarizing plate (15) which serves also as said one
polarizing plate (17), and which reflects, of two
linearly-polarized components of an incident light which are
orthogonal to each other, one polarized component, and lets the
other polarized component permeate said reflection/permeation means
(10,14,15).
9. The liquid crystal display device according to claim 1, further
comprising at least one retardation plate (18, 19) which is
arranged between said pair of polarizing plates (16, 17).
10. The liquid crystal display device according to claim 9, wherein
two of said retardation plate (18, 19) are arranged so as to
sandwich said first substrate (3) and said second substrate
(4).
11. The liquid crystal display device according to claim 1, further
comprising a scattering layer (20) which is arranged between said
other polarizing plate (16) and said first substrate (3) or said
second substrate (4) on a side of said other polarizing plate
(16).
12. A liquid crystal display device comprising a liquid crystal
display element including: a first substrate (3) and a second
substrate (4) which are arranged so as to oppose to each other; at
least one first electrode (6) which is formed on one of opposing
internal surfaces of said first substrate (3) and said second
substrate (4); a plurality of second electrodes (7) which are
formed on the other of the opposing internal surfaces of said first
substrate (3) and said second substrate (4), and which form a
plurality of pixels (80) arranged in a matrix in an area opposing
to said first electrode (6) on the one internal surface; a liquid
crystal layer (5) which is sealed in a predetermined gap between
said first substrate (3) and said second substrate (4); a pair of
polarizing plates (16, 17) which are arranged so as to sandwich
said first substrate (3) and said second substrate (4); and a
reflection/permeation layer (10,14,15) which is provided between
said liquid crystal layer (5) and one of said pair of polarizing
plates (16, 17), and which forms a reflection display region for
reflecting a light coming to a region predefined in each of said
plurality of pixels (80), and a permeation display region for
letting a light coming to other than the reflection display region
permeate said reflection/permeation layer (10,14,15), and a surface
light source (25) which is arranged so as to oppose to the other of
said pair of polarizing plates (16, 17), and which emits a light
toward said liquid crystal display element (1), and lets lights
coming to said surface light source (25) from a side of the
opposing other polarizing plate (16) and from a side opposing to
this side permeate said surface light source (25).
13. The liquid crystal display device according to claim 12,
further comprising two retardation plates (18, 19) which are
arranged between said pair of polarizing plates (16, 17) so as to
sandwich said first substrate (3) and said second substrate
(4).
14. The liquid crystal display device according to claim 12,
further comprising a scattering layer (20) which is arranged
between said other polarizing plate (16) and said first substrate
(3) or said second substrate (4) on a side of said other polarizing
plate (16).
15. The liquid crystal display device according to claim 12,
wherein a part of said liquid crystal layer (5) that corresponds to
the reflection display region is thinner than a part of said liquid
crystal layer (5) that corresponds to the permeation display
region.
16. The liquid crystal display device according to claim 12,
wherein: said first and second electrodes (6, 7) are made of
transparent electrodes; and said reflection/permeation layer
comprises a reflection film which is formed so as to correspond to
the reflection display region and the permeation display region of
each pixel (80).
17. A portable apparatus comprising a liquid crystal display device
including: a first substrate (3) and a second substrate (4) which
are arranged so as to oppose to each other; a at least one first
electrode (6) which is formed on one of opposing internal surfaces
of said first substrate (3) and said second substrate (4); a
plurality of second electrodes (7) which are formed on the other of
the opposing internal surfaces of said first substrate (3) and said
second substrate (4), and which forms a plurality of pixels (80)
arranged in a matrix in an area opposing to said first electrode
(6) on the one internal surface; a liquid crystal layer (5) which
is sealed in a predetermined gap between said first substrate (3)
and said second substrate (4); a pair of polarizing plates (16, 17)
which are arranged so as to sandwich said first substrate (3) and
said second substrate (4); reflection/permeation means (10,14,15)
which is provided between said liquid crystal layer (5) and one of
said pair of polarizing plates (16, 17), and which reflects a part
of a light coming to each of said plurality of pixels (80) defined
by said first electrode (6) and said second electrodes (7) and lets
the other part of the light permeate said reflection/permeation
means (10,14,15); and a surface light source (25) which is arranged
so as to oppose to the other of said pair of polarizing plates (16,
17), and which emits a light toward said opposing other polarizing
plate (16), and les lights coming to said surface light source (25)
from a side of the opposing other polarizing plate (16) and from a
side opposing to this side permeate said surface light source (25),
and a body which is provided with display windows on its two
opposing external surfaces, and inside which said liquid crystal
display device is accommodated, wherein said liquid crystal display
device is accommodated in said body such that a front surface of
said liquid crystal display device is faced with said display
window on one of the two external surfaces, and a back surface of
said liquid crystal display device is faced with said display
window on the other of the two external surfaces.
18. The portable apparatus according to claim 17, wherein said
portable apparatus is a portable phone (40).
19. The portable apparatus according to claim 17, wherein said
portable apparatus is a personal computer (60).
Description
TECHNICAL FIELD
[0001] The present invention relates to a both surface display type
liquid crystal display device and a portable apparatus having a
both surface display function.
BACKGROUND ART
[0002] As disclosed in Unexamined Japanese Patent Application KOKAI
Publication No. H10-90678 and Unexamined Japanese Patent
Application KOKAI Publication No. 2001-290445, a liquid crystal
display device in which two liquid crystal display elements are
disposed back to back with their display surfaces facing the
opposite directions from each other, and a surface light source for
emitting a light toward both the liquid crystal display elements is
disposed between them, is known as a both surface display type
liquid crystal display device to be used in a portable apparatus
such as a portable phone, which has a display function on both
surfaces of its case.
[0003] However, using two liquid crystal display elements as
described above costs high, and both surface display with the use
of one liquid crystal display element is desired.
[0004] As a liquid crystal display device for both surface display
using one liquid crystal display element, there is proposed a
liquid crystal display device in which the screen area of a liquid
crystal display element is divided into a first screen portion and
a second screen portion so that an image to be viewed from the
front is displayed by the first screen portion and an image to be
viewed from the back is displayed by the second screen portion, as
disclosed in Unexamined Japanese Patent Application KOKAI
Publication No. 2000-193946 and Unexamined Japanese Patent
Application KOKAI Publication No. 2001-305525.
[0005] However, in a both surface display type liquid crystal
display device having the screen area of its liquid crystal display
element divided into a first and a second screen portions, the
entire display area of the liquid crystal display element has a
size corresponding to the size of the display screen for the front
plus the size of the display screen for the back which are arranged
side by side. Therefore, the occupation area of this liquid crystal
display device is much larger than that of a display screen for
either front or back display. Accordingly, this liquid crystal
display device can not be used in a portable apparatus such as a
portable phone, in which the mount space for a liquid crystal
display device is limited.
DISCLOSURE OF INVENTION
[0006] It is an object of the present invention to provide a liquid
crystal display device which is capable of both surface display
using one liquid crystal display element, capable of reducing its
occupation area, and capable of displaying an image to be viewed
from one surface and an image to be viewed from the other surface
in a display manner using a light from a surface light source and
in a display manner using an external light existing in the
external environment.
[0007] It is another object of the present invention to provide a
liquid crystal display device which is capable of being
miniaturized as a portable apparatus having a both surface display
function, capable of displaying images to be viewed from the
respective surfaces in a sufficiently large screen size, and
capable of displaying images to be viewed form the respective
surfaces in a display manner using a light from a surface light
source of the liquid crystal display device and in a display manner
using an external light.
[0008] To achieve the above objects, a liquid crystal display
device according to a first aspect of the present invention
comprises:
[0009] a first substrate (3) and a second substrate (4) which are
arranged so as to oppose to each other;
[0010] at least one first electrode (6) which is formed on one of
opposing internal surfaces of the first substrate (3) and the
second substrate (4);
[0011] a plurality of second electrodes (7) which are formed on the
other of the opposing internal surfaces of the first substrate (3)
and the second substrate (4), and which form a plurality of pixels
(80) arranged in a matrix in an area opposing to the first
electrode (6) on the one internal surface;
[0012] a liquid crystal layer (5) which is sealed in a
predetermined gap between the first substrate (3) and the second
substrate (4);
[0013] a pair of polarizing plates (16, 17) which are arranged so
as to sandwich the first substrate (3) and the second substrate
(4); and
[0014] reflection/permeation means which is provided between the
liquid crystal layer (5) and one of the pair of polarizing plates
(16, 17), and which reflects a part of a light coming to each of
the plurality of pixels (80) and lets the other of the light
permeate the reflection/permeation means; and
[0015] a surface light source (25) which is arranged so as to
oppose to the other of the pair of polarizing plates (16, 17), and
which emits a light toward the opposing other polarizing plate
(16), and lets lights coming to the surface light source (25) from
a side of the opposing other polarizing plate (16) and from a side
opposing to this side permeate the surface light source (25).
[0016] This liquid crystal display device displays an image to be
viewed from the front by letting a light from the surface light
source arranged at the front of the liquid crystal display element
come to the liquid crystal display element, reflecting a part of
the light coming to each of the plurality of pixels from the front
of the liquid crystal display element by the reflection/permeation
means, and emitting the reflected light toward the front of the
surface light source, and displays an image to be viewed from the
back by letting the other part of the light permeate the
reflection/permeation means and emitting this light toward the back
of the liquid crystal display element.
[0017] Since this liquid crystal display device displays an image
to be viewed from the front by reflecting a part of a light coming
to each of the plurality of pixels from the front of the liquid
crystal display element, and displays an image to be viewed from
the back by letting the other part of the light permeate, this
liquid crystal display device can display both of an image to be
viewed from the front and an image to be viewed from the back by
using the entire display area of the liquid crystal display
element. Accordingly, the display area of the liquid crystal
display element needs only to have a size corresponding to the
display screen for either front display or back display.
[0018] Accordingly, with this liquid crystal display device, it is
possible to perform both surface display with the use of only one
liquid crystal display element, and to make the occupation area of
the liquid crystal display device smaller.
[0019] Further, in this liquid crystal display device, the surface
light source which emits a light toward the liquid crystal display
element and lets lights coming from its front and its back permeate
therethrough is arranged at the front of the liquid crystal display
element. Because of this, this liquid crystal display device can
let an external light (a light in the external environment) coming
from the front of the surface light source permeate the surface
light source and then come to the liquid crystal display element,
can emit a part of this light that is reflected by the
reflection/permeation means toward the front of the surface light
source, and can emit the other part of the light that permeates the
reflection/permeation means toward the back of the liquid crystal
display element, and at the same time, can let an external light
coming from the back of the liquid crystal display element permeate
the reflection/permeation means, a liquid crystal cell, and the
surface light source so as to be emitted toward the front.
Accordingly, this liquid crystal display device can display an
image to be viewed from the front by reflection display using a
light from the surface light source, by reflection display using an
external light coming from the front of the surface light source,
and by permeation display using an external light coming from the
back of the liquid crystal display element, and can display an
image to be viewed from the back by permeation display using a
light from the surface light source and by permeation display using
an external light coming from the front of the surface light
source.
[0020] As described above, according to this liquid crystal display
device of the present invention, both surface display can be
achieved with the use of one liquid crystal display element, the
occupation area can be reduced, and both of an image to be viewed
from one surface (front surface) and an image to be viewed from the
other surface (back surface) can be displayed in a display manner
using a light from the surface light source and in a display manner
using an external light which is a light in the external
environment.
[0021] In this liquid crystal display device of the present
invention, it is preferred that the reflection/permeation means is
constituted by a half-transparent and half-reflection film (10)
which reflects and allows permeation of, an incident light with a
predetermined reflection ratio and a predetermined permeation
ratio.
[0022] Further, it is preferred that the reflection/permeation
means is arranged on the internal surface of the first substrate
(3) or the second substrate (4) on a side of the one polarizing
plate (17). The reflection/permeation means may be constituted by a
reflection film (14) having an open portion (14a) and a reflection
portion (14b) formed for each of the pixels (80) to constitute a
partial reflection/permeation layer which reflects, of a light
coming to each of the pixels (80), a light that comes to the
reflection portion (14b), and lets a light that comes to the open
portion (14a) permeate the reflection/permeation means. It is
preferred that the partial reflection/permeation layer is
constituted by a metal reflection film in which an opening having a
predetermined size is formed for each of the plurality of pixels
(80). Further, the reflection/permeation means may be constituted
by a polarized light separating element (15) which reflects, of two
different polarized components of an incident light, one polarized
component, and lets the other polarized component permeate the
reflection/permeation means.
[0023] The reflection/permeation means may be constituted by a
reflecting/polarizing plate which serves also as the one polarizing
plate (17), and which reflects, of two linearly-polarized
components of an incident light which are orthogonal to each other,
one polarized component, and lets the other polarized component
permeate the reflection/permeation means. Further, it is preferred
that at least one retardation plate (18, 19) is arranged between
the pair of polarizing plates (16, 17), and a scattering layer (20)
is arranged between the other polarizing plate (16) and the first
substrate (3) or the second substrate (4) on a side of the other
polarizing plate (16).
[0024] A liquid crystal display device according to a second aspect
of the present invention comprises:
[0025] a first substrate (3) and a second substrate (4) which are
arranged so as to oppose to each other;
[0026] at least one first electrode (6) which is formed on one of
opposing internal surfaces of the first substrate (3) and the
second substrate (4);
[0027] a plurality of second electrodes (7) which are formed on the
other of the opposing internal surfaces of the first substrate (3)
and the second substrate (4), and which form a plurality of pixels
(80) arranged in a matrix in an area opposing to the first
electrode (6) on the one internal surface;
[0028] a liquid crystal layer (5) which is sealed in a
predetermined gap between the first substrate (3) and the second
substrate (4);
[0029] a pair of polarizing plates (16, 17) which are arranged so
as to sandwich the first substrate (3) and the second substrate
(4);
[0030] a liquid crystal display element which is provided between
the liquid crystal layer (5) and one of the pair of polarizing
plates (16, 17), and which includes a reflection/permeation layer
which forms a reflection display region for reflecting a light
coming to a region predefined in each of the plurality of pixels
(80), and a permeation display region for letting a light coming to
other than the reflection display region permeate the
reflection/permeation layer; and
[0031] a surface light source (25) which is arranged so as to
oppose to the other of the pair of polarizing plates (16, 17), and
which emits a light toward the liquid crystal display element, and
lets lights coming to the surface light source (25) from a side of
the opposing other polarizing plate (16) and from a side opposing
to this side permeate the surface light source (25).
[0032] As described above, the reflection/permeation layer may be
formed to correspond to a predetermined region and a region other
than the predetermined region in each of the plurality of pixels,
so that partial reflection/permeation for reflecting, of a light
coming to each of the plurality of pixels, a light that comes to
the reflection display region, and letting a light that comes to
the permeation display region permeate may be performed. With this
structure, it is possible to display an image to be viewed from the
front by emitting alight toward the front from the predetermined
region in each of the plurality of pixels of the liquid crystal
display element and to display an image to be viewed from the back
by emitting a light toward the back from the region other than the
predetermined region in each of the plurality of pixels regardless
of whether the display is performed by using a light from the
surface light source or by using an external light.
[0033] The reflection/permeation means may be constituted by a
polarized light separating element (15) which reflects, of two
different polarized components of an incident light, one polarized
component, and lets the other polarized component permeate the
reflection/permeation means.
[0034] Further, it is preferred that at least one retardation plate
(18, 19) is arranged between the pair of polarizing plates (16,
17), and a scattering layer (20) is arranged between the other
polarizing plate (16) and the first substrate (3) or the second
substrate (4) on a side of the other polarizing plate (16).
[0035] It is preferred that the liquid crystal display element of
this liquid crystal display device comprises a liquid crystal layer
(5) in which a part that corresponds to the reflection display
region is thinner than a part that corresponds to the permeation
display region. With this structure, it is possible to unify
display characteristics such as contrast between reflection display
and permeation display.
[0036] A portable apparatus according to a third aspect of the
present invention comprises:
[0037] a liquid crystal display device including: [0038] a first
substrate (3) and a second substrate (4) which are arranged so as
to oppose to each other; [0039] a at least one first electrode (6)
which is formed on one of opposing internal surfaces of the first
substrate (3) and the second substrate (4); [0040] a plurality of
second electrodes (7) which are formed on the other of the opposing
internal surfaces of the first substrate (3) and the second
substrate (4), and which forms a plurality of pixels (80) arranged
in a matrix in an area opposing to the first electrode (6) on the
one internal surface; [0041] a liquid crystal layer (5) which is
sealed in a predetermined gap between the first substrate (3) and
the second substrate (4); [0042] a pair of polarizing plates (16,
17) which are arranged so as to sandwich the first substrate (3)
and the second substrate (4); [0043] reflection/permeation means
which is provided between the liquid crystal layer (5) and one of
the pair of polarizing plates (16, 17), and which reflects a part
of a light coming to each of the plurality of pixels (80) defined
by the first electrode (6) and the second electrodes (7) and lets
the other part of the light permeate the reflection/permeation
means; and [0044] a surface light source (25) which is arranged so
as to oppose to the other of the pair of polarizing plates (16,
17), and which emits a light toward the opposing other polarizing
plate (16), and les lights coming to the surface light source (25)
from a side of the opposing other polarizing plate (16) and from a
side opposing to this side permeate the surface light source (25),
and
[0045] a body which is provided with display windows on its two
opposing external surfaces, and inside which the liquid crystal
display device is accommodated,
[0046] wherein the liquid crystal display device is accommodated in
the body such that a front surface of the liquid crystal display
device is faced with the display window on one of the two external
surfaces, and a back surface of the liquid crystal display device
is faced with the display window on the other of the two external
surfaces.
[0047] This portable apparatus can be applied to any of a portable
phone, a digital camera, a personal computer, and a video
camera.
[0048] According to this portable apparatus, since the liquid
crystal display device performs both surface display with the use
of one liquid crystal display element, the occupation area and
volume required by the liquid crystal display device inside the
portable apparatus is only the occupation area and volume of
approximately one liquid crystal display element. Accordingly, this
portable apparatus can be miniaturized. Further, images to be
displayed on both surfaces can be displayed in a sufficiently large
screen size.
[0049] Further, since the liquid crystal display device displays an
image to be viewed from the front and an image to be viewed from
the back in a display manner using a light from the surface light
source and in a display manner using an external light, this
portable apparatus can display the images to be displayed on both
surfaces in a display manner using a light from the surface light
source of the liquid crystal display device and in a display manner
using an external light.
[0050] This portable apparatus of the present invention can be
miniaturized by providing display windows to two opposing external
surfaces of the portable apparatus respectively, and mounting the
liquid crystal display device of the present invention inside the
portable apparatus such that the front surface of the liquid
crystal display device faces the display window on one of the two
external surfaces and the back surface of the liquid crystal
display device faces the display window on the other of the two
external surfaces. Further, this portable apparatus can display
both images to be viewed from the front and the back in a
sufficiently large screen size, and can display images on both
surfaces in a display manner using a light from the surface light
source of the liquid crystal display device and in a display manner
using an external light.
BRIEF DESCRIPTION OF DRAWINGS
[0051] These objects and other objects and advantages of the
present invention will become more apparent upon reading of the
following detailed description and the accompanying drawings in
which:
[0052] FIG. 1 is an exploded perspective view of a liquid crystal
display device according to a first embodiment of the present
invention;
[0053] FIG. 2 is a fragmentary sectional view of the liquid crystal
display device shown in FIG. 1;
[0054] FIG. 3 is a plan view of a surface light source of the
liquid crystal display device shown in FIG. 1;
[0055] FIG. 4 is a side view of the surface light source shown in
FIG. 3;
[0056] FIG. 5 is an exemplary diagram showing the arrangement of a
solid light emitting element, a light guiding member, and a light
guiding plate of the surface light source shown in FIG. 3;
[0057] FIG. 6 is a fragmentary sectional view of a liquid crystal
display device according to a second embodiment of the present
invention;
[0058] FIG. 7 is a fragmentary sectional view of a liquid crystal
display device according to a third embodiment of the present
invention;
[0059] FIG. 8 is a fragmentary sectional view of a liquid crystal
display device according to a fourth embodiment of the present
invention;
[0060] FIGS. 9A and 9B are perspective views of a portable phone
utilizing a liquid crystal display device of the present
invention;
[0061] FIGS. 10A and 10B are perspective views of a digital camera
utilizing a liquid crystal display device of the present
invention;
[0062] FIGS. 11A and 11B are perspective views of a personal
computer utilizing a liquid crystal display device of the present
invention; and
[0063] FIGS. 12A and 12B are perspective views of a video camera
utilizing a liquid crystal display device of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0064] Liquid crystal display devices will be described below as
embodiments of the present invention with reference to the
accompanying drawings.
First Embodiment
[0065] An embodiment of a liquid crystal display device of the
present invention will now be explained below. FIG. 1 to FIG. 5
show a liquid crystal display device according to a first
embodiment of the present invention. FIG. 1 is an exploded
perspective view of the liquid crystal display device, and FIG. 2
is a fragmentary sectional view of the liquid crystal display
device.
[0066] As shown in FIG. 1 and FIG. 2, the liquid crystal display
device according to the present embodiment comprises a liquid
crystal display element 1, and a surface light source 25 arranged
in front (in the upper part in the drawings) of the liquid crystal
display element 1 (in the upper part in the drawings).
[0067] The liquid crystal display element 1 comprises a liquid
crystal cell 2, reflection/permeation means 10 provided at the back
(in the lower part in the drawings) of a liquid crystal layer 5 of
the liquid crystal cell 2, and a front polarizing plate 16 and a
back polarizing plate 17 which are arranged in front of and at the
back of the liquid crystal cell 2.
[0068] In the liquid crystal cell 2, the liquid crystal layer 5 is
provided between a transparent substrate (front substrate) 3 at the
front (in the upper part in the drawing) and a transparent
substrate (back substrate) 4 at the back (in the lower part in the
drawings) which are, as shown in FIG. 2, arranged oppositely from
each other. At least one transparent electrode 6 is provided to one
of the opposing internal surfaces of the front substrate 3 and back
substrate 4, and a plurality of transparent electrodes 7 forming a
plurality of pixels 80 arranged in a matrix in the area opposing to
the at least one transparent electrode 6 are provided to the other
of the internal surfaces of the substrates.
[0069] The liquid crystal cell 2 is an active matrix type. The
transparent electrode 6 provided to the internal surface of the
front substrate 3 is a monolithic-film-like opposing electrode 6,
and the transparent electrodes 7 provided to the internal surface
of the back substrate 4 are a plurality of pixel electrodes 7
arranged in a row direction and a column direction to form a
matrix.
[0070] The plurality of pixel electrodes 7 are connected
respectively to a plurality of TFTs (Thin Film Transistors) 8 which
are provided to the internal surface of the back surface 4 so as to
correspond to the pixel electrodes 7. The plurality of TFTs are
connected to unillustrated gate lines and data lines which are
provided to the internal surface of the back substrate 4.
[0071] The liquid crystal cell 2 comprises color filters 9R, 9G,
and 9B in plural colors, for example, red, green, and blue, which
correspond respectively to the plurality of pixels 80. These color
filters 9R, 9G, and 9B are formed on the internal surface of one of
the substrates, for example, the front substrate 3, so as to cover
the entire area of each pixel 80. The opposing electrode 6 is
formed on the color filters 9R, 9G, and 9B.
[0072] The reflection/permeation means 10 provided behind the
liquid crystal layer 5 of the liquid crystal cell 2 reflects part
of a light coming to each of the plurality of pixels 80 from the
front side of the liquid crystal cell 2, and allows other lights to
permeate therethrough. In the present embodiment, the
reflection/permeation means 10 is a half-transparent and
half-reflection film which is made of a very thin aluminum alloy
film having a film thickness of approximately 0.025 .mu.m or less
and which reflects or allows permeation of an incident light with a
predetermined reflection ratio and a predetermined permeation
ratio. The reflection/permeation means 10 will hereinafter be
referred to as a half-transparent and half-reflection film 10.
[0073] The half-transparent and half-reflection film 10 is formed
on the internal surface of the back substrate 4 of the liquid
crystal cell 2 so as to correspond to the entire area of each of
the plurality of pixels 80.
[0074] The plurality of pixel electrodes 7 are formed on the
plurality of half-transparent and half-reflection films 10
corresponding to the plurality of pixels 80 respectively.
[0075] In the present embodiment, the pixel electrodes 7 are formed
directly upon the half-transparent and half-reflection films 10 as
shown in FIG. 2. However, the half-transparent and half-reflection
films 10 may be covered with an insulation film, and the pixel
electrodes 7 may be formed on the insulation film. In this case,
the half-transparent and half-reflection films 10 may be formed as
a monolithic film entirely covering the display area where the
plurality of pixels 80 are arranged in a matrix.
[0076] Aligning films 11 and 12 are provided respectively to the
internal surfaces of the front substrate 3 and back substrate 4 of
the liquid crystal cell 2 so as to cover the transparent electrode
6 and the transparent electrodes 7.
[0077] The front substrate 3 and the back substrate 4 are connected
to each other via a frame-like seal member 13 (see FIG. 1) which
encloses the display area where the pixels 80 are arranged, and the
liquid crystal layer 5 is provided in an area enclosed by the
frame-like seal member 13 between the front substrate 3 and the
back substrate 4.
[0078] Liquid crystal molecules of the liquid crystal layer 5 have
their aligning direction near the front and back substrates 3 and 4
defined by the aligning films 11 and 12, and they are oriented in
an initial aligning state which is predefined between the front and
back substrates 3 and 4.
[0079] The polarizing plates 16 and 17 arranged at the front and at
the back of the liquid crystal cell 2 are absorptive polarizing
plates 16 and 17 which have absorption axes (not illustrated) and
permeation axes 16a and 17a in orthogonal directions to each other,
absorb, of two linearly-polarized lights orthogonal to each other
of an incident light, one polarized light, and let the other
polarized light permeate.
[0080] The liquid crystal display element 1 of the present
embodiment is a TN (Twisted Nematic) type liquid crystal display
element of a normally white mode. The liquid crystal molecules of
the liquid crystal display 5 of the liquid crystal cell 2 are
twist-orientated at a twist angle of substantially 90.degree.
between the front and back substrates 3 and 4, and the absorptive
polarizing plates 16 and 17 are arranged with their permeation axes
16a and 17a substantially orthogonal to each other.
[0081] The liquid crystal display element 1 further comprises
retardation plates 18 and 19 which are arranged between the liquid
crystal cell 2 and the polarizing plate 16 at the front and between
the liquid crystal cell 2 and the polarizing plate 17 at the back,
and a light scattering layer (hereinafter referred to as scattering
layer) 20 which is arranged between the liquid crystal cell 2 and
the retardation plate 18 at the front, in order to improve the
display contrast and the view angle.
[0082] The surface light source 25 arranged at the front of the
liquid crystal display element 1 (at the front of the front
polarizing plate 16) emits a light toward the entire display area
where the plurality of pixels 80 of the liquid crystal display
element 1 are arranged, and allows a light coming thereto from its
front and its back to permeate therethrough.
[0083] FIG. 3 and FIG. 4 are the plan view and the side view of the
surface light source 25, and FIG. 5 is an exemplary diagram showing
a light emitted from a light guiding member and a light guiding
plate of the surface light source 25.
[0084] As shown in FIG. 3 and FIG. 4, the surface light source 25
of the present embodiment comprises a light guiding plate 26, a
light guiding member 31 arranged at the side of the light guiding
plate 26, a retardation plate 36 arranged between the light guiding
plate 26 and the light guiding member 31, and a light emitting
element 38 arranged at the side of the light guiding member 31.
[0085] The light guiding plate 26 is constituted by a transparent
plate made of an acryl resin plate having an area opposing to the
entire display area of the liquid crystal display element 1. One
end surface of the light guiding plate 26 constitutes an incident
surface 27 from which a light comes to the light guiding plate 26.
One of the two plate surfaces of the transparent plate constituting
the light guiding plate 26 constitutes a flat emission surface 28
from which a light guided by the transparent plate is emitted, and
the other plate surface constitutes a reflection surface 29 for
internally reflecting a light coming from the incident surface 27
so as to be emitted from the emission surface 28.
[0086] The reflection surface 29 of the light guiding plate 26 is
constituted by a plurality of prism units 30 which are formed
densely in parallel with one another side by side over the entire
surface of the other plate surface of the light guiding plate 26,
and which internally reflect light coming from the incident surface
27 of the light guiding plate 26 in a direction in which an angle
to the normal of the emission surface 28 is smaller.
[0087] The plurality of prism units 30 are long and slender prism
units which are parallel with the incident surface 27 of the light
guiding plate 26 and have a length corresponding to the entire
width of the light guiding plate 26, and whose cross section has a
trapezoidal shape. Of both the side surfaces of each of the prism
units 30, the side surface at the side of the incident surface 27
is formed as a steep-angle surface which is approximately
perpendicular to the emission surface 28, and the other side
surface is formed as an inclined surface which is inclined in the
direction of the incident surface 27 toward the external surface of
the reflection surface 29 at an angle of 30 to 60 degrees
(preferably, approximately 45 degrees) to the emission surface 28.
The top surface between these side surfaces (steep-angle surface
and inclined surface) is formed as a flat surface parallel with the
emission surface 28.
[0088] FIG. 3 and FIG. 4 show the plurality of prism units 30
exaggeratedly largely. However, the prism units 30 are formed in a
pitch smaller than the pixel pitch of the liquid crystal cell
2.
[0089] The light guiding plate 26 is for guiding a light coming
from the incident surface 27 so as to be emitted from the emission
surface 28. A light coming into the light guiding plate 26 from the
incident surface 27 either goes straight in the light guiding plate
26 as shown by arrows in FIG. 3, or is internally reflected on the
emission surface 28 by total internal reflection at the interface
with the external air (atmosphere) to come into any of the inclined
surfaces of the plurality of long and slender prism units 30 of the
reflection surface 29, and to be internally reflected on the
inclined surface by total internal reflection at the interface with
the external air toward a direction in which an angle to the normal
of the emission surface 28 is smaller and then emitted from the
emission surface 28.
[0090] The light guiding member 31 arranged at the side of the
light guiding plate 26 is made of a slender transparent material
(for example, acryl resin) having a square stick shape having a
length corresponding to the incident surface 27 of the light
guiding plate 26. One side surface of the light guiding member 31
forms a slender emission surface 33 for emitting a light. One of
two end surfaces intersecting with the slender emission surface 33
of the slender transparent material forms an incident surface 32
from which a light comes to the slender transparent material. The
other side surface that is opposing to the slender emission surface
33 forms a reflection surface 34 for internally reflecting a light
coming from the incident surface 32 so as to be emitted from the
slender emission surface 33.
[0091] The reflection surface 34 at the other side surface of the
light guiding member 31 is constituted by a plurality of prism
units 35 which are formed densely in parallel with one another side
by side over the entire surface of the other side surface, and
which internally reflect a light coming from the incident surface
32 of the light guiding member 31 toward a direction in which an
angle to the normal of the slender emission surface 33 at the one
side surface of the light guiding member 31 is smaller.
[0092] The plurality of prism units 35 are slender prism units
which are parallel with the incident surface 32 of the light
guiding member 31 and have a length corresponding to the entire
width of the other side surface of the light guiding member 31, and
whose cross section has a triangular shape. Of both the side
surfaces of each of the prism units 35, the side surface at the
side of the incident surface 32 is formed as a steep-angle surface
which is approximately perpendicular to the slender emission
surface 33, and the other side surface is formed as an inclined
surface which is inclined in the direction of the incident surface
32 toward the external surface of the reflection surface 34 at an
angle of 30 to 60 degrees (preferably, approximately 45 degrees) to
the slender emission surface 33.
[0093] FIG. 3 shows the plurality of prism units 35 exaggeratedly
largely. However, the prism units 35 are actually formed in a pitch
approximately the same as the pitch of the prism units 30 on the
reflection surface 29 of the light guiding plate 26.
[0094] The light guiding member 31 is for guiding a light coming
from the incident surface 32 to be emitted from the slender
emission surface 33 at the one side surface of the light guiding
member 31. A light coming into the light guiding member 31 from the
incident surface 32 either goes straight in the light guiding
member 31 as shown by arrows in FIG. 3, or is internally reflected
on the slender emission surface 33 by total internal reflection at
the interface with the external air so as to come to any of the
inclined surfaces of the plurality of prism units 35 of the
reflection surface 34, and to be internally reflected on the
inclined surface by total internal reflection at the interface with
the external air toward a direction in which an angle to the normal
of the slender emission surface 33 is smaller, and then to be
emitted from the entire surface of the slender emission surface 33
with a uniform distribution of intensity.
[0095] The light guiding member 31 has its slender emission surface
33 opposing to the incident surface 27 of the light guiding plate
26, such that the slender emission surface 33 of the light guiding
member 31 and the incident surface 27 of the light guiding plate 26
are arranged in parallel with each other.
[0096] In the present embodiment, a reflector 37 is provided behind
the reflection surface 34 of the light guiding member 31, in order
to return a light permeating the reflection surface 34 and leaking
behind the light guiding member 31 back to the light guiding member
31.
[0097] The retardation plate 36 arranged between the light guiding
plate 26 and the light guiding member 31 is a .lamda./2 retardation
plate for providing a phase difference of 1/2 of a wavelength
between a normal light and an abnormal light of a permeation light.
The retardation plate 36 rotates the polarization plane of a
linearly-polarized component of a light emitted from the slender
emission surface 33 of the light guiding member 31 by substantially
90 degrees, and then lets the light come to the incident surface 27
of the light guiding plate 26.
[0098] The .lamda./2 retardation plate 36 has a slender shape
corresponding to the entire incident surface 27 of the light
guiding plate 26 and the entire slender emission surface 33 of the
light guiding member 31. The .lamda./2 retardation plate 36 is
arranged between the incident surface 27 of the light guiding plate
26 and the slender emission surface 33 of the light guiding member
31 with one surface adhered to the incident surface 27 of the light
guiding plate 26 by a transparent adhesive agent and the other
surface adhered to the slender emission surface 33 of the light
guiding member 31 by a transparent adhesive agent.
[0099] The light emitting element 38 arranged so as to oppose to
the incident surface 32 of the light guiding member 31 is a solid
light emitting element 38 which is constituted by an LED (Light
Emitting Diode) and which emits a white light. For example, a red
LED, a green LED, and a blue LED are molded by a transparent resin
to constitute the solid light emitting element 38, and a white
light made by mixing red, green, and blue lights emitted from these
LEDs is emitted from the solid light emitting element 38.
[0100] In the surface light source 25, a light emitted from the
solid light emitting element 38 comes into the light guiding member
31 from the incident surface 32, is internally reflected on the
reflection surface 34 opposite to the slender emission surface 33
of the light guiding member 31 to be emitted from the entire
slender emission surface 33 of the light guiding member 31 with a
uniform distribution of intensity toward the incident surface 27 of
the light guiding plate 26, and then comes to the entire incident
surface 27 of the light guiding plate 26 while keeping the uniform
distribution of intensity so as to be internally reflected on the
reflection surface 29 of the light guiding plate 26 and emitted
from the entire emission surface 28 of the light guiding plate 26.
With this surface light source 25, a light having a uniform
distribution of strength can be emitted from the entire emission
surface 28 of the light guiding plate 26 by using a small number of
light emitting element.
[0101] Further, in the surface light source 25, a light emitted
from the slender emission surface 33 of the light guiding member 31
comes into the incident surface 27 of the light guiding plate 26
after the polarization plane of a linearly-polarized component of
the light is rotated by substantially 90 degrees by the .lamda./2
retardation plate 36 arranged between the incident surface 27 of
the light guiding plate 26 and the slender emission surface 33 of
the light guiding member 31. Therefore, of a light coming into the
light guiding member 31 from the incident surface 32 to be
internally reflected on the reflection surface 34 of the light
guiding member 31 and emitted from the slender emission surface 33
of the light guiding member 31 and coming into the light guiding
plate 26 from the incident surface 27, a linearly-polarized
component having a high intensity can be internally reflected on
the reflection surface 29 of the light guiding plate 26 with a high
reflection intensity and can be emitted from the emission surface
28 of the light guiding plate 26 as a light having a sufficient
intensity.
[0102] As described above, the light guiding plate 26 lets a light
coming from the incident surface 27 go straight in the light
guiding plate 26 or be internally reflected on the emission surface
28 to come to the reflection surface 29 to be internally reflected
on the reflection surface 29 and emitted from the emission surface
28. A linearly-polarized component that vibrates in the direction
perpendicular to a plane including the incident light to the
reflection surface 29 and its reflection light (such a component
will hereinafter be referred to as S wave) is internally reflected
with a higher intensity than that for a linearly-polarized
component that vibrates within the plane (hereinafter referred to
as P wave).
[0103] Further, as described above, the light guiding member 31
lets a light coming from the incident surface 32 be internally
reflected on the reflection surface 34 to be emitted from the
slender emission surface 33. An S wave, which is a
linearly-polarized component vibrating in the direction
perpendicular to a plane including the incident light to the
reflection surface 34 and its reflection light is internally
reflected with a higher intensity than that for a P wave, which is
a linearly-polarized component vibrating within the plane.
[0104] Accordingly, of the light emitted from the slender emission
surface 33 of the light guiding member 31, the intensity of the
S-wave polarized component is higher than that of the P-wave
polarized component.
[0105] Since the reflection surface 29 of the light guiding plate
26 and the reflection surface 34 of the light guiding member 31 are
arranged so as to intersect with each other at an angle of 90
degrees, a light emitted from the slender emission surface 33 of
the light guiding member 31 is let to come into the light guiding
plate 26 from the incident surface 27 after its polarization plane
is rotated by 90 degrees by the .lamda./2 retardation plate 36.
[0106] Accordingly, of a light emitted from the slender emission
surface 33 of the light guiding member 31, an S wave S1 having a
high intensity comes to the reflection surface 29 of the light
guiding plate 26 as an S wave S2 which is to be reflected by the
reflection surface 29 with a high reflection intensity. Thus, the
surface light source 25 can let a polarized component having a high
light intensity that is emitted from the slender emission surface
33 of the light guiding member 31 be internally reflected on the
reflection surface 29 of the light guiding plate 26 with a high
reflection intensity, and thus can let a light having a sufficient
intensity be emitted from the emission surface 28 of the light
guiding plate 26.
[0107] Since the surface light source 25 comprises the light
guiding plate 26 in which one end surface of a transparent plate
forms the incident surface 27 from which a light comes, one of two
plate surfaces of the transparent plate forms the emission surface
28 for emitting a light guided in the transparent plate, and the
other plate surface forms the reflection surface 29 for internally
reflecting a light coming from the incident surface 27 to be
emitted from the emission surface 28, and the light guiding member
31 for guiding a light from the solid light emitting element 38
toward the incident surface 27 of the light guiding plate 26, a
light having a sufficient intensity can be emitted from the entire
emission surface 28 of the light guiding plate 26 with a uniform
distribution of intensity.
[0108] Since the surface light source 25 of the present embodiment
comprises only one solid light emitting element 38 constituted by
an LED as a light emitting element, it is possible to reduce the
cost required, and reduce the amount of electricity to be
consumed.
[0109] Further, since the light emitting intensity of the solid
light emitting element 38 can be changed by controlling the drive
voltage for the solid light emitting element 38, it is possible to
arbitrary adjust the intensity of a light to be emitted from the
emission surface 28 of the light guiding plate 26.
[0110] Further, in the surface light source 25, the reflection
surface 34 of the light guiding member 31 is constituted by the
plurality of prism units 35 for internally reflecting a light
coming from the incident surface 32 of the light guiding member 31
toward a direction in which an angle to the normal of the slender
emission surface 33 of the light guiding member 31 is smaller, it
is possible to let a light emitted from the slender emission
surface 33 of the light guiding member 31 come into the light
guiding plate 26 from around a direction perpendicular to the
incident surface 27 and let the light prevail uniformly in the
light guiding plate 26 to be emitted from the entire emission
surface 28 of the light guiding plate 26 as a light having a more
uniform distribution of intensity.
[0111] Further, in the surface light source 25, the reflection
surface 29 of the light guiding member 26 is constituted by the
plurality of prism units 30 for internally reflecting a light
coming from the incident surface 27 of the light guiding plate 26
toward a direction in which an angle to the normal of the emission
surface 28 of the light guiding plate 26 is smaller, a light having
a high frontal luminance (the luminance of a light emitted in a
direction near the normal of the emission surface 28 of the light
guiding plate 26) can be emitted from the emission surface 28 of
the light guiding plate 26.
[0112] The liquid crystal display device of the present embodiment
performs display by letting a light from the surface light source
25 come to the liquid crystal display element 1 from its front
surface. A light emitted from the emission surface 28 of the light
guiding plate 26 of the surface light source 25 is polarized by the
front polarizing plate 16 of the liquid crystal display element 1
to be a linearly-polarized light parallel with the permeation axis
16a as shown by arrows in FIG. 2, permeates the front retardation
plate 18 to be scattered by the scattering layer 20, and comes to
the liquid crystal cell 20 from its front.
[0113] The light coming to the liquid crystal cell 20 from its
front is colored by the color filters 9R, 9G, and 9B corresponding
to the respective pixels 80 of the liquid crystal cell 2 and comes
to the liquid crystal layer 5. While permeating the liquid crystal
layer 5, this light is subjected to a birefringence effect
corresponding to the aligning state of the liquid crystal molecules
that is changed by an electric field applied between the
transparent electrode 6 and the transparent electrode 7 of each
pixel 80, and then comes to the half-transparent and
half-reflection film 10 on the internal surface of the back
substrate 4 of the liquid crystal cell 2. Part of the light coming
to the half-transparent and half-reflection film 10 is reflected by
the half-transparent and half-reflection film 10 in accordance with
its reflection ratio, and the rest of the light permeates the
half-transparent and half-reflection film 10.
[0114] The light reflected by the half-transparent and
half-reflection film 10 again permeates the liquid crystal layer 5
and the color filters 9R, 9G, and 9B to be emitted to the front of
the liquid crystal cell 2 and scattered by the scattering layer 20,
and permeates the front retardation plate 18 to come to the front
polarizing plate 16. Of this light, a polarized component parallel
to the permeation axis 16a of the front polarizing plate 16
permeates the front polarizing plate 16 and also permeates the
light guiding plate 26 of the surface light source 25 to be emitted
to the front of the surface light source 25, and a polarized
component parallel to the absorption axis of the front polarizing
plate 16 is absorbed into the front polarizing plate 16, thereby an
image to be viewed from the front is displayed.
[0115] On the other hand, of the light coming to the liquid crystal
cell 2 from its front, the light permeating the half-transparent
and half-reflection film 10 is emitted toward the back of the
liquid crystal cell 2. The light emitted toward the back of the
liquid crystal cell 2 permeates the back retardation plate 19 and
comes to the back polarizing plate 17. Of the light coming to the
back polarizing plate 17, a polarized component parallel to the
permeation axis 17a of the back polarizing plate 17 permeates the
back polarizing plate 17 to be emitted to the back, and a polarized
component parallel to the absorption axis of the back polarizing
plate 17 is absorbed into the back polarizing plate 17, thereby an
image to be viewed from the back is displayed.
[0116] In the present embodiment, since the liquid crystal display
element 1 is a normally white mode type, both of the image to be
viewed from the front and the image to be viewed from the back are
color images in which, a light emitted from a non-electric-field
pixel (a pixel whose liquid crystal molecules are in an initial
aligning state) that is sandwiched between the transparent
electrodes 6 and 7 between which no electric field is applied
permeates the front and back polarizing plates 16 and 17 to be
emitted to the front and back and displayed as bright display
having any of red, green, and blue colors, and a light emitted from
an electric-field-applied pixel that is sandwiched between the
transparent electrodes 6 and 7 between which an electric field by
which liquid crystal molecules are oriented to stand substantially
perpendicularly to the front and back substrates 3 and 4 is
applied, is absorbed into the front and back polarizing plates 16
and 17 to be displayed as dark display having a black color.
[0117] That is, the present liquid crystal display device lets a
light from the surface light source 25 arranged in front of the
liquid crystal display element 1 come to the liquid crystal display
element 1, lets a part of the light coming to the plurality of
pixels 80 of the liquid crystal cell 2 from the front of the liquid
crystal display element 1 be reflected on the half-transparent and
half-reflection film 10 and emitted toward the front of the surface
light source 25 so that an image to be viewed from the front will
be displayed, and lets the other part of the light permeate the
half-transparent and half-reflection film 10 to be emitted toward
the back of the liquid crystal display element 1 so that an image
to be viewed from the back will be displayed.
[0118] Since the present liquid crystal display device displays an
image to be viewed from the front by reflecting a part of a light
coming to the plurality of pixels 80 of the liquid crystal cell 2
from the front of the liquid crystal display element 1 and displays
an image to be viewed from the back by allowing the other part of
the light to permeate, it can display both of the image to be
viewed from the front and the image to be viewed from the back by
using the entire display area (an area where the plurality of
pixels 80 of the liquid crystal cell 2 are arranged in a matrix) of
the liquid crystal display element 1. Accordingly, the display area
of the liquid crystal display element 1 needs only to have a size
corresponding to the display screen for either front display or
back display.
[0119] Therefore, according to the present liquid crystal display
device, it is possible to achieve both surface display by using
only one liquid crystal display element 1, and to reduce the
occupation area of the liquid crystal display device in a case
where the liquid crystal display device is mounted on an apparatus,
to an area approximately the same as the display screen for only
either front display or back display.
[0120] Further, since the present liquid crystal display device is
structured by arranging one surface light source 25 in front of the
liquid crystal display element 1, it is possible to reduce the
occupation area and volume of the liquid crystal display device in
an apparatus, to approximately the area and volume of the liquid
crystal display element 1.
[0121] Further, since the present liquid crystal display device is
structured such that the liquid crystal display element 1 includes
the liquid crystal cell 2 and the half-transparent and
half-reflection film 10 which is provided behind the liquid crystal
layer 5 for reflecting a part of a light coming to the plurality of
pixels 80 from the front of the liquid crystal cell 2 and letting
the other part of the light permeate the half-transparent and
half-reflection film 10, and the surface light source 25 for
emitting a light toward the entire display area where the plurality
of pixels 80 of the liquid crystal display element 1 are arranged
and letting lights coming from the front and back permeate the
surface light source 25 is arranged in front of the liquid crystal
display element 1, it is possible to, as shown by broken arrows in
FIG. 2, let an external light (a light in an external environment)
coming from the front of the surface light source 25 permeate the
surface light source 25 to come into the liquid crystal cell 2, let
a part of this light that is reflected on the half-transparent and
half-reflection film 10 be emitted toward the front of the surface
light source 25, let the other part of this light that permeates
the half-transparent and half-reflection film 10 be emitted toward
the back of the liquid crystal display element 1, and let an
external light coming from the back of the liquid crystal display
element 1 permeate the half-transparent and half-reflection film
10, the liquid crystal cell 2, and the surface light source 25 to
be emitted toward the front.
[0122] Accordingly, the present liquid crystal display device can
display an image to be viewed from the front by reflection display
using a light from the surface light source 25, by reflection
display using an external light coming from the front of the
surface light source 25, and by permeation display using an
external light coming from the back of the liquid crystal display
element 1, and can display an image to be viewed from the back by
permeation display using a light from the surface light source 25
and by permeation display using an external light coming from the
front of the surface light source 25.
[0123] In case of display using an external light, an image to be
viewed from the front is displayed by both of reflection of an
external light coming from the front and permeation of an external
light coming from the back in an environment where the liquid
crystal display device has an external light coming thereto from
both of its front and its back, and is displayed by reflection of
an external light coming from the front in an environment where an
external light does not come to the liquid crystal display device
from its back.
[0124] Further, in case of display using an external light, if the
intensity of an external light that comes to the liquid crystal
display device is insufficient and thus a display having sufficient
brightness can not be obtained, the surface light source 25 can be
used as an auxiliary light source, so that a light having an
intensity supplementing the intensity of the external light will be
emitted from the surface light source 25 and thereby a display
having sufficient brightness will be obtained.
[0125] As described above, the present liquid crystal display
device is structured such that the surface light source 25 that
emits a light toward the liquid crystal display element 1 and lets
lights coming from its front and back permeate therethrough is
arranged in front of the liquid crystal display element 1 including
the liquid crystal cell 2 and the half-transparent and
half-reflection film 10 which is provided behind the liquid crystal
layer 5 for reflecting a part of a light coming from the front of
the liquid crystal cell 2 to the plurality of pixels 80 and letting
the other part of the light permeate the half-transparent and
half-reflection film 10. Accordingly, it is possible to obtain both
surface display with the use of one liquid crystal display element
1, to reduce the occupation area and volume of the liquid crystal
display device, and to display an image to be viewed from the front
and an image to be viewed from the back in a display manner using a
light from the surface light source 25 and in a display manner
using an external light which is a light in the external
environment.
[0126] Further, since the present liquid crystal display device is
provided, behind the liquid crystal layer 5 of the liquid crystal
cell 2 of the liquid crystal display element 1, with the
half-transparent and half-reflection film 10 that reflects an
incident light or lets this incident light permeate therethrough
with a predetermined reflection ratio and a predetermined
permeation ratio as reflection/permeation means, it is possible to
let a light be emitted toward the front and back from the entire
area of the plurality of pixels 80 of the liquid crystal cell 2,
and to display both of an image to be viewed from the front and an
image to be viewed from the back by using the entire area of the
plurality of pixels 80 of the liquid crystal cell 2 regardless of
whether the display is performed by using a light from the surface
light source 25 or by using an external light.
[0127] Further, the present liquid crystal display device is
provided, between the liquid crystal cell 2 of the liquid crystal
display device 1 and the front polarizing plate 16 and between the
liquid crystal cell 2 and the back polarizing plate 17, with the
retardation plates 18 and 19 for improving the display contrast and
the view angle, and is provided, between the liquid crystal cell 2
and the front retardation plate 18, with the scattering layer 20,
it is possible to emit a light which is scattered by the scattering
layer 20 and thereby has a uniform distribution of luminance toward
the front and the back. Accordingly, both of an image to be viewed
from the front and an image to be viewed from the back can be a
high quality image having a sufficient contrast and a sufficient
view angle, and having no unevenness in the luminance.
[0128] In the present embodiment, the scattering layer 20 is
arranged between the liquid crystal cell 2 and the front
retardation plate 18. However, the scattering layer 20 may be
arranged between the front polarizing plate 16 and the front
retardation plate 18.
Second Embodiment
[0129] FIG. 6 is a fragmentary sectional view of a liquid crystal
display device according to a second embodiment of the present
invention. The liquid crystal display element 1 of the liquid
crystal display device of the present embodiment is provided with a
reflection film 14 as reflection/permeation means behind the liquid
crystal layer 5 of the liquid crystal cell 2. The reflection film
14 has open portions 14a each of which is formed in a region 82
defined in each of a plurality of pixels 80 of the liquid crystal
cell 2, and reflection portions 14b each of which is formed in
another region 81 defined in each of the plurality of pixels 80.
The reflection film 14 is a partial reflection/permeation layer 14
which reflects, of a light coming to each of the plurality of
pixels 80, a light that comes to the reflection portions 14b, and
lets a light that comes to the open portions 14a permeate
therethrough. In the present embodiment, it is preferable that the
reflection film 14 be a single-sided reflection film in which a low
reflection treatment is applied to the surface opposite to the
surface facing the liquid crystal layer 5, and a specular surface
treatment is applied to the surface facing the liquid crystal layer
5. The reflection film 14 is formed on the internal surface of the
back substrate 4 of the liquid crystal cell 2 to be fitted to
approximately 1/2 of the area of each of the pixels 80 arranged in
a matrix. Each of the plurality of pixel electrodes 7 is formed
with its one part (approximately 1/2 of each pixel electrode 7)
overlaid directly upon the reflection film 14 or, if the reflection
film 14 is covered with a transparent insulation film, upon this
transparent insulation film.
[0130] Since the liquid crystal display device of the present
embodiment is the same as the liquid crystal display device of the
first embodiment, except that the partial reflection/permeation
layer 14 replaces the half-transparent and half-reflection film 10
of the first embodiment as the reflection/permeation means provided
behind the liquid crystal layer 5 of the liquid crystal cell 2, the
same components as those in the first embodiment will be denoted by
the same reference numerals and the explanation for such components
will be omitted.
[0131] The present liquid crystal display device lets one or both
of a light from the surface light source 25 and an external light
coming from the front of the surface light source 25 come to the
liquid crystal display element 1 from its front, and lets a part of
the light coming to each of the plurality of pixels 80 of the
liquid crystal cell 2, i.e. a light that comes to the region
(reflection display region) 81 within each of the plurality of
pixels 80 that corresponds to the reflection portion 14b of the
reflection film 14 be reflected by the reflection portion 14b and
emitted toward the front, and lets the other part of the light,
i.e. a light that comes to the region (permeation display region)
82 within each of the plurality of pixels 80 that corresponds to
the open portion 14a of the reflection film 14 permeate the open
portion 14a to be emitted toward the back.
[0132] Further, if an external light comes to the liquid crystal
display element 1 also from its back, the present liquid crystal
display device lets a light, of the light coming from the back,
that permeates the open portion 14a and comes to each of the
plurality of pixels 80 of the liquid crystal cell 2 be emitted
toward the front.
[0133] That is, the present liquid crystal display device displays
an image to be viewed from the front by using one or both of a
light that comes to the plurality of pixels 80 of the liquid
crystal cell 2 from the front of the liquid crystal display element
1 (this light including one or both of a light from the surface
light source 25 and an external light coming from the front of the
surface light source 25) and then is reflected by the reflection
portion 14b, and a light (an external light coming from the back of
the liquid crystal display element 1) that comes to the plurality
of pixels 80 of the liquid crystal cell 2 after permeating the open
portion 14a from the back of the liquid crystal display element 1,
and displays an image to be viewed from the back by using a light
that comes to the plurality of pixels 80 of the liquid crystal cell
2 from the front and permeates the open portion 14a.
[0134] Accordingly, with the present liquid crystal display device,
likewise the liquid crystal display device of the first embodiment,
it is possible to obtain both surface display with the use of one
liquid crystal display element 1, to reduce the occupation area and
volume of the liquid crystal display device, and to display both of
an image to be viewed from the front and an image to be viewed from
the back in a display manner using a light from the surface light
source 25 and in a display manner using an external light which is
a light in the external environment.
[0135] Since the present liquid crystal display device comprises,
as the reflection/permeation means, the reflection film 14 which is
formed behind the liquid crystal layer 5 of the liquid crystal cell
2 of the liquid crystal display element 1 so as to correspond to
the regions 81 and 82 of each of the plurality of pixels 80 of the
liquid crystal cell 2, and lets a light, of a light coming to each
of the plurality of pixels 80, that comes to the reflection portion
14b be reflected thereon, and a light that comes to the open
portion 14a permeate therethrough, it is possible to display an
image to be viewed from the front by letting a light be emitted
toward the front from the predetermined region 81 within each of
the plurality of pixels 80 of the liquid crystal cell 2, and
display an image to be viewed from the back by letting a light be
emitted toward the back from the other region 82 within each of the
plurality of pixels 80 regardless of whether the display is
performed by using a light from the surface light source 25 or by
using an external light.
[0136] A part of the liquid crystal layer 5 that corresponds to the
reflection display region 81 is thinner than a part of the liquid
crystal layer 5 that corresponds to the permeation display area 82.
Due to this, it is possible to unify display characteristics such
as contrast between reflection display and permeation display.
[0137] In the present embodiment, the reflection portion 14b is
formed so as to correspond to 1/2 of the area of each of the
plurality of pixels 80 of the liquid crystal cell 2. However, the
shapes of the reflection portion 14b and open portion 14a and the
area ratio between them may be arbitrary. Further, the reflection
portion 14b and the open portion 14a may be formed in one pixel 80
in plural numbers respectively.
Third Embodiment
[0138] FIG. 7 is a fragmentary sectional view of a liquid crystal
display device according to a third embodiment of the present
invention. The liquid crystal display element 1 of the liquid
crystal display device of the present embodiment is provided as
reflection/permeation means, behind the liquid crystal layer 5 of
the liquid crystal cell 2, with a polarized light separating
element 15 for reflecting, of two different polarized components of
an incident light, one polarized component, and letting the other
polarized component permeate therethrough.
[0139] In the present embodiment, the polarized light separating
element 15 is a reflecting/polarizing element for reflecting, of
two linearly-polarized components orthogonal to each other of an
incident light, one polarized component, and letting the other
polarized component permeate therethrough. In the present
embodiment, a reflecting/polarizing plate which has a permeation
axis and a reflection axis (both not illustrated) in orthogonal
directions to each other, and which reflects, of two
linearly-polarized components orthogonal to each other of an
incident light, one polarized component having a vibration surface
parallel to the reflection axis and lets the other polarized
component having a vibration surface parallel to the permeation
axis permeate therethrough, is used as the polarized light
separating element 15. The polarized light separating element 15
will hereinafter be referred to as reflecting/polarizing plate.
[0140] In the present embodiment, the reflecting/polarizing plate
15 is arranged at the back of the back substrate 4 of the liquid
crystal cell 2, and the back polarizing plate (absorptive
polarizing plate) 17 which is arranged at the back portion of the
liquid crystal display element 1 in the first and second
embodiments is omitted. Further, the back retardation plate 19
which is arranged at the back portion of the liquid crystal display
element 1 in the first and second embodiments is also omitted.
[0141] The liquid crystal display element 1 of the present
embodiment is a TN type liquid crystal display element whose
display to be viewed from the front is in a normally white mode,
and the reflecting/polarizing plate 15 is arranged such that its
permeation axis is substantially parallel with the permeation axis
16a of the absorptive polarizing plate 16 which is arranged at the
front of the liquid crystal cell 2, and its reflection axis is
substantially orthogonal to the permeation axis 16a of the
absorptive polarizing plate 16.
[0142] The liquid crystal display device of the present embodiment
is the same as the liquid crystal display device of the first
embodiment, except that the reflection/permeation means behind the
liquid crystal layer 5 of the liquid crystal cell 2 is the
reflecting/polarizing plate 15 which serves also as a back
polarizing plate. Therefore, the same components as those in the
first embodiment are denoted by the same reference numerals and
explanation of such components will be omitted.
[0143] The present liquid crystal display device lets one or both
of a light from the surface light source 25 and an external light
coming from the front of the surface light source 25 come to the
liquid crystal display element 1 from its front, lets a part of the
light coming to each of the plurality of pixels 80 of the liquid
crystal cell 2, i.e. a polarized component parallel with the
reflection axis of the reflecting/polarizing plate 15 arranged at
the back of the liquid crystal cell 2 be reflected by the
reflecting/polarizing plate 15 and emitted toward the front, and
lets the other part of the light, i.e. a polarizing component
parallel with the permeation axis of the reflecting/polarizing
plate 15 permeate the reflecting/polarizing plate 15 to be emitted
toward the back.
[0144] In a case where an external light comes to the liquid
crystal display element 1 also from its back, the present liquid
crystal display element 1 lets a part of the light coming from the
back, that permeates the reflecting/polarizing plate 15 and comes
to the plurality of pixels 80 of the liquid crystal cell 2 be
emitted toward the front.
[0145] That is, the present liquid crystal display device displays
an image to be viewed from the front by using one or both of a
light that comes to each of the plurality of pixels 80 of the
liquid crystal cell 2 from the front of the liquid crystal display
element 1 (this light including one or both of a light from the
surface light source 25 and an external light coming form the front
of the surface light source 25) and is reflected by the
reflecting/polarizing plate 15 and a light (an external light
coming from the back of the liquid crystal display element 1) that
permeates the reflecting/polarizing plate 15 from the back of the
liquid crystal display element 1 and comes to each of the plurality
of pixels 80 of the liquid crystal cell 2, and displays an image to
be viewed from the back by using a light that comes to each of the
plurality of pixels 80 of the liquid crystal cell 2 from the front
and permeates the reflecting/polarizing plate 15.
[0146] Accordingly, with the present liquid crystal display device,
it is possible to achieve both surface display with the use of one
liquid crystal display element 1, to reduce the occupation area of
the liquid crystal display device, and to display both of an image
to be viewed from the front and an image to be viewed from the back
in a display manner using a light from the surface light source 25
and in a display manner using an external light which is a light in
the external environment, likewise the liquid crystal display
device of the first embodiment.
[0147] In the present liquid crystal display device, since a part
of an external light coming from the back is reflected by the
reflecting/polarizing plate 15, the background of the entire back
screen looks like a specular surface due to the reflected light. An
image to be viewed from the back is displayed in the specular
surface background by a light that comes from the front and
permeates the reflecting/polarizing plate 15.
[0148] Since the present liquid crystal display device comprises as
the reflection/permeation means, the reflecting/polarizing plate 15
for reflecting, of two different linearly-polarized components of
an incident light, one polarized component, and letting the other
polarized component permeate therethrough behind the liquid crystal
layer 5 of the liquid crystal cell 2 of the liquid crystal display
element 1, it can let a light be emitted from the entire area of
the plurality of pixels 80 of the liquid crystal cell 2 toward the
front and the back and display both of an image to be viewed form
the front and an image to be viewed from the back by using the
entire area of the plurality of pixels 80 of the liquid crystal
cell 2, regardless of whether the display is performed by using a
light from the surface light source 25 or by using an external
light.
Fourth Embodiment
[0149] FIG. 8 is a fragmentary sectional view of a liquid crystal
display device according to a fourth embodiment of the present
invention. The liquid crystal display device of the present
embodiment comprises a light scattering layer (hereinafter referred
to as scattering layer) 21 behind the reflecting/polarizing plate
15 of the third embodiment.
[0150] The present liquid crystal display device lets an external
light coming from the back of the liquid crystal display element 1
be scattered by the scattering layer 21 and come to the
reflecting/polarizing plate 15, and lets a light returning to the
back by being reflected by the reflecting/polarizing plate 15 (a
polarized component having a vibration surface parallel with the
reflection axis of the reflecting/polarizing plate 15) and a light
that comes from the front of the liquid crystal display element 1
to be emitted toward the back be scattered by the scattering layer
21.
[0151] The present liquid crystal display device can change the
background of the back screen made by the light reflected by the
reflecting/polarizing plate 15 from the specular surface background
of the above third embodiment to a white background due to
scattering of the reflected light, and can restrict floating of the
dark display level of the image to be viewed from the back due to
scattering of the reflected light, thereby the contrast of the
image to be viewed from the back can be improved.
[0152] In the third and fourth embodiments, a polarized light
separating element constituted by the reflecting/polarizing plate
15 is provided as the reflection/permeation means behind the liquid
crystal layer 5 of the liquid crystal cell 2 of the liquid crystal
display element 1. As long as having a polarized light separating
characteristic of reflecting, of two different polarized components
of an incident light, one polarized component and letting the other
polarized component permeate, the polarized light separating
element may be structured by sandwiching a circularly-polarized
light separating plate (for example, a polarized light separating
plate made of a cholesteric liquid crystal film) for reflecting, of
two circularly-polarized components of an incident light rotating
rightward and leftward respectively, one circularly-polarized
component and letting the other circularly-polarized component
permeate therethrough, between a pair of retardation plates
(.lamda./4 plates) one of which circularly polarizes a
linearly-polarized light coming thereto and lets this light come to
the circularly-polarized light separating plate, and the other of
which linearly polarizes the circularly-polarized light emitted
from the circularly-polarized light separating plate and emits this
light.
[0153] The liquid crystal display device of the first to fourth
embodiments comprises a TN type liquid crystal display element 1.
However, the liquid crystal display element is not limited to the
TN type, but a liquid crystal display element of an STN (Super
Twisted Nematic) type, a non-twisted homogeneous aligning type, a
ferroelectric type, an antiferroelectric type, etc. may be
used.
[0154] Further, the liquid crystal display element is not limited
to a normally white mode type, but may be a normally black mode
type. The liquid crystal cell is not limited to an active matrix
type, but may be a simple matrix type.
[0155] Further, in the surface light source 25 of the liquid
crystal display device of the above-described embodiments, the
reflection surface 34 of the light guiding member 31 is constituted
by the plurality of prism units 35 which internally reflect a light
coming from the incident surface 32 of the light guiding member 31
toward a direction in which an angle to the normal of the slender
emission surface 33 of the light guiding member 31 is smaller.
However, the reflection surface 34 of the light guiding member 31
may be constituted by continuous inclined surfaces which are
inclined toward the slender emission surface 33 in the direction
from the incident surface 32 to its opposing surface of the light
guiding member 31.
[0156] Further, in the surface light source 25 of the
above-described embodiments, the reflection surface 29 of the light
guiding plate 26 is constituted by the plurality of prism units 30
which internally reflect a light coming from the incident surface
27 of the light guiding plate 26 toward a direction in which an
angle to the normal of the emission surface 28 of the light guiding
member 26 is smaller. However, the reflection surface 29 of the
light guiding plate 26 may be constituted by continuous inclined
surfaces which are inclined toward the emission surface 28 in the
direction from the incident surface 27 to its opposing surface of
the light guiding plate 26.
[0157] Further, in the surface light source 25 of the
above-described embodiments, one solid light emitting element 38 is
arranged so as to oppose to the incident surface 32 of the light
guiding member 31. However, in a case where the area of the
incident surface 32 of the light guiding member 31 is larger than
that of the solid light emitting element 38, a plurality of solid
light emitting elements 38 may be arranged so as to oppose to the
incident surface 32 of the light guiding member 31.
[0158] Further, in the surface light source 25 of the
above-described embodiments, one end surface of the light guiding
plate 26 is formed as the incident surface 27, the light guiding
member 31 whose one end surface is formed as the incident surface
32 is arranged so as to oppose to the incident surface 27 of the
light guiding plate 26, and the solid light emitting element 38 is
arranged so as to oppose to the incident surface 32 of the light
guiding member 31. However, both of the end surfaces of the light
guiding member 31 may be formed as incident surfaces 32
respectively, and solid light emitting elements 38 may be arranged
so as to oppose to both of the incident surfaces 32. Further, both
of the end surfaces of the light guiding plate 26 may be formed as
incident surfaces 27, and .lamda./2 retardation plates 36 and light
guiding members 31 may be arranged so as to oppose to both of the
incident surfaces 27 as well as solid light emitting elements 38
may be arranged so as to oppose to the incident surfaces 32 of
these light guiding members 31 on both sides.
[0159] Further, the surface light source 25 arranged at the front
of the liquid crystal display element 1 may not comprise the light
guiding member 31, but may comprise a light emitting element
constituted by a straight tubular cold-cathode tube which is
arranged so as to oppose to the incident surface 27 of the light
guiding member 26, as long as the surface light source 25 keeps its
function of emitting a light toward the liquid crystal display
element 1 and letting lights coming from both its front and back
permeate therethrough.
[0160] Next, an example where the liquid crystal display device of
the present invention is applied to a portable apparatus will be
explained. FIG. 9A and FIG. 9B are perspective views of a portable
phone as a portable apparatus. FIG. 10A and FIG. 10B are
perspective views of a digital camera as a portable apparatus. FIG.
11A and FIG. 11B are perspective views of a personal computer as a
portable apparatus. FIG. 12A and FIG. 12B are perspective views of
a digital video camera as a portable apparatus.
[0161] The portable apparatus shown in FIG. 9A and FIG. 9B is a
folding portable phone 40. The portable phone 40 comprises a body
41 having a keyboard 42 on the top surface thereof, and a lid 43
which has display sections 44a and 44b on the two opposing external
surfaces thereof, and is rotatably opened and closed with respect
to the body 41.
[0162] While the lid 43 is opened as shown in FIG. 9A, the portable
phone 40 displays main information such as addressee data and
e-mails which are to be sent or have been received on the main
display section 44a on the internal surface (the surface facing the
user of the portable phone 40 when the lid 43 is opened) of the lid
43. While the lid 43 is closed as shown in FIG. 9B, the portable
phone 40 displays sub information such as a clock and addressor
data on the sub display section 44b on the external surface of the
of the lid 43. The display sections 44a and 44b on both surfaces of
the portable phone 40 are provided with display windows 45a and 45b
on the internal surface and external surface of the lid 43. The
liquid crystal display device of any one of the above-described
embodiments, for example the liquid crystal display device of the
first embodiment is set inside the lid 43 such that the front
surface of the liquid crystal display device, i.e. the surface on
the side of the light guiding plate 26 of the surface light source
25 is positioned so as to be viewed from the display window 45a on
the internal surface of the lid 43, and the back surface of the
liquid crystal display device, i.e. the surface on the side of the
back polarizing plate 17 of the liquid crystal display element 1 is
positioned so as to be viewed from the display window 45b on the
external surface of the lid 43.
[0163] The portable phone 40 is provided with display drive means
for driving the liquid crystal cell 2 of the liquid crystal display
element 1 of the liquid crystal display device in a manner that the
portable phone 40 displays an image reversely in the left-to-right
or right-to-left direction between when the lid 43 is opened and
when the lid 43 is closed. Accordingly, a proper image having no
reverse can be displayed on the main display section 44a on the
internal surface of the lid 43 and on the sub display section 44b
on the external surface of the lid 43.
[0164] FIG. 10A and FIG. 10B show a thin digital camera 50. The
digital camera 50 comprises display sections 54a and 54b at
positions corresponding to each other back to back on the two
opposing external surfaces of its camera body 51 provided with a
photographing lens 52 and a finder 53, i.e. the back surface (the
surface facing the user) shown in FIG. 10A, and the front surface
(the surface facing the photo subject) shown in FIG. 10B.
[0165] The digital camera 50 displays an image being photographed
and an already photographed and stored image on the main display
section 54a on the back surface and on the sub display section 54b
on the front surface. The display sections 54a and 54b on the both
surfaces of the digital camera 50 are provided with display windows
55a and 55b on the back surface and front surface of the camera
body 51. The liquid crystal display device of any one of the
above-described embodiments, for example the liquid crystal display
device of the first embodiment is set inside the camera body 51
such that the front surface of the liquid crystal display device
(the front surface of the light guiding plate 26 of the surface
light source 25) is positioned so as to be viewed from the display
window 55a on the back surface of the camera body 51, and the back
surface of the liquid crystal display device (the back surface of
the back polarizing plate 17 of the liquid crystal display element
1) is positioned so as to be viewed from the display window 55b on
the front surface of the camera body 51.
[0166] The digital camera 50 can display an image being
photographed and an already photographed and stored image on either
of the main display section 54a and the sub display section 54b
that is selected, and can also display such an image on both of the
main display section 54a and the sub display section 54b at the
same time. In a case where displaying an image on either of the
main display section 54a and the sub display section 54b that is
selected, the digital camera 50 can display this image properly
with no reverse on either of the main display section 54a and the
sub display section 54b that is selected, by driving the liquid
crystal cell 2 of the liquid crystal display element 1 of the
liquid crystal display device in a manner that the image is
displayed reversely in the left-to-right or right-to-left direction
between when the image is displayed on the main display section 54a
and when the image is displayed on the sub display section 54b. In
a case where displaying an image on both of the main display
section 54a and the sub display section 54b at the same time, the
digital camera 50 displays a proper image on one of the display
sections 54a and 54b, for example, on the main display section 54a,
and displays on the other display section 54b, an image reversed
left-side right or right-side left from the proper image on the
main display section 54a.
[0167] FIG. 11A and FIG. 11B show a lap-top personal computer 60.
The personal computer 60 comprises a body 61 having a keyboard 62
on the top surface thereof, and a lid 63 which has display sections
64a and 64b on its two opposing external surfaces and is rotatably
opened and closed with respect to the body 61.
[0168] While the lid 63 is opened as shown in FIG. 11A, the lap-top
personal computer 60 displays main information on the main display
section 64a on the internal surface (the surface facing the user of
the personal computer 60 when the lid 63 is opened) of the lid 63.
While the lid 63 is closed as shown in FIG. 11B, the personal
computer 60 displays sub information on the sub display section 64b
on the external surface of the of the lid 63. The display sections
64a and 64b on both surfaces of the personal computer 60 are
provided with display windows 65a and 65b on the internal surface
and external surface of the lid 63. The liquid crystal display
device of any one of the above-described embodiments, for example
the liquid crystal display device of the first embodiment is set
inside the lid 63 such that the front surface of the liquid crystal
display device (the front surface of the light guiding plate 26 of
the surface light source 25) is positioned so as to be viewed from
the display window 65a on the internal surface of the lid 63, and
the back surface of the liquid crystal display device (the back
surface of the back polarizing plate 17 of the liquid crystal
display element 1) is positioned so as to be viewed from the
display window 65b on the external surface of the lid 63.
[0169] Even when the lid 63 is closed, the lap-top personal
computer 60 can partly display a clock and illustrations in a part
of the sub display section 64b on the external surface of the lid
63, or can display a television image on the entire sub display
section 64b. By driving the liquid crystal cell 2 of the liquid
crystal display element 1 of the liquid crystal display device in a
manner that an image is displayed reversely in the left-to-right or
right-to-left direction between when the lid 63 is opened and when
the lid 63 is closed, the personal computer 60 can display a proper
image having no reverse on both of the main display section 64a on
the internal surface of the lid 63 and the sub display section 64b
on the external surface of the lid 63.
[0170] The lap-top personal computer 60 may be so structured as to
include a transparent touch input panel which would be arranged at
the sub display section 64b on the external surface of the lid 63
so as to be overlaid on the back surface of the liquid crystal
display device. With this structure, even when the lid 63 is
closed, the personal computer 60 can be used for inputting
information from the touch input panel and displaying this
information on the sub display section 64b.
[0171] FIG. 12A and FIG. 12B show a video camera 70. The video
camera 70 comprises a camera body 71 which are provided with a
photographing lens 72 and a finder 73 and which has a monitor
storage unit 74 in its one side surface, and a monitor unit 75
which has display sections 76a and 76b on its two opposing external
surfaces and which is used by being stood from the monitor storage
unit 74.
[0172] The video camera 70 displays an image being photographed and
an already photographed and stored image on the main display
section 76a on the back surface of the monitor unit 75 shown in
FIG. 12B and on the sub display section 76b on the front surface of
the monitor unit 75 shown in FIG. 12A. The display sections 76a and
76b on both surfaces of the monitor unit 75 are provided with
display windows 77a and 77b on the back surface and front surface
of the monitor unit 75. The liquid crystal display device of any
one of the above-described embodiments, for example the liquid
crystal display device of the first embodiment is set inside the
monitor unit 75 such that the front surface of the liquid crystal
display device (the front surface of the light guiding plate 26 of
the surface light source 25) is positioned so as to be viewed from
the display window 77a on the back surface of the monitor unit 75,
and the back surface of the liquid crystal display device (the back
surface of the back polarizing plate 17 of the liquid crystal
display element 1) is positioned so as to be viewed from the
display window 77b on the front surface of the monitor unit 75.
[0173] The video camera 70 can display an image being photographed
and an already photographed and stored image on either of the main
display section 76a and sub display section 76b of the monitor unit
75 that is selected, and can also display such an image on both of
the main display section 76a and the sub display section 76b at the
same time. In a case where displaying an image on either of the
main display section 76a and the sub display section 76b that is
selected, the video camera 70 can display this image properly with
no reverse on either of the main display section 76a and the sub
display section 76b that is selected, by driving the liquid crystal
cell 2 of the liquid crystal display element 1 of the liquid
crystal display device in a manner that the image is displayed
reversely in the left-to-right or right-to-left direction between
when the image is displayed on the main display section 76a and
when the image is displayed on the sub display section 76b . In a
case where displaying an image on both of the main display section
76a and the sub display section 76b at the same time, the video
camera 70 displays a proper image on one of the display sections
76a and 76b, for example, on the main display section 76a, and
displays on the other display section 76b, an image reversed
left-side right or right-side left from the proper image on the
main display section 76a.
[0174] Since the liquid crystal display device which is mounted
inside the portable apparatuses 40, 50, 60, and 70 shown in FIGS.
9A and 9B to FIGS. 12A and 12B performs both surface display with
the use of one liquid crystal display element 1, the occupation
area and volume required by the liquid crystal display device
inside each apparatus is only the occupation area and volume of
approximately one liquid crystal display element 1. Accordingly,
each apparatus can be miniaturized. Further, each apparatus can
display images on both surfaces in a sufficiently large screen
size, and can be manufactured at a lower cost than an apparatus in
which a both surface display type liquid crystal display device
including two liquid crystal display elements is mounted.
[0175] Further, since the liquid crystal display device displays
images to be viewed from the front and back in a display manner
using a light from the surface light source 25 and in a display
manner using an external light, the apparatuses 40, 50, 60, and 70
can display images on both surfaces in a display manner using a
light from the surface light source 25 of the liquid crystal
display device and in display manner using an external light.
[0176] The present invention can be applied not only to the
portable phone 40, the digital camera 50, the lap-top personal
computer 60, and the video camera 70 described above, but also to
other portable apparatuses. In that case too, display windows may
be provided on two opposing external surfaces of the apparatus, and
any of the above-described liquid crystal display devices may be
mounted inside the apparatus such that the front surface of the
liquid crystal display device faces the display window on one of
the two external surfaces of the apparatus and the back surface of
the liquid crystal display device faces the display window on the
other of the two external surfaces.
[0177] Various embodiments and changes may be made thereunto
without departing from the broad spirit and scope of the invention.
The above-described embodiments are intended to illustrate the
present invention, not to limit the scope of the present invention.
The scope of the present invention is shown by the attached claims
rather than the embodiments. Various modifications made within the
meaning of an equivalent of the claims of the invention and within
the claims are to be regarded to be in the scope of the present
invention.
[0178] This application is based on Japanese Patent Application No.
2002-314388 filed on Oct. 29, 2002 and including specification,
claims, drawings and summary. The disclosure of the above Japanese
Patent Application is incorporated herein by reference in its
entirety.
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