U.S. patent application number 16/427916 was filed with the patent office on 2019-09-19 for liquid crystal display device.
This patent application is currently assigned to Mitsubishi Electric Corporation. The applicant listed for this patent is Mitsubishi Electric Corporation. Invention is credited to Eri IKEGAMI, Yasunori NIWANO.
Application Number | 20190285952 16/427916 |
Document ID | / |
Family ID | 62107795 |
Filed Date | 2019-09-19 |
United States Patent
Application |
20190285952 |
Kind Code |
A1 |
IKEGAMI; Eri ; et
al. |
September 19, 2019 |
LIQUID CRYSTAL DISPLAY DEVICE
Abstract
A liquid crystal display device includes a liquid crystal panel,
a transparent protective member, and a transparent adhesive
material. The liquid crystal panel is an in-plane switching liquid
crystal panel including a TFT substrate, a counter substrate
sandwiching a liquid crystal layer between the counter substrate
and the TFT substrate, and a transparent conductive film being
provided on a surface opposite to the liquid crystal layer of the
counter substrate, a side of the transparent conductive film being
a side of a display surface. The transparent protective member
covers a surface on the side of the display surface of the liquid
crystal panel. The transparent adhesive material attaches the
transparent protective member on the surface on the side of the
display surface. The transparent conductive film has a film
thickness ranging from 120 nm to 160 nm.
Inventors: |
IKEGAMI; Eri; (Tokyo,
JP) ; NIWANO; Yasunori; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Mitsubishi Electric Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
Mitsubishi Electric
Corporation
Tokyo
JP
|
Family ID: |
62107795 |
Appl. No.: |
16/427916 |
Filed: |
May 31, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15801850 |
Nov 2, 2017 |
10365519 |
|
|
16427916 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 2001/133331
20130101; G02F 2202/28 20130101; G02F 2202/22 20130101; G02F
1/133308 20130101; G02F 1/133512 20130101; G02F 1/1368 20130101;
G02F 2203/05 20130101; G02F 2001/133334 20130101; G02F 1/133502
20130101; G02F 1/134363 20130101; G02F 1/133514 20130101; G02F
2201/503 20130101 |
International
Class: |
G02F 1/1343 20060101
G02F001/1343; G02F 1/1335 20060101 G02F001/1335; G02F 1/1368
20060101 G02F001/1368; G02F 1/1333 20060101 G02F001/1333 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2016 |
JP |
2016-222038 |
Claims
1. A liquid crystal display device, comprising: an in-plane
switching liquid crystal panel including a TFT substrate, a counter
substrate sandwiching a liquid crystal layer between said counter
substrate and said TFT substrate, and a transparent conductive film
being provided on a surface opposite to said liquid crystal layer
of said counter substrate, a side of said transparent conductive
film being a side of a display surface; a transparent protective
member covering a surface on said side of said display surface of
said liquid crystal panel; and a transparent adhesive material
attaching said transparent protective member on said surface on
said side of said display surface, wherein said transparent
conductive film has a film thickness ranging from 25 nm to 40
nm.
2. The liquid crystal display device according to claim 1, further
comprising a light-shielding film being disposed to have a frame
shape with an opening portion along a periphery of a surface of
said transparent protective member closer to said liquid crystal
panel, wherein said transparent conductive film extends at least
from a periphery of a display region in which a video is displayed
on said liquid crystal panel to a boundary part of said opening
portion in said light-shielding film in a planar view.
3. The liquid crystal display device according to claim 1, wherein
a thin film layer having an antireflection function is provided on
a surface of said transparent protective member.
4. The liquid crystal display device according to claim 1, wherein
said transparent conductive film is a sputtering film.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional of U.S. patent application
Ser. No. 15/801,850 filed Nov. 2, 2017, which claims benefit of
priority to Japanese Patent Application 2016-222038 filed Nov. 15,
2016, the entire content of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to a liquid crystal display
device, and particularly to a liquid crystal display device in
which a transparent protective member is attached on a front
surface of an in-plane switching liquid crystal panel with a
transparent adhesive material.
Description of the Background Art
[0003] In a liquid crystal display device including an in-plane
switching liquid crystal panel in which a voltage is applied in
parallel with a substrate surface, an electrode is provided in a
substrate in which a drive element such as a thin film transistor
(TFT) is formed (also referred to as "the TFT substrate" or "the
array substrate"), but is not provided in a counter substrate in
which a color filter, for example, is provided (also referred to as
"the color filter (CF) substrate). Thus, an external electrical
field such as a static electricity entering from a side of the
counter electrode or a charge-up on a surface of the counter
electrode may cause a defect in a display on the liquid crystal
panel.
[0004] Accordingly, adopted in the liquid crystal display device
including a conventional general in-plane switching liquid crystal
panel, as a measure against an electrostatic discharge (ESD)
described above, is a structure that an indium thin oxide (ITO)
film having a film thickness of approximately 25 nm is formed on a
glass surface located on a side of a display surface of the counter
substrate (that is to say, a side opposite to the TFT substrate) so
as to suppress the external electrical field entering from the side
of the counter substrate. The above ITO film can be functionally
referred to as "the transparent conductive film", or also referred
to as "the back surface ITO" because it is provided on a back side
with respect to a surface on which the color filter is
disposed.
[0005] In the meanwhile, in a case where the back surface ITO is
provided, a difference of refraction index between the back surface
ITO, a polarization plate disposed on an upper surface of the back
surface ITO, and the glass on the counter substrate located below
the back surface ITO causes an interface reflection and increases a
reflection ratio of the liquid crystal panel, thereby causing a
problem. Considered as a main factor of the increase in the
reflection ratio in the above configuration is a reflection at an
interface between the polarization plate and the back surface ITO
and a reflection at an interface between the back surface ITO and
the glass on the counter substrate. These reflection elements
largely double the reflection ratio of the liquid crystal panel
compared with a liquid crystal display device which does not
include the back surface ITO.
[0006] As a method of improving the reflection ratio, for example,
Japanese Patent Application Laid-Open No. 2009-250989 describes a
method of placing a low refraction index film on an upper layer or
a lower layer of the back surface ITO for purpose of reducing the
reflection at the interface between the polarization plate and the
back surface ITO or the reflection at the interface between the
back surface ITO and the glass as described above, thereby causing
the film thickness of the back surface ITO to be relatively thin,
that is approximately 10 nm to 20 nm.
[0007] In the meanwhile, as a method of enhancing the effect
against the ESD, Japanese Patent Application Laid-Open No.
2012-155258 describes a method applying a resin layer into which
conductive inorganic particles are mixed to form a transparent
conductive film having a thickness of approximately 0.2 .mu.m to 5
.mu.m, and using the transparent conductive film as the back
surface ITO. Japanese Patent Application Laid-Open No. 10-293207
describes an example of using an ITO film, which is formed to be
relatively thick, that is 145 nm or 180 nm, for example, by
sputtering, as the back surface ITO.
[0008] Recently, a liquid crystal display device to be placed
outside, for example, includes a transparent protective plate (also
referred to as "a transparent protective member" or "a cover
glass") made of resin or glass, for example, on a side of a front
surface (that is to say, a display surface) of the liquid crystal
panel to protect the liquid crystal panel against an external
impact, for example. If there is an air layer between the liquid
crystal panel and the protective plate in the above case, an
external light entering from the side of the front surface of the
liquid crystal panel is reflected by front and back surface of the
protective plate and the front surface of the liquid crystal panel,
thus a problem that a visibility in the display of the liquid
crystal panel reduces occurs.
[0009] Accordingly, applied is a configuration of filling a
transparent resin between the liquid crystal panel and the
protective plate or a configuration of attaching the liquid crystal
panel and the protective plate with a transparent adhesive material
such as a light transmissive adhesive sheet made of resin
therebetween, for example. The configuration similar to the above
description is applied to the liquid crystal display device
including a touch panel on the front surface of the liquid crystal
panel to prevent the air layer from being formed between the touch
panel and the liquid crystal panel. As described above, the liquid
crystal display device including the protective plate or the touch
panel on the side of the front surface of the liquid crystal panel
(collectively referred to as "the front surface panel" hereinafter)
has the configuration of placing the resin layer (the injected
resin or the light-transmissive adhesive sheet) between the liquid
crystal panel and the front surface panel to suppress the formation
of the air layer.
[0010] As described above, the liquid crystal display device
including the front surface panel originally has the problem of the
reflection caused by the formation of the air layer between the
front surface panel and the liquid crystal panel as described
previously, so that the measure described above has been taken.
However, the configuration of including the front surface panel has
also been started to be applied to the liquid crystal display
device including the in-plane switching liquid crystal panel
including the back surface ITO described previously, so that the
increase in the reflection ratio occurring compositely in the front
surface panel, the resin layer, and the back surface ITO also
becomes one of the additional problems.
SUMMARY
Problem to be Solved by the Invention
[0011] However, in a case of applying the method of adding the low
refraction index film on the upper layer or the lower layer of the
back surface ITO, thereby causing the back surface ITO to be
relatively thin, that is approximately 10 nm to 20 nm as described
in Japanese Patent Application Laid-Open No. 2009-250989, a process
of forming the low refraction index film and a material of the low
refraction index film are necessary to add the low refraction index
film, thereby causing a cost increase as a matter of course.
Furthermore, the thinned back surface ITO has a high resistance, so
that the effect against the ESD, which is the intended purpose for
forming the back surface ITO, is reduced.
[0012] Japanese Patent Application Laid-Open Nos. 2012-155258 and
10-293207 in the above description describe the method of enhancing
the effect against the ESD, but do not describe the method of
improving the reflection ratio. Particularly, with regard to the
problem of the reflection ratio in the liquid crystal display
device including the front surface panel on the side of the display
surface of the in-plane switching liquid crystal panel described
above, Japanese Patent Application Laid-Open Nos. 2012-155258 and
10-293207 have no description of the configuration of including the
front surface panel, thus do not disclose the effective method of
improving the reflection ratio in the structure that the front
surface panel is disposed on the side of the display surface.
[0013] Provided is a liquid crystal display device capable of
suppressing an external electrical field entering from a side of a
counter substrate and suppressing a reflection of an external light
entering from a side of a display surface at the same time.
Means to Solve the Problem
[0014] A liquid crystal display device according to the present
invention includes a liquid crystal panel, a transparent protective
member, and a transparent adhesive material. The liquid crystal
panel is an in-plane switching liquid crystal panel including a TFT
substrate, a counter substrate sandwiching a liquid crystal layer
between the counter substrate and the TFT substrate, and a
transparent conductive film being provided on a surface opposite to
the liquid crystal layer of the counter substrate, a side of the
transparent conductive film being a side of a display surface. The
transparent protective member covers a surface on the side of the
display surface of the liquid crystal panel. The transparent
adhesive material attaches the transparent protective member on the
surface on the side of the display surface. The transparent
conductive film has a film thickness ranging from 120 nm to 160
nm.
Effects of the Invention
[0015] According to the present invention, the transparent
conductive film has the film thickness ranging from 120 nm to 160
nm, thus the liquid crystal display device, in which the
transparent protective member is attached on the in-plane switching
liquid crystal panel with the transparent adhesive member, can
suppress an external electrical field entering from a side of the
counter substrate and suppress the reflection of an external light
entering from a side of the display surface at the same time.
[0016] These and other objects, features, aspects and advantages of
the present invention will become more apparent from the following
detailed description of the present invention when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is an exploded perspective view of a liquid crystal
display device according to an embodiment 1.
[0018] FIG. 2 is a cross sectional view of the liquid crystal
display device according to the embodiment 1.
[0019] FIG. 3 is a drawing for describing a reflection in the
liquid crystal display device according to the embodiment 1.
[0020] FIG. 4 is a drawing illustrating a film thickness dependency
of a transparent conductive film with respect to a reflection ratio
in the liquid crystal display device.
[0021] FIG. 5 is a perspective view of a counter substrate and a
transparent conductive film according to an embodiment 3.
[0022] FIG. 6 is a cross sectional view of the counter substrate
and the transparent conductive film according to the embodiment
3.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Embodiments of the present invention are described based on
the drawings hereinafter.
Embodiment 1
[0024] <Configuration of Liquid Crystal Display Device>
[0025] FIG. 1 is an exploded perspective view schematically
illustrating an example of a configuration of a liquid crystal
display device 100 according to the embodiment 1 of the present
invention. FIG. 2 is a cross sectional view taken along an arrow
A-A illustrated in FIG. 1.
[0026] As illustrated in FIGS. 1 and 2, the liquid crystal display
device 100 includes a transparent protective member 1, a
transparent adhesive material 2, a light-shielding film 3, an
adhesive material 4, a liquid crystal panel 5, a housing 11, and a
backlight unit 12.
[0027] The liquid crystal panel 5 is an in-plane switching liquid
crystal panel and includes, as illustrated in FIG. 2, polarization
plates 6 and 10, a transparent conductive film 7, a counter
substrate 8, and a TFT substrate 9. In the liquid crystal panel 5,
two glass substrates, that is to say, the TFT substrate 9 being a
first substrate and the counter substrate 8 being a second
substrate are disposed to face each other, and these two substrates
sandwich a liquid crystal layer (not shown) therebetween. The
polarization plate 10 is attached on an outer surface (that is to
say, a surface opposite to the liquid crystal layer) of the TFT
substrate 9. The polarization plate 6 is attached on a surface of
the transparent conductive film 7, which will be described
hereinafter, opposite to the counter electrode 8.
[0028] A circuit portion of a pixel including the TFT is formed on
a surface of the TFT substrate 9 on which the liquid crystal layer
is disposed. In the meanwhile, a color filter and a light-shielding
film (a black matrix: BM), for example, are formed on a surface of
the counter substrate 8 closer to a side where the liquid crystal
layer is disposed. The transparent conductive film 7 for
suppressing an entry of an external electrical field, for example,
is formed on an outer surface of the counter substrate 8 (that is
to say, between the polarization plate 6 and the counter substrate
8). The transparent conductive film 7 needs to be formed in at
least a region covering a display region 5a in which a video is
displayed on the liquid crystal panel 5 (also referred to as "the
display area"), but is disposed to cover the entire outer surface
of the counter substrate 8 in the present embodiment. Although not
shown in the drawings, the transparent conductive film 7 is
grounded and connected via a conductive paste or a conductive tape
provided on a frame region outside the display region 5a in the
liquid crystal panel 5.
[0029] In the present embodiment, the transparent conductive film 7
is a sputtering film (specifically, an ITO film) formed by
sputtering with a predetermined film thickness ranging from 120 nm
to 160 nm. Herein, the transparent conductive film 7 having an
average thickness of 140 nm and variation range of .+-.10% is
formed as an example. A film deposition temperature (a substrate
temperature) at the time of sputtering is appropriately adjusted to
adjust a film quality (or a resistivity) so that a sheet resistance
in the transparent conductive film 7 having the predetermined film
thickness ranges from 10.OMEGA./.quadrature. to
25.OMEGA./.quadrature..
[0030] The liquid crystal panel 5 is housed in a housing 11
together with the backlight unit 12. The transparent protective
member 1 is attached on a display surface on which the video is
displayed on the liquid crystal panel 5 (that is to say, the
surface of the polarization plate 6 opposite to the counter
substrate 8) via the transparent adhesive material 2 to cover the
display surface. It is also applicable to place an index matching
layer (a lamination film of a low refraction index layer and a high
refraction index layer) between the transparent adhesive material 2
and the polarization plate 6 to attach the transparent adhesive
material 2 on the polarization plate 6 via the index matching
layer. An AR treatment (an antireflection treatment) may be
appropriately performed on an outer surface of the transparent
protective member 1 (that is to say, a surface of the transparent
protective member 1 opposite to the transparent adhesive material
2). The transparent protective member 1 may be replaced with a
touch panel, for example.
[0031] The transparent protective member 1 is attached on the
surface of the liquid crystal panel 5 with the transparent adhesive
material 2, and also is attached on and fixed to the housing 11
with the adhesive material 4 disposed on a periphery of a surface
of the transparent protective member 1 closer to the liquid crystal
panel 5. When the size of transparent adhesive material 2 is
changed to be substantially the same as that of the transparent
protective member 1, the transparent protective member 1 can be
fixed to both the surface of the liquid crystal panel 5 and the
housing 11 only with the transparent adhesive material 2, and the
adhesive material 4 may be omitted in the above case.
[0032] The transparent adhesive material 2 suppresses the formation
of an air layer in an area where the transparent adhesive material
2 is applied, thus can be appropriately selected from a resin layer
such as an injection resin or a light-transmissive adhesive sheet.
A combination of the material is selected so that the transparent
adhesive material 2 has substantially the same refraction index as
the transparent protective member 1 or a difference of the
refraction index between the transparent adhesive material 2 and
the transparent protective member 1 is at least equal to or smaller
than 30% of the larger refraction index.
[0033] As illustrated in FIGS. 1 and 2, the light-shielding film 3,
having a shape along the periphery of the surface of the
transparent protective member 1 closer to the side where the liquid
crystal panel 5 is disposed, is formed on the periphery. The
light-shielding film 3 is formed to have a frame shape with an
opening portion 3a, and a size of the opening portion 3a is the
same or slightly smaller than that of the polarization plate 6 in a
planar view, and is substantially the same as that of the display
region 5a in the liquid crystal panel 5. The light-shielding film 3
prevents light emitted from the backlight unit 12 from being
visually recognized from the outside of the display region 5a in
the liquid crystal display panel 5 or prevents light leaked from
the periphery of the counter substrate 8 from being visually
recognized from the side of the display surface. The
light-shielding film 3 is a film formed by printing a black ink,
for example, thus is also referred to as "a black-framed printing",
for example, in some cases.
[0034] <Operation and Effect>
[0035] Subsequently, an operation and an effect obtained in a
structure of the liquid crystal display device 100 according to the
present embodiment 1 are described in detail hereinafter.
[0036] FIG. 3 is a drawing for describing a reflection in the
liquid crystal display device 100. FIG. 3 illustrates an enlarged
lamination structure of the transparent protective member 1 to the
counter substrate 8 in the liquid crystal display device 100. As
indicated by arrows in FIG. 3, the reflection in the liquid crystal
display device 100 occurs due to an interference of a surface
reflection and an interface reflection on each of the layers of the
transparent protective member 1 to the counter substrate 8. In the
example in FIG. 3, the reflection in the liquid crystal display
device 100 occurs due to the interference of the reflection on each
of the surface of the transparent protective member 1 (that is to
say, the surface on the side of the display surface of the liquid
crystal display device 100), the interface between the transparent
protective member 1 and the transparent adhesive material 2, the
interface between the transparent adhesive material 2 and the
polarization plate 6, the interface between the polarization plate
6 and the transparent conductive film 7, and the interface between
the transparent conductive film 7 and the counter substrate 8.
[0037] "The reflection in the liquid crystal display device 100" in
the present description indicates, as described above, the
reflection occurring due to the interference of the reflection
light, which is the external light entering from the side of the
display surface of the liquid crystal display device 100 and then
reflected by the surface of the transparent protective member 1,
with the interface reflection of the light entering inside the
liquid crystal display device 100 from the opening portion 3a in
the light-shielding film 3 and then reflected by each interface
between the layers described above.
[0038] In the present embodiment, the AR treatment is performed on
the surface of the transparent protective member 1 to reduce the
reflection on the surface thereof. When the AR treatment is
performed, the transparent protective member 1 becomes the
transparent protective member 1 including a thin film layer having
an antireflection function on the surface thereof. Since the
transparent adhesive material 2 has substantially the same
refraction index as the transparent protective member 1, the
reflection on the interface between the transparent protective
member 1 and the transparent adhesive material 2 is reduced. The
reflection on the interface between the transparent adhesive
material 2 and the polarization plate 6 can be reduced by
sandwiching the index matching layer therebetween. As the other
reflection element, the reflection due to the interference of the
surface reflection on the transparent conductive film 7 with the
reflection on the interface between the transparent conductive film
7 and the counter substrate 8 significantly contributes to the
reflection ratio of the liquid crystal display device 100.
[0039] FIG. 4 is a drawing illustrating a film thickness dependency
of a transparent conductive film with respect to a reflection ratio
in the liquid crystal display device. Described hereinafter using
FIG. 4 is an influence of the film thickness of the transparent
conductive film 7 on the reflection due to the interference of the
surface reflection on the transparent conductive film 7
significantly contributing to the reflection ratio of the liquid
crystal display device 100 with the reflection on the interface
between the transparent conductive film 7 and the counter substrate
8 (referred to as "the first reflection component" hereinafter) and
the reflection including the other reflection as well as the
reflection described above in a structure having the transparent
protective member 1 and the transparent adhesive material 2
(referred to as "the second reflection component" hereinafter).
[0040] Each of graphs indicated by a solid line and a dotted line
in FIG. 4 indicates the film thickness dependency of the
transparent conductive film with respect to the reflection ratio
occurring due to the interference of the reflection on the surface
and the interface between each layer calculated using a model, in
which the lamination structure of laminating the glass substrate
used for the counter substrate, the transparent conductive film,
and the polarization plate in this order is simplified, at incident
angles of 8 degrees and 30 degrees as a typical example. Data
indicated by these graphs (also simply referred to as "the
calculation value" hereinafter) is used for referencing the first
reflection component (the reflection due to the interference of the
surface reflection on the transparent conductive film 7 with the
reflection on the interface between the transparent conductive film
7 and the counter substrate 8).
[0041] Furthermore, data plotted by black circles in FIG. 4
indicates the film thickness dependency of the transparent
conductive film with respect to the overall reflection ratio
measured using an experimental sample in which a transparent layer
corresponding to the transparent adhesive material 2 (specifically,
an oil layer having a refraction index of 1.5 for simplifying the
experiment) and a cover glass corresponding to the transparent
protective member 1 are disposed in this order on a side of a
display surface of an in-plane switching liquid crystal panel. This
data (also simply referred to as "the measured value" hereinafter)
is used for referencing the second reflection component (the
reflection including the reflection as well as the first reflection
component in the structure having the transparent protective member
1 and the transparent adhesive material 2).
[0042] Firstly, the graphs of the calculation value in FIG. 4 show
that the reflection ratio can be significantly reduced when the
transparent conductive film has the film thickness ranging from 0
nm to 25 nm and from 120 nm to 160 nm. However, the range from 0 nm
to 25 nm is not preferable regarding the effect against the ESD,
and it is shown that the reflection ratio can be significantly
reduced as long as the transparent conductive film 7 has a
predetermined film thickness ranging from 120 nm to 160 nm or the
average thickness of 140 nm and variation range of .+-.10%, as the
example of the predetermined film thickness, adopted in the
embodiment 1. This result corresponds to a case where the liquid
crystal display device 100 particularly has a configuration, that
is, the AR treatment is performed on the surface of the transparent
protective member 1, the transparent adhesive material 2 and the
transparent protective member 1 have substantially the same
refraction index, and the index matching layer is disposed on the
interface between the transparent adhesive material 2 and the
polarization plate 6, thus the reflection due to the interference
of the surface reflection on the transparent conductive film 7 with
the reflection on the interface between the transparent conductive
film 7 and the counter substrate 8 mainly has the influence on the
reflection ratio of the liquid crystal display device 100.
[0043] In the meanwhile, the data of the measured value in FIG. 4
shows that the film thickness dependency of the transparent
conductive film, particularly an absolute value of the reflection
ratio in a thickness region where the reflection ratio is reduced
slightly increases due to the influence of the reflection except
the first reflection component (particularly, the reflection
influenced by the cover glass and the transparent layer). This
result corresponds to a case of omitting the following
configuration from the liquid crystal display device 100, that is,
the AR treatment is performed on the surface of the transparent
protective member 1, the transparent adhesive material 2 and the
transparent protective member 1 have substantially the same
refraction index, and the index matching layer is disposed on the
interface between the transparent adhesive material 2 and the
polarization plate 6, for example. However, the data of the
measured value indicates the same tendency as the graph of the
calculation value, thus shows that the reflection ratio can be
significantly reduced when the transparent conductive film has the
film thickness ranging from 0 nm to 25 nm and from 120 nm to 160
nm. Accordingly, it is also shown that the reflection ratio can be
significantly reduced as long as the transparent conductive film 7
has a predetermined film thickness ranging from 120 nm to 160 nm or
the average thickness of 140 nm and variation range of .+-.10%, as
the example of the predetermined film thickness, adopted to the
liquid crystal display device 100 according to the embodiment 1.
Moreover, it is shown that since the transparent conductive film 7
has relatively the large thickness ranging from 120 nm to 160 nm,
the effect against the ESD (the effect of suppressing the entry of
the external electrical field and the charge-up) can also be
effectively obtained.
[0044] With regard to the degree of the reduction in the reflection
ratio, the reflection ratio can be reduced by approximately 35% to
120% compared with the case where the transparent conductive film
has the conventional general film thickness ranging from 25 nm to
70 nm.
[0045] As described above, in the liquid crystal display device 100
including the transparent protective member 1 attached on the
in-plane switching liquid crystal panel 5 via the transparent
adhesive member 2 according to the embodiment 1, the film thickness
of the transparent conductive film 7 formed on the counter
substrate 8 is set within the range from 120 nm to 160 nm, thus the
function of suppressing the reflection of the external light
entering from the side of the display surface and suppressing the
external electrical field entering from the side of the counter
substrate can be achieved at the same time.
[0046] Moreover, in the liquid crystal display device 100 according
to the embodiment 1, the transparent conductive film 7 is the
sputtering film formed by sputtering. The transparent conductive
film 7 is therefore made up of the transparent conductive film
material having relatively the low resistivity compared with a case
where the transparent conductive film is formed of a coating-type
transparent conductive film material, and further has the
relatively large thickness ranging from 120 nm to 160 nm.
Accordingly, the sheet resistance in the transparent conductive
film 7 is set within the range from 10.OMEGA./.quadrature. to
25.OMEGA./.quadrature.. As a result, the resistance value of the
transparent conductive film 7 is set lower than the general sheet
resistance of 30.OMEGA./.quadrature., thus the effect against the
ESD is further enhanced. The transparent conductive film 7
satisfying both the range of the film thickness and the relatively
low resistance described above can be formed at the relatively low
cost.
[0047] The liquid crystal display device 100 according to the
embodiment 1 includes the opening portion in the light-shielding
film 3 having substantially the same size as the display region 5a,
and more properly, the opening portion 3a in the light-shielding
film 3 is provided to be slightly larger than the opening portion
in the black matrix which is the light-shielding film provided in a
surrounding part of the display region 5a on the side of the liquid
crystal panel 5 (the counter substrate 8) determining an outline of
the display region 5a. The opening portion 3a is set in such a
manner in many cases so that the size or the position of a boundary
of the display region 5a does not fluctuate due to a misalignment
caused by a relatively low accuracy in a position adjustment
between the liquid crystal panel 5 and the transparent protective
material 1 on which the light-shielding film 3 is provided. When a
dummy pixel region with a constant black display is provided in the
surrounding part of the display region 5a, a boundary of the
opening portion 3a may be set within the dummy pixel region in some
cases, however, the opening portion 3a is set larger than the
display region 5a in any case. Furthermore, a region, in which the
transparent conductive film 7 having the film thickness ranging
from 120 nm to 160 nm is formed, covers the display region 5a and
the entire outer surface of the counter substrate 8, that is to
say, the region in the counter substrate 8 facing the
light-shielding film 3.
[0048] When the liquid crystal display device 100 is in inactive
state (or a black-display state) in the above structure, a mutual
effect of the low reflection ratio of the liquid crystal display
device 100 caused by the effect according to the basic
configuration of the present invention causes a boundary between
the light-shielding film 3 formed on the transparent protective
member 1 and the surrounding part of the display region 5a in the
liquid crystal panel 5 to be hardly seen. As a result, the
configuration of the liquid crystal display device 100 according to
the embodiment 1 can obtain the effect of improving the visibility
of the boundary between the light-shielding film 3 formed on the
transparent protective member 1 and the surrounding part of the
display region 5a in the liquid crystal panel 5. Herein, the
boundary between the light-shielding film 3 and the surrounding
part of the display region 5a specifically indicates the boundary
between a black state of the light-shielding film 3 and a black
state of the pixel in a black display state or the black matrix in
the liquid crystal panel 5 (the surrounding part of the display
region 5a). The transparent conductive film 7 needs to be located
in at least a boundary part between the light-shielding film 3 and
the surrounding part of the display region 5a in the liquid crystal
panel 5 in a planar view so as to obtain the above effect. That is
to say, since the transparent conductive film 7 is formed in the
region covering the display region 5a, it needs to extend at least
from the periphery of the display region 5a to the boundary part of
the opening portion 3a in the light-shielding film 3 in a planar
view.
Embodiment 2
[0049] In the liquid crystal display device 100 according to the
embodiment 1, the display on the liquid crystal panel 5 is colored
in some cases when the transparent conductive film 7 is set to have
a specific film thickness, which is relatively thick, ranging from
120 nm to 160 nm. For example, when the transparent conductive film
7 is set to have a film thickness which causes the display on the
liquid crystal panel 5 to be colored to blue-green, specifically, a
transmission rate or a reflection ratio relatively increases in a
range of film thickness from 480 nm to 500 nm corresponding to a
wavelength range of blue-green in a single body of the liquid
crystal panel 5.
[0050] Accordingly, for example, the color caused by the
transparent conductive film 7 can be offset and reduced by using a
member whose transmission characteristics are adjusted as a
constituent member other than the transparent conductive film 7.
Specifically, when the display is colored to blue-green as the
example described above, for example, it is applicable to combine
the other constituent member whose light transmission rate in the
wavelength range from 480 nm to 500 nm is relatively lower than a
light transmission rate in the other wavelength range.
[0051] Although the configuration in the liquid crystal panel 5 or
the configuration other than the liquid crystal panel 5 in the
liquid crystal display device may be selected as the member for
adjusting the transmission characteristics, it is preferable to
select the transparent protective member 1 from the perspective
that a material can be comparatively easily selected. In the liquid
crystal display device according to the embodiment 2, applied as
the transparent protective member 1 is a transparent protective
member having the transmission characteristics to offset the
transmission characteristics of the transparent conductive film 7
(for example, the transmission characteristics that the light
transmission rate in the wavelength range from 480 nm to 500 nm is
relatively lower than the light transmission rate in the other
wavelength range so as to reduce the coloring of blue-green, as the
above description). Since the configuration in the liquid crystal
display device according to the embodiment 2 other than the
transparent protective member 1 is similar to that of the liquid
crystal display device 100 according to the embodiment 1, the
detailed description is omitted.
[0052] In the configuration of the liquid crystal display device
according to the embodiment 2 described above, the transparent
protective member 1 having the transmission characteristics of
offsetting the transmission characteristics of the transparent
conductive film 7 is used, thus the coloring of the display can be
improved in addition to the fact that the effect similar to the
embodiment 1 can be obtained.
Various Modification Examples of the Embodiment 2
[0053] As a further modification example of the embodiment 2
described above, for example, transmission characteristics of the
other member may be adjusted instead of the transparent protective
member 1. Some modification examples of partially changing the
configuration in the embodiment 2 are described hereinafter.
[0054] <First modification example of the embodiment 2>
[0055] In the present modification example, a member whose
transmission characteristics are adjusted is used as the
transparent adhesive material 2 without adjusting the transmission
characteristics of the transparent protective member 1 in the
liquid crystal display device according to the embodiment 2.
[0056] In the present modification example, the transparent
adhesive material 2 having the transmission characteristics of
offsetting the transmission characteristics of the transparent
conductive film 7 is used, thus the coloring of the display can be
improved in the manner similar to the embodiment 2.
Second Modification Example of the Embodiment 2
[0057] In the present modification example, a substrate whose
transmission characteristics are adjusted is used as the counter
substrate 8 without adjusting the transmission characteristics of
the transparent protective member 1 in the liquid crystal display
device according to the embodiment 2. In the present modification
example, a chromaticity of the color filter included in the counter
substrate 8 is adjusted to adjust the transmission rate of the
counter substrate 8. The chromaticity of the color filter may be
adjusted by a ratio of the opening for each pixel of R (red), G
(green), and B (blue) (that is to say, a ratio of an area of the
opening portion of the black matrix to an area of the pixels), or
it is also applicable to adjust transmission rate characteristics
for each wavelength of each color material layer of RGB. A method
of adjusting the transmission rate characteristics for each
wavelength of each color material layer includes changing a
thickness of the color material layer or changing a contained
amount of colorant mixed to develop the color.
[0058] In the present modification example, the counter substrate 8
having the transmission characteristics of offsetting the
transmission characteristics of the transparent conductive film 7
is used, thus the coloring of the display can be improved. Since
the adjustment of the chromaticity of the color filter in the
counter substrate 8 is one of the common practices performed in
designing a general color specification, thus is preferable from
the perspective that the transmission characteristics of the
counter substrate 8 can be adjusted comparatively easily.
[0059] The embodiment 2 and each modification example thereof
describe the case of improving the coloring of the display using
one member having the transmission characteristics of offsetting
the transmission characteristics of the transparent conductive film
7, however, the coloring of the display may also be improved using
a plurality of members having transmission characteristics of
offsetting the transmission characteristics of the transparent
conductive film 7.
Embodiment 3
[0060] In the liquid crystal display device according to the
embodiment 2 and the various modification examples, the coloring of
the display caused by the transparent conductive film 7 is improved
using the member having the transmission characteristics of
offsetting the transmission characteristics of the transparent
conductive film 7. In the meanwhile, in the liquid crystal display
device according to the embodiment 3, the coloring of the display
caused by the transparent conductive film 7 is improved by forming
a trimmed pattern (or an opening pattern) provided in a row in at
least the display region 5a having an influence on the coloring of
the display in the transparent conductive film 7.
[0061] FIG. 5 is a perspective view schematically illustrating an
example of the configuration of the counter substrate 8 and the
transparent conductive film 7 in the liquid crystal display device
according to the embodiment 3. FIG. 6 is a cross sectional view
taken along an arrow B-B illustrated in FIG. 5. Arrows in FIG. 6
schematically illustrate a reflection of the external light by the
transparent conductive film 7 and the counter substrate 8. Since
the configuration in the liquid crystal display device according to
the present embodiment other than the counter substrate 8 and the
transparent conductive film 7 is similar to that of the liquid
crystal display device 100 according to the embodiment 1, the
detailed description is omitted.
[0062] As illustrated in FIGS. 5 and 6, the transparent conductive
film 7 in the present embodiment has a linear trimmed pattern
provided in a row (that is to say, a region from which the counter
substrate 8 is exposed), and in contrast, a pattern formed by the
remaining transparent conductive film 7 also has a linear pattern
provided in a row. Each pattern of the transparent conductive film
7 having the linear shape may be connected by the transparent
conductive film 7 in an outer side of the display region 5a and
grounded and connected in the manner similar the transparent
conductive film 7 of the embodiment 1. Alternatively, each linear
pattern of the transparent conductive film 7 may also be used as a
wire pattern. For example, when the counter substrate 8 is
configured to have a function as a touch panel, the linear pattern
of the transparent conductive film 7 may also be used for a sensor
wire of the touch panel.
[0063] In the present embodiment, as illustrated in FIG. 6, the
effect similar to the embodiment 1 can be obtained in the area
where the transparent conductive film 7 is included, and the
reflection component of the transparent conductive film 7
disappears in the area where the transparent conductive film 7 is
not included, thus the reflection ratio as the whole liquid crystal
display device can be suppressed. Moreover, since the transparent
conductive film 7 is formed by patterning, an absolute amount of
the transparent conductive film 7 is reduced, thus the coloring the
display can be improved.
[0064] The trimmed pattern provided in a row in the transparent
conductive film 7 in the present embodiment is not limited to the
linear trimmed pattern, but a configuration of providing a
rectangular opening pattern in a row or a configuration of
providing a slit-like opening pattern in a row is also applicable,
and the effect similar to the above description can be obtained as
long as the display region 5a includes the part from which the
counter substrate 8 is exposed.
Embodiment 4
[0065] In the liquid crystal display device according to the
embodiment 3, the coloring of the display caused by the transparent
conductive film 7 is improved by forming the trimmed pattern (or
the opening pattern) provided in a row in at least the display
region 5a having the influence on the coloring of the display in
the transparent conductive film 7. In the meanwhile, in the liquid
crystal display device according to the embodiment 4, the coloring
of the display caused by using the transparent conductive film 7 is
improved by causing the transparent conductive film 7 to have a
comparatively thin film thickness within a range which is not
applied in the embodiment 1.
[0066] Herein, reviewing particularly the graph of the calculation
value of the film thickness dependency of the transparent
conductive film with respect to the reflection ratio in the liquid
crystal display device in FIG. 4 which is referenced in the
embodiment 1, the reflection ratio can be significantly reduced
when the transparent conductive film has the film thickness ranging
from 0 nm to 25 nm and from 120 nm to 160 nm as described
previously, however, it is shown that the reflection ratio can be
reduced to some degree when the transparent conductive film has the
film thickness ranging from 25 nm to 40 nm. In the meanwhile, also
regarding the effect against the ESD, when the transparent
conductive film has the film thickness ranging from 25 nm to 40 nm,
the effect against the ESD can be expected to some degree compared
with the case of having the film thickness ranging from 0 nm to 25
nm. Moreover, the problem regarding the coloring of the display
which is the problem in the embodiment 2 and the subsequent
embodiments does not arise in this comparatively thin film
thickness range. Accordingly, in the liquid crystal display device
according to the embodiment 4, the film thickness of the
transparent conductive film 7 formed on the counter substrate 8 is
set within the range from 25 nm to 40 nm. Moreover, the operation
of reducing the reflection ratio in the present embodiment 4
achieved from the operation of the transparent conductive film 7 is
smaller than that of the embodiment 1, thus the transparent
protective member 1 at least whose surface is subject to the AR
treatment is used. Since the configuration in the liquid crystal
display device according to the embodiment 4 other than the
transparent conductive film 7 and the transparent protective member
1 is similar to that of the liquid crystal display device 100
according to the embodiment 1, the detailed description is
omitted.
[0067] As described above, in the liquid crystal display device
including the transparent protective member 1 attached on the
in-plane switching liquid crystal panel 5 via the transparent
adhesive member 2 according to the embodiment 4, the film thickness
of the transparent conductive film 7 formed on the counter
substrate 8 is set within the range from 25 nm to 40 nm, thus the
function of suppressing the reflection of the external light
entering from the side of the display surface and suppressing the
external electrical field entering from the side of the counter
substrate can be achieved on some level, and the effect enabling
the improvement of the coloring of the display can be obtained at
the same time. The transparent protective member 1 whose surface is
subject to the AR treatment, that is to say, the transparent
protective member 1 including the thin film layer, which has the
antireflection function, on the surface is used together, thus the
function of suppressing the reflection can be complemented.
Accordingly, the transparent protective member 1 having such a
configuration is particularly effective in the present embodiment
4.
[0068] According to the present invention, the above embodiments
can be arbitrarily combined, or each embodiment can be
appropriately varied or omitted within the scope of the
invention.
[0069] While the invention has been shown and described in detail,
the foregoing description is in all aspects illustrative and not
restrictive. It is therefore understood that numerous modifications
and variations can be devised without departing from the scope of
the invention.
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