JP2002148605A - Reflective liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflective liquid crystal display device displaying with excellent contrast while minimizing any yellow-tinged display. SOLUTION: Coloring layers 41, 42 are formed in a region of a CF(color filter) substrate 40 opposite to bus wiring lines 5 mutually lying side by side lengthwise and breadthwise on a TFT(thin film transistor) substrate 20 so as to overlap with each other. As a result, thickness dx of the liquid crystal layer 11 corresponding to the region can surely be made not to be thicker than d0 of the liquid crystal layer thickness corresponding to the vicinity of the center of the pixel, consequently can be made thinner than the upper limit of the gap length to suppress a yellow-tinged display and the display color can surely be prevented from being yellowed with reflected light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device, and more particularly to a structure for reducing yellowing of display.

[0002]

2. Description of the Related Art Japanese Patent Application Laid-Open No. 2000-171794 discloses a method for manufacturing a reflection type liquid crystal display device in which a reflection electrode is arranged on a liquid crystal side, using a single layer of a positive photosensitive resin and performing one exposure. That the base pattern for forming unevenness of the reflective electrode and the contact hole pattern are formed at the same time,
A technique for simplifying a manufacturing process is disclosed.

[0003] FIG. 4 shows the T
FIG. 5 is a plan view of a conventional reflective liquid crystal display device having a TFT substrate of the same type as the FT substrate, as viewed from the liquid crystal side.
FIG. 5 is a cross-sectional view of a TFT substrate, a liquid crystal, and a CF (color filter) substrate cut along a plane orthogonal to the TFT substrate passing through a cutting line AA ′ in FIG. The configuration of the reflection type liquid crystal display device will be described below in the order of manufacturing steps.

First, a first bus wiring 102 serving also as a gate electrode 122 is formed on a first transparent substrate 101, and a first insulating film 103 serving also as a gate insulating film is formed so as to cover the first bus wiring 102. A gate electrode 122 is formed on the first insulating film 103.
A semiconductor region 104 constituting an active layer of the TFT is formed so as to be located above, and a second bus line 1 for connecting and wiring with the semiconductor region 104 is formed on the first insulating film 103.
05 and a drain electrode 125 are formed. The first insulating film 1 covering the second bus wiring 105 and the drain electrode 125
03, a protective insulating film 106 is formed. Subsequently, a surface roughening treatment is performed on the surface of the protective insulating film 106.
An opening 107 is opened in a part of the protective insulating film 106 to connect the drain electrode 125.

[0005] Subsequently, aluminum is deposited on the protective insulating film 106 and patterned to form a reflective electrode 108 for the first.
The TFT substrate 120 is obtained by forming the bus wiring 102, the second bus wiring 105, and the area other than the TFT area.

Next, on the second transparent substrate 131, R, G, and B color layers 141, 142,
143 is formed so as to face the reflective electrode 108 of the TFT substrate 120. Subsequently, the color layers 141, 142, 14
3, a transparent electrode 144 is formed, and finally, a polarizing plate 146 is formed on the opposite surface of the second transparent substrate 131 to obtain the CF substrate 140.

The thus obtained TFT substrate 120
The TFT substrate 120 and the CF substrate 140 are completed by printing an alignment film on the surface of the uppermost layer of each of the CF substrate 140 and the CF substrate 140 by a method such as offset printing.

Finally, the TFT substrate 120 and the CF substrate 14
The alignment film of No. 0 is used as an alignment film 109 by rubbing, alignment molecules of the alignment film are arranged in a predetermined direction, and a cell gap material is sandwiched between the two substrates so as to have a predetermined interval. To obtain a liquid crystal layer 111.

[0009]

In the reflection type liquid crystal display device formed as described above, the R, G and B color layers 14 constituting the three primary colors are formed on the second transparent substrate 131.
1, 142, and 143, as shown in FIGS.
First bus wiring 102 and second bus wiring 1 of FT board 120
05 and the second transparent substrate 131 facing the region defined by
Is formed in the area of the second transparent substrate 131 facing the first bus wiring 102 and the second bus wiring 105 of the TFT substrate 120.

Further, as shown in FIG.
Reflective electrode 1 located between the first bus line 25 and the second bus line 105
08 (a liquid crystal layer corresponding to the surface showing the average value of the unevenness when the unevenness of the surface due to the reflective electrode 108 is taken into account). The gap length d)
(Μm), and the refractive index anisotropy of the liquid crystal material forming the liquid crystal layer 111 is represented by Δn. At this time, it is well known that the behavior of the incident light depends on the retardation Δnd represented by the product of the gap length d (μm) and the refractive index anisotropy Δn of the liquid crystal material. In the case of the reflection type liquid crystal display device as shown in FIG. 5, the light incident from the second transparent substrate 131 side is the thickness d of the liquid crystal layer 111 at the incident portion.
(Μm), the color characteristics as shown in FIG. 3 are exhibited.

As can be seen from the characteristics shown in FIG.
The yellow colored limit to the reflected light in question is a * -b
* When the color system is set to +15 or less from the origin, the liquid crystal
The value of the retardation Δnd in the layer 111 is 250
nm or less (preferably in the range of 180 nm to 250 nm).
Box). At this time, the liquid crystal layer 111
The value of the refractive index anisotropy Δn of the liquid crystal molecules constituting
Then, the gap length d near the pixel center_O(Μ
m) is 3.1 μm or less (preferably from 2.3 μm
(Between 3.1 μm). Only
Then, the second bus wiring 105 on the TFT substrate 120 side (or
The first bus wiring 102) and the second transparent substrate on the CF substrate 140 side
Liquid crystal layer 11 sandwiched in a region facing plate 131
1 thickness d_YIs any of the color layers 141, 142, and 143
Compared to the thickness d of the color layer
As a result, the gap is increased by the thickness of the color layer. Color layer thickness
Since only 1 μm to 2 μm is usually used,
Gap length d in this part _YIs on the reflector
Gap length d_OAt least about 1 μm thicker than
Increase the retardation in this part by 80nm
The Rukoto. For this reason, the filter on the second bus wiring
In some cases, a portion exceeding 250 nm occurs, and the CF group
Incident from the plate 140 side and reflected by the reflector 107
Emit light with a large degree of yellowing to the light
This causes yellowing of the display.

As described above, in the reflection type liquid crystal display device, the color of the reflected light is greatly affected by the gap of the liquid crystal element (the thickness of the liquid crystal layer).
The reflected color rapidly turns yellow, and when the gap becomes thinner, the color turns blue. However, since the yellowing of the display is generally disliked, the control of the gap is important.

An object of the present invention is to provide a reflection type liquid crystal display device capable of performing display with good contrast while minimizing display with yellow.

[0014]

A reflection type liquid crystal display device according to the present invention comprises a plurality of first bus lines formed in parallel on a first substrate and insulated from the first bus lines. And
A second bus line formed in parallel with each other while intersecting with the first bus line; and a second bus line formed on the first substrate so as to cover the first bus line and the second bus line. TF
A TFT substrate having a T-side insulating film, a reflective electrode formed on the TFT-side insulating film, and an alignment film formed on the TFT-side insulating film so as to cover the reflective electrode; A plurality of color layers having different colors formed on each other, a transparent electrode covering the color layer, and an alignment film covering the transparent electrode,
A reflective liquid crystal display device comprising: a color filter substrate having a polarizing plate formed on a second substrate opposite to the color layer; and a liquid crystal layer sandwiched between the TFT substrate and the color filter substrate. Wherein the retardation Δnd _O of the liquid crystal layer corresponding to the center of the pixel area defined by the first bus wiring and the second bus wiring is a predetermined range Δnd for suppressing the yellow coloring of the reflected light. _{M IN to} Δn
When set to d _MAX, the formed stacked in the second region on the substrate on which a plurality of color layers of different colors are opposite to the second bus lines to each other, and, above at least said second bus lines Retardation Δn of liquid crystal layer located
The basic configuration is that d _X is set to be equal to or smaller than Δnd _MAX . The reflection type liquid crystal display device having the basic configuration of the present invention has the following application forms.

First, the retardation Δn of the liquid crystal layer
d _O and Δnd _X are retardations of a liquid crystal layer sandwiched between the substantially flat surface of the TFT substrate and the substantially flat surface of the color filter substrate when the surface of the reflective electrode is substantially flat. When the surface of the electrode has irregularities, a retardation of a liquid crystal layer sandwiched between a surface of the TFT substrate corresponding to a portion exhibiting an average value of the amplitude of the irregularities and a substantially flat surface of the color filter substrate; The retardation Δnd _{O of the} layer is 180
It is set to ２５０250 nm.

Further, a second bus line opposed to the second bus line is provided.
The width in which the plurality of color layers having different colors are formed in a region on the substrate is 0.5 to 1.0 times the width of the second bus wiring.

Further, a second bus line opposed to the first bus line is provided.
Also in the region on the substrate, the plurality of color layers having different colors are formed so as to overlap with each other, and the retardation Δnd _Z of the liquid crystal layer located above the first bus wiring is Δn
It is set to d _MAX or less.

Also, a second bus line opposed to the first bus line is provided.
The width in which the plurality of color layers having different colors are formed in an overlapped manner in the region on the substrate is 0.5 to 1.0 times the width of the first bus wiring.

Further, the reflective electrode is formed by opening a region corresponding to the upper part of the first bus wiring and the second bus wiring.

Finally, the twist angle of the liquid crystal in the liquid crystal layer is 65-80 °, preferably 70.5-74.
5 °.

[0021]

Next, a reflection type liquid crystal display device according to an embodiment of the present invention will be described with reference to FIG. Here, FIG. 1A is a plan view of the TFT substrate as viewed from the liquid crystal side, and FIG. 1B is a cut line A in FIG. 1A.
A TFT substrate on a plane passing through -A ′ and orthogonal to the TFT substrate,
FIG. 3 is a cross-sectional view when a liquid crystal and a CF (color filter) substrate are cut. The present invention is characterized by the formation of the color layer on the CF substrate side and the liquid crystal layer sandwiched between the TFT substrate and the CF substrate.

The feature of this embodiment is that the retardation Δ of the liquid crystal layer corresponding to the center of the pixel electrode shown in FIG.
Δn that minimizes nd _O to minimize yellow coloring of reflected light
When set to d _{MIN to} Δnd _MAX , a region on the second substrate facing the second bus line (a region facing a region in which a plurality of color layers of different colors of the color layer on the CF substrate side are formed in an overlapping manner) ), The retardation Δnd _X of the liquid crystal layer is
It is set to be less than Δnd _MAX .

Next, the structure of this embodiment will be described with reference to FIG.

First, a first bus wiring 2 serving also as a gate electrode 22 is formed on the first transparent substrate 1, and a first insulating film 3 serving also as a gate insulating film is formed so as to cover the first bus wiring 2. First
On the insulating film 3, a semiconductor region 4 constituting an active layer of the TFT is formed so as to be located above the gate electrode 22, and on the first insulating film 3, a semiconductor region 4 for connecting and wiring with the semiconductor region 4 is formed. The two bus lines 5 and the drain electrode 25 are formed. First covering the second bus line 5 and the drain electrode 25
A protective insulating film 6 is formed on the insulating film 3, and an opening 7 is opened in a part of the protective insulating film 6 to connect the drain electrode 25. Subsequently, aluminum is deposited on the protective insulating film 6 and patterned, and the reflective electrode 8 is formed in a region excluding the first bus line 2, the second bus line 5, and the TFT region, thereby obtaining the TFT substrate 20.

Next, on the second transparent substrate 31, R, G, and B color layers 41, 42, and 43 constituting the three primary colors each face the pixel electrode 25 of the TFT substrate 20 to a thickness of about 1 μm. However, the color layers 41, 42, and 43 are formed so as to overlap in the boundary region between the adjacent pixel electrodes 25. Subsequently, the transparent electrodes 4 covering the color layers 41, 42 and 43 are covered.
4 is formed, and finally, a polarizing plate 46 is formed on the surface on the opposite side of the first transparent substrate 31 to obtain the CF substrate 40.

An alignment film is printed on the uppermost surface of each of the thus obtained TFT substrate 20 and CF substrate 40 by a method such as offset printing, so that the TFT substrate 20 and the CF substrate 40 are formed. Complete.

The alignment film of the TFT substrate 20 and the CF substrate 40 thus obtained is used as an alignment film 9 by rubbing, and alignment film molecules are arranged in a predetermined direction, and the cell gap is set so that the two substrates have a predetermined interval. The material is sandwiched and combined, and in the gap, for example, the twist angle is 65 to 80 °,
Desirably, the liquid crystal 10 of 70.5 to 74.5 ° is sealed to obtain the liquid crystal layer 11.

FIG. 2 shows a sectional structure of the thus-formed reflective liquid crystal display device of the present embodiment, taken along line AA ′ in FIG.

As shown in FIG. 2, the liquid crystal layer 11 is sandwiched in a region where the second bus line 5 on the TFT substrate 20 and the region where the color layers 41 and 42 on the CF substrate overlap each other face each other.
Is the retardation of Δnd _X and the drain electrode 2
When the retardation of the liquid crystal layer 11 sandwiched between the color layer 42 and the substantially central portion of the reflective electrode 8 located between the first bus line 5 and the second bus line 5 is Δnd _O , the light enters from the CF substrate 40 side. Then, the light is reflected by the reflective electrode 8 and is again
The light emitted from the side shows a colored characteristic as shown in FIG. 3 according to the change of the retardation Δnd.

The characteristic shown in FIG. 3 is that the change in the reflective display color with respect to the change in the retardation Δnd in the liquid crystal layer 11 is represented by a
It is the result plotted in the * -b * color specification plane. From FIG. 3, the limit distance with a yellow mark, which is particularly problematic in the display, is b.
When it is 15 or less in the * direction, the value of the retardation Δnd allowed for the liquid crystal layer 11 is 250 nm or less, preferably 180 nm to 250 nm. At this time,
The refractive index anisotropy Δn of the liquid crystal material constituting the liquid crystal layer 11
Is 0.08, the value of the gap length d allowed in the liquid crystal layer 11 is 3.1 μm or less (preferably 2.3 μm).
m to 3.1 μm), the range of d = d _MAX can be set.

Therefore, in the example of this embodiment, the gap length d _O (μm) of the liquid crystal layer 11 near the center of the pixel is set to 2.
And sets between 3.1μm from 3 [mu] m, the gap length d _X of the liquid crystal layer 11 and the region overlapping the second bus line 5 and the CF substrate side color layer 41 and color layer 42 is sandwiched in the region facing 3 It has to be set to 1 μm or less.

Here, the definition of the gap length is shown in FIG.
As shown, the reflection electrode 8 itself is formed in an uneven shape,
When the surface of the alignment film 9 is formed to be uneven, the surface of the alignment film 9 located at the height of the average value of the height of the unevenness is sandwiched between the surface of the alignment film 9 of the CF substrate facing the position. The thickness of the liquid crystal layer.

Therefore, when the reflective electrode is formed flat unlike the present embodiment, the thickness of the liquid crystal layer sandwiched between the alignment film surface of the TFT substrate and the alignment film surface of the CF substrate is simply reduced. , The gap length.

The meaning that the gap length d _X is set to 3.1 μm or less may be zero, that is, as long as the reflective electrode 8 and the transparent electrode 44 are not short-circuited.
This means that the alignment film 9 of the TFT substrate 20 and the alignment film 9 of the CF substrate 40 may be in contact with each other, or may be formed so as to have a slight gap. However, when the value of the gap length d allowed for the liquid crystal layer 11 is set in the range of 2.3 μm to 3.1 μm, the gap length d _X
Is also preferably set to 2.3 μm to 3.1 μm.

In order to reliably satisfy this condition, an overlapping area of the color layers 41 and 42 is formed in the area on the CF substrate side facing the second bus wiring 5.

With the above-mentioned structure of the reflection type liquid crystal display device, it is possible to prevent the display color from yellowing due to the reflected light of the light incident from the CF substrate toward the liquid crystal layer.

[0037] In this embodiment, an example of overlapping different color layer in two layers, as described above, to the d _X below d _MAX is the extent permitted as a reflective liquid crystal display device In the range, a structure in which two or more same color layers are overlapped, a structure in which two or more different color layers are selected and three or more layers are stacked, or a structure in which another substance other than the color layer is stacked on the color layer Obviously, the object of the present invention can be achieved. Also, the thickness of the color layer was about 1 μm,
Changing the d _X by changing the color layer thickness of itself, it is also possible to adjust the d _X by changing the thickness of the color layer in color.

Further, by stacking the color layers in the vertical direction, d _x is set to d _x
In addition to the structure below _MAX , the TFT substrate 20 and C
Although misalignment between the F substrate occurs, so that the thickness d _X of the liquid crystal layer 11 is also affected by this falls below d _{M AX,} a width color layer is formed to overlap the first bus 0 of the width of the wiring 5.
What is necessary is just to design so that it may become 5 to 1.0 times. For example, assuming that the width of the first bus wiring 5 is 6.0 μm, the color layers may be designed so that the overlapping width is 3.0 to 6.0 μm.

In the above description, the region in which the color layer is formed on the second transparent substrate 31 is described as the region facing the second bus line 5, but the region facing the first bus line 2 is described. In the area of the second transparent substrate 31 to be
It is formed by in the same manner as the region facing overlapping color layers on the second transparent substrate 31, of course also be possible as a thickness d _Z also below d _MAX structure of the liquid crystal layer corresponding to the region It is.

Furthermore, the area where the color layer is formed on the second transparent substrate 31 is not the area facing the second bus wiring 5 but the second transparent substrate 3 facing the first bus wiring 2.
A structure formed only in one region is also considered as a modification of the present embodiment.

[0041]

In the reflection type liquid crystal display device according to the present invention, a color layer is formed in a region of the CF substrate facing the bus wirings running in parallel on the TFT substrate vertically and horizontally. The thickness of the liquid crystal layer (panel gap)
The thickness of the liquid crystal layer corresponding to the vicinity of the center of the pixel can be reliably set to be equal to or less than the thickness of the liquid crystal layer. This can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view of a TFT substrate of a reflection type liquid crystal display device for describing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a graph for explaining a yellowing phenomenon of a reflective liquid crystal display device.

FIG. 4 is a plan view of a TFT substrate of a conventional reflective liquid crystal display device.

FIG. 5 is a sectional view of a conventional reflective liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 1st transparent substrate 2, 102 1st bus wiring 3, 103 1st insulating film 4, 104 Semiconductor area 5, 105 2nd bus wiring 6, 106 Protective insulating film 7, 107 Opening 8, 108 Reflection electrode 9 , 109 orientation film 10, 110 liquid crystal 11, 111 liquid crystal layer 20, 120 TFT substrate 22, 122 gate electrode 25, 125 drain electrode 31, 131 second transparent substrate 40, 140 CF substrate 41, 42, 43, 141, 142, 143 color layer 44, 144 transparent electrode

Claims (9)

[Claims] A plurality of first bus lines formed in parallel with each other on a first substrate, insulated from the first bus lines, and arranged in parallel with each other while intersecting with the first bus lines. A second bus line formed by running, a TFT-side insulating film formed on the first substrate to cover the first bus line and the second bus line, and a TFT-side insulating film formed on the first substrate. A TFT substrate having a reflective electrode formed thereon and an alignment film formed on the TFT-side insulating film to cover the reflective electrode; and a plurality of different colors formed on the second substrate. A color filter substrate having a layer, a transparent electrode covering the color layer, an alignment film covering the transparent electrode, and a polarizing plate formed on a second substrate opposite to the color layer;
A reflective liquid crystal display device comprising a substrate and a liquid crystal layer sandwiched between the color filter substrates, the reflective liquid crystal display device corresponding to a central portion of a pixel area defined by the first bus wiring and the second bus wiring. Retardation of liquid crystal layer Δnd _O
A predetermined range Δnd for suppressing the yellow coloring of the reflected light
When setting _{MIN to} Δnd _MAX , the plurality of color layers different in color from each other are formed so as to overlap in a region on the second substrate facing the second bus wiring, and at least the second bus wiring A reflection type liquid crystal display device, wherein a retardation Δnd _X of a liquid crystal layer located above is set to Δnd _MAX or less. 2. The retardation Δnd _{O of the} liquid crystal layer.
And Δnd _X are retardations of a liquid crystal layer sandwiched between the substantially flat surface of the TFT substrate and the substantially flat surface of the color filter substrate when the surface of the reflective electrode is substantially flat, The retardation of a liquid crystal layer sandwiched between a surface corresponding to a portion of the TFT substrate exhibiting an average value of the amplitude of the irregularities and a substantially flat surface of the color filter substrate when the surface has irregularities. Reflective liquid crystal display. 3. The retardation Δnd _{O of the} liquid crystal layer.
The reflective liquid crystal display device according to claim 2, wherein is set to 180 to 250 nm. 4. A width in which the plurality of color layers having different colors are formed in a region on the second substrate facing the second bus wiring is set to be equal to 0. 2 of the width of the second bus wiring. 5
4. The reflective liquid crystal display device according to claim 1, wherein the ratio is 1.0 to 1.0. 5. A plurality of color layers different in color from each other are also formed in a region on the second substrate opposite to the first bus line, and are located above the first bus line. The retardation Δnd _{Z of the} liquid crystal layer is Δnd _MAX
5. The reflective liquid crystal display device according to claim 1, wherein the reflective liquid crystal display device is set as follows. 6. The width in which the plurality of color layers having different colors are overlapped with each other in a region on the second substrate opposed to the first bus wiring is equal to 0. 1 of the width of the first bus wiring. 5
The reflective liquid crystal display device according to claim 1, wherein the ratio is 1.0 to 1.0 times. 7. The reflection type liquid crystal according to claim 1, wherein the reflection electrode is formed by opening a region corresponding to an area above the first bus wiring and the second bus wiring. Display device. 8. The liquid crystal layer has a twist angle of 65 to 65.
The reflective liquid crystal display device according to claim 1, wherein the angle is 80 °. 9. The liquid crystal layer has a twist angle of 70.
The reflective liquid crystal display device according to claim 1, wherein the angle is 5 to 74.5 °.