JP2001091934A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the lowering of the opening ratio of a pixel even when position-shifting is occurred in arrangement of one transparent substrate to the other transparent substrate. SOLUTION: This liquid crystal display device is provided with a thin film transistor driven by the supply of a scanning signal from a gate signal line and a pixel electrode receiving a video signal from a drain signal line through the thin film transistor in each pixel region of a face of a liquid crystal side of one transparent substrate of transparent substrates disposed being opposed to each other through the liquid crystal. The pixel electrode is formed by utilizing a color filter formed in the pixel region as a lower layer and has a light shielding layer formed by putting the thin film transistor on it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, for example, a liquid crystal display called an active matrix type.

[0002]

2. Description of the Related Art In a liquid crystal display device called an active matrix type, a scanning signal from a gate signal line is applied to a pixel region on a liquid crystal side of one of a pair of transparent substrates disposed through a liquid crystal. And a pixel electrode to which a video signal is supplied from a drain signal line via the thin film transistor.

On the liquid crystal side surface of the other transparent substrate, a black matrix layer is formed to define each pixel region so as to border each pixel region. The color filter is formed so as to cover (substantial pixel area).

[0004]

In recent years, liquid crystal display devices having such a structure have tended to increase the pixel density in order to perform high-definition pixel display. Devices such as miniaturization of thin film transistors and the like have been devised.

However, even if this is done, if the position of the other transparent substrate is misaligned with respect to the one transparent substrate, the gate signal line or the drain signal line protrudes into the opening region of the black matrix layer. However, there is a disadvantage that the aperture ratio is reduced by an amount corresponding to the protruding signal lines.

Accordingly, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a pixel having an aperture ratio of one pixel even if the position of the other transparent substrate is misaligned with respect to the other transparent substrate. It is an object of the present invention to provide a liquid crystal display device which does not cause a reduction in the display.

[0007]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

That is, the liquid crystal display device according to the present invention comprises:
A thin film transistor driven by the supply of a scanning signal from a gate signal line to each pixel region on a liquid crystal side surface of one of the transparent substrates opposed to each other via a liquid crystal, and a drain signal line via the thin film transistor A pixel electrode to which a video signal is supplied from the pixel electrode, the pixel electrode is formed with a color filter formed in a pixel region as a lower layer, and a light shielding layer is formed so as to cover at least the thin film transistor. It is characterized by the following.

In the liquid crystal display device having the above-described structure, a light-shielding film (black matrix) and a color filter are formed on the transparent substrate on which the thin film transistors and the pixel electrodes are formed.

[0010] Therefore, even if a displacement occurs when the other transparent substrate is disposed with respect to the one transparent substrate, the aperture ratio of each pixel region is kept unchanged.

Also, the gap between the transparent substrates, in other words, the thickness of the liquid crystal layer can be made uniform only by uniformly flattening the surfaces of the light shielding film and the color filter formed on one of the transparent substrates. This has the effect of improving display quality.

Further, since the surfaces of the light-shielding film and the color filter formed on one of the transparent substrates are uniformly flattened, no unevenness is generated on the alignment film formed on the upper surface thereof. This has the effect that it can be performed.

Further, since the pixel electrode is formed with the color filter interposed, the coupling capacitance generated between the pixel electrode and the signal line can be reduced, and the signal delay and the like can be reduced. It works.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the liquid crystal display device according to the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view showing one pixel region on the liquid crystal side of one of the transparent substrates disposed opposite to each other via the liquid crystal.

The pixel regions are arranged in a matrix on a transparent substrate. Therefore, the pixel regions on the left and right sides and the upper and lower sides of the pixel region shown in FIG.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1 together with the other transparent substrate.

First, in FIG. 1, there is a glass substrate 201, and a base insulating film 20 is formed on the surface of the glass substrate 201.
2 are formed. The base insulating film 202 has a function of preventing impurity ions in the glass substrate 201 from entering a thin film transistor TFT described later.

A semiconductor layer 100 made of a polycrystalline silicon film is formed for each pixel region of the base insulating film 202.

Here, each pixel region refers to a rectangular region surrounded by a gate signal line 205 and a drain signal line 203, which will be described later.
5 so as to intersect.

On the surface of the glass substrate 201, an insulating film 204 is formed so as to cover the semiconductor layer 100.

On the surface of the insulating film 204, the gate signal line 2 extends in the x-direction and is juxtaposed in the y-direction in FIG.
05 is formed.

Here, the gate signal line 205 is formed so as to cross the semiconductor layer 100 as described above.

Thus, by forming a source electrode and a drain electrode on the surface of the semiconductor layer 100 with the gate signal line 205 therebetween, a part of the gate signal line 205 is formed as a gate electrode and the insulating film is formed. Thus, a thin film transistor TFT having an MIS structure as a gate insulating film is formed.

Except for the semiconductor region immediately below the gate signal line 20, the semiconductor regions connected to the source electrode and the drain electrode are regions doped with, for example, phosphorus (P).

The source electrode 21 of the thin film transistor TFT
0 and the drain electrode 211 are formed on the first protective film 209 through through holes formed in the first protective film 209 formed on the entire surface of the glass substrate 201 and the insulating film 204 thereunder. It is formed simultaneously with the formation of 203.

That is, the drain signal lines 203 extending in the y direction in FIG.
9, a part of the drain signal line 203 is extended to form a drain electrode 211,
The source electrode 21 is separated from the drain signal line 203.
0 is formed.

Then, a second protective film 212 is formed over the entire surface of the glass substrate 201.
Are formed with through holes exposing a part of the source electrode 210. This through hole is formed in the source electrode 2
A hole for connecting the pixel electrode 10 to a pixel electrode described later.

The surface of the second protective film 212 covers most of the pixel area, that is, the gate signal line 205,
Drain signal line 203 and thin film transistor TFT
The color filter 214 is formed in a portion excluding the formation region of.

A pixel electrode 216 made of, for example, an ITO (Indium-Tin-Oxide) film is formed on the upper surface of the color filter 214, and a part of the pixel electrode 216 is formed to extend on the side wall of the color filter 214. The extending portion is connected to the source electrode 210 of the thin film transistor TFT through the through hole formed in the second protective film 212.

From the above, the color filter 214
By forming the trapezoidal shape such that the side wall has a smooth slope, it is possible to avoid disconnection of the pixel electrode 216 due to the step of the color filter 214.

Since the pixel electrode 216 is formed with the color filter 214 interposed therebetween,
The coupling capacitance generated between the pixel electrode 216 and the gate signal line 205 or the drain signal line 203 can be reduced,
This has the effect of reducing signal delay and the like.

A light shielding film (BM) 217 containing a black pigment such as carbon black is formed in a recess formed between the color filters in each pixel region. Is formed so as to be embedded in the recess, and the color filter 2
14 and the surface are flush.

In this embodiment, the light-shielding film (BM) 217 is formed so as to cover the respective regions of the gate signal line 205, the drain signal line 203, and the thin film transistor TFT, thereby forming the pixel electrode 216 in each pixel region. It is formed so as to border.

Further, on the surfaces of the light-shielding film (BM) 217 and the pixel electrode 216, an alignment film 10 common to each pixel region is provided.
1 is formed.

The orientation film 101 is a film for determining the initial orientation direction of the molecules of the liquid crystal 102 which is in direct contact with the orientation film.

As described above, the light shielding film (BM) 2
By forming the surfaces of the color filter 17 and the color filter 214 flush with each other without unevenness, the rubbing treatment of the alignment film 101 can be made uniform, thereby providing an effect of improving display quality.

On the surface of the other glass substrate 105 facing the liquid crystal 102 on the liquid crystal side, for example, ITO
(Indium-Tin-Oxide) film, a common electrode 104 common to each pixel region is formed.
On the surface of No. 4, an alignment film 103 is formed.

From this, since the color filter 214 and the light-shielding film (BM) 217 are not formed on the glass substrate 105 and the surface thereof is a flat surface without unevenness, The rubbing process can be made uniform, which has the effect of improving display quality.

On the glass substrate 105 side, a member (color filter 214 light shielding film (BM)) defining a pixel region
217), even if the glass substrate 105 is misaligned with respect to the glass substrate 201, this does not cause a reduction in the aperture ratio.

Hereinafter, an embodiment of a method of manufacturing the liquid crystal display device having the above-described structure will be described with reference to FIGS.

Step 1 (FIG. 3A) A so-called alkali-free glass substrate 201 is prepared, and a base insulating film 202 made of a SiO ₂ film is formed over the entire surface of the glass substrate 201 by, for example, a plasma CVD method.

Then, after forming an a-Si film over the entire surface of the base insulating film 202 by, for example, a plasma CVD method, the polycrystalline silicon film 203 is formed by irradiating an excimer laser.

Step 2 (FIG. 3B) The polycrystalline silicon film 203 is formed in a desired pattern by a selective etching method using a photolithography technique.

This polycrystalline silicon film is formed as the semiconductor layer 100 of the thin film transistor TFT.

Then, the entire surface of the glass substrate 201 is covered with the semiconductor layer 100 by, for example, plasma C.
An insulating film 204 made of SiO ₂ is formed by the VD method.

The insulating film 204 functions as a gate insulating film of the thin film transistor, and may be SiN or the like.

Step 3 (FIG. 3C) A metal film such as chromium or aluminum is formed on the entire surface of the glass substrate 201 by, for example, a sputtering method, and is patterned by a selective etching method by a photolithography technique. A signal line 205 and a gate electrode of a thin film transistor which is formed as a part of the gate signal line 205 are formed.

Then, ions such as phosphorus or boron are implanted over the entire surface of the glass substrate 201.

The ions are implanted into the surface of the polycrystalline silicon film 203 by using the gate electrode as a mask. The source region 206 and the drain region 207 of the thin film transistor TFT are formed on the surface, and a channel region is formed between these regions. 208 are formed.

Step 4 (FIG. 3D) An insulating film 209 made of, for example, an SiO ₂ film is formed over the entire surface of the glass substrate 201, and the insulating film 209 is formed on the source region 206 of the polycrystalline silicon film 203. A through hole exposing a part and a part of the drain region 207 is formed.

Then, a metal film such as chromium is formed on the entire surface of the glass substrate 201 and is patterned to form a source electrode 210 and a drain electrode 211 formed as a part of a drain signal line. .

Step 5 (FIG. 3E) An insulating film 212 made of, for example, SiO ₂ is formed on the entire surface of the glass substrate 201, and a through hole exposing a part of the source electrode 210 is formed in the insulating film 21. Form.

Step 6 (FIG. 3F) Next, for example, a red color filter is formed. First, a colored polyimide precursor in which a red pigment is dispersed is applied to the entire surface of the glass substrate 201, and dried by pre-baking to form a red colored resin layer.

Then, the red color resin layer is patterned by a selective etching method using a photolithography technique to form a red color filter 214.

Thereafter, a colored polyimide precursor in which a blue pigment is dispersed is applied to the entire surface of the glass substrate 201, and a blue color filter 215 is formed using the same method as described above.

Although not shown, a green color filter is formed by the same method.

In this case, for each color filter, the pigment dispersion amount, the coating amount of the colored polyimide precursor and the like are adjusted in order to make their layer thickness uniform. The coupling capacitance between the pixel electrode 216 and a signal line (a gate signal line or a drain signal line) is determined so as to be reduced to a level that does not cause any inconvenience in circuit operation.

Since the coupling capacitance also affects the dielectric constant of the color filter, the thickness of the color filter can be reduced by selecting a material having a small dielectric constant.

Step 7 (FIG. 3G) An ITO (Indium-Tin-Oxide) film is formed on the entire surface of the glass substrate 201 by, for example, a sputtering method.
By patterning this, the transparent pixel electrode 21 is formed.
6 is formed.

The transparent electrode 216 has a pattern in which a part thereof extends along the side wall of the color filter and is connected to the source electrode 210 of the thin film transistor through a through hole formed in the insulating film 212.

Step 8 (FIG. 3H) A polyimide precursor solution containing a black pigment such as carbon black is applied to the entire surface of the glass substrate 201, and the surface is etched until the transparent pixel electrode 216 is exposed. .

Thus, the light shielding layer 217 is formed in a state where the light shielding layer 217 is buried in the recess between the color filters.

In the above embodiment, the gate signal line 20
5, the drain signal line 203, and the thin film transistor T
The light shielding film 217 is formed so as to cover the FT. However, it goes without saying that the light shielding film 217 may be configured to cover the thin film transistor TFT and, for example, the drain signal line 203. This is because the gate signal line 205 itself has a sufficient light shielding function.

In this case, the boundary between color filters of different colors in adjacent pixel regions is positioned on the drain signal line 203, and they are formed so that the surface thereof is flush with the light shielding film 217. The rubbing of the alignment film 101 can be made uniform.

In the above-described embodiment, the thin film transistor TFT has a so-called staggered structure in which the gate electrode is positioned above the semiconductor layer. However, the present invention is not limited to this. Needless to say, the present invention can be applied to a so-called inverted staggered structure which is positioned lower than the lower layer.

Further, in the above-described embodiment, a so-called vertical electric field type (transparent substrate) in which a pixel electrode composed of a transparent electrode is formed on one transparent substrate side and a common electrode composed of a transparent electrode is formed on the other transparent substrate side. (A method of controlling the light transmittance of the liquid crystal by generating an electric field in the vertical direction).

However, a so-called horizontal electric field type having a pixel electrode on one transparent substrate and a counter electrode for controlling the light transmittance of the liquid crystal by generating an electric field in the horizontal direction on the transparent substrate between the pixel electrodes. Needless to say, this can also be applied.

The reason is that the situation is the same even in the case of the horizontal electric field type.

[0070]

As will be apparent from the above description, according to the liquid crystal display device of the present invention, even if the position of one transparent substrate is misaligned with respect to the other transparent substrate, the aperture ratio of the pixel is reduced. Can be obtained without causing a decrease in

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a pixel configuration of a liquid crystal display device according to the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a process chart showing one embodiment of a method for manufacturing a liquid crystal display device according to the present invention.

[Explanation of symbols]

104: common electrode, 102: liquid crystal, 203: drain signal line, 205: gate signal line, 214, 215: color filter, 216: pixel electrode, 217: light shielding film (B
M).

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) G09F 9/30 312 G09F 9/30 338 338 G02F 1/136 500 H01L 29/786 H01L 29/78 612Z 21/336 619B F Terms (Reference) 2H091 FA02Y FA34Y FB02 FB12 FD04 FD05 FD06 GA07 GA13 GA16 2H092 JA25 JA40 JA44 JA46 JB05 JB52 JB58 KA04 KA18 KB04 MA17 NA07 PA08 PA09 5C094 AA10 AA13 AA25 AA42 EA03 EA03 EA03 CB04 FB12 FB15 GB10 5F110 AA04 AA30 BB01 CC02 DD02 DD13 EE02 EE03 EE44 FF02 FF03 FF30 GG02 GG13 GG45 HJ01 HJ13 HL02 NN02 NN23 NN45 NN52 NN80 PP03 QQ11 5G435 AA03 BB12 CC09 CC12 FF13

Claims (6)

[Claims] 1. A thin film transistor driven by supply of a scanning signal from a gate signal line to each pixel region on a liquid crystal side surface of one of the transparent substrates opposed to each other via a liquid crystal, and And a pixel electrode to which a video signal is supplied from a drain signal line via a color filter formed in a pixel region. The pixel electrode is formed as a lower layer, and at least the light-shielding layer covers the thin film transistor. A liquid crystal display device characterized by being formed. 2. The liquid crystal display device according to claim 1, wherein a part of the pixel electrode extends along a side wall of a color filter under the pixel electrode and is connected to a source electrode of the thin film transistor. 3. The liquid crystal display device according to claim 2, wherein the color filter has a flared shape with a sloped side wall. 4. The liquid crystal display device according to claim 1, wherein the surfaces of the color filter and the light shielding layer are flush with each other. 5. A pixel region defined by a region surrounded by an adjacent gate signal line and an adjacent drain signal line, wherein the light-shielding film is formed so as to cover the gate signal line and the drain signal line. The liquid crystal display device according to claim 1. 6. The liquid crystal display device according to claim 2, wherein a part of a pixel electrode connected to a source electrode of the thin film transistor along a side wall of the color filter is covered with a light shielding film.