JPH01289915A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To enable easily visible display by using hard inorg. spacers consisting of glass fibers or alumina in the sealing material at the periphery between substrates, using intra-surface spacers consisting of plastic between the substrates and holding these spacers by varying the intra-surface distribution densities of the spacers. CONSTITUTION:The sizes of the spacer 10 in the sealing material 9 and the intra-surface spacers 11 are optimized according to the thicknesses of TFTs, light shielding films and color filters. The hard spacer consisting of the glass fiber, etc., which have high sealing reliability and allow strict control of the sealing thickness spacing is used for the spacer 10 in the seal and plastic beads having a low modulus of elasticity is used for the intra-surface spacers 11. These spacers are effectual in preventing the fault of the TFTs or the degradation in the characteristics thereof as well as to prevent exposing of the oriented films on picture element electrodes. The uniformization of the intra-surface cell spacing and the spraying of the spacers at the min. required amt. are enabled by changing the spraying density of the spacers 11 between the intra-surface central part and peripheral part. The problem of a degradation in display quality such as haze is obviated.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an active matrix liquid crystal display device (TPT-LCD) in which a display electrode array is constructed using thin film transistors (hereinafter referred to as TPT) as switching elements.
In particular, the present invention is designed to prevent TPT failure and control the gap between substrates to improve display quality.

[Conventional technology]

Conventionally, the method of controlling the gap between the substrates of a liquid crystal display device is to control the gap by using a sealing material used for bonding the substrates mixed with a gap control material such as M2O3 powder, glass beads, or glass fiber. Additionally, a method has been adopted in which a gap control material such as glass fiber is dispersed within the display surface.

FIG. 5 shows a cross-sectional view of a conventional liquid crystal display device disclosed in, for example, Japanese Patent Application Laid-Open No. 55-57821.
0 is an upper electrode and a lower electrode provided on each of the substrates 17 and 19 and faces each other, 9 is a sealing material provided around the side substrates 17 and 19, 10 is a spacer in the sealing material 9, and 11 is a spacer between the substrates. In-plane spacers, 13 are polarizing plates provided on the outer surfaces of side substrates 17 and 19, and 21 is a liquid crystal.

FIG. 6 is a plan view of one pixel of a TFT array substrate of an active matrix liquid crystal display device consisting of a TFT array substrate having a TFT array and a counter electrode substrate having a counter electrode, and FIG. 7 is a seal portion with the counter substrate. 6 is a sectional view taken along the line ■-■ in FIG. 6.

6″ and 7, 1 is a TFT array substrate, 2
1 is a TFT on the array substrate 1, 3 is a display electrode formed on the surface of the array substrate 1, 4 is a counter electrode substrate placed opposite the array substrate 1, 5 is a light shielding film, 6 is a color filter, and 7 is formed on this substrate 4. 8 is an alignment film, 9 is a peripheral sealing material between the TFT array substrate 1 and the counter electrode substrate 4, 10 is a spacer in the sealing material 9, 11 is an in-plane spacer between both substrates, and 21 is a liquid crystal. . On the other hand, 22 is a gate electrode line, 2
3 is a source electrode line, 24 is a drain electrode line, 25 is a gate electrode 1, 26, 27 is amorphous silicon, and 28 is a gate insulating film.

Next, a method of controlling the gap of a normal monochrome LCD as shown in FIG. 5 will be explained.

For example, a glass fiber with a diameter of 10 μm has a diameter of approximately 50 μm.
Cut it into lengths and create a mixture using isopropylarzole or Freon as a medium. Then, a glass fiber mixture is sprayed and dispersed in the form of a mist on the − side of the substrate to form in-plane spacers 11 . And the same <
By press-bonding a mixture of 1011 m of in-seal spacers 10 to a printed substrate, the in-plane gap can be controlled to a glass fiber diameter of 10 μm.

On the other hand, the TFT array 2 having the structure as shown in FIGS. 6 and 7
The gap between the display electrodes (thickness of the liquid crystal layer) in the case of a TFT-L, CD, in which a TPT substrate 1 having a TPT substrate 1 and a counter substrate 4 having a color filter are bonded together is the gap between the TFT array 2 and the light-shielding film 5, It is affected not only by the unevenness of the color filler and filter 6, but also by the size balance of the in-plane spacer and in-seal spacer, and by the mechanical properties of the spacer material such as the dispersion density and modulus of elasticity, and it is difficult to control a uniform gap unless all of these factors are controlled. I can't.

[Problem to be solved by the invention]

Conventional liquid crystal display devices are configured as described above, so if the cell spacing in a TPT-color LCD is non-uniform, it will cause non-uniform background, non-uniform coloring, and variations in electro-optical characteristics, which will cause display quality problems. .

In addition, when glass fiber is used for the in-plane spacer 11 as shown in FIGS. 6 and 7, the glass fiber has 1) long length and sharp edges compared to its diameter, and 2) hardness and elastic modulus. Because of the high resistance, the glass fiber on top of the TPT applies pressure to the T'FT during crimping, causing fluctuations in transistor characteristics and destruction.If the glass fiber is on the pixel electrode, it may damage the alignment film on the pixel electrode during crimping, causing damage to the pixel. There are problems such as exposing the electrodes and causing display defects.

Note that since the alignment film on the pixel electrode has the role of a DC cut film for the liquid crystal layer, exposing the pixel electrode also poses a problem in DC resistance reliability.

As a means of solving these problems,
No. 179, Japanese Unexamined Patent Publication No. 62-148927, etc.
A method has been proposed in which spacers are selectively formed in parts other than the FT part and the pixel electrode.

Also, although it does not specifically explain TPT-LCD, Japanese Patent Application Laid-open Nos. 60-257427 and 60-260022
It is conceivable to use a spacer made of plastic beads as proposed in the above publication.

However, in the former example, there is a problem that forming the selective spacer material increases the cost, and in the latter example, there is a problem as described below.

FIG. 8 is a cross-sectional model diagram of a liquid crystal cell when plastic beads are used as in-plane spacers.

In the figure, 1 is a T'FT array substrate, 4 is a counter substrate, 9 is a peripheral sealing material, and 11 is a plastic bead as an in-plane spacer. In the examples shown in FIGS. 7 and 8, it is difficult to uniformly control the in-plane cell gaps, especially when forming a liquid crystal display element with a large screen size. TFT with seal material 9
When the seal width between the substrate 1 and the counter substrate 4 is 2 m, the area of the seal part relative to the screen size is approximately 7 in 5 inch size.
%, about 5% for 10 inch size. If only the in-seal spacer or in-plane spacer is not distributed enough in the seal part, the entire surface is evenly pressurized when the side substrates are bonded together by thermocompression, so the seal part alone cannot maintain the rigidity of the entire panel. The cell gap at the center of the screen tends to become smaller.

Glass fiber, which has been used as a spacer material so far, has a high elastic modulus of 7000 kg/mm2 and high thermal stability, and it has good controllability of the cell gap even in small quantities, especially when used as a spacer inside a seal. High performance and seal reliability.

When plastic beads are used as the in-plane spacer, the elastic modulus is lower than that of glass fibers, so in such an example, the amount of deformation of the spacer at the center of the plane is smaller than that of the in-plane periphery, as shown in the cross-sectional view of the model in Figure 8. The amount of deformation is larger than the amount of deformation in the area, and the cell gap at the center of the plane becomes smaller. Therefore, in order to use plastic beads as an in-plane spacer, a large amount of spraying is required since the elastic modulus is lower than that of glass fibers.

If there are a large amount of spacers within the display screen, clouding of the screen called haze occurs, degrading the display quality.

This invention was made to solve these problems, and it prevents TPT failure and deterioration of characteristics, makes cell gaps uniform throughout the panel surface, makes background coloring uniform, and makes electro-optic characteristics uniform. An object of the present invention is to obtain an active matrix type liquid crystal display device that can provide an easy-to-see display.

[Means to solve the problem]

The liquid crystal display device according to the present invention optimizes the size of the spacer in the sealing material and the in-plane spacer, and uses a hard spacer such as a glass fiber as the spacer in the sealing material, and uses a plastic spacer with a low elastic modulus as the in-plane spacer. In addition, the density of dispersion of the in-plane spacers is changed between the in-plane central part and the peripheral part to make the cell gaps on the effective display surface uniform.

[For production]

In this invention, the size of the spacer in the seal material and the spacer in the plane are optimized by the thickness of the TPT, the light-shielding film, and the color filter, and the spacer in the seal is set to have a high sealing reliability and a strict seal thickness gap. Since a hard spacer such as a glass fiber that can be controlled is used and a plastic bead with a low elastic modulus is used as an in-plane spacer, it is effective in preventing TPT failure and characteristic deterioration and in preventing exposure of the alignment film on the pixel electrode.

In addition, by changing the distribution density of in-plane spacers between the central and peripheral parts of the plane, it is possible to make the in-plane cell gaps uniform and to spray the minimum amount of spacers required, which eliminates the problem of deterioration of display quality such as haze. do not have.

[Example] Hereinafter, an example of the liquid crystal display device of the present invention will be described with reference to the drawings.

Figure 1 shows a TFT with a screen size of 10 inches in which a TFT array substrate and a counter substrate are bonded together in one embodiment of the present invention.
A plan view of the PT-LCD, Figure 2 is the same as ■-■ in Figure 1.
3 is an enlarged sectional view of the seal portion and the vicinity of one pixel, and FIG. 4 is a conceptual diagram of a method of dispersing in-plane spacers on a TFT array substrate.

In each figure, 1 is a TFT array substrate, 2 is a TFT array on this array substrate 1, 3 is a display pixel electrode formed on the surface of the array substrate 1, 4 is a counter electrode substrate arranged to face the array substrate 1, and 5 is a A light shielding film (black mask) provided on the surface (lower surface) of the counter electrode substrate 4, 6 a color filter, and 7 a counter electrode. 8 is an alignment film formed on the surfaces of the side substrates 1 and 4; 9 is a peripheral sealing material between both substrates; 10 is a sealing material 9
Inner spacer, 11 is an in-plane spacer, 12 is a sealing material, 13
is a polarizing plate provided on the outer surface of the side substrate 1.4, and 14 is a cell gap between the substrates. Further, in FIG. 4, 15 is a spray nozzle, and 16 is a center-to-center robot pattern mask.

First, as shown in Figures 1 to 3, a glass fiber spacer with a diameter of 9.5 m is mixed into the heat-curable epoxy sealant, stirred and mixed, and the sealant is pressed onto the color filter surface side of the counter electrode substrate 4. Screen printing was performed so that the sticker width was approximately 2 lins.

Next, as shown in Figure 4, the elastic modulus at room temperature is approximately 500 kg.
/ mm” with a diameter of 6.5 μm plastic beads [
Micropearls (trade name: Building Blocks Fine Chemicals)] were mixed and dispersed in an isopropyl alcohol solution at a dispersion rate of 300 pieces/lllll112, and then the liquid was mixed and dispersed in the center of the screen size through a mask 16 that could be selectively sprayed. The TFT array substrate 1 is sprayed from the spray nozzle 15 using air pressure.
Sprayed on top.

The opening area of the open pattern mask in the center of the screen is 10
When the screen size is inches, it may be about 10% to 15%.

Next, a similar dispersion solution having a concentration of the same plastic beads at a dispersion density of 100 pieces/mm 2 was sprayed through a mask that could selectively spray only the peripheral area of the screen size.

Note that the size of the spacer 10 in the sealant and the spacer 11 in the plane is such that when the cell gap 14 is 8 μm, the maximum height of the TFT array is 1.5 μI, and the thickness of the light shielding part 5 of the opposing substrate and the color filter 6 of the pixel. is constant at 1.5 μm, according to the following calculation.

Spacer diameter in sealing material (9.5 μm) = Maximum height of TFT (1.5 μm) Spacer diameter in ten planes (6.5 μm) + thickness of color filter (1.5 μm) Next, the sealing material was printed. A counter electrode substrate 4 and a TFT array substrate 1 on which in-plane spacers are scattered are stacked together using a stacking device having an appropriate optical system.

Next, the TFT array substrate 1 and the counter electrode substrate 4 are stacked on top of each other.
was set in a thermocompression press and thermocompression bonded for 180° CIO minutes. After liquid crystal was injected under vacuum through the seal opening of the thermocompression-bonded side substrate, the opening was sealed with a sealant 12.

The in-plane cell gap of this panel was 8.0±0.1 μm, which was highly uniform in the plane, and a uniform background coloring was obtained, and a cell with no haze and a good display appearance was obtained. In addition, since a plastic spacer with a low elastic modulus was used as the in-plane spacer, the TP
T characteristic deterioration and failure rate have decreased.

As a comparative example, the in-plane cell gap of a cell in which 300 or more of the same in-plane spacers as in the above example were uniformly distributed over the entire surface per 2 cylinders was 8.
Although the in-plane uniformity is high at 0±0.1p, haze is noticeable over the entire surface due to the large amount of spacers, and the display appearance is poor.

In addition, the same in-plane spacers are uniformly distributed over the entire surface at a rate of 100 pieces/mm2.
The in-plane cell gap is 8 because the amount of sprayed cells is small.
．． The in-plane uniformity was poor at 0±0.6 IIm, and the background coloring was uneven, color unevenness was noticeable, and the display appearance was poor.

In the above example, Micropearl (manufactured by Building Blocks Fine Chemicals) with a room temperature elastic modulus of about 500 kg/mm2 was used as the plastic beads, but the room temperature elastic modulus was about 110.
Similar results can be obtained using Epostor (manufactured by Nippon Shokubai Chemical Co., Ltd.) of 0 kg/mm''.

〔Effect of the invention〕

As explained above, this invention optimizes the size of the spacer in the sealing material and the in-plane spacer by the thickness of the TPT, the light-shielding film, and the color filter, and then the spacer in the sealing column with high seal reliability. We use a hard spacer such as glass fiber that can strictly control the seal thickness gap, and we use plastic beads with a low elastic modulus for the in-plane spacer to prevent TPT failure and characteristic deterioration and to prevent exposure of the alignment film on the pixel electrode. effective.

In addition, by changing the distribution density of in-plane spacers between the central and peripheral parts of the plane, it is possible to make the in-plane cell gaps uniform and to spray the minimum amount of spacers required, which eliminates the problem of deterioration of display quality such as haze. TPT- with low cost and high display quality.
This has the advantage that color liquid crystal display devices can be manufactured.

In addition, in the above embodiment, a method of selectively dispersing spacers using a mask pattern was explained as a method of selectively dispersing spacers in the central part and peripheral part of the panel surface, but methods such as automatic control of the spray pattern are also possible, and the effects of the present invention can be achieved. Similar effects can be expected at a lower cost.

[Brief explanation of the drawing]

FIG. 1 shows T in an embodiment of the liquid crystal display device of the present invention.
FT color LCD plan view, Figure 2 is a sectional view taken along the line ■-■ in Figure 1, Figure 3 is an enlarged sectional view of Figure 2, and Figure 4 is a TFT.
A conceptual diagram of the method of dispersing in-plane spacers onto an array substrate, Fig. 5 is a cross-sectional view of a liquid crystal display device using the conventional spacer dispersing method, and Fig. 6 is a TPT-1 when using the conventional glass fiber spacer. A plan view of one pixel on the TFT substrate of a color LCD, FIG. 7 is a diagram showing ■-■ in FIG.
8 is a cross-sectional model diagram of a liquid crystal cell using the conventional spacer dispersion method when plastic beads are used as in-plane spacers. 1... TFT array substrate, 2... TFT array, 3
... Display pixel electrode, 4... Counter electrode substrate, 5...
Light shielding film (black mask), 6... color filter,
7... Counter electrode, 8... Alignment film, 9... Sealing material, 10... Spacer in sealing material, 11... In-plane spacer, 12... Sealing material, 13... Polarizing plate, 14...
-Cell gap, 15...Spray nozzle, 16...Robot pattern mask between central parts. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a liquid crystal display device comprising a thin film transistor array substrate having a thin film transistor array on its surface, a counter electrode substrate, and a liquid crystal interposed between the two substrates, a hard material such as glass fiber or alumina is included in the sealing material around the two substrates. A liquid crystal display device characterized in that an inorganic spacer is used, a plastic in-plane spacer is used between the two substrates, and the in-plane distribution density of the spacer is varied.