JPS6396634A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To extremely minimize the dispersion in the gap thickness of two sheets of glass substrates and to obtain good image quality by specifying the dispersion density of spacers at the time of sticking the substrates to each other via the spherical spacers. CONSTITUTION:Transparent electrode layers 3 and oriented films 4 are laminated on two sheets of the glass substrates 2. The substrates are stuck to each other via the peripheral sealing material and resinous spherical spacers 5 and are exposed to a high temp. under pressurization. The spacers generate creep strain and the gap thickness decreases to the value smaller than the target if the dispersion density of the spacers is small at this time. The dispersion density of the spacers is, thereupon, increased to >=120 pieces/mm<2> and <=250 pieces/mm<2>. The generation of plastic strain and the degradation in contrast are prevented and the dispersion in the gap thickness is extremely minimized if the spacers are formed to such dispersion density. The good image quality is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device using resin spherical spacers to increase the thickness of a liquid crystal cell.

BACKGROUND OF THE INVENTION Conventionally, the following steps have been considered in manufacturing liquid crystal display elements. That is, spacers such as glass fibers are uniformly dispersed on the alignment film of one of two glass substrates on which a transparent electrode layer and an alignment film are formed, and this spacer and the other glass substrate are Two glass substrates are bonded together with a sealant screen-printed on the periphery of one, and after the sealant is cured under pressure at high temperatures, liquid crystal is injected into the gap between the side substrates.

In the above-described process, glass fiber has conventionally been generally used as a spacer material to uniformly create the gap between the two glass substrates to a predetermined size over the entire substrate.

However, when spacers are dispersed on a substrate by a method such as aerial dispersion, many of the rod-shaped glass fibers are dispersed on the substrate in a vertical direction due to the influence of static electricity. When the substrates are bonded together, the glass fibers may damage the transparent electrode layer, which is one of the causes of defects due to short-circuiting of the counter electrode. In order to prevent a decrease in process yield due to such defects, it has been proposed to use spherical resin bead spacers instead of rod-shaped glass fibers as spacer materials. That is, in the case of a spherical bead spacer, unlike a rod-shaped glass fiber, it stands perpendicularly to the substrate due to static electricity and does not pierce the transparent electrode layer, thereby causing no damage to the transparent electrode layer.

Problems to be Solved by the Invention However, when resin beads are used as spacers, there are the following problems.

That is, bead spacers are dispersed on one of two glass substrates on which a transparent electrode layer and an alignment film are laminated, and after bonding to the other glass substrate on which a sealant is printed on the periphery, a sealant is applied. In order to create a gap during curing, the flask is placed under high temperature under pressure. At this time, high temperature and high pressure are also applied to the bead spacer, so if the dispersion density is low, that is, the amount of beads that cover the substrate is small, the bead spacer will suffer from creep strain. The color filter used for color display is made of a gelatin-based soft material, so when pressurized, it creates a slight dent in the area where the spacer is, so the gap thickness between the side substrates may be much larger than the target size. I end up with something small.

On the other hand, if the dispersion density of bead spacers is sufficiently increased, there are problems in image quality, such as local non-orientation due to aggregation and a decrease in contrast.

Furthermore, even if the manufacturing method does not involve pressurizing at high temperatures, if the dispersion density is low, gap unevenness will occur in the plane of one channel, or the amount of elastic deformation of the bead spacer will increase, resulting in a gap There is evil while the thickness decreases, etc. The present invention aims to solve the above problems.

Means for Solving the Problems The present invention comprises laminating a transparent electrode layer and an alignment film on at least one of two glass substrates, and surrounding the two glass substrates with a peripheral sealing material and a resin spherical spacer. The two glass substrates are laminated to face each other through the glass substrate, and the liquid crystal is sealed in the gap between the two glass substrates, the gap is set to 4 to 8 μm, and the diameter of the spherical spacer is set to be the same as or slightly larger than the gap, The dispersion density of the resin spherical spacers having a diameter corresponding to the gap is 120 pieces/mm2 or more and 250 pieces/mm2 or more.
This is a liquid crystal display device characterized in that the size is less than mm2.

Effect As described above, by setting the dispersion density of spherical spacers to 120 pieces/M or more and 250 pieces/mm2 or less, the gap thickness between the two glass substrates can be set more accurately, and the image quality is not degraded. It is something that never happens.

Example An embodiment of the present invention will be described below with reference to FIG.

Figure 2 shows the relationship between the dispersion density of bead spacers on a substrate and the gap thickness between two substrates.
This is a plot of bead spacers having a compressive modulus of elasticity on the order of kq/ff and having three types of diameters close to the inter-substrate gap thickness. In addition, the curve 1 in Figure 2 is for a bead spacer with a diameter 0.5 to 1.0 μm larger than the target gap thickness, and the curve 2 is for a bead spacer with a diameter larger than the target gap thickness in the range of 0.5 μm or less. ,
3 is based on a bead spacer having a diameter smaller than the target gap thickness in the range of 0.6 μm or less.

Further, in the curing process of the sealant, a pressure of 1 atmosphere is applied to both surfaces of the glass substrate at 150° C. for 2 hours.

As is clear from the curve shown in Figure 2, the dispersion density is 12
When it is less than 0 pieces/+u, the gradient of the inter-substrate gap thickness with respect to the dispersion density is quite large, and it is 120 pieces/+u.
It becomes almost constant once you surpass your friend.

That is, in a region where the dispersion density of bead spacers is 120 pieces/pull or less, the load applied to each bead spacer is quite large, and it is considered that plastic strain due to creep occurs. Therefore, the gap thickness varies greatly due to slight variations in the dispersion density. On the other hand, in a region where the dispersion density exceeds 120 particles/ao+, the load applied to the bead spacer causes almost no plastic strain due to creep, and the amount of elastic deformation is approximately constant. Therefore, the bead spacer hardly undergoes plastic deformation due to creep.
If the dispersion density is set to 0 particles/zm or more, a liquid crystal display device with a nearly constant gap thickness can be obtained.

On the other hand, when the dispersion density exceeds 250 particles/ff11, it enters the region shown by the shaded area in Figure 2, and in this region, contrast decreases and local non-conformity due to aggregation of bead spacers occurs. Deterioration of image quality, such as orientation, is observed. Therefore, the dispersion density is 120 pieces/y to obtain the target gap thickness that is almost constant and does not affect the image quality.
It is preferable that the number is not less than xy and not more than 250 pieces/H.

In addition, in the case of bead spacers with a diameter 0.5 to 1 Q pH larger than the target gap, which is represented by the 10 curve in Fig. 2, in the region where the dispersion density is close to 250 pieces/h, the range of the target gap thickness is Slightly exceeds the limit, and image quality is likely to deteriorate. Therefore, 0.5 to 1
．． When using bead spacers having a diameter larger by 0 μm, it is better to control the dispersion density in the smaller range of 120 beads/gate to 250 beads/mm 2 . On the other hand, in the case of a bead spacer having a diameter smaller than the optimum gap value, represented by curve 3, the gap thickness is overall smaller than the target range. However, in general, when the gap thickness is small, there are many problems in terms of image quality, such as a decrease in contrast, and defects such as a 7th hole are likely to occur in the manufacturing process. On the other hand, if the gap thickness is large,
Although there are problems in image quality, such as the responsiveness of the liquid crystal being slightly deteriorated, it is stable in manufacturing, and a liquid crystal display device with relatively stable characteristics can be obtained as long as the size does not exceed 1 μm. Therefore, what is the optimal gear thickness in terms of contrast, viewing angle, etc.? Once set, the selection criteria for the spacer diameter to be used is preferably one that has a slightly larger diameter within a range of not more than 1 μm than the optimum gap thickness, taking into account the distortion of the bead spacer.

As described above, according to the present invention, the target gap accuracy can be maintained even when the substrate is pressurized at high temperatures when curing the peripheral sealing material after dispersing the resin bead spacers, and the liquid crystal display can have no adverse effect on image quality. The device can be stably obtained.

Two glass substrates with a thickness of 1fi on which a transparent electrode layer and an alignment film are formed are used, and 120 pieces/mm2 of resin beads with a diameter of 6 μm and a high compressive modulus (more than 1 kg/ynt) are placed on one of the substrates. After uniformly dispersing the particles at a density of less than 250 pieces/Mm, they were bonded to the other substrate with a sealant applied to the periphery, and a pressure of 1 atmosphere was applied to the substrate at 150°C for 2 hours. Here, the optimum gap thickness is set to 5.8 μm in terms of contrast and viewing angle.

The results are shown in FIG. As shown in Fig. 3, the dispersion density varied from 120 pieces/mm2 to 250 pieces/H, but as shown in Fig. 3, the liquid crystal display device with almost constant target gap thickness accuracy was stable. obtained.

FIG. 1 is a cross-sectional view showing a part of the structure of a liquid crystal display device according to the present invention, in which 1 is a polarizing plate, 2 is a glass plate, 3 is a transparent electrode layer, 4 is an alignment film, and 5 is a resin bead spacer. ,6
is the liquid crystal layer.

Note that the above-mentioned gap thickness is 4 to 8 μm, and the spacer diameter can be the same or slightly larger (about +1 μm).

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, it is possible to provide a liquid crystal display device that exhibits extremely small variations in gap thickness and provides good image quality.

[Brief explanation of the drawing]

FIG. 1 is a sectional front view of a portion of a liquid crystal display device according to an embodiment of the present invention, and FIGS. 2 and 3 are characteristic diagrams showing the relationship between the dispersion density and the inter-substrate gap thickness, which are used to explain the device. 1...Polarizing plate, 2...Glass plate, 3.
...Transparent electrode layer, 4...Alignment film, 5...
...Bead spacer, 6...Liquid crystal layer. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 2 01θI! l lπ zoo 2. Li
3θθzu6sa 'i 1J5 Sword ((Ien/mnru2ji Figure 3

Claims (2)

[Claims] (1) A transparent electrode layer and an alignment film are laminated and formed on at least one of two glass substrates, and the two glass substrates are bonded to face each other with a peripheral sealant and a resin spherical spacer interposed therebetween; The liquid crystal is sealed in a gap between the two glass substrates, the gap is set to 4 to 8 μm, and the diameter of the spherical spacer is set to be the same as or slightly larger than the gap, and has a diameter corresponding to the gap. The dispersion density of the resin spherical spacers is 120 pieces/mm^2 or more and 250 pieces/mm^2 or more.
A liquid crystal display device characterized in that the size is less than mm^2. (2) The liquid crystal display device according to claim 1, wherein the resin spherical spacer has a diameter that is 1 μm or less larger than the gap between the two glass substrates bonded together.