JPH1164864A - Production of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a liquid crystal display device by which high grade display is available by uniformly finishing cell gaps near a seal for sealing. SOLUTION: A seal for encapsulating 14 is line-shaped and encloses a liquid crystal encapsulating region of the inside. A dummy seal 22 is constituted by regularly arranging a number of granular sealants and respective granular sealants are circular. After the seal for encapsulating 14 and the dummy seal 22 are formed on one surfaces of respective glass plates, the respective glass plates are superposed and are stuck together. Thereafter respective glass plates are cut along parting lines 23 to obtain two sets of respective substrates. Then liquid crystal is poured in the liquid crystal encapsulating region enclosed with the seal for encapsulating 14 between respective substrates and then encapsulating entrance 14a is sealed to complete a liquid crystal cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a liquid crystal display device.

[0002]

2. Description of the Related Art As is well known, a method of manufacturing a liquid crystal display device includes a method of forming a plurality of liquid crystal enclosing regions (corresponding to a plurality of display screen regions) on one of two substrates. After printing an encapsulation seal, overlaying the other substrate on top of it and attaching both substrates by pressing, cutting these substrates so that each liquid crystal encapsulation area is separated, Some say that they form cells.

However, as the size of the liquid crystal cell increases and its occupied area increases, the number of liquid crystal cells manufactured from a pair of substrates decreases, and the printing area of the sealing seal also decreases. For this reason, an excessive load is applied to the encapsulation seal at the time of press-pressing, and the load becomes large, so that when the encapsulation seal is heat-cured after press-fitting, the encapsulation seal expands significantly, and the shape of the encapsulation seal is disturbed. .
Also, due to the large load, deformation of the gap material occurs,
The yield of liquid crystal cells has been reduced, and the reduction in the yield has led to a significant increase in the cost of products.

In order to solve such a problem, Japanese Patent Laid-Open Publication No.
In Japanese Patent Application Laid-Open No. 4-9426, an auxiliary seal is provided in the vicinity of the outer periphery of an encapsulation seal on one substrate, and the other substrate is superimposed and adhered thereon. The seal is removed to form at least one liquid crystal cell. Also, here, without specially seeking the shape of the auxiliary seal, for example, triangular, square, pentagonal, polygonal, circular,
It is said that an oval shape or the like is acceptable. Alternatively, it is preferable to arrange the auxiliary seals so that a load is evenly applied to the sealing seal when the pair of substrates is pressed and attached.

In Japanese Patent Application Laid-Open No. 8-313917, the width of the sealing seal is reduced at each of the shorter sides of the rectangular pattern of the sealing seal surrounding the liquid crystal enclosing area, and each of the longer sides is reduced. In the sealing seal, the width of the sealing seal is increased, and thus, when a pair of substrates are pressed and adhered, a unit area per unit area generated between the shorter side and the longer side of the sealing seal. It prevents the liquid crystal sealed area from bending due to the difference in load. Here, each of the line-shaped auxiliary seals is arranged around the sealing seal.

[0006]

In recent years, however, liquid crystal display devices capable of displaying a high-definition display such as SVGA, XGA and the like and a large-screen display, and replacing a CRT have been developed. There is a demand in the market for a large-sized liquid crystal display device or the like that can be used as a desktop used in a computer. In order to meet these demands, a liquid crystal display device, particularly a color liquid crystal display device using an STN (super twisted nematic) type liquid crystal, has a high contrast (for example, a contrast of 30: 1 or more), a high luminance, and a fast response ( For example, a response speed of 200 ms or less), high display quality, and low power consumption are required.

In particular, high display quality has a trade-off relationship with high contrast and high brightness, and improvement under more severe conditions is required with improvement in response speed of liquid crystal. . One method for achieving high display quality is to make the cell gap (equivalent to the distance between a pair of substrates) uniform, which has been urgently needed. In particular, the occurrence of color unevenness in the vicinity of the sealing seal due to the accuracy of the cell gap in the vicinity of the sealing seal has become a problem, and it has been necessary to improve this.

However, the above-mentioned Japanese Patent Application Laid-Open No. 64-9426
The publication does not mention the finishing accuracy of the cell gap near the sealing seal. In addition, even if the arrangement of the auxiliary seals described in this publication is devised, for example, the auxiliary seal is arranged near the sealing seal, the cell gap in the vicinity of the sealing seal cannot be made uniform.

According to the technique described in the above-mentioned Japanese Patent Application Laid-Open No. 8-313917, the width of the sealing seal is reduced on each shorter side of the rectangular pattern of the sealing seal that borders the liquid crystal sealing area. Even if the width of the sealing seal was increased in each of the longer sides, the cell gap in the vicinity of the sealing seal could not be uniformly finished.

In view of the above, the present invention has been made to solve the above-mentioned conventional problems, and has an object to provide a liquid crystal display device capable of uniformly finishing a cell gap in the vicinity of a sealing seal and thereby performing high-quality display. It is intended to provide a manufacturing method.

[0011]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a plurality of sealing seals which border a liquid crystal sealing area on at least one of a pair of substrates; A step of forming a dummy seal composed of a plurality of granular sealing materials scattered outside the seal, a step of superposing and arranging the respective substrates, and a step of injecting liquid crystal into a liquid crystal sealing region between the respective substrates. Have.

According to the present invention, the dummy seal made of a plurality of scattered granular sealing materials is arranged outside the sealing seal which borders the liquid crystal sealing area. Therefore, when sandwiching the sealing between the substrates, a dummy seal made of a plurality of scattered granular sealing materials is also sandwiched between the substrates. For this reason, each substrate is supported by each granular sealing material of the dummy seal. That is, each substrate is supported at a plurality of points. As a result, the stress acting on each substrate is dispersed, and the stress is not concentrated only in the vicinity of the sealing seal, so that the cell gap can be made uniform. Further, when the substrates are bonded together, air escapes from between the substrates. At this time,
In the case of a dummy seal made of each granular sealing material, this air is sufficiently dispersed and flows, so that the substrates can be bonded together while maintaining a uniform cell gap.

When the granular seal materials of the dummy seal are regularly arranged, the stress acting on each substrate is sufficiently dispersed.

On the other hand, when a large pattern of auxiliary seals is arranged or a line-shaped auxiliary seal is arranged as in the prior art, the stress acting on each substrate can be sufficiently dispersed. could not. In addition, when the substrates are bonded to each other, a portion where air easily escapes and a portion where air hardly escapes are generated between the substrates, which causes a non-uniform cell gap.

In the case of a dummy seal made of each granular sealing material as in the present invention, when each substrate is bonded, each granular sealing material extends evenly, and this forms a uniform cell gap. .

On the other hand, when each auxiliary seal having a large pattern is arranged or each dummy seal having a linear pattern is arranged as in the prior art, when each substrate is bonded, each auxiliary seal or each There was a difference in the amount of stretching of the sealing material between the dummy seals, which caused the cell gap to be non-uniform.

Here, the advantages of the dummy seal made of each granular sealing material will be described in more detail. In an STN type liquid crystal display device or a ferroelectric type liquid crystal display device, even a small change in the cell gap caused by the undulation of the substrate,
This causes display unevenness. In particular, with the recent increase in the performance of liquid crystals,
There is a growing demand for improvements in display unevenness.

When a dummy seal made of a granular sealing material is sandwiched between each substrate as in the present invention, each substrate is supported at a plurality of points, so that the stress acting on each substrate is dispersed, The swell can be suppressed. If one focuses on one granular sealing material, the substrate moves like a seesaw with this granular sealing material as a fulcrum. Since there are many such fulcrums, the substrate is maintained substantially parallel to other substrates. Thus, the cell gap can be kept uniform.

The dummy seal is formed by printing a sealing material.
In consideration of the bonding strength between the substrates, it is preferable that the granular seal materials of the dummy seal are regularly arranged and the granular seal materials are formed densely. The diameter of each granular sealing material may be substantially the same as the width of the sealing seal.

According to a third aspect of the present invention, the method may further include a step of separating the area where the dummy seal is formed from each substrate.

According to a fourth aspect of the present invention, a color filter is formed on at least one of the substrates, and only in a region of the color filter existing outside the sealing seal.
A dummy seal may be formed.

If the dummy seal is formed only in the area of the color filter existing outside the sealing seal, the cell gap is not affected by the thickness of the color filter (film thickness: 1 to 2 μm). Only

This color filter may be formed of a plurality of hues, a single color, or a light-shielding layer.

Similarly, instead of a color filter, another type of layer is formed on the substrate, and if this layer affects the cell gap, the layer may be located outside the encapsulation seal in the area of the layer. Only when a dummy seal is formed, it is not necessary to be affected by the thickness of this layer.

According to a fifth aspect of the present invention, a liquid crystal display device comprises:
It may be an STN liquid crystal display device or a ferroelectric liquid crystal display device.

As described above, in the STN type liquid crystal display device and the ferroelectric type liquid crystal display device, even a small change in the cell gap caused by the undulation of the substrate causes display unevenness. The present invention that forms a simple cell gap is very effective.

[0027]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a main part showing a color STN type liquid crystal display device manufactured by one embodiment of the manufacturing method of the present invention. In the figure, a pair of substrates 1 and 2 are transparent plates such as a glass plate and a transparent synthetic resin plate which are arranged to face each other, and R (red), G
(Green) and B (blue) picture elements 3 and a black mask 4 covering between the picture elements 3 are formed, an overcoat film 5 functioning as a protective film, and a transparent display electrode made of ITO are formed thereon. 6, and an alignment film 7 are sequentially formed, and on the other substrate 2,
A transparent display electrode 11, an insulating film 12, and an alignment film 13 are sequentially formed. Each substrate 1, 2 on which various thin films are formed
Are sealing seals 14 arranged on the peripheral portion of each of the substrates 1 and 2.
Are pasted together. Here, a thermosetting one-part epoxy sealing material is used as the material of the sealing seal 14.

The sealing seal 14 contains a number of spacers 15 inside the seal. In addition, this sealing seal 1
A large number of in-cell spacers 16 are scattered in a region surrounded by 4 (liquid crystal sealing region). The cell gap between each of the substrates 1 and 2 is determined by these spacers 15 and 16. Then, a liquid crystal is sealed in the cell gap to form a liquid crystal layer 17.

The sealing seal 14 may be formed on any of the substrates 1 and 2, for example, after being formed on the substrate 1, these substrates 1 and 2 are bonded together.

Next, an embodiment of a manufacturing method for manufacturing such a color STN type liquid crystal display device will be described.

First, materials used for the color STN type liquid crystal display device will be described. As each of the substrates 1 and 2, a soda glass plate having an outer size of 370 × 480 mm and a thickness of 0.7 mm is applied.
To form two liquid crystal cells. A color filter is previously formed on one of the two glass plates.

An epoxy resin (XN-21S) manufactured by Mitsui Toatsu is used as the sealing seal 14 and a dummy seal described later.
In this epoxy resin, a large number of glass beads serving as the spacers 15 in each seal are mixed in advance.

In one embodiment of the manufacturing method of the present invention, each of the picture elements 3, the black mask 4, and the overcoat film is provided on one of the two glass plates for each of two liquid crystal cell regions. 5, a display electrode 6, and an alignment film 7 are sequentially formed, and a display electrode 11, an insulating film 12, and an alignment film 13 are formed on the other glass plate for each of two liquid crystal cell regions. Then, an alignment process is performed on the alignment films 7 and 13 of these glass plates.

Thereafter, on one of the glass plates,
That is, an epoxy resin is applied to one glass plate 21 as shown in FIG. 2 by a screen printing method to form the sealing seal 14 and the dummy seal 22. If the glass plate 21 has a color filter, the dummy seal 22 is formed outside the encapsulation seal 14 and only in the area of the color filter (the area inside the dotted line). If this glass plate 21 does not have a color filter, when this glass plate 21 is superimposed on the other glass plate having a color filter, only the region of the color filter is provided outside the sealing seal 14. A dummy seal 22 is formed so as to overlap. Further, the dummy seal 22 is formed so as to avoid the dividing line 23 of each glass plate.

As is apparent from FIG. 2, the sealing seal 14 is used.
Are line-shaped, and surround the liquid crystal sealed area inside. On the other hand, the dummy seal 22 is formed by regularly arranging a large number of granular seal materials, and each granular seal material is circular. The diameter of each granular sealing material is set to 0.4 mm, which is the same as the width of the sealing seal 14, and the pitch is set to 2 mm in consideration of the ease of printing the dummy seal 22.

Next, after forming the sealing seal 14 and the dummy seal 22 on one of the glass plates,
As shown in FIG. 3, a plurality of sets of respective glass plates are overlapped and sandwiched between a pair of press plates 31 and 32, and each set of glass plates is heated (for example, 8 kg / cm ² ) while being pressed (for example, 8 kg / cm ² ). (180 ° C.), and a pair of glass plates is attached to each pair via the sealing seal 14 and the dummy seal 22.

The pair of glass plates thus bonded are subjected to an after-bake treatment, and thereafter, the respective glass plates are cut along a cutting line 23 shown in FIG.
Get 2. The sealing seal 14 between the substrates 1 and 2
Liquid crystal is injected into the liquid crystal enclosed area surrounded by
1 is completed, the liquid crystal cell shown in FIG. 1 is completed. Therefore, here, two liquid crystal cells are obtained from two glass plates.

As described above, when the respective glass plates are superposed and bonded together with the dummy seal 22 formed only outside the enclosing seal 14 and only in the color filter region, each glass plate becomes Since it is supported by the granular sealing material, the stress acting on these glass plates is dispersed, and the cell gap is made uniform. Further, when the glass plates are stacked, the air is sufficiently dispersed and flows from between the glass plates, so that the glass plates can be bonded together while keeping the cell gap uniform. Furthermore, each granular sealing material of the dummy seal 22 extends evenly, and this forms a uniform cell gap. Further, since the dummy seal 22 is formed only in the region of the color filter existing outside the encapsulation seal 14, the effect that the cell gap changes due to the thickness (film thickness of 1 to 2 μm) of the color filter can be avoided. . Such effects can be applied not only to the color filter but also to other types of films. Therefore, when avoiding the effects, it is necessary to form the dummy seal 22 only in the region of the film existing outside the sealing seal 14. Good.

Next, the effect of the liquid crystal display device manufactured by the manufacturing method of the above embodiment was experimentally examined, and the result will be described.

Here, 12. having the sectional structure of FIG.
A type 1 color STN type liquid crystal display device (cell gap: 6.7 μm) is an object of the experiment. Each spacer 15 having a diameter of 6.
FIG. 4 shows the experimental results when 8 μm glass beads were applied and these glass beads were mixed at a weight ratio of 8%, and the experimental results when 6.9 μm diameter glass beads were mixed at a weight ratio of 8%. FIG. 5 shows the results of experiments in which glass beads having a diameter of 7.0 μm were mixed at a weight ratio of 8%.

For comparison with this embodiment, as shown in FIG. 7, an encapsulation seal 14 and a line-shaped auxiliary seal 42 are formed on a glass plate 41, and this glass plate 41 is bonded to another glass plate. Thereafter, these glass plates were cut to produce a liquid crystal cell for comparison, and an experiment was also performed on the liquid crystal cell for comparison. Then, each seal spacer 15 mixed in the sealing seal 14 has a diameter of 6.8 μm.
FIG. 8 shows the experimental results when m glass beads were applied and the glass beads were mixed at a weight ratio of 8%.
FIG. 9 shows an experimental result when glass beads having a diameter of 6.9 μm were mixed at a weight ratio of 8%, and FIG. 10 shows an experimental result when glass beads having a diameter of 7.0 μm were mixed at a weight ratio of 8%. Is shown.

In each experiment, 50 samples of a liquid crystal display device were manufactured, and these samples were evaluated.
Experimental results have been obtained.

FIGS. 4 to 6 and FIGS. 8 to 10A show the results of evaluating cell gaps in the vicinity of four sides of the liquid crystal sealing region, and the results are shown in graphs. (B) of each figure evaluates the cell gap in the vicinity of the four corners of the liquid crystal sealing region, and shows the result in a graph.

In each graph, the horizontal axis represents the degree of the cell gap, and the vertical axis represents the frequency of occurrence of the liquid crystal cell having the cell gap on the horizontal axis (the frequency of occurrence for 50 samples is shown as a percentage). Represents.

The degree of the cell gap is “x” when the cell gap is too small, “△” when the cell gap is small, “○” when the cell gap is slightly small, “◎” when the cell gap is just good, “◎”, Is slightly larger, "○" indicates that the cell gap is large, "△" indicates that the cell gap is too large, and "X" indicates that the cell gap is too large. "◎" and "○" indicate non-defective products, and "△"
Represents a non-defective product, and "x" represents a defective product. Products classified as “◎”, “○” and “△” are handled as products.

As is clear from comparison of these graphs, in the case of the liquid crystal display device of the above embodiment, the variation of the cell gap is very small, and the yield rate is high. On the other hand, in the case of the comparative example, the variation in the cell gap is large, and the yield rate is low.

FIG. 11 conceptually shows the degree of undulation of the glass plate 21 in the liquid crystal display device manufactured by the manufacturing method of the above embodiment. As shown in FIG. 11, since the glass plate 21 is supported by each granular sealing material of the dummy seal 22, the stress acting on the glass plate 21 is dispersed, and the cell gap becomes uniform.

On the other hand, in the liquid crystal display device of the comparative example, as shown in FIG. 12, the glass plate 41 is supported only by the sealing seal 14 and the line-shaped auxiliary seal 42. Stress acting on
Large undulations occur in the glass plate 41, and the cell gap becomes non-uniform.

Further, in the respective manufacturing steps of the liquid crystal display device of the above embodiment and the liquid crystal display device of the comparative example, when a pair of glass plates are laminated, interference fringes are observed on these glass plates. The cell gap was evaluated based on the interference fringes.

In the case of the liquid crystal display device of the comparative example, the interference fringes generated from the end points of the glass plate reached the liquid crystal sealing region beyond the auxiliary seal 42 and the sealing seal 14.

On the other hand, in the case of the liquid crystal display device of the above embodiment, the interference fringes generated from the end points of the glass plate were dispersed and absorbed at the portion of the dummy seal 22, and did not reach the liquid crystal sealing region. . No interference fringes were generated between the dummy seal 22 and the sealing seal 14.

Therefore, in the liquid crystal display device of the above embodiment, it can be said that the cell gap is maintained with very high precision in the vicinity of the sealing seal 14 and the dummy seal 22.

The present invention may be embodied in various other forms without departing from its spirit or essential characteristics. Therefore, the above-described embodiment is merely an example in every aspect, and the scope of the present invention is shown by the claims, and is not limited by the specification text.

Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

[0055]

As described above, according to the present invention, a dummy seal composed of a plurality of scattered granular seal materials is provided.
It is located outside the sealing seal that borders the liquid crystal sealing area. Therefore, when sandwiching the sealing between the substrates, a dummy seal made of a plurality of scattered granular sealing materials is also sandwiched between the substrates.
For this reason, each substrate is supported by each granular sealing material of the dummy seal. That is, each substrate is supported at a plurality of points. As a result, the stress acting on each substrate is dispersed, and the stress is not concentrated only in the vicinity of the sealing seal, so that the cell gap can be made uniform. Also,
When the substrates are bonded, air escapes from between the substrates. At this time, in the case of a dummy seal made of each granular sealing material, this air is sufficiently dispersed and flows, so that the substrates can be bonded together while maintaining a uniform cell gap.

When the granular seal materials of the dummy seal are regularly arranged, the stress acting on each substrate is sufficiently dispersed.

In the case of a dummy seal made of each granular sealing material as in the present invention, when each substrate is bonded, each granular sealing material extends evenly, and this forms a uniform cell gap. .

According to a third aspect of the present invention, the method may further include a step of separating the area where the dummy seal is formed from each substrate.

According to a fourth aspect of the present invention, a color filter is formed on at least one of the substrates, and only in a region of the color filter existing outside the sealing seal.
A dummy seal may be formed.

If the dummy seal is formed only in the area of the color filter existing outside the sealing seal, the cell gap is not affected by the thickness of the color filter (film thickness of 1 to 2 μm). Only

The color filter may be formed of a plurality of hues, a single color, or a light shielding layer.

Similarly, when another type of layer is formed on the substrate instead of the color filter, if a dummy seal is formed only in the area of the layer existing outside the sealing seal, It is not affected by the thickness of the layer.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a color STN type liquid crystal display device manufactured by one embodiment of a manufacturing method of the present invention.

FIG. 2 is a plan view showing an enclosing seal and a dummy seal on a glass plate used in the manufacturing method of the embodiment.

FIG. 3 is a view showing a step of pressing each glass plate in the manufacturing method of the embodiment.

FIG. 4 is a graph showing evaluation of a liquid crystal display device manufactured by the manufacturing method of this embodiment, in which glass beads having a diameter of 6.8 μm are applied as spacers for maintaining a cell gap.

FIG. 5 is a graph showing evaluation of a liquid crystal display device manufactured by the manufacturing method of this embodiment, in which glass beads having a diameter of 6.9 μm are applied as spacers for maintaining a cell gap.

FIG. 6 is a graph showing evaluation of a liquid crystal display device manufactured by the manufacturing method of this embodiment, in which glass beads having a diameter of 7.0 μm are applied as spacers for maintaining a cell gap.

FIG. 7 is a plan view showing an encapsulation seal and an auxiliary seal on a glass plate used for manufacturing a liquid crystal display device of a comparative example.

FIG. 8 is a graph showing an evaluation of a liquid crystal display device of a comparative example in which glass beads having a diameter of 6.8 μm are used as spacers for maintaining a cell gap.

FIG. 9 is a graph showing evaluation of a liquid crystal display device of a comparative example in which glass beads having a diameter of 6.9 μm are used as spacers for maintaining a cell gap.

FIG. 10 is a graph showing an evaluation of a liquid crystal display device of a comparative example in which glass beads having a diameter of 7.0 μm are used as spacers for maintaining a cell gap.

FIG. 11 is a diagram conceptually showing the degree of undulation of a substrate in a liquid crystal display device manufactured by the manufacturing method of this embodiment.

FIG. 12 is a diagram conceptually showing the degree of undulation of a substrate in a liquid crystal display device of a comparative example.

[Explanation of symbols]

 1, substrate 3 picture element 4 black matrix 5 overcoat film 6, 11 display electrode 7, 13 orientation film 12 insulating film 14 sealing seal 15 spacer in seal 16 spacer in cell 17 liquid crystal layer 21 glass plate 22 dummy seal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Manabu Ano 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Kyohei Isobata 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka In the company

Claims (5)

[Claims] 1. A step of forming, on at least one of a pair of substrates, a plurality of sealing seals for bordering a liquid crystal sealing area, and a dummy seal made of a plurality of granular sealing materials scattered outside the sealing seal. A method of manufacturing a liquid crystal display device, comprising: a step of superposing and opposing each substrate; and a step of injecting a liquid crystal into a liquid crystal sealing region between the substrates. 2. The liquid crystal display device according to claim 1, wherein each granular sealing material of the dummy seal is regularly arranged. 3. The method for manufacturing a liquid crystal display device according to claim 1, further comprising a step of separating a region where the dummy seal is formed from each substrate. 4. The liquid crystal display device according to claim 1, wherein a color filter is formed on at least one of the substrates, and a dummy seal is formed only in a region of the color filter existing outside the sealing seal. Production method. 5. The method according to claim 1, wherein the liquid crystal display is an STN liquid crystal display or a ferroelectric liquid crystal display.