JPH06331993A - Production of liquid crystal panel - Google Patents

Abstract

PURPOSE:To assure the gap uniformity and seal perfectness of the liquid crystal panel. CONSTITUTION:The liquid crystal panel is produced by applying a sealing material on one of a pair of substrates 2 and 3 and sticking these substrates to each other to adhere the substrates, then encapsulating a liquid crystal between both substrates 2 and 3. A pair of parallel surface plates 11 and 12 adhered with elastic buffer sheets 13, 14 of 50 to 70 deg. hardness and <=1mm thickness on the respective opposite surfaces are prepd. in the sticking stage. Both substrates 2, 3 are respectively attracted and held on the elastic buffer sheets 13, 14 facing each other in the state of aligning these substrates to each other. A pair of the parallel surface plates 13, 14 are thereafter closed and a prescribed pressure is applied thereon to stick the substrates 2, 3 to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal panel. More specifically, the present invention relates to a step of applying a sealing material to at least one of a pair of substrates and sticking them together.

[0002]

2. Description of the Related Art First, a general structure of a liquid crystal panel will be briefly described with reference to FIG. (A) shows a cross-sectional shape, and the liquid crystal panel 1 has a cell structure in which a pair of substrates 2 and 3 are bonded to each other with a sealing material 4. A liquid crystal 5 is filled in the gap between the two substrates 2 and 3. (B) shows the planar shape of the liquid crystal panel.
As shown in the figure, a sealing material 4 is arranged along the peripheral portion of the liquid crystal panel 1 so as to surround the central display area 6. A notch 7 for injecting liquid crystal into a part of the band-shaped sealing material 4.
Is provided. The notch 7 is sealed with a sealing material 8 after the liquid crystal is injected. Matrix pixels are formed on the inner surface of the lower substrate 2 so as to be included in the display area 6. Each pixel is composed of a pixel electrode and a switching thin film transistor. Further, a lead electrode 9 for external connection is formed on the exposed end surface of the lower substrate 2. On the other hand, a counter electrode, a color filter, etc. are formed on the inner surface of the upper substrate 3.

Next, a general method of manufacturing the above-mentioned active matrix type liquid crystal panel will be briefly described. First, an alignment film is applied to each of a substrate on which pixels are formed in a matrix and a substrate on which a counter electrode and a color filter are formed, and then rubbing is performed to perform an alignment treatment. next,
The sealing material is applied to either one of the two substrates by screen printing or the like. Next, the two substrates are stacked and then a predetermined pressure is applied to bond them. After that, the sealing material is cured to fix the two substrates to each other, and then liquid crystal is injected into the gap to complete the liquid crystal panel. Here, the step of bonding a pair of substrates by pressure is a factor that greatly affects the uniformity of the gap size between the substrates and the seal integrity of the display area. A pressure type press has been conventionally used for this bonding step, and is disclosed in, for example, Japanese Patent Laid-Open No. 3-38615.

[0004]

Generally, the pressure press used in the step of laminating liquid crystal panels is provided with a pair of vertical opening / closing type surface plates. With this platen open, a pair of substrates is set on each facing surface. Next, the platen is closed and pressure is applied to bond the pair of substrates to each other. On this occasion,
The parallelism of the surface plate is an important parameter that affects the gap uniformity and the seal integrity of the liquid crystal panel. However, generally, the accuracy of the surface plate parallelism of the pressure press is limited to about 50 μm in terms of processing. On the other hand, the gap of the liquid crystal panel needs to be uniformly controlled in the order of 3 to 5 μm over the entire display area. In this respect, the parallel accuracy of the surface plate is about 50μ.
Since m is the limit, in reality, it is extremely difficult to precisely control the gap size of the liquid crystal panel on the order of μm.
When the gap dimension is not uniform, display unevenness appears on the liquid crystal panel, which causes a problem of greatly reducing the yield.

When the parallelism of the pressure press surface plate is poor,
Since the pressure distribution in the substrate varies and an excessive or excessive pressure is locally applied to the substrate, the seal shape is disturbed and the integrity of the seal is impaired. Also, the substrate itself has 30 to 5
A warp of about 0 μm is included, which may act synergistically with the mechanical error of the parallel platen to further increase the variation in the pressure distribution within the substrate. As a result, there is a problem that the integrity of the seal is impaired and the yield and reliability of the liquid crystal panel are reduced.

In order to make this point easier to understand,
A modification of the seal shape due to pressure will be briefly described with reference to FIG. (A) shows a normal seal shape, and when a normal pressure is uniformly applied, the width dimension of the seal material becomes substantially constant. (B) shows an abnormal shape that occurs when an excessively small pressure is locally applied, and the width dimension of the sealing material is locally smaller than the designed value. In the worst case, the sealing material may be broken. When the seal breaks, moisture or the like enters the liquid crystal sealed in the display area from the outside, and the moisture resistance decreases. (C) represents an abnormal shape of the seal material that occurs when an excessive pressure is locally applied, and the seal width locally expands. The seal shape thus crushed is not preferable because it causes gap nonuniformity and the like.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art, an object of the present invention is to provide a manufacturing method capable of ensuring the gap uniformity and the seal integrity of a liquid crystal panel. To do. The following measures have been taken in order to achieve this object. That is, according to the present invention, in a method of manufacturing a liquid crystal panel in which a sealing material is applied to one of a pair of substrates, the substrates are bonded to each other and then liquid crystal is sealed between both substrates, the hardness is 50 ° to 70 °. Prepare a pair of parallel surface plates with elastic cushioning sheets each having a thickness of 1 mm or less mounted on the opposing surfaces, and after adsorbing and holding the two substrates on the opposing elastic cushioning sheets in a state where they are aligned with each other, The method is characterized by including the step of closing the parallel platen and applying a predetermined pressure to bond the two substrates to each other. As the elastic buffer sheet, for example, a silicone rubber sheet can be used.
Further, an ultraviolet curing type can be used as the sealing material. In this case, the pre-process of printing the UV-curable sealing material on one of the pair of substrates, and taking out the parallel platen from the parallel platen while irradiating them with ultraviolet rays and adhering and fixing them to each other The subsequent process is performed. It is also possible to use a thermosetting sealing material instead of the ultraviolet curing type. In this case, a pre-process of printing a thermosetting sealant on one of the pair of substrates and a heat treatment while the substrates are bonded to each other while being pressed and held on the parallel platen An additional step of adhesively fixing each other is performed.

A panel sticking device was devised to carry out the above-described method for manufacturing a liquid crystal panel. This panel sticking device has a pair of rigid parallel surface plates that can be opened and closed, and a hardness of 50 ° to 70 ° and a thickness of 1 mm attached to the opposing surfaces of each rigid parallel surface plate.
The following elastic cushioning sheets, a means for adsorbing and holding a pair of substrates on the surface of each elastic cushioning sheet, a means for aligning the two substrates with each other, a pair of rigid parallel platens and applying a predetermined pressure to both substrates And a means for bonding.

[0009]

According to the present invention, in the process of bonding a pair of substrates, the pressure is applied with the elastic cushioning sheet interposed, and the local pressure variation is absorbed to make the pressure distribution uniform. I am trying to become. As a result, the gap uniformity and the seal integrity of the liquid crystal panel can be improved.
In particular, since the elastic cushioning sheet is preliminarily attached to the parallel surface plate, workability in the laminating process can be remarkably improved. or,
By setting the hardness of the elastic cushioning sheet to 50 ° to 70 ° and setting the thickness to 1 mm or less, mechanical errors and the like of the parallel platen are almost completely absorbed and the pressure distribution is made constant.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a schematic diagram showing a panel sticking device used in a method for manufacturing a liquid crystal panel according to the present invention. (A) shows the open state of the panel sticking device,
Similarly, (B) represents the closed state. As shown,
The panel sticking apparatus is provided with a pair of rigid parallel platens 11 and 12 that can be opened and closed. These surface plates are, for example, SUS
It consists of materials. Elastic cushioning sheets 13 and 14 are attached to the opposing surfaces of the rigid parallel surface plates 11 and 12, respectively. Each elastic cushioning sheet has a hardness of 50 ° to 70 ° and a thickness of 1 mm or less. For example, a silicone rubber sheet can be used as the material. Alternatively, a Teflon sheet may be adopted instead. Further, a means for adsorbing and holding the pair of substrates 1 and 2 which are the work pieces on the surfaces of the elastic buffer sheets 13 and 14 is provided. This suction means is, for example, each elastic cushioning sheet 13,
14 is a vacuum hole provided so as to penetrate therethrough. or,
Means for aligning the two substrates 1, 2 with each other are also provided. This alignment means can be constituted by, for example, an XY table incorporated in the lower surface plate 12.
Finally, a means for closing the pair of rigid parallel plates 11 and 12 and applying a predetermined pressure to bond the two substrates 2 and 3 together is included. This pressure applying means is, for example, the upper surface plate 1
It consists of a pressure plunger 15 connected to 1. The upper surface plate 11 is connected to the C-shaped column 1 via the pressure plunger 15.
The lower surface plate 12 is fixed to the base portion of the C-shaped column 16 as well.

Continuing to refer to FIG. 1, the method of manufacturing the liquid crystal panel according to the present invention will be described in detail. Usually, the pair of substrates 2 and 3 are bonded to each other with a pressing force of about 1 to 5 kg / cm ² . The pair of substrates 2 and 3 are adsorbed to the upper and lower surface plates 11 and 12 in the opened state via elastic cushioning sheets 13 and 14, respectively. It should be noted that a sealing material is previously applied to at least one of the inner surfaces of the substrates by screen printing or the like. In this example, this sealing material is made of an ultraviolet curable resin. Instead of this, a thermosetting resin may be used.
After performing the alignment by the alignment marks provided on the upper and lower substrates 2 and 3, the upper surface plate 11 is lowered to bond the both substrates 2 and 3 to each other. In general,
The parallel accuracy of the rigid surface plate provided in the panel attachment device is about 5
The limit is 0 μm, and it is difficult to uniformly control the substrate gap size after bonding on the order of 3 to 5 μm. Also, considering the influence of the warp of the substrate (about 30 to 50 μm), the pressure distribution in the substrate is deviated, and if this is left as it is, the gap size becomes nonuniform and the seal shape is disturbed. Therefore, in the present invention, the upper and lower surface plates 1
Elastic buffer sheets are attached to the substrates 1 and 12, respectively, and the substrates 2 and 3 are attached to the substrates by applying pressure while adsorbing the substrates. Since both substrates are pressed against each other via the elastic cushioning sheet, local variations in pressure are dispersed, the pressure distribution becomes constant, and gap uniformity and seal integrity can be secured. Also, if minute foreign matter adheres to the surface of the surface plate, the local pressure concentrates only on that portion, but it is possible to absorb this abnormal pressure by interposing an elastic buffer sheet. Further, since the elastic cushioning sheet comes into contact with the surface of the substrate, it is possible to prevent the occurrence of flaws and cracks.

As the elastic buffer sheet which is a characteristic component of the present invention, for example, a silicone rubber sheet can be used. As described above, the hardness of the elastic cushioning sheet is 50.
It is set in the range of ° to 70 ° and the thickness is set to 1 mm or less. If the thickness is 1 mm or more, the elastic deformation becomes excessive and the gap size uniformity deteriorates. Similarly, when the hardness is 50 ° or less, the elastic deformation becomes excessive and the uniformity of the gap dimension deteriorates. On the other hand, the hardness is 70 °
In the above case, the elasticity of the cushioning sheet is insufficient, and variations in pressure distribution cannot be sufficiently absorbed, and the integrity of the seal is impaired.

In this embodiment, an ultraviolet curable material is used as the sealing material. In this case, both substrates are attached to each other and then taken out from the parallel platen and irradiated with ultraviolet rays to bond and fix the two substrates to each other. When a thermosetting material is used as the sealing material, both substrates are bonded to each other by performing heat treatment while the substrates are bonded to each other while being pressed and held on the parallel platen. In this case, a heater or the like may be built in the parallel platen.

Next, an experiment was conducted to confirm the effect of the buffer sheet, and the results are shown in Table 1 below.

[Table 1] In this experiment, samples were prepared with and without a buffer sheet to evaluate the seal integrity. The elastic cushioning sheet used is a silicone rubber sheet having a hardness of 50 ° and a thickness of 0.3.
mm. As is clear from Table 1, the defective sealing rate reached 30 to 40% when the bonding step was performed without the buffer sheet. In addition, this defective seal rate is shown in FIG.
The normal shape shown in (A) above is regarded as a good product, and the same as in (B),
The abnormal shape shown in (C) is calculated as a defective product. On the other hand, when the bonding step is performed using the elastic cushioning sheet, the defective sealing rate can be reduced to 15 to 20%.

Next, an experiment was conducted by changing the material of the buffer sheet, and the results are shown in Table 2 below.

[Table 2] In this experiment, seal integrity and gap uniformity were evaluated. Regarding the seal integrity, the seal shape was visually observed, and a good one was indicated by a circle, and a poor one was indicated by a cross. Regarding the gap uniformity, a good grade is represented by a circle, a somewhat good grade is represented by a triangle, and a poor grade is represented by a cross. As is clear from Table 2, when the cushioning sheet is not used, the gap uniformity is basically good, but the seal integrity is impaired.
Further, when clean paper having a thickness of about 0.3 mm was used, the gap uniformity was about the same level as when the buffer sheet was not used, and the seal integrity was considerably impaired. Clean paper lacks elasticity and cannot obtain the desired cushioning effect. On the other hand, when silicone rubber sheets having a thickness of 0.3 mm and hardnesses of 50 ° and 70 ° were used, extremely good results were obtained in terms of seal integrity and gap uniformity.

Finally, for reference, an example of a liquid crystal panel manufactured by the manufacturing method according to the present invention is shown in FIG. This liquid crystal panel is an active matrix type, and pixels arranged in a matrix are formed on one substrate 2. In this example, only three pixels are exemplarily shown. Each pixel is composed of a pixel electrode 21 and a switching thin film transistor 22 for driving the pixel electrode 21. Another substrate 3 is arranged to face the substrate 2 with a predetermined gap. A black mask 31, a color filter 32, and a counter electrode 33 are sequentially formed on the inner surface of the substrate 3. A liquid crystal 5 having, for example, a twisted nematic orientation is held between the substrates 2 and 3. According to the present invention, the pair of upper and lower substrates 2 and 3 are attached to each other by the sealing material 4. In the laminating step, since a pair of elastic buffer sheets are interposed to apply pressure, the sealing material 4
There is no deformation and the gap size is kept uniform. Therefore, the display quality and reliability of the active matrix type liquid crystal panel are good. Needless to say, the present invention is not limited to the active matrix type liquid crystal panel, but can be applied to various types of liquid crystal panels such as a simple matrix type.

[0017]

As described above, according to the present invention, a pair of parallel surface plates having elastic cushioning sheets each having a hardness of 50 ° to 70 ° and a thickness of 1 mm or less are mounted on opposite surfaces, After each substrate is attracted and held on the opposing elastic buffer sheets in a state of being aligned with each other, the pair of parallel platens are closed and a predetermined pressure is applied to bond the both substrates to each other. As a result, the pressing force distribution becomes constant. As a result, the sealing shape of the outer peripheral portion of the panel is improved, the yield can be improved, and stable panel manufacturing can be achieved. Further, there is an effect that the gap uniformity of the liquid crystal panel is also improved. When foreign matter adheres to the substrate or the like, since pressure is applied through the elastic cushioning sheet, variations in pressure due to the foreign matter can be absorbed, and there is an effect that defects and cracks on the substrate surface can be prevented. Further, since the seal shape of the liquid crystal panel is improved, the effect of improving reliability including moisture resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing a panel sticking device used for carrying out a method for manufacturing a liquid crystal panel according to the present invention.

FIG. 2 is a cross-sectional view showing an example of a liquid crystal panel manufactured by a manufacturing method according to the present invention.

FIG. 3 is a schematic diagram showing a general configuration of a conventional liquid crystal panel.

FIG. 4 is a schematic view showing an abnormal shape of a sealing material.

[Explanation of symbols]

 1 Liquid Crystal Panel 2 Substrate 3 Substrate 4 Sealing Material 5 Liquid Crystal 11 Surface Plate 12 Surface Plate 13 Elastic Buffer Sheet 14 Elastic Buffer Sheet 15 Pressurizing Plunger

Claims (5)

[Claims] 1. A method of manufacturing a liquid crystal panel, wherein a sealing material is applied to one of a pair of substrates, the substrates are adhered to each other, and then liquid crystal is sealed between the two substrates, wherein a hardness is 50 ° to 70 ° and a thickness is 50 ° to 70 °. Prepare a pair of parallel surface plates with elastic buffer sheets of 1 mm or less attached to the opposite surfaces,
A liquid crystal comprising a step of adhering the two substrates to each other in a state where they are aligned with each other by adsorbing and holding them on opposing elastic cushioning sheets, then closing a pair of parallel platens and applying a predetermined pressure to attach the two substrates to each other. Panel manufacturing method. 2. The method of manufacturing a liquid crystal panel according to claim 1, wherein the elastic buffer sheet is a silicone rubber sheet. 3. A pre-process of printing a UV-curable sealing material on one of the pair of substrates, and taking out the parallel platen from the parallel platen and irradiating it with ultraviolet rays to bond the two substrates to each other. The method for manufacturing a liquid crystal panel according to claim 1, including a post-process. 4. A pre-process of printing a thermosetting sealing material on one of a pair of substrates, and a heat treatment is performed while the substrates are bonded to each other while being pressurized and held on the parallel platen. The method of manufacturing a liquid crystal panel according to claim 1, comprising an additional step of adhering to each other. 5. A pair of rigid parallel surface plates that can be opened and closed,
The hardness of each rigid parallel surface plate is 50 ° to 7
An elastic cushioning sheet having a thickness of 1 mm or less at 0 °, a means for adsorbing and holding a pair of substrates on the surface of each elastic cushioning sheet, a means for aligning the two substrates with each other, and a pair of rigid parallel surface plates for closing a predetermined pressure. And a panel sticking device having means for sticking both substrates together.