KR100240611B1 - The method of manufacturing lcd element - Google Patents

Abstract

A pair of electrode substrates are bonded via a sealing material and a spacer. Then, the space between the pair of electrode substrates is stepwise evacuated to reduce the pressure, and the cell gap of the liquid crystal display element is controlled by pressing with atmospheric pressure. Thus, the sealing edge can be prevented from being disturbed by the foaming of the sealing material, and a liquid crystal display element having a good sealing edge linearity can be obtained. In addition, since the movement of the spacer in the vicinity of the exhaust port is prevented, generation of display color unevenness can be eliminated, and a liquid crystal display element having favorable display characteristics can be obtained. Further, since the sealing edge is not disturbed, a liquid crystal display element having excellent cell gap uniformity can be obtained.

Description

Method for manufacturing liquid crystal display element

FIG. 1 is a cross-sectional view showing a schematic structure of a liquid crystal display element manufactured by a method of manufacturing a liquid crystal display element according to the present invention. FIG.

FIG. 2 is a graph showing a pressure change in a gap between a pair of electrode substrates and a temperature change in a sealing material. FIG.

3 is a plan view of the electrode substrate;

4 is a cross-sectional view showing a singing state of the spacer with respect to the overcoat film;

DESCRIPTION OF THE REFERENCE NUMERALS

1: electrode substrate 2: sealing material

3: spacer 4: clamp jig

5: Clearance between a pair of electrode substrates 6: Outlet

7: liquid crystal display element part 8: part other than liquid crystal display element

9: Color filter

The present invention relates to a method of manufacturing a liquid crystal display element, and more particularly, to a method of manufacturing a liquid crystal display element using a pressing method in which a space between a pair of electrode substrates is evacuated to reduce pressure in the step of bonding a pair of electrode substrates.

Conventionally, when manufacturing a liquid crystal display device, the cell gap (thickness of the liquid crystal layer) in the liquid crystal display device is controlled based on the following steps after bonding a pair of electrode substrates. That is, after a thermosetting sealing material as a sealing material and a pair of electrode substrates are bonded to each other via a spacer, a pair of bonded electrode substrates are laminated in several sets, and the plurality of electrode substrates are pressed and heated simultaneously by using a press machine .

However, in the above-described method, the pair of electrode substrates are pressed mechanically by the press machine, resulting in the following problems. That is, even if the parallelism and the surface smoothness of the upper and lower press plates provided on the press machine and the surface smoothness of the bonded pair of electrode substrates are excellent, it is difficult to uniformly press the entire surface of the electrode substrate. Further, since pressing is performed in a state in which a plurality of electrode substrates are laminated, if the press is uniformly performed in the surface of a set of electrode substrates, nonuniformity in the surface of the press is accumulated. As a result, the uniformity of the cell gap may be impaired. Further, if foreign substances are present on the electrode substrate, the load applied to the electrode substrate is locally increased, and as a result, display color irregularity is liable to occur.

Therefore, a method of attempting to improve the inconvenience as described above, that is, the unevenness of the press and the influence of foreign substances, is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 4-291320 and Japanese Unexamined Patent Application Publication No. 6-175097.

Japanese Patent Application Publication No. 4-291320 discloses a method of putting a pair of bonded electrode substrates in a wrapping bag and evacuating the inside of the packed bag to reduce the pressure. That is, this method is a method in which a pair of electrode substrates is used as a closed space, and pressing is performed by using a pressure difference between the internal pressure of the packaging bag and the atmospheric pressure. In this prior art, after evacuating the interior of the package bag and reducing the pressure, the air outlet is closed and the thermosetting sealing material is heated and cured. At this time, since the sealing material is prevented from foaming and the sealing edge is prevented from being disturbed, the pressure after exhaust is set in the range of 20 to 1.2 Torr.

On the other hand, Japanese Unexamined Patent Publication No. 6-175097 discloses a method of discharging a pair of electrode substrates joined together in the same manner as described above in a closed space to reduce the pressure, thereby performing the pressing using the pressure difference between the internal pressure and the atmospheric pressure.

According to this method, the entire surface of the electrode substrate can be uniformly pressed. Further, since the electrode substrate and the sealing material are bonded under a vacuum atmosphere, air can be prevented from remaining on the bonding surface between the electrode substrate and the sealing material.

However, in the method disclosed in Japanese Patent Application Laid-Open No. 4-291320, the sealing material is not cured simultaneously by press and heating using the pressure difference between the internal pressure of the packaging bag and the atmospheric pressure. As a result, there arises a problem that it is difficult to form the sealing portion well, that is, to prevent disturbance of the sealing edge. In addition, when foreign matter is mixed in the inside of the package bag, there arises a problem that display color unevenness due to non-uniformity of the press easily occurs.

Further, in the method disclosed in Japanese Patent Laid-Open No. Hei 6-175097, the atmosphere present in the liquid crystal display element portion between the pair of electrode substrates is exhausted only from the exhaust port portion of the liquid crystal display element. Therefore, in the initial stage of the exhaust, a large pressure difference is generated between the portion constituting the liquid crystal display element and the portion constituting the liquid crystal display element between the pair of electrode substrates. As a result, there arises a problem that the sealing material itself is foamed and the sealing edge is liable to be disturbed. Further, in the initial stage of the exhaust, since the atmosphere flows near the exhaust port part quickly, the spacer of the liquid crystal display element part is liable to move. As a result, there arises a problem that display color irregularity is apt to occur.

[Technical Problem]

An object of the present invention is to provide a method for manufacturing a liquid crystal display element which is capable of forming a good sealing portion and which has no display color unevenness caused by movement of spacers in the vicinity of an exhaust port and which is excellent in cell gap uniformity .

In order to achieve the above object, a method of manufacturing a liquid crystal display element according to the present invention comprises a first step of bonding a pair of electrode substrates through a sealing material and a spacer, and a step of discharging the pair of electrode substrates stepwise And a second step of controlling the cell gap by pressing under reduced pressure and atmospheric pressure.

According to the above configuration, the pair of electrode substrates can be bonded via the sealing material and the spacer. Then, the space between the pair of electrode substrates is evacuated and decompressed, whereby the pair of electrode substrates are pressed by the atmospheric pressure and the cell gap is controlled.

At this time, since the exhaustion between the pair of electrode substrates is performed stepwise, the pressure difference between the portion constituting the liquid crystal display element and the portion constituting the liquid crystal display element between the pair of electrode substrates is less certainly than the conventional one Loses. Thereby, the sealing material is prevented from being foamed. Further, the flow rate of the atmosphere in the vicinity of the exhaust port becomes slower than that in the conventional case where the exhaust is performed at once, and the movement of the spacer in the vicinity of the exhaust port is suppressed.

Therefore, according to the above configuration, disturbance of the sealing edge can be prevented by foaming the sealing material, and a liquid crystal display element having a good sealing edge linearity can be obtained. Further, since movement of the spacer in the vicinity of the exhaust port is prevented, generation of display color unevenness can be prevented, and a liquid crystal display element having favorable display characteristics can be obtained.

Preferably, a thermosetting material is used as the sealing material, the sealing material is heated simultaneously with the evacuation, and the pressure between the electrode substrates reaches the final target value before reaching the curing temperature of the sealing material The following actions and effects can be obtained.

That is, for example, the thermosetting resin softens until it reaches a predetermined curing temperature by heating, and hardens when it reaches the curing temperature. Here, if the sealing material is cured before the electrode substrate reaches the final target pressure, sufficient press can not be performed, and the uniformity of the cell gap is deteriorated.

Thus, when the space between the electrode substrates is evacuated and the pressure is reduced and the heating is performed, sufficient press can be performed by sufficiently softening the sealing material when the pressure between the electrode substrates reaches the final target pressure. Therefore, according to the above configuration, since the pressure between the electrode substrates reaches the final target value before reaching the curing temperature of the sealing material, the pressing can be sufficiently performed while the sealing material is softened, A liquid crystal display element having excellent properties can be obtained.

Other objects, features and advantages of the present invention will be more fully understood from the following description. Further, advantages of the present invention will become apparent from the following description with reference to the accompanying drawings.

[Structure and operation of the invention]

[Embodiment 1]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG.

FIG. 1 is a cross-sectional view showing a schematic structure of a liquid crystal display element manufactured by a method of manufacturing a liquid crystal display element according to the present invention. This liquid crystal display element comprises a pair of electrode substrates 1, 1 made of glass or plastic, a sealing material 2 made of thermosetting epoxy resin, a spacer 3 made of plastic beads, for example, . The sealing material 2 and the spacer 3 are sandwiched between the pair of electrode substrates 1 and 1. A method of manufacturing a liquid crystal display element having such a structure will be described below.

First, transparent electrodes made of, for example, ITO (Indium Tin Oxide) are formed in a predetermined pattern on a pair of electrode substrates 1, 1 by photolithography. Next, an alignment film (not shown) made of, for example, polyimide resin is formed on the pair of electrode substrates 1, 1, and alignment treatment is performed by printing, rubbing, or the like. Subsequently, the pair of electrode substrates 1 and 1 are bonded to each other with a thermosetting sealing material 2 having a thermosetting temperature of 160 占 폚 and spacers 3 interposed therebetween. The above-mentioned sealing material 2 is pattern-formed by, for example, printing. In the present embodiment, the weight ratio of the spacer 3 mixed in the sealing material 2 to the sealing material 2 is 8%.

The method for forming the electrode substrate material, the method for forming the pattern thereof, the method for forming the alignment film material, the alignment treatment method, the sealing material (2) and the method for forming the sealing pattern, the spacer (3) Is not limited to a specific material.

Next, the periphery of the bonded pair of electrode substrates 1, 1 is sandwiched by the clamp jig 4.

Then, the gap 5 between the pair of electrode substrates 1 and 1 is evacuated in the profile shown in Fig. 2, and the pressure is reduced to, for example, a pressure P1 of 500 Torr. At this time, the gap 5 is exhausted from the exhaust port 6 provided in the clamp jig 4 to reduce the pressure. In the following description, the point at which the pressure of the gap 5 reaches P1 is referred to as a reference point.

In addition, the material and shape of the clamp jig 4 used in the present invention are not particularly limited. The reference point is not limited to the time point when the pressure of the gap 5 reaches 500 Torr. That is, an optimum pressure is selected as a reference point so as to obtain a liquid crystal display element having a good sealing portion and excellent in cell gap uniformity without display color unevenness caused by the movement of the spacer 3 in the vicinity of the exhaust port 6 .

In the present embodiment, the press between the pair of electrode substrates 1 and 1 and the heating of the sealing material 2 are performed at the same time by the methods shown in Examples 1 to 3 below.

[Example 1]

In this embodiment, the pressure P1 is maintained for 20 minutes from the reference point to the time T1. This is because the portions 7 constituting the liquid crystal display element between the pair of electrode substrates 1 and 1 shown in Fig. 3 and the portion 8 constituting the liquid crystal display element are made substantially equal in pressure. Thereafter, the pressure of the gap 5 is reduced to a pressure P2 of, for example, 200 Torr for 10 minutes from time T1 to time T2. At this time, the exhaust speed is 100 psi / min. Then, the pressure P2 is maintained for 25 minutes from the time T2 to the time T4, and the depressurization by the exhaust, that is, the press is terminated.

On the other hand, in synchronism with this press, the thermosetting sealing material 2 is heated and cured with a profile as shown in Fig. That is, the sealing material 2 is heated to a heat curing temperature of 160 占 폚 for 40 minutes from the reference point to the time T3. In this case, when the temperature of the sealing material 2 reaches the thermosetting temperature, the pressure finally reaches P2 so that a good press can be performed. Thereafter, the above-mentioned heat curing temperature is maintained for 15 minutes from time T3 to time T4, and the heating is terminated.

Although the pressure of the gap 5 is finally reduced to 200 Torr in the present embodiment, it is not particularly limited to this pressure. That is, the optimum pressure can be selected so as to obtain a liquid crystal display element having a good sealing portion and excellent cell gap uniformity without display color unevenness caused by the movement of the spacer 3 in the vicinity of the exhaust port 6. [

Next, after performing the after-baking at a temperature of 170 DEG C for 90 minutes, the pair of electrode substrates 1, 1 are cut and cut into a predetermined shape. Thereafter, a liquid crystal material is injected into the pair of electrode substrates 1, 1 to obtain a liquid crystal display element. Table 1 shows the state of the sealing portion in the thus obtained liquid crystal display element, the result of judging the non-mobility of the spacer 3, and the overall evaluation.

[Example 2]

In this embodiment, for example, the pressure P1 of 500 Torr is maintained for 20 minutes from the reference point to time T1. Thereafter, the pressure of the gap (5) is reduced to a pressure P2 of, for example, 200 Torr for 20 minutes from time T1 to T2. The exhaust speed at this time is 50 kPa / min. Then, the pressure P2 is maintained for 15 minutes from the time T2 to the time T4, and the depressurization by the exhaust, that is, the press is terminated.

On the other hand, in synchronism with this press, the thermosetting sealing material 2 is heated and cured with a profile as shown in Fig. That is, the sealing material 2 is heated to a heat curing temperature of 160 占 폚 for 40 minutes from the reference point to the time T3. In this case, when the temperature of the sealing material 2 reaches the thermosetting temperature, the pressure finally reaches P2 so that a good press can be performed. Thereafter, the above-mentioned heat curing temperature is maintained for 15 minutes from time T3 to time T4, and the heating is terminated. The liquid crystal display device is obtained by following the same steps as in the first embodiment. Table 1 shows the state of the sealing portion in the thus obtained liquid crystal display element, the result of judging the non-mobility of the spacer 3, and the overall evaluation.

[Example 3]

In this embodiment, the pressure P1 of, for example, 500 Torr is maintained for 20 minutes from the reference point to time T1. Thereafter, the pressure of the gap 5 for five minutes from time T1 to time T2 is reduced to a pressure P2 of, for example, 200 Torr. The exhaust speed at this time is 200 psi / min. Then, the pressure P2 is maintained for 30 minutes from the time T2 to the time T4, and the depressurization by the exhaust, that is, the press is terminated.

On the other hand, the thermosetting sealing material 2 is heated and cured in a profile shown in FIG. 2 in synchronism with this press. That is, the sealing material 2 is heated to a heat curing temperature of 160 占 폚 for 40 minutes from the reference point to the time T3. In this case, when the temperature of the sealing material 2 reaches the thermosetting temperature, the pressure finally reaches P2 so that a good press can be performed. Thereafter, the above-mentioned heat curing temperature is maintained for 15 minutes from time T to time T4, and the heating is terminated. The liquid crystal display device is obtained by following the same steps as in the first embodiment. Table 1 shows the state of the sealing portion in the thus obtained liquid crystal display element, the result of judging the non-mobility of the spacer 3, and the overall evaluation.

[Table 1]

From the results shown in Table 1, the state of the sealing portion and the non-mobility of the spacer 3 are good or slightly good when the exhaust speed is 50 to 200 kPa / min. This is considered to be because the sealing edge is not disturbed because there is no foaming from the sealing material 2. Further, in the above-described method, since the exhaust of the gap 5 is performed stepwise, it can be considered that the movement of the spacer 3 in the vicinity of the exhaust port 6 is suppressed.

Therefore, according to the above-described method, no disturbance of the sealing edge due to foaming from the sealing material 2 is caused, so that a liquid crystal display element having a good sealing edge linearity can be obtained. In addition, since the movement of the spacer 3 in the vicinity of the exhaust port 6 is suppressed, display color irregularity due to the movement of the spacer 3 is not generated, and as a result, a liquid crystal display element having good display characteristics can be obtained. Further, as shown in FIG. 4, since the amount of decompression of the spacer 3 with respect to the overcoat film 10 on the color filter 9 is reduced, a liquid crystal display element having good cell gap uniformity can be obtained.

In addition, it can be seen that particularly good results are obtained in terms of the state of the sealing portion and the non-mobility of the spacer 3 when the exhaust speed is 50 to 100 kPa / min. Therefore, the exhaust speed is preferably in the range of 50 to 100 cd / min.

On the other hand, it is known that an excellent liquid crystal display element can be obtained comprehensively if the exhaust speed is slower than 50 cd / min. However, in this case, it takes too much time and productivity is poor. Therefore, the exhaust speed should be at least 50 ㎣ / min.

In this embodiment, as shown in the pressure profile of Fig. 2, the decompression operation of two stages is performed, but the decompression operation of three or more stages may be performed.

[Embodiment 2]

Other embodiments of the present invention will be described below with reference to Figs. 1 to 4 with reference to Embodiments 4 to 6. Fig. For convenience of explanation, the members having the same functions as those of the member used in the first embodiment are denoted by the same reference numerals and the description thereof will be omitted.

[Example 4]

This embodiment is the same as the first embodiment except that the mixing amount of the spacers 3 in the sealing material 2 is 10% by weight with respect to the sealing material 2. The amount of the spacer 3 mixed with the sealing material 2 in the thus obtained liquid crystal display element, the state of the spacer 3 being dented into the overcoat film 10, and the nonfading property of the sealing material 2 were determined Results, and comprehensive evaluation are shown in Table 2.

[Example 5]

This embodiment is the same as the first embodiment except that the mixing amount of the spacers 3 in the sealing material 2 is 4% by weight with respect to the sealing material 2. The amount of the spacer 3 mixed with the sealing material 2 in the thus obtained liquid crystal display element, the state of the spacer 3 being dented into the overcoat film 10, and the nonfading property of the sealing material 2 were determined Results, and comprehensive evaluation are shown in Table 2.

[Example 6]

This embodiment is the same as the first embodiment except that the mixing amount of the spacers 3 in the sealing material 2 is 15% by weight with respect to the sealing material 2 in this embodiment. The amount of the spacer 3 mixed with the sealing material 2 in the thus obtained liquid crystal display element, the state of the spacer 3 being dented into the overcoat film 10, and the nonfading property of the sealing material 2 were determined Results, and comprehensive evaluation are shown in Table 2.

[Table 2]

From the results of Table 2, it can be seen that when the amount of the spacer 3 to be mixed with the sealing material 2 is 4%, the overcoat film 10 (10) on the color filter 9 of the spacer 3, as compared with the liquid crystal display element obtained in Example 1 ) Is slightly increased. This is because the load applied to each spacer 3 increases. However, the non-releasability of the sealing mark 2 is good. Therefore, in this case, the uniformity of the cell gap can be improved more comprehensively than the conventional method.

When the amount of the spacer 3 mixed with the sealing material 2 is 15%, the sealing material 2 is peeled from the electrode substrate 1 with a small probability when an impact is applied to the electrode substrate 1, . This is because the amount of the spacer 3 to be mixed is excessively large, so that the contact area between the sealing material 2 and the electrode substrate 1 is reduced and the bonding strength is weakened. However, also in this case, it is understood that the amount of the inserting to the overcoat film 10 on the color filter 9 of the spacer 3 is small and the cell gap uniformity is good.

In addition, when the amount of the spacer 3 to be mixed with the sealing material 2 is 8 to 10%, the load applied to each spacer 3 at the time of pressing becomes optimum. As a result, the amount of the inserting of the spacers 3 onto the overcoat film 10 on the color filter 9 is small, and the sealing material 2 is hardly peeled off.

Therefore, from the comprehensive evaluation in Table 2, it can be understood that when the amount of the spacer 3 to be mixed with the sealing material 2 is 4 to 10%, the amount of storage in the overcoat film 10 on the color filter 9 of the spacer 3 is The cell gap uniformity near the sealing portion can be improved. Preferably, if the mixing amount is 8 to 10%, the amount of storage of the spacer 3 in the overcoat film 10 on the color filter 9 is reliably reduced to reliably improve the cell gap uniformity in the vicinity of the sealing portion .

As described above, the method for manufacturing a liquid crystal display element according to the present invention comprises a first step of bonding a pair of electrode substrates 1, 1 via a sealing material 2 and a spacer 3, And a second step of controlling the cell gap by evacuating stepwise between the first and second electrodes (1, 1) and pressing it under atmospheric pressure.

According to the above configuration, since exhausting is performed stepwise between the pair of electrode substrates 1, 1, the portion 7 constituting the liquid crystal display element between the pair of electrode substrates 1, And the pressure difference between the portion 8 constituting the display element and the portion 8 which does not constitute the display element becomes lower than in the prior art. Thereby, the sealing material 2 is prevented from being foamed. In addition, compared with the conventional case where the exhaust is performed at once, the flow rate of the air near the exhaust port 6 is slowed, and the movement of the spacer 3 in the vicinity of the exhaust port 6 is suppressed.

Therefore, according to the above configuration, it is possible to prevent the sealing edge from being disturbed by the foaming of the sealing material 2, and it is possible to obtain a liquid crystal display element having a good sealing edge linearity. In addition, since the movement of the spacer 3 in the vicinity of the exhaust port 6 is prevented, the occurrence of display color unevenness can be prevented, and a liquid crystal display element having good display characteristics can be obtained.

In the method of manufacturing a liquid crystal display element according to the present invention, in the second step, the exhaust is temporarily stopped when a predetermined pressure is reached between the electrode substrates (1, 1) And the above-described evacuation is repeated after the pressures of the portion 7 constituting the liquid crystal display element and the portion 8 constituting the liquid crystal display element become substantially equal to each other.

According to the above configuration, when the gap 5 between the pair of electrode substrates 1 and 1 reaches a predetermined pressure (for example, 500 Torr), the evacuation is temporarily stopped and the gap between the pair of electrode substrates 1, After the pressure difference between the portion 7 constituting the liquid crystal display element and the portion 8 constituting the liquid crystal display element are substantially equalized, the evacuation is repeated again. Accordingly, the pressure difference between the portion 7 constituting the liquid crystal display element and the portion 8 constituting the liquid crystal display element between the pair of electrode substrates 1 and 1 is substantially eliminated. In addition, compared with the conventional case where the exhaust is performed at once, the flow rate of the air near the exhaust port 6 is slowed, and the movement of the spacer 3 in the vicinity of the exhaust port 6 is suppressed.

Therefore, according to the above configuration, it is possible to prevent the sealing edge from being disturbed by the foaming of the sealing material 2, thereby obtaining a liquid crystal display element having a good sealing edge linearity. In addition, since the movement of the spacer 3 in the vicinity of the exhaust port 6 is prevented, the occurrence of display color unevenness can be prevented, and a liquid crystal display element having favorable display characteristics can be obtained.

The method of manufacturing a liquid crystal display element according to the present invention is characterized in that a thermosetting material is used as the sealing material 2 and the sealing material 2 is heated simultaneously with the evacuation to form the electrode substrate 1 ) Reaches the final target value before reaching the curing temperature of the sealing material (2).

Therefore, when the space between the electrode substrates 1 and 1 reaches the final target pressure (for example, 200 Torr) when the space between the electrode substrates 1 and 1 is evacuated and the pressure is reduced, Has not yet hardened and is in a state of being sufficiently softened. Therefore, when the sealing material 2 is being softened, the press can be sufficiently performed, and as a result, a liquid crystal display element having excellent cell gap uniformity can be obtained.

It will be understood by those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit or scope of the inventions or the technical scope of the present invention. And various changes may be made within the scope of the claims.

Claims (7)

A first step of joining a pair of electrode substrates via a sealing material and a spacer; And a second step of evacuating and reducing the pressure between the pair of electrode substrates and controlling the cell gap by pressing with atmospheric pressure, wherein the second step is a step of maintaining the pressure between the pair of electrode substrates at a predetermined pressure Wherein the liquid crystal display device is a liquid crystal display device. The liquid crystal display device according to claim 1, wherein the second step is a step of temporarily stopping the decompression when the electrode substrate reaches a predetermined pressure, And repeating the decompression again after the pressure is substantially equalized. The method of manufacturing a liquid crystal display element according to claim 1, wherein the space between the pair of electrode substrates is evacuated at an evacuation rate of 50 to 200 cd / min. The method for manufacturing a liquid crystal display element according to claim 1, wherein the pair of electrode substrates are exhausted at an exhausting rate of 50 to 100 kPa / min. The method according to claim 1, further comprising the steps of: using a thermosetting material as the sealing material; heating the sealing material simultaneously with the evacuation; and before the pressure between the electrode substrates reaches the curing temperature of the sealing material, Of the liquid crystal display element. The method for manufacturing a liquid crystal display element according to claim 1, wherein the spacer is mixed in the sealing material in a weight ratio of 4% to 10% with respect to the sealing material. The method for manufacturing a liquid crystal display element according to claim 1, wherein the spacer is mixed in the sealing material in a weight ratio of 8% to 10% with respect to the sealing material.