JP2844486B2 - Manufacturing method of liquid crystal display element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display element used for a liquid crystal television or the like, and more particularly, to an alignment film on an inner surface of a transparent substrate constituting the liquid crystal display element. And a method of forming a film such as an insulating film and a protective film.

[Conventional technology]

As shown in FIG. 7, a liquid crystal display element is generally formed by a pair of transparent substrates 1 and 2 opposed to each other at a predetermined interval with a sealing material 3 interposed therebetween. Liquid crystal 4 is sealed in the sealed space.

The inner surface of one of the transparent substrates 1 is provided in one direction (the seventh direction).
In the figure, a strip-shaped color filter 5 extending long in the left-right direction parallel to the paper surface is provided, and this color filter 5 is arranged in a direction orthogonal to the one direction (in FIG. 7,
A plurality of colors are arranged alternately in the order of red, green, blue, and the like (in a direction perpendicular to the paper surface). The entire surface of the color filter 5 is covered with a protective film 6 made of a resin such as polyimide, and a transparent electrode 7 made of an ITO film or the like extending in one direction is formed on the protective film 6 so as to correspond to the color filter 5. , Are arranged at regular intervals in a direction orthogonal to the one direction. Further, the upper surface is covered with an alignment film 8, which is in direct contact with the liquid crystal 4.

On the inner surface of the other transparent substrate 2, a plurality of transparent electrodes 9 made of an ITO film or the like extending in a direction orthogonal to the transparent electrode 7 are arranged at regular intervals. A region facing the electrode 7 forms a pixel region. The transparent electrode 9 is covered with an alignment film 10,
This alignment film 10 is in direct contact with the liquid crystal 4.

In the color liquid crystal display device having the above configuration, films such as the protective film 6 and the alignment films 8 and 10 are formed on the inner surfaces of the transparent substrates 1 and 2. As an example of a method of forming these films, a process of forming a protective film 6 for a color filter will be described below.

First, a material to be the protective film 6 is applied on one of the transparent substrates 1 on which the color filters 5 are formed by offset printing or the like. In the offset printing, for example, as shown in FIG. 8, a liquid protective film material 12 dropped from a nozzle 11 is used.
Is transported while being stretched thinly and evenly with a plurality of rollers 13, and is adhered to the surface of a printing relief plate 15 provided on the peripheral surface of a roller-shaped plate cylinder 14, and is transferred onto a moving stage 16. Of the transparent substrate 1 placed on the color filter 5 of the transparent substrate 1. When the material for the protective film is applied on the color filter 5 in this way, it is preliminarily dried, heated and cured, so that the solid protective film 6 can be finally obtained.

[Problems to be solved by the invention]

In the above-described conventional method for manufacturing a color liquid crystal display element,
After the protective film material is applied on the color filter 5 of the transparent substrate 1 by the printing method and then preliminarily dried, the material for the protective film still having fluidity before curing has a low height. Thus, there is a problem that the film gradually flows toward the edge, and the film thickness at the edge portion of the color filter 5 becomes thin, so that the coverage of the color filter 5 becomes poor.

Further, since the thermal expansion coefficients of the transparent substrate 1, the color filter 5, the protective film 6, and the ITO formed on the protective film 6 are different from each other, after the protective film 6 is cured, heat treatment in a subsequent process is performed. At this time, a stress is generated due to the difference in the coefficient of thermal expansion described above, and the stress is concentrated on a portion where the thickness of the protective film 6 is small. There is also a problem that the transparent electrode 7 may be disconnected.

Then, the present inventors improved the coverage of the edge portion of the color filter 5 without deteriorating the flatness of the protective film 6 and prevented the occurrence of cracks at the edge portion by the following method. Proposed. In other words, by applying and drying the material for the protective film a plurality of times on the color filter 5 formed on the inner surface of one of the pair of transparent substrates 1 and 2, the protection comprising a plurality of layers is achieved. This is a method of forming a film. When the application and drying of the material for the protective film are performed a plurality of times in this manner, a plurality of thin protective films can be laminated, and thus a thicker protective film as a whole can be obtained. Moreover, since there is no need to use a material having a high viscosity, the flatness of the surface of the protective film is maintained, and the film thickness is further increased.
The coating property at the edge portion of the above is greatly improved, and the occurrence of cracks can be prevented.

However, when a material for a protective film is applied by a printing method using a relief plate 15 as shown in FIG. 8, generally, as shown in FIG. 9, an edge portion of the protective film 6 obtained by this method (ie, (A portion corresponding to the peripheral edge portion of the relief plate 15). The height of the projection 6a is the tenth
As shown in the figure, the thickness is almost proportional to the film thickness. As the film thickness increases, the height of the protrusion 6a also increases. From this, the coating and drying of the material for the protective film are performed a plurality of times as described above, and as shown in FIG.
1, 62, 63), the respective protrusions 61a, 62a, 63a of the protective films 61, 62, 63 overlap with each other, so that the protective film material is further applied and dried only once. There was a problem that it would be expensive.

When the protrusions are high in this way, the transparent electrode 7 provided on the protective film 6 tends to be disconnected at the protrusions. Further, a transparent substrate 2 facing the transparent substrate 1 is placed on the transparent substrate 1.
When matching, the above-mentioned protrusion contacts the transparent substrate 2 and the gap becomes non-uniform, or the gap material for regulating the gap is placed on the protrusion, and the gap becomes similarly non-uniform. In some cases.

In addition, as described above, when a film having a plurality of layers is formed by performing coating and drying of the film material a plurality of times, a problem that a protrusion is formed at an edge portion of the film is caused by the following problem.
This also occurs not only when the above-described protective film 6 is formed but also when various films such as an insulating film and an alignment film are formed on the inner surfaces of the transparent substrates 1 and 2 of the liquid crystal display element.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to manufacture a liquid crystal display element capable of suppressing projections generated at an edge portion thereof even when a film having a plurality of layers is formed. It is to provide a method.

[Means for Solving the Problems] The present invention relates to a method for manufacturing a liquid crystal display element, comprising a step of forming a film having a predetermined thickness on the inner surface of a transparent substrate constituting a liquid crystal display element. The step of applying, drying and baking the material is repeated a plurality of times while sequentially reducing the applied area, so that the desired thickness is formed by a plurality of layers having different sizes. It is a feature.

The step of applying and drying the above-mentioned film material may be a step of drying and firing each time the film material is applied once, or applying the film material a plurality of times, It is also possible to have a process of drying and firing.
It is also possible to adopt a process in which a film material is applied a plurality of times, left at room temperature, and then dried.

Means for sequentially reducing the coating area of the film material is as follows:
When the film material is applied by a printing method using a relief printing plate, it can be realized by sequentially reducing the size of the relief printing plate.

[Action]

When a film material is coated on a transparent substrate, dried, and fired, projections occur at the edge of the film as described above. Such coating and drying steps are performed in a plurality of steps while sequentially reducing the coating area. When performed repeatedly, the positions of the protrusions generated at the edge portions of the respective films formed thereby are shifted from each other by an amount corresponding to the application area of each film material,
Therefore, the protrusions do not overlap each other as in the related art. Therefore, the overall height of the projection is kept as low as possible.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are cross-sectional views showing a process of forming a protective film for a color filter which is a main part of a manufacturing process according to one embodiment of the present invention.

In the present embodiment, first, as shown in FIG. 1 (a), on a transparent substrate 1 made of glass or the like, on the surface of which a plurality of color filters 5 of red, green, blue, etc. are formed in a stripe shape. By the offset printing as shown in FIG.
After repeated application, pre-drying is performed at a low temperature, followed by baking to perform main curing, thereby forming a first-layer protective film 61.

Next, a second region is formed on the first protective film 61 by a method similar to the method of forming the first protective film 61 in a narrow area where the edges do not overlap each other. The protective film 62 of the layer is formed to overlap. However, in this case, the application of the material for the protective film is performed using a relief plate smaller in size than the relief plate used when the first-layer protective film 61 is formed. For example, as shown in FIG. 2, in the case of using a relief plate 15 ₁ for forming the first layer of the protective film 61, this dimension of each side of the longitudinal and transverse directions than only d are small relief plate 15 _{Use 2} . The dimension d at this time can be arbitrarily selected within a range of, for example, 0.1 to 2.0 mm. In this way, by using the small relief printing plate 15 ₂ in size than the first layer, on the inner side of the edge portion of the first layer of the protective film 61, to position the edge portions of the second layer of the protective film 62 be able to.

Through the above steps, the protective film 6 having a two-layer structure of the first protective film 61 and the second protective film 62 is formed.
After that, the transparent electrode 7 is formed on the protective film 6 as in the prior art.
And a transparent electrode 9 is also formed on the inner surface of the other transparent substrate 2 and the upper surface thereof is covered with an alignment film 10, and these two transparent substrates 1 and 2 are sealed. By laminating through the material 3 and sealing the liquid crystal 4 therein, a color liquid crystal display device as shown in FIG. 3 is obtained.

According to this embodiment, carried out repeatedly twice applying and drying steps of the protective film material as described above, letterpress 15 ₁ the size of the relief plate 15 ₂ to be used used in the first round at its second round By making the application area of the protective film material smaller sequentially, the following effects can be obtained. That is, as is clear from FIG. 1B, the position of the protrusion 62a generated at the edge portion of the second-layer protective film 62 is
Than the position of the projections 61a that occurred at the edges of the first layer of the protective film 61, apart two letterpress 15 _1, 15 are different frequency from each other ₂ size, thus the protrusions each other as shown in FIG. 11 Since there is no overlap, the height of the projections can be kept low overall.

In order to specifically show this effect, the height from the surface of the transparent substrate 1 to the top of the projection 62a of the second protective film 62 (the highest point of the projection) and the two protective films 61 and 62 were combined. The relationship with the film thickness at the center of the protective film 6 is shown by a solid line in FIG. In addition, for comparison, a conventional protective film having a two-layer structure formed using the same letterpress having the same size is also shown by a broken line in FIG. Then, as is clear from the figure, the tendency that the height of the protrusion increases according to the film thickness can be seen in both, but the height of the protrusion itself is significantly lower in the present embodiment. I understand. For example, a film thickness of 2.5μ
In comparison with the case of m, the average height of the projections in the prior art is 4.5 μm and the maximum value is 6.5 μm, whereas the average height of the projections in this example is 3.5 μm.
The maximum value is 4.5 μm at m, which is extremely low in this embodiment.

If the height of the projection can be kept low in this way,
The step of the transparent electrode 7 provided on the protective film 6 at the projection is reduced, and thus the disconnection which has conventionally occurred at the projection can be avoided. Further, since the height of the projection is low, the projection does not come into contact with the opposing transparent substrate 2, so that the gap can be maintained uniform.

In addition, since the film material was immediately applied twice and then dried, the flatness of the surface of the applied film was improved as compared with the case where the material was simply applied once, and thus, The flatness of the film obtained by curing by subsequent drying can be improved.

Next, FIG. 5 is a sectional view showing the structure of a protective film obtained according to another embodiment of the present invention.

In the embodiment shown in FIG. 1, a process consisting of continuous application and drying of the material for the protective film is repeated twice while the coating area is gradually reduced. The process comprising the continuous application and drying of the material for the protective film, which is the same as that of the above-mentioned embodiment, is repeated n times (n ≧ 3) while the application area is gradually reduced. In this embodiment, the embodiment as well, small Toppan 15 ₁ of size for each step as shown in FIG. 6, 1
By using 15 ₂ ,..., 15 _n , the first
The protective film 6 having an n-layer structure including the protective film 61 of the layer, the protective film 62 of the second layer,..., And the protective film 6n of the nth layer is obtained.

According to the present embodiment, not only can the height of the entire projections be reduced as compared with the case where a relief plate of the same size is used, but also the film thickness of the protective film 6 can be further increased. A protective film having more excellent flatness and coverage can be obtained, and an arbitrary film thickness can be obtained by appropriately setting the number of times of repeating the above-mentioned steps of coating and drying.

In each of the above embodiments, the number of times of immediately and continuously applying the material for the protective film is set to two times, but it may be set to one time or three or more times. However, it can be said that increasing the number of continuous coatings improves the flatness according to the number of continuous coatings.

Further, as a step of applying and drying the material for the protective film,
The film material may be allowed to stand at room temperature after being applied a plurality of times, and then dried. In this way, since the film is left in a state of fluidity before being cured, the high portion of the film flows toward the low portion, and thus the thickness between the edge portion and the central portion of the film is reduced. The difference is small, and a flatter film can be obtained.

Further, the present invention is applicable not only to the formation of a protective film for a color filter in the color liquid crystal display device having the structure shown in FIG. It can be applied to the formation of various films.

〔The invention's effect〕

According to the present invention, the step of applying a film material on a transparent substrate, drying and baking is performed a plurality of times while sequentially reducing the applied area, so that projections generated at the edge portion of the film are formed. Since the positions can be shifted from each other and the projections do not overlap with each other, the overall height of the projections can be suppressed as low as possible. Therefore, it is possible to prevent the occurrence of defects such as disconnection of the transparent electrode on the edge portion of the film and unevenness of the gap.

[Brief description of the drawings]

1 (a) and 1 (b) are cross-sectional views showing a process of forming a protective film for a color filter which is a main part of a manufacturing process according to one embodiment of the present invention, and FIG. 2 is a relief plate used in the embodiment. FIG. 3 is a cross-sectional view showing the structure of a color liquid crystal display device obtained by the same embodiment. FIG. 4 is a relationship between the height of the protrusion and the film thickness in the embodiment and the conventional example. FIG. 5 is a cross-sectional view showing the structure of a protective film obtained by another embodiment of the present invention, FIG. 6 is a plan view showing the size of a relief plate used in the embodiment, FIG. 7 is a cross-sectional view showing the structure of a conventional color liquid crystal display element, FIG. 8 is a view showing a step of applying a protective film by offset printing, and FIG. FIG. 10 is a diagram showing the relationship, FIG. 10 is a diagram showing a general relationship between the height of the protrusion and the film thickness, FIG. Is a sectional view showing the structure of a protective film made of a plurality of layers obtained by performing the coating and drying of the protective film material stacked a plurality of times. 1, 2 ... transparent substrate, 3 ... sealing material, 4 ... liquid crystal, 5 ... color filter, 6 ... protective film, 6a ... projection, 7, 9 ... transparent electrode, 8, 10 ... orientation Film 15 (15 ₁ , 15 ₂ , 15 ₃ , 15 ₄ , 15 _n ) ... letterpress, 61 ... 1st protective film, 62 ... 2nd protective film, 63 ... 3rd Protective film of the 64th layer Protective film of the 4th layer 6n Protective film of the nth layer.

Claims (4)

(57) [Claims] 1. A method for manufacturing a liquid crystal display element, comprising: forming a film having a predetermined thickness on an inner surface of a transparent substrate constituting a liquid crystal display element. The baking step is performed a plurality of times while sequentially reducing the application area thereof, whereby the film having the predetermined thickness is formed by a plurality of layers having different sizes. Production method. 2. The method according to claim 1, wherein the step of applying, drying and firing the film material is a step of applying the film material multiple times, followed by drying and firing. Method for manufacturing a liquid crystal display element. 3. The step of applying, drying and baking the film material is a step of coating the film material a plurality of times, leaving the film material to stand at room temperature, and then drying and baking. The method for manufacturing a liquid crystal display device according to claim 1. 4. The method according to claim 1, wherein the coating of the film material is performed by a printing method using a relief printing plate, and the size of the relief printing plate is sequentially reduced to sequentially reduce the application area. A method for manufacturing a liquid crystal display device according to any one of the above.