JPH03200217A - Production of liquid crystal display element - Google Patents

Abstract

PURPOSE:To obtain flat films which are free from undulations on the surface by applying materials for films wet on wet plural times on a transparent substrate, then drying the coatings to form the films. CONSTITUTION:The material for the protective films is immediately applied wet on wet twice by a printing method on the transparent substrate 1 to obtain the protective film 21' of the 1st layer in a semi-liquid state. The film is in succession rested at room temp. in this state to obtain the protective film 21'' having the flattened surface. The material for the protective films is immediately applied wet on wet twice by the similar printing method on the protective film 21 of the 1st layer after curing by predrying, thereby the 2nd layer in a semi-liquid state is obtd. The films are rested in this state at room temp., by which the protective film 22'' having the flattened surface is obtd. The protective film 22'' is thereafter predried to be cured, by which the solid protective film 22 of the 2nd layer is obtd. The protective film 20s of the two-layered structure having excellent flatness are obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a liquid crystal display element used in a liquid crystal television or the like, and in particular, an alignment film is formed on the inner surface of a transparent substrate constituting the liquid crystal display element. , relates to improvements in methods for forming films such as insulating films and protective films.

[Traditional techniques]

The color liquid crystal display element has -M as shown in FIG.
A pair of transparent substrates 1.2 are arranged facing each other at a predetermined interval with a sealing material 3 in between, and a liquid crystal 4 is sealed in a sealed space formed by the transparent substrates 1.2 and the sealing material 3.

On the inner surface of one transparent substrate 1, there are a plurality of color filters 5 of red, green, blue, etc. extending in one direction (in FIG. 3, the horizontal direction parallel to the plane of the paper) and perpendicular to that direction. They are arranged alternately in the direction (in FIG. 3, the direction perpendicular to the plane of the paper). The entire surface of these color filters 5 is
It is covered with a protective film 6 made of resin such as polyimide, on which a plurality of transparent electrodes 7 made of an ITO film or the like extending in the same direction as the color filter 5 are arranged at regular intervals in a direction perpendicular to that direction. It is set up. Furthermore, the top thereof is covered with an alignment film 8, and this alignment film 8 is in direct contact with the liquid crystal 4.

Further, on the inner surface of the other transparent substrate 2, a plurality of transparent electrodes 9 made of ITO film or the like extending in a direction perpendicular 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, and this alignment film 10 is in direct contact with the liquid crystal 4.

The color liquid crystal display element having the above structure has a transparent substrate 1.2.
Films such as a protective film 6 and alignment films 8 and 10 are formed on the inner surface of the substrate. As an example of a method for forming these films, a process for forming a protective film 6 for a color filter will be described below.

First, one transparent substrate 1 on which a color filter 5 is formed
A material that will become the protective film 6 is applied thereon by a normal printing method. In the above printing method, for example, as shown in FIG. Letterpress printing plate 1 provided on the surface
This is done by attaching it to the surface of the transparent substrate 1 and printing it on the color filter 5 of the transparent substrate 1 placed on the moving stage 16. Once the protective film material is applied onto the color filter 5 in this way, it is pre-dried and cured to form a solid protective film 6.
can be obtained.

[Problem to be solved by the invention]

In the conventional method for manufacturing a liquid crystal display element described above, when a material with high viscosity is used as the material for the protective film, the transparent substrate I
When the protective film material is printed on the protective film material, undulations in film thickness as shown in FIG. 6 occur on the surface of the film, and these undulations form stripes 17 as shown in FIG. 5 on the transparent substrate 1. Thereafter, even when the protective film 6 is formed by pre-drying and curing the film with such stripes 17, the above-mentioned stripes remain as they are, so when the finally completed liquid crystal display element is turned on, , the above stripes result from non-uniform liquid crystal layer thickness, and this difference in liquid crystal layer thickness results in a difference in transmitted light intensity.
Therefore, there was a problem in that the film was visible to the naked eye as it was.

Such problems occur not only in the above-mentioned protective film 6 but also in various films such as insulating films and alignment films formed on the inner surface of the transparent substrate of the liquid crystal display element.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a method for manufacturing a liquid crystal display element that can obtain a flat film without waviness on the surface.

(Means for Solving the Problems) The present invention provides a method for manufacturing a liquid crystal display element that includes a step of forming a film on the inner surface of a transparent substrate constituting the liquid crystal display element, in which a film material is applied multiple times on the transparent substrate. The film is characterized in that the film is formed by applying multiple layers and then drying them.

Further, the method is characterized in that the film is formed by coating the film material on the transparent substrate multiple times, leaving it at room temperature, and then drying it.

Further, the method is characterized in that a film consisting of multiple layers is formed by performing the film forming step multiple times on the transparent substrate.

[For production]

When the film material is applied multiple times before drying, the surface flatness of the applied film becomes better than when it is applied only once, and the resulting film hardens during subsequent drying. The surface of the film also has improved flatness.

If the film material is left at room temperature after being applied multiple times, the film will be left in a fluid state before it hardens, so the high parts of the film will flow towards the low parts.
Therefore, the difference in the height of the surface waviness becomes smaller, and a film that is flatter than the above case can be obtained.

Even if the above coating and drying process (or coating, leaving at room temperature, and drying) is repeated multiple times, a flat film with little waviness can be obtained, and by adjusting the number of repetitions, any desired film can be obtained. Thickness can be obtained.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1(a) to 1(f) are cross-sectional views showing the process of forming a protective film for a color filter, which is the main part of the manufacturing process of an embodiment of the present invention.

In this embodiment, as shown in FIG. 1(a), first, as shown in FIG. The protective film material is immediately coated twice using the printing method shown in Figure 3 to obtain a semi-liquid first layer protective film 21'.

Since the protective film material is applied twice before it dries, the surface of the film becomes flatter compared to the conventional case where it is applied only once.

Next, by leaving this state at room temperature for, for example, 5 minutes or more, a protective film 21" whose surface is further flattened as shown in FIG. 1(b) is obtained. In this way, the surface of the film is flattened. This is because the membrane is left in a semi-liquid state at room temperature, so the higher undulations on the membrane surface begin to flow towards the lower undulations, reducing the difference in height between the undulations on the surface. Considering these effects, as a material for protective film,
Materials that flow easily, specifically materials with low surface tension such as calpitol-based and cellosolve-based solvents, are desirable, and materials that do not have a very high viscosity, such as 2
It is desirable to have a viscosity of about 0 to 1000 cp.

Thereafter, the protective film 21'' is pre-dried and cured to obtain a solid first layer protective film 21 as shown in FIG. 1(C).The thickness of this protective film 21 is as follows: The thickness is reduced by about 20 to 30% compared to the thickness of the protective film 21'' before curing, and the flatness of the film surface is further improved. Note that the above-mentioned preliminary drying is desirably carried out at about 40 to 150°C for about 1 to 30 minutes.

Next, a second protective film is formed on the first protective film 21 by applying the same method as the method for forming the first protective film 21. That is, first, as shown in FIG. 1(d), a protective film material is immediately coated twice on the cured first layer protective film 21 by the same printing method as above. By doing so, a second protective film 22' which is still in a semi-liquid state is obtained. Subsequently, by leaving this state at room temperature, a protective film 22'' whose surface is further flattened is obtained as shown in FIG. 1(e).

Thereafter, the protective film 22# is pre-dried and cured to obtain a solid second-layer protective film 22 as shown in FIG. 1(f).

Through the above steps, the protective film 20 having a two-layer structure of the first protective film 21 and the second protective film 22 is formed.

According to this embodiment, in addition to immediately applying the protective film material twice as described above, the material is allowed to stand at room temperature before it hardens, and these steps are repeated twice.
Since the process is repeated several times, it is possible to obtain a protective film 20 having a two-layer structure with excellent flatness. Even if an attempt was made to measure the surface waviness (film thickness variation) of the protective film 20 obtained in this example using a film thickness meter, the surface was so flat that measurement was impossible. Specifically, Table 1 shows that when comparing the surface conditions between the conventional case where the coating is applied only once and the case where the coating is applied twice immediately as in this example, the results are clearly shown in Table 1. As shown, it was found that the present example was superior in both "dispersion" and "waviness width". In particular, in the case of this example, the undulation width could be suppressed to a very small value of 100 to 200 people. In addition, "undulation width" is
It refers to the difference in height between the highest peak and the lowest valley of the waviness, and "variation" refers to the variation in in-plane film thickness, where the waviness width is X and the standard of film thickness distribution. When the deviation is σ, it is expressed as (3σ/x)Xioo [%].

Table 1 Next, FIG. 2 is a sectional view showing the structure of a protective film obtained according to another embodiment of the present invention.

In the above example, the process consisting of two consecutive applications of the protective film material, standing at room temperature, and drying was repeated twice, but in this example, the same protective film material as in the above example was used. The process consisting of two consecutive coatings, standing at room temperature, and drying is repeated n times (n≧3).

In this embodiment, the first protective film 31, the second
Protective layer 8I film 32,..., protective film 3 for nth layer
A protective film 30 having an n-layer structure made of n is obtained.

According to this example, a protective film with even better flatness can be obtained, and by appropriately setting the number of times the above steps of coating, leaving at room temperature, and drying can be repeated, any film thickness can be obtained. Obtainable.

In each of the above embodiments, the protective film material was applied two times in succession, but it may be applied three or more times, and the flatness improves as the number of times increases.

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

〔Effect of the invention〕

According to the present invention, since the material for the film is applied multiple times in an uncured state and then dried, it is possible to form a film with extremely excellent flatness.

Furthermore, if the coating is applied several times in succession and then left uncured at room temperature, the flatness can be further improved.

In addition, even better flatness can be obtained by repeating the process of continuous coating and drying (or continuous coating, leaving at room temperature, and drying) several times, and by adjusting the number of times. It is also possible to obtain any film thickness.

[Brief explanation of drawings]

FIGS. 1(a) to (f) are cross-sectional views showing the process of forming a protective film for a color filter, which is the main part of the manufacturing process of one embodiment of the present invention. FIG. 2 is another embodiment of the present invention. Figure 3 is a cross-sectional view showing the structure of a general color liquid crystal display element, Figure 4 is a diagram showing the process of applying a protective film using a printing method, Figure 5 is a cross-sectional view showing the structure of the protective film obtained by 6 is a plan view showing stripes on the substrate surface obtained by the conventional method of forming a protective film, and FIG. 6 is an enlarged sectional view taken along the line AA in FIG. 4 showing undulations on the film surface. DESCRIPTION OF SYMBOLS 1... Transparent substrate, 20... Protective film with two-layer structure, 21... First-layer protective film, 22... Second-layer protective film, 30... N-layer structure Protective film, 31... First layer protective film, 32... Second layer protective film, 33... Third layer protective film, 3n... Nth layer protective film .

Claims (3)

[Claims] (1) In a method for manufacturing a liquid crystal display element, which includes a step of forming a film on the inner surface of a transparent substrate constituting the liquid crystal display element, the film material is coated multiple times on the transparent substrate and then dried. A method for manufacturing a liquid crystal display element, the method comprising forming a film. (2) A method for manufacturing a liquid crystal display element, which includes a step of forming a film on the inner surface of a transparent substrate constituting the liquid crystal display element, wherein a film material is coated on the transparent substrate multiple times and then left at room temperature; A method for manufacturing a liquid crystal display element, characterized in that the film is formed by subsequent drying. (3) A method for manufacturing a liquid crystal display element, characterized in that a film consisting of multiple layers is formed by repeating the film forming step according to claim 1 or 2 a plurality of times.