JPH0237324A - Production of polyimide oriented film - Google Patents

Abstract

PURPOSE:To obtain the title film for a liquid crystal display which is capable of rapidly conditioning and applying and has a high uniformity by forming the oriented film on a substrate plate by applying a solution contg. 9.6-28.8wt.% of cellosolve (CnH2n+10 CH2CH2OH) in a polyimide solution or its precursor solution of polyamic acid, on the substrate plate. CONSTITUTION:The oriented film is formed on the substrate plate by applying the solution contg. 9.6-28.8wt.% of the cellosolve (2-alkyl ethanol) in the polyimide solution or its precursor solution of polyamic acid. Namely, the surface tension between the polyimide solution and ITO is reduced by incorporating the cellosolve in the polyimide solution, whereby the polyimide and the ITO are liable to stick with each other, and the flatness of a coated film and the film quality of the polyimide are improved. Thus, the polyimide oriented film with excellent uniformity of film thickness and film quality is formed, even in the case of forming the oriented film on a TFT and a colored filter with many ruggedness, and a liquid crystal device with high production yield is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for producing a polyimide alignment film for producing high-quality liquid crystal display devices with good yield.

(B) Prior Art Alignment films for liquid crystal display devices are classified into inorganic alignment films and organic alignment films depending on the materials used.

At present, inorganic alignment films are used only for special purposes due to their mass-producibility.

Examples of a-machine alignment film materials include PVA, polyamide, polyimide, polyimideamide, etc., and as L, polymers made of compounds that are rigid at the molecular level, such as polyimide with high heat resistance, are often used.

Methods for producing liquid crystal alignment films include deimping, spinner coating, printing, and the like, and currently, the printing and tilling method is most commonly used from the viewpoint of mass production.

On the other hand, the display quality of liquid crystal display devices is progressing year by year, particularly in the direction of higher pixel density and larger screens, and higher yields are required.

Thin film transistor (TPT) is a method to improve display quality.
active matrix type liquid crystal panels using
The method of lining for Wl't and parts has become mainstream, and in particular, the uniformity of the inner film quality in these two methods is an important point to obtain uniform display and high yield. It has become.

In the case of a normal TN type without active elements, the voltage applied during driving is not affected by the unevenness of the film quality of the alignment film and is applied as an effective value to the liquid crystal, but in the case of an active matrix type using TPT, In this case, the voltage applied to the liquid crystal varies greatly depending on the properties of the alignment film, and with conventional alignment films using polyimide, the image on the liquid crystal display device may become non-uniform, resulting in low yields.

Furthermore, in the case of the STN type, which is greatly influenced by the thickness and quality of the alignment film, if the thickness of the polyimide alignment film is uneven, the alignment is affected, resulting in a low yield.

Conventionally, in order to improve the non-uniformity of polyimide alignment films,
Adding an epoxy compound to the precursor polyamic acid has been considered (Japanese Patent Publication No. 62-56495). However, it is difficult to uniformly mix two types of viscous polymers in a solution, and the adjustment is difficult. The drawback was that it was time consuming.

(c) Problems to be Solved by the Invention In view of the above-mentioned points, the present invention provides a method for obtaining a polyimide alignment film for liquid crystal displays that can be quickly adjusted and coated and has high uniformity.

(d) Means for Solving the Problems The present invention is a method for manufacturing a liquid crystal display device in which a polyimide alignment film is molded onto a substrate on which electrodes are formed.
The alignment film is formed on the substrate using a solution containing 9.6 to 28.8% of n+10CH2CH20H).

(e) By adding action ethyl cellosolve, polyimide solution and I
The surface tension with TO decreases, making it easier to number each other,
The flatness of the coating film is improved, and the quality of the polyimide film is improved.

(f) Example When forming an alignment film in the present invention, N-methyl-2- and lolidone (NMP) were added to a commercially available polyamine chloride solution.
A printing liquid is prepared by mixing a diluted solution with a butyl cellosolve solution.

For example, in an active matrix color liquid crystal panel having a TPT, a liquid crystal alignment film is formed on a substrate having a TPT or a color filter.

With respect to the direction perpendicular to the surface of the substrate on which the alignment film is formed, a step difference of several μn1 occurs in the substrate for TF'r and color filters.

In the above board, polyamic acid solution (Nissan Chemical
Sunever 130) 6wt% (hereinafter abbreviated as %),
NMP 74.8%, Butyl Cell Solsolve 19.2%
The adjustment liquid mixed in the ratio of 150 ~
The polyimide alignment film polymerized and cured at 200"C had good liquid crystal alignment and film thickness uniformity.

Similarly, polyamic acid solution (Nissan Chemical Sunever 2)
170) 6%, NMP 73.6%, and butyl cellosolve 20.4%.The polyimide alignment film is printed by offset printing and polymerized and cured at 150-200"C, which improves the alignment of liquid crystals and the film. The thickness uniformity was good.

On a similar substrate, a polyimide solution (Japan Synthetic Rubber
JIB) 5%, γ-butyrolactam (2-pyrrolidone) 85.5%, and butyl cellosolve 9.5% were mixed at a ratio of 9.5%, and offset printing was carried out at 130-180°C.
The polyimide alignment film polymerized and cured in the above had good liquid crystal alignment and uniformity of film I\.

Similarly, polyimide solution (Japan Synthetic Rubber JIA) 5%
On the other hand, a polyimide alignment film obtained by offset printing a conditioning liquid mixed at a ratio of 63.8% of 2-pyrrolidone and 31.2% of butyl cellosolve, and polymerized and cured at 130 to 180'C has excellent liquid crystal alignment and film thickness. The uniformity was good.

The preferred amount of butyl cellosolve to be added to the diluted polyimide solution differs depending on the type of polyimide solution, but if the amount of butyl cellosolve added exceeds 35%, polyimide oriented film fibers will begin to precipitate in the diluted solution, making it difficult to add. The amount is about 60%
In this case, the average film thickness of the liquid crystal alignment film, the variation in film thickness, and the yield of the liquid crystal panel when printed on the ITO substrate using the Kenpo method, in which the uniformity of the alignment film was significantly impaired due to the polyimide M fibers. Table 1 shows a comparison with the conventional method.

table Table 2 shows the effect on the precipitation of carbon.

Table 2 Table 1 shows the results when an alignment film was formed using a 6% polyamic acid solution (Sunever 130) to which NMP and butyl cellosolve were added, and σ is the thickness of the formed polyimide alignment film. It is the standard deviation.

Table 1 shows that the alignment film of the present invention has higher uniformity than the conventional alignment film to which butyl cellosolve is not added.

In addition, Table 2 shows the amount of butyl cellosolve added to the yield of liquid crystal panels, variations in film thickness, and polyimide Table 2 shows the amount of butyl cellosolve added to 6% polyamic acid solution (Nissan Chemical Sunever 130) and N
The results are for a mixed solution of M P and butyl cellosolve, but polyimide solutions (J IB, J IA) 5% and 2
- Regarding the mixture of pyrrolidone and butylcellosolve,
The yield was highest when the amount of butyl cellosolve added was around 20 wt%.

From Table 2, as the amount of butyl cellosolve added increases, the yield of liquid crystal flannel increases up to 20%, but when it reaches 35% to 10% or more, polyimide in 1t^ increases. It can be seen that the alignment film quality f deteriorates due to precipitation.

(g) Effects of the invention As explained above, according to the present invention, T
Even on PT or color filters, alignment film 1rJ,
Furthermore, it is possible to form a boronimide alignment film with excellent uniformity in alignment film quality, and to provide a method for assembling a liquid crystal display device with a high yield.

Claims (1)

[Claims] 1) In a method for producing a polyimide alignment film in which a polyimide alignment film is formed on a substrate on which an electrode is formed, cell solve (2-Al
1. A method for producing a polyimide alignment film, which comprises forming an alignment film on a substrate using a solution containing 9.6 to 28.8 wt % of oxyethanol. 2) The method for producing a polyimide alignment film according to claim 1, wherein the cellosolve is any one of methyl cellosolve, ethyl cellosolve, and butyl cellosolve.