JP2524031B2 - Liquid crystal alignment film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. In particular, the present invention relates to a liquid crystal alignment film that greatly affects display characteristics.

[0002]

2. Description of the Related Art A liquid crystal display device is an indispensable technology as a man-machine interface.

One of the key technologies in the production of liquid crystal display devices is a technology for aligning liquid crystal molecules.

Conventionally, in the conventional process, at present, it is general to rub the polyimide alignment film with fibers such as rayon to stretch and orient the main chain (so-called rubbing operation). As the alignment film, a polyimide alignment film obtained by coating and condensing a polyamic acid obtained by polymerizing an acid anhydride having a skeleton of only aromatic and a diamine having a skeleton of mostly aromatic, or using a cycloaliphatic skeleton is used. A polyimide alignment film formed by applying a polyamic acid obtained by polymerizing an acid anhydride containing a group and a diamine whose skeleton is mostly aromatic and thermally reacting it is used ("New findings for pretilt generation and process stability assurance"). Fukuro Yuzen pp63 '91 September issue Nikkei Microdevices).

The alicyclic group is usually incorporated in the skeleton of an acid anhydride, and the alkyl group in the side chain, the fluoroalkyl group or the cyclohexane group, which more efficiently generates the pretilt of the liquid crystal molecule, is incorporated in the diamine. Incorporate in acid anhydride.

[0006]

Recently, liquid crystal display devices are required to have faster display response, and on the other hand, multi-gradation display is required as OA terminals.
This inevitably requires a technique for achieving more uniform liquid crystal display performance, which is large and requires a further improvement in the alignment technique of liquid crystal molecules. In the category of prior art,
Inevitably, the yield decreases.

[0007] Industrially, there is a social demand for further cost reduction, which requires improvement in production yield, which requires further improvement in alignment technology.

As described above, in the process, at present, it is general to rub the polyimide alignment film with fibers such as rayon to stretch and orient the main chain (so-called rubbing operation). At this time, the alignment film is greatly scraped, a large amount of scrap dust is generated, the scraping is remarkably caused locally, and the main chain is locally stretched largely. This affects the display and tends to reduce the production yield.

In a liquid crystal alignment film obtained by coating a polyamic acid solution prepared by polymerizing an acid anhydride having a skeleton containing an alicyclic group and a diamine having a skeleton of almost aromatic carboxylic acid and thermally reacting them,
The surface free energy tends to be slightly low, and the coating performance is somewhat difficult. Further, the film quality is soft, and moreover, it is susceptible to plastic deformation. That is, stretching of the main chain is relatively easy, but abrasion tends to occur.

The coating property is somewhat good in a liquid crystal alignment film formed by coating a polyamic acid solution prepared by polymerizing an acid anhydride having a skeleton of only aromatic and a diamine having a skeleton of almost aromatic and thermally reacting the solution. However, the film tends to be hard and brittle. This tends to suppress shaving, but also tends to cause local shaving and local stretching of the main chain. This directly leads to non-uniformity in the display.

At present, in the production of liquid crystal display devices, cleaning is often performed after rubbing in order to make the display uniform and improve the production yield. Up until now, organic cleaning using iso-propyl alcohol, etc. and CFC cleaning have been the mainstream, but in the future it is urgent to switch to cleaning using pure water from the perspective of global environmental issues and the Fire Service Act. Is.

Also in washing with water after rubbing, although depending on the average molecular weight, a polyamic acid solution prepared by polymerizing an acid anhydride having a skeleton containing an alicyclic group and a diamine having a skeleton containing almost all aromatic compounds is applied and subjected to a thermal reaction. In the liquid crystal alignment film thus formed,
Stains are likely to appear, and it is relatively difficult to get out in a liquid crystal alignment film formed by applying a polyamic acid solution prepared by polymerizing an acid anhydride having a skeleton of only aromatic and a diamine having a skeleton of mostly aromatic and thermally reacting. .

In any case, at present, there are advantages and disadvantages. In view of the above problems, it is an object of the present invention to provide a liquid crystal alignment film having an advantage in rubbing.

[0014]

In order to solve the above problems SUMMARY OF THE INVENTION The liquid crystal alignment film of the present invention, an acid anhydride skeleton composed of an aromatic only, Ri Do from the backbone is almost aromatic, fluorine atom
Yes polyamic acid obtained by polymerizing and no diamine organic group containing a child, an acid anhydride skeleton containing alicyclic, skeleton Ri is Do Most aromatic organic group containing a fluorine atom
Is no diamine solution was mixed with the polyamic acid obtained by polymerizing a coating, it is also of a ing by thermal reaction.

[0015]

[Action] The essence of the present invention, an acid anhydride skeleton composed of an aromatic only, Ri Do from the backbone is almost aromatic, fluorine atom
An acid anhydride nature of the alignment film obtained from the polyamic acid obtained by polymerizing and no diamine organic group, skeleton containing alicyclic containing, Ri Do Most aromatic skeleton, fluorine
Each of the properties of the alignment film obtained from a polyamic acid obtained by polymerizing a diamine having no atom-containing organic group is improved by mixing different ones.

[0016]

Embodiments of the present invention will be described below.

[0017] and (EXAMPLE 1) skeleton acid anhydride containing an alicyclic, skeleton Ri is Do Most aromatic, as polyamic acid solution prepared by polymerization of not having diamine organic group containing a fluorine atom, Nissan The product number SE-4110 polyamic acid solution was obtained from Kagaku Co., Ltd. An acid anhydride skeleton composed of an aromatic only skeleton Ri is Do Most aromatic organic group containing a fluorine atom Yes
As a polyamic acid solution obtained by polymerizing a diamine that does not exist, a product number PSI-A2204- from Nitrogen Petrochemical Co., Ltd.
An M01 polyamic acid solution was obtained. These were mixed so that the solid content concentration of the former and that of the latter were about 2: 8. After confirming that the mixture was uniformly mixed, printing was performed on the substrate. The total solid content concentration of this ink was about 5%. This was heated at 60 ° C. for 5 minutes and further heated at 250 ° C. for 30 minutes for condensation (referred to as polyimide C). When the smoothness of the resulting film surface was measured by a step meter (Taristep manufactured by Nippon Vacuum Co., Ltd.), it was relatively good.

A polyimide film obtained from only the SE-4110 polyamic acid solution is referred to as polyimide A,
A polyimide film obtained from only the PSI-A2204-M01 polyamic acid solution is referred to as polyimide B.

Rubbing treatment was carried out using rayon fibers as usual. Shavings were scarce and desirable. Next, cleaning after rubbing was performed using pure water and a cleaning machine. No inconvenience such as appearance of spots was observed.

For the purpose of making a super twisted nematic liquid crystal display device using this substrate, pre-tilt of nematic liquid crystal on this substrate, using this substrate, in an arrangement of liquid crystal molecules twisted by 240 °, , Stability of twist of liquid crystal molecules (referred to as d / p range in this field) was investigated. The pretilt angle was almost the same as that of the polyimide B, and the stability of twist was also the same as that of the polyimide B (usually, in the case of the polyimide B, the pretilt and twist stability were generally higher. From the point of, it is superior to polyimide A). That is,
In the case of this example, regarding pretilt and twist stability,
No special disadvantages will occur.

A panel was manufactured by a usual method and a predetermined nematic liquid crystal was injected. When viewing the display characteristics on a large number of panels, the rate of non-defective products improved, and the defects related to the rubbing operation drastically decreased.

[0022] and (Example 2) skeleton acid anhydride containing an alicyclic, skeleton Ri is Do Most aromatic, as polyamic acid solution prepared by polymerization of not having diamine organic group containing a fluorine atom, Nissan A product number SE-150 polyamic acid solution was obtained from Kagaku Co., Ltd. Has an acid anhydride skeleton composed of an aromatic only skeleton Ri is Do Most aromatic organic group containing a fluorine atom
As a polyamic acid solution obtained by polymerizing diamine with no diamine, product number PSI-A2001-from Nitrogen Petrochemical Co., Ltd.
An M01 polyamic acid solution was obtained. These were mixed so that the solid content concentration of the former and that of the latter were about 2: 8. After confirming that the mixture was uniformly mixed, printing was performed on the substrate. The total solid content concentration of this ink was about 5%. This was heated at 60 ° C. for 5 minutes and further heated at 250 ° C. for 30 minutes to be condensed (designated as polyimide F). When the smoothness of the resulting film surface was measured by a step meter (Taristep manufactured by Nippon Vacuum Co., Ltd.), it was relatively good.

A polyimide film obtained from only the SE-150 polyamic acid solution is referred to as polyimide D, and P
A polyimide film obtained from only the SI-A2001-M01 polyamic acid solution is referred to as polyimide E.

A rubbing treatment was carried out using rayon fibers as usual. Shavings were scarce and desirable. Next, cleaning after rubbing was performed using pure water and a cleaning machine. No inconvenience such as appearance of spots was observed.

For the purpose of making a super-twisted nematic liquid crystal display device using this substrate, pre-tilt of nematic liquid crystal on this substrate, using this substrate, an alignment of liquid crystal molecules twisted by 240 ° was used in advance. , Stability of twist of liquid crystal molecules (referred to as d / p range in this field) was investigated. The pretilt angle was almost the same as that of the polyimide E, and the stability of twist was also the same as that of the polyimide E (usually, in the case of the polyimide E, the pretilt and twist stability were From the point of, it is superior to polyimide D). That is,
In the case of this example, regarding pretilt and twist stability,
No special disadvantages will occur.

A panel was manufactured by a usual method and a predetermined nematic liquid crystal was injected. When viewing the display characteristics on a large number of panels, the rate of non-defective products improved, and the defects related to the rubbing operation drastically decreased.

[0027]

As described above, the present invention proposes an alignment film which is superior in the rubbing operation and greatly contributes to the industry.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshio Iwai 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yoshihiro Kimura 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (56) References Japanese Patent Laid-Open No. 1-180519 (JP, A)

Claims (1)

(57) [Claims] 1. An acid anhydride having a skeleton consisting of only aromatic compounds,
Skeleton Ri is Do Most aromatic, organic containing a fluorine atom
A polyamic acid obtained by polymerizing and no diamine group, and skeleton acid anhydride containing an alicyclic, Ri Do Most aromatic skeleton, Zia <br/> having no organic group containing a fluorine atom A liquid crystal alignment film formed by applying a solution in which a polyamic acid obtained by polymerizing min is mixed and thermally reacting.