Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified... – Alignment layer of specified composition
Reexamination Certificate
2001-12-26
2004-05-25
Hampton-Hightower, P. (Department: 1711)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
Alignment layer of specified composition
C428S001260, C428S473500, C528S125000, C528S128000, C528S170000, C528S172000, C528S173000, C528S174000, C528S179000, C528S183000, C528S185000, C528S220000, C528S188000, C528S229000, C528S350000, C528S353000
Reexamination Certificate
active
06740371
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel diaminobenzene derivative, a polyimide synthesized by using the compound as one of stating materials, and a liquid crystal alignment film containing the polyimide. More particularly, it relates to a diamine having a specific structure, which is industrially readily producible, a polyimide employing it, and a liquid crystal alignment film. The polyimide synthesized by using the diamine of the present invention, is particularly useful for an alignment film of a liquid crystal display device.
BACKGROUND ART
Heretofore, polyimides have been widely used as protecting materials or insulating materials in the electric and electronic fields, by virtue of high mechanical strength, heat resistance and solvent resistance, as their characteristics. However, developments in the electric and electronic fields in recent years have been remarkable, and increasingly high properties have been required also for materials to be used. Especially in the application to alignment films for liquid crystal display devices, polyimides have been mainly employed because of the uniformity and durability of the coating film surface. However, in an attempt for high densification and high performance of liquid crystal displays, the surface properties of polyimide coating films have become important, and it has become necessary to impart a new property which conventional polyimides do not have.
A liquid crystal display device is a display device utilizing an electro-optical change of liquid crystal and has undergone a remarkable development as a display device for various displays in recent years in view of the characteristics such that it is small in size and light in weight as a device and its power consumption is small. Especially, a twisted nematic type (TN-type) electric field effect liquid crystal display device is a typical example, wherein nematic liquid crystal having positive dielectric anisotropy is employed so that liquid crystal molecules are aligned in parallel with a substrate at the interface of each of a pair of mutually opposing electrode substrates, and the two substrates are combined so that the directions for alignment of liquid crystal molecules are orthogonal to each other.
In such a TN-type liquid crystal display device, it is important that long axis directions of liquid crystal molecules are aligned uniformly in parallel with the substrate surface and further that the liquid crystal molecules are aligned with a certain inclined alignment angle (hereinafter referred to as a tilt angle) against the substrate. As typical methods for aligning liquid crystal molecules in such a manner, two methods have been known heretofore.
The first method is a method which comprises vapor depositing an inorganic substance such as silicon oxide from an oblique direction to a substrate to form an inorganic film on the substrate, so that the liquid crystal molecules are aligned in the direction of vapor deposition. This method is not industrially efficient, although uniform alignment with a constant tilt angle can be obtained.
The second method is a method which comprises forming an organic coating film on a substrate surface, and rubbing its surface in a predetermined direction with a cloth of e.g. cotton, nylon or polyester, so that liquid crystal molecules are aligned in the rubbing direction. By this method, constant alignment can be obtained relatively easily, and industrially, this method is primarily employed. As the organic film, polyvinyl alcohol, polyoxyethylene, polyamide or polyimide may, for example, be mentioned. However, from the viewpoint of the chemical stability, thermal stability, etc., polyimide is most commonly employed.
In the field of liquid crystal alignment films, it has been difficult to obtain a high tilt angle constantly by the method of rubbing an organic film such as polyimide. As a means to solve such difficulty, JP-A-62-297819 proposes a treating agent for liquid crystal alignment made of a mixture of a long chain alkyl compound with a polyimide precursor. Further, JP-A-64-25126 discloses a treating agent for liquid crystal alignment made of a polyimide using, as a starting material, a diamine having an alkyl group. Thus, many attempts have been made to increase the tilt angle of liquid crystal by introducing an alkyl group into polyimide, and it has been made possible to increase the tilt angle.
In recent years, there have been remarkable developments in the TN display device, and many new properties are now required also for a liquid crystal alignment film. Among them, it has been increasingly important to satisfy stabilization of the tilt angle and improvement in the uniformity of alignment simultaneously, from the viewpoint of improvement of the essential properties of the liquid crystal alignment film. As is evident also from JP-A-64-25126, an alkyl diamine which has been heretofore been known and mainly used, is characterized in that an alkyl group is connected to a phenylene diamine structure. However, if a conventional alkyl group-containing diamine is employed, there has been a problem that when a polyimide is to be synthesized, the alkyl group acts as a steric hindrance, whereby the reactivity tends to be low, and it takes time for polymerization, or in some cases, polymerization does not proceed substantially. Taking time for the polymerization is problematic from the viewpoint of the industrial production, and the low polymerization reactivity is problematic from the viewpoint of the durability as an alignment film of polyimide. Further, when copolymerization with another diamine is carried out, such a low reactivity brings about a difference in the reaction rate. The resulting polyimide is not necessarily uniform form the viewpoint of the uniformity of the repeating units. Consequently, when it is made into a liquid crystal alignment film, even if a desired tilt angle may be obtained, the film has not necessarily been satisfactory from the viewpoint of the uniformity of liquid crystal alignment.
These problems are extremely important subjects to be solved to further improve the properties of a high quality, high precision liquid crystal display device represented by a future TN device. Namely, it has been desired to develop an alkyl diamine having an excellent reactivity, a polyimide containing it as a constituting element and a polyimide liquid crystal orientation film, which contribute to the solution of such problems.
DISCLOSURE OF THE INVENTION
The present invention has been made under the above circumstances. The present inventors have conducted extensive studies in detail and systematically to accomplish the above object, and as a result, have completed the present invention.
Namely, the present invention relates to a diaminobenzene derivative represented by the general formula (1):
(wherein each of X and P which are independent of each other, is a single bond or a bivalent organic group selected from —O—, —COO—, —OCO—, —CONH— and —NHCO—, Q is a C
1-22
straight chain alkyl group or straight chain fluoroalkyl group, a is an integer of from 1 to 4 and represents the number of substituents, R is a substituent selected from fluorine, a methyl group and a trifluoromethyl group, and b is an integer of from 0 to 4 and represents the number of substituents).
Further, the present invention relates to a polyimide obtained by reacting a diamine containing at least 1 mol % of a diaminobenzene derivative represented by the general formula (1):
(wherein each of X and P which are independent of each other, is a single bond or a bivalent organic group selected from —O—, —COO—, —OCO—, —CONH— and —NHCO—, Q is a C
1-22
straight chain alkyl group or straight chain fluoroalkyl group, a is an integer of from 1 to 4 and represents the number of substituents, R is a substituent selected from fluorine, a methyl group and a trifluoromethyl group, and b is an integer of from 0 to 4 and represents the number of substituents), with at least one compound selected from a tetracarboxylic dianhydride and its derivatives, to obt
Endou Hideyuki
Fukuro Hiroyoshi
Hosaka Kazuyoshi
Isogai Hideyuki
Nawata Hideyuki
Hampton-Hightower P.
Nissan Chemical Industries Ltd.
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