Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-11-05
2001-05-22
Hampton-Hightower, P. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S026000, C528S043000, C528S172000, C528S173000, C528S183000, C528S188000, C528S220000, C528S229000, C528S350000, C528S353000, C428S001100, C428S001200, C428S001230, C428S001260
Reexamination Certificate
active
06235867
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a liquid crystal-aligning agent used in production of liquid crystal display devices. More particularly, the present invention relates to a liquid crystal-aligning agent capable of providing a liquid crystal display device having a high pretilt angle stability.
BACKGROUND ART
Liquid crystal display devices are currently in wide use as a thin display. Liquid crystal display devices of general use are a twisted nematic (TN) type and a super twisted nematic (STN) type. In producing these liquid crystal display devices, as disclosed in JP-B-62-38689 an alignment layer is necessary for allowing a liquid crystal interposed between two substrates with transparent electrodes, to align in a particular direction relative to the substrates. Further in the liquid crystal display devices of TN type and STN type, the liquid crystal must be aligned in inclination, i.e. at a pretilt angle relative to the substrate surfaces. This needs to be achieved by the liquid crystal-aligning agent used. The pretilt angle is required to be 4 to 8° in, for example, the STN type. As the liquid crystal-aligning agent capable of achieving such a high pretilt angle, there are mentioned a polyimide precursor solution as described in JP-A-1-177514 and a soluble polyimide solution as described in JP-A-3-261915. In the liquid crystal display devices produced using such a liquid crystal-aligning agent, however, there are problems that the pretilt angle is not sufficiently stable and decreases in a high-temperature environment of 80° C. or higher, etc., inviting poor display.
As a different method for achieving a high pretilt angle, there is introduction of siloxane structure as described in JP-A-3-164714. In this method, however, introduction of a siloxane structure to a high degree makes bad the alignment of the liquid crystal and, therefore, in some cases the siloxane structure can not be introduced in an amount necessary to obtain a sufficient pretilt angle.
As liquid crystal display devices have come to possess improved properties in recent years, it has become necessary that materials for the alignment layer possess more properties than before. Specifically, the materials for the alignment layer must give a stable pretilt angle as mentioned above and have good electrical properties and, in the production of liquid crystal devices, must show uniform film formability, anti-rubbing property, etc. Further, since a lower temperature has come to be employed in production of liquid crystal display devices in recent years, the materials for the alignment layer must show the above-mentioned properties at levels equal to or higher than the past levels even when a firing temperature lower than 200° C. is employed.
DISCLOSURE OF THE INVENTION
The present invention relates to a liquid crystal-aligning agent which overcomes the above-mentioned problems of conventional liquid crystal-aligning agents and which is capable of providing a liquid crystal display device having a high pretilt angle stability.
That is, the present invention provides a liquid crystal-aligning agent comprising, as the resin component, a polyimide precursor containing a chemical structure represented by the following formula (1):
Preferred embodiments of the present invention include the above liquid crystal-aligning agent wherein the polyimide precursor is a polyamic acid, and the above liquid crystal-aligning agent wherein the polyimide precursor is a polyamic acid ester.
The present invention further provides a liquid crystal-aligning agent comprising, as the essential components, the above polyimide precursor and a polyimide precursor represented by the following general formula (2):
(wherein Y is a tetravalent aliphatic group, Z is a bivalent aromatic group, and R is H or an alkyl group).
DETAILED DESCRIPTION OF THE INVENTION
The liquid crystal-aligning agent of the present invention comprising, as the resin component, a polyimide precursor containing a structure represented by the formula (1) can allow a liquid crystal to make good alignment and makes it possible to obtain a high pretilt angle.
The polyimide precursor containing a structure resented by the formula (1), used in the present invention can be obtained by reacting 1,4-bis(3-aminopropyldimethylsilyl)benzene with a tetracarboxylic acid dianhydride or the like in a polar solvent. A polyamic acid can be obtained when a tetracarboxylic acid dianhydride is used. A polyamic acid ester can be obtained when the polyamic acid is esterified or when the above reaction is conducted using a tetracarboxylic acid diester.
Examples of the tetracarboxylic acid dianhydride are pyromellitic acid dianhydride, 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, 3,3′,4,4′-benzophenonetetracarboxylic acid dianhydride, butanetetracarboxylic acid dianhydride, cyclobutanetetracarboxylic acid dianhydride, cyclopentanetetacarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, bicyclo[2,2,2]octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, and 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalenesuccinic acid dianhydride. The tetracarboxylic acid dianhydride, however, is not restricted to these examples.
The polyamic acid ester can be obtained by reacting a tetracarboxylic acid dianhydride with an alcohol (e.g. methanol, ethanol, 1-propanol or 2-propanol) to form a tetracarboxylic acid diester, and subjecting the diester to condensation under dehydration with a diamine, or by subjecting a polyamic acid to condensation under dehydration with an alcohol.
In producing the polyimide precursor containing a structure represented by the formula (1), used in the present invention, a diamine other than 1,4-bis(3-aminopropyldimethylsilyl)benzene may be used as long as the use does not impair the effect of the structure represented by the formula (1). Examples of the diamine are p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, 3,3′-dimethylbenzidine, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 1,3-(3-aminophenoxy)benzene, 1,3-(4-aminophenoxy)benzene, 1,4-(3-aminophenoxy)benzene, 1,4-(4-aminophenoxy)benzene, 4,4′-(4-aminophenoxy)biphenyl, 2,2-bis[4,4′-(4-aminophenoxy)phenyl]propane, 2,2-bis[4,4′-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4,4′-(4-aminophenoxy)phenyl]sulfone, 1,3-bis(4-aminophenoxy)-propane, 1,4-bis(4-aminophenoxy)butane, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,10-diaminodecane, 1,12-diaminododecane, 1,4-diaminocyclohexane, and 4,4′-diaminodicyclohexylmethane. The diamine is not restricted to these examples.
In the present invention, when the liquid crystal-aligning agent comprises, as the resin components, both of the polyimide precursor containing a structure represented by the formula (1) and the polyimide precursor represented by the general formula (2), very good electrical properties are obtained.
The polyimide precursor represented by the general formula (2), used in the present invention can be obtained by reacting an aliphatic tetracarboxylic acid dianhydride or the like with an aromatic diamine in a polar solvent. A polyamic acid can be obtained when an aliphatic tetracarboxylic acid dianhydride is used, and a polyamic acid ester can be obtained when the polyamic acid is esterified or when an aliphatic tetracarboxylic acid diester is used in the above reaction.
Examples of the aliphatic tetracarboxylic acid dianhydride used for obtaining the polyimide precursor represented by the general formula (2) used in the present invention are butanetetracarboxylic acid dianhydride, cyclobutanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic a
Eguchi Toshimasa
Takeda Toshiro
Hampton-Hightower P.
Smith , Gambrell & Russell, LLP
Sumitomo Bakelite Company Limited
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