Liquid crystal aligning agent and process for producing...

Compositions – Liquid crystal compositions – Containing nonchiral aligning agents

Reexamination Certificate

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Details

C428S001260, C428S001200

Reexamination Certificate

active

06224788

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal aligning agent and to a process for producing a liquid crystal alignment film using the same. More specifically, it relates to a liquid crystal aligning agent which is used for the formation of a liquid crystal alignment film and capable of having liquid crystal alignment properties by exposure to linearly polarized radiation without carrying out a rubbing treatment and to a process for producing a liquid crystal alignment film using the same.
2. Description of the Background
There have been known liquid crystal display devices having TN (twisted nematic) type and STN (super twisted nematic) type liquid crystal cells in which nematic liquid crystals having positive dielectric anisotropy are sandwiched between substrates provided with transparent electrodes having a liquid crystal alignment film and the major axis of a liquid crystal molecule is continuously twisted at an angle of 90° or more between the substrates.
Means for aligning liquid crystals in the above liquid crystal cell include a method (rubbing treatment) in which an organic film is formed on the surface of a substrate and the surface of the organic film is rubbed with a cloth of rayon or the like in one direction to provide liquid crystal alignment properties, a method in which silicon oxide is vapor deposited obliquely on the surface of a substrate, a method in which a monomolecular film having a long-chain alkyl group is formed by Langmuir-Blodgett's technique (LB technique), and the like. However, as the size of a substrate to be treated is restricted and the alignment uniformity of liquid crystals is unsatisfactory in these means, it is general that the alignment by rubbing of liquid crystals, which is advantageous in terms of treatment time and treatment cost, is industrially employed.
The alignment by rubbing of liquid crystals, however, has a problem that dust and static electricity are ready to be generated during the processing. When static electricity is generated, dust is adhered to the surface of the alignment film, thereby causing a display defect. In the case of a substrate having TFT (thin film transistor) devices, the circuit destruction of the TFT devices is caused by the generated static electricity, thereby reducing yield. Further, a liquid crystal display device whose pixel pattern will become finer and finer in the future has a problem in rubbing uniformity because the substrate has surface irregularities due to an increase in the density of pixels.
It is therefore an object of the present invention to provide a novel liquid crystal aligning agent.
It is another object of the present invention to provide a liquid crystal aligning agent of which the alignment of liquid crystals can be controlled with ease, and which does not produce static electricity and dust, can be mass-produced and is used to form a liquid crystal alignment film.
It is still another object of the present invention to provide a process for producing a liquid crystal alignment film using the liquid crystal aligning agent of the present invention.
Other objects and advantages of the present invention will become apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention can be attained by a liquid crystal aligning agent which is composed of a polymer comprising at least one moiety selected from the group consisting of a moiety represented by the following formula (1):
 —P
1
—CR
1
═CR
2
—CO—Q
1
—  (1)
wherein P
1
and Q
1
are independently a divalent organic group having an aromatic ring, and R
1
and R
2
are independently a hydrogen atom or an alkyl group,
a moiety represented by the following formula (2):
wherein P
2
is a monovalent organic group having an aromatic ring, Q
2
is a trivalent organic group having an aromatic ring, and R
3
and R
4
are independently a hydrogen atom or an alkyl group,
a moiety represented by the following formula (3):
P
3
—CR
5
═CR
6
—CO—Q
3
—  (3)
wherein P
3
is a monovalent organic group having an aromatic ring, Q
3
is a divalent organic group having an aromatic ring, and R
5
and R
6
are independently a hydrogen atom or an alkyl group,
a moiety represented by the following formula (4):
—P
4
—CR
7
═CR
8
—CO—Q
4
  (4)
wherein P
4
is a divalent organic group having an aromatic ring, Q
4
is a monovalent organic group having an aromatic ring, and R
7
and R
8
are independently a hydrogen atom or an alkyl group,
and a moiety represented by the following formula (5):
wherein P
5
is a trivalent organic group having an aromatic ring, Q
5
is a monovalent organic group having an aromatic ring, and R
9
and R
10
are independently a hydrogen atom or an alkyl group.
The present invention will be described in detail hereinafter.
Liquid Crystal Aligning Agent
The liquid crystal aligning agent of the present invention is composed of a polymer comprising a moiety represented by any one of the above formulas (1), (2), (3), (4) and (5). These moieties are sensitive to radiation. The term “sensitive” as used herein means that when the moiety is exposed to radiation, the energy level of the moiety is increased by a photochemical excitation and then the moiety releases its energy to return to a stable state.
The moieties represented by the above formulas (1), (2), (3), (4) and (5) are common in that they have a conjugated enone structure (to be referred to as “specific structure” hereinafter).
In the above formula (1), P
1
and Q
1
are independently a divalent organic group having an aromatic ring, preferably an organic group having 6 to 20 carbon atoms. The organic group may contain a halogen atom. Illustrative examples of the organic group include 1,2-phenylene group, 1,3-phenylene group, 1,4-phenylene group, 4,4′-biphenylene group and the like.
In the above formula (1), R
1
and R
2
are independently a hydrogen atom or an alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The alkyl group may be straight-chain or branched-chain. Illustrative examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, n-pentyl group, n-hexyl group and the like.
In the above formula (2), P
2
is a monovalent organic group having an aromatic ring, preferably an organic group having 6 to 20 carbon atoms. The organic group may contain a halogen atom. Illustrative examples of the organic group include 4-pentylphenyl group, 4-fluorophenyl group, 3,4-difluorophenyl group, 3,4,5-trifluorophenyl group, 4-octylphenyl group, 4-pentylbiphenyl group, 4-octylbiphenyl group, 4-fluorobiphenyl group, 3,4-difluorobiphenyl group, 3,4,5-trifluorobiphenyl group, 4-octyl-1-naphthyl group, 5-pentyl-1-naphthyl group, 6-octyl-2-naphthyl group, 9-anthracenyl group, 10-pentyl-9-anthracenyl group and the like.
In the above formula (2), Q
2
is a trivalent organic group having an aromatic ring, preferably an organic group having 6 to 20 carbon atoms. The organic group may contain a halogen atom. Illustrative examples of the organic group include groups represented by the following formulas.
In the above formula (2), R
3
and R
4
are independently a hydrogen atom or an alkyl group. Illustrative examples of the alkyl group are the same as those listed for R
1
and R
2
in the above formula (1).
In the above formula (3), P
3
is a monovalent organic group having an aromatic ring, preferably an organic group having 6 to 20 carbon atoms. The organic group may contain a halogen atom. Illustrative examples of the organic group are the same as those listed for P
2
in the above formula (2).
In the above formula (3), Q
3
is a divalent organic group having an aromatic ring, preferably an organic group having 6 to 20 carbon atoms. The organic group may contain a halogen atom. Illustrative examples of the organic group are the same as those listed for Q
1
in the above formula (1).

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