Diamino compounds, polyamic acids, polyimides, liquid...

Details Diamino compounds, polyamic acids, polyimides, liquid... Diamino compounds, polyamic acids, polyimides, liquid...

1999-10-22

2001-05-29

Thomas, Alexander S. (Department: 1772)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

Alignment layer of specified composition

C428S001230, C428S001270, C428S473500, C548S548000, C548S547000, C528S353000

Reexamination Certificate

active

06238752

ABSTRACT:

TECHNICAL FIELD
This invention relates to a diamino compound having a photosensitive group in the side chain thereof, a polyamic acid and a photo crosslinking polyimide, a liquid crystal aligning film using said polyimide, and a liquid crystal display device using said aligning film.
BACKGROUND ART
Recently, there have been demands for the display of word processors, notebook computers, etc. to have a lighter weight and a thinner thickness and to consume less electric power, and a superior liquid crystal display device is expected to be developed for a flat display satisfying these requirements. A liquid crystal display device is provided with a liquid crystal aligning film having a predetermined pretilt angle so as to align liquid crystal molecules to a given direction. As a method for preparing such aligning films, a rubbing process wherein a thin film of a polymeric compound such as a polyimide formed on a substrate is rubbed toward a certain direction with a cloth such as rayon, a process wherein silicon dioxide is subjected to oblique evaporation, etc. are known.
However, although the rubbing process has been widely applied in the industrial field as a convenient and inexpensive process, it has the problems of the formation of dusts, the generation of static electricity and the like.
The oblique evaporation process costs too much to be scaled up.
Under these circumstances, a photo-orientation process has recently attracted attention of the industry. In such a process for the preparation of an aligning film according to this photo-orientation method, a thin film of a photosensitive polymeric compound is formed on a substrate and a polarized ultraviolet light or a laser light is irradiated thereto, whereby only the photosensitive groups in line with the irradiated polarized light may photochemically react to develop anisotropy on the aligning film and align liquid crystal molecules. This process can provide the advantages of no generation of static electricity or no contamination of impurities because the other members are not in contact with the thin film coated over the substrate.
Several photo-aligning films utilizing photodimerization of a polarized light irradiated to polyvinyl cinnamate and derivatives thereof are disclosed, for example, in M. Schadt et al., Jpn. J. Appl. Phys., 31, 2155 (1992) or Japanese Patent No. 2608661. However, these aligning films have the drawbacks of a low heat stability, an inferior retention of shape and an easily turbulent alignment of liquid crystal.
Vinyl polymers having arylmaleimide residues in the side chain thereof are disclosed as a photosensitive group having a higher sensitivity in Japanese Patent Publication No. 13198/1976 and so on, but no examples of utilizing them as an aligning film for liquid crystal display device is disclosed therein.
The present inventors have made earnest studies, and as a result, have found out that a polyimide having an &bgr;,&bgr;-substituted maleimide group in the side chain thereof may be rapidly dimerized in the side chain thereof at a high sensitivity, and that the crosslinked film is excellent in a heat stability and a retention of shape and also shows a favorable alignment of liquid crystal, upon which this invention has been completed.
DISCLOSURE OF INVENTION
More specifically, the constitution of this invention is as described below.
(1) A diamino compound represented by the formula [1]:
in which G
1
is a trivalent organic group of 2-20 carbon atoms, G
2
is independently a single bond, —COO—, —OCO—, —NHO—, —CONH—, —O—, —S—, or —CO—, G
3
is a single bond or an alkylene group of 1-20 carbon atoms, X and Y are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, or an alkyl group, a haloalkyl group, an alkoxy group or a haloalkoxy group, each alkyl or alkoxy group having 1-12 carbon atoms, or a cycloalkyl group of 3-8 carbon atoms or a trans-4-alkylcyclohexyl group of 9-14 carbon atoms, and m is an integer of 0-3.
(2) A polyamic acid which comprises a structural unit represented by the formula [2]:
in which G
1
, G
2
, G
3
, X and Y are as defined above, G
5
is independently a single bond, or a bond of —CH
2
—, —O—, —CO—, —SO
2
—, —C(CH
3
)
2
— or —C(CF
3
)
2
—, and rings A and B are each independently a benzene ring or a cyclohexane ring; and has a logarithmic viscosity number of 0.1-5.0 dl/g as measured in N-methyl-2-pyrrolidone at the concentration of 0.5 g/dl at the temperature of 30±0.01° C.
(3) A polyamic acid which comprises a structural unit represented by the above formula [2] and a structural unit represented by the formula [3]:
in which G
6
is independently a single bond, or a bond of —CH
2
—, —O—, —CO—, —SO
2
—, —C(CH
3
)
2
— or —C(CF
3
)
2
—, rings A and B are each independently a benzene ring or a cyclohexane ring, and G
4
is a divalent organic group of 2-36 carbon atoms or a polysiloxane group of the formula [4]:
in which R
99
is an alkylene group of 1-6 carbon atoms or a phenylene group, R
100
independently may be the same or different and is an alkyl group of 1-3 carbon atoms or a phenyl group, and a, b, and c are 0 or a positive number with a relation of 1≦a+b+c ≦100; and has a logarithmic viscosity number of 0.1-5.0 dl/g as measured in N-methyl-2-pyrrolidone at the concentration of 0.5 g/dl at the temperature of 30±0.01° C.
(4) A polyimide obtained by imidation of the polyamic acid as disclosed in the above (2) or (3) and subsequent irradiation of a polarized ultraviolet light.
(5) An aligning film for a liquid crystal display device using a thin film comprising the polyimide as disclosed in the above (4).
(6) An aligning film for a liquid crystal display device which is obtained by imidation of the polyamic acid as disclosed in the above (2) or (3), subsequent irradiation of a polarized ultraviolet light and the resulting photoreaction of a portion of the polyimide side chains.
(7) A liquid crystal display device which comprises an aligning film for a liquid crystal display device as disclosed in the above (4)-(6).
(8) A liquid crystal display device as disclosed in the above (7) wherein a liquid crystal composition comprises at least one compound selected from the group consisting of the compounds of the formulae [5], [6] and [7]:
in which R
1
is an alkyl group of 1-10 carbon atoms wherein any non-adjacent methylene groups may be substituted with —O— or —CH═CH— and any hydrogen atoms may be substituted with fluorine atoms; R
2
is a fluorine atom, a chlorine atom, —OCF
3
, —OCF
2
H, —CF
3
, —CF
2
H, —CFH
2
, —OCF
2
CF
2
H or —OCF
2
CFHCF
3
; L
1
and L
2
are each independently a hydrogen atom or a fluorine atom; Z
1
and Z
2
are each independently 1,2-ethylene, 1,4-butylene, —COO—, —CF
2
O—, —OCF
2
—, —CH=CH— or a single bond; ring C is trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or 1,4-phenylene wherein a hydrogen atom may be substituted with a fluorine atom; and ring D is trans-1,4-cyclohexylene or 1,4-phenylene wherein a hydrogen atom may be substituted with a fluorine atom.
(9) A liquid crystal display device as disclosed in the above (7) wherein a liquid crystal composition comprises at least one compound selected from the group consisting of the compounds of the formulae [8] and [9]:
in which R
3
and R
5
are each independently an alkyl group of 1-10 carbon atoms wherein any non-adjacent methylene groups may be substituted with —O— or —CH═CH— and any hydrogen atoms may be substituted with fluorine atoms; R
4
is a group of —CN or —C≡C—CN; ring E is trans-1,4-cyclohexylene, 1,4-phenylene, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl; ring F is trans-1,4-cyclohexylene, 1,4-phenylene wherein a hydrogen atom may be substituted with a fluorine atom, or pyrimidine-2,5-diyl; ring G is trans-1,4-cyclohexylene or 1,4-phenylene; Z
3
is 1,2-ethylene, —COO—, or a single bond; L
3
, L
4
and L
5
are each independently a hydrogen atom or a fluorine atom; and e, f a

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