GB2328947A

GB2328947A - Resin composition for liquid crystal aligning film

Info

Publication number: GB2328947A
Application number: GB9819051A
Authority: GB
Inventors: Shizuo Murata; Haruo Kato
Original assignee: Chisso Corp
Current assignee: JNC Corp
Priority date: 1997-09-05
Filing date: 1998-09-01
Publication date: 1999-03-10
Anticipated expiration: 2018-09-01
Also published as: GB2328947B; JP3918247B2; JPH1184392A; GB9819051D0

Abstract

There are provided a novel resin composition for a liquid crystal aligning film, a liquid crystal aligning film, a liquid crystal display, and liquid crystal display element using it for use in a ferroelectric liquid crystal display system by applying a polymer which contains a polyimide made of diamino compounds which contain at least one selected from 1,2-bis(4-aminophenyl)ethane and 4,4'-ethylene di-meta-toluidine, and tetracarboxylic dianhydrides including pyromellitic dianhydride as an essential component.

Description

DESCRIPTION Resin Composition for Liquid Crystal Aligning Film, Liquid Crystal Aligning Film, Liquid Crystal Display, and Liquid Crystal Display Element Technical Field This invention relates to a resin composition for a liquid crystal aligning film which can improve display properties, a liquid crystal aligning film using the said composition, a liquid crystal display, and a liquid crystal display element, by improving the first stage orientation condition of a liquid crystal molecule in a ferroelectric liquid crystal element.

Background Art A nematic liquid crystal mode has been used in the conventional liquid crystal display element as a mainstream. There are a twisted nematic (TN type) liquid crystal element and a super twisted birefringence effect (SBE type) liquid crystal display element as a liquid crystal display element using the above-mentioned nematic liquid crystal mode. Regarding to TN type liquid crystal element, there is a fault that a drive margin becomes narrow and it stops obtaining sufficient contrast as multiplexisation of a drive system proceeds. Moreover, when a SBE type liquid crystal display element which is an improved TN type liquid crystal display element, using a twisted large angle, is used for a large capacity display, there is a fault that a contrast is reduced or a response speed becomes slow.

Then, to remove these kind of fault, a liquid crystal display element which used a chiral smectic C liquid crystal, i.e., a ferroelectric liquid crystal, was proposed by N.A. Clark and S.T. Lagerwall in 1980 (US Patent 4367924; Japanese Patent Application Laid-open No. 56-107216).

This liquid crystal display element is a liquid crystal display element using a turning force which makes the polarity of spontaneous polarisation of a ferroelectric liquid crystal, and the polarity of an electric field adjust unlikely to the display element of a nematic liquid crystal using the electric field effect of utilising the dielectric anisotropy of the conventional liquid crystal molecule. This liquid crystal display element can be characterised by twin stability, memory property, a high-speed response, a wide view angle, etc. That is, if a ferroelectric liquid crystal is injected into a cell whose gap was kept thin as shown in Figure 1, then it being influenced by the substrate boundary surface, the spiral structure of a ferroelectric liquid crystal will come loose.

And, bistability is produced with a mixture of a domain which is stabilized by a liquid crystal moleculell's inclininig only to angle of 17(+0) to the smectic layer normal line 12, and a stabilized domain by its inclining only to 18(-0) at a reverse direction.

By applying an electric field 16 to the ferroelectric liquid crystal in this cell, the direction of the liquid crystal molecule 11 and its spontaneous polarisation 15 can be arranged uniformly. And, switching which changes the orientation of the liquid crystal molecule 11 to another condition becomes freely done by changing the polarity of the electric field 16.

As a birefringence light varies in connection with this switching action, the ferroelectric liquid crystal in a cell can control the transmitted light by sandwiching a cell between polarisers. Furthermore, even if it stops impression of an electric field 16, since orientation of the liquid crystal molecule 11 is maintained according to the orientation regulation power of a boundary surface at the condition before an electric field impression stoppage, a memory effect can also be obtained. Moreover, since spontaneous polarisation and the electric field of a liquid crystal effect the time necessary for switching directly, it has 1/1000 or less of a high-speed response to a nematic liquid crystal display element, and thereby, it can be displayed with high-speed.

Then, application to a liquid crystal display device of a high-resolution and large display capacitance or a space modulation element which can convert light into memory process with high speed is vigorously studied by utilising the superior characteristic of this ferroelectric liquid crystal.

However, there were many problems also in Clark and Lagerwall type liquid crystal display element. First, as compared with the usual nematic liquid crystal, the liquid crystal of the chiral smectic C phase which shows a ferroelectricity has a low symmetry of a molecule, and since the crystallinity was furthermore high, there was a fault that it was difficult to make the orientation uniformly.

That is, it has been considered by the model of an original ferroelectric liquid crystal that the layer structure of smectic C phase take a structure perpendicular to the substrate called the book shelf type which is shown in Figure 2 wherein 9 and 10 are substrates, 13 is a smectic layer, and 12 is a smectic layer normal line.

However, in fact, when the orientation method by the conventional rubbing was employed, the layer structure was analysed using the small angle scattering method of X-ray to take a structure which bent to a "v" character shape called chevron shown in Figure 3, wherein 9 and 10 are substrates, 13 is a smectic layer, and 14 is a joint part of the chevron structures.

[T.P. Rieker, N.A. Clark, et al. Phys. Rev. Lett., 59, p 2658 (1987)].

Since the direction where this layer bends into the character is not uniform, but it forms in the direction of 2 kinds, a domain or a linear defect is generated at the point where layers of 2 directions contact, and the direction of layers is the same, but orientation condition differs slightly.

Furthermore, the orientation which was made a uniaxial orientation treatment of the upper and lower substrates in the same the direction is obtained by rubbing in the same direction.

However, if the case which a pre-tilt angle is generated by rubbing is considered, 2 domains where the bending direction of a smectic layer differs to the direction of the pre-tilt angle generated by uniaxial orientation treatment as shown in Figure 4 exist. Kanbe et al. has named this C1 and C2 from the relation of a pre-tilt angle.

[Ferroelectrics 114, p3 (1991)].

Meanwhile, in C1 and C2 orientations, as shown in Figure 5, there exist two orientation. One is uniform (U) orientation which shows an extinction position, and the other is twisted (T) orientation which does not show an extinction position. That is, in the ferroelectric liquid crystal cell of a parallel rubbing, there exist 4 orientation conditions of C1U, C1T, C2U and C2T from which an optical characteristic differs.

[Proc. Japan Display '92 Hiroshima, p519 (1992)].

As ClT and C2T do not have an extinction position, they do not suit to the orientation of a high contrast essentially, but since ClU and C2U have an extinction position, they may be able to realise a high contrast.

ClU and C2U orientations have their characteristics in each, therefore the display mode, device composition, and the drive system which employed each feature are reported.

The device using ClU orientation is reported in Japanese Patent Application Laid-open No. Hei 1-59389. And, as a device using C2U orientation, there are Japanese Patent Application Laid-open No. Hei 62-56933 and "Joers/Alvey" Ferroelectric Multiplexing Scheme: [Ferroelectric 122, p63 (1991)3 etc.

In the device using C2U orientation, though it was reported that'a satisfactory contrast is obtained by "Joers/Alvey Ferroelectric Multiplexing Scheme, when a liquid crystal cell is actually produced, a high contrast is not obtained easily.

As the largest cause, it is mentioned ununiform orientation of a liquid crystal cell influences the contrast. Since to obtain the liquid crystal cell which has a high contrast, it is important that C2U orientation is uniformly obtained in a whole surface.

In Japanese Patent Application Laid-open No. Hei 7-175068, it is described that uniform C2U orientation was obtained by the employment of a polyimide film as an aligning film which was prepared by a condensation reaction of 2,2- bis[4 - (4aminophenoxy) phenyl] propane as a main amine component and 1, 2, 4, 5-benzene tetracarboxylic dianhydride as a main carboxylic acid component.

However, when a device was actually produced, an orientation defect was generated slightly in the surface. Even when it performed a voltage impression process, a whole surface did not become uniform completely and the defect of orientation remained.

The subject which this invention tends to solve is to supply the resin composition for liquid crystal aligning films which is characterised by the bending direction of a smectic layer being the same as the direction of a uniaxial orientation process by the reduction of the orientation defect produced due to the layer structure represented by the chevron structure which a ferroelectric liquid crystal holds, the liquid crystal aligning film formed therewith, liquid crystal display and liquid crystal display element using this.

Summary of Invention These inventors researched zealously in view of the problem of the prior art to complete this invention by finding out a fact that it is very effective to use a specific polyimide as a liquid crystal aligning film to solve the problem.

That is, the first of this invention relates to a resin composition for polyimide liquid crystal aligning film, wherein the diamino compound contains at least one kind of 1, 2bis(4-amino phenyl)ethane or 4,4'-ethylene-dimeta-toluidine and tetracarboxylic dianhydrides including pyromellitic dianhydride as an essential component which comprises the polyimide. The second and the following of this invention relate to a liquid crystal aligning film using this resin composition, a liquid crystal display and a liquid crystal display element using this liquid crystal aligning film.

Disclosure of Invention The preferable mode of the resin composition for liquid crystal aligning film of this invention relates to a polyimide which comprise 15 to 80 mol * (preferably 30 to 80 mol %) of at least a compound selected from 1, 2- bis (4-amino phenyl) ethane and 4, 4'- ethylene di- meta-toluidine among the diamino compounds, and 40 mol % or more of pyromellitic dianhydride among the tetracarboxylic dianhydride.

The more preferable mode of the resin composition for liquid crystal aligning film of this invention relates to a polyimide which comprises 15 to 80 mol % (preferably 30 to 80 mol %) of at least a compound selected from 1, 2- bis (4-amino phenyl) ethane and 4, 4'- ethylene di- meta-toluidine among the diamino compounds and the rest of the diamines is 2,2-bis(4-(4- aminophenoxy)phenyl)propane, and 40 mol % or more of pyromellitic dianhydride among the tetracarboxylic dianhydride.

Brief Description of Drawings [FIGURE 1] It is a figure showing the principle of operation of a ferroelectric liquid crystal.

[FIGURE 2] It is a figure showing the book shelf layer structure of a ferroelectric liquid crystal cell.

(FIGURE 3] It is a figure showing the chevron layer structure of a ferroelectric cell.

[FIGURE 4] It is a model figure of C1 orientation and C2 orientation in the chevron layer structure of chiral smectic C phase.

[FIGURE 5] They are a figure (TW) showing a twisted orientation and a figure (U) of a uniform orientation, in the chevron layer structure of a ferroelectric liquid crystal cell.

[FIGURE 6] It is a sectional drawing showing a ferroelectric liquid crystal cell composition.

Detailed Description of the Preferred Embodiments Though at least one of the diamines selected from 1, 2- bis (4-amino phenyl)ethane and 4, 4'- ethylene di- meta-toluidine are used as a diamine for this invention, the following diamino compounds can also be used together. However, the sum of those amines are preferably 85 mol % or less (more preferably 70 mol % or less).

2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, m-phenylene diamine, p- phenylene diamine, m-xylylene diamine, p-xylylene diamine, 2,2'-diamino diphenyl propane, 4, 4'- diamino diphenylether, 4,4'- diamino diphenylmethane, benzidine, 1, 1-bis (4- (4-aminophenoxy)phenyl) cyclohexane, 1,1-bis(4-(4-aminophenoxy)phenyl)-4-methylcyclohexane, 1,1-bis(4-(4-aminophenoxy)phenyl)-4-ethylcyclohexane, 1,1-bis(4-(4-aminophenoxy)phenyl)-4-propylcyclohexane, 1,1-bis(4-(4-aminophenoxy)phenyl)-4-butylcyclohexane, 1,1-bis(4-(4-aminophenoxy)phenyl]-4-pentylcyclohexane, bis(4-(4-aminobenzyl)phenyl)methane, 1,1-bis(4-(4-aminobenzyl)phenylicyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-methylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-ethylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl]-4-n-propylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-n-butylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl]-4-n-pentylcyclohexane, 4,4'-para-aminophenoxy-biphenyl, 1, 1-bis (4- (4-aminobenzyl)phenyl) cyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-methylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-ethylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-propylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-butylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-pentylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-hexylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-heptylcyclohexane, 1,1-bis(4-(4-aminobenzyl)phenyl)-4-octylcyclohexane, 1, 1-bis (4- (4-aminobenzyl) phenyl) methane.

These compounds can be used with single, or even if with combination of 2 or more compounds. Moreover, if the purpose of this invention is attainable, it will not be limited to these compounds.

As a tetracarboxylic dianhydride, pyromellitic dianhydride is an essential component, but other aromatic tetracarboxylic dianhydride, alicyclic tetracarboxylic dianhydride, aliphatic tetracarboxylic dianhydride can be used together.

However, preferably, the amounts of those compounds are 60mol% or less.

The following compounds can be specifically enumerated.

Aliphatic and alicyclic tetracarboxylic dianhydrides such as ethylene tetracarboxylic dianhydride, decahydronaphthalene-1, 4, 5, 8-tetra carboxylic dianhydride, 4,8-dimethyl-1, 2, 3, 5, 6, 7-hexahydro naphthalene-l, 2, 5 6-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, butane-1,2,3,4-tetracarboxylic dianhydride, bicyclo (2,2,2)-oct(7)-ene-2,3,5,6-tetracarboxylic dianhydride, clohexane-1,2,5,6-tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, 3,3'-bicyclo hexyl-l, 1', 2, 2'-tetra carboxylic dianhydride, 2,3,5-tricarboxy cyclopentyl acetic acid dianhydride, 5-(2,5-dioxo tetrahydro fural) -3-methyl-3-cyclohexene-1, 2-dicarboxylic dianhydride, 1,3, 3a, 4,5, 9b-hexahydro-5-tetrahydro-2, 5-dioxo-3-furanyl) - naphtho[1,2,-c]-furan-1,3-dione, 3,5,6-tri carboxy norbornane-2-acetic dianhydride, 2, 3, 4, 5-tetrahydrofurane tetracarboxylic dianhydride, aromatic tetra carboxylic dianhydrides such as 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'- biphenyl sulphone tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 3,3',4,4'-biphenylether tetracarboxylic dianhydride, 3,3',4,4'-dimethyl diphenyl silane tetracarboxylic dianhydride, 3,31,4, 4'-tetraphenyl silane tetracarboxylic dianhydride, 1,2,3,4-furan tetracarboxylic dianhydride, 4,4' -bis (3, 4-dicarboxy phenoxy) diphenyl sulfide dianhydride, 4,4' -bis (3, 4-dicarboxy phenoxy)diphenyl sulphone dianhydride, 4,4'- bis (3,4-dicarboxy phenoxy)diphenyl propane dianhydride, 3, 3', 4, 4'- perfluoro pylidene diphthalic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, bis(phthalic acid)phenyl sulfine oxide dianhydride, p-phenylene-bis(triphenyl phthalic acid) dianhydride, m-phenylene-bis(triphenyl phthalic acid) dianhydride, bis (triphenylphthalic acid)-4,4'-diphenylether dianhydride, bis(triphenyl phthalic acid)-4,4'-diphenylmethane dianhydride, pyromellitic dianhydride, can be mentioned.

These compounds can be used with single, or even if with combination of 2 or more compounds.

Moreover, in the liquid crystal aligning film material of this invention, an amino silicon compound or a diamino silicon compound can be employed to improve adhesion to a substrate.

As an amino silicon compound, para aminophenyl trimethoxy silane, para aminophenyl triethoxy silane, methamino phenyl trimethoxy silane, methamino phenyl triethoxy silane, amino propyl trimethoxy silane, amino propyl triethoxy silane, etc. are mentioned.

As a diamino silicon compound, 1,3-bis(3-amino propyl)-1, 1,3,3- tetraphenyl disiloxane, 1,3-bis(3-amino propyl)1,1,3,3- tetramethyl disiloxane, 1, 3-bis (4-amino butyl)-1, 1,3,3- tetramethyl disiloxane, etc. are mentioned.

As a polar organic solvent used for performing reaction to obtain a polymer employed as a resin component of a liquid crystal aligning film material of this invention, the following is enumerated. N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrolidone, dimethyl sulfoxide, hexamethyl phosphoramide, phenol, tetrahydrofurane, dioxane, (gamma)butyrolactone, etc.

2 or more kinds of solvent described above may be used together.

Moreover, solvents for general purpose, such as 2-alkoxyl ethanol, carbitol , toluene, and xylene, can also be used together with these polar organic solvents in the range which does not make the solubility of a polyimide resin or its precursor reduce.

Furthermore, it is also possible to mix and use polymers, such as a polyamic acid or a polyimide which has an different composition with the polymers of this invention, polyester, polyamide, and acrylics to the extent (preferably less than 50 mol % or less) which does not deteriorate the physical properties of this polymer.

The polyimide liquid crystal aligning film material of this invention can be obtained by conversion polyimide precursor with heating at 100-400 t and/or chemical treatment by dehydrating agents such as acetic anhydride into polyimide.

Electrodes are provided in the side which the liquid crystal on a liquid crystal display faces, and the liquid crystal aligning film obtained from a liquid crystal aligning film resin composition is formed on the substrates and the electrodes, to form a liquid crystal display element.

The formation on the liquid crystal substrate of the polyimide layer which consists of a liquid crystal aligning film resin composition of this invention, is performed by drying or dehydrating the above-mentioned polyimide precursor to form closed rings inside of the molecule, that is, to convert the precursor into a polyimide layer, after applying the above mentioned resin composition for liquid crystal aligning film on the glass substrate on which transparent electrodes, such as ITO (Indium Tin Oxide), were formed, for example. As a method for coating, printing method, dip coating spray method, etc. are used. Dehydration temperature for ring formation can be arbitrarily chosen in 100-400 t, preferably in 150-330"C.

Moreover, the heating time is 1 minute to 6 hours, preferably, 1 minute to 3 hours.

To improve adhesion of the polyimide layer of this aligning film with a glass substrate, a coupling agent, such as a silane coupling agent or a titanium coupling agent, may be applied together between the two layers.

The rate of imidation of the polyimide layer formed thus is 50 % or more, which is used as a liquid crystal aligning film by rubbing treatment of that surface. A liquid crystal display element can be obtained by a well-known method using the liquid crystal display substrate which has a liquid crystal aligning film.

This invention is not limited with the kind of liquid crystal, so far as the liquid crystal which has a ferroelectricity is used as a liquid crystal for a liquid crystal display element, however, satisfactory orientation can also be obtained with the liquid crystal which has an antiferroelectricity.

When the resin composition for a liquid crystal aligning film of this invention is used as a liquid crystal aligning film and a liquid crystal element for a ferroelectric liquid crystal device, good orientation having few orientation defect can be obtained.

It is not certain why the orientation defect of a ferroelectric liquid crystal decreases when this aligning film is used, however, it is considered that the liquid crystal itself does not prevent from forming of layer structure spontaneously since the interaction of the polymer and a liquid crystal molecule is weak (an anchoring energy is small), that is, the boundary surface interaction of a liquid crystal and an aligning film is weak.

Example Hereinafter, this invention is explained through Examples, the technical range of this invention is not limited by these Examples.

The liquid crystal cell used for these Examples was prepared by the following. As shown in Figure 6, after a transparent electrode with a thickness of 50-5000 angstroms, preferably 100-2000 angstroms is formed on a glass substrate, a polyimide film of thickness of approximately 600 angstroms was formed on it by spin-coating a polyamic acid solution diluted at about 2 % by weight and temporary baking at 80 OC for 5 minutes, subsequently baking at 220 t for 30 minutes. After this, the polyimide aligning film was formed by rubbing of the surface of the polyimide film using a cloth of a rayon type (YA-18R, a product of Yoshikawa Processing co.) and a uniaxial orientation treatment was carried out.

Subsequently, the upper and the lower substrates were adhered together by sealing agent made from an epoxy resin at intervals of 2 micrometers with a silica spacer, to make the aligning films oppose mutually keeping the direction of rubbing almost the same.

Next, a liquid crystal which shows chiral smectic C phase was heated and injected between the space of the upper and the lower substrates to prepare a liquid crystal cell.

Furthermore, a liquid crystal display device was prepared by making a polarisation axes situated in the upper and the lower cells cross almost orthogonally, and by making one of the optical axes of the polarization plates be nearly in accord with any one polarisation axis of the liquid crystal of the cell.

The mode of orientation was investigated on the liquid crystal display devices which inj ected CS-1014 or CS-1022, the products made by Chisso Corp., as a liquid crystal which shows chiral smectic C phase.

Synthetic example 1 To 100ml four necked flask equipped with a thermometer, a stirrer, a raw material insertion opening, and a nitrogen gas inlet, 1.203g (5.665 mmol) of 1,2-bis(4-aminophenyl)ethane, 2,2357g (5.665 mmol) of 2,2-bis[4-(4-aminophenoxy)phenyl] propane, 94g of dehydrated NMP were introduced and stirred to dissolve under dry nitrogen atmosphere. Keeping the temperature of the reaction system at 20 t or less, 2.4715g (11.33mmol) of pyromellitic dianhydrides was added and reacted for 15 hours at room temperature to obtain polymer A solution, the solid concentration being 6% by weight, and the molar ratio of 1,2bis (4-amino phenyl) ethane, 2,2-bis [4- (4-aminophenoxy) phenyl)propane and pyromellitic dianhydride being 5:5:10. The viscosity of this solution was lOOmPa * s (E type viscositymeter was used at t) and weight average molecular weight was 98,000 (measured by a gel permeation chromatography, hereinafter the same method was employed.).

Synthetic example 2 To 100ml four necked flask equipped with a thermometer, a stirrer, a raw material insertion opening and a nitrogen gas inlet, 1.2283g(5.786mmol) of 1,2-bis(4-amino phenyl)ethane, 2.3751g(5.786mmol) of 2,2- bis[4-(4-aminophenoxy)phenyl] propane and 94g of dehydrated NMP were introduced and stirred to dissolve under dry nitrogen atmosphere. Keeping the temperature of the reaction system at 20 t or less, 1.2620g (5.786mmol) of pyromellitic dianhydride and 1.1347g (5.786mmol) of cyclobutane tetracarboxylic dianhydride were added and reacted for 15 hours at room temperature to obtain polymer B solution, the solid concentration being 6% by weight, and the molar ratio of l,2-bis(4-amino phenyl)ethane, 2,2-bis [4- (4-aminophenoxy)phenyl]propane, pyromellitic dianhydride and cyclobutane tetracarboxylic dianhydride being 5:5:5:5. The viscosity of this solution was 300mPa * S (E type viscosity meter was used at 25 t) and weight average molecular weight was 166,000.

Synthetic example 3 Reaction was carried out by the same method as synthetic example 2 except using 4,4'-ethylene di-meta-toluidine instead of l,2-bis(4-aminophenyl)ethane to obtain polymer C solution, the molar ratio of 4,4'-ethylene di- meta-toluidine, 2,2 bis[4-(4-amino phenoxy)phenyl]propane, pyromellitic dianhydride and cyclobutane tetracarboxylic dianhydride being 5:5:5:5, and the solid content being 6% by weight. The viscosity of this solution was 250mPa * s (E type viscosity meter was used at 25 "C) and weight average molecular weight was 145,000.

Synthetic example 4 Reaction was carried out by the same method as synthetic example 1 except using 4, 4'-diamino diphenylmethane instead of 1,2-bisl4-aminophenyl)ethane to obtain polymer D solution, the molar ratio of 4,4'-diamino diphenylmethane, 2,2- bis[4-(4amino phenoxy)phenyl]propane and pyromellitic dianhydride and being 5:5:10, and the solid content being 6% by weight. The viscosity of this solution was ll0mPa * s (E type viscositymeter was used at 25 t) and weight average molecular weight was 115,000.

Furthermore, reaction was carried out by the same method as synthetic example 2 except using 4,4'-diamino diphenylmethane instead of 1,2-bis(4-aminophenyl)ethane to obtain polymer E solution, the molar ratio of 4, 4'-diamino diphenylmethane, 2,2- bis[4-(4-aminophenoxy)phenyl]propane, pyromellitic dianhydride and cyclobutane tetracarboxylic dianhydride being 5:5:5:5, and the solid content being 6% by weight. The viscosity of this solution was 280mPa * s (E type viscosity meter was used at 25 t) and weight average molecular weight was 140,000.

Moreover, reaction was carried out by the same method as synthetic example 2 except using 1, 2-bis (4-aminophenyl) ethane as the whole diamine to obtain polymer F solution, the molar ratio of 1,2-bis(4-aminophenyl)ethane, pyromellitic dianhydride and cyclobutane tetracarboxylic dianhydride being 10:5:5, and the solid content being 6% by weight. The viscosity of this solution was 52mPa * s (E type viscosity meter was used at 25 t) and weight average molecular weight was 85,000.

Reaction was carried out by the same method as synthetic example 2 except using 2,2-bis[4-(4-amino phenoxy)phenyl] propane as the whole diamine to obtain polymer G solution, the molar ratio of 2,2-bis[4-(4-amino phenoxy)phenyl] propane, pyromellitic dianhydride and cyclobutane tetracarboxylic dianhydride being 10:5:5, and the solid content being 6% by weight. The viscosity of this solution was 60mPa * s (E type viscosity meter was used at 25 t) and weight average molecular weight was 98,000.

The results obtained were shown in Table 1, wherein "the ratio of C2tJ to overall orientation" means the average value of the ratio of the C2U orientation of 4 points chosen randomly in the same cell by measuring the ratio of the area where C2U orientation was existing to that of the whole orientation in the visual field which enlarged the produced cell to 100 ID=

TABLE 1

NAME OF FILM LIQUID CRYSTAL:CS-1014 LIQUID CRYSTAL:CS-1022 SAMPLE THICKNESS DEGREE OF ORIENTATION OF LIQUID RATIO OF C2U (%) TO DEGREE OF ORIENTATION OF LIQUID RATIO OF C2U (%) ( ) CRYSTAL TOTAL ORIENTATION CRYSTAL TO TOTAL ORIENTATION POLYMER A 385 GOOD: Uniform orientation of C2U 100 GOOD: Uniform orientation of C2U 100 is obtained on the whole surface. is obtained on the whole surface.

POLYMER B 403 GOOD: Uniform orientation of C2U 100 GOOD:A slight orientation of C2T 98 is obtained on the whole surface. is observed but uniform orientation of C2U is obtained when voltage is charged on cell.

POLYMER C 390 GOOD: A slight orientation of C2T 96 GOOD: A partly mixed orientation 85 is observed but uniform of C2T and C1T is observed but orientation of C2U is obtained uniform orientation of C2U is when voltage is charged on cell. obtained when voltage is charged on cell.

POLYMER D 415 32 POOR: Mixed orientation of C2U, 20 C2T, C1U and C1T is observed.

POLYMER E 398 POOR: Mixed orientation of C2U, 40 POOR: Mixed orientation of C2U, 29 C2T, C1U and C1T is observed. C2T, C1U and C1T is observed.

POLYMER F 405 POOR: Orientation is disordered C2U orientation POOR: Orientation is disordered C2U orientation such an extent that C2 cannot be such an extent that C2 cannot be orientation cannot be recognized. orientation cannot be recognized. discriminated from that of C1. discriminated from that of C1.

POLYMER G 412 POOR: Mixed orientation of C2U, 50 POOR: Mixed orientation of C2U, 35 C2T, C1U and C1T is observed and C2T, C1U and C1T is observed and uniform orientation of C2U cannot uniform orientation of C2U cannot be observed though voltage is be observed though voltage is charged. charged.

A display element having few orientation defect has come to be obtained from these experiments by using the resin compositions for liquid crystal aligning films of the synthetic examples 1-3.

Industrial Applicability The aligning film using the resin composition for liquid crystal aligning films of this invention can reduce the orientation defect produced since it has the layer structure represented by the chevron structure which a ferroelectric liquid crystal used to have. Therefore the liquid crystal display device using the aligning film of this invention is a high-resolution ferroelectric liquid crystal display element, and can be applied to the liquid crystal display device of the terminal of an OA apparatus etc.

Claims

CLAIMS 1. A resin composition for a liquid crystal aligning film for use in a ferroelectric liquid crystal display system which comprises a polyimide characterized by preparation from diamino compounds which contain at least one selected from 1,2-bis (4-aminophenyl) ethane and 4,4'-ethylene di-meta-toluidine, and tetracarboxylic dianhydrides including pyromellitic dianhydride as an essential component.
2. A resin composition for a liquid crystal aligning film according to Claim 1 wherein diamino compounds constituting the polyimide include 15 to 80 mol % of at least one selected from 1,2-bis (4-aminophenyl) ethane and 4,4 '-ethylene di-metatoluidine, and tetracarboxylic dianhydrides include 40 mol% or more of pyromellitic dianhydride.
3. A resin composition for a liquid crystal aligning film according to Claim 1 wherein diamino compounds constituting the polyimide include 15 to 80 mol% of at least one selected from 1, 2-bis (4-aminophenyl) ethane and 4,4 '-ethylene di-metatoluidine, and also include 2,2-bis(4-(4aminophenoxy)phenyl)propane as a residual amine, and tetracarboxylic dianhydrides include 40 mol% or more of pyromellitic dianhydride.
4. A liquid crystal aligning film formed of the resin composition for liquid crystal aligning film described in either of Claims 1, 2 or 3.
5. A liquid crystal display having the liquid crystal aligning film described in Claim 4.
6. A liquid crystal display element which is characterised by a ferroelectric liquid crystal being interposed between the substrates which have a pair of transparent electrodes, on whose surface, the aligning film described in Claim 4 was placed.
7. A ferroelectric liquid crystal display element which have a ferroelectric liquid crystal interposed between substrates having a pair of transparent electrodes, whose surface, the aligning film described in Claim 4 is placed on and also the uniaxial orientation treatment is applied to, characterised in that the liquid crystal have a smectic layer sturucture, whose bending direction is identical with that of uniaxial orientation treatment of aligning film.