JP3081952B2 - Method for processing alignment film for liquid crystal display element and method for manufacturing liquid crystal display element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating an alignment film for a liquid crystal display device, a method for producing a liquid crystal display device, and a liquid crystal display device produced by this method with very little display unevenness. More specifically, a method for treating an alignment film for a liquid crystal display element, comprising irradiating soft X-rays in a gas after performing an alignment treatment on the alignment film used for the liquid crystal display element, and performing an alignment treatment of the alignment film Irradiating soft X-rays in a gas after the process to reduce the unevenness of display of the liquid crystal display element to improve the quality and the yield thereof, and the liquid crystal manufactured by the method. It relates to a display element.

[0002]

2. Description of the Related Art Liquid crystal display devices have a low driving voltage, are light in weight and have high image quality, and are therefore being actively introduced into the field of OA equipment such as personal computers and word processors. Since liquid crystal display elements used for these applications are required to display characters and drawings, it is inevitable to produce large-screen, multi-pixel, high-definition liquid crystal display elements with no display defects. A method is needed. As the liquid crystal display element, a twisted nematic mode in which the arrangement direction of nematic liquid crystal molecules is twisted by 90 degrees on the surface of a pair of upper and lower electrode substrates is generally used. The twist angle of the above liquid crystal molecules is 180
An object having a size as large as 300 degrees is also known as a super twisted nematic mode. In recent years, in order to perform matrix display, color display, or the like, an active matrix type twist using an MIM (metal-insulating phase-metal) element for turning on / off a large number of pixel electrodes or a TFT (field-effect thin film transistor) element The development of nematic mode liquid crystal display devices has become active.

[0003]

As an alignment film used in such a liquid crystal display device, an organic material such as polyimide or polyamide is mainly used. The polyimide-based alignment film is a material having a large surface polarity. In particular, since the surface of the alignment film is activated after performing the alignment treatment, ionic or polar impurities are easily adsorbed. Then, in the portion where the impurities are adsorbed, the alignment ability of the alignment film changes, the impurities function as a capacitor, or the state of the electric double layer that may occur at the interface between the liquid crystal and the alignment film changes. This causes display unevenness of the liquid crystal display element for image display. The display unevenness of this liquid crystal display element is based on the fact that unevenness of brightness, contrast or chromaticity exists in only a part of the screen,
There are a wide variety, such as those that are spread over the entire screen. For example, (1) unevenness of dust generated around minute dust mixed in the liquid crystal display element, (2) unevenness of sealant generated around the sealant of the liquid crystal display element, (3) liquid crystal injection port of the liquid crystal display element And (4) cleaning unevenness caused by impurities mixed in cleaning the liquid crystal display element.

[0004] In recent years, minute dust in the air, especially dust unevenness caused by fatty acids generated from the human body, has become a serious problem. With the progress of clean technology, it is rare that large trash is mixed in, but it is still difficult to completely remove small trash. It is considered that ionic or polar impurities are eluted from the dust even if minute dust of about 1 micron enters, and the dust affects the surroundings and appears as noticeable unevenness. recently,
In order to remove the minute dust, a cleaning process using pure water or an organic solvent is performed after the alignment process.
In order to increase the cleaning power, it is common to combine physical cleaning methods such as brushing, jet spraying, or ultrasonic cleaning, which is effective for removing minute dust. However, trace amounts of impurities are also contained in the cleaning solution, and it is still difficult to completely remove them. Further, uneven cleaning caused by impurities contained in the cleaning liquid is a new problem. On the other hand, in addition to attempts to reduce impurities mixed in the device, it has been proposed to control the adsorptivity of the alignment film to reduce the influence of impurities.
Japanese Patent Application Laid-Open No. 1-185617 discloses a method of suppressing the adsorption of impurities on the surface of an alignment film by fluorinating the surface of the alignment film and preventing display unevenness of a liquid crystal panel. However, although the method of this publication is effective in suppressing the adsorption of impurities, the surface state of the alignment film is extremely changed by the fluorination treatment, so that the alignment ability of the alignment film is deteriorated. There was such a problem.

[0005] The force acting when an ionic or polar impurity is adsorbed on the surface of the alignment film is considered to be a hydrogen bond, a dipole-dipole interaction, a Coulomb-Coulomb interaction, or the like. In general, since such interactions are greater between those having a large polarity, it is considered that adsorption of impurities can be suppressed by reducing the polar component of the surface energy of the alignment film. Methods for reducing the surface energy of the alignment film include (1) a method of adjusting the molecular structure of the alignment film and adding an additive to the alignment film, and (2) a treatment with a surface treatment agent after forming the alignment film. And (3) a method of irradiating ultraviolet rays in an atmosphere in which oxygen or ozone is present after performing the orientation treatment. Among them, the methods (1) and (2) are not preferable because various characteristics of the alignment film itself such as the alignment ability and the electrical characteristics are greatly changed.
The method (3) is not preferable because the alignment film is deteriorated by the irradiation of ultraviolet rays.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and a method of treating an alignment film for a liquid crystal display device, which reduces the surface energy of the alignment film. And a manufacturing method capable of preventing display unevenness of a liquid crystal display element by using the method for treating an alignment film, and a liquid crystal display element manufactured by this method without display unevenness. . In the method for treating an alignment film for a liquid crystal display element of the present invention, a rubbing treatment is performed on an alignment film made of an organic polymer material applied on a transparent substrate provided with a transparent electrode.
It is characterized in that the line is irradiated for 5 seconds or more. That is,
When soft X-rays having a long wavelength are irradiated, gas ions generated by the ionizing action are adsorbed on the alignment film, and the polar component of the surface energy of the alignment film is reduced, so that display unevenness of the liquid crystal display element can be prevented. This can be understood as a phenomenon in which gas ions generated by the soft X-ray irradiation are adsorbed on the adsorption sites on the surface activated by the alignment treatment, and the surface cannot adsorb any more impurities.

The atmosphere for irradiating the soft X-rays of the present invention is not particularly limited as long as it is in a gas. Preferred gases include oxygen, nitrogen, carbon dioxide, water vapor, helium, neon, argon and mixtures thereof. The effect of reducing the surface energy of a substance by soft X-ray irradiation in the present invention is not limited to the surface treatment of the alignment film for a liquid crystal display element, but can be used for essentially any substance. The soft X-rays having a long wavelength used in the present invention have a very low energy and a very low permeability to a substance. This can be easily shielded by a transparent vinyl chloride plate or the like, does not pose a danger to the human body, and is preferable in terms of safety management. Further, it is considered that this also works advantageously in that the alignment film is not deteriorated.

The soft X-ray irradiator used in the present invention has a soft X-ray energy of 4 to 9.5 kiloelectron volts (ke).
There is no particular limitation as long as the output can be controlled stably in V). The soft X-ray irradiation time is 2 seconds or more, preferably 5 to 300 seconds. If the irradiation time is shorter than 2 seconds, the effect of reducing the surface energy by soft X-ray irradiation will be small. The soft X-ray irradiation distance is not particularly limited, but is usually adjusted to 1500 mm or less, and preferably 10 to 400 mm.

In the method of manufacturing a liquid crystal display device according to the present invention, a transparent electrode is provided on a pair of transparent substrates, an alignment film made of an organic polymer substance is formed on the transparent electrode, and the alignment film is rubbed. After assembling the substrate facing each other via a spacer, a method for manufacturing a liquid crystal display element including a step of enclosing a liquid crystal material, a soft X-ray is applied to the alignment film for 5 seconds in a gas after rubbing the alignment film in a gas. Irradiation is characterized above. In the manufacturing method of the liquid crystal display device of the present invention, the soft X
The cleaning treatment with the cleaning liquid can be performed before the irradiation with the X-rays, or the cleaning treatment can be performed after the irradiation with the soft X-rays. Examples of the cleaning method include brushing, jet spray, steam cleaning, and ultrasonic cleaning. These methods may be performed alone or in combination. As the cleaning liquid, pure water or various alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol, aromatic hydrocarbons such as benzene, toluene, and xylene, halogen solvents such as methylene chloride, and ketones such as acetone and methyl ethyl ketone are used. Although it can be used, it is not limited to these. Needless to say, these cleaning solutions are sufficiently purified and contain few impurities.

In the present invention, a polyimide resin is preferably used as a material for the alignment film. As a polyimide, a precursor represented by the general formula (1)

[0011]

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(Wherein, R ₁ represents a tetravalent alicyclic, aromatic or heterocyclic hydrocarbon residue, and may have a group such as halogen in the group, and R ₂ represents a divalent group. Which may have -O-, -S-, or a halogen atom or a cyano group in the group), and a product produced using a polyamic acid having a structural unit represented by: Used. That is, as the polyamic acid, tetracarboxylic dianhydride having an aromatic ring such as pyromellitic dianhydride, or alicyclic tetracarboxylic dianhydride such as cyclobutanoic tetracarboxylic dianhydride can be used as a diamino acid. A polyamic acid obtained by reacting a compound is preferably used.

Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 2,2', 3,3'-biphenyltetracarboxylic dianhydride. Acid dianhydride, 2,3,3 ', 4'
-Biphenyltetracarboxylic dianhydride, 3,3 ',
4,4′-benzophenonetetracarboxylic dianhydride,
2,3,3 ′, 4′-benzophenonetetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) sulfonic acid dianhydride An aromatic tetracarboxylic dianhydride such as 1,2,5,6-naphthalenetetracarboxylic dianhydride or 2,3,6,7-naphthalenetetracarboxylic dianhydride; As the formula tetracarboxylic acid, cyclobutane, cyclohexane, cyclooctane,
Examples thereof include dianhydrides of alicyclic tetracarboxylic acids having a ring such as bicyclooctane and those having the following structural formulas.

[0014]

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The diamino compound which is another raw material of the polyamic acid includes 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-bis [4- (4-aminophenoxy) phenyl] -4-butylcyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-pentylcyclohexane,
1,1-bis [4- (4-aminophenoxy) phenyl] -4-hexylcyclohexane, 1,1-bis [4
-(4-aminophenoxy) phenyl] -4-heptylcyclohexane, 1,1-bis [4- (4-aminophenoxy) phenyl] -4-octylcyclohexane,

2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,2-bis [4
-(4-aminophenoxy) phenyl] pentane, 2,
2-bis [4- (4-aminophenoxy) phenyl] hexane, 2,2-bis [4- (4-aminophenoxy)
Phenyl] heptane, 2,2-bis [4- (4-aminophenoxy) phenyl] octane, 2,2-bis [4-
(4-aminophenoxy) phenyl] nonane, 2,2-
Bis [4- (4-aminophenoxy) phenyl] decane, 2,2-bis [4- (4-aminophenoxy) phenyl] dodecane, 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-butyl Cyclohexane, 1,
1-bis [4- (4-aminobenzyl) phenyl] -4
-Pentylcyclohexane, 1,1-bis [4- (4-
Aminobenzyl) phenyl] methane,

4,4′-diaminophenyl ether,
4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, 4,4'-di (meth-aminophenoxy) diphenylsulfone, 4,4 '-(para-amino Phenoxy) diphenyl sulfone, ortho-phenylenediamine, meta-phenylenediamine, para-phenylenediamine, benzidine, 2,2′-diaminobenzophenone, 4,4′-diaminobenzophenone, 4,4′-
Diaminodiphenyl-2,2′-propane, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,
There are aromatic diamino compounds such as 2-bis [4- (4-aminophenoxy) phenyl] hexamethylpropane, and alicyclic diamino compounds such as 1,4-diaminocyclohexane and 4,4'-diaminodicyclohexylmethane. However, the tetracarboxylic dianhydride and the diamino compound which are the raw materials of the alignment film used in the present invention are not limited to these. Further, the acid anhydride and the diamino compound may be used in combination of two or more thereof.

In order to provide a polyimide alignment film according to the present invention on a substrate, since a polyimide compound is generally insoluble in a solvent, a polyamic acid obtained by condensation of a tetracarboxylic dianhydride and a diamino compound as a precursor thereof is used. Is dissolved in a solvent, applied on a substrate, and then heated to imidize. Specifically, the polyamic acid is N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF), dimethylsulfoxide (DMSO), butylcellosolve (BC), ethyl carbitol, propylene glycol It is dissolved in a solvent such as monobutyl ether or 3-methyl-3-methoxybutanol to prepare a 0.1 to 30% by weight solution, preferably a 1 to 10% by weight solution, and the solution is brushed, dipped, Coating is performed by a spin coating method, a spray method, a printing method, or the like to form a coating film on a substrate. After coating film formation, 50 to 150 ° C, preferably 80 to 1
After evaporating the solvent at 20 ° C, a heat treatment is performed at 150 ° C to 400 ° C, preferably 180 ° C to 280 ° C, and a dehydration ring-closing reaction is performed to provide a liquid crystal alignment film made of a polybenzylimide polymer film. . If the adhesion of the obtained polymer film to the substrate is not good, after performing a surface treatment with a silane coupling agent on the substrate surface in advance and then forming the polymer film, the adhesion is improved. . After the organic polymer film is provided on the substrate surface in this manner, the coated surface is rubbed in a certain direction with a cloth or the like to obtain a liquid crystal alignment film.

On this substrate, a transparent electrode, specifically, an IT
A transparent electrode such as O (indium oxide-tin oxide) is formed. Further, an insulating film may be formed under the electrode for the purpose of preventing alkali elution from the substrate,
Further, a polarizing plate, a color filter film, a light transmission preventing film, or the like may be provided in the cell. As these other cell components, appropriate components can be used according to the configuration of a conventional liquid crystal element. A cell is formed using such a substrate, and after the liquid crystal is injected, the injection port is sealed. Alternatively, a liquid crystal display element may be formed by dispersing liquid crystal on a substrate, then superposing the substrates, and sealing the liquid crystal so that the liquid crystal does not leak.
As the liquid crystal used in the liquid crystal display device of the present invention, a liquid crystal to which a dichroic dye is added in addition to a normal nematic liquid crystal,
Any ferroelectric liquid crystal or any other liquid crystal that can be used for a normal display device can be used. Examples of the liquid crystal component that can be used in the present invention include a liquid crystal compound represented by the following general formula (2) and a liquid crystal compound represented by the following general formula (3).

[0020]

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Wherein R ₁ represents a linear alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and R ₂ represents a linear alkyl group having 1 to 10 carbon atoms. alkyl group or alkyloxy group, -CN, fluorine atom, chlorine atom, -CF _3, -CHF _2, represents -OCF ₃ or -OCHF _2, S ₁ and S ₂ represents a hydrogen atom, a fluorine atom, a chlorine atom, - Represents CF ₃ , —CHF ₂ , —OCF _3, or —OCHF _2, which may be the same or different, and Z ₁ represents —COO—, —CH ₂
CH ₂ -, - C≡C- or a single bond, A ₁ is

[0022]

Embedded image Represents ),

[0023]

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(Wherein R ₃ is the same as R ₃ in the general formula (2))
Has the same meaning as ₁ , R ₄ has the same meaning as R ₂ in formula (2), and S ₃ and S ₄ have the same meaning as S ₁ and S ₂ in formula (2), respectively, Z ₂ and Z ₃ may be the same or different from each other, and have the same meaning as Z _{1 in the} general formula (2), and A ₂ and A ₃ represent the general formula It has the same meaning as A _{1 in} (2), and these may be the same or different. The components of these liquid crystal compositions may be a single component or a mixture of multiple components. As the liquid crystal mixture used in the liquid crystal display device of the present invention, compounds other than those described above can be used as long as the object of the invention is not impaired.

Further preferred embodiments of the present invention include the following (A)
(A) to (c). (A) After rubbing a polyimide-based alignment film formed on a transparent substrate provided with a transparent electrode, the alignment film is soft X in air.
A method for treating an alignment film, comprising irradiating a line with light for a certain time period of 5 to 300 seconds. (A) A method for treating an alignment film in which soft X-ray energy is 4 to 9.5 kiloelectron volts (keV) in the preceding paragraph. (C) The method for treating an alignment film according to item (a), wherein the distance between the alignment film and the soft X-ray source is 10 to 400 mm. (D) In the above item (a), the soft X-ray energy is 4
A method for treating an alignment film, which comprises irradiating soft X-rays with an alignment film placed at a distance of 10 to 400 mm from a radiation source of 9.5 keV. (E) A transparent electrode is provided on a pair of transparent substrates, a polyimide-based alignment film is formed on the transparent electrodes, the alignment film is subjected to a rubbing process, and the substrates are assembled to face each other via a spacer. In a method of manufacturing a liquid crystal display device including a step of enclosing a material, after rubbing the alignment film, irradiating the alignment film with soft X-rays for 5 to 300 seconds in air. Production method. (F) In the preceding paragraph, the energy of soft X-rays is 4 to 9.5.
A method for manufacturing a liquid crystal display element having kilo-electron volts (keV). (G) In the above item (e), 10 to 40 minutes from the soft X-ray source.
A method for manufacturing a liquid crystal display element, wherein soft X-rays are irradiated with an alignment film at a distance of 0 mm. (H) In the above item (e), the energy of the soft X-ray is 4
A method for manufacturing a liquid crystal display device, comprising irradiating soft X-rays with an alignment film placed at a distance of 10 to 400 mm from a radiation source of 9.5 keV. (G) A transparent electrode is provided on a pair of transparent substrates, a polyimide-based alignment film is formed on the transparent electrodes, the alignment film is subjected to a rubbing treatment, and the substrates are assembled by facing each other via a spacer. In a liquid crystal display element prepared by enclosing a liquid crystal mixture containing at least one compound represented by the general formula (1) or (2), the alignment film is softened in air for 5 to 300 seconds after rubbing. A liquid crystal display device which is receiving X-ray irradiation. (G) In the preceding paragraph, the energy of the soft X-ray is 4 to 9.5.
A liquid crystal display device receiving soft X-ray irradiation of kiloelectron volts (keV). (C) In the above (g), the energy of the soft X-ray is 4
From a source that is ~ 9.5 kiloelectron volts (keV)
A liquid crystal display device receiving soft X-ray irradiation with an alignment film at a distance of up to 400 mm.

[0026]

The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples. In addition, the measuring method of the surface energy used in these examples is as follows. The surface energy of the alignment film was measured and calculated by using two liquids whose polar components and dispersion components of the surface energy were known and measuring their contact angles. The value of the contact angle is related to the surface energy from the following equation. Shows the case where a liquid having a surface energy gamma _L to a solid surface (the surface energy of the solid and gamma _S) is in equilibrium contact angle theta. In this system, Y
The equation of “ung” is established. [gamma] _S = [gamma] _SL + [gamma] _L cos [theta] Here, [gamma] _SL is the energy acting between the solid and the liquid and is related to the interaction force at the interface. Attachment work Wa = γ _S + γ _L - represented by gamma _SL, when combined with equation becomes _{Wa = γ L (1 + cosθ} ). Here, if the surface energy is divided into a dispersion component (γ ^D ) and a polar component (γ ^P ) based on the idea of Forkes et al., Then γ = γ ^D + γ ^P. Here, assuming that the dispersive component of the surface energy interacts only with the dispersive component and the polar component interacts only with the polar component, Wa = (γ _S ^D γ _L ^D ) ^1/2 + (γ _S ^P γ _L ^P ) ^1/2 From the formula, γ _L (1 + cos θ) = (γ _S ^D γ _L ^D ) ^1/2 + (γ _S ^P γ _L ^P ) ^1/2 From this, two kinds of liquids having known surface energy dispersion components and polar components are used. By measuring the contact angle, the variance component and the polar component of the surface energy of the substrate can be calculated. In the following example, pure water (H ₂ O) and ethylene glycol (E
G) was used to determine the surface energy. The dispersion component and the polar component of the surface energy used are as follows. γ _L ^D γ _L ^P γ _L H ₂ O 22.0 50.2 72.2 (ergcm ^-2 ) EG 29.3 19.0 48.3 (ergcm ^-2 )

Example 1 A polyamic acid solution was obtained by polymerizing 3.46 g of 4,4'-diaminophenyl ether, 4.36 g of pyromellitic dianhydride and 0.11 g of para-aminophenyl trimethoxysilane. Butyl cellosolve (BC)
And N-methyl-2-pyrrolidone (NMP) in a weight ratio of 1: 1 was added to dilute the polyamic acid to 3% by weight, and this solution was placed on a transparent glass substrate provided with an ITO electrode on one side. Coating was performed by a spin coating method (spinner method). The application conditions were 3000 rpm for 15 seconds. After the coating was dried at 100 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an air oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes, and a polyimide film having a thickness of about 600 Å was formed on the transparent electrode. Obtained on the substrate provided. By the same operation, a total of five alignment films were obtained and used for the next test.
After performing an alignment treatment on the obtained alignment film using a rubbing cloth,
The four substrates were irradiated with soft X-rays from a position 50 mm perpendicular to the film surface using a soft X-ray irradiator (C4870) manufactured by Hamamatsu Photonics Co., Ltd. The soft X-ray irradiation time is 6
The test was performed under each condition of seconds, 15 seconds, 30 seconds, and 60 seconds. The energy of the soft X-ray irradiator was 6 keV, and the tube voltage and tube current were 9.5 kV and 0.2 mA, respectively. The surface energy of the film formed by this method was measured immediately at room temperature after the soft X-ray irradiation treatment. The surface energy of the film rapidly decreased with the soft X-ray irradiation time. The contact angles of pure water and ethylene glycol of the film with a soft X-ray irradiation time of 60 seconds were 67.4 degrees and 51.8 degrees, respectively, and the value of the polar component of the surface energy was 23.7 ergcm ^-2 .

The polyimide film prepared in the same manner was irradiated with soft X-rays for 60 seconds, and the substrate was subjected to ultrasonic cleaning treatment and drying treatment in pure water. Using this substrate, a liquid crystal cell having a cell thickness of 6 microns and a twist angle of 240 ° is assembled, and a liquid crystal for STN manufactured by Chisso Corporation (trade name LIX)
ON 4032-000XX). 12 after encapsulation
The liquid crystal element was obtained by performing an isotropic treatment at 0 ° C. for 30 minutes and gradually cooling to room temperature. In the same manner, ten liquid crystal elements were prepared, and the obtained elements were energized to check for display unevenness. As a result, display unevenness was slightly observed in three elements, but in the remaining seven elements, No uneven display was observed.

Comparative Example 1 Ten liquid crystal display elements were prepared in the same manner as in Example 1 except that soft X-ray irradiation was not performed. The contact angles of the formed film with pure water and ethylene glycol were 64.6 degrees and 51.4 degrees, respectively, and the value of the polar component of the surface energy was 28.3 ergcm ^-2 .
When the obtained ten elements were energized and the presence or absence of display unevenness was examined, display unevenness was observed in all the elements, and remarkable display unevenness was particularly observed in the seven elements. FIG. 1 shows the results obtained from Example 1 and Comparative Example 1.
4 shows a relationship between a soft X-ray irradiation time and a polar component of surface energy. FIG. 1 shows that the sample after soft X-ray irradiation (Example 1) has a smaller surface energy than the sample without soft X-ray irradiation (Comparative Example 1).

Example 2 Using 50 g of dehydrated and purified NMP as a solvent, 7.43 g of 1,1-bis [4- (4-aminobenzyl) phenyl] -4-cyclohexane and 3.69 of pyromellitic dianhydride were used.
g was reacted while cooling. One hour later, 0.11 g of paraaminophenyltrimethoxysilane was added and reacted at 20 ° C. for 1 hour. Thereafter, 51.1 g of NMP was added to the reaction solution.
Then, a clear solution of 10% by weight of polyamic acid was obtained. The viscosity of this solution at 25 ° C. is 18
It was 70 centipoise. This solution was mixed with a mixed solvent of BC and NMP (1: 1) to make the polyamic acid 3% by weight.
Then, the solution was applied on a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method). The application conditions were 4500 rpm for 15 seconds. After the coating film was dried at 100 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an air oven over 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to provide a polyimide film having a film thickness of about 600 Å. Five substrates were obtained. After the obtained alignment film is subjected to an alignment treatment using a rubbing cloth, a soft X-ray irradiator (C487, manufactured by Hamamatsu Photonics KK) is applied to the four substrates.
Using 0), soft X-rays were irradiated from a position 50 mm perpendicular to the film surface. The irradiation time of the soft X-ray was 6 seconds, 15 seconds,
The test was performed under each condition of 30 seconds and 60 seconds. The energy of the soft X-ray irradiator was 6 keV, and the tube voltage and tube current were 9.5 kV and 0.2 mA, respectively.

The surface energy of the film formed by this method was measured immediately at room temperature after the soft X-ray irradiation treatment. The surface energy of the film rapidly decreased with the soft X-ray irradiation time. The contact angles of pure water and ethylene glycol of the film with a soft X-ray irradiation time of 60 seconds were 75.0 degrees and 54.2 degrees, respectively, and the value of the polar component of the surface energy was 1
It was 3.8 ergcm ^-2 . The substrate obtained by irradiating the rubbed polyimide film under the same conditions with soft X-rays for 60 seconds as described above was subjected to ultrasonic cleaning in pure water and drying treatment. Using this substrate, 10 liquid crystal cells having a cell thickness of 6 microns and a twist angle of 240 ° were assembled, and a liquid crystal for STN manufactured by Chisso Corporation (trade name: LIXON 4032) was used.
000XX). After the encapsulation, an isotropic treatment was performed at 120 ° C. for 30 minutes, and the resultant was gradually cooled to room temperature to obtain a liquid crystal element. When current was applied to the obtained liquid crystal display elements and the presence or absence of display unevenness was examined, display unevenness was not observed in all the elements.

Comparative Example 2 Ten liquid crystal elements were prepared in the same manner as in Example 2 except that soft X-ray irradiation was not performed. The contact angles of pure water and ethylene glycol of the alignment film formed by this method were 73.4 degrees and 60.6 degrees, respectively, and the value of the polar component of the surface energy was 21.1 ergcm ^-2 . When the obtained elements were energized to check for display unevenness, display unevenness was observed in eight elements,
In particular, remarkable display unevenness was observed in five elements.

FIG. 2 shows the relationship between the soft X-ray irradiation time and the polar component of the surface energy obtained in Example 2 and Comparative Example 2. FIG. 2 shows that the sample after soft X-ray irradiation (Example 2)
Indicates that the surface energy is smaller than that of the sample not irradiated with soft X-rays (Comparative Example 2).

Example 3 8.06 g of 2,2-bis [4- (4-aminophenoxy) phenyl] propane and pyromellitic dianhydride
36 g and paraaminophenyl trimethoxysilane 0.
11 g was polymerized to obtain a polyamic acid solution. A 1: 1 mixed solution of butyl cellosolve and NMP was added to this solution to dilute the polyamic acid to 3% by weight, and then applied on a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method). . The application condition is 3000 rpm,
15 seconds. After drying at 100 ° C for 10 minutes after coating,
The temperature was raised to 200 ° C. over 1 hour in an air oven, and heat treatment was performed at 200 ° C. for 90 minutes.
Glass substrate 5 with Angstrom polyimide film
I got one. After the obtained alignment film is subjected to an alignment treatment using a rubbing cloth, soft X-rays are applied to the four substrates from a position 50 mm in the direction perpendicular to the film surface using a soft X-ray irradiator (C4870) manufactured by Hamamatsu Photonics Co., Ltd. Irradiated for seconds. The energy of the soft X-ray irradiator was 6 keV, and the tube voltage and tube current were 9.5 kV and 0.2 mA, respectively. The surface energy of the film formed by this method was measured immediately at room temperature after the soft X-ray irradiation treatment. The surface energy of the film rapidly decreased with the soft X-ray irradiation time. Soft X
The contact angles of pure water and ethylene glycol of the film with a line irradiation time of 60 seconds were 71.0 degrees and 55.2 degrees, respectively, and the value of the polar component of the surface energy was 20.5 ergc.
m ^-2 . The obtained polyimide film was subjected to an ultrasonic cleaning treatment and a drying treatment in pure water. Using this substrate, a liquid crystal cell having a cell thickness of 6 μm and a twist angle of 240 ° was assembled, and a liquid crystal for STN manufactured by Chisso Corporation (trade name: LIX)
ON 4032-00XX). 120 after encapsulation
The liquid crystal display device was obtained by performing isotropic treatment at 30 ° C. for 30 minutes and gradually cooling to room temperature. In the same manner, ten liquid crystal elements were simultaneously formed, and the resulting elements were energized to check for display unevenness. As a result, display unevenness was slightly observed in the two elements, but the remaining eight elements were used. No unevenness in display was observed in.

Comparative Example 3 Ten liquid crystal elements were prepared in the same manner as in Example 3 except that soft X-ray irradiation was not performed. The contact angles of the formed film with pure water and ethylene glycol were 65.6 degrees and 50.4 degrees, respectively, and the value of the polar component of the surface energy was 25.6 ergcm ^-2 . Also,
When current was applied to the obtained devices and the presence or absence of display unevenness was examined, display unevenness was observed in all the devices, and in particular, 7
Significant display unevenness was observed in one element.

Example 4 1,1-bis [4- (4-aminophenoxy) phenyl] -4-trans-4-ethylcyclohexane 7.0
5 g, 2.18 g of pyromellitic dianhydride, 0.65 g of cyclobutanetetracarboxylic acid and 0.09 g of paraaminophenyltrimethoxysilane were polymerized to obtain a polyamic acid solution. To this solution was added a mixed solution of butyl cellosolve and NMP at a weight ratio of 1: 1 to reduce the amount of polyamic acid to 3%.
After dilution to weight%, it was applied on a transparent glass substrate provided with an ITO electrode on one side by a spin coating method (spinner method).
The application conditions were 3000 rpm for 15 seconds. After coating 1
After drying at 00 ° C. for 10 minutes, the temperature was raised to 200 ° C. in an air oven for 1 hour, and heat treatment was performed at 200 ° C. for 90 minutes to obtain a glass substrate provided with a polyimide film having a thickness of about 600 Å. Was. After the obtained alignment film was subjected to an alignment treatment using a rubbing cloth, soft X-rays were irradiated for 60 seconds from a position 50 mm perpendicular to the film surface using a soft X-ray irradiation device (C4870) manufactured by Hamamatsu Photonics KK . The energy of the soft X-ray irradiator was 6 keV, and the tube voltage and tube current were 9.5 kV and 0.2 mA, respectively. The surface energy of the film formed by this method was measured immediately at room temperature after the soft X-ray irradiation treatment. The contact angles of pure water and ethylene glycol of this film were 69.8 degrees and 54.9 degrees, respectively, and the value of the polar component of the surface energy was 22.3 ergcm ^-2 .

The obtained polyimide film was subjected to an ultrasonic cleaning treatment and a drying treatment in pure water. Using this substrate, a liquid crystal cell having a cell thickness of 6 μm and a twist angle of 240 ° was assembled, and a liquid crystal for STN manufactured by Chisso Corporation (trade name: LIX)
ON 4032-000XX). 12 after encapsulation
The liquid crystal element was obtained by performing an isotropic treatment at 0 ° C. for 30 minutes and gradually cooling to room temperature. Ten liquid crystal display elements were prepared in the same manner, and current was applied to the obtained elements to check for display unevenness. As a result, display unevenness was slightly observed in three elements, but the remaining seven elements were not. No display unevenness was observed in the device.

Comparative Example 4 Ten liquid crystal elements were prepared in the same manner as in Example 4 except that soft X-ray irradiation was not performed. The contact angles of pure water and ethylene glycol of the film formed by this method were 65.0 degrees and 50.9 degrees, respectively, and the value of the polar component of the surface energy was 27.1 ergcm ^-2 .
When the obtained liquid crystal display element was energized and examined for display unevenness, display unevenness was observed in all the elements, and remarkable display unevenness was observed particularly in eight elements.

[0039]

As described above, a method of irradiating soft X-rays in a gas after performing an alignment treatment on an alignment film,
The display quality of the liquid crystal display device can be improved by reducing the display unevenness of the liquid crystal display element, and the yield of the product can be improved.

[Brief description of the drawings]

FIG. 1 shows the relationship between the soft X-ray irradiation time obtained from Example 1 and Comparative Example 1 and the polar component of the surface energy.

FIG. 2 shows the relationship between the soft X-ray irradiation time and the surface energy polar component obtained from Example 2 and Comparative Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Satoshi Tanioka 2-17-17 Tatsumidaihigashi, Ichihara-shi, Chiba (72) Inventor Norio Murata 545-9, Shiitsu, Shizuhara-shi, Chiba-ken (72) Inventor Makoto Kawano Chino, Nagano Prefecture Tamagawa character Harayama 11400-1078 Inside Iinuma Gauge Mfg. Co., Ltd. (72) Inventor Masayuki Hirano 1126 Nomachi, Hamamatsu-shi, Shizuoka Prefecture Inside Hamamatsu Photonics Co., Ltd. (56) References JP-A-5-323322 (JP, A) JP-A-4-284419 (JP, A) WO 94/5138 (WO, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/13, 1/1337

Claims (4)

(57) [Claims] After rubbing an alignment film made of an organic polymer material formed on a transparent substrate provided with a transparent electrode, a distance from the alignment film to a soft X-ray source is 1500 mm or less.
4 is an energy of the source to the alignment film in a gas is below
A method for treating an alignment film for a liquid crystal display device, comprising irradiating a soft X-ray of 9.5 keV for 5 seconds or more to reduce surface energy on the film. 2. A transparent electrode is provided on a pair of transparent substrates, and an alignment film made of an organic polymer substance is formed on the transparent electrode,
After rubbing the alignment film, assembling the substrate so that the substrates face each other via a spacer, and enclosing a liquid crystal material, in a method of manufacturing a liquid crystal display element, the alignment film is rubbed and then softened from the alignment film. Distance to X-ray source is 150
The energy of the radiation source is applied to the alignment film in a gas of 0 mm or less.
Is irradiated with soft X-rays of 4 to 9.5 keV for 5 seconds or more,
A method for producing an alignment film for a liquid crystal display device, comprising reducing surface energy on the film. 3. A transparent electrode is provided on a pair of transparent substrates, and an alignment film made of an organic polymer substance is formed on the transparent electrode.
After rubbing the alignment film, assembling the substrate with the substrates facing each other via a spacer, and then assembling a liquid crystal material, in a liquid crystal display device, the alignment film is rubbed and then soft X-rays are generated from the alignment film. The distance to the source is 1500mm or less
The energy of the radiation source is 4 to 9.
A liquid crystal display device characterized by receiving irradiation of soft X-rays of 5 keV for 5 seconds or more to reduce surface energy on the film. 4. A liquid crystal material according to the general formula (2) or the general formula (3): (In these formulas, R1 and R3 are each independently a linear alkyl group having 1 to 10 carbon atoms or a linear alkyl group having 2 carbon atoms.
R2 and R4 each independently represent a linear alkyl or alkyloxy group having 1 to 10 carbon atoms, -CN, a fluorine atom, a chlorine atom, -C
F3, -CHF2, -OCF3 or -OCHF2
And S1, S2, S3 and S4 each independently represent a hydrogen atom, a fluorine atom, a chlorine atom, -CF3, -CH
F2, -OCF3 or -OCHF2 is converted to Z1, Z
2 and Z3 are each independently -COO-, -CH2
CH 2 —, —C≡C— or a single bond, and A 1, A 2 and A 3 each independently represent 4. A liquid crystal display device according to claim 3 , which is a liquid crystal mixture containing at least one compound represented by the following formula: