JP3236586B2 - Method for manufacturing substrate with liquid crystal alignment film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an alignment layer having an excellent liquid crystal alignment characteristic with a smaller photoirradiation quantity in the method for manufacturing the liquid crystal alignment layer using a photoalignment treatment method. SOLUTION: The method for manufacturing a substrate with the liquid crystal alignment layer has a stage for applying a solution containing an alignment layer material having a photosensitive group to a substrate surface and a baking stage of executing the photoalignment treatment to align the alignment layer material molecules in a specific direction by irradiating the unbaked coating film with polarized UV rays and baking and curing the coating film after the photoalignment treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a substrate having a liquid crystal alignment film as a member for a liquid crystal display panel, and more particularly, to a method for manufacturing a liquid crystal alignment film in which molecules constituting a coating film are aligned in a certain direction using polarized ultraviolet rays. About the method.

2. Description of the Related Art Conventionally, a liquid crystal alignment film for a liquid crystal display panel is formed by applying a solution in which a compound having a film forming property is dissolved on the surface of a substrate on which electrodes are formed, and baking to form a film. It is manufactured by a method (rubbing method) of strongly rubbing the surface of the coating with a cloth or the like in a certain direction.

However, according to the rubbing method, fiber scraps and scraps generated from the surface of a cloth or a coating cause display unevenness, and rubbing generates static electricity, which damages a transistor formed on a substrate. This can cause Furthermore, when the substrate area is large, rubbing unevenness occurs, and this unevenness causes a liquid crystal alignment defect.

[0003] In order to solve such a problem, a photo-alignment method has been developed and put into practical use. The photo-alignment method is a method of orienting coating constituent molecules in a certain direction using polarized ultraviolet rays, and is a non-contact type which does not directly contact the substrate surface, so that problems such as generation of scraps and generation of static electricity do not occur. However, this technique is still an evolving technique, and has problems such as requiring a large amount of ultraviolet light for orientation, prolonging the production time, and failing to obtain sufficient orientation. Therefore, further improvement in productivity as well as improvement in orientation is required.

[0004]

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a method capable of producing an alignment film having excellent liquid crystal alignment with a smaller amount of ultraviolet irradiation.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies on a photo-alignment method using polarized ultraviolet light, and have found that when polarized ultraviolet light is irradiated in a state where the film constituent molecules are easily moved, the alignment efficiency is significantly improved. The present inventors have completed the present invention having the following configuration.

That is, the present invention provides a coating film forming step of applying a compound having a photosensitive group to the surface of a liquid crystal display panel substrate to form a coating film, and irradiating the coating film surface with polarized ultraviolet light. An ultraviolet irradiation step of orienting the compound molecules in a direction corresponding to the polarization direction of, and a baking step of baking the coating film after the ultraviolet irradiation step, a method for manufacturing a substrate with a liquid crystal alignment film, at least comprising: Features.

This configuration is characterized in that after coating the compound on the substrate surface and before baking the substrate, the coating film surface is irradiated with polarized ultraviolet light. However, before the firing, the coating film is still hardened. Therefore, the coating film constituting molecules are easily moved. Therefore, when the coating film at this stage is irradiated with polarized ultraviolet light,
The coating film constituting molecules can be oriented in a specific direction with less polarized ultraviolet energy. On the other hand, the molecules oriented in a specific direction by irradiation with polarized ultraviolet rays will have orientation (anisotropic) in a specific direction in a subsequent firing step.
Polymerization / curing or rearrangement while maintaining Therefore, according to the above configuration, a rubbingless substrate with a liquid crystal alignment film can be manufactured with high production efficiency.

The manufacturing method of the present invention having the above configuration can be further configured as follows. The ultraviolet irradiation step is a step of causing a photopolymerization reaction between compound molecules having a photosensitive group in a direction corresponding to the polarization direction of polarized ultraviolet light, and the baking step is performed by causing the compound molecules and / or the compound molecule to adhere to the substrate surface. A step of performing a thermal polymerization reaction can be provided.

In general, when a group of molecules is irradiated with polarized ultraviolet rays, the molecules receive ultraviolet energy and the molecules are oriented in a specific direction corresponding to the polarized ultraviolet rays. However, if the orientation is weak in physical and chemical constraints, when energy is subsequently applied from the outside, the orientation is re-oriented to a method corresponding to the energy, and the initial orientation state changes. However, in the above configuration, in the ultraviolet irradiation step, the compound molecules are photopolymerized in a direction corresponding to the polarization direction, and the compound molecules are chemically linked to each other. Therefore, the alignment state is stabilized, and the alignment state is unlikely to change due to externally applied energy (heat during firing, rubbing against the alignment film surface, and the like).

Further, in the above-described structure, a baking step of thermally polymerizing the compound molecules and / or the compound molecules with the substrate surface is employed, so that the baking step causes the compound molecules in the coating film to polymerize and harden. A firm film is formed, and the firm film is strongly bonded to the substrate surface. Therefore, according to this configuration, it is possible to obtain a substrate with a liquid crystal alignment film having stable alignment properties, and having excellent durability and binding properties to the substrate surface.

Here, the photopolymerization reaction means that a photosensitive group in a direction corresponding to the polarization direction of polarized ultraviolet rays is excited by receiving light energy, and molecules are chemically linked to each other via the photosensitive group portion. It refers to a reaction that is bonded (cross-linked). Also,
The thermal polymerization reaction refers to a chemical reaction between molecules and / or molecules and a substrate surface due to thermal energy at the time of firing. Examples of the thermal polymerization reaction include a dehydration condensation reaction.

In the method of the present invention, the step of irradiating the ultraviolet rays may be a step of irradiating the compound molecules with ultraviolet rays in an amount capable of causing a photopolymerization reaction between the compound molecules in a direction corresponding to the polarization direction of the polarized ultraviolet rays. May be a step of heating at a temperature at which the compound in the coating film can be thermally melted.

This structure is characterized in that the compound is irradiated with a polarized ultraviolet ray to such an extent that the compound molecules are photopolymerized and baked at a temperature at which the compound of the coating film can be melted by heat.
When the solid compound aggregate is heated at a temperature equal to or higher than the melting temperature, the binding between the molecules is released by the melting, so that the individual compound molecules can move easily. Therefore, the compound molecules are rearranged in the cooling process after the heat melting, and a dense and uniform film is formed. And when rearranging compound molecules,
Since the anisotropy and orientation of the compound molecules influence, the alignment state formed in the ultraviolet irradiation step is maintained. As a result, according to this configuration, a dense and uniform rubbingless alignment film is manufactured with high productivity. be able to. This configuration is particularly effective when a compound having no thermopolymerizability is used.

In the firing step in each of the above aspects of the present invention, firing is preferably performed at a temperature of 400 ° C. or less. If the firing temperature exceeds 400 ° C., the alignment formed by the irradiation of polarized ultraviolet rays disappears, and inconveniences such as the decomposition of the alignment film material being started occur.

In the manufacturing method of the present invention, the step of forming a coating film in each of the above-described structures is performed by dissolving or dispersing a compound having a photosensitive group in a solvent, and the solution is formed on the surface of a substrate for a liquid crystal display panel. And a drying step of removing the solvent from the application surface after the application of the compound solution. With this configuration, the compound having a photosensitive group can be thinly and uniformly applied to the substrate surface, and since polarized light is irradiated after removing the solvent from the coated surface, ultraviolet energy is applied to the solvent in the coating film. It is not absorbed. Therefore, the alignment efficiency in relation to the amount of polarized ultraviolet light irradiation is further increased.

In the above-described manufacturing method having a drying step, a washing step of washing the coating film surface with a washing liquid after the drying step can be added. When the coating surface is washed, excess compound molecules are removed to form a monomolecular layer-like coating film. When the monomolecular layer-like ultrathin coating film is used, the irradiation effect in the polarized ultraviolet irradiation step is enhanced. Therefore, an alignment film having excellent liquid crystal alignment characteristics can be obtained efficiently.

In the production method of the present invention, in each of the structures described above, a polyimide having a photosensitive group or a polyimide precursor having a photosensitive group can be used as the compound. By the way, since polyimide has good film-forming properties and chemical resistance, it has been conventionally used as an alignment film material.
A manufacturing procedure of application to a substrate → drying → firing → rubbing treatment is employed. The reason why the orientation treatment (rubbing treatment) is performed at the final stage of the production in the conventional method is that when the rubbing treatment is performed on the soft coating film before firing, the coating film is deformed, and the polyimide precursor such as polyamic acid is used. This is because, when a body was used, it was considered that an alignment treatment should be performed after the precursor was thermally polymerized into a polyimide by firing.

In contrast to such a conventional method, in the present invention, a liquid crystal alignment film is manufactured by a manufacturing procedure of coating → (drying) → polarizing ultraviolet irradiation → firing regardless of whether polyimide or polyimide precursor is used. However, according to this manufacturing procedure, since the irradiation efficiency of polarized ultraviolet light is high, the compound molecules constituting the coating film can be oriented in a specific direction by irradiation of a small amount of polarized ultraviolet light. Further, even in the case of polyimide or the like, according to this manufacturing method in which the alignment treatment is performed with polarized ultraviolet rays, there is no generation of abrasion and static electricity, so that the manufacturing yield and the reliability of the alignment film are improved.

Here, in this production method, when polyimide itself is used as the compound having a photosensitive group (coating material), the firing temperature in the firing step is preferably higher than the thermal melting temperature of the polyimide. When heated to a temperature higher than the heat melting temperature, the polyimide aggregate is melted and the molecules are easily moved, so that the polyimide aggregate is rearranged in a specific direction. Further, as a result of the unevenness of the coating film being healed, a uniform and dense coating can be formed.

On the other hand, when a polyimide precursor is used as the coating material, it is preferably fired at a temperature higher than the thermal polymerization temperature of the polyimide precursor, and more preferably at a temperature higher than the thermal polymerization temperature of the polyimide precursor and lower than the decomposition temperature. Bake.
When calcination is performed at a temperature equal to or higher than the thermal polymerization temperature, the polyimide precursor is polymerized and cured to form a firm film made of polyimide. When the coating film composed of the polyimide precursor is irradiated with polarized ultraviolet light, the precursor is oriented in a specific direction, or the precursor is photopolymerized in a specific direction, or the photosensitive group portion is decomposed, and so on. The body molecules have anisotropy. And since the characteristics formed at this time are not completely lost in the subsequent firing,
The fired film has orientation. That is, the predetermined effect of the present invention can be obtained even when the polyamide precursor is used.

In each of the configurations described above,
As the compound, a silane compound containing a linear carbon chain can be used. The silane-based compound containing a linear carbon chain can be firmly bound to the substrate surface by chemical bonding, and it is easy to form a monomolecular layer film composed of adsorbed molecules. And, a monomolecular layer coating (a coating consisting of a group of adsorbed molecules) composed of a silane compound containing a linear carbon chain
Has a structure that is convenient for imparting liquid crystal orientation by irradiation with polarized ultraviolet rays, so that a rubbingless alignment film having excellent liquid crystal orientation can be formed by irradiation with a smaller amount of polarized ultraviolet rays.

In each of the configurations described above,
A compound having a cinnamoyl group as a photosensitive group can be used. Since the cinnamoyl group is excellent in photosensitivity, it is convenient to impart orientation by irradiation with polarized ultraviolet rays.

In each of the configurations described above,
A compound having a chalconyl group as a photosensitive group can be used. The carbon-carbon double bond part of the chalconyl group has particularly high photosensitivity, and the molecules are cross-linked at the carbon-carbon double bond part by irradiation with polarized ultraviolet rays to form a stable alignment structure. Therefore, it is particularly convenient as a liquid crystal alignment film material for photo alignment.

[0024]

Embodiments of the present invention will be described.
The present invention relates to a method for manufacturing a substrate provided with a liquid crystal alignment film for forming a liquid crystal alignment film on a substrate. In a typical embodiment, a compound having film-forming properties and having a photosensitive group is first dissolved in a solvent to form a solution, and this solution is applied to the surface of a liquid crystal display panel substrate and dried to form a coating film. After that, the surface of the coating film is irradiated with polarized ultraviolet light to orient the compound molecules in the coating film in a specific direction. Thereafter, the coating is fired to form a solid coating having liquid crystal alignment characteristics on the substrate. The manufacturing method of the present invention will be described in relation to a conventional method.

In the conventional method, after a solution containing a film-forming material is applied to a substrate surface, the surface of the coating film is baked to form a film-forming compound into a firm film, and then the film surface is rubbed. Orientation was provided. The reason for adopting such a manufacturing procedure in the conventional method is that the coating before baking is in an unpolymerized and uncured state and is soft, so if this surface is rubbed with a cloth or the like, the coating may peel or deform. I do. For this reason, baking was first performed to polymerize and cure the coating film, and the coating film was strongly bonded to the substrate surface.

Conventionally, even in the method using polarized ultraviolet rays for the alignment treatment, a procedure of irradiating polarized ultraviolet rays after firing has been adopted. The reason for this was that the conventional production line was assembled so as to perform the orientation treatment at the final stage of the production process, and that this was common knowledge in the art, and that the orientation treatment was performed before firing. Is considered to cause the orientation state to be broken by firing.

However, contrary to the conventional wisdom, the present inventors have intensively studied that the orientation characteristics formed before firing are not necessarily lost by firing, and that when polarized ultraviolet rays are irradiated before firing, less irradiation is required. It has been found that the compound molecules can be efficiently oriented in a certain direction by the amount.
That is, in the present invention, a compound having film-forming properties and having a photosensitive group is applied to a substrate surface to form a coating film, and before this coating film is subjected to the baking treatment, polarized ultraviolet rays are irradiated. In this case, since the coating film is not polymerized and cured, the degree of freedom of each molecule constituting the coating film is high. Therefore, the compound molecules can be oriented in a direction corresponding to the polarization direction of the polarized ultraviolet light by irradiating a smaller amount of the polarized ultraviolet light.

By the way, when molecules are oriented simply in a direction corresponding to the polarization direction (hereinafter, referred to as simple orientation), the molecules are aligned with each other in the photosensitive group portion (hereinafter referred to as a simple orientation). When the molecular assembly group becomes anisotropic as a result of cross-linking with a part that is excited by receiving polarized ultraviolet light (hereinafter, referred to as cross-linked orientation), the result is that the photosensitive group part corresponding to the polarization direction is decomposed. There are three cases in which the molecular assembly group becomes anisotropic (hereinafter referred to as decomposition orientation). In any case, the alignment state formed by the irradiation of polarized ultraviolet light is It is not completely lost by the firing performed. Therefore, according to the production method of the present invention, a film having liquid crystal orientation can be reliably formed, and a film having excellent liquid crystal orientation (liquid crystal orientation film) can be formed with a smaller irradiation amount.

The firing step in the production method of the present invention has two technical significances. One is to cause the compound to undergo a thermal polymerization reaction, and the other is to heat the solid compound to a temperature higher than the heat melting temperature and melt it, increase the degree of freedom of the molecules, and rearrange the molecules. That is. However, needless to say, a firing step in which rearrangement and thermal polymerization proceed simultaneously may be employed. For example, if the main purpose of baking is to cause the compound to undergo a thermal polymerization reaction, it is not necessary to heat the compound to a temperature higher than the heat melting temperature. May occur simultaneously. When the molecules are rearranged by firing, a uniform (homogeneous) and dense film can be formed.

The intensity of the polarized ultraviolet light used in the production method of the present invention is preferably such that the light-sensitive group is excited to cause a crosslinking reaction. Since the anisotropy (or orientation state) due to cross-linking is sterically structurally stable,
This is because better liquid crystal alignment characteristics can be obtained.

The firing temperature is generally 150
C. or higher, preferably 150 to 400C, more preferably 150 to 250C. When the temperature is lower than 150 ° C., the polymerization curing reaction may be insufficient, and the binding with the substrate may be insufficient. This is because a film cannot be obtained.

The drying temperature is less than 150 ° C.
Preferably 50 to 150 ° C, more preferably 80 to 15
0 ° C. When the drying temperature is 150 ° C. or higher, a thermal polymerization reaction (curing reaction) occurs, and the orientation of the compound molecules due to the irradiation of polarized ultraviolet rays is not smoothly performed.
If the temperature is lower than 80 ° C., it becomes difficult to sufficiently remove the solvent.

The coating method in the production method of the present invention is not particularly limited, and for example, a spin coating method, a roller coating method and the like can be used. Alternatively, a method in which a compound having film forming properties and having a photosensitive group is dissolved in a solvent to form a solution, and the substrate is immersed in this solution may be used.

The compound having a photosensitive group used in the production method of the present invention is preferably a compound having a cinnamoyl group (Chemical Formula 1), and more preferably a compound having a chalconyl group (Chemical Formula 2). Is good. With these compounds, photo-alignment can be performed with a small amount of polarized ultraviolet light irradiation.

[0035]

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[0036]

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In addition, a polyimide having a photosensitive group or a polyimide precursor having a photosensitive group is used because it has excellent film-forming properties and chemical stability (chemical resistance) of a film after the film is formed on a liquid crystal material. Is good.

Further, a silane compound having a photosensitive group and containing a linear carbon chain is more preferable. When the silane compound contains a linear carbon chain, a monomolecular layer-like ultra-thin film can be formed, and an alignment film having excellent liquid crystal alignment can be formed efficiently. In addition, the silane-based compound can be polymerized and cured at a lower temperature than polyimide, and has excellent binding properties to a substrate.

Examples of the above-mentioned polyimide having a photosensitive group include a compound represented by the following general formula.

[0040]

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Wherein R is a hydrocarbon group, an oxygen-containing hydrocarbon group, or a fluorine-containing hydrocarbon group, and R ′ is a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorine-containing hydrocarbon group, or a sulfur-containing hydrocarbon. And n represents an integer of 1 or more. Table 1 lists typical combinations of R and R '.

[0042]

[Table 1]

Examples of the polyimide precursor include polyamic acid and polyamide.

Next, a method for producing a liquid crystal alignment film using polyimide or a polyimide precursor will be described. First, a method using a polyimide precursor will be described. After a precursor solution such as polyamic acid is applied to the substrate and the solvent is dried, the surface of the coating film is irradiated with polarized ultraviolet rays to orient the precursor molecules in a specific direction. This orientation and the like are described above.
(Simple orientation, cross-linking orientation, decomposition orientation). Next, the substrate on which the coating film is formed is fired at a temperature equal to or higher than the thermal polymerization temperature of the precursor, and the precursor molecules oriented in a specific direction are thermally polymerized to form a polyimide film having liquid crystal orientation.

The polymerization process in which polyimide is formed by firing is shown in the following chemical formula 4.

[0046]

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R is a hydrocarbon group, an oxygen-containing hydrocarbon group or a fluorine-containing hydrocarbon group, R ′ is a hydrocarbon group,
An oxygen-containing hydrocarbon group, a fluorine-containing hydrocarbon group, a sulfur-containing hydrocarbon group, and n is an integer of 1 or more.

On the other hand, when using polyimide itself,
First, polyimide is converted to n-methyl-2-pyrrolidinone (NM
Dissolve in a solvent such as P) to form a solution. Then, apply this solution to the substrate and dry to form a polyimide coating,
Irradiating this coating film surface with polarized ultraviolet light,
(Simple orientation, cross-linking orientation, decomposition orientation). From the viewpoint of providing stable liquid crystal alignment, it is preferable to perform cross-linking alignment by irradiation with polarized ultraviolet light.

Next, the substrate surface is fired at a temperature equal to or higher than the heat melting temperature of the polyimide. By this baking, the coating film is melted by heat and the polyimide molecules can move freely, and the polyimide molecules are rearranged in the cooling process, so that a dense and uniform-density polyimide film is formed. This coating has liquid crystal orientation.

In the production method of the present invention, a silane compound containing a linear carbon chain can be suitably used as a coating material. Examples of such a silane compound include compounds represented by the following general formula.

YpSiX3-p (Formula 8) wherein X is a halogen, an isocyanate group, an alkoxy group, Y is a hydrocarbon group having a photosensitive group, an oxygen-containing hydrocarbon group having a photosensitive group, and a photosensitive group. And a silicon-containing hydrocarbon group having a photosensitive group, and p is an integer of 0 to 3. The following are representative silane compounds.

C6H5CH = CH (CH2) 6SiCl3 (Equation 9)

C6H5CH = CH (CH2) 6Si (CH3) 2 (CH2) 10SiCl3 (Equation 10)

C6H5CH = CH (CH2) 6Si (OC2H5) 3 (Formula 11)

C6H5CH = CH (CH2) 6Si (NCO) 3 (Formula 12)

CF3C6H4CH = CH (CH2) 6OSi (OC2H5) 3 (Equation 13)

These silane compounds can be easily chemically bonded to the substrate surface and polymerized and cured at a low firing temperature of 150 to 200 ° C. Further, these silane compounds easily form an extremely thin monomolecular film composed of a group of chemisorbed molecules. Furthermore, when the coating film made of these silane compounds before calcination is irradiated with polarized ultraviolet light, it can be cross-linked in a specific direction with a smaller irradiation amount. From the above, when these silane compounds are used as the alignment film material, the shortening of the tact time and the improvement of the alignment property in the optical alignment can be realized at the same time. By using these, a photo-alignment alignment film can be formed with high production efficiency.

Here, the manufacturing method of the present invention will be described chemically with reference to FIG. FIG. 1 is a diagram showing a process of manufacturing an alignment film when the above (Equation 9) is used as a coating material. When the silane compound solution of the above formula (9) is applied to the substrate surface, a dehydrochlorination reaction occurs between the silane compound and the hydroxyl group on the substrate surface, and the silane compound is siloxane-bonded to the substrate surface. This reaction is the dehydrochlorination reaction 1. The chemisorption reaction forms a chemisorption film composed of a group of chemisorption molecules. The reaction in which the compound molecule chemically bonds to the substrate surface by such a reaction is generally called a chemisorption reaction.

The siloxane bond is formed by the S of the silane compound.
Since the reaction is a reaction between iCl groups and OH groups, if the silane compound solution contains a large amount of water, the reaction is hindered. If the surrounding atmosphere contains a large amount of water, the chemical adsorption to the substrate surface may occur. Be inhibited. Therefore, in order to smoothly advance the chemisorption reaction on the substrate surface, in the coating process, OH
Use a non-aqueous solvent not containing active hydrogen such as
The coating operation is preferably performed in an atmosphere of about% RH or less.

The drying step in FIG. 1 is for the purpose of removing the solvent of the silane compound solution, and FIG. 1 shows a case where this drying is performed in air containing a humidity exceeding 35% RH. It is. When drying is performed in air containing humidity, a dehydrochlorination reaction 2 occurs between the remaining Cl portion of the silane compound chemically adsorbed and the water simultaneously with the drying of the solvent, and the Cl portion is inactivated. After removing the solvent in an anhydrous atmosphere, the dehydrochlorination reaction 2 may be performed by exposing the substrate surface to humidity.

The ultraviolet irradiation step in FIG. 1 is a step of causing a cross-linking reaction (photopolymerization) through a bond of a carbon-carbon double bond portion of a chemisorbed molecule. In this step, the adsorbed molecule is cross-linked in a specific direction. As a result, the coating has an orientation.

The firing step in FIG. 1 is a process in which OH portions are dehydrated to form siloxane bonds between chemically adsorbed molecules or between compound adsorbed molecules and the substrate. Since this reaction is a reaction in which molecules are polymerized at high temperature, such a reaction is referred to as a thermal polymerization reaction in this specification. By this thermal polymerization reaction, the chemically adsorbed film becomes a more firm film.

In the production method of the present invention, a compound in which the photosensitive group is a cinnamoyl group can be suitably used. Examples of the compound having a cinnamoyl group include the following compounds. When these are used as an alignment film material, photoalignment can be performed with a small amount of polarized ultraviolet light irradiation, so that the tact time in the liquid crystal panel manufacturing process can be reduced. Note that the cinnamoyl group refers to the chemical structure shown in Chemical Formula 1 above.

[0064] Here, Z is a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorine-containing hydrocarbon group, a silicon-containing hydrocarbon group, a sulfur-containing hydrocarbon group, or a silicon compound, and n is an integer of 1 or more.

As a typical example of the above (Equation 14),
The following (Equation 15) can be exemplified.

Further, as the compound in which the photosensitive group is a cinnamoyl group, a compound having a cinnamoyl group introduced into the substituent R or R 'of the polyimide may be used.

As a typical example of (Formula 14) when n = 1, a silane compound represented by the following (Formula 16) can be given. X3Si-O- (CH2) 6-O-CO-CH = CH-C6H5 (Formula 16) where X is a halogen, an isocyanate group, or an alkoxy group.

In the production method of the present invention, a compound in which the photosensitive group is a chalconyl group (formula 2) can be preferably used, and examples of such a compound include the following compounds.

[0069]

[0070] Here, Z is a hydrocarbon group, an oxygen-containing hydrocarbon group, a fluorine-containing hydrocarbon group, a silicon-containing hydrocarbon group, a sulfur-containing hydrocarbon group, or a silicon compound, and n is an integer of 1 or more.

The following (Equation 19) is a typical example of the above (Equation 17).

A typical example of the above (Equation 17) when n = 1 is the following (Equation 20). Here, X is a halogen, an isocyanate group, or an alkoxy group.

On the other hand, the following (Equation 21) is a typical example of (Equation 18).

A typical example of the above (Equation 18) when n = 1 is the following (Equation 22). Here, X is a halogen, an isocyanate group, or an alkoxy group.

The chalconyl-type compounds exemplified above are excellent in photosensitivity. Therefore, when these compounds are used as an alignment film material, photo-alignment can be realized with a smaller amount of polarized ultraviolet light irradiation. The time can be further reduced.

The compound in which the photosensitive group is a chalconyl group may be, for example, a compound in which a chalconyl group is introduced into the substituents R and R 'of the polyimide shown in Table 1 above.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the contents of the present invention will be specifically described based on embodiments. (First Example Group) Three substrates shown in FIG. 2 having circular ITO (Idium tin oxide) electrodes formed on the surface were prepared. Further, a polyimide represented by Chemical Formula 5 was prepared as an alignment film material, and this was dissolved in n-methyl-2-pyrrolidinone at a concentration of 5 wt% to form a coating solution. This solution is spin-coated on the surface of the substrate on which the ITO electrode has been formed so that the film thickness after firing becomes 50 nm.
For 50 minutes to form a coating film having a thickness of 50 nm.

Next, using a UV lamp, the coating surface of each substrate was irradiated with 254 nm polarized UV light at an irradiation energy of 0.5 J / cm ² (A1) and 1 J / cm ² (A
2) Irradiation was performed at ² J / cm ² (A3). Thereafter, baking was performed at 250 ° C. for 60 minutes to produce the substrates with alignment films A1 to A3 according to the first example group.

[0079]

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(First Comparative Example Group)
With the alignment films of the first comparative example group X1 to X3 in the same manner as the first example group, except that baking was performed at 0 ° C. for 60 minutes, and then the polarized UV light was irradiated on the coated film surface after the baking. A substrate was prepared. In this comparative example group, baking (hereinafter referred to as pre-baking) is performed before irradiation with polarized UV light.
Firing after light irradiation (hereinafter referred to as post-firing) is not performed.

[Evaluation of First Group of Alignment Films] A test liquid crystal cell was prepared, and the alignment characteristics of the respective alignment films prepared above were examined. Specifically, the two substrates with alignment films prepared above (prepared under the same conditions) were placed with the alignment film surface inside,
The liquid crystal cells were opposed to each other so that the alignment directions became crossed Nicols, and a left-twisted TN (twist nematic) liquid crystal was sealed between both substrates to form a test liquid crystal cell. Polarizing plates are arranged on both outer surfaces of the test liquid crystal cell, and visible light is transmitted from one surface,
On the other surface side, the light transmission state (bright and dark state) was visually observed, and the minute light and dark state (domain state) was observed using a polarizing microscope. Furthermore, voltage ON, O
FF was performed and the contrast ratio was determined. Table 2 shows these results.
It was shown to.

[0082]

[Table 2]

As shown in Table 2, the first embodiment group A1 to A3 in which polarized UV light was irradiated before the firing was performed.
The contrast ratio was remarkably large in each of the first comparative example groups X1 to X3 irradiated with light. The difference between the post-firing method (Example group) and the pre-firing method (Comparative example group) was most conspicuous in A1 and X1 where the light irradiation amount was the smallest.
That is, in the orientation observation, uniform and good liquid crystal orientation was confirmed in Example A1, but it was confirmed that the liquid crystal orientation was uneven in X1. From the comparison between A1 and X3, it was confirmed that the post-firing method can provide a contrast ratio equal to or higher than that of the pre-firing method with a quarter of the polarized UV irradiation dose in the pre-firing method.

As described above, it was demonstrated that the method of manufacturing the group of examples in which polarized UV light irradiation was performed before the baking treatment provided excellent liquid crystal alignment and a high contrast ratio as compared with the group of comparative examples. In addition, the height of the photo-alignment efficiency by the post-firing method is
It contributes to improvement of productivity and improvement of liquid crystal alignment characteristics.

(Second Embodiment Group) As in the case of the first embodiment group, three substrates on which circular ITO electrodes were formed were prepared. On the other hand, a compound of the above formula (Formula 15) having a cinnamoyl group was prepared as an alignment film material, and this compound and n-
A coating solution having a concentration of 5% by weight was prepared using methyl-2-pyrrolidinone. Then, this coating solution was applied to the substrate surface by spin coating so that the film thickness after firing became 50 nm, and dried at 85 ° C. for 10 minutes to form a coating film.

Next, on the coating surface of each of the above substrates,
Using a UV lamp, polarized UV light having a wavelength of 365 nm was converted to an energy amount of 0.25 J / cm ² (A4) and 0.5 J, respectively.
/ Cm ² (A5) and 1 J / cm ² (A6). Thereafter, baking was performed at 220 ° C. for 60 minutes to produce a substrate with an alignment film of A4 to A6 according to the second example group.

(Second Comparative Example Group)
With the alignment films of the second comparative example group X4 to X6 in the same manner as the second example group, except that baking was performed at 0 ° C. for 60 minutes, and then the polarized UV light was irradiated to the coated film surface after the baking. A substrate was prepared. In this comparative example group, similarly to the first comparative example group, pre-firing is performed, and post-firing after the irradiation of the polarized UV light is not performed.

[Evaluation of the Second Group of Alignment Films] The alignment state of the second group of alignment films was observed in the same manner as in the evaluation of the first group of alignment films. Table 3 shows the results.

[0089]

[Table 3]

The results in Table 3 show the same tendency as in Table 2 above, and the contrast ratios of Examples A4 to A6 according to the post-firing method are remarkably higher than Comparative Examples X4 to X6 according to the pre-firing. Was high. Further, in the case of the post-baking method, the light irradiation amount is 0.1.
Although good orientation was obtained even at 25 J / cm ² (A4), orientation was insufficient with the pre-baking method (X4).

By the way, the alignment film material and the wavelength of the polarized UV light are different between the first embodiment group and the second embodiment group.
In the example group (Table 2), polyimide (Formula 5) is used as the alignment film material, and a wavelength of 254 nm is used as the polarized UV light. In contrast, in the second embodiment group (Table 3), a compound having a cinnamoyl group (formula 15) was used as an alignment film material, and 36
A wavelength of 5 nm is used. Comparing the contrast ratio between the first embodiment group and the second embodiment group based on such a difference in the manufacturing conditions, the second embodiment group has a longer wavelength UV light. It is evident that a higher contrast ratio is obtained compared to the first example group, despite the use and lower dose. This result was obtained by using a compound having a photosensitive group having a cinnamoyl group, and applying the post-baking method according to the present invention.
This means that a liquid crystal panel having an excellent contrast ratio can be realized with less polarized UV light.

(Third Embodiment Group) As the substrate, the same substrate as used in the first embodiment group and the like was used. On the other hand, as an alignment film material, X having OC2H
Using the silane compound of the above (Formula 16), which is 5, the silane compound was dissolved in N-methyl-2-pyrrolidinone at a concentration of 0.5 wt% to form a coating film solution. Then, the entire substrate is immersed in this solution for 1 minute, and then the substrate is
A silane compound was applied to the substrate surface by a method of pulling up at a speed of m / sec.

Thereafter, the coated surface was dried at a temperature of 85 ° C. for 15 minutes to remove the solvent. A series of operations of dipping, pulling up and drying the substrate were performed in an anhydrous atmosphere having a relative humidity of 5% or less. After the coating film surface was exposed to a normal atmosphere having a relative humidity of about 40 RH% to 70 RH%, the coating film surface was irradiated with polarized UV light of 365 nm using a UV lamp. The irradiation energy amounts of polarized UV light to each substrate were 0.1 J / cm 2 (A7) and 0.25 J / cm 2 (A
8), 0.5 J / cm2 (A9), 1 J / cm2 (A1
0).

After irradiation with polarized UV light, the substrate was heated at 150 ° C. for 1 hour.
By performing a baking treatment of heating for 5 minutes, a substrate with an alignment film of A7 to A10 according to the third example group was manufactured.

The silane compound of formula (16) wherein X is OC2H5 is chemically adsorbed on the substrate surface by a dealcoholization reaction.

(Third Comparative Example Group) Following drying of the coating film surface,
Substrates with an alignment film of X7 to X10 according to the third comparative example group were produced in the same manner as in the third example group except that baking was performed, and thereafter, irradiation of polarized UV was performed.

(Fourth Embodiment Group) X is C as an alignment film material.
Substrates with an alignment film of A11 to A14 according to the fourth example group were manufactured under the same conditions as in the third example group except that the silane compound of the above (formula 16) was used. Note that the fourth embodiment group and the third embodiment group are represented by (Equation 16)
Is the only difference in X. In this group of examples, a film formed by chemically adsorbing a silane compound on the substrate surface is formed through a chemical reaction process substantially similar to that shown in FIG.

(Fifth Embodiment Group) The fourth embodiment is the same as the fourth embodiment except that a coating film washing step is added between the drying step and the ultraviolet irradiation step.
A15 to A according to the fifth example group in the same manner as the example group
Eighteen substrates with an alignment film were produced. Specifically, after applying the coating solution to the substrate and drying at 85 ° C. for 15 minutes to form a coating, the substrate is coated with N-methyl-2-pyrrolidinone (N
MP) to wash the coating surface, and dried again at 85 ° C. for 15 minutes. Thereafter, the coating film surface was exposed to the above-described normal atmosphere to deactivate the Cl (chlorine) portion. Then, 365n
m, irradiating with polarized UV light, and performing photo-alignment treatment.
The firing was performed.

In this embodiment group, a step of washing the coating film with a solvent was added. However, by the washing in the washing step, excessively applied molecules were removed from the substrate surface. Therefore, it is possible to form a monomolecular layer-like coating consisting essentially of molecules chemically adsorbed on the substrate surface. With such an extremely thin film, the alignment efficiency by irradiation with polarized ultraviolet rays is extremely high, so that an alignment film having excellent alignment characteristics can be manufactured with higher productivity.

(Sixth Embodiment Group) Except that a compound having a chalconyl group and wherein X is Cl, the silane compound of the above (Formula 20) was used as an alignment film material, Under the same conditions, A19 to A according to the sixth example group
22 substrates with an alignment film were produced. Also in this embodiment group, similarly to the fifth embodiment group, a liquid crystal alignment film composed of a monolayer coating film can be formed.

[Production conditions and alignment characteristics of silane compound-based photo-alignment film] The substrates with alignment films (two under the same conditions) of the third embodiment group to the sixth embodiment group and the third comparative example group were used. To assemble a left-twisted TN cell, inject a left-twisted TN liquid crystal, and apply A7 to A22, X7 to X10 T
An N liquid crystal cell was completed. The alignment characteristics of these liquid crystal cells were observed visually and using a polarizing microscope. Table 4 shows the results.

[0102]

[Table 4]

The applied voltage-transmittance characteristics (FIG. 3) were measured, and the contrast ratio and the hysteresis were calculated according to the following equations. The results are shown in Tables 5 and 6. Here, in FIG. 3, TS is the maximum transmittance, TE is the minimum transmittance,
TM is the transmittance between TS and TE. Also V
S is a voltage value that gives the transmittance TM when the voltage rises (OFF → ON), and VE is a voltage value that gives the transmittance TM when the voltage drops (ON → OFF).

Contrast ratio = TS / TE ... Hysteresis = VS-VE ...

[0105]

[Table 5]

[0106]

[Table 6]

Further, the liquid crystal cell prepared above was heated at 100 ° C.
For 1000 hours, the applied voltage-transmittance characteristic of this cell was measured, and the contrast ratio was calculated. The results are shown in Table 7.

[0108]

[Table 7]

The method for assembling the TN liquid crystal cell, the method for observing the orientation, the method for measuring the contrast ratio, and the like are the same as those described for the evaluation of the first group of alignment films.

As is clear from Table 4, the post-baking method of the present invention in which the photo-alignment is performed by using polarized ultraviolet rays before the baking treatment (the third to third baking methods).
In the group of Examples 6), good orientation was obtained with a light irradiation amount of 0.1 J / cm ² . On the other hand, a pre-baking method in which the coating film is subjected to photo-alignment after the baking treatment (third comparative example group)
In Example ² , even when the light irradiation amount was 0.25 J / cm ² , uneven alignment occurred and sufficient alignment characteristics could not be obtained.

In the third example group and the third comparative example group shown in Table 5, the example group has a significantly higher contrast ratio than the comparative example group, and the post-baking method can be applied even when a silane compound is used as the alignment film material. It proved to be suitable. Furthermore, from the comparison between the third embodiment group and the fourth to sixth embodiment groups,
Silane compound a molecular end is a Si-Cl, the molecular end than the silane compound is a Si-OC ₂ H _5, a high contrast ratio was confirmed to be obtained.

In Table 5, a comparison was made between the fifth embodiment group (cinnamoyl group) and the sixth embodiment group (chalconyl group) in which only the alignment film material was different and the other manufacturing conditions were the same.
It was confirmed that a higher contrast ratio was obtained in the sixth example group using the compound having a chalconyl group than in the fifth example group using the compound having a cinnamoyl group. This result is considered to be because the chalconyl group has a better photoreactivity than the cinnamoyl group.

Further, from a comparison between the fourth embodiment group and the fifth embodiment group which differ only in the presence or absence of a cleaning step and the same alignment film material, it was confirmed that the contrast ratio was improved by adding the cleaning step. The addition of the washing step improves the contrast ratio because excess molecules are removed by washing to form a monolayer coating, and such an ultra-thin coating increases the irradiation efficiency of polarized ultraviolet light. It is considered that each of the aligned molecules directly contributes to the liquid crystal alignment.

Table 6 shows the hysteresis of each cell. The hysteresis was smaller in the order of the third comparative example group> the third example group> the fourth example group = the fifth example group = the sixth example group. It has been demonstrated that the hysteresis property can be further reduced by adding a washing step.

Next, the storage stability of the alignment film will be described based on the results shown in Table 7. Table 7 of the third embodiment group and Tables 4 to
As is clear from the comparison with the group of 6 examples, X is C ₂
H ₅ compared with the third embodiment group using a silane compound which is O, towards the 4-6 embodiment group using a silane compound X is Cl is, 100 ° C., the contrast ratio after storage for 1000 hours Was much higher. As is clear from comparison of the results in Tables 5 and 7, the degree of decrease in the contrast ratio of the third embodiment group and the third comparative example group after storage is as follows.
It was significantly larger than those of the fourth to sixth examples. From these results, it was recognized that the silane compound where X is Cl was also excellent in durability.

[0116]

As described above, the production method of the present invention comprises a coating step of applying a solution containing an alignment film material having a photosensitive group to a substrate surface to form a coating film, and a coating step prior to firing. The film surface is provided with a photo-alignment treatment for irradiating polarized ultraviolet rays to orient the alignment film material molecules in a specific direction, and a baking step of baking and curing the coating film after the photo-alignment treatment. The coating constituent molecules can be aligned without unevenness by the amount of polarized ultraviolet light irradiation. Therefore, according to the present invention, it is possible to form a liquid crystal alignment film having more excellent alignment characteristics while shortening the tact time in the optical alignment treatment.

[Brief description of the drawings]

FIG. 1 is a view for chemically explaining a manufacturing process when an alignment film material having a chemical adsorption property is used.

FIG. 2 is a substrate for a liquid crystal cell having a circular ITO electrode formed on the surface of the substrate.

FIG. 3 is a graph showing a relationship between an applied voltage and a light transmittance in a TN liquid crystal cell.

────────────────────────────────────────────────── ─── Continued from the front page (56) References JP-A-10-26760 (JP, A) JP-A-11-125823 (JP, A) JP-A-4-16927 (JP, A) JP-A-1- 302225 (JP, A) JP-A-9-80440 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1337

Claims (7)

(57) [Claims] 1. A coating film forming step of applying a heat-polymerizable polyimide precursor having a photosensitive group to the surface of a substrate for a liquid crystal display panel to form a coating film made of the polyimide precursor; Irradiate ultraviolet light to orient the polyimide precursor molecules in the coating in the direction corresponding to the polarization direction of the polarized ultraviolet light, and polarize the polyimide precursor molecules to each other through the photosensitive group part of the polyimide precursor molecule. Photopolymerized along the direction corresponding to the direction, or photodecompose the photosensitive group part of the polyimide precursor molecule along the direction corresponding to the polarization direction of polarized ultraviolet light, to the polyimide precursor molecule group in the coating film An ultraviolet irradiation step of imparting anisotropy; and a thermal polymerization step of thermally polymerizing the polyimide precursor molecules in the coating film after the ultraviolet irradiation step. Construction method. 2. The thermal polymerization step is a step of causing a thermal polymerization reaction between the polyimide precursor molecules and / or the polyimide precursor molecules and the substrate surface by heating at a temperature of 400 ° C. or lower. 3. The method for producing a substrate with a liquid crystal alignment film according to item 1. 3. The coating film forming step includes a step of applying a solution containing a heat-polymerizable polyimide precursor having a photosensitive group in a main chain to a surface of a liquid crystal display panel substrate; The method for producing a substrate with a liquid crystal alignment film according to claim 1, further comprising: a drying step of removing the solvent from the application surface after the application. 4. The method for manufacturing a substrate with a liquid crystal alignment film according to claim 3, wherein a cleaning step of cleaning a coating film surface is provided between the drying step and the polarized ultraviolet ray irradiation step. . 5. The method for producing a substrate with a liquid crystal alignment film according to claim 1, wherein the photosensitive group of the polyimide precursor is a cinnamoyl group. 6. The method for producing a substrate with a liquid crystal alignment film according to claim 1, wherein the photosensitive group of the polyimide precursor is a chalconyl group. 7. The polyimide precursor according to claim 1, wherein the polyimide precursor is a silane-based compound containing a linear carbon chain, and the coating is a monolayer coating. 3. The method for producing a substrate with a liquid crystal alignment film according to item 1.