JP2001066605A - Liquid crystal alignment layer, its manufacture and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal alignment layer effective in a liquid crystal display device without elongating time for a aligning treatment by manufacturing the liquid crystal alignment layer in a stage for applying a polymer having a specified structure on a substrate and in a stage including an operation for photo-irradiating the applied polymer. SOLUTION: The solution of a polymer 14 having a structure expressed by the formula I, II or the like is applied on a substrate 15. The polymer (resin film) 14 applied on the substrate 15 is irradiated through an optical device 13 (e.g. a Glan-tailer prism) with a polarized UV 17 generated by converting a non-polarized light 16 generated from a UV lamp 11 excited by a power source 12 to form a liquid crystal alignment layer. The (-R1)-(-R5) in the formula I and II each denotes a -H, halogen group or alkyloxy group such as a methoxyl group. And (-R6)-(R9) each denotes -H, -CN, a phenyl group, a phenoxy group, an alkyl group such as a methyl group or an alkyloxy group such as a methoxyl group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a film for promoting the orientation of liquid crystal encapsulated in a liquid crystal panel by irradiating a light on a photosensitive polymer film, thereby improving a method of manufacturing a liquid crystal display. It is useful for.

[0002]

2. Description of the Related Art Conventionally, in order to align a liquid crystal sealed in a liquid crystal panel, as shown in FIG. 3, a surface of a polymer compound (32) such as polyimide applied to a substrate (31) is coated with nylon or polyester fibers. A liquid crystal alignment film produced by a method such as a rubbing treatment of rubbing with a drum (33) around which a planted cloth (34) is wound has been used. In addition, since such rubbing treatment may cause TFT elements to be destroyed by fine dust or static electricity in the liquid crystal panel manufacturing process, recently, vinyl cinnamate polymers, azo polymers, chalcone polymers, etc. There has been proposed an optical alignment technique for imparting a liquid crystal alignment function by irradiating a linearly polarized light to a coating film.

[0003]

The rubbing treatment in which the surface of the polymer compound is physically rubbed with a planted cloth causes discharge as described above due to fine dust and static electricity, and poses a problem in a liquid crystal panel manufacturing process. In addition, the orientation direction of the liquid crystal is limited to one fixed direction over the entire surface in the substrate, and there is a problem that a region in which the orientation direction of the liquid crystal is different cannot be formed in the substrate. On the other hand, a photo-alignment technique that imparts a liquid crystal alignment function by irradiating linearly polarized light to a coating film of a vinyl cinnamate-based polymer, an azo-based polymer, or a chalcone-based polymer can provide the liquid crystal alignment function without contact. Therefore, there is no discharge due to fine dust or static electricity,
By using the mask exposure, it is possible to form regions in the substrate where the liquid crystal orientation directions are different. However, the materials reported so far require a large irradiation energy to provide a liquid crystal alignment function. For example, it has been reported in polyvinyl crystal cinnamate that an energy amount of ^{20 to} 30 J / cm ² is required to form a good alignment film in 3D15 (1998) of the Liquid Crystal Society of Japan. In addition, even with azo-based polymers,
The necessity of an energy amount of mJ / cm ² is shown in the proceedings of the Liquid Crystal Society of Japan, 2B05 (1998).
When such a material is used, in a manufacturing process of a liquid crystal panel, if a large area of mother glass is irradiated collectively, the irradiation energy density becomes low and the alignment processing time becomes long. On the other hand, it is possible to increase the irradiation energy density by increasing the size of the light source, but there is a problem that the light irradiation device becomes large-sized and is not practical.

[0004]

In view of the above-mentioned problems, the present invention has a structure represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or Chemical Formula 4 and at least Chemical Formula 5
Alternatively, a liquid crystal alignment film using a homopolymer or a copolymer represented by Chemical Formula 7, wherein the structure represented by Chemical Formula 6 is included in a side chain, and the main chain is a hydrocarbon, acrylate, methacrylate, siloxane, or the like, and production thereof Provide a way.

Embedded image However, x: y = 100-0: 0-100, n = 1-1
2, m = 1 to 12, j = 1 to 12, X, Y = none, -CO
O, -OCO -, - N = N -, - C = C-or-C 6 H 4 -, W 1, W 2 =
Formula 1 or Formula 2 or Formula 3 or Formula 4
It is a structure represented by

The polymer has, in a side chain, a mesogen component frequently used in a liquid crystalline polymer and a structure represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or Chemical Formula 4 containing a cinnamylidene (or derivative thereof) group. By irradiating a non-polarized light (hereinafter, referred to as “natural light”) or a linearly polarized light or a partially polarized light to a coating film of the polymer from a diagonal direction to a normal direction of the substrate. In addition, a liquid crystal alignment film exhibiting a pretilt angle by photocrosslinking can be formed. The photocrosslinking formula 3, in cinnamylideneacetyl group represented by _{-R 1 ~-R 9 = -H} , believed crosslinking proceeds by dimerization reaction to form a cyclobutane bond shown in Scheme 1 . This solution not only solves the occurrence of discharge due to fine dust and static electricity in the rubbing process, but also the orientation in only one direction, and uses materials such as vinyl cinnamate-based polymer, azo-based polymer, and chalcone-based polymer. The problems of the prior art, such as a longer alignment processing time and a need for a large-scale light irradiation device in the optical alignment technology, are solved.

[0006]

Embedded image The rectangle described in Reaction Formula 1 is a molecular chain containing a mesogen component, which connects the polymer main chain and the photosensitive group.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below. The homopolymer or copolymer represented by Chemical Formula 7 is
Formula 1, Formula 2, Formula 3, or Formula 4 containing a substituent such as biphenyl, terphenyl, phenylbenzoate, or azobenzene, which is frequently used as a mesogen component of a liquid crystalline polymer, and a cinnamylidene (or a derivative thereof) group. It is a polymer having a main chain of a structure such as hydrocarbon, acrylate, methacrylate, siloxane, etc., containing a side chain of a structure having a photosensitive group having the structure shown.

As a material having a photosensitive group having a similar structure, a photosensitive resin synthesized by reacting cinnamylidene acetic acid chloride with polyvinyl alcohol is disclosed by H. Tanka et al. In Journal of Polymer Science: Polymer Chemistr.
y Edition, 10, 3279 (1972). This photosensitive resin has been proposed as a material for photoresist and is said to exhibit high photosensitivity. Such a material may be used as it is for a liquid crystal alignment film material, but it cannot exhibit a pretilt angle indispensable for liquid crystal display. Further, there is no case in which a photosensitive group such as a cinnamylidene (or a derivative thereof) group is used for a liquid crystal alignment film.

A polymer coating film formed by applying (spin coating or casting) a solution of the polymer of the present invention on a substrate is non-oriented at the time of film formation, and is represented by Formula 5 or Formula 6.
Are not oriented in a specific direction. But,
When irradiating natural light from an oblique direction with respect to the substrate normal direction of the film, or irradiation of linearly polarized light or partially polarized light,
It contains a structure represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or Chemical Formula 4 in the traveling direction of the irradiated light and its vertical direction, or in the direction in which the irradiated linearly polarized light or partial polarized light has large electric field oscillation and its perpendicular direction. A difference occurs in the dimerization ratio of the photosensitive group, and as a result, the film becomes anisotropic. When liquid crystal molecules come into contact with the anisotropic film, the liquid crystal molecules are oriented by the interaction with the film. In order to proceed with the dimerization reaction, it is necessary to irradiate light having a wavelength at which the portion of the photosensitive group represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or Chemical Formula 4 can react. This wavelength is represented by Formula 1 or Formula 2 or Formula 3 or Formula 4-
Although it varies depending on the type of R ₁ to R ₉ , it is generally 200-5
00 nm, and in particular, the effectiveness of 250-450 nm is often high.

Experiments have confirmed that the polymer of the present invention can impart a liquid crystal alignment function with a relatively small amount of irradiation energy. This is presumably because light absorption is extended to a longer wavelength region and the photosensitivity is improved as compared with the case where the polymer is a cinnamic acid group having a similar structure. In FIG.
In chemical formula 7, W ₁ = chemical formula 3, x: y = 100:
0, n = 6, m = 2, X = none, -R 1 ~-R 8 = -H, -R
₉ shows spectral absorption spectra of a polymer of the present invention in which ₉ = -CN and a comparative polymer in which α-cyanocinnamylideneacetyl group is substituted with a cinnamic acid group in the same structure. It can be seen that the latter has a light absorption end near 330 nm, whereas the polymer of the present invention has a light absorption end extending to around 420 nm.

FIG. 5 shows the amount of irradiation energy required to impart a liquid crystal alignment function when a high-pressure mercury lamp is used with these two polymers. These polymers have a pretilt angle of liquid crystal molecules of 90 with increasing irradiation energy.
From 0 ° to approach 0 °, but in the comparative polymer in which α-cyanocinnamylideneacetyl group was substituted by cinnamic acid group with the same structure, the pretilt angle was 5 ° or less, but 1 ° C.
While it is estimated to be about 500 mJ / cm ² , the polymer of the present invention can achieve this at 250 mJ / cm ² .

As described above, in the liquid crystal alignment film using the polymer of the present invention and the method for producing the same, the natural light or the linearly or partially polarized light is irradiated from a direction oblique to the substrate normal direction. Accordingly, since a liquid crystal alignment function having a pretilt angle can be provided, a step of physically rubbing the substrate surface is not required, so that static electricity, dust, and the like are not generated. Furthermore, since the liquid crystal alignment function is developed with a relatively small amount of irradiation energy, an effective liquid crystal alignment film for a liquid crystal display device can be provided without lengthening the alignment processing time.

The method for synthesizing the polymer of the present invention is described below. (Polymer 1) 4-Hydroxy-4'-hydroxyethoxybiphenyl was synthesized by heating 4,4'-biphenyldiol and 2-chloroethanol under alkaline conditions. This product is added under alkaline conditions with 1,
6-Dibromohexane was reacted to synthesize 4- (6-bromohexyloxy) -4′-hydroxyethoxybiphenyl. Next, lithium methacrylate was reacted to synthesize 4-hydroxyethoxy-4 ′-(6′-biphenyloxyhexyl) methacrylate. This product was dissolved in tetrahydrofuran, and AIBN (azobisisobutyronitrile) was added as a reaction initiator and polymerized to obtain a polymer having a hydroxyl group at a side chain terminal. Separately, cinnamylidene acetic acid and thionyl chloride were reacted to synthesize cinnamylidene acetic acid chloride in tetrahydrofuran with the polymer having a hydroxyl group at the side chain terminal, thereby obtaining a polymer 1 represented by Chemical Formula 8. .

Embedded image

(Polymer 2) 4,4'-biphenyldiol and 2-chloroethanol were heated under alkaline conditions to synthesize 4-hydroxy-4'-hydroxyethoxybiphenyl. This product was reacted with 1,6-dibromohexane under alkaline conditions to obtain 4- (6
-Bromohexyloxy) -4'-hydroxyethoxybiphenyl was synthesized. Next, lithium methacrylate was reacted to give 4-hydroxyethoxy-4 ′-(6 ′).
-Biphenyloxyhexyl) methacrylate was synthesized. This product was dissolved in tetrahydrofuran, and AIBN (azobisisobutyronitrile) was added as a reaction initiator and polymerized to obtain a polymer having a hydroxyl group at a side chain terminal. Separately, α-cyanocinnamylidene acetic acid and thionyl chloride are reacted with each other to react α-cyanocinnamylidene acetic acid chloride with a polymer having a hydroxyl group at the side chain terminal in tetrahydrofuran, thereby obtaining a chemical formula. Polymer 2 shown in No. 9 was obtained.

Embedded image

A method for synthesizing a polymer having a cinnamylidene acetyl group substituted by a cinnamic acid group having a similar structure and used as a comparative example will be described. (Polymer 3) 4,4′-biphenyldiol and 2-chloroethanol were heated under alkaline conditions to synthesize 4-hydroxy-4′-hydroxyethoxybiphenyl. This product is added under alkaline conditions with 1,
6-Dibromohexane was reacted to synthesize 4- (6-bromohexyloxy) -4′-hydroxyethoxybiphenyl. Next, lithium methacrylate was reacted to synthesize 4-hydroxyethoxy-4 ′-(6′-biphenyloxyhexyl) methacrylate. Finally, cinnamoyl chloride was added under basic conditions to obtain a monomer. This monomer was dissolved in tetrahydrofuran, and AIBN (azobisisobutyronitrile) was added as a reaction initiator to polymerize, thereby obtaining a polymer 3 represented by Chemical Formula 10.

Embedded image

[0016]

1 and 2 show a method (apparatus) for producing a liquid crystal alignment film using the polymer of the present invention. Power supply (12),
An ultraviolet lamp (11) excited by (22),
The non-polarized light (16) and (26) generated in (21) was converted into polarized ultraviolet light (17) via an optical element (13) (for example, a Glan-Taylor prism), and applied to the substrate (15). Irradiation to the resin film (14) (irradiation from the normal direction of the substrate is not limited) or resin film (2) applied on the substrate (25) without passing through an optical element
4) Irradiate.

Example 1 Polymer 1 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). This substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and was converted to linearly polarized light using a Glan-Taylor prism.
/ Cm ² for 180 seconds at room temperature from the direction perpendicular to the horizontal plane. A liquid crystal E7 is prepared by fabricating two such substrates.
By filling with [Merck Japan Ltd.], a TN type liquid crystal cell having a thickness of 4.5 μm was assembled. Observation of the liquid crystal cell by crossed Nicols revealed that the liquid crystal molecules were aligned, and the pretilt angle was 7.5 °. This TN
The driving voltage of the liquid crystal cell was 2V.

Example 2 Polymer 2 was dissolved in chloroform and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). This substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and was converted to linearly polarized light using a Glan-Taylor prism.
/ Cm ² from the direction perpendicular to the horizontal plane at room temperature for 100 seconds. A liquid crystal E7 is prepared by fabricating two such substrates.
By filling with [Merck Japan Ltd.], a TN type liquid crystal cell having a thickness of 4.5 μm was assembled. Observation of the liquid crystal cell by crossed Nicols confirmed that the liquid crystal molecules were aligned, and the pretilt angle was 5.0 °. This TN
The driving voltage of the liquid crystal cell was 2V.

Comparative Example 1 Polymer 3 was dissolved in chloroform, and spin-coated to a thickness of about 100 nm on a substrate covered with ITO (indium tin oxide). This substrate was arranged so as to be inclined by 30 degrees with respect to the horizontal plane, and was converted to linearly polarized light using a Glan-Taylor prism.
/ Cm ² from the direction perpendicular to the horizontal plane at room temperature for 100 seconds. A liquid crystal E7 is prepared by fabricating two such substrates.
An attempt was made to assemble a TN type liquid crystal cell having a thickness of 4.5 μm by filling with [Merck Japan Co., Ltd.]. In this liquid crystal cell, liquid crystal molecules were close to homeotropic alignment (pretilt angle: 80 °). ), A TN type liquid crystal cell could not be produced. On the other hand, the substrate is
When the substrate is irradiated with 2.5 mW / cm ² of ultraviolet light converted into linearly polarized light using a Glan-Taylor prism from the direction perpendicular to the horizontal plane at room temperature for 500 seconds, the pretilt angle is 8. It was 0 °, and a TN type liquid crystal cell could be produced.

[0020]

As described above, according to the liquid crystal alignment film using the polymer of the present invention and the method for producing the same, natural light or linearly polarized light or partial light is obliquely oblique to the substrate normal direction. By irradiating the polarizing light, a liquid crystal alignment function having a pretilt angle can be provided, so that a process such as physically rubbing the substrate surface is unnecessary, and no static electricity, dust, etc. are generated. Therefore, defects generated in the assembly process of the liquid crystal display are significantly reduced. Further, since the liquid crystal alignment function is exhibited with a relatively small amount of irradiation energy, an effective liquid crystal alignment film for a liquid crystal display device can be provided without lengthening the alignment processing time.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a method for producing a liquid crystal alignment film using a polymer of the present invention (at the time of irradiation with polarized light).

FIG. 2 is a conceptual diagram showing a method for producing a liquid crystal alignment film using the polymer of the present invention (at the time of natural light irradiation).

FIG. 3 is an example diagram showing a conventional method for manufacturing a liquid crystal alignment film.

FIG. 4 shows spectral absorption spectra of a polymer of the present invention and a polymer for comparison.

FIG. 5 shows a change in pretilt angle of the polymer of the present invention and a polymer for comparison with the amount of light irradiation energy.

[Explanation of symbols]

 11, 21 ... ultraviolet lamp 12, 22 ... power supply 13 ... optical element (Glan-Taylor prism) 14, 24 ... resin film (polymer) 15, 25 ... substrate 16, 26: unpolarized light 17: polarized ultraviolet light

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H025 AA00 AB14 AB20 AC01 AD01 BC04 BC05 FA03 2H090 HB13Y HC05 JB02 KA05 LA16 MA11 MB14

Claims (5)

[Claims] 1. Chemical formula 1, chemical formula 2, or chemical formula 3.
Or a step of applying a polymer having a structure represented by Chemical Formula 4 onto a substrate, and a step including an operation of irradiating the applied polymer with light, characterized in that the liquid crystal alignment film and Its manufacturing method. Embedded image Embedded image Embedded image Embedded image _{However, -R 1 ~-R 5 =} -H, alkyl group such as a halogen group or a methoxy group, further _{-R 6 ~-R 9 = -H} , -C
It is an alkyl group such as N, a phenyl group, a phenoxy group, a methyl group, or an alkyloxy group such as a methoxy group. 2. The structure W ₁ represented by the chemical formula 1 or the chemical formula 2 or the chemical formula 3 or the chemical formula 4 according to claim ₁ ,
A homopolymer or copolymer of Formula 7 having a structure represented by Formula 5 or Formula 6 containing W ₂ in a side chain and having a main chain of hydrocarbon, acrylate, methacrylate, siloxane, or the like is applied on a substrate. A liquid crystal alignment film and a method for producing the same, characterized in that the film is produced in a step of performing a step of irradiating the applied polymer with light. Embedded image Embedded image Embedded image However, x: y = 100-0: 0-100, n = 1-1
2, m = 1 to 12, j = 1 to 12, X, Y = none, -CO
O, -OCO -, - N = N -, - C = C-or-C 6 H 4 -, W 1, W 2 =
Formula 1 or Formula 2 or Formula 3 or Formula 4
It is a structure represented by 3. A step of applying a homopolymer or a copolymer represented by the chemical formula 7 according to claim 2 on a substrate, and irradiating the applied polymer with light obliquely to a direction normal to the substrate. A liquid crystal alignment film and a method of manufacturing the same, characterized in that the film is manufactured in a step including an operation of performing the following steps. 4. A step of applying a homopolymer or a copolymer represented by the chemical formula 7 according to claim 2 on a substrate, and linearly polarizing the applied polymer obliquely with respect to a normal direction of the substrate. Or, in a step including an operation of irradiating partial polarization, characterized by being produced, a liquid crystal alignment film,
Its manufacturing method. 5. The method according to claim 1, 2 or 3.
A liquid crystal display device in which a liquid crystal is aligned by a liquid crystal alignment film manufactured by the manufacturing method according to claim 4.