JP2001049010A - Liquid crystal orientation film, its manufacture and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an orientation film with a relatively small quantity of irradiated energy by coating a polymer having a carbon-carbon double bond substituted with a furyl group on a substrate and irradiating it with a light. SOLUTION: This polymer has a structure of formula I, II, III, or IV. In the formulae, R1-3 are each H, a halogen, or an alkyloxy: R4-5 are each H, CN, or an alkyloxy. A homopolymer or a copolymer of formula VII having a branched chain having a structure represented by formula V or VI, and a main chain being a hydrocarbon, (meth)acrylate, a siloxane, or the like, is coated on a substrate, and a light is irradiated on the coated polymer pref. from slanting direction from the normal line to the substrate. It is pref. that the irradiation is a linear polarized or a partially polarized light. In formulae V-VII, W1-W2 are groups of formulae I-IV; x:y=100-0:0-100: (n), (m), and (j) are 1-12; X and Y are single bond, COO, OCO, N=N, C=C, or C6H4. Consequently, the objective liquid crystal orientation film suitable for liquid crystal display is obtd. without prolonging an orientation treatment time.

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 orient liquid crystal sealed in a liquid crystal panel, as shown in FIG. 3, a surface of a polymer compound such as polyimide (32) applied to a substrate (31) is flocked with nylon or polyester fibers. A liquid crystal alignment film produced by a method such as a rubbing process of rubbing with a drum (33) around which a wrapped cloth (34) is wound has been used. In addition, such a rubbing process is performed in a process of manufacturing a liquid crystal panel.
Recently, fine dust and static electricity can cause the TFT element to be destroyed.In recent years, linearly polarized light has been applied to coatings such as vinyl cinnamate-based polymers, azo-based polymers, and chalcone-based polymers to achieve liquid crystal alignment functions. Photoalignment techniques to be applied have also been proposed.

[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, in the materials reported so far, irradiation energy of 0.3 to several J / cm ² is required to impart a liquid crystal alignment function. For example, polyvinyl cinnamate requires an energy amount of ^{20 to} 30 J / cm ^{2 to} obtain a good alignment film.
(1998). In addition, the azo-based polymer requires an energy amount of up to 1000 mJ / cm ² , which is reported by the Liquid Crystal Society of Japan 2B05 (1998).
Reported in. 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 imageHowever, x: y = 100-0: 0-100, n = 1-1
2, m = 1 to 12, j = 1 to 12, X, Y, = none, −
COO, -OCO-, -N = N-, -C = C-or-C₆H_Four-, W ₁, W_Two
= Chemical formula 1, Chemical formula 2, Chemical formula 3, or Chemical formula
4.

The polymer contains, in a side chain, a mesogen component frequently used in liquid crystalline polymers and a photosensitive group such as a β- (2-furyl) acryloyl (or a derivative thereof) group. By irradiating the film with non-polarized light (hereinafter, referred to as “natural light”) obliquely with respect to the substrate normal direction, or with linearly polarized light or partially polarized light, β- (2-furyl) acryloyl (or The part of the (derivative) group is crosslinked by dimerization as shown in Reaction Formula 1, and a liquid crystal alignment film exhibiting a pretilt angle can be formed. By this solution, not only the occurrence of discharge due to fine dust or static electricity in the rubbing treatment, the orientation in only one direction is solved, but also vinyl cinnamate-based polymer, azo-based polymer,
In the photo-alignment technology using a material such as a chalcone-based polymer, the problems of the conventional technology such as a long alignment treatment time and a need for a large-scale light irradiation device 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 with reference to examples. The homopolymer or copolymer represented by the chemical formula 7 is composed of a substituent such as biphenyl, terphenyl, phenylbenzoate or azobenzene, which is frequently used as a mesogen component of a liquid crystalline polymer, and β- (2-furyl)
A polymer having a side chain of a structure to which a photosensitive group such as an acryloyl (or a derivative thereof) group is bonded and having a main chain of a structure such as hydrocarbon, acrylate, methacrylate, or siloxane. As a material having a similar photosensitive group, a photosensitive resin synthesized by reacting β- (2-furyl) acrylic acid chloride with polyvinyl alcohol is described in M. Tu.
da et al., Journal of Polymer Science: Part A-
1, 7, 259 (1969). 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 where a photosensitive group such as a β- (2-furyl) acryloyl (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 the side chain portion represented by the chemical formula 5 or 6 is specified. Not facing the direction. However, when the film is irradiated with natural light, or linearly polarized light or partial polarized light, from a direction oblique to the normal direction of the substrate, the traveling direction of the irradiated light and its perpendicular direction, or the irradiated linearly polarized light or partial polarized light, There is a difference in the degree of dimerization of a photosensitive group such as a β- (2-furyl) acryloyl (or a derivative thereof) group between the direction in which the polarization electric field oscillation is large and the direction perpendicular thereto, and as a result, the film becomes anisotropic. Becomes When liquid crystal molecules come into contact with the anisotropic film, the liquid crystal molecules are oriented by the interaction with the film. This dimerization reaction is considered to form a cyclopropane bond as shown in Reaction Formula 1. In order to proceed with this dimerization reaction, a photosensitive compound represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or Chemical Formula 4 is required. Irradiation of light having a wavelength at which the moiety of the group can react is required. This wavelength is represented by the formulas -R _1-
It varies depending on the kind of R ₅ but in general 200-500n
m, and in particular, the effectiveness of 250 to 400 nm is high in many cases.

[0008] 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 because, compared to the case where the polymer is a cinnamic acid group having a similar structure, light absorption is extended to a longer wavelength region, and photosensitivity is improved. FIG. 4 shows that in chemical formula 7, W ₁ = chemical formula 3, x: y = 100: 0, n
= 6, m = 2, X = none, -R ₁ to -R ₅ = -H, and a polymer having the same structure and a β- (2-furyl) acryloyl group substituted with a cinnamic acid group. 3 shows a spectral absorption spectrum in the case of merging. It can be seen that the light-absorbing end of the polymer of the present invention extends to around 370 nm, while the latter has a light-absorbing end near 330 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.
° and approaches 0 °, but with the same structure, β- (2-
In a polymer in which a furyl) acryloyl group is substituted by a cinnamic acid group, the pretilt angle becomes 5 ° or less, but 1000 mJ.
/ Cm ² or more, whereas in the polymer of the present invention, it can be achieved at 30 mJ / cm ² .

Experiments have also confirmed that the polymer of the present invention has excellent heat resistance. FIG. 6 shows that in chemical formula 7, W ₁ = chemical formula 3, x: y = 100: 0, n = 6, m
= 2, X = none, a liquid crystal cell prepared in the polymer of the present invention the _{-R 1 ~-R 5 = -H} , a similar structure beta-(2-furyl)
FIG. 4 shows the change over time of the pretilt angle when a liquid crystal cell prepared from a polymer in which an acryloyl group is substituted with a cinnamic acid group is left in a 100 ° C. atmosphere. The liquid crystal cell produced from the polymer of the present invention did not significantly change with respect to the pretilt angle before heating of 2 ° even when left in an atmosphere of 100 ° C. for 100 hours. On the other hand, β- (2
In a liquid crystal cell prepared from a polymer in which a (furyl) acryloyl group is substituted with a cinnamic acid group, the pretilt angle before heating is 2 ° to 43 ° when left in an atmosphere of 100 ° C. for 100 hours.
Has changed greatly. This is because the β- (2-furyl) acryloyl (or derivative thereof) group has both photosensitivity and thermosetting properties, so that natural light or oblique light is applied to the polymer film obliquely to the direction normal to the substrate. It is considered that the anisotropy of the film generated by irradiating the linearly polarized light or the partially polarized light is fixed by the curing caused by the subsequent heat.

As described above, in the liquid crystal alignment film using the polymer of the present invention and the method for producing the same, it is possible to irradiate natural light or linearly or partially polarized light obliquely 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, β- (2-furyl) acrylic acid chloride synthesized by reacting β- (2-furyl) acrylic acid with thionyl chloride is reacted with the polymer having a hydroxyl group at the side chain terminal in tetrahydrofuran. Thus, Polymer 1 represented by Chemical Formula 8 was obtained.

Embedded image

[0013] In a similar structure used as a comparative example, β-
A method for synthesizing a polymer in which a (2-furyl) acrylate group is substituted with a cinnamic acid group will be described. (Polymer 2) 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 and polymerized to obtain Polymer 2 represented by Chemical Formula 9.

Embedded image

[0014]

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 polymer resin film (14) (this is not limited to irradiation from the normal direction of the substrate), or the polymer resin film (24) applied on the substrate (25) without passing through an optical element ).

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 converted to linearly polarized light using a Glan-Taylor prism.
cm ² was irradiated from a direction perpendicular to a horizontal plane at room temperature for 20 seconds. By preparing two such substrates and filling them with a liquid crystal E7 (manufactured by Merck Japan KK), a thickness of 4.
A TN type liquid crystal cell of 5 μm was assembled. Observation of the liquid crystal cell with crossed Nicols revealed that the liquid crystal molecules were aligned, and the pretilt angle was 4.5 °. The driving voltage of this TN type liquid crystal cell was 2V.

Comparative Example 1 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 converted to linearly polarized light using a Glan-Taylor prism.
cm ² was irradiated from a direction perpendicular to a horizontal plane at room temperature for 20 seconds. By preparing two such substrates and filling them with a liquid crystal E7 (manufactured by Merck Japan KK), a thickness of 4.
A TN type liquid crystal cell of 5 μm was assembled. In this liquid crystal cell, no alignment of liquid crystal molecules was observed because the liquid crystal alignment film swelled and collapsed.

Comparative 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 converted to linearly polarized light using a Glan-Taylor prism.
cm ² was irradiated for 500 seconds at room temperature from the direction perpendicular to the horizontal plane. By preparing two such substrates and filling them with a liquid crystal E7 [manufactured by Merck Japan Ltd.], a TN type liquid crystal cell having a thickness of 4.5 μm was assembled. In this liquid crystal cell, the orientation of liquid crystal molecules was confirmed, and the pretilt angle was:
8.9 °.

[0018]

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 comparative polymer.

FIG. 5 shows a change in pretilt angle depending on the amount of light irradiation energy of the polymer of the present invention and a comparative polymer.

FIG. 6: Evaluation of heat resistance of a polymer of the present invention and a comparative polymer in a liquid crystal cell (change in pretilt angle with time when left in an atmosphere of 100 ° C.)

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Ultraviolet lamp 13 ... Optical element (Gran Taylor prism) 14 ... Resin film (polymer) 15 ... Substrate

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) C08L 83:00 F term (reference) 4F071 AA14 AA14X AA33 AA33X AA67 AA67X AG12 AG13 AG15 AH12 BA02 BB02 BB13 BC01 4J035 CA13M GA02 GB05 LA03 LB20 4J100 AL71P AL74P BA02P BA12P BC43P BC44P BC52P CA04 JA39

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, an alkyloxy group such as -R ₁ to -R ₃ , -H, a halogen group or a methoxy group, and -R ₄ , -R ₅ , =-
H, —CN, or an alkyloxy group such as a methoxy group. 2. The chemical formula 1 or the chemical formula according to claim 1.
Structure W represented by Formula 2 or Formula 3 or Formula 4₁,
W_TwoWith the structure represented by Formula 5 or Formula 6 containing
In the chain, the main chain is hydrocarbon, acrylate, methacrylic
A homopolymer of the formula 7 such as
Is a step of applying a copolymer on a substrate, and
Being made in a process that involves irradiating the polymer with light
And a method for producing the same. Embedded imageEmbedded imageEmbedded imageHowever, x: y = 100-0: 0-100, n = 1-1
2, m = 1 to 12, j = 1 to 12, X, Y, = none, −
COO, -OCO-, -N = N-, -C = C-or-C₆H_Four-, W ₁, W_Two
= Chemical formula 1, Chemical formula 2, Chemical formula 3, or Chemical formula
4. 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.