JP2002038158A - Method for orienting liquid crystal molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To orient liquid crystal molecules, while controlling the inclination angle of the orientation. SOLUTION: This method for orienting the liquid crystals, comprising forming a liquid crystal layer comprising liquid crystal molecules on a substrate to orient the liquid crystal molecules, characterized by adding a pyridinium quaternary salt to the liquid crystal layer or the adjacent layer to control the inclination angle of the liquid crystal molecules by the action of the pyridinium quaternary salt.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for aligning liquid crystal molecules in which the angle of alignment can be controlled.

[0002]

2. Description of the Related Art Since liquid crystal compounds exhibit both liquid-like fluidity and crystal-like regular molecular arrangement in a liquid crystal layer, they are expected to be applied in various fields. Control is indispensable for engineering application to liquid crystal devices represented by liquid crystal displays. In particular, control of the tilt angle including the pretilt angle is one of the important issues of the current liquid crystal alignment technology.

[0003] The molecular orientation of liquid crystal is a typical one.
1) homeotropic alignment, 2) homogeneous alignment,
Three types are known: 3) tilt alignment, 4) hybrid alignment, 5) twisted alignment, 6) planar alignment, and 7) focal conic alignment. For more details, "Basic and Application of Liquid Crystal", Industrial Research Institute Publishing (1991) Year).

In general, what kind of alignment can be obtained depends on what kind of alignment treatment is to be performed on the substrate surface if the liquid crystal to be used is determined. Various methods have been proposed for the alignment treatment, which are described in detail in "Basics and Applications of Liquid Crystals", published by the Industrial Research Institute (1991). For example,
Appl. Phy for vertical or parallel orientation
s. Lett., 27, 268 (1975), App
l. Phys. Lett., Vol. 29, p. 67 (1976),
Appl. Phys. Lett., Vol. 22, p. 111 (1973)
), A method of chemically adsorbing an aligning agent such as a chromium carboxylate complex or an organic silane onto a substrate surface.
3, 18 (1974), Phys. Rev. Lett., Vol. 25, p. 67 (1976), and the like, a method of physically adsorbing an aligning agent on a substrate surface, Appl. Phys. Lett. 24th
Vol., P. 297 (1974), etc., a method of polymerizing a low molecular weight substance onto a substrate surface by plasma discharge, J. Appl. Phy.
s., 47, 1270 (1976) and the like disclose a method of polymerizing a high molecular weight substance onto a substrate surface by the action of a high electric field. Next, as a method of tilting parallel alignment
Appl. Phys. Lett., 25, 479 (1974)
For example, the oblique deposition method of depositing an oxide such as silicon oxide on a substrate surface from an oblique angle is disclosed in Japanese Patent Application Laid-Open No. H11-146572. . As another method for oblique vertical alignment, an oblique vapor deposition method in which an oxide such as silicon oxide is vapor-deposited from an oblique angle while rotating the substrate surface is disclosed in the 6th Meeting of the Liquid Crystal Symposium, p. 96 (1980). Have been. According to this method, although stable orientation having a certain tilt orientation angle can be obtained, there are problems such as low productivity for industrial production and difficulty in increasing the area.

As a method of aligning molecules, there is a method of forming an organic film on the substrate surface, rubbing the surface with a cloth such as cotton, nylon, polyester or the like in a certain direction, and aligning the liquid crystal molecules in the rubbing direction. In this method, a stable orientation can be obtained relatively easily, and therefore, this method is exclusively used industrially. Examples of the organic film include polyvinyl alcohol, polyoxyethylene, polyamide, and polyimide. Among them, polyimide is most commonly used in terms of chemical stability, thermal stability, and the like. In such a liquid crystal alignment film, it is known that the tilt angle of liquid crystal molecules changes depending on the alignment film used. For example, JP-A-5-4
Nos. 3687, 8-12759 and 8-220541
Nos. 8-220542, 9-143196, 9-230354, 9-278724, and 10-
Nos. 45690 and 10-123532 disclose various alignment films capable of tilt alignment. However, the tilt angle depends on the properties of the alignment film itself, and the angle cannot be easily adjusted. A method of controlling the alignment of liquid crystal molecules by light is also known. For example, in Functional Materials, Vol. 17, p. 13 (1997), various alignment films whose tilt angle can be controlled by light are described.
However, these methods need to use polarized light irradiation or polarized ultraviolet light irradiation, or need to change the incident angle of polarized light to adjust the inclination angle, and cannot always easily control the inclination angle. .

As described above, various orientation techniques have been proposed.
A technique for tilt-aligning a liquid crystal compound has also been disclosed.
However, none of them is sufficient from the viewpoint of controlling the tilt angle, and there has been a demand for the development of a method capable of easily controlling the tilt angle of the liquid crystal compound.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to easily control the tilt angle of the liquid crystal compound.

[0008]

The present invention provides the following (1) to
(4) A method for aligning liquid crystal molecules is provided. (1) A method of forming a liquid crystal layer containing liquid crystal molecules on a substrate and orienting the liquid crystal molecules, wherein a pyridinium quaternary salt is added to the liquid crystal layer or an adjacent layer, and the liquid crystal is formed by the action of the pyridinium quaternary salt. A method for aligning liquid crystal molecules, comprising controlling the tilt angle of molecules. (2) The method for aligning liquid crystal molecules according to claim 1, wherein the pyridinium ring of the pyridinium quaternary salt has an aliphatic amino group as a substituent. (3) The method for aligning liquid crystal molecules according to (1), wherein the pyridinium quaternary salt is represented by the following formula (I):

[0009]

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Wherein R ¹ has 1 to 30 carbon atoms.
R ² and R ³ are each independently an aliphatic group having 1 to 8 carbon atoms, or R ² and R ³ are bonded to form a nitrogen-containing heterocyclic ring; And X is an anion]. (4) The method for aligning liquid crystal molecules according to (1), wherein the pyridinium quaternary salt is represented by the following formula (II):

[0011]

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[Wherein, R ¹ has 1 to 30 carbon atoms.
R ² and R ³ are each independently an aliphatic group having 1 to 8 carbon atoms, or R ² and R ³ are bonded to form a nitrogen-containing heterocyclic ring; And X is an anion]. (5) The pyridinium salt is used in a molar ratio of 1 to the liquid crystal molecules.
Use in the range of / 1000 to 250/1000 (1)
3. The method for aligning liquid crystal molecules according to item 1. (6) The method for aligning liquid crystal molecules according to (1), wherein the liquid crystal molecules are discotic liquid crystal molecules. (7) The method for aligning liquid crystal molecules according to (1), wherein the liquid crystal molecules have a triphenylene nucleus.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In this specification, a substrate refers to a material for mounting a liquid crystal layer or a material for sandwiching a liquid crystal layer which is a component of a liquid crystal cell. Specifically, a polymer film such as a triacetyl cellulose (TAC) film or a polyethylene naphthalate (PEN) film is used. In addition, a glass plate, an ITO substrate, a color filter substrate, a quartz plate, a silicon wafer, and a polarizing plate can be used as the substrate. The substrate may be provided with an alignment layer, a transparent electrode (ITO), a color filter layer, a black matrix, and a thin film transistor. Further, an alignment process such as the formation of an electrode pattern, the rubbing process described above, and the irradiation of polarized UB may be performed. A single substrate or a pair of substrates may be used. When a pair is used, a spacer, a sealant, or the like may be used as necessary. In this specification, the layer adjacent to the liquid crystal layer is preferably a layer closest to the liquid crystal layer among layers located between the substrate and the liquid crystal layer. The layer adjacent to the liquid crystal layer may have a function as an alignment film or a transparent electrode.

The liquid crystal layer is mainly composed of liquid crystal molecules. As the liquid crystal molecules, discotic liquid crystal molecules, rod-like liquid crystal molecules, and cholesteric liquid crystal molecules are preferable. Discotech liquid crystalline molecules are particularly preferred. The discotec liquid crystal molecules preferably have a triphenylene nucleus. Two or more liquid crystal molecules may be used in combination. Components other than liquid crystal molecules (eg, dyes, dichroic dyes, polymers, polymerizers, sensitizers, phase transition temperature lowering materials, stabilizers) may be added to the liquid crystal layer. As a method for providing the liquid crystal layer on the substrate, a known method is employed. As a method of applying, a known method,
For example, curtain coating, extrusion coating, roll coating, spin coating, dip coating, bar coating, spray coating, slide coating, print coating, and the like are employed. At this time, the substrate may be provided with necessary layers and portions including the necessary processing and alignment layers as described above. As a method of injecting liquid crystal molecules between the substrates, a general method such as a dispenser method or a bell jar method is employed. Further, a liquid crystal layer may be applied to a substrate, and another substrate or a substrate to which another liquid crystal layer is applied may be combined.

In the present invention, the inclination angle of the liquid crystal molecules is controlled by using a pyridinium quaternary salt. Addition of a pyridinium quaternary salt generally increases the tilt angle of liquid crystal molecules. As a result, the tilt angle of the liquid crystal molecules can be controlled. The pyridinium ring of the pyridinium quaternary salt preferably has an aliphatic amino group as a substituent. The substitution position of the aliphatic amino group is preferably the 4-position. Pyridinium ring, other than the aliphatic amino group,
It may have another substituent (amino, hydroxyl, thiol, carboxyl, alkyl group, alkoxy group, halogen atom). The N-substituent (group bonded to the nitrogen atom) of the pyridinium quaternary salt is preferably an aliphatic group. Aliphatic groups include alkyl groups, substituted alkyl groups,
Includes alkenyl, substituted alkenyl, alkynyl and substituted alkynyl groups. The aliphatic group may have a cyclic structure. The chain aliphatic group may have a branch. Examples of the substituent of the aliphatic group include an aryl group, an alkoxy group, an alkylthio group, an amide group, an acyl group, an acyloxy group, an alkoxycarbonyl group, a carboxyl, a halogen atom, an alkoxyalkyl group, an alkyloxyoxycarbonylalkyl group, and , 2,3,3,4,4
5,5,6,6,7,7,8,8,8-pentadecafluorooctyloxycarbonylethyl. Examples of anions serving as counterions of pyridinium quaternary salts include fluorine ions, chloride ions, bromine ions, iodine ions,
Includes benzenesulfonium ions and paratoluenesulfonium ions. Pyridinium quaternary salts represented by the following formula (I) are preferred.

[0016]

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In the formula (I), R ¹ is an aliphatic group having 1 to 30 carbon atoms. Aliphatic groups include alkyl groups, substituted alkyl groups, alkenyl groups, substituted alkenyl groups, alkynyl groups, and substituted alkynyl groups.
The aliphatic group may have a cyclic structure. The cycloaliphatic group includes a group having a steroid structure. The chain aliphatic group may have a branch. Examples of the substituent of the aliphatic group include an aryl group, an alkoxy group, an alkylthio group, an amide group, an acyl group, an acyloxy group, an alkoxycarbonyl group, a carboxyl, a halogen atom, an alkoxyalkyl group, an alkyloxyoxycarbonylalkyl group,
2,2,3,3,4,4,5,5,6,6,7,7,
8,8,8-Pentadecafluorooctyloxycarbonylethyl is included.

In the formula (I), R ² and R ³ are each independently an aliphatic group having 1 to 8 carbon atoms, or a nitrogen-containing complex in which R ² and R ³ are bonded to each other. Form a ring. An aliphatic group is an alkyl group, a substituted alkyl group,
Includes alkenyl, substituted alkenyl, alkynyl and substituted alkynyl groups. A chain aliphatic group is preferred over a cyclic aliphatic group. R ² and R ³ are each independently preferably an alkyl group, a substituted alkyl group, an alkenyl group or a substituted alkenyl group, more preferably an alkyl group or a substituted alkyl group, and most preferably an alkyl group. preferable. R ² and R ³ preferably have 1 to 7 carbon atoms, and preferably have 1 to 5 carbon atoms.
Is more preferable, and most preferably 1 to 4. Examples of aliphatic groups include methyl, ethyl, n-
Propyl, isopropyl, cyclopropyl, n-butyl, sec-butyl, t-butyl group, cyclobutyl group, cyclopropylmethyl, n-pentyl, neopentyl, n-
Hexyl, cyclohexyl and n-heptyl are included. The nitrogen-containing heterocyclic ring formed by combining R ² and R ³ is
It is preferably a 5- or 6-membered ring.

In the formula (I), X is an anion. Examples of anions include chloride, bromine, iodine, p-toluenesulfonium and benzenesulfonium. Pyridinium quaternary salts represented by the following formula (II) are more preferred.

[0020]

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In the formula (II), R ¹ , R ² , R ³ and X have the same definition as in the formula (I). Below, the example of a pyridinium quaternary salt is shown.

[0022]

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[0023]

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[0024]

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

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As an example of the method of adding a pyridinium quaternary salt to a layer adjacent to a liquid crystal layer, there is a method of adding a pyridinium quaternary salt to a coating solution for forming a layer adjacent to a liquid crystal layer on a substrate. And a method of directly applying a solution of a pyridinium quaternary salt as a layer adjacent to the liquid crystal layer.However, a pyridinium quaternary salt is used in a coating solution for forming a layer adjacent to the liquid crystal layer. The addition method is preferred.
As for the amount of addition, it is adopted that an appropriate amount is added to the target tilt angle within a range that does not disturb the alignment of the liquid crystal, but the molar ratio is 1/1000 to 250/10 with respect to the liquid crystal molecules used.
It is adopted as a preferable example that it is added in the range of 00. Examples of the coating method include the above-described examples of the liquid crystal layer coating method. Examples of the method of adding the pyridinium quaternary salt to the liquid crystal layer itself include a method of adding a pyridinium quaternary salt or a solution containing the quaternary salt after coating and forming the liquid crystal layer on a substrate, or a method of adding a solution containing a pair of substrates. And then adding a pyridinium quaternary salt or a solution containing the quaternary salt after injecting liquid crystal molecules into the liquid crystal.

As an example of a method of adding liquid crystal molecules to a liquid to be injected between substrates, a liquid crystal injection liquid produced by an ordinary method may be added in an amount suitable for a desired tilt angle within a range that does not disturb the alignment of the liquid crystal. The addition of a pyridinium quaternary salt of At this time, other additives may be used in combination. The amount of addition is not limited as long as it does not disturb the alignment of the liquid crystal, but it is 1/1000 to 25/10 in molar ratio to the liquid crystal molecules used.
It is adopted as a preferable example that the addition is performed in the range of 0. As a method of adding liquid crystal molecules to a liquid applied to a substrate, an appropriate amount of a pyridinium quaternary salt for a desired tilt angle within a range that does not disturb the alignment of the liquid crystal is applied to a liquid crystal coating liquid manufactured by an ordinary method. Addition is employed. At this time,
Other additives may be used in combination. The amount of addition is not limited as long as it does not disturb the orientation of the liquid crystal, but it is preferably added in a molar ratio of 1/1000 to 25/100 with respect to the liquid crystal molecules used.

[0032]

[Example 1] (Evaluation of liquid crystal tilt angle controllability) An aqueous solution of polyvinyl alcohol modified with methacryloyloxyisocyanate described in JP-A-8-48197 was coated on a glass substrate (thickness:
(0.85 mm) with a bar coater, and dried and rubbed. Next, the following discotic liquid crystal compound (DLC) 100 was added to 400 parts by weight of methyl ethyl ketone.
A solution prepared by dissolving 1 part by weight of cellulose acetate butyrate and 0.05 part by weight of a pyridinium quaternary salt was applied by spin coating, followed by drying at room temperature. Liquid crystal layer 2
After heating to 00 degrees, the liquid crystal compound is aligned at 130 degrees,
In this state, the substrate was rapidly cooled to room temperature to fix the alignment state. The average tilt angle of the liquid crystal molecules was calculated by measuring the angle of the obtained thin film in the direction in which the retardation was minimized.

[0033]

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Used tilt controlling agent Average tilt angle Unused 27 degrees Compound 2 33 degrees Compound 3 34 degrees

Example 2 (Evaluation of liquid crystal tilt angle controllability) Thickness 100 μm, size 2
A 70 mm × 100 mm triacetyl cellulose film (Fujitac, manufactured by Fuji Photo Film Co., Ltd.) was used as a substrate. An alkyl-modified polyvinyl alcohol (MP-203, manufactured by Kuraray Co., Ltd.) was applied on the substrate to a thickness of 0.5 μm, and dried and rubbed. Next, 100 parts by weight of the discotic liquid crystal compound (DLC) used in Example 1 in 400 parts by weight of methyl ethyl ketone, 1 part by weight of a copolymer obtained from the following fluorinated monomers M-1 and M-2, and the following polyfunctional monomer (M-3) A solution obtained by dissolving 10 parts by weight of a pyridinium quaternary salt was applied using a bar coater, and then dried at room temperature. The coating layer was heated to 125 degrees to align the liquid crystal compound, and the substrate was rapidly cooled to room temperature to fix the alignment state. The average tilt angle of the liquid crystal molecules was calculated by measuring the angle of the obtained thin film in the direction in which the retardation was minimized.

[0036]

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[0037]

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Addition amount of tilt control agent used (molar ratio to liquid crystal) Average tilt angle Not used --- 33 degrees Compound 1 0.3 36 degrees Compound 2 0.3 36 degrees Compound 3 0.3 37 degrees Compound 40 3 37 degrees Compound 5 0.3 35 degrees Compound 6 0.3 37 degrees Compound 7 0.3 35 degrees Compound 8 0.3 37 degrees Compound 9 0.3 36 degrees Compound 10 0.3 37 degrees Compound 11 0.3 36 ° Compound 12 0.3 37 ° Compound 13 0.3 36 ° Compound 14 0.3 35 ° Compound 15 0.337 ° Compound 16 0.3 38 ° Compound 17 0.3 38 ° Compound 18 0.3 37 Degree Compound 19 0.3 36 Degree Compound 20 0.3 36 Degree Compound 21 0.3 38 Degree

[Embodiment 3] (Evaluation of liquid crystal tilt angle controllability) Sunever SE-610 (Nissan Chemical Co., Ltd.) was applied as an alignment film on a glass substrate using a bar coater (using a No. 4 bar), dried and rubbed. Processing was performed. Next, methyl ethyl ketone (400 parts by weight)
The discotic liquid crystal compound used in Example 1 (10
0 parts by weight), cellulose acetate butyrate (1
Parts by weight) and Compound 3 (molar ratio to liquid crystal: 0.5) were applied by spin coating, and then dried at room temperature. After heating the liquid crystal layer to 200 degrees, the liquid crystal compound was aligned at 130 degrees, and in that state, the substrate was rapidly cooled to room temperature to fix the alignment state. Based on the observation of the liquid crystal compound and the crystal rotation method, it was confirmed that the discotic liquid crystal compounds were aligned parallel to the rubbing direction and were vertically (homogeneously) and uniformly (monodomain) aligned with the substrate. . On the other hand, in the system to which the pyridinium quaternary salt was not added as a control, a uniform alignment state was not obtained.

[Example 4] (Evaluation of liquid crystal tilt angle controllability) Sunever SE-610 (Nissan Chemical Co., Ltd.) was applied as an alignment film on a glass substrate using a bar coater (using a No. 4 bar), dried and rubbed. Processing was performed. Next, methyl ethyl ketone (400 parts by weight)
The discotic liquid crystal compound used in Example 1 (10
0 parts by weight) and a solution in which Compound 3 (molar ratio to liquid crystal was 0.5) was applied by spin coating, and then dried at room temperature. On the obtained liquid crystal layer coated substrate, Sanever SE-610 was coated as an alignment film on a glass substrate with a bar coater, and dried and rubbed, and another glass substrate was bonded by rotating the rubbing direction by 180 degrees. Was. Next, after the liquid crystal layer was heated to 200 degrees, the liquid crystal compound was aligned at 130 degrees, and in that state, the substrate was rapidly cooled to room temperature to fix the alignment state. Observation with a polarizing microscope confirmed that the liquid crystal molecules were aligned in the rubbing direction and tilted with respect to the substrate, and the tilt angle was measured based on the crystal rotation method.

Used tilt controlling agent Average tilt angle Unused 32 degrees Compound 3 40 degrees

Example 5 (Evaluation of ability to control liquid crystal tilt angle) Compounds (2) and (3)
The relationship between the amount of addition and the inclination angle was examined in the same manner as in Example 2 using. As shown below, a concentration-dependent increase in the tilt angle was confirmed.

[0043]

[0044]

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H090 HB07Y HD14 KA04 MA11 MB01 MB13 4C055 AA04 BA01 CA01 DA27 DB02 DB08 GA01 4H027 BA08 BD12 DA02 DM03

Claims (7)

[Claims] 1. A method for forming a liquid crystal layer containing liquid crystal molecules on a substrate and aligning the liquid crystal molecules, wherein a pyridinium quaternary salt is added to the liquid crystal layer or an adjacent layer, and the action of the pyridinium quaternary salt is performed. A method for aligning liquid crystal molecules, wherein the tilt angle of liquid crystal molecules is controlled by the method. 2. The method for aligning liquid crystal molecules according to claim 1, wherein the pyridinium ring of the pyridinium quaternary salt has an aliphatic amino group as a substituent. 3. The method for aligning liquid crystal molecules according to claim 1, wherein the pyridinium quaternary salt is represented by the following formula (I): [Wherein, R ¹ is an aliphatic group having 1 to 30 carbon atoms; R ² and R ³ are each independently an aliphatic group having 1 to 8 carbon atoms, or R ² and R ³
And X form a nitrogen-containing heterocyclic ring; and X is an anion. 4. The method for aligning liquid crystal molecules according to claim 1, wherein the pyridinium quaternary salt is represented by the following formula (II): [Wherein, R ¹ is an aliphatic group having 1 to 30 carbon atoms; R ² and R ³ are each independently an aliphatic group having 1 to 8 carbon atoms, or R ² and R ³
And X form a nitrogen-containing heterocyclic ring; and X is an anion. 5. The method for aligning liquid crystal molecules according to claim 1, wherein the pyridinium salt is used in a molar ratio to the liquid crystal molecules in the range of 1/1000 to 250/1000. 6. The method according to claim 1, wherein the liquid crystal molecules are discotic liquid crystal molecules. 7. The method according to claim 1, wherein the liquid crystal molecules have a triphenylene nucleus.