JPH04350822A - Liquid crystal oriented film and production thereof and liquid crystal optical element - Google Patents

Abstract

PURPOSE:To form the liquid crystal oriented film which can form all of homeotropic, homogeneous and tilt orientations by one method and can form different orientation states on one substrate. CONSTITUTION:Liquid crystal molecules 6 are fixed in the oriented state to the surface of a high-polymer material 5 when a liquid crystal material is put between the cells formed by combining two sheets of base bodies successively laminated with electrode layers 2 and high-polymer precursors in such a manner that the high-polymer precursors face each other and when the high-polymer precursors are cured by irradiation with light or heating under impression of at least either of an electric field or magnetic field. This film functions as the liquid crystal oriented film 3. The orientation state of the film 3 can be changed arbitrarily by the magnitude and direction of the electric field or magnetic field at the time of curing and the formation of the different orientation states on the one substrate is possible as well. This liquid crystal oriented film 3 is usable in combination with other liquid crystal oriented films and liquid crystals and the formation of various kinds of the oriented films is possible.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a liquid crystal alignment film and a method for manufacturing the same. Used in liquid crystal optical elements such as shutters.

0002

2. Description of the Related Art It is known that the arrangement of liquid crystal molecules varies depending on the surface condition of a substrate constituting a liquid crystal cell. In order to utilize the optical properties of liquid crystal, it is necessary that liquid crystal molecules are regularly arranged in a certain area. Methods for aligning liquid crystal molecules include homeotropic alignment, in which the major axes of liquid crystal molecules are perpendicular to the substrate, homogeneous alignment, in which they are parallel, and tilt alignment, in which they are tilted at a certain angle. Conventionally, the method for creating a liquid crystal alignment film that obtains homeotropic alignment is to treat the surface of a glass substrate with an organic silane coupling agent having a long-chain alkyl group; A rubbing method is known in which the surface of the substrate is rubbed in one direction with absorbent cotton or gauze, or a rubbing method is known in which a polymer film of polyvinyl alcohol or polyimide is created on the substrate surface and the surface is rubbed with absorbent cotton or gauze. . Furthermore, as a method for creating a liquid crystal alignment film that obtains tilt alignment, SiO and TiO2
A method is known in which the film is deposited obliquely to the substrate. [Liquid Crystal Device Handbook (Nikkan Kogyo Shimbun) p.
240-257]

As described above, there are three alignment states of liquid crystals: homeotropic alignment, homogeneous alignment, and tilted alignment, and the methods for producing each are different. In the treatment with an organic silane coupling agent, since the surface of the substrate is chemically treated, there is a drawback that reproducibility and uniformity are low due to differences in the activity of the substrate surface. In the rubbing method, the surface of the substrate and the polymer film are rubbed in one direction with absorbent cotton or gauze, which has the disadvantage that static electricity is generated on the film surface and dust and the like adhere to the film surface, damaging the TFT (thin film transistor). Further, although the oblique vapor deposition method is an effective means for obtaining oblique orientation, it has the disadvantage that there is a limit to the inclination angle, and at the same time, since it is created by vapor deposition, it is difficult to increase the area and the mass productivity is low. Furthermore, with conventional methods, it has been impossible to freely change the surface condition of the liquid crystal alignment film depending on the location.

An object of the present invention is to provide a liquid crystal alignment film that can form a stable alignment film over a large area with good reproducibility without contaminating dust or generating static electricity, and a method for manufacturing the same. Another object is to provide a means for freely changing the surface condition of a liquid crystal alignment film depending on the location.

0004

[Means for Solving the Problems] The present invention is characterized in that a polymer material that is hardened by light or heat is used as a liquid crystal alignment film. When curing these polymeric substances,
If the liquid crystal molecules on the surface of a polymer material are kept in a predetermined alignment state,
The polymer material after hardening functions as a liquid crystal alignment film.

[0005] Furthermore, the method for manufacturing a liquid crystal alignment film of the present invention includes:
A liquid crystal material is placed between a cell in which two substrates on which an electrode layer and a polymer precursor layer are successively laminated are combined so that the polymer precursors face each other, and the polymer precursor is layered under the application of at least one of an electric field or a magnetic field. It is characterized in that liquid crystal molecules are supported on the surface of a polymer material in an oriented state by hardening the material. One of the two opposing substrates may be laminated with an arbitrary alignment film instead of the polymer precursor layer. The liquid crystal material may be injected into a cell with a fixed gap, or the liquid crystal material may be sandwiched between two substrates. In the present invention, homeotropic alignment, homogeneous alignment, and tilted alignment can be arbitrarily formed by changing the magnitude and direction of the electric field or magnetic field during curing of the polymer precursor. In addition, since the liquid crystal molecules are fixed by curing with light or heat, there is no generation of static electricity and the incorporation of dust can be prevented. Further, since it is possible to increase the area and at the same time to perform partial curing, it is possible to form different orientation states on one substrate.

The present invention also provides a liquid crystal optical element in which the liquid crystal alignment film produced in this manner is applied to at least one of two opposing substrates, and a liquid crystal material is sandwiched between the two substrates. provide.

[0007] The substrate used in the present invention is a substrate having an electrode layer such as ITO and at least one side of which is transparent, and glass, plastic, metal, etc. can be used. The two boards are
Install the electrode so that it faces the liquid crystal. Spacers used in normal liquid crystal devices can be used to set the spacing between the substrates, and the spacing is preferably about 1 μm to 5 μm.

The liquid crystal material used in the production of the liquid crystal alignment film of the present invention is not limited to a single liquid crystal compound, but may include two or more liquid crystal compounds or liquid crystal compound substances. It may be a liquid crystal material. As the liquid crystal material, any of nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, etc. can be used. The dielectric constant anisotropy can be positive or negative, and by changing the frequency,
A dual-frequency drive liquid crystal material that can take both positive and negative values may also be used.

In the liquid crystal optical element of the present invention, the liquid crystal material placed between the liquid crystal alignment films and actually driven may be the same or different from the liquid crystal used in manufacturing the liquid crystal alignment films. The liquid crystal material is not limited to a single liquid crystal compound, and may be a liquid crystal composition containing two or more types of liquid crystal compounds or substances other than liquid crystal compounds. As the liquid crystal material, any of nematic liquid crystal, smectic liquid crystal, cholesteric liquid crystal, etc. can be used. The dielectric constant anisotropy may be positive or negative, and a dual-frequency drive liquid crystal material that can take both positive and negative values by changing the frequency may also be used. It can also be used even if a dichroic dye is mixed in to make it colored.

[0010] As the polymer precursor used in the present invention, there are used a photo-curable type which is polymerized by irradiation with ultraviolet rays, electron beams, etc., and a thermo-curable type which is cured by heat. Although the polymeric material after the polymeric precursor is cured does not necessarily have to be completely transparent, it is desirable that the polymeric material has a degree of transparency that does not cause significant attenuation when light passes through the polymeric material. Furthermore, a colored polymer material can be used as required. Regarding the solidity of the polymeric substance, it is not necessary that it be rigid, and it may be flexible, elastic, or flexible.

[0011] As a photocurable polymer precursor that forms a cured product by irradiation with light, a photopolymerizable monomer or a photopolymerizable oligomer or a mixture of a photopolymerizable monomer and a photopolymerizable oligomer having an appropriate viscosity is used. can be used. Examples of photopolymerizable monomers include acrylic monomers such as bisphenol A diacrylate, bisphenol A dimethacrylate, and pentaerythol tetraacrylate, which can be used either as a single substance or as a mixture of two or more types. Examples of photopolymerizable oligomers include urethane acrylate oligomers, epoxy acrylate oligomers, and ester oligomers, and a single substance or a mixture of two or more types can be used.

As the photocuring initiator, an acetophenone type, benzoin type, benzophenone type, or thioxanthone type is used, and it may be solid or liquid, but it is preferable that it is soluble or compatible with the photocurable polymer precursor.

[0013] As the thermosetting polymer precursor, a liquid having an appropriate viscosity and curing by heating is used. Examples of the polymer precursor include urea resins, melamine resins, phenol resins, epoxy resins, alkyd resins, urethane resins, and unsaturated polyester resins, and these can be used alone or in combination. It is also possible to use a two-part curable material such as an epoxy resin and an amino resin, which is cured by mixing two parts.

[0014] In the present invention, a polymer precursor that is cured by light or heat is applied onto the electrode layer of a substrate with an electrode layer. It can also be diluted and applied.

Examples of solvents for diluting the polymer precursor include aromatic hydrocarbons such as benzene, xylene, and monochlorobenzene, ketones such as acetone, methyl ethyl ketone, and cyclohexanone, alcohols such as methanol, ethanol, and isopropanol, and acetic acid. Esters such as ethyl and methyl cellosolve; aliphatic halogenated hydrocarbons such as carbon tetrachloride, chloroform, dichloromethane, dichloroethane, and trichloroethylene; ethers such as tetrahydrofuran and dioxane; Amides such as N-dimethylformamide and sulfoxides such as dimethyl sulfoxide are used.

The coating method can be carried out using a spin coater, a spray coater, a bar coater, a dip coater or the like.

[0017] When a solvent is used, drying is desirably carried out by heating under stationary or blowing air conditions, but it is also possible to leave it at room temperature, and it is also possible to dry it under reduced pressure at room temperature or by heating. Film thickness after drying is 100 angstroms ~ 5000 angstroms
The coating is applied to a thickness of 200 angstroms to 1000 angstroms.

The gap between the substrates is determined by placing spacers such as SiO2 beads or polyethylene film on the substrates.

The magnitude of the electric field or magnetic field to be applied varies depending on the physical properties of the liquid crystal material to be fixed and the orientation state of liquid crystal molecules to be obtained. Application of an electric field and a magnetic field can also be performed simultaneously. The direction in which the magnetic field is applied is also determined by the required orientation state.

[0020] It is not necessary that the entire substrate is cured at once, and the polymer precursor may be cured in multiple steps by changing its orientation depending on the location.

A pair of liquid crystal alignment films in which liquid crystal molecules are fixed by curing a polymer precursor with light or heat under the application of an electric field, a magnetic field, or both an electric field and a magnetic field can also be used as is as a liquid crystal optical element. However, once the cell has been disassembled, it can be reassembled using another liquid crystal. Furthermore, it may be combined with a liquid crystal alignment film cured under different conditions or a liquid crystal alignment film cured under different conditions, or may be combined with an alignment film subjected to chemical treatment, rubbing treatment, or the like. At this time, it is not necessary that the liquid crystal material fixed on the polymer surface as the liquid crystal alignment film and the liquid crystal material actually driven are the same.

[0022]

[Function] When curing a polymer precursor, if the liquid crystal molecules on the surface of the polymer precursor are kept in a predetermined orientation state, the liquid crystal molecules on the surface of the polymer material after curing will be fixed in that orientation state and will be randomly generated. You can't go back to that state. Therefore, this polymer material can be used as a liquid crystal alignment film.

[0023] In order to maintain the liquid crystal molecules in a predetermined alignment state during curing, it is sufficient to continue applying an electric field or a magnetic field to the liquid crystal molecules. Either the electric field or the magnetic field may be applied, or both may be applied. Any alignment state of liquid crystal molecules can be realized by changing the magnitude and direction of the electric field or magnetic field. Therefore, in the present invention, liquid crystal alignment films in various alignment states can be easily produced with good reproducibility.

[0024] Furthermore, since rubbing is not performed as in the rubbing method, there is no contamination of dust or generation of static electricity.

Furthermore, by partially curing, different orientation states can be formed on one substrate.

[0026]

[Examples] The present invention will be explained in detail below using Examples, but the present invention is not limited to the following Examples unless the gist of the invention is exceeded.

Example 1 A mixed solution of 1 part of photopolymerizable oligomer UN9000PEP [manufactured by Neagami Kogyo Co., Ltd.], 19 parts of tetrahydrofuran, and an appropriate amount of benzophenone as a polymerization initiator was applied onto the electrode layer of a glass substrate with an electrode layer using a spin coater. and dried at 60°C for 5 hours. The thickness was approximately 2000 angstroms. Using the two same boards created in this way, we created an LCD E-8.
(manufactured by BDH) was sandwiched. Gap between substrates is 1.5μ
It was set as m. This liquid crystal cell was irradiated with ultraviolet rays for 10 seconds using a high-pressure mercury lamp while applying an AC voltage of 1 kHz and 15 V to cure the photopolymerizable oligomer. As a result of observing the obtained liquid crystal optical element with a polarizing microscope, a homeotropic liquid crystal alignment state was observed.

Example 2 Photopolymerizable oligomer M1200 [manufactured by Toagosei Co., Ltd.] 1
A mixed solution of 19 parts of tetrahydrofuran and an appropriate amount of diethoxyacetophenone as a polymerization initiator was applied onto the electrode layer of the glass substrate with an electrode layer using a spin coater, and dried at 60° C. for 5 hours. The thickness was approximately 1500 angstroms. A dual-frequency drive liquid crystal NR-1012XX [manufactured by Chisso Corporation] was sandwiched between two identical substrates thus prepared. The gap between the substrates was 1 μm. 4 in this liquid crystal cell
The photopolymerizable oligomer was cured by irradiating it with ultraviolet rays for 10 seconds using a high-pressure mercury lamp while applying an AC voltage of 0 kHz (Δε<0) and 20 V. As a result of observing the obtained liquid crystal optical element with a polarizing microscope, a homogeneous liquid crystal alignment state was observed.

Example 3 A mixed solution of 1 part of photopolymerizable oligomer UN9000PEP (manufactured by Neagami Kogyo Co., Ltd.), 19 parts of tetrahydrofuran, and an appropriate amount of benzophenone as a polymerization initiator was applied onto the electrode layer of a glass substrate with an electrode layer using a spin coater. and dried at 60°C for 5 hours. The thickness was approximately 2000 angstroms. Using the two same boards created in this way, we created an LCD E-8.
(manufactured by BDH) was sandwiched. The gap between the substrates was 2 μm. The photopolymerizable oligomer was cured by irradiating ultraviolet rays for 10 seconds with a high-pressure mercury lamp while applying an AC voltage of 1 kHz and 5 V to this liquid crystal cell. 5° to the vertical direction
It was confirmed by the crystal rotation method that a tilted liquid crystal alignment state was obtained.

Example 4 A mixed solution of 1 part of photopolymerizable oligomer UN9000PEP [manufactured by Neagami Kogyo Co., Ltd.], 19 parts of tetrahydrofuran, and an appropriate amount of benzophenone as a polymerization initiator was applied onto the electrode layer of a glass substrate with an electrode layer using a spin coater. and dried at 60°C for 5 hours. The thickness was approximately 1000 angstroms. Using the two same boards created in this way, we created an LCD E-8.
(manufactured by BDH) was sandwiched. The gap between the substrates was 1 μm. This liquid crystal cell was irradiated with ultraviolet rays for 10 seconds using a high-pressure mercury lamp while a magnetic field of 10,000 Gauss was applied to cure the photopolymerizable oligomer. As a result of observing the obtained liquid crystal optical element with a polarizing microscope, a homeotropic liquid crystal alignment state was observed.

Example 5 A mixed solution of 1 part of photopolymerizable oligomer UN9000PEP [manufactured by Neagami Kogyo Co., Ltd.], 19 parts of tetrahydrofuran, and an appropriate amount of benzophenone as a polymerization initiator was applied onto the electrode layer of a glass substrate with an electrode layer using a spin coater. and dried at 60°C for 5 hours. The thickness was approximately 1000 angstroms. A dual-frequency drive liquid crystal NR-1012XX (manufactured by Chisso Corporation) was sandwiched between two identical substrates thus prepared. The gap between the substrates was 1.5 μm. Half of this liquid crystal cell was masked with an ultraviolet blocking film. This liquid crystal cell was irradiated with ultraviolet rays for 10 seconds using a high-pressure mercury lamp while an AC voltage of 1 kHz and 10 V was applied. As a result, the photopolymerizable oligomer hardens only in the areas irradiated with ultraviolet rays,
A homeotropic liquid crystal alignment state was obtained. Next, the mask was removed, and ultraviolet rays were irradiated for 10 seconds using a high-pressure mercury lamp while applying an AC voltage of 50 kHz and 10 V to the liquid crystal cell. As a result, the photopolymerizable oligomer in the uncured portion was cured, a homogeneous liquid crystal alignment state was obtained, and different alignment states could be formed on a single substrate.

Example 6 Photopolymerizable oligomer M1200 [manufactured by Toagosei Co., Ltd.] 1
A mixed solution of 19 parts of tetrahydrofuran and an appropriate amount of diethoxyacetophenone as a polymerization initiator was applied onto the electrode layer of the glass substrate with an electrode layer using a spin coater, and dried at 60° C. for 5 hours. The thickness was approximately 1500 angstroms. A dual-frequency drive liquid crystal NR-1012XX [manufactured by Chisso Corporation] was sandwiched between two identical substrates thus prepared. The gap between the substrates was 1 μm. 1 in this liquid crystal cell
The photopolymerizable oligomer was cured by irradiating the photopolymerizable oligomer with ultraviolet light for 10 seconds using a high-pressure mercury lamp while applying an AC voltage of 00 Hz (Δε>0) and 20 V. As a result of observing the obtained liquid crystal optical element with a polarizing microscope, a homeotropic liquid crystal alignment state was observed. One sheet of this alignment film and one sheet of the alignment film prepared in Example 2 were combined. The gap between the boards is 1
It was set as μm. Liquid crystal NR-1012XX was injected into the liquid crystal cell. A hybrid orientation state was thereby obtained.

[0033]

As explained above, the present invention relates to a liquid crystal alignment film in which liquid crystal molecules are fixed in an oriented state to a polymer film, and the liquid crystal can be moved in any direction by an applied electric field, a magnetic field, or both an electric field and a magnetic field. Can be fixed in the oriented state. By this method, it is possible to form a stable liquid crystal alignment film without contaminating dust or generating static electricity. Furthermore, it is possible to create films with different orientation states depending on the location.

[Brief explanation of the drawing]

FIG. 1 shows an example of a cross-sectional view of a liquid crystal optical element according to the present invention.

FIG. 2 shows an example of an alignment state of a liquid crystal optical element according to the present invention.

[Explanation of symbols]

1 Board 2　Electrode layer 3. Liquid crystal alignment film 4 Liquid crystal layer 5. Polymer substances 6 Liquid crystal molecules

Claims (4)

[Claims] 1. A liquid crystal alignment film comprising a polymer material that is cured by light or heat, and having liquid crystal molecules fixed on the surface in a predetermined alignment state. 2. A liquid crystal material is placed between a cell in which two substrates each having an electrode layer and a polymer precursor layer sequentially laminated such that the polymer precursors face each other, and at least one of an electric field or a magnetic field is applied. 1. A method for producing a liquid crystal alignment film, characterized in that liquid crystal molecules are supported in an oriented state on the surface of a polymeric material by curing a polymeric precursor below. 3. A cell in which a substrate on which an electrode layer and a polymer precursor layer are sequentially laminated, and a substrate on which an electrode layer and an optional alignment film are sequentially laminated are combined such that the polymer precursor layer and the optional alignment film face each other. A liquid crystal alignment film characterized in that liquid crystal molecules are supported on the surface of the polymer material in an oriented state by inserting a liquid crystal material between the layers and curing the polymer precursor under the application of at least one of an electric field or a magnetic field. manufacturing method. 4. A liquid crystal material comprising two opposing substrates, an electrode layer sequentially laminated on at least one of the substrates, a liquid crystal alignment film according to claim 1, and a liquid crystal material sandwiched between the two substrates. Characteristic liquid crystal optical element.