JP5493446B2 - Optical anisotropic film manufacturing method and rubbing treatment method - Google Patents

Description

  The present invention relates to a method for producing an optical anisotropic film used for an image display device or the like.

Conventionally, an optical anisotropic film is incorporated in an image display device. The optically anisotropic film is used as a retardation film or a polarizing film (also referred to as a polarizer) due to its optical characteristics.
The optically anisotropic film can be obtained, for example, by applying a coating liquid containing a lyotropic liquid crystalline compound onto a substrate (solution casting method) and curing the coating film.

In producing the optical anisotropic film by the solution casting method, the following methods 1 to 4 are performed in order to align the lyotropic liquid crystalline compound.
Method 1: A lyotropic liquid crystalline compound is aligned by a shearing force applied to a coating solution (Patent Document 1).
Method 2: After peeling the coating film from the substrate, the lyotropic liquid crystalline compound is oriented by stretching the coating film (Patent Document 2).
Method 3: A photoactive molecular layer (photo-alignment film) is formed on a substrate, and a lyotropic liquid crystal compound is applied to the surface of the photo-alignment film to align the lyotropic liquid crystal compound (Patent Document 3).
Method 4: By rubbing the substrate, a surface having an alignment regulating force is formed, and a coating liquid is applied to the surface of the substrate to align the lyotropic liquid crystalline compound (Patent Document 4). .

When the method 1 is used, the lyotropic liquid crystalline compound may not be well aligned due to the coating conditions of the coating liquid and / or the structure of the lyotropic liquid crystalline compound. When the method 2 is used, the lyotropic liquid crystalline compound may not be well aligned, and in addition, the coating film may be damaged during stretching due to the thickness of the coating film. When the method 3 is used, a photo-alignment film must be formed, and the formation process is complicated.
On the other hand, the rubbing process (Method 4) has been widely used since it can be carried out relatively easily.

The rubbing process is a process of rubbing the substrate surface in a predetermined direction using a rubbing cloth. An alignment regulating force is applied to the surface of the base material that has been subjected to the rubbing treatment. The alignment regulating force means a function of aligning the liquid crystalline compound in a predetermined direction.
Although the principle by which the alignment regulating force is imparted to the surface of the base material is not clear, it is generally considered as follows (1) to (3).
(1) A physical groove is formed on the surface of the substrate by rubbing treatment. (2) The molecules on the substrate surface are stretched and oriented by rubbing treatment. (3) Static electricity (electric anisotropy) is generated on the surface of the substrate by the rubbing treatment.

Special table flat 8-511109 JP 2004-333849 A JP-A-7-261024 JP2008-26425

  However, the alignment regulation force may not be sufficiently imparted by simply performing the rubbing treatment on the substrate surface. Even when a coating liquid containing a lyotropic liquid crystalline compound is applied to the surface of a substrate having insufficient alignment regulating power, the lyotropic liquid crystalline compound does not align well. Therefore, the improvement is demanded.

In the production line for optically anisotropic films, a long substrate is used. After rubbing the surface of the long base material, a coating liquid containing a lyotropic liquid crystalline compound is applied to the surface of the base material. However, in an actual production line, the coating liquid is not applied immediately after the rubbing treatment. For example, the following (a) to ( There are various situations or processes such as c).
(A) A foreign substance (for example, a conveyance roller in a production line) contacts the surface of the base material after the rubbing treatment. (B) The long base material after the rubbing treatment is once made into a roll and transported or stored. (C) A protective film is bonded to the back surface of the long base material after the rubbing treatment.
Due to various points such as the above (a) to (c), the orientation regulating force on the surface of the substrate once rubbed may be reduced or disappeared on a part or all of the surface (hereinafter referred to as “decrease”). Or “disappearance” is referred to as “attenuation”). Even if the coating liquid is applied to the surface of the base material in which the orientation regulating force is attenuated, the lyotropic liquid crystalline compound is not well aligned.

A first object of the present invention is to provide a method for producing an optically anisotropic film having a well-oriented lyotropic liquid crystalline compound that can impart sufficient alignment regulating force to a substrate surface by rubbing treatment.
The second object of the present invention is to provide a rubbing treatment method capable of imparting a sufficient orientation regulating force to the substrate surface.

The present invention relates to a method for producing an optical anisotropic film, which comprises forming an optical anisotropic film containing a lyotropic liquid crystalline compound on a substrate, a pre-rubbing step for performing a rubbing treatment on the surface of the substrate , after the pre-rubbing a heating step of performing heat treatment on the substrate surface, and rubbing step of rubbing treatment is performed on the heat-treating the substrate table surface been, coating containing a lyotropic liquid crystalline compound on the substrate surface subjected to the rubbing treatment And a coating process for coating the liquid.
Preferably, in the rubbing step, after the heat-treated substrate surface is cooled, the cooled substrate surface is rubbed, or the heat-treated substrate surface is cooled to room temperature. Then, a rubbing treatment is performed on the cooled substrate surface.

Since the manufacturing method of the present invention performs a pre-rubbing process on the substrate surface, a sufficient alignment regulating force can be imparted to the substrate surface. Then, after heating the base material surface, the optically anisotropic film in which the lyotropic liquid crystalline compound is well oriented can be obtained by rubbing the base material surface .
When the rubbing treatment is performed on the heat-treated substrate surface, the principle that a sufficient alignment regulating force can be imparted to the substrate surface is not clear, but the present inventors presume as follows.
The rubbing process is a process of rubbing the substrate surface in a predetermined direction using a rubbing cloth. During this treatment, friction occurs between the rubbing cloth and the substrate surface. This rubbing causes twisting of the rubbing cloth and / or dropping of fibers of the rubbing cloth. For this reason, the orientation regulating force cannot be sufficiently imparted to the surface of the substrate simply by performing the rubbing treatment on the surface of the substrate. On the other hand, when the heat treatment is performed as in the present invention, the friction can be reduced, and twisting of the rubbing cloth, dropping of fibers of the rubbing cloth, and the like can be suppressed. Therefore, according to this invention, the base material which has sufficient orientation control force can be formed.
In addition, when the surface of the cooled substrate is rubbed after the heat treatment as in a preferred production method, a sufficient alignment regulating force can be imparted to the substrate surface. By applying a coating liquid containing a lyotropic liquid crystalline compound on the surface of a substrate having a sufficient alignment regulating force, an optical anisotropic film in which the lyotropic liquid crystalline compound is well oriented can be obtained.

In a preferred production method of the present invention, the heat treatment is a treatment for bringing the temperature of the substrate surface to 50 ° C. to 90 ° C.
In another preferable production method of the present invention, the rubbing treatment in the rubbing step is a treatment of rubbing the surface of the substrate using a rubbing cloth containing a hydrophilic material.
Another preferable production method of the present invention further includes a hydrophilization step of performing a hydrophilization treatment on the substrate surface after the rubbing step and before the coating step.
In another preferable production method of the present invention, the coating liquid containing the lyotropic liquid crystalline compound is an aqueous solution in which the lyotropic liquid crystalline compound is dissolved.

Moreover, according to another situation of this invention, the rubbing processing method is provided.
The rubbing treatment method of the present invention comprises a pre-rubbing step for rubbing the substrate surface,
A heating step of performing a heat treatment on the surface of the base material after the pre-rubbing , and a rubbing step of performing a rubbing treatment on the surface of the base material subjected to the heat treatment.
Preferably, in the rubbing step, after the heat-treated substrate surface is cooled, the cooled substrate surface is rubbed, or the heat-treated substrate surface is cooled to room temperature. Then, a rubbing treatment is performed on the surface of the substrate.

The method for manufacturing an optically anisotropic film and the rubbing treatment method according to the present invention provide a sufficient alignment regulating force for performing a rubbing treatment on the substrate surface after the heat treatment is performed on the substrate surface that has been subjected to the pre-rubbing treatment. A substrate having the same can be obtained. By applying a coating liquid containing a lyotropic liquid crystalline compound on the surface of the substrate, an optically anisotropic film in which the lyotropic liquid crystalline compound is well oriented can be obtained. Therefore, according to the manufacturing method of the present invention, an optical anisotropic film having excellent optical characteristics can be obtained. By incorporating the obtained optically anisotropic film into, for example, an image display device, an image display device having excellent display characteristics can be provided.

The reference diagram which represented typically the heating process and rubbing process of this invention. The reference figure which represented typically the hydrophilization process, coating process, and drying process of this invention.

The present invention is a method for producing an optical anisotropic film in which an optical anisotropic film containing a lyotropic liquid crystalline compound is formed on a substrate. The production method of the present invention has at least the following heating step, rubbing step and coating step, and preferably has a pre-rubbing step, a hydrophilization step, a drying step, and / or other steps.
The rubbing treatment method of the present invention includes at least the following heating step and rubbing step.

Pre-rubbing step: a step of rubbing the substrate surface.
Heating step: a step of heating the substrate surface.
Rubbing step: A step of rubbing the surface of the base material subjected to the heat treatment.
Hydrophilization process: The process of hydrophilizing the rubbing-treated substrate surface.
Coating process: The process of applying the coating liquid containing a lyotropic liquid crystalline compound on the base-material surface which performed the said hydrophilic treatment.
Drying step: a step of drying the coating film formed by the coating step to obtain an optically anisotropic film.

[Pre-rubbing process]
This step is performed as necessary. The method for producing an optical anisotropic film and the rubbing treatment method of the present invention can impart a sufficient alignment regulating force to the substrate surface by performing a rubbing step. For this reason, this process (pre-rubbing process) may be performed or this may not be performed.
The pre-rubbing step may be performed by the same method as the rubbing step described later, or may be different from the rubbing step described later.

(Base material)
The base material is not particularly limited as long as the coating liquid can be developed substantially uniformly and can be a support for the coating liquid. The substrate is preferably excellent in transparency.
For example, as a base material, films, such as a polymer film, a glass plate, etc. are mentioned. The substrate is preferably a film because it can be continuously rubbed by roll-to-roll.
When the substrate is a film, the surface thereof may be a film having a hydrophilic surface (including a film formed entirely of a hydrophilic material and a film having a surface subjected to hydrophilization treatment), or a hydrophobic film. (Including a film formed entirely of a hydrophobic material and a film whose surface has been subjected to a hydrophobic treatment). The meanings of hydrophilicity and hydrophobicity will be described later. It is preferable to use a film having a hydrophobic surface because the pre-rubbing treatment can be performed satisfactorily.
The material of the base material is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate; polypropylenes, polyolefins having a cyclic or norbornene structure, olefins such as ethylene / propylene copolymers, and celluloses such as diacetyl cellulose and triacetyl cellulose. System; and the like. Since the pre-rubbing treatment can be performed satisfactorily, the substrate is preferably an olefin film. As the olefin-based film, for example, “ZEONOR [registered trademark]” manufactured by Nippon Zeon Co., Ltd., “ARTON [registered trademark]” manufactured by JSR Corporation, etc. are preferably used.

In addition, a laminated film in which two or more polymer films are laminated may be used as the substrate, or an alignment film containing polyimide or the like is formed on the surface of the film (surface on which rubbing treatment is performed). A film may be used.
The thickness of the substrate is appropriately designed according to the material and the like. When a base material is a polymer film, the thickness becomes like this. Preferably it is 300 micrometers or less, More preferably, it is 5-200 micrometers, Most preferably, it is 10-100 micrometers.

Furthermore, the shape of the substrate is preferably long. By using a long base material, continuous processing is possible by roll-to-roll.
In addition, the said elongate base material means the film whose vertical dimension is fully longer than a horizontal dimension. The length of the long base material is, for example, 100 m or more, preferably 300 m or more, and more preferably 1000 m or more. The long base material may be wound in a roll shape.

[Heating process]
This step is a step of performing heat treatment on the substrate surface.
When the pre-rubbing process is performed, the surface of the base material subjected to the pre-rubbing process is heated.
When the pre-rubbing step is not performed, the base material exemplified in the column of [Pre-rubbing step] is appropriately selected, and the base material surface is subjected to heat treatment.

FIG. 1 is a reference diagram of the rubbing treatment method (heating step and rubbing step) of the present invention.
As shown in FIG. 1, a roll 10 around which a long substrate 1 is wound is set at the end of a processing line. The base material 1 is pulled out from the roll 10 and transported through a transport roller (not shown), and the base material 1 is passed through a heating device 2 provided in the middle of the line. While passing through the heating device 2, the substrate surface 1a is heated.

In the treatment, it is preferable to heat only the surface of the substrate on which the rubbing treatment is performed. But you may heat the surface and back surface of a base material.
The means for heating treatment (heating device) is not particularly limited, and examples thereof include a hot air circulation dryer that can circulate hot air in the device, a heater using far infrared rays, a heated roller, a heat pipe roller, and the like. Since the entire surface of the substrate can be heated substantially uniformly, it is preferable to use a hot-air circulating dryer.

The heat treatment is preferably a treatment for bringing the temperature of the substrate surface to 50 ° C. to 90 ° C., more preferably a treatment for bringing the temperature to 60 ° C. to 80 ° C., and further preferably a treatment for bringing the temperature to 65 ° C. to 75 ° C. is there. When the temperature of the substrate surface is less than 50 ° C., the effect of performing the heat treatment is not sufficiently exhibited. On the other hand, when the temperature of the substrate surface exceeds 90 ° C., the substrate may be bent or contracted.
Although the time of the said heat processing is not specifically limited, Preferably it is 1 minute-10 minutes, More preferably, it is 2 minutes-5 minutes. When the heat treatment time is less than 1 minute, the effect of performing the heat treatment is not sufficiently exhibited. On the other hand, when the heat treatment time exceeds 10 minutes, the substrate may shrink.

  The surface of the base material after the heat treatment is preferably hydrophobized as compared with that before the heat treatment. Usually, when the heat treatment is performed at the above temperature and time, the surface of the base material is hydrophobized as compared with that before the heat treatment. However, when the hydrophobicity of the substrate surface before the heat treatment is high, the degree of hydrophobicity of the substrate surface before and after the heat treatment may hardly change even when the heat treatment is performed on the substrate surface.

Here, in the present specification, hydrophobic means a property having a weak affinity with water, and hydrophilic property means a property having a strong affinity with water. In the present specification, hydrophobization means changing the surface of the base material to be hydrophobic, and hydrophilization means changing the surface of the base material to be hydrophilic.
The difference between the hydrophobicity and the hydrophilicity can be distinguished by, for example, the contact angle of water on the substrate surface.
For example, the contact angle of water on the surface of the substrate by the heat treatment is increased by 10% or more, preferably by 15% to 80%, more preferably by 20% to 60%, as compared with that before the heat treatment. To do.
However, the rate of increase (%) is expressed by the formula: {(contact angle of substrate surface after heat treatment−contact angle of substrate surface before heat treatment) / contact angle of substrate surface after heat treatment} × 100 Is required.
The contact angle can be measured using a solid-liquid interface analyzer (product name: Drop Master 300, manufactured by Kyowa Interface Science Co., Ltd.) (measuring condition: 0.5 μl droplet). Contact angle measurement, temperature 23 ° C.).

[Rubbing process]
This step is a step of performing a rubbing treatment on the substrate surface after the heat treatment.
The rubbing treatment may be performed on the substrate surface that is in a high temperature state by heat treatment, or may be performed on the substrate surface in a state cooled to room temperature after the heat treatment.
In FIG. 1, the base material 1 after the heat treatment is guided to a rubbing device 3 provided on the rear side of the heating device 2 via a transport roller (not shown). While the substrate 1 passes through the rubbing device 3, the surface 1a is rubbed.
The rubbing device 3 is provided with a pair of drive rollers 31, 32, a conveyor belt 33 of an endless track laid between the drive rollers 31, 32, and can be moved up and down above the conveyor belt 33. A rubbing roller 34, and a plurality of backup rollers 35 that support the lower surface of the conveying belt 33 and are arranged to face the rubbing roller.
In addition, before and after the rubbing device 3, an electrostatic removal device, a dust removal device, or the like may be installed as necessary.

The substrate 1 is conveyed while being in contact with the upper surface of the conveyance belt 33. The upper surface of the transport belt 33 is a mirror-finished metal surface (the entire transport belt 33 may be made of metal). As the degree of mirror finish, the arithmetic average surface roughness Ra (JIS B 0601 (1994)) is 0.02 μm or less, preferably 0.01 μm or less. The tension applied to the conveyor belt 33 is preferably 0.5 to 20 kgf / mm ² , more preferably ² to 15 kgf / mm ² .

The rubbing roller 34 has a cylindrical core material and a rubbing cloth wound around the outer peripheral surface of the core material.
As the rubbing cloth, for example, a raised cloth can be used.
As the rubbing cloth, it is preferable to use a cloth containing a hydrophilic material (for example, hydrophilic fibers), and it is more preferable to use a raised cloth containing a hydrophilic material (for example, hydrophilic fibers). Examples of the hydrophilic material include compounds having a polar group (for example, a hydroxyl group, an amino group, an amide group, a carboxyl group, etc.) in the molecule. Specific examples of the hydrophilic material include rayon, cotton, acetate, nylon, and mixtures thereof.

The rotation axis of the rubbing roller 34 is configured to be set at an arbitrary shaft angle with respect to the conveyance direction A of the substrate 1. For example, the rotation axis of the rubbing roller 34 can be arranged at right angles to the transport direction A of the base material 1 or can be inclined with respect to the transport direction A (for example, an inclination angle of 0 to 45 degrees). .
When the pre-rubbing step is performed, the shaft angle of the rubbing roller in the rubbing step is preferably set to be substantially the same as the shaft angle of the rubbing roller in the pre-rubbing step.

  The plurality of backup rollers 35 are provided to support the lower surface of the conveyor belt 33 that supports the substrate 1. By providing these backup rollers 35, the rubbing process can be stably performed even if the rubbing roller 34 with the rotation axis inclined is pushed in or the pushing amount of the rubbing roller 34 is increased. it can.

  The heat-treated substrate 1 is guided onto the conveyor belt 33 via a conveyor roller (not shown). The upper surface of the conveyor belt 33 conveys the substrate 1 by the drive rollers 31 and 32, and the substrate surface 1a is rubbed while passing through the rubbing roller 34.

In the rubbing step, the rubbing strength is not particularly limited, but is preferably 800 mm or more, and more preferably 800 mm to 1200 mm.
By setting the rubbing strength to 800 mm or more, even if blocking occurs in the base material, a substantially uniform orientation regulating force can be applied to the surface of the base material.
However, the rubbing strength is defined by the following formula.
Formula: RS = N · M (1 + 2πr · nr / v)
The RS represents the rubbing strength. N represents the number of times of rubbing (corresponding to the number of rubbing rollers. In the example shown in FIG. 1, the number of times of rubbing is 1). Said M represents the amount of pushing (mm) with respect to the base-material surface of a rubbing roller. The π represents a circumference ratio. The r represents a radius (mm) of a rubbing roller (including a rubbing cloth). The nr represents the number of rotations (rpm) of the rubbing roller. Said v represents the conveyance speed (mm / sec) of a base material.

  Various conditions during the rubbing process, such as the number of times of rubbing, are not particularly limited and can be set as appropriate. For example, the rotation number of the rubbing roller can be set to 1 to 3000 rpm, and preferably 500 to 2000 rpm. The pushing amount of the rubbing roller can be set to, for example, 100 to 2000 μm, and preferably 100 to 1000 μm. Moreover, the conveyance speed of the said base material can be set to 0.5-50 m / min, for example, Preferably it is 0.5-10 m / min.

  The base material 1 rubbed by the rubbing device 3 is wound around a roll 11. The base material 1 is transported and stored in a roll shape, and used for the next step.

When the pre-rubbing step is performed, the orientation regulating force can be sufficiently repaired with respect to the base material surface in which the orientation regulating force is attenuated by contact with foreign matter after the pre-rubbing process.
When the pre-rubbing step is not performed, a sufficient alignment regulating force can be newly imparted to the substrate surface.

When the rubbing treatment is performed on the surface of the substrate after the heat treatment, a sufficient alignment regulating force can be imparted to the surface of the substrate. This is apparent with reference to the following examples and comparative examples. Although the principle which can provide this sufficient orientation control force is not clear, the present inventors estimate as follows.
The rubbing process is a process of rubbing the substrate surface in a predetermined direction using a rubbing cloth. During this treatment, friction occurs between the rubbing cloth and the substrate surface. This rubbing causes twisting of the rubbing cloth and / or dropping of fibers of the rubbing cloth. In particular, when the surface of a hydrophilic substrate is rubbed with a rubbing cloth containing a hydrophilic material, the rubbing cloth is easily twisted or the fibers are easily dropped. However, if the heat treatment is performed on the surface of the base material, friction between the rubbing cloth and the base material surface can be reduced. This reduction in friction is presumed to be the result of hydrophobizing the substrate surface by heat treatment or other factors.
By simply performing a rubbing treatment on the substrate surface as in the prior art, a sufficient orientation regulating force cannot be imparted to the substrate surface. When the heat treatment is performed prior to the rubbing treatment as in the present invention, the rubbing cloth can be prevented from being twisted or the fibers can be prevented from dropping due to the reduction of friction, and a sufficient orientation regulating force can be imparted in a predetermined direction on the substrate surface. Application of sufficient alignment regulating force to the substrate surface makes it possible to satisfactorily align the lyotropic liquid crystalline compound in the coating solution applied onto the substrate.
In a method for producing an optically anisotropic film by coating a coating liquid containing a lyotropic liquid crystalline compound on a substrate, it is particularly important to use a substrate having a sufficient alignment regulating force.

[Hydrophilization process]
This step is performed as necessary.
In particular, when the coating liquid containing a lyotropic liquid crystalline compound is an aqueous solution, it is preferable to perform a hydrophilic treatment. Since the substrate surface is hydrophobized by the heating step, the substrate surface can be changed to hydrophilic by performing a hydrophilic treatment. By hydrophilizing the substrate surface, the coating liquid (aqueous solution) containing the lyotropic liquid crystalline compound is not repelled from the substrate surface, and the coating liquid can be satisfactorily applied to the substrate surface.

FIG. 2 is a reference diagram of the hydrophilization process, coating process and drying process of the present invention.
As shown in FIG. 2, the roll 11 of the base material 1 wound after the rubbing treatment is set at the end of the coating line. The base material 1 is pulled out from the roll 11, transported through a transport roller (not shown), and passed through the hydrophilization treatment device 4. While passing through the hydrophilization treatment device 4, the substrate surface 1a is hydrophilized.

After the hydrophilization treatment, the water contact angle on the substrate surface is preferably 5 ° to 60 °, more preferably 5 ° to 50 °, and even more preferably 5 ° to 45 °.
The method for measuring the contact angle of water is the same as described above.
Any appropriate method can be adopted as the hydrophilic treatment. The hydrophilic treatment may be, for example, a dry treatment or a wet treatment. Examples of the dry treatment include discharge treatment such as corona treatment, plasma treatment, and glow discharge treatment, flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment such as ultraviolet ray treatment, and electron beam treatment. Examples of the wet treatment include ultrasonic treatment using a solvent such as water and acetone, alkali treatment, anchor coat treatment, and the like. These treatments may be used alone or in combination of two or more. Preferably, the hydrophilic treatment is a corona treatment, a plasma treatment, an alkali treatment, or an anchor coat treatment.

[Coating process]
This step is a step of applying a coating liquid onto the surface of the substrate after the rubbing step (or after a hydrophilization step performed as necessary). The coating liquid is a liquid in which a lyotropic liquid crystalline compound is dissolved in a solvent.
In FIG. 2, the coating liquid 5 is placed on the surface 1a of the substrate 1, and the coating film 7 is formed while moving the coater device 6 (for example, a bar coater).

(Lyotropic liquid crystalline compounds)
The lyotropic liquid crystalline compound means a compound having a property (lyotropic liquid crystalline) that causes a phase transition between an isotropic phase and a liquid crystal phase by changing the temperature and concentration of the solution in a solution in a solvent. To do. The isotropic phase means a phase in which the macroscopic optical properties do not vary depending on the direction (not exhibiting optical anisotropy).
The lyotropic liquid crystalline compound exhibits a liquid crystal phase in a solution state and has a property of forming supramolecules. The structure of the supramolecule is not particularly limited, and examples thereof include a micelle structure such as a spherical structure, a columnar structure, and a tubular structure; a lamellar structure; The liquid crystal phase of the lyotropic liquid crystalline compound can be confirmed and identified by an optical pattern observed with a polarizing microscope.

The lyotropic liquid crystalline compound used in the production method of the present invention is not particularly limited.
As the lyotropic liquid crystalline compound, a compound having a discotic structure is preferable, and a compound capable of forming a supramolecule having a columnar structure is more preferable.

The lyotropic liquid crystalline compound may be a compound capable of forming a retardation film after film formation, or may be a compound capable of forming a polarizing film after film formation.
Further, the lyotropic liquid crystalline compound may or may not show absorption in the visible light region (wavelength 380 nm to 780 nm). An optically anisotropic film formed using a lyotropic liquid crystalline compound exhibiting absorption in the visible light region can be used as a polarizing film. An optical anisotropic film formed using a lyotropic liquid crystalline compound that does not exhibit absorption in the visible light region can be used as a retardation film.
The polarizing film is an optical film having a function of transmitting specific linearly polarized light from natural light or polarized light. A retardation film is an optical film that exhibits birefringence (anisotropy of refractive index) in its plane and / or in the thickness direction. Such a retardation film includes, for example, one having an in-plane and / or thickness direction birefringence of 1 × 10 ⁻⁴ or more at a wavelength of 590 nm.

  Examples of lyotropic liquid crystalline compounds that can form a polarizing film include azo, anthraquinone, perylene, indanthrone, imidazole, indigoid, oxazine, phthalocyanine, triphenylmethane, pyrazolone, stilbene, Examples thereof include diphenylmethane, naphthoquinone, merocyanine, quinophthalone, xanthene, alizarin, acridine, quinoneimine, thiazole, methine, nitro, and nitroso compounds. Examples of the lyotropic liquid crystalline compound include JP-A-2006-047966, JP-A-2005-255846, JP-A-2005-154746, JP-A-2002-090526, JP-A-8-511109. And the compounds described in JP-A-2004-528603. Preferably, a dichroic dye is used as the lyotropic liquid crystalline compound, and an azo dye is more preferably used. These can be used alone or in combination of two or more.

  In addition, as said azo compound, what is represented, for example by following formula (I) is preferable.

In the formula (I), R represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, or a substituted or unsubstituted phenyl group, M represents a counter ion, and X represents A hydrogen atom, a halogen atom, a nitro group, a cyano group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an —SO ₃ M group is represented. Examples of the counter ion include a hydrogen atom, an alkali metal atom, and an alkaline earth metal atom.

Examples of the lyotropic liquid crystalline compound that can form a retardation film include quinoxaline-based, acridine-based, and polymethine-based compounds.
The lyotropic liquid crystalline compound forming the retardation film is preferably a quinoxaline compound.
A quinoxaline-based compound is a lyotropic liquid crystalline compound containing a quinoxaline derivative unit in its molecular structure. More preferably, the quinoxaline-based compound includes an acenaphtho [1,2-b] quinoxaline derivative unit in the molecular structure, and particularly preferably an acenaphtho having at least one of a —SO ₃ M group and a —COOM group. 1,2-b] quinoxaline derivative units.

(solvent)
There is no restriction | limiting in particular in the solvent used for melt | dissolution of a lyotropic liquid crystalline compound.
Common solvents can be broadly classified into hydrophobic solvents and hydrophilic solvents.
Hydrophobic solvents include ethers such as diethyl ether; aromatic hydrocarbons such as benzene and toluene; cyclic hydrocarbons such as hexane; halogenated hydrocarbons such as tetrachloroethylene; ketones; And higher alcohols.
Examples of hydrophilic solvents include water; primary alcohols such as methanol, ethanol, propanol and butanol; secondary alcohols such as isopropanol and isobutanol; tertiary alcohols such as tert-butanol; ethylene glycol and propylene Examples include diols such as glycol and butylene glycol; polyols such as polyethylene glycol; cyclic amines such as pyridine and imidazole; cyclic ethers such as tetrahydrofuran; cellosolves such as methyl cellosolve and ethyl cellosolve; acetone and the like.
These solvents may be used alone or in combination of two or more.

The solvent used is preferably a hydrophilic solvent, and more preferably water, lower alcohols having 1 to 5 carbon atoms, and / or cellosolves.
Particularly preferably, water alone or a mixed solvent of water and the above hydrophilic solvent other than water is used. When water is used, the water preferably has an electric conductivity of 20 μS / cm or less, more preferably 0.001 μS / cm to 10 μS / cm. By using water having an electric conductivity in the above range, it is possible to form a coating film having a small thickness variation and spreading substantially uniformly on the substrate.

(Coating fluid)
The coating liquid can be prepared by dissolving the lyotropic liquid crystalline compound in the solvent.
The concentration of the lyotropic liquid crystalline compound in the coating solution is preferably 1 to 50% by mass. When the concentration is less than 1% by mass, it is necessary to apply the coating solution very thick in order to obtain an optical anisotropic film having predetermined optical characteristics. For this reason, at the time of coating of a coating liquid, there exists a possibility of producing a liquid flow, a coating spot, etc. When the concentration exceeds 50% by mass, the viscosity of the coating solution increases, and there is a possibility that the coating solution cannot be applied to the substrate surface substantially uniformly. In addition, the said density | concentration means the density | concentration of the single-piece | unit when one type of lyotropic liquid crystalline compound is used, and when two or more types of lyotropic liquid crystalline compounds are used, it means the total density | concentration of each compound.
Further, the viscosity of the coating liquid is preferably 0.1 mPa · s to 30 mPa · s, and more preferably 0.5 mPa · s to 3 mPa · s. However, the viscosity is a value measured with a rheometer (manufactured by Haake, product name “Rheostress 600”, measurement condition: double cone sensor shear rate 1000 (1 / s)).
The pH of the coating solution is preferably 4 to 10, more preferably 6 to 8.

Arbitrary additives may be added to the coating liquid. Examples of the additive include a surfactant, a plasticizer, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a flame retardant, a colorant, an antistatic agent, a compatibilizing agent, a crosslinking agent, and an increase agent. An example is a sticky agent. These additives may be used alone or in combination of two or more. Among the additives, the surfactant improves the wettability and coating property of the coating liquid to the substrate surface.
The addition amount of the additive is preferably more than 0 and 10 parts by mass or less with respect to 100 parts by mass of the coating liquid.

The said coating liquid is applied to the base-material surface after a rubbing process (or after the hydrophilization process performed as needed). The coating method of the coating liquid is not particularly limited, and is a bar coating method, ink jet method, gravure coating method, slit coating method, slide coating method, spray method, protruding coating method, dip coating method, die coating method, knife coating method. , Blade coating method, roll coating method and the like.
Preferably, the coating liquid is applied while being cast in the conveying direction of the long substrate.
Moreover, the casting speed of the coating liquid is not particularly limited, but is 100 mm / min or more, preferably 500 mm / min to 8000 mm / min. If it is the said casting speed, a coating film with small thickness variation can be formed.
After coating, the lyotropic liquid crystalline compound is aligned in a predetermined direction by the alignment regulating force on the substrate surface.

[Drying process]
This step is a step of drying the coating film formed in the coating step.
Since the coating film usually contains a large amount of solvent, it cannot be used as an optically anisotropic film as it is. For this reason, an appropriate optically anisotropic film can be obtained by drying this and fixing the orientation of the lyotropic liquid crystalline compound.

  In FIG. 2, the coating film 7 is dried by a drying device 8. The coating film after drying is the optically anisotropic film of the present invention. The optically anisotropic film is usually wound on a roll 12 while being laminated on the substrate 1.

As a method for drying the coating film, an appropriate method can be adopted depending on the type of the substrate and the type of the solvent of the coating solution.
The drying method may be natural drying or forced drying. A drying device is used for forced drying. In the case of natural drying, the coating film dries while the substrate is being conveyed without using a drying device. Preferably, the drying method is natural drying. If it is naturally dried, it is possible to obtain an optically anisotropic film having no particular thickness variation.
The drying temperature is not particularly limited as long as the liquid crystal phase of the lyotropic liquid crystalline compound in the coating film is not shifted in phase. The said drying temperature is 10 to 80 degreeC, for example, Preferably it is 20 to 60 degreeC.
The drying time of the coating film is appropriately selected depending on the drying temperature and the type of solvent. The drying time is, for example, 1 second to 120 minutes, preferably 10 seconds to 5 minutes.
The thickness of the dried coating film (optically anisotropic film) is not particularly limited, but is preferably 1 nm to 500 nm, and more preferably 10 nm to 400 nm.

[Other processes]
The production method of the present invention may include a step of performing a water resistance treatment on the optically anisotropic film obtained as described above.
Specifically, on the surface of the optical anisotropic film (surface opposite to the surface in contact with the substrate surface), aluminum salt, barium salt, lead salt, chromium salt, strontium salt, and two or more in the molecule A solution containing at least one compound salt selected from the group consisting of compound salts having an amino group is brought into contact. By contacting the solution, the compound salt layer is formed on the surface of the optically anisotropic film. By forming such a compound salt layer, the surface of the optical anisotropic film can be insoluble or hardly soluble in water.

Moreover, the manufacturing method of this invention may have the process of laminating | stacking a transparent protective film on the surface of the optically anisotropic film obtained as mentioned above.
The production method of the present invention may have other steps in addition to the above-described water resistance step and protective film laminating step.

[Optical properties of optical anisotropic film]
The optically anisotropic film obtained by the production method of the present invention typically has properties of a polarizing film or a retardation film, although it varies depending on the type of the lyotropic liquid crystalline compound.

When the optically anisotropic film has the property of a polarizing film, the degree of polarization is preferably 98% or more, more preferably 98.5% or more. The single transmittance is preferably 25% or more, more preferably 27% or more.
The degree of polarization and single transmittance can be determined by the measurement methods described in the following examples.

When the optical anisotropic film has the properties of a retardation film, the optical anisotropic film has a desired retardation value. The in-plane retardation value (Re [590]) and / or thickness direction retardation value (Rth [590]) at a wavelength of 590 nm of the optically anisotropic film is, for example, 10 nm or more, preferably 20 nm to 300 nm. It is. The Re [590] can be obtained by Re [590] = (nx−ny) × d where the thickness is d (nm), and the Rth [590] has a thickness of d (nm). , Rth [590] = (nx−nz) × d.
Examples of the phase difference value measuring device include a product name “KOBRA-WPR” manufactured by Oji Scientific Instruments Co., Ltd.

[Uses of optical anisotropic films]
The use of the optically anisotropic film obtained by the production method of the present invention is not particularly limited.
When the optically anisotropic film of the present invention has properties of a polarizing film, a polarizing plate can be formed by laminating a retardation film thereon. As the retardation film, a retardation film obtained by the production method of the present invention may be used, or a conventionally known retardation film may be used.
Moreover, when the optical anisotropic film of this invention has the property of retardation film, a polarizing plate can be comprised by laminating | stacking a polarizing film on this. As the polarizing film, a polarizing film obtained by the production method of the present invention may be used, or a conventionally known polarizing film may be used. Each of the polarizing plates may be laminated with an arbitrary protective film.
The optically anisotropic film of the present invention is usually used in a state where it is laminated on a substrate without peeling off from the substrate. But the said optically anisotropic film can also be peeled and used from the said base material. Since the base has a function of protecting the optical anisotropic film, the base can be used as a protective film for the optical anisotropic film when the base is not peeled off.

  When another optical film as described above is laminated on the optically anisotropic film of the present invention, any appropriate adhesive layer is provided between them practically. Examples of the material for forming the adhesive layer include an adhesive, a pressure-sensitive adhesive, and an anchor coat agent.

  The optically anisotropic film obtained by the production method of the present invention can be preferably used as a constituent member of an image display device. In the case where the image display device is a liquid crystal display device, preferred applications are a television, a portable device, a video camera and the like.

  The present invention will be described in detail using examples and comparative examples. In addition, this invention is not limited only to the following Example. Each measuring method used in Examples and Comparative Examples is as follows.

[Measuring method]
(1) Measurement of optical anisotropic film thickness:
Using a scanning electron microscope (manufactured by JEOL, product name “JSM-7500F”), the cross section of the optically anisotropic film was observed and the thickness thereof was measured.
(2) Measuring method of single transmittance and degree of polarization:
Using a spectrophotometer [manufactured by JASCO Corporation, product name “V7100”], the surface of the optical anisotropic film to be measured is set perpendicular to the polarized light emitted from the prism, and transmitted at 23 ° C. the rate _{k 2} was measured. Further, after rotating the optical anisotropic film by 90 °, the transmittance k ₁ was measured in the same manner. By substituting the obtained k ₁ and k ₂ into the following formulas 1 and 2, the transmittance and the degree of polarization were obtained.
Formula 1: Single transmittance (%) = (k ₁ + k ₂ ) / 2
Formula 2: Polarization degree (%) = (k ₁ −k ₂ ) / (k ₁ + k ₂ ) × 100
Incidentally, k ₁ represents a transmittance of the maximum transmittance direction of linearly polarized light, k ₂ represents a transmittance of a linearly polarized light in a direction perpendicular to the maximum transmittance direction.
(3) Observation of disorder of orientation Place a commercially available polarizing plate on a white light source, place an optical anisotropic film on it, rotate the optical anisotropic film left and right, and rotate the absorption axis of the optical anisotropic film. The shift (that is, light leakage) was visually observed. When the shift of the absorption axis was large, it was evaluated that there was an alignment disorder, and when it was small, it was evaluated that there was no alignment disorder.

[Pre-rubbing treatment 1]
Pull out a 100 μm-thick cycloolefin film (made by Nippon Zeon Co., Ltd., trade name “Zeonor [registered trademark]”) rolled into a roll shape and use a rubbing apparatus as shown in FIG. The surface of the film was rubbed continuously. The surface of the film after the rubbing treatment was subjected to a corona treatment and then wound up into a roll again (hereinafter, this pre-rubbed film is referred to as “base (1)”). The configuration of the rubbing apparatus and the rubbing conditions are as follows.
(Rubbing device configuration and rubbing conditions)
Film conveyance speed: 1 m / min.
Axial angle of rotation axis of each backup roller: 90 ° with respect to the film conveyance direction.
Material of rubbing cloth: Cotton cloth (manufactured by Yoshikawa Chemical Co., Ltd., trade name “YA-25-C”).
Axis angle of the rotation axis of the rubbing roller: 0 ° with respect to the film conveyance direction.
The rotational speed of the rubbing roller: 1000 rpm.
Pushing amount of rubbing roller: 20 mm.
Rubbing strength: 1000 mm.

[Pre-rubbing process 2]
Instead of the cycloolefin film, a saponified triacetylcellulose film (trade name “TAC film” manufactured by Konica Minolta Opto Co., Ltd.) having a thickness of 80 μm and a length of 1000 m was used, and corona treatment The film was rubbed in the same manner as in the pre-rubbing process 1 except that the film was wound into a roll (hereinafter referred to as “base material”). (2) ").

[Preparation of coating solution]
p-Methoxyaniline is diazotized according to a conventional method (the method described in Yutaka Hosoda, “Theoretical Manufacturing, Dye Chemistry, 5th Edition”, issued July 15, 1968, Technique Hall, pages 135-152). -Amino-7-naphthalenesulfonic acid was subjected to a coupling reaction to obtain a monoazo compound. Further, this was diazotized and subjected to a coupling reaction with 3-amino-5-hydroxy-2,7-naphthalenedisulfonic acid to obtain a crude product. This was salted out with lithium chloride to obtain an azo compound of the following formula (II).
The obtained azo compound was dissolved in ion-exchanged water to prepare a coating solution having a concentration of 5% by mass.

[Example 1]
The said base material (1) wound by roll shape was pulled out, and the process which heats the surface of the said base material (1) to 70 degreeC was performed for 1 hour using the hot air circulation type dryer. After the surface after the heat treatment was cooled to room temperature, the surface of the substrate (1) was subjected to a rubbing treatment in the same manner as the rubbing apparatus and rubbing conditions of the pre-rubbing treatment 1. The surface of the base material (1) after the rubbing treatment was subjected to corona treatment as a hydrophilic treatment. Using the wire bar (# 4) on the surface of the base material (1) after the corona treatment, the coating solution is coated and left to stand for 10 minutes to dry naturally. A film was formed. The obtained optically anisotropic film had the properties of a polarizing film. The thickness of this optical anisotropic film was 350 nm.

  The transmittance and polarization degree of the optically anisotropic film of Example 1 were measured, and further, the disorder of the orientation of the azo compound was observed. The results are shown in Table 1.

[Example 2]
An optical anisotropic film was formed in the same manner as in Example 1 except that the base material (2) was used instead of the base material (1). The obtained optically anisotropic film had the properties of a polarizing film. The thickness of this optical anisotropic film was 340 nm.
Table 1 shows the results such as the transmittance of the optical anisotropic film of Example 2.

[Comparative Example 1]
The substrate (1) wound in a roll shape is pulled out, and the surface is coated with a coating solution using a wire bar (# 4), and left to stand for 10 minutes to dry naturally. A membrane was formed. The obtained optically anisotropic film had the properties of a polarizing film. The thickness of this optical anisotropic film was 350 nm. The same aqueous solution as that used in Example 1 was used as the coating solution.
Table 1 shows the results such as the transmittance of the optically anisotropic film of Comparative Example 1.

[Comparative Example 2]
The base material (1) wound in a roll shape was pulled out, and a rubbing treatment was performed on the surface in the same manner as the rubbing apparatus and rubbing conditions of the pre-rubbing treatment 1. An optical anisotropic film is formed on the base material by applying a coating solution to the surface of the base material (1) after rubbing using a wire bar (# 4) and allowing it to stand for 10 minutes to dry naturally. Formed. The obtained optically anisotropic film had the properties of a polarizing film. The thickness of this optical anisotropic film was 350 nm. The same aqueous solution as that used in Example 1 was used as the coating solution.
The results of the transmittance of the optical anisotropic film of Comparative Example 2 are shown in Table 1.

[Evaluation]
In Examples 1 and 2 in which the heat treatment was performed before the rubbing treatment, it can be seen that the liquid crystal compounds are extremely well aligned.
On the other hand, it can be seen that Comparative Example 1 in which the rubbing treatment was not performed has a low degree of polarization and the liquid crystalline compound is not well aligned.
Moreover, the comparative example 2 which did not heat-process before a rubbing process also has a low degree of polarization. From the comparison between Example 1 and Comparative Example 2, when the heat treatment is performed before the rubbing treatment, a sufficient alignment regulating force can be imparted to the substrate surface.

The method for producing an optical anisotropic film of the present invention can be preferably used for producing an optical anisotropic film having excellent optical characteristics.
The rubbing treatment method of the present invention can be preferably used for production of a substrate having a sufficient alignment regulating force.

  DESCRIPTION OF SYMBOLS 1 ... Base material, 1a ... Base material surface, 2 ... Heating device, 3 ... Rubbing device, 4 ... Hydrophilization processing device, 5 ... Coating liquid, 6 ... Coater device, 7 ... Coating film, 10, 11, 12 ... Base roll

Claims (10)

A method for producing an optically anisotropic film comprising forming an optically anisotropic film containing a lyotropic liquid crystalline compound on a substrate,
A pre-rubbing process for rubbing the substrate surface;
A heating step of performing heat treatment on the surface of the substrate after the pre-rubbing,
A rubbing step of performing a rubbing treatment on the surface of the substrate that has been subjected to the heat treatment,
A coating step of coating a coating liquid containing a lyotropic liquid crystalline compound on the surface of the base material subjected to the rubbing treatment;
A method for producing an optically anisotropic film having   The method for producing an optically anisotropic film according to claim 1, wherein, in the rubbing step, the surface of the base material subjected to the heat treatment is cooled, and then the rubbing treatment is performed on the cooled base material surface.   The method for producing an optical anisotropic film according to claim 1, wherein, in the rubbing step, the surface of the base material subjected to the heat treatment is cooled to room temperature, and then the rubbing treatment is performed on the cooled base material surface.   The method for producing an optically anisotropic film according to any one of claims 1 to 3, wherein the heat treatment is a treatment for bringing the temperature of the substrate surface to 50 ° C to 90 ° C.   The method for producing an optically anisotropic film according to any one of claims 1 to 4, wherein the rubbing treatment in the rubbing step is a treatment of rubbing the surface of the base material using a rubbing cloth containing a hydrophilic material.   The method for producing an optical anisotropic film according to any one of claims 1 to 5, further comprising a hydrophilization step of performing a hydrophilization treatment on the surface of the substrate after the rubbing step and before the coating step.   The method for producing an optical anisotropic film according to claim 6, wherein the coating liquid containing the lyotropic liquid crystalline compound is an aqueous solution in which the lyotropic liquid crystalline compound is dissolved. A pre-rubbing process for rubbing the substrate surface;
A heating step of performing heat treatment on the surface of the substrate after the pre-rubbing,
A rubbing treatment method comprising a rubbing step of rubbing the surface of the base material subjected to the heat treatment.   The rubbing treatment method according to claim 8, wherein, in the rubbing step, the surface of the base material subjected to the heat treatment is cooled, and then the rubbing treatment is performed on the cooled base material surface.   The rubbing treatment method according to claim 8, wherein in the rubbing step, the surface of the base material subjected to the heat treatment is cooled to room temperature, and then the rubbing treatment is performed on the cooled base material surface.

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