JP2009080250A - Method of manufacturing laminated body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of stably manufacturing a laminated body which is free from vaporization unevenness or coating unevenness and minimized in dispersion of transmittance (5% or less), and has an optical anisotropic membrane having a high dichroic ratio (20 or more) by an easy operation. <P>SOLUTION: A coating solution having a property in which viscosity is reduced when shear rate is increased (thixotropy) is used, and the viscosity of the coating solution is reduced, when applied to a substrate, by applying a large shear rate to thereby prevent the coating unevenness. The vaporization unevenness is hardly caused since the coating solution is never excessively diluted to reduce the viscosity. The coating solution is within a concentration range in which it develops a liquid crystal phase, a lyotropic liquid crystal compound in the coating solution can be oriented by shearing stress. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a laminate having optical anisotropy used as a polarizing film or a retardation film.

  In a liquid crystal display, a polarizing plate and a retardation plate are used to control the optical rotation and birefringence of light passing through the liquid crystal. In the organic EL display, a circularly polarizing plate is used to prevent reflection of external light.

  Conventionally, for these polarizing plates, polarized light obtained by orienting molecules such as dyes by dissolving or adsorbing iodine or a dichroic organic dye in a polymer film such as polyvinyl alcohol and stretching the film in one direction. The child (stretching method) has been widely used. However, polarizers manufactured by the stretching method are problematic in that heat resistance and light resistance are not sufficient depending on the dyes and polymer materials used, and the yield of film bonding during display panel manufacture is poor. Was also a problem. Furthermore, since it is necessary to stretch a wide film with an increase in the size of the display panel, it has been a problem that the film forming apparatus is increased in size.

  On the other hand, a coating solution containing a dichroic dye exhibiting a liquid crystal phase is applied to a substrate such as a glass plate or a polymer film while applying a shear stress, and the dichroic dye in the coating film is oriented by the shear stress. A method (coating method) for producing a polarizing film (optically anisotropic film) is known (Patent Document 1). The coating method is attracting attention because it can produce a polarizing plate that is thinner and has better heat resistance than the stretching method. At this time, it is known that a polarizing plate with good optical anisotropy can be obtained by using a dichroic dye that forms a dye aggregate by intermolecular interaction such as a lyotropic liquid crystal phase in a coating solution. ing.

However, the coating liquid of the lyotropic liquid crystal compound generally has a high viscosity. For this reason, there is a problem that streaky coating unevenness is likely to occur when the coating liquid is thinly applied. When the viscosity is lowered by diluting the coating liquid, coating unevenness can be avoided, but since the amount of volatilization of the solvent increases, there arises a problem that volatilization unevenness occurs and minute irregularities are easily generated on the surface of the coating film. Furthermore, since the diluted coating liquid may be out of the concentration range exhibiting the liquid crystal phase, there arises a problem that it becomes difficult to align the lyotropic liquid crystal compound by shear stress.
JP 2007-61755 A

  An object of the present invention is a production method capable of stably producing a laminate having an optically anisotropic film having no volatilization unevenness and coating unevenness, small variation in transmittance (5% or less), and high dichroic ratio (20 or more). Is to provide.

  The present inventors diligently studied to solve the problems of the conventional method. As a result, by using a coating liquid having a property (thixotropic property) in which the viscosity decreases when the shear rate is high, a uniform and highly oriented optical property is obtained. It has been found that a membrane can be obtained. That is, in the case of a coating solution having a large thixotropy, it is possible to reduce the viscosity of the coating solution by applying a large shear rate when it is applied to the substrate, thereby preventing coating unevenness. Since this method does not dilute the coating solution excessively to reduce the viscosity, volatilization unevenness hardly occurs. Furthermore, since the coating liquid is in a concentration range exhibiting a liquid crystal phase, the lyotropic liquid crystal compound in the coating liquid can be aligned by shear stress.

The gist of the present invention is as follows.
(1) The method for producing a laminate of the present invention is a method for producing a laminate comprising a substrate and an optical anisotropic film formed and laminated on the substrate, wherein the coating solution has a temperature of 23 ° C. and a shear rate of 100. the ratio of sec ^-1 _V 100 the viscosity at (23 ° C.), a viscosity at a shear rate of 1000 sec ^-1 and _{V 1000 (23 ℃), V} 100 (23 ℃) and _{V 1000 (23 ℃): V} 100 (23 ° C) / V ₁₀₀₀ (23 ° C) is a thixotropic index Ti, and the coating liquid containing a lyotropic liquid crystal compound and a solvent and having a thixotropic index Ti of 1.2 or more is applied onto the substrate. Applying a shear stress to the liquid to orient the lyotropic liquid crystal compound, and forming and laminating an optically anisotropic film on the substrate.
(2) The method for producing a laminate of the present invention is a method for producing a laminate comprising a substrate and an optical anisotropic film formed and laminated on the substrate, the coating solution having a temperature of 23 ° C. and a shear rate of 100. the ratio of sec ^-1 _V 100 the viscosity at (23 ° C.), a viscosity at a shear rate of 1000 sec ^-1 and _{V 1000 (23 ℃), V} 100 (23 ℃) and _{V 1000 (23 ℃): V} 100 (23 ° C) / V ₁₀₀₀ (23 ° C) when the thixotropic index Ti is used, the coating liquid containing a lyotropic liquid crystal compound and a solvent and having a thixotropic index Ti of 1.2 or more is applied onto the substrate, and the coating liquid is applied after the application. Applying a shear stress to the coating film comprising the above, orienting the lyotropic liquid crystal compound, and forming and laminating an optically anisotropic film on the substrate. To.
(3) The method for producing a laminate of the present invention is characterized in that the coating solution has a viscosity V ₁₀₀₀ (23 ° C.) at 23 ° C. and a shear rate of 1000 sec− ¹ of 10 mPa · s to 200 mPa · s. “MPa · s” is a unit of viscosity and is “millipascal second”.
(4) In the method for producing a laminate of the present invention, the difference between V ₁₀₀ (23 ° C.) and V ₁₀₀₀ (23 ° C.) of the coating liquid: {V ₁₀₀ (23 ° C.) − V ₁₀₀₀ (23 ° C.)} is 10 mPa -It is more than s.
(5) The manufacturing method of the laminated body of this invention is further characterized by further including the process of heat-drying the said coating film after application | coating of the said coating liquid.
(6) The method for producing a laminate of the present invention is characterized in that the drying temperature in the case of the heat drying is 50 ° C to 120 ° C.
(7) The method for producing a laminate of the present invention is characterized in that the total solid concentration of the coating liquid is 12% by weight to 50% by weight.
(8) The method for producing a laminate of the present invention is characterized in that the thickness of the coating film after drying, that is, the optically anisotropic film, is 0.05 μm to 5 μm.
(9) The method for producing a laminate of the present invention is characterized in that the dichroic ratio of the optical anisotropic film is 20 or more at a wavelength of 550 nm.
(10) The method for producing a laminate of the present invention is characterized in that the laminate has a thickness of 5 μm to 500 μm.
(11) In the method for producing a laminate of the present invention, the substrate is an alkali-free glass plate, or a styrene resin, a (meth) acrylic resin, a polyester resin, a polyolefin resin, a norbornene resin, or a polyimide resin. It consists of a resin film of any one of cellulose resin, polyvinyl alcohol resin, and polycarbonate resin.

  According to the present invention, there is practically no volatilization unevenness and coating unevenness, and a laminate having an optically anisotropic film having a small transmittance variation (5% or less) and a high dichroic ratio (20 or more) can be stably produced. A manufacturing method is provided.

[Production method of the present invention]
The method for producing a laminate of the present invention is a method for producing a laminate comprising a substrate and an optically anisotropic film comprising a coating film formed and laminated on the substrate, comprising a lyotropic liquid crystal compound and a solvent, and a thixotropy. A coating liquid with an index Ti of 1.2 or more is applied to the substrate, and shear stress is applied to the coating liquid at the time of application or the coated film to orient the lyotropic liquid crystal compound to form an optically anisotropic film on the substrate. -It is characterized by including the process of laminating | stacking. Thixotropy index Ti is, 23 ° C., the viscosity _V 100 at a shear rate of 100 sec ^-1 and (23 ° C.), the ratio of the viscosity _{V 1000} at a shear rate of 1000 sec _{^{-1 (23 ℃): Ti =}} V 100 (23 ℃) / It is defined as V ₁₀₀₀ (23 ° C.).

FIG. 1 schematically shows a graph of the relationship between the shear rate (horizontal axis) and the viscosity (vertical axis) for (a) the coating liquid of the present invention and (b) the conventional coating liquid. The viscosity on the vertical axis is an arbitrary scale. The temperature of the coating solution is 23 ° C. The viscosity at a shear rate of 1000 seconds- ¹ is a measure of the viscosity at the time of application, and the viscosity at a shear rate of 100 seconds- ¹ is a measure of the viscosity at the time of drying. Since the coating liquid (a) of the present invention has thixotropy, the viscosity decreases as the shear rate increases. Therefore, in the coating liquid of the present invention, V ₁₀₀ (23 ° C.)> V ₁₀₀₀ (23 ° C.), and the thixotropy index Ti is larger than 1. On the other hand, since the viscosity of the conventional coating liquid (b) hardly changes even if the shear rate is changed, it does not have thixotropy and the thixotropy index Ti is about 1.0.

  The manufacturing method of the laminated body of this invention may include arbitrary processes other than said process. Preferably, the method further includes a step of heating and drying the coating film after applying the coating liquid.

  The optically anisotropic film according to the present invention is a film having anisotropy in optical properties such as absorptivity and refractive index in two orthogonal directions in the layer, and functions as a linearly polarizing film, a circularly polarizing film, and a retardation film. Have For this reason, it is preferable that the laminated body of this invention is used for a polarizing film and a phase difference film.

[Liquid properties of coating liquid]
The coating liquid used in the present invention has thixotropic properties. The thixotropy can be quantitatively evaluated by the thixotropy index Ti. The greater the thixotropy index Ti, the greater the thixotropy, and the closer the thixotropy index Ti is to 1, the smaller the thixotropy and the greater the Newtonian fluidity.

  The thixotropy index Ti of the coating liquid used in the present invention is 1.2 or more, preferably 1.2 to 4.0, more preferably 1.2 to 3.0. If the thixotropy index Ti of the coating liquid is less than 1.2, even if shear stress is applied, the viscosity of the coating liquid does not become very small, so coating unevenness is likely to occur. To prevent coating unevenness, the coating liquid is diluted to reduce the viscosity. Volatilization unevenness is likely to occur. On the other hand, if the thixotropy index Ti exceeds 4.0, the fluidity of the coating liquid at the time of drying may become too low to obtain a coating film having a desired thickness.

  The thixotropic index Ti of the coating liquid used in the present invention is appropriately increased or decreased by changing the concentration of the lyotropic liquid crystal compound in the coating liquid, the type of substituent introduced into the lyotropic liquid crystal compound, and the type of solvent, for example. Is possible. For example, the thixotropic index Ti can be increased by increasing the molecular weight of the lyotropic liquid crystal compound. Alternatively, the thixotropic index Ti can be increased by adding a polyacrylic acid or cellulose compound. On the other hand, the thixotropy index Ti can be reduced by using a poor solvent such as alcohols and pyrrolidones as the solvent. Alternatively, a coating solution having a specific thixotropy index Ti can be appropriately selected from various coating solutions by measuring the thixotropy index Ti using a commercially available viscometer (for example, RHEo Stress 600 manufactured by HAAKE).

The viscosity V ₁₀₀₀ (23 ° C.) at 23 ° C. and a shear rate of 1000 seconds ⁻¹ of the coating liquid used in the present invention is preferably 10 mPa · s to 200 mPa · s, more preferably 20 mPa · s to 150 mPa · s. Yes, and particularly preferably 100 mPa · s to 150 mPa · s. When the viscosity V ₁₀₀₀ (23 ° C.) of the coating liquid is less than 10 mPa · s, the fluidity of the coating liquid is too high, and a coating film having a desired thickness may not be obtained. On the other hand, when the viscosity V ₁₀₀₀ (23 ° C.) of the coating liquid exceeds 200 mPa · s, the flowability of the coating liquid is too low, and streaky coating unevenness may occur. When the viscosity V ₁₀₀₀ (23 ° C.) of the coating liquid is in the range of 10 mPa · s to 200 mPa · s, a moderate shear stress is applied to align the lyotropic liquid crystal compound, and a coating film having a uniform target thickness is obtained. be able to.

The difference between V ₁₀₀ (23 ° C.) and V ₁₀₀₀ (23 ° C.) of the coating liquid used in the present invention, {V ₁₀₀ (23 ° C.) − V ₁₀₀₀ (23 ° C.)] is preferably 10 mPa · s or more, More preferably, it is 20 mPa · s to 200 mPa · s. If {V ₁₀₀ (23 ° C.) − V ₁₀₀₀ (23 ° C.)} is a coating liquid of 20 mPa · s to 200 mPa · s, both application unevenness and volatilization unevenness can be prevented simultaneously.

  The total solid content concentration of the coating liquid used in the present invention is not particularly limited, but is preferably 12% by weight to 50% by weight, and more preferably 12% by weight to 30% by weight. If the total solid content concentration is in the above range, volatilization unevenness hardly occurs and a coating liquid showing a stable liquid crystal phase can be obtained.

[Composition of coating solution]
The coating liquid used in the present invention contains a lyotropic liquid crystal compound and a solvent. The coating liquid can contain any additive. Examples of additives include surfactants, leveling agents, antioxidants, binder resins, monomers, curing agents, plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, colorants, Examples include a flame retardant, an antistatic agent, a compatibilizing agent, a thickener, and a coupling agent. The amount of the additive is suitably more than 0 parts by weight and 5 parts by weight or less with respect to 100 parts by weight of the lyotropic liquid crystal compound. When a surfactant is added to the solution, the wettability and coating property of the dichroic dye to the substrate surface can be improved. As the surfactant, a nonionic surfactant is preferable.

[Lyotropic liquid crystal compound]
The lyotropic liquid crystalline compound used in the present invention refers to a liquid crystal compound having a property of causing an isotropic phase-liquid crystal phase transition by changing temperature and concentration. The coating liquid exhibits a liquid crystal phase by the action of the lyotropic liquid crystal compound. There are no particular limitations on the liquid crystal phase to be expressed, and examples include a nematic liquid crystal phase, a smectic liquid crystal phase, and a cholesteric liquid crystal phase. A nematic liquid crystal phase is preferable. These liquid crystal phases are confirmed and identified by an optical pattern observed with a polarizing microscope.

The lyotropic liquid crystal compound used in the present invention preferably has a hydrophilic substituent in order to impart solubility to a hydrophilic solvent. The hydrophilic substituent is preferably at least one substituent selected from the group consisting of —COOM, —SO ₃ M, —PO ₃ M, —OH, and —NH ₂ . Examples of M include hydrogen ions, ions of group 1 metals such as Li, Na, K, and Cs, ammonium ions, and the like.

  The lyotropic liquid crystal compound used in the present invention is preferably an organic compound that absorbs light of any wavelength in the wavelength range of 400 nm to 780 nm. The optical anisotropic film obtained by the orientation of the lyotropic liquid crystal compound preferably exhibits absorption dichroism at a wavelength of 550 nm.

  As the lyotropic liquid crystal compound used in the present invention, a water-soluble dichroic dye is usually used. Specific examples of the dichroic dye used in the present invention include azo dyes, anthraquinone dyes, perylene dyes, indanthrone dyes, imidazole dyes, indigoid dyes, oxazine dyes, phthalocyanine dyes, triphenyl dyes. Phenylmethane dye, pyrazolone dye, stilbene dye, diphenylmethane dye, naphthoquinone dye, methocyanine dye, quinophthalone dye, xanthene dye, alizarin dye, acridine dye, quinoneimine dye, thiazole dye, methine System dyes, nitro dyes, nitroso dyes, and the like. Among these, azo dyes, anthraquinone dyes, perylene dyes, indanthrone dyes, and imidazole dyes are preferable. These can be used alone or in admixture of two or more. In order to obtain a black polarizing film, it is preferable to use a plurality of types having different absorption spectra.

These dichroic dyes are preferably sulfonic acid groups (—SO ₃ H), carboxyl groups (—COOH), salts thereof, nitrogen-based substituents (—NH ₂ , —NHR, —NR _2). , —NR ¹ R ² (wherein R, R ¹ and R ² are monovalent organic groups)), particularly preferably an organic compound containing a sulfonic acid group or a salt thereof. Introduction of a sulfonic acid group into a dichroic dye is effective in improving the solubility in water. As the number of sulfonic acid groups introduced into the dichroic dye increases, the solubility in water increases. The number of sulfonic acid groups is appropriately selected in consideration of both the solubility in water and the water resistance of the optically anisotropic film.

Furthermore, specific examples of the dichroic dye used in the present invention include compounds represented by the general formula (1).
(Chromogen) (SO ₃ M) _n ... General formula (1)
(N represents an integer of 1 or more, and M represents a cation).

  As M in the general formula (1), hydrogen ions, ions of Group 1 metals such as Li, Na, K, and Cs, ammonium ions, and the like are preferable. Moreover, as a chromogen site | part, what contains an azo derivative unit, an anthraquinone derivative unit, a perylene derivative unit, an imidazole derivative unit, and / or an indanthrone derivative is preferable.

  In the dichroic dye represented by the general formula (1), chromogens such as azo compounds and polycyclic compound structures in the solution become hydrophobic sites, and sulfonic acid and its salts become hydrophilic sites. Hydrophobic sites and hydrophilic sites gather together due to the balance, and the lyotropic liquid crystal is expressed as a whole.

式（２）中、Ｒ^１は水素または塩素であり、Ｒ^２は水素、アルキル基、ＡｒＮＨまたはＡｒＣＯＮＨである。このアルキル基としては炭素数が１〜４のアルキル基が好ましく、中でもメチル基やエチル基がより好ましい。アリール基（Ａｒ）としては置換または無置換のフェニル基が好ましく、中でも無置換または４位を塩素で置換したフェニル基がより好ましい。またＭは上記一般式（１）と同様である。

式（３）〜式（５）において、Ａは、式（ａ）または式（ｂ）で表されるものであり、ｎは２〜３である。ＡのＲ^３は水素、アルキル基、ハロゲンまたはアルコキシ基、Ａｒは置換または無置換のアリール基を示す。アルキル基としては炭素数が１〜４のアルキル基が好ましく、中でもメチル基やエチル基がより好ましい。ハロゲンは臭素または塩素が好ましい。またアルコキシ基は炭素数が１または２個のアルコキシ基が好ましく、中でもメトキシ基がより好ましい。アリール基としては置換または無置換のフェニル基が好ましく、中でも無置換あるいは４位をメトキシ基、エトキシ基、塩素もしくはブチル基で、または３位をメチル基で置換したフェニル基が好ましい。Ｍは上記一般式（１）と同様である。

式（６）においてｎは３〜５であり、Ｍは上記一般式（１）と同様である。

式（７）においてＭは上記一般式（１）と同様である。

式（８）においてＭは上記一般式（１）と同様である。 Specific examples of the dichroic dye represented by the general formula (1) include compounds represented by the following formulas (2) to (8).

In formula (2), R ¹ is hydrogen or chlorine, and R ² is hydrogen, an alkyl group, ArNH or ArCONH. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group. The aryl group (Ar) is preferably a substituted or unsubstituted phenyl group, and more preferably an unsubstituted or phenyl group substituted with chlorine at the 4-position. M is the same as in the general formula (1).

In Formula (3)-Formula (5), A is represented by Formula (a) or Formula (b), and n is 2-3. R ^{3 in} A represents hydrogen, an alkyl group, a halogen or an alkoxy group, and Ar represents a substituted or unsubstituted aryl group. The alkyl group is preferably an alkyl group having 1 to 4 carbon atoms, and more preferably a methyl group or an ethyl group. Halogen is preferably bromine or chlorine. The alkoxy group is preferably an alkoxy group having 1 or 2 carbon atoms, and more preferably a methoxy group. As the aryl group, a substituted or unsubstituted phenyl group is preferable, and among them, a phenyl group which is unsubstituted or substituted at the 4-position with a methoxy group, ethoxy group, chlorine or butyl group or at the 3-position with a methyl group is preferable. M is the same as in the general formula (1).

In the formula (6), n is 3 to 5, and M is the same as the general formula (1).

In the formula (7), M is the same as the general formula (1).

In the formula (8), M is the same as the general formula (1).

  Examples of the introduction (sulfonation) of the sulfonic acid group into the organic compound in the above compound include a method in which sulfuric acid, chlorosulfonic acid or fuming sulfuric acid is allowed to act on the organic compound to replace the nucleus hydrogen with the sulfone group. . The salt in the above compound is a compound in which a hydrogen atom formed by acid dissociation is substituted with a monovalent ion such as lithium ion, potassium ion, cesium ion or ammonium ion.

  Other specific examples of the dichroic dye used in the present invention include JP-A-2006-047966, JP-A-2005-255846, JP-A-2005-154746, JP-A-2002-090526, Special Table. Examples thereof include dichroic dyes described in JP-A-8-511109 and JP-T-2004-528603.

  Commercially available dichroic dyes can also be used in the present invention. Examples of this include C.I. I. DirectB67, DSCG (INTAL), RU31.156, Metyl orange, AH6556, Sirius Supra Blown RLL, Benzopurpurin, Copper-tetoracarboxyphthalocyanine, Acid Red 266, Cyanine Dye, Violet 20, Perylenebiscarboximides, Benzopurpurin 4B, Methyleneblue (Basic Blue 9), Brilliant Yellow, Acid red 18, Acid red 27, and the like.

[solvent]
The solvent used in the present invention is not particularly limited as long as it can uniformly dissolve or disperse the lyotropic liquid crystal compound. The solvent is preferably a hydrophilic solvent. Examples of the hydrophilic solvent include water, alcohols, and cellosolves. Water-soluble solvents such as alcohols, ethers, cellosolves, dimethylsulfoxide, dimethylformamide may be added to water. Water-soluble compounds such as glycerin and ethylene glycol may be added. These additives can be used to adjust the solubility of the water-soluble liquid crystal compound and the drying speed of the aqueous solution. The amount of these solvents added is preferably 100 parts by weight or less with respect to 100 parts by weight of water in the aqueous solution.

[substrate]
There is no restriction | limiting in particular in the board | substrate used for this invention, The thing of a single layer may be sufficient and the laminated body of multiple layers (for example, alignment film is included) may be sufficient. Specific examples of the substrate include a glass plate and a resin film. When the substrate includes an alignment film, the alignment film is preferably subjected to an alignment treatment. Examples of the substrate including the alignment film include a substrate in which a glass film is coated with a polyimide film. This polyimide film is provided with orientation by a known method, for example, mechanical orientation treatment such as rubbing in a certain direction or chemical orientation treatment such as photo-alignment treatment. The alignment treatment of the substrate can be carried out by a known method described in “Liquid Crystal Handbook” (Maruzen Co., Ltd., issued on October 30, 2000), pages 226 to 239.

  The glass plate of the substrate is preferably used for a liquid crystal cell, for example, non-alkali glass. Examples of commercially available glass plates include 1737 manufactured by Cornig, AN635 manufactured by Asahi Glass, and NA-35 manufactured by NH Techno Glass.

  When a resin film is used as the substrate, the substrate can have flexibility, which is suitable for applications that require flexibility. The surface of the resin film may be subjected to orientation treatment by rubbing or the like. Alternatively, an alignment film made of another material may be formed on the surface of the resin film. The material of the resin film used for the substrate is not particularly limited as long as it is a film-forming resin, but a styrene resin, a (meth) acrylic acid resin, a polyester resin, a polyolefin resin, a norbornene resin, a polyimide resin Examples include resins, cellulose resins, polyvinyl alcohol resins, and polycarbonate resins.

  The thickness of the substrate is not particularly limited except that it can be determined depending on the application, but is generally in the range of 1 μm to 1000 μm.

[Application]
The coating method used in the present invention is not particularly limited as long as the coating liquid is uniformly coated, and a coating method using an appropriate coater is employed. Examples of the coating apparatus include a slide coater, a slot die coater, a bar coater, a rod coater, a roll coater, a flexographic printing machine, a screen printing machine, a curtain coater, a spray coater, and a spin coater. Of these, a slide coater, a slot die coater, and a bar coater are preferable in that the shear stress and shear rate can be increased.

[Orientation]
The lyotropic liquid crystal compound used in the present invention can be aligned by flow when a shear stress is applied in a liquid crystal state. The lyotropic liquid crystal compound forms supramolecular aggregates in a liquid crystal state, and when a coating liquid containing the supramolecular aggregates is flowed by applying a shear stress, the major axis direction of the supramolecular aggregates is aligned in the flow direction. The orientation means may be used in combination with shearing stress, orientation treatment such as rubbing treatment or photo-alignment treatment, or orientation by a magnetic field or electric field.

[Shear stress]
The shear stress used in the present invention can be generated, for example, by applying a coating liquid onto the substrate using the above coater. Alternatively, the shearing stress can be generated by rubbing the coating liquid applied on the substrate with a metal or plastic rod or plate in one direction, or spraying the coating liquid on the substrate with an arbitrary spraying device. . The shear stress may be applied when the coating liquid is applied onto the substrate, or may be applied to the coating film after being applied onto the substrate.

[Dry]
The drying means used in the present invention is not particularly limited, and for example, natural drying, reduced pressure drying, heat drying and the like are used. The coating liquid having a thixotropy index Ti of 1.2 or more used in the present invention has a high viscosity because it has a low shear rate after being applied to the substrate, and is not easily affected by the outside (wind or the like). In addition, the coating liquid used in the present invention is less likely to cause volatilization unevenness than conventional coating liquids, and a high degree of orientation is obtained. Therefore, in the production method of the present invention, the coating liquid can be heated and dried after the coating liquid is applied. As the heating and drying means, a drying method using an arbitrary drying apparatus such as an air circulation type drying oven or a hot roll is used. The drying temperature in the case of heat drying is preferably 50 ° C to 120 ° C, more preferably 80 ° C to 100 ° C. Within the above drying temperature range, volatilization unevenness is unlikely to occur, and the residual solvent of the coating film can be reduced in a short time.

[Laminated body and optically anisotropic film]
The laminate obtained by the production method of the present invention includes a substrate and an optically anisotropic film containing a lyotropic liquid crystal compound formed on the substrate. The laminate may include other layers as long as it includes a substrate and an optically anisotropic film. For example, a protective layer made of a resin may be provided on the surface of the optical anisotropic film. Alternatively, a smooth layer, a release layer, an easy-adhesion layer, or the like can be provided in advance on the front and back surfaces of the substrate. The thickness of the laminate of the present invention is preferably 5 μm to 500 μm.

  The optically anisotropic film preferably exhibits absorption dichroism at a wavelength of 550 nm. Such an optically anisotropic film is used as a polarizer, for example. The dichroic ratio of the optically anisotropic film is preferably 20 or more, more preferably 30 or more, at a wavelength of 550 nm. The thickness of the optical anisotropic film is preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 1 μm. When the thickness is within the above range, good optical characteristics can be obtained. The dichroic ratio is measured by making the linearly polarized measurement light incident using a spectrophotometer and measuring the transmittance so that the electric field vector of the polarized light of the measurement light is parallel and orthogonal to the orientation direction of the optical anisotropic film. Can be calculated.

[Uses of laminates and optically anisotropic films]
The laminate and the optically anisotropic film obtained by the present invention are used for various optical elements taking advantage of optical anisotropy, and can be suitably used particularly as a polarizing plate and a retardation plate. Applications of laminates and optically anisotropic films include, for example, OA equipment such as personal computer monitors, notebook computers, and copiers, mobile phones, watches, digital cameras, personal digital assistants (PDAs), portable devices such as portable game equipment, video Household equipment such as cameras, TVs and microwave ovens, back monitors, car navigation system monitors, car audio equipment and other in-vehicle equipment, display equipment such as information monitors for commercial stores, surveillance equipment such as surveillance monitors, nursing care Liquid crystal display devices such as monitors and medical monitors.

  The optical anisotropic film may be peeled off from the substrate, or may be used as it is. When the laminated body is used for optical applications, the substrate is preferably transparent in the visible light wavelength region. When peeled from the substrate, it can be preferably laminated on another support or optical element.

このコーティング液をスライド式コーターを用いてガラス板上に剪断応力をかけながら塗布し、厚み０．４μｍの光学異方膜を作製した。コーティング液と光学異方膜の特性を表１に示す。コーティング液のチクソトロピーインデックスＴｉが１．７９と非常に大きいため、光学異方膜は二色比が２８と非常に高く、透過率のばらつきも５％と少なく、ムラ（塗布ムラと揮発ムラ）もほとんど見られなかった。 [Example 1]
The concentration of a solution containing a perylene compound having the following chemical structure, which is a lyotropic liquid crystal compound (NO15 manufactured by Optiva) was adjusted to prepare a coating solution so that the total solid content was 16% by weight. When observed with a polarizing microscope, this coating solution showed a nematic liquid crystal phase.

This coating solution was applied onto a glass plate using a slide coater while applying a shear stress to produce an optically anisotropic film having a thickness of 0.4 μm. Table 1 shows the characteristics of the coating liquid and the optically anisotropic film. Since the thixotropy index Ti of the coating solution is very large at 1.79, the optical anisotropic film has a very high dichroic ratio of 28, a small variation in transmittance of 5%, and unevenness (coating unevenness and volatilization unevenness). It was hardly seen.

[Example 2]
Water was added to the same lyotropic liquid crystal compound-containing solution (No. 15 manufactured by Optiva) as in Example 1 so that the total solid concentration was 10% by weight. A polyacrylic thickener (SN thickener 615 manufactured by San Nopco) was added to the lyotropic liquid crystal compound in an amount of 3% by weight to prepare a coating solution. When observed with a polarizing microscope, this coating solution showed a nematic liquid crystal phase. This coating solution was applied onto a glass plate using a slide coater while applying a shear stress to produce an optically anisotropic film having a thickness of 0.5 μm. Table 1 shows the characteristics of the coating liquid and the optically anisotropic film. Since the thixotropy index Ti of the coating liquid is as large as 1.46, the optical anisotropic film has a high dichroic ratio of 22 and the transmittance variation is as small as 5%, and there is almost no unevenness (coating unevenness and volatilization unevenness). It was.

[Comparative Example 1]
Water was added to the same lyotropic liquid crystal compound-containing solution (No. 15 manufactured by Optiva) as in Example 1 so that the total solid concentration was 10% by weight. A coating solution was prepared by adding 10% by weight of hydroxylpropylcellulose (NISSO HPC H manufactured by Nippon Soda Co., Ltd.) to the lyotropic liquid crystal compound. When observed with a polarizing microscope, this coating solution showed a nematic liquid crystal phase. This coating solution was applied onto a glass plate using a slide coater while applying a shear stress to produce an optically anisotropic film having a thickness of 0.5 μm. Table 1 shows the characteristics of the coating liquid and the optically anisotropic film. Since the thixotropy index Ti of the coating liquid was as small as 1.09, the optical anisotropic film had a low dichroic ratio of 12, a very large variation in transmittance of 15%, and coating unevenness was also observed. The cause of coating unevenness is considered to be because the viscosity V _{1000 at a} shear rate of 1000 seconds ^{−1 which} is a measure of the viscosity at the time of coating is as large as 220 mPa · s.

[Comparative Example 2]
Water was added to a solution containing the same lyotropic liquid crystal compound as in Example 1 (No. 15 manufactured by Optiva) to adjust the coating solution so that the total solid concentration was 10% by weight. When observed with a polarizing microscope, this coating solution showed a nematic liquid crystal phase. This coating solution was applied onto a glass plate using a slide coater while applying a shear stress to produce an optically anisotropic film having a thickness of 0.4 μm. Table 1 shows the characteristics of the coating liquid and the optically anisotropic film. Since the thixotropy index Ti of the coating solution was as small as 1.08, the optical anisotropic film had a low dichroic ratio of 16, a large variation in transmittance of 8%, and volatilization unevenness was also observed. The cause of volatilization unevenness is considered to be excessive dilution with water.

［評価］
以上説明した実施例と比較例の特性から分かるように、チクソトロピーインデックスＴｉが１．２未満のコーティング液を用いた場合は、揮発ムラまたは塗布ムラがなく、透過率のばらつきが小さく（５％以下）、二色比の高い（２０以上）光学異方膜は作製し難い。逆にチクソトロピーインデックスＴｉが１．２以上のコーティング液を用いた場合はムラがなく、透過率のばらつきが小さく（５％以下）、二色比の高い（２０以上）光学異方膜を作製することができる。 [Comparative Example 3]
A coating solution containing an azo compound having the following chemical structure, which is a lyotropic liquid crystal compound, and water and having a total solid content concentration of 2% by weight was prepared. When observed with a polarizing microscope, this coating solution showed a nematic liquid crystal phase. This coating solution was applied onto a glass plate using a slide coater while applying a shear stress to produce an optically anisotropic film having a thickness of 0.2 μm. Table 1 shows the characteristics of the coating liquid and the optically anisotropic film. Since the thixotropy index Ti of the coating solution was 1.00, that is, there was no thixotropy, the optical anisotropic film had a very low dichroic ratio of 3, a large variation in transmittance of 10%, and volatilization unevenness was also observed. The cause of volatilization unevenness is considered to be excessive dilution with water.

[Evaluation]
As can be seen from the characteristics of the examples and comparative examples described above, when a coating solution having a thixotropy index Ti of less than 1.2 is used, there is no volatilization unevenness or application unevenness, and the transmittance variation is small (5% or less). ), An optically anisotropic film having a high dichroic ratio (20 or more) is difficult to produce. Conversely, when a coating solution having a thixotropy index Ti of 1.2 or more is used, an optically anisotropic film having no unevenness, small variation in transmittance (5% or less), and high dichroic ratio (20 or more) is produced. be able to.

[Measurement and evaluation method]
Viscosity measurement method thixotropic index Ti: HAAKE Co. RheoStress600 _V 100 (23 _℃) under the following conditions _was used to measure the _{V 1000} (23 ℃).
Cone: C35 / 1 (35 mm diameter, 1 ° tilt angle)
・ Solvent trap; used ・ Gap; 0.050 mm
・ Measurement temperature: 23 ℃
・ Shear rate: 10 sec- ^{1 to} 4000 sec- ¹
Measurement method of dichroic ratio and transmittance: Using a spectrophotometer equipped with a Glan-Thompson polarizer (U-4100 manufactured by JASCO Corp.), linearly polarized measuring light with a wavelength of 550 nm is incident and a straight line in the maximum transmittance direction. The polarized light transmittance k ₁ and the linearly polarized light transmittance k ₂ in the direction orthogonal to the maximum transmittance direction were determined, and the dichroic ratio and transmittance were calculated by the following equations.
・ Dichroic ratio = log (1 / k ₂ ) / log (1 / k ₁ )
Transmittance = (k ₁ + k ₂ ) / 2
The average value of the dichroic ratio was determined by measuring 9 points in total, 3 points in the vertical direction and 3 points in the horizontal direction at intervals of 2 cm from the side of the sample of 8 cm long × 8 cm wide. The dichroic ratio in Table 1 is this average value. The transmittance was also measured at the same nine points, and (maximum value−minimum value) was regarded as the variation in transmittance in Table 1.
Evaluation method of unevenness: Light from a fluorescent lamp was applied to a sample of 8 cm long × 8 cm wide, and the unevenness was visually observed. The volatilization unevenness appears to be wrinkled on the surface of the sample, and the coating unevenness can be distinguished because a stripe parallel to the coating direction is visible.

(A) Graph of relationship between shear rate (horizontal axis) and viscosity (vertical axis) for coating liquid of the present invention and (b) conventional coating liquid

Claims (11)

A method for producing a laminate comprising a substrate and an optical anisotropic film formed and laminated on the substrate,
The viscosity of the coating solution at 23 ° C. and a shear rate of 100 seconds ⁻¹ is V ₁₀₀ (23 ° C.), and the viscosity at a shear rate of 1000 seconds ⁻¹ is V ₁₀₀₀ (23 ° C.), and V ₁₀₀ (23 ° C.) and V ₁₀₀₀ (23 C)) ratio: When V ₁₀₀ (23 ° C.) / V ₁₀₀₀ (23 ° C.) is the thixotropic index Ti,
Applying the coating liquid containing a lyotropic liquid crystal compound and a solvent having a thixotropic index Ti of 1.2 or more onto the substrate, and applying a shear stress to the coating liquid during application to orient the lyotropic liquid crystal compound; A method for producing a laminate, comprising a step of forming and laminating an optically anisotropic film thereon. A method for producing a laminate comprising a substrate and an optical anisotropic film formed and laminated on the substrate,
The viscosity of the coating solution at 23 ° C. and a shear rate of 100 seconds ⁻¹ is V ₁₀₀ (23 ° C.), and the viscosity at a shear rate of 1000 seconds ⁻¹ is V ₁₀₀₀ (23 ° C.), and V ₁₀₀ (23 ° C.) and V ₁₀₀₀ (23 C)) ratio: When V ₁₀₀ (23 ° C.) / V ₁₀₀₀ (23 ° C.) is the thixotropic index Ti,
The coating liquid containing a lyotropic liquid crystal compound and a solvent and having a thixotropic index Ti of 1.2 or more is applied onto the substrate, and after application, a shear stress is applied to the coating film made of the coating liquid to align the lyotropic liquid crystal compound. A method for producing a laminate comprising the steps of forming and laminating an optically anisotropic film on the substrate. 3. The laminate according to claim 1, wherein the coating liquid has a viscosity V ₁₀₀₀ (23 ° C.) at 23 ° C. and a shear rate of 1000 sec− ¹ of 10 mPa · s to 200 mPa · s. Method. The difference between V ₁₀₀ (23 ° C.) and V ₁₀₀₀ (23 ° C.) of the coating solution: {V ₁₀₀ (23 ° C.) − V ₁₀₀₀ (23 ° C.)} is 10 mPa · s or more. The manufacturing method of the laminated body in any one of Claim 3.   The method for producing a laminate according to any one of claims 1 to 4, further comprising a step of heating and drying the coating film after application of the coating liquid.   The method for producing a laminate according to claim 5, wherein a drying temperature in the case of the heat drying is 50C to 120C.   The method for producing a laminate according to any one of claims 1 to 6, wherein the total solid concentration of the coating liquid is 12 wt% to 50 wt%.   The method for producing a laminate according to any one of claims 1 to 7, wherein a thickness of the dried coating film, that is, an optically anisotropic film, is 0.05 to 5 µm.   The method for producing a laminate according to claim 8, wherein the dichroic ratio of the optically anisotropic film is 20 or more at a wavelength of 550 nm.   The thickness of the said laminated body is 5 micrometers-500 micrometers, The manufacturing method of the laminated body in any one of Claims 1-9 characterized by the above-mentioned.   The substrate is an alkali-free glass plate, styrene resin, (meth) acrylic acid resin, polyester resin, polyolefin resin, norbornene resin, polyimide resin, cellulose resin, polyvinyl alcohol resin, polycarbonate resin The manufacturing method of the laminated body in any one of Claims 1-10 characterized by consisting of any resin film of these.

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