JP2009053631A - Method for manufacturing laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for stably manufacturing a laminate, in which there is no defective orientation (multidomain) and which has optical anisotropy of a high dichroic ratio, by a simple operation. <P>SOLUTION: The method for manufacturing the laminate is provided with an optically anisotropic layer containing a lyotropic liquid crystal compound, and a base material, and comprises steps of: (1) preparing a solution containing at least one lyotropic liquid crystal compound and a solvent; (2) applying the solution prepared in the step (1) onto the base material having ≤20°C surface temperature to form an applied solution layer; and (3) volatilizing the solvent in the applied solution layer formed in the step (2) to orient the lyotropic liquid crystal compound during the volatilization time and form the optically anisotropic layer on the base material. <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, polarizers obtained by orienting molecules such as dyes by dissolving or adsorbing iodine or dichroic organic dyes in a polymer film such as polyvinyl alcohol and stretching the film in one direction for these polarizing plates. Has been widely used.

  However, the conventional polarizer produced in this way has a problem that heat resistance and light resistance are not sufficient depending on the dye or polymer material used. In addition, there is a problem that the yield of the bonding of the films at the time of manufacturing the display panel is poor. Furthermore, since a wide film needs to be stretched with an increase in the size of the display panel, it has also been a problem that the film forming apparatus becomes very large.

  Therefore, a solution containing a dichroic dye exhibiting a liquid crystal phase is applied to a substrate such as a glass plate or a transparent film to form a coating film, and the dichroic dye is oriented using the regulatory power of the substrate substrate. A method of manufacturing a polarizing film by making them have been studied (for example, Patent Documents 1 and 2).

  In addition, a method for producing a polarizing film by orienting a dichroic dye exhibiting a liquid crystal phase using strain stress or shear stress at the time of coating has been studied (for example, Patent Document 3).

  However, polarizing films obtained by these known coating methods are not necessarily sufficient in terms of performance (dichroic ratio, alignment completeness), manufacturing stability and simplicity.

  For example, the conventional method for realizing the alignment structure by the regulation force of the base has a possibility of causing poor alignment (multi-domain) at the time of drying the solution after application, and has a problem in manufacturing stability.

In addition, it is difficult to establish a coating mechanism that can stably realize sufficient orientation in the conventional method of realizing an oriented structure by strain stress or shear stress during coating.
JP 2007-61755 A US Patent No. 24000877 JP-T 8-511109

  An object of the present invention is to provide a production method capable of stably producing a laminate having optical anisotropy having a high dichroic ratio and no orientation failure (multi-domain) by a simple operation.

  As a result of intensive studies to solve the above problems, the present inventors have found the following production method and have completed the present invention.

  When the present inventors diligently examined the production conditions for obtaining an optically anisotropic layer having high orientation, the optical anisotropy obtained in the method of applying hot air to the surface of the coating layer of the solution (Patent Document 1, paragraph 0058). It has been found that the reason why the orientation of the side layer is incomplete is that the drying time of the coating layer is too short.

  That is, in the above method, since the drying time of the coating layer is too short, the lyotropic liquid crystal compound is fixed before the lyotropic liquid crystal compound in the coating layer is sufficiently aligned. The tendency for the orientation to decrease in this way is particularly remarkable in a solution that does not exhibit a liquid crystal phase before coating but exhibits a liquid crystal phase due to an increase in the concentration of the lyotropic liquid crystal compound during the volatilization process of the solvent.

  In the method for producing a laminate of the present invention, a solution containing a lyotropic liquid crystal compound and a solvent is applied onto a substrate to form a coating layer, and the lyotropic liquid crystal compound is aligned in the process of volatilization of the solvent in the coating layer. An optically anisotropic layer is formed on the material. In particular, by controlling the volatilization rate of the solvent in the coating layer, the time required for complete alignment of the lyotropic liquid crystal compound is secured, so that alignment failure (multi-domain) does not occur. It is characterized by.

  According to the production method of the present invention, by applying a solution containing a lyotropic liquid crystal compound on a substrate having a surface temperature of 20 ° C. or less, the volatilization rate of the solvent becomes slow, and sufficient time is obtained for the alignment of the lyotropic liquid crystal compound. It is done. As a result, an optically anisotropic layer having no alignment failure (multi-domain) and uniform and high orientation can be obtained.

  (A) The manufacturing method of the laminated body of this invention is a manufacturing method of a laminated body provided with the optically anisotropic layer containing a at least 1 type of lyotropic liquid crystal compound, and a base material, Comprising: At least 1 type of lyotropic liquid crystal compound and a solvent are included. A step (1) of preparing a solution containing the step, a step (2) of applying the solution obtained in the step (1) on a substrate having a surface temperature of 20 ° C. or less, and forming a coating layer of the solution; And (3) forming an optically anisotropic layer on the substrate by volatilizing the solvent of the coating layer obtained in 2) and orienting the lyotropic liquid crystal compound in the volatilization process.

  (B) In the manufacturing method of the laminated body of this invention, time for a coating layer to show a liquid crystal phase in process (3) is 80 second or more, It is characterized by the above-mentioned.

  (C) In the method for producing a laminate of the present invention, the solution prepared in step (1) does not exhibit liquid crystallinity in step (1), and the liquid crystal phase is changed in steps (2) and (3). It is characterized by showing.

  (D) In the method for producing a laminate of the present invention, the solution prepared in step (1) does not exhibit liquid crystallinity in step (1), and the liquid crystal phase is changed in step (2) or step (3). It is characterized by showing.

  (E) The method for producing a laminate of the present invention is characterized in that the concentration of the lyotropic liquid crystal compound in the solution prepared in step (1) is 0.1 wt% to 40 wt%.

  (F) In the manufacturing method of the laminated body of this invention, process (3) includes the process of volatilizing a solvent, heating up a coating layer, It is characterized by the above-mentioned.

  (G) In the manufacturing method of the laminated body of this invention, process (3) includes the process of volatilizing a solvent, preventing a coating layer from condensing.

  (H) The method for producing a laminate of the present invention is characterized in that the optically anisotropic layer exhibits absorption dichroism at a wavelength of 550 nm.

  (I) In the manufacturing method of the laminated body of this invention, the dichroic ratio of an optically anisotropic layer is 20 or more in wavelength 550nm, It is characterized by the above-mentioned.

  According to the present invention, a laminate having no orientation failure (multi-domain) and high optical anisotropy (for example, a dichroic ratio of 20 or more at a wavelength of 550 nm is 20 or more, 30 or more) is stably produced by a simple operation. A possible manufacturing method is provided.

  The manufacturing method of the laminated body of this invention is a manufacturing method of a laminated body provided with the optically anisotropic layer containing an at least 1 type of lyotropic liquid crystal compound, and a base material, Comprising: The following process (1)-process (3) are carried out. Including.

  Step (1) is a step of preparing a solution containing at least one lyotropic liquid crystal compound and a solvent.

  Step (2) is a step of applying the solution obtained in step (1) onto a substrate having a surface temperature of 20 ° C. or lower to form a solution coating layer on the substrate.

  Step (3) is a step of volatilizing the solvent of the coating layer obtained in step (2) and orienting the lyotropic liquid crystal compound in the volatilization process to form an optically anisotropic layer on the substrate.

  According to the production method of the present invention, the time during which the coating layer exhibits the liquid crystal phase can be lengthened, so that a sufficient time for the alignment of the lyotropic liquid crystal compound can be obtained. As a result, an optically anisotropic layer having no alignment failure (multi-domain) and high uniformity can be obtained.

  In the production method of the present invention, the time during which the coating layer exhibits the liquid crystal phase is preferably 80 seconds or more, and more preferably 100 seconds to 250 seconds.

  The optically anisotropic layer 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 among them, a linearly polarizing film, a circularly polarizing film, and a retardation film And the like having a function as. The laminate of the present invention is preferably used for a polarizing film and a retardation film.

[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. 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. These liquid crystal phases are confirmed and identified by an optical pattern observed with a polarizing microscope.

  The solubility of the lyotropic liquid crystal compound used in the present invention in the solvent is preferably 0.5 mmol to 100 mmol, more preferably 5 mmol to 50 mmol, with respect to 100 g of the solvent.

The lyotropic liquid crystal compound used in the present invention is preferably water-soluble and preferably has a hydrophilic substituent in order to impart water solubility. 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 .

  The lyotropic liquid crystal compound used in the present invention is an organic compound that absorbs light of any wavelength in the wavelength range of 400 nm to 780 nm. Moreover, it is preferable that the optically anisotropic layer obtained by the orientation of the lyotropic liquid crystal compound 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 layer.

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.

  Specific examples of the dichroic dye represented by the general formula (1) include compounds represented by the following formulas (2) to (8).

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。

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).

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。

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).

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。

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

式（７）においてＭは上記一般式（１）と同様である。

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

式（８）においてＭは上記一般式（１）と同様である。

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.

[Base material]
There is no restriction | limiting in particular in the base material used for this invention, The thing of a single layer may be sufficient and the laminated body which consists 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.

  The surface of the substrate has anisotropy that orients the lyotropic liquid crystal compound. Therefore, it is preferable that an alignment film that has been subjected to an alignment treatment such as rubbing is formed on the surface of the substrate. As such a base material, the base material with which the polyimide film was coated on the glass plate is mentioned, for example. 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. Regarding the alignment treatment of the substrate for controlling the alignment direction of the water-soluble liquid crystal compound (dichroic dye), see “Liquid Crystal Handbook” (Maruzen Co., Ltd., issued on October 30, 2000), pages 226 to 239, etc. The known methods described can be used.

  The glass plate of the base material is preferably used for a liquid crystal cell, and is, for example, alkali-free 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 base material, the base material 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 base material is not particularly limited as long as it is a transparent resin having film-forming properties, but a styrene resin, a (meth) acrylic acid resin, a polyester resin, a polyolefin resin, a silicone resin, Illustrative examples include fluorine resins, polyimide resins, triacetyl cellulose resins, polyvinyl alcohol resins, and polycarbonate resins.

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

[Step (1)]
Step (1) of the present invention is a step of preparing a solution containing at least one lyotropic liquid crystal compound and a solvent.

[solvent]
Any solvent can be used. The solvent is preferably an aqueous solvent. Examples of the aqueous solvent include water, alcohols, and cellosolves.

  As an aqueous solvent, water-soluble solvents such as alcohols, ethers, cellosolves, dimethylsulfoxide, and 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.

[Preparation of solution]
The concentration of the solution is preferably 0.1 wt% to 40 wt%, more preferably 1 wt% to 10 wt%. Preferably, the solution does not exhibit liquid crystallinity in step (1), and exhibits a liquid crystal phase in either or both of step (2) and step (3). Step (2) and step (3) will be described later.

  Such a solution is usually prepared by diluting a solution exhibiting liquid crystallinity. The solution of the present invention, i.e., which does not exhibit liquid crystallinity in step (1) and exhibits a liquid crystal phase in either step (2) or step (3) or both, is liquid crystal even in step (1). Since a lyotropic liquid crystal compound can be in a liquid crystal phase for a longer time than a solution exhibiting properties, an optically anisotropic layer having no orientation failure (multidomain) and a high dichroic ratio is obtained. Cheap. The pH of the solution is preferably pH 6-8.

  In addition, the solution may be a binder resin, a monomer, a curing agent, a plasticizer, a surfactant, a heat stabilizer, a light stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, a colorant, a flame retardant, an antistatic agent, if necessary. An additive selected from a compatibilizer, a thickener, a leveling agent, a coupling agent and the like may be included. The addition amount of the additive is desirably 10% by weight or less of the total amount of the solution.

  When a surfactant is added to the solution, the wettability and coating properties of the dichroic dye to the substrate surface can be improved. As the surfactant, a nonionic surfactant is preferable. The addition amount of the surfactant is preferably 5% by weight or less of the total amount of the aqueous solution.

[Step (2)]
Step (2) of the present invention is a step in which the solution obtained in step (1) is applied onto a substrate having a surface temperature of 20 ° C. or lower to form a solution coating layer. With such a cooled substrate (surface temperature is 20 ° C. or lower), the coating layer is cooled immediately after coating. The surface temperature of the substrate at the time of applying the solution is preferably 4 ° C to 12 ° C, more preferably 4 ° C to 6 ° C.

[Application]
As the coating method, a coating method using an appropriate coater is employed. The coating method is not particularly limited as long as the coating layer is uniformly coated, and known methods such as rod coat coating, roll coater coating, flexographic printing, screen printing, curtain coater coating, spray coater coating, spin coating coating, and the like. Used as appropriate. The thickness of the coating layer is preferably 0.01 μm to 10 μm.

[Coating layer]
The coating layer of the solution refers to a layer obtained by thinly spreading the solution on the surface of the base material in a sheet form. The coating layer is a layer in a state from immediately after the application of the solution to drying and solidifying, and the solvent may be volatilized to some extent. For example, when the total weight of the solvent immediately after coating is 100, the coating layer contains more than 20 and 100 or less solvent.

[Step (3)]
In the step (3) of the present invention, the solvent of the coating layer of the solution obtained in the step (2) is volatilized, and in the volatilization process, the lyotropic liquid crystal compound contained in the solution is aligned to form an optically different material on the substrate. This is a step of forming a side layer.

[Volatile]
As the solvent volatilization means, for example, natural drying or heat drying is used. In the step (3), in order to obtain an optically anisotropic layer having higher orientation, it is preferable to volatilize the solvent of the coating layer by 80% by weight. Furthermore, it is preferable to volatilize 95% by weight or more. The solvent may be volatilized while the laminate including the base material and the coating layer is cooled. However, when water droplets adhere to the surface of the coating layer due to condensation, the lyotropic liquid crystal compound in the coating layer is dissolved in the water droplets and aligned. The degree may decrease. Therefore, the step (3) preferably includes a step of volatilizing the solvent of the coating layer while raising the temperature of the coating layer in order to prevent condensation.

[Orientation]
The lyotropic liquid crystal compound can be aligned by any method during the volatilization process of the solvent. For example, the lyotropic liquid crystal compound can be aligned in a direction parallel or orthogonal to the alignment treatment direction by using a substrate subjected to alignment treatment. As means for aligning the lyotropic liquid crystal compound, any means such as a magnetic field and an electric field can be used in addition to the alignment treatment of the substrate.

[Laminate]
The laminate obtained by the production method of the present invention includes an optically anisotropic layer containing at least one lyotropic liquid crystal compound and a substrate. The laminate may include other layers. For example, a protective layer made of a resin may be provided on the surface of the optically anisotropic layer. Alternatively, a smooth layer, a release layer, an easy-adhesion layer, and the like can be provided in advance on the front and back surfaces of the base material.

[Optically anisotropic layer]
The optically anisotropic layer preferably exhibits absorption dichroism at a wavelength of 550 nm. Such an optically anisotropic layer is used as a polarizer, for example. The dichroic ratio of the optically anisotropic layer is preferably 20 or more, more preferably 30 or more, at a wavelength of 550 nm.

  The dichroic ratio is measured by making a linearly polarized measurement light incident using a spectrophotometer and measuring the transmittance so that the electric field vector of the polarization of the measurement light is parallel and orthogonal to the orientation direction of the optical anisotropic layer. Can be calculated.

[Use of laminate and optical anisotropic layer]
The laminate and the optically anisotropic layer obtained by the present invention are used for various optical elements taking advantage of optical anisotropy, and can be particularly suitably used as a polarizing plate and a retardation plate. In this case, the dichroic ratio of the oriented coating layer is preferably 20 or more at a wavelength of 550 nm. More preferably, it is 30 or more.

  Applications of laminates and optically anisotropic layers 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, televisions 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 optically anisotropic layer may be peeled off from the substrate, or may be used as it is. When the laminated body is used for optical purposes, the substrate is preferably transparent in the visible light wavelength region. When it peels from a base material, Preferably it can laminate | stack and use on another support body and an optical element.

  FIG. 1 schematically shows the state of phase transfer in the solvent volatilization process for Examples and Comparative Examples of the present invention. In FIG. 1, the horizontal axis represents the concentration of the lyotropic liquid crystal compound in the coating layer, and the vertical axis represents the temperature of the coating layer. As shown in FIG. 1, the lyotropic liquid crystal compound exhibits a liquid crystal phase when the concentration is low, but moves to a crystal phase when the concentration is high. Further, when the temperature is low, a liquid crystal phase is shown, but when the temperature is high, it moves to an isotropic phase. The boundary between the isotropic phase / liquid crystal phase / crystal phase is indicated by a broken line.

  Therefore, after forming a coating layer of a lyotropic liquid crystal compound solution (isotropic phase) on the substrate and volatilizing the solvent, as the concentration of the lyotropic liquid crystal compound in the coating layer increases, the lyotropic liquid crystal compound becomes isotropic phase → liquid crystal phase. → Perform phase transfer in the order of crystalline phase.

At this time, when the coating layer of the solution is formed at room temperature (23 ° C.) as in the comparative example (straight line parallel to the horizontal axis), the section showing the liquid crystal phase is T ₂ on the graph because the coating layer is always at room temperature. . For short time intervals T ₂ showing a liquid crystal phase in the comparative example, lyotropic liquid crystal compound in the coating layer is oriented from being fixed moved to the crystalline phase while not performed sufficiently. As a result, alignment failure (multidomain) occurs, and a uniform and highly oriented optically anisotropic layer cannot be obtained.

On the other hand, as in the embodiment of the present invention (oblique line), the substrate is cooled in a cold room to form a solution coating layer, and then the substrate and the coating layer are placed at room temperature. to gradually increase to room temperature temperature zone exhibits a liquid crystal phase is the T ₁ of the on the graph. The time interval T ₁ showing the liquid crystal phase Example, longer than the time interval T ₂ showing the liquid crystal phase of the comparative example, the orientation of the lyotropic liquid crystal compound is sufficiently performed during this time. As a result, an optically anisotropic layer having no alignment failure (multi-domain) and uniform and high orientation can be obtained.

In the present invention, the time interval T ₁ showing the liquid crystal phase is preferably at least 80 seconds, more preferably from 100 seconds to 250 seconds.

  In the present invention, the substrate cooling temperature is such that the surface temperature of the substrate is 20 ° C. or less, preferably 4 ° C. to 12 ° C., more preferably 4 ° C. to 6 ° C.

[Example]
Water was added to a solution (trade name “NO-15” manufactured by Optiva) containing a perylene-based liquid crystal compound (water-soluble) having —SO ₃ H to prepare a concentration of 7% by weight.

  Next, the polymer film (trade name “ZEONOR” manufactured by Nippon Zeon Co., Ltd.) that has been subjected to rubbing treatment and corona treatment (hydrophilization treatment) on the surface is cooled in a cold greenhouse until the surface temperature reaches 4.6 ° C. With the temperature maintained at the above temperature, the above solution was applied to the surface of the polymer film using a wire bar (third count) to form a coating layer having a thickness of 5 μm.

  Immediately after the formation of the coating layer, the laminate (polymer film and coating layer) is transferred to a room temperature (23 ° C.) room, and while raising the temperature of the laminate (returning the temperature of the laminate to room temperature), the solvent in the coating layer (Moisture) was volatilized 80% by weight over 208 seconds. The time during which the coating layer exhibited a liquid crystal phase during this period immediately after coating was 120 seconds.

  The optically anisotropic layer of the laminate thus obtained had a dichroic ratio of 24.8 at a wavelength of 550 nm and was uniform with no orientation failure (multidomain).

[Comparative example]
A laminate was prepared in the same manner as in Example except that the polymer film was not cooled and the solution was applied at room temperature (23 ° C.) to form a coating layer. In the comparative example, the time required to volatilize 80% by weight of the solvent (water) in the coating layer was 147 seconds. The time during which the coating layer exhibited a liquid crystal phase during the period immediately after coating was 69 seconds.

  The optically anisotropic layer of the laminate of the comparative example thus obtained had a dichroic ratio of 21.4 at a wavelength of 550 nm and was nonuniform with poor alignment (multidomain).

[Measurement methods used in Examples and Comparative Examples]
Measurement method of dichroic ratio: Using a spectrophotometer equipped with a Glan-Thompson polarizer (product name “U-4100” manufactured by JASCO Corporation), linearly polarized measuring light having a wavelength of 550 nm is incident, and the following k ₁ and the demand k _2, was calculated from the following equation.
Formula; dichroic ratio = log (1 / k ₂ ) / log (1 / k ₁ )
Formula; simple substance transmittance = (k ₁ + k ₂ ) / 2
Wherein 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.

  Measurement method of substrate surface temperature: Measurement was performed by attaching a thermocouple to the substrate surface.

Schematic diagram of phase transfer in solvent evaporation process of coating layer

Claims (9)

A method for producing a laminate comprising an optically anisotropic layer containing at least one lyotropic liquid crystal compound and a substrate, the step (1) of preparing a solution containing at least one lyotropic liquid crystal compound and a solvent;
Applying the solution obtained in the step (1) onto a substrate having a surface temperature of 20 ° C. or less to form a coating layer of the solution;
A step (3) of volatilizing the solvent of the coating layer obtained in the step (2) and orienting the lyotropic liquid crystal compound in the volatilization process to form an optically anisotropic layer on the substrate. A method for producing a laminate, comprising:   The method for producing a laminate according to claim 1, wherein in the step (3), the time during which the coating layer exhibits a liquid crystal phase is 80 seconds or longer.   The solution prepared in the step (1) does not exhibit liquid crystallinity in the step (1) but exhibits a liquid crystal phase in the step (2) and the step (3). The manufacturing method of the laminated body of Claim 1 or Claim 2.   The solution prepared in the step (1) does not exhibit liquid crystallinity in the step (1) but exhibits a liquid crystal phase in the step (2) or the step (3). The manufacturing method of the laminated body of Claim 1 or Claim 2.   The lyotropic liquid crystal compound concentration of the solution prepared in the step (1) is 0.1 wt% to 40 wt%, and the production of the laminate according to any one of claims 1 to 4 Method.   The said process (3) includes the process of volatilizing the said solvent, raising the temperature of the said application layer, The manufacturing method of the laminated body in any one of Claims 1-5 characterized by the above-mentioned.   The said process (3) includes the process of volatilizing the said solvent so that the said coating layer may not condense, The manufacturing method of the laminated body in any one of Claims 1-5 characterized by the above-mentioned.   The method for producing a laminate according to claim 1, wherein the optically anisotropic layer exhibits absorption dichroism at a wavelength of 550 nm.   The method for producing a laminate according to any one of claims 1 to 8, wherein the dichroic ratio of the optically anisotropic layer is 20 or more at a wavelength of 550 nm.

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