JP2006293025A - Manufacturing method of anisotropic dyestuff film, anisotropic dyestuff film and polarizing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an anisotropic dyestuff film with a high dichroic ratio, the anisotropic dyestuff film with the high dichroic ratio and a polarizing element using the same. <P>SOLUTION: The manufacturing method of the anisotropic dyestuff film is characterized by applying a dyestuff solution onto a base material under an environmental condition of ≤1,600 Pa steam pressure. Otherwise the manufacturing method of the anisotropic dyestuff film is characterized by applying the dyestuff solution onto the base material under an environmental condition of ≤50% relative humidity. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an anisotropic dye film, and more particularly to a method for producing an anisotropic dye film having high dichroism.

In an LCD (liquid crystal display), a linearly polarizing plate and a circularly polarizing plate are used to control optical rotation and birefringence in display. Also in OLED (organic EL element), a circularly polarizing plate is used to prevent reflection of external light.
Conventionally, in these polarizing plates (polarizing elements), iodine or an organic dye having dichroism is dissolved or adsorbed in a polymer material such as polyvinyl alcohol, and the film is stretched in a film shape in one direction. A polarizing element obtained by orienting a dye or the like has been widely used. However, the conventional polarizing element produced in this way has problems such as insufficient heat resistance and light resistance depending on the dye and polymer material used; poor yield of bonding of the films during production of the liquid crystal device; there were.

Therefore, a solution containing a dichroic dye is applied on a substrate such as glass or transparent film to form a film containing the dichroic dye, and the dichroic dye is oriented using intermolecular interaction or the like. Thus, a method for producing a polarizing film by using (see, for example, Patent Documents 1 and 2 and Non-Patent Documents 1 and 2) has been studied. For use as a polarizing element, a polarizing film having a high dichroic ratio is required in order to obtain higher polarizing performance, but a polarizing film manufactured by a conventional method can obtain a high dichroic ratio. There was a problem that it was not possible to obtain better polarization performance.
US Pat. No. 2,400,877 JP-T 8-511109 Dreyer, JF, Phys. And Colloid Chem., 1948, 52, 808., “The Fixing of Molecular Orientation” Dreyer, JF, Journal de Physique, 1969, 4, 114., “Light Polarization From Films of Lyotropic Nematic Liquid Crystals”

  An object of the present invention is to provide a production method for obtaining an anisotropic dye film (polarizing film) with few defects and a high dichroic ratio.

As a result of intensive studies by the present inventors, it was found that an anisotropic dye film having few defects and a high dichroic ratio can be obtained by controlling the environmental conditions when forming the film, and the present invention has been achieved. .
That is, the present invention is a method for producing an anisotropic dye film by applying a dye solution onto a substrate, which is applied under environmental conditions where the water vapor pressure is 1600 Pa or less or the relative humidity is 50% or less. The present invention resides in a method for producing an anisotropic dye film, an anisotropic dye film obtained by the production method, and a polarizing element using the anisotropic dye film.

According to the production method of the present invention, an anisotropic dye film having few defects and a high dichroic ratio can be obtained.
Further, an anisotropic dye film having high surface smoothness can be obtained, and when used as a polarizing element, there is an effect of preventing light scattering.

The description of the constituent requirements described below is an example (representative example) of the embodiment of the present invention, and the contents are not specified.
The anisotropic dye film referred to in the present invention differs from the electromagnetic properties in any two directions selected from a total of three directions in the three-dimensional coordinate system of the thickness direction of the dye film and any two in-plane orthogonal directions. It is a dye film having a directivity. Examples of electromagnetic properties include optical properties such as absorption and refraction, and electrical properties such as resistance and capacitance. Examples of the film having optical anisotropy such as absorption and refraction include a linearly polarizing film, a circularly polarizing film, a retardation film, and a conductive anisotropic film.

That is, the present invention is preferably used for a polarizing film, a retardation film, and a conductive anisotropic film, and more preferably used for a polarizing film.
The present invention is a method for producing an anisotropic dye film by applying a dye solution onto a substrate, characterized in that the dye solution is applied under an environmental condition where the water vapor pressure is 1600 Pa or less or the relative humidity is 50% or less. The present invention relates to a method for producing an anisotropic dye film.

(Base material)
Examples of the substrate include glass, triacetate resin, acrylic resin, polyester resin, triacetyl cellulose, or urethane-based resin film. Moreover, in order to control the orientation direction of a pigment | dye, in order to control the orientation direction of a pigment | dye on this base material surface, the known method as described in "Liquid Crystal Handbook" (Maruzen Co., Ltd., issued on October 30, 2000) pp. An alignment treatment layer may be provided.
The dye solution is formed on the substrate by coating, and the dye solution usually contains a dye and a solvent, and may further contain an additive.

(Dye)
As the dye used in the dye solution, a dichroic dye is usually used. The dye is preferably a dye having a liquid crystal phase for alignment control. Here, the dye having a liquid crystal phase means a dye exhibiting lyotropic liquid crystallinity in a solvent.
Specific examples of the dye include azo dyes, stilbene dyes, cyanine dyes, phthalocyanine dyes, and condensed polycyclic dyes (perylene and oxazine dyes). Among these dyes, azo dyes that can take a high molecular arrangement in the anisotropic dye film are preferable.
An azo dye means a dye having at least one azo group. The number of azo groups in one molecule is preferably 2 or more, preferably 6 or less, more preferably 4 or less, from the viewpoint of color tone and production.
Of the azo dyes, trisazo dyes represented by the following formula (1) are preferable.

(In the formula, D ¹ and E ¹ each independently represent a phenylene group which may have a substituent, or a naphthylene group which may have a substituent,
G ¹ represents a carboxy group, a sulfo group, or a phosphate group,
Q ¹ may have a halogen atom, a hydroxyl group, a nitro group, an amino group which may have a substituent, an alkyl group having 1 to 4 carbon atoms which may have a substituent, or a substituent. Represents an alkoxy group having 1 to 3 carbon atoms, a carboxy group, or a sulfo group, and Q ² and Q ³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms that may have a substituent, or The phenyl group which may have a substituent is represented, p represents 0 or 1, and t represents 1 or 2. In the present invention, “may have a substituent” means having one or more substituents.

Here, the trisazo dye represented by the above formula (1) will be described.
The trisazo dye is usually a black water-soluble dichroic dye. The trisazo dye has a molecular structure in which substituents giving strong attractive force to other molecules are arranged at specific positions on both ends of the molecular long axis, and D ¹ and E ¹ have hydrophobicity, so that each molecule is hydrophobic. Interaction (hydrophobic interaction), making it easy for molecules to form an associated state.

In the above formula (1), D ¹ and E ¹ represent a phenylene group which may have a substituent or a naphthylene group which may have a substituent. As the phenylene group, a 1,4-phenylene group is preferable, and as the naphthylene group, a 1,4-naphthylene group is preferable in order to exhibit a hydrophobic interaction. As a substituent of this phenylene group, an optionally substituted alkyl group having 1 to 4 carbon atoms (for example, methyl group, ethyl group, n-propyl group, n-butyl group, etc.), substituent group An alkoxy group having 1 to 4 carbon atoms (for example, a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, etc.), or a substituent that may have a carbon number of 2 A group having a small polarity such as an acylamino group of ˜7 (for example, acetylamino group, benzoylamino group, etc.) is preferable from the viewpoint of improving associative property due to hydrophobic interaction in forming a lyotropic liquid crystal.

  As a substituent of the naphthylene group, a group having a small polarity such as an alkoxy group having 1 to 4 carbon atoms (for example, methoxy group, ethoxy group, etc.) which may have a substituent forms a lyotropic liquid crystal. From the viewpoint of improving the association property due to the hydrophobic interaction. Examples of the substituent that the alkyl group, alkoxy group, and acylamino group may have include a hydroxy group, an alkyl group, and an alkoxy group.

G ¹ is preferably a sulfo group, a carboxy group, or a phosphate group because they are substituents that give a strong attractive force as described above, and a sulfo group is particularly preferable in that it gives an attractive force in a wide pH range.
Q ¹ is a halogen atom, a hydroxyl group, a nitro group, an amino group which may have a substituent (preferably an acylamino group such as an acetylamino group or a benzoylamino group), a carbon which may have a substituent, Represents an alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, etc.), an optionally substituted alkoxy group having 1 to 3 carbon atoms, a carboxy group, and a sulfo group, and particularly preferably a hydrogen atom. , Hydroxyl group, carboxy group, and sulfo group. Examples of the substituent that the alkyl group and alkoxy group may have include a hydroxy group, an alkyl group, and an alkoxy group. Here, in the present invention, “may have a substituent” means that it may have one or more substituents.

Q ² and Q ³ each independently have a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, etc.) or a substituent. A particularly preferred phenyl group, and particularly preferred is that either Q ² or Q ³ is a hydrogen atom. Examples of the substituent that the alkyl group and the phenyl group may have include a hydroxy group, a carboxy group, and a sulfo group.

p represents 0 or 1, and t represents a number of 1 or 2.
The azo dye represented by the formula (1) exhibits a black color, but among them, a dye having an excitation purity of 0% to 12% is preferable for use in an anisotropic dye film. That is, when a dye having a stimulus purity of 0% to 12% is used, there is no disorder of molecular orientation caused by mixing different molecules, and high dichroism can be exhibited.

Here, the stimulus purity refers to the wavelength corresponding to the intersection with the extended spectral locus as a principal wavelength by connecting the chromaticity coordinate N of the standard light and the chromaticity coordinate C of the obtained pigment from a chromaticity diagram. Calculate from the ratio of each point. The chromaticity coordinates C are obtained by adding a dye to water to obtain an aqueous dye solution, measuring the visible light transmittance of this aqueous solution with a spectrophotometer, and calculating the chromaticity xy under the CIE1964 XYZ color system, D65 standard light source. be able to. The stimulating purity of a pigment means that measured and calculated as a pigment aqueous solution by adding the pigment to water. In addition, as a calculation method thereof, a publicly known publication described in “New Color Science Handbook” edited by the Japan Color Society, published by the University of Tokyo Press, November 25, 1989 (2nd revision), pages 104 to 105, etc. It can be determined by a method.

The azo dye represented by the formula (1) is preferably a dye having a stimulus purity of 0% to 12%, but the stimulus purity is 0% or more, more preferably 9% or less, and most preferably 6% or less. is there.
The molecular weight of the dye represented by the formula (1) is usually 595 or more, usually 1500 or less, preferably 1200 or less in the form of a free acid.

  Moreover, since the pigment | dye in this invention is used as a pigment | dye solution, it is preferable that it is soluble in a solvent, and it is still more preferable that it is water-soluble. Accordingly, as a substituent that imparts water solubility, a dye having an acidic group such as a sulfo group, a carboxy group, or a phosphoric acid group, a basic group such as an amino acid group, or a soluble group such as a hydroxyl group is preferable. In particular, it preferably has a sulfo group or a carboxy group.

The molecular weight of the dye in the present invention is preferably 200 or more, particularly 350 or more, and usually 5000 or less, particularly 3500 or less in a free state that does not take a salt form, from the viewpoints of color tone and production.
In addition, the dye preferably has a relaxation time of 10 seconds or less. In the present invention, the orientation relaxation time is a polarization microscope under crossed Nicols, as described in Hiroya Ashiya “Introduction to Polarizing Microscopes of Polymer Materials” (published by Agne Technology Center, Inc., published on October 15, 2001). Represents the time when the light transmittance after applying 1000 [1 / s] to the dye solution for 10 seconds when it is observed at is returned to the light transmittance before applying the shear.

In the present invention, the above-described dyes can be used alone, but two or more of these may be used in combination, and dyes other than the above exemplified dyes are blended and used to such an extent that the orientation is not lowered. Thus, anisotropic dye films having various hues can be produced.
Examples of blending dyes when blending other dyes include C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 34, C.I. I. Direct Yellow 86, C.I. I. Direct Yellow 142, C.I. I. Direct
Yellow 132, C.I. I. Acid Yellow 25, C.I. I. Direct Orange 39, C.I. I. Direct Orange 72, C.I. I. Direct Orange 79, C.I. I. Acid Orange 28, C.I. I. Direct Red 39, C.I. I. Direct Red 79, C.I. I. Direct
Red 81, C.I. I. Direct Red 83, C.I. I. Direct Red
89, C.I. I. Acid Red 37, C.I. I. Direct Violet 9, C.I. I. Direct Violet 35, C.I. I. Direct Violet 48, C.I. I. Direct Violet 57, C.I. I. Direct Blue 1, C.I. I. Direct Blue 67, C.I. I. Direct Blue 83, C.I. I. Direct Blue 90, C.I. I. Direct Green 42, C.I. I. Direct Green 51, C.I. I. Direct Green 59 etc. are mentioned.

(solvent)
As the solvent, water, a water-miscible organic solvent, or a mixture thereof is suitable. Specific examples of the organic solvent include alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and glycerin, glycols such as ethylene glycol and diethylene glycol, cellosolves such as methyl cellosolve and ethyl cellosolve, or a mixture of two or more. A solvent is mentioned.

(concentration)
The concentration of the dye in the dye solution is usually 0.01% by weight or more, particularly preferably 0.1% by weight or more, and usually 50% by weight or less, particularly preferably 30% by weight or less. If the dye concentration is too low, sufficient dichroism cannot be obtained in the obtained anisotropic dye film. If the dye concentration is too high, the viscosity becomes high and uniform thin film coating may be difficult, or the dye may precipitate.

(Additive)
The dye solution may further contain additives such as a surfactant and a pH adjuster as necessary. Additives can improve wettability and coatability.
As the surfactant, any of anionic, cationic and nonionic can be used. The concentration of the additive is sufficient to obtain the desired effect, and the concentration in the dye solution is usually 0.05% by weight or more and 0.5% by weight or less as an amount that does not inhibit the orientation of the dye molecules. .
In addition, for the purpose of suppressing instability such as salt formation and aggregation of the dye in the dye solution, generally known pH adjusters such as acids and alkalis are mixed before and after mixing the components of the dye solution. Alternatively, the pH may be adjusted by adding either during mixing.

Furthermore, as additives other than those described above, known additives described in “Additive for Coating”, Edited by J. Bieleman, Willey-VCH (2000) can also be used.
Moreover, the additive which has a moisturizing effect can be mix | blended. Examples include glycerin, urea, ethylene glycol and the like. When these additives having a moisturizing effect are used, there is a high possibility that the dye solution will absorb moisture, and the properties of the dye solution may change as described in detail below. Therefore, the effect of the present invention can be expected particularly when such additives are blended.

(Method for producing anisotropic dye film)
In the present invention, as a method of applying the dye solution to the substrate, Yuji Harasaki, “Coating Engineering” (Asakura Shoten Co., Ltd., published on March 20, 1971) pp. 253-277 and “Molecular Cooperation” supervised by Kunihiro Ichimura. Materials Creation and Application ”(CMC Publishing Co., Ltd., published on March 3, 1998), pages 118 to 149, etc., for example, spin coating on a substrate previously subjected to orientation treatment Examples thereof include a coating method such as a coating method, a spray coating method, a bar coating method, a roll coating method, and a blade coating method.

(Environmental condition)
The present invention is characterized in that, when the dye solution is applied onto the substrate, it is applied under an environmental condition where the water vapor pressure is 1600 Pa or less. Preferably it is 1000 Pa or less, More preferably, it is 500 Pa or less, Most preferably, it is 300 Pa or less. Conventionally, since the application is performed in a normal room and not in a dry atmosphere, the environment is such that the water vapor pressure is higher than 1600 Pa or the relative humidity is higher than 50%. It was. Here, the environmental condition referred to in the present invention refers to the surrounding environment in which the film is formed, preferably the environment of the coating part and the substrate part in the coating apparatus during coating, and more preferably Is an environment where a coating apparatus is installed at the time of coating.

In addition, the present invention is characterized in that when the dye solution is applied on the substrate, it is applied under an environmental condition where the relative humidity is 50 RH% or less. Preferably it is 30 RH% or less, More preferably, it is 20 RH% or less, Most preferably, it is 10 RH% or less. It is more preferable that the water vapor pressure is 1600 Pa or less and the relative humidity is 50 RH% or less.
As described above, by controlling the water vapor pressure or the relative humidity as the environmental conditions, it is possible to improve the dichroic ratio of the anisotropic dye film and obtain an anisotropic dye film with few defects.

The reason why the above effect is obtained is assumed as follows. By controlling the water vapor pressure and the relative humidity at the time of application, it is possible to prevent the dye solution from absorbing moisture when forming the dye film. Thereby, since it is possible to prevent changes in liquid properties such as viscoelasticity of the dye solution, it is presumed that a dye film having high reproducibility, high dichroic ratio and few defects can be formed.
As described above, examples of a method for setting the environmental condition to have a water vapor pressure of 1600 Pa or less or a relative humidity of 50 RH% or less include a method of applying in a space where the humidity can be controlled, such as a clean room or a dry room.
Moreover, the temperature at the time of application is usually 0 ° C. or higher, preferably 10 ° C. or higher, usually 80 ° C. or lower, preferably 40 ° C. or lower.

(Dry)
The coating film formed by coating is usually dried. As drying conditions, it is preferable to dry under an environmental condition where the water vapor pressure is 1600 Pa or less in order to prevent disorder of the orientation of the coating film, which is considered to be due to relaxation of orientation and thermal convection. Preferably it is 1000 Pa or less, More preferably, it is 500 Pa or less, Most preferably, it is 300 Pa or less. Similarly, it is preferable to dry under an environmental condition where the relative humidity is 50 RH% or less. Preferably it is 30 RH% or less, More preferably, it is 20 RH% or less, Most preferably, it is 10 RH% or less. The method for controlling the water vapor pressure and the relative humidity is the same as that at the time of application.

It is estimated that the coating film can be dried rapidly after the coating film is formed under the drying conditions. By this rapid drying, it is possible to prevent the orientation disorder of the coating film considered to be due to the relaxation of orientation, thermal convection and the like. Thereby, an anisotropic dye film having high orientation can be obtained, and this anisotropic dye film is presumed to exhibit a high dichroic ratio.
The drying is usually performed at 0 ° C. or higher, preferably 10 ° C. or higher, usually 180 ° C. or lower, preferably 120 ° C. or lower. If the upper limit is exceeded, the crystal structure may change or the substrate may be deformed, and if it is lower than the lower limit, the interaction between the aggregates in the coating becomes stronger, which increases the stress during drying and There is a risk of increasing distortion, which is not preferable.

As a drying method, it is preferable to use a reduced pressure treatment. Examples of the decompression method include the following methods. The coating film obtained by applying the dye solution on the substrate is put in a reduced pressure processing apparatus and subjected to a reduced pressure treatment. For example, a decompression processing apparatus as shown in FIGS. 3 and 4 can be used. Details of the decompression apparatus include the method described in JP-A-2004-169975.

Regarding the pressure reduction condition, the pressure finally reached is preferably 2 × 10 ⁴ Pa or less, more preferably 1 × 10 ⁴ Pa or less, and particularly preferably 1 × 10 ³ Pa or less. Further, it is preferably ¹ Pa or more, more preferably 1 × 10 ¹ Pa or more. The decompression conditions are described in Japanese Patent Application No. 2004-372264.
It is also preferable to use air drying as a drying method. As an air drying method, it is desirable to use air having a dew point of −30 ° C. or lower at 0.6 MPa or lower so that the surface of the dye film is not disturbed.

Furthermore, substrate heating may be used in combination as a drying method. Thereby, it is preferable that the temperature of the coating film is 180 ° C. or lower, desirably 120 ° C. or lower.
In the present invention, after drying, treatments such as stretching and photo-alignment may be further performed to improve the orientation of the dye.

(Anisotropic dye film)
The film thickness of the anisotropic dye film of the present invention is usually a film thickness after drying, preferably 10 nm or more, more preferably 50 nm or more, preferably 30 μm or less, more preferably 1 μm or less. If the thickness of the anisotropic dye film exceeds 30 μm, it may be difficult to obtain uniform orientation of the dye molecules within the film, and if it is less than 10 nm, it may be difficult to obtain a uniform film thickness. Therefore, it is not preferable.

  The anisotropic dye film of the present invention is used with a protective layer provided if necessary. This protective layer is formed by lamination with a transparent polymer film such as triacetate, acrylic, polyester, polyimide, triacetyl cellulose, or urethane film, and is put to practical use.

(Polarizing element)
Further, when the anisotropic dye film of the present invention is used for various display elements such as LCD and OLED, the anisotropic dye film is directly formed on an electrode substrate constituting these display elements, A base material on which the anisotropic dye film is formed may be used as a constituent member of these display elements.
The anisotropic dye film of the present invention functions as a polarizing film that obtains linearly polarized light, circularly polarized light, elliptically polarized light, etc. by utilizing the anisotropy of light absorption, as well as a film forming process and a dye solution containing a substrate and a dye. Thus, it is possible to make it functional as various anisotropic films such as refraction anisotropy and conduction anisotropy, and it is possible to obtain various kinds of polarizing elements that can be used for various purposes.
The polarizing element of the present invention uses the anisotropic dye film of the present invention, but is formed when the anisotropic dye film of the present invention is formed on a substrate to form the polarizing element of the present invention. In addition to the protective layer as described above, a layer having various functions such as an adhesive layer and an antireflection layer may be laminated and used as a laminate. Good.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example, unless the summary is exceeded.
In addition, the dichroic ratio (D) was measured after measuring the transmittance of the anisotropic dye film with a spectrophotometer (Otsuka Electronics Co., Ltd. “instant multi-photometry system MCPD2000”) in which an iodine polarizing element is arranged in the incident optical system. The following formula was used for calculation.

Dichroic ratio (D) = Az / Ay
Az = -log (Tz)
Ay = -log (Ty)
Tz: transmittance for polarized light in the absorption axis direction of the dye film
Ty: Transmittance for polarized light in the polarization axis direction of the dye film In the following, “part” means “part by weight”.

Example 1
In 80.8 parts of water, 15 parts of the following exemplified dye (I), 5 parts of galactose and 0.2 part of nonionic surfactant Emulgen 109P (manufactured by Kao Corporation) were stirred and dissolved to obtain a dye solution.

Prepare a base material (polyimide film thickness of about 800 mm), on which a polyimide alignment film is formed by a silk printing method on a glass substrate (75 mm x 25 mm, thickness 1 mm), and then rubbed with a cloth in advance. In addition, the above dye solution was coated with a bar coater (using “No. 2” manufactured by Tester Sangyo Co., Ltd.) under the environmental conditions of a water vapor pressure of 317 Pa, a relative humidity of 10% RH and a temperature of 25 ° C. Obtained. Then, the anisotropic dye film | membrane with a film thickness of about 0.4 micrometer was obtained by making it dry on environmental conditions of 25 degreeC, 317 Pa, and 10% RH. The water vapor pressure and the relative humidity were controlled by an environmental test room ESPEC EX-DSP6-12E manufactured by Tabay Espec Corp. (currently Espec Corp.).
When the dichroic ratio of the obtained anisotropic dye film was measured, the results as shown in FIGS. 1 and 2 were obtained. The dichroic ratio was 8. It was found that a high dichroic ratio was obtained.

(Example 2)
The environmental conditions at the time of application were, except that the water vapor pressure was 1583 Pa, the relative humidity was 50% RH and 25 ° C., and the environmental conditions at the time of drying were that the water vapor pressure was 1583 Pa, the relative humidity was 50% RH and 25 ° C. In the same manner as in Example 1, an anisotropic dye film was obtained.
When the dichroic ratio of the obtained anisotropic dye film was measured, the results as shown in FIGS. 1 and 2 were obtained. The dichroic ratio was 7. It was found that a high dichroic ratio was obtained.

(Comparative Example 1)
The environmental conditions at the time of application were, except that the water vapor pressure was 2691 Pa, the relative humidity was 85% RH and 25 ° C., and the environmental conditions at the time of drying were that the water vapor pressure was 2691 Pa, the relative humidity was 85% RH and 25 ° C. In the same manner as in Example 1, an anisotropic dye film was obtained.
When the dichroic ratio of the obtained anisotropic dye film was measured, the results as shown in FIGS. 1 and 2 were obtained. The dichroic ratio was 3, and the dichroic ratio was lower than in Examples 1 and 2.
From the results of Example 1, Example 2 and Comparative Example 1, an anisotropic dye film having a high dichroic ratio can be obtained by controlling the environmental conditions at the time of application to a water vapor pressure of 1600 Pa or less or a relative humidity of 50 RH% or less. It turns out that it is obtained. It was also found that a higher dichroic ratio was obtained as the water vapor pressure or relative humidity was lower.

Graph showing the relationship between water vapor pressure and dichroic ratio Graph showing the relationship between relative humidity and dichroic ratio The figure which shows the example of the decompression processing equipment The figure which shows the example of the decompression processing equipment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper chamber 2 Lower chamber 3 Stage 4 Coating substrate 5 Lifting shaft 6 Vacuum seal member 7 Exhaust port 8 Vacuum seal member 9 Gas introduction port 10 Airflow control plate 11 Sub decompression chamber 12 Open / close valve 13 Decompression chamber

Claims (7)

A method for producing an anisotropic dye film by applying a dye solution onto a substrate, wherein the anisotropic dye film is applied under an environmental condition having a water vapor pressure of 1600 Pa or less. A method for producing an anisotropic dye film by applying a dye solution onto a substrate, wherein the anisotropic dye film is applied under an environmental condition having a relative humidity of 50% or less. 3. The method for producing an anisotropic dye film according to claim 1, wherein after the application, the water vapor pressure is dried under an environmental condition of 1600 Pa or less. The method for producing an anisotropic dye film according to claim 1 or 2, wherein after the coating, the film is dried under an environmental condition of a relative humidity of 50% or less. The method for producing an anisotropic dye film according to claim 1, wherein the dye contained in the dye solution is a dye having a liquid crystal phase. The anisotropic dye film manufactured by the manufacturing method as described in any one of Claims 1-5. A polarizing element using the anisotropic dye film according to claim 6.

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