JP2006201759A - Method of forming anisotropic dye film, anisotropic dye film and polarizing element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic dye film having high dichromatic ratio and high surface smoothness, and to provide a polarizing element having the effect of preventing scattering of light. <P>SOLUTION: The method of forming the anisotropic dye film is carried out by after applying a dye solution containing at least a dye, such as a dichromatic dye and a solvent on a base material, such as glass or a polymer film, to form a dye film and vacuum-treating the dye film. The anisotropic dye film is obtained using the method of forming the anisotropic dye film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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 a high dichroic ratio.

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. Polarizing films obtained by orienting dichroic dyes have been widely used. However, the conventional polarizing film manufactured in this way has insufficient heat resistance and light resistance depending on the dye or polymer material used; problems such as poor yield of bonding of the polarizing film when manufacturing a liquid crystal device; was there.

Therefore, a film containing a dichroic dye is formed on a substrate such as glass or a transparent film by a wet film-forming method in which a solution containing a dichroic dye is applied, and two colors are used by utilizing intermolecular interaction. A method for producing a polarizing film by orienting a functional dye (for example, see Patent Documents 1 and 2 and Non-Patent Documents 1 and 2) has been studied.
In the use as a polarizing element, in order to obtain higher polarization performance, a polarizing film with high dichroism is required. However, the conventional art described in Patent Documents 1 and 2 and Non-Patent Documents 1 and 2 is required. The polarizing film produced by this method has a problem that a high dichroic ratio cannot be obtained and a more excellent polarizing performance cannot be obtained.
US Pat. No. 2,400,877 JP-T 8-511109 Dreyer, JF, Phys. And Colloid Chem., 1948, 52, 808., “TheFixing of Molecular Orientation” Dreyer, JF, Journal de Physique, 1969, 4, 114., “LightPolarization From Films of Lyotropic Nematic Liquid Crystals”

  An object of the present invention is to provide a method for obtaining an anisotropic dye film having a high dichroic ratio in a method for producing an anisotropic dye film.

As a result of intensive studies by the present inventors, it was found that an anisotropic dye film having a high dichroic ratio can be obtained by forming a film containing a dye by a wet film forming method and then subjecting the dye solution to a reduced pressure treatment. The present invention has been reached.
The reason why an anisotropic dye film having a high dichroic ratio can be obtained by performing the decompression process is presumed as follows. By performing the reduced pressure treatment, the dye film can be rapidly dried after the dye film is formed. By this rapid drying, it is possible to prevent the disorder of the orientation of the dye film, which is considered to be due to the relaxation of orientation and thermal convection. Thereby, a dye film having high orientation can be obtained, and this dye film is presumed to exhibit a high dichroic ratio.

According to the production method of the present invention, an anisotropic dye film having 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 anisotropy. 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 anisotropic dye film of the present invention is usually produced by a wet film forming method. The wet film forming method referred to in the present invention refers to a method in which a dye solution is prepared as a coating solution and then applied onto a substrate, and the dye is oriented and / or laminated. The dye solution referred to in the present invention usually means a solution containing a dye and a solvent.
Examples of the substrate include glass, triacetate, acrylic, polyester, triacetyl cellulose, and a urethane 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.
(i) Dye A dichroic dye is usually used as the dye used in the anisotropic dye film of the present invention. Preferred examples 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 particularly preferable.

An azo dye means a dye having at least one azo group. The number of azo groups in one molecule is preferably 1 or more, more preferably 2 or more, preferably 6 or less, and more preferably 4 or less, from the viewpoint of color tone and production.
Among the azo dyes, a dye represented by the following formula (1) is preferable.

(Wherein D ¹ and E ¹ 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;
Q ² and Q ³ each independently represent a hydrogen atom, an optionally substituted alkyl group having 1 to 4 carbon atoms, or an optionally substituted phenyl group,
p represents 0 or 1, and t represents 1 or 2. )
Here, the trisazo dye represented by the above formula (1) will be described.

The trisazo dye is a water-soluble black dichroic dye. The trisazo dye has a molecular structure in which substituents that give strong attractive force to other molecules are arranged at specific positions on both ends of the molecular long axis, and D ¹ ,
Since E ¹ has hydrophobicity, interaction between the molecules is due to hydrophobicity (hydrophobic interaction)
It is easy to make an association state between molecules.
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 the 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.) and a substituent group 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 may form 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), an optionally substituted carbon, Represents an alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, etc.), an alkoxy group having 1 to 3 carbon atoms, a carboxy group, and a sulfo group, which may have a substituent, 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.

Q ² and Q ³ may each independently have a hydrogen atom, a substituent, an alkyl group having 1 to 4 carbon atoms (for example, a methyl group, an ethyl group, etc.), or a substituent. It is a good 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, and among them, a dye having an excitation purity of 0% to 12% is preferable. 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, it is preferable that the pigment | dye in this invention is water-soluble in order to use for the said wet film forming method. Therefore, 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.

Moreover, it is preferable that the pigment | dye in this invention is a pigment | dye which has a liquid crystal phase. Here, the pigment having a liquid crystal phase means that a mixture of a pigment and a miscible solvent exhibits lyotropic liquid crystallinity.
In addition, the dye preferably has a relaxation time of 10 seconds or less. In the present invention, the orientation relaxation time is measured with a polarizing microscope under crossed Nicols, as described in Hiroya Ashiya “Introduction to Polarizing Microscopes for Polymer Materials” (published by Agne Technology Center, Inc., published on October 15, 2001). When observed, it represents the time for the light transmittance to return to the light transmittance before changing the shear after applying 1000 [1 / s] to the dye solution for 10 seconds.

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.

(ii) As a solvent solvent, water, an organic solvent miscible with water, 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.

(iii) 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 30% by weight, although it depends on the film forming conditions. % Or less is preferable. If the dye concentration is too low, sufficient optical transparency and dichroism cannot be obtained in the obtained anisotropic dye film, and if it is too high, the dye may precipitate in the dye solution.

(iv) Others 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.

(v) Method for Forming Anisotropic Dye Film When forming the anisotropic dye film of the present invention by a wet film forming method, a dye solution is usually applied to a substrate.
As a method of applying a dye solution to a substrate, Yuji Harasaki, “Coating Engineering” (Asakura Shoten Co., Ltd., published on March 20, 1971), pages 253 to 277 and Kunihiro Ichimura supervised “ Application ”(CMC Publishing Co., Ltd., published on March 3, 1998), pages 118 to 149, etc., for example, spin coating method, spray coating on a substrate previously subjected to orientation treatment Examples thereof include a coating method such as a method, a bar coating method, a roll coating method, and a blade coating method.

  The temperature at the time of application | coating of the dye solution on the base material is 0 degreeC or more and 80 degrees C or less normally, Preferably it is 40 degrees C or less. The humidity is usually 10% RH or more, preferably 30% RH or more, and usually 80 RH% or less.

(vi) Decompression treatment The method for producing an anisotropic dye film of the present invention is characterized by subjecting the dye film to a depressurization treatment after coating the dye solution on a substrate. The dye film can usually be dried by subjecting it to a reduced pressure treatment.

  In the conventional method for producing an anisotropic dye film, a dye solution is applied onto a substrate and then naturally dried. That is, conventionally, drying was performed under normal pressure, but it was difficult to obtain an anisotropic dye film having high dichroism by this drying method. This is presumably because the pigment orientation is disturbed after the pigment solution is applied onto the substrate and the pigment film is formed. According to the present invention, the dye film can be rapidly dried after the dye film is formed by performing the reduced pressure treatment. By this rapid drying, it is possible to prevent the disorder of the orientation of the dye film, which is considered to be due to the relaxation of orientation and thermal convection. Thereby, a dye film having high orientation can be obtained, and this dye film is presumed to exhibit a high dichroic ratio.

The decompression treatment referred to in the present invention means that the dye film is placed under decompression conditions. At this time, it is preferable to keep the base material having the dye film horizontal so as not to flow from the high part to the bottom part.
The shorter the time it takes to start the decompression treatment of the dye film after coating, the better, and it is preferably 1 second or more and 30 seconds or less.
Examples of the decompression method include the following methods. The dye film obtained by applying the dye solution on the substrate is put into a reduced pressure processing apparatus and subjected to a reduced pressure treatment. For example, a decompression apparatus as shown in FIGS. 9 and 10 can be used. Details of the decompression processing apparatus are described in JP-A No. 2004-169975.

As the conditions for the decompression treatment, the pressure in the system where the dye film is present 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. Usually, the pressure finally reached in the system is preferably as described above. If the upper limit is exceeded, drying may not be possible and the orientation may be disturbed. If the lower limit is not reached, drying may be too rapid and defects may occur.
The decompression time is preferably 5 seconds or more and 180 seconds or less. If the upper limit is exceeded, the dye film cannot be dried quickly before orientation relaxation, and the orientation may be disturbed. If the lower limit is not reached, drying may not be possible and the orientation may be disturbed.

Further, the temperature in the system during the decompression treatment is preferably 10 ° C. or more and 60 ° C. or less. If the value exceeds the upper limit, convection may occur during drying, resulting in the occurrence of non-uniformity in the coating film. If the value is less than the lower limit, the film cannot be dried and orientation may be disturbed.
Moreover, when apply | coating a pigment | dye film | membrane by the wet film forming method, you may heat a base material and may cool it. The temperature of the substrate at this time is preferably 10 ° C. or higher and 60 ° C. or lower. If the upper limit is exceeded, the orientation may be disturbed before drying under reduced pressure, and if it is lower than the lower limit, water droplets may adhere to the substrate surface, which may impede coating. The substrate may be heated when the dye film applied by the wet film forming method is dried under reduced pressure. The temperature of the substrate at this time is preferably 60 ° C. or less. If the upper limit is exceeded, the orientation may be disturbed before drying under reduced pressure.

(vii) Anisotropic Dye Film The thickness of the anisotropic dye film of the present invention is usually the film thickness after drying, preferably 10 nm or more, more preferably 50 nm or more, preferably 30 μm or less, more preferably 1 μm. It is as follows. 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.

(viii) Element In addition, when the anisotropic dye film of the present invention is used as a polarizing filter or the like for various display elements such as LCDs and OLEDs, the anisotropic dye film is directly applied to the electrode substrate or the like constituting these display elements. A base material on which an anisotropic dye film is formed or an 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, and also includes a film forming process and a composition 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 above-described anisotropic dye film of the present invention, but it may be a polarizing element consisting only of an anisotropic dye film, or an anisotropic dye film on a substrate. It may be a polarizing element. A polarizing element having an anisotropic dye film on a substrate is referred to as a polarizing element including the substrate.
When the anisotropic dye film of the present invention is formed on a substrate and used as a polarizing element, the formed anisotropic dye film itself may be used. In addition to the protective layer as described above, an adhesive layer Or a layer having an optical function such as an antireflection layer, an alignment film, a function as a retardation film, a function as a brightness enhancement film, a function as a reflection film, a function as a transflective film, a function as a diffusion film, etc. Layers having various functions may be laminated by a wet film formation method or the like, and used as a laminate.
These layers having optical functions can be formed, for example, by the following method.
The layer having a function as a retardation film is subjected to, for example, a stretching process described in Japanese Patent No. 2841377, Japanese Patent No. 3094113, or a process described in Japanese Patent No. 3168850. Can be formed.
In addition, the layer having a function as a brightness enhancement film may be formed by forming a fine hole by a method as described in, for example, JP 2002-169025 A or JP 2003-29030 A, or the center of selective reflection. It can be formed by overlapping two or more cholesteric liquid crystal layers having different wavelengths.
The layer having a function as a reflective film or a transflective film can be formed using a metal thin film obtained by vapor deposition or sputtering.
The layer having a function as a diffusion film can be formed by coating the protective layer with a resin solution containing fine particles.
The layer having a function as a retardation film or an optical compensation film can be formed by applying and aligning a liquid crystal compound such as a discotic liquid crystal compound or a nematic liquid crystal compound.
The anisotropic dye film using the dye of the present invention can be directly formed on a high heat resistant substrate such as glass, and a liquid crystal display can be obtained from the point that a high heat resistant polarizing element can be obtained. In addition to organic EL displays, it can be suitably used for applications requiring high heat resistance such as liquid crystal projectors and in-vehicle display panels.

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) is measured after measuring the transmittance of the anisotropic dye film with a spectrophotometer (“instant multi-photometry system MCPD2000” manufactured by Otsuka Electronics Co., Ltd.) 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 to polarization in the direction of the polarization axis of the dye film Also, the relaxation time of the orientation is the light transmittance after applying a 1000 [1 / s] shear to the dye solution for 10 seconds when observed under crossed Nicols. It represents the time to return to the light transmittance before changing the shear.

In the following, “part” means “part by weight”.
Example 1
The following pigment (I) 15 parts, galactose 5 parts and nonionic surfactant Emulgen 109P (manufactured by Kao) 0.2 parts were stirred and dissolved in 79.8 parts of water to obtain a dye solution.

  A substrate (polyimide film thickness of about 800 mm) on which a polyimide alignment film was formed by a silk printing method on a glass substrate (75 mm × 25 mm, thickness 1 mm) was prepared by rubbing with a cloth in advance. The dye solution was applied to this with a bar coater (using “No. 2” manufactured by Tester Sangyo Co., Ltd.) and then subjected to reduced pressure to obtain an anisotropic dye film having a thickness of about 0.4 μm.

The decompression treatment conditions were as follows.
・ About 2 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 30 seconds from the start of decompression,
・ About 2 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 20 seconds from the start of decompression,
・ About 2 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 10 seconds from the start of decompression,
・ About 1 × 10 ² Pa in about 10 seconds from the start of decompression,
・ About 5 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 10 seconds from the start of decompression
Moreover, the time until the pressure reduction treatment was started was about 5 to 10 seconds. Moreover, the following was used for the pressure reduction processing apparatus.

Decompression treatment apparatus: It has a decompression chamber of about 150 cm ^{3, and} the decompression chamber has two decompression sections and one decompression section. One of the two decompression sections is connected to an oil rotary vacuum pump (eg ULVAC Kiko GLD-201) of about 200 l / min, and the other is a mechanical booster pump of about 800 l / min (eg ULVAC Kiko MBS). -050). The two decompression units and the one decompression unit are provided with a mechanism for adjusting the decompression speed and the decompression speed. The decompression chamber has a mechanism for keeping the contact area of the substrate small in order to prevent drying unevenness due to heat conduction.

  The coating conditions were 25 ° C., 50% RH and 25 ° C., 10% RH. When the dichroic ratio of the obtained anisotropic dye film was measured, the result as shown in FIG. 1 was obtained. From the results in FIG. 1, the dichroic ratio was 15.2 on average, and it was confirmed that the dichroic ratio of the anisotropic dye film was improved by performing the decompression treatment.

(Comparative Example 1)
After applying the dye solution, an anisotropic dye film was obtained in the same manner as in Example 1 except that the pressure reduction treatment was not performed and the dye film was naturally dried. The natural drying conditions were any of 25 ° C., 50% RH and 25 ° C., 10% RH according to the coating conditions of each film.
When the dichroic ratio of the obtained anisotropic dye film was measured, the result as shown in FIG. 1 was obtained. From the result of FIG. 1, the dichroic ratio was an average of 6.3, and the dichroic ratio was lower than that obtained by performing the decompression treatment.

(Example 2)
In 84.7 parts of water, 15 parts of the exemplified dye (I), 0.1 part of polyethylene glycol, and 0.2 part of nonionic surfactant Emulgen 109P (manufactured by Kao Corporation) were stirred and dissolved to obtain a dye solution.
Prepare a substrate (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. Then, the dye solution was applied to this with a bar coater (using “No. 2” manufactured by Tester Sangyo Co., Ltd.) and then subjected to reduced pressure to obtain an anisotropic dye film having a thickness of about 0.4 μm.

The decompression conditions were about 2 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 30 seconds from the start of decompression. The coating conditions were 22 ° C. and 36% RH.
FIG. 2 shows the surface properties of the anisotropic dye film obtained by the reduced pressure treatment. The surface properties were observed with a laser microscope (Lasertec, LaserMicroscope 1LM11) at an objective lens of 80 times. still,
The length between two vertical white dotted lines shown in the figure is 10 μm.
As is apparent from the results of FIG. 2, an anisotropic dye film having high surface smoothness could be obtained. Therefore, it is thought that it is effective in preventing light scattering on the surface.

(Example 3)
An anisotropic dye film was obtained in the same manner as in Example 2 except that a glass substrate having a size of 150 mm × 75 mm and a thickness of 1 mm was used and the dye solution was applied with a slot die coater.
FIG. 3 shows the surface properties of the anisotropic dye film. The observation conditions and the like of the surface properties are the same as in Example 2. As is apparent from the results of FIG. 3, an anisotropic dye film having high surface smoothness could be obtained. Therefore, it is considered effective for preventing light scattering. Moreover, the result of having measured the dichroic ratio of this anisotropic dye film | membrane is shown in FIG. The dichroic ratio was 12.

(Comparative Example 2)
After applying the dye solution, an anisotropic dye film was obtained in the same manner as in Example 2 except that the pressure reduction treatment was not performed and the dye film was naturally dried.
The natural drying conditions were 22 ° C. and 36% RH.
FIG. 5 shows the surface properties of the anisotropic dye film obtained by natural drying. It could not be said to be an anisotropic dye film having high surface smoothness.

(Comparative Example 3)
An anisotropic dye film was obtained in the same manner as in Comparative Example 2 except that a glass substrate having a size of 150 mm × 75 mm and a thickness of 1 mm was used and the dye solution was applied with a slot die coater.
FIG. 6 shows the surface properties of the anisotropic dye film. It could not be said to be an anisotropic dye film having high surface smoothness.
The results of measuring the dichroic ratio of this anisotropic dye film are shown in FIG. The dichroic ratio was about 7. The dichroic ratio was lower than that of the anisotropic dye film obtained by the reduced pressure treatment. It was confirmed that the dichroic ratio of the anisotropic dye film was improved by the reduced pressure treatment.
Example 4
In the same manner as in Example 1, 15 parts of Exemplified dye (I) shown below, 5 parts of galactose, and 0.2 part of nonionic surfactant Emulgen 109P (manufactured by Kao Corporation) were stirred and dissolved in 79.8 parts of water to obtain a dye solution. It was.
A substrate (polyimide film thickness of about 800 mm) on which a polyimide alignment film was formed by a silk printing method on a glass substrate (75 mm × 25 mm, thickness 1 mm) was prepared by rubbing with a cloth in advance. The dye solution was added to the bar coater (“No. 2 manufactured by Tester Sangyo Co., Ltd.).
After application, the anisotropic dye film having a film thickness of about 0.4 μm was obtained by performing a reduced pressure treatment.
The decompression treatment conditions were as follows.
・ About 2 × 10 ⁴ Pa in about 5 seconds from the start of decompression and about 1 × 10 ² Pa in about 10 seconds from the start of decompression
Further, the time until the pressure reduction treatment was started was about 5 seconds, and the same pressure reduction treatment apparatus as in Example 1 was used.
The coating conditions were 25 ° C. and 50% RH. When the reflectance of the obtained anisotropic dye film was measured (measuring device: Hitachi U3500-type self-recording spectrophotometer, measuring conditions: 380 to 780 nm, R% mode), as shown in (1) of FIG. Results were obtained. From this result, it was found that the average reflectance of the surface subjected to the reduced pressure treatment was 9.5%, and that the scattering of light on the surface was reduced by performing the reduced pressure treatment.
(Comparative Example 4)
When the reflectance of the obtained anisotropic dye film was measured in the same manner as in Example 4 except that natural drying was performed without performing the decompression treatment, the result as shown in FIG. 8 (2) was obtained. From this result, it was found that the reflectance of the surface subjected to the reduced pressure treatment was 2.3% on average, and that the scattering of light on the surface increased unless the reduced pressure treatment was performed.

The graph which compared with the case where it reduced-pressure-processed and the case where it dried naturally about the relationship between a single-piece | unit transmittance | permeability and dichroic ratio (Example 1, Comparative Example 1). Example of surface properties of anisotropic dye film when decompressed (Example 2) FIG. 3 is a diagram of the surface properties of an anisotropic dye film when subjected to a reduced pressure treatment (Example 3). Diagram of dichroic ratio of anisotropic dye film when decompressed (Example 3) Diagram of surface properties of anisotropic dye film when naturally dried (Comparative Example 2) Diagram of surface properties of anisotropic dye film when naturally dried (Comparative Example 3) Diagram of dichroic ratio of anisotropic dye film when naturally dried (Comparative Example 3) The figure which compared the relationship between a wavelength and a reflectance in the case of carrying out pressure reduction processing and natural drying (Example 4, Comparative Example 4) 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 1 0 Airflow control board 1 1 Sub decompression chamber 1 2 On-off valve 1 3 Decompression chamber

Claims (6)

  A method for producing an anisotropic dye film, comprising: applying a dye solution onto a substrate to form a dye film; and then subjecting the dye film to a reduced pressure treatment. The method for producing an anisotropic dye film according to claim 1, wherein the decompression treatment is performed at 5 × 10 ⁴ Pa or less.   The method for producing an anisotropic dye film according to claim 1 or 2, wherein the dye contained in the dye solution is a dye having a liquid crystal phase.   The method for producing an anisotropic dye film according to any one of claims 1 to 3, wherein the relaxation time of the orientation of the dye contained in the dye solution is 10 seconds or less.   The anisotropic dye film manufactured by the manufacturing method as described in any one of Claims 1-4.   A polarizing element using the anisotropic dye film according to claim 5.

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