WO2016171127A1

WO2016171127A1 - Polarizing element formed by stacking film having high retardation and layer containing dichroic dye, and display device provided with same

Info

Publication number: WO2016171127A1
Application number: PCT/JP2016/062361
Authority: WO
Inventors: 典明望月; 吉田　昇平
Original assignee: 日本化薬株式会社; 株式会社ポラテクノ
Priority date: 2015-04-20
Filing date: 2016-04-19
Publication date: 2016-10-27
Also published as: JPWO2016171127A1; HK1243495A1; KR20170138497A; CN107533178A; JP6505833B2; CN107533178B; TW201702646A; TWI708965B

Abstract

The purpose of the present invention is to provide a polarizing element that can be easily manufactured and has excellent polarization performance, and a display device that is provided with the polarizing element. A polarizing element of the present invention is characterized in that a stretched film having a retardation of 3000-50000 nm and a layer containing at least one type of dichroic dye are stacked therein and in that the thickness of the stretched film is 20-500 μm. This polarizing element employing this specific stretched film exhibits a high degree of polarization, specifically, a degree of polarization of 85% or higher, and exhibits high dichroism, specifically, dichroism of five or higher.

Description

A polarizing element in which a film having high retardation and a layer containing a dichroic dye are laminated, and a display device provided with the polarizing element

The present invention relates to a polarizing element in which a film having high retardation and a layer containing a dichroic dye are laminated. The present invention also relates to a display device provided with the polarizing element.

In general, polarizing elements used in liquid crystal display devices, sunglasses, goggles, etc., adsorb dichroic dyes such as iodine or dichroic dyes on a film made of a polymer material such as polyvinyl alcohol. Subsequently, the obtained film is uniaxially stretched, and the dichroic dye molecules are oriented in a certain direction, or the polymer film is uniaxially stretched and then the dichroic dye is adsorbed. However, since the polarization axis and the absorption axis of the polarizing element obtained by these methods are perpendicular to each other, the shape of the polarizing element is usually limited to a flat plate shape. Further, for the production of such a polarizing element, the polyvinyl alcohol film is swelled and dyed, and subsequently subjected to a stretching treatment in an aqueous boric acid solution, followed by a washing treatment and a drying treatment, and then the obtained film. The complicated process of bonding a protective film to an adhesive was required. Further, it has been required to provide a polarizing element at a desired portion more simply.

In view of the problems of such a conventional polarizing element, Non-Patent Document 1 discloses a method for producing a polarizer by orienting dichroic dye molecules in a certain direction by rubbing treatment. However, the coating property of the dye solution on the substrate is lowered due to scratches and dust on the substrate caused by the rubbing process in the rubbing process, and electrical scratches caused by static electricity. For this reason, there is a portion (coating failure) that is not coated on the obtained dye film, and as a result, the polarization performance quality of the polarizing element having the dye film is not satisfactory.

Patent Document 1 discloses a technique for obtaining a polarizer having high polarization performance by orienting dichroic dye molecules in contact with the photo-alignment film in an arbitrary direction using the photo-alignment film. However, when the surface of the dye film of the polarizing element is observed with an atomic force microscope (AFM), a portion where the dichroic dye is uniformly oriented and a portion where the dichroic dye is hardly present and are not oriented. (Crater) exists. For this reason, the polarizing performance of the obtained polarizing element has not been able to meet sufficient requirements as a practical level in the polarizing element for display elements.

In Patent Document 2, in order to further improve the uniformity of the orientation of the dichroic dye molecules and the polarization performance of the obtained polarizing element, the generation of craters is reduced as much as possible, and the orientation of the dichroic dye compound is increased overall. A method of manufacturing a polarizing element at a practical level for a display element is disclosed. The polarizing element uses a liquid crystalline polymer thin film having a photoactive group as an alignment film, irradiates the thin film with linearly polarized light, aligns the molecular axes of the photoactive groups of the polarized light irradiation portion in a certain direction, and then another micropattern. After irradiating linearly polarized light having different polarization axes through a mask, a dichroic dye solution is applied onto the thin film with a roll coater so that a specific range of pressure is applied in a direction perpendicular to the substrate. By the manufacturing method. However, in the production of the polarizing element, it is necessary to apply a specific pressure between the roll and the substrate, and the pressing pressure must be strictly controlled. Therefore, it is desired to develop a polarizing element having excellent polarization performance that can be manufactured more easily without requiring such strict pressure control.

JP-A-7-261024 Japanese Patent No. 4175455

A polarizing element having a dye film obtained by applying a composition containing a conventional dichroic dye does not have a sufficiently satisfactory polarizing performance due to the influence of rubbing treatment or the like. Therefore, it is necessary to further improve the polarization performance. It is also desired to manufacture a polarizing element having excellent polarization performance more easily.

Therefore, an object of the present invention is to provide a polarizing element excellent in polarization performance that can be easily manufactured, and a display device provided with the polarizing element.

As a result of intensive studies to solve the above problems, the present inventor laminated a stretched film having a retardation of 3000 to 50000 nm and a layer containing a dichroic dye, and the thickness of the stretched film was 20 to 500 μm. It was newly found that a polarizing element excellent in polarization performance that can be easily produced can be obtained by using the polarizing element.

That is, the gist configuration of the present invention is as follows.
(1) A polarizing element comprising a stretched film having a retardation of 3000 to 50000 nm and a layer containing one or more dichroic dyes, wherein the stretched film has a thickness of 20 to 500 μm. .
(2) The polarizing element according to (1), wherein the stretched film is made of polyethylene terephthalate.
(3) The polarizing element according to (1) or (2), wherein the dichroic ratio is 5 or more.
(4) The molecular anisotropy larger than the molecular anisotropy imparted to the surface of the stretched film is further imparted in the same direction as the stretch axis of the stretched film. The polarizing element as described in any one of (3).
(5) The film further comprises a retardation film having a slow axis or a fast axis of retardation at an angle of 10 ° to 100 ° with respect to the major axis direction of the film on the stretched film ( 1) The polarizing element as described in any one of (4).
(6) The polarizing element according to any one of (1) to (5), wherein at least one of the dichroic dyes is a compound represented by the following formula (1) or a salt thereof: .

(In the formula (1),
X ₁ represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having 1 to 3 carbon atoms,
X ₂ and X ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, Having one or two substituents of one or two types selected from the group consisting of a hydroxyl group and a sulfonic acid group;
R ₁ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms. Represents a phenyl group substituted with an alkoxyl group, an amino group or a sulfo group,
m is 0 or 1 and n is 1 or 2)
(7) The polarizing element according to (6), wherein X ₁ is a compound represented by the following formula (3) or a salt thereof as a substituent.

(In formula (3), j is 1 or 2)
(8) The layer containing the dichroic dye further contains a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene block polymer, any one of (1) to (7) The polarizing element as described in one.
(9) A display device provided with the polarizing element according to any one of (1) to (8).

The polarizing element of the present invention, wherein a film having a retardation of 3000 to 50000 nm and a layer containing a dichroic dye are laminated, has a high retardation of 20 to 500 μm as a substrate. A stretched film is used. The polarizing element of the present invention using such a specific stretched film exhibits a high degree of polarization, particularly a degree of polarization of 85% or more, and a high dichroism, particularly 5 or more. Therefore, a polarizing element excellent in polarizing performance can be obtained by using the specific stretched film in the present invention as the substrate. Moreover, the polarizing element of the present invention is obtained by laminating a specific base material and a layer containing a dichroic dye. Therefore, according to the configuration of the present invention, it is possible to obtain a high-performance polarizing element excellent in polarization performance and easily manufactured.

Hereinafter, the present invention will be described in detail. In the following, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value. Unless otherwise specified, the compounds (substituents) represented by the formulas (1) to (3) are represented in the form of a free acid, and the free acid salt is, for example, a sulfonic acid group or a hydroxy group. Means salt. Further, in the following description, unless otherwise specified, in order to avoid complication, “a compound represented by formula (1) or a salt thereof”, “a compound represented by formula (2) or a salt thereof”, “substitution” The compound represented by the formula (3) or a salt thereof as a group is respectively “the compound represented by the formula (1)”, “the compound represented by the formula (2)”, “the compound represented by the formula (3) For the sake of convenience.

First, the polarizing element constituting the present invention will be described. The polarizing element of the present invention is a polarizing element in which a stretched film having a retardation of 3000 to 50000 nm and a layer containing a dichroic dye are laminated, and the thickness of the stretched film is 20 to 500 μm.

(Stretched film)
The polarizing element of the present invention uses a stretched film having a retardation of 3000 to 50000 nm as a substrate. The material of the stretched film is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate, resins such as polycarbonate, polystyrene, polyetheretherketone, polyphenylene sulfide, and cycloolefin polymer. Among these, polycarbonate or polyester is particularly preferable. These resins have excellent transparency, thermal and mechanical properties, can easily control the retardation of the film by stretching, and have a high degree of crystallinity after stretching. There is less dimensional change such as heat shrinkage after stretching than the polyvinyl alcohol film used in the polarizing element, and therefore, the dimensional change is extremely less than that of the polarizing element using the conventional polyvinyl alcohol film. be able to. In addition, the stretched film used in the present invention has such a high retardation as described above even if it has a relatively thin thickness of 20 to 500 μm. As a material for such a stretched film, in particular polyester represented by polyethylene terephthalate has a large intrinsic birefringence, and even if the thickness of the stretched film is relatively thin, it is most suitable because a high retardation can be obtained relatively easily. Material.

The higher the molecular orientation in the stretched film, that is, the higher the retardation, the better the orientation of the dichroic dye molecules applied on the stretched film. Therefore, in order to obtain a polarizing element having a high degree of polarization, it is preferable to use a stretched film having a high retardation. As described above, the retardation range of the stretched film used in the polarizing element of the present invention is 3000 to 50000 nm. A polymer film having a retardation exceeding 50000 nm is not preferable because it easily stiffens and the thickness of the film is correspondingly increased. As a result, the handleability as an industrial material is lowered. On the other hand, from the viewpoint of visibility, it is preferable to use a stretched film having a retardation range of 3000 to 30000 nm. It is known that when a display screen is observed through a polarizing plate such as polarized sunglasses, it has a particularly good performance that exhibits a strong interference color. On the other hand, when the retardation is in the range of 3000 to 30000 nm, such interference does not appear and good visibility can be secured. However, when the retardation is less than 3000 nm, when the display screen is observed through a polarizing plate such as polarized sunglasses, a strong interference color is exhibited. Therefore, the envelope shape is different from the emission spectrum of the light source, and as a result, good visibility is ensured. This is not possible, and the performance of the polarizing element is degraded. Therefore, the retardation range of the stretched film used in the polarizing element of the present invention is 3000 to 50000 nm, the preferred lower limit of retardation is 4500 nm, the more preferred lower limit is 6000 nm, the still more preferred lower limit is 8000 nm, and the still more preferred lower limit. The value is 10,000 nm, and the preferable upper limit of retardation is 30000 nm.

The method for producing a stretched film used in the polarizing element of the present invention is not particularly limited as long as the stretched film characteristics defined in the present invention are satisfied. Examples of the stretched film used include films described in JP 2012-230390 A and JP 2012-256014 A, and Cosmo Shine (super-birefringence) which is a polyethylene terephthalate film manufactured by Toyobo. Type film (SRF film)). By using such a stretched film, molecular anisotropy is expressed on the film surface, and the dichroic dye molecules can be oriented. The state in which the film is stretched means that anisotropy is expressed with respect to the orientation of the dichroic dye molecules on the film surface, and retardation is expressed. The manifestation of this anisotropy can be measured by diffraction measurement by X-ray measurement, phase difference measurement, anisotropic IR absorption analysis, or the like. In particular, “Alexander, LE Diffraction Methods in polymer Science New York” 1969, Chapter 4, p. In the orientation coefficient obtained by the fc calculation method described in 241-252, fc should be 0.3 or more, preferably 0.5 or more, more preferably 0.7 or more, and 0.9 or more. Particularly preferred. The method of stretching the film is not particularly limited as long as anisotropy develops. In particular, by using a uniaxially stretched film, dichroism is subsequently applied in the application of a solution containing a dichroic dye. The dye molecules exhibit high orientation in the stretching direction, and as a result, a polarizing element having a high degree of polarization can be obtained.

In the present invention, the retardation (retardation value) is a parameter defined by the product of the biaxial refractive index anisotropy on the film and the thickness of the film. It is a scale to show. Therefore, this retardation can be obtained by measuring the refractive index and thickness in the biaxial direction, and for example, using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (manufactured by Oji Scientific Instruments). Can be sought.

By performing corona discharge treatment or ultraviolet irradiation on the stretched film as the substrate, the dichroism of the polarizing element described later can be improved, and the polarization characteristics of the resulting polarizing element can be enhanced. The corona discharge treatment can be applied by using various commercially available corona discharge treatment machines as an apparatus for performing the corona discharge treatment, and the use of a corona treatment machine having an aluminum head is particularly preferable. The condition of the corona discharge treatment is 20 to 400 W · min / m ² , preferably about 50 to 300 W · min / m ² as the energy density in one corona discharge treatment. In addition, when one corona discharge treatment is insufficient, the corona discharge treatment may be performed twice or more. Similarly, ultraviolet irradiation can be applied by using various commercially available ultraviolet irradiation apparatuses. The wavelength of the ultraviolet rays used is not particularly limited, but for example, far ultraviolet rays of 300 nm or less are preferable. Further, the ultraviolet irradiation is preferably performed under an oxygen stream, and the irradiation time of ultraviolet rays is sufficient if it is several minutes at the longest.

(Dichroic dye)
The polarizing element of the present invention has a layer containing a dichroic dye in order to form a dye film as an element exhibiting a polarizing function. A dichroic dye is used as a material for forming a layer containing a dichroic dye, and the dichroic dye is a compound that exhibits polarization by being arranged in a certain direction by itself or in an aggregate. . Examples of such dichroic dyes include dye compounds such as azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, and anthraquinone dyes. Etc. The dichroic dye used in the present invention is a compound that exhibits lyotropic liquid crystal properties under a certain solvent composition, dye concentration, and temperature conditions. For example, supervised by Masahiro Irie, “Application of Functional Dyes”, First Printing Plate, CMC Co., Ltd., June 2002, p. 102-104. The dichroic dye is preferably a water-soluble azo dye, and among them, a compound having an aromatic ring structure is more preferable. As the aromatic ring structure, for example, in addition to benzene, naphthalene, anthracene, phenanthrene, a heterocyclic ring such as thiazole, pyridine, pyrimidine, pyridazine, pyrazine, quinoline, or a quaternary salt thereof, further, benzene, naphthalene, etc. In particular, a hydrophilic substituent such as a sulfonic acid group, a carboxylic acid group, an amino group, or a hydroxyl group, or a salt of a sulfonic acid group or a carboxylic acid group is introduced into these aromatic rings. Preferably it is.

Specific examples of such dichroic dyes include C.I. I. Direct Orange 39, C.I. I. Direct Orange 41, C.I. I. Direct Orange 49, C.I. I. Direct Orange 72, C.I. I. Direct Red 2, C.I. I. Direct Red 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. 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 Blue1, C.I. I. Direct Blue 15, C.I. I. Direct Blue 67, C.I. I. Direct Blue 78, C.I. I. Direct Blue 83, C.I. I. Direct Blue 90, C.I. I. Direct Blue 98, C.I. I. Direct Blue 151, C.I. I. Direct Blue 168, C.I. I. Direct Blue 202, C.I. I. Direct Green 42, C.I. I. Direct Green 51, C.I. I. Direct Green 59, C.I. I. Direct Green 85, C.I. I. Direct Yellow 4, C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 26, C.I. I. Direct Yellow 44, C.I. I. Direct Yellow 50, Moldant Yellow 26, C.I. I. No. 27865, C.I. I. No. 27915, C.I. I. No. 27920, C.I. I. No. 29058, C.I. I. No. In addition, JP-A-1-161202, JP-A-1-172906, JP-A-1-172907, JP-A-1-183602, JP-A-1-248105, JP-A-1 And dichroic dyes described in JP-A-9-230142 and JP-A-9-230142.

Among the dichroic dyes shown in the above specific examples, compounds represented by the following formula (1) or (2) are particularly preferable, and compounds represented by the formula (1) are particularly preferable. The compound represented by Formula (1) and Formula (2) exists as a free acid or its salt. The salt of the free acid is not particularly limited, and may be any salt such as an alkali metal salt such as Li, Na, or K, or a quaternary ammonium salt. By using such a dichroic dye, the polarization performance of the obtained polarizing element can be improved.

(In the formula (1),
X ₁ represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having 1 to 3 carbon atoms,
X ₂ and X ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, Having one or two substituents of one or two types selected from the group consisting of a hydroxyl group and a sulfonic acid group;
R ₁ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms. Represents a phenyl group substituted with an alkoxyl group, an amino group or a sulfo group,
m is 0 or 1,
n is 1 or 2. )

(In the formula (2),
Y ₁ represents a naphthyl group having one or two sulfonic acid groups, and further having a hydroxyl group or an alkoxy group having 1 to 3 carbon atoms,
Y ₂ and Y ₃ each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, Having one or two substituents of one or two types selected from the group consisting of a hydroxyl group and a sulfonic acid group;
R ₂ represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms. Represents a phenyl group substituted with an alkoxyl group, an amino group or a sulfo group,
As phenylazo group

Is substituted at any of the 5-position, 6-position, 7-position or 8-position of the terminal naphthyl group,
R ₃ and R ₄ each independently represent a hydrogen atom, a hydroxyl group, a sulfonic acid group, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms,
q is 0 or 1;
p is 1 or 2. )

Specific examples of the compound represented by the above formula (1) include, for example,

Etc.

Moreover, as a specific example of the compound represented by Formula (2), for example,

Etc.

Among compounds represented by formula (1) or formula (2), X ₁ in formula (1) or Y ₁ in formula (2) is a compound represented by the following formula (3) as a substituent. By having it, the polarizing performance can be further improved. In particular, it is represented by the formula (1) having a compound represented by the following formula (3) as a substituent in that it has a high dichroic ratio alone. The use of compounds is preferred. The said substituent exists also as a free acid or its salt similarly to the compound represented by Formula (1) and Formula (2). The salt of the free acid is not particularly limited, and may be any salt such as an alkali metal salt such as Li, Na, or K, or a quaternary ammonium salt.

(In formula (3), j is 1 or 2.)

The dichroic dyes used in the present invention may be used alone or in combination of two or more. The combined use of such two or more dichroic dyes is not particularly limited, but by using an additional dichroic dye, the dichroic ratio of the dichroic dye can be further improved. it can.

Next, a method for producing the polarizing element of the present invention will be described. In the polarizing element of the present invention, a solution containing the dichroic dye described above is applied to the stretched film as the base material described above, and then dried to form a layer containing the dichroic dye on the stretched film. It is produced by. Since the layer containing the formed dichroic dye exhibits a polarizing function, a laminate composed of a base material and a layer containing the dichroic dye may be used as a polarizing element. A laminated body in which a protective layer or the like is further laminated on the surface of the contained layer may be used as the polarizing element.

In order to orient the dichroic dye molecules on the stretched film as the substrate, a solution (coating solution) containing the dichroic dye is prepared. The solvent as the coating solution is not particularly limited as long as the dichroic dye to be used can be dissolved. For example, water, alcohols, ethers, pyridine, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) ), N-methylpyrrolidinone (NMP), dimethylacetamide (DMAC), dimethylimidazoline (DMI), etc. Among these, only one kind of solvent may be included, or a plurality of solvents may be included. It may be. In particular, when a water-soluble dichroic dye is used, water or a mixed solvent with the above organic solvent mainly containing water is preferable as the solvent. The amount of the organic solvent mixed with water is arbitrary, but is preferably 0 to 50% by mass, particularly preferably 0 to 20% by mass with respect to water. The concentration of the dichroic dye in the coating solution is preferably 0.1 to 25% by mass, more preferably 0.3 to 10% by mass, and further preferably 0.5 to 5% by mass.

Moreover, the polarizing element of the present invention has a layer containing a dichroic dye formed using a coating solution further containing a compound of polyoxyethylene polyoxypropylene alkyl ether or polyoxyethylene polyoxypropylene block polymer. Thus, the polarization performance can be further improved. When the layer containing the dichroic dye further contains such a compound, it is possible to improve a coating defect that has occurred at the time of application in the production of a dye film on a substrate. These compounds may be used alone or in combination of two or more. The concentration of these compounds in the coating solution is preferably 0.001% by mass to 5% by mass, more preferably 0.01% by mass to 2% by mass, and still more preferably 0.05% by mass to 1.0% by mass. % By mass.

Next, the solution containing this dichroic dye is dropped on the surface of the stretched film of the present invention as a base material, and contains a dichroic dye having a uniform thickness on the stretched film by a coater or spin coating method. A layer to be applied, ie, a coating film is provided. The method of providing the coating film is not particularly limited as long as the solution containing the dichroic dye can be applied. For example, the stretched film of the present invention is applied to the solution containing the dichroic dye. , A method of applying the solution with a bar coder, etc., a method of applying with an inkjet printer application device such as a piezo method, thermal method, bubble jet (registered trademark) method used for home use or commercial use, spin coater Rotating coating method, roll coater coating, flexographic printing, screen printing, gravure printing, curtain coater coating, spray coater coating, etc., especially roll coater coating, curtain coater coating, spray coating with spray coater The method is preferred.

Further, the substrate containing the dichroic dye solution is dried to form a solid dichroic dye layer to obtain a layer containing the dichroic dye of the present invention. Although the drying conditions vary depending on the type of solvent, the type of dichroic dye, the amount of the solution containing the applied dichroic dye, the concentration of the dichroic dye, etc., the drying temperature is preferably 5 to 100 ° C. Is 10 to 50 ° C., and the humidity is 20 to 95% RH, preferably about 30 to 90% RH.

The thickness of the layer containing the dichroic dye of the present invention is preferably thinner from the viewpoint of improving polarization characteristics, for example, 0.001 to 10 μm, particularly 0.05 to 2 μm. In addition, in order to form a layer containing the dichroic dye of the present invention within such a thickness range, the thickness of the coating film coated with a solution containing the dichroic dye is 2 to 10 μm. The thickness is preferably 3 to 5 μm.

Further, the stretched film of the present invention to which a solution containing a dichroic dye is applied may be further subjected to heat treatment and / or humidification treatment. By performing the heat treatment and / or the humidification treatment, the adhesion of the layer containing the dichroic dye to the stretched film of the present invention, the polarization performance of the resulting polarizing element, the dichroic ratio and the durability can be improved. it can. The temperature of the heat treatment is room temperature to 110 ° C., preferably 60 to 90 ° C., and the humidity of the humidification treatment is about 40 to 95% RH, preferably about 50 to 90% RH.

The polarizing element of the present invention thus obtained has a dichroic ratio (Rd). The dichroic ratio is generally defined as the ratio of absorbance along the absorption axis to absorbance along the transmission axis. The dichroic ratio of the polarizing element of the present invention is calculated by the following formula (4). If the dichroic ratio is 5 or more, it means that the polarizing function is exhibited. The dichroic ratio of the polarizing element of the present invention is 5 or more, preferably 10 or more, more preferably 15 or more, and still more preferably 20 or more. When the dichroic ratio is less than 5, the degree of polarization is less than 65%, and the function as a polarizing element is not sufficient. The polarization degree of the polarizing element usually needs to be 65% or more, preferably 70% or more, more preferably 80% or more. The degree of polarization is the ratio of the light intensity of the polarized component to the total light intensity, and the higher the degree of polarization, the higher the polarization performance. In the following formula (4), Ky is the transmittance of the axis that transmits the most light when the polarized light is incident, and Kz is the transmission of the axis that absorbs the most light when the polarized light is incident. Rate.

As a method for further improving the dichroic ratio of the polarizing element of the present invention, molecular anisotropy imparted to the surface of the stretched film in the same direction as the stretch axis of the stretched film with respect to the surface of the stretched film in the present invention. The dichroic ratio can be further improved by further imparting molecular anisotropy larger than the property. Examples of a method of developing a larger molecular anisotropy than the stretched film include a method of rubbing a stretched film. Such rubbing is exemplified in, for example, Japanese Patent Application Laid-Open Nos. 06-110059 and 2002-90743. Although the measurement of the molecular anisotropy of the surface of a stretched film is not specifically limited, For example, it measures by the measuring method used for the anchoring measurement of the alignment film for liquid crystals. Also, an apparatus for measuring such molecular anisotropy is not particularly limited, and for example, MARITEX SCOTT's Ray Scan can be used.

On the stretched film of the present invention, on the surface of the film having a slow axis or a fast axis having a phase difference of 10 ° to 100 ° at an angle different from the major axis direction of the film, molecular anisotropy in the major axis direction It is also possible to produce a polarizing element in which a retardation film exhibiting properties is further laminated. Such a retardation film is obtained by imparting molecular anisotropy in the major axis direction by rubbing or the like on the surface of a retardation film having a slow axis or a fast axis of retardation at an arbitrary angle, Thereby, the polarization axis or absorption axis of the polarizing element can be arbitrarily controlled. That is, with respect to the major axis direction of the film, a further retardation film having a slow axis or a fast axis of retardation at an angle different from the angle and showing molecular anisotropy on the surface in the major axis direction, By using the stretched film of the present invention, it is possible to produce a polarizing element having a slow axis or a fast axis as a retardation axis and an absorption axis or a polarization axis at an angle different from the retardation axis. Become. The angle formed by the retardation axis of the retardation film and the absorption axis or polarization axis of the polarizing element is most preferably 15 °, 45 °, 75 °, or 90 °. The reason why such an angle is preferable is that, in general, when linearly polarized light is to be controlled to circularly polarized light, a film having a phase difference of 1/4 with respect to the length of the wavelength to be controlled is used as the absorption axis of the polarizing element. It is known that it is installed at 45 ° to the angle. Further, as a method for reversing the polarization axis of linearly polarized light, it is known to install a film having a phase difference of 1/2 with respect to the length of the wavelength to be controlled at 90 °. The reason why the film is placed at 15 ° or 75 ° with respect to the absorption axis or the polarization axis of the polarizing element is that such an angle has a prescription (1/4) for a wide range of wavelengths. This is because the axis angle is generally used in a broadband achromatic phase difference plate). Thereby, it becomes possible to arbitrarily control the polarization axis or the absorption axis of the polarizing element.

Although the layer containing the dichroic dye of the present invention prepared as described above is in a solid state such as amorphous or crystalline, the layer containing the dichroic dye is usually inferior in mechanical strength. The surface of the layer is provided with a rake treatment, a crosslinking treatment with a silane coupling agent, or a protective layer. Rake is to electrically bond metal ions or the like to a dichroic dye exhibiting water solubility. Making a dichroic dye into a rake is sometimes called rake or insolubilization. Suitable compounds for rake include aluminum chloride, iron chloride, calcium chloride, barium chloride, nickel chloride, magnesium chloride, copper chloride, barium acetate, nickel acetate, etc. The dichroic dye is not particularly limited as long as it can be bonded to each other and the dichroic dye can be insolubilized in water. Further, the crosslinking treatment with a silane coupling agent is not particularly limited. For example, a silane coupling agent as described in JP 2011-53234 A is subjected to a crosslinking treatment by heating, and the two A layer containing a chromatic dye can be immobilized. The protective layer is usually a coating containing a dichroic dye with a transparent polymer film that is UV curable or thermosetting, or a laminate with a transparent polymer film such as a polyester film or cellulose acetate film. It is provided by the coating method. The protective layer can be provided as a polymer coating layer or as a laminate layer of a film. The transparent polymer or film forming the transparent protective layer is preferably a transparent polymer or film having high mechanical strength and good thermal stability. As a substance used as a transparent protective layer, for example, cellulose acetate resin such as triacetyl cellulose or diacetyl cellulose or film thereof, acrylic resin or film thereof, polyvinyl chloride resin or film thereof, nylon resin or film thereof, polyester resin or film thereof A film, a polyarylate resin or a film thereof, a cyclic polyolefin resin having a cyclic olefin such as norbornene or a film thereof, polyethylene, polypropylene, a polyolefin having a cyclo or norbornene skeleton or a copolymer thereof, a main chain or a side chain Examples include imide and / or amide resins or polymers or films thereof. In addition, a resin having liquid crystallinity or a film thereof can be provided as the transparent protective layer. The thickness of the protective layer is, for example, about 0.5 to 200 μm. One or more resins or films serving as protective layers can be provided on one or both sides of the polarizing element. When a plurality of protective layers are used, these protective layers may be the same or different. Good.

The polarizing element of the present invention can be used for polarized sunglasses, goggles and the like. Furthermore, in the polarizing element of the present invention, when a stretched film prepared from the above material is used as the base material, it is required when a normal polyvinyl alcohol film base material is used in the manufacture of the polarizing element of the present invention. No dichroic dye adsorption or stretching treatment in a boric acid solution is required. Therefore, it is possible to obtain a polarizing element in which there is no dimensional change of the substrate and no shrinkage. The ability to manufacture a polarizing element without dimensional change is particularly effective for displays that require a polarizing element to be provided on one side of a display device such as a flexible display or an organic electroluminescence display (commonly referred to as OLED). Therefore, the polarizing element of the present invention can be provided in a display device such as a flexible display or an organic electroluminescence display. Further, unlike conventional methods for producing polarizing elements, the dichroic dye is applied to the stretched film of the present invention as a substrate without imposing strict conditions required for coating the dichroic dye. The polarizing element of the present invention is very easy to produce because a polarizing element can be easily obtained by simply applying a solution containing dichroic acid, then drying and providing a layer containing a dichroic dye on the substrate. It is.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, the transmittance | permeability shown in an Example was performed as follows.

The transmittance and dichroic ratio (Rd) of each wavelength were measured using a spectrophotometer (manufactured by JASCO Corporation: V-7100). At this time, the transmittance of each wavelength when the layer containing the dichroic dye is measured in one layer is the transmittance Ts, and the layers containing the two dichroic dyes have the same absorption axis direction. The transmittance in the case of superimposition was defined as parallel transmittance Tp, and the transmittance in the case where the layers containing two dichroic dyes were superposed so that their absorption axes were orthogonal to each other was defined as orthogonal transmittance Tc.

The degree of polarization ρ was determined from the parallel transmittance Tp and the orthogonal transmittance Tc according to the equation (5).

Example 1
C. as a dichroic dye is applied to the non-adhesion treated surface of a stretched film (Cosmo Shine SRF film manufactured by Toyobo Co., Ltd.) having a retardation of 10500 nm and a thickness of 100 μm. I. A solution containing 4 parts by weight of Direct Blue 67, 0.15 parts by weight of polyoxyethylene polyoxypropylene alkyl ether (Emalgen MS-110 manufactured by Kao Corporation), and 100 parts by weight of water is spaced 3 μm from the stretched film. It apply | coated using the coating machine provided with the glass rod set so that it might become. The obtained coating film was left in an environment of 25 ° C. and 70% humidity for 1 minute to dry the solvent. Furthermore, the dried coating film was heat-treated and humidified for 5 minutes in an environment of 60 ° C. and 90% humidity to obtain a layer containing a dichroic dye having a thickness of 0.15 μm. An acrylic resin-based ultraviolet curable resin composition (SPC-920C manufactured by Nippon Kayaku Co., Ltd.) is applied on the obtained layer containing the dichroic dye so that the thickness of the protective layer after curing is 3 μm. The resin composition was cured by applying with a spin coater and then irradiating with ultraviolet rays, and a protective layer was provided on the layer containing the dichroic dye. The polarizing element thus obtained was used as a measurement sample.

Example 2
A rubbing cloth (MK0012 manufactured by Myonaka Pile Textile Co., Ltd.) is applied to the non-adhesive treated surface of the stretched film having a retardation of 10500 nm used in Example 1 along the direction of 0 ° with respect to the slow axis of the stretched film. A measurement sample was prepared in the same manner as in Example 1 except that the rubbing treatment was further performed with a wound roll under the condition of a speed of 100 rpm and a load of 5 kgf. At this time, the angle of the stretched film with respect to the slow axis was measured by KOBRA-21ADH (manufactured by Oji Scientific Instruments).

Example 3
The rubbing treatment was performed with a roll in which a rubbing cloth was wound along the direction of 45 ° with respect to the slow axis of the stretched film on the non-easy-adhesion treated surface of the stretched film having a retardation of 10500 nm used in Example 1. A measurement sample was prepared in the same manner as in Example 2 except that.

Example 4
The rubbing treatment was performed on the non-adhesive treated surface of the stretched film having a retardation of 10500 nm used in Example 1 with a roll in which a rubbing cloth was wound along the direction of 90 ° with respect to the slow axis of the stretched film. A measurement sample was prepared in the same manner as in Example 2 except for the above.

Example 5
Instead of the stretched film having a retardation of 10500 nm used in Example 1 as a substrate, a stretched film of polyethylene terephthalate having a retardation of 35000 nm (SKYGREEN PETG K2012 (manufactured by Mitsubishi Corporation Plastics) was melted at 230 ° C. A measurement sample was prepared in the same manner as in Example 1 except that an unstretched PET film molded to a film thickness of 100 μm was uniaxially stretched about 4 times.

Example 6
As a base material, instead of the film having a retardation of 10500 nm used in Example 1, a stretched film of polyethylene terephthalate having a retardation of 3500 nm (SKYGREEN PETG K2012 (manufactured by Mitsubishi Corporation Plastics) was melted at 230 ° C. to 100 μm. A measurement sample was prepared in the same manner as in Example 1 except that an unstretched PET film molded to have a film thickness of about 2.1 times was uniaxially stretched about 2.1 times.

Comparative Example 1
Instead of the stretched PET film of Example 1, as a base material, unstretched PET film formed by melting SKYGREEN PETG K2012 (manufactured by Mitsubishi Corporation Plastics) at 230 ° C. to a film thickness of 100 μm. A measurement sample was prepared in the same manner as in Example 1 except that was used.

Comparative Example 2
A measurement sample was prepared in the same manner as in Example 1 except that the unstretched PET film of Comparative Example 1 was uniaxially stretched 1.5 times to obtain a film having a retardation of 1000 nm.

Table 1 shows Ts, Tp, Tc, ρ, and Rd at the wavelength with the highest degree of polarization obtained by measuring the samples obtained in Examples 1 to 6 and Comparative Examples 1 and 2.

As is clear from the results in Table 1, the polarizing elements of the present invention using stretched films having retardation values in Examples 1 to 6 exhibit a high degree of polarization (ρ) and a high dichroic ratio (Rd). I understand that.

On the other hand, in Comparative Example 1 using an unstretched film having no retardation and in Comparative Example 2 in which the retardation value is outside the definition of the present invention, the degree of polarization (ρ) is less than 65%, and two colors Since the ratio (Rd) is also less than 5, it can be seen that the function as a polarizing element is not sufficient.

From the above results, the polarizing element of the present invention exhibits a high degree of polarization of 85% or more and a high dichroism of 5 or more. Furthermore, in the production of the polarizing element of the present invention, it is not necessary to adsorb a dichroic dye or to be stretched in a boric acid solution, which is necessary when a normal polyvinyl alcohol film base material is used. The polarizing element can be produced without any dimensional change or shrinkage of the substrate. That is, the polarizing element of the present invention is merely a laminate of a specific base material and a layer containing a dichroic dye. From this, it can be seen that the polarizing element of the present invention is a polarizing element that has excellent polarization performance and can be easily produced.

The polarizing element of the present invention is not a polarizing element using a polyvinyl alcohol resin film like a conventional polarizing element, but by applying a solution containing a dichroic dye to a stretched substrate having a specific retardation. Since a polarizing element can be produced, processes such as swelling, dyeing and stretching required in conventional processes are unnecessary, and the polarizing element can be produced easily. In addition, since a polarizing element film can be formed using only a dichroic dye as a component exhibiting a polarizing function, an ultrathin polarizing element can be formed. Furthermore, since a polarizing element can be produced by applying a solution containing a dichroic dye, it is not limited to the shape of a flat polarizing element such as a conventional polarizing plate, It is also possible to form a spherical polarizing element. In particular, the conventional stretched film can only form a polarizing plate that allows polarized light perpendicular to the stretching direction to pass, but the polarizing element of the present invention arbitrarily sets the orientation direction with respect to the rubbed substrate. Therefore, it is possible to form a polarizing element provided with a fine pattern and a polarization property in an arbitrary direction.

Claims

A polarizing element comprising a stretched film having a retardation of 3000 to 50000 nm and a layer containing one or more dichroic dyes, wherein the stretched film has a thickness of 20 to 500 μm.
The polarizing element according to claim 1, wherein the stretched film is made of polyethylene terephthalate.
The polarizing element according to claim 1 or 2, wherein the dichroic ratio is 5 or more.
The molecular anisotropy larger than the molecular anisotropy provided to the surface of the stretched film is further imparted in the same direction as the stretching axis of the stretched film. The polarizing element according to claim 1.
5. The retardation film according to claim 1, further comprising a retardation film having a slow axis or a fast axis of retardation at an angle of 10 ° to 100 ° with respect to a major axis direction of the film. A polarizing element according to 1.
The polarizing element according to any one of claims 1 to 5, wherein at least one of the dichroic dyes is a compound represented by the following formula (1) or a salt thereof.

(In the formula (1),
X 1 represents a phenyl group or a naphthyl group having one or two sulfonic acid groups and a hydroxyl group or an alkoxy group having 1 to 3 carbon atoms,
X 2 and X 3 each independently represent a phenylene group or a naphthylene group, and the phenylene group or naphthylene group is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, Having one or two substituents selected from the group consisting of a hydroxyl group and a sulfonic acid group,
R 1 represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an acetyl group, a benzoyl group, an unsubstituted phenyl group, an alkyl group having 1 to 4 carbon atoms, or an alkyl group having 1 to 4 carbon atoms. And a phenyl group substituted with an alkoxyl group, an amino group or a sulfo group, m is 0 or 1, and n is 1 or 2.
The polarizing element according to claim 6, wherein X 1 is a compound represented by the following formula (3) or a salt thereof as a substituent.

(In formula (3), j is 1 or 2)
8. The layer according to claim 1, wherein the layer containing the dichroic dye further contains a polyoxyethylene polyoxypropylene alkyl ether or a polyoxyethylene polyoxypropylene block polymer. 9. Polarizing element.
A display device provided with the polarizing element according to any one of claims 1 to 8.