WO2018212091A1 - 偏光素子、並びにこれを用いた偏光板及び液晶表示装置 - Google Patents
偏光素子、並びにこれを用いた偏光板及び液晶表示装置 Download PDFInfo
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- WO2018212091A1 WO2018212091A1 PCT/JP2018/018326 JP2018018326W WO2018212091A1 WO 2018212091 A1 WO2018212091 A1 WO 2018212091A1 JP 2018018326 W JP2018018326 W JP 2018018326W WO 2018212091 A1 WO2018212091 A1 WO 2018212091A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
- C08J5/18—Manufacture of films or sheets
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/16—Nitrogen-containing compounds
- C08K5/22—Compounds containing nitrogen bound to another nitrogen atom
- C08K5/23—Azo-compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L29/00—Compositions of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
- C08L29/02—Homopolymers or copolymers of unsaturated alcohols
- C08L29/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2329/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal, or ketal radical; Hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Derivatives of such polymer
- C08J2329/02—Homopolymers or copolymers of unsaturated alcohols
- C08J2329/04—Polyvinyl alcohol; Partially hydrolysed homopolymers or copolymers of esters of unsaturated alcohols with saturated carboxylic acids
Definitions
- the present invention relates to a polarizing element, a polarizing plate, and a liquid crystal display device containing iodine and an azo compound.
- a polarizing element is generally produced by adsorbing and orienting a dichroic dye, iodine or a dichroic dye, onto a polyvinyl alcohol resin film.
- a polarizing plate is manufactured by bonding a protective film made of triacetyl cellulose or the like to at least one surface of the polarizing element via an adhesive layer. The polarizing plate is used for a liquid crystal display device or the like.
- a polarizing element using iodine as a dichroic dye is called an iodine-based polarizing element.
- a polarizing element using a dichroic dye as a dichroic dye is called a dye-based polarizing element.
- a protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizing element via an adhesive layer to form a polarizing plate, which is used for a liquid crystal display device or the like.
- dye-based polarizing plates are characterized by excellent heat resistance, wet heat durability and stability, and high color selectivity by blending.
- the transmittance is low, that is, the contrast is low as compared with an iodine polarizing plate having the same degree of polarization. Therefore, it is desired to develop a polarizing element having high durability, various color selectivity, higher transmittance and high polarization characteristics.
- Iodine polarizing plates are widely used for general liquid crystal monitors, liquid crystal televisions, mobile phones, PDAs and the like because they exhibit higher transmittance and higher degree of polarization, that is, higher contrast than dye-based polarizing plates.
- iodine-based polarizing plates are superior to dye-based polarizing plates in terms of optical properties, they are inferior to dye-based polarizing plates in terms of optical durability, for example, if iodine-based polarizing plates are left under high temperature and high humidity.
- problems such as an increase in transmittance due to decolorization and a decrease in the degree of polarization have occurred.
- Patent Document 1 and Patent Document 2 an improvement method using a protective film as described in Patent Document 1 and Patent Document 2, and a protective film of triacetyl cellulose as described in Patent Document 3 and Patent Document 4 are adhered. It is known to improve wet heat durability by a method of modifying an adhesive. In addition, there is an example in which durability is improved as an iodine-based polarizing plate by treating a polyvinyl alcohol-based resin film instead of improving the durability by a protective film or an adhesive. As one of them, Patent Documents 5, 6 and 7 describe durability improvement by acid treatment and pH control.
- Patent Document 5 a polarizing film whose durability is improved by using a stretched polyvinyl alcohol resin stretched film obtained by immersing a polyvinyl alcohol resin film formed from a boron compound-containing polyvinyl alcohol resin film in an acidic aqueous solution.
- Patent Document 6 discloses the production of a polarizing film excellent in moisture and heat resistance, in which a film made of a polyvinyl alcohol-based resin is oxidized in an oxidation bath containing an oxidizing agent such as hydrogen peroxide containing an alkali metal iodide. A method is disclosed.
- Patent Document 7 discloses that an iodine-based polarizing film having improved wet heat resistance by treating a polyvinyl alcohol film that has been subjected to uniaxial stretching and iodine adsorption orientation treatment with an aqueous boric acid solution having a pH of 4.5 or less. A manufacturing method is disclosed. Although examination for such durability has been carried out, the production cost of the iodine-based polarizing plate is high, and sufficient durability has not been achieved.
- the transmittance does not depend on the wavelength in both parallel and orthogonal positions, and the transmittance is constant at each wavelength.
- the reason why it is yellowish in the parallel position and bluish in the orthogonal position is that the wavelength dependence of the transmittance differs between the parallel position and the orthogonal position, and the transmittance is not constant at each wavelength.
- PVA polyvinyl alcohol
- iodine used as a base material
- iodine used as a dichroic dye
- PVA polyvinyl alcohol
- iodine used as a dichroic dye
- the absorption at 480 nm is said to be due to a complex of polyiodine I 3 — and PVA
- the absorption at 600 nm is said to be due to a complex of polyiodine I 5 — and PVA.
- the degree of polarization at 480 nm based on the complex of polyiodine I 3 — and PVA is higher than the degree of polarization at 600 nm based on the complex of polyiodine I 5 — and PVA.
- the transmittance at 600 nm is higher than the transmittance at 480 nm in the parallel position, and a phenomenon of yellowing in the parallel position has occurred.
- the transmittance at each wavelength is made constant in the parallel position, the transmittance at 600 nm is lower than the transmittance at 480 nm in the orthogonal position, and a phenomenon of blue coloring at the orthogonal position has occurred. Furthermore, since there is no absorption based on 550 nm, which has the highest human visibility, there is a problem that color control is difficult. That is, since the degree of polarization (dichroic ratio) of each wavelength is not constant, wavelength dependency has occurred. In addition, not only when iodine is used as the dichroic dye, but also when an azo compound having dichroism is used, wavelength dependence occurs between the parallel position and the orthogonal position.
- the polarization degree (dichroic ratio) of each wavelength must be constant. Even when a polarizing element is manufactured using one type of dichroic dye, it is difficult to control the transmittance at the parallel position and the orthogonal position, and when a polarizing element is manufactured by blending a plurality of dichroic dyes. It is extremely difficult to precisely control the relationship between the transmittance and dichroism in the parallel position and orthogonal position of each dichroic dye.
- Patent Document 8 and Patent Document 9 disclose methods for improving the hue of a polarizing plate.
- Patent Document 8 discloses a polarizing plate in which the absolute value of the neutral coefficient calculated from the parallel hue and the orthogonal hue is in the range of 0 to 3.
- the spectral transmittance at a wavelength of 410 to 750 nm is within ⁇ 30% of the average value, and the transmission at a wavelength of 410 to 750 nm when two polarizing films are overlapped and the polarization axes are orthogonal to each other.
- a polarizing film for antiglare glasses having a rate of 2% or less is disclosed.
- Patent Document 10 includes an a * value and a * value of a hue obtained in accordance with JIS Z 8729 at the time of measuring a single transmittance.
- the absolute value of the b * value is within 1
- the absolute value of the a * value and b * value obtained by measuring the two base materials parallel to the absorption axis direction is within 2
- a polarizing element is disclosed in which the absolute value of the a * value and b * value obtained by measuring the two substrates perpendicular to the absorption axis direction is within 2 and the single transmittance is 35% or more. Has been.
- the a * value of the parallel hue calculated from JIS Z 8729 is ⁇ 1.67 to ⁇ 1.32, and b *. Since the value is 2.66 to 3.51, it can be seen that it is yellowish green in parallel position. Further, the a * value of the orthogonal hue is 0.49 to 0.69, but since the b * value is ⁇ 3.40 to ⁇ 1.81, it can be seen that the orthogonal hue is blue.
- the polarizing film disclosed in Patent Document 9 is a polarizing film in which the absolute value of color coordinate values a and b in the UCS color space is 2 or less when measured with one polarizing film.
- the achromatic color in the parallel position and the orthogonal position where the two sheets were stacked was not achieved.
- permeability of a polarizing film is as low as 31.95% and 31.41%. Therefore, it has not been applicable to fields requiring high transmittance and high contrast, in particular, fields such as liquid crystal display devices and organic electroluminescence.
- Patent Document 10 solves the technical problems in Patent Document 8 and Patent Document 9, but further improvement in performance is demanded as a polarizing element that exhibits an achromatic color in parallel and orthogonal positions.
- the present invention has been made in view of the above circumstances, and provides a polarizing element, a polarizing plate, and a liquid crystal display device having high durability while having high transmittance and high contrast of an iodine polarizing plate. For the purpose.
- one of the objects of the present invention is that when two polarizing elements are overlapped so that the absorption axis directions are parallel to each other, an achromatic white color can be expressed, and the two polarizing elements are orthogonal to each other in the absorption axis direction.
- a polarizing element, a polarizing plate and a liquid crystal display device capable of expressing an achromatic black color when superimposed.
- the present inventors have produced a polarizing plate containing a specific azo compound in a base material, thereby having high polarization degree and high transmittance while being high.
- the inventors have found that a polarizing element exhibiting durability can be obtained, and have completed the present invention.
- a polarizing element comprising a substrate containing iodine and an azo compound represented by the following formula (1) or a salt thereof:
- Ag 1 represents a phenyl group having a substituent or a naphthyl group having a substituent
- Bg and Cg are each independently represented by the following formula (2) or formula (3), and at least one of them:
- Xg 1 represents an amino group which may have a substituent, a phenylamino group which may have a substituent, or a benzoylamino group which may have a substituent.
- Rg 1 represents a hydrogen atom, a lower alkyl group, a lower alkoxy group or a lower alkoxy group having a sulfo group
- k represents an integer of 0 to 2
- Rg 2 and Rg 3 each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group.
- Xg 1 represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. Represents a good benzoylamino group, and k 1 and k 2 each independently represents an integer of 0 to 2.
- Ar 1 represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent
- Rr 1 and Rr 2 each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxy group.
- a lower alkoxy group having a group or a sulfo group, Xr 1 is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, A benzoyl group which may have a substituent or a benzoylamino group which may have a substituent).
- the absolute value of the a * value and b * value in the L * a * b * color system is When the substrate is measured alone, both are 1 or less, [2] The polarizing element according to [5], wherein when the two substrates are overlapped and measured so that the absorption axis directions are parallel to each other, both are 2 or less.
- the absolute value of the a * value in the L * a * b * color system is 4 or less, and the absolute value of the b * value is 8 or less.
- the difference between the average value of transmittance at 550 nm to 600 nm and the average value of transmittance at 400 nm to 460 nm is 5% or less, and the average value of transmittance at 600 nm to 670 nm and the average value of transmittance at 550 nm to 600 nm
- the average value of the transmittance at 550 nm to 600 nm and the transmission at 400 nm to 460 nm The difference between the average value of the transmittance is 2% or less, and the difference between the average value of the transmittance at 600 nm to 670 nm and the average value of the transmittance at 550 nm to 600 nm is 1% or less,
- the polarizing element according to any one of [6] to [8].
- a polarizing plate comprising the polarizing element according to any one of [1] to [11] and a transparent protective layer formed on at least one surface of the polarizing element.
- a liquid crystal display device having the polarizing element according to any one of [1] to [11] or the polarizing plate according to [12].
- the polarizing element of the present invention achieves high durability while having high transmittance and high contrast comparable to iodine-based polarizing plates.
- the polarizing element can express achromatic white when the two polarizing elements are stacked so that the absorption axis directions are parallel to each other, and the two polarizing elements are orthogonal to each other in the absorption axis direction.
- an achromatic black color can be expressed.
- the polarizing element of the present invention can be used for polarizing plates and liquid crystal display devices.
- the polarizing element of the present invention is characterized by containing a substrate containing iodine and an azo compound represented by the following formula (1) or a salt thereof.
- an azo compound represented by the following formula (1) or a salt thereof represented by the following formula (1) or a salt thereof.
- the base material is not particularly limited as long as it can contain iodine and the azo compound represented by the formula (1) or a salt thereof, and examples thereof include a molded body formed from a hydrophilic polymer.
- the hydrophilic polymer include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, polyacrylate resins, and the like.
- a polyvinyl alcohol-based resin is preferable as the base material from the viewpoint of processability, dyeability, crosslinkability, and the like.
- the shape of a base material is not specifically limited, It is preferable that it is a film form.
- the polarizing element of the present invention contains an azo compound represented by the formula (1) or a salt thereof.
- Ag 1 represents a phenyl group having a substituent or a naphthyl group having a substituent.
- Ag 1 is a phenyl group, it preferably has at least one sulfo group or carboxy group as a substituent.
- the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group, a sulfo group.
- the other substituent is more preferably a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a nitro group, or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, or an ethoxy group. Group or carboxy group.
- the lower alkoxy group having a sulfo group is preferably linear alkoxy, and the substitution position of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably Is a 3-sulfopropoxy group.
- the number of substituents possessed by the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but only the 4-position is preferably a combination of the 2-position and 4-position and a 3-position and 5-position.
- Ag 1 is a naphthyl group having a substituent
- the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and other substituents include a sulfo group, a hydroxy group, a carboxy group, or a lower alkoxy group having a sulfo group.
- the naphthyl group preferably has two or more sulfo groups as substituents.
- the lower alkoxy group having a sulfo group is preferably linear alkoxy, and the substitution position of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably Is a 3-sulfopropoxy group.
- the sulfo group is preferably substituted at the 4,8-position and at the 6,8-position, more preferably at the 6,8-position.
- the substitution position of the sulfo group is preferably a combination of the 1, 3, 6 positions.
- “may have a substituent” means that a case where no substituent is present is included.
- an optionally substituted phenyl group includes an unsubstituted mere phenyl group and a phenyl group having a substituent.
- the “lower” in the lower alkyl group and the lower alkoxy group has 1 to 4 carbon atoms (C1 to 4), preferably 1 to 3 carbon atoms (C1 to 3).
- Bg and Cg are each independently represented by Formula (2) or Formula (3), and at least one of Bg and Cg is represented by Formula (2).
- Rg 1 to Rg 3 each independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group.
- Rg 1 is preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, more preferably a hydrogen atom, a methyl group, or a methoxy group, and particularly preferably a hydrogen atom or a methoxy group.
- the lower alkoxy group having a sulfo group is preferably linear alkoxy, and the substitution position of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably Is a 3-sulfopropoxy group.
- the substitution positions of the azo group are the 1-position and 4-position
- the substitution position of Rg 1 is preferably the 2-position or the 3-position.
- Rg 1 The substitution position of is more preferably the 3-position.
- k represents an integer of 0 to 2.
- Rg 2 and Rg 3 are each independently a hydrogen atom, a methyl group, a methoxy group, a 3-sulfopropoxy group, or a 4-sulfopropoxy group.
- Xg 1 represents an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, or a benzoylamino group that may have a substituent.
- Xg 1 is preferably an amino group which may have a substituent, a phenylamino group which may have a substituent, or a benzoylamino group which may have a substituent, more preferably amino Group, phenylamino group and benzoylamino group, particularly preferably phenylamino group.
- the amino group which may have a substituent is preferably one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. And more preferably an amino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, and a sulfo group.
- the phenylamino group which may have a substituent is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group.
- a phenylamino group having a substituent more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group; .
- the substitution position is not particularly limited, but one of the substituents is preferably p-position with respect to the amino group of the phenylamino group.
- the phenylazo group is preferably a phenylazo group having 1 to 3 substituents selected from the group consisting of a hydrogen atom, a hydroxy group, a lower alkyl group, a lower alkoxy group, an amino group, a hydroxyl group, and a carboxyethylamino group.
- the benzoylamino group which may have a substituent is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group.
- the azo compound represented by the formula (1) is represented by the formula (4) in order to improve performance.
- the azo compound represented by the formula (1) is represented by the formula (5) because the performance is improved.
- Ag 1 represents a phenyl group or naphthyl group having a substituent
- Rg 4 and Rg 5 each independently represents a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group.
- Xg 1 represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a benzoylamino which may have a substituent.
- k 1 and k 2 each independently represents an integer of 0 to 2.
- the content of the azo compound represented by the formula (1) or the formula (1) and the formula (6) or the salt thereof in the aqueous dye solution in which the substrate is immersed is the aqueous solution 100.
- the amount is preferably 0.0001 to 5 parts by weight, more preferably 0.001 to 1 part by weight with respect to parts by weight.
- the weight ratio of the azo compound represented by the formula (1) and the azo compound represented by the formula (6) can be arbitrarily set, but is preferably 5: 1 to 1: 5, It is more preferably 5: 1 to 2: 1, and particularly preferably 3: 1 to 2: 1.
- Examples of the azo compound represented by the formula (1) or a salt thereof include, for example, JP-A-1-161202, JP-A-01-172907, JP-A-01-248105, JP-A-01-265205, and Although it can be synthesized by a method described in, for example, Kaihei 01-172907, it is not limited thereto.
- Specific examples of the azo compound represented by the formula (1) include, for example, C. I. Direct Blue 34, C. I. Direct Blue 69, C. I. Direct Blue 70, C. I. Direct Blue 71, C. I. Direct Blue 72, C. I. Direct Blue 75, C. I. Direct Blue 78, C. I. Direct Blue 81, C. I. Direct Blue 82, C. I. Direct Blue 83, C. I. Direct Blue 186, C. I. Direct Blue 258, Benzo Fast Chrome Blue FG (C.I. 34225), Benzo Fast Blue BN (C.I. 34120), C. I. Direct Green 51, Etc.
- the polarizing element of the present invention may further contain an azo compound represented by formula (6) or a salt thereof.
- Ar 1 represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent
- Rr 1 and Rr 2 each independently represent a hydrogen atom, a lower alkyl group, Represents a lower alkoxy group having a lower alkoxy group or a sulfo group
- Xr 1 is an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent.
- Ar 1 represents a phenyl group or a naphthyl group which may have a substituent.
- the phenyl group which may have a substituent is preferably a phenyl group having at least one sulfo group or carboxy group.
- the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group, a sulfo group.
- the other substituents are more preferably a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a nitro group, or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, a carboxy group. It is a group.
- the lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal.
- a 3-sulfopropoxy group and a 4-sulfobutoxy group are more preferable, and a 3-sulfopropoxy group is particularly preferable.
- the phenyl group which may have a substituent preferably has one or two substituents, and the substitution position is not particularly limited. However, only the 4-position, the 2-position and the 4-position, and the 3-position The 5-position combination is preferred.
- the naphthyl group which may have a substituent is preferably a naphthyl group having at least one sulfo group.
- the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents are a lower alkoxy group having a sulfo group, a hydroxy group, a carboxy group, or a sulfo group. Is preferred.
- the lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal.
- a 3-sulfopropoxy group and a 4-sulfobutoxy group are more preferable, and a 3-sulfopropoxy group is particularly preferable.
- the substitution position of the sulfo group is preferably a combination of 4-position and 8-position, 6-position and 8-position, and more preferably a combination of 6-position and 8-position.
- the substitution position of the sulfo group is preferably a combination of the 1-position, 3-position, and 6-position.
- Xr 1 is an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzoyl group that may have a substituent, or a substituent.
- the amino group which may have a substituent is an amino group having one or two substituents selected from the group consisting of a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group.
- the phenylamino group which may have a substituent is one selected from the group consisting of an unsubstituted phenylamino group or a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. Or it is preferable that it is a phenylamino group which has two substituents.
- the phenylazo group which may have a substituent is an unsubstituted phenylazo group or a group selected from the group consisting of a hydroxy group, a lower alkyl group, a lower alkoxy group, an amino group and a carboxyethylamino group.
- a phenylazo group having three substituents is preferred.
- the benzoyl group which may have a substituent has an unsubstituted benzoyl group or one substituent selected from the group consisting of a hydroxyl group, an amino group, a carboxyl group, a sulfo group, and a carboxyethylamino group
- a benzoyl group is preferred.
- the benzoylamino group which may have a substituent is an unsubstituted benzoylamino group or a benzoylamino group having one substituent selected from the group consisting of a hydroxy group, an amino group and a carboxyethylamino group. Preferably there is. More preferably, they are a phenylamino group which may have a substituent and a benzoylamino group which may have a substituent. Particularly preferred is a phenylamino group which may have a substituent.
- the substitution position is not particularly limited, but when there is one substituent, the p-position is preferred.
- Rr 1 or Rr 2 each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group.
- they are a hydrogen atom, a lower alkyl group, and a lower alkoxy group, More preferably, they are a hydrogen atom, a methyl group, and a methoxy group.
- the lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal.
- a 3-sulfopropoxy group and a 4-sulfobutoxy group are more preferable, and a 3-sulfopropoxy group is particularly preferable.
- azo compound represented by the formula (6) examples include C. I. Direct Red 81, C. I. Direct Red 117, C. I. Direct Violet 9, C. I. Direct Red 127, Examples thereof include azo compounds described in JP-A No. 2003-215338, JP-A No. 9-302250, and International Publication No. 2000/037973.
- Examples of the method for obtaining the azo compound represented by the formula (6) include methods described in JP-A No. 2003-215338, JP-A No. 9-302250, International Publication No. 2000/037973, and the like. However, it is not limited to these.
- the polarizing element is an azo compound other than the azo compound represented by the formula (1) or the formula (1) and the formula (6) as a color correction to the extent that the performance according to the effect of the present invention is not impaired. It may contain. As other azo compounds to be contained, those having high dichroism are particularly preferable. For example, An azo compound as shown in Non-Patent Document 1, C. I. Direct. Yellow12, C. I. Direct Yellow 28, C. I. Direct. Yellow44, C. I. Direct. Orange 26, C. I. Direct. Orange 39, C. I. Direct. Orange 107, C. I. Direct. Red2, C. I. Direct. Red31, C. I. Direct. Red79, C. I. Direct. Red247, C. I. Direct.
- Green80 C. I. Direct. Green59
- the azo compounds described in JP-A-57-145155, JP-A-3-12606, JP-A-2001-33627, JP-A-2002-296417, and JP-A-60-156759 are disclosed. Can be mentioned.
- An azo compound having a phenyl J acid in the trisazo structure can be suitably used, and the azo compound described in JP-A-3-12606 is represented by formula (1) or formula (1) and It is particularly suitable for use in a polarizing element together with the azo compound represented by the formula (6) or a salt thereof.
- azo compound besides a free acid, it can use as alkali metal salt (for example, sodium salt, potassium salt, lithium salt), ammonium salt, or salt of amines.
- alkali metal salt for example, sodium salt, potassium salt, lithium salt
- ammonium salt or salt of amines.
- other azo compounds are not limited to these, and azo compounds having a known dichroism can be used.
- azo compounds having a known dichroism can be used.
- optical characteristics are particularly improved.
- Other azo compounds may be used alone or in combination.
- the polarizing element preferably contains an azo compound represented by the formula (1) or a salt thereof and an azo compound represented by the formula (6) or a salt thereof.
- the ratio of the azo compound represented by the formula (1) or a salt thereof and the azo compound represented by the formula (6) or a salt thereof in the aqueous dye solution to be used can be arbitrarily set, but 5: 1 Is preferably ⁇ 1: 5, more preferably 5: 1 to 2: 1, and particularly preferably 3: 1 to 2: 1.
- the polarizing element can sufficiently express brightness when used in a liquid crystal display device as long as the visibility correction single transmittance of the polarizing element is 35%, but is not limited thereto.
- the visibility corrected single transmittance is preferably 38% or more, more preferably 39% or more, and particularly preferably 40% or more.
- the visibility corrected single transmittance exceeds 45%, the degree of polarization decreases and the contrast decreases, but it can function as a polarizing plate having high transmittance.
- the visibility correction transmittance is preferably 45% or less, more preferably 44% or less, and particularly preferably 43.5% or less. It is.
- the visibility corrected single transmittance is a single transmittance obtained by correcting the visibility using the C light source 2 ° field of view described in JIS Z 8781-4: 2013. Visibility corrected single transmittance is calculated for each wavelength of 400 to 700 nm for each measurement sample (for example, polarizing element or polarizing plate), and further, a 2 ° field of view (C light source) ) Can be obtained by correcting the visibility.
- the polarizing element preferably has a degree of polarization of 99% or more. If the degree of polarization of the polarizing element is 99% or more, the polarizing function can be expressed even when used in a liquid crystal display device.
- the degree of polarization is preferably 99.9% or more, more preferably 99.95% or more.
- the L * a * b * color system is an object color display method defined by the International Commission on Illumination (abbreviated as CIE). This display method is also adopted in JIS Z 8781-4: 2013. In the present invention, the a * value and b * value in the L * a * b * color system are calculated according to JIS Z 8781-4: 2013. Hereinafter, the a * value and b * value obtained when measuring with one polarizing element (single unit) are referred to as “a * -s” and “b * -s”.
- a * value and the b * value when two polarizing elements are measured so that the absorption axis directions are parallel to each other are referred to as “a * ⁇ p” and “b * ⁇ p”.
- the a * value and b * value when two polarizing elements are measured with the absorption axis directions being perpendicular to each other are referred to as “a * ⁇ c” and “b * ⁇ c”.
- the polarizing element in one embodiment, preferably, in the embodiment in which the polarizing element contains an azo compound represented by the formula (6) or a salt thereof, the polarizing element has an absolute value of a * -s and b * -s of 1 or less.
- a * -p and b * -p have absolute values of 2 or less.
- the absolute values of a * -p and b * -p are 1.5 or less
- the absolute values of a * -c and b * -c are 1.5 or less. More preferably, the absolute values of a * -p and b * -p are 1.0 or less.
- the polarizing element of the present invention contains an azo compound represented by the formula (6) or a salt thereof, the polarizing element has an absolute value of a * -c of 4 or less, and b * The absolute value of -c is preferably 8 or less. More preferably, the absolute value of a * -c is 2 or less, and the absolute value of b * -c is 4.0 or less, and more preferably, the absolute value of a * -c is 1 or less, and b * The absolute value of -c is 2.0 or less.
- the absolute values of a * -c and b * -c are both 1.0 or less, and in this case, a person cannot feel that the polarizing element is colored in parallel and orthogonal positions. Therefore, it becomes a favorable polarizing element.
- the degree of polarization is 99% or more, the difference in brightness between the parallel position and the orthogonal position is large, and the transmittance in the dark state is low, so that the hue at the orthogonal position is hardly understood as human sensitivity.
- the hue at the orthogonal position does not necessarily have an absolute value of a * -c of 4 or less and an absolute value of b * -c of 8 or less, but has a strong intensity. Since this is not the case when a backlight or the like is used, the absolute values of a * -c and b * -c are preferably small values.
- the absolute values of the a * value and b * value in the L * a * b * color system are measured when the substrate is measured alone. Is also 1 or less, and when two substrates are stacked and measured so that the absorption axis directions are parallel to each other, both are 2 or less, and the two substrates are stacked so that the absorption axis directions are orthogonal to each other. Then, in order to obtain a polarizing element that is 2 or less, it is preferable to control the transmittance of each wavelength.
- the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is orthogonal to the absorption axis direction of the polarizing element is Ky, that is, the transmission axis (non-absorbing axis) of the polarizing element.
- the transmittance when the absolute polarized light irradiated to the direction is parallel, and measured by irradiating the absolute polarized light so that the vibration direction of the light is parallel to the absorption axis direction of the polarizing element Assuming that the wavelength transmittance is Kz, that is, the transmittance when the absolute polarized light irradiated with respect to the direction of the transmission axis (non-absorption axis) of the polarizing element is orthogonal, the average value of Ky at 550 nm to 600 nm And the average value of Ky at 400 nm to 460 nm is preferably 5% or less, and the difference between the average value of Ky at 600 nm to 670 nm and the average value of Ky at 550 nm to 600 nm is preferably 3% or less.
- the difference between the average value of Ky at 550 nm to 600 nm and the average value of Ky at 400 nm to 460 nm is 3.5% or less, and the average value of Ky at 600 nm to 670 nm and the Ky at 550 nm to 600 nm The difference from the average value is 2.5% or less.
- the difference between the average value of Ky at 550 nm to 600 nm and the average value of Ky at 400 nm to 460 nm is 3% or less, and the average value of Kz at 600 nm to 670 nm and the average value of Kz at 550 nm to 600 nm
- the difference is 2% or less.
- Absolutely polarized light means polarized light that has passed through a polarizing plate having a degree of polarization of approximately 100% when irradiated from a standard light source, and means approximately 100% polarized light. .
- the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 400 nm to 460 nm is 2% or less, and the difference between the average value of Kz at 600 nm to 670 nm and the average value of Kz at 550 nm to 600 nm is It is preferable that it is 1% or less. More preferably, the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 400 nm to 460 nm is 1.5% or less, and the average value of Kz at 600 nm to 670 nm and the Kz at 550 nm to 600 nm The difference from the average value is 0.5% or less.
- the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 400 nm to 460 nm is 1% or less, and the average value of Kz at 600 nm to 670 nm and the average value of Kz at 550 nm to 600 nm Is 0.1% or less.
- the polarizing element includes, for example, production of a polyvinyl alcohol resin, production of a raw film, swelling treatment, dyeing treatment, first washing treatment, treatment containing a crosslinking agent and / or a water resistance agent, stretching treatment, and second washing treatment. It is manufactured by performing a drying process in order. Note that some of these processes can be omitted.
- the manufacturing method of a polyvinyl alcohol-type resin is not specifically limited, A well-known method is employable.
- the polyvinyl alcohol resin can be obtained, for example, by saponifying a polyvinyl acetate resin.
- the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith.
- Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.
- the degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 95 mol% or more.
- This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used.
- the polymerization degree of a polyvinyl alcohol-type resin means a viscosity average polymerization degree, and can be calculated
- the degree of polymerization is usually about 1,000 to 10,000, preferably about 1,500 to 6,000.
- a polyvinyl alcohol-based resin is formed into a raw film.
- the method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be employed.
- the raw film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol and the like as a plasticizer.
- the content of the plasticizer is 5 to 20% by weight, preferably 8 to 15% by weight in the raw film.
- the film thickness of the original film is not particularly limited, but is preferably about 5 ⁇ m to 150 ⁇ m, more preferably about 10 ⁇ m to 100 ⁇ m.
- the raw film obtained as described above is further subjected to a swelling treatment.
- the swelling treatment is performed by immersing the original film in a solution at 20 to 50 ° C. for 30 seconds to 10 minutes.
- the solution is preferably an aqueous solution.
- the draw ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. Since swelling also occurs in a dyeing process, which will be described later, this swelling process may be omitted when the time for producing the polarizing element is shortened.
- the dyeing process is performed on the original film after the swelling process (or on the original film in which the swelling process is omitted).
- the dyeing treatment is a treatment of dyeing the film after the swelling treatment with iodine and the azo compound represented by the formula (1), the formula (1), and the formula (6) or a salt thereof.
- the dyeing with iodine is performed, for example, by immersing the film after the swelling treatment in a dyeing solution containing iodine and iodide.
- an iodide For example, potassium iodide, ammonium iodide, cobalt iodide, zinc iodide etc.
- Potassium iodide and ammonium iodide are preferable. These iodides can be used alone or in combination.
- the iodine concentration in the dyeing solution is preferably 0.0001% to 0.5% by weight, more preferably 0.001% to 0.4% by weight, and particularly preferably 0.0001% by weight. ⁇ 0.3% by weight.
- the dyeing with the azo compound represented by the formula (1) or the formula (1) and the formula (6) or a salt thereof may be performed by, for example, treating the film after the swelling treatment with the formula (1) in the form of free acid. Alternatively, it is carried out by immersing in an azo compound represented by formula (1) and formula (6) or a dyeing solution containing a salt thereof.
- the solution temperature in the dyeing treatment is preferably 5 to 60 ° C., more preferably 20 to 50 ° C., and particularly preferably 35 to 50 ° C.
- the time for dipping in the solution can be appropriately adjusted, but is preferably 30 seconds to 20 minutes, more preferably 1 to 10 minutes.
- the dyeing solution is preferably an aqueous solution.
- the dyeing method is preferably a method of immersing in a dyeing solution, but a method of applying the dyeing solution to the film after the swelling treatment can also be adopted.
- the dyeing solution may contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, and the like as a dyeing assistant.
- the content of the dyeing assistant can be arbitrarily adjusted depending on the time and temperature depending on the dyeability of the dichroic dye, but is preferably 0 to 5% by weight, more preferably 0.05 to 2% by weight.
- the staining with iodine and the staining with the azo compound may be performed simultaneously. However, the staining with the azo compound may be performed after the staining with the iodine, or the staining with the iodine may be performed after the staining with the azo compound. It is preferable from the viewpoint of management and productivity.
- the azo compound represented by the formula (1) or the formula (1) and the formula (6) may be used as a free acid or a salt.
- the salt include alkali metal salts such as lithium salt, sodium salt, and potassium salt, or ammonium salt and alkylamine salt. Preferably, it is a sodium salt.
- the first cleaning process is a process of cleaning the dyeing solution attached to the film surface by the dyeing process. By performing the first cleaning process, it is possible to prevent the dye from being mixed into the solution used in the next process.
- water is generally used as a cleaning liquid.
- the washing method is preferably a method of immersing the dyed film in the washing liquid, but a method of applying the washing liquid to the dyed film can also be adopted.
- the washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds.
- the temperature of the cleaning liquid in the first cleaning process needs to be a temperature at which the film after the dyeing process does not dissolve. Generally, it is washed at 5 to 40 ° C. However, the first cleaning process may be omitted because there is no problem in performance without performing the first cleaning process.
- a treatment containing a crosslinking agent and / or a water resistance agent After the first cleaning treatment (or after the dyeing treatment), a treatment containing a crosslinking agent and / or a water resistance-imparting agent can be performed.
- the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy
- titanium compounds such as sulfate, and other examples include ethylene glycol glycidyl ether and polyamide epichlorohydrin.
- water-proofing agent examples include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride. Of these, boric acid is most preferred. Only one type of cross-linking agent or water-proofing agent may be used, or a plurality thereof may be used in combination.
- a method of immersing the film after the first washing treatment (or after the dyeing treatment) in a solution containing a crosslinking agent and / or a water resistance agent is preferable, but the film after the first washing treatment (or after the dyeing treatment).
- a method of applying a solution containing a crosslinking agent and / or a water resistance-imparting agent may be employed.
- the solution is preferably an aqueous solution.
- the content of the crosslinking agent and / or waterproofing agent in the solution is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight, taking boric acid as an example.
- the temperature of the solution is preferably 5 to 70 ° C, more preferably 5 to 50 ° C.
- the treatment time is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes. However, it is not essential to contain a cross-linking agent and / or a water-resistant agent. If it is desired to shorten the time, this processing may be omitted when the cross-linking treatment or the water resistance treatment is unnecessary.
- the stretching process is a process of stretching the film uniaxially.
- the stretching method may be either a wet stretching method or a dry stretching method.
- the draw ratio is 3 times or more, preferably 5 to 7 times.
- the temperature of the air medium is preferably room temperature to 180 ° C.
- the treatment is preferably performed in an atmosphere having a humidity of 20 to 95% RH (relative humidity).
- the heating method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but the stretching method is not limited.
- the film can be stretched in one stage, but can also be performed by multistage stretching of two or more stages.
- the film after the first washing treatment is preferably stretched while being immersed in a solution containing a crosslinking agent and / or a water resistance agent.
- a crosslinking agent and / or a water resistance agent examples include those described above.
- the content of the crosslinking agent and / or waterproofing agent in the solution is preferably 0.5 to 15% by weight, more preferably 2.0 to 8.0% by weight, taking boric acid as an example.
- the draw ratio is preferably 2 to 8 times, more preferably 5 to 7 times.
- the temperature of the solution is preferably 40 to 60 ° C, more preferably 45 to 58 ° C.
- the stretching time is usually 30 seconds to 20 minutes, preferably 2 to 5 minutes.
- the film can be stretched in one stage, but can also be performed by multistage stretching of two or more stages.
- a washing treatment for washing the film surface (hereinafter referred to as “second washing treatment”).
- the cleaning method is preferably a method of immersing the stretched film in a cleaning solution, but a method of applying a cleaning solution to the stretched film can also be employed.
- the cleaning process can be performed in one stage, and the multi-stage process of two or more stages can be performed.
- the washing time is preferably 1 second to 5 minutes.
- the temperature of the cleaning liquid is not particularly limited, but is usually 5 to 50 ° C., preferably 10 to 40 ° C.
- Examples of the solvent used in the first and second cleaning treatments include water, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and tetraethylene.
- Examples include, but are not limited to, glycols, alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. A mixture of one or more of these solvents can also be used.
- the most preferred solvent is water.
- an aqueous potassium iodide solution is preferably used as the second cleaning treatment.
- a drying process for drying the film is performed.
- the drying process can be performed by natural drying.
- the surface may be compressed using a roll, the moisture on the surface may be removed by an air knife or a water-absorbing roll, or air drying may be performed.
- the drying temperature is preferably 20 to 100 ° C, more preferably 60 to 100 ° C.
- the drying time is preferably 30 seconds to 20 minutes, more preferably 5 to 10 minutes.
- the said method consists of a base material containing an azo compound represented by iodine and formula (1), or formula (1) and formula (6) or a salt thereof, and has high transmittance, contrast and high durability.
- a polarizing element having the same can be obtained.
- the polarizing plate of the present invention includes a polarizing element and a transparent protective layer formed on at least one surface of the polarizing element, that is, one or both surfaces.
- a transparent protective layer can be provided on at least one surface of the polarizing element by applying a polymer to at least one surface of the polarizing element, followed by drying or heat treatment.
- a polymer formed into a film is used as a transparent protective layer, and after the transparent protective layer is bonded to at least one surface of the polarizing element, it is transparent on at least one surface of the polarizing element by drying or heat treatment.
- a protective layer can be provided.
- a transparent polymer having high mechanical strength and good thermal stability is preferable.
- examples of such polymers include cyclic polyolefin resins having a cyclic olefin as a monomer, such as cellulose acetate resins such as triacetyl cellulose and diacetyl cellulose, acrylic resins, polyvinyl chloride resins, nylon resins, polyester resins, polyarylate resins, and norbornene. , Polyethylene, polypropylene, cycloolefin polymer resin, polyolefin having a norbornene skeleton or a copolymer thereof, and a resin having an imide group and / or an amide group in the main chain or side chain.
- the polymer forming the transparent protective layer may be a liquid crystal polymer.
- the thickness of the transparent protective layer is, for example, about 0.5 ⁇ m to 200 ⁇ m.
- An adhesive is required to attach the transparent protective layer to at least one surface of the polarizing element.
- the adhesive agent which has polyvinyl alcohol as a main component is preferable.
- the polyvinyl alcohol adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nippon Synthetic Chemical Co., Ltd.), EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and the like.
- a crosslinking agent and / or a waterproofing agent can be mixed in the polyvinyl alcohol-based adhesive.
- the polyvinyl alcohol-based adhesive may contain a copolymer of maleic anhydride and isobutylene, or a modified product thereof.
- maleic anhydride and isobutylene copolymer examples include isoban # 18 (manufactured by Kuraray Co., Ltd.) and isoban # 04 (manufactured by Kuraray Co., Ltd.).
- the ammonia-modified maleic anhydride-isobutylene copolymer includes isoban # 104 (manufactured by Kuraray Co., Ltd.) and isoban # 110 (manufactured by Kuraray Co., Ltd.).
- As the crosslinking agent a water-soluble polyfunctional epoxy compound can be used.
- water-soluble polyfunctional epoxy compound examples include polyglycerol polyglycidyl ether (Denacol EX-521 (manufactured by Nagase Chemtech)), 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (TETRAD-C). (Mitsubishi Gas Chemical Co., Ltd.)).
- adhesives such as urethane adhesives, acrylic adhesives, and epoxy adhesives can be used.
- additives such as zinc compounds, chlorides and iodides can be simultaneously contained at a concentration of about 0.1 to 10% by weight.
- the polarizing plate When the polarizing plate is bonded to a display device such as a liquid crystal or organic electroluminescence, for example, various functional layers for improving the viewing angle and / or contrast, and a layer having brightness enhancement on the surface which will become a non-exposed surface later. Can be provided.
- a display device such as a liquid crystal or organic electroluminescence
- an adhesive is preferably used.
- various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer are provided on the exposed surface after bonding. Can do.
- a coating method is preferable for producing the layer having various functions, but a film having the function can be bonded through an adhesive or a pressure-sensitive adhesive. Examples of the various functional layers include a layer for controlling the phase difference.
- the polarizing plate has the same optical characteristics as the polarizing element.
- the absolute values of the a * value and the b * value in the L * a * b * color system are both 1 or less when the polarizing plate is measured alone, and the two polarizing plates have absorption axes. Both are 2 or less when measured so that the directions are parallel to each other, and both are 2 or less when measured with the two polarizing plates stacked so that the absorption axis directions are orthogonal to each other. Thereby, an achromatic color is shown in the parallel position and the orthogonal position.
- the polarizing element or polarizing plate can be used in a liquid crystal display device.
- the liquid crystal display device using the polarizing element or the polarizing plate of the present invention is a liquid crystal display device having high reliability, maintaining high contrast for a long time, and having high color reproducibility.
- the polarizing element or polarizing plate of the present invention is provided with a protective layer or functional layer, a support, etc. as necessary, and includes a liquid crystal projector, a calculator, a watch, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, polarizing glasses, and car navigation. , And indoor and outdoor measuring instruments and displays. In particular, it is effectively used in reflective liquid crystal display devices, transflective liquid crystal display devices, organic electroluminescence, and the like.
- the polarizing plate of the present invention may have a support on at least one surface. Since a support body is bonded together with a polarizing plate, what has a plane part is preferable.
- the support include a molded product made of an inorganic material such as glass, quartz, and sapphire, and an organic plastic plate such as acrylic and polycarbonate. Since it is an optical use, the support is preferably a glass molded product.
- the glass molded product include a glass plate, a lens, and a prism (for example, a triangular prism and a cubic prism). Examples of the glass material include soda glass and borosilicate glass.
- a lens attached with a polarizing plate can be used as a condenser lens with a polarizing plate in a liquid crystal projector.
- a prism attached with a polarizing plate can be used as a polarizing beam splitter with a polarizing plate or a dichroic prism with a polarizing plate in a liquid crystal projector.
- a polarizing plate may be attached to the liquid crystal cell.
- the thickness and size of the support are not particularly limited.
- a polarizing plate provided with glass
- the polarizing plate of the present invention is applied to the coated surface.
- coating a transparent adhesive (adhesion) agent to a polarizing plate you may stick a support body to this application
- the adhesive (adhesive) agent used here is preferably, for example, an acrylic ester-based one.
- this polarizing plate is normal to stick a retardation layer to a support body, but you may stick a polarizing plate to a support body.
- Example A1 A polyvinyl alcohol film (VF-PS, manufactured by Kuraray Co., Ltd.) having a saponification degree of 99% or more and an average polymerization degree of 2400 was immersed in warm water at 40 ° C. for 2 minutes and subjected to a swelling treatment so as to be 1.30 times. Next, the swelling-treated film was mixed with 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, and C.I. I. Direct Blue 71 (present compound example 1-9) was immersed in a 45 ° C.
- VF-PS polyvinyl alcohol film having a saponification degree of 99% or more and an average polymerization degree of 2400
- aqueous solution in which 0.30 part by weight of the compound was dissolved for 3 minutes and 30 seconds to contain the azo compound in the film (azo compound dyeing step).
- the obtained film was made into boric acid (manufactured by Societazia lardrello sp.) 28.6 g / L, iodine (manufactured by Junsei Chemical Co., Ltd.) 0.25 g / L, and potassium iodide (Junsei Chemical Co., Ltd.) (Manufactured) 100 parts of an aqueous solution prepared to have a concentration of 17.7 g / L was further diluted to 2000 parts with water and immersed in an aqueous solution at a temperature of 30 ° C.
- the obtained film was stretched in a boric acid aqueous solution (30.0 g / L) at 50 ° C. for 5 minutes so that the stretch ratio was 5.0 times.
- an immersion treatment was performed in an aqueous potassium iodide solution (50 g / L) at 30 ° C. for 20 seconds while maintaining the tension state of the obtained film (cleaning step).
- the obtained film was dried at 70 ° C. for 9 minutes to obtain a polarizing element.
- a polarizing plate was obtained by laminating an alkali-treated triacetyl cellulose film (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) with a polyvinyl alcohol adhesive on the obtained polarizing element.
- the obtained polarizing plate maintained the optical characteristics of the polarizing element.
- a polarizing plate was cut into a 40 mm square, and a durability test sample using the polarizing plate of the present application was prepared by sticking to a transparent plate glass via an adhesive layer (AD-ROC manufactured by Polatechno Co., Ltd.). A measurement sample was obtained.
- Example A2 The azo compound used in the azo compound dyeing step is C.I. I.
- a measurement sample was prepared in the same manner as in Example A1, except that Direct Blue 75 (Compound Example 1-3 of the present application) was changed to 0.30 part by weight.
- Example A3 A measurement sample was prepared in the same manner as in Example A1, except that the azo compound used in the azo compound dyeing step was changed to 0.30 part by weight of the present compound example 1-14.
- Example A4 A measurement sample was prepared in the same manner as in Example A1, except that the azo compound used in the azo compound staining step was changed to 0.30 part by weight of Compound Example 1-18 of the present application.
- Example A5 The azo compound used in the azo compound dyeing step is C.I. I.
- Direct Blue 75 present compound example 1-3 0.30 parts by weight and C.I. I.
- a measurement sample was prepared in the same manner as in Example A1, except that the amount was changed to 0.12 part by weight of Direct Red 81 (Compound Example 6-12).
- Example A6 The azo compound used in the azo compound staining step was 0.30 part by weight of Compound Example 1-7 of the present application and Compound Example No. described in JP-A No. 2003-215338. 1 (Application Compound Example 6-1) A measurement sample was prepared in the same manner as in Example A1, except that the amount was changed to 0.12 parts by weight.
- Example A7 The azo compound used in the azo compound dyeing step was 0.30 part by weight of the present compound example 1-17 and compound example No. described in JP-A-2003-215338. 1 (Application Compound Example 6-1) A measurement sample was prepared in the same manner as in Example A1, except that the amount was changed to 0.12 parts by weight.
- Comparative Example A1 A measurement sample was prepared in the same manner as in Example 1, except that an iodine-based polarizing element not containing a dichroic dye was prepared according to the formulation of Comparative Example 1 described in JP-A-2008-066252.
- Example A2 A measurement sample was prepared in the same manner as in Example 1 except that an iodine-based polarizing plate SKN-18243P manufactured by Polatechno Co., Ltd. was used as a commercially available iodine-based polarizing plate.
- Example B1 The azo compound used in the azo compound dyeing step of Example A1 was obtained by adding 0.30 part by weight of Compound Example 1-20 of this application and Compound Example No. described in JP-A No. 2003-215338. 1 (Application Compound Example 6-1) was changed to 0.12 parts by weight, the dyeing time was changed from 2 minutes to 2 minutes 45 seconds in the iodine compound dyeing step, and the concentration of the potassium iodide aqueous solution was changed in the washing step.
- a measurement sample was prepared in the same manner as in Example A1 except that the amount was changed from 50 g / L to 25 g / L.
- Example B2 A measurement sample was prepared in the same manner as in Example B1, except that the staining time was changed from 2 minutes to 2 minutes and 20 seconds in the first iodine compound staining step.
- Example B3 A measurement sample was prepared in the same manner as in Example B1 except that the staining time was changed from 2 minutes to 2 minutes and 10 seconds in the first iodine compound staining step.
- Example B4 In the azo compound dyeing step, 0.12 part by weight of the present compound example 6-1 was added to C.I. I. A measurement sample was prepared in the same manner as in Example B1, except that the amount was changed to 0.15 parts by weight of Direct Red 81 (Compound Example 6-12 of the present application).
- Example B5 A measurement sample was prepared in the same manner as in Example B1, except that 0.12 parts by weight of the present compound example 6-1 was changed to 0.12 parts by weight of the present compound example 6-9 in the azo compound staining step.
- Example B6 A measurement sample was prepared in the same manner as in Example B1, except that 0.30 part by weight of the present compound example 1-20 was changed to 0.28 part by weight of the present compound example 1-6 in the azo compound staining step.
- Example B7 A measurement sample was prepared in the same manner as in Example B1, except that 0.30 part by weight of the present compound example 1-20 was changed to 0.30 part by weight of the present compound example 1-15 in the azo compound staining step.
- Example B8 A measurement sample was prepared in the same manner as in Example B1, except that 0.30 part by weight of the present compound example 1-20 was changed to 0.30 part by weight of the present compound example 1-7 in the azo compound staining step.
- Example B9 A measurement sample was prepared in the same manner as in Example B1, except that 0.30 part by weight of the present compound example 1-20 was changed to 0.30 part by weight of the present compound example 1-17 in the azo compound staining step.
- Example B10 In the first iodine compound staining step, a measurement sample was prepared in the same manner as in Example B1, except that the staining time was changed from 2 minutes to 1 minute 30 seconds.
- Comparative Example B1 A measurement sample was prepared in the same manner as in Example B1, except that an iodine-based polarizing element not containing a dichroic dye was prepared according to the formulation of Comparative Example 1 described in JP-A-2008-065222.
- Example B2 Reference is made to the method of Example 1 described in JP-A-11-218611, and C.I. I. Direct Orange 39 0.04% by weight, C.I. I. Dichroic dye obtained by a staining solution containing 0.02% by weight of Direct Red 81, 0.06% by weight of an azo compound of the following formula (7), and 0.04% by weight of an azo compound of the following formula (8) A constant sample was prepared in the same manner as in Example B1, except that a polarizing element was prepared using only the same.
- Example B4 With reference to the method of Example 1 described in JP-A-2004-251962, C.I. I. Obtained by a staining solution containing 0.020% by weight of Direct Orange 39, 0.028% by weight of a sodium salt of an azo compound of the following formula (10), and 0.013% by weight of a sodium salt of the azo compound of the following formula (11) A measurement sample was prepared in the same manner as in Example B1, except that a polarizing element was prepared using only the obtained dichroic dye.
- Each transmittance was measured at intervals of 5 nm.
- Each optical characteristic (transmittance, degree of polarization, hue, etc.) was calculated based on JIS Z 8781-4: 2013 (C light source 2 ° field of view).
- the visibility correction single transmittance Ys, the visibility correction parallel transmittance Yp, and the visibility correction orthogonal transmittance Yc were calculated by performing the visibility correction based on the C light source 2 ° field of view chromaticity function.
- Contrast Contrast (CR) was calculated
- CR Yp / Yc
- a * value, b * value L * a * b * The a * value and b * value in the color system were measured using a spectrophotometer [“H-4100” manufactured by Hitachi, Ltd.].
- a * -s and b * -s are a * value and b * value when measured with one measurement sample, respectively.
- a * -p and b * -p are the a * value and the b * value when two measurement samples are measured so that the absorption axis directions are parallel to each other.
- a * -c and b * -c are a * values and b * values when two measurement samples are measured so that the absorption axis directions are perpendicular to each other.
- Average transmittance at 410 to 750 nm The average transmittance at a wavelength of 410 to 750 nm was determined for each measurement sample. The average transmittance was calculated by averaging the single transmittance Ts in the wavelength region of 410 to 750 nm.
- the parallel color means a color observed in a state where two measurement samples are overlapped so that the absorption axis directions are parallel to each other.
- the orthogonal color means a color observed in a state where two measurement samples are overlapped so that the absorption axis directions are orthogonal to each other.
- the hue indicates a neutral color as the a * value and the b * value are closer to zero.
- a * value is positive, it shows reddish color, when it is negative, it shows green color
- b * value is positive, it shows yellowish color, and when it becomes negative, it shows blue color.
- the transmittance Ky of each wavelength measured by irradiating with absolute polarized light is measured so that the absorption axis direction of the measurement sample and the absorption axis direction of the absolute polarizing plate are parallel to each other, and the absorption of the measurement sample is measured.
- the transmittance Kz of each wavelength measured by irradiating with absolute polarized light was measured while the axial direction and the absorption axis direction of the absolute polarizing plate were perpendicular to each other.
- the average value of Ky and the average value of Kz at 400 nm to 460 nm, the average value of Ky and the average value of Kz at 550 nm to 600 nm, the average value of Ky and the average value of Kz at 600 nm to 670 nm were calculated.
- Table 1 below shows the initial visibility corrected single transmittance (Ys-s), initial visibility corrected orthogonal transmittance (Yc ⁇ ) of the measurement samples obtained in Examples A1 to A7 and Comparative Examples A1 and A2. s), and the initial degree of polarization ( ⁇ -s), and as a durability test, the visibility corrected single transmittance (Ys-e) after 1000 hours at 93% relative humidity and 65 ° C. Sensitivity corrected orthogonal transmittance (Yc-e) and polarization degree ( ⁇ -e) are shown. Further, Table 1 shows the amount of change in single transmittance and polarization degree after the durability test from the beginning.
- Examples A1 to A7 have comparable transmittance and high degree of polarization compared to Comparative Examples A1 and A2.
- the film has extremely high durability compared with the conventional iodine-based polarizing plate. That is, the polarizing plate obtained by using the polarizing element of the present invention achieves high durability even in an environment where high temperature and humidity are applied while realizing the same transmittance and high polarization degree and contrast as the iodine-based polarizing plate. It turns out that the sex is maintained. From this result, it can be seen that the liquid crystal display device using the polarizing element or polarizing plate of the present invention is a liquid crystal display device that can maintain high contrast in the long term with high reliability in addition to high luminance and high contrast. .
- Table 2 shows Ys, Yp, and Yc, ⁇ y, CR, a * -s, b * -s, a * -p of the measurement samples obtained in Examples B1 to B10 and Comparative Examples B1 to B4. , B * -p, a * -c, and b * -c, the average transmittance of 410 to 750 nm, and the visual evaluation results of the parallel color and the orthogonal color are shown.
- the visibility corrected single transmittance Ys is 35 to 45%, but the absolute values of a * -s and b * -s are 1 or less.
- the absolute values of a * -p and b * -p are 2 or less, it can be seen that the polarizing plate exhibits an achromatic white color at the parallel position.
- the polarizing plate of the present invention exhibits a good contrast (CR) as compared with a comparative example having a substantially equivalent average transmittance.
- CR good contrast
- the polarizing element is also a polarizing plate obtained by laminating an alkali-treated triacetyl cellulose film (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) as a transparent protective layer using a polyvinyl alcohol-based adhesive. It was found that it was maintained. That is, the polarizing plate obtained using the polarizing element of the present invention has the same performance as the polarizing element of the present invention.
- the average transmittance from 410 nm to 750 nm exceeds 40.5%, which is described in Examples 1 and 2 of Japanese Patent No. 3357803. 31 It was found to have a higher transmittance than a polarizing plate of ⁇ 32%. In addition, when the average transmittance exceeds 40%, the L value also exceeds 70, so that the polarizing element is satisfactory.
- Comparative Example B1 does not contain the azo compounds represented by the formulas (1) and (6) or salts thereof as the free acid, the absolute values of a * -p and b * -p It was found that the value exceeded 2 and it was yellowish green in parallel position. In Comparative Examples B2 to B4, it was found that the absolute value of b * -p greatly exceeded 2 in spite of being a dye-based polarizing plate, and yellow or yellowish green was exhibited in parallel position. This indicates that even a dye-based polarizing plate cannot exhibit the effect of the polarizing plate of the present application unless it has a specific structure.
- the polarizing plate of the present application shows an achromatic white color at the parallel position and an achromatic black color at the orthogonal position, and the performance is improved as compared with the conventional achromatic polarizing plate.
- Table 3 shows the average value of Ky and the average value of Kz at 400 nm to 460 nm and the average value of Ky and the value of Kz at 550 nm to 600 nm of the measurement samples obtained in Examples B1 to B10 and Comparative Examples B1 to B4. The average value, the average value of Ky and the average value of Kz at 600 nm to 670 nm are shown. Further, Table 3 shows the absolute value of the difference between the average value of Ky at 400 nm to 460 nm and the average value of Ky at 550 nm to 600 nm, and the difference between the average value of Kz at 400 nm to 460 nm and the average value of Kz at 550 nm to 600 nm.
- Absolute value of the difference between the average value of Ky at 550 nm to 600 nm and the average value of Ky at 600 nm to 670 nm, and the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 600 nm to 670 nm Indicates an absolute value.
- the difference between the average value of Ky at 550 nm to 600 nm and the average value of Ky at 400 nm to 460 nm is 5% or less, and the average of Ky at 600 nm to 670 nm
- the difference between the average value of Ky at 550 nm to 600 nm is 3% or less
- the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 400 nm to 460 nm is 2% or less
- 600 nm The difference between the average value of Kz at ⁇ 670 nm and the average value of Kz at 550 nm to 600 nm is 1% or less.
- the polarizing plate of the present application can express achromatic white in parallel position and achromatic black in orthogonal position while having high transmittance.
- the liquid crystal display device using the polarizing element or polarizing plate of the present invention has not only high brightness and high contrast, but also high reliability, long-term high contrast, and high color reproducibility. It becomes a device.
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Abstract
Description
[1]
ヨウ素及び下記式(1)で表されるアゾ化合物又はその塩を含有する基材からなる偏光素子:
(式中、Ag1は置換基を有するフェニル基又は置換基を有するナフチル基を表し、Bg及びCgは、各々独立に、下記式(2)又は式(3)で表され、少なくともいずれか一方が式(2)を表し、Xg1は、置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、又は置換基を有してもよいベンゾイルアミノ基を表す)
(式中、Rg1は水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表し、kは0~2の整数を表す)
(式中、Rg2及びRg3は各々独立に水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表す)。
[2]
式(1)で表されるアゾ化合物が下記式(4)で表される[1]に記載の偏光素子:
(式中、Ag1、Bg、Cg、及びXg1は、請求項1で定義した通りである)。
[3]
式(1)におけるXg1が、アミノ基、フェニルアミノ基、及びベンゾイルアミノ基からなる群から選択される基である[1]又は[2]に記載の変更素子。
[4]
式(1)で表されるアゾ化合物が、下記式(5)で表される[1]乃至[3]のいずれか一項に記載の偏光素子。
(式中、Ag1は置換基を有するフェニル基又は置換基を有するナフチル基を表し、Rg4及びRg5は各々独立に水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表し、Xg1は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、又は、置換基を有してもよいベンゾイルアミノ基を表し、k1及びk2は各々独立に0~2の整数を表す。)
[5]
さらに、下記式(6)で表されるアゾ化合物又はその塩を含有する[1]乃至[4]のいずれか一項に記載の偏光素子:
(式中、Ar1は置換基を有してもよいフェニル基又は置換基を有してもよいナフチル基を表し、Rr1及びRr2は各々独立に、水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表し、Xr1は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、置換基を有してもよいベンゾイル基、又は置換基を有してもよいベンゾイルアミノ基を表す)。
[6]
L*a*b*表色系におけるa*値及びb*値の絶対値が、
前記基材を単体で測定したときに、いずれも1以下であり、
前記基材2枚を吸収軸方向が互いに平行になるよう重ねて測定したときに、いずれも2以下である
ことを特徴とする[5]に記載の偏光素子。
[7]
前記基材2枚を吸収軸方向が互いに直交するよう重ねて測定したときに、L*a*b*表色系におけるa*値の絶対値が4以下、b*値の絶対値が8以下であることを特徴とする[6]に記載の偏光素子。
[8]
偏光素子の吸収軸方向に対して光の振動方向が直交するように絶対偏光光を照射して測定した各波長の透過率Kyにおいて、
550nm~600nmにおける透過率の平均値と400nm~460nmにおける透過率の平均値との差が5%以下であり、かつ、600nm~670nmにおける透過率の平均値と550nm~600nmにおける透過率の平均値との差が3%以下であることを特徴とする[6]又は[7]に記載の偏光素子。
[9]
偏光素子の吸収軸方向に対して光の振動方向が平行となるように絶対偏光光を照射して測定した各波長の透過率Kzにおいて
550nm~600nmにおける透過率の平均値と400nm~460nmにおける透過率の平均値との差が2%以下であり、かつ、600nm~670nmにおける透過率の平均値と550nm~600nmにおける透過率の平均値との差が1%以下であることを特徴とする、[6]乃至[8]のいずれか一項に記載の偏光素子。
[10]
視感度補正単体透過率が35~45%である、[1]乃至[9]のいずれか一項に記載の偏光素子。
[11]
基材が、ポリビニルアルコール系樹脂フィルムである[1]乃至[10]のいずれか一項に記載の偏光素子。
[12]
[1]乃至[11]のいずれか一項に記載の偏光素子と、該偏光素子の少なくとも一方の面に形成した透明保護層とを備える偏光板。
[13]
[1]乃至[11]のいずれか一項に記載の偏光素子又は[12]に記載の偏光板を有する液晶表示装置。
本発明の偏光素子は、ヨウ素及び下記式(1)で表されるアゾ化合物又はその塩を含有する基材を含有することを特徴とする。以下、本発明の偏光素子を詳細に説明する。
基材は、ヨウ素及び式(1)で表されるアゾ化合物又はその塩を含有させることができるものであれば特に限定されず、例えば、親水性高分子から成形される成形体が挙げられる。親水性高分子としては、例えば、ポリビニルアルコール系樹脂、アミロース系樹脂、デンプン系樹脂、セルロース系樹脂、ポリアクリル酸塩系樹脂などが挙げられる。アゾ化合物又はそれらの塩を基材に含有させる場合、加工性、染色性及び架橋性などの観点から、基材としてポリビニルアルコール系樹脂が好ましい。基材の形状は特に限定されないが、フィルム状であることが好ましい。
基材にヨウ素を含有させる際、ヨウ素のみでは溶媒に溶解しにくく、基材へ含有させにくいため、ヨウ化カリウム、ヨウ化アンモニウム、ヨウ化銅、ヨウ化ナトリウム、ヨウ化カルシウム、ヨウ化コバルト、ヨウ化亜鉛などのヨウ化物、塩化ナトリウム、塩化リチウム、塩化カリウムなどの塩化物をヨウ素と共に含有させる方法が一般的に用いられる。
本発明の偏光素子は式(1)で表されるアゾ化合物又はその塩を含有する。
式(1)において、Ag1は、置換基を有するフェニル基又は置換基を有するナフチル基を表す。Ag1がフェニル基である場合は、その置換基としてスルホ基又はカルボキシ基を少なくとも1つ有することが好ましい。フェニル基が置換基を2つ以上有する場合は、その置換基の少なくとも1つがスルホ基又はカルボキシ基であり、その他の置換基が、スルホ基、カルボキシ基、低級アルキル基、低級アルコキシ基、スルホ基を有する低級アルコキシ基、ニトロ基、アミノ基、アセチルアミノ基、又は低級アルキルアミノ基置換アミノ基であることが好ましい。その他の置換基は、より好ましくは、スルホ基、メチル基、エチル基、メトキシ基、エトキシ基、カルボキシ基、ニトロ基、又はアミノ基であり、特に好ましくはスルホ基、メチル基、メトキシ基、エトキシ基、又はカルボキシ基である。スルホ基を有する低級アルコキシ基としては、直鎖アルコキシが好ましく、スルホ基の置換位置はアルコキシ基末端であることが好ましく、より好ましくは3-スルホプロポキシ基及び4-スルホブトキシ基であり、特に好ましくは3-スルホプロポキシ基である。フェニル基が有する置換基の数は1又は2が好ましく、置換位置は特に限定されないが、4位のみ、2位と4位の組合せ、及び3位と5位の組合せが好ましい。
C.I.Direct Blue 34、
C.I.Direct Blue 69、
C.I.Direct Blue 70、
C.I.Direct Blue 71、
C.I.Direct Blue 72、
C.I.Direct Blue 75、
C.I.Direct Blue 78、
C.I.Direct Blue 81、
C.I.Direct Blue 82、
C.I.Direct Blue 83、
C.I.Direct Blue 186、
C.I.Direct Blue 258、
Benzo Fast Chrome Blue FG(C.I.34225)、
Benzo Fast Blue BN(C.I.34120)、
C.I.Direct Green 51、
等が挙げられる。
一態様において、本発明の偏光素子は式(6)で表されるアゾ化合物又はその塩をさらに含有してもよい。
式(6)中、Ar1は置換基を有してもよいフェニル基又は置換基を有してもよいナフチル基を表し、Rr1及びRr2は各々独立に、水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表し、Xr1は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、置換基を有してもよいベンゾイル基、又は置換基を有してもよいベンゾイルアミノ基を表す。
C.I.Direct Red 81、
C.I.Direct Red 117、
C.I.Direct Violet 9、
C.I.Drect Red 127、
特開2003-215338号公報、特開平9-302250号公報、国際公開第2000/037973号などに記載されているアゾ化合物
が挙げられる。
非特許文献1に示されるようなアゾ化合物、
C.I.Direct.Yellow12、
C.I.DirectYellow28、
C.I.Direct. Yellow44、
C.I.Direct.Orange26、
C.I.Direct.Orange39、
C.I.Direct.Orange107、
C.I.Direct.Red2、
C.I.Direct.Red31、
C.I.Direct.Red79、
C.I.Direct.Red247、
C.I.Direct.Green80、
C.I.Direct.Green59、
特開昭57-145155号公報、特開平3-12606号公報、特開2001-33627号公報、特開2002-296417号公報、及び特開昭60-156759号公報に記載されたアゾ化合物
等が挙げられる。トリスアゾ構造にフェニルJ酸を有するアゾ化合物を好適に用いることができ、特開平3-12606号公報に記載されるアゾ化合物を、ヨウ素、遊離酸として式(1)、又は、式(1)及び式(6)で表されるアゾ化合物又はそれらの塩とともに偏光素子に用いることが特に好適である。上記他のアゾ化合物としては、遊離酸の他、アルカリ金属塩(例えばナトリウム塩、カリウム塩、リチウム塩)、アンモニウム塩、又はアミン類の塩として用いることができる。ただし、他のアゾ化合物はこれらに限定されず、公知の二色性を有するアゾ化合物を用いることが出来る。他のアゾ化合物を、遊離酸、その塩、又はその銅錯塩の形式で含有させることで、特に、光学特性が向上する。この他のアゾ化合物は、1種のみで用いてもよいし、複数を混合して用いてもよい。
上記偏光素子は、偏光素子の視感度補正単体透過率が35%であれば、液晶表示装置に用いて、十分に明るさを表現することができるがそれに限定されるものではない。視感度補正単体透過率は、好ましくは38%以上、より好ましくは39%以上、特に好ましくは40%以上である。視感度補正単体透過率が45%を超えると、偏光度が低下やコントラストが低下するが、高い透過率を有した偏光板として機能するすることが出来る。ただし、高い偏光度や高コントラストを求める分野では視感度補正透過率は45%以下が好ましく、さらに好ましくは44%以下、特に好ましくは43.5%以下である。である。
上記偏光素子は、偏光度が99%以上であることが好ましい。偏光素子の偏光度が99%以上であれば、液晶表示装置に用いても、偏光機能を表現することができる。偏光度は、好ましくは99.9%以上、より好ましくは99.95%以上である。
L*a*b*表色系は、国際照明委員会(略称CIE)で規定する物体色の表示方法である。この表示方法は、JIS Z 8781-4:2013においても採用されている。本発明において、L*a*b*表色系におけるa*値及びb*値は、JIS Z 8781-4:2013に従い算出される。以下では、偏光素子1枚(単体)で測定したときに求められるa*値及びb*値を、「a*-s」及び「b*-s」という。また、偏光素子2枚を吸収軸方向が互いに平行になるよう重ねて測定したときのa*値及びb*値を、「a*-p」及び「b*-p」という。また、偏光素子2枚を吸収軸方向が互いに直交するように重ねて測定したときのa*値及びb*値を、「a*-c」及び「b*-c」という。
一態様において、好ましくは上記偏光素子が式(6)で表されるアゾ化合物又はその塩を含有する態様において、偏光素子は、a*-s及びb*-sの絶対値が1以下であり、a*-p及びb*-pの絶対値が2以下である。好ましくは、a*-p及びb*-pの絶対値が1.5以下であり、かつ、a*-c及びb*-cの絶対値が1.5以下である。さらに好ましくは、a*-p及びb*-pの絶対値が1.0以下である。a*及びb*の絶対値が0.5異なるだけでも、人は色の違いが感じることができるため、a*及びb*を制御することは非常に重要である。特に、a*-s、b*-s、a*-p、b*-pの絶対値がいずれも1.0以下であれば、平行位及び直交位で、人が色みを帯びていると感じることはできず、特に良好な偏光素子となる。
一態様において、好ましくは本発明の偏光素子が式(6)で表されるアゾ化合物又はその塩を含有する態様において、偏光素子は、a*-cの絶対値が4以下、及び、b*-cの絶対値が8以下であることが好ましい。より好ましくは、a*-cの絶対値が2以下、及び、b*-cの絶対値が4.0以下であり、さらに好ましくは、a*-cの絶対値が1以下、及び、b*-cの絶対値が2.0以下である。特に好ましくはa*-c、b*-cの絶対値がいずれも1.0以下であり、その場合、平行位及び直交位で偏光素子が色みを帯びていると人が感じることはできず、良好な偏光素子となる。ただし、偏光度が99%以上あると、平行位と直交位の明暗の差が大きく、かつ、暗状態での透過率が低いため、人の感度として直交位での色相はほとんど分からなくなる。そのため、偏光度99%あれば必ずしも直交位の色相はa*-cの絶対値が4以下、及び、b*-cの絶対値が8以下である必要はないが、ただし、強い強度を有するバックライト等を用いた場合にはこの限りではないため、a*-c及びb*-cの絶対値が小さい値であることが良い。
視感度補正単体透過率が任意の透過率である偏光素子において、L*a*b*表色系におけるa*値及びb*値の絶対値が、基材を単体で測定したときに、いずれも1以下であり、基材2枚を吸収軸方向が互いに平行になるよう重ねて測定したときに、いずれも2以下であり、基材2枚を吸収軸方向が互いに直交するよう重ねて測定したときに、いずれも2以下である偏光素子を得るためには、各波長の透過率を制御することが好ましい。
以下、基材として、ポリビニルアルコール系樹脂フィルムを例にして、具体的な偏光素子の製造方法を説明する。偏光素子は、例えば、ポリビニルアルコール系樹脂の製造、原反フィルムの作製、膨潤処理、染色処理、第1洗浄処理、架橋剤及び/又は耐水化剤を含有させる処理、延伸処理、第2洗浄処理、乾燥処理を順に行うことによって製造される。なお、これらの一部の処理は省略することが可能である。
ポリビニルアルコール系樹脂の製造方法は、特に限定されるものではなく、公知の方法を採用することができる。ポリビニルアルコール系樹脂は、例えば、ポリ酢酸ビニル系樹脂をケン化することにより得ることができる。ポリ酢酸ビニル系樹脂としては、酢酸ビニルの単独重合体であるポリ酢酸ビニルのほか、酢酸ビニル及びこれと共重合可能な他の単量体との共重合体などが例示される。酢酸ビニルと共重合可能な他の単量体としては、例えば、不飽和カルボン酸類、オレフィン類、ビニルエーテル類、不飽和スルホン酸類などが挙げられる。ポリビニルアルコール系樹脂のケン化度は、通常85~100モル%程度であり、好ましくは95モル%以上である。このポリビニルアルコール系樹脂は、さらに変性されていてもよく、例えば、アルデヒド類で変性したポリビニルホルマールやポリビニルアセタールなども使用できる。またポリビニルアルコール系樹脂の重合度は、粘度平均重合度を意味し、当該技術分野において周知の手法によって求めることができる。重合度は、通常1,000~10,000程度、好ましくは1,500~6,000程度である。
次に、ポリビニルアルコール系樹脂を製膜し、原反フィルムを作製する。ポリビニルアルコール系樹脂を製膜する方法は特に限定されるものでなく、公知の方法を採用することができる。原反フィルムは、可塑剤としてグリセリン、エチレングリコール、プロピレングリコール、低分子量ポリエチレングリコールなどを含有してもよい。可塑剤の含有量は原反フィルム中5~20重量%であり、好ましくは8~15重量%である。原反フィルムの膜厚は特に限定されないが、5μm~150μm程度であることが好ましく、より好ましくは10μm~100μm程度である。
上記により得られた原反フィルムには、さらに膨潤処理が施される。膨潤処理は原反フィルムを20~50℃の溶液に30秒~10分間浸漬させることによって行われる。溶液は水溶液が好ましい。延伸倍率は1.00~1.50倍で調整することが好ましく、より好ましくは1.10~1.35倍である。後述する染色処理においても膨潤するため、偏光素子を作製する時間を短縮する場合には、この膨潤処理を省略してもよい。
膨潤処理の後の原反フィルムに(又は膨潤処理が省略された原反フィルムに)、染色処理が施される。染色処理は、膨潤処理後のフィルムを、ヨウ素、並びに、式(1)、又は、式(1)及び式(6)で表されるアゾ化合物又はそれらの塩を用いて染色する処理である。ヨウ素による染色は、例えば、膨潤処理後のフィルムをヨウ素及びヨウ化物を含有した染色用溶液に浸漬させることによって行われる。ヨウ化物としては特に限定されないが、例えば、ヨウ化カリウム、ヨウ化アンモニウム、ヨウ化コバルト、ヨウ化亜鉛などが挙げられ、ヨウ化カリウム、ヨウ化アンモニウムが好ましい。またこれらヨウ化物は、単独、又は複数を組合せて用いることが可能である。染色用溶液におけるヨウ素の濃度は、好ましくは0.0001重量%~0.5重量%であり、より好ましくは0.001重量%~0.4重量%であり、特に好ましくは0.0001重量%~0.3重量%である。
染色方法は、染色用溶液に浸漬させる方法が好ましいが、膨潤処理後のフィルムに染色用溶液を塗布する方法を採用することもできる。染色用溶液は、染色助剤として、炭酸ナトリウム、炭酸水素ナトリウム、塩化ナトリウム、硫酸ナトリウム、無水硫酸ナトリウム、トリポリリン酸ナトリウムなどを含有してもよい。染色助剤の含有量は、二色性染料の染色性による時間、温度によって任意に調整できるが、0~5重量%が好ましく、0.05~2重量%がより好ましい。
染色処理の後、次の処理を行う前に洗浄処理(以下、「第1洗浄処理」という)を行うことができる。第1洗浄処理とは、染色処理でフィルム表面に付着した染色用溶液を洗浄する処理である。第1洗浄処理を行うことによって、次の処理で使用する溶液中に染料が混入するのを抑制することができる。第1洗浄処理では、一般的に洗浄液として水が用いられる。洗浄方法は、染色処理後のフィルムを洗浄液に浸漬させる方法が好ましいが、染色処理後のフィルムに洗浄液を塗布する方法を採用することもできる。洗浄時間は、特に限定されないが、好ましくは1~300秒、より好ましくは1~60秒である。第1洗浄処理での洗浄液の温度は、染色処理後のフィルムが溶解しない温度であることが必要となる。一般的には5~40℃で洗浄される。ただし、第1洗浄処理を行わなくても性能に問題は出ないため、この第1洗浄処理を省略してもよい。
第1洗浄処理の後(又は染色処理後)、架橋剤及び/又は耐水化剤を含有させる処理を行うことができる。架橋剤としては、例えば、ホウ酸、ホウ砂又はホウ酸アンモニウムなどのホウ素化合物、グリオキザール又はグルタルアルデヒドなどの多価アルデヒド、ビウレット型、イソシアヌレート型又はブロック型などの多価イソシアネート系化合物、チタニウムオキシサルフェイトなどのチタニウム系化合物が挙げられ、他にもエチレングリコールグリシジルエーテル、ポリアミドエピクロルヒドリンなどが挙げられる。耐水化剤としては、例えば、過酸化コハク酸、過硫酸アンモニウム、過塩素酸カルシウム、ベンゾインエチルエーテル、エチレングリコールジグリシジルエーテル、グリセリンジグリシジルエーテル、塩化アンモニウム又は塩化マグネシウムなどが挙げられる。これらの内、ホウ酸が最も好ましい。架橋剤、耐水化剤は1種のみ用いてもよく、複数を組み合わせて用いてもよい。
架橋剤及び/又は耐水化剤を含有させる処理を行った後に、延伸処理を行う。延伸処理とは、フィルムを1軸に延伸する処理である。延伸方法は湿式延伸法又は乾式延伸法のどちらでもよい。延伸倍率は3倍以上、好ましくは5~7倍である。
フィルムを1段で延伸することもできるが、2段以上の多段延伸により行うこともできる。
延伸処理を行った後には、フィルム表面に架橋剤及び/又は耐水化剤が析出するか、又は異物が付着することがあるため、フィルム表面を洗浄する洗浄処理(以下、「第2洗浄処理」という)を行うことができる。洗浄方法は、延伸処理後のフィルムを洗浄液に浸漬させる方法が好ましいが、延伸処理後のフィルムに洗浄液を塗布する方法を採用することもできる。1段で洗浄処理することもできるし、2段以上の多段処理をすることもできる。洗浄時間は1秒~5分が好ましい。洗浄液の温度は特に限定されないが、通常5~50℃、好ましくは10~40℃である。
上記工程の後に、フィルムを乾燥させる乾燥処理を行う。乾燥処理は、自然乾燥により行うことができる。乾燥効率をより高めるために、ロールを用いて圧縮したり、エアーナイフ又は吸水ロール等によって表面の水分を除去してもよく、送風乾燥を行ってもよい。乾燥温度は、20~100℃が好ましく、60~100℃がより好ましい。乾燥時間は30秒~20分が好ましく、より好ましくは5~10分である。
本発明の偏光板は、偏光素子と、偏光素子の少なくとも一方の面、すなわち片面又は両面に形成した透明保護層とを備える。偏光素子の少なくとも一方の面にポリマーを塗布した後、乾燥又は熱処理を行うことにより、偏光素子の少なくとも一方の面に透明保護層を設けることができる。また、ポリマーをフィルム状に成形したものを透明保護層とし、透明保護層を偏光素子の少なくとも一方の面と貼り合わせた後、乾燥又は熱処理を行うことにより、偏光素子の少なくとも一方の面に透明保護層を設けることができる。
上記偏光素子又は偏光板は、液晶表示装置に用いることができる。
[測定試料の作製]
(実施例A1)
ケン化度99%以上の平均重合度2400のポリビニルアルコールフィルム(クラレ社製 VF-PS)を40℃の温水に2分浸漬し、1.30倍になるように膨潤処理を行った。次に、膨潤処理したフィルムを、水1500重量部、トリポリリン酸ナトリウム1.5重量部、無水硫酸ナトリウム1.5重量部、及びC.I.Direct Blue 71(本願化合物例1-9)0.30重量部が溶解した45℃の水溶液に3分30秒間浸漬させて、フィルムにアゾ化合物を含有させた(アゾ化合物染色工程)。次に、得られたフィルムを、ホウ酸(Societa chimica lardrello s.p.a社製)28.6g/L、ヨウ素(純正化学社製)0.25g/L、及びヨウ化カリウム(純正化学社製)17.7g/Lの各濃度となるように調製した100部の水溶液をさらに2000部になるよう水で希釈して30℃の温度とした水溶液に2分間浸漬させて、フィルムにヨウ素化合物を含有させた(ヨウ素化合物染色工程)。次に、得られたフィルムを、ホウ酸水溶液(30.0g/L)中で50℃で5分間、延伸倍率が5.0倍になるように延伸処理を行った。次に、得られたフィルムの緊張状態を保ちつつ、ヨウ化カリウム水溶液(50g/L)中30℃で20秒間浸漬処理を行った(洗浄工程)。次に、得られたフィルムに対して70℃で9分間乾燥処理を行い、偏光素子を得た。
得られた偏光素子に対して、ポリビニルアルコール接着剤を用いて、アルカリ処理したトリアセチルセルロースフィルム(富士写真フィルム社製 ZRD-60)をラミネートして偏光板を得た。得られた偏光板は偏光素子の光学特性を維持していた。
偏光板を40mm角にカットし、粘着層(ポラテクノ社製 AD-ROC)を介して、透明板ガラスに貼付することによって、本願の偏光板を用いた耐久性試験サンプルを作製し、実施例A1の測定試料とした。
アゾ化合物染色工程において用いたアゾ化合物をC.I.Direct Blue75(本願化合物例1-3)0.30重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
アゾ化合物染色工程において用いたアゾ化合物を本願化合物例1-14 0.30重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
アゾ化合物染色工程において用いたアゾ化合物を本願化合物例1-18 0.30重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
アゾ化合物染色工程において用いたアゾ化合物をC.I.Direct Blue 75(本願化合物例1-3)0.30重量部及びC.I.Direct Red 81(本願化合物例6-12)0.12重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
アゾ化合物染色工程において用いたアゾ化合物を本願化合物例1-7 0.30重量部及び特開2003-215338号公報に記載の化合物例No.1(本願化合物例6-1)0.12重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
アゾ化合物染色工程において用いたアゾ化合物を本願化合物例1-17 0.30重量部及び特開2003-215338号公報に記載の化合物例No.1(本願化合物例6-1)0.12重量部に変えたこと以外は、実施例A1と同様に測定試料を作製した。
特開2008-065222号公報に記載の比較例1の処方に従い二色性染料を含まないヨウ素系偏光素子を作製した以外は、実施例1と同様に測定試料を作製した。
市販され一般に用いられているヨウ素系偏光板として、ポラテクノ社製ヨウ素系偏光板 SKN-18243Pを使用し以外は、実施例1と同様に測定試料を作製した。
実施例A1のアゾ化合物染色工程において用いたアゾ化合物を本願化合物例1-20 0.30重量部及び特開2003-215338号公報に記載の化合物例No.1(本願化合物例6-1)0.12重量部に変えたこと、ヨウ素化合物染色工程において染色時間を2分間から2分45秒間に変えたこと、並びに洗浄工程においてヨウ化カリウム水溶液の濃度を50g/Lから25g/Lに変えたこと以外は、実施例A1と同様に測定試料を作製した。
第一ヨウ素化合物染色工程おいて染色時間を2分間から2分20秒間に変えた以外は、実施例B1と同様に測定試料を作製した。
第一ヨウ素化合物染色工程おいて染色時間を2分間から2分10秒間に変えた以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例6-1 0.12重量部をC.I.Direct Red 81(本願化合物例6-12)0.15重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例6-1 0.12重量部を本願化合物例6-9 0.12重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例1-20 0.30重量部を本願化合物例1-6 0.28重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例1-20 0.30重量部を本願化合物例1-15 0.30重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例1-20 0.30重量部を本願化合物例1-7 0.30重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
アゾ化合物染色工程において本願化合物例1-20 0.30重量部を本願化合物例1-17 0.30重量部に変えたこと以外は、実施例B1と同様に測定試料を作製した。
第一ヨウ素化合物染色工程おいて、染色時間を2分間から1分30秒間に変えた以外は、実施例B1と同様に測定試料を作製した。
特開2008-065222号公報に記載の比較例1の処方に従い二色性染料を含まないヨウ素系偏光素子を作製した以外は、実施例B1と同様に測定試料を作製した。
特開平11-218611号公報に記載の実施例1の方法を参考とし、C.I.Direct Orange 39 0.04重量%、C.I.Direct Red 81 0.02重量%、下記式(7)のアゾ化合物0.06重量%、及び下記式(8)のアゾ化合物0.04重量%を含有する染色液によって得られた二色性染料のみを用いて偏光素子を作製した以外は、実施例B1と同様に定試料を作製した。
特開2001-033627号公報に記載の実施例3の方法を参考とし、下記式(9)のアゾ化合物0.04重量%、C.I.Direct Orange 39 0.03重量%、上記式(7)のアゾ化合物0.04重量%、及び上記式(8)のアゾ化合物0.03重量%を含有する染色液によって得られた二色性染料のみを用いて偏光素子を作製した以外は、実施例B1と同様に測定試料を作製した。
特開2004-251962号公報に記載の実施例1の方法を参考とし、C.I.Direct Orange 39 0.020重量%、下記式(10)のアゾ化合物のナトリウム塩0.028重量%、及び下記式(11)のアゾ化合物のナトリウム塩0.013重量%を含有する染色液によって得られた二色性染料のみを用いて偏光素子を作製した以外は、実施例B1と同様に測定試料を作製した。
(1)視感度補正単体透過率
上記にて作製した測定試料の単体での各波長の透過率を単体透過率Tsとした。また、測定試料を2枚用いて、吸収軸方向が互いに平行になるよう重ねて測定した際の各波長の透過率を平行透過率Tpとし、2枚の測定試料を吸収軸方向が互いに直交するように重ねて測定した際の各波長の透過率を直交透過率Tcとした。
単体透過率Ts、平行透過率Tp、及び直交透過率Tcを、分光光度計〔日立製作所社製“U-4100”〕を用いて測定した。5nm間隔で各透過率を測定した。JIS Z 8781-4:2013(C光源2°視野)に基づき各光学特性(透過率、偏光度、色相等)を算出した。
C光源2°視野等色度関数に基づいて視感度補正を行うことにより、視感度補正単体透過率Ys、視感度補正平行透過率Yp、及び視感度補正直交透過率Ycを算出した。
偏光度ρyは、視感度補正平行透過率Yp及び視感度補正直交透過率Ycから、下記計算式により求めた。
ρy={(Yp-Yc)/(Yp+Yc)}1/2×100
コントラスト(CR)は、視感度補正平行透過率Yp及び視感度補正直交透過率Ycから、下記計算式により求めた。
CR=Yp/Yc
L*a*b*表色系におけるa*値及びb*値を分光光度計〔日立製作所社製“U-4100”〕を用いて測定した。a*-s及びb*-sは、それぞれ測定試料1枚で測定したときのa*値及びb*値である。a*-p及びb*-pは、それぞれ測定試料2枚を吸収軸方向が互いに平行になるよう重ねて測定したときのa*値及びb*値である。a*-c及びb*-cは、測定試料2枚を吸収軸方向が互いに直交するよう重ねて測定したときのa*値及びb*値である。
各測定試料について、波長410~750nmの平均透過率を求めた。平均透過率は、410~750nmの波長領域における上記単体透過率Tsを、平均して算出した。
色の観察として、平行位の色及び直交位の色をそれぞれ観察した。平行位の色とは、測定試料2枚を吸収軸方向が互いに平行になるよう重ねた状態で観察した色を意味する。また、直交位の色とは、測定試料2枚を吸収軸方向が互いに直交するよう重ねた状態で観察した色を意味する。なお、上記L*a*b*表色系では、a*値、b*値のそれぞれがゼロに近いほど色相がニュートラル色を示すことを表している。一般的にa*値がプラスになると赤味を示し、マイナスになると緑色を示し、b*値がプラスになると黄味を示し、マイナスになると青味を示す。
絶対偏光光照射時の透過率を、分光光度計〔日立製作所社製“U-4100”〕を用いて測定し、JIS Z 8781-4:2013(C光源2°視野)に基づき各光学特性(透過率、偏光度、色相等)を算出した。透過率を測定するにあたり、光源と測定試料との間に、視感度補正透過率43%で偏光度99.99%のヨウ素系偏光板(ポラテクノ社製 SKN-18043P)を絶対偏光板として設置し、絶対偏光光を測定試料に入射できるようにした。なお、SKN-18043Pの保護層は紫外線吸収能のないトリアセチルセルロースである。
加えて、本発明の偏光板はほぼ同等の平均透過率を有する比較例と比較して良好なコントラスト(CR)を示すことが分かる。
さらに偏光度が99%以上を有することによって、直交位において無彩色の黒色を示すことが分かる。
また、偏光素子に、ポリビニルアルコール系接着剤を用いて、透明保護層として、アルカリ処理したトリアセチルセルロースフィルム(富士写真フィルム社製 ZRD-60)をラミネートした偏光板においても、偏光素子の光学特性を維持していることが分かった。すなわち、本発明の偏光素子を用いて得られる偏光板は、本発明の偏光素子と同様の性能を有する。
さらに表3には、400nm~460nmにおけるKyの平均値と550nm~600nmにおけるKyの平均値との差の絶対値、400nm~460nmにおけるKzの平均値と550nm~600nmにおけるKzの平均値との差の絶対値、550nm~600nmにおけるKyの平均値と600nm~670nmにおけるKyの平均値との差の絶対値、及び550nm~600nmにおけるKzの平均値と600nm~670nmにおけるKzの平均値との差の絶対値を示す。
一態様において、特定の2種類のアゾ化合物を組合せて基材に含有させたヨウ素系偏光板を作製することにより、高い透過率を有しながらも、平行位で無彩色の白色を表現でき、かつ、直交位で無彩色の黒色を表現できることを見出した。
本偏光素子を用いることにより実用性に優れた液晶表示装置を得る可能となり非常に有用である。
Claims (13)
- ヨウ素及び下記式(1)で表されるアゾ化合物又はその塩を含有する基材からなる偏光素子:
(式中、Ag1は置換基を有するフェニル基又は置換基を有するナフチル基を表し、Bg及びCgは、各々独立に、下記式(2)又は式(3)で表され、少なくともいずれか一方が式(2)を表し、Xg1は、置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、又は置換基を有してもよいベンゾイルアミノ基を表す)
(式中、Rg1は水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表し、kは0~2の整数を表す)
(式中、Rg2及びRg3は各々独立に水素原子、低級アルキル基、低級アルコキシ基、又はスルホ基を有する低級アルコキシ基を表す)。 - 式(1)におけるXg1が、アミノ基、フェニルアミノ基、及びベンゾイルアミノ基からなる群から選択される基である請求項1又は2に記載の変更素子。
- L*a*b*表色系におけるa*値及びb*値の絶対値が、
前記基材を単体で測定したときに、いずれも1以下であり、
前記基材2枚を吸収軸方向が互いに平行になるよう重ねて測定したときに、いずれも2以下である
ことを特徴とする請求項5に記載の偏光素子。 - 前記基材2枚を吸収軸方向が互いに直交するよう重ねて測定したときに、L*a*b*表色系におけるa*値の絶対値が4以下、b*値の絶対値が8以下であることを特徴とする請求項6に記載の偏光素子。
- 偏光素子の吸収軸方向に対して光の振動方向が直交するように絶対偏光光を照射して測定した各波長の透過率Kyにおいて、
550nm~600nmにおける透過率の平均値と400nm~460nmにおける透過率の平均値との差が5%以下であり、かつ、600nm~670nmにおける透過率の平均値と550nm~600nmにおける透過率の平均値との差が3%以下であることを特徴とする請求項6又は7に記載の偏光素子。 - 偏光素子の吸収軸方向に対して光の振動方向が平行となるように絶対偏光光を照射して測定した各波長の透過率Kzにおいて
550nm~600nmにおける透過率の平均値と400nm~460nmにおける透過率の平均値との差が2%以下であり、かつ、600nm~670nmにおける透過率の平均値と550nm~600nmにおける透過率の平均値との差が1%以下であることを特徴とする、請求項6乃至8のいずれか一項に記載の偏光素子。 - 視感度補正単体透過率が35~45%である、請求項1乃至9のいずれか一項に記載の偏光素子。
- 基材が、ポリビニルアルコール系樹脂フィルムである請求項1乃至10のいずれか一項に記載の偏光素子。
- 請求項1乃至11のいずれか一項に記載の偏光素子と、該偏光素子の少なくとも一方の面に形成した透明保護層とを備える偏光板。
- 請求項1乃至11のいずれか一項に記載の偏光素子又は請求項12に記載の偏光板を有する液晶表示装置。
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