TWI845816B - Optical film, polarizing plate and organic electroluminescent image display device - Google Patents

Abstract

The subject of the present invention is to provide an optical film, a polarizing plate having the same, and an organic electroluminescent image display device. When the optical film is suitable for use in an image display device, it not only has high transparency and is light-proof, but also has excellent light resistance and durability under strict environmental conditions. The optical film of the present invention is an optical film containing a thermoplastic resin, and is characterized by containing a compound having a structure shown in the following general formula (1). (In the formula, Z represents a heteroaryl group having two or more heteroatoms, which may have a substituent.)

Description

Optical film, polarizing plate and organic electroluminescent image display device

The present invention relates to an optical film, a polarizing plate and an organic electroluminescent image display device, and more specifically to an optical film which, when used in an image display device, not only has high transparency and prevents light leakage, but also has excellent light resistance and durability under strict environmental conditions.

In an organic electroluminescent (hereinafter also referred to as "organic EL") image display device, the reflection of external light by the internal metal plate is significant, so a combination of a λ/4 phase difference film and a polarizer anti-reflection film is used. When a cyclic olefin resin (hereinafter also referred to as "COP") is used as the material of the phase difference film, reflection leakage occurs at a specific wavelength due to the influence of the wavelength dispersion. In order to suppress reflection leakage, a layer containing a pigment that absorbs light of a specific wavelength (hereinafter also referred to as a "specific wavelength light absorption layer") must be installed in the display. The specific wavelength light absorption layer can be in the display, can be set at any position, and can be set as the λ/4 phase difference film.

However, when a retardation film is produced by directly adding a pigment to a resin, the pigment interacts with the resin and accelerates the photodegradation of the pigment.

For example, Patent Document 1 discloses a method of adding a dye that absorbs light with a wavelength near 400nm to an adhesive layer in order to protect an organic EL element, and Patent Document 2 discloses a method of adding a dye that absorbs light selected from near 470nm and near 600nm to an adhesive in order to improve the brightness or visibility of an organic EL image display device.

These technologies mainly add pigments or UV absorbers to the adhesive, but because the adhesive layer is thin, it is difficult to evenly add the compound to be functional.

Furthermore, Patent Document 3 states that in order to block ultraviolet rays and a portion of visible light from the outside, multiple pigment compounds can be placed in any layer of the functional layer. Patent Document 4 states that an indole compound is contained in a thickener, etc., or Patent Document 5 states that a specific structural pigment compound having a cyano group and an ester group is added to a resin or a functional layer, but all pigment compounds also have the problem of insufficient light resistance. [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Publication No. 2017-165941 [Patent Document 2] Japanese Patent Publication No. 5599740 [Patent Document 3] Japanese Patent Publication No. 2017-198991 [Patent Document 4] International Publication No. 2017/15996 [Patent Document 5] Japanese Patent Publication No. 2018-200463

[Problem solved by the invention]

The present invention is made in view of the above-mentioned problems and situations, and the solution is to provide an optical film suitable for image display devices, which has high transparency and prevents light leakage, and has excellent light resistance and durability under strict environmental conditions, a polarizing plate and an organic electroluminescent image display device having the same. [Means for solving the problem]

The inventors of the present invention have attempted to solve the above-mentioned problems and have examined the causes of the above-mentioned problems. They have found that an optical film containing a thermoplastic resin, when containing a compound of a specific structure, can be used in an image display device. The optical film has high transparency and prevents light leakage, and also has excellent light resistance and durability under strict environmental conditions.

That is, the above-mentioned problems related to the present invention are solved by the following means.

1. An optical film containing a thermoplastic resin, characterized in that it contains a compound having a structure represented by the following general formula (1).

(In the formula, Z represents a heteroaryl group having two or more heteroatoms, which may have a substituent.)

2. The optical film described in item 1, wherein the aforementioned Z is any one of the following structural formulas.

(The group represented by the above structural formula may further have a substituent. In addition, R represents a substituent.)

3. The optical film described in item 2, wherein the aforementioned Z is any one of the following structural formulas.

(The group represented by the above structural formula may further have a substituent. In addition, R represents a substituent.)

4. The optical film according to any one of items 1 to 3, wherein the energy level of the highest occupied molecular orbital of the compound having the structure represented by the general formula (1) is -5.85 eV or less.

5. The optical film according to any one of items 1 to 4, wherein the thermoplastic resin is a cyclic olefin resin or an acrylic resin.

6. The optical film according to item 5, wherein the cyclic olefin resin has a polar group.

7. An optical film as described in any one of items 1 to 6, characterized in that the compound having the structure represented by the general formula (1) is contained in the thermoplastic resin in an amount within the range of 0.01 to 20 mass %.

8. The optical film described in any one of items 1 to 7, further comprising a functional layer.

9. The optical film described in item 8, wherein the functional layer contains the compound having the structure represented by the general formula (1).

10. The optical film described in any one of items 1 to 9, wherein the optical film is a λ/4 retardation film.

11. A polarizing plate characterized by having the optical film described in any one of items 1 to 10.

12. An organic electroluminescent image display device characterized by having an optical film described in any one of items 1 to 10 or a polarizing plate described in item 11. [Effect of the invention]

By means of the above-mentioned means of the present invention, an optical film suitable for image display devices can be provided, which not only has high transparency and light leakage prevention, but also has excellent light resistance and durability under strict environmental conditions, a polarizing plate having the same, and an organic electroluminescent image display device.

Although the manifestation mechanism or action mechanism of the effect of the present invention is not yet clear, it can be inferred as follows.

As the λ/4 retardation film, a cyclic olefin resin film can be used from the viewpoints of low hygroscopicity and good dimensional stability.

However, due to the wavelength dispersion characteristics of the display panel, the cyclic olefin resin film is prone to leak reflected light in a specific wavelength region (short wavelength region) when used as a λ/4 phase difference film for a circular polarizer in an organic electroluminescent (hereinafter also referred to as "organic EL") image display device. If the leakage of reflected light is significant, the color of the reflected light is likely to be reduced.

In order to suppress the color degradation caused by reflected light as described above, the inventors of the present invention have examined adding a pigment compound that absorbs light in the wavelength region to the film. In order to enable the organic EL image display device to be used in a high temperature and high humidity environment, it is required that the degradation of the organic EL element by external light can be suppressed. In addition, since the pigment compound is also degraded by incident light, the light resistance of the compound itself is also required.

In order to solve such a problem, it is believed that if a pigment compound with a specific structure is used, light degradation can also be suppressed, and if it is further combined with a specific thermoplastic resin, a λ/4 retardation film with improved overall durability can be produced.

As a result of the review, it was found that if the pigment compound of the aforementioned specific structure has a structure with a dicyano group, the cyano group will reduce the energy level of the highest occupied molecular orbital (HOMO), that is, the oxidation potential will be reduced, so that photooxidation can be inhibited, and thus the light resistance of the pigment compound can be improved. Then, it was found that if the energy level of the highest occupied molecular orbital (HOMO) of the pigment compound is not easy to interact with the energy level of the thermoplastic resin, the deterioration of light resistance or durability can be further suppressed.

[Type of implementation of the invention]

The optical film of the present invention is an optical film containing a thermoplastic resin, and is characterized by containing the compound having the structure represented by the general formula (1). This feature is a technical feature common to or corresponding to the following embodiments.

As an embodiment of the present invention, from the perspective of the effect of the present invention, it is preferred that Z in the structure represented by the general formula (1) is any of the groups represented by the structures represented by claim 2 or claim 3, from the perspective of obtaining an optical film with an excellent balance between light leakage prevention and light resistance.

Furthermore, it is preferred that the energy level of the highest occupied molecular orbital of the compound having the structure represented by the general formula (1) is -5.85 eV or less, from the viewpoint of obtaining an optical thin film having excellent durability.

Furthermore, if the thermoplastic resin is a cyclic olefin resin or an acrylic resin, it is preferred from the viewpoint that an optical film having excellent light leakage prevention, light resistance and durability can be obtained. In addition, since the cyclic olefin resin has a polar group, the energy level of the highest occupied molecular orbital of the pigment and the energy level of the resin are unlikely to interact with each other, thereby suppressing the deterioration of light resistance or durability.

In the present invention, the compound having the structure represented by the general formula (1) is preferably contained in the thermoplastic resin in an amount of 0.01 to 20% by mass. If the amount is less than 0.01% by mass, the effect of the present invention is small, and if the amount is more than 20% by mass, precipitation (also called leakage) from the film is likely to occur under high temperature and high humidity.

The optical film preferably has a functional layer, and the functional layer preferably contains the compound having the structure represented by the general formula (1). Examples of the functional layer include a hard coating layer, a bonding layer, a smoothing layer, or a light scattering layer, but the hard coating layer is preferred from the viewpoint of imparting damage resistance to the optical film.

The optical film of the present invention is preferably a λ/4 phase difference film, and by being provided with a polarizing plate, a circular polarizing plate for preventing reflection can be provided.

Furthermore, the organic electroluminescent image display device of the present invention is characterized by having the optical film or polarizing plate of the present invention.

The present invention, its components, and the forms and aspects of the present invention are described in detail below. In this case, "~" means that the numerical values described before and after it are included as the lower limit and the upper limit.

≪Overview of the optical film of the present invention≫ The optical film of the present invention is an optical film containing a thermoplastic resin, and is characterized in that it contains a compound having a structure represented by the following general formula (1).

According to the present invention, by using a compound having a structure shown in general formula (1), the energy level of the highest occupied molecular orbital (HOMO) can be lowered. By lowering the energy level of HOMO, the oxidation potential can be lowered, and photo-oxidation can be inhibited. In other words, the light resistance of the pigment compound can be improved.

The HOMO of the compound having the structure represented by the general formula (1) can be calculated by molecular orbital calculation using B3LYP as a functional and 6-31G(d) as a basis function using molecular orbital calculation software. The software is not particularly limited and the HOMO can be obtained in the same manner using either one.

In the present invention, Gaussian09 (Revision C.01, M. J. Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, Inc. of the United States was used as software for molecular orbital calculation.

In addition, the optical film of the present invention is preferably transparent, and the so-called "transparent" means that the light transmittance is 80% or more, which can be measured using a spectrophotometer (such as U-3300 manufactured by Hitachi High-Tech Science) according to JIS K 7375:2008 "Plastics - Method for obtaining total light transmittance and total light reflectance".

The constituent elements of the present invention are described in detail below.

[1] Compounds having a structure represented by general formula (1) The present invention relates to compounds having a structure represented by general formula (1) (hereinafter also referred to as "pigment compounds") having the following structure.

(In the formula, Z represents a heteroaryl group having two or more heteroatoms, which may have a substituent.)

In the formula, Z further represents any group shown in the following structural formula, and may further have a substituent. For the following structural formula, R represents a substituent.

Among them, it is also preferred that the aforementioned Z is any one of the groups shown in the following structural formulas from the viewpoint of exhibiting the effects of the present invention. In the following structural formulas, R represents a substituent.

The above R represents a substituent, and examples thereof include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom, etc.), an alkyl group (methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, 2-ethylhexyl, etc.), a cycloalkyl group (cyclohexyl, cyclopentyl, 4-n-dodecylcyclohexyl, etc.), an alkenyl group (vinyl, allyl, etc.), a cycloalkenyl group (2-cyclopenten-1-yl, 2-cyclohexen-1-yl, etc.), an alkynyl group (ethynyl, propynyl, etc.), an aromatic alkyl group (phenyl, p-tolyl, naphthyl, etc.), an aromatic heterocyclic group (2-pyrrolyl, 2-furyl, 2-thienyl, pyrrolyl, imidazolyl, oxazolyl, thiazolyl, benzimidazolyl, benzoxazolyl, 2-benzothiazolyl, pyrazolone, pyridyl, pyridone, 2-pyrimidinyl, triazine, pyrazolyl, 1,2,3-triazolyl, 1,2,4-triazolyl, oxazolyl, isoxazolyl, 1,2,4-oxadiazolyl, 1,3,4-oxadiazolyl, thiazolyl, isothiazolyl, 1,2,4-thiadiazolyl, 1,3,4-thiadiazolyl, cyano, hydroxyl, nitro, carboxyl, alkoxy (methoxy, ethoxy, isopropoxy, tert-butyloxy, n-octyloxy, 2-methoxyethoxy, etc.), aryloxy (phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy, 3-nitrophenoxy, 2- a tetradecylaminophenoxy group, etc.), an acyloxy group (formyloxy, acetyloxy, neopentyloxy, stearyloxy, benzyloxy, p-methoxyphenylcarbonyloxy, etc.), an amino group (amino, methylamino, dimethylamino, anilino, N-methyl-anilino, diphenylamino, etc.), an amide group (formylamino, acetylamino, neopentylamino, laurylamino, benzylamino, etc.), an alkyl and arylsulfonylamino group (methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino, 2,3,5-trichlorophenylsulfonylamino, p-methylphenylsulfonylamino, etc.), a hydroxyl group, an alkylthio group (methylthio, ethylthio, n-decylsulfonylamino, etc.), hexaalkylthio, etc.), arylthio (phenylthio, p-chlorophenylthio, m-methoxyphenylthio, etc.), aminosulfonyl (N-ethylaminosulfonyl, N-(3-dodecyloxypropyl)aminosulfonyl, N,N-dimethylaminosulfonyl, N-acetylaminosulfonyl, N-benzylaminosulfonyl, N-( The invention also includes various groups such as aminoformyl (N′-phenylaminoformyl)aminosulfonyl group, sulfonic acid group, acyl group (acetyl group, neopentylbenzyl group, etc.), aminoformyl group (aminoformyl group, N-methylaminoformyl group, N,N-dimethylaminoformyl group, N,N-di-n-octylaminoformyl group, N-(methylsulfonyl)aminoformyl group, etc.).

Although the pigment compound having the structure represented by the general formula (1) according to the present invention is shown below as an example, the present invention is not limited thereto.

The molecular weight of the pigment compound is not particularly limited, but it is preferably not too large in order to easily enter between molecules of the cyclic olefin resin or acrylic resin, for example, 100 to 1000 is preferred. The molecular weight of the pigment compound can be calculated from the formula weight of the chemical structure by, for example, a specific chemical structure using an NMR (Nuclear Magnetic Resonance) device.

The maximum absorption wavelength of the pigment compound is preferably in the range of 370 to 460 nm, more preferably in the range of 400 to 440 nm. When the maximum absorption wavelength of the pigment compound is within the above range, the optical film can easily absorb light in the wavelength region appropriately, so when the optical film is used as a λ/4 phase difference film in an organic EL image display device, the light leakage of the reflected light in the wavelength region can be further suppressed. The maximum absorption wavelength of the pigment compound can be obtained by measuring the absorption spectrum of the pigment compound in dichloromethane using an ultraviolet-visible spectrophotometer UV-2450 manufactured by Shimadzu Corporation.

The pigment compound may be synthesized or a commercial product may be used. For example, the pigment compound 12 may be synthesized by the following process.

1.5 g of compound (12-1) and 0.697 g of malononitrile were measured out in a 100 mL three-head piston, and 40 mL of toluene was added to dissolve them. Then, 0.817 g of morpholine was dropped, and the temperature was raised and heated to reflux for 4 hours. After the reaction was completed, the solvent was removed under reduced pressure, and 10 mL of methanol was added and stirred in a suspended state. The precipitate was filtered and dried to obtain 1.89 g (yield 96%) of the powder of the exemplified pigment compound 12. The structure can be confirmed by NMR.

The content of the pigment compound is preferably in the range of 0.01 to 20% by mass relative to the cyclic olefin resin. When the content of the pigment compound is 0.01% by mass or more, light in a specific wavelength region is appropriately absorbed, and for example, the effect of suppressing light leakage of reflected light in an organic EL image display device and improving light resistance can be obtained. When the content of the pigment compound is less than 20% by mass, not only is it not easy to leak out, but also the brightness reduction can be suppressed if the light absorption in a specific wavelength region of the optical film is not too high. From the same point of view, the content of the pigment compound is preferably in the range of 0.015 to 10% by mass relative to the cyclic olefin resin.

[2] Thermoplastic resin Thermoplastic resin materials related to the present invention are not particularly limited as long as they can be used as films after film formation. For example, as thermoplastic resins used for polarizing plates, cellulose ester resins such as triacetylcellulose (TAC), cellulose acetate propionate (CAP), and diacetylcellulose (DAC) or cycloolefin resins such as cycloolefin polymers (hereinafter also referred to as COP, cycloolefin resins), polypropylene resins such as polypropylene (PP), acrylic resins such as polymethyl methacrylate (PMMA), and polyester resins such as polyethylene terephthalate (PET) can be used.

Among them, cyclic olefin resins or acrylic resins are preferred from the viewpoint of optical properties such as phase difference and physical properties such as durability.

[2.1] Cycloolefin resin The cycloolefin resin contained in the optical film of the present invention is preferably a polymer of a cycloolefin monomer, or a copolymer of a cycloolefin monomer and other copolymerizable monomers.

The cycloolefin monomer is preferably a cycloolefin monomer having a norbornene skeleton, and more preferably a cycloolefin monomer having a structure represented by the following general formula (A-1) or (A-2).

In general formula (A-1), R ¹ to R ⁴ each independently represent a hydrogen atom, a alkyl group having 1 to 30 carbon atoms, or a polar group. p represents an integer from 0 to 2. However, R ¹ to R ⁴ may not all represent hydrogen atoms at the same time, R ¹ and R ² may not represent hydrogen atoms at the same time, and R ³ and R ⁴ may not represent hydrogen atoms at the same time.

In general formula (A-1), as the alkyl group having 1 to 30 carbon atoms represented by R ¹ to R ⁴ , for example, a alkyl group having 1 to 10 carbon atoms is preferred, and a alkyl group having 1 to 5 carbon atoms is more preferred. The alkyl group having 1 to 30 carbon atoms may further have a linking group containing a halogen atom, an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom. Examples of such a linking group include bivalent polar groups such as a carbonyl group, an imino group, an ether bond, a silyl ether bond, and a thioether bond. Examples of the alkyl group having 1 to 30 carbon atoms include a methyl group, an ethyl group, a propyl group, and a butyl group.

In general formula (A-1), examples of polar groups represented by R ¹ to R ⁴ include carboxyl, hydroxyl, alkoxy, alkoxycarbonyl, aryloxycarbonyl, amino, amide and cyano. Among them, carboxyl, hydroxyl, alkoxycarbonyl and aryloxycarbonyl are preferred. From the perspective of ensuring solubility during film formation from a solution, alkoxycarbonyl and aryloxycarbonyl are preferred.

From the viewpoint of improving the heat resistance of the optical film, p in the general formula (A-1) is preferably 1 or 2. When p is 1 or 2, the resulting polymer becomes bulky and the glass transition temperature tends to be increased.

In general formula (A-2), ^R5 represents a hydrogen atom, a alkyl group having 1 to 5 carbon atoms, or an alkylsilyl group having an alkyl group having 1 to 5 carbon atoms. ^R6 represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an amino group, an amide group, a cyano group, or a halogen atom (a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom). p represents an integer of 0 to 2.

In the general formula (A-2), R ⁵ is preferably a alkyl group having 1 to 5 carbon atoms, more preferably a alkyl group having 1 to 3 carbon atoms.

In the general formula (A-2), R ⁶ preferably represents a carboxyl group, a hydroxyl group, an alkoxycarbonyl group, or an aryloxycarbonyl group. From the viewpoint of ensuring solubility during film formation from the solution, an alkoxycarbonyl group or an aryloxycarbonyl group is more preferred.

In general formula (A-2), p is preferably 1 or 2 from the viewpoint of improving the heat resistance of the optical film. When p is 1 or 2, the resulting polymer becomes bulky, which tends to increase the glass transition temperature.

Cycloolefin monomers having a structure represented by general formula (A-2) are preferred from the viewpoint of improving solubility in organic solvents. Generally, organic compounds have their solubility in organic solvents improved because their crystallinity is reduced by breaking down their symmetry. ^R5 and ^R6 in general formula (A-2) have low symmetry because only the carbon atoms of the ring structure on one side of the symmetry axis of the molecule are replaced. That is, cycloolefin monomers having a structure represented by general formula (A-2) have high solubility and are therefore suitable for manufacturing optical films by solution casting.

The content ratio of the cycloolefin monomer having the structure represented by the general formula (A-2) in the polymer of the cycloolefin monomer is, for example, 70 mol% or more, preferably 80 mol% or more, and more preferably 100 mol% relative to the total of all cycloolefin monomers constituting the cycloolefin resin. When the cycloolefin monomer having the structure represented by the general formula (A-2) is contained in a certain amount or more, the phase difference (retardation) value is easily increased because the orientation of the resin is improved.

Specific examples of the cycloalkene monomer having the structure represented by the general formula (A-1) are shown in Compounds 1 to 14 below, and specific examples of the cycloalkene monomer having the structure represented by the general formula (A-2) are shown in Exemplary Compounds 15 to 34.

Examples of the cycloolefin monomer and the copolymerizable monomer include a cycloolefin monomer and a ring-opening copolymerizable monomer and a cycloolefin monomer and an addition copolymerizable monomer.

Examples of the copolymerizable monomers capable of ring-opening copolymerization include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene.

Examples of copolymerizable monomers that can be addition-copolymerized include compounds containing unsaturated double bonds, vinyl cyclic hydrocarbon monomers, and (meth)acrylates. Examples of compounds containing unsaturated double bonds include olefin compounds having 2 to 12 carbon atoms (preferably 2 to 8), and examples thereof include ethylene, propylene, and butene. Examples of vinyl cyclic hydrocarbon monomers include vinyl cyclopentene monomers such as 4-vinylcyclopentene and 2-methyl-4-isopropenylcyclopentene. Examples of (meth)acrylates include alkyl (meth)acrylates having 1 to 20 carbon atoms such as methyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and cyclohexyl (meth)acrylate.

The content ratio of the cycloolefin monomer in the copolymer of the cycloolefin monomer and the copolymerizable monomer is, for example, 20 to 80 mol %, preferably 30 to 70 mol % based on the total of all monomers constituting the copolymer.

The cycloolefin resin is as described above, and is preferably a polymer obtained by polymerization or copolymerization of a cycloolefin monomer having a norbornene skeleton, preferably a cycloolefin monomer having a structure represented by the general formula (A-1) or (A-2). Examples thereof include the following.

(1) A ring-opening polymer of a cycloolefin monomer (2) A ring-opening copolymer of a cycloolefin monomer and a copolymerizable monomer capable of ring-opening copolymerization therewith (3) A hydrogenated product of the ring-opening (co)polymer of (1) or (2) above (4) A hydrogenated (co)polymer obtained by cyclizing the ring-opening (co)polymer of (1) or (2) above by Friedel-Crafts reaction (5) A ring-opening copolymer of a cycloolefin monomer and a copolymer containing an unsaturated bicyclic monomer =Saturated copolymers of compounds having a bond (6) Addition copolymers of cycloolefin monomers and vinyl cycloolefin monomers and their hydrogenates (7) Interchange copolymers of cycloolefin monomers and (meth)acrylates The polymers of (1) to (7) above can be obtained by any known method, for example, by the method described in Japanese Patent Publication No. 2008-107534 or Japanese Patent Publication No. 2005-227606. For example, the catalyst or solvent used in the above (2) ring-opening copolymerization can be, for example, the one described in paragraphs 0019 to 0024 of Japanese Patent Publication No. 2008-107534. The catalyst used in the hydrogenation of (3) and (6) may be, for example, those described in paragraphs 0025 to 0028 of Japanese Patent Application Laid-Open No. 2008-107534. The acidic compound used in the Friedel-Crafts reaction of (4) may be, for example, those described in paragraph 0029 of Japanese Patent Application Laid-Open No. 2008-107534. The catalyst used in the addition polymerization of (5) to (7) may be, for example, those described in paragraphs 0058 to 0063 of Japanese Patent Application Laid-Open No. 2005-227606. The cross-copolymerization reaction of (7) may be carried out by the method described in paragraphs 0071 and 0072 of Japanese Patent Application Laid-Open No. 2005-227606.

Among them, the polymers of (1) to (3) and (5) are preferred, and the polymers of (3) and (5) are more preferred. That is, from the viewpoint of increasing the glass transition temperature of the obtained cycloolefin resin and increasing the light transmittance, the cycloolefin resin is preferably one containing at least one of the structural unit represented by the following general formula (B-1) and the structural unit represented by the following general formula (B-2), and is preferably one containing only the structural unit represented by the general formula (B-2), or one containing both the structural unit represented by the general formula (B-1) and the structural unit represented by the general formula (B-2). The structural unit represented by the general formula (B-1) is a structural unit derived from the cycloalkene monomer represented by the general formula (A-1), and the structural unit represented by the general formula (B-2) is a structural unit derived from the cycloalkene monomer represented by the general formula (A-2).

In the general formula (B-1), X represents -CH=CH- or -CH ₂ CH ₂ -. R ¹ to R ⁴ and p have the same meanings as R ¹ to R ⁴ and p in the general formula (A-1).

In general formula (B-2), X represents -CH=CH- or -CH ₂ CH ₂ -. R ⁵ to R ⁶ and p have the same meanings as R ⁵ to R ⁶ and p in general formula (A-2).

The cycloolefin resin of the present invention may be a commercial product. Examples of commercial products of the cycloolefin resin include Arton G (e.g., G7810), Arton F, Arton R (e.g., R4500, R4900, and R5000), and Arton RX manufactured by JSR Corporation.

The intrinsic viscosity [η]inh of the cycloolefin resin measured at 30°C is preferably in the range of 0.2 to 5 cm ³ /g, more preferably in the range of 0.3 to 3 cm ³ /g, and even more preferably in the range of 0.4 to 1.5 cm ³ /g.

The number average molecular weight (Mn) of the cycloolefin resin is preferably in the range of 8,000 to 100,000, more preferably in the range of 10,000 to 80,000, and more preferably in the range of 12,000 to 50,000. The weight average molecular weight (Mw) of the cycloolefin resin is preferably in the range of 20,000 to 300,000, more preferably in the range of 30,000 to 250,000, and more preferably in the range of 40,000 to 200,000. The number average molecular weight or weight average molecular weight of the cycloolefin resin can be measured by gel permeation chromatography (GPC) and converted to polystyrene.

<Gel Permeation Chromatography> Solvent: Dichloromethane Column: Shodex K806, K805, K803G (Use 3 connected columns manufactured by Showa Denko Co., Ltd.) Column temperature: 25℃ Sample concentration: 0.1 mass % Detector: RI Model 504 (manufactured by GLScience) Pump: L6000 (manufactured by Hitachi, Ltd.) Flow rate: 1.0mL/min Calibration curve: Use the calibration curve of 13 samples in the range of Mw=500~2800000 using standard polystyrene STK standard polystyrene (manufactured by Tosoh Co., Ltd.). It is better for users to use 13 samples at almost equal intervals.

When the intrinsic viscosity [η]inh, the number average molecular weight and the weight average molecular weight are within the above ranges, the heat resistance, water resistance, chemical resistance, mechanical properties and film forming processability of the cycloolefin resin become good.

The glass transition temperature (Tg) of cycloolefin resin is usually above 110°C, preferably in the range of 110-350°C, more preferably in the range of 120-250°C, and even more preferably in the range of 120-220°C. When Tg is above 110°C, deformation under high temperature conditions is easily suppressed. On the other hand, when Tg is below 350°C, molding becomes easy and degradation of the resin caused by heat during molding is easily suppressed.

The content of the cycloolefin resin is preferably 70% by mass or more, more preferably 80% by mass or more, relative to the film.

[2.2] Acrylic resin The acrylic resin related to the present invention is a polymer of acrylic acid ester or methyl acrylate, and also includes copolymers with other monomers.

Therefore, the acrylic resin of the present invention also contains methyl acrylate resin. Although not particularly limited, the resin preferably contains 50-99% by weight of methyl methacrylate units and 1-50% by weight of other copolymerizable monomer units.

As other units constituting the acrylic resin formed by copolymerization, there can be mentioned alkyl methacrylates having an alkyl group with 2 to 18 carbon atoms, alkyl acrylates having an alkyl group with 1 to 18 carbon atoms, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methacrylic acid, acrylamides such as acrylamide morpholine and N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, divalent carboxylic acids containing an unsaturated group such as maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, N-substituted maleimide, glutarimide, glutaric anhydride, and the like.

From the above units, as copolymerizable monomers for forming the units except for glutarimide and glutaric anhydride, monomers corresponding to the above units can be cited. That is, monomers such as alkyl methacrylates having an alkyl group with 2 to 18 carbon atoms, alkyl acrylates having an alkyl group with 1 to 18 carbon atoms, hydroxyalkyl acrylates such as isobornyl methacrylate and 2-hydroxyethyl acrylate, α,β-unsaturated acids such as acrylic acid and methyl acrylate, acrylamides such as acrylamide morpholine and N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, divalent carboxylic acids containing an unsaturated group such as maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, maleic anhydride, maleimide, and N-substituted maleimide can be cited.

The glutarimido unit can be formed, for example, by reacting an intermediate polymer having a (meth)acrylate unit with a primary amine (imidizing agent) to form an imidized polymer (see JP-A-2011-26563).

The glutaric anhydride unit can be formed, for example, by heating an intermediate polymer having a (meth)acrylate unit (see Patent No. 4961164).

Among the above-mentioned constituent units in the acrylic resin of the present invention, those containing isobornyl methacrylate, acrylamide, N-hydroxyphenylmethacrylamide, N-vinylpyrrolidone, styrene, hydroxyethyl methacrylate, maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride or glutarimide are particularly preferred from the viewpoint of mechanical strength.

The acrylic resin of the present invention preferably has a weight average molecular weight (Mw) in the range of 50,000 to 1,000,000, more preferably 100,000 to 1,000,000, and particularly preferably 200,000 to 800,000, from the viewpoint of being able to control dimensional changes due to changes in the temperature and humidity environment, or from the viewpoint of improving the releasability from a metal support during film production, the drying property of an organic solvent, the heat resistance, and the mechanical strength.

When the K is 50,000 or more, the heat resistance and mechanical strength are excellent, and when it is 1,000,000 or less, the peeling property from the metal support and the drying property of the organic solvent are excellent.

The method for producing the acrylic resin of the present invention is not particularly limited, and any of the known methods such as suspension polymerization, emulsion polymerization, bulk polymerization or solution polymerization can be used. As the polymerization initiator, conventional peroxide-based and azo-based ones can be used, and redox-based ones can also be used. The polymerization temperature is carried out in the range of 30 to 100° C. for suspension or emulsion polymerization, and in the range of 80 to 160° C. for bulk or solution polymerization. In order to control the reduced viscosity of the obtained copolymer, alkyl mercaptan or the like can be used as a chain transfer agent to carry out the polymerization.

When the glass transition temperature Tg of the acrylic resin is in the range of 80 to 120°C, it is preferable from the viewpoint of maintaining the mechanical strength of the film.

As the acrylic resin related to the present invention, commercially available ones can be used. For example, Delpet 60N, 80N, 980N, SR8200 (all manufactured by Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88, EMB-143, EMB-159, EMB-160, EMB-161, EMB-218, EMB-229, EMB-270, EMB-273 (all manufactured by Mitsubishi Rayon Co., Ltd.), KT75, TX400S, IPX012 (all manufactured by Denki Kagaku Kogyo Co., Ltd.), etc. Two or more acrylic resins may be used in combination.

The acrylic resin of the present invention preferably contains an additive. As an example of the additive, acrylic particles (rubber elastic particles) described in International Publication No. 2010/001668 may be preferably contained for the purpose of improving the mechanical strength of the film or adjusting the dimensional change rate. Examples of commercial products of such multi-layer acrylic granular composites include "METABLE NW-341" manufactured by Mitsubishi Rayon Corporation, "Kane Ace" manufactured by Kaneka Corporation, "Pararoid" manufactured by Kureha, "Acryloid" manufactured by Roam and Hearth, "Staphyroid" manufactured by Aika, Inc., Chemisnow MR-2G, MS-300X (all manufactured by Soken Chemical Co., Ltd.), and "ParapetSA" manufactured by Kuraray Company. These can be used alone or in combination of two or more.

The volume average particle size of the acrylic particles is less than 0.35 μm, preferably in the range of 0.01 to 0.35 μm, and more preferably in the range of 0.05 to 0.30 μm. When the particle size is above a certain value, the film can be easily stretched under heating, and when the particle size is below a certain value, the transparency of the obtained film is not easily damaged.

From the viewpoint of flexibility, the optical film of the present invention preferably has a bending elasticity (JIS K7171) of 1.5 GPa or less. The bending elasticity is preferably 1.3 GPa or less, and more preferably 1.2 GPa or less. The bending elasticity varies depending on the type or amount of acrylic resin or rubber elastic particles in the film. For example, the more rubber elastic particles are contained, the smaller the bending elasticity will generally become. In addition, when a copolymer of an alkyl methacrylate and an alkyl acrylate is used as an acrylic resin, rather than a homopolymer of an alkyl methacrylate, the bending elasticity can generally be made smaller.

[3] Other components The optical film of the present invention may further contain other components other than those mentioned above within the scope that does not impair the effects of the present invention. Examples of other components include matting agents, ultraviolet absorbers, phase difference adjusters (phase difference increasing agents, phase difference reducing agents), plasticizers, antioxidants, light stabilizers, antistatic agents, exfoliants, and thickeners. Among them, from the perspective of giving the surface of the optical film a rough surface and giving it a proper degree of lubricity, it is preferable that the optical film contains a matting agent.

(Matting agent) Matting agent is microparticles. The microparticles can be inorganic microparticles or resin microparticles. Examples of inorganic microparticles include microparticles of inorganic compounds such as silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate. Among them, inorganic microparticles are preferably silicon dioxide microparticles because they are less likely to increase the haze value of optical films and can effectively reduce the coefficient of friction.

Examples of the silicon dioxide fine particles include AEROSIL 200V, AEROSIL R972V, and AEROSIL R812 (all manufactured by Nippon Aerosil Co., Ltd.).

Examples of resin particles include particles of silicone resin, fluorine resin, acrylic resin, etc. Among them, silicone resin particles are preferred, and resin particles having a three-dimensional network structure are particularly preferred. Examples of resin particles include TOSPEARL 103, TOSPEARL 105, TOSPEARL 108, TOSPEARL 120, TOSPEARL 145, TOSPEARL 3120, and TOSPEARL 240 (all manufactured by Toshiba Silicone Co., Ltd.).

The average particle size of the primary particles of the microparticles is preferably in the range of 0.005 to 0.4 μm, more preferably in the range of 0.01 to 0.3 μm. These microparticles may also be contained as secondary aggregates having a particle size in the range of 0.05 to 0.3 μm.

The content of the microparticles relative to the optical film is preferably in the range of 0.01-3.0 mass %, more preferably in the range of 0.01-2.0 mass %. In addition, the dynamic friction coefficient of the surface of the optical film is preferably in the range of 0.2-1.0.

[4] Method for manufacturing optical film [4.1] Physical properties of optical film (Phase difference Ro) From the perspective of using the optical film as a λ/4 phase difference film, the phase difference Ro in the in-plane direction measured at a wavelength of 550nm and an environment of 23°C and 55%RH is preferably in the range of 100~170nm, and more preferably in the range of 130~150nm.

Ro is defined as follows.

Formula (1): Ro = ( _nx - _ny ) × d (In formula (1), _nx represents the refractive index of the film in the direction of the in-plane retardation axis (the direction in which the refractive index changes the most), _ny represents the refractive index of the film in the direction perpendicular to the in-plane retardation axis, and d represents the thickness of the film (nm).) The in-plane retardation axis of the optical film can be confirmed by automatic complex refractometer Axo scanning (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRIX). When the optical film is used as a λ/4 phase difference film, the angle of the in-plane retardation axis of the optical film to the width direction is preferably in the range of 40 to 50 degrees, and more preferably in the range of 43 to 47 degrees.

Ro can be measured by the following method.

1) The optical film was humidified in an environment of 23°C and 55% RH for 24 hours. The average refractive index of the film was measured using an Abbe refractometer, and the thickness d was measured using a commercially available micrometer.

2) The retardation Ro of the humidified film at a measurement wavelength of 550 nm was measured using an automatic complex refractometer Axo Scan (Axo Scan Mueller Matrix Polarimeter: manufactured by AXOMETRIX) in an environment of 23°C and 55%RH.

The phase difference Ro of the optical film can be adjusted by, for example, the monomer composition or stretching conditions of the cycloolefin resin.

(Residual solvent content) Optical thin films can be preferably made by solution casting and therefore may contain residual solvent. The residual solvent content for optical thin films is preferably less than 700 ppm, and preferably in the range of 30 to 700 ppm. The residual solvent content can be adjusted during the manufacturing step of the optical thin film by the drying conditions of the dopant cast on the support.

The amount of residual solvent in optical thin films can be measured by headspace gas chromatography. In headspace gas chromatography, the sample is sealed in a container, heated, and the gas in the container is quickly injected into the gas chromatography when the container is full of volatile components. The volatile components are quantified under mass analysis and compound identification. In the headspace method, gas chromatography makes it possible to observe the total absorption peak of the volatile components, and at the same time, by using an analysis method that utilizes electromagnetic interaction, it is also possible to combine the quantification of volatile substances or monomers with high precision.

(Thickness) The thickness of the optical film of the present invention is not particularly limited, but is preferably in the range of 10 to 80 μm, and more preferably in the range of 10 to 60 μm.

[4.2] Method for manufacturing optical film The optical film of the present invention can be manufactured through the following steps: 1) preparing a dopant containing the above-mentioned cycloolefin resin or acrylic resin, the above-mentioned pigment compound and a solvent, 2) casting the obtained dopant on a support, drying and peeling off to obtain a cast film, and 3) stretching the obtained cast film. In addition, the optical film of the present invention can be further manufactured through the following steps; 4) drying the stretched cast film, 5) cutting both ends of the obtained optical film and applying embossing, and 6) rolling up.

In step 1) (dope preparation step), a cycloolefin resin or an acrylic resin and a pigment compound are dissolved or dispersed in a solvent to prepare a dope.

The solvent used for the doping contains at least an organic solvent (good solvent) that can dissolve cycloolefin resins. Examples of good solvents include chlorine-based organic solvents such as dichloromethane or non-chlorine-based organic solvents such as methyl acetate, ethyl acetate, acetone, and tetrahydrofuran. Among them, dichloromethane is preferred.

The solvent used for the dopant may further contain a weak solvent. Examples of weak solvents include linear or branched aliphatic alcohols having 1 to 4 carbon atoms. If the ratio of alcohol in the dopant increases, the film tends to gel and it becomes easier to peel off from the metal support. Examples of linear or branched aliphatic alcohols having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Among these, ethanol is preferred from the viewpoint of the stability of the dopant, a relatively low boiling point, and good drying properties.

In step 2) (casting step), the obtained dopant is cast on a support. The dopant can be cast by discharging it from a casting die.

The dopant cast on the support is moved from the support by a peeling roll until it can be peeled off, and the solvent is evaporated. As a method for evaporating the solvent, there are a method of facing the cast dopant to the wind, a method of transferring heat from the back side of the support by liquid, and a method of transferring heat from the front and back sides by radiant heat.

Thereafter, the cast film obtained by evaporating the solvent is peeled off by a peeling roll.

The residual solvent amount of the cast film on the support during stripping depends on the drying conditions and the length of the support, but can be in the range of 50-120 mass %. If stripping is performed with a large amount of residual solvent, the cast film will be too soft, making it easy to damage the flatness during stripping, and wrinkles and longitudinal stripes will be easily generated by the stripping tension. Therefore, the residual solvent amount during stripping is determined in consideration of these points. The residual solvent amount is defined by the following formula.

Residual solvent amount (mass %) = (mass of cast film before heat treatment - mass of cast film after heat treatment) / (mass of cast film after heat treatment) × 100 The heat treatment for measuring the residual solvent amount was performed at 115°C for 1 hour.

In step 3) (stretching step), the cast film obtained by peeling off the support is stretched.

Stretching can be performed to match the required optical properties, and it is preferred to stretch in one or more directions of the width direction (TD direction), the conveying direction (MD direction), and the oblique direction. For example, when manufacturing an optical film that functions as a λ/4 phase difference film, it is preferred to stretch in the oblique direction.

The stretching ratio depends on the required optical properties, but when used as a λ/4 retardation film, for example, it is preferably in the range of 1.05 to 4.0 times, and more preferably in the range of 1.5 to 3.0 times.

The stretching ratio (times) is defined as the film size in the stretching direction after stretching/the film size in the stretching direction before stretching. When biaxial stretching is performed, the above stretching ratios are preferred for each of the TD and MD directions.

The stretching temperature (drying temperature during stretching) is the same as above. When the glass transition temperature of the cycloolefin resin is taken as Tg, it is preferably in the range of (Tg+2)~(Tg+50)℃, and more preferably in the range of (Tg+5)~(Tg+30)℃. When the stretching temperature is (Tg+2)℃ or higher, the solvent can be easily volatilized appropriately, and the stretching tension can be easily adjusted to an appropriate range. When it is below (Tg+50)℃, the solvent is not easy to volatilize, and the elongation is not easy to be impaired. The stretching temperature is the same as above, and it is preferably measured as the ambient temperature such as (a) the temperature inside the stretching machine.

The amount of residual solvent in the film at the start of stretching is preferably about the same as the amount of residual solvent in the film at the time of stripping, for example, preferably in the range of 20 to 30 mass %, more preferably in the range of 25 to 30 mass %.

The stretching of the film in the TD direction (width direction) can be performed, for example, by fixing the two ends of the film with clamps or pins and then expanding the intervals of the clamps or pins in the advancing direction (the tentering method). The stretching of the film in the MD direction can be performed, for example, by setting a peripheral speed difference for a plurality of rollers and utilizing the peripheral speed difference of the rollers (the roller method). In particular, the tentering method in which the two ends of the cast film are clamped with clamps or the like and stretched is preferred because it can improve the flatness or dimensional stability of the film. By stretching the cast film in both the MD direction and the TD direction, it is preferred to stretch in the diagonal crossing direction of the MD direction and the TD direction (diagonal stretching).

In step 4) (drying step), the stretched cast film is further dried to obtain an optical film.

The cast film can be dried, for example, by transporting the cast film with a plurality of conveyor rollers (for example, a plurality of conveyor rollers arranged in a staggered manner when viewed from the side). There is no particular limitation on the drying means, and hot air, infrared rays, heating rollers or microwaves can be used. From the perspective of simplicity, hot air drying is preferred.

In step 5) (cutting and embossing step), both ends of the obtained optical film in the width direction are cut. The cutting of both ends of the optical film can be performed by a slitting machine.

Next, embossing (rolling) is applied to both ends of the optical film in the width direction. Embossing can be performed by pressing a heated embossing roller against both ends of the optical film. Fine concavities and convexities are formed on the surface of the embossing roller, and the embossing roller is pressed against both ends of the optical film to form concavities and convexities at both ends. By such embossing, the winding deviation or closure (films sticking to each other) at the next winding start can be greatly suppressed.

In step 6) (rolling up step), the obtained optical film is rolled up to obtain a roll.

That is, the optical film is rolled up on a core while being transported to form a roll. The optical film can be rolled up by any method using a commonly used winding machine, a torque method, a constant tension method, a taper tension method, a program tension control method with constant internal stress, and the like.

The roll length of the optical film in the roll is preferably in the range of 1000-7200m. The width of the optical film is preferably in the range of 1000-3000mm.

[5] Other functional layers The optical film of the present invention preferably has a functional layer, and the functional layer preferably has a compound having a structure represented by the general formula (1). Examples of the functional layer include a hard coating layer, an antistatic layer, an antireflection layer, a slippery layer, a bonding layer, an antiglare layer, and a barrier layer. However, when installing an organic EL image display device, it is preferred to provide a hard coating layer in order to improve the scratch resistance.

[5.1] Hard coating layer The hard coating layer used in the present invention is preferably a layer having excellent mechanical film strength (abrasion resistance, pencil hardness) because it contains an active ray curing resin. That is, it is a layer mainly composed of a resin that is cured by a crosslinking reaction by irradiation with active rays (also called active energy rays) such as ultraviolet rays or electron rays. As the active ray curing resin, it is preferred to use a component containing a monomer having an ethylenically unsaturated double bond, and the active ray curing resin layer is formed by curing it by irradiation with active rays such as ultraviolet rays or electron rays. As active ray curing resins, representative examples include ultraviolet curing resins and electron beam curing resins, and resins that are cured by ultraviolet irradiation are preferred from the viewpoint of excellent mechanical film strength (abrasion resistance, pencil hardness). As ultraviolet curing resins, for example, ultraviolet curing acrylate resins, ultraviolet curing urethane acrylate resins, ultraviolet curing polyester acrylate resins, ultraviolet curing epoxy acrylate resins, ultraviolet curing polyol acrylate resins, or ultraviolet curing epoxy resins are preferred, and ultraviolet curing acrylate resins are preferred.

The products for sale include Adeka Putmer N series, Sunrad H-601, RC-750, RC-700, RC-600, RC-500, RC-611, RC-612 (all manufactured by Sanyo Chemical Industries, Ltd.), Aronix M-6100, M-8030, M-8060, Aronix M-215, Aronix M-315, Aronix M-313, Aronix M-327 (all manufactured by Toagosei Co., Ltd.), NK-ester A-TMM-3L, NK-ester AD-TMP, NK-ester ATM-35E, NK-ester A-DOG, NK-ester A-IBD-2E, A-9300, A-9300-1CL (all manufactured by Shin-Nakamura Chemical Industries, Ltd.), PE-3A (manufactured by Kyoei Chemical Co., Ltd.), etc. The above-mentioned active ray-curing resins may be used alone or in combination of two or more.

In order to promote the curing of the active-ray curing resin for the hard coating layer, it is preferred that a photopolymerization initiator is contained. As the photopolymerization initiator, it is preferred that the mass ratio of the photopolymerization initiator to the active-ray curing resin is in the range of 20:100 to 0.01:100. As the photopolymerization initiator, specifically, an alkyl phenone system, acetophenone, benzophenone, hydroxybenzophenone, miller's ketone, α-amino oxime ester, thioxanone, etc. and their derivatives can be cited, but there is no particular limitation.

As such a photopolymerization initiator, commercial products may be used. For example, IRGACURE 184, IRGACURE 907, and IRGACURE 651 manufactured by BASF Japan Co., Ltd. are preferred.

The thickness of the hard coating layer is preferably in the range of 0.1 to 50 μm, and more preferably in the range of 1 to 20 μm, from the viewpoint of improving the hard coating property and improving the transparency of the optical film. The method for forming the hard coating layer is not particularly limited, and for example, a method can be cited in which a coating liquid for forming a hard coating layer containing the above-mentioned components is prepared, the coating liquid is applied by a wire rod, etc., and the coating liquid is hardened by heat or ultraviolet rays to form a hard coating layer. In the hard coating layer, it is preferable to contain a compound having a structure represented by general formula (1) of the present invention, so that light resistance can be further improved and scratch resistance can be imparted. The content of the above-mentioned UV-curable resin is preferably in the range of 0.1 to 40% by mass, more preferably in the range of 0.1 to 20% by mass.

[6] Polarizing plate The polarizing plate of the present invention has polarizers and an optical film of the present invention disposed on at least one side.

FIG1 is a cross-sectional view showing the structure of a polarizing plate 100. As shown in FIG1 , the polarizing plate 100 of the present invention has a polarizer 101, an optical film 102 of the present invention disposed on one side, an opposing film 103 disposed on the other side, and two bonding layers 104 disposed between the polarizer 101 and the optical film 102 and between the polarizer 101 and the opposing film 103.

(For polarizer 101) Polarizer 101 is a device that only passes light with a polarization plane in a certain direction. It is a polyvinyl alcohol-based stretched film mixed with iodine or dichroic pigment.

The thickness of the polarizer 101 is in the range of 5 to 40 μm, preferably in the range of 5 to 30 μm, and particularly preferably in the range of 5 to 20 μm.

(About the optical film 102) The optical film 102 can be used as a phase difference film, for example, it can be used as a λ/4 phase difference film of a circular polarizing plate used in an organic EL image display device.

For the in-plane of the optical film 102, the angle formed by the in-plane retardation axis of the optical film 102 with respect to one side of the rectangular film shape is preferably in the range of 30-60°, preferably 45°. And the aforementioned side corresponds to the width direction of the long optical film 102. In addition, the angle formed by the in-plane retardation axis of the optical film 102 and the absorption axis (or transmission axis) of the polarizer 101 is preferably in the range of 30-60°, preferably 45°.

The optical film 102 may further have other layers arranged on the opposite side of the polarizer 101 (for example, it may further have a hard coating layer, a low refractive index layer, and an anti-reflection layer) according to the purpose. In addition, the optical film 102 may further have an easy-to-bond layer (not shown) arranged on the side of the polarizer 101.

(For the opposite film 103) The opposite film 103 can be the optical film of the present invention, or other optical films (i.e., protective films). It is preferred to use the optical film of the present invention with a hard coating layer on the outermost surface.

Examples of the protective films sold include cellulose ester films sold (e.g., Konica Minolta Tuck KC8UX, KC5UX, KC4UX, KC8UCR3, KC4SR, KC4BR, KC4CR, KC4DR, KC4FR, KC4KR, KC8UY, KC6UY, KC4UY, KC4UE, KC8UE, KC8UY-HA, KC2UA, KC4UA, KC6UA, KC8UA, KC2UAH, KC4UAH, KC6UAH, all manufactured by Konica Minolta Co., Ltd., Fuji Tuck T40UZ, Fuji Tuck T60UZ, Fuji Tuck T80UZ, Fuji Tuck TD80UL, Fuji Tuck TD60UL, Fuji Tuck TD40UL, Fuji Tuck R02, Fuji TuckR06, manufactured by Fuji Film Co., Ltd.).

As the cycloolefin-based film for sale, various grades of Zeonoa Film(R), a cycloolefin polymer (COP) molded product manufactured by Nippon Zeon Co., Ltd., are preferably used.

The thickness of the opposing film 103 is, for example, in the range of 5 to 100 μm, preferably in the range of 40 to 80 μm.

(Regarding the connecting layer 104) The connecting layer 104 can be disposed between the polarizer 101 and the optical film 102, and between the polarizer 101 and the opposite film 103.

The adhesive layer 104 may be a layer obtained from a water-based adhesive described below, or may be a cured layer of an ultraviolet curing adhesive.

The thickness of the adhesive layer 104 is not particularly limited, and is, for example, in the range of 0.01 to 10 μm, preferably in the range of 0.01 to 5 μm.

The polarizing plate 100 may be in a long shape, or in a sheet shape obtained by cutting a long polarizing plate along the width direction.

(Physical Properties) (T ₁ /T ₂ ) When an aluminum reflective material is laminated on an optical film of a polarizing plate via an adhesive layer, the reflectivity of the polarizing plate at a wavelength of 460 nm is T ₁ (%), and the reflectivity of the polarizing plate at a wavelength of 650 nm is T ₂ (%). The polarizing plate preferably satisfies the following formula (2).

Formula (2): 0＜T ₁ /T ₂ ＜2.6 When T ₁ /T ₂ is less than 2.6, the reflectivity of light with a wavelength of 460nm will not be too high, and the leakage of reflected light near the wavelength can be suppressed, so that, for example, the color of reflected light in an organic EL image display device can be improved. Moreover, when T ₁ /T ₂ exceeds 0, for example, the luminescence in the above wavelength region in the organic EL image display device is difficult to be blocked by the pigment compound, so the reduction of brightness can be suppressed. T ₁ /T ₂ is preferably 2.5 or less.

(Color difference ΔE(a ^* b ^* )) The color difference ΔE(a ^* b ^* ) of the polarizing plate is preferably less than 25, more preferably less than 20. When the color difference ΔE(a*b*) of the polarizing plate is within the above range, the color of reflected light in the organic EL image display device can be improved, for example.

The T ₁ /T ₂ and the color difference ΔE (a ^* b ^* ) of the polarizing plate can be measured by the following procedure.

1) An aluminum reflective material is laminated on the optical film of the polarizing plate through an adhesive layer to prepare a polarizing plate sample. An acrylic adhesive is used as the adhesive.

2) The spectral reflectance and color difference ΔE (a ^* b ^* ) of the obtained polarizing plate sample were measured by a spectrophotometer (CM3700d manufactured by Konica Minolta) using the SCI method.

The T ₁ /T ₂ and the color difference ΔE(a ^* b ^* ) of the polarizing plate can be adjusted by the type and content of the pigment compound represented by the general formula (1).

(Manufacturing method of polarizing plate 100) Polarizing plate 100 can be obtained by laminating polarizer 101 and optical film 102 of the present invention via an adhesive. As the adhesive, a water-based adhesive or a UV-curable adhesive is used.

<Water-based adhesive> Examples of water-based adhesives include water-based adhesives containing polyvinyl alcohol resins (such as completely saponified polyvinyl alcohol aqueous solutions).

<Ultraviolet curing adhesive> The composition of ultraviolet curing adhesive is a photo-radical polymerizable composition, a photo-cation polymerizable composition, or a mixed composition of these.

Examples of the photo-radical polymerizable composition include a composition having a radical polymerizable compound containing a polar group such as a hydroxyl group or a carboxyl group as described in Japanese Patent Application Laid-Open No. 2008-009329 and a radical polymerizable compound containing no polar group.

The free radical polymerizable compound is preferably a compound having a free radical polymerizable ethylenic unsaturated bond. Preferred examples of the compound having a free radical polymerizable ethylenic unsaturated bond include a compound having a (meth)acryl group. Examples of the compound having a (meth)acryl group include N-substituted (meth)acrylamide compounds and (meth)acrylate compounds. (Meth)acrylamide means acrylamide or methacrylamide.

Examples of photo-cationic polymerizable compositions include (α) a cationically polymerizable compound disclosed in Japanese Unexamined Patent Application Publication No. 2011-028234, (β) a photo-cationic polymerization initiator, a photosensitizer that exhibits maximum absorption at a wavelength longer than (γ) 380 nm, and a UV-curable adhesive composition containing (δ) a naphthalene-based photosensitizing auxiliary.

The following is an example of using a UV curable adhesive. The polarizing plate 100 of the present invention can be obtained by the following steps: 1) performing a pre-treatment step to facilitate bonding on the bonding surface of the optical film and the opposite film (pre-treatment step), 2) bonding the polarizer and the optical film (or the opposite film) by using a UV adhesive, and 3) irradiating the laminate obtained by bonding with UV rays to cure the UV adhesive (curing step).

(1) Pre-treatment step Perform easy-bonding treatment on the polarized bonding surface of the optical film and the counter film. Examples of easy-bonding treatment include corona treatment and plasma treatment.

(2) Lamination step The UV curing adhesive is applied to at least one of the polarizer and the optical film (or the opposite film). There is no particular limitation on the method of applying the UV curing adhesive, and examples thereof include doctor blade, wire rod, die coating, comma coater, gravure coating machine, etc.

Then, the polarizer and optical film or counter film can be bonded by UV curing adhesive. Then, the two sides of the bonded laminate are clamped and pressed by pressure rollers. The material of the pressure roller can be metal or rubber.

(3) Curing step Next, the laminated material bonded by the UV-curable adhesive is irradiated with UV light to cure the UV-curable adhesive. In this way, the polarizer is bonded to the optical film or the counter film by the UV-curable adhesive. Furthermore, the curing of the UV-curable adhesive on one side of the polarizer and the curing of the UV-curable adhesive on the other side of the polarizer can be performed sequentially or simultaneously. From the perspective of improving the manufacturing efficiency of the polarizing plate, it is preferred that the curing of the UV-curable adhesive on one side of the polarizer and the curing of the UV-curable adhesive on the other side of the polarizer be performed simultaneously.

The UV irradiation conditions may be any conditions that can cure the UV curable adhesive, for example, the integrated light intensity is preferably in the range of 50 to 1500 mJ/cm ² , more preferably in the range of 100 to 500 mJ/cm ² .

The line speed during the manufacture of polarizing plates depends on the curing time of the adhesive, but for example, the range of 1 to 500 m/min is preferred, and the range of 5 to 300 m/min is more preferred. If the line speed is 1 m/min or more, productivity can be easily improved, and damage to the optical film or the opposite film can be reduced. In addition, if the line speed is less than 500 m/min, the UV curing adhesive is sufficiently cured, and good adhesion is easily obtained.

Thus, in the curing step, a high temperature environment may be created by ultraviolet irradiation or heating to accelerate curing. Also, even if the adhesive is a water-based adhesive, a high temperature environment may be created by heating to accelerate bonding or dry the adhesive.

In contrast, the optical film of the present invention has excellent light resistance and durability, and even if the polarizer and the optical film are placed in a high temperature environment, a polarizing plate with suppressed light leakage can be obtained. By suppressing light leakage of the polarizing plate, the organic EL image display device having the polarizing plate can suppress weak light leakage caused by external light reflection during black display.

[7] Image display device The optical film of the present invention can be used as an optical film (phase difference film, protective film) for image display devices such as organic EL image display devices or liquid crystal display devices. The optical film of the present invention can also be preferably used as a phase difference film (λ/4 phase difference film) for organic EL image display devices.

[7.1] Organic EL image display device Figure 2 shows an exploded cross-sectional view of an organic EL image display device 200.

The organic EL image display device 200 includes an organic EL element 300 (display unit), a polarizing plate 100 (circular polarizing plate), and a bonding layer 400 disposed therebetween.

The organic EL element 300 has a metal electrode 302, a light-emitting layer 303, a transparent electrode (such as ITO) 304, and a sealing layer 305 in this order on a substrate 301 such as glass or polyimide. The metal electrode 302 may also be composed of a reflective electrode and a transparent electrode.

The metal electrode 302 can function as a cathode. When it is desired to facilitate electron injection and improve light emission efficiency, it is preferred to use a material with a small work function, and Mg-Ag and Al-Li are generally used.

The luminescent layer 303 is a composite of organic thin films, for example, a composite of a hole injection layer formed of a triphenylamine derivative and a luminescent layer formed of a fluorescent organic solid such as anthracene, or a composite of such a luminescent layer and an electron injection layer formed of a perylene derivative, or a composite of such a hole injection layer, a luminescent layer, and an electron injection layer.

The transparent electrode 304 functions as an anode and is usually made of a transparent conductor such as indium tin oxide (ITO).

Then, by inputting a voltage between the metal electrode 302 and the transparent electrode 304, holes and electrons are injected into the light-emitting layer 303. The energy generated by the recombination of the holes and electrons excites the fluorescent material, and the excited fluorescent material emits light when it returns to the base state.

The polarizing plate 100 is disposed on the identification side of the organic EL element 300. The polarizing plate 100 is the aforementioned polarizing plate 100 (refer to FIG. 1 ), and the optical film 102 (λ/4 phase difference film) is disposed between the organic EL element 301 and the polarizer 101. The angle between the transmission axis (or absorption axis) of the polarizer 101 and the in-plane retardation axis of the optical film 102 is as described above, and it is preferably bonded to 45° (or 135°).

The counter film 103 preferably further has a hard coating layer (not shown) disposed on the identification side (the reverse side of the polarizer 101). The hard coating layer can not only prevent the surface scratches of the organic EL image display device, but also reduce the bending of the polarizer 100. In addition, a reflection prevention layer can be further formed on the hard coating layer.

The bonding layer 400 is disposed between the organic EL element 300 and the polarizing plate 100 to bond them. Examples of the bonding agent constituting the bonding layer 400 include thermosetting adhesives (epoxy-based thermosetting adhesives, urethane-based thermosetting adhesives, acrylic-based thermosetting adhesives, etc.), hot melt adhesives, etc. (rubber-based hot melt adhesives, polyester-based hot melt adhesives, polyolefin-based hot melt adhesives, ethylene-vinyl acetate resin-based hot melt adhesives, polyurethane resin hot melt adhesives, etc.).

(Function) In such an organic EL image display device 200, when a voltage is input to the metal electrode 302 and the transparent electrode 304, electrons are injected into the light-emitting layer 303 from the metal electrode 302 as a cathode, and holes are injected from the transparent electrode 304 as an anode. The two are recombined in the light-emitting layer 303 to generate visible light corresponding to the light-emitting characteristics of the light-emitting layer 303. The light generated by the light-emitting layer 303 is directly or reflected by the metal electrode 302, and then taken out to the outside through the transparent electrode 304 and the polarizing plate 100.

The light-emitting layer 303 can be formed into an extremely thin film with a thickness of about 10 nm. Therefore, the light-emitting layer 303 also allows light to pass almost completely, similarly to the transparent electrode 304. As a result, when the light is not emitting, the light that enters the organic EL image display device 200 from the outside, passes through the sealing layer 305, the transparent electrode 304 and the light-emitting layer 303, reaches the metal electrode 302, is reflected at the metal electrode 302, and passes through the light-emitting layer 303, the transparent electrode 302 and the sealing layer 305 again, and goes out to the surface side of the organic EL device 200. At this time, the optical film 102 can suppress the light reflected at the metal electrode 302 from leaking out to the surface side of the organic EL image display device 200, thereby reducing the reflection of external light.

That is, when the light is not emitted, half of the external light incident from the outside of the organic EL image display device 200 by indoor lighting or the like is absorbed by the polarizer 101 of the polarizing plate 100, but the remaining half is not absorbed and is transmitted as linearly polarized light and incident on the optical film 102 (λ/4 phase difference film). The light incident on the optical film 102 is converted into circularly polarized light because the transmission axis of the polarizer 101 and the in-plane retardation axis of the optical film 102 intersect at 45° (or 135°).

When the circularly polarized light emitted from the optical film 102 is reflected by the mirror surface of the metal electrode 302 of the organic EL element 300, the phase is reversed by 180 degrees, and it becomes reverse circularly polarized light. The reflected light is incident on the optical film 102 and is converted into linearly polarized light perpendicular to the transmission axis (parallel to the absorption axis) of the polarizer 101, so it is absorbed by the polarizer 101 and can be suppressed from being emitted to the outside.

Then, in the present invention, an optical film 102 containing a specific pigment compound is used. Thus, the optical film 102 can also convert light in a specific wavelength region (which is not converted into the desired linear polarization in a cycloolefin resin film that does not contain a pigment compound) into linear polarization perpendicular to the transmission axis (parallel to the absorption axis) of the polarizer 101. Thus, the reflected light in the specific wavelength region can suppress the reduction in the color of the reflected light caused by leakage through the transmission axis of the polarizer 101. Furthermore, even if the optical film 102 contains a pigment compound, it has excellent light resistance, and thereby it can also suppress display unevenness. [Example]

The following examples are given to specifically illustrate the present invention, but the present invention is not limited thereto. In addition, when "parts" or "%" are used in the examples, they represent "parts by mass" or "% by mass" unless otherwise specified.

[Example 1] 1. Materials for optical thin films (1) Cycloolefin resin ≪Synthesis of cycloolefin resin 1≫ 100 parts by mass of purified toluene and 100 parts by mass of norbornene carboxylic acid methyl ester (see the following structural formula A) were added to a reactor. Next, 25 mmol% (based on monomer mass) of ethylhexanoate-Ni dissolved in toluene, 0.225 mol% (based on monomer mass) of tri(pentafluorophenyl)boron, and 0.25 mol% (based on monomer mass) of triethylaluminum dissolved in toluene were added to the reactor and reacted for 18 hours while stirring at room temperature. After the reaction was completed, the reaction mixture was added to excess ethanol to form a polymer precipitate. After purification precipitation, the obtained solid component was dried at 65°C for 24 hours under vacuum drying to obtain a cycloolefin resin (P-1) (weight average molecular weight Mw: 140,000, Tg: 140°C). The weight average molecular weight was measured by the above method.

(2) Pigment compounds The exemplary pigment compounds and comparative compounds listed in Table I were prepared, and the HOMO energy level (eV) was calculated.

The energy level of HOMO calculated by molecular orbital calculation of the exemplary pigment compound and the comparative compound having the structure represented by the general formula (1) can be calculated by using a molecular orbital calculation software using B3LYP as a functional and 6-31G(d) as a basis function as a calculation method. The software is not particularly limited, and the calculation can be performed in the same manner using either software.

The present invention was calculated using Gaussian09 (Revision C. 01, M. J. Frisch, et al, Gaussian, Inc., 2010.) manufactured by Gaussian, Inc., USA as a software for molecular orbital calculation. The energy level values of HOMO of the calculation results are shown in Table I.

≪Example of Synthesis of Dye Compound≫

<Example Dye Compound 9>

Measure 1 g of compound (9-1) and 0.277 g of malononitrile in a 100 mL three-head piston, add 18 mL of toluene and dissolve. Then, drop 0.332 g of morpholine, heat and reflux for 4 hours. After the reaction is completed, remove the solvent under reduced pressure, add 5 mL of methanol, and stir in a suspended state. After filtering and drying the precipitate, 0.33 g (yield 28%) of the powder of the exemplified pigment compound 9 is obtained. The structure is confirmed by NMR.

<Example Pigment Compound 23>

Weigh 1 g of compound (23-1) and 0.497 g of malononitrile in a 100 mL three-piston, and add 40 mL of toluene to dissolve them. Then, drop 0.596 g of morpholine, heat and reflux for 4 hours. After the reaction is completed, remove the solvent under reduced pressure, add 5 mL of methanol, and stir in a suspended state. After filtering and drying the precipitate, 0.24 g (yield 18%) of the exemplified pigment compound 23 powder is obtained. The structure is confirmed by NMR.

(Measurement of maximum absorption wavelength) The maximum absorption wavelength of the above-mentioned compound was obtained by measuring the absorption spectrum of the pigment compound in dichloromethane using UV-2450 manufactured by Shimadzu Corporation, and is recorded in Table II. In addition, the so-called "maximum absorption wavelength" in the invention means the wavelength (nm) showing the maximum and maximum absorbance (absorption intensity) of the absorption spectrum of the compound obtained when measuring the absorption spectrum of the above-mentioned compound.

2. Preparation and evaluation of optical film <Preparation of optical film 101> (Preparation of microparticle additive solution) The following ingredients were mixed in a dissolving device for 50 minutes and then dispersed with Menton Gorin. The particles were further dispersed with a mill to reduce the particle size of the secondary particles to a predetermined size. Fine Mett NF manufactured by Nippon Seisen Co., Ltd. was filtered to prepare a microparticle additive solution.

Microparticles (AEROSILR812: manufactured by Nippon Aerosil, primary average particle size: 7nm, apparent density 50g/L): 4 parts by mass Dichloromethane: 48 parts by mass Ethanol: 48 parts by mass

(Preparation of dopant) The following ingredients were placed in a sealed container while being stirred thoroughly, and the temperature was raised to 80°C and maintained for 1 hour. Next, the mixture was cooled to 30°C and filtered through a filter with a pore size of 5μm to obtain dopant A-1.

Cycloolefin resin 1:                100 parts by mass Dichloromethane:                          302 parts by mass Ethanol:                          18 parts by mass Exemplary pigment compound 1:                     0.1 parts by mass Microparticle additive solution:                    10 parts by mass

(Production of optical film 101) On an endless metal support driven at a speed of 30m/min, the prepared dopant is cast from a casting mold, and dried on the support facing a 40°C drying wind until a self-supporting cast film (film-like object) is obtained. Thereafter, the cast film is cooled to 10°C and peeled off from the support. Thereafter, the peeled cast film is dried at 110°C for 30 minutes, and then stretched at 170°C in a direction of 45° (oblique direction) in the width direction to a magnification of 2 times. In this way, an optical film 101 with a film thickness of 40μm having an in-plane retardation axis in a direction of about 45° in the width direction is obtained. The optical film 101 is a film that has a retardation value Ro of 145 nm as confirmed by the aforementioned retardation value evaluation method and functions as a λ/4 plate.

<Production of optical films 102 to 119> For the production of optical film 101, except that the exemplary pigment compound was changed to that described in Table III, optical films 102 to 119 were produced in the same manner.

≪Evaluation≫ ＜Light transmittance＞ Light transmittance was measured using a spectrophotometer (U-3300 manufactured by Hitachi High-Tech Science) in accordance with JIS K 7375:2008 "Plastics - Methods for determination of total light transmittance and total light reflectance". If the light transmittance is 80% or more, it is evaluated as "0", and if it is less than 80%, it is evaluated as "△".

<Light resistance test> The optical film prepared as described above was subjected to a light resistance test. The prepared film was continuously irradiated with light of a xenon lamp (60 W/m ² ) for 100 hours. The absorbance of the film before (0 hour) and after (100 hours) irradiation was measured with a spectrophotometer, and the pigment residue rate was determined according to the following formula (1). Formula (1) Pigment residue rate (%) = {(A ₁₀₀ )/(A ₀ )}×100 (However, A ₀ represents the absorbance before irradiation with a xenon lamp, and A ₁₀₀ represents the absorbance after irradiation with a xenon lamp) The so-called "absorbance" represents the absorbance at the maximum wavelength of absorption of each compound. The higher the pigment residue rate, the more difficult it is for the compound to be decomposed by light, and the higher the light resistance. Light fastness was evaluated according to the following criteria.

A: Pigment residual rate is 65% or more B: Pigment residual rate is 40% or more and less than 65% C: Pigment residual rate is 10% or more and less than 40% D: Pigment residual rate is less than 10%

<Durability: Evaluation of leakage> After placing each optical film in a high temperature and high humidity environment of 60°C and 90%RH for 1000 hours, the presence of leakage (crystallization) on the surface of the optical film was visually observed and the leakage was evaluated according to the following criteria.

◎: No leakage was found on the surface of the optical film ○: Some leakage was found on the surface of the optical film △: Some leakage was found on the surface of the optical film ×: Clear leakage was found on the surface of the optical film The composition of the optical film and the above evaluation results are shown in Table III.

From the results in Table III, it can be seen that the optical film of the present invention has excellent light transmittance, light resistance and durability when using the pigment compound having the structure represented by the general formula (1) of the present invention.

[Example 2] <Preparation of optical film 201> 19.7 parts by mass of urethane acrylate (UA-1100H manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.1 parts by mass of photopolymerization initiator (IRGACURE 184 manufactured by BASF), 0.3 parts by mass of modified silicone (KF-351A manufactured by Shin-Etsu Chemical Co., Ltd.), 0.05 parts by mass of Emargen 404 (manufactured by Kao Chemical Co., Ltd.), 39.5 parts by mass of propylene glycol monomethyl ether (PGME), 39.5 parts by mass of methyl acetate, and 0.1 parts by mass of exemplary pigment compound 6 were mixed and stirred thoroughly to prepare a coating composition. The obtained coating composition was coated on the COP substrate with a wire bar to a thickness of 25 μm, dried, and UV-cured to produce an optical film 201 having a functional layer (hard coating layer) with a thickness of 5 μm.

<Production of optical films 202-212> For the production of optical film 201, optical films 202-212 were produced in the same manner except that the exemplary pigment compound was changed to that described in Table IV. For the produced optical films 201-212, the light resistance and durability were evaluated in the same manner as in Example 1. The results are shown in Table IV.

From the results in Table IV, it can be seen that the optical film of the present invention has excellent light transmittance, light resistance and durability as in Example 1 by using the compound having the structure represented by the general formula (1) of the present invention in the functional layer.

[Example 3] Using the optical films prepared in Examples 1 and 2, polarizing plates were prepared and evaluated.

<Production of polarizing plate 301> (1) Production of polarizers A 60μm thick long polyvinyl alcohol film was continuously transported by a guide roller while being immersed in a dyeing bath (30°C) prepared by iodine and potassium iodide for dyeing and 2.5 times stretching. It was then stretched and crosslinked 5 times in an acid bath (60°C) added with boric acid and potassium iodide. The resulting 12μm thick iodine-PVA polarizer was dried in a dryer at 50°C for 30 minutes to obtain a polarizer with a moisture content of 4.9%.

(2) Preparation of UV-curable adhesive The following components were mixed to obtain a liquid UV-curable adhesive (UV adhesive). 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate:     ...

(3) Preparation of polarizing plate After applying the corona treatment to the bonding surface of the optical film 101, the prepared UV curing adhesive was applied to a dry thickness of 3μm by a coating device equipped with a chambered doctor. In addition, the bonding surface of the Konica Minolta Tuck KC4CT (thickness 40μm, manufactured by Konica Minolta) as the counter film was similarly applied with the corona treatment, and the UV curing adhesive was applied to a dry thickness of 3μm.

Immediately thereafter, the optical film 101 is placed on one side of the polarizer prepared above, and the TAC film, which is the opposite film, is placed on the other side by means of a UV curable adhesive in a roll-to-roll manner. The lamination is performed until the retardation axis (or phase advance axis) of the optical film 101 and the absorption axis (or transmission axis) of the polarizer are aligned (the angle between the in-plane retardation axis of the optical film 101 and the absorption axis of the polarizer is 45°). Thereafter, while the laminate is transported at a linear speed of 20 m/min, ultraviolet light is irradiated toward the optical film 106 side by means of a metal halogen lamp in order to make the integrated light quantity in the wavelength range of 280-320 nm to be 320 mJ/ ^cm2 . Thus, the ultraviolet curing adhesive is cured to obtain the polarizing plate 301. Since the polarizing plate 301 is manufactured in a roll-to-roll manner, the long polarizing plate is finally cut along the width direction to obtain the polarizing plate 301 in a thin sheet form.

The manufactured polarizing plate 301 is bonded to the portion of the polarizing plate on the identification side of the organic EL image display device that is peeled off for sale, and the optical film 101 side of the above-mentioned polarizing plate becomes the organic EL element side, thereby manufacturing the organic EL image display device 301.

<Production of polarizing plate and organic EL image display device 302~319> For the production of polarizing plate 301, except that optical film 101 is changed to that described in Table V, polarizing plates 302~319 and organic EL image display devices 302~319 are produced in the same manner. For the produced polarizing plates 301~319 and organic EL image display devices 301~319, the same evaluation as in Example 1 and the following light leakage evaluation are performed, and the results are shown in Table V.

<Light leakage evaluation> The organic EL image display device produced above was stored in an environment of 60℃･90%RH for 500 hours, and then placed at room temperature and humidity (23℃･55%RH) for 24 hours. The occurrence of display unevenness due to light leakage on the screen during black display was visually observed in a dark room and evaluated according to the following criteria. ○: No display unevenness due to light leakage △: Display unevenness due to light leakage was slightly confirmed ×: Display unevenness due to light leakage was obviously generated

As can be seen from Table V, by using the optical film of the present invention, a polarizing plate and an organic EL image display device with excellent light resistance and durability and no light leakage can be obtained. [Industrial Applicability]

The optical film of the present invention not only has high transparency and can prevent light leakage, but also has excellent light resistance and durability under more severe environmental conditions, so it can be suitably used in polarizing plates or organic electroluminescent image display devices.

100: Polarizing plate 101: Polarizer 102: Optical film 103: Opposite film 104: Adhesion layer 200: Organic EL image display device 300: Organic EL element 301: Substrate 302: Metal electrode 303: Luminescent layer 304: Transparent electrode 305: Sealing layer 400: Adhesion layer

[FIG. 1] is a cross-sectional view showing the structure of the polarizing plate 100. [FIG. 2] is an exploded cross-sectional view showing the organic EL image display device 200.

100: Polarizing plate

101: Polariton

102: Optical film

103: Opposite film

104: Next layer

Claims (7)

An optical film is a thermoplastic resin containing a cyclic olefin resin or an acrylic resin, which contains a compound having a structure represented by the following general formula (1);

(wherein, Z is any one of the following structural formulas;

(the group represented by the above structural formula may further have a substituent; and R represents a substituent). The energy level of the highest occupied molecular orbital of the compound having the structure represented by the general formula (1) is less than -5.85 eV, and the compound having the structure represented by the general formula (1) is contained in the range of 0.01 to 20 mass % relative to the thermoplastic resin. As in the optical film of claim 1, the cyclic olefin resin has a polar group. The optical film of claim 1 further comprises a functional layer. As in claim 3, the optical film, wherein the functional layer contains a compound having a structure shown in the general formula (1). As in claim 1, the optical film is a λ/4 phase difference film. A polarizing plate characterized by having an optical film as described in any one of claims 1 to 5. An organic electroluminescent image display device characterized by having an optical film as described in any one of claims 1 to 5 or a polarizing plate as described in claim 6.

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