CN112334799A - Polarizer, polarizing film, optical film, and image display device - Google Patents

Abstract

The present invention provides a polarizer comprising a durability-enhancing layer on at least one surface, wherein the durability-enhancing layer is formed from a curable composition containing a compound (A) having a pH-rise of 3.0 or less even when 0.5 equivalent of a basic component is added in a titration test at 60 ℃. The compound (A) is preferably gamma-butyrolactone (meth) acrylate. In addition, it is preferable that at least a part of the compound (a) contained in the curable composition is polymerized, it is preferable that the curable composition further contains a polymerization initiator, and it is preferable that the durability improving layer is formed of a cured product layer of the curable composition.

Description

Polarizer, polarizing film, optical film, and image display device

Technical Field

The present invention relates to a polarizer having a durability-enhancing layer on at least one surface thereof. The present invention also relates to a polarizing film in which a transparent protective film is laminated on at least one surface of a polarizer. The polarizing film may be used alone or in combination with an optical film having the polarizing film laminated thereon to form an image display device such as a Liquid Crystal Display (LCD), an organic EL display, a CRT, or a PDP.

Background

In watches, mobile phones, PDAs, notebook computers, monitors for computers, DVD players, TVs, and the like, liquid crystal display devices are rapidly on the market. A liquid crystal display device is a device that visualizes the polarization state of a liquid crystal switch, and uses a polarizer in view of the display principle. In particular, in applications such as TVs, high brightness, high contrast, and wide viewing angles are increasingly required, and polarizing films are also increasingly required to have high transmittance, high polarization, high color reproducibility, and the like.

As the polarizer, an iodine polarizer having a structure in which iodine is adsorbed to polyvinyl alcohol (hereinafter, also referred to as "PVA") and stretched is generally most widely used from the viewpoint of having high transmittance and high degree of polarization. Generally, a polarizing film is used in which a transparent protective film is laminated on both surfaces of a polarizer by using a so-called aqueous adhesive in which a polyvinyl alcohol-based material is dissolved in water (patent document 1). As the transparent protective film, cellulose triacetate having high moisture permeability or the like is used. When the aqueous adhesive is used (so-called wet lamination), a drying step is required after the polarizer and the transparent protective film are bonded.

On the other hand, an active energy ray-curable adhesive is proposed instead of the aqueous adhesive. When the polarizing film is produced using the active energy ray-curable adhesive, the productivity of the polarizing film can be improved because a drying step is not required. For example, a radical polymerization type active energy ray-curable adhesive using an N-substituted amide monomer as a curable component has been proposed (patent document 2). The adhesive layer formed using the active energy ray-curable adhesive described in patent document 2 can sufficiently withstand, for example, a water resistance test for evaluating the presence or absence of discoloration or peeling after immersion in hot water at 60 ℃ for 6 hours. However, in recent years, there has been a demand for an adhesive for polarizing films that has improved water resistance to such an extent that it can withstand a more severe water resistance test, for example, when the adhesive is immersed (saturated) in water and then peeled off from the end claws, and evaluated for the presence or absence of peeling.

Patent document 3 below reports a technique of forming a resin layer on the surface of a polarizer for the purpose of suppressing degradation of the polarizer, but it is clear that there is still room for further improvement in the technique in order to sufficiently suppress degradation of the polarizer under severe humidification conditions.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2001-296427

Patent document 2: japanese patent laid-open No. 2012 and 052000

Patent document 3: japanese patent laid-open No. 2000-199819

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a polarizer and a polarizing film in which deterioration of optical characteristics is suppressed even in a humidified environment.

Another object of the present invention is to provide an optical film using the polarizing film; and an image display device using the polarizing film or the optical film.

Means for solving the problems

As a result of intensive studies to solve the above problems, the present inventors have found that a durability-improving layer is formed on at least one surface of a polarizer from a curable composition containing a compound having a buffer-like action, whereby deterioration in optical characteristics of the polarizer and a polarizing film provided with the polarizer can be suppressed even in a humidified environment, and have completed the present invention.

That is, the present invention relates to a polarizer comprising a durability-enhancing layer on at least one surface, wherein the durability-enhancing layer is formed from a curable composition containing a compound (a) and the pH of the compound (a) is increased to within 3.0 in a titration test at 60 ℃.

In the polarizer, the compound (a) is preferably γ -butyrolactone (meth) acrylate.

In the polarizer, it is preferable that at least a part of the compound (a) contained in the curable composition is polymerized.

In the polarizer, the curable composition preferably further contains a polymerization initiator.

In the polarizer, the durability-enhancing layer is preferably formed of a cured product layer of the curable composition.

The present invention also relates to a polarizing film including any one of the polarizers described above.

In the polarizing film, it is preferable that a transparent protective film is laminated on at least one surface of the polarizer, and the transparent protective film is laminated on the side of the durability-enhancing layer included in the polarizer.

In the polarizing film, an adhesive layer is preferably further provided between the durability enhancing layer and the transparent protective film.

The present invention also relates to an optical film in which at least 1 sheet of the polarizing film described above is laminated, or an image display device using the polarizing film described above or the optical film described above.

ADVANTAGEOUS EFFECTS OF INVENTION

As described above, an iodine polarizer having a structure in which iodine is adsorbed to PVA and stretched is generally used as a polarizer. In the present invention, the polarizer has a durability-improving layer formed of a curable composition containing a compound (a) having a similar buffering action on at least one surface thereof, and specifically, the compound (a) has a pH rise of 3.0 or less in a titration test at 60 ℃. Therefore, deterioration of the optical characteristics of the polarizer can be suppressed even in a humidified environment. The reason for obtaining this effect is not clear, but it is considered that one of the reasons is that a durability improving layer having a buffer action like that is provided on the surface of the polarizer can reduce a significant pH change of the polarizer even in a humidified environment, and thus, the iodine complex existing on the surface of the polarizer can be stabilized.

In the polarizing film of the present invention in which a transparent protective film is laminated on at least one surface of the polarizer, for example, when an adhesive layer is interposed between the polarizer and the transparent protective film, deterioration of optical properties of the polarizing film can be suppressed even in a humidified environment. The reason for obtaining this effect is not clear, but it is considered that one of the reasons is that the durability-improving layer can reduce a significant pH change of the polarizer even in a humidified environment, and thus hydrolysis of the covalent bond or hydrogen bond formed between the functional group such as a hydroxyl group present on the polarizer surface and the functional group of the adhesive layer can be suppressed. This stabilizes the iodine complex present on the polarizer surface.

The polarizing film of the present invention may be provided with a polarizer having at least one surface provided with the specific durability enhancing layer, and the transparent protective film may not be provided on the durability enhancing layer. In this polarizing film, the durability-improving layer suppresses deterioration of optical characteristics of the polarizer in a humidified environment, and also exerts a protective function instead of the transparent protective film.

Detailed Description

The present invention relates to a polarizer having a durability-enhancing layer on at least one surface thereof. Hereinafter, each configuration will be described.

< layer for improving durability >

The durability-enhancing layer is formed from a curable composition containing a compound (A) which has a pH increase of 3.0 or less in a titration test at 60 ℃ even when a basic component is added in an amount of 0.5 equivalent.

Compound (a) is a compound showing a similar buffering action, and is a compound showing a behavior as described below: for example, when the pH is measured by adding 0.1M-NaOH aqueous solution to 100ml of 0.1M-aqueous solution, the pH rise with respect to the amount of NaOH added is temporarily stabilized, and then the inflection point is displayed again, and the pH rises. By exhibiting such a buffering effect, a significant pH change of the polarizer can be reduced even in a humidified environment.

The compound (a) is not particularly limited as long as it is a compound having a pH rise of 3.0 or less even when 0.5 equivalent of a basic component is added in a titration test at 60 ℃. Examples of such compounds include γ -butyrolactone (meth) acrylate.

The compound (a) may be contained in the curable composition as it is, or may be contained in the curable composition in a state where at least a part of the compound (a) has been polymerized. Further, at least a part of the compound (A) may be copolymerized with another copolymerizable monomer. When the compound (a) is contained in the curable composition in a state where at least a part thereof is polymerized, for example, a layer containing the curable composition may be provided on at least one surface of the polarizer by a coating method or the like described later, and dried as necessary to form a durability-improving layer.

When the content of the compound (a) in the durability-enhancing layer is too small, the deterioration of the optical characteristics of the polarizer may not be sufficiently suppressed in a humidified environment. Therefore, the content of the compound (a) in the durability-enhancing layer is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 80% by weight or more.

The curable composition to be a raw material for forming the durability enhancing layer may be composed of only the compound (a), or may contain a polymerization initiator, a solvent, an additive, and a compound (B) represented by general formula (1) described later, in addition to the compound (a).

When the curable composition contains a polymerization initiator in addition to the compound (a) and the durability-improving layer is formed from a cured product layer of the curable composition, the durability improvement of the polarizer is improved by fixing the compound (a) and a polymer thereof in the vicinity of the polarizer. As a result, deterioration of the optical characteristics of the polarizer can be suppressed suitably, which is preferable. As a method for forming the durability enhancing layer by the cured product layer, for example, a method for forming a cured product layer (durability enhancing layer) by applying a curable composition containing at least the compound (a) and a polymerization initiator to a polarizer and irradiating the curable composition with active energy rays described later can be cited. The active energy ray that can be used is described later.

In the present invention, as the polymerization initiator, a photopolymerization initiator is preferably used. The photopolymerization initiator can be suitably selected depending on the active energy ray. In the case of curing by ultraviolet rays or visible light, a photopolymerization initiator that is cleaved by ultraviolet rays or visible light is used. Examples of the photopolymerization initiator include: benzophenone compounds such as benzil, benzophenone, benzoylbenzoic acid, and 3, 3' -dimethyl-4-methoxybenzophenone; aromatic ketone compounds such as 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone, α -hydroxy- α, α' -dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, and α -hydroxycyclohexyl phenyl ketone; acetophenone compounds such as methoxyacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxyacetophenone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, etc.; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, and anisoin methyl ether; aromatic ketal compounds such as benzil dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; optically active oximes such as 1-phenyl-1, 1-propanedione-2- (o-ethoxycarbonyl) oxime; thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2, 4-dimethylthioxanthone, isopropylthioxanthone, 2, 4-dichlorothioxanthone, 2, 4-diethylthioxanthone, 2, 4-diisopropylthioxanthone and dodecylthioxanthone; camphorquinone; a halogenated ketone; acyl phosphine oxides; acyl phosphonates and the like.

As the photopolymerization initiator, a compound represented by the following general formula (3); or a combination of a compound represented by the general formula (3) and a photopolymerization initiator having high sensitivity to light of 380nm or more as described later.

[ chemical formula 1]

(in the formula, R⁶And R⁷represents-H, -CH₂CH₃-iPr or Cl, R⁶And R⁷May be the same or different). When the compound represented by the general formula (3) is used, the adhesiveness is superior to that when a photopolymerization initiator having high sensitivity to light of 380nm or more is used alone. Among the compounds represented by the general formula (3), R is particularly preferable⁶And R⁷is-CH₂CH₃Diethyl thioxanthone (ll). The composition ratio of the compound represented by the general formula (3) to the compound (A) in the curable composition is preferably 0.5 to 4.0% by weight, more preferably 1.0 to 2.5% by weight.

Further, it is preferable to add a polymerization initiation aid as needed. Examples of the polymerization initiation aid include: triethylamine, diethylamine, N-methyldiethanolamine, ethanolamine, 4-dimethylaminobenzoic acid, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, etc., with ethyl 4-dimethylaminobenzoate being particularly preferred. When a polymerization initiator aid is used, the amount thereof to be added is usually 0 to 5% by weight, preferably 0 to 4% by weight, and most preferably 0 to 3% by weight, based on the total amount of the compound (A).

Further, a known photopolymerization initiator may be used in combination as necessary. Since the transparent protective film having UV absorption ability does not transmit light of 380nm or less, it is preferable to use a photopolymerization initiator having high sensitivity to light of 380nm or more as the photopolymerization initiator. Specifically, there may be mentioned: 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone, 2- (dimethylamino) -2- [ (4-methylphenyl) methyl ] -1- [4- (4-morpholino) phenyl ] -1-butanone, 2,4, 6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide, bis (. eta.5-2, 4-cyclopentadien-1-yl) bis (2, 6-difluoro-3- (1H-pyrrol-1-yl) phenyl) titanium and the like.

In particular, as the photopolymerization initiator, in addition to the photopolymerization initiator of the general formula (3), a compound represented by the following general formula (4);

[ chemical formula 2]

(in the formula, R⁸、R⁹And R¹⁰represents-H, -CH₃、-CH₂CH₃-iPr or Cl, R⁸、R⁹And R¹⁰May be the same or different). As the compound represented by the general formula (4), commercially available 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropan-1-one (trade name: IRGACURE907, manufacturer: BASF) can be suitably used. Further, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -1-butanone (trade name: IRGACURE369, manufacturer: BASF), 2- (dimethylamino) -2- [ (4-methylphenyl) methyl group]-1- [4- (4-morpholinyl) phenyl]1-butanone (trade name: IRGACURE379, manufacturer: BASF) is preferred because of its high sensitivity. The composition ratio of the compound represented by the general formula (4) to the compound (A) in the curable composition is preferably 0.5 to 4.0% by weight, more preferably 1.0 to 2.5% by weight.

As the solvent that can be contained in the curable composition, a solvent that can stably dissolve or disperse the compound (a) and the polymer thereof, a polymerization initiator, and the like is preferable. The solvent may be an organic solvent, water, or a mixed solvent thereof. The solvent may be selected from, for example: esters such as ethyl acetate, butyl acetate, and 2-hydroxyethyl acetate; ketones such as methyl ethyl ketone, acetone, cyclohexanone, methyl isobutyl ketone, diethyl ketone, methyl n-propyl ketone, and acetylacetone; tetrahydrofuran (THF), bis

Cyclic ethers such as alkanes; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic alcohols such as methanol, ethanol, n-propanol, isopropanol and cyclohexanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and diethylene glycol monoethyl ether; glycol ether acetates such as diethylene glycol monomethyl ether acetate and diethylene glycol monoethyl ether acetate; and so on.

Examples of additives that can be contained in the curable composition include: surfactant, plasticizer, tackifier, low molecular weight polymer, polymerizable monomer, surface lubricant, leveling agent, antioxidant, preservative, light stabilizer, ultraviolet absorbent, polymerization inhibitor, silane coupling agent, titanium coupling agent, inorganic or organic filler, metal powder, particle, foil and the like.

As a method for forming a durability-enhancing layer on a polarizer using a curable composition, a method of directly immersing the polarizer in a treatment bath of the curable composition, or a known coating method can be suitably used. Specific examples of the coating method include: roll coating, gravure coating, reverse coating, roll brushing, spray coating, air knife coating, and die coating, but are not limited thereto.

When the curable composition contains a polymerization initiator, the durability enhancing layer may be formed by forming a cured product layer on at least one surface of the polarizer by curing the curable composition, or the durability enhancing layer may be formed by forming a durability enhancing layer made of an uncured curable composition on at least one surface of the polarizer and laminating the durability enhancing layer with the transparent protective film, and then curing the curable composition to form a durability enhancing layer including a cured product layer.

< polarizer >

The polarizer is not particularly limited, and various polarizers can be used. Examples of polarizers include: a polyolefin-based alignment film obtained by uniaxially stretching a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially acetalized polyvinyl alcohol-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film, while adsorbing a dichroic material such as iodine or a dichroic dye, a dehydrated polyvinyl alcohol-based film, or a desalted polyvinyl chloride-based film. Among these, a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine is preferable. The thickness of the polarizers is generally 1 to 30 μm.

A polarizer obtained by uniaxially stretching a polyvinyl alcohol film dyed with iodine can be produced, for example, as follows: the polyvinyl alcohol is dyed by immersing in an aqueous iodine solution and stretched to 3 to 7 times the original length. If necessary, the substrate may be immersed in an aqueous solution of boric acid, potassium iodide, or the like. If necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol film with water, not only stains and an anti-blocking agent on the surface of the polyvinyl alcohol film can be washed, but also unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol film. The stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed after stretching with iodine. Stretching may also be carried out in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

However, in mobile applications such as cellular phones, a thin polarizer having a thickness of 10 μm or less is expected to be more desirable from the viewpoint of design and compactness, but if the polarizer is made thin, deterioration of optical characteristics particularly in a humidified environment tends to be remarkable. However, even when the polarizer of the present invention is a thin polarizer having a thickness of 10 μm or less, since the optical enhancement layer is provided on at least one surface, deterioration of optical characteristics can be suppressed even in a humidified environment. From the viewpoint of thinning, the thickness of the polarizer is preferably 1 to 7 μm. Such a thin polarizer is preferable in that the thickness unevenness is small, the visibility is excellent, the dimensional change is small, and the thickness of the polarizing film is reduced.

Representative examples of the thin polarizer include: a thin polarizing film described in Japanese patent laid-open publication No. Sho-51-069644, Japanese patent laid-open publication No. 2000-338329, WO2010/100917, and the specification of PCT/JP2010/001460, or the specification of Japanese patent application No. 2010-269002 and the specification of Japanese patent application No. 2010-263692. These thin polarizing films can be obtained by a production method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as PVA-based resin) layer and a stretching resin base material in a state of a laminate and a step of dyeing. With this production method, even if the PVA-based resin layer is thin, it can be stretched while being supported by the resin base material for stretching without causing troubles such as breakage due to stretching.

As the thin polarizing film, among the manufacturing methods including the step of stretching in a state of a laminate and the step of dyeing, it is preferable to obtain the thin polarizing film by a manufacturing method including the step of stretching in an aqueous boric acid solution as described in WO2010/100917 pamphlet, PCT/JP2010/001460, japanese patent application 2010-269002, and japanese patent application 2010-263692, in view of being capable of stretching at a high magnification and improving polarizing performance, and particularly preferable to obtain the thin polarizing film by a manufacturing method including the step of stretching in an air atmosphere in an auxiliary manner before stretching in an aqueous boric acid solution as described in japanese patent application 2010-269002 and japanese patent application 2010-263692.

The surface modification treatment of the polarizer may be performed before the formation of the durability enhancing layer and the easy adhesion layer described later. Examples of the surface modification treatment include corona treatment, plasma treatment, and ITRO treatment, and corona treatment is particularly preferable. By performing the corona treatment, reactive functional groups such as carbonyl groups and amino groups are formed on the polarizer surface, and the adhesion to the durability-improving layer is improved. Further, impurities on the surface can be removed by the ashing effect, or unevenness on the surface can be reduced, whereby a polarizing film having excellent appearance characteristics can be produced.

In the polarizer of the present invention, before the durability improving layer is formed, the easy adhesion layer may be formed on the polarizer, and the durability improving layer may be formed on the easy adhesion layer. The easy adhesion layer preferably contains a compound (B) represented by the following general formula (1),

[ chemical formula 3]

(wherein X is a functional group containing a reactive group, R¹And R²Each independently represents a hydrogen atom, an optionally substituted aliphatic hydrocarbon group, an aryl group or a heterocyclic group). When the easy-adhesion layer containing the compound (B) is formed on the polarizer, the boronic acid group and/or boronic acid ester group of the compound (B) reacts with the functional group such as the hydroxyl group of the polarizer, and further reacts with the compound (a) for forming the durability enhancing layer. Therefore, the adhesion between the polarizer and the durability improving layer is improved, which is preferable.

The aliphatic hydrocarbon group includes a linear or branched alkyl group having 1 to 20 carbon atoms and optionally having a substituent, a cyclic alkyl group having 3 to 20 carbon atoms and optionally having a substituent, and an alkenyl group having 2 to 20 carbon atoms, the aryl group includes a phenyl group having 6 to 20 carbon atoms and optionally having a substituent, a naphthyl group having 10 to 20 carbon atoms and optionally having a substituent, and the heterocyclic group includes, for example, a group having a 5-or 6-membered ring containing at least one hetero atom and optionally having a substituent. They may be connected to each other to form a ring. In the general formula (1), as R¹And R²The alkyl group is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 3 carbon atoms, and most preferably a hydrogen atom.

The compound (B) represented by the general formula (1) may be present in the easy-adhesion layer in an unreacted state or may be present in the easy-adhesion layer in a state in which each functional group is reacted. The phrase "the compound (B) represented by the general formula (1) is contained in the easy adhesion layer" means that, for example, at least 1 molecule of the compound (B) represented by the general formula (1) is present in the easy adhesion layer. However, in order to improve the adhesion between the polarizer and the durability improving layer and to more suitably suppress the deterioration of the optical durability of the polarizer, it is preferable to form an easy-adhesion layer on at least a part of the polarizer surface on the side where the durability improving layer is formed, and more preferably to form the easy-adhesion layer on the entire polarizer surface on the side where the durability improving layer is formed, by using an easy-adhesion composition containing the compound (B) represented by the general formula (1).

X in the compound (B) represented by the general formula (1) is a functional group having a reactive group. Examples of the reactive group contained in X include: hydroxyl group, amino group, aldehyde group, carboxyl group, vinyl group, (meth) acryloyl group, styryl group, (meth) acrylamide group, vinyl ether group, epoxy group, oxetanyl group, α, β -unsaturated carbonyl group, mercapto group, halogen group, and the like. Among them, in order to react with the carbon-carbon double bond of the monomer (a) to improve the adhesion between the polarizer and the durability improving layer, the reactive group contained in X is preferably at least 1 reactive group selected from a vinyl group, a (meth) acryloyl group, a styryl group, a (meth) acrylamide group, a vinyl ether group, an epoxy group, an oxetanyl group and a mercapto group, and is preferably at least 1 reactive group selected from a (meth) acryloyl group, a styryl group and a (meth) acrylamide group.

Preferable specific examples of the compound (B) represented by the general formula (1) include compounds represented by the following general formula (1'),

[ chemical formula 4]

(wherein Y is an organic group, X, R)¹And R²The same as described above). Further, the following compounds (1a) to (1d) can be suitably exemplified.

[ chemical formula 5]

In the present invention, the compound (B) represented by the general formula (1) may be a compound in which a reactive group is directly bonded to a boron atom, but as shown in the above-mentioned specific examples, the compound (B) represented by the general formula (1) is preferably a compound in which a reactive group is bonded to a boron atom through an organic group, that is, a compound represented by the general formula (1'). When the compound (B) represented by the general formula (1) is a compound bonded to a reactive group through an oxygen atom bonded to a boron atom, for example, the optical characteristics of the polarizer tend to deteriorate. On the other hand, the compound (B) represented by the general formula (1) is preferable because it has no boron-oxygen bond, has a boron-carbon bond by bonding to an organic group via a boron atom, and contains a reactive group (in the case of the general formula (1'), since deterioration of optical characteristics of the polarizer can be suppressed. The organic group specifically means an organic group having 1 to 20 carbon atoms which may have a substituent, and more specifically, examples thereof include: a linear or branched alkylene group having 1 to 20 carbon atoms and optionally having a substituent, a cyclic alkylene group having 3 to 20 carbon atoms and optionally having a substituent, a phenylene group having 6 to 20 carbon atoms and optionally having a substituent, a naphthylene group having 10 to 20 carbon atoms and optionally having a substituent, and the like.

Examples of the compound (B) represented by the general formula (1) include, in addition to the above-mentioned compounds, esters of (meth) acrylic acid esters and boric acid, such as esters of hydroxyethyl acrylamide and boric acid, esters of hydroxymethyl acrylamide and boric acid, esters of hydroxyethyl acrylate and boric acid, and esters of hydroxybutyl acrylate and boric acid.

As a method for forming an easy adhesion layer on the surface of the polarizer on the side where the durability enhancement layer is to be formed, using an easy adhesion composition containing the compound (B) represented by the general formula (1), for example, the following methods can be cited: an easily adhesive composition containing the compound (B) represented by the general formula (1) is produced and formed on the surface of the polarizer on the side where the durability-improving layer is to be formed by coating or the like. In the easy-adhesion composition, as components that may be contained in addition to the compound (B) represented by the general formula (1), there may be mentioned solvents, additives, radical polymerizable compounds described later, and the like.

When the easy adhesion composition contains a solvent, the easy adhesion composition may be applied to the surface of the polarizer on the side where the durability-improving layer is to be formed, and a drying step or a curing treatment (heat treatment or the like) may be performed as necessary.

As the solvent and the additive that may be contained in the easy adhesion composition, those that may be contained in the curable composition may be used. As for the method of forming the easy-adhesion layer on the polarizer using the easy-adhesion composition, the same method as the above-described method of forming the durability improving layer on the polarizer using the curable composition can be used.

When the content of the compound (B) represented by the general formula (1) in the easy-adhesion layer is too small, the proportion of the compound (B) represented by the general formula (1) present on the surface of the easy-adhesion layer may decrease, and the easy-adhesion effect may decrease. Therefore, the content of the compound (B) represented by the general formula (1) in the easy-adhesion layer is preferably 1% by weight or more, more preferably 20% by weight or more, and further preferably 40% by weight or more.

In the present invention, when the thickness of the easy adhesion layer provided in the polarizer is too large, the cohesive force of the easy adhesion layer may be reduced, and the easy adhesion effect may be reduced. Therefore, the thickness of the easy adhesion layer is preferably 2000nm or less, more preferably 1000nm or less, and further preferably 500nm or less. On the other hand, the lowest limit of the thickness of the easy-adhesion layer for sufficiently exhibiting the effect is at least the thickness of the monomolecular film of the compound represented by the general formula (1), and is preferably 1nm or more, more preferably 2nm or more, and further preferably 3nm or more.

As described above, the compound (B) represented by the general formula (1) is not only used for forming an easy adhesion layer, but also can be added to the curable composition together with the compound (a). In this case, the compound (B) reacts and/or interacts with the polarizer and the compound (a), whereby the compound (a) is reliably fixed in the vicinity of the polarizer, and the durability improvement of the polarizer is further improved. As a result, deterioration of the optical characteristics of the polarizer can be suppressed suitably, which is preferable.

The polarizing film of the present invention comprises a polarizer having a durability-enhancing layer formed of a curable composition containing a compound (A) having a carbon-carbon double bond and a cyclic skeleton on at least one surface thereof. In the polarizing film of the present invention, a transparent protective film may be laminated on at least one surface of the polarizer. The polarizer and the transparent protective film may be laminated together with the durability-improving layer interposed therebetween, and the durability-improving layer provided in the polarizer and the transparent protective film may be further laminated together with the adhesive layer interposed therebetween. The adhesive layer will be described below.

< adhesive layer >

The thickness of the adhesive layer is preferably 0.01 to 3.0 μm. If the thickness of the adhesive layer is too thin, the cohesive force of the adhesive layer is insufficient, and the peel force is reduced, which is not preferable. When the thickness of the adhesive layer is too large, peeling is likely to occur when stress is applied to the cross section of the polarizing film, and peeling failure due to impact occurs, which is not preferable. The thickness of the adhesive layer is more preferably 0.1 to 2.5 μm, and most preferably 0.5 to 1.5 μm.

The adhesive layer is formed by curing the adhesive composition. The adhesive composition can be cured in a form roughly classified into a heat curing form and an active energy ray curing form. Examples of the thermosetting resin include polyvinyl alcohol resin, epoxy resin, unsaturated polyester, urethane resin, acrylic resin, urea resin, melamine resin, phenol resin, and the like, and a curing agent is used in combination as needed. As the thermosetting resin, a polyvinyl alcohol resin or an epoxy resin is more preferably used. Active energy ray-curable resins can be classified into electron beam-curable resins, ultraviolet-curable resins, and visible light-curable resins based on active energy rays. The curing forms can be classified into radical polymerizable adhesive compositions and cationic polymerizable adhesive compositions. In the present invention, an active energy ray having a wavelength ranging from 10nm to less than 380nm is referred to as ultraviolet ray, and an active energy ray having a wavelength ranging from 380nm to 800nm is referred to as visible light.

In the production of the polarizing film of the present invention, as described above, the polarizing film is preferably curable by active energy rays. Further, visible light curability by visible light of 380nm to 450nm is particularly preferable.

Examples of the curable component contained in the radical polymerizable adhesive composition include radical polymerizable compounds used in radical polymerizable adhesive compositions. Examples of the radical polymerizable compound include compounds having a radical polymerizable functional group having a carbon-carbon double bond such as a (meth) acryloyl group or a vinyl group. Any of monofunctional radical polymerizable compounds and difunctional or higher polyfunctional radical polymerizable compounds can be used as the curable component. These radical polymerizable compounds may be used alone in 1 kind, or in combination with 2 or more kinds. As these radical polymerizable compounds, for example, compounds having a (meth) acryloyl group are preferable. In the present invention, (meth) acryloyl means acryloyl and/or methacryloyl, and "(meth)" means the same as defined below.

Examples of the monofunctional radical polymerizable compound include compounds represented by the following general formula (2).

[ chemical formula 6]

(in the formula, R³Is a hydrogen atom or a methyl group, R⁴And R⁵Each independently is a hydrogen atom, an alkyl group, a hydroxyalkyl group, an alkoxyalkyl group or a cyclic ether group, R⁴And R⁵Optionally forming a cyclic heterocyclic ring). The number of carbon atoms of the alkyl moiety of the alkyl group, hydroxyalkyl group, and/or alkoxyalkyl group is not particularly limited, and may be, for example, 1 to 4. In addition, R⁴And R⁵Examples of the optionally formed cyclic heterocyclic ring include N-acryloylmorpholine.

Specific examples of the compound represented by the general formula (2) include: n-alkyl group-containing (meth) acrylamide derivatives such as N-methyl (meth) acrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and N-hexyl (meth) acrylamide; n-hydroxyalkyl (meth) acrylamide-containing derivatives such as N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, and N-methylol-N-propyl (meth) acrylamide; and N-alkoxy group-containing (meth) acrylamide derivatives such as N-methoxymethylacrylamide and N-ethoxymethylacrylamide. Examples of the cyclic ether group-containing (meth) acrylamide derivative include heterocyclic ring-containing (meth) acrylamide derivatives in which the nitrogen atom of the (meth) acrylamide group forms a heterocyclic ring, and examples thereof include N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine. Among these, N-hydroxyethyl acrylamide and N-acryloyl morpholine can be suitably used in view of excellent reactivity, obtaining a cured product with a high elastic modulus, and excellent adhesion to a polarizer.

The content of the compound represented by the general formula (2) in the adhesive composition is preferably 0.01 to 80% by weight, more preferably 5 to 40% by weight, from the viewpoint of improving the adhesiveness and water resistance when the polarizer and the transparent protective film are adhered to each other through the adhesive layer.

The adhesive composition used in the present invention may contain, as a curable component, other monofunctional radical polymerizable compounds in addition to the compound represented by the general formula (1). Examples of the monofunctional radical polymerizable compound include various (meth) acrylic acid derivatives having a (meth) acryloyloxy group. Specific examples thereof include: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, (C1-20) alkyl (meth) acrylates such as t-amyl (meth) acrylate, 3-pentyl (meth) acrylate, 2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, hexadecyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) acrylate, and n-octadecyl (meth) acrylate.

Examples of the (meth) acrylic acid derivative include: cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and cyclopentyl (meth) acrylate; aralkyl (meth) acrylates such as benzyl (meth) acrylate; polycyclic (meth) acrylates such as 2-isobornyl (meth) acrylate, 2-norbornyl methyl (meth) acrylate, 5-norbornen-2-yl methyl (meth) acrylate, 3-methyl-2-norbornyl methyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and dicyclopentanyl (meth) acrylate; (meth) acrylic esters having an alkoxy group or a phenoxy group such as 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, and alkylphenoxypolyethylene glycol (meth) acrylate; and so on. Of these, dicyclopentenyloxyethyl acrylate and phenoxyethyl acrylate are preferable in terms of excellent adhesion to various protective films.

Further, examples of the (meth) acrylic acid derivative include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, and 12-hydroxylauryl (meth) acrylate, hydroxy-containing (meth) acrylates such as [4- (hydroxymethyl) cyclohexyl ] methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate; epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate glycidyl ether; halogen-containing (meth) acrylates such as 2,2, 2-trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, and 3-chloro-2-hydroxypropyl (meth) acrylate; alkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate; oxetanyl (meth) acrylates such as 3-oxetanyl methyl (meth) acrylate, 3-methyloxetanyl methyl (meth) acrylate, 3-ethyloxetanyl methyl (meth) acrylate, 3-butyloxetanyl methyl (meth) acrylate, and 3-hexyloxetanyl methyl (meth) acrylate; and (meth) acrylates having a heterocyclic ring such as tetrahydrofurfuryl (meth) acrylate and butyrolactone (meth) acrylate, hydroxypivalic acid neopentyl glycol (meth) acrylic acid adducts, and p-phenylphenol (meth) acrylate. Among them, 2-hydroxy-3-phenoxypropyl acrylate is preferable because it has excellent adhesion to various protective films.

Examples of the monofunctional radical polymerizable compound include: carboxyl group-containing monomers such as (meth) acrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

Examples of the monofunctional radical polymerizable compound include: lactam-type vinyl monomers such as N-vinylpyrrolidone, N-vinyl-epsilon-caprolactam and methyl vinyl pyrrolidone; vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinylpyridine

Vinyl monomers having a nitrogen-containing heterocycle such as oxazole and vinyl morpholine.

When the adhesive composition used in the present invention contains a hydroxyl group-containing (meth) acrylate, a carboxyl group-containing (meth) acrylate, a phosphoric group-containing (meth) acrylate, or the like having high polarity among monofunctional radical polymerizable compounds, the adhesive force to various substrates is improved. The content of the hydroxyl group-containing (meth) acrylate is preferably 1 to 30 wt% with respect to the resin composition, and when the content is too large, the water absorption of the cured product becomes high, and the water resistance may deteriorate. The content of the carboxyl group-containing (meth) acrylate is preferably 1 to 20 wt% based on the resin composition, and when the content is too large, the optical durability of the polarizing film is lowered, which is not preferable. The phosphoric group-containing (meth) acrylate includes 2- (meth) acryloyloxyethyl acid phosphate, and the content thereof is preferably 0.1 to 10% by weight based on the resin composition, and when the content is too large, the optical durability of the polarizing film is lowered, which is not preferable.

As the monofunctional radical polymerizable compound, a radical polymerizable compound having an active methylene group can be used. The radical polymerizable compound having an active methylene group is a compound having an active methylene group and an active double bond group such as a (meth) acrylic group at a terminal or in a molecule. Examples of the active methylene group include: acetoacetyl, alkoxymalonyl, cyanoacetyl, or the like. The active methylene group is preferably an acetoacetyl group. Specific examples of the radical polymerizable compound having an active methylene group include: acetoacetoxyethyl alkyl (meth) acrylates such as 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxyethyl propyl (meth) acrylate, and 2-acetoacetoxyethyl-1-methylethyl (meth) acrylate; 2-ethoxymalonyloxyethyl (meth) acrylate, 2-cyanoacetoxyethyl (meth) acrylate, N- (2-cyanoacetoxyethyl) acrylamide, N- (2-propionylacetyloxybutyl) acrylamide, N- (4-acetoacetoxyethylmethylbenzyl) acrylamide, N- (2-acetoacetylaminoethyl) acrylamide and the like. The radical polymerizable compound having an active methylene group is preferably acetoacetoxyethyl (meth) acrylate.

Further, examples of the bifunctional or higher polyfunctional radical polymerizable compound include: n, N' -methylenebis (meth) acrylamide, tripropylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, 1, 10-decanediol diacrylate, 2-ethyl-2-butylpropanediol di (meth) acrylate, bisphenol A ethylene oxide adduct di (meth) acrylate, bisphenol A propylene oxide adduct di (meth) acrylate, bisphenol A diglycidyl ether di (meth) acrylate, neopentyl glycol di (meth) acrylate, tricyclodecane derivativeDimethanol di (meth) Acrylate, Cyclic Trimethylolpropane formal (meth) Acrylate, di (meth) Acrylate

Esters of (meth) acrylic acid and polyhydric alcohol such as alkanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and EO-modified diglycerol tetra (meth) acrylate, and 9, 9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl]Fluorene. As specific examples, ARONIX M-220 (manufactured by Toyo Seisaku-Sho Co., Ltd.), LIGHT ACRYLATE 1,9ND-A (manufactured by Kyowa Kagaku K.K.), LIGHT ACRYLATE DGE-4A (manufactured by Kyowa Kagaku K.K.), LIGHT ACRYLATE DCP-A (manufactured by Kyowa Kagaku K.K.), SR-531 (manufactured by Sartomer Co., Ltd.), CD-536 (manufactured by Sartomer Co., Ltd.) and the like are preferable. Further, as necessary, there may be mentioned: various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, various (meth) acrylate monomers, and the like. The polyfunctional (meth) acrylamide derivative is preferably contained in the adhesive composition because it has a high polymerization rate and excellent productivity and also has excellent crosslinkability when the resin composition is cured.

From the viewpoint of satisfying both of the adhesiveness to polarizers and various transparent protective films and the optical durability under severe environments, it is preferable to use a monofunctional radical polymerizable compound and a polyfunctional radical polymerizable compound in combination as the radical polymerizable compound. In general, it is preferable to use a combination of 3 to 80 wt% of a monofunctional radical polymerizable compound and 20 to 97 wt% of a polyfunctional radical polymerizable compound with respect to 100 wt% of a radical polymerizable compound.

When a curable component is used as the active energy ray-curable component, the adhesive composition used in the present invention can be used as an active energy ray-curable adhesive composition. The active energy ray-curable adhesive composition does not need to contain a photopolymerization initiator when an electron beam or the like is used as an active energy ray, but preferably contains a photopolymerization initiator when ultraviolet rays or visible light is used as an active energy ray. As the photopolymerization initiator, the same photopolymerization initiator as used for forming the durability enhancing layer can be used.

When a radical polymerizable compound having an active methylene group is used as the radical polymerizable compound in the active energy ray-curable adhesive composition, it is preferable to use the radical polymerizable compound in combination with a radical polymerization initiator having a hydrogen abstraction action. According to this configuration, the adhesiveness of the adhesive layer of the polarizing film is significantly improved even immediately after the polarizing film is taken out from a high-humidity environment or from water (in an undried state). The reason is not clear, but is considered to be the following reason. That is, the radical polymerizable compound having an active methylene group is polymerized together with other radical polymerizable compounds constituting the adhesive layer, and enters the main chain and/or side chain of the base polymer in the adhesive layer to form the adhesive layer. In this polymerization process, if a radical polymerization initiator having a hydrogen abstraction action is present, a base polymer constituting the adhesive layer is formed, and hydrogen is abstracted from a radical polymerizable compound having an active methylene group, thereby generating a radical in the methylene group. The methylene group that generates a radical reacts with a hydroxyl group of a polarizer such as PVA to form a covalent bond between the adhesive layer and the polarizer. As a result, it is presumed that the adhesiveness of the adhesive layer of the polarizing film is significantly improved particularly in a non-dried state.

In the present invention, examples of the radical polymerization initiator having a hydrogen abstraction action include: thioxanthone radical polymerization initiators, benzophenone radical polymerization initiators, and the like. The radical polymerization initiator is preferably a thioxanthone radical polymerization initiator. Examples of the thioxanthone-based radical polymerization initiator include compounds represented by the above general formula (3). Specific examples of the compound represented by the general formula (3) include:thioxanthone, dimethylthioxanthone, diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and the like. Among the compounds represented by the general formula (3), R is particularly preferable⁶And R⁷is-CH₂CH₃Diethyl thioxanthone (ll).

When the active energy ray-curable adhesive composition contains a radical polymerizable compound having an active methylene group and a radical polymerization initiator having a hydrogen abstraction action, the total amount of the curable components is preferably 100% by weight, and the radical polymerizable compound having an active methylene group and the radical polymerization initiator are preferably contained in an amount of 1 to 50% by weight and 0.1 to 10% by weight, respectively, based on the total amount of the adhesive composition.

As described above, in the present invention, in the presence of a radical polymerization initiator having a hydrogen abstraction action, a radical is generated from a methylene group of a radical polymerizable compound having an active methylene group, and the methylene group reacts with a hydroxyl group of a polarizer such as PVA to form a covalent bond. Therefore, in order to generate radicals from the methylene group of the radical polymerizable compound having an active methylene group and to form the covalent bond sufficiently, the radical polymerizable compound having an active methylene group is preferably contained in an amount of 1 to 50% by weight, more preferably 3 to 30% by weight, based on 100% by weight of the total amount of the curable components. In order to sufficiently improve the water resistance and the adhesiveness in a non-dried state, it is preferable to set the radical polymerizable compound having an active methylene group to 1% by weight or more. On the other hand, if it exceeds 50 wt%, poor curing of the adhesive layer may occur. The radical polymerization initiator having a hydrogen abstraction action is preferably contained in an amount of 0.1 to 10% by weight, more preferably 0.3 to 9% by weight, based on the total amount of the adhesive composition. In order to sufficiently progress the hydrogen abstraction reaction, it is preferable to use 0.1% by weight or more of a radical polymerization initiator. On the other hand, if it is more than 10% by weight, it may not be completely dissolved in the composition.

The cationically polymerizable compound used in the cationically polymerizable adhesive composition can be classified into a monofunctional cationically polymerizable compound having 1 cationically polymerizable functional group in a molecule and a polyfunctional cationically polymerizable compound having 2 or more cationically polymerizable functional groups in a molecule. Since the monofunctional cationic polymerizable compound has a low liquid viscosity, the liquid viscosity of the resin composition can be reduced by adding the monofunctional cationic polymerizable compound to the resin composition. Further, the monofunctional cationic polymerizable compound often has a functional group that can exhibit various functions, and by containing the monofunctional cationic polymerizable compound in the resin composition, various functions can be exhibited in the resin composition and/or the cured product of the resin composition. The polyfunctional cationic polymerizable compound is preferably contained in the resin composition because it can 3-dimensionally crosslink a cured product of the resin composition. The ratio of the monofunctional cationic polymerizable compound to the polyfunctional cationic polymerizable compound is preferably in the range of 10 to 1000 parts by weight based on 100 parts by weight of the monofunctional cationic polymerizable compound. Examples of the cationically polymerizable functional group include an epoxy group, an oxetane group, and a vinyl ether group. Examples of the compound having an epoxy group include an aliphatic epoxy compound, an alicyclic epoxy compound, and an aromatic epoxy compound, and since the compound has excellent curability and adhesiveness, it is particularly preferable to contain an alicyclic epoxy compound as the cationic polymerization curable adhesive composition of the present invention. Examples of the alicyclic epoxy compound include 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate, caprolactone-modified products of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate, trimethylcaprolactone-modified products, valerolactone-modified products, and the like, and specifically include CELLOXIDE 2021, CELLOXIDE 2021A, CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085 (the above is made by Dailuo Chemical industries Co., Ltd.), Cyracure UVR-6105, Cyracure UVR-6107, Cyracure 30, R-6110 (the above is made by Dow Chemical Japan Ltd.). The cationic polymerization curable adhesive composition of the present invention preferably contains a compound having an oxetanyl group because of its effect of improving curability and reducing the liquid viscosity of the composition. Examples of the oxetanyl group-containing compound include 3-ethyl-3-hydroxymethyloxetane, 1, 4-bis [ (3-ethyl-3-oxetanyl) methoxymethyl ] benzene, 3-ethyl-3- (phenoxymethyl) OXETANE, bis [ (3-ethyl-3-oxetanyl) methyl ] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) OXETANE, novolak OXETANE and the like, and are commercially available as ARON oxolane oxtane OXT-101, ARON oxolane oxtane OXT-121, ARON oxolane oxtane OXT-211, ARON oxolane OXT-221 and ARON oxolane oxtane OXT-212 (available from east asia corporation). The cationic polymerization curable adhesive composition of the present invention preferably contains a compound having a vinyl ether group because of its effect of improving curability and reducing the liquid viscosity of the composition. Examples of the compound having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether, triethylene glycol divinyl ether, cyclohexanedimethanol monovinyl ether, tricyclodecane vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, pentaerythritol-type tetravinyl ether, and the like.

The cationic polymerization curable adhesive composition contains at least 1 compound selected from the compounds having an epoxy group, the compounds having an oxetanyl group and the compounds having a vinyl ether group described above as a curable component, and all of them are cured by cationic polymerization, and therefore a photo cationic polymerization initiator is blended. The photo cation polymerization initiator generates a cation species or lewis acid by irradiation of active energy rays such as visible light, ultraviolet rays, X-rays, electron beams, and the like, thereby initiating a polymerization reaction of an epoxy group or an oxetanyl group. As the photo cation polymerization initiator, a photo acid generator described later can be suitably used. In addition, in the case of using the adhesive composition used in the present invention as the visible light-curable, it is particularly preferable to use a photo cation polymerization initiator having high sensitivity to light of 380nm or more, but since the photo cation polymerization initiator is a compound which usually exhibits maximum absorption in the vicinity of 300nm or a wavelength region shorter than 300nm, by blending a photosensitizer which exhibits maximum absorption in light of a wavelength region longer than that, specifically, longer than 380nm, it is possible to sense light of a wavelength in the vicinity thereof and promote generation of cationic species or acid from the photo cation polymerization initiator. As the photosensitizer, for example: anthracene compounds, pyrene compounds, carbonyl compounds, organic sulfur compounds, sulfides, redox compounds, azo and diazo compounds, halogen compounds, photoreducing pigments, etc., and these may be mixed with 2 or more of them. Particularly, anthracene compounds are preferable because they are excellent in photosensitizing effect, and specific examples thereof include Anthracure UVS-1331 and Anthracure UVS-1221 (manufactured by Kawasaki Kasei Co., Ltd.). The content of the photosensitizer is preferably 0.1 to 5% by weight, more preferably 0.5 to 3% by weight.

The adhesive composition used in the present invention preferably contains the following components in addition to the above components.

The active energy ray-curable adhesive composition used in the present invention may contain an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer, in addition to the curable component of the radical polymerizable compound. When the active energy ray-curable adhesive composition contains the above component, curing shrinkage at the time of curing the composition by irradiation with active energy rays can be reduced, and interface stress between the adhesive and an adherend such as a polarizer and a transparent protective film can be reduced. As a result, the adhesive layer can be prevented from being deteriorated in adhesiveness to the adherend. In order to sufficiently suppress the curing shrinkage of the cured product layer (adhesive layer), the content of the acrylic oligomer is preferably 20% by weight or less, more preferably 15% by weight or less, relative to the total amount of the adhesive composition. When the content of the acrylic oligomer in the adhesive composition is too large, the reaction rate when the composition is irradiated with an active energy ray may be rapidly decreased, and curing may be poor. On the other hand, the acrylic oligomer is preferably contained in an amount of 3 wt% or more, more preferably 5 wt% or more, based on the total amount of the adhesive composition.

In view of workability and uniformity in application, the active energy ray-curable adhesive composition is preferably low in viscosity, and therefore an acrylic oligomer obtained by polymerizing a (meth) acrylic monomer is also preferably low in viscosity. The weight average molecular weight (Mw) of the low-viscosity acrylic oligomer capable of preventing curing shrinkage of the adhesive layer is preferably 15000 or less, more preferably 10000 or less, and particularly preferably 5000 or less. On the other hand, in order to sufficiently suppress cure shrinkage of the cured product layer (adhesive layer), the weight average molecular weight (Mw) of the acrylic oligomer is preferably 500 or more, more preferably 1000 or more, and particularly preferably 1500 or more. Specific examples of the (meth) acrylic monomer constituting the acrylic oligomer include: (meth) acrylic acid (C1-20) alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, 2-methyl-2-nitropropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, tert-pentyl (meth) acrylate, 3-pentyl (meth) acrylate, 2-dimethylbutyl (meth) acrylate, n-hexyl (meth) acrylate, cetyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 4-methyl-2-propylpentyl (meth) acrylate, and n-octadecyl (meth) acrylate, And for example: cycloalkyl (meth) acrylates (e.g., cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, etc.), (aralkyl (meth) acrylates (e.g., benzyl (meth) acrylate, etc.), polycyclic (meth) acrylates (e.g., 2-isobornyl (meth) acrylate, 2-norbornyl methyl (meth) acrylate, 5-norborn-2-ylmethyl (meth) acrylate, 3-methyl-2-norbornyl methyl (meth) acrylate, etc.), hydroxyl-containing (meth) acrylates (e.g., hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2, 3-dihydroxypropylmethylbutyl (meth) acrylate, etc.), alkoxy-or phenoxy-containing (meth) acrylates ((2-methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, etc.), 2-ethoxyethyl (meth) acrylate, 2-methoxymethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, ethylcarbitol (meth) acrylate, phenoxyethyl (meth) acrylate, and the like, epoxy group-containing (meth) acrylates (e.g., glycidyl (meth) acrylate, and the like), halogen-containing (meth) acrylates (e.g., 2,2, 2-trifluoroethyl (meth) acrylate, 2,2, 2-trifluoroethyl ethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, hexafluoropropyl (meth) acrylate, octafluoropentyl (meth) acrylate, heptadecafluorodecyl (meth) acrylate, etc.), alkylaminoalkyl (meth) acrylates (e.g., dimethylaminoethyl (meth) acrylate, etc.), and the like. These (meth) acrylates may be used singly or in combination of 2 or more. Specific examples of the acrylic oligomer include "ARUFON" manufactured by east asia synthetic co., ltd, "ACTFLOW" manufactured by seiko chemical co., ltd, "JONCRYL" manufactured by BASF Japan ltd.

The active energy ray-curable adhesive composition may contain a photoacid generator. When the photoacid generator is contained in the active energy ray-curable adhesive composition, the water resistance and durability of the adhesive layer can be greatly improved as compared with the case where the photoacid generator is not contained. The photoacid generator can be represented by the following general formula (5).

General formula (5)

[ chemical formula 7]

L⁺X^-

(in the formula, L⁺Means of being arbitrary

A cation. In addition, X^-Is selected from PF6₆ ^-、SbF₆ ^-、AsF₆ ^-、SbCl₆ ^-、BiCl₅ ^-、SnCl₆ ^-、ClO₄ ^-Dithiocarbamate anion, SCN^-The counter anion of (1). )

Next, for the counter anion X in the general formula (5)^-The description is given.

In principle on the counter anion X in the general formula (5)^-The anion is not particularly limited, but a non-nucleophilic anion is preferable. When the counter anion X is a non-nucleophilic anion, the counter anion X is not likely to cause intramolecular coexistence of the cation, and nucleophilicity of various materials used in combinationAs a result, the stability of the photoacid generator itself represented by the general formula (4) and the composition using the same over time can be improved. The term "non-nucleophilic anion" as used herein refers to an anion having a low ability to cause nucleophilic reaction. Examples of such anions include: PF (particle Filter)₆ ^-、SbF₆ ^-、AsF₆ ^-、SbCl₆ ^-、BiCl₅ ^-、SnCl₆ ^-、ClO₄ ^-Dithiocarbamate anion, SCN^-And the like.

Specifically, the "CYRACURE UVI-6992", "CYRACURE UVI-6974" (manufactured by Dow chemical Japan Limited, supra), "Adekaoptomer SP 150", "Adekaoptomer SP 152", "Adekaoptomer SP 170", "Adekaoptomer SP 172" (manufactured by Dow chemical Co., Ltd), "IRGACURE 250" (manufactured by Ciba specialty Chemicals Inc.), "CI-5102", "CI-2855" (manufactured by Nippon Soda Co., Ltd), "San-Aid SI-60L", "San-Aid SI-80L", "San-Aid SI-100L", "San-Aid SI-110L", "San-Aid SI-180L" (manufactured by Sanxin Co., Ltd), "CPI-100P" (manufactured by Sanco., Ltd), "WPI-113" WPI-6974 "(manufactured by Sanco., WPI-101L)," WPI-116 WPI-116 "manufactured by Sanxin Corp, Japan", and "WPI-100A" (manufactured by Sanp-100L, manufactured by Sanp-Aid Chemicals Corp Ltd., "WPI-100L", "WPI-113", and "WPI-116, "WPI-044", "WPI-054", "WPI-055", "WPAG-281", "WPAG-567", and "WPAG-596" (both manufactured by Wako pure chemical industries, Ltd.) are preferable examples of the photoacid generator of the present invention.

The content of the photoacid generator is 10 wt% or less, preferably 0.01 to 10 wt%, more preferably 0.05 to 5 wt%, and particularly preferably 0.1 to 3 wt% with respect to the total amount of the adhesive composition.

In the active energy ray-curable adhesive composition, a photoacid generator and a compound containing either an alkoxy group or an epoxy group may be used in combination in the active energy ray-curable adhesive composition.

When a compound having 1 or more epoxy groups in a molecule or a polymer (epoxy resin) having 2 or more epoxy groups in a molecule is used, a compound having two or more functional groups reactive with epoxy groups in a molecule may be used in combination. Among them, examples of the functional group reactive with an epoxy group include: carboxyl, phenolic hydroxyl, mercapto, primary or secondary aromatic amino, and the like. In view of three-dimensional curability, it is particularly preferable to have 2 or more of these functional groups in one molecule.

Examples of the polymer having 1 or more epoxy groups in the molecule include epoxy resins including bisphenol a type epoxy resins derived from bisphenol a and epichlorohydrin, bisphenol F type epoxy resins derived from bisphenol F and epichlorohydrin, bisphenol S type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, bisphenol a novolac type epoxy resins, bisphenol F novolac type epoxy resins, alicyclic epoxy resins, diphenyl ether type epoxy resins, hydroquinone type epoxy resins, naphthalene type epoxy resins, biphenyl type epoxy resins, fluorene type epoxy resins, 3-functional epoxy resins, polyfunctional epoxy resins such as 4-functional epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, hydantoin type epoxy resins, isocyanurate type epoxy resins, aliphatic chain epoxy resins, and the like, these epoxy resins may be halogenated or hydrogenated. Examples of commercially available epoxy resin products include: JER code 828, 1001, 801N, 806, 807, 152, 604, 630, 871, YX8000, YX8034, YX4000, EPICLON830, EXA835LV, HP4032D, HP820, EP4100 series manufactured by ADEKA, EP4000 series, EPU series, Daicel Chemical Industries, CELLOXIDE series (2021, 2021P, 2083, 2085, 3000, etc.) manufactured by Ltd, Epolead series, EHPE series, YD series, YDF series, YDCN series, YDB series, phenoxy resins (polyhydroxy polyethers synthesized from bisphenols and epichlorohydrin and having Epoxy groups at both ends; YP series, etc.) manufactured by Nagamtse Chemicals, Decolon series, Corporation, etc., but not limited thereto. These epoxy resins may be used in combination of 2 or more

The compound having an alkoxy group in the molecule is not particularly limited as long as it has 1 or more alkoxy groups in the molecule, and known compounds can be used. Typical examples of such compounds include melamine compounds, amino resins, and silane coupling agents.

The amount of the compound containing either an alkoxy group or an epoxy group is usually 30% by weight or less based on the total amount of the adhesive composition, and if the content of the compound in the composition is too large, the adhesiveness is lowered and the impact resistance in the drop weight test may be deteriorated. The content of the compound in the composition is more preferably 20% by weight or less. On the other hand, from the viewpoint of water resistance, the compound is preferably contained in the composition in an amount of 2% by weight or more, more preferably 5% by weight or more.

When the adhesive composition used in the present invention is active energy ray-curable, an active energy ray-curable compound is preferably used as the silane coupling agent, but the same water resistance can be provided even if the silane coupling agent is not active energy ray-curable.

As a specific example of the silane coupling agent, the above-exemplified organosilicon compounds can be used.

The amount of the silane coupling agent is preferably in the range of 0.01 to 20 wt%, more preferably 0.05 to 15 wt%, and still more preferably 0.1 to 10 wt% based on the total amount of the adhesive composition. This is because the storage stability of the adhesive composition is deteriorated when the amount is more than 20% by weight, and it is difficult to sufficiently exhibit the effect of the adhesive water resistance when the amount is less than 0.1% by weight.

When the adhesive composition used in the present invention contains a compound having a vinyl ether group, the adhesion between the polarizer and the adhesive layer is preferably improved in water resistance. The reason for obtaining this effect is not clear, but it is presumed that one of the reasons is that the adhesion between the polarizer and the adhesive layer is improved by the interaction between the vinyl ether group of the compound and the polarizer. In order to further improve the water resistance of adhesion between the polarizer and the adhesive layer, the compound is preferably a radical polymerizable compound having a vinyl ether group. The content of the compound is preferably 0.1 to 19 wt% based on the total amount of the adhesive composition.

The adhesive composition used in the present invention may contain a compound that causes keto-enol tautomerism. For example, in an adhesive composition containing a crosslinking agent or an adhesive composition that can be used in combination with a crosslinking agent, a mode including the compound that causes keto-enol tautomerism can be preferably employed. This can suppress excessive viscosity increase, gelation, and formation of a microgel product in the adhesive composition after the organometallic compound is compounded, and can achieve the effect of extending the pot life of the composition.

As the above-mentioned compound which causes keto-enol tautomerism, various β -dicarbonyl compounds can be used. Specific examples thereof include: beta-diketones such as acetylacetone, 2, 4-hexanedione, 3, 5-heptanedione, 2-methylhexane-3, 5-dione, 6-methylheptane-2, 4-dione, and 2, 6-dimethylheptane-3, 5-dione; acetoacetic acid esters such as methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, and tert-butyl acetoacetate; propionyl acetates such as propionyl ethyl acetate, propionyl isopropyl acetate, and propionyl tert-butyl acetate; isobutyryl acetic acid esters such as isobutyryl ethyl acetate, isobutyryl isopropyl acetate, and isobutyryl tert-butyl acetate; malonic esters such as methyl malonate and ethyl malonate; and so on. Among these, acetylacetone and acetoacetates are suitable examples. The above-mentioned keto-enol tautomerism-generating compounds may be used alone, or 2 or more thereof may be used in combination.

The amount of the compound which causes keto-enol tautomerism can be, for example, 0.05 to 10 parts by weight, preferably 0.2 to 3 parts by weight (for example, 0.3 to 2 parts by weight) relative to 1 part by weight of the organometallic compound. If the amount of the above compound is less than 0.05 part by weight based on 1 part by weight of the organometallic compound, it may be difficult to exhibit sufficient effects in use. On the other hand, if the amount of the compound used is more than 10 parts by weight relative to 1 part by weight of the organometallic compound, the compound excessively interacts with the organometallic compound and it may become difficult to exhibit the intended water resistance.

In addition, various additives may be added to the adhesive composition used in the present invention as other optional components within a range not impairing the object and effect of the present invention. Examples of the additive include polymers or oligomers such as epoxy resins, polyamides, polyamideimides, polyurethanes, polybutadienes, polychloroprenes, polyethers, polyesters, styrene-butadiene block copolymers, petroleum resins, xylene resins, ketone resins, cellulose resins, fluorine-based oligomers, silicone-based oligomers, and polythioether-based oligomers; polymerization inhibitors such as phenothiazine and 2, 6-di-tert-butyl-4-methylphenol; a polymerization initiation aid; leveling agent; a wettability modifier; a surfactant; a plasticizer; an ultraviolet absorber; an inorganic filler; a pigment; dyes, and the like.

The additive is usually 0 to 10% by weight, preferably 0 to 5% by weight, and most preferably 0 to 3% by weight, based on the total amount of the adhesive composition.

From the viewpoint of coatability, the viscosity of the adhesive composition used in the present invention is preferably 100cp or less at 25 ℃. On the other hand, when the adhesive composition of the present invention exceeds 100cp at 25 ℃, the temperature of the adhesive composition may be controlled at the time of application and adjusted to 100cp or less. The viscosity is more preferably in the range of 1 to 80cp, most preferably 10 to 50 cp. The viscosity can be measured using an E-type viscometer TVE22LT manufactured by eastern mechanical co.

In addition, from the viewpoint of safety, it is preferable to use a material having low skin irritation as the curable component in the adhesive composition used in the present invention. Skin irritation can be judged by the p.i.i.index. P.i.i. is widely used as an index indicating the degree of skin damage and is measured by the Draize method. The measurement value is represented by a range of 0 to 8, and the smaller the value, the lower the irritation, but the larger the error of the measurement value, so that it is preferable to grasp the value as a reference value. The p.i.i.i. is preferably 4 or less, more preferably 3 or less, and most preferably 2 or less.

< polarizing film >

The polarizing film of the present invention comprises a polarizer, and a durability-enhancing layer comprising a curable composition containing a compound (A) having a carbon-carbon double bond and a cyclic skeleton is provided on at least one surface of the polarizer. In the polarizing film of the present invention, a transparent protective film may be laminated on at least one surface of the polarizer. Further, an adhesive layer is preferably further provided between the durability enhancing layer and the transparent protective film. Hereinafter, a polarizing film further including an adhesive layer between the durability enhancing layer and the transparent protective film will be described as an example.

The polarizing film of the present invention can be produced, for example, by a method for producing a polarizing film comprising:

a first coating step (1) of coating a curable composition containing a compound (A) on the bonding surface of the polarizer to form a durability enhancing layer; a curing step of curing the curable composition constituting the durability-enhancing layer; a second coating step of coating the adhesive composition on the bonding surface of the transparent protective film; a bonding step of bonding the durability-improving layer-forming surface of the polarizer to the adhesive composition-coated surface of the transparent protective film; and an adhesion step of irradiating the polarizer side or the transparent protective film side with an active energy ray to cure the adhesive composition to obtain an adhesive layer, and adhering the polarizer and the transparent protective film via the obtained adhesive layer. An easy adhesion layer forming step of forming an easy adhesion layer on at least one surface of the polarizer may be added before the first coating step 1, and the first coating step 1 of coating the easy adhesion layer forming surface of the polarizer with the curable composition may be performed. Further, before the easy adhesion layer forming step, a treatment step of performing a surface modification treatment on at least one surface of the polarizer may be performed.

The surface modification treatment can be performed not only on the polarizer but also on the transparent protective film. The surface modification treatment includes corona treatment, plasma treatment, and ITRO treatment, and particularly corona treatment is preferable.

The method of applying the adhesive composition to the transparent protective film may be appropriately selected depending on the viscosity of the composition and the target thickness, and examples thereof include: reverse coaters, gravure coaters (direct, reverse, or offset), bar reverse coaters, roll coaters, die coaters, wire wound bar coaters, and the like. The viscosity of the adhesive composition used in the present invention is preferably 3 to 100 mPas, more preferably 5 to 50 mPas, and most preferably 10 to 30 mPas. When the viscosity of the adhesive composition is high, the surface smoothness after application is insufficient, and appearance defects occur, which is not preferable. The adhesive composition used in the present invention may be applied after the composition is heated or cooled to adjust the viscosity to a preferred range.

The polarizer and the transparent protective film are bonded to each other through the adhesive composition applied as described above. The polarizer and the transparent protective film may be bonded to each other by a roll laminator or the like.

The adhesive composition used in the present invention is preferably used in the form of an active energy ray-curable adhesive composition. The active energy ray-curable adhesive composition can be used in an electron beam-curable, ultraviolet-curable, or visible light-curable form. From the viewpoint of productivity, the embodiment of the adhesive composition is preferably a visible light-curable adhesive composition.

The active energy ray-curable adhesive composition is formed by bonding a polarizer and a transparent protective film, and then irradiating the polarizer with active energy rays (e.g., electron beams, ultraviolet rays, visible light, etc.) to cure the active energy ray-curable adhesive composition. The irradiation direction of the active energy ray (electron beam, ultraviolet ray, visible light, etc.) may be any appropriate direction. Irradiation is preferably from the transparent protective film side. If the irradiation is performed from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, visible light, and the like).

In the electron beam curing, any suitable conditions may be employed as long as the irradiation conditions of the electron beam are conditions under which the active energy ray-curable adhesive composition can be cured. For example, the acceleration voltage for electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250 kV. If the acceleration voltage is less than 5kV, the electron beam may not reach the adhesive and may be insufficiently cured, and if the acceleration voltage is more than 300kV, the penetration force through the sample may be too strong and damage may be caused to the transparent protective film and the polarizer. The dose of the radiation is 5 to 100kGy, and more preferably 10 to 75 kGy. When the irradiation dose is less than 5kGy, the adhesive is insufficiently cured, and when it exceeds 100kGy, the transparent protective film and the polarizer are damaged, and the mechanical strength is reduced and the polarizer is yellowed, so that the optical characteristics cannot be obtained.

The electron beam irradiation is usually carried out in an inert gas, and may be carried out in an atmosphere with a small amount of oxygen introduced as required. Oxygen is introduced as appropriate depending on the material of the transparent protective film, and the surface of the transparent protective film which is in contact with the first electron beam is in contact with the oxygen, whereby oxygen inhibition occurs, damage to the transparent protective film can be prevented, and only the adhesive can be efficiently irradiated with an electron beam.

In the method for producing a polarizing film of the present invention, it is preferable to use, as the active energy ray, an active energy ray containing visible light having a wavelength range of 380nm to 450nm, particularly an active energy ray having the largest dose of visible light having a wavelength range of 380nm to 450 nm. In the case of using a transparent protective film (ultraviolet-opaque transparent protective film) having ultraviolet absorptivity for ultraviolet curing or visible light curing, since light having a wavelength shorter than 380nm is absorbed, the light having a wavelength shorter than 380nm does not reach the active energy ray-curable adhesive composition and does not contribute to the polymerization reaction. Further, light having a wavelength shorter than 380nm absorbed by the transparent protective film is converted into heat, and the transparent protective film itself generates heat, which causes defects such as curling and wrinkling of the polarizing film. Therefore, in the present invention, when ultraviolet-curing or visible light-curing is employed, it is preferable to use a device that does not emit light having a wavelength shorter than 380nm as the active energy ray generating device, and more specifically, the ratio of the cumulative illuminance in the wavelength range of 380 to 440nm to the cumulative illuminance in the wavelength range of 250 to 370nm is preferably 100:0 to 100:50, and more preferably 100:0 to 100: 40. As the active energy ray of the present invention, a metal halide lamp in which gallium is sealed, and an LED light source which emits light in a wavelength range of 380 to 440nm are preferable. Alternatively, a light source containing ultraviolet rays and visible light such as a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, an incandescent lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a metal halide lamp, a fluorescent lamp, a tungsten lamp, a gallium lamp, an excimer laser, or sunlight may be used, or ultraviolet rays having a wavelength shorter than 380nm may be blocked by a band-pass filter and used. In order to improve the adhesion performance of the adhesive layer between the polarizer and the transparent protective film and to prevent curling of the polarizing film, it is preferable to use a gallium-sealed metal halide lamp and to use an active energy ray having a wavelength of 405nm obtained by using a band-pass filter capable of blocking light having a wavelength shorter than 380nm or an LED light source.

In the ultraviolet-curable or visible-light-curable property, the active energy ray-curable adhesive composition is preferably heated before irradiation with ultraviolet rays or visible light (heating before irradiation), and in this case, the temperature is preferably heated to 40 ℃ or higher, more preferably 50 ℃ or higher. In addition, it is also preferable to heat the active energy ray-curable adhesive composition after irradiation with ultraviolet rays or visible light (heating after irradiation), and in this case, it is preferable to heat the composition to 40 ℃ or higher, more preferably to 50 ℃ or higher.

The active energy ray-curable adhesive composition used in the present invention can be suitably used in particular for forming an adhesive layer for bonding a polarizer to a transparent protective film having a light transmittance of less than 5% at a wavelength of 365 nm. Here, the active energy ray-curable adhesive composition of the present invention contains the photopolymerization initiator of the general formula (3) and can be cured to form an adhesive layer by irradiating ultraviolet rays through a transparent protective film having UV absorbability. Therefore, even in a polarizing film in which transparent protective films having UV absorbing ability are laminated on both surfaces of a polarizer, the adhesive layer can be cured. Of course, the adhesive layer can be cured also for a polarizing film in which a transparent protective film having no UV absorbing ability is laminated. The transparent protective film having UV absorption ability means a transparent protective film having a transmittance of light of 380nm of less than 10%.

Examples of the method for imparting UV absorption capability to the transparent protective film include: a method of incorporating an ultraviolet absorber into a transparent protective film, and a method of laminating a surface treatment layer containing an ultraviolet absorber on the surface of a transparent protective film.

Specific examples of the ultraviolet absorber include: conventionally known oxybenzophenone compounds, benzotriazole compounds, salicylate compounds, benzophenone compounds, cyanoacrylate compounds, nickel complex salt compounds, triazine compounds, and the like.

After the polarizer and the transparent protective film are bonded, the active energy ray (e.g., electron beam, ultraviolet ray, visible light, etc.) is irradiated to cure the active energy ray-curable adhesive composition, thereby forming an adhesive layer. The irradiation direction of the active energy ray (electron beam, ultraviolet ray, visible light, etc.) may be from any appropriate direction. Irradiation is preferably from the transparent protective film side. If the irradiation is performed from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, visible light, and the like).

When the polarizing film of the present invention is produced by a continuous production line, the line speed varies depending on the curing time of the adhesive composition, and is preferably 1 to 500m/min, more preferably 5 to 300m/min, and still more preferably 10 to 100 m/min. When the linear velocity is too low, productivity is insufficient, or damage to the transparent protective film is too large, and a polarizing film that can withstand a durability test or the like cannot be produced. When the line speed is too high, the curing of the adhesive composition may be insufficient, and the desired adhesiveness may not be obtained.

In the polarizing film of the present invention, the polarizer and the transparent protective film may be suitably bonded together via an adhesive layer formed of a cured product layer of the active energy ray-curable adhesive composition, but a 2 nd easy-adhesion layer may be provided between the transparent protective film and the adhesive layer. The 2 nd easy-adhesion layer may be formed of various resins having, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone skeleton, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like. These polymer resins may be used singly or in combination of 2 or more. In addition, other additives may be added when forming the 2 nd easy-adhesion layer. Specifically, a thickener, an ultraviolet absorber, an antioxidant, a stabilizer such as a heat stabilizer, and the like can be further used.

In general, the 2 nd easy-adhesion layer is provided in advance on the transparent protective film, and the polarizer and the 2 nd easy-adhesion layer side of the transparent protective film are bonded together with an adhesive layer interposed therebetween. The formation of the 2 nd easy adhesion layer may be performed as follows: the material for forming the 2 nd easy-adhesion layer is applied to the transparent protective film by a known technique and dried. The material for forming the 2 nd easy-adhesion layer is usually prepared as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of application, and the like. The thickness of the 2 nd easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and further preferably 0.05 to 1 μm. In this case, too, it is preferable that the total thickness of the 2 nd easy-adhesion layer is within the above range.

< transparent protective film >

The transparent protective film is preferably excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like. Examples thereof include: polyester polymers such AS polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such AS cellulose diacetate and cellulose triacetate, acrylic polymers such AS polymethyl methacrylate, styrene polymers such AS polystyrene and acrylonitrile-styrene copolymer (AS resin), and polycarbonate polymers. Further, polyethylene, polypropylene, polyolefin having a cyclic or norbornene structure, polyolefin polymer such as ethylene-propylene copolymer, vinyl chloride polymer, polyamide polymer such as nylon and aromatic polyamide, imide polymer, sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, polyaryl ester polymer, polyacetal polymer, epoxy polymer, or a mixture of the above polymers may be cited as examples of the polymer forming the transparent protective film. The transparent protective film may contain 1 or more kinds of any appropriate additives. Examples of additives include: ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50 wt% or less, there is a fear that high transparency and the like originally possessed by the thermoplastic resin cannot be sufficiently expressed.

Further, as the transparent protective film, there can be mentioned a polymer film described in Japanese patent laid-open No. 2001-343529 (WO01/37007), for example, a resin composition containing (A) a thermoplastic resin having a substituted and/or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitrile group in a side chain. Specifically, a film of a resin composition containing an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer is exemplified. As the film, a film formed from a mixed extrusion of a resin composition or the like can be used. These films have a small phase difference and a small photoelastic coefficient, and therefore can eliminate problems such as unevenness due to strain of the polarizing film, and have a small moisture permeability, and therefore have excellent humidification durability.

In the polarizing film, the transparent protective film preferably has a moisture permeability of 150g/m²The time is less than 24 h. According to this configuration, moisture in the air is less likely to enter the polarizing film, and a change in the moisture percentage of the polarizing film itself can be suppressed. As a result, curling and dimensional change of the polarizing film due to storage environment can be suppressed.

The transparent protective film provided on one or both surfaces of the polarizer is preferably a transparent protective film excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like, and particularly, the moisture permeability is more preferably 150g/m²Less than 24h, particularly preferably 120g/m²A time of 24 hours or less, preferably 5 to 70g/m²The time is less than 24 h. The moisture permeability was determined by the method described in examples.

As a material for forming the transparent protective film satisfying the low moisture permeability, for example, polyester resins such as polyethylene terephthalate and polyethylene naphthalate; a polycarbonate resin; a polyarylate resin; amide resins such as nylon and aromatic polyamide; polyolefin polymers such as polyethylene, polypropylene and ethylene-propylene copolymers, cyclic olefin resins having a cyclic or norbornene structure, (meth) acrylic resins, or mixtures thereof. Among the above resins, polycarbonate-based resins, cyclic polyolefin-based resins, and (meth) acrylic resins are preferable, and cyclic polyolefin-based resins and (meth) acrylic resins are particularly preferable.

The thickness of the transparent protective film may be suitably determined, and is generally preferably 5 to 100 μm, particularly preferably 10 to 60 μm, and more preferably 13 to 40 μm in view of strength, handling properties such as handling properties, and thin layer properties.

The polarizer and the protective film may be bonded to each other by a roll laminator. The method of laminating the protective films on both surfaces of the polarizer may be selected from a method of bonding a polarizer and 1 protective film and then further bonding another protective film 1, and a method of simultaneously bonding a polarizer and 2 protective films. The former method, i.e., a method of bonding a polarizer and 1 protective film and then further bonding another 1 protective film is preferable because inclusion of bubbles generated during bonding can be significantly reduced.

< optical film >

The polarizing film of the present invention can be practically used as an optical film laminated with another optical layer. The optical layer is not particularly limited, and examples thereof include optical layers used in the formation of liquid crystal display devices and the like, such as retardation films (including wave plates such as 1/2-wave plates and 1/4-wave plates), optical compensation films, brightness enhancement films, reflection plates, and reflection/transmission plates. These optical layers can be used in the present invention in the form of a base film with an easy-adhesion layer, and if necessary, can be subjected to surface modification treatment to have reactive functional groups such as hydroxyl groups, carbonyl groups, and amino groups. Therefore, an easy adhesion treatment retardation film comprising a compound represented by the above general formula (1) on at least one surface of a retardation film having at least a reactive functional group on the surface thereof, particularly a retardation film with an easy adhesion layer having an easy adhesion layer formed thereon and containing a compound represented by the above general formula (1), is preferable because the adhesiveness between the retardation film and the adhesive layer can be improved, and as a result, the adhesiveness is particularly improved.

As the retardation film, a retardation film having a front retardation of 40nm or more and/or a thickness direction retardation of 80nm or more can be used. The front retardation is usually controlled to be in the range of 40 to 200nm, and the thickness direction retardation is usually controlled to be in the range of 80 to 300 nm.

As the phase difference plate, there are: birefringent films obtained by uniaxially or biaxially stretching a polymer material, alignment films of liquid crystal polymers, retardation plates obtained by supporting alignment layers of liquid crystal polymers with films, and the like. The thickness of the retardation film is not particularly limited, and is generally about 20 to 150 μm.

As the retardation film, a reverse wavelength dispersion type retardation film satisfying the following formulas (1) to (3) can be used:

0.70＜Re[450]/Re[550]＜0.97···(1)

1.5×10^-3＜Δn＜6×10^-3···(2)

1.13＜NZ＜1.50···(3)

(wherein Re 450 and Re 550 are in-plane retardation values of the retardation film measured by light having wavelengths of 450nm and 550nm at 23 ℃, respectively; Δ n is in-plane birefringence, nx-ny, where nx-NZ is the thickness-direction birefringence and nx-ny, where NZ is the thickness-direction refractive index of the retardation film, and NZ is the ratio of nx-NZ to nx-ny, where nx-NZ is the thickness-direction birefringence, and nx-ny is the in-plane birefringence) where the refractive indices of the retardation film in the slow axis direction and the fast axis direction are nx and ny, respectively).

The polarizing film or the optical film having at least 1 polarizing film laminated thereon may be provided with an adhesive layer for adhesion to other members such as a liquid crystal cell. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a pressure-sensitive adhesive using a polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine polymer, or a rubber as a base polymer can be suitably selected and used. In particular, an acrylic pressure-sensitive adhesive which is excellent in optical transparency, exhibits appropriate adhesive properties such as wettability, cohesiveness and adhesiveness, and is excellent in weather resistance and heat resistance can be preferably used.

The adhesive layer may be provided on one side or both sides of the polarizing film or the optical film in the form of a laminated layer of layers of different compositions, kinds, or the like. In addition, when the polarizing film and the optical film are provided on both surfaces, adhesive layers having different compositions, kinds, thicknesses, and the like may be formed on the front and back surfaces of the polarizing film and the optical film. The thickness of the adhesive layer may be suitably determined depending on the purpose of use, adhesion, etc., and is usually 1 to 500. mu.m, preferably 1 to 200. mu.m, and particularly preferably 1 to 100. mu.m.

The exposed surface of the adhesive layer is temporarily covered with a separator by adhesion for the purpose of preventing contamination and the like until the adhesive layer is actually used. This prevents contact with the adhesive layer in a normal processing state. As the separator, a conventionally specified suitable separator such as a separator obtained by coating a suitable thin layer body such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, a net, a foamed sheet, a metal foil, or a laminate thereof with a suitable release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, if necessary, can be used in addition to the above thickness conditions.

< image display apparatus >

The polarizing film or optical film of the present invention can be preferably used for formation of various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to a conventional method. That is, the liquid crystal display device is generally formed by appropriately assembling a liquid crystal cell with a polarizing film or an optical film and, if necessary, components such as an illumination system, and incorporating a driver circuit, and the like. As the liquid crystal cell, any type of liquid crystal cell such as TN type, STN type, pi type, or the like can be used.

A suitable liquid crystal display device such as a liquid crystal display device in which a polarizing film or an optical film is disposed on one side or both sides of a liquid crystal cell, a liquid crystal display device using a backlight or a reflector in an illumination system, or the like can be formed. In this case, the polarizing film or the optical film of the present invention may be disposed on one side or both sides of the liquid crystal cell. In the case where a polarizing film or an optical film is provided on both sides, they may be the same or different. Further, in the formation of the liquid crystal display device, appropriate members such as a diffusion plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, and a backlight may be disposed in appropriate positions in 1 layer or 2 layers or more.

Examples

Examples of the present invention are described below, but the embodiments of the present invention are not limited to these examples.

< polarizer >

First, a laminate having a 9 μm-thick PVA layer formed on an amorphous PET substrate was subjected to auxiliary stretching at a stretching temperature of 130 ℃ in a gas atmosphere to form a stretched laminate, and then the stretched laminate was dyed to form a colored laminate, and the colored laminate was further stretched in an aqueous boric acid solution at a stretching temperature of 65 ℃ so that the total stretching ratio was 5.94 times, thereby forming an optical film laminate including a 5 μm-thick PVA layer. By such 2-step stretching, an optical film laminate comprising a PVA layer having a thickness of 5 μm, which constitutes a thin polarizer in which the PVA molecules of the PVA layer formed on the amorphous PET substrate are highly oriented and iodine adsorbed by dyeing is highly oriented in one direction in the form of a polyiodide complex, can be obtained.

< transparent protective film >

100 parts by weight of the imidized MS resin described in production example 1 of JP-A-2010-284840 and 0.62 parts by weight of a triazine-based ultraviolet absorber (product name: T-712, manufactured by ADEKA) were mixed at 220 ℃ by means of a twin-screw kneader to prepare resin pellets. The obtained resin pellets were dried at 100.5kPa and 100 ℃ for 12 hours, extruded from a T-die by a single-screw extruder at a die temperature of 270 ℃ and molded into a film shape (thickness: 160 μm). Further transporting the film along the direction of its transportStretching in an atmosphere of 150 ℃ (thickness 80 μm), then coating with an easy-adhesive agent containing a water-based urethane resin, and stretching in a direction perpendicular to the film conveying direction in an atmosphere of 150 ℃ to obtain a film with a thickness of 40 μm (moisture permeability 58 g/m)²24 h).

< active energy ray >

As the active energy ray, a visible light (metal halide lamp in which gallium is sealed) irradiation device was used: fusion uv systems, inc. Light HAMMER10, valve: v valve, peak illuminance: 1600mW/cm²Cumulative dose of radiation 1000/mJ/cm²(wavelength 380-440 nm). The illuminance of visible light was measured by using the Sola-Check system manufactured by Solatell corporation.

(titration test of Compound (A))

As compound (a), γ -butyrolactone acrylate (GBLA) was selected and subjected to a titration test, whereby it was confirmed that GBLA showed a similar buffering action. As shown in table 1, when 0.1M _ NaOH aqueous solution was added dropwise to a 0.1M _ GBLA aqueous solution adjusted to 60 ℃, and the pH rise was measured, even when 50.2g (0.5 eq) of the 0.1M _ NaOH aqueous solution was added dropwise, the pH increased by only 2.5 as compared to before the addition.

From the results of this titration experiment, it can be understood that GBLA shows a similar buffering effect.

(preparation of curable composition)

An adhesive composition containing 3 parts by weight of IRGACURE907 (polymerization initiator, manufactured by BASF) and 3% by weight of KAYACURE DETX-S (polymerization initiator, manufactured by Nippon Kayaku Co., Ltd.) was prepared based on 100 parts by weight of GBLA.

(preparation of easy-adhesion composition)

An easy-adhesion composition was prepared which contained 5.1 parts by weight of acryloylmorpholine, 0.2 parts by weight of Olfine EXP4200 (manufactured by rixin chemical) and 87.9 parts by weight of pure water, based on 6.9 parts by weight of a 15% by weight isopropyl alcohol solution of 4-vinylphenylboronic acid.

< polarizer with easy adhesion layer >

The easy-adhesion composition was applied to the PVA surface of the optical film laminate comprising a PVA layer having a thickness of 5 μm of the polarizer using a wire bar (No. 2, manufactured by first chemical and physical Co., Ltd.), and the solvent was removed by hot air drying at 60 ℃ for 2 minutes, thereby producing a polarizer with an easy-adhesion layer.

(preparation of adhesive composition)

An adhesive composition containing 3 parts by weight of IRGACURE907 (polymerization initiator, manufactured by BASF) and 3% by weight of KAYACURE DETX-S (polymerization initiator, manufactured by Nippon Kayaku Co., Ltd.) was prepared based on 100 parts by weight of 1, 9-nonanediol diacrylate (manufactured by Kyoeisha Co., Ltd.).

(preparation of polarizing film)

Example 1

The curable composition was applied to the easy-adhesion layer surface side of the polarizer with the easy-adhesion layer using an MCD coater (manufactured by Fuji mechanical Co., Ltd.) (cell shape: number of honeycomb and gravure rolls: 1000 pieces/inch, rotation speed: 140%/pair line speed) to a thickness of 0.7 μm, thereby forming a durability improving layer. Next, a transparent protective film was laminated on the durability-improved layer side of the polarizer by using a roller machine. Then, the above-mentioned visible light was irradiated from the side of the transparent protective film to which the polarizer was bonded with an active energy ray irradiation device, the curable composition constituting the durability-enhancing layer was cured, the polarizer and the transparent protective film were bonded, and then the transparent protective film was dried with hot air at 70 ℃ for 3 minutes, and the amorphous PET substrate laminated on the other side of the polarizer was peeled off and removed, thereby obtaining a polarizing film having a transparent protective film on one side of the polarizer. The lamination was carried out at a line speed of 25 m/min.

Example 2

The curable composition was applied to the easy-adhesion layer surface side of the polarizer with the easy-adhesion layer using an MCD coater (manufactured by Fuji mechanical Co., Ltd.) (cell shape: number of honeycomb and gravure rolls: 1000 pieces/inch, rotation speed: 140%/pair line speed) to a thickness of 0.7 μm, thereby forming a durability improving layer. Next, a polyester film (manufactured by DIAFOIL S-10038 μm Mitsubishi chemical) was laminated on the durability-improving layer side of the polarizer by using a roll machine. Then, the curable composition constituting the durability enhancing layer is cured by irradiating the bonded polyester film with the visible light from the side of the polyester film with an active energy ray irradiation device. Subsequently, the polyester film was peeled off. The adhesive composition was applied to the bonding surface of the transparent protective film to a thickness of 0.7 μm using an MCD coater (manufactured by Fuji mechanical Co., Ltd.) (cell shape: number of honeycomb and gravure rolls: 1000, rotation speed: 140%/pair line speed), and the durability-improving layer-forming surface of the polarizer was bonded to the adhesive composition-applied surface of the transparent protective film using a roll coater. Then, the above visible light was irradiated from the side of the transparent protective film to be bonded by an active energy ray irradiation apparatus to cure the adhesive composition constituting the adhesive layer, followed by hot air drying at 70 ℃ for 3 minutes to peel off and remove the amorphous PET substrate laminated on the other side of the polarizer, thereby obtaining a polarizing film having a transparent protective film on one side of the polarizer. The lamination was carried out at a line speed of 25 m/min.

Example 3

The curable composition was applied to the easy-adhesion layer surface side of the polarizer with the easy-adhesion layer using an MCD coater (manufactured by Fuji mechanical Co., Ltd.) (cell shape: number of honeycomb and gravure rolls: 1000 pieces/inch, rotation speed: 140%/pair line speed) to a thickness of 0.7 μm, thereby forming a durability-improving layer. Next, a polyester film (manufactured by DIAFOIL S-10038 μm Mitsubishi chemical) was laminated on the durability-improving layer side of the polarizer by using a roll machine. Then, the curable composition constituting the durability enhancing layer is cured by irradiating the bonded polyester film with the visible light from the side of the polyester film with an active energy ray irradiation apparatus. Next, the polyester film was peeled off to obtain a polarizing film including a polarizer having a durability-enhancing layer on one surface.

Comparative example 1

A polarizing film was produced in the same manner as in example 2, except that a polarizer having no durability-enhancing layer was used as the polarizer.

Comparative example 2

A polarizing film including a polarizer having an adhesive layer on one surface thereof was obtained in the same manner as in example 2, except that an adhesive composition was applied instead of the curable composition.

The polarizing films obtained in the above examples and comparative examples were subjected to the following evaluations, and the evaluation results are shown in table 1.

(humidification durability test)

The transmittance and the degree of polarization of the produced polarizing film were measured using a spectral transmittance measuring instrument with an integrating sphere (Dot-3 c, institute of color technology, village). The degree of polarization P is determined by applying the transmittance (parallel transmittance: Tp) when 2 sheets of the same polarizing films are stacked so that the transmission axes thereof are parallel to each other and the transmittance (orthogonal transmittance: Tc) when the two polarizing films are stacked so that the transmission axes thereof are orthogonal to each other to the following equation.

Polarization degree P (%) { (Tp-Tc)/(Tp + Tc) }^1/2×100

Each transmittance is a transmittance represented by a Y value measured in a 2-degree field of view (C light source) according to JIS Z8701 and corrected in visibility, assuming that the fully polarized light transmitted through the glan-taylor prism polarizer is 100%. The polarizing plate surface of the polarizing film was subjected to corona treatment, an acrylic adhesive having a thickness of 20 μm was attached, the other surface of the acrylic adhesive was attached to alkali-free glass, and the initial values of the degree of polarization P and the transmittance defined above were measured. Then, the polarizing film with glass was placed in an atmosphere of 60 ℃ and 95% RH for 48 hours, and the degree of polarization of the polarizing film with glass over time was measured. The change in the degree of polarization is defined as a value obtained by subtracting the initial degree of polarization P from the degree of polarization P after the lapse of time.

The smaller the absolute value of the change in the degree of polarization, the more excellent the humidification durability.

Claims (10)

1. A polarizer having a durability-enhancing layer on at least one surface,

the durability-enhancing layer is formed from a curable composition containing a compound (A) which has a pH increase of 3.0 or less in a titration test at 60 ℃ even when a basic component is added in an amount of 0.5 equivalent.

2. A polarizer according to claim 1,

the compound (A) is gamma-butyrolactone (methyl) acrylate.

3. Polarizer according to claim 1 or 2,

at least a part of the compound (A) contained in the curable composition is polymerized.

4. A polarizer according to any of claims 1 to 3,

the curable composition further contains a polymerization initiator.

5. A polarizer according to claim 4,

the durability-enhancing layer is formed from a cured product layer of the curable composition.

6. A polarizing film comprising the polarizer according to any one of claims 1 to 5.

7. The polarizing film of claim 6,

a transparent protective film is laminated on at least one surface of the polarizer,

the transparent protective film is laminated on the durability-improving layer side of the polarizer.

8. The polarizing film of claim 7,

an adhesive layer is further provided between the durability enhancing layer and the transparent protective film.

9. An optical film comprising at least 1 polarizing film according to any one of claims 6 to 8 laminated thereon.

10. An image display device using the polarizing film according to any one of claims 6 to 8 or the optical film according to claim 8.