JP7399807B2 - Polarizing film, laminated polarizing film, image display panel, and image display device - Google Patents

Description

The present invention relates to a polarizing film, a laminated polarizing film, an image display panel, and an image display device.

Conventionally, polarizing films used in various image display devices such as liquid crystal display devices and organic EL display devices have been dyed (using iodine, dichroic dyes, etc.) because they have both high transmittance and high degree of polarization. A polyvinyl alcohol film (containing a dichroic substance) is used. The polarizing film is manufactured by subjecting a polyvinyl alcohol film to various treatments such as swelling, dyeing, crosslinking, and stretching in a bath, followed by washing and drying. Further, the polarizing film is usually used as a polarizing film (polarizing plate) in which a protective film such as triacetyl cellulose is bonded to one or both sides of the polarizing film using an adhesive.

The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as necessary, and the polarizing film or the laminated polarizing film (optical laminate) is used as a liquid crystal cell or an organic EL element. etc., and a front transparent member such as a front transparent plate (window layer) or a touch panel on the viewing side through an adhesive layer or an adhesive layer, and can be used as the various image display devices mentioned above. used.

In recent years, the applications of these types of image display devices have been expanding, such as being used not only for mobile devices such as mobile phones and tablet terminals, but also for in-vehicle image display devices such as car navigation devices and rear view monitors. There is. Along with this, the polarizing film and the laminated polarizing film are required to have higher durability under harsher environments (e.g., high temperature environments) than was previously required. A polarizing film for the purpose of ensuring this has been proposed (Patent Document 1).

In addition, dye-based polarizing films that use dichroic dyes such as azo compounds generally require higher temperatures and It is known that the light resistance under high humidity conditions is excellent (Patent Document 2). It has been disclosed that the adhesive used contains a hindered amine compound (Patent Document 3).

Further, in order to improve the heat resistance of a polarizing plate, it is specifically disclosed that a water-insoluble HALS (Hindered Amine Light Stabilizer) is added to an adhesive containing an epoxy compound (Patent Document 4). .

Special Publication No. 2012-516468 Japanese Patent Application Publication No. 2001-240762 Japanese Patent Application Publication No. 2005-338343 Korean Patent Application Publication No. 10-2015-0114149

On the other hand, as mentioned above, polarizing films and laminated polarizing films using iodine-based polarizing films, which are said to have inferior light resistance under high-temperature and high-humidity conditions than dyed-based polarizing films, are Another problem is that the polarizing film becomes colored and its single transmittance decreases. In particular, an image display device constructed by laminating the above-mentioned polarizing film or laminated polarizing film between an image display cell and a front transparent member via an adhesive layer or an adhesive layer is suitable for coloring the polarizing film. There was a problem in that there was a significant decrease in single transmittance.

In view of the above circumstances, an object of the present invention is to provide a polarizing film that is excellent in suppressing a decrease in single transmittance due to coloring of the polarizing film in a high-temperature environment.

Another object of the present invention is to provide a polarizing film, a laminated polarizing film, an image display panel, and an image display device that are excellent in suppressing the reduction in unit transmittance due to coloring of the polarizing film.

That is, the present invention provides a polarizing film in which a transparent protective film is bonded to at least one surface of a polarizing film via an adhesive layer, the polarizing film being formed by adsorbing and orienting iodine to a polyvinyl alcohol film. The adhesive layer includes a hindered amine compound, and the hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C.

The present invention also relates to a laminated polarizing film in which the polarizing film is bonded to an optical layer.

The present invention also relates to an image display panel in which the polarizing film or the laminated polarizing film is bonded to an image display cell.

The present invention also relates to an image display device including a front transparent member on the polarizing film or laminated polarizing film side of the image display panel.

Although the details of the working mechanism of the effect in the polarizing film of the present invention are partially unknown, it is estimated as follows. However, the present invention does not need to be interpreted as being limited to this mechanism of action.

In the polarizing film of the present invention, a transparent protective film is bonded to at least one surface of the polarizing film via an adhesive layer, and the adhesive layer is dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. Contains water-soluble hindered amine compounds. Further, the polarizing film is formed by adsorbing and aligning iodine on a polyvinyl alcohol film. As described in Patent Documents 2 and 3 above, it is said that iodine-based polarizing films are generally inferior to dye-based polarizing films in terms of durability such as heat resistance. It is assumed that this is because the iodine contained in the polyvinyl alcohol accelerates the deterioration phenomenon called polyenation, which occurs due to the dehydration reaction of polyvinyl alcohol in a high-temperature environment.

On the other hand, when the water-soluble hindered amine compound contained in the adhesive layer of the present invention is exposed to a high temperature environment, a part of the hindered amine compound is eluted from the adhesive layer and comes close to the adhesive layer. It is estimated that the iodine-based polarizing film seeps into the iodine-based polarizing film. In particular, in an image display device configured by providing a front transparent member, the polarizing film, and an image display cell in this order, the hindered amine compound contained in the adhesive layer, when exposed to a high temperature environment, A part of the hindered amine compound tends to seep into the iodine-based polarizing film because it moves (remains) inside the image display device along with the moisture present inside (the moisture present in the adhesive layer, adhesive layer, etc.). It is estimated that As a result, it is estimated that the hindered amine compound in the polarizing film can efficiently capture the radicals generated in the above-mentioned polyenization reaction in a high-temperature environment. It is possible to suppress the decline in the rate.

<Hindered amine compound>
The hindered amine compound of the present invention is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. The hindered amine compounds may be used alone or in combination of two or more.

The hindered amine compound is used in an amount of 2 parts by weight per 100 parts by weight of water at 25°C, from the viewpoint that a part of the hindered amine compound is easily eluted from the adhesive layer and seeps into the iodine polarizing film adjacent to the adhesive layer. It is preferable that it can be dissolved in parts by weight or more, and more preferably 5 parts by weight or more can be dissolved in 100 parts by weight of water at 25°C.

In addition, the molecular weight of the hindered amine compound is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of efficiently capturing radicals generated in the polyenation reaction. preferable.

（一般式（１）中、Ｒ^１は、オキシラジカル、水素原子、ヒドロキシ基、または炭素原子数が１～３０のアルキル基、ヒドロキシアルキル基、ヒドロキシアルコキシ基、もしくはアルコキシ基を表し、Ｒ^２からＲ^５は、独立して、水素原子、または炭素原子数が１～１０のアルキル基を表し、ｎは０または１を表す。）なお、一般式（１）中の、点線部の左は任意の有機基を示す。 The hindered amine compound of the present invention is a secondary amine or tertiary amine in which the carbon adjacent to the amino group is substituted with an alkyl group to sterically protect the amino group, and includes, for example, an organic group having the following structure. Examples include compounds having the following. Note that the exemplified compounds may include structures that cannot be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C. It can be immediately confirmed whether 1 part by weight or more can be dissolved in 100 parts by weight of water at 25°C.

(In general formula (1), R ¹ represents an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group, a hydroxyalkoxy group, or an alkoxy group, and from R ² R ⁵ independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n represents 0 or 1.) In general formula (1), the part to the left of the dotted line is optional. represents an organic group.

The hindered amine compound is a known compound, and is described, for example, in columns 5 to 11 of US Pat. No. 4,619,956 and columns 3 to 5 of US Pat. No. 4,839,405. 2,2,6,6-tetraalkylpiperidine compounds, or acid addition salts thereof or complexes thereof with metal compounds, such as those described above.

（一般式（２）中、Ｒ^１は、オキシラジカル、水素原子、ヒドロキシ基、または炭素原子数が１～３０のアルキル基、ヒドロキシアルキル基、ヒドロキシアルコキシ基、もしくはアルコキシ基を表し、Ｒ^２からＲ^５は、独立して、水素原子、または炭素原子数が１～１０のアルキル基を表し、Ｒ^６は水素原子、または炭素原子数が１～１０のアルキル基、アシル基、もしくはアリール基を表し、ｎは０または１を表す。）

（一般式（３）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^７およびＲ^８は、独立して、水素原子、または炭素原子数が１～１０のアルキル基、アシル基、もしくはアリール基を表す。）

（一般式（４）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^９からＲ^１１は、独立して、水素原子、または炭素原子数が１～１０のアルキル基、アシル基、アミノ基、アルコキシ基、ヒドロキシ基、もしくはアリール基を表す。）

（一般式（５）中、Ｒ^１からＲ^５、およびｎは、上記と同様であり、Ｒ^１２は、水素原子、または炭素原子数が１～１０のアルキル基、アミノ基、アルコキシ基、ヒドロキシ基、もしくはアリール基を表す。） Examples of the compound having the above organic group include compounds represented by the following general formulas (2) to (5).

(In general formula (2), R ¹ represents an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group having 1 to 30 carbon atoms, a hydroxyalkyl group, a hydroxyalkoxy group, or an alkoxy group, and from R ² R ⁵ independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R ⁶ independently represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms. (n represents 0 or 1.)

(In general formula (3), R ¹ to R ⁵ and n are the same as above, and R ⁷ and R ⁸ are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, (Represents an acyl group or an aryl group.)

(In general formula (4), R ¹ to R ⁵ and n are the same as above, and R ⁹ to R ¹¹ are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, Represents an acyl group, amino group, alkoxy group, hydroxy group, or aryl group.)

(In general formula (5), R ¹ to R ⁵ and n are the same as above, and R ¹² is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxy group or aryl group)

In the general formulas (1) to (5), R ¹ is preferably an oxy radical, a hydrogen atom, a hydroxy group, or an alkyl group, from the viewpoint of efficiently suppressing accelerated deterioration of polyvinyl alcohol; It is more preferable that Furthermore, in the general formulas (1) to (5), R ² to R ⁵ are preferably alkyl groups having 1 to 6 carbon atoms from the viewpoint of availability and water solubility; is more preferably 1 to 3 alkyl groups. In addition, in the general formula (2), from the viewpoint of availability and water solubility, R ⁶ is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. preferable. Furthermore, in the general formula (3), from the viewpoint of availability and water solubility, R ⁷ and R ⁸ are preferably independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; More preferably, it is an atom. Furthermore, in the general formula (4), from the viewpoint of availability and water solubility, R ⁹ to R ¹¹ are preferably hydrogen atoms or alkyl groups having 1 to 10 carbon atoms. Furthermore, in the general formula (5), from the viewpoint of availability and water solubility, R ¹² is preferably a hydroxy group, an amino group, or an alkoxy group. In the general formulas (1) to (5), n is preferably 1 from the viewpoint of availability.

<Polarizing film>
In the polarizing film of the present invention, a transparent protective film is bonded to at least one surface of the polarizing film via an adhesive layer, and the polarizing film is formed by adsorbing and aligning iodine to a polyvinyl alcohol film. , the adhesive layer includes the hindered amine compound.

<Polarizing film>
The polarizing film of the present invention is formed by adsorbing and aligning iodine on a polyvinyl alcohol film. The polyvinyl alcohol (PVA) film has transparency in the visible light region and can disperse and adsorb iodine, and can be used without particular limitation. Further, the thickness of the PVA film used as the original film is preferably about 1 to 100 μm, more preferably about 1 to 50 μm.

Examples of the material for the polyvinyl alcohol film include polyvinyl alcohol or derivatives thereof. Examples of the polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and those modified with their alkyl esters, acrylamide, etc. can be mentioned. The average degree of polymerization of the polyvinyl alcohol is preferably about 100 to 10,000, more preferably about 1,000 to 10,000, and even more preferably about 1,500 to 4,500. . Further, the saponification degree of the polyvinyl alcohol is preferably about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol%. In addition, the said average polymerization degree and the said saponification degree can be calculated|required according to JISK6726.

The content of iodine in the polarizing film is preferably 1% by weight or more and 15% by weight or less. In the polarizing film, the iodine content is preferably 1.5% by weight or more, more preferably 2% by weight or more, from the viewpoint of suppressing color fading during a durability test, and From the viewpoint of preventing polyenization, the content is preferably 12% by weight or less, more preferably 10% by weight or less.

The polarizing film can be produced, for example, by dyeing the polyvinyl alcohol film by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. If necessary, it can also be immersed in an aqueous solution of boric acid, potassium iodide, or the like. Furthermore, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. Washing a polyvinyl alcohol film with water not only removes dirt and anti-blocking agents from the surface of the polyvinyl alcohol film, but also swells the polyvinyl alcohol film to prevent uneven dyeing and other unevenness. be. Stretching may be carried out after dyeing with iodine, stretching may be carried out while dyeing, or stretching may be carried out before dyeing with iodine. Stretching can be performed in an aqueous solution of boric acid, potassium iodide, etc. or in a water bath.

The thickness of the polarizing film is preferably about 1 to 50 μm, more preferably about 1 to 25 μm. In particular, in order to obtain a polarizing film with a thickness of 8 μm or less, the above-mentioned JP 2009-098653, JP 2012-073580, JP 2013-238640, Patent No. 4691205, and Patent No. No. 4751481, etc., discloses a method for manufacturing a thin polarizing film using a laminate including a polyvinyl alcohol resin layer formed on a resin base material such as a thermoplastic resin as the polyvinyl alcohol film. Applicable.

<Adhesive layer>
The adhesive layer of the present invention is formed of an adhesive. As the adhesive, various adhesives used for polarizing films can be used, such as isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, water-based polyesters, etc. . These adhesives are usually used as adhesives made of an aqueous solution (aqueous adhesives), and contain a solid content of 0.5 to 60% by weight. Among these, polyvinyl alcohol adhesives are preferred, and acetoacetyl group-containing polyvinyl alcohol adhesives are more preferred.

The water-based adhesive may contain a crosslinking agent. As the crosslinking agent, a compound having at least two functional groups in one molecule that is reactive with components such as polymers constituting the adhesive is usually used, such as alkylene diamines; isocyanates; epoxies; Aldehydes; examples include amino-formaldehydes such as methylol urea and methylol melamine. The amount of the crosslinking agent in the adhesive is usually about 10 to 60 parts by weight per 100 parts by weight of components such as polymers constituting the adhesive.

In addition to the above adhesives, examples of the adhesive include active energy ray curable adhesives such as ultraviolet ray curable adhesives and electron beam curable adhesives. Examples of the active energy ray-curable adhesive include (meth)acrylate adhesives. Examples of the curable component in the (meth)acrylate adhesive include a compound having a (meth)acryloyl group and a compound having a vinyl group. Examples of compounds having a (meth)acryloyl group include alkyl (meth)acrylates having 1 to 20 carbon atoms, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates. ) acrylate; hydroxyl group-containing (meth)acrylate; epoxy group-containing (meth)acrylate such as glycidyl (meth)acrylate; and the like. (Meth)acrylate adhesives include hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acrylate. It may also contain a nitrogen-containing monomer such as acryloylmorpholine. The (meth)acrylate adhesive contains tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, EO as a crosslinking component. It may also contain a polyfunctional monomer such as modified diglycerol tetraacrylate. Moreover, a compound having an epoxy group or an oxetanyl group can also be used as a cationic polymerization-curable adhesive. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds can be used.

The adhesive may contain appropriate additives as necessary. Examples of the additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trapping agents, and antioxidants. agents, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, and the like.

The adhesive may be applied to either the transparent protective film side (or the functional layer side described later), the polarizing film side, or both. After bonding, a drying process is performed to form an adhesive layer consisting of a coated and dried layer. After the drying step, ultraviolet rays or electron beams can be irradiated if necessary. The thickness of the adhesive layer is not particularly limited, and when a water-based adhesive or the like is used, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm. When using an electron beam curing adhesive or the like, the thickness is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

In the adhesive layer, the content of the hindered amine compound in the adhesive layer is preferably 70% by weight or less. The adhesive layer preferably accounts for 1% by weight or more, more preferably 5% by weight or more in the adhesive layer, from the viewpoint of suppressing a decrease in single transmittance due to coloring of the polarizing film in a high-temperature environment. It is preferably 10% by weight or more, more preferably 60% by weight or less, and more preferably 50% by weight or less.

<Transparent protective film>
The transparent protective film of the present invention is not particularly limited, and various transparent protective films used for polarizing films can be used. As the material constituting the transparent protective film, for example, a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. is used. Examples of the thermoplastic resin include cellulose ester resins such as triacetylcellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyether sulfone resins, polysulfone resins, polycarbonate resins, nylon, and aromatic resins. Polyamide resins such as group polyamides, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic polyolefin resins having a cyclo or norbornene structure (norbornene resins) ), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Further, the transparent protective film may include a cured layer formed from a thermosetting resin or an ultraviolet curable resin such as (meth)acrylic, urethane, acrylic urethane, epoxy, silicone, or the like. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

The thickness of the transparent protective film can be determined as appropriate, but generally from the viewpoint of strength, workability such as handleability, thin layer property, etc., it is preferably about 1 to 500 μm, and about 1 to 300 μm. The thickness is more preferably about 5 to 100 μm.

When the transparent protective films are attached to both sides of the polarizing film, the transparent protective films on both sides may be the same or different.

As the transparent protective film, a retardation plate having a front retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more can be used. The frontal retardation is usually controlled in the range of 40 to 200 nm, and the thickness direction retardation is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate also functions as a transparent protective film, so that it is possible to reduce the thickness.

Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material, an oriented film of a liquid crystal polymer, and a film in which an oriented layer of a liquid crystal polymer is supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. Note that the phase plate may be used by bonding it to a transparent protective film that does not have a phase difference.

The transparent protective film may contain any suitable additives such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, color inhibitors, flame retardants, antistatic agents, pigments, colorants, etc. You can stay there. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.

A functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer or an anti-glare layer can be provided on the surface of the transparent protective film on which the polarizing film is not bonded. Note that the functional layers such as the hard coat layer, antireflection layer, antisticking layer, diffusion layer, and antiglare layer can be provided on the protective film itself, or may be provided separately from the protective film. can.

In the polarizing film of the present invention, it is sufficient that at least one surface of the polarizing film is bonded to the transparent protective film via the adhesive layer, and the other surface (the other surface) of the polarizing film and the transparent The protective film or the other surface of the polarizing film and the functional layer are usually bonded together via an adhesive layer or the adhesive layer. Further, an image display cell or a front transparent member, which will be described later, can be directly bonded to the other surface (the other surface) of the polarizing film via the adhesive layer.

As the adhesive forming the adhesive layer, various adhesives used in polarizing films can be used, such as rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl adhesives, etc. Examples include alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylporolidone adhesives, polyacrylamide adhesives, cellulose adhesives, and the like. Among these, acrylic adhesives are preferred. The acrylic adhesive contains an acrylic polymer as a base polymer, and examples thereof include the acrylic adhesive described in JP-A No. 2017-75998.

The adhesive layer can be formed by, for example, applying the adhesive to a release-treated separator, drying it to form an adhesive layer, and then transferring it to a polarizing film or the like, or applying the adhesive to a polarizing film, etc. Examples include a method of applying the adhesive onto a film or the like and drying it to form an adhesive layer. The thickness of the adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably about 2 to 50 μm.

The transparent protective film and the polarizing film, or the polarizing film and the functional layer may be laminated via an intervening layer such as a surface modification treatment layer, an adhesive layer, a block layer, a refractive index adjustment layer, etc. .

Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, and saponification treatment.

Examples of the easy-adhesive agent forming the easy-adhesive layer include forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone system, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. Can be mentioned. The easily bonding layer is usually provided in advance on a protective film, and the easily bonding layer side of the protective film and the polarizing film are laminated using the pressure-sensitive adhesive layer or the adhesive layer.

The blocking layer is a layer having a function of preventing impurities such as oligomers and ions eluted from the transparent protective film from migrating (invading) into the polarizing film. The block layer may be any layer as long as it has transparency and can prevent impurities leached from a transparent protective film, etc. Materials for forming the block layer include, for example, urethane prepolymer-based forming materials, cyanoacrylates, etc. Examples include system forming materials, epoxy forming materials, and the like.

The refractive index adjusting layer is a layer provided to suppress a decrease in transmittance due to reflection between layers having different refractive indexes, such as the transparent protective film and the polarizing film. Examples of the refractive index adjusting material forming the refractive index adjusting layer include forming agents containing various resins and additives, such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins.

<Laminated polarizing film>
The laminated polarizing film (optical laminate) of the present invention has the polarizing film bonded to an optical layer. The optical layer is not particularly limited, but may be used, for example, in the formation of a liquid crystal display device such as a reflective plate, a semi-transmissive plate, a retardation plate (including a 1/2 or 1/4 wavelength plate), a viewing angle compensation film, etc. One or more optical layers that are sometimes used can be used. The laminated polarizing film is particularly a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a transflective plate is further laminated on the polarizing film, and a retardation plate is further laminated in the polarizing film. Examples include an elliptical polarizing film or a circularly polarizing film, a wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, or a polarizing film in which a brightness enhancement film is further laminated on the polarizing film.

On one or both sides of the polarizing film or the laminated polarizing film, an image display cell such as a liquid crystal cell or an organic EL element, and other front transparent members such as a front transparent plate or a touch panel on the viewing side are provided. An adhesive layer for bonding the members together may be provided. A pressure-sensitive adhesive layer is suitable as the adhesive layer. The adhesive forming the adhesive layer is not particularly limited, but examples include those having a base polymer such as an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer. It can be selected and used as appropriate. In particular, pressure-sensitive adhesives containing acrylic polymers that have excellent optical transparency, exhibit appropriate wettability, cohesiveness, and adhesive properties, and are excellent in weather resistance, heat resistance, etc. are preferably used.

The adhesive layer can be attached to one or both sides of the polarizing film or the laminated polarizing film by any appropriate method. For attaching the adhesive layer, for example, a method of preparing an adhesive solution and applying it directly onto the polarizing film or the laminated polarizing film using an appropriate developing method such as a casting method or a coating method, or a method of applying the adhesive solution directly onto the polarizing film or the laminated polarizing film, or using a separator. Examples include a method of forming an adhesive layer thereon and transferring it onto the polarizing film or the laminated polarizing film. The thickness of the adhesive layer can be determined as appropriate depending on the purpose of use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm. In this way, the polarizing film or the laminated polarizing film in which an adhesive layer is provided on at least one surface is referred to as a polarizing film with an adhesive layer or a laminated polarizing film with an adhesive layer.

It is preferable that the exposed surface of the adhesive layer is temporarily covered with a separator for the purpose of preventing contamination until it is put into practical use. This can prevent contamination of the adhesive layer under normal handling conditions. As the separator, for example, appropriate thin materials such as plastic films, rubber sheets, paper, cloth, non-woven fabrics, nets, foam sheets, metal foils, laminates thereof, silicone-based, long-chain alkyl-based, etc. A material coated with an appropriate release agent such as fluorine-based or molybdenum sulfide is used.

<Image display panel and image display device>
In the image display panel of the present invention, the polarizing film or the laminated polarizing film is bonded to an image display cell. Further, the image display device of the present invention includes a front transparent member on the polarizing film or laminated polarizing film side (viewing side) of the image display panel.

Examples of the image display cell include a liquid crystal cell and an organic EL cell. Examples of the liquid crystal cell include a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, and a transflective liquid crystal cell that uses both external light and light from a light source. Any semi-reflective liquid crystal cell may be used. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) includes a polarizing film on the side opposite to the viewing side of the image display cell (liquid crystal cell), and further includes a light source. Placed. It is preferable that the polarizing film on the light source side and the liquid crystal cell are bonded together via a suitable adhesive layer. As a driving method for the liquid crystal cell, any type of driving method can be used, such as VA mode, IPS mode, TN mode, STN mode, or bend alignment (π type).

As the organic EL cell, for example, a cell in which a transparent electrode, an organic light-emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light-emitting body (organic electroluminescence light-emitting body) is preferably used. The organic light emitting layer is a laminate of various organic thin films, such as a laminate of a hole injection layer made of a triphenylamine derivative or the like and a light emitting layer made of a fluorescent organic solid such as anthracene; Various layer configurations may be adopted, such as a laminate of a light emitting layer and an electron injection layer made of a perylene derivative, or a laminate of a hole injection layer, a light emitting layer, and an electron injection layer.

Examples of the front transparent member disposed on the viewing side of the image display cell include a front transparent plate (window layer), a touch panel, and the like. As the front transparent plate, a transparent plate having appropriate mechanical strength and thickness is used. As such a transparent plate, for example, a transparent resin plate such as acrylic resin or polycarbonate resin, or a glass plate is used. As the touch panel, for example, various touch panels such as a resistive film type, a capacitance type, an optical type, an ultrasonic type, etc., a glass plate, a transparent resin plate, etc. having a touch sensor function are used. When a capacitive touch panel is used as the front transparent member, it is preferable that a front transparent plate made of glass or a transparent resin plate is provided further on the viewing side than the touch panel.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples.

<Example 1>
<Preparation of polarizing film>
A polyvinyl alcohol film having an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed in a 20°C swelling bath (water bath) for 30 seconds between rolls with different circumferential speed ratios to stretch it 2.2 times in the transport direction while swelling (swelling step), and then, The iodine concentration of the final polarizing film obtained in a dyeing bath at 30°C (an aqueous iodine solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) is 3. While adjusting the concentration so that the concentration is 60% by weight, it is immersed for 30 seconds and dyed while dyeing. (dying process). Next, the dyed polyvinyl alcohol film was immersed for 28 seconds in a 40°C cross-linking bath (an aqueous solution with a boric acid concentration of 3.0% by weight and a potassium iodide concentration of 3.0% by weight) to restore the original polyvinyl alcohol. The film was stretched up to 3.6 times in the transport direction (crosslinking step). Furthermore, the obtained polyvinyl alcohol film was immersed for 60 seconds in a 61°C stretching bath (an aqueous solution with a boric acid concentration of 4.0% by weight and a potassium iodide concentration of 5.0% by weight) to restore the original polyvinyl alcohol film. After stretching the alcohol film to 6.0 times in the transport direction (stretching step), the film was immersed for 10 seconds in a 35°C cleaning bath (an aqueous solution with a potassium iodide concentration of 2.0% by weight) (cleaning). process). The washed polyvinyl alcohol film was dried at 40° C. for 30 seconds to produce a polarizing film. The thickness of the polarizing film was 18 μm.

[Method for measuring iodine content (wt%) in polarizing film]
Regarding the polarizing film, the iodine concentration (weight %) was determined using the following formula using a fluorescent X-ray analyzer (manufactured by Rigaku Co., Ltd., trade name "ZSX-PRIMUS IV", measurement diameter: ψ 20 mm).
Iodine concentration (wt%) = 14.474 x (fluorescent X-ray intensity) / (film thickness) (kcps/μm) The coefficient for calculating the concentration differs depending on the measuring device, but the coefficient can be calculated using an appropriate calibration curve. It can be found using

<Preparation of polarizing film>
As an adhesive, a polyvinyl alcohol resin containing an acetoacetyl group (average degree of polymerization 1,200, degree of saponification 98.5 mol%, degree of acetoacetylation 5 mol%), methylolmelamine, and general formula (6) An aqueous solution containing a hindered amine compound shown in the following in a weight ratio of 3:1:4 was used. Using this adhesive, a 47 μm thick triacetyl cellulose film (moisture permeability 342 g/(m ² 24 h), Konica Minolta After laminating the film using a roll laminating machine, the transparent protective film was laminated to both sides of the polarizing film by heating and drying in an oven (temperature: 60°C, time: 4 minutes). A polarizing film was produced. The single transmittance of the polarizing film was 39.7%. The hindered amine compound represented by the following general formula (6) is a compound that dissolves in an amount of 1 part by weight or more per 100 parts by weight of water at 25°C.

<Preparation of acrylic adhesive>
A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was charged into a four-necked flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser. Furthermore, to 100 parts of the monomer mixture (solid content), 0.1 part of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate, and nitrogen gas was added while stirring gently. After introducing the flask and purging it with nitrogen, a polymerization reaction was carried out for 8 hours while maintaining the liquid temperature in the flask at around 55° C. to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 1.8 million. Thereafter, based on 100 parts of the solid content of the obtained acrylic polymer solution, 0.02 part of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Takenate D110N", trimethylolpropane/xylylene diisocyanate adduct), silane A solution of an acrylic adhesive composition was prepared by adding 0.2 part of a coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-41-1056"). Next, the solution of the acrylic adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (manufactured by Mitsubishi Chemical Polyester Film, trade name "MRF38", separator film) treated with a silicone release agent, after drying. was applied so that the thickness of the adhesive layer was 20 μm, and dried at 90° C. for 1 minute to form an adhesive layer on the surface of the separator film. Next, the adhesive layer formed on the separator film was transferred to one side of the polarizing film produced above to produce a polarizing film with an adhesive layer.

<Production of pseudo image display device (laminate)>
The polarizing film with the adhesive layer obtained above was cut into a size of 45 x 40 mm so that the absorption axis of the polarizing film was the long side, and a glass plate (pseudo image display cell) was pasted through the adhesive layer. Then, another glass plate (pseudo front transparent member) was attached to the other side of the polarizing film with a 200 μm thick acrylic acid monomer-free adhesive (manufactured by Nitto Denko Corporation, product name ``LUCIACS CS9868''). , a pseudo image display device (laminate) was produced.

[Evaluation of single transmittance in high temperature environment]
The pseudo image display device (laminate) obtained above was left in a hot air oven at a temperature of 105° C. for 48 hours, and the single transmittance (ΔTs) before and after being put in (heated) was measured. Single transmittance was measured using a spectrophotometer (manufactured by Murakami Color Research Institute Co., Ltd., product name "DOT-3") and evaluated based on the following criteria. The single transmittance is a Y value corrected for visual sensitivity using the 2-degree field of view (C light source) of JIS Z 8701-1982. Note that the measurement wavelength is 380 to 700 nm (every 10 nm). The results are shown in Table 1.
ΔTs (%) = Ts ₄₈ - Ts ₀
Here, Ts ₀ is the single transmittance of the pseudo image display device (laminate) before heating, and Ts ₄₈ is the single transmittance of the pseudo image display device (laminate) after heating for 48 hours.
○: 5≧ΔTs (%)≧0
×: ΔTs (%) > 5, or ΔTs (%) < 0

The ΔTs (%) preferably satisfies 5≧ΔTs (%)≧0, and more preferably satisfies 4≧ΔTs (%)≧0.

<Example 2>
<Production of polarizing film, polarizing film, and pseudo image display device (laminate)>
In the production of a polarizing film, a hindered amine compound represented by general formula (7) is added to both adhesives used at a weight ratio of 4:3 to polyvinyl alcohol resin to influence the curing reaction of the adhesive. The same procedure as in Example 1 was carried out, except that potassium hydroxide was added at a molar ratio of 1:1 to the hindered amine compound to adjust the pH (neutralization) so as not to give Through this operation, a polarizing film, a double-sided protective polarizing film, and a pseudo image display device (laminate) were produced. The single transmittance of the polarizing film was 40.0%. Note that the hindered amine compound represented by the following general formula (7) is a compound that dissolves at least 1 part by weight in 100 parts by weight of water at 25°C.

<Example 3>
<Production of polarizing film, polarizing film, and pseudo image display device (laminate)>
In the production of polarizing films, a hindered amine compound represented by general formula (8) is added to both adhesives used at a weight ratio of 4:3 to polyvinyl alcohol resin to influence the curing reaction of the adhesive. The procedure was the same as in Example 1, except that the pH was adjusted (neutralized) by adding hydrochloric acid at a molar ratio of 1:1 to the hindered amine compound so as not to give Thus, a polarizing film, a double-sided protective polarizing film, and a pseudo image display device (laminate) were produced. The single transmittance of the polarizing film was 39.9%. The hindered amine compound represented by the following general formula (8) is a compound that dissolves in an amount of 1 part by weight or more per 100 parts by weight of water at 25°C.

<Example 4>
<Production of polarizing film, polarizing film, and pseudo image display device (laminate)>
In producing the polarizing film, an aqueous solution containing a polyvinyl alcohol resin containing an acetoacetyl group, methylol melamine, and a hindered amine compound represented by general formula (6) in a weight ratio of 7:2:1 was used as an adhesive. Except for this, a polarizing film, a double-sided protective polarizing film, and a pseudo image display device (laminate) were produced in the same manner as in Example 1. The single transmittance of the polarizing film was 39.7%.

<Comparative example 1>
<Production of polarizing film, polarizing film, and pseudo image display device (laminate)>
In preparing the polarizing film, a polarizing film, a polarizing film, and a pseudo image display device (laminated body) were prepared in the same manner as in Example 1, except that the hindered amine compound represented by general formula (6) was not added. ) was created. The single transmittance of the polarizing film was 39.6%.

<Comparative example 2>
<Production of polarizing film, polarizing film, and pseudo image display device (laminate)>
In the production of a polarizing film, 35 parts by weight of N-hydroxyethyl acrylamide (HEAA), 50 parts by weight of acryloylmorpholine (ACMO), 5 parts by weight of photoinitiator "IRGACURE 819" (manufactured by BASF), and general formula (9) were used as adhesives. ) (trade name: ADEKA STAB LA-52, manufactured by ADEKA) was mixed with 10 parts by weight, and the mixture was applied onto a polarizing film so that the thickness of the adhesive layer after curing was 1.0 μm. A polarizing film, a polarizing film, and a pseudo image display device (a laminate) were prepared in the same manner as in Example 1, except that the polarizing film was prepared by irradiating ultraviolet rays as active energy rays and curing the adhesive. ) was created. Ultraviolet irradiation was performed using a gallium-filled metal halide lamp, irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., bulb: V bulb, peak illuminance: 1600 mW/cm ² , cumulative irradiation amount 1000/mJ/cm ² (wavelength 380 to 440 nm) ), and the illuminance of ultraviolet light was measured using the Sola-Check system manufactured by Solatell. The single transmittance of the polarizing film was 39.6%. Note that the hindered amine compound represented by the following general formula (9) is a compound that does not dissolve at least 1 part by weight in 100 parts by weight of water at 25°C.

Using the pseudo image display devices (laminates) of the Examples and Comparative Examples obtained above, the above [Evaluation of single transmittance in a high temperature environment] was performed. The results are shown in Table 1.

Claims (6)

A polarizing film in which a transparent protective film is bonded to at least one surface of the polarizing film via an adhesive layer,
The polarizing film is formed by adsorbing and orienting iodine on a polyvinyl alcohol film,
The adhesive layer contains a hindered amine compound,
The hindered amine compound is a water-soluble hindered amine compound that can be dissolved in 1 part by weight or more in 100 parts by weight of water at 25°C ,
A polarizing film characterized in that the content of the hindered amine compound in the adhesive layer is 1% by weight or more . The polarizing film according to claim 1, wherein the adhesive layer is a layer formed from a water-based adhesive. 3. The polarizing film according to claim 1 , wherein the content of the hindered amine compound in the adhesive layer is 70% by weight or less. A laminated polarizing film, characterized in that the polarizing film according to any one of claims 1 to 3 is laminated to an optical layer. An image display panel characterized in that the polarizing film according to any one of claims 1 to 3 or the laminated polarizing film according to claim 4 is laminated to an image display cell. An image display device comprising a front transparent member on the polarizing film or laminated polarizing film side of the image display panel according to claim 5 .