JP2018028696A - Polarizing plate, optical film and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate having sufficient optical characteristics and adhesive force even when a cellulose ester film is used as a transparent protective film.SOLUTION: The polarizing plate has first and second transparent protective films bonded to either surface of a polarizer via an adhesive layer formed by irradiating an active energy ray-curable adhesive with active energy rays. At least the first transparent protective film is a cellulose ester film with an unevenly distributed plasticizer, which comprises a plasticizer and a cellulose ester and has an uneven distribution of the plasticizer on one surface of the film; and the surface side where the plasticizer is unevenly distributed in the cellulose ester film with the unevenly distributed plasticizer is bonded to the polarizer via the adhesive layer.SELECTED DRAWING: None

Description

  The present invention relates to a polarizing plate in which a transparent protective film is provided on both surfaces of a polarizer via an adhesive formed of an active energy ray-curable adhesive. The polarizing plate can form an image display device such as a liquid crystal display device (LCD), an organic EL display device, a CRT, or a PDP alone or as an optical film in which the polarizing plate is laminated.

  The liquid crystal display device visualizes the polarization state by switching of the liquid crystal, and from the display principle, a polarizing plate is used in which a transparent protective film is bonded to both sides of the polarizer with an adhesive layer. As a polarizer, for example, an iodine-based polarizer having a stretched structure obtained by adsorbing iodine to polyvinyl alcohol has a high transmittance and a high degree of polarization, and is therefore widely used as the most common polarizer. As the transparent protective film, a cellulose ester film such as triacetyl cellulose having a high moisture permeability is used.

  Since the cellulose ester film has high moisture permeability, a water-based adhesive such as a polyvinyl alcohol-based adhesive is often used when a polarizing plate is produced using the cellulose ester film as a transparent protective film. However, in the method for producing a polarizing plate using an aqueous adhesive, a drying step is required after the polarizer and the transparent protective film are bonded together. In the case of having such a drying step, a polarizing plate with good adhesion can be obtained unless the moisture content of the polarizer is relatively high in order to enhance the adhesion with the polarizer. Can not. However, the polarizing plate thus obtained has a problem that sufficient optical characteristics (polarization characteristics and the like) cannot be obtained.

  On the other hand, as an adhesive used for manufacturing a polarizing plate, an active energy ray-curable adhesive that does not contain water or an organic solvent has been proposed (Patent Document 1). However, the active energy ray-curable adhesive has insufficient adhesive strength with the cellulose ester film as compared with the water-based adhesive.

Further, an image display device such as a liquid crystal display device applied to the polarizing plate is used in various environments. Therefore, it is desired that the polarizing plate has durability such as heat resistance under a high temperature environment and moisture resistance under a high humidity environment. In recent years, it has been desired to satisfy durability particularly in mobile applications such as mobile phones. However, the cellulose ester film that is usually used as a transparent protective film has a problem in that the phase difference changes greatly in a high-humidity environment, resulting in display unevenness on the panel. In response to this problem, Patent Document 2 proposes to use a film containing a cellulose ester film and a (meth) acrylic resin having a low moisture permeability as the transparent protective films on both sides of the polarizer. Patent Document 2 describes that the display unevenness can be reduced. Also in Patent Document 3, it is proposed to use an acrylic resin film as a transparent protective film of a polarizing plate.

JP 2010-286754 A JP 2009-151289 A JP 2009-145397 A

  The present invention is a polarizing plate in which a transparent protective film is provided on both surfaces of a polarizer via an adhesive layer, and the optical properties and adhesive force are obtained even when a cellulose ester film is used as the transparent protective film. It is an object to provide a polarizing plate that can be satisfied.

  Another object of the present invention is to provide an optical film using the polarizing plate, and to provide an image display device such as a liquid crystal display device using the polarizing plate and the optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the polarizing plate shown below, and have completed the present invention.

That is, in the present invention, the first and second transparent protective films are bonded to both surfaces of the polarizer via an adhesive layer formed by irradiating the active energy ray-curable adhesive with active energy rays. A polarizing plate,
At least the first transparent protective film is a plasticizer unevenly distributed cellulose ester film comprising a plasticizer and a cellulose ester, and wherein the plasticizer is unevenly distributed on one surface,
It is related with the polarizing plate by which the surface side where the plasticizer is unevenly distributed in the said plasticizer uneven distribution cellulose-ester film is bonded through the said adhesive bond layer.

  In the polarizing plate, the plasticizer unevenly distributed cellulose ester film has a thickness of 1 μm or more, and plasticity in the range from the surface side where the plasticizer is unevenly distributed to the thickness of 5 nm in the plasticizer unevenly distributed cellulose ester film. The proportion (a) of the agent is preferably larger than the proportion (b) of the plasticizer in the range from the surface side where the plasticizer is not unevenly distributed to 5 nm.

  In the polarizing plate, a phosphorus plasticizer can be used as a plasticizer contained in the plasticizer unevenly distributed cellulose ester film. The proportion (a) of the phosphorus plasticizer based on the phosphorus atom in the phosphorus plasticizer is preferably 0.5 to 3 atomic%.

  In the polarizing plate, as the plasticizer unevenly distributed cellulose ester film, nx> ny> nz (however, the direction in which the in-plane refractive index is maximum is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction is It is possible to use a retardation plate that satisfies the relationship of Z axis, and the refractive indexes in the respective axial directions are nx, ny, and nz.

In the polarizing plate, as the second transparent protective film, the moisture permeability can be used following 120g ^/ m 2 ^/ 24h. The second transparent protective film is preferably a film containing a (meth) acrylic resin, a cyclic polyolefin resin, or a polyester resin.

  In the polarizing plate, the active energy ray curable adhesive is preferably a radical curable active energy ray curable adhesive containing a radical polymerizable compound.

  The present invention also relates to an optical film in which at least one polarizing plate is laminated.

  Furthermore, the present invention relates to an image display device according to the present invention, wherein the polarizing plate and / or the optical film is used. In such an optical film and image display device, the polarizer of the polarizing plate and the transparent protective film are firmly bonded via the adhesive layer, and the durability and water resistance of the adhesive layer are excellent.

  In the present invention, in the polarizing plate, a cellulose ester film is used as the first transparent protective film on at least one side of the polarizer. The cellulose ester film is a plasticizer unevenly distributed cellulose ester film in which a plasticizer is unevenly distributed on one surface, and the plasticizer unevenly distributed surface side is bonded to a polarizer with an active energy ray-curable adhesive. Thus, the polarizing plate of the present invention combines a cellulose ester film, which is a transparent protective film, and an active energy ray-curable adhesive, but the cellulose ester film is a plasticizer unevenly distributed cellulose ester film, and is therefore unevenly distributed in the film. By the action of the plasticizer, the penetrating power of the active energy ray curable adhesive (especially the ultraviolet curable adhesive) is affected and the adhesive strength can be satisfied.

  Further, in the polarizing plate of the present invention, a low-moisture-permeable transparent protective film is used as the second transparent protective film, so that the cellulose ester film is used as the first transparent protective film in a high-temperature environment. It is possible to satisfy the durability such as the heat resistance in and the humidity resistance in a high humidity environment. Moreover, when the 1st transparent protective film serves also as a phase difference plate, a phase difference change can be suppressed and a display nonuniformity can also be suppressed small when a polarizing plate is applied to a liquid crystal panel.

  In the polarizing plate of the present invention, an active energy ray-curable adhesive is used for forming the adhesive layer. An active energy ray-curable adhesive does not have moisture in the adhesive itself, and provides a polarizing plate excellent in optical characteristics (polarization characteristics) and durability without causing destruction of the PVA-iodine complex in the polarizer. Can do.

  In the polarizing plate of the present invention, the first and second transparent protective films are bonded to both sides of the polarizer via an adhesive layer formed by irradiating the active energy ray-curable adhesive with active energy rays. ing.

<Polarizer>
The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a functional material and uniaxially stretched, polyvinyl alcohol dehydrated products and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 80 μm or less. The thickness of the polarizer is usually preferably 15 to 35 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  In addition, the moisture content of a polarizer can be adjusted with arbitrary appropriate methods. For example, there is a method of controlling by adjusting the conditions of the drying process in the manufacturing process of the polarizer.

  As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness 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, the durability is excellent, and the thickness of the polarizing plate can be reduced.

  As the thin polarizer, representatively, JP-A-51-069644, JP-A-2000-338329, WO2010 / 100917 pamphlet, PCT / JP2010 / 001460 specification, or Japanese Patent Application 2010- The thin polarizing film described in 269002 specification and Japanese Patent Application No. 2010-263692 specification can be mentioned. These thin polarizing films can be obtained by a production method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a stretching resin base material in a laminated state and a step of dyeing. With this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without problems such as breakage due to stretching by being supported by the stretching resin substrate.

<First transparent protective film>
The 1st transparent protective film of this invention contains a cellulose ester as a main raw material. Any appropriate material can be adopted as the cellulose ester. Preferably, the cellulose ester is a lower fatty acid ester having 6 or less carbon atoms in cellulose. Specific examples include cellulose esters such as cellulose acetate, cellulose propionate, and cellulose butyrate in which the hydroxyl group of cellulose is esterified with the same lower fatty acid, cellulose acetate propionate, cellulose acetate butyrate, and the like in which the hydroxyl group of cellulose is different. Examples thereof include those esterified with a fatty acid, and a cellulose ester in which a hydroxyl group of cellulose is substituted with an acetyl group and / or a propionyl group is particularly preferable. These can be used alone or in combination of two or more.

  When the said cellulose ester contains an acetyl group as a substituent of a lower fatty acid, the acetyl substitution degree becomes like this. Preferably it is 3 or less, More preferably, it is 0.5-3, Most preferably, it is 1-3. When the cellulose ester contains a propionyl group as a substituent of the lower fatty acid, the propionyl substitution degree is preferably 3 or less, more preferably 0.5 to 3, particularly preferably 1 to 3. Further, when the cellulose ester is a mixed fatty acid ester in which a part of the hydroxyl group of cellulose is substituted with an acetyl group and the other part is substituted with a propionyl group, the sum of the degree of acetyl substitution and the degree of propionyl substitution is , Preferably it is 1-3, More preferably, it is 2-3. At this time, the acetyl substitution degree is preferably 0.5 to 2.5, and the propionyl substitution degree is preferably 0.3 to 1.5.

  The degree of acetyl substitution (or propionyl substitution) refers to the number of hydroxyl groups attached to carbons at the 2, 3, 6 positions in the cellulose skeleton with acetyl groups (or propionyl groups). The acetyl group (or propionyl group) may be biased to any of the carbons at the 2, 3, 6 positions in the cellulose skeleton, or may exist on average. The said acetyl substitution degree can be calculated | required by ASTM-D817-91 (test methods, such as a cellulose acetate). Moreover, the said propionyl substitution degree can be calculated | required by ASTM-D817-96 (test methods, such as a cellulose acetate).

  The cellulose ester preferably has a weight average molecular weight (Mw) measured by a gel permeation chromatograph (GPC) method using a tetrahydrofuran solvent, preferably 30,000 to 500,000, more preferably 50,000 to 400,000. Most preferably, it is 80,000-300,000. When the weight average molecular weight is in the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  The molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of the cellulose ester is preferably 1.5 to 5.5, and more preferably 2 to 5.

  The first transparent protective film contains a plasticizer in addition to the cellulose ester. As the plasticizer, for example, a phosphorus-based plasticizer containing a phosphorus atom can be used. Examples of phosphorus plasticizers include phosphate esters. Examples of the phosphoric acid ester include triphenyl phosphate, resorcinol bisdi 2,6 xylenyl phosphate, tricresyl phosphate, trixylenyl phosphate, and the like. In addition, examples of the plasticizer include an ester plasticizer obtained from a carboxylic acid compound and an alcohol compound; a polyvalent carboxylic acid polyvalent ester obtained from a polyvalent carboxylic acid and a monohydric alcohol.

  Although the thickness of the 1st transparent protective film of this invention can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and a handleability, and thin-layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  The plasticizer is unevenly distributed on one side of the first transparent protective film. The uneven distribution of the plasticizer in the first transparent protective film refers to a state in which the plasticizer is not uniformly dispersed in the thickness direction of the film and is unevenly distributed on one surface. The uneven distribution of the plasticizer is, for example, when the ratio (a) of the plasticizer in the range from one surface of the film (surface where the plasticizer is unevenly distributed) to the thickness of 5 nm is the other surface of the film (the plasticizer is This can be confirmed by showing a larger value than the proportion (b) of the plasticizer in the range from the (unevenly distributed surface) side to 5 nm. That is, the uneven distribution of the plasticizer can be confirmed by confirming that there is a difference in the proportion of the plasticizer on both surfaces (outermost surface) of the plasticizer unevenly distributed cellulose ester film. The proportion (b) of the non-uniformly distributed plasticizer is preferably as small as possible, and it is particularly preferable that no plasticizer is present.

  When the plasticizer is a phosphorus plasticizer, the ratio (a) of the phosphorus plasticizer based on the phosphorus atom in the phosphorus plasticizer, that is, the ratio (a) of the unevenly distributed phosphorus plasticizer is 0. 0.5-3 atomic% is preferable. On the other hand, the proportion (b) of the non-distributed plasticizer may be a value smaller than the proportion (a), but as described above, the proportion (b) of the non-distributed plasticizer is preferably as small as possible, In particular, 0 atomic% is preferable. The proportions (a) and (b) of the phosphorus plasticizer can be measured using ESCA.

  In addition, in the 1st transparent protective film used by this invention, 1 or more types of arbitrary appropriate additives other than the plasticizer may be contained. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; lubricants; antistatic agents; flame retardants;

  The content ratio of the optional additive in the first transparent protective film of the present invention is preferably 0 to 5% by weight, more preferably 0 to 2% by weight, and still more preferably 0 to 0.5% by weight.

  The 1st transparent protective film (plasticizer uneven distribution cellulose-ester film) of this invention can be manufactured, for example by the method of an Example reference.

  The 1st transparent protective film of this invention can be used as a phase difference plate. By changing the type of the substituent of the lower fatty acid of the cellulose ester and the degree of substitution of the lower fatty acid, the retardation value of the obtained retardation plate can be controlled. Moreover, in order to control a phase difference, a phase difference improvement agent and a phase difference control agent can also be contained.

  The 1st transparent protective film used as the said phase difference plate can use what satisfies the relationship of nx> ny> nz, for example. The in-plane retardation of the retardation plate is usually controlled in the range of 40 to 300 nm, and the thickness direction retardation is usually controlled in the range of 80 to 320 nm. Furthermore, the in-plane retardation is preferably 40 to 100 nm, the thickness direction retardation is preferably 100 to 320 nm, and the Nz coefficient is preferably 1.8 to 4.5. The Nz coefficient is typically about 3.5 to 4.5. According to such a retardation plate, the viewing angle characteristics in the perspective direction can be improved. It is particularly suitable when applied to an IPS mode or VA mode liquid crystal display device.

  As the transparent protective film used as the retardation plate, for example, a biaxial retardation plate satisfying a refractive index relationship of nx> ny> nz is used. Control of these phase differences can be obtained by uniaxially stretching or biaxially stretching a polymer film containing a cellulose ester in the longitudinal direction or the transverse direction.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as for the purpose of compensating for various wavelength plates or birefringence of a liquid crystal layer, compensation for viewing angle, and the like. What laminated | stacked the phase difference plate more than a seed | species, and controlled optical characteristics, such as phase difference, etc. may be used.

<Second transparent protective film>
The 2nd transparent protective film of this invention is not restrict | limited in particular, Various transparent protective films conventionally used for the polarizing plate can be used. As a material constituting the second transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is used. Specific examples of such thermoplastic resins include cellulose ester resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, Polyamide resins such as nylon and aromatic polyamide, 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. Also about a 2nd transparent protective film, the additive similar to a 1st transparent protective film can be contained.

  Although the thickness of the 2nd transparent protective film of this invention can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and a handleability, and thin-layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

The second transparent protective film, from the viewpoint of durability, moisture permeability is preferably of a following low moisture permeability 120g / m 2 / ^24h. The moisture permeability is preferably not more than 200g ^/ m 2 ^/ 24h, more preferably not more than 100g ^/ m 2 ^/ 24h. The moisture permeability is determined by the method described in the examples.

  As a material for forming the transparent protective film that satisfies the low moisture permeability, for example, among the resins, (meth) acrylic resins, cyclic polyolefin resins, or polyester resins are preferable.

The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg is 115 ° C. or higher, the polarizing plate can be excellent in durability. Although the upper limit of Tg of the (meth) acrylic resin is not particularly limited, it is preferably 170 ° C. or lower from the viewpoint of moldability and the like. From the (meth) acrylic resin, a film having in-plane retardation (Re) and thickness direction retardation (Rth) of almost zero can be obtained.

  As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, Methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.). Preferably, poly (meth) acrylate C1-6 alkyl such as poly (meth) acrylate methyl is used. More preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

  Specific examples of (meth) acrylic resins include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. And high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. It is because it has high mechanical strength by high heat resistance, high transparency, and biaxial stretching.

  Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

  A specific example of the cyclic polyolefin resin is preferably a norbornene resin. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as the cyclic polyolefin resin. As specific examples, trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, product names “ARTON” manufactured by JSR Corporation, “TOPAS” manufactured by TICONA, and product names manufactured by Mitsui Chemicals, Inc. “APEL”.

  The second transparent protective film can also be used as a retardation plate.

  Functional layers such as a hard coat layer, an antireflection layer, an anti-sticking layer, a diffusion layer or an antiglare layer can be provided on the surfaces of the first and second transparent protective films to which the polarizer is not adhered. The functional layers such as the hard coat layer, antireflection layer, antisticking layer, diffusion layer and antiglare layer can be provided on the second transparent protective film itself, or separately from the transparent protective film. It can also be provided as.

<Active energy ray-curable adhesive>
In the polarizing plate of the present invention, an active energy ray-curable adhesive is used for bonding the polarizer and the first and second transparent protective films. The adhesive layer (cured product layer) formed by irradiating active energy rays has higher durability than the aqueous adhesive layer and is preferable from the viewpoint of optical properties.

  The active energy ray-curable adhesive according to the present invention is an adhesive that is cured by an active energy ray such as an electron beam or ultraviolet ray, and can be used, for example, in an electron beam curable type or an ultraviolet ray curable type. As the active energy ray curable adhesive in the present invention, an ultraviolet curable adhesive is preferable because it can be easily experimented with general-purpose equipment. On the other hand, since electron beam curable adhesives do not use photoinitiators, they can be used with materials that do not transmit light (metal films and high-concentration pigments), and are characterized by improved adhesion. There are equipment limitations compared to adhesives.

  Moreover, as the active energy ray curable adhesive used in the present invention, for example, a photo radical curable adhesive can be used. When the photo radical curable active energy ray curable adhesive is used as an ultraviolet curable adhesive, the adhesive contains (A) a radical polymerizable compound and (B) a photo polymerization initiator.

≪ (A) Radical polymerizable compound≫
The (A) radical polymerizable compound can be used without particular limitation as long as it is a compound having a vinyl group containing at least one carbon-carbon double bond, a (meth) acryloyl group, and the like. In the present invention, (A) Among the radical polymerizable compound represented by the following general formula ^{_{(1): CH 2 = C}} (R 1) -CONH 2-m - (X-O-R 2) m (1)
(R ¹ represents a hydrogen atom or a methyl group, X represents a —CH ₂ — group or a —CH ₂ CH ₂ — group, R ² represents a — (CH ₂ ) _n —H group (where n is 0, 1 Or an N-substituted amide monomer represented by 2) and m represents 1 or 2.

  Specific examples of the N-substituted amide monomer represented by the general formula (1) include, for example, N-hydroxyethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-ethoxyethyl (meth) acrylamide, etc. are mentioned. These N-substituted amide monomers can be used singly or in combination of two or more.

  As the N-substituted amide monomer represented by the general formula (1), commercially available products can also be suitably used. Specifically, for example, N-hydroxyethyl acrylamide (trade name “HEAA”, manufactured by Kojin Co., Ltd.), N-methoxymethyl acrylamide (trade name “NMMA”, manufactured by MRC Unitech Co., Ltd.), N-butoxymethyl acrylamide (trade name) “NBMA” (manufactured by MRC Unitech), N-methoxymethylmethacrylamide (trade name “Wassmer 2MA”, manufactured by Kasano Kosan Co., Ltd.), and the like.

  As the N-substituted amide monomer represented by the general formula (1), N-hydroxyethyl (meth) acrylamide is suitable. The N-substituted amide-based monomer exhibits good adhesion to a transparent protective film using a low moisture content polarizer or a material with low moisture permeability. Among the monomers exemplified above, N- Hydroxyethyl acrylamide exhibits particularly good adhesion.

  The active energy ray-curable adhesive (A) is a monofunctional compound having an N-substituted amide monomer other than that represented by the general formula (1), various aromatic rings and a hydroxy group as a radical polymerizable compound. You may contain the compound etc. which have (meth) acrylate, urethane (meth) acrylate, polyester (meth) acrylate, various (meth) acryloyl groups. However, when considering the adhesiveness and water resistance of the adhesive layer, the ratio of the N-substituted amide monomer represented by the general formula (1) to the total amount of the (A) radical polymerizable compound is 30 to 95. % By weight is preferable, and 35 to 90% by weight is more preferable.

  Examples of N-substituted amide monomers other than those represented by the general formula (1) include N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, and N, N-diethyl (meth) acrylamide. , N-isopropylacrylamide, N-butyl (meth) acrylamide, N-hexyl (meth) acrylamide, aminomethyl (meth) acrylamide, aminoethyl (meth) acrylamide, mercaaptomethyl (meth) acrylamide, mercaptoethyl (meth) acrylamide N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine and the like. Among these, N-acryloylmorpholine is preferable, and it is preferable to use it in combination with N-hydroxyethylacrylamide, which is an N-substituted amide monomer other than that represented by the general formula (1).

  As the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, various monofunctional (meth) acrylates having an aromatic ring and a hydroxy group can be used. The hydroxy group may exist as a substituent of the aromatic ring, but in the present invention, it exists as an organic group (bonded to a hydrocarbon group, particularly an alkylene group) that bonds the aromatic ring and the (meth) acrylate. Those that do are preferred.

  Examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include a reaction product of a monofunctional epoxy compound having an aromatic ring and (meth) acrylic acid. Examples of the monofunctional epoxy compound having an aromatic ring include phenyl glycidyl ether, t-butylphenyl glycidyl ether, and phenyl polyethylene glycol glycidyl ether. Specific examples of the monofunctional (meth) acrylate having an aromatic ring and a hydroxy group include, for example, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-hydroxy-3-t-butylphenoxypropyl (meth) Acrylate, 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate, etc. are mentioned.

  Moreover, as said urethane (meth) acrylate, the hydroxyl group of the one end of diol compounds, such as (meth) acrylate which has an isocyanate group, and polyalkylene glycols, such as polyurethane diol, polyester diol, polyether diol, polyethylene glycol, polypropylene glycol, etc. And a reaction product thereof.

As a compound having a (meth) acryloyl group, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate C 1-12 alkyl (meth) acrylates such as lauryl (meth) acrylate; (meth) acrylic acid alkoxyalkyl monomers such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl; ) 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, (meta Acrylic acid Hydroxyl group-containing monomers such as 0-hydroxydecyl, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; Acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; acrylic acid Caprolactone adducts: styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid And sulfonic acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate and the like. (Meth) acrylamide; maleimide, N-cyclohexylmaleimide, N-phenylmaleimide and the like;
Aminoethyl (meth) acrylate, aminopropyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, 3- (3-pyridinyl) propyl (meth) ) (Meth) acrylic acid alkylaminoalkyl monomers such as acrylates; N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyocta And nitrogen-containing monomers such as succinimide monomers such as methylene succinimide.

  In the case where the active energy ray-curable adhesive further contains a monomer having two or more carbon-carbon double bonds, particularly preferably a polyfunctional (meth) acrylate monomer, as the radically polymerizable compound (A). It is preferable because the water resistance of the adhesive layer is improved. In consideration of the water resistance of the adhesive layer, the monomer having two or more carbon-carbon double bonds is more preferably hydrophobic. Monomers having two or more hydrophobic carbon-carbon double bonds, particularly hydrophobic polyfunctional (meth) acrylate monomers include, for example, tricyclodecane dimethanol diacrylate, divinylbenzene, N, N′-methylene. Bisacrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) Acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol glycol di (meth) acrylate, glycerin di (meth) acrylate, EO modified glycerin tri (meth) acrylate, EO modified diglycerin tetra ( (Meth) acrylate, (meth) acrylic acid 2- (2-vinyloxyethoxy) ethyl, bisphenol A-EO adduct di (meth) acrylate, trimethylolpropane tri (meth) acrylate, hydroxypivalic acid neope Luglycol (meth) acrylic acid adduct, EO-modified trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, Cyanuric acid EO-modified di (meth) acrylate, isocyanuric acid EO-modified tri (meth) acrylate, ε-caprolactone-modified tris ((meth) acryloxyethyl) isocyanurate, 1,1-bis ((meth) acryloyloxymethyl) ethyl Examples include isocyanate, a polymer of 2-hydroxyethyl (meth) acrylate and 1,6-diisocyanate hexane, 9,9-bis [4- (2- (meth) acryloyloxyethoxy) phenyl] fluorene, and the like.

  (A) The ratio of the monomer having two or more carbon-carbon double bonds to the total amount of the radical polymerizable compound is preferably 5 to 70% by weight, and more preferably 10 to 65% by weight. . When this ratio is less than 5% by weight, sufficient water resistance may not be obtained. On the other hand, when it exceeds 50% by weight, sufficient adhesion may not be obtained.

≪ (B) Photopolymerization initiator≫
(B) A photoinitiator generate | occur | produces a radical by irradiating an active energy ray.
(B) Examples of the photopolymerization initiator include a hydrogen abstraction type photopolymerization initiator and a cleavage type photopolymerization initiator. Any of the photopolymerization initiators can be used alone or in combination.

  (B) The content of the photopolymerization initiator is preferably 0.01 to 10 parts by weight, and preferably 0.05 to 5 parts by weight with respect to the total amount of the active energy ray-curable adhesive. More preferred is 0.1 to 3 parts by weight.

  Moreover, when using the active energy ray hardening-type adhesive which concerns on this invention by an electron beam hardening type, the said (B) photoinitiator can be used arbitrarily for the said adhesive. Moreover, you may add the sensitizer which raises the cure rate and sensitivity by an electron beam represented by the carbonyl compound.

  Moreover, various additives can be mix | blended with the said active energy ray hardening-type adhesive agent as another arbitrary component in the range which does not impair the objective and effect of this invention. Examples of such additives include various polymers or oligomers; polymerization inhibitors; polymerization initiation assistants; leveling agents; wettability improvers; surfactants; plasticizers; ultraviolet absorbers; silane coupling agents; And dyes. However, in the active energy ray-curable adhesive, the content of the above-described additive is preferably 0.005 to 20 parts by weight with respect to the total amount of the active energy ray-curable adhesive, and 0.01 to 10 weights. More preferably, it is 0.1 to 5 parts by weight.

<Polarizing plate>
The polarizing plate of the present invention, after applying an active energy ray-curable adhesive on the surface forming the adhesive layer of the polarizer and / or the surface forming the adhesive layer of the first and second transparent protective films, A polarizer and a transparent protective film are bonded together, and then the active energy ray-curable adhesive is cured by active energy ray irradiation to form an adhesive layer. In the first transparent protective film (plasticizer unevenly distributed cellulose ester film), the unevenly distributed side of the film surface on which the plasticizer is unevenly bonded is bonded to the polarizer via an adhesive layer.

  The polarizer, the first transparent protective film, and the second transparent protective film may be subjected to surface modification treatment before applying the active energy ray-curable adhesive. Specific examples of the treatment include corona treatment, plasma treatment, and saponification treatment.

  The coating method of the active energy ray-curable adhesive is appropriately selected depending on the viscosity of the composition and the target thickness. Examples of coating methods include reverse coaters, gravure coaters (direct, reverse and offset), bar reverse coaters, roll coaters, die coaters, bar coaters, rod coaters and the like. In addition, for coating, a method such as a dapping method can be appropriately used.

  Moreover, it is preferable to apply the active energy ray-curable adhesive so that the thickness of the adhesive layer is 0.01 to 7 μm. The thickness of the adhesive layer is more preferably 0.01 to 5 μm, further preferably 0.01 to 2 μm, and most preferably 0.01 to 1 μm. The thickness of the adhesive layer is preferably set to 0.01 μm or more from the viewpoint that the adhesive force itself obtains cohesive force to obtain adhesive strength. On the other hand, the thickness of the adhesive layer is preferably 7 μm or less from the viewpoint of durability of the polarizing plate.

  A polarizer and a transparent protective film are bonded together through the adhesive applied as described above. Bonding of the polarizer and the transparent protective film can be performed with a roll laminator or the like.

  After laminating the polarizer and the first and second transparent protective films, an active energy ray (electron beam, ultraviolet ray, etc.) is irradiated to cure the active energy ray-curable adhesive to form an adhesive layer. The irradiation direction of active energy rays (electron beam, ultraviolet ray, etc.) can be irradiated from any appropriate direction. Preferably, it irradiates from the transparent protective film side. When irradiated from the polarizer side, the polarizer may be deteriorated by active energy rays (electron beams, ultraviolet rays, etc.).

  When the polarizing plate according to the present invention is produced in a continuous line, the line speed depends on the curing time of the adhesive, but is preferably 1 to 500 m / min, more preferably 5 to 300 m / min, and still more preferably 10 to 100 m / min. min. When the line speed is too low, productivity is poor, or damage to the transparent protective film is too great, and a polarizing plate that can withstand a durability test or the like cannot be produced. When the line speed is too high, the adhesive is not sufficiently cured, and the target adhesiveness may not be obtained.

  In the polarizing plate of the present invention, the polarizer and the first and second transparent protective films are bonded through an adhesive layer formed by a cured product layer of the active energy ray-curable adhesive, An easy-adhesion layer can be provided between the first and second transparent protective films and the adhesive layer. The easy adhesion layer can be formed of, for example, various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Moreover, you may add another additive for formation of an easily bonding layer. Specifically, a stabilizer such as a tackifier, an ultraviolet absorber, an antioxidant, and a heat resistance stabilizer may be used.

  The easy-adhesion layer is usually provided in advance on the first and second transparent protective films, and the easy-adhesion layer side of the transparent protective film and the polarizer are bonded together with an adhesive layer. The easy-adhesion layer is formed by coating and drying the material for forming the easy-adhesion layer on the transparent protective film by a known technique. The material for forming the easy-adhesion layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying and the smoothness of coating. The thickness of the easy adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. Note that a plurality of easy-adhesion layers can be provided, but also in this case, the total thickness of the easy-adhesion layers is preferably in the above range.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  The optical film in which the optical layer is laminated on the polarizing plate can be formed by a method of laminating separately in the manufacturing process of a liquid crystal display device or the like. It is excellent in stability and assembly work, and has the advantage of improving the manufacturing process of a liquid crystal display device and the like. Appropriate bonding means such as an adhesive layer can be used for lamination. When adhering the above polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell can be provided on the polarizing plate or the optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as an overlapping layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers, such as a different composition, a kind, and thickness, in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

  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. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, an appropriate thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet, metal foil, or a laminate thereof, or a silicone-based or long sheet as necessary. Appropriate ones according to the prior art, such as those coated with an appropriate release agent such as a chain alkyl type, fluorine type or molybdenum sulfide, can be used.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply conventionally. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used. In the liquid crystal display device, the polarizing plate of the present invention preferably has the first transparent protective film side disposed on the liquid crystal cell side.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is arranged on one side or both sides of a liquid crystal cell, or a backlight or a reflecting plate used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a single layer or a suitable layer such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

<Production of polarizer>
A polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 75 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dyed while being immersed in an aqueous solution of 0.3% concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) and stretched to 3.5 times. Then, it extended | stretched so that the total draw ratio might be 6 times in 65 degreeC borate ester aqueous solution. After extending | stretching, it dried for 3 minutes in 40 degreeC oven, and obtained the PVA-type polarizer (23 micrometers in thickness).

<First transparent protective film>
≪Reference Example 1≫
A plasticizer unevenly distributed cellulose ester film having a thickness of 80 μm was obtained. The proportion (a) of the phosphorus plasticizer based on phosphorus atoms on the unevenly distributed side of the film is 0.5 atomic%; the proportion (b) of the phosphorus plasticizer based on phosphorus atoms on the opposite side of the unevenly distributed side of the film is 0 atomic% ;Met.

The plasticizer unevenly distributed cellulose ester film was produced by the following method.
100 parts by weight of cellulose triacetate (acetyl substitution degree 2.88, number average molecular weight 150,000),
10 parts by weight of triphenyl phosphate (phosphorus plasticizer),
Ethylphthalyl ethyl glycolate 2 parts by weight Tinuvin 326 (manufactured by Ciba Specialty Chemicals) 1 part by weight AEROSIL 200V (manufactured by Nippon Aerosil Co., Ltd.) 0.1 parts by weight Needle-like TiO ₂ (manufactured by Ishihara Sangyo Co., Ltd., trade name FTL-) 100) 5 parts by weight Methylene chloride (boiling point: 40.2 ° C.) 660 parts by weight Ethanol 40 parts by weight The above materials were sequentially introduced into the dope melting vessel 1 and the temperature in the vessel was raised from 20 ° C. to 80 ° C. Thereafter, the mixture was stirred for 3 hours while maintaining the temperature at 80 ° C. to completely dissolve the cellulose triacetate. After that, the stirring was stopped, the liquid temperature was lowered to 55 ° C., and immediately after passing through the connected pipe, the liquid was sent to the filter through the liquid feed pump, and the dope was supplied at 1 atm of methylene chloride as the main solvent thereof. Filtration was performed at a boiling point (40.2 ° C.) at + 5 ° C. or higher (55 ° C.).

At this time, the filtration was performed using a cellulose filter with the dope flow rate during filtration set to 60 kg / (hr · m ² ).

  The dope filtered as described above was cast on a support made of a stainless steel endless belt through a casting die kept at 30 ° C. by circulating hot water. The dope viscosity at the time of casting was 50 poise.

  And after making it dry on a support body until the residual solvent amount in a web became 100 weight%, the web was peeled from the support body with the peeling roll.

  Next, the web was introduced into a tenter, both ends of the web were clipped, and the web was stretched 1.1 times in the width direction. Thereafter, the web is dried with a drying device having a transport roll in which the webs are arranged in a staggered manner at 100 ° C., and the cellulose triacetate film is wound up by a winder to finally produce a cellulose triacetate film having a thickness of 80 μm. did.

≪Reference example 2≫
A cellulose ester film having an uneven plasticizer thickness of 80 μm was obtained. The proportion (a) of phosphorus plasticizer based on phosphorus atoms on the unevenly distributed side of the film is 3 atomic%; the proportion (b) of phosphorus plasticizer based on phosphorus atoms on the opposite side of the unevenly distributed side of the film is 0 atomic%; there were. The film was prepared in the same manner as in Reference Example 1 except that the blending ratio of triphenyl phosphate was changed to 60 parts by weight in Reference Example 1.

≪Measurement of plasticizer ratio≫
The ratio of plasticizer (a: atomic%) and (b: atomic%) in the plasticizer unevenly distributed cellulose ester film was measured by ESCA based on phosphorus atoms in the plasticizer. The ratio (a) is in the range from the surface side where the plasticizer is unevenly distributed to the thickness of 5 nm (unevenly distributed side), and the ratio (b) is 5 nm thick from the surface side on the side opposite to the unevenly distributed side. This was done for the range up to (unevenly distributed side).

Acrylic resin film <the second transparent protective film> Thickness 60 [mu] m, moisture permeability ^30g / m 2 / 24h. Thickness 60 [mu] m, moisture permeability ^30g / m 2 / 24h of polyethylene les terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation: T602E50) · Thickness 50 [mu] m, moisture permeability ^9g / m 2 / 24h cyclic polyolefin resin film (Zeonor film, Nippon Zeon Manufactured by ZB12-52125).

≪Water vapor permeability of transparent protective film≫
The moisture permeability was measured according to a moisture permeability test (cup method) of JIS Z0208. A sample cut to a diameter of 60 mm was set in a moisture permeable cup containing about 15 g of calcium chloride, and the temperature was 40 ° C. and the humidity was 90% R.D. H. The placed in a constant temperature machine, to determine the moisture permeability by measuring the weight increase of calcium chloride before and after allowing to stand for 24 hours ^{(g / m 2 / 24h)} .

<Active energy rays>
As an active energy ray, ultraviolet rays (gallium filled metal halide lamp) Irradiation device: Fusion UV Systems, Inc. Light HAMMER10 bulb: V bulb Peak illuminance: 1600 mW / cm ² , integrated irradiation amount 1000 / mJ / cm ² (wavelength 380 to 440 nm) )It was used. In addition, the illumination intensity of the ultraviolet-ray was measured using the Sola-Check system by Solatell.

<Preparation of active energy ray-curable adhesive>
As the radical polymerizable compound (A), 38.3 parts of N-hydroxyethylacrylamide (manufactured by Kojin Co., Ltd.),
19.1 parts of tripropylene glycol diacrylate (trade name: Aronix M-220, manufactured by Toagosei Co., Ltd.) as the radical polymerizable compound (B),
As the radical polymerizable compound (C), 38.3 parts of acryloylmorpholine (manufactured by Kojin Co., Ltd.) and 1.4 parts of photopolymerization initiator (trade name: KAYACURE DETX-S, diethylthioxanthone, Nippon Kayaku Co., Ltd.) Were mixed and stirred at 50 ° C. for 1 hour to obtain an active energy ray-curable adhesive.

<Preparation of aqueous adhesive>
Polyvinyl alcohol-based resin containing acetoacetyl group (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) to 100 parts, Under temperature conditions, an aqueous solution dissolved in pure water and adjusted to a solid content concentration of 3.7% was prepared. An aqueous adhesive solution was prepared by adding 18 parts of an aqueous colloidal alumina solution (average particle size 15 nm, solid content concentration 10%, positive charge) to 100 parts of the aqueous solution.

Example 1
<Preparation of polarizing plate>
The acrylic resin film was used as the second transparent protective film. After forming a 0.5 μm-thick urethane-based easy-adhesive layer on the acrylic resin film, the active energy ray-curable adhesive is applied to the easy-adhesive layer with an MCD coater (manufactured by Fuji Machine Co., Ltd.) ( (Cell shape: honeycomb, gravure roll wire number: 1000 / inch, rotational speed 140% / vs line speed) was applied so that the thickness of the adhesive layer was 0.5 μm. Next, the first transparent protective film (plasticizer unevenly distributed cellulose ester film) and the second transparent protective film (acrylic resin film) were bonded to both sides of the polarizer with a roll machine via the adhesive. The 1st transparent protective film bonded together the surface where the plasticizer is unevenly distributed. Then, it heated to 50 degreeC using IR heater from both sides of the bonded 1st and 2nd transparent protective film, and the said ultraviolet-ray was irradiated to both surfaces, and the active energy ray hardening-type adhesive agent was hardened. Furthermore, it dried with hot air at 70 degreeC for 3 minute (s), and the polarizing plate which has a transparent protective film on both surfaces of a polarizer was obtained. The line speed of bonding was 25 m / min.

Examples 2 to 4 and Comparative Examples 1 to 4
In Example 1, except that the type of the first and second transparent protective films, the bonding side of the first transparent protective film, and the type of adhesive were changed as shown in Table 1, as in Example 1, A polarizing plate was obtained. In addition, when the cyclic polyolefin-type resin film was used as a 2nd transparent protective film, instead of forming an easily adhesive layer in an acrylic resin film, the corona treatment was performed.

[Evaluation]
The following evaluation was performed about the polarizing plate obtained by the Example and the comparative example. The results are shown in Table 2.

(Measurement of degree of polarization)
The single transmittance T, parallel transmittance Tp, and orthogonal transmittance Tc of the polarizing plate were measured using an ultraviolet-visible spectrophotometer (V7100 manufactured by JASCO Corporation). These transmittances are Y values measured by a JISZ8701 two-degree field of view (C light source) and corrected for visibility. The degree of polarization P was determined by the following equation using the above transmittance.
Polarization degree P (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
Table 1 shows the degree of polarization when the single transmittance is 42.8%.

(Adhesive strength)
The obtained polarizing plate was cut into a size of 15 mm × 150 mm to obtain a sample. The sample was affixed on the glass plate with a double-sided adhesive tape (Nitto Denko Corporation, No. 500). The sample (polarizing plate) is preliminarily provided with a gap between the transparent protective film and the polarizer, and the peel is chucked to a variable angle peel tester (manufactured by Asahi Seiko Co., Ltd.) to give a peel strength (N / 15 mm). It was measured. The measurement conditions were normal temperature (23 ° C.), peel angle: 90 degrees, and peel speed: 3000 mm / min. Table 1 shows values obtained by averaging data between 50 mm and 100 mm of the obtained measurement data.

Claims (10)

A polarizing plate in which first and second transparent protective films are bonded to both surfaces of a polarizer via an adhesive layer formed by irradiating an active energy ray-curable adhesive with active energy rays. ,
At least the first transparent protective film is a plasticizer unevenly distributed cellulose ester film comprising a plasticizer and a cellulose ester, and wherein the plasticizer is unevenly distributed on one surface,
The polarizing plate characterized in that the plasticizer is unevenly distributed in the plasticizer unevenly-distributed cellulose ester film, and the surface side where the plasticizer is unevenly distributed is bonded via the adhesive layer. The plasticizer unevenly distributed cellulose ester film has a thickness of 1 μm or more, and
In the plasticizer unevenly distributed cellulose ester film, the proportion (a) of the plasticizer in the range from the surface side where the plasticizer is unevenly distributed to the thickness of 5 nm is plastic in the range from the surface side where the plasticizer is not unevenly distributed to 5 nm. The polarizing plate according to claim 1, wherein the polarizing plate is larger than the ratio (b) of the agent.   The polarizing plate according to claim 1 or 2, wherein the plasticizer contained in the plasticizer unevenly distributed cellulose ester film contains a phosphorus plasticizer.   The polarizing plate according to claim 3, wherein the proportion (a) of the phosphorus plasticizer based on phosphorus atoms in the phosphorus plasticizer is 0.5 to 3 atomic%.   The plasticizer unevenly distributed cellulose ester film has nx> ny> nz (where the in-plane refractive index has the maximum X-axis direction, the direction perpendicular to the X-axis has the Y-axis, and the thickness direction has the Z-axis, The polarizing plate according to any one of claims 1 to 4, wherein the polarizing plate satisfies a relationship of nx, ny, and nz in the axial refractive index. The second transparent protective film, a polarizing plate according to any one of claims 1 to 5, wherein the moisture permeability is not more than 120g / m 2 / ^24h.   The polarizing plate according to claim 1, wherein the second transparent protective film contains a (meth) acrylic resin, a cyclic polyolefin resin, or a polyester resin.   The polarizing plate according to claim 1, wherein the active energy ray curable adhesive is a radical curable active energy ray curable adhesive containing a radical polymerizable compound.   9. An optical film, wherein at least one polarizing plate according to claim 1 is laminated.   An image display device comprising the polarizing plate according to claim 1 or the optical film according to claim 9.