JP5041532B2 - Polarizing plate, optical film and image display device - Google Patents

Description

  The present invention relates to a polarizing plate. 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, triacetyl cellulose having a high moisture permeability is used.

  An image display device such as a liquid crystal display device to which the polarizing plate is applied 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, particularly in mobile applications such as mobile phones, it is desired to reduce the thickness of image display devices, and it is also desired to reduce the thickness of polarizing plates. However, as the polarizing plate is made thinner, it becomes difficult to satisfy the durability.

  On the other hand, the transparent protective film used for the polarizing plate is bonded to the polarizer with an adhesive, but when creating the polarizing plate, when the polarizer and the transparent protective film are bonded together, there is a nick (knic defect). There are problems that occur. A knick is a local irregularity defect that occurs at the interface between a polarizer and a transparent protective film. For such nicks, there has been proposed a method of laminating a transparent protective film on a surface of a polyvinyl alcohol film adjusted in water content with a calender roll under predetermined conditions as a polarizer. (Patent Document 1). In addition, the nick is particularly likely to occur when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol adhesive.

Japanese Patent Laid-Open No. 10-166519

  An object of this invention is to provide the polarizing plate which is thinned and can satisfy durability.

  Another object of the present invention is to provide an optical film in which the polarizing plate is laminated, 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 the polarizing plate shown below and have completed the present invention.

That is, the present invention is a polarizing plate in which a transparent protective film is provided on both surfaces of a polyvinyl alcohol polarizer via an adhesive layer,
The transparent protective film comprises a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic ester unit,
And the thickness for one piece of transparent protective film: T1 (micrometer) is 10-35 micrometers,
The ratio (T2 / T1) of the thickness of the polarizer: T2 (μm) to the thickness: T1 (μm) of one transparent protective film satisfies 0.8 to 1.8. The present invention relates to a polarizing plate.

  In the polarizing plate, the adhesive layer is a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm, and the metal compound colloid is polyvinyl alcohol. It can form from the adhesive agent for polarizing plates mix | blended in the ratio of 200 weight part or less with respect to 100 weight part of type | system | group resin.

  The metal compound colloid is preferably at least one selected from alumina colloid, silica colloid, zirconia colloid, titania colloid and tin oxide colloid. Further, the metal compound colloid preferably has a positive charge, and alumina colloid is particularly preferable.

  In the polarizing plate, it is preferable that the (meth) acrylic resin further has an aromatic vinyl unit.

  In the polarizing plate, it is preferable that the (meth) acrylic resin further contains a styrene resin.

In the polarizing plate, the transparent protective film preferably has a moisture permeability of 250 g / m ² or less.

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

  The present invention also relates to an image display device using the polarizing plate or the optical film.

  In the present invention, as the polarizing plate, the thickness of one transparent protective film: T1 (μm) is 10 to 35 μm, and the thickness of the transparent protective film: T1 (μm), the thickness of the polarizer The ratio (T2 / T1) of T2 (μm) satisfies 0.8 to 1.8. Thus, the polarizing plate of the present invention is a polarizing plate in which the thickness of the transparent protective film and the polarizer is set to be thin, and the thickness is reduced.

  Moreover, in this invention, the transparent protective film uses what contains the (meth) acrylic-type resin which has a glutarimide unit and a (meth) acrylic acid ester unit. The (meth) acrylic resin has low moisture permeability and can satisfy durability such as heat resistance under a high temperature environment and humidity resistance under a high humidity environment even in a thin polarizing plate.

  In the present invention, when a polyvinyl alcohol-based adhesive containing a metal compound colloid having an average particle diameter of 1 to 100 nm is used for forming an adhesive layer for bonding a polarizer and a transparent protective film, Occurrence of the nick is suppressed by the action of the metal compound colloid. Thereby, the yield at the time of producing a polarizing plate can be improved, and the productivity of a polarizing plate improves, As a result, the productivity of a liquid crystal panel improves.

  The metal compound colloid preferably has a positive charge. A metal compound colloid having a positive charge has a greater effect of suppressing the occurrence of nicks than a metal compound colloid having a negative charge. Among these, alumina colloid is suitable as the metal compound colloid having a positive charge.

  As the polarizing plate adhesive for forming the adhesive layer, a polyvinyl alcohol resin can be used, but the present invention is particularly suitable when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol resin. It is. An adhesive using a polyvinyl alcohol-based resin containing an acetoacetyl group can form an adhesive layer having excellent water resistance. On the other hand, in the adhesive for polarizing plates using a polyvinyl alcohol-based resin containing an acetoacetyl group, many occurrences of nicks were observed. In the adhesive for polarizing plates of the present invention, the metal compound colloid is blended. Thus, the occurrence of nicks in the polarizing plate adhesive using a polyvinyl alcohol-based resin containing an acetoacetyl group can be suppressed. Thereby, it has water resistance and can suppress the generation of nicks.

  Hereinafter, the polarizing plate of the present invention will be described. In the polarizing plate of the present invention, a transparent protective film is provided on both surfaces of a polyvinyl alcohol polarizer via an adhesive layer.

  As the polyvinyl alcohol-based polarizer, one obtained by dying a polyvinyl alcohol resin film with a dichroic substance (typically iodine or a dichroic dye) and uniaxially stretching is used. The polymerization degree of the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film is preferably 100 to 10,000, more preferably 1000 to 5,000. If the degree of polymerization is too low, the film tends to be stretched when performing predetermined stretching, and if the degree of polymerization is too high, tension may be abnormally required for stretching, and mechanical stretching may not be possible.

  The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any appropriate method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). Although the thickness of a polarizer is suitably set according to the objective and use of LCD with which a polarizing plate is used, it is 5-63 micrometers normally, Preferably it is 10-50 micrometers, More preferably, it is 20-40 micrometers.

  As a manufacturing method of the polarizer, any appropriate method is adopted depending on the purpose, material used, conditions and the like. For example, the system which uses the said polyvinyl alcohol-type resin film for a series of manufacturing processes including a swelling, dyeing | staining, bridge | crosslinking, extending | stretching, a water washing, and a drying process is employ | adopted normally. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol-based resin film in a liquid containing a solution used in each step. The order, number of times, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing and drying can be appropriately set according to the purpose, materials used and conditions. For example, several processes may be performed simultaneously in one step, and the swelling process, the dyeing process, and the crosslinking process may be performed simultaneously. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. For example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath filled with water. By this treatment, dirt on the surface of the polyvinyl alcohol-based resin film and an anti-blocking agent can be washed, and unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based resin film. Glycerin, potassium iodide or the like is appropriately added to the swelling bath. The temperature of the swelling bath is usually about 10 to 60 ° C., and the immersion time in the swelling bath is usually about 0.1 to 10 minutes.

  The dyeing process is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. The dichroic substance is usually used in a proportion of 0.01 to 0.5 parts by weight, preferably 0.02 to 0.4 parts by weight, with respect to 100 parts by weight of the solvent. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.01 to 10 parts by weight, more preferably 0.02 to 8 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The temperature of the dyeing bath is usually about 10 to 70 ° C., and the immersion time in the dyeing bath is usually about 1 second to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polyvinyl alcohol-based resin film in a treatment desire containing a crosslinking agent. Arbitrary appropriate crosslinking agents are employ | adopted as a crosslinking rate. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These may be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. The crosslinking agent is usually used at a ratio of 2 to 15 parts by weight, preferably 3 to 10 parts by weight, with respect to 100 parts by weight of the solvent. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot be obtained. When the concentration of the crosslinking agent exceeds 15 parts by weight, the stress generated in the film during stretching increases, and the resulting polarizing plate may shrink. It is desirable that the solution of the crosslinking bath further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as those in the dyeing process. The temperature of the crosslinking bath is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polyvinyl alcohol-based resin film is usually 4 times or more. Preferably it is 4-8 times, More preferably, it is 5-6.5 times. When the cumulative draw ratio is less than 4, it becomes difficult to obtain a polarizing plate having a high degree of polarization. When the cumulative draw ratio exceeds 8 times, the polyvinyl alcohol-based resin film may be easily broken. Arbitrary appropriate methods are employ | adopted as a specific method of extending | stretching. For example, when a wet stretching method is employed, a polyvinyl alcohol resin film is stretched at a predetermined magnification in a treatment bath. As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polyvinyl alcohol-based resin film subjected to the above-described various treatments in a treatment bath. The unnecessary residue of the polyvinyl alcohol-based resin film can be washed away by the water washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide, sodium iodide, etc.). The concentration of the aqueous iodide solution is preferably 0.1 to 10% by weight. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is 1 second to 1 minute. The washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process are adjusted suitably. For example, the water washing step includes a step of immersing the polyvinyl alcohol resin film subjected to the above various treatments in an aqueous potassium iodide solution (0.1 to 10% by weight, 10 to 60 ° C.) for about 1 second to 1 minute, and pure water. Including rinsing process. In the water washing step, an organic solvent having compatibility with water (for example, ethanol) may be added as appropriate in order to improve the surface of the polarizer and increase the drying efficiency of the polarizer.

  Arbitrary appropriate methods (For example, natural drying, ventilation drying, heat drying) may be employ | adopted for a drying process. For example, the drying temperature in the case of heat drying is usually about 20 to 150 ° C., preferably 40 to 100 ° C., and the drying time is usually about 1 to 10 minutes. A polarizer is obtained as described above.

  The polarizer used in the present invention has a moisture content of preferably 15% by weight or less, more preferably 0 to 14% by weight, and still more preferably 1 to 14% by weight. When the moisture content is larger than 15% by weight, the dimensional change of the obtained polarizing plate becomes large, and there may be a problem that the dimensional change under high temperature or high temperature and high humidity becomes large.

  The moisture content of the polarizer of the present invention may be adjusted by any appropriate method. For example, there is a method of controlling by adjusting the conditions of the drying process in the manufacturing process of the polarizer.

  The moisture content of the polarizer is measured by the following method. That is, the polarizer was cut out to a size of 100 × 100 mm, and the initial weight of this sample was measured. Subsequently, this sample was dried at 120 ° C. for 2 hours, the dry weight was measured, and the moisture content was measured by the following formula. Moisture content (% by weight) = {(initial weight−dry weight) / initial weight} × 100. The weight was measured three times, and the average value was used.

  The thickness (T2) of these polarizers is not particularly limited, but is generally 5 to 63 μm, preferably 10 to 50 μm, more preferably 20 to 40 μm.

  Moreover, a transparent protective film uses what comprises the (meth) acrylic-type resin which has a glutarimide unit and a (meth) acrylic acid ester unit in both surfaces of a polyvinyl alcohol-type polarizer. The (meth) acrylic resin preferably has an aromatic vinyl unit.

  The (meth) acrylic resin preferably has a glutarimide unit represented by the following general formula (1) and a (meth) acrylic acid ester unit represented by the general formula (2).

Here, R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, R ³ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, Or an aryl group having 6 to 10 carbon atoms.

Here, R ⁴ and R ⁵ each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, R ⁶ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, Or an aryl group having 6 to 10 carbon atoms.

The first structural unit represented by the general formula (1) (hereinafter sometimes referred to as a glutarimide unit) is preferably R ¹ and R ² are hydrogen or a methyl group, R ³ is hydrogen, A methyl group or a cyclohexyl group. The case where R ¹ is a methyl group, R ² is hydrogen, and R ³ is a methyl group is particularly preferred. The glutarimide unit may be of a single type or may include a plurality of types having different R ¹ , R ² , and R ³ .

The second structural unit represented by the general formula (2) (hereinafter sometimes referred to as (meth) acrylic acid ester or (meth) acrylic acid structural unit) is preferably methyl acrylate or ethyl acrylate. , Methyl methacrylate, ethyl methacrylate and the like. Of these, methyl methacrylate is particularly preferred. These second structural units may be of a single type, and may include a plurality of types in which R ⁴ , R ⁵ , and R ⁶ are different.

  The (meth) acrylic resin is more preferably a glutarimide unit represented by the general formula (1), a (meth) acrylic acid ester unit represented by the general formula (2), and the following general formula (3). The structural unit of the aromatic vinyl unit represented by these. The aromatic vinyl unit has an effect of reducing a phase difference that occurs when a (meth) acrylic resin is stretched for the purpose of improving mechanical strength after being formed into a film by a casting method, a melt extrusion method or the like.

Here, R ⁷ represents hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ⁸ represents an aryl group having 6 to 10 carbon atoms.

Preferred examples of the third structural unit represented by the general formula (3) (hereinafter sometimes referred to as an aromatic vinyl unit) include styrene and α-methylstyrene. Of these, styrene is particularly preferred. These third structural units may be of a single type or may include a plurality of types in which R ⁷ and R ⁸ are different.

  The content of the glutarimide unit represented by the general formula (1) in the (meth) acrylic resin is represented by the glutarimide unit represented by the general formula (1) and the general formula (2) (meta ) 60 to 95% by weight is preferred, more preferably 65 to 90% by weight, and still more preferably 70 to 90% by weight, based on the total of acrylic ester units. When a glutarimide unit is smaller than this range, the heat resistance of the film obtained may be insufficient, or transparency may be impaired. On the other hand, if it exceeds this range, the heat resistance is unnecessarily increased and it becomes difficult to form a film, the mechanical strength of the resulting film becomes extremely brittle, and the transparency may be impaired.

  When the (meth) acrylic resin has an aromatic vinyl unit represented by the general formula (3), a glutarimide unit represented by the general formula (1), represented by the general formula (2) (meta ) Based on the total of the acrylic ester unit and the aromatic vinyl unit represented by the general formula (3), the glutarimide unit represented by the general formula (1) and the general formula (2) (meta) ) The total of acrylic ester units is preferably 50 to 90% by weight, more preferably 55 to 90% by weight, and still more preferably 60 to 85% by weight. In this case, the ratio of the glutarimide unit represented by the general formula (1) and the (meth) acrylic acid ester unit represented by the general formula (2) is the same as described above. And content of the aromatic vinyl unit represented by General formula (3) is the glutarimide unit represented by General formula (1), the (meth) acrylic acid ester unit represented by General formula (2), and Preferably it is 10 to 50 weight%, More preferably, it is 10 to 45 weight%, More preferably, it is 15 to 40 weight% on the basis of the sum total of the aromatic vinyl unit represented by General formula (3). When the aromatic vinyl unit is larger than this range, the heat resistance of the resulting film is insufficient and the photoelastic coefficient may be increased. When the aromatic vinyl unit is smaller than this range, the mechanical strength of the film may be decreased.

  When the (meth) acrylic resin is further added with a styrene resin, the same effect as when the (meth) acrylic resin has an aromatic vinyl unit can be obtained. Examples of the styrene resin include acrylonitrile-styrene copolymer. In this case, it is preferable that the content of the aromatic vinyl unit in the styrene resin falls within the above range.

  The (meth) acrylic resin may contain a fourth structural unit. As the fourth structural unit, nitrile monomers such as acrylonitrile and methacrylonitrile, maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide can be used.

  The (meth) acrylic resin may be a linear (linear) polymer, or may be a block polymer, a core-shell polymer, a branched polymer, a ladder polymer, or a crosslinked polymer. There is no problem even if the block polymer is A-B type, A-B-C type, A-B-A type, or any other type. There is no problem even if the core-shell polymer is composed of only one core and only one shell, or each layer is a multilayer.

  The (meth) acrylic resin is a unit that can be imidized in the same manner as the glutarimide resin described in US Pat. No. 3,284,425, US Pat. No. 4,246,374, and JP-A-2-153904. It is obtained by imidizing a resin having a unit capable of imidization with ammonia or a substituted amine, using a resin obtained by using methyl methacrylate or the like as a main raw material.

  The (meth) acrylic resin can be obtained, for example, by imidizing a copolymer of methyl methacrylate and styrene (hereinafter referred to as MS resin) by the above method. In the present invention, it is preferable to imidize MS resin having a styrene content of 10 to 50% by weight, more preferably imidizing MS resin having a styrene content of 15 to 40% by weight, and a styrene content of 20 to 30% by weight. More preferably, the MS resin is imidized.

  Examples of the (meth) acrylic resin having a glutarimide unit, a (meth) acrylic acid ester unit, and an aromatic vinyl unit include JP 2006-309033 A, JP 2006-317560 A, and JP 2006-328329 A. JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492, JP-A-2006-337493, JP-A-2006-337469, and the like.

The (meth) acrylic resin preferably has a weight average molecular weight of 1 × 10 ⁴ to 5 × 10 ⁵ . If the weight average molecular weight is less than the above value, the mechanical strength in the case of film is insufficient, and if it is more than the above value, the viscosity at the time of melting may be high, and the productivity of the film may decrease. is there. The weight average molecular weight was determined in terms of polystyrene using a gel permeation chromatograph (GPC system, manufactured by Tosoh Corporation). Tetrahydrofuran was used as the solvent.

  The glass transition temperature of the (meth) acrylic resin is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, and further preferably 130 ° C. or higher.

The (meth) acrylic resin preferably has a small photoelastic coefficient. Used in the present invention (meth) photoelasticity coefficient of the acrylic resin is preferably not more than ^{20 × 10- 12 m 2 / N} , more preferably 10 × 10 ^-12 m ² / N or less, and still more preferably 5 × or less 10- ¹² m ² / N. If the absolute value of the photoelastic coefficient is larger than 20 × 10- ¹² m ² / N, the optical distortion is caused by stress, light leakage is likely to occur. In particular, the tendency becomes remarkable in a high temperature and high humidity environment.

  The photoelastic coefficient means that when an external force is applied to an isotropic solid to cause stress (ΔF), it temporarily exhibits optical anisotropy and exhibits birefringence (Δn). The ratio of stress to birefringence is called the photoelastic coefficient (c) and is represented by the following formula: c = Δn / ΔF.

  The (meth) acrylic resin has a total light transmittance of preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more, as measured by a method according to ASTM-D-1003. is there. The turbidity of the film is preferably 2% or less, more preferably 1% or less, and still more preferably 0.5% or less.

The thickness (T1) of the transparent protective film is 10 to 35 μm, preferably 20 to 30 μm. The thickness (T1) of the transparent protective film is selected so that the ratio (T2 / T1) is 0.8 to 1.8 in relation to the thickness (T2) of the polarizer. The ratio (T2 / T1) is preferably 0.8 to 1.5. When the thickness ( T1 ) of the transparent protective film is less than 10 μm, or when the ratio (T2 / T1) is greater than 1.8, durability such as heat resistance and moisture resistance is not sufficient, and the polarizer There is a problem that the shrinkage cannot be suppressed and cracks occur, and the market demand cannot be satisfied. Furthermore, the obtained polarizing plate is likely to be broken or easily broken. On the other hand, when the thickness ( T1 ) of the transparent protective film is larger than 35 μm, or when the ratio (T2 / T1) is smaller than 0.8, it is difficult to satisfy the demand for thinning in mobile applications and the like. In addition, although the total thickness of the polarizing plate obtained is set by the said ratio (T2 / T1), it is preferable that it is 50-105 micrometers from a viewpoint which satisfies thickness reduction and handling property, Furthermore, it is preferable that it is 55-100 micrometers.

  The transparent protective film containing the (meth) acrylic resin of the present invention is usually obtained by forming the (meth) acrylic resin into a film by melt extrusion or the like. The resulting film can be uniaxially or biaxially stretched to improve film strength. Although stretching may cause a phase difference, a desired phase difference can be obtained by controlling the content of the aromatic vinyl unit or the styrene resin and the stretching ratio. The draw ratio is usually about 1 to 3 times in the longitudinal and lateral directions.

  Although the retardation of the transparent protective film of the present invention is not particularly limited, those having an in-plane retardation of less than 40 nm and a thickness direction retardation of less than 80 nm are usually used. The in-plane phase difference Re is represented by Re = (nx−ny) × d. The thickness direction retardation Rth is represented by Rth = (nx−nz) × d. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny). [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. In addition, it is preferable that a transparent protective film has as little color as possible. A protective film having a thickness direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the transparent protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  On the other hand, a phase difference plate having an in-plane retardation of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used as the transparent protective film of the present invention. The in-plane 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 functions also as a transparent protective film, so that the thickness can be reduced.

Moreover, since the transparent protective film of this invention uses the said (meth) acrylic-type resin and has the said thickness, it can satisfy the moisture permeability of 250 g / m < ² > or less, and is preferable at a durable point. The moisture permeability is further preferably 200 g / m ² or less.

  In addition, 1 or more types of arbitrary appropriate additives may be contained in the transparent protective film used by this invention. 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; plasticizers; lubricants; antistatic agents; flame retardants;

  The content of the additive in the 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 surface of the transparent protective film to which the polarizer is not adhered may be subjected to a hard coat layer, an antireflection treatment, an antisticking treatment, or a treatment for diffusion or antiglare.

  The hard coat treatment is applied for the purpose of preventing scratches on the surface of the polarizing plate. For example, a transparent protective film with a cured film excellent in hardness, sliding properties, etc. by an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the film. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the transparent protective film itself, or can be provided separately from the transparent protective film as an optical layer.

  The adhesive layer used for laminating the polarizer and the transparent protective film is not particularly limited as long as it is optically transparent, and water-based, solvent-based, hot-melt-based, and radical-curing types are used. A water-based adhesive or a radical curable adhesive is suitable.

  Although it does not specifically limit as a water-system adhesive agent which forms an adhesive bond layer, For example, a vinyl polymer type | system | group, a gelatin type, a vinyl type latex type, a polyurethane type, an isocyanate type, a polyester type, an epoxy type etc. can be illustrated. Such an adhesive layer composed of an aqueous adhesive can be formed as an aqueous solution coating / drying layer, etc., but when preparing the aqueous solution, a catalyst such as a crosslinking agent, other additives, and an acid can be used as necessary. Can be blended. As the water-based adhesive, an adhesive containing a vinyl polymer is preferably used, and the vinyl polymer is preferably a polyvinyl alcohol resin. The polyvinyl alcohol-based resin can contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. In particular, when a polyvinyl alcohol polymer film is used as the polarizer, it is preferable from the viewpoint of adhesiveness to use an adhesive containing a polyvinyl alcohol resin. Furthermore, an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable from the viewpoint of improving durability.

  Polyvinyl alcohol resin is polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Examples thereof include modified polyvinyl alcohols that have been converted into ethers, ethers, grafts, or phosphoric esters. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives and the like. . These polyvinyl alcohol resins can be used singly or in combination of two or more.

  The polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of adhesiveness, the average degree of polymerization is about 100 to 5000, preferably 1000 to 4000, the average saponification degree is about 85 to 100 mol%, preferably 90 to 100 mol%. It is.

  A polyvinyl alcohol-based resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto, and a polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. And the like. Another example is a method in which diketene gas or liquid diketene is brought into direct contact with polyvinyl alcohol.

  The degree of acetoacetyl group modification of the polyvinyl alcohol-based resin containing an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. If it is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient and unsuitable. The degree of acetoacetyl group modification is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. When the acetoacetyl group modification degree exceeds 40 mol%, the effect of improving water resistance is small. The degree of acetoacetyl modification is a value measured by NMR.

  As a crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. A compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene diamine and hexamethylene diamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (Isocyanates such as 4-phenylmethane triisocyanate, isophorone diisocyanate and ketoxime block product or phenol block product thereof; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexane Diol diglycidyl ether, trimethylolpropane triglycidyl ether, jig Epoxys such as sidylaniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; Aldehydes: amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; further sodium, potassium, magnesium, calcium, aluminum, iron And salts of divalent metals such as nickel or trivalent metals and oxides thereof, among which amino-formaldehyde resins and dia Dehydrates are preferred, amino-formaldehyde resins are preferably compounds having a methylol group, and dialdehydes are preferably glyoxal, particularly methylol melamine, which is a compound having a methylol group. As the crosslinking agent, a coupling agent such as a silane coupling agent or a titanium coupling agent can be used.

  The amount of the crosslinking agent can be appropriately designed according to the type of polyvinyl alcohol resin, etc., but is usually about 4 to 60 parts by weight, preferably 10 to 55 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. Degree, more preferably 20 to 50 parts by weight. In such a range, good adhesiveness can be obtained.

  In order to improve the durability, a polyvinyl alcohol resin containing an acetoacetyl group is used. Also in this case, the crosslinking agent is used in the range of about 4 to 60 parts by weight, preferably about 10 to 55 parts by weight, and more preferably 20 to 50 parts by weight, as described above, with respect to 100 parts by weight of the polyvinyl alcohol resin. Is preferred. When the amount of the crosslinking agent is too large, the reaction of the crosslinking agent proceeds in a short time and the adhesive tends to gel. As a result, the pot life as an adhesive is extremely shortened, making industrial use difficult. From this point of view, the blending amount of the crosslinking agent is used in the above blending amount. However, since the resin solution of the present invention contains the metal compound colloid, the blending amount of the crosslinking agent is large as described above. Even if it exists, it can be used with good stability.

  As the polarizing plate adhesive of the present invention, a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle size of 1 to 100 nm is preferably used. The resin solution is usually used as an aqueous solution. The concentration of the resin solution is not particularly limited, but is 0.1 to 15% by weight, preferably 0.5 to 10% by weight in consideration of coating properties and storage stability.

  The metal compound colloid is one in which fine particles are dispersed in a dispersion medium, and is electrostatically stabilized due to mutual repulsion of the same kind of charge of the fine particles, and has permanent stability. The average particle diameter of the metal compound colloid (fine particles) is 1 to 100 nm. When the average particle diameter of the colloid is within the above range, the metal compound can be dispersed substantially uniformly in the adhesive layer, the adhesiveness can be ensured, and the nick can be suppressed. The range of the average particle diameter is considerably smaller than the wavelength range of visible light, and even if the transmitted light is scattered by the metal compound in the formed adhesive layer, the polarization characteristics are not adversely affected. The average particle size of the metal compound colloid is preferably 1 to 100 nm, more preferably 1 to 50 nm.

  Various types of metal compound colloids can be used. For example, colloids of metal compounds such as alumina, silica, zirconia, titania, tin oxide, aluminum silicate, calcium carbonate, and magnesium silicate; colloids of metal salts such as zinc carbonate, barium carbonate, and calcium phosphate And colloids of minerals such as celite, talc, clay and kaolin.

  The metal compound colloid is dispersed in a dispersion medium and exists in a state of a colloid solution. The dispersion medium is mainly water. In addition to water, other dispersion media such as alcohols can also be used. The solid content concentration of the metal compound colloid in the colloid solution is not particularly limited, but is generally about 1 to 50% by weight, and more preferably 1 to 30% by weight. In addition, as the metal compound colloid, those containing an acid such as nitric acid, hydrochloric acid, and acetic acid as a stabilizer can be used.

  Metal compound colloids are electrostatically stabilized and can be classified into those having a positive charge and those having a negative charge. Metal compound colloids are non-conductive materials. Positive charge and negative charge are distinguished by the charge state of the colloidal surface charge in the solution after the adhesive preparation. The charge of the metal compound colloid can be confirmed, for example, by measuring the zeta potential with a zeta potential measuring machine. The surface charge of a metal compound colloid generally varies with pH. Therefore, the charge in the state of the colloidal solution of the present application is affected by the pH of the adjusted adhesive solution. The pH of the adhesive solution is usually set in the range of 2 to 6, preferably 2.5 to 5, more preferably 3 to 5, and further 3.5 to 4.5. In the present invention, a metal compound colloid having a positive charge has a greater effect of suppressing the occurrence of nicks than a metal compound colloid having a negative charge. Examples of the positively charged metal compound colloid include alumina colloid, zirconia colloid, titania colloid, and tin oxide colloid. Among these, alumina colloid is particularly preferable.

  A metal compound colloid is mix | blended in the ratio (converted value of solid content) of 200 weight part or less with respect to 100 weight part of polyvinyl alcohol-type resin. Moreover, by setting the blending ratio of the metal compound colloid within the above range, it is possible to suppress the occurrence of nicks while ensuring the adhesion between the polarizer and the transparent protective film. The compounding ratio of the metal compound colloid is preferably 10 to 200 parts by weight, more preferably 20 to 175 parts by weight, and further preferably 30 to 150 parts by weight. When the compounding ratio of the metal compound colloid exceeds 200 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin, the ratio of the polyvinyl alcohol resin in the adhesive is reduced, which is not preferable from the viewpoint of adhesiveness. The mixing ratio of the metal compound colloid is not particularly limited, but is preferably set to the lower limit of the above range in order to effectively suppress nicks.

  Although the viscosity of the resin solution which is an adhesive for polarizing plates is not particularly limited, those having a range of 1 to 50 mPa · s are used. The nick generated in the production of the polarizing plate tends to increase as the viscosity of the resin solution decreases. However, according to the polarizing plate adhesive of the present invention, a range of 1 to 20 mPa · s can be obtained. Even in the low viscosity range, the occurrence of nicks can be suppressed, and the occurrence of nicks can be suppressed regardless of the viscosity of the resin solution. A polyvinyl alcohol resin containing an acetoacetyl group cannot be increased in polymerization degree compared to a general polyvinyl alcohol resin and has been used at a low viscosity as described above. Even when a polyvinyl alcohol-based resin containing an acetyl group is used, the occurrence of nicks caused by the low viscosity of the resin solution can be suppressed.

  The method for preparing the resin solution that is the polarizing plate adhesive is not particularly limited. In general, a resin solution is prepared by mixing a polyvinyl alcohol resin and a crosslinking agent and blending a metal compound colloid with a mixture having an appropriate concentration. In addition, when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol resin or when the amount of the crosslinking agent is large, the polyvinyl alcohol resin and the metal are considered in consideration of the stability of the solution. After mixing the compound colloid, the cross-linking agent can be mixed in consideration of the use time of the resulting resin solution. In addition, the density | concentration of the resin solution which is an adhesive agent for polarizing plates can also be adjusted suitably after preparing a resin solution.

  Examples of the radical curable adhesive include various active energy ray curable types such as an electron beam curable type and an ultraviolet ray curable type, and a thermosetting type, but there are active energy ray curable types that can be cured in a short time. preferable. In particular, an electron beam curable type is preferable. An electron beam curable adhesive can be used. By using an electron beam for the adhesive curing method used to bond the polarizer and the transparent protective film (ie, dry lamination), a heating step such as an ultraviolet curing method becomes unnecessary, and the productivity is extremely high. can do.

  Examples of the curable component include a compound having a (meth) acryloyl group and a compound having a vinyl group. These curable components may be monofunctional or bifunctional or higher. Moreover, these curable components can be used individually by 1 type or in combination of 2 or more types. As these curable components, for example, compounds having a (meth) acryloyl group are suitable. For example, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and various (meth) acrylates. Examples thereof include acrylate monomers.

  In addition, a compound having a (meth) acryloyl group, particularly a monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, a nitrogen-containing (meth) acrylate, or a carboxyl group-containing (meth) acrylate is used as the curable component. The curable component is suitable as an electron beam curable adhesive, and a polarizing plate having good adhesion to a polarizer and a transparent protective film can be obtained by using the adhesive. For example, even when a polarizer with a low moisture content is used, and when a material with low moisture permeability is used as the transparent protective film, the adhesive of the present invention exhibits good adhesion to them. As a result, a polarizing plate with good dimensional stability can be obtained.

  When the curable component is used, a polarizing plate having a small dimensional change can be produced, so that it is possible to easily cope with an increase in the size of the polarizing plate, and it is possible to suppress the production cost from the viewpoint of yield and number. Further, since the polarizing plate obtained in the present invention has good dimensional stability, it is possible to suppress the occurrence of unevenness in the image display device due to the external heat of the backlight.

  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) Examples thereof include acrylate and 2-hydroxy-3-phenyl polyethylene glycol propyl (meth) acrylate.

  Examples of the nitrogen-containing monomer include a heterocyclic ring-containing acrylic having a heterocyclic ring such as a morpholine ring such as N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, and N-acryloylpyrrolidine, a piperidine ring, a pyrrolidine ring, and a piperazine ring. Monomer. Examples of the nitrogen-containing monomer include maleimide, N-cyclohexylmaleimide, N-phenylmaleimide; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N -Hexyl (meth) acrylamide, N-methyl (meth) acrylamide, N-butyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide, N- (N-substituted) amide monomers such as isopropylacrylamide, N-methylol (meth) acrylamide, N-hydroxyethyl (meth) acrylamide, N-methylol-N-propane (meth) acrylamide; aminoethyl (meth) acrylate, ( T) (Meth) acrylic acid such as aminopropyl acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, 3- (3-pyridyl) propyl (meth) acrylate Alkylaminoalkyl monomers; succinimide monomers such as N- (meth) acryloyloxymethylenesuccinimide, N- (meth) acryloyl-6-oxyhexamethylenesuccinimide, N- (meth) acryloyl-8-oxyoctamethylenesuccinimide, etc. It is done. For example, the nitrogen-containing monomer is preferably a heterocyclic ring-containing acrylic monomer, and particularly preferably N-acryloylmorpholine.

  Examples of the carboxyl group monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and the like. Of these, acrylic acid is preferred.

  In addition to the above, compounds having a (meth) acryloyl group include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, and isononyl. Alkyl (meth) acrylates having 1 to 12 carbon atoms such as (meth) acrylate and lauryl (meth) acrylate; (meth) acrylic acid alkoxyalkyl systems such as (meth) acrylic acid methoxyethyl and (meth) acrylic acid ethoxyethyl Monomer: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy (meth) acrylate Octyl, (meth) acrylic acid 10-H Hydroxyl-containing monomers such as loxydecyl, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) -methyl acrylate; acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone addition of acrylic acid Products; sulfones such as 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 Acid group-containing monomers; phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate.

  As the curable component, a monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, a nitrogen-containing monomer, and a carboxyl group monomer are preferably used. It is preferable to contain these components as curable components in an amount of 50% by weight or more in order to obtain a polarizing plate having an adhesive layer having good adhesion to the polarizer and the transparent protective film. Furthermore, it is preferable also from points, such as coating property and workability. The ratio of the curable component is preferably 60% by weight or more, more preferably 70% by weight or more, and further preferably 80% by weight or more.

  As the curable component, a bifunctional or higher curable component can be used. The bifunctional or higher curable component is preferably a bifunctional or higher (meth) acrylate, particularly a bifunctional or higher epoxy (meth) acrylate. The bifunctional or higher functional epoxy (meth) acrylate is obtained by reacting a polyfunctional epoxy compound with (meth) acrylic acid. Various examples of the polyfunctional epoxy compound can be exemplified. Examples of the polyfunctional epoxy compound include aromatic epoxy resins, alicyclic epoxy resins, and aliphatic epoxy resins.

  Examples of the aromatic epoxy resin include bisphenol type epoxy resins such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of bisphenol S; phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde Examples thereof include novolak-type epoxy resins such as phenol novolac epoxy resins; glycidyl ethers of tetrahydroxyphenylmethane, glycidyl ethers of tetrahydroxybenzophenone, and polyfunctional epoxy resins such as epoxidized polyvinylphenol.

  Examples of the alicyclic epoxy resins include hydrogenated products of the above-mentioned aromatic epoxy resins, cyclohexane-based, cyclohexylmethyl ester-based, cicyclohexylmethyl ether-based, spiro-based, and tricyclodecane-based epoxy resins.

  Examples of the aliphatic epoxy resin include polyglycidyl ethers of aliphatic polyhydric alcohols or alkylene oxide adducts thereof. Examples include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane triglycidyl ether, polyethylene glycol diglycidyl ether, propylene. Polyethers of polyether polyols obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohols such as glycol diglycidyl ether, ethylene glycol, propylene glycol, and glycerin Examples thereof include glycidyl ether.

  The epoxy equivalent of the epoxy resin is usually in the range of 30 to 3000 g / equivalent, preferably 50 to 1500 g / equivalent.

  The bifunctional or higher epoxy (meth) acrylate is preferably an epoxy (meth) acrylate of an aliphatic epoxy resin, particularly preferably an epoxy (meth) acrylate of a bifunctional aliphatic epoxy resin.

  Among the curable components, a compound having a (meth) acryloyl group, in particular, a monofunctional (meth) acrylate having an aromatic ring and a hydroxy group, a nitrogen-containing (meth) acrylate, a carboxyl group-containing (meth) acrylate, It is suitable as an electron beam curable adhesive, and by using the adhesive, a polarizing plate having good adhesion to a polarizer and a transparent protective film can be obtained. For example, even when a polarizer with a low moisture content is used, and when a material with low moisture permeability is used as the transparent protective film, the adhesive of the present invention exhibits good adhesion to them. As a result, a polarizing plate with good dimensional stability can be obtained.

  The curable adhesive contains a curable component, and in addition to the above components, a radical initiator is added depending on the type of curing. When the adhesive is used as an electron beam curable type, it is not particularly necessary that the adhesive contains a radical initiator, but when used as an ultraviolet curable type or a thermosetting type, a radical initiator is used. Used. The usage-amount of a radical initiator is about 0.1-10 weight part normally per 100 weight part of sclerosing | hardenable components, Preferably, it is 0.5-3 weight part.

  The adhesive may contain a metal compound filler. With the metal compound filler, the fluidity of the adhesive layer can be controlled, the film thickness can be stabilized, and a polarizing plate having a good appearance, uniform in-plane and no adhesive variation can be obtained.

  Various types of metal compound fillers can be used. Examples of the metal compound include metal oxides such as alumina, silica, zirconia, titania, aluminum silicate, calcium carbonate and magnesium silicate; metal salts such as zinc carbonate, barium carbonate and calcium phosphate; celite, talc, clay and kaolin And the like. Further, these metal compound fillers may be those having a surface modified.

  The average particle diameter of the metal compound filler is usually about 1 to 1000 nm, more preferably 10 to 200 nm, and further preferably 10 to 100 nm. If the average particle diameter of the metal compound filler is within the above range, the metal compound can be dispersed substantially uniformly in the adhesive layer, ensuring adhesion, and having a good appearance and in-plane uniform adhesion. You can get sex.

  It is preferable to mix | blend the compounding quantity of a metal compound filler in the ratio of 200 weight part or less with respect to 100 weight part of sclerosing | hardenable components. In addition, by setting the blending ratio of the metal compound filler in the above range, in-plane uniform adhesiveness can be obtained with a good appearance while ensuring the adhesiveness between the polarizer and the transparent protective film. The blending ratio of the metal compound filler is preferably 1 to 100 parts by weight, more preferably 2 to 50 parts by weight, and further preferably 5 to 30 parts by weight. When the compounding ratio of the metal compound filler exceeds 100 parts by weight with respect to 100 parts by weight of the curable component, the ratio of the curable component in the adhesive is reduced, which is not preferable from the viewpoint of adhesiveness. The mixing ratio of the metal compound filler is not particularly limited, but is preferably set to the lower limit of the above range in order to obtain in-plane uniform adhesiveness while ensuring adhesiveness and good appearance. .

  In addition, the adhesive for polarizing plate includes various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, plasticizers, leveling agents, foaming inhibitors, antistatic cracks, hydrolysis stabilizers, and other stabilizers. A stabilizer such as can also be blended. Further, the metal compound colloid and the metal compound filler in the present application are non-conductive materials, but may contain fine particles of a conductive substance. In addition, examples of additives include sensitizers that increase the curing speed and sensitivity by electron beams typified by carbonyl compounds, coupling agents such as silane coupling agents and titanium coupling agents, and adhesives typified by ethylene oxide. Accelerators, additives that improve wettability with the transparent protective film, acryloxy group compounds, hydrocarbons (natural and synthetic resins), and the like.

  The polarizing plate can be obtained by laminating a transparent protective film on both sides of a polarizer via an adhesive layer. Between the adhesive layer and the transparent protective film or the polarizer, an undercoat layer or an easy adhesion treatment is obtained. A layer or the like may be provided. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment (saponification treatment), and coating treatment for forming an easy adhesive layer. Among these, a coating treatment or an alkali treatment for forming an easy-adhesive layer is preferable. Various easy-adhesive materials such as polyol resin, polycarboxylic acid resin, polyester resin, and silicone resin can be used for forming the easy-adhesive layer. The thickness of the easy-adhesive layer is usually about 0.001 to 10 μm, more preferably about 0.001 to 5 μm, and particularly preferably about 0.001 to 1 μm.

  When the adhesive layer is formed of a water-based adhesive or the like, the thickness of the adhesive layer is about 10 to 300 nm. The thickness of the adhesive layer is more preferably 10 to 200 nm, and still more preferably 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and obtaining a sufficient adhesive force. Further, as described above, the thickness of the adhesive layer is preferably designed to be larger than the average particle diameter of the metal compound colloid contained in the polarizing plate adhesive.

  The method of adjusting the thickness of the adhesive layer is not particularly limited, and examples thereof include a method of adjusting the solid content concentration of the adhesive solution and an adhesive application device. The method for measuring the thickness of the adhesive layer is not particularly limited, but cross-sectional observation measurement using SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) is preferably used. The application operation of the adhesive is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed.

  After applying the water-based adhesive, the polarizer and the transparent protective film are bonded together with a roll laminator or the like. Application | coating of the said adhesive agent may be performed to any of a transparent protective film and a polarizer, and may be performed to both. After the bonding, a drying process is performed to form an adhesive layer composed of a coating dry layer. A drying temperature is about 5-150 degreeC, Preferably it is 30-120 degreeC, is 120 second or more, Furthermore, it is 300 second or more.

  On the other hand, when the adhesive layer is formed of a curable adhesive (electron beam curable adhesive), the thickness of the adhesive layer is preferably 0.1 to 20 μm, more preferably 0.2 to It is 10 μm, more preferably 0.3 to 8 μm. When the thickness is small, the cohesive force of the adhesive force itself cannot be obtained, and the adhesive strength may not be obtained. When the thickness of the adhesive layer exceeds 20 μm, the cost increases and the effect of curing shrinkage of the adhesive itself appears, which may adversely affect the optical properties of the polarizing plate.

  After laminating the polarizer and the transparent protective film, the adhesive is cured by irradiation with an electron beam or the like. The irradiation direction of the electron beam 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 the electron beam.

  Any appropriate condition can be adopted as the electron beam irradiation condition as long as the adhesive can be cured. For example, in the electron beam irradiation, the acceleration voltage is preferably 5 kV to 300 kV, and more preferably 10 kV to 250 kV. If the acceleration voltage is less than 5 kV, the electron beam may not reach the adhesive and may be insufficiently cured. If the acceleration voltage exceeds 300 kV, the penetration force through the sample is too strong and the electron beam rebounds, There is a risk of damaging the polarizer. The irradiation dose is 5 to 100 kGy, more preferably 10 to 75 kGy. When the irradiation dose is less than 5 kGy, the adhesive becomes insufficiently cured, and when it exceeds 100 kGy, the transparent protective film and the polarizer are damaged, resulting in a decrease in mechanical strength and yellowing, thereby obtaining predetermined optical characteristics. I can't.

  Electron beam irradiation is usually performed in an inert gas, but if necessary, it may be performed in the atmosphere or under a condition in which a small amount of oxygen is introduced. Depending on the material of the transparent protective film, by appropriately introducing oxygen, the transparent protective film surface where the electron beam first hits can be obstructed to prevent oxygen damage and prevent damage to the transparent protective film. An electron beam can be irradiated efficiently.

  When performing the said manufacturing method by a continuous line, although it depends on the hardening time of an adhesive agent, Preferably it is 1-500 m / min, More preferably, it is 5-300 m / min, More preferably, it is 10-100 m / 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.

  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.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  Specific examples of the reflective polarizing plate include those in which a reflective layer is formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum on one side of a transparent protective film matted as necessary. Moreover, the transparent protective film contains fine particles so as to have a surface fine concavo-convex structure and a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has an advantage that incident light is diffused by irregular reflection to prevent directivity and glaring appearance and to suppress unevenness in brightness and darkness. The transparent protective film containing fine particles also has an advantage that incident light and its reflected light are diffused when passing through it, and light and dark unevenness can be further suppressed. The reflective layer of the fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is formed by transparent the metal by an appropriate method such as a vapor deposition method such as a vacuum vapor deposition method, an ion plating method, a sputtering method, or a plating method. It can be performed by a method of directly attaching to the surface of the protective layer.

  Instead of the method of directly applying the reflecting plate to the transparent protective film of the polarizing plate, the reflecting plate can be used as a reflecting sheet provided with a reflecting layer on an appropriate film according to the transparent film. Since the reflective layer is usually made of metal, the usage form in which the reflective surface is covered with a transparent protective film, a polarizing plate or the like is used to prevent the reflectance from being lowered due to oxidation, and thus to maintain the initial reflectance for a long time. In addition, it is more preferable to avoid a separate attachment of the protective layer.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell, and displays an image by reflecting incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device or the like that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptically polarizing plate is effectively used for black and white display without the above color by compensating (preventing) the coloration (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twist nematic (STN) type liquid crystal display device. It is done. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has an antireflection function. Specific examples of the retardation plate include a birefringent film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefins, polyarylate, and polyamide. And an alignment film of a liquid crystal polymer, and a liquid crystal polymer alignment layer supported by a film. The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of the liquid crystal layer, viewing angle, and the like. What laminated | stacked the phase difference plate and controlled optical characteristics, such as phase difference, etc. may be used.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, an alignment film such as a retardation film or a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. Birefringent polymer film, biaxially stretched film such as polymer with birefringence with a controlled refractive index in the thickness direction that is uniaxially stretched in the plane direction and stretched in the thickness direction, etc. Used. Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer for the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloration due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expanding the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is, when light is incident through the polarizer from the back side of the liquid crystal cell without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost polarized. It is absorbed by the polarizer and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, approximately 50% of the light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display or the like is reduced accordingly, resulting in a dark image. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflective layer provided on the rear side thereof. Repeatedly re-enter the brightness enhancement film, and the brightness enhancement film transmits only polarized light whose polarization direction is such that the polarization direction of light reflected and inverted between the two can pass through the polarizer. Therefore, light such as a backlight can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

  A diffusion plate may be provided between the brightness enhancement film and the reflective layer. The polarized light reflected by the brightness enhancement film is directed to the reflective layer or the like, but the installed diffuser plate uniformly diffuses the light passing therethrough and simultaneously cancels the polarized state and becomes a non-polarized state. That is, the diffuser plate returns the polarized light to the original natural light state. The light in the non-polarized state, that is, the natural light state is directed toward the reflection layer and the like, reflected through the reflection layer and the like, and again passes through the diffusion plate and reenters the brightness enhancement film. Thus, while maintaining the brightness of the display screen by providing a diffuser plate that returns polarized light to the original natural light state between the brightness enhancement film and the reflective layer, etc., the brightness unevenness of the display screen is reduced at the same time, A uniform and bright screen can be provided. By providing such a diffuser plate, it is considered that the first incident light has a moderate increase in the number of repetitions of reflection, and in combination with the diffusion function of the diffuser plate, a uniform bright display screen can be provided.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things such as a thing can be used.

  Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis as described above, the transmitted light is incident on the polarizing plate with the polarization axis aligned as it is, thereby efficiently transmitting while suppressing absorption loss due to the polarizing plate. Can be made. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable to make it enter into a polarizing plate. Note that circularly polarized light can be converted to linearly polarized light by using a quarter wave plate as the retardation plate.

  A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region exhibits, for example, a retardation layer that functions as a quarter-wave plate for light-color light having a wavelength of 550 nm and other retardation characteristics. It can be obtained by a method of superposing a retardation layer, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

  In addition, the cholesteric liquid crystal layer can also be obtained by reflecting circularly polarized light in a wide wavelength range such as a visible light region by combining two or more layers having different reflection wavelengths and having an overlapping structure. Based on this, transmitted circularly polarized light in a wide wavelength range can be obtained.

  Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers like the above-described polarization separation type polarizing plate. Therefore, a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above-mentioned reflective polarizing plate or transflective polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the 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 may be provided on the polarizing plate described above or an 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.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc. An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. 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 40 μm, preferably 5 to 30 μm, particularly preferably 10 to 25 μm. If it is thinner than 1 μm, the durability will be poor, and if it is thicker than 40 μm, it will be liable to float or peel off due to foaming, resulting in poor appearance.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to 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, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  In order to improve the adhesion between the polarizing plate and the pressure-sensitive adhesive layer, an anchor layer can be provided between the layers.

  As the material for forming the anchor layer, an anchor agent selected from polyurethane, polyester, and polymers containing an amino group in the molecule is preferably used, and polymers containing an amino group in the molecule are particularly preferred. . Polymers containing an amino group in the molecule ensure good adhesion because the amino group in the molecule exhibits an interaction such as a reaction or ionic interaction with the carboxyl group in the pressure-sensitive adhesive.

  Examples of polymers containing an amino group in the molecule include polymers of amino-containing group-containing monomers such as polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, dimethylaminoethyl acrylate, and the like.

  An antistatic agent may be added to the anchor layer in order to impart antistatic properties. Antistatic agents for imparting antistatic properties include ionic surfactant systems, conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline, metal oxide systems such as tin oxide, antimony oxide, and indium oxide. In particular, from the viewpoint of optical properties, appearance, antistatic effect, and antistatic effect heating and stability during humidification, a conductive polymer system is preferably used. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used. When a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, it is possible to suppress deterioration of the optical film substrate due to an organic solvent during coating.

  In the present invention, the polarizer, the transparent protective film, the optical film, and the like that form the polarizing plate described above, and each layer such as the adhesive layer include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylates. It may be a compound having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a compound based on nickel or a nickel complex salt compound.

  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 according to the former. As the liquid crystal cell, any type such as a TN type, STN type, π type, VA type, IPS type, or the like can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector 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 a liquid crystal display device, for example, a single layer or a suitable part 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.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the phosphor material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle between the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In each example, parts and% are based on weight unless otherwise specified.

(Measurement of phase difference)
The refractive index nx, ny, nz at a wavelength of 590 nm of the transparent protective film is measured by an automatic birefringence measuring device (manufactured by Oji Scientific Instruments, automatic birefringence meter KOBRA21ADH) based on the parallel Nicol rotation method. A phase difference Re and a thickness direction phase difference Rth were calculated.

(Moisture permeability)
According to the moisture permeability test (cup method) of JIS Z0208, this is a value obtained by measuring the number of g of water vapor passing through a sample of area 1 m ² in 24 hours in an atmosphere of a temperature of 40 ° C. and a humidity of 92% RH.

(Viscosity of adhesive aqueous solution)
The prepared adhesive aqueous solution (normal temperature: 23 ° C.) was measured with a rheometer (RSI-HS, manufactured by HAAKE).

(Average colloid particle size)
The alumina colloidal aqueous solution was measured by a dynamic light scattering method (light correlation method) with a particle size distribution meter (manufactured by Nikkiso Co., Ltd., Nanotrac UPA150).

(Production of polarizer)
A polymer film [trade name “9P75R” manufactured by Kuraray Co., Ltd.] (average polymerization degree 2400, saponification degree 99.9 mol%) having a thickness of 75 μm as a main component of polyvinyl alcohol and iodine and iodine maintained at 30 ± 3 ° C. In a dyeing bath containing potassium halide, uniaxial stretching was performed 2.5 times while dyeing using a roll stretching machine. Next, in an aqueous solution bath containing boric acid and potassium iodide held at 60 ± 3 ° C., the film was uniaxially stretched so as to be 6 times the original length of the polyvinyl alcohol film while performing a crosslinking reaction. The obtained film was dried for 30 minutes in an air circulating constant temperature oven at 50 ± 1 ° C. to obtain a polarizer having a moisture content of 26% and a thickness of 27 μm.

(Transparent protective film)
The following were used.
Transparent protective film 1: MS resin (MS-200; copolymer of methyl methacrylate / styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) is imidized with monomethylamine (imidization ratio: 90%). The obtained imidized MS resin has a glutarimide unit represented by the general formula (1) (wherein R ¹ and R ³ are methyl groups, R ² is a hydrogen atom), and the general formula (2) A (meth) acrylic acid ester unit represented by (R ⁴ is a hydrogen atom, R ⁵ and R ⁶ are methyl groups), and an aromatic vinyl unit represented by the general formula (3) (R ⁷ is a hydrogen atom) , R ⁸ is a phenyl group). For the imidization, a mesh type co-rotating twin screw extruder having a diameter of 15 mm was used. The set temperature of each temperature control zone of the extruder was 230 ° C., the screw rotation speed was 150 rpm, MS resin was supplied at 2.0 kg / hr, and the supply amount of monomethylamine was 40 parts by weight with respect to the MS resin. MS resin was introduced from the hopper, and the resin was melted and filled with a kneading block, and then monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. By-products after the reaction and excess methylamine were devolatilized by reducing the pressure at the vent port to -0.08 MPa. The resin that came out as a strand from a die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer. The imidized MS resin was melt-extruded to form a transparent protective film (Re = 2 nm, Rth = 2 nm) having a predetermined thickness.

In the obtained imidized MS resin, the ratio of the general formula (1) (imidation rate) was measured at room temperature using the product pellets as they were and using the TravelIR manufactured by SensIR Technologies, Inc. . From the obtained spectrum, the absorption intensity (Abs _Ester) attributed to the ester carbonyl group of 1720 cm ^-1, the imidization ratio from the ratio of the absorption intensity assignable to an imide carbonyl group of 1660cm ^-1 (Abs _imide) (Im % (IR)). Here, the imidation rate refers to the proportion of the imide carbonyl group in all carbonyl groups.

  Transparent protective film 2: A 40 μm thick triacetyl cellulose film (Fuji Film Co., Ltd., Re = 1 nm, Rth = 50 nm) was used.

(Preparation of 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. The viscosity of the adhesive aqueous solution was 9.6 mPa · s. The pH of the aqueous adhesive solution was in the range of 4-4.5. This is referred to as an adhesive 1. Also, an adhesive aqueous solution was prepared by adding no alumina colloid aqueous solution to the adhesive 1. The viscosity of the aqueous adhesive solution was 7.0 mPa · s. The pH of the aqueous adhesive solution was in the range of 4-4.5. This is referred to as an adhesive 2.

Example 1
(Creation of polarizing plate)
Two sheets of the transparent protective film 1 (thickness 35 μm) were prepared by applying the adhesive 1 so that the thickness of the adhesive layer after drying was 80 nm. Application of the adhesive was performed under a temperature condition of 23 ° C. 30 minutes after the preparation. Next, the transparent protective film 1 with the adhesive was bonded to both sides of the polarizer under a temperature condition of 23 ° C. with a roll machine, and then dried at 55 ° C. for 6 minutes to prepare a polarizing plate. The ratio (T2 / T1) = (27/35) = 0.8.

Examples 2-5, Comparative Examples 1-3
In Example 1, the polarizing plate was prepared in the same manner as in Example 1 except that the transparent protective film type, thickness, and adhesive type were changed as shown in Table 1. Table 1 also shows the moisture permeability of the transparent protective film, the total thickness of the polarizing plate, and the ratio (T2 / T1).

(Evaluation)
The following evaluation was performed about the obtained polarizing plate. The results are shown in Table 1.

(Optical characteristics: durability)
Each of the polarizing plates was put in an environment of 85 ° C. and 85% RH for 250 hours. The change rate of the optical characteristics (transmittance, polarization degree, hue) before and after the polarizing plate was charged was calculated. The results were evaluated according to the following criteria.
○: When the change rate of the optical characteristics is 3% or less.
(Triangle | delta): When the change rate of an optical characteristic is 3 to 10%.
X: When the change rate of optical characteristics exceeds 10%.

(Measurement of transmittance and degree of polarization)
The optical properties of the polarizing plate were measured with a spectrophotometer with an integrating sphere (V7100 manufactured by JASCO Corporation). The transmittance for each linearly polarized light was measured with 100% of the completely polarized light obtained through the Grantera-prism polarizer. The single transmittance, parallel transmittance (H ₀ ) and orthogonal transmittance (H ₉₀ ) were measured at a wavelength of 550 nm, and the degree of polarization was determined from the values by the following formula. Note that these transmittances are Y values obtained by correcting the visibility with a J1SZ 8701 2 degree visual field (C light source). Polarization degree (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100

(Hue)
A square test piece (5 cm × 5 cm) was cut out from the polarizing plate and used alone using a spectrophotometer (integral sphere-type transmittance measuring machine) [Murakami Color Research Laboratory Co., Ltd., product name “DOT-3”]. Hue b was measured.

(Handling properties)
Handling was evaluated according to the following criteria.
○: The polarizing plate bends but does not break when the polarizing plate is held horizontally.
Δ: A crack occurs at the gripped end when the end of the polarizing plate is held horizontally.
X: Wrinkles and cuts occur in the transparent protective film during the production of the polarizing plate.

(Adhesion)
At the end of the polarizing plate, a cutter edge was inserted between the polarizer and the transparent protective film. In the insertion portion, the polarizer and the transparent protective film were gripped and pulled in opposite directions. At this time, when the polarizer and / or the transparent protective film was broken and could not be peeled off, the adhesion was judged to be good: “◯”. On the other hand, when a part or all peeled between the polarizer and the transparent protective film, the adhesion was poor: “x” was judged.

(Peeling amount)
A sample was prepared by cutting the polarizing plate so as to be 50 mm in the absorption axis direction of the polarizer and 25 mm in the direction perpendicular to the absorption axis. The sample was immersed in warm water at 60 ° C., and the amount of peeling (mm) at the end of the sample was measured over time. The amount of peeling (mm) was measured with a caliper. The amount of peeling (mm) after 5 hours is shown in Table 1.

(Appearance evaluation: Knick defect)
A sample was prepared by cutting out the polarizing plate to be 1000 mm × 1000 mm. A sample polarizing plate was placed under a fluorescent lamp. Another polarizing plate was installed on the light source side of the polarizing plate of the sample so that the respective absorption axes were perpendicular to each other, and in this state, the number of points through which light was lost (knic defects) was counted.

Claims (9)

A polarizing plate in which a transparent protective film is provided on both surfaces of a polyvinyl alcohol polarizer via an adhesive layer,
The transparent protective film comprises a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic ester unit,
The thickness of one transparent protective film: T1 (μm) is 10 to 35 μm, and the thickness of the polarizer: T2 (μm) is 20 to 40 μm,
The ratio (T2 / T1) of the thickness of the polarizer: T2 (μm) to the thickness of one transparent protective film: T1 (μm) (T2 / T1) satisfies 0.8 to 1.8 ,
The adhesive layer is a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle size of 1 to 100 nm, and
The metal compound colloid is formed from an adhesive for a polarizing plate blended at a ratio of 200 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol-based resin . Metal compound colloid, colloidal alumina, colloidal silica, zirconia colloid, the polarizing plate according to claim 1, wherein the at least one selected from titania colloids and tin oxide colloid. The polarizing plate according to claim 1 or 2 , wherein the metal compound colloid has a positive charge. The polarizing plate according to claim 3 , wherein the metal compound colloid is an alumina colloid. The (meth) acrylic resin, polarizing plate according to any one of claims 1 to 4, further characterized by having an aromatic vinyl unit. The (meth) acrylic resin, polarizing plate according to any one of claims 1 to 5, characterized in that further contains a styrene-based resin. The transparent protective film, the polarizing plate according to any one of claims 1 to 6, wherein the moisture permeability is less than 250 g / m @ 2. Optical film polarizing plate according to any one of claims 1 to 7, characterized in that it is laminated at least one. An image display device, wherein the optical film of the polarizing plate or claim 8, wherein according to any one of claims 1 7 is used.