JP4874219B2 - 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. The polarizing plate is used by laminating an optical compensation layer such as a biaxial retardation film in order to compensate the liquid crystal panel. The transparent protective film is also used as a base material for the optical compensation layer.

  An image display device such as a liquid crystal display device applied to the polarizing plate is used in various environments. Therefore, it is desired that the polarizing plate has durability such as heat resistance under a high temperature environment and moisture resistance under a high humidity environment. However, as a transparent protective film, the triacetyl cellulose or the like usually used has a problem that the phase difference changes greatly in a high humidity environment and display unevenness occurs on the panel. In particular, when the optical compensation layer is laminated on the polarizing plate, the optical compensation cannot be sufficiently performed due to display unevenness.

  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.

JP 2006-119203 A

  The present invention is a polarizing plate having an adhesive layer, a transparent protective film, and an optical compensation layer in this order on at least one surface of a polarizer, and suppresses display unevenness even when the polarizing plate is applied to a liquid crystal panel. It is an object to provide a polarizing plate that can be used.

  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 having an adhesive layer, a transparent protective film and an optical compensation layer in this order on at least one surface of a polarizer,
Nx>ny> nz (where the in-plane refractive index is maximized in the X-axis, the direction perpendicular to the X-axis is the Y-axis, and the thickness direction is the Z-axis). The refractive index is nx, ny, nz), and
The transparent protective film contains a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic acid ester unit, and has an in-plane retardation of less than 40 nm and a thickness direction retardation of less than 80 nm. The polarizing plate characterized by this.

  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, a polyimide layer can be suitably used as the optical compensation layer. As the optical compensation layer, a layer formed of a liquid crystal material can be suitably used.

  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, at least on one side of the polarizing plate, the transparent protective film used together with the optical compensation layer contains a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic ester unit, and a surface. Those having an internal retardation of less than 40 nm and a thickness direction retardation of less than 80 nm are used. The (meth) acrylic resin has low moisture permeability and can satisfy durability such as heat resistance under a high temperature environment and moisture resistance under a high humidity environment. Even when a polarizing plate is applied to a liquid crystal panel. Display unevenness can be reduced.

  In addition, the polarizing plate of the present invention improves the contrast ratio in the front and oblique directions of the liquid crystal display device in various drive modes by appropriately controlling the retardation value of the biaxial retardation film that is the optical compensation layer. You can also.

  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 with reference to the drawings. FIG. 1 is a schematic cross-sectional view for explaining a polarizing plate according to a representative embodiment of the present invention. As shown in FIG. 1, the polarizing plate 10 of the present invention includes a first adhesive layer 12, a first transparent protective film 132, and a first optical compensation layer 131 in this order on at least one surface of a polarizer 11. Have. The first transparent protective film 132 and the first optical compensation layer 131 can be sequentially laminated on the polarizer 11, and the first transparent protective film 132 and the first optical compensation layer 131 can be It can be used as the laminated film 13. In FIG. 1, the case where it uses as the 1st laminated | multilayer film 13 is shown. The first transparent protective film 132 and the first optical compensation layer 131 can also be provided on both sides. On the other side, it is shown as a second transparent protective film 132 'and a second optical compensation layer 131'.

  As shown in FIG. 1A, the polarizing plate 10 includes a polarizer 11 and a first laminated film 13 attached to one side of the polarizer 11 via a first adhesive layer 12. The first laminated film 13 includes a first optical compensation layer 131 and a first transparent protective film 132. The polarizer 11 and the first laminated film 13 are stuck so that the first transparent protective film 132 faces the polarizer 11. That is, the first transparent protective film 132 and the polarizer 11 are bonded via the first adhesive layer 12.

  In another embodiment, as shown in FIG. 1B, the first laminated film 13 includes a first anchor coat layer between the first optical compensation layer 131 and the first transparent protective film 132. 133 is further included. By providing the first anchor coat layer 133, the adhesiveness and adhesion durability between the first optical compensation layer 131 and the first transparent protective film 132 can be remarkably improved. According to the embodiment illustrated in FIGS. 1A and 1B, the liquid crystal panel (as a result, a liquid crystal display device) can be contributed to thinning.

  In the present invention, the first laminated film 13 can be provided only on one side of the polarizer 11, and the second laminated film 13 ′ may be provided on the other side of the polarizer 11. FIGS. 1C and 1D show an embodiment in which a first laminated film 13 and a second laminated film 13 ′ are provided on both sides of the polarizer 11. According to the embodiment of FIG. 1 (c), the first having the first (and second) optical compensation layer 131 (131 ′) and the first (and second) transparent protective film 132 (132 ′). A (and second) laminated film 13 (13 ′) is attached to each side of the polarizer 11 via a first (and second) adhesive layer 12 (12 ′). According to the embodiment of FIG. 1 (d), the first (and second) optical compensation layer 131 (131 ′), the first (and second) anchor coat layer 133 (133 ′) and the first (and The first (and second) laminated film 13 (13 ′) having the second) transparent protective film 132 (132 ′) is interposed through the first (and second) adhesive layer 12 (12 ′). Are attached to the respective sides of the polarizer 11. The first laminated film 13 having the first optical compensation layer 131 and the first transparent protective film 132 is attached to one side of the polarizer 11, and the second optical compensation layer 131 ′ and the second optical compensation layer 131 ′ are attached to the opposite side. It goes without saying that a second laminated film 13 ′ having an anchor coat layer 133 ′ and a second transparent protective film 132 ′ may be attached. When the first and second laminated films 13 and 13 ′ are provided on both sides of the polarizer 11, the materials constituting the laminated films 13 and 13 ′ may be the same or different from each other. According to the embodiment illustrated in FIGS. 1C and 1D, the resulting polarizing plate has very little curl (warpage) due to its symmetrical structure. Furthermore, since both sides of the polarizer are protected by the transparent protective film, a polarizing plate having very excellent durability can be obtained.

  In the present invention, if the first laminated film 13 as described above is provided on one side of the polarizer 11, any appropriate second transparent protective film 14 is provided on the opposite side of the polarizer 11. Also good. Figures (e) and (f) show an embodiment in which a first laminated film 13 is provided on one side of the polarizer 11 and any suitable second transparent protective film is provided on the opposite side. According to the embodiment of FIG. 1 (e), the first laminated film 13 having the first optical compensation layer 131 and the first transparent protective film 132 is bonded to the polarizer via the first adhesive layer 12. 11 is adhered to one side, and any appropriate second transparent protective film 14 is adhered to the opposite side of the polarizer 11 through a second adhesive layer 12 ′. According to the embodiment of FIG. 1 (f), the first laminated film 13 having the first optical compensation layer 131, the first anchor coat layer 133, and the first transparent protective film 132 is the first adhesive. An appropriate second transparent protective film 14 is attached to one side of the polarizer 11 through the agent layer 12, and is attached to the opposite side of the polarizer 11 through the second adhesive layer 12 ′. Yes. According to the embodiment illustrated in FIGS. 1E and 1F, a polarizing plate that can achieve both durability, productivity, and economy can be obtained.

  In the present invention, the first transparent protective film 132 on one side where the first optical compensation layer 131 is provided contains a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic acid ester unit. The material of the second transparent protective film 132 ′ used for the second laminated film 13 ′ and any appropriate second transparent protective film 14 is not particularly limited. Further, a polyvinyl alcohol adhesive containing a metal compound colloid is preferably used for the first adhesive layer 12, but a polyvinyl alcohol adhesive containing a metal compound colloid also for the second adhesive layer 12 ′. An agent is preferably used.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a functional material and uniaxially stretched, polyvinyl alcohol dehydrated products, and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm, preferably 10 to 50 μm, and more preferably 20 to 40 μm.

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

  Any appropriate moisture content may be adopted as the moisture content of the polarizer, but it is preferably 5 to 40%, more preferably 10 to 30%, and most preferably 20 to 30%.

  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.

  As the polarizer used in the present invention, in addition to the above-described polarizer, for example, a polarizer obtained by stretching a polymer film kneaded with a dichroic material and oriented in a certain direction, a dichroic material and a liquid crystal A guest-host type O-type polarizer (US Pat. No. 5,523,863, Japanese Patent Publication No. 3-503322) and a lyotropic liquid crystal in which a liquid crystal composition containing a functional compound is aligned in a certain direction An E-type polarizer oriented in the direction (US Pat. No. 6,049,428) or the like can also be used.

  On at least one side of the polarizer, the first transparent protective film on which the optical compensation layer is laminated contains a (meth) acrylic resin having a glutarimide unit and a (meth) acrylic acid ester unit. 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.

  Although the thickness of a 1st transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. From the viewpoint of thinning, the thickness of the transparent protective film is preferably 5 to 100 μm. In addition, a nick becomes easy to produce, so that a 1st transparent protective film becomes thin.

  The first 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.

Moreover, the 1st transparent protective film containing the (meth) acrylic-type resin of this invention can satisfy the moisture permeability of 300 g / m < ² > or less, and is preferable at a durable point. The moisture permeability is further preferably 250 g / m ² or less, and more preferably 200 g / m ² or less.

  As described above, in the present invention, on at least one side of the polarizer, the first transparent protective film on the side on which the first optical compensation layer is laminated uses one containing the (meth) acrylic resin. The second transparent protective film or any appropriate second transparent protective film on which the second optical compensation layer is laminated on the other side can adopt the same thickness as that of the first transparent protective film. As the material for forming the second transparent protective film on the other side, various materials can be used in addition to the materials exemplified for the first transparent protective film. As the material for forming the second transparent protective film on the other side, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. In addition, normally, a second transparent protective film is bonded to the polarizer by an adhesive layer. As the second transparent protective film, (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, silicone A thermosetting resin such as a system or an ultraviolet curable resin can be used.

  The retardation of the transparent protective film of the present invention (including both the first and second films) has an in-plane retardation of less than 40 nm and a thickness direction retardation of less than 80 nm. 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.

  The transparent protective film used in the present invention (hereinafter, unless otherwise specified, the transparent protective film includes both the first and second) may contain one or more arbitrary appropriate additives. . 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 optical compensation layer (including both the first and second cases, the same applies hereinafter) is nx> ny> nz (however, the direction in which the in-plane refractive index is maximum is the X axis, and the direction perpendicular to the X axis is the Y axis) A biaxial retardation film satisfying the relationship of the thickness direction as the Z axis and the refractive indexes in the respective axial directions as nx, ny, and nz) is used.

  As the optical compensation layer, for example, a polyimide layer can be used. The polyimide layer can be obtained, for example, by applying a polyimide solution to the surface of the transparent protective film and drying it. The polyimide layer may further contain any appropriate additive as required. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and thickeners. Etc. The kind and amount of the additive used can be appropriately set according to the purpose. The amount of the additive used is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and most preferably 3 parts by weight or less with respect to 100 parts by weight of the total solid content in the polyimide layer.

  Arbitrary appropriate polyimide may be employ | adopted as a polyimide which comprises a polyimide layer. Specific examples include aromatic polyimide, thermoplastic polyimide, thermosetting polyimide, fluorine-containing polyimide, photosensitive polyimide, alicyclic polyimide, liquid crystalline polyimide, and polysiloxane block polyimide. These polyimides may be used alone or in combination of two or more. Furthermore, the resin composition etc. which blended polyamic acid which is a precursor of a polyimide and a polyimide can also be used.

In this specification, “aromatic polyimide” refers to a polyimide having an aromatic ring structure in the molecule. Specific examples of the aromatic polyimide include a trade name “KAPTON” manufactured by DuPont. “Thermoplastic polyimide” refers to a material that softens without causing a chemical reaction by heating, exhibits plasticity, and solidifies upon cooling. Specific examples of the thermoplastic polyimide include trade name “AURUM” manufactured by Mitsui Chemicals, Inc. The term “thermosetting polyimide” refers to one in which the terminal group of an oligomer having a terminal functional group in the molecule and having a weight average molecular weight of 1000 to 7000 is crosslinked and cured by thermal cleavage. Specific examples of the thermosetting polyimide include trade name “Kerimid 601” manufactured by Phone-Poulenc. “Fluorine-containing polyimide” refers to those having a C—F bond such as —CF ₂ — group or —CF ₃ group in the molecule. “Photosensitive polyimide” refers to a compound having a photoreactive group (for example, cinnamoyl group, diazo group, etc.) that causes a decomposition reaction or a crosslinking reaction by light in the molecule and causes a difference in solubility before and after the reaction. “Alicyclic polyimide” refers to a polyimide having an alicyclic structure in the molecule. “Liquid crystal polyimide” refers to a polyimide that exhibits a liquid crystal phase upon heating or addition of a solvent. “Polysiloxane block polyimide” refers to one having a polydimethylsiloxane structure in the molecular structure.

  The polyimide can be typically obtained by reaction of tetracarboxylic dianhydride and diamine. Arbitrary appropriate methods may be employ | adopted as a method of making the said tetracarboxylic dianhydride and diamine react. For example, chemical imidization that proceeds in two steps may be used, or thermal imidization that proceeds in one step.

  As a specific example of the above chemical imidation, diamine is dissolved in a polar amide solvent such as dimethylacetamide or N-methylpyrrolidone, and tetracarboxylic dianhydride is added to this solution as a solid at room temperature. Upon stirring, the solid tetracarboxylic dianhydride dissolves, and a ring-opening polymerization addition reaction takes place with the diamine with heat generation, increasing the viscosity of the polymerization solution and producing polyamic acid (first step) ). Next, there is a method in which a dehydrating agent such as acetic anhydride is added to the reaction solution containing the polyamic acid and heated to cause a dehydration cyclization reaction to generate polyimide (second step).

  As a specific example of the thermal imidization, a diamine, tetracarboxylic dianhydride and isoquinoline (catalyst) are dissolved in a high-boiling organic solvent such as m-cresol in a reaction vessel equipped with a Dean-Stark apparatus. When the solution is heated at 175 to 180 ° C. while stirring, a method in which a dehydration cyclization reaction occurs and a polyimide is generated can be mentioned.

  Examples of the tetracarboxylic dianhydride used in the present invention include pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, naphthalene tetracarboxylic dianhydride, and heterocyclic aromatic tetracarboxylic dianhydride. 2,2'-substituted biphenyltetracarboxylic dianhydride and the like.

  Examples of the pyromellitic dianhydride include pyromellitic dianhydride, 3,6-diphenylpyromellitic dianhydride, 3,6-bis (trifluoromethyl) pyromellitic dianhydride, 3, Examples include 6-dibromopyromellitic dianhydride and 3,6-dichloropyromellitic dianhydride. Examples of the benzophenone tetracarboxylic dianhydride include 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,3,3 ′, 4′-benzophenone tetracarboxylic dianhydride, 2 , 2 ', 3,3'-benzophenone tetracarboxylic dianhydride and the like. Examples of the naphthalenetetracarboxylic dianhydride include 2,3,6,7-naphthalene-tetracarboxylic dianhydride, 1,2,5,6-naphthalene-tetracarboxylic dianhydride, 2 , 6-dichloro-naphthalene-1,4,5,8-tetracarboxylic dianhydride and the like.

  Examples of the heterocyclic aromatic tetracarboxylic dianhydride include, for example, thiophene-2,3,4,5-tetracarboxylic dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride. Pyridine-2,3,5,6-tetracarboxylic dianhydride and the like. Examples of the 2,2'-substituted biphenyltetracarboxylic dianhydride include 2,2'-dibromo-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2' -Dichloro-4,4 ', 5,5'-biphenyltetracarboxylic dianhydride, 2,2'-bis (trifluoromethyl) -4,4', 5,5'-biphenyltetracarboxylic dianhydride Etc.

  Other examples of the aromatic tetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and bis (2,3-dicarboxyphenyl) methane dianhydride. Bis (2,5,6-trifluoro-3,4-dicarboxyphenyl) methane dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride, 4, 4′-bis (3,4-dicarboxyphenyl) -2,2-diphenylpropane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 4,4′-oxydiphthalic dianhydride, Bis (3,4-dicarboxyphenyl) sulfonic dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-[4,4'-isopropylidene-di ( -Phenyleneoxy)] bis (phthalic anhydride), N, N- (3,4-dicarboxyphenyl) -N-methylamine dianhydride, bis (3,4-dicarboxyphenyl) diethylsilane dianhydride And so on. Among these, examples of the tetracarboxylic dianhydride suitable for the present invention include 2,2′-substituted biphenyltetracarboxylic dianhydride. More preferred is 2,2′-bis (trihalomethyl) -4,4 ′, 5,5′-biphenyltetracarboxylic dianhydride, and particularly preferred is 2,2′-bis (3,4). Dicarboxyphenyl) -hexafluoropropane dianhydride.

  The diamine used in the present invention is not particularly limited, and examples thereof include benzenediamine, diaminobenzophenone, naphthalenediamine, heterocyclic aromatic diamine, and other aromatic diamines.

  Examples of the benzenediamine include o-, m- and p-phenylenediamine, 2,4-diaminotoluene, 1,4-diamino-2-methoxybenzene, 1,4-diamino-2-phenylbenzene and 1, Examples thereof include benzenediamine such as 3-diamino-4-chlorobenzene. Examples of the diaminobenzophenone include 2,2′-diaminobenzophenone and 3,3′-diaminobenzophenone. Examples of the naphthalenediamine include 1,8-diaminonaphthalene and 1,5-diaminonaphthalene. Examples of the heterocyclic aromatic diamine include 2,6-diaminopyridine, 2,4-diaminopyridine, and 2,4-diamino-S-triazine.

  In addition to these, the above diamines include 4,4′-diaminobiphenyl, 4,4′-diaminodiphenylmethane, 4,4 ′-(9-fluorenylidene) -dianiline, 2,2′-bis (trifluoro). Methyl) -4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diaminodiphenylmethane, 2,2′-dichloro-4,4′-diaminobiphenyl, 2,2 ′, 5,5 ′ -Tetrachlorobenzidine, 2,2-bis (4-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenyl) propane, 2,2-bis (4-aminophenyl) -1,1,1, 3,3,3-hexafluoropropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 1,3-bis (3-aminophenoxy) benzene, 1 3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) Biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 4,4'-diaminodiphenyl thioether, 4,4'-diaminodiphenyl sulfone and the like can also be mentioned. Among these, diamine suitable for the present invention includes 2,2-bis (trifluoromethyl) -4,4'-diaminobiphenyl.

  As the polyimide used in the present invention, at least one obtained by reacting the above tetracarboxylic dianhydride and diamine can be appropriately selected and used. However, the polyimide is not limited to these, and any appropriate polyimide can be adopted as long as the effects of the present invention can be obtained. A polyimide excellent in transparency, solubility, mechanical strength, thermal stability, moisture barrier property, retardation value stability, etc. is preferably used. In the present invention, a fluorine-containing polyimide having a C—F bond in the molecule is preferably used because it is particularly excellent in transparency and solubility. Specific examples of fluorine-containing polyimides include “Latest Polyimide” p. 274-p. And polyimide disclosed in H.275 (2002 edition). More preferably, 2,2′-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride is used as the tetracarboxylic dianhydride and 2,2-bis (trifluoromethyl) -4 is used as the diamine. Polyimide composed of repeating units represented by the following formula (4) obtained by using 4,4′-diaminobiphenyl is used.

  Moreover, as a polyimide of another embodiment, the thing of the structure shown by following General formula (5) is mention | raise | lifted. The polyimide which has the structure of following General formula (5) can make an optical compensation layer thin. In the following general formula (5), when the sum of X and Y is 100, X is 30 to 70, and Y is 70 to 30.

  As a weight average molecular weight (Mw) of the polyimide used in the present invention, a dimethylformamide solution (10 mM lithium bromide and 10 mM phosphoric acid was added to make a 1 L dimethylformamide solution) was used as a developing solvent. The weight average molecular weight (Mw) of the polyethylene oxide standard is preferably 20,000 to 180,000, more preferably 50,000 to 150,000, and most preferably 70,000 to 130,000. If it is said range, the polyimide layer excellent in mechanical strength can be obtained. In addition, the optical properties of the polarizing plate of the present invention hardly change even when exposed to high temperatures and high humidity.

  Any appropriate imidization rate can be adopted as the imidization rate of the polyimide used in the present invention. The imidization ratio is preferably 90% or more, more preferably 95% or more, and most preferably 98% or more. The imidation ratio can be determined from a peak integral intensity ratio between a proton peak derived from polyamic acid, which is a polyimide precursor, and a proton peak derived from polyimide, in a nuclear magnetic resonance (NMR) spectrum.

  The thickness of the polyimide layer is preferably 1 to 10 μm, more preferably 1 to 8 μm, particularly preferably 1 to 6 μm, and most preferably 1 to 5 μm. By bonding such a very thin polyimide layer to the polarizer via a specific adhesive layer (described later), the adhesion between the polyimide layer and the polarizer can be significantly improved. As a result, it is possible to obtain a polarizing plate that does not peel off or float on the entire surface even when laminated on a polarizer. In general, polyimide has a large absolute value of the photoelastic coefficient. Therefore, when used in a liquid crystal display device by laminating with a polarizer, the phase difference value is shifted due to the contraction stress of the polarizer or the heat of the backlight. There is a case where a problem that it is easy to cause unevenness. However, since the polyimide layer used in the present invention is a thin layer and can obtain a large retardation value, display characteristics with excellent optical uniformity can be obtained.

  Although there is no restriction | limiting in particular as the amount of residual volatile components of the said polyimide layer, Preferably it exceeds 0 and 5% or less, More preferably, it exceeds 0 and is 3% or less. If it is such a range, the polyimide layer excellent in stability of retardation value is obtained. The amount of residual volatile components of the polyimide layer can be determined from the amount of weight loss before and after heating when heated at 250 ° C. for 10 minutes.

  The transmittance of the polyimide layer measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and most preferably 90% or more. Usually, polyimide is easily colored yellow or brown. For example, a polyimide layer having a thickness exceeding 1 μm is difficult to obtain a high transmittance. However, according to the present invention, by using a polyimide having a bulky atom or substituent in the molecular structure (for example, a polyimide having a fluorine atom (for example, C—F bond)), a desired thickness direction retardation is obtained. The value can be realized with a very thin layer thickness, and a polyimide layer having a very high transmittance can be obtained.

  The above-mentioned polyimide layer is a biaxial film that has a refractive index distribution satisfying nx> ny> nz by stretching after applying and drying a polyimide solution, applying tension in the film plane, and increasing molecular orientation in the stretching direction. It can be used as a crystalline retardation film. Note that satisfying the above nx> ny> nz can also be said as satisfying Rth> Re. Although the polyimide layer is stretched in the form of a laminated film together with a transparent protective film, it is possible to apply a uniform tension in the width direction even though it is very thin. According to said method, the polyimide layer excellent in the uniformity of retardation value and thickness uniformity can be obtained. The biaxial retardation film preferably has an Nz coefficient of 2.0 or more. On the other hand, the polyimide solution is applied to a base film different from the transparent polymer film, and then dried to form a polymer layer, which is obtained by integrally stretching the base film and the polymer layer. The biaxial retardation film can be transferred to a transparent protective film with an adhesive and used.

  Any appropriate method can be adopted as the stretching method. Specific examples include a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and a longitudinal and transverse sequential biaxial stretching method. As the stretching means, any suitable stretching machine such as a roll stretching machine, a tenter stretching machine, or a biaxial stretching machine can be used. Moreover, when performing heat extending | stretching, temperature may be changed continuously and may be changed in steps. The stretching process may be divided into two or more times. The stretching direction may be the film longitudinal direction (MD direction) or the width direction (TD direction). Moreover, you may extend | stretch in the diagonal direction (diagonal extending | stretching) using the extending | stretching method of FIG. 1 of Unexamined-Japanese-Patent No. 2003-262721.

  Re of the polyimide layer used as the biaxial retardation film is preferably 10 to 350 nm, more preferably 30 to 200 nm, and most preferably 40 to 100 nm. The Re of the polyimide layer can be optimized according to the orientation mode of the liquid crystal display device and the type of other retardation plate used in the liquid crystal display device. The Re of the polyimide layer can be appropriately adjusted by changing the thickness of the polyimide layer, the stretching temperature, the stretching ratio, and the like.

  The in-plane birefringence (Δn [xy]) of the polyimide layer used as the biaxial retardation film is preferably 0.00050 to 0.10, more preferably 0.0010 to 0.0050. Yes, most preferably 0.0015 to 0.035. Δn [xy] of the polyimide layer can be optimized according to the alignment mode of the liquid crystal display device and the type of other retardation plate used in the liquid crystal display device. Δn [xy] of the polyimide layer can be appropriately adjusted by changing the thickness of the polyimide layer, the stretching temperature, the stretching ratio, and the like.

  The smaller the variation of the slow axis angle (also referred to as the orientation angle) of the polyimide layer used as the biaxial retardation film, the higher the contrast ratio in the front direction of the liquid crystal display device. As the variation in the orientation angle, the range of the variation in the orientation angle at the five measurement points provided at equal intervals in the film width direction is preferably ± 2.0 ° to ± 1.0 °, and more preferably ± It is 1.0 ° to ± 0.5 °, and most preferably ± 0.5 ° or less. The orientation angle can be determined using the product name “KOBRA21-ADH” manufactured by Oji Scientific Instruments.

  Rth of the polyimide layer used as the biaxial retardation film is preferably 50 to 900 nm, more preferably 80 to 500 nm, and most preferably 100 to 400 nm. The Rth of the polyimide layer can be optimized according to the alignment mode of the liquid crystal display device and the type of other retardation plate used in the liquid crystal display device. Rth of the polyimide layer can be appropriately adjusted by changing the thickness of the polyimide layer, the stretching temperature, the stretching ratio, and the like.

  The birefringence (Δn [xz]) in the thickness direction of the polyimide layer used as the biaxial retardation film is preferably 0.007 to 0.23, more preferably 0.015 to 0.12. Most preferably, it is 0.03-0.09. Δn [xz] of the polyimide layer can be optimized according to the alignment mode of the liquid crystal display device and the type of other retardation plate used in the liquid crystal display device. Δn [xz] of the polyimide layer can be appropriately adjusted by changing the kind of polyimide used, the stretching temperature, the stretching ratio, and the like.

  In the polyimide layer used as the biaxial retardation film, the relationship between the absorption axis of the polarizer and the slow axis of the polyimide layer is not particularly limited, but is preferably parallel, orthogonal or 45 °. . The dispersion between the slow axis of the polyimide layer and the absorption axis of the polarizer is preferably 0 ± 1.0 °, more preferably 0 ± 0.5 °, when both are arranged in parallel. Preferably, it is 0 ± 0.3 °. When both are arranged orthogonally, the variation is preferably 90 ± 1.0 °, more preferably 90 ± 0.5 °, and most preferably 90 ± 0.3 °. When both are arranged at 45 °, the variation is preferably 45 ± 1.0 °, more preferably 45 ± 0.5 °, and most preferably 45 ± 0.3 °.

  As the optical compensation layer satisfying the relationship of nx> ny> nz, a biaxial retardation film other than the polyimide layer can be used. Examples of materials other than polyimide include polyamide, polyester, polyetherketone, polyamideimide, and polyesterimide. Also for this material, a material treated in the same manner as the above polyimide can be used. In addition, a film obtained by uniaxially or biaxially stretching a material having birefringence can be used. As the material having birefringence, a material having excellent transparency in the visible light region and a transmittance of 80% or more is preferable. Such materials include norbornene resin, cellulose resin, polycarbonate, polyether ketone, polypropylene, polyvinyl alcohol, polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymer, styrene / maleic anhydride copolymer, maleimide / styrene copolymer. Examples thereof include polymers. These biaxial retardation films preferably have the same Re, Rth, thickness and the like as the polyimide layer.

  The optical compensation layer is usually used as a laminated film together with a transparent protective film. The transparent protective film and the optical compensation layer may be laminated directly or via an anchor coat layer.

  The total thickness of the laminated film is preferably 10 to 200 μm, more preferably 20 to 160 μm, and most preferably 30 to 110 μm. If it is said range, it can have sufficient mechanical strength.

  The transmittance of the laminated film measured with light having a wavelength of 590 nm at 23 ° C. is preferably 80% or more, more preferably 85% or more, and most preferably 90% or more.

  The Re of the laminated film is preferably more than 0 and 700 nm or less, more preferably more than 0 and 350 nm or less, and most preferably more than 0 and 200 nm or less. By setting it as said range, the contrast ratio of the diagonal direction at the time of using for a liquid crystal display device can be improved further.

  Rth of the laminated protective film is preferably 50 to 1100 nm, more preferably 80 to 650 nm, and most preferably 100 to 480 nm. By setting it as said range, the contrast ratio of the diagonal direction at the time of using for a liquid crystal display device can be improved further.

  As a material constituting the anchor coat layer, any appropriate material that can improve the adhesion and adhesion between the transparent protective film and the optical compensation layer can be used. In addition, a material excellent in transparency, thermal stability, low birefringence and the like is preferable. Examples of such a material include thermoplastic resins mainly composed of polyester, polyacryl, polyurethane, polyvinylidene chloride, and the like.

  The anchor coat layer may further contain any appropriate additive as required. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, ultraviolet absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and thickeners. Etc. The kind and amount of the additive used can be appropriately set according to the purpose. For example, the use amount of the additive is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and most preferably 3 parts by weight with respect to 100 parts by weight of the total solid content in the anchor coat layer. Less than parts by weight.

  As the material constituting the anchor coat layer, among the thermoplastic resins described above, those mainly composed of polyester are preferably used. More preferably, the main component is a modified polyester obtained by copolymerizing polyurethane and polyester. Such a modified polyester is produced by the method described in JP-A-8-122969, [0025] to [0032]. Specific examples of the modified polyester include Toyobo Co., Ltd. trade name “Byron UR series” (organic solvent dispersion).

  The glass transition temperature (Tg) of the anchor coat layer is preferably −20 to + 20 ° C., more preferably −10 to + 10 ° C., and particularly preferably −5 to + 5 ° C. In addition, a glass transition temperature can be measured by the method according to JISK7121-1987 by differential scanning calorimetry (DSC) measurement.

  Any appropriate thickness can be adopted as the thickness of the anchor coat layer. The thickness of the anchor coat layer is preferably 0.2 to 1.5 μm, more preferably 0.4 to 1.2 μm, and most preferably 0.7 to 1.0 μm. Within the above range, even if the polarizing plate of the present invention is exposed to a high-temperature and high-humidity environment, the polarizing plate has excellent durability and does not peel off or float between the optical compensation layer and the transparent protective film. Can be obtained.

  The anchor coat layer is formed, for example, by applying a coating liquid containing a thermoplastic resin such as polyester at a predetermined ratio to the surface of the transparent protective film and drying it. Any appropriate method can be adopted as a method for preparing the coating solution. For example, a commercially available solution or dispersion may be used, a solvent may be further added to the commercially available solution or dispersion, or a solid content may be dissolved or dispersed in various solvents. Any appropriate method can be adopted as a coating method of the coating liquid. For example, a coating method using a coater can be used.

  The total solid content concentration of the coating liquid may vary depending on the type of anchor coat layer forming material, solubility, coating viscosity, wettability, thickness after coating, and the like. In order to obtain an anchor coat layer having high surface uniformity, the total solid content is preferably 2 to 100 parts by weight, more preferably 10 to 80 parts by weight, based on 100 parts by weight of the solvent. Yes, most preferably 20-60 parts by weight.

  As the viscosity of the coating solution, any appropriate viscosity can be adopted as long as it can be applied. As the viscosity, a value measured at a shear rate of 1000 (1 / s) at 23 ° C. is preferably 2 to 50 (mPa · s), more preferably 5 to 40 (mPa · s). Preferably it is 10-30 (mPa * s). If it is said range, the anchor coat layer excellent in surface uniformity can be formed.

  The adhesive layer used for laminating the polarizer and the first transparent protective film (on the other surface, for example, the second transparent protective film) is not particularly limited as long as the adhesive layer is optically transparent. Various types of hot melt type and radical curable type are used, and an aqueous type adhesive or a radical curable type adhesive is preferable.

  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. In addition, by setting the blending ratio of the metal compound colloid within the above range, the occurrence of nicks while ensuring the adhesion between the polarizer and the first transparent protective film (for example, the second transparent protective film on the other surface) Can be suppressed. 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, it has good adhesion to the polarizer and the first transparent protective film (for example, the second transparent protective film on the other surface). The polarizing plate which has is 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. Moreover, by ensuring that the blending ratio of the metal compound filler is in the above range, the adhesive property between the polarizer and the first transparent protective film (on the other surface, for example, the second transparent protective film) is secured and good. In appearance, uniform in-plane adhesion can be obtained. 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.

  Below, the manufacturing method of the polarizing plate of this invention is demonstrated on behalf of the case where an optical compensation layer is a polyimide layer. The method for producing a polarizing plate of the present invention comprises a step of applying a polyimide solution or dispersion on the surface of a transparent protective film and drying to obtain a laminated film having a polyimide layer on the transparent protective film; And a step of bonding the laminated film and the polarizer through an adhesive so as to face the child. Preferably, the manufacturing method of the present invention is a step of modifying the surface of the transparent protective film after the polyimide solution coating / drying step (before the obtained laminated film and polarizer bonding step). Can be included. By performing the surface modification treatment, the wettability of the adhesive to the transparent protective film is improved, and the adhesiveness with the pressure-sensitive adhesive layer laminated on the transparent protective film is improved. Hereinafter, a preferable example of the method for producing a polarizing plate of the present invention will be described with reference to the drawings, and then the details of each step will be described.

  FIG. 2 is a schematic diagram for explaining the outline of the polyimide solution coating step and the transparent protective film surface modification treatment step. FIG. 2 illustrates a case where the surface modification process employs a dry process such as a corona process or an ozone process. A transparent protective film is supplied from the feeding unit 310, and the polyimide solution is applied to the surface of the transparent protective film in the coater unit 320. The transparent protective film coated with the polyimide solution is sent to the drying means 330, and the solvent is evaporated to form a laminated film having a polyimide layer and a transparent protective film. Next, the laminated film is sent to the surface modification processing unit 340 to modify the surface of the transparent protective film. This laminated film is taken up by the take-up unit 350 and used for the bonding step. When the surface modification of the transparent protective film is not performed or when a wet process described later is performed, the surface modification process step performed in the surface modification processing unit 340 can be omitted. Or after performing the said dry process, you may further perform the below-mentioned wet process. By combining the dry treatment and the wet treatment, the adhesion between the polarizer and the transparent protective film of the laminated film can be further improved.

  FIG. 3 illustrates a case where the surface modification process employs a wet process such as an alkali process. The laminated film obtained through the process of FIG. 2 (however, the surface modification treatment may be omitted) is supplied from the feeding unit 410 and passed through the treatment liquid bath 420. Next, the laminated film is sent to the drying means 430, and the treatment liquid is removed. Finally, the laminated film is wound up by the winding unit 440 and used for the bonding process. In addition, it cannot be overemphasized that the coating process of a polyimide solution and the wet surface modification process process of a transparent protective film may be performed continuously.

  FIG. 4 is a schematic diagram for explaining the outline of the bonding process between the laminated film and the polarizer. The laminated film is supplied from the first feeding unit 511, and the adhesive is applied to the surface of the transparent protective film in the coater unit 520. On the other hand, a polarizer is supplied from the second extension unit 512. The laminated film to which the adhesive is applied and the polarizer are bonded together by the bonding roller 530, sent to the drying means 540, the adhesive is dried, and an adhesive layer is formed. In this way, a polarizing plate is produced. The obtained polarizing plate is wound up by the winding unit 550.

  Hereafter, each process of the manufacturing method of this invention is demonstrated in detail.

(Polyimide solution coating method)
Any appropriate solution can be adopted as the polyimide solution used in the production method of the present invention as long as the effects of the present invention are obtained. The solution may be obtained by dissolving polyimide powder or pellets in a solvent, or a reaction solution obtained in the polyimide synthesis process may be used as it is. In the present invention, those obtained by dissolving polyimide powder in a solvent are preferably used. This is because a polyimide layer with few optical defects such as defects and bright spots can be obtained.

  The total solid content concentration of the polyimide solution can vary depending on the type of polyimide used, solubility, coating viscosity, wettability, target thickness, and the like. The total solid content is preferably 2 to 100 parts by weight, more preferably 10 to 50 parts by weight, and most preferably 10 to 40 parts by weight with respect to 100 parts by weight of the solvent. Within the above range, it is possible to form a polyimide layer that is very thin and excellent in surface uniformity and optical uniformity.

  As the solvent, any appropriate liquid substance capable of uniformly dissolving the polyimide to form a solution can be adopted. The solvent may be a nonpolar solvent such as benzene or hexane, or may be a polar solvent such as water or alcohol. The solvent may be an inorganic solvent such as water, and alcohols, ketones, ethers, esters, aliphatic and aromatic hydrocarbons, halogenated hydrocarbons, amides, cellosolves, etc. The organic solvent may be used.

  Specific examples of the solvent include alcohols such as n-butanol, 2-butanol, cyclohexanol, isopropyl alcohol, t-butyl alcohol, glycerin, ethylene glycol, 2-methyl-2,4-pentadiol, phenol, Parachlorophenol etc. are mentioned. Ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pentanone, 2-hexanone, 2-heptanone, and the like. Examples of ethers include diethyl ether, tetrahydrofuran, dioxane, anisole and the like. Esters include ethyl acetate, butyl acetate, methyl lactate and the like. Aliphatic and aromatic hydrocarbons include n-hexane, benzene, toluene, xylene and the like. Examples of halogenated hydrocarbons include chloroform, dichloromethane, carbon tetrachloride, dichloroethane, trichloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and the like. Examples of amides include dimethylformamide and dimethylacetamide. Examples of cellosolves include methyl cellosolve, ethyl cellosolve, and methyl cellosolve. These solvents are used alone or in admixture of two or more kinds of solvents selected arbitrarily. In addition, said solvent is a mere illustration and the solvent used for this invention is not limited to these.

  Particularly preferred solvents include cyclopentanone, cyclohexanone, methyl isobutyl ketone, methyl ethyl ketone, toluene, ethyl acetate, tetrahydrofuran and the like. These solvents do not cause erosion that has a practically adverse effect on the transparent protective film, and can sufficiently dissolve the polyimide.

  The boiling point of the solvent is preferably 55 to 230 ° C, more preferably 70 to 150 ° C. By selecting a solvent having a boiling point in the above range, it is possible to prevent the solvent in the polyimide solution from rapidly evaporating in the drying step and obtain a polyimide layer with high surface uniformity. Examples of the solvent having a boiling point in the above range include ketone solvents such as cyclopentanone, cyclohexanone, and methyl isobutyl ketone.

  As the viscosity of the polyimide solution, any appropriate viscosity can be adopted depending on the purpose. The viscosity measured at a shear rate of 1000 (1 / s) at 23 ° C. is preferably 50 to 600 (mPa · s), more preferably 100 to 300 (mPa · s), and most preferably. Is 120 to 200 (mPa · s). Within the above range, it is possible to form a polyimide layer that is very thin and excellent in surface uniformity and optical uniformity.

  There is no restriction | limiting in particular as a method of coating the said polyimide solution, The coating system using arbitrary appropriate coaters can be used. Specific examples of the above coater include reverse roll coater, forward rotation roll coater, gravure coater, knife coater, rod coater, slot orifice coater, curtain coater, fountain coater, air doctor coater, kiss coater, dip coater, bead coater, blade coater, cast Examples include a coater, a spray coater, a spin coater, an extrusion coater, and a hot melt coater. Among these, a reverse roll coater, a normal rotation roll coater, a gravure coater, a rod coater, a slot orifice coater, a curtain coater, and a fountain coater are preferably used in the present invention. With the coating method using the above coater, a polyimide layer that is very thin and excellent in surface uniformity and optical uniformity can be formed.

  The coating thickness of the polyimide solution can be appropriately adjusted depending on the total solid content concentration of the polyimide solution, the coating viscosity, and the type of coater. The coating thickness is preferably 2 to 30 μm, more preferably 5 to 25 μm, and most preferably 8 to 22 μm. By coating with such a thickness, a polyimide layer having a desired thickness (resulting in excellent adhesion and adhesion durability with a polarizer) can be obtained after drying. Furthermore, if it is said range, the polyimide layer excellent in surface uniformity and optical uniformity can be formed very thinly.

  Any appropriate drying method may be employed as the method for drying the polyimide solution. As a specific example of the drying method, an air circulation type constant temperature oven in which hot air or cold air circulates, a heater using microwaves or far infrared rays, a roll heated for temperature control, a heat pipe roll, a metal belt, or the like was used. Examples thereof include a heating method and a temperature control method.

  The drying temperature of the polyimide solution is preferably 50 to 250 ° C, more preferably 80 to 150 ° C. Drying may be performed at a constant temperature, or may be performed while increasing or decreasing the temperature stepwise or continuously. By performing a stepwise drying process, a polyimide layer having even better surface uniformity can be formed. Specific examples of stepwise drying include, for example, primary drying at a temperature of 40 to 140 ° C. (preferably 40 to 120 ° C.) and then a temperature of 150 to 250 ° C. (preferably 150 to 180 ° C.). A two-stage drying process in which subsequent drying is performed can be mentioned.

  Any appropriate drying time can be adopted as the drying time of the polyimide solution. In order to obtain a polyimide layer having excellent surface uniformity, the drying time is preferably 1 to 20 minutes, more preferably 1 to 15 minutes, and most preferably 2 to 10 minutes.

(Surface modification treatment)
Any appropriate method can be adopted as the surface modification treatment. For example, the surface modification treatment may be a dry treatment or a wet treatment. Specific examples of the dry treatment include discharge treatment such as corona treatment and glow discharge treatment, flame treatment, ozone treatment, UV ozone treatment, ionizing active ray treatment such as ultraviolet treatment and electron beam treatment, and the like. Of these, UV ozone treatment, corona treatment and / or plasma treatment are preferably used in the present invention. This is because continuous production is possible and the economy and workability are excellent.

  In this specification, “UV ozone treatment” refers to treatment of the film surface by irradiating with ultraviolet rays while blowing air containing ozone. In addition, “corona treatment” means that corona discharge is generated by ionizing the air between electrodes by dielectric breakdown by applying high frequency and high voltage between the grounded dielectric roll and the insulated electrode. The film surface is treated by passing the film through. “Plasma treatment” means that when a glow discharge occurs in an inorganic gas such as a low-pressure inert gas, oxygen, or halogen gas, the film is passed through a low-temperature plasma generated by ionizing part of gas molecules. The one that treats the film surface.

  The atmosphere for performing the surface modification treatment is not particularly limited, and examples thereof include an air atmosphere, a nitrogen atmosphere, and an argon atmosphere. Further, the temperature of the atmosphere during the treatment is preferably 23 to 80 ° C, more preferably 23 to 60 ° C, and most preferably 23 to 50 ° C.

  The time for performing the surface modification treatment is not particularly limited, but is preferably 5 seconds to 10 minutes, more preferably 10 seconds to 5 minutes, and most preferably 20 seconds to 3 minutes. In the present invention, the surface modification treatment is performed so that the contact angle of water on the surface of the transparent protective film is preferably 10 to 70 °, more preferably 15 to 60 °, and most preferably 20 to 50 °. Done.

  A representative example of the wet treatment includes alkali treatment. “Alkali treatment” refers to treatment of a surface by immersing a laminated film in an alkali treatment solution obtained by dissolving a basic substance in water or an organic solvent. As described in the explanation of FIG. 3 above, the adhesiveness between the polarizer and the transparent protective film of the laminated film can be further improved by combining the dry treatment and the wet treatment (alkali treatment). Details of this reason are unclear, but during the alkali treatment process, the surface free energy increases by modifying the surface of the transparent protective film to saponify the surface so that more functional groups are present, and by providing irregularities on the surface. It is speculated that there is something happening.

  Any appropriate substance can be adopted as the basic substance. Specific examples include sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, copper hydroxide, aluminum hydroxide, iron hydroxide, ammonium hydroxide, sodium hydrogen carbonate and the like.

  The pH of the alkaline treatment liquid is preferably 8 to 13, and more preferably 9 to 13. The said pH can be calculated | required by the method according to JISZ8802-1986.

  The alkali treatment is preferably performed in an aqueous solution or a liquid phase in an organic solvent. From the viewpoint of economy, stability, etc., it is preferable to carry out in an aqueous solution. The temperature of the liquid phase during the alkali treatment is preferably 23 to 80 ° C, more preferably 23 to 60 ° C, and most preferably 23 to 50 ° C.

  The time for performing the alkali treatment is not particularly limited, but is preferably 5 seconds to 10 minutes, more preferably 10 seconds to 5 minutes, and most preferably 20 seconds to 3 minutes.

  Any appropriate method can be adopted as a drying method after the alkali treatment. For example, an air circulation type constant temperature oven in which hot or cold air circulates, a heater using microwaves or far infrared rays, a heating roll for temperature adjustment, a heating method using a heat pipe roll or a metal belt, or a temperature control method Can be mentioned.

  Although there is no restriction | limiting in particular as drying temperature after performing the said alkali treatment, Preferably it is 30-180 degreeC, More preferably, it is 40-150 degreeC, Especially preferably, it is 50-130 degreeC. If it is said range, the water | moisture content adhering to the surface of a laminated | multilayer film can fully be removed.

  Bonding of the laminated film and the polarizer can be achieved using any appropriate method. For example, according to the embodiment illustrated in FIG. 4, a coating liquid containing the adhesive at a predetermined ratio is applied to the surface of the transparent protective film of the laminated film, and the adhesive is in a wet state. Bonding can be achieved by bringing the adhesive into contact with the polarizer and drying the adhesive. There is no restriction | limiting in particular as a method of coating the coating liquid containing the said adhesive agent, The coating system mentioned above can be used. Moreover, the coating method of FIG. 2 and FIG. 5 of Unexamined-Japanese-Patent No. 11-179871 can also be used.

  The method for laminating the laminated film and the polarizer is not limited to the illustrated example, and any appropriate method can be adopted. Specific examples include hot melt lamination, non-solvent lamination, wet lamination, dry lamination, and the like. In the present invention, wet lamination suitable for a water-soluble adhesive is preferably used as shown in FIG.

  The polarizing plate has a first laminated film (first transparent protective film side) on one side of the polarizer and, for example, a second laminated film or any suitable second transparent protective film on the other side. Can be obtained by laminating an adhesive layer between the adhesive layer and the first or second laminated film or the second transparent protective film and the polarizer. Etc. 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. For the formation of the easy-adhesive layer, various easy-adhesive materials such as polyol resin, polycarboxylic acid resin, and polyester resin can be used. 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 first laminated film (first transparent protective film side), on the other side, for example, the second laminated film or any suitable second transparent protection The film is bonded with a roll laminator or the like. For the application of the adhesive, the first laminated film (first transparent protective film side) may be applied to either the second laminated film or the polarizer, for example, on the other side. Also good. 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 the polarizer and the first laminated film (first transparent protective film side) are bonded on the other side, for example, the second laminated film or any appropriate second transparent protective film, an electron beam or the like To cure the adhesive. The irradiation direction of the electron beam can be irradiated from any appropriate direction. Preferably, the first laminated film (first transparent protective film side) is irradiated on the other side, for example, from the second laminated film or any appropriate second 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.

  FIG. 5 is a schematic cross-sectional view of a liquid crystal panel according to a preferred embodiment of the present invention. The liquid crystal panel 100 includes a liquid crystal cell 20, retardation plates 30 and 30 ′ disposed on both sides of the liquid crystal cell 20, and polarizing plates 10 and 10 ′ disposed on the outer sides of the respective retardation plates. As the retardation plates 30 and 30 ′, any appropriate retardation plate can be adopted depending on the purpose and the alignment mode of the liquid crystal cell. Further, depending on the purpose and the alignment mode of the liquid crystal cell, one or both of the retardation plates 30 and 30 'may be omitted. At least one of the polarizing plates 10, 10 'is the polarizing plate of the present invention described above. The polarizing plates 10 and 10 ′ are typically arranged so that their absorption axes are orthogonal to each other. The liquid crystal cell 20 includes a pair of glass substrates 21 and 21 ′, and a liquid crystal layer 22 as a display medium disposed between the substrates. One substrate (active matrix substrate) 21 includes a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the active element, and a signal line for supplying a source signal. Provided (none shown). The other glass substrate (color filter substrate) 21 'is provided with a color filter (not shown). The color filter may be provided on the active matrix substrate 21. A distance (cell gap) between the substrates 21 and 21 'is controlled by a spacer (not shown). An alignment film (not shown) made of polyimide, for example, is provided on the side of the substrates 21, 21 ′ in contact with the liquid crystal layer 22.

  FIG. 6 is a schematic perspective view illustrating a typical arrangement of the polarizing plate of the present invention in the liquid crystal panel of the present invention. For simplicity, only the lower side (backlight side) of the liquid crystal cell is illustrated and described, but the polarizing plate of the present invention may be disposed only on the upper side (viewing side) of the liquid crystal cell and on both sides of the liquid crystal cell. Needless to say, they may be arranged. It should also be noted that the phase difference plate is omitted in FIG. As shown in FIGS. 6A to 6F, when the polarizing plate 10 of the present invention is used, the first laminated film 13 is disposed between the liquid crystal cell 20 and the polarizer 11. Is done. As described above, the optical characteristics of the first optical compensation layer 131, the first transparent protective film 132, and the first anchor coat layer (not shown in FIG. 6) of the first laminated film 13 are the same as those of the liquid crystal display device. Optimized not to affect display characteristics. A second laminated film 13 ′ may be disposed outside the polarizer 11, and any appropriate second transparent protective film 14 may be disposed. The first optical compensation layer 131 substantially exhibits birefringence and therefore has a slow axis. The absorption axis of the polarizer 11 and the slow axis of the first optical compensation layer 131 are preferably They are arranged in parallel, orthogonal or at an angle of 45 °. According to the embodiments of FIGS. 6A and 6B, it is possible to optically compensate particularly for a VA mode liquid crystal cell without using a retardation plate. According to the embodiments of FIGS. 6E and 6F, it is possible to optically compensate particularly for the OCB mode liquid crystal cell without using a retardation plate.

  Applications of the polarizing plate and the liquid crystal panel of the present invention include liquid crystal display devices such as personal computers, liquid crystal televisions, mobile phones, and personal digital assistants (PDAs), organic electroluminescence displays (organic EL), projectors, and projection televisions. And an image display device such as a plasma television. Especially, the polarizing plate and liquid crystal panel of this invention are used suitably for a liquid crystal display device, and are used especially suitably for a liquid crystal television.

  The type of the liquid crystal display device is not particularly limited, and any of a transmissive type, a reflective type, and a reflective transflective type can be used. Examples of liquid crystal cells used in the liquid crystal display device include twisted nematic (TN) mode, super twisted nematic (STN) mode, horizontal alignment (ECB) mode, vertical alignment (VA) mode, and in-plane switching (IPS) mode. And various liquid crystal cells such as a liquid crystal cell of a bend nematic (OCB) mode, a ferroelectric liquid crystal (SSFLC) mode, and an antiferroelectric liquid crystal (AFLC) mode. Among these, the retardation film and the polarizing plate of the present invention are particularly preferably used for TN mode, VA mode, IPS mode, and OCB mode liquid crystal display devices. Most preferred are VA mode and OCB mode liquid crystal display devices.

  The above-mentioned twisted nematic (TN) mode liquid crystal cell is a nematic liquid crystal having a positive dielectric anisotropy sandwiched between a pair of substrates. The one that is twisted. Specific examples include the liquid crystal cell described in “Liquid Crystal Dictionary” on page 158 (1989) and the liquid crystal cell described in JP-A-63-279229.

  The liquid crystal cell in the vertical alignment (VA) mode uses a voltage-controlled birefringence (ECB) effect, and a nematic liquid crystal having a negative dielectric anisotropy between transparent electrodes is applied when no voltage is applied. A vertically aligned liquid crystal cell. Specific examples include liquid crystal cells described in JP-A-62-210423 and JP-A-4-153621. Further, as described in JP-A No. 11-258605, the VA mode liquid crystal cell is provided with a substrate provided with a slit in a pixel or a substrate on which a protrusion is formed in order to enlarge a viewing angle. By using it, it may be a multi-domain MVA mode liquid crystal cell. Furthermore, as described in JP-A-10-123576, a chiral agent is added to the liquid crystal so that the nematic liquid crystal is substantially vertically aligned when no voltage is applied and twisted multi-domain alignment is applied when a voltage is applied. A liquid crystal cell may be used.

  The in-plane switching (IPS) mode liquid crystal cell is a so-called sandwich cell in which a liquid crystal is sealed between two parallel substrates using the voltage controlled birefringence (ECB) effect. In this state, nematic liquid crystal that is homogeneously aligned in a non-conductive state is made to respond with an electric field parallel to the substrate (also referred to as a transverse electric field). Specifically, Techno Times Publishing “Monthly Display July” p. 83-p. 88 (1997 edition) and “Liquid Crystal vol. 2 No. 4” published by the Japanese Liquid Crystal Society. 303-p. 316 (1998 edition), when the upper and lower polarizing plates are arranged orthogonally so that the major axis of the liquid crystal molecules and the polarizing axis of the incident side polarizing plate coincide with each other, the display is completely black without an electric field. When there is an electric field, the liquid crystal molecules are those that can obtain transmittance according to the rotation angle by rotating while keeping parallel to the substrate.

  The liquid crystal cell of the above-mentioned bend nematic (OCB: Optically Compensated Bend or Optically Compensated Birefringence) mode is a voltage-controlled birefringence (ECB: Electrically controlled birefringence effect using a positively controlled birefringence effect). The liquid crystal is a bend-aligned liquid crystal cell in which twisted alignment exists in the center when no voltage is applied. The OCB mode liquid crystal cell is also referred to as a “π cell”. Specific examples include those described in Kyoritsu Publishing Co., Ltd. “Next Generation Liquid Crystal Display” (2000), pages 11 to 27, and those described in JP-A-7-084254.

  By using the polarizing plate of the present invention for such various liquid crystal cells, contrast, hue and / or viewing angle characteristics can be improved, and the function can be maintained for a long time.

  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).

(Polyimide reagent)
2,2'-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride was manufactured by Clariant Japan Ltd., and 2,2-bis (trifluoromethyl) -4,4'-diamino was used. Biphenyl manufactured by Wakayama Seika Kogyo Co., Ltd. was used. All other chemicals were purchased from Wako Pure Chemical Industries.

(Measurement method of imidation rate)
^{Using a 1} H-NMR apparatus [manufactured by JEOL Ltd., product name “LA400”], the peak integrated intensity derived from polyamic acid NH near 11 ppm is X, 7.0 to 8.5 ppm polyamic acid and polyimide derived from aromatic ring The peak integrated intensity was determined as Y, and the equation: A (%) = ((Y-6X) / Y) × 100.

(Measurement method of molecular weight of polyimide)
Polyethylene oxide was calculated as a standard sample by a gel permeation chromatograph (GPC) method. Specifically, it measured with the following apparatuses, instruments, and measurement conditions.
Sample: A sample was dissolved in an eluent to prepare a 0.1 wt% solution.
Pretreatment: left for 8 hours and filtered through a 0.45 μm membrane filter.
・ Analyzer: “HLC-8020GPC” manufactured by Tosoh Corporation
・ Column: Tosoh GMHXL + GMHXL + G2500HXL
Column size: 7.8 mmφ x 30 cm each (total 90 cm)
Eluent: Dimethylformamide (added with 10 mM lithium bromide and 10 mM phosphoric acid to make up to 1 L dimethylformamide solution)
-Flow rate: 0.8 ml / min.
・ Detector: RI (differential refractometer)
-Column temperature: 40 ° C
・ Injection volume: 100 μl

(Measurement method of moisture content of polarizer and polarizing plate)
Using a Karl Fischer moisture meter [product name “MKA-610” manufactured by Kyoto Electronics Industry Co., Ltd.], a polarizing plate cut into a size of 10 mm × 30 mm was placed in a 150 ± 1 ° C. heating furnace, and nitrogen gas (200 ml / min. ) Was bubbled into the titration cell solution and measured.

(Thickness measurement method)
When the thickness was less than 10 μm, measurement was performed using a thin film spectrophotometer [manufactured by Otsuka Electronics Co., Ltd., “instant multiphotometry system MCPD-2000”]. When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “K-351C type”.

<Production of polarizer>
A polyvinyl alcohol film having an average polymerization degree of 2400, a saponification degree of 99.9 mol%, and a thickness of 75 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Subsequently, the film was stretched to 3.5 times while dyeing in an iodine solution of 0.3 wt% (weight ratio: iodine / potassium iodide = 0.5 / 8) at 30 ° C. for 1 minute. Next, the total draw ratio was stretched to 6 times while being immersed in a 3% by weight boric acid ester aqueous solution at 65 ° C. for 10 seconds. Then, it dried for 3 minutes in 40 degreeC oven, and obtained the 30-micrometer-thick polarizer.

<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, and then a transparent protective film (thickness 40 μm, Re = 2 nm, Rth = 2 nm) biaxially stretched twice in length and twice in width was used.

In the obtained imidized MS resin, the ratio of the general formula (1) (imidation rate) was measured at room temperature using TravelIR manufactured by SensIR Technologies, using the product pellets as they were. did. 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 3.6% 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
<Synthesis of polyimide>
2,2'-bis (3,4-dicarboxyphenyl) -hexafluoropropane dianhydride in a reaction vessel (500 mL) equipped with a mechanical stirrer, Dean-Stark device, nitrogen inlet tube, thermometer and condenser tube 17.77 g (40 mmol) and 2,2-bis (trifluoromethyl) -4,4′-diaminobiphenyl 12.81 g (40 mmol) were added. Subsequently, a solution in which 2.58 g (20 mmol) of isoquinoline was dissolved in 275.21 g of m-cresol was added, and the mixture was stirred at 23 ° C. for 1 hour (600 rpm) to obtain a uniform solution. Next, the reaction vessel was heated using an oil bath so that the temperature in the reaction vessel became 180 ± 3 ° C., and stirred for 5 hours while maintaining the temperature to obtain a yellow solution. After further stirring for 3 hours, heating and stirring were stopped, and the mixture was allowed to cool and returned to room temperature. As a result, the polymer precipitated as a gel.

  Acetone was added to the yellow solution in the reaction vessel to completely dissolve the gel-like material to prepare a diluted solution (7% by weight). When this diluted solution was gradually added to 2 L of isopropyl alcohol while stirring, a white powder was precipitated. This powder was collected by filtration and poured into 1.5 L of isopropyl alcohol for washing. Further, the same operation was repeated once again for washing, and then the powder was again collected by filtration. This was dried in a 60 ° C. air-circulating constant temperature oven for 48 hours and then dried at 150 ° C. for 7 hours to obtain a polyimide as a white powder (yield 85%). The polyimide had a polymerization average molecular weight (Mw) of 124,000 and an imidation ratio of 99.9%.

<Creation of laminated film>
17.7 parts by weight of the polyimide (white powder) obtained above was dissolved in 100 parts by weight of methyl isobutyl ketone (boiling point 116 ° C.) to prepare a polyimide solution having a concentration of 15% by weight. This polyimide solution was applied to the surface of the transparent protective film 1 in one direction with a rod coater. Next, the film was dried for 5 minutes in an air circulating constant temperature oven at 135 ± 1 ° C. to evaporate the solvent, and a polyimide layer having a thickness of 3.0 μm was formed on the transparent protective film 1 to produce a laminated film. While heating the laminated film in an air circulating constant temperature oven at 150 ± 1 ° C., using a tenter stretching machine, the longitudinal direction of the film is fixed and uniaxially stretched 1.1 times in the width direction, and then in the width direction. The relaxation treatment was performed at 0.97 times. The stretched polyimide layer (Re = 50 nm, Rth = 150 nm, Nz = 3) also functioned as a biaxial retardation film.

<Creation of polarizing plate>
What apply | coated the said adhesive 1 so that the thickness of the adhesive bond layer after drying was set to 80 nm on each single side | surface of the said laminated | multilayer film (transparent protective film 1 side) and the transparent protective film 2 was prepared. The adhesive was applied 30 minutes after the preparation under a temperature condition of 23 ° C. Next, the laminated film with adhesive and the transparent protective film 2 were 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.

Example 2 and Comparative Examples 1 and 2
A polarizing plate was produced in the same manner as in Example 1 except that the type of the transparent protective film and the adhesive was changed as shown in Table 1 in the production of the polarizing plate of Example 1.

(Evaluation)
The following evaluation was performed about the obtained polarizing plate. The results are shown in Table 2.

(Display unevenness)
The polarizing plate was cut out to 160 mm × 90 mm so that the absorption axis of the polarizer was 45 ° with respect to the long side. An acrylic pressure-sensitive adhesive layer was attached to the laminated film surface (optical compensation layer side) of the polarizing plate. A sample in which the polarizing plate with the pressure-sensitive adhesive layer was attached to both surfaces of the glass plate so that the absorption axes of the polarizing plates (polarizers) were orthogonal to each other was used as a sample. The sample was subjected to a heating test (80 ° C., 100 hours) and a humidification test (60 ° C., 90% RH, 100 hours). After the test, visual observation and luminance were measured.

Visual observation is based on the following evaluation.
○: No display unevenness or partial display unevenness is observed.
X: Display unevenness is seen on the entire surface.

Luminance is measured by placing a test sample on the backlight and installing it on the opposite side (position 50 cm away from the top plate) (2D color distribution measuring device, Konica Minolta). : CA-1500). The brightness is measured by measuring the brightness (A: cd / m ² ) of the part (dark part) that appears as unevenness and the brightness (B: cd / m ² ) of the part (bright part) without unevenness (A / B). ) Was used as an indicator. The larger the value of the luminance difference (A / B), the larger the in-plane luminance unevenness.

(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. Table 2 shows the amount of peeling (mm) after 5 hours.

(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.

It is a schematic sectional drawing for demonstrating the polarizing plate by typical embodiment of this invention. It is a schematic diagram explaining the outline | summary of the coating process and surface modification treatment process of a polyimide solution in the manufacturing method of this invention. It is a schematic diagram which illustrates the case where the surface modification process process in the manufacturing method of this invention employ | adopts wet processing. It is a schematic diagram explaining the outline | summary of the bonding process of the laminated | multilayer film and polarizer in the manufacturing method of this invention. It is a schematic sectional drawing of the liquid crystal panel by preferable embodiment of this invention. It is a schematic perspective view explaining the typical arrangement | positioning of the polarizing plate in the liquid crystal panel of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 10 'Polarizing plate 11 Polarizer 12, 12' Adhesive layer 13 Laminated film 131, 131 'Optical compensation layer 132, 132' Transparent protective film 20 Liquid crystal cell 21, 21 'Substrate 22 Liquid crystal layer 30, 30' Phase difference Plate 100 LCD panel

Claims (10)

A polarizing plate having an adhesive layer, a transparent protective film and an optical compensation layer in this order on at least one surface of a polarizer,
Nx>ny> nz (where the in-plane refractive index is maximized in the X-axis, the direction perpendicular to the X-axis is the Y-axis, and the thickness direction is the Z-axis). The refractive index is nx, ny, nz), and
The transparent protective film is made contains a (meth) acrylic resin having a glutarimide units and (meth) acrylic acid ester units, and less than the in-plane retardation is 40 nm, Ri 80nm less der thickness direction retardation ,
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
Colloidal metal compound, a polarizing plate, wherein relative to 100 parts by weight of the polyvinyl alcohol-based resin, an der Rukoto those formed from adhesive for polarizing plate that is blended in an amount of 200 parts by weight or less. 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 optical compensation layer, polarizing plate according to any one of claims 1 to 6, characterized in that a polyimide layer. The optical compensation layer, polarizing plate according to any one of claims 1 to 7, characterized in that it is formed by the liquid crystal material. An optical film, wherein at least one polarizing plate according to any one of claims 1 to 8 is laminated. An image display device comprising the optical film of the polarizing plate or claim 9, wherein according to any one of claims 1-8 is used.