JP4803833B2 - Manufacturing method of polarizing plate, polarizing plate, optical film, and image display device - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate. Moreover, this invention relates to the polarizing plate obtained by the said manufacturing method. The polarizing plate is an optical film obtained by laminating the polarizing plate alone, or a flat panel display such as a liquid crystal display device (hereinafter abbreviated as LCD) or an electroluminescence display device (hereinafter abbreviated as ELD), or an image such as a PDP. A display device can be formed.

  In general, polarizing plates for flat panel displays, particularly polarizing plates used in LCDs, are mainly made of polyvinyl alcohol film. In order to obtain sufficient optical properties as an LCD, a polarizing plate is preferably used by stretching a polyvinyl alcohol-based film containing a dichroic material such as iodine and pasting a transparent protective film thereon. ing. The polyvinyl alcohol polarizer is easily contracted because it is made by stretching. In addition, since the polyvinyl alcohol film uses a hydrophilic polymer, it is very easily deformed particularly under humidified conditions. Moreover, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. For this reason, a polarizing plate is used in which a transparent protective film is bonded to both sides or one side of the polarizer to supplement the strength. The polarizing plate is manufactured by bonding a polarizer and a transparent protective film with an adhesive. For the adhesion between the polyvinyl alcohol polarizer and the transparent protective film, a polyvinyl alcohol adhesive, which is mainly an aqueous solution, is used.

  As the transparent protective film used for the polarizing plate, triacetyl cellulose is mainly used. However, since triacetyl cellulose has a high moisture permeability, it can be smoothly dried after pasting the polarizer after applying the adhesive when creating the polarizing plate, but the moisture resistance is not sufficient, After creating the polarizing plate, it is easily affected by the external environment due to water. Therefore, the obtained polarizing plate has a problem that its characteristics are easily changed depending on the external environment from the initial state.

  In order to solve the above problems, a cyclic olefin-based resin having a low moisture permeability has been proposed as a material for the transparent protective film, instead of triacetylcellulose. However, a transparent protective film having a low moisture permeability such as a cyclic olefin resin does not sufficiently release moisture in the drying process after being bonded to a polarizer, and the obtained polarizing plate has a high moisture content and is polarized. The optical characteristics such as degree deteriorate.

  As a method of bonding a transparent protective film using a cyclic olefin resin and a polyvinyl alcohol polarizer, for example, a method of bonding via an acrylic pressure-sensitive adhesive layer has been proposed (Patent Document 1). However, this method has a problem that thermocompression bonding is required and the heating time is long, so that the polyvinyl alcohol polarizer is discolored and the degree of polarization is significantly reduced. Furthermore, since heating for a long time is required, there is a problem that the production efficiency is low and the film is deformed.

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 2). In addition, the nick is particularly likely to occur when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol adhesive.
Japanese Patent Laid-Open No. 5-212828 JP 2006-119203 A

  The present invention is a method for producing a polarizing plate in which a polyvinyl alcohol-based polarizer is used as a polarizer, a low-moisture-permeable material is used as a transparent protective film, and these are bonded with a water-based adhesive. The object is to provide a method by which a plate can be produced.

  Another object of the present invention is to provide a polarizing plate obtained by the production method. Moreover, it aims at providing image display apparatuses, such as an optical film which laminated | stacked the said polarizing plate, and also the LCD and ELD which used the said polarizing plate and the optical film.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the object can be achieved by the following method for producing a polarizing plate, and have completed the present invention. That is, the present invention is as follows.

That is, the present invention is a method for producing a polarizing plate having a drying step after laminating a transparent protective film with an aqueous adhesive on both surfaces of a polarizer,
The polarizer is a polyvinyl alcohol polarizer,
Transparent protective film, the moisture permeability is less 150g / m ² / 24h,
The drying temperature in the drying step is in the range of 70 to 90 ° C., and the drying step has a plurality of drying zones, and the drying temperature of the drying zone increases from the first drying zone to the final drying zone. It is related with the manufacturing method of the polarizing plate characterized by setting so that may become high.

  In the manufacturing method of the said polarizing plate, it is preferable that the temperature of a 1st drying zone is the range of 70-80 degreeC.

  In the manufacturing method of the said polarizing plate, it is preferable that the temperature difference between each drying zone is 0.5-10 degreeC in several drying zones.

  In the manufacturing method of the said polarizing plate, it is preferable that the drying time in a drying process is 10 minutes or more.

In the method for producing a polarizing plate, the aqueous adhesive 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 preferably blended at a ratio of 200 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.

  In the method for producing a polarizing plate, 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 manufacturing method of the said polarizing plate, this invention is suitable when the polyvinyl alcohol-type resin used for an aqueous adhesive is a polyvinyl alcohol-type resin containing an acetoacetyl group.

  In the method for producing the polarizing plate, it is preferable that the crosslinking agent used for the aqueous adhesive contains a compound having a methylol group.

  In the method for producing a polarizing plate, the amount of the crosslinking agent used in the aqueous adhesive is preferably 10 to 60 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin.

  In the manufacturing method of the polarizing plate, the thickness of the adhesive layer is 10 to 300 nm, and the thickness of the adhesive layer is larger than the average particle diameter of the metal compound colloid contained in the aqueous adhesive. Is preferred. By setting the thickness of the adhesive layer within the above range, the metal compound colloid can be dispersed substantially uniformly in the adhesive layer. Moreover, by making the thickness of the adhesive layer larger than the average particle diameter of the metal compound colloid, it is possible to suppress the thickness unevenness of the adhesive layer and form an adhesive layer with good adhesiveness.

  Moreover, this invention relates to the polarizing plate obtained by the said manufacturing method.

  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.

  As a conventional method for producing a polarizing plate, a polyvinyl alcohol polarizer is used as a polarizer, a low moisture permeability material is used as a transparent protective film, and these are bonded together with an aqueous adhesive such as a polyvinyl alcohol adhesive. When manufacturing a plate, the transparent protective film has a low water vapor transmission rate, so when it is pasted, it is in a so-called “steamed” state when it is subjected to a drying process in an environment with a lot of moisture. It is considered that the optical characteristics are deteriorated. On the other hand, when using a transparent protective film with low moisture permeability, there is a problem that it takes too much drying time if the drying temperature is lowered in order to avoid the “steaming” state. In addition, in such a conventional method for producing a polarizing plate, an annealing step is provided after the drying step, and a considerable burden is imposed on the cost.

  Then, in the manufacturing method of the polarizing plate of this invention, when using a polyvinyl-alcohol-type polarizer as a polarizer and using a low moisture permeability material as a transparent protective film, the drying temperature of a drying process is 70-90 degreeC. A drying step having a plurality of drying zones is set in a high range, and the plurality of drying zones are set so that the drying temperature becomes higher from the first drying zone to the final drying zone. Yes. Thus, even when using a polyvinyl alcohol-type polarizer and a low moisture-permeable transparent protective film by setting the drying process so as to increase stepwise at a predetermined high temperature, the optical characteristics A favorable polarizing plate is obtained. It is considered that moisture is quickly removed in the initial drying zone of the drying step, and adhesion is improved in the final drying zone. Moreover, according to the manufacturing method of this invention, it is not necessary to provide an annealing process separately after a drying process, and the total time of the drying process and annealing process after bonding a polarizer and a transparent protective film can be shortened. On the other hand, by not providing an annealing step, it is possible to set a longer processing time for each drying zone in the drying step (for example, to reduce the line speed in a continuous line), and to remove moisture from the initial drying zone. Removal can be performed efficiently.

  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 water-based 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. . 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 aqueous adhesive using a polyvinyl alcohol-based resin containing an acetoacetyl group, many occurrences of nicks were observed. In the aqueous adhesive of the present invention, acetoacetyl was added by blending the metal compound colloid. Generation of nicks in an aqueous adhesive using a polyvinyl alcohol-based resin containing a group can be suppressed. Thereby, it has water resistance and can suppress the generation of nicks.

  The polarizer used in the production method of the present invention is a polyvinyl alcohol polarizer. Examples of the polarizer include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, ethylene / vinyl acetate copolymer partially saponified films, and iodine and dichroic dyes. Examples thereof include those obtained by adsorbing a chromatic material and uniaxially stretching. Among these, a polarizer made of a dichroic substance such as a polyvinyl alcohol film and iodine or a dichroic dye is preferable. The thickness of these polarizers is not particularly limited, but is generally about 5 to 80 μm.

  As a polyvinyl alcohol film, a film formed by any method such as a casting method, a casting method or an extrusion method in which a stock solution in which a polyvinyl alcohol resin is dissolved in water or an organic solvent is cast is appropriately used. can do. The degree of polymerization of the polyvinyl alcohol-based resin is preferably about 100 to 5000, and more preferably 1400 to 4000.

  A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine or the like and uniaxially stretching can be produced, for example, by the following method.

  In the dyeing process, the polyvinyl alcohol film is immersed in a dyeing bath at about 20 to 70 ° C. to which iodine is added for about 1 to 20 minutes to adsorb iodine. The iodine concentration in the dyeing bath is usually about 0.1 to 1 part by weight per 100 parts by weight of water. In the dyeing bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of about 0.02 to 20 parts by weight, preferably 2 to 10 parts by weight. These additives are particularly preferable for increasing the dyeing efficiency. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The polyvinyl alcohol film may be subjected to a swelling treatment at about 20 to 60 ° C. for about 0.1 to 10 minutes in a water bath or the like before being dyed in an aqueous solution containing iodine or a dichroic dye. 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.

  The dyed polyvinyl alcohol film can be cross-linked as necessary. The composition of the aqueous crosslinking solution used for the crosslinking treatment is usually about 1 to 10 parts by weight per 100 parts by weight of water, alone or mixed with a crosslinking agent such as boric acid, borax, glyoxal, and glutaraldehyde. The concentration of the crosslinking agent is determined in consideration of the balance between the optical properties and the contraction of the polarizing plate caused by the stretching force generated in the polyvinyl alcohol film.

  In the crosslinking bath, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. An auxiliary such as iodide may be added in an amount of 0.05 to 15% by weight, preferably 0.5 to 8% by weight. These additives are particularly preferable from the viewpoint of obtaining in-plane uniform characteristics of the polarizer. The temperature of the aqueous solution is usually about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time is not particularly limited, but is usually about 1 second to 15 minutes, preferably 5 seconds to 10 minutes. In addition to the water solvent, a small amount of an organic solvent compatible with water may be contained.

  The total draw ratio of the polyvinyl alcohol film is about 3 to 7 times, preferably 5 to 7 times the original length. When the total draw ratio exceeds 7 times, the film is easily broken. Stretching may be performed after dyeing with iodine, may be performed while dyeing or crosslinking, or may be dyed with iodine after stretching. The stretching method and the number of stretching are not particularly limited, and may be performed only in any one step. Moreover, you may perform several times in the same process.

  In addition, the polyvinyl alcohol film subjected to iodine adsorption alignment treatment is further added to an aqueous iodide solution such as potassium iodide having a water temperature of about 10 to 60 ° C., preferably about 30 to 40 ° C. and a concentration of 0.1 to 10% by mass. A step of dipping for 1 minute to 1 minute can be provided. In the iodide aqueous solution, auxiliary agents such as zinc sulfate and zinc chloride may be added. Moreover, the water washing process and the drying process can be provided in the polyvinyl alcohol-type film which performed the iodine adsorption orientation process.

  The moisture content of the polarizer after drying is preferably 15 to 35% by weight, and more preferably 20 to 30% by weight. By setting the moisture content within the above range, it is possible to prevent a decrease in optical properties when drying after bonding the polarizer and the protective film through an adhesive. That is, if the moisture content is too high, there is a problem that heat resistance and adhesive strength are liable to decrease, and if the moisture content is too low, there is a problem that unevenness in nicks and appearance tends to occur. By doing so, it is possible to prevent such a decrease in optical characteristics.

Transparent protective film used in the manufacturing method of the present invention, moisture permeability using the following low moisture permeability material 150g / m ² / 24h. Preferably the moisture permeability is 0~140g / m ² / 24h, further particularly 0~120g / m ² / 24h. Low moisture permeability materials include polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, (meth) acrylic resin, cyclo or norbornene Resins, polyarylate resins, and mixtures thereof.

  Moreover, the polymer film described in JP-A-2001-343529 (WO01 / 37007), for example, (A) a thermoplastic resin having a substituted and / or unsubstituted imide group in the side chain, and (B) a substitution in the side chain And / or a resin composition containing a thermoplastic resin having unsubstituted phenyl and a nitrile group. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. A lactone ring-containing acrylic resin (resin described in JP-A-2005-146084) can be used.

  Although the thickness of a 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. The transparent protective film is particularly suitable when the thickness is 5 to 150 μm.

  In addition, when providing a transparent protective film on both sides of a polarizer, the protective film which consists of the same polymer material may be used by the front and back, and the protective film which consists of a different polymer material etc. may be used.

  As the transparent protective film of the present invention, among the above, in terms of moisture permeability and optical properties, it is preferable to use a polyimide resin, a norbornene resin, or a (meth) acrylic resin.

  As the polyimide resin, for example, a polymer film formed from a resin composition as described in JP-A-2001-343529 (WO01 / 37007) can be used. More specifically, it is a mixture of a thermoplastic resin having a substituted imide group or an unsubstituted imide group in the side chain and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a cyano group in the side chain. Specific examples include a resin composition having an alternating copolymer composed of isobutene and N-methylenemaleimide and an acrylonitrile / styrene copolymer tight.

  Norbornene-based resin is a general generic name for resins obtained from cyclic olefins such as norbornene, tetracyclododecene, and derivatives thereof. Are listed. Specifically, ring-opening polymers of cyclic olefins, addition polymers of cyclic olefins, random copolymers of cyclic olefins and α-olefins such as ethylene and propylene, and these are modified with unsaturated carboxylic acids or their derivatives. Examples of such graft-modified products can be given. Furthermore, these hydrides are mentioned. Examples of the products include ZEONEX and ZEONOR manufactured by ZEON Corporation, ARTON manufactured by JSR Corporation, and TOPAS manufactured by TICONA Corporation.

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

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

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

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

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

  As the (meth) acrylic resin, an acrylic resin having a structural unit of unsaturated carboxylic acid alkyl ester and a structural unit of glutaric anhydride can be used. Examples of the acrylic resin include Japanese Patent Application Laid-Open Nos. 2004-70290, 2004-70296, 2004-163924, 2004-292812, 2005-314534, and 2006. No. 131898, JP 2006-206881 A, JP 2006-265532 A, JP 2006-283013 A, JP 2006-299005 A, JP 2006-335902 A, and the like. It is done.

  In addition, as the (meth) acrylic resin, a thermoplastic resin having a glutarimide unit, a (meth) acrylic ester unit, and an aromatic vinyl unit can be used. Examples of the thermoplastic resin include JP 2006-309033 A, JP 2006-317560 A, JP 2006-328329 A, JP 2006-328334 A, JP 2006-337491 A, and JP 2006. -337492, JP-A-2006-337493, JP-A-2006-337569, and the like.

  As the transparent protective film, one having a front phase difference of less than 40 nm and a thickness direction retardation of less than 80 nm is usually used. The front phase difference Re is represented by Re = (nx−ny) × d. The thickness direction retardation Rth is represented by Rth = (nx−nz) × d. The Nz coefficient is represented by Nz = (nx−nz) / (nx−ny). [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. In addition, it is preferable that a transparent protective film has as little color as possible. A protective film having a thickness direction retardation value of −90 nm to +75 nm is preferably used. By using a film having a thickness direction retardation value (Rth) of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the transparent protective film can be almost eliminated. The thickness direction retardation value (Rth) is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  On the other hand, as the transparent protective film, a phase difference plate having a phase difference with a front phase difference of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be used. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a transparent protective film, so that the thickness can be reduced.

  Examples of the retardation plate include a birefringent film formed by uniaxially or biaxially stretching a polymer material. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm.

  The retardation plate may have an appropriate retardation according to the purpose of use, such as those for the purpose of compensating for various wavelength plates or birefringence of liquid crystal layers and compensation of viewing angle, etc. It may be one in which retardation plates are stacked and optical characteristics such as retardation are controlled.

  The retardation plate has a relationship of nx = ny> nz, nx> ny> nz, nx> ny = nz, nx> nz> ny, nz = nx> ny, nz> nx> ny, nz> nx = ny. What is satisfactory is selected and used according to various applications. Note that ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.

  For example, in a phase difference plate that satisfies nx> ny> nz, a surface plate having a front phase difference of 40 to 100 nm, a thickness direction phase difference of 100 to 320 nm, and an Nz coefficient of 1.8 to 4.5 is used. Is preferred. For example, in a retardation plate (positive A plate) that satisfies nx> ny = nz, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, for a retardation plate (negative A plate) that satisfies nz = nx> ny, it is preferable to use a retardation plate that satisfies a front phase difference of 100 to 200 nm. For example, in a retardation plate satisfying nx> nz> ny, it is preferable to use a retardation plate having a front phase difference of 150 to 300 nm and an Nz coefficient exceeding 0 to 0.7. Further, as described above, for example, nx = ny> nz, nz> nx> ny, or nz> nx = ny can be used.

  The transparent protective film can be appropriately selected according to the applied liquid crystal display device. For example, in the case of VA (including Vertical Alignment, MVA, and PVA), it is desirable that at least one of the polarizing plates (cell side) has a retardation. As specific phase differences, it is desirable that Re = 0 to 240 nm and Rth = 0 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> ny> nz, nx> nz> ny, nx = ny> nz (positive A plate, biaxial, negative C plate) are desirable. When polarizing plates are used above and below the liquid crystal cell, both the upper and lower sides of the liquid crystal cell may have a phase difference, or any one of the upper and lower transparent protective films may have a phase difference.

  For example, in the case of IPS (including In-Plane Switching, FFS), both cases where the transparent protective film on one side of the polarizing plate has a phase difference and does not have a phase difference can be used. For example, when there is no phase difference, it is desirable that the liquid crystal cell does not have a phase difference both above and below (cell side). In the case where the liquid crystal cell has a phase difference, it is desirable that the liquid crystal cell has a phase difference in the upper and lower sides, or the upper and lower sides have a phase difference (for example, nx> nz> ny on the upper side). Biaxial film satisfying the relationship, when there is no retardation on the lower side, positive A plate on the upper side, and positive C plate on the lower side). When it has a phase difference, it is desirable that Re = −500 to 500 nm and Rth = −500 to 500 nm. In terms of the three-dimensional refractive index, nx> ny = nz, nx> nz> ny, nz> nx = ny, nz> nx> ny (positive A plate, biaxial, positive C plate) are desirable.

  In addition, the film which has the said phase difference can be separately bonded to the transparent protective film which does not have a phase difference, and the said function can be provided.

  The surface of the transparent protective film that adheres to the polarizer can be subjected to an easy adhesion treatment. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment, and coating treatment for forming an easy adhesive layer. Among these, the coating process which forms an easily adhesive layer is suitable. 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 0.01 to 10 μm, more preferably about 0.05 to 5 μm, and particularly preferably about 0.1 to 1 μm.

  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. Examples of the fine particles to be included in the formation of the surface fine concavo-convex structure include conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like having an average particle diameter of 0.5 to 20 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 the surface fine uneven structure, the amount of fine particles used is generally about 2 to 70 parts by weight, preferably 5 to 50 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.

  A water-based adhesive is used for bonding the polarizer and the transparent protective film. Although it does not specifically limit as an aqueous adhesive, 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 aqueous 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 diameter of 1 to 100 nm is preferably used. The resin solution is usually used as an aqueous solution. The concentration of the resin solution is not particularly limited, but is 0.1 to 15% by weight, preferably 0.5 to 10% by weight in consideration of coating properties and storage stability.

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

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

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

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

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

  The viscosity of the resin solution that is an aqueous adhesive is not particularly limited, but a resin solution in the range of 1 to 50 mPa · s is 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 aqueous adhesive of the present invention, a low viscosity such as in the range of 1 to 20 mPa · s. Also in this 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 an aqueous 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 a water-system adhesive agent can also be adjusted suitably after preparing a resin solution.

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

  The polarizing plate of the present invention is produced by bonding the polyvinyl alcohol polarizer and the transparent protective film together with the aqueous adhesive.

  Application of the adhesive may be performed on either side of the polarizer or the transparent protective film, or may be performed on both sides. The application operation is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed.

  The polarizing plate can be obtained by laminating a transparent protective film on both sides of a polarizer via an adhesive layer, and the above-mentioned undercoat layer or easy layer is interposed between the adhesive layer and the transparent protective film or the polarizer. An adhesion treatment layer or the like may be provided.

  The thickness of the adhesive layer formed with an aqueous adhesive or the like 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 so as to be larger than the average particle diameter of the metal compound colloid contained in the aqueous adhesive.

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

  After applying the water-based adhesive, the polarizer and the transparent protective film are bonded together with a roll laminator or the like. Application | coating of the said adhesive agent may be performed to any of a transparent protective film and a polarizer, and may be performed to both.

  After the bonding, a drying step is performed to form an adhesive layer composed of a coating dry layer. The drying process is performed at a drying temperature in the range of 70 to 90 ° C., and the drying process has a plurality of drying zones. The drying temperature of the drying zone is increased from the first drying zone to the final drying zone. The temperature is set to be high. When the drying temperature has a temperature range outside the above range, the obtained polarized light can be obtained even if the drying temperature of the plurality of drying zones is set so as to increase from the first drying zone to the final drying zone. The optical properties (polarization degree, etc.) of the plate are not sufficient. Further, the drying process has a plurality of drying zones. The number of drying zones is preferably about 2 to 15 zones, more preferably 2 to 10 zones.

  Further, the drying temperature of the drying zone is set so that the drying temperature becomes higher as it goes from the first drying zone to the final drying zone. Although the drying temperature of each drying zone should just be in the range of 70-90 degreeC, the temperature of a 1st drying zone may be the range of 70-80 degreeC from the point of avoiding a "steaming" state. preferable. In addition, although the temperature of each drying zone is gradually increased, the temperature difference between the drying zones is in the range of 0.5 to 10 ° C, further 1 to 8 ° C, and more preferably 1 to 7 ° C. It is preferable to set. The temperature difference between the drying zones may be the same or different, so that the temperature difference between the drying zones becomes smaller from the first drying zone to the final drying zone, or Although it can be set to be large, the temperature difference between the drying zones decreases from the first drying zone to the final drying zone from the viewpoint of avoiding the “steaming” state at high temperature and high humidity. It is preferable to set so that

  The drying time in the drying step is appropriately set so that the drying is sufficiently completed so that the adhesive layer can be formed, and further, the total drying time of each drying zone is 10 minutes or more. Is preferably set so that it is 10 minutes to 40 minutes, more preferably 10 minutes to 20 minutes. Moreover, it is preferable to install so that the drying time of each drying zone may be 0.1 minute-10 minutes, Furthermore, 0.2 minute-5 minutes. In addition, the drying time of each drying zone may be the same or different, and the drying time of each drying zone is shortened from the first drying zone to the final drying zone, or It can also be set to be long. In general, the first drying zone is preferably set to be shorter than the drying time after the second drying zone by functioning as a preliminary drying zone. The first drying zone is preferably installed so that the drying time is 5 to 30 seconds, further 5 to 25 seconds, and further 5 to 20 seconds. On the other hand, the drying time after the second drying zone is preferably set to be 1 minute to 10 minutes, more preferably 1 minute to 7 minutes, and further preferably 1 minute to 5 minutes. Moreover, when performing the said manufacturing method with a continuous line, although a line speed is set in consideration of the drying temperature of each drying zone, it is 5-40 m / min, Furthermore, 5-20 m / min, Furthermore, 5-10 m / Min.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

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

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

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

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

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

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

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

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

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

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

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

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

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

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

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

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

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

  Examples and the like specifically showing the configuration and effects of the present invention will be described below.

(Moisture permeability)
According to the moisture permeability test (cup method) of JIS Z0208, the water vapor permeability of the transparent protective film is the number of grams of water vapor that passes through a sample of area 1 m ² in 24 hours in an atmosphere of temperature 40 ° C. and humidity 92% RH. It was measured.

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

(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).

(Average particle diameter of metal compound filler)
It was measured by a dynamic light scattering method (light correlation method) with a particle size distribution meter (Nikkiso Co., Ltd., Nanotrac UPA150).

<Creating a 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. The moisture content of the obtained polarizer was 25%.

<Preparation of adhesive>
Polyvinyl alcohol-based resin containing acetoacetyl group (average polymerization degree: 1200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) to 100 parts, Under temperature conditions, an aqueous solution dissolved in pure water and adjusted to a solid content concentration of 3.7% was prepared. An aqueous adhesive solution was prepared by adding 18 parts of an aqueous colloidal alumina solution (average particle size 15 nm, solid content concentration 10%, positive charge) to 100 parts of the aqueous solution. The viscosity of the adhesive aqueous solution was 9.6 mPa · s. The pH of the aqueous adhesive solution was in the range of 4-4.5. This is referred to as an adhesive 1. Also, an adhesive aqueous solution was prepared by adding no alumina colloid aqueous solution to the adhesive 1. The viscosity of the adhesive aqueous solution was 5 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.

<Transparent protective film>
As a transparent protective film, norbornene resin film: the (Nippon Zeon Co., Ltd., trade name ZEONOR, thickness 40 [mu] m, moisture permeability 6g / m ² / 24h) was used.

Example 1
<Creation of polarizing plate>
The adhesive 1 is applied on one side of the transparent protective film so that the thickness of the adhesive layer after drying is about 55 nm, and the transparent protection with adhesive on both sides of the polarizer at a temperature of 23 ° C. It was set as the laminated body which bonded the film with the roll machine. The line speed was 8 m / min. Subsequently, after passing the laminate through the first drying zone (line length: 2 m, passage time: 15 seconds, temperature: 73 ° C.) at this line speed, a total of four drying zones from the second to the fifth are obtained. (Each line length: 24 m for each, each passing time: all for 3 minutes, temperature: 78 ° C., 82 ° C., 84 ° C., 85 ° C. in order) were continuously passed through to make a polarizing plate.

Examples 2-4, Comparative Examples 1-3
A polarizing plate was produced in the same manner as in Example 1 except that the conditions of each drying zone and the type of adhesive were changed as shown in Table 1 in Example 1. In addition, the same value shown in Table 1 is employ | adopted for each line length and each passing time of the 2nd thru | or 5th drying zone. In Comparative Example 3, an annealing step for 30 minutes at 70 ° C. was further provided after the drying step.

(Evaluation)
The following evaluation was performed on the polarizing plates obtained in the examples and comparative examples, and the results are shown in Table 1.

(Degree of polarization)
Two pieces of 2cm x 2cm size are prepared by punching the polarizing plate, and the spectrophotometer [product name "Murakami Color Research Laboratory Co., Ltd." DOT-3 "].

(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 provided on the black light, and a sample polarizing plate was placed thereon. The two polarizing plates were installed so that their respective absorption axes were orthogonal, and in this state, the number of locations where light escaped (knic defects) was counted.

Claims (15)

A method for producing a polarizing plate having a drying step after laminating a transparent protective film with an aqueous adhesive on both sides of a polarizer,
The polarizer is a polyvinyl alcohol polarizer,
Transparent protective film, the moisture permeability is less 150g / m ² / 24h,
The drying temperature in the drying step is in the range of 70 to 90 ° C., and the drying step has a plurality of drying zones, and the drying temperature of the drying zone increases from the first drying zone to the final drying zone. The manufacturing method of the polarizing plate characterized by setting so that it may become high.   The method for producing a polarizing plate according to claim 1, wherein the temperature of the first drying zone is in the range of 70 to 80 ° C.   The method for producing a polarizing plate according to claim 1 or 2, wherein the plurality of drying zones have a temperature difference between the drying zones of 0.5 to 10 ° C.   The method for producing a polarizing plate according to claim 1, wherein the drying time in the drying step is 10 minutes or more. The aqueous adhesive is a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle size of 1 to 100 nm, and
The method for producing a polarizing plate according to claim 1, wherein the metal compound colloid is blended at a ratio of 200 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.   6. The method for producing a polarizing plate according to claim 5, wherein the metal compound colloid is at least one selected from alumina colloid, silica colloid, zirconia colloid, titania colloid and tin oxide colloid.   The method for producing a polarizing plate according to claim 5 or 6, wherein the metal compound colloid has a positive charge.   The method for producing a polarizing plate according to claim 7, wherein the metal compound colloid is an alumina colloid.   The method for producing a polarizing plate according to claim 5, wherein the polyvinyl alcohol resin is a polyvinyl alcohol resin containing an acetoacetyl group.   The method for producing a polarizing plate according to claim 5, wherein the crosslinking agent contains a compound having a methylol group.   The method for producing a polarizing plate according to any one of claims 5 to 10, wherein the amount of the crosslinking agent is 10 to 60 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin.   The thickness of the adhesive layer formed by the water-based adhesive is 10 to 300 nm, and the thickness of the adhesive layer is larger than the average particle diameter of the metal compound colloid contained in the water-based adhesive. The manufacturing method of the polarizing plate in any one of Claims 5-11. A polarizing plate obtained by the production method according to claim 1 ,
The polarizing plate, on both sides of the polyvinyl alcohol-based polarizer, and moisture permeability are laminated following the transparent protective film 150g / m ² / 24h through the formed adhesive layer by aqueous adhesive,
The degree of polarization is 99.98% or more, and
In this polarizing plate, a sample cut out to be 50 mm in the absorption axis direction of the polarizer and 25 mm in the direction perpendicular to the absorption axis is immersed in warm water at 60 ° C., and the end of the sample is peeled off after 5 hours. A polarizing plate characterized in that a value (mm) measured with a caliper is 0.2 mm or less .
  An optical film, wherein at least one polarizing plate according to claim 13 is laminated.   An image display device comprising the polarizing plate according to claim 13 or the optical film according to claim 14.