JP2006221158A - Polarizing plate and its manufacturing method, and optical film and image display device using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate which is constituted by bonding a protective film on one side or both sides of a polarizing film across an adhesion layer and which has improved in-plane uniformity by suppressing stripe-shaped protruded and recessed nonuniformity. <P>SOLUTION: The polarizing plate is constituted by bonding the protection film on one side or both sides of the polarizing film across the adhesion layer. Thickness of the adhesion layer is 52nm or less. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polarizing plate used for an image display device such as a liquid crystal display device (LCD) and an electroluminescence display device (ELD) and a method for producing the same. The present invention also relates to an optical film including the polarizing plate and an image display device having the polarizing plate or the optical film.

  A polarizing plate used for an image display device is required to have a high transmittance and a high degree of polarization in order to provide a bright image with good color reproducibility. In general, such a polarizing plate is obtained by staining a polyvinyl alcohol (PVA) film with a dichroic substance such as iodine or a dichroic dye to form a polarizing film, and then forming triacetyl on both sides of the polarizing film. It is manufactured by laminating a protective film made of a polymer film such as a cellulose film.

Such a polarizing plate is required to have a uniform image display, so-called excellent in-plane uniformity, in addition to excellent optical characteristics such as transmittance, polarization degree, and hue. With respect to this in-plane uniformity, the in-plane uniformity of the polarizing plate has been improved as an improvement in the unevenness of the polarizing film (see, for example, Patent Document 1) and the unevenness of the protective film (see, for example, Patent Document 2). A technique for improving the performance is disclosed. However, with the recent increase in the size of image display devices and the improvement in image quality, the demand for in-plane uniformity required for polarizing plates becomes stricter, and streaky unevenness (straight unevenness) confirmed by the density of reflected light. Thus, new mode unevenness has occurred, and it cannot be said that sufficient uniformity has been obtained. The stripe unevenness occurs in the same direction as the MD direction (flow direction) in the substantially central portion of the polarizing plate.
JP 2001-290025 A JP 2002-221620 A

  In view of the above problems, the present invention is a polarizing plate in which a protective film is bonded to one side or both sides of a polarizing film via an adhesive layer or an adhesive layer, which suppresses streaky unevenness and achieves in-plane uniformity. It aims at providing the outstanding polarizing plate and its manufacturing method. Furthermore, it aims at providing the optical film which laminated | stacked at least 1 layer of optical function layer on this polarizing plate, and the image display apparatus which has the said polarizing plate or the said optical film.

  The present inventors have intensively studied to solve the above-mentioned problems. As a result, they have found that the above object can be achieved by the following polarizing plate and the production method thereof, and have completed the present invention.

  The present invention relates to a polarizing plate in which a protective film is bonded to one side or both sides of a polarizing film via an adhesive layer or an adhesive layer, and the thickness of the adhesive layer or the adhesive layer is 52 nm or less. The moisture content of the polarizing film when the polarizing plate is bonded is preferably 15% by weight to 26% by weight.

  As a method for producing a polarizing plate according to the present invention, a protective film is bonded to one or both sides of a polarizing film using an adhesive or a pressure-sensitive adhesive, and then heated and dried. Alternatively, an adhesive or a pressure-sensitive adhesive is laminated so that the thickness of the pressure-sensitive adhesive layer is 52 nm or less. At this time, when the protective film is bonded to one side or both sides of the polarizing film using an adhesive or a pressure-sensitive adhesive, the polarizing film is bonded after adjusting the moisture content to 15 to 26% by weight. Is preferred.

  The present invention relates to an optical film in which at least one optical functional layer is laminated on the polarizing plate or the polarizing plate obtained by the manufacturing method, and relates to the polarizing plate or an image display device having the optical film. Is.

  As described above, the polarizing plate of the present invention is obtained by bonding a protective film to one or both sides of a polarizing film via an adhesive layer or an adhesive layer, and the thickness of the adhesive layer or the adhesive layer is 52 nm or less. It is characterized by that. Such a polarizing plate suppresses the uneven unevenness of streaks that are visible even when applied to an image display device, and can provide a polarizing plate having excellent in-plane uniformity. Furthermore, by using this polarizing plate, an image display device with high resolution and high contrast can be realized.

  The polarizing plate in the present invention is a polarizing plate in which a protective film is bonded to one side or both sides of a polarizing film via an adhesive layer or adhesive layer having a thickness of 52 nm or less. At this time, the adhesive layer or the pressure-sensitive adhesive layer is formed of an adhesive or a pressure-sensitive adhesive, and is not particularly limited. However, the adhesive layer or the pressure-sensitive adhesive layer is lighter or thinner than the pressure-sensitive adhesive. The adhesive is preferably used in that it is easy to use. Such an adhesive or pressure-sensitive adhesive is generally applied to one or both sides of a polarizing film or a protective film, the polarizing film and the protective film are bonded together, dried, and then the polarizing film, the adhesive layer or the pressure-sensitive adhesive layer, and the protective film are laminated. The polarizing plate becomes.

  If the thickness of the adhesive layer or the pressure-sensitive adhesive layer after drying in the polarizing plate is 52 nm or less, the effect of the present invention can be obtained. Especially, it is preferable that it is 35 nm or less, and 29 nm or less is more preferable. If this thickness is too thick, it will be difficult to maintain the in-plane uniformity of the adhesive layer or the pressure-sensitive adhesive layer, causing streaky unevenness, and the effects of the present invention cannot be obtained. Further, the minimum thickness of the adhesive layer or the adhesive layer is not particularly limited because it depends on the type of the adhesive layer or the adhesive layer, but is preferably 5 nm or more, and more preferably 10 nm or more. It is more preferable. If the thickness of the adhesive layer or the pressure-sensitive adhesive layer is too thin, it is difficult to obtain the minimum necessary adhesive force as a polarizing plate, and a new appearance defect is likely to occur.

  Although it does not specifically limit as an adhesive agent which forms an contact bonding layer, and an adhesion processing method, For example, the adhesive agent etc. which contain a vinyl polymer can be used. The adhesive layer made of such an adhesive can be formed as an aqueous solution coating / drying layer, etc. In preparing the aqueous solution, a crosslinking agent, other additives, and a catalyst such as an acid are also blended as necessary. be able to. The vinyl polymer in the adhesive 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 polarizing film, 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.

  The polyvinyl alcohol-based resin is not particularly limited, but an average degree of polymerization of about 100 to 3000 and an average degree of saponification of about 85 to 100 mol% are preferable from the viewpoint of adhesiveness. Further, the concentration of the aqueous adhesive solution may be appropriately determined according to the target thickness of the adhesive layer, and is not particularly limited, but is preferably 0.1 to 15% by weight, More preferably, it is 5 to 10% by weight. If this solution concentration is too high, the viscosity will increase too much, and streaky unevenness will tend to occur. If the solution concentration is too low, the coating properties will be poor and unevenness will tend to occur.

  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 (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, unsaturated carboxylic acids such as (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.

  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. Moreover, the method of making diketene gas or liquid diketene contact directly to polyvinyl alcohol is mentioned.

  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, which is inappropriate. 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 degree of acetoacetyl modification exceeds 40 mol%, the number of reaction points with the cross-linking agent decreases, and the effect of improving water resistance is small. Such a modification degree of acetoacetyl group can be measured using a nuclear magnetic resonance apparatus (NMR).

  As a crosslinking agent, what is generally used for an adhesive can be used without any particular limitation. For example, in the case of an adhesive using a polyvinyl alcohol resin as described above, a functional group having reactivity with a polyvinyl alcohol resin. A compound having at least two groups can be preferably used. For example, ethylenediamine, triethylenediamine, hexamethylenediamine and other alkyl diamines having two alkylene groups and two amino groups; 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, diglycol Epoxys such as dianiline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; Aminoformaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylol melamine, acetoguanamine, benzoguanamine and formaldehyde condensates; sodium, potassium, magnesium, calcium, aluminum, iron, nickel, etc. And divalent or trivalent metal salts and oxides thereof, among which amino-formaldehyde resins, Methylol compounds having Chiroru groups are preferred.

  The compounding amount of the crosslinking agent is generally about 0.1 to 35 parts by weight with respect to 100 parts by weight of the resin, and 10 to 25 parts by weight are preferably used. , 30 parts by weight or more and 46 parts by weight or less, more preferably 32 parts by weight or more and 40 parts by weight or less of a cross-linking agent is blended in exchange for shortening the time from the preparation of the adhesive to the adhesive layer (working time). It is also effective to do.

  The adhesive layer or the adhesive layer further includes a coupling agent such as a silane coupling agent or a titanium coupling agent, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and the like. An agent may be included.

  As long as the polarizing plate has a protective film bonded to one or both sides of the polarizing film via an adhesive layer or an adhesive layer, various conditions such as the number of the polarizing film, protective film, and adhesive layer or adhesive layer However, an undercoat layer, an easy adhesion treatment layer, or the like may be provided between the adhesive layer or the pressure-sensitive adhesive layer and the protective film or the polarizing film.

  As a method of bonding the polarizing film and the protective film through the adhesive layer or the pressure-sensitive adhesive layer, a conventionally known method may be appropriately used, and is not particularly limited. For example, the method of crimping | bonding by passing between a pair of rolls of a 1st roll and a 2nd roll with the adhesive agent (solution) or adhesive (solution) which adjusted the density | concentration and the viscosity is mentioned. In particular, in the present invention, since the adhesive layer or the pressure-sensitive adhesive layer is thinned to such an extent that it is not generally used, the concentration of the adhesive solution or the pressure-sensitive adhesive solution is adjusted, and the distance between the rolls to be pressure-bonded or the roll The thickness of the adhesive layer or the pressure-sensitive adhesive layer in the polarizing plate can be adjusted by appropriately adjusting the material, the roll diameter, the conveying speed at the time of bonding, and the like, and controlling the pressure applied to the adhesive layer or the pressure-sensitive adhesive layer. For example, in order to thin the adhesive layer or the adhesive layer, in addition to reducing the concentration of the adhesive solution or the adhesive solution (base concentration) and reducing the distance between the rolls to be bonded, Controls such as using a hard material and a material having a smaller diameter of the roll are also important.

  In the roll coating, it is preferable to use a metal roll as the first roll and use an elastic roll coated with a rubber layer or a resin layer on a metal core as the second roll. By the elastic force of the rubber layer or the resin layer in the elastic roll as the second roll, the thickness of the adhesive layer or the pressure-sensitive adhesive layer can be controlled to 52 nm or less, and streaky unevenness in the polarizing plate can be suppressed.

In roll coating with a pair of rolls, the gap (H) between the rolls when one roll is an elastic roll having an elastic layer,
H = 2 × (μV) ^1/2 (LR / E) ^1/3 (1 / W) ^1/6
It is known that Here, μ: viscosity of the coating liquid, V: coating speed, L: thickness of the elastic layer, E: hardness of the elastic layer, R: roll diameter, W: laminating pressure. Chemical Engineering Science Vol.43, No.10, P2673-2684 (1988). In the present invention, with reference to the above formula of the gap (H), this is applied to the adhesive layer or adhesive layer between the polarizing film and the protective film in the production of the polarizing plate, and the thickness of the adhesive layer or adhesive layer Was controlled to 52 nm or less, and the conditions for producing a polarizing plate were examined.

  A metal roll can be preferably used as the first roll. A metal roll having a higher surface hardness than the second roll is used. Examples of the material for the metal roll include iron, stainless steel, titanium, and aluminum. As the metal tall, an iron roll is preferable from the viewpoint of cost effectiveness.

  As the second roll, for example, an elastic roll in which a metal core is coated with a rubber layer or a resin layer can be preferably used. The hardness of the rubber layer or resin layer is preferably 60 or more, more preferably 80 or more. Moreover, 90 or less is preferable in order to prevent the film surface from being damaged. The hardness at this time can be measured using a commercially available durometer (type A), for example, by the method disclosed in JIS K6253 (1997).

  Furthermore, as the diameter of the first roll and the second roll, the smaller the diameter, the smaller the area in contact with the film, so that the pressure applied to the film surface is relatively high. For this reason, the roll diameter is preferably 250 mm or less, more preferably 200 mm or less, and even more preferably 150 mm or less. However, if the diameter becomes too small, the durability of the roll becomes weak, and a sufficient force cannot be applied. Therefore, it is preferable to use a roll of 30 mm or more, and more preferably a roll of 70 mm or more.

  Moreover, although there exists a tendency for an adhesive layer or an adhesion layer to become thick, so that the conveyance speed at the time of bonding is quick, it is not restrict | limited in particular, It is preferable to adjust normally about 2 m / min-50 m / min.

  Further, the lamination pressure applied to the adhesive layer or the pressure-sensitive adhesive layer at the time of bonding is not particularly limited and is appropriately set. The lamination pressure is preferably about 0.2 to 1 MPa, more preferably about 0.2 to 0.6 MPa, from the viewpoint of easy adjustment and productivity of the polarizing plate. Laminate pressure is measured using a pressure-sensitive paper “Prescale (Ultra Low Pressure: LLLW)” manufactured by Fuji Photo Film Co., Ltd., and the color change of the pressure-sensitive paper is binarized by computer image processing. It is obtained from the approximate expression of the produced pressure standard line.

  In addition, a dry laminating method in which an adhesive or a pressure-sensitive adhesive can be bonded in a solvent-free or low-solvent state can be preferably used for bonding. As this dry laminating method, a conventionally known dry laminating adhesive and a laminating method may be used, but by using this method in addition to the present invention, there is an effect of further reducing streaky unevenness. I know I can get it.

  Examples of the dry laminating adhesive include a two-component curable adhesive, a two-component solvent-type adhesive, and a one-component solventless adhesive. Two-component curable adhesives are acrylic, and two-component solvent-based adhesives are polyester, aromatic polyester, aliphatic polyester, polyester / polyurethane, polyether / polyurethane, one-component solventless adhesive. As the agent (moisture curable type), a polyether / polyurethane resin or the like can be used.

  The moisture content of the polarizing film when the polarizing film and the protective film are bonded is not particularly limited, but if it is too low, streaky unevenness tends to occur when the polarizing plate is used, and conversely the moisture content is high. If it is too high, it becomes difficult to control in terms of durability, adhesive strength, and thickness of the adhesive layer or the pressure-sensitive adhesive layer. Therefore, the moisture content of the polarizing film when the protective film is bonded to the polarizing film in the present invention is preferably 15 to 26% by weight, more preferably 19 to 25% by weight, and further 22 to 22%. It is especially preferable to set it as 25 weight%. The moisture content of such a polarizing film can generally be adjusted by the conditions of the drying process during the manufacturing process of the polarizing film, but if necessary, a separate humidity conditioning process is provided, soaking in a water bath, spraying water droplets, or again Heat drying or reduced pressure drying may be performed. Although it depends on the conditions of the drying treatment, a PVA polarizing film produced by a wet method usually has a moisture content of about 26 to 33% by weight in a state where it is not adjusted. The moisture content can be obtained by heating and drying for about 60 to 180 seconds.

  As the polarizing film, a polymer film such as a polyvinyl alcohol (PVA) film that is dyed with a dichroic substance such as iodine or a dichroic dye and uniaxially stretched is usually used. The thickness of such a polarizing film is not particularly limited, but is about 5 to 80 μm. As the thickness of the polarizing film is thinner, streaky unevenness tends to be visible, so that the polarizing film is preferably used when the thickness of the polarizing film is 40 μm or less. In particular, when the thickness of the polarizing film is 25 μm or less, the effect of the present invention becomes remarkable.

  As optical properties of the polarizing film, the single transmittance when measured with the polarizing film alone is preferably 43% or more, and more preferably in the range of 43.3 to 45.0%. Moreover, it is preferable that the orthogonal transmittance measured by superposing two polarizing films so that the absorption axes of the two polarizing films are 90 ° with each other is smaller, and practically 0.00% The content is preferably 0.050% or less and more preferably 0.030% or less. The degree of polarization is preferably 99.90% or more and 100% or less for practical use, and particularly preferably 99.93% or more and 100% or less. Even when measured as a polarizing plate, it is preferable to obtain optical characteristics substantially equivalent to this.

  As a polymer film which forms a polarizing film, various things can be used without being specifically limited. For example, PVA dehydration is applied to hydrophilic polymer films such as polyvinyl alcohol (PVA) film, polyethylene terephthalate (PET) film, ethylene / vinyl acetate copolymer film, partially saponified film, and cellulose film. Examples thereof include polyene-based oriented films such as treated products and polyvinyl chloride dehydrochlorinated products. Among these, since it is excellent in the dyeability by dichroic substances, such as an iodine, it is preferable to use a PVA-type film.

  The degree of polymerization of the polymer film material is generally 500 to 10,000, preferably in the range of 100 to 6000, and more preferably in the range of 1400 to 4000. Furthermore, in the case of a saponified film, the saponification degree is preferably 75 mol% or more, more preferably 98 mol% or more, for example, from the viewpoint of solubility in water, and 98.3 to 99.8 mol. % Is more preferable.

  When a PVA-based film is used as the polymer film, the PVA-based film can be formed by any method such as a casting method in which a stock solution dissolved in water or an organic solvent is cast, a casting method, an extrusion method, or the like. Can be used as appropriate. The phase difference value at this time is preferably 5 nm to 100 nm. In order to obtain a polarizing film having a uniform in-plane, it is preferable that the in-plane retardation variation in the PVA-based film is as small as possible, and the in-plane retardation variation in the PVA-based film is 10 nm or less at a measurement wavelength of 1000 nm. Preferably, it is 5 nm or less.

  Although the manufacturing method of the said polarizing film is not limited to this, Generally, it can divide roughly into a dry-type stretching method and a wet-stretching method. As a manufacturing process of a polarizing film by a wet stretching method, an appropriate method can be used depending on the conditions. For example, the polymer film includes swelling, dyeing, crosslinking, stretching, washing with water, and a drying treatment process. A method of manufacturing by a series of manufacturing steps is common. In each of these treatment steps except the drying treatment step, each treatment is performed while being immersed in a bath made of various solutions. The order, number of times, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing and drying in each treatment step are not particularly limited, and several treatments are performed simultaneously in one treatment step. It is not necessary to perform some processes. For example, the stretching process may be performed after the dyeing process, or may be performed simultaneously with the swelling or the dyeing process, or may be performed after the stretching process. Furthermore, it is also preferable to perform the crosslinking treatment before and after the stretching treatment. Moreover, as an extending | stretching process, although an appropriate method can be used without being limited, For example, in the case of roll extending | stretching, the method of extending | stretching by the peripheral speed difference of the roll between rolls is used. Furthermore, additives such as boric acid, borax or potassium iodide may be added to each treatment as appropriate. Therefore, the polarizing film may contain boric acid, zinc sulfate, zinc chloride, potassium iodide and the like as necessary. Furthermore, in some of these processes, the film may be stretched in the flow direction or the width direction as appropriate, and a water washing process may be performed for each process.

  As the swelling treatment step, for example, the polymer film is immersed in a treatment bath (swelling bath) filled with water. As a result, the polymer film is washed with water, and the surface of the polymer film can be cleaned of stains and anti-blocking agents, and the effect of preventing unevenness such as uneven dyeing can be expected by swelling the polymer film. In this swelling bath, glycerin, potassium iodide or the like may be appropriately added, and the concentration to be added is preferably 5% by weight or less for glycerin and 10% by weight or less for potassium iodide. The temperature of the swelling bath is about 20 to 45 ° C., and the immersion time in the swelling bath is about 2 to 180 seconds. Further, the polymer film may be stretched in this swelling bath, and the stretching ratio at that time is about 1.1 to 3.5 times.

  Examples of the dyeing process include a method of dyeing the polymer film by immersing the polymer film in a treatment bath (dye bath) containing a dichroic substance such as iodine. A conventionally known substance can be used as the dichroic substance, and examples thereof include iodine and organic dyes. Organic dyes include, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First orange S, first black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination. Among them, in the present invention, iodine is preferably used because it is excellent in optical characteristics such as the degree of polarization and the effect of reducing streaky unevenness according to the present invention can be easily obtained.

  As the dye bath solution, a solution in which the dichroic substance is dissolved in a solvent can be used. As the solvent, water such as pure water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic substance is about 0.010 to 10% by weight. The immersion time of the polymer film in this dyeing bath is not particularly limited, but is about 0.5 to 20 minutes, and the temperature of the dyeing bath is about 5 to 42 ° C. The polymer film may be stretched in this dyeing bath, and the cumulative draw ratio integrated with the draw ratio in the previous treatment step is about 1.1 to 3.5 times.

  Further, when iodine is used as the dichroic substance, it is preferable to further add an iodide to the dyeing bath because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. The addition ratio of these iodides should just be about 0.010-10 weight% in the said dyeing | staining bath. Especially, it is preferable to add potassium iodide, and it is preferable that the ratio (weight ratio) of iodine and potassium iodide exists in the range of 1: 5 to 1: 100. Furthermore, for the purpose of improving the in-plane uniformity of the film, a crosslinking agent such as a boron compound may be added as appropriate.

  In addition to the method of immersing in a dyeing bath as described above, the dyeing treatment may be, for example, a method of applying or spraying an aqueous solution containing a dichroic substance to the polymer film, and forming the polymer film Sometimes, a method of mixing a dichroic substance in advance may be used.

  In the crosslinking treatment step, for example, the polymer film is immersed in a treatment bath (crosslinking bath) containing a crosslinking agent. A conventionally known substance can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination. When two or more types are used in combination, for example, a combination of boric acid and borax is preferable, and the addition ratio (molar ratio) is about 4: 6 to 9: 1. As a solvent for the crosslinking bath, water such as pure water is generally used, but an organic solvent compatible with water may be included. The concentration of the crosslinking agent in the crosslinking bath is about 1 to 10% by weight.

  In the crosslinking bath, iodide may be added from the point that uniform characteristics in the plane of the polarizing film can be obtained. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples thereof include titanium, and the content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Among these, a combination of boric acid and potassium iodide is preferable, and the ratio (weight ratio) of boric acid and potassium iodide is preferably in the range of 1: 0.1 to 1: 3.5, and 1: 0 More preferably, it is in the range of 5 to 1: 2.5. The temperature of the crosslinking bath is usually 20 to 70 ° C., and the immersion time is usually about 1 second to 15 minutes. Further, as in the dyeing process, the crosslinking process may use a method of applying or spraying a solution containing a crosslinking agent, or a stretching process may be performed simultaneously with the crosslinking process. The cumulative draw ratio at this time is about 1.1 to 3.5 times.

  As the stretching treatment step, in the case of the wet stretching method, stretching is performed so that the cumulative stretching ratio is about 2 to 7 times in a state of being immersed in a treatment bath (stretching bath). As the solution for the stretching bath, a solution obtained by adding various metal salts and iodine, boron or zinc compounds in a solvent such as water, ethanol or various organic solvents is preferably used. Especially, it is preferable to use the solution which added about 2-18 weight% of boric acid and / or potassium iodide, respectively. When boric acid and potassium iodide are used simultaneously, the content ratio (weight ratio) is preferably about 1: 0.1 to 1: 4. The temperature of this stretching bath is preferably about 40 to 67 ° C.

  In the water washing treatment step, for example, by immersing the polymer film in a treatment bath (water washing bath), unnecessary residues such as boric acid attached in the previous treatment can be washed away. Iodide may be added to the aqueous solution. For example, sodium iodide or potassium iodide is preferably used. The temperature of the washing bath is about 10 to 60 ° C. The number of times of the water washing treatment is not particularly limited and may be carried out a plurality of times, and it is preferable to appropriately adjust the type and concentration of the additive in each water washing bath.

  In addition, when pulling up the polymer film from each treatment bath, in order to prevent the occurrence of dripping, a conventionally known liquid break roll such as a pinch roll may be used, or the liquid is scraped off with an air knife, etc. Excess water may be removed by this method.

  As the drying treatment step, a conventionally known drying method such as natural drying, blow drying, or heat drying can be used. For example, in heat drying, the heating temperature is about 20 to 80 ° C., and the drying time is about 1 to 10 minutes. Moreover, it can extend | stretch suitably also in this drying process process.

  Furthermore, the final draw ratio (total draw ratio) of the polarizing film obtained by the treatment step is preferably 3.0 to 7.0 times. If the total draw ratio is less than 3.0 times, it is difficult to obtain a polarizing film having a high degree of polarization, and if it exceeds 7.0 times, the film tends to break.

  Moreover, the manufacturing method of a polarizing film is not limited to the said manufacturing method, You may manufacture a polarizing film using another manufacturing method. For example, a dichroic substance may be kneaded into a polymer film such as a dry stretching method or polyethylene terephthalate (PET), formed into a film, and stretched, or uniaxially oriented liquid crystal is used as a host. O type using a chromatic dye as a guest (US Pat. No. 5,523,863, JP-T-3-503322), E type using dichroic lyotropic liquid crystal (US) Patent No. 6,049,428).

As the protective film, in order to protect the polarizing film, a film excellent in transparency, mechanical strength, thermal stability, isotropy and the like is preferable. The thickness of the protective film is generally about 1 to 300 μm, and more preferably about 5 to 100 μm. In particular, the unevenness on the streaks in the problem of the present invention becomes more visible when a relatively thin protective film is used, and therefore the thickness of the protective film is preferably about 5 to 60 μm. The effect of the present invention on the polarizing plate is remarkable. Moreover, it is preferable to saponify the protective film surface with an alkali etc. from points, such as a polarization characteristic, durability, and an adhesive characteristic improvement. The moisture permeability of such a protective film is about 0.5 to 5000 g / m ² · 24 h according to the measurement according to JIS Z0208 (cup method) at a temperature of 40 ° C. and a relative humidity of 90%.

  Examples of the material for forming the protective film include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile and styrene. Examples thereof include styrene polymers such as polymers (AS resins) and polycarbonate polymers. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the protective film. The protective film can also be formed as a cured layer of an acrylic, urethane, acrylic urethane, epoxy, silicone, or other thermosetting or ultraviolet curable resin. Among these, a cellulose polymer and a polyolefin polymer film having a cyclo or norbornene structure are preferable, and the effect of the present invention is particularly remarkable when a protective film made of triacetyl cellulose is used.

  When this protective film is bonded to both sides of the polarizing film, those having different characteristics may be used on each side. Examples of the characteristics include thickness, material, light transmittance, tensile elastic modulus, presence / absence of an optical functional layer, and the like.

  The polarizing plate can be used as an optical film in which at least one optical functional layer is further laminated. Examples of the optical functional layer include a hard coat treatment layer, an antireflection treatment layer, a sticking prevention treatment layer, a surface treatment layer such as a diffusion layer or an antiglare treatment layer, and an alignment liquid crystal for the purpose of viewing angle compensation or optical compensation. Layer. Furthermore, image display devices such as polarization conversion elements, reflectors, transflective plates, retardation plates (including wavelength plates (λ plates) such as 1/2 and 1/4), viewing angle compensation films, brightness enhancement films, etc. There may be mentioned one in which one or two or more optical films used for forming are laminated. In particular, the polarizing plate is a reflective polarizing plate or a semi-transmissive polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is laminated, an elliptical polarizing plate or a circular polarizing plate in which a retardation plate is laminated, a viewing angle compensation layer, or a viewing angle. A wide viewing angle polarizing plate in which a compensation film is laminated or a polarizing plate in which a brightness enhancement film is laminated is preferably used.

  In the case of laminating the optical functional layer, generally, the surface treatment layer and the alignment liquid crystal layer may be directly laminated on a film such as a polarizing plate, but the optical functional layer composed of various films is the adhesive layer or the adhesive layer. A method of laminating through layers is preferably used. As the adhesive layer or the adhesive layer at this time, an adhesive layer made of an adhesive is particularly preferably used.

  The pressure-sensitive adhesive layer made of a pressure-sensitive adhesive can be formed of a suitable pressure-sensitive adhesive according to the prior art such as acrylic, silicone-based, polyester-based, polyurethane-based, polyether-based, or rubber-based. This adhesive has the following features: prevention of foaming and peeling phenomenon due to moisture absorption, deterioration of optical properties due to thermal expansion differences, prevention of warping of liquid crystal cells, and formation of a high-quality and durable image display device. It is preferable that the pressure-sensitive adhesive layer has a low moisture absorption rate and excellent heat resistance, and further, it does not require a high-temperature process for curing and drying from the viewpoint of preventing changes in optical properties such as polarizing plates. Those that do not require a long curing process or drying time are preferred. From such a viewpoint, an acrylic pressure-sensitive adhesive is preferably used for the polarizing plate and the optical film. Further, fine particles may be added to the pressure-sensitive adhesive to form a pressure-sensitive adhesive layer that exhibits light diffusibility.

  This adhesive layer or pressure-sensitive adhesive layer may be provided on a necessary surface as necessary. For example, when referring to a polarizing plate comprising a polarizing film and a protective film as in the present invention, if necessary, one side of the polarizing plate Or what is necessary is just to provide an adhesive layer or an adhesion layer in both surfaces, ie, the surface on the opposite side sticking with a polarizing film in a protective film. Thus, the thickness after drying of the adhesive layer or the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive when used for laminating the optical functional layer is not particularly limited, but is generally about 1 to 500 μm, 200 μm is preferable, and 10 to 100 μm is more preferable. By setting the thickness of the adhesive layer or the pressure-sensitive adhesive layer within this range, the stress accompanying the dimensional behavior of the polarizing plate and the optical functional layer can be relaxed.

  When the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive is exposed on the surface, it is preferable to temporarily cover with a separator for the purpose of preventing contamination until the pressure-sensitive adhesive layer is put to practical use. As the separator, an appropriate film according to the above-described protective film or the like, which is provided with a release coat with an appropriate release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide, if necessary, is used. preferable.

  The hard coat treatment is applied for the purpose of preventing scratches on the polarizing plate surface. For example, a hard film with an excellent UV curable resin such as acrylic or silicone is applied to the surface of the protective film. It can be formed by a method added to the above. 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.

  Anti-glare treatment is applied for the purpose of preventing external 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, a roughening method using a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included for forming the surface fine concavo-convex structure are composed of, for example, silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide and the like having an average particle size of 0.5 to 50 μm, Transparent fine particles such as inorganic fine particles that may have conductivity and organic fine particles composed of a crosslinked or uncrosslinked polymer are used. When the surface fine uneven structure is formed, the amount of the fine particles used is generally about 2 to 70 parts by weight with respect to 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 optical function layers such as the antireflection layer, the antisticking layer, the diffusion layer and the antiglare layer can be provided directly on the polarizing plate, or can be provided as a separate film from the polarizing plate.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer to form a liquid crystal display device that reflects incident light from the viewing side (display side) and displays it. The 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 side of the polarizing plate through a protective film or the like as necessary.

  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. When a liquid crystal display device is used in a relatively bright atmosphere, the incident light from the viewing side (display side) is reflected to display an image. 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.

  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.

  As a retardation plate, a birefringent film formed by uniaxially or biaxially stretching a polymer film, an alignment film obtained by aligning a liquid crystal monomer and then cross-linking and polymerizing, an alignment film of a liquid crystal polymer, an alignment layer of a liquid crystal polymer Known films such as those 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 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. An appropriate material for the purpose of preventing coloring or the like due to a change in the viewing angle based on the phase difference of the liquid crystal cell or expanding the viewing angle for good viewing can be used. In addition, from the viewpoint of achieving a wide viewing angle with good visibility, an optical compensation position in which an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of a tilted alignment layer of a discotic liquid crystal polymer, is supported by a triacetyl cellulose film. A phase difference plate can be preferably used.

  Examples of the polarization conversion element include an anisotropic reflection polarization element and an anisotropic scattering polarization element. For example, the PCF series made by Nitto Denko, the DBEF series made by 3M company, etc. can be mentioned. A reflective grid polarizer can also be preferably used as the anisotropic reflective polarizing element. Examples thereof include Micro Wires manufactured by Maxtek. On the other hand, examples of the anisotropic scattering type polarizing element include DRPF manufactured by 3M.

  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 be incident to obtain transmitted light in a predetermined polarization state, and light other than the predetermined polarization state is reflected without being transmitted. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer provided on the rear side thereof and re-incident on the brightness enhancement film, and a part or all of the light is transmitted as light in a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the improvement film and supplying polarized light that is difficult to absorb to the polarizing film to increase the amount of light that can be used for liquid crystal image display and the like.

  Moreover, the polarizing plate of this invention may consist of what laminated | stacked the polarizing plate and the optical function layer of 2 layers or 3 layers or more like said 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 semi-transmissive polarizing plate and a retardation plate are combined may be used.

  An optical film in which the optical functional 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 the liquid crystal display device and the like can be improved. Appropriate adhering means such as an adhesive layer can be used for lamination. When adhering the polarizing plate and the other optical functional layer, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  In addition, each layer such as the polarizing plate, the optical functional layer, the adhesive, and the pressure-sensitive adhesive layer absorbs ultraviolet rays such as salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex compounds. It may be provided with ultraviolet absorbing ability by an appropriate method such as a method of treating with an agent.

  The polarizing plate according to the present invention can be preferably used for forming an image display device such as a liquid crystal display device (LCD) or an electroluminescence display device (ELD).

  The polarizing plate can be preferably used for forming a liquid crystal display device, for example, a liquid crystal display device such as a reflective type, a semi-transmissive type, or a transmissive / reflective type in which a polarizing plate is arranged on one side or both sides of a liquid crystal cell. Can be used. The liquid crystal cell substrate may be either a plastic substrate or a glass substrate. The liquid crystal cell forming the liquid crystal display device is arbitrary. For example, an appropriate type such as an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twist nematic type or a super twist nematic type, etc. A liquid crystal cell may be used.

  Moreover, when providing a polarizing plate and an optical film in the both sides of a liquid crystal cell, they may be the same and may differ. Furthermore, when forming the liquid crystal display device, for example, appropriate components such as a prism array sheet, a lens array sheet, a light diffusion plate, and a backlight can be arranged in one or more layers at appropriate positions.

  Next, an organic electroluminescence device (organic EL display device) will be described. In general, 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 EL 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, It is also known to have various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative, etc., or a laminate of these hole injection layer, light emitting layer, and electron injection layer. 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 fluorescent 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 expected from this, the current and the emission intensity show strong nonlinearity due to rectification with respect to the applied voltage.

  In the 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 usually a transparent electrode formed of a transparent conductor such as indium tin oxide (ITO) is used. Used as the anode. 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 including an organic EL light emitting device including a transparent electrode on the surface side of an organic light emitting layer that emits light by applying a voltage and a metal electrode on the back surface side of the organic light emitting layer, on the surface side of the transparent electrode While providing a polarizing plate, a phase difference 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 film to π / 4. .

  The present invention will be described more specifically with reference to the following examples and comparative examples. However, the present invention is not limited to these examples and comparative examples.

Example 1
(Preparation of polarizing film)
Using a polyvinyl alcohol (PVA) film having a thickness of 50 μm (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., M-5000), the film was stretched up to 2.5 times while being immersed in 30 ° C. pure water for 60 seconds, Dye for 45 seconds in a 30 ° C. aqueous iodine solution (weight ratio: pure water / iodine (I) / potassium iodide (KI) = 100 / 0.01 / 1) and immerse in a 3% by weight aqueous boric acid solution for 30 seconds. The film was stretched in a 4% by weight boric acid aqueous solution to a stretching ratio of 5.8 times, immersed in a 5% by weight KI aqueous solution for 10 seconds, and then dried at 60 ° C. for 3 minutes while maintaining the film tension. Thus, a polarizing film was obtained. The polarizing film had a thickness of 19 μm and a moisture content of 23.2%.

(Preparation of adhesive)
100 parts by weight of PVA resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd .: Gosenol) and 35 parts by weight of a cross-linking agent (manufactured by Dainippon Ink Chemical Co., Ltd .: Watersol) are dissolved in 3760 parts by weight of pure water to form an adhesive. Was prepared.

(Preparation of polarizing plate)
A triacetyl cellulose (TAC) film (manufactured by Fuji Photo Film Co., Ltd .: UZ-40T) having a thickness of 40 μm was bonded to both surfaces of the obtained polarizing film using the prepared adhesive. For bonding, an iron roll having a diameter of 100 mm is used as the first roll, while a rubber roll (hardness: 65 degrees, thickness: 3.5 mm) around the iron core is used as the second roll. Bonding was performed in a form in which the rubber roll was used for pressure bonding from above and below. At this time, the laminating pressure of the bonded portion was 0.38 MPa. The conveyance speed was 5.8 m / min. Then, it dried at 60 degreeC for 3 minute (s), and was set as the polarizing plate. The thickness of the adhesive layer after drying the polarizing plate was 22 nm.

Example 2
In Example 1 (Preparation of polarizing film), a 75 μm thick PVA film (manufactured by Kuraray Co., Ltd., polymerization degree 2400) was used. A polarizing film having a thickness of 27 μm and a moisture content after drying of 24.8% was obtained. A TAC film with a thickness of 80 μm (manufactured by Fuji Photo Film Co., Ltd .: UZ-80T) was bonded to both surfaces of this polarizing film in the same manner as in Example 1 to produce a polarizing plate. The thickness of the adhesive layer after drying the polarizing plate was 31 nm.

Example 3
In the drying of Example 1 (preparation of polarizing film), a polarizing film having a thickness of 19 μm and a moisture content of 26.7% after drying by drying at 25 ° C. for 1.5 minutes while maintaining the tension of the film. Got. A TAC film similar to that in Example 1 was bonded to both surfaces of this polarizing film, and a polarizing plate was produced in the same manner as in Example 1. In this case, the first roll uses an iron roll having a diameter of 200 mm, and the second roll has a diameter of 200 mm with a rubber layer (hardness 80 degrees, thickness 7 mm) around the iron core. The rubber roll was used. At this time, the laminating pressure of the bonded portion was 0.42 MPa. The conveyance speed was 5.8 m / min. The thickness of the adhesive layer after drying the polarizing plate was 49 mm.

Example 4
In Example 1 (Preparation of polarizing film), a PVA film with a thickness of 75 μm (manufactured by Kuraray Co., Ltd., polymerization degree 2400) was prepared, and dried at 60 ° C. for 5 minutes, whereby the thickness was 27 μm, A polarizing film having a moisture content of 19.8% after drying was obtained. A TAC film similar to that in Example 1 was bonded to both surfaces of this polarizing film in the same manner as in Example 1 to produce a polarizing plate. For the bonding at this time, an iron roll having a diameter of 200 mm was used as the first roll, while a 200 mm diameter having a rubber layer (hardness 65 degrees, thickness 7 mm) around the iron core as the second roll. The rubber roll was used. At this time, the laminating pressure of the bonded portion was 0.26 MPa. The conveyance speed was 5.8 m / min. The thickness of the adhesive layer after drying the optical plate was 49 nm.

Example 5
In the drying of Example 1 (preparation of polarizing film), a polarizing film having a thickness of 19 μm and a moisture content of 14.6% after drying was obtained by drying while blowing air at 80 ° C. for 4.5 minutes. . A TAC film similar to that in Example 1 was bonded to both surfaces of this polarizing film in the same manner as in Example 1 to produce a polarizing plate. For the bonding at this time, an iron roll having a diameter of 200 mm was used as the first roll, while a 200 mm diameter having a rubber layer (hardness 65 degrees, thickness 7 mm) around the iron core as the second roll. The rubber roll was used. At this time, the laminating pressure of the bonded portion was 0.26 MPa. The conveyance speed was 5.8 m / min. The thickness of the adhesive layer after drying the polarizing plate was 51 nm.

Comparative Example 1
In the drying of Example 1 (preparation of polarizing film), a polarizing film having a thickness of 19 μm and a moisture content of 26.9% after drying was obtained by drying at 25 ° C. for 1 minute while maintaining the tension of the film. It was. A TAC film similar to that in Example 1 was bonded to both surfaces of this polarizing film in the same manner as in Example 1 to produce a polarizing plate. For the bonding at this time, a rubber roll having a diameter of 200 mm having a rubber layer (hardness 80 degrees, thickness 7 mm) around the iron core was used for both the first roll and the second roll. At this time, the laminating pressure of the bonded portion was 0.28 MPa. The conveyance speed was 5.8 m / min. The thickness of the adhesive layer after drying the polarizing plate was 54 nm.

Comparative Example 2
In the drying of Example 1 (preparation of polarizing film), a polarizing film having a thickness of 19 μm and a moisture content of 28.3% after drying by drying at 25 ° C. for 1.5 minutes while maintaining the tension of the film. Got. A TAC film similar to that in Example 1 was bonded to both surfaces of this polarizing film in the same manner as in Example 1 to produce a polarizing plate. For the bonding at this time, an iron roll having a diameter of 200 mm was used as the first roll, while a 200 mm diameter having a rubber layer (hardness 65 degrees, thickness 7 mm) around the rubber core as the second roll. The rubber roll was used. At this time, the laminating pressure of the bonded portion was 0.26 MPa. The conveyance speed was 8.7 m / min. The thickness of the adhesive layer after drying the polarizing plate was 78 nm.

  About the polarizing plate produced by the Example and the comparative example, it evaluated by the following method.

(Adhesive layer thickness measurement method)
It measured from the cross-sectional photograph obtained by FE-TEM (Field Emission Transmission Electron Microscope) measurement.

(Method for measuring moisture content of polarizing film)
A sample of 180 mm × 500 mm was cut out from the obtained polarizing film, and its initial weight (W (g)) was measured. The sample was left in a drier at 120 ° C. for 2 hours, and then the weight after drying (D (g)) was measured. From these measured values, the moisture content was determined by the following formula.
Moisture content (%) = {(WD) / W} × 100

(Appearance evaluation method of polarizing plate)
A 50 mm × 60 mm sample was cut out from the obtained polarizing plate and fixed in a flat state. A black paper with a larger area than the sample was laid under the sample. Under the fluorescent lamp, the reflected light was reflected on the surface of the sample. The reflected light from the fluorescent lamp on the sample surface was visually evaluated from a state almost horizontal to the sample surface. The contents of evaluation are as follows.
○: Even fine streaky unevenness on the surface of the polarizing plate cannot be visually recognized.
Δ: Minute streaky unevenness on the polarizing plate surface can be visually recognized.
X: Clear stripe-like unevenness on the polarizing plate surface can be visually recognized.

(Magnitude of change in surface roughness of the polarizing plate (tilt))
About the stripe-shaped unevenness | corrugation nonuniformity of the surface of a polarizing plate, the data of uneven | corrugated distribution were measured using the contact-type surface roughness meter (The product made by Tenor-Instruments; P-11). Measurement conditions are stylus pressure: 8 mg, scanning speed: 0.4 mm / second, frequency: 50 Hz, scanning length: 30 mm, Cut-Off: 0.28-1.4 mm. The unevenness distribution data was Fourier-analyzed to obtain the period and amplitude matching the unevenness, and the magnitude (inclination) of the unevenness change was calculated from the result. It is recognized that as the magnitude of the unevenness change (inclination) is smaller, the stripe-shaped unevenness unevenness is smaller.

  About the said Example and a comparative example, manufacturing conditions (1st roll, 2nd roll, laminating pressure), the thickness and moisture content of the polarizing film at the time of sticking a protective film, the thickness of the contact bonding layer after polarizing plate drying, and Table 1 summarizes the results of the evaluation of the appearance of the polarizing plate (streaky unevenness unevenness) and the evaluation of the magnitude of the unevenness change (tilt).

  As is clear from the results in Table 1 above, when the thickness of the adhesive layer is 52 nm or less, it becomes difficult to confirm streaky unevenness in the plane of the polarizing plate. It becomes easier to see. In addition, the polarizing film with a moisture content in the range of 15 to 26% by weight when the protective film is bonded has particularly excellent in-plane uniformity evaluated by the unevenness of the streaky pattern visually. I understand.

Claims (15)

  A polarizing plate, wherein a protective film is bonded to one side or both sides of a polarizing film via an adhesive layer or an adhesive layer, and the thickness of the adhesive layer or the adhesive layer is 52 nm or less.   The polarizing plate according to claim 1, wherein the polarizing film has a moisture content of 15 to 26% by weight when a protective film is bonded to one or both sides of the polarizing film via an adhesive layer or an adhesive layer.   The polarizing plate according to claim 1 or 2, wherein the polarizing film has a thickness of 5 to 40 µm.   In the method for producing a polarizing plate, in which a protective film is bonded to one side or both sides of a polarizing film using an adhesive or an adhesive, and then dried by heating, the thickness of the adhesive layer or the adhesive layer after drying is 52 nm or less. A method for producing a polarizing plate, comprising laminating an adhesive or a pressure-sensitive adhesive as described above.   When the protective film is bonded to one side or both sides of the polarizing film using an adhesive or a pressure-sensitive adhesive, the polarizing film is adjusted and bonded so that the moisture content is 15 to 26% by weight. Item 5. A method for producing a polarizing plate according to Item 4.   The method for producing a polarizing plate according to claim 4 or 5, wherein the polarizing film has a thickness of 5 to 40 µm.   The adhesive or pressure-sensitive adhesive is applied between the polarizing film and the protective film, and these are pressure-bonded by passing between a pair of rolls of a first roll and a second roll. The manufacturing method of the polarizing plate in any one.   The method for producing a polarizing plate according to claim 7, wherein the first roll is a metal roll, and the second roll is an elastic roll in which a metal core is coated with a rubber layer or a resin layer. .   The method for producing a polarizing plate according to claim 8, wherein the first roll is an iron roll.   The method for producing a polarizing plate according to claim 8 or 9, wherein the rubber layer or the resin layer of the second roll has a hardness of 60 or more and 90 or less.   The method for producing a polarizing plate according to claim 7, wherein the first roll and the second roll have a roll diameter of 30 mm or more and 250 mm or less.   It is a manufacturing method of the polarizing plate which bonds a protective film to the single side | surface or both surfaces of a polarizing film using an adhesive agent, Comprising: It bonds together using the adhesive agent for dry laminates. The manufacturing method of the polarizing plate of description.   The polarizing plate obtained by the manufacturing method in any one of Claims 4-12.   An optical film obtained by laminating at least one optical functional layer on the polarizing plate according to claim 1, 2 or 13.   The image display apparatus which has a polarizing plate of Claim 1, 2, or 13 or an optical film of Claim 14.