JP2019066717A - Polarizing plate, image display device, and method for manufacturing polarizing plate - Google Patents

Abstract

To provide a method for manufacturing a polarizing plate that has high adhesion with another optical member and can improve the display characteristics of an image display device.SOLUTION: A method for manufacturing a polarizing plate of the present invention is a method for manufacturing a polarizing plate having a polyester resin base material, and a polarizer laminated on one side of the polyester resin base material and having a thickness of 10 μm or less. The method includes: dyeing and drawing a laminate having a polyvinyl alcohol resin layer formed on one side of the polyester resin base material to obtain a polarizer; and performing heat treatment on the laminate of the polyester resin base material and polarizer. The drawing includes underwater drawing treatment having a draw ratio of 2.55 times or more, and the maximum heating temperature in the heat treatment is 100°C or higher.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate, an image display device, and a method of manufacturing the polarizing plate.

  There has been proposed a method of obtaining a thin polarizer by forming a polyvinyl alcohol-based resin layer on a polyester-based resin base material, and stretching and dyeing this laminate (for example, Patent Document 1). A method of manufacturing such a polarizer is noted, for example, as it can contribute to thinning of the image display device.

  The said polarizer can be used in the state laminated | stacked on the said polyester-based resin base material, and, in this case, a polyester-based resin base material is used as a protective layer of a polarizer (patent document 2). As a result, a laminate of a polyester-based resin substrate and a polarizer can be used as a polarizing plate without laminating a protective film to a polarizer, which can contribute to, for example, cost reduction of an image display device.

JP 2000-338329 A Patent No. 4797833 gazette

  However, the polarizing plate as described above has a problem that adhesion with other optical members is insufficient, and further, when it is used in an image display device, display characteristics are insufficient.

  The present invention has been made to solve the above-mentioned conventional problems, and the main object thereof is a polarizing plate which has high adhesion to other optical members and can improve the display characteristics of the image display device, It is an object of the present invention to provide a method of manufacturing such a polarizing plate and an image display device provided with such a polarizing plate.

The method for producing a polarizing plate of the present invention is a method for producing a polarizing plate having a polyester resin substrate and a polarizer having a thickness of 10 μm or less laminated on one side of the polyester resin substrate, The polyvinyl alcohol-based resin layer is used as a polarizer by dyeing and stretching a laminate having a polyvinyl alcohol-based resin layer formed on one side of the resin substrate, and the polyester-based resin substrate and the polarizer Heat treatment of the layered product of the above, and the above-mentioned stretching includes in-water stretching treatment having a draw ratio of 2.55 or more, and the maximum heating temperature in the above-mentioned heat treatment is 100 ° C. or more.
In one embodiment, the maximum heating temperature in the heat treatment is 115 ° C. or less.
According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate has a polyester-based resin base and a polarizer laminated on one side of the polyester-based resin base, the thickness of the polarizer is 10 μm or less, and the haze value is less than 1.6%. When the surface on the polarizer side is bonded to the glass via an adhesive and stored at 60 ° C./90% Rh for 500 hours, no peeling occurs from the glass.
According to another aspect of the present invention, an image display device is provided. This image display apparatus has the above-mentioned polarizing plate.

  According to the present invention, there is provided a polarizing plate having high adhesion to other optical members and capable of improving the display characteristics of the image display device, a method of manufacturing such a polarizing plate, and such a polarizing plate. An image display apparatus can be provided.

It is a schematic sectional drawing of the polarizing plate which concerns on one Embodiment of this invention. It is a schematic sectional drawing of the laminated body of the polyester-type resin base material and PVA-type resin layer which are used by the manufacturing method of the polarizing plate by one Embodiment of this invention. It is the schematic which shows the manufacturing process of the polarizing plate which concerns on one embodiment.

  Hereinafter, although the embodiment of the present invention is described, the present invention is not limited to these embodiments.

A. Method of Manufacturing Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate obtained by the method of manufacturing a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 has a polyester resin base 20 and a polarizer 10 laminated on one side of the polyester resin base 20. The thickness of the polarizer 10 is 10 μm or less.

  The manufacturing method of the polarizing plate 100 is a PVA system by dyeing | staining and extending | stretching the laminated body 200 (FIG. 2) in which the polyvinyl alcohol-type resin layer (PVA-type resin layer) 11 was formed in one side of the polyester-type resin base material 20. The method includes forming the resin layer 11 as the polarizer 10 and heating the laminate of the polyester resin base material 20 and the polarizer 10. The stretching includes a stretching treatment in water in which the stretching ratio is 2.55 times or more, and the maximum heating temperature in the heat treatment is 100 ° C. or more. The maximum heating temperature in the above heat treatment is preferably 115 ° C. or less. According to the above manufacturing method, it is possible to obtain a polarizing plate in which the adhesion to another optical member and the display characteristics of the image display device are compatible. A conventional manufacturing method, that is, a polarizing plate obtained by stretching and dyeing a laminate of a polyester-based resin substrate and a PVA-based resin layer, has sufficient adhesion to other optical members and an image display device. In some cases, it has been impossible to simultaneously achieve good display characteristics. Specifically, in the polarizing plate obtained by the conventional manufacturing method as described above, when the surface on the polarizer side is bonded to another optical member and placed in a high temperature and high humidity environment, the polarizing plate in the stretching direction Peeling from the optical member may occur at both ends or glare may occur on the display screen when used in an image display device. According to the new finding according to the present invention, the above-mentioned production method can control the crystallinity and the crystal size of the polyester resin base material of the polarizing plate within an appropriate range, whereby other optical members and It has been found that the adhesiveness of the above and the display characteristics (antiglare property) of the image display device can be compatible.

  FIG. 3: is schematic which shows the manufacturing process of the polarizing plate which concerns on one Embodiment. Typically, in the manufacturing process of the polarizing plate according to the present embodiment, the laminate 200 of the polyester-based resin base material 20 and the PVA-based resin layer 11 is fed out from the feeding portion 101, and boric acid aqueous solution is obtained by the rolls 111 and 112. After immersion in bath 110 (insolubilization treatment), it is immersed in a bath 120 of an aqueous solution of a dichroic substance (iodine) and potassium iodide by rolls 121 and 122 (staining treatment). Then, it is immersed in a bath 130 of an aqueous solution of boric acid and potassium iodide by rolls 131 and 132 (crosslinking treatment). Next, while immersing the laminate 200 in the boric acid aqueous solution stretching bath 140, tension is applied in the longitudinal direction (longitudinal direction, transport direction, MD direction) by the rolls 141 and 142 having different speed ratios to stretch ( Underwater stretching process). Next, the laminate 200 stretched in water is immersed in a potassium iodide aqueous solution bath 150 by means of rolls 151 and 152 (washing treatment) and subjected to drying treatment (not shown). Next, the laminate 200 is placed in an oven 160 (heat treatment) to obtain the polarizing plate 100 of the present embodiment. Thereafter, the obtained polarizing plate 100 is wound by a winding unit 170. Although illustration is omitted, the in-air stretching process may be performed before the laminate 200 is subjected to the insolubilizing process. In addition, the manufacturing process shown in FIG. 3 is an example, and the frequency | count of said process, order, etc. are not specifically limited.

A-1. Laminated Body of Polyester-Based Resin Base Material and PVA-Based Resin Layer A laminated body of a polyester-based resin base material and a PVA-based resin layer may be produced by any appropriate method. Preferably, by applying a coating solution containing a PVA-based resin on a polyester-based resin substrate and drying, a laminate having a PVA-based resin layer formed on one side of the polyester-based resin substrate can be obtained. In one embodiment, the composition for easily adhesive layer formation is coated on a polyester resin substrate and dried to form an easily adhesive layer, and a PVA resin layer is formed on the easily adhesive layer. .

  As a forming material of a polyester-based resin base material, for example, alicyclic dicarboxylic acid or alicyclic ring containing polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), isophthalic acid, cyclohexane ring and the like Copolymerized PET (PET-G) containing a diol or the like of the formula, other polyesters, copolymers and blends thereof, and the like can be used. Among them, amorphous (non-crystallized) PET or copolymerized PET is preferably used. These resins are amorphous in the unstretched state and have excellent stretchability suitable for high magnification stretch, and can impart heat resistance and dimensional stability by being crystallized by stretching and heating. Furthermore, the heat resistance of the extent which can apply | coat and dry PVA-type resin in the unstretched state is securable.

  The glass transition temperature (Tg) of the polyester resin substrate is preferably 170 ° C. or less. By using such a polyester-based resin substrate, stretchability can be sufficiently secured while suppressing crystallization of the PVA-based resin layer. It is more preferable that the temperature is 120 ° C. or less in consideration of good plasticization of the polyester resin base material by water and stretching in water. In one embodiment, the glass transition temperature of the polyester resin substrate is preferably 60 ° C. or higher. By using such a polyester-based resin substrate, the polyester-based resin substrate is deformed (for example, generation of unevenness, sagging, wrinkles, etc.) when applying and drying a coating solution containing a PVA-based resin described later. Etc. can be prevented. In addition, stretching of the laminate can be performed at a suitable temperature (for example, about 60 ° C. to 70 ° C.). In another embodiment, a glass transition temperature lower than 60 ° C. may be applied if the polyester-based resin substrate is not deformed when applying and drying a coating solution containing a PVA-based resin. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

  In one embodiment, the polyester resin base material preferably has a water absorption of 0.2% or more, more preferably 0.3% or more. Such polyester resin base material absorbs water, and the water acts as a plasticizer and can be plasticized. As a result, the stretching stress can be significantly reduced in the in-water stretching, and the stretchability can be excellent. On the other hand, the water absorption rate of the polyester resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a polyester-based resin base material, the dimensional stability of the polyester-based resin base material significantly decreases at the time of production, and it is possible to prevent such a problem that the appearance of the obtained laminate is deteriorated. In addition, it is possible to prevent breakage during stretching in water or peeling of the PVA-based resin layer from the polyester-based resin substrate. In addition, a water absorption is a value calculated | required according to JISK7209.

  The thickness of the polyester resin substrate (the thickness before stretching described later) is preferably 20 μm to 300 μm, and more preferably 50 μm to 200 μm. There exists a possibility that formation of a PVA-type resin layer may become difficult as it is less than 20 micrometers. If it exceeds 300 μm, for example, it may take a long time for the polyester resin base material to absorb water during stretching in water, and an excessive load may be required for stretching.

  Arbitrary suitable resin may be adopted as PVA system resin which forms a PVA system resin layer. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined in accordance with JIS K 6726-1994. By using a PVA resin having such a degree of saponification, a polarizer having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

  The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

  The coating liquid containing a PVA-based resin is typically a solution in which the above-mentioned PVA-based resin is dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferred. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film in close contact with the polyester resin substrate. In one embodiment, the coating solution comprises a halide. Any appropriate halide can be adopted as the above-mentioned halide. For example, iodide and sodium chloride can be mentioned. The iodide includes, for example, potassium iodide, sodium iodide and lithium iodide. Among these, preferred is potassium iodide. The amount of halide in the coating solution is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA resin, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA resin It is a department. When the amount of the halide relative to 100 parts by weight of the PVA resin exceeds 20 parts by weight, the halide may bleed out and the finally obtained polarizer may become cloudy. The high-temperature stretching (auxiliary stretching) in air before stretching the laminate of the PVA-based resin layer containing a halide and the polyester-based resin substrate in boric acid water allows the PVA-based resin layer after the auxiliary stretching to be performed. The crystallization of the PVA-based resin can be promoted. As a result, when the PVA-based resin layer is immersed in liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizer finally obtained.

  You may mix | blend an additive with a coating liquid. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As surfactant, a nonionic surfactant is mentioned, for example. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the obtained PVA-based resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. The adhesion between the polyester-based resin base and the PVA-based resin layer can be improved by using the easy-adhesion component. As a result, for example, defects such as peeling of the PVA-based resin layer from the polyester-based resin substrate can be suppressed, and the below-mentioned dyeing and underwater stretching can be favorably performed. For example, a modified PVA such as acetoacetyl-modified PVA is used as the easy adhesion component.

  Any appropriate method can be adopted as a method of applying the coating solution. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (a comma coating method etc.) and the like can be mentioned. The coating / drying temperature of the coating solution is preferably 50 ° C. or more.

  The thickness of the PVA-based resin layer (the thickness before stretching described later) is preferably 3 μm to 20 μm.

  Before forming the PVA-based resin layer, the polyester-based resin substrate may be subjected to surface treatment (for example, corona treatment etc.), or the composition for forming an easy adhesion layer is coated on the polyester-based resin substrate (coating Processing). By performing such treatment, the adhesion between the polyester resin substrate and the PVA resin layer can be improved. As a result, for example, defects such as peeling of the PVA-based resin layer from the polyester-based resin substrate can be suppressed, and the below-described dyeing and stretching can be favorably performed.

  The composition for easily adhesive layer formation preferably contains a polyvinyl alcohol-based component. Any appropriate PVA-based resin may be used as the polyvinyl alcohol-based component. Specifically, polyvinyl alcohol and modified polyvinyl alcohol are mentioned. Examples of the modified polyvinyl alcohol include polyvinyl alcohol modified with an acetoacetyl group, a carboxylic acid group, an acrylic group and / or a urethane group. Among these, acetoacetyl-modified PVA is preferably used. As acetoacetyl-modified PVA, a polymer having at least a repeating unit represented by the following general formula (I) is preferably used.

  In the above formula (I), the ratio of n to l + m + n is preferably 1% to 10%.

  The average degree of polymerization of acetoacetyl-modified PVA is preferably 1000 to 10000, preferably 1200 to 5000. The degree of saponification of the acetoacetyl-modified PVA is preferably 97 mol% or more. The pH of a 4% by weight aqueous solution of acetoacetyl-modified PVA is preferably 3.5 to 5.5.

  The composition for easily adhesive layer formation may further contain a polyolefin-based component, a polyester-based component, a polyacrylic-based component and the like according to the purpose and the like. Preferably, the composition for easy adhesion layer formation further comprises a polyolefin-based component.

  Any appropriate polyolefin-based resin may be used as the polyolefin-based component. As an olefin component which is a main component of polyolefin resin, C2-C6 olefin hydrocarbons, such as ethylene, propylene, isobutylene, 1-butene, 1-pentene, 1-hexene, are mentioned, for example. These can be used alone or in combination of two or more. Among these, olefin hydrocarbons having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene and 1-butene are preferable, and ethylene is more preferably used.

  The proportion of the olefin component in the monomer component constituting the polyolefin resin is preferably 50% by weight to 95% by weight.

  It is preferable that the said polyolefin resin has a carboxyl group and / or its anhydride group. Such a polyolefin resin can be dispersed in water, and an easily adhesive layer can be formed well. As a monomer component which has such a functional group, unsaturated carboxylic acid and its anhydride, the half ester of unsaturated dicarboxylic acid, a half amide are mentioned, for example. Specific examples of these include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid and crotonic acid. The molecular weight of the polyolefin resin is, for example, 5,000 to 8,000.

  In the composition for easily adhesive layer formation, the compounding ratio (the former: the latter (solid content)) of the polyvinyl alcohol-based component and the polyolefin-based component is preferably 5:95 to 60:40, more preferably 20:80 to 50. : 50. If the amount of the polyvinyl alcohol-based component is too large, the adhesion may not be obtained sufficiently. Specifically, the peeling force required for peeling the polarizer from the polyester-based resin base material may be reduced, and sufficient adhesion may not be obtained. On the other hand, when the amount of the polyvinyl alcohol-based component is too small, the appearance of the obtained polarizing plate may be impaired. Specifically, in the formation of the easy adhesion layer, problems such as the coating film becoming cloudy may occur, and it may be difficult to obtain a polarizing plate having an excellent appearance.

  The composition for easily adhesive layer formation is preferably a water system. The easy adhesion layer forming composition may contain an organic solvent. Examples of the organic solvent include ethanol, isopropanol and the like. The solid content concentration of the composition for easily adhesive layer formation is preferably 1.0% by weight to 10% by weight.

  Any appropriate method can be adopted as a method of applying the composition for easily adhesive layer formation. After application of the composition for easy adhesion layer formation, the coating film may be dried. The drying temperature is, for example, 50 ° C. or more.

A-2. In-Air Stretching Process The in-air stretching process includes a hot roll stretching step of stretching by the circumferential speed difference between the hot rolls while conveying the laminate in the longitudinal direction. The air-drawing process typically includes a zone drawing process and a hot roll drawing process. The order of the zone drawing process and the heat roll drawing process is not limited, and the zone drawing process may be performed first, or the heat roll drawing process may be performed first. The zone stretching step may be omitted. In one embodiment, the zone drawing step and the hot roll drawing step are performed in this order.

  The stretching temperature of the laminate can be set to any appropriate value according to the forming material of the polyester resin base material, the stretching method, and the like. The stretching temperature in the aerial stretching process is preferably not less than the glass transition temperature (Tg) of the polyester resin substrate, more preferably the glass transition temperature (Tg) of the polyester resin substrate + 10 ° C. or more, particularly preferably Tg + 15 ° C. It is above. On the other hand, the upper limit of the stretching temperature of the laminate is preferably 170 ° C. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin and to suppress a defect due to the crystallization (for example, to prevent the orientation of the PVA-based resin layer by stretching). it can.

A-3. Insolubilization treatment The above-mentioned insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Water resistance can be imparted to the PVA-based resin layer by performing the insolubilization treatment. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20 ° C to 50 ° C. Preferably, the insolubilization treatment is performed before the above-described in-water stretching and the above-mentioned dyeing treatment.

A-4. Dyeing treatment Dyeing of the PVA-based resin layer is typically performed by adsorbing iodine to the PVA-based resin layer. As the adsorption method, for example, a method of immersing a PVA-based resin layer (laminated body) in a staining solution containing iodine, a method of applying the staining solution to a PVA-based resin layer, the staining solution to a PVA-based resin layer The method of spraying etc. are mentioned. Preferably, it is a method of immersing a PVA-based resin layer (laminated body) in a staining solution. It is because iodine can be adsorbed well.

  The staining solution is preferably an aqueous iodine solution. The compounding amount of iodine is preferably 0.1 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of water. In order to enhance the solubility of iodine in water, it is preferable to add an iodide to an aqueous iodine solution. Specific examples of iodide are as described above. The compounding amount of iodide is preferably 0.02 parts by weight to 20 parts by weight, more preferably 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of water. The liquid temperature at the time of dyeing of the staining liquid is preferably 20 ° C. to 50 ° C. in order to suppress the dissolution of the PVA-based resin. In the case of immersing the PVA-based resin layer in the staining solution, the immersion time is preferably 5 seconds to 5 minutes in order to secure the transmittance of the PVA-based resin layer. The dyeing conditions (concentration, liquid temperature, immersion time) can be set such that the degree of polarization or single transmittance of the finally obtained polarizer falls within a predetermined range. In one embodiment, the immersion time is set so that the degree of polarization of the obtained polarizer is 99.98% or more. In another embodiment, the immersion time is set so that the single transmittance of the obtained polarizer is 40% to 44%.

  The staining process may be performed at any appropriate timing. Preferably, it is carried out before in-water stretching.

A-5. Crosslinking treatment The above crosslinking treatment is typically performed by immersing the PVA-based resin layer (laminate) in a boric acid aqueous solution. Water resistance can be given to a PVA-type resin layer by giving a crosslinking process. The concentration of the boric acid aqueous solution is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Moreover, when performing a crosslinking process after the said dyeing | staining process, it is preferable to mix | blend iodide further. By blending an iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The compounding amount of iodide is preferably 1 part by weight to 5 parts by weight with respect to 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20 ° C to 60 ° C. Preferably, the crosslinking treatment is carried out before the in-water stretching treatment. In a preferred embodiment, the air-drawing process, the dyeing process and the crosslinking process are carried out in this order.

A-6. In-Water Stretching Process As described above, the manufacturing process of the polarizing plate includes stretching the laminate in water in a stretching bath. Specifically, the film is drawn in water in a direction parallel to the air-drawing direction of the laminate. According to in-water stretching, stretching can be performed at a temperature lower than the glass transition temperature (typically, about 80 ° C.) of the above-mentioned polyester resin base material and PVA-based resin layer, and the PVA-based resin layer can be crystallized. While suppressing, it can be stretched to a high magnification. As a result, a polarizer having excellent optical properties (for example, the degree of polarization) can be produced. In the present specification, “parallel direction” includes the case of 0 ° ± 5.0 °, preferably 0 ° ± 3.0 °, more preferably 0 ° ± 1.0 °. .

  As described above, the stretching ratio in the in-water stretching treatment is 2.55 times or more, more preferably 2.65 times or more, and still more preferably 2.75 times or more. On the other hand, the upper limit of the draw ratio is preferably 5.0 times, more preferably 5.5 times. If the draw ratio in water is too high, there is a problem that the polarizer breaks. By setting the draw ratio in the above range and setting the maximum heating temperature in the heat treatment described later in a predetermined range, peeling from the glass under a high temperature and high humidity environment is suppressed, and the haze value is A sufficiently low polarizer may be obtained. Therefore, the polarizing plate which made compatible the adhesiveness with other optical members, and the display characteristic (antiglare property) of an image display may be obtained.

  The stretching temperature in the in-water stretching process is preferably 40 ° C. to 85 ° C., more preferably 50 ° C. to 70 ° C. If it is the above temperature, it can extend | stretch to high magnification, suppressing melt | dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the polyester-based resin base material is preferably 60 ° C. or more in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is less than 40 ° C., there is a possibility that the film can not be stretched well even in consideration of the plasticization of the polyester resin base material by water. On the other hand, the higher the stretching temperature, the higher the solubility of the PVA-based resin layer, which may make it impossible to obtain excellent optical properties. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

  Any appropriate method can be adopted as the drawing method in the underwater drawing process. Specifically, it may be fixed end stretching or free end stretching. The stretching direction of the laminate is substantially the stretching direction (longitudinal direction) of the above-described air-drawing. Stretching of the laminate may be performed in one step or in multiple steps.

  Stretching in water is preferably performed by immersing the laminate in an aqueous solution of boric acid (stretching in boric acid). By using a boric acid aqueous solution as a stretching bath, the PVA resin layer can be provided with rigidity to withstand the tension applied during stretching and water resistance which is not dissolved in water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink it with a PVA resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, the film can be favorably stretched, and a polarizer having excellent optical properties (for example, the degree of polarization) can be produced.

  The aqueous boric acid solution is preferably obtained by dissolving boric acid and / or a borate in water which is a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight with respect to 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizer with higher characteristics can be produced. In addition to boric acid or a borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent can also be used.

  In the case where a dichroic substance (typically, iodine) is adsorbed in advance to the PVA-based resin layer by the dyeing treatment, preferably, an iodide is blended in the above-mentioned stretching bath (boric acid aqueous solution). By blending an iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. 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. Among these, preferred is potassium iodide. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.

  By combining the polyester-based resin base material and stretching in water (stretching in boric acid), it can be stretched at a high magnification, and a polarizer having excellent optical properties (for example, the degree of polarization) can be produced. . Specifically, the maximum draw ratio is preferably 5.0 times or more, more preferably 5.5 times or more, still more preferably 6. times the original length of the laminate (including the in-air draw ratio). 0 times or more. In the present specification, the "maximum stretch ratio" refers to the stretch ratio immediately before the laminate breaks, separately confirms the stretch ratio at which the laminate breaks, and refers to a value 0.2 lower than that value. In addition, the maximum draw ratio of the laminated body using the said polyester-type resin base material may become high rather than extending | stretching by in-air extending | stretching only through in-water extending | stretching.

A-7. Cleaning Treatment Cleaning treatment is typically performed by immersing the PVA-based resin layer in a potassium iodide aqueous solution. The drying temperature in the drying treatment is preferably 30 ° C to 100 ° C.

A-8. Heat treatment The heat treatment is carried out after stretching in water. By the heat treatment, crystallization of the polyester resin substrate can proceed.
The heat treatment is typically performed by heating the transport roll disposed in the heating means 160 (using a so-called heat drum roll (heat roll)) (heat drum roll heating system). In one embodiment, the heating means 160 is an oven, and may use a heating method (oven heating method) by blowing hot air into the oven. By using the heating drum roll heating method and the oven heating method in combination, it is possible to suppress a sharp temperature change between the heating drum rolls, and it is possible to easily control the contraction in the width direction of the laminate. The temperature in the oven oven is preferably 30 ° C to 100 ° C. Moreover, the heating time by oven is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m / s to 30 m / s. In addition, the said wind speed is the wind speed in oven, and it can measure with a mini-vane type digital anemometer.

  By heating using a heat drum roll, a curl can be suppressed and a polarizer excellent in appearance can be manufactured. Specifically, by heating in a state where the laminate is placed along a heat drum roll, crystallization of the polyester resin base material can be efficiently promoted and the degree of crystallization can be increased relatively Even if the heating temperature is low, the crystallinity of the polyester resin substrate can be favorably increased. As a result, the rigidity of the polyester-based resin base material is increased, and the polyester-based resin base material can endure the shrinkage of the PVA-based resin layer due to heating, and curling is suppressed. Moreover, by using a heat drum roll, since it can heat, maintaining a layered product in a flat state, generation | occurrence | production of not only curl but wrinkles can be suppressed.

  Within the heating means 160, a plurality of heat drum rolls may be arranged, and each heat drum roll may be set to a different temperature. In the heating means 160, usually 2 to 20, preferably 4 to 10 heat drum rolls may be arranged. The contact time (total contact time) between the laminate and the heat drum roll is preferably 1 second to 300 seconds. The heating conditions can be controlled by adjusting the temperature of the heat drum roll, the number of heat drum rolls, the contact time with the heat drum roll, and the like.

  The maximum heating temperature is 100 ° C. or more, more preferably 105 ° C. or more, when the temperature of the heat drum roll set to the highest temperature among the plurality of heat drum rolls is the “maximum heating temperature”. The upper limit of the maximum heating temperature is preferably 115 ° C. By setting the maximum heating temperature in the heat treatment to the above range and setting the draw ratio in the above-described in-water stretching treatment to the predetermined range, peeling from the glass under a high temperature and high humidity environment is suppressed, and A polarizing plate with a sufficiently low haze value can be obtained. Therefore, the polarizing plate which made compatible the adhesiveness with other optical members, and the display characteristic (antiglare property) of an image display may be obtained. The temperature of the heat drum roll can be measured by a contact thermometer. The contact time of the laminate to the heating drum roll maintained at the maximum heating temperature (total contact time in the case of multiple heating drum rolls at the maximum heating temperature) is preferably 0.2 seconds to 2 seconds. More preferably, it is 0.5 second-2 seconds. In addition, "contact time" shall mean time until an arbitrary one point on a laminated body contacts the peripheral face of a heat drum roll kept at maximum heating temperature, and it leaves.

B. Configuration of Polarizing Plate As described above, the polarizing plate has a polyester resin substrate and a polarizer with a thickness of 10 μm or less laminated on one side of the polyester resin substrate. The haze value of the polarizing plate of the present invention is less than 1.6%. The polarizing plate does not peel off from the glass when the polarizer side surface is bonded to the glass via an acrylic adhesive and stored at 60 ° C./90% Rh for 500 hours. The thickness of the polyester resin substrate is preferably 10 μm to 200 μm, and more preferably 20 μm to 150 μm. The polarizer is preferably laminated in close contact with one surface of the polyester resin substrate (in other words, without an adhesive layer). The polarizing plate preferably has an easy adhesion layer between the polyester resin base material and the polarizer. The polarizing plate may have a protective film on the side opposite to the polyester resin base of the polarizer. The polyester-based resin substrate typically functions as a protective layer of a polarizer. The polarizing plate of the present embodiment has high adhesion to the optical member when the surface on the polarizer side is bonded to another optical member, and can suppress peeling under a high temperature and high humidity environment, and further, displays an image. The glare of the display screen of the device can be suppressed. That is, the polarizing plate of the present invention can achieve both the adhesion to other optical members and the display characteristics (antiglare property) of the image display device.

  The polarizer is essentially a PVA-based resin layer in which iodine is adsorbed and oriented. The thickness of the polarizer is 10 μm or less as described above, preferably 7.5 μm or less, and more preferably 5 μm or less. On the other hand, the thickness of the polarizer is preferably 0.5 μm or more, more preferably 1.5 μm or more. If the thickness is too thin, the optical properties of the resulting polarizer may be degraded. The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more, and still more preferably 42.0% or more. The degree of polarization of the polarizer is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

  Examples of the material for forming the protective film include cellulose resins such as (meth) acrylic resins, diacetyl cellulose and triacetyl cellulose, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. Resin, polyamide-based resin, polycarbonate-based resin, copolymer resin of these, etc. may be mentioned. The thickness of the protective film is preferably 10 μm to 100 μm.

  The easy-adhesion layer may be a layer formed substantially only of the composition for forming the easy-adhesion layer, and the composition for forming the easy-adhesion layer and the material for forming the polarizer are mixed (including compatibility) It may be a layer or a region. By forming the easy adhesion layer, excellent adhesion can be obtained. The thickness of the easy adhesion layer is preferably about 0.05 μm to 1 μm. The easily bonding layer can be confirmed, for example, by observing the cross section of the polarizing plate with a scanning electron microscope (SEM).

C. Image Display Device The polarizing plate described in the item B obtained by the manufacturing method according to the item A can be applied to an image display device such as a liquid crystal display device. Therefore, the present invention includes an image display device using the above polarizing plate. An image display device according to an embodiment of the present invention includes the polarizing plate described in the above item B.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, the measuring method and evaluation method of each characteristic are as follows.
(1) Thickness It measured using the digital micrometer (The Anritsu company make, product name "KC-351C").
(2) Antiglare Evaluation Using the haze meter (trade name "HN-150" manufactured by Murakami Color Science Laboratory, Inc.) according to the method of determining the haze value of the polarizing plate of each Example and Comparative Example according to JIS 7136 It was measured. The evaluation of the antiglare property of the polarizing plate was regarded as good (○) when the haze value was less than 1.6%, and was regarded as defective (×) when the haze value was 1.6% or more.
(3) Adhesion evaluation The long polarizing plates obtained in Examples and Comparative Examples were cut into a size of 100 mm (MD direction) × 100 mm (TD direction), and used as evaluation samples. The polarizer side of the above sample for evaluation is bonded to glass via an acrylic pressure-sensitive adhesive (thickness 20 μm, manufactured by Nitto Denko Corporation, product name “general-purpose adhesive for polarizing plate”) at 60 ° C./90% Rh After storing for 500 hours, the presence or absence of peeling from the glass at the end of the evaluation sample was confirmed. Moreover, when the sample for evaluation had peeled from glass, the length (peeling length) of the peeled part was measured. The adhesion of the polarizing plate is evaluated as good (○) when there is no peeling from the glass at the end of the evaluation sample, and defective when there is peeling from the glass at the end of the evaluation sample (×) And

Example 1
A long and amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm, degree of IPA modification: 5 mol%) was used as a polyester resin substrate. (Deterioration degree = [ethylene isophthalate unit] / [ethylene terephthalate unit + ethylene isophthalate unit])
Corona treatment (treatment conditions: 50 W · min / m ² ) is applied to one side of the polyester resin base material, and acetoacetyl modified polyvinyl alcohol (PVA) (manufactured by Japan Synthetic Chemical Industry Co., Ltd., trade name) The thickness after drying is a mixed solution (solid content concentration: 4.0%) of a mixture of purified polyolefin resin aqueous dispersion (product name: "Arrow base SE1030N" manufactured by Unitika, Inc.) and purified water of Gosefamer Z200 ") The coating was applied to 2000 nm and dried at 65 ° C. for 2 minutes to form a primer layer. Here, the solid content blending ratio of acetoacetyl-modified PVA and modified polyolefin in the mixed solution was 30:70. Then, 90 parts by weight of PVA (degree of polymerization 4200, degree of saponification 99.2 mol%) and 10 parts by weight of acetoacetylated PVA (trade name "Gosefamer Z410" manufactured by Japan Synthetic Chemical Industry Co., Ltd.) on the undercoat layer surface An aqueous solution containing a PVA-based resin compounded and potassium iodide in an amount of 13 parts by weight based on 100 parts by weight of the PVA-based resin is coated at 25 ° C. and dried at 60 ° C. for 3 minutes to obtain 13 μm-thick PVA A base resin layer was formed. Thus, a laminate was produced.
The obtained laminate was uniaxially stretched free end uniaxially twice in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds in an oven at 140 ° C. (air-assisted extension).
Then, the laminate was immersed in an insolubilization bath (a solution of boric acid obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) having a liquid temperature of 40 ° C. for 30 seconds (insolubilization treatment).
Then, it is immersed in a dyeing bath having a liquid temperature of 30 ° C. (iodine aqueous solution obtained by blending 0.2 parts by weight of iodine with 100 parts by weight of water and 1.5 parts by weight of potassium iodide) for 60 seconds It was done (staining process).
Then, it was immersed in a crosslinking bath having a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 100 parts by weight of water and 5 parts by weight of boric acid) for 30 seconds (Crosslinking treatment).
Thereafter, a stretching bath (stretching bath temperature: an aqueous solution obtained by blending 3 parts by weight of boric acid and 5 parts by weight of potassium iodide with 100 parts by weight of the aqueous solution) of the laminate. While immersing at 67 ° C., uniaxial stretching was performed in the longitudinal direction (longitudinal direction) by 2.75 times (total stretching ratio: 5.5 times) between rolls different in peripheral speed (in-water stretching treatment).
Thereafter, the laminated body was immersed in a washing bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 3.5 parts by weight of potassium iodide with 100 parts by weight of water) (washing treatment).
Then, the laminate is heated at 80 ° C. to 100 ° C. in an oven maintained at 80 ° C., and the total contact time to the heated roll maintained at 100 ° C. is 1 second. It heat-processed while conveying using a heating roll as it became.
Thus, a long polarizing plate 1 in which a 5 μm thick polarizer was laminated on a polyester resin substrate was obtained. The polarizing plate 1 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Example 2
A polarizing plate 2 was obtained in the same manner as in Example 1, except that the maximum heating temperature was 105 ° C., and the total contact time was 1 second. The polarizing plate 2 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Example 3
A polarizing plate 3 was obtained in the same manner as in Example 1 except that the maximum heating temperature was 110 ° C., and the total contact time was 1 second. The polarizing plate 3 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Example 4
A polarizing plate 4 was obtained in the same manner as Example 2, except that the laminate was stretched in the longitudinal direction by 2.55 times (total stretching ratio: 5.1 times) while immersed in a stretching bath (total stretching ratio: 5.1 times). The The polarizing plate 4 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 1
A polarizing plate 5 was obtained in the same manner as in Example 1, except that the maximum heating temperature was 80 ° C., and the total contact time was 1 second. The polarizing plate 5 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 2
A polarizing plate 6 was obtained in the same manner as in Example 1, except that the maximum heating temperature was 95 ° C., and the total contact time was 1 second. The polarizing plate 6 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 3
The laminate was stretched 2.4 times in the longitudinal direction in the oven (air-assisted extension), and stretched 2.30 times (total stretch ratio: 5.5 times) while immersed in the stretching bath (total stretch ratio: 5.5 times) A polarizing plate 7 was obtained in the same manner as in Example 1 except that the stretching processing in water) and the maximum heating temperature was 65 ° C., and the total contact time was 1 second. The polarizing plate 7 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 4
A polarizing plate 8 was obtained in the same manner as in Comparative Example 3, except that the maximum heating temperature was 75 ° C., and the total contact time was 1 second. The polarizing plate 8 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 5
A polarizing plate 9 was obtained in the same manner as in Comparative Example 3 except that the maximum heating temperature was 100 ° C., and the total contact time was 1 second. The polarizing plate 9 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 6
A polarizing plate 10 was obtained in the same manner as in Comparative Example 3 except that the maximum heating temperature was 105 ° C., and the total contact time was 1 second. The polarizing plate 10 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 7
A polarizing plate 11 was obtained in the same manner as in Comparative Example 3, except that the maximum heating temperature was 110 ° C., and the total contact time was 1 second. The polarizing plate 11 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 8
The laminate was stretched 2.6 times in the longitudinal direction in the oven (air-assisted extension) and stretched 2.10 times (total stretch ratio: 5.5 times) in the longitudinal direction while immersed in the stretching bath (total stretch ratio: 5.5) A polarizing plate 12 was obtained in the same manner as in Example 1 except that the film was stretched in water. The polarizing plate 12 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

Comparative Example 9
The laminate was stretched in the oven in the longitudinal direction by 2.4 times (air-assisted stretching), and while immersed in a stretching bath, the laminate was stretched in the longitudinal direction by 2.50 times (total stretching ratio: 6.0 times) ( A polarizing plate 13 was obtained in the same manner as in Example 1 except that the film was stretched in water. The polarizing plate 13 was subjected to the evaluation of the haze value and the adhesion. The results are shown in Table 1.

  As is apparent from Table 1, the polarizing plate obtained with an in-water draw ratio of 2.55 times or more and a maximum heating temperature of 100 ° C. or more in heat treatment was good in both the antiglare property and the adhesion. there were.

  The polarizing plate manufactured by the manufacturing method of this invention is used suitably for image display apparatuses, such as a liquid crystal display device and an organic electroluminescence display.

10 Polarizer 11 PVA-Based Resin Layer 20 Polyester-Based Resin Base 100 Polarizing Plate 200 Laminated Body

Claims (4)

A manufacturing method of a polarizing plate having a polyester resin substrate and a polarizer having a thickness of 10 μm or less laminated on one side of the polyester resin substrate,
The polyvinyl alcohol-based resin layer is used as a polarizer by dyeing and stretching a laminate in which a polyvinyl alcohol-based resin layer is formed on one side of the polyester-based resin substrate, and the polyester-based resin substrate and the above Heat-treating the laminate with the polarizer,
The method for producing a polarizing plate, wherein the stretching includes a stretching treatment in water in which a stretching ratio is 2.55 times or more, and a maximum heating temperature in the heat treatment is 100 ° C. or more.   The manufacturing method of the polarizing plate of Claim 1 whose maximum heating temperature in the said heat processing is 115 degrees C or less. A polyester-based resin substrate, and a polarizer laminated on one side of the polyester-based resin substrate,
The thickness of the polarizer is 10 μm or less,
The haze value is less than 1.6%,
The polarizing plate which does not peel from the said glass when the surface by the side of the said polarizer is bonded together to glass via an adhesive agent, and it stores at 60 degreeC / 90% Rh for 500 hours. The image display apparatus provided with the polarizing plate of Claim 3.