WO2019069755A1

WO2019069755A1 - Polarizing plate, image display device, and production method for polarizing plate

Info

Publication number: WO2019069755A1
Application number: PCT/JP2018/035613
Authority: WO
Inventors: 善則南川; 健太郎池嶋; 後藤　周作; 咲美 ▲徳▼岡
Original assignee: 日東電工株式会社
Priority date: 2017-10-03
Filing date: 2018-09-26
Publication date: 2019-04-11
Also published as: CN111183378B; CN111183378A; JP2019066715A; JP7240090B2; TWI771503B; KR20200064078A; TW201935047A

Abstract

Provided is a polarizing plate having little heat shrinkage behavior and having suppressed peeling. The polarizing plate has a polyester resin base material and a polarizer laminated on one side of the polyester resin base material. The polarizer thickness is no more than 10 µm and the polyester resin base material has an elastic modulus of at least 2.70 GPa.

Description

Polarizing plate, image display device, and method of manufacturing polarizing plate

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, when the polarizer-side surface of the polarizing plate is bonded to a display cell or another optical member such as a retardation plate through an adhesive, the heat shrinkage behavior of the polyester resin base material is large. Peeling of the polarizing plate may occur under high temperature and high humidity environment.

The present invention has been made to solve the above-mentioned conventional problems, and the main object thereof is a polarizing plate having a small heat shrinkage behavior and suppressing peeling, an image display device provided with the above polarizing plate, and a polarizing plate It is to provide a manufacturing method of

The polarizing plate of the present invention 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 polyester-based resin base Modulus of 2.70 GPa or more.
In one embodiment, the polarizer is laminated on one side of the polyester-based resin substrate without an adhesive layer.
In one embodiment, an easily bonding layer is provided between the polyester resin substrate and the polarizer.
In one embodiment, the polyester resin substrate functions as a protective layer of the polarizer.
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 another aspect of the present invention, a method of manufacturing the above polarizing plate is provided. The manufacturing method is to form a polyvinyl alcohol resin layer on one side of the polyester resin base material to form a laminate, and dye and stretch the laminate to obtain the polyvinyl alcohol resin layer as a polarizer. And heating the laminate of the polyester-based resin substrate and the polarizer after the stretching, the temperature of the stretching bath in the stretching being 67.degree. C. or less, and the heat treatment in the heat treatment. The maximum heating temperature is 102 ° C. or more, or the temperature of the stretching bath in the above stretching is 69 ° C. or less, and the maximum heating temperature in the above heat treatment is 105 ° C. or more.

According to the present invention, it is possible to provide a polarizing plate having a small heat shrinkage behavior and suppressing peeling, an image display apparatus provided with the above polarizing plate, and a method of manufacturing the polarizing plate.

It is a sectional view of a polarizing plate concerning one embodiment of the present 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. Overall Configuration of Polarizing Plate FIG. 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention. As shown in FIG. 1, the polarizing plate 10 has a polyester resin base 11 and a polarizer 12 laminated on one side of the polyester resin base 11. The thickness of the polarizer 12 is 10 μm or less. The elastic modulus of the polyester resin base material 11 is 2.70 GPa or more. The elastic modulus of the polyester-based resin substrate 11 is typically measured by a nanoindentation method using an indentation tester (typically, a nano indenter). More specifically, the elastic modulus (E) of the polyester resin substrate 11 is obtained by pressing a probe (indentor) against the surface of the polyester resin substrate to be measured, based on the displacement-load hysteresis curve. From the obtained contact rigidity S and the contact projected area A between the indenter and the polyester resin base material, it is calculated by the following equation.
^{^{E = S × π 1/2 / 2A}} 1/2
The polarizer 12 is preferably laminated in close contact with one surface of the polyester resin substrate 11 (in other words, without an adhesive layer). The polarizing plate 10 preferably has an easy adhesion layer (not shown) between the polyester resin substrate 11 and the polarizer 12. The polarizing plate 10 may have a protective film (not shown) on the side of the polarizer 12 opposite to the polyester resin substrate 11. The polyester resin substrate 11 typically functions as a protective layer of the polarizer 12. In the conventional polarizing plate, peeling from the optical member may occur at both ends in the stretching direction of the polarizing plate when the surface on the polarizer side is bonded to another optical member and placed in a high temperature and high humidity environment. On the other hand, in the polarizing plate 10 of the present embodiment, the heat shrinkage behavior of the polyester resin substrate 11 is small when the surface on the polarizer 12 side is bonded to another optical member, and under the high temperature and high humidity environment. Peeling can be suppressed.

B. The polarizer is substantially a polyvinyl alcohol-based resin layer (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.

Arbitrary suitable resin may be adopted as PVA system resin which forms the above-mentioned 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%, and more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined according to 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 according to JIS K 6726-1994.

C. Polyester-Based Resin Substrate As described above, the polyester-based resin substrate has an elastic modulus of 2.70 GPa or more. The elastic modulus is preferably 2.70 GPa to 4.50 GPa, more preferably 2.80 GPa to 3.90 GPa. Thereby, the shrinkage of the polyester resin base material under high temperature and high humidity environment can be suppressed, and as a result, when the polarizing plate is bonded to the optical member, the polyester resin base material is prevented from peeling from the optical member. obtain. The elastic modulus is the temperature of the stretching bath when the laminate of the polyester resin base material and the polyvinyl alcohol resin layer is stretched in water, and the highest at the time of heat treatment after stretching in water in the manufacturing method of the polarizing plate described later. By setting the heating temperature appropriately, it can be controlled within the desired numerical range.

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, and copolymers and blends thereof 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 is preferably 10 μm to 200 μm, and more preferably 20 μm to 150 μm.

D. Protective Film The polarizing plate 10 may have a protective film on the side opposite to the polyester resin substrate 11 of the polarizer 12 as described above. 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.

E. Easy Adhesion Layer The polarizing plate 10 may have an easy adhesion layer between the polyester resin substrate 11 and the polarizer 12 as described above. 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).

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. Examples of the olefin component which is the main component of the polyolefin resin include olefin hydrocarbons having 2 to 6 carbon atoms such as ethylene, propylene, isobutylene, 1-butene, 1-pentene and 1-hexene. 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 80,000.

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.

F. Method of Producing Polarizing Plate The method of producing a polarizing plate of the present invention comprises forming a PVA-based resin layer on one side of a polyester-based resin substrate to form a laminate, and dyeing and stretching the laminate to obtain a PVA-based resin And making the layer into a polarizer, and heating the laminate of the polyester resin substrate and the polarizer after stretching. The temperature of the stretching bath is 67 ° C. or less, and the maximum heating temperature in the heat treatment is 102 ° C. or more, or the temperature of the stretching bath is 69 ° C. or less, and the maximum heating temperature in the heat treatment is 105 ° C or more.

FIG. 2: is schematic which shows the manufacturing process of the polarizing plate which concerns on one Embodiment. In the manufacturing process of the polarizing plate according to the present embodiment, typically, a laminate 10 ′ of a polyester-based resin base material and a PVA-based resin layer is drawn out from a drawing out part 101, and rolls 111 and 112 After being immersed in the 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 10 ′ 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. The PVA-based resin layer is used as a polarizer by (in-water stretching treatment). Next, the laminate 10 '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 10 ′ is placed in the heating unit 160 and heated (heat treatment) to obtain the polarizing plate 10 of the present embodiment. Thereafter, the obtained polarizing plate 10 is wound by a winding unit 170. Although illustration is omitted, it is possible to perform air-drawing processing before subjecting the laminate 10 ′ to insolubilization processing. In addition, the manufacturing process shown in FIG. 2 is an example, and the frequency | count of said process, order, etc. are not specifically limited.

F-1. Production of Laminate As a method of forming a PVA-based resin layer on a polyester-based resin substrate, any appropriate method may be employed. Preferably, a coating solution containing a PVA-based resin is applied onto a polyester-based resin substrate and dried to form a PVA-based resin layer. In one embodiment, a composition for forming an easy adhesion layer is applied onto a polyester resin substrate and dried to form an easy adhesion layer, and a PVA resin layer is formed on the easy adhesion layer. Do.

The forming material of the polyester resin base material is as described in the section C above. 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.

The coating solution is typically a solution in which the 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 the 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 (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.

F-2. In-Air Stretching The stretching method of air-assisted stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, uniaxial stretching through a laminate between rolls with different peripheral speeds) Method). In one embodiment, 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.

F-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.

F-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 (laminate) 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 solution 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.

F-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 aqueous boric acid 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.degree. C. to 60.degree. 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.

F-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 stretched in water in a direction parallel to the stretching 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 °. .

The stretching temperature in the in-water stretching (liquid temperature of the stretching bath) is 69 ° C. or less, more preferably 67 ° C. or less. The lower limit of the solution temperature of the stretching bath is preferably 40 ° C, more preferably 50 ° C. By setting the liquid temperature of the stretching bath within the above range, the elastic modulus of the polyester resin substrate can be adjusted to a value within the preferred range, in combination with the maximum heating temperature in the heat treatment described later. Furthermore, 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 temperature of the stretching bath, 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, more preferably the original length of the laminate (including the draw ratio of the laminate). 6.0 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.

F-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 process is preferably 30 ° C. to 100 ° C.

F-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 to easily control the contraction in the width direction of the laminate 10 ′. . The temperature in the oven oven is preferably 30.degree. C. to 100.degree. The heating time by the oven is preferably 1 second to 300 seconds. The wind speed of 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 10 'is placed along the heat drum roll, the crystallization of the polyester resin substrate can be efficiently promoted to increase the degree of crystallization. Even at a relatively low heating temperature, 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, since it can heat, maintaining laminated body 10 'in a flat state by using a heat | fever drum roll, 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 10 '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 highest heating temperature is 102 ° C. or higher, more preferably 105 ° C. or higher, when the temperature of the thermal drum roll set to the highest temperature among the plurality of heat drum rolls is the “maximum heating temperature”. Preferably it is 110 degreeC or more. The upper limit of the maximum heating temperature is preferably 150 ° C., more preferably 120 ° C. By setting the maximum heating temperature in the heat treatment to be in the above range, it is possible to adjust the durability index of the polyester resin base material to a value within the preferable range together with the temperature of the stretching bath in the underwater stretching process. 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 seconds to 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.

G. Image Display Device The polarizing plate described in the items A to E obtained by the manufacturing method described in the item F 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 items A to E.

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 The thickness was measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
(2) Elastic modulus About the polyester-type resin base material of the polarizing plate obtained by the Example and the comparative example, using a nano indenter (Hysitron Inc. make, "Triboindenter"), the nano indene under the following measurement conditions The elastic modulus was measured by the transfer method. Specifically, the probe (indentor) of the nano indenter is pressed into the surface of the polarizing plate on the polyester resin substrate side, and the contact stiffness S obtained from the displacement-load hysteresis curve, the indenter, and the polyester resin substrate The following equation is calculated from the contact projected area A between them.
Elastic modulus (E) = S × π ^1/2 / 2A ^1/2
(Measurement condition)
・ Measurement method: Single indentation method ・ Measurement temperature: 25 ° C
・ Indentation speed: about 2 nm / sec
・ Pushing depth: about 2000 nm
-Probe: made of diamond, Berkovich type (triangular pyramid type)
(3) Adhesion evaluation The long polarizing plates obtained in Examples and Comparative Examples were cut into a size of 150 mm (MD direction) × 200 mm (TD direction), and used as an evaluation sample. The polarizer side of the sample for evaluation is attached to the glass through an acrylic adhesive, and after storing for 500 hours at 60 ° C./90% Rh, the presence or absence of peeling from the glass at the end of the sample for evaluation is confirmed did. In addition, when the sample for evaluation was peeled from the glass, the length of the peeled portion was measured.

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 Let (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 brought into contact with the heating roll maintained at 110 ° C., the maximum heating temperature, in an oven maintained at 80 ° C., with a plurality of heating rolls maintained at 80 to 110 ° C. The heat treatment was carried out while conveying using a heating roll so that the total of 1 sec.
Thus, a long polarizing plate 1 in which a 5 μm thick polarizer was laminated on a polyester resin substrate was obtained. The elastic modulus of the polyester resin base material of the polarizing plate 1 was 3.15 GPa. When the polarizing plate 1 was subjected to the above adhesion evaluation, peeling from the glass did not occur.

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 elastic modulus of the polyester resin base material of the polarizing plate 2 was 2.85 GPa. The polarizing plate 2 was subjected to the same evaluation as in Example 1. 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 102 ° C., and the total contact time was 1 second. The elastic modulus of the polyester resin base material of the polarizing plate 3 was 2.70 GPa. The polarizing plate 3 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Example 4
The procedure of Example 1 was repeated except that the laminate was stretched in water using a stretching bath having a temperature of 69 ° C., and the maximum heating temperature was 105 ° C., and the total contact time was 1 second. The polarizing plate 4 was obtained. The elastic modulus of the polyester resin base material of the polarizing plate 4 was 2.72 GPa. The polarizing plate 4 was subjected to the same evaluation as in Example 1. 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 100 ° C., and the total contact time was 1 second. The elastic modulus of the polyester resin base material of the polarizing plate 5 was 2.65 GPa. The polarizing plate 5 was subjected to the same evaluation as in Example 1. 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 elastic modulus of the polyester resin base material of the polarizing plate 6 was 2.37 GPa. The polarizing plate 6 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Comparative Example 3
A polarizing plate 7 was obtained in the same manner as in Example 1 except that the temperature in the furnace was set to 60 ° C., and the maximum heating temperature was 60 ° C., and the total contact time was 1 second. The elastic modulus of the polyester resin base material of the polarizing plate 7 was 2.10 GPa. The polarizing plate 7 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Comparative Example 4
A polarizing plate 8 was obtained in the same manner as in Example 4 except that the maximum heating temperature was 102 ° C., and the total contact time was 1 second. The elastic modulus of the polyester resin base material of the polarizing plate 8 was 2.57 GPa. The polarizing plate 8 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

Comparative Example 5
A polarizing plate 9 was obtained in the same manner as in Example 4 except that the maximum heating temperature was 100 ° C., and the total contact time was 1 second. The elastic modulus of the polyester resin base material of the polarizing plate 9 was 2.50 GPa. The polarizing plate 9 was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

As apparent from Table 1, the polarizing plate having an elastic modulus of 2.70 GPa or more did not peel off from the glass even when placed in a high temperature and high humidity environment.

The polarizing plate of the present invention is suitably used for image display devices such as liquid crystal display devices and organic EL display devices.

10 Polarizing Plate 11 Polyester Resin Base 12 Polarizer

Claims

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 polarizing plate whose elastic modulus of the said polyester-based resin base material is 2.70 GPa or more.
The polarizing plate according to claim 1, wherein the polarizer is laminated on one side of the polyester resin substrate without an adhesive layer.
The polarizing plate of Claim 1 or 2 which has an easily bonding layer between the said polyester-type resin base material and the said polarizer.
The polarizing plate according to any one of claims 1 to 3, wherein the polyester-based resin substrate functions as a protective layer of the polarizer.
An image display comprising the polarizing plate according to any one of claims 1 to 4.
It is a manufacturing method of the polarizing plate in any one of Claims 1-4, Comprising:
Forming a polyvinyl alcohol-based resin layer on one side of the polyester-based resin substrate to form a laminate;
And making the polyvinyl alcohol-based resin layer a polarizer by dyeing and stretching the laminate, and heating the laminate of the polyester-based resin substrate and the polarizer after the stretching. ,
The temperature of the stretching bath in the stretching is 67 ° C. or lower, and the maximum heating temperature in the heat treatment is 102 ° C. or higher, or
The manufacturing method of the polarizing plate whose temperature of the extending | stretching bath in the said extending | stretching is 69 degrees C or less, and the maximum heating temperature in the said heat processing is 105 degrees C or more.