JP2022038978A - Optical laminate and method of manufacturing polarizing plate using the same - Google Patents

Abstract

To provide an optical laminate as an intermediate product for manufacturing a polarizing plate comprising a thin polarizer with high productivity.SOLUTION: An optical laminate according to an embodiment of the present invention comprises a resin base material, a first polarizer layer provided on one side of the resin base material, and a second polarizer layer provided on the other side of the resin base material. A peel force between the resin base material and the second polarizer layer is greater than that between the resin base material and the first polarizer layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical laminate and a method for manufacturing a polarizing plate using the optical laminate.

A method has been proposed in which a polyvinyl alcohol-based resin layer is formed on a resin base material, and the laminate is stretched and dyed to obtain a polarizing element (for example, Patent Document 1). According to such a method, a polarizing element having a thin thickness can be obtained. With the widespread use of polarizing plates containing such a thin polarizing element, it is desired to reduce the cost and improve the productivity that can realize it.

Japanese Patent No. 3325560

A main object of the present invention is to provide an optical laminate as an intermediate capable of producing a polarizing plate containing a thin polarizing element with high productivity.

The optical laminate according to the embodiment of the present invention includes a resin base material, a first polarizing element layer provided on one side of the resin base material, and a second provided on the other side of the resin base material. It has two polarizing layers. The peeling force between the resin base material and the second polarizing element layer is larger than the peeling force between the resin base material and the first polarizing element layer.
In one embodiment, the peeling force between the resin base material and the second polarizing element layer is 0.1 N / 15 mm or more larger than the peeling force between the resin base material and the first polarizing element layer. ..
In one embodiment, the peeling force between the resin base material and the second polarizing element layer is 0.5 N / 15 mm or more.
In one embodiment, the optical laminate is provided with an easy-adhesive layer between the resin substrate and the second polarizing layer. In one embodiment, the easy-adhesive layer contains a polyvinyl alcohol-based component and a polyolefin-based component. In one embodiment, the polyvinyl alcohol-based component comprises acetacetyl-modified polyvinyl alcohol.
In one embodiment, the optical laminate further has a first protective layer on the opposite side of the first polarizing element layer from the resin substrate. In one embodiment, the optical laminate further has a second protective layer on the opposite side of the second polarizing layer to the resin substrate.
According to another aspect of the present invention, there is provided a method for manufacturing a polarizing plate. In this production method, a first polyvinyl alcohol-based resin layer is formed on one side of the resin base material; and a second polyvinyl alcohol-based resin layer is formed on the other side of the resin base material; The laminate of the resin base material, the first polyvinyl alcohol-based resin layer, and the second polyvinyl alcohol-based resin layer is subjected to stretching and dyeing, and the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer are subjected to stretching and dyeing. The system resin layer is used as a first polarizing element layer and a second polarizing element layer, respectively, to obtain the above optical laminate; a first protective layer on the opposite side of the first polarizing element layer from the resin base material. The laminate of the first polarizing layer and the first protective layer is peeled off from the optical laminate to form a first polarizing plate; and the resin substrate and the first. The laminated body with the polarizing element layer of 2 is used as a second polarizing plate;

According to the embodiment of the present invention, the polarizing material is provided on both sides of the resin base material, and the peeling force between the resin base material and one polarizing element layer is higher than the peeling force between the resin base material and the other polarizing element layer. Also large optical laminates are provided. By using such an optical laminate, two polarizing plates can be manufactured by a method substantially similar to the method for manufacturing one polarizing plate in the manufacture of a polarizing plate containing a thin polarizing element. In other words, the manufacturing efficiency can be substantially doubled. Therefore, according to the embodiment of the present invention, a polarizing plate containing a thin polarizing element can be manufactured with high productivity. Further, by using such an optical laminate, the two polarizing plates can be manufactured without any defect (typically, without undesired peeling and peeling failure).

It is a schematic sectional drawing of the optical laminated body by one Embodiment of this invention. 2 (a) to 2 (d) are schematic cross-sectional views illustrating an example of a method for manufacturing a polarizing plate using an optical laminate according to an embodiment of the present invention. It is a schematic diagram which shows an example of the drying shrinkage process using the heating roll in the production of the polarizing element used for the optical laminated body by embodiment of this invention.

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

A. Overall Configuration of Optical Laminate Figure 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 of the illustrated example includes a resin base material 10, a first polarizing element layer 21 provided on one side of the resin base material 10 (sometimes referred to as a first main surface), and a resin base material. It has a second polarizing layer 2 provided on the other side of the ten (sometimes referred to as a second main surface). In the embodiment of the present invention, the peeling force between the resin base material 10 and the second polarizing element layer 22 is larger than the peeling force between the resin base material 10 and the first polarizing element layer 21. With such a configuration, by using the optical laminate, the method is almost the same as the method for manufacturing one polarizing plate (that is, with high productivity), and there is no problem (typically). Two polarizing plates can be manufactured (without undesired peeling or poor peeling). For convenience, it is stated that "the peeling force between the resin base material and the second polarizing element layer is larger than the peeling force between the resin base material and the first polarizing element layer", but the resin base material and the polarizing element layer are used. The peeling force may be greater on one side than on the other, and therefore the peeling force between the resin substrate and the first polarizing element layer may be greater than the peeling force between the resin substrate and the second polarizing element layer. Further, for convenience, in the illustrated example, the first polarizing element layer is on the upper side and the second polarizing element layer is on the lower side, but the first polarizing element layer is on the lower side and the second polarizing element layer is on the upper side. You may. In the method for manufacturing a polarizing plate, which will be described later, typically, the first polarizing element layer having a small peeling force can be peeled from the optical laminate.

The first main surface and / or the second main surface of the resin base material may be subjected to a surface modification treatment (for example, a corona treatment). Further / or, an easy-adhesion layer (not shown) may be formed on the first main surface and / or the second main surface of the resin base material. By appropriately setting the presence / absence, type and degree of surface modification treatment for the first main surface and / or the second main surface, and the presence / absence, thickness and type of the easy-adhesion layer, the resin substrate and the first surface can be used. The peeling force from the polarizing element layer and the peeling force from the resin base material and the second polarizing element layer can be in a desired relationship.

The peeling force between the resin base material and the second polarizing element layer is preferably 0.1 N / 15 mm or more, more preferably 0.3 N / 15 mm, more than the peeling force between the resin base material and the first polarizing element layer. As described above, it is more preferably 0.5 N / 15 mm or more, particularly preferably 0.8 N / 15 mm or more, and particularly preferably 1.0 N / 15 mm or more. When the difference in peeling force is within such a range, two polarizing plates can be obtained from the optical laminate without any trouble (typically, without undesired peeling and peeling failure). The upper limit of such a difference in peeling force may be, for example, 1.5 N / 15 mm.

The peeling force between the resin base material and the second polarizing element layer is preferably 0.2 N / 15 mm or more, more preferably 0.5 N / 15 mm or more, and further preferably 0.7 N / 15 mm or more. It is particularly preferably 1.0 N / 15 mm or more, and particularly preferably 1.2 N / 15 mm or more. The upper limit of the peeling force between the resin base material and the second polarizing element layer can be, for example, 2.0 N / 15 mm. The peeling force between the resin base material and the first polarizing element layer is preferably 0.1 N / 15 mm or more, more preferably 0.1 N / 15 mm to 0.7 N / 15 mm, and further preferably 0.1 N. It is / 15 mm to 0.5 N / 15 mm, and particularly preferably 0.1 N / 15 mm to 0.3 N / 15 mm. When the peeling force between the resin base material and the respective polarizing element layers is within such a range, the desired difference in peeling force can be easily realized.

If necessary, the optical laminate may further have a first protective layer 31 on the opposite side of the resin base material 10 of the first polarizing layer 21 as shown in the illustrated example, and the second polarizing layer may be provided. A second protective layer 32 may be further provided on the opposite side of the child layer 22 from the resin base material 10. These protective layers support the polarizing element layer during the production of the polarizing plate described later, and serve as the protective layer in the finally obtained polarizing plate.

Hereinafter, the components of the optical laminate will be described in more detail. The first polarizing element layer and the second polarizing element layer will be collectively described as a polarizing element layer, and the first protective layer and the second protective layer will be collectively described as a protective layer. When it is necessary to distinguish between the first protector layer and the second protector layer, and the first protective layer and the second protective layer, "first" and "second" are specified. ..

B. Resin base material Any suitable material can be adopted as the constituent material of the resin base material 10. The resin base material is typically composed of a thermoplastic resin. Specific examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, (meth) acrylic resins, polyamide resins, polycarbonate resins, and their co-weights. Combined resin can be mentioned. Preferably, a polyethylene terephthalate resin is used. Among them, an amorphous polyethylene terephthalate resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as a dicarboxylic acid and a copolymer further containing cyclohexanedimethanol as a glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 170 ° C. or lower. By using such a resin base material, it is possible to sufficiently secure stretchability while suppressing crystallization of the PVA-based resin layer. Considering that the resin base material is plasticized with water and well stretched in water, the temperature is more preferably 120 ° C. or lower. In one embodiment, the glass transition temperature of the resin substrate is preferably 60 ° C. or higher. By using such a resin base material, when the coating liquid containing the PVA-based resin described later is applied and dried, the resin base material is deformed (for example, unevenness, tarmi, wrinkles, etc. are generated). Can be prevented. Further, the laminated body can be stretched at a suitable temperature (for example, about 60 ° C. to 70 ° C.). In another embodiment, the glass transition temperature may be lower than 60 ° C. as long as the resin base material is not deformed when the coating liquid containing the PVA-based resin is applied and dried. The glass transition temperature (Tg) is a value obtained according to JIS K 7121.

In one embodiment, the resin base material preferably has a water absorption rate of 0.2% or more, more preferably 0.3% or more. Such a resin base material absorbs water, and the water can act as a plasticizer to be plasticized. As a result, the stretching stress can be significantly reduced in the stretching in water, and the stretchability can be excellent. On the other hand, the water absorption rate of the resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, it is possible to prevent problems such as deterioration of the appearance of the obtained laminated body due to a significant decrease in dimensional stability of the resin base material during manufacturing. In addition, it is possible to prevent the PVA-based resin film from breaking or peeling from the resin base material during stretching in water. The water absorption rate is a value obtained according to JIS K 7209.

The thickness of the resin substrate in the optical laminate (that is, after stretching) is preferably 10 μm to 150 μm, more preferably 15 μm to 100 μm.

C. Polarizer The polarizing element (hereinafter, simply referred to as a polarizing element) constituting the polarizing element layer is typically composed of a polyvinyl alcohol (PVA) -based resin film containing a dichroic substance (typically iodine). Will be done. The substituents constituting the first polarizing element layer and / or the second polarizing element layer preferably contain an acetacetyl-modified PVA-based resin. With such a configuration, the difference in the desired peeling force can be easily realized. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight, when the total amount of the PVA-based resin is 100% by weight. ..

The boric acid content of the stator is preferably 10% by weight or more, more preferably 13% by weight to 25% by weight. When the boric acid content of the stator is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the iodine content described later, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. The boric acid content can be calculated, for example, as the amount of boric acid contained in the polarizing element per unit weight by using the following formula from the neutralization method.

The iodine content of the splitter is preferably 2.0% by weight or more, more preferably 2.0% by weight to 10% by weight. When the iodine content of the stator is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the above boric acid content, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. As used herein, the term "iodine content" means the amount of all iodine contained in the polarizing element (PVA-based resin film). More specifically, in the substituent, iodine exists in the form of iodine ion (I ⁻ ), iodine molecule (I ₂ ), polyiodide ion (I ₃ ⁻ , I ₅ ⁻ ), etc., as used herein. Iodine content means the amount of iodine that includes all of these forms. The iodine content can be calculated, for example, by a calibration curve method for fluorescent X-ray analysis. The polyiodine ion exists in a state where the PVA-iodine complex is formed in the substituent. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA ・ I _3- ⁾ has an absorption peak near 470 nm, and the complex of PVA and triiodide ion (PVA ・ I _5- ⁾ is around 600 nm. Has an absorptive peak. As a result, polyiodide ions can absorb light over a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodide ions present in the form of a complex with PVA may mainly contribute to the absorption performance of the stator.

The thickness of the splitter is preferably 1 μm to 10 μm, more preferably 1 μm to 8 μm, and further preferably 2 μm to 5 μm.

The splitter preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance Ts of the polarizing element is preferably 40.0% to 48.0%, more preferably 41.0% to 46.0%. The degree of polarization P of the polarizing element is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more. The single transmittance is typically a Y value measured with an ultraviolet-visible spectrophotometer and corrected for luminosity factor. The degree of polarization is typically obtained by the following formula based on the parallel transmittance Tp and the orthogonal transmittance Tc measured by using an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
Degree of polarization (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

D. Protective layer The protective layer is formed of any suitable film that can be used as a protective layer for the stator. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. , Polyester-based, polycarbonate-based, polyolefin-based, (meth) acrylic-based, acetate-based transparent resins and the like. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, and silicone, or ultraviolet curable resins can also be mentioned. In addition to this, for example, glassy polymers such as siloxane-based polymers can also be mentioned. Further, the polymer film described in JP-A-2001-343529 (WO01 / 37007) can also be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain. Can be used, and examples thereof include a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer. The polymer film can be, for example, an extruded product of the above resin composition.

If necessary, the protective layer may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment. Further / or, if necessary, the protective layer is provided with a process for improving visibility when visually recognizing through polarized sunglasses (typically, a (elliptical) circular polarization function is provided, and an ultra-high phase difference is provided. It may be given). By performing such processing, excellent visibility can be realized even when the display screen is visually recognized through a polarizing lens such as polarized sunglasses.

The thickness of the protective layer is preferably 50 μm or less, more preferably 5 μm to 40 μm. When the surface treatment is applied, when the protective layer is surface-treated, the thickness of the protective layer is the thickness including the thickness of the surface treatment layer.

E. Easy-adhesive layer The easy-adhesive layer preferably contains a polyvinyl alcohol-based component and a polyolefin-based component. With such a composition, it is possible to obtain an optical laminate having both excellent adhesion and excellent appearance. As the polyvinyl alcohol-based component, any suitable PVA-based resin can be used. Specific examples thereof include polyvinyl alcohol and modified polyvinyl alcohol. 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, acetacetyl-modified PVA is preferably used. As the 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 acetacetyl-modified PVA is preferably 97 mol% or more. The pH of the 4 wt% aqueous solution of acetoacetyl-modified PVA is preferably 3.5 to 5.5. The degree of polymerization and the degree of saponification can be determined according to JIS K 6726-1994.

Any suitable polyolefin-based resin can 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, olefinic 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 components constituting the polyolefin resin is preferably 50% by weight to 95% by weight.

The polyolefin-based resin preferably has a carboxyl group and / or an anhydride group thereof. Such a polyolefin-based resin can be dispersed in water, and an easy-adhesion layer can be well formed. Examples of the monomer component having such a functional group include unsaturated carboxylic acid and its anhydride, half ester of unsaturated dicarboxylic acid, and half amide. 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, 5000 to 80,000.

The compounding ratio of the polyvinyl alcohol-based component and the polyolefin-based component in the easy-adhesion layer is preferably 5:95 to 60:40, more preferably 20:80 to 50:50. If there are too many polyvinyl alcohol-based components, sufficient adhesion may not be obtained. Specifically, the peeling force required for peeling the polarizing element layer from the resin base material may decrease, and sufficient adhesion may not be obtained. On the other hand, if the amount of polyvinyl alcohol-based components is too small, the appearance of the obtained laminate may be impaired. Specifically, problems such as clouding of the easy-adhesive layer may occur, making it difficult to obtain an optical laminate having an excellent appearance.

The thickness of the easy-adhesion layer is preferably 0.5 μm to 3 μm, and more preferably 0.8 μm to 2 μm. If the thickness of the easy-adhesion layer is too thin, sufficient peeling force may not be obtained. On the other hand, if the thickness of the easy-adhesion layer is too thick, cissing occurs when the PVA-based resin coating layer (finally becomes a polarizing element) described later is formed, and the obtained coating film becomes uneven. However, it may be difficult to obtain an optical laminate having an excellent appearance.

The easy-adhesive layer can be formed by applying and drying a composition for forming an easy-adhesive layer containing a polyvinyl alcohol-based component, a polyolefin-based component, an additive depending on the purpose, and an aqueous medium on a resin base material.

F. Method for manufacturing a polarizing plate The optical laminate according to the above items A to E can be suitably used for manufacturing a polarizing plate. Therefore, the embodiment of the present invention also includes a method for manufacturing a polarizing plate. The manufacturing method is to form a first polyvinyl alcohol (PVA) -based resin layer on the first main surface of the resin base material; to form a second PVA-based resin layer on the second main surface of the resin base material. That; the laminate of the resin base material, the first PVA-based resin layer, and the second PVA-based resin layer is subjected to stretching and dyeing, and the first PVA-based resin layer and the second PVA-based resin layer are subjected to. The resin layer is used as a first polarizing layer and a second polarizing layer, respectively, to obtain the above optical laminate; a first protective layer is provided on the opposite side of the first polarizing layer from the resin base material. To be provided; the laminate of the first polarizing layer and the first protective layer is peeled from the optical laminate to form a first polarizing plate; and the resin substrate and the second. The laminated body with the polarizing element layer of the above is used as a second polarizing plate; Hereinafter, each step of the manufacturing method will be described with reference to FIGS. 2 (a) and 2 (d).

F-1. Formation of PVA-based Resin Layer First, as shown in FIG. 2A, a first PVA-based resin layer 21'is formed on the first main surface of the resin base material (thermoplastic resin base material) 10. The first PVA-based resin layer is typically formed by applying a coating liquid containing a halide and a PVA-based resin to the first main surface of a thermoplastic resin base material and drying it.

As described above, the coating liquid contains a halide and a PVA-based resin. The coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, 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 preferable. 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 thermoplastic resin base material. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Additives may be added to the coating liquid. Examples of the additive include a plasticizer, a surfactant and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

As the PVA-based resin, any suitable resin can be adopted. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the 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-based resin having such a degree of saponification, a polarizing element having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur. As described above, the PVA-based resin preferably contains an acetacetyl-modified PVA-based resin.

The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the intended 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.

As the halide, any suitable halide can be adopted. For example, iodide and sodium chloride can be mentioned. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.

The amount of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is a department. If the amount of the halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out and the finally obtained polarizing element may become cloudy.

Generally, the stretching of the PVA-based resin layer increases the orientation of the polyvinyl alcohol molecules in the PVA-based resin. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become more oriented. The orientation may be disturbed and the orientation may decrease. In particular, when the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin. In this case, the tendency of the degree of orientation to decrease is remarkable. For example, while stretching a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water. On the other hand, by preparing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material, and stretching the laminate in air at a high temperature (auxiliary stretching) before stretching it in boric acid water. , Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecule 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 makes it possible to improve the optical characteristics of the polarizing element obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water.

Any appropriate method can be adopted as the coating method of the coating liquid. 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 (comma coating method, etc.) and the like can be mentioned. The coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.

The thickness of the first PVA-based resin layer is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

The second PVA-based resin layer 22'is formed on the second main surface of the thermoplastic resin base material 10 by the same procedure as described above. In this way, as shown in FIG. 2A, a laminate of the substrate, the first PVA-based resin layer, and the second PVA-based resin layer (hereinafter, resin substrate / PVA-based resin layer laminate). ) Is obtained. The first PVA-based resin layer (finally, the first polarizing element layer) and the second PVA-based resin layer (finally, the second polarizing element layer) to be formed are the same. It may have a configuration or a configuration different from each other.

As described above, the first and / or second main surfaces of the thermoplastic resin substrate may be subjected to surface modification treatment (for example, corona treatment) and / or an easy-adhesion layer may be formed. good.

F-2. Formation of Polarizer Layer Next, the resin base material / PVA-based resin layer laminate was subjected to stretching and dyeing, and as shown in FIG. 2 (b), the first PVA-based resin layer 21'was subjected to the first polarizing element. The layer 21 is used, and the second PVA-based resin layer 22'is used as the second polarizing element layer 22. As a result, the optical laminate according to the above items A to E is obtained. For example, the polarizing element layer is formed by a method including subjecting a resin base material / PVA-based resin layer laminate to an aerial auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. obtain. Such a method is described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The description of these patent documents is incorporated herein by reference.

F-2-1. Aerial auxiliary stretching treatment In particular, in order to obtain high optical properties, a two-stage stretching method that combines dry stretching (auxiliary stretching) and boric acid water stretching is selected. By introducing auxiliary stretching as in the case of two-stage stretching, it is possible to stretch while suppressing the crystallization of the thermoplastic resin base material, and excessive crystallization of the thermoplastic resin base material in the subsequent stretching in boric acid water. This solves the problem that the stretchability is lowered, and the laminated body can be stretched at a higher magnification. Furthermore, when the PVA-based resin is applied on the thermoplastic resin base material, it is compared with the case where the PVA-based resin is applied on a normal metal drum in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material. Therefore, it is necessary to lower the coating temperature, and as a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical characteristics cannot be obtained. On the other hand, by introducing auxiliary stretching, it is possible to improve the crystallinity of the PVA-based resin even when the PVA-based resin is applied on the thermoplastic resin, and it is possible to achieve high optical characteristics. Become. At the same time, by increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration and dissolution of the orientation of the PVA-based resin when immersed in water in a subsequent dyeing step or stretching step. , It becomes possible to achieve high optical characteristics.

The stretching method of the aerial auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Although good, free-end stretching can be positively adopted in order to obtain high optical properties. In one embodiment, the aerial stretching treatment includes a heating roll stretching step of stretching the laminate by the difference in peripheral speed between the heating rolls while transporting the laminated body in the longitudinal direction thereof. The aerial stretching treatment typically includes a zone stretching step and a heating roll stretching step. The order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heating roll stretching step are performed in this order. Further, in another embodiment, in the tenter stretching machine, the film is stretched by grasping the end portion of the film and widening the distance between the tenters in the flow direction (the widening of the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (perpendicular to the flow direction) is set to approach arbitrarily. Preferably, it can be set to be closer to the free end stretching with respect to the stretching ratio in the flow direction. In the case of free-end stretching, the shrinkage rate in the width direction = (1 / stretching ratio) ^1/2 .

The aerial auxiliary stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The draw ratio in the aerial auxiliary stretching is preferably 2.0 to 3.5 times. The maximum draw ratio when the aerial auxiliary stretching and the underwater stretching are combined is preferably 5.0 times or more, more preferably 5.5 times or more, still more preferably 6.0 times with respect to the original length of the laminated body. That is all. In the present specification, the "maximum draw ratio" means the draw ratio immediately before the laminate breaks, and separately confirms the draw ratio at which the laminate breaks, and means a value 0.2 lower than that value.

The stretching temperature of the aerial auxiliary stretching can be set to an arbitrary appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably the glass transition temperature (Tg) or higher of the thermoplastic resin base material, more preferably the glass transition temperature (Tg) of the thermoplastic resin base material (Tg) + 10 ° C. or higher, and particularly preferably Tg + 15 ° C. or higher. On the other hand, the upper limit of the stretching temperature is preferably 170 ° C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and suppress defects due to the crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). can.

F-2-2. Insolubilization treatment, dyeing treatment and cross-linking treatment If necessary, an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing a PVA-based resin layer in a boric acid aqueous solution. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, a cross-linking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The cross-linking treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. Details of the insolubilization treatment, the dyeing treatment and the crosslinking treatment are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 (above).

F-2-3. Underwater stretching treatment The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80 ° C.), and the PVA-based resin layer is crystallized. It is possible to stretch at a high magnification while suppressing the above. As a result, a stator having excellent optical characteristics can be manufactured.

Any suitable method can be adopted as the stretching method of the laminated body. Specifically, it may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Preferably, free-end stretching is selected. The stretching of the laminate may be carried out in one step or in multiple steps. In the case of performing in multiple stages, the draw ratio (maximum draw ratio) of the laminated body described later is the product of the draw ratios of each stage.

The underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid water stretching). By using the boric acid aqueous solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer. Specifically, boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, can be stretched satisfactorily, and a stator having excellent optical characteristics can be produced.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and particularly preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is. 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 polarizing element having higher characteristics can be produced. In addition to boric acid or 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.

Preferably, the iodide is added to the stretching bath (boric acid aqueous solution). By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, and more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.

The stretching temperature (liquid temperature of the stretching bath) is preferably 40 ° C. to 85 ° C., more preferably 60 ° C. to 75 ° C. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing dissolution. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60 ° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40 ° C., it may not be stretched well even in consideration of the plasticization of the thermoplastic 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, and there is a possibility that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by stretching in water is preferably 1.5 times or more, more preferably 3.0 times or more. The total draw ratio of the laminated body is preferably 5.0 times or more, more preferably 5.5 times or more, with respect to the original length of the laminated body. By achieving such a high draw ratio, it is possible to manufacture a polarizing element having extremely excellent optical characteristics. Such a high draw ratio can be achieved by adopting an underwater stretching method (boric acid underwater stretching).

F-2-4. Dry shrinkage treatment The dry shrinkage treatment may be performed by heating the entire zone by heating the zone, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably both are used. By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminated body and produce a polarizing element having an excellent appearance. Specifically, by drying the laminated body along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the dry shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 2% to 6%. By using the heating roll, the laminated body can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.

FIG. 3 is a schematic view showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. For example, one surface of the laminate 200 (for example, thermoplasticity) is arranged. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin substrate surface).

Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and particularly preferably 70 ° C. to 80 ° C. The crystallinity of the thermoplastic resin can be satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with an air blowing means. By using both drying with a heating roll and hot air drying together, a steep temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30 ° C to 100 ° C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.

F-2-5. Other Treatments Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

As described above, as shown in FIG. 2B, the optical laminate according to the above items A to E can be obtained.

F-3. Fabrication of Polarizing Plate Next, as shown in FIG. 2C, the first protective layer 31 is laminated on the opposite side of the resin substrate 10 of the first polarizing element layer 21. The first protective layer may support the first polarizing layer when the first polarizing layer (including the polarizing plate including the polarizing plate) is peeled off. Finally, as shown in FIG. 2D, the laminate of the first polarizing layer 21 and the first protective layer 31 can be peeled off from the optical laminate to obtain the first polarizing plate 201. .. The remaining portion (a laminate of the resin base material 10 and the second polarizing element layer 22) becomes the second polarizing plate 202. That is, in the second polarizing plate 202, the resin base material 10 can function as a protective layer. Before peeling, the second protective layer 32 may be laminated on the side opposite to the resin base material 10 of the second polarizing element layer 22. In this case, the second polarizing plate has a resin base material, a second polarizing element layer, and a second protective layer. As described in the above item A, in the optical laminate, the peeling force between the resin base material and the second polarizing element layer is set to be larger than the peeling force between the resin base material and the first polarizing element layer. Thereby, two polarizing plates can be obtained from the optical laminate without any trouble (typically, without undesired peeling and peeling failure).

After peeling, another protective layer may be laminated on the opposite side of the first polarizing layer 21 to the first protective layer 31 in the first polarizing plate 201. Further, when the second protective layer 32 is laminated on the side opposite to the resin base material 10 of the second polarizing element layer 22 before peeling, the resin base material may be peeled off from the second polarizing plate. The second polarizing plate from which the resin base material has been peeled off may be used as it is, or another protective layer may be laminated on the peeled surface.

As described above, two polarizing plates (first polarizing plate and second polarizing plate) can be obtained from one optical laminate.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.
(1) Thickness Measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000").
(2) Peeling force An adhesive layer is provided on the surface of one of the polarizing layers of the optical laminates of Examples and Comparative Examples, the optical laminate is attached to a glass plate, and the surface of the other polarizing layer is used for reinforcement. A polyimide tape (polyimide adhesive tape No. 360A manufactured by Nitto Denko Corporation) was attached to prepare a sample for measurement. Make a notch with a cutter knife between the polarizing element layer on the polyimide tape side of this measurement sample and the resin substrate so that the polarizing element layer and the polyimide tape are at an angle of 90 ° with respect to the resin substrate surface. The force (N / 15 mm) required for start-up and peeling at a peeling speed of 3000 mm / min was measured by an angleable type adhesive / film peeling analyzer "VPA-2" (manufactured by Kyowa Surface Chemistry Co., Ltd.).

[Example 1]
1. 1. Formation of PVA-based resin layer As a resin base material, an amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ° C. is used. board.
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, Nippon Synthetic Chemical Industry Co., Ltd. A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin mixed with the trade name "Gosefimer Z200") at a ratio of 9: 1.
The first main surface of the resin base material was subjected to corona treatment. The first PVA-based resin layer (thickness 11 μm) was formed by applying the above coating liquid to the corona-treated first main surface and drying at 60 ° C.
Next, the second main surface of the resin base material was subjected to corona treatment. An easy-adhesive layer was formed on the second main surface treated with corona. Specifically, acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z200", polymerization degree 1200, saponification degree 99.0 mol% or more, acetacetyl modification degree 4.6%) A mixture of a 4.0% aqueous solution, a modified polyolefin resin aqueous dispersion (manufactured by Unitica, trade name "Arrow Base SE1030N", solid content concentration 22%) and pure water (solid content concentration 4.0%) was prepared. The mixture was applied so that the thickness after drying was 2 μm, and dried at 60 ° C. for 3 minutes to form an easy-adhesion layer. Here, the solid content mixing ratio of the acetacetyl-modified PVA and the modified polyolefin in the mixed solution was 30:70. Next, the surface of the easy-adhesion layer was subjected to corona treatment, and the coating liquid was applied to the corona-treated surface and dried at 60 ° C. to form a second PVA-based resin layer (thickness 11 μm). In this way, a resin base material / PVA-based resin layer laminate was produced.

2. 2. Preparation of Polarizer Layer The resin base material / PVA-based resin layer laminate obtained above is placed 2.0 times in the vertical direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120 ° C. Stretched (auxiliary stretching in the air).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Then, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the obtained polarizing element layer had a predetermined simple substance transmittance. In this example, 0.2 parts by weight of iodine was mixed with 100 parts by weight of water, and 1.0 part by weight of potassium iodide was mixed and immersed in the obtained iodine aqueous solution for 60 seconds (dyeing treatment). ..
Then, it was immersed in a cross-linked bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, the laminate is immersed in an aqueous solution of boric acid having a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water). However, uniaxial stretching was performed between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction) (underwater stretching treatment).
Then, the laminate was immersed in a washing bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the dry shrinkage treatment was 2%.
In this way, an optical laminate having a first polarizing element layer (thickness 5 μm) and a second polarizing element layer (thickness 5 μm) on both sides of the resin base material (thickness 30 μm) was obtained. The peeling force between the resin base material and the first polarizing element layer was 0.2 N / 15 mm, and the peeling force between the resin base material and the second polarizing element layer was 1.2 N / 15 mm.

3. 3. Preparation of Polarizing Plate An acrylic film (thickness 40 μm) as a first protective layer was bonded to the opposite side of the resin substrate of the first polarizing element layer via an ultraviolet curable adhesive. Specifically, the curable adhesive was coated so as to have a total thickness of 1.0 μm, and bonded using a roll machine. Then, a UV ray was irradiated from the acrylic film side to cure the adhesive.
Next, the laminated body of the first polarizing element layer and the first protective layer was peeled off from the optical laminated body to obtain a first polarizing plate. By the peeling, a second polarizing plate was obtained as a laminate of the resin base material and the second polarizing element layer. There was no problem with peeling, and both the first polarizing plate and the second polarizing plate were obtained satisfactorily. Further, in the obtained second polarizing plate, there was no practical problem in the adhesion between the resin base material and the second polarizing element layer. The results are shown in Table 1.

[Example 2]
An optical laminate was produced in the same manner as in Example 1 except that the thickness of the easy-adhesion layer was 1 μm. The peeling force between the resin base material and the first polarizing element layer was 0.2 N / 15 mm, and the peeling force between the resin base material and the second polarizing element layer was 0.8 N / 15 mm. Further, in the same manner as in Example 1, a first polarizing plate and a second polarizing plate were obtained from the optical laminate. There was no problem with peeling, and both the first polarizing plate and the second polarizing plate were obtained satisfactorily. Further, in the obtained second polarizing plate, there was no practical problem in the adhesion between the resin base material and the second polarizing element layer. The results are shown in Table 1.

[Example 3]
The first PVA-based resin layer is formed without corona treatment on the first main surface of the resin base material, and only the corona treatment is applied to the second main surface (that is, an easy-adhesion layer is formed). An optical laminate was produced in the same manner as in Example 1 except that a second PVA-based resin layer was formed. The peeling force between the resin base material and the first polarizing element layer was 0.1 N / 15 mm, and the peeling force between the resin base material and the second polarizing element layer was 0.2 N / 15 mm. Further, in the same manner as in Example 1, a first polarizing plate and a second polarizing plate were obtained from the optical laminate. There was no problem with peeling, and both the first polarizing plate and the second polarizing plate were obtained satisfactorily. Further, in the obtained second polarizing plate, the adhesive force between the resin base material and the second polarizing element layer was insufficient, but it was sufficiently practical if the second protective layer was provided. .. The results are shown in Table 1.

[Comparative Example 1]
The first main surface of the resin base material was subjected to corona treatment to form the first PVA-based resin layer, and the second main surface was subjected to corona treatment only (that is, without forming an easy-adhesion layer). ) An optical laminate was produced in the same manner as in Example 1 except that the second PVA-based resin layer was formed. The peeling force between the resin base material and the first polarizing element layer was 0.2 N / 15 mm, and the peeling force between the resin base material and the second polarizing element layer was 0.2 N / 15 mm. Further, an attempt was made to obtain a first polarizing plate and a second polarizing plate from the optical laminate in the same manner as in Example 1, but peeling occurred between the resin base material and the second polarizing element, and the second polarizing plate was formed. The polarizing plate of No. 2 could not be obtained. The results are shown in Table 1.

[evaluation]
As is clear from comparing Examples 1 to 3 with Comparative Example 1, according to the embodiment of the present invention, the peeling force between the resin base material and the second polarizing element layer is controlled by the resin base material and the first polarizing layer. By increasing the peeling force from the child layer, two polarizing plates can be satisfactorily obtained from one optical laminate.

The optical laminate of the present invention can be suitably used for producing a polarizing plate.

10 Resin base material 21 First polarizing element layer 22 Second polarizing element layer 31 First protective layer 32 Second protective layer 100 Optical laminated body

Claims (9)

It has a resin base material, a first polarizing element layer provided on one side of the resin base material, and a second polarizing element layer provided on the other side of the resin base material.
The peeling force between the resin base material and the second polarizing element layer is larger than the peeling force between the resin base material and the first polarizing element layer.
Optical laminate. The first aspect of the present invention, wherein the peeling force between the resin base material and the second polarizing element layer is 0.1 N / 15 mm or more larger than the peeling force between the resin base material and the first polarizing element layer. Optical laminate. The optical laminate according to claim 1 or 2, wherein the peeling force between the resin base material and the second polarizing element layer is 0.5 N / 15 mm or more. The optical laminate according to claim 3, wherein an easy-adhesive layer is provided between the resin base material and the second polarizing element layer. The optical laminate according to claim 4, wherein the easy-adhesive layer contains a polyvinyl alcohol-based component and a polyolefin-based component. The optical laminate according to claim 5, wherein the polyvinyl alcohol-based component contains acetacetyl-modified polyvinyl alcohol. The optical laminate according to any one of claims 1 to 6, further comprising a first protective layer on the opposite side of the first polarizing element layer from the resin base material. The optical laminate according to claim 7, further comprising a second protective layer on the opposite side of the second polarizing element layer from the resin base material. Forming the first polyvinyl alcohol-based resin layer on one side of the resin substrate,
Forming a second polyvinyl alcohol-based resin layer on the other side of the resin base material,
The laminate of the resin base material, the first polyvinyl alcohol-based resin layer, and the second polyvinyl alcohol-based resin layer is subjected to stretching and dyeing, and the first polyvinyl alcohol-based resin layer and the second polyvinyl alcohol-based resin layer are subjected to stretching and dyeing. The optical laminate according to any one of claims 1 to 6 is obtained by using the alcohol-based resin layer as a first polarizing element layer and a second polarizing element layer, respectively.
To provide the first protective layer on the opposite side of the first polarizing element layer from the resin base material.
The laminate of the first polarizing layer and the first protective layer is peeled from the optical laminate to form a first polarizing plate, and
The laminate of the resin base material and the second polarizing element layer is used as the second polarizing plate.
A method for manufacturing a polarizing plate, including.

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