KR102562326B1 - Laminate and method of manufacturing the laminate - Google Patents

Abstract

The present invention provides a laminate having excellent adhesion in which both peeling from the resin substrate side and peeling from the polyvinyl alcohol-based resin layer side are suppressed.
The laminate of the present invention is a laminate having a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin layer in this order, wherein the undercoat layer and the polyvinyl alcohol-based resin layer are provided in this order on the resin substrate. It is formed by eluting 5% by volume to 70% by volume of the undercoat coating layer in the undercoat coating layer and the polyvinyl alcohol-based resin coating layer, and the undercoat coating layer is polyvinyl alcohol Two or more types of resin components including system components are included, and the blending ratio of the polyvinyl alcohol-based component in the resin component of the undercoat coating layer is 5% to 50%.

Description

Laminate and method of manufacturing the laminate

The present invention relates to a laminate having a polyvinyl alcohol-based resin layer.

A method of obtaining a polarizing film by forming a polyvinyl alcohol-based resin layer on a resin substrate, dyeing and stretching the laminate has been proposed (for example, Patent Document 1). According to such a method, since a polarizing film having a thin thickness is obtained, it is attracting attention as being able to contribute to a reduction in the thickness of, for example, an image display device.

The polarizing film may be used as it is stacked on the resin substrate. In such an embodiment, it is required that the polyvinyl alcohol-based resin layer (polarizing film) and the resin substrate have sufficient adhesion. Specifically, the polyvinyl alcohol-based resin layer should not be peeled off from the resin substrate in the production of the polarizing film (e.g., in stretching and transport), the polarizing film and the resin substrate should not be peeled off during rework, processing (e.g., It is required that the polarizing film or the resin substrate not be lifted against impact during punching) or during use.

In order to improve the adhesion, it is proposed to provide an undercoat layer containing a polyvinyl alcohol-based material between a resin substrate and a polyvinyl alcohol-based resin layer (Patent Document 2). According to this technique, although peeling from the resin substrate side can be preferably suppressed, suppression of peeling from the polyvinyl alcohol-based resin layer side is insufficient.

Japanese Unexamined Patent Publication No. 2000-338329 Japanese Patent No. 4950357

The present invention has been made to solve the above problems, and its main object is to provide a laminate having excellent adhesion in which both peeling from the resin substrate side and peeling from the polyvinyl alcohol-based resin layer side are suppressed.

ADVANTAGE OF THE INVENTION According to this invention, the laminated body which has a resin base material, an undercoat layer, and a polyvinyl alcohol-type resin layer in this order is provided. In the undercoat layer and the polyvinyl alcohol-based resin layer, 5% to 70% by volume of the undercoat coated layer in the undercoat coated layer and the polyvinyl alcohol based resin coated layer provided in this order on the resin substrate corresponds It is formed by eluting to a polyvinyl alcohol-type resin coating layer. In addition, the undercoat coating layer contains two or more types of resin components containing polyvinyl alcohol-based components, and the blending ratio of the polyvinyl alcohol-based component in the resin component in the undercoat coating layer is 5% to 50%. am.

In one embodiment, the thickness of the undercoat layer is 0.2 μm to 2.0 μm.

In one embodiment, the polyvinyl alcohol-based component includes acetoacetyl-modified polyvinyl alcohol.

In one embodiment, the undercoat coating layer includes the polyvinyl alcohol-based component and the polyolefin-based component.

In one embodiment, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (polyvinyl alcohol-based component: polyolefin-based component) is 5:95 to 50:50.

According to another situation of this invention, the manufacturing method of the laminated body which has a resin base material, an undercoat layer, and a polyvinyl alcohol-type resin layer in this order is provided. The manufacturing method of the laminate includes forming an undercoat coating layer on one side of a resin substrate and forming a polyvinyl alcohol-based resin coating layer on the surface of the undercoat coating layer, and 5% to 70% by volume of the undercoat coating layer. It includes eluting the volume % into the polyvinyl alcohol-based resin coating layer to make the undercoat coating layer and the polyvinyl alcohol-based resin coating layer respectively an undercoat layer and a polyvinyl alcohol-based resin layer. The undercoat coating layer contains two or more types of resin components including a polyvinyl alcohol-based component, and the blending ratio of the polyvinyl alcohol-based component in the resin component of the undercoat coating layer is 5% to 50%.

In one embodiment, the thickness of the undercoat layer is 0.2 μm to 2.0 μm.

In one embodiment, the polyvinyl alcohol-based component includes acetoacetyl-modified polyvinyl alcohol.

In one embodiment, the undercoat coating layer includes the polyvinyl alcohol-based component and the polyolefin-based component.

In one embodiment, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (polyvinyl alcohol-based component: polyolefin-based component) is 5:95 to 50:50.

According to another situation of this invention, the optical laminated body which has a resin substrate, an undercoat layer, and a polarizing film in this order is provided. The optical laminate is a polarizing film in which a dichroic material is adsorbed and oriented in a polyvinyl alcohol-based resin layer of the laminate.

According to another situation of this invention, the manufacturing method of the optical laminated body which has a resin base material, an undercoat layer, and a polarizing film in this order is provided. The manufacturing method of the said optical laminated body manufactures the laminated body which has a resin base material, an undercoat layer, and a polyvinyl alcohol-type resin layer in this order by the manufacturing method of the said laminated body, and the said polyvinyl alcohol-type resin layer It includes dyeing and stretching to make a polarizing film.

According to the present invention, an undercoat coating layer containing a resin substrate and a polyvinyl alcohol-based component and a polyvinyl alcohol-based resin coating layer are formed in this order, and a portion of the undercoat coating layer is a predetermined polyvinyl alcohol-based resin coating layer. By eluting at an elution rate of , a layered product having excellent adhesion can be obtained.

1 is a SEM observation photograph of an undercoat application layer cross section (a) and an undercoat layer cross section (b) in the manufacture of a laminate of a reference example.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

A. Manufacturing method of laminate

The present invention provides a method for producing a laminate comprising a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") layer in this order. The manufacturing method of the laminate of the present invention,

Forming an undercoat coating layer on one side of the resin substrate and forming a PVA-based resin coating layer on the surface of the undercoat coating layer;

Eluting 5% by weight to 70% by weight of the undercoat coating layer into the PVA-based resin coating layer to make the undercoat coating layer and the PVA-based resin coating layer an undercoat layer and a PVA-based resin layer, respectively. do.

A-1. Formation of the undercoat coating layer

The undercoat coating layer is typically formed by applying a composition for forming an undercoat layer to one side of a resin substrate.

Any suitable material can be employed as a constituent material of the resin substrate. Examples thereof include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins, olefin-based resins such as polypropylene, (meth)acrylic-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. there is. Preferably, a polyethylene terephthalate-based resin is used. Among them, amorphous polyethylene terephthalate-based resins are preferably used. Specific examples of the amorphous polyethylene terephthalate-based resin include copolymers further containing isophthalic acid as dicarboxylic acid and copolymers further containing cyclohexanedimethanol as glycol.

The glass transition temperature (Tg) of the resin substrate is preferably 170°C or lower. By using such a resin substrate, it is possible to sufficiently secure stretchability while suppressing crystallization of the PVA-based resin layer in production of an optical laminate described later. It is more preferable that it is 120 degreeC or less in consideration of performing plasticization of the resin base material with water and extending|stretching in water satisfactorily. In one embodiment, the glass transition temperature of the resin substrate is preferably 60°C or higher. By using such a resin substrate, problems such as deformation of the resin substrate (e.g., occurrence of irregularities, sagging, wrinkles, etc.) can be prevented when a coating solution containing a PVA-based resin described later is applied and dried. there is. In addition, stretching of the laminate can be performed at a desired temperature (for example, about 60°C to 70°C). In another embodiment, the glass transition temperature lower than 60°C may be sufficient as long as the resin substrate does not deform during application and drying of the coating liquid containing the PVA-based resin. In addition, the glass transition temperature (Tg) is a value obtained according to JIS K 7121.

In one embodiment, the resin substrate preferably has a water absorption of 0.2% or more, more preferably 0.3% or more. Such a resin substrate can absorb water and can be plasticized by the water acting as a plasticizer. As a result, the stretching stress can be greatly reduced in the underwater stretching, and the stretching property can be excellent. On the other hand, the water absorption of the resin substrate 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 significantly deteriorating the dimensional stability of the resin base material during production of the optical laminate and deterioration of the appearance of the obtained optical laminate. Moreover, it can prevent fracture|rupture at the time of extending|stretching in water, or peeling of a PVA system resin layer from a resin base material. In addition, water absorption is a value determined according to JIS K 7209.

The thickness of the resin substrate is preferably 20 μm to 300 μm, more preferably 30 μm to 200 μm.

The surface of the resin substrate may be subjected to a surface modification treatment (eg, corona treatment) in advance, or an easily adhesive layer may be formed. According to such a process, adhesiveness can further be improved.

The composition for forming the undercoat layer includes two or more resin components including a polyvinyl alcohol-based component. Any appropriate PVA-based resin can be used as the polyvinyl alcohol-based component. Specifically, polyvinyl alcohol and denatured polyvinyl alcohol are exemplified. Examples of the modified polyvinyl alcohol include polyvinyl alcohol modified with an acetoacetyl group, a carboxylic acid group, an acryl group, and/or a urethane group. Among these, acetoacetyl-modified PVA is preferably used. As the acetoacetyl-modified PVA, a polymer having at least a repeating unit represented by the following formula (I) is preferably used.

[Formula (I)]

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

The average degree of polymerization of the 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 higher. The pH of a 4% by weight aqueous solution of acetoacetyl-modified PVA is preferably 3.5 to 5.5. In addition, the average degree of polymerization and degree of saponification can be obtained according to JIS K 6726-1994.

As other resin components that can be used together with the polyvinyl alcohol-based component, any suitable resin component can be used. Specific examples include polyolefin-based components, polyester-based components, polyurethane-based components, polypropylene-based components, styrene-butadiene-based components, vinylidene chloride-based components, and vinyl chloride-based components. By using the other resin component in combination with the polyvinyl alcohol-based component, a laminate having excellent adhesion can be obtained. Further, in the case of using a polyolefin-based component, an effect of improving the external appearance can be obtained in addition to the improvement of the adhesiveness.

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

Among the monomer components constituting the polyolefin-based resin, the proportion of the olefin component 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-based resin can be dispersed in water, and an undercoat layer can be formed satisfactorily. Examples of the monomer component having such a functional group include unsaturated carboxylic acids and their anhydrides, half esters and half amides of unsaturated dicarboxylic acids. Specific examples thereof 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 80000.

As the polyester-based component, any suitable polyester-based resin may be used. As a specific example of polyester-type resin, the copolymer formed by polycondensation of a dicarboxylic acid component and a glycol component is mentioned.

The dicarboxylic acid component constituting the polyester resin is not particularly limited, and examples thereof include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 3-tert-butylisophthalic acid, oxalic acid, succinic acid, and anhydride. Succinic acid, adipic acid, azelaic acid, sebacic acid, dodecane diacid, icosane diacid, fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, dimer acid, etc. alicyclic dicarboxylic acids such as unsaturated aliphatic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acids, 1,3-cyclohexanedicarboxylic acids, 1,2-cyclohexanedicarboxylic acids, tetrahydrophthalic acids, and anhydrides thereof.

The glycol component constituting the polyester resin is not particularly limited, and examples thereof include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 2-methyl-1,3- propanediol, 1,5-pentanediol, neopentylglycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, etc. and alicyclic glycols such as aliphatic glycols, 1,4-cyclohexanedimethanol, and 1,3-cyclobutane dimethanol.

The molecular weight of the polyester-based resin is, for example, 5000 to 80000.

In the composition for forming the undercoat layer, the blending ratio of the polyvinyl alcohol-based component and the other resin component (polyvinyl alcohol-based component: other resin component, solid content weight ratio) is 5:95 to 50:50, more preferably 20 :80 to 50:50. If the compounding ratio of the polyvinyl alcohol-based component is outside the above range, there is a risk that sufficient adhesion may not be obtained. Specifically, when peeling the PVA-based resin layer from the resin substrate, the required peeling force decreases and there is a possibility that sufficient adhesiveness may not be obtained. On the other hand, when the polyvinyl alcohol-based component is too small, the peeling force required when peeling the resin substrate from the PVA-based resin layer decreases, and there is a risk that sufficient adhesion may not be obtained.

The composition for forming an undercoat layer is preferably water-based. The composition for forming the undercoat layer may contain an organic solvent. As an organic solvent, ethanol, isopropanol, etc. are mentioned, for example. The solid content concentration of the composition for forming an undercoat layer is preferably 1.0% by weight to 10% by weight.

You may mix|blend additives with the composition for undercoat layer formation. As an additive, a crosslinking agent etc. are mentioned, for example. Examples of the crosslinking agent include methylol compounds such as oxazoline, boric acid, and trimethylolmelamine, carbodiimide, isocyanate compounds, and epoxy compounds. The compounding amount of additives in the composition for forming an undercoat layer can be appropriately set depending on the purpose and the like. For example, the blending amount of the crosslinking agent is preferably 10 parts by weight or less, more preferably 0.01 to 10 parts by weight, still more preferably 0.1 parts by weight, based on 100 parts by weight of the total of the polyvinyl alcohol-based component and other resin components. part to 5 parts by weight.

Arbitrary suitable methods can be adopted as a method of applying the composition for forming an undercoat layer. For example, roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spray coating method, knife coating method (comma coating method etc.), etc. are mentioned.

The composition for forming the undercoat layer is preferably applied so that the obtained undercoat coating layer has a thickness (thickness after drying) of 0.3 μm to 3.0 μm, preferably 0.5 μm to 2.0 μm. If the thickness of the undercoat coating layer is too thin, there is a risk that sufficient adhesiveness may not be obtained. On the other hand, if the thickness of the undercoat coating layer is too thick, problems such as non-uniformity in the coating film obtained during formation of the PVA-based resin coating layer described later may occur.

After application of the composition for forming an undercoat layer, the coating film may be dried. The drying temperature is, for example, 50°C or higher.

A-2. Formation of PVA-based resin coating layer

The PVA-based resin coating layer is typically formed by applying a coating liquid containing a PVA-based resin to the surface of the undercoat coating layer. The surface of the undercoat coating layer to which the coating solution containing the PVA-based resin is applied may be previously subjected to surface modification treatment (eg, corona treatment). According to such a process, adhesiveness can further be improved.

As a coating liquid containing the said PVA-type resin, the solution which melt|dissolved the PVA-type resin in the solvent is used typically. Any suitable resin can be employed as the PVA-based resin. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification 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 film having excellent durability can be obtained. When the degree of saponification is too high, there is a possibility of gelation.

The average degree of polymerization of the PVA-based resin may be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. In addition, the average degree of polymerization can be obtained according to JIS K 6726-1994.

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. can be heard These can be used individually or in combination of 2 or more types. Among these, water is preferable. The concentration of the PVA-based resin in the coating liquid is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed.

You may mix|blend additives 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 adhesive component is mentioned, for example. Adhesion can be further improved by using an easily adhesive component. As the easily adhesive component, for example, modified PVA such as acetoacetyl-modified PVA is used.

As the method of applying the coating liquid, the same method as the method of applying the composition for forming the undercoat layer may be employed. After application, the coating film may be dried. Drying may be room temperature (about 25°C) drying or heat drying (for example, 50°C or higher).

A-3. Elution of the undercoat coating layer to the PVA-based resin coating layer

Elution of the undercoat coating layer to the PVA-based resin coating layer is due to the high affinity between the polyvinyl alcohol-based component in the undercoat coating layer and the PVA-based resin in the PVA-based resin coating layer, It may occur spontaneously simultaneously with formation (substantially application of the coating liquid). In addition, the elution may decrease or end according to a decrease in the driving force due to the concentration gradient of the polyvinyl alcohol-based component or the like. In the present invention, the reduction in the thickness of the undercoat coating layer due to the elution stops and the elution is considered to be completed when the thickness reaches a certain level, and the subsequent undercoat coating layer and the PVA-based resin coating layer are respectively undercoated. layer and PVA-based resin layer.

By the elution, 5% by volume to 70% by volume, preferably 8% by volume to 50% by volume, more preferably 10% by volume to 40% by volume of the undercoat coating layer elutes to the PVA-based resin coating layer. When the elution rate is within the range, a layered product having excellent adhesion can be obtained. The dissolution rate can be increased by, for example, increasing the compounding ratio of the polyvinyl alcohol-based component in the composition for forming an undercoat layer.

The temperature environment during elution is not particularly limited, and may be, for example, 20°C to 100°C, preferably 30°C to 80°C, and more preferably 40°C to 70°C. In addition, the time required for elution (time from application of the coating liquid to completion of elution) may be, for example, from immediately after coating to about 10 minutes. The elution treatment may also serve as a drying treatment of the coating film at the time of forming the PVA-based resin coating layer.

The thickness of the undercoat layer formed through the elution is preferably 0.2 μm to 2.0 μm, more preferably 0.3 μm to 1.8 μm. Further, the thickness of the PVA-based resin layer is typically 3 µm to 40 µm, more preferably 3 µm to 20 µm.

B. laminate

The present invention also provides a laminate having a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin layer in this order. In the laminate, the undercoat layer and the polyvinyl alcohol-based resin layer are composed of 5% by volume to 70% by volume of the undercoat-coated layer and the polyvinyl-alcohol-based resin coated layer provided in this order on the resin substrate. It is formed by volume % eluting to the said polyvinyl alcohol-type resin coating layer. Therefore, in one embodiment of the present invention, the PVA-based resin layer of the laminate includes an elution component derived from the undercoat coating layer, and the undercoat layer is formed by remaining after excluding the elution component from the undercoat coating layer. It can be. In addition, the undercoat coating layer contains two or more types of resin components containing polyvinyl alcohol-based components, and the blending ratio of the polyvinyl alcohol-based component in the resin component of the undercoat coating layer is 5% to 50%. am. By setting it as such a structure, both peeling from the resin base material side and peeling from the polyvinyl alcohol-type resin layer side can be suppressed, and excellent adhesiveness can be obtained.

The laminate of the present invention can be typically manufactured by the manufacturing method described in the above item A. Therefore, the materials and methods for forming each layer can be made as described in item A.

C. Manufacturing method of optical laminate

This invention also provides the manufacturing method of the optical laminated body which has a resin base material, an undercoat layer, and a polarizing film in this order. The manufacturing method of the optical laminate of the present invention includes producing a laminate having a resin base material, an undercoat layer, and a PVA-based resin layer in this order by the manufacturing method of the laminate described in item A, and the PVA coefficient It includes dyeing and stretching the stratum into a polarizing film. In addition to dyeing and stretching, the PVA-based resin layer may be suitably subjected to treatment for turning the PVA-based resin layer into a polarizing film. Examples of treatment for forming a polarizing film include insolubilization treatment, crosslinking treatment, washing treatment, and drying treatment. In addition, the number of times, order, etc. of such a process are not specifically limited.

(dye treatment)

The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance. Preferably, it is carried out by adsorbing a dichroic substance to the PVA-based resin layer. As the adsorption method, for example, a method of immersing a PVA-based resin layer (laminate) in a dye containing a dichroic substance, a method of coating the dye solution on a PVA-based resin layer, and a method of applying the dye solution to a PVA-based resin layer. The method of spraying etc. are mentioned. Preferably, it is a method of immersing a PVA-type resin layer in a dyeing solution. This is because dichroic substances can adsorb satisfactorily.

Examples of the dichroic substance include iodine and organic dyes. These can be used individually or in combination of 2 or more types. The dichroic material is preferably iodine. When iodine is used as the dichroic material, the dye solution is preferably an iodine aqueous solution. The compounding amount of iodine is preferably 0.1 part by weight to 0.5 part by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to blend iodide in an aqueous solution of iodine. 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. Among these, potassium iodide is preferable. The blending amount of iodide is preferably from 0.02 part by weight to 20 parts by weight, more preferably from 0.1 part by weight to 10 parts by weight, based on 100 parts by weight of water.

The liquid temperature of the dyeing solution at the time of dyeing is preferably 20°C to 50°C in order to suppress dissolution of the PVA-based resin. In the case of immersing the PVA-based resin layer in the dye solution, the immersion time is preferably 5 seconds to 5 minutes in order to ensure the transmittance of the PVA-based resin layer. In addition, the dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the finally obtained polarizing film falls within a predetermined range. In one embodiment, the immersion time is set so that the degree of polarization of the polarizing film obtained is 99.98% or more. In another embodiment, the immersion time is set such that the single transmittance of the resulting polarizing film is 40% to 44%.

(stretching treatment)

Arbitrary suitable methods are employable as a method of stretching the laminate. Specifically, it may be fixed-end stretching (eg, a method using a tenter stretching machine) or free-end stretching (eg, a method of uniaxially stretching a laminate by passing it between rolls having different circumferential speeds). In addition, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) may be used, or sequential biaxial stretching may be used. Stretching of the laminate may be performed in one step or in multiple steps. When performing in multiple steps, the draw ratio (maximum draw ratio) of the layered product described later is the product of the draw ratios of each step.

The stretching treatment may be an underwater stretching method performed while immersing the laminate in a stretching bath, or an air stretching method. In one embodiment, the underwater stretching treatment is performed at least once, and the underwater stretching treatment and the air stretching treatment are preferably combined. According to underwater stretching, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80° C.) of the resin substrate or the PVA-based resin layer, and the PVA-based resin layer can be stretched at a high magnification while suppressing crystallization thereof. . As a result, a polarizing film having excellent polarization characteristics can be manufactured.

As the stretching direction of the laminate, any suitable direction can be selected. In one embodiment, it extends in the longitudinal direction of a long picture-shaped laminated body. Specifically, the laminate is conveyed in the longitudinal direction, and it is the conveyance direction (MD). In another embodiment, it extends in the width direction of a long picture-shaped laminated body. Specifically, the laminate is conveyed in the longitudinal direction and is a direction (TD) orthogonal to the conveyance direction (MD).

The stretching temperature of the laminate can be set to any appropriate value depending on the forming material of the resin substrate, the stretching method, and the like. In the case of adopting the air stretching method, the stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate, more preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate (Tg) + 10°C, particularly preferably Tg+ It is 15 ℃ or more. On the other hand, the stretching temperature of the laminate is preferably 170°C or lower. By stretching at such a temperature, rapid crystallization of the PVA-based resin can be suppressed, and problems caused by the crystallization (eg, obstruction of orientation of the PVA-based resin layer by stretching) can be suppressed.

When employing an underwater stretching method as the stretching method, the liquid temperature of the stretching bath is preferably 40°C to 85°C, more preferably 50°C to 85°C. At such a temperature, it can be extended at a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60°C or higher in relation to formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40°C, there is a risk that satisfactory stretching may not be possible even considering plasticization of the resin substrate by water. On the other hand, as the temperature of the stretching bath becomes higher, the solubility of the PVA-based resin layer increases, and there is a possibility that excellent polarization characteristics may not be obtained.

When employing the underwater stretching method, it is preferable to immerse the laminate in boric acid aqueous solution and extend it (boric acid underwater stretching). By using an aqueous solution of boric acid as the stretching bath, the PVA-based resin layer can be provided with rigidity capable of withstanding the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can generate tetrahydroxyboric acid anion in an aqueous solution and cross-link it with PVA-based resin through hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and a polarizing film that can be stretched satisfactorily and has excellent polarization characteristics can be produced.

The aqueous solution of boric acid is preferably obtained by dissolving boric acid and/or a boric acid salt in water as a solvent. The concentration of boric acid is preferably 1 to 10 parts by weight based on 100 parts by weight of water. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing film with higher characteristics can be produced. In addition to boric acid or borate salts, 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, iodide is incorporated into the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably from 0.05 parts by weight to 15 parts by weight, more preferably from 0.5 parts by weight to 8 parts by weight, based on 100 parts by weight of water.

The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes. Preferably, the underwater stretching treatment is performed after the dyeing treatment.

The draw ratio (maximum draw ratio) of the laminate is preferably 4.0 times or more, more preferably 5.0 times or more with respect to the original length of the laminate. Such a high draw ratio can be achieved, for example, by adopting an underwater stretching method (boric acid underwater stretching). In addition, in this specification, "maximum draw ratio" refers to the draw ratio immediately before the laminate is broken, and the draw ratio at which the laminate is broken is checked separately, and refers to a value 0.2 lower than that value.

(insolubilization treatment)

The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. In particular, when employing an underwater stretching method, water resistance can be imparted to the PVA-based resin layer by performing insolubilization treatment. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. The liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20°C to 40°C. Preferably, the insolubilization treatment is performed after the laminate is produced and before the dyeing treatment or the underwater stretching treatment.

(Crosslinking treatment)

The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. By performing a crosslinking treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight based on 100 parts by weight of water. In addition, when crosslinking treatment is performed after the dyeing treatment, it is preferable to further mix iodide. By blending iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 to 5 parts by weight based on 100 parts by weight of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20°C to 50°C. Preferably, the crosslinking treatment is performed before the underwater stretching treatment. In a preferred embodiment, the dyeing treatment, the crosslinking treatment, and the underwater stretching treatment are performed in this order.

(cleaning treatment)

The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.

(dry processing)

The drying temperature in the drying treatment is preferably 30°C to 100°C.

D. Optical stack

The present invention also provides an optical laminate having a resin substrate, an undercoat layer, and a polarizing film in this order. In the optical laminate of the present invention, the polyvinyl alcohol-based resin layer of the laminate described in item A may be a polarizing film in which a dichroic substance is adsorbed and oriented.

The thickness of the polarizing film is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 7 μm or less, and particularly preferably 6 μm or less. On the other hand, the thickness of the polarizing film is preferably 1.0 μm or more, more preferably 2.0 μm or more.

The polarizing film is substantially the above PVA-based resin layer in which a dichroic substance is adsorbed and oriented, and preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. In this case, the single transmittance of the polarizing film (PVA-based resin layer) is preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, and particularly preferably 43.0% or more. The degree of polarization of the polarizing film (PVA-based resin layer) is preferably 99.8% or higher, more preferably 99.9% or higher, still more preferably 99.95% or higher.

The optical layered body of the present invention can be typically manufactured by the method for manufacturing an optical layered body described in item C.

E. Uses of Optical Stacks

According to the optical layered body of the present invention, the resin substrate can be used as an optical member as it is without peeling from the polarizing film. In this case, the resin substrate may function as, for example, a protective film for the polarizing film. Alternatively, the optical function film may be laminated on the polarizing film of the optical laminate through an arbitrary appropriate adhesive layer, and then the resin substrate may be peeled off. The optical functional film may function as, for example, a polarizing film protective film or a retardation film.

Example

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. In addition, the measuring method of thickness is as follows. In addition, 'parts' and '%' in the following Examples and Comparative Examples represent 'parts by weight' and '% by weight', respectively.

(thickness)

It was measured using a digital micrometer (manufactured by Anritz, product name 'KC-351C').

(dissolution rate)

It was computed by the following formula.

Dissolution rate (%) = ([Thickness of the undercoat coating layer before applying the coating liquid] - [Thickness of the undercoat layer]) / [Thickness of the undercoat coating layer before applying the coating liquid] × 100

[Example 1]

As the resin substrate, a long, amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 µm) with a water absorption of 0.75% and a Tg of 75°C was used.

Corona treatment was performed on one side of the resin substrate, and acetoacetyl-modified PVA (manufactured by Japan Synthetic Chemical Corporation, trade name "Gosefimer Z200", polymerization degree 1200, saponification degree 99.0 mol% or more, acetoacetyl modification degree 4.6 on this corona-treated surface) %) and a modified polyolefin resin aqueous dispersion (manufactured by Unitica, trade name: 'Alobase SE1030N', solid content concentration: 22%) and pure water (solid content concentration: 4.0%). It was applied to a thickness of 2000 nm and dried at 60°C for 3 minutes to form an undercoat coating layer. Here, the solid content mixing ratio of acetoacetyl-modified PVA and modified polyolefin in the mixture was 30:70.

Next, corona treatment was performed on the surface of the undercoat coating layer, and polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree) were applied to the corona-treated surface. A PVA-based resin coating layer having a thickness of 11 μm was formed by coating and drying an aqueous solution containing 99.0 mol% or more of 99.0 mol% or more of Nippon Synthetic Chemical Industry, trade name 'Gosehwamer Z200') in a 9:1 ratio at 25 ° C.

Then, it was allowed to stand at 65°C for 10 minutes or more to elute the components of the undercoat coating layer to the PVA-based resin coating layer. In this way, a laminate comprising the resin substrate, the undercoat layer, and the PVA-based resin layer in this order was produced.

The obtained layered product was uniaxially stretched at the free end by 2.0 times in the machine direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 120°C (air assisted stretching).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment).

Next, 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 film had a predetermined transmittance. In this example, 0.2 parts by weight of iodine and 1.0 parts by weight of potassium iodide were blended with respect to 100 parts by weight of water, and immersed for 60 seconds in an aqueous solution of iodine (dyeing treatment).

Next, it was immersed in a crosslinking bath (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) at a liquid temperature of 30°C for 30 seconds (crosslinking treatment).

After that, while the layered product is immersed in an aqueous solution of boric acid at 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), between rolls with different circumferential speeds In the machine direction (longitudinal direction), uniaxial stretching was performed so that the total stretching ratio was 5.5 times (submerged stretching).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30°C (washing treatment).

In this way, an optical laminate (polarizing plate) in which a polarizing film having a thickness of 5 µm was formed on one side of a resin substrate having a thickness of 30 µm was obtained.

[Example 2]

An optical laminate was obtained in the same manner as in Example 1, except that the mixture was applied to a thickness of 1000 nm after drying.

[Example 3]

An optical laminate was obtained in the same manner as in Example 1, except that the mixture was applied to a thickness of 500 nm after drying.

[Example 4]

An optical laminate was obtained in the same manner as in Example 1 except that the solid content mixing ratio of acetoacetyl-modified PVA and modified polyolefin in the mixture was 50:50.

[Example 5]

When forming the undercoat coating layer, a 4.0% aqueous solution of acetoacetyl-modified PVA (gosefimer Z200), a modified polyolefin resin aqueous dispersion (Unitica Co., Ltd., trade name 'Alobase SD1030N', product name 'Alobase SD1030N', solid content concentration 22%) and pure water were mixed. An optical laminate was obtained in the same manner as in Example 1 except for using the mixed liquid (solid content concentration: 4.0%).

[Example 6]

In the formation of the undercoat coating layer, a 4.0% aqueous solution of acetoacetyl-modified PVA (gosefimer Z200), a modified polyolefin resin aqueous dispersion (manufactured by Unitica, trade name 'Alobase SE1035NJ2', 22% solid content concentration) and pure water were mixed. An optical laminate was obtained in the same manner as in Example 4 except for using the mixed liquid (solid content concentration: 4.0%).

[Example 7]

In the formation of the undercoat coating layer, a 4.0% aqueous solution of acetoacetyl-modified PVA (manufactured by Japan Synthetic Chemical Corporation, trade name 'Gosefimer Z410', degree of polymerization 2200, degree of saponification 97.5-98.5%, degree of acetoacetyl modification 4.6%) and Optical laminate in the same manner as in Example 1 except for using a mixture of a modified polyolefin resin aqueous dispersion (manufactured by Unitica Co., Ltd., trade name 'Alobase SE1030N', solid content concentration 22%) and pure water (solid content concentration 4.0%) got

[Example 8]

In the same manner as in Example 1, except that the draw ratio of air assisted stretching was increased to 4.0 and insolubilization treatment and water stretching were not performed, an undercoat layer was placed on one side of a 37 μm thick resin substrate, and a polarized light having a thickness of 6 μm An optical laminate with a film formed thereon was obtained.

[Example 9]

In the formation of the undercoat coating layer, it is the same as in Example 1 except that a mixture of 10 g of a 4.0% aqueous solution of acetoacetyl-modified PVA (Gosefimer Z200) and 62.5 g of polyester aqueous emulsion resin (Elitel KT0507E6) was used. Thus, an optical laminate was obtained. Here, the solid content mixing ratio of acetoacetyl-modified PVA and polyester in the mixture was 50:50.

[Comparative Example 1]

An optical laminate was obtained in the same manner as in Example 1 except that a PVA-based resin coating layer (PVA-based resin layer) was directly formed on the resin substrate without forming an undercoat coating layer.

[Comparative Example 2]

An optical laminate was obtained in the same manner as in Example 3 except for using a 4.0% aqueous solution of acetoacetyl-modified PVA (Gosefimer Z200) at the time of forming the undercoat coating layer.

[Comparative Example 3]

An optical laminate was obtained in the same manner as in Example 2, except that a 4.0% aqueous solution of acetoacetyl-modified PVA (Gosefimer Z200) was used in the formation of the undercoat coating layer.

[Comparative Example 4]

An optical laminate was obtained in the same manner as in Example 1 except for using a 4.0% aqueous solution of acetoacetyl-modified PVA (Gosefimer Z200) in the formation of the undercoat coating layer.

[Comparative Example 5]

When forming the undercoat coating layer, the optical A laminate was obtained.

[Comparative Example 6]

An optical laminate was obtained in the same manner as in Example 3 except for using a polyester aqueous emulsion resin (manufactured by Unitica, trade name 'Elitel KT0507E6') in the formation of the undercoat coating layer.

[Comparative Example 7]

An optical laminate was obtained in the same manner as in Example 2, except that a polyester aqueous emulsion resin (manufactured by Unitica, trade name 'Elitel KT0507E6') was used in the formation of the undercoat coating layer.

(adhesion evaluation)

With respect to the above Examples and Comparative Examples, adhesion was evaluated by measuring PVA peel force and substrate peel force. The evaluation results are summarized in Table 1. In addition, the method of measuring the PVA peeling force and substrate peeling force is as follows.

(PVA peel strength)

To a glass plate, the obtained optical laminate was applied and bonded to the resin substrate surface side with an adhesive, and a reinforcing polyimide tape (Nitto Denko Co., Ltd., polyimide adhesive tape No. 360A) was bonded to the polarizing film surface, for measurement. A sample was made. A cut was made with a cutter knife between the polarizing film and the resin substrate of the sample for measurement, and the polarizing film and the reinforcing polyimide tape were raised to form an angle of 90° C. with respect to the surface of the resin substrate, and the peeling speed was 3000 mm/min. The force (N/15 mm) required at the time of peeling was measured with a free angle type adhesion/film peeling analyzer "VPA-2" (manufactured by Kyowa Keimyeon Chemical Co., Ltd.).

(substrate peeling force)

A sample for measurement was prepared by applying an adhesive to the glass plate and attaching the obtained optical layered body to the polarizing film surface side. Force (N /15 mm) was measured by the 'VPA-2'.

[Table 1]

As shown in Table 1, it can be seen that the optical laminates of Examples had both PVA peeling force and base material peeling force of 0.6 N or more, and excellent adhesion. Further, the optical laminates of Examples 1 to 7 and 9 maintain sufficient adhesiveness even when they are stretched in water. On the other hand, in Comparative Example 1 in which no undercoat layer is formed and Comparative Examples 2 to 5 in which the undercoat coating layer contains only a polyvinyl alcohol-based component, sufficient adhesion against peeling from the PVA-based resin layer (polarizing film) side is obtained. cannot be obtained Further, in Comparative Examples 6 and 7 in which the undercoat coating layer did not contain a polyvinyl alcohol-based component, sufficient adhesion to peeling from the resin substrate side could not be obtained.

[Reference Example 1]

A laminate was obtained in the same manner as in Example 9, except that the mixed solution was applied so that the thickness after drying was 1.7 μm. The result of SEM observation (6500 times) of the cross section of the undercoat coating layer (cross section of the [resin substrate/undercoat coating layer] laminate) is shown in Fig. 1(a), and the cross section of the undercoat layer ([resin substrate/undercoat coating layer]) The result of SEM observation (6500 times) of the cross section of the laminate of [undercoat layer/PVA resin layer] is shown in Fig. 1(b). As shown in FIGS. 1(a) and 1(b), an undercoat layer having a thickness of 0.6 μm was formed by eluting the polyvinyl alcohol-based component or the like from the undercoat coating layer formed to a thickness of 1.7 μm.

The laminate of the present invention is preferably used, for example, in an image display device. Specifically, liquid crystal TVs, liquid crystal displays, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copiers, printers, fax machines, clocks, liquid crystal panels such as microwave ovens, antireflection plates for organic EL devices, etc. are suitable. it is used

Claims (12)

A laminate having a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin layer in this order,
In the undercoat layer and the polyvinyl alcohol-based resin layer, in the undercoat coating layer and the polyvinyl alcohol-based resin coating layer provided in this order on the resin substrate, 5% to 70% by volume of the undercoat coating layer is the above. It is formed by eluting to a polyvinyl alcohol-based resin coating layer,
The undercoat coating layer contains two or more resin components including a polyvinyl alcohol-based component,
The laminate, wherein the blending ratio of the polyvinyl alcohol-based component in the resin component of the undercoat coating layer is 5% by weight to 50% by weight. According to claim 1,
The laminated body whose thickness of the undercoat layer after completion of elution of the said undercoat coating layer to the polyvinyl alcohol-type resin coating layer is 0.2 micrometer - 2.0 micrometer. According to claim 1,
The laminated body in which the said polyvinyl alcohol-type component contains acetoacetyl denatured polyvinyl alcohol. According to claim 1,
The layered product, wherein the undercoat coating layer contains the polyvinyl alcohol-based component and the polyolefin-based component. According to claim 4,
A laminate wherein the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (polyvinyl alcohol-based component: polyolefin-based component) is 5:95 to 50:50 based on weight. A method for producing a laminate having a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin layer in this order,
forming an undercoat coating layer on one side of the resin substrate, and forming a polyvinyl alcohol-based resin coating layer on the surface of the undercoat coating layer;
5% by volume to 70% by volume of the undercoat coating layer is eluted into the polyvinyl alcohol-based resin coating layer to form the undercoat coating layer and the polyvinyl alcohol-based resin coating layer, respectively. Including making a resin layer,
The undercoat coating layer includes two or more resin components including a polyvinyl alcohol-based component,
The manufacturing method according to claim 1 , wherein the blending ratio of the polyvinyl alcohol-based component in the resin component of the undercoat coating layer is 5% by weight to 50% by weight. According to claim 6,
The manufacturing method in which the thickness of the undercoat layer after elution of the said undercoat coating layer to the polyvinyl alcohol-type resin coating layer is completed is 0.2 micrometer - 2.0 micrometer. According to claim 6,
The manufacturing method in which the polyvinyl alcohol-based component includes acetoacetyl-modified polyvinyl alcohol. According to claim 6,
The manufacturing method in which the said undercoat application layer contains the said polyvinyl alcohol-type component and the polyolefin-type component. According to claim 9,
The manufacturing method, wherein the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (polyvinyl alcohol-based component: polyolefin-based component) is 5:95 to 50:50 based on weight. An optical laminate having a resin substrate, an undercoat layer, and a polarizing film in this order,
An optical laminate in which the polyvinyl alcohol-based resin layer of the laminate according to any one of claims 1 to 5 is a polarizing film in which a dichroic substance is adsorbed and oriented. Producing a laminate having a resin substrate, an undercoat layer, and a polyvinyl alcohol-based resin layer in this order by the method for manufacturing a laminate according to any one of claims 6 to 10;
Including dyeing and stretching the polyvinyl alcohol-based resin layer to form a polarizing film,
The manufacturing method of the optical laminated body which has a resin base material, an undercoat layer, and a polarizing film in this order.