CN110741291A

CN110741291A - Laminate, method for producing laminate, polarizing plate, and method for producing polarizing plate

Info

Publication number: CN110741291A
Application number: CN201880039559.1A
Authority: CN
Inventors: 石丸咲美; 滨本大介
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2017-06-13
Filing date: 2018-06-07
Publication date: 2020-01-31
Also published as: WO2018230429A1; TW201902713A; KR102562328B1; JP6921953B2; JPWO2018230429A1; KR20200017398A; TWI771430B

Abstract

The invention provides kinds of laminates with excellent adhesiveness between a polyester resin base material and a polyvinyl alcohol resin layer, wherein the laminate comprises a polyester resin base material with an easy-adhesion layer formed on the surface thereof and a polyvinyl alcohol resin layer laminated on the polyester resin base material through the easy-adhesion layer, the water contact angle of the easy-adhesion layer is more than 70 degrees immediately after water is dropped on the easy-adhesion layer, and the water contact angle is reduced by more than 2 degrees after 30 seconds from the dropping.

Description

Laminate, method for producing laminate, polarizing plate, and method for producing polarizing plate

Technical Field

The present invention relates to laminates, methods for producing laminates, polarizing plates, and methods for producing polarizing plates.

Background

methods of forming a polyvinyl alcohol resin layer on a polyester resin substrate and stretching and dyeing the laminate to obtain a thin polarizer have been proposed (for example, patent document 1).

The polyester resin base material can be used as a protective layer for a polarizer without peeling off and removing it. Thus, the laminate of the polyester resin base material and the polarizer can be used as a polarizing plate without attaching a protective film to the polarizer, and this contributes to cost reduction of the image display device, for example.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2000-338329

Disclosure of Invention

Problems to be solved by the invention

However, a polarizing plate which is a laminate of a polyester resin base material and a polarizer obtained by the above-described method may have insufficient adhesion between the polyester resin base material and the polarizer.

The present invention has been made to solve the above conventional problems, and a main object thereof is to provide kinds of laminates excellent in adhesion between a polyester resin base and a polyvinyl alcohol resin layer, a method for producing such laminates, a polarizing plate excellent in adhesion between a polyester resin base and a polarizer, and a method for producing such a polarizing plate.

Means for solving the problems

The laminate of the present invention comprises: the water contact angle of the easy adhesion layer is more than 70 degrees immediately after water is dripped on the easy adhesion layer, and the water contact angle is reduced by more than 2 degrees after 30 seconds passes after the dripping.

In embodiment , the easy adhesion layer includes a polyvinyl alcohol component and a polyolefin component.

In embodiment , the ratio of the polyvinyl alcohol component to the polyolefin component is 10: 90 to 50: 50.

According to another aspect of the present invention, there is provided a method of manufacturing a laminate, the method including forming an easy adhesion layer on a surface of a polyester resin base material, and forming a polyvinyl alcohol resin layer on a surface of the easy adhesion layer, wherein a water contact angle of the easy adhesion layer is 70 ° or more immediately after dropping water to the easy adhesion layer, and decreases by 2 ° or more after 30 seconds from the dropping.

According to another aspect of the present invention, there is provided a method for producing kinds of polarizing plates, the method comprising dyeing and stretching the laminate to obtain a polarizer from the polyvinyl alcohol resin layer.

According to another aspect of the present invention, there is provided a kinds of polarizing plate comprising a polyester resin base material having an easy adhesion layer formed on a surface thereof, and a polarizer laminated on the polyester resin base material with the easy adhesion layer interposed therebetween, wherein the polarizer has a thickness of 10 μm or less, a water contact angle of the easy adhesion layer is 70 ° or more immediately after dropping water to the easy adhesion layer, and decreases by 2 ° or more after 30 seconds has elapsed from the dropping.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, by using the easy-adhesion layer having a water contact angle of 70 ° or more immediately after water is dropped and a water contact angle of 2 ° or more decreased 30 seconds after water is dropped, a laminate excellent in adhesion between kinds of polyester resin substrates and a polyvinyl alcohol resin layer, a method for producing such a laminate, and a polarizing plate excellent in adhesion between a polyester resin substrate and a polarizer can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view of a polarizing plate of embodiment of the present invention.

Description of the symbols

10 polyester resin base Material

20 easy adhesive layer

30 polyvinyl alcohol resin layer

100 laminated body

Detailed Description

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

A. Laminated body

FIG. 1 is a schematic cross-sectional view of a laminated body embodiment of the present invention, wherein the laminated body 100 comprises a polyester resin base 10 having an easy adhesion layer 20 formed on the surface thereof, and a polyvinyl alcohol (PVA) -based resin layer 30 laminated on the polyester resin base 10 via the easy adhesion layer 20. the water contact angle of the easy adhesion layer 20 is 70 ℃ or more immediately after water is dropped on the easy adhesion layer 20, and decreases by 2 ℃ or more after 30 seconds from the time of dropping, the change (decrease) with time of the water contact angle is typically obtained by measuring the water contact angle (θ 1) immediately after water is dropped on the easy adhesion layer and the water contact angle (θ 2) 30 seconds from the time of dropping, subtracting θ 1 from θ 2. the water contact angle after water is dropped on the easy adhesion layer is typically measured 1 second from the time of dropping. in the embodiment , the easy adhesion layer 20 contains a polyvinyl alcohol-based component and a polyolefin-based component, and the laminated body is preferably manufactured by a method comprising the steps of stretching and producing a laminated body comprising the above-mentioned steps.

A-1. polyester resin base Material

As the material for forming the polyester-based resin substrate, for example, there can be used: polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), isophthalic acid, copolymerized PET (PET-G) containing an alicyclic dicarboxylic acid or alicyclic diol containing a cyclohexane ring or the like, and other polyesters, and copolymers and mixtures thereof. Among them, amorphous (uncrystallized) PET or copolymerized PET is preferably used. These resins are amorphous in an unstretched state and have excellent stretchability suitable for high-ratio stretching, and can be crystallized by stretching or heating to impart heat resistance and dimensional stability. Further, the PVA-based resin can be applied and dried in an unstretched state with sufficient heat resistance.

The glass transition temperature (Tg) of the polyester resin base material is preferably 170 ℃ or less, and by using such a polyester resin base material, sufficient stretchability can be ensured while suppressing crystallization of the PVA resin layer, and from the viewpoints of plasticization of the polyester resin base material with water and good stretching in an aqueous solution, it is more preferably 120 ℃ or less, and in the embodiment, the glass transition temperature of the polyester resin base material is preferably 60 ℃ or more, and by using such a polyester resin base material, defects such as deformation (for example, generation of unevenness, relaxation, wrinkles, and the like) of the polyester resin base material can be prevented when a coating liquid containing the PVA resin described later is applied and dried, and in the embodiment, the laminate can be well stretched as long as the polyester resin base material is not deformed when the coating liquid containing the PVA resin is applied and dried, the glass transition temperature can be lower than 60 ℃.

The water absorption rate of the polyester resin base material in the embodiment is preferably 0.2% or more, more preferably 0.3% or more, and such polyester resin base material absorbs water and water can play a role of a plasticizer to plasticize, and as a result, tensile stress can be greatly reduced in aqueous solution stretching, and excellent stretchability is obtained, and further , the water absorption rate of the polyester resin base material is preferably 3.0% or less, more preferably 1.0% or less, and by using such polyester resin base material, problems such as a significant decrease in dimensional stability of the polyester resin base material during production and deterioration in appearance of the resulting laminate can be prevented, and further, breakage during aqueous solution stretching or peeling of the PVA resin layer from the polyester resin base material can be prevented, and the water absorption rate is a value determined in accordance with JIS K7209.

The thickness of the polyester resin base material is preferably 20 to 300. mu.m, more preferably 30 to 200. mu.m.

The polyester resin base material may be subjected to a surface modification treatment (e.g., corona treatment) in advance, and these treatments may further improve the adhesion .

A-2. easy adhesive layer

As described above, the water contact angle of the easy adhesion layer is 70 ° or more immediately after the water is dropped, and decreases by 2 ° or more after 30 seconds from the dropping. The water contact angle of the easy adhesion layer immediately after the water addition is preferably 75 ° to 85 °. The change with time of the water contact angle occurring 30 seconds after the dropping is preferably-2 ° (decrease by 2 °) to-5 ° (decrease by 5 °). The easy adhesion layer has a water contact angle of 70 ° or more immediately after water is dropped, and the change (decrease) with time of the water contact angle occurring 30 seconds after the water is dropped is 2 ° or more, whereby the composition for forming the easy adhesion layer can be dissolved into the PVA type resin layer when the PVA type resin layer is formed on the easy adhesion layer. Specifically, when the coating layer of the PVA based resin is formed on the easy adhesion layer by changing the water contact angle from-2 DEG to-5 DEG with time, about 10% to 34% by volume of the composition for forming the easy adhesion layer can be eluted to the coating layer of the PVA based resin. This improves the adhesion between the polyester resin base and the PVA resin layer.

The easy adhesion layer may be a layer substantially formed only of the composition for forming an easy adhesion layer described later, or may be a layer or a region in which the composition for forming an easy adhesion layer is mixed (including compatibility) with the PVA-based resin layer described later, and the easy adhesion layer is formed, so that excellent adhesion can be obtained.

The easy adhesion layer preferably contains a polyvinyl alcohol component and a polyolefin component. By making the composition as described above, the water contact angle of the easy-adhesion layer and the change in water contact angle with time can be made to be within the above-described ranges, and as a result, a laminate excellent in adhesion between the polyester resin base and the PVA resin layer can be obtained. Further, by dyeing and stretching the laminate, a polarizing plate having excellent adhesion between the polyester resin base material and the polarizer can be obtained. Any suitable PVA-based resin can be used as the polyvinyl alcohol-based component. Specific examples thereof include polyvinyl alcohol and modified polyvinyl alcohol. Examples of the modified polyvinyl alcohol include polyvinyl alcohols modified with an acetoacetyl group, a carboxylic acid group, an acryloyl group and/or a carbamate group. Of these, acetoacetyl group-modified PVA is preferably used. As the acetoacetyl group-modified PVA, a polymer having at least a repeating unit represented by the following general formula (I) is preferably used.

[ chemical formula 1]

In the 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, more preferably 1200 to 5000. The saponification degree of the acetoacetyl group-modified PVA is preferably 97 mol% or more. The pH of a 4 wt% aqueous solution of the acetoacetyl-modified PVA is preferably 3.5 to 5.5. The average polymerization degree and the saponification degree can be determined in accordance with JIS K6726-.

Any suitable polyolefin-based resin can be used for 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 may be used alone, or two or more kinds may be used in combination. Among these, olefin hydrocarbons having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, and 1-butene are preferably used, and ethylene is more preferably used.

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

The polyolefin-based resin preferably contains a carboxyl group and/or an acid anhydride group thereof. Such polyolefin resin can be dispersed in water and can form an easy-adhesion layer smoothly. Examples of the monomer component having such a functional group include unsaturated carboxylic acids and anhydrides thereof, half esters and half amides of unsaturated dicarboxylic acids. Specific examples thereof include acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, and crotonic acid.

The polyolefin resin has a molecular weight of 5000 to 80000, for example.

In the easy-adhesion layer, the blending ratio of the polyvinyl alcohol component and the polyolefin component (the former: the latter (solid component)) is preferably 10: 90 to 50: 50, and more preferably 20: 80 to 50: 50. if the polyvinyl alcohol component is too large, sufficient adhesion may not be obtained, specifically, when the PVA-based resin layer is peeled from the polyester-based resin substrate, the peeling force required is reduced, and sufficient adhesion may not be obtained, while, in the other , if the polyvinyl alcohol component is too small, the appearance of the resulting laminate may be impaired, specifically, when the easy-adhesion layer is formed, there is a possibility that a defect such as white turbidity of the coating film occurs, and a laminate having excellent appearance may not be obtained.

A-3.PVA based resin layer

Any suitable PVA type resin may be used for forming the PVA type resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification was determined in accordance with JIS K6726-. By using the PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. When the saponification degree is too high, gelation may occur.

The average polymerization degree 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, and more preferably 1500 to 4300. The average polymerization degree can be determined in accordance with JIS K6726-.

The thickness of the PVA based resin layer is typically 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less, and in addition , the thickness of the PVA based resin layer is preferably 1.0 μm or more, and more preferably 2.0 μm or more.

B. Method for producing laminate

The laminate of the present invention can be produced by any suitable method, and in embodiment , the laminate is produced by a method comprising the steps of forming an easy-adhesion layer on the surface of a polyester resin base material, and forming a PVA-based resin layer on the surface of the easy-adhesion layer.

B-1. formation of easy adhesion layer

Any suitable method can be used for forming the easy-adhesion layer on the surface of the polyester resin substrate. Typically, the easy adhesion layer can be formed by applying the easy adhesion layer-forming composition to the surface of a polyester resin substrate and drying the composition. In the easy-adhesion layer-forming composition, the blending ratio of the polyvinyl alcohol component to the polyolefin component (the former: the latter (solid component)) is preferably 10: 90-50: 50, more preferably 20: 80-50: 50.

the composition for forming an easy-adhesion layer is preferably aqueous. The composition for forming an easy adhesion layer may contain an organic solvent. Examples of the organic solvent include ethanol and isopropanol. The solid content concentration of the composition for forming an easy-adhesion layer is preferably 1.0 to 10% by weight.

The easy adhesion layer-forming composition may contain an additive. Examples of the additive include a crosslinking agent. Examples of the crosslinking agent includeMethylol compounds such as oxazoline, boric acid and trimethylolmelamine, carbodiimides, isocyanate compounds and epoxy compounds. Group for forming easy adhesive layerFor example, the amount of the crosslinking agent is preferably 10 parts by weight or less, more preferably 0.01 to 10 parts by weight, and further preferably 0.1 to 5 parts by weight in the step , based on 100 parts by weight of the total of the polyvinyl alcohol component and the polyolefin component.

The method for applying the composition for forming an easy-adhesion layer may be any appropriate method. Examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and doctor blade coating (comma coating).

The coating film may be dried after the composition for forming an easy adhesion layer is applied. The drying temperature is, for example, 50 ℃ or higher.

B-2 formation of PVA-based resin layer

As a method for forming the PVA-based resin layer on the surface of the easy-adhesion layer, any appropriate method can be used. The PVA-based resin layer is preferably formed by applying a coating liquid containing a PVA-based resin to the surface of the easy-adhesion layer formed on the polyester-based resin substrate and drying the coating liquid.

As the coating liquid containing a PVA-based resin, typically, a solution obtained by dissolving the PVA-based resin in a solvent is used. 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. They may be used alone or two or more of them may be used in combination. Among these, water is preferred. The PVA-based resin concentration of 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.

The coating liquid may contain an additive, for example, a plasticizer, a surfactant, and the like, the plasticizer may contain a polyol such as ethylene glycol or glycerin, the surfactant may contain a nonionic surfactant, and these may be used in order to improve the uniformity, dyeability, and stretchability of the obtained PVA resin layer in step , the additive may contain an easily adhesive component, and the adhesion between the polyester resin substrate and the PVA resin layer may be improved by using the easily adhesive component.

As a method for applying the coating liquid, the same method as that for applying the composition for forming an easily adhesive layer can be used. The coating film may be dried after coating. The drying temperature in this case is preferably 50 ℃ or higher.

Before the PVA-based resin layer is formed, the easy adhesion layer may be subjected to a surface treatment (for example, corona treatment). By performing such treatment, the adhesion between the polyester resin base and the PVA resin layer can be improved.

C. Polarizing plate

A polarizing plate comprising a polyester resin base material having an easy adhesion layer formed on the surface thereof, and a polarizer laminated on the polyester resin base material with the easy adhesion layer interposed therebetween, wherein the thickness of the polarizing film is 10 [ mu ] m or less, the easy adhesion layer is as described in the above item A-2, and the easy adhesion layer is formed by the method as described in the above item B-1, whereby a polarizing plate having excellent adhesion between the polyester resin base material and the polarizer can be obtained, and the polarizing plate can have a protective film on the side of the polarizer opposite to the easy adhesion layer.

C-1 polarizer

The polarizer is substantially a PVA-based resin layer after orientation by iodine adsorption, the thickness of the polarizer is preferably 10 μm or less, preferably 7.5 μm or less, more preferably 5 μm or less, further , the thickness of the polarizer is preferably 0.5 μm or more, more preferably 1.5 μm or more, and if the thickness is too thin, there is a concern that the optical characteristics of the polarizer obtained may decrease, the polarizer preferably exhibits absorption dichroism at any wavelength among wavelengths of 380nm to 780nm, the monomer transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more, further is preferably 42.0% or more, the degree of polarization of the polarizer is preferably 99.8% or more, more preferably 99.9% or more, and further is preferably 99.95% or more.

The PVA based resin forming the PVA based resin layer is as described in the above item A-3.

C-2 protective film

The polarizing plate may have a protective film on the side opposite to the easy-adhesion layer of the polarizer as described above, and examples of the material for forming the protective film include (meth) acrylic resins, cellulose resins such as cellulose diacetate and cellulose triacetate, cycloolefin resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate, polyamide resins, polycarbonate resins, and copolymer resins thereof, and the thickness of the protective film is preferably 10 to 100 μm.

D. Method for manufacturing polarizing plate

The method of producing a polarizing plate of the present invention comprises dyeing and stretching the laminate described in item a above to produce a polarizing plate from the PVA-based resin layer, and the embodiment may comprise subjecting the laminate to various treatments such as dyeing, stretching, insolubilizing, crosslinking, washing, and drying.

D-1 stretching treatment in gas atmosphere

The stretching process of the auxiliary stretching in the gas atmosphere may be fixed-end stretching (for example, a method of stretching using a tenter stretcher) or free-end stretching (for example, a method of uniaxially stretching a laminate by passing the laminate between rolls having different peripheral speeds). in embodiment , the stretching process in the gas atmosphere includes a hot roll stretching step of feeding the laminate in the longitudinal direction thereof and a stretching step of by a peripheral speed difference between the hot rolls.

The stretching temperature at the time of stretching treatment in a gas atmosphere 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) +10 ℃, particularly preferably equal to or higher than Tg +15 ℃, and is an upper limit of the stretching temperature of the laminate, and stretching at such a temperature suppresses rapid progress of crystallization of the PVA-based resin and suppresses defects caused by the crystallization (for example, the orientation of the PVA-based resin layer is inhibited by stretching).

The stretch ratio of the laminate can be set to any appropriate value depending on the material for forming the resin base material, and the like. The stretching ratio in the stretching treatment in a gas atmosphere is preferably 1.5 times or more and 3.0 times or less.

D-2. insolubilization

The insolubilization is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. By performing insolubilization treatment, water resistance can be imparted to the PVA-based resin layer. The concentration of the aqueous boric acid solution is preferably 1 to 4 parts by weight with respect to 100 parts by weight of water. The liquid temperature of the insolubilization bath (aqueous boric acid solution) is preferably 20 to 50 ℃. The insolubilization treatment is preferably performed before the stretching and dyeing treatment in an aqueous solution.

D-3 dyeing treatment

The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance. Preferably, the dichroic material is adsorbed on the PVA-based resin layer. Examples of the adsorption method include: a method of immersing the PVA-based resin layer (laminate) in a dyeing liquid containing a dichroic material, a method of applying the dyeing liquid to the PVA-based resin layer, a method of spraying the dyeing liquid onto the PVA-based resin layer, and the like. Preferably, the laminate is immersed in a dyeing solution. Since the dichroic substance can be well adsorbed.

Examples of the dichroic substance include iodine and an organic dye. They may be used alone or two or more of them may be used in combination. The dichroic substance is preferably iodine. When iodine is used as the dichroic material, the dyeing liquid is preferably an aqueous iodine solution. The amount of iodine is preferably 0.05 to 5.0 parts by weight based on 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide to the aqueous iodine solution. 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, titanium iodide, and the like. Of these, potassium iodide is preferred. The amount of the iodide is preferably 0.3 to 15 parts by weight based on 100 parts by weight of water.

The liquid temperature of the dyeing liquid at the time of dyeing is preferably 20 to 40 ℃, and the immersion time is preferably 10 to 300 seconds when the PVA type resin layer is immersed in the dyeing liquid, and if such conditions are satisfied, the dichroic material can be sufficiently adsorbed to the PVA type resin layer, and the dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or the monomer transmittance of the polarizer finally obtained falls within a predetermined range, and in the embodiment, the immersion time is set so that the polarization degree of the polarizer obtained becomes 99.98% or more, and in the embodiment, the immersion time is set so that the monomer transmittance of the polarizer obtained becomes about 40%.

D-4. crosslinking treatment

The crosslinking treatment is typically performed by immersing the PVA-based resin layer (laminate) in an aqueous boric acid solution, and the water resistance of the PVA-based resin layer can be imparted by performing the crosslinking treatment, the concentration of the aqueous boric acid solution is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water, and when the crosslinking treatment is performed after the dyeing treatment, it is preferable to add steps of iodide, and the dissolution of iodine adsorbed to the PVA-based resin layer can be suppressed by adding iodide, and the amount of iodide is preferably 1 to 5 parts by weight with respect to 100 parts by weight of water, and specific examples of iodide are as described above, the liquid temperature of the crosslinking bath (aqueous boric acid solution) is preferably 20 to 60 ℃.

D-5 stretching treatment in aqueous solution

Specifically, fixed-end stretching (for example, a method using a tenter) or free-end stretching (for example, a method of passing the laminate between rolls having different peripheral speeds to perform uniaxial stretching) may be used.

In the embodiment, the laminate is transported in the longitudinal direction, i.e., the transport direction (MD) of the laminate, in the embodiment, the laminate is stretched in the width direction of the elongated laminate, and in particular, the laminate is transported in the longitudinal direction, i.e., The Direction (TD) orthogonal to the transport direction (MD).

The stretching temperature of the laminate may be set to any suitable value depending on the material of the resin substrate, the stretching method, and the like, and the stretching temperature is preferably 40 to 85 ℃, more preferably 50 to 85 ℃, and the resin substrate may be stretched at a high ratio while dissolution of the PVA-based resin layer is suppressed, and more specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60 ℃ or higher in consideration of the relationship with the formation of the PVA-based resin layer, and in this case, if the stretching temperature is lower than 40 ℃, there is a concern that the resin substrate cannot be stretched well even if plasticized with water, and in addition, , the solubility of the PVA-based resin layer increases as the temperature of the stretching bath increases, and excellent optical properties cannot be obtained.

The stretching in an aqueous solution is preferably performed by immersing the laminate in an aqueous solution of boric acid (stretching in an aqueous solution of boric acid). By using an aqueous boric acid solution as a stretching bath, the PVA-based resin layer can be given rigidity enough to withstand the tension applied during stretching and water resistance not dissolving in water. Specifically, boric acid generates tetrahydroxyborate anions in an aqueous solution, and is crosslinked with the PVA-based resin by hydrogen bonds. As a result, rigidity and water resistance can be imparted to the PVA based resin layer, and the PVA based resin layer can be stretched well, and a polarizer having excellent optical characteristics (for example, degree of polarization) can be produced.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate in water as a solvent. The boric acid concentration is preferably 1 to 10 parts by weight relative to 100 parts by weight of water. When the boric acid concentration is 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizer 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 may be used.

When a dichroic material (represented by iodine) is adsorbed on the PVA-based resin layer by dyeing treatment in advance, it is preferable to add an iodide to the stretching bath (aqueous boric acid solution). The iodine compound can suppress elution of iodine adsorbed on the PVA-based resin layer. 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, titanium iodide, and the like. Of these, potassium iodide is preferred. The concentration of the iodide is preferably 0.05 to 15 parts by weight, more preferably 0.5 to 8 parts by weight, based on 100 parts by weight of water.

The stretch ratio (maximum stretch ratio) of the laminate is typically 4.0 times or more, preferably 5.0 times or more, with respect to the original length of the laminate. Such a high draw ratio can be achieved by, for example, drawing in an aqueous solution (drawing in an aqueous boric acid solution). In the present specification, the "maximum stretching ratio" means a stretching ratio of the laminate just before the fracture, and is a value lower than the value of 0.2 in which the stretching ratio of the laminate at the fracture is separately confirmed.

The stretching treatment in the aqueous solution is preferably performed after the dyeing treatment.

D-6. cleaning treatment

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

D-7. drying treatment

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

Examples

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The measurement method and evaluation method of each characteristic are as follows.

(1) Thickness of

Measured using a digital micrometer (product name "KC-351C" manufactured by Anritsu Co., Ltd.).

(2) Water contact angle

The water contact angle of the easy adhesion layer was measured using an automatic contact angle meter (DM500) manufactured by synechia interface science ltd, and analyzed using a FAMAS (contact angle measurement insert). Ultrapure water was used as the water for measurement, and the droplets were 0.5. mu.l.

After an easy adhesion layer was formed on the surface of a polyester resin substrate, the water contact angle (θ 1) after 1 second from the dropping of water onto the easy adhesion layer and the water contact angle (θ 2) after 30 seconds from the dropping were measured, and the change (θ 2- θ 1) with time occurring after 30 seconds from the water contact angle was calculated.

< example 1>

1. Production of laminate

As the polyester resin base material, an amorphous ethylene isophthalate copolymer (IPA copolymer PET) film (thickness: 100 μm) having a long length, a water absorption of 0.75% and a Tg of 75 ℃ was used.

One surface of the polyester resin substrate was subjected to corona treatment, and a mixture solution (solid content concentration 4.0%) obtained by mixing a 4.0% aqueous solution of acetoacetyl group-modified PVA (product name "GOHSEFIMER Z200", polymerization degree 1200, saponification degree 99.0 mol% or more, acetoacetyl group-modification degree 4.6%, manufactured by japan synthetic chemical industries, inc., trade name "ARROW BASE SE 1030N", solid content concentration 22%) and pure water was applied to the corona-treated surface so that the dried thickness became 2000nm, and then dried at 60 ℃ for 3 minutes to form an easy-adhesion layer. Here, the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was 50: 50.

next, the surface of the easy-adhesion layer was subjected to corona treatment, and the corona-treated surface was coated with 9: a PVA-based resin layer having a thickness of 11 μm was formed by drying an aqueous solution containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl-modified degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon synthetic chemical industries, Ltd., trade name "GOHSEFIMER Z200") at a ratio of 1. The laminate was produced as described above.

2. Manufacture of polarizer

The resultant laminate was subjected to free-end uniaxial stretching 2.0 times (auxiliary stretching in a gas atmosphere) in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120 ℃.

Next, the laminate was immersed in an insolubilization bath (an aqueous boric acid solution prepared by adding 4 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (insolubilization treatment).

Subsequently, the polarizing plate was immersed in a dyeing bath at a liquid temperature of 30 ℃ while adjusting the iodine concentration and immersion time, so that the obtained polarizing plate could have a predetermined transmittance. In this example, an aqueous iodine solution prepared by adding 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide to 100 parts by weight of water was immersed for 60 seconds (dyeing treatment).

Subsequently, the substrate was immersed in a crosslinking bath (aqueous boric acid solution prepared by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 30 seconds (crosslinking treatment).

Thereafter, while the laminate was immersed in an aqueous boric acid solution (aqueous solution prepared by adding 4 parts by weight of boric acid and 5 parts by weight of potassium iodide to 100 parts by weight of water) at a liquid temperature of 70 ℃, the laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls at different circumferential speeds to adjust the total stretching ratio to 5.5 times (stretching in an aqueous solution).

Thereafter, the laminate was immersed in a cleaning bath (aqueous solution containing 4 parts by weight of potassium iodide per 100 parts by weight of water) at a liquid temperature of 30 ℃ (cleaning treatment).

thus obtained was a polarizing plate having a polarizer with a thickness of 5 μm formed on one side of a polyester resin substrate with a thickness of 30 μm.

< example 2>

Except that the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was set to 30: a polarizing plate was obtained in the same manner as in example 1 except for 70.

< example 3>

Except that the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was 20: a polarizing plate was obtained in the same manner as in example 1 except for 80.

< example 4>

Except that the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was set to 10: a polarizing plate was obtained in the same manner as in example 1 except for 90.

< comparative example 1>

A polarizing plate was obtained in the same manner as in example 1, except that a 4.0% aqueous solution of acetoacetyl group-modified PVA (GOHSEFIMER Z200) was used for forming the easy adhesion layer.

< comparative example 2>

Except that the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was set to 90: a polarizing plate was obtained in the same manner as in example 1 except for 10.

< comparative example 3>

Except that the solid content mixing ratio of the acetoacetyl group-modified PVA to the modified polyolefin in the mixed solution was set to 70: a polarizing plate was obtained in the same manner as in example 1 except for 30.

< comparative example 4>

A polarizing plate was obtained in the same manner as in example 3 except that a mixed solution (solid content concentration 4.0%) of a modified polyolefin resin aqueous dispersion (product name "ARROW BASE SE 1030N" manufactured by Unitika, product name: solid content concentration 22%) and pure water was used for forming the easy-adhesion layer.

(evaluation)

The adhesion was evaluated for the above examples and comparative examples by measuring the PVA peel force and the substrate peel force. The evaluation results are summarized in table 1. The PVA peeling force and the substrate peeling force were measured as follows.

(PVA peeling Strength)

After applying an adhesive to the polyester resin substrate surface side, the obtained polarizing plate was bonded to a glass plate, and a reinforcing polyimide tape (polyimide pressure-sensitive adhesive tape No.360A, manufactured by hitto electrical corporation) was bonded to the polarizing plate surface, to prepare a sample for measurement. After a cut was made between the polarizer and the polyester resin substrate of the sample for measurement with a cutter knife, the force (N/15mm) required for peeling the polarizer and the polyimide tape for reinforcement at a peeling speed of 3000mm/min by taking them up at an angle of 90 degrees with respect to the polyester resin substrate was measured with an angle-variable pressure-sensitive adhesive/coating peel analyzer "VPA-2" (manufactured by CO. interfacial Chemicals Co., Ltd.).

(base peeling force)

After applying an adhesive to the polarizer side, the obtained polarizing plate was bonded to a glass plate to prepare a sample for measurement. After a cut was made between the polarizer and the polyester resin base material of the sample for measurement by using a cutter knife, the force (N/15mm) required for peeling the polyester resin base material at a peeling speed of 3000mm/min by picking up the base material at an angle of 90 DEG with respect to the polarizer was measured by using the aforementioned "VPA-2".

[ Table 1]

As is clear from table 1, the easy-adhesion layers of the polarizing plates of examples 1 to 4 had a water contact angle of 70 ° or more immediately after water was dropped and the water contact angle of the easy-adhesion layers was reduced by 2 ° or more after 30 seconds from the dropping, and therefore the polarizer had excellent adhesion to the polyester resin base material.

Industrial applicability

The laminate of the present invention can be suitably used for producing a polarizing plate. The polarizing plate of the present invention can be suitably used for image display devices such as liquid crystal display devices and organic EL display devices.

Claims

1, laminate comprising a polyester resin base material having an easy-adhesion layer formed on the surface thereof, and a polyvinyl alcohol resin layer laminated on the polyester resin base material with the easy-adhesion layer interposed therebetween,

the water contact angle of the easy adhesion layer is 70 ° or more immediately after water is dropped on the easy adhesion layer, and decreases by 2 ° or more after 30 seconds from the dropping.

2. The laminate according to claim 1, wherein the easy adhesion layer contains a polyvinyl alcohol component and a polyolefin component.

3. The laminate according to claim 2, wherein the blending ratio of the polyvinyl alcohol-based component to the polyolefin-based component is 10: 90-50: 50.

4, A method of making a laminate, the method comprising:

forming an easy-adhesion layer on the surface of the polyester resin base material; and

forming a polyvinyl alcohol resin layer on the surface of the easy-bonding layer,

5, A method for manufacturing a polarizing plate, comprising:

dyeing and stretching the laminate of of any one of claims 1 to 3, thereby making the polyvinyl alcohol-based resin layer into a polarizer.

6, kinds of polarizing plates, which have a polyester resin base material having an easy-adhesion layer formed on the surface thereof, and a polarizer laminated on the polyester resin base material with the easy-adhesion layer interposed therebetween,

the thickness of the polarizer is less than 10 μm,