TWI771430B - Layered body, method for producing layered body, polarizing plate, and method for producing polarizing plate - Google Patents

Abstract

The present invention provides a laminate having excellent adhesion between a polyester-based resin substrate and a polyvinyl alcohol-based resin layer. The laminate has: a polyester-based resin substrate with an easy-bonding layer formed on the surface; and a polyvinyl alcohol-based resin layer that is laminated on the polyester-based resin substrate through the easy-bond layer; the water contact angle of the easily-bonded layer is just about It is 70° or more when the water drops to the easy-bonding layer, and decreases by 2° or more after 30 seconds after the drop.

Description

Layered body, method for producing layered body, polarizing plate, and method for producing polarizing plate

The present invention relates to a laminate, a method for manufacturing the laminate, a polarizing plate, and a method for manufacturing a polarizing plate.

Background of the Invention There is a document that proposes a method for producing a thin polarizer by forming a polyvinyl alcohol-based resin layer on a polyester-based resin substrate, extending and dyeing the laminate (for example, Patent Document 1). For example, the method for manufacturing the polarizer has been attracting attention as it can contribute to the reduction of the thickness of the image display device.

The above polyester-based resin substrate can be used as a protective layer of a polarizer without peeling off. This makes it possible to directly use the laminate of the polyester-based resin substrate and the polarizer as a polarizer instead of a protective film for the polarizer, which can contribute to cost reduction of, for example, an image display device.

Prior Art Document Patent Document Patent Document 1: Japanese Patent Laid-Open No. 2000-338329

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION However, a polarizing plate, which is a laminate of a polyester-based resin substrate and a polarizer obtained by the above-mentioned method, has adhesiveness between the polyester-based resin substrate and the polarizer. Insufficient situation.

The present invention is made in order to solve the above-mentioned conventional problems, and its main object is to provide a laminate having excellent adhesion between a polyester-based resin base material and a polyvinyl alcohol-based resin layer, a method for producing the laminate, and a polymer A polarizing plate excellent in adhesion between an ester resin base material and a polarizer, and a method for producing the polarizing plate.

MEANS TO SOLVE THE PROBLEM The laminated body of this invention has the polyester-type resin base material on which the easily bonding layer is formed on the surface; The water contact angle of the above-mentioned easily bonding layer is 70° or more when water is just dropped onto the above-mentioned easily bonding layer, and will decrease by more than 2° after 30 seconds after the drop. In one embodiment, the easily bonding layer contains a polyvinyl alcohol-based component and a polyolefin-based component. In one embodiment, the blend ratio of the polyvinyl alcohol-based component and the polyolefin-based component is 10:90 to 50:50. According to another aspect of the present invention, a method for manufacturing a laminate can be provided. The manufacturing method of the laminated body comprises the following steps: forming an easily bonding layer on the surface of the polyester resin base material; and forming a polyvinyl alcohol-based resin layer on the surface of the easily bonding layer; When the water drops to the easily bonding layer, it is 70° or more, and it decreases by 2° or more in 30 seconds after the drop. According to another aspect of the present invention, a method for manufacturing a polarizing plate is provided. The manufacturing method of the polarizing plate includes the steps of dyeing and extending the above-mentioned laminated body, thereby forming the above-mentioned polyvinyl alcohol-based resin layer into a polarizer. According to another aspect of the present invention, a polarizing plate can be provided. The polarizing plate has: a polyester-based resin substrate with an easily-adhesive layer formed on the surface; The water contact angle of the adhesive layer was 70° or more immediately after water was dropped on the easily bonding layer, and decreased by 2° or more 30 seconds after the drop.

Advantageous Effects of Invention According to the present invention, a polyester-based resin base material and polyethylene can be provided by using an easy-bonding layer having a water contact angle of 70° or more immediately after the drop of water and a decrease of 2° or more in 30 seconds after the drop. A laminate having excellent adhesion of an alcohol-based resin layer, a method for producing the laminate, and a polarizing plate having excellent adhesion between a polyester-based resin substrate and a polarizer.

Modes for Carrying Out the Invention Embodiments of the present invention will be described below, 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 according to an embodiment of the present invention. The laminate 100 includes a polyester resin substrate 10 having an easily bonding layer 20 formed on the surface thereof, and a polyvinyl alcohol (PVA) resin layer 30 laminated on the polyester resin substrate 10 through the easily bonding layer 20 . The water contact angle of the easily bonding layer 20 is 70° or more immediately after water is dropped on the easily bonding layer 20 , and decreases by 2° or more after 30 seconds after dropping. The time-dependent change (decrease) of the above-mentioned water contact angle can be represented by measuring the water contact angle (θ1) immediately after dropping the water on the easy-bond layer, and the water contact angle (θ2) after 30 seconds after the dropping. Calculated by subtracting θ1 from θ2. The water contact angle immediately after the drop of water onto the easy-bond layer is represented by the water contact angle measured 1 second after the drop. In one embodiment, the easily bonding layer 20 contains a polyvinyl alcohol-based component and a polyolefin-based component. At this time, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component is preferably 10:90 to 50:50. Thereby, the laminated body excellent in the adhesiveness of a polyester-type resin base material and a PVA-type resin layer can be obtained. In one embodiment, the above-mentioned laminate can be used to produce a polarizing plate. The manufacturing method of the polarizing plate is described later in the section D, and includes the following steps: dyeing and extending the laminate, thereby making the PVA-based resin layer into a polarizer.

A-1. Polyester-based resin base The material for forming the polyester-based resin base material, for example, can be used: polyethylene terephthalate (PET), polybutylene terephthalate (PBT), Polyethylene naphthalate (PEN), isophthalic acid, copolymerized PET (PET-G) containing cyclohexane ring-containing alicyclic dicarboxylic acids or alicyclic diols, etc., and other polyesters, as well as copolymers and blends of these. Among them, amorphous (uncrystallized) PET or copolymerized PET is preferably used. These resins are amorphous in an unstretched state, have excellent stretchability suitable for high-rate stretching, and are crystallized by stretching and heating to impart heat resistance and dimensional stability. In addition, it is possible to secure the heat resistance of a practical level to coat and dry the PVA-based resin in an unstretched state.

The glass transition temperature (Tg) of the polyester-based resin substrate is preferably 170°C or lower. By using such a polyester-based resin base material, the crystallization of the PVA-based resin layer can be suppressed, and extensibility can be sufficiently ensured. Considering the viewpoints of plasticizing the polyester-based resin base material with water and smooth underwater stretching, the temperature is more preferably 120° C. or lower. In one embodiment, the glass transition temperature of the polyester-based resin substrate is preferably 60°C or higher. By using the polyester-based resin base material, the polyester-based resin base material can be prevented from being deformed (eg, unevenness, slump, wrinkle, etc.) when a coating liquid containing the PVA-based resin described later is applied and dried. and other adverse situations. In addition, the laminated body can be favorably stretched at a suitable temperature (for example, about 60° C. to 70° C.). In another embodiment, the glass transition temperature may be lower than 60° C. as long as the polyester-based resin substrate is not deformed when the coating liquid containing the PVA-based resin is applied and dried. In addition, glass transition temperature (Tg) is the value calculated|required based on JISK7121.

In one embodiment, the water absorption rate of the polyester-based resin substrate is preferably 0.2% or more, more preferably 0.3% or more. Such polyester-based resin substrates absorb water, and water acts as a plasticizer for plasticization. As a result, the elongation stress can be greatly reduced in water elongation, and the elongation is excellent. On the other hand, the water absorption rate of the polyester-based resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a polyester-based resin base material, the dimensional stability of the polyester-based resin base material at the time of production can be prevented from being significantly reduced, and the appearance of the resulting laminate can be prevented from deteriorating. It is possible to prevent the PVA-based resin layer from being broken or peeled off from the polyester-based resin substrate when extended in water. In addition, the water absorption rate is the value calculated|required based on JISK7209.

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

Surface modification treatment (for example, corona treatment, etc.) may be performed on the surface of the polyester-based resin substrate in advance. Adhesion can be further improved by these treatments.

A-2. Easy-bond layer As described above, the water contact angle of the easily-bonded layer is 70° or more immediately after water is dropped, and decreases by 2° or more after 30 seconds after dropping. When the water is just dropped, the water contact angle of the easy-bond layer should be 75°~85°. The temporal change of the contact angle of water generated after 30 seconds after dropping should be -2° (2° decrease) ~ -5° (5° decrease). The easy-bond layer has a water contact angle of 70° or more immediately after the drop of water, and a temporal change (decrease) of the water contact angle that occurs 30 seconds after the drop is 2° or more. In the case of a PVA-based resin layer, the composition for forming an easily bonding layer can be eluted into the PVA-based resin layer. Specifically, when the time-dependent change of the above-mentioned water contact angle is -2° to -5° and the coating layer of the PVA-based resin can be formed on the easy-bonding layer, 10% by volume of the composition for forming the easy-bonding layer About 34% by volume can be dissolved into the coating layer of PVA resin. Thereby, the adhesiveness of a polyester-type resin base material and a PVA-type resin layer can be improved.

The easily bonding layer may be a layer formed substantially only from the composition for forming an easily bonding layer described later, or a layer in which the composition for forming an easily bonding layer and the PVA-based resin layer described later are mixed (including compatibility) or area. By forming the easily adhesive layer, excellent adhesion can be obtained. The thickness of the easy-bonding layer is preferably 500 nm to 3000 nm, more preferably 800 nm to 2000 nm. If the thickness of the easily bonding layer is too thin, there is a possibility that sufficient adhesiveness cannot be obtained. On the other hand, if the thickness of the easy-bond layer is too thick, when the PVA-based resin coating layer described later is formed, there may be problems such as sagging and unevenness of the obtained coating film, making it difficult to obtain the appearance. There is a possibility of an excellent laminated body, and the easily bonding layer in this case can be confirmed by, for example, observing a cross section of the laminated body with a scanning electron microscope (SEM).

The easily bonding layer preferably contains a polyvinyl alcohol-based component and a polyolefin-based component. By making it into the above-mentioned composition, the water contact angle and the water contact angle of the easy-bonding layer can be changed over time into the angle within the above-mentioned range, and as a result, the adhesion between the polyester-based resin substrate and the PVA-based resin layer can be obtained. Laminates with excellent properties. Furthermore, by dyeing and extending the above-mentioned laminate, a polarizing plate excellent in adhesion between the polyester-based resin base material and the polarizer can be obtained. Arbitrary and appropriate PVA-type resin can be used for a polyvinyl alcohol-type component. Specifically, polyvinyl alcohol and modified polyvinyl alcohol may be mentioned. The modified polyvinyl alcohol is, for example, polyvinyl alcohol modified with an acetoxyacetyl group, a carboxylic acid group, an acryl group and/or a urethane group. Among these, PVA modified with an acetyl acetyl group is suitable. A polymer having at least a repeating unit represented by the following general formula (I) is preferably used for the acetylacetate group-modified PVA.

[Chemical formula 1]

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 acetylacetate group-modified PVA is preferably 1000-10000, more preferably 1200-5000. The degree of saponification of the acetylacetate-modified PVA should preferably be above 97 mol%. The pH of the 4 wt % aqueous solution of the acetylacetate group-modified PVA is preferably 3.5 to 5.5. In addition, the average polymerization degree and saponification degree can be calculated|required by JISK6726-1994.

Arbitrary and appropriate polyolefin-type resin can be used for the said polyolefin-type component. The main component of the polyolefin-based resin, that is, the olefin component, includes, for example, olefin-based 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 in combination of two or more. Among these, olefinic hydrocarbons having 2 to 4 carbon atoms such as ethylene, propylene, isobutylene, and 1-butene are preferably used, and ethylene is more preferably used.

Among the monomer components constituting the above-mentioned polyolefin-based resin, the proportion of the olefin component is preferably 50% by weight to 95% by weight.

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

The molecular weight of the polyolefin resin is, for example, 5,000 to 80,000.

In the easily bonding layer, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (the former: the latter (solid content)) is preferably 10:90 to 50:50, more preferably 20:80 to 50:50. When there are too many polyvinyl alcohol-type components, sufficient adhesiveness may not be acquired. Specifically, when the PVA-based resin layer is peeled off from the polyester-based resin base material, the required peeling force may decrease and sufficient adhesion may not be obtained. On the other hand, if the polyvinyl alcohol-based component is too small, the appearance of the resulting laminate may be damaged. Specifically, there is a fear that inconveniences such as cloudiness of the coating film may occur when the easily adhesive layer is formed, and it may be difficult to obtain a laminate having an excellent appearance.

A-3. PVA-based resin layer Arbitrary and appropriate resins can be used for the PVA-based resin forming the above-mentioned PVA-based resin layer. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers can be obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. The degree of saponification is obtained according to JIS K 6726-1994. By using the PVA-based resin having the above degree of saponification, a polarizing film excellent in durability can be obtained. When the degree of saponification is too high, there is a risk of gelation.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000~10000, preferably 1200~4500, more preferably 1500~4300. In addition, the average degree of polymerization can be calculated|required based on JISK6726-1994.

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. On the other hand, the thickness of the PVA-based resin layer is preferably 1.0 μm or more, and more preferably 2.0 μm or more.

B. Manufacturing method of laminated body The laminated body of this invention can be manufactured by arbitrary and appropriate methods. In one embodiment, the above-mentioned lamination system is produced by a method including the following steps: forming an easily bonding layer on the surface of a polyester resin base material; and forming a PVA-based resin layer on the surface of the easily bonding layer.

B-1. Formation of easily bonding layer Any appropriate method can be adopted as a method for forming the easily bonding layer on the surface of the polyester resin base material. Typically, the easily bonding layer can be formed by applying the composition for forming an easily bonding layer to the surface of a polyester-based resin substrate and drying it. In the composition for forming an easily bonding layer, the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component (the former: the latter (solid content)) is preferably 10:90 to 50:50, more preferably 20:80 to 20:80. 50:50.

The composition for forming an easily bonding layer is preferably an aqueous system. The composition for forming an easily bonding layer may contain an organic solvent. Ethanol, isopropanol, etc. are mentioned as an organic solvent. The solid content concentration of the composition for forming an easily bonding layer is preferably 1.0% by weight to 10% by weight.

唑啉、硼酸、三羥甲基三聚氰胺等羥甲基化合物、碳二亞胺、異氰酸酯化合物、環氧化合物等。易接著層形成用組成物之添加物摻混量可應目的等適當設定。舉例而言，相對於聚乙烯醇系成分與聚烯烴系成分合計100重量份，交聯劑之摻混量宜為10重量份以下，更宜為0.01重量份~10重量份，又更宜為0.1重量份~5重量份。Additives may be blended in the composition for forming an easily adhesive layer. As an additive, a crosslinking agent etc. are mentioned, for example. Cross-linking agents such as

Methylol compounds such as oxazoline, boric acid, and trimethylol melamine, carbodiimides, isocyanate compounds, epoxy compounds, and the like. The blending amount of the additive of the composition for forming an easily bonding layer can be appropriately set according to the purpose and the like. For example, with respect to 100 parts by weight of the polyvinyl alcohol-based component and the polyolefin-based component in total, the blending amount of the crosslinking agent is preferably 10 parts by weight or less, more preferably 0.01 to 10 parts by weight, and more preferably 0.1 parts by weight to 5 parts by weight.

Arbitrary and appropriate methods can be employ|adopted for the coating method of the composition for easy bonding layer formation. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a blade coating method (comma coating method, etc.) etc. are mentioned.

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

B-2. Formation of PVA-based resin layer Any appropriate method can be adopted for the method of forming the PVA-based resin layer on the surface of the easily bonded layer. The PVA-based resin layer is preferably formed by applying a coating liquid containing a PVA-based resin to the surface of the easy-bonding layer formed on the polyester-based resin substrate and drying it.

The coating liquid containing the PVA-based resin means that a solution obtained by dissolving the above-mentioned PVA-based resin in a solvent is used. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, etc. Amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Among these, water is preferred. The concentration of the PVA-based resin in the coating solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as it is the said resin concentration, a uniform coating film can be formed.

Additives can also be mixed in the coating liquid. Examples of additives include plasticizers, surfactants, and the like. As a plasticizer, polyhydric alcohols, such as ethylene glycol and glycerol, are mentioned, for example. As a surfactant, a nonionic surfactant is mentioned, for example. These can be used in order to further improve the uniformity, dyeability, and extensibility of the obtained PVA-based resin layer. Moreover, as an additive, an easily attachable component is mentioned. The adhesiveness between the polyester-based resin substrate and the PVA-based resin layer can be improved by using the easy-adhesion component. As a result, problems such as peeling of the PVA-based resin layer from the polyester-based base material can be suppressed, and dyeing and underwater stretching, which will be described later, can be performed favorably. As the easy-to-attach component, modified PVA such as acetylacetate modified PVA can be used.

As the coating method of the coating liquid, the same method as the coating method of the composition for forming an easily bonding layer described above can be adopted. After coating, the coating film can be dried. The drying temperature at this time is preferably above 50°C.

Before forming the PVA-based resin layer, a surface treatment (eg, corona treatment, etc.) may also be applied to the easily bonding layer. The adhesiveness between the polyester-based resin base material and the PVA-based resin layer can be improved by performing the above-mentioned treatment.

C. Polarizing plate The polarizing plate of the present invention includes a polyester-based resin substrate having an easily adhesive layer formed on the surface thereof, and a polarizer layered on the polyester-based resin substrate through the easily adhesive layer. The thickness of the polarizing film is 10 μm or less. The easily bondable layer is as described in the above-mentioned item A-2, and the formation method of the easily-bonded layer is as described in the above-mentioned item B-1. Thereby, a polarizing plate having excellent adhesion between the polyester-based resin substrate and the polarizer can be obtained. The polarizer may also have a protective film on the opposite side of the polarizer to the easy-bond layer.

C-1. Polarizer The polarizer is essentially a PVA-based resin layer in which iodine is oriented by adsorption. The thickness of the polarizer is 10 μm or less as described above, preferably 7.5 μm or less, and more preferably 5 μm or less. On the other hand, the thickness of the polarizer is preferably 0.5 μm or more, more preferably 1.5 μm or more. If the thickness is too thin, the optical properties of the resulting polarizer may be degraded. The polarizer should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more, and more preferably 42.0% or more. The degree of polarization of the polarizer should preferably be above 99.8%, preferably above 99.9%, and more preferably above 99.95%.

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

C-2. Protective film As described above, the polarizing plate may have a protective film on the opposite side of the polarizer to the easily bonding layer. Examples of materials for forming the protective film include (meth)acrylic resins, cellulose-based resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin-based resins, olefin-based resins such as polypropylene, and polyterephthalene. Ester-based resins such as ethylene formate-based resins, polyamide-based resins, polycarbonate-based resins, copolymer resins of these, and the like. The thickness of the protective film is preferably 10 μm to 100 μm.

D. Manufacturing method of polarizing plate The manufacturing method of polarizing plate of the present invention includes the steps of dyeing and extending the laminate described in the above-mentioned item A, thereby forming the PVA-based resin layer into a polarizer. In one embodiment, the layered body may be subjected to various treatments such as dyeing treatment, stretching treatment, insolubilization treatment, cross-linking treatment, washing treatment, and drying treatment. These treatments can be appropriately selected according to the purpose. In addition, the processing order, processing sequence, number of processing times, and the like can be appropriately set. Each process will be described below.

D-1. Aerial stretching treatment The stretching method of aerial auxiliary stretching can be fixed-end stretching (such as stretching using a tenter stretching machine), or free-end stretching (such as passing the laminated body between rollers with different peripheral speeds) and uniaxial extension method). In one embodiment, the in-air stretching treatment includes a heat roll stretching step of extending the layered body with the difference in peripheral speed between the heat rolls while conveying the above-mentioned layered body in the longitudinal direction thereof. The in-air stretching process typically includes a zone stretching step and a thermal roll stretching step. In addition, the sequence of the area extending step and the heating roller extending step is not limited. The area extending step may be performed first, or the heating roller extending step may be performed first. The region extension step can also be omitted. In one embodiment, the zone extending step and the thermal roller extending step are performed in this order.

The stretching temperature of the laminate can be set to an arbitrary and appropriate value according to the material for forming the resin base material and the like. The stretching temperature during the air stretching treatment is preferably higher than the glass transition temperature (Tg) of the resin substrate, and the glass transition temperature (Tg) of the resin substrate +10°C or higher is more suitable, and Tg+15°C or higher is particularly suitable. On the other hand, the upper limit of the stretching temperature of the laminate is preferably 170°C. Stretching at such a temperature can suppress rapid progress of crystallization of the PVA-based resin, thereby suppressing inconveniences caused by the crystallization (eg, hindering the orientation of the PVA-based resin layer due to elongation).

The stretching ratio of the layered product can be set to an arbitrary and appropriate value according to the forming material of the resin base material and the like. The stretching ratio of the air stretching treatment is preferably 1.5 times or more and 3.0 times or less.

D-2. Insolubilization Treatment The above insolubilization treatment is performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. Water resistance can be imparted to the PVA-based resin layer by performing the insolubilization treatment. The concentration of the boric acid aqueous solution is preferably 1 to 4 parts by weight relative to 100 parts by weight of water. The temperature of the insoluble bath (boric acid aqueous solution) is preferably 20°C to 50°C. The insolubilization treatment should be carried out before water extension or dyeing treatment.

D-3. Dyeing treatment The above-mentioned dyeing treatment is performed by dyeing the PVA-based resin layer with a dichroic substance. It is preferable to carry out by making a dichroic substance adsorb|suck on the PVA-type resin layer. The adsorption method includes, for example, a method of immersing a PVA-based resin layer (layered body) in a dyeing solution containing a dichroic substance, a method of applying the dyeing solution to the PVA-based resin layer, and the dyeing solution A method of spraying on the PVA-based resin layer, etc. A method of immersing the layered body in the dyeing solution is suitable. Because it can adsorb dichroic substances well.

As said dichroic substance, iodine and an organic dye are mentioned, for example. These may be used alone or in combination of two or more. Dichroic substances are preferably iodine. When iodine is used as the dichroic substance, the above-mentioned dyeing solution is preferably an aqueous iodine solution. The blending amount of iodine is preferably 0.05 parts by weight to 5.0 parts by weight with respect to 100 parts by weight of water. In order to improve the solubility of iodine in water, it is suitable to mix iodide in the iodine aqueous 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, and titanium iodide. Among them, potassium iodide is preferred. The blending amount of the iodide is preferably 0.3 to 15 parts by weight relative to 100 parts by weight of water.

The temperature of the dyeing solution during dyeing is preferably 20°C to 40°C. When the PVA-based resin layer is immersed in the dyeing solution, the immersion time is preferably 10 seconds to 300 seconds. Under these conditions, the dichroic substance can be sufficiently adsorbed to the PVA-based resin layer. In addition, dyeing conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or the single transmittance of the polarizer finally obtained falls within a predetermined range. In one embodiment, the immersion time is set so that the degree of polarization of the obtained polarizer becomes 99.98% or more. In another embodiment, the immersion time is set so that the single transmittance of the obtained polarizer is about 40%.

D-4. Cross-linking treatment The above-mentioned cross-linking treatment is typically performed by immersing the PVA-based resin layer (layered body) in an aqueous solution of boric acid. By performing the 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 5 parts by weight relative to 100 parts by weight of water. In addition, when the crosslinking treatment is performed after the above dyeing treatment, it is preferable to further blend iodide. By blending the iodide, the elution of the iodine adsorbed on the PVA-based resin layer can be suppressed. The blending amount of iodide is preferably 1 to 5 parts by weight relative to 100 parts by weight of water. Specific examples of the iodide are as described above. The liquid temperature of the cross-linking bath (boric acid aqueous solution) is preferably 20°C to 60°C. The cross-linking treatment is preferably carried out before the extension treatment in water. A more ideal embodiment is to carry out in-air extension treatment, dyeing treatment and cross-linking treatment in sequence.

D-5. Underwater extension treatment Any and appropriate methods can be adopted for the extension method of the underwater extension treatment. Specifically, it can be either fixed-end stretching (eg, a method of using a tenter stretching machine) or free-end stretching (eg, a method of uniaxial stretching by passing the laminated body between rolls with different peripheral speeds). In addition, it can be synchronous biaxial stretching (for example, a method using a synchronous biaxial stretching machine) or stepwise biaxial stretching. The extension of the laminate may be performed in one stage or in multiple stages. When it is carried out in multiple stages, the stretching ratio (maximum stretching ratio) of the layered body is the product of the stretching ratios of each stage.

An arbitrary and appropriate direction can be selected for the extending direction of the laminate. In one embodiment, it extends along the longitudinal direction of the elongated laminate. Specifically, the layered body is transported in the longitudinal direction, that is, its transport direction (MD). In another embodiment, it extends along the width direction of the elongated laminated body. Specifically, the laminate is transported in the longitudinal direction, that is, the direction (TD) orthogonal to the transport direction (MD).

The stretching temperature of the laminate can be set to an arbitrary and appropriate value according to the forming material of the resin base material, the stretching method, and the like. The extension temperature is preferably 40°C to 85°C and more preferably 50°C to 85°C. As long as the temperature is within the above-mentioned temperature, the PVA-based resin layer can be suppressed from being dissolved, and at the same time, it can be stretched at a high rate. Specifically, as described above, in consideration of the relationship with the formation of the PVA-based resin layer, the glass transition temperature (Tg) of the resin substrate is preferably 60° C. or higher. At this time, if the stretching temperature is lower than 40° C., even if it is considered to plasticize the resin base material with water, it may not be possible to stretch well. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a fear that excellent optical properties cannot be obtained.

The stretching in water is preferably performed by immersing the layered body in an aqueous solution of boric acid (stretching in water with boric acid). By using the boric acid aqueous solution as the stretching bath, the PVA-based resin layer can be imparted with rigidity capable of withstanding the tension applied during stretching and water resistance insoluble in water. Specifically, boric acid generates tetrahydroxyboronic acid anion in an aqueous solution and can be cross-linked with PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer and good extension can be obtained, and a polarizer having excellent optical properties (eg, degree of polarization) can be produced.

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

If a dichroic substance (represented by iodine) has been adsorbed on the PVA-based resin layer by dyeing treatment in advance, it is suitable to mix the iodide in the stretching bath (boric acid aqueous solution). By blending the iodide, the elution of the iodine adsorbed on the PVA-based resin layer can be suppressed. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among them, potassium iodide is preferred. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, relative to 100 parts by weight of water.

The stretching magnification (maximum stretching magnification) of the layered body is 4.0 times or more, preferably 5.0 times or more, on a representative basis of the original length of the layered body. The high extension ratio can be achieved by using, for example, an underwater extension method (boric acid water extension). In addition, the "maximum stretching ratio" in the present specification means the stretching ratio before the layered body is fractured, and is a value lower than the value by 0.2 after confirming the stretching ratio at which the layered body is fractured.

The extension treatment in water should be carried out after the dyeing treatment.

D-6. Cleaning Treatment The above cleaning treatment can be 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 should be 30℃~100℃. Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. In addition, the measurement method and evaluation method of each characteristic are as follows. (1) Thickness Measured using a digital micrometer (manufactured by Anritsu, product name "KC-351C"). (2) Water contact angle The water contact angle of the easily bonding layer was measured using an automatic contact angle meter (DM500) manufactured by Kyowa Interface Science Co., Ltd., and analyzed using FAMAS (contact angle measurement plug-in program). As the water system for measurement, ultrapure water was used, and the titration was 0.5 μl. After forming an easily bondable layer on the surface of the polyester-based resin substrate, the water contact angle (θ1) after 1 second after water was dropped on the easily bondable layer, and the water contact angle (θ2) after 30 seconds after dropping, were measured. The temporal change (θ2-θ1) of the water contact angle over 30 seconds was calculated.

<Example 1> 1. Fabrication of laminated body polyester-based resin base material A long strip, water absorption rate 0.75%, Tg 75°C amorphous isophthalic acid copolymer polyethylene terephthalate (IPA copolymer PET) is used Thin film (thickness: 100 μm). Corona treatment is applied to one side of the polyester resin base material, and the mixed solution (solid content concentration 4.0%) is applied on the corona treated side so that the thickness after drying becomes 2000 nm, and the temperature is 60°C. It was dried for 3 minutes to form an easily bonding layer, and the mixed solution was a modified PVA of acetyl acetyl group (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200", degree of polymerization 1200, degree of saponification 99.0 mol% or more, A 4.0% aqueous solution of acetyl acetyl group modification degree of 4.6%), an aqueous dispersant for modified polyolefin resin (manufactured by Unitika, trade name "ARROW BASE SE1030N", solid content concentration 22%) mixed with pure water . Here, the mixing ratio of the solid content of the acetylacetate-modified PVA and the modified polyolefin in the mixed solution is 50:50. Then, corona treatment is applied to the surface of the easily adhesive layer, and the corona treated surface is coated with polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and ethylene glycol in a ratio of 9:1 at 25°C. An aqueous solution of PVA modified with acetoacetyl group (degree of polymerization 1200, degree of acetoacetyl group modification 4.6%, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") and dried, Then, a PVA-based resin layer with a thickness of 11 μm was formed. A layered body was produced as described above. 2. Fabrication of polarizers The obtained laminates were uniaxially stretched by 2.0 times at the free end in the longitudinal direction (longitudinal direction) between rollers with different peripheral speeds in an oven at 120°C (in-air extension). Next, the layered body was immersed in an insolubilization bath (a 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 (insolubility treatment). Next, the obtained polarizing plate was immersed in a dyeing bath with a liquid temperature of 30° C. while adjusting the iodine concentration and the immersion time so that the obtained polarizing plate had a predetermined transmittance. In the present example, it was immersed in an iodine aqueous solution obtained by blending 0.2 parts by weight of iodine and 1.0 parts by weight of potassium iodide with respect to 100 parts by weight of water for 60 seconds (dyeing treatment). Next, it was immersed for 30 seconds in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment) . Then, while immersing the layered body in an aqueous solution of boric acid at a liquid temperature of 70° C. (an aqueous solution obtained by mixing 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 the rollers with different peripheral speeds The longitudinal direction (longitudinal direction) was uniaxially stretched so that the total stretching magnification was 5.5 times (in-water stretching). Then, the layered body was immersed in a cleaning bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30°C (cleaning treatment). As described above, a polarizing plate in which a polarizer with a thickness of 5 μm was formed on one side of a polyester-based resin substrate with a thickness of 30 μm was obtained.

<Example 2> A polarizing plate was obtained in the same manner as in Example 1, except that the solid content mixing ratio of the acetylacetate group-modified PVA and the modified polyolefin in the mixed solution was 30:70.

<Example 3> A polarizing plate was obtained in the same manner as in Example 1, except that the solid content mixing ratio of the acetylacetate group-modified PVA and the modified polyolefin in the mixed solution was 20:80.

<Example 4> A polarizing plate was obtained in the same manner as in Example 1, except that the solid content mixing ratio of the acetylacetate group-modified PVA and the modified polyolefin in the mixed solution was set to 10:90.

<Comparative Example 1> A polarizing plate was obtained in the same manner as in Example 1, except that a 4.0% aqueous solution of acetylacetate-modified PVA (GOHSEFIMER Z200) was used in forming the easily adhesive layer.

<Comparative Example 2> A polarizing plate was obtained in the same manner as in Example 1, except that the solid content mixing ratio of the acetylacetate group-modified PVA and the modified polyolefin in the mixed solution was 90:10.

<Comparative Example 3> A polarizing plate was obtained in the same manner as in Example 1, except that the solid content mixing ratio of the acetylacetate group-modified PVA and the modified polyolefin in the mixed solution was 70:30.

<Comparative Example 4> To form the easily adhesive layer, a mixed solution ( A polarizing plate was produced in the same manner as in Example 3, except that the solid content concentration was 4.0%.

(Evaluation) Adhesion was evaluated by measuring the PVA peeling force and the substrate peeling force with respect to the above-mentioned Examples and Comparative Examples. The evaluation results are summarized in Table 1. The measurement methods of PVA peel force and substrate peel force are as follows. (PVA peeling force) The obtained polarizing plate was coated with an adhesive on the surface side of the polyester resin base material, and then attached to a glass plate, and then a reinforcing polyimide tape (Nitto Denko (Nitto Denko) was attached to the polarizer surface. Co., Ltd.), Polyimide Adhesive Tape No. 360A), and produced a sample for measurement. After a slit was made between the polarizer and the polyester resin substrate of the sample for measurement with a cutter, an angle-variable adhesive and film peeling analyzer "VPA-2" (manufactured by Kyowa Interface Chemical Co., Ltd.) was used. ), measure the force required to lift the polarizer and the polyimide tape for reinforcement at an angle of 90° relative to the surface of the polyester resin substrate and peel it off at a peeling speed of 3000mm/min (N/15mm ). (Substrate peeling force) The obtained polarizing plate was coated with an adhesive on the polarizer surface side, and was attached to a glass plate to prepare a sample for measurement. After making a cut between the polarizer and the polyester-based resin substrate of the sample for measurement with a cutting knife, the polyester-based resin substrate was measured at 90° with respect to the polarizer surface by the above-mentioned "VPA-2" measurement. The force (N/15mm) required to pick up at an angle of ° and peel it off at a peeling speed of 3000mm/min. [Table 1]

It can be clearly seen from Table 1 that the water contact angle of the easily bonding layer of the polarizing plates of Examples 1 to 4 is 70° or more when the water is just dropped, and the water contact angle of the easily bonding layer is 30 seconds after dropping. It is reduced by 2° or more, so the adhesion between the polarizer and the polyester-based resin substrate is excellent.

INDUSTRIAL APPLICABILITY The laminate of the present invention is applicable to the production of polarizing plates. The polarizing plate of the present invention can be suitably used in image display devices such as liquid crystal display devices and organic EL display devices.

10‧‧‧Polyester-based resin substrate 20‧‧‧Easy bonding layer 30‧‧‧Polyvinyl alcohol-based resin layer 100‧‧‧Laminated body

FIG. 1 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.

10‧‧‧Polyester resin base material

20‧‧‧Easy bonding layer

30‧‧‧Polyvinyl alcohol resin layer

100‧‧‧Laminate

Claims (5)

A laminate comprising: a polyester-based resin substrate having an easily bonding layer formed on the surface; and a polyvinyl alcohol-based resin layer, which are laminated on the polyester-based resin substrate through the easily bonding layer; the easily bonding layer contains a polymer The water contact angle of the vinyl alcohol-based component and the polyolefin-based component and the easily bonding layer is 70° or more immediately after water is dropped on the easily bonding layer, and decreases by 2° or more 30 seconds after the drop. The laminate according to claim 1, wherein the blending ratio of the polyvinyl alcohol-based component and the polyolefin-based component is 10:90 to 50:50. A method for manufacturing a laminate, comprising the steps of: forming an easily bonding layer on the surface of a polyester resin substrate; and forming a polyvinyl alcohol-based resin layer on the surface of the easily bonding layer; the easily bonding layer containing a polyvinyl alcohol-based component The water contact angle with the polyolefin-based component and the easily bonding layer is 70° or more immediately after water is dropped on the easily bonding layer, and decreases by 2° or more 30 seconds after the drop. A method for manufacturing a polarizing plate, comprising the steps of: dyeing and extending the laminate as claimed in claim 1 or 2, thereby forming the polyvinyl alcohol-based resin layer into a polarizer. A polarizing plate comprising: a polyester-based resin substrate with an easily-bonded layer formed on the surface; and a polarizer, which is laminated on the polyester-based resin substrate through the easily-bonded layer; the thickness of the polarizer is 10 μm or less; the aforementioned The easy-bonding layer contains polyvinyl alcohol-based components and polyolefin-based components; The water contact angle of the easily bonding layer was 70° or more immediately after water was dropped on the easily bonding layer, and decreased by 2° or more 30 seconds after the drop.

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