CN106353846A - Manufacturing method of polarizing plate - Google Patents

Abstract

The invention provides a manufacturing method of a polarizing plate, which is used to provide a resin base material having excellent stripping performance. The manufacturing method of the polarizing plate comprises steps that the tensioning and the dyeing of the strip-shaped resin base material (11) and a stacked body (10) of a polyvinyl alcohol resin layer (12) disposed on the single side of the strip-shaped resin base materials (11) are carried out, and a polarizing film (12) is formed on the resin base materials (11); a protection thin film (20) is disposed on the side layer of the polarizing film (12) of the stacked body (10), and a polarizing thin film stacked body (100) is manufactured; a wedge-shaped cutter (1) narrowed gradually toward a cutting edge is used to cut the two end parts of the polarizing thin film stacked body (100) in a width direction. During the cutting, the thicker part of the cutter (1) is disposed on the resin base material (11), and the thinner part of the cutter (1) is disposed on the protection thin film (20) side so that the cutting edge of the cutter (1) abuts against the polarizing thin film stacked body (100).

Description

Manufacturing method of polarizing plate

technical field

The present invention relates to a method for manufacturing a polarizing plate.

Background technique

A polarizing plate including a polarizing film is used in image display devices such as liquid crystal display devices. As a method of obtaining this polarizing film, for example, a method has been proposed in which a laminate having a resin base material and a polyvinyl alcohol (PVA)-based resin layer is stretched, and then dyed to obtain polarized light on the resin base material. Membrane method (for example, Patent Document 1). Since such a method can obtain a thin polarizing film, it contributes to the reduction in thickness of image display devices in recent years, and has attracted attention for this reason.

However, the above-mentioned polarizing film is usually laminated with a protective film and used as a polarizing plate. In this case, the above-mentioned resin base material may be peeled from the polarizing film, and in this case, there is a problem that a peeling failure of the resin base material is likely to occur.

prior art literature

patent documents

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

Contents of the invention

The problem to be solved by the invention

The present invention was made to solve the above-mentioned conventional technical problems, and an object of the present invention is to provide a method for manufacturing a polarizing plate excellent in peelability of a resin substrate.

solutions to problems

The method for producing a polarizing plate of the present invention includes the steps of stretching and dyeing a laminate having a long resin substrate and a polyvinyl alcohol-based resin layer provided on one side of the resin substrate, thereby A step of forming a polarizing film on the resin substrate; a step of laminating a protective film on the polarizing film side of the laminate to produce a polarizing film laminate; The process of cutting both ends of the width direction. When dicing, the edge of the dicing blade is brought into contact with the polarizing film laminate so that the relatively thick portion of the dicing blade is positioned on the resin substrate side and the relatively thin portion of the dicing blade is positioned on the protective film side.

In one embodiment, cutting is performed using the above-mentioned rotary cutting knife and a bed knife, and the cutting edge of the cutting knife partially overlaps with the knife edge of the bed knife.

In one embodiment, the overlapping length L (mm) of the overlapping and the thickness d (mm) of the polarizing film laminate satisfy the relationship of d≦L≦d+15.

In one embodiment, the rotational speed of the cutting blade is 90% to 130% relative to the transport speed of the polarizing film laminate.

In one embodiment, the step of peeling the above-mentioned resin base material from the above-mentioned polarizing film laminate after the above-mentioned dicing is further included.

In one embodiment, the indentation hardness of the surface of the protective film exceeds 0.21 GPa.

In one embodiment, the protective film has a resin film and a surface treatment layer formed on one side of the resin film.

In one embodiment, the pencil hardness of the surface treatment layer surface is H or more.

In one embodiment, the above-mentioned surface treatment layer has anti-glare properties.

According to other aspects of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the above-mentioned manufacturing method.

The effect of the invention

According to the present invention, it is possible to cut the widthwise end of a polarizing film laminate obtained by laminating a protective film on a polarizing film provided on a resin base material so that the blade portion of the dicing blade is in contact with the resin base material side. Excellent peelability of resin substrates is obtained. As a result, a polarizing plate excellent in appearance can be manufactured while maintaining high productivity.

Description of drawings

FIG. 1 is a partial cross-sectional view of a laminated body according to one embodiment of the present invention.

Fig. 2 is a schematic diagram showing an example of the cutting step of the present invention, and is a perspective view showing a cutting part.

3 is a schematic diagram showing an example of the cutting process of the present invention, (a) is a view of a cutting blade and a bed knife viewed from the side, and (b) is an explanatory diagram showing the state of cutting with the cutting blade.

Explanation of reference signs

10 stacks

11 resin substrate

12 Polyvinyl alcohol-based resin layer (polarizing film)

20 protective film

100 Polarizing film laminate

detailed description

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

The method for producing a polarizing plate of the present invention includes the steps of stretching and dyeing a laminate having a long resin substrate and a polyvinyl alcohol-based resin layer provided on one side of the resin substrate, thereby A process of forming a polarizing film on a resin substrate; a process of laminating a protective film on the polarizing film side of the laminate to produce a polarizing film laminate; and a process of cutting the widthwise end of the polarizing film laminate with a dicing knife. Hereinafter, each step will be described.

A. Production of polarizing film

A-1. Laminated body

FIG. 1 is a partial cross-sectional view of a laminated body according to one embodiment of the present invention. The laminated body 10 has a resin base material 11 and a polyvinyl alcohol-based resin layer 12 provided on one side of the resin base material. The laminated body 10 is produced by providing a polyvinyl alcohol-based resin layer 12 on a long resin substrate 11 . Any appropriate method can be adopted as a method for producing the laminate. In one embodiment, a coating liquid containing a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") is coated on a resin substrate, and dried as necessary to produce a laminate. In another embodiment, a laminated body is produced by laminating a film containing a PVA-based resin on a resin base material. Here, the film containing the PVA-based resin can be laminated using any appropriate adhesive layer.

Any appropriate material can be adopted as a material for forming the above-mentioned resin base material. For example, ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, (meth)acrylic resins, polyamide resins, polycarbonate resins, etc. Resins, their copolymer resins. A polyethylene terephthalate-based resin is preferably used. Among these, amorphous polyethylene terephthalate-based resins are particularly preferably used. Specific examples of amorphous polyethylene terephthalate-based resins include copolymers further containing isophthalic acid as dicarboxylic acid, and copolymers further containing cyclohexanedimethanol as diol. things.

The glass transition temperature (Tg) of the resin substrate is preferably 120°C or lower, more preferably 100°C or lower. This is because, when the laminate is stretched, crystallization of the PVA-based resin layer can be suppressed, and stretchability (especially stretchability in underwater stretching) can be sufficiently ensured. As a result, a polarizing film having excellent optical characteristics (for example, degree of polarization) can be produced. On the other hand, the glass transition temperature of the resin substrate is preferably 60° C. or higher. In addition, glass transition temperature (Tg) is the value calculated|required based on JISK7121.

The water absorption of the resin substrate is preferably 0.2% or more, more preferably 0.3% or more. Such a resin base material can absorb water, and water can act as a plasticizer to be plasticized. As a result, tensile stress can be significantly reduced and excellent stretchability can be achieved. On the other hand, the water absorption of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, troubles such as deterioration of the appearance of the obtained polarizing film due to a marked decrease in the dimensional stability of the resin base material during production can be prevented. In addition, it is possible to prevent breakage and peeling of the PVA-based resin layer from the resin base material at the time of stretching in water. In addition, the water absorption rate is the value calculated|required based on JISK7209.

The thickness of the resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. Surface modification treatment (for example, corona treatment, etc.) may be performed on the surface of the resin base material, and an easily bonding layer may be formed thereon. By such a treatment, a laminate excellent in the adhesiveness between the resin base material and the PVA-based resin layer can be obtained.

Any appropriate resin can be adopted as the PVA-based resin for forming the above-mentioned PVA-based resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol % to 100 mol %, preferably 95.0 mol % to 99.95 mol %, more preferably 99.0 mol % to 99.93 mol %. The degree of saponification can be determined based on JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizing film excellent in durability can be obtained. When the saponification is too high, gelation may occur.

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 1,000 to 10,000, preferably 1,200 to 4,500, more preferably 1,500 to 4,300. In addition, the average degree of polymerization can be calculated based on JISK 6726-1994.

As the above-mentioned coating liquid, a solution obtained by dissolving the above-mentioned PVA-based resin in a solvent is typically used. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, and polyalcohols such as trimethylolpropane. , Ethylenediamine, diethylenetriamine and other amines. These solvents may be used alone or in combination of two or more. Among them, water is preferable. The concentration of the PVA-based resin in the solution can be set to any appropriate value. For example, it can be set according to the degree of polymerization, saponification degree, etc. of PVA-type resin. The PVA-type resin density|concentration of a solution is 3 weight part - 20 weight part with respect to 100 weight part of solvents, for example.

Additives may be contained in the above coating liquid. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As surfactant, a nonionic surfactant is mentioned, for example. These additives can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer. Moreover, as an additive, an easy-adhesive component is mentioned, for example. By using an easily bonding component, the adhesiveness of a resin base material and a PVA-type resin layer can be improved. As a result, for example, defects such as peeling of the PVA-based resin layer from the resin base material can be suppressed, and dyeing and underwater stretching, which will be described later, can be performed satisfactorily. As the easy-adhesion component, modified PVA such as acetoacetyl-modified PVA is used, for example.

Any appropriate method can be adopted as the coating method of the coating liquid. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method etc.) etc. are mentioned. The coating and drying temperature of the coating liquid is, for example, 20°C or higher, preferably 50°C or higher.

The thickness of the PVA-based resin layer is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm. The width (before stretching) of the laminate can be set to any appropriate value. Typically, it is 1500 mm or more, preferably 2000 mm to 5000 mm.

A-2. Stretching

Any appropriate method can be adopted as the method for stretching the laminate. Specifically, it may be fixed-end stretching (for example, a method using a tenter), or open-end stretching (for example, a method of uniaxially stretching a laminate by passing between rolls having different peripheral speeds). In addition, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) or sequential biaxial stretching may be used. The stretching of the laminate may be performed in one step or in multiple steps. When carrying out in multiple stages, the stretch ratio (maximum stretch ratio) of the laminated body mentioned later is the product of the stretch ratio of each stage.

Stretching may be an underwater stretching method in which the laminate is immersed in a stretching bath, or an in-air stretching method. It is preferable to perform underwater stretching at least once, and it is more preferable to combine aerial stretching and underwater stretching. By stretching in water, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80°C) of the above-mentioned resin base material and PVA-based resin layer, and the crystallization of the PVA-based resin layer can be suppressed. Stretch the PVA-based resin layer. As a result, a polarizing film having excellent optical characteristics can be produced. When aerial stretching and underwater stretching are combined, underwater stretching is preferably performed after aerial stretching. It should be noted that, when the underwater stretching can be performed well, the adhesiveness between the resin base material and the PVA-based resin layer can be excellent, and the effect of improving the peelability of the resin base material through the cutting process described later can be achieved. become noticeable.

Any appropriate direction can be selected as the stretching direction of the laminate. In one embodiment, the elongated laminate is stretched in the longitudinal direction. Specifically, the laminate is conveyed in the longitudinal direction, and the stretching direction is its conveyance direction (MD). In another embodiment, the elongated laminate is stretched in the width direction. Specifically, the laminate is conveyed in the longitudinal direction, and the stretching direction is a direction (TD) perpendicular to the conveyance direction (MD).

The stretching temperature of the laminate can be set to any appropriate value according to the forming material of the resin base material, the stretching method, and the like. When the in-air stretching method is adopted, the stretching temperature is preferably above the glass transition temperature (Tg) of the resin base material, more preferably above the glass transition temperature (Tg) of the resin base material + 10° C., and particularly preferably Tg + 15 °C. ℃ or more. On the other hand, the stretching temperature of the laminate is preferably 170° C. or lower. Stretching at such a temperature suppresses rapid crystallization of the PVA-based resin, thereby suppressing defects caused by the crystallization (for example, disturbance of orientation of the PVA-based resin layer by stretching).

When the underwater stretching method is adopted as the stretching method, the liquid temperature of the stretching bath is preferably 40°C to 85°C, more preferably 50°C to 85°C. When the above temperature is used, the dissolution of the PVA-based resin layer can be suppressed and high-magnification stretching can be performed. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60° C. or higher in relation to the formation of the PVA-based resin layer. In this case, when the stretching temperature is lower than 40° C., there is a possibility that satisfactory stretching may not be possible even considering the plasticization of the resin base material by water. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical properties cannot be obtained.

When the underwater stretching method is adopted, it is preferable to stretch the laminate by immersing it in an aqueous solution of boric acid (boric acid underwater stretching). By using the boric acid aqueous solution as a stretching bath, rigidity capable of withstanding tension applied during stretching and water resistance insoluble in water can be imparted to the PVA-based resin layer. Specifically, boric acid generates a tetrahydroxyborate anion in an aqueous solution, and can cross-link with a PVA-based resin through a hydrogen bond. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, stretching can be performed favorably, and a polarizing film having excellent optical characteristics can be produced.

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

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

The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretch ratio (maximum stretch ratio) of the laminate is preferably 5.0 times or more relative to the initial length of the laminate. Such a high stretching ratio can be obtained by using, for example, an underwater stretching method (boric acid underwater stretching). The stretching ratio of the laminated body by stretching in water is preferably 2.0 times or more. It should be noted that, in this specification, "maximum stretching ratio" refers to the stretching ratio immediately before the fracture of the laminated body, and the stretching ratio at which fracture of the laminated body is confirmed separately, and "maximum stretching ratio" refers to the ratio of the laminated body to fracture. The value of the stretch ratio is lower than the value of 0.2.

Underwater stretching is preferably performed after dyeing described later.

A-3. Dyeing

The above-mentioned dyeing is typically performed by dyeing the PVA-based resin layer with a dichroic substance. It is preferably performed by allowing the PVA-based resin layer to adsorb a dichroic substance. As the adsorption method, for example, a method of immersing a PVA-based resin layer (laminated body) in a dyeing liquid containing a dichroic substance, a method of applying the dyeing liquid to a PVA-based resin layer, and a method of applying the dyed liquid to a PVA-based resin The method of spraying the dyeing solution layer by layer, etc. A method of immersing the PVA-based resin layer in a dyeing solution is preferred. This is because the dichroic substance can be adsorbed well.

Examples of the dichroic substance include iodine and organic dyes. These dichroic substances can be used alone or in combination of two or more. The dichroic substance is preferably iodine. When iodine is used as the dichroic substance, the above-mentioned dyeing solution is preferably an iodine aqueous solution. It is preferable that the compounding quantity of iodine is 0.1 weight part - 0.5 weight part with respect to 100 weight part of water. In order to increase the solubility of iodine in water, it is preferable to mix an iodide compound in an iodine aqueous solution. Examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide Wait. Among them, potassium iodide is preferable. The compounding quantity of an iodide is preferably 0.02-20 weight part with respect to 100 weight part of water, More preferably, it is 0.1-10 weight part.

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

A-4. Others

In addition to stretching and dyeing, the above-mentioned laminate may be suitably given a treatment for forming the PVA-based resin layer into a polarizing film. As a process for forming a polarizing film, an insolubilization process, a crosslinking process, a washing process, a drying process, etc. are mentioned, for example. It should be noted that the number, order, and the like of these processes are not particularly limited.

The above insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Water resistance can be provided to a PVA-type resin layer by performing an insolubilization process. 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 liquid temperature of the insolubilization bath (boric acid aqueous solution) is preferably 20°C to 50°C. The insolubilization treatment is preferably performed before the above-mentioned underwater stretching and the above-mentioned dyeing treatment.

The above-mentioned crosslinking treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Water resistance can be imparted to a PVA-type resin layer by performing a crosslinking process. 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 performing crosslinking treatment after the above-mentioned dyeing treatment, it is preferable to further compound iodide. By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. It is preferable that the compounding quantity of an iodide is 1 weight part - 5 weight part with respect to 100 weight part of water. Specific examples of iodide are as described above. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably 20°C to 60°C. The crosslinking treatment is preferably performed before the above-mentioned underwater stretching. In a preferred embodiment, dyeing treatment, crosslinking treatment, and underwater stretching are carried out in this order.

The above cleaning treatment is typically performed by immersing the PVA-based resin layer in an aqueous potassium iodide solution. The drying temperature in the above drying treatment is preferably 30°C to 100°C.

A-5. Polarizing film

The polarizing film is substantially a PVA-based resin film in which a dichroic substance is adsorbed and oriented. The thickness of the polarizing film is preferably 10 μm or less, more preferably 7 μm or less, particularly preferably 5 μm or less. On the other hand, the thickness of the polarizing film is preferably 0.5 μm or more, more preferably 1.0 μm or more. The polarizing film preferably exhibits absorption dichroism at any wavelength from 380 nm to 780 nm. The single sheet transmittance of the polarizing film is preferably 40.0% or higher, more preferably 41.0% or higher, still more preferably 42.0% or higher, particularly preferably 43.0% or higher. The degree of polarization of the polarizing film is preferably 99.8% or higher, more preferably 99.9% or higher, and still more preferably 99.95% or higher.

B. Fabrication of Polarizing Film Laminate

After the above-mentioned various treatments were performed on the laminate (PVA-based resin layer), a protective film was laminated on the polarizing film (PVA-based resin layer) side of the laminate to produce a polarizing film laminate. Specifically, elongated protective films are laminated on the above-mentioned laminated body so that the respective longitudinal directions are aligned.

The above-mentioned stretching may cause curling of the laminated body. Curls tend to occur at the widthwise end portions of the laminate. One of the causes of curling is considered to be shrinkage due to stretching. When the laminate is stretched, there is a difference in shrinkage force between the PVA-based resin layer and the resin base material (generally, the shrinkage force of the PVA-based resin layer is greater), and curling may occur due to the difference in shrinkage force. The shrinking direction is generally a direction approximately perpendicular to the stretching direction, and when the laminate is stretched in the longitudinal direction (longitudinal stretching), convex curls may occur on the resin substrate side approximately parallel to the stretching direction. On the other hand, when stretching the laminated body in the width direction (transverse stretching), specifically, when the ends of the laminated body are gripped by clips of a tenter and stretched, after stretching, the clips may be stretched. Curling due to tension applied to the outside in the width direction occurs in the vicinity of the grip portion. In this way, regardless of longitudinal stretching or lateral stretching, curling tends to occur at the ends in the width direction of the laminate. A polarizing film laminate obtained by laminating a protective film on a laminate can suppress curl well.

The width of the protective film is set, for example, according to the width of the polarizing film of the laminate. Specifically, it may be larger or smaller than the width of the polarizing film, or substantially the same. In one embodiment, it is set larger than the width of the polarizing film. In this case, it is preferable to laminate|stack so that a protective film may protrude to the outside of both width directions of a polarizing film. The width of the protective film can be set to any appropriate value. Typically, it is 500 mm or more and 3000 mm or less, preferably 1000 mm or more and 2500 mm or less.

The above-mentioned protective film includes a resin film. Examples of the forming material of the resin film include cellulose-based resins such as cellulose triacetate (TAC), cycloolefin-based resins such as norbornene-based resins, olefin-based resins such as polyethylene and polypropylene, and polyester-based resins. , (meth)acrylic resin, etc. In addition, "(meth)acrylic resin" means an acrylic resin and/or a methacrylic resin.

As said (meth)acrylic resin, the (meth)acrylic resin which has a glutarimide structure is used, for example. (Meth)acrylic resins having a glutarimide structure (hereinafter also referred to as glutarimide resins) are described in, for example, Japanese Patent Application Laid-Open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Patent Laid-Open No. Japanese Patent Laid-Open No. 2006-328329, Japanese Patent Laid-Open No. 2006-328334, Japanese Patent Laid-Open No. 2006-337491, Japanese Patent Laid-Open No. 2006-337492, Japanese Patent Laid-Open No. 2006-337493, and Japanese Patent Laid-Open No. 2006-337569 Gazette, JP 2007-009182 Gazette, JP 2009-161744 Gazette, JP 2010-284840 Gazette. These descriptions are incorporated in this specification as a reference.

In one embodiment, the protective film has the above-mentioned resin film and a surface treatment layer formed on one side of the resin film. At this time, the protective film is laminated on the laminate so that the resin film is positioned on the laminate side. In such an embodiment, the effect of improving the peelability of the resin base material by the dicing method described later can be remarkably obtained.

The thickness of the surface treatment layer is typically 20.0 μm or less, preferably 3.0 μm to 15.0 μm, more preferably 5.0 μm to 10.0 μm.

The pencil hardness of the surface of the surface treatment layer under a load of 500 g based on JIS K 5600-5-4 is preferably H or higher, more preferably 2H or higher.

Examples of the material for forming the surface treatment layer include thermosetting resins and ultraviolet curable resins. As the thermosetting resin and the ultraviolet curable resin, for example, a curable compound having at least one of an acrylate group and a methacrylate group can be used. Specifically, silicone resins, polyester resins, polyether resins, epoxy resins, polyurethane resins, amide resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyenes, Oligomers or prepolymers of acrylates, methacrylates, etc. of polyfunctional compounds such as resins, polyols, etc.

The surface treatment layer may have antiglare properties. By having anti-glare properties, it is possible to prevent reduction in visibility of transmitted light due to reflection of outdoor light on the surface of the image display device, for example. Anti-glare properties can be obtained by imparting unevenness to the surface of the surface treatment layer. Impartment of the concavo-convex shape is performed by any appropriate method. Typical examples include roughening (for example, sandblasting, embossing) and compounding of fine particles. When fine particles are used, the fine particles may be inorganic fine particles or organic fine particles. The average particle diameter of the fine particles is preferably 0.5 μm to 20 μm. The compounding quantity of fine particles is preferably 2 to 70 parts by weight, more preferably 5 to 50 parts by weight with respect to 100 parts by weight of the resin.

The thickness of the protective film (the total thickness when the protective film has a resin film and a surface treatment layer formed on one side of the resin film) is typically 10 μm to 100 μm.

The indentation hardness of the protective film surface is, for example, more than 0.21 GPa, preferably more than 0.25 GPa, more preferably 0.30 GPa or more, even more preferably 0.35 GPa or more. When it exists in such a range, the effect of improving the peelability of a resin base material by the dicing method mentioned later can be acquired remarkably. In addition, a polarizing plate excellent in scratch resistance and durability can be obtained. On the other hand, the indentation hardness of the surface of the protective film is, for example, 0.50 GPa or less. In addition, in this specification, "indentation hardness" means the value at the indentation depth 450nm measured with the micro-indentation hardness tester.

The arithmetic mean roughness Ra of the surface of the protective film is preferably 0.3 μm to 2.0 μm. In addition, arithmetic mean roughness Ra is based on the regulation of JISB0601.

Lamination of the protective film typically uses an adhesive. Specifically, a protective film is attached to the surface of the polarizing film using an adhesive. Any appropriate adhesive is used as the adhesive. For example, water-based adhesives, solvent-based adhesives, active energy ray-curable adhesives, and the like are used.

In one embodiment, a water-based adhesive containing a PVA-based resin is used as the adhesive. The average degree of polymerization of the PVA-based resin contained in the water-based adhesive is preferably about 100 to 5000, more preferably 1000 to 4000, from the viewpoint of adhesiveness. The average degree of saponification is preferably about 85 mol % to 100 mol %, more preferably 90 mol % to 100 mol %, from the viewpoint of adhesiveness.

The PVA-based resin contained in the water-based adhesive preferably contains an acetoacetyl group. This is because excellent adhesion between the PVA-based resin layer and the protective film and excellent durability can be achieved. The acetoacetyl group-containing PVA-based resin is obtained, for example, by reacting a PVA-based resin with diketene by an arbitrary method. The acetoacetyl modification degree of the acetoacetyl group-containing PVA-based resin is typically 0.1 mol % or more, preferably about 0.1 mol % to 40 mol %, more preferably 1 mol % to 20 mol %, particularly preferably 2 mol% to 7 mol%. In addition, the modification degree of acetoacetyl group is the value measured by NMR.

The resin concentration of the water-based adhesive is preferably 0.1% by weight to 15% by weight, more preferably 0.5% by weight to 10% by weight.

The thickness at the time of application of the adhesive can be set to any appropriate value. For example, it is set so that the adhesive bond layer which has the target thickness can be obtained after heating (drying). The thickness of the adhesive layer is preferably 10 nm to 300 nm, more preferably 10 nm to 200 nm, particularly preferably 20 nm to 150 nm.

Heating is preferably performed after laminating the protective film. The heating temperature is preferably 50°C or higher, more preferably 55°C or higher, still more preferably 60°C or higher, particularly preferably 80°C or higher. In addition, the heating performed after laminating|stacking a protective film may also be used as the drying process of the said laminated body. In addition, heating may be performed after dicing described later, but heating is preferably performed before dicing. This is because cutting can be performed with higher precision.

The thickness of the polarizing film laminate is, for example, 30 μm to 150 μm.

c. cutting

The width direction end part of the said polarizing film laminated body is slit into a strip shape. The diced sheet obtained by dicing preferably includes the above-mentioned resin substrate, a polarizing film, and a protective film. The cutting width is, for example, 10 mm to 100 mm from the end of the polarizing film or the protective film. As described above, curling tends to occur at the end portions in the width direction of the laminate, and bonding failure (such as wrinkles) between the laminate and the protective film tends to occur at the end portions in the width direction. Removing the defective bonding portion by dicing can suppress the peeling failure (for example, breakage) of the resin base material described later.

2 and 3 are schematic diagrams showing an example of the cutting process. FIG. 2 is a perspective view showing the cutting part. FIG. An explanatory diagram of the state of cutting with a cutter. Both ends 101 , 101 in the width direction of the polarizing film laminate 100 having the laminate 10 and the protective film 20 are cut along the longitudinal direction 30 by a dicing blade. By using the cutter, productivity can be made excellent. In addition, the deformation of the cut end can be suppressed, and the reduction in peelability of the resin base material due to the deformation can be avoided.

As shown in FIG. 3 , the polarizing film laminate 100 is cut using a cutting blade 1 and a bottom knife 2 for supporting the polarizing film laminate 100 . The cutting blade 1 and the bed knife 2 are supported so that respective blades partially overlap each other. The overlapping length L is set according to, for example, the thickness of the polarizing film laminate to be cut. The overlapping length L preferably satisfies the relationship of d≦L≦d+0.15 mm with respect to the thickness d (mm) of the polarizing film laminate. The overlapping length L is, for example, 0.2 mm to 2.0 mm. The cutter shaft 1 a and the bottom knife shaft 2 a are arranged parallel to the polarizing film laminate 100 . The polarizing film laminate 100 is conveyed in the direction of the arrow so that the resin base material 11 faces the dicing blade 1 . The polarizing film laminate 100 is passed between the dicing knife 1 and the bed knife 2 to slit the width direction end into a strip shape. The transport speed of the polarizing film laminate 100 is set, for example, in the range of 10 m/min to 50 m/min.

The bedknife 2 is not fixed on the bedknife shaft 2a but is free to rotate (for example in a counterclockwise direction). The cutting blade 1 is mounted on the cutting blade shaft 1a by being spring biased so as to abut against the bed knife 2 by any suitable supporting mechanism, and rotates integrally with the cutting blade shaft 1a (for example, in a clockwise direction). The contact pressure between the cutting blade and the bed knife is set according to the shape of the blade described later, for example. The contact pressure between the cutting blade and the bed knife is, for example, 2.0N to 10.0N. The rotation speed of the cutter is preferably about the same as or faster than the transport speed of the polarizing film laminate. Specifically, the rotational speed of the cutter blade is set to, for example, 90% to 130%, preferably 95% to 130%, and more preferably 98% to 130% with respect to the transport speed of the polarizing film laminate.

The outer diameters of the cutting knife and the bed knife are, for example, 90.0 mm to 110.0 mm. As for the bed knife 2, in order to support the polarizing film laminated body 100 at a cutting position, the blade uses a wide blade as shown in a figure. In the illustrated example, one side 1b of the cutting blade 1 is a vertical surface, and the other side 1c is a wedge surface. The wedge angle of the wedge surface is, for example, 20° to 60°. In addition, the diced sheet obtained by dicing is removed by winding up or suction, for example.

In the illustrated example, the cutting is performed in such a way that the relatively thicker part of the wedge-shaped cutting blade 1 narrowing toward the blade is located on the resin substrate 11 side, and the relatively thinner part of the cutting blade 1 is located on the protective film 20 side. The blade of the knife 1 is in contact with the polarizing film laminate 100, and by making the blade of the dicing blade abut against the resin substrate side of the polarizing film laminate in this way, it is possible to suppress damage to the cutting portion (especially the end surface of the protective film). The polarizing film laminate was cut sideways. Specifically, a stretchable resin base material is softer than a protective film and less likely to be damaged by a dicing knife. As a result, defects such as cracking at the cut portion can be suppressed, and the detachability of the resin base material described later can be remarkably improved. The indentation hardness (during cutting) of the surface of the resin substrate is, for example, 0.25 GPa or less, preferably 0.21 GPa or less.

D. Stripping process

After the above dicing, the resin substrate is peeled from the polarizing film laminate. According to the present invention, excellent peelability of the resin substrate can be obtained by performing dicing as described above. As a result, a polarizing plate excellent in appearance can be manufactured while maintaining high productivity. In addition, the peeled resin base material is recovered by winding up, for example.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. In addition, the measurement method of each characteristic is as follows.

1. Thickness

Measurement was performed using a digital micrometer (manufactured by ANRITSU CORPORATION, product name "KC-351C").

2. Water absorption

Measurement was performed based on JIS K 7209.

3. Glass transition temperature (Tg)

Measurement was performed based on JIS K 7121.

4. Pencil hardness

Measurement was performed based on JIS K 5600-5-4 (load: 500 g).

5. Indentation hardness

A glass plate was bonded to the surface of the film (laminate) via an epoxy resin layer having a thickness of 100 μm, and this was used as a sample for measurement. The sample was placed on a sample stage (aluminum stage) of a microindentation hardness tester (manufactured by MTS Corporation, product name "NanoIndenter SA2"), and measured at a temperature of 25° C. and a measurement sensor approach speed of 5 nm/min.

[Example 1]

(manufacturing of laminated body)

As the resin substrate, a long amorphous isophthalic acid-co-polyethylene terephthalate (IPA-co-PET) film (width: 4000mm, thickness: 100μm) with a water absorption rate of 0.75% and a Tg of 75°C was used. ).

Corona treatment is carried out on one side of the resin substrate, and then at 60° C., 90 parts by weight of polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA are coated on the corona treatment surface. (Polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") 10 parts by weight of an aqueous solution is dried to form PVA with a thickness of 10 μm A resin layer is used to produce a laminated body.

The obtained laminate was uniaxially stretched to 2.0 times in the longitudinal direction at the free end between rolls having different circumferential speeds in an oven at 115° C. (in-air stretching). Thereafter, the laminate was wound up into a roll.

While unwinding the laminated body from the rolled laminated body roll, both ends in the width direction of the laminated body were cut so that the width after cutting was 2500 mm.

Next, the laminated body was immersed in an insolubilization bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilization treatment).

Then, the laminated body was immersed in a dyeing bath having a liquid temperature of 30° C., and the iodine concentration and immersion time were adjusted so that the obtained polarizing plate had a predetermined transmittance. In this example, the laminated body was immersed for 60 seconds in an iodine aqueous solution obtained by mixing 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 (dyeing treatment).

Next, the laminate was immersed 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) at a liquid temperature of 30° C. for 30 seconds (crosslinking treatment).

After that, while immersing the laminated body in a boric acid aqueous solution having 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), the laminate was passed between rollers having different peripheral speeds. This laminate was uniaxially stretched to 2.7 times in the longitudinal direction (stretching in water).

Thereafter, the laminate was immersed in a cleaning bath (an 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 for 10 seconds, and then dried with warm air at 60°C for 60 seconds. (washing and drying process).

As described above, a polarizing film having a thickness of 5 μm was formed on a resin base material (thickness: 40 μm).

Next, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER (registered trademark) Z-200", resin concentration: 3% by weight) was coated on the polarizing film surface of the laminate, and then bonded to form a A methacrylic resin film having a glutarimide structure with a thickness of 40 μm and an anti-glare layer (pencil hardness: 2H) with a thickness of 10 μm was heated in an oven maintained at 60° C. for 5 minutes to obtain a protective film/polarizer/ A polarizing film laminate (thickness: 85 μm) having a resin base structure. The indentation hardness of the protective film surface of the polarizing film laminate was 0.42 GPa, and the indentation hardness of the resin substrate surface was 0.19 GPa.

Thereafter, as shown in FIGS. 2 and 3 , the cutting edge (wedge angle: 45°) of the dicing knife was brought into contact with the resin base material side, and the polarizing film laminated body was aligned at a distance of 30 mm from the edge of the polarizing film. Both ends in the width direction are cut. During dicing, the contact pressure between the dicing knife and the bed knife was 5N, the overlapping length L between the dicing knife and the bed knife was 0.24 mm, and the rotational speed of the dicing knife was 102% of the transport speed of the polarizing film laminate.

As above, a polarizing plate was obtained.

[Example 2]

A polarizing plate was obtained in the same manner as in Example 1, except that the rotational speed of the cutter blade and the bed knife was set to 95% of the conveyance speed of the polarizing film laminate during dicing.

[Example 3]

A polarizing plate was obtained in the same manner as in Example 1 except that an anti-glare layer was not formed on a methacrylic resin film having a glutarimide structure with a thickness of 40 μm. Here, the indentation hardness of the surface of the methacrylic resin film was 0.28 GPa.

[Example 4]

A polarizing plate was obtained in the same manner as in Example 1 except that a cellulose triacetate film (manufactured by KONICA MINOLTA, INC., trade name "KC4UY", thickness 40 μm) was attached to the surface of the polarizing film of the laminate. Here, the indentation hardness on the surface of the cellulose triacetate film was 0.26 GPa.

[Example 5]

A polarizing plate was obtained in the same manner as in Example 1 except that a norbornene-based resin film (manufactured by JSR Corporation, trade name "ARTON", thickness 35 μm) was bonded to the surface of the polarizing film of the laminate. Here, the indentation hardness of the norbornene resin film surface was 0.22 GPa.

[Comparative example 1]

When dicing, except having brought the blade of the dicing knife into contact with the protective film side of the polarizing film laminate, it carried out similarly to Example 1, and produced the polarizing plate.

[Comparative example 2]

When cutting, except having brought the blade of a dicing knife into contact with the protective film side of the polarizing film laminate, it carried out similarly to Example 3, and produced the polarizing plate.

[Comparative example 3]

When dicing, except having brought the blade of the dicing knife into contact with the protective film side of the polarizing film laminate, it carried out similarly to Example 4, and produced the polarizing plate.

[Comparative example 4]

When cutting, except having brought the blade of a dicing knife into contact with the protective film side of the polarizing film laminate, it carried out similarly to Example 5, and produced the polarizing plate.

From the polarizing plates obtained in the respective examples and comparative examples, the resin substrate was peeled in the longitudinal direction, and the peelability was evaluated. Table 1 shows the evaluation results.

Table 1

In each Example, continuous peeling was possible without fracture. On the other hand, in each comparative example, peeling failure (crack) occurred.

Using a microscope (magnification: 10 times) to observe the end surface (cut surface) of each polarizing plate, no cracks were confirmed in each example, but in each comparative example, cracks were confirmed on the protective film (especially the surface treatment layer). crack.

Industrial availability

The polarizing plate of the present invention is suitably used as a protective film for liquid crystal panels of liquid crystal televisions, liquid crystal displays, portable phones, digital cameras, video cameras, portable game machines, vehicle navigation systems, copiers, printers, facsimile machines, clocks, microwave ovens, etc., and organic EL equipment. Reflective film.

Claims (10)

1. A method for manufacturing a polarizing plate, comprising the steps of: A step of stretching and dyeing a laminate having a long resin substrate and a polyvinyl alcohol-based resin layer provided on one side of the resin substrate to form a polarizing film on the resin substrate, a step of laminating a protective film on the polarizing film side of the laminate to produce a polarizing film laminate, and A step of cutting both ends in the width direction of the polarizing film laminate with a wedge-shaped cutting knife that gradually narrows toward the blade; When performing the dicing, the dicing blade is made such that a relatively thick portion of the dicing blade is positioned on the resin substrate side and a relatively thin portion of the dicing blade is positioned on the protective film side. The blade of the knife was in contact with the polarizing film laminate. 2 . The manufacturing method according to claim 1 , wherein the cutting is performed using the rotary cutting blade and the bed knife, and a blade portion of the cutting blade partially overlaps with a blade portion of the base knife. 3 . 3. The manufacturing method according to claim 2, wherein the overlapping length L of the overlapping and the thickness d of the polarizing film laminate satisfy the relationship of d≤L≤d+15, wherein the overlapping length L The unit is mm, and the unit of the thickness d is mm. 4. The manufacturing method according to claim 2, wherein the rotational speed of the cutting blade is 90% to 130% of the transport speed of the polarizing film laminate. 5. The manufacturing method according to claim 1, further comprising a step of peeling the resin substrate from the polarizing film laminate after the dicing. 6. The manufacturing method according to claim 1, wherein the indentation hardness of the surface of the protective film exceeds 0.21 GPa. 7. The manufacturing method according to claim 1, wherein the protective film has a resin film and a surface treatment layer formed on one side of the resin film. 8. The manufacturing method according to claim 7, wherein the pencil hardness of the surface of the surface treatment layer is H or more. 9. The manufacturing method according to claim 8, wherein the surface treatment layer has antiglare properties. The polarizing plate obtained by the manufacturing method in any one of Claims 1-9.