JP2019091084A - Method of manufacturing polarizing plate - Google Patents

Abstract

To provide a method of manufacturing a polarizing plate having excellent appearance.SOLUTION: A method of manufacturing a polarizing plate includes: a step of forming a long-sized resin base material and a polyvinyl alcohol resin layer on one side of the resin base material to thereby obtain a laminate 10; a step of dying the polyvinyl alcohol resin layer; a step of stretching the laminate 10; a step of slitting a width-directional end 10a of the laminate 10 before stretching; and a step of sticking the long-sized protective film to the polyvinyl alcohol resin layer after dying and stretching. The width of the laminate 10 after stretching corresponds to the width of the laminate at the time of sticking.SELECTED DRAWING: Figure 2

Description

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

  In a liquid crystal display device which is a typical image display device, polarizing films are disposed on both sides of a liquid crystal cell due to the image forming method. As a method for producing a polarizing film, for example, a method is proposed in which a laminate having a resin substrate and a polyvinyl alcohol (PVA) -based resin layer is stretched and subjected to a dyeing treatment to obtain the polarizing film on the resin substrate (E.g., Patent Document 1). According to such a method, since a thin polarizing film can be obtained, it is noted that it can contribute to thinning of the image display apparatus in recent years.

  By the way, a protective film is usually bonded together and the said polarizing film is used as a polarizing plate. When a protective film is attached to the polarizing film (laminated body) formed on the above-mentioned resin base material, there is a problem that it is easy to produce a fold and wrinkle at an end. Therefore, it has been proposed to remove the end of the laminate before bonding the protective film (Patent Document 2). However, according to such a method, there is a problem that the appearance of the obtained polarizing plate is inferior.

JP 2000-338329 A Patent No. 5124704 specification

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a method for producing a polarizing plate having an excellent appearance.

The method for producing a polarizing plate of the present invention comprises the steps of: obtaining a laminate by forming a polyvinyl alcohol-based resin layer on one side of a long resin substrate and the resin substrate; and stretching the laminate in the air; A step of dyeing the polyvinyl alcohol-based resin layer, a step of stretching the laminate in water, a step of slitting an end portion in a width direction of the laminate after the in-air stretching and before the in-water stretching; And a step of bonding a long protective film to the polyvinyl alcohol resin layer after the underwater stretching, and the width of the laminate after the underwater stretching corresponds to the width of the laminate at the time of the bonding .
In one embodiment, the method further includes the step of rolling the laminate in a roll.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent effectively that a foreign material mixes in between the PVA-type resin layer and a protective film in the bonding process with a protective film by slitting before extending | stretching. Specifically, if slitting is performed in a state in which the orientation of the PVA-based resin layer is increased by stretching, a sag tends to occur at the slit end, and the sag may become a foreign substance at the time of bonding. In addition, the PVA-based resin layer in a state of high orientation may be easily torn and it may be difficult to slit. Therefore, by slitting before drawing, it is possible to effectively prevent the generation of air bubbles associated with the mixing of foreign matter and the mixing of foreign matter while performing the slitting well. As a result, a polarizing plate excellent in appearance can be obtained. Furthermore, since knurling etc. can be removed before stretching if the above-mentioned wrinkles, folds, irregularities such as winding tightness, and knurling are formed in advance in the width direction end of the laminate, stretching is performed stably. Can.

FIG. 1 is a partial cross-sectional view of a laminate according to one embodiment of the present invention. It is an external appearance perspective view which shows an example of the slit process of this invention.

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

  The manufacturing method of the polarizing plate of the present invention comprises a step of obtaining a laminate by forming a long resin substrate and a PVA-based resin layer on one side of the resin substrate (lamination step), and dyeing the PVA-based resin layer Step (dying step), step of stretching the laminate (stretching step), step of slitting the widthwise end of the laminate (slit step), and a long protective film is attached to the PVA-based resin layer And a combining step (bonding step). Each step will be described below.

A. Lamination Process FIG. 1 is a partial cross-sectional view of a laminate according to a preferred embodiment of the present invention. The laminate 10 has a resin base 11 and a polyvinyl alcohol resin layer 12. The laminate 10 is produced by forming a polyvinyl alcohol-based resin layer 12 on a long resin base 11. Any appropriate method may be employed as a method of forming the polyvinyl alcohol-based resin layer 12. In one embodiment, a PVA-based resin layer 12 is formed by applying a coating solution containing a polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) on the resin base material 11 and drying.

  Any appropriate material may be employed as a material for forming the 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, and copolymer resins thereof can be mentioned. Preferably, a polyethylene terephthalate resin is used. Among them, amorphous polyethylene terephthalate resin is preferably used. Specific examples of the amorphous polyethylene terephthalate resin include a copolymer further containing isophthalic acid as a dicarboxylic acid, and a copolymer further containing cyclohexane dimethanol as a glycol.

  The glass transition temperature (Tg) of the resin substrate is preferably 120 ° C. or less, more preferably 100 ° C. or less. When extending | stretching a laminated body, it is because extending property (especially in in-water extending | stretching) can fully be ensured, suppressing crystallization of a PVA-type resin layer. As a result, it is possible to manufacture a polarizing film having excellent optical properties (for example, the degree of polarization). On the other hand, the glass transition temperature of the resin substrate is preferably 60 ° C. or higher. The glass transition temperature (Tg) is a value determined according to JIS K 7121.

  The water absorption rate of the resin substrate is preferably 0.2% or more, and more preferably 0.3% or more. Such resin base material absorbs water, and the water acts as a plasticizer and can be plasticized. As a result, the stretching stress can be significantly reduced, and the stretchability can be excellent. On the other hand, the water absorption of the resin substrate is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin substrate, it is possible to prevent defects such as deterioration in the appearance of the obtained polarizing film due to the dimensional stability of the resin substrate being significantly reduced at the time of production. Moreover, it can prevent breaking at the time of extending | stretching in water, or peeling of a PVA-type resin layer from a resin base material. In addition, a water absorption is a value calculated | required according to JISK7209.

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

  Arbitrary suitable resin may be adopted as PVA system resin which forms the above-mentioned PVA system resin layer. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying an ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The degree of saponification can be determined in accordance with JIS K 6726-1994. By using a PVA resin having such a degree of saponification, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur.

  The average degree of polymerization of the PVA-based resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

  As the coating solution, typically, a solution in which the PVA-based resin is dissolved in a solvent is used. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferred. The PVA-based resin concentration of the solution may be set to any appropriate value. For example, it is set according to the degree of polymerization or the degree of saponification of the PVA-based resin. The PVA-based resin concentration of the solution is, for example, 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent.

  The coating solution may contain an additive. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As surfactant, a nonionic surfactant is mentioned, for example. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the obtained PVA-based resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. The adhesion between the resin substrate and the PVA-based resin layer can be improved by using the easy-adhesion component. As a result, for example, defects such as peeling of the PVA-based resin layer from the resin base material can be suppressed, and the below-mentioned dyeing and underwater stretching can be favorably performed. For example, a modified PVA such as acetoacetyl-modified PVA is used as the easy adhesion component.

  Any appropriate method can be adopted as a method of applying the coating solution. 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 (a comma coating method etc.) and the like can be mentioned. The coating / drying temperature of the coating solution is, for example, 20 ° C. or more, preferably 50 ° C. or more.

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

  In one embodiment, the PVA-based resin layer (laminate) is stretched in advance. For example, the PVA-based resin layer (laminate) is stretched in the longitudinal direction (for example, by an air stretching method). The draw ratio of the said extending | stretching is 1.5 times-3.5 times, for example, Preferably it is 2.0 times-3.0 times. The stretching temperature is, for example, 95 ° C to 150 ° C.

B. Dyeing Step The above dyeing is typically performed by dyeing the PVA-based resin layer with a dichroic substance. Preferably, it is carried out by adsorbing a dichroic substance to the PVA-based resin layer. As the adsorption method, for example, a method of immersing a PVA-based resin layer (laminate) in a staining solution containing a dichroic substance, a method of applying the staining solution to a PVA-based resin layer, a PVA-based staining solution The method etc. of spraying to a resin layer are mentioned. Preferably, it is a method of immersing a PVA-based resin layer in a staining solution. It is because a dichroic substance can be adsorbed well.

  Examples of the dichroic substance include iodine and organic dyes. These 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 staining solution is preferably an aqueous iodine solution. The compounding amount of iodine is preferably 0.1 parts by weight to 0.5 parts by weight with respect to 100 parts by weight of water. In order to enhance the solubility of iodine in water, it is preferable to add an iodide to an aqueous iodine solution. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. Etc. Among these, preferred is potassium iodide. The compounding amount of the iodide is preferably 0.02 parts by weight to 20 parts by weight, more preferably 0.1 parts by weight to 10 parts by weight with respect to 100 parts by weight of water.

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

C. Stretching step Any appropriate method can be adopted as a stretching method of the laminate. Specifically, fixed end stretching (for example, a method using a tenter stretching machine) may be used, or free end stretching (for example, a method for uniaxially stretching a laminate between rolls having different peripheral speeds) may be used. Moreover, simultaneous biaxial stretching (for example, a method using a simultaneous biaxial stretching machine) may be used, or sequential biaxial stretching may be used. Stretching of the laminate may be performed in one step or in multiple steps. When it carries out in multiple steps, the draw ratio (maximum draw ratio) of the below-mentioned layered product is the product of the draw ratio of each step.

  The stretching may be an underwater stretching method performed while immersing the laminate in a stretching bath, or may be an air stretching method. Preferably, the in-water stretching is performed at least once, and more preferably, the in-air stretching and the in-water stretching are combined. According to in-water stretching, stretching can be performed at a temperature lower than the glass transition temperature (typically, about 80 ° C.) of the above-mentioned resin base material or PVA-based resin layer, and the PVA-based resin layer is suppressed while suppressing its crystallization. , Can be stretched to a high magnification. As a result, it is possible to manufacture a polarizing film having excellent optical properties. When combining in-air stretching and in-water stretching, it is preferable to perform in-water stretching after in-flight stretching.

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

  The stretching temperature of the laminate can be set to any appropriate value depending on the forming material of the resin base, the stretching method, and the like. When the air stretching method is employed, the stretching temperature is preferably at least the glass transition temperature (Tg) of the resin substrate, more preferably at the glass transition temperature (Tg) of the resin substrate + 10 ° C. or more, particularly preferably Tg + 15 ° C. It is above. On the other hand, the stretching temperature of the laminate is preferably 170 ° C. or less. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin and to suppress a defect due to the crystallization (for example, to prevent the orientation of the PVA-based resin layer by stretching). it can.

  When the in-water stretching system is adopted as the stretching system, the liquid temperature of the stretching bath is preferably 40 ° C. to 85 ° C., more preferably 50 ° C. to 85 ° C. If it is such temperature, it can extend | stretch to high magnification, suppressing melt | dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin substrate is preferably 60 ° C. or more in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is less than 40 ° C., there is a possibility that the film can not be stretched well even in consideration of 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, which may make it impossible to obtain excellent optical properties.

  When the in-water stretching method is adopted, it is preferable to immerse the laminate in a boric acid aqueous solution and stretch it (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, the PVA resin layer can be provided with rigidity to withstand the tension applied during stretching and water resistance which is not dissolved in water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink it with a PVA resin by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, the film can be stretched satisfactorily, and a polarizing film having excellent optical properties can be produced.

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

  Preferably, iodide is blended in the above-mentioned stretching bath (boric acid aqueous solution). By blending an iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight 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 draw ratio (maximum draw ratio) of the laminate is preferably 5.0 or more times the original length of the laminate. Such a high draw ratio can be achieved, for example, by adopting an in-water stretching method (stretching in boric acid in water). The draw ratio by in-water stretching of the laminate is preferably 2.0 times or more. In addition, in this specification, "the largest draw ratio" means the draw ratio immediately before the laminate breaks, separately confirms the draw ratio at which the laminate breaks, and means a value 0.2 lower than that value. .

  Preferably, in-water stretching is performed after the above dyeing.

D. Slitting Process FIG. 2 is an external perspective view showing an example of the slitting process. As shown in FIG. 2, the width direction end portions 10 a and 10 a of the laminate 10 are slit along the longitudinal direction 20 of the laminate 10 before the stretching. The slit piece 10a which is slit includes the resin base material and the PVA-based resin layer. The slit width (width of the slit piece) is typically 10 mm to 1000 mm. In one embodiment, the slit width is set such that the width of the laminate after the stretching (the width of the laminate at the time of bonding described later) corresponds to the width of the protective film described later. By matching the widths of the two in this manner, it is possible to eliminate the wrinkles at the end in the width direction, and to stably bond the laminate and the protective film. When the stretching is longitudinal stretching (MD stretching), the slit width may be set in consideration of the fact that the width of the laminate may be reduced by the stretching. Specifically, the slit width may be set to be smaller than that after slitting.

  By slitting before extending | stretching, in the bonding process with the protective film mentioned later, it can prevent effectively that a foreign material mixes between a PVA-type resin layer and a protective film. Specifically, if slitting is performed in a state in which the orientation of the PVA-based resin layer is increased by stretching, a sag tends to occur at the slit end, and the sag may become a foreign substance at the time of bonding. In addition, the PVA-based resin layer in a state of high orientation may be easily torn and it may be difficult to slit. Therefore, by slitting before drawing, it is possible to effectively prevent the generation of air bubbles associated with the mixing of foreign matter and the mixing of foreign matter while performing the slitting well. As a result, a polarizing plate excellent in appearance can be obtained. Furthermore, since knurling etc. can be removed before stretching if the above-mentioned wrinkles, folds, irregularities such as winding tightness, and knurling are formed in advance in the width direction end of the laminate, stretching is performed stably. Can.

  In addition to the above, by slitting before stretching, it is possible to obtain a polarizing film extremely excellent in optical characteristics. Specifically, in the case of performing stretching (longitudinal uniaxial stretching) by the peripheral speed difference between rolls, L / W is increased by slitting the end in the width direction before stretching, and the orientation and optics of the polarizing film obtained The characteristics can be significantly improved. In addition, L shows the distance between extending | stretching (The distance to which tension is added by the circumferential speed difference between rolls), and W shows the width | variety of a laminated body.

  When stretching of the laminate is performed in multiple steps, the laminate may be stretched in advance as described above before slitting. Specifically, slitting may be performed at least before final stage drawing. The orientation and optical properties of the resulting polarizing film can be further improved by slitting and stretching in a state in which the orientation of the PVA-based resin layer is increased by stretching in advance. In this case, it is preferable to perform stretching before slitting to such an extent that the above-mentioned sagging does not occur at the time of slitting. Moreover, it is preferable to set the draw ratio of the extending | stretching after a slit high. The stretching ratio of the stretching after slitting is, for example, 1.5 times or more, preferably 2.0 times or more. It is because the orientation and optical characteristics of the obtained polarizing film can be further improved by largely stretching in the state where the L / W is high.

  Preferably, the slit is performed before the staining. By slitting before dyeing, it is possible to more effectively prevent foreign matter from mixing between the PVA-based resin layer and the protective film in the step of bonding with a protective film described later. Specifically, the PVA-based resin layer may be crosslinked and become brittle (for example, by iodine) by dyeing. When slitting in such a state, slit scraps are easily produced, and the slit scraps can become foreign matter at the time of bonding. Therefore, by slitting before dyeing, it is possible to more effectively prevent the generation of air bubbles caused by mixing of foreign matter and foreign matter. As a result, a polarizing plate excellent in appearance can be obtained.

  Any appropriate method may be adopted as the slitting method of the laminate. For example, the long laminate may be slit while wound in the longitudinal direction, or may be slit without being wound. Examples of the slit (cutting) means include cutting blades such as round blades and countersinks, and lasers. The slit piece is preferably removed by winding or suction.

E. Others In addition to the above, the laminate may be appropriately subjected to a treatment for making the PVA-based resin layer into a polarizing film. Examples of the treatment for forming a polarizing film include insolubilization treatment, crosslinking treatment, washing treatment, and drying treatment. The number, timing, order, and the like of these processes are not particularly limited.

  The insolubilization treatment is typically performed by immersing the PVA-based resin layer in a boric acid aqueous solution. Water resistance can be imparted to the PVA-based resin layer by performing the insolubilization treatment. The concentration of the aqueous boric acid solution is preferably 1 part by weight to 4 parts by weight with respect 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. Preferably, the insolubilization treatment is performed before the above-described in-water stretching and the above-mentioned dyeing treatment.

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

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

  In one embodiment, the laminate is wound into a roll to form an original roll, and the slit is performed after winding. The winding tension is typically 300N to 600N. The winding may be performed such that the PVA-based resin layer is on the inner side (core material side), or may be performed such that the PVA-based resin layer is on the outer side. When the laminate is wound up in the process of manufacturing a polarizing film, for example, if there is partial film thickness unevenness in the laminate, winding tightness or wrinkles occur. Such problems are likely to occur at the end in the width direction. Therefore, stretching can be stably performed by performing the slit after winding. In addition, since the film is slit after being wound up, raw film rolls of the same width can be used regardless of the width of the protective film to be bonded, which can contribute to improvement in productivity.

F. Pasting process After the above-mentioned dyeing and stretching, a protective film is pasted together to a PVA system resin layer (polarization film) of a layered product. Specifically, a long protective film is attached to the PVA-based resin layer in such a manner that the longitudinal directions thereof are aligned with each other. In one embodiment, the width of the stretched laminate corresponds to the width of the laminate at the time of bonding. Specifically, between the stretching step and the bonding step, the laminate is not substantially subjected to a new slitting process.

  The width of the protective film may 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.

  Any appropriate resin film may be employed as the protective film. As a material for forming the protective film, for example, cellulose resins such as triacetyl cellulose (TAC), cycloolefin resins such as norbornene resin, olefin resins such as polyethylene and polypropylene, polyester resin, (meth) acrylic resin Resin etc. are mentioned. In addition, "(meth) acrylic-type resin" means acrylic resin and / or methacrylic resin.

  The thickness of the protective film is typically 10 μm to 100 μm. In addition, various surface treatments may be given to the protective film. The protective film can function not only as a protective film of a polarizing film but also as a retardation film or the like.

  Any appropriate adhesive or pressure-sensitive adhesive is used for laminating the protective film. In one embodiment, an adhesive is applied to the surface of the polarizing film to bond the protective film. The adhesive may be a water-based adhesive or a solvent-based adhesive. Preferably, a water-based adhesive is used.

  Any appropriate water-based adhesive may be employed as the water-based adhesive. Preferably, a water-based adhesive containing a PVA-based resin is used. 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 to 100 mol%, more preferably 90 to 100 mol% from the viewpoint of adhesion.

  The PVA-based resin contained in the water-based adhesive preferably contains an acetoacetyl group. It is because it is excellent in the adhesiveness of a PVA-type resin layer and a protective film, and excellent in durability. The acetoacetyl group-containing PVA-based resin can be obtained, for example, by reacting a PVA-based resin with diketene by an arbitrary method. The acetoacetyl group modification degree of the acetoacetyl group-containing PVA resin is typically 0.1 mol% or more, preferably about 0.1 mol% to about 40 mol%, more preferably about 1 mol% to 20 mol %, Particularly preferably 2 mol% to 7 mol%. The acetoacetyl group modification degree is a 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 application thickness of the adhesive may be set to any appropriate value. For example, after heating (drying), an adhesive layer having a desired thickness is set to be obtained. The thickness of the adhesive layer is preferably 10 nm to 300 nm, more preferably 10 nm to 200 nm, and particularly preferably 20 nm to 150 nm.

  After bonding a protective film to a PVA-type resin layer, it is preferable to heat. The heating temperature is preferably 50 ° C. or more, more preferably 60 ° C. or more, particularly preferably 80 ° C. or more. In addition, the heating performed after bonding a protective film may be combined with the above-mentioned drying process.

G. Peeling Step In one embodiment, the resin base material is peeled from the PVA-based resin layer (polarizing film). Preferably, before peeling the resin base material, the end in the width direction of the polarizing film laminate in which the protective film is bonded to the laminate is slit. Poor bonding (for example, wrinkles) is likely to occur at the bonding portion between the widthwise end of the laminate and the protective film, and by achieving excellent peelability of the resin substrate by removing this portion with a slit. Can. Specifically, the occurrence of peeling failure (for example, breakage) of the resin base material caused by the above-mentioned defective bonding portion as a starting point can be prevented, and the resin base material can be peeled well. As a result, it is possible to obtain a polarizing plate more excellent in appearance.

H. Polarizing Plate The polarizing plate of the present invention has the above-mentioned polarizing film and the above-mentioned protective film disposed on one side of this 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, and 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 of 380 nm to 780 nm. The single transmittance of the polarizing film is preferably 40.0% or more, more preferably 41.0% or more, still more preferably 42.0% or more, and particularly preferably 43.0% or more. The polarization degree of the polarizing film is preferably 99.8% or more, more preferably 99.9% or more, and still more preferably 99.95% or more.

EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. In addition, the measuring method of each characteristic is as follows.
1. Thickness It measured using the digital micrometer (The Anritsu company make, brand name "KC-351C").
2. Glass transition temperature (Tg)
It measured according to JISK7121.

Example 1
(Preparation of laminate)
As a resin base material, a long, amorphous, isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (width: 4000 mm, thickness: 100 μm) having a water absorption coefficient of 0.75% and a Tg of 75 ° C. was used.
One side of the resin substrate is subjected to corona treatment, and 90 parts by weight of polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl modified PVA (polymerization degree 1200, acetoacetyl modification degree) An aqueous solution containing 10 parts by weight of 4.6%, degree of saponification of 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefamer Z200", is applied and dried at 60 ° C to a thickness of 10 μm. A PVA-based resin layer was formed to prepare a laminate.

The obtained laminate was subjected to free-end uniaxial stretching 2.0 times in the longitudinal direction between rolls with different peripheral speeds in an oven at 115 ° C. (in-air stretching). Thereafter, the laminate was wound into a roll.
While unrolling the laminate from the roll of the laminate wound in a roll, both ends in the width direction of the laminate were respectively slit so that the width after the slit was 2500 mm.
Next, the laminate was immersed in an insolubilizing bath (aqueous solution of boric acid obtained by blending 3 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Subsequently, it 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 this example, 0.2 parts by weight of iodine was mixed with 100 parts by weight of water, and it was immersed in an aqueous iodine solution obtained by mixing 1.0 parts by weight of potassium iodide for 60 seconds (staining treatment) .
Then, it was immersed for 30 seconds in a crosslinking bath having a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) (crosslinking treatment) ).
Thereafter, the laminate is immersed in an aqueous solution of boric acid at a liquid temperature of 70 ° C. (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) Uniaxial stretching was performed 2.7 times in the longitudinal direction between rolls different in speed (stretching in water).
After that, the laminate is immersed in a washing bath with a liquid temperature of 30 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) for 10 seconds, and then heated with a hot air of 60 ° C. It was made to dry for a second (washing and drying process).
Thus, a 5 μm-thick polarizing film was formed on the resin substrate.

  Subsequently, a PVA-based resin aqueous solution (trade name "Gosefimer (registered trademark) Z-200", resin concentration: 3% by weight) is applied to the surface of the polarizing film of the laminate, and the length is long. A triacetyl cellulose film (Konica Minolta Co., Ltd., trade name “KC4UY”, 40 μm thick) having a width corresponding to the width of the polarizing film is attached and heated in an oven maintained at 60 ° C. for 5 minutes to obtain a polarizing plate I got

Example 2
The polarizing plate was produced like Example 1 except having slit so that the width after a slit might be set to 2100 mm.

Comparative Example 1
A polarizing plate was produced in the same manner as in Example 1 except that the timing of slitting was after stretching in water.

(Evaluation)
The following evaluation was performed about the obtained polarizing plate. The evaluation results are summarized in Table 1.
1. Appearance The obtained polarizing plate was visually observed.
2. Degree of polarization The single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) of the polarizing plate were measured using a UV-visible spectrophotometer (product name "V7100" manufactured by JASCO Corporation), The degree of polarization (P) was determined by the following equation.
Degree of polarization (P) (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
In addition, said Ts, Tp, and Tc are Y value which measured by 2 degree visual field (C light source) of JISZ8701, and performed visual sensitivity correction | amendment.
3. Orientation (evaluation method of orientation function of PVA)
The measuring device is a Fourier transform infrared spectrophotometer (FT-IR) (Perkin
A trade name: "SPECTRUM 2000" manufactured by Elmer, Inc. was used. Evaluation of the surface of the PVA-based resin layer was performed by measurement of total reflection attenuation spectroscopy (ATR) using polarized light as measurement light. The calculation of the orientation function was performed according to the following procedure. The measurement was carried out with the measured polarization at 0 ° and 90 ° with respect to the stretching direction. It calculated according to (Equation 1) described below using the intensity | strength of 2941 cm < ^-1 > of the acquired spectrum. The following intensity I as a reference peak to 3330cm ^-1, using the value of 2941cm ^-1 / 3330cm -1. When f = 1, the alignment is complete, and when f = 0, the alignment is random. Moreover, the peak of 2941 cm ^-1 is said to be absorption due to vibration of the main chain (-CH _2- ) of PVA.
(Expression 1) f = (3 <cos 2θ> -1) / 2 = (1-D) / [c (2D + 1)]
However,
c = (3cos2β-1) / 2
β = 90 deg⇒f = −2 × (1−D) / (2D + 1)
θ: molecular chain / stretching direction β: molecular chain / transition dipole moment D = (I⊥) / (I //), (the value of D increases as the PVA is oriented)
I⊥: intensity measured when polarized light is incident perpendicularly to the stretching direction I //: intensity measured when polarized light is incident parallel to the stretching direction

  The polarizing plate of the present invention is a liquid crystal television, a liquid crystal display, a mobile phone, a digital camera, a video camera, a portable game machine, a car navigation system, a copier, a printer, a fax machine, a watch, a liquid crystal panel such as a watch or a microwave, a reflection of an organic EL device It is suitably used as a protective film.

10 laminate 11 resin base 12 polyvinyl alcohol resin layer (polarizing film)

Claims (2)

A step of obtaining a laminate by forming a polyvinyl alcohol-based resin layer on one side of a long resin base and the resin base;
Drawing the laminate in the air;
Dyeing the polyvinyl alcohol-based resin layer;
Stretching the laminate in water;
Slitting the end in the width direction of the laminate after the in-air stretching and before the in-water stretching;
And a step of laminating a long protective film on the polyvinyl alcohol-based resin layer after the dyeing and stretching in water,
The width of the laminate after the underwater stretching corresponds to the width of the laminate at the time of the bonding,
The manufacturing method of a polarizing plate. The manufacturing method according to claim 1, further comprising the step of winding the laminate in a roll.

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