JP2016126131A - Method of manufacturing polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: 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 for producing a polarizing plate.

  In a liquid crystal display device which is a typical image display device, polarizing films are arranged 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 base material and a polyvinyl alcohol (PVA) resin layer is stretched and dyed to obtain a polarizing film on the resin base material. (For example, Patent Document 1). According to such a method, a polarizing film having a small thickness can be obtained, and thus has been attracting attention as being able to contribute to the recent thinning of image display devices.

  By the way, the polarizing film is usually used as a polarizing plate with a protective film attached thereto. When a protective film is bonded to the polarizing film (laminate) formed on the resin base material, there is a problem that folding or wrinkling is likely to occur at the end. Then, removing the edge part of a laminated body before bonding a protective film is proposed (patent document 2). However, according to such a method, there exists a problem that the external appearance of the polarizing plate obtained is inferior.

JP 2000-338329 A Japanese Patent No. 5124704

  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 a step of forming a long resin base material and a polyvinyl alcohol resin layer on one side of the resin base material to obtain a laminate, and dyeing the polyvinyl alcohol resin layer. A step of stretching the laminate, a step of slitting the widthwise end of the laminate before the stretching, and a long protective film on the polyvinyl alcohol resin layer after the dyeing and stretching. The width of the laminated body after stretching corresponds to the width of the laminated body at the time of bonding.
In one embodiment, slitting is performed so that the width of the laminated body after stretching corresponds to the width of the protective film.
In one embodiment, the slit is performed before the staining.
In one embodiment, the process further includes a step of winding the laminate into a roll shape, and the slit is performed after the winding.
In one embodiment, the stretching is longitudinal uniaxial stretching.
In one embodiment, the stretching is underwater stretching.
In one embodiment, the draw ratio of the drawing is 2.0 times or more.
In one embodiment, the laminate is stretched in multiple stages.
In one embodiment, the laminate is stretched in advance before the slit.
According to another aspect of the present invention, a polarizing plate is provided. This polarizing plate is obtained by the above production method.

  According to this invention, it can prevent effectively that a foreign material mixes between a 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 has been increased by stretching, a crust is likely to be generated at the end of the slit, and this crust can become a foreign substance during bonding. Moreover, the PVA-type resin layer in a state with high orientation is easy to tear, and slits may be difficult. Therefore, by performing slitting before stretching, it is possible to effectively prevent the generation of bubbles and the generation of bubbles accompanying the mixing of foreign matters while performing the slits satisfactorily. As a result, a polarizing plate excellent in appearance can be obtained. Furthermore, unevenness such as the above-mentioned wrinkles, folds, tightening, etc., and if knurling is formed in advance in the width direction end of the laminate, the knurling can be removed before stretching, so that stable stretching is performed. Can do.

It is a fragmentary sectional view of the layered product by 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 polarizing plate production method of the present invention includes a long resin base material, a step of forming a PVA resin layer on one side of the resin base material to obtain a laminate (lamination step), and a dyeing of the PVA resin layer. A step of performing (dyeing step), a step of stretching the laminate (stretching step), a step of slitting the end in the width direction of the laminate (slit step), and attaching a long protective film to the PVA resin layer And a step of bonding (bonding step). Hereinafter, each process will be described.

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

  Any appropriate material can be adopted as the material for forming the resin base material. Examples thereof include 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. Preferably, a polyethylene terephthalate resin is used. Among these, 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 cyclohexanedimethanol as a glycol.

  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, stretchability (particularly in water stretching) can be sufficiently secured while suppressing crystallization of the PVA-based resin layer. As a result, a polarizing film having excellent optical characteristics (for example, the degree of polarization) can be manufactured. On the other hand, the glass transition temperature of the resin substrate is preferably 60 ° C. or higher. In addition, a glass transition temperature (Tg) is a value calculated | required according to JISK7121.

  The water absorption rate of the resin base material is preferably 0.2% or more, and more preferably 0.3% or more. Such a resin base material absorbs water, and the water can act as a plasticizer to be plasticized. As a result, the stretching stress can be greatly reduced and the stretchability can be excellent. On the other hand, the water absorption rate of the resin base material is preferably 3.0% or less, more preferably 1.0% or less. By using such a resin base material, it is possible to prevent problems such as the dimensional stability of the resin base material being significantly reduced during production and the appearance of the resulting polarizing film being deteriorated. Moreover, it can prevent that it breaks at the time of extending | stretching in water, or a PVA-type resin layer peels 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, more preferably 50 μm to 200 μm. The surface of the resin base material may be subjected to surface modification treatment (for example, corona treatment) or an easy-adhesion layer may be formed. According to such a process, the laminated body excellent in the adhesiveness of a resin base material and a PVA-type resin layer can be obtained.

  Arbitrary appropriate resin may be employ | adopted as PVA-type resin which forms the said PVA-type resin layer. Examples thereof include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizing film having excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation.

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

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

  The coating solution may contain an additive. Examples of the additive include a plasticizer and a surfactant. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability and stretchability of the resulting PVA-based resin layer. Moreover, as an additive, an easily bonding component is mentioned, for example. By using the easy-adhesion component, the adhesion between the resin base material and the PVA-based resin layer can be improved. As a result, for example, problems such as peeling of the PVA resin layer from the resin base material can be suppressed, and dyeing and underwater stretching described later can be performed satisfactorily. As the easily adhesive component, for example, modified PVA such as acetoacetyl-modified PVA is used.

  Any appropriate method can be adopted as a coating method of the coating solution. Examples thereof include 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 and the like). The coating / drying temperature of the coating solution is, for example, 20 ° C. or higher, preferably 50 ° C. or higher.

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

  In one embodiment, the PVA-type resin layer (laminated body) is previously extended | stretched. 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 drawing is, for example, 1.5 to 3.5 times, preferably 2.0 to 3.0 times. The stretching temperature is, for example, 95 ° C to 150 ° C.

B. Dyeing step The dyeing is typically performed by dyeing the PVA resin layer with a dichroic substance. Preferably, it is performed by adsorbing a dichroic substance to the PVA resin layer. Examples of the adsorption method include a method of immersing a PVA resin layer (laminated body) in a staining solution containing a dichroic substance, a method of applying the staining solution to a PVA resin layer, and a method of applying the staining solution to a PVA system. Examples include a method of spraying on the resin layer. Preferably, it is a method of immersing the PVA resin layer in the staining solution. It is because a dichroic substance can adsorb | suck favorably.

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

  The liquid temperature during dyeing of the dyeing liquid is preferably 20 ° C. to 50 ° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the staining solution, the immersion time is preferably 5 seconds to 5 minutes in order to ensure the transmittance of the PVA resin layer. The staining conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the finally obtained polarizing film is within a predetermined range. In one embodiment, immersion time is set so that the polarization degree of the polarizing film obtained may be 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 process Any suitable method can be adopted as a stretching method of the laminate. Specifically, it may be fixed end stretching (for example, a method using a tenter stretching machine) or free end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Moreover, 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 stage or in multiple stages. When performed in multiple stages, the draw ratio (maximum draw ratio) of the laminate described later is the product of the draw ratios of the respective stages.

  The stretching may be an underwater stretching method performed by immersing the laminate in a stretching bath, or an air stretching method. Preferably, underwater stretching is performed at least once, and more preferably, air stretching and underwater stretching are combined. According to the stretching in water, the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80 ° C.) of the resin base material and the PVA resin layer while suppressing the crystallization. It can be stretched at a high magnification. As a result, a polarizing film having excellent optical characteristics can be manufactured. In addition, when combining air extending | stretching and underwater extending | stretching, it is preferable to perform underwater extending | stretching after air extending | stretching.

  Any appropriate direction can be selected as the stretching direction of the laminate. In one embodiment, it extends | stretches in the longitudinal direction of an elongate laminated body. Specifically, the laminate is transported in the longitudinal direction, which is the transport direction (MD). In another embodiment, it extends | stretches in the width direction of an elongate laminated body. Specifically, the laminate is transported in the longitudinal direction, and the direction (TD) is orthogonal to the transport direction (MD).

  The stretching temperature of the laminate can be set to any appropriate value depending on the resin base material, the stretching method, and the like. When adopting the air stretching method, the stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate, more preferably the glass transition temperature (Tg) of the resin substrate + 10 ° C., and particularly preferably Tg + 15 ° C. That's it. On the other hand, the stretching temperature of the laminate is preferably 170 ° C. or lower. By stretching at such a temperature, it is possible to suppress rapid progress of crystallization of the PVA-based resin, and to suppress problems due to the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). it can.

  When the underwater stretching method is employed 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. If it is such temperature, it can extend | stretch at high magnification, suppressing melt | dissolution of a PVA-type resin layer. Specifically, as described above, the glass transition temperature (Tg) of the resin base material 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 the stretching cannot be satisfactorily performed even in consideration of plasticization of the resin base material with 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 employing an underwater stretching method, it is preferable to stretch the laminate by immersing it in an aqueous boric acid solution (stretching in boric acid in water). By using an aqueous boric acid solution as the stretching bath, the PVA resin layer can be provided with rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water. Specifically, boric acid can form a tetrahydroxyborate anion in an aqueous solution and crosslink 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 boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 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 resin layer can be effectively suppressed, and a polarizing film having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.

  Preferably, an iodide is blended in the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. Specific examples of the iodide are as described above. 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 draw ratio (maximum draw ratio) of the laminate is preferably 5.0 times or more with respect to the original length of the laminate. Such a high draw ratio can be achieved, for example, by adopting an underwater drawing method (boric acid underwater drawing). The draw ratio of the laminate by drawing in water is preferably 2.0 times or more. In the present specification, the “maximum stretch ratio” refers to a stretch ratio immediately before the laminate is ruptured. Separately, a stretch ratio at which the laminate is ruptured is confirmed, and a value that is 0.2 lower than that value. .

  Preferably, underwater stretching is performed after the dyeing.

D. Slit Process FIG. 2 is an external perspective view showing an example of the slit process. As shown in FIG. 2, the width direction end portions 10 a and 10 a of the laminated body 10 are slit along the longitudinal direction 20 of the laminated body 10 before the stretching. The slit piece 10a that is slit includes the resin base material and the PVA resin layer. The slit width (the width of the slit piece) is typically 10 mm to 1000 mm. In one embodiment, the slit width is set so that the width of the laminated body after stretching (the width of the laminated body in the case of bonding described later) corresponds to the width of the protective film described later. Thus, by adjusting both widths, the wrinkles at the end portions in the width direction can be eliminated, and the laminate and the protective film can be stably bonded together. When the stretching is longitudinal stretching (MD stretching), the slit width can be set considering that the width of the laminate can be reduced by stretching. Specifically, the slit width can be set smaller than slitting after stretching.

  By slitting before stretching, it is possible to effectively prevent foreign matters from being mixed between the PVA-based resin layer and the protective film in the bonding step with the protective film described later. Specifically, if slitting is performed in a state in which the orientation of the PVA-based resin layer has been increased by stretching, a crust is likely to be generated at the end of the slit, and this crust can become a foreign substance during bonding. Moreover, the PVA-type resin layer in a state with high orientation is easy to tear, and slits may be difficult. Therefore, by performing slitting before stretching, it is possible to effectively prevent the generation of bubbles and the generation of bubbles accompanying the mixing of foreign matters while performing the slits satisfactorily. As a result, a polarizing plate excellent in appearance can be obtained. Furthermore, unevenness such as the above-mentioned wrinkles, folds, tightening, etc., and if knurling is formed in advance in the width direction end of the laminate, the knurling can be removed before stretching, so that stable stretching is performed. Can do.

  In addition to the above, a polarizing film having excellent optical properties can be obtained by slitting before stretching. Specifically, when performing stretching (longitudinal uniaxial stretching) due to the difference in peripheral speed between rolls, L / W is increased by slitting the end in the width direction before stretching, and the orientation / optical properties of the resulting polarizing film The characteristics can be greatly improved. In addition, L shows the distance between extending | stretching (distance to which tension | tensile_strength is added by the peripheral speed difference between rolls), W shows the width | variety of a laminated body.

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

  Preferably, the slit is performed before the staining. By slitting before dyeing, it is possible to more effectively prevent foreign matters from being mixed between the PVA-based resin layer and the protective film in the bonding step with the protective film described later. Specifically, the PVA-based resin layer can be crosslinked (for example, due to iodine) and become brittle due to dyeing. When slitting in such a state, slit scraps are likely to be formed, and the slit scraps can become a foreign object during bonding. Therefore, by slitting before dyeing, it is possible to more effectively prevent foreign substances from being mixed and the generation of bubbles accompanying the mixing of foreign substances. As a result, a polarizing plate excellent in appearance can be obtained.

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

E. Other In addition to the above, the laminate may be appropriately subjected to a treatment for using the PVA resin layer as a polarizing film. Examples of the treatment for forming the polarizing film include insolubilization treatment, crosslinking treatment, washing treatment, and drying treatment. Note that the number, timing, order, and the like of these processes are not particularly limited.

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

  The crosslinking treatment is typically performed by immersing the PVA resin layer in an aqueous boric acid solution. By performing the crosslinking treatment, water resistance can be imparted to the PVA resin layer. The concentration of the boric acid aqueous solution is preferably 1 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 an iodide further. By blending iodide, elution of iodine adsorbed on the PVA resin layer can be suppressed. The blending 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 the 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 performed before the underwater stretching. In a preferred embodiment, the dyeing process, the crosslinking process and the underwater stretching are performed in this order.

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

  In one embodiment, the said laminated body is wound up in roll shape and it is set as an original fabric roll, and the said slit is performed after winding up. The winding tension is typically 300N to 600N. The winding may be performed so that the PVA-based resin layer is on the inner side (core material side), or may be performed so that the PVA-based resin layer is on the outer side. When the laminated body is wound up in the manufacturing process of the polarizing film, for example, if the laminated body has partial film thickness unevenness, winding tightening and wrinkles are generated. Such a problem is likely to occur at the end in the width direction. Therefore, it can extend | stretch stably by performing the said slit after winding. Moreover, since it slits after winding up, regardless of the width | variety of the protective film to bond, the original fabric roll of the same width can be used, and it can contribute to the improvement of productivity.

F. Bonding process After the dyeing and stretching, a protective film is bonded to the PVA resin layer (polarizing film) of the laminate. Specifically, a long protective film is bonded to the PVA-based resin layer so that the longitudinal directions thereof are aligned. In one embodiment, the width of the layered product after stretching corresponds to the width of the layered product at the time of bonding. Specifically, a new slit process is not substantially given to a laminated body between the said extending process and a bonding process.

  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.

  Any appropriate resin film can be adopted as the protective film. Examples of the protective film forming material include cellulose resins such as triacetyl cellulose (TAC), cycloolefin resins such as norbornene resins, olefin resins such as polyethylene and polypropylene, polyester resins, and (meth) acrylic resins. Examples thereof include resins. The “(meth) acrylic resin” refers to an acrylic resin and / or a methacrylic resin.

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

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

  Any appropriate aqueous adhesive may be employed as the aqueous adhesive. Preferably, an aqueous adhesive containing a PVA resin is used. The average degree of polymerization of the PVA resin contained in the aqueous adhesive is preferably about 100 to 5000, more preferably 1000 to 4000, from the viewpoint of adhesiveness. The average saponification degree is preferably about 85 mol% to 100 mol%, more preferably 90 mol% to 100 mol%, from the viewpoint of adhesiveness.

  The PVA resin contained in the aqueous adhesive preferably contains an acetoacetyl group. This is because the adhesiveness between the PVA resin layer and the protective film is excellent and the durability can be excellent. The acetoacetyl group-containing PVA resin can be obtained, for example, by reacting a PVA resin and diketene by an arbitrary method. The degree of acetoacetyl group modification of the acetoacetyl group-containing PVA 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%. The degree of acetoacetyl group modification 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 thickness at the time of application | coating of an adhesive agent can be set to arbitrary appropriate values. For example, it is set so that an adhesive layer having a desired thickness is obtained after heating (drying). 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.

  It is preferable to heat after bonding a protective film to the PVA resin layer. The heating temperature is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, and particularly preferably 80 ° C. or higher. In addition, you may serve as the above-mentioned drying process for the heating performed after bonding a protective film.

G. Stripping Step In one embodiment, the resin substrate is stripped from the PVA resin layer (polarizing film). Preferably, before peeling off the resin base material, the widthwise end of the polarizing film laminate in which a protective film is bonded to the laminate is slit. Bonding failure (for example, wrinkles) is likely to occur at the bonded portion between the widthwise end of the laminate and the protective film, and by removing this portion with a slit, excellent releasability of the resin base material is achieved. Can do. Specifically, it is possible to prevent the resin base material from being peeled off (for example, breakage) starting from the joint failure portion and to peel the resin base material satisfactorily. As a result, it is possible to obtain a polarizing plate that is superior in appearance.

H. Polarizing plate The polarizing plate of the present invention comprises the polarizing film and the protective film disposed on one side of the polarizing film. The polarizing film is substantially a PVA 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, further 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 further preferably 99.95% or more.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. In addition, the measuring method of each characteristic is as follows.
1. Thickness Measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”).
2. Glass transition temperature (Tg)
It measured according to JIS K7121.

[Example 1]
(Production of laminate)
As the resin base material, an elongated, amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (width: 4000 mm, thickness: 100 μm) having a water absorption rate of 0.75% and Tg of 75 ° C. was used.
One side of the resin substrate was subjected to corona treatment, and on this corona treated surface, 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 4.6 parts by weight of 4.6%, a degree of saponification of 99.0 mol% or more, manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name “Gosefimer Z200”) at 60 ° C. and dried, A PVA resin layer was formed to prepare a laminate.

The obtained laminate was uniaxially stretched at a free end 2.0 times in the longitudinal direction between rolls having different peripheral speeds in an oven at 115 ° C. (in-air stretching). Thereafter, the laminate was wound into a roll.
While unwinding the laminated body from the laminated body roll wound up in a roll shape, both ends in the width direction of the laminated body were slit so that the width after slitting was 2500 mm.
Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Subsequently, it was immersed in a dyeing bath having a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the obtained polarizing plate had a predetermined transmittance. In this example, 0.2 parts by weight of iodine was blended with 100 parts by weight of water, and immersed in an aqueous iodine solution obtained by blending 1.0 part by weight of potassium iodide (dyeing treatment). .
Subsequently, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds (crosslinking treatment). ).
Thereafter, the laminate was immersed in a boric acid aqueous solution (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) at a liquid temperature of 70 ° C. Uniaxial stretching was performed 2.7 times in the longitudinal direction between rolls having different speeds (in-water stretching).
Thereafter, the laminate was immersed in a washing bath having a liquid temperature of 30 ° C. (an aqueous solution obtained by adding 4 parts by weight of potassium iodide to 100 parts by weight of water), and then heated with hot air at 60 ° C. for 60 seconds. It was dried for 2 seconds (cleaning / drying process).
In this way, a polarizing film having a thickness of 5 μm was formed on the resin substrate.

  Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “GOHSEIMER (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the polarizing film surface of the laminate. A triacetyl cellulose film (manufactured by Konica Minolta, trade name “KC4UY”, thickness 40 μm) having a width corresponding to the width of the polarizing film is bonded, heated in an oven maintained at 60 ° C. for 5 minutes, and polarizing plate Got.

[Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that the slit was made to have a width of 2100 mm.

[Comparative Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the timing for performing the slit 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. Polarization degree Using a UV-visible spectrophotometer (manufactured by JASCO Corporation, product name “V7100”), the single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) of the polarizing plate are measured, The degree of polarization (P) was determined by the following equation.
Polarization degree (P) (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
Note that Ts, Tp, and Tc are Y values measured with a two-degree field of view (C light source) of JIS Z 8701 and corrected for visibility.
3. Orientation (PVA orientation function evaluation method)
The measuring device is a Fourier transform infrared spectrophotometer (FT-IR) (Perkin
Elmer, trade name: “SPECTRUM2000”) was used. The surface of the PVA resin layer was evaluated by measuring total reflection attenuation (ATR) using polarized light as measurement light. The orientation function was calculated according to the following procedure. Measurement was carried out with the measured polarized light at 0 ° and 90 ° with respect to the stretching direction. It calculated according to (Formula 1) described below using the intensity | strength of 2941cm < ^-1 > of the obtained spectrum. The following intensity I as a reference peak to 3330cm ^-1, using the value of 2941cm ^-1 / 3330cm -1. Note that perfect orientation is obtained when f = 1, and random orientation when f = 0. The peak at 2941 cm ⁻¹ is said to be absorption due to vibration of the main chain (—CH ₂ —) of PVA.
(Formula 1) f = (3 <cos 2θ> −1) / 2 = (1−D) / [c (2D + 1)]
However,
c = (3cos2β-1) / 2
β = 90deg => f = -2 × (1-D) / (2D + 1)
θ: Molecular chain / stretch direction β: Molecular chain / transition dipole moment D = (I⊥) / (I //), (The value of D increases as PVA is oriented.)
I⊥: Intensity when measured with polarized light incident in a direction perpendicular to the stretching direction I //: Intensity when measured with polarized light incident in a direction 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 clock, a microwave oven, etc., and a reflection of an organic EL device. It is suitably used as a prevention film.

DESCRIPTION OF SYMBOLS 10 Laminated body 11 Resin base material 12 Polyvinyl alcohol-type resin layer (polarizing film)

Claims (10)

Forming a laminate by forming a polyvinyl alcohol-based resin layer on one side of the long resin substrate and the resin substrate; and
Dyeing the polyvinyl alcohol-based resin layer;
Stretching the laminate,
Before stretching, slitting the end of the laminate in the width direction;
A step of bonding a long protective film to the polyvinyl alcohol-based resin layer after the dyeing and stretching,
The width of the laminated body after stretching corresponds to the width of the laminated body at the time of bonding,
Manufacturing method of polarizing plate.   The manufacturing method of Claim 1 which slits so that the width | variety of the laminated body after the said extension may respond | correspond to the width | variety of the said protective film.   The manufacturing method of Claim 1 or 2 which performs the said slit before the said dyeing | staining.   The manufacturing method according to any one of claims 1 to 3, further comprising a step of winding the laminate into a roll shape, wherein the slit is performed after the winding.   The manufacturing method according to claim 1, wherein the stretching is longitudinal uniaxial stretching.   The manufacturing method according to claim 1, wherein the stretching is underwater stretching.   The manufacturing method in any one of Claim 1 to 6 whose draw ratio of the said extending | stretching is 2.0 times or more.   The manufacturing method in any one of Claim 1 to 7 with which the said laminated body is extended | stretched in multiple steps.   The manufacturing method according to any one of claims 1 to 8, wherein the laminate is stretched in advance before the slit.   A polarizing plate obtained by the production method according to claim 1.

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