JP6152128B2 - Manufacturing method of polarizer - Google Patents

Description

  The present invention relates to a method for manufacturing a polarizer. In more detail, this invention relates to the manufacturing method of the polarizer which has a non-polarizing part.

  Some image display devices such as mobile phones and notebook personal computers (PCs) are equipped with internal electronic components such as cameras. Various studies have been made for the purpose of improving the camera performance and the like of such an image display device, but further improvement in camera performance and the like is desired due to the rapid spread of smartphones and touch panel type information processing devices. . Further, in order to cope with the diversification and high functionality of the shape of the image display device, a polarizer having a partially non-polarizing portion is required.

  Usually, the non-polarizing part is formed by drilling the polarizer, but there is a problem that a crack occurs in the polarizer during the processing. Therefore, after stretching a laminated film obtained by forming a polyvinyl alcohol-based resin layer on the surface of the resin base film, a stain-proof layer is formed on the surface of the polyvinyl alcohol-based resin layer, and dyed with a dichroic dye. A method of manufacturing a polarizer having a polarizing portion has been proposed (see Patent Document 1).

  However, the dye-resisting layer formed on the surface of the polyvinyl alcohol-based resin layer needs to be washed and removed after dyeing depending on the forming material. Even when the stain-proof layer is not removed, since the stain-proof layer is partially present on the surface of the polarizer, for example, there is a problem that bubbles are easily generated when the protective film is bonded. In addition, there is a problem that a non-polarized portion having a predetermined shape cannot be obtained due to a problem such that a part of the dye-proof layer peels off from the surface of the polyvinyl alcohol resin layer at the time of dyeing, and the accuracy is poor. Therefore, a new method for producing a polarizer having a non-polarizing part is desired.

JP 2014-2111548 A

  The present invention has been made to solve the above problems, and a main object thereof is to provide a method for producing a polarizer having a non-polarizing portion with high productivity.

The method for producing a polarizer of the present invention includes a step of forming a polyvinyl alcohol resin layer on a resin substrate to obtain a laminate, a step of dyeing the polyvinyl alcohol resin layer with iodine, and stretching the laminate. And a step of forming a non-polarizing part by bringing a basic solution into contact with the polyvinyl alcohol-based resin layer after the dyeing and stretching.
In one embodiment, the iodine content in the non-polarizing part is 1.0% by weight or less.
In one embodiment, the said basic solution is made to contact in the state coat | covered with the surface protection film so that the said polyvinyl alcohol-type resin layer surface might expose at least one part.
In one embodiment, a through hole is formed in the surface protective film.
In one embodiment, the basic solution is brought into contact with a polyvinyl alcohol resin layer having a thickness of 13 μm or less.
In one embodiment, the laminate is obtained by applying a coating solution containing a polyvinyl alcohol-based resin to the resin base material.
In one embodiment, the laminate is stretched after the dyeing.
In one embodiment, the stretching is underwater stretching.
In one embodiment, after the protective film is bonded to the polyvinyl alcohol resin layer side of the laminate, the resin base material is peeled off, and the polarization obtained by attaching the surface protective film to the peeled surface so as to be peeled off. The basic solution is brought into contact with the film laminate.
In one embodiment, the polarizing film laminate is elongated, and through holes are formed in the surface protection film at predetermined intervals in the longitudinal direction and / or the width direction.
In one embodiment, the acidic solution is brought into contact with the portion of the polyvinyl alcohol-based resin layer in contact with the basic solution.

  According to the present invention, a polarizer having a non-polarizing part can be obtained by a simple operation of bringing a basic solution into contact with a dyed / stretched polyvinyl alcohol resin layer. Further, according to the present invention, the laminate can be stretched even after dyeing, and a polarizer having excellent optical characteristics can be obtained.

1 is a plan view of a polarizer according to one embodiment of the present invention. FIG.

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

A. Polarizer FIG. 1 is a plan view of a polarizer according to one embodiment of the invention. The polarizer 1 has a non-polarizing portion 2 formed thereon. The non-polarization part 2 is formed by making content of the dichroic substance contained in a polarizer smaller than the other site | part 3. FIG. According to such a configuration, cracks and delamination are mechanically compared (for example, by a method of mechanical engraving using a sculpture blade punching, a plotter, a water jet, or the like), compared to a case where a through hole is formed. Quality problems such as (delamination) and paste sticking are avoided. Also, since the content of the dichroic substance itself is reduced, the transparency of the non-polarizing part is maintained better than when the non-polarizing part is formed by decomposing the dichroic substance with laser light or the like. Is done.

  In the illustrated example, the small circular non-polarizing portion 2 is formed at the center of the upper end portion of the polarizer 1, but the number, arrangement, shape, size, etc. of the non-polarizing portions can be appropriately designed. For example, it is designed according to the position, shape, size, etc. of the camera hole part of the mounted image display device. In this case, it is preferable that the non-polarizing part is substantially circular with a diameter of 10 mm or less.

  The transmittance of the non-polarizing part (for example, the transmittance measured with light having a wavelength of 550 nm at 23 ° C.) is preferably 50% or more, more preferably 60% or more, still more preferably 75% or more, and particularly preferably 90% or more. It is. With such transmittance, desired transparency can be ensured. For example, when the non-polarization part is made to correspond to the camera hole part of the image display device, it is possible to prevent an adverse effect on the photographing performance of the camera.

  The polarizer (excluding the non-polarized part) preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer (excluding the non-polarizing part) is preferably 40.0% or more, more preferably 42.0% or more, still more preferably 42.5% or more, and particularly preferably 43.0% or more. is there. The degree of polarization of the polarizer (excluding the non-polarizing part) is preferably 99.8% or more, more preferably 99.9% or more, and further preferably 99.95% or more.

  The thickness of the polarizer is preferably 13 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less. By setting it as such thickness, the non-polarizing part which was excellent in surface smoothness (for example, generation | occurrence | production of wrinkles etc. was suppressed) could be formed, having high transparency. As a result, for example, when the non-polarizing part is associated with the camera hole part of the image display device, it is possible to more effectively prevent adverse effects on the camera performance. Moreover, a non-polarizing part can be favorably formed by setting it as the said thickness. For example, a non-polarizing part can be formed in a short time in contact with a basic solution described later. On the other hand, the thickness of the polarizer is preferably 1.0 μm or more, more preferably 2.0 μm or more.

  As the dichroic substance, iodine is preferably used. By using iodine, for example, a non-polarizing part can be satisfactorily formed by contact with a basic solution described later.

  The non-polarizing part is a part having a smaller content of the dichroic material than the other part. The content of the dichroic material in the non-polarizing part is preferably 1.0% by weight or less, more preferably 0.5% by weight or less, and still more preferably 0.2% by weight or less. When the content of the dichroic substance in the non-polarizing part is within such a range, desired transparency can be imparted to the non-polarizing part. For example, when a non-polarization part is made to correspond to the camera hole part of the image display device, it is possible to realize a very excellent photographing performance from the viewpoints of both brightness and color. On the other hand, the lower limit value of the content of the dichroic substance in the non-polarizing part is usually not more than the detection limit value. When iodine is used as the dichroic substance, the iodine content of the non-polarizing part is obtained from a calibration curve prepared in advance using a standard sample, for example, from the X-ray intensity measured by fluorescent X-ray analysis.

  The difference between the content of the dichroic substance in the other part and the content of the dichroic substance in the non-polarizing part is preferably 0.5% by weight or more, more preferably 1% by weight or more.

  Any appropriate resin can be used as a material for forming the polarizer. Preferably, polyvinyl alcohol resin (hereinafter referred to as “PVA resin”) is used. Examples of the PVA resin 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-based resin is usually 85 to 100 mol%, preferably 95.0 mol% or more, more preferably 99.0 mol% or more, and particularly preferably 99.93 mol% or more. . The saponification degree can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a saponification degree, a polarizer having excellent durability can be obtained.

  The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. Average polymerization degree is 1000-10000 normally, Preferably it is 1200-6000, More preferably, it is 2000-5000. The average degree of polymerization can be determined according to JIS K 6726-1994.

B. Method for Producing Polarizer The polarizer includes, for example, a step of forming a PVA resin layer on a resin substrate to obtain a laminate, a step of dyeing the PVA resin layer with iodine, and a step of stretching the laminate And a step of forming a non-polarizing part by bringing a basic solution into contact with the PVA resin layer after dyeing and stretching. According to such a method, a polarizer satisfying the thickness and the optical characteristics (single transmittance, polarization degree) can be obtained.

B-1. Production of Laminate Any appropriate resin can be used as a material for forming the resin base material. Examples thereof include ester resins such as polyethylene terephthalate resins, olefin resins such as cycloolefin resins and 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 polarizer having excellent optical properties (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 substrate, it is possible to prevent problems such as the dimensional stability of the resin substrate being significantly reduced during production and the appearance of the resulting polarizer 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. The resin base material can be used as it is as a protective film.

  The laminate can be produced by any appropriate method. For example, it is produced by applying a coating liquid containing the PVA-based resin to a resin substrate and drying it as necessary. Moreover, it produces by laminating | stacking the film containing the said PVA-type resin on a resin base material by arbitrary appropriate methods.

  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.

  The thickness of the PVA-based resin layer (before stretching) is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm, and still more preferably 3 μm to 15 μm.

B-2. Dyeing As the dyeing method, for example, a method of immersing a PVA resin layer (laminated body) in a dyeing solution containing iodine, a method of applying the dyeing solution to a PVA resin layer, and a method of applying the dyeing solution to a PVA resin The method of spraying on a layer is mentioned. Preferably, a method of immersing the PVA resin layer in the staining solution is used.

  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 blending amount of iodide is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of water.

  The liquid temperature of the staining liquid is preferably 20 ° C to 50 ° C. The immersion time is preferably 5 seconds to 5 minutes. The staining conditions (concentration, liquid temperature, immersion time) can be set so that the polarization degree or single transmittance of the finally obtained polarizer falls within a predetermined range.

B-3. Stretching Any appropriate 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 stretch ratio of the laminate described later is the product of the stretch ratios of the respective stages.

  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 laminate is preferably stretched 4.0 times or more from the original length, more preferably 5.0 times or more.

  The stretching method is not particularly limited, and may be, for example, an air stretching method or an underwater stretching method performed while the laminate is immersed in a stretching bath. 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 polarizer 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.

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

  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. 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.

  Preferably, an iodide is blended in the boric acid aqueous solution. This is because when the PVA resin layer is dyed in advance, elution of iodine can be suppressed. 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 underwater stretching is preferably performed after dyeing. This is because the stretchability can be improved. As described above, one of the features of the present invention is that the laminate can be stretched after dyeing. According to the present invention, stretching in water can be performed satisfactorily.

  As described above, it is preferable to combine underwater stretching and in-air stretching. In one embodiment, the laminate is subjected to a dyeing process after being stretched in the air at, for example, 95 ° C to 150 ° C, and then stretched by stretching in water. In this case, the draw ratio of the laminate by air drawing is, for example, 1.5 to 3.5 times, and preferably 2.0 to 3.0 times. Moreover, the draw ratio of the laminate by drawing in water is preferably 2.0 times or more.

B-4. Contact of Basic Solution The non-polarizing part is preferably formed by bringing a basic solution into contact with the PVA resin layer. When using an iodine as a dichroic substance, the iodine content of a contact part can be easily reduced by making a basic solution contact the desired site | part of a PVA-type resin layer. Specifically, the basic solution can penetrate into the PVA-based resin layer by contact. The iodine complex contained in the PVA resin layer is reduced by the base contained in the basic solution to become iodine ions. By reducing the iodine complex to iodine ions, the transmittance of the contact portion can be improved. And the iodine which became the iodine ion moves to the solvent of a basic solution from a PVA-type resin layer. The non-polarizing part thus obtained can maintain its transparency well. Specifically, when the transmittance is improved by destroying the iodine complex, iodine remaining in the PVA-based resin layer may form an iodine complex again with the use of the polarizer, and the transmittance may decrease. When the iodine content is reduced, such a problem is prevented.

  Arbitrary appropriate methods can be employ | adopted as a contact method of a basic solution. For example, the method of dripping, coating, and spraying a basic solution with respect to the PVA-based resin layer, and the method of immersing the PVA-based resin layer in the basic solution are exemplified. When contacting the basic solution, by any appropriate means (for example, protective film, surface protective film) so that the basic solution does not come in contact with other than the desired site (so that the concentration of the dichroic substance is not lowered). The PVA resin layer may be protected. The protective film can be used as it is as a protective film for a polarizer. The surface protective film is temporarily used when manufacturing the polarizer. Since the surface protective film is removed from the polarizer at any appropriate timing, typically, the surface protective film is bonded to the PVA-based resin layer via an adhesive layer.

  Any appropriate basic compound can be used as the basic compound contained in the basic solution. Examples of the basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide, and inorganic alkali metal salts such as sodium carbonate. , Organic alkali metal salts such as sodium acetate, aqueous ammonia and the like. Among these, an alkali metal hydroxide is preferable, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are more preferable. By using a basic solution containing an alkali metal hydroxide, the iodine complex can be efficiently ionized, and the non-polarizing part can be formed more easily. These basic compounds may be used alone or in combination of two or more.

  Any appropriate solvent can be used as the solvent of the basic solution. Specific examples include water, alcohols such as ethanol and methanol, ethers, benzene, chloroform, and mixed solvents thereof. Among these, water and alcohol are preferably used because iodine ions can be favorably transferred to the solvent.

  The density | concentration of a basic solution is 0.01N-5N, for example, Preferably it is 0.05N-3N, More preferably, it is 0.1N-2.5N. When the concentration of the basic solution is in such a range, the non-polarizing part can be efficiently formed.

  The liquid temperature of a basic solution is 20 to 50 degreeC, for example, Preferably it is 25 to 50 degreeC. By contacting the basic solution at such a temperature, the non-polarizing part can be formed efficiently.

  The contact time of the basic solution is set according to, for example, the thickness of the PVA-based resin layer and the type and concentration of the basic compound contained in the basic solution. The contact time is, for example, 5 seconds to 30 minutes, preferably 5 seconds to 5 minutes.

  The thickness of the polarizer may correspond to the thickness of the PVA-based resin layer at the time of contact with the basic solution.

  In one embodiment, the PVA-based resin layer surface is coated with a surface protective film so that at least a part of the surface is exposed when the basic solution is contacted. The polarizer in the illustrated example is manufactured by, for example, attaching a surface protection film in which small circular through holes are formed to a PVA resin layer, and bringing a basic solution into contact therewith. At that time, it is preferable that the other side of the PVA-based resin layer (side on which the surface protective film is not disposed) is also protected.

  The thickness of the surface protective film is typically 20 μm to 250 μm, preferably 30 μm to 150 μm. The surface protective film is preferably a film having a high hardness (for example, elastic modulus). This is because deformation of the through hole can be prevented. Surface protective film forming materials include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Etc. Preference is given to ester resins (especially polyethylene terephthalate resins). The details of the protective film will be described later.

  In a preferred embodiment, a polarizing film laminate obtained by peeling a resin base material after laminating a protective film on the PVA-based resin layer side of the laminate, and attaching the surface protective film to the peeled surface in a peelable manner. Contact with a basic solution. By pre-adhering a protective film different from the resin base material on one side of the PVA-based resin layer in advance, even if the thickness of the PVA-based resin layer is thin as described above, the surface protective film is excellently bonded. be able to. Moreover, the polarizing film laminated body obtained can be extremely excellent in conveyance property. In addition, when a polarizing film laminated body is elongate, the through-hole is formed in the longitudinal direction and / or the width direction in the surface protection film at predetermined intervals, for example.

  In the said embodiment, the protective film is bonded together only on the one side of the PVA-type resin layer. In such a configuration, curling is likely to occur (particularly when the thickness of the PVA-based resin layer is 15 μm or more), and problems such as poor bonding of the surface protective film and reduced transportability are likely to occur. Is thin as described above, the occurrence of curling can be satisfactorily suppressed.

B-5. Others Before the contact with the basic solution, the PVA resin layer may be subjected to any appropriate treatment other than the dyeing / stretching. For example, insolubilization treatment, cross-linking treatment, washing treatment, and drying treatment can be mentioned.

(Insolubilization treatment)
The insolubilization treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. In particular, when an underwater stretching method is employed, water resistance can be imparted to the PVA-based resin layer by performing insolubilization treatment. 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 40 ° C. Preferably, the insolubilization process is performed after the laminate is manufactured and before the dyeing process or the underwater stretching process.

(Crosslinking treatment)
The crosslinking treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous 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 4 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 50 ° C. Preferably, the crosslinking treatment is performed before the underwater stretching treatment. In a preferred embodiment, the dyeing process, the crosslinking process and the underwater stretching process are performed in this order.

(Cleaning process)
The cleaning treatment is typically performed by immersing the PVA resin layer in an aqueous potassium iodide solution.

(Drying process)
The drying temperature of the drying treatment is preferably 30 ° C to 100 ° C.

  In one embodiment, the basic solution is removed from the PVA resin layer by any appropriate means after contacting the PVA resin layer. According to such embodiment, the fall of the transmittance | permeability of the non-polarizing part accompanying use of a polarizer can be prevented more reliably, for example. Specific examples of the method for removing the basic solution include washing, wiping removal with a waste cloth, suction removal, natural drying, heat drying, air drying, vacuum drying, and the like. Preferably the basic solution is washed. Examples of the solution used for washing include water (pure water), alcohols such as methanol and ethanol, acidic aqueous solutions, and mixed solvents thereof. Preferably, water is used. The number of washings is not particularly limited, and may be performed a plurality of times. When the basic solution is removed by drying, the drying temperature is, for example, 20 ° C to 100 ° C.

  Preferably, the acidic solution is brought into contact with the portion of the PVA-based resin layer in contact with the basic solution. By contacting with an acidic solution, the basic solution remaining in the non-polarizing part can be removed to a better level. Moreover, the dimensional stability (durability) of a non-polarizing part can be improved. The contact with the acidic solution may be performed after the basic solution is removed or may be performed without removing the basic solution.

  Any appropriate acidic compound can be used as the acidic compound contained in the acidic solution. Examples of the acidic compound include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and hydrogen fluoride, and organic acids such as formic acid, oxalic acid, citric acid, acetic acid, and benzoic acid. Among these, the acidic compound contained in the acidic solution is preferably an inorganic acid, and more preferably hydrochloric acid, sulfuric acid, or nitric acid. These acidic compounds may be used alone or in combination of two or more.

  As the solvent for the acidic solution, those exemplified as the solvent for the basic solution can be used. The density | concentration of an acidic solution is 0.01N-5N, for example, Preferably it is 0.05N-3N, More preferably, it is 0.1N-2.5N.

  The liquid temperature of the acidic solution is, for example, 20 ° C to 50 ° C. The contact time of the acidic solution is, for example, 5 seconds to 5 minutes. In addition, the contact method of an acidic solution can employ | adopt the method similar to the contact method of the said basic solution. Moreover, an acidic solution can be removed from a PVA-type resin layer. As a method for removing the acidic solution, a method similar to the method for removing the basic solution may be employed.

C. Polarizing plate The polarizing plate of this invention has the said polarizer. The polarizing plate typically includes a polarizer and a protective film disposed on at least one side of the polarizer. As the protective film, the resin base material may be used as it is, or a film different from the resin base material may be used. Examples of the material for forming the protective film include cellulose resins such as diacetyl cellulose and triacetyl cellulose, (meth) acrylic resins, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. , Polyamide resins, polycarbonate resins, and copolymer resins thereof.

  The surface of the protective film where the polarizer is not laminated may be subjected to a treatment for the purpose of a hard coat layer, antireflection treatment, diffusion or antiglare as a surface treatment layer. For example, the surface treatment layer is preferably a layer having a low moisture permeability for the purpose of improving the humidification durability of the polarizer. The hard coat treatment is performed for the purpose of preventing scratches on the polarizing plate surface. The hard coat layer can be formed by, for example, a method of adding a cured film excellent in hardness, slipping properties, etc., to an appropriate ultraviolet curable resin such as acrylic or silicone. The hard coat layer preferably has a pencil hardness of 2H or more. The antireflection treatment is performed for the purpose of preventing the reflection of external light on the surface of the polarizing plate, and is based on the interference action of light as disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-248173. Such as a thin layer type that prevents reflection by using a canceling effect of reflected light, or a structure type that exhibits low reflectivity by imparting a fine structure to the surface as disclosed in JP 2011-2759 A, etc. This can be achieved by forming a low reflective layer. Anti-glare treatment is performed for the purpose of preventing the outside light from being reflected on the polarizing plate surface and obstructing the viewing of the transmitted light through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. Or by applying a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The thickness of the protective film is preferably 10 μm to 100 μm. The protective film is typically laminated on the polarizer via an adhesive layer (specifically, an adhesive layer or an adhesive layer). The adhesive layer is typically formed of a PVA adhesive or an activated energy ray curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive.

D. Image display apparatus The image display apparatus of this invention has the said polarizing plate. Examples of the image display device include a liquid crystal display device and an organic EL device. Specifically, the liquid crystal display device includes a liquid crystal panel having a liquid crystal cell and the polarizing plate disposed on one side or both sides of the liquid crystal cell. The organic EL device includes an organic EL panel in which the polarizing plate is disposed on the viewing side. Typically, the polarizer is arranged so as to correspond to the camera hole part of the image display device on which the non-polarizing part is mounted.

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. Water absorption was measured according to JIS K 7209.
3. Glass transition temperature (Tg)
It measured according to JIS K7121.

[Example 1]
(Production of laminate)
As the resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a long 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 polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6) were applied to this corona-treated surface. %, A saponification degree of 99.0 mol% or more, an aqueous solution containing 9: 1 ratio of Nippon Gosei Kagaku Kogyo Co., Ltd., trade name “Gosefimer Z200”) was applied and dried at 25 ° C. to a thickness of 11 μm. A PVA resin layer was formed to prepare a laminate.

(Preparation of polarizing plate)
The obtained laminate was immersed in an insolubilization bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) 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 1.5 parts by weight of potassium iodide (dyeing treatment). .
Subsequently, 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 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. However, uniaxial stretching was performed 5.0 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds (in-water stretching).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 30 ° C. (cleaning treatment).

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

(Formation of non-polarizing part)
The resin base material was peeled from the obtained polarizing plate, and a surface protective film having a circular through hole with a diameter of 4 mm formed on the peeled surface (polarizer surface) was bonded, and this was bonded to 1 mol / L (1N). It was immersed in an aqueous sodium hydroxide solution for 10 seconds (alkali treatment), and then immersed in 0.1N hydrochloric acid for 30 seconds (acid treatment). Then, it dried at 60 degreeC, the surface protection film was peeled, and the polarizing plate which has a non-polarizing part was obtained. A PET film (thickness 38 μm, manufactured by Mitsubishi Plastics, trade name: Diafoil) on which a 5 μm thick adhesive layer was formed was used as the surface protective film.

[Example 2]
The obtained laminate was subjected to the insolubilization treatment after free end uniaxial stretching in the longitudinal direction (longitudinal direction) 2.0 times between rolls having different peripheral speeds in an oven at 120 ° C. (air-assisted stretching). A polarizing plate having a non-polarizing part was obtained in the same manner as in Example 1 except that the stretching in water was performed so that the total stretching ratio was 5.5.

[Example 3]
Polarized light having a non-polarizing part in the same manner as in Example 1 except that a polarizer having a thickness of 12 μm was formed on the resin substrate and that the immersion time in the aqueous sodium hydroxide solution was 30 seconds in the alkali treatment. I got a plate.

[Example 4]
(Production of laminate)
A polyvinyl alcohol film having a thickness of 20 μm (polymerization degree 4300, saponification degree 99.3 mol%) and a resin base material as an adhesive PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer ( (Registered trademark) Z-200 ", resin concentration: 3% by weight) to obtain a laminate. As the resin base material, a 100-μm-thick amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (Tg 75 ° C., water absorption 0.75%) having a corona treatment was used.

(Preparation of polarizing plate)
The obtained laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) 2.0 times between rolls having different peripheral speeds in an oven at 120 ° C. (in-air stretching).
Next, the obtained laminate was immersed in a swelling bath (pure water) having a liquid temperature of 30 ° C. (swelling treatment).
Next, the laminate 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, 0.15 parts by weight of iodine and 100 parts by weight of potassium iodide were mixed for 60 seconds with 100 parts by weight of water (dyeing treatment). .
Subsequently, 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 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. However, uniaxial stretching was performed between the rolls having different peripheral speeds so that the stretching ratio in the longitudinal direction was 5.5 times (in-water stretching).

Subsequently, a PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer (registered trademark) Z-200”, resin concentration: 3% by weight) is applied to the polyvinyl alcohol film surface of the laminate, A triacetyl cellulose film (manufactured by Konica Minolta, trade name “KC4UY”, thickness 40 μm) was bonded and heated in an oven maintained at 60 ° C. for 5 minutes to prepare a polarizing plate having a polarizer having a thickness of 8 μm.
Then, the non-polarizing part was formed like Example 1, and the polarizing plate which has a non-polarizing part was obtained.

[Example 5]
The use of a 30 μm thick PVA film (Kuraray Co., Ltd., PE3000), the iodine concentration of the dyeing bath was set to 0.1% by weight, and the immersion time in the aqueous sodium hydroxide solution was set to 30 seconds in the alkali treatment. Except for this, a polarizing plate having a non-polarizing part was obtained in the same manner as Example 4.

[Example 6]
(Production of laminate)
A polyvinyl alcohol film having a thickness of 20 μm (polymerization degree 4300, saponification degree 99.3 mol%) and a resin base material as an adhesive PVA-based resin aqueous solution (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name “Gosefimer ( (Registered trademark) Z-200 ", resin concentration: 3% by weight) to obtain a laminate. As the resin base material, a 100-μm-thick amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (Tg 75 ° C., water absorption 0.75%) having a corona treatment was used.

  It has a non-polarization part like Example 1 except having used the above-mentioned layered product, and having made iodine concentration of a dyeing bath into 0.15 weight%, and potassium iodide concentration into 1.0 weight%. A polarizing plate was obtained.

[Example 7]
(Production of laminate)
A cycloolefin resin film (manufactured by JSR, ARTON) having a Tg of about 120 ° C. was used as the resin base material.
An aqueous solution of polyvinyl alcohol resin having a polymerization degree of 4300 and a saponification degree of 99.2% was applied on one side of the resin base material at 80 ° C. and dried to form a PVA resin layer having a thickness of 12 μm, thereby producing a laminate. .

(Preparation of polarizing plate)
The obtained laminate was stretched to a stretch ratio of 4.5 times by free end uniaxial stretching under heating at 140 ° C. The thickness of the PVA resin layer after the stretching treatment was 5 μm (air stretching).
Next, it is immersed for 60 seconds in a dyeing bath at 30 ° C. (iodine aqueous solution obtained by blending 0.5 parts by weight of iodine and 3.5 parts by weight of potassium iodide with respect to 100 parts by weight of water). (Staining treatment).
Subsequently, it was immersed for 60 seconds in a crosslinking bath having a liquid temperature of 60 ° C. (a boric acid aqueous solution obtained by blending 5 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water). (Crosslinking treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) (cleaning treatment).

After washing, 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 surface of the PVA-based resin layer of the laminate. And a triacetyl cellulose film (trade name “KC4UY”, manufactured by Konica Minolta, Inc., thickness 40 μm) were bonded together and heated in an oven maintained at 60 ° C. for 5 minutes to produce a polarizing plate having a polarizer having a thickness of 5 μm. .
Then, the non-polarizing part was formed like Example 1, and the polarizing plate which has a non-polarizing part was obtained.

The following evaluation was performed about each Example. The evaluation results are shown in Table 1. The polarization degree of the polarizer is a value at a single transmittance of 42.0%.
1. Optical characteristics In each Example, the sample which changed the diameter of the small hole of the surface protection film into 20 mm was produced separately, and these were used for the measurement.
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 polarizer are measured, and the degree of polarization is measured. (P) was determined by the following equation. 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.
Polarization degree (P) (%) = {(Tp−Tc) / (Tp + Tc)} ^1/2 × 100
2. Appearance of non-polarizing part The appearance of the non-polarizing part (part corresponding to the small hole of the surface protective film) was observed with an optical microscope (OLYMPUS, MX61, magnification: 5 times).

  In each example, a non-polarizing part was formed satisfactorily. In Example 7, the degree of polarization was lower than the others. In Example 3 and Example 5, the wrinkle of the grade which cannot be visually confirmed in the non-polarization part was confirmed. Since wrinkles are generated after the alkali treatment (before the acid treatment), it is predicted that the wrinkles are generated by partially absorbing water in the contact portion of the basic solution and expanding by subsequent treatment.

  The polarizer of the present invention is suitably used for an image display device with a camera (liquid crystal display device, organic EL device) such as a mobile phone such as a smartphone, a notebook PC, or a tablet PC.

1 Polarizer 2 Non-polarizing part

Claims (10)

Forming a polyvinyl alcohol resin layer on a resin substrate to obtain a laminate;
Staining the polyvinyl alcohol-based resin layer with iodine;
Stretching the laminate,
And after the dyeing and stretching, forming a non-polarizing part by bringing a basic solution into contact with the polyvinyl alcohol-based resin layer,
The method for producing a polarizer, wherein the step of forming the non-polarizing part is a step of forming a non-polarizing part by bringing a basic solution into contact with a polyvinyl alcohol resin layer having a thickness of 8 μm or less.   The manufacturing method of Claim 1 whose iodine content in the said non-polarization part is 1.0 weight% or less.   The manufacturing method of Claim 1 or 2 which makes the said basic solution contact in the state coat | covered with the surface protection film so that the polyvinyl alcohol-type resin layer surface might expose at least one part.   The manufacturing method of Claim 3 with which the through-hole is formed in the said surface protection film.   The manufacturing method in any one of Claim 1 to 4 with which the said laminated body is obtained by apply | coating the coating liquid containing a polyvinyl alcohol-type resin to the said resin base material.   The manufacturing method according to claim 1, wherein the laminate is stretched after the dyeing.   The manufacturing method according to claim 6, wherein the stretching is underwater stretching. Wherein the resin substrate is peeled off, the resin base material of the laminate is adhered to a peelable surface protective film peeled surface after bonding the protective film to a polyvinyl alcohol-based resin layer side of the laminate The manufacturing method in any one of Claim 1 to 7 which makes the said basic solution contact the obtained polarizing film laminated body.   The manufacturing method according to claim 8, wherein the polarizing film laminate is elongated, and through holes are formed in the surface protective film at predetermined intervals in the longitudinal direction and / or the width direction.   The manufacturing method in any one of Claim 1 to 9 which makes an acidic solution contact the site | part which contacted the said basic solution of the said polyvinyl alcohol-type resin layer.