JP6357069B2 - Manufacturing method of laminate - Google Patents

Description

  The present invention relates to a method for manufacturing a laminate. Specifically, it is related with the manufacturing method of the laminated body which has a resin base material and the polyvinyl alcohol (PVA) type-resin layer formed on this resin base material.

  There has been proposed a method of obtaining a polarizing film by forming a polyvinyl alcohol-based resin layer on a resin substrate and stretching and dyeing the laminate (for example, Patent Document 1). According to such a method, a polarizing film having a small thickness can be obtained, and thus, for example, it has been attracting attention as being able to contribute to a reduction in thickness of an image display device. However, since such a manufacturing method uses a resin base material, there is a problem that the manufacturing process is easily restricted. Specifically, it takes an enormous amount of time to manufacture to achieve sufficient polarization characteristics, and conversely, the quality of the polarizing film obtained when priority is given to manufacturing efficiency (for example, appearance, polarization characteristics, stretchability) There is a problem that is insufficient.

JP 2000-338329 A

  The present invention has been made to solve the above-described conventional problems, and a main object of the present invention is to provide a laminate that can produce a polarizing film that is excellent in production efficiency and quality. .

In the method for producing a laminate of the present invention, a polyvinyl alcohol-based resin layer is formed by applying a coating liquid containing a polyvinyl alcohol-based resin on the other surface of a resin base material that is in contact with one surface of the support surface. The process of carrying out is included. The laminate of the present invention is subjected to a stretching treatment.
In one embodiment, the temperature of the said support body surface is more than the glass transition temperature (Tg) of the said resin base material.
In one embodiment, the support surface is a metal surface.
In one embodiment, the said support body surface is a surrounding surface of a roll.
In one embodiment, the polyvinyl alcohol resin layer has a thickness of 20 μm or less.
In one embodiment, the glass transition temperature (Tg) of the said resin base material is 100 degrees C or less.
In one embodiment, after apply | coating the said coating liquid, the process of drying a coating film using the heated metal roll is further included.
In one embodiment, the surface temperature of the said metal roll is more than the glass transition temperature (Tg) of the said resin base material.
According to another situation of this invention, the manufacturing method of a polarizing film is provided. The manufacturing method of this polarizing film uses the laminated body obtained by the said manufacturing method.
In one embodiment, the process of extending the above-mentioned layered product in water is included.
According to another situation of this invention, the manufacturing method of a polarizing plate is provided. The manufacturing method of this polarizing plate includes the process of laminating | stacking a protective film on the polarizing film obtained by the said manufacturing method.

  According to the present invention, by applying a coating liquid containing a polyvinyl alcohol-based resin to the other surface of the resin base material whose one surface is in contact with the support surface, it is excellent in production efficiency and quality. Can provide a laminate capable of producing an excellent polarizing film. Specifically, when applying the coating liquid, since the resin base material is supported by the support, deformation such as wrinkles can be suppressed even if the resin base material is heated. As a result, it is possible to significantly reduce the drying time of the coating film and to obtain a laminate having excellent surface uniformity. By performing various treatments on such a laminate, a polarizing film having an excellent appearance can be produced.

It is a schematic sectional drawing of the laminated body by one Embodiment of this invention. It is the schematic which shows an example of the manufacturing method of the laminated body of this invention.

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

A. Laminate FIG. 1 is a schematic cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 10 is obtained by forming a polyvinyl alcohol-based resin (hereinafter referred to as “PVA-based resin”) layer 12 on one surface of the resin substrate 11.

A-1. Resin Base Material Any appropriate material can be adopted as a constituent material of 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 100 ° C. or lower, more preferably 80 ° C. or lower. By using such a resin base material, it is possible to sufficiently ensure stretchability (particularly in water stretching) while suppressing crystallization of the PVA-based resin layer in stretching of the laminate described later. As a result, a polarizing film having excellent polarization characteristics can be manufactured. On the other hand, the glass transition temperature of the resin base material is preferably 40 ° C. or higher, more preferably 60 ° C. or higher. By using such a resin base material, the production efficiency can be further improved. In addition, a glass transition temperature (Tg) is a value calculated | required according to JISK7121.

  In one embodiment, the resin base material preferably has a water absorption rate of 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.

A-2. Formation of PVA-based resin layer The PVA-based resin layer is formed by applying a coating liquid containing a PVA-based resin on one surface of the resin base material. Since the coating liquid is directly applied to the resin base material, a laminate having excellent adhesion between the resin base material and the PVA-based resin layer can be obtained. Any appropriate resin can be adopted as the PVA-based resin. 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 a PVA resin in a solvent is typically used. Examples of the solvent for dissolving the PVA resin include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polymethyl alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. Used. 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 PVA resin concentration is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the resin substrate can be formed.

  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.

  When the coating liquid is applied, the other surface (the surface opposite to the coating surface) of the resin substrate is in contact with the support surface. According to such a form, since the resin base material is supported by the support body, even if the resin base material is heated, deformation such as wrinkles can be suppressed. As a result, the drying time of the coating film can be remarkably shortened, and a laminate having excellent surface uniformity can be obtained. Any appropriate form can be adopted as the support as long as it can support the resin substrate. Examples thereof include a roll shape and a plate shape (sheet shape).

  In a preferred embodiment, the resin substrate is brought into contact with the heated support surface to heat the resin substrate. The temperature of the support surface can be set to be equal to or higher than the glass transition temperature (Tg) of the resin substrate. On the other hand, the temperature of the support surface is preferably Tg + 20 ° C. or lower, more preferably Tg + 10 ° C. or lower. Moreover, the temperature of the support surface is preferably 100 ° C. or lower. When the temperature exceeds 100 ° C., there is a high possibility of appearance defects such as bubbles due to bumping of the solvent (water) of the coating solution.

  Preferably, the support surface is a metal surface. By adopting the metal surface, the resin base material can be more reliably supported. Further, by employing a metal surface, heat can be rapidly applied to the resin substrate and / or the coating solution. For example, when heat is rapidly applied in a state where the coating solution contains a large amount of moisture, crystallization of the PVA-based resin is promoted, and a PVA-based resin layer having extremely excellent water resistance can be formed. As a result, a below-mentioned stretchability in water can be remarkably improved, and a polarizing film having excellent polarization characteristics can be obtained. Moreover, it can contribute also to simplification of the process (for example, insolubilization process) for setting it as the below-mentioned polarizing film. In addition to this, by adopting a metal surface, it is easy to control the temperature of the coated surface, and high temperature and high pressure can be achieved during coating. Under high temperature and high pressure, for example, the concentration of the PVA resin in the coating solution can be set high.

  Examples of the metal material constituting the metal surface include nickel, chromium, copper, and stainless steel. These may be used alone or in combination of two or more. In one embodiment, the support surface is the peripheral surface of a roll (drum). In this case, it is preferable that the roll peripheral surface is made of a metal that hardly corrodes and obtains a specular gloss. Further, from the viewpoint of enhancing the durability of the roll, the roll peripheral surface may have a single layer structure of a nickel layer, a chromium layer or a nickel / chromium alloy layer, or a multilayer structure. In another embodiment, the support surface is the surface of a belt. In this case, the entire belt may be made of a metal material (for example, a stainless steel belt), or a metal surface may be made by forming a metal layer on the belt surface.

  The surface roughness (maximum height Ry) of the support surface is preferably 5S or less, more preferably 3S or less, from the viewpoint of bringing the resin base material into uniform contact with the support.

  When coating, the coating solution can be set to any appropriate temperature. Typically, it is 20 ° C to 100 ° C. The coating liquid can be set to be equal to or higher than the glass transition temperature (Tg) of the resin base material. Since the coating liquid is applied in a state where the resin base material is in contact with the support surface, deformation of the resin base material can be suppressed even when coating is performed at such a liquid temperature. As a result, the drying time of the coating film can be significantly shortened. The temperature of the coating solution is preferably 60 ° C. or higher, more preferably 80 ° C. or higher.

  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, and a knife coating method (comma coating method, etc.).

  The coating solution is preferably applied such that the thickness of the obtained PVA-based resin layer is 20 μm or less, and more preferably 15 μm or less. The coating solution can be applied at any suitable temperature. Preferably it is 20 degreeC or more, More preferably, it is 50 degreeC or more.

  FIG. 2 is a schematic view showing an example of a method for producing a laminate according to the present invention. In the illustrated example, one surface of the resin base material 11 fed out from the roll R1 is brought into contact with the peripheral surface of a metal roll (heat roll) R2 heated to a predetermined temperature, and the metal roll R2 of the resin base material 11 and The coating solution discharged from the die is applied to a position corresponding to the contact portion of the substrate to form the PVA-based resin layer 12 to obtain the laminate 10. In the illustrated example, the coating film is dried by bringing the laminate 10 into contact with metal rolls (heat rolls) R3 and R4 heated to a predetermined temperature. The diameter of the roll R2 as the support is typically 0.5 m to 2.0 m. The width of the roll R2 is typically 2 m to 5 m.

  The production of the laminate of the present invention is not limited to the illustrated example, and can be appropriately changed. For example, in the illustrated example, two heated metal rolls (heat rolls) are used for drying, but more may be used. Further, in the illustrated example, the deformation of the resin base material is suppressed, and the drying time of the coating film can be remarkably shortened, so that it is dried using a hot roll. Good. The drying temperature is typically 50 ° C to 100 ° C. The surface temperature of the hot roll can be set to be equal to or higher than the glass transition temperature (Tg) of the resin base material. On the other hand, the surface temperature of the hot roll is preferably Tg + 20 ° C. or lower, more preferably Tg + 10 ° C. or lower. In addition, when drying using two or more heat rolls like the example of illustration, the temperature of each heat roll can be set to each.

  The distance between adjacent rolls (distance between surfaces) is preferably 30 cm or less, more preferably 10 cm or less, still more preferably 5 cm or less, and particularly preferably 3 cm or less. If it is such a range, a laminated body can be stably floated by the accompanying flow etc. by rotation of a roll.

B. Polarizing film The polarizing film of the present invention is produced by subjecting the PVA resin layer of the laminate to a treatment for forming a polarizing film.

  Examples of the treatment for obtaining the polarizing film include dyeing treatment, stretching treatment, insolubilization treatment, crosslinking treatment, washing treatment, and drying treatment. These processes can be appropriately selected depending on the purpose. Further, the processing order, the processing timing, the number of processing times, and the like can be appropriately set. Each process will be described below.

(Dyeing process)
The dyeing process 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%.

(Extension process)
Any appropriate method can be adopted as a method for stretching 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 treatment may be an underwater stretching method performed by immersing the laminate in a stretching bath, or an air stretching method. Preferably, the underwater stretching treatment is performed at least once, and more preferably, the underwater stretching treatment and the air stretching treatment 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 polarization characteristics can be manufactured.

  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 polarization characteristics 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 polarization characteristics 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 employing an underwater drawing method (boric acid underwater drawing). 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, the underwater stretching process is performed after the dyeing process.

(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 in the drying process is preferably 30 ° C to 100 ° C.

  The obtained 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 8 μm or less, still 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 1.0 μm or more, more preferably 2.0 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.

C. Polarizing plate The polarizing plate of the present invention has the polarizing film. Preferably, the polarizing plate includes the polarizing film and a protective film disposed on at least one side of the polarizing film. 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 (meth) acrylic resins, cellulose resins such as diacetyl cellulose and triacetyl cellulose, cycloolefin resins, olefin resins such as polypropylene, and ester resins such as polyethylene terephthalate resins. , Polyamide resins, polycarbonate resins, and copolymer resins thereof. The thickness of the protective film is preferably 10 μm to 100 μm.

  In one embodiment, the said resin base material is peeled from a polarizing film, and another film is laminated | stacked. The protective film may be laminated on the polarizing film via an adhesive layer, or may be laminated in close contact (without an adhesive layer). The adhesive layer is typically formed of an adhesive or a pressure-sensitive adhesive.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples.

[Example 1]
(Production of laminate)
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, Nippon Synthetic Chemical Industry Co., Ltd. An aqueous solution (23 ° C.) containing a 9: 1 ratio of the product name “GOHSEFIMAR Z200”) was prepared.
Subsequently, as a resin base material, a corona treatment is applied to one side of an elongated isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of 75 ° C. The surface opposite to the corona-treated surface was firmly brought into contact with the peripheral surface of the metal roll heated to 80 ° C. The above aqueous solution is applied at a position corresponding to the contact portion with the peripheral surface of the metal roll of the resin base material in a 60 ° C. atmosphere, and then dried by contacting with a plurality of hot rolls heated to 80 ° C., having a thickness of 10 μm. A PVA-based resin layer was formed to obtain a laminate.

(Preparation of polarizing film)
The obtained laminate was stretched uniaxially at the free end 2.0 times in the longitudinal direction between rolls having different peripheral speeds in an oven at 120 ° C. (air-assisted stretching).
Next, the 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 1.0 part 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 in the longitudinal direction so that the total stretching ratio was 5.5 (stretching in water).
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).

(Preparation of polarizing plate)
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 surface of the PVA-based resin layer of the laminate. A triacetyl cellulose film (manufactured by Konica Minolta, trade name “KC4UY”, thickness 40 μm) was heated in an oven maintained at 60 ° C. for 5 minutes.
Thereafter, the resin substrate was peeled off to obtain a polarizing plate in which a protective film was disposed on one side of a polarizing film having a thickness of 4 μm.

[Example 2]
A polarizing plate was produced in the same manner as in Example 1 except that a PVA-based resin layer having a thickness of 15 μm was formed on the resin substrate when the laminate was produced.

[Example 3]
A polarizing plate was produced in the same manner as in Example 1 except that the temperature of the metal roll was set to 100 ° C. when applying the aqueous solution.

[Example 4]
When applying the aqueous solution, a polarizing plate was produced in the same manner as in Example 1 except that the temperature of the aqueous solution was 80 ° C.

[Comparative Example 1]
A polarizing plate was obtained in the same manner as in Example 1 except that the aqueous solution was applied to a resin substrate heated to 60 ° C. without bringing one surface of the resin substrate (the surface opposite to the coated surface) into contact with the metal roll. Was made.

[Comparative Example 2]
A polarizing plate was obtained in the same manner as in Example 2 except that the aqueous solution was applied to a resin substrate heated to 60 ° C. without bringing one surface of the resin substrate (the surface opposite to the coated surface) into contact with the metal roll. Was made.

[Comparative Example 3]
A polarizing plate was produced in the same manner as in Comparative Example 1 except that the aqueous solution was applied to a resin substrate heated to 80 ° C.

[Comparative Example 4]
A polarizing plate was produced in the same manner as in Comparative Example 1 except that the aqueous solution was applied to a resin substrate heated to 100 ° C.

[Comparative Example 5]
A polarizing plate was produced in the same manner as in Comparative Example 1 except that the temperature of the aqueous solution was 80 ° C. when applying the aqueous solution.

[Comparative Example 6]
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (polymerization degree 1200, acetoacetyl modification degree 4.6%, saponification degree 99.0 mol% or more, Nippon Synthetic Chemical Industry Co., Ltd. 80 ° C. so that the thickness after drying is 10 μm on a metal roll heated to 80 ° C. It was applied under an atmosphere. Various treatments were applied to the obtained PVA-based resin film to try to produce a polarizing film.

[Comparative Example 7]
An attempt was made to produce a polarizing film in the same manner as in Comparative Example 6 except that the thickness of the PVA-based resin film was 15 μm.

(Evaluation)
The following evaluation was performed about each Example and the comparative example.
1. Film-formability Upon application and drying of the aqueous solution, the deformation of the resin base material and the occurrence of wave curls and wrinkles accompanying this deformation were visually observed.
2. Drying time The time from application of the aqueous solution until the stickiness of the surface of the PVA-based resin layer disappeared was measured, and the ratio of the time required for drying when the drying time of Comparative Example 1 was taken as 100 was calculated. In addition, the presence or absence of stickiness was confirmed by sensory evaluation.
3. Stretchability (underwater stretching)
The above-described stretching in water was performed manually and performed with a stretching machine, and it was confirmed whether or not stretching was possible up to a total stretching ratio of 5.5 times.

  In each example, the PVA resin layer was excellent in film formability, and the drying time was much shorter than those in Comparative Examples 1 and 2. In embodiments such as Comparative Examples 1 and 2, a very large drying oven is required. In Comparative Examples 3 to 5, wrinkles were generated on the resin substrate during application of the aqueous solution, and the obtained polarizing film had a problem in appearance. In Comparative Examples 6 and 7, the laminate could not be stretched in water. Specifically, the PVA resin film was broken during stretching in water.

  The polarizing film of the present invention is suitably used for an image display device, for example. Specifically, LCD TVs, LCDs, mobile phones, digital cameras, video cameras, portable game machines, car navigation systems, copy machines, printers, fax machines, watches, microwave ovens, etc., anti-reflection plates for organic EL devices Etc. are suitably used.

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

Claims (8)

A laminate is prepared by applying a coating solution containing a polyvinyl alcohol resin to the other surface of the resin base material, one surface of which is in contact with the support surface, which is a metal surface, to form a polyvinyl alcohol resin layer. And a process of
A method for producing a polarizing film, comprising a step of stretching the laminate.
The manufacturing method of a polarizing film whose thickness of this polyvinyl alcohol system resin layer is 20 micrometers or less .   The manufacturing method of Claim 1 whose temperature of the said support body surface is more than the glass transition temperature (Tg) of the said resin base material.   The manufacturing method of Claim 1 or 2 whose said support body surface is a surrounding surface of a roll. The manufacturing method in any one of Claim 1 to 3 whose glass transition temperature (Tg) of the said resin base material is 100 degrees C or less. The manufacturing method in any one of Claim 1 to 4 which further includes the process of drying a coating film using the heated metal roll, after apply | coating the said coating liquid. The manufacturing method of Claim 5 whose surface temperature of the said metal roll is more than the glass transition temperature (Tg) of the said resin base material. The manufacturing method of the polarizing film in any one of Claim 1 to 6 including the process of extending | stretching the said laminated body in water. The manufacturing method of a polarizing plate including the process of laminating | stacking a protective film on the polarizing film obtained by the manufacturing method in any one of Claim 1 to 7 .

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