Polyvinyl alcohol resin film and method for producing same

Abstract

Provided are: a polyvinyl alcohol-based resin film which is capable of suppressing the occurrence of damage on the surface of the film and which has excellent appearance; and a method for producing the polyvinyl alcohol-based resin film. The polyvinyl alcohol resin film according to the present invention has a thickness of 45 [mu] m or less, a water absorption of 1-10%, and a static friction coefficient of 2.55 or less with respect to a stainless steel plate after being humidified at 40 DEG C and 90% RH for 2 hours, the resin film being elongated and having a width of 2000 mm or more, and the average degree of polymerization of the polyvinyl alcohol resin being 3000 or more.

Description

Technical Field

[0001] The present invention relates to a polyvinyl alcohol-based resin film and a method for manufacturing the same. Background Art

[0002] Polyvinyl alcohol-based resin films are used for various applications such as packaging materials (for example, Patent Document 1). In addition, as an application of polyvinyl alcohol-based resin films, polarizers for image display devices and the like are known.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-143297 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In recent years, optical components that meet higher appearance standards than the high definition of organic EL displays and lens magnification projection in virtual reality (VR) applications have been demanded. Therefore, a polyvinyl alcohol-based resin film that suppresses the generation of damage on the film surface and has excellent appearance is required.

[0008] Means for Solving the Problems

[0009] 1. The polyvinyl alcohol-based resin film according to an embodiment of the present invention has a thickness of 45 μm or less, a water absorption rate of 1% to 10%, and a static friction coefficient against a stainless steel plate of 2.55 or less after conditioning at 40°C and 90% RH for 2 hours. The polyvinyl alcohol-based resin film is in a long strip shape and has a width of 2000 mm or more, and the polyvinyl alcohol-based resin film contains a polyvinyl alcohol-based resin having an average degree of polymerization of 3000 or more.

[0010] 2. The arithmetic mean surface roughness Ra of the polyvinyl alcohol-based resin film described in 1 above may be 0.05 μm or less.

[0011] 3. The deviation in thickness in the width direction of the polyvinyl alcohol-based resin film described in 1 or 2 above may be 1 μm or less.

[0012] 4. The polyvinyl alcohol-based resin film described in any one of 1 to 3 above may be a layer formed by coating a solution containing the above polyvinyl alcohol-based resin on a substrate.

[0013] 5. The polyvinyl alcohol-based resin film described in any one of 1 to 4 above may be used for manufacturing a polarizer.

[0014] 6. In another embodiment of the present invention, there is provided a method for manufacturing a polyvinyl alcohol-based resin film having a static friction coefficient of 2.55 or less with respect to a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours. The method for manufacturing the polyvinyl alcohol-based resin film sequentially includes: coating a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer to produce an intermediate laminate; and dry stretching the intermediate laminate while heating at 130°C or higher.

[0015] 7. In yet another aspect of the present invention, there is provided a method for manufacturing a polarizer. The method for manufacturing a polarizer according to an embodiment of the present invention includes: dyeing a polyvinyl alcohol-based resin film having a static friction coefficient of 2.55 or less with respect to a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours with a dichroic substance.

[0016] 8. The method for manufacturing a polarizer described in 7 above sequentially includes: coating a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer to produce an intermediate laminate; and dry stretching the intermediate laminate while heating at 130°C or higher; the manufacturing method may further include obtaining the above polyvinyl alcohol-based resin film.

[0017] Advantages of the Invention

[0018] According to an embodiment of the present invention, there can be provided a polyvinyl alcohol-based resin film and a method for manufacturing the same, which can suppress the generation of damage to the film surface and have excellent appearance in various manufacturing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram for explaining a method for manufacturing a polarizer according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] A. Polyvinyl Alcohol-Based Resin Film

[0021] The thickness of the polyvinyl alcohol (hereinafter also referred to as PVA) - based resin film according to an embodiment of the present invention is 45 μm or less, the water absorption rate is 1% to 10%, the static friction coefficient with respect to a stainless - steel plate after conditioning at 40 °C and 90% RH for 2 hours is 2.55 or less. The resin film is in a long - strip shape and has a width of 2000 mm or more, and the resin film contains a polyvinyl alcohol - based resin having an average degree of polymerization of 3000 or more. The polyvinyl alcohol - based resin film can be used for various purposes. In addition, the long - strip resin film is typically conveyed while being in contact with a roller and supplied to each process. As a result, sometimes scratches are generated on the surface of the PVA - based resin film, and the appearance of the film deteriorates. As one cause of the deterioration of the film appearance, it is considered that due to a change in the film placement environment (such as humidity), the resistance on the surface of the PVA - based resin film changes, and scratches are generated on the surface of the PVA - based resin film due to friction caused by contact with the roller. It should be noted that these scratches are fine scratches that do not cause problems in conventional image display devices. The polyvinyl alcohol - based resin film according to an embodiment of the present invention can suppress the influence of the manufacturing environment and the type of manufacturing process on the resistance of the film surface even when being conveyed while in contact with a roller, and can suppress scratches on the surface of the PVA - based resin film.

[0022] The thickness of the PVA - based resin film is 45 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. The thickness of the PVA - based resin film is, for example, 1 μm or more. When the thickness of the PVA - based resin film is in the above range, the generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol - based resin film with excellent appearance can be obtained.

[0023] The water absorption rate of the PVA - based resin film is 1% to 10%, preferably 2% to 9%, more preferably 3% to 8%, further preferably 3.5% to 7%, and particularly preferably 4% to 6%. When the water absorption rate of the PVA - based resin film is in the above range, the generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol - based resin film with excellent appearance can be obtained. In this specification, the water absorption rate of the PVA - based resin film refers to the value measured by the following method.

[0024] <Method for measuring water absorption rate>

[0025] A 1 - cm square measurement sample is cut out from the PVA - based resin film. The measurement sample is set in a moisture adsorption - desorption measurement device (for example, manufactured by Hiden, product name “IGA - SORP”). Then, the measurement sample is held at 23 °C and 0% RH for 600 minutes, and further held at 40 °C and 90% RH for 120 minutes. Let the weight W1 after being held at 23 °C and 0% RH and the weight after being held at 40 °C and 90% RH for 120 minutes be W2, and it is calculated by the following formula.

[0026] Water absorption rate (%) = (W2 - W1) / W1 × 100

[0027] The static friction coefficient of the PVA resin film against a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours is 2.55 or less, more preferably 2.5 or less, further preferably 2.1 or less, and particularly preferably 1.5 or less. The smaller the static friction coefficient, the more preferable it is, for example, 0.15 or more. In this specification, the static friction coefficient of the PVA resin film against a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours refers to the value measured by the following method.

[0028] <Static friction coefficient after conditioning at 40°C and 90% RH for 2 hours>

[0029] Condition the PVA resin film (15 cm × 4 cm) at 40°C and 90% RH for 2 hours. Then, fix the conditioned PVA resin film to a sliding piece weighing 200 g, and set it on a smooth stainless steel plate (made of SUS304, surface roughness Ra = 0.05 μm) so that the contact area is 40 cm 2 . Use Autograph (for example, manufactured by Shimadzu Corporation, product name "AG-IS") to measure the static frictional force according to JIS K7125, and calculate the static friction coefficient from the following formula.

[0030] Static friction coefficient = Static frictional force / 1.96

[0031] The PVA resin film is in a long strip shape with a width of 2000 mm or more. The width of the PVA resin film is preferably 2100 mm or more. The width of the PVA resin film is, for example, 2800 mm or less. In a resin film with a wide width, thickness deviation in the width direction and generation of scratches caused by contact with a roller may become more significant. Even when the width of the PVA resin film of the present invention is 2000 mm or more, generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol-based resin film with excellent appearance can be obtained. In this specification, the long strip shape means an elongated shape where the length is sufficiently long relative to the width, for example, including an elongated shape where the length is 10 times or more, preferably 50 times or more, relative to the width.

[0032] The arithmetic mean surface roughness Ra of the PVA resin film is preferably 0.05 μm or less, more preferably 0.03 μm or less, and further preferably 0.02 μm or less. When the arithmetic mean roughness Ra is within the above range, generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol-based resin film with excellent appearance can be obtained. The arithmetic mean surface roughness Ra of the PVA resin film is, for example, 0.001 μm or more.

[0033] The deviation in the thickness in the width direction of the PVA-based resin film is preferably 1 μm or less, more preferably 0.5 μm or less, and still more preferably 0.3 μm or less. When the deviation in the thickness in the width direction of the PVA-based resin film is within the above range, generation of scars on the film surface can be suppressed, and a polyvinyl alcohol-based resin film with excellent appearance can be obtained.

[0034] The crystallinity of the PVA-based resin film is preferably 45% to 55%, more preferably 48% to 53%. If the crystallinity is within the above range, for example, when used as a polarizer, end discoloration can be suppressed. The crystallinity of the PVA-based resin film can be measured by the following method.

[0035] (Evaluation method for the crystallinity of PVA)

[0036] As an analysis device for X-ray analysis, any suitable device can be used. For example, as an X-ray diffractometer, the product name "SmartLab" manufactured by Rigaku Corporation can be cited, and as a two-dimensional detector, the product name "HyPix3000" manufactured by Rigaku Corporation can be cited.

[0037] A PVA-based resin layer with a thickness of 150 μm is used as a sample. When the thickness of the PVA-based resin layer is less than 150 μm, samples are prepared by overlapping PVA-based resin layers so that the total thickness becomes approximately 150 μm. Let the wavelength of X-rays pass through the sample perpendicularly to the thickness direction of the sample, and scattered light is detected using a two-dimensional detector arranged on the side opposite to the light source with respect to the sample, obtaining a two-dimensional scattering image. After background correction of the obtained scattering image, omnidirectional angle (360°) integration is performed with the beam center as the axis, obtaining a one-dimensional distribution of the X-ray integrated intensity with respect to the scattering angle 2θ. Next, for the obtained one-dimensional distribution, within the range of the scattering angle 2θ = 14° to 28.5°, waveform separation of the crystalline peak and the amorphous peak is performed, and the crystallinity (%) is calculated by the following formula.

[0038] Crystallinity (%) = crystalline peak area / (crystalline peak area + amorphous peak area) × 100

[0039] The PVA-based resin film can be formed using any suitable PVA-based resin. As the above PVA-based resin, any suitable resin can be used. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymer can be cited. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer is obtained by saponifying ethylene-vinyl acetate copolymer.

[0040] The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined in accordance with JIS K6726-1994. By using a PVA-based resin with such a saponification degree, a PVA-based resin film with excellent durability can be obtained. When the saponification degree is too high, the coating solution is prone to gelation, and when forming a PVA-based resin film by coating, there is a concern that it is difficult to form a uniform coating film.

[0041] The average degree of polymerization of the PVA-based resin is 3000 or more, preferably 3500 or more, more preferably 3800 or more, and further preferably 4000 or more. The generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol-based resin film with excellent appearance can be obtained. The average degree of polymerization of the PVA-based resin is, for example, 4500 or less. It should be noted that the average degree of polymerization can be determined in accordance with JIS K6726-1994.

[0042] The PVA-based resin film contains any appropriate other components in addition to the PVA-based resin. As the other components, halides are preferably included. As the halides, any appropriate halides can be used. As the halides, for example, iodides and sodium chloride can be cited. As the iodides, for example, potassium iodide, sodium iodide, and lithium iodide can be cited. Among them, potassium iodide is preferred. The content of the halide can be set to any appropriate value. For example, the content of the halide in the PVA-based resin solution (resulting in the PVA-based resin layer) used in the formation of the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight relative to 100 parts by weight of the PVA-based resin.

[0043] B. Method for manufacturing a polyvinyl alcohol-based resin film

[0044] The method for manufacturing a polyvinyl alcohol-based resin film according to an embodiment of the present invention sequentially includes: coating a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer, and producing an intermediate laminate; dry stretching the intermediate laminate while heating at 130°C or higher; and conveying the intermediate laminate by bringing it into contact with a guide roller. According to the method for manufacturing a polyvinyl alcohol-based resin according to an embodiment of the present invention, a polyvinyl alcohol-based resin film having a static friction coefficient of 2.55 or less against a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours can be obtained. As a method for adjusting the static friction coefficient of the resin film, a method of using a lubricant such as glycerol is known. According to the method for manufacturing a polyvinyl alcohol-based resin film according to an embodiment of the present invention, the static friction coefficient of the resin film surface can be adjusted without adding a lubricant or the like.

[0045] B-1. Production of the intermediate laminate

[0046] The method for manufacturing a polyvinyl alcohol-based resin film includes: coating a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer, and producing an intermediate laminate. When the polyvinyl alcohol-based resin layer that finally becomes the PVA-based resin film is a layer formed by coating a solution containing a polyvinyl alcohol-based resin on a substrate, it is possible to further suppress the static friction coefficient against a stainless steel plate after conditioning at 40°C and 90% RH for 2 hours.

[0047] The intermediate laminate is produced by forming a resin layer on a resin substrate. The resin substrate can be set to any appropriate structure as long as it can support the resin layer from one side. Examples of the forming material of the resin substrate include ester-based resins such as polyethylene terephthalate-based resins, cycloolefin-based resins, olefin-based resins such as polypropylene, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof. Among them, cycloolefin-based resins (e.g., norbornene-based resins) and amorphous polyethylene terephthalate-based resins are preferred. Specific examples of the amorphous polyethylene terephthalate-based resins include copolymers further containing isophthalic acid as a dicarboxylic acid and copolymers further containing cyclohexanedimethanol as a diol. The thickness of the resin substrate is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm.

[0048] The resin substrate can be pre-treated with a surface modification treatment (e.g., corona treatment, etc.), or an adhesive layer can be formed on the resin substrate. By performing such a treatment, the adhesion between the resin substrate and the PVA-based resin layer can be improved. It should be noted that the surface modification treatment and / or the formation of the adhesive layer can be carried out before or after the stretching of the resin substrate as required.

[0049] Any appropriate method can be adopted for the formation method of the above PVA-based resin layer. Preferably, a coating solution containing a PVA-based resin is coated on the stretched resin substrate and dried to form a PVA-based resin layer. The thickness of the PVA-based resin layer is 45 μm or less, preferably 30 μm or less, more preferably 20 μm or less, and further preferably 10 μm or less. The thickness of the PVA-based resin film is preferably 1 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more.

[0050] The above-mentioned coating solution is typically a solution obtained by dissolving the above-mentioned PVA-based resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, amines such as ethylenediamine and diethylenetriamine. They can be used alone or in combination of two or more. Among them, water is preferably used. The concentration of the PVA-based resin in the coating solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. If the resin concentration is such, a uniform coating film that adheres to the resin substrate can be formed.

[0051] Additives can also be blended in the coating solution. Examples of the additives include plasticizers, surfactants, etc. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerol. Examples of the surfactant include nonionic surfactants. They can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

[0052] As a coating method of the coating solution, any appropriate method can be adopted. Examples include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, doctor blade coating (comma coating, etc.).

[0053] B-2. Dry stretching

[0054] Next, the obtained intermediate laminate is dry-stretched while being heated at 130 °C or higher. The dry stretching can be fixed-end stretching (for example, a method of stretching using a tenter), or free-end stretching (for example, a method of uniaxially stretching the laminate by passing it between rolls with different circumferential speeds). Dry stretching is preferably carried out by fixed-end stretching using a tenter. For fixed-end stretching, in a tenter equipped with a plurality of clamps as holding means, the end of the film is held, and the distance between the tenters is extended in the moving direction, thereby performing stretching (the extension of the distance between the tenters becomes the stretching ratio).

[0055] The stretching temperature for dry stretching is 130 °C or higher, preferably 140 °C or higher, and more preferably 150 °C or higher. In addition, the stretching temperature is, for example, 170 °C or lower. The stretching temperature can be adjusted by any appropriate method. For example, dry stretching can be carried out in a furnace set at the above temperature, or stretching can be carried out while contacting hot air set at the above temperature, or stretching can be carried out while contacting a roll heated to the above temperature.

[0056] The draw ratio in dry drawing can be set to any appropriate value. The draw ratio in dry drawing is preferably 2.2 times or more, more preferably 2.3 times or more, and further preferably 2.5 times or more. When the draw ratio in dry drawing is within the above range, the generation of scratches on the film surface can be suppressed, and a polyvinyl alcohol-based resin film with excellent appearance can be obtained.

[0057] In one embodiment, the intermediate laminate can be shrunk in the width direction in the dry drawing process. In the dry drawing process, if stretching in the length direction and shrinking in the width direction are performed, it is possible to suppress defects such as film breakage and perform stretching (stretching in the length direction) at a higher temperature. In this embodiment, shrinking in the width direction can be performed after stretching in the length direction, stretching in the length direction can be performed after shrinking in the width direction, or stretching in the length direction and shrinking in the width direction can be performed simultaneously. In the case of performing stretching in the length direction and shrinking in the width direction simultaneously, for example, the tracks of the tenter stretching machine can be set to a conical shape with a continuously decreasing distance between the tracks. That is, in the stretching device, while reducing the distance between the tracks (the width of the laminate) from the width W1 before the stretching process to the width W2 of the specified film, the clamp interval in the conveying direction can be expanded from L1 to the specified width L2. Details of such a method of stretching in the length direction and shrinking in the width direction are described, for example, in Japanese Patent No. 6563201. The entire description of these gazettes is incorporated herein by reference.

[0058] In this embodiment, as the tenter stretching device, for example, a stretching device having a pair of tracks and a plurality of clamps can be used. The pair of tracks has a straight portion with a constant distance between the tracks and a tapered portion with a continuously decreasing distance between the tracks. The plurality of clamps can travel while changing the clamp interval on each track. According to such a stretching device, in a state where the two side edge portions of the intermediate laminate are held by the clamps, by changing the clamp interval in the conveying direction (the distance between the clamps on the same track) and the clamp interval in the width direction (the distance between the clamps on different tracks), stretching and shrinking of the intermediate laminate can be achieved. The draw ratio in the length direction can be controlled by adjusting the clamp interval in the conveying direction (the holding interval in the holding process) L1 before the stretching process and the clamp interval in the conveying direction L2 at the end of the dry drawing (L2 / L1). The shrinkage rate in the width direction can be controlled by adjusting the change amount of the distance between the tracks. Specifically, by controlling the distance between the tracks W2 at the end of the shrinkage process in the width direction with respect to the distance between the tracks W1 in the shrinkage process in the width direction, the shrinkage rate (%) in the width direction ({1 - (W2) / (W1)} × 100) can be controlled. For example, the smaller the ratio of W2 to W1, the greater the shrinkage rate that can be obtained.

[0059] In the case including stretching in the length direction and shrinkage in the width direction, the stretching ratio in the length direction is preferably 2.0 to 3.5 times, more preferably 2.4 to 3.0 times. When the stretching ratio is within the above range, the stretchability (total stretching ratio) of the intermediate laminate is further improved, and it can be stretched well even at high temperatures. In addition, the shrinkage rate in the width direction is preferably 25% or more, more preferably 30% or more, and further preferably 32% or more. In addition, the shrinkage rate in the width direction is, for example, 50% or less. If the shrinkage rate in the width direction is within the above range, the intermediate laminate can be stretched at a higher stretching ratio.

[0060] In the case of performing stretching in the length direction and shrinkage in the width direction, it may include a first dry stretching and shrinking step and a second dry stretching and shrinking step. The first dry stretching and shrinking step includes dry stretching in the length direction while heating and causing shrinkage in the width direction, and the second dry stretching and shrinking step includes dry stretching the intermediate laminate in the length direction while heating at a temperature lower than the highest heating temperature of the first dry stretching and shrinking step and causing shrinkage in the width direction. If the first and second dry stretching and shrinking steps are included, the orientation of the obtained PVA-based resin film can be adjusted.

[0061] B-3. Conveyance in contact with a guide roller

[0062] The dry-stretched PVA-based resin film is then conveyed to any appropriate next step while being in contact with a guide roller. The guide roller is used, for example, to control the movement, direction change, and speed of the long strip-shaped film. The guide roller is made of any appropriate material. Typically, the guide roller is a metal roller made of stainless steel (SUS), iron, aluminum, etc. The PVA-based resin layer formed on the intermediate laminate comes into contact with the guide roller during conveyance, and due to the friction between the surface of the PVA-based resin layer and the surface of the guide roller, local scratches may be generated on the surface of the resin film. These scratches may cause appearance problems in the final product (such as a polarizer). According to the method for manufacturing a PVA-based resin film of an embodiment of the present invention, even in the case including a step of conveying while being in contact with a guide roller, the appearance of the finally obtained product (a product using the PVA-based resin film) can be improved.

[0063] C. Method for manufacturing a polarizer

[0064] The manufacturing method of the polarizer according to an embodiment of the present invention includes: dyeing a polyvinyl alcohol-based resin film having a static friction coefficient of 2.55 or less with respect to a stainless steel plate after being conditioned at 40 °C and 90% RH for 2 hours with a dichroic substance. As described above, a PVA-based resin film having a static friction coefficient of 2.55 or less with respect to a stainless steel plate after being conditioned at 40 °C and 90% RH for 2 hours can suppress the generation of scratches on the film surface. Therefore, according to the manufacturing method of the polarizer according to the embodiment of the present invention, a polarizer with excellent appearance can be obtained.

[0065] Figure 1 It is a schematic diagram for explaining the manufacturing method of the polarizer according to an embodiment of the present invention. In the manufacturing method of the polarizer shown in the figure, the above-mentioned dyeing process, crosslinking process, stretching process, hue adjustment process, and drying shrinkage process are continuously performed. More specifically, the long strip-shaped PVA-based resin film 1 is conveyed from the blank roll 21 toward the winding roll 22, and between the blank roll 21 and the winding roll 22, the dyeing process, crosslinking process, stretching process, hue adjustment process, and drying shrinkage process are sequentially performed on the PVA-based resin film 1. In one embodiment, the PVA-based resin film 1 is conveyed in such a manner that it is successively immersed in a dyeing bath 2B (dyeing solution), a crosslinking bath 2C (crosslinking solution), a stretching bath 2D (stretching solution), and a hue adjustment bath 2E (hue adjustment solution) by using a plurality of rolls 24 and then passes through a heat drying unit 23. It should be noted that in the case where the PVA-based resin film is a PVA-based resin layer contained in a laminate, by immersing the laminate containing the PVA-based resin layer in the above-mentioned respective baths (respective liquids), the PVA-based resin layer is brought into contact with the respective baths (respective liquids).

[0066] As shown in the figure example, in a typical manufacturing method of a polarizer, the PVA-based resin film is supplied to each process while being in contact with a plurality of rolls. When the PVA-based resin film used as the blank of the polarizer is a PVA-based resin film having a static friction coefficient of 2.55 or less with respect to a stainless steel plate after being conditioned at 40 °C and 90% RH for 2 hours, even when it is supplied to each process while being in contact with a plurality of rolls, the generation of scratches on the surface of the PVA-based resin film can be suppressed, and a polarizer with excellent appearance can be obtained.

[0067] In the method for manufacturing a polarizer according to an embodiment of the present invention, the PVA-based resin film used only needs to have a static friction coefficient against a stainless steel plate of 2.55 or less after conditioning at 40 °C and 90% RH for 2 hours, and any suitable PVA-based resin film can be used. The PVA-based resin film described in item A above can be preferably used. The PVA-based resin film described in item A above can be obtained by the method described in item B above. The method for manufacturing a polarizer according to an embodiment of the present invention may further include: a step of producing a PVA-based resin film, that is, coating a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer to produce an intermediate laminate; dry stretching the intermediate laminate while heating at 130 °C or higher; and conveying the intermediate laminate by bringing it into contact with a guide roller. The PVA-based resin film can be used as a single layer or in the state of a PVA-based resin layer formed on any suitable substrate, that is, in the state of a laminate having a PVA-based resin layer.

[0068] C-1. Dyeing step

[0069] In the dyeing step, the PVA-based resin film is dyed with a dichroic substance. It is preferably carried out by adsorbing the dichroic substance on the PVA-based resin layer. As this adsorption method, for example, a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing a dichroic substance, a method of coating a dyeing solution on the PVA-based resin layer, a method of spraying a dyeing solution on the PVA-based resin layer, etc. can be cited. The method of immersing the laminate in a dyeing solution containing a dichroic substance is preferred. This is because the dichroic substance can be adsorbed well. It should be noted that the laminate can be immersed in the dyeing solution on both sides or only on one side.

[0070] As the above dichroic substance, for example, iodine and organic dyes can be cited. They can be used alone or in combination of two or more. The dichroic substance is preferably iodine. When iodine is used as the dichroic substance, the above dyeing solution is preferably an iodine aqueous solution. The compounding amount of iodine is preferably 0.1 part by weight to 1.0 part by weight with respect to 100 parts by weight of water. In order to improve the solubility of iodine in water, an iodide salt is preferably compounded in the iodine aqueous solution. As the iodide salt, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. can be cited. Among them, potassium iodide and sodium iodide are preferred. The compounding amount of the iodide salt is preferably 0.3 part by weight to 15 parts by weight with respect to 100 parts by weight of water.

[0071] The liquid temperature during dyeing of the dyeing solution is preferably 20 °C to 40 °C. When immersing the PVA-based resin layer in the dyeing solution, the immersion time is preferably 5 seconds to 300 seconds. Under such conditions, the dichroic substance can be sufficiently adsorbed on the PVA-based resin layer.

[0072] As a process for producing a polarizer, any appropriate process may be included. As other processes, for example, an insolubilization process, a dyeing process, a crosslinking process, a stretching process, a cleaning process, a drying (moisture content adjustment, drying shrinkage) process, etc. may be cited. Other processes can be carried out at any appropriate timing.

[0073] The above-mentioned insolubilization process and crosslinking process are typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. The above-mentioned cleaning process is typically carried out by immersing the PVA-based resin layer in an aqueous potassium iodide solution. The drying temperature in the above-mentioned drying process is preferably 30°C to 100°C.

[0074] In the stretching process, stretching is carried out by any appropriate method. The stretching process can be carried out simultaneously with the dyeing process, the insolubilization process, and / or the crosslinking process, or can be carried out separately. In the case of separate execution, other stretching processes can be carried out at any appropriate timing. Stretching is preferably carried out by performing wet stretching after dry stretching (air-assisted stretching) on a laminate having a PVA-based resin layer. In one embodiment, the manufacturing method of the polarizer can be carried out continuously with the manufacturing process of the PVA-based resin film. In this embodiment, the process of dry stretching the intermediate laminate having a PVA-based resin layer, for example, the process of dry stretching while heating at 130°C or higher on one side, also functions as air-assisted stretching in the manufacturing process of the polarizer, and the stretchability of the intermediate laminate (PVA-based resin film) is improved.

[0075] Wet stretching is typically carried out by immersing the laminate in a stretching bath. The method of wet stretching can be fixed-end stretching or free-end stretching (for example, a method of uniaxially stretching the laminate by passing it between rollers with different circumferential speeds), and the stretching of the laminate can be carried out in one stage or in multiple stages. When carried out in multiple stages, the stretching ratio of the laminate described later is the product of the stretching ratios of each stage.

[0076] Wet stretching is preferably carried out by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). The aqueous boric acid solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and further preferably 3 parts by weight to 5 parts by weight relative to 100 parts by weight of water. By making the boric acid concentration 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizer with higher characteristics can be manufactured. It should be noted that in addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

[0077] Preferably, an iodide is compounded in the above-described stretching bath (aqueous boric acid solution). By compounding the iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. 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. The concentration of the iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, relative to 100 parts by weight of water.

[0078] The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C or higher, more preferably 60°C or higher. At such a temperature, dissolution of the PVA-based resin layer can be suppressed and stretching can be performed at a high magnification. The stretching temperature is, for example, 75°C or lower. The higher the stretching temperature, the higher the solubility of the PVA-based resin layer, and there is a concern that excellent optical properties may not be obtained. The impregnation time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

[0079] The stretching magnification based on wet stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretching magnification of the laminate (the stretching magnification obtained by combining air-assisted stretching and stretching in water) is preferably 5.0 times or more, more preferably 5.5 times or more, relative to the original length of the laminate. By achieving such a high stretching magnification, a polarizer with extremely excellent optical properties can be manufactured. Such a high stretching magnification can be achieved by adopting a stretching method in water (stretching in aqueous boric acid).

[0080] Drying can be performed by any suitable method. In one embodiment, it is preferably further included to heat while conveying in the length direction to cause shrinkage in the width direction. The drying shrinkage treatment is preferably performed in the order of dry stretching, dyeing treatment, wet stretching, and drying shrinkage treatment.

[0081] The shrinkage rate in the width direction of the laminate based on drying is preferably 1% to 10%, more preferably 2% to 8%, and further preferably 4% to 6%. By using a heating roll, the laminate can be continuously shrunk in the width direction while being conveyed, and high productivity can be achieved.

[0082] By adjusting the heating temperature (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, etc., the drying conditions can be controlled. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, and further preferably 70°C to 90°C. According to such a temperature, the crystallinity of the thermoplastic resin can be increased to suppress curling, and extremely excellent durability can be imparted to the laminate. In addition, the temperature of the heating roll can be measured by a contact thermometer. The contact time (total contact time) of the laminate with the heating roll is preferably 1 second to 300 seconds, more preferably 1 second to 20 seconds, and further preferably 1 second to 10 seconds.

[0083] The heating roller can be set in a heating furnace (such as an oven) or in a normal production line (under room temperature environment). It is preferably set in a heating furnace equipped with an air supply means. By combining the drying based on the heating roller and the hot air drying, the rapid temperature change between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of the hot air drying is preferably 30°C to 100°C. In addition, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10m / s to 30m / s. It should be noted that the wind speed is the wind speed in the heating furnace and can be measured by a mini-vane digital anemometer.

[0084] D. Polarizer

[0085] The polarizer (PVA resin layer of the long strip laminate) produced by the manufacturing method including the above-mentioned other steps is essentially a PVA resin film formed by adsorbing and oriented dichroic substances. The polarizer preferably shows absorption dichroism at any wavelength of 380nm to 780nm. The single transmittance (Ts) of the polarizer is preferably 39% or more, more preferably 40% or more, further preferably 41% or more, and particularly preferably 42% or more. In addition, the theoretical upper limit of the single transmittance is 50%, and the practical upper limit is 46%. In addition, the single transmittance (Ts) is a Y value measured using the 2-degree field of view (C light source) of JIS Z8701 and corrected for visual sensitivity. For example, it can be measured using the product name "V-7100" manufactured by JASCO Corporation. The polarization degree of the polarizer is preferably 99% or more, more preferably 99.90% or more, and further preferably 99.95% or more.

[0086] The thickness of the polarizer is, for example, 20 μm or less, preferably 12 μm or less, and may be 8 μm or less. On the other hand, the thickness of the PVA-based resin layer is preferably 1 μm or more, more preferably 2 μm or more.

[0087] The polarizer can be used in any appropriate manner. Specifically, it can be used in the form of a single-layer PVA-based resin film, in the form of a laminate of a resin substrate and a PVA-based resin film, or in the form of a laminate (i.e., a polarizer) in which a protective film is disposed on at least one of the PVA-based resin film or the PVA-based resin film.

[0088] E. Polarizer

[0089] The polarizing plate has a polarizer and a protective film disposed on at least one side of the polarizer. As a forming material of the protective film, for example, cellulose-based resins such as diacetate cellulose and triacetate cellulose, (meth)acrylic resins, cycloolefin resins, olefin resins such as polypropylene, ester resins such as polyethylene terephthalate resins, polyamide resins, polycarbonate resins, copolymer resins thereof, etc. can be cited.

[0090] The thickness of the protective film is preferably 10 μm to 80 μm. Typically, the protective film is laminated on the polarizer via an adhesive layer (specifically, an adhesive layer, a binder layer). Typically, the adhesive layer is formed of a PVA-based adhesive or an active energy ray-curable adhesive. Typically, the binder layer is formed of an acrylic binder. In the case of using a laminate of a resin substrate / PVA-based resin film (polarizer), it is preferable that the resin substrate can be peeled off after laminating the protective film on the surface of the polarizer opposite to the resin substrate. If necessary, another protective film can be laminated on the peeled surface. By peeling off the resin substrate, curling can be more reliably suppressed.

[0091] Practically, the polarizing plate has a binder layer as the outermost layer. Typically, the binder layer becomes the outermost layer on the image display device side. A release liner is temporarily adhered to the binder layer in a peelable manner to protect the binder layer until actual use, and a roll can be formed.

[0092] The polarizing plate can further have any appropriate optical functional layer according to the purpose. As a representative example of the optical functional layer, a retardation film (optical compensation film) and a surface treatment layer can be cited. For example, a retardation film (not shown) can be disposed between the protective film and the binder layer. The optical properties of the retardation film (e.g., refractive index ellipsoid, in-plane retardation, thickness-direction retardation) can be appropriately set according to the purpose, characteristics of the image display device, etc. For example, in the case where the image display device is an IPS-mode liquid crystal display device, a retardation film with a refractive index ellipsoid of nx > ny > nz and a retardation film with a refractive index ellipsoid of nz > nx > ny can be disposed. The retardation film can also serve as a protective film. In this case, the protective film disposed on the image display device side can be omitted. Conversely, the protective film can also have an optical compensation function (i.e., can have an appropriate refractive index ellipsoid, in-plane retardation, and thickness-direction retardation corresponding to the purpose). It should be noted that "nx" is the refractive index in the direction in which the refractive index in the film plane reaches the maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the film plane, and "nz" is the refractive index in the thickness direction.

[0093] The surface treatment layer can be disposed further outside the protective film on the outer side (not shown). Representative examples of the surface treatment layer include a hard coat layer, an antireflection layer, and an antiglare layer. The surface treatment layer is preferably a layer with low moisture permeability, for example, for the purpose of improving the humidity resistance of the polarizer. The hard coat layer is provided for the purpose of preventing damage to the surface of the polarizing plate. The hard coat layer can be formed, for example, by attaching a cured coating film with excellent hardness, sliding properties, etc. formed from a suitable ultraviolet curable resin such as an acrylic-based or silicone-based resin to the surface. As the hard coat layer, a pencil hardness of 2H or more is preferred. The antireflection layer is a low reflection layer provided for the purpose of preventing reflection of external light on the surface of the polarizing plate. As the antireflection layer, for example, there can be cited a thin film type that uses the cancellation effect of reflected light brought about by the interference of light to prevent reflection as disclosed in Japanese Patent Laid-Open No. 2005-248173, and a surface structure type that exhibits a low reflectance by imparting a fine structure to the surface as disclosed in Japanese Patent Laid-Open No. 2011-2759. The antiglare layer is provided for the purpose of preventing the reflection of external light on the surface of the polarizing plate from hindering the visual recognition of the transmitted light of the polarizing plate, etc. The antiglare layer is formed, for example, by imparting a fine uneven structure to the surface by a suitable method such as a roughening method based on a sandblasting method or an embossing method, or a method of compounding transparent fine particles. The antiglare layer can also function as a diffusion layer (such as a viewing angle expansion function, etc.) that diffuses the transmitted light of the polarizing plate to expand the viewing angle, etc. Instead of providing the surface treatment layer, the same surface treatment can be applied to the surface of the protective film on the outer side.

[0094] Examples

[0095] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0096] [Example 1]

[0097] As the thermoplastic resin substrate, an amorphous isophthalic acid copolyethylene terephthalate film (thickness: 100 μm) in the form of a long strip with a Tg of about 75°C was used, and corona treatment was performed on one side of the resin substrate with a width of 2000 mm or more. 13 parts by weight of potassium iodide was added to 100 parts by weight of a PVA-based resin obtained by mixing polyvinyl alcohol (degree of polymerization 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER", degree of polymerization 2500) in a ratio of 9:1, and the resulting product was dissolved in water to prepare a PVA aqueous solution (coating solution).

[0098] The above PVA aqueous solution was coated on the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.

[0099] The obtained laminate is stretched 2.7 times in the longitudinal direction of the laminate at 150 °C using a tenter stretching device, and shrunk 37.5% in the width direction to obtain a laminate having a PVA-based resin film (thickness: 8 μm) (air-assisted stretching). The stretching and shrinking are performed simultaneously.

[0100] Next, the laminate having the PVA-based resin film is immersed in an insolubilization bath at a liquid temperature of 40 °C (an aqueous boric acid solution obtained by compounding 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).

[0101] Next, in a dyeing bath at a liquid temperature of 30 °C (an aqueous iodine solution obtained by compounding iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water), it is immersed for 60 seconds while adjusting the concentration so that the monomer transmittance (Ts) of the finally obtained polarizer becomes a desired value (dyeing treatment).

[0102] Next, it is immersed in a crosslinking bath at a liquid temperature of 40 °C (an aqueous boric acid solution obtained by compounding 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (crosslinking treatment).

[0103] Then, while immersing the laminate in an aqueous boric acid solution at a liquid temperature of 64 °C (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight), it is uniaxially stretched between rolls having different circumferential speeds in the longitudinal direction (length direction) so that the total stretching ratio becomes 5.5 times (in-water stretching treatment).

[0104] Then, the laminate is immersed in a cleaning bath at a liquid temperature of 20 °C (an aqueous solution obtained by compounding 3 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).

[0105] Then, while drying in an oven maintained at about 90 °C, it is brought into contact with a heating roll made of stainless steel (SUS) having a surface temperature maintained at about 75 °C (dry shrinkage treatment).

[0106] Through the above operations, a laminate having a PVA-based resin layer (polarizer) with a thickness of 5 μm on a resin substrate is obtained.

[0107] [Examples 2 to 3]

[0108] As described in Table 1, the stretching temperature and stretching ratio of the air-assisted stretching are changed, and other than that, a laminate having a PVA-based resin layer (polarizer) is obtained in the same manner as in Example 1.

[0109] (Comparative Example 1)

[0110] As described in Table 1, the stretching temperature and stretching ratio of the air-assisted stretching are changed, and other than that, a laminate having a PVA-based resin layer (polarizer) is obtained in the same manner as in Example 1.

[0111] (Comparative Example 2)

[0112] A PVA-based resin film with a thickness of 30 μm (manufactured by Kuraray, product name "PE3000") was stretched 1.2 times in the transport direction while being immersed in a 30°C water bath for 1 minute. Subsequently, it was immersed in an aqueous solution at 30°C with an iodine concentration of 0.04 wt% and a potassium concentration of 0.3 wt% for dyeing, and stretched 2 times based on the unstretched film (original length). Then, while immersing this stretched film in an aqueous solution at 30°C with a boric acid concentration of 3 wt% and a potassium iodide concentration of 3 wt%, it was further stretched to 3 times based on the original length. Subsequently, while immersing it in an aqueous solution at 60°C with a boric acid concentration of 4 wt% and a potassium iodide concentration of 5 wt%, it was further stretched to 6.0 times based on the original length, and dried at 70°C for 2 minutes to obtain a PVA-based resin layer (polarizer) with a thickness of 12 μm.

[0113] (Comparative Example 3)

[0114] A polarizer was obtained by using a PVA-based resin film with a thickness of 45 μm instead of the PVA-based resin film with a thickness of 30 μm and operating in the same manner as in Comparative Example 2.

[0115] [Evaluation]

[0116] The following evaluations were performed on the strip-shaped laminates obtained in the examples and comparative examples. The results are shown in Table 1.

[0117] 1. Thickness

[0118] For a thickness of 10 μm or less, it was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). For a thickness exceeding 10 μm, it was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C").

[0119] 2. Water Absorption

[0120] For Examples 1 to 3 and Comparative Example 1, a 1 cm square measurement sample was cut out from the PVA-based resin layer peeled from the laminate after the air stretching and shrinkage processing. For Comparative Examples 2 and 3, a 1 cm square measurement sample was cut out from the PVA-based resin film used for manufacturing the polarizer. The measurement sample was set in a moisture adsorption / desorption measurement device (manufactured by Hiden, product name "IGA-SORP"), and maintained at 23°C and 0% RH for 600 minutes. Further, it was maintained at 40°C and 90% RH for 120 minutes. Let the weight W1 after being maintained at 23°C and 0% RH and the weight after being maintained at 40°C and 90% RH for 120 minutes be W2, and the water absorption was calculated by the following formula.

[0121] Water absorption rate (%) = (W2 - W1) / W1 × 100

[0122] 3. Coefficient of static friction

[0123] For Examples 1 to 3 and Comparative Example 1, the PVA-based resin layers peeled from the laminated bodies after the in-air stretching and shrinking process were each cut into 15 cm × 4 cm as specimens. For Comparative Examples 2 and 3, the PVA-based resin films used for manufacturing polarizers were each cut into 15 cm × 4 cm as specimens. After conditioning at 40 °C and 90% RH for 2 hours, the PVA-based resin films were fixed to a sliding piece weighing 200 g and placed on a smooth stainless steel plate (made of SUS304, surface roughness Ra = 0.05 μm) in such a way that the contact area became 40 cm 2 ². Using an Autograph (manufactured by Shimadzu Corporation, product name “AG-IS”), the static friction force was measured in accordance with JIS K7125, and the coefficient of static friction was calculated from the following formula.

[0124] Coefficient of static friction = Static friction force / 1.96

[0125] As Reference Examples 1 to 5, for the PVA-based resin layers (Reference Examples 1 to 3) peeled from the laminated bodies after the in-air stretching and shrinking process of Examples 1 to 3 and the PVA-based resin films used in Comparative Examples 2 and 3 (Reference Examples 4 and 5), no conditioning was performed, and except for this, the coefficient of static friction was measured in the same manner as described above.

[0126] 4. Scratch generation frequency

[0127] The polarizers obtained in the examples and comparative examples were cut into 10 cm squares as specimens. A searchlight (manufactured by GENTOS Co., product name “MG-886R”) was arranged perpendicular to the MD direction of the specimen, and light was irradiated onto the surface of the specimen from a position where the angle between the light irradiated by the searchlight and one surface of the specimen was 45° and the distance between the surface of the specimen and the searchlight was 10 cm. The surface of the polarizer was visually inspected for scratches. It should be noted that a sample with a depth of 0.05 μm or more, a length of 0.2 mm or more, and a width of 0.2 μm or more was defined as a scratch. If the number of scratches was 0, it was recorded as ◎ (best); if it was 1 or more and 5 or less, it was recorded as 〇 (good); if it exceeded 5, it was recorded as × (room for improvement). In addition, for Examples 1 to 3 and Comparative Example 1, light was irradiated from the resin substrate side.

[0128]

[0129] [Evaluation]

[0130] In Examples 1 to 3 of the present invention, generation of minute scratches on the surface of the polarizer was suppressed.

[0131] Industrial Applicability

[0132] When using the polyvinyl alcohol-based resin film of the embodiment of the present invention, generation of scratches on the film surface can be suppressed, and a product with excellent appearance can be provided. A polarizer produced using the polyvinyl alcohol-based resin film of the embodiment of the present invention can be suitably used for an image display device that requires higher precision.

Claims

1. A polyvinyl alcohol-based resin film having a thickness of 45 μm or less, a water absorption rate of 1% to 10%, a static friction coefficient against a stainless steel plate of 2.55 or less after humidity conditioning at 40°C and 90% RH for 2 hours, the polyvinyl alcohol-based resin film being in a long strip shape with a width of 2000 mm or more, and the polyvinyl alcohol-based resin film containing a polyvinyl alcohol-based resin having an average degree of polymerization of 3000 or more.

2. The polyvinyl alcohol-based resin film according to claim 1, having an arithmetic mean surface roughness Ra of 0.05 μm or less.

3. The polyvinyl alcohol-based resin film according to claim 2, having a thickness deviation in the width direction of 1 μm or less.

4. The polyvinyl alcohol-based resin film according to claim 3, which is a layer formed by coating a solution containing the polyvinyl alcohol-based resin on a substrate.

5. The polyvinyl alcohol-based resin film according to claim 1, which is used for the manufacture of a polarizer.

6. A method for manufacturing a polyvinyl alcohol-based resin film, wherein the static friction coefficient of the polyvinyl alcohol-based resin film against a stainless steel plate after conditioning at 40 °C and 90% RH for 2 hours is 2.55 or less, and the manufacturing method successively comprises: Coat a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer, and produce an intermediate laminate; and dry-stretch the intermediate laminate while heating at 130°C or higher.

7. A manufacturing method of a polarizer, comprising: Dye a polyvinyl alcohol-based resin film having a static friction coefficient against a stainless steel plate of 2.55 or less after humidity conditioning at 40°C and 90% RH for 2 hours with a dichroic substance.

8. The manufacturing method of the polarizer according to claim 7 sequentially includes: Coat a solution containing a polyvinyl alcohol-based resin on a substrate to form a polyvinyl alcohol-based resin layer, and produce an intermediate laminate; and dry-stretch the intermediate laminate while heating at 130°C or higher; the manufacturing method further includes obtaining the polyvinyl alcohol-based resin film.

Images