Manufacturing method of long-sized laminate

Abstract

To provide a manufacturing method of a long-sized laminate capable of drawing at a high drawing ratio even in a high temperature.SOLUTION: A method is for manufacturing a long-sized laminate including a resin base material and a polyvinyl alcohol resin layer with a degree of crystallinity 45% to 55%. The method includes a drawing contraction process including: drawing, in a longer direction, an intermediate laminate including the resin base material and the polyvinyl alcohol resin layer, by using a tenter drawing device having a plurality of grips as holding means; and contracting the intermediate laminate in a width direction in a contracting direction. In the drawing contraction process, a draw ratio N (times) in the longer direction and a contraction rate ΔW(%) in the width direction satisfy 0.135<ΔW / N<0.145.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a method for producing a long laminate, and more particularly to a method for producing a long laminate using a tenter stretching device. [Background technology]

[0002] By stretching a resin film, various properties such as physical strength, heat resistance, surface properties, and moisture permeability can be imparted to the film, and thus stretched resin films are used in a variety of applications (for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2023 / 120642 [Patent Document 2] Patent No. 7168115 Summary of the Invention [Problem to be solved by the invention]

[0004] Heat treatment is known as a means of improving various properties (e.g., strength) of resin films. However, heat treatment at higher temperatures may reduce the stretchability of the resin film, and the properties that can be obtained by stretching may not be fully imparted to the resin film. In addition, there is a risk that stretching itself may not be possible due to film breakage, etc. Therefore, there is a need for a manufacturing method that allows stretching at a high stretch ratio even at high temperatures. The present invention has been made to solve this problem, and its main object is to provide a manufacturing method for a long laminate that can be stretched at a high stretch ratio even at high temperatures. [Means for solving the problem]

[0005] 1. A method for producing a long laminate according to an embodiment of the present invention is a method for producing a long laminate having a resin substrate and a polyvinyl alcohol-based resin layer having a crystallinity of 45% to 55%, and includes a stretching and shrinking treatment that involves stretching an intermediate laminate having the resin substrate and the polyvinyl alcohol-based resin layer in the longitudinal direction using a tenter stretching device equipped with a plurality of clips as holding means, and shrinking the intermediate laminate in the width direction, wherein the stretching and shrinking treatment is performed such that the stretching ratio N (times) in the longitudinal direction and the shrinkage rate ΔW (%) in the width direction satisfy 0.135<ΔW / N<0.145. 2. In the method for producing a long laminate as described in 1 above, the stretching ratio N in the longitudinal direction may be 2.0 times to 3.5 times. 3. The method for producing a long laminate according to 1 or 2 above may further include another stretching step, and the total stretching ratio in the method for producing a long laminate may be 5.0 times to 6.0 times. 4. In the method for producing a long laminate described in any one of 1 to 3 above, the stretching and shrinking treatment may include a first stretching and shrinking treatment, which involves stretching the intermediate laminate in the longitudinal direction at a treatment temperature of 150°C or higher and shrinking it in the width direction. 5. In the method for producing a long laminate described in 4 above, the stretching and shrinking treatment may further include a second stretching and shrinking treatment following the first stretching and shrinking treatment, which includes stretching the intermediate laminate in the longitudinal direction at a treatment temperature of less than 150°C and shrinking it in the width direction. 6. In another aspect of an embodiment of the present invention, there is provided a long laminate, which is obtainable by the method for producing a long laminate described in any one of 1 to 5 above. [Effects of the Invention]

[0006] According to an embodiment of the present invention, a method for producing a long laminate that can be stretched at a high draw ratio even at high temperatures can be obtained. Furthermore, according to the method for producing a long laminate of an embodiment of the present invention, film breakage can be suppressed even when stretched at high temperatures, and a long laminate having excellent properties can be efficiently produced. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic plan view illustrating the overall configuration of an example of a stretching device that can be used in the production method of the present invention. [Figure 2] FIG. 2 is a schematic plan view of the main part of the stretching device of FIG. [Figure 3] FIG. 2 is a schematic plan view of the main part of the stretching device of FIG. [Figure 4] FIG. 1 is a schematic diagram illustrating an example of an MD stretching / TD shrinkage process. [Figure 5] FIG. 10 is a schematic diagram illustrating another example of the MD stretching / TD shrinkage process. [Figure 6] FIG. 2 is a schematic diagram illustrating an example of an MD stretching / TD shrinking process including a first stretching / shrinking treatment and a second stretching / shrinking treatment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Manufacturing method of long laminate A manufacturing method according to an embodiment of the present invention is a method for producing a long laminate having a resin substrate and a polyvinyl alcohol (hereinafter also referred to as PVA)-based resin layer having a crystallinity of 45% to 55%. The manufacturing method for a long laminate according to an embodiment of the present invention includes a stretching and shrinking treatment, which involves stretching an intermediate laminate having a resin substrate and a polyvinyl alcohol-based resin layer in the longitudinal direction and shrinking the intermediate laminate in the width direction using a tenter stretching device equipped with multiple clips as gripping means. Specifically, the longitudinal stretching includes increasing the clip spacing in the conveying direction of the long resin film, and the widthwise shrinkage includes decreasing the clip spacing in the width direction. In the manufacturing method for a long laminate according to an embodiment of the present invention, the longitudinal stretching ratio N (times) and the widthwise shrinkage ratio ΔW (%) satisfy the relationship 0.135<ΔW / N<0.145. In the stretching and shrinkage treatment, if the longitudinal stretching ratio N and the widthwise shrinkage ratio ΔW satisfy the relationship described above, stretchability can be improved. Furthermore, adjusting the shrinkage rate in the width direction can eliminate problems (e.g., film breakage) that occur when stretching at a high ratio. Furthermore, it can suppress the occurrence of defects such as breakage even at high temperatures (e.g., 150°C or higher), making it possible to stretch the intermediate laminate at a higher temperature and a higher stretch ratio. As a result, a long laminate having a polyvinyl alcohol-based resin layer with a crystallinity of 45% to 55% can be obtained. Furthermore, by stretching at a higher temperature and a high stretch ratio, various properties can be imparted to the PVA-based resin layer.

[0009] ΔW / N preferably satisfies 0.137<ΔW / N<0.143, more preferably 0.138<ΔW / N<0.140. When ΔW / N is within the above range, the intermediate laminate can be stretched and shrunk at a high draw ratio and a high shrinkage rate even at high temperatures, and a long laminate having a PVA-based resin layer with a higher crystallinity can be obtained, for example.

[0010] A-1. Preparation of intermediate laminate The intermediate laminate is produced by forming a PVA-based resin layer on a resin substrate. The resin substrate may have any suitable configuration as long as it can support the PVA-based resin layer from one side.

[0011] Examples of materials for forming the resin substrate include ester resins such as polyethylene terephthalate resins, cycloolefin resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Among these, preferred are cycloolefin resins (e.g., norbornene resins) and amorphous polyethylene terephthalate resins. Specific examples of amorphous polyethylene terephthalate resins include copolymers further containing isophthalic acid as a dicarboxylic acid and copolymers further containing cyclohexanedimethanol as a glycol. The thickness of the resin substrate is preferably 20 μm to 300 μm, and more preferably 50 μm to 200 μm.

[0012] The resin substrate may be previously subjected to a surface modification treatment (e.g., corona treatment, etc.), or an easy-adhesion layer may be formed on the resin substrate. By performing such treatment, the adhesion between the resin substrate and the PVA-based resin layer can be improved. The surface modification treatment and / or the formation of the easy-adhesion layer may be performed before or after stretching the resin substrate, which is performed as needed.

[0013] Any appropriate method can be used to form the PVA-based resin layer. Preferably, the PVA-based resin layer is formed by applying a coating liquid containing a PVA-based resin onto a resin substrate that has been subjected to a stretching treatment, followed by drying.

[0014] Any appropriate resin can be used as the PVA-based resin. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The saponification degree can be determined in accordance with JIS K 6726-1994. By using a PVA-based resin with such a saponification degree, a PVA-based resin layer with excellent durability can be obtained. If the saponification degree is too high, the coating liquid is likely to gel, making it difficult to form a uniform coating film.

[0015] The average degree of polymerization of the PVA resin can be appropriately selected depending on the purpose. The average degree of polymerization is usually 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. The average degree of polymerization can be determined in accordance with JIS K 6726-1994.

[0016] Any appropriate method can be used to form the PVA-based resin layer. Preferably, the PVA-based resin layer is formed by applying a coating liquid containing a PVA-based resin onto a resin substrate that has been subjected to a stretching treatment, followed by drying. The thickness of the PVA-based resin layer is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

[0017] The coating liquid is typically a solution in which the PVA resin is dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Of these, water is preferred. The concentration of the PVA resin in the coating liquid is preferably 3 to 20 parts by weight per 100 parts by weight of the solvent. Such a resin concentration allows the formation of a uniform coating film that adheres closely to the resin substrate.

[0018] Additives may be blended into the coating solution. Examples of additives include plasticizers and surfactants. Examples of plasticizers include polyhydric alcohols such as ethylene glycol and glycerin. Examples of surfactants include nonionic surfactants. These can be used to further improve the uniformity, dyeability, and stretchability of the resulting PVA-based resin layer.

[0019] Any appropriate method can be used to apply the coating liquid, such as roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (such as comma coating).

[0020] A-2. Stretching and shrinking treatment An intermediate laminate having a resin substrate and a PVA-based resin layer is subjected to a stretching / shrinking process using a tenter stretching device equipped with multiple clips as gripping means, which involves stretching the intermediate laminate in the longitudinal direction (hereinafter also referred to as MD stretching) and shrinking it in the width direction (hereinafter also referred to as TD shrinkage). Specifically, both side edges of the intermediate laminate are gripped with a clip spacing L1 in the conveyance direction, and the intermediate laminate is stretched in the longitudinal direction by expanding the clip spacing from L1 to L2, and the intermediate laminate is shrunk in the width direction by decreasing the clip spacing in the width direction. The order of MD stretching and TD shrinkage can be appropriately set depending on the purpose. For example, MD stretching may be performed first, TD shrinkage may be performed first, or MD stretching and TD shrinkage may be performed simultaneously.

[0021] The tenter stretching device may be, for example, a stretching device equipped with a pair of rails having a straight section where the rail-to-rail distance is constant and a tapered section where the rail-to-rail distance continuously decreases, and multiple clips that can run on each rail while changing the clip spacing. With such a stretching device, the intermediate laminate can be stretched and shrunk by holding both side edges of the intermediate laminate with the clips and changing the clip spacing in the conveyance direction (the distance between the clips on the same rail) and the clip spacing in the width direction (the distance between the clips on different rails).

[0022] FIG. 1 is a schematic plan view illustrating the overall configuration of an example of a stretching device that can be used in the manufacturing method of the present invention. A stretching device that can be used in the manufacturing method of the present invention will be described with reference to FIG. 1. The stretching device 100 has endless rails 10L and 10R symmetrically arranged on both the left and right sides in a plan view. In this specification, the left endless rail, as viewed from the entrance side of the intermediate laminate, is referred to as the left endless rail 10L, and the right endless rail is referred to as the right endless rail 10R. A number of clips 20 for holding the laminate are disposed on each of the left and right endless rails 10L and 10R. The clips 20 move circulating in a loop, guided by their respective rails. The clips 20 on the left endless rail 10L move circulating counterclockwise, and the clips 20 on the right endless rail 10R move circulating clockwise. In the illustrated stretching apparatus, a gripping zone A, an MD stretching zone B, a TD shrinkage zone C, and a release zone D are provided in this order from the entrance side of the intermediate laminate to the exit side. Note that these zones refer to zones where the intermediate laminate is substantially gripped, stretched in the MD, contracted in the TD (or contracted in the TD and stretched in the MD), and released, and do not refer to mechanically or structurally independent compartments. It should also be noted that the length ratio of each zone in the stretching apparatus in FIG. 1 differs from the actual length ratio.

[0023] In the gripping zone A and the MD stretching zone B, the left and right endless rails 10R, 10L are straight sections with a constant rail-to-rail distance. Typically, the left and right endless rails 10R, 10L are configured to be approximately parallel to each other with a rail-to-rail distance corresponding to the initial width of the intermediate laminate to be processed. In the TD shrinking zone C, the left and right endless rails 10R, 10L are tapered sections with a continuously decreasing rail-to-rail distance. Typically, the left and right endless rails 10R, 10L are configured so that the rail-to-rail distance gradually decreases from the MD stretching zone B side toward the release zone D side until it corresponds to the post-shrinkage width of the intermediate laminate. In the release zone D, the left and right endless rails 10R, 10L are straight sections with a constant rail-to-rail distance, typically configured so that they are approximately parallel to each other with a rail-to-rail distance corresponding to the post-shrinkage width of the intermediate laminate.

[0024] The clip 20 on the left endless rail 10L (left clip) and the clip 20 on the right endless rail 10R (right clip) can move circumferentially independently. For example, the drive sprockets 30a and 30b of the left endless rail 10L are driven to rotate counterclockwise by electric motors 40a and 40b, and the drive sprockets 30a and 30b of the right endless rail 10R are driven to rotate clockwise by electric motors 40a and 40b. As a result, a running force is applied to the clip support members (not shown) of the drive rollers (not shown) engaged with the drive sprockets 30a and 30b. This causes the left clip 20 to move circumferentially in the counterclockwise direction, and the right clip 20 to move circumferentially in the clockwise direction. By independently driving the left electric motor and the right electric motor, the left clip 20 and the right clip 20 can be moved circumferentially independently.

[0025] The clip size is preferably 12 mm to 40 mm, and more preferably 15 mm to 35 mm. If the clip size is less than 12 mm, the stretching tension may not be maintained and the laminate may break, or the strength of the clip conveying section may be insufficient, resulting in drive malfunction. If the clip size exceeds 40 mm, the area that is not stretched near the clip may become large, causing unevenness at the edge, or cracks may occur on the surface of the resin film due to local stretching of the non-gripped section. Here, the clip size refers to the width of the gripped area.

[0026] Furthermore, the left clip 20 and the right clip 20 are each a variable pitch type. That is, the clip spacing (clip pitch) between the left and right clips 20, 20 in the conveying direction (MD) can change independently as they move. Variable pitch clips can be realized by any appropriate configuration, such as the configuration described in JP 2008-23775 A.

[0027] 2 and 3 are schematic plan views of the main parts of the stretching apparatus of FIG. 1. FIG. 2 is a schematic plan view of the rails of the stretching apparatus of FIG. 1, at the transition from the MD stretching zone B to the TD contraction zone C. FIG. 3 is a schematic plan view of the rails of the stretching apparatus of FIG. 1, at the transition from the TD contraction zone C to the release zone D. As shown in FIGS. 2 and 3, both ends of the tapered section are bent sections 11 and 12, respectively, which are bent at a predetermined angle (θ1), thereby enabling connection to a straight section with a constant rail-to-rail distance. The bend angle can be appropriately set depending on the desired shrinkage rate and productivity. The bend angle θ1 can be, for example, 1° to 20°.

[0028] The stretching device illustrated in FIG. 1 is configured to perform MD stretching and TD shrinkage in this order, and MD stretching can also be performed during TD shrinkage. Specifically, the MD stretching and TD shrinkage steps may include gripping both side edges of the intermediate laminate with clips at a clip spacing of L1 in the conveying direction (gripping step), stretching the intermediate laminate in the longitudinal direction by expanding the clip spacing in the conveying direction from L1 to L2 while passing the intermediate laminate through a straight section (MD stretching step), and shrinking the intermediate laminate in the width direction by passing the intermediate laminate through a tapered section (TD shrinkage step). If necessary, the method may further include releasing the clips gripping the intermediate laminate (releasing step). FIGS. 4 and 5 are schematic diagrams illustrating an example of a shrinkage-stretching step including these steps. Each step in the shrinkage-stretching step will be described in more detail below with reference to these figures.

[0029] First, in the gripping step (gripping zone A), left and right clips 20 grip both side edges of an intermediate laminate 50 taken into a stretching device at a fixed gripping interval (clip interval), and the intermediate laminate 50 is transported to the MD stretching zone B by the movement of each clip 20 guided by left and right endless rails. The gripping intervals (clip intervals) of both side edges in gripping zone A are typically equal to each other. The clip interval is the distance between the centers of adjacent clips.

[0030] Next, in the MD stretching step (MD stretching zone B), the intermediate laminate 50 held by the left and right clips 20 is stretched in the longitudinal direction (MD stretching) while being conveyed. The MD stretching of the intermediate laminate 50 is performed by gradually increasing the moving speed of the clips 20 in the conveying direction and expanding the clip spacing in the conveying direction from L1 to L2. The longitudinal stretch ratio N (L2 / L1) can be controlled by adjusting the clip spacing in the conveying direction (clamping spacing in the gripping step) L1 at the entrance of the MD stretching zone B and the clip spacing in the conveying direction L2 at the exit of the MD stretching zone B.

[0031] As described above, the stretching ratio N in the longitudinal direction is calculated by L2 / L1. The stretching ratio N in the longitudinal direction is preferably 2.0 to 3.5, and more preferably 2.4 to 3.0. When the stretching ratio is within the above range, the stretchability (total stretching ratio) of the intermediate laminate is further improved, and good stretching can be achieved even at high temperatures.

[0032] If the clip spacing L1 is too large, stress that causes the intermediate laminate 50 to shrink in the width direction will be generated in the portions not held by the clips 20, which may result in unevenness in the properties of the resulting long laminate. Therefore, the clip spacing L1 is typically set to a spacing that is equal to or smaller than the spacing that prevents such unevenness from occurring.

[0033] The clip distance L1 is preferably 100 mm or less, more preferably 60 mm or less, and even more preferably 40 mm or less. L1 is not limited as long as the clip distance L2 described below can be achieved after stretching, and can be, for example, 25 mm or more.

[0034] On the other hand, if the clip spacing L1 is set to a predetermined value or less as described above, the clip spacing L2 after MD stretching may also be small depending on the stretch ratio, causing interference such as contact between the clips 20 in the tapered portion (particularly in the bent portion), making it impossible to achieve the desired shrinkage ratio (as a result, the total stretch ratio may not be sufficiently high). Therefore, typically, the clip spacing L2 is set to a spacing that is greater than or equal to the spacing that prevents the clips 20 from interfering with each other when the intermediate laminate 50 passes through the tapered TD shrinkage zone C (particularly in the bent portion). By setting L2 in this manner, L1 can be reduced without being limited to the spacing that prevents clips from interfering with each other in the bent portion. Note that "no interference between the clips" means that the clips, their supporting members, and spacing adjustment mechanisms can move through the bent portion as set without coming into contact with each other.

[0035] The clip spacing L2 can be appropriately set depending on the bending angle, the size and shape of the clip, etc. The clip spacing L2 is preferably 25 mm to 300 mm, and more preferably 35 mm to 150 mm. If the clip spacing L2 is within the above range, interference between the clips 20 at the tapered portion (especially the bending portion) can be avoided in the TD shrinking step, and a sufficient bending angle can be achieved, and more uniform shrinkage can be achieved.

[0036] The stretching temperature (MD stretching) of the intermediate laminate can be set to any appropriate value depending on the material forming the resin substrate, etc. The stretching temperature is typically equal to or higher than the glass transition temperature (Tg) of the resin substrate, preferably equal to or higher than the glass transition temperature (Tg) of the resin substrate + 10°C, and more preferably equal to or higher than Tg + 15°C. In one embodiment, the stretching temperature of the intermediate laminate is preferably equal to or higher than 145°C, more preferably equal to or higher than 150°C, and even more preferably equal to or higher than 160°C. The method for producing a long laminate according to an embodiment of the present invention suppresses the occurrence of defects such as breakage of the laminate even at the above temperatures, and can stretch the laminate at a high stretch ratio even at high temperatures. The stretching temperature (MD stretching) of the intermediate laminate is, for example, equal to or lower than 170°C.

[0037] Next, in the width direction (TD) shrinkage process (TD shrinkage zone C), the intermediate laminate 50 held by the left and right clips 20 is transported in the longitudinal direction and shrunk in the width direction (TD shrinkage). In the TD shrinkage zone C, the left and right endless rails 10R, 10L are tapered so that the rail-to-rail distance continuously decreases, and the intermediate laminate 50 shrinks in the width direction by passing through this zone. The TD shrinkage rate can be controlled by adjusting the amount of change in the rail-to-rail distance. Specifically, the smaller the ratio of the rail-to-rail distance at the exit of the TD shrinkage zone C (the end on the release zone D side) to the rail-to-rail distance at the entrance of the TD shrinkage zone C (the end on the MD stretch zone B side), the greater the shrinkage rate that can be obtained.

[0038] The shrinkage factor in the width direction ΔW (%) ({1-(width of laminate at the exit of TD shrinkage zone C: W2) / (width of laminate at the entrance of TD shrinkage zone C: W1)} × 100) can be set to any appropriate value so that the stretch ratio N (times) in the longitudinal direction and the shrinkage factor in the width direction ΔW (%) satisfy 0.135<ΔW / N<0.145. The shrinkage factor in the width direction ΔW is preferably 25% or more, more preferably 30% or more, and even more preferably 32% or more. Furthermore, the shrinkage factor in the width direction ΔW is, for example, 50% or less. When the shrinkage factor in the width direction ΔW is within the above range, the intermediate laminate can be stretched at a higher stretch ratio.

[0039] In the embodiment illustrated in FIG. 4, only the width direction shrinkage of the intermediate laminate 50 is performed in the TD shrinkage step. In this case, the intermediate laminate 50 is passed through the TD shrinkage zone C while maintaining the clip spacing (L2) in the conveyance direction. On the other hand, in the embodiment illustrated in FIG. 5, the width direction shrinkage and longitudinal stretching of the intermediate laminate 50 are performed in the TD shrinkage step. In this case, the clip spacing in the conveyance direction is expanded from L2 to L3 while the intermediate laminate 50 is passed through the TD shrinkage zone C. In the MD stretching step and the TD shrinkage step, MD stretching is performed in multiple stages, thereby making it possible to increase the final stretch ratio. Furthermore, simultaneous TD shrinkage and MD stretching can have the effect of suppressing warping and wrinkles.

[0040] The temperature environment in the TD shrinking step may be the same as the stretching temperature in the MD stretching step.

[0041] In one embodiment, the stretching and shrinking treatment preferably includes a first stretching and shrinking treatment, which involves stretching the intermediate laminate in the longitudinal direction at a treatment temperature of 140°C or higher and shrinking it in the width direction. Furthermore, the stretching and shrinking treatment more preferably includes a second stretching and shrinking treatment, which involves stretching the intermediate laminate in the longitudinal direction at a treatment temperature of less than 150°C and shrinking it in the width direction, following the first stretching and shrinking treatment. As described above, the method for producing a long laminate according to an embodiment of the present invention can suppress the occurrence of defects such as breakage, even when stretched at a high temperature of 150°C or higher, and can perform the stretching and shrinking treatment at a high stretch ratio and a high shrinkage rate. Furthermore, including the second stretching and shrinking treatment can appropriately control the orientation of the laminate. Therefore, it is possible to obtain a laminate with small variation in the orientation angle in the width direction. For example, when the resulting long laminate is used in a polarizing film production process, a long laminate capable of producing a polarizing film with high axial accuracy can be obtained.

[0042] FIG. 6 is a schematic diagram illustrating an example of an MD stretching / TD shrinking process including a first stretching / shrinking treatment and a second stretching / shrinking treatment. In the illustrated example, the intermediate laminate 50 is stretched and shrunk in a stretching / shrinking treatment zone SS. The stretching / shrinking treatment zone SS includes, in this order, a first stretching / shrinking treatment zone SS1 for performing the first stretching / shrinking treatment and a second stretching / shrinking treatment zone SS2 for performing the second stretching / shrinking treatment. In SS1, the treatment temperature (hereinafter also referred to as the first treatment temperature) is preferably 150°C or higher, more preferably 160°C or higher. The first treatment temperature is, for example, 170°C or lower. In this specification, the first treatment temperature refers to the maximum temperature achieved in the first stretching / shrinking treatment. The first stretching / shrinking treatment zone SS1 may be maintained at the first treatment temperature throughout the first stretching / shrinking treatment zone, or may be gradually increased to reach the first treatment temperature. A preheating zone PH may be provided before the stretching / shrinking treatment zone SS. The provision of a preheating zone can prevent wrinkles, folds, sagging, and other problems caused by sudden changes in film temperature. The temperature of the preheating zone can be set to any appropriate value. The temperature of the preheating zone is, for example, 70°C to 140°C, preferably 80°C to 130°C, and more preferably 90°C to 130°C.

[0043] In the illustrated example, the intermediate laminate 50 that has been subjected to the first stretching and shrinking treatment is then transported to the second stretching and shrinking treatment zone SS2 and subjected to the second stretching and shrinking treatment. The treatment temperature in the second stretching and shrinking treatment zone (hereinafter also referred to as the second treatment temperature) is preferably less than 140°C, more preferably 120°C or less, and even more preferably 110°C or less. The second treatment temperature is, for example, 90°C or higher. In the second stretching and shrinking treatment zone SS2, the second treatment temperature may be maintained throughout the second stretching and shrinking treatment zone, or the temperature may be further decreased in stages from the second treatment temperature. When the temperature is further decreased from the second treatment temperature, the heating temperature in the second stretching and shrinking treatment zone SS2 may be decreased in stages.

[0044] Finally, in the release step (release zone D), the clips 20 gripping the intermediate laminate 50 are released. Typically, in the release step, the inter-clip distance and the clip interval are both kept constant. If necessary, the intermediate laminate 50 is cooled to a desired temperature, and then the clips are released. Details of such a method of longitudinal stretching and widthwise contraction are described, for example, in Japanese Patent No. 6,563,201. The entire disclosures of these publications are incorporated herein by reference.

[0045] A-3. Long laminate According to the manufacturing method of the long laminate of the embodiment of the present invention, a long laminate having a PVA-based resin layer with a crystallinity of 45% to 55% can be obtained. As described above, according to the manufacturing method of the long laminate of the embodiment of the present invention, it is possible to stretch and shrink an intermediate laminate at a high draw ratio and a high shrinkage percentage even at a high temperature. As a result, a long laminate having a PVA-based resin layer with a high crystallinity of 45% to 55% can be obtained. The long laminate obtained by the manufacturing method of the long laminate of the embodiment of the present invention can be suitably used in applications requiring a PVA-based resin layer with a high crystallinity. In this specification, the crystallinity of PVA refers to the value calculated by X-ray diffraction (XRD) analysis as the percentage of the crystalline peak area to the sum of the crystalline peak area and the amorphous peak area.

[0046] (Method for evaluating the crystallinity of PVA) Any appropriate analytical device can be used for the X-ray analysis, including, for example, the "SmartLab" X-ray diffraction device manufactured by Rigaku Corporation and the "HyPix3000" 2D detector manufactured by Rigaku Corporation. A 150 μm thick PVA-based resin layer is used as the sample. If the PVA-based resin layer is less than 150 μm thick, the PVA-based resin layers are stacked to a total thickness of approximately 150 μm. X-rays with a wavelength of 1.5406 Å are transmitted through the sample perpendicular to the thickness direction, and scattered light is detected using a two-dimensional detector placed on the opposite side of the sample from the light source, resulting in a two-dimensional scattering image. After background correction, the obtained scattering image is integrated over the entire azimuthal angle (360°) around the beam center to obtain a one-dimensional profile of the integrated X-ray intensity versus the scattering angle 2θ. Next, waveform separation of the crystalline and amorphous peaks is performed on the obtained one-dimensional profile within the scattering angle 2θ range of 14° to 28.5°, and the crystallinity (%) is calculated using the following formula: Crystallinity (%) = crystalline peak area / (crystalline peak area + amorphous peak area) × 100

[0047] The orientation function of the PVA-based resin layer is preferably 0.25 to 0.40, more preferably 0.30 to 0.38, and even more preferably 0.32 to 0.38. When the orientation function is within the above range, the PVA-based resin layer can be suitably used, for example, as a polarizing film. The orientation function (f) can be determined, for example, by attenuated total reflection (ATR) measurement using a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as the measurement light. Specifically, the measurement is carried out with the stretching direction of the polarizing film parallel and perpendicular to the polarization direction of the measurement light, and the 2941 cm of the obtained absorbance spectrum is measured. -1 The intensity I is calculated according to the following formula using the intensity of 3330 cm -1 is used as the reference peak, and 2941 cm -1 / 3330cm -1 The value is: When f=1, it is fully oriented, and when f=0, it is random. Also, 2941 cm -1 The peak is thought to be an absorption caused by the vibration of the main chain (-CH2-) of PVA in the polarizing film. f=(3 <cos 2 θ>-1) / 2 =(1-D) / [c(2D+1)] =-2×(1-D) / (2D+1) however, c=(3cos 2 β-1) / 2, 2941 cm -1 For vibration, β=90°. θ: angle of molecular chain relative to stretching direction β: Angle of the transition dipole moment relative to the chain axis D=(I ⊥ ) / (I / / ) (In this case, the more the PVA molecules are oriented, the larger D becomes.) I ⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are perpendicular I / / : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are parallel

[0048] A-4. Other processes As described above, the method for producing a long laminate according to an embodiment of the present invention can produce a long laminate having a polyvinyl alcohol-based resin layer with a crystallinity of 45% to 55%. The method for producing a long laminate according to an embodiment of the present invention may further include any other appropriate steps depending on the intended use of the long laminate. In one embodiment, the long laminate according to an embodiment of the present invention may be a long laminate having a PVA-based resin layer capable of functioning as a polarizing film. The longitudinal direction, which is the stretching direction, essentially corresponds to the absorption axis direction of the resulting polarizing film. Hereinafter, a method for producing a long laminate having a PVA-based resin layer capable of functioning as a polarizing film will be specifically described.

[0049] When producing a long laminate having a PVA-based resin layer capable of functioning as a polarizing film, any appropriate steps may be included as other steps. Examples of the other steps include an insolubilization step, a dyeing step, a crosslinking step, a stretching step other than the above-mentioned stretching step, a washing step, and a drying step (adjusting the moisture content). The other steps may be performed at any appropriate timing.

[0050] The dyeing step is typically a step of dyeing the PVA-based resin layer with a dichroic substance. Preferably, the dyeing step is carried out by adsorbing the dichroic substance into the PVA-based resin layer. Examples of the adsorption method include immersing the PVA-based resin layer (laminate) in a dyeing solution containing the dichroic substance, applying the dyeing solution to the PVA-based resin layer, and spraying the dyeing solution onto the PVA-based resin layer. Preferably, the laminate is immersed in a dyeing solution containing the dichroic substance, because this method allows for good adsorption of the dichroic substance. Both sides of the laminate may be immersed in the dyeing solution, or only one side may be immersed.

[0051] Examples of the dichroic substance include iodine and organic dyes. These may 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 dye solution is preferably an iodine aqueous solution. The amount of iodine to be added is preferably 0.1 to 1.0 part by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add an iodide salt to the iodine aqueous solution. Examples of iodide salts include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Among these, potassium iodide and sodium iodide are preferred. The amount of iodide salt to be added is preferably 0.3 to 15 parts by weight per 100 parts by weight of water.

[0052] The temperature of the dye solution during dyeing is preferably 20° C. to 40° C. When the PVA-based resin layer is immersed in the dye solution, the immersion time is preferably 5 to 300 seconds. Under these conditions, the dichroic substance can be sufficiently adsorbed into the PVA-based resin layer.

[0053] The insolubilizing step and the crosslinking step are typically carried out by immersing the PVA resin layer in an aqueous solution of boric acid. The washing step is typically carried out by immersing the PVA resin layer in an aqueous solution of potassium iodide. The drying temperature in the drying step is preferably 30°C to 100°C.

[0054] The separate stretching step may be any appropriate stretching step. The separate stretching step may be dry stretching or wet stretching. Examples of the stretching method include roll stretching. By performing the separate stretching step, the final stretching ratio can be further increased. Preferably, the separate stretching step includes a wet stretching step. If the separate stretching step is further included, the total stretching ratio in the process of producing the long laminate can be further improved, and as a result, a polarizing film with excellent optical properties can be obtained. The separate stretching step may be performed simultaneously with the dyeing step, the insolubilizing step, and / or the crosslinking step, or may be performed separately. If performed separately, the separate stretching step may be performed at any appropriate timing.

[0055] When a separate stretching step is performed, the total stretching ratio in the method for producing a long laminate is preferably 5.0 to 6.0 times, more preferably 5.2 to 5.8 times. If the total stretching ratio is within the above range, a long laminate having a PVA-based resin layer (polarizing film) with even better optical properties can be obtained. In this specification, the total stretching ratio refers to the sum of the stretching ratio in the stretch-shrinking treatment and the stretching ratio in the separate stretching step.

[0056] Drying is carried out by any appropriate method. In one embodiment, it is preferable to further include a drying shrinkage treatment in which the film is heated while being transported in the longitudinal direction, thereby shrinking the film by 2% or more in the width direction. The drying shrinkage treatment is preferably carried out in the order of dry stretching, dyeing, wet stretching, and drying shrinkage treatment. In this embodiment, the PVA-based resin layer preferably contains a halide. Any appropriate halide can be used as the halide. Examples of halides include iodide and sodium chloride. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferred. The content of the halide in the PVA-based resin solution used to form the PVA-based resin layer (and consequently the PVA-based resin layer) is preferably 5 to 20 parts by weight per 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably carried out using a heated roll, and the temperature of the heated roll is preferably 60 to 120°C. The shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably 2% or more.

[0057] A-5.Polarizing film The polarizing film produced by the above-described production method is essentially a PVA-based resin film having a dichroic substance adsorbed and aligned therein. The polarizing film preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single-piece transmittance (Ts) of the polarizing film is preferably 39% or higher, more preferably 40% or higher, even more preferably 41% or higher, and particularly preferably 42% or higher. The theoretical upper limit of the single-piece transmittance is 50%, and the practical upper limit is 46%. The single-piece transmittance (Ts) is the Y value measured using a 2-degree visual field (C light source) according to JIS Z8701 and corrected for luminous efficiency. It can be measured, for example, using a product named "V-7100" manufactured by JASCO Corporation. The degree of polarization of the polarizing film is preferably 99% or higher, more preferably 99.90% or higher, and even more preferably 99.95% or higher.

[0058] The thickness of the polarizing film is, for example, 12 μm or less, preferably 8 μm or less, and may be 6 μm or less, while the thickness of the PVA-based resin layer is preferably 1 μm or more, more preferably 2 μm or more.

[0059] The polarizing film produced by the above-described production method can have excellent axial accuracy. Specifically, the variation in the orientation angle of the polarizer is less than 0.3°, preferably less than 0.2°, and more preferably 0.18° or less. The smaller the variation in the orientation angle of the polarizer, the better, and it may even be 0°. In this specification, the variation in the orientation angle of the polarizer refers to the absolute value of the difference between the maximum and minimum orientation angles in the width direction of the polarizer. The orientation angle of the polarizer can be measured by any appropriate method. For example, it can be measured using an "Axoscan" product manufactured by Axometrics.

[0060] The polarizing film may be used in any appropriate manner. Specifically, the polarizing film may be used as a single-layer PVA-based resin film, as a laminate of a resin substrate and a PVA-based resin film, or as a laminate in which a protective film is disposed on at least one of the PVA-based resin film and the PVA-based resin film (i.e., a polarizing plate).

[0061] B. Polarizing plate The polarizing plate has a polarizing film and a protective film disposed on at least one side of the polarizing film. Examples of materials for forming the protective film include cellulose-based resins such as diacetyl cellulose and triacetyl cellulose, (meth)acrylic resins, cycloolefin-based resins, olefin-based resins such as polypropylene, ester-based resins such as polyethylene terephthalate-based resins, polyamide-based resins, polycarbonate-based resins, and copolymer resins thereof.

[0062] The thickness of the protective film is preferably 10 μm to 80 μm. The protective film is typically laminated on the polarizing film via an adhesive layer (specifically, an adhesive layer or a pressure-sensitive adhesive layer). The adhesive layer is typically formed of a PVA-based adhesive or an activation energy ray-curable adhesive. The pressure-sensitive adhesive layer is typically formed of an acrylic pressure-sensitive adhesive. When a laminate of a resin substrate / PVA-based resin film (polarizing film) is used, the resin substrate can preferably be peeled off after laminating a protective film on the surface of the polarizing film 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.

[0063] In practice, polarizing plates have a pressure-sensitive adhesive layer as their outermost layer. This pressure-sensitive adhesive layer is typically the outermost layer on the image display device side. A release liner is temporarily and removably attached to the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until actual use and to enable roll formation.

[0064] The polarizing plate may further include any appropriate optically functional layer depending on the purpose. Representative examples of optically functional layers include a retardation film (optical compensation film) and a surface treatment layer. For example, a retardation film may be disposed between the protective film and the pressure-sensitive adhesive layer (not shown). The optical properties of the retardation film (e.g., refractive index ellipsoid, in-plane retardation, thickness retardation) may be appropriately set depending on the purpose, characteristics of the image display device, etc. For example, when the image display device is an IPS-mode liquid crystal display device, a retardation film having a refractive index ellipsoid of nx>ny>nz and a retardation film having a refractive index ellipsoid of nz>nx>ny may be disposed. The retardation film may also serve as a protective film. In this case, the protective film disposed on the image display device side may be omitted. Conversely, the protective film may have an optical compensation function (i.e., it may have a refractive index ellipsoid, in-plane retardation, and thickness retardation appropriate for the purpose). Here, "nx" is the refractive index in the direction in which the refractive index in the film plane is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction in the film plane perpendicular to the slow axis, and "nz" is the refractive index in the thickness direction.

[0065] The surface treatment layer may be disposed further outside the outer protective film (not shown). Typical examples of the surface treatment layer include a hard coat layer, an anti-reflection layer, and an anti-glare layer. The surface treatment layer is preferably a layer with low moisture permeability, for example, for the purpose of improving the humidity durability of the polarizing film. The hard coat layer is provided for the purpose of preventing scratches on the polarizing plate surface. The hard coat layer can be formed, for example, by adding a cured film made of an appropriate ultraviolet-curable resin such as an acrylic or silicone resin, which has excellent hardness and slip properties, to the surface. The hard coat layer preferably has a pencil hardness of 2H or more. The anti-reflection layer is a low-reflection layer provided for the purpose of preventing reflection of external light on the polarizing plate surface. Examples of anti-reflection layers include a thin-layer type, as disclosed in JP 2005-248173 A, which prevents reflection by utilizing the cancellation effect of reflected light due to light interference, and a surface structure type, as disclosed in JP 2011-2759 A, which imparts a microstructure to the surface to achieve low reflectance. Anti-glare layers are provided for purposes such as preventing external light from reflecting off the polarizing plate surface and impairing the visibility of light transmitted through the polarizing plate. Anti-glare layers are formed by imparting a micro-convex / concave structure to the surface using appropriate methods, such as surface roughening methods such as sandblasting or embossing, or incorporating transparent fine particles. The anti-glare layer may also function as a diffusion layer (e.g., a viewing angle widening function) to diffuse light transmitted through the polarizing plate and widen the viewing angle. Instead of providing a surface treatment layer, a similar surface treatment may be applied to the surface of the outer protective film. [Example]

[0066] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0067] [Example 1] <Intermediate laminate manufacturing process> As a resin substrate, an amorphous PET substrate (100 μm thick) was prepared. An aqueous PVA solution was applied to the amorphous PET substrate and dried at a temperature of 60°C. Thus, a PVA-based resin layer with a thickness of 13 μm was formed on the amorphous PET substrate to produce a laminate.

[0068] <MD stretching and TD shrinking process> The obtained laminate was subjected to MD stretching and TD shrinking using a stretching device similar to that shown in Fig. 6. Specifically, in the gripping zone, both side edges of the intermediate laminate were gripped and conveyed in the longitudinal direction, and passed through the preheating zone PH (set temperature: 90°C). Next, in the stretching and shrinking treatment zone SS including the first stretching and shrinking treatment zone SS1 and the second stretching and shrinking treatment zone SS2, the temperature was raised in the first stretching and shrinking treatment zone so that the first stretching and shrinking treatment temperature became 150°C, and then the temperature was lowered from 150°C to 105°C in the second stretching treatment zone. In the stretching and shrinking treatment zone, it was shrunk by 33.36% in the width direction and stretched 2.4 times in the longitudinal direction at the same time. Thereafter, in the release zone D, the clips gripping the laminate were released to produce a long laminate. The clip size was 15 mm.

[0069] Next, the long laminate was immersed in an insolubilization bath (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment). Next, it was immersed in a dyeing bath (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer became a desired value (dyeing treatment). Next, it was immersed in a crosslinking bath (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Thereafter, while the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt%, potassium iodide concentration: 5 wt%) at a liquid temperature of 64°C, uniaxial stretching was performed in the longitudinal direction (length direction) between rolls with different peripheral speeds so that the total stretching ratio became 5.5 times (stretching treatment in water). Thereafter, the laminate was immersed in a cleaning bath (aqueous solution obtained by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, the film was dried in an oven maintained at about 90°C, and brought into contact with a stainless steel (SUS) heated roll whose surface temperature was maintained at about 75°C (drying shrinkage treatment). In this way, a polarizer having a thickness of 5.5 μm was obtained on the resin substrate. An HC-TAC film was attached to the surface of the polarizer obtained above (the surface opposite to the resin substrate) via a UV-curable adhesive. The HC-TAC film was a triacetyl cellulose (TAC) film (thickness 25 μm) with a hard coat (HC) layer (thickness 7 μm) formed on it, and the TAC film was attached to the polarizer side. Next, the resin substrate was peeled off to obtain a polarizing plate having a configuration of HC layer / TAC film (protective layer) / polarizer.

[0070] [Examples 2 to 6] A long laminate was prepared in the same manner as in Example 1, except that the first stretching and shrinking treatment temperature, the stretching ratio and the shrinkage rate in the stretching and shrinking treatment were changed as shown in Table 1, and then a polarizing plate was obtained in the same manner as in Example 1.

[0071] (Comparative Example 1) A laminate of an amorphous PET substrate / PVA layer was produced in the same manner as in Example 1. Next, the laminate was uniaxially stretched at its free end 2.4 times in the machine direction (longitudinal direction) between rolls with different peripheral speeds in an oven at 130°C, and shrunk by 25.68% in the width direction. The dyeing process and subsequent procedures were the same as in Example 1 to produce a long laminate, and then a polarizing plate was obtained in the same manner as in Example 1.

[0072] (Comparative Example 2) In Comparative Example 1, an attempt was made to produce a long laminate in the same manner as in Comparative Example 1, except that the processing temperature for the stretching and shrinking treatment was set to 150°C, but the laminate broke and it was not possible to produce a long laminate.

[0073] (Comparative Examples 3 to 7) A long laminate was obtained in the same manner as in Example 1, except that the temperature in the first stretching and shrinking treatment, the stretch ratio in the stretching and shrinking treatment, and the shrinkage rate were changed as shown in Table 1.

[0074] [evaluation] The long laminates obtained in the examples and comparative examples were evaluated as follows, and the results are shown in Table 1. 1. Thickness Thicknesses of 10 μm or less were measured using an interference film thickness meter (Otsuka Electronics Co., Ltd., product name "MCPD-3000"), and thicknesses of more than 10 μm were measured using a digital micrometer (Anritsu Corporation, product name "KC-351C").

[0075] 2. Polarization degree and single transmittance The resin substrate was peeled off from the PVA-based resin layer (polarizing film) of the long laminate obtained in each Example or Comparative Example. The PVA-based resin layer was then measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V-7100") to determine the single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc, which were then used as the Ts, Tp, and Tc values of the polarizer, respectively. These Ts, Tp, and Tc values are Y values measured using a 2-degree visual field (C light source) according to JIS Z8701 and corrected for luminosity. From the obtained Tp and Tc, the degree of polarization P was calculated using the following formula. Polarization degree P(%)={(Tp-Tc) / (Tp+Tc)} 1 / 2 ×100

[0076] 3. Crystallinity of PVA The X-ray diffraction device used was a Rigaku Corporation product called "SmartLab," and the two-dimensional detector used was a Rigaku Corporation product called "HyPix3000." The PVA-based resin layer was peeled from the polarizing plate obtained in the Examples and Comparative Examples. Next, PVA-based resin layers were stacked to a total thickness of approximately 150 μm to prepare a sample. X-rays with a wavelength of 1.5406 Å were transmitted through the sample perpendicular to the thickness direction, and scattered light was detected using a two-dimensional detector placed on the opposite side of the sample from the light source, resulting in a two-dimensional scattering image. The obtained scattering image was subjected to background correction, and then integrated over the entire azimuthal angle (360°) with the beam center as the axis to obtain a one-dimensional profile of the integrated X-ray intensity versus scattering angle 2θ. Next, waveform separation of the crystalline and amorphous peaks was performed on the obtained one-dimensional profile within the scattering angle 2θ range of 14° to 28.5°, and the crystallinity (%) was calculated using the following formula: Crystallinity (%) = crystalline peak area / (crystalline peak area + amorphous peak area) × 100

[0077] 4. Orientation Function The polarizing films obtained in the examples and comparative examples were subjected to attenuated total reflection (ATR) spectroscopy of the polarizing film surface using a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, product name: "Frontier") and polarized infrared light as the measurement light. Germanium crystallites were used as the crystallites to which the polarizing film was adhered, and the angle of incidence of the measurement light was 45°. The orientation function was calculated using the following procedure. The incident polarized infrared light (measurement light) was polarized light (s-polarized light) vibrating parallel to the surface to which the germanium crystal sample was adhered, and the absorbance spectrum of each was measured with the stretching direction of the polarizing film positioned perpendicular (⊥) and parallel ( / / ) to the polarization direction of the measurement light. From the obtained absorbance spectrum, the λ / λ (3330 cm -1 Intensity) was used as a reference (2941 cm -1 The intensity (I) was calculated. ⊥ is obtained from the absorbance spectrum obtained when the stretching direction of the polarizing film is placed perpendicular (⊥) to the polarization direction of the measurement light (2941 cm -1 strength) / (3330cm -1 In addition, I / / is obtained from the absorbance spectrum obtained when the stretching direction of the polarizing film is arranged parallel ( / / ) to the polarization direction of the measurement light (2941 cm -1 strength) / (3330cm -1 Intensity), where (2941 cm -1 Intensity) is the bottom of the absorbance spectrum, 2770 cm -1 and 2990cm -1 2941cm when using this as the baseline -1 is the absorbance of (3330cm -1 Strength) is 2990cm -1 and 3650cm -1 3330cm when the baseline is -1 The absorbance of the obtained I ⊥ and I / / The orientation function f was calculated according to Equation 1. When f = 1, it is completely oriented, and when f = 0, it is random. -1 The peak at 3330cm is said to be due to the vibration of the main chain (-CH2-) of PVA in the polarizing film. -1 The peak is said to be due to the vibration of the hydroxyl group of PVA. (Formula 1)f=(3<cos2θ> -1) / 2 =(1-D) / [c(2D+1)] however c=(3cos 2 β-1) / 2 So, as mentioned above, 2941cm -1 If we use β=90°, then f=-2×(1-D) / (2D+1). θ: angle of molecular chain relative to stretching direction β: Angle of the transition dipole moment relative to the chain axis D=(I ⊥ ) / (I / / ) I ⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are perpendicular I / / : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing film are parallel

[0078] 5.Bleaching the edges A test piece (50 mm × 50 mm) was cut from the polarizing plate obtained above, with two opposing sides in the stretching direction of the polarizer and in a direction perpendicular to the stretching direction. The test piece was then attached to an alkali-free glass plate with an adhesive to prepare a measurement sample. This measurement sample was heated and humidified in an oven at 65°C and 95% RH for 240 hours. It was then placed in a crossed-Nicol configuration with a standard polarizing plate and the state of edge discoloration of the polarizer was examined under a microscope. Specifically, the amount of discoloration from the polarizer edge (edge discoloration amount: μm) was measured. An Olympus MX61L microscope was used to measure the edge discoloration amount from images taken at 10x magnification. The average of the edge discoloration amount a in the stretching direction and the edge discoloration amount b in the direction perpendicular to the stretching direction was taken as the edge discoloration amount. The evaluation criteria for edge discoloration amount were as follows. The evaluation results are shown in Table 1. ◎ (Best): Edge discoloration amount 350 μm or less ○ (Good): Edge discoloration amount is over 350 μm and 400 μm or less △ (Good): Edge discoloration amount is over 400 μm and 700 μm or less × (Room for improvement): Edge discoloration exceeds 700 μm

[0079] [Table 1]

[0080] [evaluation] The PVA-based resin layer of the long laminate obtained by the manufacturing method of the embodiment of the present invention had a high degree of crystallinity. When the PVA-based resin layer of the long laminate was used as a polarizing film, it had excellent optical properties and edge discoloration was suppressed. In Example 6, wrinkles were observed in the laminate during transportation, but these were not serious enough to cause practical problems. [Industrial Applicability]

[0081] The production method of the present invention can perform a stretching and shrinking treatment of an intermediate laminate at a high draw ratio and a high shrinkage rate even at high temperatures. According to the production method of the embodiment of the present invention, a long laminate having a PVA-based resin layer with a high crystallinity can be obtained. [Explanation of symbols]

[0082] 10 Rail 20 clips 50 Intermediate laminate 100 Stretching equipment

Claims

1. A method for producing a long laminate having a resin substrate and a polyvinyl alcohol-based resin layer having a crystallinity of 45% to 55%, comprising the steps of: a stretching and shrinking treatment including stretching an intermediate laminate having a resin substrate and a polyvinyl alcohol-based resin layer in the longitudinal direction and shrinking the intermediate laminate in the width direction using a tenter stretching device equipped with a plurality of clips as a gripping means, In the stretching and shrinking treatment, the stretching ratio N (times) in the longitudinal direction and the shrinkage rate ΔW (%) in the width direction satisfy 0.135<ΔW / N<0.

145.

2. The method for producing a long laminate according to claim 1, wherein the stretching ratio N in the longitudinal direction is 2.0 to 3.5 times.

3. The method for producing a long laminate according to claim 2, further comprising another stretching step, wherein the total stretching ratio in the method for producing the long laminate is 5.0 times to 6.0 times.

4. The method for producing a long laminate according to claim 1, wherein the stretching and shrinking treatment comprises a first stretching and shrinking treatment comprising stretching the intermediate laminate in the longitudinal direction at a treatment temperature of 150°C or higher and shrinking it in the width direction.

5. The method for producing a long laminate according to claim 4, wherein the stretching and shrinking treatment further comprises a second stretching and shrinking treatment, following the first stretching and shrinking treatment, comprising stretching the intermediate laminate in the longitudinal direction at a treatment temperature of less than 150°C and shrinking it in the width direction.

6. A long laminate obtained by the manufacturing method according to any one of claims 1 to 5.

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