Laminated film and its manufacturing method

Abstract

To provide a laminated film that can reduce the contamination of a production device therefor while having excellent slipperiness.SOLUTION: A laminated film comprises a resin layer (a) comprising a resin (A), and a resin layer (b) provided on at least one principal face of the resin layer (a) and comprising particles and a resin (B). As measured by TPD-MS method under a helium gas, the total amount of gas released from the resin layer (b) when the temperature of the resin layer (b) is raised from 25°C to 280°C at a rate of 10°C / min is 30 wt.ppm or less relative to the weight of the resin layer (b).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminated film and a method for producing the same. [Background technology]

[0002] A polarizing plate used in a liquid crystal display device or the like usually includes a polarizer and a polarizer protective film for protecting the polarizer. Patent Documents 1 and 2 disclose polarizer protective films containing fine particles. Patent Documents 3 and 4 describe laminated films in which a surface layer is further laminated on a resin layer containing an ultraviolet absorber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3499974 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-011394 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-181615 [Patent Document 4] International Publication No. 2020 / 085326 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to use a resin film in an optical element such as an image display device, the resin film is required to have few defects such as scratches. Depending on the type of resin forming the resin film, the resin film may have low slip properties. When a resin film with low slip properties is wound into a roll, defects such as scratches may increase. Therefore, the inventors have devised a laminated film in which a resin layer formed from a material containing resin and particles is laminated on a resin layer in order to improve the slipperiness of the resin film, regardless of the type of resin that forms the resin film.

[0005] However, in the process of producing such a laminated film by extrusion molding, contamination may adhere to the production equipment, such as the cooling roll, resulting in a deterioration in the quality of the laminated film.

[0006] Therefore, there is a demand for a laminate film that has good slip properties while reducing contamination of the production equipment, and a method for producing such a laminate film. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the dirt adhering to the manufacturing equipment is caused by a resin layer formed of a material containing a resin and particles laminated on a laminate film. The present inventors have found that the above problem can be solved by using a specific resin layer as the resin layer containing a resin and particles, and have completed the present invention. That is, the present invention provides the following.

[0008] [1] A laminated film comprising a resin layer (a) containing a resin (A) and a resin layer (b) provided on at least one main surface of the resin layer (a) and containing particles and a resin (B), A laminated film, wherein the total amount of gas released from the resin layer (b) when the temperature of the resin layer (b) is raised from 25°C to 280°C at a rate of 10°C / min, as measured under helium gas by a TPD-MS method, is 30 ppm by weight or less based on the weight of the resin layer (b). [2] A method for producing the laminated film according to [1], The manufacturing method includes: Step (1) of heating the resin (A) to obtain a molten resin (A'); Step (2) of kneading the particles and the resin (B) using a twin-screw extruder; Step (3) of heating the particles and the resin (B) to obtain a molten resin (B'); and a step (4) of extruding the molten resin (A') and the molten resin (B') into layers, In the step (2), venting is performed from the twin-screw extruder. A method for manufacturing a laminated film. [3] The method for producing a laminated film according to [2], wherein the step (2) comprises kneading the particles and the resin (B) in the twin-screw extruder to obtain a kneaded mixture of the particles and the resin (B), and the step (3) comprises heating the kneaded mixture of the particles and the resin (B) to obtain the molten resin (B'), and the step (3) is carried out after the step (2). [4] The method for producing a laminated film according to [2], wherein the steps (2) and (3) are carried out simultaneously using the same twin-screw extruder. [5] The method for producing a laminated film according to any one of [2] to [4], wherein the inner diameter D of the twin-screw extruder and the length Lv from the outlet of the twin-screw extruder to the vent port satisfy the following formula (1): 2< Lv / D ≦15 (1) [6] The method for producing a laminated film according to any one of [2] to [5], wherein the venting is carried out at a suction pressure of more than 1 kPa and not more than 100 kPa. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a laminate film that has good slip properties and is capable of reducing contamination of production equipment; and a method for producing such a laminate film. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a laminated film according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a laminated film according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and can be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below can be combined as appropriate. In addition, in the drawings, the same components are designated by the same reference numerals, and their description may be omitted.

[0012] In the following description, a "long" film refers to a film having a length that is 5 times or more its width, preferably 10 times or more its width, and specifically refers to a film having a length that can be wound into a roll for storage or transportation. There is no particular upper limit to the length of the film, and it can be, for example, 100,000 times or less its width.

[0013] [1. Laminated film] [1.1. Overview of laminated film] A laminated film according to one embodiment of the present invention comprises a resin layer (a) containing a resin (A), and a resin layer (b) provided on at least one main surface of the resin layer (a) and containing particles and a resin (B), wherein the total amount of gas released from the resin layer (b) when the temperature of the resin layer (b) is raised from 25°C to 280°C at a rate of 10°C / min, as measured by TPD-MS under helium gas, is 30 ppm by weight or less based on the weight of the resin layer (b).

[0014] The laminate film has a resin layer (b) containing particles and a resin (B) provided on at least one main surface of the resin layer (a), so that whether the resin layer (a) is a layer with high slipperiness or a layer with low slipperiness, the resin layer (b) imparts good slipperiness to the laminate film, thereby reducing blocking of the laminate film and preventing scratches on the laminate film.

[0015] On the other hand, the laminated film tends to contaminate the manufacturing equipment more easily than a film that does not have a particle-containing resin layer (b). Although this does not limit the scope of the present invention, the contamination of the manufacturing equipment is presumed to be due to residual solvent contained in the particles contained in the resin layer (b) and volatile decomposition components generated by heating the particles.

[0016] In the laminated film, the total amount of gas released from the resin layer (b) under specified conditions is usually 30 ppm by weight or less, preferably 20 ppm by weight or less, more preferably 10 ppm by weight or less, and even more preferably 5 ppm by weight or less, based on the weight of the resin layer (b). It is preferably 0 ppm by weight, but may be 1 ppm by weight or more.

[0017] When the total amount of gas released from the resin layer (b) under predetermined conditions is within the above range, contamination of the production equipment can be reduced when producing a laminate film with reduced blocking. In particular, when the laminate film is produced by a melt extrusion method, contamination of the rolls for cooling the extruded laminate film can be effectively reduced.

[0018] The total amount of gas released from the resin layer (b) can be measured under helium gas by TPD-MS (Temperature Programmed Desorption-Mass Spectrometry). The temperature is increased at a rate of 10°C / min, and the total amount of gas released from 25°C to 280°C is measured based on the weight of the sample resin layer (b).

[0019] The resin layer (b) to be used as a sample can be prepared by peeling the surface resin layer (b) from the laminated film using a microtome, and then weighing out 1 mg of the peeled resin layer (b).

[0020] [1.2. Resin layer (a)] The resin layer (a) contains a resin (A). The resin (A) is preferably a thermoplastic resin, which generally contains a polymer and optional components that are used as needed. As the polymer that can be contained in the resin (A), an alicyclic structure-containing polymer is preferred because it can improve the heat resistance and moisture resistance of the laminated film.

[0021] The alicyclic structure-containing polymer refers to a polymer containing an alicyclic structure in the main chain and / or side chain. As the alicyclic structure-containing polymer, an alicyclic structure-containing polymer containing an alicyclic structure in the main chain is preferred from the viewpoint of improving the mechanical strength and heat resistance of the laminated film.

[0022] Examples of the alicyclic structure include saturated alicyclic hydrocarbon (cycloalkane) structures, unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures, etc. Among them, from the viewpoints of mechanical strength, heat resistance, etc., cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are more preferred.

[0023] The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 or more, preferably 5 or more, and usually 30 or less, preferably 20 or less, more preferably 15 or less. By ensuring that the number of carbon atoms constituting the alicyclic structure falls within the above range, the mechanical strength, heat resistance, and formability of the laminated film are highly balanced, which is preferable.

[0024] The proportion of repeating units containing an alicyclic structure in the alicyclic structure-containing polymer can be appropriately selected depending on the intended use of the laminate film. The proportion of repeating units containing an alicyclic structure in 100% by weight of the alicyclic structure-containing polymer is preferably 55% by weight or more, more preferably 70% by weight or more, even more preferably 90% by weight or more, and is usually 100% by weight or less. When the proportion of repeating units containing an alicyclic structure in the alicyclic structure-containing polymer is within the above range, the transparency and heat resistance of the laminate film can be effectively improved.

[0025] Examples of the polymer having an alicyclic structure include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrogenated products thereof. Among these, norbornene polymers and hydrogenated products thereof are preferred because of their good transparency and moldability.

[0026] Examples of norbornene-based polymers include ring-opening polymers of monomers having a norbornene structure and their hydrogenated products; and addition polymers of monomers having a norbornene structure and their hydrogenated products. Examples of ring-opening polymers of monomers having a norbornene structure include ring-opening homopolymers of one type of monomer having a norbornene structure, ring-opening copolymers of two or more types of monomers having a norbornene structure, and ring-opening copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of addition polymers of monomers having a norbornene structure include addition homopolymers of one type of monomer having a norbornene structure, addition copolymers of two or more types of monomers having a norbornene structure, and addition copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith. Examples of these polymers include the polymers disclosed in, for example, JP 2002-321302 A.

[0027] Specific examples of norbornene polymers and hydrogenated products thereof include "ZEONOR" manufactured by Nippon Zeon Co., Ltd.; "ARTON" manufactured by JSR Corporation; and "TOPAS" manufactured by TOPAS ADVANCED POLYMERS.

[0028] The resin (A) may contain one type of alicyclic structure-containing polymer alone, or may contain two or more types of alicyclic structure-containing polymers in any combination at any ratio. From the viewpoint of significantly exhibiting the advantages of the present invention, the proportion of the alicyclic structure-containing polymer in the resin (A) is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and is usually 100% by weight or less.

[0029] Resin (A) may contain optional components other than the polymer, as long as the effects of the present invention are not significantly impaired. Examples of optional components include stabilizers such as antioxidants, heat stabilizers, and near-infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments; and antistatic agents. Resin (A) may contain one optional component alone, or two or more optional components in any combination in any ratio.

[0030] The resin (A) may contain an ultraviolet absorber as an optional component. This allows the laminate film to acquire resistance to ultraviolet light. Therefore, when a laminate film containing an ultraviolet absorber is used as an optical film such as a polarizer protective film, the laminate film and the object to be protected, such as a polarizer protected by this laminate film, can be effectively protected from deterioration due to ultraviolet light.

[0031] Examples of the ultraviolet absorber that can be used include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, acrylonitrile-based ultraviolet absorbers, and hydroxyphenyltriazine-based ultraviolet absorbers. Among them, as the ultraviolet absorber, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2,4-di-tert-butyl-6-(5-chlorobenzotriazol-2-yl)phenol, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]-phenol, 2,4-bis(2-hydroxy-4-butoxyphenyl)-6-(2,4-dibutoxyphenyl)-1,3,5-triazine, and the like are preferably used. The ultraviolet absorber may be used alone or in combination of two or more kinds in any ratio.

[0032] The weight ratio of the ultraviolet absorber in the resin (A) is preferably 1.0 wt% or more, more preferably 3.0 wt% or more, and preferably 23 wt% or less, more preferably 10 wt% or less. When the weight ratio of the ultraviolet absorber is equal to or greater than the lower limit of the above range, ultraviolet rays can be effectively blocked. When the concentration of the ultraviolet absorber is equal to or less than the upper limit of the above range, point defects in the laminate film due to poor dispersion of the ultraviolet absorber can be suppressed, and a decrease in the strength of the laminate film can be suppressed.

[0033] The thickness of the resin layer (a) can be set arbitrarily depending on the intended use of the laminated film, etc. The thickness of the resin layer (a) may be, for example, 1 μm or more and 99 μm or less.

[0034] [1.3. Resin layer (b)] The resin layer (b) contains particles and a resin (B). Resin (B) is preferably a thermoplastic resin. Thermoplastic resins typically contain a polymer and optional components that are used as needed. Examples of optional components include the same components as those that may be contained in resin (A).

[0035] The polymer that can be contained in resin (B) may be the same as or different from the polymer that can be contained in resin (A). By making the polymer that can be contained in resin (B) the same as the polymer that can be contained in resin (A), the affinity between resin layer (a) and resin layer (b) is usually increased, and therefore the adhesive strength between resin layer (a) and resin layer (b) can be increased. As the polymer that can be contained in the resin (B), an alicyclic structure-containing polymer is preferred because it can improve the heat resistance and moisture resistance of the laminated film.

[0036] Examples of the alicyclic structure-containing polymer that can be contained in the resin (B) include the same examples and preferred examples as the alicyclic structure-containing polymer that can be contained in the resin (A).

[0037] The resin (B) may contain one type of alicyclic structure-containing polymer alone, or may contain two or more types of alicyclic structure-containing polymers in any combination at any ratio. From the viewpoint of significantly exhibiting the advantages of the present invention, the proportion of the alicyclic structure-containing polymer in the resin (B) is preferably 80% by weight or more, more preferably 85% by weight or more, even more preferably 90% by weight or more, and is usually 100% by weight or less.

[0038] The particles contained in the resin layer (b) may be inorganic particles, organic particles, or composite particles combining inorganic and organic materials. Hereinafter, the particles contained in the resin layer (b) may also be referred to as particles C. Particles C may be used alone or in combination of two or more types in any ratio.

[0039] In one embodiment, the particles C are preferably organic particles, and more preferably organic polymer particles, from the viewpoint of facilitating adjustment of the refractive index of the particles and narrowing the spread of the particle size distribution.

[0040] Examples of organic polymers that can form particles C include crosslinked copolymers of methyl methacrylate and styrene, and crosslinked polymers containing an alicyclic structure. From the viewpoint of facilitating adjustment of the refractive index, particles C are preferably particles of a crosslinked copolymer of methyl methacrylate and styrene. When the resin (B) contains an alicyclic structure-containing polymer, the particles C are preferably particles of an alicyclic structure-containing crosslinked polymer from the viewpoint of obtaining particles having a refractive index close to that of the resin (B).

[0041] As described above, particles C may be particles of a crosslinked copolymer of methyl methacrylate and styrene. Here, the crosslinked copolymer of methyl methacrylate and styrene is a copolymer of methyl methacrylate, styrene, and a crosslinkable monomer. Examples of the crosslinkable monomer include polyfunctional monomers containing two or more polymerizable groups per molecule, such as divinylbenzene, ethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,5-pentanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and tripropylene glycol dimethacrylate. The crosslinked copolymer particles can be obtained, for example, by suspension polymerization of a monomer mixture containing methyl methacrylate, styrene, and a crosslinkable monomer. The weight ratio of methyl methacrylate, styrene, and the crosslinkable monomer can be set arbitrarily.

[0042] The particles of the crosslinked copolymer of methyl methacrylate and styrene are commercially available in a variety of average particle sizes, and these can be used. An example of a commercially available product of such particles is "Techpolymer" manufactured by Sekisui Plastics Co., Ltd.

[0043] As described above, particles C may be particles of an alicyclic structure-containing crosslinked polymer. Here, the alicyclic structure-containing crosslinked polymer is a polymer containing a structure in which repeating units containing an alicyclic structure are crosslinked. Examples and preferred examples of the alicyclic structure contained in the alicyclic structure-containing crosslinked polymer, the preferred range of the number of carbon atoms constituting the alicyclic structure, and the preferred range of the proportion of repeating units containing the alicyclic structure are the same as the examples and preferred ranges described for the alicyclic structure-containing polymer in resin (B). When resin (B) contains an alicyclic structure-containing polymer, by using particles C as particles of an alicyclic structure-containing crosslinked polymer, the refractive index of particles C can be made close to the refractive index of resin (B) containing an alicyclic structure-containing polymer that can be contained in resin layer (b), thereby effectively reducing the internal haze of the laminate film.

[0044] Examples of the crosslinked polymer containing an alicyclic structure include norbornene-based crosslinked polymers, monocyclic olefin-based crosslinked polymers, cyclic conjugated diene-based crosslinked polymers, vinyl alicyclic hydrocarbon-based crosslinked polymers, and hydrogenated versions thereof. Among these, norbornene-based crosslinked polymers and hydrogenated versions thereof are preferred due to their good transparency.

[0045] Examples of norbornene-based crosslinked polymers include crosslinked polymers of monomer units having a norbornene structure and hydrogenated products thereof; crosslinked copolymers of a monomer having a norbornene structure and any monomer copolymerizable therewith and hydrogenated products thereof; and copolymers thereof. The copolymers may be ring-opening copolymers or addition copolymers of monomers having a norbornene structure.

[0046] Examples of the alicyclic structure-containing crosslinked polymer that can be used include particles crosslinked by suspension polymerization of a monomer having a norbornene structure in the presence of a crosslinking agent, and particles crosslinked by crosslinking a polymer having a norbornene structure in the presence of a crosslinking agent.

[0047] Particles C may be inorganic particles. Examples of inorganic particles include silica particles, synthetic zeolite particles, and glass particles. From the viewpoint of achieving a uniform particle size distribution, particles C are preferably silica particles. Silica particles having various average particle sizes are commercially available, and these can be used. Examples of commercially available products include the "QSG" series manufactured by Shin-Etsu Chemical Co., Ltd., the "Seahoster" series manufactured by Nippon Shokubai Co., Ltd., and "Admanano" manufactured by Admatechs Co., Ltd.

[0048] The number average particle diameter of the particles C is preferably 0.10 μm or more, more preferably 0.20 μm or more, and preferably 0.80 μm or less, more preferably 0.50 μm or less. When the number average particle diameter is equal to or greater than the lower limit, the slipperiness of the laminated film can be made sufficient. When the number average particle diameter is equal to or less than the upper limit, the internal haze of the laminated film can be reduced. Furthermore, when a melt containing the resin (B) and the particles C is passed through a polymer filter, clogging of the polymer filter can be reduced. Therefore, a decrease in productivity of the laminated film can be suppressed.

[0049] When the particles C are organic particles, the number average particle size of the particles C is preferably 0.1 μm or more, more preferably 0.2 μm or more, and preferably 0.8 μm or less, more preferably 0.5 μm or less.

[0050] When the particles C are inorganic particles, the number average particle size of the particles C is preferably 0.1 μm or more, and preferably 0.5 μm or less, more preferably 0.3 μm or less.

[0051] The number average particle size of particles C is a value obtained by measurement using a particle size distribution measuring device by a laser diffraction / scattering method.

[0052] It is preferable that the volume fraction of coarse particles having a particle diameter of 1 μm or more in particles C is small. This can further reduce clogging of the polymer filter when a melt containing resin (B) and particles C is passed through the polymer filter, thereby improving the productivity of the laminated film. The volume fraction of coarse particles having a particle diameter of 1 μm or more in particles C is preferably 1% or less, more preferably 0.1% or less, and is usually 0% or more, preferably 0%, but may be 0.01% or more. In calculating the proportion of coarse particles, the upper limit of the particle diameter of the coarse particles is not particularly limited, but can be, for example, 1 mm or less. However, since particles with a particle diameter greater than 1 mm are completely removed in normal production, even if particles greater than 1 mm are included in the calculation, the preferred range of the proportion of coarse particles is the same as the value described above. The volume ratio of the coarse particles in the particles C can be reduced by classifying the particles C by sieving or the like to remove the coarse particles.

[0053] The refractive index nb of the resin (B) and the refractive index nc of the particles C preferably satisfy the following formula: |nb-nc|≦0.03 When the refractive index nb and the refractive index nc satisfy the above formula, the internal haze of the laminated film can be further reduced. The value of |nb-nc| is more preferably 0.02 or less, further preferably 0.01 or less, and is usually 0 or more, ideally 0, but may be 0.005 or more. The refractive index can be measured using light with a wavelength of 589 nm by the method described in the Examples.

[0054] In the resin layer (b), the weight proportion of particles C is preferably 3% by weight or more, more preferably 4% by weight or more, even more preferably 5% by weight or more, and preferably 10% by weight or less, more preferably 9% by weight or less, even more preferably 8% by weight or less, where the total weight of particles C and resin (B) is 100% by weight.

[0055] By having the weight proportion of particles C in the resin layer (b) be equal to or greater than the lower limit, even if the laminated film is a long film exceeding 2000 m in length and is subjected to a large load near the core when rolled, the improved slipperiness of the film makes it less likely for blocking to occur near the core, and makes it less likely for defects such as scratches to occur.

[0056] When the weight proportion of particles C in the resin layer (b) is equal to or less than the upper limit, the surface roughness of the resin layer (b) is appropriate, and an increase in external haze of the laminate film is suppressed. As a result, when the laminate film is used as a component of an image display device, the visibility of the image display device can be improved. Furthermore, when an optional additional layer such as a hard coat layer is laminated on the laminate film, adhesion between the resin layer (b) and the additional layer is improved. Furthermore, when the weight proportion of particles C in the resin layer (b) is equal to or less than the upper limit, it is advantageous in terms of manufacturing costs. Furthermore, when producing a material for constituting the resin layer (b), poor dispersion of particles C in the resin (B) can be suppressed.

[0057] The resin layer (b) may contain an ultraviolet absorber in addition to the resin (B) and the particles C. From the viewpoint of suppressing bleed-out of the ultraviolet absorber, the weight ratio of the ultraviolet absorber in the resin layer (b) to 100 parts by weight of the resin (B) is preferably 2 parts by weight or less, more preferably 1 part by weight or less, and is usually 0 parts by weight or more, and may be 0 parts by weight or 0.1 parts by weight or more.

[0058] The thickness of the resin layer (b) is preferably 1 μm or more, more preferably 1.5 μm or more, and preferably 5 μm or less, more preferably 3 μm or less. When the thickness of the resin layer (b) is equal to or greater than the lower limit, the thickness can be easily controlled when forming the resin layer (b) by extrusion molding such as coextrusion. When the thickness of the resin layer (b) is equal to or less than the upper limit, the slipperiness of the resin layer (b) containing the particles C is balanced with the decrease in strength of the resin layer (b), improving the strength of the laminate film. Furthermore, breakage of the laminate film during transport is suppressed, improving the handleability of the laminate film. When the laminate film has multiple resin layers (b), it is preferable that the thickness of each resin layer (b) be within the above range.

[0059] The ratio of the thickness of the resin layer (b) to the thickness of the resin layer (a) (thickness of the resin layer (b) / thickness of the resin layer (a)) is preferably 0.32 or less, more preferably 0.25 or less, and even more preferably 0.11 or less. When this ratio is equal to or less than the upper limit, the strength of the laminated film can be improved. Furthermore, this ratio is preferably 0.02 or more, more preferably 0.04 or more. When this ratio is equal to or greater than the lower limit, the thickness of the laminated film can be more effectively controlled. Here, when the laminated film has multiple resin layers (b), it is preferable that the thickness of each resin layer (b) is within the above range.

[0060] [1.4. Structure of laminated film] A laminate film according to one embodiment of the present invention has a resin layer (a) and a resin layer (b). The laminate film may be a laminate film consisting of only two layers, the resin layer (a) and the resin layer (b). The laminate film may have an optional layer in addition to the resin layer (a) and the resin layer (b). The optional layer may be one layer or two or more layers. Furthermore, when two or more optional layers are present, the optional layers may be layers having the same thickness, material, etc., or may be layers of different thicknesses, material, etc. The position of the optional layer can be set arbitrarily. From the viewpoint of making the laminate film thinner, it is preferable that the laminate film has no layers other than the resin layer (a) and the resin layer (b).

[0061] The laminate film may have two resin layers (b). When the laminate film has two resin layers (b), the laminate film is usually a laminate film having resin layer (b), resin layer (a), and resin layer (b) in this order, and resin layer (b) is usually provided on the two main surfaces of resin layer (a). It is preferable that resin layer (b) is arranged on both surfaces of the laminate film, and each of the two resin layers (b) is exposed on each of both surfaces of the laminate film. When the laminate film has two resin layers (b), they may be referred to as resin layer (b1) and resin layer (b2), respectively.

[0062] From the viewpoint of suppressing the bleeding out of additives such as ultraviolet absorbers that may be contained in the resin layer (a) and further improving the slip properties, the laminated film preferably has two resin layers (b), namely, a first resin layer (b), a resin layer (a), and a second resin layer (b) in this order.

[0063] When the laminate film has two resin layers (b), the two resin layers (b) may be made of the same material and have the same thickness, or may be made of the same material but different thicknesses, or may be made of materials with different types of components, weight ratios of components, etc. When the laminate film has two resin layers (b), this can facilitate production and can suppress curling of the laminate film, so the two resin layers (b) are preferably made of the same material and have the same thickness.

[0064] The laminated film may have a plurality of resin layers (a). When the laminated film has a plurality of resin layers (a), the plurality of resin layers (a) may be composed of materials having different types of components, weight ratios of components, etc.

[0065] The layer structure of the laminated film according to the embodiment of the present invention will be described below with reference to the drawings. 1 is a cross-sectional view schematically illustrating a laminated film according to one embodiment of the present invention. The laminated film 100 of this embodiment includes a resin layer (a) 110 and a resin layer (b) 120 arranged so as to be in contact with a surface 110U, which is one of the main surfaces of the resin layer (a). The resin layer (b) 120 is arranged on the outermost surface of the laminated film 100, and a surface 120U of the resin layer (b) 120 is exposed.

[0066] 2 is a cross-sectional view schematically illustrating a laminate film according to another embodiment of the present invention. The laminate film 200 of this embodiment includes a resin layer (b) 221, a resin layer (a) 210, and a resin layer (b) 222, in this order. The resin layer (b) 221 is disposed so as to contact a surface 210U, which is one of the main surfaces of the resin layer (a) 210. The resin layer (b) 222 is disposed so as to contact a surface 210D, which is the other main surface of the resin layer (a) 210. The resin layer (b) 221 and the resin layer (b) 222 are disposed on the outermost surfaces of the laminate film 200, and the surface 221U of the resin layer (b) 221 and the surface 222D of the resin layer (b) 222 are exposed.

[0067] [1.5. Thickness, length and characteristics of laminated film] (Thickness) The thickness of the laminated film can be set to any thickness, but is preferably 10 μm or more and 100 μm or less, and more preferably 10 μm or more and 80 μm or less.

[0068] (length of laminated film) The laminate film may be in the form of a sheet or a long film. The laminate film of this embodiment is preferably in the form of a long film roll, since it can reduce the occurrence of defects such as blocking and scratches near the winding core. When the laminate film is long, the length of the laminate film may exceed 2000 m. Even when the laminate film of this embodiment is wound into a roll like this, it can reduce the occurrence of defects such as blocking and scratches near the winding core, as described above.

[0069] (UV transmittance) The laminate film preferably has low ultraviolet transmittance. The laminate film preferably has a transmittance of ultraviolet light at a wavelength of 380 nm of 4% or less, more preferably 1% or less, and usually 0% or more, and may even be 0%. A laminate film having an ultraviolet transmittance of the above upper limit or less can be suitably used as a protective film for components of an image display device (particularly components of an organic electroluminescence element, polarizers, etc.). The ultraviolet transmittance can be measured using a spectrophotometer (for example, the "V-7200DS" manufactured by JASCO Corporation).

[0070] By incorporating an ultraviolet absorber into any of the layers constituting the laminate film, the ultraviolet transmittance of the laminate film can be reduced. Of the layers constituting the laminate film, the resin layer (a) may contain an ultraviolet absorber, the resin layer (b) may contain an ultraviolet absorber, both the resin layer (a) and the resin layer (b) may contain an ultraviolet absorber, or any layer other than the resin layer (a) and the resin layer (b) may contain an ultraviolet absorber. When the laminate film is a film containing an ultraviolet absorber, it is preferable that the resin layer (a) contains an ultraviolet absorber and the resin layer (b) does not contain an ultraviolet absorber.

[0071] (Slipperiness: static friction coefficient) The laminate film has excellent slip properties. The slip properties can be evaluated by determining the static friction coefficient of the laminate film using a friction tester in accordance with JIS K7125 under a load of 1 kgf. The static friction coefficient of the laminate film, determined by the method described in the Examples section, is preferably 0.4 or more, preferably 0.8 or less, and more preferably 0.7 or less.

[0072] When the static friction coefficient of the laminate film measured under a load of 1 kgf is equal to or greater than the lower limit, the slipperiness of the laminate film can be made appropriate, and the handling properties of the laminate film when wound can be improved. Furthermore, when the static friction coefficient of the laminate film measured under a load of 1 kgf is equal to or less than the upper limit, blocking near the winding core can be reduced, and defects such as scratches can be reduced, even if a large load is applied near the winding core when the laminate film is rolled, such as a long film exceeding 2000 m in length.

[0073] (internal haze) The laminated film according to one embodiment of the present invention has low internal haze. The internal haze of the laminate film is preferably less than 0.7%, more preferably 0.6% or less, even more preferably 0.5% or less, particularly preferably 0.2% or less, and is usually 0.0% or more, ideally 0.0%. Because the internal haze of the laminate film is low, the laminate film can be suitably used as a component of an image display device that requires high-definition display performance. The internal haze of the laminate film can be measured using a haze meter.

[0074] [2. Manufacturing method of laminated film] "2.1. Overview of laminated film manufacturing method" The laminated film can be produced by any method, but is preferably produced by a production method including the following steps (1) to (4). Step (1): Heating resin (A) to obtain molten resin (A'). Step (2): Kneading the particles and the resin (B) using a twin-screw extruder. Step (3): Heating the particles and the resin (B) to obtain a molten resin (B'). Step (4): The molten resin (A') and the molten resin (B') are extruded into layers. Here, in the step (2), venting is performed from the twin-screw extruder.

[0075] The method for producing the laminated film may include any optional step in addition to the steps (1) to (4).

[0076] Step (4) is usually carried out after steps (1) to (3). Steps (1) and (3) are preferably carried out simultaneously. Step (3) is usually carried out after step (2) or simultaneously with step (2).

[0077] The heating of resin (A) in step (1) can be carried out using an extruder such as a single-screw extruder or a twin-screw extruder. When resin (A) contains optional components such as an ultraviolet absorber in addition to the polymer, the polymer and optional components may be fed into a twin-screw extruder and heated while being kneaded to melt resin (A) containing the optional components. Molten resin (A') is obtained by step (1). The heating temperature in step (1) can be appropriately set depending on the glass transition temperature (Tg) of the polymer contained in resin (A) and the weight proportion of optional components, such as an ultraviolet absorber, that may be contained in resin (A). The heating temperature in step (1) is preferably Tg + 80°C or higher, more preferably Tg + 90°C or higher, even more preferably Tg + 100°C or higher, and preferably Tg + 140°C or lower, more preferably Tg + 130°C or lower, and even more preferably Tg + 120°C or lower. Here, Tg represents the glass transition temperature of the polymer contained in resin (A). By setting the heating temperature in step (1) to be equal to or higher than the lower limit, the fluidity of molten resin (A') can be improved. Furthermore, by setting the heating temperature to be equal to or lower than the upper limit, decomposition of molten resin (A') can be suppressed.

[0078] The kneading in step (2) is carried out using a twin-screw extruder. The twin-screw extruder may be of any type. The twin-screw extruder may be a counter-rotating twin-screw extruder or a co-rotating twin-screw extruder, but is preferably a co-rotating twin-screw extruder in terms of particle dispersibility.

[0079] The twin-screw extruder used in step (2) is equipped with a vent port for venting. The twin-screw extruder may have only one vent port or may have multiple vent ports. The vent port is usually provided on the circumferential surface of the barrel of the twin-screw extruder. By connecting a pressure reducing device to the vent port, volatile substances can be sucked from inside the barrel of the twin-screw extruder. When the twin-screw extruder has multiple vent ports, venting may be performed from multiple vent ports. Preferably, the twin-screw extruder has only one vent port, and venting is performed from a single vent port.

[0080] In step (2), venting can prevent the production equipment from being contaminated by residual solvent, volatile decomposition products of resin (B) or particles when the material containing resin (B) and particles is melted and extruded.

[0081] Venting is preferably carried out so that the inner diameter D of the twin-screw extruder and the axial length Lv from the outlet of the twin-screw extruder to the vent port satisfy the following formula (1). 2< Lv / D ≦15 (1) The value of (axial length Lv from the outlet of the twin-screw extruder to the vent port) / (axial inner diameter D) is more preferably 3 or more, more preferably 10 or less, and even more preferably 8 or less. When the value of Lv / D exceeds 2, it is possible to suppress the resin (B) from being sucked through the vent port, thereby improving operational stability. When the value of Lv / D is equal to or less than the upper limit, it is possible to efficiently vent the volatile components contained in the resin (B).

[0082] Venting is performed so that the suction pressure (absolute pressure) is preferably 100 kPa or less, more preferably 40 kPa or less, even more preferably 30 kPa or less, even more preferably 25 kPa or less, even more preferably 20 kPa or less, and preferably exceeds 1 kPa, more preferably exceeds 5 kPa. A suction pressure exceeding 1 kPa can prevent resin (B) from being suctioned through the vent port, improving operational stability. A suction pressure of equal to or less than the upper limit of the above range can efficiently vent volatile components contained in resin (B).

[0083] The particles and resin (B) in step (3) can be heated using an extruder such as a single-screw extruder or a twin-screw extruder. The heating temperature in step (3) can be appropriately set depending on the glass transition temperature (Tg) of the polymer contained in resin (B) and the glass transition temperature of the particles. The heating temperature in step (3) is preferably Tg + 80°C or higher, more preferably Tg + 90°C or higher, even more preferably Tg + 100°C or higher, and preferably Tg + 140°C or lower, more preferably Tg + 130°C or lower, and even more preferably Tg + 120°C or lower. Here, Tg represents the glass transition temperature of the polymer contained in resin (B). By setting the heating temperature in step (3) to the aforementioned lower limit or higher, the fluidity of molten resin (B') can be improved. Furthermore, by setting the heating temperature to the aforementioned upper limit or lower, decomposition of molten resin (B') can be suppressed.

[0084] The extrusion of the molten resin (A') and the molten resin (B') into layers in step (4) can be carried out by a co-extrusion molding method. Examples of the co-extrusion molding method include the co-extrusion T-die method, the co-extrusion inflation method, and the co-extrusion lamination method, with the co-extrusion T-die method being preferred. Examples of the co-extrusion T-die method include the feedblock method and the multi-manifold method, with the feedblock method being preferred in terms of simplifying the equipment configuration.

[0085] The molten resin (A') and the molten resin (B') extruded into layers in step (4) are usually cooled. An example of a cooling means is a cooling roll. When a cooling roll is used as the cooling means, the molten resin (A') and the molten resin (B') extruded into layers are cast onto the cooling roll and conveyed, whereby the molten resin (A') and the molten resin (B') extruded into layers are cooled and solidified, and a laminated film in which the resin layer (a) and the resin layer (b) are laminated is produced.

[0086] The temperature of the cooling roll is preferably Tg-10° C. or lower, more preferably Tg-20° C. or lower, even more preferably Tg-30° C. or lower, and preferably Tg-80° C. or higher, where Tg represents the glass transition temperature of the polymer contained in the resin (A).

[0087] The method for producing a laminated film may include a step of stretching the laminated film extruded in step (4) by any method. For example, the laminate film may be a film that has undergone any stretching step after step (4), such as longitudinal uniaxial stretching, transverse uniaxial stretching, longitudinal and transverse simultaneous biaxial stretching, sequential biaxial stretching, or oblique stretching. Therefore, the laminate film may be an unstretched film, or a stretched film. The laminate film is preferably an unstretched film. Unstretched films are preferred from three viewpoints: they are less likely to disrupt the polarization of an image display device, particles are less likely to fall off during film production, and cohesive failure is less likely to occur near the surface layer of the laminate film, ensuring adhesive strength between the laminate film and other components.

[0088] [2.2. First embodiment of method for producing laminated film] In the method for producing a laminated film according to the first embodiment, the step (2) includes kneading the particles and the resin (B) in the twin-screw extruder to obtain a kneaded mixture of the particles and the resin (B), and the step (3) includes heating the kneaded mixture of the particles and the resin (B) to obtain the molten resin (B'), and the step (3) is carried out after the step (2).

[0089] In the method for producing a laminated film according to this embodiment, steps (2) and (3) are not performed simultaneously, but step (3) is performed after step (2). In step (2), as described above, venting is performed from the twin-screw extruder. The venting conditions can be the same as the preferred conditions described above.

[0090] Step (2) may further include a step of molding the kneaded product of the particles obtained by kneading with the twin-screw extruder and the resin (B) into pellets.

[0091] In step (3), examples of the apparatus for heating the kneaded material to obtain the molten resin (B') include a single-screw extruder and a twin-screw extruder, with the single-screw extruder being preferred since it allows for a simpler apparatus configuration.

[0092] The manufacturing method of this embodiment has the advantage that venting is performed in the step of obtaining a kneaded product of the particles and resin (B), which effectively reduces contamination of the manufacturing equipment used in the subsequent steps and also reduces foreign matter (dye deposits) adhering to the die opening.

[0093] [2.3. Second embodiment of the method for producing laminated film] In the method for producing a laminated film according to this embodiment, the steps (2) and (3) are carried out simultaneously using the same twin-screw extruder. That is, in this production method, particles and resin (B) are supplied to the twin-screw extruder and heated while being kneaded to obtain a molten resin (B') containing the particles and a melt of resin (B). In step (2), as described above, venting is performed from the twin-screw extruder. The venting conditions can be the same as the preferred conditions described above.

[0094] In the production method of this embodiment, the average residence time from the vent port of the twin-screw extruder used in steps (2) and (3) until the molten resin (A') and the molten resin (B') are extruded in layers in step (4) (usually to the die outlet of the extruder) is preferably 4 hours or less, more preferably 2 hours or less, and usually longer than 0 hours. By keeping the average residence time at or below the upper limit, decomposition of the resin (B) and the particles can be effectively suppressed.

[0095] The manufacturing method of this embodiment has the advantage that venting is performed during the process of heating the particles and resin (B) to obtain molten resin (B'), which allows for efficient reduction of volatile impurities generated before the extrusion process and also reduces foreign matter (dye deposits) adhering to the die opening.

[0096] [3. Uses of laminated film] The laminated film has good slip properties and reduced defects such as scratches, and can therefore be suitably used as an optical film such as a polarizer protective film. [Example]

[0097] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0098] In the following description, the units "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and atmospheric pressure (1 atm) unless otherwise specified.

[0099] [Evaluation method] (Measurement of outgassing amount from resin layer (b) using TPD-MS method) The resin layer (b1) was peeled off from the laminated film using a microtome. 1 mg of the peeled resin layer (b1) was weighed out. The weighed sample of the resin layer (b1) was set in a mass spectrometer equipped with a heating device. The mass spectrometer was equipped with a heating device manufactured by TRC and a mass spectrometer "GCMS-QP2020(14)" manufactured by Shimadzu Corporation. Before heating the sample, a carrier gas (helium) was continuously flowed into the measurement chamber for 15 minutes or more. The sample was then heated from room temperature (25°C) to 400°C at a rate of 10°C / min, and the generated gas was measured by mass spectrometry to obtain the total mass of the gas released from the sample during heating from room temperature to 280°C. The mass spectrometry conditions were as follows: ·MS sensitivity Gain 1.60kV Mass range m / z = 10 to 300 Atmosphere: Helium flow (50 mL / min) The ratio (ppm by weight) of the total weight of gas released from the sample during heating from room temperature to 280°C to the weight of the weighed sample was calculated.

[0100] (Thickness of each film layer) The film was sliced ​​into 0.05 μm thick slices using a microtome ("RV-240" manufactured by Yamato Koki Co., Ltd.), and the cross sections were observed under a microscope to measure the thickness of each layer.

[0101] (glass transition temperature of resin) The glass transition temperature of the resin was measured by differential scanning calorimetry using a Hitachi DSC7020. The measurement was carried out in a nitrogen atmosphere with a heating rate of 20°C / min and a holding time of 30 min.

[0102] (refractive index) The refractive index of the resin or particles was measured using the Becke method (JIS K7142). The refractive index was measured by immersing the resin pellets or particles in a liquid with a known refractive index and checking the outline of the resin pellets or particles. The microscope light source used was a monochromatic sodium D line with a wavelength of 589 nm.

[0103] (number average particle size) The number average particle size of the particles was measured by the following method. A water slurry with a particle concentration of 2% by weight was prepared and measured by the laser diffraction / scattering method using a Seishin Enterprise Co., Ltd. "LMS-3000".

[0104] (Roll contamination) The time from the start of production of the laminated film until contamination of the cooling roll began was measured. The presence or absence of roll contamination was judged based on the number of irregularity defects transferred to the laminated film due to contamination, according to the following procedure. (procedure) The laminated film was cut to a length of 1.5 m, and a projection test was carried out by placing the projector, laminated film, and screen in that order. The projector used was the "S-light" manufactured by the Japan Technology Center. The distance between the projector and the laminated film was 2300 mm. The distance between the laminated film and the screen was 200 mm. The height of the unevenness of the laminated film detected by this method was measured using a Zygo laser interferometer, and the number of unevennesses with heights exceeding 300 nm was 1 / m 2 If the roll was found to be contaminated, the roll was judged to be contaminated.

[0105] (Film static friction coefficient) The static friction coefficient of the film obtained in each example was measured using a friction tester ("TR-2" manufactured by Toyo Seiki Seisakusho) in accordance with JIS K7125. Measurements were performed under the following conditions: test piece size: 140mm x 65mm, load: 1kgf, speed: 500mm / min. The smaller the static friction coefficient, the greater the slipperiness of the film.

[0106] [Example 1] (Preparation of material for resin layer (a)) 95 parts by weight of Zeonor 1600 (glass transition temperature 160°C, refractive index 1.53) manufactured by Zeon Corporation and 5 parts by weight of an ultraviolet absorber (ADEKA STAB LA-31 (2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol] manufactured by ADEKA Corporation) were fed into a co-rotating twin-screw extruder (TEX-44αII manufactured by The Japan Steel Works, Ltd., inner diameter DΦ=25 mm, barrel length L / D=42) and kneaded at a kneading temperature of 260°C to obtain resin (A) for resin layer (a). Resin (A) was extruded in the form of strands from a twin-screw extruder and molded using a pelletizer to obtain pellets of resin (A). "ZEONOR 1600" is a resin containing an alicyclic structure-containing polymer (norbornene-based polymer). "ADK STAB LA-31" is a benzotriazole-based ultraviolet absorber.

[0107] (Preparation of Materials for Resin Layer (b1) and Resin Layer (b2): Kneading Step) 95 parts by weight of Zeon Corporation's "ZEONOR 1600" (glass transition temperature 160 °C, refractive index 1.53) as resin (B) and 5 parts by weight of Sekisui Plastics Co., Ltd.'s polymer beads "TECHPOLYMER" (number average particle diameter 0.5 μm, refractive index 1.53) as particles C were fed into a co-rotating twin-screw extruder (Japan Steel Works, Ltd.'s "TEX-44αII" model, inner diameter DΦ = 25 mm, barrel length L / D = 42 mm) equipped with a vent port. The mixture was kneaded at a kneading temperature of 270 °C while venting at a suction pressure of 20 kPa (absolute pressure) through the vent port to obtain a kneaded product of particles and resin (B) (resin (B')). The axial length Lv from the outlet of the twin-screw extruder to the vent port (where venting is performed) divided by the inner diameter D of the twin-screw extruder (Lv / D)) was 3. Resin (B') was extruded in the form of a strand from a twin-screw extruder and molded with a pelletizer to obtain pellets of resin (pr) for resin layer (b1) and resin layer (b2). Techpolymer is a microparticle of a cross-linked copolymer of methyl methacrylate and styrene. The absolute value of the difference between the refractive index nb of resin (B) and the refractive index nc of particle C (|nb-nc|) is 0.

[0108] (Production of Laminated Film: Extrusion Process of Molten Resin (A') and Molten Resin (B')) A laminated film was produced by coextrusion using a two-type, three-layer multilayer extruder (manufactured by Shibaura Machine Co., Ltd.) equipped with a feed block. The feed block was designed to form a laminate having a three-layer structure of resin layer (b1), resin layer (a), and resin layer (b2). The feed block was connected to a first single-screw extruder for melting the resin for forming resin layer (a) to obtain molten resin (A') and extruding it, and a second single-screw extruder for melting the resin for forming resin layers (b1) and (b2) to obtain molten resin (B') and extruding it. Pellets of resin (A) were supplied to the first single-screw extruder as the resin for resin layer (a), and pellets of resin (pr) were supplied to the second single-screw extruder as the resin for resin layers (b1) and (b2). The laminated molten resin was extruded from a die connected to a feed block onto a cooling roll and cooled to obtain a laminated film having a resin layer (b1), a resin layer (a), and a resin layer (b2) in this order. The resin temperature during extrusion was 265°C, and the cooling roll temperature was 130°C. The extrusion conditions were adjusted so that the thicknesses of the resin layer (b1) and the resin layer (b2) were each 2 μm, the thickness of the resin layer (a) was 36 μm, and the total thickness of the laminated film was 40 μm.

[0109] The obtained laminated film was evaluated by the above-mentioned methods.

[0110] [Example 2] A laminated film was produced by coextrusion using a two-type, three-layer multilayer extruder (manufactured by Shibaura Machine Co., Ltd.) equipped with a feed block. The feed block has a structure capable of forming a laminate having a three-layer structure of resin layer (b1), resin layer (a), and resin layer (b2). The feed block is connected to a first twin-screw extruder (manufactured by Shibaura Machine Co., Ltd., "TEM-41SS," inner diameter DΦ=41 mm, barrel length L / D=42) for melting and extruding the resin for forming resin layer (a), and a second twin-screw extruder (manufactured by Shibaura Machine Co., Ltd., "TEM-41SS," inner diameter DΦ=41 mm, barrel length L / D=42) equipped with a vent port for melting and extruding the resin for forming resin layer (b1) and resin layer (b2).

[0111] (Kneading melt extrusion process) 95 parts by weight of alicyclic structure-containing resin "ZEONOR 1600" manufactured by Zeon Corporation (glass transition temperature 160°C, refractive index 1.53) and 5 parts by weight of ultraviolet absorber (ADEKA CORPORATION "ADEKA STAB LA-31") were fed into a first twin-screw extruder and kneaded and melted at a temperature of 260°C, and the resulting molten resin (molten resin (A')) was fed into a feed block. Resin (B) was 95 parts by weight of Zeon Corporation's "Zeonor 1600" (glass transition temperature 160 ° C, refractive index 1.53), an alicyclic structure-containing resin, and particles C were 5 parts by weight of Sekisui Plastics Co., Ltd.'s polymer beads "Techpolymer" (number average particle size 0.5 μm, refractive index 1.53). The mixture was fed into a second twin-screw extruder and melted by kneading at a kneading temperature of 270 ° C while venting through the vent port at a suction pressure of 25 kPa (absolute pressure). The resulting molten resin (molten resin (B')) was fed to the feed block. The axial length Lv from the outlet of the second twin-screw extruder to the vent port for venting, divided by the inner diameter D of the twin-screw extruder, was 3 (Lv / D). The absolute value of the difference (|nb-nc|) between the refractive index nb of the resin (B) and the refractive index nc of the particles C is zero.

[0112] The laminated molten resin was extruded from a die connected to a feed block onto a cooling roll and cooled to obtain a laminated film having a resin layer (b1), a resin layer (a), and a resin layer (b2) in this order. The resin temperature during extrusion was 265°C, and the cooling roll temperature was 130°C. The extrusion conditions were adjusted so that the thicknesses of the resin layers (b1) and (b2) were each 2 μm, the thickness of the resin layer (a) was 36 μm, and the total thickness of the laminated film was 40 μm. The extrusion conditions were also adjusted so that the average residence time of the resin from the vent port of the second twin-screw extruder to the die was 4 hours.

[0113] The obtained laminated film was evaluated by the above-mentioned methods.

[0114] [Example 3] The extrusion conditions were adjusted so that the average residence time of the resin from the vent port of the second twin-screw extruder to the die was 2 hours. Except for the above, the same procedure as in Example 2 was repeated to obtain a laminated film. The obtained laminated film was evaluated by the above-mentioned method.

[0115] [Comparative Example 1] In (Preparation of materials for resin layer (b1) and resin layer (b2)), venting was not performed through the vent port of the twin-screw extruder. Except for the above, the same operation as in Example 1 was carried out to obtain a laminated film. The obtained laminated film was evaluated by the above-mentioned method.

[0116] [result] The results are shown in Table 1. In Table 1, the abbreviations have the following meanings. "ZNR1600": "ZEONOR 1600" manufactured by Zeon Corporation "UVA": UV absorber (ADEKA "ADEKA STAB LA-31") "Particle C": Polymer beads "Techpolymer" manufactured by Sekisui Plastics Co., Ltd. "Lv / D": The axial length Lv from the outlet of the twin-screw extruder to the vent port where venting is performed, divided by the inner diameter D of the twin-screw extruder

[0117] [Table 1]

[0118] From the above results, it can be seen that the laminated films of Examples 1 to 3, in which the outgassing amount of the resin layer (b) measured under specified conditions was 30 ppm by weight or less, had a low static friction coefficient and good slip properties, yet reduced roll contamination. Furthermore, the laminated film of Comparative Example 1 caused a large degree of contamination of the roll. [Explanation of symbols]

[0119] 100 Laminated Film 110 Resin layer (a) 110U side 120 Resin layer (b) 120U side 200 Laminated Film 210 Resin layer (a) 210U side 210D surface 221 Resin layer (b) 221U side 222 Resin layer (b) 222D surface

Claims

1. A method for producing a laminated film, comprising: The laminated film is a resin layer (a) containing a resin (A); and a resin layer (b) provided on at least one main surface of the resin layer (a) and containing particles and a resin (B), the particles are particles of a crosslinked copolymer of methyl methacrylate and styrene, The resin (B) contains an alicyclic structure-containing polymer, the total amount of gas released from the resin layer (b) when the resin layer (b) is heated from 25°C to 280°C at a rate of 10°C / min, as measured by a TPD-MS method under helium gas, is 30 ppm by weight or less based on the weight of the resin layer (b); The manufacturing method includes: Step (1) of heating the resin (A) to obtain a molten resin (A'); (2) a step of kneading the particles and the resin (B) using a twin-screw extruder; A step (3) of heating the particles and the resin (B) to obtain a molten resin (B'); and a step (4) of extruding the molten resin (A') and the molten resin (B') into a layer; In the step (2), venting from the twin-screw extruder is performed at a suction pressure of 20 kPa or more and 100 kPa or less. A method for manufacturing a laminated film.

2. 2. The method for producing a laminated film according to claim 1, wherein the step (2) comprises kneading the particles and the resin (B) in the twin-screw extruder to obtain a kneaded mixture of the particles and the resin (B), and the step (3) comprises heating the kneaded mixture of the particles and the resin (B) to obtain the molten resin (B'), and the step (3) is performed after the step (2).

3. The method for producing a laminated film according to claim 1, wherein the steps (2) and (3) are carried out simultaneously using the same twin-screw extruder.

4. A method for manufacturing a laminated film as described in Claim 3, wherein the average residence time of the molten resin (B') until the molten resin (A') and the molten resin (B') are extruded in layers from a vent port in the twin-screw extruder is 4 hours or less.

5. The method for producing a laminated film according to any one of claims 1 to 4, wherein an inner diameter D of the twin-screw extruder and a length Lv from an outlet of the twin-screw extruder to a vent port satisfy the following formula (1): 2< Lv / D ≦15 (1)

Images