Laminated film and its manufacturing method

Abstract

To provide a film with excellent solvent resistance and excellent adhesion to an adhesive.SOLUTION: A laminated film includes: a first resin layer, which is a layer of resin (A) that includes a crystalline polymer, has a crystallization initiation temperature Tc (A) and is in an amorphous state; and a second resin layer, which is a layer of resin (B) that includes a crystalline polymer, has a crystallization initiation temperature Tc (B) and is in a crystalline state. The laminated film satisfies the following formula (1): (Tc(A)-Tc(B))>0°C (1).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] Laminated films containing a layer formed from a crystalline resin are known (Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 204146 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-144726 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-152932 Summary of the Invention [Problem to be solved by the invention]

[0004] Resins containing polymers having crystallinity (hereinafter also referred to as crystalline polymers) are expected to have heat resistance and are sometimes used as materials for optical films such as polarizer protective films. However, even if a film formed from a resin containing a crystalline polymer has heat resistance, when it is attached to another component using an adhesive, it may have insufficient adhesion to the adhesive and may easily peel off from the other component.

[0005] Therefore, there is a demand for a film that has excellent heat resistance and excellent adhesion to adhesives, and a method for producing a film that has such excellent properties. [Means for solving the problem]

[0006] The present inventors conducted extensive research to solve the above-mentioned problems, and as a result, found that the above-mentioned problems can be solved by a laminated film comprising a layer of a predetermined resin (A) in an amorphous state and a layer of a predetermined resin (B) in a crystalline state, in which the crystallization onset temperature of the resin (A) and the crystallization onset temperature of the resin (B) have a predetermined relationship, and thus completed the present invention. That is, the present invention provides the following.

[0007] [1] A first resin layer, which is a layer of a resin (A) that contains a crystalline polymer, has a crystallization onset temperature Tc(A), and is in an amorphous state; and a second resin layer which is a layer of resin (B) which contains a crystalline polymer, has a crystallization onset temperature Tc(B), and is in a crystalline state; A laminated film that satisfies the following formula (1): (Tc(A)-Tc(B))>0℃ (1) [2] Further comprising a third resin layer which is a layer of the resin (A), The laminated film according to [1], wherein the second resin layer is provided between the first resin layer and the third resin layer. [3] The laminated film according to [1] or [2], wherein the resin (A) further contains an amorphous polymer. [4] The laminated film according to any one of [1] to [3], which satisfies the following formula (2): (Tc(A)-Tc(B))≧15℃ (2) [5] The laminated film according to any one of [1] to [4], wherein the resin (A) and the resin (B) each independently contain a cyclic olefin polymer. [6] A method for producing the laminated film according to any one of [1] to [5], A step (1) of melting a resin (a) containing a crystalline polymer and having the crystallization onset temperature Tc(A) and a resin (b) containing a crystalline polymer and having the crystallization onset temperature Tc(B), respectively; A method for producing a laminated film, comprising: (2) extruding a layer of the molten resin (a) and a layer of the molten resin (b) to obtain a laminated film. [7] The step (2) The laminated film is heated to a temperature T h The method for producing the laminated film according to [6], comprising a step of heat-treating the film. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a laminated film that is excellent in heat resistance and adhesion to an adhesive; and a method for producing a laminated film having such excellent properties. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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.

[0011] 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.

[0012] In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effects of the present invention, for example, within a range of ±3°, ±2°, or ±1°.

[0013] In the following description, the MD (machine direction) refers to the direction in which the film flows on the production line, and the TD (traverse direction) refers to the direction parallel to the film surface and perpendicular to the MD. For convenience, the longitudinal direction of a long film may be referred to as the MD direction of the film, and the width direction as the TD direction of the film.

[0014] The glass transition temperature Tg and melting point Tm of a polymer or resin can be measured by the following method. First, the polymer or resin is melted by heating, and the molten polymer or resin is rapidly cooled with dry ice. Next, using this polymer or resin as a test specimen, the glass transition temperature Tg and melting point Tm of the polymer or resin can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode).

[0015] In the following description, unless otherwise specified, the term "adhesive" refers not only to adhesives in the narrow sense (adhesives having a shear storage modulus of 1 MPa to 500 MPa at 23°C after irradiation with energy rays or after heat treatment), but also to pressure-sensitive adhesives having a shear storage modulus of less than 1 MPa at 23°C.

[0016] [1. Laminated film] [1.1. Overview of laminated film] A laminate film according to one embodiment of the present invention comprises a first resin layer made of resin (A) and a second resin layer made of resin (B). Resin (A) contains a crystalline polymer, has a crystallization onset temperature Tc(A), and is in an amorphous state. Resin (B) contains a crystalline polymer, has a crystallization onset temperature Tc(B), and is in a crystalline state. The laminated film of the present embodiment satisfies the following formula (1). (Tc(A)-Tc(B))>0℃ When the laminated film has the above-mentioned structure, the laminated film can be a film having excellent adhesion to an adhesive and excellent heat resistance.

[0017] The laminate film of this embodiment further includes a third resin layer, which is a layer of resin (A). The second resin layer is provided between the first resin layer and the third resin layer. That is, the laminate film of this embodiment includes the first resin layer, the second resin layer, and the third resin layer in this order. The laminate film does not necessarily have to include a third resin layer, but it is preferable that the laminate film includes a third resin layer on both sides thereof from the viewpoint of effectively improving adhesion to the adhesive.

[0018] [1.2. Structure of laminated film] The structure of the laminated film according to this embodiment will be further explained with reference to the drawings: Figure 1 is a cross-sectional view that schematically shows a laminated film according to one embodiment of the present invention. The laminated film 100 comprises, in this order, a first resin layer 110 which is a layer of resin (A), a second resin layer 120 which is a layer of resin (B), and a third resin layer 130 which is also a layer of resin (A). The first resin layer 110 and the second resin layer 120 are in direct contact with each other without any other layer interposed therebetween. The second resin layer 120 and the third resin layer 130 are in direct contact with each other without any other layer interposed therebetween. The direct contact between the second resin layer 120 and the first resin layer 110 and the direct contact between the second resin layer 120 and the third resin layer 130 can effectively improve the adhesion to the adhesive of the laminated film and the heat resistance. In addition, the thickness of the laminated film can be reduced.

[0019] The thickness of the laminated film is not particularly limited and may be set appropriately depending on the intended use of the laminated film, but is, for example, preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less.

[0020] The thickness of the second resin layer is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and preferably 80 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less. When the thickness of the second resin layer is equal to or greater than the lower limit, the solvent resistance and heat resistance of the laminate film can be effectively improved. Furthermore, when the thickness of the second resin layer is equal to or less than the upper limit, the laminate film can be made thinner.

[0021] The thickness of the first resin layer is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, and preferably 50 μm or less, more preferably 15 μm or less, even more preferably 10 μm or less, even more preferably 8 μm or less.

[0022] The preferred thickness of the third resin layer may be in the same range as the preferred thickness of the first resin layer.

[0023] When the thickness of the first resin layer or the third resin layer is equal to or greater than the lower limit, the adhesiveness of the laminate film to an adhesive can be effectively improved. When the thickness of the first resin layer or the third resin layer is equal to or less than the upper limit, the solvent resistance and heat resistance of the laminate film can be effectively improved.

[0024] The thickness of the first resin layer and the thickness of the third resin layer may be different from each other, but are preferably the same. The ratio of the thickness of the first resin layer to the thickness of the third resin layer (first resin layer / third resin layer) is preferably 110 / 90 to 90 / 110, more preferably 105 / 95 to 95 / 105, and even more preferably 101 / 99 to 99 / 101. This effectively reduces the amount of curl in the laminated film.

[0025] The ratio of the thickness of the first resin layer to the thickness of the second resin layer (first resin layer / second resin layer) is preferably 1 / 20 or more, more preferably 1 / 15 or more, even more preferably 1 / 10 or more, and is preferably 1 / 1 or less, more preferably 1 / 2 or less, even more preferably 1 / 5 or less, thereby enabling the adhesion to adhesives and heat resistance of the laminated film to be improved effectively in a balanced manner.

[0026] The laminated film may be an unstretched film, or may be a stretched film.

[0027] The laminated film may be a continuous film or a sheet of film.

[0028] [1.3. Resins forming each layer] The first resin layer and the third resin layer are layers of resin (A). Therefore, the first resin layer and the third resin layer are formed from resin (A) and contain only resin (A). The resin (A) forming the first resin layer and the third resin layer contains a crystalline polymer. The second resin layer is a layer of resin (B). Therefore, the second resin layer is formed from resin (B) and contains only resin (B). The resin (B) forming the second resin layer contains a crystalline polymer.

[0029] A crystalline polymer refers to a polymer having crystallinity. A crystalline polymer refers to a polymer having a melting point Tm. The melting point Tm of a polymer can be measured by a differential scanning calorimeter (DSC). Therefore, a crystalline polymer refers to a polymer whose melting point Tm can be observed by a differential scanning calorimeter (DSC).

[0030] The crystalline polymer may have either positive or negative intrinsic birefringence, with crystalline polymers having positive intrinsic birefringence being preferred.

[0031] Examples of crystalline polymers include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN); polyolefins such as polyethylene (PE) and polypropylene (PP); and cyclic olefin polymers described below.

[0032] The crystalline polymer is preferably a cyclic olefin polymer. Hereinafter, a crystalline cyclic olefin polymer may be referred to as a "crystalline cyclic olefin polymer."

[0033] The crystalline cyclic olefin polymer may have an alicyclic structure in its molecule. Such a crystalline cyclic olefin polymer may be, for example, a polymer obtainable by polymerization using a cyclic olefin as a monomer, or a hydrogenated product thereof. The use of the crystalline cyclic olefin polymer can improve the mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight of the laminated film.

[0034] Examples of alicyclic structures include cycloalkane structures and cycloalkene structures. Among these, cycloalkane structures are preferred because they facilitate the production of laminated films with excellent properties such as thermal stability. The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, and preferably 30 or less, more preferably 20 or less, and even more preferably 15 or less. When the number of carbon atoms contained in one alicyclic structure is within the above range, mechanical strength, heat resistance, and moldability are highly balanced.

[0035] In the crystalline cyclic olefin polymer, the proportion of structural units having an alicyclic structure relative to all structural units is preferably 30% by weight or more, more preferably 50% by weight or more, and even more preferably 70% by weight or more. When the proportion of structural units having an alicyclic structure is as high as described above, heat resistance can be improved. The proportion of structural units having an alicyclic structure relative to all structural units can be 100% by weight or less. In addition, in the crystalline cyclic olefin polymer, the remainder other than the structural units having an alicyclic structure is not particularly limited and can be appropriately selected depending on the intended use.

[0036] Examples of the crystalline cyclic olefin polymer include the following polymers (α) to (δ): Among these, polymer (β) is preferred because it is easy to obtain a laminated film having excellent heat resistance. Polymer (α): A ring-opening polymer of a cyclic olefin monomer, which is crystalline. Polymer (β): A hydrogenated product of polymer (α) that is crystalline. Polymer (γ): An addition polymer of a cyclic olefin monomer, which has crystallinity. Polymer (δ): A hydrogenated product of polymer (γ) that is crystalline.

[0037] Specifically, the crystalline cyclic olefin polymer is preferably a crystalline ring-opening polymer of dicyclopentadiene or a crystalline hydrogenated ring-opening polymer of dicyclopentadiene. Among these, a crystalline hydrogenated ring-opening polymer of dicyclopentadiene is particularly preferred. Here, the ring-opening polymer of dicyclopentadiene refers to a polymer in which the proportion of dicyclopentadiene-derived structural units to all structural units is usually 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 100% by weight.

[0038] The hydrogenated ring-opening polymer of dicyclopentadiene preferably has a high ratio of racemo dyads. Specifically, the ratio of racemo dyads in the repeating units of the hydrogenated ring-opening polymer of dicyclopentadiene is preferably 51% or more, more preferably 70% or more, and even more preferably 85% or more. A high ratio of racemo dyads indicates high syndiotactic stereoregularity. Therefore, the higher the ratio of racemo dyads, the higher the melting point of the hydrogenated ring-opening polymer of dicyclopentadiene tends to be. The proportion of racemo-dyads is 13 It can be determined based on C-NMR spectral analysis.

[0039] As the polymer (α) to polymer (δ), polymers obtained by the production method disclosed in WO 2018 / 062067 can be used.

[0040] As the crystalline cyclic olefin polymer, commercially available products can also be used, such as "ZEONEXC2420" manufactured by Zeon Corporation.

[0041] The melting point Tm of the crystalline polymer is preferably 200° C. or higher, more preferably 230° C. or higher, and preferably 290° C. or lower. When a crystalline polymer having such a melting point Tm is used, a laminate film having an even better balance between formability and heat resistance can be obtained.

[0042] Generally, a crystalline polymer has a glass transition temperature Tg. The specific glass transition temperature Tg of a crystalline polymer is not particularly limited, but is generally 85°C or higher and generally 170°C or lower.

[0043] The weight-average molecular weight (Mw) of the crystalline polymer is preferably 1,000 or more, more preferably 2,000 or more, and preferably 1,000,000 or less, more preferably 500,000 or less. A crystalline polymer having such a weight-average molecular weight has an excellent balance between moldability and heat resistance.

[0044] The molecular weight distribution (Mw / Mn) of the crystalline polymer is preferably 1.0 or more, more preferably 1.5 or more, and preferably 4.0 or less, more preferably 3.5 or less. Here, Mn represents the number average molecular weight. A crystalline polymer having such a molecular weight distribution has excellent moldability.

[0045] The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer can be measured in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a developing solvent. If the polymer is insoluble in cyclohexane, the weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) can be measured in terms of polyisoprene using toluene as a solvent.

[0046] The crystalline polymer may be used alone or in combination of two or more kinds in any ratio.

[0047] Resin (A) and resin (B) may each independently contain optional components in addition to the crystalline polymer. Examples of optional components include antioxidants, light stabilizers, waxes, nucleating agents, fluorescent brighteners, ultraviolet absorbers, inorganic fillers, colorants, flame retardants, flame retardant aids, antistatic agents, plasticizers, near-infrared absorbers, lubricants, fillers, and any polymer other than the crystalline polymer. One type of optional component may be used alone, or two or more types may be used in combination in any ratio.

[0048] The proportion of the crystalline polymer in resin (A) is preferably 30% by weight or more, more preferably 32% by weight or more, even more preferably 35% by weight or more, and preferably 70% by weight or less, more preferably 65% ​​by weight or less, even more preferably 60% by weight or less. When the proportion of the crystalline polymer in resin (A) is at least the lower limit of the above range, the solvent resistance and heat resistance of the laminated film can be improved. When the proportion of the crystalline polymer in resin (A) is at most the upper limit of the above range, the adhesion of the laminated film to adhesives can be improved.

[0049] The proportion of the crystalline polymer in resin (B) is preferably 75% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more, and is usually 100% by weight or less, and may be 100% by weight. When the proportion of the crystalline polymer in resin (B) is at least the lower limit of the above range, the solvent resistance and heat resistance of the laminate film can be improved.

[0050] Resin (A) preferably further contains an amorphous polymer in addition to the crystalline polymer. An amorphous polymer refers to a polymer that does not have crystallinity. A polymer that does not have crystallinity refers to a polymer that does not have a melting point Tm. Therefore, an amorphous polymer refers to a polymer whose melting point Tm cannot be observed by differential scanning calorimetry (DSC). By including an amorphous polymer in resin (A), resin (A) can be easily made amorphous.

[0051] The amorphous polymer may have either positive or negative intrinsic birefringence, with an amorphous polymer having positive intrinsic birefringence being preferred.

[0052] The amorphous polymer is preferably a cyclic olefin polymer. That is, the amorphous polymer is preferably a cyclic olefin polymer that does not have a melting point. Hereinafter, a cyclic olefin polymer that does not have a melting point may be referred to as an "amorphous cyclic olefin polymer." Amorphous cyclic olefin polymers are excellent in mechanical properties, heat resistance, transparency, low moisture absorption, dimensional stability, and light weight.

[0053] The amorphous cyclic olefin polymer may have a cyclic structure in its molecule. Usually, the structural unit of the amorphous cyclic olefin polymer has an alicyclic structure. The amorphous cyclic olefin polymer may be a polymer having an alicyclic structure in the main chain, a polymer having an alicyclic structure in the side chain, a polymer having alicyclic structures in the main chain and the side chain, or a mixture of two or more of these in any ratio. Among these, from the viewpoint of mechanical strength and heat resistance, it is preferable that the amorphous cyclic olefin polymer has an alicyclic structure in the main chain.

[0054] Examples of the alicyclic structure include saturated alicyclic hydrocarbon (cycloalkane) structures and unsaturated alicyclic hydrocarbon (cycloalkene, cycloalkyne) structures. Among these, from the viewpoints of mechanical strength and heat resistance, cycloalkane structures and cycloalkene structures are preferred, and cycloalkane structures are particularly preferred.

[0055] The number of carbon atoms contained in one alicyclic structure is preferably 4 or more, more preferably 5 or more, and preferably 30 or less, more preferably 20 or less, and even more preferably 15 or less. When the number of carbon atoms constituting the alicyclic structure is within this range, mechanical strength, heat resistance, and moldability are well balanced.

[0056] In the amorphous cyclic olefin polymer, the ratio of structural units having an alicyclic structure to all structural units is preferably 55% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. When the ratio of structural units having an alicyclic structure to all structural units is within this range, transparency and heat resistance are excellent.

[0057] Examples of amorphous cyclic olefin polymers include norbornene polymers, monocyclic cyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, and hydrogenated versions thereof. Among these, norbornene polymers and hydrogenated versions thereof have good moldability.

[0058] Examples of norbornene polymers and their hydrogenated products 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 other monomers 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 other monomers copolymerizable therewith. Examples of these polymers include the polymers disclosed in, for example, JP 2002-321302 A and WO 2017 / 145718 A. Among these, the hydrogenated products of ring-opening polymers of monomers having a norbornene structure are particularly suitable from the viewpoints of moldability, heat resistance, low moisture absorption, dimensional stability, light weight, and the like.

[0059] Examples of monomers having a norbornene structure include bicyclo[2.2.1]hept-2-ene (common name: norbornene), tricyclo[4.3.0.1 2,5 ]Deca-3,7-diene (common name: dicyclopentadiene), tetracyclo[4.4.0.1 2,5 .1 7,10]dodec-3-ene (trivial name: tetracyclododecene), 5-phenyl-2-norbornene, 5-(4-methylphenyl)-2-norbornene, 5-(1-naphthyl)-2-norbornene, 9-(2-norbornen-5-yl)-carbazole, 1,4-methano-1,4,4a,4b,5,8,8a,9a-octahydrofluorene, 1,4-methano-1,4,4a,9a-tetrahydrofluorene (trivial name: methanotetrahydrofluorene) 1,4-methano-1,4,4a,9a-tetrahydrofluorene), 1,4-methano-1,4,4a,9a-tetrahydrodibenzofuran, 1,4-methano-1,4,4a,9a-tetrahydrocarbazole, 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene, 1,4-methano-1,4,4a,9,10,10a-hexahydrophenanthrene; and derivatives of these compounds (for example, those having a substituent on the ring).

[0060] Examples of the substituent include alkyl groups such as methyl, ethyl, propyl, and isopropyl groups; alkylidene groups; alkenyl groups; and polar groups. Examples of the polar group include heteroatoms and atomic groups containing heteroatoms. Examples of heteroatoms include oxygen, nitrogen, sulfur, silicon, and halogen atoms. Specific examples of the polar group include halogen groups such as fluoro, chloro, bromo, and iodine; carboxyl groups; carbonyloxycarbonyl groups; epoxy groups; hydroxy groups; oxy groups; alkoxy groups; ester groups; silanol groups; silyl groups; amino groups; nitrile groups; sulfonic groups; cyano groups; amide groups; and imide groups. The number of substituents may be one or two or more. The types of the two or more substituents may be the same or different. However, from the viewpoint of obtaining an amorphous resin with low saturated water absorption and excellent moisture resistance, it is preferable that the norbornene-based monomer has a small amount of polar groups, and more preferably does not have any polar groups.

[0061] Examples of the amorphous cyclic olefin polymers include "ZEONEX" manufactured by Zeon Corporation; "ARTON" manufactured by JSR Corporation; "APEL" manufactured by Mitsui Chemicals; and "TOPAS" manufactured by Polyplastics Co., Ltd.

[0062] The glass transition temperature Tg of the amorphous polymer is preferably 90° C. or higher, more preferably 100° C. or higher, even more preferably 110° C. or higher, and is preferably 200° C. or lower, more preferably 190° C. or lower, even more preferably 180° C. or lower. When the glass transition temperature Tg of the amorphous polymer is within the above range, it is possible to effectively improve both the adhesion to adhesives and the heat resistance of the laminated film.

[0063] The weight-average molecular weight (Mw) of the amorphous polymer is preferably 10,000 or more, more preferably 15,000 or more, even more preferably 20,000 or more, and is preferably 100,000 or less, more preferably 80,000 or less, even more preferably 50,000 or less. When the weight-average molecular weight is within the above range, the mechanical strength and moldability of the resin (A) are well balanced.

[0064] The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the amorphous polymer is preferably 1.2 or more, more preferably 1.5 or more, even more preferably 1.8 or more, and preferably 3.5 or less, more preferably 3.0 or less, even more preferably 2.7 or less. When the molecular weight distribution is at least the lower limit of the above range, the productivity of the polymer can be increased and production costs can be reduced. On the other hand, when it is at most the upper limit, the amount of low-molecular-weight components is reduced, thereby suppressing relaxation during exposure to high temperatures and improving the stability of the laminate film.

[0065] The amorphous polymer may be used alone or in combination of two or more kinds in any ratio.

[0066] The amount of the amorphous polymer that can be contained in the resin (A) is preferably 30% by weight or more, more preferably 35% by weight or more, even more preferably 40% by weight or more, and is preferably 70% by weight or less, more preferably 68% by weight or less, even more preferably 65% ​​by weight or less, based on 100% by weight of the resin (A). When the amount of the amorphous polymer is within the above range, it is possible to effectively improve both the adhesion to adhesives and the heat resistance of the laminated film.

[0067] Resin (B) may or may not contain an amorphous polymer. The amount of amorphous polymer that can be contained in resin (B) is preferably 25% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less, based on 100% by weight of resin (B). It is usually 0% by weight or more, but may be 0% by weight. It is preferable that resin (B) does not contain an amorphous polymer.

[0068] [1.4. Resin characteristics] Resin (A) has a crystallization onset temperature Tc(A), and resin (B) has a crystallization onset temperature Tc(B). The crystallization onset temperature Tc of a resin can be measured by the following method. The resin is melted by heating. The melted resin is rapidly cooled with dry ice. Next, the crystallization onset temperature Tc of this resin can be measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode). The crystallization onset temperature Tc can be obtained as the value at the top of the exothermic peak during the heating process.

[0069] The laminated film generally satisfies the following formula (1). (Tc(A)-Tc(B))>0℃ (1) The laminated film preferably satisfies the following formula (2). (Tc(A)-Tc(B))≧15℃ (2)

[0070] The value of (Tc(A)-Tc(B)) is usually greater than 0°C, preferably 15°C or greater, more preferably 20°C or greater, even more preferably 25°C or greater, and preferably 110°C or less, more preferably 105°C or less, even more preferably 100°C or less. When the value of (Tc(A) - Tc(B)) is within the above range, a laminate film containing a layer of resin (A) in an amorphous state and a layer of resin (B) in a crystalline state can be easily produced. In addition, both the adhesion to adhesives and the heat resistance of the laminate film can be effectively improved.

[0071] The resin (A) forming the first resin layer and the third resin layer is usually in an amorphous state, and the resin (B) forming the second resin layer is usually in a crystalline state. Here, whether a resin is in an amorphous state is confirmed by the crystallinity of the polymer contained in the resin being less than 5%. When the crystallinity of the polymer contained in the resin is less than 5%, typically, no crystalline portion is observed in the resin when a cross section of the resin is observed with a transmission electron microscope (TEM). When a resin is in a crystalline state, whether a polymer contained in the resin is in a crystallinity of 5% or more. When the crystallinity of the polymer contained in the resin is 5% or more, typically, crystalline portion is observed in the resin when a cross section of the resin is observed with a transmission electron microscope (TEM).

[0072] The cross section of the resin can be observed by TEM using the following method. -Preparation of samples for TEM observation The resin layer to be observed is cut at room temperature using a microtome (diamond knife) to obtain resin slices. The sample feed during cutting is 50 nm. The resin slice is then exposed to the vapor of a staining solution containing ruthenium for 120 seconds to stain it, and a sample for TEM observation is prepared. TEM observation conditions As the TEM, for example, "HT7700" manufactured by Hitachi High-Technologies Corporation can be used. The accelerating voltage may be 100 kV. The observation magnification can be 1000 to 20000 times. The observation area may be 15 μm×15 μm.

[0073] When the first resin layer and the third resin layer are formed from a resin (A) in an amorphous state and the second resin layer is formed from a resin (B) in a crystalline state, the laminated film has excellent adhesion to adhesives and excellent solvent resistance and heat resistance.

[0074] The crystallinity of the polymer contained in the resin can be measured by X-ray diffraction in accordance with JIS K 0131. Specifically, the diffracted X-ray intensity from the crystallized portion is measured using a wide-angle X-ray diffractometer (e.g., "RINT 2000" manufactured by Rigaku Corporation), and the crystallinity can be calculated from the ratio to the total diffracted X-ray intensity using the following formula (I): Xc=K·Ic / It (I) In the above formula (I), Xc represents the crystallinity of the test sample, Ic represents the diffracted X-ray intensity from the crystalline portion, It represents the total diffracted X-ray intensity, and K represents the correction term.

[0075] The crystallinity of the polymer contained in resin (B) is usually 5% or more, preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more, and is preferably 70% or less, more preferably 65% ​​or less, and even more preferably 60% or less. When the crystallinity of the polymer contained in resin (B) is at least the lower limit of the above range, the solvent resistance and heat resistance of the laminate film can be effectively improved, and when it is at most the upper limit of the above range, the adhesion of the laminate film to an adhesive can be effectively improved.

[0076] The crystallinity of the polymer contained in each of the resins (A) and (B) can be adjusted using a conventionally known method. For example, increasing the amount of crystalline polymer contained in the resin tends to increase the crystallinity. Furthermore, by adding an amorphous polymer to the resin and increasing the amount of the amorphous polymer in the resin, the crystallinity tends to decrease. Furthermore, stretching the resin layer tends to increase the crystallinity. Furthermore, by subjecting the resin layer to heat treatment at a temperature equal to or higher than the crystallization onset temperature Tc of the resin and lower than the melting point Tm, the degree of crystallization tends to increase. Furthermore, the addition of a crystal nucleating agent to the resin tends to increase the degree of crystallinity.

[0077] Resin (A) usually has a melting point Tm(A) that is preferably 250°C or higher, more preferably 255°C or higher, and even more preferably 260°C or higher, and is preferably 280°C or lower, more preferably 275°C or lower, and even more preferably 270°C or lower.

[0078] The crystallization onset temperature Tc(A) of the resin (A) is preferably 160°C or higher, more preferably 165°C or higher, even more preferably 170°C or higher, and preferably 240°C or lower, more preferably 235°C or lower, even more preferably 230°C or lower.

[0079] Resin (B) typically has a melting point Tm(B) that is preferably 255°C or higher, more preferably 260°C or higher, and even more preferably 263°C or higher, and is preferably 280°C or lower, more preferably 275°C or lower, and even more preferably 270°C or lower.

[0080] [1.5. Properties of laminated film] (adhesion) The laminated film has excellent adhesion to an adhesive. The adhesion to an adhesive can be evaluated by the following method. A test film made of a resin containing a cyclic olefin polymer is prepared. One side of each of the film to be evaluated and the test film is subjected to corona treatment. An ultraviolet-curable adhesive is applied to each of the corona-treated sides of the film to be evaluated and the corona-treated side of the test film, and the adhesive-applied sides are bonded together, allowing the adhesive to cure. This results in a sample film comprising the film to be evaluated and the test film.

[0081] The sample film is cut to a width of 15 mm, and the film side to be evaluated is attached to the surface of a slide glass with an adhesive.

[0082] A 90-degree peel test is performed by clamping the test film at the tip of a force gauge and pulling it in the normal direction to the surface of the glass slide. If the film has good adhesion, and the test film is torn without being able to be peeled, the adhesion is good.

[0083] (Solvent resistance) The laminate film has excellent solvent resistance. The solvent resistance of the laminate film can be confirmed by folding the laminate film, dropping n-hexane onto the crease, and holding it for 30 seconds, and then checking whether any cracks appear on the surface of the laminate film.

[0084] (Heat resistance) The laminate film has excellent heat resistance. The heat resistance of the laminate film can be evaluated by measuring the heat shrinkage (%) of the laminate film in a heating test in which the laminate film is heated in an oven heated to 200°C for 10 minutes. The heat shrinkage of the laminate film in the heating test is preferably less than 0.5%, and ideally 0%.

[0085] (Hayes) The laminate film preferably has a small haze. The haze of the laminate film is preferably 2.0% or less, more preferably 1.0% or less, particularly preferably 0.5% or less, and ideally 0.0%. Haze measurement can be performed using an NDH-7000 (manufactured by Nippon Denshoku) in accordance with JIS K7361-1997.

[0086] [2. Manufacturing method of laminated film] The laminated film can be produced by any method. For example, the laminate film can be produced by a method including a step of separately producing each layer (first resin layer, second resin layer, and optional third resin layer) included in the laminate film and a step of laminating these layers. The step of laminating each layer may include a step of overlapping each layer in the thickness direction, a step of pressurizing each overlapped layer, and a step of heating each overlapped layer.

[0087] Also for example, the laminated film can be produced by melt coextrusion. The laminated film is preferably produced by a production method including the following steps (1) and (2). Step (1): Melting a resin (a) containing a crystalline polymer and having the crystallization onset temperature Tc(A) and a resin (b) containing a crystalline polymer and having the crystallization onset temperature Tc(B). Step (2): A layer of the molten resin (a) and a layer of the molten resin (b) are extruded to obtain a laminated film. The method for producing a laminated film, which includes the steps (1) and (2), will be described below.

[0088] [2.1. Process (1)] In step (1), the resin (a) and the resin (b) are each melted. Resin (a) is a material for the aforementioned resin (A), and like resin (A), it contains a crystalline polymer and has a crystallization onset temperature Tc(A). Resin (a) may be in an amorphous state or a crystalline state. Resin (a) usually has the same composition as resin (A). Resin (b) is a material for the aforementioned resin (B), and like resin (B), it contains a crystalline polymer and has a crystallization onset temperature Tc(B). Resin (b) may be in an amorphous state or a crystalline state. Resin (b) usually has the same composition as resin (B).

[0089] Resin (a) and resin (b) can be melted using any melting device. Examples of the melting device include a single-screw extruder and a twin-screw extruder. These extruders may be connected to a polymer filter to remove impurities contained in the resin.

[0090] The temperature at which resin (a) is melted (cylinder temperature when melted using an extruder) is usually equal to or higher than the glass transition temperature Tga of resin (a), preferably equal to or higher than Tma, and preferably equal to or lower than Tma + 100° C., more preferably equal to or lower than Tma + 50° C. Here, Tma means the melting point of resin (a).

[0091] The temperature at which resin (b) is melted (when melted using an extruder, the cylinder temperature) is usually equal to or higher than the glass transition temperature Tgb of resin (b), preferably equal to or higher than Tmb, and preferably equal to or lower than Tmb + 100°C, more preferably equal to or lower than Tmb + 50°C. means the melting point of resin (b).

[0092] [2.2. Process (2)] In step (2), a layer of the molten resin (a) and a layer of the molten resin (b) are extruded to obtain a laminate film. Step (2) may include step (2a) of extruding the layer of the molten resin (a) and the layer of the molten resin (b) to form a molten resin film, and then step (2aa) of cooling the molten resin film to obtain a laminate film.

[0093] The step (2) includes a step (2b) of preheating the cooled laminated film, a step (2c) of stretching the laminated film, and a step (2d) of heating the laminated film to a temperature T lower than the crystallization onset temperature Tc(A). h The method may include a step (2d) of heat-treating the resulting mixture at a temperature of 1000° C. or less. Step (2b) is usually carried out before steps (2c) and (2d). Steps (2c) and (2d) are usually carried out in this order. When step (2c) is not carried out, step (2d) is usually carried out after step (2b).

[0094] (Process (2a): Extrusion process) Any extrusion molding device can be used as the device for extruding a layer of the molten resin (a) and a layer of the molten resin (b) to form a molten resin film. For example, a multi-layer extruder equipped with a feed block or a multi-layer extruder equipped with a multi-layer die can be used.

[0095] (Step (2aa): Cooling step of molten resin film) The cooling body that the molten resin film first comes into contact with is not particularly limited, but a casting roll is usually used. The casting roll temperature is preferably (Tga - 40°C) or higher, and preferably (Tga + 70°C) or lower.

[0096] (Step (2b): Preheating step) The step of preheating the laminated film obtained by cooling the molten resin film is preferably carried out at a temperature lower than the crystallization onset temperature Tc(A) of the resin (A). Specifically, the preheating temperature is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher, and is preferably 160°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower. Preheating the laminated film at a temperature within the above range can suppress the progress of crystallization of the crystalline polymer in the resin (A) forming the first resin layer and the third resin layer, thereby effectively improving the adhesion of the laminated film to an adhesive.

[0097] (Process (2c): Stretching process) Stretching is preferably performed at a stretching temperature lower than the crystallization onset temperature Tc(A) of resin (A). Specific stretching temperatures are preferably 110°C or higher, more preferably 115°C or higher, and even more preferably 120°C or higher, and are preferably Tc(A)-20°C or lower, more preferably Tc(A)-25°C or lower, and even more preferably Tc(A)-30°C or lower. When stretching is performed at a stretching temperature within this range, the polymer molecules in the laminate film can be effectively oriented while suppressing the progress of crystallization of the crystalline polymer in resin (A) forming the first resin layer and the third resin layer. This effectively improves the adhesion of the laminate film to an adhesive, and easily allows the laminate film to exhibit desired optical properties.

[0098] The stretching ratio for the stretching can be set depending on the desired optical properties of the laminated film. Specific stretching ratios are preferably greater than 1, more preferably 1.1 or more, particularly preferably 1.2 or more, and preferably 5 or less, more preferably 4 or less, particularly preferably 3 or less. When biaxial stretching is performed, it is preferable that the overall stretching ratio, which is expressed as the product of the stretching ratio in one direction and the stretching ratio in the other direction, falls within the above-mentioned range.

[0099] The stretching may be, for example, uniaxial stretching in which stretching is performed in one direction, or biaxial stretching in which stretching is performed in two non-parallel directions. Furthermore, the biaxial stretching may be simultaneous biaxial stretching in which stretching is performed in two directions simultaneously, or sequential biaxial stretching in which stretching is performed in one direction and then in the other direction.

[0100] (Step (2d): Heat treatment step) The heat treatment of the laminated film is carried out at a temperature Tc(A) lower than the crystallization starting temperature of the resin (A). h It is preferable to carry out the heat treatment at a temperature higher than the crystallization starting temperature Tc(B) of the resin (B). h is preferably Tc(B)+5°C or higher, more preferably Tc(B)+10°C or higher, even more preferably Tc(B)+15°C or higher, and is preferably Tc(A)-5°C or lower, more preferably Tc(A)-10°C or lower, even more preferably Tc(A)-15°C or lower. Heat treatment of the laminated film at or above the lower limit of the above temperature range promotes crystallization of the crystalline polymer in the resin (B) forming the second resin layer, effectively improving the heat resistance and solvent resistance of the laminated film. Heat treatment at or below the upper limit of the above temperature range inhibits crystallization of the crystalline polymer in the resin (A) forming the first and second resin layers, effectively improving the adhesion of the laminated film to adhesives.

[0101] (cooling process) The heat-treated laminated film is usually cooled, for example, to room temperature (20°C ± 15°C).

[0102] [2.3. Other processes] Further, optional steps include a step of trimming the laminated film, a step of subjecting the laminated film to a surface treatment, and the like.

[0103] [3. Uses of laminated film] The laminated film has excellent adhesiveness to adhesives and solvent resistance, and can therefore be suitably used as a protective film for optical elements such as polarizers, and as a component of high-frequency substrates. [Example]

[0104] 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.

[0105] 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.

[0106] [Evaluation method] (crystallinity) The crystallinity of each layer contained in the film was measured by the following method. When the film had a monolayer structure, the film was used as a sample as it was. When the film was a laminate film, a monolayer film was produced using the same resin as each layer of the laminate film and under the same melt extrusion and heat treatment conditions as the laminate film, and the monolayer film was used as a sample. Specifically, an extruded film having a monolayer structure was produced by introducing the same type of resin pellets, which are the material for the monolayer film, into both the first single-screw extruder and the second single-screw extruder of an extrusion molding machine described below, and the extruded film was treated under the same conditions as the laminate film to obtain a monolayer film for evaluating crystallinity.

[0107] The crystallinity of the polymer contained in the sample film was confirmed by X-ray diffraction in accordance with JIS K 0131. Specifically, the diffracted X-ray intensity from the crystallized portion was determined using a wide-angle X-ray diffractometer (RINT 2000, manufactured by Rigaku Corporation), and the crystallinity was calculated from the ratio to the overall diffracted X-ray intensity using the following formula (I). Xc=K·Ic / It (I) In the above formula (I), Xc represents the crystallinity of the test sample, Ic represents the diffracted X-ray intensity from the crystalline portion, It represents the total diffracted X-ray intensity, and K represents the correction term. The crystallinity of the polymer contained in each layer of the laminated film was measured using a single layer film as a sample.

[0108] (Measurement of glass transition temperature Tg, crystallization onset temperature Tc, and melting point Tm) The glass transition temperature Tg, crystallization onset temperature Tc, and melting point Tm of the sample were measured as follows. First, the sample pellets were melted by heating. The melted sample was then rapidly cooled with dry ice. Next, the glass transition temperature Tg, crystallization onset temperature Tc, and melting point Tm of this sample were measured using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min (heating mode). The value at the top of the exothermic peak during the heating process was taken as the crystallization onset temperature Tc.

[0109] (Observation of resin by TEM) When the film had a single layer structure, the film was used as a sample as it was.When the film was a laminated film, a single layer film was produced using the same resin as each layer of the laminated film under the same melt extrusion and heat treatment conditions as the laminated film, and the single layer film was used as a sample. -Preparation of samples for TEM observation The resin film to be observed was cut at room temperature using a microtome (diamond knife) to obtain resin slices. The sample feed during cutting was 50 nm. The resin slice was then stained by exposing it to the vapor of a staining solution containing ruthenium for 120 seconds to prepare a sample for TEM observation. TEM observation conditions The TEM used was the Hitachi High-Tech "HT7700." The acceleration voltage was 100 kV. The observation magnification was 1000 to 20000 times. The observation area was 15 μm×15 μm. Under the above conditions, the resin layer to be observed was observed by TEM. If the presence of crystalline parts was confirmed within the observed range, it was judged as "crystals present," and if the presence of crystalline parts was not confirmed within the observed range, it was judged as "crystals not present."

[0110] (Adhesion with UV-curable adhesives) A test film made from "ZEONEX790R" manufactured by Zeon Corporation was prepared. One side of each of the film to be evaluated and the test film was subjected to corona treatment. An adhesive was applied to the corona-treated side of the film to be evaluated and the corona-treated side of the test film, and the adhesive-applied sides were bonded together and the adhesive was cured. An ultraviolet-curing adhesive ("CRB Series" manufactured by Toyochem Co., Ltd.) was used as the adhesive. This resulted in a sample film comprising the film to be evaluated and the test film.

[0111] The sample film was then cut to a width of 15 mm, and the film side to be evaluated was attached to the surface of a glass slide with an adhesive, using a double-sided adhesive tape (manufactured by Nitto Denko Corporation, product number "CS9621").

[0112] A 90-degree peel test was performed by clamping the test film at the tip of a force gauge and pulling it in the normal direction to the surface of the glass slide. The force measured when the test film peeled off was the force required to peel the test film from the film being evaluated, and the magnitude of this force was measured as the peel strength of the film to be evaluated. When the adhesion between the films was good and the test film tore without peeling, the adhesion was rated "good." When the test film did not tear and peeled with a force exceeding the measurement precision (over 0.5 N), the adhesion was rated "fair." When the film peeled off easily and with a force below the lower limit of measurement precision (0.5 N or less), the adhesion was rated "poor."

[0113] (Solvent resistance) The film to be evaluated was cut into a rectangular shape measuring 5 cm in length and 2 cm in width to obtain a sample film. The sample film was cut so that the long side of the sample film was parallel to the MD direction and the short side was parallel to the TD direction. Here, the MD direction and TD direction are the directions of the film before cutting. The sample film was bent so that the fold was parallel to the short side (TD direction) of the sample film, and the sample film was fastened with a clip so that the diameter of the bent part was 5 mm. A drop of n-hexane was dropped onto the crease using a 1 mL dropper and held there for 30 seconds, after which the sample film was removed from the clip. The solvent resistance of the film was evaluated according to the following criteria. Good: No cracks on the sample film surface. Poor: Cracks appear on the surface of the sample film and / or the sample film breaks.

[0114] (Heat resistance) The film to be evaluated was cut into a 120 mm × 120 mm square to obtain a sample film. The cutting was performed so that each side of the sample film was parallel to the MD or TD direction. Here, the MD and TD directions are the directions of the film before cutting. Markings were made on the inside of the sample film at the four corners of a square measuring approximately 100 mm x 100 mm. The four sides of the square with the marked corners were then measured using a universal projector (Nikon V-12BDC) to determine the pre-heating dimensions. The sample film was then placed in an oven heated to 200°C and heated for 10 minutes. The sample film was then removed from the oven, and the four sides of the square with the marked corners were measured in the same manner as for measuring the pre-heating dimensions to determine the post-heating dimensions. The shrinkage rates in the MD and TD directions were calculated from the dimensions before and after heating. The shrinkage rate was calculated from the average of the two sides (MD or TD) of the square with the marked corners. An average heat shrinkage rate in the MD and TD directions of 0.5% or more was rated "poor," and an average heat shrinkage rate of less than 0.5% was rated "good."

[0115] [Preparing the resin] The resins used in each of the Examples and Comparative Examples were prepared according to the following procedure. (Amorphous COP) As the amorphous COP, a commercially available pellet-shaped amorphous resin, "ZEONEX790R" manufactured by Zeon Corporation, was prepared. The amorphous COP contains 99% by weight of an amorphous cyclic olefin polymer (glass transition temperature: 163°C).

[0116] (COP1) As COP1, a commercially available pellet-shaped crystalline resin, "ZEONEXC2420" manufactured by Zeon Corporation, was prepared. COP1 contains 99% by weight of a crystalline cyclic olefin polymer (glass transition temperature 93°C).

[0117] (COP2 to COP4) The amorphous COP and COP1 were mixed in the weight ratio shown in Table 1, charged into the hopper of a twin-screw kneading extruder, and kneaded in the extruder to obtain a kneaded mixture. The twin-screw kneading extruder had a ratio L / D of 41 between the effective screw length L and the screw diameter D, and a screw diameter of 25 mm. The operating conditions of the twin-screw kneading extruder were as follows: Barrel temperature setting: 275~280℃ Die temperature setting: 275℃ Screw rotation speed = 200 rpm

[0118] The kneaded product was extruded from the extruder in the form of a strand, which was then chopped using a strand cutter to obtain pellet-shaped crystalline resins COP2 to COP4.

[0119] The compositions (weight ratios), glass transition temperatures Tg, melting points Tm, and crystallization onset temperatures Tc of COP1 to COP4 and the amorphous COP are shown in Table 1. The melting points Tm and crystallization onset temperatures Tc of the amorphous COP were not observed.

[0120] [Table 1]

[0121] [Examples 1 to 3] (1-1. Step (1): Melting of Resin) An extruder was prepared, which was equipped with a feed block, a single layer die, a first single screw extruder of double flight type, and a second single screw extruder. The first single-screw extruder was equipped with a leaf-disc-shaped polymer filter with a 3 μm opening, a screw diameter D of 50 mm, and a ratio L / D of 28 between the screw length L and the screw diameter D. The second single-screw extruder was equipped with a leaf-disc-shaped polymer filter with a 3 μm opening, a screw diameter D of 50 mm, and a ratio L / D of 30 between the screw length L and the screw diameter D. This extrusion molding machine is configured so that molten resin (molten resin (b)) for forming the second resin layer (core layer) is fed from a first single-screw extruder via a feed block to a single-layer die, and molten resin (molten resin (a)) for forming the first resin layer and the third resin layer (skin layer) is fed from a second single-screw extruder via a feed block to the single-layer die, and a molten resin film having a layer structure of (layer of resin (a)) / (layer of resin (b)) / (layer of resin (a)) can be continuously extruded from the single-layer die.

[0122] Pellets of COP1, a crystalline resin, were introduced into the first single-screw extruder, melted, and fed to the single-layer die via a feed block. COP1 was introduced into the first single-screw extruder via a hopper installed in the extruder. The extruder temperature was 280°C.

[0123] On the other hand, pellets of the resin (resin (a)) shown in the table below were introduced into a second single-screw extruder as the material for the first and third resin layers, melted, and fed to the single-layer die via a feed block. The extruder temperature was 280°C.

[0124] (1-2. Step (2a): Extrusion of molten resin) COP1 and resin (a) were extruded from a single-layer die of an extruder in a molten state at 280° C. This resulted in the continuous formation of a molten resin film having, in this order, a layer formed from resin (a) (skin layer), a layer formed from COP1 (core layer), and a layer formed from resin (a) (skin layer) (co-extrusion molding process).

[0125] The extruded molten resin film was cast onto a cooling roll. The temperature of the cooling roll was set to 80°C. This cooled the molten resin film to obtain a laminated film. The obtained laminated film was made of two types of resin and had a three-layer structure. That is, the laminated film had, in this order, a skin layer as a first resin layer formed from resin (a), a core layer as a second resin layer formed from resin (b), and a skin layer as a third resin layer formed from resin (a). The thickness of the laminated film was 60 μm. The thickness ratio of the first resin layer, the second resin layer, and the third resin layer was 5 μm / 50 μm / 5 μm, that is, 1 / 10 / 1. The thickness ratio was confirmed by cutting the obtained laminated film with a microtome and observing the cross section with an optical microscope.

[0126] (1-3. Step (2b): Preheating step) The obtained laminated film was cut into squares measuring 200 mm on each side. The cutting was performed so that each side of the square-shaped laminated film was parallel to the MD or TD direction of the laminated film before cutting. The cut square-shaped laminated film was preheated at 130°C for 30 seconds using a batch-type biaxial stretching device (manufactured by Eto Co., Ltd.) with the four sides of the film fixed with clips.

[0127] (1-4. Process (2d): Heat treatment process) Next, the laminated film was subjected to a heat treatment step in which it was heated at 180° C. for 3 minutes, and then cooled to room temperature (23° C.) to obtain a heat-treated laminated film.

[0128] The heat-treated laminated film was evaluated by the above-mentioned method. Furthermore, a monolayer film was produced using the same resin as that for forming each layer of the laminated film under the same conditions as the laminated film, and the crystallinity of the monolayer film was measured and observed by TEM. The crystallinity value obtained from the monolayer film was taken as the crystallinity of the polymer contained in each layer of the laminated film.

[0129] [Example 4] In Example 3 (1-3. Step (2b): preheating step), the laminated film was preheated at a temperature of 130° C. for 15 seconds. Except for the above, the same procedure as in Example 3 was carried out to obtain a preheated laminated film.

[0130] The preheated laminated film was then subjected to the following stretching step. (Process (2c): Stretching process) While maintaining the temperature at 130° C., the film was stretched to 1x in the MD direction and 2x in the TD direction over 15 seconds, where MD and TD are the directions of the laminated film before being cut.

[0131] Next, the stretched laminated film was subjected to the same operation as in Example 3 (1-4. Step (2d): heat treatment step) to obtain a heat-treated laminated film.

[0132] The heat-treated laminated film was evaluated by the above-mentioned method. Furthermore, a monolayer film was produced using the same resin as that for forming each layer of the laminated film under the same conditions as the laminated film, and the crystallinity of the monolayer film was measured and observed by TEM. The crystallinity value obtained from the monolayer film was taken as the crystallinity of the polymer contained in each layer of the laminated film.

[0133] [Example 5] In (1-2. Step (2a): Extrusion of molten resin), the extrusion amount was adjusted so that the thickness of the resulting laminated film would be 150 μm and the thickness ratio of the first resin layer, the second resin layer, and the third resin layer would be 1 / 1 / 1. That is, in the laminated film, the thickness ratio of the first resin layer, the second resin layer, and the third resin layer was 50 μm / 50 μm / 50 μm. Except for the above, the same procedure as in Example 1 was carried out to obtain a heat-treated laminated film.

[0134] The heat-treated laminated film was evaluated by the above-mentioned method. Furthermore, a monolayer film was produced using the same resin as that for forming each layer of the laminated film under the same conditions as the laminated film, and the crystallinity of the monolayer film was measured and observed by TEM. The crystallinity value obtained from the monolayer film was taken as the crystallinity of the polymer contained in each layer of the laminated film.

[0135] [Comparative Example 1] In Example 1 (1-3. Step (2b): preheating step), the laminated film was preheated at a temperature of 130° C. for 15 seconds. Except for the above, the same procedure as in Example 1 was carried out to obtain a preheated laminated film.

[0136] The preheated laminated film was then subjected to the following stretching step. (Process (2c): Stretching process) While maintaining the temperature at 130° C., the film was stretched to 1x in the MD direction and 2x in the TD direction over 15 seconds, where MD and TD are the directions of the laminated film before being cut.

[0137] Next, the stretched laminated film was subjected to the same operation as in Example 1 (1-4. Step (2d): heat treatment step) to obtain a heat-treated laminated film.

[0138] The heat-treated laminated film was evaluated by the above-mentioned method. Furthermore, a monolayer film was produced using the same resin as that for forming each layer of the laminated film under the same conditions as the laminated film, and the crystallinity of the monolayer film was measured and observed by TEM. The crystallinity value obtained from the monolayer film was taken as the crystallinity of the polymer contained in each layer of the laminated film.

[0139] Comparative Example 2 In Example 1 (1-1. Step (1): Melting of resin), pellets of COP1 were introduced into the second single-screw extruder. In Example 1 (1-2. Step (2a): Extrusion of molten resin), a molten resin film having a single-layer structure formed from COP1 was continuously formed from the single-layer die. The preheated monolayer film was cooled to room temperature (23° C.) without carrying out the step (1-4. Step (2d): heat treatment step) of Example 1. Except for the above, the same procedure as in Example 1 was carried out to obtain a monolayer film, which was then evaluated by the above-mentioned method.

[0140] Comparative Example 3 In Example 1 (1-1. Step (1): Melting of resin), pellets of COP1 were introduced into the second single-screw extruder. In Example 1 (1-2. Step (2a): Extrusion of molten resin), a molten resin film having a single-layer structure formed from COP1 was continuously formed from the single-layer die. Except for the above, the same procedure as in Example 1 was carried out to obtain a monolayer film, which was then evaluated by the above-mentioned method.

[0141] Comparative Example 4 In Example 1 (1-1. Step (1): Melting of resin), pellets of COP2 were introduced into each of the first single-screw extruder and the second single-screw extruder. In Example 1 (1-2. Step (2a): Extrusion of molten resin), a molten resin film having a single-layer structure formed from COP2 was continuously formed from the single-layer die. Except for the above, the same procedure as in Example 1 was carried out to obtain a monolayer film, which was then evaluated by the above-mentioned method.

[0142] Comparative Example 5 In Example 1 (1-1. Step (1): Melting of Resin), pellets of amorphous COP were introduced into each of the first single-screw extruder and the second single-screw extruder. In Example 1 (1-2. Step (2a): Extrusion of molten resin), a molten resin film having a single-layer structure made of an amorphous COP was continuously formed from a single-layer die. Except for the above, the same procedure as in Example 1 was carried out to obtain a monolayer film, which was then evaluated by the above-mentioned method.

[0143] Comparative Example 6 In Example 1 (1-1. Step (1): Melting of resin), pellets of amorphous COP were introduced into the second single-screw extruder. In Example 1 (1-2. Step (2a): Extrusion of molten resin), COP1 and the amorphous COP were extruded from the single-layer die of the extruder in a molten state at 280° C. This resulted in the continuous formation of a molten resin film having, in this order, a skin layer formed from the amorphous COP, a core layer formed from COP1, and another skin layer formed from the amorphous COP. In Example 1 (1-3. Step (2b): preheating step), the preheating temperature was set to 160°C. In Example 1 (1-4. Step (2d): heat treatment step), the heating temperature was set to 160°C. Except for the above, the same procedure as in Example 1 was carried out to obtain a heat-treated laminated film.

[0144] The heat-treated laminated film was evaluated by the above-mentioned method. Furthermore, a monolayer film was produced using the same resin as that for forming each layer of the laminated film under the same conditions as the laminated film, and the crystallinity of the monolayer film was measured and observed by TEM. The crystallinity value obtained from the monolayer film was taken as the crystallinity of the polymer contained in each layer of the laminated film.

[0145] [result] The results are shown in the table below. In the table below, for convenience, a film having a single layer structure is described as a film having only the second resin layer. The ratios shown in the "Thickness ratio" column in the table below mean (thickness of first resin layer) / (thickness of second resin layer) / (thickness of third resin layer). The "stretching ratio" in the table below refers to the ratio calculated from (stretching ratio in MD direction) x (stretching ratio in TD direction).

[0146] [Table 2]

[0147] [Table 3]

[0148] From the above results, the following points can be seen. The laminated films of Examples 1 to 5, which have a first resin layer and a third resin layer formed from an amorphous resin (A) with a crystallinity of less than 5%, and a second resin layer formed from a crystalline resin (B) with a crystallinity of 5% or more but 40%, are evaluated as having good adhesion to adhesives, solvent resistance, and heat resistance.

[0149] The laminated film of Comparative Example 1, which has a first resin layer and a third resin layer formed from a crystalline resin (A) with a crystallinity of 5% or more, is evaluated as poor in terms of adhesion to an adhesive.

[0150] Moreover, the laminated films according to Comparative Examples 2 to 5, which do not have a first resin layer, are evaluated as being poor in either adhesion to an adhesive or heat resistance.

[0151] The laminated film according to Comparative Example 6, in which the second resin layer is formed from a resin that does not contain a crystalline polymer, is evaluated as being poor in heat resistance. [Explanation of symbols]

[0152] 100 Laminated Film 110 First resin layer 120 Second resin layer 130 Third resin layer

Claims

1. A first resin layer, which is a layer of resin (A) that contains a crystalline polymer, has a crystallization onset temperature Tc(A), and is in an amorphous state; and a second resin layer which is a layer of resin (B) which contains a crystalline polymer, has a crystallization onset temperature Tc(B), and is in a crystalline state; A laminated film that satisfies the following formula (1): The resin (B) comprises a cyclic olefin polymer. (Tc(A)-Tc(B))>0℃ (1)

2. Further comprising a third resin layer which is a layer of the resin (A), The laminated film according to claim 1 , wherein the second resin layer is provided between the first resin layer and the third resin layer.

3. The laminated film according to claim 1 or 2, wherein the resin (A) further contains an amorphous polymer.

4. The laminate film according to any one of claims 1 to 3, which satisfies the following formula (2): (Tc(A)-Tc(B))≧15℃ (2)

5. The laminate film according to any one of claims 1 to 4, wherein the resin (A) contains a cyclic olefin polymer.

6. A method for producing a laminated film, comprising: The laminated film is The resin layer comprises a first resin layer, which is a layer of resin (A) that contains a crystalline polymer and is in an amorphous state, having a crystallization onset temperature Tc(A), and a second resin layer, which is a layer of resin (B) that contains a crystalline polymer and is in a crystalline state, having a crystallization onset temperature Tc(B), The following formula (1) is satisfied: (Tc(A)-Tc(B))>0℃ (1) The manufacturing method includes: A step (1) of melting a resin (a) containing a crystalline polymer and having the crystallization onset temperature Tc(A) and a resin (b) containing a crystalline polymer and having the crystallization onset temperature Tc(B), respectively; a step (2) of extruding a layer of the molten resin (a) and a layer of the molten resin (b) to obtain a laminated film; The method for producing a laminated film, wherein the step (2) comprises a step of heat-treating the laminated film at a temperature T h that is lower than the crystallization onset temperature Tc(A).

7. The laminated film, Further comprising a third resin layer which is a layer of the resin (A), The method for producing a laminated film according to claim 6 , wherein the second resin layer is provided between the first resin layer and the third resin layer.

8. A method for producing a laminated film as described in claim 6 or 7, wherein the resin (A) of the laminated film further contains an amorphous polymer.

9. A method for producing a laminated film described in any one of claims 6 to 8, wherein the laminated film satisfies the following formula (2): (Tc(A)-Tc(B))≧15℃ (2)

10. A method for producing a laminated film described in any one of claims 6 to 9, wherein the resin (A) and the resin (B) each independently contain a cyclic olefin-based polymer.

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