JP2021054070A - Laminated film - Google Patents

Abstract

To provide a laminated film having a low phase difference and excellent even in quality or productivity, and a method for manufacturing the same.SOLUTION: The laminated film including an A layer and a B layer having crystal melting energy ΔHm (J/g) different from each other is provided in which both surfaces of the A layer are in contact with the B layer, the retardation of the A layer is 0.0 nm or more and 180 nm or less, the surface orientation coefficient of the B layer is 0.0300 or more and 0.1700 or less, and when ΔHmA (J/g) denotes ΔHm of the A layer and ΔHmB (J/g) denotes ΔHm of the B layer, ΔHmB-ΔHmA is 5.0 (J/g) or more, and the peel strength of at least one of the B layer and the A layer is 1.0 g/50 mm or more and 100 g/50 mm or less.SELECTED DRAWING: None

Description

The present invention relates to a laminated film having a low retardation layer and a protective layer.

In recent years, in the field of flat panel displays and touch panels, there is an increasing demand for optical films having various low phase differences such as polarizing element protective films and transparent conductive films. In such an optical film, in addition to usually having a low phase difference, improvement in quality, reduction in thickness unevenness, dimensional stability at high temperature, productivity and the like are also required.

So far, various studies have been made on films and methods for producing them in order to improve the above characteristics. For example, a laminated film of a target film layer and a protective layer is vertically stretched by a roll-type stretcher, and then the protective layer is peeled off and laterally stretched or heat-treated in a non-contact manner on a roll. There is known a method for producing a film that reduces scratches and the like due to slipping on the surface (Patent Document 1). Further, there is also known a method of producing a film having both optical characteristics and handleability by adding gels of different sizes to a cyclic olefin resin having excellent optical characteristics to form a film (Patent Document 2). Further, it is also known that a biaxially oriented cyclic olefin resin film having a draw ratio of 1.1 to 1.8 times in each direction becomes an optical film having excellent heat resistance, optical characteristics, and dimensional stability. (Patent Document 3).

Japanese Unexamined Patent Publication No. 2001-30351 Japanese Unexamined Patent Publication No. 2009-227932 Japanese Unexamined Patent Publication No. 2011-93285

However, in the technique described in Patent Document 1, productivity is improved by integrating the target film layer and the protective layer to form a film, but the conditions of stretching and heat treatment are limited, so that the ring is cyclic. There is a problem that it is difficult to apply it to the production of a low retardation film containing an olefin resin as a main component. The technique described in Patent Document 2 is excellent in that a high-quality film can be obtained, but when long-term storage or transportation is required, a step of attaching a protective layer afterwards is required to prevent scratches or the like. Therefore, it is inferior in terms of productivity, cost, and versatility. Further, although the film of Patent Document 3 is a biaxially oriented film, it is insufficient to be a low retardation film because the draw ratio remains at a maximum of 3.24 times in terms of area magnification. It is not clear about the improvement.

An object of the present invention is to overcome these problems of the prior art and to provide a laminated film having a low phase difference and excellent quality and productivity, and a method for producing the same.

The present invention employs the following means in order to solve such a problem.
(1) The crystal melting energy ΔHm (J / g) has different layers A and B, both surfaces of the layer A are in contact with the layer B, and the retardation of the layer A is 0.0 nm or more and 180 nm or less. , When the plane orientation coefficient of the B layer is 0.0300 or more and 0.1700 or less, ΔHm of the A layer is ΔHm _A (J / g), and ΔHm of the _B layer is ΔHm B (J / g), ΔHm. _{B −} ΔHm _A is 5.0 (J / g) or more, and the peel strength between at least one B layer and the A layer is 1.0 g / 50 mm or more and 100 g / 50 mm or less. Laminated film.
(2) When the solubility parameter of the A layer is SP _A (cal / cm ³ ) ^1/2 and the solubility parameter of the B layer is SP _B (cal / cm ³ ) ^1/2 , | SP _A- SP The laminated film according to (1), wherein _{B | is 0.5 or more and 4.0 or less.}
(3) The laminated film according to (1) or (2), wherein the haze is 0.5% or more and 3.0% or less.
(4) The laminated film according to any one of (1) to (3), wherein the glass transition temperature (Tg _{A) of the A layer is more than 100 ° C. and 170 ° C. or less.}
(5) The laminated film according to any one of (1) to (4), wherein the layer A contains an amorphous resin as a main component.
(6) The amorphous resin is at least one resin selected from polypropylene-based resin, cyclic olefin-based resin, polystyrene resin, polycarbonate resin, acrylic resin, polyester resin, and polyamide resin. The laminated film according to (5).
(7) The laminated film according to any one of (1) to (6), wherein the number of times the layer A has reached bending fracture is 100 times or more and 10,000 times or less.
(8) The laminated film according to any one of (1) to (7), wherein the surface roughness Ra of one side or both sides of the A layer is 1 nm or more and 100 nm or less.
(9) The laminated film according to any one of (1) to (8), wherein the minute endothermic peak temperature (Tmeta) of the B layer is 120 ° C. or higher and 220 ° C. or lower.
(10) The plane refractive index of the B layer is 1.6000 or more and 1.6600 or less, and the thickness direction refractive index of the B layer is 1.4800 or more and 1.5700 or less. The laminated film according to any one of 1) to (9).
(11) The crystalline parameter (ΔTcg) of the B layer is 10 ° C. or higher and 100 ° C. or lower, and the ΔHm _B is 15.0 J / g or higher and 50.0 J / g or lower (1). ) To (10).
(12) The laminated film according to any one of (1) to (11), wherein the glass transition temperature (Tg _{B) of the B layer is 30 ° C. or higher and 100 ° C. or lower.}
(13) The laminated film according to any one of (1) to (12), wherein the B layer contains a crystalline resin as a main component.
(14) The laminated film according to (13), wherein the crystalline resin is a polyester resin.
(15) The method for producing a laminated film according to any one of (1) to (14), wherein the molten resin composition for obtaining the layer A is the molten resin composition A and the B. When the molten resin composition for obtaining a layer is a molten resin composition B, it is obtained by a coextrusion laminating step and a coextrusion laminating step in which the molten resin composition A and the molten resin composition B are coextruded and laminated. It has a casting step of cooling and solidifying the laminated body, a stretching step of stretching the sheet obtained by the casting step in at least one direction, and a heat treatment step of heat-treating at a temperature of _{Tg A} + 20 ° C. or higher and Tg _{A + 120 ° C. or lower in this order.} A method for producing a laminated film.
(16) The method for producing a laminated film according to (15), wherein the crystallinity of the B layer in the casting step is controlled to be 10% or more and 30% or less.
(17) The method for producing a laminated film according to (15) or (16), wherein the molten resin composition B is laminated on both sides of the molten resin composition A in a coextrusion laminating step.
(18) The method for producing a laminated film according to (17), wherein the compositions of the molten resin composition B located on each surface side of the molten resin composition A are different from each other.
(19) Any of (15) to (18), characterized in that a widening step of individually widening the molten resin composition A and the molten resin composition B is provided upstream of the coextrusion laminating step. The method for producing a film according to.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a laminated film having a low phase difference and excellent quality and productivity, and a method for producing the same.

The laminated film of the present invention has layers A and B having different crystal melting energies ΔHm (J / g) from each other, both surfaces of the layer A are in contact with the layer B, and the retardation of the layer A is 0.0 nm or more. It is 180 nm or less, the plane orientation coefficient of the B layer is 0.0300 or more and 0.1700 or less, ΔHm of the A layer is ΔHm _A (J / g), and ΔHm of the _B layer is ΔHm B (J / g). Occasionally, ΔHm _{B − ΔHm A} is 5.0 (J / g) or more, and the peel strength between at least one B layer and A layer is 1.0 g / 50 mm or more and 100 g / 50 mm or less. It is a feature. Hereinafter, the present invention will be specifically described.

From the viewpoint of protecting the A layer, the laminated film of the present invention has the A layer and the B layer having different crystal melting energies ΔHm (J / g), and both surfaces of the A layer and the B layer are in contact with each other. is important. ΔHm is a value indicating how much the resin constituting the layer was in a crystallized state, and is an index of the hardness of the layer. That is, the higher ΔHm, the higher the hardness of the layer. The ΔHm can be measured by a method based on JIS K-7122 (1987 version). Further, "the two surfaces of the A layer are in contact with the B layer" means that the B layer / A layer / B layer has at least one laminated structure in which the layers are directly laminated in this order. In the laminated film of the present invention, the A layer is assumed to be used for optical applications and the like, and the B layer plays a role of protecting the A layer. In such an embodiment, each B layer located on both sides of the A layer functions as a protective layer of the A layer. Therefore, a film in which the B layers on both sides are peeled off from the laminated film of the present invention (hereinafter referred to as the A layer). (Sometimes referred to as a film)) can be suitably used for optical applications and the like because it suppresses the occurrence of scratches and irregularities due to friction with the roll and collision of foreign substances in the winding process and the like.

The laminated structure of the laminated film of the present invention is not particularly limited as long as both surfaces of the A layer and the B layer are in contact with each other. For example, B / A / B is the least laminated structure for achieving the effect of the present invention, but a super-multilayer structure having 100 or more layers such as B / A / B / A / B ... It is also possible to have a C / B / A / B configuration or a C / B / A / B / C configuration in which a C layer is provided on the outside of the B. The thickness ratio (A: B) of the A layer to the B layer is not particularly limited, but is preferably 1: 10 to 1: 100 from the viewpoint of film formation stability and protection performance, and is preferably 1: 10 to 1. : 20 is more preferable.

In the B / A / B configuration, the thickness of each B layer may be the same or different as long as the effect of the present invention is not impaired. Further, the thickness ratio of each layer in the B / A / B configuration is not particularly limited as long as the effect of the present invention is not impaired, but from the viewpoint of film forming stability and protection performance, 1: 1: 1 to 1:20: It is preferably 1.

From the viewpoint of protecting the A layer, the laminated film of the present invention _{has ΔHm B −} ΔHm _{A when ΔHm of the A layer is ΔHm A} (J / g) and ΔHm of the B layer is ΔHm _B (J / g). It is important that is 5.0 (J / g) or more. Since the ΔHm of the B layer is higher than the ΔHm of the A layer, the B layer can exhibit high protection performance. From the above viewpoint, ΔHm _{B −} ΔHm _A is preferably 10.0 J / g or more and 50.0 J / g or less. As a method of setting _{ΔHm B − ΔHm A} to 5.0 (J / g) or more or the above-mentioned preferable range, for example, a method of selecting the resin constituting the A layer and the B layer in consideration of the difference of ΔHm can be mentioned. .. More specifically, satisfies the .DELTA.Hm _B> .DELTA.Hm _A, and by selecting the resin such that the difference therebetween is large, it is possible to increase the ΔHm _B -ΔHm _A.

From the viewpoint of easily obtaining the A layer film, it is important that the peel strength between at least one B layer and the A layer of the laminated film of the present invention is 1.0 g / 50 mm or more and 100 g / 50 mm or less. With such an embodiment, it becomes easy to separate the A layer and the B layer. More specifically, if the peel strength between the B layer and the A layer is less than 1.0 g / 50 mm, delamination occurs with a small force, and a problem of peeling occurs in the transport process or the processing process. On the other hand, if the peeling strength between the B layer and the A layer exceeds 100 g / 50 mm, the adhesion between the B layer and the A layer becomes excessively strong, which makes it difficult to peel the two and at the time of peeling. The problem is that tears and residues are generated. From the above viewpoint, the peel strength between the B layer and the A layer is preferably 2.0 g / 50 mm or more and 50 g / 50 mm or less. Further, from the above viewpoint, the peel strength between at least one B layer and the A layer may be 1.0 g / 50 mm or more and 100 g / 50 mm or less, or the above-mentioned preferable range, but from the viewpoint of easily obtaining the A layer film. Therefore, it is preferable that the peel strength between the B layer and the A layer on both sides is 1.0 g / 50 mm or more and 100 g / 50 mm or less, or the above-mentioned preferable range. The peel strength between the B layer and the A layer refers to the peel strength between the B layer and the A layer when peeled at 180 °, which is measured according to JIS K 6854-2 (1999 edition).

In the laminated film of the present invention, the peel strength between the B layer and the A layer as a method for the 1.0 g / 50 mm or more 100 g / 50 mm or less or the above preferred range, the solubility parameter of the A layer _SP A (cal / cm ³ ) When ^1/2 and the solubility parameter of the B layer are set to SP _B (cal / cm ³ ) ^1/2 , a method of adjusting | SP _A- SP _B | can be preferably used. Normally, the peel strength between the B layer and the A layer _{can be suppressed to be low by increasing | SP A-} SP _B |. Therefore, when it is desired to reduce the peel strength between the B layer and the A layer, | SP _A- The resin constituting each layer may be selected so that _{SP B | becomes large.} Specifically, from the viewpoint of achieving both reduction of peeling in the transport process and processing process and suppression of residue during peeling, | SP _A- SP _B | is preferably 0.5 or more and 4.0 or less, and 1.0 or more. 3.0 or less is more preferable. Further, as another method, the peel strength between the B layer and the A layer can be controlled by adjusting the heat treatment conditions after stretching and the thickness of the laminated film. More specifically, the peel strength between the B layer and the A layer can be increased by setting the heat treatment temperature to be equal to or higher than the glass transition temperature of the A layer and increasing the thickness of the laminated film.

In the present invention, the solubility parameters SP _A (cal / cm ³ ) ^1/2 and SP _B (cal / cm ³ ) ^1/2 are calculated by Fedors, which can be calculated relatively easily based on the molecular structural formula. Use the method. In the calculation method of Fedors, it is considered that the solubility of the molecular aggregation energy density and the molar molecular volume changes depending on the type and number of substituents, and the solubility parameter value δ (cal / cm ³ ) according to the following formula (1). ^1/2 is estimated. Here, _Ecoh (cal / mol) represents the aggregation energy, and V represents the molar molecular volume (cm ³ / mol).

Since the solubility parameter SP value of the thermoplastic resin can be estimated using the Fedor formula based on the repeating structural unit of the molecular chain, the solubility parameter SP value of the thermoplastic resin containing the structural unit derived from the copolymerization component. Calculates the ratio according to the ratio of each structural unit. The solubility parameter SP values of typical thermoplastic resins are polypropylene: 8.0 (cal / cm ³ ) ^1/2 , polyethylene terephthalate: 10.7 (cal / cm ³ ) ^1/2 , and polystyrene: 9. .4 (cal / cm ³ ) ^1/2 , polymethyl methacrylate: 9.3 (cal / cm ³ ) ^1/2 , polybutylene terephthalate: 10.0 (cal / cm ³ ) ^1/2 , nylon 6: 12.7 (cal / cm ³ ) ^1/2 , Polypropylene: 9.9 (cal / cm ³ ) ^1/2 , COP: 8.6 (cal / cm ³ ) ^1/2 , COC: 7.8 (cal) / Cm ³ ) ^1/2 , ABS resin: 10.0 (cal / cm ³ ) ^1/2 , polypropylene: 8.0 (cal / cm ³ ) ^{1/2, and the} like. When each layer contains a plurality of components, the mass ratio of each component is multiplied by the SP value of each component, and the total value is taken as the SP _A value and the SP _B value.

In the laminated film of the present invention, it is important that the retardation of the A layer is 0.0 nm or more and 180 nm or less. With such an aspect, it is possible to reduce the rainbow unevenness of the A layer and secure the visibility. Therefore, the film from which the B layers on both sides are peeled off from the laminated film of the present invention (hereinafter, may be referred to as an A layer film) has rainbow unevenness as well as visibility as in optical applications such as protector protection. It can be used for applications that require mitigation.

If the retardation of the A layer exceeds 180 nm, problems such as rainbow unevenness and deterioration of visibility occur in the film composed of the A layer, which makes it difficult to use for the above-mentioned applications. From the viewpoint of improving the visibility of the film composed of the A layer and reducing the rainbow unevenness, the retardation of the A layer is preferably 0.0 nm or more and 100 nm or less, more preferably 0.0 nm or more and 10 nm or less, and particularly preferably 0. It is 0.0 nm or more and 1.0 nm or less.

The retardation of the A layer in the present invention is a value obtained by measuring the phase difference of the A layer film with respect to a light beam having a wavelength of 548.3 nm using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Measurement Co., Ltd. And.

Examples of the method for setting the retardation of the A layer to 0.0 nm or more and 180 nm or less or the above-mentioned preferable range include a method in which the main component of the A layer is an amorphous resin. More specifically, it is possible to reduce the retardation of the A layer by increasing the content ratio of the amorphous resin in the A layer or by using a stronger amorphous resin. The principal component means a component contained in excess of 50% by mass when all the components constituting the layer are taken as 100% by mass. When a plurality of types of components corresponding to the amorphous resin are contained, it can be interpreted that the amorphous resin is the main component if the total amount of the components corresponding to the amorphous resin exceeds 50% by mass. Hereinafter, the "main component" can be interpreted in the same manner. In the present invention, the amorphous resin refers to a resin having a crystal melting energy ΔHm obtained from a differential scanning calorimeter DSC of less than 5.0 J / g. Further, the strength of amorphousness is determined by the value of ΔHm, and the lower the ΔHm, the stronger the amorphousness. That is, the resin having ΔHm of 0.0 J / g is the most amorphous resin, and the resin having ΔHm of 5.0 J / g is the most amorphous crystalline resin.

When the main component of the A layer is a crystalline resin, the retardation of the A layer is set to 0 by a method of stretching at a uniform magnification in two orthogonal directions or a method of performing heat treatment after stretching to relax the orientation of the molecules. It can be 0.0 nm or more and 180 nm or less, or the above-mentioned preferable range. The heat treatment conditions at this time are preferably performed under the conditions of the crystal melting peak temperature (Tm ° C.) or higher and Tm + 80 ° C. or lower of the crystalline resin.

The resin in the A layer of the laminated film of the present invention is not particularly limited as long as the effect of the present invention is not impaired, but from the viewpoint of optical quality, polypropylene resin, cyclic olefin resin, polystyrene resin, polycarbonate resin, acrylic resin, polyester. It is preferably at least one resin selected from the resin and the polyamide resin. Here, at least one kind of resin is a mode in which it is a single component, a mode in which a plurality of types of resins in the same category are contained (for example, a mode in which a plurality of types of cyclic olefin resins are contained), and a mode in which resins in different categories are contained. (For example, an embodiment containing two or more components in total of a cyclic olefin resin and a polystyrene resin).

In the present invention, the polypropylene-based resin means a polymer in which the total of polypropylene-derived components (polypropylene units) is more than 50 mol% and 100 mol% or less when the total constituent units of the resin are 100 mol%. .. Specifically, various polypropylene-based resins such as polypropylene, ethylene-propylene copolymer, ethylene-propylene-butene copolymer, methylpentene polymer and the like can be used. Further, a polymer composed of α-olefin monomers such as ethylene, propylene, butene-1, butene-1, 4-methylpentene-1, hexene-1, and octene-1, and a random copolymer composed of the α-olefin monomer. , A block copolymer composed of the α-olefin monomer and the like can also be used.

In the present invention, the cyclic olefin resin refers to a cyclic olefin resin (hereinafter, may be referred to as COP) or a cyclic olefin copolymer resin (hereinafter, may be referred to as COC). The cyclic olefin resin (COP) means a resin in which only a "repetitive unit containing a cyclic olefin skeleton in the main chain" (hereinafter, may be referred to as a cyclic olefin unit) is polymerized, and a cyclic olefin copolymer resin (Cyclic olefin copolymer resin). COC) means a resin in which a cyclic olefin unit and a "repetitive unit composed of an olefin unit containing no cyclic olefin skeleton in the main chain" (hereinafter, may be referred to as a non-cyclic olefin unit) are copolymerized.

Cyclic olefins (cyclic olefin units) constituting COP and COC include monocyclic olefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, cyclopentadiene, and 1,3-cyclohexadiene, and bicyclo [2,2,1] hept-. 2-ene, 5-methyl-bicyclo [2,2,1] hepta-2-ene, 5,5-dimethyl-bicyclo [2,2,1] hept-2-ene, 5-ethyl-bicyclo [2, 2,1] hept-2-ene, 5-butyl-bicyclo [2,2,1] hept-2-ene, 5-ethylidene-bicyclo [2,2,1] hept-2-ene, 5-hexyl- Bicyclo [2,2,1] hept-2-ene, 5-octyl-bicyclo [2,2,1] hept-2-ene, 5-octadecil-bicyclo [2,2,1] hept-2-ene, 5-Methylidene-bicyclo [2,2,1] hept-2-ene, 5-vinyl-bicyclo [2,2,1] hept-2-ene, 5-propenyl-bicyclo [2,2,1] hept- Bicyclic olefins such as 2-ene, tricyclo [4,3,0,12.5] deca-3,7-diene, tricyclo [4,3,0,12.5] deca-3-ene, tricyclo [4] , 3,0,12.5] Undeca-3,7-diene or tricyclo [4,3,0,12.5] Undeca-3,8-diene or partial hydrogenating these (or cyclopentadiene and cyclohexene) Tricyclo [4,3,0,12.5] undeca-3-ene; 5-cyclopentyl-bicyclo [2,2,1] hept-2-ene, 5-cyclohexyl-bicyclo [2,2] , 1] Tricyclic olefins such as hept-2-ene, 5-cyclohexenylbicyclo [2,2,1] hept-2-ene, 5-phenyl-bicyclo [2,2,1] hepta-2-ene, Tetracyclo [4,4,0,12.5,17.10] dodeca-3-ene, 8-methyltetracyclo [4,4,0,12.5,17.10] dodeca-3-ene, 8- Ethyltetracyclo [4,4,0,12.5,17.10] dodeca-3-ene, 8-methylidenetetracyclo [4,4,0,12.5,17.10] dodeca-3-ene , 8-Echilidene tetracyclo [4,4,0,12.5,17.10] dodeca-3-ene, 8-vinyltetracyclo [4,4,0,12.5,17.10] dodeca-3 -En, 8-propenyl-tetracyclo [4,5,0,12.5 , 17.10] Dodeca-3-ene, a tetracyclic olefin, 8-cyclopentyl-tetracyclo [4,5,0,12.5, 17.10] dodeca-3-ene, 8-cyclohexyl-tetracyclo [4, 4,0,12.5,17.10] dodeca-3-ene, 8-cyclohexenyl-tetracyclo [4,4,0,12.5,17.10] dodeca-3-ene, 8-phenyl-cyclopentyl -Tetracyclo [4,4,0,12.5,17.10] Dodeca-3-ene, Tetracyclo [7,4,13.6,01.9,02.7] Tetradeca-4,9,11,13 -Tetraene, Tetracyclo [8,4,14.7,01.10,03.8] Pentadeca-5,10,12,14-Tetraene, Pentacyclo [6,6,13.6,02.7,09.14] ] -4-Hexadecene, pentacyclo [6,5,1,13.6,02.7,09.13] -4-pentadecene, pentacyclo [7,4,0,02.7,13.6,110.13] ] -4-Pentadecene, heptacyclo [8,7,0,12.9,14.7,111.17,03.8,012.16] -5-eikosen, heptacyclo [8,7,0,12.9] , 03.8, 14.7, 012.17, 113.16] -14-Eikocene and other polycyclic olefins such as tetramers. These cyclic olefins can be used alone or in combination of two or more.

Among the above, from the viewpoint of productivity and surface properties, bicyclo [2,2,1] hept-2-ene (hereinafter sometimes referred to as norbornene) and tricyclo [4,3,0,12.5] deca Tricyclic olefins having 10 carbon atoms (hereinafter, may be referred to as tricyclodecene) such as -3-ene, tetracyclo [4,5,0,12.5, 17.10] dodeca-3-ene, etc. , A tetracyclic olefin having 12 carbon atoms (hereinafter referred to as tetracyclododecene), cyclopentadiene, 1,3-cyclohexadiene and the like are preferably used.

Examples of the method for producing COP include known methods such as addition polymerization of cyclic olefin monomers and ring-opening polymerization. For example, norbornene, tricyclodecene, tetracyclododecene, and derivatives thereof are subjected to ring-opening metathesis polymerization. After that, a method of addition polymerization of norbornene and its derivative, a method of addition polymerization of cyclopentadiene and cyclohexadiene 1,2-, 1,4-addition polymerization and then hydrogenation and the like can be mentioned.

The acyclic olefin (acyclic olefin unit) constituting the COC in the present invention may be in either a mode in which the side chain contains a cyclic olefin skeleton or a mode in which the side chain does not contain a cyclic olefin skeleton, but the productivity and cost From this point of view, it is preferable that the side chain does not contain a cyclic olefin, that is, a so-called chain olefin (chain olefin unit). Preferred chain olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-. Methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1- Examples thereof include hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like. Among these, ethylene can be particularly preferably used from the viewpoint of productivity and cost.

Examples of the method for producing COC include known methods such as addition polymerization of a cyclic olefin monomer and a non-cyclic olefin monomer, and specific examples thereof include a method of addition-copolymerizing norbornene and its derivatives with ethylene.

From the viewpoint of heat resistance, the molar ratio of the cyclic olefin unit and the acyclic olefin unit of COC in the layer A is the cyclic olefin unit (mol%) / acyclic olefin unit (mol) when all the constituent units are 100 mol%. %) = 60/40 to 85/15, more preferably 65/35 to 80/20. By setting the molar ratio of the cyclic olefin units in the COC to 60 mol% or more when all the constituent units are 100 mol%, the glass transition temperature is not excessively lowered and the heat resistance of the A layer is improved.

When COP is used in the A layer, norbornene, tricyclodecene, tetracyclododecene, and derivatives thereof are hydrogenated after ring-opening metathesis polymerization as the COP in the A layer from the viewpoint of productivity and surface characteristics. The resin is a particularly preferable embodiment. When COC is used in the A layer, a copolymer of norbornene and ethylene is a particularly preferable embodiment as the COC in the A layer from the same viewpoint.

A resin having low polarity such as COC and COP in the A layer is used as an optical film by peeling the B layer from the viewpoint of improving the adhesion with a coating film layer such as a polarizer or other adhesive layer. It may contain a polar group. Examples of the polar group include a carboxyl group, an acid anhydride group, an epoxy group, an amide group, an ester group, a hydroxyl group and the like, and these polar groups in a resin having low polarity such as COC and COP are There may be one type or a plurality of types as long as the effects of the present invention are not impaired. Further, as a method of incorporating a polar group into a resin having a low polarity such as COC or COP, a method of grafting and / or copolymerizing an unsaturated compound having a polar group can be mentioned. Examples of unsaturated compounds having a polar group include (meth) acrylic acid, maleic acid, maleic anhydride, itaconic anhydride, glycidyl (meth) acrylate, alkyl (meth) acrylate (1 to 10 carbon atoms) ester, and maleic acid. Examples thereof include alkyl (1 to 10 carbon atoms) esters, (meth) acrylamide, and -2-hydroxyethyl (meth) acrylate.

When the layer A contains a cyclic olefin resin such as COC or COP as a main component, the layer A may contain all the components thereof or other resin components. Examples of other resin components include acyclic olefin resins. The acyclic olefin resin refers to a resin in which only acyclic olefin units are polymerized.

Examples of the acyclic olefin resin include a polymer composed of α-olefin monomers such as ethylene, propylene, butene-1, penten-1, 4-methylpentene-1, hexene-1, and octene-1, and the α-. Examples thereof include a random copolymer composed of an olefin monomer and a block copolymer composed of the α-olefin monomer. Specific examples include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, various polyethylene-based resins such as ethylene-α / olefin copolymer polymerized using a metallocene catalyst, polypropylene, and ethylene-. Examples thereof include various polypropylene-based resins such as propylene copolymers and ethylene-propylene-butene copolymers, and methylpentene polymers. When the layer A contains such an acyclic olefin resin, its brittleness can be alleviated.

Among these acyclic olefin resins, various polyethylene resins and various polypropylene resins are preferably used from the viewpoint of compatibility with COC and COP. When the A layer contains a polyethylene-based resin or a polypropylene-based resin, it is possible to reduce the shear stress in the extrusion process in addition to alleviating the brittleness. Therefore, it is possible to suppress the generation of foreign matter due to cross-linking. The polyethylene-based resin has a total of 50 mol% or more and 100 mol% or less, more preferably more than 50 mol% and 100, when the total constituent units of the resin are 100 mol%. It means a polymer of an embodiment of mol% or less.

The polystyrene-based resin is a polymer obtained by polymerizing a styrene monomer. The polystyrene resin in the layer A is preferably a styrene-based polymer having a syndiotactic structure (syndiotactic polystyrene-based resin, hereinafter sometimes referred to as SPS-based resin). A syndiotactic structure is a stereochemical structure in which phenyl groups or substituted phenyl groups, which are side chains of a main chain formed from carbon-carbon bonds, are alternately located in opposite directions. Means structure. The degree of stereoregularity (tacticity) of the SPS-based resin can be quantified by the nuclear magnetic resonance method (13C-NMR method) using isotope carbon. The tacticity of the SPS-based resin measured by the 13C-NMR method is a chain consisting of several monomer units, for example, a diad for two, a triad for three, and a pentad for five. It can be indicated by the ratio of those in which the three-dimensional arrangement of the structural units is inversely syndiotactic (racemic diad, etc.). The SPS-based resin in the present invention is usually 75% or more, preferably 85% or more, or 60% or more, preferably 75% or more, or 30% or more, preferably 50% of racemic pentad. It is a styrene-based polymer having the above syndiotacticity. Types of styrene-based polymers as SPS-based resins include polystyrene, poly (alkylstyrene), poly (halogenated styrene), poly (alkyl halide styrene), poly (alkoxystyrene), poly (vinyl benzoic acid ester), and so on. Examples thereof include these hydrides and the like, mixtures thereof, and copolymers containing these as main components. Poly (alkyl styrene) includes poly (methyl styrene), poly (ethyl styrene), poly (isopropyl styrene), poly (territory butyl styrene), poly (phenyl styrene), poly (vinyl naphthalene), and poly (vinyl styrene). ) Etc. can be mentioned. Examples of poly (halogenated styrene) include poly (chlorostyrene), poly (bromostyrene), poly (fluorostyrene) and the like. Examples of poly (alkyl styrene halogenated) include poly (chloromethyl styrene). Examples of poly (alkoxystyrene) include poly (methoxystyrene) and poly (ethoxystyrene).

The polycarbonate resin is a polymer obtained by reacting a dihydroxydiaryl compound with a phosgene or a carbonic acid ester such as diphenyl carbonate. Examples of dihydroxydiaryl compounds used in polycarbonate resins include 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A), bis (4-hydroxyphenyl) methane, and 1,1-bis (4-hydroxy). Phenyl) ethane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydroxyphenyl) octane, bis (4-hydroxyphenyl) phenylmethane, 2,2-bis (4-hydroxyphenyl) -3-Methylphenyl) propane, 1,1-bis (4-hydroxy-3-3rd butylphenyl) propane, 2,2-bis (4-hydroxy-3-bromophenyl) propane, 2,2-bis (4) Bis (hydroxyaryl) alkane compounds such as 4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-3,5-dichlorophenyl) propane, 1,1-bis (4-hydroxy) Bis (hydroxyaryl) cycloalkane compounds such as phenyl) cyclopentane and 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxy-3,3'-dimethyl Dihydroxydiaryl ether compounds such as diphenyl ether, dihydroxydiaryl sulfide compounds such as 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxy-3,3'-dimethyldiphenyl sulfoxide. Dihydroxydiarylsulfoxide compounds such as 4,4'-dihydroxydiphenylsulfone, dihydroxydiarylsulfone compounds such as 4,4′-dihydroxy-3,3′-dimethyldiphenylsulfone, etc. are examples, but are limited thereto. Not done. Further, these may be used alone or in a plurality of types as needed.

Further, as the polycarbonate resin in the present invention, a compound having three or more phenolic hydroxyl groups may be used in addition to the above-mentioned dihydroxydiaryl compound. Examples are fluoroglucin, 4,6-dimethyl-2,4,6-tri (4-hydroxyphenyl) -heptene, 2,4,6-dimethyl-2,4,6-tri- (4-hydroxyphenyl)-. Heptane, 1,3,5-tri- (4-hydroxyphenyl) -benzol, 1,1,1-tri- (4-hydroxyphenyl) -ethane and 2,2-bis [4,4- (4,4) '-Dihydroxydiphenyl) -cyclohexyl] -propane and the like can be mentioned.

The polycarbonate resin of the present invention is a polycarbonate resin whose main constituent unit is 2,2-bis (4-hydroxyphenyl) propane (commonly known as bisphenol A) as a dihydroxydiaryl compound, from the viewpoint of heat resistance and moisture heat resistance. preferable. The main structural unit referred to here is a structural unit that accounts for 80 mol% or more of 100 mol% of the total dihydroxydiaryl units used in the polycarbonate resin. From the above viewpoint, the bisphenol A unit is more preferably 90 mol% or more, and further preferably 95 mol% or more, out of 100 mol% of the total dihydroxydiaryl units. In the present invention, the polycarbonate resin preferably has a number average molecular weight (Mn) of 10,000 or more and 50,000 or less from the viewpoint of melt extrusion. It is more preferably 12,000 or more and 40,000 or less, and further preferably 15,000 or more and 30,000 or less.

Acrylic resin refers to a polymer of acrylic acid ester or methacrylic acid ester. The acrylic resin in the A layer is preferably a polymer mainly composed of alkyl methacrylate. Specifically, it may be a homopolymer of alkyl methacrylate or a copolymer using two or more kinds of alkyl methacrylate, and 50 mol% or more and less than 100 mol% alkyl methacrylate and 0 mol%. It may be a copolymer with a monomer other than alkyl methacrylate in an amount of more than 50 mol% or less. As the alkyl methacrylate, those having an alkyl group having 1 to 4 carbon atoms are usually used, and methyl methacrylate is particularly preferably used. Further, the monomer other than alkyl methacrylate may be a monofunctional monomer having one polymerizable carbon-carbon double bond in the molecule, or two or more polymerizable carbons in the molecule. -Although it may be a polyfunctional monomer having a carbon double bond, a monofunctional monomer is particularly preferably used. Examples thereof include alkyl acrylates such as methyl acrylate and ethyl acrylate, styrene-based monomers such as styrene and alkylstyrene, and unsaturated nitriles such as acrylonitrile and methacrylonitrile. When alkyl acrylate is used as the copolymerization component, the alkyl group usually has about 1 to 8 carbon atoms. When the total amount of the monomer for obtaining the acrylic resin is 100 mol%, the alkyl methacrylate is preferably 70 mol% or more, more preferably 80 mol% or more, still more preferably 90 mol% or more, and particularly preferably. Is 99 mol% or less.

The polyester resin refers to a resin having a structure in which a dicarboxylic acid unit and a diol unit are repeatedly connected. Specific examples of the polyester resin that can be used for the A layer include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, and polylactic acid. Further, the polyester resin may be a homoresin having a single dicarboxylic acid unit or diol unit, or may be a copolymer in which at least one of the dicarboxylic acid unit and the diol unit is a plurality of types for the purpose of enhancing amorphousness. .. Alternatively, it may be a blend of polyester resin in which two or more kinds are compatible with each other.

The polyester resin has 1) polycondensation of a dicarboxylic acid component or an ester-forming derivative thereof (hereinafter collectively referred to as "dicarboxylic acid component") and a diol component, and 2) a carboxylic acid or a carboxylic acid derivative portion and a hydroxyl group in one molecule. It can be obtained by polycondensation of the compound having and a combination of 1) and 2). Further, the polyester resin can be polymerized by a conventional method.

In 1), as the dicarboxylic acid component, malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecandioic acid, dimer acid, eicosandioic acid, pimeric acid, azelaic acid, methylmalonic acid, Aliphatic dicarboxylic acids such as ethylmalonic acid, adamantandicarboxylic acid, norbornenedicarboxylic acid, isosorbide, cyclohexanedicarboxylic acid, alicyclic dicarboxylic acid such as decalindicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid Acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenyl Aromatic dicarboxylic acids such as sulfodicarboxylic acid, 5-sodium sulfoisophthalic acid, phenylendandicarboxylic acid, anthracendicarboxylic acid, phenanthrangecarboxylic acid, 9,9'-bis (4-carboxyphenyl) fluoric acid, or ester derivatives thereof, etc. Is a typical example. Further, these may be used alone or in a plurality of types.

Examples of the diol component include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol, and cyclohexane. Alicyclic diols such as dimethanol, spiroglycol and isosorbide, fragrances such as bisphenol A, 1,3-benzenedimethanol, 1,4-benzendimethanol, and 9,9'-bis (4-hydroxyphenyl) fluorene. Group diols are a typical example. Further, these may be used alone or in a plurality of types as needed.

In the present invention, the total light transmittance of the A layer film is preferably 80% or more and 98% or less. When the total light transmittance is within this range, the display on a display or the like becomes bright and easy to see. In order to set the total light transmittance of the A layer within the above range, at least one selected from highly transparent resins such as the above-mentioned cyclic olefin resin, polystyrene resin, polycarbonate resin, acrylic resin, polyester resin, and polyamide resin is selected. It is preferable to use a kind of resin.

From the viewpoint of achieving both heat resistance and mechanical strength, the laminated film of the present invention preferably has a glass transition temperature (Tg _A ) of layer A of more than 100 ° C. and 170 ° C. or lower. In the present invention, the glass transition temperature (Tg _A ) of the A layer can be measured according to JIS K-7121 (1987 edition) (the same applies to _{the glass transition temperature (Tg B) of the B layer).} In such an aspect, in addition to dimensional stability at high temperature, flatness and mechanical strength are improved, so that the A layer film can be suitably used in applications requiring heat resistance. As a method of setting the glass transition temperature (Tg _A ) of the A layer to more than 100 ° C and 170 ° C or less, for example, a method of using a resin having a glass transition temperature of more than 100 ° C and 170 ° C or less for the A layer can be mentioned. Be done. When the glass transition temperature of the A layer exceeds 100 ° C., it is possible to realize sufficient heat resistance to withstand use at a high temperature. Further, when the glass transition temperature of the A layer is 170 ° C. or lower, sufficient mechanical strength can be ensured.

In the laminated film of the present invention, the number of times the layer A has reached bending fracture is preferably 100 times or more and 10,000 times or less, and more preferably 1,000 times or more and 10,000 times or less. By setting the number of times the A layer reaches bending fracture 100 times or more, the punching workability and repeated bending resistance of the A layer are improved, so that the A layer film is suitable for optical applications such as foldable smartphones where flexibility is required. Can be used for. From the above viewpoint, it is preferable that the number of times the bending fracture is reached is large, but the number of times the bending fracture is reached is accompanied by strong molecular orientation. Therefore, if the number of times the bending fracture is reached is excessively increased, there is a high possibility that the retardation will be impaired, so that the upper limit of the number of times the bending fracture is reached is 10,000 times.

In the present invention, the number of times the A layer reaches bending fracture is defined as the number of times the A layer film sample cut into a size of 110 mm in length (test direction) and 15 mm in width is subjected to a load of 1,000 g and bent according to JIS P-8115 (2001 version). The bending test is performed at an angle of 135 ° to the left and right (R: + 135 °, L: -135 °), a bending speed of 175 times / minute, and a chuck tip R: 0.38 mm. .. The test direction at this time is the direction in which the breaking strength is the highest.

The breaking strength for determining the test direction can be measured as follows. A tensile test was performed using a tensile tester (Tencilon UCT-100 manufactured by Orientec) under the conditions of a temperature of 25 ° C., 63% Rh, a crosshead speed of 300 mm / min, a width of 10 mm, and a sample length of 50 mm, and the film sample broke. The value obtained by reading the strength at the time is defined as the breaking strength (MPa).

Examples of the method for setting the number of times the layer A reaches bending resistance fracture 100 times or more and 10,000 times or less or the above-mentioned preferable range include a method of adding a highly flexible resin. As the highly flexible resin, for example, an elastomer can be used, and when the main component of the layer A is a cyclic olefin resin, the number of times the bending fracture is reached can be improved by adding an olefin elastomer or the like. ..

In the laminated film of the present invention, the surface roughness Ra of one side or both sides of the layer A is preferably 1 nm or more and 100 nm or less, more preferably 1 nm or more and 80 nm or less, and further preferably 1 nm or more and 35 nm or less. In such an aspect, since the A-layer film exhibits high smoothness and excellent surface characteristics, it is possible to display very high-definition when used for optical applications such as displays.

In the present invention, the surface roughness Ra of the layer A can be measured using an AFM (atomic force microscope). The AFM (atomic force microscope) is not particularly limited as long as it can be measured, and for example, "NanoScope" (registered trademark) V Dimension Icon manufactured by BrukerAXS can be used. The measurement procedure and conditions when using the device are as follows. First, a measurement sample is cut into pieces of about 1 cm square, fixed to a silicon wafer with an epoxy resin, and pretreated with a silver paste. Then, a silicon cantilever is applied as a probe, and the surface of the A layer film sample is scanned in the tapping mode under the conditions of a scanning range of 3 μm square and a scanning speed of 0.4 Hz at room temperature (25 ° C.) and in the air. From the data thus obtained, the three-dimensional average roughness is calculated under the condition of a cutoff of 3 nm using the software (Nanoscape Analysis) attached to the AFM, and this is defined as the surface roughness Ra (nm).

As a method of setting the surface roughness Ra of one side or both sides of the layer A to 1 nm or more and 100 nm or less or the above-mentioned preferable range, a method of adjusting the draw ratio can be mentioned. More specifically, the surface roughness Ra can be controlled to be low by increasing the area stretching ratio, and from the viewpoint of easily setting the surface roughness Ra to a desired range, the stretching ratio is 5 in terms of area magnification. It is preferably twice or more, and particularly preferably nine times or more.

The thickness of the A layer in the laminated film of the present invention is not particularly limited as long as the effect of the present invention is not impaired, but from the viewpoint of handleability, it is preferably 1 μm or more and 100 μm or less, and more preferably 5 μm or more and 80 μm or less. It is preferable, and it is more preferably 10 μm or more and 50 μm or less.

The A layer in the laminated film of the present invention has a heat shrinkage rate of −1.0% at 100 ° C. from the viewpoint of achieving heat resistance to the extent that it reduces positional deviation and wrinkles when used as an A layer film for optical applications. It is preferably 1.0% or more. Examples of the method of setting the heat shrinkage rate at 100 ° C. in the above range include a method of setting the glass transition temperature of the A layer to 110 ° C. or higher.

In the laminated film of the present invention, it is important that the plane orientation coefficient of the B layer is 0.0300 or more and 0.1700 or less from the viewpoint of allowing the B layer to function as a protective layer. With such an embodiment, the crystallization and orientation of the B layer are sufficiently promoted, and the B layer serves as a protective layer. "The plane orientation coefficient of the B layer is 0.0300 or more and 0.1700 or less" means that the plane orientation coefficient of at least one B layer is 0.0300 or more and 0.1700 or less, and more preferably A. It means that the plane orientation coefficient of the B layer on both sides of the layer is 0.0300 or more and 0.1700 or less. Hereinafter, unless otherwise specified, the parameters related to the B layer can be interpreted in the same manner. If the plane orientation coefficient of the B layer is less than 0.0300, the film surface is easily scratched, and the protective property of the laminated film is inferior. Further, in the case of the resin used for the B layer, it is difficult to set the plane orientation coefficient to a value larger than 0.1700 from the viewpoint of resin characteristics and technical viewpoints, so this is set as the upper limit.

The plane orientation coefficient of the B layer can be measured by the following method. First, using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting solution, and using an Abbe refractometer at 25 ° C., the refractive indexes in the longitudinal direction, the width direction, and the thickness direction (nMD, nTD, respectively). nZD) is calculated. Then, the plane orientation coefficient (fn) is calculated from the obtained refractive index by the following formula (2).
fn = (nMD + nTD) /2-nZD ... (2).

Examples of the method in which the plane orientation coefficient is within the above range include a method of using a crystalline resin as the resin constituting the B layer and stretching the resin. Specific examples of the crystalline resin constituting the B layer include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, polyester resin such as polylactic acid, polyamide resin such as nylon 6, polypropylene and the like. Examples include olefin resin. Further, usually, the plane orientation coefficient of the B layer can be increased by increasing the stretching ratio.

If a polyester resin or a polyamide resin is used as the crystalline resin constituting the B layer, in order to set the plane orientation coefficient to 0.0300 or more and 0.1700 or less, the area magnification is stretched to 3 times or more and 16 times or less. Is preferable. If polypropylene is used as the crystalline resin constituting the B layer, it is preferably stretched at an area magnification of 10 times or more and 36 times or less.

In the laminated film of the present invention, from the viewpoint of improving the function of the B layer as a protective layer, the plane refractive index of the B layer is 1.6000 or more and 1.6600 or less, and the thickness direction refractive index of the B layer is high. It is preferably 1.4800 or more and 1.5700 or less. Here, "the plane refractive index of the B layer is 1.6000 or more and 1.6600 or less" means that the refractive indexes (nMD, nTD) in the longitudinal direction and the width direction measured by the above method are both 1.6000 or more. It means that it is 1.6600 or less, and the refractive index in the thickness direction of the B layer means the refractive index (nZD) in the thickness direction measured by the above-mentioned method. With such an embodiment, the orientation and crystallization of the B layer are promoted, and the function of the B layer as a protective layer is improved.

Examples of the method of setting the nMD and nTD of the B layer to 1.6000 or more and 1.6600 or less and the nZD to 1.4800 or more and 1.5700 or less include a method of producing a laminated film by biaxial stretching. ..

In order to keep the refractive index in each direction within the above range, if the polyester resin or polyamide resin described above is used as the resin constituting the B layer, it is preferable to stretch the resin to 5 times or more and 16 times or less in terms of area magnification. If polypropylene is used as the crystalline resin constituting the B layer, it is preferably stretched at an area magnification of 10 times or more and 36 times or less. Further, as another method, the refractive index in each of the above-mentioned directions can be increased by heat treatment after stretching.

In the laminated film of the present invention, the thickness of the B layer is not particularly limited, but is preferably 1 μm or more from the viewpoint of the function as a protective layer, and preferably 100 μm or less from the viewpoint of handleability. From the above viewpoint, it is preferably 2 μm or more and 50 μm or less, and more preferably 5 μm or more and 25 μm or less. Further, the thickness of the B layer may be the same or different on both sides.

In the laminated film of the present invention, the minute endothermic peak temperature (Tmeta) of the B layer is preferably 120 ° C. or higher and 220 ° C. or lower from the viewpoint of mechanical strength and dimensional stability of the B layer. The peak indicates the thermal history in the manufacturing process, and indicates the temperature in the so-called heat treatment process after biaxial stretching. With such an embodiment, crystallization proceeds without melting the B layer, and characteristics such as mechanical strength and dimensional stability are improved, so that the function of the B layer as a protective layer is improved. Further, when the main component of the A layer is a crystalline resin, the retardation of the A layer can be lowered. From the above viewpoint, it is preferable that the minute endothermic peak temperature (Tmeta) of the B layer is 120 ° C. or higher and 220 ° C. or lower, and the melting point is Tm-80 ° C. or higher and the melting point Tm-5 ° C. or lower.

The Tmeta of the B layer can be obtained from the temperature-increasing crystallization peak temperature Tcc (° C.) and the melting point Tm (° C.) of the B layer measured by a method according to JIS K-7121 (1987 version). Specifically, the temperature of the peak of the exothermic peak obtained from the DSC curve when the temperature of 5 mg of the sample of the layer alone was raised from 25 ° C to 20 ° C / min to 300 ° C was defined as Tcc, and the temperature of the endothermic peak was defined as Tcc. The melting point is Tm, and the minute endothermic peak seen at the midpoint between Tm and Tcc is Tmeta (° C.). In addition, ΔTcg described later is a value obtained by subtracting _{Tg B from Tcc.}

In the laminated film of the present invention, the crystallinity parameter (ΔTcg) of the B layer is preferably 10 ° C. or higher and 100 ° C. or lower from the viewpoint of suppressing stretching unevenness. The laminated film of the present invention can be suitably produced, for example, by laminating a composition for obtaining a layer A and a composition for obtaining a layer B, cooling and solidifying them, and co-stretching them. When this method is used, when a laminated body having a layer structure in which an intermediate layer is sandwiched between the same outer layers, such as the laminated film of the present invention, is stretched to form a laminated film, horizontal unevenness due to adhesion or the like and glass of the B layer are formed. From the viewpoint of suppressing stretching unevenness due to an excessively high temperature with respect to the transition temperature, it is usually preferable that the glass transition temperature of the B layer is at least the glass transition temperature of the A layer or higher. However, in the laminated film of the present invention, it is preferable to use a resin having different crystallinity and SP value between the A layer and the B layer, so that the glass transition temperature is inevitably different between the A layer and the B layer. It becomes a design, and the degree of freedom in resin selection is low. Based on this point, in the laminated film of the present invention, by setting the crystallinity parameter ΔTcg of the B layer within the above range, crystallization is promoted in the casting step after being extruded from the T die, thereby in the stretching step. Adhesion can be prevented and uneven stretching due to excessive temperature can be suppressed. Therefore, deterioration of quality due to uneven thickness and uneven orientation is suppressed. From the above viewpoint, the crystallinity parameter ΔTcg of the B layer is preferably 20 ° C. or higher and 70 ° C. or lower, and more preferably 20 ° C. or higher and 60 ° C. or lower.

In the laminated film of the present invention, the crystal melting energy ΔHm _B of the B layer is preferably 15.0 J / g or more and 50.0 J / g or less. When ΔHm _B is in the above range, the surface hardness of the B layer is high, and high protection performance can be realized. Examples of _{the method in which ΔHm B} is in the above range include a method of using a resin having a crystal melting energy of 15.0 J / g or more and 50.0 J / g or less as the branches constituting the B layer.

In the laminated film of the present invention, the glass transition temperature (Tg _B ) of the B layer is preferably 30 ° C. or higher and 100 ° C. or lower from the viewpoint of improving film forming stability and reducing stretching unevenness. Controlling the crystallinity parameter (ΔTcg) of the B layer within the above range is also preferable for preventing adhesion, but further, by bringing the glass transition temperature between the A layer and the B layer closer to each other, the film formation stability is further improved. Stretching unevenness can be suppressed. Therefore, from the above viewpoint, the glass transition temperature of the B layer is preferably 30 ° C. or higher and 100 ° C. or lower.

In the laminated film of the present invention, it is preferable that the B layer contains a crystalline resin as a main component. Examples of the crystalline resin include an olefin resin, a polyamide resin, and a polyester resin. In the laminated film of the present invention, a polyester resin is preferable among the crystalline resins from the viewpoint of versatility and biaxial stretchability. As the olefin resin, polyamide resin, and polyester resin, the above-mentioned resins having crystallinity can be used.

In the laminated film of the present invention, the B layers located on both surface layers may have different compositions as long as the effects of the present invention are not impaired. Further, the B layer in the laminated film of the present invention has a main role of protecting the A layer and imparting handleability by thickening the B layer. For example, one B layer has handleability. It can also be a mode in which the other layer B plays a role of peeling from the layer A and transferring to another material. As the latter B layer in this embodiment, for example, as long as the requirements of the present invention are satisfied, the resins listed above as the resins constituting the B layer can be used alone or in combination as appropriate.

The laminated film of the present invention preferably has a haze of 0.5% or more and 3.0% or less from the viewpoint of brightening the display when used for a display or the like. In the present invention, haze can be measured based on JIS K-7136 (2000 edition). As a means for setting the haze of the laminated film within the above range, a method of using a highly transparent resin for the laminated film (particularly the A layer) can be mentioned. Examples of such resins include polyolefin resins, polyimide resins, polyether ether ketone resins, polypropylene resins, cyclic olefin resins, polystyrene resins, polycarbonate resins, acrylic resins, polyester resins, polyamide resins, and cellulose resins. Examples include resin. Above all, from the viewpoint of colorless transparency and versatility, it is preferable to use at least one resin selected from polypropylene-based resin, cyclic olefin-based resin, polystyrene resin, polycarbonate resin, acrylic resin, polyester resin, and polyamide resin.

Hereinafter, the method for producing the laminated film of the present invention will be described. In the method for producing a laminated film of the present invention, when the molten resin composition for obtaining the A layer is the molten resin composition A and the molten resin composition for obtaining the B layer is the molten resin composition B, A coextrusion laminating step of coextruding and laminating the molten resin composition A and the molten resin composition B, a casting step of cooling and solidifying the laminate obtained by the coextrusion laminating step, and at least one sheet obtained by the casting step. It is characterized by having a stretching step of stretching in a direction and a heat treatment step of heat-treating at a temperature of _{Tg A} + 20 ° C. or higher and Tg _{A + 120 ° C. or lower in this order.}

In the method for producing a laminated film of the present invention, from the viewpoint of improving the laminating accuracy, it is preferable to have a widening step for individually widening the molten resin composition A and the molten resin composition B upstream of the coextrusion laminating step. In the method for producing a laminated film of the present invention, since the molten resin composition A and the molten resin composition B usually contain resins having different melt viscosities and SP values as main components, the molten resin compositions are merged, and then the same. When the laminated resin is widened in the manifold, stacking disorder (also referred to as flow mark) may occur due to a difference in melt viscosity, a difference in melt tension, and a difference in SP value. Therefore, it is preferable that each molten resin composition is individually widened and then laminated. To widen each molten resin composition individually, for example, a multi-manifold die can be used.

In the method for producing a film of the present invention, when the molten resin composition for obtaining the A layer is the molten resin composition A and the molten resin composition for obtaining the B layer is the molten resin composition B, the molten resin composition is used. It is important to have a coextrusion laminating step in which the product A and the molten resin composition B are coextruded and laminated. With such an embodiment, the B layer as the protective layer and the A layer as the low retardation layer for optics can be formed at once. The molten resin composition A preferably contains an amorphous resin as a main component, and the molten resin composition B preferably contains a crystalline resin as a main component. The resins that can be suitably used for the molten resin compositions A and B are the same as those described above as those that can be suitably used for each layer of the laminated film of the present invention.

As long as the molten resin composition A and the molten resin composition B are co-extruded and laminated, the laminated structure does not matter, but when it is required to have the B layer as the protective layer on both sides, the molten resin is used. It is preferable to laminate the molten resin composition B on both sides of the composition A. Further, the composition of the molten resin composition B located on each surface side of the molten resin composition A in this embodiment may be the same or different from each other.

It is important that the method for producing a laminated film of the present invention includes a casting step of cooling and solidifying the laminated body obtained by the coextrusion laminating step. In the casting step, it is preferable to control the crystallinity of the B layer to 10% or more and 30% or less from the viewpoint of reducing roll adhesion and stretching unevenness. As a method of controlling the crystallinity of the B layer to 10% or more and 30% or less, for example, a method of adjusting the cast temperature (the temperature of the cast drum) can be mentioned. More specifically, it is preferable that the cast temperature is equal to or higher than the glass transition temperature of the resin constituting the B layer and equal to or lower than the glass transition temperature of the resin constituting the B layer. At this time, the crystallinity of the B layer can be increased by setting the cast temperature higher than the glass transition temperature, and the crystallinity is most easily achieved by setting the crystallinity peak temperature (Tcc ° C.) of the B layer. By setting the crystallinity of the B layer within the above range, roll adhesion and uneven stretching can be suppressed even if the glass transition temperature of the B layer is lower than the glass transition temperature of the A layer.

It is important that the method for producing a laminated film of the present invention includes a stretching step of stretching the sheet obtained by the casting step in at least one direction. Usually, when a resin having low crystallinity is used as the A layer, which is a low retardation layer, the dimensional stability is remarkably lowered by stretching, so that stretching the amorphous resin is a method that is rarely taken. However, in the present invention, in consideration of dimensional stability, which is a problem when stretching the amorphous resin, the glass transition temperature Tg _{A of the} A layer is higher than that of the A layer with the B layer as the protective layer arranged on both sides. Stretch at a much higher temperature. By this step, not only the dimensional stability as a laminated film can be maintained, but also the surface roughness can be reduced by stretching, the equal quality can be improved by improving the in-plane uniformity of physical properties, and it becomes easy to widen and thin the film. At this time, the stretching may be performed in at least one direction, and the case of biaxial stretching is not particularly limited, but sequential biaxial stretching, simultaneous biaxial stretching, and inflation method can be used. The draw ratio and temperature in each direction during stretching can be appropriately set according to the type of resin of each composition, and for example, the main component of the molten resin composition A is a cyclic olefin, and the molten resin. When the main component of the composition B is a crystalline polyester resin, it is preferably 100 ° C. or higher and 160 ° C. or lower, 3 times or more and 16 times or less, and more preferably 5 times or more and 16 times or less.

It is important that the method for producing a laminated film of the present invention includes a heat treatment step of heat-treating the _{layer A at a glass transition temperature of Tg A} + 20 ° C. or higher and Tg _{A + 120 ° C. or lower.} In this heat treatment step, the protective function is improved by the progress of the orientation crystallization of the B layer, while the improvement of the thermal dimensional stability and the reduction of the phase difference value can be realized at the same time by the progress of the relaxation of the orientation of the A layer. .. The apparatus used in the heat treatment step is not particularly limited, and a known apparatus such as a tenter apparatus can be used.

The laminated film thus obtained is cooled in a subsequent transfer step, once wound as an intermediate roll by a wide winder, and then cut into a required width and length by a slitter to obtain a final product.

The method for producing a laminated film of the present invention can not only form the B layer as a protective layer and the A layer as a low retardation layer for optics at once, but also improve the quality of the A layer while maintaining the low retardation property. The function can be enhanced as a protective layer of the B layer by orientation crystallization.

Since the laminated film of the present invention is a low retardation film (A layer film) with a protective layer (B layer) that can be easily peeled off, the protective layer is peeled off to form a polarizer protective film, a protective film for defect inspection, and a transparent film. It can be suitably used as various optical films such as conductive films.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. The characteristics were measured by the following methods. Further, in each Example and Comparative Example, regardless of whether both outermost layers are the same or different, the layer structure is B1 layer / A layer / B2 layer, but in the description of the measurement method and evaluation method of each item, The B1 layer and the B2 layer are not distinguished and are referred to as the B layer.

(1) Thickness of Laminated Film and Each Layer The total thickness of the laminated film was measured by measuring the thickness of the sample cut out from the film at five arbitrary locations using a dial gauge and calculating the average value thereof. When measuring the layer thickness of each layer of the laminated film, a metallurgical microscope LeicaDMLM manufactured by Leica Microsystems Co., Ltd. is used to observe the cross section of the film under the condition of a magnification of 100 times, take a photograph of the transmitted light, and use a microscope. After measuring the thickness at an arbitrary 5 points for each layer by the length measuring function of, the average value was calculated and used as the layer thickness of each layer.

_{(2) Glass transition temperature (Tg A} , Tg _B ) of A layer and B layer, temperature rise crystallization peak temperature Tcc, melting point Tm, micro endothermic peak temperature Tmeta, ΔTcc, crystal melting energy ΔHm
According to JIS K7121 (1999), the differential scanning calorimetry robot DSC-RDC6220 manufactured by Seiko Denshi Kogyo Co., Ltd. is used, and the “disk session” SSC / 5200 is used for data analysis, and the glass transition temperature (Tg _A , For Tg _B ) [° C.], temperature-raising crystallization peak temperature Tcc [° C.], melting point Tm [° C.], microheat absorption peak temperature Tmeta [° C.], JIS K-7121 (1987 version), crystal melting energy ΔHm [J / g] was measured and analyzed in accordance with JIS K-7122 (1987 edition). The ΔTcg in the B layer was defined as the value obtained by subtracting _{Tg B from Tcc.} The measurement of each item was carried out individually by peeling the A layer and the B layer from the laminated film. Specifically, the temperature of the apex of the exothermic peak obtained from the DSC curve when the temperature of 5 mg of the peeled sample of each layer alone was raised from 25 ° C. to 20 ° C./min to 300 ° C. was obtained from the Tcc and DSC curves. The temperature of the apex of the endothermic peak was defined as the melting point Tm, and the minute endothermic peak observed at the midpoint between Tm and Tcc was defined as Tmeta. When the melting point was not observed, it was set as "ND". Regarding the measurement of crystalline raw materials, in order to remove the influence of crystallization during pelletizing, the temperature is raised from 25 ° C to 20 ° C / min to 300 ° C, the sample is held at 300 ° C for 5 minutes, and then 25 ° C. The sample was taken out in an atmosphere and rapidly cooled to an amorphous state. After storage at 25 ° C. for 5 minutes, the temperature of the apex of the exothermic peak when the temperature was raised from 25 ° C. to 300 ° C. at 20 ° C./min as 2ndRun was defined as the temperature rise crystallization temperature (Tcc) of 2ndRun. When there were a plurality of temperature-rising crystallization peaks and crystal melting peaks, the temperature having the largest absolute value of calorific value was adopted.

(3) Quality of A-layer film After peeling A-layer from B-layer and pasting a film cut to a size of 10 cm x 10 cm on a black mount, hold a fluorescent lamp to observe the state of the film, and observe the state of the film as follows. Evaluation was performed based on the criteria.
A: No gel-like foreign matter, undulating unevenness, or streaks were visually observed on the film.
B: Gel-like foreign matter, waviness-like unevenness, and streaks were visually observed on the film.

(4) Restoration A value obtained by measuring the phase difference with respect to a light beam having a wavelength of 548.3 nm using an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Measurement Co., Ltd. was used as a retardation value. The measurement was performed once for a single film consisting of only the A layer from which the B layers on both sides were peeled off.

(5) Delamination strength between layer A and layer B The peel strength at 180 ° measured according to JIS K 6854-2 (1999 edition) was used. The A layer and the B layer were peeled off on any one side, and the B layer and the A layer were peeled off on the bonded side and the B layer alone side. At this time, the width of the test piece for the peel strength test was 50 mm, the tensile test speed was 50 mm / min, measurements were taken at three different locations, and the average value of the obtained measured values was taken as the delamination strength.

(6) Dissolution parameter SP value (SP _A , SP _B )
In the present invention, a Fedors calculation method that can be calculated relatively easily based on the molecular structural formula is used. In the calculation method of Fedors, it is considered that the solubility of the molecular aggregation energy density and the molar molecular volume changes depending on the type and number of substituents, and the solubility parameter value δ (cal / cm ³ ) according to the following formula (1). ^1/2 is estimated. Here, _Ecoh (cal / mol) represents the aggregation energy, and V represents the molar molecular volume (cm ³ / mol).

Since the solubility parameter SP value of the thermoplastic resin can be estimated using the Fedor formula based on the repeating structural unit of the molecular chain, the solubility parameter SP value of the thermoplastic resin including the structural unit derived from the copolymerization component. Decided to calculate the ratio according to the ratio of each structural unit. The solubility parameter SP value was rounded off to the second decimal place of the estimated value calculated based on Fedor's formula. The solubility parameter SP values of typical thermoplastic resins are polypropylene: 8.0 (cal / cm ³ ) ^1/2 , polyethylene terephthalate: 10.7 (cal / cm ³ ) ^1/2 , and polystyrene: 9. .4 (cal / cm ³ ) ^1/2 , polymethyl methacrylate: 9.3 (cal / cm ³ ) ^1/2 , polybutylene terephthalate: 10.0 (cal / cm ³ ) ^1/2 , nylon 6: 12.7 (cal / cm ³ ) ^1/2 , Polypropylene: 9.9 (cal / cm ³ ) ^1/2 , COP: 8.6 (cal / cm ³ ) ^1/2 , COC: 7.8 (cal) / Cm ³ ) ^1/2 , ABS resin: 10.0 (cal / cm ³ ) ^1/2 , polypropylene: 8.0 (cal / cm ³ ) ^{1/2, and the} like. When a plurality of components were included, the mass ratio of each component was multiplied by the SP value of each component, and the total value was taken as the SP value of the plurality of components.

(7) Total light transmittance was measured based on JIS K-7136 (2000 version) using a direct reading haze computer manufactured by Haze Suga Test Instruments Co., Ltd. The measurement was performed three times each, and the average value was used as the haze of the laminated film.

(8) Number of times of bending and breaking reached The B layers on both sides were peeled off from the laminated film to obtain a film composed of the A layer alone. 15 °, 30 °, 45 °, 60 °, 75 °, 90 °, 105 °, 120 to the right in any one direction (0 °) of the film consisting of the A layer alone, and parallel to the film surface from that direction. The breaking strength in each direction rotated by °, 135 °, 150 °, and 165 ° was measured, and the film sample was cut into a rectangle of 110 mm (test direction) × width 15 mm with the direction having the highest breaking strength as the test direction. After that, using a MIT folding resistance tester (Testing machine No. 702 manufactured by Maze), a load of 1,000 g and a bending angle of 135 ° to the left and right were applied to the film sample according to JIS P-8115 (2001 version). A bending test was performed at (R: + 135 °, L: -135 °), a bending speed of 175 times / minute, and a chuck tip R: 0.38 mm, and the number of bendings when the film sample was broken was defined as the number of times the film sample reached bending breakage. .. The test was carried out three times, and the average value was adopted.

The breaking strength was measured as follows. A tensile test was performed using a tensile tester (Tencilon UCT-100 manufactured by Orientec) under the conditions of a temperature of 25 ° C., 63% Rh, a crosshead speed of 300 mm / min, a width of 10 mm, and a sample length of 50 mm, and the film sample broke. The value obtained by reading the strength at the time was taken as the breaking strength. The same measurement was performed 5 times, and the average value was taken as the breaking strength (MPa) of the film sample.

(9) Bending resistance Based on the number of times the bending fracture was reached measured by the method of (8), the determination was made as follows. The evaluation was ◎ and ○.
⊚: The number of times the bending fracture was reached was 1,000 times or more.
◯: The number of times the bending fracture was reached was 100 times or more and less than 1,000 times.
X: The number of times the bending fracture was reached was less than 100 times.

(10) Surface Roughness Ra
The B layers on both sides were peeled off from the laminated film to obtain a film composed of the A layer alone. Using an AFM (atomic force microscope) "NanoScope" (registered trademark) V Dimension Icon manufactured by BrukerAXS, the surface roughness Ra of a film composed of a single layer A was measured by the following procedure. First, the measurement sample was cut into pieces of about 1 cm square, fixed to a silicon wafer with an epoxy resin, and pretreated with a silver paste. After that, a silicon cantilever is applied as a probe, and in tapping mode, under the conditions of a scanning range of 3 μm square and a scanning speed of 0.4 Hz, the surface of a film sample composed of a single layer A in the air at room temperature (25 ° C). Was scanned. From the data thus obtained, the three-dimensional average roughness was calculated under the condition of a cutoff of 3 nm using the software (Nanoscape Analysis Ver.8.15) attached to the AFM. The same measurement was performed 5 times, and the average value of the obtained three-dimensional average roughness was obtained and used as Ra (nm).

(11) Refractive index, plane orientation coefficient fn
Using a sodium D line (wavelength 589 nm) as a light source, using methylene iodide as a mounting solution, and using an Abbe refractometer at 25 ° C., the refractive indexes in the longitudinal direction, width direction, and thickness direction of the film (nMD, nTD, nZD, respectively). ) Was asked. From the obtained refractive index, the plane orientation coefficient (fn) of the B layer was calculated by the following formula (2).
fn = (nMD + nTD) /2-nZD ... (2)
(12) Film-forming stability The film was formed for 1 hour, and the case where there was no trouble of film tear was evaluated as ◯ (pass), and the case where it occurred was evaluated as × (fail).

(13) Iridescent unevenness A film consisting of a single layer A of 10 cm square was attached to one surface of a polarizer with a degree of polarization of 99.9%, which was created by adsorbing and orienting iodine in PVA to form a test piece. .. A laminator roll set at 85 ° C. was used for bonding. When the created test piece and the polarizing plate to which the film is not attached are superposed on the LED light source (A3-101 manufactured by Tritec) in the arrangement of cross Nicol, 50 with respect to the normal direction of the test piece plane. The visibility from the angle of ° was confirmed and evaluated according to the following criteria. Further, in the same manner, a test piece to which a film composed of a single layer A of 30 cm square was bonded was also produced, and the same evaluation was performed. As for the evaluation result, S to C were accepted.
S: No interference color was observed in any of the evaluations of 10 cm square and 30 cm square.
A: No interference color was observed in the evaluation of 10 cm square, and a slight interference color was observed in the evaluation of 30 cm square.
B: A slight interference color was observed in both the evaluation of 10 cm square and the evaluation of 30 cm square.
C: A slight interference color was observed in the evaluation of 10 cm square, and the interference color was clearly visible in the evaluation of 30 cm square.
D: Interference color was clearly seen in the evaluation of 10 cm square and the evaluation of 30 cm square.
(14) Detachability Based on the values of delamination strength between the A layer and the B layer measured by the method described in (5), the evaluation was made according to the following criteria. The evaluation was ◎ and ○.
⊚: The delamination strength between the A layer and the B layer was 2.0 g / 50 mm or more and 50 g / 50 mm or less.
◯: The delamination strength between the A layer and the B layer was 1.0 g / 50 mm or more and less than 2.0 g / mm, or more than 50 g / 50 mm and 100 g / 50 mm or less.
×: Neither ◎ nor ○ was applicable.

(15) Heat resistance A film composed of a 100 mm square A layer alone is hung in a hot air oven at 100 ° C. in a tree shape so as not to come into contact with the upper, lower, left and right walls, stored for 12 hours, and then heat-treated. The flatness of the film was visually evaluated according to the following criteria. The evaluation was ◎ and ○.
⊚: There was no change from before the heat treatment.
◯: There were some wrinkles and wrinkles on the film, but there was no problem.
X: The film was wrinkled and wrinkled to the extent that it became a problem.

(16) Brittleness A laminated film having a width of 300 mm and a length of 200 m (6 inches, 350 mm long core winding) is prepared, and the core is rewound to a 3 inch, 350 mm long core under the following conditions, while changing the transport speed and tension. The evaluation was performed according to the following criteria.
A: No tear occurred even when rewinding at a speed of 10 m / min and a transport tension of 70 N / m.
B: No tear occurred even when rewinding at a speed of 5 m / min and a transport tension of 50 N / m, but a tear occurred when the speed was changed to 10 m / min and a transport tension of 70 N / m.
C: A tear occurred when the vehicle was rewound at a speed of 5 m / min and a transport tension of 50 N / m.

(17) Heat Shrinkage Rate at 100 ° C. A film composed of a single layer A was cut into a rectangle having a length of 150 mm and a width of 10 mm in the longitudinal direction and the width direction, respectively, and used as a sample. Marked lines were drawn on the sample at intervals of 100 mm (positions of 50 mm from the center to both ends), and a 3 g weight was hung and placed in a hot air oven heated to 100 ° C. for 30 minutes for heat treatment. The distance between the marked lines after the heat treatment was measured, and the heat shrinkage rate was calculated by the following formula (3) from the change in the distance between the marked lines before and after the heating.

Heat shrinkage rate (%) = {(distance between marked lines before heat treatment)-(distance between marked lines after heat treatment)} / (distance between marked lines before heat treatment) × 100 ... (3).

(18) Protectiveness First, the laminated film was scraped under the following conditions using a rubbing tester. Next, the appearance of the A layer alone, in which both B layers were peeled off from the laminated film that had been rubbed, was visually confirmed, and if no scratches were visible, ◎ (pass), slight scratches were observed, but there was a practical problem. If there was no such thing, it was evaluated as ○ (pass), and if obvious scratches were observed, it was evaluated as × (fail).
<Scratch condition>
Evaluation environmental conditions: 25 ° C, 60% RH
Rubbing material: Steel wool (manufactured by Nippon Steel Wool Co., Ltd., grade No. 0000), wrapped around the rubbing tip (1 cm x 1 cm) of a tester that comes into contact with the sample, and fixed with a band.
Distance traveled (one way): 13 cm
Rubbing speed: 13 cm / sec Load: 500 g / cm ²
Tip contact area: 1 cm x 1 cm
Number of rubbing: 10 round trips (20 times).

[Resin, additive]
In the following examples or comparative examples, the following resins and additives were used. Regarding the resin, polyethylene A, polyester C, polyester D, polyester E, polyamide resin A, and polypropylene A are crystalline resins, and the other resins are amorphous resins.
(Polystyrene A)
A polystyrene resin obtained by polymerizing a styrene monomer. MFR 9.0g / 10min at 230 ° C
(Acrylic resin A)
A polymethyl methacrylate resin obtained by polymerizing methyl methacrylate. MFR 5.0g / 10min at 230 ° C
(Polycarbonate resin A)
A polycarbonate resin obtained by polycondensing bisphenol A and phosgene. MVR12cm at 300 ℃ ³ / 10min
(Cyclic olefin resin A (COP-A))
Cyclic olefin polymer obtained by polymerizing ethylene with a polymer obtained by ring-opening polymerization of a cyclic olefin-based monomer (glass transition temperature Tg = 115 ° C.)
(Cyclic olefin copolymer resin A (COC-A))
Ethylene-norbornene copolymer resin A (norbornene unit content ratio: about 76 mol%: glass transition temperature Tg = 140 ° C.) 60% by mass and ethylene-norbornene copolymer resin B (norbornene unit content ratio 65 mol%: glass transition temperature Tg) = 80 ° C.) A resin obtained by dry-blending 40% by mass.
(Polyethylene A)
LLDPE obtained by polymerizing ethylene. MFR 8.0g / 10min at 190 ° C
(Polyester A)
Polyester resin containing 100 mol% of terephthalic acid unit as dicarboxylic acid unit, 21 mol% of ethylene glycol unit as glycol unit, 46 mol% of 1,4-cyclohexylenemethanol unit, and 33 mol% of isosorbide unit (intrinsic viscosity). 0.72).
(Polyester B)
Spiroglycol 30 mol% copolymerized polyethylene terephthalate (intrinsic viscosity 0.65).
(Polyester C)
A polyethylene terephthalate resin having 100 mol% of terephthalic acid unit as a dicarboxylic acid unit and 100 mol% of ethylene glycol unit as a glycol unit (intrinsic viscosity 0.65).
(Polyester D)
A polybutylene terephthalate resin (intrinsic viscosity 1.40) in which the dicarboxylic acid unit is 100 mol% terephthalic acid unit and the glycol unit is 1-4, butanediol unit is 100 mol%.
(Polyester E)
An isophthalic acid copolymer polyethylene terephthalate resin containing 88 mol% of terephthalic acid unit and 12 mol% of isophthalic acid unit as a dicarboxylic acid unit and 100 mol% of ethylene glycol unit as a glycol unit (intrinsic viscosity 0.70).
(Polyester F)
2,6-naphthalenedicarboxylic acid is used as the dicarboxylic acid component, and polyethylene glycol (average molecular weight 400, m × n is 10 or more) is 6 mol% of the total diol component and ethylene glycol is 6 mol% of the total diol component as the diol component. Polyethylene terephthalate resin (inherent viscosity 0.70) copolymerized so as to be 94 mol%.
(Polyester G)
An isophthalic acid copolymer polyethylene terephthalate resin containing 83 mol% of a terephthalic acid unit and 17 mol% of an isophthalic acid unit as a dicarboxylic acid unit and 100 mol% of an ethylene glycol unit as a glycol unit (intrinsic viscosity 0.70).
(Polyester H)
A polyester resin containing 95 mol% of terephthalic acid unit and 5 mol% of isophthalic acid unit as dicarboxylic acid unit and 100 mol% of 1,4-cyclohexylenemethanol unit as glycol unit (intrinsic viscosity 0.72).
(Polyamide resin A)
Nylon resin "Amiran" (registered trademark) CM1017 manufactured by Toray Industries, Inc.
(Polypropylene A)
Homopolypropylene obtained by polymerizing propylene. MFR 7.0 g / 10 min at 230 ° C.
(Polypropylene B)
Ethylene-propylene copolymerized polypropylene resin obtained by copolymerizing 9 mol% of ethylene. MFR 8.0 g / 10 min at 230 ° C.
(Particle Master A)
A particle master (intrinsic viscosity 0.62) containing wet silica particles having an average particle diameter of 1.2 μm in polyester C at a particle concentration of 2% by mass.
(Particle Master B)
A particle master (intrinsic viscosity 1.20) containing wet silica particles having an average particle diameter of 1.2 μm in polyester D at a particle concentration of 2% by mass.
(Particle Master C)
A particle master (intrinsic viscosity 0.68) containing wet silica particles having an average particle diameter of 1.2 μm in polyester F at a particle concentration of 2% by mass.

(Examples 1 to 15, Comparative Examples 1 to 5)
It has a three-layer structure of B1 layer / A layer / B2 layer. The raw material composition of each layer is as shown in Table 1, and each is supplied to a separate single-screw extruder (L / D = 28), melted at the temperatures shown in Table 2, and then passed through a leaf disk filter having a filtration accuracy of 30 μm. I let you. Then, after laminating so as to form a B1 layer / A layer / B2 layer (see the table for the laminated thickness ratio) in the feed block installed on the upper part of the die, the table is formed from the T die (lip gap: 0.4 mm). It was discharged in the form of a sheet on a mirror-finished cast roll (surface roughness 0.2 s) controlled to the temperature described in 2. At that time, the cast position was set to 10 ° forward from the top of the cast roll, and static electricity was applied by a wire-shaped electrode having a diameter of 0.1 mm to bring the B1 layer side into close contact with the cast roll to obtain a cast film. Then, the film was stretched in the longitudinal direction and the width direction by the stretching temperature, stretching ratio, and stretching method shown in Table 2, and finally heat-treated at the temperatures shown in Table 2 to obtain a laminated film. Each item was evaluated for the obtained laminated film or each layer obtained by peeling the laminated film. The evaluation results are shown in Tables 3-8. In Comparative Example 1, each item was not evaluated because the film was melted and torn in the heat treatment step and the film could not be collected.
(Examples 16 to 22)
It has a three-layer structure of B1 layer / A layer / B2 layer. The raw material composition of each layer is as shown in Table 1, and each is supplied to a separate single-screw extruder (L / D = 28), melted at the temperatures shown in Table 2, and then passed through a leaf disk filter having a filtration accuracy of 30 μm. I let you. After that, each layer was guided to an individual manifold by a converter installed on the upper part of the multi-manifold die, and the resin layer was widened independently. After that, the resin layer widened at the land portion immediately before being discharged from the mouthpiece was laminated in the same manner as in Example 1 except that the resin layer was laminated so as to form a B1 layer / A layer / B2 layer (see the table for the laminated thickness ratio). I got a film. In addition, each item was evaluated for the obtained laminated film or each layer obtained by peeling the laminated film. The evaluation results are shown in Tables 3-8.

The laminated film of the present invention is a laminated film having an A layer which is a low retardation layer and a B layer which is a protective layer showing a constant plane orientation coefficient in contact with both layers of the A layer, and is easily selected from the A layer and the B layer. Because it can be peeled off and has excellent optical characteristics and protection performance, for example, it is used for optical compensation applications such as polarizer protective films mounted on display devices such as displays, and optics such as transparent conductive films and low retardation films for inspection. It can be suitably used as an application.

Claims (19)

It has layers A and B with different crystal melting energies ΔHm (J / g) from each other.
Both surfaces of layer A are in contact with layer B,
The retardation of layer A is 0.0 nm or more and 180 nm or less.
The plane orientation coefficient of layer B is 0.0300 or more and 0.1700 or less.
When ΔHm of the A layer is ΔHm _A (J / g) and ΔHm of the B layer is ΔHm _B (J / g), ΔHm _{B −} ΔHm _A is 5.0 (J / g) or more.
Moreover, the laminated film is characterized in that the peel strength between at least one B layer and the A layer is 1.0 g / 50 mm or more and 100 g / 50 mm or less. When the solubility parameter of the A layer is SP _A (cal / cm ³ ) ^1/2 and the solubility parameter of the B layer is SP _B (cal / cm ³ ) ^1/2 , | SP _A- SP _B | The laminated film according to claim 1, wherein the laminated film is 0.5 or more and 4.0 or less. The laminated film according to claim 1 or 2, wherein the haze is 0.5% or more and 3.0% or less. The laminated film according to any one of claims 1 to 3, wherein the glass transition temperature (Tg _{A) of the A layer exceeds 100 ° C. and is 170 ° C. or lower.} The laminated film according to any one of claims 1 to 4, wherein the layer A contains an amorphous resin as a main component. 5. The non-crystalline resin is at least one resin selected from a polypropylene resin, a cyclic olefin resin, a polystyrene resin, a polycarbonate resin, an acrylic resin, a polyester resin, and a polyamide resin. The laminated film described in. The laminated film according to any one of claims 1 to 6, wherein the number of times the layer A has reached bending fracture is 100 times or more and 10,000 times or less. The laminated film according to any one of claims 1 to 7, wherein the surface roughness Ra of one side or both sides of the layer A is 1 nm or more and 100 nm or less. The laminated film according to any one of claims 1 to 8, wherein the minute endothermic peak temperature (Tmeta) of the B layer is 120 ° C. or higher and 220 ° C. or lower. Claims 1 to 1, wherein the plane-direction refractive index of the B layer is 1.6000 or more and 1.6600 or less, and the thickness-direction refractive index of the B layer is 1.4800 or more and 1.5700 or less. 9. The laminated film according to any one of 9. Claims 1 to 10 are characterized in that the crystalline parameter (ΔTcg) of the B layer is 10 ° C. or higher and 100 ° C. or lower, and the ΔHm _B is 15.0 J / g or higher and 50.0 J / g or lower. The laminated film according to any one of. The laminated film according to any one of claims 1 to 11, wherein the glass transition temperature (Tg _{B) of the B layer is 30 ° C. or higher and 100 ° C. or lower.} The laminated film according to any one of claims 1 to 12, wherein the B layer contains a crystalline resin as a main component. The laminated film according to claim 13, wherein the crystalline resin is a polyester resin. A method for producing a laminated film according to any one of claims 1 to 14.
When the molten resin composition for obtaining the A layer is the molten resin composition A and the molten resin composition for obtaining the B layer is the molten resin composition B,
A coextrusion laminating step of coextruding and laminating a molten resin composition A and a molten resin composition B,
A casting process in which the laminate obtained by the coextrusion lamination process is cooled and solidified.
A stretching step of stretching the sheet obtained by the casting step in at least one direction,
_A method for producing a laminated film, which comprises, in this order, a heat treatment step of heat-treating at a temperature of Tg A + 20 ° C. or higher and Tg _{A + 120 ° C. or lower.} The method for producing a laminated film according to claim 15, wherein the crystallinity of the B layer in the casting step is controlled to be 10% or more and 30% or less. The method for producing a laminated film according to claim 15 or 16, wherein in the coextrusion laminating step, the molten resin composition B is laminated on both surfaces of the molten resin composition A. The method for producing a laminated film according to claim 17, wherein the compositions of the molten resin composition B located on each surface side of the molten resin composition A are different from each other. The film according to any one of claims 15 to 18, further comprising a widening step of individually widening the molten resin composition A and the molten resin composition B upstream of the coextrusion laminating step. Production method.