Laminated film

Abstract

To provide a laminated film which can reduce curling generated when one surface is heated.SOLUTION: A laminated film is formed by laminating an upper surface layer (B1), a base material layer (A) and a lower surface layer (B2) in this order. The base material layer (A) contains an olefinic resin and a filler. The upper surface layer (B1) contains a crystalline resin and an amorphous resin. The lower surface layer (B2) contains at least a crystalline resin, and further contains an amorphous resin or does not contain the amorphous resin. A content C1(g / m2) of the amorphous resin per unit area in the upper surface layer (B1) is larger than a content C2(g / m2) of the amorphous resin per unit area in the lower surface layer (B2).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] This invention relates to a laminated film. [Background technology]

[0002] Traditionally, resin films such as polypropylene have been used as label paper and printing paper. Such resin films may have one side heated by embossing or lamination of molten resin.

[0003] When one side of a resin film is heat-treated, that side heats preferentially. As a result, one side shrinks more strongly than the other, which can cause curling. One known method to suppress curling is to anneal the resin film to remove residual stress within the film. Another known method is to incorporate an amorphous resin, which is relatively resistant to heat shrinkage, into the resin film to suppress the overall heat shrinkage of the resin film (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2016-107504 [Patent Document 2] Japanese Patent Publication No. 2012-066434 [Overview of the project] [Problems that the invention aims to solve]

[0005] When annealing is performed, the manufacturing process is expanded, thus increasing manufacturing costs. Furthermore, attempting to suppress curling by incorporating amorphous resins limits the available materials. Amorphous resins are generally more expensive than crystalline resins, and manufacturing costs increase as the amount incorporated increases.

[0006] An object of the present invention is to provide a laminated film capable of reducing curling that occurs when heat treatment is performed on one surface.

Means for Solving the Problems

[0007] As a result of intensive studies conducted by the present inventors to solve the above problems, they have found that the above problems can be solved by providing curl-adjusting resin layers on both sides of a base material layer and adjusting the content of an amorphous resin in each resin layer, and thus completed the present invention. That is, the present invention is as follows.

[0008] [1] A laminated film in which an upper surface layer (B1), a base material layer (A), and a lower surface layer (B2) are laminated in this order, the base material layer (A) contains an olefin-based resin and a filler, the upper surface layer (B1) contains a crystalline resin and an amorphous resin, the lower surface layer (B2) contains at least a crystalline resin, and further contains an amorphous resin, or does not contain the amorphous resin, the content C1 of the amorphous resin per unit area in the upper surface layer (B1) (g / m 2 ) is greater than the content C2 of the amorphous resin per unit area in the lower surface layer (B2) (g / m 2 ) laminated film.

[0009] [2] The amorphous resin is a cyclic olefin-based resin or a petroleum resin The laminated film according to [1] above.

[0010] [3] The contents C1 and C2 of the amorphous resin satisfy the following formula (1) (1) 0.1≦C1-C2≦10 The laminated film according to [1] or [2] above.

[0011] [4] The crystalline resin is a propylene-based resin The laminated film according to any one of [1] to [3] above.

[0012] [5] The olefin resin is a propylene resin. A laminated film according to any of the above [1] to [4].

[0013] [6] The upper layer (B1) or the lower layer (B2) further contains filler. A laminated film according to any of the above [1] to [5].

[0014] [7] The upper layer (B1) is provided with a coating layer (D), The coating layer (D) contains an ethyleneimine resin. The laminated film described in [6] above.

[0015] [8] The surface of the laminated film on the upper layer (B1) side is the surface that is heat-treated. A laminated film according to any of the above [1] to [7]. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a laminated film that can reduce curling that occurs when one side is subjected to heat treatment. [Brief explanation of the drawing]

[0017] [Figure 1] This figure illustrates a laminated film that has exhibited reverse curling. [Figure 2] This is a cross-sectional view showing an example of a laminated film. [Figure 3] A cross-sectional view showing another example of a laminated film. [Figure 4] This is a diagram illustrating the method for evaluating curl characteristics. [Modes for carrying out the invention]

[0018] The laminated film of the present invention will be described in detail below. The following is an example (representative example) of the present invention, and the present invention is not limited thereto.

[0019] In the following explanation, the term "(meth)acrylic" refers to both acrylic and methacrylic.

[0020] [Laminated film] The laminated film of the present invention comprises an upper layer (B1), a base layer (A), and a lower layer (B2) in this order. Specifically, the upper layer (B1) is provided on one surface of the base layer (A), and the lower layer (B2) is provided on the other surface.

[0021] In the present invention, the base layer (A) contains an olefin resin. The top layer (B1) contains a crystalline resin and a content per unit area (g / m²). 2 ) contains amorphous resin with C1 (C1>0). On the other hand, the bottom layer (B2) contains crystalline resin and a content per unit area (g / m²). 2 The material contains an amorphous resin with a content of C2 (C2≧0). The content of amorphous resin C1 in the upper layer (B1) is greater than the content of amorphous resin C2 in the lower layer (B2).

[0022] Normally, when a film containing crystalline resin is heat-treated on one side, such as by embossing or lamination of molten resin, the heated side will curl inward. This is because the directly heated side heats preferentially over the other side, causing the crystalline resin in the film on that side to shrink more strongly than on the other side. In this specification, this curl inward on the heated side is referred to as a positive curl. In the laminated film of the present invention, when the upper layer (B1) side is heat-treated, the upper layer (B1) side heats preferentially, resulting in stronger thermal shrinkage in the upper layer (B1) than in the lower layer (B2), and thus a positive curl inward on the upper layer (B1) side.

[0023] However, the laminated film of the present invention already has a slight curl in the opposite direction to the positive curl, that is, a slight curl in which the surface of the lower layer (B2) is concave. In this specification, this curl in which the surface opposite to the heat-treated surface is concave is called a reverse curl. Such a reverse curl occurs during the manufacturing process due to various differences, such as the difference in the content of amorphous resin between the upper layer (B1) and the lower layer (B2). Furthermore, since the lower layer (B2), which has a lower amorphous resin content than the upper layer (B1), is more susceptible to thermal shrinkage, the reverse curl that occurs during the manufacturing process becomes even larger when the entire film is heated in an oven or the like. This phenomenon occurs to some extent, albeit to a weaker degree, even when one-sided heating is performed, such as embossing on one side or lamination of molten resin, because the entire film is heated unevenly by conductive heat transfer. Therefore, the positive curl that occurs in the laminated film due to heat treatment on one side is canceled out and reduced by the originally present reverse curl and the additional reverse curl that occurs when the entire film is heated. Therefore, it is possible to provide a laminated film with minimal curling even when processing involving heat treatment, such as embossing on one side or lamination of molten resin.

[0024] Figure 1 illustrates a laminated film that has undergone reverse curling. In Figure 1, the laminated film 11 has an upper layer B1, a base layer A, and a lower layer B2. As shown in Figure 1, due to the difference in composition between the lower layer B2 and the upper layer B1, the laminated film 11 exhibits reverse curling during manufacturing, where the surface on the lower layer B2 side is concave.

[0025] For example, when laminating molten resin onto a portion of one side, the molten resin is heat-pressed onto the surface of the upper layer B1 in the direction of the arrow, forming a resin layer 1a. At this time, each layer containing crystalline resin shrinks due to heat, causing the heated surface on the upper layer B1 side to become concave, i.e., positive curl occurs. However, in the laminated film of the present invention, not only positive curl occurs, but also reverse curl occurs due to the difference in shrinkage between the lower layer B2 and the upper layer B1. The reverse curl generated during manufacturing and the reverse curl generated during bonding cancel out the positive curl, thus reducing the positive curl.

[0026] When the laminated film of the present invention is a stretched film, positive curl is more likely to occur due to residual stress. However, with the laminated film of the present invention, positive curl can be reduced without annealing, thus eliminating the need for the annealing process and contributing to increased efficiency and lower costs in the production process. Furthermore, with the laminated film of the present invention, curl can be easily controlled by the content of amorphous resin in the upper layer (B1) and lower layer (B2).

[0027] Furthermore, since positive curl can be canceled out not only by the reverse curl that occurs during manufacturing but also by additional reverse curl that occurs during post-manufacturing heat treatment, it is possible to set a lower level of reverse curl that occurs during manufacturing. This reduces the impact that reverse curl that occurs during manufacturing has on the handling of the laminated film afterward.

[0028] The present invention exhibits the above effects in laminated films of any structure, but the effects are particularly remarkable when there is residual stress inside the film, for example, when the laminated film includes a stretched film or a film that has not been annealed after stretching. Specifically, the present invention is suitable for laminated films that include a stretched film with a stretching ratio in the longitudinal direction (MD: Machine Direction) of 2 times or more, and in particular for laminated films that include the stretched film as a base layer with a large proportion of its thickness.

[0029] In addition to the top layer (B1), base layer (A), and bottom layer (B2) described above, the laminated film of the present invention may have other layers as needed. For example, the laminated film of the present invention may have a coating layer (D) on the top layer (B1) to improve adhesion with ink used for printing. The coating layer (D) may also be provided on the bottom layer (B2).

[0030] Figure 2 illustrates a laminated film 12 with a coating layer (D) provided. The laminated film 12 comprises a base layer A and an upper layer B1 and a lower layer B2 on both sides of the base layer A. In this example of the laminated film 12, a coating layer D is provided on the upper layer B1.

[0031] A printed layer 2 can be formed by printing on this coating layer D. The printed layer 2 consists of ink components transferred by printing. A melt-bonded resin layer 3 can also be provided on the coating layer D. The resin layer 3 is, for example, a layer of thermoplastic resin provided for decoration by laminating it in a molten state on a part of one side, a hot-melt type adhesive, or a heat-seal resin used on the adhesive surface of a label. From the viewpoint of ease of processing, it is preferable that the resin used for the resin layer 3 is a thermoplastic resin with a low melting point. The following explains each layer.

[0032] (Base material layer (A)) The base layer (A) contains an olefin resin and a filler, providing the laminated film with excellent mechanical strength.

[0033] <Olefin resin> Specific examples of olefin resins include propylene resins and ethylene resins.

[0034] The propylene-based resin is not particularly limited as long as propylene is used as the main monomer. For example, isotactic polymers or syndiotactic polymers obtained by homopolymerizing propylene can be used. Alternatively, propylene-α-olefin copolymers, which are copolymers of propylene as the main component with α-olefins such as ethylene, 1-butene, 1-pentene, or 1-hexene, can also be used. The copolymer may have a binary system or a multi-component system of ternary or more monomer components, and may be a random copolymer or a block copolymer. Furthermore, a propylene homopolymer and a propylene copolymer may be used in combination.

[0035] For example, ethylene-based resins have a density of 0.940 to 0.965 g / cm³. 3High-density polyethylene, density 0.920~0.935 g / cm³ 3 Medium-density polyethylene, density 0.900 g / cm³ 3 More than 0.920g / cm 3 Examples include copolymers mainly composed of linear low-density polyethylene (less than 100%), ethylene, etc., copolymerized with α-olefins such as propylene, butene, and hexene; maleic acid-modified ethylene-vinyl acetate copolymers; ethylene-vinyl acetate copolymers; ethylene-acrylic acid copolymers; ethylene-alkyl acrylate copolymers; ethylene-alkyl methacrylate copolymers; metal salts of ethylene-methacrylic acid copolymers; ethylene-cyclic olefin copolymers; or maleic acid-modified polyethylene.

[0036] Furthermore, graft-modified olefin resins can be used as needed to improve moldability. Known methods can be used for graft modification. Specifically, graft-modified products using unsaturated carboxylic acids or their derivatives as graft monomers can be mentioned. Examples of the above unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, or citraconic acid. Examples of the above unsaturated carboxylic acids include acid anhydrides, esters, amidates, imides, or metal salts of the above unsaturated carboxylic acids.

[0037] Specific examples of graft monomers include maleic anhydride. Graft monomers can typically be used in amounts of 0.005 to 10% by mass, preferably 0.01 to 5% by mass, relative to the olefin resin.

[0038] As the olefin resin used for the base layer (A), one of the above may be used alone, or two or more may be used in combination. From the viewpoint of moisture resistance, moldability, mechanical strength, and cost, the base layer (A) is preferably a resin film of a propylene resin or an ethylene resin, and a propylene resin is more preferable. Among these, a propylene homopolymer is preferred as the main raw material for the base layer (A) because it is easy to handle.

[0039] From the viewpoint of film moldability, propylene-based resins can be used in combination with resins having a melting point equivalent to or lower than that of propylene homopolymers. Such resins include ethylene-based resins, specifically high-density or low-density polyethylene. The amount of ethylene-based resin added can be 2 to 25% by mass relative to the total amount of resin components.

[0040] <Filler> Examples of fillers that can be used in the base layer (A) include inorganic fillers and organic fillers. Inorganic fillers are preferred. The whiteness or opacity of the film can be easily adjusted by the addition of fillers. Furthermore, pores are easily formed inside the film starting from the fillers, making it possible to lighten the base layer (A) and, consequently, the laminated film. If the base layer (A) is porous, the thermal insulation properties of the laminated film are also easily improved. If the base layer (A) is a resin film in which an ethylene resin is added to a propylene resin, fibrillary pores are easily formed by the addition of fillers, which is preferable.

[0041] <<Inorganic filler>> As inorganic fillers, inorganic particles such as calcium carbonate, calcined clay, silica, diatomaceous earth, white clay, talc, titanium dioxide, barium sulfate, barium titanate, alumina, zeolite, or glass fiber can be used. Calcium carbonate is particularly preferred. The average particle size of the inorganic filler, as measured by a laser diffraction particle size analyzer, is usually 0.01 to 15 μm, and preferably 0.1 to 5 μm.

[0042] <<Organic Filler>> As the organic filler, it is preferable to select a resin of a different type from the olefin resin that is the main component of the base layer (A). Examples of such organic fillers include polymers such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, nylon-6, nylon-6,6, cyclic polyolefin, polystyrene, or polymethacrylate, which have a melting point higher than that of the olefin resin (e.g., 170-300°C) or a high glass transition temperature (e.g., 170-280°C), and which are immiscible organic particles.

[0043] The inorganic and organic fillers mentioned above can be used individually or in combination as fillers. The filler content in the base layer (A) (total amount if inorganic and organic fillers are used in combination) is preferably 0 to 60% by mass, and more preferably 0 to 50% by mass.

[0044] <Other ingredients> The substrate layer (A) may further contain, if necessary, a heat stabilizer (antioxidant), a light stabilizer, a dispersant, a lubricant, or a nucleating agent. As a heat stabilizer, for example, sterically hindered phenolic antioxidants, phosphorus-based antioxidants, or amine-based antioxidants can be used, usually in a range of 0.001 to 1% by mass. As a light stabilizer, for example, sterically hindered amine-based light stabilizers, benzotriazole-based light stabilizers, or benzophenone-based light stabilizers can be used, usually in a range of 0.001 to 1% by mass. Examples of dispersants or lubricants include silane coupling agents, higher fatty acids such as oleic acid and stearic acid, metal soaps, polyacrylic acid, polymethacrylic acid, or salts thereof. These can typically be used in amounts ranging from 0.01% to 4% by mass, for example, to disperse fillers.

[0045] <Layer configuration> The base material layer (A) may be a single layer or a multilayer structure of two or three or more layers. Multilayering makes it possible to impart various functions to the base material layer (A), such as mechanical properties, writing properties, abrasion resistance, or suitability for secondary processing.

[0046] The base layer (A) preferably includes a stretched film stretched in at least one axial direction, and from the viewpoint of increasing whiteness or opacity, the base layer (A) more preferably includes a porous stretched film having voids inside. The base layer (A) including the stretched film has high moisture resistance and mechanical strength, and excellent thickness uniformity, so a laminated film with excellent post-processing properties can be obtained. If the base material layer (A) has a multilayer structure, the number of stretching axes for each layer may be 1 axis / 1 axis, 1 axis / 2 axes, 2 axes / 1 axis, 1 axis / 1 axis / 2 axes, 1 axis / 2 axes / 1 axis, 2 axes / 1 axis / 1 axis, 1 axis / 2 axes / 2 axes, 2 axes / 2 axes / 1 axis, or 2 axes / 2 axes / 2 axes.

[0047] <Porosity> From the viewpoint of weight reduction or improvement of whiteness, the porosity of the base layer (A) is preferably greater than 0%, preferably 50% or less, and more preferably 40% or less. If the porosity is 50% or less, it is easier to maintain strength. The above porosity can be determined from the ratio of the area occupied by voids in a certain region of the cross-section of the film observed with an electron microscope.

[0048] (Top layer (B1) and bottom layer (B2)) The upper layer (B1) and lower layer (B2) are provided on both sides of the base layer (A), respectively, to adjust the curl of the laminated film.

[0049] In the present invention, the top surface layer (B1) contains a crystalline resin and an amorphous resin. As will be described in detail later, in the present specification, a crystalline resin refers to a resin having oriented molecular chain portions (crystalline portions). In contrast, an amorphous resin refers to a resin that does not have the aforementioned crystalline portions, or has an extremely small amount of the aforementioned crystalline portions even if it contains them. Whether or not a resin has crystalline portions to an extent that it exhibits crystallinity can be determined based on whether or not the resin has a melting point, that is, whether or not it has a clear melting peak in differential scanning calorimetry (DSC) performed with temperature increase at a constant rate. In the present specification, when the peak area of the melting peak in DSC is 20 J / g or more, it is determined that the resin has a clear melting peak.

[0050] Further, in the present invention, the bottom surface layer (B2) contains a crystalline resin, and may further contain an amorphous resin. As described above, the bottom surface layer (B2) does not need to contain an amorphous resin as long as the content of the amorphous resin per unit area in the bottom surface layer (B2) is smaller than that in the top surface layer (B1).

[0051] <Difference in amorphous resin content> Specifically, the content C1 (g / m 2 ) of the amorphous resin per unit area of the top surface layer (B1) and the content C2 (g / m 2 ) of the amorphous resin per unit area of the bottom surface layer (B2) satisfy C1>C2. Here, C1>0 and C2≧0.

[0052] From the viewpoint of effectively canceling positive curling, it is preferable that the contents C1 and C2 of the amorphous resin satisfy the following formula (1). (1) 0.1≦C1-C2≦10

[0053] Various methods can be selected to adjust the amorphous resin content in the upper layer (B1) and lower layer (B2). For example, it can be adjusted by increasing or decreasing the amorphous resin content in a single layer (ML) within the upper layer (B1). Alternatively, it can be adjusted by increasing or decreasing the basis weight of only one layer (ML) while maintaining a constant overall thickness of the upper layer (B1).

[0054] Depending on the thickness of each layer and the magnitude of the C1 and C2 content, a larger difference (C1-C2) is more likely to cause reverse curl. Therefore, from the viewpoint of maximizing reverse curl, a difference (C1-C2) of 0.2 or more is more preferable, and 0.3 or more is even more preferable. If the positive curl is not large, from the viewpoint of suppressing excessive reverse curl, a difference (C1-C2) of 8 or less is more preferable, and 6 or less is even more preferable.

[0055] The above-mentioned contents (C1) and (C2) can be adjusted by varying the mass ratio of crystalline resin to amorphous resin in the layers, or the thickness of the layers, between the upper layer (B1) and the lower layer (B2).

[0056] The upper layer (B1) or the lower layer (B2) preferably further contains a filler, and it is more preferable that both the upper layer (B1) and the lower layer (B2) contain a filler. The inclusion of a filler reduces the amount of resin components, which are expensive. In addition, the filler improves opacity and suppresses the occurrence of appearance defects such as shark skin and interface roughness.

[0057] <Layer configuration> The top layer (B1) may be a single layer or a multilayer structure. In the case of a multilayer structure, the components and mixing ratios of the materials in each layer may be the same or different.

[0058] Furthermore, it is preferable that the upper layer (B1) and the lower layer (B2) include a stretched film that is stretched in at least one axial direction. Stretching makes it easier to obtain a film with a uniform thickness with reduced variation and excellent strength.

[0059] In the upper layer (B1) and lower layer (B2), it is preferable that the layer containing amorphous resin is placed on the substrate layer side of the outermost layer, rather than on the outermost layer. Layers containing amorphous resin are less prone to pore formation and absorb less ink compared to layers without amorphous resin. By placing such a layer on the substrate layer side, it is possible to prevent a decrease in the ink absorption of the outermost layer and, consequently, a decrease in printing performance. However, if the application is not for printing, there is no particular problem even if the layer containing amorphous resin is placed on the outermost layer.

[0060] Figure 3 illustrates a laminated film 13 in which the upper layer (B1) and lower layer (B2) have a multilayer structure. In the laminated film 13, the upper layer B1 and the lower layer B2 each have a three-layer structure. The upper layer B1 has, in order from the substrate layer side, a skin layer B11, a core layer B12, and a skin layer B13. The lower layer B2 has, in order from the substrate layer side, a skin layer B21, a core layer B22, and a skin layer B23.

[0061] In the laminated film 13, core layers B12 and B22 contain crystalline resin and amorphous resin, respectively. On the other hand, skin layers B11, B13, B21, and B23 contain crystalline resin but do not contain amorphous resin. The amorphous resin content (mass%) in core layers B12 and B22 is the same. Also, the total thickness of the upper layer B1 and the lower layer B2 is the same, but core layer B12 is thicker than core layer B22. Therefore, the amorphous resin content C1 per unit area of ​​the upper layer B1 is greater than the amorphous resin content C2 per unit area of ​​the lower layer B2.

[0062] Furthermore, in the laminated film 13, a coating layer D is also provided on the bottom layer B2. By printing on this coating layer D, a printed layer 2 can be formed.

[0063] <Top layer (B1)> The top layer (B1) is provided on the heat-treated surface side of the laminated film, following processes such as embossing or lamination of molten resin on one side. From the viewpoint of effectively counteracting positive curl, it is preferable that only the surface of the top layer (B1) is heat-treated.

[0064] <<Crystalline resin>> Examples of crystalline resins that can be used for the top layer (B1) include common resins such as olefin resins, ester resins, amide resins, and (meth)acrylic acid resins, with olefin resins being preferred among them.

[0065] Examples of olefin resins include homopolymers of α-olefins having 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, and 1-hexene; and copolymers of 2 to 5 of these α-olefins. Among these, it is preferable to use at least one of a propylene resin containing propylene as a raw material monomer and an ethylene resin containing ethylene as a raw material monomer. From the viewpoint of moldability, propylene resins are preferred, and the combined use of propylene resins and ethylene resins is more preferable. As for ethylene resins, high-density polyethylene is preferred because it has good moldability.

[0066] Examples of polyester polymers include polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate.

[0067] Examples of polyamide polymers include nylon-6 and nylon-6,6.

[0068] Crystalline resins are resins that are not amorphous resins, and the degree of crystallinity of crystalline resins is preferably 40-95%. For example, if the crystalline resin is a propylene homopolymer, its degree of crystallinity is preferably 45-70% and more preferably 45-60% from the viewpoint of reverse curl generation. The degree of crystallinity of a resin can be derived from the heat of fusion Hm (J / g) of the resin measured by DSC (Differential Scanning Calorimeter) and the heat of fusion Hp (J / g) when the resin is a perfect crystal (100% crystallinity) using the following formula (a). Crystallinity (%)=Hm / Hp×100 (a)

[0069] In equation (a), Hp is determined as a theoretical value specific to each resin; the Hp of polypropylene homopolymer is 209 (J / g), and the Hp of high-density polyethylene is 293 (J / g). Hm is measured and calculated as the melting peak area when the resin is heated to a temperature above its melting point of 30°C under conditions of a heating rate of 10°C / min and a nitrogen flow rate of 100 mL / min, cooled at 20°C / min, and then reheated under the same conditions as above.

[0070] In the upper layer (B1), it is preferable that the amorphous resin is uniformly dispersed within the crystalline resin. This makes it easier for thermal shrinkage to occur uniformly in the laminated film, and makes it easier to suppress warping.

[0071] A structure in which amorphous resin is uniformly arranged within a crystalline resin can be obtained by extruding or stretching a mixed resin containing both amorphous and crystalline resins in predetermined proportions. The phase structure of the resin can be confirmed by observing the cross-section of the laminate when it is cut in the thickness direction using an electron microscope such as a TEM.

[0072] <<Amorphous resin>> Amorphous resins are resins that do not have substantially crystalline portions, and typically have a degree of crystallinity of 10% or less, preferably 5% or less, more preferably 1%, and even more preferably 0%.

[0073] Examples of amorphous resins that can be used for the top layer (B1) include cyclic olefin resins, petroleum resins, polyester resins such as polyethylene terephthalate resin, amorphous propylene copolymer resins, and polymethyl (meth)acrylate resins. These amorphous resins may be used individually or in combination of two or more. From the viewpoint of reverse curl generation, cyclic olefin resins or petroleum resins are more preferred, and petroleum resins are even more preferred.

[0074] Examples of cyclic olefin resins include ring-opening polymers derived from cyclic olefins represented by the following general formula (1), hydrides of said polymers, and addition polymers of cyclic olefin monomers represented by the general formula (1) and ethylene.

[0075] [ka] [In general formula (1), n ​​represents 0 or a positive integer. R 1 ~R 12 Each of these independently represents an atom or substituent selected from the group consisting of hydrogen atoms, halogen atoms, and hydrocarbon groups. 9 ~R 12 These may be bonded to each other to form a monocyclic or polycyclic group, and the monocyclic or polycyclic group may have a double bond. 9 and R 10 toga, or R 11 and R 12 Both may form one alkylidene group.

[0076] Examples of petroleum resins include unsaturated hydrocarbon resins obtained by polymerizing higher unsaturated hydrocarbon compounds present in high-temperature pyrolysis oils such as naphtha, for example, mainly C5 or C9 fractions remaining after extracting the necessary fractions from the cracked oil, specifically butadiene, piperylene, isoprene, dicyclopentadiene, terpenes, styrene, methylstyrene, vinyltoluene, indene, methylindene, and mixtures thereof, using an acidic catalyst, and saturated hydrocarbon resins obtained by hydrogenating said unsaturated hydrocarbon resins. Among petroleum resins, it is preferable to use polystyrene resins mainly composed of styrene-based components such as styrene or methylstyrene.

[0077] Examples of polystyrene-based resins include polystyrene, high-impact polystyrene, styrene-grafted polyethylene copolymer, styrene-grafted polypropylene copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer, and styrene-butadiene resin, with homopolystyrene being preferred among them.

[0078] <<Mass ratio of crystalline resin to amorphous resin>> In the upper layer (B1), the mass ratio of crystalline resin to amorphous resin can be appropriately set based on the relationship with the amorphous resin content C2 in the lower layer (B2). From the viewpoint of generating sufficient reverse curl, the amorphous resin content in the upper layer (B1) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of crystalline resin. From the viewpoint of suppressing excessive reverse curl or cost, the content is preferably 20 parts by mass or less per 100 parts by mass of crystalline resin.

[0079] <<Filler>> For the top layer (B1), the same filler as the base layer (A) described above can be used, and the preferred type of filler is also the same as for the base layer (A).

[0080] The filler content in the top layer (B1) is not particularly limited, but from the viewpoint of cost reduction or whitening, it is preferably 20% by mass or more, and more preferably 30% by mass or more. From the viewpoint of maintaining strength, the content is preferably 60% by mass or less, and more preferably 50% by mass or less.

[0081] <Bottom layer (B2)> For the bottom layer (B2), the crystalline resin, amorphous resin, and filler that can be used are the same as those used for the top layer (B1), and the preferred types of each material are also the same. The types of crystalline resin, amorphous resin, and filler used for the bottom layer (B2) may be the same as or different from those used for the top layer (B1).

[0082] <<Mass ratio of crystalline resin to amorphous resin>> The mass ratio of crystalline resin to amorphous resin in the lower layer (B2) can be appropriately set based on the relationship with the amorphous resin content C1 in the upper layer (B1). From the viewpoint that incorporating amorphous resin into the lower layer (B2) allows for finer adjustment of reverse curl, the amorphous resin content in the lower layer (B2) is preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, per 100 parts by mass of crystalline resin. From the viewpoint of suppressing excessive reverse curl or cost, the content is preferably 20 parts by mass or less per 100 parts by mass of crystalline resin.

[0083] (Coat layer (D)) The coating layer (D) may be provided on the top layer (B1) or the bottom layer (B2). Ink transfer by printing or lamination of molten resin may be performed on the coating layer (D). The coating layer (D) can be formed by applying a coating liquid to the surface of the upper layer (B1) or the lower layer (B2) and drying it.

[0084] The coating liquid that forms the coating layer (D) contains an adhesive resin. Examples of adhesive resins include ethyleneimine resins or emulsion resin particles, with ethyleneimine resins being preferred.

[0085] <Ethyleneimine-based resin> The coating layer (D) preferably contains components derived from ethyleneimine resin. Ethyleneimine resin has high affinity for various inks and is presumed to enhance adhesion between the ink and the surface of the coating layer (D). It is also thought to enhance adhesion with the resin laminated on top of the coating layer (D).

[0086] The content of ethyleneimine resin in the coating solution is preferably 1 part by mass or more, more preferably 2 parts by mass or more, on a solid content basis, while it is preferably 40 parts by mass or less, and more preferably 30 parts by mass or less. If the content is above the lower limit, ink adhesion tends to improve, and if it is below the upper limit, blocking of the laminated film tends to decrease.

[0087] <Emulsion> The coating layer (D) may contain components derived from a resin particle emulsion (hereinafter sometimes simply referred to as emulsion), to the extent that it does not impair the effects of the present invention.

[0088] Here, emulsion-derived components refer to residual components remaining after the emulsion dispersion medium in the coating solution for the coating layer (D) has evaporated. For example, residual components include resin particles in the emulsion and other components added as needed. These components may include modified forms that have been altered during the process of forming the coating layer (D). The resin particles in the residual components exist in particulate form in the coating layer (D), but may melt and deform due to overheating during printing.

[0089] An emulsion is a liquid in which fine particulate resin particles are emulsified or dispersed in a dispersion medium. In this invention, resin particles refer to fine particulate resin particles dispersed in a dispersion medium that constitute an emulsion. From the viewpoint of ease of handling, an O / W (oil-in-water) emulsion in which resin particles are emulsified or dispersed in an aqueous dispersion medium is preferred.

[0090] By including emulsion-derived components in the coating layer (D), good ink adhesion and long-term stability of printed images can be obtained in various printing methods such as offset printing, fused thermal transfer printing, or electrophotographic printing.

[0091] <<Types of resin>> Examples of resins that can be used as resin particles in the emulsion include urethane resins, olefin copolymers, and styrene resins. Among these, urethane resins or olefin copolymers are preferred from the viewpoint of adhesion to the ink, and urethane resins are even more preferred. Among olefin copolymers, ethylene-(meth)acrylic acid copolymers and ethylene-methyl acrylate copolymers (EMA) are preferred.

[0092] <Other ingredients> The coating layer (D) may contain other additives, such as antistatic agents, as needed, to the extent that they do not impair printability.

[0093] <<Antistatic agent>> Antistatic agents can reduce dust adhesion due to static electricity on the film surface, or problems caused by static electricity during printing. The antistatic agent is not particularly limited, and cationic, anionic, amphoteric, or nonionic antistatic agents can be used. Furthermore, low molecular weight antistatic agents or high molecular weight (polymer) antistatic agents may also be used.

[0094] Examples of cationic antistatic agents include those having an ammonium salt structure or a phosphonium salt structure. Examples of anionic antistatic agents include those having the structure of an alkali metal salt such as sulfonic acid, phosphoric acid, or carboxylic acid. Examples of alkali metal salts of these acids include lithium salts, sodium salts, or potassium salts. Anionic antistatic agents may also have the structure of an alkali metal salt such as acrylic acid, methacrylic acid, or (anhydride) maleic acid in their molecular structure.

[0095] Examples of amphoteric antistatic agents include those that contain both cationic and anionic antistatic structures within the same molecule. Amphoteric antistatic agents may also be betaine-type antistatic agents. Examples of nonionic antistatic agents include ethylene oxide polymers having an alkylene oxide structure, and polymers having ethylene oxide polymerization components in their molecular chains. Other examples of antistatic agents include polymer-type antistatic agents that contain boron in their molecular structure.

[0096] Preferably, a nitrogen-containing polymer-type antistatic agent is used as the antistatic agent, and more preferably, a tertiary nitrogen or quaternary nitrogen-containing acrylic resin is used. These antistatic agents may be used individually or in combination of two or more types.

[0097] The amount of antistatic agent added to the coating solution is preferably 5 parts by mass or more, and preferably 80 parts by mass or less, in terms of solid content. If the amount of antistatic agent added is above the lower limit, antistatic performance is easily obtained, and if it is below the upper limit, sufficient ink transferability is easily obtained during printing.

[0098] [Characteristics of laminated films] (Overall thickness) The overall thickness of the laminated film is preferably 10 μm or more, more preferably 50 μm or more, and even more preferably 100 μm or more. The thicker the laminated film, the greater its resistance to curling, making it less prone to curling. The overall thickness of the laminated film is preferably 1500 μm or less, more preferably 1000 μm or less, and even more preferably 300 μm or less. When the overall thickness of the laminated film is 1500 μm or less, it is possible to reduce the weight, and handling tends to improve.

[0099] (Thickness of each layer) The thickness of the base layer (A) is preferably 10 μm or more, and more preferably 30 μm or more. If the thickness of the base layer (A) is above the lower limit, it tends to be easier to obtain rigidity and resilience as a base material. The thickness of the base layer (A) is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 200 μm or less. If the thickness of the base layer (A) is below the upper limit, the base layer (A) itself, which is one of the sources of curling, becomes thinner, making it easier to suppress positive curling after heat treatment.

[0100] The ratio of the thickness of the base layer (A) to the total thickness of the laminated film is preferably 90% or less, preferably 75% or less, and more preferably 65% ​​or less. The lower the proportion of the base layer, which contains olefin resin, has high mechanical strength, and can be a cause of curling, the easier it is to suppress positive curling after heat treatment. In particular, when the base layer is a biaxially oriented film, the internal stress is higher and the thermal shrinkage rate is larger than that of an unoriented or uniaxially oriented film, so it is preferable that the proportion of the base layer is below the above upper limit. The ratio of the thickness of the base layer (A) is preferably 20% or more, more preferably 40% or more, and even more preferably 50% or more. When the ratio is 20% or more, sufficient mechanical strength for easy transport is easily obtained.

[0101] The thicknesses of the upper layer (B1) and the lower layer (B2) can be appropriately determined to adjust the amorphous resin content C1 and C2 per unit area of ​​each layer. From the viewpoint of ease of manufacturing and generating sufficient reverse curl, the thickness of the upper layer (B1) and the lower layer (B2) is preferably 0.5 μm or more, and more preferably 1 μm or more. From the viewpoint of adjusting the balance of curl, the thickness of the upper layer (B1) and the lower layer (B2) is preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 100 μm or less.

[0102] The thickness of the coating layer (D) is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more, while it is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 1 μm or less. If the thickness is within this range, a laminated film with a texture similar to general printing paper can be obtained.

[0103] [Method for manufacturing laminated film] The laminated film of the present invention can be manufactured by laminating an upper layer (B1), a base layer (A), and a lower layer (B2) in this order, and the manufacturing method is not particularly limited. For example, the laminated film of the present invention can be manufactured by forming and laminating films of an upper layer (B1), a base layer (A), and a lower layer (B2). Furthermore, a coating liquid for forming a coating layer (D) can be applied to the upper layer (B1) or the lower layer (B2) to form a coating layer (D).

[0104] (Film forming and lamination) As a method for forming the film, for example, casting, calendering, rolling, or inflation molding can be used, in which molten resin is extruded into a sheet shape using single-layer or multi-layer T-dies, I-dies, etc., connected to a screw-type extruder. The film may also be formed by casting or calendering a mixture of thermoplastic resin and an organic solvent or oil, and then removing the solvent or oil.

[0105] Methods for laminating films include co-extrusion, extrusion lamination, and coating, and these can also be combined. In co-extrusion, each layer of resin composition, which has been melt-kneaded in separate extruders, is laminated and extruded in a feed block or multi-manifold, performing film formation and lamination in parallel. In extrusion lamination, a resin composition is extruded onto a pre-formed film to laminate the film. In coating, a resin solution, emulsion, or dispersion is applied onto the film and dried to form and laminate the film.

[0106] (Stretching) Each layer may be stretched individually before lamination, or they may be stretched together after lamination. Furthermore, the unstretched and stretched layers may be stretched again after lamination.

[0107] Methods for stretching a film include, for example, longitudinal stretching using the difference in peripheral speed of a group of rolls, transverse stretching using a tenter oven, sequential biaxial stretching combining these methods, rolling, simultaneous biaxial stretching using a combination of a tenter oven and a pantograph, and simultaneous biaxial stretching using a combination of a tenter oven and a linear motor. In addition, simultaneous biaxial stretching (inflation molding), in which molten resin is extruded into a tube shape using a circular die connected to a screw-type extruder and then air is blown into it, can also be used.

[0108] When stretching is performed, the stretching temperature is preferably in a range above the glass transition temperature of the thermoplastic resin used in the film if the thermoplastic resin is amorphous. If the thermoplastic resin is crystalline, the stretching temperature is preferably in a range above the glass transition temperature of the amorphous portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin, specifically a temperature 2 to 60°C lower than the melting point of the thermoplastic resin.

[0109] The stretching speed is not particularly limited, but from the viewpoint of stable stretch molding, it is preferably in the range of 20 to 350 m / min. Furthermore, the stretching ratio can be appropriately determined considering the characteristics of the thermoplastic resin used. For example, when stretching a resin film containing a propylene homopolymer or copolymer thereof in one direction, the stretching ratio is usually 1.2 times or more at the lower limit, preferably 2 times or more, and more preferably 4 times or more, while the upper limit is usually 12 times or less, and preferably 10 times or less. When biaxial stretching is performed, the stretching ratio is the area stretching ratio, which is usually 1.5 times or more at the lower limit, preferably 10 times or more, while the upper limit is usually 60 times or less, and preferably 50 times or less.

[0110] (Surface treatment) From the viewpoint of improving adhesion with the coating layer (D), it is preferable that the upper layer (B1) or lower layer (B2) is surface-treated and its surface is activated. Surface treatments include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, or ozone treatment, and these treatments can be combined. Among these, corona discharge treatment or flame treatment is preferred, and corona treatment is more preferred.

[0111] When performing corona discharge treatment, the discharge rate is preferably 600 J / m 2 (10W min / m 2 ) or more, more preferably 1,200 J / m 2 (20W min / m 2 ) or more, preferably 12,000 J / m 2 (200W min / m 2 ) or less, more preferably 10,800 J / m 2 (180W min / m 2 ) or less. The discharge rate when performing flame processing is preferably 8,000 J / m 2 The above is true, and more preferably 20,000 J / m 2 While the above is true, preferably 200,000 J / m 2 The following, and more preferably 100,000 J / m 2 The following applies:

[0112] (Formation of the coating layer (D)) The coating layer (D) can be formed by preparing a coating liquid for forming the coating layer (D) and applying it to the upper layer (B1) or the lower layer (B2).

[0113] <Preparation of coating solution> The coating solution for forming the coating layer (D) can be prepared by adding additives as needed to an aqueous solution of the ethyleneimine resin mentioned above.

[0114] The solid content concentration of the coating solution is preferably 0.1% by mass or more, more preferably 1.5% by mass or more, preferably 20% by mass or less, and more preferably 15% by mass or less, based on the total amount of the coating solution.

[0115] The coating liquid can be applied using coating equipment such as a roll coater, blade coater, bar coater, air knife coater, size press coater, gravure coater, die coater, lip coater, or spray coater.

[0116] The coating amount is 0.05 g / m² as the solid content after drying. 2 Preferably, it should be 0.10 g / m 2 It is more preferable that the amount be greater than or equal to 0.15 g / m 2 It is particularly preferable that the amount be greater than or equal to 1.40 g / m². 2 Preferably, it is 0.50 g / m 2 It is more preferable that the following is the case: 0.30 g / m 2 It is more preferable that the following is the case: 0.24 g / m 2 The following is particularly preferable: By ensuring the coating amount is above the lower limit mentioned above, adhesion to UV-curing inks used for offset printing, which are generally considered to have poor adhesion, tends to improve. On the other hand, because emulsions are not highly tacky, they can suppress the decrease in adhesion to offset printing inks caused by excessive coating amount.

[0117] The formation of the coating layer (D) is preferably carried out continuously by the roll-to-roll method. This improves the productivity of the laminated film. Furthermore, since the thickness of the coating layer (D) can be adjusted relatively easily with the roll-to-roll method, it is possible to easily manufacture laminated films with desired textures, such as thinning the coating layer (D) while maintaining printability. The formation of the coating layer (D) may be carried out using the same lines as those used to form each of the other layers, or it may be carried out using separate lines.

[0118] (printing) A printed layer can be formed by printing on the surface of the coating layer (D) of the laminated film of the present invention. Various known printing methods can be used, including offset printing, gravure printing, flexographic printing, letterpress printing, screen printing, inkjet recording, thermal recording, thermal transfer recording, and electrophotographic recording. Among these, offset printing, gravure printing, or flexographic printing are preferred as they easily produce printed materials with excellent weather resistance and water resistance, and gravure printing is preferred for packaging applications. Furthermore, oil-based inks, water-based inks, or UV-curable inks can be used as printing inks.

[0119] (Heat treatment of laminated film) The laminated film of the present invention can be subjected to heat treatment on the surface of the upper layer (B1). Specifically, this includes embossing to impart design features and lamination of molten resin. The molten resin may be laminated partially or completely. For example, a thermoplastic resin melted by heat treatment can be partially laminated to create decorative letters or pictures. Alternatively, a hot-melt adhesive can be applied or melt-extruded onto all or part of the surface of the upper layer (B1), and then the adhesive can be melted by heat treatment and laminated. The laminated film can be adhered to an object via this melted adhesive. Furthermore, a heat-seal resin layer provided on a label can be superimposed on all or part of the surface of the upper layer (B1), and then a heat-seal resin layer can be melted by heat treatment and laminated. The label can be adhered to the laminated film via this melted heat-seal resin layer. [Examples]

[0120] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Unless otherwise specified, "parts," "%," etc., in the examples refer to mass-based measurements.

[0121] [Raw materials] The raw materials used in the examples and comparative examples are as follows: (Crystalline resin) <pp>Propylene homopolymer (product name: Novatec PP MA3, manufactured by Nippon Polypropylene Co., Ltd.) <pe>High-density polyethylene resin (product name: Novatec HD US070G, manufactured by Nippon Polyethylene Co., Ltd.) (Amorphous resin) <apel>Cyclic olefin resin (product name: Apel 6011T, manufactured by Mitsui Chemicals, Inc.) <ps>Homopolystyrene (MFR: 7.5 g / min (measurement conditions: 200°C, 5 kgf), density: 1.05 g / cm³) 3 Vicat softening temperature: 94°C (measurement conditions: 50°C / hr, 50N) (Filler) Heavy calcium carbonate (product name: Softon 1800, manufactured by Bihoku Funka Kogyo Co., Ltd., average particle size: 1.25 μm)

[0122] Table 1 below lists the materials mentioned above. [Table 1]

[0123] The material for the coating layer (D) was prepared as follows: (Ethyleneimine resin) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet tube, 100 parts by mass of polyethyleneimine aqueous solution (product name: Epomin P-1000, degree of polymerization: 1600, manufactured by Nippon Shokubai Co., Ltd.), 10 parts by mass of glycidol, and 10 parts by mass of propylene glycol monomethyl ether were added. After purging the system with nitrogen, a modification reaction was carried out at 80°C for 16 hours under a nitrogen atmosphere to obtain a glycidol-modified polyethyleneimine aqueous solution with a solid content of 20% by mass, which was used as the ethyleneimine-based resin.

[0124] (Antistatic agent) In a four-necked flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen gas inlet tube, 35 parts by mass of dimethylaminoethyl methacrylate, 20 parts by mass of ethyl methacrylate, 20 parts by mass of cyclohexyl methacrylate, 25 parts by mass of stearyl methacrylate, 150 parts by mass of ethyl alcohol, and 1 part by mass of azobisisobutyronitrile were added. After purging the system with nitrogen, the polymerization reaction was carried out at a temperature of 80°C for 6 hours under a nitrogen atmosphere. Next, 70 parts by mass of a 60% by mass ethyl alcohol solution of 3-chloro-2-hydroxypropylammonium chloride were added, and the reaction was continued at 80°C for 15 hours. The ethyl alcohol was removed by distillation while adding water dropwise, and finally an aqueous solution of quaternary ammonium salt-containing acrylic resin with a solid content of 30% was obtained, which was used as an antistatic agent.

[0125] (Coating liquid) An aqueous solution containing 0.5% by mass of the above-mentioned ethyleneimine resin and 1.2% by mass of an antistatic agent was prepared and used as a coating solution. The concentrations of each component mentioned above represent the solid content concentration of each component relative to the total coating solution.

[0126] [Manufacturing of laminated films] (Example 1) A resin composition (a) consisting of 67 parts by mass of polypropylene resin (PP) (Novatec PP MA3), 10 parts by mass of polyethylene resin (PE) (Novatec HD US070G), and 23 parts by mass of heavy calcium carbonate (Softon 1800) was melt-kneaded in an extruder set to 230°C. The mixture was then supplied to an extrusion die set to 250°C and co-extruded into a sheet. This sheet was then cooled to 60°C using a cooling device to obtain an unstretched sheet. This unstretched sheet was heated to 135°C and stretched five times in the longitudinal direction using the difference in peripheral speed of the roll group to form a base layer (A).

[0127] Next, a resin composition (b1) consisting of 49.4 parts by mass of polypropylene resin (PP) (Novatec PP MA3), 3.5 parts by mass of polyethylene resin (PE) (Novatec HD US070G), 1.8 parts by mass of amorphous resin (APEL) (APEL 6011T), and 45.3 parts by mass of heavy calcium carbonate (Softon 1800) was melt-kneaded in an extruder set to 230°C. Furthermore, a resin composition (b2) consisting of 50.3 parts by mass of polypropylene resin (PP) (Novatec PP MA3), 3.5 parts by mass of polyethylene resin (PE) (Novatec HD US070G), 0.9 parts by mass of amorphous resin (APEL) (APEL 6011T), and 45.3 parts by mass of heavy calcium carbonate (Softon 1800) was melt-kneaded in a separate extruder set to 230°C.

[0128] Each extruder was used to extrude the resin compositions (b1) and (b2) onto both sides of the base layer (A), and the mixture was cooled to 60°C using a cooling device. This resulted in a three-layer sheet in which the top layer (B1) made of resin composition (b1), the base layer (A), and the bottom layer (B2) made of resin composition (b2) were laminated in that order. This three-layer sheet was heated to approximately 150°C using a tenter oven and stretched 8.5 times in the transverse direction. After heat treatment by heating to 160°C, it was cooled to 60°C and the edges were slit.

[0129] Next, using a continuous coating equipment, an energy density of 4200 J / m² was applied to the surface of the top layer (B1) of the three-layer sheet. 2 Corona discharge treatment was performed using the specified settings. Next, the coating liquid was applied to the top layer (B1) and dried in a 60°C hot air drying facility to form the coating layer (D). The solid content of the coating layer (D) after drying was 0.23 g / m². 2 That was the case.

[0130] Next, the material was wound up using a roll winding device to obtain a three-layer laminated film (total layer thickness: 250 μm, individual layer thickness: - / 50.5 μm / 150 μm / 50 μm, number of stretching axes for each layer: - / 1 axis / 2 axes / 1 axis) in the order of coating layer (D) / top layer (B1) / base layer (A) / bottom layer (B2).

[0131] (Examples 2, 3 and Comparative Example 1) Laminated films for Examples 2, 3, and Comparative Example 1 were obtained in the same manner as in Example 1, except that the content and thickness of each material in the upper layer (B1) and lower layer (B2) were changed as shown in Table 2.

[0132] (Example 4) The laminated film of Example 4 was obtained in the same manner as in Example 3, except that the amorphous resin used in the upper layer (B1) and lower layer (B2) was changed to 0.9 parts by mass of polystyrene (PS) (homopolystyrene), and the thickness of each layer was changed as shown in Table 2.

[0133] [evaluation] The curl properties of the laminated films in each example and comparative example were evaluated as follows.

[0134] (Curling) The laminated films obtained in each example and comparative example were cut to a size of 35 mm x 35 mm to prepare samples.

[0135] <Before heat treatment> As shown in Figure 4, the prepared sample 51 was placed on a flat glass plate 52, and the height d (mm) of the four corners that were raised from the glass plate 52 was measured with a ruler. Next, the sample 51 was turned over, and the height d of the four corners that were raised from the glass plate 52 was measured again with a ruler. Of the two sides, the average value of the height d (mm) of the four corners on the side with the higher height d was obtained as an evaluation value representing the curliness before heat treatment.

[0136] <After heat treatment> As shown in Figure 4, the prepared sample 51 was placed on a flat glass plate 52. Next, the entire upper layer (B1) of the sample 51 was subjected to single-sided heat treatment at 100°C for 1 second using a hot stamping machine. The arrows in Figure 4 indicate the direction in which heat was applied by the hot stamping machine. Subsequently, the average value of the height d (mm) of the four corners was determined as an evaluation representing the curlability after heat treatment, in the same manner as before the heat treatment.

[0137] Furthermore, a positive sign was used for the evaluation value representing curl, and a negative sign was used for reverse curl.

[0138] Table 2 shows the evaluation results. [Table 2]

[0139] Comparative Example 1 shows that when the amorphous resin content C1 and C2 are the same on both sides of the laminated film, no curl occurs before heat treatment, but a large positive curl exceeding 3 mm occurs after heat treatment. In contrast, Examples 1 to 4, which satisfy C1 > C2, show that the curl after heat treatment is 3 mm or less, and the positive curl is canceled out. Although reverse curl occurs before heat treatment, the size of the reverse curl is small, at 2 mm or less in all cases, and does not affect the handling of the laminated film, such as transport for printing. [Explanation of symbols]

[0140] 11~13...Laminated film, A...Base layer, B1...Top layer, B2...Bottom layer< / ps> < / apel> < / pe> < / pp>

Claims

1. A laminated film in which an upper layer (B1), a base layer (A), and a lower layer (B2) are laminated in this order, The base layer (A) contains an olefin resin and a filler, The upper layer (B1) contains a crystalline resin and an amorphous resin, The lower layer (B2) contains a crystalline resin and an amorphous resin, The content of the amorphous resin per unit area in the upper layer (B1) C1 (g / m²) ２ ) is the content C2 (g / m²) of the amorphous resin per unit area in the lower layer (B2). ２ Larger than ) The content C1 and C2 of the amorphous resin satisfy the following formula (1) (1) 0.3 ≤ C1 - C2 ≤ 8, laminated film.

2. The amorphous resin is a cyclic olefin resin or a petroleum resin. The laminated film according to claim 1.

3. The crystalline resin is a propylene-based resin. The laminated film according to claim 1 or 2.

4. The olefin resin is a propylene resin. A laminated film according to any one of claims 1 to 3.

5. The upper layer (B1) or the lower layer (B2) further contains a filler. A laminated film according to any one of claims 1 to 4.

6. The upper layer (B1) is provided with a coating layer (D), The coating layer (D) contains an ethyleneimine resin. The laminated film according to claim 5.

7. The surface of the laminated film on the upper layer (B1) side is the surface that is heat-treated. A laminated film according to any one of claims 1 to 6.

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