JP2023147470A - Laminated resin film and method for producing the same - Google Patents

Abstract

To provide a laminated resin film using a recycled plastic material and having high concealability, and a method for producing the same.SOLUTION: A laminated resin film has a concealing layer having a concealing surface layer and a concealing core layer containing a recycled plastic raw material of a polyolefin-based resin and a black pigment, the laminated resin film having a whiteness of 85% or more and an opacity of 99% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated resin film and a method for manufacturing the same.

In addition to conventional paper (natural pulp paper), synthetic papers such as polyethylene terephthalate film, polyamide film, and polyolefin film are used as printing paper. Among them, polyolefin film is a synthetic paper that has been proposed as a waterproof printing paper in place of natural pulp paper (for example, see Patent Document 1). These synthetic papers are useful as materials for poster paper, wrapping paper, labels, and the like.
In addition, a laminated resin film for white printing, which has high concealment properties and has little print bleed through, is provided for a wide range of uses such as various POPs for sales promotion, posters, and stickers. In order to impart high hiding properties to the laminated resin film, for example, a white pigment such as titanium oxide is blended into the resin material constituting the film to form a white layer, a black pigment such as carbon black is blended to form a black layer, A technique for increasing opacity by using these as a laminate has been reported (see, for example, Patent Documents 2 and 3).

Japanese Unexamined Patent Publication No. 56-118437 Japanese Patent Application Publication No. 11-091042 Japanese Patent Application Publication No. 2003-326654

On the other hand, as environmental awareness has increased in recent years, there has been a demand for reducing the amount of plastic waste, and recycled materials from plastic waste are desired in various fields. However, recycled plastic materials, which are recycled materials, have variations in color tone, impurity content, and the like. For this reason, even if an attempt was made to manufacture a resin film using only recycled plastic materials as a raw material, stable opacity could not be achieved, and it was difficult to obtain a laminated resin film with high hiding power.

An object of the present invention is to provide a laminated resin film that uses recycled plastic material and has high hiding properties, and a method for producing the same.

As a result of intensive studies to solve the above problems, the present inventors found that the above problems could be solved by having a specific layer structure and containing recycled plastic raw materials and black pigment in the specific layers. , completed the invention. More specifically, it is a laminated resin film having a concealing layer, the concealing layer having a concealing surface layer, a concealing core layer containing a recycled plastic raw material of polyolefin resin and a black pigment, The inventors have discovered that the above problems can be solved by using a laminated resin film that has whiteness and opacity, and have completed the present invention.
That is, the present invention is as follows.

(1) A laminated resin film having a hiding layer,
The concealing layer has a concealing surface layer and a concealing core layer containing a recycled plastic raw material of polyolefin resin and a black pigment,
The whiteness is 85% or more and the opacity is 99% or more.
Laminated resin film.
(2) The recycled plastic raw material of the polyolefin resin contains a coloring material,
The laminated resin film according to (1).
(3) the opacity of the concealing surface layer is 75% to 100%;
(2) The laminated resin film as described in (2).
(4) the concealing surface layer has a porous structure;
The laminated resin film according to any one of (1) to (3).
(5) the concealing surface layer is stretched;
The laminated resin film according to any one of (1) to (4).
(6) the porosity of the concealing surface layer is 1 to 70%;
The laminated resin film according to any one of (1) to (5).
(7) The concealing surface layer contains a white pigment, and the content of the white pigment in the concealing surface layer is 0.1 to 5% by mass.
The laminated resin film according to any one of (1) to (6).
(8) The thickness of the concealing surface layer is 10 to 300 μm.
The laminated resin film according to any one of (1) to (7).
(9) The concealing core layer contains a polyolefin resin.
The laminated resin film according to any one of (1) to (8).
(10) The concealing core layer contains a polyolefin resin having a melting point of 145° C. or lower.
The laminated resin film according to any one of (1) to (9).
(11) The content of the black pigment in the concealing core layer is 0.3 to 5% by mass.
The laminated resin film according to any one of (1) to (10).
(12) further comprising a printed layer in contact with the concealing surface layer, and the printed layer has a surface resistivity of 1×10 ¹ to 9× ¹⁰ Ω as measured in accordance with JIS K6911:2006;
The laminated resin film according to any one of (1) to (11).
(13) The ratio of the thickness of the concealing core layer to the total thickness of the laminated resin film is 10 to 70%.
The laminated resin film according to any one of (1) to (12).
(14) The standard deviation in the width direction of the opacity of the laminated resin film is less than 5%.
The laminated resin film according to any one of (1) to (13).
(15) A method for producing a laminated resin film having a hiding layer, comprising:
The concealing layer has a concealing surface layer and a concealing core layer containing a recycled plastic raw material of polyolefin resin and a black pigment,
forming the concealing surface layer and the concealing core layer by extrusion lamination;
A method for producing a laminated resin film.

According to the present invention, it is possible to provide a laminated resin film that uses recycled plastic material and has high hiding properties, and a method for producing the same.

FIG. 1 is a cross-sectional view showing the structure of a laminated resin film according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing the structure of a laminated resin film according to an embodiment of the present invention.

Hereinafter, the laminated resin film of the present invention will be explained in detail. The following description is one embodiment of the present invention, and the present invention is not limited thereto.
In the following description, the term "(meth)acrylic" refers to both acrylic and methacrylic. The description of "(co)polymer" refers to both homopolymers and copolymers.

[Laminated resin film]
FIG. 1 is a cross-sectional view showing the structure of a laminated resin film according to an embodiment of the present invention.
The laminated resin film 10 of the present invention includes a concealing layer 1. The concealing layer 1 includes a concealing core layer 2 and concealing surface layers 3a and 3b provided on both surfaces of the concealing core layer 2, respectively.

The concealing core layer in the laminated resin film of the present invention contains a recycled plastic raw material of polyolefin resin and a black pigment. The laminated resin film of the present invention is laminated so that both sides of the black layer, which is the concealing core layer, are covered with the white layer, which is the concealing surface layer, so that when viewed from one side, the printing on the other side is transparent. It also improves visibility during double-sided printing, and has high concealment properties. The laminated resin film of the present invention has a whiteness of 85% or more and an opacity of 99% or more.

<Whiteness>
In this specification, "whiteness" refers to a value calculated from L, a, and b values measured using a Hunter color difference meter in accordance with JIS L1015:1999. As the Hunter type color difference meter, for example, SM Colormeter SM-T manufactured by Suga Test Instruments Co., Ltd. can be used.
The whiteness of the laminated resin film of the present invention is 85% or more, preferably 87% or more, and more preferably 90% or more. When the whiteness of the laminated resin film is 85% or more, it is easy to obtain a laminated resin film having high hiding properties. Furthermore, the visibility of printed content printed on the laminated resin film tends to be improved. There is no particular upper limit to the whiteness, and it may be 100%, 99% or less, or 98% or less.

<Opacity>
As used herein, "opacity" means a value measured in accordance with "Paper and paperboard - Opacity test method (paper backing) - Diffuse illumination method" specified in JIS P8149:2000. do.
The opacity of the laminated resin film of the present invention is 99% or more. If the opacity of the laminated resin film is 99% or more, the printing on one side will not show through when viewed from the other side, and the legibility of characters printed on the printed side will tend to improve. . In addition, it is possible to suppress the colored substances and impurities contained in the colored recycled plastic raw material from being seen through.
Each layer will be explained below.

(hidden layer)
The hiding layer has a hiding surface layer and a hiding core layer containing a recycled plastic raw material of polyolefin resin and a black pigment. The hiding layer has the function of increasing the whiteness and opacity of the laminated resin film and imparting high hiding properties to the laminated resin film.

<Hidden core layer>
The concealing core layer has a function of increasing the opacity of the laminated resin film. Further, the concealing core layer has a relatively stronger breaking strength than the concealing surface layer, and has a function of imparting mechanical strength such as stiffness to the laminated resin film. The concealing core layer is a non-stretched layer from the viewpoint that high moldability can be easily obtained even if the content of various components such as the recycled plastic raw material and black pigment of the polyolefin resin described below is designed relatively freely. It is preferable. On the other hand, the concealing core layer can also be a stretched layer from the viewpoint of obtaining higher mechanical strength. In particular, when the concealing core layer is a stretched porous layer containing filler, the opacity of the laminated resin film can be further increased.
The concealing core layer may have a single layer structure, or may have a multilayer structure of two or more layers.

<<Recycled plastic raw material for polyolefin resin>>
The concealing core layer contains recycled plastic raw material of polyolefin resin.
The recycled plastic raw material for polyolefin resin refers to recycled plastic raw material containing polyolefin resin as a thermoplastic resin.
Recycled plastic raw materials are raw materials obtained by recycling plastic molded bodies. Plastic molded articles are products distributed on the market, and are obtained by known molding methods such as extrusion molding, injection molding, press molding, cast molding, or solvent casting. The recycled plastic raw material may be a colored recycled plastic raw material containing a coloring agent, or may be an uncolored recycled plastic raw material containing no coloring agent. From the viewpoint of further exerting the effects of the present invention, the recycled plastic raw material is preferably a colored recycled plastic raw material containing a colorant. When a coloring material is contained as a recycled plastic raw material, the coloring material is not particularly limited, and may be a known pigment, dye, or the like.
If the film contains recycled plastic raw materials, the film may be colored due to the recycled plastic raw materials. However, it has been found that resin films that normally use recycled plastic raw materials are perceived to be colored by the recycled plastic raw materials, and their whiteness and opacity are not stable. According to the present invention, the laminated layer is provided with a hiding layer and has specific whiteness and opacity, so that it has high hiding properties even if it contains recycled plastic raw materials, and does not perceive coloration derived from recycled plastic raw materials. A resin film can be obtained.

Examples of polyolefin resins include polypropylene resins and polyethylene resins. Among polyolefin resins, it is preferable to use polypropylene resins from the viewpoints of cost, water resistance, and chemical resistance.

The polypropylene resin is not particularly limited as long as propylene is used as the main monomer. Examples include isotactic polymers or syndiotactic polymers obtained by homopolymerizing propylene. It is also a copolymer of propylene, which is the main component, and α-olefins such as ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. , propylene-α-olefin copolymer, and the like. The copolymer may be a multi-component system in which the monomer components are binary or ternary or more, and may be a random copolymer or a block copolymer. Moreover, a propylene homopolymer and a propylene copolymer may be used together.

Examples of polyethylene resin include high density polyethylene with a density of 0.940 to 0.965 g/cm ³ , medium density polyethylene with a density of 0.920 to 0.934 g/cm ³ , and density of 0.900 to 0.920 g / ^cm3 linear low-density polyethylene, a copolymer mainly composed of ethylene and copolymerized with α-olefins such as propylene, butene, hexene, heptene, octene, and 4-methylpentene-1, ethylene-acrylic Acid copolymers, ethylene-acrylic acid alkyl ester copolymers, ethylene-methacrylic acid alkyl ester copolymers, metal salts of ethylene-methacrylic acid copolymers (metals include zinc, aluminum, lithium, sodium, potassium, etc.), and ethylene-cyclic olefin copolymers.

The content of the recycled plastic raw material of the polyolefin resin in the concealing core layer is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and 20% by mass from the viewpoint of reducing the environmental load. % or more is even more preferable, and 30 mass % or more is particularly preferable. On the other hand, the content is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less from the viewpoint of reducing opacity variation, suppressing decrease in interlayer strength, and formability. preferable. The content of the recycled plastic raw material of the polyolefin resin based on the entire plastic raw material of the concealing core layer is preferably 5% by mass or more, more preferably 10% by mass or more, and 20% by mass from the viewpoint of reducing environmental load. % or more is more preferable, and it is especially preferable that it is 30 mass % or more. On the other hand, the content is preferably 80% by mass or less, more preferably 70% by mass or less, and 60% by mass or less, from the viewpoint of reducing opacity variation, suppressing decrease in interlayer strength, and formability. It is more preferable that it is less than % by mass. When the concealing core layer is a non-stretched layer, even if it contains a high content of recycled plastic raw material of polyolefin resin, it can be easily manufactured without problems in moldability.

The concealing core layer may contain recycled plastic raw materials containing thermoplastic resins other than polyolefins as long as the effects of the present invention are not impaired. Thermoplastic resins other than polyolefin resins in recycled plastic raw materials are not particularly limited, and include, for example, polyester resins, polyamide resins, polyvinyl chloride resins, polystyrene resins, and polycarbonate resins. Two or more types of these resins may be contained.

<<Black pigment>>
The hiding core layer contains a black pigment with excellent light absorption. Examples of the black pigment include carbon black, oil smoke, vegetable black, bone char, graphite, and oxide black pigments. Among these, carbon black is preferably used as the black pigment, particularly from the viewpoint of excellent hiding properties.

The average particle diameter of the black pigment may be appropriately set depending on desired performance such as pigment dispersibility, hiding property, printing characteristics, etc., and is not particularly limited. For example, the average particle diameter of the black pigment is preferably 0.01 μm or more, more preferably 0.1 μm or more. On the other hand, the average particle diameter is preferably 20 μm or less, more preferably 10 μm or less.
The average particle diameter of the black pigment refers to the arithmetic mean diameter determined by observing the black pigment with an electron microscope.

From the viewpoint of obtaining sufficient opacity, the content of the black pigment in the hiding core layer is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 0.7% by mass or more. On the other hand, the content is preferably 5% by mass or less, more preferably 4% by mass or less, and even more preferably 3% by mass or less, from the viewpoint of suppressing delamination with the concealing surface layer.
Further, from the viewpoint of suppressing variations in opacity, the content of the black pigment in the hiding core layer is preferably 1 part by mass or more, and preferably 2 parts by mass or more, based on 100 parts by mass of recycled plastic raw material. The amount is preferably 5 parts by mass or more, and more preferably 5 parts by mass or more. On the other hand, from the viewpoint of moldability, the content is preferably 50 parts by mass or less, and preferably 30 parts by mass or less.

The concealing core layer may contain colored pigments other than black pigments as long as the effects of the present invention are not impaired. Specific examples of colored pigments include known inorganic pigments and organic pigments. In addition, when containing colored pigments other than black pigments, the content of pigments (including colored pigments other than black pigments) in the concealing core layer should be determined from the viewpoint of suppressing delamination from the concealing surface layer. It is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less, based on 100 parts by mass. Further, from the viewpoint of suppressing variations in opacity, the content of the pigment in the concealing core layer is preferably 1 part by mass or more based on 100 parts by mass of recycled plastic raw material.

<<Polyolefin resin>>
The concealing core layer preferably contains virgin plastic raw materials in addition to recycled plastic raw materials within a range that does not impede the effects of the present invention. The virgin plastic raw material is not particularly limited, but from the viewpoint of compatibility with recycled plastic raw materials, polyolefin resins are preferred. As the polyolefin resin, the same ones as mentioned for the recycled plastic raw materials can be used.
The content of the polyolefin resin in the concealing core layer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 40% by mass or more, and even more preferably 60% by mass or more. Particularly preferred. On the other hand, the content is preferably 95% by mass or less, more preferably 85% by mass or less, even more preferably 75% by mass or less, and particularly preferably 65% by mass or less.

<<Polyolefin resin having a melting point of 145°C or less>>
Moreover, it is preferable that the concealing core layer contains a polyolefin resin having a melting point of 145° C. or lower. If the concealing core layer contains recycled plastic raw materials, the interlaminar strength between the concealing core layer and the adjacent layer may decrease; however, by containing a polyolefin resin with a melting point of 145°C or less, the interlaminar strength may decrease. There is a tendency to suppress the decline in
Examples of polyolefin resins having a melting point of 145° C. or lower include polyethylene resins, propylene-ethylene copolymers, propylene-α-olefin copolymers, and polyethylene-α-olefin copolymers.
The melting point can be measured by differential scanning calorimetry (DSC).

The content of the polyolefin resin having a melting point of 145° C. or lower in the concealing core layer is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of suppressing a decrease in interlaminar strength. . On the other hand, the content is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

＜＜Filler＞＞
The concealing core layer may contain a filler different from the black pigment to the extent that the effects of the present invention are not impaired. When a filler is contained, examples of the filler that can be used in the concealing core layer include known inorganic fillers and organic fillers. In addition, when the concealing core layer contains a filler, the content of the filler in the concealing core layer (the total amount when an inorganic filler and an organic filler are used together) is not particularly limited, but pores are removed during stretch molding. From the viewpoint of easily obtaining and achieving opacity, the content is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more. On the other hand, the content is preferably 75% by mass or less, more preferably 65% by mass or less, and even more preferably 55% by mass or less, from the viewpoint of easily obtaining suitable mechanical strength, water resistance, etc.

<<Other additives>>
The concealing core layer can further contain additives such as a heat stabilizer (antioxidant), a light stabilizer, a dispersant, a lubricant, or a nucleating agent, if necessary.
As the heat stabilizer, for example, a sterically hindered phenolic antioxidant, a phosphorus antioxidant, or an amine antioxidant can be used, usually in a range of 0.001 to 1% by mass.
As the light stabilizer, for example, a sterically hindered amine light stabilizer, a benzotriazole light stabilizer, or a benzophenone light stabilizer can be used, usually within a range of 0.001 to 1% by mass.
Examples of the dispersant or lubricant 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 be used, for example, for the purpose of dispersing fillers, usually within a range of 0.01 to 4% by mass.

The concealing core layer may be a non-stretched film, but from the viewpoint of improving the strength of the resin film, it is preferably stretched in at least one axial direction.

＜＜Thickness＞＞
The thickness of the concealing core layer is preferably 10 μm or more, more preferably 50 μm or more, even more preferably 100 μm or more, and 150 μm from the viewpoint of contributing to the environment by using more recycled plastic raw materials and obtaining higher hiding performance. The above is particularly preferable. Further, from the viewpoint of reducing the weight of the laminated resin film and easily improving handling properties, the thickness of the concealing core layer is preferably 500 μm or less, more preferably 450 μm or less, and even more preferably 400 μm or less.

<Hidden surface layer>
The concealing surface layer has the function of increasing the whiteness and opacity of the laminated resin film.
The concealing surface layer may have a single layer structure, or may have a multilayer structure of two or more layers.

<<Thermoplastic resin>>
The concealing surface layer contains a thermoplastic resin. The thermoplastic resin that can be used for the concealing surface layer is the same as the material listed in the item of the concealing core layer, and the preferable materials are also the same as those for the concealing core layer.

<<White pigment>>
Preferably, the concealing surface layer contains a white pigment. As the white pigment, various known ones can be used and there is no particular limitation. By containing a white pigment, the degree of whiteness can be increased, and the transparency of the laminated resin film can also be reduced. In consideration of the hiding properties required for white printing, examples of white pigments that are preferably used include titanium oxide, barium sulfate, calcium sulfate, and zinc oxide. Among these, titanium oxide is particularly preferred because it has high hiding power and excellent whiteness. As titanium oxide, any of the rutile type (tetragonal high temperature type), anatase type (tetragonal low temperature type), and brookite type (orthorhombic type) may be used. Various commercially available products include, for example, titanium oxide particles manufactured by Ishihara Sangyo Co., Ltd. (trade name: TYPEQUE). Further, titanium oxide is generally produced by a sulfuric acid method and a chlorine method, but from the viewpoint of whiteness, a pigment produced by a chlorine method is preferable because it has a higher whiteness and is superior. Further, as the titanium oxide, surface-modified titanium oxide that has been subjected to alumina surface treatment or silica surface treatment can be used.

The average particle diameter of the white pigment may be appropriately set depending on desired performance such as pigment dispersibility, hiding property, printing characteristics, etc., and is not particularly limited. For example, the average particle diameter of the white pigment is preferably 0.01 μm or more, more preferably 0.1 μm or more. On the other hand, the average particle diameter is preferably 20 μm or less, more preferably 10 μm or less.
The average particle diameter of the white pigment refers to the arithmetic mean diameter determined by observing the white pigment with an electron microscope.

From the viewpoint of increasing whiteness, the content of the white pigment in the concealing surface layer is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. On the other hand, the content is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of increasing interlaminar strength.

＜＜Filler＞＞
The concealing surface layer is preferably a porous membrane having a porous structure in which a large number of fine pores (foamed cells, voids, etc.) are formed. The pores in the concealing surface layer can be formed by, for example, a foaming method, an internal paper forming method, a solvent extraction method, or the like. Further, a preferable method for producing the concealing surface layer is an internal paper forming method. In this internal paper forming method, a resin composition containing a thermoplastic resin and a filler that serves as the core of pore formation is formed into a film by a known method, and the resulting film is uniaxially or biaxially stretched. , many fine pores are formed inside. Thereby, the concealing surface layer can be made whiter, more opaque, and lighter.

From the viewpoint of forming the above-mentioned porous structure, the concealing surface layer preferably contains a filler different from the white pigment. If the concealing surface layer contains a filler, the whiteness and opacity of the concealing surface layer can be increased by the internal paper forming method described above.
When containing a filler, examples of the filler that can be used in the concealing core layer include inorganic fillers and organic fillers.

Examples of inorganic fillers include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, diatomaceous earth, titanium oxide, zinc oxide, barium sulfate, silicon oxide, magnesium oxide, or these in combination with fatty acids, polymeric surfactants, or electrostatic charges. Examples include inorganic particles whose surface has been treated with an inhibitor or the like. Among these, heavy calcium carbonate, light calcium carbonate, calcined clay, or talc are preferred because they have good pore moldability and are inexpensive. From the viewpoint of increasing opacity, titanium oxide, zinc oxide, or barium sulfate is preferable.

The organic filler is not particularly limited, but it is preferable to use organic particles that are incompatible with the thermoplastic resin, have a melting point or glass transition temperature higher than that of the thermoplastic resin, and are finely dispersed under the melt-kneading conditions of the thermoplastic resin. For example, when the thermoplastic resin is a polyolefin resin, examples of the organic filler include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyamide, polycarbonate, polyethylene sulfide, polyphenylene sulfide, polyimide, polyether ketone, polyether ether Examples include organic particles such as ketones, polymethyl methacrylate, poly-4-methyl-1-pentene, homopolymers of cyclic olefins, and copolymers of cyclic olefins and ethylene. Further, fine powder of a thermosetting resin such as melamine resin may be used, and it is also preferable to crosslink the thermoplastic resin to make it insolubilized.
The melting point (°C) and glass transition temperature (°C) of the resin can be measured by differential scanning calorimetry (DSC).

The inorganic filler and the organic filler may be selected from the above and used alone, or may be used in combination of two or more. When two or more types are combined, it may be a combination of an inorganic filler and an organic filler.

The average particle diameter of the inorganic filler and the organic filler is preferably large from the viewpoint of ease of mixing with the thermoplastic resin. In addition, the average particle diameter of the inorganic filler and organic filler makes it difficult to cause problems such as film breakage or reduction in the strength of the hiding layer during stretching when stretching creates pores inside to improve opacity. From this point of view, it is preferable to be small. Specifically, the average particle diameter of the inorganic filler and the organic filler is preferably 0.01 μm or more, more preferably 0.1 μm or more, and still more preferably 0.5 μm or more. Moreover, the average particle diameter of the inorganic filler and the organic filler is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

The average particle diameter of the inorganic filler and organic filler is determined by observing the cut surface of the layer with an electron microscope and measuring the maximum diameter of at least 10 particles.The average particle diameter of the inorganic filler and organic filler is determined by dispersing it in the thermoplastic resin by melt-kneading and dispersion. It can be determined as the average dispersed particle diameter when

When the concealing surface layer contains a filler, the content of the filler in the concealing surface layer (the total amount when an inorganic filler and an organic filler are used together) is not particularly limited, but the amount of pores that are obtained during stretch molding is not particularly limited. From the viewpoint of easy whitening and opacity, the content is preferably 5% by mass or more, more preferably 8% by mass or more, and even more preferably 10% by mass or more. On the other hand, the content is preferably 75% by mass or less, more preferably 65% by mass or less, and even more preferably 55% by mass or less, from the viewpoint of easily obtaining suitable mechanical strength.

<<Other additives>>
The concealing surface layer can further contain additives such as a heat stabilizer (antioxidant), a light stabilizer, a dispersant, a lubricant, or a nucleating agent, if necessary. The additives that can be used in the concealing surface layer are the same as those listed under the heading of the concealing core layer, and the preferred materials are also the same as those for the concealing core layer.

<<Stretched film>>
The concealing surface layer may be a non-stretched film or a stretched film, but from the viewpoint of increasing whiteness as described above, it is preferably a stretched film stretched in at least one direction.
When the concealing surface layer has a multilayer structure, it preferably includes a stretched film stretched in at least one direction, and more preferably includes a porous stretched film having pores inside. Since the concealing surface layer containing the stretched film has high mechanical strength and excellent uniformity in thickness, a laminated resin film with excellent post-processability can be obtained. Moreover, the degree of whiteness can be increased.
When the concealing surface layer has a multilayer structure, the number of stretching axes for each layer is 1 axis/1 axis, 1 axis/2 axis, 2 axis/1 axis, 1 axis/1 axis/2 axis, 1 axis/2 axis/ It may be one axis, two axes/one axis/one axis, one axis/two axes/two axes, two axes/two axes/one axis, or two axes/two axes/two axes.

<<Porosity>>
When the concealing surface layer has a porous structure, the porosity, which represents the proportion of pores in the concealing surface layer, is preferably 1% or more, and 5% or more, from the viewpoint of increasing whiteness and opacity. More preferably, it is at least 10%, and even more preferably 10% or more. From the viewpoint of maintaining mechanical strength, the porosity is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less.

The porosity can be determined from the area ratio occupied by pores in a certain area of the cross section of the concealing surface layer observed with an electron microscope. Specifically, any part of the concealing surface layer is cut out, embedded in epoxy resin and solidified, and then cut perpendicularly to the surface direction of the concealing surface layer using a microtome, and the cut surface becomes the observation surface. Attach it to the observation sample stand so that it looks like this. Deposit gold or gold-palladium on the observation surface, observe the pores at any magnification that is easy to observe with an electron microscope (for example, 500x to 3000x magnification), and capture the observed area as image data. . The obtained image data is subjected to image processing using an image analysis device, and the area ratio (%) of the pore portion can be determined to obtain the porosity (%). In this case, the porosity of the concealing surface layer can be determined by averaging the measured values observed at ten or more arbitrary locations.

Note that normally, the higher the filler content, the higher the porosity and the higher the whiteness or opacity of the concealing surface layer. The filler content or porosity can be selected depending on the transparency or whiteness required for the laminated resin film.

＜＜Thickness＞＞
The thickness of the concealing surface layer is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 60 μm or more, from the viewpoint of obtaining sufficient concealability. Further, since the weight of the laminated resin film is reduced and the handling property is easily improved, the thickness of the concealing surface layer is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 150 μm or less.

(Printing layer)
The laminated resin film of the present invention may further have a printed layer if necessary.
FIG. 2 is a cross-sectional view showing the structure of a laminated resin film according to an embodiment of the present invention.
As shown in FIG. 2, the printed layers 4a, 4b may be provided on the side of the hiding surface layer 3a, 3b opposite to the hiding core layer 2, respectively.

The printing layer has an antistatic function, and by imparting antistatic performance to the label portion, it has the function of making it difficult to cause trouble in the printing process and improving handling properties. Moreover, the printing layer has a function of improving adhesion with printing ink and improving printability.
The printing layer is preferably formed by molding a solution containing an antistatic polymer, a polymeric binder, etc. into a thin film by a molding method described below.

It is preferable that the printing layer contains an antistatic agent. Moreover, it is preferable that the printing layer contains a polymer binder and pigment particles. The lower limit of the content of the antistatic agent is usually 0.1% by mass, preferably 0.5% by mass, more preferably 1% by mass, and the upper limit is usually 100% by mass, more preferably 70% by mass. %, more preferably 50% by mass. The lower limit of the content of the polymer binder is usually 0% by mass, preferably 0.5% by mass, and more preferably 50% by mass, and the upper limit is usually 99.9% by mass, preferably 99% by mass. .5% by weight, more preferably 99% by weight. Further, the lower limit of the content of pigment particles is usually 0% by mass, and the upper limit thereof is usually 70% by mass, preferably 69.5% by mass, and more preferably 49% by mass. More specifically, the printing layer preferably contains 0.1 to 100% by weight of an antistatic agent, 0 to 99.9% by weight of a polymer binder, and 0 to 70% by weight of pigment particles. Further, the printing layer more preferably contains 0.5 to 70% by mass of an antistatic agent, 30 to 99.5% by mass of a polymer binder, and 0 to 69.5% by mass of pigment particles. Further, it is more preferable that the printing layer contains 1 to 50% by weight of an antistatic agent, 50 to 99% by weight of a polymer binder, and 0 to 49% by weight of pigment particles.

<Antistatic agent>
Antistatic agents are added to impart antistatic properties to the printing layer, and are typified by stearic acid monoglyceride, alkyl diethanolamine, sorbitan monolaurate, alkylbenzene sulfonate, alkyl diphenyl ether sulfonate, etc. low molecular weight organic compound-based antistatic agents; conductive inorganic fillers represented by ITO (indium doped tin oxide), ATO (antimony doped tin oxide), graphite whiskers, etc.; molecules such as polythiophene, polypyroyl, polyaniline, etc. So-called electronically conductive polymers that exhibit conductivity due to pi electrons in their chains; nonionic polymer-based antistatic agents such as polyethylene glycol and polyoxyethylene diamine; polyvinylbenzyltrimethylammonium chloride, quaternized polydimethylaminoethyl methacrylate, etc. quaternary ammonium salt type copolymers; polymers with antistatic function represented by alkali metal salt-containing polymers such as alkali metal ion additives to alkylene oxide group- and/or hydroxyl group-containing polymers; It is not particularly limited to these. Any one of these may be used alone, or two or more may be used in combination.

Each of these antistatic agents has its own characteristics. For example, the antistatic performance of low molecular weight organic compound-based antistatic agents tends to be greatly affected by environmental humidity. On the other hand, a polymer having an antistatic function is preferable as an antistatic agent used in this embodiment because it has a small influence on the adhesion and transferability of the ink and is almost free from coloration.

Among these, polymers containing alkali metal salts such as alkali metal ion additives to polymers containing alkylene oxide groups and/or hydroxyl groups, and quaternary ammonium salts such as polyvinylbenzyltrimethylammonium chloride and quaternized polydimethylaminoethyl methacrylate. The type copolymer has good antistatic performance, and the effect of environmental humidity on the antistatic performance is small, so it is more preferable as the antistatic agent used in this embodiment.

The molecular weight of the alkali metal salt-containing polymer is preferably a weight average molecular weight of 10,000 to 1,000,000 as measured by gel permeation chromatography (GPC). When the molecular weight is 10,000 or more, the polymer is less likely to ooze out from the formed coating layer, so sufficient water resistance tends to be easily obtained. When the molecular weight is 1 million or less, it is easy to mix with the binder component, so coating defects are less likely to occur, and a uniform antistatic effect tends to be easily obtained.

<Polymer binder>
The printing layer may contain a polymer binder if necessary. The polymer binder is used as appropriate for the purpose of having adhesion to the film on which the printing layer is provided or to another film and improving adhesion to the printing ink.

Specific examples of polymer binders include acrylic ester copolymers, methacrylic ester copolymers, acrylic amide-acrylic ester copolymers, acrylic amide-acrylic ester-methacrylic ester copolymers, and Acrylamide derivatives and (meth)acrylic ester polymers such as oxazoline group-containing acrylic ester polymers; polyethyleneimine, alkyl-modified polyethyleneimine having 1 to 12 carbon atoms, poly(ethyleneimine-urea), poly( Polyethyleneimine polymers such as ethyleneimine adducts (ethyleneimine-urea), polyamine polyamides, ethyleneimine adducts of polyamine polyamides, and epichlorohydrin adducts of polyamine polyamides; polyvinylpyrrolidone, polyethylene glycol, etc., as well as vinyl acetate resins. , urethane resin, polyether resin, polyester resin, urea resin, terpene resin, petroleum resin, ethylene-vinyl acetate copolymer, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer resin, vinylidene chloride resin, vinyl chloride-chloride Vinylidene copolymer resin, chlorinated ethylene resin, chlorinated propylene resin, butyral resin, silicone resin, nitrocellulose resin, styrene-acrylic copolymer resin, styrene-butadiene copolymer resin, acrylonitrile-butadiene copolymer, etc. Examples include, but are not particularly limited to.

These polymer binders may be used alone or in combination of two or more. These polymer binders can be used in diluted or dispersed form in an organic solvent or water. Among these, urethane resins such as polyether urethane, polyester polyurethane, and acrylic urethane, acrylic acid ester copolymers, and polyethyleneimine polymers are compatible with the aforementioned ionic polymers having antistatic functions. It is preferable because it has good solubility and is stable when mixed to form a paint, making it easy to apply.

<Crosslinking agent>
When the printing layer contains a polymer binder, it is preferable that the polymer binder is crosslinked with a crosslinking agent. Crosslinking of the polymer binder tends to improve the water abrasion resistance of the printed portion on the surface of the printed layer.

As the crosslinking agent, conventionally known crosslinking agents can be used. Examples of crosslinking agents that can be used include metal crosslinking agents such as zirconium ammonium carbonate, epoxy crosslinking agents such as polyglycerol polyglycidyl ether, polyamide epichlorohydrin resin, polyamine epichlorohydrin resin, and epichlorohydrin of polyamine polyamide. Examples include epichlorohydrin crosslinking agents such as phosphorus adducts, and oxazoline crosslinking agents such as oxazoline group-containing polymers. From the viewpoint of improving the water abrasion resistance of the surface of the printed layer, the binder is composed of one or more selected from the group consisting of the above-mentioned metal crosslinking agents, epoxy crosslinking agents, epichlorohydrin crosslinking agents, and oxazoline crosslinking agents. Preferably, it is crosslinked.

<Pigment particles>
The printing layer may contain pigment particles as necessary. Pigment particles improve the fixation of printing ink due to their oil absorption properties, improve surface texture and gloss as extender pigments, improve whiteness as white pigments, improve anti-blocking performance by imparting surface roughness, and provide light resistance and weather resistance as UV reflective materials. It can be selected and used as appropriate in consideration of performance imparting such as improvement in properties.

Organic and inorganic fine powders are used as pigment particles, and specific examples include silicon oxide, calcium carbonate, calcined clay, titanium oxide, zinc oxide, barium sulfate, diatomaceous earth, acrylic particles, styrene particles, polyethylene particles, Polypropylene particles etc. can be used. The particle diameter of the pigment particles is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 3 μm or less. Further, the particle diameter of the pigment particles is preferably 0.01 μm or more, more preferably 0.1 μm or more. When the particle size of the pigment molecules is equal to or less than the above upper limit, it is possible to suppress the pigment particles from falling off from the formed printed layer and the resulting reduction in powder blowing. Furthermore, when the particle size of the pigment molecules is equal to or larger than the above lower limit, undulations are formed on the surface of the printed layer, which tends to prevent blocking when the laminated resin films are stacked and stored. The content of pigment particles in the printing layer may be appropriately set depending on the desired performance and is not particularly limited, but the lower limit thereof is preferably 0% by mass, and the upper limit thereof is preferably 70% by mass, More preferably, it is 60% by mass, and still more preferably 45% by mass. More specifically, the content of pigment particles in the printing layer is preferably 0 to 70% by weight, more preferably 0 to 60% by weight, and still more preferably 0 to 45% by weight. When the content of pigment particles is below the above range, the amount of binder resin is sufficient, which improves the cohesive force of the printing layer, improves the adhesion to the concealing surface layer, and improves the adhesion of the printing ink. Peeling can be suppressed.

<Thickness>
The thickness of the printed layer is preferably 0.01 μm or more, more preferably 0.1 μm or more, and even more preferably 0.3 μm or more from the viewpoint of stably exhibiting antistatic performance. In addition, the thickness of the printed layer is preferably 50 μm or less, and 30 μm or less, from the viewpoint of suppressing its own weight and supporting its own weight with electrostatic attraction and self-adhesion to prevent it from peeling off from the adherend. is more preferable, and even more preferably 10 μm or less.

<Surface resistivity>
The surface resistivity of the printed layer is preferably 1×10 ⁻¹ Ω or more, more preferably 1×10 ¹ Ω or more, and even more preferably 1×10 ⁸ Ω or more. On the other hand, the surface resistivity is preferably 9×10 ¹² Ω or less, more preferably 5×10 ¹² Ω or less, and even more preferably 1×10 ¹² Ω or less. If the surface resistivity of the printing layer is within the above range, it tends to be possible to suppress the occurrence of sticking to rolls, blocking between films, etc. during the printing process.
The surface resistivity of the printed layer is measured in accordance with JIS K6911:2006.

(Characteristics of laminated resin film)
<Variation of opacity in the width direction>
Although the laminated resin film of the present invention has high opacity, it is preferable that the variation in the opacity is small. The standard deviation of the opacity in the laminated resin film in the width direction is preferably 8% or less, more preferably 7% or less, and even more preferably 5% or less. When the standard deviation in the width direction with respect to opacity is 8% or less, higher hiding performance can be obtained and a decrease in yield in manufacturing can be suppressed. On the other hand, the standard deviation in the width direction for the opacity of the laminated resin film can be 0.1% or more, 0.2% or more, or 0.3% or more.

<Interlayer strength between hidden surface layer and hidden core layer>
The interlaminar strength between the concealing surface layer and the concealing core layer in the laminated resin film of the present invention is preferably 1300 gf/15 mm or more, more preferably 1400 gf/15 mm or more, and even more preferably 1500 gf/15 mm or more. If the interlayer strength is 1300 gf/15 mm or more, it will be difficult to peel off when performing secondary processing such as printing, printing, cutting, etc. on the laminated resin film. On the other hand, the interlayer strength between the concealing surface layer and the concealing core layer is preferably 5000 gf/15 mm or less, more preferably 4000 gf/15 mm or less, and even more preferably 3000 gf/15 mm or less.

<Thickness>
The laminated resin film of the present invention includes at least a concealing core layer and a concealing surface layer, and the total thickness thereof is preferably 20 μm or more, more preferably 80 μm or more, and even more preferably 160 μm or more. On the other hand, the total thickness of the laminated resin film is preferably 800 μm or less, more preferably 650 μm or more, and even more preferably 550 μm or less.

The ratio of the thickness of the concealing core layer to the total thickness of the laminated resin film of the present invention is preferably 10% or more, more preferably 12% or more, and even more preferably 15% or more. When the thickness is 10% or more, sufficient mechanical strength and opacity tend to be obtained. On the other hand, the ratio of the thickness of the printing core layer to the thickness of all layers of the laminated resin film is preferably 70% or less, more preferably 65% or less, and even more preferably 50% or less.

The ratio of the thickness of the concealing surface layer to the total thickness of the laminated resin film of the present invention is preferably 10% or more, more preferably 12% or more, and even more preferably 14% or more. When the thickness is 10% or more, sufficient whiteness and opacity tend to be obtained. On the other hand, the ratio of the thickness of the concealing surface layer to the thickness of all the layers of the laminated resin film is preferably 70% or less, more preferably 60% or less, and even more preferably 50% or less.

(Method for manufacturing laminated resin film)
The concealing core layer or concealing surface layer in the laminated resin film (hereinafter, the "concealing core layer or concealing surface layer in the laminated resin film" is also referred to as "each layer in the laminated resin film") is usually made of the above-mentioned thermoplastic resin. It can be obtained by mixing other components contained in the layer and then molding. The molding method is not particularly limited, and various known molding methods can be used alone or in combination.

Each layer in the laminated resin film is formed using cast molding, calendar molding, rolling molding, inflation molding, etc., in which molten resin is extruded into a sheet through a single-layer or multi-layer T-die, I-die, etc. connected to a screw extruder, for example. , it can be formed into a film. Each layer in the laminated resin film may be formed by casting or calendering a mixture of a thermoplastic resin and an organic solvent or oil, and then removing the solvent or oil.

Each layer in the laminated resin film may be formed separately, and the formed layers may be laminated to form a laminate of the laminated resin film. Alternatively, a laminate may be obtained by molding together with other layers. Examples of the lamination method include a coextrusion method, an extrusion lamination method, and a coating method.
In the coextrusion method, a resin composition for a base material layer and a resin composition for a heat-sensitive adhesive layer are supplied to a multilayer die, and the resin compositions are laminated within the multilayer die and extruded. According to the coextrusion method, lamination is performed in parallel with film forming.
In the extrusion lamination method, a concealing core layer is first formed, a molten resin composition for a concealing surface layer is laminated thereon, and the layers are nipped with rolls while being cooled. According to the extrusion lamination method, film forming and lamination are performed in separate steps.
The laminated resin film of the present invention preferably includes a step of forming the concealing surface layer and the concealing core layer by extrusion lamination.

<Stretching>
As described above, each layer in the laminated resin film may be a non-stretched layer or a stretched layer, but the concealing surface layer is preferably a stretched layer.

Stretching methods include, for example, a longitudinal stretching method using a difference in the peripheral speed of a group of rolls, a lateral stretching method using a tenter oven, a sequential biaxial stretching method that combines these, a rolling method, and a simultaneous biaxial stretching method that uses a combination of a tenter oven and a pantograph. Examples include an axial stretching method and a simultaneous biaxial stretching method using a combination of a tenter oven and a linear motor. Alternatively, a simultaneous biaxial stretching (inflation molding) method can be used in which a molten resin is extruded into a tube shape using a circular die connected to a screw extruder, and then air is blown into the tube.

The concealing core layer and the concealing surface layer may be stretched individually before each layer is laminated, or may be stretched together after being laminated. Alternatively, the stretched layers may be stretched again after being laminated.

When the thermoplastic resin used in each layer is an amorphous resin, the stretching temperature during stretching is preferably in a range equal to or higher than the glass transition point of the thermoplastic resin. In addition, when the thermoplastic resin is a crystalline resin, the stretching temperature must be within a range that is above the glass transition point of the amorphous portion of the thermoplastic resin and below the melting point of the crystalline portion of the thermoplastic resin. The temperature is preferably 2 to 60°C lower than the melting point of the thermoplastic resin.

The stretching speed is not particularly limited, but from the viewpoint of stable stretching and forming, it is preferably within the range of 20 to 350 m/min.
Further, the stretching ratio can also be appropriately determined in consideration of the characteristics of the thermoplastic resin used. For example, when stretching a thermoplastic resin film containing a propylene homopolymer or a copolymer thereof in one direction, the stretching ratio is usually about 1.2 times or more, preferably about 2 times or more. , usually 12 times or less, preferably 10 times or less. In addition, the stretching ratio in the case of biaxial stretching is usually 1.5 times or more, preferably 10 times or more, but usually 60 times or less, preferably 50 times or less. .
If the stretching ratio is within the above range, the desired porosity can be obtained and the opacity can be easily improved. In addition, the film is less likely to break, and stable stretch molding tends to be possible.

<Surface treatment>
The surface of the concealing core layer is preferably activated by being subjected to oxidation treatment from the viewpoint of increasing the adhesion with the concealing surface layer. Further, the surface of the concealing surface layer may be subjected to oxidation treatment. Oxidation treatment tends to be able to adjust surface wettability and suppress printing bleeding.
Examples of the oxidation treatment include corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, and ozone treatment, and these treatments can be combined. Among these, corona discharge treatment or flame treatment is preferred, and corona discharge treatment is more preferred.

The amount of discharge when performing corona discharge treatment is preferably 600 J/m ² (10 W min/m ² ) or more, more preferably 1,200 J/m ² (20 W min/m ² ) or more. On the other hand, it is preferably 12,000 J/m ² (200 W·min/m ² ) or less, more preferably 10,800 J/m ² (180 W·min/m ² ) or less. The discharge amount when performing flame treatment is preferably 8,000 J/m ² or more, more preferably 20,000 J/m ² or more, and preferably 200,000 J/m ² or less, and more Preferably it is 100,000 J/m ² or less.

As a coating means when providing a printed layer, specifically, coating means such as gravure coating, Meyer bar coating, roll coating, blade coating, size press coating, etc. can be employed. Further, the coating amount can generally be 0.01 to 20 g/m ² , preferably 0.1 to 15 g/m ² .

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In addition, descriptions such as "parts" and "%" in the examples mean descriptions based on mass unless otherwise specified.

(Production of recycled plastic)
Using ultraviolet curing flexo ink (product name: "UV Flexo CF", manufactured by T&K TOKA Co., Ltd.), it was printed onto synthetic paper (product name: FPG130, manufactured by Yupo Corporation) at a speed of 60 m/min. Printed in color. Next, this was passed under an ultraviolet irradiator (metal halide lamp, 100 W/cm, 1 lamp, manufactured by I-Graphic Co., Ltd.) at a speed of 60 m/min to dry the ink on the printing surface, thereby obtaining a flexographic print. Ta. Recycled plastic, which is a raw material for recycled plastic, was obtained by extracting and refining the polypropylene component from flexo printed matter. The obtained recycled plastic was a colored recycled plastic raw material containing coloring components derived from printing ink.

(Preparation of resin composition)
<Preparation of resin composition (a)>
Propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C) 79.5 parts by mass, titanium dioxide (Ishihara Sangyo Co., Ltd., product name: CR60, average particle size: 0.2 μm) 0.5 parts by mass, heavy calcium carbonate (Bihoku Funka Kogyo Co., Ltd., product name: Softon 1800, average particle size: 1.2 μm (measured) Method: Air permeation method)) A resin composition (a) consisting of 20.0 parts by mass was prepared.

<Preparation of resin composition (b)>
Propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C) 95.0 parts by mass, titanium dioxide (Ishihara Sangyo Co., Ltd., trade name: CR60, average particle diameter: 0.2 μm) A resin composition (b) consisting of 5.0 parts by mass was prepared.

<Preparation of resin composition (c)>
99.5 parts by mass of propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16kg load): 5g/10 minutes, melting point: 165°C), titanium dioxide (Ishihara Sangyo) Co., Ltd., trade name: CR60, average particle diameter: 0.2 μm) A resin composition (c) was prepared.

<Preparation of resin composition (d)>
Propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C) 64.5 parts by mass, propylene-ethylene random copolymer 30.0 parts by mass of polymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FW4B, MFR (230°C, 2.16kg load): 6.5g/10 minutes, melting point: 140°C), recycled produced above 5.0 parts by mass of plastic, carbon black master patch (manufactured by Koshigaya Kasei Kogyo Co., Ltd., product name: ROYAL BLACK 9031P, MFR (230° C., 2.16 kg load): 1 g/10 minutes, pigment concentration: 40%) 0. A resin composition (d) consisting of 5 parts by mass was prepared.

<Resin compositions (e) to (h)>
Each resin composition was prepared in the same manner as resin composition (d), except that the blending ratios of propylene homopolymer, propylene-ethylene random copolymer, recycled plastic, and carbon black master patch were changed as shown in Table 1. (e) to (h) were prepared.

<Resin composition (i)>
49.0 parts by mass of propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C), recycled produced above 50.0 parts by mass of plastic, carbon black master patch (manufactured by Koshigaya Kasei Kogyo Co., Ltd., product name: ROYAL BLACK 9031P, MFR (230°C, 2.16 kg load): 1 g/10 minutes, pigment concentration: 40%) 1. A resin composition (i) consisting of 0 parts by mass was prepared.

<Resin composition (j)>
50.0 parts by mass of propylene homopolymer (manufactured by Nippon Polypro Co., Ltd., product name: Novatec PP FY4, MFR (230°C, 2.16 kg load): 5 g/10 minutes, melting point: 165°C), recycled produced above A resin composition (j) consisting of 50.0 parts by mass of plastic was prepared.

The constituent components of the resin compositions (a) to (j) are shown in Table 1 below.

(Preparation of coating liquid)
<Coating liquid preparation example 1>
20 parts by mass of quaternary nitrogen-containing acrylic resin (manufactured by Mitsubishi Chemical Corporation, trade name: Saftomer ST3200) (solid content equivalent, secondary amino group-containing polymer aqueous solution (manufactured by BASF Japan Corporation, trade name: Polymin SK) An aqueous solution containing 40 parts by mass (in terms of solid content) and 40 parts by mass (in terms of solid content) of epichlorohydrin adduct of polyamine polyamide (manufactured by Seiko PMC Co., Ltd., trade name: WS4082) was prepared as a coating liquid.

(Example 1)
After melt-kneading the resin composition (a) at a temperature of 220°C with an extruder, it is fed into an extrusion die set at 250°C and extruded into a sheet, which is then cooled to 60°C with a cooling device to form a non-stretched sheet. I got it. This unstretched sheet was heated to 135° C. and stretched 5 times in the longitudinal direction using the difference in circumferential speed between the roll groups. Next, the stretched sheet was cooled to 60° C., heated to about 150° C. using a tenter oven, stretched 8.5 times in the transverse direction, and further heated to 160° C. for heat treatment. Thereafter, it was cooled to 60° C., and the edges were slit to obtain a biaxially stretched sheet with a thickness of 80 μm. After subjecting the surface of the obtained biaxially stretched sheet to corona discharge treatment, the coating solution obtained in Preparation Example 1 was applied to one side to a solid content of 0.050 g/m ² and dried to form a two-sided sheet with a printed layer on one side. An axially stretched sheet was obtained.
Next, the resin composition (d) is melt-kneaded in an extruder at a temperature of 220°C, and then fed into an extrusion die set at 250°C and extruded into a sheet. The side without the printing layer of the above-mentioned biaxially stretched sheet with a printed layer on one side is thermally laminated on both sides to a thickness of 410 μm (thickness of each layer: 80/250/80 μm, number of stretching for each layer: biaxial/non-stretched/biaxial). ) was obtained.The laminated resin film of Example 1 was obtained.
In the obtained laminated resin film, the layer formed using the resin composition (a) is the concealing surface layer, the layer formed using the resin composition (d) is the concealing core layer, and the layer formed using the resin composition (d) is the concealing core layer. The formed layer corresponds to a printing layer.

(Examples 2 to 4, 6, 8, 9 and Comparative Example 1)
In Example 1, the laminated resins of Examples 2 to 4, 6, 8, 9 and Comparative Example 1 were prepared in the same manner as in Example 1, except that the resin composition of each layer was changed as shown in Table 3 below. Got the film.

(Examples 5 and 7)
Laminated resin films of Examples 5 and 7 were obtained in the same manner as in Example 1, except that the resin composition and thickness of the concealing core layer were changed as shown in Table 3 below.

[evaluation]
(thickness)
The overall thickness of the laminated resin film of each Example and Comparative Example was measured in accordance with JIS K7130:1999 using a constant pressure thickness measuring device (manufactured by Techlock Co., Ltd., trade name: PG-01J). In addition, the thickness of each layer in the laminated resin film of each Example and Comparative Example was determined by cooling the sample to be measured with liquid nitrogen to a temperature of -60°C or less, and then applying a razor blade (thick film) to the sample placed on a glass plate.・Create a sample for cross-sectional observation by cutting at right angles with Japan Co., Ltd., product name: Proline Blade), and place the obtained sample under a scanning electron microscope (JEOL Co., Ltd., product name: JSM) -6490) was used to observe the cross section, and the boundary line for each thermoplastic resin composition was determined from the composition appearance, and the thickness was determined by multiplying the overall thickness of the laminated resin film by the thickness ratio of each layer observed.

(porosity)
The porosity (%) of each layer in the laminated resin film of each Example and Comparative Example was determined from the ratio of the area occupied by pores in a certain area of the cross section of the laminated resin film observed with an electron microscope. Cut out an arbitrary part of the laminated resin film to be measured, embed it in epoxy resin and solidify it, then use a microtome to cut it perpendicular to the surface direction of the printing paper to be measured, so that the cut surface is the observation surface. It was attached to the observation sample stand so that it looked like this. Gold or gold-palladium or the like was deposited on the observation surface, and the pores in the laminated resin film were observed using an electron microscope at a magnification of 1000 times, and the observed area was captured as image data. Image processing of the obtained image data was performed using an image analysis device, boundaries between each layer were determined, and the area ratio (%) of the pore portion in a certain area of each layer was determined. The measured values observed at ten arbitrary locations were averaged to determine the porosity (%) of each layer.

(Opacity)
In accordance with JIS P8149:2000 ("Paper and paperboard - Opacity test method (backing of paper) - Diffused illumination method"), the color of each laminated resin film of each example and comparative example after measuring the thickness Each sample was measured once using a meter (trade name: SM Color Computer, manufactured by Suga Test Instruments Co., Ltd.), and the average value of all the samples was determined and used as the opacity.

(Variation in opacity in the width direction)
The opacity of each of the laminated resin films of Examples and Comparative Examples was measured at intervals of 50 mm in the width direction, and the standard deviation thereof was calculated, which was defined as the variation in opacity in the width direction.

(whiteness)
The hue of the laminated resin film of each Example and Comparative Example, that is, the lightness index L and chromaticness index a, b of the Hunter color system, was measured using a Hunter type color difference meter (trade name "SM Colormeter SM-T", Suga Test). (manufactured by Kisha). The whiteness was calculated according to the method described in JIS L1015:1999.

(concealability)
The hiding properties of the laminated resin films of each Example and Comparative Example were evaluated based on the following criteria.
○: Whiteness is 85% or more and opacity is 99% or more.
×: Whiteness is less than 85% and opacity is less than 99%.

(Interlaminar strength between hidden surface layer and hidden core layer)
In accordance with JIS Z 1707, one end of the laminated resin film of each example and comparative example was peeled into a concealing surface layer and a concealing core layer, one end of each layer was attached to both grips of a tensile tester, and the test speed was 300 mm. Tensile stress was applied at a rate of 1/min, and the maximum stress until complete peeling was measured. The test was conducted twice, and the average value was determined, which was taken as the interlayer strength between the concealing surface layer and the concealing core layer.

(Print suitability)
[Flexo printed matter]
The laminated resin film obtained in each Example and Comparative Example was treated with small slits, and one side of the film was printed with a flexo printing machine (trade name "TCL", manufactured by Taiyo Kikai Seisakusho Co., Ltd.) and an ultraviolet curable flexo ink. (Product name "UV Flexo CF", manufactured by T&K TOKA Co., Ltd.) was used to print the product name, manufacturer, sales company name, instructions for use, precautions, etc. in an environment of 23°C and 50% relative humidity. Patterns including information, barcodes, and designs were printed in four colors at a speed of 60 m/min. Next, this was passed under an ultraviolet irradiator (metal halide lamp, 100 W/cm, 1 lamp, manufactured by I-Graphic Co., Ltd.) at a speed of 60 m/min to dry the ink on the printing surface, thereby obtaining a flexographic print. Ta.

<Surface resistivity>
The laminated resin films obtained in each of the Examples and Comparative Examples were cut into A4 size pieces, and left for one week at a temperature of 10° C. and a relative humidity of 30%. Next, the surface resistivity of the surface of the printed layer of the same sample was measured under conditions of a temperature of 10° C. and a relative humidity of 30% using a double ring method electrode in accordance with JIS K6911:2006.

<Ink adhesion>
The flexographic printed matter using the laminated resin film of each Example and Comparative Example was punched out into a label shape, and cellophane tape (LP-18, manufactured by Nichiban) was pasted on top of the print, and after adhering it with a finger, the base material was Peeling was performed at 180 degrees at a speed that did not cause internal destruction, and peeling of the print was judged based on the following criteria.
○: No peeling of printing was observed.
Δ: Peeling of the print is observed, but the peel strength is high and there is no problem in practical use.
×: Peeling of the print was observed, the peel strength was low, and it was not suitable for practical use.

(Environmental contribution)
Among the plastic materials used in the laminated resin films of each Example and Comparative Example, the mass percentage of recycled plastic was calculated.

As shown in Table 3, the laminated resin films of Examples 1 to 9 had high whiteness and opacity, and had excellent hiding properties, interlayer strength, and printability.
On the other hand, the laminated resin film of Comparative Example 1 in which the hiding core layer did not contain a black pigment had low opacity and did not have high hiding properties.

1 Hiding layer 2 Hiding core layer 3a Hiding surface layer 3b Hiding surface layer 4a Printing layer 4b Printing layer 10 Laminated resin film

Claims (15)

A laminated resin film having a hiding layer,
The concealing layer has a concealing surface layer and a concealing core layer containing a recycled plastic raw material of polyolefin resin and a black pigment,
The whiteness is 85% or more and the opacity is 99% or more.
Laminated resin film. The laminated resin film according to claim 1, wherein the recycled plastic raw material of the polyolefin resin contains a colorant. The opacity of the concealing surface layer is 75% to 100%.
The laminated resin film according to claim 1 or 2. the concealing surface layer has a porous structure;
The laminated resin film according to any one of claims 1 to 3. the concealing surface layer is stretched;
The laminated resin film according to any one of claims 1 to 4. The porosity of the concealing surface layer is 1 to 70%,
The laminated resin film according to any one of claims 1 to 5. The concealing surface layer contains a white pigment, and the content of the white pigment in the concealing surface layer is 0.1 to 5% by mass.
The laminated resin film according to any one of claims 1 to 6. The thickness of the concealing surface layer is 10 to 300 μm.
The laminated resin film according to any one of claims 1 to 7. The concealing core layer contains a polyolefin resin.
The laminated resin film according to any one of claims 1 to 8. The concealing core layer contains a polyolefin resin having a melting point of 145° C. or less,
The laminated resin film according to any one of claims 1 to 9. The content of the black pigment in the concealing core layer is 0.3 to 5% by mass,
The laminated resin film according to any one of claims 1 to 10. It further has a printed layer in contact with the concealing surface layer, and the printed layer has a surface resistivity of 1×10 ¹ to 9× ¹⁰ Ω as measured in accordance with JIS K6911:2006.
The laminated resin film according to any one of claims 1 to 11. The ratio of the thickness of the concealing core layer to the total thickness of the laminated resin film is 10 to 70%.
The laminated resin film according to any one of claims 1 to 12. The standard deviation in the width direction of the opacity of the laminated resin film is less than 5%.
The laminated resin film according to any one of claims 1 to 13. A method for producing a laminated resin film having a hiding layer, the method comprising:
The concealing layer has a concealing surface layer and a concealing core layer containing a recycled plastic raw material of polyolefin resin and a black pigment,
forming the concealing surface layer and the concealing core layer by extrusion lamination;
A method for producing a laminated resin film.

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