JP7693357B2 - Marking film and manufacturing method thereof - Google Patents

Description

The present invention relates to a marking film.

For example, surface decoration methods for uneven molded products have been attracting attention in recent years for the purpose of increasing the added value of molded products and giving them a luxurious feel. As the surfaces of molded products often have complex three-dimensional shapes, one such surface decoration method is to apply a pattern to the molded product and then protect and paint this pattern layer. However, this method requires labor and time in the work process, resulting in increased costs.

For this reason, there is a demand for a method of directly adhering a marking film to a molded product with a concave-convex shape, which requires fewer steps and can decorate the surface at low cost. For example, Patent Document 1 discloses a method for manufacturing a laminated molded product that includes a lamination step in which a marking film is laminated onto the surface of a molded product with a concave-convex shape by vacuum forming (TOM forming).

On the other hand, it is known to give marking films a low gloss matte finish in order to give them a luxurious feel (Patent Document 2).

JP 2015-196288 A JP 2001-205755 A

The inventors discovered that when a low-gloss matte marking film is directly adhered to an uneven molded product, the marking film is stretched, reducing the unevenness of the surface and widening the gap between adjacent bumps, resulting in a loss of the matte look of the marking film.

The present invention was invented to solve the above problems, and aims to provide a marking film that can suppress the loss of matte finish even when stretched by molding.

The marking film according to the present invention, which achieves the above object, has an adhesive layer, a colored layer, and a transparent layer adjacent to the colored layer, the transparent layer containing transparent particles and at least one resin selected from the group consisting of a urethane resin, a fluorine-containing resin, and an acrylic resin, and has a glossiness of 1 to 50. The colored layer is a concealing layer. The transparent layer has an uneven shape, the thickness of the transparent layer is 30 to 50 μm, and the volume average particle diameter of the transparent particles is 1 to 30 μm.

When the marking film described above is stretched by molding, the transparent particles suppress the decrease in the unevenness of the surface, and also cause new convex portions to appear in the concave portions between adjacent convex portions where the spacing between them has increased. Therefore, even when the marking film is stretched by molding, the decrease in the matte feel can be suppressed.

1 is a schematic cross-sectional view showing the state of the marking film according to the present embodiment before stretching. 2 is a schematic cross-sectional view showing the state of the marking film according to the present embodiment after stretching. FIG. 1 is a schematic cross-sectional view showing the state after stretching of a marking film according to a comparative example. FIG. 10A to 10C are diagrams for explaining the effect of the marking film according to the present embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings. In the description of the drawings, the same elements are given the same reference numerals, and duplicate explanations will be omitted. In addition, the dimensional ratios in the drawings have been exaggerated for the convenience of explanation, and may differ from the actual ratios.

In this specification, the range "X to Y" means "X or more and Y or less." In addition, unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20 to 25°C) and relative humidity of 45 to 55%.

The marking film 1 according to this embodiment will be described below with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view showing the state of the marking film 1 according to this embodiment before stretching. Figure 2 is a schematic cross-sectional view showing the state of the marking film 1 according to this embodiment after stretching.

As shown in FIG. 1, the marking film 1 according to this embodiment has, from the top to the bottom, a transparent layer 10, a colored layer 20, an adhesive layer 30, and a release liner 40.

The breaking elongation of the marking film 1 is preferably 250 to 600%. Having the breaking elongation of the film in this range improves the work efficiency when attaching the film to a molded product with projections and recesses. The breaking elongation can be determined by holding a sample in a tensile testing device and then measuring the tensile strength at a pulling speed of 200 mm/min in accordance with JIS K 7127:1999.

The gloss of the marking film 1 is 1 to 50, and preferably 3 to 30. When the gloss of the marking film 1 is in this range, it is given a moderate matte feel. Here, gloss refers to the 60-degree specular gloss. The 60° specular gloss is measured using a gloss meter "VG7000" manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS Z8741:1997. The 60° specular gloss can be controlled by the content of transparent particles in the transparent layer, the particle diameter of the transparent particles in the transparent layer, the surface roughness of the transparent layer, etc.

The difference between the glossiness of the marking film 1 after stretching 200% and the glossiness before stretching is preferably within 20 (the glossiness after stretching 200% is within ±20 of the glossiness before stretching), more preferably within 10, and even more preferably 4 or less. By keeping the difference within this range, the matte feel before and after stretching is about the same, and the impact on visibility is reduced.

<Transparent layer 10>
The transparent layer 10 is a major component of the marking film 1, and may be made of various materials depending on the application of the marking film 1. Considering that the marking film 1 will be attached to the surface of the uneven molded product by a vacuum forming method or the like, the material constituting the transparent layer 10 needs to be stretchable to an extent that it can follow the three-dimensional shape of the uneven molded product.

The transparent layer 10 contains a urethane resin, a fluorine-containing resin, or an acrylic resin. By containing a urethane resin or an acrylic resin in the transparent layer 10 in this way, the scratch resistance and weather resistance of the transparent layer 10 are improved, and the transparency of the transparent layer 10 is improved, thereby improving the visibility of the colored layer 20. The transparent layer 10 may contain a known pigment.

As the urethane-based resin, a thermoplastic polyurethane resin is preferred. The thermoplastic polyurethane resin is obtained by at least reacting a polyisocyanate, a high molecular weight polyol, and a chain extender. Specifically, it is preferable to obtain the thermoplastic polyurethane resin by reacting a chain extender with a terminal isocyanate urethane prepolymer obtained by reacting a polyisocyanate with a high molecular weight polyol. Examples of the polyisocyanate include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. The polyisocyanate may be a trimethylolpropane adduct-type modified product of the above polyisocyanate, a biuret-type modified product reacted with water, or an isocyanurate-type modified product containing an isocyanurate ring. The high molecular weight polyol is an organic compound having two or more hydroxyl groups and a number average molecular weight of 400 or more, preferably 1000 to 3000, and examples thereof include macropolyols such as polyether polyols, polyester polyols, polycarbonate polyols, acrylic polyols, epoxy polyols, natural oil polyols, silicone polyols, fluorine polyols, polyolefin polyols, and polyurethane polyols. The high molecular weight polyols may be used alone or in combination of two or more. The method for preparing the isocyanate-terminated urethane prepolymer is not particularly limited, and examples thereof include a method in which a polyisocyanate, a high molecular weight polyol, a urethane catalyst added as necessary, and a solvent used as necessary are charged into a reactor and reacted. Examples of the chain extender include low molecular weight polyhydric alcohols having a number average molecular weight of less than 400, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, and sorbitol; low molecular weight polyamine compounds, such as ethylenediamine, 1,3-propanediamine, hexamethylenediamine, diaminocyclohexylmethane, piperazine, 2-methylpiperazine, isophoronediamine, diethylenetriamine, and triethylenetetramine; 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, and di-2-hydroxyethylpropylenediamine; Examples of such chain extenders include diamines having a hydroxyl group in the molecule, such as di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine; alkylene dihydrazines, such as methylene dihydrazine, ethylene dihydrazine, and propylene dihydrazine; saturated or unsaturated dihydrazines, such as adipic acid dihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, phthalic acid dihydrazide, and itaconic acid dihydrazide; and dimer diamines in which the carboxyl group of a dimer acid is converted to an amino group. In addition, these chain extenders can be used as chain terminators by using an excess amount relative to the isocyanate groups in the prepolymer.

Examples of fluorine-containing resins include polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, etc. Among these, the fluorine-containing resins preferably include ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-perfluoroalkoxyethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and polychlorotrifluoroethylene.

Acrylic resin refers to a resin produced by polymerization using (meth)acrylic monomer as the main monomer component. Here, the main component refers to 50% by mass or more (up to 100% by mass) of the monomer component, preferably 80% by mass or more. Examples of (meth)acrylic monomers that can be used include acrylic acid esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, hexyl acrylate, cyclohexyl acrylate, lauryl acrylate, and stearyl acrylate; acrylic acid; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, lauryl methacrylate, and stearyl methacrylate; methacrylic acid; and the like. The (meth)acrylic monomers can also be used as a mixture of two or more types.

Acrylic resins may contain other monomers copolymerizable with (meth)acrylic monomers as monomers during polymerization, such as carboxyl group-containing monomers or anhydrides thereof, such as itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid; sulfonic acid group-containing monomers, such as sodium vinyl sulfonate; aromatic vinyl compounds, such as styrene and substituted styrenes; cyano group-containing monomers, such as acrylonitrile; olefins, such as ethylene, propylene, and butadiene; vinyl esters, such as vinyl acetate; vinyl chloride; and amide group-containing monomers, such as acrylamide, methacrylamide, N-vinylpyrrolidone, and N,N-dimethylacrylamide.

A crosslinking agent may also be used in combination with the urethane resin, silicon-containing fluororesin, or acrylic resin. Examples of crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents.

In addition, materials other than the urethane resin, fluorine-containing resin, or acrylic resin are not particularly limited, but examples include polyolefins such as polyethylene, polypropylene, polybutene, and polybutadiene, vinyl chloride resin, and polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Among these, polyethylene, unstretched polypropylene, acrylic resin, and vinyl chloride resin are preferred in consideration of stretchability (ability to follow three-dimensional shapes), transparency, design, durability, and cost. The above materials may be used alone or in the form of a mixture of two or more kinds. The transparent layer 10 may be composed of a single resin layer, or may be composed of a laminate of different types of resin layers.

The thickness of the transparent layer 10 is not particularly limited, but taking into consideration stretchability (ability to conform to three-dimensional shape), breaking strength, abrasion resistance, etc., it is preferably 5 to 200 μm, more preferably 10 to 150 μm, and even more preferably 30 to 50 μm. With such a thickness, molding can be easily performed.

The transparent layer 10 has the function of protecting the colored layer 20, so from the viewpoint of ensuring visibility, it is necessary for the transparent layer 10 to have high transparency. Specifically, the total light transmittance of the transparent layer 10 is preferably 70% or more (upper limit 100%), and more preferably 80% or more.

To prevent contamination of the transparent layer 10, a fluororesin layer can be laminated. Methods for laminating the fluororesin layer include coating a paint containing a fluororesin on the transparent layer, melt co-extruding the transparent layer and the fluororesin layer, and laminating a fluororesin film on the transparent layer via an adhesive layer. From the viewpoint of suppressing a decrease in the matte feel, the thickness of the fluororesin layer is preferably 10 μm or less, and more preferably 1 to 8 μm.

Examples of fluororesins include polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymers, ethylene-chlorotrifluoroethylene copolymers, tetrafluoroethylene-perfluoroalkoxyethylene copolymers, tetrafluoroethylene-hexafluoropropylene copolymers, polychlorotrifluoroethylene, silicon-containing fluororesins, etc. Examples of silicon-containing fluororesins that can be used include those described in JP-A-2001-163927, JP-A-2001-206918, JP-A-2004-115792, etc.

As shown in FIG. 1, the transparent layer 10 contains transparent particles 11. The transparent particles 11 are preferably spherical. Here, the spherical shape does not only mean a perfect sphere, but may be an ellipse, an approximately spherical shape, or a shape with fine holes or irregularities on the surface. A ratio of the minor axis to the major axis of 1:1 to 1:2 is preferable as a spherical shape. Since aggregation is suppressed and the effect of the present invention is more easily achieved, it is more preferable that the transparent particles are perfect spherical. The material constituting the transparent particles 11 is not particularly limited, but examples thereof include synthetic resins such as crosslinked (meth)acrylic resins, crosslinked styrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins, and copolymers thereof; inorganic substances such as silica, calcium carbonate, and barium sulfate. Among them, crosslinked (meth)acrylic resin particles are preferably used as the transparent particles, and crosslinked methyl methacrylate (PMMA) particles are more preferably used, since the difference in refractive index between the transparent particles and the urethane resin or acrylic resin is small, transparency is easily ensured, and the effect of the present invention is easily obtained. The crosslinked (meth)acrylic acid resin particles are made from (meth)acrylic acid esters such as methyl methacrylate and n-butyl methacrylate. There are no particular limitations on the crosslinking agent, but commonly used crosslinking agents include epoxy crosslinking agents and isocyanate crosslinking agents. The refractive index of the transparent particles is preferably 2.0 or less, and more preferably 1.2 to 1.6.

The hardness of the transparent particles 11 is greater than the hardness of the transparent layer 10.

The volume average particle diameter of the transparent particles 11 is not particularly limited, but for example, when the thickness of the transparent layer 10 is 30 to 50 μm, the volume average particle diameter of the transparent particles 11 is preferably 1 to 30 μm, more preferably 1 to 15 μm, even more preferably 5 to 12 μm, and particularly preferably greater than 7.5 μm and equal to or less than 10 μm.

Here, if the volume average particle diameter is less than 1 μm, the effect described below will not be exhibited properly. Also, if the volume average particle diameter is more than 30 μm, the amount of resin around the transparent particles will be relatively reduced, which may cause the transparent layer to break when the marking film is stretched, and there is a risk that the film will not be stretched properly.

The transparent particles 11 may be particles having the same volume average particle size in the transparent layer 10, or particles having different volume average particle sizes may be mixed and included in the transparent layer 10.

The amount of transparent particles 11 added is preferably 5 to 35% by mass of the transparent layer 10, and more preferably 10 to 30% by mass. For example, if it is less than 5% by mass, the effect described below will not be exhibited favorably. If it is more than 35% by mass, the amount of resin around the transparent particles will be relatively reduced, which may cause the transparent layer to break when the marking film is stretched, and there is a risk that it will not be stretched favorably.

The 10-point average surface roughness (Rz _JIS ) of the surface side (the side facing the adhesive layer) of the transparent layer 10 is 0.1 to 30 μm. When Rz _JIS is equal to or greater than the above lower limit, a suitable matte feel can be imparted, and when Rz JIS is equal to or less than the above upper limit, transparency is easily ensured. The 10-point average surface roughness (Rz _JIS ) is defined by JIS B0601:2001.

The method for forming the transparent layer 10 is not particularly limited, but for example, a dispersion liquid (hereinafter, transparent layer forming dispersion liquid) is prepared by dispersing resin, transparent particles, and other optional components in a solvent, and then the transparent layer is formed by a solvent casting method in which the dispersion liquid is cast onto a process paper or process film (hereinafter, also simply referred to as process paper, etc.) to a predetermined dry thickness. Alternatively, the transparent layer may be formed by applying the transparent layer forming dispersion liquid onto a colored layer using a solvent casting method.

Examples of the material of the process film include synthetic resin films such as polyethylene terephthalate, polyethylene naphthalate, polyimide, and polypropylene. The process film may have a release layer of alkyd resin, silicone, or the like on these synthetic resin films. In this case, the transparent layer 10 is formed on the release layer forming surface. Examples of the process paper include fine paper, medium-quality paper, glassine paper, art paper, coated paper, and cast-coated paper. The thickness of the process paper, etc. is preferably 5 to 200 μm, more preferably 15 to 100 μm. The process paper, etc. may have an uneven surface. By casting the transparent layer forming dispersion liquid on the process paper, etc. having such an uneven shape, the uneven shape of the process paper, etc. is transferred to the transparent layer. Therefore, the transparent layer has an uneven shape, and for example, it is easy to control the 10-point average surface roughness (Rz) of the transparent layer surface as described above, and it is easy to obtain a matte feel. Process paper, etc. having unevenness can be obtained by a conventionally known method.

In this way, the resin contained in the transparent resin layer can be used to form the transparent layer by solvent casting. By using the solvent casting method, it is easy to control the physical properties by adding a crosslinking agent, and when directly applied to a colored layer, adhesion to the colored layer can be improved.

<Colored layer 20>
The colored layer 20 is a concealing layer that prevents the base of the uneven molded product from being seen through the transparent layer 10. For this reason, it is preferable that the concealing rate of the colored layer 20 is high. If the "concealment" is defined more quantitatively, the concealing rate of the colored layer 20 according to the present invention is 70% or more. The "concealment rate" is an index showing the ability to shield the color of the base, and is defined by JIS K5600-4-1:1999. After the marking film 1 is attached to the white and black parts of the concealment rate test paper, the respective tristimulus values YW and YB are measured, and the concealment rate ratio YB/YW is calculated as a percentage. This concealment rate is preferably 75% or more, more preferably 78% or more.

The colored layer 20 can be, for example, a layer containing a black pigment such as carbon black. With such a configuration, the colored layer 20 in the marking film 1 of this embodiment is black in color.

The colored layer 20 may be a glittering layer. The glittering layer is a layer having glittering (metallic feel). There is no particular restriction on the specific configuration of the glittering layer, and conventionally known knowledge may be appropriately referred to. As an example, the glittering layer may be a metal thin film layer formed by a dry film forming method such as vapor deposition or sputtering, or may be a glittering pigment-containing layer containing a glittering pigment and a binder. When the glittering layer is formed by vapor deposition or sputtering, vapor deposition or sputtering is performed on the transparent layer 10 having the transparent particles 11. When the glittering layer is a metal thin film layer, examples of the metals constituting the metal thin film layer include chromium, indium, tin, and aluminum. When the glittering layer is a glittering pigment-containing layer, there is no particular restriction on the glittering pigment contained in the glittering pigment-containing layer, and conventionally known knowledge may be appropriately referred to. Examples of the glittering pigment include one or more types selected from the group consisting of aluminum materials, pearl pigments, and glass materials. Specific examples of aluminum materials include aluminum powder, aluminum paste, and aluminum flakes. Aluminum powder is a metallic pigment that does not contain a solvent component, and includes materials in which aluminum particles are coated with resins such as acrylic resins. Aluminum paste is a material in which scaly fine particles of aluminum are surface-treated and made into a paste using an organic solvent or the like. An example of aluminum flakes is a material in which an aluminum vapor deposition film is made into a pigment. An example of a pearl pigment is white pearl, which is made by pulverizing mica and then surface-treating it. An example of a glass material is a scaly glass flake, or a glittering pigment type material in which the flakes are further coated with a metal or metal oxide.

When the colored layer is a photoluminescent layer, a colored transparent layer may be provided on the upper side of the photoluminescent layer. In this case, it is preferable to provide an adhesive layer between the transparent layer 10 and the colored transparent layer. In this configuration, the colored layer is formed by performing vapor deposition or sputtering on the colored transparent layer, and the transparent layer 10 including the transparent particles 11 is laminated on top of this colored layer via the adhesive layer.

The colored transparent layer contains, as forming materials, for example, a colorant and a binder.

A known pigment can be used as the colorant. The color of the pigment is not particularly limited, but examples include red and blue.

Examples of binders include vinyl chloride resin, acrylic resin, polyester resin, alkyd resin, epoxy resin, polyurethane resin, and acrylic urethane resin. These binders can also be used in combination with crosslinking agents such as amino resin, methylolated melamine resin, alkyl etherified melamine resin, urea resin, and polyisocyanate compounds.

In this way, by placing a colored transparent layer on top of the glossy layer, the design is improved.

To quantitatively define a preferred form of "black", the colored layer 20 in the marking film 1 according to the present invention has a reflection density of 0.5 or more. "Reflection density" is a type of optical density, and is defined as "-log10 (reflectance)" using reflectance (= amount of light reflected from the reflecting surface/amount of light incident on the reflecting surface). For example, when the reflectance is 10%, the reflection density is calculated as (-log10 (0.1)) = 1, and when the reflectance is 1%, the reflection density is calculated as (-log10 (0.01)) = 2. Conversely, when the reflection density is 0.5 or more, the reflectance is (1/10) 1/2 (= about 31.6%) or less. This reflection density is preferably 0.8 or more, more preferably 1.0 or more, even more preferably 1.3 or more, particularly preferably 1.7 or more, and most preferably 2.0 or more.

The colored layer 20 may be a printed layer formed by screen printing using an ink containing a pigment such as carbon black. However, the means for forming the colored layer 20 is not limited to this, and the layer may be formed by, for example, offset printing, flexographic printing, gravure printing, spray painting, bar coating, etc. Furthermore, the colored layer may be formed by a calendar method, an extrusion method, a solution casting method, etc.

In this embodiment, the colored layer 20 is made black, and carbon black, which is a carbon particle, is added to the colored layer 20 as a means for making the layer black and functioning as a concealing layer. Various types of carbon black are known, such as oil furnace black, channel black, lamp black, thermal black, and acetylene black. Any of these can be used in this embodiment. The colored layer is not limited to being black. In addition to the above carbon black, examples of colorants contained in the colored layer include graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, composite oxide-based black pigments, and anthraquinone-based organic black pigments.

There is no particular restriction on the average particle diameter of the carbon particles used, and any form that can achieve the above-mentioned hiding ratio (preferably, hiding ratio and reflection density) can be appropriately adopted. As an example, the average particle diameter of the carbon particles is preferably 10 to 100 nm, more preferably 20 to 80 nm, and particularly preferably 25 to 70 nm. The average particle diameter of the carbon particles can be obtained, for example, by randomly selecting several to several tens of carbon particles from a photograph taken with an electron microscope and calculating the arithmetic mean value from the particle diameters of the selected individual carbon particles (the maximum length connecting any two points on the contour line).

The amount of black pigment contained in the colored layer 20 is not particularly limited, and can be set appropriately to an amount that can achieve the desired hiding ratio. As an example, the amount of black pigment contained in the colored layer 20 is preferably 1 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 10 to 15 parts by mass, relative to 100% by mass of the solid content constituting the colored layer 20.

The colored layer 20 preferably contains a binder. Examples of binders that can be used include vinyl chloride resin, acrylic resin, polyester resin, alkyd resin, epoxy resin, polyurethane resin, and acrylic urethane resin. These binders can also be used in combination with crosslinking agents such as amino resin, methylolated melamine resin, alkyl etherified melamine resin, urea resin, and polyisocyanate compounds.

There are no particular limitations on the amount of binder used, but as an example, the binder content in the colored layer 20 is preferably 3 to 40 parts by mass, more preferably 5 to 35 parts by mass, and even more preferably 10 to 30 parts by mass, relative to 100% by mass of the solid content constituting the colored layer 20.

The thickness of the colored layer is not particularly limited, but is, for example, 50 to 200 μm.

The colored layer may contain stabilizers (e.g., Ba-Zn-based, etc.), lubricants, fillers, processing aids, plasticizers, softeners, metal powders, antifogging agents, UV shielding agents such as UV scattering agents or UV absorbing agents, antioxidants, antistatic agents, twist retardants, etc. as needed.

<Pressure-sensitive adhesive layer 30>
The adhesive used in the adhesive layer 30 is not particularly limited, and may be an acrylic adhesive, a rubber adhesive, a silicone adhesive, a urethane adhesive, a polyester adhesive, a styrene-diene block copolymer adhesive, a vinyl alkyl ether adhesive, etc. The above adhesives may be used alone or in combination of two or more kinds.

From the viewpoint of adhesive reliability, acrylic adhesives are particularly suitable for use as adhesives. The acrylic polymer that constitutes the acrylic adhesive is formed by using an adhesive (meth)acrylic acid alkyl ester as the main monomer component, and, as necessary, a monomer (copolymerizable monomer) that can be copolymerized with the (meth)acrylic acid alkyl ester having cohesive properties and a copolymerizable monomer having a crosslinkable functional group.

Examples of adhesive (meth)acrylic acid alkyl esters include butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and octyl (meth)acrylate. These may be used alone or in combination of two or more.

Examples of copolymerizable monomers having aggregating properties include methyl (meth)acrylate, vinyl acetate, styrene, and acrylonitrile. These may be used alone or in combination of two or more.

Examples of copolymerizable monomers having a crosslinkable functional group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and (meth)acrylic acid. These may be used alone or in combination of two or more types.

The weight-average molecular weight of the acrylic polymer is not particularly limited, but is preferably 100,000 to 1,000,000. The weight-average molecular weight is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC).

The adhesive preferably contains a crosslinking agent in addition to the acrylic polymer. Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents. The amount of crosslinking agent added is preferably 0.001 to 10 parts by mass, and more preferably 0.005 to 2.0 parts by mass, per 100 parts by mass of the acrylic polymer.

The adhesive layer 30 may contain, as necessary, light stabilizers, antioxidants, colorants, fillers, antistatic agents, tackifiers, wetting agents, leveling agents, thickeners, defoamers, preservatives, etc.

The thickness of the adhesive layer 30 is not particularly limited, but from the standpoint of adhesion and thin film, a range of 10 to 100 μm is preferable.

The adhesive strength of the adhesive layer 30 to the uneven molded product is preferably 10 N/25 mm or more. The adhesive strength to the uneven molded product is measured by attaching the adhesive layer surface of the marking film 1 to a SUS plate and measuring the adhesive strength after 24 hours in a 180° direction at a test speed of 300 mm/min using a tensile tester according to JIS Z0237:2009. More specifically, the adhesive strength to the uneven molded product is a value measured by the following method: the marking film 1 is left to stand for one day under standard conditions (23°C, 50% RH), the release liner is peeled off, and the adhesive layer surface is attached to a SUS304 steel plate. After leaving it to stand under standard conditions for 24 hours, the adhesive strength is measured according to JIS Z0237:2009. Specifically, the film is peeled off in a 180° direction at a test speed of 300 mm/min using a tensile tester, and the adhesive strength is measured. The values are converted into peel force per 25 mm of film width (N/25 mm).

<Release Liner 40>
The release liner 40 is a member having the function of protecting the adhesive layer 30 and preventing a decrease in adhesiveness. The release liner 40 is peeled off from the marking film 1 when the marking film 1 is attached to a molded product having projections and recesses. Therefore, the marking film 1 in this embodiment also includes a marking film that does not have a release liner 40.

Examples of the release liner 40 include, but are not limited to, plastic films such as polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and polyolefin films such as polypropylene and polyethylene; and papers such as fine paper, glassine paper, kraft paper, and clay-coated paper.

The thickness of the release liner 40 is usually about 10 to 400 μm. In addition, a layer of a release agent composed of silicone or the like may be provided on the surface of the release liner 40 to improve the releasability of the adhesive layer 30. When such a layer is provided, the thickness of the layer is usually about 0.01 to 5 μm.

Methods for stretching the marking film 1 are not particularly limited, but examples include TOM molding, insert molding, press molding, and in-mold molding.

Next, the effect of the marking film 1 according to this embodiment will be described with reference to Figures 2 to 4. Figure 2 is a schematic cross-sectional view showing the state of the marking film 1 according to this embodiment after stretching. Figure 3 is a schematic cross-sectional view showing the state of the marking film 900 according to the comparative example after stretching. Figure 4 is a diagram for explaining the effect of the marking film 1 according to this embodiment.

For example, as shown in FIG. 3, in the case where the transparent layer 910 does not contain transparent particles, stretching the film by 200% reduces the height H of the irregularities and increases the distance L between adjacent protrusions, reducing the matte appearance of the marking film 900. The reduced matte appearance results in glossiness.

In contrast, according to the marking film 1 of this embodiment, the transparent layer 10 contains transparent particles 11, so when the marking film 1 is stretched, as shown in FIG. 2, the transparent particles 11 suppress the decrease in the height H of the surface irregularities, and the transparent particles 11 cause new convexities 10A and 10B to appear in the concave portions between adjacent convexities where the spacing has increased. Therefore, with the marking film 1 of this embodiment, the decrease in the matte feel can be suppressed even when it is stretched.

The mechanism of suppressing the decrease in the matte finish described above will be described in detail below with reference to Figure 4. Note that the numerical values in the following explanation are merely examples, and the present invention is not limited to these numerical values.

Figure 4 (A) is a cross-sectional view showing the transparent layer 910 in the marking film 900 according to the comparative example. Figure 4 (B) is a cross-sectional view showing the transparent layer 10 in the marking film 1 according to the embodiment. Figure 4 (C) is a cross-sectional view showing the transparent layer 10 in the marking film 1 according to the embodiment.

The transparent layers 10, 910 have a thickness of, for example, 40 μm. The marking film 900 of the comparative example does not contain transparent particles. The marking film 1 of the embodiment shown in FIG. 4(B) contains one transparent particle 11 with a diameter of 10 μm. The marking film 1 of the embodiment shown in FIG. 4(C) contains two transparent particles 11 with a diameter of 10 μm in the stacking direction (vertical direction).

In this state, when the marking film 900 according to the comparative example is stretched by 200%, the thickness of the transparent layer 910 decreases from 40 μm to 20 μm, the height of the convex parts decreases, and the matte finish decreases, as shown in FIG. 4(A).

In contrast, when the marking film 1 according to the embodiment shown in FIG. 4(B) is stretched by 200%, the thickness of the 30 μm transparent layer 10, which is the portion of the 40 μm transparent layer 10 that does not contain the transparent particles 11, is reduced to 15 μm, while the thickness of the 10 μm transparent layer 10, which is the portion that contains the transparent particles 11, remains approximately 10 μm. Therefore, the overall thickness of the transparent layer 10 is 25 μm, which is an increase of 5 μm compared to the marking film 900 according to the comparative example, and therefore the decrease in the matte finish can be suppressed.

Furthermore, when the marking film 1 according to the embodiment shown in FIG. 4(C) is stretched by 200%, the thickness of the 20 μm transparent layer 10, which is the portion of the 40 μm transparent layer 10 that does not contain the transparent particles 111, is reduced to 10 μm, while the thickness of the 20 μm transparent layer 10, which is the portion that contains the transparent particles 11, remains approximately 20 μm. Therefore, the thickness of the entire transparent layer is 30 μm, which is an increase of 10 μm compared to the marking film 900 according to the comparative example, and therefore the decrease in the matte finish can be further suppressed.

<Example>
Next, the effects of the present invention will be described using the following comparative examples and examples.

After preparing a dispersion of urethane resin and transparent particles in a solvent, this was applied to a processing paper (EV130TPD, manufactured by Lintec Corporation), heated and dried to form a transparent layer 10 with a thickness of 40 μm.

The transparent particles 11 used were spherical microparticles of cross-linked polymethyl methacrylate, Techpolymer MB30X-8 (average particle size: 8 μm, manufactured by Sekisui Plastics Co., Ltd.).

Next, 100 parts by weight of acrylic urethane resin and 10 parts by weight of carbon black [manufactured by Mitsubishi Chemical Corporation, product name "RCF#44", average primary particle size 24 nm] were dispersed in a solvent to prepare a dispersion, which was then applied to the transparent layer 10 and heated and dried to obtain a colored layer 20 having a thickness of 30 μm.

A 30 μm acrylic resin was used as the adhesive layer 30.

A 50 μm thick polyethylene terephthalate (PET) was used as the release liner 40. A 100 nm thick silicone release agent was applied to the surface of the laminate on the release liner 40 side.

As a comparative example, a marking film was prepared in which the transparent layer did not contain transparent particles. As Example 1, a marking film was prepared in which the transparent layer contained 5% transparent particles by mass. As Example 2, a marking film was prepared in which the transparent layer contained 15% transparent particles by mass. As Example 3, a marking film was prepared in which the transparent layer contained 25% transparent particles by mass. As Example 4, a marking film was prepared in which the transparent layer contained 35% transparent particles by mass.

Table 1 shows the results of surface roughness Rz and 60% specular gloss after the marking films of the comparative example, Example 1, Example 2, Example 3, and Example 4 were stretched 150% and 200%.

From Table 1, it can be seen that the greater the amount of transparent particles added to the transparent layer, the more the deterioration of the matte finish is suppressed.

1. Marking film,
10 transparent layer,
11 Transparent particles,
20 colored layer,
30 Pressure-sensitive adhesive layer,
40 Release liner.

Claims (6)

A pressure-sensitive adhesive layer, a colored layer, and a transparent layer adjacent to the colored layer,
the transparent layer includes transparent particles and at least one resin selected from the group consisting of a urethane-based resin, a fluorine-containing resin, and an acrylic-based resin;
The gloss level is 1 to 50,
The colored layer is a concealing layer,
The transparent layer has an uneven shape,
A marking film , wherein the transparent layer has a thickness of 30 to 50 μm, and the transparent particles have a volume average particle size of 1 to 30 μm . 2. The marking film according to claim 1, wherein the transparent layer has a 10-point average surface roughness of 0.1 to 30 μm on a side facing the adhesive layer. 3. The marking film according to claim 1 , wherein the glossiness after 200% stretching is within ±20% of the glossiness before stretching. The marking film according to claim 1 , wherein the transparent particles are spherical. The marking film according to any one of claims 1 to 4 , wherein the amount of the transparent particles added is 5 to 35% by mass of the transparent layer. A method for producing a marking film having a pressure-sensitive adhesive layer, a colored layer, and a transparent layer adjacent to the colored layer, comprising:
A method for manufacturing a marking film, comprising: applying a dispersion liquid in which at least one resin selected from the group consisting of urethane-based resins, fluorine-containing resins, and acrylic-based resins, and transparent particles are dispersed in a solvent to a process paper having an uneven surface to form the transparent layer.