Graphic sheet, graphic sheet with protective film, method of manufacturing the same, and method of using the same

Abstract

To provide a graphic sheet which prevents peeling of a printed layer, maintains image quality over a long period of time and has high durability, even if an image is formed by inkjet printing, a graphic sheet with a protective film, a method for manufacturing the same, and a method for using the same.SOLUTION: A graphic sheet 1 includes a surface resin layer 2, an ink receiving layer 3, a printed layer 4, an ink substrate layer 5, and an adhesive layer 6 in this order, wherein the printed layer 4 is an inkjet printed layer, when the printed layer 4 is cut at an angle of 45° from the side of the surface resin layer 2, and peel off test is performed thereon, the printed layer 4 is not peeled or the printed layer 4 is subjected to cohesion breakage. There is provided a graphic sheet 10 with a protective film, wherein a protective film 7 is stuck to the outer surface of the surface resin layer 2, and a release film 8 is stuck to the outer surface of the adhesive layer 6.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a graphic sheet containing a printing layer, a graphic sheet with a protective film, a method for manufacturing the same, and a method for using the same.

Background Art

[0002] Japanese automobile number plates generally form convex portions having shapes such as place names and numbers on an aluminum plate coated with white paint by embossing, and print a coloring layer using ink such as green on the convex portions. In other countries, there are examples of number plates using graphic sheets, retroreflective sheets, etc. in addition to vehicle identification, and in recent years, such products have also begun to be used in Japan. Such number plates are formed by laminating a graphic sheet, a retroreflective sheet, etc. on a base plate.

[0003] Patent Document 1 proposes a graphic film for license plates with high whiteness, and it is proposed to suppress the occurrence of defects such as film breakage and floating during embossing and over time. In addition, the applicant of the present application has proposed in Patent Document 2 a graphic sheet that includes, in order from the viewing side, a surface resin layer, a printing layer on the back side of the surface resin layer, an ink underlayer, and an adhesive layer. The surface resin layer is a polycarbonate-based urethane resin. In particular, the ink underlayer uses an alkyd melamine resin, has good embossing suitability, weather resistance, and adhesion to the ink layer. Furthermore, an after clear coat or overlaminate is not required, and even after being attached to a base material such as a base plate for a number plate, it is difficult to peel off without damage and has high security. In Patent Document 3, the applicant has proposed a graphic sheet that solves the yellowing problem.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] However, the aforementioned conventional technology had a problem where the printed layer would peel off depending on the color and density when an image was formed using inkjet printing. When the printed layer peels off, it can cause swelling, damage to the image, and a decrease in quality, making it impossible to use the license plate for an extended period.

[0006] To solve the aforementioned conventional problems, the present invention provides a highly durable graphic sheet, a graphic sheet with a protective film, a method for manufacturing the same, and a method for using the same, in which the printed layer does not peel off even when an image is formed by inkjet printing, and the image quality is maintained for a long period of time. [Means for solving the problem]

[0007] The present invention comprises a surface resin layer, an ink receiving layer, a printing layer, an ink underlay layer, and an adhesive layer in that order, wherein the printing layer is an inkjet printing layer, and when cut at a 45° angle from the surface resin layer side and subjected to a peel-off test, the printing layer either does not peel off or the printing layer undergoes cohesive failure.

[0008] The graphic sheet with protective film of the present invention has a protective film attached to the outer surface of the surface resin layer and a release film attached to the outer surface of the adhesive layer.

[0009] The present invention provides a method for manufacturing a graphic sheet with a protective film, A surface resin layer is formed on the surface of the substrate film for process A by casting, B. An ink receiving layer is formed on the surface of the surface resin layer by a casting method. C A printed layer is formed on the surface of the ink receiving layer by inkjet printing. D. An ink underlayer is formed on the surface of the ink receiving layer and the printing layer by a casting method. E. An adhesive layer is formed on the surface of a separately prepared release film by casting. F The adhesive layer is attached to the surface of the ink base layer. G A method for manufacturing a graphic sheet with a protective film, which includes the step of peeling off the base film for the above process and laminating a protective film onto the surface resin layer.

[0010] The method of using the graphic sheet with protective film of the present invention involves attaching the graphic sheet with protective film to a base plate, creating a symbol by embossing or debossing, peeling off the protective film, then placing a symbol ink layer on top of the symbol and burning it to form a license plate with the graphic sheet attached. [Effects of the Invention]

[0011] The graphic sheet of the present invention comprises a surface resin layer, an ink receiving layer, a printing layer, an ink underlay layer, and an adhesive layer in this order, the printing layer being an inkjet printing layer, and when cut at a 45° angle from the surface resin layer side and subjected to a peel-off test, the printing layer either does not peel off or undergoes cohesive failure. This provides a graphic sheet with a protective film that does not peel off, maintains image quality for a long period of time, and is highly durable, thus providing a graphic sheet, a graphic sheet with a protective film, a method for manufacturing the same, and a method for using the same. In other words, by placing an ink receiving layer on top of the surface resin layer and a printing layer on top of that, the printing layer adheres so strongly to the ink receiving layer that it either does not peel off or undergoes cohesive failure. As a result, a graphic sheet with high durability that maintains image quality for a long period of time can be obtained. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic cross-sectional view of a graphic sheet in one embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of a graphic sheet with a protective film, in which a protective film and a release film are laminated on the graphic sheet of Figure 1. [Figure 3] Figures 3A - F are schematic cross-sectional views showing the manufacturing process of the graphic sheet with a protective film of Figure 2. [Figure 4] Figure 4 is a schematic front view of a number plate manufactured by attaching a graphic sheet to a base plate for a vehicle, performing embossing, peeling off the protective film, and forming a symbol ink layer on the surface of the convex portion. [Figure 5] Figure 5 is a schematic partial cross-sectional view of Figure 4. [Figure 6] Figure 6A is a schematic cross-sectional view showing a peel-off test of a graphic sheet in an embodiment of the present invention, and Figure 6B is a schematic cross-sectional view showing cohesive failure. [Figure 7] Figure 7A is a schematic cross-sectional view showing a peel-off test of a conventional graphic sheet, and Figure 7B is a schematic cross-sectional view showing interfacial failure.

Embodiments for Carrying Out the Invention

[0013] The inventors of the present invention examined why the inkjet printing layer peels off in the conventional example. As a result, when the ink underlayer is an alkyd melamine layer, there are almost no problems with cyan and yellow at a setting density of 10 - 100% of the inkjet printer, but floating or peeling occurs with magenta at 40 - 100% and with orange at 20 - 100%. Also, when the ink underlayer is an alkyd isocyanate, there are almost no problems with cyan at a setting density of 10 - 100% of the inkjet printer, but floating or peeling occurs with magenta at 60 - 100%, with yellow at 70 - 100%, and with orange at 30 - 100%. That is, it was found that floating or peeling is likely to occur in the case of magenta-based and orange-based colors with high concentrations. Therefore, the present invention was completed by conceiving to dispose an ink receiving layer with good adhesion to the inkjet printing layer on the surface resin layer and disposing a printing layer thereon.

[0014] The present invention includes a surface resin layer, an ink receiving layer, a printing layer, an ink underlayer, and an adhesive layer in this order when viewed from the viewing direction (EY). Since the printing layer is encapsulated by the surface resin layer, the ink receiving layer, and the ink underlayer, it is not damaged. The printing layer is visible from the outside through the surface resin layer. And the printing layer and the ink receiving layer are firmly adhered to the ink receiving layer so that they do not peel off even in a peel-off test or the printing layer undergoes cohesive failure. As a result, high image quality can be maintained for a long time, and a highly durable graphic sheet can be obtained. In the present invention, in the peel-off test, first, a cutter is inserted at an angle of 45° from the surface resin layer side and cut. Usually, the cutter is inserted at an angle of 90°, but it is set at 45° to create more severe conditions. Next, an adhesive tape is attached onto the surface resin layer in a direction perpendicular to the cut portion and peeled off. Whether it is cohesive failure or interfacial failure is determined by observing with an optical microscope.

[0015] For the printing layer, it is preferable to use an inkjet printer to eject ink in a dot shape from a nozzle and color the subject as dots when the coloring density is low. In this state, the peeling problem of the printing layer is less likely to occur. However, when the coloring density becomes high, the ink ejected from the nozzle forms a continuous film, and the peeling problem of the printing layer is likely to occur. Therefore, when the ratio of the colored ink portion per unit area is 50% or more, the effect of the present invention becomes higher.

[0016] The ink receiving layer is preferably a copolymer or a multi-component copolymer resin containing a vinyl group, and / or a resin containing a urethane bond, or a mixture thereof. More specifically, the ink receiving layer is preferably a vinyl chloride-vinyl acetate-vinyl alcohol resin, a vinyl chloride-vinyl acetate-hydroxyacrylate resin, a vinyl chloride-vinyl acetate resin, a vinyl acetate resin, a styrene-acrylic resin, a polyvinyl butyral resin, a polyester-based polyurethane resin, or a polyether-based polyurethane resin. Thereby, the affinity with the printing layer becomes high, and peeling of the printing layer is less likely to occur.

[0017] The thickness of the ink receiving layer is preferably 0.1 to 30 μm, more preferably 0.5 to 28 μm, and even more preferably 1 to 25 μm. With these thicknesses, the overall thickness can be reduced, making it suitable for applications such as automobile license plates.

[0018] Additives such as leveling agents, UV absorbers, plasticizers, and curing agents may be added to the ink receiving layer.

[0019] Preferred leveling agents include acrylic, silicone, fluorine, and acetylene glycol types. Examples of acrylic leveling agents include "Polyflow No. 85" manufactured by Kyoeisha Chemical Co., Ltd. Examples of silicone leveling agents include "Polyflow KL-100" manufactured by Kyoeisha Chemical Co., Ltd. Examples of fluorine leveling agents include the "Surflon" series manufactured by AGC Seimi Chemical Co., Ltd. Examples of acetylene glycol leveling agents include the "Orphine" series manufactured by Nisshin Chemical Industry Co., Ltd.

[0020] Preferred UV absorbers include benzotriazole, benzoate, benzoxazinon, benzophenone, and triazine types. Benzotriazole types include BASF's "Tinuvin 900". Benzoate types include BASF's "Tinuvin 120". Benzoxazinon types include Dansha Japan's "DXSORB 3638". Benzophenone types include Sankyo Kasei's "Dislizer E". Triazine types include Dansha Japan's "DXSORB 400".

[0021] Preferred plasticizers include phthalate esters, adipic acid esters, polyesters, phosphate esters, and epoxidized vegetable oils. Examples of phthalate esters include "DUP" from Mitsubishi Chemical Corporation. Examples of adipic acid esters include "DOA" from Mitsubishi Chemical Corporation. Examples of polyesters include the "Polysizer" series from DIC Corporation. Examples of phosphate esters include "P0273" from Tokyo Chemical Industry Co., Ltd. Examples of epoxidized vegetable oils include the "ADEKAsizer" series from ADEKA Corporation.

[0022] Preferred curing agents include epoxy, melamine, isocyanate, oxazoline, and carbodiimide types. Examples of epoxy curing agents include "TETRAD-C" from Mitsubishi Gas Chemical Company. Examples of melamine curing agents include the "Amidia" series from DIC Corporation. Examples of isocyanate curing agents include the "Barnock" series from DIC Corporation. Examples of oxazoline curing agents include the "Epocross" series from Nippon Shokubai Co., Ltd. Examples of carbodiimide curing agents include the "Carbodilite" series from Nisshinbo Chemical Co., Ltd.

[0023] The surface resin layer is preferably made of at least one resin selected from urethane resin, alkyd resin, acrylic resin, and polyvinyl chloride resin.

[0024] The following describes each type of resin. <Ink receiving layer> The ink receiving layer is preferably made of vinyl chloride-vinyl acetate-vinyl alcohol resin, vinyl chloride-vinyl acetate-hydroxyacrylate resin, vinyl chloride-vinyl acetate resin, or polyester polyurethane resin. Examples of vinyl chloride-vinyl acetate-vinyl alcohol resin, vinyl chloride-vinyl acetate-hydroxyacrylate resin, and vinyl chloride-vinyl acetate resin include "Solvine" manufactured by Nisshin Chemical Co., Ltd. Examples of polyester polyurethane resins include "Hydran" manufactured by DIC Corporation and "Rezamin" manufactured by Dainichi Seika Kogyo Co., Ltd.

[0025] <Ink underlayer> The ink underlayer is an alkyd resin, and a resin cured with a melamine-free curing agent can be used. Preferably, the curing agent is at least one selected from isocyanate-based curing agents, epoxy-based curing agents, oxazoline-based curing agents, carbodiimide-based curing agents, and aziridine-based curing agents. This prevents yellowing of the graphic sheet during high-temperature baking. Resins cured with isocyanate-based curing agents, epoxy-based curing agents, oxazoline-based curing agents, carbodiimide-based curing agents, and aziridine-based curing agents are referred to as alkyd-isocyanate resin, alkyd-epoxy resin, alkyd-oxazoline-based resin, alkyd-carbodiimide-based resin, and alkyd-aziridine-based resin, respectively.

[0026] Alkyd melamine resin may be used for the ink underlayer. Alkyd melamine resin is a mixture of alkyd resin and melamine resin as a curing resin component. Alkyd resin is a synthetic resin produced by the condensation polymerization of polybasic acids or fatty acids (or fatty oils) and polyhydric alcohols. Examples of polybasic acids include phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, succinic acid, adipic acid, sebacic acid, and benzoic acid. Examples of fatty acids include soybean oil, coconut oil, linseed oil, castor oil, dehydrated castor oil, safflower oil, tall oil, and palm kernel oil. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, trimethylolethane, trimethylolpropane, and glycerin. The alkyd resin made from the above raw materials may also be modified with resins such as acrylic, urethane, epoxy, phenol, and silicone. Examples of commercially available products include the "Beccolight" series from DIC Corporation and the "Amirac" series from Kansai Paint Co., Ltd. Melamine resin, used as a curing resin component, is generally a resin produced by adding and condensing melamine and formaldehyde, and then etherifying it with an aliphatic monohydric alcohol (such as methanol or butanol). Commercially available options include DIC's "Super Beccamine" series. Alkyd melamine resin is widely used in the automotive paint industry and is favored because it has a proven track record of being used in regular license plates overseas. Furthermore, it has excellent processability, especially low-temperature embossing properties at 1-5°C. The ink underlayer is preferably a transparent resin or a resin containing a white pigment. When colored white, it has high opacity, and even if thin, the substrate will not be visible. The amount of whitening agent added is preferably 1 to 50 parts by weight, more preferably 5 to 30 parts by weight, and even more preferably 5 to 10 parts by weight, per 100 parts by weight of the ink underlayer or adhesive layer.

[0027] Isocyanate-based curing agents refer to polyisocyanates, which are compounds containing two or more isocyanate groups in one molecule. Examples of polyisocyanates include aliphatic polyisocyanates such as methylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polyisocyanates such as cyclohexane diisocyanate and isophorone diisocyanate; aromatic polyisocyanates such as toluene diisocyanate and methylene bisphenyl diisocyanate; adducts, biuretes, and isocyanurates of the aforementioned polyisocyanates; blocked isocyanates obtained by protecting the isocyanate groups of the aforementioned polyisocyanates with a blocking agent; and modified forms of the aforementioned polyisocyanates. Examples of modified forms of the aforementioned polyisocyanates include polyisocyanate modified forms obtained by modifying the isocyanate compound with allophanate bonds, urea bonds, uretdione bonds, etc. As the isocyanate-based curing agent, aliphatic and alicyclic polyisocyanates are preferred due to their excellent resistance to heat yellowing and weathering. Commercially available isocyanate-based curing agents include the "Barnock" series from DIC Corporation, the "Coronate" series from Tosoh Corporation, and the "Duranate" series from Asahi Kasei Corporation.

[0028] Epoxy curing agents refer to epoxy resins, which are compounds containing two or more epoxy groups in one molecule. Examples of epoxy resins include aliphatic epoxy resins, which are glycidyl ethers of aliphatic polyhydric alcohols such as ethylene glycol, glycerin, trimethylolpropane, and polyethylene glycol, and glycidyl esters of aliphatic polyhydric carboxylic acids such as malonic acid, succinic acid, adipic acid, and 1,2,3,4-butanetetracarboxylic acid. Other examples include alicyclic epoxy resins such as bis(2,3-epoxycyclopentyl) ether, 3,4-epoxycyclohexylmethyl, 3',4'-epoxycyclohexanecarboxylate, bis(3,4-epoxycyclohexylmethyl) adipate, and limonene dioxide, as well as aromatic epoxy resins, which are glycidyl ethers of aromatic polyhydric alcohols such as bisphenol A, bisphenol F, bisphenol AD, and novolac, and glycidyl esters of aromatic polyhydric carboxylic acids such as phthalic acid, 1,4-naphthalenedicarboxylic acid, trimellitic acid, and pyromellitic acid. Aliphatic and alicyclic epoxy resins are preferred as the epoxy curing agents due to their excellent resistance to heat yellowing and weathering. Commercially available epoxy curing agents include the "Epiclon" series from DIC Corporation, the "TETRAD" series from Mitsubishi Gas Chemical Company, and the "ADEKA Resin EP" series from ADEKA Corporation.

[0029] Oxazoline-based curing agents are compounds containing two or more oxazoline groups in one molecule. Examples of oxazoline-based curing agents include polyhydric oxazolines such as 2,2'-bis-(2-oxazoline), 2,2'-methylene-bis-(2-oxazoline), and 2,2'-(1,4-phenylene)-bis(2-oxazoline), and copolymers consisting of oxazoline group-containing monomers such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. The oxazoline group-containing monomers may be used individually or in combination of two or more types. Copolymers of monomers containing oxazoline groups and monomers that do not contain oxazoline groups are also acceptable. Commercially available oxazoline-based curing agents include the "Epocross" series manufactured by Nippon Shokubai Co., Ltd.

[0030] Carbodiimide-based curing agents are compounds containing two or more carbodiimide groups in a single molecule. Examples of carbodiimide-based curing agents include poly(4,4'-diphenylmethanecarbodiimide), poly(dicyclohexylmethanecarbodiimide), and poly(diisopropylcarbodiimide). Commercially available carbodiimide-based curing agents include the "Carbodilite" series manufactured by Nisshinbo Chemical Co., Ltd.

[0031] Aziridine-based curing agents are compounds containing two or more aziridine groups in a single molecule. Examples of aziridine-based curing agents include 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4'bis(ethyleneiminocarbonylamino)diphenylmethane. Commercially available aziridine-based curing agents include the "Chemitite" series manufactured by Nippon Shokubai Co., Ltd.

[0032] The ratio of the melamine-free curing agent to be added is 5 to 50 parts by weight, preferably 5 to 30 parts by weight, and more preferably 10 to 20 parts by weight, of the alkyd resin per 100 parts by weight of the curing agent.

[0033] <Surface resin layer> The surface resin layer is not particularly limited, but at least one selected from urethane resin, alkyd resin, acrylic resin, and polyvinyl chloride resin is preferred. Urethane resins are polymer compounds containing urethane bonds, produced by reactions between polyisocyanates and polyols. Examples of polyisocyanates include aliphatic polyisocyanates such as methylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate; alicyclic polyisocyanates such as cyclohexane diisocyanate and isophorone diisocyanate; aromatic polyisocyanates such as toluene diisocyanate and methylene bisphenyl diisocyanate; adducts, biuretes, and isocyanurates of the aforementioned polyisocyanates; blocked isocyanates obtained by protecting the isocyanate groups of the aforementioned polyisocyanates with a blocking agent; and modified polyisocyanates. Examples of modified polyisocyanates include polyisocyanate modified compounds obtained by modifying the isocyanate compounds with allophanate bonds, urea bonds, uretdione bonds, carbodiimide bonds, and the like. Polyols include polycarbonate-based polyols, polyether-based polyols, and polyester-based polyols, and the urethane resins synthesized from them are called polycarbonate-based urethane resins, polyether-based urethane resins, and polyester-based urethane resins, respectively. For the surface resin layer, water-based polycarbonate-based urethane resins are preferred due to their excellent weather resistance, heat resistance, and chemical resistance. Water-based resins are safe during manufacturing and use, environmentally friendly, and odorless. Commercially available water-based polycarbonate-based urethane resins, water-based polyether-based urethane resins, and water-based polyester-based urethane resins include the "Rezamin" series from Dainichi Seika Kogyo Co., Ltd. and the "Nipporan" series from Tosoh Corporation. For alkyd resins, the same alkyd resins used in the ink underlayer can be used.

[0034] Acrylic resins are polymer compounds and their derivatives obtained by polymerizing acrylic monomers. Examples of acrylic monomers include methyl acrylate, ethyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, methoxybutyl acrylate, and other acrylic and methacrylic acid derivatives, as well as acrylic acid and methacrylic acid. Acrylic monomers may be used individually or in combination of two or more types. Copolymers of acrylic monomers with other monomers such as styrene, butadiene, and vinyl acetate are also acceptable. Commercially available acrylic resins include the "Acrydic" series from DIC Corporation.

[0035] Vinyl chloride resin is a polymer compound obtained by polymerizing vinyl chloride monomer and its derivatives. Vinyl chloride monomer may be used alone, or it may be a copolymer with other monomers such as ethylene or vinyl acetate. Commercially available vinyl chloride resins include vinyl chloride-vinyl acetate copolymer resins such as the "Solvine" series manufactured by Nisshin Chemical Industry Co., Ltd.

[0036] The thickness of the surface resin layer is preferably 10 to 50 μm, and more preferably 15 to 45 μm. The thickness of the ink underlayer is preferably 10 to 50 μm, and more preferably 15 to 45 μm. The thickness of the adhesive layer is preferably 15 to 60 μm, and more preferably 20 to 55 μm. The thickness of the graphic sheet is preferably 100 μm or less, and more preferably 50 to 100 μm. With this thickness, a graphic sheet can be made that is difficult to peel off after being attached to a substrate such as a base plate, resulting in a highly secure graphic sheet. Furthermore, it also has excellent low-temperature embossing properties. If the thickness of the graphic sheet exceeds 100 μm, embossing or debossing properties, security properties, and resistance to heat yellowing will be impaired.

[0037] It is preferable that the surface resin layer contains a curing agent. This allows the surface resin layer to have good solvent resistance. The curing agent to be added to the surface resin layer can be melamine-based, carbodiimide-based, oxazoline-based, etc., but melamine-based is preferred. It is preferable to add a formalin scavenger to the surface resin layer. When a melamine-based curing agent is added to the surface resin layer, there is a problem in that the formaldehyde produced by the thermal decomposition of the melamine-based curing agent reacts with the surface resin layer and causes yellowing, but this can be improved by adding a formalin scavenger to the surface resin layer. As the formalin scavenger, at least one selected from compounds having an amino group or an amide group in the molecule, such as urea, ethylene urea, thiourea, and melamine, is preferred. A commercially available product containing the above compound is "FineTex FC-KP" (trade name) [manufactured by DIC Corporation], which is a nitrogen-based formaldehyde scavenger. The formalin scavenger is preferably added in an amount of 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and even more preferably 0.1 to 2 parts by weight, per 100 parts by weight of the surface resin layer.

[0038] It is preferable to add at least one selected from blue pigments and purple pigments to the surface resin layer and / or ink underlayer. This is because, although there is a problem that the graphic sheet may take on a slight yellowish tint due to the effects of ultraviolet absorbers and other substances included to improve the weather resistance of each layer, the yellowish tint of the graphic sheet can be neutralized by adding at least one selected from blue pigments and purple pigments as a complementary color to yellow. The amount of pigment added is preferably 0.001 to 1 part by weight, more preferably 0.01 to 0.1 parts by weight, and even more preferably 0.01 to 0.05 parts by weight, when each of the surface resin layer and ink underlayer is 100 parts by weight.

[0039] The adhesive layer is preferably cured with an acrylic resin as the base polymer and a curing agent that does not contain aromatic components. One of the causes of yellowing is the yellowing of the adhesive layer. Conventional adhesive layers are formed with an acrylic resin as the base polymer and an isocyanate curing agent that contains aromatics. Such aromatic isocyanate curing agents can cause yellowing because the aromatic rings easily absorb visible light. Therefore, by adding an isocyanate curing agent and an epoxy curing agent that do not contain aromatics, a graphic sheet with excellent heat resistance to yellowing can be made. As for the epoxy curing agent, the same epoxy curing agent used in the ink underlayer can be used. The amount of aromatic-free isocyanate curing agent and epoxy curing agent to be added is preferably 0.001 to 1 part by weight, more preferably 0.001 to 0.1 parts by weight, and even more preferably 0.005 to 0.01 parts by weight, when the acrylic resin is 100 parts by weight.

[0040] The adhesive layer may contain resins such as acrylic resins, natural rubber, or synthetic rubber, but it is preferable that it contains acrylic resins. Acrylic resins have high adhesive strength and high weather resistance. As the acrylic resin, a polymer-based acrylic resin containing at least one of an acrylic acid ester copolymer and an acrylic prepolymer as the main component, or a modified acrylic resin in which a tackifier and a monomer that imparts cohesive force are further added to the acrylic resin, is preferred.

[0041] At least one of the ink underlayer and the adhesive layer can be colored in any color. For example, white, green, yellow, red, blue, purple, black, etc. Among these, it is preferable that they be colored white. In particular, it is preferable that both the ink underlayer and the adhesive layer be colored white. The ink underlayer and adhesive layer provide high opacity, so that the substrate is not visible even when thin. The amount of colorant added is preferably 1 to 50 parts by weight, more preferably 5 to 30 parts by weight, and even more preferably 5 to 10 parts by weight, per 100 parts by weight of the ink underlayer or adhesive layer.

[0042] A protective film is preferably attached to the outer surface of the surface resin layer, and a release film is preferably attached to the outer surface of the adhesive layer. Having a protective film on the outer surface of the surface resin layer protects the inner layer, and having a release film on the outer surface of the adhesive layer is convenient when attaching it to a base plate.

[0043] The protective film can be any commercially available surface protection film with a thickness of, for example, 30 to 90 μm. It is used to prevent surface scratches during transportation and processing. The graphic sheet is attached to the vehicle base plate, embossed, and then peeled off before the symbol ink layer is formed on the raised surface. Therefore, it is necessary to follow the graphic sheet during embossing. For example, a polyester (PET) film with a thickness of 25 to 50 μm can be used as the release film.

[0044] The thickness of the graphic sheet is preferably 300 μm or less, more preferably 100 to 300 μm, and even more preferably 150 to 250 μm. It is preferable that the graphic sheet has properties that make it difficult to reuse, such as stretching or breaking, when peeled off after being attached to a substrate. This helps prevent the theft of the graphic sheet and also prevents the theft of parts of the design, such as emblems, from being cut out. The graphic sheet should preferably be a sheet for vehicle license plates. Using graphic sheets on vehicle license plates has not only aesthetic benefits but also serves as a promotional tool for international sporting events, international expositions, local government advertising, and various other events.

[0045] The present invention's method for manufacturing a graphic sheet with a protective film includes the following steps. A surface resin layer is formed on the surface of the substrate film for process A by casting. B. An ink receiving layer is formed on the surface of the surface resin layer by a casting method. C. A printed layer is formed on the surface of the ink receiving layer by inkjet printing. D. An ink underlayer is formed on the surface of the ink receiving layer and the printing layer by a casting method. E. An adhesive layer is formed on the surface of a separately prepared release film by casting. F The adhesive layer is bonded to the surface of the ink base layer. G The substrate film for the above process is peeled off and the protective film is laminated onto the surface resin layer. For example, a graphic sheet with a protective film is obtained by peeling off the polyethylene terephthalate film (PET, 50 μm thick) of the graphic sheet itself and laminating a protective film onto it for the purpose of protecting the graphic sheet and ensuring it conforms to the graphic sheet during embossing. Because the surface resin layer, ink receiving layer, ink underlayer, and adhesive layer are formed by a casting method, the adhesion between layers is high, the overall thickness can be reduced, and it is difficult to peel off without damaging it, resulting in a highly secure graphic sheet. Regarding the process of forming the adhesive layer, although this description describes the process of forming the adhesive layer on the release PET and then laminating the adhesive layer onto the surface of the ink base layer, it is also possible to form the adhesive layer on the surface of the ink base layer and then laminate the release PET film onto the adhesive layer.

[0046] The method of using the graphic sheet with protective film of the present invention is as follows: (1) The graphic sheet with protective film is attached to the base plate, (2) Create a symbol by embossing or debossing, (3) Peel off the protective film, (4) After that, a layer of ink for the symbols is placed on top of the symbols and baked, and the graphic sheet is attached to form a license plate. The license plate with the graphic sheet attached may be sprayed with a water-repellent, oil-repellent, and stain-resistant spray. The baking temperature can be approximately 125°C to 160°C as an example.

[0047] The following explanation will be given using the drawings. In the following drawings, the same reference numerals indicate the same component. Figure 1 is a schematic cross-sectional view of a graphic sheet 1 in one embodiment of the present invention. This graphic sheet 1 includes, in this order, a surface resin layer 2, an ink receiving layer 3 on the back side of the surface resin layer 2, a printing layer 4 on the back side thereof, an ink underlay layer 5, and an adhesive layer 6. The arrow EY indicates the viewing direction (the same applies below). Figure 2 is a schematic cross-sectional view of a graphic sheet 10 with a protective film, in which a protective film 7 is attached to the outside of the surface resin layer 2 of the graphic sheet 1 and a release film 8 is attached to the outside of the adhesive layer 6. The product form is as shown in Figure 2. Figures 3A-F are schematic cross-sectional views showing the manufacturing process of the graphic sheet 10 with protective film. Figure 3A shows the process of forming a polycarbonate-based urethane surface resin layer 2 on the surface of the process substrate film 9 by casting. Figure 3B shows the process of forming an ink receiving layer 3 on the surface of the surface resin layer 2, and then forming a printed layer 4 on that surface by inkjet printing. Figure 3C shows the process of forming an ink underlayer 5 containing an alkyd melamine resin on the surface of the ink receiving layer 3 and the printing layer 4 by a casting method. Figure 3D shows the process of forming an adhesive layer 6 on the surface of a separately prepared release film 8 by casting. Figure 3E shows the process of bonding the adhesive layer 6 to the surface of the ink base layer 5. Figure 3F shows the process of peeling off the process substrate film 9 and laminating the protective film 7 onto the surface resin layer 2. Figure 4 is a schematic front view of a license plate 11 manufactured by attaching the graphic sheet with protective film to a vehicle base plate, embossing it, peeling off the protective film, and forming a symbol ink layer on the raised surface. The patterns around the letters (the surrounding heart shape and rounded shape) are chromatic image parts 14a and 14b. Various emblem designs may also be added to any location. The printed layer is chromatic according to the CIE color difference formula specified by the International Commission on Illumination, in accordance with JIS Z 8781-4:2013. *It is preferable that an image is formed that includes chromatic colors with values ​​from 0 to 85. L * The value represents the brightness of the color on a scale of 0 to 100, with values ​​closer to 0 indicating darker colors and values ​​closer to 100 indicating brighter colors. * While conventional graphic sheets tended to have the printed layer peel off easily when displaying chromatic images with values ​​between 0 and 85, the graphic sheet of the present invention can adhere so strongly to the ink receiving layer that the printed layer does not peel off or the printed layer undergoes cohesive failure.

[0048] Figure 5 is a schematic partial cross-sectional view of Figure 4. First, a graphic sheet with a protective film is attached to the base plate 12, and the symbol "Osaka 600 ka 20-25" shown in Figure 4 is created by embossing. After peeling off the protective film, a symbol ink layer 13 is placed on top of this symbol. 1 is the graphic sheet with the protective film peeled off. Then, the ink is baked on. The baking temperature can be approximately 125°C to 160°C, for example. This makes it possible to create a license plate with a highly secure graphic sheet attached. [Examples]

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following examples, "parts" refers to "parts by weight" unless otherwise specified, and "%" refers to "weight percent" unless otherwise specified. Also, the amount of curing agent added in the following table is expressed in parts by weight on a solid content basis.

[0050] <Printing method> The inkjet printer used was a Mimaki JV-300, and prints were made using cyan (C), magenta (M), yellow (Y), and orange (Or) at set densities of 10-100%. A set density of 10-100% is also referred to as "ink density 10-100%". <Adhesion evaluation: Peel-off test> As shown in Figures 6A-B and 7A-B, first, the graphic sheet 1 was attached to a 1 mm thick aluminum plate 13, left at 125°C for 10 minutes, then cooled to room temperature (25°C), and a peel-off test was performed. In the peel-off test, a cutter was made from the surface resin layer side at an angle of α = 45°. Next, adhesive tape was applied from above the surface resin layer in a direction perpendicular to the cut, and it was peeled off quickly at an angle of β = approximately 60°. Whether it was cohesive failure or interfacial failure was determined by observation with an optical microscope. Figure 6A is a schematic cross-sectional view showing a peel-off test of a graphic sheet in one embodiment of the present invention, and Figure 6B is a schematic cross-sectional view showing cohesive failure. Figure 7A is a schematic cross-sectional view showing a peel-off test of a conventional graphic sheet, and Figure 7B is a schematic cross-sectional view showing interfacial failure. • Evaluation criteria for peel-off tests ○: The adhesive tape peeled off smoothly from the surface resin layer, and there were no abnormalities. △: The ink receiving layer undergoes cohesive failure, resulting in peeling or lifting. ×: The surface resin layer and the ink layer undergo interfacial fracture, resulting in peeling or lifting. <Color measurement evaluation> In accordance with JIS Z 8781-4:2013, L is measured according to the CIE color difference formula specified by the International Commission on Illumination. * The value was calculated. Note that L * The value represents the brightness of a color on a scale of 0 to 100, with values ​​closer to 0 indicating darker colors and values ​​closer to 100 indicating brighter colors. The measurements were performed using a portable spectrophotometer manufactured by X-Rite, product name "eXact Advanced". This spectrophotometer "eXact Advanced" has an optical system with an illumination angle of 45 degrees and a reception angle of 0 degrees, measures with a measurement diameter of 2.0 mm, and can measure in multiple color spaces such as CIE L*a*b*, CIE L*C*h°, and CIE XYZ. When determining the L* value, CIE L*a*b* was used, with a D65 light source / observer field of view angle of 2 degrees, and measurements were performed using no M0(No) filter for color-related values.

[0051] [Common materials] <Surface resin layer> (1) Aliphatic polycarbonate urethane resin solution "Rezamin D-6300" (product name) [manufactured by Dainichi Seika Kogyo Co., Ltd.] (solids content 30%) 80.0 parts (2) Polymer-based UV absorber "XL07-0016" (product name) [manufactured by Lion Specialty Chemicals] (solids content 32%) 20 parts (3) Urethane resin "SN Thickener A-812" (product name) [manufactured by Sunopco] (solids content 100%) 0.2 parts (4) Acetylene glycol resin "Orphine E-1004" (product name) [manufactured by Nisshin Chemical Industry Co., Ltd.] (solids content 100%) 0.5 parts <Ink underlayer> I. Composition of Alkyd Melamine Resin Solution (1) Alkyd resin solution "Beckolite CF-743-50" (product name) [manufactured by DIC Corporation] (solids content 50%) 46 parts (2) Vinyl chloride vinyl acetate copolymer resin solution (solid content 25%) 27 parts (3) Leveling agent (solid content 0.05%) 0.06 parts (4) Plasticizer "Polysizer W-2310" (product name) [manufactured by DIC Corporation] (solids content 99%) 1.3 parts (5) Epoxy of fatty acid glycerides "A-130P" (trade name) [manufactured by ADEKA] (solids content 100%) 0.3 parts (6) Antioxidant "EVERNOX-10" (product name) [manufactured by EVERSPRING CHEMICAL CO.,LTD.] (solids content 100%) 0.15 parts (7) UV absorber "Dislizer E" (product name) [manufactured by Sankyo Kasei Co., Ltd.] (solid content 100%) 1.1 parts (8) Methylated melamine resin (60% solids) 8.4 parts (9) Butylated melamine resin (60% solids) 4.2 parts (10) 0.15 parts of alkyl acid phosphate ester (60% solids content) as a catalyst II. Composition of Alkyd Isocyanate-Based Transparent Resin Solutions (1) Alkyd resin solution "Beckolite CF-743-50" (product name) [manufactured by DIC Corporation] (solids content 50%) 46 parts (2) Vinyl chloride vinyl acetate copolymer resin solution (solid content 25%) 27 parts (3) Leveling agent (0.03% solids, 0.06 parts) (4) Plasticizer "Polysizer W-2310" (product name) [manufactured by DIC Corporation] (solids content 99%) 1.3 parts (5) Fatty acid phosphate epoxy "A-130P" (product name) [Manufactured by ADEKA Corporation] (100% solids) 0.3 parts (6) Antioxidant "EVERNOX-10" (product name) [manufactured by EVERSPRING CHEMICAL CO.,LTD.] (100% solids) 0.15 parts (7) UV absorber "Dislizer E" (product name) [manufactured by Sankyo Kasei Co., Ltd.] (100% solids) 1.1 parts (8) Isocyanate-based curing agent "Barnock DN-950" (product name) [manufactured by DIC Corporation] 11.3 parts Furthermore, the ink underlayer may be made into a white resin by containing 4.0 parts of titanium dioxide paste. <Adhesive layer> (1) Acrylic resin "Acryset AST-8207" (product name) [manufactured by Nippon Shokubai Co., Ltd.] (solids content 35%) 100 units (2) 10 parts ethyl acetate as solvent (3) 20 units of toluene (4) Titanium dioxide "Titanium Paste E" (product name) [manufactured by Nippon Shokubai Co., Ltd.] 10 units as a white coloring agent (5) 0.01 part of alicyclic epoxy resin curing agent "TETRAD-C" (product name) [manufactured by Mitsubishi Gas Chemical Company] as a curing agent.

[0052] (Example 1) <Surface resin layer> A polycarbonate-based urethane transparent resin solution was applied by casting onto a 50 μm thick polyester film "CM50" (product name) [manufactured by Nakamoto Pax Co., Ltd.], which is a process substrate film, so that the thickness after drying would be 25 μm. The film was then heated and dried under normal pressure at 70°C for 50 seconds, 100°C for 50 seconds, 120°C for 1 minute and 40 seconds, and 100°C for 50 seconds in that order to form a surface resin layer. The thickness was 25 μm. <Print receiving layer> A vinyl chloride-vinyl acetate resin solution (manufactured by Nisshin Chemical Industry Co., Ltd., trade name "Solvine C5R") was used on the aforementioned surface resin layer, diluted with toluene as a solvent to a solid concentration of 21% to prepare a casting solution, and a printable receiving layer was formed by the casting method. The thickness was 5 μm. <Print layer> A printed layer was formed on the aforementioned print-receiving layer by inkjet printing. <Ink underlayer> An alkyd melamine resin solution was applied to the printed layer by casting to a thickness of 20 μm after drying. The ink undercoat was then formed by heating and drying under normal pressure at 70°C for 2 minutes and 10 seconds, 100°C for 1 minute and 5 seconds, and 130°C for 2 minutes and 10 seconds in that order. The thickness was 20 μm. <Adhesive layer> A white adhesive solution A was applied by casting onto the release surface of a 38 μm thick polyester film ("Ester Film E7002 #38," manufactured by Toyobo Co., Ltd.) so that the thickness after drying would be 33 μm. An adhesive layer was then prepared by heating and drying under normal pressure at 70°C for 1 minute and then at 100°C for 2 minutes. The thickness was 33 μm. <Laminated bonding> The adhesive side of this adhesive layer was bonded to the ink base layer. After peeling the process substrate film from the surface resin layer, a protective film was bonded to the surface resin layer to obtain the graphic sheet body. The thickness of this graphic sheet body was 190 μm.

[0053] (Example 2) The procedure was carried out in the same manner as in Example 1, except that the alkyd melamine resin solution was replaced with an alkyd isocyanate resin solution as the ink underlayer. The thickness of the graphic sheet itself was 190 μm.

[0054] (Example 3) As the print-receiving layer, vinyl chloride-vinyl acetate-vinyl alcohol resin (manufactured by Nisshin Chemical Industry Co., Ltd., trade name "Solvine A") was used, diluted with toluene as a solvent, and prepared as a casting solution with a solid concentration of 15%. The print-receiving layer was formed by the casting method. The thickness was 5 μm. The rest of the procedure was the same as in Example 1. The thickness of the graphic sheet itself was 190 μm.

[0055] (Example 4) The procedure was carried out in the same manner as in Example 3, except that the alkyd melamine resin solution was replaced with an alkyd isocyanate resin solution as the ink underlayer. The thickness of the graphic sheet itself was 190 μm.

[0056] (Example 5) As the print-receiving layer, a polyester-based polyurethane resin solution (manufactured by Dainichi Seika Kogyo Co., Ltd., product name "Rezamin NE-302HV") was used, diluted with toluene and isopropyl alcohol as solvents to a solid concentration of 10% to form a cast solution, and the print-receiving layer was formed by the casting method. The thickness was 5 μm. The rest of the procedure was the same as in Example 1. The thickness of the graphic sheet itself was 190 μm.

[0057] (Example 6) The procedure was carried out in the same manner as in Example 5, except that the alkyd melamine-based white resin solution was replaced with an alkyd isocyanate-based white resin solution as the ink underlayer. The thickness of the graphic sheet itself was 190 μm.

[0058] (Example 7) As the print-receiving layer, a polyester-based polyurethane resin solution (DIC Corporation, product name "Hydran APX-101H") was used, diluted with water as the solvent to a solid concentration of 40% to form a cast solution, and the print-receiving layer was formed by the casting method. The thickness was 5 μm. The rest of the procedure was the same as in Example 1. The thickness of the graphic sheet itself was 190 μm.

[0059] (Example 8) The procedure was carried out in the same manner as in Example 7, except that the alkyd melamine-based white resin solution was replaced with an alkyd isocyanate-based white resin solution as the ink underlayer. The thickness of the graphic sheet itself was 190 μm.

[0060] (Comparative Example 1) The procedure was carried out in the same manner as in Example 1, except that a print receiving layer was not provided.

[0061] (Comparative Example 2) The procedure was carried out in the same manner as in Example 2, except that a print receiving layer was not provided. The above conditions and results are summarized in Tables 1-6.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] [Table 4]

[0066] [Table 5]

[0067] [Table 6]

[0068] In Tables 3-6 above, the L* values ​​indicated by an "x" or a gray background correspond to the areas where adhesion delamination occurred due to interfacial fracture. When printing in magenta monochrome, in the comparative example, peeling occurs due to interfacial failure at L*68 or below. However, depending on the settings of the ink receiving layer, peeling does not occur at L*68 or below but above 50, and peeling occurs due to cohesive failure even at L*49 or below. Furthermore, if a more preferable ink receiving layer is set, peeling does not occur even at L*49 or below. Similarly, in the case of yellow, in the comparative example, peeling occurs due to interfacial fracture when L*87 or lower, but peeling does not occur when L*87 or lower depending on the setting of the ink receiving layer. Similarly, in the case of orange, in the comparative example, peeling occurs due to interfacial failure when L*86 or less, but depending on the setting of the ink receiving layer, peeling does not occur when L*86 or less but above 71, and peeling occurs due to cohesive failure even when L*70 or less. Furthermore, if a more preferable ink receiving layer is set, peeling does not occur even when L*70 or less.

[0069] (Example 9) Adhesion was evaluated under the conditions of Example 1 when the thickness of the receiving layer was varied. Specifically, the evaluation was performed using PVC-vinyl acetate (solvine C5R) as the ink receiving layer material and alkyd melamine as the ink underlayer. The results are shown in Table 7.

[0070] [Table 7]

[0071] As is clear from the results above, it was confirmed that Examples 1-9 are graphic sheets in which the printed layer does not peel off or the printed layer undergoes cohesive failure in the peel-off test. [Industrial applicability]

[0072] The graphic sheet of the present invention can be used as a vehicle license plate, as well as as a decorative film or sheet for signs, automobiles, buildings, and the like. [Explanation of symbols]

[0073] 1. Graphics sheet 2 Surface resin layer 3. Ink receiving layer 4 printing layer 5. Ink underlayer 6 Adhesive layer 7. Protective film 8 Release film 9-Step Substrate Film 10 Graphic Sheets with Protective Film 11 License plate 12 base plate 13. Ink layer for symbols 14a,14b Chromatic image part EY Viewing Direction

Claims

1. It includes a surface resin layer, an ink receiving layer, a printing layer, an ink underlay layer, and an adhesive layer in this order. The ink receiving layer is at least one selected from the group consisting of vinyl chloride-vinyl acetate-vinyl alcohol resin, vinyl chloride-vinyl acetate-hydroxyacrylate resin, vinyl chloride-vinyl acetate resin, and polyester-based polyurethane resin. The printing layer is an inkjet printing layer, A graphic sheet in which, when cut at a 45° angle from the surface resin layer and subjected to a peel-off test, the printed layer does not peel off from the ink receiving layer or the printed layer undergoes cohesive failure.

2. The graphic sheet according to claim 1, wherein the thickness of the ink receiving layer is 0.1 to 30 μm.

3. The graphic sheet according to claim 1 or 2, wherein the surface resin layer is at least one selected from the group consisting of urethane resin, alkyd resin, acrylic resin, and polyvinyl chloride resin.

4. The graphic sheet according to claim 3, wherein the urethane resin is one selected from the group consisting of a water-based polycarbonate-based urethane resin, a water-based polyether-based urethane resin, and a water-based polyester-based urethane resin.

5. The graphic sheet according to claim 1 or 2, wherein the surface resin layer, ink receiving layer, printing layer, ink underlayer layer, and adhesive layer are a transparent resin or a resin containing any colored pigment.

6. The graphic sheet according to claim 1 or 2, wherein the thickness of the graphic sheet is 300 μm or less.

7. The aforementioned printed layer is made in accordance with JIS Z 8781-4:2013, using the CIE color difference formula specified by the International Commission on Illumination. * A graphic sheet according to claim 1 or 2, wherein an image is formed that includes chromatic colors with values ​​from 0 to 85.

8. The graphic sheet according to claim 1 or 2, wherein the graphic sheet is a sheet for a vehicle's license plate.

9. A graphic sheet with a protective film, wherein a protective film is attached to the outer surface of the surface resin layer and a release film is attached to the outer surface of the adhesive layer, according to claim 1 or 2.

10. A method for manufacturing a graphic sheet with a protective film according to claim 9, A surface resin layer is formed on the surface of the substrate film for process A by casting, B. An ink receiving layer is formed on the surface of the surface resin layer by a casting method. C. A printed layer is formed on the surface of the ink receiving layer by inkjet printing. D. An ink underlayer is formed on the surface of the ink receiving layer and the printing layer by a casting method, and E. An adhesive layer is formed on the surface of a separately prepared release film by a casting method. F The adhesive layer is attached to the surface of the ink base layer. G A method for manufacturing a graphic sheet with a protective film, comprising the step of peeling off the substrate film for the process and laminating a protective film onto the surface resin layer.

11. A method for using a graphic sheet with a protective film as described in claim 9, The graphic sheet with the protective film is attached to the base plate. Create a symbol by embossing or debossing. Remove the protective film, A method of using a graphic sheet to create a license plate by placing a layer of symbol ink on top of the aforementioned symbols and then attaching the graphic sheet.

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