Adhesive film

Abstract

To provide an adhesive film which is excellent in adhesion of a printing layer.SOLUTION: An adhesive film 10 has a base material 11 and an adhesive layer 12 laminated on one surface of the base material 11, wherein the base material 11 is formed of a polyurethane resin containing a silane coupling agent. On a surface opposite to the adhesive layer 12 of the base material 11, a printing layer 15 can be formed. Onto a surface opposite to the base material 11 of the adhesive layer 12, an adherend 20 can be bonded.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an adhesive film.

Background Art

[0002] Adhesive films are used for purposes such as protecting the surface of an article or decorating the surface. For example, Patent Document 1 describes that a decorative molding film obtained by laminating an adhesive layer formed from an acrylic adhesive on a polyvinyl chloride film as a base material can flexibly follow even a three-dimensional curved surface.

[0003] Further, Patent Document 2 describes that in an adhesive sheet for sticking on the surface of a painted steel sheet of an automobile, the base material includes a hard layer made of a polycarbonate-based polyurethane and a soft layer made of a polyester-based polyurethane, and the adhesive layer is formed from an acrylic adhesive having a carboxyl group-containing ethylenically unsaturated monomer or the like as a copolymerization component.

[0004] Also, Patent Document 3 describes a thin film marking sheet in which an adhesive layer is laminated on one surface of a base material made of an unstretched film of a polyester-based or polycarbonate-based polyurethane resin, and a decorative display layer is provided on the other surface of the base material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] Adhesive films used on the surface of articles may be decorated by printing on the substrate. Patent Document 1 describes that by adding a plasticizer to polyvinyl chloride film, it becomes stretchable, which facilitates adhesion to three-dimensional curved surfaces, and has excellent printability for decorative molding. However, because organochlorine compounds are used, the applications may be limited.

[0007] Patent Document 2 describes applying an adhesive sheet to protect the vehicle body from chipping, a phenomenon in which objects such as pebbles are thrown up and damage the vehicle body, but it does not describe applying printing or other modifications to the adhesive sheet. Patent Document 3 describes forming a decorative display layer on the other side of the substrate by metal deposition, printing, foil stamping, etc., and states that it is preferable to apply a transparent resin on top of the decorative display layer to form a protective layer (top coat clear layer).

[0008] Forming a protective layer on top of the printed layer can effectively suppress peeling of the printed layer. However, the process of forming the protective layer is complicated. Also, depending on the type of article, the process of applying a transparent resin may not be easily carried out. To improve the adhesion of the printed layer to the substrate, it is conceivable to apply an easy-adhesion layer, such as a primer, to the surface on the substrate where the printed layer is formed. However, the process of forming an easy-adhesion layer is complicated. Also, depending on the type of article, the process of forming an easy-adhesion layer may not be easily carried out.

[0009] This invention has been made in view of the above circumstances, and aims to provide an adhesive film with excellent adhesion of the printed layer. [Means for solving the problem]

[0010] To solve the aforementioned problems, the present invention provides an adhesive film comprising a base material and an adhesive layer laminated on one side of the base material, wherein the base material is made of a polyurethane resin containing a silane coupling agent.

[0011] The content of the silane coupling agent in the substrate may be 0.1 to 2 parts by weight per 100 parts by weight of the polyurethane resin. More preferably, it may be 0.2 to 1.0 part by weight. The silane coupling agent comprises a first silane coupling agent having an epoxy group as an organic functional group, and a second silane coupling agent having an acrylic group as an organic functional group, wherein the weight ratio of the first silane coupling agent to the second silane coupling agent may be 0.5:1 to 1:0.5, or 0.7:1 to 1:0.7.

[0012] The polyurethane resin may be crosslinked with a crosslinking agent. The polyurethane resin may be a polycarbonate-based polyurethane. A cover film may be provided on the side of the substrate opposite to the adhesive layer. A printed layer may be formed on the surface of the substrate opposite to the adhesive layer. The adhesive layer may have a release film on the side opposite to the substrate. The glass to be adhered may be bonded to the side of the adhesive layer opposite to the substrate. [Effects of the Invention]

[0013] According to the present invention, the adhesion of the printed layer can be improved. [Brief explanation of the drawing]

[0014] [Figure 1] This is a cross-sectional view showing an example of an adhesive film. [Figure 2] This is a cross-sectional view showing an example of an object to which an adhesive film has been laminated. [Modes for carrying out the invention]

[0015] The present invention will be described below based on preferred embodiments.

[0016] Fig. 1 shows an example of an adhesive film. The adhesive film 10 includes a base material 11 and an adhesive layer 12 laminated on one side of the base material 11. The surface of the base material 11 opposite to the adhesive layer 12 is a decorative surface 11a that can be decorated by printing or the like. The surface of the adhesive layer 12 opposite to the base material 11 is an adhesive surface 12a that can be adhered to an article or the like.

[0017] The base material 11 is formed from a polyurethane resin containing a silane coupling agent. Thereby, even when the decorative surface 11a is decorated by printing or the like, the adhesion of the decoration to the base material 11 can be improved.

[0018] The polyurethane resin is not particularly limited as long as it is a resin mainly composed of a reaction product of a polyol and a polyisocyanate, and can be appropriately selected from known polyurethane resins and used. The base material 11 may contain one kind of polyurethane resin, or may contain two or more kinds of polyurethane resins.

[0019] Examples of the polyol include alkylene glycol, dialkylene glycol, polyalkylene glycol, polyether polyol, polyurethane polyol, polyester polyol, polycarbonate polyol, lactone polyol, etc. The polyol may be a diol having two hydroxyl groups in one molecule, or a triol having three hydroxyl groups in one molecule. The polyol may have four or more hydroxyl groups.

[0020] The polyisocyanate may be a diisocyanate having two isocyanate groups in one molecule, or a triisocyanate having three isocyanate groups in one molecule. The polyisocyanate may have four or more isocyanate groups. Examples of the diisocyanate include aromatic diisocyanates such as tolylene diisocyanate (TDI) and xylylene diisocyanate (XDI), and aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), and isophorone diisocyanate (IPDI).

[0021] A linear polyurethane resin can be obtained by reacting at least one diol with at least one diisocyanate. A crosslinked polyurethane resin can be obtained by using a compound having three or more hydroxyl groups per molecule as at least a part of the polyol, or by using a compound having three or more isocyanate groups per molecule as at least a part of the polyisocyanate. Using a crosslinked polyurethane resin can improve the mechanical strength and durability of the substrate 11, even in the case of adhesive films 10 that require mechanical strength and durability, such as shatterproof films.

[0022] A polyurethane resin having unreacted hydroxyl groups relative to isocyanate groups can be crosslinked by reacting it with polyisocyanate as a crosslinking agent. A polyurethane resin having isocyanate groups can also be crosslinked by reacting it with polyol as a crosslinking agent. The crosslinking agent for the polyurethane resin is not limited to polyisocyanate or polyol; any suitable crosslinking agent capable of reacting with functional groups such as hydroxyl groups and isocyanate groups of the polyurethane resin may be used. The ratio of the crosslinking agent can be set as appropriate, but for example, 5 to 20 parts by weight of the crosslinking agent per 100 parts by weight of the polyurethane resin is a good example. Any of the above polyurethane resins can be used, but polycarbonate-based polyurethane may also be used. In that case, there is the advantage of relatively superior durability.

[0023] The thickness of the substrate 11 is not particularly limited, but for example, it can be about 30 to 150 μm. The thickness of the substrate 11 is more preferably 100 μm or less, and even more preferably 80 μm or less. The method for forming the substrate 11 is not particularly limited, and can be inflation molding, extrusion molding, solution casting, hot pressing, calendering, cutting, etc.

[0024] For example, when forming the substrate 11 by solution casting, the polyurethane resin dissolved in a solvent can be applied to a predetermined coating surface, and then the solvent can be dried to form a film of polyurethane resin. The solvent is not particularly limited, but examples include hydrocarbon solvents such as toluene and cyclohexane; alcohol solvents such as methanol, ethanol, and isopropyl alcohol; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; and ester solvents such as ethyl acetate.

[0025] After forming a film of a thermoplastic or solvent-soluble polyurethane resin, the polyurethane resin may be crosslinked by reacting it with a crosslinking agent added to the polyurethane resin. This makes it easier to achieve both processability suitable for forming the base material 11 and durability suitable for the application of the base material 11.

[0026] From the viewpoint of durability against moisture, etc., it is preferable to use a polycarbonate-based or polyether-based polyurethane resin with low hydrolysis properties. From the viewpoint of coating properties and productivity in solution casting, etc., the weight-average molecular weight (Mw) of the polyurethane resin before crosslinking is preferably about 10,000 to 100,000, and may also be about 25,000 to 60,000. The gel fraction of the polyurethane resin after crosslinking is preferably about 50 to 90%, and preferably about 70 to 80%.

[0027] The substrate 11 of the embodiment contains a silane coupling agent. (C) Examples of silane coupling agents include compounds having at least one organic functional group and at least one hydrolyzable group in one molecule. Examples of hydrolyzable groups include alkoxy groups such as methoxy groups and ethoxy groups bonded to a silicon atom. Examples of organic functional groups include epoxy groups, acryloxy groups, methacryloxy groups, vinyl groups, amino groups, isocyanate groups, and acid anhydride groups. In the following description, acryloxy groups or methacryloxy groups may be collectively referred to as (meth)acryloxy groups.

[0028] Examples of silane coupling agents having an epoxy group include 3-glycidoxypropyltrialkoxysilane, 3-glycidoxypropylmethyldialkoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrialkoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldialkoxysilane, 5,6-epoxyhexyltrialkoxysilane, and 5,6-epoxyhexylmethyldialkoxysilane.

[0029] Examples of silane coupling agents having a (meth)acryloxy group include 3-(meth)acryloxypropyltrialkoxysilane, 3-(meth)acryloxypropylmethyldialkoxysilane, and 3-(meth)acryloxypropyldimethylalkoxysilane. Examples of silane coupling agents having a vinyl group include vinyltrialkoxysilane and p-styryltrialkoxysilane.

[0030] Examples of silane coupling agents having an amino group include 3-aminopropyltrialkoxysilane, 3-(phenylamino)propyltrialkoxysilane, 3-(2-aminoethylamino)propyltrialkoxysilane, and 3-(2-aminoethylamino)propylmethyldialkoxysilane. Examples of silane coupling agents having an isocyanate group include 3-isocyanatetopropyltrialkoxysilane and 3-isocyanatetopropylmethyldialkoxysilane. Examples of silane coupling agents having an acid anhydride group include 3-(trialkoxysilyl)propyl succinic anhydride and 3-(methyldialkoxysilyl)propyl succinic anhydride.

[0031] The proportion of the silane coupling agent can be set as appropriate, but for example, 0.1 to 2 parts by weight of the silane coupling agent per 100 parts by weight of the polyurethane resin is a possible ratio. The base material 11 may contain two or more types of silane coupling agents. In that case, the total amount of the two or more types of silane coupling agents may be 0.1 to 2 parts by weight per 100 parts by weight of the polyurethane resin. The organic functional group of the silane coupling agent is preferably selected according to the type of resin contained in the printing ink.

[0032] The silane coupling agents having epoxy groups, and the silane coupling agents having amino groups, ureido groups, and / or isocyanurate groups, are relatively effective in improving the adhesion of thermosetting inks. Furthermore, the silane coupling agents having (meth)acryloxy groups, and the silane coupling agents having vinyl groups, are relatively effective in improving the adhesion of UV-curing inks.

[0033] The silane coupling agent may include a first silane coupling agent having an epoxy group as an organic functional group, and a second silane coupling agent having an acrylic group as an organic functional group. In this case, adhesion to both thermosetting inks and UV-curing inks can be improved, increasing versatility. The weight ratio of the first silane coupling agent to the second silane coupling agent may be 0.5:1 to 1:0.5. In this case, it is possible to improve adhesion to both thermosetting inks and UV-curing inks in a well-balanced manner. The weight ratio of the first silane coupling agent to the second silane coupling agent may be 0.7:1 to 1:0.7.

[0034] The substrate 11 may contain additives such as colorants, stabilizers, antioxidants, and flame retardants as needed. If no colorants or other additives are added to the substrate 11, it can be given high transparency. Examples of the transparency of the substrate 11 include a total light transmittance of 90% or more and a haze of 2% or less.

[0035] The adhesive layer 12 is formed from an adhesive. The adhesive is not particularly limited and can be appropriately selected from known adhesives depending on the article to which the adhesive film 10 is bonded. The adhesive layer 12 may be laminated so as to be in contact with the substrate 11. Other layers may be interposed between the substrate 11 and the adhesive layer 12. From the viewpoint of transparency, weather resistance, etc., examples include acrylic adhesives and polyester adhesives.

[0036] Examples of acrylic adhesives include adhesives using acrylic polymers copolymerized with main monomers such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and isononyl acrylate, and comonomers such as acrylonitrile, vinyl acetate, methyl methacrylate, and ethyl acrylate, or with functional monomers such as acrylic acid, methacrylic acid, hydroxyethyl acrylate, hydroxybutyl acrylate, glycidyl methacrylate, and N-methylol methacrylamide. To improve the adhesive strength of the acrylic polymer, crosslinking agents such as polyisocyanate compounds, polyfunctional epoxy compounds, polyfunctional epoxy compounds, and metal chelate compounds may be used.

[0037] Polyester adhesives include those using polyester polymers obtained by polycondensation of polycarboxylic acids such as dicarboxylic acids and polyols such as diols. Examples of dicarboxylic acids include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. Examples of diols include alkylene glycol, dialkylene glycol, polyalkylene glycol, and polyether glycol. To improve the adhesive strength of the polyester polymer, crosslinking agents such as polyisocyanate compounds, polyfunctional epoxy compounds, and metal chelate compounds may be used.

[0038] The method for forming the adhesive layer 12 is not particularly limited, but an adhesive composition containing an adhesive (polymer) and a crosslinking agent may be applied to the substrate 11, and then the adhesive may be crosslinked with the crosslinking agent by curing (aging) to form the adhesive layer 12. The ratio of the crosslinking agent can be set as appropriate, but for example, 1 to 10 parts by weight of the crosslinking agent per 100 parts by weight of the adhesive is a possible ratio. The adhesive may also be applied to a sheet other than the substrate 11, dried, and then the adhesive layer 12 may be transferred onto the substrate 11. Other layers may be interposed between the substrate 11 and the adhesive layer 12, and the substrate 11 and the adhesive layer 12 may be in contact with each other.

[0039] The thickness of the adhesive layer 12 is not particularly limited, but for example, it can be about 10 to 50 μm. The adhesive layer 12 may have tackiness at room temperature (in the range of 5 to 35°C), or it may have tackiness at temperatures higher than room temperature.

[0040] The thickness of the adhesive film 10, which includes the base material 11 and the adhesive layer 12, is not particularly limited, but for example, it can be about 40 to 200 μm. Here, the thickness of the adhesive film 10 does not include the thickness of the cover film 13 and release film 14 described below. The thickness of the adhesive film 10 is more preferably 100 μm or less.

[0041] To protect the decorated surface 11a, the adhesive film 10 may have a cover film 13 on the side opposite to the adhesive layer 12 of the substrate 11. The cover film 13 is not particularly limited, but can be made of polyester resin film, polyamide resin film, acrylic resin film, polyolefin resin film, cellulose resin film, cellophane film, paper, resin laminated paper, metal foil, resin laminated metal foil, metal vapor-deposited resin film, etc.

[0042] The cover film 13 may be opaque or semi-transparent, but a highly transparent cover film 13 is preferable because the condition of the decorated surface 11a can be easily checked visually without removing the cover film 13. The cover film 13 may be an unstretched resin film or a stretched resin film. The cover film 13 may have a layer of a release agent, such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl-based release agent, on the side that contacts the decorated surface 11a. The cover film 13 does not need to have a release agent on the side that contacts the decorated surface 11a.

[0043] To protect the adhesive surface 12a, the adhesive film 10 may have a release film 14 on the side of the adhesive layer 12 opposite to the substrate 11. The release film 14 is not particularly limited, but can be made from polyester resin film, polyamide resin film, acrylic resin film, polyolefin resin film, cellulose resin film, cellophane film, paper, resin laminated paper, metal foil, resin laminated metal foil, metal vapor-deposited resin film, etc.

[0044] The release film 14 may be opaque or semi-transparent, but a highly transparent release film 14 is preferable because the condition of the adhesive surface 12a can be easily checked visually without removing the release film 14. The release film 14 may be an unstretched resin film or a stretched resin film. The release film 14 may have a layer of release agent such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl-based release agent on the side that contacts the adhesive surface 12a. The release film 14 may not have a release agent on the side that contacts the adhesive surface 12a.

[0045] Figure 2 shows an example of a substrate 20 to which an adhesive film 10 is laminated. A printed layer 15 is formed on the base material 11, and the substrate 20 is laminated to the adhesive layer 12. The order of the steps of forming the printed layer 15 on the base material 11 and laminating the substrate 20 to the adhesive layer 12 is not limited, but it is preferable to form the printed layer 15 on the base material 11 first, and then laminate the substrate 20 to the adhesive layer 12. The process may also include a step of cutting the adhesive film 10 to a size suitable for the substrate 20. It is preferable to print on the base material 11 before cutting the adhesive film 10.

[0046] Since the decorative surface 11a of the adhesive film 10 is formed from the base material 11 described above, the printed layer 15 can be easily attached without the need to provide an easy-adhesion layer such as a primer. If a cover film 13 is provided to protect the decorative surface 11a, the cover film 13 is removed before printing. After forming the base material 11, the printed layer 15 may be formed without providing a cover film 13 on the decorative surface 11a.

[0047] The method for forming the printed layer 15 is not particularly limited, but examples include gravure printing, letterpress printing, offset printing, screen printing, and inkjet printing. The printed layer 15 may be formed over the entire surface of the decorative surface 11a, or it may be formed over a portion of the decorative surface 11a. Two or more printed layers 15 may be stacked on top of each other. Different printed layers 15 may be formed in different areas of the decorative surface 11a. Decorations other than the printed layer 15 may be applied to the decorative surface 11a. Examples of other decorative layers include metal vapor deposition layers by sputtering, etc.

[0048] The ink for forming the printed layer 15 may contain a coloring agent such as a pigment or dye, and a binder. The binder is not particularly limited, but examples include polyamide resin, polyurethane resin, polyester resin, polyvinyl chloride resin, polyvinyl acetate resin, acrylic resin, epoxy resin, polybutadiene resin, and cyclocompound rubber. The ink may also contain a solvent such as water, an organic solvent, or a vegetable oil. After printing, the ink can be dried by the evaporation of the solvent or the curing of the ink. Heating or ultraviolet irradiation may be performed to accelerate the drying of the ink.

[0049] Before the adhesive film 10 is bonded to the substrate 20, the release film 14 is removed from the adhesive layer 12. This allows the adhesive film 10 to be bonded to the substrate 20 via the adhesive layer 12. The substrate 20 may be an electronic device with a glass display surface, housing, etc. The material of the surface of the substrate 20 that comes into contact with the adhesive layer 12 is not particularly limited, but examples include glass, metal, and plastic. The substrate 20 is not limited to articles with a flat surface to which the adhesive film 10 is bonded, but may also be an article with a curved surface.

[0050] The method for laminating the adhesive film 10 to the adherend 20 is not particularly limited, but it is sufficient to make the adhesive layer 12 adhere to the adherend 20 by using pressure, suction, etc. The pressure method may be a mechanical method such as a roll member, a rod-shaped member, or a plate-shaped member, or it may be a pressure medium method using a fluid such as a liquid or gas. It is preferable to temporarily attach the adhesive film 10 to the adherend 20 and then apply pressure from the surrounding liquid to pressurize it isotropically. The pressure medium may be warm water. As for the suction method, one example is a method that uses a vacuum to suck the air between the adhesive film 10 and the adherend 20.

[0051] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. [Examples]

[0052] The present invention will be specifically described below with reference to examples.

[0053] (Example 1) A polyurethane solution containing 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Dainichi Seika Kogyo Co., Ltd., trade name Diferamine® MAU8288A, weight-average molecular weight 50,000), 10 parts by weight of a TDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate® L-45E) as a crosslinking agent, and 0.2 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-403) and 0.2 parts by weight of 3-acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-5103) as silane coupling agents was used to form a 60 μm thick film by solution casting to prepare the substrate of Example 1.

[0054] (Examples 2 and 3) The substrates for Examples 2 and 3 were prepared using the same manufacturing method as in Example 1, but with only the amount of each silane coupling agent added changed as shown in Table 1.

[0055] (Example 4) A polyurethane solution containing 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Tosoh Corporation, trade name Nipponan® 5199, weight-average molecular weight 30,000), 4 parts by weight of an HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate® LHX) as a crosslinking agent, and 0.5 parts by weight of 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-403) and 0.5 parts by weight of 3-acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-5103) as silane coupling agents was used to form a 60 μm thick film by solution casting to prepare the substrate for Example 4.

[0056] (Examples 5 and 6) Using the same manufacturing method as in Example 1, the substrates for Examples 5 and 6 were prepared by using only 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-403) as the silane coupling agent, and by changing the amount of additive as shown in Table 1.

[0057] (Examples 7 and 8) The substrates for Examples 7 and 8 were prepared using the same manufacturing method as in Example 1, but with only 3-acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name KBM-5103) used as the silane coupling agent, and with the addition amount changed to that shown in Table 1.

[0058] (Comparative Example 1) Without adding a silane coupling agent to the polyurethane solution, a polyurethane solution containing 100 parts by weight of the above-mentioned polycarbonate-based polyurethane resin and 10 parts by weight of a crosslinking agent was used to form a 60 μm thick film by solution casting, thereby producing the substrate for Comparative Example 1.

[0059] (Comparative Example 2) A commercially available thermoplastic polyurethane elastomer (TPU) film (manufactured by Okura Industries Co., Ltd., product name: Silklon® SNY97, thickness 80 μm) was cut to the specified dimensions to prepare the substrate for Comparative Example 2.

[0060] (Evaluation method) UV-curing ink (acrylic) and thermosetting ink (epoxy) were used to print on different areas of the same substrate. For the UV-curing ink (acrylic), Fujikura Chemicals Co., Ltd., product name: VB2979U, was used. The evaluation ink concentrate was applied to a 25 μm thick release film to a dry thickness of 5 μm, and dried at 120°C for 1 minute. The dried printed layer was laminated to the urethane surface of the substrate, and a metal halide lamp (cumulative light intensity 1000 mJ / cm²) was used from the urethane side. 2 The material was irradiated with UV light. After curing, the release film was peeled off to form the printed layer.

[0061] For the thermosetting ink (epoxy type), we used RUX-710 Black, manufactured by Seiko Advance Co., Ltd. 100 parts by weight of the undiluted ink was mixed with 2 parts by weight of RUX hardener, also manufactured by Seiko Advance Co., Ltd. The mixture was stirred until uniform, and then degassed under reduced pressure to prepare the evaluation ink. This evaluation ink was applied to a urethane surface to a dry thickness of 5 μm and dried at 80°C for 10 minutes.

[0062] Next, the initial adhesion of the substrates immediately after the two types of printing described above was evaluated according to the grid test method specified in JIS K5400 as follows. 100 cuts were made on the surface of each printed layer based on the grid test method, and cellophane adhesive tape was attached to the surface of the cut printed layer in a length of approximately 50 mm. The tape was then rubbed with an eraser to adhere it to the printed layer. One to two minutes after the tape was attached, the end of the tape was held perpendicular to the printed layer surface and instantly peeled off, and the number of squares from which the print had peeled off was counted. If the number of squares from which the print peeled off out of 100 squares was A according to the grid test method immediately after printing, it was recorded as "A / 100" in Table 2.

[0063] For adhesion after the hot water test, printed materials were prepared by printing on a substrate in the same manner as for initial adhesion. These materials were then immersed in 80°C hot water for 30 minutes, and the substrates removed from the hot water were tested for peeling of the printed layer using the aforementioned grid test method.

[0064] (Evaluation results) Table 2 shows the evaluation results for the substrates of Examples 1-8 and Comparative Examples 1-2.

[0065] [Table 1]

[0066] [Table 2]

[0067] As shown in Table 2, regarding initial adhesion, no peeling occurred in the UV-curing ink and thermosetting ink printing layers on any of the substrates in Examples 1-8 and Comparative Examples 1-2. In the substrates of Examples 1 to 4, no peeling occurred in either the UV-curing ink or the thermosetting ink printing layer, even after the hot water test. In the substrates of Examples 5 and 6, the UV-curing ink print layer peeled off completely after the hot water test. In the substrate of Example 5, the thermocuring ink print layer did not peel off even after the hot water test, but in the substrate of Example 6, which contained less silane coupling agent, the thermocuring ink print layer peeled off slightly after the hot water test. In the substrates of Examples 7 and 8, the printed layer of the thermocuring ink peeled off completely after the hot water test. In the substrate of Example 7, the printed layer of the UV-curing ink did not peel off even after the hot water test, but in the substrate of Example 8, which contained less silane coupling agent, the printed layer of the UV-curing ink peeled off slightly after the hot water test. In the substrates of Comparative Examples 1 and 2, complete delamination of all squares was observed in both the UV-curing ink and the thermosetting ink printing layers after the hot water test.

[0068] (Method of manufacturing adhesive film) An adhesive layer can be formed on one side of the substrate (60 μm thick) of Example 1 using a polyester-based adhesive or an acrylic-based adhesive. For example, an adhesive containing a crosslinking agent and a solvent may be applied to the substrate so that the thickness after drying is 20 μm, the solvent may be dried, and then the adhesive may be crosslinked by curing (aging). Examples 2 to 8 can also have adhesive layers formed in the same manner as Example 1. [Explanation of Symbols]

[0069] 10...Adhesive film, 11...Substrate, 11a...Decorative surface, 12...Adhesive layer, 12a...Adhesive surface, 13...Cover film, 14...Release film, 15...Printed layer, 20...Substrate.

Claims

1. An adhesive film comprising a base material and an adhesive layer laminated on one side of the base material, The substrate is made of a polyurethane resin containing a silane coupling agent. The silane coupling agent comprises a first silane coupling agent having an epoxy group as an organic functional group, and a second silane coupling agent having an acrylic group as an organic functional group, wherein the weight ratio of the first silane coupling agent to the second silane coupling agent is 0.5:1 to 1:0.

5. An adhesive film characterized in that the side of the substrate opposite to the adhesive layer is a printable decorative surface.

2. The adhesive film according to claim 1, characterized in that the content of the silane coupling agent in the substrate is 0.1 to 2 parts by weight per 100 parts by weight of the polyurethane resin.

3. The adhesive film according to claim 1 or 2, characterized in that the polyurethane resin is crosslinked with a crosslinking agent.

4. The adhesive film according to any one of claims 1 to 3, characterized in that the polyurethane resin is a polycarbonate-based polyurethane.

5. The adhesive film according to any one of claims 1 to 4, characterized in that it has a cover film on the surface of the substrate opposite to the adhesive layer.

6. The adhesive film according to any one of claims 1 to 4, characterized in that a printing layer is formed on the surface of the substrate opposite to the adhesive layer.

7. The adhesive film according to any one of claims 1 to 6, characterized in that the adhesive layer has a release film on the side opposite to the substrate.

8. The adhesive film according to any one of claims 1 to 6, characterized in that the glass of the adherend is bonded to the side of the adhesive layer opposite to the substrate.

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