Adhesive film

Abstract

The present application provides an adhesive film with excellent followability to a three-dimensional surface. The adhesive film (10) comprises a substrate (11) and an adhesive layer (12) laminated on one side of the substrate (11), the substrate (11) is formed of a polyurethane resin crosslinked by a crosslinking agent, the 50% stress of the laminate of the substrate (11) and the adhesive layer (12) is 10-29 MPa, the breaking stress is 30-69 MPa, the breaking elongation is 200-350%, and the initial adhesive force of the adhesive film (10) measured after the film is just attached to a glass of a bonded object (20) is 2 N / 25 mm or less.

Description

Technical Field

[0001] This invention relates to adhesive films. Background Technology

[0002] Adhesive films are used for purposes such as protecting the surface of an item or decorating its surface.

[0003] For example, Patent Document 1 describes a decorative molding film that can softly follow three-dimensional curved surfaces by using a polyvinyl chloride film as a substrate and laminating an adhesive layer formed by an acrylic adhesive.

[0004] In addition, Patent Document 2 describes an adhesive sheet for attaching to the surface of a painted steel sheet of an automobile, wherein the substrate comprises a rigid layer formed of polycarbonate polyurethane and a soft layer formed of polyester polyurethane, and the adhesive layer is formed of an acrylic adhesive with a copolymer component such as an olefin unsaturated monomer containing a carboxyl group.

[0005] In addition, Patent Document 3 describes a thin film marking sheet, which has an adhesive layer laminated on one side of a substrate formed of a non-stretchable film of polyester or polycarbonate polyurethane resin, and a decorative display layer provided on the other side of the substrate.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 6577380

[0009] Patent Document 2: Japanese Patent No. 4886969

[0010] Patent Document 3: Japanese Patent Application Publication No. 2003-295769 Summary of the Invention

[0011] Technical issues

[0012] Regarding adhesive films used on the surface of articles, decoration is sometimes applied by printing on the substrate. Patent Document 1 describes a method that, by adding a plasticizer to a polyvinyl chloride film, achieves excellent elongation and printability for decorative molding, facilitating adhesion to three-dimensional curved surfaces. However, the use of organochlorine compounds may limit its applications.

[0013] In Patent Document 2, there is a record of attaching adhesive sheets to a three-dimensional curved surface to protect the car body from chipping caused by small stones or other objects bouncing up, but there is no record of cross-linking polyurethane resin.

[0014] Patent document 3 describes that even if the polyurethane resin of the substrate is a non-crosslinked linear urethane resin, it exhibits the strong physical properties of a crosslinked polymer, but there is no record of crosslinking the polyurethane resin.

[0015] To improve the ability to follow three-dimensional surfaces, it becomes difficult to follow the three-dimensional surface if the adhesive layer is pasted onto the substrate before it follows the surface.

[0016] The present invention was made in view of the above circumstances, and its objective is to provide an adhesive film with excellent conformability to three-dimensional curved surfaces.

[0017] Technical solution

[0018] To address the aforementioned issues, the present invention provides an adhesive film characterized by comprising a substrate and an adhesive layer laminated on one side of the substrate, wherein the substrate is formed of a polyurethane resin crosslinked using a crosslinking agent, the laminate having a 50% stress of 10–29 MPa, a breaking stress of 30–69 MPa, and an elongation at break of 200–350%, and the initial adhesive force of the adhesive film, measured immediately after being bonded to the glass of the adherend, is 2 N / 25 mm or less. The lower limit of the initial adhesive force is not limited, but may be 0.1 N / 25 mm.

[0019] The permanent adhesive strength of the adhesive film, measured after being applied to the glass substrate and heated to 80°C, can be 16 N / 25 mm or higher. There is no upper limit to the permanent adhesive strength; it can be 50 N / 25 mm.

[0020] The adhesive layer can be formed by crosslinking a polyester adhesive with a glass transition temperature (Tg) of -5°C to 19°C.

[0021] The storage modulus G' of the adhesive layer, obtained by dynamic viscoelasticity measurement at 20°C, can be 1.0 MPa or higher. There is no upper limit to the storage modulus G', which can be 10 MPa.

[0022] A cover film may be provided on the side of the substrate opposite to the adhesive layer.

[0023] A printed layer may be formed on the side of the substrate opposite to the adhesive layer.

[0024] A release film may be provided on the side of the adhesive layer opposite to the substrate.

[0025] Glass to be adhered can be bonded to the side of the adhesive layer opposite to the substrate.

[0026] Technical effect

[0027] According to the present invention, the ability to follow three-dimensional curved surfaces can be improved. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view showing an example of an adhesive film.

[0029] Figure 2 This is a cross-sectional view showing an example of an object to be bonded with an adhesive film.

[0030] Figure 3 This is a cross-sectional view showing an example of an adhesive film following an object with a three-dimensional curved surface.

[0031] Symbol Explanation

[0032] 10…Adhesive film, 11…Substrate, 11a…Decorative surface, 12…Adhesive layer, 12a…Adhesive surface, 13…Cover film, 14…Release film, 15…Printed layer, 20…Adhesive substrate, 21…Flat surface, 22…Curved surface Detailed Implementation

[0033] The present invention will now be described based on preferred embodiments.

[0034] Figure 1 An example of an adhesive film is shown. The adhesive film 10 includes a substrate 11 and an adhesive layer 12 laminated on one side of the substrate 11. The side of the substrate 11 opposite to the adhesive layer 12 becomes a decorative surface 11a capable of being printed or decorated. The side of the adhesive layer 12 opposite to the substrate 11 becomes an adhesive surface 12a capable of being bonded to articles or the like.

[0035] The substrate 11 is formed of polyurethane resin cross-linked by a cross-linking agent. As a result, even when the adhesive surface 12a is bonded to an object with a three-dimensional curved surface, the ability to follow the three-dimensional curved surface can be improved.

[0036] As for polyurethane resins, there are no particular limitations as long as the resin is mainly composed of the reaction product of polyols and polyisocyanates, and it is appropriate to select from known polyurethane resins. The substrate 11 may contain one type of polyurethane resin or two or more types of polyurethane resins.

[0037] Examples of polyols include alkylene glycols, dialkylene glycols, polyalkylene glycols, polyether polyols, polyurethane polyols, polyester polyols, polycarbonate polyols, and lactone polyols. A polyol can be a diol with two hydroxyl groups per molecule or a triol with three hydroxyl groups per molecule. Polyols can also have four or more hydroxyl groups.

[0038] As a polyisocyanate, it can be a diisocyanate having two isocyanate groups per molecule or a triisocyanate having three isocyanate groups per molecule. Polyisocyanates can have four or more isocyanate groups. Examples of diisocyanates include aromatic diisocyanates such as toluene diisocyanate (TDI) and xylylene diisocyanate (XDI), and aliphatic diisocyanates such as hexamethylene diisocyanate (HDI), pentaethylene diisocyanate (PDI), and isophorone diisocyanate (IPDI).

[0039] Linear polyurethane resins can be obtained by reacting at least one diol with at least one diisocyanate. Cross-linked polyurethane resins can be obtained by using a compound having three or more hydroxyl groups as at least a portion of the polyol, or by using a compound having three or more isocyanate groups as at least a portion of the polyisocyanate. Using cross-linked polyurethane resins improves the mechanical strength and / or durability of the substrate 11, even in the case of adhesive films 10 requiring mechanical strength and / or durability, such as anti-spray films.

[0040] Polyurethane resins can be crosslinked by reacting a polyisocyanate as a crosslinking agent with a polyurethane resin having hydroxyl groups that are unreacted relative to the isocyanate groups. Crosslinking can also be achieved by reacting a polyol as a crosslinking agent with a polyurethane resin having isocyanate groups. The crosslinking agent for polyurethane resins is not limited to polyisocyanates and / or polyols; suitable crosslinking agents capable of reacting with functional groups such as hydroxyl and / or isocyanate groups present in the polyurethane resin can also be used. The proportion of the crosslinking agent can be appropriately set; for example, 5 to 20 parts by weight of crosslinking agent relative to 100 parts by weight of polyurethane resin can be used.

[0041] While the thickness of the substrate 11 is not particularly limited, examples include approximately 30 to 150 μm. More preferably, the thickness of the substrate 11 is 100 μm or less, and even more preferably 80 μm or less. As for the method of forming the substrate 11, there is no particular limitation, and examples include blow molding, extrusion molding, solution casting, hot pressing, calendering, and cutting.

[0042] For example, when the substrate 11 is formed by solution casting, the polyurethane resin dissolved in the solvent can be coated onto a predetermined coating surface and then dried to form a film. While not particularly limited, examples of solvents include hydrocarbon solvents such as toluene and cyclohexane; alcohol solvents such as methanol, ethanol, and isopropanol; ketone solvents such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; and ester solvents such as ethyl acetate.

[0043] Alternatively, after forming a film from a thermoplastic or solvent-soluble polyurethane resin, a crosslinking agent added to the polyurethane resin can be reacted to crosslink the polyurethane resin. This allows for a balance between processability suitable for forming the substrate 11 and durability suitable for the application of the substrate 11.

[0044] From the viewpoint of durability against moisture, etc., polyurethane resins with low hydrolytic activity are preferred. From the viewpoint of coating properties and productivity, such as in solution casting, the weight-average molecular weight (Mw) of the polyurethane resin before crosslinking is preferably around 10,000 to 100,000. The gel fraction of the crosslinked polyurethane resin is preferably around 50% to 90%, more preferably around 70% to 80%.

[0045] The laminate having a substrate 11 and an adhesive layer 12 in the embodiment has a 50% stress of 10-29 MPa, a breaking stress of 30-69 MPa, and an elongation at break of 200-350%. Therefore, even when the adhesive surface 12a is bonded to an object with a three-dimensional curved surface, the ability to follow the three-dimensional curved surface can be improved. Furthermore, when the adhesive film 10 is bonded to glass, even if the glass breaks, the anti-scattering property can be improved.

[0046] The 50% stress is the stress (MPa) at which tensile force is applied to a test piece formed from a laminate having a substrate 11 and an adhesive layer 12, and the elongation becomes 50%. A higher 50% stress results in greater durability against tensile forces, and is therefore preferred.

[0047] Fracture stress is the stress (MPa) at which a test piece fractures when tensile force is applied to it and the test piece breaks. A higher fracture stress results in greater durability against tensile fracture and is therefore preferred.

[0048] Elongation at break is the elongation (%) of a test piece when it breaks after tensile force is applied to it, which is a laminate consisting of a substrate 11 and an adhesive layer 12. To achieve conformity to three-dimensional curved surfaces, a moderate elongation at break is desirable, but excessive elongation at break can cause the substrate 11 to over-elongate and become prone to loosening.

[0049] 50% stress, breaking stress, and elongation at break can be measured using a tensile testing apparatus manufactured by, for example, Shimadzu Corporation. When the adhesive film 10 has a cover film 13 or a release film 14, the laminate having the substrate 11 and the adhesive layer 12 is in a state where it does not have a cover film 13 or a release film 14, respectively.

[0050] The substrate 11 can be supplemented with additives such as colorants, stabilizers, antioxidants, and flame retardants as needed. The substrate 11 can achieve high transparency without the addition of colorants or similar additives. Examples of transparency of the substrate 11 include a total light transmittance of 90% or more and a haze of 2% or less.

[0051] The adhesive layer 12 is formed of an adhesive. The adhesive is not particularly limited and can be appropriately selected from known adhesives depending on the item to which the adhesive film 10 is to be bonded. The adhesive layer 12 can be laminated in contact with the substrate 11. Other layers may also be sandwiched between the substrate 11 and the adhesive layer 12. Polyester-based adhesives are examples of adhesives suitable for applications requiring transparency and weather resistance.

[0052] Examples of polyester adhesives include those that utilize polyester polymers obtained by polycondensation of dicarboxylic acids (such as dicarboxylic acids) and polyols (such as diols). Examples of dicarboxylic acids include adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and cyclohexanedicarboxylic acid. Examples of diols include alkylene glycols, diallyl glycols, polyalkylene glycols, and polyether glycols. To improve the adhesive strength of polyester polymers, crosslinking agents such as polyisocyanate compounds, polyfunctional epoxy compounds, and metal chelating compounds can be used.

[0053] The method for forming the adhesive layer 12 is not particularly limited, but the adhesive layer 12 can be formed by coating an adhesive composition containing an adhesive (polymer) and a crosslinking agent onto a substrate 11 and then crosslinking the adhesive with the crosslinking agent through aging. The proportion of the crosslinking agent can be appropriately set; for example, 1 to 10 parts by weight of the crosslinking agent relative to 100 parts by weight of the adhesive can be listed. Alternatively, the adhesive can be coated into a sheet other than the substrate 11, dried, and then the adhesive layer 12 can be transferred onto the substrate 11. Other layers can also be sandwiched between the substrate 11 and the adhesive layer 12, and the substrate 11 and the adhesive layer 12 can also be in contact with each other.

[0054] While the thickness of the adhesive layer 12 is not particularly limited, examples include approximately 10 to 50 μm. The adhesive layer 12 can be tacky at room temperature (5 to 35°C) and also at temperatures above room temperature. For example, in the case of an adhesive layer 12 that is tacky in warm water above room temperature, the glass transition temperature (Tg) of the adhesive is preferably around -5°C to 19°C. For example, the adhesive layer 12 can be formed by crosslinking a polyester adhesive with a glass transition temperature (Tg) of -5°C to 19°C. In the crosslinked adhesive layer 12, the Tg is preferably around 30°C. Therefore, in addition to improving the surface conformability of the adhesive film 10, the durability of the adhesive layer 12 is also improved, thus enhancing the glass's anti-scattering properties.

[0055] The storage modulus G' of the adhesive layer 12, obtained by dynamic viscoelasticity measurement at 20°C, is preferably 1.0 MPa or higher. This means that the adhesive layer 12 has a harder property than that of a typical adhesive at 20°C. The vibration frequency for the dynamic viscoelasticity measurement is, for example, 1 Hz.

[0056] At room temperature, the initial adhesive force, measured immediately after the adhesive film 10 is applied to the glass of the substrate, is preferably 2 N / 25 mm or less. Therefore, during the initial stage when the adhesive film 10 exhibits initial adhesive force, the adhesive layer 12 can easily displace relative to the substrate, and the surface following ability of the adhesive film 10 is excellent.

[0057] Furthermore, the permanent adhesive force, measured after the adhesive film 10 is applied to the glass of the substrate and heated to 80°C, is preferably 16 N / 25 mm or more. Thus, at the stage where the adhesive film 10 exhibits permanent adhesive force, the adhesive layer 12 adheres tightly to the substrate and easily maintains its conformal to the curved surface. It should be noted that heating to 80°C as the condition for measuring permanent adhesive force is an example from the viewpoint of easily reaching the stage where the adhesive film 10 exhibits permanent adhesive force. Under the conditions of use of the adhesive film 10, permanent adhesive force can be exhibited by heating to a temperature different from 80°C, or by leaving it at room temperature for a long time (e.g., 24 hours or more).

[0058] While the thickness of the adhesive film 10, which includes the substrate 11 and the adhesive layer 12, is not particularly limited, examples of which are approximately 40 to 200 μm are given. Here, the thickness of the adhesive film 10 refers to the thickness of the laminate having the substrate 11 and the adhesive layer 12, excluding the thickness of the cover film 13 and the release film 14 described below. More preferably, the thickness of the adhesive film 10 is 100 μm or less.

[0059] To protect the decorative surface 11a, the adhesive film 10 may have a cover film 13 on the side of the substrate 11 opposite to the adhesive layer 12. While not particularly limited, the cover film 13 may 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.

[0060] The cover film 13 can be opaque or semi-transparent, but it is preferable to use a highly transparent cover film 13, as the condition of the decorative surface 11a can be easily confirmed visually even without peeling off the cover film 13. The cover film 13 can be a non-stretched resin film or a stretched resin film. The cover film 13 may have a layer of release agent such as a silicone-based release agent, a fluorinated release agent, or a long-chain alkyl release agent on the side of the cover film 13 that contacts the decorative surface 11a. Alternatively, the side of the cover film 13 that contacts the decorative surface 11a may not have a release agent.

[0061] 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 may 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.

[0062] The release film 14 can be opaque or semi-transparent, but it is preferable to use a highly transparent release film 14, as the condition of the adhesive surface 12a can be easily confirmed visually even without peeling off the release film 14. The release film 14 can be a non-stretched 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 fluorinated release agent, or a long-chain alkyl release agent on the side in contact with the adhesive surface 12a. The release film 14 may also not have a release agent on the side in contact with the adhesive surface 12a.

[0063] exist Figure 2An example of an adherend 20 to which the adhesive film 10 is bonded is shown. A printed layer 15 is formed on a substrate 11, and the adherend 20 is bonded to an adhesive layer 12. While the order of the steps of forming the printed layer 15 on the substrate 11 and bonding the adherend 20 to the adhesive layer 12 is not limited, it is preferable that the adherend 20 is bonded to the adhesive layer 12 after the printed layer 15 is formed on the substrate 11. A step of cutting the adhesive film 10 to a size suitable for the adherend 20 may also be included. Printing on the substrate 11 is preferably performed before cutting the adhesive film 10.

[0064] When printing on the substrate 11, an easily adhesive layer such as a primer can be applied to the decorative surface 11a as needed. If a cover film 13 is provided to protect the decorative surface 11a, the cover film 13 can be removed before printing. Alternatively, the printing layer 15 can be formed on the decorative surface 11a without the cover film 13 after the substrate 11 is formed.

[0065] 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 can be formed on the entire surface of the decorative surface 11a or on a portion of the decorative surface 11a. Two or more printed layers 15 can be overlapped. Different printed layers 15 can be formed in different areas of the decorative surface 11a. Decorations other than the printed layer 15 can also be applied to the decorative surface 11a. Examples of other decorative layers include metal vapor deposition layers based on sputtering, etc.

[0066] The ink used to form the printing layer 15 may contain coloring materials such as pigments and dyes, and a binder. There are no particular limitations on the binder, but examples include polyamide resins, polyurethane resins, polyester resins, polyvinyl chloride resins, polyvinyl acetate resins, acrylic resins, epoxy resins, polybutadiene resins, and cyclic rubbers. The ink may contain solvents such as water, organic solvents, and vegetable oils. After printing, the ink can dry through solvent evaporation and ink curing. To promote ink drying, heating or ultraviolet irradiation may be used.

[0067] Before applying the adhesive film 10 to the substrate 20, the release film 14 is removed from the adhesive layer 12. Thus, the adhesive film 10 can be adhered to the substrate 20 via the adhesive layer 12. The substrate 20 can be an electronic device that uses glass in its display surface, housing, etc. While the material of the surface of the substrate 20 in contact with the adhesive layer 12 is not particularly limited, examples include glass, metal, and plastic. Figure 3 As shown, the conformability of the adhesive film 10 is also excellent when the substrate 20, which has a flat portion 21 and a curved portion 22, is adhered to it. The curved portion 22 is not limited to being provided on one side around the flat portion 21, but may also be provided on the two opposite sides, or on each of the surrounding sides (if the flat portion 21 is rectangular, then it has four sides).

[0068] There is no particular limitation on the method of attaching the adhesive film 10 to the substrate 20, as long as pressure, suction, or other methods are used to seal the adhesive layer 12 to the substrate 20. As for the pressure method, it can be a mechanical method such as a roller component, a rod-shaped component, or a plate-shaped component, or it can be a method using a fluid pressure medium such as a liquid or gas. Preferably, after the adhesive film 10 is temporarily attached to the substrate 20, isotropic pressure is applied from the pressure of the surrounding liquid. The pressure medium can be warm water. As for the suction method, one example is using a vacuum to remove the air between the adhesive film 10 and the substrate 20.

[0069] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention.

[0070] 【Example】

[0071] The present invention will be specifically described below through examples.

[0072] (Substrate manufacturing)

[0073] Nine types of polyurethane resin substrates were manufactured according to formulations 1 to 9 shown in Table 1.

[0074] In Formulation 1, a polyurethane solution containing 100 parts by weight of polycarbonate-based polyurethane resin (manufactured by Dai Nippon Seika Co., Ltd., trade name DAIFERAMINE (registered trademark) MAU8288A, weight average molecular weight 50,000) and 10 parts by weight of TDI-based polyisocyanate (manufactured by Tosoh Co., Ltd., trade name Coronate (registered trademark) L-45E) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0075] In Formulation 2, 100 parts by weight of the above-mentioned polycarbonate-based polyurethane resin (manufactured by Dai Nippon Seika Co., Ltd., trade name DAIFERAMINE (registered trademark) MAU8288A, weight average molecular weight 50,000) are used to prepare a polyurethane solution without adding a crosslinking agent, and a film with a thickness of 60 μm is formed as a substrate by solution casting.

[0076] In Formulation 3, a polyurethane solution containing 100 parts by weight of polycarbonate-based polyurethane resin (manufactured by Tosoh Corporation, trade name Nipporan (registered trademark) 5199, weight average molecular weight 30,000) and 4 parts by weight of HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate (registered trademark) HX) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0077] In Formulation 4, a polyurethane solution containing 100 parts by weight of polycarbonate-based polyurethane resin (manufactured by Tosoh Corporation, trade name Nipporan (registered trademark) 5230, weight average molecular weight 60,000) and 4 parts by weight of HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate (registered trademark) HX) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0078] In Formulation 5, a polyurethane solution containing 100 parts by weight of polycarbonate-based polyurethane resin (manufactured by Dai Nippon Seika Co., Ltd., trade name DAIFERAMINE (registered trademark) MAU8288A, weight average molecular weight 50,000) and 15 parts by weight of TDI-based polyisocyanate (manufactured by Tosoh Co., Ltd., trade name Coronate (registered trademark) L-45E) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0079] In Formulation 6, a polyurethane solution containing 100 parts by weight of polyether-based polyurethane resin (manufactured by Daihatsu Seika Co., Ltd., trade name Resamine (registered trademark) 8883HV, weight average molecular weight 80,000) and 4 parts by weight of HDI-based polyisocyanate (manufactured by Tosoh Co., Ltd., trade name Coronate (registered trademark) HX) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0080] In Formulation 7, 100 parts by weight of polyether-based polyurethane resin (manufactured by Daihatsu Seika Co., Ltd., trade name Resamine (registered trademark) 8883HV, weight average molecular weight 80,000) are used to prepare a polyurethane solution without adding a crosslinking agent, and a film with a thickness of 60 μm is formed as a substrate by solution casting.

[0081] In Formulation 8, a polyurethane solution containing 100 parts by weight of polyether-based polyurethane resin (manufactured by Daihatsu Seika Co., Ltd., trade name Resamine (registered trademark) 8883HV, weight average molecular weight 80,000) and 6 parts by weight of HDI-based polyisocyanate (manufactured by Tosoh Co., Ltd., trade name Coronate (registered trademark) HX) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0082] In Formulation 9, a polyurethane solution containing 100 parts by weight of polycarbonate-based polyurethane resin (manufactured by Fujikura Chemicals Co., Ltd., trade name USV1402, weight average molecular weight 20,000) and 10 parts by weight of HDI-based polyisocyanate (manufactured by Tosoh Co., Ltd., trade name Coronate (registered trademark) HX) as a crosslinking agent is used to form a 60 μm thick film as a substrate by solution casting.

[0083] In addition, a commercially available thermoplastic polyurethane elastomer resin (TPU) film (manufactured by Okura Kogyo Co., Ltd., trade name SILK RON (registered trademark) SNY97, thickness 80μm) was cut into predetermined sizes to prepare the substrate of Comparative Example 8.

[0084] Table 1

[0085]

[0086] (Manufacturing of the adhesive layer)

[0087] On one side of each substrate obtained in the above manner, adhesive layers A to D are formed with the compositions shown in Table 2 to obtain various adhesive films.

[0088] Adhesive layer A is an adhesive obtained by adding 4 parts by weight of the aforementioned crosslinking agent (trade name Coronate L-45E) to 100 parts by weight of a polyester adhesive (manufactured by Mitsubishi Chemical Corporation, trade name Nichigo Polyester S-0097, weight average molecular weight 20,000, Tg = 1°C), forming an adhesive layer with a thickness of 20 μm on one side of the substrate. The adhesive layer is formed by applying the adhesive containing the crosslinking agent and solvent to the substrate in a manner that results in a dried thickness of 20 μm, allowing the solvent to dry, and then crosslinking the adhesive through curing (aging).

[0089] Adhesive layer B is an adhesive obtained by adding 0.8 parts by weight of the above-mentioned crosslinking agent (trade name Coronate L-45E) to 100 parts by weight of an acrylic adhesive (manufactured by Fujimori Kogyo Co., Ltd., trade name TR-499, weight average molecular weight 450,000, Tg = -30℃), and forming an adhesive layer with a thickness of 20 μm on one side of the substrate in the same manner as adhesive A.

[0090] Adhesive layer C is an adhesive obtained by adding 4 parts by weight of the above-mentioned crosslinking agent (trade name Coronate L-45E) to 100 parts by weight of polyester adhesive (manufactured by Mitsubishi Chemical Corporation, trade name Nichigo Polyester XNP-1013, weight average molecular weight 30,000, Tg=16℃), and forms an adhesive layer with a thickness of 20 μm on one side of the substrate in the same manner as adhesive A.

[0091] Adhesive D is an adhesive obtained by adding 4 parts by weight of the above-mentioned crosslinking agent (trade name Coronate L-45E) to 100 parts by weight of polyester adhesive (manufactured by Mitsubishi Chemical Corporation, trade name Nichigo Polyester S-0091, weight average molecular weight 25,000, Tg = -10℃), and forms an adhesive layer with a thickness of 20 μm on one side of the substrate in the same manner as adhesive A.

[0092] Table 2

[0093]

[0094] (Manufacturing of Examples 1-5 and Comparative Examples 1-8)

[0095] As shown in Table 3, the substrates of each formulation 1-9 and the substrate of Comparative Example 8 were combined with adhesive layers A-D to manufacture adhesive films of Examples 1-5 and Comparative Examples 1-8, respectively. The thickness of each adhesive film is shown in Table 3.

[0096] For the crosslinked adhesives used in Examples 1-5 and Comparative Examples 1-8, the glass transition temperature (Tg) and storage modulus G' (MPa) of the crosslinked adhesive layer at 20°C were measured. The storage modulus G' of the adhesive layer was determined using the method according to JIS K 7244-10. The results are shown in Table 3.

[0097] (Method for determining the initial adhesion force of the adhesive film to glass)

[0098] Using a rubber roller, a polyester film strip (25 μm thick polyester substrate) was adhered to the substrate side of the adhesive film without allowing air ingress. The release film on the adhesive layer side was then peeled off, and the film was adhered to a glass plate using a 2 kg load rubber roller without allowing air ingress, thus creating an evaluation sample. Within 10 minutes of adhering the adhesive film of the evaluation sample to the glass, the adhesive layer was peeled off from the glass at a peel angle of 180° and a peel speed of 300 mm / min, and the adhesive force (N / 25 mm) was measured. The measured value was taken as the initial adhesive force.

[0099] (Method for determining the permanent adhesion of adhesive film to glass)

[0100] A polyester film strip (25 μm thick) was bonded to the substrate side of the adhesive film using a rubber roller without allowing air ingress. The release film on the adhesive layer side was then peeled off, and the film was bonded to a glass plate using a 2 kg load rubber roller without allowing air ingress. The resulting laminate was then autoclaved at 0.5 MPa, 80°C, and for 20 minutes to prepare evaluation samples. The evaluation samples were then allowed to stand at 23 ± 5°C for at least 12 hours. The adhesive layer was then peeled from the glass at a peel angle of 180° and a peel speed of 300 mm / min, and the adhesive force (N / 25 mm) was measured. The measured value was taken as the permanent adhesive force.

[0101] (Methods for determining 50% stress, breaking stress, and elongation at break of adhesive films)

[0102] Samples of the adhesive film were collected with dimensions of 150 mm in the flow direction and 15 mm in the width direction. The distance between the fixtures was set to 100 mm, and a tensile test was conducted at a tensile speed of 300 mm / min in a laminated state containing the substrate and adhesive layer. The stress at break was defined as the breaking stress, the elongation at break as the breaking elongation, and the stress at 50% elongation as the 50% stress.

[0103] (Evaluation method for the surface following performance of adhesive films)

[0104] Regarding the surface conformability of the adhesive film, for a glass substrate with a curved surface (width in top view: 10mm, curvature angle of 70 degrees) around a 7cm × 15cm flat portion, the conformability of the adhesive film when it is adhered to its entire surface is visually evaluated. Excellent cases are rated ○, and poor cases are rated ×. An excellent case indicates that the film can be adhered to the entire curved surface without gaps or wrinkles. A poor case indicates that gaps or wrinkles occur in at least a portion of the curved surface, or that the adhesive film is damaged.

[0105] (Evaluation method for the anti-scattering property of adhesive films)

[0106] Regarding the anti-scattering performance of the adhesive film, when the adhesive film is adhered to a glass substrate and the center of the substrate is struck with a metal sheet, causing the substrate to break, an excellent result is rated as ○, and a poor result is rated as ×. An excellent result indicates that the broken glass does not detach from the adhesive film and falls, and the adhesive film is not damaged. A poor result indicates that the broken glass separates from the adhesive film and falls, or the adhesive film is damaged.

[0107] (Evaluation Results)

[0108] Table 3 shows the evaluation results of the adhesive films of Examples 1-5 and Comparative Examples 1-8. The total thickness of the adhesive film is equal to the combined thickness of the substrate and the adhesive layer.

[0109] Table 3

[0110]

[0111] As shown in Table 3, the adhesive films of Examples 1 to 5 have a moderate range of 50% stress, breaking stress, and elongation at break, low initial adhesive force, and excellent surface following ability of the adhered object.

[0112] The adhesive films in Comparative Examples 3 and 8 have poor surface following properties because of their high elongation before being applied to the substrate.

[0113] The adhesive films of Comparative Examples 1, 2, 4, 5, 6, and 7 have high initial adhesive force and adhere firmly when the adhesive film is temporarily fixed to the object being adhered, thus exhibiting poor surface following ability.

[0114] The adhesive films of Examples 1-5 showed that the substrate was not damaged when the glass broke, and the adhesive layer did not peel off, demonstrating excellent anti-scattering properties.

[0115] The adhesive films in Comparative Examples 3 and 8 showed poor anti-scattering properties when the glass broke and the substrate was damaged.

[0116] The adhesive films of Comparative Examples 4, 5, and 7 peeled off when the glass broke, indicating poor anti-scattering properties.

Claims

1. An adhesive film, characterized in that, It comprises a substrate and an adhesive layer laminated on one side of the substrate. The substrate is composed of a polyurethane resin cross-linked using a cross-linking agent. Regarding the proportion of the crosslinking agent, relative to 100 parts by weight of the polyurethane resin, the crosslinking agent is 5 to 20 parts by weight. The adhesive layer is formed by crosslinking a polyester adhesive. The laminate having the substrate and the adhesive layer has a 50% stress of 10–29 MPa, a breaking stress of 30–69 MPa, and an elongation at break of 200–350%. The initial adhesive force of the adhesive film is less than 2N / 25mm. The initial adhesive force is measured by applying a 2kg load rubber roller to the glass of the object to be bonded and peeling the adhesive layer from the glass within 10 minutes at a peel angle of 180° and a peel speed of 300mm / min.

2. The adhesive film as described in claim 1, characterized in that, The permanent adhesive strength of the adhesive film, measured after being applied to the glass of the object to be adhered to and heated to 80°C, is greater than 16 N / 25 mm.

3. The adhesive film as described in claim 1 or 2, characterized in that, The adhesive layer is formed by crosslinking the polyester adhesive with a glass transition temperature (Tg) of -5°C to 19°C.

4. The adhesive film as described in claim 1 or 2, characterized in that, The energy storage modulus G' of the adhesive layer, obtained by dynamic viscoelasticity measurement at 20°C, is above 1.0 MPa.

5. The adhesive film as described in claim 1 or 2, characterized in that, The substrate has a cover film on the side opposite to the adhesive layer.

6. The adhesive film as described in claim 1 or 2, characterized in that, A printed layer is formed on the side of the substrate opposite to the adhesive layer.

7. The adhesive film as described in claim 1 or 2, characterized in that, A release film is provided on the side of the adhesive layer opposite to the substrate.

8. The adhesive film as described in claim 1 or 2, characterized in that, The glass of the object to be bonded is attached to the side of the adhesive layer opposite to the substrate.

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