JP2022145538A - adhesive film - Google Patents

Abstract

To provide an adhesive film which is excellent in followability to a three-dimensional curved surface.SOLUTION: An adhesive film 10 includes a base material 11, and an adhesive layer 12 laminated on one surface of the base material 11, wherein the base material 11 is composed of a polyurethane resin crosslinked with a crosslinking agent, the laminate having the base material 11 and the adhesive layer 12 has a 50% stress of 10-29 MPa, a stress at rupture of 30-69 MPa and elongation at break of 200-350%, and the adhesive film 10 has an initial adhesive force measured immediately after bonded to glass of an adherend 20 of 2 N/25 mm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to adhesive films.

Adhesive films are used for the purpose of protecting the surfaces of articles, decorating the surfaces, and the like.
For example, in Patent Document 1, it is possible to flexibly follow a three-dimensional curved surface by using a decorative molding film in which a polyvinyl chloride film is used as a base material and an adhesive layer formed from an acrylic adhesive is laminated. is described.

Further, Patent Document 2 discloses a pressure-sensitive adhesive sheet for affixing to the surface of a painted steel plate of an automobile, in which the base material includes a hard layer made of polycarbonate polyurethane and a soft layer made of polyester-based polyurethane, and the pressure-sensitive adhesive layer is It is described that it is formed from an acrylic pressure-sensitive adhesive containing a carboxyl group-containing ethylenically unsaturated monomer or the like as a copolymer component.

Further, Patent Document 3 discloses a thin film marking sheet in which an adhesive layer is laminated on one surface of a base material made of a non-stretched film of a polyester-based or polycarbonate-based polyurethane resin, and a decorative display layer is provided on the other side of the base material. is described.

Japanese Patent No. 6577380 Japanese Patent No. 4886969 JP 2003-295769 A

Adhesive films used on the surface of articles are sometimes decorated by printing or the like on the base material. Patent Document 1 describes that by adding a plasticizer to a polyvinyl chloride film, the elongation that facilitates attachment to a three-dimensional curved surface and the printability for decorative molding are improved. However, the use of an organic chlorine compound may limit its applications.

Patent Document 2 describes that an adhesive sheet is attached to a three-dimensional curved surface in order to protect the vehicle body from chipping, which is a phenomenon in which objects such as pebbles are thrown up and damage the vehicle body. There is no description of cross-linking the
Patent Document 3 describes that even a non-crosslinked linear urethane resin as a base material exhibits tough physical properties like a crosslinked polymer, but there is no description of crosslinking the polyurethane resin.

If the adhesive layer adheres to the adherend before the adhesive layer conforms to the three-dimensional curved surface in order to enhance the conformability to the three-dimensional curved surface, conformability to the three-dimensional curved surface becomes difficult.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive film having excellent conformability to a three-dimensional curved surface.

In order to solve the above problems, the present invention provides an adhesive film comprising a substrate and an adhesive layer laminated on one side of the substrate, wherein the substrate is a polyurethane resin crosslinked with a crosslinking agent. A laminate having the base material and the adhesive layer has a 50% stress of 10 to 29 MPa, a breaking stress of 30 to 69 MPa, and a breaking elongation of 200 to 350%. Provided is an adhesive film characterized by having an initial adhesive strength of 2 N/25 mm or less measured immediately after being stuck to a glass. Although the lower limit of the initial adhesive strength is not limited, it may be 0.1 N/25 mm.

The adhesive film may have a permanent adhesive strength of 16 N/25 mm or more, which is measured after heating to a temperature of 80° C. after bonding to glass as an adherend. Although the upper limit of the permanent adhesive strength is not limited, it may be 50 N/25 mm.
The adhesive layer may be formed by cross-linking a polyester-based adhesive having a glass transition temperature (Tg) of -5°C to 19°C.
A storage elastic modulus G′ of the adhesive layer obtained by dynamic viscoelasticity measurement at 20° C. may be 1.0 MPa or more. Although the upper limit of the storage elastic modulus G' is not limited, it may be 10 MPa.

A cover film may be provided on the surface 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.
A release film may be provided on the surface of the adhesive layer opposite to the substrate.
An adherend glass may be bonded to the surface of the adhesive layer opposite to the base material.

According to the present invention, followability to a three-dimensional curved surface can be improved.

It is a sectional view showing an example of an adhesion film. FIG. 2 is a cross-sectional view showing an example of an adherend to which an adhesive film is attached; FIG. 3 is a cross-sectional view showing an example in which an adhesive film follows an adherend having a three-dimensional curved surface.

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

FIG. 1 shows an example of an adhesive film. The adhesive film 10 includes a substrate 11 and an adhesive layer 12 laminated on one side of the substrate 11 . The surface of the substrate 11 opposite to the adhesive layer 12 is a decorative surface 11a on which decoration such as printing is possible. The surface of the adhesive layer 12 opposite to the substrate 11 is an adhesive surface 12a that can be attached to an article or the like.

The base material 11 is made of a polyurethane resin crosslinked with a crosslinking agent. As a result, even when an adherend having a three-dimensional curved surface is attached to the adhesive surface 12a, it is possible to improve the conformability to the three-dimensional curved surface.

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 substrate 11 may contain one type of polyurethane resin, or may contain two or more types of polyurethane resins.

Examples of polyols include alkylene glycol, dialkylene glycol, polyalkylene glycol, polyether-based polyol, polyurethane-based polyol, polyester-based polyol, polycarbonate-based polyol, and lactone-based polyol. The polyol may be a diol having two hydroxyl groups per molecule or a triol having three hydroxyl groups per molecule. The polyol may have 4 or more hydroxyl groups.

The polyisocyanate may be a diisocyanate having two isocyanate groups per molecule, or a triisocyanate having three isocyanate groups per molecule. Polyisocyanates may have 4 or more isocyanate groups. Diisocyanates 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). be done.

A linear polyurethane resin can be obtained by reacting at least one or more diols with at least one or more diisocyanates. Crosslinking is achieved by using a compound having 3 or more hydroxyl groups per molecule as at least a portion of the polyol, or using a compound having 3 or more isocyanate groups per molecule as at least a portion of the polyisocyanate. Structured polyurethane resin can be obtained. The use of a crosslinked polyurethane resin can improve the mechanical strength and durability of the substrate 11 even in the case of the adhesive film 10 that requires mechanical strength and durability, such as a shatterproof film.

The polyurethane resin can be crosslinked by reacting a polyisocyanate as a crosslinking agent with the polyurethane resin having a hydroxyl group that has not reacted with the isocyanate group. A polyurethane resin having an isocyanate group can also be crosslinked by reacting a polyol as a crosslinking agent with the polyurethane resin. The cross-linking agent for the polyurethane resin is not limited to polyisocyanate and polyol, and an appropriate cross-linking agent capable of reacting with functional groups such as hydroxyl groups and isocyanate groups possessed by the polyurethane resin may be used. . The ratio of the cross-linking agent can be set as appropriate, and for example, 5 to 20 parts by weight of the cross-linking agent can be used with respect to 100 parts by weight of the polyurethane resin.

Although the thickness of the base material 11 is not particularly limited, it is, for example, about 30 to 150 μm. The thickness of the base material 11 is more preferably 100 μm or less, and even more preferably 80 μm or less. A method for forming the substrate 11 is not particularly limited, and examples thereof include inflation molding, extrusion molding, solution casting, heat pressing, calendering, and cutting.

For example, when forming the base material 11 by solution casting, the polyurethane resin can be formed into a film by applying a polyurethane resin dissolved in a solvent to a predetermined coating surface and then drying the solvent. The solvent is not particularly limited, but 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; Examples include ester-based solvents.

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

From the viewpoint of durability against moisture and the like, it is preferable to use a polycarbonate-based or polyether-based polyurethane resin with low hydrolyzability. From the viewpoint of coatability and productivity in solution casting and the like, the weight average molecular weight (Mw) of the polyurethane resin before cross-linking is preferably about 10,000 to 100,000. The gel fraction of the polyurethane resin after cross-linking is preferably about 50-90%, more preferably about 70-80%.

The laminate having the substrate 11 and the adhesive layer 12 of the embodiment has a 50% stress of 10 to 29 MPa, a breaking stress of 30 to 69 MPa, and a breaking elongation of 200 to 350%. As a result, even when an adherend having a three-dimensional curved surface is attached to the adhesive surface 12a, it is possible to improve the conformability to the three-dimensional curved surface. In addition, even if the glass is broken while the pressure-sensitive adhesive film 10 is attached to the glass, the anti-scattering property of preventing the glass from scattering can be improved.

The 50% stress is the stress (MPa) when a tensile force is applied to the test piece formed from the laminate having the substrate 11 and the adhesive layer 12 and the elongation rate reaches 50%. A higher 50% stress is preferred because it increases durability against tensile forces.

The breaking stress is the stress (MPa) when a tensile force is applied to a test piece formed from a laminate having the substrate 11 and the adhesive layer 12 and the test piece breaks. The higher the breaking stress, the higher the resistance to breakage due to tension, which is preferable.

The breaking elongation is the elongation rate (%) when a tensile force is applied to a test piece formed from a laminate having the substrate 11 and the adhesive layer 12 and the test piece breaks. A moderate elongation at break is desirable in order to obtain conformability to a three-dimensional curved surface, but an excessive elongation at break causes the base material 11 to stretch too much and loosen easily.

The 50% stress, breaking stress, and breaking elongation can be measured using, for example, a tensile tester manufactured by Shimadzu Corporation. When the adhesive film 10 has the cover film 13 or the release film 14, the laminate having the substrate 11 and the adhesive layer 12 does not have the cover film 13 or the release film 14, respectively.

Additives such as colorants, stabilizers, antioxidants, and flame retardants may be added to the base material 11 as necessary. The base material 11 can impart high transparency when no colorant or the like is added. Examples of the transparency of the substrate 11 include a total light transmittance of 90% or more and a haze of 2% or less.

The adhesive layer 12 is made of an adhesive. The adhesive is not particularly limited, and can be appropriately selected from known adhesives according to the article or the like to which the adhesive film 10 is attached. The adhesive layer 12 may be laminated so as to be in contact with the base material 11 . Another layer may be interposed between the substrate 11 and the adhesive layer 12 . From the standpoint of transparency, weather resistance, etc., polyester-based adhesives and the like can be used.

Examples of the polyester-based pressure-sensitive adhesive include pressure-sensitive adhesives using polyester-based polymers obtained by polycondensation of polycarboxylic acids such as dicarboxylic acids and polyols such as diols. Dicarboxylic acids include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid and the like. Diols include alkylene glycol, dialkylene glycol, polyalkylene glycol, polyether glycol and the like. In order to improve the adhesive strength of the polyester-based polymer, cross-linking may be performed using a cross-linking agent such as a polyisocyanate compound, a polyfunctional epoxy compound, a polyfunctional epoxy compound, or a metal chelate compound.

The method of forming the adhesive layer 12 is not particularly limited, but after applying an adhesive composition containing an adhesive (polymer) and a cross-linking agent to the base material 11, the adhesive is cross-linked with the cross-linking agent by curing (aging). Alternatively, the adhesive layer 12 may be formed. The ratio of the cross-linking agent can be set as appropriate. The adhesive layer 12 may be transferred onto the base material 11 after the adhesive is applied to a sheet other than the base material 11 and dried. Another layer 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.

Although the thickness of the adhesive layer 12 is not particularly limited, it is, for example, about 10 to 50 μm. The adhesive layer 12 may have tackiness at room temperature (within the range of 5 to 35° C.), or may have tackiness at temperatures higher than room temperature. For example, in the case of the adhesive layer 12 having tackiness in hot water higher than normal temperature, the glass transition temperature (Tg) of the adhesive is preferably about -5°C to 19°C. For example, the adhesive layer 12 may be formed by cross-linking a polyester-based adhesive having a glass transition temperature (Tg) of -5°C to 19°C. The adhesive layer 12 after cross-linking preferably has a Tg of about 30°C. As a result, the durability of the adhesive layer 12 is improved in addition to the curved surface followability of the adhesive film 10, so that the anti-scattering property of the glass can be improved.

It is preferable that the storage elastic modulus G′ of the adhesive layer 12 obtained by dynamic viscoelasticity measurement at 20° C. is 1.0 MPa or more. This means that the adhesive layer 12 has properties at 20° C. that are harder than general adhesives. The vibration frequency for dynamic viscoelasticity measurement is, for example, 1 Hz.

At room temperature, the initial adhesive force measured immediately after bonding the adhesive film 10 to the glass adherend is preferably 2 N/25 mm or less. As a result, when the adhesive film 10 develops initial adhesive strength, the adhesive layer 12 is easily displaced with respect to the adherend, and the adhesive film 10 has excellent curved surface followability.

Moreover, it is preferable that the permanent adhesive strength measured after bonding the adhesive film 10 to the adherend glass and heating to a temperature of 80° C. is 16 N/25 mm or more. As a result, when the adhesive film 10 exhibits permanent adhesive strength, the adhesive layer 12 adheres to the adherend and easily maintains a state of following the curved surface. As a condition for measuring the permanent adhesive strength, heating at a temperature of 80° C. is an example from the viewpoint of making the adhesive film 10 easily reach the stage where the permanent adhesive strength is exhibited. As for the usage conditions of the adhesive film 10, the permanent adhesive strength may be developed by heating to a temperature different from 80° C., and the permanent adhesive strength is developed after being left at room temperature for a long time (for example, 24 hours or more). may

Although the thickness of the adhesive film 10 including the substrate 11 and the adhesive layer 12 is not particularly limited, it is, for example, about 40 to 200 μm. Here, the thickness of the adhesive film 10 is the thickness of the laminate having the substrate 11 and the adhesive layer 12 described above, and does not include the thickness of the cover film 13 and release film 14 described below. As for the thickness of the adhesion film 10, 100 micrometers or less are more preferable.

In order to protect the decorative surface 11 a, the adhesive film 10 may have a cover film 13 on the surface of the substrate 11 opposite to the adhesive layer 12 . Examples of the cover film 13 include, but are not limited to, polyester resin film, polyamide resin film, acrylic resin film, polyolefin resin film, cellulose resin film, cellophane film, paper, resin-laminated paper, metal foil, and resin-laminated metal. A foil, a metal-deposited resin film, or the like can be used.

The cover film 13 may be opaque or translucent, but if a highly transparent cover film 13 is used, the state of the decorative surface 11a can be easily visually confirmed without peeling off the cover film 13. ,preferable. The cover film 13 may be an unstretched resin film or a stretched resin film. The cover film 13 may have a release agent layer such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl-based release agent on the surface that contacts the decorative surface 11a. The surface of the cover film 13 that contacts the decorative surface 11a may not have a release agent.

In order to protect the adhesive surface 12a, the adhesive film 10 may have a release film 14 on the surface of the adhesive layer 12 opposite to the substrate 11. Examples of the release film 14 include, but are not limited to, 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. A foil, a metal-deposited resin film, or the like can be used.

The release film 14 may be opaque or translucent, but if a highly transparent release film 14 is used, the state of the adhesive surface 12a can be easily visually confirmed without peeling off the release film 14. preferable. The release film 14 may be a non-stretched resin film or a stretched resin film. The release film 14 may have a release agent layer such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl-based release agent on the surface that contacts the adhesive surface 12a. The release film 14 does not have to have a release agent on the side that contacts the adhesive surface 12a.

FIG. 2 shows an example of an adherend 20 to which the adhesive film 10 is attached. A printed layer 15 is formed on the substrate 11 , and an adherend 20 is attached to the adhesive layer 12 . The order of the step of forming the printed layer 15 on the substrate 11 and the step of bonding the adherend 20 to the adhesive layer 12 is not limited, but after forming the printed layer 15 on the substrate 11, the adhesive layer 12 It is preferable to bond the adherend 20 together. A step of cutting the pressure-sensitive adhesive film 10 to a size suitable for the adherend 20 may be included. Printing on the base material 11 is preferably performed before cutting the adhesive film 10 .

When printing on the substrate 11, an easy-adhesion layer such as a primer may be provided on the decorative surface 11a, if necessary. When the 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 the cover film 13 on the decorative surface 11a.

A method for forming the printing layer 15 is not particularly limited, but printing methods such as gravure printing, letterpress printing, offset printing, screen printing, and inkjet can be used. The printed layer 15 may be formed on the entire surface of the decorative surface 11a, or may be formed on a partial region of the decorative surface 11a. Two or more layers of the printed layer 15 may be laminated. Different printed layers 15 may be formed in different regions of the decorative surface 11a. Decoration other than the printed layer 15 may be applied to the decorative surface 11a. Other decorative layers include, for example, a metal deposition layer formed by sputtering or the like.

The ink for forming the print layer 15 may contain coloring materials such as pigments and dyes, and a binder. Examples of binders include, but are not limited to, polyamide resins, polyurethane resins, polyester resins, polyvinyl chloride resins, polyvinyl acetate resins, acrylic resins, epoxy resins, polybutadiene resins, and cyclized rubbers. The ink may contain solvents such as water, organic solvents and vegetable oils. After printing, the ink can be dried by volatilizing the solvent or curing the ink. In order to promote drying of the ink, heating, ultraviolet irradiation, or the like may be carried out.

The release film 14 is removed from the adhesive layer 12 before bonding the adhesive film 10 to the adherend 20 . As a result, the adhesive film 10 can be attached to the adherend 20 via the adhesive layer 12 . The adherend 20 may be an electronic device using glass for the display surface, housing, and the like. The material of the surface of the adherend 20 that contacts the adhesive layer 12 is not particularly limited, but examples thereof include glass, metal, and plastic. As shown in FIG. 3, the followability is also excellent when the adhesive film 10 is adhered to the adherend 20 having the flat portion 21 and the curved portion 22 . The curved surface portion 22 may be provided not only on one side around the flat portion 21 but also on two opposing sides or on each of the surrounding sides (four sides if the flat portion 21 is rectangular).

The method of bonding the adhesive film 10 to the adherend 20 is not particularly limited, but the adhesive layer 12 may be adhered to the adherend 20 using pressure, suction, or the like. As a pressurization method, a mechanical method using a roll member, a rod-like member, a plate-like member, or the like, or a pressure medium method using a fluid such as liquid or gas may be used. After temporarily attaching the pressure-sensitive adhesive film 10 to the adherend 20, it is preferable to isotropically pressurize by applying liquid pressure from the surroundings. The pressure medium may be hot water. Examples of the suction method include a method of sucking air between the adhesive film 10 and the adherend 20 using a vacuum.

Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

EXAMPLES The present invention will be specifically described below with reference to examples.

(Manufacture of base material)
Nine kinds of substrates made of polyurethane resin were produced according to formulations 1 to 9 shown in Table 1.
In formulation 1, 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., trade name Diferamine (registered trademark) MAU8288A, weight average molecular weight 50,000), and a TDI-based polyisocyanate (manufactured by Tosoh Corporation, Using a polyurethane solution containing 10 parts by weight of Coronate (registered trademark) L-45E), a film having a thickness of 60 μm was formed as a substrate by a solution casting method.

In Formulation 2, 100 parts by weight of the polycarbonate-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., trade name Diferamine (registered trademark) MAU8288A, weight average molecular weight 50,000) was used, and a polyurethane solution was prepared without adding a cross-linking agent. A film having a thickness of 60 μm was formed by a solution casting method to form a substrate.

In Formulation 3, 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Tosoh Corporation, trade name NIPPOLAN (registered trademark) 5199, weight average molecular weight 30,000), HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate) as a cross-linking agent Using a polyurethane solution containing 4 parts by weight of (registered trademark) HX), a film having a thickness of 60 μm was formed as a substrate by a solution casting method.

In Formulation 4, 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Tosoh Corporation, trade name NIPPOLAN (registered trademark) 5230, weight average molecular weight 60,000), and HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate) as a cross-linking agent. Using a polyurethane solution containing 4 parts by weight of (registered trademark) HX), a film having a thickness of 60 μm was formed as a substrate by a solution casting method.

In prescription 5, 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., product name Diferamine (registered trademark) MAU8288A, weight average molecular weight 50,000), and a TDI-based polyisocyanate (manufactured by Tosoh Corporation, Using a polyurethane solution containing 15 parts by weight of Coronate (registered trademark) L-45E), a film having a thickness of 60 μm was formed as a substrate by a solution casting method.

In formulation 6, 100 parts by weight of a polyether-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., trade name Rezamin (registered trademark) 8883HV, weight average molecular weight 80,000), and HDI-based polyisocyanate (manufactured by Tosoh Corporation) as a cross-linking agent , trade name Coronate (registered trademark) HX) was used as a substrate to form a film having a thickness of 60 μm by a solution casting method.

In Formulation 7, 100 parts by weight of a polyether-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., trade name Lezamin (registered trademark) 8883HV, weight average molecular weight 80,000) was used, and a polyurethane solution was prepared without adding a cross-linking agent. A film having a thickness of 60 μm was formed by a solution casting method to form a substrate.

In prescription 8, 100 parts by weight of a polyether-based polyurethane resin (manufactured by Dainichiseika Kogyo Co., Ltd., trade name Rezamin (registered trademark) 8883HV, weight average molecular weight 80,000), and HDI-based polyisocyanate (manufactured by Tosoh Corporation) as a cross-linking agent , trade name Coronate (registered trademark) HX) 6
Using a polyurethane solution containing parts by weight, a film having a thickness of 60 μm was formed as a substrate by a solution casting method.

In Formulation 9, 100 parts by weight of a polycarbonate-based polyurethane resin (manufactured by Fujikura Kasei Co., Ltd., trade name USV1402, weight average molecular weight 20,000), and HDI-based polyisocyanate (manufactured by Tosoh Corporation, trade name Coronate (registered trademark)) as a cross-linking agent. HX) was used to form a film having a thickness of 60 μm by a solution casting method using a polyurethane solution containing 10 parts by weight.

In addition, a commercially available thermoplastic polyurethane elastomer resin (TPU) film (manufactured by Okura Kogyo Co., Ltd., trade name Silklon (registered trademark) SNY97, thickness 80 μm) was cut into a predetermined size to prepare a base material of Comparative Example 8. did.

(Production of adhesive layer)
Adhesive layers A to D having the compositions shown in Table 2 were formed on one side of each substrate obtained as described above to obtain various adhesive films.
Adhesive layer A comprises 100 parts by weight of a polyester adhesive (Mitsubishi Chemical Corporation, trade name Nichigo Polyester S-0097, weight average molecular weight 20,000, Tg = 1 ° C.), the above crosslinking agent (trade name Coronate L -45E) Using an adhesive to which 4 parts by weight was added, an adhesive layer having a thickness of 20 μm was formed on one side of the substrate. The adhesive layer is formed by applying an adhesive containing a cross-linking agent and a solvent to the base material so that the thickness after drying is 20 μm, drying the solvent, and further cross-linking the adhesive by curing (aging). did.

Adhesive layer B is composed of 100 parts by weight of an acrylic adhesive (manufactured by Fujimori Industry Co., Ltd., trade name TR-499, weight average molecular weight 450,000, Tg = -30 ° C.), the above crosslinking agent (trade name Coronate L-45E ) was added to form an adhesive layer having a thickness of 20 μm on one side of the substrate in the same manner as the adhesive A.

Adhesive layer C comprises 100 parts by weight of a polyester adhesive (Mitsubishi Chemical Corporation, trade name Nichigo Polyester XNP-1013, weight average molecular weight 30,000, Tg = 16 ° C.), the above crosslinking agent (trade name Coronate L -45E) Using an adhesive to which 4 parts by weight was added, an adhesive layer having a thickness of 20 μm was formed on one side of the base material in the same manner as the adhesive A.

Adhesive D is 100 parts by weight of a polyester adhesive (manufactured by Mitsubishi Chemical Corporation, trade name Nichigo Polyester S-0091, weight average molecular weight 25,000, Tg = -10 ° C.), and the above crosslinking agent (product An adhesive layer having a thickness of 20 μm was formed on one side of the substrate in the same manner as the adhesive A, using an adhesive to which 4 parts by weight of Meiko Coronate L-45E) was added.

(Production of Examples 1-5 and Comparative Examples 1-8)
As shown in Table 3, the adhesive films of Examples 1 to 5 and Comparative Examples 1 to 8 were prepared by combining the substrates of formulations 1 to 9 and the substrate of Comparative Example 8 with the adhesive layers A to D, respectively. manufactured. The thickness of each adhesive film was as shown in Table 3.

Regarding the adhesives after crosslinking used in Examples 1 to 5 and Comparative Examples 1 to 8, the glass transition temperature (Tg) of the adhesive layer after crosslinking, and the storage elastic modulus G' (MPa) of the adhesive layer at 20 ° C. ) was measured. The storage modulus G' of the adhesive layer was determined by a method according to JIS K 7244-10. Table 3 shows the results.

(Method for measuring initial adhesive strength of adhesive film to glass)
A polyester film tape (thickness of the polyester base material: 25 μm) was attached to the surface of the adhesive film on the base side using a rubber roller so as not to allow air to enter. Then, a rubber roller with a load of 2 kg was used to laminate so that no air entered, to prepare an evaluation sample. Within 10 minutes after the adhesive film of the evaluation sample was attached to the glass, the adhesive layer was peeled off from the glass at a peeling angle of 180° and a peeling speed of 300 mm/min, and the adhesive strength (N/25 mm) was measured. did. The obtained measured value was defined as the initial adhesive strength.

(Method for measuring permanent adhesive strength of adhesive film to glass)
A polyester film tape (thickness of the polyester base material: 25 μm) was attached to the surface of the adhesive film on the base side using a rubber roller so as not to allow air to enter. A rubber roller with a load of 2 kg was used to laminate the laminate so that no air entered, and the obtained laminate was autoclaved under the conditions of 0.5 MPa, 80° C., and 20 minutes to prepare an evaluation sample. The evaluation sample was allowed to stand in an environment at a temperature of 23 ± 5 ° C. for 12 hours or more, and the adhesive layer and the glass were peeled off under the conditions of a peeling angle of 180 ° and a peeling speed of 300 mm / min. ) was measured. The obtained measured value was defined as the permanent adhesive strength.

(Measurement method of 50% stress, breaking stress and breaking elongation of adhesive film)
A sample piece of the adhesive film was taken with dimensions of 150 mm in the machine direction and 15 mm in the width direction. The distance between chucks was set to 100 mm, and a tensile test was carried out at a tensile speed of 300 mm/min in the state of the laminate having the substrate and the adhesive layer. The stress at break was defined as the breaking stress, the elongation at break was defined as the breaking elongation, and the stress at 50% elongation was defined as the 50% stress.

(Evaluation method for curved surface followability of adhesive film)
The curved surface conformability of the adhesive film was measured by applying the adhesive film to a glass adherend having a curved surface portion (width in plan view: 10 mm, cross section bending angle of 70 degrees) around a flat portion of 7 cm × 15 cm. The followability when the entire surface was laminated was visually evaluated, and the case of being excellent was evaluated as ◯, and the case of being poor was evaluated as x. A case of being excellent indicates a case where the adhesive could be adhered over the entire curved surface without any gaps or wrinkles. A bad case means that at least a part of the curved surface has gaps or wrinkles, and the pressure-sensitive adhesive film is torn.

(Evaluation method for anti-scattering property of adhesive film)
The anti-scattering property of the adhesive film is evaluated by hitting the central part of the adherend with a metal piece while the adhesive film is attached to the adherend made of glass to damage the adherend. A bad case was evaluated as x. "Excellent" means that the broken glass does not separate from the adhesive film and does not break and the adhesive film does not break. The film is torn.

(Evaluation results)
Table 3 also shows the evaluation results of the adhesive films of Examples 1 to 5 and Comparative Examples 1 to 8. The total thickness of the adhesive film is equal to the combined thickness of the substrate and the adhesive layer.

As shown in Table 3, the pressure-sensitive adhesive films of Examples 1 to 5 have a moderate range of 50% stress, breaking stress, and breaking elongation, have small initial adhesive strength, and have excellent curved surface conformability to adherends. rice field.
The pressure-sensitive adhesive films of Comparative Examples 3 and 8 had poor curved-surface followability because they had a large elongation before bonding the pressure-sensitive adhesive film to the adherend.
The pressure-sensitive adhesive films of Comparative Examples 1, 2, 4, 5, 6, and 7 had a large initial pressure-sensitive adhesive force, and were strongly stuck together when temporarily fixed to the adherend, resulting in poor curved surface followability.

In the adhesive films of Examples 1 to 5, the substrate did not break when the glass broke, the adhesive layer did not peel off, and the anti-scattering property was excellent.
The pressure-sensitive adhesive films of Comparative Examples 3 and 8 had poor anti-scattering properties because the base material was broken when the glass was broken.
The adhesive films of Comparative Examples 4, 5, and 7 had poor anti-scattering properties because the adhesive layer was peeled off when the glass was broken.

DESCRIPTION OF SYMBOLS 10... Adhesive film, 11... Base material, 11a... Decorating surface, 12... Adhesive layer, 12a... Adhesive surface, 13... Cover film, 14... Release film, 15... Printing layer, 20... Adherend, 21... Plane surface Part 22: Curved surface part.

Claims (8)

An adhesive film comprising a substrate and an adhesive layer laminated on one side of the substrate,
The base material is made of a polyurethane resin crosslinked with a crosslinking agent,
The laminate having the base material and the adhesive layer has a 50% stress of 10 to 29 MPa, a breaking stress of 30 to 69 MPa, and a breaking elongation of 200 to 350%,
The pressure-sensitive adhesive film has an initial pressure-sensitive adhesive strength of 2 N/25 mm or less, which is measured immediately after the pressure-sensitive adhesive film is adhered to glass as an adherend. 2. The adhesive film according to claim 1, wherein the adhesive film has a permanent adhesive strength of 16 N/25 mm or more, which is measured after heating to a temperature of 80[deg.] C. after bonding to glass as an adherend. The pressure-sensitive adhesive film according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is formed by cross-linking a polyester pressure-sensitive adhesive having a glass transition temperature (Tg) of -5°C to 19°C. The adhesive film according to any one of claims 1 to 3, wherein the storage elastic modulus G' of the adhesive layer obtained by dynamic viscoelasticity measurement at 20°C is 1.0 MPa or more. The pressure-sensitive adhesive film according to any one of claims 1 to 4, further comprising a cover film on the surface of the substrate opposite to the pressure-sensitive adhesive layer. The pressure-sensitive adhesive film according to any one of claims 1 to 4, wherein a printed layer is formed on the surface of the substrate opposite to the pressure-sensitive adhesive layer. The pressure-sensitive adhesive film according to any one of claims 1 to 6, further comprising a release film on the surface of the pressure-sensitive adhesive layer opposite to the substrate. The pressure-sensitive adhesive film according to any one of claims 1 to 6, wherein the surface of the pressure-sensitive adhesive layer opposite to the base material is adhered to glass as an adherend.

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