阅读说明：本技术 固化型粘合粘接片、及固化型粘合粘接片的制造方法 (Curable adhesive sheet and method for producing curable adhesive sheet ) 是由 田中亚树子 新田步 保井淳 于 2020-03-17 设计创作，主要内容包括：本发明涉及固化型粘合粘接片,其具备由粘合粘接剂组合物形成的粘合粘接剂层,所述粘合粘接剂组合物包含：环氧树脂、潜在性固化剂和凝胶化剂,前述潜在性固化剂具有45℃以上且120℃以下的反应开始温度。(The present invention relates to a curable adhesive sheet comprising an adhesive layer formed from an adhesive composition, the adhesive composition comprising: an epoxy resin, a latent curing agent, and a gelling agent, wherein the latent curing agent has a reaction initiation temperature of 45 ℃ to 120 ℃.)

1. A curable adhesive sheet comprising an adhesive layer formed from an adhesive composition,

the adhesive composition comprises: epoxy resin, latent curing agent and gelling agent,

the latent curing agent has a reaction initiation temperature of 45 ℃ or higher and 120 ℃ or lower.

2. The curable adhesive sheet according to claim 1, wherein the latent curing agent is an amine compound.

3. The curable adhesive sheet according to claim 1 or 2, wherein the latent curing agent is contained in an amount of 15 to 40 parts by mass based on 100 parts by mass of the epoxy resin.

4. The curable adhesive sheet according to any one of claims 1 to 3, wherein the gelling agent is a core-shell acrylic resin.

5. The curable adhesive sheet according to any one of claims 1 to 4, wherein the gelling agent is contained in an amount of 5 to 40 parts by mass based on 100 parts by mass of the epoxy resin.

6. The curable adhesive sheet according to any one of claims 1 to 5, wherein 50% by mass or less of the epoxy resin is an epoxy resin that is solid at 25 ℃.

7. A method for manufacturing a curable adhesive-bonding sheet, comprising:

a step (1) of preparing an adhesive composition containing: an epoxy resin, a latent curing agent having a reaction initiation temperature of 45 ℃ to 120 ℃, and a gelling agent; and

and (2) forming a sheet-like pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and holding the pressure-sensitive adhesive layer at 30 to 43 ℃ to form a sheet.

Technical Field

The present invention relates to a curable adhesive sheet and a method for producing a curable adhesive sheet.

Background

Conventionally, in the electronics industry, adhesives for a semi-structure are used for mechanically bonding many components in an electronic device. The adhesive for a semi-structure is typically used by coating a liner with a latent curing agent to produce an adhesive tape for a semi-structure.

When a component in an electronic device is bonded using a semi-structural adhesive tape, there is a problem that a high curing activation temperature may damage a fine member in the electronic device.

In view of the above problems, adhesive tapes that can be cured at a relatively low temperature are being studied. For example, patent document 1 discloses a low-temperature curable epoxy adhesive tape comprising: a curing agent layer having a 1 st surface and a 2 nd surface opposite thereto, and comprising a Scrim (Scrim), a binder layer at least partially enclosing the Scrim, and a latent curing agent dispersed in the binder layer; a 1 st epoxy layer disposed on the 1 st surface of the curing agent layer; and a 2 nd epoxy layer disposed on the 2 nd surface of the curing agent layer.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-525984

Disclosure of Invention

Problems to be solved by the invention

In order to produce an adhesive sheet, it is necessary to form a resin composition containing an epoxy or acrylic solid material into a sheet. When a resin composition containing such a solid material is formed into a sheet, it is necessary to coat the surface of a release film or the like with the composition as uniformly as possible. Therefore, it is conceivable that the resin composition is once heated to reduce the viscosity, and then various materials are mixed or once dissolved in a solvent, and then the resin composition is applied to a release film or the like and dried to form a sheet.

However, when a resin composition containing a latent curing agent is used, the curing reaction starts at the stage of sheeting when the resin composition is heated to reduce its viscosity. In addition, the same problem occurs when a solvent is used. Therefore, it is difficult to form a sheet by the above-described method.

Accordingly, an object of the present invention is to provide a curable adhesive sheet having adhesiveness and being curable at low temperature, and a method for producing the same.

Means for solving the problems

The present inventors have made intensive studies to solve the above problems. As a result, they have found that a curable adhesive sheet which can be cured at a low temperature and has adhesive properties can be provided by using a latent curing agent having a specific reaction initiation temperature as a curing agent and using a gelling agent, and have completed the present invention.

One embodiment of the present invention relates to a curable adhesive sheet including an adhesive layer formed from an adhesive composition, the adhesive composition including: an epoxy resin, a latent curing agent, and a gelling agent, wherein the latent curing agent has a reaction initiation temperature of 45 ℃ to 120 ℃.

In one embodiment of the present invention, in the curable pressure-sensitive adhesive sheet, the latent curing agent is preferably an amine compound.

In one embodiment of the present invention, the curable adhesive sheet preferably contains 15 to 40 parts by mass of the latent curing agent per 100 parts by mass of the epoxy resin.

In one embodiment of the present invention, in the curable pressure-sensitive adhesive sheet, the gelling agent is preferably a core-shell type acrylic resin.

In one embodiment of the present invention, the curable adhesive sheet preferably contains 5 to 40 parts by mass of a gelling agent per 100 parts by mass of the epoxy resin.

In one embodiment of the present invention, in the curable adhesive sheet, 50% by mass or less of the epoxy resin is preferably an epoxy resin which is solid at 25 ℃.

One embodiment of the present invention relates to a method for producing a curable adhesive sheet, including: a step (1) of preparing an adhesive composition containing: an epoxy resin, a latent curing agent having a reaction initiation temperature of 45 ℃ to 120 ℃, and a gelling agent; and (2) forming a sheet-like pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition, and holding the pressure-sensitive adhesive layer at 30 to 43 ℃ to form a sheet.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiments of the present invention, a curable adhesive sheet having adhesive properties and curable at low temperature and a method for producing the same can be provided. The sheet has adhesiveness in an uncured state, and therefore can be attached to an adherend in the form of a sheet, and can also exhibit adhesiveness by low-temperature curing.

Drawings

Fig. 1 is a view showing a curable adhesive sheet 1 (without a base material) according to an embodiment of the present invention.

Fig. 2 is a view showing a curable adhesive sheet (with a base material) according to an embodiment of the present invention. Fig. 2 (a) is a view showing a curable pressure-sensitive adhesive sheet 2a having a pressure-sensitive adhesive layer only on one surface of a base material, and fig. 2 (b) is a view showing a curable pressure-sensitive adhesive sheet 2b having a pressure-sensitive adhesive layer on both surfaces of a base material.

Fig. 3 is a view showing a state in which the pressure-sensitive adhesive layer 11 in the curable pressure-sensitive adhesive sheet according to the embodiment of the present invention is disposed on the 1 st adherend 31.

Fig. 4 is a diagram showing an adhesive structure 100 obtained by using a curable adhesive sheet according to an embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The present invention is not limited to the embodiments described below.

In the present specification, "a to B" indicating a range means "a to B inclusive". In the present specification, "mass%" and "weight%" are used as the same meaning, and "parts by mass" and "parts by weight" are used as the same meaning.

[ curing type adhesive sheet ]

The curable adhesive sheet according to an embodiment of the present invention is characterized by comprising an adhesive layer formed from an adhesive composition comprising: an epoxy resin, a latent curing agent, and a gelling agent, wherein the latent curing agent has a reaction initiation temperature of 45 ℃ to 120 ℃. The curable adhesive sheet according to one embodiment of the present invention is an uncured adhesive sheet having adhesive properties. The sheet has adhesiveness in an uncured state, and therefore can be attached to an adherend in the form of a sheet, and can also exhibit adhesiveness by low-temperature curing.

The curable adhesive sheet according to an embodiment of the present invention includes an adhesive layer formed from an adhesive composition. Hereinafter, each component contained in the pressure-sensitive adhesive composition will be described in detail.

< epoxy resin >

The adhesive composition according to one embodiment of the present invention contains an epoxy resin.

The kind of the epoxy resin is not particularly limited. Examples thereof include bisphenol epoxy resins such as bisphenol a epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, and hydrogenated bisphenol a epoxy resin, naphthalene epoxy resin, biphenyl epoxy resin, bicyclic epoxy resin, alicyclic epoxy resin, triglycidyl isocyanurate epoxy resin, hydantoin epoxy resin, glycidyl ether epoxy resin, glycidyl amino epoxy resin, and the like.

Preferred examples thereof include bisphenol epoxy resins, and more preferred examples thereof include bisphenol a epoxy resins and bisphenol F epoxy resins.

The epoxy resins may be used alone or in combination of 2 or more.

The epoxy resin may be in any form of liquid, semisolid, and solid at room temperature.

The epoxy resin which is liquid at normal temperature is specifically liquid at 25 ℃. The viscosity of the liquid epoxy resin is, for example, 30 pas or more, preferably 80 pas or more at 25 ℃. The viscosity of the liquid epoxy resin is, for example, 500 pas or less, preferably 300 pas or less at 25 ℃.

The epoxy resin which is solid at normal temperature is specifically solid at 25 ℃. The softening point of the solid epoxy resin is, for example, 70 ℃ or higher, preferably 75 ℃ or higher.

The epoxy resin contained in the adhesive composition according to one embodiment of the present invention is preferably an epoxy resin that is solid at 25 ℃. The epoxy resin contained in the adhesive composition according to one embodiment of the present invention is more preferably an epoxy resin that is solid at 25 ℃ in an amount of 45% by mass or less, and still more preferably an epoxy resin that is solid at 25 ℃ in an amount of 30% by mass or less.

In addition, the epoxy resin contained in the adhesive composition according to an embodiment of the present invention is preferably an epoxy resin that is solid at 25 ℃ in an amount of 0% by mass or more, and more preferably an epoxy resin that is solid at 25 ℃ in an amount of 10% by mass or more.

By setting 50 mass% or less of the epoxy resin to be a solid epoxy resin at 25 ℃, the viscosity of the adhesive composition is not excessively high, and the curing agent and the gelling agent can be easily mixed. Further, by making 10% by mass or more of the epoxy resin be a solid epoxy resin at 25 ℃, the time required for forming a sheet can be shortened.

The compounding ratio of the epoxy resin is, for example, 40 mass% or more, preferably 50 mass% or more, relative to the total amount of the pressure-sensitive adhesive composition. The compounding ratio of the epoxy resin is, for example, 100 mass% or less, preferably 70 mass% or less, with respect to the total amount of the pressure-sensitive adhesive composition. By setting the range above, a more convenient and strong adhesion can be achieved.

The pressure-sensitive adhesive composition according to an embodiment of the present invention may contain a resin other than an epoxy resin. Examples thereof include silicone compounds, polyhydric alcohol compounds such as polypropylene glycol, urethane resins, and acrylic resins.

< latent curing agent >

The pressure-sensitive adhesive composition according to one embodiment of the present invention contains a latent curing agent.

The latent curing agent is a curing agent which is solid at normal temperature (specifically, 25 ℃) and is activated at a predetermined temperature to be compatible with an epoxy resin to cure the epoxy resin. In particular, one embodiment of the present invention is characterized in that the latent curing agent starts to be activated at a temperature ranging from 45 ℃ to 120 ℃. That is, the latent curing agent has a reaction initiation temperature of 45 ℃ or higher and 120 ℃ or lower.

When the reaction start temperature of the latent curing agent is in the above range, the reaction can be performed at a relatively low temperature during curing while preventing the initiation of curing during the preparation and storage of the resin composition.

The latent curing agent in one embodiment of the present invention has a reaction initiation temperature of 120 ℃ or lower, preferably 100 ℃ or lower. The latent curing agent in one embodiment of the present invention has a reaction initiation temperature of 45 ℃ or higher, preferably 50 ℃ or higher.

The reaction initiation temperature of the latent curing agent in one embodiment of the present invention can be measured, for example, by the following method.

About 5mg of a resin composition prepared by mixing 20 parts by mass of a latent curing agent with 100 parts by mass of a bisphenol F type epoxy resin (jER806, manufactured by Mitsubishi chemical corporation) was weighed in a closed sample cell made of aluminum, and Heat Flow (Heat Flow) behavior of the resin composition was obtained at a temperature rise rate of 2 ℃/min under a nitrogen atmosphere of 50 mL/min using a temperature control DSC (trade name "Q-2000", manufactured by TA Instruments Inc.). The heat generation starting temperature, which is the temperature at which the heat flow behavior at this time increases, is set as the reaction starting temperature of the latent curing agent.

The latent curing agent in one embodiment of the present invention is not particularly limited in its kind as long as it has the reaction initiation temperature. Examples thereof include amine compounds, urea compounds, amide compounds, dihydrazide compounds, imidazole compounds, and imidazoline compounds.

Examples of the amine compound include ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, amine adducts thereof, m-phenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone.

Examples of the urea-based compound include 3- (3, 4-dichlorophenyl) -1, 1-Dimethylurea (DCMU), N ' -phenyl-N, N-dimethylurea, and 1,1 ' - (methyl-m-phenylene) bis (3,3 ' -dimethylurea).

Among such urea compounds, 3- (3, 4-dichlorophenyl) -1, 1-Dimethylurea (DCMU) is preferably used.

Examples of the amide compound include polyamide.

Examples of the hydrazide-based compound include dihydrazides such as adipic acid dihydrazide.

Examples of the imidazole-based compound include methylimidazole, 2-ethyl-4-methylimidazole, ethylimidazole, isopropylimidazole, 2, 4-dimethylimidazole, phenylimidazole, undecylimidazole, heptadecylimidazole, and 2-phenyl-4-methylimidazole.

Examples of the imidazoline-based compound include methylimidazoline, 2-ethyl-4-methylimidazoline, ethylimidazoline, isopropylimidazoline, 2, 4-dimethylimidazoline, phenylimidazoline, undecylimidazoline, heptadecylimidazoline, and 2-phenyl-4-methylimidazoline.

Such latent curing agents may be used alone or in combination.

Among such latent curing agents, amine compounds are preferably used.

The compounding ratio of such a latent curing agent is, for example, 15 to 40 parts by mass, preferably 20 to 35 parts by mass, and more preferably 20 to 30 parts by mass, based on 100 parts by mass of the epoxy resin. By setting the range, the initiation of curing during storage can be prevented, and the reaction can be carried out at a relatively low temperature during curing.

< gelling agent >

The pressure-sensitive adhesive composition according to one embodiment of the present invention contains a gelling agent.

The pressure-sensitive adhesive composition according to an embodiment of the present invention contains a gelling agent, and thus the pressure-sensitive adhesive composition is solidified (gelled) and can maintain a sheet shape. Therefore, the composition can be applied more uniformly to the surface of a release film, a substrate, or the like by containing a gelling agent, and can be formed into a sheet.

The gelling agent is not particularly limited as long as it has the above-described effects. For example, silica powder surface-treated with a silane coupling agent or the like, mineral fibers such as sepiolite, and a core-shell type acrylic resin are used. Among them, the core-shell type acrylic resin is preferable from the viewpoint of compatibility with the epoxy resin.

The core-shell type is, for example, pearl-like fine particles in which a core layer made of a thermoplastic resin such as an acrylic resin is covered with a shell layer made of the same resin as or another resin than the core layer. The multilayer structure may be formed according to the application.

Examples of the core-shell type acrylic resin include a core-shell type emulsion in which an acrylic, styrene-acrylic, or styrene-methacrylic resin is used for a core layer, and an acrylic, styrene-acrylic, or styrene-methacrylic resin is used for a shell layer. Specific examples thereof include Dianal (registered trademark) LP-3106, Dianal (registered trademark) LP-3109, manufactured by Mitsubishi chemical corporation, JONCRYL (registered trademark) 74J, JONCRYL (registered trademark) 537, PDX7677, manufactured by BASF corporation, and Zefiac, manufactured by Aica Kogyo Co., Ltd.

The compounding ratio of such a gelling agent is, for example, 5 to 40 parts by mass, preferably 10 to 30 parts by mass, and more preferably 10 to 20 parts by mass, based on 100 parts by mass of the epoxy resin. By setting the amount to the above range, the coating can be applied more uniformly to the surface of a release film, a substrate, or the like, and the sheet can be easily formed.

< other ingredients >

The pressure-sensitive adhesive composition according to an embodiment of the present invention may contain a filler such as silica, mica, or calcium carbonate for the purpose of adjusting the elastic modulus of the cured layer. The amount of the filler is not particularly limited, and is, for example, 1 part by mass or more, preferably 10 parts by mass or more, per 100 parts by mass of the adhesive composition. The amount of the filler is, for example, 100 parts by mass or less, preferably 80 parts by mass or less, per 100 parts by mass of the pressure-sensitive adhesive composition.

The curable adhesive sheet according to an embodiment of the present invention includes an adhesive layer formed from the adhesive composition. The pressure-sensitive adhesive sheet of the present embodiment may be a base-less pressure-sensitive adhesive sheet having a form in which a pressure-sensitive adhesive layer is held on a release sheet as shown in fig. 1, or may be a base-attached pressure-sensitive adhesive sheet having a form in which a pressure-sensitive adhesive layer is provided on one surface or both surfaces of a sheet-like base (support) as shown in fig. 2 (a) and (b). The term "adhesive sheet" as used herein includes articles such as adhesive tapes, adhesive labels, and adhesive films.

The adhesive layer is typically formed continuously, but is not limited to the above form. For example, the pressure-sensitive adhesive layer may be formed in a regular or random pattern such as dots or stripes. The adhesive sheet of the present embodiment may be in the form of a roll or a sheet. Alternatively, the adhesive sheet may be processed into various shapes.

The curable adhesive sheet according to an embodiment of the present invention may be in the form of a base-attached adhesive sheet including a base material bonded to the other back surface of the adhesive layer. Fig. 2 (a) is a schematic cross-sectional view showing an example of a configuration in which an adhesive layer is formed on one surface of a base material in a curable adhesive sheet according to an embodiment of the present invention. The pressure-sensitive adhesive sheet 2a shown in fig. 2 (a) includes a base material 21 and a pressure-sensitive adhesive layer 11 formed on one surface of the base material.

As another embodiment, fig. 2 (b) is a schematic cross-sectional view showing a configuration example in which adhesive layers are formed on both surfaces of the base material 21. The pressure-sensitive adhesive sheet 2b shown in fig. 2 (b) includes a base material 21, and a 1 st pressure-sensitive adhesive layer 11 and a 2 nd pressure-sensitive adhesive layer 12 formed on both surfaces of the base material.

Examples of the substrate that imparts toughness to the pressure-sensitive adhesive layer include glass cloth, resin-impregnated glass cloth, synthetic resin nonwoven fabric, metal foil, carbon fiber, polyester film, and foam sheet.

The glass cloth is made of glass fibers, and known glass cloths can be mentioned. Among such glass cloths, a silane coupling agent-treated glass cloth subjected to a treatment with a silane coupling agent is preferable in view of adhesion between the base material and the pressure-sensitive adhesive layer.

Examples of the silane coupling agent include known silane coupling agents such as aminosilane, epoxy silane, and acryloxy silane. Such silane coupling agents may be used alone or may be used in combination. Among such silane coupling agents, preferable examples include epoxy silanes.

The resin-impregnated glass cloth is obtained by impregnating the glass cloth with a synthetic resin such as a thermosetting resin or a thermoplastic resin, and known resin-impregnated glass cloths can be mentioned.

Examples of the thermosetting resin include epoxy resin, urethane resin, melamine resin, and phenol resin. Examples of the thermoplastic resin include a vinyl acetate resin, an ethylene-vinyl acetate copolymer (EVA), a vinyl chloride resin, and an EVA-vinyl chloride resin copolymer. The thermosetting resin and the thermoplastic resin may be used individually or in combination (for example, a melamine resin and a vinyl acetate resin may be used in combination).

Examples of the synthetic resin nonwoven fabric include polypropylene resin nonwoven fabric, polyethylene resin nonwoven fabric, and ester resin nonwoven fabric.

Examples of the metal foil include known metal foils such as aluminum foil and steel foil.

The carbon fiber is a fabric made of a fiber containing carbon as a main component, and known carbon fibers can be mentioned.

Examples of the polyester film include a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, and a polybutylene terephthalate (PBT) film.

The foam sheet is an amorphous crosslinked type, and examples thereof include resins such as polyurethane, polyolefin (polyethylene, polypropylene, and copolymers thereof), silicone, and acrylic, and rubbers.

Among such substrates, glass cloth is preferable. By using glass cloth as a base material, a flexible adhesive sheet having high insulation reliability can be provided, and potential difference corrosion which may occur when different metal materials such as iron-aluminum are joined can be prevented.

The thickness of such a substrate is, for example, 25 μm or more, preferably 50 μm or more. The thickness of the base material is, for example, 300 μm or less, preferably 250 μm or less.

If the thickness of the substrate is less than 25 μm, the hardness required as the substrate cannot be secured, and the workability of the adhesive sheet for adhesion may be lowered. On the other hand, when the thickness of the base material is within the above range, the adhesion workability of the adhesive sheet can be improved.

[ method for producing curable adhesive sheet ]

The method for producing a curable adhesive sheet according to an embodiment of the present invention includes: a step (1) of preparing an adhesive composition containing: an epoxy resin, a latent curing agent having a reaction initiation temperature of 45 ℃ to 120 ℃, and a gelling agent; and a step (2) of forming the pressure-sensitive adhesive layer into a sheet form from the pressure-sensitive adhesive composition, and holding the pressure-sensitive adhesive layer at 30 to 43 ℃ to form a sheet.

Hereinafter, each step will be explained.

< step (1) of preparing an adhesive composition comprising an epoxy resin, a latent curing agent having a reaction initiation temperature of 45 ℃ to 120 ℃ inclusive, and a gelling agent >

The step (1) is a step of preparing the pressure-sensitive adhesive composition according to one embodiment of the present invention. In order to obtain the pressure-sensitive adhesive composition according to one embodiment of the present invention, for example, a resin composition is prepared by blending an epoxy resin, a latent curing agent, and a gelling agent. The above-mentioned components can be used in the same manner for each component.

< step (2) of forming a sheet-like pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition, holding the pressure-sensitive adhesive layer at 30 ℃ to 43 ℃ and forming the pressure-sensitive adhesive layer into a sheet

When a sheet is produced using the pressure-sensitive adhesive composition prepared in the step (1), first, a sheet-like pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition is formed. Therefore, in the case of no substrate, the pressure-sensitive adhesive composition is formed into a sheet shape on the surface of the release film.

In the case of the tape base, the pressure-sensitive adhesive composition is formed into a sheet shape on the base. Hereinafter, an embodiment in which the release film is formed in a sheet shape on the surface without a base material will be described by way of example, but the embodiment of the present invention is not limited thereto.

Specifically, as shown in fig. 1, after the pressure-sensitive adhesive composition is applied to the surface of the release film 13, another release film 14 is disposed from the side on which the pressure-sensitive adhesive composition is applied (the surface opposite to the contact surface with the release film), and the pressure-sensitive adhesive layer 11 is formed in a sheet shape between the release films. That is, the pressure-sensitive adhesive layer 11 can be formed in a sheet-like form between the release films 13 and 14 by sandwiching the pressure-sensitive adhesive composition between 2 sheets of the release films 13 and 14.

The release film is, for example, a release sheet having a substantially rectangular flat plate shape, and the upper surface and the lower surface are formed in a flat shape.

The release film is formed of a resin material such as a vinyl polymer such as polyolefin (specifically, polyethylene, polypropylene) or ethylene-vinyl acetate copolymer (EVA), a polyester such as polyethylene terephthalate or polycarbonate, or a fluororesin such as polytetrafluoroethylene. The release film may be made of a metal material such as iron, aluminum, or stainless steel.

The release film is preferably a polyester film, and more preferably a polyethylene terephthalate film.

If necessary, the surface of the release film may be subjected to an appropriate release treatment.

The thickness of the release film is, for example, 10 μm or more and 1000 μm or less.

Examples of the coating method for coating the adhesive composition on the surface of the release film include a doctor blade method, a roll method, a screen method, and a gravure method.

In this way, a sheet-like pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition is formed on the release film.

In the case of a tape-attached substrate and a pressure-sensitive adhesive layer formed on the substrate, a direct method of forming a pressure-sensitive adhesive layer by directly applying a pressure-sensitive adhesive composition can be used, as in the case of a pressure-sensitive adhesive layer formed on a release film. Alternatively, a transfer method of transferring the pressure-sensitive adhesive layer formed on the release film to a base material may be used.

Then, the pressure-sensitive adhesive layer formed in a sheet form on the release film or the base material is held at 30 to 43 ℃. Thereby, the gelling agent is solidified to form a sheet. By maintaining the pressure-sensitive adhesive layer formed in a sheet form at 30 to 43 ℃, activation of the latent curing agent and curing of the pressure-sensitive adhesive composition can be prevented.

The holding temperature of the pressure-sensitive adhesive layer formed in a sheet form is 30 to 43 ℃, preferably 33 to 40 ℃.

The holding time of the pressure-sensitive adhesive layer formed in a sheet form is not particularly limited as long as activation of the latent curing agent does not occur and the pressure-sensitive adhesive composition is cured, and is usually 1 to 7 days, preferably 2 to 4 days.

In order to secure adhesiveness after curing, the thickness of the pressure-sensitive adhesive layer formed into a sheet is, for example, 50 μm or more, preferably 80 μm or more, and more preferably 100 μm or more. The thickness of the pressure-sensitive adhesive layer formed into a sheet is, for example, 2000 μm or less, preferably 1000 μm or less, and more preferably 700 μm or less. Particularly, the thickness of the pressure-sensitive adhesive layer is preferably 100 to 700 μm in order to achieve both good curability and high adhesiveness after curing.

Next, a method of using the curable adhesive sheet according to the embodiment of the present invention will be described. Hereinafter, a method (without a base material) of bonding adherends (the 1 st adherend and the 2 nd adherend) to each other will be described by way of example, but the method of using the curable pressure-sensitive adhesive sheet in the embodiment of the present invention is not limited thereto.

First, the pressure-sensitive adhesive layer 11 formed into a sheet is transferred from a release film to the surface of the 1 st adherend 31. Specifically, first, the pressure-sensitive adhesive layer 11 is brought into contact with the 1 st adherend 31, and then the release film is peeled off from the pressure-sensitive adhesive layer 11.

When the pressure-sensitive adhesive layer 11 is sandwiched by 2 release films, for example, first, one release film is peeled off. Next, the exposed surface of the exposed adhesive layer 11 is brought into contact with the 1 st adherend 2, and then the release film is peeled from the adhesive layer 11.

Thereby, as shown in fig. 3, the pressure-sensitive adhesive layer 11 is disposed on the 1 st adherend 31.

Next, the pressure-sensitive adhesive layer 11 disposed on the 1 st adherend 31 is brought into contact with the 2 nd adherend 41 on the side on which the pressure-sensitive adhesive layer 11 is disposed. The method of bringing the 2 nd adherend 41 into contact with the side of the 1 st adherend 31 on which the pressure-sensitive adhesive layer 11 is disposed is not particularly limited, and any method can be employed.

After the 1 st adherend 31 and the 2 nd adherend 41 are brought into contact with each other via the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 is heated and cured, whereby the 1 st adherend 31 and the 2 nd adherend 41 are strongly bonded, and a bonded structure 100 as shown in fig. 4 can be produced.

In the case of the adhesive sheet with a base material, the adhesive sheet with a base material and the adherend can be firmly bonded to each other by placing the adhesive sheet with a base material on the adherend by bringing the surface of the adhesive layer opposite to the base material into contact with the adherend and then heating the adhesive layer. That is, a bonded structure in which the adhesive sheet with a substrate and an adherend are bonded can be manufactured.

The pressure-sensitive adhesive composition according to the embodiment of the present invention contains a latent curing agent having a reaction initiation temperature of 45 ℃ or higher and 120 ℃ or lower, and therefore the pressure-sensitive adhesive layer formed from the composition can be cured at a relatively low temperature.

The temperature at which the pressure-sensitive adhesive layer is heat-cured is, for example, 70 ℃ to 150 ℃. The temperature at which the pressure-sensitive adhesive layer is heat-cured is preferably 75 ℃ or higher, and more preferably 80 ℃ or higher. The temperature at the time of heat curing the adhesive layer is preferably 120 ℃ or lower, and more preferably 100 ℃ or lower.

The reaction time for heat curing the adhesive layer varies depending on the temperature, and is, for example, 5 to 120 minutes, preferably 10 to 60 minutes, and more preferably 20 to 40 minutes.

Specifically, it is preferably cured under any of the following heating conditions (1) to (5).

(1) Heating at a temperature of 70 ℃ or higher and less than 80 ℃ for 30 to 120 minutes. More preferably, the heating is carried out for 40 to 100 minutes.

(2) Heating at 80-90 deg.C for 20-100 min. More preferably, the heating is carried out for 25 to 90 minutes.

(3) Heating at a temperature of 90 ℃ or higher and less than 100 ℃ for 10 to 60 minutes. More preferably, the heating is carried out for 15 to 45 minutes.

(4) Heating at a temperature of 100 ℃ or higher and less than 120 ℃ for 10 to 40 minutes. More preferably, the heating is carried out for 15 to 30 minutes.

(5) Heating at a temperature of 120 ℃ or higher and less than 150 ℃ for 5 to 30 minutes. More preferably, the heating is carried out for 10 to 20 minutes.

The shear adhesion of the pressure-sensitive adhesive layer formed as described above is preferably 5MPa or more, more preferably 7MPa or more, and still more preferably 10MPa or more. When the shear adhesion of the pressure-sensitive adhesive layer is 5MPa or more, the pressure-sensitive adhesive layer is preferable because the pressure-sensitive adhesive layer has excellent adhesiveness and can easily and reliably adhere the 1 st adherend to the 2 nd adherend.

The shear adhesion of the adhesive layer was measured by the following method.

A curable adhesive sheet cut to a width of 25 mm. times.10 mm in length was attached to the tip of SPCC (JISG3141) having a width of 25 mm. times.100 mm in length. times.1.6 mm in thickness, and the other SPCC was superposed on the tip of the adhesive sheet, fixed with a jig, and then cured at 80 ℃ for 30 minutes. The test piece thus obtained was stretched at 5 mm/min in the longitudinal direction by a tensile tester AG-X (manufactured by Shimadzu corporation), and the test force at the time of peeling was measured. The shear adhesion was calculated by the following formula.

Shear adhesion (MPa) test force (N)/250mm²

Examples

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples.

(sheet property)

The sheet properties were evaluated by determining whether the pressure-sensitive adhesive composition could be formed into a sheet. The composition was evaluated as "good" when it could be formed into a sheet, and as "poor" when it could not be formed into a sheet.

(adhesiveness)

The adhesiveness was evaluated by the presence or absence of adhesiveness (stickiness) of the sheet thus produced. The sheet was evaluated to be "good" when having adhesiveness and evaluated to be "poor" when not having adhesiveness. In table 1, "-" indicates that sheeting, which is a precondition for evaluation of adhesiveness, could not be achieved.

(shear adhesion)

A curable adhesive sheet having a cut width of 25 mm. times.10 mm in length was attached to the tip of SPCC (JISG3141) having a width of 25 mm. times.100 mm in length. times.1.6 mm in thickness, and the other SPCC was superposed on the tip of the adhesive sheet, fixed by a jig, and cured at 80 ℃ for 30 minutes. The test piece thus obtained was stretched at 5 mm/min in the longitudinal direction by a tensile tester AG-X (manufactured by Shimadzu corporation), and the test force at the time of peeling was measured. The shear adhesion was calculated by the following formula.

Shear adhesion (MPa) test force (N)/250mm²

In table 1, "-" indicates no measurement, and "no measurement" indicates that the shear adhesion cannot be measured because there is no sheet property or adhesiveness.

(reaction initiation temperature of latent curing agent)

The reaction initiation temperature of the latent curing agent used in the examples, comparative examples and reference examples was measured by the following method.

About 5mg of a resin composition prepared by mixing 20 parts by mass of a latent curing agent with 100 parts by mass of a bisphenol F type epoxy resin (jER806, manufactured by Mitsubishi chemical corporation) was weighed in a closed sample cell made of aluminum, and the heat flow behavior of the resin composition was obtained at a temperature rise rate of 2 ℃/min under a nitrogen atmosphere of 50 mL/min using a temperature control DSC (trade name "Q-2000", manufactured by TA Instruments Inc.). The heat generation starting temperature, which is the temperature at which the heat flow behavior at this time increases, is set as the reaction starting temperature of the latent curing agent.

[ preparation of adhesive composition ]

(example 1)

An adhesive composition was prepared by mixing 100 parts by mass of a liquid bisphenol F-type epoxy resin (trade name "jER 806", manufactured by mitsubishi chemical corporation), 20 parts by mass of an amine compound (trade name "Fujicure FXR-1020", manufactured by T & KTOKA corporation) as a latent curing agent, and 20 parts by mass of a core-shell type acrylic resin (trade name "Dianal (registered trade name) LP-3106", manufactured by mitsubishi chemical corporation) as a gelling agent. The reaction initiation temperature of the latent curing agent was 54 ℃ as measured by the above method.

The pressure-sensitive adhesive layer was formed into a sheet shape by pressing with a manual hydraulic vacuum heating press (product name "11 FD", manufactured by hokken corporation) between 2 sheets of release paper laminated with polyethylene so that the thickness of the pressure-sensitive adhesive composition obtained above became 200 μm, and the sheet was allowed to stand at 35 ℃ for 5 days to obtain an uncured curable pressure-sensitive adhesive sheet.

(example 2)

90 parts by mass of a liquid bisphenol F-type epoxy resin (trade name "jER 806", manufactured by Mitsubishi chemical corporation) and 10 parts by mass of a solid bisphenol F-type epoxy resin (YDF-2005RD, manufactured by Nissan iron Japan chemical Co., Ltd.) were hot-melted and mixed. Thereafter, the temperature was returned to room temperature, and 30 parts by mass of an amine compound (trade name "Fujicure FXR-1020" manufactured by T & KTOKA) as a latent curing agent and 20 parts by mass of a core-shell type acrylic resin (trade name "Dianal (registered trade name) LP-3106" manufactured by Mitsubishi chemical corporation) as a gelling agent were mixed to prepare a pressure-sensitive adhesive composition. Sheeting was conducted in the same manner as in example 1, except that the sheet was allowed to stand at 35 ℃ for 3 days.

(example 3)

A mixture 1 was obtained by heat-melting 15 parts by mass of a liquid aliphatic epoxy resin (trade name "SR-4 GL", manufactured by Kazakh Kagaku K.K.), 30 parts by mass of a solid bisphenol F-type epoxy resin (trade name "YDF-2005 RD", manufactured by Nikki Kabushiki Kaisha) and 15 parts by mass of a solid high heat-resistant epoxy resin (trade name "HP 4700", manufactured by DIC K.K.). Further, 40 parts by mass of a liquid bisphenol F-type epoxy resin (trade name "jER 806", manufactured by Mitsubishi chemical corporation), 30 parts by mass of an amine compound (trade name "Fujicure FXR-1020", manufactured by T & KTOKA) as a latent curing agent, and 10 parts by mass of a core-shell type acrylic resin (trade name "Dianal (registered trade name) LP-3106", manufactured by Mitsubishi chemical corporation) as a gelling agent were mixed to obtain a mixture 2. Thereafter, the mixture 1 and the mixture 2 were mixed by a mixer to obtain an adhesive composition. Sheeting was conducted in the same manner as in example 1, except that the sheet was allowed to stand at 35 ℃ for 1 day.

Comparative example 1

The procedure of example 1 was repeated except that no gelling agent was added.

(reference example 1)

The procedure of example 1 was repeated except that the prepared pressure-sensitive adhesive composition was allowed to stand at 80 ℃ for 10 minutes.

The above examples were evaluated for the presence or absence of sheet properties and adhesiveness, and the shear adhesion was measured. The results are shown in Table 1.

[ Table 1]

TABLE 1

Examples 1 to 3 were able to be formed into sheets and also had adhesive properties. In addition, curing at a low temperature of 80 ℃ can be achieved. Further, the sheets of examples 1 to 3 were confirmed to exhibit adhesiveness by curing. In particular, the sheet of example 3 was confirmed to have high adhesion by curing.

On the other hand, the pressure-sensitive adhesive composition of comparative example 1 was liquid and could not be formed into a sheet because it contained no gelling agent.

In addition, in reference example 1 in which the pressure-sensitive adhesive composition in example 1 was held at 80 ℃ for 10 minutes, sheeting was achieved, but the resin was cured and the pressure-sensitive adhesive property was lost.

While various embodiments have been described above with reference to the drawings, the present invention is not limited to the above examples. Various modifications and alterations will be apparent to those skilled in the art within the scope of the claims, and it is needless to say that they are within the scope of the present invention. In addition, the respective components in the above embodiments may be arbitrarily combined without departing from the scope of the invention.

The present application is based on japanese patent application No. 3/28/2019 (japanese patent application No. 2019-065068), and the content thereof is incorporated by reference into the present application.

Description of the reference numerals

1. 2a, 2b curable pressure-sensitive adhesive sheet

11. 12 adhesive layer

13. 14 Release film

21 base material

31 st adherend

41 nd 2 nd adherend

100 bonded structure