JP6043240B2 - Adhesive sheet for electronic equipment - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive sheet for electronic equipment having high impact resistance adhesion and excellent punching ability into a fine shape.

In an electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device, an adhesive sheet is used for assembly. Specifically, for example, an adhesive sheet is used to bond a cover panel for protecting the surface of an electronic device to a touch panel module or a display panel module, or to bond a touch panel module and a display panel module. Yes. Such a pressure-sensitive adhesive sheet is required to have various performances including adhesiveness. For example, it is required to have impact-resistant adhesive that does not peel from the adherend even when subjected to an impact from the outside.

Examples of a method for improving the impact resistance adhesion of the pressure-sensitive adhesive sheet include a method using a buffering base material such as a foam. Patent Documents 1 and 2 describe a pressure-sensitive adhesive sheet for electronic equipment, which includes a crosslinked polyolefin resin foam sheet and a specific acrylic pressure-sensitive adhesive layer laminated and integrated on one surface of the cross-linked polyolefin resin foam sheet. Yes.

However, in recent years, with the enlargement of screens of electronic devices and diversification of designs, there is a demand for pressure-sensitive adhesive sheets that can be processed more finely as pressure-sensitive adhesive sheets used for assembly. However, the pressure-sensitive adhesive sheet having a foam as a base material has a problem that it is inferior in punching into a fine shape.
Examples of the base material excellent in processability include a polyethylene terephthalate (PET) film, but when a base material having a low buffering property such as a PET film is used, it is as high as when a foam is used. It was difficult to develop impact resistance adhesion.

JP 2010-215906 A JP 2011-168727 A

An object of this invention is to provide the adhesive sheet for electronic devices which is high in impact-resistant adhesiveness and excellent in the punching workability to a fine shape.

The present invention has a pressure-sensitive adhesive layer containing 100 parts by weight of an acrylic copolymer and 20-30 parts by weight of a terpene phenol resin having a softening point of 110 ° C. or less, and the acrylic copolymer comprises (a) 2 Ethyl hexyl acrylate 24.7-58.98% by weight, (b) butyl acrylate 30-50% by weight, (c) methyl acrylate 10-20% by weight, (d) acrylic acid 1-5% by weight, and (e ) It is obtained by copolymerizing a mixed monomer containing 0.02 to 0.3% by weight of (meth) acrylate having a hydroxyl group, and has a weight average molecular weight (Mw) of 400,000 to 1,000,000 and a weight average molecular weight / number average molecular weight. (Mw / Mn) is 8.0 or more, and the pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet for electronic equipment that is crosslinked to a gel fraction of 35 to 50% by a crosslinking agent.
The present invention is described in detail below.

The inventor of the present invention contains a specific acrylic copolymer and a specific terpene phenol resin, and these have a pressure-sensitive adhesive layer that is cross-linked to a specific range of gel fraction by a cross-linking agent. High impact-resistant adhesiveness can be expressed even when a low-buffering base material such as a PET film is used instead of a base material having a buffering base such as foam, and it is necessary to use a foam. Therefore, the present inventors have found that it is excellent in punching workability into a fine shape and completed the present invention.

The pressure-sensitive adhesive sheet for electronic equipment of the present invention has a pressure-sensitive adhesive layer containing 100 parts by weight of an acrylic copolymer and 20 to 30 parts by weight of a terpene phenol resin having a softening point of 110 ° C. or lower.
The acrylic copolymer comprises (a) 2-ethylhexyl acrylate 24.7 to 58.98% by weight, (b) butyl acrylate 30 to 50% by weight, (c) methyl acrylate 10 to 20% by weight, and (d) acrylic. It is obtained by copolymerizing a mixed monomer containing 1 to 5% by weight of an acid and (e) 0.02 to 0.3% by weight of a (meth) acrylate having a hydroxyl group.

When the amount of 2-ethylhexyl acrylate (a) is less than 24.7% by weight, the adhesive strength of the pressure-sensitive adhesive layer is reduced, and impact resistance is reduced. When the amount of 2-ethylhexyl acrylate (a) exceeds 58.98% by weight, the punching processability of the pressure-sensitive adhesive layer is lowered.

When the amount of the butyl acrylate (b) is less than 30% by weight, the pressure-sensitive adhesive layer becomes too soft and the punching processability is lowered. When the amount of butyl acrylate (b) exceeds 50% by weight, the pressure-sensitive adhesive layer becomes too hard, and impact resistance adhesion is lowered.

When the methyl acrylate of (c) is less than 10% by weight, the impact resistance adhesiveness of the pressure-sensitive adhesive layer is lowered. It is estimated that by copolymerizing 10% by weight or more of the methyl acrylate of (c) above, the side chain of the acrylic copolymer is reduced, thereby improving the linearity of the molecular chain and increasing the entanglement of the molecular chain. The For this reason, when the pressure-sensitive adhesive layer is deformed by receiving an impact, it is presumed that the energy absorption due to the entanglement of molecular chains is increased, and the impact resistance adhesion is improved.
In addition, since the cross-linked structure of the molecular chain is deformed mainly by elastic deformation, it is difficult to convert impact stress into fluid deformation energy, and it is difficult to absorb and disperse. For this reason, the impact stress is stored as elastic energy in the cross-linked structure, the stress dispersibility at the interface with the adherend is lowered, and the impact resistance adhesion is lowered. On the other hand, the entangled structure of molecular chains is different from the crosslinked structure, and can be plastically deformed, and can absorb and disperse by converting impact stress into energy of flow deformation. For this reason, it is thought that the increase in a certain amount of entanglement leads to an improvement in impact resistance adhesion.
When the methyl acrylate of the above (c) exceeds 20% by weight, the pressure-sensitive adhesive layer becomes too hard due to an increase in the glass transition temperature (Tg), and impact resistance adhesion is lowered.

When the acrylic acid (d) is less than 1% by weight, the adhesive strength of the pressure-sensitive adhesive layer is lowered. When the acrylic acid of (d) exceeds 5% by weight, the pressure-sensitive adhesive layer becomes too hard due to an increase in the glass transition temperature (Tg), and impact resistance adhesion is lowered.

The (e) hydroxyl group-containing (meth) acrylate is a component that is cross-linked by an isocyanate cross-linking agent described later. By copolymerizing the (meth) acrylate having a hydroxyl group (e) above in an amount of 0.02 to 0.3% by weight, it becomes easy to adjust the gel fraction of the pressure-sensitive adhesive layer to a specific range, and impact resistance is improved. The pressure-sensitive adhesive layer can be made high and excellent in punching workability into a fine shape.
When the (e) hydroxyl group-containing (meth) acrylate is less than 0.02% by weight, the pressure-sensitive adhesive layer becomes too soft and punching processability is lowered. When the (e) hydroxyl group-containing (meth) acrylate exceeds 0.3% by weight, the cross-linking density of the pressure-sensitive adhesive layer is increased, and the plastic deformation is reduced and elastic deformation is mainly performed. Sex is reduced.
Examples of the (meth) acrylate having a hydroxyl group include 2-hydroxyethyl (meth) acrylate and 2-hydroxybutyl ethyl (meth) acrylate.

In addition to the monomers (a) to (e), the mixed monomer may contain other vinyl monomers copolymerizable with the monomers (a) to (e) as necessary.

In order to copolymerize the mixed monomer to obtain the acrylic copolymer, the mixed monomer may be radically reacted in the presence of a polymerization initiator. A conventionally known method is used as a method of radically reacting the mixed monomer, that is, a polymerization method, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
The said polymerization initiator is not specifically limited, For example, an organic peroxide, an azo compound, etc. are mentioned. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether and the like. These reaction solvents may be used alone or in combination of two or more.

The acrylic copolymer has a weight average molecular weight (Mw) of 400,000 to 1,000,000 and a weight average molecular weight / number average molecular weight (Mw / Mn) of 8.0 or more.
When the weight average molecular weight (Mw) of the acrylic copolymer is less than 400,000, the stickiness of the pressure-sensitive adhesive layer becomes too high, and the punching processability is lowered. When the weight average molecular weight (Mw) of the acrylic copolymer exceeds 1,000,000, the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer is lowered, and impact resistance is lowered.

When the weight average molecular weight / number average molecular weight (Mw / Mn) of the acrylic copolymer is less than 8.0, the impact resistance adhesiveness of the pressure-sensitive adhesive layer is lowered. Increasing the weight average molecular weight / number average molecular weight (Mw / Mn) of the acrylic copolymer (set to 8.0 or more) increases the amount of the low molecular weight acrylic copolymer component and causes the pressure-sensitive adhesive layer to flow. It is estimated that it becomes easy to deform. For this reason, it is presumed that the interfacial adhesion of the pressure-sensitive adhesive layer is improved and the impact stress is easily dispersed and relaxed, and the impact resistance adhesion is improved.
In addition, a weight average molecular weight (Mw) and a number average molecular weight (Mn) are measured as a polystyrene conversion molecular weight by GPC (Gel Permeation Chromatography: Gel permeation chromatography) method. Specifically, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were obtained by filtering a diluted solution obtained by diluting an acrylic copolymer with tetrahydrofuran (THF) 50 times with a filter, and obtaining the filtrate. Is measured as a polystyrene-equivalent molecular weight by the GPC method. In the GPC method, for example, 2690 Separations Model (manufactured by Water) can be used.

By appropriately adjusting the polymerization conditions (for example, the type or amount of the polymerization initiator), it becomes easy to adjust the weight average molecular weight (Mw) of the acrylic copolymer within the above range. In order to obtain an acrylic copolymer having a large weight average molecular weight / number average molecular weight (Mw / Mn) in the above range relatively easily, it is preferable to use solution boiling polymerization as a polymerization method.

By blending 20-30 parts by weight of the terpene phenol resin having a softening point of 110 ° C. or less with respect to 100 parts by weight of the acrylic copolymer, the adhesive strength of the pressure-sensitive adhesive layer is increased, and impact resistance is improved. improves.
When the softening point of the terpene phenol resin exceeds 110 ° C., the pressure-sensitive adhesive layer becomes too hard, and the impact resistance adhesiveness decreases.
The softening point is a softening point measured by the JIS K2207 ring and ball method.

When the terpene phenol resin having a softening point of 110 ° C. or lower is less than 20 parts by weight, the adhesive strength of the pressure-sensitive adhesive layer is lowered, and impact resistance adhesiveness is lowered. When the terpene phenol resin having a softening point of 110 ° C. or lower exceeds 30 parts by weight, the pressure-sensitive adhesive layer becomes too hard due to an increase in the glass transition temperature (Tg), and impact resistance adhesion is lowered.

The pressure-sensitive adhesive layer is crosslinked to a gel fraction of 35 to 50% with a crosslinking agent.
The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Especially, since it is excellent in the adhesive stability with respect to a base material, an isocyanate type crosslinking agent is preferable. Examples of the isocyanate-based crosslinking agent include aliphatic isocyanate-based crosslinking agents such as Coronate HX (manufactured by Nippon Polyurethane Industry Co., Ltd.), Coronate L (manufactured by Nippon Polyurethane Industry Co., Ltd.), and Mytec NY260A (manufactured by Mitsubishi Chemical Corporation). .
0.1-6 weight part is preferable with respect to 100 weight part of said acrylic copolymers, and, as for the compounding quantity of the said crosslinking agent, 0.3-5 weight part is more preferable.

When the gel fraction of the pressure-sensitive adhesive layer is less than 35%, the pressure-sensitive adhesive layer becomes too soft and the punching processability is lowered. When the gel fraction of the pressure-sensitive adhesive layer exceeds 50%, the cross-linking density of the pressure-sensitive adhesive layer becomes high, the plastic deformability is lowered and the elastic deformation is the main component, so that the impact resistance adhesion is lowered.
The gel fraction is measured as follows. First, a pressure-sensitive adhesive sheet for electronic equipment was cut into a flat rectangular shape of 50 mm × 100 mm to prepare a test piece. After the test piece was immersed in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate. , And dried at 110 ° C. for 1 hour. The weight of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). In addition, the release film for protecting an adhesive layer shall not be laminated | stacked on the test piece.
Gel fraction (% by weight) = 100 × (W ₂ −W ₀ ) / (W ₁ −W ₀ ) (1)
(W ₀ : weight of substrate, W ₁ : weight of test piece before immersion, W ₂ : weight of test piece after immersion and drying)

As a method for obtaining a pressure-sensitive adhesive layer that has been crosslinked to the above-mentioned gel fraction by the above-mentioned cross-linking agent, the above-mentioned cross-linking agent is added to form a cross-linked structure between the main chains of the resin constituting the pressure-sensitive adhesive layer. The method is preferred. By appropriately adjusting the type or amount of the cross-linking agent, it becomes easy to adjust the gel fraction of the pressure-sensitive adhesive layer to the above range, high impact resistance adhesiveness, and excellent punching workability into fine shapes. It can be used as an agent layer.

The pressure-sensitive adhesive layer may contain plasticizers, emulsifiers, softeners, fillers, additives such as pigments and dyes, and other resins such as rosin resins, if necessary.

Although the thickness of the said adhesive layer is not specifically limited, 50-150 micrometers is preferable. If the thickness of the pressure-sensitive adhesive layer is less than 50 μm, impact resistance adhesion may be deteriorated. When the thickness of the pressure-sensitive adhesive layer exceeds 150 μm, punching workability may be deteriorated.

The pressure-sensitive adhesive sheet for electronic equipment of the present invention may be a non-support type that does not have a base material, or a support type that has a base material. In the case of a support type, it is preferable that the said adhesive layer is formed on both surfaces of a base material.
The pressure-sensitive adhesive sheet for electronic devices of the present invention contains a specific acrylic copolymer and a specific terpene phenol resin as described above, and these are cross-linked to a specific range of gel fraction by a cross-linking agent. Therefore, it is possible to express high impact-resistant adhesiveness even in the case of having a low-buffering base material such as a PET film rather than a base material having a buffering base such as foam. Since there is no need to use a body, it is excellent in punching into fine shapes.

The substrate is not particularly limited, but is preferably not a foam. For example, a polyolefin resin film such as a polyethylene film or a polypropylene film, a polyester resin film such as a PET film, an ethylene-vinyl acetate copolymer film, a poly Examples thereof include a vinyl chloride resin film and a polyurethane resin film. Among these, a polyester resin film is preferable from the viewpoint of excellent punchability.
Further, a black-printed base material for preventing light transmission, a white-printed base material for improving light reflectivity, a metal-deposited base material, and the like can also be used.

Although the thickness of the said base material is not specifically limited, 20-100 micrometers is preferable and 25-75 micrometers is more preferable. When the thickness of the base material is less than 20 μm, the punching workability or mechanical strength of the pressure-sensitive adhesive sheet for electronic equipment may be lowered. When the thickness of the base material exceeds 100 μm, the pressure-sensitive adhesive sheet for electronic equipment becomes too strong, and it may be difficult to adhere and adhere together along the shape of the adherend.

The method for producing the pressure-sensitive adhesive sheet for electronic equipment of the present invention is not particularly limited. For example, the acrylic copolymer, the terpene phenol resin having a softening point of 110 ° C. or less, the cross-linking agent, and other as necessary. Are mixed with the above ingredients and stirred to prepare a pressure-sensitive adhesive solution. Subsequently, the pressure-sensitive adhesive solution is applied to a release-treated PET film and dried to form a pressure-sensitive adhesive layer. And a method of transferring the material to the substrate. Further, the pressure-sensitive adhesive layer may be transferred onto the opposite surface of the substrate in the same manner.

Although the use of the adhesive sheet for electronic devices of the present invention is not particularly limited, it is preferably used for assembling an electronic device (for example, a mobile phone, a portable information terminal, etc.) equipped with an image display device or an input device. Specifically, for example, it is preferably used for bonding a cover panel for protecting the surface of the electronic device to the touch panel module or the display panel module, or bonding the touch panel module and the display panel module. Furthermore, the adhesive sheet for electronic devices of the present invention may be used for bonding a film with a metal thin film to a support (PET film or the like) or the like in a touch panel module.
Moreover, the shape of the adhesive sheet for electronic devices of the present invention in these applications is not particularly limited and may be a rectangle or the like, but a frame shape is preferable.

In FIG. 1, the schematic diagram which shows the electronic device which bonded the cover panel on the surface of the touch panel module using the adhesive sheet for electronic devices of this invention is shown. In the electronic device 1 shown in FIG. 1, a cover panel 3 is bonded to the surface of the touch panel module 4 by an electronic device pressure-sensitive adhesive sheet 2 punched into a frame shape.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet for electronic devices which is high in impact-resistant adhesiveness and excellent in the punching property to a fine shape can be provided.

It is a schematic diagram which shows the electronic device which bonded the cover panel on the surface of the touch panel module using the adhesive sheet for electronic devices of this invention.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

(Examples 1-17 and Comparative Examples 1-21)
(1) Preparation of acrylic copolymer (1-1) A predetermined amount of a reaction solvent shown in the table was added to a reactor equipped with a thermometer, a stirrer and a cooling tube by boiling point polymerization, and then the reactor was Heating was started to reflux. Subsequently, after adding a predetermined amount of the polymerization initiator shown in the table to the reactor, the monomers shown in the table were added dropwise over 2 hours. After completion of the dropwise addition, the same amount of polymerization initiator as that at the start was added, and the mixture was further heated to reflux for 6 hours to conduct a polymerization reaction, thereby obtaining an acrylic copolymer solution. In the table, “boiling point” described in the polymerization method column means that boiling point polymerization was performed.
(1-2) A predetermined amount of monomer and reaction solvent shown in the table were added to a reactor equipped with a copolymer thermometer, a stirrer, and a cooling tube by constant temperature polymerization, and then the reactor was heated to 60 ° C. Subsequently, a predetermined amount of a polymerization initiator shown in the table was added to the reactor to initiate the polymerization reaction. During the reaction, the reactor was appropriately heated and cooled so that the temperature of the reactor became constant at 60 ° C. The reaction was continued for 8 hours to obtain an acrylic copolymer solution. In the table, “constant temperature” described in the polymerization method column means that constant temperature polymerization was performed.

(2) Molecular Weight Measurement of Acrylic Copolymer Diluted solution obtained by diluting the obtained acrylic copolymer 50 times with tetrahydrofuran (THF) is filtered (material: polytetrafluoroethylene, pore diameter: 0.2 μm) And a measurement sample was prepared. This measurement sample is supplied to a gel permeation chromatograph (manufactured by Water, 2690 Separations Model), and GPC measurement is performed under the conditions of a sample flow rate of 1 ml / min and a column temperature of 40 ° C., and the polystyrene equivalent molecular weight of the acrylic copolymer is measured. Were measured to determine the weight average molecular weight (Mw) and the weight average molecular weight / number average molecular weight (Mw / Mn). GPC LF-804 (manufactured by Showa Denko) was used as the column, and a differential refractometer was used as the detector.

(3) Manufacture of double-sided pressure-sensitive adhesive sheet To the obtained acrylic copolymer solution, a predetermined amount of terpene phenol resin and rosin ester resin shown in the table are added to 100 parts by weight of the nonvolatile content (dried at 110 ° C. for 1 hour). Then, ethyl acetate was added and stirred. Further, an isocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., Coronate L45) was added in a predetermined amount shown in the table and stirred to obtain a pressure-sensitive adhesive solution having a nonvolatile content of 30% by weight. . In the table, the amount of the crosslinking agent indicates the weight part of the non-volatile content of the crosslinking agent. The terpene phenol resin and rosin ester resin used are shown below.
-Terpene phenol resin Softening point: 80 ° C. (Yasuhara Chemical Co., Ltd., YS Polyster T80)
-Terpene phenol resin Softening point: 100 ° C. (Yasuhara Chemical Co., Ltd., YS Polyster T100)
-Terpene phenol resin Softening point: 115 ° C. (Yasuhara Chemical Co., Ltd., YS Polyster T115)
-Terpene phenol resin Softening point: 150 ° C (Yasuhara Chemical Co., Mighty Ace G150)
・ Hydrogenated rosin ester resin Softening point: 70 ° C. (Arakawa Chemical Industries, Ester Gum H)
Polymerized rosin ester resin Softening point: 135 ° C. (Arakawa Chemical Industries, Pencel D135)

The obtained pressure-sensitive adhesive solution was applied to a 50 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying was 100 μm, and then dried at 70 ° C. for 10 minutes. This pressure-sensitive adhesive layer was transferred onto a PET film having a thickness of 50 μm and subjected to a release treatment. Further, the pressure-sensitive adhesive layer was transferred onto the opposite surface of the substrate in the same manner to obtain a double-sided pressure-sensitive adhesive sheet. In addition, the release film for protecting an adhesive layer was laminated | stacked on the adhesive layer of both surfaces of a base material.

(4) Measurement of gel fraction The obtained double-sided PSA sheet was cut into a flat rectangular shape of 50 mm x 100 mm to produce a test piece, and the release film was peeled off. After immersing the test piece in ethyl acetate at 23 ° C. for 24 hours, the test piece was taken out from ethyl acetate and dried at 110 ° C. for 1 hour. The weight of the test piece after drying was measured, and the gel fraction was calculated using the following formula (1).
Gel fraction (% by weight) = 100 × (W ₂ −W ₀ ) / (W ₁ −W ₀ ) (1)
(W ₀ : weight of substrate, W ₁ : weight of test piece before immersion, W ₂ : weight of test piece after immersion and drying)

<Evaluation>
The following evaluation was performed about the double-sided adhesive sheet obtained by the Example and the comparative example. The results are shown in Tables 1-5.

(1) Adhesive strength The obtained double-sided pressure-sensitive adhesive sheet was cut into a strip having a width of 25 mm to prepare a test piece, and one release film was peeled off to expose the pressure-sensitive adhesive layer. After placing this test piece on a polycarbonate resin plate so that the pressure-sensitive adhesive layer faces the polycarbonate resin plate, a test was performed by reciprocating a 2 kg rubber roller on the test piece at a speed of 300 mm / min. The piece and the polycarbonate resin plate were bonded together, and then allowed to stand at 23 ° C. for 30 minutes to prepare a test sample. This test sample was subjected to a tensile test in the 90 ° direction at a peeling speed of 300 mm / min according to JIS Z0237, and the adhesive strength (N / 25 mm) was measured.

(2) Punching workability The obtained double-sided pressure-sensitive adhesive sheet was punched into a frame shape having an outer dimension of 46 × 61 mm and a width of 1 mm with a Thomson blade to produce a test piece. From the workability when removing this test piece from the Thomson blade, the punching workability was evaluated.
X: The test piece did not peel off from the blade, and it was difficult to obtain the test piece while maintaining the frame shape. ○: The test piece was difficult to peel off from the blade, but the test piece could be obtained while maintaining the frame shape. did it

(3) Impact resistance adhesion One release film of the test piece (frame shape) obtained in (2) above was peeled and removed, and a polycarbonate plate (made by Takiron Co., Ltd., hereinafter referred to as PC hereinafter) having an outer dimension of 55 × 65 mm and a thickness of 1 mm. The plate was attached using a roller. Subsequently, the other release film was peeled and removed, and the center of the opening of the PC plate and the test piece were placed on a PC plate having an outer dimension of 80 × 115 mm and a thickness of 2 mm provided with an opening of 38 × 50 mm in the center. Gently place it so that it is almost coincident with the center, put a 5 kg weight from the top for 10 seconds and paste the two PC plates together, and then let stand at 23 ° C for 24 hours to perform adhesion curing and prepare a test sample did. This test sample is set on a fixing jig so that the PC plate with the opening is on the upper surface, and a shock is applied by dropping a 300 g weight through the opening to the PC plate on the lower surface from a drop height of 5 cm. It was. When peeling was not recognized, the drop height was raised in steps of 5 cm, impact was applied again, and the drop height at which peeling was recognized was measured. The measurement was performed at 23 ° C.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive sheet for electronic devices which is high in impact-resistant adhesiveness and excellent in the punching property to a fine shape can be provided.

1 Electronic device 2 Adhesive sheet for electronic device 3 Cover panel 4 Touch panel module 5 Display panel module

Claims (2)

Having a pressure-sensitive adhesive layer containing 100 parts by weight of an acrylic copolymer and 20 to 30 parts by weight of a terpene phenol resin having a softening point of 110 ° C. or less,
The acrylic copolymer is
(A) 2-ethylhexyl acrylate 24.7 to 58.98% by weight,
(B) 30-50% by weight of butyl acrylate,
(C) 10-20% by weight of methyl acrylate,
(D) 1-5% by weight acrylic acid, and
(E) It is obtained by copolymerizing a mixed monomer containing 0.02 to 0.3% by weight of (meth) acrylate having a hydroxyl group, and has a weight average molecular weight (Mw) of 400,000 to 1,000,000 and a weight average molecular weight / number. The average molecular weight (Mw / Mn) is 8.0 or more,
The pressure-sensitive adhesive layer is crosslinked to a gel fraction of 35 to 50% with a crosslinking agent, and is a pressure-sensitive adhesive sheet for electronic equipment. The pressure-sensitive adhesive sheet for electronic equipment according to claim 1, comprising a base material, wherein the base material is not a foam.

Images