Electrically conductive film, and electrically peelable adhesive sheet and laminate using the same

Abstract

To provide an electrically conductive film which includes a plastic film and a metal vapor-deposited layer excellently adhered to each other, and has good electric peelability even after stored under high temperature and high humidity for a long period of time, and a laminate using the electrically conductive film.SOLUTION: An electrically conductive film is provided, having a copper vapor-deposited layer, an aluminum vapor-deposited layer, and a coating layer in this order on at least one surface of a plastic film, wherein the coating layer has a structure derived from a resin and a curing agent. An aluminum base material is arranged on the coating layer as an electrically conductive support. When a voltage of 5 V is applied to the electrically conductive film and the electrically conductive support, the adhesive strength between the electrically conductive film and the electrically conductive support is 5.0 N / 25 mm or less both before and after exposure under conditions of 65°C and 90% RH for 500 hours.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a conductive film and a laminate using the same. [Background technology]

[0002] In electronic component manufacturing processes, etc., there is an increasing demand for rework to improve yields and recycling by disassembling and recovering components after use. In order to meet such demands, double-sided pressure-sensitive adhesive sheets that have a certain degree of adhesive strength as well as a certain degree of releasability are sometimes used to bond components in electronic component manufacturing processes, etc.

[0003] As a double-sided pressure-sensitive adhesive sheet that realizes both adhesive strength and peelability, a pressure-sensitive adhesive sheet (electrostatic pressure-sensitive adhesive sheet) having an electrically peelable pressure-sensitive adhesive layer made of an electrically peelable pressure-sensitive adhesive composition that peels off when a voltage is applied to the adhesive layer is provided. Air-peelable pressure-sensitive adhesive sheets are known (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 064925 Summary of the Invention [Problem to be solved by the invention]

[0005] Such an adhesive sheet may be composed of only an electrically peelable adhesive layer, but it is preferable to use an electrically peelable adhesive layer having a high adhesive property in view of handling and flowability. In consideration of ease of use, the pressure-sensitive adhesive sheet is preferably one having a substrate.

[0006] In addition, the substrate must be conductive in order to apply a voltage to the electrically peelable adhesive layer. However, for example, if metal foil is used as the base material, burrs may be generated during the punching process of the adhesive sheet. If such burrs exist, a short circuit occurs between the metal foil and the adherend, resulting in electrical peeling. There is a risk that it will no longer be possible to apply voltage to the release adhesive layer.

[0007] Therefore, the substrate used in the electrically peelable pressure-sensitive adhesive sheet is preferably a substrate having a conductive layer, such as a metal vapor-deposited thin film, formed on a substrate such as a plastic film.

[0008] However, in such a configuration, there is a risk of peeling between the plastic film and the metal vapor deposition layer when the electrically peelable adhesive layer is peeled off due to insufficient adhesion between the plastic film and the metal vapor deposition layer.

[0009] In addition, since it is necessary to peel the film even after it has been left to stand for a long period of time, there has been a demand for a conductive film that retains conductivity even after long-term storage under temperature and humidity conditions and that peels smoothly from the electrically peelable pressure-sensitive adhesive layer when a voltage is applied.

[0010] Therefore, an object of the present invention is to provide a conductive film that has excellent adhesion between a plastic film and a metal vapor deposition layer and has good electrical peelability even after long-term storage under high temperature and humidity conditions, and a laminate using the same. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention has the following configuration. (1) A conductive film having a copper vapor deposition layer, an aluminum vapor deposition layer, and a coating layer in this order on at least one side of a plastic film, the coating layer having a structure obtained from a resin and a hardener, A conductive film in which, when an aluminum substrate is placed on the coating layer as a conductive support, and a voltage of 5 V is applied to the conductive film and the conductive support, the adhesion strength between the conductive film and the conductive support is 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65°C and 90% RH. (2) The conductive film according to the above (1), wherein the coating layer has a structure obtained from a polyester resin and a hexamethylene diisocyanate curing agent, and the thickness of the coating layer is 100 nm or more and 200 nm or less. (3) The conductive film according to (1) or (2) above, wherein the surface resistance of the coating layer surface after exposure for 500 hours under conditions of 65°C and 90% RH is E+8Ω / □ or less. (4) A laminate comprising an electrically peelable adhesive layer and a conductive support laminated on the coating layer of the conductive film according to any one of (1) to (3) above. (5) The laminate according to (4) above, in which, when a voltage of 5 V is applied between the conductive film and the conductive support, the adhesion strength between the conductive film and the conductive support is 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65°C and 90% RH. Effect of the Invention

[0012] According to the present invention, it is possible to obtain a conductive film that retains good adhesion, conductivity, and electrical peelability even when exposed to high temperature and high humidity for a long period of time, and a laminate using the same. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a layer structure diagram of an example of a laminate in which an electrically peelable adhesive layer and a conductive support are laminated on a conductive film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The conductive film of the present invention is a conductive film having a copper vapor-deposited layer, an aluminum vapor-deposited layer, and a coating layer in this order on at least one surface of a plastic film, the coating layer having a structure obtained from a resin and a curing agent, When an aluminum substrate is placed on the coating layer as a conductive support, and a voltage of 5 V is applied to the conductive film and the conductive support, the adhesion strength between the conductive film and the conductive support is 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65°C and 90% RH.

[0015] In the conductive film of the present invention, the plastic film does not need to be particularly limited in type as long as it has suitability for coating and deposition processing. Representative examples of plastic films include films and sheets made of polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polybutylene 2.6 naphthalate, polyolefins such as polyethylene and polypropylene, aliphatic polyamides such as nylon 6 and nylon 12, aromatic polyamides, polyimides, and copolymers of these polymers with other organic substances. Among these films, when considering processability, toughness, heat and cold resistance, chemical resistance, and the like, it is preferable that the plastic film in the conductive film of the present invention is a film made of polyethylene terephthalate.

[0016] The plastic film may contain various additives, such as an antistatic agent, a lubricant, and an antioxidant.

[0017] The thickness of the plastic film is not particularly limited, but considering suitability for machining such as deposition processing, it is desirable for the thickness to be 6 to 100 μm.

[0018] The surface of the plastic film may be subjected to a surface modification treatment such as corona treatment, flame treatment, plasma treatment, ion treatment, anchor coat, etc. From the viewpoint of adhesion between the copper vapor deposition layer and the plastic film after long-term exposure to high temperature and humidity, as described below, and from the viewpoint of production costs, it is preferable that the surface modification treatment is a plasma treatment. As a method of plasma treatment, a method in which plasma treatment is performed using a planar magnetron type plasma treatment electrode while continuously running the base film is preferable.

[0019] The conductive film of the present invention has a copper vapor-deposited layer on at least one side of a plastic film. The copper vapor-deposited layer has a deposition amount of 5 ng / cm 2 More than 20ng / cm 2 The deposition weight of the copper vapor deposition layer is preferably 5 ng / cm2 or less. 2 When the thickness is more than 1000 nm, sufficient adhesion with the aluminum vapor deposition layer described below can be easily obtained. 2 If it is less than this, industrial productivity will improve.

[0020] The method for measuring the amount of copper deposition layer adhesion was to cut the conductive film into a 10 cm wide and 10 cm long sample, immerse the cut sample in 20 ml of nitric acid for 24 hours, measure the copper absorbance (324.8 nm) of the resulting solution with an atomic absorption spectrophotometer (Shimadzu Corporation, AA-6300 type), and calculate the amount of copper deposition layer adhesion. The average value obtained using four cut samples was taken as the amount of copper deposition layer adhesion (ng / cm 2 ) is used. The method for making the amount of adhesion of the copper vapor-deposition layer fall within the above range is not particularly limited, but examples thereof include a method of coating a plastic film with a coating liquid containing copper and then removing the solvent, a method of spraying a copper-containing liquid onto a plastic film by a spray, a method of blasting a plastic film with copper, and a method of sputtering copper in a vacuum atmosphere. After forming a copper vapor-deposition layer on the plastic film, the plastic film may be wound up and then provided with an aluminum vapor-deposition layer, which will be described later, or the plastic film may be unwound, and then a copper vapor-deposition layer may be formed and then provided with an aluminum vapor-deposition layer in-line. From the viewpoint of removing and cleaning the attached gas, water vapor, oligomers, foreign matter, etc. on the plastic film surface and forming a copper vapor-deposition layer on the plastic film surface, and from the viewpoint of cost, a method of unwounding a plastic film in a vacuum atmosphere, sputtering copper, forming a copper vapor-deposition layer, and then continuously providing an aluminum vapor-deposition layer is preferred. A preferred method for sputtering a copper vapor deposition layer is to use copper as the material for a planar magnetron electrode, and sputter copper in-line onto a plastic film in a plasma atmosphere while generating a strong magnetic field on the electrode surface.

[0021] The conductive film of the present invention has an aluminum vapor-deposited layer. From the viewpoint of cost, the aluminum vapor-deposited layer is preferably formed continuously after the copper vapor-deposited layer is formed, and more preferably, the copper vapor-deposited layer is formed and then continuously, by evaporating aluminum in a vacuum atmosphere and depositing it on the plastic film.

[0022] The thickness of the aluminum vapor deposition layer is preferably 30 nm or more and 200 nm or less. When the thickness of the aluminum vapor deposition layer is 30 nm or more, sufficient conductivity is easily obtained, and electrical peeling is easily improved. In addition, when the thickness of the aluminum vapor deposition layer is 200 nm or less, the vapor deposition processability is improved, and costs are easily suppressed. The thickness of the aluminum vapor deposition layer is measured by taking a small piece for a transmission electron microscope in the cross-sectional direction of the conductive film using a microtome, observing the cross-section of the small piece using a transmission electron microscope (TEM, manufacturer: JEOL Ltd., type name: JEM-10111, accelerating voltage 100 V, magnification 200,000 times), measuring the thickness of the aluminum vapor deposition layer at three points in the TEM observation image, and the average value of the obtained values ​​is the thickness of the aluminum vapor deposition layer.

[0023] The conductive film of the present invention has a coating layer. The coating layer can be formed, for example, by a reaction between a resin and a curing agent. The resin of the coating layer is preferably an acrylic resin, a polyester resin, or a urethane resin. Among them, the resin of the coating layer is more preferably a polyester resin, since it has a high reaction efficiency with the curing agent and is easy to form a strong coating layer.

[0024] Examples of the curing agent include an isocyanate curing agent, an epoxy curing agent, a melamine curing agent, etc. Among them, in terms of durability against long-term storage under high temperature and humidity and pot life, it is preferable that the curing agent is a hexamethylene diisocyanate (hereinafter, sometimes referred to as HDI) curing agent.

[0025] The method for forming the coating layer is not particularly limited, but methods such as gravure coating, reverse coating, kiss coating, die coating, and bar coating can be used.

[0026] The thickness of the coating layer is preferably 100 nm or more and 200 nm or less. When the thickness of the coating layer is 100 nm or more, the surface resistance of the coating layer surface after exposure for 500 hours under conditions of 65°C and 90% RH is likely to be E+8Ω / □ or less. When the thickness of the coating layer is 200 nm or less, the surface resistance is likely to be E+8Ω / □ or less.

[0027] The conductive film of the present invention preferably has a surface resistance value of E+8Ω / □ or less of the coating layer surface after exposure for 500 hours under conditions of 65°C and 90% RH. By having a surface resistance value of E+8Ω / □ or less, sufficient conductivity is easily obtained. Since a smaller surface resistance value is preferable, the lower limit is not particularly limited, but is usually E+5Ω / □, and more preferably E+1Ω / □. As a means for setting the surface resistance value in the above range, for example, a method of setting the thickness of the coating layer in the above range can be mentioned.

[0028] The laminate of the present invention comprises an electrically peelable adhesive layer and a conductive support laminated on the coating layer of the conductive film of the present invention.

[0029] Examples of the conductive support in the laminate of the present invention include foils (thickness less than 100 μm) or plates (thickness 100 μm or more) made of metals such as aluminum, copper, silver, gold, etc., alloys of these metals, and conductive metal oxides (such as indium tin oxide), fabrics containing fibers mixed with or coated with these metals or alloys, resin sheets containing these metals or alloys, and resin plates provided with a layer made of these metals, alloys, or conductive metal oxides.

[0030] In the laminate of the present invention, the electrically peelable adhesive layer refers to an electrically peelable adhesive composition (hereinafter simply referred to as an adhesive composition) containing an acrylic adhesive or a polyester adhesive and an electrolyte. The acrylic adhesive and the polyester adhesive are not particularly limited as long as the electrically peelable adhesive layer has adhesiveness. These adhesives may be newly synthesized adhesives or commercially available adhesives.

[0031] In the conductive film and laminate of the present invention, when a voltage of 5V is applied between the conductive film and the conductive support, the adhesive strength between the conductive film and the conductive support is preferably 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65°C and 90% RH. By having an adhesive strength of 5.0 N / 25 mm or less both before and after exposure for 500 hours, peeling is unlikely to occur except in the electrically peelable adhesive layer. The lower limit of the adhesive strength is not particularly limited, but is usually about 2.0 N / 25 mm. In the present invention, the adhesive strength is measured under the conditions described in the section 1) Peelability (Method of Measuring Adhesion Strength) of [Evaluation Method] described later. EXAMPLES

[0032] The present invention will be described in detail below with reference to examples, although the present invention is not limited to the following examples.

[0033] [How to make the laminate] A method for producing a laminate is shown.

[0034] (Preparation of Acrylic Polymer) An acrylic adhesive was obtained by polymerizing a monomer mixture consisting of 91 parts by mass of n-butyl acrylate (Mitsubishi Chemical), 8 parts by mass of acrylic acid (Mitsubishi Chemical), and 1 part by mass of 2-hydroxyethyl methacrylate (Nippon Shokubai), 0.2 parts by mass of azobisisobutyronitrile (AIBN, Junsei Chemical) as a polymerization initiator, and 186 parts by mass of a solvent (ethyl acetate:toluene (mass ratio) = 9:1) in a nitrogen stream at 85°C for 5 hours. The obtained acrylic adhesive contained 35% by mass of resin (acrylic polymer: mass average molecular weight approximately 800,000) and had a viscosity of 7000 mPa s.

[0035] (Preparation of Adhesive Composition) 100 parts by mass of the acrylic adhesive (35 parts by mass of acrylic polymer) was mixed with 2.0 parts by mass of Coronate L-55E (manufactured by Nippon Polyurethane Co., Ltd.) as an isocyanate crosslinking agent and ionic liquid A (1-hexylpyridinium bis(trifluoromethanesulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.); ionic conductivity 1.8 × 10 -3 To the mixture were added 3.5 parts by mass of a copolymer of 1,000 s / cm and 3.5 parts by mass of polyethylene glycol (PEG, average molecular weight 400, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a migration promoter, and the mixture was stirred at room temperature for 10 minutes and degassed to obtain a pressure-sensitive adhesive composition.

[0036] The adhesive composition was coated on the coating layer of the conductive film and dried at 100° C. for 2 minutes to form an electrically peelable adhesive layer having a thickness of 40 μm on the coating layer of the conductive film. An aluminum substrate (100 μm, manufacturer: Takeuchi Metal Foil Co., Ltd., type: A1N30H-O) was laminated onto the obtained electrically peelable adhesive layer as a conductive support, and a 2 kg rubber roller was rolled back and forth five times under its own weight on the plastic film of the conductive film to bring the electrically peelable adhesive layer and the aluminum substrate into close contact with each other. The laminate was then stored in an atmosphere of 40° C. for 3 days to obtain a laminate.

[0037] [Evaluation method] 1) Peelability (Method of measuring adhesion strength) The laminate was cut to a width of 25 mm and a length of 300 mm to obtain a test piece. The obtained test piece was stored for 500 hours under conditions of 65°C and 90% RH, and electrodes were attached to the conductive film and aluminum substrate of the test piece before storage and before storage, and a voltage of 5 V and a current of 2.5 A were applied for 3 minutes using a DC power supply (manufacturer: A&D, type: AD-8724D). The adhesion strength between the electrically peelable adhesive layer of the laminate and the aluminum substrate was measured at a peel angle of 180° and a tensile speed of 300 mm / s using a universal tensile tester (manufacturer: Orientec, type: Tensilon UTM-4-100). The peelability of the test piece with an adhesion strength of 5.0 N / 25 mm or less was evaluated as ○, and the peelability of the test piece with an adhesion strength of more than 5.0 N / 25 mm was evaluated as ×.

[0038] 2) Surface resistance The surface resistance of the conductive film coating layer surface was measured using a low resistivity meter (Loresta AX MCP-T370, manufactured by Mitsubishi Chemical Analytech Co., Ltd.) with the DC 4-terminal method. The surface resistance was measured after storage at 65°C, 90% RH for 500 hours and before storage. When the surface resistance was E+8Ω / □ or less, it was judged as ◯, and when the surface resistance exceeded E+8Ω / □, it was judged as ×.

[0039] 3) Method for measuring the amount of copper deposition layer The conductive film was cut into a 10 cm wide and 10 cm long sample, which was then immersed in 20 ml of nitric acid for 24 hours. The copper absorbance (324.8 nm) of the resulting solution was measured using an atomic absorption spectrophotometer (Shimadzu AA-6300 type) to calculate the amount of adhesion. These calculations were performed using four different cut samples, and the average of the obtained values ​​was calculated as the amount of adhesion (ng / cm 2 ) was decided.

[0040] 4) Measurement method for thickness of aluminum deposition layer and coating layer A small piece for a transmission electron microscope was taken from the conductive film in the cross-sectional direction using a microtome, and the cross-section of the small piece was observed using a transmission electron microscope (TEM, manufacturer: JEOL Ltd., type name: JEM-10111, acceleration voltage 100V, magnification 200,000 times) to obtain a TEM observation image. The thickness of the aluminum deposition layer in the obtained TEM observation image was measured at three points, and the average of the obtained values ​​was taken as the thickness of the aluminum deposition layer, and the thickness of the coating layer was measured, and the average of the obtained values ​​was taken as the thickness of each layer.

[0041] Example 1 A 38 μm-thick polyethylene terephthalate film (type name: T62) manufactured by Toray Industries, Inc. was coated on one side with 10 ng / cm under plasma discharge using a continuous vacuum deposition device. 2 After forming the copper vapor deposition layer, an aluminum vapor deposition layer was continuously formed so that the thickness of the layer was 49 nm, and an aluminum vapor deposition film was obtained. A mixture of polyester resin (PET-2 manufactured by Dainichi Seika Chemicals Co., Ltd.) and HDI (hexamethylene diisocyanate)-based hardener (VMD hardener manufactured by Dainichi Seika Chemicals Co., Ltd.) was coated on the aluminum vapor deposition layer of the aluminum vapor deposition film thus obtained using a gravure coater so that the coating layer had a thickness of 150 nm, forming a coating layer, and a conductive film was obtained. A laminate was produced using the obtained conductive film based on the above-mentioned [Method of producing a laminate]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0042] Example 2 A conductive film was obtained in the same manner as in Example 1, except that the thickness of the coating layer was changed to 100 nm. A laminate was produced using the obtained conductive film according to the above-mentioned [Method of producing a laminate]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0043] Example 3 A conductive film was obtained in the same manner as in Example 1, except that the thickness of the coating layer was changed to 200 nm. A laminate was produced using the obtained conductive film according to the above-mentioned [Method of Producing a Laminate]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0044] Comparative Example 1 A conductive film was obtained in the same manner as in Example 1, except that a copper vapor deposition layer was not formed. A laminate was produced using the obtained conductive film according to the above-mentioned [Laminate Production Method]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0045] Comparative Example 2 A conductive film was obtained in the same manner as in Example 1, except that the thickness of the coating layer was changed to 95 nm. A laminate was produced using the obtained conductive film according to the above-mentioned [Method of producing a laminate]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0046] Comparative Example 3 A conductive film was obtained in the same manner as in Example 1, except that the thickness of the coating layer was changed to 210 nm. A laminate was produced using the obtained conductive film according to the above-mentioned [Laminate Production Method]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0047] Comparative Example 4 A conductive film was obtained in the same manner as in Example 1, except that no coating layer was formed. A laminate was produced using the obtained conductive film according to the above-mentioned [Method of Producing a Laminate]. The surface resistance value of the obtained conductive film and the peelability of the laminate were evaluated. The results are shown in Table 1.

[0048] [Table 1] [Explanation of symbols]

[0049] 1. Plastic film 2 Copper deposition layer 3. Aluminum deposition layer 4 Coating Layer 5 Electrically peelable adhesives 6. Conductive Support 7 Conductive Film 8 Laminate

Claims

1. A conductive film having a copper vapor deposition layer, an aluminum vapor deposition layer and a coating layer in this order on at least one surface of a plastic film, the coating layer having a structure obtained from a resin and a curing agent, A conductive film in which, when an aluminum substrate is placed on the coating layer as a conductive support, and a voltage of 5 V is applied to the conductive film and the conductive support, the adhesion strength between the conductive film and the conductive support is 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65°C and 90% RH.

2. 2. The conductive film according to claim 1, wherein the coating layer has a structure obtained from a polyester resin and a hexamethylene diisocyanate curing agent, and the coating layer has a thickness of 100 nm or more and 200 nm or less.

3. 3. The conductive film according to claim 1, wherein the surface resistance of the coating layer surface after exposure to conditions of 65° C. and 90% RH for 500 hours is E+8 Ω / □ or less.

4. 3. A laminate comprising the conductive film according to claim 1 or 2, and an electrically peelable adhesive layer and a conductive support layer laminated on the coating layer.

5. 5. The laminate according to claim 4, wherein when a voltage of 5 V is applied between the conductive film and the conductive support, the adhesion strength between the conductive film and the conductive support is 5.0 N / 25 mm or less both before and after exposure for 500 hours under conditions of 65° C. and 90% RH.

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