JP7645090B2 - Conductive film and laminate using same - Google Patents

Description

The present invention relates to a conductive film and a laminate using the same.

In electronic component manufacturing processes, etc., there is an increasing demand for rework to improve yields and recycling, such as disassembling and recovering components after use. 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 peelability are sometimes used to join components in electronic component manufacturing processes, etc.

As a double-sided pressure-sensitive adhesive sheet that realizes both adhesive strength and releasability, a pressure-sensitive adhesive sheet (electrically peelable pressure-sensitive adhesive sheet) having an electrically peelable pressure-sensitive adhesive layer made of an electrically peelable pressure-sensitive adhesive composition that peels off upon application of a voltage to the adhesive layer is known (Patent Document 1).

International Publication No. 2017/064925

Such a pressure-sensitive adhesive sheet may consist of only an electrically peelable pressure-sensitive adhesive layer, but in consideration of ease of handling and distribution, it is preferable that the pressure-sensitive adhesive sheet be one having a substrate.

In addition, the substrate needs to be conductive in order to apply a voltage to the electrically peelable pressure-sensitive adhesive layer, but if a metal foil is used as the substrate, burrs are likely to occur during punching of the pressure-sensitive adhesive sheet. If such burrs exist, a short circuit may occur between the metal foil and the adherend, making it impossible to apply a voltage to the electrically peelable pressure-sensitive adhesive layer.

Therefore, it is preferable to use a substrate for an electrically peelable adhesive sheet that has a conductive layer, such as a metal vapor deposition thin film, formed on a substrate such as a plastic film.

However, with this type of 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.

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

The object of the present invention is therefore to provide a conductive film and a laminate using the same that have excellent adhesion between a plastic film and a metal deposition layer and good electrical peelability even after long-term storage under high temperature and humidity conditions.

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 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 adhesive 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 to conditions of 65° C. and 90% RH for 500 hours 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 the above (4), 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.

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

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.

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.

In the conductive film of the present invention, the type of plastic film does not need to be particularly limited as long as it has suitability for coating and vapor 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.

The plastic film may contain various additives, such as antistatic agents, lubricants, antioxidants, etc.

There are no particular limitations on the thickness of the plastic film, but considering suitability for machining such as deposition processing, it is desirable for the thickness to be between 6 and 100 μm.

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 coating, 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. A preferable method of plasma treatment is a method in which plasma treatment is performed using a planar magnetron type plasma treatment electrode while the substrate film is continuously traveling.

The conductive film of the present invention has a copper vapor deposition layer on at least one side of a plastic film. The deposition amount of the copper vapor deposition layer is preferably 5 ng/cm2 or ^more and 20 ng/cm2 or ^less . When the deposition amount of the copper vapor deposition layer is 5 ng/ ^cm2 or more, sufficient adhesion with the aluminum vapor deposition layer described below is easily obtained. Furthermore, when the deposition amount of the copper vapor deposition layer is 20 ng/cm2 or ^less , industrial productivity is improved.

The method for measuring the amount of adhesion of the copper vapor deposition layer is to prepare a cut sample by cutting the conductive film into a width of 10 cm and a length of 10 cm, immerse the cut sample in 20 ml of nitric acid for 24 hours, and then measure the copper absorbance (324.8 nm) of the obtained solution with an atomic absorption spectrophotometer (AA-6300 type manufactured by Shimadzu Corporation) to calculate the amount of adhesion of the copper vapor deposition layer. The average value obtained using four cut samples is taken as the amount of adhesion of the copper vapor deposition layer (ng/cm ² ). The method for making the amount of adhesion of the copper vapor deposition layer within the above-mentioned range is not particularly limited, but examples thereof include a method of coating a plastic film with a copper-containing coating liquid and then removing the solvent, a method of spraying a copper-containing liquid onto a plastic film by spraying, a method of blasting copper onto a plastic film, and a method of sputtering copper in a vacuum atmosphere. After preparing a copper vapor deposition layer on a plastic film, the film may be wound up, and then an aluminum vapor deposition layer described later may be provided, or the plastic film may be unwound, and then a copper vapor deposition layer may be prepared, and then an aluminum vapor deposition layer may be provided in-line as it is. From the viewpoint of removing and cleaning the plastic film surface with adhering gases, water vapor, oligomers, foreign matter, etc., and forming a copper vapor-deposited layer on the plastic film surface, and also from the viewpoint of cost, a method is preferred in which the plastic film is unwound in a vacuum atmosphere, copper is sputtered to form a copper vapor-deposited layer, and then an aluminum vapor-deposited layer is continuously provided. As a method for sputtering a copper vapor-deposited layer, it is preferred to use copper as the material for a planar magnetron electrode, and sputter copper in-line on the plastic film in a plasma atmosphere while generating a strong magnetic field on the electrode surface.

The conductive film of the present invention has an aluminum vapor deposition layer. From a cost perspective, it is preferable to form the aluminum vapor deposition layer continuously after forming the copper vapor deposition layer, and it is more preferable to form the copper vapor deposition layer and then continuously evaporate aluminum in a vacuum atmosphere and deposit it on the plastic film.

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 properties are easily improved. Furthermore, when the thickness of the aluminum vapor deposition layer is 200 nm or less, the suitability for deposition processing 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 of the obtained values is the thickness of the aluminum vapor deposition layer.

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 for the coating layer is preferably an acrylic resin, a polyester resin, or a urethane resin. Of these, it is more preferable that the resin for the coating layer is a polyester resin, since it has a high reaction efficiency with the curing agent and is easy to form a strong coating layer.

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

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.

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

The conductive film of the present invention preferably has a surface resistance value of E+8 Ω/□ 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+8 Ω/□ or less, sufficient conductivity is more likely to be obtained. Since a smaller surface resistance value is preferable, the lower limit is not particularly limited, but is usually E+5 Ω/□, and more preferably E+1 Ω/□. As a means for setting the surface resistance value within the above range, for example, a method of setting the thickness of the coating layer within the above range can be mentioned.

The laminate of the present invention is formed by laminating an electrically peelable adhesive layer and a conductive support on the coating layer of the conductive film of the present invention.

Examples of conductive supports in the laminate of the present invention include metals such as aluminum, copper, silver, and gold, alloys of these metals, foils (thickness less than 100 μm) and plates (thickness 100 μm or more) made of 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 layers made of these metals, alloys, or conductive metal oxides.

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) that contains an acrylic adhesive or a polyester adhesive and an electrolyte solution. The acrylic adhesive and the polyester adhesive are not particularly limited as long as the electrically peelable adhesive layer has adhesive properties. These adhesives may be newly synthesized adhesives or commercially available adhesives.

In the conductive film and laminate of the present invention, when a voltage of 5 V 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 less likely to occur other than 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 1) Peelability (Method of measuring adhesive strength) in the [Evaluation method] section described later.

The present invention will be specifically described below based on examples. However, the present invention is not limited to the following examples.

[Method of producing laminate]
A method for producing a laminate is shown.

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

(Preparation of Adhesive Composition)
To 100 parts by mass of the acrylic adhesive (35 parts by mass of acrylic polymer), 2.0 parts by mass of Coronate L-55E (manufactured by Nippon Polyurethane Co., Ltd.) as an isocyanate crosslinking agent, 3.5 parts by mass of ionic liquid A (1-hexylpyridinium bis(trifluoromethanesulfonyl)imide (manufactured by Kanto Chemical Co., Ltd.); ionic conductivity 1.8×10 ⁻³ 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 were added, and the mixture was stirred at room temperature for 10 minutes and degassed to obtain an adhesive composition.

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 with a thickness of 40 μm on the coating layer of the conductive film. An aluminum substrate (100 μm, manufacturer: Takeuchi Metal Foil Industries Co., Ltd., type: A1N30H-O) was attached as a conductive support to the obtained electrically peelable adhesive layer, 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. The laminate was then stored in an atmosphere of 40°C for 3 days to obtain a laminate.

[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 a voltage of 5 V and a current of 2.5 A were applied for 3 minutes using a DC power source (manufacturer: A&D, type name: 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 Co., Ltd., type name: 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 ×.

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

3) Method for measuring the amount of adhesion of the copper vapor deposition layer A cut sample was prepared by cutting the conductive film into a width of 10 cm and a length of 10 cm, and the cut sample was immersed in 20 ml of nitric acid for 24 hours. The copper absorbance (324.8 nm) of the obtained solution was then measured with an atomic absorption spectrophotometer (AA-6300 type manufactured by Shimadzu Corporation) to calculate the amount of adhesion. These calculations were performed using four different cut samples, and the average of the obtained values was taken as the amount of adhesion (ng/ ^cm2 ).

4) Method for measuring 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 100 V, 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 measured 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.

Example 1
A copper vapor deposition layer of 10 ng/cm ² was formed on one side of a 38 μm-thick polyethylene terephthalate film (type name: T62) manufactured by Toray Industries, Inc., under plasma discharge using a continuous vacuum deposition apparatus, and then an aluminum vapor deposition layer was continuously formed to a thickness of 49 nm to obtain an aluminum vapor deposition film. A mixture of a polyester resin (PET-2 manufactured by Dainichiseika Chemicals Co., Ltd.) and an HDI (hexamethylene diisocyanate)-based hardener (VMD hardener manufactured by Dainichiseika 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 to form a coating layer, thereby obtaining a conductive film. 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.

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 based on 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.

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.

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.

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 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.

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 based on 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.

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 [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.

Reference Signs List 1 Plastic film 2 Copper vapor deposition layer 3 Aluminum vapor deposition layer 4 Coating layer 5 Electrically peelable adhesive 6 Conductive support 7 Conductive film 8 Laminate

Claims (5)

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 curing agent and a thickness of 100 nm or more and 200 nm or less,
A conductive film in which , when an electrically peelable adhesive layer and an aluminum substrate as a conductive support are disposed in this order on the coating layer, and a voltage of 5 V is applied to the conductive film and the conductive support, the adhesive 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 claim 1, wherein the coating layer has a structure obtained from a polyester resin and a hexamethylene diisocyanate curing agent. The conductive film according to claim 1 or 2, in which the surface resistance of the coating layer surface after exposure to conditions of 65°C and 90% RH for 500 hours is E+8Ω/□ or less. A laminate comprising an electrically peelable adhesive layer and a conductive support laminated on a coating layer of the conductive film according to any one of claims 1 to 3. 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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