Conductive adhesive sheet with release layer

Abstract

To provide a conductive adhesive sheet with a release layer that can suppress the occurrence of curling after manufacturing. [Solution] The conductive adhesive sheet with a release layer of the present invention comprises a base material, a conductive layer, and an adhesive layer in that order, and a release layer disposed on the adhesive layer side of the conductive adhesive sheet, wherein the base material is made of a flame-retardant material, the conductive layer comprises a conductive material and a binder, the conductive material comprises at least one selected from conductive polymer materials and carbon materials, the adhesive layer comprises an adhesive and a flame retardant, the thickness of the conductive adhesive sheet is 50 to 200 μm, and the 180° peel force of the release layer on the conductive adhesive sheet is 0.03 to 0.15 N / 25 mm.

Description

Technical Field

[0001] The present application relates to a conductive adhesive sheet with a release layer that absorbs electromagnetic waves from the microwave band to the millimeter wave band.

Background Art

[0002] With the development of wireless communication technologies represented by mobile phones, various devices and sensors are being wirelessly connected to networks. Also, in the medical field, from the perspective of infection prevention, devices are becoming cordless, and medical devices are starting to be wirelessly connected. These communications require high-speed large-capacity at relatively short distances and use high frequencies. With the increase in devices using such high frequencies, the risk of malfunctions due to noise generated by the devices and interference with the used electromagnetic waves, etc., causing problems in electronic devices and communications is increasing. Furthermore, in recent years, the installation of millimeter wave radars for the purpose of preventing automobile collision accidents has also started. Malfunctions in these medical and automotive field devices affect human lives, so there must be no malfunction. Therefore, there is an increasing need to apply electromagnetic wave absorbers as countermeasures against malfunctions due to device noise and interference, so-called EMC (Electromagnetic Compatibility), to circuit elements and transmission lines that transmit and receive electromagnetic waves from the microwave band to the millimeter wave band.

[0003] ]] By providing electromagnetic noise suppression sheets to society, it is possible to contribute to the achievement of three of the 17 Sustainable Development Goals (SDGs) established by the United Nations: Goal 3 (Ensure healthy lives and promote well-being for all people of all ages), Goal 9 (Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation), and Goal 12 (Ensure sustainable consumption and production patterns).

[0004] Conventional electromagnetic wave absorbing sheets that utilize the magnetic loss of magnetic materials are ineffective in suppressing high-frequency noise. Therefore, a highly safe conductive adhesive sheet has been proposed that can be attached to electronic devices, has electromagnetic wave absorption performance in the microwave to millimeter wave band from 1 to 30 GHz, and can also address overheating problems in electronic devices (Patent Document 1).

[0005] The conductive adhesive sheet proposed in Patent Document 1 typically uses aramid paper, which is easily stretched and absorbs moisture, as the base material. A release film made of PET film or the like, which is difficult to stretch and absorbs moisture, is attached to the adhesive layer side to produce a conductive adhesive sheet with a release film. More specifically, a conductive adhesive sheet with a release film is produced by first preparing a base material with a conductive layer and a release film with an adhesive layer, and then laminating them together while applying tension to each. At that time, both the base material and the release film are stretched by the tension, but because the stretching characteristics of the base material made of aramid paper and the release film made of PET film are different, the base material is stretched more than the release film. Therefore, when the tension is released after the base material and the release film are laminated together, the greatly stretched base material shrinks more than the release film. As a result, immediately after lamination, there is a problem in which the conductive adhesive sheet with a release film curls on the base material side (hereinafter also referred to as the curling problem immediately after manufacturing).

[0006] Subsequently, when the manufactured conductive adhesive sheets with release films are stored in the air for a long period of time, the substrate and release film have different rates of expansion due to moisture absorption. As a result, the substrate, which has a relatively high rate of expansion due to moisture absorption, expands more than the release film due to moisture in the air, causing the conductive adhesive sheets with release films to curl towards the release film side (hereinafter also referred to as the post-storage curling problem).

[0007] In any of the above cases, the occurrence of curling presents a problem: it becomes difficult to perform secondary processing such as cutting or punching on the conductive adhesive sheet with release film.

[0008] Furthermore, Patent Document 2 is a prior art document related to the conductive adhesive sheet of the present application. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2024 / 095699 [Patent Document 2] Japanese Patent Publication No. 2017-54734 [Overview of the project] [Problems that the invention aims to solve]

[0010] This invention solves the above problems and provides a conductive adhesive sheet with a release layer that can suppress curling after manufacturing and allows for easy secondary processing. [Means for solving the problem]

[0011] The conductive adhesive sheet with a release layer of the present invention comprises a base material, a conductive layer, and an adhesive layer in that order, and a release layer disposed on the adhesive layer side of the conductive adhesive sheet, wherein the base material is made of a flame-retardant material, the conductive layer comprises a conductive material and a binder, the conductive material comprises at least one selected from conductive polymer materials and carbon materials, the adhesive layer comprises an adhesive and a flame retardant, the thickness of the conductive adhesive sheet is 50 to 200 μm, and the 180° peel force of the release layer on the conductive adhesive sheet is 0.03 to 0.15 N / 25 mm. [Effects of the Invention]

[0012] According to this invention, it is possible to provide a conductive adhesive sheet with a release layer that can suppress the occurrence of curling after manufacturing and has electromagnetic wave absorption performance in the microwave to millimeter wave band from 1 to 30 GHz. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a conductive adhesive sheet with a release layer according to an embodiment. [Modes for carrying out the invention]

[0014] (Conductive adhesive sheet with release layer) An embodiment of the conductive adhesive sheet with a release layer of the present invention will now be described. The conductive adhesive sheet with a release layer of this embodiment comprises a base material, a conductive layer, and an adhesive layer in that order, and a release layer disposed on the adhesive layer side of the conductive adhesive sheet, wherein the base material is made of a flame-retardant material, the conductive layer comprises a conductive material and a binder, the conductive material comprises at least one selected from conductive polymer materials and carbon materials, the adhesive layer comprises an adhesive and a flame retardant, the thickness of the conductive adhesive sheet is 50 to 200 μm, and the 180° peel force of the release layer on the conductive adhesive sheet is 0.03 to 0.15 N / 25 mm.

[0015] In the conductive adhesive sheet with a release layer of this invention, the 180° peel force of the release layer on the conductive adhesive sheet is set to 0.03 to 0.15 N / 25 mm, thereby suppressing both the occurrence of curl immediately after manufacturing and the occurrence of curl after storage. The reason for this is as follows.

[0016] The inventors of the present invention investigated the mechanism of curling in conventional conductive adhesive sheets with release layers and concluded that it is due to the large peeling force of the release layer on the conductive adhesive sheet. In other words, as mentioned above, if the peeling force of the release layer on the conductive adhesive sheet is large, when the substrate expands and contracts after the release layer and conductive adhesive sheet are bonded together, the release layer is pulled and follows the expanding and contracting substrate. If the substrate expands, the entire sheet curls towards the release layer, and if the substrate contracts, the entire sheet curls towards the substrate.

[0017] Therefore, in order to suppress the occurrence of the curl described above, it was considered that the peeling force of the release layer on the conductive adhesive sheet should be reduced so that the release layer is not easily pulled by the substrate even when the substrate expands and contracts. When the 180° peeling force of the release layer on the conductive adhesive sheet was investigated, it was found that setting the peeling force to 0.03~0.15N / 25mm suppresses both the curl toward the substrate immediately after manufacturing and the curl toward the release layer after storage. Furthermore, the above peeling force is more preferably 0.03~0.10N / 25mm, and even more preferably 0.03~0.06N / 25mm. If the above peeling force is greater than 0.15N / 25mm, curl is more likely to occur. On the other hand, if the above peeling force is less than 0.03N / 25mm, there is a risk that the release layer will peel off unnecessarily.

[0018] The above explains why the present invention can suppress both the occurrence of curl immediately after manufacturing and the occurrence of curl after storage. Furthermore, in the conductive adhesive sheet with a release layer of the present invention, when the Young's modulus of the release layer at 0.2% strain is A and the Young's modulus of the conductive adhesive sheet at 0.2% strain is B, it is preferable to set the Young's modulus ratio: A / B to 0.75 to 1.50, and more preferably to 0.75 to 1.00. As a result, the elongation characteristics of the substrate and the release layer are close, so even when tension is applied to the conductive layer substrate and the adhesive layer release layer while bonding them together, the substrate and the release layer are stretched to the same extent, and when the tension is removed after bonding, they shrink to the same extent. As a result, curl immediately after bonding can be suppressed more effectively.

[0019] Furthermore, in the conductive adhesive sheet with a release layer of the present application, since the conductive layer contains a conductive material, the conductive layer has an electromagnetic wave absorption function, and can absorb electromagnetic waves of higher frequencies compared to the electromagnetic wave absorption layer made of a conventional magnetic material. Also, the conductive layer contains a binder, which can impart flexibility to the entire conductive adhesive sheet and makes it easy to conform to the surface shape of the electronic device to which the conductive adhesive sheet is attached. Further, since the base material is made of a flame-retardant material and the adhesive layer contains a flame retardant, when used by bonding to an electronic device for which noise influence prevention is desired, it can cope with heat generation troubles of the electronic device, etc., and can provide a highly safe conductive adhesive sheet.

[0020] If the surface electrical resistance value on the base material side of the conductive adhesive sheet with a release layer of the present application is too low or too high, it becomes difficult to exhibit the absorption performance for electromagnetic waves of a specific frequency. In a conductive adhesive sheet used by bonding with an adhesive or the like to an electronic device for which noise influence prevention is desired, the surface electrical resistance value on the base material side of the conductive adhesive sheet suitable for exhibiting electromagnetic wave absorption performance in the band of microwaves to millimeter waves from 1 to 30 GHz is preferably 50 to 200 Ω / square, and more preferably 80 to 150 Ω / square.

[0021] Hereinafter, the conductive adhesive sheet with a release layer of the present embodiment will be described based on the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the conductive adhesive sheet with a release layer of the present embodiment. In FIG. 1, the conductive adhesive sheet 100 with a release layer includes a conductive adhesive sheet 10 composed of a base material 11, a conductive layer 12 disposed on the base material 11, a migration prevention layer 13 disposed on the conductive layer 12, and an adhesive layer 14 disposed on the migration prevention layer 13, and a release layer 20 disposed on the adhesive layer 14 side of the conductive adhesive sheet 10.

[0022] Hereinafter, each component of the conductive adhesive sheet with a release layer of the present embodiment will be described.

[0023] <Base material> The substrate used in the conductive adhesive sheet of this embodiment is made of a flame-retardant material. By using a flame-retardant material for the substrate, it is possible to address overheating problems in electronic devices that use conductive adhesive sheets, and to provide a highly safe conductive adhesive sheet. The substrate is usually used in the form of a film or sheet made of flame-retardant resin.

[0024] As the above-mentioned flame-retardant material, a flame-retardant resin material or a resin material containing a flame retardant can be used. A flame-retardant resin material is a resin material in which the resin itself is flame-retardant, and examples include polyamide (aramid), polyimide, and polyphenylene sulfide. Examples of films or sheets made of flame-retardant resin using the above-mentioned flame-retardant resin material include Teijin DuPont Advanced Paper's aramid paper "Nomex" (registered trademark) using heat-resistant and flame-retardant meta-aramid fibers, Xenomax Japan's high heat-resistant polyimide film "Xenomax" (registered trademark), Toray Industries' "Mictron" (registered trademark) as a para-aromatic polyamide (aramid) film, and Toray Industries' "Torelina" (registered trademark) as a polyphenylene sulfide film. Among these, aramid paper containing aramid fibers is preferred.

[0025] Furthermore, a resin material containing a flame retardant is a resin material that does not have flame retardancy but contains a flame retardant. Examples of flame-retardant resin films using the above-mentioned flame-retardant resin material include "Tetron UF" (product name) from Toyobo Co., Ltd., "Fumilon" (registered trademark) from Wako Chemical Co., Ltd., "Diaramy" (registered trademark) from Mitsubishi Chemical Corporation, "Upilon" (registered trademark) from Mitsubishi Engineering Plastics Corporation, and "Sunroid Eco Sheet Polycarbonate PHF Series" (product name) from Sumitomo Bakelite Corporation.

[0026] The thickness of the flame-retardant substrate composed of the above-mentioned flame-retardant material is preferably 25 to 180 μm, and more preferably 80 to 150 μm. If the thickness is less than 25 μm, the flame retardancy standard UL94VTM cannot be satisfied, and the flame retardancy of the substrate cannot be ensured. On the other hand, if the thickness is greater than 180 μm, although flame retardancy is not a problem, the flexibility of the film or sheet made of flame-retardant resin decreases, which reduces its conformability when attached to electronic components or makes it difficult to wrap around wiring, etc. If the thickness is 50 μm or more, the flame retardancy standard VTM-2 (minimum standard) can be satisfied. Furthermore, if the thickness is 100 μm or more, the flame retardancy standard VTM-0, which is stricter than VTM-2, can be satisfied.

[0027] <Conductive layer> The conductive layer used in the conductive adhesive sheet of this embodiment includes a conductive material and a binder, wherein the conductive material includes at least one selected from conductive polymer materials and carbon materials. By including a conductive material in the conductive layer that includes at least one selected from conductive polymer materials and carbon materials, the surface electrical resistance value on the substrate side of the conductive adhesive sheet can be set within the range of 50 to 200 Ω / square. By setting the surface electrical resistance value within the range of 50 to 200 Ω / square, electromagnetic wave absorption performance in the microwave to millimeter wave band from 1 to 30 GHz can be imparted to the conductive adhesive sheet.

[0028] Furthermore, by including a binder in the conductive layer, a conductive layer with high hardness and high adhesion to the substrate can be formed. Moreover, because the conductive layer includes a binder, a conductive layer with small variations in thickness can be formed on the substrate, making the surface electrical resistance of the entire conductive layer uniform.

[0029] The thickness of the conductive layer is preferably 0.5 μm or more and 2.0 μm or less. If the thickness of the conductive layer is less than 0.5 μm, the surface electrical resistance of the conductive layer increases, making it difficult to keep the surface electrical resistance of the substrate side of the conductive adhesive sheet below 200 Ω / square. If the thickness of the conductive layer exceeds 2.0 μm, it is possible to keep the surface electrical resistance of the substrate side of the conductive adhesive sheet below 200 Ω / square, but the overall thickness of the conductive adhesive sheet increases, which reduces the flexibility of the conductive adhesive sheet, making it difficult to follow when attaching it to electronic components or to wrap it around wiring, etc.

[0030] [Conductive polymer materials] As the conductive polymer material, it is preferable to use a polythiophene-based conductive polymer. The polythiophene-based conductive polymer is an organic polymer with electromagnetic wave absorption capabilities in the microwave to millimeter wave band of 1 to 30 GHz, and its main chain is composed of a π-conjugated system. It is conductive and absorbs almost no light in the visible light region, thus enabling the formation of a conductive layer with high transparency. Therefore, by laminating a conductive layer using a polythiophene-based conductive polymer onto a transparent substrate, a conductive adhesive sheet with high light transmittance can be formed.

[0031] Examples of the above polythiophene-based conductive polymers include poly(thiophene), poly(3-methylthiophene), poly(3-ethylthiophene), poly(3-propylthiophene), poly(3-butylthiophene), poly(3-hexylthiophene), poly(3-heptylthiophene), poly(3-octylthiophene), poly(3-decylthiophene), poly(3-dodecylthiophene), poly(3-octadecylthiophene), poly(3-bromothiophene), poly(3-chlorothiophene), and poly (3-iodothiophene), poly(3-cyanothiophene), poly(3-phenylthiophene), poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene), poly(3-hydroxythiophene), poly(3-methoxythiophene), poly(3-ethoxythiophene), poly(3-butoxythiophene), poly(3-hexyloxythiophene), poly(3-heptyloxythiophene), poly(3-octyloxythiophene), poly(3-decyloxythiophene), poly(3- Poly(3,4-Octadecyloxythiophene), Poly(3,4-Dihydroxythiophene), Poly(3,4-Dimethoxythiophene), Poly(3,4-Diethoxythiophene), Poly(3,4-Dipropoxythiophene), Poly(3,4-Dibutoxythiophene), Poly(3,4-Dihexyloxythiophene), Poly(3,4-Diheptyloxythiophene), Poly(3,4-Dioctyloxythiophene), Poly(3,4-Didecyloxythiophene), Poly(3,4 Examples include poly(3,4-didodecyloxythiophene), poly(3,4-ethylenedioxythiophene), poly(3,4-propylenedioxythiophene), poly(3,4-butenedioxythiophene), poly(3-methyl-4-methoxythiophene), poly(3-methyl-4-ethoxythiophene), poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene), poly(3-methyl-4-carboxyethylthiophene), and poly(3-methyl-4-carboxybutylthiophene).

[0032] The above polythiophene-based conductive polymers may be used individually or in combination of two or more types.

[0033] To enhance the electrical conductivity of the above-mentioned polythiophene-based conductive polymer, it is preferable to use a dopant in combination. Suitable dopants include halogens such as iodine and chlorine, Lewis acids such as BF3 and PF5, protonic acids such as nitric acid and sulfuric acid, transition metals, alkali metals, amino acids, nucleic acids, surfactants, dyes, chloranil, tetracyanoethylene, TCNQ, and the like.

[0034] It is preferable to use a mixture (also known as PEDOT / PSS) in which poly(3,4-ethylenedioxythiophene) is used as the polythiophene-based conductive polymer and polystyrene sulfonic acid is used as the dopant. It is also preferable to use a mixture (also known as PEDOT / PSS / PTS) in which poly(3,4-ethylenedioxythiophene) is used as the polythiophene-based conductive polymer and polystyrene sulfonic acid and p-toluenesulfonic acid are used as the dopant.

[0035] The content of the conductive polymer material in the conductive layer is preferably 10 to 40% by mass relative to the total solid content. By setting the content within this range, the surface electrical resistance value of the substrate side of the conductive adhesive sheet can be set within the range of 50 to 200 Ω / square, and electromagnetic wave absorption performance in the microwave to millimeter wave band of 1 to 30 GHz can be imparted to the conductive adhesive sheet.

[0036] On the other hand, if the content of the conductive polymer material is less than 10% by mass, conductive paths become difficult to form in the conductive layer, making it difficult to lower the surface electrical resistance of the substrate side of the conductive adhesive sheet. Furthermore, if the content exceeds 40% by mass, the effect of reducing the surface electrical resistance saturates, and the binder content in the conductive layer decreases relatively, reducing the strength of the conductive layer and making it easier for adhesion to the substrate and the migration prevention layer described later to decrease.

[0037] [Carbon materials] The carbon materials mentioned above are electromagnetic wave absorbing materials that have electromagnetic wave absorbing functions in the microwave to millimeter wave band from 1 to 30 GHz. Specifically, examples include graphite; carbon black (acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, etc.); graphene; carbon nanotubes (single-wall carbon nanotubes, multi-wall carbon nanotubes, branched carbon nanotubes, branched multi-wall carbon nanotubes); and carbon fibers.

[0038] As the carbon material mentioned above, carbon black with an average particle size of 10 to 300 nm is particularly preferred. This carbon black has excellent conductivity and can exhibit electromagnetic wave absorption function even when used in small quantities. The average particle size of the carbon black can be measured using a particle size distribution analyzer such as the "LA-920" manufactured by Horiba, Ltd.

[0039] The content of the carbon material in the conductive layer is preferably 30 to 70% by mass relative to the total solid content. By setting the content within this range, the surface electrical resistance of the substrate side of the conductive adhesive sheet can be set within the range of 50 to 200 Ω / square, and electromagnetic wave absorption performance in the microwave to millimeter wave band from 1 to 30 GHz can be imparted to the conductive adhesive sheet.

[0040] On the other hand, if the carbon material content is less than 30% by mass, conductive paths become difficult to form in the conductive layer, making it difficult to lower the surface electrical resistance of the substrate side of the conductive adhesive sheet. Furthermore, if the content exceeds 70% by mass, the effect of reducing the surface electrical resistance saturates, and the binder content in the conductive layer decreases relatively, reducing the strength of the conductive layer and making it easier for adhesion to the substrate and the migration prevention layer described later to decrease.

[0041] [Binder] The above-mentioned binders can include binders containing fluorine-based resins such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-acrylic copolymer, and polyvinylidene fluoride-hexafluoropropylene copolymer; and binders containing polyvinyl alcohol resin, acrylic resin, polyester resin, polycarbonate resin, polyurethane resin, polystyrene resin, polyvinyl chloride resin, polyvinylidene chloride resin, and polyvinyl acetate resin.

[0042] <Adhesive layer> The adhesive layer used in the conductive adhesive sheet of this embodiment contains an adhesive and a flame retardant.

[0043] The thickness of the adhesive layer is preferably 10 to 50 μm, and more preferably 15 to 40 μm. If the thickness is less than 10 μm, sufficient adhesive strength may not be obtained. Furthermore, if the thickness exceeds 50 μm, the adhesive effect of the adhesive layer saturates, and the total thickness of the conductive adhesive sheet increases, which reduces the flexibility of the conductive adhesive sheet, making it difficult to follow the shape of electronic components when attached or to wrap around wiring, etc.

[0044] [Adhesive] The adhesive layer preferably contains an acid-free crosslinked resin as an adhesive. This suppresses the change in the surface electrical resistance of the conductive layer over time under high temperature and high humidity conditions, and also prevents corrosion of the adherend.

[0045] The above-mentioned acid-free crosslinked resin refers to a crosslinked polymer formed by polymerizing monomers that do not contain acidic groups such as carboxyl groups, sulfonic acid groups, and phosphate groups, and then further crosslinking the acid-free polymer with a crosslinking agent. The above-mentioned monomers that do not contain acidic groups contain functional groups such as hydroxyl groups and amino groups in order to undergo a crosslinking reaction with the crosslinking agent. However, the above-mentioned acid-free crosslinked resin means that it does not intentionally lack acidic groups, and does not mean that no acidic groups are detected at all, and it also means that trace amounts of acid that are inevitably mixed in during the manufacturing process of the adhesive layer are acceptable.

[0046] As an acid-free polymer having functional groups other than acidic groups used to form the above-mentioned acid-free crosslinked resin, at least one of the following can be used: acrylic resins, urethane resins, rubber resins, silicone resins, etc.

[0047] The crosslinking agent used to form the above-mentioned acid-free crosslinked resin is not particularly limited, but for example, epoxy crosslinking agents, isocyanate crosslinking agents, imine crosslinking agents, metal chelating crosslinking agents, melamine crosslinking agents, etc., can be used. Among these, epoxy crosslinking agents, isocyanate crosslinking agents, and metal chelating crosslinking agents are preferred. This is because using epoxy crosslinking agents, isocyanate crosslinking agents, and metal chelating crosslinking agents allows crosslinking of acid-free polymers having functional groups other than acidic groups to proceed even under relatively low temperature conditions such as room temperature.

[0048] [Flame retardant] The above-mentioned flame retardants can include organic flame retardants such as phosphorus-containing compounds and halogen-containing compounds, and inorganic flame retardants such as metal hydroxides and antimony compounds. Among these, it is preferable to use phosphorus-containing compounds, which are superior in both flame retardancy and safety.

[0049] Examples of the phosphorus-containing compounds mentioned above include red phosphorus compounds, phosphate compounds, phosphate ester compounds, ammonium phosphate compounds, or polymer compounds obtained by polymerizing these.

[0050] The phosphorus-containing compounds described above can be used in combination of two or more types. Depending on their structure, phosphorus-containing compounds can exhibit high flame retardancy, excellent solubility, or excellent compatibility with resins and adhesives. To achieve both flame retardancy and adhesive strength, it is necessary to understand the properties of these phosphorus-containing compounds and combine two or more types to create an adhesive layer with superior flame retardancy and adhesive strength. Specifically, to exhibit excellent flame retardancy, for example, it is better to add a large amount of ammonium polyphosphate. However, adding too much ammonium polyphosphate will reduce the adhesive strength of the adhesive layer. Therefore, when a large amount of ammonium polyphosphate is added, for example, adding a phosphate ester further can achieve both flame retardancy and adhesive strength. In this way, the desired performance of the adhesive layer, such as achieving both flame retardancy and adhesive strength, can be obtained.

[0051] The content of the phosphorus-containing compound in the adhesive layer (the total content if two or more phosphorus-containing compounds are used) is preferably 10 to 60% by mass, and more preferably 20 to 50% by mass, relative to the total solids. If the content is less than 10% by mass, the UL94VTM-2 standard of the UL94VTM flame retardancy standard cannot be satisfied, and sufficient flame retardancy may not be obtained. If the content exceeds 60% by mass, the amount of adhesive in the adhesive layer becomes relatively small, and the adhesive strength and holding power of the conductive adhesive sheet to the adherend may not be obtained. In other words, when the content is 10 to 60% by mass, both flame retardancy and adhesive strength / holding power can be achieved more effectively. Furthermore, when the content is 20 to 50% by mass, both flame retardancy and adhesive strength / holding power can be achieved even more effectively.

[0052] [Other ingredients] To control the adhesive strength, tackifiers may be added to the adhesive layer as needed. Examples of tackifiers include rosin resins, terpene resins, terpene phenol resins, synthetic petroleum resins, and hydrogenated resins thereof. In addition, colorants such as dyes and pigments, UV absorbers, inorganic fillers, etc., may be added as needed.

[0053] <Migration prevention layer> In the conductive adhesive sheet of this embodiment, it is preferable to place a migration prevention layer between the conductive layer and the adhesive layer. The migration prevention layer is made of a resin material and, by being placed between the conductive layer and the adhesive layer, can prevent flame retardants contained in the adhesive layer and low molecular weight components of the adhesive from migrating from the adhesive layer to the conductive layer.

[0054] The thickness of the migration prevention layer is preferably 0.1 to 2.0 μm, and more preferably 0.3 to 1.0 μm. If the thickness is less than 0.1 μm, the flame retardant contained in the adhesive layer and the low molecular weight components of the adhesive will migrate to the conductive layer over time, resulting in an increase in the surface electrical resistance of the conductive layer, making it difficult to maintain the surface electrical resistance of the substrate side of the conductive adhesive sheet at 200 Ω / square or less. Furthermore, if the thickness is greater than 2.0 μm, the total thickness of the conductive adhesive sheet increases, reducing its flexibility, which can lead to reduced conformability when attaching it to electronic components or difficulty in wrapping it around wiring, etc.

[0055] [Resin materials] Examples of the above-mentioned resin materials include acrylic resins, polyester resins, polyurethane resins, and polystyrene resins. Polymer compounds having highly polar functional groups such as hydroxyl groups exhibit excellent gas barrier properties. In particular, polymers with a high hydroxyl group content in their molecules, such as polyvinyl alcohol resins, ethylene-vinyl alcohol copolymer resins, and butenediol-vinyl alcohol copolymer resins, are preferred because they exhibit particularly excellent gas barrier properties and can easily prevent the migration of adhesive layer components to the conductive layer even when used as a thin film layer.

[0056] Examples of the polyvinyl alcohol resins mentioned above include "Exceval" (registered trademark) manufactured by Kuraray Co., Ltd., "Gosenol" (registered trademark) manufactured by Mitsubishi Chemical Corporation, and "Denka Poval" (registered trademark) manufactured by Denka Co., Ltd. Examples of the ethylene-vinyl alcohol copolymer resins mentioned above include "Eval" (registered trademark) manufactured by Kuraray Co., Ltd., "STRADER" (registered trademark) and "Excevia" (registered trademark) manufactured by Sumitomo Chemical Co., Ltd., and "Soanol" (registered trademark) manufactured by Mitsubishi Chemical Corporation. Examples of the butenediol-vinyl alcohol copolymer resins mentioned above include "Nichigo G-Polymer" (registered trademark) manufactured by Mitsubishi Chemical Corporation.

[0057] Furthermore, when the resin material of the migration prevention layer is a polymer compound having highly polar functional groups such as hydroxyl groups, and especially when the resin material of the migration prevention layer is a polyvinyl alcohol resin, an ethylene-vinyl alcohol copolymer resin, or a butenediol-vinyl alcohol copolymer resin, it is preferable that the flame retardant of the adhesive layer is a phosphorus-containing compound, and it is even more preferable to use two or more phosphorus-containing compounds. In this case, a conductive adhesive sheet with more effective flame retardancy can be realized by combining a flame-retardant adhesive layer and a migration prevention layer.

[0058] When the aforementioned adhesive layer is combined with the migration prevention layer, as described above, the content of the phosphorus-containing compound in the adhesive layer (total content if two or more phosphorus-containing compounds are used) is preferably 10 to 60% by mass, and more preferably 20 to 50% by mass, relative to the total solid content. When the content is 10% by mass or more, the UL94VTM-2 standard of the UL94VTM flame retardancy standard can be satisfied, and sufficient flame retardancy can be ensured. Furthermore, when the content is 60% by mass or less, the adhesive strength and holding power of the conductive adhesive sheet to the adherend can be ensured. In other words, by setting the content in the range of 10 to 60% by mass, the excellent barrier properties of the migration prevention layer, as well as the balance between flame retardancy and adhesive strength and holding power, can be effectively demonstrated. Furthermore, when the content is 20 to 50% by mass, the excellent barrier properties of the migration prevention layer, as well as the balance between flame retardancy and adhesive strength and holding power, can be even more effectively demonstrated.

[0059] [Other ingredients] In order to impart properties such as gas barrier properties, adhesion, and coating strength to the above-mentioned resin material, a filler with excellent barrier properties such as silica or alumina, or a curing agent such as epoxy or isocyanate may be added to the resin material to form a migration prevention layer.

[0060] <Exfoliation layer> The type of release layer used in the conductive adhesive sheet with a release layer of this embodiment is not particularly limited as long as the 180° peel force of the release layer relative to the conductive adhesive sheet can be set to 0.03 to 0.15 N / 25 mm, but it is preferable that the release layer be made of release paper. This makes the material of the release layer closer to the material of the base material, and as a result the expansion and contraction characteristics of the base material and the release layer become similar, which can further suppress both the occurrence of curl immediately after manufacturing and the occurrence of curl after storage.

[0061] The above-mentioned release paper comprises a base layer and a release agent layer. As the base layer, a resin base layer made of polyethylene terephthalate (PET), polyethylene, polypropylene, etc., or a paper base layer made of high-quality paper, kraft paper, glassine paper, etc., can be used. The above-mentioned release paper is formed by coating the base layer with a release agent. Examples of the above-mentioned release paper include ZACOS's "Z-series", Nippa's "J-series", Toyobo's "Cosmopeel (registered trademark)", Toray's "Therapeel (registered trademark)", Panac's "Panapeel (registered trademark)", Sumika Kakoshi's "Smirries (registered trademark)", and San-ei Kaken's "SK Separator".

[0062] The release agent used in the above-mentioned release paper is not particularly limited as long as it can reduce the adhesion at the bonding surface of the release paper, but for example, silicone resin, long-chain alkyl vinyl monomer polymer, fluorinated alkyl vinyl monomer polymer, polyvinyl alcohol carbamate, etc. can be used. In particular, silicone-based release agents containing the above-mentioned silicone resin have excellent properties for improving the release performance of the release paper surface. However, when a silicone-based resin is used in the adhesive layer of the conductive adhesive sheet to which the above-mentioned release paper is bonded, it is preferable to use a fluororesin such as fluorinated alkyl vinyl monomer polymer as the release agent. The amount of release agent adhering to the above-mentioned release paper after drying or the basis weight is usually 0.2 to 2 g / m². 2 Preferably, 0.4 to 1.0 g / m 2 This is preferable.

[0063] The above-mentioned silicone-based mold release agent is not particularly limited, but for example, Dow Toray's "DOWSIL® LTC series," Asahi Kasei Wacker Silicone's "DEHESIVE® series," Shin-Etsu Silicone's "KM series" and "KF series," and Arakawa Chemical Industries' "Silicolise" can be preferably used.

[0064] By using the above-mentioned release paper, the adhesion at the bonding surface of the release paper can be reduced, making it easier to set the 180° peel force of the release layer relative to the adhesive layer of the conductive adhesive sheet in the range of 0.03 to 0.15 N / 25 mm.

[0065] Furthermore, when the Young's modulus of the release layer at 0.2% strain is A, and the Young's modulus of the conductive adhesive sheet at 0.2% strain is B, it is preferable to select the material of the release layer such that the Young's modulus ratio: A / B is between 0.75 and 1.50. This allows for more effective suppression of curling immediately after bonding, as described above. [Examples]

[0066] The present application will be described in detail below using examples. However, the present application is not limited to the following examples. Unless otherwise specified, "parts" below means "parts by mass".

[0067] (Example 1) <Preparation of paint for forming a conductive layer> The following components were added and mixed to prepare conductive layer-forming coating a1. (1) Polythiophene-based conductive polymer dispersion (manufactured by Soken Chemical Co., Ltd., trade name "Bellazol (registered trademark) WED-SM", conductive polymer: PEDOT-PSS, solid content concentration: 1.5% by mass, solvent: water): 55.0 parts (2) Binder solution (water-soluble polyester resin solution, manufactured by Go-o Chemical Co., Ltd., product name "Pluscoat (registered trademark) Z-565", solid content concentration: 25.0% by mass, solvent: water): 10.0 parts (3) Solvent (dimethyl sulfoxide): 5.0 parts (4) Solvent (n-propyl alcohol): 20.0 parts (5) Pure water: 10.0 parts

[0068] <Formation of conductive layer> Next, a 130 μm thick aramid paper containing flame-retardant material (manufactured by Teijin DuPont Advanced Papers, Ltd., trade name "Nomex® 410") was used as a substrate. The conductive layer-forming coating a1 was applied to one main surface of the substrate using a bar coater, and then dried at 110°C for 3 minutes. This produced a conductive sheet with a conductive layer formed on one main surface. The thickness of the conductive layer was 1.0 μm.

[0069] <Preparation of coating for forming migration prevention layer> The following components were added and mixed to prepare coating b1 for forming a migration prevention layer. (1) Butenediol-vinyl alcohol copolymer resin (manufactured by Mitsubishi Chemical Corporation, trade name "Nichigo G-Polymer (registered trademark) BVE8049Q"): 4.0 parts (2) Solvent (ethanol): 26.0 parts (3) Pure water: 70.0 parts

[0070] <Formation of a migration prevention layer> Next, the above-mentioned migration prevention layer-forming coating b1 was applied to the conductive layer side of the previously prepared conductive sheet using a bar coater, and then dried at 100°C for 3 minutes. This produced a conductive sheet with a migration prevention layer, in which the conductive layer and the migration prevention layer were laminated on one main surface. The thickness of the migration prevention layer was 0.5 μm.

[0071] <Preparation of adhesive layer-forming coating> The following components were added and mixed to prepare adhesive layer-forming coating c1. (1) Acid-free resin adhesive (manufactured by Daido Chemical Industries, Ltd., product name "Daikalac (registered trademark) 5021", solid content concentration: 30.0% by mass, solvent: ethyl acetate): 58.3 parts (2) Isocyanate-based crosslinking agent (manufactured by Tosoh Corporation, trade name "Coronate® HX", solid content concentration: 100.0% by mass): 0.1 parts (3) Tackifier (terpene resin, manufactured by Yasuhara Chemical Co., Ltd., product name "YS Polystar K125"): 3.5 parts (4) Flame retardant (phosphate ester, manufactured by Daihachi Chemical Industry Co., Ltd., product name "CR-741"): 7.0 parts (5) Flame retardant (ammonium polyphosphate, manufactured by Budenheim, trade name "TERRAJU(registered trademark) C-30"): 7.0 parts (6) Solvent (ethyl acetate): 24.1 parts

[0072] <Formation of conductive adhesive sheet with release layer> A 50 μm thick release film (manufactured by Nippa Co., Ltd., product name "J0-L"), which had one side of a PET film surface-treated with a silicone-based release agent, was coated with the above-mentioned adhesive layer-forming coating c1 on its release surface and dried at 80°C for 5 minutes to form an adhesive layer with a thickness of 35 μm on the release film.

[0073] Next, the adhesive layer of the release film was superimposed on the migration prevention layer side of the previously prepared conductive sheet with migration prevention layer, pressed together with a 2kg rubber roller, and aged for 48 hours in a 40°C atmosphere to produce a conductive adhesive sheet with release film.

[0074] Next, the conductive adhesive sheet with release film was cut to lengths of 300 mm in the MD direction (adhesive layer processing flow direction) and 200 mm in the TD direction (direction perpendicular to the adhesive layer processing flow direction). After removing the release film, the surface-treated side of a 113 μm thick release paper (manufactured by Sumika Kakoshi Co., Ltd., product name "Sumirezu SL-80KCM"), which had one side of the high-quality paper surface-treated with a silicone-based release agent, was pressed onto the adhesive layer side using a 5 kg rubber roller to obtain the conductive adhesive sheet with release layer of Example 1.

[0075] (Example 2) A conductive adhesive sheet with a release layer for Example 2 was prepared in the same manner as in Example 1, except that the release paper (Sumireze® SL-80KCM) was replaced with a 115 μm thick release paper (manufactured by Sumika Kakoshi Co., Ltd., product name "Sumireze SL-80KCN") which was surface-treated on both sides of high-quality paper with a silicone-based release agent.

[0076] (Example 3) The release paper (Sumireze® SL-80KCM) was replaced with a 100 μm thick release paper (manufactured by Sumika Kakoshi Co., Ltd., product name "Sumireze® SLB-50WD (#1405)") on both sides of high-quality paper, which was surface-treated with a silicone-based release agent. The only difference was that the easily release side was pressed against the adhesive layer. The conductive adhesive sheet with a release layer of Example 3 was prepared in the same manner as in Example 1.

[0077] (Example 4) The release paper (Sumireze® SL-80KCM) was replaced with a 100 μm thick release paper (manufactured by Sumika Kakoshi Co., Ltd., product name "Sumireze® SLB-50WD (#1405)") which was surface-treated on both sides of high-quality paper with a silicone-based release agent, and the heavily release surface was pressed against the adhesive layer side. Except for these changes, the conductive adhesive sheet with a release layer of Example 4 was prepared in the same manner as in Example 1.

[0078] (Example 5) Except for changing the thickness of the adhesive layer to 15 μm, a conductive adhesive sheet with a release film was prepared in the same manner as in Example 1. Then, without replacing the release film with release paper, the conductive adhesive sheet with the release film was cut to lengths of 300 mm in the MD direction and 200 mm in the TD direction to obtain the conductive adhesive sheet with a release layer of Example 5.

[0079] (Comparative Example 1) After preparing a conductive adhesive sheet with a release film in the same manner as in Example 1, the conductive adhesive sheet with the release film was cut to lengths of 300 mm in the MD direction and 200 mm in the TD direction, without replacing the release film with release paper, to obtain the conductive adhesive sheet with a release layer of Comparative Example 1.

[0080] (Comparative Example 2) A conductive adhesive sheet with a release layer for Comparative Example 2 was prepared in the same manner as in Example 1, except that a 100 μm thick release film (manufactured by Nippa Co., Ltd., product name "J4"), which had one side of a PET film surface-treated with a silicone-based release agent, was used as the release layer, and the surface-treated side was pressed against the adhesive layer.

[0081] The conductive adhesive sheets with release layers of Examples 1-4 and Comparative Examples 1-2 were evaluated as follows.

[0082] <Measurement of total thickness> After removing the release layer from the fabricated conductive adhesive sheet, the total thickness of the conductive adhesive sheet was measured using a dial gauge.

[0083] <Adhesive strength> The prepared conductive adhesive sheet with a release layer was cut to a width of 25 mm and a length of 150 mm. The release layer was then peeled off, and the adhesive side was attached to a stainless steel plate (SUS304). A 2 kg roller was used to press the sheet down, moving it back and forth once at a speed of 5 mm / second. The time between pressing and measuring the adhesive strength was set to 24 to 36 hours. The pressed conductive adhesive sheet was then peeled off in a 180° direction at a speed of 5 mm / second using a tensile testing machine, and the adhesive strength was measured. The measurement environment was a room with a temperature of 23 ± 3°C and a relative humidity of 50 ± 10%.

[0084] <Peeling force> The prepared conductive adhesive sheet with a release layer was cut to a width of 25 mm and a length of 200 mm. The base material side of the conductive adhesive sheet with the release layer was then placed on a backing plate of a tensile testing machine, and the release layer was peeled off in a 180° direction at a speed of 300 mm / second using the tensile testing machine to measure the peel force. The peel force was measured at 20 mm intervals with n=3, and the average value was taken as the 180° peel force. The measurement environment was a room with a temperature of 23±3℃ and a relative humidity of 50±10%.

[0085] Young's modulus The Young's modulus at 0.2% strain for the release layer used (release paper, release film) and the conductive adhesive sheet after the release layer was removed was determined by the following method.

[0086] After cutting the release layer and conductive adhesive sheet to a width of 10 mm and a length of 200 mm, each was placed in a tensile testing machine and subjected to tensile tests with n=3 at a speed of 50 mm / min and a gauge length of 50 mm. The tensile stress at 0.2% strain was measured, and the average value was taken as the Young's modulus at 0.2% strain. All sample cutting and tensile testing were performed indoors at a temperature of 23 ± 3°C and a relative humidity of 50 ± 10%.

[0087] <Curl> The prepared conductive adhesive sheet with a release layer was cut into 200 mm squares. The cut samples were placed on a glass plate with the release layer side facing down and left for 24 hours in an environment with a temperature of 30°C and a relative humidity of 60%. The distance from the glass surface to the edge or center of the sample was measured, and the degree of curl was evaluated as follows. Evaluation A: When the distance between the glass surface and the edge or center of the sample is less than 5 mm. Evaluation B: When the distance between the glass surface and the edge or center of the sample is 5 mm or more but less than 20 mm. Evaluation C: When the distance between the glass surface and the edge or center of the sample is 20 mm or more but less than 40 mm. Evaluation D: When the distance between the glass surface and the edge or center of the sample is 40 mm or more, or when the sample is curled in a cylindrical shape.

[0088] The results described above, along with the composition of the fabricated conductive adhesive sheet with release layer, are shown in Table 1.

[0089] [Table 1]

[0090] Table 1 shows that in the conductive adhesive sheets with release layers of Examples 1 to 5, the 180° peel force of the release layer on the conductive adhesive sheet was set to 0.03 to 0.15 N / 25 mm, which sufficiently suppressed the occurrence of curl in the conductive adhesive sheets with release layers.

[0091] On the other hand, in Comparative Examples 1 and 2, where the 180° peel force of the release layer on the conductive adhesive sheet fell outside the range of 0.03 to 0.15 N / 25 mm, the occurrence of curling in the conductive adhesive sheet with the release layer could not be suppressed.

[0092] With respect to embodiments of the present application including the above-described examples 1 to 5, the following additional forms are further disclosed. (Appendix Form 1) A conductive adhesive sheet with a release layer, comprising a base material, a conductive layer, and an adhesive layer in that order, and a release layer disposed on the adhesive layer side of the conductive adhesive sheet, The aforementioned substrate is made of a flame-retardant material. The conductive layer comprises a conductive material and a binder. The conductive material includes at least one selected from conductive polymer materials and carbon materials. The adhesive layer comprises an adhesive and a flame retardant. The thickness of the conductive adhesive sheet is 50 to 200 μm. A conductive adhesive sheet with a release layer, characterized in that the 180° peel force of the release layer on the conductive adhesive sheet is 0.03 to 0.15 N / 25 mm. (Appendix Form 2) A conductive adhesive sheet with a release layer according to Appendix Form 1, wherein when the Young's modulus of the release layer at 0.2% strain is A, and the Young's modulus of the conductive adhesive sheet at 0.2% strain is B, the Young's modulus ratio: A / B is 0.75 to 1.50. (Appendix 3) The release layer is made of release paper, The conductive adhesive sheet with a release layer according to appended form 1 or 2, wherein the adhesive layer side of the release paper is treated with a silicone-based release agent. (Appendix Form 4) A conductive adhesive sheet with a release layer according to any of the appendix forms 1 to 3, wherein the base material contains aramid fibers. (Appendix Form 5) A conductive adhesive sheet with a release layer according to any of the appendix forms 1 to 4, wherein the surface electrical resistance value of the substrate side is 50 to 200 Ω / square. (Appendix Form 6) A conductive adhesive sheet with a release layer according to any of the appendix forms 1 to 5, wherein the thickness of the substrate is 25 to 180 μm. (Appendix Form 7) A conductive adhesive sheet with a release layer according to any of the appendix forms 1 to 6, wherein the thickness of the conductive layer is 0.5 to 2.0 μm. (Appendix form 8) Further comprising a migration prevention layer between the conductive layer and the adhesive layer, The aforementioned migration prevention layer is a conductive adhesive sheet with a release layer as described in any of the appended forms 1 to 7, wherein the migration prevention layer is made of a resin material. (Appendix Form 9) The conductive adhesive sheet with a release layer according to Appendix Form 8, wherein the thickness of the migration prevention layer is 0.1 to 2.0 μm. [Explanation of Symbols]

[0093] 100 Conductive adhesive sheets with release layer 10 Conductive adhesive sheet 11 Base material 12. Conductive layer 13. Transition prevention layer 14 Adhesive layer 20. Exfoliation layer

Claims

1. A conductive adhesive sheet with a release layer, comprising a base material, a conductive layer, and an adhesive layer in that order, and a release layer disposed on the adhesive layer side of the conductive adhesive sheet, The aforementioned substrate is made of a flame-retardant material. The conductive layer comprises a conductive material and a binder. The conductive material includes at least one selected from conductive polymer materials and carbon materials. The adhesive layer comprises an adhesive and a flame retardant. The thickness of the conductive adhesive sheet is 50 to 200 μm. A conductive adhesive sheet with a release layer, characterized in that the 180° peel force of the release layer on the conductive adhesive sheet is 0.03 to 0.15 N / 25 mm.

2. The conductive adhesive sheet with a release layer according to claim 1, wherein when the Young's modulus of the release layer at 0.2% strain is A, and the Young's modulus of the conductive adhesive sheet at 0.2% strain is B, the Young's modulus ratio: A / B is 0.75 to 1.

50.

3. The aforementioned release layer is made of release paper, The conductive adhesive sheet with a release layer according to claim 1, wherein the adhesive layer side of the release paper is treated with a silicone-based release agent.

4. The conductive adhesive sheet with a release layer according to claim 1, wherein the base material includes aramid fibers.

5. The conductive adhesive sheet with a release layer according to claim 1, wherein the surface electrical resistance value of the substrate side is 50 to 200 Ω / square.

6. The conductive adhesive sheet with a release layer according to claim 1, wherein the thickness of the substrate is 25 to 180 μm.

7. The conductive adhesive sheet with a release layer according to claim 1, wherein the thickness of the conductive layer is 0.5 to 2.0 μm.

8. The conductive layer and the adhesive layer further include a migration prevention layer, The conductive adhesive sheet with a release layer according to any one of claims 1 to 7, wherein the migration prevention layer is made of a resin material.

9. The conductive adhesive sheet with a release layer according to claim 8, wherein the thickness of the migration prevention layer is 0.1 to 2.0 μm.

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