JP5396073B2 - Conductive adhesive sheet and method for producing the same - Google Patents

Description

 The present invention relates to a conductive pressure-sensitive adhesive sheet, and more particularly to a conductive pressure-sensitive adhesive sheet that has conductivity in the thickness direction and the surface direction and is preferably used for electromagnetic wave shielding, grounding for preventing static electricity, and the like. Moreover, this invention relates to the manufacturing method of this electroconductive adhesive sheet.

 Various types of conductive adhesive sheets are used in various electronic devices. For example, the anisotropic conductive pressure-sensitive adhesive sheet has conductivity in the thickness direction, and is used to adhere various electronic devices on a substrate to ensure conduction. Moreover, the electroconductive adhesive sheet by which an adhesive layer is formed in the one or both surfaces of electroconductive base materials, such as metal foil, has electroconductivity also in a surface direction, and is used for uses, such as an electromagnetic wave shield. Among such conductive adhesive sheets, those having conductivity in the thickness direction and the surface direction are applied to uses such as an electromagnetic wave shield and an antistatic ground sheet.

 As such a conductive pressure-sensitive adhesive sheet having conductivity in the thickness direction and the surface direction, for example, in Patent Document 1 (Japanese Patent Laid-Open No. 2006-117747), “a pressure-sensitive adhesive composed of a conductive layer made of conductive metal foil and a pressure-sensitive adhesive” is disclosed. The conductive layer is laminated, and the conductive layer is supported on the surface of the adherend by the adhesive force of the pressure-sensitive adhesive layer, and is a conductive pressure-sensitive adhesive tape used for electromagnetic wave shielding, between the conductive layer and the pressure-sensitive adhesive layer. The conductive metal foil has a burr formed in the direction of the pressure-sensitive adhesive layer so that the conductive metal foil can be electrically conductive in the thickness direction where the conductive layer is provided with a base material layer made of fiber fabric. An electroconductive pressure-sensitive adhesive tape characterized in that a hole is provided and the burr penetrates the pressure-sensitive adhesive layer.

  This conductive pressure-sensitive adhesive tape is obtained by piercing a sharp rod-like body from the conductive layer side, generating burrs from the conductive layer, and penetrating the burrs through the fiber fabric layer and the pressure-sensitive adhesive layer (see Examples and the like).

Patent Document 2 (Japanese Patent Publication No. 5-40402) discloses an anisotropic conductive adhesive sheet composed of an adhesive component and conductive metal particles, and Patent Document 3 (Patent No. 3256659) An anisotropic conductive film in which conductive particles are dispersed in an adhesive layer is disclosed.
JP 2006-117747 A Japanese Patent Publication No. 5-40402 Japanese Patent No. 3256659

 However, in the conductive adhesive tape of Patent Document 1, the through hole may be deformed and the burr may be pushed back to the conductive layer side. In other words, the burr extending from the conductive layer penetrates the fiber fabric layer, but due to the elasticity and repulsive force of the fiber fabric layer, the burr is pushed back in the direction of the conductive layer, resulting in poor conduction or reduced through holes. There is a risk. Moreover, in order to form the burr | penetration which penetrates a textile fabric layer and an adhesive layer, a certain size is required for a through-hole, and the diameter of the through-hole in an Example is 1 mm. Accordingly, since a large number of visible holes are formed on the surface of the base material, the appearance is impaired and it becomes difficult to print the surface of the base material. In addition, since a large number of through-holes are formed in a large area on the pressure-sensitive adhesive layer surface, the pressure-sensitive adhesive area is narrowed, and the adhesive force to the adherend may be reduced. Furthermore, since the fiber fabric layer is included, the total thickness of the tape is increased, which hinders downsizing of the device.

 In addition, the anisotropic conductive adhesive sheet of Patent Document 2 and the anisotropic conductive film of Patent Document 3 exhibit conductivity only in the thickness direction and are used for joining electrodes and terminals in electronic devices. It is a directionally conductive adhesive film and does not have conductivity in the surface direction of the sheet or film.

 The present invention has been made in view of the prior art as described above, and is a conductive pressure-sensitive adhesive sheet having conductivity in the thickness direction and the surface direction, which can be electrically connected to an adherend, and can be used for appearance and printing. It aims at providing the electroconductive adhesive sheet which is excellent also in aptitude and can make whole thickness thin.

 The gist of the present invention aimed at solving such problems is as follows.

(1) It consists of a base material having a conductive layer and an adhesive layer formed on the surface of the conductive layer,
Conductive carbon particles are blended in the adhesive layer,
A conductive pressure-sensitive adhesive sheet in which the ratio A of the thickness A of the pressure-sensitive adhesive layer to the average particle size B of the conductive carbon particles, B / A is in the range of 0.50 to 0.99.

(2) The conductive pressure-sensitive adhesive sheet according to (1), wherein the thickness A of the pressure-sensitive adhesive layer is 10 to 40 μm and the average particle size B of the conductive carbon particles is in the range of 8 to 38 μm.

(3) The conductive adhesive sheet according to (1) or (2), wherein the conductive carbon particles have an aspect ratio of 0.50 to 0.99.

(4) Any of (1) to (3), wherein the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains 3 to 50 parts by mass of conductive carbon particles with respect to 100 parts by mass of the solid content of the adhesive resin. The conductive adhesive sheet according to 1.

(5) The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains 5 to 50 parts by mass of conductive carbon fine particles having an average particle diameter of 20 to 80 nm with respect to 100 parts by mass of the solid content of the adhesive resin. The conductive adhesive sheet according to any one of to (4).

(6) On the release-treated surface of the release sheet, a coating solution of an adhesive composition containing 3 to 50 parts by mass of conductive carbon particles is applied to a solid content of 100 parts by mass of the adhesive resin and dried. Forming a pressure-sensitive adhesive layer,
And a step of bonding the pressure-sensitive adhesive layer on the surface of the conductive layer of the substrate having the conductive layer.

 According to the present invention, the conductive adhesive has conductivity in the thickness direction and the surface direction, can be electrically connected to the adherend, is excellent in appearance and printability, and can be reduced in total thickness. A sheet is provided. Moreover, according to the manufacturing method of this invention, the above electroconductive adhesive sheets can be manufactured simply.

  Hereinafter, the present invention will be described more specifically with reference to the drawings.

 As shown in FIG. 1, a conductive adhesive sheet 10 according to the present invention comprises a base material 1 having a conductive layer 1a and an adhesive layer 2 formed on the surface of the conductive layer 1a. Is composed of conductive carbon particles 3.

 The substrate 1 itself may be a single layer of the conductive layer 1a, or a laminate of the conductive layer 1a and the support sheet 1b. In FIG. 1, the base material 1 showed the case where it was a laminated body of the conductive layer 1a and the support sheet 1b.

 The conductive layer 1a may be a metal foil such as an aluminum foil or a copper foil, and may be a conductive paste layer formed on at least one surface of the support sheet 1b or a metal film formed by sputtering, vapor deposition, plating, or the like. May be. The thickness of the conductive layer 1a is not particularly limited. For example, when the base material 1 is composed of a single layer of the conductive layer 1a, the conductive layer 1a is preferably a metal foil, and the thickness thereof has a self-supporting property, preferably about 5 to 100 μm. . In addition, when the conductive layer 1a is a conductive paste layer, a vapor deposition film, or a sputtering film formed on the support sheet 1b, the thickness may be small as long as it has necessary conductivity. In general, in the case of a conductive paste layer, the thickness is preferably about 0.1 to 50 μm, and in the case of a deposited film or a sputtering film, it is preferably about 0.01 to 5 μm. In the case of a film, the thickness is preferably about 0.01 to 50 μm. Moreover, since the electroconductive adhesive sheet 10 can be utilized also as a display label, it is preferable that the base material 1 is a laminated body of the electroconductive layer 1a and the support sheet 1b, especially in order to improve printing and printing suitability. In addition, when laminating | stacking the metal foil as the conductive layer 1a on the support sheet 1b, what was mentioned above can be used.

 The support sheet 1b is not particularly limited. For example, a paper base such as glassine paper, coated paper, cast coated paper, impregnated paper, synthetic paper, and dust-free paper, and a thermoplastic resin such as polyethylene are laminated on these paper base materials. Laminated paper, polyethylene resin, polyolefin resin such as polypropylene resin, polyester resin such as polybutylene terephthalate resin, polyethylene terephthalate resin, plastic film such as acetate resin, polyamide resin, polyimide resin, ABS resin, polystyrene resin, vinyl chloride resin , Sheets and the like. In particular, films manufactured from polyester-based materials have good heat resistance, excellent mechanical strength, and are relatively inexpensive. Therefore, various electronic parts and precision products that are used in the present invention are used. And is used in the present invention.

 The support sheet 1b may be an unstretched film, or a stretched film stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral. Although the thickness in particular of the support sheet 1b is not restrict | limited, Usually, it is 10-200 micrometers, Preferably it is 25-150 micrometers. The support sheet 1b may be a single layer film or a laminated film. The support sheet 1b may be colored or colorless and transparent.

 In addition, printing or printing may be performed on the front surface or the back surface of the substrate 1. Therefore, the substrate 1 may be provided with a heat-sensitive recording layer, a print image receiving layer capable of performing thermal transfer, ink jetting, laser printing, and the like, a printability improving layer, and the like. These print image receiving layer, printability improving layer and the like are preferably formed on the surface of the support sheet 1b.

  For the purpose of improving the adhesion to the adhesive layer 2 provided thereon, the conductive layer 1a of the substrate 1 may be oxidized or concavo-convex as long as desired without impairing the conductivity of the conductive layer 1a. Physical or chemical surface treatment can be applied. Examples of the oxidation method include corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the concavo-convex method include a sand blast method and a solvent treatment method. .

  In the conductive pressure-sensitive adhesive sheet 10 of the present invention, a pressure-sensitive adhesive layer 2 in which conductive carbon particles 3 are blended is provided on the surface of the conductive layer 1 a of the substrate 1. The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive resin and conductive carbon particles 3. As the adhesive resin, conventionally known various pressure-sensitive adhesives are used. Such adhesive resin is not limited in any way, but for example, adhesives such as rubber, acrylic, polyester, urethane, silicone, and polyvinyl ether are used. The pressure-sensitive adhesive is appropriately selected according to the standard of the electronic device to which the conductive sheet is applied. For example, in a hard disk drive or the like, an electronic component may cause a trouble due to a low molecular weight silicone compound contained in a silicone-based pressure-sensitive adhesive. However, silicone-based pressure-sensitive adhesives can naturally be used for applications where there is no problem with contamination of the silicone compound.

 Among the above-mentioned pressure-sensitive adhesives, acrylic pressure-sensitive adhesives, polyester-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and the like are preferably used, and acrylic pressure-sensitive adhesives are particularly preferably used from the viewpoints of versatility and handleability.

 Acrylic pressure-sensitive adhesives include, for example, (meth) acrylic acid ester homopolymers, copolymers containing two or more (meth) acrylic acid ester units, and (meth) acrylic acid esters and other functional monomers. What contains at least 1 sort (s) chosen from the copolymer with a monomer is used. Examples of the (meth) acrylate ester include butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, and (meth) acrylic. Acid nonyl, decyl (meth) acrylate, and the like can be mentioned. Examples of the functional monomer include hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate, carboxylic acid group-containing monomers such as (meth) acrylic acid, (Meth) acrylamide, dimethyl (meth) acrylamide, N-vinylmorpholine, N-allylmorpholine, N- (meth) acryloylmorpholine and the like can be mentioned.

  As one of the functional monomer components, N-vinyl morpholine, N-allyl morpholine, which is an ethylenically unsaturated monomer having a 6-membered heterocyclic ring each having a nitrogen atom and an oxygen atom, N- Use of (meth) acryloylmorpholine or the like is preferable because it exhibits performance as a crosslinking accelerator in the reaction with a crosslinking agent described later. Among these, N- (meth) acryloylmorpholine is preferably used from the viewpoint of particularly good copolymerizability with other monomer components.

 The conductive pressure-sensitive adhesive sheet is applied to various electronic devices, and in particular, may be stuck on a conductive adherend. Therefore, from the viewpoint of suppressing oxidation (corrosion) on the surface of the conductive adherend, a pressure-sensitive adhesive that does not contain an acid group is preferable. For example, a pressure-sensitive adhesive that does not use a carboxylic acid group-containing monomer is preferable.

 Moreover, the said adhesive may be bridge | crosslinked by crosslinking agents, such as an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, an aziridine type crosslinking agent, and a chelate type crosslinking agent. As the isocyanate-based crosslinking agent, tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, trimethylolpropane-modified TDI, or the like is used. . As the epoxy-based crosslinking agent, ethylene glycol glycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane diglycidyl ether, diglycidylaniline, diglycidylamine and the like are used. Examples of aziridine-based crosslinking agents include 2,2-bishydroxymethylbutanol-tris [3- (1-aziridinyl) pronate], 4,4-bis (ethyleneiminocarboxyamino) diphenylmethane, tris-2,4,6- (1 -Aziridinyl) -1,3,5-triazine, tris [1- (2-methyl) aziridinyl] phosphine oxide, hexa [1- (2-methyl) -aziridinyl] triphosphatriazine and the like are used. As the chelate-based crosslinking agent, aluminum chelate, titanium chelate or the like is used. By appropriately adjusting the amount of the cross-linking agent, the necessary adhesive properties can be expressed for various adherends. The cross-linking agent may be used not only alone but also in combination of two or more as required.

  The pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer 2 contains conductive carbon particles 3 in addition to the pressure-sensitive adhesive resin. In the present invention, particles having an average particle size smaller than the thickness of the pressure-sensitive adhesive layer 2 are used as the conductive carbon particles 3 included in the pressure-sensitive adhesive layer 2 from the viewpoints of conductivity and adhesiveness. Specifically, the ratio of the thickness A of the pressure-sensitive adhesive layer 2 to the average particle diameter B of the conductive carbon particles 3, B / A is 0.50 to 0.99, preferably 0.60 to 0.00. The conductive carbon particles 3 are selected so as to be in the range of 96. In addition, the average particle diameter of the conductive carbon particles 3 is determined by a measurement method described in Examples described later.

 Generally, in the conductive pressure-sensitive adhesive sheet of the present invention, the thickness A of the pressure-sensitive adhesive layer 2 is 10 to 40 μm, preferably 15 to 30 μm, and the average particle size B of the conductive carbon particles 3 is usually 8. It is in the range of -38 μm, preferably 12-28 μm. When the average particle diameter of the conductive carbon particles 3 is too large compared to the thickness of the pressure-sensitive adhesive layer 2, the conductive carbon particles protrude from the surface of the pressure-sensitive adhesive layer, or the protruding conductive carbon particles The effective surface area of the pressure-sensitive adhesive layer surface is reduced by contacting the adherend only through the pressure-sensitive adhesive covering the top. As a result, the adhesive strength with the conductive layer 1a and the adherend is lowered. For example, a pressure-sensitive adhesive composition containing conductive carbon particles having a large particle size is directly coated on the conductive layer 1a and dried to form a pressure-sensitive adhesive layer having a thickness smaller than the average particle size of the conductive carbon particles. In such a case, there is no problem in the adhesive strength between the pressure-sensitive adhesive layer and the conductive layer 1a, but the conductive carbon particles protrude from the surface of the pressure-sensitive adhesive layer, and the effective surface area of the pressure-sensitive adhesive layer is reduced. Adhesive strength of becomes insufficient. In addition, when a pressure-sensitive adhesive composition containing conductive carbon particles having a large particle size is applied to a release sheet and dried to form a pressure-sensitive adhesive layer, and then transferred to the conductive layer 1a, Since the conductive carbon particles protrude from the surface of the pressure-sensitive adhesive layer, sufficient adhesive strength may not be obtained between the conductive layer 1a and the adhesive layer. On the other hand, when the ratio (B / A) between the thickness A of the pressure-sensitive adhesive layer 2 and the average particle diameter B of the conductive carbon particles 3 is in the above range, the conductive carbon particles 3 are embedded in the pressure-sensitive adhesive layer. The surface of the pressure-sensitive adhesive layer becomes smooth and adheres to the conductive layer 1a and the adherend with sufficient adhesive strength.

 The conductive carbon particles 3 preferably have a spherical shape, and the aspect ratio is preferably 0.50 to 0.99, and more preferably 0.55 to 0.90. The aspect ratio is expressed by (short axis number average diameter) / (major axis number average diameter) of conductive carbon particles. The short axis number average diameter and the long axis number average diameter are the number average particle diameters obtained by measuring the long axis diameters of 20 carbon particles randomly selected in a transmission electron micrograph and calculating the arithmetic average value thereof.

 When the conductive carbon particles 3 have a spherical shape, the contact frequency between the conductive carbon particles becomes uniform, the contact between the conductive layer 1a and the adherend is stabilized via the conductive carbon particles, and the conduction path is Since it is uniformly formed in the pressure-sensitive adhesive layer, there is no variation between lots or portions of the pressure-sensitive adhesive sheet in terms of conductivity in the thickness direction. On the other hand, if the conductive carbon particles have an indefinite shape, the contact frequency between the conductive carbon particles becomes non-uniform, and the conductivity in the thickness direction varies from lot to lot, or a part with an adhesive sheet and other parts And conductivity may be different.

 Further, the smaller the variation in the particle diameter of the conductive carbon particles 3, the better. When there are too many coarse particles in the conductive carbon particles 3, the conductive carbon particles 3 may protrude from the pressure-sensitive adhesive layer 2, and the effective surface area of the pressure-sensitive adhesive layer may decrease. Therefore, the variation in the particle diameter of the conductive carbon particles 3 is preferably 40% or less, particularly preferably 30% or less in terms of CV value (coefficient of variation).

 The CV value is defined as CV (%) = (standard deviation of particle size / average value of particle size) × 100.

  The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer 2 is preferably 3 to 50 parts by weight, preferably 5 to 40 parts by weight, and more preferably 5 to 40 parts by weight of the conductive carbon particles 3 with respect to 100 parts by weight of the solid content of the pressure-sensitive adhesive resin. Preferably it contains 10-30 mass parts. If the content of the conductive carbon particles 3 is too small, the contact frequency between the conductive carbon particles decreases, a conduction path is not formed, and the conductivity in the thickness direction may decrease. On the other hand, if the content of the conductive carbon particles 3 is excessive, the ratio of the conductive carbon particles 3 on the surface of the pressure-sensitive adhesive layer increases, the effective surface area of the pressure-sensitive adhesive layer decreases, and the conductive layer 1a or the adherend There is a risk that the adhesive strength will decrease.

  Moreover, the adhesive composition that forms the adhesive layer 2 may contain conductive carbon fine particles 4 as shown in FIG. 2. The average particle diameter of the conductive carbon fine particles 4 is in the range of 20 to 80 nm, preferably 25 to 70 nm, and more preferably 30 to 60 nm. When the conductive carbon fine particles 4 are blended in the pressure-sensitive adhesive composition, the conductive carbon fine particles 4 are 5 to 50 parts by mass, preferably 8 to 40 parts by mass with respect to 100 parts by mass of the solid content of the adhesive resin. More preferably, it is used at a ratio of 10 to 30 parts by mass. When such conductive carbon fine particles 4 are blended in the pressure-sensitive adhesive layer, the conductive carbon fine particles 4 are formed between the conductive carbon particles having a large particle diameter or between the conductive carbon particles 3 and the conductive layer 1a or the adherend. The conductive path is easily formed, and the conductivity in the thickness direction is improved. However, if the content of the conductive carbon fine particles 4 is excessive, the effective surface area of the pressure-sensitive adhesive layer is reduced, and the adhesive strength to the conductive layer 1a and the adherend may be reduced.

  As the conductive carbon particles 3 used in the present invention, carbon graphite having a specific gravity of about 2.2 is preferably used, and as the conductive carbon fine particles 4, carbon black having a specific gravity of about 1.8 to 1.9 is preferable. Used.

  When metal particles with high specific gravity are used as the conductive particles, the metal particles settle over time after adjusting the coating liquid of the pressure-sensitive adhesive composition, and the distribution of the conductive particles in the resulting pressure-sensitive adhesive layer is It may not be constant and conductivity may vary from lot to lot. In addition, even after the coating liquid is applied, the metal particles may settle in the coating film, and the dispersion of the metal particles may become uneven in the pressure-sensitive adhesive layer after drying, thereby impairing the conductivity in the thickness direction.

  Further, the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer includes additives generally contained in pressure-sensitive adhesives for ordinary pressure-sensitive adhesive sheets, such as tackifiers, ultraviolet absorbers, antioxidants, and colorants. Alternatively, an antistatic agent or the like may be included as necessary.

 When the conductive pressure-sensitive adhesive sheet 10 of the present invention configured as described above is attached to a conductive adherend, the conductive carbon particles 3 in the pressure-sensitive adhesive layer come into contact with the conductive adherend, and the conductive adherend And the conductive layer 1a of the substrate 1 are electrically connected. Therefore, it can conduct in the vertical direction (thickness direction) and the surface direction. In addition, since the thickness of the conductive pressure-sensitive adhesive sheet 10 of the present invention is substantially equal to the total thickness of the base material 1 and the pressure-sensitive adhesive layer 2, it is possible to reduce the thickness and prevent downsizing of the device. There is no.

  As mentioned above, although the case where the base material 1 was the laminated body of the conductive layer 1a and the support sheet 1b was demonstrated to the conductive adhesive sheet 10 of this invention as an example, the base material 1 is not limited to this structure. For example, when the conductive layer 1a has sufficient supportability, the substrate 1 may be a single layer of the conductive layer 1a.

 Moreover, in the electroconductive adhesive sheet 10 of this invention, in order to protect the adhesive layer 2 before the use, the peeling sheet 5 may be laminated | stacked on the adhesive layer 2 surface. The release sheet 5 may be used as it is without peeling off the release sheet used in the production of the conductive adhesive sheet 10 of the present invention, which will be described later, from the adhesive layer 2, and is used in the production of the conductive adhesive sheet 10. After peeling off the release sheet, another release sheet may be temporarily attached.

 There is no restriction | limiting in particular as a peeling base material in the peeling sheet 5, It can select suitably from the various base materials conventionally known as a base material of a peeling sheet. As such a peeling substrate, for example, a paper substrate such as glassine paper, coated paper, cast coated paper, dust-free paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper substrates, or polyethylene terephthalate, Examples thereof include polyester films such as polybutylene terephthalate and polyethylene naphthalate, polyolefin films such as polypropylene and polymethylpentene, plastic films such as polycarbonate films and cellulose acetate films, and laminated sheets containing these. Although there is no restriction | limiting in particular as the thickness of this peeling base material, Usually, 10-150 micrometers is desirable.

  When a plastic film is used as the release substrate of the release sheet 5, the surface on the side where the release agent layer of the plastic film is provided as desired for the purpose of improving the adhesion between the plastic film and the release agent layer. Further, a physical or chemical surface treatment such as an oxidation method or a roughening method can be performed. Examples of the oxidation method include corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment and the like, and examples of the concavo-convex method include a sand blast method and a solvent treatment method. . These surface treatment methods are appropriately selected depending on the type of the release substrate, but in general, the corona discharge treatment method is preferably used from the viewpoints of effects and operability. Moreover, primer treatment can also be performed.

  Silicone resin, long chain alkyl resin, alkyd resin, fluororesin, polybutadiene rubber, butyl rubber, styrene-butadiene copolymer, polyisoprene rubber, ethylene polypropylene copolymer are used as the release agent for forming the release agent layer in the release sheet. In view of the silicone contamination described above, it may be preferable to use a release agent that is not a silicone resin.

  Coating of the release agent on the release substrate is conventionally known, for example, bar coating method, reverse roll coating method, knife coating method, roll knife coating method, gravure coating method, air doctor coating method, doctor blade coating method, etc. It can be performed by a coating method. Although there is no restriction | limiting in particular in the thickness of a release agent layer, Usually, 0.01-5 micrometers is desirable.

 Next, the manufacturing method of the electroconductive adhesive sheet 10 which concerns on this invention is demonstrated.

  In the manufacturing method according to the present invention, first, a substrate 1 having a conductive layer 1a is prepared. Separately from this, a coating liquid of the pressure-sensitive adhesive composition is prepared. The coating liquid is obtained by mixing the above-mentioned adhesive resin, conductive carbon particles 3 and, if necessary, conductive carbon fine particles 4 using an appropriate dispersion medium. The pressure-sensitive adhesive layer 2 is formed on the release sheet 5 by coating and drying the obtained coating liquid on the release sheet 5. The pressure-sensitive adhesive layer 2 can be formed by a conventionally known coating method such as a bar coating method, a reverse roll coating method, a knife coating method, a roll knife coating method, a gravure coating method, an air doctor coating method, or a doctor blade coating method. Next, the conductive adhesive sheet 10 of the present invention is obtained by bonding the pressure-sensitive adhesive layer 2 to the conductive layer 1a side of the substrate 1 described above. Specific examples and preferred examples of the substrate 1, the pressure-sensitive adhesive layer 2, and the release sheet 5 are the same as described above. By passing through such a process, the electroconductive adhesive sheet 10 with high adhesiveness of the electroconductive layer 1a surface of the base material 1 and the adhesive layer 2 is obtained. Moreover, what is necessary is just to peel the peeling sheet 5 when using the electroconductive adhesive sheet 10. FIG. Moreover, the coating liquid of the said adhesive composition can be directly apply | coated and dried on the conductive layer 1a of the base material 1, and a conductive adhesive sheet can also be obtained.

 The conductive adhesive sheet of the present invention has conductivity in the thickness direction and the surface direction, and is preferably used for applications such as an electromagnetic wave shield and an antistatic ground sheet. For example, by attaching the conductive adhesive sheet of the present invention across the surface of a component that is easily charged and the surface of the housing, the charged component and the housing are electrically connected, and the static electricity of the charged component is grounded. be able to. Therefore, the conductive pressure-sensitive adhesive sheet of the present invention can be suitably used, for example, for grounding a motor part and a housing of a hard disk drive.

(Example)
EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

 In the present invention, the average particle diameter of the conductive carbon particles and the conductive carbon fine particles, and the adhesive force and conductivity of the conductive adhesive sheet were evaluated as follows.

[Average particle diameter and aspect ratio of conductive carbon particles and conductive carbon fine particles]
The average particle size of the conductive carbon particles and the conductive carbon fine particles was determined by measuring the major axis diameter of 20 carbon particles randomly selected with an electron micrograph and calculating the number average particle size as the arithmetic average value. .

 As for the aspect ratio, the major axis diameter and the minor axis diameter of 20 particles randomly selected with an electron micrograph were measured in the same manner as described above, and the minor axis number average diameter and major axis number average diameter were calculated. Number average diameter) / (major axis number average diameter).

 Moreover, CV value which shows the dispersion | variation in the particle size of electroconductive carbon particle was calculated | required from the following formula from the said measurement result.

CV (%) = (standard deviation of particle size / average value of particle size) × 100
[Adhesive force]
In accordance with JIS Z 0237, the adhesive strength of the conductive adhesive sheet 30 minutes after pasting on the adherend (SUS) was measured by a 180 ° peeling method at 23 ° C. and 50% RH.

[Conductivity evaluation]
As shown in FIG. 3, it laminated | stacked on the both ends of the glass plate G with the copper foil surface of the polyethylene terephthalate film (Cu / PET) with a copper foil facing up. The copper foils separated (separated distance: 50 mm) are bonded and connected to the copper foil surface with a conductive adhesive sheet 10 (length: 70 mm, width: 10 mm) so that both ends have a sticking area of 10 mm × 10 mm. It was measured with a tester (manufactured by Hioki Electric Co., Ltd., trade name “HIOKI 3801 Digital High Tester”, measurement mode: auto range) whether or not the foils are conducting.

Example 1
[Creation of release sheet]
A polyethylene terephthalate (PET) film (manufactured by Mitsubishi Polyester Film: T100) having a thickness of 50 μm was used as a release substrate of the release sheet.

 On the PET film, 100 parts by weight of polyurethane (manufactured by Dainippon Ink and Chemicals: Chrisbon 5150S, solid content 50% by weight) and 5 parts by weight of isocyanate cross-linking agent (manufactured by Dainippon Ink and Chemicals: Crisbon NX) in a methyl ethyl ketone solution. Then, it was diluted to a solid content concentration of 1% by weight, applied so that the film thickness after drying was 0.15 μm, and dried at 100 ° C. for 1 minute to form a primer layer.

A release layer was formed on the primer layer to obtain a release sheet. The release layer was formed by adding 100 parts by weight of 1,4-polybutadiene (manufactured by JSR: BR-01, solid content 5% by weight) and 1 part by weight of an antioxidant (manufactured by Ciba Specialty Chemicals Co., Ltd .: IRGANOXHP2251) in toluene. It is diluted with a solvent to a solid content concentration of 0.5% by weight, applied onto the primer layer so that the film thickness after drying is 0.1 μm, dried at 100 ° C. for 30 seconds, and then fused H bulb 240 w / cm 1 The coating layer was irradiated with ultraviolet rays using a belt conveyor type ultraviolet irradiation device with light at a conveyor speed of 40 m / min (ultraviolet irradiation conditions: 100 mJ / cm ² ).

[Preparation of pressure-sensitive adhesive composition]
83.0 parts by weight of butyl acrylate, 2.0 parts by weight of 2-hydroxyethyl acrylate, 15.0 parts by weight of N-acryloylmorpholine, 0.1 part by weight of azobisisobutyronitrile as a polymerization initiator, ethyl acetate A polymerization catalyst solution in which 150 parts by weight is placed in a reactor, the temperature is raised to 80 to 90 ° C. while stirring, a polymerization reaction is performed, and 0.1 part by weight of azobisisobutyronitrile is dissolved in 10 parts by weight of toluene. The polymer was polymerized over 7 hours with sequential addition. A 40% solution of an acrylic copolymer was prepared by adding a diluting solvent (a mixed solvent of toluene and ethyl acetate) after completion of the reaction.

 1 part by weight of a tolylene diisocyanate (TDI) cross-linking agent (Coronate L55E, manufactured by Nippon Polyurethane Co., Ltd.) is blended with 100 parts by weight (40 parts by weight as a solid content) of this acrylic copolymer solution, and a solution of an adhesive resin Adjusted.

 Carbon graphite (made by Nippon Graphite Co., Ltd., trade name CGC-15, average particle size 17.26 μm, aspect ratio 0.68, CV value 20) with respect to 100 parts by mass of the solid content of the adhesive resin solution. .9%) was blended in an amount of 10 parts by mass to prepare a coating solution for the pressure-sensitive adhesive composition.

[Creation of conductive adhesive sheet]
The pressure-sensitive adhesive composition coating solution was applied to the release agent layer surface of the release sheet so that the thickness after drying was 20 μm, and then dried at 100 ° C. for 1 minute to form an adhesive layer. Next, a copper foil surface side of the base material obtained by laminating a 35 μm thick copper foil as a conductive layer on one side of a polyethylene terephthalate film film (Mitsubishi polyester film: PET50 (N)) and a pressure-sensitive adhesive of the above pressure-sensitive adhesive layer The surface was contacted and stacked to produce a conductive adhesive sheet.

  The adhesive strength and electrical conductivity of the obtained conductive adhesive sheet were evaluated. The results are shown in Table 1.

(Example 2)
[Preparation of pressure-sensitive adhesive composition]
10 parts by mass of carbon graphite (trade name CGC-15, manufactured by Nippon Graphite Co., Ltd.) as conductive carbon particles and carbon as conductive carbon fine particles with respect to 100 parts by mass of the solid content of the adhesive resin solution prepared in Example 1 10 parts by mass of black (manufactured by Mitsubishi Chemical Co., Ltd., trade name # 3050B, average particle size 50 nm) was blended to prepare a coating solution for the pressure-sensitive adhesive composition.

[Creation of conductive adhesive sheet]
A conductive pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition coating liquid was used and the thickness of the pressure-sensitive adhesive layer after drying was 23 μm.

  The adhesive strength and electrical conductivity of the obtained conductive adhesive sheet were evaluated. The results are shown in Table 1.

(Examples 3 and 4, Comparative Examples 1 and 2 and Reference Example)
A conductive pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the blending amounts of carbon graphite and carbon black and the thickness of the pressure-sensitive adhesive layer were changed as shown in Table 1. The results are shown in Table 1.

Sectional drawing of the one aspect | mode of the electroconductive adhesive sheet which concerns on this invention is shown. Sectional drawing of the one aspect | mode of the electroconductive adhesive sheet which concerns on this invention is shown. It is the schematic which shows the conductivity evaluation method in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 1a ... Conductive layer 1b ... Support sheet 2 ... Adhesive layer 3 ... Conductive carbon particle 4 ... Conductive carbon fine particle 5 ... Release sheet 10 ... Conductive adhesive sheet G ... Glass plate

Claims (9)

A base material having a conductive layer, and a pressure-sensitive adhesive layer formed on the surface of the conductive layer,
The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains conductive carbon particles having an average particle diameter of 8 to 38 μm and conductive carbon fine particles having an average particle diameter of 20 to 80 nm,
A conductive pressure-sensitive adhesive sheet in which the ratio A of the thickness A of the pressure-sensitive adhesive layer to the average particle size B of the conductive carbon particles, B / A is in the range of 0.50 to 0.99. The conductive adhesive sheet according to claim 1, wherein the adhesive layer has a thickness A of 10 to 40 μm .   The conductive adhesive sheet according to claim 1 or 2, wherein the conductive carbon particles have an aspect ratio of 0.50 to 0.99.   The electroconductive property in any one of Claims 1-3 in which the adhesive composition which forms an adhesive layer contains 3-50 mass parts of conductive carbon particles with respect to 100 mass parts of solid content of an adhesive resin. Adhesive sheet.   The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains 5 to 50 parts by mass of conductive carbon fine particles having an average particle diameter of 20 to 80 nm with respect to 100 parts by mass of the solid content of the adhesive resin. The electroconductive adhesive sheet in any one. The base material is a conductive layer made of a metal foil or a metal film;
A laminate with a support sheet made of a plastic film,
The film forming the support sheet is made of any one of a plastic such as polyolefin resin, polyester resin, acetate resin, polyamide resin, polyimide resin, ABS resin, polystyrene resin, or vinyl chloride resin. The electroconductive adhesive sheet of description.   The conductive pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive containing no acid group.   The electroconductive pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which is used for an electromagnetic wave shield or a ground sheet for preventing static electricity. On the release treatment surface of the release sheet, 3 to 50 parts by weight of conductive carbon particles having an average particle diameter of 8 to 38 μm and an average particle diameter of 20 to 20 parts per 100 parts by weight of the solid content of the pressure-sensitive adhesive resin. Applying a coating solution of an adhesive composition containing conductive carbon fine particles of 80 nm and drying to form an adhesive layer;
And a step of bonding the pressure-sensitive adhesive layer on the surface of the conductive layer of the substrate having the conductive layer.

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