JP2002056719A - Anisotropic electroconductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic electroconductive sheet which shows an electroconductivity in a state without any pressure and in the pressurized state by a small force in a thickness direction and which shows a higher electroconductivity in a pressurized state by a large force in a thickness direction than that in the state without any pressure and in the pressurized state by a small force in a thickness direction. SOLUTION: This anisotropic electroconductive sheet comprises a sheet substrate composed of elastomer, electroconductive fibers arranged to extend in a thickness direction in this sheet substrate, and electroconductive particles to show contained magnetism in a state orienting in the thickness direction in the sheet substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive sheet having conductivity in a thickness direction.

[0002]

2. Description of the Related Art An anisotropic conductive elastomer sheet has conductivity only in the thickness direction, or has a pressurized conductive portion which has conductivity only in the thickness direction when pressed in the thickness direction. And it is possible to achieve a compact electrical connection without using means such as soldering or mechanical fitting, and it is possible to absorb mechanical shocks and strains and make a soft connection Because of these features, using such features, for example, computers,
In the fields of electronic digital watches, electronic cameras, computer keyboards, etc., it is widely used as a connector for achieving an electrical connection between circuit devices, for example, a printed circuit board and a leadless chip carrier, a liquid crystal panel, etc. ing.

In electrical inspection of a circuit device such as a printed circuit board or a semiconductor integrated circuit, an electrode to be inspected formed on one surface of a circuit device to be inspected and an electrode formed on the surface of the inspection circuit substrate. In order to achieve electrical connection with the test electrode, an anisotropic conductive elastomer sheet is interposed between the test electrode region of the circuit device and the test electrode region of the test circuit board. I have.

Heretofore, as such anisotropic conductive elastomer sheets, those having various structures are known. For example, as an anisotropic conductive elastomer sheet showing conductivity in the absence of pressure, a sheet base made of insulating rubber, conductive fibers arranged in a state of being oriented to extend in the thickness direction, carbon Conductive rubber containing black or metal powder and insulating rubber alternately laminated along the surface direction (Japanese Patent Laid-Open No. 50-94495)
For example, are known. On the other hand, as an anisotropic conductive elastomer sheet which exhibits conductivity when pressed in the thickness direction, a sheet obtained by uniformly dispersing metal particles in an elastomer (see JP-A-51-93393), A plurality of conductive path forming portions extending in the thickness direction and an insulating portion for insulating these from each other are formed by distributing the non-uniform magnetic material particles in the elastomer (JP-A-53-147772). Japanese Patent Application Laid-Open No. 61-250906 discloses a structure in which a step is formed between the surface of a conductive path forming portion and an insulating portion.

[0005]

However, in the field of electronic parts or electronic parts applied equipment, in the field of no pressure or in the state of being pressed in the thickness direction with a small force,
A certain degree of conductivity in the thickness direction (for example, a volume resistivity of 1
× 10 ⁷ to 1 × 10 ¹² Ω · m), and in a state of being pressed in the thickness direction with a large force, a higher conductivity (for example, volume resistivity) than a state of no pressure or a state of being pressed with a small force Is 1 × 10 ⁻² to 1 × 10 ⁷ Ω · m), but such an anisotropic conductive elastomer sheet is not known until now.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to show conductivity in a state where no pressure is applied or in a state where a small force is applied in the thickness direction and to provide a large force. An object of the present invention is to provide an anisotropic conductive sheet that exhibits higher conductivity when pressed in the thickness direction with no pressure or when pressed in the thickness direction with a small force.

[0007]

An anisotropic conductive sheet according to the present invention comprises a sheet base made of an elastomer, conductive fibers arranged in the sheet base so as to extend in the thickness direction, and a sheet base. And conductive particles exhibiting magnetism contained in a state of being aligned in the thickness direction.

[0008] In the anisotropic conductive sheet of the present invention, it is preferable that the conductive particles are contained in a state of being dispersed in a plane direction of the sheet base. Further, a conductivity-imparting substance may be dispersed in the sheet base, and the conductivity-imparting substance is at least one selected from a substance exhibiting conductivity by itself and a substance exhibiting conductivity by absorbing moisture. It is preferably a species material.

Further, in the anisotropic conductive sheet of the present invention,
Means that no pressure is applied and the strain rate is S ₀[However, S₀Is 0
A value selected from the range of ~ 3 (%)]
Volume in the thickness direction when pressed in the thickness direction
R with resistance₀And the distortion rate is S₀% Than ΔS [however,
ΔS is a value selected from the range of 10 to 20 (%)]% or more
In the state where it is pressed in the thickness direction so that it becomes a large value
Let the volume resistivity in the thickness direction be R₁And the volume specific resistance
Anti-R₀Is 1 × 10⁷~ 1 × 10¹²Ω · m range,
Volume resistivity R₀And volume resistivity R₁And the ratio (R₀/ R
₁) Is 1 × 10^Two~ 1 × 10^TenPreferably in the range of
New

[0010]

According to the anisotropic conductive sheet of the present invention, the conductive fibers are arranged in the sheet base made of the elastomer so as to extend in the thickness direction. In the pressed state, the conductive fiber exhibits conductivity according to the electrical characteristics of the conductive fiber.Moreover, the sheet base contains conductive particles oriented in the thickness direction, and thus is large. In a state where pressure is applied in the thickness direction by force, a conductive path extending in the thickness direction of the sheet substrate is formed by the conductive particles, and thus, a pressure is applied in the thickness direction with no pressure or with a small force. It shows higher conductivity than the state.

[0011]

Embodiments of the present invention will be described below in detail. FIG. 1 is an explanatory cross-sectional view showing a configuration of an example of the anisotropic conductive sheet of the present invention. This anisotropic conductive sheet is made of a sheet substrate 1 made of an elastomer.
In the sheet substrate 10, conductive fibers F are arranged along a surface direction so as to extend in the thickness direction of the sheet substrate 10, and further, conductive particles P exhibiting magnetism are provided in the sheet substrate 10. Are contained in such a state that they are aligned in the thickness direction and are dispersed in the surface direction of the sheet base 10. In the present invention, the conductive fiber F is the sheet substrate 1
Although it is necessary to be arranged so as to extend in the thickness direction of 0, “arranged to extend in the thickness direction” means the same direction as the thickness direction of the sheet base (hereinafter, this direction is referred to as “Z direction”). ) Means that they are arranged to extend in a direction inclined at an angle of 30 ° or less with respect to the Z direction.

The thickness of the sheet base 10 is not particularly limited, but is usually 0.05 to 1 mm, preferably 0.1 to 0.5 mm. As the elastomer constituting the sheet base 10, a polymer substance having a crosslinked structure is preferable. Various materials can be used as the curable polymer substance forming material that can be used to obtain the crosslinked polymer substance, and specific examples thereof include polybutadiene rubber, natural rubber, polyisoprene rubber, and styrene-
Conjugated diene rubbers such as butadiene copolymer rubber and acrylonitrile-butadiene copolymer rubber and hydrogenated products thereof, and block copolymers such as styrene-butadiene-diene block copolymer rubber and styrene-isoprene block copolymer Rubber and their hydrogenated products,
Examples include chloroprene, urethane rubber, polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene-propylene copolymer rubber, and ethylene-propylene-diene copolymer rubber. In the above, when weather resistance is required for the obtained anisotropic conductive sheet, it is preferable to use a material other than the conjugated diene rubber, and particularly, from the viewpoint of moldability and electrical characteristics, use of silicone rubber Is preferred.

[0013] The silicone rubber is preferably one obtained by crosslinking or condensing a liquid silicone rubber. The liquid silicone rubber preferably has a viscosity of 10 ⁵ poise or less at a strain rate of 10 ⁻¹ sec, and may be any of condensation type, addition type, and those containing a vinyl group or a hydroxyl group. Good. Specifically, dimethylsilicone raw rubber, methylvinylsilicone raw rubber, methylphenylvinylsilicone raw rubber and the like can be mentioned.

Among these, liquid silicone rubber containing a vinyl group (vinyl group-containing polydimethylsiloxane)
Is usually obtained by subjecting dimethyldichlorosilane or dimethyldialkoxysilane to hydrolysis and condensation reaction in the presence of dimethylvinylchlorosilane or dimethylvinylalkoxysilane, for example, followed by fractionation by repeated dissolution-precipitation. Also,
The liquid silicone rubber containing vinyl groups at both ends is anionically polymerized with a cyclic siloxane such as octamethylcyclotetrasiloxane in the presence of a catalyst, and uses, for example, dimethyldivinylsiloxane as a polymerization terminator and other reaction conditions (for example, , The amount of the cyclic siloxane and the amount of the polymerization terminator). Here, as a catalyst for anionic polymerization, alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C. Such a vinyl group-containing polydimethylsiloxane preferably has a molecular weight Mw (weight average molecular weight in terms of standard polystyrene; the same applies hereinafter) of 10,000 to 40,000. In addition, from the viewpoint of heat resistance of the obtained conductive path element, the molecular weight distribution index (the value of the ratio Mw / Mn between the standard polystyrene-equivalent weight average molecular weight Mw and the standard polystyrene-equivalent number average molecular weight Mn; the same applies hereinafter) is 2. The following are preferred.

On the other hand, liquid silicone rubber containing hydroxyl groups (hydroxyl group-containing polydimethylsiloxane) is usually prepared by hydrolyzing dimethyldichlorosilane or dimethyldialkoxysilane in the presence of dimethylhydrochlorosilane or dimethylhydroalkoxysilane. And condensation reaction, for example,
It is obtained by performing fractionation by repeating precipitation.
Further, cyclic siloxane is anionically polymerized in the presence of a catalyst, and dimethylhydrochlorosilane, methyldihydrochlorosilane or dimethylhydroalkoxysilane is used as a polymerization terminator, and other reaction conditions (for example, the amount of the cyclic siloxane and the polymerization termination) are used. Amount of agent)
Can also be obtained by appropriately selecting Here, as a catalyst for anionic polymerization, alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C. Such hydroxyl group-containing polydimethylsiloxane is,
It is preferable that the molecular weight Mw is 10,000 to 40,000. Further, from the viewpoint of heat resistance of the obtained conductive path element, those having a molecular weight distribution index of 2 or less are preferable.
In the present invention, either one of the above-mentioned vinyl group-containing polydimethylsiloxane and hydroxyl group-containing polydimethylsiloxane can be used, or both can be used in combination.

In the present invention, an appropriate curing catalyst can be used to cure the polymer-forming material. As such a curing catalyst, an organic peroxide, a fatty acid azo compound, a hydrosilylation catalyst, or the like can be used. Specific examples of the organic peroxide used as the curing catalyst include benzoyl peroxide, bisdicyclobenzoyl peroxide, dicumyl peroxide, and ditertiary butyl peroxide. Specific examples of the fatty acid azo compound used as a curing catalyst include azobisisobutyronitrile. Specific examples of the catalyst which can be used as a catalyst for the hydrosilylation reaction include chloroplatinic acid and salts thereof, a siloxane complex containing a platinum-unsaturated group, a complex of vinylsiloxane and platinum, and platinum and 1,3-divinyltetramethyldisiloxane. And a complex of triorganophosphine or phosphite with platinum, acetylacetate platinum chelate, and a complex of cyclic diene and platinum. The amount of the curing catalyst used is appropriately selected in consideration of the type of the polymer substance-forming material, the type of the curing catalyst, and other curing treatment conditions. 15 parts by weight.

The material constituting the conductive fibers F contained in the sheet base 10 is not particularly limited, and may be non-magnetic or magnetic. In the state of pressurization or in the state of pressurization with a small pressure, in that the volume specific resistance in the range described later is easily obtained, as the nonmagnetic conductive fiber, carbon fiber, on the surface of a fiber such as polyamide fiber, Tin, solder, those formed with a conductive coating film made of a non-magnetic metal such as copper, or those obtained by further forming an insulating coating film on the surface of this conductive coating film, phosphor bronze, Fibers made of a non-magnetic metal such as beryllium copper, SUS, or aluminum and having an insulating coating film formed on the surface thereof can be suitably used. A fiber such as an amide fiber, on which a conductive coating film made of a conductive magnetic material such as nickel, cobalt, iron, ferrite or an alloy thereof is formed, or on the surface of the conductive coating film Those having an insulating coating film formed thereon and those having an insulating coating film formed on the surface of a fiber made of a conductive magnetic material such as nickel or iron can be suitably used. In the above, as a material constituting the insulating coating film, an organic material such as polyimide, electrodeposited polyimide, polystyrene, polymethyl methacrylate, or a fluororesin, or an inorganic material such as silica can be used. The coverage of the insulating coating film on the conductive fiber F is appropriately set according to the intended conductivity of the anisotropic conductive sheet, and is, for example, 50 to 99%, and preferably 70 to 95%. %.

The diameter of the conductive fiber F is usually 5 to 100 μm.
m, preferably 10 to 50 μm. The length of the conductive fiber F is preferably 50 to 150% of the thickness of the sheet substrate 10, more preferably 60 to 120%, and specifically, 0.05 to 1 mm, preferably 0.1 to 1%. 1
０．５0.5 mm. The density of the conductive fibers F in the sheet base 10 is appropriately set according to the purpose of use of the anisotropic conductive sheet and the type of the conductive fibers F, but is 1 × 10 ³ to 1 × 10 ³ per cm ^{2 in} the cross section in the plane direction. 1x1
0 It is preferable that ^six is contained, more preferably from ^{1 × 10 4 ~1 × 10 5} .

As the conductive particles P contained in the sheet base 10, conductive particles exhibiting magnetism can be easily aligned in the thickness direction of the sheet base 10 by applying a magnetic field. Used. Specific examples of such conductive particles P include nickel, iron,
Particles made of a metal exhibiting magnetism such as cobalt or particles made of an alloy thereof or particles containing these metals, or these particles as core particles, and gold, silver, palladium, rhodium or the like on the surface of the core particles ZrFe ₂ , Fe plated with conductive metal that is difficult to oxidize
Be ₂ , FeRh, MnZn, Ni ₃ Mn, FeCo,
FeNi, Ni ₂ Fe, MnPt ₃ , FePd, FeP
d ₃ , Fe ₃ Pt, FePt, CoPt, CoPt ₃ ,
Particles made of a ferromagnetic intermetallic compound such as Ni ₃ Pt, or these particles as core particles, and gold,
Plated with a conductive metal such as silver, palladium or rhodium which is difficult to oxidize; Chemical formula: M ¹ O · Fe ₂ O ₃
(However, M ¹ is Mn, Fe, Ni, Cu, Zn, M
It indicates metals such as g, Co, and Li. ), A mixture thereof (for example, Mn—Zn ferrite, Ni—Zn ferrite, etc.), FeMn ₂ O ₄
Cobaltite represented by the chemical formula: M ² O · Co ₂ O ₃ (where M ² represents a metal such as Fe, Ni, etc.), Ni _0.5 Zn _0.5 Fe ₂ O ₄ , Ni
_0.35 Zn _0.65 Fe ₂ O ₄ , Ni _0.7 Zn _0.2 Fe _0.1 F
Particles made of a ferromagnetic metal oxide such as e ₂ O ₄ , Ni _0.5 Zn _0.4 Fe _0.1 Fe ₂ O ₄ , or these particles as core particles, and the surface of the core particles is oxidized with gold, silver, palladium, rhodium, or the like. Non-magnetic metal particles, glass beads, particles made of an inorganic substance such as carbon, or polystyrene, particles made of a polymer such as polystyrene cross-linked with divinylbenzene as core particles, The core particles may be obtained by plating the surface with a conductive magnetic material such as nickel or cobalt, or may be obtained by coating the core particles with both a conductive magnetic material and a conductive metal that is difficult to oxidize.
Further, these conductive particles may have an insulating film formed on the surface for the purpose of adjusting the conductivity. Here, metal oxide,
An inorganic material such as a silicon oxide compound, or an organic material such as a resin or a coupling agent can be used. In the above,
Means for coating the surface of the core particles with a conductive metal is not particularly limited, but may be, for example, chemical plating or electrolytic plating.

In the case where the conductive particles P are formed by coating the surface of a core particle with a conductive metal, from the viewpoint of obtaining stable conductivity over a long period of time, the coating of the conductive metal on the surface of the particles is preferred. The ratio (the ratio of the conductive metal covering area to the surface area of the core particles) is preferably 40% or more, more preferably 45% or more, and particularly preferably 47 to 95%. The amount of the conductive metal to be coated is appropriately set according to the intended conductivity of the anisotropic conductive sheet, but is preferably 0.5 to 50% by weight of the core particles, more preferably 1 to 50% by weight. -30% by weight, more preferably 3-25% by weight, particularly preferably 4-20% by weight. When the conductive metal to be coated is gold,
The coating amount is preferably 2.5 to 30% by weight of the core particles, more preferably 3 to 20% by weight, further preferably 3.5 to 15% by weight, and particularly preferably 4 to 10% by weight.
% By weight. When the conductive metal to be coated is silver, the coating amount is preferably 3 to 50% by weight of the core particles, more preferably 4 to 40% by weight, and further preferably 5 to 30% by weight. % By weight, particularly preferably 6 to 2%
0% by weight.

The number average particle diameter of the conductive particles P is 1
The thickness is preferably from 1000 to 1000 m, more preferably from 2 to 500 m, still more preferably from 5 to 300 m, and particularly preferably from 10 to 200 m. The particle diameter distribution (Dw / Dn) of the conductive particles P is preferably 1 to 10, more preferably 1.01 to 7, further preferably 1.05 to 5, and particularly preferably 1.1. ~ 4. By using the conductive particles P satisfying such conditions, in the obtained anisotropic conductive sheet, sufficient electrical contact between the conductive particles arranged in the thickness direction can be obtained. Also,
When a magnetic field is applied to the sheet forming material layer described later in the thickness direction, the conductive particles P move when the conductive particles are oriented so as to be aligned in the thickness direction to form a chain. It becomes easy to arrange the fibers F so as to extend in the thickness direction. The shape of the conductive particles P is not particularly limited. However, since the conductive particles P can be easily dispersed in the polymer substance-forming material, they have a spherical shape, a star shape, or a shape in which these are aggregated. It is preferably a lump formed by the secondary particles.

The water content of the conductive particles P is preferably 5% or less, more preferably 3% or less, further preferably 2% or less, and particularly preferably 1% or less. By using the conductive particles satisfying such conditions, it is possible to prevent or suppress the generation of bubbles during the curing treatment of the polymer substance forming material.

The proportion of the conductive particles P in the sheet substrate 10 is appropriately selected according to the purpose of use of the anisotropic conductive sheet and the type of the conductive particles to be used. It is preferably selected from the range of 30%, preferably 5 to 15%. If this ratio is less than 3%, it may be difficult to form a conductive path having sufficiently small electric resistance. On the other hand, when this ratio exceeds 50%, the obtained anisotropic conductive sheet may be fragile. When a magnetic field is applied to the sheet molding material layer described later in the thickness direction,
As a result of the conductive particles P and the conductive fibers F interfering with each other,
It may be difficult to reliably achieve the orientation of the conductive particles P and the arrangement of the conductive fibers F.

In the anisotropic conductive sheet of the present invention, in order to adjust the conductivity in the thickness direction when no pressure is applied or when pressed with a small force, a non-magnetic conductive sheet is provided in the sheet base 10. An imparting substance can be contained. As such a conductivity-imparting substance, a substance exhibiting conductivity per se (hereinafter, also referred to as “self-conducting substance”), a substance exhibiting conductivity by absorbing moisture (hereinafter, referred to as “self-conducting substance”).
Also referred to as “moisture-absorbing conductive substance”. ) Can be used, and these self-conductive substances and moisture-absorbing conductive substances are
Either one can be used or both can be used in combination.

As the self-conductive substance, generally, a substance exhibiting conductivity by free electrons in a metal bond, a substance in which charge transfer occurs due to the movement of surplus electrons, and a substance in which charge transfer occurs due to the movement of vacancies And an organic polymer substance having a π bond along the main chain and exhibiting conductivity by the interaction thereof, and a substance which causes charge transfer by the interaction of a group in a side chain. Specifically, non-magnetic metals such as platinum, gold, silver, copper, aluminum, manganese, zinc, tin, lead, indium, molybdenum, niobium, tantalum and chromium; copper dioxide, zinc oxide, tin oxide, titanium oxide, etc. Non-magnetic conductive metal oxides; conductive fiber materials such as whisker and potassium titanate; semiconductive materials such as germanium, silicon, indium phosphorus and zinc sulfide; carbon-based materials such as carbon black and graphite; polyacetylene-based polymers And a conductive polymer substance such as a heterocyclic polymer such as a polyphenylene-based polymer and a thiophenylene-based polymer, and these can be used alone or in combination of two or more as a conductivity-imparting substance.

As the moisture-absorbing conductive substance, a substance that generates ions and carries a charge by the ions, a substance having a highly polar group such as a hydroxyl group or an ester group, or the like can be used. Specifically, cation-forming substances such as quaternary ammonium salts and amine compounds; aliphatic sulfonates, higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher alcohol phosphates, Substances which generate both anions such as higher alcohol ethylene oxide addition phosphoric acid ester salts; Substances which generate both cations and anions such as bedyne compounds; Silicon compounds such as chloropolysiloxane, alkoxysilane, alkoxypolysilane and alkoxypolysiloxane , Conductive urethane,
High molecular substances such as polyvinyl alcohol or a copolymer thereof, higher alcohols such as ethylene oxide, polyethylene glycol fatty acid esters and polyhydric alcohol fatty acid esters, and substances having large polar groups such as polysaccharides are used. These can be used alone or in combination of two or more as a conductivity-imparting substance.

Also, among the above-mentioned moisture-absorbing conductive substances, they have high heat resistance, good compatibility with elastic polymer substances,
Aliphatic sulfonates are preferred in that they do not cause polymerization inhibition in the formation of the elastic polymeric material. Such aliphatic sulfonates include 1-decane sulfonate and 1-decane sulfonate.
Undecane sulfonate, 1-dodecane sulfonate,
1-tridecane sulfonate, 1-tetradecane sulfonate, 1-pentadecane sulfonate, 1-hexadecane sulfonate, 1-heptadecane sulfonate, 1
Those having an alkyl group having 10 to 20 carbon atoms, such as -octadecanesulfonic acid salt, 1-nonadecanesulfonic acid salt, 1-eicosandecasulfonic acid salt, and isomers thereof are preferable. As the salt, an alkali metal salt such as lithium, sodium, and potassium is preferable, and a sodium salt is particularly preferable because it has higher heat resistance.

The proportion of the conductivity-imparting substance in the sheet substrate 10 is appropriately set according to the type of the conductivity-imparting substance and the desired degree of conductivity. When used alone, 10 parts by weight or less, preferably 8 parts by weight or less, based on 100 parts by weight of the elastomer constituting the sheet base 10, is made of a nonmagnetic conductive metal oxide as a conductivity-imparting substance. When used alone, 40 parts by weight or less, preferably 30 parts by weight or less, based on 100 parts by weight of the elastomer constituting the sheet base 10, and when using solely carbon black as the conductivity-imparting substance, Is 40 parts by weight or less, preferably 30 parts by weight or less, based on 100 parts by weight of the elastomer constituting the sheet base 10, When the conductive polymer is used alone, it is 30 parts by weight or less, preferably 25 parts by weight or less, based on 100 parts by weight of the elastomer constituting the sheet base 10, and the moisture-absorbing conductive substance is used as the conductivity-imparting substance. When used alone, it is set within a range of 40 parts by weight or less, preferably 30 parts by weight or less based on 100 parts by weight of the elastomer constituting the sheet base 10.
In the case where the above-mentioned various conductivity-imparting substances are used in combination, the ratio is set in consideration of the above range.

The sheet base 10 may contain an inorganic filler, such as ordinary silica powder, colloidal silica, airgel silica, and alumina, if necessary. By including such an inorganic filler,
The thixotropic property of the material for forming the sheet base 10 is ensured, the viscosity thereof is increased, and the dispersion stability of the conductive particles is improved, and the sheet base 10 having high strength is obtained. The use amount of such an inorganic filler is not particularly limited, but using a large amount is not preferable because the orientation of the conductive particles cannot be sufficiently achieved by the magnetic field.

In such an anisotropic conductive sheet, a sheet
So that the conductive fibers F extend in the thickness direction in the substrate 10.
Because they are arranged, the anisotropic conductive sheet
State or state pressed in the thickness direction with small force
Shows the conductivity according to the electrical characteristics of the conductive fiber F.
You. The degree of this conductivity depends on the use of the anisotropic conductive sheet.
It is set appropriately according to the purpose, but specifically, anisotropic conductive
Sheet without pressure and strain rate is S₀[However, S
₀Is a value selected from the range of 0 to 3 (%)]
In the state of being pressed in the thickness direction so that
Volume resistivity R in the thickness direction of the conductive sheet ₀But 1 ×
10⁷~ 1 × 10¹²Preferably in the range of Ω · m
And more preferably 1 × 10⁸~ 1 × 10¹¹Ω ・ m range
It is an enclosure. In order to obtain such conductivity,
Select the type of conductive fiber, and determine the content of the conductive fiber.
Can be adjusted. The anisotropic conductive sheet is 1 cm
^Two0 to 5g, preferably 0 to 2g per load
By applying pressure in the direction of₀(%)The value of the
Should be obtained.

On the other hand, the sheet base 10 has
Conductive particles P are contained in a state of being aligned in
Because the anisotropic conductive sheet has a large force in the thickness direction
Under pressure, the chain of conductive particles P causes
Since a conductive path extending in the thickness direction of the substrate is formed,
As a result, the thickness can be reduced with no pressure or with a small force.
It shows higher conductivity than the state pressed in the direction. This conductive
The degree of the property depends on the intended use of the anisotropic conductive sheet.
It is set appropriately, but specifically, the anisotropic conductive sheet
Only rate is S₀% [ΔS] [however, ΔS is 10 to 20
(Value selected from the range of (%)]
When pressed in the thickness direction, the anisotropic conductive
Volume resistivity R in the thickness direction of the conductive sheet₁Against the body
Product specific resistance R₀Ratio (R₀/ R₁) Is 1 × 10^Two~ 1 ×
10 ^TenAnd more preferably 1
× 10^Three~ 1 × 10⁹Range. Such conductivity
The type of conductive particles P used to obtain
Then, the content ratio of the conductive particles may be adjusted. Ma
The anisotropic conductive sheet is 1 cm^Two5-1000 per
g, preferably in the thickness direction with a load of 10 to 500 g
By doing so, the distortion rate S₀+ ΔS (%)
I just need to get it.

In the above, the volume resistivity in the thickness direction of the anisotropic conductive sheet can be measured as follows. Non-pressurized volume specific resistance: A metal film is formed on one surface of an anisotropic conductive sheet by a sputtering device, and the wiring connected to the insulation resistance meter is bonded to the surface of this metal film with a conductive adhesive. I do. Then, by pressing the other surface of the anisotropic conductive sheet with the measuring electrode having an electrode diameter of 50 mm connected to the insulation resistance meter, the surface of the measuring electrode is sufficiently provided on the other surface of the anisotropic conductive sheet. Then, the surface of the measurement electrode is brought into contact with the other surface of the anisotropic conductive sheet, that is, in a non-pressurized state. Then, in this state, a current having an appropriate voltage value or current value is supplied between the measurement electrode and the metal film, and after elapse of one minute, the volume resistivity in the thickness direction of the anisotropic conductive sheet is measured. Volume resistivity in the state of being pressed in the thickness direction: Anisotropic conductive sheet is connected to an insulation resistance meter, and the electrode diameter is 5
Placed between the 0 mm measuring electrode and the pressing electrode,
The anisotropic conductive sheet is pressed by the pressing electrode until a required strain rate is obtained, and in this state, the volume resistivity in the thickness direction of the anisotropic conductive sheet is measured.

The above-described anisotropic conductive sheet can be manufactured, for example, by the following method. First, conductive fibers, conductive particles exhibiting magnetism, and a non-magnetic conductivity-imparting substance used as necessary are dispersed in a liquid polymer substance forming material that becomes an insulating elastomer by curing treatment. A fluid sheet molding material is prepared, and as shown in FIG. 2, the sheet molding material is injected into a mold 20 to form a sheet molding material layer 10A. Here, the mold 20 is an upper mold 21 made of a rectangular ferromagnetic plate.
The lower mold 22 is arranged so as to face each other via a rectangular frame-shaped spacer 23, and a cavity is formed between the lower surface of the upper mold 21 and the upper surface of the lower mold 22.

Next, for example, an electromagnet or a permanent magnet is disposed on the upper surface of the upper die 21 and the lower surface of the lower die 22, and a parallel magnetic field is applied to the sheet molding material layer 10A in the mold in the thickness direction thereof. Act in the direction. as a result,
In the sheet forming material layer 10A, the conductive particles P dispersed in the sheet forming material layer are oriented so as to be aligned in the thickness direction while maintaining the state of being dispersed in the plane direction as shown in FIG. At the same time, the conductive fibers F are arranged so as to extend in the thickness direction as the conductive particles P move. On the other hand, when a conductivity-imparting substance is used, since the conductivity-imparting substance is nonmagnetic, it remains dispersed in the sheet forming material layer 10A even when a parallel magnetic field acts. Then, in this state, the sheet molding material layer 10A is cured to form the sheet substrate 10 made of an elastomer.
A conductive material having conductive fibers F arranged in the sheet base 10 so as to extend in the thickness direction thereof and conductive particles P contained in the sheet base 10 so as to be aligned in the thickness direction. A sheet is obtained.

In the above, the intensity of the parallel magnetic field applied to the sheet molding material layer 10A is 0.02 to 1.5 on average.
The size that becomes T is preferable. When a parallel magnetic field is applied in the thickness direction of the sheet forming material layer 10A by the permanent magnet, the permanent magnet has a parallel magnetic field strength within the above range.
-Co-based alloy), ferrite or the like. The curing treatment of the sheet forming material layer 10A can be performed in a state where the parallel magnetic field is applied, but can also be performed after the operation of the parallel magnetic field is stopped. The curing treatment of the sheet molding material layer 10A is appropriately selected depending on the material used, but is usually performed by a heat treatment. The specific heating temperature and heating time are appropriately set in consideration of the type of the material for the polymer substance constituting the sheet molding material layer 10A, the time required for the movement of the conductive particles P, and the like.

According to the anisotropic conductive sheet having the above structure,
The conductive fibers F are contained in the sheet base 10 made of an elastomer.
Are arranged so as to extend in the thickness direction. Therefore, in a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force, the conductive fiber F exhibits conductivity according to the electrical characteristics, and furthermore, the sheet Since the conductive particles P are contained in the base 10 in a state of being aligned in the thickness direction, the sheet base 10 is formed by a chain of the conductive particles P in a state where the conductive particles P are pressed in the thickness direction by a large force. Thus, a conductive path extending in the thickness direction is formed, thereby exhibiting higher conductivity than in a non-pressed state or a state in which the conductive path is pressed in the thickness direction with a small force.

Such an anisotropic conductive sheet of the present invention comprises:
By bringing the connected object into contact with one side or applying pressure with a small force, static electricity on the surface of the connected object,
Capacitance, the microscopic surface distribution state of the amount of electricity such as the amount of ions can be transferred and held on the surface of the anisotropic conductive sheet. By applying pressure with a large force, the microscopic surface distribution state of the transferred and held amount of electricity can be moved to the other surface of the anisotropic conductive sheet. Specifically, the anisotropic conductive sheet of the present invention is used, for example, for moving the capacitance distribution on the surface of an inspection object to a measurement unit in a capacitance type electrical inspection device such as a printed wiring board. It is useful as a sensor unit, and according to such an electrical inspection device, the capacitance distribution on the surface of the inspection object can be expressed as a two-dimensional image. Further, for example, converting an ion pattern image generated from a writing device such as a laser printer or an electrostatic pattern image of a roll portion of an electronic copying device into an electric pattern image via the anisotropic conductive sheet of the present invention. Can be. Further, according to the anisotropic conductive sheet of the present invention, the present invention is not limited to the above example, and may include static electricity, capacitance,
A microscopic surface distribution state of an electric quantity such as an ion quantity can be expressed as a two-dimensional electric pattern image.
In addition, the anisotropic conductive sheet of the present invention can be used in various applications in which the conventional anisotropic conductive sheet is used, for example, as a connector for achieving electrical connection between circuit devices, or as a circuit device. It can be used as a connector used for electrical inspection.

In the anisotropic conductive sheet of the present invention, by using an appropriate conductive particle P, a chain formed by the conductive particles P functions as a heat conduction path.
It can be used as a heat conductive sheet such as a heat radiating sheet. For example, by bringing the anisotropic conductive sheet of the present invention into contact with a heating element such as a heating component of an electronic device, and pressing the anisotropic conductive sheet intermittently and repeatedly in the thickness direction, a certain amount of heat is generated from the heating element. Dissipates heat intermittently through the anisotropic conductive sheet, and as a result, the temperature of the heating element can be kept constant. In addition, the anisotropic conductive sheet of the present invention can be used as an electromagnetic radiation absorbing sheet, thereby reducing, for example, electromagnetic noise generated from electronic components and the like.

[0039]

EXAMPLES The present invention will now be described by way of specific examples, which should not be construed as limiting the invention thereto.

<Example 1> Addition type liquid silicone rubber 1
A sheet molding material was prepared by adding and mixing 50 parts by weight of conductive fibers and 90 parts by weight of conductive particles in 00 parts by weight. Above, as the conductive fiber, a carbon short fiber (average length t = 0.2 mm, average diameter 10 μm, manufactured by Osaka Gas Chemical Co., Ltd.) coated with ferrite plating at a weight ratio of 40% is used. ,
Further, a surface coated with a liquid polyimide resin material at a coverage of 60% and subjected to a curing treatment at a temperature of 200 ° C. is used. As conductive particles, particles made of MnFe ₂ O ₄ (manganese ferrite) (number average particle diameter) 5 μm).

A mold for forming an anisotropic conductive sheet comprising upper and lower molds each made of a rectangular iron plate having a thickness of 5 mm and a rectangular frame-shaped spacer having a thickness of 0.2 mm was prepared. The prepared sheet molding material was injected into the mold cavity to form a sheet molding material layer. Next, electromagnets are arranged on the upper surface of the upper mold and the lower surface of the lower mold, and a 1T parallel magnetic field is applied to the sheet molding material layer in the thickness direction thereof at 100 ° C. for 2 hours. By subjecting the layer to a curing treatment, a sheet substrate having a thickness of 0.2 mm was formed to produce an anisotropic conductive sheet having the configuration shown in FIG. The density of the conductive fibers in the sheet base of the anisotropic conductive sheet is 5 × 10 ⁴ /
cm ² , and the content of the conductive particles is 15% by volume.
%Met.

Example 2 Addition type liquid silicone rubber 1
A sheet molding material was prepared by adding and mixing 60 parts by weight of conductive fibers, 70 parts by weight of conductive particles, and 20 parts by weight of a conductivity-imparting substance in 00 parts by weight. In the above, as the conductive fiber, a carbon short fiber coated with nickel (average length 0.2 mm, average diameter 8.5 μm, manufactured by Westin) was coated with the electrodeposited polyimide resin material at a coverage of 80%. Surface coated, temperature 200
℃ used after subjected to a curing treatment, as the conductive _{particles, Ni 0.5 Zn 0.5 Fe 2 O} 4 with a more composed particles (number average particle diameter of 3 [mu] m), as a conductivity-imparting material, a zinc oxide powder (self Conductive material).

A mold for forming an anisotropic conductive sheet comprising upper and lower molds each made of a rectangular iron plate having a thickness of 5 mm and a rectangular frame-shaped spacer having a thickness of 0.2 mm was prepared. The prepared sheet molding material was injected into the mold cavity to form a sheet molding material layer. Next, electromagnets are arranged on the upper surface of the upper mold and the lower surface of the lower mold, and a 1T parallel magnetic field is applied to the sheet molding material layer in the thickness direction thereof at 100 ° C. for 2 hours. By subjecting the layer to a curing treatment, a sheet substrate having a thickness of 0.2 mm was formed to produce an anisotropic conductive sheet having the configuration shown in FIG. The density of the conductive fibers in the sheet substrate of the anisotropic conductive sheet is 1 × 10 ⁵ fibers /
cm ² , and the content ratio of the conductive particles is 13 by volume fraction.
%Met.

Example 3 Addition type liquid silicone rubber 1
A sheet molding material was prepared by adding and mixing 60 parts by weight of conductive fibers, 70 parts by weight of conductive particles, and 5 parts by weight of a conductivity-imparting substance in 00 parts by weight. In the above, as the conductive fiber, a carbon short fiber coated with nickel (average length 0.2 mm, average diameter 8.
5 μm, manufactured by Westin Co.) and surface-coated with an electrodeposited polyimide resin material at a coverage of 80%, and subjected to a curing treatment at a temperature of 200 ° C.
Particles composed of i _0.5 Zn _0.5 Fe ₂ O ₄ (number average particle diameter 3 μm) were used, and as the conductivity-imparting substance, sodium alkane sulfonate (moisture-absorbing conductive substance) having an alkyl group having 5 to 15 carbon atoms was used. . An anisotropic conductive sheet having a configuration shown in FIG. 1 and having a thickness of 0.2 mm was manufactured in the same manner as in Example 2 except that this sheet molding material was used. The density of the conductive fibers in the sheet substrate of the anisotropic conductive sheet was 2 × 10 ⁶ fibers / cm ² , and the content ratio of the conductive particles was 14% by volume.

Comparative Example 1 An anisotropic conductive sheet for comparison was produced in the same manner as in Example 1 except that a sheet molding material was prepared without using conductive fibers.

<Evaluation of Electrical Properties of Anisotropic Conductive Sheet> The electrical properties of the anisotropic conductive sheets according to Examples 1 to 3 and Comparative Example 1 were evaluated as follows. [Volume resistivity in the thickness direction in the state of no pressurization] An ion sputtering device (E10
10, manufactured by Hitachi Science Co., Ltd.) to form a metal film having a thickness of 100 nm using Au-Pd as a target. A wiring connected to an insulation resistance meter (4339A high resistance meter, manufactured by HP) was bonded to the surface of the metal film with a conductive adhesive containing silver. And
By pressing the other surface of the anisotropic conductive sheet with the measuring electrode having an electrode diameter of 50 mm connected to the insulation resistance meter, the surface of the measuring electrode is sufficiently adhered to the other surface of the anisotropic conductive sheet. Then, the surface of the measurement electrode was brought into contact with the other surface of the anisotropic conductive sheet, that is, in a non-pressurized state. Then, in this state, a current having an appropriate voltage value or current value is supplied between the measurement electrode and the metal film, and 1
After a lapse of minutes, the volume resistivity of the anisotropic conductive sheet in the thickness direction was measured. [Volume resistivity in a state of being pressed in the thickness direction] An anisotropic conductive sheet was connected to an insulation resistance meter (4339A high resistance meter, manufactured by HP), and a measuring electrode having an electrode diameter of 50 mm and a pressing electrode were used. Placed between the electrodes,
20% distortion rate of anisotropic conductive sheet by pressing electrode
, And in this state, the volume resistivity in the thickness direction of the anisotropic conductive sheet was measured. The results are shown in Table 1.

[0047]

[Table 1]

[Charge Transfer and Mobility] As shown in FIG. 4, an anisotropic conductive sheet 1 is disposed on a ground plate 40, and a urethane resin roll is placed immediately above the anisotropic conductive sheet 1. 45 were arranged. The roll 45 is formed by accumulating electric charges on the surface thereof by a discharge treatment by a Tesla coil, and has a surface potential of 500 ± 50.
V (Trek Japan surface electrometer "Model 520-
1 "). Then, the roll 45 is gradually lowered to come into contact with the surface of the anisotropic conductive sheet 1 (in a non-pressurized state). The surface potential of the conductive sheet 1 was measured by a surface potentiometer “Model 520-1”. Then roll 4
5, the surface of the anisotropic conductive sheet 1 is pressurized so that its distortion rate becomes 20%, and is maintained for 1 minute in this state. The surface potential of the conductive sheet 1 was measured by a surface potentiometer “Model 520-1”. The above operation was performed ten times in total, and the average value of the surface potential and the variation in the value were obtained. The results are shown in Table 2 above.

[0049]

[Table 2]

As is clear from the results in Table 2, Examples 1 to
According to the anisotropically conductive sheet according to No. 3, by bringing the surface of the roll 45 into contact with the surface of the anisotropically conductive sheet, the charge on the surface of the roll 45 can be reproduced with high reproducibility on the surface of the anisotropically conductive sheet. Transfer was confirmed. Further, it was confirmed that when the surface of the anisotropic conductive sheet was pressed by the roll 45, the charge on the surface of the roll 45 moved to the ground plate via the anisotropic conductive sheet. On the other hand, in the anisotropic conductive sheet according to Comparative Example 1,
The charge on the surface of the roll 45 could not be stably transferred to the surface.

[0051]

As described above, according to the present invention,
In a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force, conductivity is exhibited, and in a state where pressure is applied in the thickness direction with a large force, a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force An anisotropic conductive sheet showing higher conductivity can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a configuration of an example of an anisotropic conductive sheet of the present invention.

FIG. 2 is an explanatory sectional view showing a state in which a sheet molding material layer is formed in a mold.

FIG. 3 is an explanatory cross-sectional view showing a state in which a parallel magnetic field is applied to a sheet forming material layer in a thickness direction.

FIG. 4 is an explanatory view showing an apparatus used for evaluating electric characteristics of an anisotropic conductive sheet in Examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Anisotropic conductive sheet 10 Sheet base 10A Sheet molding material layer 20 Die 21 Upper die 22 Lower die 23 Spacer 40 Earth plate 45 Roll F Conductive fiber P Conductive particles

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 7/02 C08K 7/02 9/02 9/02 C08L 101/00 C08L 101/00 (72) Inventor Ryoji Setaka 2-11-24 Tsukiji, Chuo-ku, Tokyo F-term in JSR Co., Ltd. (reference) 4F071 AA67 AB03 AD01 AE15 AF37Y AH12 BC01 4J002 AC011 AC031 AC061 AC071 AC081 AC091 BB151 BC033 BP011 CE003 CF001 CL041CK03 DA02 DL007 EV257 FA042 FA046 FA087 FB072 FB073 FB077 FD112 FD113 FD116 FD117 GQ00 GQ02 5G307 HA02 HB01 HB03 HC02

Claims (5)

[Claims] 1. A sheet base made of an elastomer, conductive fibers arranged in the sheet base so as to extend in a thickness direction thereof, and a magnetic material contained in the sheet base so as to be aligned in the thickness direction. An anisotropic conductive sheet, characterized by comprising conductive particles having the formula: 2. The method according to claim 1, wherein the conductive particles are contained in a state of being dispersed in a plane direction of the sheet substrate.
The anisotropic conductive sheet according to 1. 3. The anisotropic conductive sheet according to claim 1, wherein a conductivity imparting substance is dispersed in the sheet base. 4. The conductivity-imparting substance according to claim 3, wherein the conductivity-imparting substance is at least one substance selected from a substance exhibiting conductivity by itself and a substance exhibiting conductivity by absorbing moisture. Anisotropic conductive sheet. 5. Pressure is applied in the thickness direction so that the pressure-free state and the strain rate are S ₀ [where S ₀ is a value selected from the range of ₀ to 3 (%)]% or less. The volume resistivity in the thickness direction in the state is R _0, and the thickness direction is set so that the strain rate is greater than S ₀ % by ΔS [however, ΔS is a value selected from the range of 10 to 20 (%)]% or more. Assuming that the volume resistivity in the thickness direction in the state of being pressurized is R ₁ , the volume resistivity R ₀ is in the range of 1 × 10 ⁷ to 1 × 10 ¹² Ω · m, and the volume resistivity R ₀ and the volume The ratio to the specific resistance R ₁ (R ₀ / R
_The anisotropic conductive sheet according to claim 1, wherein 1) is in a range of 1 × 10 ² to 1 × 10 ¹⁰ .