JP3535412B2 - A conductive adhesive composition, a conductive adhesive sheet, an electromagnetic wave shielding material using the same, and an electromagnetic wave shielding flexible printed board. - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive adhesive composition having flexibility and folding resistance suitable for electromagnetic wave shielding of flexible printed circuit boards (FPCs), a conductive adhesive sheet, and a conductive adhesive sheet thereof. The present invention relates to an electromagnetic wave shield material integrated with a sheet.

[0002]

2. Description of the Related Art Conventionally, for electromagnetic wave shields of cables for connecting electronic devices, a shielded wire group in which each conductor is braided is used, but a large number of shielded wire groups are bundled together. Since it is used, it was difficult to make it small and thin. However, recently, electronic devices and their peripherals are small,
With the progress of thinner cables, there has been a demand for smaller and thinner cables themselves. Especially in laptop computers, there is a remarkable trend toward smaller size and thinner as well as higher functionality and higher performance. Along with this, the interface cable connecting the main body and the screen is changed from the bundled shielded wire group system to the flat cable,
A flexible printed circuit board (FPC) system having a smaller thickness is being changed. In addition, in order to transmit information at high speed, frequencies in a higher frequency band have been used, and FPCs are required to have electromagnetic wave shielding characteristics higher than ever. Specifically, unnecessary electromagnetic waves from the inside of the FPC are emitted from the pattern for the basic clock, and currently the frequency is mainly 150 to 400 MHz. As a measure for electromagnetic wave shielding of these FPCs, a so-called solid earth plate is often used in which a copper foil is attached to one side or both sides of the FPC. However, when the copper foil is attached, the volume resistivity is usually 10 ⁷ Ω · c as electric resistance.
Since an adhesive having an insulator level of m or more is used, there is a problem that the electromagnetic wave shielding property becomes poor, and the copper foil cannot endure many bending tests, resulting in brittle fracture.

As described above, the use of FPCs has increased due to the miniaturization and thinning of electronic equipment, and along with this, the FPCs are required to have high electromagnetic wave shielding characteristics in addition to flexibility, lightness, thinness, and electrical characteristics. . Therefore, the inventors of the present application have proposed, as a method for obtaining an effective electromagnetic wave shielding property without impairing the flexibility of FPC, Japanese Patent Application No. 10-279318 and Japanese Patent Application No. 10-279318.
344854 proposes a metal fiber sheet for electromagnetic wave shielding in which a flexible metal fiber sheet is impregnated with and filled with a conductive adhesive, or laminated on one side or both sides.
-325829 has proposed a flexible printed circuit board with a metal fiber sheet for electromagnetic wave shielding and a method for manufacturing the same, and Japanese Patent Application No. 10-282094 has proposed a method for treating an electromagnetic wave shielding material in a flexible printed wiring board.

Although such an electromagnetic wave shielding method was excellent, it was not sufficient from the viewpoint of flame retardancy. That is, UL94, which is a flammability test standard for plastic materials for parts, is applied to electronic devices to which the electromagnetic wave shielding material is applied, and flame retardant grades of V-1 and V-0 levels are required. Therefore, there is a demand for an electromagnetic wave shield method having excellent difficulty that satisfies such standards.

[0005]

DISCLOSURE OF THE INVENTION The present invention has excellent flexibility without sacrificing good electrical conductivity, and is particularly suitable for electromagnetic wave shielding of flexible printed circuit boards (FPCs). The present invention provides a conductive adhesive composition having the same, a conductive adhesive sheet, an electromagnetic wave shielding material in which these are integrated with a conductive fiber sheet or a metal foil, and an electromagnetic wave shielding flexible printed circuit board.

[0006]

The present invention comprises (a) 100 parts by weight of an acrylonitrile-butadiene copolymer,
(B) Phenolic resin and / or epoxy resin 20-5
00 parts by weight, and (c) 1 to 100 parts by weight of the conductive filler per 100 parts by weight of the total of (a) and (b),
(D) for 100 parts by weight of the total of (a) and (b)
A flexible plastic composition containing at least 1 to 50 parts by weight of a brominated flame retardant having a melting point of 150 ° C. or higher.
A conductive adhesive composition for electromagnetic wave shielding of a lint substrate .

Further, the present invention is a conductive adhesive sheet for electromagnetic wave shielding of a flexible printed circuit board, characterized in that the conductive adhesive composition is formed into a sheet having a thickness of 5 to 500 μm. is there. The present invention is flexibility, characterized in that the conductive adhesive composition, impregnated or coated with the conductive fiber sheet is a surface resistivity of 1 [Omega / □ or less
It is an electromagnetic wave shield material for bull printed circuit boards . Furthermore, the present invention provides the above-mentioned conductive adhesive sheet with a surface resistivity of 1 Ω /
□ Flexible pudding characterized by being laminated on one side or both sides of the following conductive fiber sheet or metal foil
It is an electromagnetic wave shield material for printed circuit boards . Furthermore, there is provided an electromagnetic wave shielding flexible printed circuit board, which is obtained by laminating the electromagnetic wave shielding material on one side or both sides of the flexible printed circuit board.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The components constituting the conductive adhesive composition of the present invention will be described first. (A) The acrylonitrile-butadiene copolymer is an essential component for imparting flexibility, and also has a function of increasing the adhesion to the substrate, and among many elastomer materials, cold resistance, oil resistance, aging resistance,
It is selected from the viewpoints of wear resistance, folding resistance and cost. Specifically, the nitrile content is 10 to 45%, preferably a relatively high nitrile content of 20 to 45%,
Those having a molecular weight of 2 to 1,000,000, preferably 50,000 to 500,000 are suitable in the present invention. The acrylonitrile-butadiene copolymer may contain a cross-linking agent such as quinones, dialkyl peroxides and peroxyketals so that it can be self-crosslinked when heated.

(B) The phenol resin and / or the epoxy resin is a thermosetting resin and has a function of adhering to the base material. The phenol resin is preferably a resol type phenol resin, and the resol type phenol resin is preferably one or more selected from bisphenol A and an alkylphenol, or a cocondensation type phenol resin thereof. The bisphenol A type resol type phenolic resin is synthesized from bisphenol A as a starting material and has a softening point of 70 to 90 by the ring and ball method.
Those of ℃ are preferably used. The alkylphenol-type resol-type phenolic resin is synthesized by using as a starting material a compound having an alkyl group mainly at the p- and / or o-position with respect to the phenolic hydroxyl group, and the alkyl group is a methyl group or an ethyl group. , A propyl group, a t-butyl group, a nonyl group and the like.
-Butylphenol type resol type phenolic resin having a softening point of 80 to 100 ° C. according to the ring and ball method is preferably used. The resol-type phenol resin may contain a phenol component other than the above, such as p-phenylphenol or halogenated phenol, as the phenol component. Also, a small amount of novolac type phenol resin may be blended with the resole type phenol resin.

Bisphenol A as an epoxy resin
Various types such as type, novolac type, bisphenol F type, cycloaliphatic type, glycidyl ester type and the like can be used. When an epoxy resin is used in combination with a phenol resin in the present invention, a cured product having higher heat resistance can be obtained by reacting by heating. When a phenol resin is not used in combination, various curing agents are usually added to the epoxy resin, but in the present invention, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2. -Methylimidazole, 2-heptadecylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2,4-diamino-6- [2-methylimidazolyl- (1)] -Ethyl-S-triazine,
Imidazole-based curing agents such as 2,4-diamino-6- [2-ethyl-4-methylimidazolyl- (1)]-ethyl-S-triazine are preferred.

(C) As the conductive filler, Al, A
Metal powders such as u, Pt, Pd, Cu, Fe, Ni, solder, stainless steel, ITO, ferrite, and other metals, alloys, metal oxides, and conductive carbon (including graphite) powder can be used, but the cost is low. From this point, conductive carbon powder is particularly preferable. As the conductive carbon powder,
Acetylene black or graphite carbon is used, but the DBP oil absorption according to JIS-K6221 is 20.
It is preferably ˜200 ml / 100 g. If the oil absorption is less than 20 ml / 100 g, the powder particles are too large and it is difficult to obtain the desired conductivity in the adhesive composition of the present invention.
On the other hand, when it exceeds 200 ml / 100 g, the conductivity is lowered due to poor carbon dispersion. Further, in order to increase the conductivity, the conductive carbon powder and the powder of the above metal-based material can be used together. Furthermore, metal fibers, carbon fibers,
Conductive fibers such as metal plated fibers can also be used.

The (d) bromine-based flame retardant for imparting flame retardancy to the conductive adhesive composition, the conductive adhesive sheet and the electromagnetic wave shielding material of the present invention is most selected from the comparative examination of various flame retardants. It was selected because of its high flame retardant effect. Specifically, hexabromobenzene, hexabromocyclododecane, tribromophenol, hexabromobiphenyl ether, octabromobiphenyl ether, decabromobiphenyl ether, dibromocresyl glycidyl ether, tetrabromobisphenol A, tetrabromophthalic anhydride, poly Examples thereof include (pentabromobenzyl) acrylate and brominated epoxy resin, but are not limited thereto. In addition, bis (2,3-dibromopropyl) 2,3-dibromopropyl phosphate, tris (2,3-dibromopropyl) phosphate, tris (tribromoneopentyl) phosphate, etc. contain phosphorus together with bromine in the same molecule. Things can also be used.
These flame retardants can be used alone or in admixture of two or more.

In the present invention, among these brominated flame retardants, those containing 50% by weight or more of bromine are preferable, and those containing 55% by weight or more of bromine are particularly preferable.
Yes. The melting point is 150 ° C. or higher. If the bromine content is less than 55%, it is difficult to obtain the flame retardancy of V-0 of the UL standard with the flame retardant content of the present invention. When the melting point is less than 150 ° C., the initial adhesive strength of the bonded product of the electromagnetic wave shielding material of the present invention and FPC is low, and the adhesive strength when the bonded product is left in a high temperature or high temperature and high humidity environment. Causes an extremely low value .

In the present invention, it is preferable to use the stabilizer (e) in addition to the components (a) to (d). The stabilizer (e) is added for the purpose of preventing the components (a) and (b) from causing oxidative deterioration, thermal deterioration and aging due to oxygen and ozone in the air. Specifically, as a phenolic antioxidant, 2,6-di-
t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, stearyl-β- (3,5-
Di-t-butyl-4-hydroxyphenyl) propionate, 2,2-methylene-bis- (4-methyl-6-t
-Butylphenol), 4,4'-thiobis- (3-methyl-6-t-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-t-butylphenol), 1,1,3- Tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-
Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-t-butyl-
4'-hydroxyphenyl) propionate] methane,
Sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate and distearyl-3,3'-thiodipropionate, and phosphorus-based antioxidants such as triphenylphosphite and diphenylisodecylphosphite. ,
Cyclic neopentane tetrayl bis (octadecyl phosphite), tris (2,4-di-t-butylphenyl) phosphite and the like can be used. As a rubber anti-aging agent, poly (2,2,4-trimethyl-
1,2-dihydroquinoline), 6-ethoxy-1,2-
Dihydro-2,2,4-trimethylquinoline, 1- (N
-Phenylamino) -naphthalene, dialkyldiphenylamine, N, N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-2-naphthyl-p-phenylene Diamine, 2,5-di-t-butylhydroquinone, 2-mercaptobenzimidazole, nickel dibutyldithiocarbamate, tris (nonylphenyl) phosphite and the like can also be used.

The composition ratio of the above components (a) to (e) is
(A) 100 of acrylonitrile-butadiene copolymer
20 to 500 parts by weight of (b) phenol resin and / or epoxy resin, preferably 50 to 30 parts by weight, relative to parts by weight.
It is 0. In addition, the total of (a) and (b) is 100
With respect to parts by weight, (c) the conductive filler is 1 to 100 parts by weight, preferably 5 to 70 parts by weight, and (d) the brominated flame retardant is 1 to 50 parts by weight, preferably 5 to 40 parts by weight. Further, the amount of the antioxidant (e) used as a stabilizer is 1 to 10 parts by weight. When the content of (b) is less than 20% by weight, not only does the tackiness of the adhesive surface increase and handling of the sheet becomes difficult,
The heat resistance of the cured product decreases. If the content is more than 500 parts by weight, the flexibility and the adhesive force will be impaired.
When the content of (c) is less than 1 part by weight, a predetermined conductivity cannot be obtained, and when it exceeds 100 parts by weight, the flexibility and the adhesive force are lowered. Further, as for (d), if it is less than 1% by weight, sufficient flame retardancy cannot be obtained, and if it exceeds 50% by weight, the adhesive strength is similarly reduced. If the content of (e) is less than 1% by weight, the stability of the adhesive against heat deterioration may be insufficient, and if it is more than 10% by weight, the adhesive strength may be reduced.

The conductive adhesive composition of the present invention comprises (a)-
Each component (e) should be present in a state of being uniformly dissolved or dispersed, for which purpose various organic solvents can be used. Preferred organic solvents are (a) and (b)
Methyl ethyl ketone (M
EK), ketone-based solvents such as methyl isobutyl ketone (MIBK), ester-based solvents such as ethyl acetate and butyl acetate, and ether-based solvents such as tetrahydrofuran. Further, alcohol solvents such as methanol and propanol, aromatic hydrocarbon solvents such as toluene and xylene, and aliphatic hydrocarbon solvents such as ligroin and rubber volatile oil can be used as a diluting solvent.

The volume resistivity of the conductive adhesive composition of the present invention is preferably 2 × 10 ⁻² to 2 × 10 ³ Ω · cm after heat curing. The reason why the adhesive requires such conductivity is that the conductive fiber sheet or metal foil is attached to the FPC via the adhesive to obtain good electromagnetic wave shielding properties. This is because the electromagnetic waves caught by the fiber sheet or the metal foil are converted into eddy currents and leaked to the ground earth in the FPC layer through the adhesive. Therefore, the volume resistivity of the conductive adhesive composition is 2
When it exceeds × 10 ³ Ω · cm, it is difficult to effectively leak the eddy current generated by the electromagnetic wave to the ground earth in the FPC layer, and the electromagnetic wave shielding effect becomes insufficient.
On the other hand, in order to make the volume resistivity less than 2 × 10 ^-2 Ω · cm,
It is necessary to increase the compounding amount of the conductive filler to be more than the compounding amount of the present invention, in which case it becomes difficult to uniformly disperse the filler in the binder of the above (a) or (b), and the FPC
The adhesive strength with will be extremely reduced.

The method for producing a conductive adhesive composition of the present invention comprises dissolving the components (a) and (b) in the above organic solvent,
(C) is prepared by dispersing it in the solution of (a) and (b). (D) and (e) may be either dissolved or dispersed. The dispersion step, in a solvent or a solution of other components, attritor, sand mill, single or multiple components,
It is carried out by using an appropriate dispersing device such as a pearl mill. These solutions and dispersions are finally metered and mixed so that the composition ratio thereof falls within the above range.

The conductive adhesive sheet specified in claim 4 of the present invention has a thickness of 5 to 500 μm obtained by coating and drying the conductive adhesive composition on a support such as release paper or release film.
It is a sheet shape. This thickness is necessary for application to the metal fiber sheet or metal foil described below, and if the thickness is less than 5 μm, the required adhesive force cannot be obtained, while if the thickness of the conductive adhesive sheet exceeds 500 μm. The conductivity between the metal fiber sheet or metal foil and the FPC is insufficient, so that not only the electromagnetic wave shielding effect is reduced but also the flexibility is reduced. This conductive adhesive sheet is heated in order to volatilize the organic solvent contained in the conductive adhesive composition, but it is laminated with the next metal fiber sheet or metal foil and then laminated with FPC. Therefore, the adhesive component must be kept in a semi-cured state, and the composition and heating conditions are appropriately controlled to form a semi-cured sheet.

The conductive adhesive sheet of the present invention may be in the form of a sheet of adhesive alone, or a sheet (layer) on a support such as release paper or release film used in the above coating.
There are three types, that is, a form formed in a shape, and a form in which another support such as a release paper or a release film is further laminated on the coated surface, and any of them can be used.

In the electromagnetic wave shielding material specified in claim 5 of the present invention, the conductive adhesive composition has a surface resistivity of 1 Ω /
□ The following conductive fiber sheet is impregnated or applied. The present inventor has formed various conductive fibers into a sheet shape and examined the electromagnetic wave shielding properties thereof in detail, and found that the surface resistivity measured in the conductive fiber sheet shape has a good correlation with the shielding characteristics. I found it. That is, it has been found that when the surface resistivity of the conductive fiber sheet is smaller than 1Ω / □, effective electromagnetic wave shielding properties are exhibited regardless of the type of fiber.

As the conductive fibers forming the conductive fiber sheet, metal fibers, carbon fibers, metal plated fibers and the like can be used. Examples of the metal fibers include stainless fibers, titanium fibers, nickel fibers, brass fibers, copper fibers, aluminum fibers, various alloy fibers, and composite metal fibers thereof. In addition to metal fibers and carbon fibers, the metal-plated fibers are formed of Al, Au, Pt, Pd, Cu, Fe, Ni, by electroless and / or electroplating techniques on the surface of organic fibers that do not necessarily have conductivity. It is made by adhering a highly conductive metal such as solder, stainless steel, or ITO. The volume resistivity of these conductive fibers themselves is usually 10 ⁻² Ω · cm or less, but the surface resistivity of the sheet greatly differs depending on the type of conductive fibers, the porosity, and the entangled state of the fibers. However, the type of fiber is not limited as long as the sheet has a surface resistivity in the above range, and a sheet made of two or more types of fibers may be used.

As a method for forming such a conductive fiber into a sheet shape, manufacturing techniques such as woven cloth, net (knitting), non-woven fabric and papermaking can be used, but the present invention is limited to these sheet forming technologies. The electrical characteristics of the sheet formed as described above are important.
The thickness of the conductive fiber sheet is 10 to 500 μm, preferably 20 to 300 μm.
Not only is the electromagnetic wave shielding property insufficient, but the tensile strength is low, making it difficult to handle. Also, the thickness is 500
If it exceeds μm, the flexibility is lowered, which is not preferable.

The electromagnetic wave shielding material of the present invention is produced by applying a conductive adhesive composition to a conductive fiber sheet, impregnating it, printing it and then drying it by using a usual impregnation, coating or printing technique. Be seen. However, if it is difficult to directly impregnate a conductive fiber sheet with a large porosity and low tensile strength in a roll shape, it is also possible to use a flexible support such as release paper, release film or metal foil. Be seen. For example, a conductive adhesive composition is provided on the conductive fiber sheet by coating or printing in a state where the conductive fiber sheet and the flexible support are stacked. Further, a conductive fiber sheet is laminated on a conductive adhesive composition layer (conductive adhesive sheet) provided on a support by coating or printing as in the electromagnetic wave shielding material according to claim 6 of the present invention. These are then subjected to a predetermined heating / drying step to obtain the electromagnetic wave shielding material of the present invention. However, the heating conditions at this time must be such that a semi-cured state is maintained in order to bond it to the FPC thereafter. The electromagnetic wave shield material of the present invention,
It also includes a structure in which a flexible support such as a release paper, a release film or a metal foil used in the production is laminated on one side or both sides.

In the present invention, as described in claim 6, a metal foil made of the same material as the conductive fiber sheet can be used. The thickness of the metal thin film is preferably 5 to 100 μm, more preferably 10 to 50 μm. When it is thinner than 5 μm, it is difficult to handle, and when it exceeds 100 μm, the flexibility is lowered. Also, in order to improve flexibility, punched metal with many fine through holes formed on the entire surface by etching or pressing, expanded metal pulled with cuts, pleated, embossed, etc. It can be used.

The electrically conductive adhesive sheet is laminated on the electrically conductive fiber sheet and the metal foil by heating and press-bonding the both by a conventional laminating technique.
When release paper or release film is laminated on both sides of the conductive adhesive sheet before processing, it goes without saying that at least one of them is peeled off and then bonded.
Further, also in this step, the adhesive component must be kept in a semi-cured state in order to be bonded to the next FPC.

The electromagnetic shielding flexible printed circuit board of the present invention is produced by laminating the above-mentioned electromagnetic shielding material on one side or both sides of the FPC, and a normal laminating technique is used for this laminating. As the FPC used in the present invention, a polyimide film as a base material, a copper foil layer forming a circuit, and a cover film provided thereon can have various thicknesses. Furthermore, a part of the circuit has the above-mentioned ground earth function, and a circular or required shape opening having a diameter of about 1 mm to 10 mm is provided on the base material side or the coverlay film side of the ground earth. The structure has an exposed ground. In order to ensure electrical continuity between the conductive adhesive composition and the ground ground, and through the thermosetting conductive adhesive composition, the conductive fiber sheet or metal foil and the FPC
In order to improve the adhesive strength with the, heating / pressurization is performed by a pressing device as needed.

When an electromagnetic wave shielding material having a conductive fiber sheet in a laminated structure is used, detachment of the conductive fiber from the surface of the conductive fiber sheet or fluffing may occur after integration with the FPC. To prevent this,
The basis weight and porosity of the conductive fiber sheet, and the amount of the conductive adhesive composition impregnated or applied, or the thickness of the conductive adhesive sheet are optimized, and after bonding with the FPC, the conductive adhesive component. Is successfully permeated to the surface of the conductive fiber sheet. In addition, as another method, spray coating, screen printing, or the like on the surface of the conductive fiber sheet, which may cause detachment or fuzzing of the conductive fiber after integration with the FPC.
It is also possible to coat an appropriate flexible resin by a method such as roll coating.

[0029]

Example 1 A coating composition of a conductive adhesive composition having the following formulation was prepared. "Parts" means "parts by weight". -Acrylonitrile-butadiene copolymer 100 parts (trade name: NIPOL1001, manufactured by Zeon Corporation) -Bisphenol A type resol-type phenol resin 100 parts (trade name: Shonor CKM-908, manufactured by Showa Polymer Co., Ltd.)-Conductive carbon 60 parts (Brand name: Denka Black HS-100, manufactured by Denki Kagaku Kogyo) ・ High molecular weight hindered phenolic antioxidant 6 parts (Brand name: ADEKA STAB AO-60, manufactured by Asahi Denka Kogyo Co., Ltd.) ・ Brominated flame retardant : Brominated aromatic compound 30 parts (trade name: Pyrogard SR-600A, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) MEK 400 parts MIBK 300 parts

The above adhesive composition coating composition was applied on a 38 μm release PET film, and then dried with a hot air circulation dryer for 130
C., dried for 3 minutes to obtain a conductive adhesive sheet having an adhesive layer thickness of 30 .mu.m after drying.

On the other hand, a slurry of 75 parts of stainless fiber having a fiber diameter of 8 μm and a fiber length of 5 mm and 25 parts of a binding fiber (trade name: Kuraray Vinylon Fibrid VPA, manufactured by Kuraray Co., Ltd.) was slurried to obtain a metal fiber having a high metal fiber height. By preparing a compounding sheet and further sintering it, a basis weight of 50 g /
A stainless fiber sheet having m ² , porosity of 78% and thickness of 35 μm was produced.

The adhesive surface of the above conductive adhesive sheet and the stainless fiber sheet were laminated using a heat laminator under the conditions of a laminating speed of 1 m / min and a temperature of 120 ° C. to prepare an electromagnetic wave shielding material of the present invention. .

After that, the adhesive layer of the electromagnetic wave shielding material from which the release PET film has been peeled off is attached to the FPC coverlay film side, and 170 ° C., 30 kg / c
A flexible printed circuit board having an electromagnetic wave shielding property was prepared by heating and pressing for 15 minutes under m ² . The used F
The PC has a constitution of polyimide film (25 μm) / adhesive layer (20 μm) / copper foil (25 μm) / coverlay film (50 μm).

Examples 2 to 6 and Comparative Examples 1 to 4 Conductive adhesive sheets and electromagnetic waves were prepared in the same manner as in Example 1 except that the type of brominated flame retardant used in Example 1 was changed to the material shown in Table 1. A shield material and an FPC provided with the shield material were produced.

Examples 7 to 11 In the same manner as in Example 1 except that the stainless fiber sheet of Example 1 was replaced with various conductive fiber sheets shown in Table 2, a conductive adhesive sheet, an electromagnetic wave shielding material and an electromagnetic wave shield were obtained. Flexible printed circuit board was prepared.

Comparative Example 5 A conductive adhesive sheet, an electromagnetic wave shielding material and an electromagnetic wave shielding flexible printed circuit board were produced in the same manner as in Example 1 except that the brominated flame retardant was removed. Comparative Example 6 A conductive adhesive sheet, an electromagnetic wave shielding material, and an electromagnetic wave shielding flexible printed board were produced in the same manner as in Example 1 except that the material shown in Table 1 was used instead of the brominated flame retardant of Example 1. Comparative Examples 7 to 8 After producing a conductive adhesive sheet in the same manner as in Example 1 except that the stainless fiber sheet of Example 1 was replaced with various conductive fiber sheets shown in Table 2, the same as in Example 1 Then, an electromagnetic wave shielding material and an electromagnetic wave shielding flexible printed circuit board for comparison were produced.

<Evaluation Method> Flame retardance: Electromagnetic wave shielding flexible printed circuit board was subjected to a combustion test in accordance with UL94 20 mm vertical combustion test. Adhesive force: Since an accurate adhesive force cannot be measured with an electromagnetic wave shielding flexible printed circuit board, a copper foil of 105 μm and a polyimide film of 25 μm are pasted through a conductive adhesive sheet under the thermocompression bonding conditions of the examples. The combined product is used as a sample, and the 90 ° peel strength is 25 ° C.
The peel speed was measured at 50 mm / min. The target peel strength was 1 kgf / cm or more.

Volume resistivity: The adhesive layer of the conductive adhesive sheet was transferred onto a polyimide film and heated at 170 ° C. for 15 minutes to be cured, which was then measured using a low resistivity meter Lorester GP manufactured by Mitsubishi Chemical Corporation. did. Surface resistivity: The conductive fiber sheet was measured using a low-resistivity meter Lorester GP manufactured by Mitsubishi Chemical Corporation. Electromagnetic wave shielding property: Using an electromagnetic wave shielding material as a sample, the attenuation rate of an electric field of 1 GHz was measured by the Advantest method. The electromagnetic wave shield characteristic was set to 40 dB or more.

Table 1 shows the evaluation results of the difficulty and adhesive strength of Examples 1 to 6 and Comparative Examples 1 to 6 .

[Table 1]

From the above results, the effect of the brominated flame retardant is clear, and particularly when the bromine content is 55% or more, excellent flame retardancy at V-0 level is exhibited. Further, it was found that the melting point of the bromine-based flame retardant greatly affects the adhesive strength, and has a target adhesive strength of 1 kgf / cm at a melting point of 150 ° C or higher, but is slightly inferior at a temperature of 150 ° C or lower.

Examples 1 and 7 to 11 and Comparative Examples 7 to 8
Table 2 shows the evaluation results of the surface resistivity and electromagnetic wave shielding characteristics of
Shown in.

[Table 2]

As a result, by using a conductive fiber sheet having a surface resistivity of 1 Ω / □ or less, an excellent value of 50 dB or more as an electromagnetic wave shielding property could be obtained. The volume resistivity of the conductive adhesive sheets prepared in the above Examples and Comparative Examples was 15 to 25 Ω · cm. In addition, the flexibility was all good.

Example 12 A coating composition of a conductive adhesive composition having the following formulation was prepared. "Parts" means "parts by weight". -Acrylonitrile-butadiene copolymer 75 parts (trade name: NIPOL1001, manufactured by Zeon Corporation) -Bisphenol A type epoxy resin 100 parts (trade name: Epicoat 1004, manufactured by Yuka Shell Epoxy Co.)-Curing agent: 1-cyanoethyl- 2-Ethyl-4-methylimidazole 5 parts (trade name: Curezol 2E4MZ-CN, manufactured by Shikoku Chemicals Co., Ltd.) 50 parts conductive carbon (trade name: Denka Black HS-100, manufactured by Denki Kagaku Kogyo Co., Ltd.) Agent: tetrakis- [methylene-3- (3 ', 5'-di-5 parts t-butyl-4'-hydroxyphenylpropionate] methane (trade name: ADEKA STAB AO-60, manufactured by Asahi Denka Co., Ltd.) Flame Retardant: Hexabromobenzene 30 parts (Brand name: Praftay HBB (melting point 320 ° C, bromine content 84 ), Manufactured by Manac Inc.) · MEK 500 parts · MIBK 300 parts

Example 7 on 38 μm release PET film
The conductive fiber sheet used in step 1 was stacked, the coating material of the above formulation was applied onto it, and dried at 130 ° C. for 5 minutes with a hot air circulation dryer. As a result, it was possible to obtain an electromagnetic wave shielding material in which the conductive fiber sheet was substantially impregnated with the conductive adhesive composition. The electromagnetic wave shielding property of this electromagnetic wave shielding material was 62 dB. Furthermore, when this was laminated with FPC in the same manner as in Example 1, the difficulty was V-0. On the other hand, the conductive adhesive sheet obtained by applying the conductive adhesive composition to a release PET film and drying it has a volume resistivity of 22 Ω · cm, and its adhesive force has a peel strength of 1.7 kgf / cm was obtained.

[0045]

EFFECT OF THE INVENTION The conductive adhesive composition and the conductive adhesive sheet of the present invention have good adhesion and conductivity, and also have excellent difficulty. The electromagnetic wave shield material using this not only exhibits excellent electromagnetic wave shield characteristics for FPC, but also has excellent adhesiveness and flexibility with FPC, and has a high level of V-1 to V-0. It has flame retardancy.

─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-123713 (JP, A) JP-A-2-206670 (JP, A) JP-A-3-227386 (JP, A) JP-A-10- 279902 (JP, A) JP-A-11-7838 (JP, A) JP-2000-277978 (JP, A) "Handbook" editorial edition, handbook Rubber / Plastic compound drug (revised second edition), stock company Rubber Digest, October 30, 1993, 356-380 (58) Fields investigated (Int.Cl. ⁷ , DB name) C09J 4/00-201/10 H01B 1/00-1/24 H05K 9/00

Claims (7)

(57) [Claims] 1. A total of 100 parts by weight of (a) 100 parts by weight of acrylonitrile-butadiene copolymer, (b) 20 to 500 parts by weight of phenol resin and / or epoxy resin, and (a) and (b). On the other hand, (c) conductive filler 1
To 100 parts by weight, and (d) at least 1 to 50 parts by weight of a brominated flame retardant having a melting point of 150 ° C. or higher based on 100 parts by weight of the total of (a) and (b). A conductive adhesive composition for electromagnetic wave shielding of flexible printed boards . 2. A flexible according to claim 1, wherein the brominated flame retardant is characterized by containing a bromine least 55 wt%
A conductive adhesive composition for electromagnetic shielding of a printed circuit board . 3. The flexible composition according to claim 1, which further comprises 1 to 10 parts by weight of the stabilizer (e) per 100 parts by weight of the total of (a) and (b).
A conductive adhesive composition for electromagnetic shielding of a printed circuit board . 4. An electromagnetic wave of a flexible printed circuit board, characterized in that the conductive adhesive composition according to any one of claims 1 to 3 is formed into a sheet having a thickness of 5 to 500 μm.
Conductive adhesive sheet for shield . 5. A flexure characterized by impregnating or coating a conductive fiber sheet having a surface resistivity of 1 Ω / □ or less with the conductive adhesive composition according to any one of claims 1 to 3.
Electromagnetic wave shield material for sibling printed circuit boards . 6. A frame, characterized in that the electrically conductive adhesive sheet according to claim 4, wherein the surface resistivity 1 [Omega / □ was laminated on one side or both sides of the a conductive fiber sheet or a metal foil or less
Electromagnetic wave shield material for kisible printed circuit boards . 7. An electromagnetic wave shielding flexible printed circuit board, which is obtained by laminating the electromagnetic wave shielding material according to claim 5 on one side or both sides of the flexible printed circuit board.