Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Reexamination Certificate
2002-03-12
2004-08-03
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
C174S1170AS
Reexamination Certificate
active
06770820
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat cable for connecting a plurality of circuits or devices such as computers and communication devices and, particularly, to a shielded flat cable having a shielding layer which is made conductive with an earth cable.
2. Description of the Prior Art
In recent years, a flat cable
50
shown in FIGS.
3
(
a
) and
3
(
b
) has been frequently used as a connection cable for connecting devices such as computers and communication devices in place of a coaxial cable. This flat cable
50
is produced by sheathing a plurality of conductors
22
disposed in parallel to one another with an insulating member
21
A except both end portions thereof, and the conductors
22
consist of a large number of signal lines
22
S and at least one ground line
22
G.
As is already known, a coaxial cable has excellent electromagnetic wave shielding properties as a ground line surrounds signal lines. However, in the case of the above flat cable
50
, as the signal lines
22
S and the ground line
22
G are arranged in parallel to one another, noise is readily superimposed on the above signal lines
22
S.
As a flat cable used for connecting computers and communication devices which require resistance to noise, a shielded flat cable
10
A comprising an electromagnetic wave shielding layer
13
for preventing malfunctioning caused by the above noise as shown in FIGS.
4
(
a
) to
4
(
c
) is widely used. This shielded flat cable
10
A is produced by sheathing the same cable body
11
as that of the above flat cable
50
with a film-like shielding member
14
having a shielding layer
13
made of a metal film formed on one side of an insulating substrate
12
in order to protect the above plurality of conductors
22
from an electromagnetic wave. The above cable body
11
and the shielding member
14
are bonded together by a conductive adhesive. A non-insulating portion
16
devoid of the above insulating member
21
A is formed on part of the above ground line
22
G, and the above shielding layer
13
and the above ground line
22
G are made conductive with each other by the above conductive adhesive constituting an adhesive layer
15
in the above non-insulating portion
16
. Therefore, external noise is caused to flow from the above shielding layer
13
to the ground (earth) of a device body through the above ground line
22
G, thereby making it possible to ensure the electromagnetic wave shielding properties of the flat cable
10
A.
As the above conductive adhesive, there is disclosed a conductive adhesive prepared by dispersing silver particles or copper particles as a conductive material in an adhesive resin essentially composed of a thermoplastic resin having heat-sealing properties, such as polyethylene, polyester or polyamide (Japanese Laid-open Patent Application No. 7-94036). However, when silver particles are used, the cost is boosted though excellent conductivity is obtained. When copper particles are used, electromagnetic wave shielding properties deteriorate along the passage of time.
As means of solving the above problems, there is proposed a method of obtaining stable electromagnetic wave shielding properties at a low cost by using an adhesive comprising a nickel filler in place of silver particles or copper particles (Japanese Laid-open Patent Application No. 11-120831).
The conductor pattern of the cable body
11
is becoming finer and finer along with the downsizing of a device, thereby increasing the resistance values of the above conductors
22
and generating heat easily with the result that the heat resistance requirement for the shielded flat cable
10
A is becoming higher and higher. Further, the shielded flat cable
10
A is required to improve adhesion between the cable body
11
and the shielding member
14
in order to ensure connection reliability in a high-temperature and high-humidity condition in addition to the above heat resistance.
However, as the conductive adhesive used in the adhesive layer
15
of the above conventional shielded flat cable
10
A is an adhesive resin essentially composed of a thermoplastic resin, it has problems with heat resistance and the reliability of connection strength in a high-temperature and high-humidity condition.
It is an object of the present invention which has been made in view of the above problems of the prior art to provide a shielded flat cable which has excellent heat resistance and can ensure connection reliability even in a high-temperature and high-humidity condition.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a shielded flat cable comprising a cable body in which a plurality of conductors including at least one ground line is covered except at least part of the ground line with an insulating member, a shielding member having a shielding layer made of a conductive material formed on one side of an insulating substrate for sheathing the cable body, and an adhesive layer comprising an adhesive with conductive particles dispersed therein, part of the adhesive layer being in contact with a non-covered portion of the ground line for bonding the shielding member to the cable body, wherein the adhesive is a thermally or optically curable adhesive comprising a resin having heat resistance and flexibility after curing as a base resin.
According to a second aspect of the present invention, there is provided a shielded flat cable, wherein the resin is an ethylene-vinyl acetate copolymer or a copolymer of a monomer and at least one of ethylene and vinyl acetate.
According to a third aspect of the present invention, there is provided a shielded flat cable, wherein the resin is a polymer obtained by acetalizing a polyvinyl alcohol.
According to a fourth aspect of the present invention, there is provided a shielded flat cable, wherein the content of the acetal group in the polymer is 30 mol % or more.
According to a fifth aspect of the present invention, there is provided a shielded flat cable, wherein the resin is a polymer obtained by acetalizing a polyvinyl alcohol, or an acrylic resin obtained by polymerizing at least one of an acrylic monomer and a methacrylic monomer.
According to a sixth aspect of the present invention, there is provided a shielded flat cable, wherein the resin is a polyester unsaturated compound soluble in a solvent.
According to a seventh aspect of the present invention, there is provided a shielded flat cable, wherein the base resin is mixed with a phosphoric acid methacrylate and melamine-based resin.
According to an eighth aspect of the present invention, there is provided a shielded flat cable, wherein the phosphoric acid methacrylate is used in an amount of 0.1 to 60 parts by weight and the melamine-based resin is used in an amount of 0.1 to 200 parts by weight based on 100 parts by weight of the base resin.
According to a ninth aspect of the present invention, there is provided a shielded flat cable, wherein the phosphoric acid methacrylate is one or more of 2-methacryloyloxyethyl acid phosphate and diphenyl-2-methacryloyloxyethyl phosphate.
According to a tenth aspect of the present invention, there is provided a shielded flat cable, wherein the melamine-based resin is one or more of melamine resin, isobutylated melamine resin, butylated melamine resin and methylated melamine resin.
According to an eleventh aspect of the present invention, there is provided a shielded flat cable, wherein the adhesive comprises an organic peroxide or optical sensitizer in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the base resin.
According to a twelfth aspect of the present invention, there is provided a shielded flat cable, wherein the adhesive comprises at least one reactive compound selected from the group consisting of an acryloxy group-containing compound and methacryloxy group-containing compound in an amount of 0.5 to 80 parts by weight based on 100 parts by weight of the base resin.
According to a thirteenth aspect of the present invention, there is prov
Hiraoka Hidetoshi
Miura Teruo
Morimura Yasuhiro
Okada Tokuo
Sakurai Ryo
Kabushiki Kaisha Bridgestone
Nguyen Chau N.
Sughrue & Mion, PLLC
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