Stock material or miscellaneous articles – Composite – Of polycarbonate
Reexamination Certificate
2002-09-06
2004-07-06
Boykin, Terressa M. (Department: 1711)
Stock material or miscellaneous articles
Composite
Of polycarbonate
C428S208000, C428S208000, C428S208000, C428S408000, C428S902000, C428S208000
Reexamination Certificate
active
06759130
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition, a molded product employing it and an electroconductive sheet. Said electroconductive sheet is useful for packaging containers for semiconductors such as IC and electronic parts, particularly useful for carrier tapes.
BACKGROUND ART
For packaging IC, electronic parts using IC or electronic parts, injection-molded trays, vacuum-formed trays, magazines, carrier tapes (referred to also as embossed carrier tapes) etc. have been used. To prevent breakage of electronic parts such as IC due to static electricity, as the packaging containers, ones having an electroconductive filler dispersed therein have been used. As the electroconductive filler, carbon black is widely used, with which a stable surface resistivity will be obtained constantly at a low cost.
An electroconductive sheet comprising a thermoplastic resin having carbon black dispersed therein, has such drawbacks that (1) mechanical strength and processability will decrease, and (2) an electronic part will be stained by falling off of the resin containing carbon black on the surface of the electroconductive sheet by abrasion of the packaged electronic part with the electroconductive sheet. JP-A-57-205145, JP-A-62-18261, etc. have been proposed as a method to overcome the problem (1), and JP-A-9-7624, JP-A-9-76425, etc. have been proposed as a method to overcome the problem (2). However, electronic parts are getting more complex, precise and small, and packaging and mounting of electronic parts proceed at a higher speed at the present time, and accordingly, an electroconductive sheet for packaging an electronic part, which is less likely to cause staining of the electronic part, and which has improved mechanical strength, has been desired.
DISCLOSURE OF THE INVENTION
The present invention provides an electroconductive sheet for packaging an electronic part, which substantially reduces staining of the electronic part due to abrasion of the electroconductive sheet with the electronic part, and which has adequate mechanical strength to endure packaging or mounting at a high speed, and a packaging container for an electronic part. The electroconductive sheet is particularly useful for a carrier tape.
The present invention provides an electroconductive sheet comprising a substrate layer and having laminated on at least one side of the substrate layer, a surface layer of an electroconductive resin composition comprising a polycarbonate type resin and from 5 to 50 wt % of carbon black based on the polycarbonate type resin. Said electroconductive sheet is useful as an electroconductive sheet for packaging an electronic part, and said electroconductive sheet for packaging an electronic part is useful as a packaging container for an electronic part, particularly as a carrier tape.
As a constitution of the electroconductive sheet, a two-layer structure of surface layer/substrate layer, wherein the surface layer comprises an electroconductive resin composition and is placed on the side which will be in contact with the electronic part, is preferred. Further, a constitution of surface layer/substrate layer/surface layer is also preferred. Another layer may be provided between the surface layer and the substrate layer.
The polycarbonate type resin for the electroconductive resin composition is not particularly limited, and an commercially available product may be used. For example, an aromatic polycarbonate resin, an aliphatic polycarbonate resin and an aromatic-aliphatic polycarbonate may be mentioned. One obtained by polycondensation of a conventional bisphenol A with phosgene or by polycondensation of bisphenol A with carbonic acid ester, which is usually classified into an engineering plastic, may also be used. This is composed mainly of bisphenol, and produced by a phosgene method or by ester exchange, and the bisphenol to be used as the raw material may, for example, be 2,2-bis-(4-hydroxyphenyl)propane (bisphenol A), 2,4-bis-(4-hydroxyphenyl)-methyl-butane or 1,1-bis-(4-hydroxyphenyl)-cyclohexane. A homopolycarbonate, a copolycarbonate obtained by copolymerization of a carboxylic acid, or a mixture thereof, may also be used.
Carbon black to be incorporated in the electroconductive resin composition may, for example, be furnace black, channel black or acetylene black, and preferred is one having a large specific surface area and whereby a high level of electroconductivity can be obtained with a small amount of incorporation to the resin, such as KETJENBLACK or acetylene black.
The amount of carbon black to be incorporated in the electroconductive resin composition is preferably from 5 to 50 wt % based on the polycarbonate type resin. If it is less than 5 wt %, no adequate surface resistivity will be obtained to prevent breakage of an electronic part due to static electricity. If it exceeds 50 wt %, the fluidity will decrease, whereby it may be difficult to laminate the electroconductive resin composition on the substrate layer, and the mechanical strength of the electroconductive sheet to be obtained will also decrease.
The surface resistivity of the electroconductive sheet on the side on which the electroconductive resin composition is laminated, is preferably from 10
2
to 10
10
&OHgr;. If it is beyond this range, it tends to be difficult to prevent breakage of an electronic part due to static electricity.
Into the electroconductive resin composition, another resin component such as an acrylonitrile-butadiene-styrene copolymer type resin or a polybutylene terephthalate resin may be incorporated as a modifier.
As the modifier, a graft resin of an ethylene-glycidylmethacrylate type copolymer with an acrylonitrile-styrene type copolymer is suitably used. The electroconductive resin composition in this case comprises a polycarbonate type resin, and from 5 to 50 wt % of carbon black and at most 40 wt % of a graft resin of an ethylene-glycidylmethacrylate type copolymer with an acrylonitrile-styrene type copolymer, based on the polycarbonate type resin. The electroconductive resin composition may be made of a polycarbonate type resin, carbon black and a graft resin alone, or may be composed mainly of those and contain another component within a range of not impairing the purpose of the present invention.
The graft resin of an ethylene-glycidylmethacrylate type copolymer with an acrylonitrile-styrene type copolymer is a resin obtained by grafting an acrylonitrile-styrene type copolymer to an ethylene-glycidylmethacrylate type copolymer, and a resin obtained by grafting an acrylonitrile-styrene type copolymer having an acrylonitrile content of at most 50 wt % to an ethylene-glycidylmethacrylate type copolymer having a glycidylmethacrylate content of at most 45 wt %, is suitably used, which is commercially available.
The amount of the graft resin to be incorporated is at most 40 wt %, preferably from 1 to 40 wt %, more preferably from 3 to 40 wt %, based on the polycarbonate type resin. Within the above range, the mechanical strength, particularly impact strength, will be improved to endure packaging and mounting of electronic parts at a high speed. If it exceeds 40 wt %, the elastic modulus will decrease.
When the above resin composition is used for an electroconductive sheet as an electroconductive resin composition, it may be used as a monolayer electroconductive sheet or a multilayer electroconductive sheet. It may be used as a molded product by itself.
Into the electroconductive resin composition, an additive such as a lubricant, a plasticizer or a processing aid may further be incorporated as the case requires.
The electroconductive sheet is particularly useful as a carrier tape. For such an application, an electroconductive sheet for a carrier tape, which has a reduced reflection on the surface, has been desired so as to prevent malfunction of an inspection machine due to reflection on the surface of the electroconductive sheet at the time of image inspection of e.g. IC. According to the present invention, the layer of an electroconductive resin composition has a s
Higano Masanori
Kosugi Kazuhiro
Miyakawa Takeshi
Shimizu Mikio
Boykin Terressa M.
Denki Kagaku Kogyo Kabushiki Kaisha
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