Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-06-05
2001-02-27
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C428S523000, C428S344000, C428S347000, C428S35500R, C428S356000, C264S029300, C264S331160, C252S511000
Reexamination Certificate
active
06194492
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an anisotropic conductive film capable of exhibiting a conductivity only in the thickness direction thereof, which is used to be interposed between opposed circuits for connecting the circuits to each other through conductive particles contained in the film and also adhesively bonding them to each other by pressurizing and heating the film interposed therebetween.
An anisotropic conductive film is used to be formed between various terminals for adhesively bonding and also electrically connecting the terminals to each other. For example, it is used for connection of a FPC (Flexible Printed Circuit) and TAB (Taped Automated Bonding) to ITO terminals formed on a glass substrate of a liquid crystal panel.
In general, an anisotropic conductive film is characterized in that conductive particles are dispersed in an adhesive mainly containing an epoxy or phenol based resin and a hardener. As the adhesive, a one-component thermosetting type has been mainly used for the sake of convenience in use. Various attempts have been made to increase an adhesive strength of an anisotropic conductive film in order to obtain a stable reliability in connection even under a high temperature/high humidity environment.
The conventional anisotropic conductive film using an epoxy or phenol based resin, however, has a drawback in terms of low adhesive strength, poor workability and low heat/humidity resistance.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an anisotropic conductive film capable of increasing the adhesive strength, improving the workability, and enhancing the humidity/heat resistance.
To achieve the above object, according to the present invention, there is provided an anisotropic conductive film which exhibits a conductivity in the thickness direction thereof by pressurizing the film in the thickness direction, the film including: an adhesive; and conductive particles dispersed in the adhesive; wherein the adhesive is a thermosetting or photosetting adhesive containing as a main component at least one kind selected from a group consisting of (a) a polymer obtained by acetalation of a polyvinyl alcohol, (b) a compound containing an allyl group, (c) a monomer containing an acryloxy group or methacryloxy group, and (d) a polymer obtained by polymerization of one or more selected from a group consisting of an acrylic monomer and a methacrylic monomer. The above adhesive is preferably added with at least one kind of monomer selected from a group consisting of an acryloxy group-containing compound, a methacryloxy group-containing compound, and an epoxy group-containing compound in an amount of 0.5 to 80 parts by weight on the basis of 100 parts by weight of the material.
The anisotropic conductive film of the present invention using a thermosetting or photosetting adhesive mainly containing the above material has the following features:
(1) The film is good in humidity/heat resistance, and also it is good in durability, that is, it effectively exhibits characteristics thereof even after being kept under a high humidity/high temperature environment for a long period of time.
(2) The film is good in repair characteristic.
(3) The film is good in transparency.
(4) The film stably exhibits a high adhesive strength as compared with the conventional one.
(5) The film is good in light transmissivity upon positioning of electrodes because it employs the above transparent polymer, thereby enhancing the workability.
(6) The conventional film using an epoxy or phenol based resin must be heated at a temperature of 150° C. or more. On the contrary, the film of the present invention allows adhesive bonding by curing at a temperature of 130° C. or less, specifically, 100° C. or less, and particularly, in the case of using the UV curing type film, such a film allows adhesive bonding by curing at a further reduced temperature.
(7) The conventional film using an epoxy or phenol based resin, which is poor in adhesive strength, is difficult to be temporarily fixed on electrodes with such a poor adhesive strength and thereby it tends to be peeled therefrom, resulting in the degraded workability. On the contrary, the film of the present invention, which is high in adhesive strength upon temporary fixture, is good in workability.
DETAILED DESCRIPTION OF THE INVENTION
An anisotropic conductive film of the present invention includes an adhesive and conductive particles dispersed in the adhesive, characterized in that the adhesive is a thermosetting or photosetting adhesive containing as a main component at least one kind selected from a group consisting of (a) a polymer obtained by acetalation of a polyvinyl alcohol, (b) a compound containing an allyl group, (c) a monomer containing an acryloxy group or methacryloxy group, and (d) a polymer obtained by polymerization of one or more selected from a group consisting of an acrylic monomer and a methacrylic monomer.
It should be noted that the wording “main component” in the present invention means that the adhesive contains the main component in an amount of 50% by weight or more on the basis of the total weight of all the components of the adhesive except for the conductive particles and a hydrocarbon resin to be described later.
The above polymer in the item (a) is a polymer obtained by acetalation of a polyvinyl alcohol having a melt flow rate (MFR), called also melt index which is in a range of 1 to 3000, preferably 1 to 1000, more preferably 1 to 800.
The polymer obtained by acetalation of a polyvinyl alcohol preferably contains 30 mol % or more of an acetal group. If the content of the acetal group is less than 30 mol %, the humidity resistance may be made poor. As the polymer (polyvinylacetal) obtained by acetalation of a polyvinyl alcohol, there may be used a polyvinyl formal or polyvinyl butyral. In particular, a polyvinyl butyral is preferably used.
As the compound containing an allyl group in the item (b), there may be used a monomer of triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl isophthalate, or diallyl maleate; or a polymer obtained by polymerization of one or more of these monomers.
As the monomer containing an acryloxy group or a methacryloxy group in the item (c), there may be used a monomer selected from monomers of an acrylic ester and methacrylic ester. In particular, there is preferably used an ester of acrylic acid or methacrylic acid with a substituted aliphatic alcohol (having a substituent such as an epoxy group) or an unsubstituted aliphatic alcohol having 1 to 20 carbon atoms, particularly 1 to 18 carbon atoms.
Specific examples of the acrylic monomers may include alkyl acrylate in which the alkyl group has 1 to 20 carbon atoms, preferably 1 to 18 carbon atoms (including methyl acrylate, ethyl acrylate, isoamyl acrylate, lauryl acrylate, and stearyl acrylate), butoxyethyl acrylate, ethoxy-diethyleneglycol acrylate, methoxytriethyleneglycol acrylate, methoxypolyethyleneglycol acrylate, methoxydipropyleneglycol acrylate, phenoxyethyl acrylate, phenoxypolyethyleneglycol acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, 1-hydroxyethyl acrylate, isooctyl acrylate, isomyristyl acrylate, isostearyl acrylate, 2-ethylhexyldiglycol acrylate, 2-hydroxybutyl acrylate, polytetramethyleneglycol diacrylate, EO(ethyleneoxide)-modified trimethylolpropane triacrylate, perfluorooctylethyl acrylate, trimethylolpropane triacrylate, EO-modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, neopentylglycol acrylic acid/benzoic acid ester, triethyleneglycol diacrylate, polyethyleneglycol diacrylate, neopentylglycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dimethyloltricyclodecane diacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.
Specific examples of the methacrylic monomers may include alkyl methacrylate in which the alkyl group has 1 to 20 carbon atoms, preferably 1 to 18 carbon atoms (includi
Kitano Tetsuo
Kotsubo Hidefumi
Matsuse Takahiro
Morimura Yasuhiro
Sakurai Ryo
Asinovsky Olga
Bridgestone Corporation
Seidleck James J.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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