Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2001-07-26
2004-03-16
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S3550EP, C428S3550AC, C525S056000, C525S058000, C525S242000, C525S256000, C525S262000, C525S263000, C525S264000, C525S266000, C525S284000, C525S286000, C525S298000, C525S301000, C525S312000
Reexamination Certificate
active
06706391
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an anisotropically electroconductive film which gives electroconductivity only along its thickness direction, and particularly relates to an anisotropically electroconductive film which is installed between circuits to bond to each other by being heated and pressurized. The anisotropically electroconductive film also conducts the circuits due to electroconductive particles contained therein.
BACKGROUND OF THE INVENTION
An anisotropically electroconductive film consists of an adhesive in which electroconductive particles are dispersed, and it gives an electroconductivity along its thickness direction by being pressurized towards the thickness. The anisotropically electroconductive film is installed between circuits standing opposite to each other and is heated and pressurized so that the circuits are bonded and conducted electrically. The anisotropically electroconductive film gives electroconductivity only in the direction of its thickness.
The anisotropically electroconductive film may be used for connecting a flexible printed circuit board (FPC) or TAB with an ITO terminal on a glass base plate of a liquid crystal panel. The anisotropically electroconductive film forms an anisotropically electroconductive layer between various terminals so as to stick the terminals physically together and to connect the terminals electrically.
Conventional anisotropically electroconductive films are generally composed of an adhesive which consists mainly of an epoxy resin or a phenolic resin and a hardening agent, and electroconductive particles which are dispersed in the adhesive, where a one-pack type thermoset adhesive is dominantly used. Although attempts have made to improve the adhesive strength of the anisotropically electroconductive film in order to achieve a stable reliability in connection between circuits at high temperature and high humidity contents, the conventional anisotropically electroconductive films composed of an epoxy resin or phenolic resin do not have sufficiently high adhesive strength, workability or resistance to humidity and heat.
Japanese Patent Publication H10-338860A has disclosed an anisotropically electroconductive film composed of a thermoset or photosetting adhesive which consists mainly of a polyacetalized resin obtained by acetalizing polyvinyl alcohol. The anisotropically electroconductive film has a high adhesive strength, a good workability and also a high resistance to humidity and heat.
Recently a liquid crystal film of which base material is a plastic film such as polyethylene terephthalate (PET) has been used and the anisotropically electroconductive film also has been used for bonding such liquid crystal films.
When the anisotropically electroconductive film is used for bonding a liquid crystal film, it is necessary to bond the anisotropically electroconductive film to the liquid crystal film in such a manner that the highest temperature during the bonding operation does not exceed a heat-resisting temperature of the liquid crystal film. However, the heat-resisting temperature of the liquid crystal film is usually lower than the temperature as high as 150 to 200° C. at which the anisotropically electroconductive film is commonly heated during the bonding operation. Thus, the liquid crystal film may be broken if the anisotropically electroconductive film is stuck to the liquid crystal film at a temperature between 150 and 200° C.
If the anisotropically electroconductive film is stuck to the liquid crystal film at a lower temperature than the heat-resisting temperature of the liquid crystal film, the anisotropically electroconductive film is not supplied with enough quantity of heat to stick, set, or flow whereby its adhesive properties and conductive characteristics are insufficient.
Therefore, an anisotropically electroconductive film should stick firmly to polymer films having low heat-resisting temperature to give enough electroconductivity even when they are stuck at a low temperature and for a short period of time. The anisotropically electroconductive film should also stick a printed circuit board or IC chip at a low temperature and for a short period of time in order to make thermal expansion and shrinkage of the printed circuit board and IC chip small.
Japanese Patent Publication H10-338844A has disclosed an anisotropically electroconductive film composed of a thermoset or photosetting adhesive which is composed mainly of a (meth-)acrylic resin obtained by polymerizing acrylic monomers and/or methacrylic monomers.
When an anisotropically electroconductive film is used for connecting FPC with an ITO terminal formed on a base plate of a liquid crystal panel, the anisotropically electroconductive film is required to stick firmly to both ITO and silica (SiOX) for the following reasons. That is, the ITO terminal is formed on a glass base plate of the liquid crystal panel by a vapor deposition process, spattering process, ion-plating process, CVD process and the like, and the base plate of the liquid crystal panel has been recently made of polyimide or polyethylene terephthalete (PET) for the purpose of reducing the weight or thickness of the base plate.
In this case, in order to form an ITO film having a good adherence on a resin base made of polyimide, PET or the like, the whole surface of the base plate is covered with a SiO
X
(including SiO
2
) layer before the ITO is applied thereon, and thus the ITO layer is to be formed on the SiO
X
layer. The ITO layer on the SiO
X
layer is etched in order to form the ITO terminal on the SiO
X
layer. Therefore, the anisotropically electroconductive film to be used for sticking the base plate is required to have a high adhesive strength to both ITO and SiO
X
since the ITO terminal is formed on the SiO
X
layer.
However, the conventional anisotropically electroconductive film does not have a high adhesion strength to either ITO or SiO
X
, and it has been desired to be improved in their adhesion properties.
Recently, there has arisen a problem of expansion of a base plate caused due to heat or pressure applied to the anisotropically electroconductive film, since a pitch of electrodes on the base plate has been finer for the purpose of implementing circuits at a high density. There also has arisen a problem of damage to the base plate from the heat and pressure applied to the anisotropically electroconductive film, since the base plate has consisted of material having low resistance to heat and pressure for the purpose of reducing the weight and production cost thereof. Thus, anisotropically electroconductive films made from radical-reaction type materials have been developed in order to be bonded to the base plate at a lower temperature and lower pressure at which the conventional epoxy or phenolic anisotropically electroconductive film is not bonded to the base plate.
However, when the reaction rate of the adhesive is excessively increased for the purpose of lowering the temperature and pressure applied to the radical-reaction type adhesive, the adhesive loses flowability and hardens before the electroconductive particles therein contacts the electrodes so as not to provide enough electroconductivity. Furthermore, the radical-reaction type adhesive is unduly lowered in its adhesion strength when the adhesive hardens before it sufficiently wets the surface of the base plate.
SUMMARY OF THE INVENTION
It is a first object of the present invention to provide an anisotropically electroconductive film having high adhesion strength with high conductivity even when the anisotropically electroconductive film is heated at a temperature of not higher than 130° C. and for a short period of time for sticking.
In order to achieve the first object, an anisotropically electroconductive film of a first aspect consists of an adhesive in which electroconductive particles are dispersed. The adhesive is composed of a thermosetting resin composition including a base resin, at least a reactive compound, at least an organic peroxide, at least a reaction accelerating co
Hiraoka Hidetoshi
Miura Teruo
Morimura Yasuhiro
Okada Tokuo
Sakurai Ryo
Bridgestone Corporation
Chen Vivian
Kanesaka & Takeuchi
LandOfFree
Anisotropically electroconductive film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Anisotropically electroconductive film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Anisotropically electroconductive film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3292557