KR19980066134A - Anisotropic conductive film with excellent storage stability at room temperature - Google Patents

Abstract

1. Fields to which the invention described in the claims belong

The present invention relates to an anisotropic conductive film which is used for the electrical connection of a fine circuit board and is excellent in room temperature storage stability.

2. The technical problem to be solved by the invention

The adhesiveness (TACK property) does not fall even when it is left to stand at room temperature for a long time, and the anisotropic conductive film which makes packaging of a liquid crystal display board easier is provided.

3. Summary of Solution to Invention

In an anisotropic conductive film composed mainly of an adhesive polymer resin, a conductive particle, a curing agent, and a coupling agent, the bisphenol F type epoxy resin contains 5 to 20% by weight of the bisphenol F type epoxy resin in an adhesive polymer resin whose main component is room temperature. An anisotropic conductive film excellent in storage stability is produced.

4. Important uses of the invention

The anisotropic conductive film of this invention is used for the electrical contact of a fine circuit board, especially the connection of a liquid crystal display, a flexible circuit board, etc.

Description

Anisotropic conductive film excellent in room temperature storage stability.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anisotropic conductive films used for the electrical connection of fine circuit boards, in particular the connection of liquid crystal displays (LCDs) and flexible circuit boards (FPCs), and microconnections of semiconductor chips and chip-mounted circuit boards.

In general, an anisotropic conductive film is prepared by coating a resin composition composed of an adhesive polymer resin, conductive particles, a curing agent, a coupling agent, and a solvent on a release film.

In the prior art for producing such an anisotropic conductive film, a bisphenol A type epoxy resin is used alone or a bisphenol A type epoxy resin is mixed with at least one resin selected from a thermoplastic resin, a thermosetting resin or a photocurable resin as an adhesive polymer resin. I use it.

Specific examples of the thermoplastic resin, the thermosetting resin, or the photocurable resin include styrene-butadiene resin, styrene resin, ethylene-vinyl resin, acrylonitrile butadiene rubber, silicone resin, acrylic resin, epoxy resin, urethane resin, phenol resin, and amide resin. Or an acrylate resin column.

If necessary, a tackifier, a crosslinking agent, an anti-aging agent, and a coupling agent such as a rosin, a turbine resin, and a gumarodine resin may also be used as the polymer resin for the adhesive.

As a curing agent, those obtained by microencapsulating a reaction product of an amidazole with an epoxy compound with a thermoplastic resin are used.

However, the conventional anisotropic conductive film is weak in room temperature storage stability, and when left at room temperature for a long time, there arises a problem that adhesiveness (hereinafter referred to as "tack") is degraded.

In addition, the alignment process of aligning and attaching a circuit on a tab or flexible PCB on a circuit on a liquid crystal display (hereinafter referred to as LCD) becomes difficult, and great care is required when storing and using the product. The workability is lowered and the product quality is poor. As a result, a problem arises in that the LCD packaging process cannot be easily performed.

A method of connecting a liquid crystal display substrate and a driving integrated circuit thereof using a conventional anisotropic conductive film will be described in more detail with reference to FIGS. 2 and 3.

FIG. 2 is a cross-sectional view of a state before connecting a liquid crystal display substrate and a driving integrated circuit using a conventional anisotropic conductive film, and FIG. 3 is a cross-sectional view after connecting.

An anisotropic conductive film prepared by dispersing the conductive particles 5 having a diameter of 3 to 20 μm in an adhesive 6 containing bisphenol A epoxy resin as a main component and coating the same on a release-treated polyester film After sandwiching between the electrode 9 of the liquid crystal display substrate 7 and the tab electrode 10 of the driving integrated circuit 8, the anisotropic conductive film is heated to a predetermined temperature, and then the liquid crystal display substrate 7 is pressed downward. The adhesive 6 is positioned between the electrode 9 of the liquid crystal display substrate and the tab electrode 10 of the driving integrated circuit to provide an electrically conductive path.

More specifically, the anisotropic conductive film is press-bonded for 5 seconds at a temperature of 80 to 100 ° C. and a pressure of 10 kgF / cm 2 by using the self-tacking property of the film itself, and the release film 4 is removed. do. By using the self-tacking property of the film, the circuit on the glass substrate of the LCD to which the anisotropic conductive film is press-bonded is aligned with the circuit on the tab or flexible PCB, and the temperature is 170 to 180 ° C. and 20 kg. It presses for 20 second under the pressure of F / cm <2>, and connects a liquid crystal display substrate and its drive integrated circuit.

As described above, in connecting the liquid crystal display substrate and its driving integrated circuit using an anisotropic conductive film, the self-tackiness of the anisotropic conductive film is very important.

However, the conventional anisotropic conductive film is weak in room temperature storage stability, and when left to stand at room temperature for a long time, there arises a problem that the adhesion (hereinafter referred to as "tack") is reduced.

In addition, the alignment process of aligning and attaching a circuit on a tab or flexible PCB on a circuit on a liquid crystal display (hereinafter referred to as LCD) becomes difficult and requires great care in storing and using the product. The workability is lowered and the product quality is poor. As a result, a problem arises in that the LCD packaging process cannot be easily performed.

Provides an anisotropic conductive film that is excellent in storage stability at room temperature and does not degrade the tackiness even when left standing at room temperature for a long time or aligning, so that the LCD packaging process can be more easily performed.

1 is a cross-sectional view of the anisotropic conductive film of the present invention.

2 is a cross-sectional view of a state before connecting a liquid crystal display substrate and a driving integrated circuit using a conventional anisotropically conductive film.

3 is a cross-sectional view of a state after connecting a liquid crystal display substrate and a driving integrated circuit using a conventional anisotropic conductive film.

In Fig. 1, 1 is an adhesive, 2 is a metal coating layer, 3 is conductive polymer particles, and 4 is a release film. 2 to 3, 5 is an adhesive, 6 is conductive particles, 7 is a liquid crystal display substrate, 8 is an integrated circuit for driving, 9 is an electrode of the liquid crystal display substrate, and 10 is a tab electrode.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to anisotropic conductive films used for the electrical connection of fine circuit boards, in particular for the connection of liquid crystal displays (LCDs) and flexible circuit boards, and for microconnections of semiconductor chips and circuit boards for chip mounting.

In particular, the present invention relates to an anisotropic conductive film which is excellent in room temperature storage stability and does not deteriorate in tack even when left at room temperature for a long time or aligned.

More specifically, the present invention relates to an anisotropic conductive film containing a polymer resin for adhesives, conductive particles, a curing agent, and a coupling agent as a main component, wherein the bisphenol F type epoxy resin is 5 to an adhesive polymer resin containing a bisphenol A epoxy resin as a main component. It relates to the anisotropic conductive film contained in the 20% by weight.

In the present invention, as the adhesive polymer resin, bisphenol A epoxy resin and bisphenol F resin are used as essential components.

Bisphenol A type epoxy resin is a main component, and bisphenol F type epoxy resin is contained 5 to 20% by weight compared to the polymer resin for adhesives.

When the content of the bisphenol F-type epoxy resin is lower than the range of the present invention, the adhesion of the anisotropic conductive film is lowered, and when the content of the bisphenol F-type epoxy resin is higher than the range of the present invention, the film surface is too sticky and the workability is lowered. At this time, the epoxy equivalent of the bisphenol F-type epoxy resin used is in the range of 160 to 185 g, the viscosity is preferably 700 to 10,000 CPS level at 25 ℃. In addition, in the polymer resin for adhesives of the present invention, a thermoplastic resin, a thermosetting resin, and / or a photocurable resin may be selectively used together with the essential components. As specific examples of these, styrene-butadiene resin, styrene resin, ethylene-vinyl resin, acrylonitrile butadiene rubber, silicone resin, acrylic resin, epoxy resin, urethane resin, phenol resin, amide resin or acrylate resin and the like are used. do. Among these, epoxy resins include bisphenol S-type epoxy resins, phenol noblock type epoxy resins, cresol block type epoxy resins, dimer acid-modified epoxy resins, rubber-modified epoxy resins, urethane-modified epoxy resins, and two or more epoxy reactors in one molecule. Phenoxy resins, polyol modified epoxy resins and phenol noblock type epoxy resins can be used.

In addition, the conductive particles used in the present invention, the metal is cracked in the polymer beads (Bead). These particle diameters are 3-20 micrometers, and have the following characteristics. Firstly, the conductive particles have a metal beating at about 500 kPa in the polymer beads, so the specific gravity of the conductive particles is 1.5 to 2.3 similar to that of the epoxy adhesive.

As a result, the dispersion stability of the conductive particles is excellent when the coating liquid for film is removed. Third, since the base of the conductive particles is made of polymer beads, it is deformed by pressing to increase the conductive area, and the thermal expansion degree is closer to that of the hardened adhesive than the metal, so that the electrical connection reliability against temperature change is high. Fourth, since the particle size is uniform, there is little variation in conductivity at each electrode pad. Finally, since it has excellent chemical resistance in solvents such as toluene or tetrahydrofurene (THF), there is no damage to the conductive layer even when mixed with the epoxy adhesive composition.

In addition, the curing agent used in the present invention is a microencapsulation of the reaction product of the imidazole and the epoxy compound, excellent storage stability at room temperature, and can be cured quickly to improve the problem of the final technology. The amidazole compound used herein is imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-cyanoethyl-2 -Methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole and the like are used. Moreover, glycidyl ether type epoxy compounds, such as a bisphenol A type, a phenol block, a bisphenol F type, or a block bisphenol A type, are used as an epoxy compound which reacts with the above-mentioned imidazole compound, and produces | generates an imidazole derivative epoxy compound. As the thermoplastic resin encapsulating the imidazole derivative epoxy compound produced above, a polymer such as polystyrene, gelatin or polyisocyanate is used.

The hardening | curing agent of this invention is used in 10 to 50weight% of a range with respect to the polymeric resin for adhesives. If too small amount is added, curing does not occur at 130 ° C. within 2 minutes. If too much amount is added, the amount of heat generated during the curing reaction is too high, resulting in a decrease in adhesive strength of the adhesive.

Meanwhile, in the present invention, organic sulfur compounds having excellent affinity with organic substances and inorganic metals may be used as coupling agents in order to evenly disperse the conductive particles, thereby improving the dispersion speed and dispersion state of the conductive particles.

As the solvent used for preparing the polymer resin composition for an adhesive, acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, xylene, methyl alcohol, isopropyl alcohol, and / or n-butyl alcohol may be used alone or in combination. Mix and use. These solvents have high polarity to improve the mixing stability of the resin solution after blending.

The coating composition for the film prepared as described above was subjected to a knife coater, a comma coater, an air knife coater and a doctor blade on a release-treated polyester film. The coating layer is coated to have a thickness of 10 to 1,000 μm, dried and wound, and then slitted to product specifications to prepare an anisotropic conductive film. 1 shows a cross-sectional view of the anisotropic conductive film of the present invention.

At this time, the release-treated polyester film is preferably 25 ~ 200㎛ thickness. In the release process of the polyester film, a vinyl group, a hydroxyl group, or phenyl is contained in part or all of the terminal and side chains mainly on dimethylpolysiloxane, and the thermosetting silicone resin cured and reacted with a catalyst such as toluene, A solution dissolved or dispersed in an organic solvent such as xylene, methyl ethyl ketone or n-hexane is used. The concentration of these solutions is suitably in the range of 0.5 to 5.0% by weight.

The anisotropic conductive film of the present invention manufactured as described above is used to connect a liquid crystal display substrate and its integrated circuit for driving by a conventional process.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited only to the examples.

[Example 1]

34 parts by weight of YD-128 (product of Kukdo Chemical), a bisphenol A epoxy resin, 45 parts by weight of YP-50 (product of Kukdo Chemical), a phenoxy resin, and 5 parts of YDF-170 (product of Kukdo Chemical), a bisphenol F type epoxy resin Toluene: methyl ethyl ketone adhesive solution for 1 part by weight of KBM-403 (produced by Shin-Echu), which is a silane coupling agent, was prepared.

After cooling the prepared adhesive solution to room temperature, 10 parts by weight of a hardening agent HX3941 (a Ukhwa product) and gold / nickel metal were cracked in the polymer particles, and the conductive particle Ni-205 having a particle diameter of 5 ± 2 μm (red) Chemical products) 5 parts by weight of the mixture is dispersed to prepare a coating solution for film production.

The prepared coating solution for film production is coated on a release-treated polyester film and then dried in a hot air circulation oven at 80 ° C. for 1 minute to produce an anisotropic conductive film. Using an anisotropic conductive film produced, thermocompression bonding of a flexible circuit board (FPC) and a transparent conductive circuit glass substrate (ITO circuit) with a line width of 0.1 mm, pitch of 0.2 mm, a thick film of 35 μm, and 160 terminal circuits Connected by The result of measuring these adhesive force, tack peel force, connection thickness, and connection resistance is shown in Table 2.

[Examples 2 to 4 and Comparative Examples 1 to 4]

Except for changing the composition ratio of the coating liquid for film production as shown in Table 1, after producing an anisotropic conductive film in the same process as in Example 1, using the produced anisotropic conductive film, line width 0.1mm, pitch 0.2mm, thick film A flexible circuit board (FPC) having 35 µm and 160 equivalent circuits and a transparent conductive circuit glass substrate (ITO circuit) are connected by thermocompression bonding. The result of measuring these adhesive force, tack peel force, connection thickness, and connection resistance is shown in Table 2.

Physical properties measurement method is as follows.

Connection resistance (Ω) Measure by using 4-probe method after initial connection and after leaving high temperature and high humidity.

Adhesion (kg / cm) Measured by a 90 ° peel tensile test (peel test).

Tack Peeling Force (g / cm) After bonding the anisotropic conductive film and the unreleased polyester film, they are measured by a peel test.

Connection thickness (micrometer) Observe and measure with an electron microscope.

The anisotropic conductive film of this invention is excellent in normal temperature storage stability, and even if it stores for a long time at normal temperature, adhesiveness will not fall. In addition, since the adhesion is not degraded during alignment, the LCD packaging process can be more easily performed.

Claims (4)

In an anisotropic conductive film containing a polymer resin for an adhesive, a conductive particle, a curing agent, and a coupling agent as a main component, a bisphenol F-type epoxy resin is contained in an adhesive polymer resin containing 5 to 20% by weight of a bisphenol A epoxy resin as a main component. Anisotropic conductive film excellent in room temperature storage stability, characterized in that. The anisotropic conductive film having excellent room temperature storage stability according to claim 1, wherein at least one resin selected from the group consisting of a thermoplastic resin, a thermosetting resin, and / or a photocurable resin is added to the adhesive polymer resin. The anisotropic conductive film having excellent room temperature storage stability according to claim 1, wherein the epoxy equivalent of the bisphenol F-type epoxy resin is 160 to 185 g. The anisotropic conductive film having excellent room temperature storage stability according to claim 1, wherein the viscosity of the bisphenol F-type epoxy resin is 700 to 10,000 CPS at 25 ° C.