JPH11195325A - Anisotropic conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive film which has high adhesive strength, a good working property, and high moisture-heat-resistance, also which keeps conductivity in the thickness direction and insulation in the side direction, and has high adhesive power and excellent durability even after it is held under the condition of a high temperature and humidity for a long time. SOLUTION: This anisotropic conductive film is constituted by dispersing conductive particles in an adhesive agent, and by providing conductivity in the thickness direction by applying pressure in the thickness direction. The adhesive agent is a thermosetting or photosetting adhesive agent the main component of which is a polymer formed by introducing fatty series unsaturated based to side chains of polyvinyl acetal resins obtained by acetalizing polyvinl alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of interposing circuits between opposing circuits, applying pressure and heating between the circuits to connect the circuits via conductive particles, and bonding and fixing the circuits. The present invention relates to an anisotropic conductive film that provides conductivity only in the thickness direction and is used for the purpose.

[0002]

2. Description of the Related Art Anisotropic conductive films are used for flexible printed circuit (FPC).
And TAB and IT formed on the glass substrate of the liquid crystal panel
It is used when an anisotropic conductive film is formed between various terminals, such as when connecting to an O terminal, thereby bonding and electrically connecting the terminals.

[0003] Anisotropic conductive films are generally obtained by dispersing conductive particles in an adhesive mainly composed of an epoxy or phenolic resin and a curing agent. One-component thermosetting type is becoming mainstream. In addition, in order to obtain stable connection reliability even under high temperature and high humidity, the bonding strength of the anisotropic conductive film is enhanced by various methods.

However, conventional anisotropic conductive films using epoxy or phenolic resins have low adhesive strength,
The workability was poor, and there was a problem with the moisture and heat resistance.

An object of the present invention is to provide an anisotropic conductive film which is improved in the above circumstances, has high adhesive strength, good workability, and high resistance to moisture and heat.

[0006]

Means for Solving the Problems and Embodiments of the Invention In order to achieve the above object, the present invention comprises a method in which conductive particles are dispersed in an adhesive, and the pressure is applied in the thickness direction to thereby increase the thickness in the thickness direction. In an anisotropic conductive film provided with conductivity,
The adhesive may introduce an aliphatic unsaturated group into a side chain of a polyvinyl acetal resin such as a polyvinyl butyral resin obtained by acetalizing polyvinyl alcohol,
Especially vinyl butyral units, vinyl alcohol units and vinyl acetate units of polyvinyl butyral resin composed of vinyl alcohol units side chain hydroxyl groups of acrylic acid,
As a main component, a polymer obtained by introducing an aliphatic unsaturated group by acid modification with methacrylic acid or the like,
In particular, a heat or photo-curable adhesive containing an organic peroxide or a photosensitizer as a cross-linking agent (curing agent), and preferably containing a silane coupling agent and further containing an epoxy group-containing compound. The present invention provides an anisotropic conductive film characterized by the following.

The anisotropic conductive film of the present invention has the following features because it is a thermosetting or photocurable adhesive containing the above polymer as a main component as an adhesive. (1) It has excellent resistance to humidity and heat, and effectively exhibits the properties of an anisotropic conductive film even after being held for a long time under high humidity and high temperature, and has excellent durability. (2) Good repairability. (3) Good transparency. (4) Stable and high adhesiveness is exhibited as compared with conventional products. (5) By using a film made of the transparent polymer as a raw material, light transmittance at the time of electrode positioning is good,
Workability is good. (6) Conventional products such as epoxy resins require heating at 150 ° C. or higher, but according to the present invention, they can be cured and bonded at 130 ° C. or lower, particularly 100 ° C. or lower, and have UV curability. Therefore, curing and bonding at a lower temperature are also possible. (7) The conventionally used epoxy-based and phenol-based anisotropic conductive films have no tackiness, and the film is difficult to temporarily fix to the electrode due to the adhesive force, is easily peeled off, and has poor workability. Since the anisotropic conductive film has high adhesive strength at the time of temporary fixing, workability is good.

Hereinafter, the present invention will be described in more detail.
The anisotropic conductive film of the present invention is obtained by dispersing conductive particles in an adhesive. In this case, as the adhesive, a fatty acid is added to a side chain of a polyvinyl acetal resin obtained by acetalizing polyvinyl alcohol. It contains, as a main component, a polymer obtained by introducing a group-unsaturated group, for example, a vinyl group, an allyl group, a methacryl group, an acryl group or the like.

In this case, the polyvinyl acetal resin is preferably a polyvinyl butyral resin. This polyvinyl butyral resin has the following formula (1):
It is composed of a vinyl butyral unit A, a vinyl alcohol unit B and a vinyl acetate unit C, and the aliphatic unsaturated group may be introduced into any of the side chains of these units A, B and C. Are preferably introduced into the side chain of The introduction of the aliphatic unsaturated group into the side chain of the polyvinyl alcohol unit B is preferably performed by acid-modifying the side-chain hydroxyl group. Examples of the acid used for the acid modification include acrylic acid, methacrylic acid,
Stearyl acid, maleic acid, phthalic acid and the like,
As shown in the following formula (2), an aliphatic unsaturated bond can be introduced.

[0010]

Embedded image (In the formula, R represents a hydrogen atom or an alkyl group, and R ′ represents an aliphatic unsaturated group such as an alkenyl group or a group containing the same.)

In the above formula (1), the vinyl alcohol unit B is preferably 3 to 70 mol%, more preferably 5 to 50 mol%, further preferably 5 to 30 mol%, and less than 3 mol%. Poor reactivity with acid modification, 7
If it is more than 0 mol%, heat resistance and moisture resistance may be poor.

As the conductive particles used in the present invention, various kinds of conductive particles can be used as long as they are electrically good conductors. For example, metal powder such as copper, silver, and nickel, resin or ceramic powder coated with such a metal can be used. There is no particular limitation on the shape, and any shape such as a scale shape, a tree shape, a granular shape, and a pellet shape can be adopted.

In the present invention, the compounding amount of the conductive particles is
The content is preferably 0.1 to 15% by volume based on the polymer, and the average particle size is preferably 0.1 to 100 µm. In this way, by defining the blending amount and the particle size, the conductive particles are condensed between adjacent circuits and short circuit is prevented.

For curing the anisotropic conductive film of the present invention, an organic peroxide or a photosensitizer can be used. When the curable adhesive is a thermosetting adhesive, Usually, when an organic peroxide is used and the curable adhesive is a photocurable adhesive, a photosensitizer is usually used.

As the organic peroxide added for curing the anisotropic conductive film of the present invention, any organic peroxide which can be decomposed at a temperature of 70 ° C. or more to generate radicals can be used. The decomposition temperature with a half-life of 10 hours is preferably 50 ° C. or higher, and is selected in consideration of the film formation temperature, preparation conditions, curing (bonding) temperature, heat resistance of the adherend, and storage stability.

Examples of usable organic peroxides include, for example, 2,5-dimethylhexane-2,5-dihydroperoxide and 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne- 3, di-t-butyl peroxide, t-butylcumyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane,
Dicumyl peroxide, α, α′-bis (t-butylperoxyisopropyl) benzene, n-butyl-4,
4′-bis (t-butylperoxy) valerate, 1,
1-bis (t-butylperoxy) cyclohexane,
1,1-bis (t-butylperoxy) -3,3,5-
Trimethylcyclohexane, t-butylperoxybenzoate, benzoyl peroxide, t-butylperoxyacetate, methyl ethyl ketone peroxide, 2,5-dimethylhexyl-2,5-bisperoxybenzoate, butyl hydroperoxide, p-
Methane hydroperoxide, p-chlorobenzoyl peroxide, hydroxyheptyl peroxide,
Chlorohexanone peroxide, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, cumylperoxyoctoate, succinic acid peroxide, acetyl peroxide, t-butylperoxy (2-ethylhexanoate), m -Toluoyl peroxide, t-butylperoxyisobutyrate, 2,4-dichlorobenzoyl peroxide and the like. As organic peroxides,
At least one of these is used alone or in combination, and usually 0.1 to 1 part by weight based on 100 parts by weight of the polymer.
0 parts by weight are used.

As the photosensitizer (photopolymerization initiator) added for curing the anisotropic conductive film of the present invention, a radical photopolymerization initiator is suitably used. Among the radical photopolymerization initiators, benzophenone, methyl o-benzoylbenzoate, 4-benzoyl-4′-methyldiphenylsulfide, isopropylthioxanthone, diethylthioxanthone, ethyl 4- (diethylamino) benzoate and the like are examples of hydrogen abstraction initiators. Can be used. Further, among radical photopolymerization initiators, benzoin ether, benzoyl propyl ether, benzyl dimethyl ketal, and α-hydroxyalkylphenone as intramolecular cleavage type initiators and 2-hydroxy-2-methyl-
1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, alkylphenylglyoxylate, diethoxyacetophenone, and 2-methyl-1- [4
-(Methylthio) phenyl] -2-morpholinopropanone-1,2-benzyl-2-dimethylamino-1-
(4-morpholinophenyl) butanone-1 and acylphosphine oxide are used. As the photosensitizer, at least one of them is used alone or as a mixture. Usually, 0.1 to 10 parts by weight is added to 100 parts by weight of the polymer.

In order to improve and adjust the physical properties (mechanical strength, adhesiveness, optical properties, heat resistance, moisture resistance, weather resistance, crosslinking speed, etc.) of the anisotropic conductive film of the present invention, It is preferable to add a compound (monomer) having an acryloxy group, a methacryloxy group or an epoxy group.

As the compound used for this purpose, acrylic acid or methacrylic acid derivatives such as esters and amides thereof are the most common, and the ester residues include alkyl such as methyl, ethyl, dodecyl, stearyl and lauryl. In addition to the groups, cyclohexyl, tetrahydrofurfuryl, aminoethyl, 2-hydroxyethyl, 3-hydroxypropyl, 3-chloro-2-
And a hydroxypropyl group. Further, esters with polyfunctional alcohols such as ethylene glycol, triethylene glycol, polypropylene glycol, polyethylene glycol, trimethylolpropane, and pentaerythritol are also used. As the amide, diacetone acrylamide is typical. Examples of the polyfunctional crosslinking assistant include acrylic acid or methacrylic acid esters such as trimethylolpropane, pentaerythritol and glycerin. Examples of the epoxy group-containing compound include triglycidyl tris (2-hydroxyethyl) isocyanurate, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl. Ether, phenol (EO) ₅ glycidyl ether, pt
-Butylphenyl glycidyl ether, diglycidyl adipate, diglycidyl phthalate, glycidyl methacrylate, butyl glycidyl ether and the like. A similar effect can be obtained by alloying a polymer containing an epoxy group. These compounds may be used alone or as a mixture of two or more thereof, usually in an amount of 0.5 to 8 based on 100 parts by weight of the polymer.
0 parts by weight, preferably 0.5 to 70 parts by weight are used. If the amount exceeds 80 parts by weight, workability and film formability during preparation of the adhesive may be reduced.

It is preferable to add a silane coupling agent as an adhesion promoter to the anisotropic conductive film of the present invention. Examples of the silane coupling agent include vinyltriethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxy. Propyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane,
One or a mixture of two or more of γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane and the like are used. The addition amount of these silane coupling agents depends on the amount of the polymer 100
Usually, 0.01 to 5 parts by weight with respect to parts by weight is sufficient.

In the anisotropic conductive film of the present invention, a hydrocarbon resin can be added to the adhesive for the purpose of improving workability, bonding and the like. In this case, the hydrocarbon resin to be added may be either a natural resin type or a synthetic resin type. Rosin, rosin derivatives, and terpene resins are preferably used in the natural resin system. In rosin, gum resin,
Tall oil-based resins and wood-based resins can be used.
As the rosin derivative, rosin obtained by hydrogenation, heterogeneization, polymerization, esterification, and metal salification can be used. As the terpene-based resin, terpene-based resins such as α-pinene and β-pinene, as well as terpene phenol resins can be used. Further, dammar, koval, and shellac may be used as other natural resins. On the other hand, in the case of synthetic resins, petroleum resins, phenol resins, and xylene resins are preferably used. Petroleum resins include aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, hydrogenated petroleum resins, pure monomer petroleum resins,
Coumarone indene resin can be used. As the phenolic resin, an alkylphenol resin and a modified phenol resin can be used. As the xylene-based resin, a xylene resin or a modified xylene resin can be used.

The amount of the hydrocarbon resin to be added is appropriately selected, but is preferably from 1 to 200 parts by weight, more preferably from 5 to 150 parts by weight, per 100 parts by weight of the polymer.

In addition to the above additives, an antioxidant, an ultraviolet absorber, a dye, a processing aid and the like may be used in the present invention as long as the object of the present invention is not hindered.

In order to obtain the anisotropic conductive film of the present invention, the above-mentioned crosslinking agent (organic peroxide and / or photosensitizer) which generates a radical by heat or light and, if necessary, a crosslinking aid An agent, a silane coupling agent, an acryloxy group, a methacryloxy group, and an epoxy group-containing compound are added to the polymer as a main component, and conductive particles are further blended.

The anisotropic conductive film of the present invention is prepared by uniformly mixing the above-mentioned polymer with the above-mentioned additives and conductive particles, kneading the mixture with an extruder, a roll, or the like. A film can be formed in a predetermined shape by a film forming method. At the time of film formation, embossing may be performed for the purpose of preventing blocking, facilitating pressure bonding with an adherend, and the like. The film obtained as described above is adhered to a substrate (polyimide, copper foil, etc.)
Conventional methods, for example, a bonding method using a hot press, a direct laminating method using an extruder or a calender, and a thermocompression bonding method using a film laminator can be used.

Further, each component is converted into a member (separator)
Can be uniformly dissolved in a solvent that has no effect on the surface, uniformly applied to the surface of the member (separator), and temporarily adhered to another adherend (polyimide, copper foil, etc.), and then cured by heat or light. it can.

The curing conditions for the anisotropic conductive film of the present invention depend on the type of organic peroxide used in the case of thermal curing, but are usually 70 to 170 ° C., preferably 7 to 170 ° C.
0 to 150 ° C., usually for 10 seconds to 120 minutes, preferably 2
0 seconds to 60 minutes.

In the case of photocuring using a photosensitizer, many light sources emitting light in the ultraviolet to visible region can be used as a light source.
For example, an ultrahigh-pressure, high-pressure, low-pressure mercury lamp, chemical lamp, xenon lamp, halogen lamp, mercury halogen lamp, carbon arc lamp, incandescent lamp, laser light and the like can be mentioned. The irradiation time cannot be determined unconditionally depending on the type of lamp and the intensity of the light source, but is about several tens of seconds to several tens of minutes.

In order to accelerate the curing, the laminate is preliminarily 40 to 1
It may be heated to 20 ° C. and irradiated with ultraviolet rays.

In this case, conductivity is generated in the pressing direction (film thickness direction) by the pressing at the time of the above-mentioned bonding, and this pressing force is appropriately selected and is usually 5 to 50 kg / cm ² , particularly 10 to 50 kg / cm ² .
It is preferable to set the pressure to 30 kg / cm ² .

The anisotropic conductive film of the present invention has a conductivity of 10 Ω or less, particularly 5 Ω or less in the film thickness direction, and has a surface resistance of 10 ⁶ Ω or more, particularly 10 ⁹ Ω or more. Is preferred.

Further, the anisotropic conductive film of the present invention is made of, for example, FPC or TAB and an IT film on a glass substrate of a liquid crystal panel.
Used for the same applications as conventional anisotropic conductive films, such as used for connection between various terminals, such as connection with O-terminals. A crosslinked structure is formed during curing, and high adhesiveness, especially with metal Excellent adhesiveness, and excellent durability and heat resistance.

[0033]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

Examples and Comparative Examples The resins shown in Table 1 were dissolved in ethanol / toluene (50/50) and dissolved in 30% by weight.
A solution was prepared, and the components shown in Table 1 were mixed in an amount shown in Table 1 with respect to 100 parts by weight of polyvinyl butyral. A 15 μm film was obtained.

The above sample was used for bonding the flexible printed circuit board and the transparent electrode glass, and the separator was peeled off and positioned by a monitor. When an organic peroxide was used, the sample was heated and pressed at 160 ° C. for 30 seconds. When a sensitizer was used, irradiation was performed with a halogen lamp for 30 seconds, and the conduction resistance, lateral insulation resistance, and adhesive strength between the flexible printed circuit board and the transparent electrode glass were measured. In this case, the measurement was performed immediately after bonding and after storage at 85 ° C. and 85% RH for 600 hours (elapsed time). Table 1 shows the results.

[0036]

[Table 1]

[0037]

The anisotropic conductive film of the present invention has a high adhesive strength, a good workability, a high resistance to moisture and heat, and a conductivity in the thickness direction even after being kept for a long time at high humidity and high temperature. In addition, the insulating property in the surface direction is maintained, the adhesive strength is high, and the durability is excellent.

Claims (11)

[Claims] 1. An anisotropic conductive film in which conductive particles are dispersed in an adhesive and which is imparted with conductivity in the thickness direction by pressing in the thickness direction, wherein the adhesive comprises polyvinyl alcohol. An anisotropic conductive film, characterized in that it is a heat or photocurable adhesive mainly composed of a polymer obtained by introducing an aliphatic unsaturated group into a side chain of a polyvinyl acetal resin obtained by acetalization. 2. The anisotropic conductive film according to claim 1, wherein the polyacetal resin is a polyvinyl butyral resin. 3. The polymer has an aliphatic unsaturated group introduced by acid-modifying a side chain hydroxyl group of the vinyl alcohol unit of a polyvinyl butyral resin comprising a vinyl butyral unit, a vinyl alcohol unit and a vinyl acetate unit. The anisotropic conductive film according to claim 2, which is a film. 4. The anisotropic conductive film according to claim 3, which has been acid-modified with acrylic acid or methacrylic acid. 5. The anisotropic conductive film according to claim 3, wherein the vinyl alcohol unit of the polyvinyl butyral resin is 3 to 70 mol%. 6. The adhesive according to claim 1, wherein the adhesive contains an organic peroxide or a photosensitizer in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the polymer.
Item 8. The anisotropic conductive film according to item 1. 7. The adhesive comprises 0.5 to 80 parts by weight of at least one monomer selected from the group consisting of an acryloxy group-containing compound, a methacryloxy group-containing compound and an epoxy group-containing compound, based on 100 parts by weight of the polymer. The anisotropic conductive film according to any one of claims 1 to 6, wherein the film is added. 8. The adhesive according to claim 1, wherein the adhesive is obtained by adding 0.01 to 5 parts by weight of a silane coupling agent to 100 parts by weight of the polymer.
Item 8. The anisotropic conductive film according to item 1. 9. The anisotropic material according to claim 1, wherein the adhesive is obtained by adding 1 to 200 parts by weight of a hydrocarbon resin to 100 parts by weight of the polymer. Conductive film. 10. The anisotropic conductive film according to claim 1, wherein the conductive particles are contained in an amount of 0.1 to 15% by volume based on the polymer. 11. The conductive particles having a particle size of 0.1 to 10
The anisotropic conductive film according to claim 1, wherein the thickness is 0 μm.