JP2002109959A - Conductive paste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-solvent type conductive paste which enables to carry out various printings using the conductive paste without influencing the atmosphere. SOLUTION: The conductive paste contains conductive powder, a cation hardening resin component, a coating property and bending property improving material, and a dispersion property improving material as indispensable materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solventless conductive paste having low resistance and excellent coating properties and bending resistance.

[0002]

Conventionally, an information recording medium (RF-ID (Radio Frequency) for forming circuits on various electronic circuit boards and transmitting and receiving data in a non-contact state such as a non-contact type IC tag.
In the formation of an antenna for (IDentification)) and the like, the antenna is formed by printing using a conductive paste, so that mass production utilizing the advantages of the printing method can be performed. Incidentally, the conductive paste generally contains a solvent, and after printing, the pattern is fixed on the base material side by volatilization of the solvent. However, at present, various measures have been taken in the direction of reducing the burden on the environment as the increase in atmospheric CO ₂ and various types of air pollution have become problematic. It is becoming undesirable to directly discharge the solvent that evaporates in the process to the atmosphere. In order to prevent the release into the atmosphere, it may be possible to set up a recycling system or set up a detoxification facility. This has resulted in raising costs. Attempts have been made to make such conductive pastes solvent-free, but at present it has not yet achieved conductivity, flex resistance, and coating properties. In view of the above circumstances, an object of the present invention is to make a conductive paste solvent-free, and an object of the present invention is to enable various printings using a conductive paste without affecting the atmosphere.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in consideration of the above problems, and has been made in consideration of the above problems, and includes a conductive powder, a cationically curable resin composition, a coating / flexibility improving material, and a dispersibility improving material. The present invention solves the above-mentioned problems by providing a conductive paste characterized by comprising (1) and (2) as essential components. And in the present invention, the cation-curable resin composition is heat, light, an initiator for generating a cationic active species by irradiation with electromagnetic waves,
A mixture of the cationic active species and a reactive resin having a functional group that reacts with the cationic active species at a weight ratio of 0.01 / 100 to 10/100 can be used as an essential component. -The flexibility improving material can be an inorganic substance having a large specific surface area and a small apparent specific gravity and an average particle size, or a polymer compound having a low glass transition point. Further, in the present invention, the dispersibility improving material is a polyethylene glycol ester compound, a polyethylene glycol ether compound, a polyoxyethylene sorbitan ester compound, a sorbitan alkyl ester compound, an aliphatic polycarboxylic acid compound, a phosphate ester compound, a polyester acid. Examples thereof include an amide amine salt, a polyethylene oxide compound, and a fatty acid amide wax, and particularly preferably at least one of a sorbitan alkyl ester compound, a polyethylene oxide compound, and a fatty acid amide wax.

[0004]

DESCRIPTION OF THE PREFERRED EMBODIMENTS That is, the conductive paste of the present invention comprises a conductive powder, a cationically curable resin composition, a coating / flexibility improving material, and a dispersibility improving material as essential components. It is.

Conductive Powder The conductive powder is typically a metal powder, especially a silver powder. Further, a conductive metal other than silver, for example, a powder of gold, platinum, palladium, rhodium or the like may be added for controlling the resistance value and the solder erosion. These conductive powders may be used by mixing two or more kinds of powders having various shapes such as an average particle diameter, a specific surface area, and a tap density in order to control printability and sinterability well. Preferably, (1) among those called amorphous or dendritic, the average particle size is 0.05 to 1.0 μm, the specific surface area is 0.5 to 5.0 m ² / g, and the tap density is 0.3 to 1.0.
0 g / cm ³ , and (2) what is called scaly or flake-shaped, the average particle size is 1.0 to 10.0 μm.
m, specific surface area 0.5-5.0 m ² / g, tap density 1.
0 to 5.0 g / cm ³ as an essential component, (1)
It is preferable to use a mixture of (2) and (2) in a weight ratio of 60/40 to 95/5 in a proportion of 80% or more of the total conductive powder. Further, in order to improve the affinity of the powder with the organic composition in the paste and improve the dispersibility of the powder in the paste, the surface of the powder may be treated during or after the powder production process. preferable. The surface treatment agent is
Surfactants and organic compounds can be used.

Cation-Curable Resin Composition The cation-curable resin composition includes (A) an initiator for generating a cation-active species by irradiation with heat, light or electromagnetic waves;
(B) A blend of a reactive resin having a functional group that reacts with the active species at a weight ratio of 0.01 / 100 to 10/100 is an essential component. As the initiator (A), known initiators can be used, and aromatic sulfonium salt compounds,
Those which generate a cationic active species by an aromatic phosphonium salt compound, an aromatic iodonium salt compound, a diazonium salt compound, an iron arene complex compound or a combination thereof are preferred. Among these, for the salt compound, the counter anion is an antimony hexafluoride anion,
Those which are phosphorus hexafluoride anion or tetrakis (pentafluorophenyl) boron anion are preferred.
As the reactive resin (B), known resins can be used, and an alicyclic epoxy compound, an oxetane compound, an alkene oxide compound, a glycidyl ether compound, a vinyl ether compound, a propenyl ether compound, and the like are preferable, and particularly low viscosity. , Limonene dioxide, 3,
4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, 1,4-bis [(3
-Ethyl-3-oxetanylmethoxy) methyl] benzene is preferred. In any case, two or more kinds may be used in combination. The viscosity of these resins as a whole, in order to maintain the printing characteristics of kneading and paste with conductive powder,
1 to 5000 mPa · s (cpoise) at 25 ° C. is preferred, but 10 to 2000 mPa · s (cpoise)
Is more preferred. Further, in order to control reactivity, a hydroxy compound, a reaction aid serving as a hydrogen donor such as a hydrocarbon may be added, and in the case of a reaction by light, a phenothiazine derivative, a xanthone derivative, a thioxanthone derivative, an amino acid, etc. A photosensitizer such as a benzoic acid derivative, a polycyclic aromatic compound such as anthracene, phenanthrene, or perylene, or a combination thereof may be added. These addition amounts are based on the weight of (A).
0.01-100% is preferred.

Coating / Flexibility Improving Material The coating / flexibility improving material includes an inorganic substance having a large specific surface area and a small apparent specific gravity and an average particle diameter, or a high molecular compound having a low softening point. Specifically, (i) the specific surface area is 100 m ² / g or more, and the apparent specific gravity is 5
0 g / L or less, silica having an average primary particle size of 30 nm or less (for example, AEROSIL manufactured by Nippon Aerosil Co., Ltd.)
(Ii) a softening point of 100 ° C. or lower and a molecular weight of 1,000 to 500
(Iii) polyvinyl ether resin having a glass transition point of −30 ° C. or less (for example, Lutonal M40 manufactured by BASF, Inc.).
(A25) (iv) Phenoxy resin having a softening point of 100 ° C. or higher (refers to an oligomer or a polymer derived from a bisphenol compound and epichlorohydrin) (for example, Epicoat 1010, 401 manufactured by Yuka Shell Epoxy Co., Ltd.)
0P). These are respectively (ii) and (ii) due to the formation of a pseudo-crosslinked structure due to the cohesive force and the feather-like structure.
(i) increases the viscosity of the entire ink and lowers the Tg of the film, and (iv) contributes to the intended improvement in coating properties and flexibility by substantial polymerization by terminal crosslinking. These may be used alone or in combination. Among them, (i) the specific surface area is 100 m ² / g or more, the apparent specific gravity is 50 g / L or less, and the average primary particle size is 30
Particularly preferred are silica having a molecular weight of 1000 nm or less and (ii) a saturated polyester resin having a softening point of 100 ° C. or less and a molecular weight of 1,000 to 50,000.

[0008] The above-mentioned dispersibility-improving material is used to improve the dispersibility of the conductive powder in the conductive paste to improve the kneading during preparation and the preservability and coatability of the paste after adjustment. For example, polyethylene glycol ester compounds, polyethylene glycol ether compounds, polyoxyethylene sorbitan ester compounds, sorbitan alkyl ester compounds, aliphatic polycarboxylic acid compounds, phosphate ester compounds, amide amine salts of polyester acids And oxidized polyethylene-based compounds, fatty acid amide waxes, etc., and particularly preferred are sorbitan alkyl ester compounds, polyethylene oxide-based compounds, and fatty acid amide waxes, and these may be used alone or in combination.

The ratio of the weight of the conductive powder to the weight of the cationically curable resin composition and the coatability / flexibility improving material is preferably 50/50 to 95/5, more preferably 55/45 to 90. / 10. Further, within the above range, the weight ratio between the cationically curable resin composition and the coatability / flexibility improving material is preferably from 1/1 to 99/1, and more preferably from 2/1 to 80/1. . The dispersibility improving material is 0.01 to 10 with respect to the weight sum of the above.
% By weight, more preferably 0.1 to 5% by weight
It is.

Further, as long as the curing of the present invention is not impaired, known inorganic fillers such as silica, alumina and mica, various organic fillers, carbon powder, pigments, dyes, polymerization inhibitors, thickeners, thixotropic agents, A precipitation inhibitor, an antioxidant, a dispersant, various resins and the like may be added.

Known resins that can be added to the paste of the present invention can be used. For example, thermosetting resins such as phenolic resins, melamine resins, urea resins, xylene resins, alkyd resins, unsaturated polyester resins, acrylic resins, polyimide resins, furan resins, urethane resins, isocyanate compounds, cyanate compounds, polyethylene, polypropylene, and polystyrene , ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyethersulfone, polyarylate, Thermoplastic resins such as polyetheretherketone, polytetrafluoroethylene, and silicone resin; Combinations are also possible. The sum of these amounts is 35 to the total weight of the conductive powder, the cationically curable resin composition, the coatability / flexibility improver, and the dispersibility improver.
% Or less is preferable.

The method for preparing the conductive paste of the present invention includes a method in which the above-mentioned mixture is homogeneously stirred and mixed with a stirrer such as a homogenizer, and then further uniformly dispersed with a kneader such as a three-roll or kneader. It is not limited to. The viscosity of the paste of the present invention is preferably from 1000 to 1 in order to make the applicability and the print thickness after application appropriate.
It is preferably from 100,000 mPa · s (cpoise), more preferably from 10,000 to 500,000 mPa · s.

The substrate on which a pattern is formed by a known method such as screen printing, offset printing, or using a coater using the conductive paste of the present invention includes ceramic and glass, woven fabric of inorganic fiber or organic fiber, or Nonwoven fabrics, papers, composites of them with thermosetting resins or thermoplastic resins, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polyarylate, polyimides, polyamides and polyethers Amide, polyimide amide, polyacetal, polyether sulfone, polyether ether ketone, polysulfone, acrylonitrile-butadiene-styrene copolymer, polyvinyl chloride, silicone rubber You may use natural rubber, and synthetic rubber known ones such as plastic typified. In addition, on the surfaces of these substrates, chemical treatments such as coupling agent treatment and primer treatment, corona discharge treatment, plasma treatment,
Physical treatment such as ultraviolet treatment or polishing treatment may be performed.

In order to form a pattern on a substrate using the conductive paste of the present invention, a known method may be used, but usually, a coating is applied by a screen printing method or the like. In this case, the printing thickness can be arbitrarily controlled by adjusting the material of the screen (such as polyester, polyamide, or stainless steel), the mesh, the tension, and the viscosity of the paste.
5 to 100 μm, more preferably 10 to 8
0 μm.

To cure the paste of the present invention,
Electromagnetic waves including heat and light can be used, and a mixture of these methods may be used. As a heating method, a known method may be used, and an infrared ray or a high frequency may be used in combination. Also,
As electromagnetic waves including light, from microwaves to infrared, visible, ultraviolet, vacuum ultraviolet, and X-rays, wavelengths of 1 to 1
It can be used arbitrarily within a range of 10 ⁻¹² m, and a known electromagnetic wave source can be used. As a general light source in the wavelength range from infrared to ultraviolet light, use a known light source such as a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an electrodeless discharge lamp, an excimer lamp, a metal halide lamp, a xenon lamp, various lasers, and a semiconductor laser. Is possible, but 300
High pressure mercury lamps and metal halide lamps, which have a relatively large energy intensity distribution in the wavelength range of -500 nm, are particularly preferred. The light source lamp intensity is preferably 40 W / cm or more, more preferably 80 W / cm or more. Integrated sight required for photocuring is preferably 100~50000mJ / cm ² in the wavelength range of 300 to 500 nm, more preferably 500~10000mJ / cm ^2.

Hereinafter, a description will be given of an embodiment in which a conductive paste of the present invention is produced, and a pattern is printed using the paste to form a conductive path. However, the scope of the present invention is not limited to these examples. Examples 1 to 13 First, a cationically curable resin, a coatability / flexibility improver, and a dispersibility improver were mixed in a formulation as shown in Table 1, and the mixture was stirred and homogenized for 30 minutes or more under light-shielded room temperature. I do. If necessary, heat to dissolve. After returning to room temperature, add a cationic initiator, stir and homogenize, further mix silver powder,
The conductive paste of the present invention is obtained by mixing with a stirrer and further performing high shear kneading with a kneader. Using the above conductive paste, screen printing was performed on a substrate with a pattern of 1 mm width × 1 m length on a screen plate having a 180-mesh emulsion thickness of 15 μm. The thickness of the printing layer was about 15 μm. The paper used as the base material is NP manufactured by Nippon Paper Industries Co., Ltd.
I-55. As the polyethylene terephthalate film, Lumirror S manufactured by Toray Industries, Inc. was used. The curing reaction is
The thermal reaction was performed at 150 ° C. for 30 minutes in a ventilation oven, and the photoreaction was performed at 7 m / cm ² using a 160 W / cm metal halide lamp at 1100 mW / cm ² (measured by UVR-T35 manufactured by Topcon Corporation). mi
n. Irradiation was performed 5 times with a conveyor-type irradiation device.

In the base material used, no significant deterioration such as coloring, heat shrinkage, softening, embrittlement and carbonization was observed in any case. The surface resistance was determined by measuring the resistance between both ends of the pattern after curing. Table 1 shows the results. Coating properties are very good = ◎, good = ○, problematic from the comprehensive viewpoint of elongation of ink, detachment of printing plate, fine line pitch, reproducibility, etc.
Δ, coating impossible = determined by ×. The bending test was performed at 25 ° C. using a 2 kg cylindrical weight with a cross-sectional area of about 20 cm ² .
R = 0, inner fold 30 seconds load → 30 seconds left → outer fold 30 seconds load → 1 minute left → resistance value measurement, the resistance value change is + 5% or less = ◎, more than + 5% + 10% or less = ○ , +
More than 10% + less than 20% = △, more than + 20% or disconnection =
Judged by ×.

[0018]

[Table 1]

Next, Table 2 shows Comparative Examples 1 to 7. Conductive pastes were prepared in the same manner as in Examples 1 to 13 using the formulations shown in Table 2, and evaluated after printing and curing.
The evaluation criteria are the same.

[0020]

[Table 2]

Tables 1 and 2 used in the above examples were used.
The description of the material inside is shown below. Silver powder / E-20: Silvest E-20, manufactured by Tokuriki Honten, TC-20E: Silvest TC-, manufactured by Tokuriki Honten
20E Cationic curable resin / limonene dioxide: limonene dioxide (1-methyl-4- (2-methyloxiranyl) manufactured by Elphatochem Mori
-7-oxabicyclo [4.1.0] heptane), UVR-6105: CYRAC manufactured by Union Carbide
URE UVR-6105 (3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate), XDO: XDO (1,4-bis) manufactured by Toa Gosei Co., Ltd.
[(3-ethyl-3-oxetanylmethoxy) methyl] benzene)

Cation initiator / SP-170: Adeka Optomer SP-170 (aromatic sulfonium salt compound) manufactured by Asahi Denka Kogyo Co., Ltd. CP-66: Adeka Opton CP manufactured by Asahi Denka Kogyo Co., Ltd.
-66 (aromatic sulfonium salt compound), RHODORSIL 2074: RHO manufactured by Rhodia
DORSIL PHOTOINITIATOR2074
(Aromatic iodonium salt compound)

Coating / flexibility improving material / Aerosil 200CF: Nippon Aerosil Co., Ltd. silica Aerosil 200CF (specific surface area 200 m ² / g,
Apparent specific gravity 30 g / l, primary particle average diameter 12 nm), Byron 500: polyester Byron 500 manufactured by Toyobo Co., Ltd. (softening point -20 to 10 ° C, molecular weight 5000)
ト ナ ー 25000), Lutonal M40: polyvinyl methyl ether from BASF Lutonal M40 (glass transition point -49 ° C.), Epicoat 4010P: Epoxy Epicoat 4010P from Yuka Shell Epoxy (softening point 135 ° C.)

Dispersibility improving material / OP-80R: Nissan Nonion OP-80R (sorbitan alkyl ester compound) manufactured by NOF CORPORATION, 6900-20X: DISPARON 6900-20X, 4200-20 (fatty acid amide wax manufactured by Kusumoto Kasei Co., Ltd.) ): DISPARON 4200-20 (polyethylene oxide compound) manufactured by Kusumoto Kasei Co., Ltd.

[0025]

As described above, the conductive paste of the present invention comprises a conductive powder, a cation-curable resin composition,
It is characterized by comprising a coatability / flexibility improving material and a dispersibility improving material as essential components. Thus, since the conductive paste of the present invention is solvent-free, the load on the environment is extremely small compared to the conventional solvent-volatile conductive paste,
A manufacturing process with a good working environment can be constructed. Further, the printed pattern becomes voidless because it is solventless, and a conductive pattern with few defects can be easily obtained. In addition, sufficient conductivity, coating properties, and bending resistance can be ensured, and the conventional conductive paste can be easily replaced. Further, the cationically curable resin composition is heat, light, an initiator that generates a cationic active species by irradiation with electromagnetic waves,
If it contains a reactive resin having a functional group that reacts with the cationic active species, the effect of excellent practicality, such as shortening of the processing time of the conductive pattern, downsizing of the processing facility, and improvement of energy efficiency can be achieved. Is played.

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Claims (4)

[Claims] 1. A conductive paste comprising, as essential components, a conductive powder, a cationically curable resin composition, a coatability / flexibility improving material, and a dispersibility improving material. 2. The method according to claim 1, wherein the cationically curable resin composition is heated,
An initiator for generating a cationic active species by irradiation with light or electromagnetic waves and a reactive resin having a functional group that reacts with the cationic active species are used in a weight ratio of 0.01 / 100 to 10/100.
2. The conductive paste according to claim 1, wherein the conductive paste is an essential component. 3. The conductive paste according to claim 1, wherein the coating property / flexibility improving material is an inorganic substance having a large specific surface area, a small apparent specific gravity and a small average particle diameter, or a polymer compound having a low softening point. 4. The dispersibility improving material is a polyethylene glycol ester compound, a polyethylene glycol ether compound, a polyoxyethylene sorbitan ester compound, a sorbitan alkyl ester compound, an aliphatic polycarboxylic acid compound, a phosphate ester compound, or an amide of a polyester acid. The conductive paste according to claim 1, which is at least one of an amine salt, a polyethylene oxide compound, a fatty acid amide wax, a sorbitan alkyl ester compound, a polyethylene oxide compound, and a fatty acid amide wax.