JPH11154417A - Silver paste for forming electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart a thixotropic property, and to provide an excellent aptitude for screen printing and preserving stability by constituting it of a silver particle, a binder resin, a solvent and a thickener. SOLUTION: This paste is obtained by adding a thickener to publicly known silver paste which can be obtained at the market and can be easily self-perpared. A desirable adding quantity of the thickener is set to a range of about 0.01 to 10 pts.wt. per 100 pts.wt. of the solid content of the silver paste. For example, hydrogenated castor oil and aluminum stearate are used as the thickener when the silver paste is an organic solvent type, and for example, hydroxyethyl cellulose and methyl cellulose are used in the case of an aqueous type. Resin of not leaving carbonate in a pattern by baking is required as a binder resin, and resin developable after exposure may be acceptable as the binder resin in the case of being photosensitive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a silver paste for forming an electrode, and more particularly to a silver paste for forming an electrode for forming an electrode pattern in various electronic devices.

[0002]

2. Description of the Related Art Conventionally, various types of electronic devices such as plasma display panels, liquid crystal displays, and the like, thermal heads, integrated circuits, and the like require the formation of fine electrode patterns. For example, a method in which a conductive film formed by vapor deposition, sputtering, plating, screen printing, or the like is etched by photolithography, or a predetermined pattern is formed by pattern printing by screen printing using a pattern forming paste having desired characteristics. A screen printing method or the like is used in which an electrode pattern is formed by forming the above pattern, drying and firing.

[0003] Among the above-mentioned various methods, the method using etching can form an electrode pattern with high accuracy, but has a problem that the production cost is high because of the etching step. Also, for example, the image display device tends to have a large screen, and when an electrode pattern is formed on a substrate corresponding to this large screen by an etching method,
A large number of large-scale thin film forming apparatuses, exposure apparatuses, etching apparatuses, and the like are required, and there is a problem that the cost method becomes more problematic in order to cope with a large screen by the above-described etching method. In contrast to the above method, the screen printing method does not have an etching step, the steps are simpler than the above-mentioned etching method, and it is easy to cope with a large screen. Have been.

[0004]

A typical example of a conductive paste used for forming an electrode pattern in the above screen printing method is a silver paste in which silver particles are dispersed in a vehicle. , Low thixotropic properties, when used for screen printing, printability is insufficient, plate separation after printing is insufficient, or when the paste is applied thick, the pattern formed , And it was difficult to form a pattern having sharp edges.

Further, the silver particles in the silver paste settle violently, and the storage stability of the paste is insufficient. Even for short-term storage, re-dispersion of silver particles is required during use, and long-term storage is required. In the case of (1), there is a problem that it becomes difficult to redisperse the silver particles and cannot be reused. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the conventional silver paste and to provide an electrode-forming silver paste excellent in screen printing suitability and storage stability.

[0006]

The above object is achieved by the present invention described below. That is, the present invention is a silver paste for forming an electrode, comprising silver particles, a binder resin, a solvent, and a thickener. According to the present invention, by adding an appropriate amount of a thickener to a conventional silver paste, a suitable thixotropic property is imparted to the silver paste, and as a result, for forming an electrode having excellent screen printing suitability and storage stability. A silver paste is provided.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments of the invention. The silver paste for forming an electrode of the present invention can be obtained by adding a thickener to a conventionally known silver paste that can be obtained from the market.
Conventionally known silver pastes include, for example, trade name Fo
del (DC201), 7713 (both manufactured by DuPont), D-590 (manufactured by ESL) and the like can be easily prepared.

As the silver paste, there are an organic solvent-based silver paste and a water-based silver paste, both of which can be used in the present invention. The silver particles used in these silver pastes usually have a particle size of about 0.5 to 10 μm.
And about 50-95 of the solid content of the silver paste.
Used in weight percent amounts. The resin binder is used in an amount of about 5 to 50% by weight of the solid content of the silver paste. The other main component is mainly a solvent, which is used in such an amount that the solid content of the silver paste becomes about 50 to 95% by weight.

Since the silver paste needs to be fired after pattern formation to burn off organic substances, the binder resin used is a resin that does not leave carbides in the pattern by firing, for example, ethyl cellulose,
Methyl cellulose, nitrocellulose, cellulose acetate, cellulose propionate, cellulose resin such as cellulose butyrate, methyl (meth) acrylate, ethyl (meth) acrylate, normal butyl (meth) acrylate, isobutyl (meth) acrylate,
Isopropyl (meth) acrylate, 2-ethylmethyl (meth) acrylate, 2-hydroxyethyl (meth)
Suitable binder resins include polymers such as acrylates and hydroxypropyl (meth) acrylates or poly (meth) acrylates composed of copolymers of these monomers, poly-α-methylstyrene, polyvinyl alcohol, polybutene, and the like.

A feature of the present invention is that a thickener is added to the silver paste as described above. When the silver paste is an organic solvent system, as a thickener, for example, castor oil with water, aluminum stearate, zinc stearate, aluminum octylate, fatty acid amide, polyethylene oxide, dextrin fatty acid ester,
Dibenzylidene sorbitol, vegetable oil-based polymerized oil, surface-treated calcium carbonate, organic bentonite, silica, etc. are used.
It ranges from about 0.01 to 10 parts by weight per part by weight.
When the silver paste is aqueous, for example, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, sodium alginate, casein, sodium caseinate, xanthan gum, polyvinyl alcohol, modified polyether urethane, poly (acrylic acid-
Acrylate), montmorillonite and the like are used, and the preferable addition amount thereof is in the range of about 0.01 to 10 parts by weight per 100 parts by weight of the solid content of the silver paste.

The silver paste for forming an electrode of the present invention may be a non-photosensitive paste or a photosensitive paste. Preferred examples of the resin binder in the case of a non-photosensitive paste are as described above. As the binder resin in the case of a photosensitive resin, any photosensitive resin that can be subjected to development processing after exposure can be used. It may be resin. Suitable photosensitive resins contain at least an alkali-developable resin, a photopolymerizable oligomer and / or a monomer and a photopolymerization initiator, and are volatilized by firing,
It is a photosensitive resin that does not leave carbide in the electrode formed by decomposition.

Examples of the alkali-developable polymer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate and isobutyl acrylate. , Isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n
-Pentyl acrylate, n-pentyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-octyl acrylate,
n-octyl methacrylate, n-decyl acrylate, n-decyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, styrene, α-methylstyrene, one or more of N-vinyl-2-pyrrolidone, acrylic acid, methacrylic acid, dimer of acrylic acid (for example,
Toa Gosei Co., Ltd. M-5600), 2-methacryloyloxyethyl succinate, 2-acryloyloxyethyl succinate, 2-methacryloyloxyethyl phthalate, 2-acryloyloxyethyl phthalate, 2-methacryloyl hexahydrophthalate Oxyethyl, 2-acryloyloxyethyl hexahydrophthalate, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetic acid, polymers or copolymers of one or more of these acid anhydrides, etc., cellulose derivatives such as ethyl cellulose, etc. Is mentioned.

Further, there may be mentioned, for example, polymers obtained by adding an ethylenically unsaturated compound having a glycidyl group or a hydroxyl group to the above copolymer, but the invention is not limited thereto. The molecular weight of the above polymer is 5,000-30
0000, preferably 10,000 to 150,000
Is preferable. Further, other polymers such as a methacrylate polymer, an acrylate polymer, a cellulose derivative, an N-vinylpyrrolidone polymer, and polyvinyl alcohol may be blended.

As the reactive monomer constituting the photosensitive resin composition, a compound having at least one polymerizable carbon-carbon unsaturated bond can be used. Specifically, allyl acrylate, benzyl acrylate, butoxyethyl acrylate, butoxyethylene glycol acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, 2-ethylhexyl acrylate, glycerol acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl Acrylate, isobonyl acrylate, isodexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate,
Phenoxyethyl acrylate, stearyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, 1,3
-Propanediol acrylate, 1,4-cyclohexanediol diacrylate, 2,2-dimethylolpropane diacrylate, glycerol diacrylate,
Tripropylene glycol diacrylate, glycerol triacrylate, trimethylolpropane triacrylate, polyoxyethylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethylene oxide-modified pentaerythritol triacrylate, ethylene oxide-modified pentaerythritol tetra Acrylate, propylene oxide-modified pentaerythritol triacrylate, propylene oxide-modified pentaerythritol tetraacrylate, triethylene glycol diacrylate, polyoxypropyltrimethylolpropane triacrylate, butylene glycol diacrylate, 1,2,4-butanetriol triacrylate , 2,2,4-trimethyl-1,3
-Pentanediol diacrylate, diallyl fumarate, 1,10-decanediol dimethyl acrylate,
Examples thereof include pentaerythritol hexaacrylate, those obtained by changing the above acrylate to methacrylate, γ-methacryloxypropyltrimethoxysilane, 1-vinyl-2-pyrrolidone, and the like. In the present invention, the above-mentioned reactive monomers can be used as one kind or a mixture of two or more kinds or as a mixture with other compounds.

The photopolymerization initiators constituting the photosensitive resin composition include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, 4,4-bis (diethylamine) benzophenone,
α-amino acetophenone, 4,4-dichlorobenzophenone, 4-benzoyl-4-methyldiphenylketone, dibenzylketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2- Hydroxy-2-methylpropiophenone, p-tert-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone,
-Chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethylketal, benzylmethoxyethylacetal, benzoinmethylether, benzoinbutylether, anthraquinone, 2-tret-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benz Anthrone, dibenzsuberone, methyleneanthrone, 4-azidobenzylacetophenone,
2,6-bis (p-azidobenzylidene) cyclohexane, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadione-2- (o-methoxycarbonyl) oxime, 1-
Phenyl-propanedione-2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o-
Benzoyl) oxime, Michler's ketone, 2-methyl-
[4- (methylthio) phenyl] -2-morpholino-
1-propane, 2-benzyl-2-dimethylamino-1
-(4-morpholinophenyl) -butanone-1, naphthalenesulfonyl chloride, quinoline sulfonyl chloride, n-phenylthioacridone, 4,4-azobisisobutyronitrile, diphenyl disulfide, benzothiazole disulfide, triphenylphosphine,
Examples include a combination of a photoreducing dye such as camphorquinone, carbon tetrabromide, tribromophenylsulfone, benzoin peroxide, eosin, and methylene blue with a reducing agent such as ascorbic acid and triethanolamine. In the present invention, one or more of these photopolymerization initiators can be used.

Further, in the above-mentioned thermoplastic resin and photosensitive resin composition, sensitizers, polymerization terminators, chain transfer agents, leveling agents, dispersants, plasticizers, stabilizers, defoamers are added as additives. , A thickener, a suspending agent, a release agent, and the like, if necessary.

Examples of the solvent used in the present invention include alcohol solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol and i-propyl alcohol; cellosolve solvents such as methoxy alcohol and ethoxy alcohol; Carbitol solvents such as ethoxyethanol and ethoxyethoxyethanol, ester solvents such as ethyl acetate, butyl acetate, methyl methoxypropionate, ethyl ethoxypropionate and ethyl lactate; ketone solvents such as acetone, methyl isobutyl ketone and cyclohexanone; Methoxyethyl acetate,
Cellosolve acetate solvents such as ethoxyethyl acetate and ethyl cellosolve acetate; carbitol acetate solvents such as methoxyethoxyethyl acetate, ethoxyethoxyethyl acetate; ether solvents such as diethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and tetrahydrofuran; N-dimethylformamide, N,
N-dimethylacetamide, aprotic amide solvents such as N-methylpyrrolidone, lactone solvents such as γ-butyrolactone, benzene, toluene, xylene, unsaturated hydrocarbon solvents such as naphthalene, n-heptane, n-hexane, Organic solvents such as saturated hydrocarbon solvents such as n-octane are exemplified.

Among these solvents, cellosolve acetate solvents such as ethyl cellosolve acetate such as methoxyethyl acetate, ethoxyethyl acetate and ethyl cellosolve acetate; carbitol acetate solvents such as methoxyethoxyethyl acetate and ethoxyethoxyethyl acetate; Preferred are ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and propylene glycol diethyl ether, and ester solvents such as methyl methoxypropionate, ethyl ethoxypropionate and ethyl lactate.

The essential components of the silver paste of the present invention are as described above, but other various additives can be added as needed. Examples of the additives include a low-melting glass frit powder, a sensitizer, a polymerization terminator, a chain transfer agent, a leveling agent, a dispersant, a plasticizer, a stabilizer, and an antifoaming agent.

When the electrode-forming silver paste of the present invention as described above is non-photosensitive, a desired electrode pattern is formed on the substrate by screen printing or the like, and after drying, the electrode pattern is heated to a temperature at which the glass substrate does not deteriorate. For example, about 400-6
By firing at a temperature of 50 ° C., a desired electrode pattern can be formed. On the other hand, when the electrode-forming silver paste of the present invention is photosensitive, the electrode pattern can be formed by screen printing in the same manner as described above, and the electrode-forming silver paste is solid-coated on the substrate. After drying, the electrode pattern is exposed to the dried film via a photomask to form a latent image, and the latent image is developed with, for example, an alkaline developer to form a desired electrode pattern. Preferably, by forming a silver paste for electrode formation on the substrate by screen printing, a pattern slightly thicker than the desired electrode pattern, and exposing and developing this through a photomask having an accurate pattern, Waste of expensive silver paste for forming electrodes can be suppressed.

[0021]

Next, the present invention will be described more specifically with reference to examples. In the description, parts and% are based on weight unless otherwise specified. Example 1 Photosensitive silver paste DC201 (Fode) manufactured by DuPont
In 1), since the thixotropic property is low, the suitability for screen printing is low, the separation of the plate is poor, and pinholes are generated on the coating surface, and when the pattern is printed, the edge of the pattern flows and bleeds. Then, Troy Six XYZ (water-added castor oil-based thickener, manufactured by Troy Chemical Co.) or Dispalon # 305 (manufactured by Kusumoto Kasei) was added to the above paste.
%, The paste was given thixotropic properties as shown in FIG. When screen printing was performed using the paste to which the thickener was added, the pinholes on the application surface that were seen before the addition were not seen in the paste after the addition, and the edges when performing pattern printing were not Sharpening was achieved by adding a thickener.

Example 2 A photosensitive silver paste having the following components was prepared. 100 parts of a polymer obtained by adding 7 mol% of glycidyl methacrylate to a methyl methacrylate / methacrylic acid copolymer 100 parts of ethylene oxide-modified trimethylolpropane acrylate 60 parts of a polymerization initiator (Irgacure 907 manufactured by Ciba Geigy KK) 15 parts of dipropylene glycol Monomethyl ether 100 parts ・ Silver powder 650 parts ・ Glass frit (softening point 550 ° C, coefficient of thermal expansion 80 × 10 ^-7 / ° C) 40 parts

Since the paste has Newtonian fluid properties and does not have thixotropic properties, it is poor in screen printing suitability and pinholes occur on the coated surface. In addition, solids settle during storage and are easily separated. Then, when 5 parts of a thickener (Troixix XYZ) was added to the paste, thixotropic properties were exhibited, printability was improved, and pinholes on the application surface were not generated. In addition, storage stability was improved, and sedimentation of solids did not occur.

[0024]

According to the present invention, a suitable thixotropic property is imparted to a silver paste by adding an appropriate amount of a thickener to a conventional silver paste, and as a result, screen printing suitability and storage stability are obtained. This provides a silver paste for forming an electrode which is excellent in quality.

[Brief description of the drawings]

FIG. 1 is a view for explaining the thixotropic properties of a silver paste of Example 1.

Claims (3)

[Claims] 1. A silver paste for forming an electrode, comprising silver particles, a binder resin, a solvent, and a thickener. 2. The silver paste for forming an electrode according to claim 1, comprising a photosensitive resin as a binder resin. 3. The method according to claim 1, wherein the content of the thickener is 0.0% of the silver paste.
The silver paste for forming an electrode according to claim 1, wherein the content is in the range of 1 to 10% by weight.