JPH05209139A - Photosensitive conductive paste composition and its storage - Google Patents

Abstract

PURPOSE:To provide the subject photosensitive conductive paste composition for making a pattern using photolithography, subsequently baking it and forming a conductive material layer of copper and to provide the subject method for storing the same paste composition. CONSTITUTION:The objective photosensitive conductive paste composition can be obtained by blending a copper powder of remarkably low oxygen content with a photosensitive resin composition having a carboxylic group. The objective method for storing the paste composition is characterized by storage in an atmosphere of remarkably low oxygen content. The paste composition enables formation of a thick-film fine pattern having a high conductivity and the storage method enables remarkable improvement of the shelf life of the photosensitive conductive paste composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photopolymerizable conductive paste composition for patterning by photoengraving technique and forming a metal conductor layer by a subsequent firing step, and a storage method thereof.

[0002]

2. Description of the Related Art Conventionally, a non-photosensitive paste material in which an inorganic binder is mixed with an organic powder is screen-printed to obtain a patterned thick film insulator, resistor or conductor layer on a high density multilayer circuit board. It has been practiced to form a pattern on a substrate by using a printing technique such as the above, and to scatter the organic binder in the subsequent firing step.

However, in the screen printing method, an insulator having a line width of 100 μm or less, which is industrially stable,
It has been difficult to form patterns such as resistors and conductors. Further, near this limit, there is a problem that the screen plate making accuracy is poor and an error is likely to occur, which makes it difficult to increase the pattern density. Therefore, research has been conducted on a photosensitive paste in which a photosensitive resin composition and an inorganic powder are mixed for the purpose of obtaining a high-density pattern that exceeds the limit of the screen printing method. In particular, the conductor paste material, which has a high demand for fine wiring patterns, is important,
Regarding this conductor paste composition, studies have been conducted on a photosensitive conductive paste composition in which a photosensitive resin and a metal powder are mixed (for example, JP-A Nos. 54-121967 and 54-13591). Gazette, JP-A-59-14
3149, European Patent Application Publication 414166
No. 414167).

In order to obtain higher electric conductivity, low residual carbon during firing and high dimensional stability due to volume shrinkage, it is necessary to contain extremely high metal powder. In addition, the finer the pattern to be formed, the higher the electrical conductivity of the metal pattern is required. However, in general, a system containing metal powder has low light transmittance, and it is difficult to form a pattern using a photosensitive conductive paste material containing metal powder in a high concentration. For example, in the above-mentioned JP-A-54-121967, JP-A-54-13591, and JP-A-59-143149, in the description of the examples containing the metal powder, the largest amount of the metal powder was used. The system included was 45% by weight. Pattern formation using photolithography in a copper paste composition containing 70% by weight of copper powder in a photosensitive resin component composed of polymethylmethacrylate, a bifunctional acrylate monomer and a benzyldimethylketal polymerization initiator described in this patent. However, the curability in the depth direction of the exposed portion was insufficient and a pattern could not be formed.

European Patent Application Publication No. 4141
No. 67, in the description of the example in which 82 wt% of copper powder is contained, a sheet resistance value of 4 is obtained at a film thickness of about 10 μm.
mΩ / □ has been obtained, but this value is only about half the electrical conductivity of bulk copper, and in order to obtain a conductor with higher electrical conductivity, higher concentration of copper Must be included.

An example of using a polymer containing a carboxyl group is the above-mentioned European Patent Application Publication No. 414166,
No. 414167. The polymers used in the examples of these patents had a very low molecular weight of 7,000, which was insufficient for forming fine patterns.

[0007]

In order to form a fine pattern, as is clear from the comparison between Example 1 and Comparative Example 3 of the present invention, a polymer having a relatively large molecular weight of 60,000 or more is used, It is necessary to increase the contrast of the solubility of the exposed area and the unexposed area in the developing solution. However, when a polymer having a molecular weight of 30,000 or more and having a monomer unit containing a carboxyl group in an amount of more than 5% by weight is used, the viscosity of the prepared paste composition is so high that the fluidity of the paste composition is completely lost. Also, a new problem, which was completely unexpected from the prior art, was caused that the solubility of the unexposed portion not irradiated with light was lowered.

By the way, a conventional technique using a polymer containing no carboxyl group, for example, JP-A-54-121 is used.
In systems similar to those described in JP 967, JP 54-13591 A and JP 59-143149 A, surface oxidation of oxygen present in an oxygen content exceeding 0.5 wt. Even in a system using an advanced copper powder, a decrease in photocurability is not particularly seen as compared with a system in which the oxygen content is reduced as much as possible, and extremely high viscosity of the paste composition and solubility of an unexposed portion No problems such as decline were observed. Further, no decrease in photocuring sensitivity of the photopolymerizable conductive paste composition during storage in air was particularly observed.

The present invention is capable of forming a thick film fine pattern having a very high electric conductivity, contains a metal powder in a high concentration, and has a long-term stable paste composition and long-term stable storage. The purpose is to provide a method.

[0010]

The present inventors have found that a photosensitive resin composition containing a monomer unit having a carboxyl group in the repeating unit of a polymer in an amount of more than 1 mol% and an oxygen content of 0. In the photopolymerizable conductive paste composition with 2 wt% or less of the copper-based metal powder, the decrease in the solubility of the unexposed area can be suppressed, and since the metal powder is contained in a high concentration, the electrical conductivity of the bulk metal copper is reduced. It is possible to form a fine pattern having extremely high electric conductivity comparable to that of the paste composition, and by storing the paste composition in an atmosphere in which oxygen is blocked, the paste composition is in a good storage state. I found that I can get new.

That is, in the present invention, a composition containing a copper-based metal powder having a very small amount of surface oxide and a polymer containing a carboxyl group is effective as a conductive paste, and as a storage method thereof, an inert gas having a very low oxygen concentration is used. By storing in a gas atmosphere or under vacuum, it is possible to suppress the extremely high viscosity and the deterioration of the solubility of the unexposed portion that would lose the fluidity of the paste composition, which has not been a problem at all in the past. It is based on the discovery of totally unexpected effects. Moreover, by using a polymer containing a monomer unit having a carboxyl group in an amount of more than 1 mol% and having a molecular weight of 60,000 or more, it is possible to obtain a fine pattern having a high solubility contrast between the exposed portion and the unexposed portion in a developing solution. The discovery that it was possible led to the completion of the present invention.

The present invention is as follows. 1. 20 to 500 parts by weight of a copper-based metal powder having an oxygen content of 0.2% by weight or less is added to 5 parts by weight of a photosensitive resin composition consisting of the following three components (A), (B) and (C). A photopolymerizable conductive paste composition comprising: (A): A polymer formed from one or more ethylenically unsaturated compounds, the weight of which contains at least 1 mol% of monomer units of ethylenically unsaturated compounds containing one or more carboxyl groups. 50 parts by weight of a polymer having an average molecular weight of 50,000 or more (B): 10 to 300 parts by weight of a polymerizable polyfunctional monomer (C): 0.1 to 10 parts by weight of a photopolymerization initiator 1. The method for storing a photopolymerizable conductive paste composition according to claim 1, wherein the method is stored in an inert gas atmosphere having an oxygen concentration of 1000 ppm or less or under a vacuum.

In the photopolymerizable conductive paste composition of the present invention, patterning by photolithography is possible even if the metal powder is contained in a high concentration of 83% by weight or more. In addition, this paste material made it possible to form a metal fine pattern having extremely high electrical conductivity in the firing process following exposure and development. The present invention provides a photopolymerizable compound obtained by adding a polymerizable polyfunctional monomer and a photopolymerization initiator to a polymer to impart photosensitivity, and further mixing a conductive metal powder with a photosensitive resin composition formed from the compound. A conductive paste composition (hereinafter referred to as a paste composition) is provided. Further, a conductor layer containing a metal as a main component is formed by a step of exposing and developing this composition and a step of baking thereafter.

The photosensitive resin composition in the present invention comprises three components of a polymer, a polymerizable polyfunctional monomer and a photopolymerization initiator, which will be described in detail below. The polymer used in the present invention is a polymer formed from one or more kinds of ethylenically unsaturated compounds, and contains at least 1 mol% of a monomer unit of an ethylenically unsaturated compound containing one or more carboxyl groups. And a weight average molecular weight (hereinafter, referred to as molecular weight) of 60,000 or more. Although various compounds can be used as the ethylenically unsaturated compound of the polymer used in the present invention, a monomer which is easily depolymerized or decomposed by heat to form a polymer in which carbon and other substances hardly remain is preferable. As examples of the monomer unit usable in the present invention, various polymerizable vinyl monomers can be used, and examples thereof include compounds represented by the following chemical formula 1 and cyclic acid anhydride type compounds such as maleic anhydride.

[0015]

[Chemical 1]

[Wherein R₁, R₂, R₃, R_FourIs hydrogen
Child, halogen atom, carboxyl group, ester group, amine
Group, acyl group, alkoxy group, hydroxyl group, ace
Toxyl group, lower alkyl group, phenyl group, or halo
Gen atom, carboxyl group, ester group, hydroxyl
Substituents such as group, amino group, acrylic group, methacrylic group
A lower alkyl group substituted by or a general formula-COO
R_FiveOr-CONHR _Five[In the formula, R_FiveIs a hydrogen atom,
Sil group, alkyl group having 1 to 18 carbon atoms, or alkyl group
Ester group, hydroxy group, allyl group, acyl group,
Tylene oxide group, carboxylic anhydride group, acrylic group,
Substitution product with methacrylic group, or formula (CH₂-C
HR₆-O)_nR₇(In the formula, R₆Is hydrogen or methyl group, R
₇Is an alkyl group having 1 to 4 carbon atoms, n = 1 to 9)
Groups, or halogen atoms, alkyl groups, haloalkyl groups
With a substituent such as a kill group, a carboxyl group, or a hydroxyl group
A substituted phenyl group is shown. ] As an example,
For example, the following monomers may be mentioned. Methylmetha
Acrylate, ethyl methacrylate, butyl methacrylate
Relate, isobutyl methacrylate, lauryl meta
Acrylate, methyl acrylate, ethyl acrylate
Butyl acrylate, stearyl acrylate, 2
-Hydroxymethacrylate, 2-hydroxymethyl
Methacrylate, hydroxypropylmethacrylate
, Hydroxybutyl methacrylate, glycidyl meth
Methacrylates such as tacrylate or acrylate
, Styrene, chloromethylstyrene, α-methyl
Styrene, hydroxystyrene, ethylene, vinyl chloride
And vinyl acetate.

Of these, polymers containing methylmethacrylate, styrene and α-methylstyrene are particularly preferable because they have particularly excellent thermal decomposability even when fired in a non-oxidizing atmosphere. As an ethylenically unsaturated compound having a carboxyl group which is an example of the unsaturated compound represented by the above chemical formula 1, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and the like are preferable. is there.

Substituents that readily react with H ₂ O or alkali to form carboxylic acids and carboxylates, such as various carboxylic acid anhydride groups, also exhibit the same effect as the carboxyl group. Examples thereof include the above-mentioned carboxyl group obtained by reacting a lower fatty acid anhydride, a lower fatty acid halide or the like with a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid. Mention may be made of carboxylic acid anhydrides of ethylenically unsaturated compounds. Alternatively, a cyclic acid anhydride type compound such as maleic anhydride can be used.

The polymer used usually has a weight average molecular weight of 6
Between 3 and 3 million polymers are used. Use of a low molecular weight polymer having a weight average molecular weight of less than 60,000 is not preferable because the contrast of solubility between the exposed area and the unexposed area in the developing solution is deteriorated. On the other hand, if the molecular weight exceeds 3,000,000, the solubility in a solvent and a developing solution deteriorates, which becomes a problem in the step of preparing and developing the paste composition. Also,
The increase in viscosity of the paste composition becomes extremely remarkable, which is not preferable. A polymer having a molecular weight of 60,000 to 1,000,000 is more preferable, and a polymer having a molecular weight of 100,000 to 1,000,000 is more preferable. Further, it is preferable to use a polymer having a uniform molecular weight distribution in order to improve the developing characteristics.

In the polymer used in the present invention, the content of the carboxyl group-containing monomer unit in the polymer cannot be generally stated because it depends on the balance with the polymerizable polyfunctional monomer, but it must be 1 mol% or more. Is. Especially when an aqueous developer is used, it is preferably 5 mol% or more,
More preferably 10 mol% or more, particularly preferably 15 mol%
It is at least mol%. If the content of the carboxyl group-containing monomer unit is too low, it becomes difficult to dissolve in the aqueous developer, which is not preferable. Further, when developing with a polar organic solvent, the upper limit of the content of the carboxyl group-containing monomer unit is not particularly limited, but when developing with a nonpolar organic solvent, the content of the carboxyl group-containing monomer unit is 10 mol. % Or less is preferable. If the carboxyl group-containing monomer unit is contained in an amount of more than 10 mol%, it becomes insoluble in a nonpolar organic solvent, which is not preferable.

The polymerizable polyfunctional monomer used in the present invention is a compound having in its molecule two or more functional groups which undergo a radical polymerization reaction or a cationic polymerization reaction by the action of a photopolymerization initiator. For example, acryl group, methacryl group, acrylamide group, maleic acid ester, allyl group, vinyl ether, vinylamino group, glycidyl group,
Examples thereof include compounds containing an acetylenic unsaturated group and the like in the molecule. These compounds undergo a polymerization reaction by the action of a photopolymerization initiator, form an interpenetrating network structure with the polymer, and thereby gelate to form a polymerization composition which is insoluble in a developing solution.

Various compounds can be used as the radically polymerizable polymerizable polyfunctional monomer (hereinafter referred to as radical polymerizable monomer), but the polyfunctional acrylate or polyfunctional methacrylate monomer is particularly highly polymerizable and easily gels. Therefore, it is preferable. For example, polyethylene glycol diacrylate such as diethylene glycol diacrylate, triethylene glycol diacrylate, and tetraethylene glycol diacrylate, or polyurethane diacrylates and their corresponding methacrylates, pentaerythritol triacrylate,
Trimethylol propane triacrylate, trimethylol methane triacrylate, ethylene oxide modified trimethylol propane triacrylate having the structure shown in Chemical formula 2 below, propylene oxide modified trimethylol propane triacrylate having the structure shown in Chemical formula 3 below, and structure shown in Chemical formula 4 below Showing epichlorohydrin-modified trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, tetramethylolmethane tetraacrylate, ethylene oxide-modified phosphate triacrylate having the structure shown in Chemical formula 5 below, and the structure shown in Chemical formula 6 below Epichlorohydrin modified glycerol triacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydrate Polyfunctional acrylate or methacrylate monomers corresponding thereto, such as represented by carboxymethyl pentaacrylate like can be selected. It is also possible to use polyfunctional acrylates obtained by introducing an acrylate group through esterification reaction or amidation reaction of butanediol monoacrylate, polyethylene glycol acrylate or the like with a carboxyl group-containing polymer such as polymethacrylic acid, polyacrylic acid, polymaleic acid or the like. it can.

In particular, a paste composition having high photopolymerization sensitivity was obtained in a system using bifunctional, trifunctional and tetrafunctional monomers. These polymerizable polyfunctional monomers may be used alone or as a mixture. It is preferable to use a polyfunctional monomer as the photosensitive resin composition in the present invention, but a monofunctional monomer may be contained. Its content is 50% by weight or less, preferably 30% by weight or less. If the content of the monofunctional monomer exceeds 50% by weight, the curability of the exposed portion of the paste composition becomes insufficient, which is not preferable.

[0024]

[Chemical 2]

[0025]

[Chemical 3]

[0026]

[Chemical 4]

[0027]

[Chemical 5]

[0028]

[Chemical 6]

The cationically polymerizable polymerizable polyfunctional monomer (hereinafter referred to as cationically polymerizable monomer) includes
A compound or the like which undergoes an ordinary ring-opening polymerization reaction or vinyl polymerization reaction can be used. A compound having an epoxy group, a cyclohexene oxide group, a tricyclodecene oxide group, a cyclopentene oxide group or the like in the molecule can be used as the compound for ring-opening polymerization. For example, allyl glycidyl ether, n-butyl glycidyl ether, phenyl glycidyl ether, vinyl cyclohexene monooxide, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, butanediol diglycidyl ether,
Examples thereof include vinylcyclohexenedioide, trimethylolpropane triglycidyl ether, and glycerin triglycidyl ether. Further, as a photopolymerizable monomer for vinyl polymerization, vinyl ether group, p-methoxystyrene, α-methylstyrene, p-in the molecule.
Examples thereof include compounds containing methylstyrene, isobutene, butadiene and the like. These cationically polymerizable monomers may be used alone or as a mixture. Especially 2
Functional, trifunctional and tetrafunctional monomers are preferred because of high sensitivity.
A monofunctional monomer can be added, but the addition amount thereof is 50% by weight or less, preferably 30% by weight or less based on the whole monomers. Same as for radically polymerizable monomers 5
If the monofunctional monomer is added in an amount of more than 0% by weight, the formation of an interpenetrating network structure with the polymer will be insufficient, resulting in deterioration of gelation, which is not preferable.

The photopolymerization initiator in the present invention is added in an amount of 0.1 to 10 parts by weight based on 50 parts by weight of the polymer (A). When the amount of the photopolymerization initiator added is less than 0.1 part by weight, the photocurability of the paste composition is low, which is not preferable. Also,
Even if it is added in an amount of more than 10 parts by weight, the photocurability is not improved and conversely the curability is lowered, which is not preferable. As the photopolymerization initiator of the present invention, it is possible to use an ordinary compound which generates a radical or a Lewis acid by a photochemical reaction after irradiation with visible light, near ultraviolet light or ultraviolet light, but in the ultraviolet light region in consideration of workability and the like. A compound having high spectral sensitivity is preferable. As a compound that induces a radical polymerization reaction,
Benzophenones, vicinal ketones such as diacetyl, benzyl, α-pyridyl, acyloins such as benzoin, pivaloin, α-pyridoin, benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether,
Benzoin isobutyl ether, benzyl dimethyl ketal, acetophenones such as 4-phenoxydichloroacetophenone, 4-tert-butyl-dichloroacetophenone, diethoxyacetophenone, thioxanthone system such as 2,4-diethylthioxanthone, 2,4
-Dimethylthioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-dipropylthioxanthone and other thioxanthone derivatives, anthraquinones such as ethylanthraquinone, benzanthraquinone, diaminoanthraquinone, and the like. Besides, camphorquinone, 4,4′-bis (dimethylamino) benzophenone, dibenzosuberone, 4,4′-diethylisophthalophenone and acylphosphine oxide can be selected. Particularly preferred are benzophenones, thioxanthone and its derivatives, and anthraquinones. These can be used alone or as a mixture of two or more kinds.

As the photopolymerization initiator for inducing the cationic polymerization reaction, PF such as aryldiazonium, diarylhalonium, triphenylphosphonium, dialkyl-4-hydroxysulfonium, dialkyl-4-hydroxydiphenylsulfonium and allene-iron complex is used.
₆ ⁻ , AsF ₆ ⁻ , BF ₄ ⁻ , SbF ₆ ⁻ salt and the like can be mentioned.

Further, an amine photoinitiating aid can be added. The photoinitiator does not activate itself by UV irradiation, but when used in combination with a photoinitiator that induces a radical reaction, the photopolymerization initiating reaction is promoted compared to the use of a photoinitiator alone, which makes the curing reaction efficient. However, mainly aliphatic and aromatic amines are used. For example, triethylenetetramine, triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-methyldiethanolamine, diethylaminoethylmethacrylate, Michler's ketone, 4,
4'-diethylaminophenone, 4-dimethylaminobenzoic acid ethyl ester, 4-dimethylaminobenzoic acid (n-butoxy) ethyl ester, 4-dimethylaminobenzoic acid isoamyl and the like can be mentioned. Especially Michler's ketone, 4,
Aromatic amines such as 4'-diethylaminophenone, ethyl 4-dimethylaminobenzoate, (n-butoxy) ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate are preferred. The photoinitiator aid is 0.1 to 10 parts by weight, preferably 0.
It can be added in the range of 5 to 5 parts by weight. Addition outside the above range is not preferable because it does not contribute to the improvement of the photocurability of the paste composition.

The proportion of the polymer and the polymerizable polyfunctional monomer in the photosensitive resin composition used in the present invention is important for the pattern forming characteristics of the photopolymerizable conductive paste composition. It is desirable that each ratio be in the following range. Polymer 50 parts by weight Polymerizable polyfunctional monomer 10 to 300 parts by weight If the amount of the polymerizable polyfunctional monomer exceeds 300 parts by weight, it becomes difficult to maintain a good viscosity as a paste composition. Further, the pattern formability in the exposure and development steps is deteriorated, which is not preferable. On the other hand, when the amount of the polymerizable polyfunctional monomer is 10 parts by weight or less, the difference in solubility between the exposed area and the unexposed area in the developing step decreases, and the pattern formability deteriorates, which is not preferable. Preferably 20 to 100 parts by weight, more preferably 30 to 80 parts by weight of the polymerizable polyfunctional monomer is added to the polymer.

If necessary, a thermal polymerization inhibitor, a solvent, an anticorrosive agent for preventing surface oxidation and the like can be added. As the thermal polymerization inhibitor, conventionally known hydroquinone, methylhydroquinone, t-butylcatechol, pyrogallol, phenol and its derivatives, salts of copper or iron and the like can be used. Thermal polymerization can be suppressed by adding about 0.01 to 1 part by weight to the photosensitive resin composition 100.

The solvent is added to adjust the paste viscosity when the photopolymerizable conductive paste composition of the present invention is applied onto a substrate, and the boiling point of the solvent is 60 to 26.
Operability is better at 0 ° C. Those having a temperature of 60 ° C. or lower have high volatility, which causes a problem that viscosity is increased during kneading of the paste and storage stability is lowered. Also, 260 ℃
When the above-mentioned materials are used, the drying becomes insufficient, and it becomes difficult to bring them into close contact with the mask surface during exposure. Suitable solvents include, for example, n-methylpyrrolidone, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate and other high boiling point polyhydric alcohol derivatives, xylene and other high boiling point aromatic compounds, There are ketones, esters, and terpenes.

The copper-based metal powder used in the present invention is copper powder, copper alloy powder, or copper powder whose surface is coated with another metal. Although not particularly limited as a metal forming an alloy with copper,
Precious metals such as gold, silver, palladium, platinum, aluminum,
Metals such as indium, zinc and nickel are preferable, and noble metals such as gold, silver, palladium and platinum, and aluminum are particularly preferable. Further, as the metal for coating the surface of the copper powder, noble metals such as gold, silver, platinum and palladium, and metals such as nickel, aluminum and tungsten can be used, but gold, silver, platinum and palladium are preferably used. It is a precious metal.

The surface of the copper-based metal powder having a small particle size is easily oxidized and the oxygen content in the powder is large. When a powder having a high oxygen content is used, the viscosity of the paste increases during paste preparation or storage, and the paste state cannot be maintained. To avoid such problems,
Oxygen content in the powder due to surface oxidation is 0.2 wt% or less, preferably 0.15 wt%, more preferably 0.1
It is effective to use the copper-based metal powder in an amount of not more than wt% and to make the atmosphere as oxygen-free as possible during and after mixing with the carboxyl group-containing photosensitive resin composition. In order to obtain a copper-based metal powder having a lower oxygen content, reduction treatment of the surface oxide layer by firing in a reducing gas atmosphere is effective. Further, when exposed to an oxygen atmosphere after reduction, reoxidation of the surface occurs rapidly, so that the operation after the reduction treatment is also preferably carried out in an inert gas atmosphere having an extremely low oxygen content. In addition, when the powder containing the oxide is used, there is a problem that the developability of the unexposed portion which is not irradiated with light is deteriorated.

The ratio of the copper-based metal powder to the photosensitive resin composition is 20 to 500 parts by weight, preferably 25 to 300 parts by weight of the copper-based metal powder to the total amount of 5 parts by weight of the photosensitive resin composition.
The amount can be selected in the range of 25 parts by weight, more preferably 25 to 95 parts by weight. When the proportion of the copper-based metal powder is less than 25 parts by weight, since the packing density is low, the conductive powder does not sinter well during firing and forms a conductor layer having high electrical conductivity and sufficient strength. I can't. Further, since the organic component cannot be sufficiently scattered, a film having a large amount of residual carbon is formed, which is not preferable. Further, volume shrinkage becomes remarkable in the firing step, which causes a problem that dimensional stability is lowered. Further, if the proportion of the copper-based metal powder exceeds 500 parts by weight, the pattern cannot be formed because the content of the photosensitive resin composition is too small.

The shape of the copper-based metal powder may be spherical, columnar, flaky, or any other shape. The particle size of the powder varies depending on the size and film thickness of the conductor pattern to be formed. Generally, when forming a pattern having a line width of about 100 μm, a particle size of 50 μm or less can be used. In particular, in order to obtain a pattern having a line width of about 50 μm, the particle size of the powder used is usually 0.01 to 20 μm, preferably 0.05 to 10 μm. .. It is also possible to use a powder having a particle size distribution in this range. When particles smaller than 0.01 μm are used, it is difficult to form a pattern because they are easily oxidized and have poor light transmittance. Further, in order to obtain a pattern of about 50 μm, 2
If particles larger than 0 μm are used, the pattern resolution is low. It is also possible to use a powder which has been subjected to a surface treatment such as coating a copper-based metal powder whose surface is easily oxidized with a polymer or the like.

As a method for kneading the photopolymerizable conductive paste composition, an ordinary method using a roll mill, a three-roll mill or the like can be used, but it is extremely effective to use a three-roll mill capable of finely dispersing even primary particles. is there. Further, in the case of a copper-based metal that is easily oxidized, it is effective to suppress the increase in viscosity when the paste composition is kneaded with a three-roll mill in an inert gas atmosphere with an extremely low oxygen content.

In order to store the photopolymerizable conductive paste composition without increasing the viscosity, the oxygen concentration is 1000 pp.
It is necessary to store under an atmosphere of an inert gas such as m or less of nitrogen, argon, neon, krypton, xenon or under vacuum, preferably 100 ppm or less, more preferably 50 ppm or less. Also,
It is preferable to keep the storage temperature at a low temperature of 20 ° C. or lower.

As described above, in a paste composition using a copper-based metal powder having an oxygen content of more than 0.2% by weight and a polymer having a carboxyl group-containing monomer unit of more than 1 mol%, air is used. In the case of storing the paste composition in the above, it was observed that the solubility of the unexposed portion not exposed to light in the developing solution was lowered and the paste composition became extremely viscous, but The content is 0.
When a copper-based metal powder of 2% by weight or less was used, a new effect was found that these phenomena could be suppressed for a short period of time even if a polymer having a molecular weight of 60,000 or more was used. Furthermore, as a result of studying a method for stably storing the paste composition for a longer period of time, in order to solve these problems, an oxygen content of 0.2 wt% or less copper-based metal powder is used, In addition, it is necessary to store in an atmosphere in which the oxygen concentration is suppressed to 1000 ppm or less.

The photopolymerizable conductive paste composition of the present invention can be applied to a substrate by a usual method using screen printing, a roll coater, a doctor blade or the like. The thickness of the paste composition applied on the substrate is not particularly limited, but it is preferably 50 μm or less in order to obtain a pattern of about 50 μm.

The photopolymerizable conductive paste composition is applied to a substrate, dried and then exposed to visible light, near-ultraviolet light or ultraviolet light. Considering the operability of the preparation and patterning process of the photopolymerizable conductive paste composition, it is preferable to use a compound having a spectral sensitivity in the near-ultraviolet or the wavelength range of the ultraviolet region as a photopolymerization initiator.
It is preferable to use a light source that emits light on the shorter wavelength side. For example, ultra high pressure mercury lamp, high pressure mercury lamp, xenon lamp,
Alternatively, a light source such as a laser that emits light in this wavelength range can be used.

In the carboxyl group-containing photosensitive resin composition used in the present invention, since the dispersibility of the metal powder is extremely high, when developing with an aqueous developer or an organic solvent developer after exposure, the metal powder in the unexposed portion is exposed. Is a photosensitive resin composition such as polymethylmethacrylate, polystyrene, poly-α-methylstyrene, etc., which unravels in the form of fine particles outside the system, and even in a composition containing a high concentration of metal powder, the unraveling speed is extremely fast. Further, it has much better developing characteristics than the case where a conventional photosensitive resin composition using a polymer containing no carboxyl group is developed with an organic solvent. As a result, in a paste composition in which a copper-based metal powder and a photosensitive resin composition containing a carboxyl group are mixed, a fine pattern is formed even in a paste composition containing a high concentration of metal powder, which has been impossible so far. Became possible.

A weak alkaline aqueous solution is preferred as the aqueous developer. Examples of alkaline developers include inorganic alkalis such as sodium carbonate, sodium hydroxide, potassium hydroxide, and ammonia, and organic alkali aqueous solutions such as hydroxytrimethylammonium, 2-hydroxyethyltrimethylammonium, and organic amines such as ethanolamine. Can be used. The concentration of the alkaline aqueous solution is 0.1% by weight or more and 5% by weight or less, preferably 0.3% by weight.
It is from 2% by weight to 2% by weight. Even if an alkaline aqueous solution having a concentration higher than 5% by weight is used, the developing rate is not improved, and if an aqueous solution diluted with less than 0.1% by weight is used, the developing rate becomes slow, which is not preferable. After rinsing the unexposed area with an alkaline aqueous solution, a rinse step of removing excess alkaline solution with water is effective.

As the organic solvent-based developer, any solvent which dissolves the photosensitive resin composition used in the present invention can be used, and the solubility contrast between the exposed and unexposed areas of the developer is increased. Therefore, the solubility can be adjusted by adding a solvent in which the photosensitive resin composition is hardly soluble. The developing method used in the present invention may be a conventional method. For example, a dipping method of immersing in a developing solution, a spraying method of spraying the developing solution and the like can be mentioned. Particularly, the spray developing method is extremely effective for forming a fine pattern.

In the present invention, a metal pattern having high electric conductivity can be obtained through a step of firing the paste composition pattern formed in the developing step. The step of baking means a step of scattering the photosensitive resin composition in the paste composition and sintering the metal powder. In the case of a copper-based metal that is easily oxidized, firing in a non-oxidizing atmosphere is preferable. As a gas for forming the non-oxidizing atmosphere, an inert gas such as nitrogen, helium, argon or neon can be used, and the oxygen concentration is preferably kept at 100 ppm or less, preferably 50 ppm or less. The baking temperature varies depending on the type of the photosensitive resin composition used, but it is necessary to be at least a decomposition temperature of the photosensitive resin composition or more in order to scatter organic components. Moreover, since the copper-based metal powders sinter each other when the temperature is higher than the sintering temperature of the copper-based metal used, a conductor layer having high electrical conductivity can be obtained. Therefore, the firing temperature varies depending on the type of the photosensitive resin composition and the metal, but is usually 30
In the range of 0 to 1200 ° C, preferably 400 to 1000 ° C
The range of is used.

[0049]

EXAMPLES The present invention will be specifically described by the following examples and comparative examples, but the present invention is not limited thereto. The weight average molecular weight shown in the following examples was measured using the following GPC (gel permeation chromatography).
GPC: manufactured by JASCO, [pump: TRI ROTAR-V, column: Shodex A-800P (pre-column), A-80M x 2 series,
Eluent: A calibration curve was prepared using THF and a standard polystyrene sample, and the weight average molecular weight was measured. ]

[0050]

Example 1 Methyl methacrylate 65 mol%, methacrylic acid mol% and butyl acrylate 10 mol%.
To 50 parts by weight of a copolymer having a molecular weight of about 130,000,
50 parts by weight of ethylene oxide-modified trimellilol propane triacrylate whose molecular structure is shown in the following chemical formula 2,
1.5 parts by weight of 4-diethylthioxanthone, 3.5 parts by weight of ethyl 4-dimethylaminobenzoate, and 130 parts by weight of n-methylpyrrolidone were stirred to obtain a photosensitive resin composition.

[0051]

[Chemical 7]

With respect to 5 parts by weight of this photosensitive resin composition,
45 parts by weight of copper powder having an average particle size of 3 μm was mixed in a nitrogen atmosphere for 3 times.
The mixture was kneaded with this roll mill to obtain a photopolymerizable conductive paste composition. The obtained paste composition has an oxygen concentration of 10 ppm
It was sealed in a container under the following nitrogen atmosphere. The paste state was still maintained after 5 days. The oxygen concentration in the copper powder used was an oxygen and nitrogen simultaneous analyzer (Horiba Seisakusho, E
As a result of measurement using MGA-650 type), it was 0.1% by weight. This paste composition was applied onto an alumina ceramics substrate using a roll coater and dried in an oven at 70 ° C. The film thickness after drying was 20 μm. Next, light of a 250 W ultra-high pressure mercury lamp was irradiated for 600 seconds in a nitrogen atmosphere through an exposure mask, and heat treatment was performed at 70 ° C. for 15 minutes. Thereafter, spray development was performed using a 1 wt% sodium carbonate aqueous solution as a developing solution. The photomask used for forming the pattern is shown in FIG. In this pattern, it was possible to pattern up to a line width of 40 μm. This is stored in a nitrogen atmosphere with an oxygen concentration of 10 ppm or less at 900 ° C. for 30 minutes.
Bake for minutes. The thickness of the pattern left on the substrate is 13μ
m and had the luster of metallic copper. Also,
Similar to the above method, the line width is 1 mm, the length is 40 mm,
A line pattern having a film thickness of 13 μm after firing was formed and the volume resistivity was measured and found to be 2.6 μΩ · cm. This was a value close to 1.7 μΩ · cm, which is the volume resistivity of metallic copper.

[0053]

Example 2 100 parts by weight of pentaerythritol triacrylate, 3 parts by weight of isopropylthioxanthone, and 10 parts by weight of ethyl 4-dimethylaminobenzoate based on 50 parts by weight of a copolymer composed of 94 mol% of methyl methacrylate and 6 mol% of methacrylic acid. Parts, and 130 parts by weight of ethylene glycol monoethyl ether were stirred to obtain a photosensitive resin composition. This resin composition 5
25 parts by weight of copper powder having an average particle diameter of 2 μm was kneaded with 3 parts by weight in a nitrogen atmosphere having an oxygen concentration of 10 ppm or less using a three-roll mill to prepare a photopolymerizable conductive paste composition. The obtained paste composition was enclosed in a vacuum pack while being cooled with a refrigerant. The oxygen content of the copper powder used is
As a result of measurement using the same device as in Example 1, it was 0.15% by weight. This paste composition was applied on the entire surface of a ceramic substrate with a film thickness of 25 μm using a roll coater, and dried at 70 ° C. After that, it is the ultraviolet light source 25
A 0 W ultra-high pressure mercury lamp was used for 600 seconds to expose through a photomask in a nitrogen atmosphere having an oxygen concentration of 3 to 5% to form a latent image. Further, this was developed by spray development using 1,1,1-trichloroethane as a developing solution. As a result of forming an image using the photomask shown in FIG. 1, it was possible to develop up to a pattern of 40 μm. Further, it was held at 500 ° C. for 30 minutes in a nitrogen atmosphere to remove the organic binder component, and then heated to 900 ° C. to sinter the particles to obtain a conductor layer having metallic copper luster. The volume resistivity of the conductor obtained after firing was 3 μΩ · cm.

[0054]

Example 3 Photosensitive resin composition 5 having the same composition as in Example 1
Average particle size 3 with an oxygen concentration of 0.08% by weight relative to parts by weight
95 parts by weight of copper powder of μm was kneaded using a three-roll mill to obtain a photopolymerizable conductive paste composition. Oxygen concentration 10p
As a result of refrigeration storage under a nitrogen atmosphere of pm or less, the paste state was still maintained after 3 days. This paste composition was applied onto a ceramic substrate using a roll coater.
It was coated on the entire surface in a thickness of μm, and exposed, developed and baked in the same manner as in Example 1. As a result, a 60 μm pattern could be obtained in the photomask pattern shown in FIG.

[0055]

Example 4 With respect to 5 parts by weight of the same photosensitive resin composition as in Example 1, the particle size was distributed to 0.2 to 4 μm and the average particle size was 2.
45 parts by weight of copper powder having a particle diameter of μm was mixed in a nitrogen atmosphere having an oxygen concentration of 10 ppm or less using a three-roll mill to obtain a photopolymerizable conductive paste composition. 1 of the obtained paste composition
It was coated on an alumina substrate in a film thickness of 5 μm. The oxygen content of the copper powder used was 0.1% by weight or less. Example 1
Exposure and development were carried out in the same manner as in, and formation of a 40 μm pattern was confirmed in the photomask pattern. The volume resistivity of the metal copper thin film obtained after firing is 2 μΩ
・ It was cm. The obtained paste was refrigerated and stored under a nitrogen atmosphere of 10 ppm or less, and as a result, the paste state was still maintained after 4 days.

[0056]

Example 5 Copolymer of styrene and maleic acid monoester (manufactured by Monsanto Co., trade name, Scripset 5
Example 1 except that 50) was used as a polymer and the paste composition was coated on an alumina substrate to a film thickness of 20 μm.
A metal copper pattern having a film thickness of 13 μm and a line width of 80 μm could be obtained in the same manner as in.

[0057]

Example 6 As a polymer, 65 mol% of methyl methacrylate, 15 mol% of methacrylic acid, and 1 butyl acrylate.
0 mol% and 2-hydroxymethyl methacrylate 1
50 parts by weight of a copolymer having a molecular weight of 150,000 consisting of 0 mol%, a mixture of 5 parts by weight of benzophenone and 0.8 parts by weight of 4,4′-dimethylaminobenzophenone as a photopolymerization initiator, and a metal powder As an average particle size of 3μ
m, and patterning was attempted in the same manner as in Example 1 except that 20 parts by weight of copper powder having an oxygen content of 0.1% by weight was used.
As a result, a metal copper pattern having a film thickness of 10 μm and a line width of 60 μm was obtained through the steps of coating, exposing, developing and baking on the substrate. As a result of refrigerating and storing the obtained paste composition in a nitrogen atmosphere having an oxygen concentration of 30 ppm or less, the paste state was still maintained after 3 days.

[0058]

Example 7 20 parts by weight of a polymerizable polyfunctional monomer,
A photopolymerizable conductive paste composition was prepared under the same conditions as in Example 1 except that 30 parts by weight of copper powder having an average particle diameter of 3 μm and an oxygen content of 0.08% by weight was used to form a metallic copper pattern. As a result, a copper pattern having a film thickness of 10 μm and a line width of 60 μm was obtained.

[0059]

Example 8 50 parts by weight of a polymerizable polyfunctional monomer,
Photopolymerizable conductive paste composition as in Example 1 except that the copper-silver alloy powder having an average particle size of 2 to 4 μm and an oxygen content of 0.08% by weight (silver content 5% by weight) was 25 parts by weight. Then, a metal copper pattern was formed. As a result, the film thickness 10
A copper pattern having a line width of 60 μm and a line width of 60 μm was obtained. The volume resistivity of the metal pattern obtained after firing was 2.6 μΩ · cm.

[0060]

Example 9 As a polymer, 6 mol% of maleic anhydride,
A film thickness was obtained in the same manner as in Example 2 except that a copolymer composed of 6 mol% of styrene and 88 mol% of methyl methacrylate was used, and a copper powder having an average particle size of 3 μm and an oxygen content of 0.08% by weight was used. A copper pattern having a line width of 20 μm and a line width of 60 μm was obtained.

[0061]

Comparative Example 1 Photosensitive resin composition 5 having the same composition as in Example 1
45 parts by weight of copper powder having an oxygen content of 0.5% by weight, a particle size of 0.2 to 4 μm and an average particle size of 2 to 3 μm are mixed with 3 parts by weight using a three-roll mill. When stored in air, the viscosity of the photopolymerizable paste composition gradually increased, and after leaving for 10 minutes, the fluidity was completely lost and the composition was hardened and the paste state could not be maintained.

[0062]

Comparative Example 2 Photosensitive resin composition 5 having the same composition as in Example 1
Oxygen content 3% by weight, average particle size 1 μm with respect to parts by weight
45 parts by weight of the copper powder were mixed using a three-roll mill to obtain a photopolymerizable conductive paste composition. This paste composition was immediately applied to a ceramic substrate with a film thickness of 20 μm and exposed and developed in the same manner as in Example 1, but the elution of the unexposed portion into the alkali developing solution was extremely poor and the contrast was low. I only got the pattern. Further, this paste composition was left in the air, and after 20 minutes, the viscosity was extremely increased and the paste state could not be maintained.

[0063]

Comparative Example 3 A paste composition was prepared in the same manner as in Example 1 except that a polymer having a molecular weight of 38,000 was used. This paste composition was applied on an alumina substrate in a film thickness of 20 μm, and exposed and developed in the same manner as in Example 1.
However, the contrast of the solubility of the exposed area and the unexposed area in the developing solution is low, and 100 μm due to poor development of the unexposed area.
A fine pattern of m or less could not be formed.

[0064]

The thick film fine pattern having high electric conductivity can be formed, and the storage stability of the photopolymerizable conductive paste composition can be dramatically improved.

[0065]

[Brief description of drawings]

[0066]

FIG. 1 is an explanatory diagram showing a photomask pattern used during exposure.

[0067]

[Explanation of symbols]

 20. Pattern line width (μm) 40. Pattern line width (μm) 60. Pattern line width (μm) 80. Pattern line width (μm) 100. Pattern line width (μm) 120. Pattern line Width (μm) 140. Pattern line width (μm) 160. Pattern line width (μm) 200. Pattern line width (μm) A. Twice the pattern line width B. 1.5 times the pattern line width

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01B 1/22 A 7244-5G H05K 1/14 J 7047-4E

Claims (2)

[Claims] 1. A copper-based metal powder having an oxygen content of 0.2% by weight or less based on 5 parts by weight of a photosensitive resin composition comprising the following three components (A), (B) and (C): A photopolymerizable conductive paste composition comprising 500 parts by weight. (A): A polymer formed from one or more ethylenically unsaturated compounds, the weight of which contains at least 1 mol% of monomer units of ethylenically unsaturated compounds containing one or more carboxyl groups. Polymer having an average molecular weight of 60,000 or more 50 parts by weight (B): 10 to 300 parts by weight of a polymerizable polyfunctional monomer (C): 0.1 to 10 parts by weight of a photopolymerization initiator 2. The method for storing a photopolymerizable conductive paste composition according to claim 1, wherein the method is stored in an inert gas atmosphere having an oxygen concentration of 1000 ppm or less or under vacuum.