JPH0644819A - Conductive paste and conductive coating - Google Patents

Abstract

(57) [Summary] [Constitution] In a conductive paste containing a conductive powder, an organic binder, an additive, a solvent and an adhesion improver,
The organic binder contains one or more kinds of melamine resin, xylene resin and / or its derivative, and a coupling agent as an adhesion improver in the conductive paste solid content of 0.
001-5.0 weight% is contained, The electroconductive paste characterized by the above-mentioned. [Effect] According to the present invention, the adhesion can be improved without lowering the conductivity, and in particular, the high adhesion can be maintained in the solder heat resistance test after absorbing moisture, and the overall excellent performance can be obtained. Therefore, according to the present invention, it is possible to easily and stably form an electromagnetic wave shield layer having extremely high reliability and high effect on a circuit board. Further, it can be effectively used for wiring of circuit boards, electronic device parts, electrodes of circuit parts, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive paste using an organic material as a binder, and a conductive coating film using this conductive paste. More specifically, it is a paper / phenol resin substrate or glass / epoxy resin substrate. After applying by screen printing etc. on the circuit board of, it is heat-cured to form a conductive coating film that has excellent adhesion and conductivity, and that maintains high adhesion during solder heat resistance test especially after absorbing moisture. The present invention relates to a conductive paste suitable for use as a conductor for electromagnetic wave noise of a circuit board or for wiring of a circuit board, and a conductive coating film obtained by coating or printing this conductive paste and curing the same. .

[0002]

2. Description of the Related Art Generally, a conductive paste is basically composed of an organic binder such as epoxy resin, saturated polyester resin, acrylic resin, phenol resin, amino resin (hereinafter sometimes abbreviated as a binder), a conductive powder and a solvent. Is configured. This conductive paste has been conventionally used as a conductor for a circuit board. Recently, attempts have been made to use a conductive paste as an electromagnetic wave shielding material for printed circuit boards. That is,
This application is for a printed wiring board in which a conductive layer having a circuit pattern including a ground pattern is formed on a substrate, except that the conductive layer is formed on the substrate except for the ground pattern portion of the surface of the substrate on which the conductive layer is provided. An insulating layer is provided so as to cover it, and a conductive paste is printed so as to cover the insulating layer of this board and connect it to the ground pattern to form an electromagnetic wave shield layer, which is used as a conductor of the circuit board for electromagnetic wave noise suppression. (See Japanese Patent Application Laid-Open Nos. 63-15497, 55-29276 and 4-30598).

[0003]

Among the above-mentioned conductive pastes, the conductive copper paste has recently been attracting attention as a conductor replacing the conductive silver paste because it is cheaper than the conductive silver paste. . This conductive copper paste is required to have various physical properties such as high conductivity, adhesion, durability, and printability, but copper is essentially more easily oxidized than silver, and an electrically insulating oxide film is formed by oxidation. Since it has a drawback of being formed, there remains a practically large problem in terms of maintaining the adhesiveness and conductivity for a long period of time in a paste state or a heat-cured film state.

On the other hand, the relationship between the conductivity and the adhesiveness is generally a trade-off relationship in the conventional conductive paste, and there is a dilemma that the conductivity decreases when the adhesiveness is improved. Therefore, there has been a strong demand in the art for a technique of improving the respective physical properties without adversely affecting the conductivity and the adhesion. Until now, various coupling agents have been added as a measure for improving the adhesion. For example, a method of adding a polysiloxane oil containing a silane coupling agent (Japanese Patent Laid-Open No. 48-56723), a method of adding a silane compound to a silver paste to improve adhesion to a metal frame (special Kaihei 1-189806), a method of adding an epoxysilane-based monomer to improve adhesion (Japanese Patent Laid-Open No. 12509/1990), and the like have been proposed.

However, these methods have an adverse effect that the coupling agent is adsorbed on the surface of the metal powder to cause contact resistance, resulting in a decrease in conductivity. In addition, even though it is effective for improving the adhesion immediately after the paint / paste is prepared, the storage stability is insufficient, the dispersion structure is destroyed after long-term storage, and the adhesion is blank (no coupling agent added). It was below the level of and had a fatal trouble. These tendencies particularly appear when copper powder having a high surface activity is used, which is a serious obstacle to practical use. The purpose of the present invention is to solve the problem exactly at this point, without causing a decrease in conductivity, maintaining high adhesion even in a harsh environment such as solder heat resistance test after absorbing moisture,
An object of the present invention is to provide a conductive paste having excellent storage stability (dispersion state, adhesion), and a conductive coating film obtained by coating or printing the conductive paste and curing the same.

[0006]

In view of the present situation, the inventors of the present invention have made extensive studies as to the improvement of the adhesiveness of the conductive paste, and as a result, have found that an appropriate coupling agent having a specific chemical structure can be used as the adhesiveness improver. It was found that the above problems can be solved by using an amount and a specific organic binder,
The present invention has been completed.

That is, the gist of the present invention is (1) in a conductive paste containing a conductive powder, an organic binder, an additive, a solvent and an adhesion improver, a melamine resin, a xylene resin and / or the same as the organic binder. A conductive paste containing at least one derivative, and containing a coupling agent as an adhesion improver in the range of 0.001 to 5.0% by weight in the solid content of the conductive paste, and ( 2) The present invention relates to a conductive coating film, which is obtained by applying or printing this conductive paste on a substrate and then curing it. Examples of the coupling agent used in the conductive paste of the present invention include silane coupling agents, titanium coupling agents, zirconium coupling agents, aluminum coupling agents, and chromium coupling agents. The silane coupling agent represented by the general formula (1) is preferably used in view of solder heat resistance after moisture absorption.

[0008]

[Chemical 5]

[In the formula, A is Cl, —OC _n H _{2n + 1} , —N
_{CO, CH 2 = C (CH} 3) hydrolyzable groups selected from -O-; T is H, F, CF _3, amino group, alicyclic epoxy group, an epoxy group, a carboxyl group, a hydroxyl group, a phenol group, Phenyl group, acetal group, alkyl group, alkoxy group, methacryloxy group, Schiff base, silanol group, thiol group, vinyl group, quaternary ammonium salt, isocyanate group, metal, imidazole group, polyoxyalkylene group; E is a carbon number 1 20 alkyl groups; R is O;
S, NH, NR '(R ' represents Ar or C _n H _{2n + 1),} represents OCO, COO, and Ar. f is an integer of 1 to 3, and f A's may be the same or different,
The (3-f) E's may be the same or different. g is an integer of 0 to 10; h is an integer of 0 or 1; i is an integer of 0 to 10. However, when A is an NCO group, T is selected from functional groups other than amino group, carboxyl group, hydroxyl group, thiol group and imidazole group. ]

The method for producing the coupling agent in the present invention is not particularly limited, and for example, the amino group-introduced type can be obtained by subjecting trichlorosilane or methyldichlorosilane to a hydrosilylation reaction with an amine analog. It is also possible to use a commercially available product.

Specific examples of the silane-based coupling agent represented by the general formula (1) include vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; γ-glycidoxypropyltriethoxysilane, γ- Glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, β- (3,3
4 epoxy cyclohexyl) ethyl triethoxysilane or other epoxy type; γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, γ-aminopropylmethyldimethoxysilane, N-β ( Aminoethyl) γ
-Aminopropyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-
β (aminoethyl) γ-aminopropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldiethoxysilane, N-β (aminohexyl) γ
-Aminopropyltriethoxysilane, N-β (aminohexyl) γ-aminopropyltrimethoxysilane, N
-Β (aminohexyl) γ-aminopropylmethyldiethoxysilane, N-β (aminohexyl) γ-aminopropylmethyldiethoxysilane, N-phenyl-γ-aminopropyltriethoxysilane, N-phenyl-γ-
Amino-based compounds such as aminopropyltrimethoxysilane; γ-
Methacryloxy-based compounds such as methacryloxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropylmethyldimethoxysilane; γ-mercaptopropyltriethoxysilane,
mercapto type such as γ-mercaptopropyltrimethoxysilane; alkyl type such as methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane; polyoxyethylenepropyltri Polyoxyalkylenes such as ethoxysilane and polyoxyethylenepropyltriethoxysilane; 3
-Ureido-based compounds such as ureidopropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropylmethyldiethoxysilane; vinyltri (methoxy-ethoxy) silane, N- (1,3-dimethylbutylidene) -3- (Triethoxysilyl) -1-propanamine, 3-4,5 dihydroimidazolepropyltriethoxysilane, methylsilyltriisocyanate, tetraisocyanate and the like can be mentioned.

[0012] Of these, preferable examples of those having little adverse effect on conductivity and excellent long-term stability of the conductive paste are γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane,
γ-glycidoxypropylmethyldimethoxysilane, γ
-Aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldiethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, N-β (aminohexyl)
Examples include γ-aminopropyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, polyoxyethylenepropyltrimethoxysilane, and polyoxyethylenepropyltriethoxysilane. More preferably, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-aminopropylmethyldiethoxysilane, N
Examples include -β (aminoethyl) γ-aminopropyltriethoxysilane, dimethyldiethoxysilane, and polyoxyethylenepropyltriethoxysilane. Further, in the present invention, those in which the coupling agent represented by the general formula (1) is modified with a solvent such as butyl carbitol to control the hydrolyzability can be effectively used. The above coupling agents may be used alone or
A mixture of two or more species can be used.

The content of the coupling agent in the conductive paste of the present invention is 0.001 to 5.0% by weight (in the solid content of the conductive paste), preferably 0.001 to the total weight excluding the solvent. 1.0% by weight, more preferably 0.00
It is 1 to 0.1% by weight. If the compounding amount is less than 0.001% by weight, the absolute amount of the adhesion improving agent is insufficient, and the effect of improving the adhesiveness is poor, and if it exceeds 0.1% by weight, the combination of the organic binder and the additive causes In some cases, the adverse effect on conductivity cannot be ignored. If it exceeds 5.0% by weight, the conductivity will be greatly lowered even if any combination of organic binders and additives is used, and it cannot be used. As described above, the addition of the coupling agent has a problem that although the adhesion is improved, the conductivity is lowered. However, in the present invention, even if the amount of the coupling agent is increased, the adverse effect on the conductivity is small, and the long-term stability of the conductive paste is excellent. This is because the present invention uses a melamine resin, a xylene resin and / or a derivative thereof, a hydroxystyrene-based polymer and / or a derivative thereof described below as an organic binder, and in particular, a hydroxystyrene-based polymer and / or Alternatively, it is remarkable when a derivative thereof or an alkyl etherified melamine resin is used. In the present invention, by using the above-mentioned coupling agent as an adhesion improver, high adhesion is exhibited and the cured coating film shows excellent environmental stability.

As the organic binder used in the conductive paste of the present invention, a thermosetting resin is an essential component, but in addition to this, a thermoplastic resin and a resin which is neither a thermosetting resin nor a thermoplastic resin are contained. You may have. As the thermosetting resin in the present invention, a melamine resin, a thermosetting xylene resin and / or a derivative thereof is effectively used.

As the melamine resin in the present invention, generally known products and commercially available products can be used, but those having a weight average molecular weight of 500 or more and 50,000 or less are preferable. For example, a resin in which formalin is added and condensed to the amino group of melamine, or an epoxy-modified melamine resin, a phenol-modified melamine resin, an acrylic-modified melamine resin, a butylated urea melamine co-condensed resin, a butylated melamine / guanamine co-condensed resin, an alkyl etherified melamine. Resin etc. are mentioned. Of these, alkyl etherified melamine resins, epoxy modified melamine resins, phenol modified melamine resins and acrylic modified melamine resins are preferable, and alkyl etherified melamine resins are more preferable. You may use these melamine resins individually or in mixture of 2 or more types.

Examples of the alkyl etherified melamine resin include methyl etherified melamine resin, n-butyl etherified melamine resin, iso-butyl etherified melamine resin and the like. For example, Super Beckamine (trade name) manufactured by Dainippon Ink and Chemicals, or There is Uban (trade name) manufactured by Mitsui Toatsu Chemicals, Inc. Among these alkyl etherified melamine resins, those having a weight average molecular weight (Mw) of 500 to 50,000 and an etherification degree of 10 to 9 are preferable.
In the range of 5% (6 alkyl ether groups are introduced into one unit of triazine ring at 100%), more preferably in the range of Mw of 1,000 to 30,000 and the degree of etherification of 20 to 80%. It is a melamine resin, most preferably a melamine resin having an Mw of 1000 to 20,000 and an etherification degree of 30 to 60%. Mw is 5
If it is less than 00, the flexibility of the cured coating film will be insufficient, and if it exceeds 50,000, the adhesion and conductivity will be poor. When the degree of etherification is less than 10%, the melamine resin is unstable, and the pot life of the conductive paste is shortened, and when it exceeds 95%, the curing speed decreases and a sufficient dense coating film cannot be obtained under normal curing conditions. This is because it becomes difficult to obtain good adhesion and conductivity.

The most preferable alkyl etherified melamine resin among these is represented by the general formula (3):

[0018]

[Chemical 6]

[Wherein, among the substituents of U ^{1 to} U ⁶ ,
4 are hydrogen atoms, the rest represent -CH ₂ OU ',
U'represents a hydrogen atom or an alkyl group having 3 or more carbon atoms. However, the number of —CH ₂ OU ′ groups (U ′ is an alkyl group) / the number of —CH ₂ OU ′ groups (U ′ is a hydrogen atom or an alkyl group) is in the range of 0.7 to 1.0. ] At least 50 mol% or more of the melamine formaldehyde compound represented by the following (hereinafter abbreviated as MF compound) is contained in the resin.

The MF compound in the present invention is (1) U ¹
Among the substituents of ~U ^6, a 1-4 is a hydrogen atom (presence 1-4 is NH groups of free not methylolated), rest 'represent, U' -CH ₂ OU is a hydrogen atom or Represents an alkyl group having 3 or more carbon atoms. ₍₂₎ (- CH 2 O
U ′ group (U ′ is an alkyl group)) / (— CH ₂ OU ′ group (U ′ is a hydrogen atom or an alkyl group)) is 0.7 to 1.
In the range of 0, that is, at least 70% or more of the number of methylol groups bonded to the melamine skeleton is alkyl etherified, and the ratio of free methylol groups is less than 30%. The alkyl etherified melamine resin according to the present invention Is characteristic in containing 50 mol% or more of such an MF compound.

In the above MF compound, when 5 or more of the substituents of U ^{1 to} U ⁶ are hydrogen atoms, that is, when the number of bound formalin is 1 or less, a solvent or a mixture of the produced melamine resin is used. The compatibility with the hydroxystyrene copolymer and / or its derivative becomes poor,
The possibility that melamine resin will precipitate increases. Further, when all the substituents of U ^{1 to} U ⁶ are not hydrogen atoms, that is, when all of them are —CH ₂ OU ′, the adhesion to the base material is lowered.

Further, the (-CH ₂ OU 'group (U' is an alkyl group)) / (-CH ₂ OU 'group (U' is a hydrogen atom or an alkyl group)) is less than 0.7, that is, -CH ₂ When the proportion of free methylol groups in the OU 'group is 30% or more, the flexibility of the obtained coating film becomes poor. U'here
May be linear or branched as long as it is an alkyl group having 3 or more carbon atoms, and one having 3 or more carbon atoms is usually used.
It preferably has 3 to 10 carbon atoms. Further, when U ′ is an alkyl group having 2 or less carbon atoms, there is a problem of poor printability, which is not preferable. Further, if the content of the MF compound in the melamine resin is less than 50 mol%, excellent coating film physical properties cannot be obtained.

The above-mentioned melamine resin is produced, for example, by reacting melamine with formalin and performing alkyl etherification with an excess of alcohols. In this case, the amount of formalin to be reacted is appropriately 2 to 5 per 1 melamine nucleus, and the bound methylol group is 70
% Or more is required to be alkyl etherified.

The MF compound in which U'in the general formula (3) is an alkyl group is produced, for example, by using a compound represented by U'OH as an alcohol through the following reaction.

[0025]

[Chemical 7]

Examples of alcohols used in the alkyl etherification reaction in this case include U'-containing aliphatic or alicyclic alcohols having 3 or more carbon atoms. When a melamine resin modified with an alcohol having 2 or less carbon atoms is used, it is impossible to maintain the performance satisfactory in the workability of printing (generation of pin holes or the like in the coating film) as described above.

That is, as the alcohols used in the above reaction formula, n-propanol, iso-propanol, n-butanol, iso-butanol, sec-butanol, tert-butanol, n-amyl alcohol, iso-amyl alcohol. , Tert-amyl alcohol, n-hexyl alcohol, sec-hexyl alcohol, 2-methylpentanol, sec-hexyl alcohol, 2-ethylbutyl alcohol, sec-heptyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol, sec- Octyl alcohol,
Cyclohexanol; As ether alcohols,
For example, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether; Examples of ketone alcohols include acetonylmethanol, diacetone alcohol, and pyruvyl alcohol. The alcohols may be used alone or in combination of two or more, and the alcohol is also a solvent in the above reaction. Considering the printability of the paste, the solvent in the obtained melamine resin is preferably replaced with a high-boiling point solvent having a temperature of 120 ° C. or higher before use. The weight average molecular weight of the alkyl etherified melamine resin thus obtained is preferably 300 to 20,000, more preferably 800 to 10,000. This is because if the molecular weight is less than 300 or greater than 20,000, the conductivity will decrease. In addition, the weight average molecular weight of the melamine resin /
The number average molecular weight ratio is preferably from 1 to 5.

Examples of the thermosetting xylene resin and / or its derivative include xylene-phenol resole resin, melamine-modified xylene resin, urethane-modified xylene resin, polyol-modified xylene resin, etc., and xylene-phenol containing a curing agent. A novolac resin can be used as well.

In the present invention, in addition to the above various melamine resins, thermosetting xylene resins and / or derivatives thereof, other thermosetting resins can be used. For example, amino resins other than melamine resins and phenols. Known heat of resin, urea resin, alkyd resin, silicon resin, furan resin, unsaturated polyester resin, epoxy resin, polyurethane resin, polyester / polyol resin, acrylic resin, methylolated hydroxystyrene polymer and / or its derivative A curable resin may be used. Of these, considering the long-term storage stability of the conductive paste and the environmental stability of the cured coating film, amino resins and phenol resins are particularly preferable, and amino resins are most preferable.
These thermosetting resins may be used alone or in combination of two or more. As the amino resin other than the melamine resin, generally known products and commercially available products can be used, but those having a weight average molecular weight of 500 or more and 50,000 or less are preferable. Examples thereof include resins in which formalin is added and condensed to amino groups such as urea, guanamine, aniline, and sulfonamide, butylated urea resins, and amino / alkyd cocondensation resins.

As the phenol resin, generally known ones and commercially available ones can be used. For example, phenol, cresol, xylenol, p-alkylphenol, chlorophenol, bisphenol A, phenolsulfonic acid, resorcin and various modified phenols and the like phenols can be used. A resin obtained by adding and condensing an aldehyde such as formalin and furfural to a resin having a hydroxyl group. Resol type phenol resin is particularly preferable. For example, PL4348, PL22 manufactured by Gunei Chemical Industry Co., Ltd.
11, GM-1, GM-2, Dainippon Ink and Chemicals, Inc.
Plit Orphen 5010 and the like. When a novolac type phenol resin is used, it is preferable to use hexamethylenetetramine together. In the present invention, by incorporating such a phenolic resin, even if a silane coupling agent is blended, a conductive paste excellent in long-term stability can be obtained with almost no decrease in conductivity. it can.

As the organic binder of the conductive paste of the present invention, a thermoplastic resin can be used together with the above thermosetting resin. As such a thermoplastic resin, a thermoplastic xylene resin and / or a derivative thereof, a hydroxystyrene-based polymer and / or a derivative thereof can be effectively used. By including these thermoplastic resins, it is possible to improve solder heat resistance, conductivity, and migration resistance particularly after moisture absorption.

Examples of the thermoplastic xylene resin and / or its derivative include alkylphenol-modified xylene resin, xylene-phenol novolac resin, polyhydric alcohol-modified xylene resin, and carboxylic acid-modified xylene resin.

Such a hydroxystyrene polymer and / or its derivative has a weight average molecular weight of 10
It is more preferable to contain those having an amount of from 0 to 2,000,000,
By adding this binder component, conductivity, adhesion,
Performance such as durability and printability is improved. This hydroxystyrene polymer and / or its derivative is disclosed in
Those described in JP-A-2283, JP-A-3-2248 and JP-A-3-173007 are preferable. For example, those represented by the following general formula (2) can be given.

[0034]

[Chemical 8]

[Wherein, l and m are m ≧ 0 and l ≧ 3, and the average molecular weight of the organic polymer of the general formula (2) is 1000, respectively.
Up to 2 million, k, p, and u represent average values in the polymer, and their ranges are 0 ≦ k ≦ 2 and 2, respectively.
0 ≦ p ≦ 2, 0 ≦ u ≦ 2, but k + p + u> 0, R ¹ ~
R ³ is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, Q is a polymerizable vinyl monomer, Y and Z are the same or different, and

[0036]

[Chemical 9]

Alternatively, it is selected from an alkyl group having 1 to 18 carbon atoms or an aryl group. (In the formula, M is a hydrogen atom, an organic cation such as an alkali metal, an alkaline earth metal or an amine, Y ¹ and Y ² are halogens, Y ³ is a halogen ion, a counter ion such as an organic acid anion and an inorganic acid anion, W is S or O, R ^{4 to} R ⁸ are the same or different and are alkyl derivatives such as linear or branched alkyl groups or hydroxylalkyl groups, aromatic groups or hydrogen atoms, and R ⁶ and R ⁷ are N atoms. R ^{9 to} R ¹⁵ are the same or different and are linear or branched alkyl groups, alkyl derivatives such as hydroxylalkyl groups, aromatic groups, or hydrogen atoms, q,
s represents 0 or 1, r represents 0, 1 or 2. )]

The hydroxystyrene-based polymer represented by the general formula (2) and the derivative thereof have a hydroxy group which may or may not have a substituent represented by Y or Z in the general formula (2). Styrene, hydroxy-
Copolymer of only hydroxystyrene-based monomers such as α-methylstyrene or hydroxy-α-ethylstyrene, or these hydroxystyrene-based monomers and other polymerizable vinyl-based monomers (Q) Can be a copolymer of The hydroxystyrene-based monomer of the polymerized unit may be an ortho body, a meta body, a para body or a mixture thereof, but a para body or a meta body is preferable.

Other vinyl-based monomers (Q) in the case of copolymers include anionic and cationic ionic monomers, nonionic monomers, methacrylates, vinyl esters, vinyl ethers, Known compounds such as malate and α-olefin can be mentioned. In the present invention, as described above, the copolymerization of hydroxystyrene-based monomers may be carried out, but when copolymerized with another polymerizable vinyl-based monomer (Q), a hydroxystyrene-based monomer is used. The ratio of the body / the other vinyl-based monomer (Q) is preferably 1/10 to 20/1 in terms of molar ratio. The ratio of vinyl monomer (Q) is 10 than that of hydroxystyrene monomer.
If the amount exceeds the double amount (molar ratio), the effect of the hydroxystyrene-based monomer will not be exhibited, which is not preferable, and if the ratio of the vinyl-based monomer (Q) is less than 1/20, the effect of copolymerization will not be exhibited. There is no need to dare to copolymerize with the vinyl monomer (Q). Therefore, in the present invention, the number of such vinyl monomers (Q) is m ≧ 0. These hydroxystyrene polymers and their derivatives can be easily prepared by known methods. (CGOv
erberger, JC Salamone, S.Yaroslavsky, J.Am.Chem.So
c., 89,6231 (1967); DIPackham, J.Chem.Soc., 2617 (196
4); M. Kato, J. Polym. Sci., Part A-1, 7, 2175 (1969)).

In the present invention, in addition to the above-mentioned thermoplastic xylene resin and / or its derivative, hydroxystyrene polymer and / or its derivative, other thermoplastic resins can be effectively used, for example, saturated polyester. Known thermoplastic resins such as resin, polyurethane resin, polyamide resin, acrylic resin, butyral resin, and novolac type phenol resin can be used. The above-mentioned thermoplastic resin used in the present invention may be used alone or
You may use it in mixture of 2 or more types.

The organic binder in the present invention further comprises
You may contain the xylene resin and / or its derivative which are neither thermosetting resin nor thermoplastic resin.

The content of the binder in the conductive paste of the present invention is 5 to 50% by weight, preferably 5 to 40% by weight, based on the total weight excluding the solvent. Adhesion is reduced due to insufficient amount, the fluidity of the resulting composition is deteriorated, the printability is reduced and the conductive powder is easily oxidized during heat curing,
The flexibility and conductivity are reduced. The amount of binder is 50
On the other hand, when it exceeds the weight%, the absolute amount of the conductive powder is insufficient and the conductivity required for forming a circuit cannot be obtained. Further, when the melamine resin is contained in the above organic binder, the blending amount thereof is 1 to 100% by weight, preferably 5 to
It is 80% by weight. When the xylene resin and / or its derivative is contained, the compounding amount thereof is 1 to 100% by weight, preferably 5 to 80% by weight. When the hydroxystyrene polymer and / or its derivative is contained, the compounding amount thereof is usually 1 to 95% by weight, preferably 5 to 70% by weight. If less than 1% by weight, the effect is low, 95
If it exceeds 5% by weight, it becomes difficult to obtain conductivity. When the phenol resin and / or its derivative is contained, the compounding amount thereof is 1 to 95% by weight, preferably 5 to 80% by weight.

Examples of the conductive powder used in the present invention include metal powders such as copper powder, silver powder, nickel powder, and aluminum powder, and solid powders having a metal layer consisting of the above-mentioned metal coating layer on the surface. Copper powder is particularly preferable.
The form of the conductive powder may be any of dendritic, flake-like, spherical, and indefinite, but is preferably dendritic electrolytic copper powder produced by electrolysis or spherical powder. The average particle size is preferably 30 μm or less,
From the viewpoint of high density and multiple contact point filling, dendritic powder of 1 to 10 μm is more preferable. However, the average particle diameter referred to here means a volume-based median diameter obtained by "LA-500 type laser diffraction particle size distribution measuring device" manufactured by Horiba Ltd. If the average particle size exceeds 30 μm, it becomes difficult to densely fill the conductive powder, and the conductivity decreases, and
This is because the printability becomes poor. Further, when the surface-treated copper powder is used, particularly excellent conductivity, durability and printability are easily obtained. Since it is not necessary to attach solder to the surface of the copper paste and its coating film of the present invention, an organic surface treatment agent may be used. The conductive powder may be used alone or in a mixed system. It is preferable that the purity of the metal powder is high. In particular, the copper powder is most preferably the same as the purity of the copper foil or the plated copper layer used for the conductor of the circuit board.

In the present invention, the action and effect of the adhesion improver is more remarkably exhibited when the metallic copper powder is used, and therefore the present invention is particularly important for the production of the conductive copper paste. The content of the conductive powder in the conductive paste of the present invention is 50 to 95% by weight, preferably 70 to 90% by weight, more preferably 80 to 90% by weight based on the total weight excluding the solvent. %. 50% by weight
If it is less than 100% by weight, sufficient conductivity cannot be obtained. On the contrary, if it exceeds 95% by weight, the conductive powder is not sufficiently bound, the resulting coating film becomes brittle, the moisture resistance is lowered, and the conductivity is deteriorated.

In the conductive paste of the present invention, it is extremely important to select additives other than the coupling agent. Depending on the type of additive, the effect of the coupling agent may not be obtained, or the long-term stability of the paste may be significantly reduced. Benzoic acid and / or its derivative, ester carboxylic acid, ether carboxylic acid, and the like can be used in the present invention.
One or more known reducing agents or chelating agents can be used (for example, the compounds described in Japanese Patent Application No. 2-341074 and Japanese Patent Application No. 2-341076), or known compounds. ).

Preferably, benzoic acid, methylbenzoic acid, ethylbenzoic acid, propylbenzoic acid, butylbenzoic acid, hexylbenzoic acid, octylbenzoic acid, nonylbenzoic acid,
Decylbenzoic acid, dodecylbenzoic acid, tetradecylbenzoic acid, hexadecylbenzoic acid, octadecylbenzoic acid,
Benzoic acid such as methoxybenzoic acid, ethoxybenzoic acid, butoxybenzoic acid, octyloxybenzoic acid, tetradecyloxybenzoic acid and / or its derivatives; monohexyl oxalate, monohexyl malonate, monohexyl succinate, monooctyl succinate, succinic acid. Acid monooleyl, glutaric acid monohexyl, adipic acid monohexyl, maleic acid monohexyl, maleic acid monooctyl, maleic acid monooleyl, monomethyl phthalate, monobutyl phthalate, phthalic acid monohexyl, phthalic acid monooctyl, phthalic acid monooleyl, naphthalenedicarboxylic acid monohexyl, Pelargonoyloxyacetic acid, oleoyloxyacetic acid, 3-peragonoyloxypropionic acid, 3-oleoyloxypropionic acid, 4-peragonoyloxybutanoic acid, 6 Butyryloxy hexanoic acid,
Ester carboxylic acids such as enanthyloxybenzoic acid and enanthyloxynaphthoic acid; butyloxyacetic acid
Ether carboxylic acids such as octyloxyacetic acid and tetradecaneoxyacetic acid, alkanolamines such as triethanolamine, alkylamines such as triethylamine and palmitinamine, o-aminophenol, 2-amino-
4-methylphenol, o-aminothiophenol, 8
-Aromatic amino compounds such as hydroxyquinoline, 2-methyl-8-hydroxyquinoline, 1-nitroso-2-naphthol, 1- (2-pyridylazo) -2-naphthol; succinic acid, propionic acid, humic acid, etc. Carboxylic acids; hydroxycarboxylic acids such as citric acid and ascorbic acid; salicylic acid compounds such as salicylic acid, sulfonylsalicylic acid, salicylamide, salicylhydroxysamic acid; and amino acids such as phenylalanine, tyrosine, anthranilic acid, and aspartic acid. From the viewpoint of paste stability, benzoic acid and its derivatives, ethercarboxylic acids, and aromatic amino compounds are more preferable.

In the present invention, the compounding amount of the above additives is usually 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight based on the total weight excluding the solvent. If the amount is less than 0.1 parts by weight, the effect of addition is not sufficient, and if it exceeds 20 parts by weight, the adhesion and migration resistance are deteriorated, which is not preferable.

Further, if necessary, known antifoaming agents, thixotropic agents, and leveling agents can be used as additives for the purpose of improving the dispersibility of the copper powder and the screen printability of the paste. The method for producing the conductive paste of the present invention can be prepared by sufficiently uniformly kneading with a disper, a ball mill, a triple roll or the like.

As the solvent that can be used here,
Benzene, toluene, hexanone, methyl isobutyl ketone, methyl amyl ketone or butyl carbitol, butyl carbitol acetate, butyl cellosolve, butyl cellosolve acetate, propylene glycol monomethyl ether acetate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol Known solvents include ethylene-based or propylene-based glycol ethers such as dimethyl ether, diester salts of dibasic acids such as dimethyl adipate, dimethyl glutarate, and dimethyl succinate.

The blending amount of the solvent varies depending on the type of kneading machine, the kneading conditions and the type of solvent. It is preferable to adjust the amount of the solvent so that the paste viscosity after the kneading can be screen-printed. As a method for producing a circuit board for electromagnetic wave noise countermeasure in which an electromagnetic wave shield layer is provided on a circuit board using the conductive paste of the present invention, there is, for example, the following method. That is, a heat-curable or UV-curable organic insulator is applied on a conductive circuit formed from a metal-clad laminate by an etched-for method except the ground pattern portion to form an insulating layer, and the insulating layer is provided on the insulating layer. Using the conductive paste according to the present invention, the conductive paste is applied to almost the entire surface of the insulating layer by screen printing so as to be connected to the ground pattern, and the conductive paste is heated and cured to form an effective electromagnetic wave shield layer. It is possible to fabricate the circuit board for electromagnetic wave noise protection. This circuit board can be effectively used as an electrostatic shield layer.

The metal-clad laminated substrate that can be used is glass.
Epoxy resin substrate, paper / phenolic resin substrate, ceramics substrate, polyimide resin substrate, flexible substrate, etc. Printed circuit technology handbook (Nikkan Kogyo Shimbun, published in 1987) Any one will do. Further, as a method of using the conductive paste of the present invention as a conductor for wiring of a circuit board, a method equivalent to a conventional method can be used. The insulating substrate to be coated is the same as above.
Any known or commercially available substrate may be used. As the wiring forming method, a method of applying by screen printing, intaglio printing, spraying or brush coating can be used. In the present invention, the conductive coating film means a cured product or a cured coating film obtained by drying and curing the conductive paste of the present invention and having a volume resistivity of 1 × 10 ⁻² Ω · cm or less. .

[0052]

The present invention will be described in more detail based on the following examples and comparative examples, but the present invention is not limited to these examples. In the examples and comparative examples, "%" in the blending amount means "% by weight".

Resin Production Example 1 Paraformaldehyde (containing 80% formaldehyde) 3 mol, n per mol of melamine in a reactor equipped with a thermometer, stirrer, reflux condenser and solvent by-product recovery device.
-Prepare 15 mol of butanol and, while stirring,
A 10 wt% aqueous solution of oxalic acid was added to adjust the pH of the reaction solution to 4.0. Thereafter, the mixture was heated and continued for 5 hours while removing water out of the system under the reflux temperature condition of the reaction solution, then cooled to 50 ° C. and adjusted to pH 7.0 with a 10% aqueous solution of caustic soda. After that, while maintaining the temperature in the system at 50 ° C or lower under heating and depressurization, excess butanol is removed from the system so that the heating residue of the resin (according to the measurement method of JIS K-5400) becomes 60%. Thus, an n-butyl etherified melamine resin (organic binder C) was obtained.

Examples 1 to 18 Preparation of paste Conductive powder shown in Table 1, adhesion improver shown in Table 2, Table 3
The organic binder shown in Table 1 and the other additives shown in Table 4 were blended so as to have the compositions shown in Tables 5 to 7 and kneaded sufficiently uniformly with a disper or a triple roll to prepare a conductive paste.

Substrate Preparation Using a glass / epoxy resin substrate (CEM-3), an organic insulating layer (S-222, HR-6 or MF manufactured by Taiyo Ink Co., Ltd.) was prepared in advance, leaving the adhesion test part with the copper foil and the electrode part. -100S, TS-17)
Printed and cured. For the pretreatment of the copper foil, a 10% aqueous solution of sulfuric acid / ammonium citrate (1: 3) was used.
After dipping at 60 ° C. for 60 seconds to dissolve the surface oxide film, it was air dried with jet air.

Paste printing The adhesion test portion and the conductivity measurement pattern (2 mm × 360 mm) were printed on the organic insulator with a screen printer equipped with a 180-250 mesh Tetoron screen using each of the obtained conductive pastes. Or printed on copper foil. Next, it was heated and cured at 140 to 160 ° C. for 10 to 30 minutes to obtain a paste cured coating film having a thickness of 30 μm.

Approximately 20μ of overcoat printing organic insulation layer (MF-200, TS-92E made by Taiyo Ink)
Printed on paste-cured coating with a thickness of m, UV-cured (high pressure mercury lamp, 1200 mJ / cm ² ) and 150 ° C x 2
It was cured by heating in 0 minutes. The results of examining various characteristics of the conductive circuit obtained in the above process are shown in Tables 5 to 7.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

[0062]

[Table 5]

[0063]

[Table 6]

[0064]

[Table 7]

Conductivity Measurement The conductivity of a coating film means the volume resistivity of the coating film which has been heat-cured by a digital multimeter (R655 manufactured by Advantest).
It is the value measured by the two-terminal method using 1). In addition,
The formula for calculating the volume resistivity is shown below. Volume resistivity (Ω · cm) = (R × t × W) / L R: Resistance value between electrodes (Ω) t: Thickness of coating film (cm)
W: Width of coating film (cm) L: Distance between electrodes (cm) Moisture resistance test Moisture resistance of the coating film is 3 at 40 ° C and 90% relative humidity.
A 00 hour standing test was performed, and the rate of change in resistance value W _R before and after the test was determined by the following equation. Resistance change rate _{W R (%) = (R} 300 -R 0) / R 0 R 0: resistance value of the coating film before test (Ω) R _{300: 300} hours the resistance after testing (Omega) W values of _R Shows the moisture resistance of the coating film as follows. A: W _R is less than 30% B: W _R is 30% or more and less than 100% C: W _R is 100% or more

Adhesion test The cross-cut cellophane tape peeling test method of JIS K 5400 (1979) was conducted to determine the number of cross- cuts of the coating film remaining on the copper foil or the organic insulating layer. The judgment criteria are as follows. A: 100/100 B: 90/100 or more and less than 100/100 C: 50/100 or more and less than 90/100 D: 0/100 or more and less than 50/100

Adhesion test during solder heat resistance test after absorbing moisture
Test Adhesion evaluation substrate formed by the above method at 40 ° C, 90%
After 96 hours of standing test in an environment of relative humidity, after immersing in an organic acid flux bath for 4 seconds, and then in a molten solder bath (Pb / Sn = 40/60) for 10 seconds,
An adhesion test was conducted. The judgment criteria are as follows. A: 100/100 B: 90/100 or more and less than 100/100 C: 50/100 or more and less than 90/100 D: 0/100 or more and less than 50/100 Evaluation criteria for printability are as follows. . ◯: Good printability Δ: Temporarily printable ×: Unprintable

Comparative Examples 1 to 5 A conductive paste having the composition shown in Table 7 was prepared as a comparative product and evaluated in the same manner as in the examples. The results are also shown in Table 7.

Tables 5 to 7 show various characteristics of the conductive paste and the conductive coating film of the present invention together with comparative examples. As shown in Examples 1 to 18, the conductive paste of the present invention has a significantly improved adhesion to the copper surface while maintaining high conductivity (10 ⁻⁵ to 10 ⁻³ Ω · cm).
Excellent in moisture resistance. In particular, it maintains high adhesion in a solder heat resistance test after absorbing moisture. On the other hand, when the conductive paste of the present invention does not use the adhesiveness improver (Comparative Examples 1, 2 and 4) or the compounding amount of the adhesiveness improver used in the present invention is not appropriate (Comparative Example 3 ) Is
It is difficult to comprehensively satisfy various physical properties. Further, even when a suitable additive was not used (Comparative Example 5), it was difficult to comprehensively satisfy various physical properties.

[0070]

Since the conductive paste of the present invention contains a coupling agent as an adhesion improver, the adhesion can be improved without lowering the conductivity, especially in a solder heat resistance test after absorbing moisture. Maintains high adhesion and has excellent overall performance. Therefore, by using the conductive paste of the present invention, it is possible to easily and stably form an electromagnetic wave shield layer having extremely high reliability and great effect on the circuit board. Further, even when it is used as a conductor for wiring of a circuit board, highly reliable wiring can be formed. Further, it can be effectively used for electrodes of electronic equipment parts, circuit parts, etc., and these effects are extremely large industrially.

Claims (8)

[Claims] 1. A conductive powder, an organic binder, an additive,
A conductive paste containing a solvent and an adhesion improver contains at least one of a melamine resin, a xylene resin and / or a derivative thereof as an organic binder, and a coupling agent as an adhesion improver containing a conductive paste solid content. The conductive paste is contained in the range of 0.001 to 5.0% by weight. 2. The conductive paste according to claim 1, further comprising a hydroxystyrene polymer and / or a derivative thereof as an organic binder. 3. The conductive paste according to claim 1, wherein the coupling agent is represented by the general formula (1). [Chemical 1] In the formulas, A is _{Cl, -OC n H 2n + 1} , -NCO, CH 2
= C (CH ₃₎ hydrolyzable groups selected from -O-; T is H, F, CF _3, amino group, alicyclic epoxy group, an epoxy group, a carboxyl group, a hydroxyl group, a phenol group, a phenyl group, acetal Group, alkyl group, alkoxy group, methacryloxy group, Schiff base, silanol group, thiol group, vinyl group, quaternary ammonium salt, isocyanate group, metal, imidazole group, polyoxyalkylene group;
E is an alkyl group having 1 to 20 carbon atoms; R is O, S, NH,
NR '(R' represents Ar or _{C n H 2n + 1),} OC
Represents O, COO, Ar. f is an integer of 1 to 3,
The f A's may be the same or different, and the (3-f) E's may be the same or different. g is an integer of 0 to 10; h is an integer of 0 or 1; i is an integer of 0 to 10.
However, when A is an NCO group, T is selected from functional groups other than amino group, carboxyl group, hydroxyl group, thiol group and imidazole group. ] 4. The conductive paste according to claim 1, wherein the hydroxystyrene-based polymer and / or its derivative is represented by the general formula (2). [Chemical 2] [In the formula, l and m are m ≧ 0 and l ≧ 3, respectively, and an arbitrary number until the average molecular weight of the organic polymer of the general formula (2) is from 10 to 2,000,000, k, p and u are weights, respectively. The average value during coalescence is shown, and the range is 0 ≦ k ≦ 2 and 0 ≦ p ≦, respectively.
2,0 ≦ u ≦ 2, but k + p + u> 0, R ^{1 to} R ³ are hydrogen atoms or alkyl groups having 1 to 5 carbon atoms, Q is a polymerizable vinyl monomer, and Y and Z are the same or different. Yes, and Alternatively, it is selected from an alkyl group having 1 to 18 carbon atoms or an aryl group. (In the formula, M is a hydrogen atom, an organic cation such as an alkali metal, an alkaline earth metal or an amine, Y ¹ and Y ² are halogens, Y ³ is a halogen ion, a counter ion such as an organic acid anion and an inorganic acid anion,
W is S or O, R ^{4 to} R ⁸ are the same or different and are alkyl derivatives such as linear or branched alkyl groups or hydroxylalkyl groups, aromatic groups or hydrogen atoms, and further R
⁶ and R ⁷ may form a ring together with the N atom. R ^{9 to} R ¹⁵ are the same or different and are linear or branched alkyl groups, or alkyl derivatives such as hydroxylalkyl groups, aromatic groups, or hydrogen atoms, q and s are 0 or 1, r is 0 and 1 Or 2 is shown. )] 5. The melamine resin is a) etherified with a lower alcohol, and the degree of etherification thereof is in the range of 10 to 95% on average, and the weight average molecular weight is in the range of 500 to 50,000. A resin, b) an epoxy-modified melamine resin having a weight average molecular weight of 500 to 50,000, c) a phenol-modified melamine resin having a weight average molecular weight of 500 to 50,000, and d) a weight average molecular weight of 500 to 50,000. 5. The conductive paste according to claim 1, which is one or more selected from the group consisting of acrylic modified melamine resins in the range. 6. The conductive paste according to claim 5, wherein the alkyl etherified melamine resin contains the melamine formaldehyde compound represented by the general formula (3) in an amount of 50 mol% or more in the resin. . [Chemical 4] [In the formula, 1 to 4 of the substituents of U ^{1 to} U ⁶ are hydrogen atoms, the rest represent —CH ₂ OU ′, and U ′ represents a hydrogen atom or an alkyl group having 3 or more carbon atoms. . However,
The number of -CH ₂ OU 'groups (U' is an alkyl group) / -CH ₂
The number of OU 'groups (U' is a hydrogen atom or an alkyl group) is in the range of 0.7 to 1.0. ] 7. The conductive paste according to claim 1, further comprising a resol-type phenol resin and / or a derivative thereof as an organic binder. Sex paste. 8. A conductive coating film obtained by coating or printing the conductive paste according to claim 1 on a substrate and curing the paste.