JP2023050084A - Conductive resin composition and method for manufacturing circuit board with heating resistor formed thereon - Google Patents

Abstract

To provide a conductive resin composition with excellent substrate adhesion and resolution, and a method for manufacturing a circuit board with a heating resistor formed thereon.SOLUTION: A conductive resin composition includes conductive fine particles (A) and a photosensitive resin composition (B), and the hydrophobicity of the conductive fine particles (A) is 30 to 50%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a conductive resin composition having excellent substrate adhesion and resolution, and a method for producing a circuit board having a heating resistor formed thereon.

In recent years, demands for miniaturization, high density, high definition, and high reliability have been increasing in electrical and electronic equipment, and an improvement in wiring pattern processing technology that satisfies these demands has been desired. In particular, miniaturization of heating resistors (electrical conductors) is an essential requirement for miniaturization and high density, and various methods have been proposed.

Among electrical and electronic devices, a thermal printhead is constructed by electrically connecting a resistor as a heating element between a pair of electrodes consisting of a common electrode made of a metal film and an individual electrode formed on an insulating substrate. , controls the application of the required voltage between both electrodes to generate heat, applies the heat to the thermal recording paper, and performs thermal recording according to the amount of heat generated by the resistor. For formation, a desired gold film is formed by repeating printing and firing using a gold paste, and a wiring pattern is formed by photolithographically processing this film.

Although the adhesion of the metal film is relatively low in such thick film printing, it is characterized in that it can be manufactured simply by coating and baking the metal paste on the substrate. That is, since film formation can be performed continuously with simple processes and equipment without requiring large-scale equipment, there are advantages of high productivity and low cost, and the method is widely used. Thick film printing uses a paste, which is a non-uniform viscous liquid in which various metals are finely divided into fine particles and dispersed in a solvent. For this reason, there is a problem that a uniform film is difficult to be formed simply by coating the substrate and baking it to form a metal film in which the metal particles are in contact with the substrate.

In addition, since gold-based paste is expensive, techniques for reducing the amount of gold used or pastes mainly composed of metals other than gold have been proposed. Many techniques have been proposed in which silver is used as an inexpensive metal with good electrical conductivity.

For example, in a conductor-forming paste that reduces the interfacial resistance value between conductor layers, does not increase the resistance value by sintering, and is capable of forming fine wiring patterns, an organic compound of silver and an organic compound of nickel It is a resinate paste made by mixing these with a resin to form a paste, and an alloy containing 95 to 99% by weight of silver and 1 to 5% by weight of nickel in the metal element components is used (Patent Reference 1).

Further, Patent Document 2 describes a photosensitive conductive paste capable of forming a thick-film conductive pattern and a method for manufacturing a conductive pattern using the paste, but does not provide sufficient information regarding adhesion to a substrate. do not have.

JP-A-5-89716 Japanese Patent No. 3218767

Conventionally, gold-based paste has been used to form heating resistors (wiring patterns) used in thermal print heads and the like. However, gold paste is very expensive, which is the biggest factor pushing up manufacturing costs. In addition, as a material to replace gold paste, silver paste using silver, which has similar characteristics, has been tested and various proposals have been made. resolution was insufficient.

The present inventors have made extensive research to solve the above problems, and have found a conductive resin composition containing conductive fine particles (A) and a photosensitive resin composition (B), In a conductive resin composition characterized in that the degree of hydrophobicity of the fine particles (A) having conductivity is 30 to 50%, the degree of hydrophobicity of the fine particles (A) having conductivity is within a specific range. It was completed by discovering that, by using the substrate, the adhesiveness of the thermal antibody formed on the substrate to the substrate and the resolution when the wiring pattern is formed on the substrate and developed are excellent.

The present invention has been completed based on the above findings, and provides a conductive resin composition and a heating resistor formed on a substrate using this conductive resin composition.

That is, the present invention can be described as follows.
Section 1. A conductive resin composition containing conductive fine particles (A) and a photosensitive resin composition (B),
A conductive resin composition, wherein the conductive fine particles (A) have a hydrophobicity of 30 to 50%.
Section 2. The photosensitive resin composition (B) contains a binder polymer (b-1), a polymerizable compound (b-2), and an initiator (b-3),
Item 2. The conductive resin composition according to Item 1, wherein the binder polymer (b-1) has an acid value of 20 to 60 mgKOH/g.
Item 3. Item 3. The conductive resin composition according to Item 1 or 2, wherein the conductive fine particles (A) have a 90% particle size of 5 μm or less.
Section 4. Item 3. The conductive resin composition according to Item 1 or 2, wherein the conductive fine particles (A) are silver or an alloy containing silver.
Item 5. Item 5. A method for producing a circuit board, wherein the conductive resin composition according to Item 4 is coated on a substrate, exposed, developed, and then baked at a temperature of 500° C. or higher to form a heating resistor.
Item 6. Item 6. The method for manufacturing a conductive circuit-forming substrate according to Item 5, wherein the substrate is ceramic.

By using the conductive resin composition of the present invention, the heat generating resistor (wiring pattern) that has undergone coating, curing, and baking has sufficient adhesion to the substrate and the heat generating resistor (wiring pattern) is formed on the substrate. , showing high resolution when developed.

The conductive resin composition will be described in detail below.

Conductive Resin Composition The conductive resin composition of the present invention is a conductive resin composition containing conductive fine particles (A) and a photosensitive resin composition (B). is characterized in that the degree of hydrophobicity of the microparticles (A) having

Fine particles having conductivity (A)
The conductive microparticles (A) of the present invention are, for example, noble metals such as gold, silver, copper and platinum group metals, single metals such as highly conductive metals such as nickel and aluminum, or single metals such as these. Examples include fine particles of an alloy containing In addition, a single metal fine particle or a combination of two or more kinds of metal fine particles of an alloy thereof may be used. Among them, fine metal particles of gold, silver, copper, or alloys containing them are preferable, and it is more preferable to mainly use fine metal particles of silver or alloys containing it, because of good conductivity. They may be used singly or in combination.

The shape of the conductive metal fine particles (A) is not particularly limited as long as the desired conductivity can be obtained. In view of the above, spherical, flaky, or a mixture of spherical and flexible particles is preferred. In addition, the mixing ratio of the spherical shape and the flex shape may be any ratio.

In addition, the particle size of the conductive metal fine particles (A) is not particularly limited. More preferably, the 90% particle size is in the range of 1.5 to 3.7 μm. The effect of the present invention can be sufficiently obtained by using the conductive metal fine particles (A) having the above average particle size. The 90% particle diameter of the conductive fine metal particles (A) in the present invention refers to a value measured with a laser diffraction particle size distribution meter.

The conductive fine particles (A) used in the present invention vary greatly in dispersibility in the conductive resin composition depending on the degree of hydrophobicity derived from the type of the surface-protecting molecule. The degree of hydrophobization of the conductive microparticles (A) can be defined by wettability, which evaluates the methanol wettability of the conductive microparticles (A). The degree of hydrophobicity of the fine particles (A) having conductivity is preferably 30 to 50%, more preferably 35 to 45%. A small numerical value of the degree of hydrophobicity means that the conductive fine particles (A) are highly hydrophilic, and when the degree of hydrophobicity of the conductive fine particles (A) is less than 30%, the conductive resin composition It cannot be distributed evenly in the material. On the other hand, when the numerical value of the hydrophobicity of the conductive fine particles (A) is large, it means that the conductive fine particles (A) have high hydrophobicity. If it exceeds 50%, the affinity with the conductive resin composition is too high, so that the resolution of the heating resistor (wiring pattern) is deteriorated when the heating resistor (wiring pattern) is formed on the substrate and developed.

The degree of hydrophobicity of the conductive microparticles (A) can be calculated from the following methanol wettability. Specifically, 0.2 g of conductive microparticles (A) is added to 50 ml of distilled water placed in a 200 ml beaker. Methanol is slowly dripped from a buret whose tip is immersed in the liquid while being stirred, and continued until the conductive microparticles (A) are entirely wetted (until they all settle down). Assuming that the amount of methanol required for sedimentation of the fine particles (A) having full conductivity is a (ml), the degree of hydrophobicity is calculated by the following formula. The liquid temperature is usually 25°C.
Hydrophobicity [%] = (a / (a + 50)) x 100

When a plurality of the conductive fine particles (A) described above are used in combination, a metal auxiliary may be used to improve the sinterability of the conductive fine particles (A). Here, the metal auxiliary agent can change the sintering speed of the metal by adding it to the conductive resin composition, and examples thereof include rhodium, nickel, and palladium.

There is a value called Ig-loss as an index representing the adhesion amount of the protective molecule on the surface of the conductive microparticles (A), which is generally several percent or less. However, this Ig-loss value is irrelevant to the effects of the present invention.

The conductive microparticles (A) may be used after attaching a protective molecule such as a fatty acid or a hydrocarbon compound such as paraffin to the surface thereof in order to prevent aggregation in the conductive resin composition.

Examples of the fatty acid of the protective molecule on the surface of the conductive fine particles (A) include higher fatty acids such as stearic acid, oleic acid, and linoleic acid.
Hydrocarbon compounds include normal paraffins and branched isoparaffins. Among them, stearic acid, oleic acid and normal paraffin are preferred.

In addition, the fatty acid or the hydrocarbon compound such as paraffin as the protective molecule on the surface of the conductive fine particles (A) is used to control the degree of hydrophobicity of the conductive fine particles (A), as described later. Substitution with other fatty acids or hydrocarbon compounds may be performed. For example, when the long-chain fatty acid is replaced with a short-chain fatty acid (e.g., glycolic acid) for the protective molecule of the conductive microparticles (A), the conductive microparticles (A) can be easily obtained at a low temperature (about 200° C.) during baking. Since detachment of the protective molecule occurs from the surface of , the microparticles (A) having conductivity that can be fired at a low temperature can be obtained. Further, when the protective molecule on the surface of the conductive microparticles (A) is substituted with a fatty acid having a carboxyl group, the carboxyl group is coordinated to the surface of the conductive microparticles (A), resulting in conductivity. Hydrogen bonding between the fine particles (A) strongly suppresses aggregation of the conductive fine particles (A), and a high-resolution heating resistor (wiring pattern) can be obtained.

The content (A) of the conductive fine particles in the conductive resin composition may be 35 to 90% by weight, more preferably 40 to 85% by weight, of the conductive resin composition. If the content is more than this range, there are too many conductive fine particles, and the applicability (printability) of the conductive resin composition is deteriorated.

Photosensitive resin composition (B)
The photosensitive resin composition (B) used in the present invention can be used without any particular limitation as long as it shows photocurability upon irradiation with active energy rays such as electron beams, ultraviolet rays, and visible rays.

The photosensitive resin composition (B) in the present invention is one which forms a corrosion-resistant image through a cross-linking reaction, a polymerization reaction and a decomposition reaction upon irradiation with light. Furthermore, the photosensitive resin composition (B) includes those that can be cured by light to obtain a cured product.

As the photosensitive resin composition (B), a compound that has absorbed an active energy ray (for example, a binder polymer (b-1) or a polymerizable compound (b-2), which will be described later) reacts alone to cause polymerization, It is preferably one that crosslinks, cures, or the like. In addition, although the compound itself that has absorbed the active energy ray does not polymerize, crosslink, or cure, other compounds contained in the photosensitive resin composition (B) (for example, the initiator (b-3) described later) It is preferable that it polymerizes, crosslinks, or cures by acting with a compound that has absorbed active energy rays. In addition, two or more kinds of compounds may be involved in that case. For example, a composition containing a polymerizable compound (b-2) and an initiator (b-3) can be exemplified.

The photosensitive resin composition (B) preferably contains a binder polymer (b-1), a polymerizable compound (b-2), and an initiator (b-3). Furthermore, the photosensitive resin composition (B) may optionally contain additives for photocurable resins other than solvents and initiators.

The content of the photosensitive resin composition (B) in the conductive resin composition may be 10 to 65% by weight, more preferably 15 to 60% by weight, based on the conductive resin composition. Further, when adding components other than the conductive fine particles (A) and the photosensitive resin composition (B) to the conductive resin composition, the content of the photosensitive resin composition (B) is 10 to 60% by weight, preferably 15 to 45% by weight, of the resin composition.

Binder polymer (b-1)
The binder polymer (b-1) is not particularly limited as long as it can be photocured without causing separation, sedimentation, precipitation, etc. even when mixed with other components of (B) in the photosensitive resin composition. be able to. Specifically, (meth)acrylate resin, epoxy resin, phenol resin, polyurethane, polystyrene, vinyl acetate polymer, polyamide, vinyl chloride-vinyl acetate copolymer, cellulose diacetate, polychloroethylene, nitrocellulose, tetron, etc. can be exemplified by a polymer having a structure of Among them, radically polymerizable (meth)acrylate resins and polystyrene are preferred.

The acid value of the binder polymer (b-1) is preferably 20-60 mgKOH/g, more preferably 10-50 mgKOH/g. If the acid value of the binder polymer (b-1) is too small, resolution will not be possible, and if the acid value of the binder polymer (b-1) is too great, the heating resistor (wiring pattern) will be over-etched when developed. Therefore, the designed heating resistor (wiring pattern) may not be obtained.

As the binder polymer (b-1), a commercially available product may be used, or it may be synthesized by a polymerization reaction. The binder polymer (b-1) may be a homopolymer, a copolymer, or a solution dissolved in a solvent.

When a copolymer is used as the binder polymer (b-1), methyl acrylate, ethyl acrylate, hydroxypropyl acrylate, butyl acrylate, glycidyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, allylbenzene, allyl glycidyl ether, allyl alcohol, methallyl alcohol, diallyl phthalate, diallylpropyl isocyanurate, diallylcyclohexanedicarboxylate, triallyl isocyanurate, triallyl cyanurate, styrene, acrylic acid, methacrylic acid, acrylic anhydride, methacrylic anhydride A copolymer of one or more compounds selected from may be used. Among them, a copolymer of methyl methacrylate, styrene and acrylic acid is preferred.

When a copolymer is used as the binder polymer (b-1), the ratio of each component may be appropriately selected. When the copolymer contains acrylic acid and other components (a so-called copolymer consisting of two types), the weight ratio of acrylic acid contained in the copolymer is 1, (Acrylic acid: other components) = 1:2 to 1:6. Further, when the copolymer contains acrylic acid and two or more other components (for example, a copolymer consisting of three kinds), the weight ratio of acrylic acid contained in the copolymer is 1, and (acrylic acid : other component 1: other component 2) = 1:1:2 to 1:3:5. Other component 1 includes, for example, methacrylic acid, and other component 2 includes, for example, styrene.

The reaction for obtaining the binder polymer (b-1) by polymerization can be carried out by a known method using the polymerizable compound described below as a starting material. Polymerization conditions may be appropriately set according to the raw materials used and their amounts. A catalyst can be used for the polymerization reaction as needed. Examples of catalysts include known catalysts such as AIBN. These can be used singly or in combination. The polymerization reaction temperature is preferably in the range of 50 to 180°C, more preferably in the range of 70 to 150°C, in order to obtain optimum reaction rate and yield.

The polymerization reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon. The pressure during the polymerization reaction may be either atmospheric pressure or pressurized pressure, but atmospheric pressure is preferred in view of the simplicity of the work. The reaction can be carried out by charging the starting material once or in portions into a reactor equipped with stirring blades and reacting them at the predetermined temperature.

The binder polymer (b-1) may be used at a solid content of 100%, or may be used as a solution dissolved in a solvent. In view of handling problems, it is preferable that the solution dissolved in the solvent has fluidity. When the binder polymer (b-1) is dissolved in a solvent and used, the solid content may be 20% or more, preferably 50% or more.

The solvent used for dissolving the binder polymer (b-1) is not particularly limited, and known solvents can be used. For example, linear, branched, secondary or polyhydric alcohols such as ethanol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, 2-butyl alcohol, hexanol, ethylene glycol; Aromatic hydrocarbons such as ketones, toluene, and xylene, petroleum-based aromatic mixed solvents such as the Swasol series (manufactured by Maruzen Petrochemical Co., Ltd.) and the Solvesso series (manufactured by Exxon Chemical Co., Ltd.), cellosolve, butyl cellosolve, etc. Carbitols such as carbitol, ethyl carbitol, and butyl carbitol, propylene glycol alkyl ethers such as propylene glycol monomethyl ether and propylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, etc. Acetic esters such as polypropylene glycol alkyl ethers, ethyl acetate, butyl acetate, cellosolve acetate, butyl cellosolve acetate, butyl carbitol acetate, propylene glycol monomethyl ether acetate, N-methylpyrrolidone, and dialkyl glycol ethers etc. can be exemplified. A solvent can be used individually or in combination of 2 or more types as appropriate.

The binder polymer (b-1) used in the photosensitive resin composition (B) is used in order to improve the balance of performance such as developability and adhesion between the heating resistor (wiring pattern) to be formed and the base material. , the polystyrene-equivalent weight average molecular weight is preferably in the range of 10,000 to 1,000,000, more preferably in the range of 20,000 to 100,000.

The amount of the binder polymer (b-1) used in the photosensitive resin composition (B) is 20 to 55 weights in terms of solid content of the binder polymer (b-1) with respect to the total amount of the photosensitive resin composition (B). % range, preferably 25 to 50% by weight.

The weight average molecular weight of the binder polymer (b-1) is a polystyrene-equivalent value obtained by gel permeation chromatography (GPC). For example, model: Shodex (manufactured by Showa Denko Co., Ltd.), columns: KF-805L, KF-803L, and KF-802 (manufactured by Showa Denko Co., Ltd.), using THF or the like as an eluent, standard It was carried out using polystyrene as a sample. Conditions for measuring the weight-average molecular weight of the binder polymer (b-1) may be appropriately selected depending on the physical properties of the polymer.

Polymerizable compound (b-2)
Examples of the polymerizable compound (b-2) include radically polymerizable compounds, among which polyfunctional (meth)acrylates have high reactivity and can increase the sensitivity of the resin composition to light. Compounds are preferred. Specifically, polyethylene glycol di(meth)acrylate (having 2 to 14 ethylene groups), trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth) Acrylates, trimethylolpropane ethoxy tri(meth)acrylate, trimethylolpropane propoxy tri(meth)acrylate, trimethylolpropane ethylene glycol adduct triacrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate , polypropylene glycol di(meth)acrylate (having 2 to 14 propylene groups), pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, di Examples include pentaerythritol hexa(meth)acrylate, tetrahydrofurfuryl acrylate, etc. Among them, polyethylene glycol di(meth)acrylate (having 2 to 14 ethylene groups), trimethylolpropane tri(meth) Acrylate, trimethylolpropane ethylene glycol adduct triacrylate, pentaerythritol tri(meth)acrylate, tetrahydrofurfuryl acrylate are preferred. Can be used alone or in appropriate combination of two or more

The polymerizable compound (b-2) in the photosensitive resin composition (B) may be used alone or in combination of multiple types, and the amount used is the same as the photosensitive resin composition ( It may be in the range of 20 to 70 parts by weight, preferably in the range of 30 to 65 parts by weight, per 100 parts by weight of the binder polymer (b-1) contained in B) in terms of solid content.

Initiator (b-3)
The initiator (b-3) can be used without particular limitation as long as it has an absorption band in the wavelength of the active energy ray and causes polymerization reaction, cross-linking reaction, curing reaction, or the like. In general, ultraviolet rays are preferably used as active energy rays for the reaction from the viewpoint of cost. Therefore, as the initiator (b-3), photoradical polymerization initiators, which are abundant in types and excellent in reactivity with monomers, are preferable.

Specific examples of photoradical polymerization initiators include benzoin, acetophenone, 2-methylanthraquinone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, and 2,4-diisopropyl. thioxanthone, benzophenone, 4-benzoyl-4'-methyldiphenylsulfide, 2,4-diisopropylxanthone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2,2-dimethoxy-1 , 2-diphenylethan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)- Phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl]-2- Methyl-propan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl) -butanone-1,2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morphonyl)phenyl]-1-butanone, 2,4,6-trimethylbenzoyl -diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 1,2-octanedione, 1-[4-(phenylthio)-,2-(O-benzoyloxime), 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone) and the like. Among them, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 1,2-octanedione, 1,2-octanedione, 1 -[4-(phenylthio)-,2-(O-benzoyloxime), 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3- yl]ethanone) is preferred, and 1,2-octanedione, 1-[4-(phenylthio)-,2-( O-benzoyloxime), 1-(O-acetyloxime)-1-[9-ethyl-6 -(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone) is more preferred.

The amount of the photopolymerization initiator (b-3) used in the photosensitive resin composition (B) is in the range of 2 to 20 parts by weight per 100 parts by weight of the solid content of the binder polymer (b-1). Any amount is sufficient, and a range of 3 to 15 parts by weight is more preferable.

Other Additives Various additives such as surface modifiers and dispersants may be added to the photosensitive resin composition (B) of the present invention, if necessary, within a range that does not affect the effects of the present invention. good too. Both are used for the purpose of preventing troubles such as cissing and pinholes, and aiming at effects such as making the composition uniform and improving substrate wettability. The amount of the additive compounded is 0.1 to 10 parts by weight per 100 parts by weight of the total weight of the conductive resin composition containing the conductive fine particles (A) and the photosensitive resin composition (B). 0.2 to 5 parts by weight is more preferred, and 0.3 to 3 parts by weight is particularly preferred.

Examples of surface conditioners include vinyl-based polymers, silicone-based polymers, fluorine-based polymer powder waxes, and the like. Vinyl-based polymers include polyalkylacrylates, polyalkylmethacrylates, polyalkylvinylethers, polybutadiene, and the like. Examples of silicone-based polymers include polydimethylsiloxane, polyphenylsiloxane, and organically modified polysiloxane. Fluoropolymers include fluorosilicone and the like. Powder waxes include polyethylene wax and the like. It may be used alone or in combination of two or more. It is desirable to be powder at room temperature.

Examples of the dispersant include those obtained by adsorbing an organic polymer to an inorganic material, such as silica-adsorbed polyacrylate and silica-adsorbed polymethacrylate. It may be used alone or in combination of two or more.

Although not particularly limited in the present invention, various pigments may be added to color the coating film.

In addition, an inorganic filler, an organic filler, a polymerization inhibitor, a plasticizer, a sintering retardant, a flame retardant, etc. may be contained within a range that does not impair the effects of the present invention.

Preparation method of conductive resin composition The conductive resin composition of the present invention is prepared by mixing or It can be adjusted by kneading.

The method of mixing or kneading these components is not particularly limited as long as each component can be uniformly dispersed or mixed in the conductive resin composition. Examples of such a method include a method using a mechanical stirrer, magnetic stirrer, ultrasonic disperser, planetary mill, ball mill, planetary mixer, three rolls, or the like. The method using a planetary mill is preferable in terms of ease of handling, and the method using three rolls is preferable in terms of uniform dispersion, and two or more methods may be combined.

Method for manufacturing a circuit board on which a heating resistor is formed As a method for manufacturing a circuit board on which a heating resistor of the present invention is formed, the above-described step of preparing the conductive resin composition of the present invention (preparation step); A process of applying a conductive resin composition on a substrate such as metal, glass, ceramics, heat-resistant plastic (coating process), and a film or negative mask corresponding to the heating resistor (wiring pattern) to be formed. A step of irradiating the coating film of the resin composition with an active energy ray to cure the coating film (exposure step), and a step of dissolving, removing, and drying the unexposed portion on the substrate with a developer (development step). can be exemplified.

In the coating step, the conductive resin composition of the present invention prepared in the preparation step is applied to metals, glass, ceramics, heat-resistant plastics, etc. (preferably, It is applied on a substrate of highly insulating glass, ceramics) and dried. The drying temperature in the coating step is preferably 60 to 120° C., and the drying time is preferably 5 to 60 minutes. In addition, the thickness of the coating film on the substrate such as metal, glass, ceramics, heat-resistant plastic is not particularly limited, but it is preferably more than 5 μm and less than 50 μm, more preferably more than 10 μm and less than 40 μm. preferable.

In the exposure process, active energy rays are applied to a coating film applied to a substrate such as metal, glass, ceramics, or heat-resistant plastic through a film or negative mask corresponding to the heating resistor (wiring pattern) to be formed. Then, the irradiated portion is polymerized, crosslinked, cured, or the like. Examples of active energy rays to be irradiated include ultraviolet rays, electron beams, X-rays, and the like, with ultraviolet rays being preferred. Low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, halogen lamps, black lights, and the like can be used as light sources. Examples of the exposure method include contact exposure with a mask, proximity exposure, projection exposure, and the like.

The exposure dose in the active energy ray irradiator is preferably 100-1000 mJ/cm 2 , more preferably 200-900 mJ/cm 2 .

In the developing step, the desired heating resistor (wiring pattern) can be obtained by using a developer to dissolve and remove the uncured, unexposed portions.

Any developer can be used without particular limitation as long as it can solubilize the unexposed portion of the conductive resin composition of the present invention. The developer to be used may be either water-based or oil-based, and the pH of the liquid may be any. For example, when a compound having an acidic group is present in the photosensitive resin composition (B), in addition to an aqueous metal alkali solution such as sodium hydroxide and sodium carbonate, an aqueous organic alkali solution such as monoethanolamine and diethanolamine is added. can be used. Specifically, a weakly alkaline aqueous solution is preferred, for example, a 5-10 wt % calcium carbonate aqueous solution is preferred.

As a developing method in the developing step, any developing method commonly used in photolithography can be used without any particular limitation. Specifically, the dipping method in which a substrate (for example, ceramic) with a cured coating film formed thereon is immersed in the developer, the spray method in which the developer is sprayed over the entire surface of the substrate, and the developer and the substrate are placed in a container. A barrel method or the like can be exemplified. The development method may be appropriately determined according to the properties of the conductive resin composition to be used. The developing method differs depending on the shape of the substrate, such as metal, glass, ceramics, and heat-resistant plastic, on which the heating resistor (wiring pattern) is to be formed. When removing the unnecessary coating film (unexposed portion), a method of washing away the coating film adhering surface with a uniform pressure by a spray method is preferable in that the resolution can be improved.

After washing with water and acid neutralization to remove unnecessary developer, the heating resistor (wiring pattern) is sintered. The sintering temperature is preferably 500-900° C., and the sintering time is preferably 30-300 minutes. By sintering the heating resistor (wiring pattern) formed on the ceramic substrate at the above sintering temperature and firing time, the photosensitive resin composition (B) contained in the conductive resin composition evaporates from the substrate. However, only conductive fine particles remain on the substrate.

Through the above steps, the conductive resin composition of the present invention can be used to form a heating resistor (wiring pattern) on a substrate made of metal, glass, ceramics, heat-resistant plastic, or the like.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited by the examples.

Materials used in Examples and Comparative Examples described later are described below.

Fine particles having conductivity (A)
Particle A1: Mitsui Kinzoku SL02 (particle shape: spherical, 90% particle size 3.5 μm, protective molecule: stearic acid)
Particle A2: Dowa Electronics Ag2.5-11F (particle shape: spherical, 90% particle diameter 1.8 μm, protective molecule: oleic acid)
Particle A3: Tokuriki TC-905 (particle shape: spherical, 90% particle size 2.6 μm, protective molecule: paraffin)
Particle A4: Dowa Electronics G35 (particle shape: mixture of spherical and flake-like, 90% particle diameter 5.2 μm, protective molecule: paraffin)
Particle A5: A4 in which the surface protective molecule is replaced with glycolic acid (particle shape: mixture of spherical and flaky particles, 90% particle diameter 3.5 μm, protective molecule: glycolic acid)
Particle A6: TRIAL3 manufactured by Mitsui Kinzoku (particle shape: spherical, 90% particle diameter 2.5 μm, protective molecule: stearic acid)

Method for Substituting Surface Protective Molecules of Conductive Fine Particles (A) In order to replace the surface protective molecules of conductive fine particles (A), the surface protective molecules of particles A4 (G35 manufactured by DOWA Electronics) are paraffin. replaced it with glycolic acid. Specifically, 1 g of glycolic acid was added to 100 g of particles A4 (G35 microparticles), diluted with the same amount of acetone as particles A4, and then stirred for 5 minutes at 1000 rpm with a planetary stirrer. After stirring, the particles were spread on a vat and air-dried to obtain particles A5 in which the protective molecules on the surface were replaced with glycolic acid.

Method for Measuring Hydrophobicity of Conductive Fine Particles (A) Hydrophobicity of each conductive fine particle (A) is evaluated by methanol wettability as shown below. 0.2 g of conductive microparticles are added to 50 ml of distilled water placed in a 200 ml beaker, and methanol is slowly added dropwise with stirring from a buret whose tip is immersed in the liquid. continued until the whole was wet (until it all settled). When the amount of methanol required for sedimentation of all the fine particles was defined as a (ml), the degree of hydrophobicity was calculated by the following formula. The liquid temperature was 25°C. Table 1 shows the measurement results.
Hydrophobicity [%] = (a / (a + 50)) x 100

The 90% particle size of the conductive fine particles (A) is evaluated with a laser diffraction particle size distribution meter. 90% means the 90th of 100 particles counted from the smallest, and is expressed as D90. The measurement was performed by Horiba LA-950V2. Table 1 shows the measurement results.

Binder polymer (b-1)
110 g, 223 g, and 75 g of methyl methacrylate, styrene, and acrylic acid were put into a 2,000 ml cylindrical round-bottomed flask, and 705 g of dipropylene glycol monomethyl ether and 30 g of AIBN were added thereto. After heating and stirring for hours, a predetermined amount of solvent was removed by distillation under reduced pressure, and 800 g of binder polymer (b-1) solution having a solid content of 50% (weight average molecular weight: 70,000, solvent: dipropylene glycol monomethyl ether) was added. Obtained.

The acid value of the binder polymer (b-1) was measured by the following method and confirmed to be 37 mgKOH/g. After removing the solvent by drying the binder polymer (b-1) with a solid content of 50% in the atmosphere at 50° C. for 12 hours, 3 g was weighed in an Erlenmeyer flask, and the solvent (toluene/methanol=7/3 (volume ratio) ) was added and dissolved. Next, 3 drops of an indicator (1% phenolphthalein/ethyl alcohol solution) was added and titration was performed with a 0.1N potassium hydroxide aqueous solution. Table 1 shows the results.
Acid value (mgKOH/g) = A x F/S
F: coefficient of 0.1N potassium hydroxide aqueous solution (f × 5.61), f = 1
V: titration volume (ml) of 0.1N potassium hydroxide aqueous solution
W: sample weight (g)

Binder monomer (b-2)
B1: Pentaerythritol triacrylate (manufactured by Fuji Film Wako Pure Chemical Industries)
B2: Tetrahydrofurfuryl acrylate (manufactured by Fuji Film Wako Pure Chemical Industries)

Initiator (b-3)
Oxime ester photopolymerization initiator: OXE-02 manufactured by BASF (1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone)

Photosensitive resin composition (B)
The amount of each component shown in Table 1 was mixed to prepare a photosensitive resin composition (B).

A glazed plate manufactured by Asuzac was prepared as a base material, and printed at 20±5 μm using an MT-300 screen printer manufactured by Micro-Tech, and the solvent was removed by drying at 80° C. for 10 minutes. Then, using a photomask with a pattern drawing simulating a φ50 μm electrode pad at the end of the line/space = 20 μm/20 μm and a straight wiring, exposure of 300 J/cm 2 with a UV irradiation machine, 5% calcium carbonate aqueous solution. It was confirmed whether a heating resistor (wiring pattern) having a thickness of 10±2 μm could be obtained through development for 20 seconds and subsequent washing with water. Further, baking was performed in an oven at 800° C. for 4 hours to remove the resin composition and complete the heating resistor (wiring pattern). The obtained heating resistor (wiring pattern) was subjected to the test described later.

Confirmation of resolution In the above process, the heating resistor (wiring pattern) was visually checked with an optical microscope, and the linearity of the straight wiring in the heating resistor (wiring pattern) and the circularity of the electrode pad were judged by 〇×. . Table 1 shows the results. Typical examples of x include disconnection, short circuit, lack of linearity and jaggedness, and lack of circles.

Tape peeling test A cellophane tape manufactured by Nichiban Co., Ltd. was applied to the coating film and strongly rubbed with a finger. Table 1 shows the evaluation results.
5: Removed quickly and no peeling 4: Removed quickly and 50% peeled, but the base material peeled 3: Removed quickly and completely peeled, but peeled slowly and no peeling 2: Slowly peeled and 50% peeled 1: Remove slowly and completely

The conductive resin composition using conductive fine particles (A) having a predetermined degree of hydrophobicity and a particle size of 90%, shown in Examples 1 to 3, was good in both resolution and tape peeling test. rice field.
In Comparative Example 1, due to the relatively large 90% particle diameter of the conductive fine particles (A), the linearity of the resolved pattern was poor, and peeling occurred in the tape peeling test.
In Example 4, the conductive microparticles (A) used in Comparative Example 1 were replaced with other molecules for their surface protective molecules. Some of the particles were physically pulverized in the stirring process during the replacement treatment, and the 90% particle size became smaller than the initial one, and the degree of hydrophobicity reached a high level of affinity with the photosensitive resin composition (B). As a result, the pattern resolution was improved, and sufficient adhesion was achieved in the tape peeling test.
In Comparative Example 2, the degree of hydrophobicity of the conductive fine particles (A) was at a low level of affinity with the photosensitive resin composition (B), and partial disconnection occurred in the pattern resolution, and the tape was peeled off. Peeling occurred in the test as well.
In Examples 5 and 6, the conductive fine particles (A) used in Example 1 were used, and the blending amounts of the conductive fine particles (A) and the photosensitive resin composition (B) were changed. . In Examples 7 and 8, the conductive fine particles (A) used in Example 2 were used, and the blending amounts of the conductive fine particles (A) and the photosensitive resin composition (B) were changed.
Also in Examples 5 to 8, both the resolution and the tape peeling test were good.

The electric/electronic device manufactured according to the present invention can be used for display devices such as displays, communication devices such as telephones, printing devices such as printers, and batteries such as all-solid-state batteries and storage batteries.

Claims (6)

A conductive resin composition containing conductive fine particles (A) and a photosensitive resin composition (B),
A conductive resin composition, wherein the conductive fine particles (A) have a hydrophobicity of 30 to 50%. The photosensitive resin composition (B) contains a binder polymer (b-1), a polymerizable compound (b-2), and an initiator (b-3),
2. The conductive resin composition according to claim 1, wherein the binder polymer (b-1) has an acid value of 20 to 60 mgKOH/g. 3. The conductive resin composition according to claim 1, wherein the conductive fine particles (A) have a 90% particle size of 5 [mu]m or less. 3. The conductive resin composition according to claim 1, wherein the conductive fine particles (A) are silver or an alloy containing silver. 5. A method for producing a circuit board, wherein the conductive resin composition according to claim 4 is coated on a substrate, exposed, developed, and baked at a temperature of 500° C. or higher to form a heating resistor. 6. The method of manufacturing a conductive circuit-forming substrate according to claim 5, wherein the substrate is ceramic.