JP5560821B2 - Photosensitive conductive paste and method for manufacturing substrate with conductive wiring - Google Patents

Description

  The present invention relates to a photosensitive conductive paste capable of forming a patterned conductive wiring on a substrate of silicon, glass, resin, ceramics, composite material or the like, and a method of manufacturing a substrate with a conductive wiring using the same. The method for producing a photosensitive conductive paste and a substrate with conductive wiring of the present invention can be suitably used for forming an electrode pattern used for a back plate of a plasma display panel, for example.

  In recent years, conductive paste for forming patterned conductive wiring by coating, drawing, and printing on substrates such as glass, ceramics, and composite materials is relatively inexpensive and excellent in microfabrication. It is used in fields such as solar cells. While maintaining and improving performances such as conductivity and fine workability, reduction of environmental burden and cost reduction have attracted attention in recent years.

  A general conductive paste used in these applications includes an inorganic powder including a conductive powder and glass frit, and an organic binder. After applying such a conductive paste in a specific pattern on a substrate or forming a conductive paste coating film having a desired pattern by patterning after coating, the organic binder is baked in air at 500 ° C. or higher. The conductive wiring made of a conductive material and glass is formed by removing and softening the glass frit.

  For example, a plasma display panel (PDP) can display at a higher speed than a liquid crystal panel and can be easily increased in size, and thus has penetrated into fields such as OA equipment and public information display devices. It is also used in the field of high-definition television.

  In the PDP, a slight gap formed between two glass substrates of a front plate and a back plate is used as a discharge space, and plasma discharge is generated between the anode electrode and the cathode electrode, and is enclosed in the discharge space. The display is performed by emitting ultraviolet light generated from the gas to a phosphor provided in the discharge space. For this reason, the electrodes are provided in stripes on the front plate and the back plate, and a plurality of electrodes are provided in parallel. The electrodes on the front plate and the electrodes on the back plate face each other with a slight gap and are orthogonal to each other. To be formed. Among the PDPs, in a surface discharge type PDP having a three-electrode structure suitable for color display by a phosphor, a plurality of electrode pairs formed of display electrodes adjacent to each other in parallel are provided on the front plate and orthogonal to each electrode pair. And a plurality of address electrodes provided on the back plate. In addition, a barrier rib for preventing crosstalk of light and securing a discharge space is formed in the space between the electrodes on the back plate. Further, a phosphor is formed in the discharge space.

  Of the electrodes, the address electrodes formed on the back plate need to have a uniform thickness and line width over a wide range. Furthermore, with the higher definition of PDPs, the fine pitch of address electrodes is progressing. When an electrode is formed using a conductive paste, the line shape is bent and swelled even after the baking process because the baking process is performed at a temperature of 500 ° C. or higher in the air as described above. There was a need to use no material. From these restrictions, it has been proposed to use a photosensitive paste using a noble metal such as silver or gold as the conductive powder (for example, Patent Document 1). However, the electrode paste used in Patent Document 1 has a problem of high cost because it contains a noble metal. On the other hand, when a metal such as aluminum or copper is used alone as an electrode material, a thick oxide film is formed in the firing step in the air, so that fusion between metal powders is hindered and resistance increases. There's a problem. Therefore, in general, a complicated process such as applying a coating layer is required to form a pattern of aluminum or copper.

  For this reason, conductive pastes using precious metal powders that are highly malleable and have excellent storage stability without being oxidized even when used alone are widely used as a PDP electrode. Electrodes using inexpensive silver are used.

  In such a conductive paste, when the amount of the organic binder is increased instead of decreasing the amount of the conductive powder, the ratio of the inorganic component in the coating film is decreased, so that the resistance value is increased or the substrate is electrically conductive. There is a problem that the adhesion strength with the wiring is reduced and the conductive wiring is peeled off from the substrate. On the other hand, if the amount of glass powder is increased instead of reducing the amount of metal powder, the adhesion strength between the substrate and the conductive wiring increases, but the glass powder softens before the organic binder component is completely removed. There is a problem in that the evaporation of the organic binder component is hindered and the conductive wiring after firing is swollen.

JP-A-10-273338

  In the present invention, even if this problem is solved and the amount of conductive powder in the photosensitive conductive paste is relatively small, the adhesion strength between the substrate and the conductive wiring is high, the resistance value is low, bulging, etc. It is an object of the present invention to provide a photosensitive conductive paste that can form a conductive wiring having a desired shape without being generated.

  In order to solve the above-described problems, the photosensitive conductive paste of the present invention has the following configuration. That is, a photosensitive conductive paste containing a conductive powder, an inorganic component including an inorganic filler composed of glass frit and ceramic powder, and a photosensitive organic component, wherein the content of the conductive powder is 50 to 70% by mass. The glass frit content is in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the conductive powder, and the inorganic filler is 0.2 to 30 parts by weight with respect to 100 parts by weight of the conductive powder. % Is a photosensitive conductive paste characterized by being in the range of%.

  When the photosensitive conductive paste of the present invention is used, even if the amount of conductive powder in the paste is relatively small, the adhesion strength between the substrate and the conductive wiring is high, the resistance value is low, and the swelling is controlled. High-definition conductive wiring can be formed.

  The conductive powder used for the photosensitive conductive paste of the present invention may be a conductive powder, and preferably contains at least one selected from the group consisting of Ag, Au, Pd, Ni, Cu, Al and Pt. Therefore, a low resistance conductive powder is preferable. These can be used independently, in an alloy state, or in a mixed powder state.

  As the particle diameter of the conductive powder, the center diameter of the volume-based distribution is preferably 0.7 to 6 μm. More preferably, it is 1.3-4 micrometers. When the particle diameter is in this range, a fine fine pattern can be formed.

The specific surface area of the conductive powder is preferably 0.3 to ^2.5 m ² / g in view of the accuracy of the conductive wiring. More preferably, the specific surface area is 0.35 to 2.0 m ² / g.

Moreover, it is preferable that the tap density of electroconductive powder is 3-6 g / cm < ² >. More preferably, it is the range of 3.5-5 g / cm < ² >. When the tap density is in this range, the binder resin component can be reduced as much as possible, the shape retention of the coating film pattern is good, the pattern system is improved, and the debinding property is improved. This is preferable because the resistance value of the conductive wiring becomes small.

  The conductive powder may be granular (particulate), polyhedral, or spherical. Among them, it is more preferable that the particle size distribution is sharp, the aggregates are few, and the shape is spherical. In this case, the spherical shape means that the sphericity is 90% by number or more. The sphericity is obtained by photographing powder with an optical microscope at a magnification of 300 times, counting the particles that can be counted, and representing the ratio of the spheres. A higher sphericity is preferable because the specific surface area is smaller and the tap density is larger.

  The glass frit in the present invention is used in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the conductive powder in order to firmly bake the conductive powder on the substrate. Preferably, it is in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the conductive powder. Further, the glass frit has an effect of sintering aid for sintering the conductive powder and an effect of lowering the conductor resistance. When the content of the glass frit is less than 3 parts by weight with respect to 100 parts by weight of the conductive powder, the adhesion strength between the substrate and the conductive wiring is reduced, causing a problem that the conductive wiring is peeled off from the substrate. Moreover, since the sinterability between the conductive powders is deteriorated, there arises a problem that the resistance of the obtained wiring is increased. On the other hand, when the content of the glass frit is more than 20 parts by weight with respect to 100 parts by weight of the conductive powder, the photosensitive organic component is not sufficiently evaporated, which causes swelling of the conductive wiring after firing. .

  The glass transition temperature (Tg) and softening point (Ts) of the glass frit used in the photosensitive conductive paste of the present invention are preferably in the range of 400 to 500 ° C. and 450 to 550 ° C., respectively. Preferably, Tg and Ts are 440 to 500 ° C. and 460 to 530 ° C., respectively. When Tg and Ts are less than 400 ° C and 450 ° C, respectively, sintering of the glass starts before the photosensitive organic components such as polymers and monomers evaporate. This is not preferable for obtaining a dense and low-resistance conductor film. When the glass frit with Tg and Ts exceeding 500 ° C. and 550 ° C., respectively, when firing at a temperature of 600 ° C. or less, sufficient adhesion strength between the conductive wiring and the substrate and a dense conductor film are difficult to obtain.

  As for the powder particle size of the glass frit, it is preferable that the average particle size is 0.5 to 1.4 μm, the 90% particle size is 1 to 2 μm, and the top size is 4.5 μm or less. If the average particle size and 90% particle size are less than 0.5 μm and 1 μm, respectively, the glass frit particle size becomes too small and ultraviolet rays are scattered to the unexposed areas, and photocuring of the edges and edges of the conductor film occurs. In some cases, the film cannot be completely developed, and there is a tendency that the conductor film pattern is cut and the resolution is lowered. When the average particle size, 90% particle size, and top size exceed 1.4 μm, 2 μm, and 4.5 μm, respectively, the coefficient of thermal expansion of the coarse glass frit differs from that of the conductive powder. Since the adhesive strength of the conductor film is lowered, the film may be peeled off, and the coarse glass frit remains in the conductor film, and the adhesive strength tends to be lowered.

In the present invention, as the composition of the glass frit, Bi ₂ O ₃ is preferably blended in the range of 30 to 70% by mass. When it is less than 30% by mass, there are few effects in terms of controlling the glass transition point and the softening point and increasing the adhesion strength of the conductor film to the substrate. On the other hand, if it exceeds 70% by mass, the softening point of the glass frit becomes low and the glass frit melts before the binder in the photosensitive conductive paste evaporates. For this reason, the debinding property of the paste is deteriorated, the sinterability of the conductor film is lowered, and the adhesive strength with the substrate tends to be lowered.

In particular, the glass frit is 30 to 70% by mass of Bi ₂ O _{3 in} terms of oxide.
SiO ₂ 5~30 mass%
B ₂ O ₃ having 6 to 20 wt%
ZrO ₂ 3-10% by mass
Al ₂ O ₃ 1-5 mass%
It is preferable that it is an alkali-free glass frit which contains 80 mass% or more of the composition range and contains substantially no Na ₂ O, K ₂ O or Li ₂ O. Within this range, a glass frit capable of firmly firing the conductor film on the substrate at a preferred firing temperature of 550 to 600 ° C. when using a glass substrate is obtained.

  The photosensitive electrically conductive paste of this invention is characterized by including an inorganic filler in the range of 0.2-30 weight part with respect to 100 weight part of electrically conductive powder. Preferably it exists in the range of 0.3-30 weight part.

  When the content of the inorganic filler is less than 0.2 parts by weight with respect to 100 parts by weight of the conductive powder, the sintering of the glass frit starts before the photosensitive organic component such as polymer or monomer evaporates, and the binder is removed. It does not work, and swelling occurs in the conductive wiring after firing. On the other hand, when the content of the inorganic filler is more than 30 parts by weight with respect to 100 parts by weight of the conductive powder, since the sintering of the conductive powder and the glass frit is largely hindered, the adhesion strength between the substrate and the conductive wiring is small. As a result, there arises a problem that the resistance becomes high. Furthermore, problems such as poor conduction due to the disconnection of the wiring are likely to occur.

  In the present invention, an inorganic filler is an inorganic powder other than a conductive powder, and means an inorganic powder that does not melt or soften during firing. Specifically, it has a softening point, melting point, decomposition point, etc. at 600 ° C. or lower. It refers to inorganic powder that does not. The inorganic filler used in the photosensitive conductive paste of the present invention is preferably at least one selected from the group consisting of titania, alumina, silica, cordierite, mullite, spinel, barium titanate and zirconia. Of these, alumina, titania, and silica are particularly preferably used. By using these fillers singly or in combination, it is possible to improve the debinding property of the conductor film and to control the swelling. The average particle size of these fillers is preferably 0.05 to 4 μm from the viewpoint of forming a fine fine pattern. More preferably, 0.1-4 micrometers is preferable.

  The photosensitive conductive paste of the present invention contains a photosensitive organic component. The photosensitive organic component preferably contains a photosensitive polymer and / or a photosensitive monomer.

  The photosensitive polymer is obtained by polymerization or copolymerization of components selected from compounds having a carbon-carbon double bond.

  By copolymerizing an unsaturated acid such as an unsaturated carboxylic acid, development with an aqueous alkali solution after exposure can be made possible. Specific examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, vinyl acetic acid, and acid anhydrides thereof. The acid value of the polymer or oligomer having an acidic group such as a carboxyl group in the side chain thus obtained is preferably 50 to 180 mgKOH / g, more preferably 70 to 140 mgKOH / g.

Examples of the photosensitive polymer include methyl (meth) acrylate, ethyl (meth) acrylate, normal butyl (meth) acrylate, isobutyl (meth) acrylate, isopropyl (meth) acrylate, 2-ethylmethyl (meth) acrylate, and 2-hydroxyl. Those obtained by adding a photoreactive group to the side chain or molecular end of an acrylic resin made of a polymer or copolymer such as ethyl (meth) acrylate are preferably used. Preferred photoreactive groups are those having an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include a vinyl group, an allyl group, an acrylic group, and a methacryl group.
The content of the photosensitive polymer in the photosensitive conductive paste of the present invention is preferably 1 to 30% by mass, and more preferably 2 to 30% by mass.

  Specific examples of the photosensitive monomer include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, sec-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, and n-pentyl. Acrylate, allyl acrylate, benzyl acrylate, butoxyethyl acrylate, butoxytriethylene glycol acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, 2-ethylhexyl acrylate, glycerol acrylate, glycidyl acrylate, heptadecafluorodecyl acrylate, 2 -Hydroxyethyl acrylate, isobornyl acrylate 2-hydroxypropyl acrylate, isodexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxyethyl acrylate, methoxyethylene glycol acrylate, methoxydiethylene glycol acrylate, octafluoropentyl acrylate, phenoxyethyl acrylate, stearyl acrylate, trifluoroethyl acrylate, Allylated cyclohexyl diacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, dipentaerythritol hexaacrylate, Dipentaerythri Monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, glycerol diacrylate, methoxylated cyclohexyl diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate, polypropylene glycol diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, acrylamide , Aminoethyl acrylate and those in which the acrylate in the molecule of the above compound is partially or entirely changed to methacrylate, γ-methacryloxypropyltrimethoxysilane, 1-vinyl-2-pyrrolidone and the like. In the present invention, one or more of these can be used.

  In the photosensitive conductive paste of the present invention, the photosensitive organic component is preferably contained in an amount of 5 to 40 parts by weight with respect to 100 parts by weight of the conductive powder from the viewpoint of sensitivity to light. Furthermore, it is preferable that 10-30 weight part is contained.

  In addition to the photosensitive organic component, the photosensitive conductive paste of the present invention further includes cellulose resins such as ethyl cellulose, methyl cellulose, nitrocellulose, cellulose acetate, cellulose propionate, and cellulose butyrate, poly-α-methyl sulfone, and polyvinyl. Non-photosensitive polymers such as alcohol or polybutene can be contained.

  Moreover, it is preferable that the photosensitive conductive paste of this invention uses a photoinitiator, a sensitizer, a polymerization inhibitor, and an organic solvent as needed.

  Specific examples of the photopolymerization initiator include benzophenone, methyl o-benzoylbenzoate, 4,4′-bis (dimethylamino) benzophenone, 4,4′-bis (diethylamino) benzophenone, 4,4′-dichloro. Benzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methylpropiophenone, p- t-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-isopropylthioxanthone, diethylthioxanthone, benzyldimethylketanol, benzylmethoxyethyl acetal, benzoin, benzoin methyl ester Ter, benzoin butyl ether, anthraquinone, 2-t-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzosuberone, methyleneanthrone, 4-azidobenzalacetophenone, 2,6-bis (p -Azidobenzylidene) cyclohexanone, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-1,2-butadion-2- (o-methoxycarbonyl) oxime, 1-phenyl-propanedione- 2- (o-ethoxycarbonyl) oxime, 1,3-diphenyl-propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxy-propanetrione-2- (o-benzoyl) oxime, Michalke , 2-methyl- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1, naphthalenesulfonyl chloride, quinoline Sulfonyl chloride, N-phenylthioacridone, 4,4′-azobisisobutyronitrile, diphenyl disulfide, benzthiazole disulfide, triphenylphosphine, camphorquinone, carbon tetrabrominated, tribromophenyl sulfone, benzoin peroxide and Eosin, methylene blue, acetophenone, anisoin, 4-benzoylbiphenyl, 2-benzyl-2- (dimethylamino) -4-morpholinobutyrophenone, dibenzosuberenone, 4,4-dihydroxybenzophenone, ethyla Traquinone, 3-hydroxyacetophenone, 3-hydroxybenzophenone, 4-hydroxybenzophenone, 2-methyl-4- (methylthio) -2-morpholinopropiophenone, 2-chlorothioxanthen-9-one, 4- (dimethylamino) Benzophenone, 4-thioxan-9-one, commercially available products such as IRGACURE369, IRGACURE907, IRGACURE1300, 4,4-bis (diethylaminobenzophenone), IRGACURE651, IRGACURE819, IRGACURE2100, IRGACURE2100, IRGACURE2100, IRGACURE2100, IRGACURE2100, IRGACURE2100 ("IRGACURE" and "DAROCUR" are registered trademarks).

  The sensitizer is preferably added to improve sensitivity. Specific examples of the sensitizer include 2,3-bis (4-diethylaminobenzal) cyclopentanone, 2,6-bis (4-dimethylaminobenzal) cyclohexanone, and 2,6-bis (4-dimethylamino). Benzal) -4-methylcyclohexanone, diethylthioxanthone, Michler's ketone, 4,4-bis (diethylamino) benzophenone, 4,4-bis (dimethylamino) chalcone, 4,4-bis (diethylamino) chalcone, p-dimethylaminocinna Myrideneindanone, p-dimethylaminobenzylideneindanone, 2- (p-dimethylaminophenylvinylene) -isonaphthothiazole, 1,3-bis (4-dimethylaminobenzal) acetone, 1,3-carbonyl-bis (4-Diethylaminobenzal) acetone, 3,3-carboni -Bis (7-diethylaminocoumarin), N-phenyl-N-ethylethanolamine, N-phenylethanolamine, N-tolyldiethanolamine, N-phenylethanolamine, isoamyl dimethylaminobenzoate, isoamyl diethylaminobenzoate, 3-phenyl Examples include -5-benzoylthiotetrazole and 1-phenyl-5-ethoxycarbonylthiotetrazole. In the present invention, one or more of these can be used. Some sensitizers can also be used as photopolymerization initiators.

  When adding a sensitizer to the photosensitive electrically conductive paste of this invention, the addition amount is 0.1-10 mass% with respect to the photosensitive organic component, More preferably, it is 0.2-5 mass%. If the amount of the sensitizer is too small, the effect of improving the photosensitivity is not exhibited, and if the amount of the sensitizer is too large, the residual ratio of the exposed portion may be too small.

  In order to improve the thermal stability during storage of the photosensitive conductive paste, it is preferable to add a polymerization inhibitor. Specific examples of the polymerization inhibitor include hydroquinone, hydroquinone monomethyl ether, N-nitrosodiphenylamine, phenothiazine, p-t-butylcatechol, N-phenylnaphthylamine, 2,6-di-t-butyl-p-methylphenol. , Chloranil, pyrogallol and the like. When adding a polymerization inhibitor, the addition amount is preferably 0.1 to 5% by mass, more preferably 0.2 to 3% by mass in the photosensitive conductive paste. If the amount of the polymerization inhibitor is too small, the effect of improving the thermal stability during storage is not exhibited, and if the amount of the polymerization inhibitor is too large, the residual ratio of the exposed portion may be too small.

  In order to adjust the viscosity of the solution, an organic solvent may be added to the photosensitive conductive paste of the present invention. Examples of the organic solvent used at this time include methyl cellosolve, ethyl cellosolve, butyl cellosolve, methyl ethyl ketone, dioxane, acetone, cyclohexanone, cyclopentanone, isobutyl alcohol, isopropyl alcohol, tetrahydrofuran, dimethyl sulfoxide, and γ-butyrolactone. It is done. These organic solvents are used alone or in combination of two or more.

  The composition of the photosensitive conductive paste of the present invention is selected in the following range as described above.

Conductive powder: 50 to 70% by mass, preferably 55 to 70% by mass with respect to the entire conductive paste
Glass frit: in the range of 3 to 20 parts by weight, preferably in the range of 5 to 20 parts by weight with respect to 100 parts by weight of the conductive powder Inorganic filler: 0.2 to 30% by weight with respect to 100 parts by weight of the conductive powder , Preferably 0.3 to 30% by mass
Photosensitive organic component: 5-40 mass% is preferable with respect to 100 weight part of electroconductive powder, More preferably, 10-30 mass%
When the amount of each component is within the above-mentioned range, the ultraviolet rays are well transmitted at the time of exposure, the function of photocuring is sufficiently exerted, the film strength of the exposed area at the time of development is increased, and the conductive wiring having fine resolution Can be formed. In addition, the adhesion strength between the substrate and the conductive wiring is high, the resistance value of the conductive wiring after firing is low, and swelling can be suppressed.

  A method for producing the photosensitive conductive paste of the present invention will be described. Add the above-mentioned conductive powder, glass frit, inorganic filler, photosensitive organic component and, if necessary, photopolymerization initiator, sensitizer, polymerization inhibitor, ultraviolet absorber, organic solvent to make a slurry of the mixture. . The slurry adjusted to have a predetermined composition is homogeneously mixed with a stirrer such as a homogenizer and then uniformly dispersed with a three roller or kneader to produce a paste.

  The viscosity of the photosensitive conductive paste is appropriately adjusted depending on the ratio of addition of conductive powder, glass frit, inorganic filler, organic solvent, organic component composition / type, plasticizer, thixotropic agent, suspending agent, organic leveling agent, etc. However, the range is preferably in the range of 10 to 150 Pa · s at 3 rpm.

  For example, in order to obtain a film thickness of 1 to 25 μm by coating the glass substrate once or twice by screen printing, a bar coater, a roller coater or an applicator, it is preferably within a range of 30 to 100 Pa · s.

  The method for producing a substrate with conductive wiring according to the present invention is characterized in that the above-mentioned photosensitive conductive paste is applied on a substrate, patterned by photolithography, and then baked to form conductive wiring. . As described above, the photosensitive conductive paste of the present invention can be processed in a fine pattern, has high adhesion strength between the substrate and the conductive wiring, has a low resistance value of the conductive wiring after firing, and suppresses swelling. be able to.

  Next, as a specific example, a method for forming an electrode of a plasma display using the photosensitive conductive paste of the present invention will be described.

  The photosensitive conductive paste of the present invention is usually applied on a glass substrate by a screen printing method. The printing thickness can be arbitrarily controlled by adjusting the screen material (made of polyester or stainless steel), a screen of 250 to 325 mesh, and adjusting the screen opening, screen tension, paste viscosity, etc. It exists in the range of 1-25 micrometers, and the range of more preferable thickness is 1-15 micrometers. When the thickness is less than 1 μm, it is difficult to obtain a uniform thickness by the printing method. On the other hand, when the thickness exceeds 25 μm, the accuracy of the electrode pattern decreases and the cross-sectional shape becomes an inverted trapezoid. Edge cutting is worse.

  As the glass substrate, glass substrates using high strain point glass such as soda glass, “PD-200” manufactured by Asahi Glass Co., Ltd., and “PP-8” manufactured by Nippon Electrochemical Co., Ltd. are usually used.

  Next, the film | membrane which apply | coated the photosensitive electrically conductive paste on a board | substrate is heated for 10 minutes at 130 degreeC, and is dried, and after evaporating a solvent, pattern exposure is carried out and the photosensitive electrically conductive paste is photocured. Next, development is carried out using the difference in solubility between the exposed portion and the unexposed portion in the developer to form an electrode pattern. For the development, an immersion method, a spray method, a brush method, or the like is used. As the developer, a solution capable of dissolving the organic components in the photosensitive conductive paste, particularly the polymer, may be used.

  Next, the substrate is baked by being held at 590 ° C. for 10 minutes in an air atmosphere, and a stripe-shaped electrode having a thickness of 2.5 μm is formed after baking.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this.

  The material used for the Example and comparative example of this invention is shown below.

Conductive powder: manufactured by a wet reduction method, silver powder having an average particle diameter of 1.70 μm, a specific surface area of 0.41 m ² / g, and a tap density of 5.0 g / cm ³ was used.

  Frit glass: Bismuth oxide (48.1% by mass) Silicon dioxide (27.5% by mass), Boron oxide (14.2% by mass), Zinc oxide (2.6% by mass), Aluminum oxide (2.8% by mass) ), Zirconium oxide (4.8% by mass), an average particle size of 0.9 μm, a glass transition point (Tg) of 465 ° C., and a thermal softening point (Ts) of 510 ° C. were used.

  Inorganic filler: Silica particles having an average particle size of 1.0 μm were used.

Photopolymer: A polymer obtained by copolymerizing acrylic acid, methyl methacrylate and styrene in a weight ratio of 40/30/30, and adding 0.4 mol of glycidyl methacrylate to 1 mol of acrylic acid (weight average molecular weight 32, 000, acid value 110)
Organic solvent 1: Diethylene glycol monobutyl ether acetate Organic solvent 2: 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate Photosensitive monomer: Trimethylolpropane triacrylate Polymerization inhibitor: Hydroquinone monomethyl ether Photopolymerization initiator : IRGACURE651
Each material was weighed in the compositions and ratios shown in Tables 1 to 3, mixed, and kneaded with three rollers to obtain 24 types of paste.

Evaluation Method First, a photosensitive conductive paste was applied to the entire surface of a glass substrate (PD-200; manufactured by Asahi Glass Co., Ltd.) having a size of 340 × 260 × 2.8 mm with a screen printer. The solvent was dried at 130 ° C. for 10 minutes, pattern exposure was performed with an ultrahigh pressure mercury lamp using a photomask, and a pattern was obtained by shower development with a 0.1% 2-aminoethanol aqueous solution at 35 ° C. Next, the substrate was baked by being held at 590 ° C. for 10 minutes in an air atmosphere, and a stripe-shaped electrode having a thickness of 2.5 μm was formed after baking.

Evaluation of swelling Using a SEM (manufactured by Hitachi High-Tech), the patterned electrode is observed obliquely from 60 ° to confirm the unevenness of the electrode. Next, the cross section of the electrode of the convex portion was observed with an SEM, and when the thickness from the substrate was 3.0 μm or more and a cavity was recognized under the electrode, it was judged that the electrode was swollen. Furthermore, the electrode average thickness (measurement range 2.0 cm, n = 100) is calculated with a surface roughness meter (manufactured by Tokyo Seimitsu). The case where there was no bulge and the average thickness was less than 3.0 μm was “◯”, and the case where the bulge was present and the average thickness was 3.0 μm or more was “x”. The evaluation results are shown in Table 3.

Evaluation of conduction characteristics The electrode line width is 40 μm, the line length is 80 cm, and the electrode conduction failure is evaluated using an inspection device (manufactured by Nidec Lead). 20,000 electrodes were inspected, and a case where the defect rate was less than 2% was indicated by “◯”, and a case where the defect rate was 2% or more was indicated by “X”. The evaluation results are shown in Table 3.

Evaluation of Resistance Value The line resistance was evaluated using a tester with an electrode line width of 65 μm and a line length of 60 cm. The case where it was 2000Ω or less was rated as “◯”, and the case where it was not possible to evaluate due to disconnection was marked as “X”. The evaluation results are shown in Table 3.

Evaluation of adhesion strength The pattern edge was evaluated using a digital force gauge DFG-5KR (manufactured by Nidec Symposium). Solder the connection jig to the pattern for adhesion strength measurement, pull it in the right angle direction, measure the strength 20 times when the measurement part of 2mm square is removed from the substrate, and find the average value, when 1.5kgf or more Is “◯”, and the case of less than 1.5 kgf is “x”. The evaluation results are shown in Table 3.

  In Examples 1 to 8 within the scope of the present application, good results were obtained in all evaluations. However, in Comparative Examples 1 to 4 in which the weight ratio of silver was too small, and in Comparative Example 8 in which there was too much filler, silver was bonded to each other. Efficiency decreased and conduction failure occurred. In Comparative Example 5 having too little glass frit, the adhesion strength was lowered, electrode peeling occurred, and poor conduction occurred. In Comparative Example 7 or Comparative Example 8 in which the glass frit is too much or the filler addition is too little, the glass frit was sintered before the organic component was evaporated, the debinding was not successful, and the electrode pattern was swollen. Occurred.

Claims (3)

A photosensitive conductive paste containing a conductive powder, an inorganic component containing an inorganic filler composed of glass frit and ceramic powder, and a photosensitive organic component, wherein the content of the conductive powder is in the range of 50 to 70% by mass And the tap density of the conductive powder is 3 to 6 g / cm ² , the content of the glass frit is in the range of 3 to 20 parts by weight with respect to 100 parts by weight of the conductive powder, and the inorganic filler Is in the range of 0.2 to 30 parts by weight with respect to 100 parts by weight of the conductive powder. 2. The photosensitive conductive paste according to claim 1, wherein the inorganic filler contains at least one of titania, alumina, silica, cordierite, mullite, spinel, barium titanate and zirconia. A photosensitive conductive paste according to claim 1 or 2 is applied on a substrate, patterned by photolithography, and then baked to form a conductive wiring. Method.