JP2001188342A - Photosensitive silver paste and image display using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive silver paste for forming a high precision minute electrode pattern. SOLUTION: The photosensitive silver paste is a photosensitive electrically conductive resin paste comprising an alkali-soluble resin, a crosslinkable monomer having an unsaturated double bond, a photopolymerization initiator, silver powder, glass frit, calcium carbonate having 0.01-1 μm average particle diameter measured by a laser diffraction method and an organic solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive silver paste and an image display device using the same.

[0002]

2. Description of the Related Art Conventionally, it has been necessary to form fine electrodes in a pattern in various electronic components such as a plasma display panel, an image display device such as a liquid crystal display device, and a thermal head. An electrode is formed by drying and firing a pattern formed by a method of forming a pattern by etching a conductive film formed by a method such as plating by a photolithography method or a method of pattern printing by a screen. .

[0003]

Of these methods, the method of forming a pattern by etching enables high-precision pattern formation, but has a drawback that the cost is increased because of the etching step. On the other hand, a printing method using a screen printing plate is advantageous because it is possible to form a pattern on a substrate corresponding to a large screen of an image display device at a relatively low cost, but it is advantageous to form a fine pattern of 50 μm or less. There was a limit on the accuracy of Accordingly, it is an object of the present invention to provide a photosensitive silver paste for forming a fine electrode pattern with high accuracy by solving the problems of the conventional electrode pattern forming method.

[0004]

Means for Solving the Problems An alkali-soluble resin (A), a crosslinkable monomer having an unsaturated double bond (B), a photopolymerization initiator (C), a silver powder (D), a glass frit (E), an average A photosensitive conductive resin paste comprising calcium carbonate (F) having a particle size of 0.01 to 1 μm as measured by a laser diffraction method, and an organic solvent (G);
The photopolymerization initiator contains dimethylbenzyl ketal and ethyl 4-dimethylaminobenzoate, and the proportion of silver powder (D) is 60 in the total solid paste resin component excluding the organic solvent (G).
~ 80wt%, glass frit (E) ratio is 0.5 ~
3wt%, calcium carbonate (F) 0.05-5wt%
And the alkali-soluble resin (A) accounts for 10 to 30 wt% of the total solid paste component, and the silver powder (D) has an average particle size of 0.5 μm to
The range of 3 μm, the maximum particle size is 5 μm or less, the average particle size of the glass frit (E) is 0.4 μm to 3 μm as measured by a laser diffraction method, the maximum particle size is 5 μm or less, and the melting point is It is in the range of 350 ° C. to 450 ° C., and the weight reduction of the alkali-soluble resin of the component (A) when heated in air at a rate of 5 ° C./min is completed at 450 ° C. Photosensitive silver paste. Furthermore, an image display device using the above-mentioned photosensitive silver paste.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The alkali-soluble resin (A) used in the present invention is a binder resin for a paste and is desirably alkali-soluble in order to enable development with an ordinary alkaline developer. Although the structure and the like are not particularly limited, it is preferable that no organic matter remains on the formed electrode in terms of conductivity after firing and reliability after being incorporated in the image display device. Therefore, it is desirable that the alkali-soluble resin (A) used in the present invention, when heated in air at a temperature rise of 5 ° C. per minute, completes the weight loss at 450 ° C. If the weight loss is not completed even if it exceeds 450 degrees, the conductivity of the circuit electrode after firing is not sufficient, which is not preferable.

As a specific example, an acrylic copolymer having an acidic group such as a carboxylic acid and an ethylenically unsaturated group is preferable, and acrylic acid, methacrylic acid, succinic acid 2 -Methacryloyloxyethyl, 2-acryloyloxyethyl succinate, 2-methacryloyloxyethyl phthalate, 2-acryloyloxyethyl phthalate, etc., and as the ethylenically unsaturated component, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl Methacrylate, n-
Propyl acrylate, n-propyl methacrylate,
Isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, t
tert-butyl methacrylate, allyl acrylate,
Examples include allyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate, and various copolymers can be used as long as the thermal decomposability during firing is not impaired.

The proportion of the alkali-soluble resin (A) of the present invention in the solid resin paste is preferably from 10 to 30% by weight. If the amount is less than 10% by weight, the solubility of the paste in an alkali developing solution decreases, and the accuracy of pattern formation deteriorates. Thus, if it exceeds 30% by weight, carbides tend to remain on the electrode after firing, resulting in a decrease in conductivity. It is not preferable.

The crosslinkable monomer (B) having an unsaturated double bond of the present invention is a compound having at least one ethylenically unsaturated double bond. It reacts with radicals generated from a photopolymerization initiator by light irradiation, and reduces the solubility in an alkali developer to form a pattern. Specific examples include allyl acrylate, benzyl acrylate, butoxyethyl acrylate, butoxyethylene glycol acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, 2-ethylhexyl acrylate, glycerol acrylate, glycidyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxyethyl acrylate. Hydroxypropyl acrylate, isobonyl acrylate, isooctyl acrylate, lauryl acrylate, 2-methoxy acrylate, methoxyethylene glycol acrylate, phenoxyethyl acrylate, stearyl acrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,5-
Pentanediol diacrylate, 1,6-hexanediol diacrylate, 1,3-propanediol diacrylate, 1,4-cyclohexanediol diacrylate, 2,2-dimethylolpropane diacrylate, glycerol diacrylate, tripropylene glycol diacrylate Acrylate, glycerol triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, ethylene oxide-modified pentaerythritol triacrylate, ethylene oxide-modified pentaerythritol tetraacrylate, propylene oxide-modified pentaerythritol tetraacrylate, propylene oxide-modified penta Erythritol triacrylate, Triethylene glycol diacrylate, polyoxyethylene propane triacrylate, butylene glycol diacrylate,
1,2,4-butanetriol triacrylate, 2,
2,4-trimethyl-1,3-pentanediol diacrylate, 1,10-decanediol dimethyl acrylate, pentaerythritol hexaacrylate and those obtained by replacing the above acrylate with methacrylate,
γ-methacryloxypropyltrimethoxysilane, 1-
Vinyl-2-pyrrolidone and the like. Two or more of the above crosslinking monomers may be used in combination.

The photopolymerization initiator (C) used in the present invention
Preferably contains dimethylbenzyl ketal and ethyl 4-dimethylaminobenzoate as essential components in order to obtain a pattern with high sensitivity. In addition to this combination, a photopolymerization initiator used for ordinary negative type photolithography may be further added. Examples of ordinary photopolymerization initiators include benzophenone, methyl o-benzoylbenzoate, 4,4-bis (dimethylamine) benzophenone, and 4,4-bis (diethylamine).
Benzophenone, α-aminoacetophenone, 4,4-
Dichlorobenzophenone, 4-benzoyl-4-methyldiphenyl ketone, dibenzyl ketone, fluorenone,
2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenyl-2-phenylacetophenone, 2-
Hydroxy-2-methylpropiophenone, pt-butyldichloroacetophenone, thioxanthone, 2-methylthioxanthone, 2-chlorothioxanthone, 2-
Isopropylthioxanthone, diethylthioxanthone, benzyl-methoxyethyl acetal, benzoin, benzoin methyl ether, benzoin butyl ether, anthraquinone, 2-t-butylanthraquinone, 2-amylanthraquinone, β-chloroanthraquinone, anthrone, benzanthrone, dibenzosuberone, methylene Anthrone, 4-azidobenzalacetophenone, 2,6-bis (p-azidobenzylidene) cyclohexanone, 2,6-bis (p-azidobenzylidene) -4-methylcyclohexanone, 2-phenyl-
1,2-butadione-2- (o-methoxycarbonyl)
Oxime, 1-phenyl-propanedione-2- (o-
Ethoxycarbonyl) oxime, 1,3-diphenyl-
Propanetrione-2- (o-ethoxycarbonyl) oxime, 1-phenyl-3-ethoxypropanetrione-2- (o-benzoyl) oxime, Michler's ketone, 2-methyl- [4- (methylthio) phenyl] -2
Morpholino-1-propanone, naphthalene sulfonyl chloride, quinoline sulfonyl chloride, N
-Phenylthioacdrine, 4,4-azobisisobutyronitrile, diphenyldisulfide, benzthiazole sulfide, triphenylphosphine, camphorquinone and the like.

The mixing ratio of dimethylbenzyl ketal and ethyl 4-dimethylaminobenzoate is from 1: 9 to 9: 1, preferably from 2: 8 to 8: 2. When the proportion of dimethylbenzyl ketal is small, there is a problem that the sensitivity is reduced, and when the proportion of ethyl 4-dimethylaminobenzoate is small, there is a problem that the resolution is reduced.

Further, a sensitizer, a polymerization inhibitor, a leveling agent, a dispersant, an antifoaming agent, a thickener, a precipitation inhibitor, and the like can be added to the above-mentioned photosensitive component as necessary.

The silver powder (D) of the present invention preferably has an average particle diameter measured usually by a laser diffraction method in the range of 0.5 μm to 3 μm. When the average particle size of the silver powder is less than 0.5 μm, the light transmittance is lowered and the sensitivity is lowered, which is not preferable. Further, when the average particle size exceeds 3 μm or the maximum particle size exceeds 5 μm, the linearity of the pattern after firing is impaired, or the fusion of the electrodes during firing does not become dense and the conductivity is reduced, which is preferable. Absent. The proportion in the silver paste solid content is preferably 60 to 80 wt%. 60wt
%, The conductivity after firing is reduced and 80 wt%.
Exceeding the range is not preferred because the alkali developability decreases.

The particulate calcium carbonate (F) used in the present invention is used for imparting a thickening action and thixotropic property to the paste to improve screen printability. Therefore, the average particle size is preferably 0.01 to 1 μm as measured by a laser diffraction method, and 0.01 μm
If it is less than 1 μm, the viscosity becomes too high and the printing workability decreases, and if it exceeds 1 μm, the effect of improving the thixotropic property decreases, which is not preferable. It is also preferable that the addition amount itself is in the range of 0.05 to 5 wt% of the total solid resin component. When the content is less than 0.05 wt%, the thickening effect and the thixotropic property improving effect are poor, and 5 wt%
%, The photosensitivity is undesirably reduced.

The glass frit (E) used in the present invention
Has an effect on adhesion to a substrate and fusion of silver powder particles during firing, and is indispensable for conductivity and reliability of a display device. The average particle size measured by a laser diffraction method is 0.1. 4 μm
３3 μm and the maximum particle size is preferably 5 μm or less. When the average particle diameter is less than 0.4 μm, the workability deteriorates, and when the average particle diameter exceeds 3 μm, or when the maximum particle diameter exceeds 5 μm, the precision of forming a fine pattern decreases, which is not preferable.
Further, the melting point of the glass frit is preferably in the range of 350 ° C to 450 ° C. Low-melting glass having a melting point of less than 350 ° C. is not preferable because a large amount of a melting point depressant is added to increase the cost, and a firing temperature of about 500 ° C. is desirable in order to maintain the reliability of the image display device.
If the melting point exceeds, silver powder is not sufficiently fused and the conductivity is lowered, which is not preferable. The amount of glass frit added is 0.5 to 3 of the total solid paste resin components excluding the organic solvent.
It is preferably wt%. If it is less than 0.5 wt%, there is a problem that the adhesion to the glass substrate is reduced,
If it exceeds 3 wt%, there is a problem that the conductivity of the circuit electrode is reduced.

The organic solvent (G) used in the present invention is used to make the paste into a desired viscosity and improve the workability of screen printing or the like.
Alcohol solvents such as ethyl alcohol, isopropyl alcohol, and n-propyl alcohol; cellosolve solvents such as methoxy alcohol and ethoxy alcohol; carbitol solvents such as methoxyethoxyethanol and ethoxyethoxyethanol; ethyl acetate, butyl acetate, and methoxypropionic acid Methyl, ethyl lactate and other ester solvents, methoxyethyl acetate, ethoxyethyl acetate, ethyl cellosolve acetate and other cellosolve acetate solvents, methoxyethoxyethyl acetate,
Carbitol acetate solvents such as ethoxyethoxyethyl acetate; ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and tetrahydrofuran; N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, etc. Aprotic amide solvent, γ
Lactone solvents such as butyrolactone; aromatic hydrocarbon solvents such as toluene, xylene and naphthalene; and organic solvents such as n-heptane, n-hexane and n-octane aliphatic hydrocarbon solvents.

The photosensitive silver paste of the present invention is prepared by weighing and blending the components in a room such as a yellow room where ultraviolet rays are blocked, and then uniformly mixing with a stirrer or the like to form a uniform paste with a three roll or kneader. I do. The viscosity of the paste is adjusted with an organic solvent according to the application, but it is usually 1,000 to 300,000 cp.
s is preferred.

When an electrode pattern for plasma display is formed using the photosensitive silver paste of the present invention, the electrode pattern is usually 5 to 30 μm on a glass substrate by a method such as screen printing.
Is applied with a thickness of Then, the coating film on the substrate is
After heating and drying at 20 ° C. for about 10 to 30 minutes, ultraviolet irradiation is performed by a photolithography method through a desired mask, and the exposed portion is photo-cured. The light source used at this time includes ultraviolet rays, electron beams, X-rays and the like, and among them, ultraviolet rays are preferable. Usually, a high-pressure mercury lamp is used. The normal exposure is preferably about 50 to 1000 (mJ / cm ² ) in consideration of productivity and the like.

Next, the unexposed portion is dissolved and removed with an alkali developer to form a pattern. Development includes an immersion method and a spray method, and the latter is used for forming a fine pattern. Usually, an aqueous alkali solution is used as the developer, but an aqueous metal alkali solution such as sodium hydroxide, calcium hydroxide, or sodium carbonate, or an organic alkali aqueous solution such as tetramethylammonium hydroxide, monoethanolamine, or diethanolamine can also be used. The concentration of a normal alkali aqueous solution is often about 0.1 to 2 wt%.

Next, the obtained pattern is baked in the air, and the alkali-soluble resin (A) which is a photosensitive organic component, a crosslinkable monomer (B), a photopolymerization initiator (C), an organic solvent (G) Is completely oxidized and evaporated. The temperature condition is 45
Baking is performed at 0 to 550 ° C. for 15 to 60 minutes, and the silver component is fused and baked on the glass substrate.

When an electrode pattern is formed using the photosensitive silver paste of the present invention, the thickness of the conductive film after firing is 5 to 10
A fine pattern having a minimum line width of about 20 μm can be formed in μm, and an image display device having high reliability and a fine pattern can be obtained. As a method for manufacturing the image display device, a conventionally known method can be used.

[0021]

The present invention will be specifically described below with reference to examples. <Example 1> Methyl methacrylate / methacrylic acid (molar ratio: the weight loss was completed at 420 ° C when the thermogravimetric loss curve (TGA) was measured in air at a temperature rise of 5 ° C per minute as an alkali-soluble resin). 90/10) Copolymer (1)
100 parts by weight, 80 parts by weight of ethylene oxide-modified trimethylolpropane acrylate, photopolymerization initiator (1)
10 parts by weight of dimethylbenzyl ketal, 10 parts by weight of ethyl 4-dimethylbenzoate as a photopolymerization initiator (2), 120 parts by weight of γ-butyrolactone, average particle size 0.8
600 parts by weight of silver having a maximum particle size of 3 μm (1), melting point 4
A paste consisting of 50 parts by weight of a glass frit (1) having an average particle size of 1.0 μm and a maximum particle size of 3.5 μm, and 10 parts by weight of calcium carbonate having an average particle size of 0.05 μm was prepared at 00 ° C., and various characteristics were evaluated. The results shown in Table 1 were obtained.

<Coating and Printing> The above paste was placed on a glass substrate (500 mm) using a 325 mesh screen.
Square, 3 mm thick) and apply at 70 ° C
The solid was dried in a minute to obtain a solid film having a thickness of 12 μm. <Exposure and development> 10-100 μm
50 to 30 using a mask having a test pattern of m
Ultraviolet rays were applied in increments of 50 (mJ / cm ² ) to 0 (mJ / cm ² ). Thereafter, unexposed portions were removed by spray development with a 0.5% by weight aqueous solution of sodium carbonate, followed by washing with water.

<Firing> The coating film printed on the glass substrate was baked in air at 500 ° C. for 60 minutes to form an electrode pattern.

<Evaluation> The thickness, resolution and specific resistance of the fired coating film were measured and evaluated. The film thickness was measured with a surface roughness meter, and the resolution was observed with a metallographic microscope. The specific resistance was calculated from the film thickness by measuring the sheet resistance.

<Examples 2 to 5, Comparative Examples 1 to 8> A photosensitive silver paste was prepared by the same method and operation as in Example 1 except for the compositions shown in Table 1, and the same method as in Example 1 was used. And the results are shown in Table 1.

[0026]

[Table 1]

[0027]

As a result of forming an electrode pattern by a photolithography method using the photosensitive silver paste of the present invention, a low resistance, excellent conductivity and a high resolution of 50 μm or less, exposure of 200 (mJ / cm ² ) or less. This is useful for forming a pattern electrode of an image display device represented by a plasma display.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01B 1/22 H01B 1/22 A 5G301 H01J 9/02 H01J 9/02 F 11/02 11/02 B F term (reference) ) 2H025 AA02 AB17 AB20 AC01 AD01 BC13 BC31 CA05 CA27 CB42 CB51 CC03 CC08 CC09 FA17 FA29 4J011 AA05 CA08 CC10 PA03 PA07 PA15 PA69 PA70 PB02 PB22 PB27 PC02 QA03 QA11 QA13 QA17 QA21 QA22 GA01 RA01 SA01A01 GC02 JA22 KA01 KA09 KA16 KB03 KB09 KB17 KB28 MA24 5C094 AA04 AA05 AA24 AA43 AA44 CA19 DA13 DB01 DB04 EA04 EB02 FB01 FB02 FB03 FB12 GB10 JA01 JA08 JA20 5G301 DA03 DA22 DA34 DA43 DD01

Claims (2)

[Claims] 1. An alkali-soluble resin (A), a crosslinkable monomer having an unsaturated double bond (B), a photopolymerization initiator (C), a silver powder (D), a glass frit (E), and a laser having an average particle diameter of laser. A photosensitive conductive resin paste composed of calcium carbonate (F) having a particle size of 0.01 to 1 μm as measured by a diffraction method and an organic solvent (G), wherein the photopolymerization initiator is dimethylbenzyl ketal, 4-dimethylaminobenzoic acid The proportion of silver powder (D) is 60 to 80 wt%, the proportion of glass frit (E) is 0.5 to 3 wt%, and calcium carbonate (F) is contained in all solid paste resin components containing ethyl and excluding organic solvent (G). Is in the range of 0.05 to 5 wt%, and the alkali-soluble resin (A) is contained in the total solid paste component in an amount of 10 to 10 wt%.
30 wt%, the average particle size of the silver powder (D) is 0.5 μm to 3 μm, the maximum particle size is 5 μm or less, as measured by the laser diffraction method, and the average of the glass frit (E) is measured by the laser diffraction method. The particle size is in the range of 0.4 μm to 3 μm, the maximum particle size is 5 μm or less, and the melting point is 35 μm.
It is in the range of 0 ° C. to 450 ° C., and the weight reduction of the alkali-soluble resin of the component (A) when heated in air at a rate of 5 ° C./min is completed at 450 ° C. Photosensitive silver paste. 2. An image display device produced using the photosensitive silver paste according to claim 1.