JPH09282937A - Conductive resin composition and method for forming conductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive paste suitable for screen printing, prevent any adverse effect from being exerted on working environment during use, and clean a jig and a container with water by using a predetermined water-soluble thermocurable resin and a water-soluble bivalent alcohol solvent. SOLUTION: A water-soluble bivalent alcohol solvent is used as an organic solvent. A thermosetting resin soluble in water and the bivalent alcohol solvent is selected as a resin, to be dissolved in the organic solvent. A conductive resin composition including conductive particles mixed and dispersed in the resultant resin dissolved in the organic solvent is used as conductive paste. The conductive resin composition including the water-soluble thermosetting resin, the conductive particles having an average particle diameter of 0.05-50μm, and the water-soluble bivalent alcohol solvent capable of dissolving the thermosetting resin is used as the conductive paste. Consequently, the conductive paste is suitable for forming a conductor on a base material by a screen printing or the like. Furthermore, use of the solvent which never emits an unpleasant odor and has low toxicity cannot exert any adverse effect on working environment and can provide excellent safety, and a container or the like can be washed with water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive resin composition suitable for screen printing and having no adverse effect on working environment, and more particularly to the above composition capable of forming a conductor by thermosetting. The present invention also relates to a method of forming a conductor using such a composition.

[0002]

2. Description of the Related Art Conventionally, conductive pastes used for forming electronic circuits and electrodes and conductive adhesives used for bonding electric parts are obtained by dissolving an oil-soluble resin in an organic solvent. Conductive particles are dispersed in a vehicle. As the organic solvent, diethylene glycol monobutyl ether, terpionel, etc., which are good solvents for the oil-soluble resin, are used. However, since these solvents have toxicity and odor, they obstruct the working environment when using such conductive paste or conductive adhesive, and it is necessary to take measures such as ventilation.

Therefore, it has been studied to form a conductor such as a pattern of an electronic circuit with an aqueous paste using an aqueous solution of a water-soluble resin as a vehicle. However, when a pattern is formed by screen printing, drying is quick. The paste will dry during the work, and the screen mask will become clogged. In addition, when a hygroscopic high boiling point solvent such as glycerin or triethylene glycol is used together to delay the drying, the solvent does not completely evaporate in the step of drying the coating film, and the coating film is exposed to high humidity. It absorbs moisture and becomes sticky. Therefore, it is not possible to obtain a water-based conductive resin paste that is practical for the above applications.

Further, when a water-soluble resin such as polyvinyl alcohol is used in combination with water and a solvent such as propylene glycol, the resin is deposited and a practical aqueous conductive paste cannot be obtained.

JP-A-6-32248 by the present inventors discloses a conductive composition containing a water-soluble resin, conductive particles and an organic solvent that dissolves the resin; and a temporary electrode formed using the conductive composition. A method of manufacturing a filter is disclosed, in which the temporary electrode after use is removed by washing with water, but it is not about formation of a conductor to be used permanently.

On the other hand, Japanese Patent Laid-Open No. 6-346006 discloses an aqueous conductive paint in which an electrolytic copper powder having a lipophilic surface treatment is dispersed in an aqueous emulsion paint in which a polyurethane resin having an average particle diameter of 200 nm or less is dispersed. Is disclosed. However, such a conductive paint is not suitable for forming electronic circuits and electrodes having a fine pattern because the screen mask is clogged because most of the solvent is water. In addition, since the resin is water-insoluble, it is necessary to use an organic solvent to wash and remove the resin after the emulsion paint that has adhered to the device, jig and / or container after use is separated or dried, improving the working environment. The effect is not enough.

[0007]

It is an object of the present invention to be suitable for forming a conductor by a method such as screen printing, which does not adversely affect the working environment at the time of use, and the device, jig and It is an object of the present invention to provide a thermosetting conductive resin composition capable of washing a container with water. Another object of the present invention is to provide a method for forming a conductor by thermosetting using the above-mentioned conductive resin composition.

[0008]

Means for Solving the Problems As a result of repeated studies to solve these problems, the present inventors have used a dihydric alcohol solvent compatible with water as an organic solvent, and also used water as a resin. By selecting a thermosetting resin that is also soluble in the dihydric alcohol solvent, dissolving it in the organic solvent, and mixing and dispersing conductive particles therein, and using the conductive resin composition obtained as a conductive paste, The inventors have found that these problems can be solved, and have completed the present invention.

That is, according to the present invention, (A) a water-soluble thermosetting resin; (B) conductive particles having an average particle size of 0.05 to 50 μm; and (C) dissolving the thermosetting resin. , A conductive resin composition containing a dihydric alcohol solvent compatible with water, and forming a coating film with such a conductive resin composition, and heating to cure the thermosetting resin And a method for forming a conductor.

The component (A) used in the present invention is water-soluble and is soluble in a dihydric alcohol solvent, which is the component (C) described later, and is a heat capable of forming a coating film after removing the solvent. It is a curable resin. Examples of such resins include water-soluble resol-type and novolac-type water-soluble phenol resins; water-soluble epoxy resins such as modified bisphenol A-type epoxy resins; water-soluble amino resins such as water-soluble melamine resins. Water-soluble maleic acid resins and the like are exemplified, and they may be used alone or in combination of two or more kinds. It is preferable to use the water-soluble phenolic resin or the water-soluble melamine resin alone or to use both in combination, since the coating has excellent solubility and curability in the component (C) and a low specific resistance is obtained by curing. Combining these with a water-soluble epoxy resin is particularly preferable for applications requiring heat resistance. The above water-soluble phenol resin alone or a combination of the water-soluble phenol resin and the water-soluble epoxy resin is preferable also because a small amount of the component (C) can be used to obtain a conductive paste having good workability.

The composition ratio of the component (A) is 1 to 3 in the composition.
0 wt% is preferable, and 2 to 20 wt% is more preferable. This is because if the amount is less than 1% by weight, the strength of the dry film is weak, and if it exceeds 30% by weight, the specific resistance becomes high.

The component (B) used in the present invention is conductive particles that impart conductivity to the resin composition of the present invention. The shape of the conductive particles may be any shape such as a spherical shape, a flaky shape, or a needle shape. Average particle size is 0.05-50μ
m, preferably 0.1 to 25 μm. In addition,
Here, the average particle size means the average of the particle diameter in the case of a spherical shape, the major axis of the particle flakes in the case of a flaky shape, and the length in the case of a needle shape. If the average particle size is less than 0.05 μm, the contact resistance is large, and if it exceeds 50 μm, the printability when used as a conductive paste is poor, and the uniformity of the coating film obtained by printing is poor.

Examples of such conductive particles include metal particles of silver, copper, nickel, zinc, ruthenium, palladium, etc .; alloy particles containing these; and carbon particles. Can be used together.

The composition ratio of the component (B) is 30 to 30 in the composition.
90 wt% is preferable, and 45-80 wt% is more preferable. This is because if it is less than 30% by weight, the specific resistance is high, and if it exceeds 90% by weight, the apparent viscosity is high and the printability is poor.

The component (C) used in the present invention is (A)
It is an organic solvent that dissolves the components and disperses the component (B) to impart fluidity suitable for printing to the resin composition of the present invention. The component (C) has low toxicity and is odorless or has a slight odor close to it so as not to adversely affect the working environment when the conductive resin composition of the present invention is used. It is necessary to use a solvent, and further, since the component (A) is compatible with water when blended as an aqueous solution, and the device, jig and container after use can be easily washed with water, It is necessary that the solvent is compatible with. In consideration of the above, a dihydric alcohol solvent compatible with water is selected. The component (C) desirably imparts excellent workability to the composition when it is printed as a conductive paste on a substrate such as porcelain. In particular, in screen printing, it has an appropriate drying property suitable for continuous printing, does not cause clogging of the screen mask, and on the other hand, does not have moisture absorption by the component (C) remaining in the coating film and stickiness due to it. The boiling point is 150
C. or higher is preferable, and 180 to 250.degree. C. is more preferable.

Examples of the component (C) include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol and 1,6-hexanediol. General formula: HOR ¹ OH (wherein R ¹ represents a linear or branched alkylene group); and general formula: HOR ² OR ³ OH such as diethylene glycol and dipropylene glycol. (In the formula, R ² and R ³ each represent a linear or branched alkylene group), and examples thereof include dihydric alcohols, and one type or two or more types may be used in combination. In some cases, 1,4-butanediol or 2,3-butanediol may be used as a part of the component (C). Of these, from the solubility of the component (A), an appropriate boiling point, low toxicity, and workability of screen printing, the general formula: HOR ¹ O
A dihydric alcohol represented by H (in the formula, R ¹ represents a linear or branched alkylene group having 3 to 6 carbon atoms) is preferable, and propylene glycol is particularly preferable.

The composition ratio of the component (C) is 1 to 3 in the composition.
0 wt% is preferable, and 2 to 10 wt% is more preferable. If it is less than 1% by weight, the apparent viscosity will be high, and if it exceeds 30% by weight, the apparent viscosity will be too low and the printability will be poor. In particular, when a water-soluble phenol resin is used alone or together with a water-soluble epoxy resin as the component (A), a conductive paste having good workability can be obtained even with 3 to 5% by weight of the component (C).

In addition to the component (C), a small amount of another organic solvent compatible with the component (C) is used as a co-solvent within a range that does not impair the working environment, which is one of the features of the present invention. It doesn't matter.

Further, water may be used in combination within a range that does not impair the adjustment of the drying property which is a feature of the present invention. This water may be added in the form of an aqueous solution of the component (A) or may be added separately. The composition ratio of water is preferably 10% by weight or less in the composition. This is because if it exceeds 10% by weight, the conductive paste is dried too quickly and printability deteriorates.

The composition of the present invention may further contain non-conductive particles as the component (D). Non-conductive particles that can be used in the present invention include calcium carbonate, silica, alumina, titanium oxide, barium sulfate and other inorganic pigments; rubber-like elastic powders such as butadiene rubber and silicone rubber; and polymethylsil. A resin powder such as sesquioxane is exemplified. The average particle size of the non-conductive particles is preferably 50 μm or less. If it exceeds 50 μm, the printability is poor and the screen mask is likely to be clogged.

The content of the component (D) is preferably 30% by weight or less based on the total solid content in the composition. When the amount of component (D) is too large, the specific resistance of the coating film obtained by curing becomes too high, and the conductivity required as a conductive material cannot be obtained.

In addition, the conductive resin composition of the present invention,
You may mix | blend additives, such as a dispersing aid, a surface treatment agent, and a defoaming agent, as needed.

The conductive resin composition of the present invention is, for example,
The component (A) and other components optionally added as necessary are dissolved in the component (C) using a stirring and mixing tank or the like, and the resulting solution is mixed with the component (B) and optionally the component (D). Can be mixed and dispersed with a triple roll or a kneader to prepare. In addition, at the time of dispersion, it is dispersed while adding a part of the component (C), or (C) is further added after the dispersion.
Some of the components and / or other optional components may be added and mixed uniformly. Thus, the apparent viscosity suitable for a desired coating film forming method such as screen printing and dipping, for example, 20 at room temperature in the case of screen printing.
It is possible to prepare a conductive resin composition of ˜500 Pa · s, preferably 20 to 50 Pa · s.

The conductive resin composition of the present invention is used as a conductive paste by applying a method such as printing or coating to a predetermined portion of the surface of a substrate such as alumina, porcelain, glass, glass reinforced epoxy resin, or polyimide film. Form a film. The coating film forming method may be screen printing using an ordinary mask such as gelatin, glue, gum arabic, or polyvinyl alcohol, as well as any method such as transfer, stamping, dispensing, dipping, etc. preferable. Then, the component (C) is completely or partially vaporized to form a coating film in a pattern, for example. In this case, in order to facilitate volatilization of the component (C), for example, by a hot air dryer, an infrared dryer, or the like,
You may heat at 50-200 degreeC according to the kind of (C) component used.

The substrate on which the coating film is formed in this manner is
Depending on the kind of the resin, for example, the component (A) can be thermally cured by heating at 80 to 180 ° C. to form a cured coating film such as an electronic circuit or an electrode on the surface of the base material.

[0026]

The conductive resin composition of the present invention is suitable for forming a conductor on the surface of a substrate by a method such as screen printing. In addition, compared to conventional compositions used for the same purpose, it does not give off a bad odor and uses a solvent with low toxicity even when inhaled, so it does not adversely affect the working environment and has a relatively high flash point. Highly safe because it can be extinguished with water. Further, there is an advantage that the apparatus, jig, container, etc. can be washed with water after the work.

Therefore, the conductive resin composition of the present invention can advantageously form a conductor such as an electronic circuit or an electrode, particularly a patterned conductor on the surface of a substrate.
In addition, the conductive resin composition of the present invention can be used as a plating base conductive paste, a resistance paste, a conductive adhesive, and the like.

The conductor obtained by the present invention is a chip capacitor, an end face base electrode of a chip resistor, a variable resistor,
It is useful as a film substrate circuit.

[0029]

The present invention will be described below with reference to examples and comparative examples. The present invention is not limited by these examples. In the examples and comparative examples, all parts are parts by weight.

Examples 1 to 6 Various resins having the compositions shown in Table 1 were dissolved in propylene glycol, conductive particles were added and mixed, and the mixture was passed through a three-roll mill to give an apparent viscosity at 25 ° C. of about 30 Pa.
A paste-like conductive resin composition of s was prepared. Using each of these compositions, on the surface of the alumina substrate,
Screen-print a pattern with a width of 1 mm and a length of 71 mm. 1
By heating at 50 ° C. for 30 minutes to volatilize the remaining solvent and cure the resin, a cured film was obtained.

The conductive resin composition and the cured film were evaluated as follows. (1) Continuous printability: Screen printing was continuously performed 50 times, and during that time, it was observed whether the apparent viscosity of the composition was increased, the screen mask was dried, clogged, and there was no print fading. (2) Odor: The odor at the stage of heating to cure the resin,
It was evaluated by the five senses. (3) Jig washability: Whether or not the conductive paste attached to the mask or squeegee used for screen printing can be washed with water was observed. (4) Specific resistance: For the cured coating film obtained as described above, the coating thickness is measured by a surface roughness / shape measuring device, and the resistance value between both ends of the sample is measured by an LCR meter, The specific resistance was calculated.

The results are shown in Table 1.

Comparative Examples 1 and 2 For comparison, the water-insoluble phenol resin and epoxy resin were dissolved in diethylene glycol monobutyl ether by the same method as in Examples 1 to 6 with the composition shown in Table 1 to obtain the conductivity. The particles were dispersed to prepare a conductive resin composition of Comparative Example 1. In addition, polyvinyl alcohol was dissolved in water to form a 20% aqueous solution, and the conductive particles were dispersed in the same manner as in Examples 1 to 6 and then volatilized water was replenished to obtain the conductivity of the composition shown in Table 1. A resin composition was prepared. About these, it evaluated by the method similar to Examples 1-6. The results are also shown in Table 1.

[0034]

[Table 1]

As is clear from Table 1, the compositions of Examples 1 to 6 according to the present invention all showed excellent continuous printability, had no odor during the operation, and the jig could be washed with water after the operation. As a result, a cured coating having excellent workability and a specific resistance was obtained. On the other hand, the composition of Comparative Example 1 produced a bad odor and could not wash the jig with water.
Moreover, the composition of Comparative Example 2 did not have good continuous printability.

Claims (3)

[Claims] 1. A water-soluble thermosetting resin; (B) conductive particles having an average particle size of 0.05 to 50 μm; and (C) a water-soluble phase that dissolves the thermosetting resin. A conductive resin composition comprising a soluble dihydric alcohol solvent. 2. (C) is of the general formula: HOR ¹ OH (wherein
The conductive resin composition according to claim 1, wherein R ¹ is a dihydric alcohol represented by a linear or branched alkylene group having 3 to 6 carbon atoms. 3. A method for forming a conductor, wherein a coating film is formed from the conductive resin composition according to claim 1 or 2, and the thermosetting resin is cured by heating.