JPH0541675B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a heat-resistant conductive varnish with improved varnish stability and conductivity. [Prior Art] Conventionally, as a heat-resistant conductive varnish, a polyimide varnish in which carbon particles are dispersed and mixed is known (for example, Japanese Patent Publication No. 39-25196). However, such conventional heat-resistant conductive varnishes have a volume resistivity of 1 to 100 Ω·cm, which is much higher than that of ordinary metal conductors, and cannot be used as a conductor.
Additionally, when a large amount of metal powder is added, the volume resistivity decreases significantly, making it close to a metal conductor, but the fluidity of the varnish disappears in a short period of time, resulting in poor stability and the disadvantage that it cannot be used as is. was. [Object of the Invention] An object of the present invention is to eliminate the above-mentioned drawbacks and provide a heat-resistant conductive varnish with excellent varnish stability. [Configuration of the Invention] In order to achieve the above object, the present invention has the following configuration, namely: (1) General formula (However, R ₁ is a trivalent or tetravalent organic group having at least 2 or more carbon atoms, R ₂ is a divalent organic group having at least 2 or more carbon atoms, and n is 1 or 2) Polymer contained as a structural unit []
Add an amine compound having 1 to 15 carbon atoms to a solution of
and metal powder [] are mixed, and the compound [] has an equivalent of 0.5 to 2 times the total carboxyl groups in the polymer [], and the metal powder [] is mixed at a ratio of 150 to 1900 g per 100 g of the polymer []. It is characterized by a heat-resistant conductive varnish made of General formula in the present invention Polymer containing as the main structural unit [ ]
(hereinafter referred to as polyimide polymer precursor)
It has a structure represented by the above general formula, and can be turned into a polymer (hereinafter referred to as a polyimide polymer) having an imide ring or other cyclic structure by heating or a suitable catalyst. In the above general formula, R ₁ is a trivalent or tetravalent organic group having at least two or more carbon atoms.
From the viewpoint of heat resistance of the polyimide polymer, it is preferable that R ₁ has a structure in which the bond to the carbonyl group of the polymer main chain is directly formed from an aromatic ring or an aromatic heterocycle. Therefore, R ₁ is preferably a trivalent or tetravalent group containing an aromatic ring or an aromatic heterocycle and having 6 to 30 carbon atoms. As a more preferable specific example of R ₁ , (In the formula, the bond represents a bond with the carbonyl group of the polymer main chain, and the carboxyl group is located at the ortho position to the bond, but this bond is not shown in the above structural formula.) etc. These include, but are not limited to: In addition, in the polymer [], R ₁ in the general formula may be composed of only one of these,
It may be a copolymer composed of two or more types. Particularly desirable R ₁ is (However, the definition of the bond in the formula is the same as above.) In the above general formula, R ₂ is a divalent organic group having at least two or more carbon atoms, but from the viewpoint of heat resistance when used as a polyimide polymer, the bond with the amide group in the main chain of the polymer is aromatic. Those having a structure formed directly from a group ring or an aromatic heterocycle are preferred. Therefore, R ₂ is preferably a divalent group containing an aromatic ring or an aromatic heterocycle and having 6 to 30 carbon atoms. Preferred specific examples of R ₂ include: (In the formula, the bond represents a bond with the amide group of the main chain.) etc. Further, these may have a nuclear substituent such as an amino group, an amide group, a carboxyl group, or a sulfonamide group within a range that does not adversely affect the heat resistance of the polyimide polymer. Among those having these nuclear substituents, particularly preferred examples include: can be mentioned. In the polymer [], R ₂ may be composed of only one type of these, or may be a copolymer composed of two or more types. Furthermore, in order to improve the adhesiveness of the polyimide polymer, it is also possible to copolymerize an aliphatic group having a siloxane structure as R ₂ within a range that does not reduce the heat resistance. As a preferred specific example, Examples include. Specific examples of polymers include pyromellitic dianhydride and 4,4'-diaminodiphenyl ether, pyromellitic dianhydride and 3,3',4,
4′-Benzophenonetetracarboxylic acid and 4,4′-
Diaminodiphenyl ether, 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride and 4,4'-diaminodiphenyl ether, 3,3',4,4'-diphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride anhydride and 4,4'-diaminodiphenyl ether, pyromellitic dianhydride and 3,3'-diaminodiphenyl sulfone, pyromellitic dianhydride and 3,3',4,
4'-Benzophenonetetracarboxylic dianhydride and 3,3'-(or 4,4'-)diaminodiphenylsulfone, 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3'-(or 4,4'-)diaminodiphenylsulfone, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3'-(or 4,4'-) ) Diaminodiphenylsulfone, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3'- (or 4,
4'-) Diaminodiphenyl sulfone, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, pyromellitic dianhydride and 3,3',4,
4'-Benzophenonetetracarboxylic dianhydride, 4,4'-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4,4'-benzophenonetetracarboxylic acid Acid dianhydride and 4,4'-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4' -diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenone Tetracarboxylic anhydride and 4,4'-diaminodiphenyl ether and bis(3-aminopropyl)tetramethyldisiloxane, pyromellitic dianhydride and 3,3'-(or 4,
4′-)diaminodiphenyl sulfone and bis(3-aminopropyl)tetramethyldisiloxane, pyromellitic dianhydride and 3,3′,4,
4'-Benzophenonetetracarboxylic dianhydride, 3,3'-(or 4,4'-)diaminodiphenylsulfone and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4, 4'-Benzophenonetetracarboxylic dianhydride, 3,3'-(or 4,4'-)diaminodiphenylsulfone and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4, 4'-biphenyltetracarboxylic dianhydride, 3,3'-(or 4,4'-)diaminodiphenylsulfone and bis(3-aminopropyl)tetramethyldisiloxane, 3,3',4,4 '-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 3,3'-(or 4,
Polyamic acids synthesized from 4'-)diaminodiphenyl sulfone and bis(3-aminopropyl)tetramethyldisiloxane are preferably used. The polymer [] may consist only of the compound represented by the above general formula, or may be a copolymer with other structural units. The amount of structural units used in the copolymerization is desirably selected within a range that does not significantly impair the heat resistance of the polyimide polymer obtained by the final heat treatment, preferably from 0 to 20 mol%. Typical examples of the structural units used in the copolymerization include polyether amic acid and polyester amic acid structural units, but the present invention is not limited thereto. In addition, as a solvent for making a polymer solution,
Mainly polar solvents are preferable from the viewpoint of solubility. Examples of polar solvents include dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-
Methyl 2-pyrrolidone, hexamethylphosphoramide and the like are preferably used. Compound [] refers to an amine compound having 1 to 15 carbon atoms, (Here, R ₃ , R ₄ and R ₅ each represent hydrogen, a substituted or unsubstituted alkyl group, or a phenyl group.) (Here, R ₆ and R ₇ each represent hydrogen or a substituted or unsubstituted alkyl group.) Examples thereof include. Specific examples include (C ₂ H ₅ ) ₃ N, (C ₃ H ₇ ) ₃ N, (C ₄ H ₉ ) ₃ N,
(C ₃ H ₇ ) ₂ NH, (C ₂ H ₄ OH) ₂ NH, (CH ₃ )C
_{( C2H5} ) _{2NH2 ,}

[Formula] (C ₂ H ₄ OH) ₂ (CH ₃ ) N, (C ₂ H ₅ ) ₂ (C ₂ H ₄ OH) N, (C ₂ H ₄ OH) ₃ N,

[Action/effect of the invention]

As described above, in the present invention, the following excellent effects can be obtained by adding and mixing a polymer solution, a compound having an amino group, and a metal powder. That is, the volume resistivity σ=1×10 ⁻⁴ to 5×10 ⁻³ Ω·cm was able to be lowered to a level where it could be used sufficiently as a conductor. 2. The stability of the varnish was greatly improved, and a varnish that could withstand practical use was obtained. Note that the effects of the present invention were evaluated based on the following criteria. 1 Stability of varnish Approximately 50 g of varnish was weighed into a 100 c.c. polyethylene wide-mouth bottle, immersed in a constant temperature bath at 30° C., and the time until a film was formed on the varnish surface was measured. 〇: Good (no film formed for more than 1 week) △: Slightly good (film formed in 1 day or more but less than 1 week) ×: Poor (film formed in less than 1 day) [Example] Next, based on the example, the present invention An embodiment of this will be described. Example 1 828.6 g of N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) solvent was weighed into a three-necked two-flask. This is added to diaminodiphenyl ether (hereinafter
Add 80g of DAE (abbreviated as DAE) to the solvent at 50°C while stirring to completely dissolve. When DAE is completely dissolved, benzophenonetetracarboxylic anhydride (hereinafter referred to as
Add 126.3g of BTDA (abbreviated as BTDA) little by little and react. React at 50°C for 4 hours. The viscosity of the finished varnish was measured using an E-type viscometer manufactured by Tokyo Keiki Co., Ltd.
It was 90 poise/30℃. 250g of this varnish
The mixture was weighed into a cc polyethylene wide-mouth bottle, and 4.85 g of diethanolamine was added thereto and mixed. 60 g of copper powder having an average particle size of 10 μm was added and mixed to the obtained varnish to obtain a desired heat-resistant conductive varnish. This varnish is
No film formation was observed for more than one week in an atmosphere of 30°C. The varnish was printed in a pattern on a glass plate by screen printing and heated for 80 minutes in an _N2 atmosphere.
℃, 150℃, 200℃, and 400℃, and heat treated for 30 minutes at each temperature to form a film with a thickness of 15μ.
A test piece with a width of 5 mm and a length of 10 cm was prepared on a glass plate, and the volume resistivity was measured.
It was 10 ^-4 Ω・cm. As is clear from the above, the heat-resistant conductive varnish obtained by the present invention has excellent varnish stability and conductivity. Example 2 A heat-resistant conductive varnish was prepared by adding 4.65 g of triethylamine instead of diethanolamine in Example 1. No film formation was observed with this varnish in an atmosphere of 30°C for more than one week. The specific volume resistivity was 3×10 ⁻⁴ Ω·cm. Comparative Example 1 A heat-resistant conductive varnish was prepared in Example 1 without adding diethanolamine. This varnish is
Formation of a film was observed within several hours in an atmosphere of 30°C.

【table】

Claims (1)

[Claims] 1. General formula (However, R ₁ is a trivalent or tetravalent organic group having at least 2 or more carbon atoms, R ₂ is a divalent organic group having at least 2 or more carbon atoms,
n is 1 or 2) in a solution of a polymer [] containing as a main structural unit, an amine compound [] having 1 to 15 carbon atoms,
metal powder [] is mixed, and the compound [] accounts for 0.5 of the total carboxyl groups in the polymer [].
~2 times equivalent, metal powder [] is polymer []100
Heat-resistant conductive varnish mixed at a ratio of 150 to 1900 g/g.