JPS61266462A - Electrically conductive silicone rubber molding and production thereof - Google Patents

Abstract

PURPOSE:To produce the titled molding having excellent reliability and useful for printing film and coating film, by adding a dimethylpolysiloxane oil to a mixture of a specified component and carbon black and/or an electrically conductive powder. CONSTITUTION:5-100pts.vol. carbon black having an average particle size of 100mum or below and/or other electrically conductive powder (e.g. gold bronze powder), a dimethylpolysiloxane oil as a crosslinking agent and a curing catalyst (e.g. platinum black) are mixed with 100pts.vol. component obtd. by mixing a heat-curable raw silicone rubber having an average degree of polymn. of 5,000-12,000 and a viscosity of 8X10<6>-15X10<6>cs at 25 deg.C with an alkenylorganopolysiloxane oil having an average degree of polymn. of 100-2,000 in a ratio of 10:1-1:10.

Description

[Detailed Description of the Invention] Industrial Application Fields The present invention relates to conductive silicone rubber contacts used in input terminals of electronic circuit devices, flexible contacts of connection terminals or components, and flexible contacts of electronic components. Conductive silicone rubber molding is useful for manufacturing elastic electrodes, thick film resistors, various sensor elements, etc., and is particularly useful for molding printed films and coating films, providing electronic and electrical parts with improved reliability. body and its manufacturing method.

Conventional technology> Conventionally, (1) Industrial Chemistry Magazine Vol. 62, No. 6 P. 88
4-890, 1959, Manami, Nishizaki. , (2)
US P 4,0 2 0,0 1 4,.

(3) Industrial Materials, Volume 27, No. 9, P43-15. 1
979 years.

Ito, Imai, (4) USP 4062813, etc.
It is a field that has been researched, developed, and clarified.
48951, (7) JP-A-Sho ss-t7i442,
(This is a technical field that has been applied and developed in Japanese Patent Application Laid-Open No. 58-205761, etc.) In (1) above, as the carbon black content in the conductive silicone rubber increases, the specific resistance decreases; It has been revealed that the electrical performance deteriorates, and in (2) and (4), the specific resistance is 10Ω or more in the 80% conductive region. (3)
In this paper, various silicone rubbers such as high-strength silicone rubber are clarified. In particular, P. 46 introduces that with the composition disclosed in (2), even screen-printed conductive silicone rubber thin layers can be completely cured. However, the problem of improving reliability as an electronic/electrical component element is due to the molded body structure and molding method mentioned above (5).
) (6) (7) Even if it is proposed as (8),
Not resolved.

<Problem to be solved by the invention> P in (3) above, 47 Table 7 shows a specific resistance of 3 X IF'Ω
- Conductive silicone rubber has been introduced, but its elongation at break is high and its strength at break is low. Such physical properties cannot withstand repeated key press tests for use as rubber contacts, and the technical field of electrical circuit devices that conduct electricity from the surface or inside of molded objects is constantly becoming denser and thinner.

Demand lower costs. As introduced in (3) above, even if a thin layer can be formed using the composition disclosed in (2), the film thickness is usually 10 to 30 μm using screen printing with high work efficiency. To obtain resistance reliability comparable to that of conventional rubber contacts, the thickness must be at least 300 μm.
is necessary, and has the disadvantage that its applications are limited to lower costs.

The present invention is a conductive silicone rubber molded article and a method for producing the same, which change the contradictory characteristics of conductivity and mechanical performance of the conventional conductive silicone rubber as described above.

The present invention provides a thin layer film with improved reliability in the fields of application disclosed in (5), (6), (7), and (8) above, particularly in printing or coating operations, and in electronic and electrical circuits. Provides highly reliable conductive silicone rubber contact elements, resistor elements, and conductors for increasing density, thinning, and lowering costs of devices.

<Means for Solving the Problems> As a means for solving the problems of the prior art, the present invention provides two methods: (a) heat-curable silicone raw rubber;

(b) 100 parts by volume of a component consisting of alkenylorganopolysiloxane oil. (-) This is a method for producing the above-mentioned molded body, which comprises adding dimethylpolysiloxane oil to the carbon black and/or silicone rubber molded body having an average particle size of 100 mμ or less and the above-mentioned composition. This will be explained in more detail.

First of all, (a) What is heat-curable silicone raw rubber? It has been developed for various uses as described in the publicly known documents (1), (2), (3), (4), (7), and (8) above. Diorganopolysiloxane gum, average degree of polymerization 5,000
~12,000. 8 x 10' to 15 x at 25°C
10' c. s. It has a viscosity of Molecules with too high a degree of polymerization tend to form gel particles or lumps, which lowers the yield when forming printed films and coating films, so the average degree of polymerization is preferably 10,000 or less.

It has at least two alkenyl groups (for example, vinyl group, allyl group, etc.) in one molecule, and it is better to remove it because it reduces the monotony of siloxane. (1) Alkenylorganopolysiloxane oil is described in the known documents (3) and (7) above. It is a diorganopolysiloxane oil with an average degree of polymerization of 100 to 2 and O O O with dimethyl/alkenylsilyl groups blocked at both ends.It is preferable that the main chain contains no functional groups such as alkenyl groups or as little as possible. the above(
If the average degree of polymerization is less than 100, the molded product will lack flexibility and become brittle, so it is preferably 150 or more. If it is more than 2,000, the modulus will be small and the tensile strength cannot be increased, so it is preferably 1, O O O or less.

The present invention is based on a mixed system of component (a) and component (b), but they may be mixed uniformly in advance as a procedure for producing the composition, but the conductive filler and crosslinking agent described below may be used. ,
Alternatively, the curing catalyst and the like may be prepared as separate formulations and later made into a uniform composition. The composition ratios of components (a) and (b) are not limited, but they can be used to prevent gel formation due to crimping of the high polymer molecules described above and secondary condensation of carbon black, which will be described later. In order to improve the workability of molding such as coating and to obtain a molded article with further improved reliability of printed films and coating films, the ratio of component (a) to component (b) should be 10:1 to 1:10. A more preferable ratio is 8:1 to 1:8, and a ratio of 7:1 to 1 improves reliability and improves film forming workability.

The basis of the present invention is that the degree of polymerization has a different distribution in which functional groups are appropriately arranged. In other words, a mixed system of raw rubber and oil is obtained, and in particular, the binding of highly polymerized molecules to the conductive filler is improved to obtain a conductive silicone rubber molded article with improved reliability. next.

(iii) Component carbon black with an average particle size of 100 mμ or less includes acetylene blank (Denka Black Denchen Blasoku EC, approximately 25 mμ manufactured by Lion Akzo Co., Ltd.), Palcan XC-72 (manufactured by Carpot Co., Ltd.), I
Examples include so-called ``various carbon blacks'' such as S-500 (manufactured by Asahi Carbon Co., Ltd.). Powders of highly conductive materials other than carbon black with an average particle size of 10 μm or less include gold, silver, palladium diplatinum, etc. , flaky powder made of nickel, copper, tin, iron, or their alloys,
Alternatively, examples include those obtained by plating the flaky powder, flaky graphite, fiber-shaped carbon or graphite, finely cut or crushed metal, carbonyl nickel, and carbonyl nickel. 10 each of the above carbon black and other conductive powder
0mμ or less, 1 or less is the above (k) (b)
Improving workability when obtaining a molded body in a mixed state with components,
In particular, when printing or coating a thin film, it is possible to achieve a clean surface finish, especially for powder particles of 10 μm or less, preferably 8 μm or less, especially flaky powder. The above component (c) may be used separately with a component having a diameter of 100 mμ or less and a component having a diameter of 10 μm or less, but the volume ratio is preferably 8 to 8:1, and more preferably 1:1.
6 to 6.1, which combines with the effects of components (a) and (b) above to provide a more reliable molded product.

Add 5 to 100 of component (C) to components (A) and (B) above.
Since it is longer than the capacitance portion, it is not convenient for high-density packaging in which particularly narrow conductive paths are formed, and the capacitance is preferably 8 or more. In addition, if it exceeds 100 parts by volume, disadvantages such as air bubbles being contained in the thin film molded product and insufficient adhesive strength even when molded into an integral molded product with insulating silicone rubber are likely to occur. It is 90 parts by volume or less, more preferably 8 parts by volume.

To obtain a conductive silicone rubber molded product by thermally vulcanizing a mixture of the above components 0) and (b), a reaction product with a known crosslinking alcohol, a complex of chloroplatinic acid and olefins,
Complex of chloroplatinic acid and vinylsiloxane.

Platinum bisacetate and other palladium catalysts.

Rhodium catalysts can be used.

The present invention relates to organic peroxide vulcanization, i.e., dicumyl peroxide, t-butyl peroxide.

Oil resistance of the conductive silicone rubber molded article of the present invention.

To improve solvent resistance, diorganopolysiloxanes into which fluorinated or nitrile alkyl groups or alkenyl groups have been introduced may be used, and titanium oxide.

Iron oxide or manganese carbonate may be added to improve flame retardancy, dry process silica or wet process silica may be added to increase rubber hardness, and if necessary, a coupling agent may be added. Good too.

The conductive silicone rubber molded article of the present invention can be molded into various shapes by a textile printing method, a transfer printing method, injection molding such as topping, roll footer molding, transbar molding, extrusion molding, and the like.

The conductive silicone rubber molded body of the present invention can be formed into a printed film or coating film by screen printing, offset printing,
For obtaining by spray coating method, known organic solvents such as toluene, mixed xylene, oil hydroxide, turpentine oil, dimethylpolysiloxane oil, DMF, n-hexane, isopropyl alcohol, ethylene glycol methyl ether acetate, ethylene glycol are used. The viscosity may be adjusted by using a unit or a mixed solvent of two or more selected solvents such as diethyl ether, ethylene glycol dimethiether, etc. 10c. A solvent selected from the range of viscosity of dimethylpolysiloxane oil 25b, which is selected from the range of viscosity of 5 c. It was from s.

Function> The conductive silicone rubber molded article of the present invention has an average particle size of 10
Due to the particle size distribution and shape of 0 μm or less and 10 μm or less, high polymer molecules tend to get involved with conductive filler particles during the blending, molding, and vulcanization process, making it a highly reliable conductive silicone that can be carried out in a particularly humid manner. A rubber molded body is obtained.

The conductive silicone rubber molded article of the present invention functions as an electronic component element such as the above-mentioned -2 thick film resistor, or as an electrode terminal.

i Example 1゜(1) Dimethylmethyl vinyl polysiloxane raw rubber with both ends capped with dimethyl vinylsilyl groups (average degree of polymerization s, ooo, converted to vinyl group siloxane unit 0-2)
(mo1%) 50 parts by volume, (2) dimethylpolysiloxane oil with both ends blocked with dimethylvinylsilyl groups (
Average degree of polymerization 320) 50 parts by volume, (3)! (4) Denka Acetylene Black (Denka Kagaku Kogyo Co., Ltd. catalog value 42 mμ)
) 18 parts by volume, (5) Dimethylsiloxane methylhydrodiene siloxane copolymer with trimethylsilyl groups endblocked at both ends as a crosslinking agent (molar ratio of dimethylsiloxane units to methylhydrosiloxane units: 1:1, viscosity at 5°C at 125°C)
c. (6) An appropriate amount of hydroquinone as a reaction retarder was prepared in an isopropyl alcohol solution. The above (1) to (6) were thoroughly mixed until a uniform state was obtained. Next, an appropriate amount of platinum catalyst was added and mixed well. this mixture.

A film was formed using a coating composition similar to that shown in Figures 1 and 2 of Japanese Patent Publication No. 55-10937 by a printing method, and then heated in an oven adjusted to 200°C for 1 hour.

Next, a film was formed on a dimethylshixane oil molded body using the above formulation by screen printing, heated for 1 minute with a hot air dryer, and then heated in an oven under the same conditions as above. After both were allowed to cool, the film thickness was measured, and the thickness of the former was approximately 30 μm, and the thickness of the latter was approximately 15 μm.When measured using a commercially available tester, the thickness of the former was 12Ω, and the thickness of the latter was 22Ω. The thin film contact was adjusted to contact the electrode plate with a dynamic pressure load of 200gr, and a repeated keystroke test was performed at 3 times per second. After 50,000 ohms, the former was 12 ohms, the latter was 20 ohms, 1
,00Ω After 10,000 cycles, the former became 18Ω and the latter became 30Ω. Damage to the contact surface.

No peeling was observed.

A 100 μm sheet-like body was formed using the above compound.

When the specific resistance was measured, it was 0.15Ω·■.

Claims (2)

[Claims] (1) 100 parts by volume of a component consisting of heat-vulcanized silicone raw rubber and alkenylorganopolysiloxane oil, and carbon black with an average particle size of 100 μm or less and/or a conductive material other than the carbon black with an average particle size of 10 μm or less A conductive silicone rubber molded body formed by thermally vulcanizing 5 to 100 parts by volume of powder of (2) 100 parts by volume of a component consisting of heat-curable silicone raw rubber and alkenylorganopolysiloxane oil, carbon black with an average particle size of 100 mμ or less, and/or
Alternatively, 5 to 100 parts by volume of powder of a conductive material other than carbon black having an average particle size of 10 μm or less and a viscosity of 1 c. at 25° C. s. ~10c. s. A method for producing a conductive silicone rubber molded article according to claim (1) above, characterized by adding dimethylpolysiloxane oil selected from the range of