JPS61235472A - Paint for resistor - Google Patents

Abstract

PURPOSE:To obtain the title paint for resistors, which does not cause rise in resistance due to anodic oxidation, produces a less sliding noise and has good resistance to moisture and heat, by blending an electrically conductive power composed of vanadium trioxide power and carbon black and a synthetic resin. CONSTITUTION:In a paint for resistance obtd. by blending an electrically conductive powder and a synthetic resin, the paint is characterized in that part of the electrically conductive powder is vanadium trioxide (V2O2) powder and the remainder thereof is carbon black in a weight ratio of the V2O2 powder to the carbon black of pref. 95:5-10:90. The paint allows the quantity of the electrically conductive powder to be increased as compared with the case where carbon black alone is used. Accordingly, the paint has good workability, because it has proper thixotropic properties required of a paint in screen printing, etc.

Description

[Detailed Description of the Invention] Industrial Fields of Use The present invention is applicable to printed wiring boards of various electronic devices, fixed resistors,
The present invention relates to resistance paints used for resistance elements such as variable resistors, electromagnetic wave shielding plates, radio wave absorption plates, antistatic plates, etc.

BACKGROUND OF THE INVENTION Conventionally, as a resistive paint, one in which conductive powder such as carbon black such as acetylene black or graphite powder is dispersed in a synthetic resin such as an epoxy resin or a phenol resin is known. In addition, for the purpose of improving workability such as printability and environmental stability such as under high load conditions, we use Sin, powder, and Ti.
There is known a resistance paint in which insulating powder such as powder is dispersed together with carbon black in a synthetic resin.

Problems to be Solved by the Invention In the case of the conventional example, since the proportion of carbon black in the resistor composition is extremely small in the high resistance region, anodic oxidation occurs when current is passed in a high humidity atmosphere.

The result of carbon black vaporizing as carbon dioxide gas.

It had the disadvantage that the resistance value increased at an accelerating rate and reached infinity (insulator). Furthermore, resistance paints containing insulating powders such as SiO□ powder, Tie powder, etc. have the disadvantage of high sliding noise when used as sliding contacts, such as resistance elements for variable resistors. Furthermore, since the current conduction bus is based on carbon black and its mutual contact, it has the disadvantage that in a high resistance region where the proportion of carbon black is small, the resistance value changes greatly when humidity or temperature changes.

The present invention solves these problems by creating a resistor that does not increase the resistance value due to anodization as in conventional methods, has low sliding noise when used as a sliding contact, and has good moisture resistance and heat resistance characteristics. The purpose is to provide paints for

Means for Solving the Problem In order to solve this problem, the present invention provides a resistive paint comprising at least a conductive powder and a synthetic resin, in which a part of the conductive powder is vanadium trioxide (V x O3). The other part is carbon black.

Function: With this structure, there is no increase in resistance due to anodization even when current is passed in a high humidity atmosphere, the moisture resistance and heat resistance are good, and when used as a sliding contact, the sliding noise is low.

Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

That is, the present invention provides a resistive paint comprising at least a conductive powder and a synthetic resin, in which a part of the conductive powder is vanadium trioxide (V, O,) powder, and the other part is composed of carbon black. , V2O.

The weight ratio of powder and carbon black is 95=5~1O:
90.

V, O, have been known for a long time, but when V2O powder alone is dispersed in a synthetic resin such as phenol resin and used as a resistance paint, it does not react in a high humidity and high temperature atmosphere as shown in Figure 1. By combining V, O, powder and carbon black, which have extremely large resistance fluctuations,
As shown in Figure 2, which shows the film structure of the resistance paint, the reason why the resistance value fluctuates extremely little in a high humidity and high temperature atmosphere is due to the structure of V2O, powder 1, and carbon black 2. It can be inferred that. That is, while V2O and powder 1 are granular, carbon black 2 has a chain-like structure called a struture. When a conductive powder with a granular or chain structure is used, the state of contact between the powder particles may be affected by the atmosphere due to moisture absorption and desorption of the synthetic resin that binds the powder particles together, as well as expansion and contraction due to heat. Depending on the condition, it can be dense or coarse. On the other hand, the resistance value is expressed as the sum of the resistance of the conductive powder itself and the contact resistance between the powders, so in the case of the granular powder or chain powder alone, the resistance value changes due to changes in temperature and humidity atmosphere. It is thought that it will become larger. As shown in Figure 2, V□
0. Mix powder 1 and carbon black 2 to make synthetic resin 3
When the synthetic resin is dispersed in the air, even if the synthetic resin absorbs and desorbs moisture due to changes in the atmosphere or expands and contracts due to heat, the conductive path 4 is easily obtained as shown in the conceptual diagram of Fig. 3, so the resistance value decreases. It is assumed that there will be little change. Furthermore, carbon black is also V
Since 2O is also a good conductive material, when used as a sliding contact, the level of sliding noise is lower than when using carbon black alone. In addition, even in the high resistance region, V, O, and O are stable with respect to temperature and humidity, and the synthetic resin ratio in the resistance film can be lowered compared to conventional ones, so moisture absorption can be reduced, so anodic oxidation is also virtually impossible. can be prevented. In addition, the resistance paint according to the present invention has a large amount of conductive powder in the paint compared to conventional carbon alone, so it has appropriate thixotropic properties and is easy to work with, such as screen printing. It's good.

Next, specific examples will be described.

Specific Example 1 Weighed and mixed 255 g of V2O powder with an average particle size of 0.2 μm, 40 g of acetylene black, and 5 g of artificial graphite to prepare 200 g of epoxy resin (Yuka Shell, product name: Epicoat 815).
20 g of a zero-order imidazole curing agent dispersed with a triple roll was added to the mixture, and ethyl carpitol acetate was added to adjust the viscosity of the paint to 31:1 to 100 poise to obtain a resistance paint.

Comparative Example 60g of acetylene black, 7g of artificial graphite and 200g of epoxy resin (Yuka Shell, product name: Epicoat 815)
20g of imidazole curing agent was added, and ethyl carpitol acetate was added to make the paint viscosity 100.
The poise was adjusted to obtain a resistance paint.

Comparative Test Example The resistive paints of Specific Example 1 and Comparative Example were each pattern-printed on a phenol laminate using a screen printing method.
The epoxy resin was cured at 60°C for 30 minutes. The following comparative tests were conducted on the respective resistance elements according to the specific example 1 and comparative example.

Test 1: Leave it in a constant temperature bath at 70°C and measure the rate of change in resistance value after 1000 hours. Test 2: Leave it in a 60°C 90-95% relative humidity bath and measure the rate of change in resistance value after 1000 hours.
Test 3: Apply a DC voltage of 24 V to both ends of the resistance element in a 60°C 90-95% relative humidity chamber, and measure the rate of change in resistance value after 1000 hours. Test 4: Silver-metsuki beryllium copper on the resistive coating. The sliding noise was measured when a metal brush was slid at a pressure of 20 g and a speed of 15 mm/sec (DC voltage of 24 V was applied across the resistance element). The results of these tests 1 to 3 are shown in Figure 4 (a). ) to (c), respectively. In addition, Fig. 4(a) to (
In c), (A) is the resistance change characteristic of specific example 1, (
B) is the resistance change characteristic of the comparative example. Additionally, the results of Test 4 are shown in the following table.

Specific Example 2 Using the same materials as in Specific Example 1 and varying the ratio of carbon black, V2O, and powder, the moisture resistance and heat resistance after 1000 hours were determined in the same manner as in the comparative test example. The rate of change in resistance was investigated.

The results are shown in FIG.

Effects of the Invention As described above, according to the present invention, there is no increase in resistance due to anodization even when current is passed in a high humidity atmosphere, the moisture resistance and heat resistance are good, and when used as a sliding contact, there is no sliding resistance. The noise is low, and the amount of conductive powder can be increased compared to carbon black alone, so it has the appropriate thixotropic properties required as paint properties for screen printing, etc., and is easy to work with. It's good. In addition, since the materials used are all inexpensive, they are extremely useful industrially.

[Brief explanation of the drawing]

The drawings show examples of the present invention. Figure 1 is a graph showing the relationship between the ratio of carbon black, V2O, and powder and resistance change characteristics, and Figure 2 is a coating film structure of a resistive paint according to the present invention. 3 are conceptual diagrams of conductive paths in a coating film, and FIGS. 4(a) to 4(c) are graphs showing comparative test examples according to the present invention and a comparative example. 1...V, O, powder, 2...carbon black,
3... Synthetic resin, 4... Conductive path agent Yoshihiro Morimoto Figure 1

Claims (1)

[Claims] 1. A resistor paint made of at least conductive powder and synthetic resin, wherein a part of the conductive powder is vanadium trioxide (V_2O_3) powder and the other part is carbon black. Paint for use. 2. The resistance paint according to claim 1, wherein the weight ratio of vanadium trioxide (V_2O_3) powder and carbon black is 95:5 to 10:90.