JPS61264070A - Coating material for resistance - Google Patents

Abstract

PURPOSE:The titled coating material, consisting of electrically conductive powder containing partially titanium nitride powder and a synthetic resin, having improved moisture and heat resistance characteristics without increasing resistance values due to anodic oxidation even on passing a current therethrough under a high humidity, and causing low sliding noises when used as a sliding contact. CONSTITUTION:A coating material consisting of (A) electrically conductive powder containing partially powder 4 of titanium nitride (TiN) and preferably carbon black 3 as the rest and (B) a synthetic resin 5, e.g. epoxy resin. The weight ratio of the TiN powder 4 to the carbon black 3 is preferably 95:5-10:90. USE:Printed circuit boards for various electrical apparatuses, resistance elements in fixed resistors, etc., electromagnetic wave shielding plates, 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,
Resistors used in resistance elements such as variable resistors, electromagnetic wave shielding plates, radio wave absorption plates, antistatic plates, etc. Conventional technology Traditionally, carbon blanks, such as acetylene black, etc., were used as conductive powders as resistance paints. It is known that graphite powder is dispersed in synthetic resins such as epoxy resins and phenol resins. In addition, 5102 powder and T
2. Description of the Related Art Resistance paints are known in which an insulating powder such as iO2 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 described above, 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, and the carbon black becomes carbonated. As a result of vaporization as a gas, the resistance value increases at an accelerating rate and has the disadvantage that it reaches infinity (insulating material). Furthermore, resistance paints containing insulating powders such as 5in2 powder and TlO2 powder have one drawback: when used as sliding contacts, such as resistance elements for variable resistors, the sliding noise becomes high. . In fact, the current conduction path is due to carbon black and its mutual contact, so in a high resistance region where the proportion of carbon black is small, the resistance value changes greatly when humidity or temperature fluctuates.

The present invention eliminates the above-mentioned conventional drawbacks, and aims to provide a resistance paint that has a low resistance value change rate, low sliding noise, is inexpensive, and has excellent printability. be.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a structure in which the conductive powder is made of at least a conductive powder and a synthetic resin, and a part of the conductive powder is titanium nitride (TiN) powder. This is what I did.

Function: With this configuration, there is no increase in resistance even in high humidity, low sliding noise as a sliding contact, and excellent printability.

Example As a result of repeated research in order to solve the above-mentioned conventional drawbacks, the present inventors found that titanium oxide (hereinafter referred to as TiN) was used in a specific proportion.
It has been found that the objective can be achieved by combining powder and carbon black.

That is, in a resistance paint made of at least conductive powder and synthetic resin, a part of the conductive powder is TiN powder, the other part is composed of carbon black, and T'i
The weight ratio of N powder and carbon blank is 95:6 to 10.
:90, it has been found that each of the conventional drawbacks can be eliminated. TiN is conventionally known, but Ti
When N powder alone is dispersed in a synthetic resin such as phenol resin to form a resistance paint, the resistance value fluctuates extremely sharply in an atmosphere of high humidity and high temperature, as shown in FIG. As shown in Figure 1, which shows the coating film structure of a resistive paint by combining carbon black and TiN powder, the variation in resistance value is extremely reduced in a high humidity and high temperature atmosphere by using carbon black 3. It can be inferred that this is caused by the structure of the TiN powder 4. That is, while the TiN powder 4 is granular, the carbon black 3 has a chain 5, -3-7 structure called a stracture. When a conductive powder with a granular structure or a chain structure is used, the contact state of the powder particles with each other is limited to the atmosphere due to moisture absorption and desorption of the synthetic resin 5 that binds the powder particles together and expansion and contraction due to heat. Depending on the state of the situation, they can be dense or mixed together. 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 be a big hit.

When the TiN powder 4 and carbon black 3 according to the present invention are mixed and dispersed in the synthetic resin 5, even if the synthetic resin 6 absorbs and desorbs moisture due to changes in the atmosphere and expands and contracts due to heat, as shown in FIG. As shown in the conceptual diagram, it is presumed that the change in resistance value is small because the conductive path 6 is easily obtained. moreover,
Since both carbon black 3 and TiN powder 4 are good conductive materials, when used as a sliding contact, the level of sliding noise is lower than when carbon alone is used. Furthermore, even in the high resistance region, TiN is stable with respect to temperature and humidity, and the synthetic resin ratio in the resistance film is 6 H compared to conventional ones.

Since moisture absorption can be reduced, anodic oxidation can also be substantially 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 has good workability in screen printing, etc. It is something.

The present invention will be explained below using specific examples.

[Example 1] 255 g of TiN powder with an average particle size of 0.2 pm, 40 g of acetylene plaque, and 6 g of artificial graphite were weighed and mixed to make an epoxy resin (Yuka Shell, product name: Epicoat 816) 2.
It was dispersed in 00g using three rolls.

Next, 20 g of an imidazole curing agent was added, and ethyl carpitol acetate was added to adjust the paint viscosity to 100 poise to obtain a resistance paint.

[Comparative example]

Acetylene black 60g 1 artificial graphite 7g epoxy resin (yuka shell, product name: Epicor) 815) 2oOg
An imidazole curing agent 7, -.

After adding 20 g of ethyl rubitol acetate, the viscosity of the paint was adjusted to 100 poise to obtain a resistance paint.

[Comparative test example]

The resistance paints of Example 1 and Comparative Example were each pattern-printed on a phenol laminate using a screen printing method.
The epoxy resin was cured at 0°C for 30 minutes. The following comparative tests were conducted on each of the resistance elements according to Example 1 and Comparative Example.

Test 1: After being left in a constant temperature bath at 0'C for 1,1000 hours, the rate of change in zero resistance value was measured.

Test 2: 60'090-95% left in a relative humidity chamber for 10
Measure the rate of change in resistance value after 00 hours.

Test 3: A DC voltage of 24 V was applied to both ends of the resistance element in a 60'C90 to 95 relative humidity chamber, and the rate of change in resistance value was measured after an i ooo time.

Test 4: Measure the sliding noise when sliding a silver mesokibe IJ IJum copper metal brush on the resistive coating at a pressure of 2°, p, 15 mm at a speed of 7 seconds (DC voltage 2 across the resistive element)
4V applied). The test results are shown in Figure 4 a+ b+ C+ and the table below.

[Example 2] The same materials as in Example 1 were used, and the moisture resistance and heat resistance after 1000 hours were measured in the same manner as in the comparative test example for resistance paints with varying ratios of carbon black and TiN powder. The resistance change rate was investigated. The results are shown in Figure 2.

Effects of the Invention As described above, according to the present invention, there is no increase in resistance due to anodic oxidation even when current is passed in a high humidity atmosphere, and the moisture and heat resistance properties are also good. When used as a sliding contact, the sliding contact It has low noise and can produce a large amount of conductive powder compared to carbon black alone, so it has the appropriate chikuntropic properties required as paint properties for screen printing, etc., so it is easy to work with. It's good. In addition, each material used is inexpensive9/,
−.

Therefore, it is extremely useful industrially.

[Brief explanation of the drawing]

Figure 1 is a diagram of the coating film structure of the resistance paint according to the present invention, Figure 2 is a curve diagram showing the ratio of carbon black and TiN powder and resistance change characteristics, and Figure 3 is a conceptual diagram of conductive paths in the coating film. ,
FIGS. 4a, b, and c are curve diagrams showing comparative test examples according to the present invention and comparative examples. 1...Moisture resistance change characteristics, 2...Heat resistance change characteristics, 3...Carbon black, 4.
...TiN powder, 6...Synthetic resin, 6.
. . . Conductive path, 7 . . . Resistance change characteristics of the example according to the present invention, 8 . . . Resistance change characteristics of the comparative example. Name of agent: Patent attorney Toshio Nakao and one other person
'+3 sun~) Mi nose ℃ size N also o4 懺 jealousy = Hoshiba umbrella - Shunida X-

Claims (3)

[Claims] (1) A resistive paint comprising at least a conductive powder and a synthetic resin, wherein a part of the conductive powder is titanium nitride (TiN) powder. (2) A resistive paint according to claim 1, wherein a part of the conductive powder is titanium nitride (TiN) powder and the other part is carbon black. (3) The resistance paint according to claim 2, wherein the weight ratio of titanium nitride (TiN) powder to carbon black is 95:5 to 10:90.