JPS5931163B2 - Method for manufacturing an organic semiconductor composed of pyrolyzed and fired carbonaceous fiber aggregate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an organic semiconductor whose electrical resistance value has significantly lower temperature dependence than a pyrolyzed and fired carbonaceous fiber aggregate obtained by firing a fibrous organic substance to a temperature higher than its pyrolysis temperature. It is something.

For example, pyrolysis-fired carbonaceous fiber aggregates produced at a firing temperature of about 1000°C or higher generally contain fibrous organic matter essentially at a temperature higher than the pyrolysis temperature so as to produce carbonaceous fibers with a distinct carbon-type structure. When firing at high temperatures, the carbon content in the fired product increases as the firing temperature increases.

Now, when a fibrous organic material is pyrolyzed and fired at a calcination temperature of about 1000°C above the pyrolysis temperature of the fibrous organic material, the pyrolysis does not result in a clear carbon-type structure (the carbon content is not sufficient). It becomes a fired carbonaceous fiber aggregate, that is, a carbonaceous fiber aggregate that exhibits the electrical resistance value of the semiconductor region (
However, the disadvantage of this carbon fiber aggregate is that the electrical resistance value changes greatly as the temperature in the atmosphere changes, that is, it has a large temperature dependence.

Table 1 Firing temperature and physical properties of pyrolyzed and fired carbonaceous fiber aggregates using polyacrylonitrile fiber precursors For example, a fibrous organic material consisting of 3000 1.5D polyacrylonitrile fibers is sintered at 650 to 1000°C. For the pyrolyzed and fired carbonaceous fiber aggregates obtained, the electrical resistance value per 1 m was measured at various atmospheric temperatures, and the electrical resistance value change rate ( The change in (ξ) when expressed as (ξ) is as shown in Figure 1.

As is clear from FIG. 1, the electrical resistance value of the carbon fiber aggregate decreases as the ambient temperature rises. and,
The above-mentioned electric resistance value change rate ξ becomes smaller as the firing temperature increases when obtaining the carbonaceous fiber aggregate, and when the firing temperature is 10
It is confirmed that when the temperature exceeds 00° C., the rate of change ξ is hardly a problem in practice. By the way, the fact that the electrical resistance value has a large temperature dependence means that, for example, when a pyrolyzed and fired carbonaceous fiber aggregate is used as a heating element or a semiconductor wire, the electrical resistance value changes during its use. , the predetermined electrical characteristics will be lost during use, which is a negative factor in practical use. In order to obtain a pyrolyzed and fired carbonaceous fiber aggregate with a small fiber aggregate, the electrical resistance value of the fiber aggregate itself is increased by reducing the total number of single fibers constituting the fiber aggregate, and the firing rate that can be utilized by that amount is increased. One possibility is to raise the temperature.

However, when using a pyrolyzed and fired carbonaceous fiber aggregate as, for example, a semiconductor wire, it is an essential condition that it has the strength necessary to be practically used as a semiconductor wire. If the total number of single fibers constituting the fiber aggregate is reduced, the strength of the fiber aggregate will inevitably decrease, making it impossible to obtain a fiber aggregate that satisfies these conditions. It is difficult to obtain a pyrolyzed and fired carbonaceous fiber aggregate whose electrical resistance value has a small temperature dependence by increasing the temperature.

In the present invention, a pyrolyzed and fired carbonaceous fiber aggregate obtained by firing a fibrous organic substance at a temperature above the thermal decomposition temperature of the fibrous organic substance to about 1000°C is treated with an aqueous copper salt solution,
Claim 1: Obtaining an organic semiconductor consisting of a pyrolyzed and fired carbonaceous fiber aggregate by heat treatment at 600°C.
In the invention, a pyrolyzed and fired carbonaceous fiber aggregate obtained by firing a fibrous organic substance at a temperature above the thermal decomposition temperature of the fibrous organic substance to about 1000°C is heat-treated at 300 to 600°C, and then a copper salt is added to the aggregate. After treatment with aqueous solution, further 300-60
According to the second aspect of the invention, an organic semiconductor consisting of a pyrolyzed and fired carbonaceous fiber aggregate is obtained by heat treatment at 0°C. The purpose of the present invention is to obtain an organic semiconductor which is a pyrolyzed and fired carbonaceous fiber aggregate obtained by firing at a certain temperature, and whose electrical resistance value has extremely low temperature dependence.

In the present invention, examples of fibrous organic substances that serve as precursors of pyrolyzed and fired carbonaceous fiber aggregates include synthetic fibers such as polyacrylonitrile and carbonaceous fibers produced from pitch.
In general, any material can be used as long as it can be modified into what is generally called a carbon fiber by firing. The specific structure and effects of the method for producing an organic semiconductor made of a pyrolyzed and fired carbonaceous fiber aggregate of the present invention will be explained below based on experimental examples.

Note that the effects based on the copper salt aqueous solution treatment and the subsequent heat treatment at 300 to 600°C in the method for producing an organic semiconductor comprising a pyrolyzed and fired carbonaceous fiber aggregate of the present invention are due to the pyrolysis caused by these treatments. It is clear that the pyrolysis and sintering temperature used to obtain the sintered carbonaceous fiber aggregate is up to about 1000°C, and the lower the pyrolysis and sintering temperature is, the more remarkable the effects of the present invention become. be. However, in order to efficiently carry out pyrolysis and sintering when pyrolyzing and sintering fibrous organic matter to obtain a carbonaceous fiber aggregate, pyrolysis and sintering must be carried out at a certain temperature or higher. This is common sense, and by the way, the typical minimum temperature at which polyacrylonitrile fiber can be thermally decomposed efficiently is approximately 700°C.
Therefore, as a carbonaceous fiber aggregate to be used when subjecting the carbonaceous fiber aggregate to the treatment of the present invention,
The following specific example will be explained based on the case of using a carbonaceous fiber aggregate made from polyacrylonitrile fibers fired using a pyrolysis firing temperature of 720°C to 850°C. Experimental Example 1 Pyrolytic calcined carbonaceous material obtained by firing 1.5D x 6000 polyacrylonitrile fibers at 27°C for 3 hours in the presence of air and then firing them at 720℃ for 7 minutes in a nitrogen atmosphere. The fiber aggregate (hereinafter abbreviated as CF6OOO aggregate) was immersed in various metal salt aqueous solutions, dried at 180°C, and then heat-treated at 4500C for 7 minutes.

The electrical resistance value of the CF6OOO aggregate treated with the above metal salt aqueous solution is cut into 1 m length, and the value measured by changing the ambient temperature is expressed as the rate of change ξ based on the electrical resistance value at 24 ° C. It is shown in Figure 2-1.

As is clear from the figure, the temperature dependence of the electrical resistance value of the system treated with a copper salt (CuCl2) aqueous solution is extremely small, and the effect is hardly visible when treated with aqueous salt solutions such as aluminum salts, lithium salts, or magnesium salts. Not yet.

For reference, after immersing in this copper salt aqueous solution, 1
The rate of change in electrical resistance value ξ of the sample dried at 80°C and omitted the next heat treatment is ξ, and this rate of change is essentially the same as the rate of change of the sample without treatment, and after the immersion treatment in a copper salt aqueous solution. about 300 to 600℃, preferably 400 to 500℃
It can be seen that heat treatment at a temperature of about °C is essential.

Experimental Example 2 Pyrolytic calcined carbonaceous material obtained by firing 1.5D x 3000 polyacrylonitrile fibers at 270°C for 3 hours in the presence of air, and then firing at 75°C for 7 minutes in a nitrogen atmosphere. The fiber aggregate was immersed in various copper salt aqueous solutions, and then 4
5. Heat treatment was performed for 7 minutes at C.

Figure 2-2 shows the electrical resistance change rate ξ of the metal salt treated system cut into 1 m length.

From the figure, it is clear that the temperature dependence of the electrical resistance value is extremely small when a CUCl2 aqueous solution is used as the copper salt. It has been confirmed that an aqueous copper salt solution has similar effects. Experimental Example 3 The CF6000 aggregate was first heat treated as the first step, then immersed in a copper salt aqueous solution as the second step, and heat treated at 450°C for 10 minutes as the final step, after which it was cut into a length of 1 m. Electrical resistance change rate ξ of the cut object
is shown in Figure 3.

From the figure, the higher the solution concentration of the CUCl2 aqueous solution, the higher the C
The greater the amount of UCl2 deposited, the smaller the temperature dependence of the electrical resistance value, and the temperature dependence of the electrical resistance value of samples that were heat-treated prior to immersion in a copper salt aqueous solution was greater than that of samples that were not heat-treated. It is clear that the size becomes slightly smaller due to the copper salt aqueous solution immersion treatment. The temperature dependence of the electrical resistance value of this material was clearly greater than that of the material that was then subjected to heat treatment, confirming that the immersion treatment in a copper salt aqueous solution and the subsequent heat treatment step are essential steps. In this case, the heat treatment that follows the immersion treatment with a copper salt aqueous solution will not be effective if the heat treatment is performed at a low temperature that does not cause any change to the fiber surface; it must be heat treated at a temperature that etches the fiber surface. Generally, the temperature is about 300 to 600°C, preferably about 400 to 500°C, for 1 to 60 minutes, preferably 2 minutes.
A heat treatment of about 25 minutes is required. Experimental example 41.5
D x 3000 polyacrylonitrile fibers were fired at 270°C for 3 hours in the presence of air, and then fired at 75°C for 7 minutes in a nitrogen atmosphere to produce a pyrolyzed and fired carbonaceous fiber aggregate (hereinafter referred to as CF3OOO-A). abbreviated as aggregate) and 1
．． 5D x 3000 polyacrylic nitrile fibers were fired at 270℃ for 3 hours in the presence of air, and then fired at 850℃ for 7 minutes in a nitrogen atmosphere to create a pyrolyzed carbonaceous fiber aggregate (hereinafter referred to as CF3OOO-B aggregate). After the first step is heat treatment for each of the 45 mm (45 mm)
Heat treatment was performed at 0°C for 7 minutes.

FIG. 4 shows the rate of change in electrical resistance value ξ of these metal salt treated systems cut into lengths of 1 m. From the figure, CF3OO
In the case of O-A aggregates and CF3OOO-B aggregates, as in the case of the CF6OOO aggregates described above, the pyrolyzed and fired carbonaceous fiber aggregates are subjected to the three steps of immersion in a heat-treated copper salt aqueous solution and heat treatment. In this case, it is clear that the electrical resistance value is modified to have a small temperature dependence. Also,
If the pyrolysis and sintering temperature is constant when obtaining a pyrolyzed and sintered carbonaceous fiber aggregate, repeated heat treatments alone are not sufficient to modify the pyrolysis and sintering temperature into one with a small temperature dependence of electrical resistance. It turns out that immersion treatment with a copper salt aqueous solution is essential. As is clear from Experimental Example 3 above, in general, the temperature dependence of the electrical resistance value of the pyrolyzed and sintered carbonaceous fiber aggregate is heat-treated before the pyrolyzed and sintered carbonaceous fiber aggregate is immersed in a copper salt aqueous solution. The heat treatment is slightly smaller than that of a material not subjected to this heat treatment, and the desired effects of the present invention are further exhibited. However, this level of difference in effectiveness can be reduced by increasing the concentration of the copper salt aqueous solution during the immersion treatment with the copper salt aqueous solution, or by increasing the heat treatment temperature after the copper salt aqueous solution treatment. Since this effect can be sufficiently achieved without heat treatment prior to the treatment, the choice of which process to adopt should be made in consideration of the economic efficiency of the process.

[Brief explanation of the drawing]

Figure 1 is a graph showing the temperature dependence of the electrical resistance change rate of a pyrolyzed and fired carbon fiber aggregate obtained by forming a fibrous organic material consisting of polyacrylonitrino fibers at 650 to 1000°C. Figures 2-1 and 2-2 are graphical representations of the temperature dependence of the rate of change in electrical resistance of polyacrylonitrile fibers treated with different metal salts after thermal decomposition. , 3 and 4 are graphical representations of the temperature dependence of the rate of change in electrical resistance of polyacrylonitrile fibers treated with varying concentrations of CUCl2 aqueous solution after thermal decomposition.

Claims (1)

[Scope of Claims] 1. Fibrous organic matter is heated to a temperature higher than the thermal decomposition temperature of the fibrous organic matter.
The pyrolyzed and fired carbonaceous fiber aggregate obtained by firing at about 1000°C is treated with a copper salt aqueous solution, and then heated to 300 to 600°C.
A method for producing an organic semiconductor comprising a pyrolyzed and fired carbonaceous fiber aggregate, characterized by heat treatment at ℃. 2 The fibrous organic material is heated to a temperature higher than the thermal decomposition temperature of the fibrous organic material.
The pyrolyzed and fired carbonaceous fiber aggregate obtained by firing at about 1000°C is heat-treated at 300-600°C, then treated with an aqueous copper salt solution, and then further heat-treated at 300-600°C. A method for producing an organic semiconductor comprising a pyrolyzed and fired carbonaceous fiber aggregate.