RESEARCH IN THE CHEMISTRY OF CARBAZOLE DERIVATIVES

64. STUDY OF THE ELECTROGRAPHIC PROPERTIES OF POLY-9-VINYLCARBAZOLE

E. E. Sirotkina, V. P. Lopatinskii, G. N. Ivanov, V. D. Pirogov

(Presented by the Scientific-Methodological Seminar of the Faculty of Chemical Technology)

In recent years poly-9-vinylcarbazole (9-PVK) has found a new field of application as photosensitive films in electrography [1]. Our studies have shown that, for this purpose, 9-PVK obtained both by polymerization of the monomer and in the process of revinylylation of vinyl acetate with carbazole can be used; the latter is distinguished by the fact that the polymer is obtained in one stage through the interaction of carbazole with vinyl acetate in acetone solution in the presence of mercury salts [2].

The polymer obtained in this process is separated into two fractions—soluble and insoluble in acetone, hereinafter designated conventionally as the low-molecular-weight fraction (LMF) and the high-molecular-weight fraction (HMF), respectively. All tests of the electrographic properties of the polymers were carried out on the apparatus [3], and film samples were applied by pouring a solution of the polymer in a solvent onto metal substrates (steel, aluminum, brass). The LMF has a high charging potential, on the order of 500–1000 V, possesses photosensitivity \((S_{\lambda})\) of \((1.0–2.5)\cdot 10^{+3}\) lux·sec, and can be used for preparing photosensitive films. The HMF does not give satisfactory films, and therefore is not capable of retaining charge on the surface of films when they are charged in a corona discharge.

In the present work our studies were directed toward utilization of the HMF in the form of compositions with various products for preparing photosensitive films. For this purpose we used the LMF of poly-9-vinylcarbazole, polystyrene, polyvinyl chloride resin, glue 88, and poly-N-vinyldiphenylamine (PVDPA), obtained by the method of revinylylation [4]. One of the shortcomings of the HMF is cracking of the films during their preparation.

When LMF-9-PVK is used as the binding component, stronger films are obtained, but at the same time the charging potential decreases and the sensitivity of the polymer film increases somewhat. Preparation of films in compositions with polystyrene, perchlorovinyl resin, and glue 88 showed that, with an increase in the amount of the latter components, the charging potential increases; however, the sensitivity decreases. The best results were obtained when testing films prepared with additions of PVDPA and glue 88. As is evident from the data of Table 1, as the amount of PVDPA increases, the charging potential rises and the high sensitivity of the polymer film is retained.

Interesting results were obtained in testing three-component films prepared at different ratios of HMF, LMF polyvinylcarbazole, and PVDPA. The data of Table 2 show that, with dif-

Table 1

Effect of the ratio of VMF 9-PVK and PVDF on electrophotographic properties

VMF — does not charge; PVDF \(\left\{ \begin{array}{l} V=(280—340)\ \text{V} \\ S_{1/2}=(3.2—3.4)\cdot 10^3\ \text{lux}\cdot\text{s}. \end{array}\right.\)

Note. Films were prepared from a benzene solution at the concentration:
* — 3.0 g of mixture per 10 ml of benzene,
** — 4.0 g of mixture per 10 ml of benzene.

Table 2

Effect of the ratio of VMF 9-PVK, NMF 9-PVK, and PVDF on electrophotographic properties

VMF — does not charge;
NMF — \(V=(180—220)\ \text{V}\);
PVDF \(\left\{ \begin{array}{l} V=(280—340)\ \text{V} \\ S_{1/2}=(3.2—3.4)\cdot 10^3\ \text{lux}\cdot\text{s}. \end{array}\right.\)

Note. Films were prepared from a benzene solution at a mixture concentration of 3.0 g per 10 ml of benzene.

In various ratios of the starting components the films have higher charging potentials than any of the starting components, but the sensitivity remains low. Elucidation of the reasons for such behavior of the studied compositions requires a special investigation.

The solvent in which the solution for preparing the film is made has a substantial effect on the electrophotographic properties of the layers. Testing of films of NMF 9-PVK using a number of solvents showed, as can be seen from Table 3, that the layers possess the greatest charging potential and photosensitivity when carbon tetrachloride and chloroform are used.

As a result of studies of electrophotographic properties it was found that, in addition to the nature of the solvent, the magnitude of the thickness of the layer itself also plays a major role. Table 4 gives the results of tests of layers prepared from benzene solutions with different concentrations of the product, on which, essentially, the thickness of the layer depends.

As can be seen, with increasing concentration of the solution the charging potential of the layer increases proportionally, while the sensitivity remai-

Table 3

Effect of the solvent on the electrophotographic properties of 9-PVK (NMF)

Note: the films were prepared from a solution at a concentration of 3.0 g of NMF per 10 ml of solvent.

Table 4

Results of tests of the electrophotographic properties of NMF 9-PVK as a function of film thickness

is high. Solvents and film thickness likewise affect the electrophotographic properties when testing the compositions considered above.

Conclusion

It has been shown that the electrophotographic properties of the high-molecular-weight fraction of poly-9-vinylcarbazole can be improved by adding poly-N-vinyldiphenylamine and glue 88.

REFERENCES

1. N. B. Sidaravichus. Problems of Radio Electronics, 12, 105, 1964.
2. V. P. Lopatinskii, E. E. Sirotkina. Izv. TPI, 111, 44, 1961.
3. I. I. Zhylevich, E. L. Nemirovskii. Electrophotography, Iskusstvo, 1961.
4. V. P. Lopatinskii, E. E. Sirotkina, Yu. P. Shekhirev. Izv. TPI, 126, 55, 1964.