US3705031A - Chlorine and bromine containing poly-9-vinylcarbazole electrophotographic polymers - Google Patents

Abstract

AN ELECTROPHOTOGRAPHIC PHOTOSENSITIVE MATERIAL COMPRISES A POLYMER CONTAINING A CHLORINE AND BROMINE SUBSTITUTED 9-VINYLCARBAZOLE UNIT.

Description

United States Patent US. CI. 96-15 18 Claims ABSTRACT OF THE DISCLOSURE An electrophotographic photosensitive material comprises a polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit.

The present invention relates to electrophotographic photosensitive materials. Hitherto, many organic compounds have been known as photoconductive materials for electrophotographic photosensitive materials, and some compounds have been known to have fairly high photosensitivity. Nevertheless in the existing state of things it can be said that examples wherein organic photoconductive materials are used as an electrophotographic photosensitive material are extremely few. Compared with inorganic photoconductive materials, the organic photoconductive materials have many superior performances providing extremely useful application techniques in the technical fields of electrophotography or photosensitive materials.

For example manufacture of transparent photosensitive films, flexible photosensitive films or photosensitive films of light weight and easy to handle is possible only by the utilization of organic photoconductive materials. Also the film forming nature, surface smoothness, further, the selectivity of charging polarity in the application to electrophotographic transfering processes are the characteristics not expectable from inorganic photoconductive materials.

The reason why organic photoconductive materials despite with those characteristics excellent in many points have been unable to contribute sufficiently up to the present time in the technical field of electrophotography is due to its low sensitivity. For example its sensitivity is remarkably lower than that of selenium and zinc oxide, the well known photosensitive materials.

An object of the present invention is to provide a high photosensitivity organic electrophotographic photosensitive materials to enhance the industrial value of electrophotographic sensitive materials remarkably.

Another object of the present invention is to provide a novel means in respect of synthesizing techniques of organic photoconductive materials by developing a manufacturing method for new organic photoconductive materials.

Further, the other object of the present invention is to provide stable organic photoconductive materials free from deterioration in photosensitivity with elapsed time during long term preservation.

Still another object of the present invention is to provide organic photoconductive materials easy to handle at the time of manufacture.

Still another object of the present invention is to provide electrophotographic photosensitive materials having high photosensitivity equivalent to or higher than inorganic photoconductive materials by applying various sensitizing means.

The present invention achieving the above mentioned respective objects resides in an electrophotographic photosensitive material which comprises a polymer having a chlorine and bromine substituted 9-vinylcarbazole unit.

In the present invention, polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit includes a polymer containing both a chlorine substituted 9-vinylcarbazole unit and a bromine substituted 9-vinylcarbazole unit, a polymer containing both a chlorine and bromine substituted 9-vinylcarbazole unit and a chlorine or bromine substituted 9-vinylcarbazole unit, and a polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit, a chlorine substituted 9-vinylcarbazole unit and a bromine substituted 9-vinylcarbazole unit as well as a polymer containing only a chlorine and bromine substituted 9-vinylcarbazole unit as a halogenated 9-vinylcarbazole unit.

The polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit may be prepared by various methods. For example, a chlorine substituted poly-9- vinylcarbazole is brominated, or a bromine substituted poly-9-vinylcarbazole is chlorinated, or a chlorine and bromine substituted 9-vinylcarbazole is polymerized or copolymerized with other monomer.

Photosensitivity of the polymer of this invention mainly depends on chlorine content. When a sensitizing means is applied thereto, the bromine content affects the photosensitivity.

In general the characteristics of the photosensitive material produced by means of the present invention are roughly as follows.

Hitherto it has been known that in case 0.5-2 bromine atoms be contained per vinylcarbazole ring it is usable as sensitive materials for electrophotography, but brominated poly-N-vinylcarbazole, though it has a bearing on the sensitizing method, compared with non-substituted homopolymers, there are cases to bring about reduction in the surface potential, therefore, in such a case it is apt to bring about lowering of the image contrast. Also in case the degree of bromine substitution be increased, solubility in organic solvents is lowered causing deterioration in coating film performance, especially it tends to become brittle etc. noticeably often giving troubles in practical use.

These inventors having rectified these defects and provide electrophotographic photosensitive materials with excellent characteristics. The chlorine and bromine substituted poly-N-vinylcarbazole without bringing about surface potential drop maintains outstanding photosensitivity, and at the same time, is excellent in the applicability to coloring matter sensitizing methods, and particularly to the so-called free radical sensitising method disclosed in US. application Ser. No. 843,809, filed July 22, 1969 and US. application Ser. 858,540, filed Sept. 16, 1969 applied for by these applicants, that is, the sensitizing methods characterized by causing free radicals produced by irradiation of radiation to act upon organic photoconductive materials, moreover by combining with those sensitizing methods, it is possible to obtain high sensitivity exceeding the inorganic photoconductive material systems. Also by enhancing substitution degree of chlorine and bromine atoms of chlorine and bromine substituted poly-N-vinylcarbazole reduction in crystallizability is observable from the X-ray dilfraction images improving placiticity and flexibility of films, and at the same time a good result is also obtainable respecting adhesion to the support.

Examples of synthesis of the chlorine and bromine substituted poly-'N-vinylcarbazole are given below.

The chlorine and bromine substituted poly-N-vinyl carbazole of the present invention may be prepared by means of successive halogenation of poly-N-vinylcarbazole, or polymerization of a chlorine and bromine substituted 9-vinylcarbazole.

'SUCCESSIVE HALOGENATION OF POLY-N- VINYLCARBAZOL'E Under appropriate conditions, at first, chlorination of poly-N-vinylcarbazole, then bromination, or bromination followed by chlorination will give the chlorine and bromine substituted poly-N-vinylcarbazole of the present invention. As halogenation reagents, various well-known reagents such as chlorine, bromine, sulfuryl chloride, -N- bromimide and peroxides etc. are usable depending upon the selection of solvents and reaction conditions. Examples in which reactions are carried out especially effectively and in smoothness are mentioned below.

( l Chlorination It has been found out that poly-N vinylcarbazole can be chlorinated approximately quantitatively and up to optional substitutability (until nCl4) by using as solvents aliphatic hydrocarbon halides such as methylene chloride, chloroform, and 1,2-dichloroethane, or aromatic hydrocarbons such as benzene and chlorobenzene and adding sulfuryl chloride, and the substitution positions are mainly at first at 8-position, next '6-position, then l-position and under normal conditions it is inferable from the infra-red spectrum that 1, 3, 6 and 8 tetra substitute is obtainable finally.

Of course substituents other than the above, particularly, in the cases of position substitution are intermixed in small amount, and distribution of substitutability of carbazole rings which exist in large amount in high molecular chains cannot necessarily be said to be uniform.

Nevertheless, so long as chlorination in the above solvent is conducted by sulfuryl chloride, the poly-N-vinylcarbazole which is easily soluble in ordinary solvents for coating is obtainable with excellent reproducibility.

EXAMPLE OF SYNTHESIS 1 Synthesis of chlorine substituted poly-N-vinylcarbazole (chlorination with sulfuryl chloride):

Appropriate experimental conditions are shown in the following Table 1.

These conditions may be modified to some extent taking into consideration the scale and economy.

TABLE 1 Maggie;zoPoly-N-vlnylcarbazole (trade name: Luvican M- Reaction conditions: Slowly stir sulfuryl chloride into poly- N-vinylcarbazole in three necked flask, then continue stirring at a specified temperature.

Quantity of solvent: 100 m1.

1 Room temperature.

"A 20 v./v. percent solution of SOzCla in methylene chloride.

In purification, the reaction solution was violently stirred into a large amount of methanol causing polymers to precipitate, and further dissolved in chlorobenzene, and the methanol precipitation was repeated twice.

In Table 2 are shown nitrogen analytical value and chlorine analytical value of the purified matter obtained subsequent to the reaction by Table 1 as well as the number of chlorine atoms nCl per carbazole ring calculated therefrom.

Shown in Table 2 are yield of the purified matter and solubility as well.

TABLE 2 Chlorine substituted poly- N, 01, N-vinylperper- Yield, earbazole cent cent 1201 g. Solubility (II) 7.00 4. 25 0 24 4.1 Easily soluble in methylene chloride and chlorobenzene. 4.2 Do. 4. 5 D0. 5.0 Do. 5. 2 D0. 5. 8 Soluble in chlorobenzene. 6. 8 D0.

Chlorination is possible by introducing chlorine gas under attentive control of conditions, besides using sulf-ury chloride as described above. For instance, introduction of fine current of chlorine gas at a temperature close to -5 C. stirring with high velocity etc., but in the cases where not so little amount of chlorine substitution is to be made respecting halogenated poly-N-vinylcarbazole of which the number of substitution of halogen atoms n is near 1.5 and above, or poly-3,6-dihalogen substituted- N-vinylcarbazole, high reproducibility is obtained comparatively with ease. In such a case temperature close to room temperature will sufficiently serve for reaction.

(2) Bromination To make bromine substitution of poly-N-vinylcarbazole to a comparatively low degree or to middle degree, particularly to the degree of nBr=2.0, a method either to cause N-bromimide and peroxides to react in chlorobenzene or cause bromine to react in pyridine is suitable. By these reagents, bromine atoms substitute mainly at first at 3-position, then at 6-position. For the purpose of conducting substitution to the degree of higher than nBr=2.0, bromine is made act in chlorobenzene. In such a case it is better to conduct substitution to the degree of nBr=2.0 by the above mentioned method before causing bromine to act.

As N-brornimides, N-bromosuccinic acid imide, N- bromo-l, 1'-dimethylsuccinic acid imide, N-bromocaprolactam, N-bromophthalimide, and as peroxides, benzoyl peroxide, lauroyl peroxide etc. are suitable.

Actual process of bromination by means of N-bromosuccinic acid imide and benzoyl peroxide is described in Helv. Chim. Acta., vol. 29, p. 579 (1946) by H. Schmidt et a1. and in Japanese patent publication No. 25,230/ 1970.

(3) Synthesis of chlorine and bromine substituted poly-N-vinylcarbazole Chlorine substituted poly-N-vinylcarbazole and bromine substituted poly-N-vinylcarbazole obtained by methods (1) and (2), respectively can be brominated and chlorinated by the same methods.

EXAMPLE OF SYNTHESIS 2 4.0 g. of chlorine substituted poly-N-vinylcarbazole (II) prepared according to the synthesis Example 1, was dissolved in 100 ml. of chlorobenzene and add 0.90 g. of N-bromosuccinic acid imide and 10 mg. of lauroyl peroxide were added thereto with stirring at C. cause to react.

Two hours later, after filtrating insoluble matters, the reaction mixture was poured into methanol with vigorous stirring and the resulting polymer was separated by filtration than again dissolved in chlorobenzene and then poured into methanol so as to cause precipitation of the polymer, and separated by filtrating and drying in a vacuum. 8.9 g. of chlorinated poly-N-vinylcarbazole (IX) were obtained.

In the similar way, chlorine and bromine substituted poly-N-vinylcarbazole (X) was obtained from 1 mol. of chlorinated poly-N-vinylcarbazole (III) which was synthesized by the synthesis Example 1 and 0.5 mol. of N-bromosuccinic imide and lauroyl peroxide; also chlorine and bromine substituted poly-N-vinylcarbazole (XI) was obtained from 1 mol. of chlorinated poly-N-vinylcarbazole (IV) and 1 mol. of N-bromosuccinic imide and lauroyl peroxide.

The whole halogen analytical value of chlorine and bromine substituted poly-N-vinylcarbazole (IX) to (XII) which were synthesized according to the above described method, the number of chlorine atoms (estimated value from Table 2) and the value of the number of bromine atoms nBr calculated from these are shown in the following Table 3.

TAB LE 3 Total Chlorine and bromine substituted halogen, poly-N-vinylcarbazole percent 'nCl 'nBr 11.

(IX) 12.0 0.24 0.22 0. 46 (X) 22. 5 0. 50 0.48 0. 98 (XI) 36. 7 1.0 0.95 1.95 (XII) 32. 5 1.4 0.53 1 93 4.0 g. of poly-N-vinylcarbazole (Luvican M-170) was dissolved in 100 ml. of chlorobenzene in a 4-necked flask having a thermometer, stirrer and reflux condenser, then adding 1.0 g. of N-bromosuccinic imide and mg. of aluroyl peroxide, and stirred for 2 hours at 80 C. to brominate.

After cooling down to room temperature, succinimide produced as a by-product was filtrated and again returned into the reaction vessel and attaching a dropping funnel to the 4-port flask and calcium chloride pipe to the reflux condenser respectively, and cooled the internal temperature to 0 C. and drop methylene chloride v./v. percent solution of sulfuryl chloride. After the dropping, the reaction mixture was stirred for one hour and the reaction mixture was poured into a large amount of methanol and the separated polymer was filtrated and again dissolved in chlorobenzene, to precipitate with methanol and dry in a vacuum, and 4.1 g. of white polymer (XIII) was obtained. The whole halogen analytical value is 12.8 percent and the infrared spectrum practically coincides with polymer (IX) synthesized previously. This method is economically advantageous as compared with the method described in the synthesis Example 2, but it only requires attention to the temperature at the time of addition o sulfuryl chloride solution.

EXAMPLE OF SYNTHESIS 4 4.0 g. of poly-9-vinylcarbazole (Luvican M-170, trade name, supplied by BASF Co.) was dissolved in 100 ml. of dried chlorobenzene in a 3-necked flask equipped with a reflux condenser with calcium chloride pipe and dropping funnel, then while cooling down to 0 C. and stirring violently, 21.5 ml. (20 v./v. percent) of methylene chloride solution of sulfuryl chloride was added dropwise. After dropping, the stirring was continued at a temperature 30 C. for 2 hours. The reaction solution was poured into methanol to precipitate polymer, and after filtration, the dropping funnel was replaced by a gas introducing pipe and the reflux condenser by an ordinary cooler, then, while introducing nitrogen, temperature was raised to 40-50 C.

Next, while cooling down to 3 C. to 0 C., chlorobenzene solution of bromine (dissolving 10 g. of bromine in chlorobenzene to make 50 ml.) was added in an amount shown in Table 4 and reaction was effected until color of bromine disappears. Then stirring violently, the reaction mixture was poured into a large amount of methanol to separate the reaction product. After filtration, the reaction product was dissolved again in chlorobenzene and after precipitating with methanol, dried in a vacuum. White polymer soluble in chlorobenzene was obtained. Yield and elementary analysis are shown in the following Table 4. Calculation of nBr was made from the whole halogen analytical values taking nCl=2.0.

Infrared spectrum of polymer of (XVI) is similar to that of 1,3,6,8-tetrachlorocarbazole (M.P. 213 C.) produced by passing a calculated quantity of chlorine gas in carbon disulfide and under reflux to carbazole and that of chlorinated poly-N-vinylcarbazole (VIII). Accordingly carbazole having halogen substitution positions at 1, 3, 6 and 8 positions is considered to constitute the main ingredient and, by bromination succeeding chlorination, bromine atoms are considered to substitute firstly at l-position then at 8-position. Also using VII synthesized according to the Example of Synthesis 1 and causing equivalent mol of bromine to act in chlorobenzene there was obtained a chlorine and bromine substituted poly-N-vinylcarbazole (XVII). This has whole halogen analytical value of 47.3%, nCl=3s0 and corresponds to nBr=0.70.

Also a polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit may be obtained by polymerizing various chlorine and bromine substituted 9-vinylcarbazole. Or also by copolymerizing with other monomers. In such a case, as chlorine and bromine substituted 9-vinylcarbazole, there are preferably mentioned monochloromonobromo-9lvinylcarbazole and dichloromonobromo-9-vinylcarbazole.

Examples of synthesis are describel below.

EXAMPLE OF SYNTHESIS 5 Synthesis of 3-chloro-6-bromo-9-vinylcarbazole Suspend 4.0 g. of 3-chlorocarbazole in 20 m1. of carbon disulfide and stirring well, and under reflux and heating, drop 20 ml. of carbon disulfide solution which contains 3.2 g. of bromine in one hour. After letting the reaction mixture to stand to cool down to room temperature, filtrate crystals and cause recrystallization from glacial acetic acid. With yield approximately MP. 198 C. (literature value 197-198 C.), 4.5 g. of 3-chloro-6-bromocarbazole are obtainable. This matter is also obtainable by brominating carbazole to produce 3-bromocarbazole (M.P. 201 C.) and further chlorinating it.

Put 4.0 g. of 3-chloro-6-bromocarbazole in conjunction with 0.07 g. of powder caustic potash, 5 ml. of methylcyclohexane into an autoclave having 100 ml. capacity and introduce acetylene to cause to react for 6 hours at temperature of 170 C. (the initial gauge pressure is approximately 25 atmospheric pressure). After allowing to stand to cool down restore to normal pressure, pour the content into water and filtrate precipitates and cause recrystallization from n-hexane. With yield approximately 76%, M.P. 135 C., 3.3 g. of 3-chloro-6-bromo-9-vinylcarbazole was obtained. Elementary analysis is as follows, and numerals in parenthesis are calculated value (percent): C, 54.0 (54.8), H, 28.6 (29.4), N, 45.0 (45.7), C1, 11.0 (11.6), Br, 25.0 (26.1). This matter is also obtainable by brominating 9-[3-chloroethylcarbazole (or 9- ethylolcarbazole), then chlorinating and subsequent treatment with alcoholic caustic potash.

EXAMPLE OF SYNTHESIS 6 Synthesis of poly-3-chloro-6-bromo-9-vinylcarbazole Put a solution consisting of 1.0 g. of 3-chloro-6-bromo- 9-vinylcarbazole and 3.0 ml. of acetonitrile into a polymerization tube made of hard glass and irradiate with a high pressure mercury arc lamp. Continue irradiation for 30 minutes after gelation, next add methanol and filtrate the precipitates, and after dissolving again in benzene precipitate with methanol. This process is repeated twice. With yield approximately 60% 0.60 g. of white polymer was obtained. The intrinsic viscosity in benzene Was (1 )=0.45.

EXAMPLE OF SYNTHESIS 7 Synthesis of copolymer of 3-chloro-6-bromo-9-vinylcarbazole and 9-vinylcarbazole Put 0.5 g. of 3-chloro-6-bromo-9-vinylcarbazole and 1.0 g. of 9-vinylcarbazole into a polymerization tube to cause nitrogen evacuation and heat up to 120 C. After 8 hours dissolve the content in chlorobenzene, then precipitate with methanol. Repeating the said operation once, 1.2 g. of white polymer and yield approximately 80% was obtained. From the elementary analysis it is considered that this matter contains chlorobromovinylcarbazole and vinylcarbazole at the molar ratio of 1.0:3.2.

EXAMPLE OF SYNTHESIS 8 Synthesis of copolymer of 3-chloro-6-bromo- 9-vinylcarbazole and styrene Dissolve 3.0 g. of 3-chloro-6-bromo-9-vinylcarbazole in 15 ml. of methylene chloride and, stirring violently, add boron trifluoride etherate at temperature of 30 C. Add methanol and, after filtration, dissolve the precipitates in benzene again to precipitate with methanol. Repeating the said operation twice, 2.0 g. of white polymer were obtained. From the nitrogen analytical value, this matter is considered to be a copolymer consisting of chlorobromovinylcarbazole and styrene in the ratio of 11.0:0.8.

EXAMPLE OF SYNTHESIS 9 Synthesis of terpolymer copolymer of 3-chloro-6-bromo- 9-vinylcarbazole, 9-vinylcarbazole and n-butyl methacrylate Dissolve 0.5 g. of 3-chloro-6-bromo-9-vinylcarbazole, 1.0 g. of 9-vinylcarbazole and 0.15 g. of butyl methacrylate in methylene chloride and cause to polymerize using azoisobutylonitrile in an atmosphere of nitrogen. By repeating chlorobenzene-methanol dissolving and precipitation for purification, there was obtained 1.3 g. of white polymer. From elementary analysis and infrared spectrum, this substance is considered to obtain chlorobromovinylcarbazole, vinylcarbazole and butyl methacrylate at the molar ratio of approximately 2.72122.

EXAMPLE OF SYNTHESIS 10 Synthesis of poly-1,3-dichloro-6-bromo-9-vinylcarbazole and poly-3,8-dichloro-6-bromo-9-vinylcarbazole Dissolving 3-bromo-carbazole (chlorinated carbazole having M.P.=199 C., obtained by conducting reflux heating of carbazole with N-bromosuccinimide and benzoyl peroxide in carbon tetrachloride and then separating crystals in alcohol) in chloroform, and adding 2 mol. of sulfuryl chloride at room temperature and conducting reflux heating to 30 minutes, there was obtained a mixture of 1,3-dichloro-6-bromocarbazole and 3,8-dichloro-6- bromocarbazole. Then, it was vinylized without separating using the method described in Example of Synthesis 5 and under the same conditions, and further putting 3 g. of the vinylized matter into a 3-necked flask for dissolving in 10 m1. of methylene chloride and substitution was made with nitrogen .gas and cooled down to 20 C. and, while stirring well, one drop of boron trifluoride etherate solution was added thereto. Immediately temperature rise was observed, and polymerization started. Stopped the polym erization by adding concentrated aqueous ammonia, then methanol was added to precipitate the polymer. Dissolving the precipitates in benzene and adding methanol caused precipitation again. Further repeating the said operation twice, polymer was obtained. Conversion ratio into polymer was 0.8. Also the polymer was soluble in chlorobenzene and result of elementary analysis was: N: 4.30% (calculated value 4.2%). Whole halogen atoms 40.1% (calculated value 42.3%).

EXAMPLE OF SYNTHESIS 11 1 3-chloro-9-vinylcarbazole To an autoclave ml. volume) were added 4.0 g. of 3-chloro-carbazole (M.P. 200 C., prepared according to Mazzara, Gazz, chim. ital., 26, II, p. 238), 0.075 g. of powdered potassium hydroxide, 0.025 g. of zinc oxide and 5 ml. of cyclohexane and shaked. Acetylene was introduced thereinto and reaction was carried out at C.- 180 C. for 6 hours (the initial pressure being 25 atmospheric pressure, .gauge). After allowed to cool to release the remaining acetylene, the contents were poured into water and the resulting precipitate was filtered and recrystallized from n hexane. The product was 3-chloro-9-vinylcarbazole, 3.6 g.; yield, about 80%, M.P. 78 C.

Analysis (percent): C, 73.4 (73.9); H, 4.20 (4.39); N, 6.10 (6.16); Cl, 15.2 (15.6). (The value in the parentheses is a calculated value.)

(2) 3-bromo-9-vinylcarbazole 3-bromocarbazole, M.P. 198 C. [prepared by a method described in Schmidt, Helv. chim. Acta., 29, 573 (1946)] was used and the procedure in (1) above was followed to give 3-bromo-9-vinylcarbazole, M.P. 83 C.

Analysis (percent): N, 5.17 (5.20); Br, 28.5 (29 .7). (The value in parentheses is a calculated value.)

(3) Copolymer of 3-chloro-9-vinylcarbazole and 3 bromo-9-vinylcarbazole 3-chloro-9-vinylcarbazole 2.0 g. and 3-bromo-9-vinylcarbazole 2.6 g. obtained above were copolymerized by the method as described in Example of Synthesis 6 and the copolymer product was repeatedly subjected to dissolution and precipitation by chlorobenzene and methanol for purification. The resulting product was soluble in methylene chloride and chlorobenzene. The infrared spectrum is almost consistent with that of the product (X) in Example of Synthesis 2 and the electrophotographic properties were also similar thereto.

As the above principal examples respecting synthesis of polymers containing a chlorine and bromine substituted 9-vinylcarbazole unit have been described, and now a description of actions and effects when used as electrophotographic photosensitive materials is given below. At first, comparison with the conventional organic photoconductive materials is made. In researches relating to organic photoconductive materials in the initial stages many compounds were reported very actively, and compounds with complex structure, various high molecular aromatic compounds or hetero-ring compounds etc. have been the subject of the study. And although some compounds with considerable high sensitivity have been introduced, but recently a tendency wherein researchs in sensitizing methods seem to form the center is observable. The reason is that none of most high sensitive organic photoconductive materials that have been known, has sensitivity sufiicient to be usable as it is without a sensitizing treatment. As a result, in utilizing organic photoconductive materials it has become an indispensable condition in the technical fiedl of organic photosensitive materials to select and apply without fail the most effective sensitizing process. As such sensitizing methods, the coloring matter sensitization process that has long been known and in which sensitizing coloring matter is added, and Lewis acid sensitization wherein Lewis acids are added is used in general without exception. In respect of the sensitization process besides the above, there is a free radical sensitization process whereof detailed description is made later. This process is characterized by giving extremely powerful sensitizing effects to organic photoconductive materials and to some of organic photoconductive materials it gives a sensitivity enabling to constitute a sensitive material with high sensitivity equivalent to or higher than that of the well-known coloring matter sensitized zinc oxide and selenium. The summarized theoretical background of these means is that, first, the coloring matter sensitizing means is to add spectral characteristic to organic photoconductive materials, and the Lewis acid sensitization is a sensitization effect based upon the appearance of C-T band (spectral adsorption sensitivity region due to complex formation) due to the growth of complex of donoracceptor between the organic photoconductive materials, while the free radical sensitization means is considered to be a structural sensitization effect wherein extremely active free radicals produced by irradiation of radiation energy bombard the organic photoconductive materials forming a sensitizing center partially.

Such being the case it is not too much to say that the industrial value of photoconductive materials depends upon the ability to provide sensitive materials which can be new highly sensitized finally according to the sensitizing means applied. The polymers of the present invention which contain a chlorine and bromine substituted 9-vinylcarbazole unit possesses in themselves high photosensitivity and by applying various sensitizing means provide novel sensitive materials improved by far relating to sensitivity, easiness of handling and stability compared with polymers which hitherto have been developed as shown in below mentioned comparison example and examples. Also it was confirmed that by applying the free radical sensitization means the said polymers provide sensitive materials with sensitivity clearly surpassing that of commercially available coloring matter sensitized zinc oxide. Furthermore, hitherto as organic photoconductive materials bromides and iodides of polyvinylcarbazole have been known, but these polymers have poor solubility in solvents particularly when the degree of halogenation is enhanced in the hope of increasing photosensitivity the solubility gets lower, and in preparing photosensitive films dilficulties are brought about respecting the selection of coating solvent and the dissolving process. Also as to the degree of halogenation of those polymers, it is known that 2 atoms per carbazole ring is the limit, and halogenation exceeding said limit is not possible. On the other hand, in case an example of bromine substituted 9-vinylcarbazole is cited, photosensitivity rises with increase in degree of bromination but maximum bromination is 2 atoms per carbazole ring, therefore, brominated-9-vinylcarbazole with maximum expected sensitivity is unobtainable practically. Also in case the free radical sensitization means is applied, the visible region sensitivity rather decreases, especially with increase in degree of bromination this tendency becomes stronger. Such being the case although brominated poly-9-vinylcarbazole is improved in its photosensitivity against poly-9-vinylcarbazole, but its practicality is discounted because of the fact that it cannot expect adequate sensitization effects in application of sensitization means for practical use, and that particularly the free radical sensitization means which is most powerful and effective for providing practically usable organic photosensitive materials cannot be adequately applied thereto. Also brominated poly-9-vinylcarbazole is unstable tending to respond to heat and long term preservation and cause debromination so that it has low commercial value. On the other hand, polymers of the present invention which contain a chlorine and bromine substituted 9-vinylcarbazole unit provides photosensitive materials having a great commercial value in the following points. That is, it goes without saying that the said polymers have sufliciently overcome the defects of the conventional brominated poly- 9-vinylcarbazole and iodized poly-9-vinylcarbazole in practical applications, in addition, the largest characteristic is that it is extremely excellent in applicability to sensitization means which brings about a practical value of organic photosensitive material. These inventors of the present invention have already confirmed that chlorinated poly-9-vinylcarbazole is extremely excellent in application value to free radical sensitization, and a chlorine and bromine substituted poly-9-vinylcarbazole has markedly improved sensitization efficiency for coloring matter sensitization as is clarified by comparison examples and examples described later, and is able to provide sensitive materials with elevated sensitivity usable without reducing free radical sensitization elfect even in combined utilization of free radical sensitization means and coloring matter sensitization means.

COMPARISON EXAMPLE Halogen atom content shows number of chlorine and bromine atoms contained per vinylcarbazole ring g 2.0 Chlorobenzene ml 40 In the table free radical sensitization shows specific sensitivity obtained by adding 10 ml. of carbon tetrabromide to the solution before applying to the film base, and putting it into a hard glass Erlenmeyer flask and while stirring applied photochemical reaction treatment at a distance of 10 cm. with a w. high pressure mercury arc lamp for 5 minutes and then allowed to stand in dark place for 24 hours then applied to the film base, and coloring matter sensitization shows the specific sensitivity in the case where application to film base was made after adding 2.0 mg. of Crystal Violet to the above mentioned solution. Free radical sensitization plus coloring matter sensitization shows the specific sensitivity in the case where the above mentioned solution whereto 100 mg. of carbon tetrabromide and 2.0 mg. of Crystal Violet had been added was applied to the film base after undergoing a photochemical reaction treatment similar to that described respecting free radical sensitization. Value of specific sensitivity was decided as 100 when the sample polymer was poly-9-vinylcarbazole and was expressed as a reciprocal of exposure amount required to attenuate the charge potential to its by exposure. The exposure light source is a tungsten lamp and the initial charge voltage was approximately 500 v. for each sample.

Free radical sensitization Halogen plus content Free Coloring coloring radical matter matter Sample Chlo Brosensisensitisensitipolymer rine mine tization zation zation Chlorine substi- 1.0 135 126 183 tuted. 2.0 169 130 190 Bromine substi- 1.0 45 148 112 tutcd. 2.0 14 159 129 Chlorine and 1. 0 1. 0 131 142 225 bromine substi- 2 0 1.0 158 138 258 tuted. 2. 0 2. 0 154 152 270 3.0 1. 0 165 147 268 Poly-N-vinyl- 100 carbazole.

As is indicated from the above table it is understandable that a chlorine and bromine substituted poly-9- vinylcarbazole of the present invention provides sensitive materials with high sensitivity when subjected to free radical sensitization and coloring matter sensitization.

The above-mentioned polymer may be used in a form of self-supporting material such as thin film or textile, or in a form of a thin layer on an electroconductive support for electrophotographic photosensitive material. For example, the polymer solution may be applied to a glass plate followed by peeling the coating after drying to obtain a self-supporting film, or the polymer melt is extruded to form fibers followed by wearing them, or the polymer solution is coated on an electronductive support. To the polymer may be added an additive for adjusting photographic property such as sensitizer and an additive for adjusting physical property of film such as plasticizer and opaque-imparting agent.

As sensitizers, there may be mentioned Lewis acids, for example, polynitro compounds such as 1,3,5-trinitrobenzene, picric acid, S-nitroacenaphthene and 2,4,7-trinitrofluorenone, carboxylic acids such as acetic acid, trifluoroacetic acid, trichloroacetic acid and salicyclic acid, sulfonic acid such as benzene sulfonic acid and p-toluene sulfonic acid, sulfonic acid chloride such as p-toluene sulfonyl chloride, and optical sensitizer such as Crystal Violet, Malachite Green, Methylene Blue, Brilliant Green, Meth'ylene Blue, Quinizaline.

As plasticizers, there may be mentioned dibutylphthalate, dioctylphthalate, tricresylphosphate and polyphenyl chloride.

Further, it has been found that a free radical sensitization by free radical former is very effective to the polymer of this invention. With respect to the free radical sensitizing method, U.S. application Ser. No. 843,809, filed July 22, 1969 now abandoned and U.S. application Ser. No. 858,540, filed Sept. 16, 1969 disclose that a remarkably sensitized electrophotographic photosensitive plate can be prepared by applying a radiation energy to a photoconductive compound in the presence of a free radical former and, if necessary, in the presence of aromatic amine or leuco form of coloring matter. When polymer of this invention is used as the photoconductive compound, a very useful electrophotographic photosensitive plate can be produced.

As free radical formers particularly effective for the polymer containing a chlorine and bromine substituted 9-vinylcarbazole unit of this invention, there may be mentioned polyhalogen compounds such as iodoform, carbon tetrabromide, bromoform, bromotrichloromethane and hexachloroethane. As aromatic amines, there may be mentioned 9-vinylcarbazole, 3 chloro 9 vinylcarbazole, 3-bromo-9-vinylcarbazole, diphenylamine, and triphenylamine.

As leuco form of coloring matters, there may be mentioned leuco Malachite Green and leuco Crystal Violet.

A solution of these components in benzene or monochlorobenzene is irradiated with a high pressure mercury lamp to cause a reaction and then coated on a support such as aluminum plate, paper and film followed by drying to form a photosensitive plate.

If desired, the free radical sensitizing method may be used together with conventional optical sensitization and Lewis acid sensitization.

The radiation energy source may be appropriately selected depending upon free radical former and solvent used. Any source may be used which can produce a free radical from the free radical former in the sensitizing treatment system. For example, a light source capable of emitting a large amount of ultraviolet ray such as mercury lamp (low pressure, high pressure, and super high pressure), metal halide lamp and xenon lamp, is preferred.

Amount of free radical former preferably ranges from one to 30% by weight of the basis of polymer, but not restricted to said range.

The electrophotographic photosensitive material according to this invention can be used for producing images by using conventional charging and developing means such as corona discharging, magnet brush development, and electrophoresis development.

The following examples are given for the purpose of illustration of this invention, but not for limiting this invention.

EXAMPLE 1 On polyethyleneterephthalate films of thick a liquid obtained by mixing 4 g. of cuprous iodide in ml. of acetonitrile whereto 30 ml. of 5% solution of polyvinylformal had been added was coated and dried making the film surface electrically conductive. Next on the said film surface a solution of following composition was applied in such manner that dried coating film would be 4 thick and dried.

Poly-N-vinylcarbazole (Luvican M-l70) g 2 2,4,7-trinitrofiuorenone mg 2 Crystal Violet mg 5 Monochlorbenzene ml 50 A photosensitive film prepared in this way was, in a dark place, charged negatively with a corona discharge device, exposed using a picture enlarging device mounted with a 500 w. tungsten lamp through micro-positive original, then dipped in a solution consisting of high boiling point petroleum solvent with carbon black dispersed therein to develop and obtained clear transcribed images. At this time the appropriate exposure and approximately 2500 lux-sec. Also for the purpose of measuring the photosensitivity attached the film prepared in this example to a rotating type electrometer and charged negatively, then exposed with the above mentioned tungsten lamp, and measured the exposure amount required to attenuate the potential down to and to A and the resultant values were 700 lux-sec. for attenuation to and 1500 lux-sec. for attenuation to Potential at the starting time of irradiation by the tungsten lamp was 500 v.

Next, in the said example as photoconductive materials, instead of poly-N-vinylcarbazole, using various chlorine and bromine substituted poly-N-vinylcarbazoles shown in the following Table 5, made measurements of the exposure required for the above mentioned /3 attenuation and attenuation. The charge potential at exposure starting time was 500 v. and measured under quite same conditions as the above. In the table E /3 and E mean the exposure amount (lux-sec.) necessary to attenuate the charge potential to /3 and Also nCl and nBr show the number of atoms of chlorine and bromine per vinylcarbazole ring.

TAB LE Photosensitivity (Sample) Chlorine and bromine substituted poly-9-vinylcarbazole 13% E (1) Compound synthesized according to synthesis examnCl=0.10 nBr=0.13 (2) Compound synthesized according to synthesis examnCl=0.l8 nBr=0.05 (3) Compound synthesized according to synthesis exam- 7LC1=0.15 nBr=0.i2 (4) Compound synthesized according to synthesis exam- 11.Cl=0.20 nBr=0.21 (6) Compound of (IX) mentioned in synthesis example 3- 110 370 (6) Compound of (X) mentioned in synthesis example 70 220 (7) Compound of (XII) mentioned in synthesis example. 65 170 (8) Compound of (XI) mentioned in synthesis example. 58 182 (9) Compound of (XV) mentioned in synthesis example 50 160 (10) Compound oi (XVI) mentioned in synthesis exam- 50 176 la (1i) Compound of (XVII) mentioned in synthesis example 51 170 As shown in these examples sensitivity of a chlorine and bromine substituted poly N vinylcarbazole generally changes continuously according to the degree of chlorination and bromination, and in the initial stages of chlorination and bromination, there is a tendency to increase with the degrees, but when a certain degree is exceeded, particularly halogenation i.e. nCl+nBr is 8 or above noticeable incremental effect of sensitivity is unobservable. Also in case B be taken as a standard of practical use, those whereof nCl+nBr is 0.4 or above give sufliciently good result in practical use, and if a broad mean value be taken, those whereof nCl and nBr are 0.2 or above always give desirable results.

EXAMPLE 2 0n solvent-proof (coated polyvinyl alcohol approximately 2 g./m. processed paper weighing 60 g./m. coated a photosensitive solution mainly consisting of various chlorine and bromine substituted poly-N-vinylcarbazole shown in the following Table 6 and after drying in a vacuum prepared electrophotographic sensitive paper. Photosensitivity and image definition of these sensitive paper are shown in Table 6. In this example the above mentioned sensitive solution were made according to three diiferent prescriptions to investigate performance of chlorine and bromine substituted poly-N-vinylcarbazole.

First, a photosensitive solution was prepared in the following manner applying the prescription for free radical sensitization in the sensitizing method column in Table 6.

Chlorine and bromine substituted poly-N-vinylcarbazole g 2.0 Carbon tetrabromide g 0.1 N-vinylcarbazole g 0.2 Monochlorobenzene ml 50 Chlorine and bromine substituted poly-N-vinylcarbazole g 2.0 Crystal Violet m 5.0 Monochlorobenzene ml 50 The above ingredients are made into a solution. Further, items shown in column for Lewis acid in table concern the solutions whereto 0.2 mg. of Lewis acid was added to give the so-called sensitizing effect by Lewis acid.

As to photosensitivity, and nCl and nBr in Table 6, the definitions thereof are the same as in Table 5.

TABLE 6 Clgorine P t an o obromine sensisuiostituted tivity po yvinylnCl Sensitizing Lewis E E Image carbazole nBr method acid 96 l property (Note 3) Freeradical 247- 21 63 Clear nC1=0'24} sensitiza- 'trini- {nBr 0'22 tion. trofluorenone. (X) 17.01- 0.50 do-...-.- 2,4,7- 19 55 D0.

nBr=0.48 trinitrofluorenone. (XII)- nCl=1.40 do 26 38 Do. 'nB1=0.53 (XI) nC1=1.00 Coloring 53 152 Slightly nBr=0.95 matter low sensitizadensity. tion. (XV) ..{nC1=2.0 }Free radical 25 75 Clear.

nBr=0.81 2l1$ltll2h on. (XVI) aCl=2. }Coloring 50 176 Slightly nBr=L70 matter low sensitizadensity. tion. (XVII)...- .{nCl=3.0 }Free radical 23 81 Clear.

nBr=1.70 sensitization. (XIV) {nCl=2.0 do 23 70 Do.

nBr=0A0 *The image property relates to a positive image reproduced obtained by at first uniformly charging the sensitive paper negatively to 6 kv. in a dark place, then through a positive type original exposed using a picture enlarging device mounted with 500 w. tungsten lamp, then dipped in a liquid developer to develop.

EXAMPLE 3 Poly-9-vinylcarbazole (Luvican M-) (as control) or photoconductive materials of the present invention g 2.0 Chlorobenzene (increase or decrease according to kinds of polymer) ml 40 2,4,7-trinitrofluorenone mg 1.0

The above Luvican M-170 is trade name of Badische Anilin und Soda Fabrik.

Photosensitive plates prepared in this manner were mounted on a rotary electrometer and were charged negatively, then exposure was made with tungsten lamp, and the reciprocals of exposure time necessary to attenuate the potential to A and to were decided as the value of photosensitivity, and the result of comparison of the sens1t1vity is shown in the following table. As the potential at starting time approximately 500 v. was chosen respecting each sample.

Value of sensitivity (comparison value) For at- For attenuation tenuation Kind 0! polymers to 16 to I10 1. Po1y-9-vinylcarbazole (Luvican M-170) (control) 1. 00 1. 00 2. Poly-3-chloro4i-bromo-9-vinylcarbazole (prepared by example of syntheiss 6) 11. 0 16. 0 3. Copolymer of 3-chloro-6-bromo-9-vinylcarbazole and 9-vinylcarbazo1e (prepared by example of synthesis 7) 5, l0 6. 10 4. Copolymer of 3chloro-6-bromo-9-vinylcarbazole and styrene (prepared by example of synthesis 8) 3. 0 2. 5 5. Terpolymer of 3-chlorofi-bromo-9-vinylcarbazole, 3-vinylcarbazole and n-butyl methacrylate (prepared by example of synthesis 9) 4. 0 3. 5 G. Poly-l,3-dichloro-6-bromo-9-vinylcarbazole and poly-3,S-dichloro-6-bromo-9-vlnylcarbazole (prepared by example of synthesis 8.01 10.2

EXAMPLE 4 Two grams of copolymer composed of 3-chloro-6-bromo-9-vinylcarbazole and 9vinylcarbazole synthesized according to synthesis Example 7 was dissolved in 35 ml. of chlorobenzene and 200 ml. of 2,4,7-trinitrofluorenone was added thereto and was applied to a sandbasted aluminium cylinder in such manner that dried coating film would be p thick. This photosensitive drum is able to form images by process of charging-exposure-development-transferring.

Similarly applying the said compound solution to an aluminium cylinder in the manner that dried coating film would be 70 thick, then on top of it polyethyleneterephthalate film 20,41 thick was laminated.

This laminate type cylinder is able to form images by means of various processes.

What is claimed is:

1. An electrophotographic photosensitive material which comprises a polymer containing a chlorine and bromine substituted poly-9-vinylcarbazole containing at least 0.2 atom of each of chlorine and bromine per one 9-vinylcarbazole ring and the sum of chlorine atom and bromine atom per one 9-vinylcarbazole ring being 0.4 atom to 4.0 atoms.

2. An electrophotographic photosensitive material according to claim 1 in which the chlorine and bromine substituted poly-9-vinylcarbazole is a polymer obtained by brominating a chlorine substituted poly-9-vinylcarbazole.

3. An electrophotographic photosensitive material according to claim 1 in which the chlorine and bromine substituted poly-9-viny1carbazole is a polymer obtained by chlorinating a bromine substituted poly-9-vinylcarbazole.

4. \An electrophotographic photosensitive material according to claim 1 in which the chlorine and bromine substituted poly-9-vinylcarbazole is that obtained by polymerizing a chlorine and bromine substituted 9-vinylcarbazole.

5. An electrophotographic photosensitive material according to claim 4 in which the chlorinated and brominated 9-vinylcarbazole is at least one of monochloromonobromo-9-vinylcarbazole and dichloro-monobromo-9- vinylcarbazole.

6. An electrophotographic photosensitive material according to claim 5 in which the monochloro-monobromo- 9-vinylcarbazole is 3-chloro-6-bromo-9-vinylcarbazole.

7. An electrophotographic photosensitive material according to claim 5 in which the dichloro-monobromo-9- vinylcarbazole is at least one of 1,3-dich1oro-6-bromo-9- vinylcarbazole and 1,6-dichloro-3-bromo-9-vinylcarbazole.

8. An electrophotographic photosensitive material according to claim 1 in which the polymer is a copolymer of a chlorine and bromine substituted 9-vinylcarbazo1e with another vinyl monomer.

9. An electrophotographic photosensitive material ac- 16 cording to claim 8 in which the vinyl monomer is 9-vinylcarbazole.

10. An electrophotographic photosensitive material according to claim 8 in which the vinyl monomer is styrene.

11. An electrophotographic photosensitive material according to claim 8 in which the vinyl monomer is a combination of 9-vinylcarbazole and styrene.

12. An electrophotographic photosensitive material according to claim 8 in which the chlorine and bromine substituted 9-vinylcarbazole is at least one of monochloromonobromo-9-vinylcarbazole and dichloro-monobromo-9- vinylcarbazole.

13. An electrophotographic photosensitive material according to claim 1 in which a sensitizer is added to the polymer.

14. An electrophotographie photosensitive material according to claim 13 in which the sensitizer is a sensitizing dye.

15. An electrophotographic photosensitive material according to claim 13 in which the sensitizing agent is a Lewis acid.

16. An electrophotographic photosensitive material according to claim 13 in which the sensitizing agent is a combination of a sensitizing dye and a Lewis acid.

17. An electrophotographic photosensitive material which comprises a polymer containing a chlorine and bromine substituted 9-vinylcarbazole repeating unit containing at least 0.2 atom of each of chlorine and bromine per one 9-vinyl carbazole ring and the sum of chlorine atom and bromine atom per one 9-vinyl carbazole ring being 0.4 atom to 4.0 atom which has been subjected to photochemical reaction treatment by applying a radiation energy thereto in the presence of a free radical former capable of producing a free radical when irradiated by a radiation energy.

18. An electrophotographic photosensitive material according to claim 17 in which a sensitizing agent is added thereto.

References Cited UNITED STATES PATENTS 3,421,891 1/1969 Inami et al 961.6

3,526,502 9/1970 Murakami et al 961.5

3,484,237 12/ 1969 Shattuck et al. 96-1.5

3,287,123 11/1966 Hoegl 96-1.5

FOREIGN PATENTS 19,751 4/1967 Japan 96-l.5

24,753 10/1968 Japan 96l.5

GEORGE F. LESMES, Primary Examiner M. B. WITIENBERG, Assistant Examiner US. Cl. X.R.

25250l; 26088.3 R, 80.3 R, 80.72