DE2517150C2 - Electrophotographic recording material - Google Patents

Description

wherein A denotes a phenyl, naphthyl, anthryl, acenaphthyl, furyl or thienyl group, which can optionally be substituted by chlorine, bromine, alkoxy, nitro, cyano and / or alkoxycarbonyl and is where R is a cyano group, a nitro group, an alkoxycarbonyl group, an aryl group or a carbamoyl group and where η is 9 or 1.

2 recording material according to claim!, Characterized by a content of 0.1 to 100 mol ¹ Zo of the sensitizer, based on the organic photoconductive compound.

3. Recording material according to claim 1 or 2, characterized by a content of polyvinyl carbazole, polyglycidyl carbazole or a by substitution of some of the chlorine atoms of polyepichlorohydrin obtained polymers as an organic photoconductive compound.

The invention relates to an electrophotographic recording material containing an organic photoconductive compound of the electron donor type and a sensitizer of the electron acceptor type. It has long been known that the insufficient sensitivity of organic, photoconductive Ver Increase bonds by adding sensitizers. These sensitizers absorb light in a certain wavelength range and transfer the excitation energy to the sensitized Molecule.

The most intensely studied class of sensitizers are dye sensitizers, particularly polymethine dyes. Examples of such dyes are known from DE-OS 14 97 118.

In such dye sensitizers, however, it is disadvantageous that the absorption maximum of the dye coincides with the sensitization maximum of the organic photoconductive compound. To increase the sensitivity of the electrophotographic recording material, the aim is on the one hand to to extend awareness to longer wavelengths. On the other hand, however, it is undesirable that the Extending light absorption to longer wavelengths, as this provides the necessary for photoconductivity

-to light transmission of the recording material is reduced. In the case of dye sensitizers, this effect leads to a fundamental problem which cannot be solved within this class of sensitizers. Another known class of sensitizers are compounds which form a donor-acceptor complex with the organic, photoconductive compound and which act as charge-transfer sensitizers are designated. Such sensitizers are known from DE-AS Il 27 218, for example. the known sensitizers of this type are, however, in terms of the transparency of their use obtained recording material and in terms of their sensitizing effect not yet satisfactory.

The object of the present invention is therefore to provide an electrophotographic drawing

tion material with increased photosensitivity in the longer-wave range, without a Lichiabsorp tion occurs at shorter wavelengths.

According to the invention, this object is achieved by an electrophotographic recording material of the type mentioned at the beginning, which is characterized by a sensitizer of the general formula

CN

A- (CH = CH) J-CH = C (I)

wherein A is a phenyl, naphthyl, anthryl, acenaphthyl, furyl or thienyl group, which can optionally be substituted by chlorine, bromine, alkoxy, nitro, cyano and / or alkoxycarbonyl and wherein R a cyano group, a nitro group, an alkoxycarbonyl group, an aryl group or a curbamoyl group and in which η is 0 or 1.

Among the sensitizers of the formula (1), preference is given to those in which A is a phenyl group, a Naphthyl group, a furyl group or a thienyl group. If A stands for one of the claimed, substituted aromatic or heteroaromatic groups, the substituents are chlorine, bromine, Alkoxy with preferably 1 to 8 and especially with 1 to 4 carbon atoms, nitro, cyano and / or alkoxycarbonyl with preferably up to 9 especially up to 5 carbon atoms are possible. Chlorine atoms or are preferred Nitro, cyano, alkoxy or alkoxycarbonyl groups. R stands for a cyano group, a nilro group, a

Alkoxycarbonyl group with preferably up to 8 and especially up to 5 carbon atoms, an aryl group with preferably up to 12 carbon atoms or for a carbamoyl group, the cyano group being preferred is.

Typical compounds of the formula (1) are listed below: Malonitriles, like

Benzalmalonitrile, p-chlorobenzalmalonitrile, p-bromobenzalmalonitrile, p-methylbenzylmalonitrile, p-Melhoxyben / amalonitrile, p-CyanobenzalmalonitriU, p-Nitrobenzalmalonitril. m-Nilrohzalmalonitril, m-Cyanobenzalmalonitril, p-Methoxycarbonylbenzalmalonitril, 2-chloro-5-nitrobenzalmalonitrile, 2,4-dichlorobenzalmalonitrile, 2-thienylmethylene malonitrile, 5-Ni * o-2-thienylmethylene malonitrile, 1-naphthylmethylene malonitrile, 2-naphthylmethylene malonitrile, 5-acenaphthylmethylene malonitrile, ^ anthracenylmethylene malonitrile, 2-furfirylidene malonitrile, S-nitro ^ -furfurylidene malonitrile or cinnamylidene malonitrile;

Acrylic ester derivatives, such as

o-cyano - ^ - phenylacrylic acid ethyl ester, e-cyano-jS-iP-cyanophenyD-acrylic acid ethyl ester, ff-cyano-jJ-ip-nitrophenyO-acrylic acid ethyl ester, e-cyano-jiHp-chlorophenyO-acrylic acid ethyl ester or <7-cyano _: /? - (1-naphthyD-acrylic acid ethyl ester;

20 ethylene derivatives, such as

I-cyano-1-nitro-2-phenylethylene, 1-cyano-1,2-bis (p-nitrophenyl) -ethylene, 1-cyano-1- (p-nitrophenyl) -2- (p-cyanophenyl) -ethylene or 1-cyano-1-4 -bisip-cyanophenyO-ethylene;

Acrylamide derivatives such as

ö-Cyano _T ye- (p-nitrophenyl) -acrylamid, a-Cyano-jS-ip-cyanophenyO-acrylamid, <7-Cyano _:) 8- (2-ch! or-5-nitrophenyl) -acrylamid, ff- Cyano-jS-naphthylacrylamide, (T-cyano ^ -fp-nitrophenyn-N-phenylacrylamide or ff-cyano ^ -ip-cyanophenyO-N-ethylacrylamide.

Preference is given to using l-naphthylmethylene malonitrile, 2-naphthylmethylene malonitrile, 2-furfurylidene malonitrile, Cinnamylidene malonitrile, p-methoxycarbonylbenzalmalonitrile and especially p-nitrobenzalmalonitrile, p-cyanobenzalmalonitrile, 2-chloro-5-nitrobenzalmalonitrile or l-cyano-1,2-bis (p-nitrophenyl) ethylene.

These compounds can usually be obtained by the condensation reaction of an aromatic aldehyde and an active methylene compound can be obtained in high yield. A conventional method of manufacture of these compounds is in Zikken Kagaku Koza Volume 18 "Reaction of organic compound II" (Nippon Kagaku-kai) (Publisher: Maruzen).

The electrophotographic recording material comprises, as a further component, one as an electron donor acting organic photoconductive compound, which with the first component, namely the sensitizer enters into charge transfer interaction. The charge transfer interaction leads to a new one Charge transfer absorption band. Typical organic photoconductive compounds that act as electron donors are aromatic compounds (preferably fused with up to 7 and especially up to 5 six-membered rings and optionally with methylene bridges or ethylene bridges), such as naphthalene, anthracene, acenaphthene, Pyrene, perylene, tetraphene, 2,3-benzochrysene, 6,7-benzopyrene, tetracene, chrysene, fluorene, phenanthrene, Triphenylene or heterocyclic compounds (heteroaromatic compounds) such as carbazole, indole, acridine, Dibenzothiophene, phenazine, benzofuran, phenothiazine, pyrazoline, benzotriazole or benzimidazole (preferably with one or two benzene rings fused heteroaromatic compounds), the aromatic Hydrocarbons or the heterocyclic compounds carry one or more substituents can. The following substituents are preferred: halogen atoms (chlorine, bromine, iodine, fluorine), Alkyl groups (preferably 1-8 and especially 1-4 carbon atoms), aryl groups (preferably up to 12 Carbon atoms), alkoxy groups (preferably up to 8 and especially up to 4 carbon atoms), aryloxy groups (preferably up to 10 carbon atoms) or amino groups (optionally with one or two Alkyl groups or aryl groups with preferably up to 4 or 10 carbon atoms). Furthermore, the typical organic photoconductive compounds acting as electron donors, polymers and Copolymers with monomer units which differ from the aromatic hydrocarbon compounds mentioned or derive the mentioned heterocyclic compounds, such as polyvinyl anthracene, polyacenaphthylene, Polyvinylpyrene, polyvinylcarbazole, polyvinylacridine, polypyrenylmethylvinylether, polyglycidylcarbazole, Polymethylene pyrene, polycarbazolyl ethyl vinyl ether, optionally with one or more substituents, such as chlorine or bromine atoms or methyl groups or dimethylamino groups. Polymers with are preferred Carbazole monomer units such as polyvinyl carbazole, polyglycidyl carbazole, polymers made by substitution part of the chlorine atoms of polyepichlorohydrin. A combination of the Sensitizer and the organic photoconductive compound acting as an electron donor, which provides charge transfer absorption bands in the visible range through charge transfer interaction.

When using the recording material according to the invention one usually dissolves the first component, namely the sensitizer and the second component, namely that which acts as an electron donor organic photoconductive compound in a solvent and coated a Keeinneten layer

carrier with the mixture obtained, whereby a photoconductive layer is obtained. The concentration of organic photoconductive compound in the recording material is usually 1-80% by weight and preferably 5-60% by weight. The amount of the sensitizer in the recording material is not subject to any Limitations and depends on the sensitivity, the color depth of the photoconductive layer and the s Miscibility and is usually 0.1-100 mol% based on the organic photoconductive compound. Suitable solvents both for the sensitizer and for the organic photoconductive compound are z. B. tetrahydrofuran, 1,2-dichloroethane, monochlorobenzene, toluene or dimethylformamide. The amount of the solvent should be sufficient to dissolve the first and second components.

Zinc plates, copper plates, paper or foils, films or plates made of plastic are suitable as layer carriers. The recording material can also contain other additives, such as conventional sensitizers, Binders, plasticizers, dyes or pigments.

The photoconductive layer produced during the coating with the recording material usually has a color which changes due to the charge transfer interaction between the first component and the second component and an associated shift of the charge transducer absorption band into the visible range, although the sensitizer and the organic photoconductive compound colorless to pale yellow compounds. The shift in the charge transfer absorption bands, which results when the components are mixed, essentially corresponds to a shift in the phosphorescence in Direction of the longer wavelength compared to the electron spectrum of the photoconductive layer and its photocurrent. It can thus be seen that the improvement in sensitivity by the sensitizer depends on the charge transfer interaction. The recording material according to the invention has a high Sensitivity and is suitable for the purposes of electrophotography, e.g. B. for photocopying purposes or for Microfilms.

Fig. 1 shows the electronic spectrum of the organic photoconductive compound, the sensitizer and of the electrophotographic recording material, the optical density being plotted against the absorption wavelength.

Fig. 2 shows the photocurrent spectrum of the organic photoconductive compound, the electrophotographic recording material and the electronic spectrum of the organic photoconductive compound ((A) versus the absorption wavelength).

3 shows the absorption spectrum of two samples, the transmission being plotted against the wavelength aul-JO.

In the following, the invention is explained in more detail with the aid of exemplary embodiments.

Production _{example 1 3} - Production of l-cyano-l, 2-bis (p-nitrophenyl) -ethylene

1.5 g of p-nitrobenzaldehyde and 1.7 g of p-nitrobenzyl cyanide are dissolved in 5 ml of hot ethanol and 0.05 ml of pyridine are added and the mixture is heated for 10 minutes. The mixture cools overnight. Crystals separate aps. These are filtered off and made from a mixture of acetone and Recrystallized ethanol. I.

1-Cyano-1,2-bis (p-nitrophenyl) -ethylene with a melting point of 216.5-2I7.5 ° C. is obtained. The product shows the following elemental analysis:

45

5.0 g of polyvinyl carbazole and 0.25 g of various sensitizers are each in 50 ml of 1,2-dichloroethane dissolved and the solution is applied with a Baker coater onto an aluminum plate with a thickness of 0.3 mm applied, which was previously treated with the sandblast. You get a layer with a Dry thickness of 15 μm as a photoconductive layer. After drying, the surface of the photoconductive layer is given a positive charge by corona discharge in the dark. The charged phololeillahige The layer is exposed to the light of a halogen lamp, the exposure time being measured for the surface potential to drop to half value. The relative sensitivity is assuming calculated that the polyvinyl carbazole itself has a speed of 1.

M)

Table 1 Sensitizer Relative Sensitive wedge

1 benzalmalonitrile 114

2 p-nitrobenza-malonitrile 308

(Wt .-%) C. H N Found (Wt .-%) 60.78 3.31 14.41 Calculated 61.02 3.07 14.23 example 1

continuation

Sensitizer Relative sensitivity

3 m-nitrobenzalmalonitrile 247

4 p-methoxybenzalmalonitrile 95

5 p-chlorobenzalmalonitrile 154

6 2,4-dichlorobenzalmalonitrile 238

7 p -cyanobenzalmalonitrile 370

8 2-chloro-5-nitrobenzalmalonitrile 667

9 9-anthracenylmethylene malonitrile 105

10 2-naphthylmethylene malonitrile 278

11 ff-Cyano ^ / Mp-cyanophenylJ-acrylethylether 154

12 1 -Cyano- 1,2-bis (p-nitrophenyl) ethylene 351

13 cinnamylidene malonitrile 267

14 2-furfurylidene malonitrile 118

15 ff-Cyano-./8-(p-nitrophenyl )-acry!amide 154

50 parts by weight of sensitizer, namely benzaimalonitrile or 2-chloro-5-nitrobenzalmalonitrile and 100 parts by weight a polymeric binder, namely cellulose acetate, are dissolved in tetrahydrofuran. As above this solution is used for coating and the layer is charged and exposed. One poses no damping of the surface potential. The sensitivity of the sensitizer given over that The light from the halogen lamp is essentially zero.

Example 2 ίο

1.0 g of polyvinyl carbazole and 0.05 g of p-nitrobenzalmalonitrile are dissolved in 10 ml of 1,2-dichloroethane. According to Example I, an aluminum plate is coated with the solution. After drying, use positively charged after a corona discharge. The charged layer is for 0.2 seconds with a tungsten filament lamp exposed with 400 lux, through a transparent positive original, whereupon the bclichtel layer is developed with a conventional developer. A sharp image is thereby obtained.

Example 3

1.0 polyvinyl carbazole and 0.2 g of p-cyanobenzalmalonitrile are dissolved in 10 ml of 1,2-dichloroethane. According to Example 1 an aluminum plate is coated with the solution. After drying, the layer is applied using positively charged after a corona discharge. The loaded layer is made with the help of a tungsten filament lamp exposed at 400 lux for 0.4 seconds through a transparent positive original. Thereafter the exposed layer is developed using the magnetic brush method. A paper is put on top of the layer and a corona discharge is carried out from the back of the paper to form the image to transfer to the paper. The image is then fixed by heating it with an infrared lamp. Man gets a sharp picture.

Example 4

Polyvinyl carbazole is brominated with N-bromosuccinimide, 188% of a brominated polymer being obtained. 10 g of the brominated polymer in O ₄ 1 g of cinnamylidene malonitrile are dissolved in 10 ml of monochlorobenzene. According to Example 2, a plate is coated with the solution and the layer is charged, exposed and developed, whereby a sharp image is obtained.

55 Example 5

Polyacenaphthylene (. Η, _{ρ / ι} = 0.052, c = 0.200 g / dl; benzene solution at 30 ⁰ C) is prepared by polymerizing acenaphthylene in the presence of boron trifluoride as a catalyst diäthylätherat in benzene. 1.0 g of polyacenaphthylene and 0.1 g of p-cyanobenzalmalonitrile and 0.1 g of chlorinated paraffin as plasticizers are dissolved in 10 ml of tetrahydrofuran. Following the procedure of Example 2, the solution is used for coating and the layer is charged and exposed for 1.5 seconds and then developed, whereby a sharp image is obtained

Example 6

1.0 g of one made by substituting 85% of the chlorine atoms of polyepichlorohydrin with carbazole Polymers and 0.2 g of p-cyanobenzalmalonitrile are dissolved in 1,2-dichloroethane. A quartz plate, which

has a transparent electrode made of a tin oxide membrane, is after the casting method with the solution coated. According to Example 3, the coating is charged, exposed, developed and the image becomes with a clear image. On the coating formed on the quartz plate is an aluminum electrode was formed by vapor deposition. To measure the photocurrent, the Spectral light from a xenon lamp exposed through a spectrograph from the transparent electrode (positive electrode) side of the product. 1 and 2 show the results of the measurements of the photocurrent and the electronic spectrum of the polymer, the sensitizer and the recording material according to the invention. In Fig. 1, curve α denotes the electronic spectrum of the polymer itself, curve b denotes the electronic spectrum of the sensitizer, and curve d denotes the electron spectrum of the recording material. In FIG. 2, curve c designates the photocurrent spectrum of the recording material according to the invention; curve d denotes the electron spectrum of the same and curve 3 denotes the photocurrent spectrum of the polymer itself.

From the dependence of the photocurrent on the wavelength, it can be seen that when the sensitizer is mixed with the polymer, the photocurrent extends into regions of longer wavelengths, which Exercise corresponds to the charge transfer absorption bands in the visible range. This shows that the sensitizing effect is enhanced by the charge transfer interaction.

Example 7

Polyglycidylcarbazole (i. _HPIL = 0.030, c = 0.199 g / dl in tetrahydrofuran at 30 ⁰ C) is prepared by polymerization of N-Glycidylcarbazol in toluene in the presence of Bortrifluoriddiäthylätherat catalyst. 1.0 g of the polyglycidyl carbazole and 0.05 g of 2-chloro-5-nitrobenzalmalonitrile are dissolved in 10 ml of tetrahydrofuran. The solution is used to coat a polyester film with a thickness of 100 μm, which has been made electronically conductive. According to Example 2, the coating is charged, exposed and developed. the The transparent copy obtained is used for slide demonstration, whereby a clear, fog-free image is obtained.

Example 8

JO 1.0 g of polyvinyl carbazole, 0.1 g of 2-naphthylmethylene malonitrile and 0.005 g of crystal violet are dissolved in 1,2-dichloroethane. According to Example 7, this solution is used for coating and the coating is charged, exposed and developed, whereby a fog-free, sharp image is obtained.

Example 9

0.3 g of 2-chloro-5-nitrobenzalmalonitrile, 3.0 g of fluorene and 5.0 g of polyvinyl acetate are dissolved in 35 ml of tetrahydrofuran. With the help of a Baker coater, an aluminum plate with a thickness of 0.3 mm, which has been sandblasted, coated with this solution to obtain a layer with a dry thickness of 15 µm. A photoconductive layer is obtained in this way. On the surface a positive charge is applied to the photoconductive layer by corona discharge in the dark. That charged electrophotographic recording material is 25 seconds long from a distance of 15 cm exposed using a 15 W fluorescent lamp as the light source. The exposure takes place through a transparent original through. Then the layer is developed with liquid developer, with a sharp image is obtained. For comparison, the procedure is repeated without fluorene. The exposure The time to form an image is 1 min and 20 seconds. Furthermore, the process is carried out without benzalmuloni tril repeated. No image is obtained, even on exposure for IU min.

Example 10

so A solution of 1.0 g of polyvinyl carbazole and OJ g of chlorinated paraffin with a chlorine content of 40% in ! 0 ml of monochlorobenzene is mixed with 0.1 g of p-cyanobenzalmalonitrile! mixed. The solution is with the help of a Baker coater applied to an electronically conductive polyester film, a layer with a dry thickness of 10 µm is obtained. The coating is then dried. A comparative sample is also used prepared by the same process, using 0.1 g of 2,4,7-trinitrofluorenone instead of p-cyanobenzalmalo nitrile is used. This is a conventional sensitizer with which the strongest sensitization effect has been achieved to date. The film coated with the p-cyanobenzalmalonitrile-containing composition is a pale yellow colored transparent film. The film coated with the composition containing 2,4,7-trinitrofluorenone is a chocolate-colored, transparent film. The absorption spectra of the two samples are shown in FIG. 3, the curve / absorption spectrum of the sample containing p-cyanobenzalmalonitrile and curve g The absorption spectrum of the sample containing 2,4,7-trinitrofluorenone is. In each case, the projection density of the sample obtained is measured by means of a transmission densitometer. The projection density is 0.22 for the sample according to the invention and 0.44 for the reference sample. The projection density of the polyester substrate is 0.16. Accordingly, in the sample according to the invention, the density of the coating itself is 0.06, while in the reference sample it has a value of 0.28. It can be seen that the inventive

Sample has excellent permeability compared to the comparative sample

When a sample of higher permeability is developed with a black toner, the image contrast is higher. Thus, according to the present invention, excellent copies with high contrast can be obtained. Each of the both samples is exposed to monochromatic light through an interference filter in order to

to compare the samples. The sensitivity is measured at a dose that increases upon exposure '/. <of the initial surface potential. The sensitivity of the sample according to the invention to an exposure at 450 nm and 500 nm has 1.5 times the sensitivity of the comparison sample. When p-nilrobenzalmalonitrile is used in place of p-cyanobenzalmalonitrile, similar results are obtained Chronology

Example 11

The polymer according to Example 6 is mixed with 5% by weight of one of the following sensitizers and further processed according to example 6. The relative sensitivities are calculated assuming that the sensitivity of the polyvinyl carbazole itself has a value of 1. The results are shown in Table 2.

Table 2

15th

Sensitizer Relative sensitivity

1 benzalmalonitrile 60

2 p-nitrobenzalmalonitrile 177

3 m-nitrobenzalmalonitrile 81

4 p -cyanobenzalmalonitrile 245

5 p-chlorobenzalmalonitrile 65

6 2,4-dichlorobenzalmalonitrile 120

7 2-chloro-5-nitrobenzalmalonitrile 231

8 4-AcetoxybenzaImalonitrile 63

9 2-fluoro-maionitrile 74

10 ff-Cyano-jff-ip-cyanophenyO-acrylic acid ethyl ester 98

11 l-cyano-1,2-bis (p-nitrophenyl) ethylene 270

12 2-furfurylidene malonitrile 44

13 cinnamylidene malonitrile 165

14 fl-jS- (P-nitrophenyl) -acrylic acid ethyl ester 107

15 ff-Cyano-./Hm-nitrophenyO-acrylic acid ethyl ester 36

16 1-naphthylmethylene malonitrile 114

17 2-naphthylmethylene malonitrile 147

18 l, l-dicyano-4- (p-cyanophenyl) -l, 3-butadiene 143

19 l, l-dicyano-4- (P-chlorophenyl) -l, 3-butadiene 150

20 1.l-dicyano-4- (p-nitrophenyl) -l, 3-butadiene 300

21 l, l-dicyano-4- (m-nitrophenyl) -l, 3-butadiene 157

Example 12

1.0 g of the polymer according to Example 6 and 0.3 g of l, l-dicyano-4- (p-cyanophenyl) -l, 3-butadiene are in 10 ml I.2-dichloroethane dissolved.

With the help of a Baker coater, one is laminated to a polyester film with a thickness of 100 μm Aluminum foil coated with a thickness of 20 μτη, so that a coating with a dry thickness of μίτι is obtained. After drying, a corona discharge (+6 KV applied voltage) in the Dark a charge is applied to the surface of the photoconductive layer. The charged photoconductive layer is exposed for 1 second under a Woliiram filament lamp of 30 lux, the exposure takes place through a transparent positive original. The exposed layer is developed with a conventional developer, a sharp image being obtained which corresponds to the original

60

For this purpose 2 sheets of drawings

Claims (1)

Patent claims: 1. Electrophotographic recording material containing an organic, photoconductive compound of the electron donor type and a sensitizer of the electron acceptor type, characterized by a sensitizer of the general formula CN A- (CH = CHVCH = ^ C \