DE2245145A1 - SUBSTITUTED AZOXYBENZENE AND THEIR USE AS DICHROITIC PHOTOCONDUCTORS - Google Patents

Description

Boeblingen, August 28, 1972 kd-fr

Applicant: International Business Machines

Corporation, Armonk, N.Y. 10504

Official File number: New registration

File number of the applicant: LE 970 029

Substituted azoxybenzenes and their use as dichroic photoconductors

The invention relates to azoxybenzenes substituted in the 4,4'-position and their use as dichroic photoconductors in electrophotographic processes, in particular in reflex copying processes.

A number of organic photoconductors are known, but most of them have not achieved technical success since their sensitivity or exposure speed is too low to work with the commercially available inorganic photoconductors, like selenium to compete. That being said, inorganic photoconductors have several disadvantages. The photoconductive Layers made from them are essentially opaque so that they are not suitable for the reflex copying process can be used. Furthermore, the photoconductive layers made of inorganic compounds are not flexible and difficult to manufacture and use.

Several organic compounds are known to have these disadvantages do not own and additionally show dichroism. They are used in electrophotography because of their dichroic behavior usable for the contact reflex copying process. In this procedure, the document to be copied is marked with a previously evenly electrostatically charged photoconductive

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Layer element brought into contact, the photoconductive Element is dichroic and therefore has a preferred axis of absorption and is uniform throughout the photoconductive element exposed with linearly polarized light, the vector of which is directed perpendicular to the absorption axis of the dichroic element so that the light is not absorbed. The polarized light that hits the document is in individual areas absorbed, usually in the dark areas of the image, and depolarized and reflected in the others, usually in the bright areas of the image. The light that is reflected from the bright areas of the image is depolarized and contains a portion with an electrical vector which is now absorbed by the photoconductive element so that on the element an image pattern that corresponds to the image pattern of the document is generated. The photoconductive element becomes conductive and electrostatic charge is dissipated, creating an electrostatic charge image corresponding to the document. A Electrophotographic reflex copying is the subject of German patent application P 17 97 306.7.

Organic compounds that have dichroic properties are described in U.S. Patents 3,489,558, 3,501,293, 3,549,358, and 3,577,444. Lots of these connections however, require long reflux times, additional purification processes and the purest starting materials in their manufacture. Furthermore, although these compounds have photoconductive and dichroic properties, they do not have maximum light absorption for the wavelength of light with which they are exposed, so that they are not suitable for optimal photocopying processes are. The previously known photoconductors have no maximum absorption for green light with a wavelength of about 560 nanometers of the commercially available photocopying lamps, so that they are not suitable for optimal photocopying processes.

The object of the invention is to provide dichroic organic photoconductors that are used in electrophotographic reflex copying processes

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LE 970 029

are usable and their spectral sensitivity for exposure used light wavelength is adapted.

The dichroic organic photoconductors according to the invention are compounds of the structural formula

wherein R and R 'are radicals of the formulas

N «= N-

CH = CHh

XOCO-, XO-, HO-

represent, in which X is a lower alkyl group and η is an integer from 0 to 2. The radicals R and R * are substituents which, as chromophores, increase the color and also determine the position of the absorption spectra so that the desired spectral sensitivity is obtained. The substituents R and R ¹ are substituents with free electron pairs, ie electron donors.

The invention is based on the following description and of the exemplary embodiments explained in more detail. The compounds are easy to prepare by irradiating certain aromatic, Primary amines containing nitro groups, with a photochemical reduction taking place. This method is described, for example, in Journal American Society 91, 5654 (1969). From the

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-A-

Nitro compounds are formed during irradiation, hydroxylamines, from which in turn substituted azoxybenzenes are formed by oxidative coupling.

The oxidative coupling reaction proceeds easily at saturation of the irradiated material with air. On the other hand, the coupling reaction can also be substituted by the anaerobic addition Nitrosobenzenes are carried out to hydroxylamines, with asymmetrically substituted azoxybenzenes being formed.

For the manufacture of photoconductive elements for electrophotography the compounds of the general formula given above are used in organic solvents, other solvents, or any mixture of solvents with which the compounds are compatible, slurried. The slurry is applied to a conductive substrate material suitable for electrophotography, then the solvent is removed, whereby a useful photoconductive element is obtained.

Instead of the preparation indicated above, the compounds of the general formula can also be used together with a resinous binder. Suitable binders are natural ones and synthetic resins in question. Examples of such resins are balsam resins, phenolic resins modified with rosin, Coumarone resins, indene resins, cellulose ethers, polyvinyl chloride, Polyvinyl acetate, acrylic polymers such as polymethacrylic esters, polystyrene, polyisobutylene, polycondensates such as phthalate resins, polyamides and Polyadducts such as polyurethanes.

The proportions of resin to photoconductive compound can vary widely, but photoconductive elements can vary widely Resin and low photoconductive compound are less desirable. Mixtures are most preferred of at least equal proportions of resin and photoconductive compound.

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All materials that meet the requirements of electrophotography can be used as substrate materials, if they are used meet, for example metals, glass, paper or plastics.

Use of the slurries of the compounds of the invention with or without resins is carried out in the usual way by spraying on, by application using a doctor blade or by means of the Meniscus treatment method and the like, followed by drying.

The compounds of the invention are useful in electrophotographic Procedure. In this process, a uniform electrostatic charge is applied to a photoconductive element applied, this is exposed imagewise to the exposed Areas to cause the charges to dissipate, and then the electrostatic image thus formed is with a colored electroscopic toner brought into contact to make it visible. Then a copy sheet is made with brought into contact with the developed image, this is transferred to the same and fixed on it. The photoconductive element is cleaned of the remaining residual toner and is then for the production of the next copy or the next Cycle ready.

Because the compounds according to the invention are also dichroic they are also suitable for use in contact reflex copying processes.

In all examples, the irradiations were carried out using a Hanovia high pressure mercury arc lamp (450 W), Type L and carried out using the filter provided for this purpose. Infrared spectra were recorded on a Perkin-Elraer Model 521 Gxtter Spectrophotometer carried out. The spectra in the visible range were recorded with a Cary Model 14 spectrophotometer.

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The electrical properties were measured on photoconductive elements measured from an aluminized polycarbonate substrate, which was protected with polyvinyl alcohol, from an oriented layer of the azoxybenzene and then from a poly-N-vinylcarbazole charge transport layer (from 5.5% benzene solution), which by means of a doctor blade with a gap setting for 0.254 mm (10 mil) wet application passed.

The compound according to Example 1 was also used in a photoconductive Built-in element, in which an aluminized anisotropic cellulose triacetate carrier instead of the polycarbonate carrier was used and checked for tension contrasts between black and white image areas when the exposure was through a 4 mm gap with a green photocopying lamp and while moving the sheet member at a speed of 6 inches per second.

example 1

Production of 4,4 • -azoxybis-p-dimethylaminoazobenzene

N = N

N-N

6.5 g (24.0 mmol) of 4-dimethylamino-4'-nitro-azobenzene were in 600 ml of n-butylamine dissolved together with 182 g of benzophenone. Nitrogen was bubbled through the resulting solution and this was irradiated until there was no starting material left. The progress of the reaction was monitored by thin layer chromatography (Silica gel plates developed with chloroform). The irradiated solution was then saturated with air and filtered. There were 4.17 g (8.4 mmol) of the azoxy coupling

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Connection received. The yield was 70%. F>300; IR spectra (KBr pellets): CH _arom 1580 cm " ¹ , CN _arom 1345 cm" ¹

t -1
and -N = N- 1312 cm; maximum absorption in the visible range

(pure substance) 560 nm.

A sample was further purified by recrystallizing three times from dimethylformamide.

Analysis;

calculated for C ₂₈ H ₂₈ NgO (492.57):

found:

C 68.27; H 5.73; N 22.45 C 68.20; H 5.69; N 22.77

Electrical Properties;

dichroic photo decay ratio:
% of the output voltage after 14 seconds:

10: 1;

5%.

voltage contrast:

Speed gap 15.24 cm x see 4 mm

white 60 V

black 480 V

420 V

Example 2

Preparation of 4,4'-azoxybis-terphenyl

2.1 g (7.64 mmol) of 4-nitroterphenyl were dissolved in 600 ml of n-butylamine dissolved together with 50 g of benzophenone. The solution was irradiated and the reaction product was made in a manner similar to Example 1 isolated. 1.23 g (2.48 mmol) of 4,4'-azoxy bis-terphenyl were obtained

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isolated in the form of a yellow powder. The yield was

65.4%. F> 300 °; IR spectra (KBr pellets) C-H 1485 and

0 ³ ^ ⁰ * ¹

1460 cm ", -N« N- 1330 cm "; maximum absorption in the visible Range (pure substance) 310 nm.

An analytical sample was further purified by three times Recrystallize from dimethylformamide.

Analysis;

calculated for C ₃₆ H ₂₆ N ₂ O (5O2.59):

found:

C 86.03; H 5.21; N 5.57 C 85.68; H 5.11; N 5.82,

Electrical Properties;

dichroic photo decay ratio:
% of the output voltage after 14 seconds:

2: 1;
70%.

Example 3

Preparation of 4,4'-azoxybis-biphenyl

2.05 g (10.3 mmol) of 4-nitrobiphenyl were photochemically in 1.0 g (2.86 mmol) 4,4'-azoxybis-biphenyl in an analogous manner as indicated in Example 2, converted. The yield was 56.04%. F> 300 °; IR spectra (KBr pellets) OH., .- 1485, 1460 ,.

1440 cm " ¹ , -N = N- 1295 cm" ¹ , CH _arom 842, 763 and 715 cm "¹; maximum absorption in the visible range (pure substance) 320 nm.

A sample was further purified by recrystallizing three times

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size from dimethylformamide.

Analysis; calculated for C ₂₄ H ₁₈ N ₂ O <35O.4O):

found:

C 82.26; H 5.18; N 8.00 C 82.16; H 5.10; N 8.09.

Electrical properties;

dichroic photo decay ratio:
% of the output voltage after 14 seconds:

2.5: 1;
20%.

Example 4

Preparation of 4,4'-azoxybis-p-dimethylaminostilbene

CH = CH

N = N

CH-CH

1.61 g (6.02 mmol) of 4-dimethylamine-4'-nitro tubes were under the same conditions as given in Example 2, converted to 0.941 g (1.92 mmol) of the azoxy coupling compound. The yield was 57.6%. F> 300 °; IR spectra (KBr pellets) 'C-H

and 1590 cm " ¹ , CN

1365 cm " ¹ , -N = N- 1310 cm" ¹ and

_aroma

" ¹

(trans-CEI = CH-) 965 cm "¹; maximum absorption in the visible range (pure substance) 490 nm.

A sample was further purified by recrystallizing three times from dimethylformamide.

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Analysis: calculated

for C ₃₂ H ₃₂ N ₄ O (488 _f 16):

found:

C 78.65; H 6.60; N 11.47 C 78.54; H 6.42; N 11.48,

Electr ical properties:

dichroic photo decay ratio:% of output voltage after 14 seconds:

9: 1; 20%

Example 5

Production of 1,1-bis-4,4'-dimethylaminophenylazoxybenzyl

methane:

2.47 g (9.37 mmol) of 4,4'-dinitrodiphenyl and 45 g of benzophenone were dissolved in 600 ml of n-butylamine and irradiated in a nitrogen atmosphere until the starting material was no longer present. The progress of the reaction was followed by thin layer chromatography (silica gel plates developed with chloroform). Then, 2.83 g (18.6 mmol) of 4-dimethylaminonitrosobenzene in 30 ml of n-butylamine were added to the irradiated mixture and the rapidly darkening solution was stirred for 1 hour in an inert atmosphere. The bis-azoxy compound was isolated by vacuum filtration, washed with 100 ml of boiling hexane, and dried at 100 ⁰ C and 10 Torr. 1.68 g (3.89 mmol) of the bis-azoxy compound are isolated.

The yield was 36.2%. F> 300; IR (KBr pellets)

0 -1

C-H 16OO and 1514 cm arom

, CN 1370 cm " ¹ and -N = N- 1330 cm" ¹ arom

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the maximum absorption in the visible range was 470 nm.

A sample was further purified by recrystallizing three times from dimethylformamide.

Analysis:

calculated for C ₂₉ H ₃₀ N ₆ O ₂ (494.58):

found:

C 70.42; H 6.11; N 17.00 C 66.66; H 4.66; N 14.92.

Electrical Properties:

dichroic photo decay ratio: 3.5: 1; % of the output voltage after 14 seconds: 16%.

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Claims (7)

2245U5 PATENT CLAIMS 1. Dichroic, organic photoconductors of the structural formula wherein R and R * are radicals of the formulas X ₂ N XOCO-, XO-, HO- represent, in which X is a lower alkyl group and η represent an integer from 0 to 2. 2. 4,4 * -azoxybis-p-dimethylaminoazobenzene. 3. 4,4 · -azoxy bis-terphenyl. 4. 4,4'-Azoxybis-biphenyl. 5. 4,4'-Azoxybis-p-diraethylaminostilbene. 6. 1,1-bis-4,4'-dimethylaminophenylazoxybenzyl methane. 7. An electrophotographic process in which an electrostatic charge image is formed on a photoconductive material is generated and then developed into a visible image, characterized in that the photoconductive 3098U / 1176 LE 970 029 22A5H5 capable layer a compound of the structural formula N = N R ¹ contains, in which R and R * radicals of the formulas X ₂ N N-N- CH-CHh XOCO-, XO-, HO- represent in which X is a lower alkyl group and η represent an integer from 0 to 2. TL ^- Ί U> f »>% 3G9 814/1 1 7 6 3 OJ Β H / Ί 1 1 U