NO132685B - - Google Patents

Description

Material for electrophotographic reproduction.

Among the modern reproduction methods, the electrophotographic method, also called "Xero-graphie", is increasingly gaining in practical importance. This dry process will be of particular interest in some areas, for example for office diversification, and consists of applying an electrostatic charge to a material consisting of a substrate and an adhesive photoconductor layer in the dark. Such material is usable for producing images by electrophotographic means. It is illuminated under a print and thus spreads the photoconductor layer's electrostatic charge in the places where it is hit by the light. The invisible electrostatic image produced in this way is made visible (developed) by dusting with finely distributed colored synthetic resin and is then made indelible and permanent (fixed) by heating the substrate, whereby the resin pix is melted on.

It is known to produce them for the method described above

necessary photoconductive, i.e. under the influence of light electrically conductive layers using selenium or sulphur, further of zinc oxide or also of organic substances such as anthracene or anthraquinone.

It has also already been considered to produce the photoconductive layers by dispersing the photoconductive substances while adding binders in solvents and applying such dispersions to electrically conductive carriers primarily on metal foils and drying. However, the resulting material does not yet satisfy the very diverse requirements that modern multiplication material has to satisfy with regard to applicability, safety of use, ease of handling and, not least, light sensitivity and durability.

A material has now been found for the electrophotographic re-reduction whose photoconductive layer is characterized by the fact that it contains 1,3-diphenyl-tetrahydroimidazoles as photoconductive substances corresponding to the general formula

in which R stands for H, alkyl, alkenyl, aralkyl, aralkenyl, aryl, substituted aryl or a heterocyclic residue, R, and R2 stands for phenyl or substituted phenyl or consists of these substances.

The term "alkenyl" refers to monovalent residues of unsaturated aliphatic carbon-water substances (olefins), for example ethenyl

(vinyl), propenyl, butenyl, etc. "Aralkenyl"

denotes monovalent residues of aryl-substituted alkenyl (analogue aralkyl).

The 1,3-diphenyl-tetrahydroimidazoles which, according to the invention, are used for the production of electrophotographic copying layers have very good photoconductivity and are particularly well suited for the production of homogeneous layers which are capable of unlimited storage. The compounds are mostly colorless.

Their preparation from N,N'-diphenyl-ethylene-diamine (dianilinoethane) and aldehydes is described for a number of 1,3-diphenyltetrahydroimidazoles in the literature.

To the extent that this is not successful, they are obtained in a simple way by condensation of equimolecular amounts of N,N.'-diphenylethylenediamine and the aldehyde corresponding to R in the general formula above in methanol with the addition of some ed-. , diacetic acid at approx. 60° C. To complete the reaction, a small excess of N,N'-diphenyl-ethylenediamine can be used.

"For example, 1,3-diphenyl-tetrahydroimidazole is prepared by boiling for five minutes a solution of 4.7 g of N,N'-diphenyl-ethylenediamine in 65 ems of methanol, to which is added 2 cm3 of 34% aqueous formaldehyde solution and a few drops of 50% acetic acid. Already upon heating, the reaction product crystallizes and is sucked off after cooling. After recrystallization from methanol, 1,3-diphenyl-tetrahydroimidazole forms colorless crystals with a melting point of 123-124°C.

In an analogous way and possibly with small modifications of the conditions maintained during the reaction, e.g. the amount of acetic acid to be added or the boiling time, all other 1,3-diphenyl-tetrahydroimidazoles to be used according to the invention are obtained". For the sake of completeness, it should be mentioned that in the preparation of compounds corresponding to the above-mentioned general formula and in which R1 and R2 are substituted phenyl residues, bring the corresponding substituted N,N'-diphenyl-ethylenediamines to reaction with aldehyde.

The following overview contains indications of an exemplary number of compounds which are to be used according to the invention of the above-mentioned general formula. In the overview, the diphenyl-ethylenediamines used as reaction components are denoted by A or B or C or D and A stands for N,N'-diphenyl-ethylenediamine

B stands for N,N'-di-(p-tolyl)-ethylenediamine C stands for N,N'-di-(p-chloro-phenyl)-ethylene-diamine

D stands for N,N'-di-(p-nitro-phenyl)-ethylene-diamine.

For the 1,3-diphenyl-tetrahydroimidazoles formed from the reaction components, consecutive numbers are given in the overview (see column 3) under which the corresponding constitutional formulas are listed in the list of formulas. In addition, the overview indicates in column 1 the ethylenediamine reaction components, in column 2 the aldehyde reaction component, in column 4 the cleaning agent from which the crude tetrahydroimidazole is recrystallized, in column 5 the melting point in degrees Celsius and in column 6 the relevant 1.3 -diphenyl-tetrahydroimidazole color.

To produce the photoconductive insulating layers, one advantageously uses solutions of the tetrahydroimidazoles which according to the invention are to be used in organic solvents, for example benzene, acetone, methylene chloride, glycol monomethyl ether and other mixtures of such solvents. One can also use mixtures of several of the tetrahydroimidazoles or the tetrahydroimidazoles to be used according to the invention in a mixture with other, preferably organic photoconductive substances to form the electrophotographic layer.

For the production of the photoconductive insulating layers, it may, as was further found, be advantageous to use the compounds corresponding to the above general formulas together with organic colloids. As such, natural and artificial resins should preferably be mentioned, for example balsam resin with rosin-modified phenolic resin and other resins with a significant rosin component, coumarone resins and indene resins and the substances that fall under the collective term "lacquer resins", to which, according to the Saecht- ling-Zebrowski published Kunststofftaschen-buch (11th edition, 1955, page 212 ff) lists converted natural substances such as cellulose esters polymers such as polyvinyl chlorides, polyvinyl acetates, polyvinyl acetals, polyvinyl ethers, polyacrylic and polymethacrylic esters, further polystyrene and isobutylene, po - shelter condensates, e.g. polyesters namely phthalate resins, alkyd resins, maleinathar pitches, maleic resin-rosin-mixed esters of higher alcohols, phenol-formaldehyde resins, especially rosin-modified phenol-formaldehyde condensates, urea-formaldehyde resins, melamine-formaldehyde condensates .

If one uses the 1,3-diphenyl-tetrahydroimidazoles which according to the invention are to be used in a mixture with organic colloids, the ratio of amounts between resin and photoconductive substance can fluctuate within wide limits. The use of mixtures of approximately equal parts of resin and tetrahydroimidazole has proven advantageous. If such mixtures of approximately equal parts of resin and 1,3-diphenyl-tetrahydroimidazole are used, these solutions in most cases give homogeneous transparent, mostly colorless layers upon drying, which can be regarded as solid solutions.

Substrates that satisfy Xerography's requirements, e.g. metal or glass plates, paper or plates or foils of electrically conductive resins or plastic resins, so-called plastics. If paper is used as a substrate for the photoconductive layers, it pays to pre-treat the paper for the photoconductive insulation layers against penetration of coating solution, e.g. with methyl cellulose in aqueous solution or polyvinyl alcohol in aqueous solution or the solution of a mixed polymer of acrylic acid methyl ester and acrylonitrile in acetone and methyl ethyl ketone or solutions of polyamides in aqueous alcohols. Aqueous dispersions also have such substances which are suitable for the pre-treatment of the paper surfaces can be used.

The solutions of the compounds to be used according to the invention from the class of tetrahydroimidazoles, possibly in mixture with the resins, are applied in the usual way to the substrates, e.g. by spraying, ironing, rolling on or in a similar way and then dried so that they form an even photoconductive layer on the substrate.

The photoconductor layers are usually charged positively or negatively by means of a corona discharge. The photosensitivity of the resulting photoconductor layers charged in this way lies essentially in the long-wave ultraviolet light from approx. 3600 to approx. 4200 Å. With a mercury high-pressure lamp, good pictures can be obtained under a publishing house with a very short exposure time.

In the visible area of the light spectrum, even after charging, the layers according to the invention are still not very sensitive. As was further found, by adding sensitizer to the photoconductive layer, their spectral sensitivity can also be brought into the visible range of the spectrum. The amounts of sensitizer that must be added to the photoconductive substances amount to 0.01-5 per cent, preferably 0.1-3 per cent. It is particularly suitable for dyes whose identification numbers are also indicated, under which they are discontinued in the "Dye Table » by Schultz

(7th edition, first volume, 1931). Examples of effective sensitizers include: triarylmethane genetic material such as brilliant green (no. 760, page 314), Victoria blue

B (No. 822 page 347), methyl violet (No. 783,

page 327), crystal violet (no. 785, page 329), acid violet 6B (no. 831, page 351), xanthene dyes, and further rhodamines, such as rhodamine B (no. 864, page 365), rhodamine 6G (no. 866, page 366), rhodamine G extra (no. 865, page 366), sulphorodamine B (no. 863, page 364) and ectsyreeosin G (no. 870, page 368) as well as phthalenes, such as eosin S (no. 883, page 375), eosin A (No. 881, page 374), erythrosin (No. 886, page 376), phloxine (No. 890, page 378), rose bengal (No. 889, page 378) and flu-orescein (No. .880, page 373); thiazine dyes, such as methylene blue (No. 1038, page 449); acridine heritable matter is, as acridine yellow (No. 901, page 383), acridine orange (No. 908, page 387), and trypaflavin (No. 906, page 386);

quinoline heritables are, as pinacyanol (No. 924, page 396) and cryptocyanin (No. 927, page 397); quinones and ketones such as alizarin (no. 1141, page 499), alizarin red S (no. 1145, page 502) and quinizarin

(No. 1148, page 504); cyanine dyes, e.g. cyanine (No. 921, page 394) and chloro-phyll.

The production of the images by electrophotographic means takes place in the following way: After the charging of the photoconductive layer, for example by means of a corona discharge using a charging device held at 6000-7000 volts, the substrate is illuminated, e.g. paper or aluminum or plastic foil with the sensitized layer under a publisher or by episcopic or diascopic projection and dusted with a soot-coloured resin powder in a known manner. The image thus becoming visible can easily be wiped away. It is therefore fixed, which can for example happen by briefly heating to approx. 120° C or depending on the burning-in temperature in the used developer with an infrared ray. The temperature can be reduced when the heat effect takes place in the presence of vapors of solvents such as trichlorethylene, carbon tetrachloride or ethyl alcohol. Fixation of the powder images is also possible by treatment with water vapor. It arises after positive publishers, positive images that are distinguished by a good contrast effect.

A rather particular advantage of electrophotographic images produced according to the invention is that they can also be converted after fixation into a printed form when the substrates are overwritten, e.g. the paper or plastic foils with a solvent for the photoconductive layer, for example with alcohol or acetic acid. This removes the image-free parts of the layer, so that the substrate can then be moistened with water. They are then rolled in in a known way with bold color that only adheres to the image locations. Positive printing forms are thus obtained from which printing can be done after clamping in an offset machine. The print runs are very high.

When transparent substrates are used, the electrophotographic images can also be used as templates for further copying onto arbitrary light-sensitive layers. The photoconductive compounds to be used according to the invention are in this respect superior to the hitherto used substances such as selenium or zinc oxide, as the latter only give unclear layers that cannot be copied, because no solid solution can be produced with these substances -nings, but only suspensions.

Also with the reflex method, according to the invention, by using a light-transmitting substrate for the photoconductive layer, images can be produced. The possibility of a reflex copy is also a step forward compared to the state of the art.

Moreover, the photoconductive layers composed according to the invention have yet another great advantage, because they can be charged both positively and negatively. With positive charging, the images are particularly good and ozone formation can hardly be observed, which appears very strongly with negative charging and because it is harmful to health, special precautions are required, e.g. arrangement of ventilators.

Example 1.

1 g of 1,3-diphenyl-2-(4'-dimethylamino-phenyl)-tetrahydroimidazole corresponding to formula 31 and 1 g of unsaponified ketone-aldehyde condensation resin, for example that produced by the company Chemische Werke Hiils AG, Mari and under the designation " Kunstharz AP" commercially available product, dissolve in 30 cm3 of glycol monomethyl ether or benzene.

About. 15 cm3 of this solution is applied by even distribution on a paper foil (format DIN A 4). After the solvent evaporates, an adhesive layer remains on the paper foil, which is electrostatically charged. When illuminating the electrically charged layer under a print by the contact method or by means of diascopic or episcopic projection, subsequent dusting with colored powder developer (soot resin mixture) and subsequent heating, also according to the per se known electrophotographic me-tode, you get a picture of the publisher.

Example 2.

One proceeds according to the instructions given in example 1, but uses 1 g of 1,3-diphenyl-2-styryl-tetrahydroimidazole corresponding to formula 9 instead of the one used in example 1 as a photoconductive substance for the production of the electrophotographic layer on paper the tetrahydroimidazole compound. The resulting image has good contrasts. The tetrahydroimidazoles corresponding to formulas 1-8 are used with equally good results.

Example 3.

The working instructions stated in example 1 are modified, with 1 g of 1,3-diphenyl-2-styryl-tetrahydroimidazole (formula 9) being used as the photoconductive substance and instead of Kunstharz AP 1 g of resin-modified maleic acid resin, for example a resin from the company Reichhold -Chemie AG, Hamburg, is marketed under the trademark "Beckacite" K 105. Images produced with this electrophotographic layer are sharp in outline and contrast.

Example 4:

0.7 g of each of 1,3-diphenyl-2-(4'-dimethylaminophenyl)-tetrahydroimidazole corresponding to formula 31, 1,3-diphenyl-2-(4'-di-ethylamino-phenyl)- tetrahydroimidazole corresponding to formula 34 and 1,3-diphenyl-2-[4'-(N-methyl-N-benzyl)-aminophenyl]-tetrahydroimidazole corresponding to formula 37 are dissolved in 30 ems of glycol monomethyl ether. About. 15 cm3 of this solution is applied to a paper foil of format DIN A 4 whose surface has been pre-treated against penetration of organic solvent. The applied solution is dried. With the now coated paper foil, electrophotographic images can be produced as described in example 1. The above compounds can be replaced with approx. equal amounts of the tetrahydroimidazoles corresponding to formulas 32, 35 or 39.

Example 5.

1 g of 1,3-di-(p-tolyl)-2-(4'-dibenzylamino-phenyl)-tetrahydroimidazole corresponding to formula 64 and 1 g of coumarone resin, for example that of the company Gesellschaft fiir Teerverwertung, Duisburg-Meiderich, commercially dissolved "Cumaronharz 701/70" in 30 cm-'' of benzene. Twice every 15 ems of this solution is successively applied to a sheet of transparent paper (80 g/m2) in format DIN A 4 to form a layer. After the solvent has evaporated, the applied layer is dried under an ultra-red ray, it then adheres firmly to the surface of the paper foil. In the electrophotographic way, images with a contrast effect are produced on these layers, which can be used as photocopy publications. If you replace the tetrahydroimidazole with formula 64 with one of the compounds corresponding to formulas 54-63 and 67-70, you get equally good images.

Example 6.

1 g of 1,3-di-(4'-chloro-phenyl-tetrahydroimidazole corresponding to formula 71 and 1 g of unsaponified ketone-aldehyde condensation resin, for example that produced by the firm Chemische Werke Huls AG, Mari and the commercially available product under the designation "Kunstharz AP", dissolve in 30 ems glycol monomethyl ether. To this solution add 0.02 g of ethyl violet

(Schultz "Farbstof f the table", 7th edition, 1st volume, no. 787) and applies this solution to paper that has been made impermeable to the penetration of organic solvents by a primer. After the solvent evaporates, a homogeneous layer remains on the paper, which adheres firmly to the paper surface. The coated paper is equipped in a known manner with a positive or negative electrostatic charge and the paper which is sensitized in this way is illuminated under a positive light, e.g. with a 100 watt incandescent lamp at a distance of 15 cm for one second. The illuminated surface is then dusted with a

with soot-colored resin powder and thereby the resulting latent positive image is made visible, which is fixed by treatment with trichlorethylene vapor.

1 instead of the above-mentioned tetrahydroimidazole corresponding to formula 74, can

the. for the production of electrophotographic

layers, the tetrahydroimidazoles corresponding to formulas 71-73 and 75-90 are used to obtain equally good images.

Example 7.

1 g of 1,3-diphenyl-2-(4'-dimethylamino-phenyl)-tetrahydroimidazole corresponding to formula 31 and 1 g of 1,3-diphenyl-2-(4'-dibenzyl-amino-phenyl)-tetrahydroimidazole corresponding to formula 38 are dissolved in 30 cm3 glycol monomethyl ether and approx. 15 ems of this solution is applied to a paper sheet of format DIN A 4, the surface of which has been pre-treated against penetration of organic solvents. When the applied solution dries, a homogeneous photoconductive insulating layer is formed. With the coated paper, it is possible to produce electrophotographic images according to the method described in example 1. By drawing on a sheet of paper on the non-fixed image dusted with soot-resin powder and repeatedly charging with a corona discharge, the resin-soot-powder image is transferred from this electrophotographic layer to the paper sheet on which an inverted image is created. If the soot-resin image is transferred onto transparent paper or a transparent plastic foil, the resulting image can be further copied, for example on Diazo photocopy paper.

Example 8.

2 g of 1,3-diphenyl-2-(4'-dimethylamino-phenyl)-tetrahydroimidazole corresponding to formula 31 and 2 g of resin-modified maleic acid resin, e.g. that of the firm Reichhold-

Chemie AG, Hamburg, under the trademark "Beckacite" K 125 commercialized product is dissolved in 60 ml of benzene. The solution is applied to a paper foil produced according to one of the American patents no.

2 534 650, 2 681 617 or 2 559 610 or on

an aluminum foil whose surface has been made fat-free. After the solvent has evaporated,

ing, a homogeneous photolen-

dende layer that adheres to the surface of the used layer carrier. On the coated foil, it is produced by electrophotogra-

fish procedure images with good contrast effects that are fixed by heating

ning and in connection is transferred in a printing form by the surface of the layer carrier,

on which the fixed image is located, over-

wipe with 96 percent alcohol, rinse well with water and rub in with 1 percent phosphoric acid and bold printing ink. You get po-

sitive printing forms from which it is printed after clamping in an offset machine.

Example 9.

0.5 g of 1,2,3-triphenyl-tetrahydroimidazole corresponding to formula 10 and 0.5 g of ketone har-

pix, e.g. that of the firm Chemische Werke Huls AG, Mari, manufactured and in man-

the section under the designation "Kunstharz SK"

dissolve in 15 cm3 of benzene. The resolution of-

transferred to paper and dried. After it be-

laid paper is negatively charged by a corona discharge, it is illuminated under a po-

sitive publisher and is dusted with a resin powder colored with soot in a manner known per se. The resulting positive image is fixed by heating. It is characterized by a good contrast effect. For manufacturing

ling of the photoconductive insulating layer, the tetrahydroimidazoles corresponding to formulas 11-30 can be used instead of the tetrahydroimidazole corresponding to formula 10.

Example 10.

0.5 g of 1,3-di-(p-tolyl-2-[quinolyl-(2')]-tetrahydroimidazole corresponding to formula 69

and 0.5 g of zinc resin, for example the product marketed by the company Robert Kraemer in Bremen under the trademark "Erkasit Zinkharz 165", is dissolved in 15 cm3 of benzene. The solution is applied to paper and dried.

After the negative charge in a corona discharge, the paper is illuminated under a po-

sitive publisher with a mercury lamp and in-

dusted with a wood-soot colored resin powder

there. A positive image appears, which is fixed by heating.

Example 11:

1 g of 1,3-diphenyl-2-(N-p-chloroethyl-N-phe nyl-4'-aminophenyl} r tetrahydroimidazole to-

corresponding to formula 36 and 1 g of unsaponified ketone-aldehyde condensation resin, example

show the product manufactured by the firm Chemische Werke Huls AG, Mari, and brought

sold under the name "Kustharz AP" is dissolved in 30 cm3 of benzene. About. 15 cm3

of this solution is under uniform

ling brought on a sheet of paper in format DIN A 4.

After the solvent evaporates,

it becomes a stuck layer on the paper. Using the coated paper, electrophotographic images are produced according to the working method described in example 1. If used in ste-

that for tetrahydroimidazoles corresponding to formula 36, a tetrahydroimidazole corresponding to one of formulas 40-53 for the preparation of the coating solution, then one also obtains

good pictures.

Example 12:

10 g post-chlorinated polyvinyl chloride, for example the product that the company Dyna-mit-Actien-Gesellschaft vormals Alfred Nobel & Co., Troisdorf, Werk Rheinfelden,

has brought to the market under the trademark "Rhenoflex", dissolve in 100 g of methyl-ethyl-

ketone. For this resolution, it becomes

first put 10 g of 1,3-diphenyl-2-(4'-diethylamino-no-phenyl)-tetrahydroimidazole corresponding to formula 34 dissolved in 50 g of toluene and then 0.015 g of rhodamine B extra (Schultz "Farbstof f the table", 7th edition , Volume 1, No. 864)

dissolved in 2 g of methanol. With the resulting solution, paper is coated using a casting device. After the applied solution has been dried to a fixed homogeneous layer, it is produced on this paper on the one in example 1 an-

given way electrophotographic direct car-

there. The photosensitivity is good. From two si-

whose described publishers can be obtained from episko-

whip way contrasty images.

Claims (3)

1. Material for electrophotographic reproduction, consisting of a substrate and an adhesive photoconductor layer, characterized by characterized by the fact that the photoconductor layer as photoconductive substance contains 1,3-diphenyl-tetrahydroimidazoles corresponding to the general formula: wherein R is hydrogen, alkyl, alkenyl, aralkyl, aralkenyl, aryl, substituted aryl, or a heterocyclic radical, and R, and R 2 are or consist of phenyl or substituted phenyl. 2. Material according to claim 1, characterized in that the 1,3-diphenyl-tetrahydroimidazoles are present in the insulation layer in mixture with organic, natural or artificial resins, possibly in the form of solid solutions. 3. Material according to claims 1 and 2, characterized in that sensitizers are also present in the photoconductor layer.