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Publication numberUS3165420 A
Publication typeGrant
Publication dateJan 12, 1965
Filing dateJun 13, 1960
Priority dateJun 27, 1959
Also published asDE1115580B
Publication numberUS 3165420 A, US 3165420A, US-A-3165420, US3165420 A, US3165420A
InventorsTomanek Martha, Behmenburg Hans, Neugebauer Wilhelm, Klupfel Kurt-Walter
Original AssigneeAzoplate Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Developer for electrophotographic purposes and process for developing an electrostatic image
US 3165420 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

United States Patent C DEVELGPER FUR ELECTRUPHQTQGRAPHEC PUR- PGSES AND PRQCES?) FUR DEVELQPFNG AN ELECTROSTATEC IMAGE Martha Torr-ranch, Hans Eehmenburg, Wilhelm Neugebatter, and Kurt-Walter Klupfel, all of Wieshaden-Biebrich, Germany, assignors, by mesne assignments, to Azoplate Corporatinn, Murray Hill, N3.

N Drawing. Filed June 13, 1960, Ser. No. 35,448 Claims priority, application Germany June 27, 1959 28 Claims. (Cl. 117-175) Electrophotographic material usually consists of a support having a layer of a photoconductive substance. This layer is provided, in the absence of light, with an electrostatic charge. Then, the material is exposed to light, either through a master or by episcopic projection, an image corresponding to the master thereby being obtained. This image is made visible by brief contact with a resin powder and, subsequently, it is fixed by heating or by the action of solvents. By this electrophotographic procedure, a copy of the master is obtained, which cannot be wiped off.

The present invention refers to a special kind of developer used for such electrophotographic processes.

Usually, the developers are composed of a mixture of a carrier and a toner. The carrier consists of grains of inorganic materials, such as tiny glass balls, iron filings, or crystals of inorganic salts, such as sodium chloride or potassium chloride.

As toner, resin powders are used which contain dyestuffs or pigments, for example carbon black. When working with the developer, the toner is positively charged, due to the triboelectric effect between the toner and the carrier material.

The photoconductive layers can be positively or negatively charged so that, after exposure beneath a master,

a positive or negative electrostatic image is obtained. An image corresponding to the master is formed when the developer, with the positively charged toner, is applied to a negative electrostatic image. But if the same developer is applied to a positively charged image, the tonal values are reversed; a negative of theoriginal charge image is formed, because the toner particles are repelled by the charged portions. These reversed images show very little contrast and some undesired marginal eflfects.

As many photoconductive layers can more easily'be charged positively than negatively, efiforts were made to find developers with toners which can be negatively charged. For this purpose organic carriers, such as crystals of tanthracene or fluorene were used, or the individual particles of an inorganic carrier material, such as glass, were coated with a resin layer and added to a toner.

By this procedure the toner is charged negatively, but the carrier crystals 13.1'6 of low mechanical strength and pulverize when used in an undesired manner. If inorganic carriers coated with organic material are used, lumps tend to be formed when coating the carrier particles with a resin layer, and, furthermore, the coated carrier particles tend to lose their round shape which impedes the cascading of the developing powder over the surface of the electrophotographic material. Moreover, the resin coat of the carrier particles is rubbed off, so that the toner is no longer uniformly charged. In some cases, the images obtained using such a toner show an ambiguous electric eflfect, e.g. they appear in part as images corresponding to the master, in part as reversed images.

Now a developer for electrophotographic purposes has been found, consisting of a carrier and a toner, which can be negatively charged, characterized in that the carrier consists of inorganic materials and the toner consists at least partially of metal resinates.

Inorganic materials suitable as carriers are: glass, metals, such as iron; and salts, such as potassium sulfate, potassium chloride and sodium chloride. Mixtures of such inorganic carriers can also be used.

In general, the carriers are used in the form of particles having an average grain size from about to about 600p. Smaller or larger carrier particles can also be used, but carriers with a grain size in the range stated above, preferably from about 100 to about 400 are preferred. Mixtures comprising carriers of different grain sizes can also be used.

Suitable toners are metal resinates, to which pigments and/or dyestuifs, preferably metallic dyestuffs may be added. Metal resinates, :also called resin soaps, are the salts of the metals of Groups l8 of the Periodic Table with resin acids (s. Rompp, Chemielexikon, 4th edition, page 1858). Preferred metal resina-tes are those of such metals as aluminum, barium, lead, calcium, cerium, iron, cobalt, copper, magnesium, manganese, and zinc. Mixtures of such metal resinates can also be used.

Resins and/or waxes and/or aromatic organic compounds having a low melting point, and substitution products thereof, can also be added. Resins which may be added to the metal resinates are natural resins, such as colophony, dammar resin, copals, e.g. Manila copal or kauri copal, and synthetic resins, such as ketone resins, maleic resins, alkyd resins, and styrene resins.

Waxes used for this purpose are natural waxes, such as carnauba wax, beeswax, Japan wax, montan wax, and synthetic waxes, such as the ones commercially available as A wax, OP wax, SPO wax, V wax, and especially the so-c-alled Gersthofener Wachse, marked as KP, S, L, and 0.

As low melting aromatic compounds there may be added unsubstituted and substituted compounds having melting points in the range of about 40 to about C. Such aromatic organic compounds are naphthols, such as l-naphthol or Z-naphthol, acenaphthene, o-phenylene diamine, resorcinol, and diphenylamine. These materials are added for the purpose of reducing the melting point of the toner mixture and increasing the adhesion thereof.

The metal resinates may be colored; for this purpose, pigments are used, such as carbon black, zinc oxide, titanium dioxide, ul-tramarine, minium, pigment red B, and pigment green B. Generally, however, not more than 10 percent of pigments should be added in order to limit the influence on the charging characteristics.

Moreover, dyestuffs can be added, which contain metal elements. In this case, larger quantities can be used, for example 50 percent, but preferably 35 percent should not be exceeded.

Dyestuffs with a metal content are e.g. complex compounds containing in their molecules copper, zinc, magnesium, iron, sodium or potassium, viz. chlorophyll or copper-, zincor magnesium-phthalocyanine or naphthol green 5. Further double salts of dyestuff molecules, for instance, the zinc double salt of toluidine blue 0, methylene green B, or acridine orange 26, are used.

Complex salts of heteropoly acids, such as phosphortungstomolybdic acid with dyestuffs may also be used, e.g. the so-called fanal dyestufis, for instance Fanal Red 613, Fanal Violet LB, and Fanal Blue B. Furthermore, metal salts of sulfonic or carboxylic acids of dyestuffs may be used, for instance Alizarin blue'olack B, and Diamant Black F. For coloring the metal resinates dyestuffs may also be used which contain no metallic components, e.g. Nigrosin, Pigment Deep Black, Auramin, Brilliant Yellow, Eosin, Rhodamine B,

and Sudan Black G. Moreover, mixtures of the above ditferent kinds of dyestutfs can be used.

For the preparation of the toner, the crushed initial materials are advantageously mixed and then finely ground, for example in a ball mill. Then, the mixture is melted, and the molten mass is thoroughly mixed, to embed the coloring particles completely in the resin. In-

sofar as they are fusible, the initial products can be melted The above developer may be used in known electrophotographic procedures.

developer powder that, when used in the method described in Example 1, forms negative images of the originals used.

Example 3 The method described in Example 1 is repeated, melting together parts by weight of a calcium resinate (KunstharzL), 30 parts by weight of a ketone resin (Kunstharz AP), and 2 parts by weight of Acridingelb G (Schultz, No. 901). After grinding and sieving, a yellow colored toner is obtained which, when mixed with sodium chloride crystals at a ratio of 2:1, forms a developer which yields reflex images of very good contrast, when used in the method of Example 1. Alternatively, an enlargement of a negative microfilm may be projected onto the negatively charged electrophotographic paper by means of a projector'and the latent enlarged image thus formed may be treated withthe developer powder. A

, positive enlargement is thus obtained. 1

For this purpose, the developer is contacted in known not struck by light during exposure and which still have an electrostatic charge. Images are formed which correspond to the master used.

The developer of the present invention is preferably used for negatively charged layers. During development, the toner adheres to those parts of the electrophotog'raphic reproduction material which were struck by light, and a visible negative image of the original is obtained. one advantage of the developers according to the present invention, that little or no marginal efiect appears at the contour lines, contrary to the. developers hitherto used. Due to the mechanical stability thereof, the developers retain a distinctly negative charge even after long use. They are particularly suitable for producing enlargements from microfilms by the electrophotographic process.

The invention will be further illustrated by reference to the fololwing specific examples:

Example 1 parts by weight of a zinc resinate (Erkazit-Harz RF) are finely ground, mixed with one part by weight of Nigrosin spirit-soluble (Schultz Farbstoiftabellen, vol. 1, 7th edition, 1931, No. 985) and 0.5 part by weight of copper-phthalocyanine and the mixture is melted. After cooling, the solidified melt is ground in a ball mill and sieved. A fraction, having an average grain size of 30- 50p, of the black-colored toner thus obtained is mixed in a ratio of 2:100 with glass balls having a diameter of about 300 The developer thus obtained is suited for the production of reflex images. For this purpose an electro-photographic paper, eg a zinc oxide paper or a metallic layer consisting e.g. of aluminum provided with a zinc layer, is given a negative electric charge of. 6000 volts by means of a corona discharge andthen exposed under an original. The developer powder is then cascaded over the paper. During this procedure, the finely distributed pigmented resin adheres to those parts of the layer which were struck by light during exposure, and a negative of the original becomes visible, which is subsequently fixed by slight heating. It shows good contrast eflect.

Example 2 The process described in Example 1 is repeated, with the exception that 50 parts byweight of magnesium resinate (Magnesium-Hartharz VII, 2), 2 parts by Weight of Fanalrot 6B (Schultz, No. 864-), and 2 parts by Weight of Sudan ll (Schultz, No. 532) are used. After grinding and sieving, a red toner is obtained which, when mixed with glass balls at a ratio of 3:100, yields a It is 7 Example 4 parts by weight of a manganese resinate (Manganresinat RMSS), 10 parts lay-weight of montan wax, and 3 parts by weight of Alizarinblauschwarz B (Schultz, No. 1195) are treated as described in Example 1. After sieving, the toner is mixed-with tiny glass balls and yields a developer powder which is suitable for the preparation of electrophotographic reflex images as described in Example 1.

Example 5 40 parts by weight of a cobalt resinate (Kobaltresinat A71) and 20 parts by Weight of colophony are melted, as described in Example 1, with 2 parts by weight'of Pigmentschwarz' B (Schultz, No; 1361) and 1 part by weight of Fanalblau B (Schultz, No. 822). After cooling, the solidified mixture is ground and sieved. The toner thus obtained is mixed, at a ratio of 3: 100, with iron powder and then distributed bymeans of a bar magnet over a latent electrostatic'image produced'in accordance with the method described in Example 1. The toner adheres to those parts of the layer which were struck by lightduring exposure. A reverse imageof the original used is thus obtained, e.g. a positive image from a negative original.

Example 6 containing about 1 percent Co, 5 percent Pb, and 1 percent Mn), 10 parts by weight of a zinc-calcium-resinate (Kunstharz 445) and 4 parts by weight of Diamanatschwarz F, (Schultz, No. .614). The mixture, is ground, sieved, and then mixed, at aratio of 2:100, with tiny glass balls. A developer is thus obtained which is suited for the production of electrophotographic reflex images. For this purpose a paper base coated,'e.g. with an organic semi-conductor (e.g. 2,5-bis-(4'-diethyl-amirio-phenyl- 1) 1,2,4 oxdiazole described in Belgian Patent No. 558,078)-is negatively charged and then exposed under an original. The developer powder is then cascaded over the paper, whereby the finely distributed colored resin adheres to those parts of thelayer which were struck by light during exposure and a'negativeof the original becomes visible. The image is fixed by treatment with trichloroethylene vapors.

Example 7 30 parts by weight of iron resinate, 5 parts by weight of copper resinate, and 1 part by weight of Direkttiefschwarz E (Schultz, No. 671) are melted together and, after cooling, are ground and sieved. The toner, having a grain size of 50-100 is mixed with glass balls in a ratio of 5:100. The developer thus obtained is suited for the production of reflex images in accordance with the method described in Example 1. Instead of copper resinate, there may be used barium or iron resinate.

Example 8 50 parts by weight of a zinc resinate (Erkazit Zinkharz 165), parts by weight of an aluminum salt of a resinic acid (aluminum salt of the Albertol acid, Albertat 175), 10 parts by weight of l-naphthol, and 2 parts by weight of Methylviolet B (Schultz, No. 783) are treated as described in Example 1. After sieving, the toner is mixed at a ratio of 3:100 with iron powder. The developer thus obtained is suited for the production of refiux images. For this purpose an electrophotographic paper, e.g. zinc oxide paper, is given a negative electric charge of 6000 volts by means of a corona discharge and then exposed under an original. Subsequently, the developer is evenly distributed over the latent electrostatic image by means of a bar magnet. The toner adheres to those parts of the layer which were struck by light during exposure so that a reverse image of the original used is obtained, e.g. a positive image of a negative original.

Example 9 50 parts by weight of a zinc resinate (Erkazit Zink RF) are ground, mixed with 1 part by weight of Nigrosin spirit-soluble (Schultz, No. 985), and then melted. After cooling, the melt is ground in a ball mill and sieved. The black-colored toner, having a grain sizeof 3050,u., is mixed with glass balls of about 300p. diameter at a ratio of 2:100. The developer thus obtained may be used for the production of direct images on layers having a positive charge. For this purpose, an electrophotographic layer, e.g. an aluminum foil provided with a selenium layer, produced by means of selenium vapors, is given a positive electric charge of 6000 volts by means of a corona discharge and then exposed under an original. Subsequently, the developer powder is cascaded over the foil. The finely distributed pigmented resin adheres to those parts of the layer which were not struck by light during exposure. An image corresponding to the original used becomes visible which is fixed by heating; it shows very good contrast.

Example 10 The procedure described in Example 1 is repeated, using for the melting process 50 parts by weight of a magnesium resinate, parts by weight of magnesiumphthalocyanine and 2 parts by weight of Methylengrun B (Schultz, No. 1040). After grinding and sieving, a green colored toner is obtained, which, when mixed with iron powder at a ratio of 3:100, yields a developer powder which may be cascaded over a latent electrostatic image produced in accordance with the method described in Example 1. From a negative original a positive image is obtained.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

What is claimed is:

1. A dry developer for electrophotographic purposes, capable of being negatively charged, comprising a finelydivided inorganic carrier having an average particle size in the range of about 100 to 600 and a finely-divided metal resinate toner having an average particle size in the range of about 1 to about 100/J, the weight ratio of carrier to toner being in the range of about 100:30 to about 100:0.1.

2. A developer according to claim 1 including a pigment.

3. A developer according to claim 1 including a dyestuff.

4. A developer according to claim 1 in which the metal of the metal resinate is selected from the group consisting of aluminum, barium, lead, calcium, cerium, iron, cobalt, copper, magnesium, manganese, and zinc.

5. A device according to claim 1 including a resin having a low melting point.

6. A developer according to claim 1 including a Wax.

7. A developer according to claim 1 including an aromatic organic compound of low molecular weight.

8. A developer according to claim 1 in which the resinate is zinc resinate.

9. A developer according to claim 1 in which the resinate is magnesium resinate.

10. A developer according to claim 1 in which the resinate is calcium resinate.

11. A developer according to claim 1 in which the resinate is manganese resinate.

12. A developer according to claim 1 in which the resinate is cobalt resinate.

13. A developer according to claim 1 in which the resinate is cobalt-lead-manganese resinate.

14. A developer according to claim 1 in which the resinate is copper resinate.

15. A dry process for developing an electrostatic image Which comprises contacting the image with a negatively charged developer comprising a finely-divided inorganic carrier having an average particle size in the range of about to 600 2 and a finely-divided metal resinate toner having an average particle size in the range of about 1 to about 100;/., the weight ratio of carrier to toner being in the range of about 100230 to about 10020.1, and fixing the image.

16. A process according to claim 15 in which the developer includes a pigment.

17. A process according to claim 15 in which the developer includes a dyestuff.

18. A process according to claim 15 in which the metal of the metal resinate is selected from the group consisting of aluminum, barium, lead, calcium, cerium, iron, cobalt, copper, magnesium, manganese, and zinc.

19. A process according to claim 15 in which the developer includes a resin having a low melting point.

20. A process according to claim 15 in which the developer includes a wax.

21. A process according to claim 15 in which the developer includes an aromatic organic compound of low molecular weight.

22. A process according to claim 15 in which the resinate is zinc resinate.

23. A process according to claim 15 in which the resinate is magnesium resinate.

24. A process according to claim 15 in which the resinate is calcium resinate.

25. A process according to claim 15 in which the resinate is manganese resinate.

26. A process according to claim 15 in which the resinate is cobalt resinate.

27. A process according to claim 15 in which the resinate is cobalt-lead-manganese resinate.

28. A process according to claim 15 in which the resinate is copper resinate.

References Cited in the file of this patent UNITED STATES PATENTS 2,019,981 Krauss Nov. 5, 1935 2,173,699 Siegel Sept. 19, 1939 2,463,044 McLean Mar. 1, 1949 FOREIGN PATENTS 693,900 Great Britain July 8, 1953

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3262806 *Dec 13, 1962Jul 26, 1966Azoplate CorpThree component magnetic developer for electrophotographic purposes and method for using it
US3272644 *Jul 31, 1963Sep 13, 1966Dennison Mfg CoDevelopment of latent electrostatic images with crystalline toners
US3278323 *Dec 26, 1963Oct 11, 1966Dick Co AbMethod of producing imaged spirit master directly from original
US3372294 *Jul 29, 1966Mar 5, 1968Gen Electrodynamics CorpCamera tube target including porous photoconductive layer comprising antimony trisulfide, free antimony and copper phthalocyanine
US3399140 *Sep 7, 1965Aug 27, 1968American Photocopy Equip CoLiquid developer for electrostatic printing
US3417019 *Dec 27, 1962Dec 17, 1968Eastman Kodak CoXerographic development
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US3627682 *Oct 16, 1968Dec 14, 1971Du PontEncapsulated particulate binary magnetic toners for developing images
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US4126454 *May 30, 1974Nov 21, 1978Xerox CorporationImaging process utilizing classified high surface area carrier materials
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Classifications
U.S. Classification430/108.8, 430/123.58, 430/109.1, 430/937, 428/402, 430/108.1, 430/108.3
International ClassificationG03G9/097, G03G9/10
Cooperative ClassificationY10S430/138, G03G9/10, G03G9/09791
European ClassificationG03G9/097F1, G03G9/10