DE2529993A1 - ELECTROSTATOGRAPHIC DEVELOPER MIX - Google Patents

Description

DR. ING. E. HOFFMANN · DIPL. ING. W. EITLE DR. RER. AAT. K. HOFFMAAN

PATKNTAmVALTE D-SOOO MÖNCHEN 81ARABELLASTRASSE 4. TELEPHONE (08Π) 911087

26958 r / zb

Xerox Corporation, Rochester, N.Y./USA

Electrostatographic developer mix

The invention relates generally to imaging systems, and more particularly improved electrostatic developer compositions for use in such systems.

The formation and development of images on the surface of photoconductive materials by electrostatographic Measures are known. In the case of basic electrostatography Process as he z. As described in US Pat. No. 2,297,691, the procedure is to obtain a uniform Electrostatic charge applies to a photoconductive insulating layer, the layer a light-shadow image exposes to dissipate the charges on the exposed areas, and that the resulting electrostatic latent image is developed by placing a finely divided electroscopic material on the image called toner is deposited. The toner is attracted to those parts of the layer that retain a charge, whereby a toner image is generated which corresponds to the electrostatic

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corresponds to latent image. This powder image can then usually electrostatically onto a carrier surface, e.g. B. paper, be transmitted. The transmitted image can subsequently be transmitted through Heat or other suitable fixation measures, e.g. B. a solvent or coating treatment on the support surface be permanently fixed.

Many methods are known to electroscopically see particles on the latent image to be developed. A development method as z. B. in U.S. Patent 2 618 582 is the so-called cascade development. In this method, a developer material, which contains relatively large carrier particles, in which finely divided toner particles electrostatically on the surface of the Carrier particles adhere, moved and rolled over the surface, which shapes the electrostatic latent image. The charged parts of the surface have a charge of the same polarity, however, it is stronger than the carrier particles. The toner and Carrier particles with opposite polarities are selected so that the toner particles are attached to the carrier particles. In order to develop a negatively charged electrostatic latent image, a toner and carrier combination is selected in that the toner is triboelectrically positive with respect to the carrier. Conversely, it will develop a positively charged electrostatic latent image is a toner-carrier combination is used in which the toner is triboelectrically negative with respect to the carrier used. The triboelectrics Relationships between the toner and the carrier depend on the relative locations of the materials in the triboelectric Turn. In this row materials are in ascending order of their ability to accept a positive charge, arranged · Each material is positive in relation to a material below it and in relation to a material above it Material negative. If the developer mixture is over the image

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If the bearing surface cascades or rolls, the toner particles are electrostatically charged from the carrier Parts of the image-bearing surface are drawn while they are away from the uncharged or background parts of the image with which they are attached be in contact, not be electrostatically attracted. The carrier particles and unused toner particles become then returned. The cascade development process is particularly well suited for developing line copy images and it is the most widely used electrostatographic developing technique. An office copier, who works according to this technique is z. As described in U.S. Patent 3,099,943.

Another technique for developing electrostatic latent Images is the magnetic brush method that z. As described in U.S. Patent 2,874,063. In this procedure a developer material composed of toner and magnetic carrier particles is attracted to and carried by a magnet. The magnetic field causes the magnetic particles to be aligned in a brush-like configuration when the magnetic brush is in Is brought into contact with the electrostatic latent image bearing surface. Thereby the toner particles from the carrier particles of the brush to the charged areas of the image-bearing surface, but not to the uncharged ones Make, pulled. Since the charged sites have an imagewise configuration, the toner materials adhere to the surface in an imagewise configuration, thereby developing the latent image.

Another method of developing electrostatic latent images is e.g. As described in U.S. Patent 3,503,776. In this method, images are formed by carrying an electrostatic latent image Surface on a generally ascending curved

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Transported away and only having the image in a contact zone a bath of developer material in contact, which is transported in a concave chamber, which is attached to the lower path adjoins the imaging surface. The contact zone extends from approximately the lowest part of the curved one Path to the top of the curved path. When the imaging surface is transported along the curved path is, then the frictional contact between the developer and the imaging surface circulates in the contact zone the developer in the bath and brings the developer material with the imaged surface into a developing configuration.

There are many other methods, e.g. B. the Aufsetzverfahren according to U.S. Patent 2,895,847, known to be electroscopic particles on the electrostatic latent image to be developed. The development process and countless modifications of which are sufficiently described in the patent literature and in other publications.

It is common in automatic reproduction machines to use as the imaging plate a photoconductor on a conductive substrate in the form of a cylindrical drum or flexible belt which is continuously rotated through a cycle of sequential operations including charging, exposure, development, transfer and cleaning. The developer chamber is loaded with a developer mixture which contains carrier particles and sufficient toner particles for hundreds of reproduction cycles. In general, freshly loaded developer mixes contain between about 1.5 and 5% toner particles, based on the weight of the developer. The initial concentration provides enough toner for many reproduction cycles without causing an undesirably high level of background toner deposition.

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Although the conventional development systems are capable of doing this are to produce images of good quality, they have serious disadvantages in certain areas of application. Sc it is in the reproduction of high contrast copies, e.g. B. of letters, plans and the like, desired, the electroscope! between powder and carrier materials to be selected so that their mutual electrical charge is relatively large, with the degree of such electrical charge in most cases on the distance between their relative positions is determined in the triboelectric series. If, however, otherwise compatible electroscope! See powder and carrier materials are separated from each other in the triboelectric series by too great a distance, then the resulting Images are very weak because the forces of attraction between the carrier and toner particles match "the forces of attraction between compete with the electrostatic latent image and the toner particles. Although in the above case the image density can be improved by increasing the toner concentration of the developer mixture, one encounters an undesirable one high background toner deposition as well as increased toner impact and agglomeration when the developer mix Contains too much toner. The initial electrostatographic charge of the plate can also be increased in order to increase the density of the deposited To improve powder images, but the plate charge would usually have to be too high for the electroscopic Powder is pulled away from the carrier particles. However, there are no excessively high electrostatographic plate charges only because of the high energy consumption needed to maintain it The electrostatographic plate required at high potentials is undesirable, but also because that. high potential causes the carrier particles to adhere to the surface of the electrostatographic plate rather than that they merely roll over the surface of the electrostatographic plate. A pressure extinction and a massive one Carrier particles are often transferred when carrier

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particles on reusable electrostatographic imaging surfaces be liable. Massive carrier transmission problems are particularly acute when the developer is in fixed-area covering machines used where excessive amounts of toner particles are removed from carrier particles, thereby leaving many carrier particles essentially stripped of toner particles. It also promotes adherence of the carrier particles on reusable electrostatographic imaging surfaces, the formation of undesirable Scratches on surfaces during image transfer and surface cleaning operations.

It will therefore be seen that many materials which otherwise have suitable properties for use as carrier particles are not suitable because they have either too high or too low a triboelectric value. Farther Uniform triboelectric surface properties can be difficult to obtain from many carrier surfaces using mass production techniques. In some cases it is it almost impossible to get quality images in high speed automatic machines when using carrier that do not have uniform triboelectric properties. Although it is possible to see the triboelectric value of one to change the insulating carrier material by mixing the carrier material with another insulating material, which has a distant triboelectric value, relatively large amounts of additional material are required, to change the triboelectric value of the original carrier material. The addition of large quantities of the material to the original carrier material in order to change its triboelectric properties, requires a Major manufacturing operation and often undesirably changes the original physical properties

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of the carrier material. It is also very important to control the triboelectric properties of carrier surfaces, to adapt the use of desired toner compositions while the other desired physical Properties of the carrier are retained. The change in the triboelectric properties of a carrier a particularly useful technique is by applying a surface coating. With this technique it is not only possible control the triboelectric properties of a carrier made of materials with desired physical properties, but it is also possible to use materials that were previously unsuitable as a carrier. So z. B. a Carriers with desirable physical properties other than hardness can be coated with a material that possesses the desired hardness and other physical properties, making the resulting product better as a carrier becomes suitable. However, as most of the carrier coating materials are inadequate in one or more of the above areas, there is a continuing need for improved electrostatographic carrier and developer mixtures and methods for their preparation.

It will also be seen that, as with other development techniques the toner is subjected to severe mechanical abrasion which tends to make the particles undesirable Break up fine dust particles. The formation of pollutants is slowed down if the toner is a tough high molecular weight Contains resin that is able to withstand the shear and impact forces that the toner creates in the machine learns. Unfortunately, however, many high molecular weight materials cannot be used in high-speed machines because they cannot be quickly fixed during the powder image heat-setting step. On the other hand are

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low molecular weight resins which can be easily heat melted at relatively low temperatures, usually undesirable, because these materials tend to form thick films on reusable photoconductor surfaces. These films tend to cause image degradation and they add to the maintenance downtime of the machine. Many low molecular weight resins decompose when used in high-speed copying and reproduction machines are exposed to melting conditionsa. In addition, there is that low molecular weight Resins tend to form sticky images on the copy sheet, which are easily soiled and often on other adjacent leaves are transferred. Furthermore, low molecular weight resins are often difficult or even impossible Can be reduced in size in conventional grinding devices. The toner materials must also be able to Charge of correct polarity when in frictional contact with the surface of substrate Cascade or batch development systems. Furthermore, many toners cannot be satisfactorily replaced by conventional ones electrostatographic development systems of reusable imaging surfaces in automatic copier and Reproduction machines are transferred. As most polymeric toner materials are based on one or more of the above have disadvantages, there is therefore a continuing need for improved toners and developers.

It is therefore an object of the invention to provide developer mixtures which overcome the above-mentioned disadvantages.

It is also an object of the invention to provide carriers and / or toner mixtures and a process for their production for To provide, through which the above-mentioned disadvantages can be overcome.

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It is another object of the invention to provide a method in order to change the triboelectric values of carrier and / or toner materials in a controllable manner, without that the other physical and chemical properties of the original carrier material are markedly changed.

It is a further object of this invention to provide manufacturing techniques for producing developer materials with finely adjusted to provide triboelectric properties.

It is another object of the invention to provide many polymeric materials, which have hitherto been unsuitable as carrier coating materials were to be rendered suitable for use as carrier coating materials and as toner materials.

It is a further object of this invention to provide developer materials with triboelectric properties, which are superior to the known carrier and toner materials.

Finally, it is another object of the invention to provide improved developer materials with better physical and chemical properties To provide properties than the known developer materials.

These goals are achieved according to the invention in such a way that one can control a chemical change of the triboelectric Makes charging potential of functional polymers that are used as clay egg »- and carrier materials. The controlled variation of the triboelectric behavior of functional polymers results in a measure to optimal triboelectronic responses to electrostatographic To obtain developer materials for specifically defined purposes. Thus, according to the invention

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monomeric and / or polymeric materials systematically chemically modified »to give structural effects, the relationships between the structure and the triboelectric properties among variously substituted aromatic parts result in »such as nitro aromatic compounds, halogen aromatic compounds, aromatic ethers and alkyl aromatics. These relationships have been shown to be extremely useful in the design of new carrier and toner materials are well suited. The invention controls the triboelectric charging properties of the toner carrier parts, thus optimal triboelectric relationships in the developer mixes received '.

It should be noted that no material is triboelectric Owns charge. Rather, the size of the triboelectric charge depends on both the toner and the carrier material away. Thus, a replacement of one of the components is possible while optimizing the triboelectric charging properties generally required to give the desired triboelectric response. That way will greater latitude available for specific electrostatographic applications. According to the invention it was found that by varying the degree of chemical modification of the polymeric materials used as toners or carrier materials used the triboelectric properties of developer materials in a continuous manner can be controlled. \

When electrostatographi see development of latent Selenium photoconductor images are generally polymers that tend to have a relatively high positive charge, suitable for use as carrier coating materials. Polymers that tend to have a relatively high negative charge ingested, * are generally for use as

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Suitable for toner materials. In the case of electrostatography Development of other latent photoconductor images, e.g. B. of zinc oxide, phthalocyanine, cadmium sulfide, polyvinylcarbazoltrinitrofluorenone the reverse is true with respect to the properties of the carriers and toners. According to the invention now the triboelectric properties of developer materials in relation to their structural composition brought and thus controlled in a predictable manner. Because the distance between a given toner-carrier pair is on the triboelectric charge scale, the triboelectric charge determined between them, the relative positions determine the sign of the triboelectric charge. Those materials those that are low on the scale prefer to take on a positive charge and those materials that are on the Standing high on the scale prefer to take on a negative charge. Suitable toner-carrier pairs can be based on their triboelectric charge relationship can be selected to meet an acceptable requirement in terms of triboelectric Charge range for a given developer housing of the electrostatographic machine to do enough.

It has been shown that the triboelectric behavior is a function of the molecular structure which is now controlled and progressive modification of the triboelectric charging properties of developer mixtures so that optimal triboelectric charging properties between toner and carrier pairs can be obtained. Thus, according to the Invention the adjustment of the triboelectric charging properties of the electrostatographic developer materials can not be done in a stepwise manner, but can be achieved in a continuous manner, thereby providing a high Degree of fine tuning of the triboelectric properties of the developer materials is obtained.

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According to the invention, the triboelektrisehen charge characteristics of monomeric and polymeric compounds can be of the monomers are modified vma polymer through a "systematic chemical alteration of the aromatic moieties. Such a modification of the aromatic functionality can be achieved by known methods, eg., By halogenation, by Itasetzung of the aromatic polymer with elemental bromine, by alkylation or acylation according to the well-known Friedel-Crafts reaction with alkyl halides and Lewis acids or by nitration using nitric acid / sulfuric acid, special reagents such as cupric nitrate / acetic anhydride Polymers cannot always be brought to completion and side reactions often occur.

For example, it is found under certain nitration conditions It has been found that nitration is accompanied by oxidation, as evidenced by the presence of hydroxyl parts indicates. However, such side reactions can be reproduced fairly well and thus their influence on the triboelectric behavior of the resulting species can be reproduced with a high degree of precision. The through this Functional groups introduced to processes can still be used for various purposes, including a covalent bonding to dyes with functional groups, the addition of modifiers for the triboelectric Charge and attachment to substrates. The extensions for these uses are numerous and obvious to those skilled in the art.

Thus, according to the invention there is a method of manufacture of developer materials with controlled triboelectric properties for electrostatographic applications Provided «The principle according to the invention can be used with any monomers, polymers or copolymers that

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contain an aromatic functionality. The invention therefore enables the controllable change the triboelectric properties of materials with optimal physical properties to develop developer materials to provide (both toner and carrier) which have improved triboelectric properties for electrostatographic Have uses while maintaining their desirable physical properties.

It has been found that the triboelectric charge assumed by nitrated aromatics is more negative than that of a non-nitrided polymer material. It should also be noted that standard nitriding is usually results in a polymer that does not charge as negatively as a nitrided / oxidized material, even if the degree of nitration is comparable. It can thus be seen that the oxidation also increases the extent of the negative triboelectric charging property of polymeric materials increased. So is z. B. found that nitration of a styrene-n-butyl methacrylate copolymer material a polymer results whose triboelectric charge potential is its use as a carrier material with various toners above the triboelectric series including those commonly known as Reverse toners are called enables.

The degree of nitration or nitration-oxidation can be controlled either stoichiometrically or kinetically so that optimal physical and triboelectric properties can be obtained. Typically, all can be appropriate Nitration processes are used to reduce the chemical to provide modified support materials of the invention. Typical nitration processes include e.g. B. the use a mild, non-hydrolytic process using reagents such as cupric nitrate and acetic acid

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anhydrides, for example, if the polymers are under usual Nitrienmgsbedingungen are hydrolytically unstable. When using of copper (II) nitrate / Bssigsäxireanhyärid is the Nitration accompanied by oxidation. Thus, a highly functional material with functional groups can be used in one stage can be obtained. The use of such functional parts enables the further addition to the polymer of modifiers for the triboelectric charge.

The "invention therefore provides for desired electrostatographic Properties made the polymer material own and there is no need to depend on external additives. The predictability and control of triboelectric properties for imaging materials is now made possible by the invention made.

It has also been found that the introduction of other electron withdrawing groups e.g. B. of halogen, chloromethyl or acyl in the aromatic parts of the polymers e.g. B. of polystyrene and styrene-n-butyl methacrylate copolymers a change causes their tendency for negative triboelectric charging. Conversely, an introduction of Electron donating parts such as methyl, t-butyl, alkoxy and alkylthio have a tendency to be positively charged. Consequently can modify the triboelectric properties of polymers containing aromatic parts selectively through a chemical Modification can be changed. The chemical modification involves the addition of functionality to the aromatic Core. It is also possible to reduce the tendency of the aromatic polymers towards triboelectric charging by means of multistage chemical modifications, but the preferred approximations are one-step transformations, e.g. B. the Nitration, hydroxylation, halogenation, sulfonation, alkylation and acylation. An alternative to the reactions

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One of the most popular polymers in many fields of application is the polymerization of aromatic monomers that have the desired substituents wear. The techniques mentioned can be applied to many polymers, e.g. B. to the above-described, and their derivatives, as well as polyesters, styrene-alkyl methacrylates, styrene-alkyl acrylates, terephthalate polyesters and phenol-formaldehyde polymers.

The chemical modification of such materials enables the modification of materials with optical physical ones Properties in such a way that their triboelectrics are seen Properties for electrostatographic purposes can be improved. The invention can therefore be used as a guideline for the preparation of developer mixtures with finely adjusted triboelectric Charge properties are used and the capacity Continuous control of such properties by varying the extent of the reaction can be used for this Purposes.

With regard to the triboelectric response, it should be noted that materials, e.g. B. obtained by nitration of styrene methacrylate copolymers, in particular carriers or carrier coatings which are excellent with regard to their crosslinkability form. This is how z. B. by using such materials now satisfactorily with the toner conventional carriers have shown an unacceptable triboelectric response. Thus coating results in the Carrier particles e.g. B. of metal beads with suitably functionalized polymers that contain a crosslinking agent, Carrier materials in which, in addition to the improved toughness, the triboelectric properties are continuous can be varied by controlling the amount of crosslinking agent in the coating composition.

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The supply of metallic carriers with functionalized polymers and the crosslinking of these materials, e.g. B. through reaction of the pendant hydroxyl groups with a crosslinking agent such as silicyanate, results in continuous control - the same triboelectric properties of the coated supports * ^ Ss has been straightened out "when the degree of conversion mmiw & t, the capacity for the positive triboelectric charge decreases." Furthermore, the degree of conversion can be controlled stoichiometrically. Furthermore, different types of crosslinking agents which are inactive towards hydroxyl groups can be used. Finally, different amine- or sulfhydroxyl-containing polymers can be used, since they show similar effects.

Any carrier material or carrier coating material can be chemically modified according to the invention in order to control the triboelectric properties. Typical materials are e.g. styrene-acrylate-organosilicon-terpolymers, Polyvinyls and polyvinylidenes, such as polystyrene, polymethylstyrene, polyesters such as polyethylene terephthalate, Polyurethanes, polysulphides, polycarbonates, thermosetting resins including phenolic resins such as phenol-formaldehyde, phenol furfural taaä resorcinol formaldehyde, amino resins such as melamine formaldehyde, Polyester resins, epoxy resins and the like. Many of the above and other typical carrier coating materials are [ z. For example, U.S. Patent 2,618,551, U.S. Patent 3,526,533, U.S. Patent 3,535,835, and U.S. Patent 3,658,500.

Any suitable thicknesses for the electrostatographic support can be used in excess. However, a carrier coating of at least a sufficient thickness that a thin, continuous wim is formed on the carrier particle is preferred because the carrier coating is then of sufficient thickness to resist abrasion and to prevent pinhole formation

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is prevented, which adversely affect the triboelectric properties of the coated carrier particles. In general, for cascade and magnetic brush development, the carrier coating can be from about 0.1 to about 10.0 weight percent based on the weight of the coated carrier particles. . The carrier coating should preferably amount to about 0.1 to about 1.0% by weight, based on the weight of the coated carrier particles, since in this case maximum durability, maximum toner impact resistance and copy quality are achieved. In order to achieve a further variation of the properties of the coated carrier particles, known additives such as plasticizers, reactive and non-reactive polymers, dyes, pigments, wetting agents and mixtures thereof can be mixed with the coating materials. A finished coated carrier particle with an average diameter between about 50 "ax and about 1000 λχ is preferred in cascade systems because the carrier particle then has sufficient density and inertia to prevent adhesion to the electrostatic image during the cascade development process the electrostatographic drum is undesirable because deep scratches can form on the drum surface during the image transfer and drum cleaning stage, especially when cleaning with a fabric cleaner such as that disclosed in US -PS 3 186 838 is carried out.

Any suitable known coated or uncoated material can be used as the core material for the beads according to the invention electrostatographic carrier bead materials can be used. Typical carrier core materials are e.g. B. sodium chloride, Aramonium chloride, aluminum potassium chloride, Rochelle salt, sodium nitrate, potassium chlorate, zirconium granules, silicon granules, Methyl methacrylate, glass, silicon dioxide, flint,

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Iron, steel, ferrite, nickel, carborundum, and mixtures thereof.

Typical resins which can be modified according to the invention for use as a toner are e.g. B. those with a melting point of at least about 43i3 ° C (110 ⁰ F), such as. B. Vinyl resins including homopolymers or copolymers of two or more vinyl monomers. Typical monomer units that can be used to form vinyl polymers are e.g. B. styrene, p-chlorostyrene, vinyl naphthalene, ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene and the like., Vinyl esters such as vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and the like., Esters of aliphatic Methylene monocarboxylic acids, such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, doäecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl a-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, such as vinyl, methacrylate, vinyl nitrile and the like. Vinyl isobutyl ether, vinyl ethyl ether and the like, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and the like, vinylidene halides such as vinylidene chloride, vinylidene chlorofluoride and the like, and N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindyrole, and N-vinylindyrole, ., as well as mixtures thereof. In general, suitable vinyl resins used in the toner have a weight average molecular weight between about 3,000 and about 500,000. The resins can be formed by polymerizing mixtures of two or more of these unsaturated monomers. The term "addition polymerization" is intended to include known polymerization techniques, ζ, B, free radicals, anionic and cationic polymerization processes.

The combination of the resin component and the colorant, regardless of whether the resin component is a homopolymer, copolymer or a mixture should be a blocking temperature

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of at least about 43.3 ° C and a viscosity of less than about 2.5 10 at temperatures of up to about 232 ° C. When the toner is characterized by a blocking temperature of less than about 43.3 ⁰ C, the toner particles tend while agglomerating storage and operation of the machine and also to form on the surface of the reusable photoreceptors unwanted metastases, the image quality of the adversely affect.

Any pigment or dye can be used as the colorant for the toner particles. Toner colorants are known. Examples are carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, Malachite Green Oxalate, Lamp Black, Rose Bengal, and mixtures thereof. The pigment bzv /. the dye should be in that Toner must be present in an amount sufficient to be highly colored to be deposited on the recording part clearly visible image generated. If z. B. conventional electrostatographic copies of typewriter documents desired the toner can be a black pigment such as carbon black or a black dye such as National's Amaplast Black Dye Aniline Products, Inc. Generally, the pigment is used in an amount of from about 1 to about 20% by weight based on the total weight of the colored toner. If the toner colorant used is a dye then can significantly smaller amounts of the dye can be used. However, since a number of the above pigments are used in electrostatographic toner compositions both glass transition and melting temperatures of the invention May affect toner compositions, their concentration should preferably not exceed about 10 wt .- # of the colored toner.

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The toner mixtures according to the invention can be any of the known ones Tonennisch- and Verahlungtechniken are produced. So z. B. the ingredients are thoroughly mixed by blending, mixing and grinding the components, whereupon the resulting mixture can be micropulverized. Another known technique for forming the toner particles is spray drying a ball milled toner mixture containing a colorant, a resin and a solvent.

If the toner materials of the present invention are to be used in a cascade development process, the toner should have an average particle size of less than about 30 / rev, preferably from about 4 to about 20 ai , for optimum results. For use in powder cloud development methods, particle diameters slightly less than 1 e are preferred.

In the production of the developer materials according to the invention, either a toner material with specially designed Properties, a substrate with specially designed properties, or both can be used. If only a carrier is used according to the invention, then any known clay materials can be used. Typical Toner materials are e.g. B. rubber copal, rubber sandarac, Colophony, Ctomarcsiindenharze, Asphalt, Gilsonite, Phenolformaldehyde resin, Rosin-modified phenol-formaldehyde resins, methacrylic resins, polystyrene resins, polypropylene resins, epoxy resins, Polyethylene resins, polyester resins and mixtures thereof. The respective The toner that is used naturally depends on the distance between the toner particles and the coated carrier in the tribo- • electrical row and the distance should be sufficient, causing the toner particles to adhere electrostatically to the carrier surface. Electroscopic toner compositions are z. See, for example, U.S. Patent 2,659,670, U.S. Patent No. 2,659,670

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2,753,308, U.S. Patent 3,079,342, U.S. Reissue Patent 25,136, and U.S. Patent 2,788,288. The toners generally have an average particle diameter between about 1 and 30 Ai.

If only one toner according to the invention is used, then any suitable coated or uncoated carrier material known in the art can be used in combination therewith. The carrier particles comprise any suitable solid material provided that the carrier particles assume a charge of an opposite polarity to that of the toner particles when brought into close contact with the toner particles such that the toner particles adhere to and surround the carrier particles. If positive reproduction of the electrostatic images is desired, then the carrier particles are selected so that the toner particles receive a charge which is opposite in polarity to that of the electrostatic image. Alternatively, when a reverse reproduction of the electrostatic image is desired, the T _r äger, is selected so that the toner particles receive a charge having the same polarity as the electrostatic image. Thus, the materials for the carrier particles are selected according to their triboelectric properties with respect to the electroscopic toner so that when they are mixed or brought into mutual contact, one component of the developer is positively charged when the other component below the first component in the triboelectric Series stands and is negatively charged when the other component is above the first component in the triboelectric series. By suitable selection of the carrier materials according to their triboelectric effects, the polarities of their charge, when they are mixed, are such that the electroscopic toner particles adhere and are coated on the surfaces of the carrier particles and that they are also attached to the part of the electro-

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static image-bearing surface, which has a greater attraction for the foner than for the carrier particles. Typical Carriers are e.g. B. Sodium Chloride, Ammonium Chloride, Aluminum Potassium Chloride, Rochelle Salt, Sodium Nitrate, Aluminum Nitrate, Potassium chlorate, zirconium granules, silicon granules, methyl methacrylate, Glass, silicon dioxide, nickel, steel, iron ferrites and the like. The carriers can be with or without one Coating can be used. Many "of the foregoing and other typical carriers are described, for example, in U.S. Patents 2,638,416. And in U.S. Pat U.S. Patent 2,658,552. A diameter of the finished coated Carrier particles of between about 50 / u and about 1000 / U is preferred because the carrier particles have a sufficient Density and inertia mean that they adhere to the electrostatic images during the cascade development process is avoided. Adhesion of the carrier beads to the electrostatographic drums is due to the formation of deep holes Surface scratches during the image transfer and drum cleaning stages are undesirable, especially then applies when cleaning is carried out with a tissue cleaner, such as that used by e.g. As described in U.S. Patent 3,186,838 will. Pressure can also be extinguished if the carrier beads are seen on the electrostatographic imaging surfaces be liable. Generally speaking, satisfactory results are obtained using about 1 part of toner with about 10-200 Parts by weight carrier is used.

The developer mixtures according to the invention can be used for development from electrostatic latent images to any suitable electrostatic latent image load-bearing surfaces are used including conventional ones photoconductive surfaces. Known photoconductive materials are e.g. B. vitreous selenium, organic or inorganic Photoconductors embedded in a non-photoconductive matrix, organic or inorganic photoconductors, which are embedded in a photoconductive matrix, and

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like that. Photoconductive materials are ζ. See, for example, U.S. Patents 2,903,542, 2,970,906, 3,121,006, 3,121,007 and 3,151 described.

In the following examples, the preparation of the invention Developer materials and their use to develop electrostatic latent images. Parts and percentages are by weight.

The following are the relative triboelectric values generated by the contact of the carrier beads with the toner particles are measured by means of a cascade device. The device includes a grounded metal plate that is connected to a arbitrary, but constant angle of elevation relative to the horizontal, e.g. B. 30 °, is provided. At the bottom of the leaning A shell is arranged on the 1st level. The shell is not attached to the inclined plane and in this way is not earthed. But it is connected to an electrometer. The material to be tested is stacked on a metal plate or made of aluminum and this is added to the inclined plane. The beads of the desired substrate will pull down the film and cascaded the electrometer cup where the charge generated by the beads is measured. From this The charge: mass ratio is calculated from the quantity and weight of the pearls. This amount is a direct measure of that triboelectric charging capacity of the polymer film. The measurement takes place at constant relative humidity and Temperature. Since the triboelectric measurements are relative, the measurements should be made under essentially for comparison purposes carried out under identical conditions.

Example I.

The relationship of the molecular structure with the triboelectric

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Behavior in. polymeric systems is of practical importance when considering ionic candidates. this is hunted down, shown. A polymer system on a polystyrene base is used for this purpose. atif based on availability and simplicity, which is the general structure

-CH ₀ CH-

2 |

wherein X is H, tC ^ H ^, Br, CH ₂ Cl, NO ₂ and CH ^. This system was investigated *. Poly (p-nitrostyrene) in which X is NO «was synthesized from polystyrene by nitration. Poly (p-bromostyrene) where X = Br was made from polystyrene using bromine / thallium acetate. Poly (chloromethyl-tyrene) in which X = CH ₂ Cl was prepared by polymerizing the corresponding monomer. Finally wurder l% poly (p-ia <etliylstyrol), wherein X - is CH ^ from which PolystfjfSfspl, X ~ CH ₂ Cl formed by reductive dehalogenation with LithiuiSaluminiiisahydrid. Films of the polymers were cast on aluminum plates from a tetrahydrofuran solution. Only the poly (p-nitrostyrene) was poured from dimethylformamide. The films were dried in vacuo at about βfPc for about 15 hours and then transferred to an iron dry box maintained at zero relative humidity without exposure to humid air. Zinkträgerteilchen were transferred to Mtelioher manner for about 15 hours in vacuo at about 120 ⁰ C dried \ MSS. The triboelektrisehen Kaskadenmessunjpen were a M.lhöhe v <m is about 1 cm and a film length of about 22.9 cm durcfegeführt "The moisture was constant using an angle of about 30 °" using saturated salt solutions to successive ·

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Values increased. The films and support particles were equilibrated for all relative humidity conditions about 20 hours prior to the measurement of the triboelectric charge. The results show that as the electron withdrawing power of the substituent increases, there is a concomitant increase in the amount of negative charges that are formed on the film. In these examples, the electron withdrawal power of the substituents increases in the following order: t - C. Hq £ CH ₃ CH ^ CH ₂ CKBr <N0 ₂ . Although both carrier beads and films can be affected by moisture, the slope of a line for a given relative humidity is only a function of the material since the same carrier is used for each film. These results show a practical method for predicting the relative triboelectric behavior of polymers substituted in the aromatic moiety, e.g. B. the foreseeable increase in the negative charge properties of the polymer. While the triboelectric charging property of blends and copolymers is generally not linearly related to composition, it is a linear function of the extent of reaction for chemical modification, as shown in the table below.

Charge of the zinc carrier beads in X nano-coulombs / g at S3 % relative humidity

tC ₄ H ₉ + 0.13

CH ₃ + 0.19

H + 0.30

CH ₂ Cl + 0.70

Br +1.1

NO _n +4.7

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Example XI

To a LjJstmg of about 40 ml of concentrated nitric acid and about 40 ml of concentrated sulfuric acid 62 _# 5 (54% molar ratio 1.00?) Were added with stirring about Stvrol g-n-butyl methacrylate copolymer added at such a rate that the temperature * did not go beyond 30 ^° C. The mixture was allowed to stand for about 2 hours, then poured into water and filtered. The solid was washed with water, dissolved in tetrahydrofuran and reprecipitated by adding dropwise to water. The latter stage was repeated several times, after which the solid was dried in vacuo. Elemental analysis showed about 42% nitration of the available phenyl groups. Films were cast from the solution onto aluminum plates and dried thoroughly. 3tahlperl§ & roit 250 / U assumed a charge of +0.1 nano-coulomb / g each when they were cascaded down this film. The starting polymer caused these beads to be about -0.29 nano-coulombs / g. The nitration of the polymer therefore markedly increased the negative charge capacity.

example

To a mixture of about 14.7 g of styrene-n-butyl methacrylate copolymer. (Molar ratio 2.54: 1.00) in about 250 ml of acetic anhydride were about 53.0 g of Cu (NO ^) ₂ with stirring. 3HpO given at such a rate that the temperature did not exceed 70 ⁰ C. The mixture was then immediately heated on a steam bath and held at about 70 ^° C. for about 1.5 hours. The mixture was poured into water and filtered. The solid was washed with water and saturated sodium bicarbonate solution. It was dissolved in tetrahydrofuran and precipitated in an aqueous solution of ethylenedinitrilotetraacetic acid dina ^ rium salt. He was then successively from the tetrahydrofuran solution in aqueous sodium bicarbonate

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solution and precipitated several times in water. It was dried in a vacuum. Elemental analysis showed that about 42 % of the available phenyl groups had been nitrated while about 50 % of the phenyl groups had been oxidized. A film was cast from the solution onto an aluminum plate and dried thoroughly. Again, using this film, steel beads at 250 / u achieved a charge of about +2 nano-coulombs / g. Steel beads (250 / u) coated with chlorinated polypropylene, which is very close to the bottom of the triboelectric series and therefore, in most materials, causes the beads to take on a very large negative charge, e.g. B. with a starting styrene-n-butyl methacrylate copolymer (molar ratio 2.54: 1.00) of about -2.2 nano-coulombs / g assumed a charge of about +0.6 nano-coulombs / g. Thus the nitrided / oxidized polymer gives a significantly higher negative charge than the nitrided polymer and yet it is lower in the triboelectric series than chlorinated polypropylene.

Example IV

A mixture of about 35.5 g of styrene-n-butyl methacrylate copolymer (molar ratio 2.54: 1.00), about 9 _f 06 g of thallium acetate sesquihydrate and about 200 ml of carbon tetrachloride was stirred at about 25 ° C for about 18 hours. About 38.8 grams of bromine was then added over about 1.5 hours with stirring. The mixture was stirred for about 6 hours and then refluxed for about 12 hours. The mixture was then poured into methanol and filtered. The dried polymer was made from tetrahydrofuran sequentially with aqueous sodium bisulfite solution, twice from aqueous sodium bicarbonate solution, twice

; precipitated from water and three times from methanol and in vacuo dried. Elemental analysis showed the presence of About 1.1 bromine atoms per phenyl group. The

■ The solution is poured onto an aluminum plate and dried thoroughly.

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net. In the cascade device steel beads took 250 to u a charge of about +0.95 nano-cculomb / g with respect to this film. With the starting copolymer, steel beads with 250 / U assumed a charge of about ≈ 0.29 nano-coulombs / g. Thus, the bromination of the polymer increases the tendency for negative charging considerably.

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Claims (27)

Claims Τ) Electrostatographic developer mix for development of electrostatic latent images on a recording surface, characterized in that that it contains finely divided particles of a functional polymer, which by systematic chemical change of the aromatic constituents of the polymer by nitration / oxidation, halogenation, acylation or alkyl substitution has been obtained to produce toner particles with controlled triboelectric charging properties to obtain. 2. Electrostatographic de-curling mixture according to claim 1, characterized in that it contains toner particles and carrier particles, at least one of which contains a functional polymer obtained by systematic chemical modification of the aromatic constituents has been. 3. Electrostatographic developer mixture according to claim 2, characterized in that the toner mixture has finely divided particles with an average particle diameter of less than about 30 / u and a colorant and a functional polymer obtained by systematic chemical change of the aromatic Includes components of the polymer by nitration / oxidation, halogenation, acylation or alkyl substitution, to provide toner particles with controlled triboelectric charging properties. 609811/0834 4. Electrostatographic developer mixture according to claim 3, characterized in that the functional Ie polymer has the general structure X
where X is H, tC H, Br, CH ₂ Cl, NO ₂ or CH ₃ . 5 ,. An electrostatographic developer mixture according to claim 3, characterized in that the polymer contains a vinyl resin with a melting point of at least about 43.3 ⁰ C. That the toner particles have 6. An electrostatographic developer mixture according to claim 3, characterized in that a blocking temperature of at least about 43.3 ° C and a melt viscosity of less than about 2.5 χ 10 poise at temperatures of up to 232 ⁰ C. 7. Electrostatographic developer mixture according to claim 3, characterized in that the polymer comprises styrene alkyl methacrylate. 8. electrostatographic developer mixture according to claim 3, characterized in that the systematic chemical change of the polymer has been stoichiometrically controlled, so that closely controlled triboelectric Properties of the toner particles can be obtained. 609811/0834 9. Electrostatographic developer mixture according to claim 3, characterized in that the systematic chemical change of the polymer is kinetically controlled so that closely controlled triboelectric properties of the toner particles can be obtained. 10. Electrostatographic developer mixture according to claim 3, characterized in that the polymer contains electron withdrawing groups in the aromatic constituents. 11. Electrostatographic developer mixture according to claim 3, characterized in that the polymer is the product of the nitration-oxidation of the aromatic constituents. 12. Electrostatographic developer mixture according to claim 11, characterized in that the polymer Contains styrene-n-butyl methacrylate. 13. Electrostatographic developer mixture according to claim 2, characterized in that the carrier particles have an average particle diameter of between about 50 / U and about 1000 Ai and comprise a functional polymer which is produced by systematic chemical change of the aromatic components of the polymer by nitration / oxidation, halogenation , Acylation or alkyl substitution to obtain carrier particles with controlled triboelectric charging properties. 14. Electrostatographic developer mixture according to claim 13, characterized in that the carrier part 609811/0834 .- Chen contain a core material that is supported by an outer coating a 'functional polymer is surrounded. 15. Electrostatographic developer mixture according to claim 13, characterized by the fact that the aromatic Polymers the general structure -CH ₂ CH- where X is H, tC ^ H _q , Br, CH ₂ Cl, NO ₂ and CH ^, in order to obtain carrier particles with controlled triboelectric charging properties. 16. Electrostatographic developer mixture according to claim 14, characterized in that the outer coating about 0.1 to about 10.0 weight percent based on weight of the carrier parts. 17. Electrostatographic developer mixture according to claim 13, characterized in that the polymer comprises styrene alkyl methaorylate. 18. Electrostatographic developer mixture according to claim 13, ' characterized "that the systematic chemical change of the polymer stoichiometric has been controlled so that closely controlled triboelectric properties of the toner particles are obtained. 19. Electrostatographic developer mixture according to claim 13, characterized in that the systematic 60981 1/0834 see chemical change of the polymer kinetically controlled has been so that closely controlled triboelectric properties of the toner particles are obtained. 20. Electrostatographic developer mixture according to claim 13, characterized in that the polymer contains electron donating groups in the aromatic constituents. 21. Electrostatographic developer mixture according to claim 13, characterized in that the polymer is the product of the nitration-oxidation of the aromatic constituents. 22. Electrostatographic developer mixture according to claim 21, characterized in that the polymer Includes styrene-n-butyl methacrylate. 23. Electrostatographic developer mixture according to claim 15, characterized in that the polymer is crosslinked. 24. Electrostatographic developer mixture according to claim 14, characterized in that the core is metallic is. 25. The electrostatographic developer mixture according to claim 2, characterized in that the finely divided toner particles adhere electrostatically to the surface of the carrier particles, the toner particles having an average particle diameter of less than about 30 / U and the carrier particles having an average particle diameter of between 50 and 1000 / a have. 609811/0834 X- - 34 - 26 ElektÄ> statogrkpMsches Abbildimgsverfahren, characterized in that a elektrostatographißöhes imaging member with a Aufzeichnungsoberfläohe Yorsieiit, one DMSS on the Aufzeichmingsoberiläche an electrostatic latent image is formed, and by bringing the electrostatic latent image with a Entwicklenaischung in Berülirung containing finely divided toner particles, which adhere electrostatically to the surface of carrier particles iait an average particle diameter of between about 50 / U and about 1000 / u, wherein at least the toner particles or the carrier particles are a fractional polymer that is produced by systematic chemical change of the aromatic constituent of the polymer by nitration / oxidation , Halogenation, acylation or alkyl substitution, and where the polymer has the general structure -CH ₂ CH- wherein X is H, tC ^ Ho, Br, CH ₂ Cl, NO ₂ or CH ^, whereby at least a portion of the finely divided toner particles is attracted to and deposited on the recording surface in conformity with the electrostatic latent image. 27. Electrostatographic imaging method according to claim 26, characterized in that the toner particles have been made from des'functional polymers. 6Ί) 98 1 1/0834 Electrostatographic imaging method according to Claim 26, characterized in that the carrier particles are made from the functional polymer. 609811/0834