JPS5913023B2 - High surface area carrier material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates generally to electrostatographic imaging systems, and more particularly to improved developer materials and uses thereof.

The formation and development of images on the surface of photoconductive materials by electrostatic means is well known.

As taught in U.S. Pat. No. 2,297,691 to C.F. exposing the layer to a light and shadow image to dissipate the charge on the areas of the layer exposed to the light, and depositing a finely divided electroscopic material, referred to in the art as a "toner", onto the image. developing the electrostatic latent image produced by the process. This toner is attracted to the areas of the ten layers, which typically retain charge, thereby forming a toner image corresponding to the electrostatic latent image. This powder image can then be transferred to a support surface such as paper. The transferred image can then be permanently fixed to the support surface, for example by heat. Instead of uniformly charging a photoconductive layer and then exposing this layer to a light and shadow image, image configuration
A latent image may be formed by electrostatically charging this layer. If it is desired to omit the powder image transfer step, the powder image can be fixed to the photoconductive layer. Other suitable fusing means such as solvent or coating 20 treatments may be substituted for the heat fusing step described above. Many methods are known for applying electroscopic particles to an electrostatic latent image to be developed.

One development method is known as cascade'' development, as described in US Pat. No. 2,618,552 to E.N. Wise. In this method, a developer material containing relatively large carrier particles with fine toner particles electrostatically adhering to the surface of the carrier particles is transferred to and rolled over an electrostatic latent image bearing surface. Or cascaded. The composition of the toner particles is selected to have a triboelectric polarity opposite that of the carrier particles. To develop a negatively charged electrostatic latent image, an electroscopic powder and carrier combination should be selected in which the powder is triboelectrically positive with respect to the carrier. Conversely, to develop a positively charged electrostatic latent image, an electroscopic powder and carrier should be selected in which the powder is triboelectrically negative with respect to the carrier. The triboelectric relationship between the powder and the carrier depends on their relative position in the triboelectric train, where each material is positively charged when in contact with a lower material in the train and is charged with a positive charge when it comes into contact with a lower material in the train. These materials are arranged in such a way that when they come into contact, they are charged with a negative charge. As this mixture cascades or rolls across the image-bearing surface, toner particles are electrostatically deposited and fixed onto the charged portions of the latent image and are not deposited onto the uncharged or background portions of the image. Most of the toner particles accidentally deposited in the background are removed by the rolling carrier, apparently due to the greater electrostatic attraction between the toner and the carrier than between the toner and the discharged background. The carrier particles and unused toner particles are then recycled. This technique is very good for developing line copy images.
Cascade development is the most widely used commercial electrophotographic development technique. A general office copier incorporating this technology is described in US Pat. No. 7,309,943. Another technique for developing electrostatic images is the 6-magnetic brush method as described, for example, in US Pat. No. 2,874,063.

In this method, a developer material containing toner and magnetic carrier particles is held by a magnet. The magnetic field of this magnet causes alignment of the magnetic carriers in a brush-like arrangement. The magnetic brush 8 is brought into contact with the electrostatic latent image and the toner particles are drawn from the brush to the electrostatic image by electrostatic attraction.
6 Touchdown (TOuchd) as described in 47.
Many other methods are known for applying electrostatic particles to the electrostatic latent image to be developed, such as ``Olvn'' development. The above development methods, along with many variations, are described in various patents and publications. and is well known to those skilled in the art through the widespread availability and use of electrostatographic imaging equipment. Automatic electrostatographic equipment continuously processes images through a cycle of continuous operations including charging, exposing, developing, transferring, and cleaning. It is common to use an electrostatographic plate in the form of a rotating cylindrical drum, which is connected to a suitable source of high potential, as described by L.E. Wallcup, USA. It is normally charged with a corona of positive polarity by a corona generator of the type described in Patent No. 2,777,957.

After forming a powder image on the electrostatic latent image during the development step, the powder image is electrostatically transferred to the support surface by a corona generating device, such as the corona device described above. In automatic equipment using a rotating drum, the support surface to which the powder image is to be transferred is moved through the equipment at the same speed as the periphery of the drum and is moved onto the drum at a transfer position provided between the drum surface and the corona generator. Contact. Transfer is effected by a corona generating device which applies a static charge to attract the powder image from the drum to the surface of the support.

The polarity of the charge required to effect image transfer depends on the visible appearance of the original copy to the reproduction and the electroscopic properties of the developing material used to effect the development. For example, when a positive reproduction is made from a positive original, it is common to use a positively polarized corona to effect the transfer of the negatively charged toner image to the surface of the support. If a positive reproduction is desired from a negative original, a positively charged developer is driven by a charged area on the plate into a discharge area to form a positive image which can be transferred by a negatively polarized corona. It is common to use materials. In either case, residual powder images and sometimes carrier particles remain on the plate after transfer. Before this plate is reused for the next cycle, the remaining images and carrier particles, if any, need to be removed to prevent ghost images from forming in the next cycle. . In the positive-to-positive replication process described above, residual developer powder as well as any carrier particles present are fixed on the plate surface by a development that is not well understood but is believed to be caused by an electric charge. This charge is substantially neutralized by the corona generating device prior to contact of the remaining powder with the cleaning device. Neutralization of charge increases the cleaning efficiency of the cleaning device. Typical electrostatographic cleaning equipment is, for example, the W.P.
．． Graff,. Jr. et al. US Patent No. 3,186,838
It is a 6-web'' type cleaning device as described in .

In the Graff-Giunier et al. patent, removal of residual powder and carrier particles on the plate is accomplished by rubbing a web of fibrous material against the surface of the imaging plate.
These inexpensive and replaceable webs of fibrous material are forced and rubbed or wiped into contact with the imaging surface and are gradually advanced to provide a clean surface to the plate, thereby removing the material from the plate. Substantially complete removal of residual powder and carrier particles occurs. While generally capable of producing images of good quality, conventional development systems suffer from significant defects in certain areas.

In the reproduction of high-contrast copies such as letters, tracings, etc., their mutual electrification is mostly governed by the distance between their relative positions in the triboelectric train, so that
It is desirable to select electroscopic powders and carrier materials.
However, when the otherwise compatible electroscopic powder and carrier material are separated from each other in the triboelectric train by too large a distance, the image produced is very faint;
The reason is that the attraction force between the carrier and the toner particles is comparable to the attraction force between the electrostatic latent image and the toner particles. Although the image density described in the above text can be improved by increasing the toner concentration in the developer mixture, when the toner concentration in the developer mixture is excessive, undesirable high background toner deposits as well as Increased toner adhesion and agglomeration result. Although the initial electrophotographic plate charge can be increased to improve the density of the deposited powder image, this plate charge usually must be too high to attract the electroscopic powder from the carrier particles. Probably. Not only is an excessively high electrostatographic plate charge undesirable because of the high power consumption required to maintain the electrostatographic plate at a high potential, but the high potential also causes carrier particles to cross and separate from the electrostatographic plate surface. This is because it does not simply rotate, causing it to adhere to the electrostatographic plate surface. When carrier particles adhere to a reusable imaging surface, print defects and bulk carryover of carrier particles often occur. Bulk carrier carryover - The problem occurs when a developer is used in a real image area application machine where an excessive amount of toner particles are removed from the carrier particles, thereby leaving many carrier particles containing few toner particles. It gets serious. Additionally, the adhesion of reusable electrostatographic imaging surface hexalia particles promotes the formation of undesirable marks on the surface during image transfer and surface cleaning operations. It is therefore clear that many materials which otherwise have properties suitable for use as carrier particles are rendered unsuitable if they have unsatisfactory triboelectric properties. Furthermore, the uniform triboelectric surface properties of many carrier surfaces are difficult to obtain in mass production methods. When non-uniform triboelectric properties are used, good quality images are in some cases almost difficult to obtain with high speed automatic machines. Although it is possible to change the triboelectric value of an insulating carrier material by incorporating into the carrier material another insulating material that has a triboelectric value that differs significantly from that of the original carrier material, A relatively large amount of additional material is required to change the triboelectric value of the carrier material. The addition of large amounts of material to the original carrier material to alter its triboelectric properties requires extensive manufacturing operations and often undesirably alters the original physical properties of the carrier material. Additionally, it is highly desirable to adjust the triboelectric properties of the carrier surface to suit the desired toner composition use while preserving other desirable physical properties of the carrier. Modifying the triboelectric properties of the carrier by applying a surface coating thereon is a particularly desirable technique. With this technique, it is not only possible to adjust the triboelectric properties of a carrier made of materials with desired physical properties, but also to use materials that are not previously suitable as carriers. Thus, for example, a carrier having desired physical properties other than hardness may be coated with a material having desired hardness as well as other physical properties to make the resulting product more useful as a carrier. Thus, there is a continuing need for good electrostatographic carriers and improved methods for obtaining them. It is therefore an object of the present invention to provide a carrier manufacturing technique and resulting product which overcomes the deficiencies mentioned above. Another object of the invention is to provide a developer material with a longer developer life.

Another object of the present invention is to provide a developer material that exhibits improved triboelectric and mechanical properties useful in electrostatographic devices using magnetic brush development devices.

Yet another object of the present invention is to provide a developer material that is less likely to form a film on an electrostatographic recording surface.

Another object of the present invention is to provide a developer material that does not exhibit a tendency to adhere to background areas of an electrostatographic imaging surface.

A further object of the present invention is to render suitable many materials which have heretofore been unsuitable as carrier materials.

Yet another object of the present invention is to provide an improved developer material having physical and chemical properties superior to those of known developer materials.

The foregoing purposes and others generally speaking are at least about 1
This is achieved by providing an electrostatographic developer material comprising a classified carrier material having a specific surface area of 50 Cd/t.

More particularly, the improved developer materials of this invention provide satisfactory results when the carrier material has a specific surface area of at least about 150 d/i.

However, if the carrier material is at least about 165 d/r
It is preferable to have a specific surface area of 100 mL because developer life is improved to provide increased copy quality in developer materials in high speed electrophotographic reproduction equipment, while maintaining low background levels and solid area development. This is because the density is maintained. If the carrier material of the present invention is at least about 175 Crit/
Optimum results are obtained when the specific surface area is r. The area ratio of carrier to toner material in a high speed magnetic brush development system is such that during development of the electrostatic latent image, the area ratio of carrier to toner material is reduced during development of the electrostatic latent image into the background areas of the electrostatic latent image while maintaining a sufficient toner concentration to provide a satisfactory solids area density. It has been found that the ratio is such that the toner concentration cannot be reduced sufficiently to be able to provide a charging potential that minimizes the adhesion of the toner material.

This problem has been overcome by providing the carrier material of the present invention with minimal specific surface area. Thus, the present invention now allows the use of developer mixtures having lower toner concentrations per carrier surface area to provide higher net charge levels. In electrophotographic processes in which a carrier material is used to provide a triboelectric charge to the toner material by contact charge transfer, the area of the carrier triboelectric charging surface has been found to be of critical importance. It has been found that this carrier charging surface area is related to the amount of toner material that can be charged to a useful tribo potential or level for a given toner material. Therefore, in accordance with the present invention, it has been found that the triboelectric charging performance of a carrier material is surface area dependent, and therefore the present invention provides an optimal carrier for any given electrostatographic development system. It can be used to design materials. Further, the classified high surface area carrier materials of the present invention have a particle size distribution having a particle size volume distribution geometric standard deviation of about 1.3 or less and an average particle size of about 100 microns or less.

The term geometric standard deviation as used herein is defined as the deviation produced in a particle size analysis measured approximately as the ratio of the particle diameter larger than 84% of a sample to that of the particle diameter larger than that of 50% of the sample. Ru. This number represents the intermediate or average particle size distribution by weight or volume of the carrier particles and has an important influence on the copy quality obtained in electrophotographic development systems. Another measure of the geometric standard deviation of the classified carrier materials of the present invention is particle size analysis, which is approximately measured as the ratio of the particle diameter larger than 50% of a sample to that of the larger particle diameter of 16% of the sample. This is the deviation that occurred. The value of 50% represents a medium or average particle size by volume of the carrier particles and has important implications with respect to determining the useful life of the developer.

In both cases, the values obtained for volume average particle diameter and geometric standard deviation are determined by dimensional analysis performed by sieve analysis using all US standard sieves from 325 to 70 mesh. It has been found that the classified carrier materials of the present invention provide satisfactory results when the particle size volume distribution geometric standard deviation is less than about 1.3 and the volume average particle diameter is less than about 100 microns.
Improved results are obtained and are preferred when the particle size volume distribution geometric standard deviation is less than or equal to about 1.2 and the volume average particle diameter is less than or equal to about 90 microns. The volume distribution geometric standard deviation of the classified carrier material of the present invention is about 1
．． 15 and the volume average particle diameter is about 85 microns or less. Any suitable particle classification method may be used to obtain the high surface area carrier materials of the present invention.

Typical particle classification methods include air classification, screening, cyclone separation, hydration, centrifugation, and combinations thereof. A preferred method of obtaining the high surface area carrier materials of the present invention is by screening. Any suitably coated or uncoated electrophotographic carrier bead material can be used as the high surface area carrier material of the present invention. Typical cascade development carriers include sodium chloride, ammonium chloride, potassium aluminum chloride, Rothsiel's salt, sodium nitrate, aluminum nitrate, potassium chlorate, particulate zircon, particulate silicon, methyl methacrylate, glass and silicon dioxide. Typical magnetic brush development carriers include nickel, steel, iron, ferrite, and the like. This carrier can be used with or without a coating. Many of these and other representative carriers include US Pat. No. 2,638,416 to L.E. Walkup et al. and E.N.
Wise) in US Pat. No. 2,618,552.
A final coated carrier particle diameter of about 30 to about 1000 microns is preferred because the carrier particles then have sufficient density and inertia to prevent adhesion to the static image during the cascade development process. For magnetic brush development, the carrier particles generally range from about 30 to about 250
It has an average diameter of microns. Generally speaking, satisfactory results are obtained when about 1 part toner is used with about 10 to 200 parts by weight of carrier. The high surface area carrier materials of the present invention may be coated with any suitable coating material.

Typical electrophotographic carrier particle coating materials include vinyl chloride monoacetate copolymers, styrene-acrylate organosilicon terpolymers, natural resins such as Kaochyuk, Korohovny, copal, Damar, Dragon's Plat, Jarap, Strax; polyolefins. Thermoplastic resins containing, such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polyvinyl and polyvinylidene, such as polystyrene, polymethylstyrene, polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polychlorinated vinyl, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone; fluorocarbons such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride: and polychlorotrifluoroethylene;
Polyamides, such as polycaprolactam and polyhexamethylene adipamide polyesters, such as polyethylene terephthalate; polyurethanes; polysulfides,
Thermosetting resins, including polycarbonate triphenolic resins, such as phenol-formaldehyde, phenol-furfural and resorcinol formaldehyde, lyamino resins, such as urea-formaldehyde and melamine formaldehyde; polyester resins: epoxy resins, etc. Many of these and other representative carrier coating materials are disclosed in L. I. Walkap's U.S. Patent No. 261,855.
1; B.B. Jaclcn
U.S. Patent No. 3,526,533: and R.J. Hagenbach.
et al., U.S. Pat. Nos. 3,533,835 and 3,658,500. Any suitable electrostatographic carrier coating thickness may be used when the high surface area carrier materials of the present invention are coated.

However, carrier coatings that are at least thick enough to form a thin continuous film on the carrier particle soil are preferred because the carrier coating then resists wear and adversely affects the triboelectric properties of the coated carrier particles. This is because the thickness is sufficient to prevent pinholes. Generally, for cascade and magnetic brush development, the carrier coating may contain from about 0.1 to about 10.0 weight percent, based on the weight of the coated carrier particles. Preferably, the carrier coating should contain from about 0.3 to about 1.5 weight percent based on the weight of the coated carrier particles for maximum durability, toner adhesion (I
This is because resistance and copy quality can be obtained. In order to obtain further variation in the properties of the coated composite carrier particles, well-known additives such as plasticizers, reactive and non-reactive polymers, dyes, pigments, wetting agents and mixtures thereof can be mixed with the coating material. . When coated with the high surface area carrier material of the present invention, the carrier coating composition can be applied to the carrier core by any conventional method, such as spraying, dipping, fluid bed coating, rolling, brushing, and the like.

The coating composition can be applied as a powder, dispersion, solution, emulsion or hotmelt. When applied as a solution, any suitable solvent may be used. Solvents with relatively low boiling points are preferred because less energy and time are required to remove the solvent following application of the coating to the carrier core. If desired, the coating may include monomers that are polymerized in situ at the surface of the core or plastisols that are gelled in situ to a non-flowing state on the surface of the core. Surprisingly, for certain poor coating methods, the carrier core material with the specific surface area chosen in this invention can yield an increased effective area, i.e., triboelectrically charged coating area per unit weight. found. Thus, increased carrier active area increases the net toner material tribocharge level for a constant toner concentration by weight in the developer mixture. Therefore, the toner concentration is minimal to provide solid area coverage, and high enough to minimize toner deposition in the background areas of the developed electrostatic latent image generated from toner particles with low or weak triboelectric charges. If it is desired to operate an electrostatographic development system at toner concentrations, these objectives can be achieved by using the high surface area carrier materials of the present invention. In accordance with the present invention, the above objectives are achieved by operating at reduced toner concentrations providing lower background deposits and allowing longer developer life. Any suitable colored or dyed electroscopic toner material may be used with the high surface carrier of the present invention.

Typical toner materials are: Sandaruck rubber, rosin, coumaron indene resin, asphaltum, gilsonite,
Phenol formaldehyde resin, methacrylic acid, polystyrene resin, polypropylene resin, epoxy resin,
Including polyethylene resins and mixtures thereof. The particular toner material to be used will depend on the separation of the toner particles from the high surface area carrier beads in the triboelectric train. Among the patents describing electroscopic toner compositions are Copley (COp);
ley) U.S. Patent No. 2,659,670; Landrigan (
Landrigan) U.S. Patent 7F62753308
; Insalco (InsalcO) U.S. Patent No. 3079
342; Carlson (Carl8On) U.S. Patent Re
issue waterfall 25136 and line blank (Rhei
nfr-) et al./F62788288.
These toners generally have an average particle diameter of about 1 to about 30 microns. Any suitable toner concentration may be used with the high surface area carrier of the present invention.

Typical toner concentrations for cascade and magnetic brush development systems are about 1 with about 10 to about 400 parts by weight carrier.
Contains some toner. Any suitable colorant, such as a pigment or dye, may be used to color the toner particles.

Toner colorants are well known and include, for example, carbon black, diglosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, quinoline yellow, methylene blue chloride, monastral blue, malachite green ozalate, Includes lamp black, rose bengal, Monastral red, stamp black BMl and mixtures thereof. The pigment or dye should be present in the toner in an amount sufficient to render it highly pigmented so that it forms a clearly visible image on the recording member. Preferably, the pigment is about 3 to about 2, based on the total weight of the pigmented toner.
It is used in an amount of 0% by weight because very good quality images are obtained. If the toner colorant used is a dye, substantially less colorant may be used. Any suitable organic or inorganic photoconductive material may be used as the recording surface with the high surface area carriers of the present invention.

Typical inorganic photoconductive materials are: sulfur, selenium, zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium strontium sulfide, cadmium sulfide, mercury iodide, mercury oxide, Includes mercury sulfide, indium trisulfide, gallium selenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfo-selenide, and mixtures thereof. Typical organic photoconductors are: quinacridone pigments, phthalocyanine pigments, triphenylamine, 2.
4-Bix (4,4'-diphenylaminophenol)-1,3,4-oxadiazole, N-isopropylcarbazole, triphenylpyrrole, 4●5-diphenylimidazolidinone, 4,5-diphenyl enyl-imidazolidinethione, 4,5-bitox-1(4'-aminophenyl)-imidazolidinone, 1,5-dicyanonaphthalene, 1,4-dicyanonaphthalene, aminohumerodinitrile, nitrophthalodinitrile, 1. 2.5.6-
Tetraazacyclooctatetraene (2, 4, 6, 8
), 2-mercaptobenzothiazole-2-phenyl-4-disphenyl oxazolone, 6-hydroxy-
2,3-di(p-methoxyphenyl)-benzofuran,
4-dimethylamino-benzylidene-benzhydrazide, 3-benzylidene-aminocarbazole, polyvinylcarbazole, (2-nitro-benzylidene)-p-bromoaniline, 2,4-diphenylquinazoline, 1,2
- Contains 4-triazine, 5-diphenyl-3-methyl-pyrazoline, 2-(45dimethylaminophenyl)-benzoxazole, 3-amine-carbazole and mixtures thereof. A typical patent describing photoconductive materials is Ullrich U.S. Patent No. 2803.
542, Bixby U.S. Patent Falls 297
0906, Middleton, US Patent Falls 3121006, Middleton US Patent Falls 3121
007 and COrrsin US Patent Falls 3
Contains 151982. The following examples further define, describe and compare methods of making the carrier materials of the present invention and utilizing them to develop electrostatic latent images.

Parts and percentages are by weight unless otherwise specified. EXAMPLE 1 About 1 toner material consisting of styrene-n-butyl methacrylate copolymer, polyvinyl butyral, and carbon black having an average particle size of about 10 to about 20 microns.
Styrene, methacrylate ester and styrene,
Carrier core material comprising about 0.6% by weight of nickel zinc ferrite coated with a carrier coating composition, based on the weight of the core material consisting of an organosilicon compound that is a terpolymer of butyl methacrylate and triethoxysilane. A control developer mixture is prepared by mixing 100 parts.

This coated ferrite carrier material has a particle size distribution as determined by sieve analysis as follows: Calculations determine that the coated ferrite carrier material has a specific surface area of approximately 128 (-!l/V).

The developer mixture is used to develop the selenium photoconductor recording surface carrying the electrostatic latent image by a "magnetic brush" development process. The magnetic field of the magnet causes alignment of the toner with the brush-like arrangement. The magnetic brush is directed to the electrostatic latent image bearing surface and development arrangement and the toner particles are drawn from the latent image hecaria particles by electrostatic attraction. The resulting copies of the standard image test pattern are of good quality up to about 25,000 copies, at which time the image background level is found to exceed the maximum value of 0.010 considered acceptable. EXAMPLES A developer mixture was prepared by mixing about 1 part of the toner material used in Example 1 with about 100 parts of the carrier material used in Example I, except that the carrier material was determined by sieve analysis to: Calculations show that the coated ferrite carrier material has a particle size distribution of approximately 1510
It is determined to have a specific surface area of fi1/7.

This developer is used to develop a selenium photoconductor recording surface bearing an electrostatic latent image under substantially the same conditions as in Example 1. Copies of the standard image test pattern results are found to be of good quality up to about 70,000 copies, at which time the image background level is found to be at a maximum value of approximately 0.010 that is considered acceptable. EXAMPLES A developer mixture was prepared by mixing about 1 part of the toner material used in the examples with about 100 parts of the carrier material used in Example 1, except that when the carrier material was measured it had the following particle size distribution: It is determined by calculation that the coated ferrite carrier material has a specific surface area of approximately 160 cr/l/F7.

This developer is used to develop a selenium photoconductor recording surface bearing a latent electrostatic image under substantially the same conditions as described in Example 1. The resulting copies of the standard image test pattern are found to be of good quality up to about 100,000 copies, and the image background level is found to be approximately at a maximum of 0.010 which is considered acceptable. EXAMPLES A developer mixture is prepared by mixing about 1 part of the toner material used in Example 1 and about 100 parts of the carrier material used in Example I, except that the carrier material was determined by sieve analysis and the following: Calculations show that the coated ferrite carrier material has a particle size distribution of approximately 168Cd/
It was determined to have a specific surface area of t.

This developer is used to develop a selenium photoconductor recording surface bearing an electrostatic latent image under substantially the same conditions as in Example 1.
The resulting copies of the standard image test pattern are found to be of good quality up to about 130,000, at which time the image background level is found to be approximately at the maximum value of 0.010 considered acceptable. Example V A developer mixture is prepared by mixing about 1 part of the toner material used in Example 1 with about 100 parts of the carrier material used in Example I, except that when the carrier material is determined by sieve analysis. It has the following particle size distribution: does not satisfy the semi-logarithm for standard deviation calculation.

Calculations show that the coated ferrite carrier material is approximately 1
77 (i/7). This developer was used to prepare a selenium photoconductor recording surface bearing an electrostatic latent image under conditions substantially identical to those in Example 1. Develop. The resulting pattern of the standard image test pattern was found to be of good quality up to about 150,000 copies, at which time the image background level was about 0.008 and still had a maximum value of 0.01 which was considered acceptable. The test is terminated at this copy count level. Thus, the high surface area carrier materials of the present invention provide improved copy quality experienced with reduced toner deposition in the background areas. It is characterized by providing

Furthermore, the high surface area carrier materials of the present invention are characterized by yielding improved mechanical performance with longer system life;
That is, these carrier materials provide substantially improved triboelectric charging properties of the developer mixture for a substantially longer period of time, thereby increasing the developer life of the developer mixture and improving retention between developer material changes. Decrease the time interval. Furthermore,
The high surface area carrier materials of the present invention are characterized as providing dense toner images and are particularly useful in magnetic brush development systems. Thus, by providing the developer materials of the present invention, substantial improvements in system life due to inherent developer life occur based on the classification and use of carrier materials with specific surface areas. Although specific materials and conditions are described in the foregoing examples of making and using the developer materials of this invention, these are intended merely as illustrations of the invention. These and other high surface area carrier materials, toner materials, substitutes and methods, such as those listed above, may be substituted for those of the examples with similar results. Other variations of this invention will occur to those skilled in the art upon reading this invention. These are included within the scope of the present invention. Next, aspects of the present invention and related matters will be listed.

(1) providing an electrostatographic imaging member having a recording surface, forming an electrostatic latent image in the soil of the recording surface, and having a specific surface area of at least about 150
．． fine toner particles that electrostatically adhere to the surface of a classified high surface area carrier material having a particle size volume distribution geometric standard deviation of 3 or less and a particle size distribution in which the carrier particles have an average particle diameter of about 100 microns or less; contacting said electrostatic latent image with a developer mixture containing said electrostatic latent image, thereby causing at least a portion of said fine toner particles to be wicked onto said recording surface in conformity with said electrostatic latent image; An electrostatographic imaging process characterized by the steps of depositing. (2
) said carrier material is at least about 165cr7L/9
The electrophotographic image forming method according to the above (1) having a specific surface area of .

(3) said carrier material is at least about 175 Cd/t;
The electrophotographic image forming method according to the above (1) having a specific surface area of .

(4) The electrostatographic imaging method according to (1) above, wherein said carrier material has a particle size volume distribution geometric standard deviation of about 1.2 or less and a volume average particle diameter of about 90 microns or less.

(5) The electrophotographic imaging method according to (1) above, wherein the carrier material has a volume distribution geometric standard deviation of about 1.15 or less and a volume average particle diameter of about 85 microns or less.

(6) An electrostatographic imaging method according to (1) above, wherein said carrier material is coated with a thin continuous film of coating material.

(7) The electrostatographic imaging method according to (6) above, wherein said coating material comprises from about 0.1 to about 10.0% by weight, based on the weight of the coated carrier particles.

(8) An electrostatographic imaging process according to paragraph 1) wherein said carrier material comprises a nickel-zinc ferrite coated with a thin continuous film of a coating composition comprising styrene, a methacrylate ester, and an organosilicon compound. (9
) A classified high surface area carrier material according to claims, wherein said carrier material has a specific surface area of at least about 1650 fL/t.

(to) said carrier material is at least about 175 CfL/
A classified high surface area carrier material according to the claims having a specific surface area of t.

A classified high surface area carrier material according to claims, wherein said carrier material has a particle size volume distribution geometric standard distribution of less than or equal to about 1.2 and a volume average particle diameter of less than or equal to about 90 microns.

1. A classified high surface area carrier material according to claim 1, wherein said carrier material has a volume distribution geometric standard deviation of less than or equal to about 1.15 and a volume average particle diameter of less than or equal to about 85 microns.

Classified high surface area carrier material according to the claims, wherein said carrier material is coated with a thin continuous film of coating material. 0.1 to about 10.
A classified high surface area carrier material according to the above-mentioned composition comprising 0% by weight.

αQ A classified high surface area carrier material according to claims wherein said carrier material comprises a nickel zinc ferrite coated with a thin continuous film of a coating composition comprising styrene, a methacrylate ester and an organosilicon compound.

Trout Specific surface area of at least about 150 Cf1vt, about 1.3
An electrostatic charge containing finely divided toner particles that adhere electrostatically to the surface of a classified high surface area carrier material having a particle size distribution with a particle size volume distribution geometric standard deviation of less than or equal to about 100 microns and a particle size distribution in which the carrier particles have an average particle diameter of less than or equal to about 100 microns. Photographic developer mixture. (a) The carrier material as described above is at least approximately 165 c.
I1L. The electrophotographic developer mixture according to (1) above, having a specific surface area of /y.

An electrophotographic developer mixture according to claim 1, wherein said carrier material has a specific surface area of at least about 175 d/f.

01 An electrostatographic developer composition according to the above, wherein the carrier material has a particle size volume distribution geometric standard deviation of about 1.2 or less and a volume average particle diameter of about 90 microns or less.

An electrostatographic developer mixture according to the present invention, wherein said carrier material has a volume distribution geometric standard deviation of about 1.15 or less and a volume average particle diameter of about 85 microns or less.

(to) An electrophotographic developer mixture according to the above, wherein the carrier material is coated with a thin continuous film of coating material.

C? ．． 1. An electrostatographic developer mixture according to the above, wherein said coating material comprises from about 0.1 to about 10.0% by weight, based on the weight of the coated carrier particles.

(23) An electrophotographic developer mixture according to the above, wherein said carrier material comprises a nickel zinc ferrite coated with a thin continuous film of a coating composition comprising styrene, a methacrylate ester and an organosilicon compound.

Claims (1)

[Claims] 1 Specific surface area of at least about 150 cm^2/g, about 1.
A classified high surface area carrier material comprising a carrier material having a particle size distribution geometric standard deviation of 3 or less and the carrier particles having an average particle diameter of about 100 microns or less.