GB2194069A - Negative-electrification finely-divided toner for use in production of erasable electrophotographic image - Google Patents

Abstract

A negatively-electrification toner for use in the production of electrophotographic image erasable by a rubber eraser consists of (a) 100 weight parts of a binder formed from melting (i) one or more species selected from lower adhesive force solid lower molecular weight polymer species and (ii) a higher melting point wax or waxy compound group species, and (b) 1 to 20 weight parts of colourant. The toner particles may be used in conjunction with carrier particles and finely divided silica particles.

Description

SPECIFICATION Negative-electrification finely-divided toner for use in production of erasable electrophotographic image The present invention relates to negative-electrification finely-divided toner for use in the formation of erasable image via the electrophotographic development. Particularly, it relates to the toner that is used to produce an electrophotographic image or pattern on a film base, or tracing (drawing) paper or paper having non-permeable surface (e.g. coat paper, art paper and the like) even upon the complete development and fixing a latent image, the fixed pattern that can be easily eliminated or reduced only by using a rubber eraser or the like.

The electrophotography is disclosed in US patent No. 2297691 and Japanese Patent Publication Nos. 42-23910 and 43-24748. There have been known some electrostatic recording techniques: one of which includes a cascade method wherein the the positive electrified electrostatic latent image is developed by dispersing the mixture of toner powder and glass beads and some additive(s) to a latent image on a photosensitive sheet; and another of which is a magnet brush developing method wherein a photosensitive body is rubbed with the mixture of toner and magnetic iron powder held on a magnet in the form of brush so as to develop a positive electrified electrostatic latent image. In those methods, the toner developed image is transferred onto paper, sheet or film base, and then fixed thereon by applying thermal treatment or solvent vapor so as to melt or dissolve the toner transferred thereon.

In the prior art, the fixed pattern on a sheet or paper can not be erased nor eliminatd by any touch with things such as operator's hand or any pile of sheets, and therefore, the prior art toner has stronger adhesive force to a paper sheet, and higher coating strength of the fixed resultant image coat so that the coating of the fixed image is strong enough against the abovementioned rubbing action such as operator's touch or sheet mutual rubbing. Therefore, essentially, the prior art fixed image can not be easily erased by an ordinary rubber eraser.

As mentioned above, the objective of the prior art duplication technique is to produce strong and durable duplicated and fixed image or pattern on the paper sheet or film base. However, there is some need of partial correction or complete elimination of a fixed image patterned after an original for further duplication. In other words, it can be desired in some cases to correct partially the fixed copy image. It is important and necessary that the second original can and should be easily produced by eliminating or removing the undesirable image or portion(s) of a fixed copy of an original, and/or further adding the necessary pattern or figure to the partially eliminated copy.

Hitherto, for this objectives, the solvent has been used to remove or eliminate partially or completely a fixed copy image from the surface of the paper sheet, because an ordinary rubber eraser can not easily eliminate nor remove a fixed image as described before. When a solvent is applied to the fixed image on an ordinary paper sheet, however, the pigment or colorant contained in the toner used in the fixed image is possibly dissolved to penetrate into the paper, resulting in some blot that can hardly be removed. Therefore, in the prior art, there is somehow limitation in the choice of solvents, in the other words, only a drawing sheet or film base into which the used solvent cannot penetrate can be used for this purpose. This is one of the shortcomings of the prior art solvent eraser technique.

Hitherto, in order to apply solvent on a copy paper sheet so as to eliminate the toner image, a vessel saturated with solvent is used to put solvent on the image to be eliminated. For example, a felt tipped pen is used to rub the image to be eliminated, thereby dissolving the coating of the fixed image and removing or wiping the remained solvent with the other thing such as rubber material, and further, after completely drying, redrawing or rewriting a desired image or figure on the location at that the image has been completely removed. Such procedure would take much trouble, and further in case of film base, some of solvents may hurt the surface of the base, thereby affecting significantly the drawing feature in correcting.Further, because the solvent contains some toxic volatile materials, much care of the operator is necessary to avoid the solvent from touching to his body and cloth, that will restrict the places at which the operator can correct the copy image.

Further, when the toner may be easily melt at the lower temperature, it is apt to be caked or conglomerated during application or storage of the toner. Particularly, the toner having the melting point at lower than 100"C has a significantly less fluidity.

It is an object of the present invention to provide negative electrification finely -divided toner that can produce through PPC(plain paper copying) copying technique a fixed image which can be easily eliminated or removed only by using a rubber eraser in stead of solvent. Upon using the inventive toner, the image can be. formed on a paper sheet by the PPC copying machine, which image as fixed can be easily eliminated only by a rubber eraser, and such elimination procedure does not hurt the surface of the paper or sheet.

Therefore, the inventive toner has the characteristics in that when the image formed by the toner is rubbed by a rubber eraser so as to be eliminated, the image coating formed from the inventive toner will and can be cut into fine particles, or ground to be peeled off, and then, conveniently removed from the paper sheet, together with the scrape of rubber eraser. It is desired that the binding force of the coating of the toner image might be lower than that of the coating to the paper so that only the coating of the image as formed can be broken while the image as formed can be enough adhesive to a paper sheet.

In accordance with the present invention, the novel toner provides such thermal characteristics of the produced coating, that it can be softened or melted at the fixing temperature used in the copying machine to stick thereby to the paper sheet, and after cooled to the room temperature, the produced coating of the fixed image does not stick to the other paper or contact matter. For example, when the fixing temperature used in the copying machine is at the range of 90"C to 120 C, the softening temperature of the used toner should be around or at this range. In order to gain such coating characteristics of the toner, the formulation of the toner must be carefully reviewed. Generally, the toner will essentially contain at least colorant(pigment), and binder material(s) (binding agent(s)), and in addition, various auxiliary agents.

Most of the toner that are now being used has the very high softening temperature at about 10000 to 180"C, and therefore, the excess quantity of thermal energy is necessary. As the result thereof, there are various limitation, for example, in selecting materials and thickness of the usable copying sheet, and various troubles are found such as trouble of sheet feeding in a copying machine.

In contrast, the inventive toner is as discussed before, containing the specific binding agent(s) which agent(s) is consisting of one species or more species selected from the group consisting of solid lower molecular weight polymer group species, and high melting temperature wax or waxy material (wax-like material) group species. Further, the inventive toner contains in addition colorant, electrification-controlling agent, and the other auxiliary agent(s). The inventive toner is produced by mixing the above mentioned binder material species components in an appropriate ratio (amount), kneading the mixture of the specific binder components under the temperature ranging 90"C to 150 C, and then, further kneading in a kneading machine having a heat roller, and allowed to be cooled.The resulting binder mixture is milled so as to form the binder particles of below 500 micron in size, and then, further ground in a grinding machine such as an air jet mill, and sieved to yield only the binder particles ranging about 5 to 20 micron in size.

It is preferable that the binding force of the coating of the toner particles produced from the inventive toner is preferably smaller than the adhesive force of the fixed image to the paper.

Further, the thermal characteristic of the toner coating should be such that the inventive toner particle can adhere to the surface of paper by softening or dissolving the toner at the temperature at that the image is fixed in a copying machine, and after allowing to cool to the room temperature, the fixed image does not adhere to the other material such as paper. For example, when the fixture temperature used in a copying machine ranges 90"C to 120 C, the softening temperature of the toner should be at the same temperature range or it's vicinity.

The new toner, therefore, has the relatively low softening point at about 90"C to 12000.

Therefore, thinner film base(38 micrometer thick) can be used, and the choice of the usable copying paper sheet can be wider with less trouble of sheet advancing or progressing in a copying machine.

In accordance with the present invention, the new toner can produce through the ordinary procedure in the common PPC copying machine a fixed image or pattern that can be easily erased or eliminated only by using an ordinary rubber eraser, in the same way as a pencil drawn pattern can be easily removed or erased by a rubber eraser. When one intends to produce copies of drawings or general figures by correcting partially the original, one can make the second corrected original for further copying by correcting partially a copy produced by copying of the first original, or eliminating only unnecessary part of the copy produced by the duplication of the first original. For this purpose, the inventive toner is very effective in that the image produced from the new toner can be easily eliminated only by using a rubber eraser.

The inventive toner can be applied to most species of a copying media available for a PPC copying machine, including a drawing paper and film base as well as an ordinary paper sheet having smooth treated surface so that it has the surface characteristics same as that of a drawing paper, such as art paper can be used at which the image produced by the novel toner can be erased or eliminated only by a rubber eraser.

The prior art toner contains as a major component a binder resin having strong adhesive force so that the fixed image can not be easily eliminated. The toner contains further a colorant, an electrification-control agent, and auxiliary agents. The toner is produced by kneading the mixture of the above binder materials and other agents in the kneading machine with a heat roller, and milling followed by sieving to get the binder particles of 5 to 20 micrometer in size.

In contrast, the inventive negative electrification powder toner for electrophotography has remarkable characteristics that have not been seen in the prior art toner. Those characteristics are that the toner can produce an image that can be eliminated only by a rubber eraser, and that the toner comprises as a binder, a mixture of one or more species selected from the group consisting of solid lower molecular weight polymer group species and higher melting point wax or waxy material group species as defined in the attached claims, in a given particle size, and further colorant(s), electrification-controlling agent(s) and auxiliary agent(s).The inventive toner is produced by heat kneading the mixture of the above defined components at the temperature of about 90"C to 150"C or kneading in an appropriate solvent, and then milling in a speed mill and finely dividing in an air jet system, followed by classification to give particles of about 5 to 20 micrometer.

The materials usable in the inventive toner are as follows: The following components should be used for the production of the inventive toner from which the rubber eraser eliminating image can be formed on any kinds of sheets and paper.

The first species which should be used as a binder material for the the production of the inventive toner is a solid lower molecular weight polymer group species with lower adhesivity.

The solid lower molecular weight polymer group species usable in the production of the inventive toner are selected from the group consisting of: (A) solid silicone varnish having molecular weight being 500 to 4000, thermo-setting semi inorganic polymeric pre-polymer, and it's derivatives, such as methyl silicone varnish, phenyl silicone varnish, methyl phenyl silicone varnish, (B) oligo-styrene and its derivatives having molecular weight being 400 to 800, (C) petroleum hydrocarbon resin and its derivatives, having molecular weight being 800 to 1500, such as aliphatic petroleum resin, aromatic petroleum resin, aliphatic aromatic copolymer, (D) cyclopentadiene analogy petroleum resin and its derivatives having molecular weight being 800 to 1500, (E) thermosetting pre-polymer such as lower molecular weight polyester resin and its derivatives, having molecular weight being 400 to 1200, (F) terpene resin and its derivatives, having molecular weight being 600 to 1200, (G) lower molecular weight polyethylene and its derivatives having molecular weight being 800 to 1500.

The lower limit of the molecular weight defined as above for each of the above defined components is determined by the consideration of that the softening point should not be too lower, that the coagulation of the resulting toner should not be affected, and that the photosen- sitive member used in a copying machine should not be too contaminatable. The upper limit of the molecular weight is determined by the consideration of that the image formed by using the new toner should be easily erased only by using an ordinary rubber eraser.

The second species which should be used as a binder material for the the production of the inventive toner is a higher melting temperature wax or wexy (wax-like) material group species.

The wax and wax-like material species usable for the production of the inventive toner is selected from the group consisting of: (A) Synthetic hydrocarbon such as Fischer Tropsch wax, (B) Synthetic wax and synthetic modified wax and natural wax, having melting point at the temperature higher than 80"C, (C) 70% chlorinated paraffin having molecular weight being about 1,150, and (D) Higher melting point solid chloronaphthalene.

Hereinafter, examples of the colorant (pigments, dyestuffs), and the auxiliary agents are as follows, but the present invention can not be limited by those.

The colorant usable as a component for the production of the toner may include carbon black, lamp black, acetylene black, channel black, diamond black, phthalocyanine blue, permanent blue, Fanal(Trademark) blue, nigrosine blue, aniline blue, Calconyl(Trademark) blue, ultramarine blue, cobalt blue, methylene blue, its chloride, pigment red, DuPont oil red, benzidine yellow, quinoline yellow, chrome yellow, chrome green, phthalocyanine green, malachite green oxalate, rose Bengal, nigrosine dye and the mixture thereof.

The auxiliary additives usable in the inventive toner may include (A) adhesion reducing agent, for example, synthetic hydrocarbon such as Fischer-Tropsch wax, petroleum natural wax such as microcrystalline wax, mineral natural wax such as montan wax, vegetable wax such as carnauba wax, synthetic modified wax such as montan wax derivatives and microcrystalline wax derivatives, (B) electrification controlling agent such as hydrophobic silica finely divided particles and surfactant, (C) fluidity accelerator, for example, graphite, molybdenum dioxide, zinc oxide, iron oxide, silicon oxide, titanium oxide, talc, marble, quartz finely divided powder, (D) flexibility improver, for example, relatively higher compatibility resin such as synthetic resin as polystyrene resin, aromatic petroleum resin, natural resin such as shellac, rosin, synthetic rubber and natural rubber, and rubber analogy, (E) detackifier such as hydrocarboneous lubricant and powdered polypropylene, (F) grindability improver such as sugar ester, ketone resin, (G) thermal resistance improver such as finely divided titanium oxide.

As before described, the toner of the present invention is in contrast to the conventional toner which has been used, and which is essentially of polymeric or medium size polymeric resin. The binder material used for the production of the toner of the present invention is essentially consisting of one or more species selected from the group consisting of a lower adhesivity solid lower molecular weight polymer, and a higher melting temperature wax or waxy (wax-like) material(s) as defined above.

The general adhesive force of wax and resin to paper can be influenced by the properties such as molecular structure, value of molecular weight, melting point or softening point, density, hardness, viscosity. Generally speaking, the larger the molecular weight is, the stronger the adhesive force is. Further, the higher the melting point or the softening point is, the stronger the adhesive force is.

In case of using resin for the binder material, the adhesive force of the thermosetting resin having crosslinked structure would be higher than that of the thermo-plastic resin having linear structure, where the softening points are substantially similar. Further, the adhesive force of the crystalline resin would be stronger than thatof amorphous resin.

In consideration of the above described properties, the toner of the present invention uses as a binder material a solid lower molecular weight polymer species having the lower adhesive force depending upon the lower molecular weight obtained in the initial condensation or polymerization. The wax or waxy compounds usable in the toner of this invention have in order several hundreds to one thousand in molecular weight, and have the lower adhesive force depending on the lower molecular weight. Further, it is to be noted that the waxy species and solid lower molecular weight polymer species used as a binder material in the toner of this invention can evidence some brittleness and gloss coat properties after heat kneading and cooling of the toner materials.

The toner of this invention uses as a binder material one or more species selected from the solid lower molecular weight polymer group species and higher melting point wax or waxy resin group species, and further contains colorant(s) in an appropriate amount. Where a thermo-setting solid lower molecular weight polymer species selected from the solid lower molecular weight polymer group, having lower adhesive force is used as a binder material, the kneading temperature and period used for the heat kneading of the binder materials should be carefully selected and- determined. Further, the curing exotherm and cure time of the binder materials should be carefully selected to obtain an appropriate adhesive force of the toner. The binder resin is more cured when the adhesive force of the toner containing the binder resin will be stronger.One of the advantages of the present invention is that the mechanism or the extent of erasing the image formed from the toner containing the binder material as above described can be controlled by using this principle.

In case of using wax or waxy resin group, it is to be noted that when the kneading temperature is higher than 1200C the binder material will be changed in properties.

The binder material used in the toner of this invention should have preferably the melting point or softening point at the temperature higher than 90"C, so that the toner should not be meltblocked nor caked nor conglomerated. However, certain auxiliary agents can control to prevent the melt- blocking and caking of the toner, and therefore a variety of formulation for the toner can be enabled to have an appropriate adhesive force by modifying the contents of the binder materials and auxiliary agents and colorant. The prior art toner which has been used has the softening point at the temperature ranging 100"C to 1800C, that is very high temperature.

Accordingly, the excess amount of heat is necessary so that the material and thickness of the copy sheets must be restrained, and the troubles such as sheet clogging or sheet feeding trouble can easily occur. In contrary, the toner of this invention using wax or waxy materials as a binder has a softening point at the lower temperature range such as about 70"C to 1300C, and therefore, the thinner film base such as 38 microns in thickness is enabled to be used, and the choice of selection for a usable and appropriate copying sheet can be widen, and in addition troubles such as sheet feeding trouble can be minimized.

In accordance with the present invention, the image or patten is developed, transferred and fixed by a PPC copying machine using the toner of this invention, and the so formed image can be easily erased only by using a rubber eraser in the same way as erasing a pencil drawn pattern by an ordinary rubber eraser. For example, in making, for example, a copy of a plan view, or a blueprint or a general typed or written material or a printed matter, when most figures or pattern or image should not be changed, but a partial figure or pattern should be changed or corrected, a copy of the first original is initially made and the second (corrected or amended or modified) original can be made from this copy by erasing partially an image or pattern, or figure, and further if desired rewriting or redrawing or adding a desired image or pattern or figure. In those cases, the copy used for this purpose can be made from the inventive toner.

The negative-electrification finely-divided toner of this invention is used to develop a latent image so that a thermally fixed image can be formed on a special sheet of paper, such as a drawing sheet, a film base, a surface-coated (non-permeation treated) sheet of paper (for example, coat paper, art paper), and the so formed image on the sheet can be easily and readily erased by using a ordinary rubber eraser such as rubber eraser, or plastic rubber eraser.

Therefore, such formed and erased and/or corrected image or patterns on the special sheet can be the second original for further reproduction.

The copied image formed by using the toner of the present invention to develop a latent image and to fix thermally the image on a special sheet of paper such as drawing paper, film base, surface-treated (surface non-permeating) paper (for example, coating paper and art paper) can be easily erased only by using an ordinary rubber eraser including rubber eraser, plastic rubber eraser. Therefore, the sheet in that the undesired image(s) has been erased and/or the necessary image(s) has been added can be used as the second original for further copying.

A reflecting exposure type copying machine such as a PPC type copying machine has been developed and widespread so that a sheet of ordinary opaque paper in stead of somehow transparent sheet such as film base and drawing (or tracing) paper which has been used in transparence exposure type copying can be used to make the second original. Therefore, it will be desired and become necessary to correct or eliminate the image formed on the opaque sheet so as to make the second original for further duplication. And therefore, the need of rubber erasing or eliminating will be increased under the consideration of such recent development and widespreading of the opaque sheet copying. And, the toner of the present invention will be and become more important and more desired.

The formulations used for the present invention are as follows, but should not be interpreted for the limitation of the invention.

EXAMPLES 1 to 24 Each of the binder formulations as shown in Table 1 was kneaded for about two hours at the temperature as shown respectively in Table 1, in the range of 90"C to 150"C in a kneading machine with roller, and then, allowed to be cooled. Each of the resulting binder resin mixtures was roughly powdered by a speed mill, and then finely-divided by a jet mill to form particulate binder material for the production of the toner. The resulting finely-divided particulate resin material was sieved to select the particles ranging 5 to 20 microns in size. Then, the resulting particulate material was mixed with finely-divided silica material in the ratio of 4 weight percent of the silica particles based on the weight of the particulate material.The used silica particles is available from Nippon Earosil as Earosil R-972. The mixture of the resin particulate material and silica particles was uniformly mixed and dispersed completely to produce the toner to be used for the present invention. The resulting silica-dispersed toner was mixed with carrier iron particles in the ratio of 3 to 5 weight parts of such silica-dispersed toner to 100 weight parts of the carrier iron particles, and then uniformly mixed to form the toner to be used for the development of an image.

As described in the foregoing, the copy image was produced in a copying machine of magnet brush technique, and the resulting duplicated images formed on a sheet was found to be an excellent image with high contrast and less fogging. After the transfer and fixture of the images, the so formed images on a film base, a drawing (tracing) paper and a coated paper were exposed to the rubbing treatment by a rubber eraser. The result is that the images were easily erased, and the remaining is so little that the image or letter can be written on the same place of the sheet on which the image had been formed by the toner of this invention. Accordingly, the image formed on an ordinary paper or sheet can be easily corrected without blot, and therefore, the ordinary copy paper can be used as the second original for further copying.

Therefore, an ordinary paper having the surface of the same characteristics as that of a drawing (tracing) paper and a film base can be used for partial correction of the image or pattern thereon only by a rubber eraser and/or a drawing means.

Table 1

Example A B C D E F G H I J K L M N O P Q R kneading temperature 1 84 - - - - - - - - - - - 8 - - - - 8 110 C 2 - 84 - - - - - - - - - - - - - 8 - 8 130 C 3 - 84 - - - - - - - - - - - 8 - - - 8 110 C 4 - 84 - - - - - - - - - 6 - - - - 2 8 150 C 5 - - 72 - - - - - - - 12 - - 8 - - - 8 120 C 6 - - 78 - - - - - - - - - - 14 - - - 8 110 C 7 - - - 35 - - - 35 - - - - 10 12 - - - 8 120 C 8 - - - 68 - - - - - - - - 16 8 - - - 8 100 C 9 - - - - 76 - - - - - - - - 10 - - 6 8 120 C 10 - - - - - 80 - - - - - - - 12 - - - 8 120 C 11 - - - - - - 80 - - - - - - 12 - - - 8 150 C 12 - - - - - - 70 - - - - - - 20 - - - 10 150 C 13 - - - - - - 70 - - - - - 10 12 - - - 8 150 C 14 - 30 - - - - 50 - - - - - - 10 - - - 10 140 C 15 - - - - - - - 78 - - - - - 14 - - - 8 120 C 16 - - 20 - - - - 62 - - - - - 10 - - - 8 120 C 17 - - - - - - - - 80 - - - - 12 - - - 8 130 C 18 - - - - - - - - - - 75 - - 15 - - - 10 130 C 19 - - - - - - - - - - 72 - 8 12 - - - 8 130 C 20 - - - - - - - - - - 80 - 4 8 - - - 8 130 C 21 - 8 - - - - - - - - 72 - - 12 - - - 8 130 C 22 - - 12 - - - - - - - 70 - - 10 - - - 8 130 C 23 - - - - - - - - - 8 76 - 8 - - - - 8 130 C 24 - - - - - - - - - - - 8 - - 84 - - 8 120 C Each content is based on weight percent In the above Table, the figures indicate the components as shown below: A; Methyl silicone varnish (available from Shin-etsu Chemical Inc. Ltd., as solid silicon varnish KB-220), molecular weight:3,300 to 3,600, softening point: 68"C to 74"C (measured by a ring and ball method) B; Phenyl silicone varnish (available from Shin-etsu Chemical Inc. Ltd., as solid silicon varnish KR-216), molecular weight:2,000 to 2,300, softening point: 72"C to 76"C (measured by a ring and ball method) C; Origomer styrene (available from Pico Inc. Ltd., as Picolastic A-75), molecular weight: about 400, softening point: about 75"C (measured by a ring and ball method) D; Aliphatic Petroleum resin (available from Mitsui Petrochemical Inc.Ltd., as Hilex G-100X), molecular weight:about 1,200, softening point: about 100"C (measured by a ring and ball method) E; Aromatic Petroleum resin (available from Mitsui Petrochemical Inc. Ltd., as Peterosin #80), molecular weight:about 500, softening point: about 80"C (measured by a ring and ball method) F; Cyclopentadiene analog petroleum resin (available from Nippon Zeon Inc. Ltd., as Quinton 15000), molecular weight:about 800, softening point: about 100"C (measured by a ring and ball method) G; Lower Molecular weight Polyester resin (available from Arakawa Chemical Inc.Ltd., as Markeed No.2), molecular weight:about 1,000 softening point: about 1200C to 1300C H; Lower Molecular weight Phenole resin (available from Gun-ei Chemical Inc. Ltd. as solid resitop PS-2780), molecular weight:about 450 to 550"C, melting point: about 78"C to 88"C I; Lower Molecular weight Terpene resin (available from Yasuhara Oil Inc. Ltd. as Crealone P-115), molecular weight:about 600, softening point: about 115"C J; Lower Molecular weight Poluethylene (available from Mitsui Petrochemical Inc. Ltd., as Hiwax 100P), molecular weight:about 900, melting point: about 116"C.

K; 70% chloinated Paraphine (available from Ajinomoto Inc. Ltd., as Enpara 70), molecular weight:about 1160, softening point: about 98"C L; Fischer Tropsch Wax (available from Sasol Ltd., as Sasol wax H1), molecular weight:about 600, softening point: about 108"C (measured by a ring and ball method) M; Microcrystalline wax (available from Nippon Seirou Inc. Ltd., as Himic 2095), melting point:about 96"C N; Synthetic Hydrocarbon (available from Nippon Seirou Inc. Ltd., as Lubacs 1151), molecular weight: about 700, melting point:about 105"C O; Higher Melting Point Solid Chloronaphthalene (available from Union Carbide Inc.Ltd., as Halowax 1013), P; Particulate Polypropyrene (available from Hoechst Japan, as Hoechstwax PP230), molecular weight:about 3000, dropping point:about 158"C Q; Titanium oxide finely-divided powder (available from Nippon Aerosil Inc. Ltd., as Titanium oxide P25) R; Carbon Black (available from Cabott Inc. Ltd., as Regal 400R) Among the above examples, Examples 3, 5, 6, 9, 10, 11 and 12 used Zerox 2090 copying machine (manufactured by Fuji Zerox Inc. Ltd.) in which the toner produced in each of the Examples, that had been mixed with carrier iron powder TSSV-100 available from Nippon Ironpowder Inc. Ltd., was applied to develop an image for testing of the toner of this invention. The remaining Examples and Shakou 920 copying machine (manufactured by Shakou Inc.Ltd.) in which the toner produced in Examples, that had been mixed with carrier iron powder EFV200/300 available from Nippon Iron-powder Inc. Ltd., was applied to develop an image for testing of the toner of this invention.

As described in the foregoings, the negative-electrification finely-divided toner of the present invention for use in correction or partial elimination of a copied image on an opaque sheet is invented to have desired properties in such as fixing properties to the usable opaque sheet. PPC (Plain Paper Copy) machine has been widespread to produce a duplicated image on an ordinary opaque sheet, the second original can be produced in such PPC system, while diazo type duplication system would be less used and transparent sheet such as film base and tracing paper would be less used to form a copied image thereon. The second original for further duplication can be produced by forming a copied image on the opaque sheet and correcting or partially eliminating undesired image and/or adding necessary pattern. Therefore, the toner of the present invention will be more needed and more important.

Claims (19)

1. A negatively-electrification toner for use in the production of electrophotographic image or pattern erasable only by an abrasive character such as using a rubber eraser, which comprises 100 weight parts of a binder formed from melting one or more species selected from the group consisting of lower adhesive force solid lower molecular weight polymer species and higher melting point wax or waxy compound group species, 1 to 20 weight parts of colorant(s).

2. A toner as claimed in Claim 1, which comprises further finely-divided silica particles in a dispersed form in a ratio of 1 to 4 weight percent based on the weight of the mixture of the binder material and the colorant and the auxiliary agent.

3. A toner as claimed in Claim 1, wherein the colorant is carbon black, lamp black, acetylene black, channel black, or diamond black.

4. A toner as claimed in Claim 1, wherein the colorant is phthalocyanine blu permanent blue, Fanal(Trademark) blue, nigrosine blue, aniline blue, Calconyl(Trademark) blue, ultramarine blue, cobalt blue, or methylene blue chloride.

5. A toner as claimed in Claim 1, wherein the colorant is pigment red, or DuPont(Trademark) oil red.

6. A toner as claimed in Claim 1, wherein the colorant is benzidine yellow, quinoline yellow, chrome yellow, chrome green, phthalocyanine green, malachi green oxalate, rose Bengal or nigrosine dye.

7. A toner as claimed in Claim 1, wherein the lower adhesive force solid lower molecular weight polymer species are (A) solid silicone varnish having molecular weight being 500 to 4000, thermo-setting semi inorganic polymeric pre-polymer, and it's derivatives, such as methyl silicone varnish, phenyl silicone varnish, methyl phenyl silicone varnish, (B) oligo-styrene and its derivatives having molecular weight being 400 to 800, (C) petroleum hydrocarbon resin and its derivatives, having molecular weight being 800 to 1500, such as aliphatic petroleum resin, aromatic petroleum resin, aliphatic aromatic copolymer, (D) cyclopentadiene analogy petroleum resin and its derivatives having molecular weight being 800 to 1500, (E) thermosetting pre-polymer such as lower molecular weight polyester resin and its derivatives, having molecular weight being 400 to 1200, (F) terpene resin and its derivatives, having molecular weight being 600 to 1200, (G) lower molecular weight polyethylene and its derivatives having molecular weight being 800 to 1500.

8. A toner as claimed in Claim 1, wherein the higher melting temperature wax or waxy (waxlike) material group species are selected from the group consisting of: (A) Synthetic hydrocarbon such as Fischer Tropsch wax, (B) Synthetic wax and synthetic modified wax and natural wax, having melting point at the temperature higher than 80"C, (C) 70% chlorinated paraffin having molecular weight being about 1, 150, and (D) Higher melting point solid chloronaphthalene.

9. A toner as claimed in Claim 1, wherein the toner contains further a electrification controlling agent such as hydrophobic silica finely-divided powder.

10. A toner as claimed in Claim 1, wherein the toner contains further a auxiliary agent such as zinc oxide, iron oxide, titanium oxide, aluminium oxide, silicon oxide, talc, quartz or marble.

11. An electrostatographic developing composition for use in developing an electrrostatic latent image, which composition comprises particulate toner material as claimed in each of the proceeding claims and carrier particles which charge the toner particles, and further comprises finely-divided silica particles.

12. The electrostatographic developing composition as claimed in Claim 11, wherein the ratio of the toner to the carrier ranges 3 to 5 percent by weight.

13. The electrostatographic developing composition as claimed in Claim 11, wherein the silica particles have a size in the ranges of 1 to 100 milimicrons, preferably 5 to 60 millimicron.

14. The developing composition as claimed in Claim 11, wherein the finely-divided silica particles are hydrophobic silica in a particulate form.

15. A process of developing an electrostatic latent image and producing the fixed electrophotographic image on an opaque sheet which image is erasable only by an abrasive force such as using a rubber eraser, which comprises developing an electrostatic latent image by the developing- composition of any one of claims 11 to 14 to give a developed image corresponding to said latent image.

16. The process of claim 15, comprising removing at least a portion of at least fixed image from the surface of the sheet by using a rubber eraser.

1 7. A toner as claimed in claim 1, substantially as hereinbefore described.

18. A composition as claimed in claim 11, substantially as hereinbefore described.

19. A process as claimed in claim 15, substantially as hereinbefore described.