GB2166881A

GB2166881A - Dry-type developing agent electrostatic latent image

Info

Publication number: GB2166881A
Application number: GB08512037A
Authority: GB
Inventors: Keisuke Hirai
Original assignee: Faco Corp Ltd
Current assignee: Faco Corp Ltd
Priority date: 1984-11-10
Filing date: 1985-05-13
Publication date: 1986-05-14
Also published as: GB8512037D0; JPS61116363A

Abstract

A developing agent for electrostatic latent image comprises a mixture of toner powder, optionally carrier, and finely-divided silica particles in a physically-dispersed particulate form.

Description

SPECIFICATION Dry-type developing agent in use for developing electrostatic latent image The present invention relates to a developing agent in use for developing in a dry type, an electrostatic latent image. More particularly, it relates to a dry-type developing agent containing finely-divided silica particles in the physically-dispersed particulate form.

It has been known in Japanese Patent Publication No. 54-20344 that the addition of silica particles to the toner controls the electrification of the toner (that means whether and how the toner is electrified positively or negatively).

There have been known the fact that finely-divided silica particles are used an an auxiliary to a developing agent for developing an electrostatic latent image.

The finely divided silica particles, when they are used as an admixture to a dry-type developing agent to develop an electrostatic latent image, give various advantages wherein the surface of the toner particles becomes slippy so that the electrification, storage stability, anti-conglomeration and fluidity of the toner are improved and further in case of the two component toner, the compatibility to the carrier and the anti-flying effect of the toner are improved further, the silica particles have advantages in giving a high contrast image with less blur, and in giving a wide latitude image with less density irregularity.

It is further known that the finely-divided silica particles would contribute to the various advantages, for example, in less need of controlling exposure, electrification feature, bias (in case of using magnetic brush), less contamination to the photosensitive body, and the expansion of life of the used photosensitive body.

There are provided various forms in that finely divided silica particles are added or incorporated as an admixture in the toner. One of these forms is that silica particles are internally or integratedly incorporated in the conventional toner particles. Process of making this developing agent comprises adding silica particles to the mixture of resin and colorant, or of resin, colorant and admixtures to be heatedly kneaded, followed by milling and classifying as in the prior art, and then dispering carrier to the resuling powder to form a developing agent.

However, the amount of the necessary silica particles is over 10 to several tens parts by weight to 100 parts of the toner for this form to function enough as a developing agent to produce the satisfactory image. It seems that such amount of the silica particles would affect a working properties of the toner. It seems that the reason why such large amount of the silica particles is needed would be that the silica particles in the prior art toner are internally and integratedly incorporated in the toner particles, in the other words, are buried in the resin and colorant, and only silica particles present at or in the neighborhood of the surface of the toner particles can function to lower the effectiveness of the silica's action.

The inventor of this invention has been investigating about the other form in that silica particles can function effectively and do not affect the working properties of the toner and found the way of lowering the necessary amount of the silica finely divided particles for the toner.

It is an object of the present invention to provide a developing agent containing less amount of the silica particles.

It is further object of the invention to provide a developing agent that produces a clear fixed image or pattern with high contrast and less fogging.

It is a still further object of the invention to provide a developing agent with high storage stability, high anti-conglomeration and high fluidity.

It is another object of the invention to provide a two component developing agent having high compatibility to the carrier.

The inventive developing agent can develop a latent image transfer safely, and fix with high constrast, wide latitude and less density irregularity.

The present invention will make the choice of the usable materials for producing the toner wider, while in the prior art the resin having a lower softening temperature can not be used because of possible conglomeration, less fluidity and possible contamination to the photosensitive body.

It has been found by the inventor that when finely divided silica particles are present in the toner powder in the physically-dispersed particulate form the amount of silica finely divided particles to be added is significantly reduced, resulting in a satisfactory image, in either case of two component developing agent system (carrier+toner powder) or one component developing agent system (toner powder containing carrier internally).

Therefore, the inventive developing agent is characterized by containing finely-divided silica particles in the dry particulate form, which are physically dispersed and present outside of the toner particles. It seems that the reason of enabling the significant reduction of necessary silica amount is that the silica particles function effectively because they are present outside of the toner particle.

In accordance with the present invention, the ratio of the finely-divided silica particles to be added to the mixture of the carrier and the toner powder in producing a three component developing agent ranges 0.001 to 15 parts by weight to 100 parts by weight of the toner powder, preferably 0.5 to 6 parts by weight per 100 parts by weight of the toner powder, and more preferably 2 to 6 parts by weight per 100 parts by weight of the toner powder.

Where the ratio of the added silica particles is not more than 0.001 parts by weight to 100 parts of the toner, there is not found any effect of controlling the electrification of the toner to be negative. When the ratio is more than 15 parts by weight per 100 parts of the toner, the weight balance in the formulation of a developing agent is apt to be affected.

The ratio of the silica finely divided particles dispersion toner to the carrier may range 2 to 3 parts by weight of the toner to 100 parts by weight of glass beads carrier in case of a developing agent for the cascade development and further, may range 4 to 6 parts by weight of the toner to 100 parts by weight of the magnetic iron powder carrier in case of producing a developing agent for the magnet brush development.

The usable size of the finely-divided silica particles for the inventive developing agent may range about 1 to 100 millimicron, preferably 5 to 60 millimicron. Outside of this range, the control to negative electrification will be lost over any species of the toner. The ordinary silica has hydrophilic silanol group at the terminal of the molecular, and the hydrophilic silanol group can be substituted by a hydrophobic group such as methyl group. When the hydrophobic powder silica with the hydrophobic group is used, the water repellency function is further added to the above mentioned functions so that a sharp image with less fogging and less blush can be produced. Such finely-divided silica particles can be available from the market. For example, there can be listed Aerosil 200, and Aerosil R972 (hydrophobic silica powder) manufactured by Nippon Aerosil Inc.

The finely-divided silica particles dispersed in the developing agent adhere to the electrostatic latent image by coulombic force, so that the supplementary toner can be the dispersion mixture of the toner and the finely-divided silica particles in the above weight ratio.

When the invention is applied to make the two component developing agent by dispersionmixing the silica finely-divided particles with the powder toner containing carrier, the weight ratio of the silica particles to the toner is the same range as in case of producing the three component developing agent, where the toner weight can be calculated by reducing the carrier weight from the total toner weight.

As discussed above, firstly the present invention facilitates utilization of the finely-divided silica particles and production of a developing agent because the developing agent can be easily produced only by physically dispersing the finely-divided silica particles to the toner and the carrier.

Secondly, the silica particles in the developing agent can shown the enough effect even at the lower amount ranging 0.1 percent to over ten percent. In the other words, the amount of the silica particles can be remarkably reduced to about one twentieth to one thirtieth of the internally incorporated silica.

Thirdly, where silica finely-divided particles are integratedly incorporated in the toner particles, the necessary content of the silica particles is controlled by the internal factor of the toner. In the inventive developing agent, the silica particles are present outside of the toner particles, and therefore, the amount is not controlled by the internal factor of the toner and can be determined only by the real functional amount of the silica particles. In the other words, all of the present silica particles can function to contribute to the above mentioned effects. Therefore, the content of the silica particles can be determined from the wider range, depending on the other contents and species of the components, or resin(s), pigment(s) and the other admixtures.

Fourthly, the developing agent of the present invention has the particulate silica dispersed in the combination of the toner and the carrier or the toner containing the carrier, and therefore, can improves significantly the negative-electrification, anti-coagulation, and fluidity of the toner irrespective of the resin and pigment used in the toner. Accordingly, all of the below-listed resins and aliphatic compounds having some difficulties for the binder in the prior art become usable as the component in the developing agent. In the other words, the present invention provides a wider variety of the developing agents required for the possible variety of the copying machines.

The prior art toner contains as a binder one or some of the following resins and aliphatic compounds that may give some practical disadvantages in producing negative electrification toner: the resin binder may include polyethylene, polyester, polyamide, maleic acid resin, xylene resin, phenol resin, cumalon resin, petroleum-originated resin, ketone resin, acryl resin, epoxy resin and the like: the aliphatic compound binder may include wax such as carnauba wax, montan wax, Ivota wax, candelilla wax, microcrystalline wax, Fischer-Tropsch wax, and ceresin wax, higher fatty acid such as stearic acid, parmitic acid, linolic acid, and oleic acid, and the metal salt thereof.

The above-listed resins and compounds become usable for production of the developing agent in accordance with the present invention.

The pigments that can be added to the toner binder may include all of the known pigments and dyestuffs, such as carbon black, iron black, channel black, metal complex dye, lamp black, acetylene black, phthalocyanine blue, Berlin blue, Prussian blue, ultramarine blue, nigrosin blue, Fanal (Trademark) blue, permanent blue, aniline red, pigment red, Hansa (Trademark) yellow, chrome yellow, and chrome green.

The present invention are more detailedly explained by the following examples.

a. Formulation of the toner Example 1 Polyamide 235 parts Carbon Black 15 parts Example 2 Oligomer polymer 235 parts (trade name "Mitsui Highwax 100P manufactured by Mitsui Petrochemicals) Carbon Black 15 parts Example 3 Non-bleached Montan Wax 235 parts Carbon Black 15 parts Example 4 Fischer-Tropsch Wax 235 parts Carbon Black 15 parts b. Production of Toner Powder The mixture of each of the above examples 1 to 4 was kneaded for one hour at the temperature of about 130"C in a kneading machine with roller, and then, allowed to cool. The resulting cold solidified mixture was divided by a hammer mill, and then more finely divided by a jet mill. The resulting finely-divided particles were sieved to select the particles ranging 5 to 20 millimicron in size, which were used as the toner for the invention.

c. Production of Developing Agent (1) Each of the two component developing agents for the cascade development (Al to A4) was produced from each of the above toners of Example 1 to 4 by mixing resin coated beads carrier and the toner in the ratio of 98 (carrier) to 2 (toner) based on weight part. Then, silica finely-divided particles (trade name: Aerosil R-972) were added in the ratio of 4 percent by weight to the toner produced from Examples 1 to 4 followed by dispersion-mixture, to produce four species (B1 to B4) of silica finely-divided particles-dispersion developing agents for cascade development.

(2) Iron powder carrier (trade name: EFV 200/300 manufactured by Nippon Iron Powder Inc.) was added to each of the toners from Examples 1 to 4 in the ratio of 96 (carrier) to 4(toner) to produce four species (C1 to C4) of two component developing agents for magnetic brush development.

Further, silica finely-divided particles (trade name: Aerosil 200) were added to each of C1 to C4 in the ratio of 4 percent by weight to the toner to produce four species (D1 to D4) of the silica finely-divided particles dispersion developing agents for brush development.

d. Comparison of Results by using Inventive Developing Agents with the Prior Art Agent The developing agents of Al to A4 and B1 to B4 as above produced were each used in a copying machine for a cascade-type development to develop a positively-electrified electrostatic latent image formed on a selenium photosensitive body, followed by transferring to an ordinary paper sheet, and heatedly fixing.

Further, the developing agents of C1 to C4 and D1 to D4 as before produced were respectively used to develop, transfer and heatedly fix an image.

It was found that all of the images produced by the two component developing agents of Al to A4 and C1 to C4 evidence narrow latitude and much fogging with less sharpness.

In contrast, all of the eight images each produced by the silica finely-divided particles dispersed developing agents (B1 to B4 and D1 to D4) have wide latitude and less fog with high sharpness and further show high contrast.

As discussed above, in accordance with the present invention, the choice of the usable materials for the production of the developing agent becomes widened. Most of resins and aliphatic compounds, of which the use has been limited in view of the electrification-control property, anti-conglomeration, and fluidity can get more utilization in the inventive developing agent. Further, most of the dyestuffs, pigments and admixtures that could not be used in the prior art become usable under the new developing agent. Therefore, the present invention would provide an easier method of research of a useful developing agent to satisfy the new requirement for a higher technology electrostatic copying machine and printer.

In general, a PPC (plain paper copy) copying machine can produce a copy image on a plain paper, drawing paper, film base and the like. When the copy images or patterns formed on a transparent sheet such as a drawing paper and a film base, are used for the second original for the further copying such as diazotype copying by correcting or eliminating the images or/and adding images to make up the second original, the correction or elimination is carried out by using a correcting liquid containing a solvent of dissolving the resin in the toner because a rubber eraser can not be used.

The formulations of Examples 2, 3 and 4 are for the purpose of producing the toner from that the rubber eraser-elimitatable image can be formed. The developing agents B1, B2, B3 and 84 are as mentioned above used for a cascade development, and the developing agents D1, D2, D3 and D4 are used for a magnetic brush development. Thereafter, the images each formed are transferred to a chemical mat treated film and fixed to form six species of the toner images respectively followed by the thermal fixation to give the fixed images. Those images can be easily eliminated or removed by ordinary rubber erasers (including rubber eraser and synthetic resin eraser).

Claims

1. A dry-type developing agent for the development of electrostatic latent image comprising the mixture of carrier and powder toner, or powder toner containing carrier, Characterized by further containing finely-divided silica particles in the physically-dispersed particulate form.

2. The developing agent as claimed in Claim 1, wherein the ratio of the finely-divided silica particles to the toner powder ranges 0.001 to 15 parts by weight to 100 parts by weight of the toner powder, preferably 0.5 to 6 parts by weight per 100 parts by weight of the toner powder.

3. The developing agent as claimed in Claim 1, wherein the ratio of the silica finely-divided particles dispersion toner to the carrier ranges 2 to 3 parts by weight of the toner to 100 parts by weight of glass beads carrier in case of a developing agent for the cascade development.

4. The developing agent as claimed in Claim 1, wherein the ratio of the silica finely-divided particles dispersion toner to the carrier ranges 4 to 6 parts by weight of the toner to 100 parts by weight of the magnetic iron powder carrier in case of a developing agent for the magnet brush development.

5. The developing agent as claimed in Claim 1, wherein the size of the finely-divided silica particles ranges about 1 to 100 millimicron, preferably 5 to 60 millimicron.

6. The developing agent as claimed in Claim 1, wherein the finely divided silica particles are hydrophobic silica in a particulate form.

7. The developing agent as claimed in Claim 2, wherein the toner contains a resin selected from the group consisting of polyethylene, polyester, polyamide, maleic acid resin, xylene resin, phenol resin, cumalon resin, petroleum originated resin, ketone resin, acryl resin, epoxy resin, carnauba wax, montan wax, Ibota wax, candelilla wax, microcrystalline wax, Fischer-Tropsch wax, ceresin wax, higher fatty acid such as stearic acid, parmitic acid, linolic acid, and oleic acid, and the metal salt thereof.

8. The developing agent as claimed in Claim 7, wherein the toner contains a resin selected from the group consisting of oligomer polyethylene, non-bleached montan wax and Fischer Tropsch wax.

9. The developing agent as claimed in Claim 7, wherein the toner contains a pigment such as carbon black, iron black, channel black, metal complex dye, lamp black, acetylene black, phthalocyanine blue, Prussian blue, ultramarine blue, nigrodin blue, Fanal (Trademark) blue, permanent blue, aniline red, pigment red, Hansa (Trademark) yellow, chrome yellow, and chrome green.

10. The developing agent as claimed in Claim 3, wherein the carrier is glass beads coated with resin.

11. The developing agent as claimed in Claim 4, wherein the carrier is iron powder carrier.

12. The developing agent as claimed in Claim 6, wherein the finely-divided silica particles are Aerosil (Trademark) selected from the group consisting of Aerosil R-972 and Aerosil 200 (Trade names), manufactured by Nippon Aerosil Inc..