EP0524016A1 - Procédé de production de toners pour l'électrophotographie et procédé de développement d'images latentes électro-statiques utilisant desdites toners - Google Patents

Procédé de production de toners pour l'électrophotographie et procédé de développement d'images latentes électro-statiques utilisant desdites toners Download PDF

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Publication number
EP0524016A1
EP0524016A1 EP92306582A EP92306582A EP0524016A1 EP 0524016 A1 EP0524016 A1 EP 0524016A1 EP 92306582 A EP92306582 A EP 92306582A EP 92306582 A EP92306582 A EP 92306582A EP 0524016 A1 EP0524016 A1 EP 0524016A1
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Prior art keywords
monomer
particles
toner particles
toner
toners
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP92306582A
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German (de)
English (en)
Inventor
Takayuki C/O Bando Chemical Ind. Ltd Nagase
Harushi C/O Bando Chemical Ind. Ltd Nagami
Mitsuhiro C/O Bando Chemical Ind. Ltd Uchino
Takashi C/O Bando Chemical Ind. Ltd Miki
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Bando Chemical Industries Ltd
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Bando Chemical Industries Ltd
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/0819—Developers with toner particles characterised by the dimensions of the particles
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/0802—Preparation methods
    • G03G9/0804—Preparation methods whereby the components are brought together in a liquid dispersing medium
    • G03G9/0806—Preparation methods whereby the components are brought together in a liquid dispersing medium whereby chemical synthesis of at least one of the toner components takes place
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G9/00—Developers
    • G03G9/08—Developers with toner particles
    • G03G9/0827—Developers with toner particles characterised by their shape, e.g. degree of sphericity

Definitions

  • This invention relates to a method of production of toners for use in electrophotography, in particular suitable for use as non-magnetic one-component toner particles, and a method of developing electrostatic latent images using such toners.
  • Toners or developing agents in the form of finely divided particles for developing electrostatic latent images in electrophotography have been heretofore produced by a so-called crushing method.
  • a colorant such as carbon black
  • an electric charge controlling agent such as a certain dyestuff
  • an anti-offset agent such as a wax
  • the resin used be brittle so that a mixture of the resin and the addtives as mentioned above be readily crushed.
  • the resultant toner is excessively finely divided during the use in an electrophotographic apparatus, and contaminates the inside of the apparatus or norms fog on developed positive images.
  • the resultant toner is apt to aggregate together and is undesirably reduced in fluidity, but also there takes place filming on an photoconductive member to deteriorate quality of positive images.
  • a charge controlling agent has an important effect upon copying performance of toners, but since the known charge controlling agents are in many cases 1-20 ⁇ m in particle size, much time is needed to disperse the agent in a resin and thus producitivity is low. Moreover, as a matter on fact, the agent can not be uniformly dispersed in a resin even after kneading over a long period of time.
  • the conventional crushing method has many disadvantages, and therefore there have been proposed in recent years many methods to produce toners directly by suspension or emulsion polymerization of a radical polymerizable monomer which contains colorants therein such as carbon black.
  • an oily monomer phase is polymerized in an aqueous phase containing a suspending agent dissolved therein such as polyvinyl alcohol. Accordingly, at least some portions of the suspending agent remain inevitably on the surface of the resultant polymer particles even after repeated washing, so that the polymer particles are very sensitive to humidity.
  • a suspending agent dissolved therein such as polyvinyl alcohol.
  • suspending agents have been heretofore known.
  • the suspending agents are divided into two.
  • One is a water soluble organic polymer
  • the other is a water insoluble or slightly soluble inorganic material. It is likely that the water soluble organic polymer is adsorbed or adheres to particles to form protective colloid around the particles, and thus produces repulsive force among the particles due to steric hindrance of the polymer, thereby to allow the particles to be dispersed stably in a medium.
  • Polyvinyl alcohol, methylcellulose and gelatin for example, are typical organic polymer suspending agents.
  • the water soluble or slightly soluble inorganic material as a suspending agent is usually used together with an anionic surfactant. It is likely that the inorganic material is adsorbed or adheres to particles to produce electrostatic repulsive force among the particles, thereby to allow the particles to be stably dispersed in a medium.
  • the inorganic material useful as a suspending agent includes an inorganic salt compound such as barium sulfate, barium carbonate, calcium sulfate, calcium carbonate, calcium phosphate, or magnesium carbonate, an inorganic polymeric material such as talc, clay, silicic acid, or diatomaceous earth, and a metal oxide such as aluminum oxide or titanium oxide.
  • the suspension polymerization in the presence of a water soluble organic polymer as a suspending agent provides polymer particles which contain excessively or undesirably finely divided particles and have a wide particle size distribution.
  • the water soluble organic polymer useful as a suspending agent is usually hydrophilic, so that it is difficult to remove such a water soluble organic polymer from the resultant polymer particles.
  • the water soluble organic polymer rather remains on the surface of the resultant polymer particles, and makes the polymer particles water-absorptive and hence adversely affects the requisite properties of toners such as electric resistivity and triboelectricity.
  • the suspension polymerization in the presence of a water insoluble or slightly soluble inorganic material provides polymer particles of a narrowed particle size distribution.
  • a large amount of such an inorganic material is needed to obtain polymer particles of a desired particle size.
  • the inorganic material is used usually together with an anionic surfactant as a suspending aid, so that there arises a problem that excessively finely divided polymer particles are produced.
  • the presence on such finely divided polymer particles in toners produce fog on electrophotographic images, or lowers fluidity of toners to cause unevenness in darkness on electrophotographic images when a large quantities of copies are made in succession.
  • a monomer and a colorant are dispersed in an aqueous medium which contains a suspending agent such as calcium phosphate and an anionic surfactant, suspension-polymerize the monomer, and then the resultant polymer particles are washed with a diluted inorganic acid solution to dissolve the calcium phosphate and then washed with water to remove the resultant water soluble calcium compound from the polymer particles, as disclosed in Japanese Patent Publication No. 63-45101.
  • This method can provide polymer particles free from the suspending agent used, however, the method fails to present resolution regarding the problem of anionic surfactant remaining on the polymer particles.
  • a further method has also been proposed, as disclosed in Japanese Patent Application Laid-open No. 2-223960.
  • a mixture of a monomer and a colorant is added under stirring to an aqueous solution containing a water-soluble inorganic acid salt and an anionic surfactant, and then a water soluble salt of polyvalent metal is added to the solution thereby to deposit a water-insoluble or slightly soluble salt of the polyvalent metal under high shear agitation while the monomer is suspension-polymerized.
  • the water-soluble inorganic acid salt for example, sodium carbonate or sodium phosphate
  • the water soluble salt of polyvalent metal for example, calcium chloride.
  • the anionic surfactant a fatty acid soap such as potassium oleate or sodium oleate.
  • This method also fails to present resolution regarding the problem of anionic surfactant remaining on the polymer particles produced.
  • toners produced by a suspension or emulsion polymerization method that the toner is substantially spherical and has a high fluidity so that there is no need of adding a fluidizing agent such as silica to the toner.
  • a fluidizing agent such as silica
  • an electrostatic latent image is formed on the surface on an photoconductive member to which electrostatic charge has been given, the latent image is developed by toner particles to a toner imaged and the toner image is transferred onto a substrate, and then the toner image is fixed thereon, to provide a copy image. Therefore, it is necessary that the toner remaining on the photoconductive member is removed therefrom after the toner image has been transferred and fixed onto the substrate to make copy image in succession.
  • a blade cleaning method is widely known according to which the toner is scraped off with a cleaning blade after the toner image has been transferred onto the substrate.
  • the blade may be formed of various elastomers, among which a polyurethane elastomer is most preferred from the stand-point of mechanical properties such as resistance to abrasion.
  • spherical toner particles enter beneath the blade when the blade scrapes the photoconductive member, and roll between the blade and the surface of photoconductive member, so that the toner particles remain on the photoconductive member after the cleaning of the member with the blade.
  • the polymer particles tend to aggregate to each other on account of unreacted monomers remaining in the reaction system or the deformed polymer particles are restored to their original spherical particles at relatively high temperatures where the polymer particles are readily deformed, on account of surface tension they possess. Namely, effective deformation of spherical polymer particles is not attained. Agitation of the polymer particles as small rates or at low temperatures also fails to effectively deform the spherical polymer particles, although the aggregation of the particles is restrained.
  • the polymer particles produced by the suspension polymerization have rather a wide particle size distribution.
  • large spherical particles might be readily deformed, but small particles are not, and accordingly there arises a wide distribution in degree of deformation.
  • small spherical particles remain undeformed and such small spherical particles elude cleaning by a blade on the photoconductive member.
  • a further method of producing toners has been recently proposed in which finely divided particles are adhered and fixed onto the toner particles by a so-called impact method, as described in Japanese Patent Application Laid-open No. 62-129866. however, since toner particles have a siginficantly wide size distribution, it is necessary that the finely divided particles are of not more than about one micron so that they are successfully fixed on the individual toner particles accoding to this method. Little improvement in blade cleanability is attained with such toner particles having such fine particles fixed thereon.
  • an image forming process such as an electrophotographic process or an eletrostatic recording process using toners includes in general the following steps.
  • a photoconductive member is electrified, an electrostatic latent image is formed on the photoconductive member by exposure of the member to the image, developing the latent image to a toner image using toners, transfer the toner image onto a recording substrate such as paper, and fix the toner image thereon by application of heat or pressure to the toner image.
  • the developing methods are divided into two.
  • One is a method wherein a two-component developing agent composed of toners and carriers is used, and the other is a method wherein a one-component developing agent is used which contains no carriers.
  • the method wherein the one-component developing agent is used has no such problems as above.
  • the method wherein the one-component developing agent is used is divided into two. one is a method wherein magnetic toners are used, and the other is a method wherein non-magnetic toners are used.
  • the polymer method transfers the toners by a magnetic adsorptive means in a developing device, so that the device is expensive and complicated.
  • the toner particles contain therein magnetic powder, and hence need a large quantity of heat so that the toner image is fixed.
  • the method wherein one-component developing agent is used (which will be hereinafter referred to as the one-component method) is promising as a method of developing electrostatic latent images, as described in Japanese Patent Application Laid-open No. 47-13088 or No. 47-13089. But on the other hand, the method involves a number of problems and has not yet become widely utilized.
  • the one-component method contains a developing device as illustrated in Fig. 1.
  • the device 4 includes a toner box 12 which contains toners 10 under stirring with a stirring blade 11.
  • the toner box 12 is provided with a toner transfer member 13 adjacent to the photoconductive member 1, and the toner transfer member 13 rotates in the opposite direction to the photoconductive member 1.
  • the toner transfer member 13 may be in contact with the photoconductive member 1 or placed close to the photoconductive member 1 with a small distance therebetween.
  • the toner transfer member 13 has a member 14 for regulating or controlling the thickness of toners forced on the member 13.
  • a member 15 which rotates in the same direction as the toner transfer member 13 or in the opposite direction in contact therewith.
  • toner transfer member 13 It is necessary to form a thin layer of toners on the toner transfer member 13 to evenly triboelectrify the toners thereon, and thus usually a doctor blade is suitably used as such a member 14 for regulating or controlling the thickness of toners.
  • a doctor blade is suitably used as such a member 14 for regulating or controlling the thickness of toners.
  • the toners form a thick layer on the toner transfer member 13 the toners in the surface layer only are electrified while the towers inside the layer are unevenly electrified, so that the toners slightly electrified are scattered to contaminate the suroundings or produce fog on fixed toner images.
  • the one-component method uses no carriers to electrify toner particles, and consequently it is difficult to electrify toner particles sufficiently.
  • the toner particles produced by the crushing method are irregular in shape, or formless, and thus they are worn at corners to produce a large amount of finely divided powder when they are made adhere in a thin layer onto the toner transfer member 13.
  • the powder adheres onto non-image areas on the photoconductive member thereby to produce fog on the resultant fixed toner images, or adheres onto the member 13 to cause insufficient electrification of toners or produce white lines on the resultant fixed toner image.
  • the toner particles produced by the polymerization method are free from such a problem as above mentioned attended by the toner particles produced by the crushing method.
  • the toner particles produced by the polymerization method are truely spherical, and accordingly they readily pass through the regulating member 14 on the member 13 to fail to form an even and thin layer on the member 13.
  • the toners are insufficiently electrified to produce fog on fixed images, but also when latent images on the photoconductive member are developed, the toners are excessively rotatable on the member 13 so that they produce fixed images with poor resolution of fine lines.
  • the thus formed toner images are transferred electrostatically onto recording paper or fixed thereonto by application of heat or pressure also, the toners readily rotate to provide blur with fine lines.
  • the toner remaining on the photoconductive body is removed therefrom usually with a cleaning blade after the toner image has been transferred onto recording paper.
  • the toner particles in the form of true spheres such as those produced by the polymerization method readily escape from cleaning with a cleaning blade, with consequence that the remaining toners are not completely removed from the photoconductive member.
  • the invention provides a method of producing toners for use in electrophotography which comprises the following steps carried out in sequence:
  • any radical polymerizable monomer which is known as usable for the production of toner by suspension polymerization is usable in the invention. Therefore, such monomers include,for example, styrene, substituted styrenes such as o-methylstyrene, m-methylstyrene, p-methylstyrene or p-chlorostyrene; vinyl esters such as vinyl acetate or vinyl propionate; acrylic acid esters such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, phenyl acrylate or ⁇ -chloromethyl acrylate; methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, propyl methacryl
  • a polyfunctional monomer may be used together with the above mentioned monomers to improve fixation and anti-offset properties of toners.
  • a polyfunctional monomer for example, divinylbenzene or ethylene glycol dimethacrylate.
  • the polyfunctional monomer when used in excess, the resultant polymer particles are too high in melting points, and poor in fixability.
  • the polyfunctional monomer may be used normally in an amount of not more than about 1 % by weight based on the radical polymerizable mononer.
  • a colorant for instance, carbon black
  • a peroxide compound with, for example, a ball mill, and is dispersed minutely and finely in the monomer.
  • the preferred peroxide compound used are acyl peroxide which is derived from a fatty acid.
  • lauroyl peroxide is preferred.
  • the mixture of the monomer and carbon black is stirred in the presence of the peroxide compound over a period of several hours to disperse the carbon black evenly in the monomer as finely divided particles of not more than one micron in particle size, preferably of not more than 0.5 microns in particle size, the dispersion of carbon black in the monomer may be carried out at room temperatures, but if desired, at elevated temperatures, for example, at about 50-80°C to accelerate the dispersion.
  • Carbon black is used in amounts of about 2-10 parts by weight in relation to 100 parts by weight of the radical polymerizable monomer.
  • the peroxide compound is used usually in an amount of about 10-50 parts, preferably of about 10-40 parts by weight, in relation to 100 parts by weight of carbon blank used.
  • the use of the peroxide compound in an amount of less than about 10 parts by weight in relation to 100 parts by weight of carbon black used fails to disperse carbon black minutely and uniformly in the monomer, whereas the use of the peroxide compound in an amount of more than about 50 parts by weight in relation to 100 parts by weight of carbon black used, the decomposition fragments of the peroxide compound used remain in the resultant polymer particles.
  • Such polymer articles undesirably smell bad when being heated and melted to fix on a recording paper during the electrophotographic process.
  • azobisnitrile polymerization initiator such as azobisisobutyronitrile or azobisdimethylvaleronitrile
  • peroxide polymerization initiator fails to uniformly and minutely disperse carbon black in the monomer, but carbon black aggregates together, and most of the carbon black used is dispersed as large particles in the monomer.
  • the monomer in part polymerizes in the presence of the azobisnitrile polymerization initiator, to increase the viscosity of the mixture of the monomer and the carbon black. This adversely affects the preparation of suspension of fine droplets of the monomer in an aqueous medium.
  • Any colorant may be used together with carbon black, if needed.
  • Such colorants may or may not be soluble in the monomer.
  • colorants in, for example, Japanese Patent Application Laid-open No. 62-246073.
  • a colorant insoluble in the monomer such a colorant may be dispersed minutely and uniformly in the monomer with aid of a peroxide compound or other suitable dispersing agent in the same manner as carbon black is dispersed in the monomer.
  • a charge controlling agent may then be dispersed evenly as finely divided particles in the monomer mixture with carbon black.
  • a charge controlling agent is added to the monomer mixture together with a dispersing agent soluble in the monomer, and the resultant mixture is stirred for, for example, about 50-200 hours, with a ball mill, thererby to pulverize and disperse the agent evenly as finely divided particles of not more than about 0.5 microns, preferably of not more than about 0.3 microns, in in the monomer.
  • This dispersion may also be carried out at elevated temperatures such as at about 50-80°C to accelerate the dispersion.
  • the charge controlling agent is used usually in an amount of about 0.01-10 parts, preferably of about 0.05-5 parts, most preferably of about 0.1-1 part by weight, in relation to 100 parts by weight of the monomer used.
  • a charge controlling agent may be incorporated into polymer particles after the preparation of polymer particles.
  • the charge controlling agent may be made to adhere physically to the particles.
  • Any charge controlling agent known in the art may be used, such as a powder of an inorganic compound, a powder of an organic compound including metallized dyes and pigments, and organic carboxylic acid metal salts, and a powder of an organic polymer.
  • carbon black and a charge controlling agent are dispersed evenly as finely divided particles in the monomer as hereinbefore described, and if necessary an additional amount of the monomer is further added to the dispersion, and then an azobisnitrile polymerization initiator is added to the dispersion, to form a monomer composition.
  • Suitable azobisnitrile polymerization initiators include, for example, azobisdimethylvaleronitrile and azobisdimethylisobutyronitrile, however, azobisdimethylvaleronitrile is especially preferred since it is highly soluble in the monomer.
  • the monomer composition in the form of a dispersion thus containing an azobisnitrile polymerization initiator is then dispersed in an aqueous medium as small droplets by use of, for example, a homogenizer, and is heated so that suspension polymerization proceeds to produce spherical polymer particles.
  • the azobisnitrile polymerization initiator is used usually in amounts of about 1-10 parts preferbly of about 2-5 parts by weight, in relation to 100 parts by weight of the monomer used.
  • the amount is less than about 1 part by weight in relation to 100 parts by weight of the monomer used, the polymerization proceeds only very slowly, and it is substantially impossible to polymerize the monomer in a high polymerization rate, while when the amount is more than about 10 parts by weight in relation to 100 parts by weight of the monomer used, the resultant polymer is low in molecular weight, and is insufficient in anti-offset properties.
  • the mixture of the monomer, carbon black, an azobisnitrile polymerization initiator, and optionally a charge controlling agent is added to an aqueous alkaline medium containing a first water soluble inorganic salt, and the mixture is vigorously stirred by use of, for example, a homogenizer, to provide an aqueous dispersion of droplets of the monomer composition of 1-30 microns, preferably in the range of 1-5 microns, in diameter, in the aqueous medium.
  • the first water soluble inorganic salt used includes, for example, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, sodium phosphate, sodium dihydrogen phosphate, sodium pyrophosphate, potassium phosphate, sodium sulfate, potassium sulfate and sodium metasilicate.
  • a second water soluble inorganic salt which reacts with the first water soluble inorganic salt to form a salt which is slightly soluble or insoluble in water, is added to the aqueous dispersion of the above mentioned monomer composition, thereby to form such an inorganic salt which is slightly soluble or insoluble in water under substantially neutral pH conditions, preferably at a pH of 6-7.
  • a water soluble inorganic acid phosphoric acid.
  • the second water soluble inorganic salt used depends upon the first water soluble inorganic salt used, but there may be preferably used chlorides or sulfates of calcium, barium, magnesium, manganese, zinc, strontium or aluminum.
  • sodium phosphate is used as the first water soluble inorganic salt, and calcium chloride as the second water soluble inorganic salt in the method of the invention.
  • calcium chloride as the second water soluble inorganic salt in the method of the invention.
  • a water insoluble or slightly soluble calcium phosphate deposits in the aqueous medium.
  • the first water soluble inorganic salts are used in an amount of 0.1-20 parts by weight, preferably 0.5-15 parts by weight, in relation to 100 parts by weight of the monomer.
  • the second water soluble inorganic salt is used in an amount equivalent to the amount of the first water soluble inorganic salt used and the inorganic acid used. It is further preferred that the amount of the second water soluble inorganic salt used is in the range of 0.1-20 parts by weight, preferably 0.5-15 parts by weight, in relation to 100 parts by weight of the monomer used.
  • the water insoluble or slightly soluble inorganic salt is deposited in the aqueous medium under the substantially neutral pH conditions, and the finely divided droplets of the monomer composition, preferably having a particle size of 1-5 microns as hereinbefore mentioned, are made unstable in the medium at a neutral pH region, and as results they are collected and coagulated to form droplets of larger particle size, preferably of 5-25 microns, most preferably 7-20 microns.
  • an alkali such as ammonia water is again added to arrange the dispersion at an alkaline pH of more than 7 and not more than 12, preferably at a pH or more than 7 and not more than 10, thereby to allow the thus enlarged droplets of the monomer composition to be dispersed again stably in the medium with the particle size distribution being shifted to the direction of larger particle size and yet to the direction of a more narrow distribution, and with substantially no undesirably finely divided droplets of the monomer composition being present in the dispersion.
  • the resultant droplets of the monomer composition have larger particle size and yet a such narrowed particle size distribution than they initially had.
  • the second water soluble inorganic salt is added to the aqueous dispersion of the monomer composition containing the first water soluble inorganic salt to form the water insoluble or slightly soluble inorganic salt at an alkaline pH region, not at a neutral pH region, then the finely divided droplets of the mononer composition do not coagulate, but exist stably as they are, so that there are obtained droplets of the monomer composition containing such finely divided droplets, and thus still having a wide particle size distribution.
  • an aqueous solution of sodium phosphate has a pH of about 12.
  • an aqueous solution of calcium chloride is added to the dispersion to deposit calcium phosphate
  • the dispersion usually has a pH more than 8. Consequently, the finely divided droplets of the monomer do not coagulate, but exist stably as they are, Even if a dispersing agent such as an anionic surfactant is added to the dispersion, the result is the same, and there is obtained a dispersion of droplets of monomer containing a large amount of finely divided droplets, and thus having a wide particle size distribution.
  • a monomer is first dispersed as finely divided droplets in an aqueous medium, and then a water insoluble or slightly soluble inorganic salt is formed therein at a substantially neutral pH region to make the above finely divided droplets of the monomer unstable so that they coagulate to form droplets of a larger particle size, and then the aqueous dispersion is again arranged at an alkaline pH of more than 7 and not more than 12, preferably at a pH of more than 7 and not more than 11, thereby to allow the above formed droplets on the monomer to be dispersed again stably in the medium,
  • the thus resultant aqueous dispersion contains droplets of the monomer having a enlarged particle size and a narrowed particle size distribution with substantially no undesirably finely divided droplets being present in the medium.
  • the resultant dispersion contains stable droplets of the monomer of a larger diameter and a more narrow particle size distribution than they initially had.
  • the dispersion is stirred at a temperature of 40-95°C, preferably 50-90°C, to suspension-polymerize the monomer, to provide polymer particles usually of particle size of 1-30 microns, and 3-25 microns in preferred embodiments, and 5-20 microns in the most preferred embodiments, and of a narrow particle size distribution.
  • polymer particles having a particle size distribution more narrow than that of droplets of monomer dispersed in an aqueous medium.
  • the resultant polymer particles are first washed with an inorganic acid solution such as a hydrochloric acid solution to dissolve the water insoluble or slightly soluble salt, and then washed with water to remove the solubilized salt from the polymer particles.
  • the polymer particles are then dried in vacuo to provide toners.
  • the thus prepared toners may be suitably used in a non-magnetic one-component developing agent in developing electrostatic latent images.
  • toners which are more suitably used as a non-magnetic one-component developing agent by deforming the polymer particles in accordance with the invention.
  • a method of developing electrostatic latent images using a non-magnetic one-component developing agent and a method of producing toners suitable for use in such a non-magnetic one-component method of developing electrostatic latent images on a photoconductive member in electrophotographic process.
  • an improvement in a method of developing electrostatic images in electrophotographic process which comprises providing eletrostatic charge on the surface of a photoconductive member, exposing the member to an image to form thereon an electrostatic latent image, forming a layer having a controlled, even and small thickness of non-magnetic one-component toner particles on the member while triboelectrifying the toner particles, and developing the latent image with the toner particles
  • the improvement comprising the use of toner particles mainly composed of disklike toner particles having a diameter of 3-30 ⁇ m, a thickness of 1-15 microns and a flatness of not more than 0.5 as the flatness of the disklike toner particles is defined as a ratio of average thickness to average diameter of the particles, or oval toner particles having a major axis of 3-30 microns in length, a minor axis of 1-25 microns in length and a flatness of not more than 0.5 as the flatness of the oval toner particles is defined as a
  • the suspension polymerization provides polymer particles which are 1-30 microns in diameter which have a flatness of not less than 0.98, the flatness being defined hereinafter.
  • the resultant polymer particles are substantially true spherical.
  • the suspension which contains the resultant substantially true spherical polymer particles may be further treated with a continuous wet type agitation mill in the presence of calcium phosphate as a suspending agent (before the resultant polymer particles are washed with a hydrochloric acid solution to remove the water insoluble or slightly soluble salt from the polymer particles).
  • the suspension of the polymer particles are treated with a continuous wet type agitation mill in the presence of calcium phosphate preferably at temperature in the range of ⁇ 10°C of the glass transition temperatures of the polymer, thereby to deform or flatten the spherical particles into disklike or oval particles, or a mixture of these.
  • the continuous wet type agitation mill is known. As illustrated in Fig. 2, the mill contains an annular stator 21 having a triangular section and a rotor 22 therein similar to the stator in shape. A milling zone 23 is formed as an annular gap of a small breadth between the stator and the rotor. The milling zone contains a milling medium 24 therein to impart mechanical impact to suspended particles to deform them so that they get flat or flattened.
  • the suspension is introduced into the milling zone through an inlet 25 at the lower part of the mill and travels along the gap, and is then separated from the medium at a separator 26.
  • the suspension which contains deformed polymer particles is obtained from an outlet 27. While the polymer particles in the suspension are deformed in the milling zone, warm water is supplied to passages 28 within the stator and the rotor to control the temperature of the suspension.
  • the milling medium also travels centrifugally along the milling zone having a W-shaped section and returns to the inlet. Zirconia, glass or steel spherules of, for example, about 0,5-3 mm in diameter are used as the milling medium, although not limited thereto.
  • treatment of the suspension containing the polymer particles with the annular, continuous, wet type agitation mill is carried out at temperatures in the range of ⁇ 10°C of the glass transition temperature of the matrix which forms the polymer.
  • the suspension is treated at temperatures lower than the glass transition temperature of the polymer by 10°C, the polymer particles crushed, rather than deformed.
  • the suspension is treated at temperatures higher than the glass transition temperature of the polymer by 10°C, the polymer particles are apt to aggregate to each other to form mass, but also the polymer particles become spherical again on account of surface tension even after the particles have been deformed, so that deformation efficiency is low.
  • the treatment is carried out usually over a period of 0.5-10 hours, preferably 2-5 hours.
  • annular, continuous, wet type agitation mill has an advantage that the rotor produces a larger shearing force in the direction of rotation than a ball mill or a sand mill, and can exert anisotropic stress on the particles, so that they are effectively deformed even when they have a significant particle size distribution. Namely, the particles are deformed irrespectively of their diameters, so that the resultant toner particles have a greatly improved blade cleanability. In addition, such particles make contact with a substrate with a large surface area when transferred from a photoconductive body, and thus fixed thereof at relatively low temperatures. Similarly, the individual particles have a large contact area on a substrate, so that a small amount of such particles produces dark images, and consumption of toner is reduced.
  • a disklike polymer particle having a diameter of 3-30 ⁇ m, a thickness of 1-15 ⁇ m and a flatness of not more than 0.5, or an oval polymer particle having a major axis 3-30 ⁇ m in length, a minor axis 1-25 ⁇ m in length and a flatness of not more than 0.5, or a mixture of these, by the deforming or flattening treatment of spherical polymer particles produced by a suspension polymerization method with the annular, continuous, wet type agitation mill according to the invention.
  • the flatness of disklike toner particles is defined as a ratio of average thickness to average diameter of the particles.
  • the flatness of the oval toner particles is defined as a ratio of twice the average thickness to the sum of length of average major axis and length of average minor axis.
  • the thus deformed toners produced by the method of the invention are mainly composed of disklike or oval particles, or a mixture of these, contrast to truely spherical particles, so that the thus deformed or flattened toner particles form readily and certainly a thin and even layer of toners on the toner transfer member, and moreover the deformed toner is prevented from rotation when they are transferred from the toner transfer member to a photoconductive member so that they provide copy images with no fog.
  • the deformed toner particles do not adhere to the transfer member and thus provide such high quality copy images as have no defects and have high resolution.
  • the toner is deformed so that it does not pass through between the cleaning blade and the photoconductive member and has an improved blade cleanability.
  • the toner has a flatness of more than 0.5, it is difficult to form a thin layer of toners on the toner transfer member, and moreover, the resultant copy images are apt to be blurred on account of rotation of toner particles when they are developed, transferred or fixed, as hereinbefore described. Further, it may happen that toner particles escape from cleaning with a cleaning blade to produce a variety of defects on the resultant copy images.
  • the toner is produced in the manner as above set forth, and the toner provides images with neither fog nor unevenness in darkness in solid images and with a high resolution.
  • the toner also provides copy images with are the same in quality as that of initial stage of copying even after continuous copying in large quantities.
  • the RAT value is an index of particle size distribution, and is defined as D40/D90 wherein D40 represents the 40% oversize particle size (diameter) in the cumulative distribution; and D90 represents the 90% oversize particle size (diameter) in the cumulative distribution.
  • D40 represents the 40% oversize particle size (diameter) in the cumulative distribution
  • D90 represents the 90% oversize particle size (diameter) in the cumulative distribution.
  • An amount of 400 parts by weight of an aqueous solution of 12 parts by weight of sodium phosphate Na3PO4 ⁇ 12H2O) was prepared and arranged at pH of 11.0 by use of phosphoric acid.
  • the above monomer composition was added to the solution, and the mixture was agitated for 10 minutes using a homogenizer "Model TK-M available from Tokushu Kakoki Kogyo K.K., Japan) at 6000 rpm to disperse the monomer composition in the aqueous solution, to prepare an aqueous dispersion containing finely divided droplets of the monomer composition of about 3 microns in number average particle size.
  • ammonia water was added under stirring to the dispersion to arrange the dispersion at a pH of 8.5, so that the enlarged droplets of the monomer composition were made stable again whereupon the droplets were found to have a volume average particle size of 8.3 microns and an RAT value of 1.56.
  • the thus prepared aqueous dispersion on the monomer composition was gently stirred at 70°C for 6 hours to polymerize the monomer.
  • the resultant polymer particles were found to have a volume average particle size of 8.1 microns and an RAT value of 1.46.
  • the polymer particles were washed with a hydrochloric acid solution, and then with water several times, followed by drying in vacuo to provide toners having a triboelectric charge of -28 ⁇ C (microcoulomb)/g.
  • the polymer was found to have a glass transition temperature of 65°C.
  • An amount of 100 parts by weight of the toners was mixed with 0.3 parts by weight on hydrophobic silica (R 972 available from Japan Aerosil K.K.) to provide a developing agent of which toner content was 5% by weight.
  • the developing agent was used in an electrophotographic device (Model LED Printer K-II available from Nippon Kentech K.K.), and was found to provide high quality copy images with no fog or no unevenness in darkness in solid images and with high resolution, There were also made 10000 sheets of copies in succession to provide high quality copy images substantially the same in quality as that of initial stage of copying.
  • Example 2 An amount of 0.5 parts by weight of lauroyl peroxide were used to disperse the same carbon black as before, and otherwise in the same manner as in Example 1, an aqueous dispersion of the monomer composition was prepared.
  • the droplets of the monomer composition in the dispersion was found to have a volume average particle size of 11.8 microns and an RAT value of 1.55.
  • the momoner was suspension-polymerized in the same manner as in Example 1 to provide toners having a volume average particle size of 11.7 microns, an RAT value of 1.48, and a triboelectric charge of -23.2 ⁇ C/g.
  • the polymer was found to have a glass transition temperature of 65°C.
  • Example 1 Using the toners thus prepared and in the same manner as in Example 1, a developing agent of which toner content was 5% by weight was prepared. The agent was also found to provide high quality copy images in the same test as in Example 1.
  • Example 2 There was prepared a monomer composition containing the same carbon black and charge controlling agent as before in the same manner as in Example 1.
  • the monomer composition was added to the above dispersion of calcium phosphate, whereupon the dispersion was found to have a pH of 8.46, and stirred vigorously at a rate of 6000 rpm for 10 minutes with the same homogenizer as hereinbefore to prepare an aqueous dispersion of the monomer composition.
  • the resultant droplets of the monomer composition were found to have a volume average particle size of 9.7 microns and an RAT value of 1.78.
  • the droplets were further found to contain finely divided droplets of about 5 microns or less in size in an amount of 30%.
  • the aqueous dispersion of the monomer composition was stirred gently at 70°C for 6 hours to polymerize the monomer.
  • the resultant polymer particles were found to have a volume average particle size of 9.6 microns and an RAT value of 1.75. These values were almost the same as those of the droplets of the monomer composition before the polymerization.
  • the polymer particles were also found to have a wide particle size distribution.
  • the polymer particles were washed with a hydrochloric acid solution, and then with water several times, followed by drying in vacuo to provide toners.
  • the agent was found to provide copy images having much fog thereon and poor resolution in the same test as in Example 1.
  • Example 2 There was prepared a monomer composition containing carbon black and charge controlling agent in the same manner as in Example 1.
  • the monomer composition was added to the above dispersion of calcium phosphate, whereupon the dispersion was found to have a pH of 8.37, and stirred vigorously at a rate of 6000 rpm for 10 minutes with the same homogenizer as hereinbefore to prepare an aqueous dispersion of the monomer composition.
  • the resultant droplets of the monomer composition were found to have a volume average particle size of 8.5 microns and an RAT value of 1.76.
  • the droplets were further found to contain finely divided droplets of about 5 microns or less in size in an amount of 25%.
  • the aqueous dispersion of the monomer composition was stirred gently at 70°C for 6 hours to polymerize the monomer.
  • the resultant polymer particles were found to have a volume average particle size of 8.2 microns and an RAT value of 1.77, and also a wide particle size distribution.
  • the polymer particles were washed with a hydrochloric acid solution, and then with water several times, followed by drying in vacuo to provide toners.
  • the agent was found to provide copy images having much fog thereon and poor resolution in the sane test as in Example 1.
  • the above monomer composition was added to the aqueous alkaline solution of sodium phosphate under stirring at a rate of 6000 rpm for 10 minutes to disperse the monomer composition in the aqueous solution, to prepare an aqueous dispersion containing finely divided droplets of the monomer composition of about 3 microns in number average particle size.
  • the monomer composition was polymerized in the same manner as in Example 1.
  • the resultant polymer particles were found to have a volume average particle size of 11.20 microns and an RAT value of 2.063, and also a wide particle size distribution.
  • the agent was found to provide copy images having much fog thereon and poor resolution in the same test as in Example 1.
  • the aqueous suspension of polymer particles prepared in Example 2 was continuously fed into an contiuous, annular, wet type agitation mill (Kobol Mill available from Shinko Pantech K.K.), as an example of such a mill is shown in Fig. 2, and the polymer particles were deformed under the conditions of temperature, suspension travelling speed and rotor peripheral speed shown in the Table 1. Zirconia spheres of 0.75-1.0 mm in diameter were used as a milling medium. The charge rate of the medium in the milling zone was 70%.
  • the toner thus deformed was used in electrophotographic copying under the conditions of temperature of 23°C and relative humidity of 60% (normal temperature and normal humidity) and under the conditions of temperature of 30°C and relative humidity of 80% (high temperature and high humidity).
  • the performance at the initial stage and after making 10000 sheets of copies were examined. Namely, the triboelectric charge of toners on the toner transfer member, adhesion of toner particles onto the member and quality of fixed images were measured. The results are shown in Tables 2 and 3.
  • the shape, average size and flatness of toner particles were measured with randomly selected 50 particles on through electromicrophotographs.
  • the triboelectric charge of the toner particles on the toner transfer member was measured with the use of specific electric charge measuring device. Namely, the toner particles in a thin layer on the toner transfer member were absorbed and trapped into a gauge, and the specific electric charge of the absorbed toners were measured.
  • Example 3 The polymer particles were deformed under the conditions as indicated in Table 1, and otherwise in the same manner as in Example 3, a toner was prepared. The performance of the toner was examined in the same manner as in Example 3.
  • Example 2 The performance of a toner prepared in Example 2 was examined as it was in the sane manner as in Example 3.
  • Example 2 The aqueous suspension of polymer particles prepared in Example 2 was treated under the conditions as shown in Table 1 to provide deformed toner particles having a flatness of 0.62. The performance of the toner was examined in the same manner as in Example 3.
  • the suspension polymerization was carried out in the same manner as before to provide polymer particles wherein the polymer had a glass transition temperature of 63°C.
  • the aqueous suspension of polymer particles was treated under the conditions as shown in Table 1. Then, a mixture of 77% by volune of water and 23% by volume of methanol containing sodium hydroxide in an amount of ten times equivalent of the vinyl acetate component in the polyvinyl alcohol used was added to the suspension and stirred at 50°C for 3 hours to saponify the polyvinyl alcohol.
  • the resultant deformed polymer particles were recovered and washed with water, and then with aqueous solution containing hydrochloric acid in an amount equivalent to the amount of sodium hydroxide used to neutralize the sodium hydroxide.
  • the polymer particles were dried under reduced pressures to provide toner particles having a flatness of 0.46.
  • Toner particles made by a method according to a first aspect of the invention give, when deformed and used in a method according to a second aspect of the invention, an even layer of controllable thickness on the toner transfer member 13.
  • the particles are then transferred by electrostatic attraction onto the photoconductive member 1 to develop its latent image to form a positive image, otherwise known as a toner image.
  • the toner image is then transferred and fixed onto paper to give the desired hard copy.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Developing Agents For Electrophotography (AREA)
EP92306582A 1991-07-17 1992-07-17 Procédé de production de toners pour l'électrophotographie et procédé de développement d'images latentes électro-statiques utilisant desdites toners Withdrawn EP0524016A1 (fr)

Applications Claiming Priority (2)

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JP3176658A JPH0519534A (ja) 1991-07-17 1991-07-17 静電潜像現像用トナーの製造方法
JP176658/91 1991-07-17

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0617334A2 (fr) * 1993-03-26 1994-09-28 Nippon Zeon Co., Ltd. Procédé de préparation de révélateur par polymérisation en suspension
EP0834777A1 (fr) * 1996-10-07 1998-04-08 Xerox Corporation Procédés de préparation de révélateurs cationiques
US5891948A (en) * 1995-06-19 1999-04-06 Curios Co., Ltd. Coating material for forming variegated patterns of granite tone and resin flakes
EP0926564A1 (fr) * 1997-12-26 1999-06-30 Canon Kabushiki Kaisha Procédé de production de toner
US5958643A (en) * 1993-09-22 1999-09-28 Minolta Co., Ltd. Liquid developer having polymer particles of a flat configuration dispersed in a dispersion medium
US5968705A (en) * 1997-05-23 1999-10-19 Nippon Zeon Co., Ltd. Process for producing a polymerized toner
EP0999476A1 (fr) * 1998-11-06 2000-05-10 Canon Kabushiki Kaisha Procédé de production de toner
WO2002035291A1 (fr) * 2000-10-25 2002-05-02 3M Innovative Properties Company Impression d'adhesifs sous forme d'image et procede de polymerisation a coalescence limitee
US6818371B2 (en) 2000-02-02 2004-11-16 Zeon Corporation Electrophotographic developer, process for producing the same, and method of forming image

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2026390A1 (de) * 1969-05-28 1971-01-07 Fuji Photo Film Co Ltd , Kanagawa (Japan) Elektrophotographischer Entwickler und Verfahren zu dessen Herstellung
EP0038208A1 (fr) * 1980-04-14 1981-10-21 Xerox Corporation Procédé de polymérisation en dispersion pour préparer des toners
EP0297839A2 (fr) * 1987-06-29 1989-01-04 Bando Chemical Industries, Limited Procédé de fabrication de toners utilisés en électrophotographie

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2026390A1 (de) * 1969-05-28 1971-01-07 Fuji Photo Film Co Ltd , Kanagawa (Japan) Elektrophotographischer Entwickler und Verfahren zu dessen Herstellung
EP0038208A1 (fr) * 1980-04-14 1981-10-21 Xerox Corporation Procédé de polymérisation en dispersion pour préparer des toners
EP0297839A2 (fr) * 1987-06-29 1989-01-04 Bando Chemical Industries, Limited Procédé de fabrication de toners utilisés en électrophotographie

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0617334A3 (fr) * 1993-03-26 1995-01-04 Nippon Zeon Co Procédé de préparation de révélateur par polymérisation en suspension.
US5427885A (en) * 1993-03-26 1995-06-27 Nippon Zeon Co., Ltd. Process for producing toner through suspension polymerization
EP0617334A2 (fr) * 1993-03-26 1994-09-28 Nippon Zeon Co., Ltd. Procédé de préparation de révélateur par polymérisation en suspension
US5958643A (en) * 1993-09-22 1999-09-28 Minolta Co., Ltd. Liquid developer having polymer particles of a flat configuration dispersed in a dispersion medium
US5891948A (en) * 1995-06-19 1999-04-06 Curios Co., Ltd. Coating material for forming variegated patterns of granite tone and resin flakes
EP0834777A1 (fr) * 1996-10-07 1998-04-08 Xerox Corporation Procédés de préparation de révélateurs cationiques
US5968705A (en) * 1997-05-23 1999-10-19 Nippon Zeon Co., Ltd. Process for producing a polymerized toner
EP0926564A1 (fr) * 1997-12-26 1999-06-30 Canon Kabushiki Kaisha Procédé de production de toner
US6054244A (en) * 1997-12-26 2000-04-25 Canon Kabushiki Kaisha Process for producing toner
EP0999476A1 (fr) * 1998-11-06 2000-05-10 Canon Kabushiki Kaisha Procédé de production de toner
US6309788B1 (en) 1998-11-06 2001-10-30 Canon Kabushiki Kaisha Process for producing toner
US6818371B2 (en) 2000-02-02 2004-11-16 Zeon Corporation Electrophotographic developer, process for producing the same, and method of forming image
US7008747B2 (en) 2000-02-02 2006-03-07 Zeon Corporation Electrophotographic developer, production process thereof and image forming process
WO2002035291A1 (fr) * 2000-10-25 2002-05-02 3M Innovative Properties Company Impression d'adhesifs sous forme d'image et procede de polymerisation a coalescence limitee
US6509128B1 (en) 2000-10-25 2003-01-21 3M Innovative Properties Company Imagewise printing of adhesives and limited coalescence polymerization method

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