Classifications

• • 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
  • G03G9/087—Binders for toner particles
  • G03G9/08784—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775
  • G03G9/08795—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775 characterised by their chemical properties, e.g. acidity, molecular weight, sensitivity to reactants
• • 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
  • G03G9/087—Binders for toner particles
  • G03G9/08784—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775
  • G03G9/08791—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775 characterised by the presence of specified groups or side chains

Definitions

• the present invention relates to resin particles having a specific size and size distribution for use as electric charge control agents in toner for developing an electrostatic image used in electrophotography, and to a dispersion polymerization method of manufacturing the same.
• the toner for developing electrostatic images used in the field of electrophotography or the like is formed from resin particles of 5 to 20 ⁇ m in size consisting of colorants, charge control agents, etc. dispersed in binding resin particles.
• the charge control agents used to confer triboelectrification ability on the resin particles include nigrosine, monoazo dyes, or metallic complexes of salicylic acid or naphthoic acid, etc.
• the charge control agents become dispersed unevenly in the resin particles, preventing uniform conferring of frictional chargeability. In view of such difficulty, there has been proposed a method wherein charge control resins having polar functional groups are mixed into binding resins to confer frictional chargeability to the toner.
• EP-A-0 330 287 discloses a toner for developing statically charged images which comprises a copolymer comprising a water soluble monomer having a group -SO 3 X in which X stands for hydrogen, sodium, potassium or calcium and an oil-soluble monomer.
• the copolymer is incorporated into a polymerizable composition comprising a polymerizable monomer, an initiator and a colorant.
• Dispersion stabilizers are used for suspension polymerization of toner particles. Fine polymer particles having a size smaller than 5 ⁇ m and 8 ⁇ m are disclosed.
• emulsion polymerization it is possible to control the compositions of the monomers in the copolymer, but since the molecular weight of the copolymer is very high, the compatibility with binding resins is low. Furthermore, in emulsion polymerization, the problem is that the size of the obtained particles is small, thus making it difficult to precipitate the particles. In dispersion polymerization, uniform polymerization is possible, but the size distribution of the obtained particles is broad and the molecular weight tends to become high, thus leaving room for improvement.
• electrophotographic toner charge control resin particles which are spheroidal and are composed mainly of a copolymer formed from at least one water-soluble monomer having an anionic group of sulfonic, carboxylic or phosphoric type and at least one oil-soluble monomer, wherein the copolymer has a weight-average molecular weight of 3,000 to 50,000, the resin particles being formed by dispersion polymerisation and having a volume median size of 3 ⁇ m to 10 ⁇ m and the ratio D 25 /D 75 of 25 volume percent integrated diameter D 25 to the 75 volume percent integrated diameter D 75 within the range of 1 to 1.4.
• anionic group be a sulfonic group or an alkali metal salt thereof.
• a preferred monomer is then styrene sulfonic acid sodium salt.
• oil-soluble monomer comprises both styrene and an acrylic monomer.
• the ratio of the water-soluble monomer to the oil-soluble monomer forming the copolymer is preferably in the range from 70:30 to 99:1 by weight.
• the present invention also provides a dispersion polymerization method for manufacturing electrophotographic toner charge control resin particles as claimed in claim 1, wherein at least one water-soluble monomer having an anionic group of sulfonic, carboxylic or phosphoric type and at least one oil-soluble monomer are dispersed and polymerized in an aqueous medium containing water and a water-miscible organic solvent in the presence of a dispersion stabilizer and a chain transfer agent and the resulting copolymer consisting of the water-soluble monomer and the oil-soluble monomer is collected in the form of particles, the polymerization including the steps of: forming a nucleus by reaction of the oil-soluble monomer and the water-soluble monomer; and growing the thus formed nucleus, the temperature being higher in the nucleus growing step than in the nucleus forming step.
• the mixing ratio of the water and the water-miscible organic solvent in the aqueous medium is in the range from 40:60 to 5:95 by weight.
• the temperature is 60 to 80°C in the nucleus forming step and 70 to 90°C in the nucleus growing step.
• the invention described herein makes possible one or more of the objectives of (1) providing charge control resin particles having a narrow size distribution and formed from a resin having a relatively low molecular weight; (2) providing charge control resin particles comprising a polymer with a low molecular weight and having a large particle size in the dispersion liquid; (3) providing charge control resin particles having good compatibility with a binding resin or with a monomer forming the binding resin and therefore capable of forming toner with the charge control resin uniformly dispersed in the binding resin; (4) providing charge control resin particles having uniform chargeability over the entire toner particles and therefore capable of forming toner having excellent charge characteristics; and (5) providing a method capable of readily producing the charge control resin particles having the above-mentioned excellent characteristics.
• reaction progresses in solution polymerization in the early stage of polymerization, to form a copolymer comprising monomers having a composition ratio that matches their reactivity ratio.
• the copolymer tries to precipitate, but since a dispersion stabilizer exists in the polymer system, it is believed that some of copolymers combine to form a relatively stable nucleus (dispersed particle).
• this nucleus is a copolymer formed from an oil-soluble monomer and a water-soluble monomer, the unreacted oil-soluble monomer and water-soluble monomer in the continuous phase are simultaneously absorbed and the polymerization progresses after formation of the nucleus, thus forming a copolymer having a relatively uniform composition.
• styrene and an acrylic monomer are used simultaneously as the oil-soluble monomer, the particle size is relatively large in the dispersion liquid and particles are readily precipitated therefrom.
• the copolymer forming the particles has a relatively low molecular weight.
• the molecular weight of the copolymer is kept low.
• the charge control resin particles have a large volume median size of 3 ⁇ m to 10 ⁇ m, and therefore, the handling thereof, including separation from a mixture liquid, is facilitated. Also, since they are formed from a low molecular weight copolymer having a weight-average molecular weight of 3,000 to 50,000, the resin particles are evenly and uniformly dissolved within a binding resin such as a styrene copolymer or in monomers forming the binding resin.
• the toner particles with the charge control resin particles dispersed therein are provided with uniform chargeability over the entire particles and exhibit excellent charge characteristics. Also, when producing toner by suspension polymerization using the charge control resin particles, since the viscosity of suspended oil does not increase and the polarity of the oil is uniform, toner particles having an extremely sharp size distribution can be obtained.
• the oil-soluble monomer used for the present invention is a monomer capable of forming a polymer having a good compatibility with binding resins.
• Hydrophobic monomers such as vinyl aromatic monomers, acrylic monomers such as vinyl ester monomer, vinyl ether monomer, and olefinic monomers are used.
• the vinyl aromatic monomers include, for example, styrene, ⁇ -methylstyrene, vinyltoluene, ⁇ -chlorostyrene, o-, m-, p-chlorostyrene, p-ethylstyrene, divinylbenzene.
• the acrylic monomers include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexylacrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ⁇ -hydroxyethyl acrylate, ⁇ -hydroxypropyl acrylate, ⁇ -hydroxybutyl acrylate, ⁇ -hydroxyethyl methacrylate, and ethyleneglycol dimethacrylate.
• the vinyl ester monomers include, for example, vinyl formate, vinyl acetate, and vinyl propionate.
• the vinyl ether monomers include, for example, vinyl-n-butyl ether, vinyl phenyl ether, and vinyl cyclohexyl ether.
• the olefinic monomers include, for example, ethylene, propylene, isobutylene, butene-1, pentene-1, and 4-methylpentene-1. Two or more of these monomers can be used simultaneously.
• the water-soluble monomer used for the present invention has an anionic group of sulfonic, carboxylic or phosphoric type.
• These acid radicals may be either in the form of salts such as sodium salt and other alkali metal salts, ammonium salt, amine salt, etc., or in the form of free acids.
• Monomers having a sulfonic group or its alkali metal salt are particularly desirable.
• Such monomers include, for example, styrenesulfonic acid, styrenesulfonic acid sodium salt, 2-acrylamide-2-methylpropanesulfonic acid, 2-phosphoxypropylmethacrylate, 2-phosphoxyethylmethacrylate, 3-chloro-2-phosphoxypropylmethacrylate, acrylic acid, methacrylic acid, fumaric acid, crotonic acid, tetrahydroterephthalic acid, itaconic acid, maleic acid, etc.
• the styrenesulfonic acid sodium salt is most preferable.
• composition al ratio of the water-soluble monomer to the oil-soluble monomer should be determined in such a manner as to obtain good compatibility with the binding resin and good charge characteristics. Generally the ratio should be in the range of 70: 30 to 99: 1, and preferably 80: 20 to 98 : 2, by weight.
• the mixing ratio of styrene and acrylic monomer is preferably in the range of 10 : 0.1 to 10: 3, by weight. If the amount of an acrylic monomer exceeds the above range, the particles tend to adhere, thereby causing difficulty in handling thereof. Moreover, other radical polymeric monomers can be included as needed. The amount of these monomers used is preferably 20 percent by weight or less.
• the mixing ratio of the oil-soluble monomer to styrenesulfonic acid sodium salt is preferably in the range of 70: 30 to 99: 1, by weight.
• chain transfer agents include, for example, octyl thioglycolate.
• Polymeric dispersion stabilizers are desirable for use as the dispersion stabilizer, and include, for example, polyacrylic acid, salts of polyacrylic acid, polymethacrylic acid, salts of polymethacrylic acid, (meth)acrylic acid-(meth)acrylic acid ester copolymer, acrylic acid-vinylether copolymer, methacrylic acid styrene copolymer, carboxylmethyl cellulose, polyethylene oxide, polyacrylamide, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose polyvinyl alcohol, etc.
• Nonionic or anionic surfactant may also be used.
• the amount of the dispersion stabilizer added is preferably 1 to 20 percent by weight, with respect to the monomers.
• the water-miscible organic solvents which can be used include, for example, lower alcohols such as methanol, ethanol, isopropanol, etc.; ketones such as acetone, methyl ethyl ketone, methyl bytyl ketone, etc.; ethers such as tetrahydrofuran, dioxane etc.; esters such as ethyl acetate, etc.; and amides such as dimethylformamide, etc.
• the mixing ratio of the water to the water-miscible organic solvent depends on the kind of the monomer and the kind of the organic solvent. Generally the ratio should be within the range of 40: 60 to 5: 95 by weight, and preferably within the range of 30: 70 to 10: 90 by weight.
• the composition ratio is preferably determined so as to have a uniform solution phase within this range.
• the amount of the medium used is 0.5 to 50 times by weight with respect to a monomer, particularly 5 to 25 times by weight being preferable.
• the charge control resin particles may be manufactured, for example, in the following manner.
• the oil-soluble monomer, water-soluble monomer, dispersion stabilizer, and if necessary, a polymerization initiator, are dissolved in a solution of water and a water-miscible organic solvent, and the chain transfer agent is further added.
• the temperature of the mixture is raised to 70 to 90°C and the liquid is then stirred for 2 to 20 hours.
• it is desirable that this process is conducted in the presence of an inert gas to suppress polymerization termination by oxygen.
• the resulting polymer is filtered, washed with water or other suitable solvent as necessary, and dried to obtain the desired resin particles.
• any hydrophobic polymerization initiator is used as the polymerization initiator.
• azo compounds such as azobisisobutyronitrile, etc. and peroxides such as cumene hydroperoxide, di-t-butylperoxide, benzoyl peroxide, lauroyl peroxide, etc. are used.
• the mixing ratio of the initiator is not specifically limited, but should generally be 0.1 to 20 percent by weight with respect to the monomer.
• the polymerization can be initiated by using gamma rays or an accelerated electron beam.
• the polymerization may be initiated by using photosensitizers in combination with ultraviolet rays.
• the thus obtained charge control resin particles have a relatively large average size of 3 to 10 ⁇ m in a dispersion liquid , so the precipitation thereof from the mixture is facilitated.
• the particles are composed of polymers having a weight of 3,000 to 50,000. Since the molecular weight is relatively low, the resin particles have good compatibility with the binding resin such as a styrene copolymer or with monomers forming the binding resin, and therefore, a toner with the charge control resin particles uniformly dispersed in the binding resin can be readily obtained.
• the toner particles with the charge control resin particles dispersed therein are provided with uniform chargeability over the entire particles and exhibit excellent charge characteristics. According to the present invention, charge control resin particles having the above-mentioned excellent characteristics can be readily manufactured.
• the obtained emulsion was observed under an optical microscope to note the formation of particles having a median size of about 6.0 ⁇ m.
• the ratio D 25 /D 75 was 1.37 and a very sharp particle size distribution was noted.
• the weight-average molecular weight measured by gel permeation chromatography (GPC) was 1.18 x 10 4 . It was possible to collect 100% of the particles in a short time using a qualitative filter.
• the obtained emulsion was observed under an optical microscope to note the formation of particles having a size of about 4.2 ⁇ m.
• the ratio D 25 /D 75 was 1.39, and the weight-average molecular weight measured on a GPC was 1.25 x 10 4 . It was possible to collect 100% of the particles in a short time using a qualitative filter.
• the mixture was charged into an aqueous solution of 1.5% calcium phosphate (pH adjusted to 11 by sodium hydroxide) and dispersed for suspension therein using a TK-Homomixer (manufactured by Tokushu Kikou Kogyo), after which the mixture was polymerized for 5 hours while being stirred in a normal manner at 80°C in a stream of nitrogen.
• the thus produced particles were filtered, washed, and dried to obtain the toner.
• the thus obtained toner was spheroidal, had good flowability, and had sharp particle size and charge amount distributions.
• the toner was evaluated in the same manner as in Example 1, and yielded good results in all evaluations.
• Toner was prepared in the same manner as in Example 2. The solubility of the styrene-styrenesulfonic sodium salt copolymer in the styrene was good. The obtained toner was evaluated in the same manner as in Example 1, and yielded good results in all evaluations.
• composition was the same as used was in Example 1 except that octyl thioglycolate the chain transfer agent and the polymerization was performed for 10 hours at a temperature of 70°C without raising the temperature during the polymerization.
• the obtained styrene-styrenesulfonic sodium salt copolymer in the emulsion had an average particle size of 1.8 ⁇ m, thus forming particles of a small size.
• the ratio D 25 /D 75 was 1.55 and the particle size distribution was broad.
• the weight-average molecular weight measured on a GPC was 10.88 x 10 4 .
• the copolymer had poor compatibility with monomers such as styrene, and it took time to dissolve the copolymer in the monomer.
• composition was the same as in Example 2 although the temperature was not raised during the polymerization but kept at 80°C throughout the polymerization.
• the obtained styrene-styrenesulfonic sodium salt copolymer contained in the emulsion coarse agglomerate which accounted for 3% of the entire particles.
• the average size of the particles was 7.2 ⁇ m.
• the ratio D 25 /D 75 was 1.70 and the particle size distribution was very broad.
• the weight-average molecular weight was 8.3 x 10 4 .
• Toner was prepared and evaluated in the same manner as in Example 2. When used, fogging was observed due to incomplete charging of toner particles, which was particularly noticeable under high temperature and high humidity conditions.
• composition was the same as that of Example 3 except that the temperature was not raised during the polymerization but was kept at 75°C throughout the polymerization.
• the styrene-styrenesulfonic sodium salt copolymer particles contained in the emulsion particles were generally less than several ⁇ m, but there were particles of 10 to 20 ⁇ m size, showing a very broad particle size distribution.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Polymerisation Methods In General (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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• 1989
  • 1989-11-30 JP JP1312481A patent/JPH0774920B2/ja not_active Expired - Lifetime
• 1990
  • 1990-11-30 DE DE1990630557 patent/DE69030557T2/de not_active Expired - Fee Related
  • 1990-11-30 EP EP19900313047 patent/EP0432946B1/en not_active Expired - Lifetime

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