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
  • G03G9/08797—Macromolecular material not specially provided for in a single one of groups G03G9/08702 - G03G9/08775 characterised by their physical properties, e.g. viscosity, solubility, melting temperature, softening temperature, glass transition temperature
• • 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
  • G03G9/08775—Natural macromolecular compounds or derivatives thereof
  • G03G9/08782—Waxes

Definitions

• the present invention relates to a dry toner for developing static charge images formed by electrophotography. More particularly, it relates to a toner for low energy fixing which is required in the case of developing static charge images in a hot roll fixing system at a decreased hot roll temperature, a decreased roll pressure, an increased rotation number of rolls or the like conditions.
• toner for developing static charge images (hereafter, referred to simply as "toner") that copying machines or printers are run at low fixing energy.
• Toner a toner for developing static charge images
• investigation for decreasing fixing energy has been focused on the resin contained in the toner and various toners have been proposed which include, for example, those whose molecular weight an/or molecular weight distribution are/is improved, those whose composition has been changed, those which contain one or more additives in the resin.
• Another method which has been proposed for lowering the energy upon fixing is a method in which an additional resin or sub-resin is added to the resin contained in the toner as the second component in order to increase the fixing property of the toner.
• this method which includes the addition of a sub-resin which has a high crystallinity with view to maintaining the glass transition temperature of the resin composition, gives rise to good results with respect to the fixing property and storage stability of the toner, it causes other problems that the presence of a highly crystalline sub-resin results in an abrupt decrease of the melt viscosity of the toner upon hot roll fixing and that offset phenomenon tends to occur because the cohesive force of the toner upon melting is weak.
• it is an object of the present invention is to provide a toner for developing static charge images which has a low fixing temperature, does not deteriorate its storage stability, causes practically no problem with respect to its offset property and is free from problems with respect to not only its thermal characteristics but also practically useful characteristics such as life property and quality of images.
• toner particles which comprises a binder resin containing a specific wax and minute particles of an additional resin adhered on the surfaces of the toner particles gives rises to good results, and thus the present invention has been accomplished.
• the present invention provides a toner for developing static charge images, comprising..
• the toner for developing static charge images according to the present invention enables its fixing at low temperatures and exhibits good image characteristics without deteriorating its storage stability and offset property.
• the toner for developing static charge images of the present invention comprises a binder resin which contains a colorant and a specific wax.
• the wax is selected from a hardened castor oil, carnauba wax and modified products derived them, which are the first feature of the toner of the present invention.
• hardened castor oil refers to a hydrogenated product derived from castor oil, for example, castor waxes commercially available from, for example, ITOH OIL MFG CO., LTD. and NIPPON OIL FATS CO., LTD.
• the modified products derived from castor oil include those whose acid value has been changed by the introduction of an acid group such as a carboxyl group by reacting castor oil with a dibasic acid utilizing one or more hydroxyl groups in one or more side chains thereof. Any dibasic acid may be introduced. However, those dibasic acids are preferred which have 2 to 20 carbon atoms such as formic acid, succinic acid and adipic acid.
• carbarnauba wax refers to a kind of a plant wax which is obtained from young leaves of carnauba plant, and modified products derived from carnauba is a substance obtained by introducing an acid group at one or more OH groups in carnauba wax.
• Commercially available carnauba wax is, for example, CARNAUBA WAX produced by NODAWAX CO., LTD.
• the toner is mixed with the wax, i.e., the above-described hardened castor oil, carnauba wax and modified products derived therefrom, singly or as a mixture.
• the amount of the wax to be mixed is suitably 5 to 50% by weight, preferably 10 to 40% by weight based on the total weight of the toner composition. If the amount of the wax is below 5% by weight, no sufficient improvement in the fixing property can be obtained. On the other hand, the amount of above 50% by weight is undesirable because the quality of images is deteriorated, for example, the luster of surfaces on which the toner is fixed becomes too high despite an advantage that its fixing property is excellent.
• the wax has a melting point in the range of 55 to 100°C. Melting points outside the above-described range are undesirable. This is because if it is below 55°C, the storage stability of the resulting toner tends to be deteriorated while the fixing property of the toner is decreased if it is above 100°C.
• the additional resin in the form of minute particles is adhered on the surfaces of the toner particles in order to improve the flowability and storage stability of the toner.
• the minute particles of the additional resin can be adhered on the surfaces of the toner particles by using conventional mixers such as a turbine type mixer, Henschel mixer and a super mixer or a device which is generally called a surface improver, for example, Nara Hybridization System produced by NARA KIKAI SEISAKUSHO, Mechano-Fusion System produced by HOSOKAWA MICRON CO., LTD., and Surfusing System produced by NIPPON PNEUMATIC INDUSTRY CO., LTD.
• the minute particles of the additional resin are preferably in the form of emulsion particles produced by emulsion polymerization.
• main monomer component of the additional resin those monomers can be employed which are generally used as a resin for toners. Examples of such monomers includes styrene, butyl acrylate, butyl methacrylate, and methyl methacrylate.
• the mean particle size of the minute particles of the additional resin must be in the range of 0.05 to 0.5 ⁇ m. If it is smaller than 0.05 ⁇ m, the dispersion of the minute particles on the surfaces of the toner particles tends to be poor while the minute particles are difficult to be adhered on the surfaces of the toner particles if it is larger than 0.5 ⁇ m.
• the glass transition temperature, Tg, of the minute particles of the additional resin must be no higher than 120°C, preferably no higher than 90°C. If the minute particles of the additional resin used have a Tg value of higher than 120°C, the fixing property of the resulting toner is deteriorated.
• the minute particles of the additional resin are used in an amount such that they can cover preferably 20 to 80% of the total surface of the toner particles, which corresponds in other words to an amount such that the minute particles are adhered on the surfaces of the toner particles in a proportion of 5 to 30 parts by weight of the minute particles per 100 parts by weight of the toner particles.
• the toner for developing static charge images according to the present invention can be produced by mixing the wax with the binder resin, colorant and other additives in predetermined proportions and melt-kneading the mixture followed by pulverizing and classifying it to form toner particles and then adhering the minute particles of the additional resin on the surfaces of the toner particles by using the above-described adhering method.
• the binder resin includes, for example, polystyrene, styrene/acrylies, polyacrylate, polyethylene, styrene/butadiene copolymer, polyamide, polyvinyl chloride, vinyl chloride/vinyl acetate copolymer, coumarone/indene resin and polyester.
• the styrene acrylics is a coplymer conprising at least one monomer selected from each of the styrene monomer group and acrylic monomer group as described in more detail below.
• the styrene monomer group comprises monomers such as styrene, o-methylstyrene, m-­ methylstyrene, p-methylstyrene, ⁇ -methylstyrene, p-­ethylstyrene, 2,4-dimethylstyrene, p-n-buthylstyrene, p-­tert-buthylstyrene p-n-hexylstyrene, p-n-octhylstyrene, p-­n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-­methoxylstyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-­dichlorostyrene; the acrylic monomer comprises
• the colorant includes pigments and dyes which are used usually as a colorant for toners for developing static charge images.
• pigments and dyes which are used usually as a colorant for toners for developing static charge images.
• examples thereof include carbon black, nigrosine dye, aniline dye, Chrome Yellow, Ultramarine Blue, Methylene Blue Chloride, Rose Bengale, magnetite and ferrite.
• various auxiliaries can be used as the other additives.
• charge control agents, antioxidants, pigments, and flowability improving agents such as colloidal silica and colloidal alumina.
• the toner for developing static charge images includes one or more of a hardened castor oil, carnauba wax and modified products derived from them which are highly crystalline and have a melting point of 55 to 100°C, resulting in that upon heat treatment with hot rolls the melt viscosity of the toner decreases abruptly and the toner is melted completely at a relatively low fixing temperature (130 to 150°C), which improves effectively the fixing strength of the toner onto a surface of transfer paper.
• the specific wax used in the present invention does not cause offset phenomenon which would other occur because of specific mechanism of the wax that it has a strong cohesive force upon heat melting and a low affinity for hot rolls.
• the flowability of the toner is improved because minute particles of the additional resin are adhered on the surfaces of the toner particles, thus imparting a good storage stability to the toner.
• the mixture of the above-described composition was heat-melt and kneaded, pulverized and classified to obtain negative-chargeable toner particles having a mean particle size of 12 ⁇ m. Thereafter, hydrophobic silica was added to the resulting composition in a proportion of 0.2 part of hydrophobic silica per 100 parts of the toner particles to obtain a toner for developing static charge images for comparison.
• a toner for developing static charge images for comparison was obtained by repeating the same procedures as in Example 2 except that the adhesion of the minute particles of the resin was omitted.
• a fixing device composed of a hot roll with its surface layer being formed by polytetrafluoroethylene and a press roll with its surface layer being formed by a silicone rubber was adjusted so as to be run at a roll pressure of 30 kg/cm and at a roll speed of 170 mm/sec.
• the temperature of the hot roll was gradually changed as shown in Table 1 and sample toners which had been imagewise transferred on transfer paper through a commercially available copier were each fixed on the paper.
• the fixed images were each rubbed with a cotton pad ("PPC PAD", a trade name for a product by DAINIC CO., LTD.). Then, the lowest possible set-up temperature at which the fixed images exhibited sufficient rubbing resistance was defined as lowest fixing temperature of the sample toner concerned.
• Each of the sample toners was transferred on transfer paper and fixed by using the above-described fixing device. This procedure was repeated at various hot roll temperatures and observation was made whether or not blurring did occur in blank portion of the transfer paper.
• the temperature range within which no blurring did occur was defined as a non-offset temperature range.
• the toner for developing static charge images according to the present invention had a low fixing temperature, a broad non-offset temperature range, good image quality and good storage stability.
• the toner obtained in Comparative Example 1 showed a high lowest fixing temperature, which means that the comparative toner is insufficient as a low energy fixing toner.
• the toner obtained in Comparative Example 2 showed a poor storage stability and its image quality was unacceptable for practical purposes.

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• Physics & Mathematics (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)

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Citations (4)

• 1989
  • 1989-07-10 JP JP1175434A patent/JPH0341465A/ja active Pending
• 1990
  • 1990-07-06 EP EP19900420320 patent/EP0408471B1/de not_active Expired - Lifetime
  • 1990-07-06 DE DE1990630468 patent/DE69030468T2/de not_active Expired - Fee Related

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