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
  • G03G9/08742—Binders for toner particles comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/08753—Epoxyresins
• • 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
  • G03G9/08742—Binders for toner particles comprising macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • G03G9/08744—Polyacetals

Definitions

• An electrophotographic dry toner which contains as a resin component a mixture comprising a solid epoxy resin as a main component and 2.5 to 25% by weight, based on the weight of said epoxy resin, of a polyvinyl acetal resin compatible with said epoxy resin.
• the toner is particularly applicable in transfer type printing.
• This invention relates to an electrophotographic dry toner.
• the invention is concerned with a dry toner which displays excellent properties when used in transfer type printing.
• a toner of this kind is prepared by fusing a thermoplastic resin togetherwith small amounts of a coloring pigment and a. charge controlling dye, cooling the *miXture and then forming the cooled mixture into particles of about 5 to 20 microns, and is used in admixture with an iron or glass powder as a carrier.
• a single photosensitive sheet is repeatedly subjected to the steps including electrostatic charging, imagewise exposure, toner development, image transfer and toner removal.
• a toner used in the transfer type printing is required to have, in addition to the properties of a toner used in direct type printing, such properties as excellent transferability, eliminability and durability. That is, the toner should have such properties that when ad- 'hered to and developed on a static latent image, it can be effectively transferred onto another paper sheet due to corona charge from the back side of said sheet, and residual toner after the transfer can be wiped ofi easily and completely by means of a cleaning brush made of an animal fur or the like.
• the resulting copy forms uneven transfer portions, fog and a ghost image (an image in which a fresh image has been superposed on a residual image of the preceding printing cycle) to give a markedly blurred image and, at the same time, the photosensitive sheet, cleaning brush and collection bag, which are repeatedly used, are greatly shortened in service life.
• the toner tends to be microfinely divided due to the revolution of developing brush or the like or to the external force applied for the stirring of freshly supplied toner,
• the transfer eificiency of the toner is affected not only by the amount of charged electricity but also'by the 3,753,910 Patented Aug 21, 1973 granularity thereof, and it is not desirable to use a toner containing fine particles of less than about 5 microns in diameter which are frequently formed when the developing agent is used continuously.
• thermoplastic resin which is the main constituent of a dry toner
• a polymer or copolymer such as .aspolystyrene, polymethacrylate, polyvinyl acetate, polyvinyl chloride or cumarone-indene, a condensation product such as xylene resin, phenol resin or polyamide, or a natural resin such as rosin, ester gum or shellac;
• toners prepared from the above-mentioned known resin components cannot satisfy such requirements as fixability and pulverizability, simultaneously with a series of properties of toners to be used in the aforesaid transfer type printing.
• a toner which contains as a resin component a mixture composed of a major proportion of a solid epoxy resin and a minor proportion of a polyvinyl acetal resin compatible with said epoxy resin, can overcome the above-mentioned drawbacks and is sufiiciently satisfactory.
• the resin mixture used in the present invention contains 2.5 to 25% by weight of the polyvinyl acetal resin based on the weight of the epoxy resin.
• the amount of the polyvinyl acetal resin is less than 2.5% by weight, no desired effect can be attained, while in case the amount thereof is more than 25 by weight, the toner is excessively solidified to become easily pulverizable, and the fixing temperature thereof becomes undesirably high.
• the polyvinyl acetal resin is used in an amount within the above-mentioned range, the resulting toner is excellent in fusibility, durability and fixability.
• the epoxy resin used in the present invention is a normally solid compound containing at least two epoxy groups in one molecule which is prepared by reacting epichlorohydrin with bisphenol and phthalic anhydride in the presence of a catalyst and has a molecular weight of 700 to 5,000 and a melting point of about 55 to 155 C.
• Examples of commercial epoxy resins of this kind include Epikote produced by Shell Co. and Araldite produced by Ciba Ltd.
• the polyvinyl acetal resin compatible with said epoxy resin is prepared by acetalizing polyvinyl alcohol with a saturated aldehyde having 1 to 3 carbon atoms in the presence of acid or alkali.
• the acetalization degree of the polyvinyl acetal resin varies depending on the kind and amount of the aldehyde or the amount of the catalyst used, but is preferably about by Weight or more in order to increase the compatibility thereof with the epoxy resin.
• Examples of commercial polyvinyl acetal resins of this kind include Denkabutyral #2000 D and Denkaformal #50 produced by Denkikagaku Kogyo Co.
• the toner of the present invention is prepared by mixing according to an ordinary physical dispersion procedure the aforesaid specific resin components with a coloring pigment and a charge-controlling dye which have heretofore been used in electrophotographic toners, and then pulverizing the resulting mixture into fine particles of about 5 to 20 microns in diameter according to the mechanical pulverization or spray-drying process.
• the toner of the present invention is low in electrification (i.e. suitable as a toner for use in transfer type printing), high in transfer ratio and excellent in elimination effect, so that even when used repeatedly, it forms no stains on the surface of the photosensitive sheet, is not repulverized nor leaves toner stains on the carrier surface, and is excellent in abrasion resistance (durability). That is, we conducted a long run test to prepare 20,000 copies according to the magnet brush method using a 3% developing agent of each of the u L present toner and a conventional toner in admixture with an. iron powder carrier.
• the amount of formed fine particles of less than 5 microns in diameter .. was up to 0.1% by weight in the case of the present toner, but was about 1.1% by weight in the case of the conventional toner, and the amount of stains left on the carrier surface was 0.15% (wt.)/total iron powder in the case of the present toner but was about 0.6% (wt.)/ total iron powde'r in the case of the conventional toner.
• the toner of the present invention has excellent properties.
• the present toner has such properties that despite of its having practically suflicient abrasion resistance as mentioned above, the toner can be easily pulveriaedinto particles of about 5 to 20 microns in diameter "of the toner image is such that thermal fixing can be 7 advantageously efiected due to favorable adhesiveness of the'toner to paper sheets at its softening temperature at the time of fusion.
• the above-mentioned developing agent was subjected to a. printing test for preparation of 10,000 copies, while adequately suplementing the toner. As the result, the developing agent maintained'an excellent copying ability substantially identical with the ability at the initial stage.
• a toner comprising a resin mixture of 85 g. of'Epikote #1002 (epoxy resin produced by Shell .Co.,- M.P. 75-85 C.) and 15 g. of Denkaformal #50 (polyvinyl formal produced by Denkika'gahu Kogyo Co., formalation degree more than 80% by weight) was prepared and used for transfer type printing in the same. manner as in-Example 1.
• the charged electricity of the toner was +65 v./g., the transfer ratio was 89% and theelimination of residual toner was such that no toner'stain wasleft at all on-the photosensitive layer even after 1,000 times 'tigue promotion test by use of a ball mill in such a mans by means 'of a conventional pulverizer, and the sharpness repeateduser
• the developing agent was subjected to a'faner that 300 g; of the developing agent was chargedinto a 300 .cc. ball mill case and revolved-for 48 hours without using balls. Thereafter, the developing agent was subjectedto a printing .test to obtainclear'copieswhich were entirely identical with those in the case where the fatigue promotion was not effected.
• EXAMPLE 4 Using the developing agent of Example 1, a negative latent image on a polyethylene-coated electrostatic recording paper was developed to obtain a clear positive copy. Further, the developing agent was subjected to treatment for 48 hours according to a fatigue promotion test method using a ball mill and then subjected to a printing test to obtain clear copies which were entirely identical with those in the case where the fatigue promotion was not effected.
• EXAMPLE 5 75 grams of Epikote #1004 (epoxy resin produced by Shell Chemical Co., M.P. 97-103 C.), g. of Denkaformal and 10 g. of Hilac-110 resin (ketone resin produced by Hitachi Chemical Co., M.P. l10-130 C.) were kneaded on two hot rolls, and the resulting mixture was sufliciently kneaded with 5 g. of carbon black and 2.5 g. of Nigrosine SSB. After cooling, the mixture was pulverized by means of a jet mill to particles of 5 to microns in diameter to obtain a positively charged toner having a charged electricity of +67 v./ g. The thus obtained toner was subjected to the same test as in Example 1. As the result, the transfer ratio was 90% by weight, and the elimination of residual toner was such that no toner stain was left on the photosensitive layer even after 1,000 times repeated use.
• the transfer ratio was 90% by weight, and the elimination of residual toner
• the developing agent was subjected to treatment for 48 hours according to a fatigue promotion test method using a ball mill and then subjected to a printing test to obtain clear copies which were entirely identical with those in the case where the fatigue promotion was not eliected.
• An electrophotographic dry toner having a particle diameter of about 5-20 microns which contains as a resin component a mixture comprising a solid epoxy resin containing at least two epoxy groups in one molecule which is prepared by reacting epichlorohydrin with bisphenol and phthalic anhydride as a main component and 2.5 to 25% by weight, based on the weight of said epoxy resin, of a polyvinyl acetal resin compatible with said epoxy resin.
• polyvinyl acetal resin is the acetalization product obtained by the reaction of polyvinyl alcohol with a C to C -saturated aliphatic aldehyde.
• An electrophotographic dry toner as claimed in claim 1 wherein said polyvinyl acetal resin has the acetalization degree of more than about 4.
• an electrophotographic dry toner composition comprising (1) a carrier and (2) toner particles having a particle diameter of about 5 to 20 microns of a fused mixture comprising a resin, pigment and a charge controlling dye, the improvement comprising a resin comprising a solid epoxy resin containing at least two epoxy groups in one molecule which is prepared by reacting epichlorohydrin with bisphenol and phthalic anhydride as a main component and 2.5 to 25% by weight, based on the weight of said epoxy resin, of a polyvinyl acetal resin compatible with said epoxy resin.

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• Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Spectroscopy & Molecular Physics (AREA)
• General Physics & Mathematics (AREA)
• Developing Agents For Electrophotography (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=13452619

Family Applications (1)

Country Status (4)

Cited By (3)

Families Citing this family (1)

Family Cites Families (3)

• 1970
  • 1970-08-15 JP JP45071161A patent/JPS4934157B1/ja active Pending
• 1971
  • 1971-08-10 US US00170665A patent/US3753910A/en not_active Expired - Lifetime
  • 1971-08-11 DE DE2140270A patent/DE2140270C3/de not_active Expired
  • 1971-08-13 GB GB3813471A patent/GB1330378A/en not_active Expired

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