Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2000-01-04
2001-05-22
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C430S109500, C430S111400
Reexamination Certificate
active
06235444
ABSTRACT:
RELATED APPLICATIONS
The present application is based on Patent Application No. 11-12938 filed in Japan, the content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrostatic latent image developing toner and a manufacturing method thereof. The toner is used to develop an electrostatic latent image in electronic photography, electrostatic recording, and electrostatic printing.
2. Description of the Related Art
In recent years, the manufacturing of toner particles using granulation methods among the wet-type methods represented by emulsion dispersion methods, suspension polymerization methods, and emulsion polymerization methods have become a focus of attention from the perspectives of reducing manufacturing costs while achieving high quality images.
Emulsion dispersion methods involve dissolving or dispersing binder resin and colorant in a suitable organic solvent to obtain a color resin solution, adding this solution to an aqueous liquid medium, and vigorously mixing the fluid to form droplets of resin solution. This material is then heated, to remove the organic solvent from the droplets to achieve granulation.
Suspension polymerization methods involve suspending polymerizable components which comprises polymerizable monomer, and polymerization initiator, colorant and other additive added as necessary in a dispersion medium to form oil droplet dispersion particles, polymerizing the monomer to form colored resin particles (toner particles).
Emulsion polymerization methods involve adding a nearly water insoluble polymerization monomer in water and attaining an emulsion state, then accomplishing granulation by polymerization using a water soluble polymerization initiator. Generally, colorant, charge control agent and the like are added post polymerization and after the particles are formed.
The dispersants used in wet-type granulation include inorganic dispersion agents and organic dispersing agents. Tribasic calcium phosphate is generally used as an inorganic dispersing agent. Since tribasic calcium phosphate effectively produces a pH of 10 to 14 in water, polyester resin is hydrolyzed by these components due to the alkalinity resistance required by the toner particles so as to cause problem at low melt temperatures and the like, and charge controllers which do not have alkalinity resistance disadvantageously loose functionality. For this reason these aspects must be considered when selecting materials, which greatly restricts the materials which can be selected for the toner. Manufacturing conditions also must be controlled because the toner component dispersion density markedly changes particle size and shape depending on the granulation conditions such as oil-in-water (O/W) emulsions and the like.
Toner manufactured by wet-type granulation methods such as emulsion dispersion, suspension polymerization, and emulsion polymerization using organic dispersing agent disadvantageously produce chargeability problems, e.g., generation of inadequately charged particles and many reverse charge toner particles. In particular, chargeability may be greatly reduced or fluctuate due to environmental conditions. This tendency may become pronounced under high temperature, high humidity conditions.
Wet-type granulation methods generally add dispersing agent or emulsifier, but the dispersing agent or emulsifier used for suspension or emulsification is removed by washing in water after granulation.
Conventionally, however, residual dispersing agent and the like adhered to the surface of the toner particles is not completely removed simply by washing in water, and this residual material on the surface of the toner may be a factor affecting toner chargeability. Various proposals have been offered to eliminate the previously described disadvantages, but none have adequately resolved these disadvantages with organic dispersing agents are used.
SUMMARY OF THE PRESENT INVENTION
An object of the present invention is to provide a toner having excellent chargeability and environmental stability, and is manufactured by a wet-type granulation method using organic dispersing agent.
The present invention relates to toner comprising a binder resin and a colorant, wherein the toner is manufactured by a wet-type granulation method using an organic dispersing agent, an aqueous extract liquid having a surface tension of 50 to 72 mN/m at 25° C., the aqueous extract liquid obtained by mixing 1 part-by-weight toner and 50 parts-by-weight distilled water for 1 hour at 80° C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the present invention, a wet-type granulation is first accomplished. The wet-type granulation method used to produce toner particles may be, for example, an emulsion dispersion method.
In the emulsion dispersion method, granulation is accomplished by dissolving or dispersing a binder resin, colorant, and other additives as necessary in a non-water-soluble organic solvent to obtain a color resin fluid, which is then subjected to emulsion dispersion in an aqueous liquid medium to form an oil-in-water (O/W) type emulsion, from which the non-water soluble organic solvent is subsequently removed. O/W emulsion indicates a suspension fluid, wherein an oil-based liquid is dispersed as droplets in an aqueous liquid medium. Furthermore, when obtaining the O/W emulsion dispersion, the resin solution is not added all at once, but desirably is added by gradual titration. In this way the toner of the present invention is readily obtained.
The binder resin used in the emulsion dispersion method is not specifically limited insofar as the binder resin is soluble in a water-insoluble organic solvent described later, and insoluble or nearly insoluble in water. Examples of useful binder resins include styrene resin, (meth)acrylic resin, styrene-(meth)acrylic copolymer resin, olefin resin, polyester resin, polyamide resin, polycarbonate resin, polyether resin, polyvinylacetate resin, polysulfone resin, epoxyresin, polyurethane resin, urea resin and like well-known types of resins used individually or in combinations of two or more.
It is desirable that the binder resin has a glass transition temperature (Tg) of 50 to 70° C., a number-average molecular weight (Mn) of 1,000 to 50,000, and more desirably 3,000 to 20,000, and a molecular weight distribution (Mw/Mn) representing the ratio of Mn and the weight-average molecular weight (Mw) of 2 to 60. When the toner of the present invention is used as an oil application fixing toner, it is desirable that the ratio Mw/Mn is 2 to 5, and when used as an oilless fixing toner, it is desirable that the ratio Mw/Mn is 20 to 50.
The organic solvent used for dissolving the binder resin is insoluble or nearly insoluble in water, and will dissolve the previously listed binder resins. Examples of useful organic solvents include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methylacetate, ethylacetate, methylethylketone, methylisobutylketone and the like used individually or in combinations of two or more. Particularly desirable are aromatic solvents such as toluene and xylene and the like, and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, carbon tetrachloride and the like.
Organic and inorganic types of pigment of various colors as listed below may be used as the colorant included in the toner of the present invention. Examples of useful black pigments include carbon black, copper oxide, manganese dioxide, aniline black, activated charcoal, nonmagnetic ferrite, magnetic ferrite, magnetite and the like.
Examples of useful yellow pigments include chrome yellow, cadmium yellow, yellow oxide, mineral fast yellow, nickel titanium yellow, naval yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow XCG, tartrazine lake and the like.
Examples of usef
Machida Junji
Nagai Yasuki
Nakamura Mitsutoshi
Shintani Yuji
Burns Doane , Swecker, Mathis LLP
Dote Janis L.
Minolta Co. , Ltd.
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