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Electrophotographic toner made by polymerizing monomers in solution in presence of colorant
| Details |
Inventors: Matsumoto, Tsunetaka; Okubo, Masayoshi; Tokuno, Toshiro;
Assignee: Mita Industrial Co., Ltd. (Osaka, JP)
Primary Examiner: Welsh; J. David
Assistant Examiner:
Attorney, Agent or Firm: Sherman and Shalloway
Disclosed is a process in which a spherical electrophotographic toner containing a colorant and having a particle size suitable for the electrophotography is directly formed in the polymerization process for formation of a binder resin. If a reaction medium capable of dissolving a monomer but incapable of dissolving a formed polymer is used and polymerization is carried out in the presence of a radical polymerization initiator in the state where the monomer, the colorant and other additives are dissolved or dispersed in the reaction medium, an electrophotographic toner having a desired particle size is obtained. According to this process, the particle size of the colored resin is stably controlled to 1 to 30 .mu.m suitable for a toner in the polymerization process, and the particle size distribution is very sharp. |
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Process of Embodiment (i) In the process of the embodiment (i), a radical-polymerizable monomer (A) and a colorant are dissolved or dispersed in a reaction medium (solvent) and polymerization is carried out in the presence of a radical polymerization initiator.
It is important that the radical-polymerizable monomer (A) and the reaction medium should be selected so that the monomer (A) is soluble in the reaction medium but the formed polymer is insoluble in the reaction medium.
The embodiment (i) of the present invention is based on the finding that if the so-selected monomer and reaction medium are used, a colored resin having a particle size larger than the particle size of resin particles obtained by customary emulsion polymerization and smaller than the particle size of resin particles obtained by customary suspension polymerization, which is in a range suitable for toner particles can be obtained.
Polymerization which is advanced in a solution is generally called solution polymerization.
In this solution polymerization, the formed polymer is dissolved in the solvent.
In the process of the present invention, the formed polymer is not dissolved in the solvent, that is, the reaction medium.
In this point, the polymerization of the present invention is distinguished from the solution polymerization.
The reasons why colored particles having a particle size within the above-mentioned specific range and a relatively sharp particles size distribution can be obtained according to the present invention are believed to be as follows, though the reasons are not limited to those described below.
In the polymerization system of the present invention, at the initial stage, the polymerization is initiated and advanced in the reaction medium, and the formed polymer chain is dispersed in the polymerization mixture and is combined with dispersed particles of the colorant having a large specific surface area.
It is believed that at the middle stage of the polymerization, the polymerization is advanced according to both the emulsion polymerization and the suspension polymerization
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Molecular Biology 
