As a method for producing a polymerized toner, for example, there is proposed a suspension polymerization method wherein a polymerizable composition is dispersed in an aqueous medium and then polymerized, as described in Japanese Patent Kokai 1-201676. This suspension polymerization method requires no pulverization, and a colorant and an additive are uniformly dispersed in comparison with a conventional method.
However, a polymerized toner obtained by this method normally has a large particle size (5 to 15.mu.) and has large particle size distribution. Therefore, a classifying step is required. When a toner having small particle size (3 to 7.mu.) which has recently been required is produced, yield is lowered.
As a method for producing a toner having a small particle size, for example, there is proposed a method based on a non-aqueous dispersion polymerization which comprises polymerizing vinyl monomers in the presence of a colorant in a dispersion solvent to which the vinyl monomers are soluble and polymerized particles therefrom are insoluble, as described in Japanese Patent Kokai Nos. 61-273552 and 62-73276.
However, in this method, there is not disclosed an improvement for finely dispersing a colorant and an additive to polymerize them and, therefore, it is remarkably difficult to allow a release agent which prevents a toner from adhering to a fixing roll to be uniformly present in polymerized particles. The release agent has no affinity with a dispersion solvent and, therefore, the release agent agglomerates in a polymerization system and deposits apart from polymerized particles, whereby, it is not practicable to contain the release agent in polymerized particles.
In Japanese Patent Kokai No. 1-137264, there is disclosed a technique for encapsulating a release agent and a polymer in toner particles, however, all possible production processes are listed and a suitable one is not specified. The polymer component described therein is not uniformly dissolved or dispersed in a dispersion solvent. Therefore, it is difficult to uniformly contain the release agent in polymerized particles, whereby, the resulting toner has large particle size distribution and comparatively large particle size.
USPTO Backgrounds
USPTO Backgrounds