5 6
generated by stirring is exerted concentrically on the The suspension polymerization method obtains core
individual minute particles 1 because one to a few min- particles by preparing a polymerization composition
ute particles 1 are present in the site of exertion of the having as components thereof a polymerizing monomer
stress. Further, the individual minute particles 1 adjoin capable of forming a resin component as a binder to be
the resin (toner core particle 2) throughout their entire 5 described more specifically hereinbelow, a polymeriza
peripheries. Thus, the minute particles 2 are eventually tion initiator, a coloring agent, and other additives,
buried readily in the toner core particle 2. In contrast, suspending the polymerization composition in a non
when charge-controlling minute particles 1 are distrib- solvent type medium, and polymerizing the resultant
uted in a high density locally on the toner core particle suspension.
2 as illustrated in FIG. la and even when the stress '0 Generally, emulsion polymerization barely produces arising from stirring happens to be exerted on this site, particles which are extremely minute in spite of their since the stress is exerted as dispersed to the multiplicity ideal particle diameter distribution. The emulsion polyof minute particles 1, the force working on the individ- merization method, therefore, is desired to be carried ual minute particles 1 is weak. Moreover, the minute out in the form ^ as seed polymerization. Specifiparticles 1 located inside the site of fixation in the high 15 callv>the seed polymerization is earned out by stirring density and parted from the periphery of the site are t0 emulsify part of a polymerizing monomer and a polyencircled with adjacent minute particles and, therefore, merization initiator in an aqueous type medium or an are sparingly allowed to adjoin the resin, the embed- acl"eous emulsifier-containing medium, then gradment of the minute particles 1 in the resin occurs only "ally adding the remainder of the polymenzmg monowith great difficulty. If this embedment occurs at all, it 20 mer dropwise to the stirred mixture thereby givmg rise affects only the minute particles which are located in t0 mmute Pa*ldes therein, and polymenzmg these parthe peripheral region of the site of fixation in the high 'lcles as seeds TM the Polymerizing monomer liquid
density Specifically, this embedment due to the stress dr0Ps colonng aSenJ and other addltlves
. , , • L <i » i f As other wet pelletization methods encompassing a
takes place in the same manner as when flat particles of „, . . r . . . , t °.
, r ~ , c c ti. » 25 process of polymenzation, a soap-free emulsion poly
a large surface area are fixed on the surface of the toner r . ^. r, , , ;. , , ,
• i -i TV. .i. , r i. menzation method, microcapsulation methods (such as
core particle 2. Thus, the amount of the charge-con- r , .' . , . .. ,
„. , ,, „ - a surface polymenzation method and an m-situ poly
trolling substance exposed on the surface of toner parti- merizationlmethod)> and a non.aque0us dispersion poly
de can be maintained relatively stably. merization method have been known.
The electrostatic latent image-developing toner-in the x Jhe nsion ffiethod duces core rtides b
first embodiment of the present invention has charge- dissolving a colori ent and other additives in a resin
controlling mmute particles fixed on the surface of a component as a binder to be described specifically here
toner core particle. The core particle of toner is made of inbe]ow md suspending the resultant solution in a non
at least a colonng agent and a binder resin. Optionally, solvent type medium
it may incorporate therein such toner property-improv- 35 The spray dry method produces core particies by
ing agents as offset-preventing agent. When the toner to dissoivmg a synthetic resin component in conjunction
be finally produced is desired to possess a magnetic with a coloring agent in a solvent and then spray drying
property, it is allowed to incorporate a magnetic pow- tj,e resuitant solution.
der therein. The method for the production of core particles to be Of course, the electrostatic latent image-developing 40 used in the electrostatic latent image-developing toner toner in the first embodiment of the present invention is 0f tne present invention, of course, is not limited to the allowed to have not only charge-controlling minute methods cited as examples above, particles but also the aforementioned additives exter- Jn the electrostatic latent image-developing toner of nally added and fixed on the surface of core particle. the present invention, the synthetic resin forming the Further, this electrostatic latent image-developing 45 core particles need not be particularly restricted but toner of the first embodiment of the present invention is may be selected from among the synthetic resins generallowed to have a fluidifying agent and other additives auy used as a binder. The synthetic resins which are externally added and fixed on the surface of core parti- effectively usable herein include thermoplastic resins c^e- such as styrene type resins, (meth)acryl type resins, In the electrostatic latent image-developing toner of 50 olefin type resins, polyester type resins, amide type the present invention, the core particle has no particular resins, carbonate resins, polyethers, and polysulfones, restriction except for the requirement that it should be thermosetting resins such as epoxy resin, urea resin, and obtained by any of the conventional methods available urethane resin, and copolymers and polymer blends for the production of toner particles. These conven- thereof, for example. The binder resins which are usable tional methods include a pulverizing method, wet pel- 55 in the present invention include not only the resins letization methods such as a suspension polymerization which are in the state of a perfect polymer as in a thermethod and an emulsion polymerization method which moplastic resin but also the resins which are in the state encompass a process of polymerization, and wet pellet- of an oligomer or a prepolymer as in a thermosetting ization methods such as a suspension method and a resin and further include polymers which partially conspray dry method which encompass no process of poly- 60 tain a prepolymer, a cross-linking agent, etc., for exammerization, for example. pie.
To be more specific, the pulverizing method obtains Recently, a desire has been expressed for a technique
core particles by mixing and blending a coloring agent which is capable of copying an image at a speed higher
in a thermoplastic resin, pulverizing the resultant mix- than is attainable at present. The toner to be used in such
ture, and classifying the powder consequently formed. 65 a high-speed system as aimed at is required to permit
Optionally, the core particles thus obtained may be quick fixation as on a transfer paper and ensure im
molded in a spherical shape as by means of a heat treat- proved separability from a fixing roller. For the purpose
ment. of obtaining a toner for use in the high-speed system,
