JPS5952254A - Encapsulated toner - Google Patents

Abstract

PURPOSE:To obtain a toner with high yield, having a uniform surface and a uniform distribution of triboelectrified charge, and prevented from forming a bridge and melt attaching, by mixing a pulverized core material with a fluidity enhancing agent, and encapsulating it after classification. CONSTITUTION:A pigment, such as carbon black, magnetic powder, and a binder resin are kneaded, and pulverized to obtain a pulverized core material, It is mixed with hydrophobic colloidal silica or the like fluidity enhancing agent, and classified to prevent bridge formation or melt attaching of the toner in the classifier. The toner is mixed and dispersed into a soln. of a styrene resin or the like to be used for outer shells and precipitated by adding water. The ppt. is washed with water, and dried, then disintegrated with a Henschel mixer to obtain a microencapsulated toner. As a result, the obtained toner has a uniform distribution of electrified charge and good fluidity, not agglomerates of the toner in capsulating, and forms a fog-free sharp image.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner for an electrophotographic developer, and particularly to a capsule toner suitable for pressure fixing.

Conventionally, as an electrophotographic method, US Pat.
Various methods are described in Publication No. 24748, etc., but all of these methods apply a uniform charge to the photoconductive layer and irradiate the photoconductive layer with a light image corresponding to the original. This forms a latent image, which is then developed with a black powder toner to become a visible image, which is transferred to paper or the like as required and permanently fixed by heat, pressure, or the like.

Conventional electrophotographic toners are generally produced by melt-kneading a resin serving as a toner binder and a pigment, cooling and pulverizing the mixture, and classifying the mixture if necessary to obtain a toner having a desired particle size. However, the surface of the toner obtained by this manufacturing method has uneven surface properties because the pigment in the resin is exposed on the surface of the toner particles, resulting in uneven distribution of triboelectric charge of the toner. There were drawbacks that made it unusable for practical use.To improve these drawbacks, USP 378
As disclosed in Japanese Patent Application No. 8994, there is one in which the periphery of a soft core material is coated with another hard resin. However, due to the soft core material of such toners, toners obtained by heating mixed-wire pulverization have reduced fluidity and problems with cohesiveness, and it is difficult to obtain the desired toner particle size and particle size distribution in the subsequent classification process. However, this classification process also has the disadvantage that bridges are formed in the classifier and fusion occurs, resulting in a decrease in toner yield.

An object of the present invention is to provide a capsule toner with excellent fluidity and agglomeration resistance. Another object of the present invention is to provide a capsule toner having a suitable particle size distribution and improved image quality.

Its feature lies in the capsule toner that is made by mixing a crushed core material and a fluidity improver, classifying the mixture, and then encapsulating it.

That is, as in the present invention, for example, the core material is obtained by heating and mixed-wire pulverization, and by externally adding and mixing a fluidity improver, it has excellent fluidity and agglomeration resistance, overcomes the drawbacks in the classifier in the classification process, and improves the average particle size. A microcapsule toner having a uniform particle size of 10 to 13 ILrn and an excellent yield can be provided.

Typical base materials that can be used in the present invention include wax compounds, ethylene-acrylic copolymers containing a large ethylene component, and ethylene-vinyl acetate copolymers. Examples of wax-based compounds include natural waxes, paraffin waxes, amide waxes, petroleum waxes, fatty acids and their metal salts,
Polyethylene glycol and its derivatives, low molecular weight polyethylene, etc. can be used. Examples of low molecular weight polyethylene include various AC polyethylenes manufactured by Allied Chemical Co., Ltd.
Examples include various sunwaxes from Sanyo Chemical, various highwaxes and Hoechst waxes from Mitsui Petrochemicals, and A-wax from BASF. Specific examples include Allied Chemical's AC polyethylene, AC-6, AC-9; Sanyo Chemical's Sunwax 171P, 151P, 131P; Mitsui Petrochemical (7) Hiwax 110P, 510P, 220F3.
20F, 210F, 310P; Hoechst PE520
etc. Alternatively, examples of oxidized types include AC680, AC655, and AC692 from Allied Chemical; PAD521PAD522 from Hoechst; and Sunwax E200 from Sanyo Chemical.

Examples of ethylene copolymers include ethylene-vinyl acetate copolymers and ethylene-acrylic copolymers; examples of the former include AC405 and AC4 manufactured by Allied Chemical Co.
00, AC401; Evaflex 550, 560, etc., manufactured by Mitsui Polychemical Co., Ltd.; examples of the latter include AC340, AC3120, etc., manufactured by Allied Chemical Co., Ltd.

The above materials are blended, heated, kneaded, and then pulverized by an appropriate method. After kneading with a roll mill, kneader, etc., it may be cooled and pulverized using a mechanical pulverizer such as a jet mill, or it may be dispersed in air or liquid in a molten state after kneading and solidified. It may be supplemented later.

In the present invention, the core material fine particles prepared as described above are then externally mixed with a fluidity improver and classified. Fluidity improvers that can be used in the present invention include, for example, hydrophobic colloidal silica, and o, i to 3.0% by weight (
(preferably 0.2 to 0.5% by weight) can be added externally.

As a method for encapsulating the above-mentioned classified core material fine particles, a phase separation method, a spray dryer method, an interfacial polymerization method, etc. can be used.

Shell materials that can be used in the invention include monopolymers of styrene and its substituted products, such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers, styrene-propylene copolymers, and styrene-propylene copolymers. Vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-octyl acrylate copolymer, Styrene-methyl methacrylate copolymer,
Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether Styrenic copolymers, such as styrene-vinyl methyl ketone copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers, styrene-maleic acid copolymers, and styrene-maleic acid ester copolymers. Copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyamide, polyacrylic butylene resin, rosin, modified rosin, terpene resin, phenolic resin, Aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, etc. can be used.

Examples of solvents that can be used to dissolve the shell material of the present invention include:
n-hexane, benzene, toluene, m-xylene, cyclohexane, chloroform, trichlene, methanol, ethanol, dioxane, THF, MEK, acetone, butyl acetate, nitroethane, DMF, N-methylformamide, 2-pyrrolidone, etc. can be used.

Further, as the coloring material of the toner of the present invention, a known dyeing agent 4 can be used. For example, various carbon blacks, aniline black, naphthol yellow, molybdenum orange,
Rhodamine lake, alizarin lake, methyl violet lake, phthalocyanine blue, nigrosine methylene blue, rose bengal, quinoline yellow, etc. can be used.

Furthermore, when the toner of the present invention is used as a magnetic toner, it can contain magnetic powder. The magnetic powder includes ferromagnetic elements, alloys and compounds containing these elements, and alloys and compounds of iron such as magnetite and ferrite, cobalt, nickel, and manganese can be used.

The microcapsule toner according to the present invention prepared in this manner has particularly excellent fluidity and cohesiveness, and a toner having a uniform particle size with a narrow particle size distribution width can be obtained in the classification step. As in the present invention, by classifying after external addition, toner aggregation is prevented even during encapsulation, the shell formation is uniform and very good, and the properties necessary for a toner can be stably supplied, resulting in clear images without fogging. is obtained.

Furthermore, problems such as bridging and fusion within the classifier during the classification process can be solved by externally adding and mixing a fluidity improver.

Next, examples will be shown. Parts are parts by weight.

(Example-1) 100 parts of low molecular weight polyethylene 60 parts of magnetic powder - After heating, kneading and cooling with a roll mill, coarsely pulverize with a cutter mill and finely pulverize with a jet mill, hydrophobic colloidal silica was added to the toner. When 0.2% externally added toner was classified using a wind classifier, no bridging or fusion occurred in the classifier, and the toner yield was 8.
At 5%, a toner with an average particle size of 12 pm was obtained. This is used as the core material.

Next, this core material was dispersed and mixed in 10 parts of a styrene resin DMF solution for the shell material, and then water was added to precipitate it. This precipitate was further rinsed with water, dried, and crushed with a Henschel mixer. Use microcapsule toner.

Next, when this microcapsule toner was subjected to development using an NP-120 copying machine (cannon acid, pressure fixing, -component development), a clear image without fogging was obtained.

(Comparative example) Example-1 except that hydrophobic colloidal silica was not externally added
As a result of the same treatment as above, bridging and fusion occurred in the classifier during the classification process, making classification impossible, so the process was discontinued.

(Example 2) Paraffin wax 100 parts Magnetic powder 60 parts Hydrophobic colloidal silica The same treatment as in Example 1 except for the external addition of 0.4% resulted in no problems in the classification process and the toner yield was 82. %, a clear image without fogging was obtained.

(Example-3) Natural wax: 100 parts Magnetic powder: 60 parts Polyester resin for shell material The process was carried out in the same manner as in Example-1 except for 10 parts of MEK solution. As a result, there were no problems in the classification process, and the toner yield was 84%. A clear image without fogging was obtained.

Applicant: Canon Co., Ltd.

Claims (1)

[Claims] A capsule toner in which a crushed core material and a fluidity improver are mixed, classified, and then encapsulated.