JPS58136050A - Microencapsulated toner for electrophotography - Google Patents

Abstract

PURPOSE:To improve the fixability, by dispersing a substance incompatible with a wall forming substance in each capsule wall in the form of a matrix. CONSTITUTION:Powder of a substance incompatible with a wall forming substance, e.g., SiO2, TiO2, ZnO2, an inorg. pigment such as carbon black, polystyrene powder, fluororesin powder or an org. pigment is dispersed in each capsule wall in the form of a matrix by 50-100%, preferably 20-30% of the amount of the wall forming substance.

Description

[Detailed description of the invention] The present invention relates to a toner for electrophotographic development.

Conventional electrophotographic methods include US Pat. No. 2,297,891;
Special Publication No. 42-23!310 and Special Publication No. 43-24
Various methods are described in Publication No. 748, etc., but
In both of these methods, a charge is uniformly applied to the photoconductive layer, a light image corresponding to the original is irradiated onto the photoconductive layer to form a latent image, and then the latent image is transferred to a black powder toner. The image is developed into a visible image, transferred to paper or the like as necessary, and permanently fixed by heat, pressure, etc.

Conventional I-toners for electrophotography are generally prepared by melt-kneading a resin 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 parts covered with resin and parts where the pigment is exposed, and the surface property is uneven, so the distribution of the amount of triboelectric charge of the toner is not uniform. In addition, when toners are made using resins with low softening points or melting points as binders in order to improve fixing properties, the toner fluidity becomes extremely poor, resulting in drawbacks such as impossibility of practical use.

USP3788 is a solution to improve these drawbacks.
As disclosed in the specification of No. 994, there is a toner in which the periphery of a soft core material is coated with another hard resin, but when such toner is fixed in a fixing device, the capsule wall is torn and the core material is exposed to the surface. Even when exposed to water, the capsule wall exists between the core material and the member to be fixed, which has the disadvantage of weakening the fixing performance.

An object of the present invention is to provide a microcapsule toner with improved fixing properties.

The object of the present invention is achieved in a microcapsule toner by dispersing in the capsule wall a matrix of substances that are incompatible with the wall-forming substance.

That is, when the toner of the present invention is developed on a photoreceptor using a general development process, and when the toner is transferred to paper and passed through a fixing device, pressure is applied to the coating layer and the coating layer is destroyed.
The capsule wall is broken into powder due to the concentration of core force between the incompatible matrix material dispersed in the coating layer and the coating layer forming resin. Since the broken wall-forming material powder is very small compared to the volume of the capsule core material 1, it is incorporated into the heat-melted or pressure-fixed core material and does not impede the fixing performance.

Examples of capsule core materials or wall-forming substances that can be used in the present invention include the following. Polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, Styrene-maleic acid copolymer, styrene-acrylic ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-ethyl acrylate copolymer,
butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate) copolymers, styrene-butyl methacrylate copolymers, styrene-phenyl methacrylate copolymers, etc.), styrene-α-methyl chloroacrylate copolymers,
Styrenic resins such as styrene-acrylonitrile-acrylic acid ester copolymers (unipolymers or copolymers containing styrene or styrene substitutes), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic acid resins, phenyl resin, epoxy resin, polyester resin,
These include low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral, and the like.

Examples of 7x-forming substances that are not compatible with wall-forming substances include inorganic pigments such as 5iOz□, Tier, and Zn0i carbon black, organic pigments, styrene powder,
It is possible to use powders of organic substances, such as fluororesin powders.

The qri content of the matrix-forming material relative to the wall-forming material is between 50 and 100% in line with the wall-forming material, preferably 20
Add ~30%.

As the encapsulation method of the present invention, a phase separation method, a spray dryer method, an air suspension method, etc. can be used.

(Example 1) Mitsui Hiwax 405MP (Mitsui Petrochemical Ogyo KK)
100 parts and 5 parts of Raven '3500 (manufactured by Columbia Carbon KK) were kneaded in a roll mill. This mixer 2
5 parts by weight and 1 part by weight of 40 toluene were placed in a magnetic ball mill pot and stirred with a stainless steel pole for 24 hours to obtain a suspension in which polyethylene wax having a particle size of 8 to 12 gm was dispersed in toluene. This is called suspension A.

Separately, 20 parts by weight of D-125 (Esso standard polystyrene resin) and R972 (5ick part by Nippon Aerosil Co., Ltd.)
) Suspension B is obtained by dispersing 10 parts by weight of the suspension in 100 parts by weight of a solvent in a magnetic ball millbot for 24 hours.

Suspension A100 weight part and suspension B50
Part by weight and 100 parts by weight of toluene were subjected to spray drying using a spray dryer manufactured by Niro Co., Ltd., to obtain capsule I-ner having a wall around polyethylene wax (silica dispersed in polystyrene).

For comparison, a capsule toner was obtained in exactly the same manner as in Example 1, except that Suspension B without silica was used.

Example 1 (7) l-+-to iron powder EFV250/4
00 mesh (manufactured by Nippon Steel Powder) D was mixed at a weight ratio of 5:95, an image was produced using an NP-6000 copying machine without passing through a fixing device, and this image was fixed using a pressure fixing device at a pressure of 30 kg/. did. Similarly, a 1.S image for comparison was also fixed using the same pressure fixing device and the same fixing pressure.

A fixation test was conducted by rubbing two image samples 30 times with a crockmeter equipped with sand and poppy rubber, and it was found that the microcapsule toner of the present invention had a 20% decrease in image density.
On the other hand, the toner using the comparative example was 40
% reduction rate.

(Example 2) AC polyethylene 1702 (manufactured by Allied Chemical) 1
00 parts by weight and 100 parts by weight of magnetic material M-32 (Toda Kogyo) were kneaded in a heated roll mill, and 30 parts by weight were mixed with THF5.
0 parts by weight was dispersed in a ball mill to obtain a THF suspension with a particle size of 5 to 15 mm. This suspension will be referred to as suspension C.

Separately, THF 100 times, Saran resin F-239
(Asahi Dow Chemical) 20 Chongyubu and Tilaniumo
Suspension D is obtained by ball milling xide P 25 (manufactured by Nippon Aerosil Co., Ltd.) with 10-fold crystal.

Suspension C100 heavy part and suspension D50
While stirring the heavy woven part and the THF100 heavy part in a beaker using a three-one motor, ion-exchanged water was dropped at a rate of 10 cc/min using a burent to surround the particles made of polyethylene and magnetic material ( Ti0 during Saran
The outer wall (in which i was dispersed) was precipitated to obtain a microcapsule toner.

Microcapsules were obtained under exactly the same conditions as in Example 2, except that suspension D without TiO≧ was used for comparison.

The two toners described above were put into an NP-120 machine, an image was produced, and the fixing properties were examined in the same manner as in Example 1.I! i. In Example 2, the density reduction rate was 10%, whereas in Comparative Example, it was 30%.

Claims (1)

[Claims] A microcapsule toner for electrophotography, characterized in that a substance incompatible with the wall-forming substance is dispersed in the capsule wall in the form of a matrix.