JPH0318862A - Manufacture of electrophotographic toner - Google Patents

Abstract

PURPOSE:To prevent occurrence of fogging by adding carbon in a stage of polymerizing a monomer or prepolymer to form a binder resin and enhancing dispersibility. CONSTITUTION:The carbon is added in the synthesizing stage of polymerizing the monomer or prepolymer to form the polymer containing the carbon uniformly dispersed into it, and an electric charge controller powder is added to this binder resin, mixed and kneaded, and pulverized and classified, thus permitting the parts high in carbon concentration to be formed in the surface of a toner, and occurrences of not charged, low charged, reversely charged toners, and the like to be prevented, and consequently, occurrence of fogging to be restrained.

Description

[Detailed Description of the Invention] [Summary] The purpose of this invention is to provide a toner with improved carbon dispersibility regarding toner constituting an electrophotographic developer. A method for manufacturing an electrophotographic toner is constructed by adding carbon to create a binder resin in which carbon is uniformly dispersed, adding a charge control agent to the resin, melting and kneading it to form a toner mass, and crushing and classifying the toner mass. do.

[Industrial application field]

The present invention relates to a toner used for electrophotographic development.

Electrophotographic technology is widely used in copying machines, but is also actively used in information devices such as printers and facsimile machines.

As an electrophotographic method, the method described in US Pat. No. 2,297,691 is well known.

That is, a uniform electrostatic charge is applied to a photoconductive insulator such as a photocondrum by corona discharge, and an electrostatic latent image is formed by irradiating a light image by various means.
Next, this latent image is developed and visualized using a colored fine powder called toner, and if necessary, the toner image is transferred to paper etc., and then fixed by applying pressure, heat, light, etc. to obtain printed matter. It is.

[Conventional technology]

The toner used to develop the electrostatic latent image is made by finely pulverizing a colorant such as carbon black into a binder resin made of natural or synthetic polymeric material to a size of about 5 to 20 microns. It is used as a two-component developer in combination with magnetic powder such as iron powder, ferrite powder, magnetite powder, etc. having an average particle size of about 100 μm, or a carrier coated with a resin.

This developer is triboelectrically charged by being mixed and stirred in the developing device, and the toner is carried to the latent image area on the photoconductive insulator while being supported on the carrier, and only the charged toner is electrostatically charged. Development is accomplished by selectively adhering to the latent image using force.

There is also a one-component developer that can be developed with the toner alone by mixing magnetic powder into the toner to impart magnetism.

In this case, the toner is frictionally charged by friction with the wall surface of the developing device and members such as the magnet roll inside the developing device, and is further held on the magnet roll by the magnetic force of the magnet roll, and the toner becomes photoconductive due to the rotation of the magnet roll. Development is performed by carrying only the charged toner to the latent image area on the insulator and adhering to the latent image due to electrical attraction.

What is important in this type of electrophotographic development process is that when the toner held on the carrier is transferred to the photoconductive insulator by the rotation of the magnetic roll, sufficient electricity is applied to the electrostatic latent image on the printed area. The objective is to ensure that the material adheres to the surface due to its attractive force.

Also, it must have sufficient electrical repulsive force against the printed background.

For that, 11! It is necessary that the amount of charge on the toner generated by frictional electrification maintains an appropriate value.

A conventional method for controlling the amount of charge on a toner to an appropriate value has been to adjust the amounts of conductive carbon and dye added to the binder of the toner.

Here, the role of the conductive carbon is to color and adjust the resistance value, and the role of the dye is to color and control the charge.These materials are powdered and mixed with a binder resin and heated.
This was done by kneading using a kneader.

However, the dispersibility of the toner produced using this method is not necessarily uniform, and therefore kneading is required two or more times, leading to an increase in manufacturing costs.

Further, there were also problems such as a tendency to cause lot differences in dispersibility.

[Problem to be solved by the invention]

As described above, toner for two-component developers is obtained by adding conductive carbon powder and charge control agent powder to a binder resin, mixing and kneading the mixture, and crushing and classifying the mixture. -Component The toner for development is obtained by adding conductive carbon powder, charge control agent powder, and magnetic powder to a binder resin, mixing and kneading the mixture, and then crushing and classifying the mixture.

However, the dispersibility of the toner produced in this way is not necessarily uniform, which requires kneading two or more times, which increases manufacturing costs.Additionally, there is a problem that loft differences in dispersibility tend to occur. It is.

[Means to solve the problem]

The above problem can be solved by adding carbon at the synthesis stage of polymerizing monomers or prepolymers to make a polymer, thereby creating a binder resin in which carbon is uniformly dispersed, adding a charge control agent to this resin, melting and kneading it, and forming a toner mass. This problem can be solved by configuring a method for producing electrophotographic toner by pulverizing and classifying toner lumps.

[Effect]

For the sake of simplicity, consider a two-component developer below. When the toner adhered to the carrier is carried to the photoconductive insulator by the rotation of the magnetic roll, it adheres to the electrostatic latent image due to the electric field. If the dispersibility of carbon is poor, there will be areas with high carbon concentration on the toner surface, resulting in localized areas with good conductivity, and since these areas have low electrical resistance, charge will be injected by the developing bias, resulting in the formation of areas with high carbon concentration. In the worst case, the charge polarity may be reversed.

In this case, uncharged, low-charged, and oppositely charged toner exist, so the electrostatic attraction between the carrier and the toner becomes small, and as a result, the toner scatters due to the rotation of the magnet roll, and the printed background area Because there is no repulsive force against the image, background smearing, or so-called "fogging", occurs in the image.

This problem can be solved by improving the dispersibility of carbon in the toner, and the present invention improves the dispersibility by adding carbon at the stage of polymerizing the binder resin from a monomer or prepolymer.

The binder resin used in the present invention may be any resin that can be used in electrophotography, and styrene acrylic resin, epoxy resin, acrylonitrile resin, polyester resin, etc. can be used alone or in combination.

Furthermore, any carbon may be used as long as it does not inhibit the polymerization reaction of the binder resin or participate in the polymerization reaction to form a polymer chain of the binder resin.

Next, the particle size of carbon used in the present invention is 0°01~
A particle size in the range of 2μ is good; if the particle size is larger than this, the dispersibility is poor, while if it is smaller than this, the mixing with the binder resin monomer or prepolymer is poor, and the carbon is likely to cause secondary aggregation.

[Example] Example 1: As monomers for the binder resin, 40 parts by weight of epichlorohydrin, 65 parts by weight of bisphenol A, and 200 parts by weight of sodium hydroxide (10% aqueous solution), carbon black ( Black Bars, manufactured by Capot, average particle size 0.024μm, specific surface area 138m2/g
) ... 5 parts by weight were added, and the mixture was heated and stirred to obtain an epoxy resin.

Next, 3 parts by weight of a metal-containing azo dye (Bontron 5-34, manufactured by Orient Chemical Co., Ltd.) as a coloring agent was added to 92 parts by weight of the epoxy resin obtained in this way, and 130 parts by weight was added using a pressure kneader. A toner mass was obtained by melt-kneading at a temperature of °C for 30 minutes.

Next, the cooled toner mass is processed into ~2M coarse toner by a Rotoplex pulverizer, and then the coarse toner is processed by a jet mill (PJM pulverizer 9) and the pulverized product is processed by an air classifier (
(manufactured by Albine) to obtain a negatively charged toner having a particle size of 5 to 20 μm.

Next, a developer consisting of 5 parts by weight of the toner thus obtained and 95 parts by weight of carrier (amorphous iron powder TSV 100/200, Japanese iron powder type) was prepared and applied to a laser printer (FACOM-
A printing test was conducted using a modified 6715D machine.

Furthermore, the amount of "fogging" in the printed background area was expressed and evaluated as the difference between the reflectance of the original paper and the reflectance of the printed background area.

Further, the reflectance was measured using a color computer 5M-3 (manufactured by Suga Test Instruments Co., Ltd.).

As a result, this toner showed no "fogging" in the printed background area, and the difference in reflectance was 0.7% or less.

Comparative Example 1: A toner was obtained in the same manner as in Example 1 except that carbon was added at the stage of kneading the resin and dye as in the conventional method.

When the printing was evaluated using the same method as in Example 1, "fogging" was observed in the background of the printing, and the difference in reflectance was 1.
It increased to 5%.

〔Effect of the invention〕

As described above, by carrying out the present invention, the dispersibility of carbon in the binder becomes uniform, and "agglomeration" is suppressed, thereby preventing deterioration of image quality.

Claims (1)

[Claims] By adding carbon at the synthesis stage of polymerizing a monomer or prepolymer to make a polymer, a binder resin in which the carbon is uniformly dispersed is created, and a charge control agent is added to the resin and melt-kneaded to form a toner mass. A method for producing toner for electrophotography, characterized in that it is obtained by pulverization and classification.