JPS60459A - Developing method of electrostatic latent image - Google Patents

Abstract

PURPOSE:To always obtain a distinct picture by using a composite magnetic toner obtained by mixing with a specified ratio a toner containing an electrostatic charge control agent charged to the opposite polarity against the potential polarity of an electrostatic latent image, and a toner containing an electrostatic charge control agent charged to the same polarity. CONSTITUTION:A one component developer of an electrophotography, an electrostatic printing, etc. is prepared with >=65wt% of a magnetic toner containing an electrostatic charge control agent charged to the opposite polarity against the potential polarity of a latent image, and <=35wt% of a magnetic toner containing an electrostatic charge control agent charged to the same potential. As for this developer, the electrostatic charge potential is held to obtain the surface potential of 5-60V in its absolute value on a developing sleeve. In this way, a distinct picture having high picture density and no fog is obtained, a toner does not stick to a sleeve, and a toner whose fluidity is good is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developing method for developing electrostatic images.

In general, many developing methods such as a magnetic brush method, a cascade method, a powder cloud method, a fur brush method, and a liquid developable method are known as methods for developing electrostatic latent images in electrophotography, electrostatic recording, electrostatic printing, and the like.

Furthermore, liquid developers, two-component developers, and -component developers are widely used in correspondence with these developing methods.

Furthermore, in recent years, magnetic-component developers have become more popular due to their ease of handling and
Because of the advantages of smaller developing equipment, easier maintenance, less edge effect, and less toner scattering, it is used for developing on electrostatic recording paper that does not require transfer, electrofax method using zinc oxide photosensitive paper, etc. High-resistance magnetic toners have been developed that are used not only in conductive magnetic toners for use in conventional applications, but also in so-called PPC copying machines that electrostatically transfer developed toner images onto plain paper.

In this case, although the high-resistance magnetic toner has good transferability during electrostatic transfer, it has a problem in that its developability deteriorates. In contrast, a high-resistance magnetic toner exhibiting triboelectric charging properties has been proposed as disclosed in Japanese Patent Laid-Open No. 55-11298.

This is an attempt to obtain good image quality by frictionally charging the high-resistance magnetic toner and the magnetic brush developing device member due to the difference in their charging series when they come into contact with each other.

However, the triboelectric charging behavior of -component magnetic toner is
It is difficult to impart an appropriate developing function to the toner because it is subtly influenced by developing conditions such as the polarity of the electrostatic latent image on the photoreceptor, the material of the developing sleeve, and the number of revolutions. In short, it has not been completely elucidated what kind of charging ability should be imparted to the toner on the developing sleeve, and what should be done about the material composition of the toner necessary for this purpose.

Conventionally, in order to control the charge of component toners, it has been accepted that charge control agents such as metal-containing dyes are added to the toner, or that silica is attached to the surface of the toner as an adjunct. Even if the toner has good charging properties, continuous copying causes charges to accumulate due to friction between the developing sleeve and the toner, causing problems such as adhesion of the toner to the sleeve and a decrease in fluidity. Therefore, it is necessary to maintain the chargeability of the toner surface at a certain level and to leak the charge so that it does not accumulate excessively.

As a solution to this problem, it has been proposed to attach carbon to the toner surface, but since carbon is electrically conductive, the toner's chargeability becomes too low, causing major problems in developing performance, such as a lack of image density. there were.

The present invention has been made in view of the above circumstances, and provides an electrostatic latent image developing method for developing an electrostatic latent image carried on an electrostatic latent image bearing surface by a composite magnetic toner having an electrical charge. The magnetic toner contains 65% by weight or more of a magnetic toner (A) containing a charge control agent that is charged to the opposite polarity to the potential polarity of the electrostatic latent image, and a charge that is charged to the same polarity as the potential polarity of the electrostatic latent image. The composite magnetic toner is characterized in that the magnetic toner (B) containing the control agent is 35% by weight or less, and the composite magnetic toner is made to retain an electrical charge so that the surface potential on the developing sleeve is 5 to 60 V in absolute value. A method for developing an electrostatic latent image is provided.

The outline of the developing method of the present invention is as follows.

A feature of the present invention is that the surface potential on the developing sleeve is controlled within a specific range by using a composite magnetic toner consisting of two types of toner containing predetermined amounts of charge control agents with different polarities.

For the magnetic toner (A>, use a negatively charged charge control agent if the photoreceptor is a positively charged type such as selenium, or a positively charged charge control agent if the photoreceptor is a negatively charged type such as ZnO). Blend.

The magnetic toner (A) is held on the sleeve by a magnet roll in the developing sleeve, and is rotated on the sleeve by mutual or independent rotation of the sleeve and the magnet roll. At this time, the magnetic toner (A) is charged to a polarity opposite to that of the electrostatic latent image mainly due to friction with the sleeve and further friction with the blade for adjusting the brush height. At the same time, magnetic toner (A
) The magnetic toner (B), which is charged with the opposite polarity, rotates on the sleeve and becomes charged with the same polarity as the electrostatic latent image on the photoreceptor due to friction with the sleeve and blade, and becomes electrostatically charged with the magnetic toner (A>). Furthermore, the magnetic toner (A) and the magnetic toner (B) rub against each other to maintain an appropriate charge. In this case, the magnetic toner (A) and the magnetic toner (B)
) is an important requirement for implementing the present invention,
The proportion of the magnetic toner (A) in the total toner Φ must be 65% by weight or more.

If the magnetic toner (A>) is less than 65% by weight, an appropriate charge cannot be obtained on the surface of the composite magnetic toner, making it impossible to develop an electrostatic latent image.

Furthermore, in the present invention, the surface potential 1 of the toner on the developing sleeve, which greatly influences the practical characteristics of the -component magnetic toner, is
We focused on this and attempted to measure it. That is, it has been found that the surface potential of the composite magnetic toner can be controlled to a lower level than that of the magnetic toner (A> alone).Then, it has been found that the surface potential of the composite magnetic toner can be controlled to a lower level than that of the magnetic toner (A> alone).Then, it has been found that the surface potential of the composite magnetic toner can be controlled to a lower level than that of the magnetic toner (A> alone. It has been found that the surface potential on the sleeve needs to be maintained at 5 to 60 V in absolute value.

The method of measuring the surface potential at this time is 800 Gauss, 600 Gauss
Stainless steel diameter 3 (1m+φ) with built-in magnet rotating at RPM
400 mg of toner was placed on the plate and the surface potential was measured after rotating for 1 liter.

The charge control agent used in the present invention is positively charged, such as nigrosine dye containing basic nitrogen or quaternary ammonium salt.
Furthermore, there are various metal-containing dyes that have negative charge. Further, as the magnetic powder, iron oxides such as magnetite, ferrites such as nickel-zinc, garnets such as yttrium-iron, magnetic metals and alloys such as nickel, iron, cobalt, and mixtures thereof are used. As the binder resin, known resins are used for pressure fixing and heat fixing. Other components of the toner may include additives for improving fixability and fluidity, electrical resistance regulators such as carbon black, pigments, and the like.

As a method for producing the magnetic toner, a known pulverization method, spray drying method, etc. can be used.

The physical properties of the magnetic toner particles are as follows: magnetic toner (A), (
B) The particle size of the tomo is 5-30μ, preferably lO-20
11 is preferred. Further, the appropriate electrical resistance is 1012 to 1016 Ω·cm under the condition of 20 KV/am.

As described above, according to the developing method of the present invention, the composite magnetic toner retains an appropriate electrical charge, so it is possible to achieve both developability and transferability, and produce sharp, high-quality images similar to two-component toner. Moreover, there is no toner adhesion to the developing sleeve, and development can be performed with excellent practical characteristics such as fluidity.

The present invention will be explained in detail below with reference to Examples.

Example The above components were melt-kneaded, cooled and pulverized to prepare a negatively charged magnetic toner <A) in which 1% of hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.) was mixed and classified to have a particle size of 35 μI or less.

The above components were melt-kneaded, cooled, pulverized, mixed with 1% hydrophobic silica (R-972 manufactured by Nippon Aerosil Co., Ltd.), and a positively charged magnetic toner (B) was prepared by classifying the particle size to 35 μ or less. 10 parts by weight of magnetic toner (B) was mixed with 100 parts by weight of the magnetic toner (A) to prepare a -component composite magnetic toner.This toner was applied to a PPC electronic copying machine using a hot roll fixing method using a selenium photoreceptor. The developing method in this case used a stainless steel developing sleeve containing a built-in magnet that was 1000 Gauss and rotated at 120 ORPM.

The developing sleeve was rotated at 30 ORPM in the opposite direction to the magnet, and the surface potential of the magnetic brush toner was adjusted to 140 Volt. When 10,000 sheets were continuously copied under these conditions, it was possible to always obtain clear image quality with an image density of 1.65 or higher and no fog. Even after copying 10,000 sheets, toner did not adhere to the sleeve and the fluidity was good.

patent applicant Tomoekawa Paper Mill Co., Ltd.

Claims (1)

[Claims] In an electrostatic latent image developing method for developing an electrostatic latent image carried on an electrostatic latent image bearing surface with a charged composite magnetic toner, the composite magnetic toner has a potential polarity opposite to that of the electrostatic latent image. Magnetic toner containing a charge control agent (A
>65% by weight or more, and the magnetic toner (B) contains a charge control agent that is charged to the same potential polarity as the potential polarity of the electrostatic latent image.
5% by weight or less, and a method for developing an electrostatic latent image, characterized in that the composite magnetic toner is charged with a charge so that the surface potential on the developing sleeve is 5 to GOV in absolute value.