JPH0363660A - Electrostatic latent image developing toner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called 1.5-component toner for developing electrostatic latent images.

Traditionally, in the development method of electrostatic latent images in electrophotography, a carrier made of magnetic powder and a non-magnetic toner made of resin particles, which are usually non-magnetic, are mixed and charged by friction, and a mag roller is used to develop the electrostatic latent image. Typical examples include a two-component development method in which magnetic brushes are formed on the magnetic roller, and an l-component development method in which a thin layer of so-called magnetic toner containing magnetic powder is formed on a mag roller and developed using a blade that also serves as a charging means. known to.

Recently, a one- and five-component type development system, which is located between these development systems, has been developed. This method involves forming a magnetic brush made of minute carriers with a particle size of 50 μm or less and magnetic toner so that most of the carrier exists on the mag roller, and increasing the relative rotational speed between the magnetic roll of the mag roller and the sleeve. The magnetic toner is charged and developed by stirring friction between the carrier and the magnetic toner on the magnetic roller. In this method,
The carrier is considered to be a part attached to the mag roller, and the developer is approximated as a one-component system consisting only of magnetic toner, and there is no need for an agitation mechanism for the magnetic toner and carrier, so the developing machine can be made more compact. There are benefits to be gained.

However, the conventionally known 1 and 5 precept type toners have the following problems. First, since the charging area of the magnetic toner is limited to the area on the developing sleeve, it is difficult to charge the toner sufficiently, and as a result, an excessive amount of toner flies to the photoreceptor during the development process, resulting in high resolution. I can't. Second, in order to solve the above problem,
When the friction between the magnetic toner and the carrier is increased by the magnetic binding force, and the charging property of the toner particles is increased, so-called voids, which are not developed or transferred, occur particularly in the fine line portions. Although the cause of such voids is not yet clear, it is believed to be due to non-uniform charging between toner particles or on the inner surface of toner particles. Furthermore, thirdly, there is a large edge effect. This edge effect is a phenomenon in which a large amount of toner is developed concentratedly in areas where the electric field strength is high at the periphery or end of the electrostatic latent image formed on the photoreceptor. When the edge effect is large, the amount of toner adhering to the thin line area increases and the amount of toner consumed increases, but conversely, the image density in the center of the solid black area decreases. Image density is uneven.

8 <"Let's do it" 1 The present invention was made in order to solve the above-mentioned problems with the conventional 1.5-class toner. It is an object of the present invention to provide a toner for developing electrostatic latent images as a 1,5 tc fraction toner that has little effect and has an appropriate consumption amount.

The toner for developing an electrostatic latent image according to the present invention has a binder resin of 100%.
When 100 to 150 parts by weight of magnetic powder and 0.5 to 3.0 parts by weight of silicone oil are contained, 0.5 to 150 parts by weight of hydrophobic silica are contained to 100 parts by weight of this magnetic toner.
It is characterized by consisting of 1.5 parts by weight and 1.0 to 30 parts by weight of magnetic powder.

In the toner for developing electrostatic latent images according to the present invention, the magnetic toner is particles containing magnetic powder and silicone oil in a binder resin, and the average particle size thereof is preferably 5.
~20 μm.

As the binder resin, for example, styrene-acrylic acid ester copolymer or polyester resin is preferably used. Furthermore, although the magnetic powder is not particularly limited, magnetite powder is usually preferably used.

Further, according to the present invention, the magnetic toner contains 100 to 150 parts by weight of magnetic powder and 0.5 to 3.0 parts by weight of silicone oil to 100 parts by weight of binder resin. will be included.

In magnetic toner, when the amount of magnetic powder is less than 100 parts by weight based on 100 parts by weight of binder resin, the magnetic binding force of the magnetic toner on the developing sleeve is too small, and the toner is not sufficiently charged. As a result, during the development process, the amount of toner flying onto the photoreceptor becomes excessive, making it impossible to obtain high resolution. When the amount is more than 150 parts by weight per 100 parts by weight, it is difficult to uniformly disperse the magnetic powder when kneading and dispersing it in the resin during the production of magnetic toner.

It seems that the silicone oil contained in the magnetic toner migrates to the surface of the magnetic toner and improves the surface uniformity, and as a result, increases the uniform charging property of the magnetic toner particles, but the hollowing mentioned above is a phenomenon. prevent the occurrence of In order to effectively obtain such an effect, in the magnetic toner, the amount of silicone oil should be set to 100 parts by weight of the binder resin.
It is necessary to set it in the range of 0.5 to 3.0 parts by weight,
Preferably, it is in the range of 0.7 to 1.5 parts by weight. The amount of silicone oil is 0.0% with respect to 100 parts by weight of the binder resin.
When it is less than 5 parts by weight, it is difficult to reliably prevent hollowing out, and on the other hand, 3.0! If the amount exceeds 1 part, slippage may occur between the screw of the kneader and the material when kneading the resin and silicone oil during toner production, making the kneading operation difficult.

The toner for developing electrostatic latent images according to the present invention can be obtained by adding hydrophobic silica and magnetic powder to 100 parts by weight of the magnetic toner as described above.

As is already well known, hydrophobic silica increases the fluidity of toner particles and improves the high-speed charging properties of the toner.

For this purpose, hydrophobic silica is used for magnetic toner 100!1
It is necessary to add 0.5 parts by weight or more per part of the toner, and if it is less than this, the fluidity of the toner is insufficient and the image density is low. On the other hand, if too much is added, it will accumulate in the developing machine as the developer is used, fluctuating the amount of charge on the toner, and thus impairing the stability of image density. Te, 1, 5
It is used in a range of parts by weight or less.

In this way, by adding hydrophobic silica to magnetic toner, the necessary image density can be secured, but the edge effect remains unsolved in developers made by adding only fluid silica to magnetic toner. . Therefore, according to the present invention, the edge effect can be eliminated by adding 1.0 parts by weight or more of magnetic powder to 100 parts by weight of the magnetic toner together with hydrophobic silica. However, if too much is added, the image density will be reduced, so the upper limit is usually 3.0 parts by weight.

The toner for developing electrostatic latent images according to the present invention includes a magnetic carrier,
For example, it is mixed with ferrite powder and used as an electrostatic latent image developer.

As mentioned above, the developing toner of the present invention is made by blending magnetic powder and silico oil into a binder resin to form a magnetic toner, which is then blended with hydrophobic silica and magnetic powder. It is possible to obtain clear images with high resolution and no hollow areas and little edge effect.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples in any way.

100 parts by weight of styrene-butyl methacrylate copolymer,
Magnetite powder (average particle size 0.5 μm, external magnetic field 10K)
Oe, coercive force 1250e, saturation magnetization 4 B, 4
es+u/g) 120 parts by weight and viscosity 100,000
1.0 parts by weight of CS silicone oil was melt-kneaded using a twin-screw kneading extruder. Thereafter, the kneaded material was cooled, coarsely pulverized with a cutter mill, finely pulverized with a jet fruit, and classified to obtain a magnetic toner having an average particle size of 11.011 m.

For 100 parts by weight of this magnetic toner, as a compounding agent,
Hydrophobic silica (R-972 manufactured by Nippon Aerosil ■) 0.8
Weight parts and magnetite powder (average particle size 0.3 μm, external magnetic field 10 KOe, coercive force 800e, saturation magnetization 84
emu/g) was added to obtain a toner for developing an electrostatic latent image.

This toner was mixed with a ferrite carrier to prepare a developer.

Laser printer (NEC PC-PR406L)
An image copying test was carried out using H〉, and the images were evaluated. Image density was measured using a Macbeth density needle.

The results are shown in Table 1.

Claims (2)

[Claims] (1) 100 parts by weight of magnetic powder per 100 parts by weight of binder resin
A magnetic toner containing 150 parts by weight of silicone oil and 0.5 to 3.0 parts by weight of silicone oil, and 0.5 to 1.5 parts by weight of hydrophobic silica and 1.5 parts by weight of magnetic powder to 100 parts by weight of this magnetic toner. A toner for developing an electrostatic latent image, comprising 0 to 3.0 parts by weight. (2) The toner for developing electrostatic latent images according to claim 1, wherein the magnetic toner has an average particle size of 5 to 20 μm.