JPS5827503B2 - magnetic toner - Google Patents

Description

Detailed Description of the Invention The present invention develops an electrostatic latent image formed on a photoreceptor such as zinc oxide paper, Se photoreceptor, ODC semiconductor, etc., and transfers the developed image onto a transfer sheet such as plain paper. This invention relates to a one-component magnetic toner used in electrophotography to obtain a final image by post-pressure fixing.

Conventionally, when dry developing electrostatic latent images, magnetic brush development has been carried out using a two-component developer, which is a mixed powder of a carrier such as iron powder and a toner consisting of a resin and a pigment such as carbon black. ing.

However, when two-component development is used, only the toner is consumed, so a means to keep the toner concentration in the developer constant and a means to mix and stir the toner and carrier are required, making the developing device complicated. There is also the problem of increasing the size.

In recent years, in order to solve these problems, so-called one-component magnetic toners containing magnetic powder and using no carrier have been developed and are being put into practical use.

Furthermore, this magnetic toner is used to develop the electrostatic latent image formed on the photoreceptor through a charging and exposure process, a transfer sheet is placed over the developed image, and the developed image is transferred by means such as a corona charger or a conductive rubber roller. It is also being applied to a copying method called the so-called PPC method, in which a final image is obtained by transferring and fixing onto a sheet.

In this PPC method, a pressure fixing method that does not require preheating time and can be started quickly is being adopted as a fixing method.

By the way, pressure fixing type magnetic toner needs to undergo plastic deformation under relatively low compressive shear stress and have good releasability from the pressure fixing roll in order to obtain sufficient fixing performance even at low pressure. .

For this reason, in pressure fixing type magnetic toners, a resin made of a copolymer of polyethylene wax and polyethylene is used, and it has been confirmed that it exhibits good pressure fixing properties.

In addition, this pressure fixing type magnetic toner is required to have good developability and transferability in order to obtain a good final image, but the above resin has no polar groups such as 10H1COOH1-C-0. Since the toner does not last long, it has poor charging properties, and when a toner made using this is used, there is a problem in that the transfer efficiency decreases.

An object of the present invention is to provide a magnetic l-ner used in a pressure fixing type PPC system that can improve transfer efficiency.

The magnetic l-ner of the present invention has a thermoplastic phase f' made of polyethylene wax and a polyethylene copolymer as one of its main components.

Specifically, Mobil W is a commercially available resin.
ax Cerese.

Mobil Wax 2305, L90Y, 602, C
rystal Wax 220 (made by Mobil)
, Microwax L-700, R-513, Mitsui No. 1
Iwatsukus 200P1400P1220Mp, 220P
, 410P (manufactured by Mitsui Petrochemicals), etc., and Evaflex 1501210-260 (M
(manufactured by Nanami Polychemical), wax type 1702.6
17.6.6.8, emulsion type 629.655
．． 690.392, copolymer type 1801405.
Examples thereof include ethylene-vinyl acetate copolymers such as Copolymer Type 540 (manufactured by Allied Chemical), and ethylene-acrylic copolymers such as Copolymer Type 540 (manufactured by Allied Chemical).

Further, the magnetic toner of the present invention contains magnetic powder as another main component.

The magnetic powder used is one with a high saturation magnetic flux density (4πIs), a low coercive force (IHC), and a high magnetic permittivity (μ), with a particle size of 1μ or less, such as FelMn.
, metal powder such as Ni, Hi-Zn ferrite, Fe3O
4. Iron oxides such as FeO3 are used, but Fe3O4 is most commonly used because of its color and other factors.

As a result of various studies, the present inventors have found that transfer efficiency can be improved by adding silicone oil together with silicon dioxide to the magnetic toner whose main components are the above-mentioned resin and magnetic powder.

This is because the addition of silicone oil to the magnetic L-Q improves the charging characteristics of the resin.

It is sufficient to add a small amount of silicone oil; if it is added in a large amount, the properties of the resin will be impaired, so the amount should be in the range of 0.05 to 2 parts by weight, preferably 0.05 to 2 parts by weight, based on 100 parts by weight of toner. It is 1 to 1.0 parts by weight.

Although silicone oil can exhibit its effects even when used alone, it is necessary to use it in combination with silicon dioxide for the following reasons.

In other words, when only silicone oil is added to the toner, phase separation and segregation of the silicone oil tends to occur during toner preparation processes such as heating and kneading of raw materials and spheroidization heat treatment, making it difficult to uniformly disperse a predetermined amount of silicone oil in the toner. However, if silicone oil is adsorbed on silicon dioxide and added to the toner, taking into account the dispersion of the resin and magnetic powder, it is possible to ensure uniform dispersion of the silicone oil into the toner. be able to.

Adsorption of silicone oil to silicon dioxide can be achieved, for example, simply by placing the two in a Hensel mixer or the like and mixing them before heating and mixing.

The amount of silicon dioxide added is determined according to the amount of silicone oil added, and is 0.01 parts by weight per 100 parts by weight of toner.
~5.0 parts by weight, preferably 0.05 parts by weight
-2.0 parts by weight.

The silicone oil used in the present invention may have a kinematic viscosity of 50 to 100,000 centistokes (C3) in order to take advantage of the charging characteristics of the resin.

These commercially available silicone oils are KF
96, KF410. There are KS61, KS702 (all manufactured by Shin-Etsu Chemical), 5H200°SH211, 5H720 (all manufactured by Toshi Silicon), etc.

Further, it is desirable that the silicon dioxide has an average particle size of 0.1 μm or less.

An example of a commercially available product is Aerosil 130°2.
00, TT6001 MOX80 (all manufactured by Nippon Aerosil), Carplex #1120° #67 (all manufactured by Shionogi & Co.), Jilton R2, Star Seal S
There are S etc.

Toners are usually produced by mixing, kneading, and grinding, followed by resistance treatment.

When a toner of the present invention was prepared in accordance with this method, the toner to which silicone oil and silicon dioxide were added had a repose angle of 32 to 37 degrees, good fluidity, and exhibited a transfer efficiency of 90% or more.

Addition of silicone oil alone shows equivalent transfer efficiency, but as the amount of silicone oil increases, the fluidity of the toner deteriorates, and some toners show a blocking state.

A toner that does not contain both silicone oil and silicon dioxide has a repose angle of 41 to 49 degrees, poor flowability, and a transfer efficiency of less than 50%, resulting in a toner with poor characteristics.

Further, even if a dye such as nigrosine or a pigment such as carbon black is added to the components used in the present invention, the effect of adding silicone oil or silicon dioxide is not diminished.

As mentioned above, copolymers of polyethylene wax and polyethylene have traditionally been used as resins in pressure fixing magnetic toners for reasons of fixability and releasability from the fixing roll. There was a problem with that.

On the other hand, the magnetic toner of the present invention has a predetermined amount of silicone oil adsorbed on silicon dioxide added uniformly and dispersed in the magnetic toner containing the above-mentioned resin. Transfer efficiency can be greatly improved by improving the chargeability of the resin.

In addition, the magnetic toner generally used in the PPC method is
Because it has high resistance and tends to have a small particle size, it has poor fluidity and tends to cause blocking. However, the magnetic toner of the present invention has excellent fluidity and does not block even at high temperatures because it contains a specified amount of silicone oil. less likely to occur.

Furthermore, in the PPC method that uses a photoreceptor with a smooth surface such as a Se photoreceptor, conventional magnetic toner that does not contain silicone oil has a strong adhesion force to the photoreceptor surface after transfer. Even if cleaning is performed, the toner is not removed, and as the number of copies increases, the amount of toner remaining on the photoreceptor surface also increases, and when several dozen copies are made, the toner adheres to the entire surface of the photoreceptor. It was no longer possible to obtain clear copies.

On the other hand, since the magnetic toner of the present invention contains silicone oil, its releasing effect is effective in preventing such toner from adhering to the surface of the photoreceptor, and even after tens of thousands of copies have been made, the surface of the photoreceptor remains intact. The surface remains clean and clear copies are obtained.

The effects of the present invention will be specifically illustrated by Examples below.

Example 1 Impregnated with 30 parts by weight of Microwax 220 (manufactured by Mrbil), Evaflex 410 (20 parts by weight, manufactured by Mitsui Polyga), 50 parts by weight of Fe304 (manufactured by Toda Kogyo), and 0.5 parts by weight of Si oil (SH200). 0.5 parts by weight of Aerosil 130 (Nippon Aerosil) was mixed for 10 minutes in a Hensel mixer, and kneaded for 20 minutes at 150° C. with two rolls.

This is processed using a show crusher and a jet mill for an average of 15
A fine powder of μ was obtained.

This was spheroidized in an air stream at 150°C and then classified to 10
A toner of ~44μ was obtained.

Using this toner, an image is formed on a zinc oxide photosensitive plate, a transfer sheet is placed on top of the toner, and a corona DC voltage is applied to transfer the image to the transfer sheet.

The obtained image is fixed by passing it through two pressure rolls with a linear pressure of 30 mm.

The images were clear and had high density and resolution.

The transfer efficiency was determined to be 92% by measuring the weight of the toner on the photosensitive plate before and after the transfer.

Further, the toner had an angle of repose of 35° and had very good fluidity.

Example 2: Iwatux 400 (20 parts by weight, manufactured by Mitsui Petrochemical) Evaflex 410 (10 parts by weight, manufactured by Mitsui Polyka) pe3o4 (manufactured by Toda Kogyo) 65 parts by weight Carbon black (Mitsubishi Kasei) 5 parts by weight and silicone oil KF96 (manufactured by Shin-Etsu Chemical) Silicon dioxide (Carplex #so) impregnated with 0.1 part by weight
, 2 parts by weight were mixed and kneaded in a Hensel mixer, pulverized, heat treated, and classified into 10 to 30 microns to obtain a toner.

The obtained toner exhibited good fluidity with an angle of repose of 32°,
The image is sharp and has high density, and the transfer efficiency is 95%.
It was excellent.

It has also been confirmed that when the magnetic toner of the present invention is applied to a PPC system using a Se photoreceptor, it is effective in preventing the phenomenon of toner undesirably adhering to the photoreceptor.

For example, in Examples 1 and 2, the toners that did not contain silicone oil and silicon dioxide adhered to the surface of the photoconductor after about 5,000 copies, whereas the toners of Examples 1 and 2 adhered to the surface of the photoconductor after about 20,000 copies. No adhesion to the surface was observed.

Claims (1)

[Claims] 1. In a pressure-fixable magnetic toner for developing an electrostatic latent image, the main components of which are a thermoplastic resin made of polyethylene wax and a co-electric material of polyethylene, and magnetic powder, 0.01 to 5.0 per 100 parts by weight of toner. Toner 10 contains silicone oil made by adsorbing silicon dioxide in the weight part of silicon dioxide.
A magnetic toner for developing electrostatic latent images, characterized in that 0.05 to 2.0 parts by weight relative to 0 parts by weight are uniformly dispersed in the toner.