JPS6342255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of developing an electrostatic latent image, and more particularly to a method of developing an electrostatic latent image using a developer substantially free of carrier particles.

Conventionally, when developing using a developer made of a mixture of carrier and toner, there has been a method using a developer made only of conductive toner to solve problems such as deterioration of the carrier and control of toner concentration in the carrier. Proposed. However, since the developed toner image is conductive, the charge is unstable and electrostatic transfer is difficult. It has only been put to practical use in devices that do this.

An object of the present invention is to solve the problems of the above-mentioned conventionally proposed methods, and to solve the problem of carrier deterioration by using a developer that does not substantially contain carrier particles.
The object of the present invention is to provide a developing method that eliminates the problem of toner density control and provides good transfer of a developed toner image.

The present invention achieves the above object by using insulating toner particles and conductive toner particles as toner particles for forming a developed image, and the mixing ratio of these particles can be automatically and stably controlled, so that the toner particles can be excellent in the long term. It is a developing method that can form an image with an insulating toner, and its characteristics are as follows. A mixed developer with a conductive toner containing a resin component and a conductive component is regulated to a developer layer of 1 mm or less, and this developer layer is supplied to the electrostatic latent image for development, and at this time, the above-mentioned insulating toner is The conductive toner is charged and attached to the electrostatic latent image with the charged charge, and the conductive toner is attached to the electrostatic latent image with the charge induced by the electrostatic latent image.As a result, the conductive toner and A developing method characterized by depositing a mixture of insulating toners.

In the present invention, a mixture of a conductive toner and an insulating toner that can be charged to a desired polarity is used as a developer. Here, the conductive toner refers to toner particles having a volume resistivity of 10 ¹⁰ Ω-cm or less, and the insulating toner refers to toner particles having a volume resistivity of 10 ¹² Ω-cm or more. Various known conductive toners can be used, but for example, when adding a conductive pigment to the toner material, the conductive pigment necessary to obtain the necessary conductivity cannot be mixed into the toner material. Since the addition amount of is very large, manufacturing is difficult, and the fixing properties are also deteriorated, it is better not to adopt this addition method but to coat the surface of the toner particles with a conductive substance. The conductive material used is preferably carbon black, iron black, etc. in order to be used as a black toner, and the coating method is to heat the thermoplastic resin toner particles to melt the surface, and then apply the method described above. A method of attaching a conductive substance can be used. There are various methods for supplying the above-mentioned mixture of conductive toner and insulating toner to the electrostatic latent image holding surface, but in order to convey these toners by a magnetic field, the toner must be a magnetic material. For this purpose, a toner using iron black as a conductive substance or a toner mixed with a magnetic substance is suitable. In a developer that is a mixture of insulating toner and conductive toner, the insulating toner is charged to a predetermined polarity by frictional charging with the conductive toner, the developer container, and the conveyance means, and the toner is statically charged. When brought close to an electrostatic latent image, it is attracted to the latent image by its electrical charge.
Conductive toner, on the other hand, adheres to the electrostatic latent image due to the charge induced therein. Ideally, both toners adhere to each other through triboelectric charging.
It is presumed that the same latent images receive the above-mentioned different forces and are simultaneously deposited on the latent image surface and transferred at the same time.

In this way, both the insulating toner and the conductive toner adhere to the latent image and are consumed, but if the consumption rate is different between the conductive toner and the insulating toner, only one toner is consumed while the other is accumulated. This is not preferable because the mixed components change. When a developer made of a mixture of conductive toner and insulating toner according to the present invention is applied to a developing device in a normal magnetic brush development method, the conductive toner hardly adheres to the latent image, and the insulating toner mainly consumed. In order to prevent this phenomenon and increase the consumption of conductive toner, it is effective to lower the resistance of the developer layer. Specifically, such measures as reducing the thickness of the developer layer or substantially lowering the resistance of the developer layer are taken.

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

First, as an insulating toner, 9 parts by weight of carbon black and 2 parts by weight of a metal-containing dye (Spirone) were added to 100 parts by weight of polystyrene (Picolastic D-125; manufactured by Etsuso Standard Co., Ltd.) at 110°C.
The mixture was thoroughly melted and kneaded using a three-roll mill controlled to the desired temperature, then cooled and solidified, and further ground using a hammer mill and a jet mill, and classified to obtain a fine powder with a particle size of 10 to 50 μm.

A conductive toner was obtained by adhering triiron tetroxide powder to the surface of the toner produced as described above. Although various methods can be considered for adhering the triiron tetroxide powder to the surface of the thermoplastic toner, the following manufacturing method was used here. Triiron tetroxide powder and toner are mixed well with the addition of an appropriate amount of methanol, the surface of the toner is sprinkled with triiron tetroxide powder, dried, and then dispersed in Isopar (trade name of Etsuo Co., Ltd.).
By heating to ℃ to soften the toner, triiron tetroxide powder was adhered to the surface of the toner. Isopar is filtered and evaporated to obtain a conductive toner. At this time, Isopar was replaced with isopropyl alcohol to speed up drying. The maximum amount of triiron tetroxide powder that could be attached to the toner without being liberated was 6:7 by weight to the toner. Therefore, a conductive toner having a ratio of triiron tetroxide to toner of 6:7 was used.
Then, the conductive toner and the insulating toner are mixed into 1:
The mixture was mixed in a ratio of 2 to 1 to prepare a developer. Carrier particles etc. are not used.

The developing device is a sleeve type magnetic brush developing device with a diameter of 45 mm, for example, Japanese Patent Application Laid-Open No. 51-43151,
What is described in Publication No. 51-84260 etc. is applied to this example. The rotation speed of the above sleeve is 100rpm
And so.

An electrostatic latent image is created using a known method, in which a photoreceptor consisting of a dispersion layer of CdS resin of about 40 microns and a polyethylene terephthalate film of 25 microns laminated on an aluminum substrate is moved at 10 cm/sec onto the photoreceptor. An electrostatic latent image was formed, and the potential was +300V in the dark areas of the image and 0V in the bright areas of the image.

When the thickness of the developer layer on the sleeve is regulated to 1 mm or less, the so-called edge effect is reduced, good images are obtained, and the conductive toner is less likely to adhere to the electrostatic latent image after such development. The ratio was also 27%, which was close to the component ratio of the original developer. When the thickness of the developer layer on the sleeve was set to 3 mm, the proportion of conductive toner in the toner adhering to the electrostatic latent image was as low as 18%, making it difficult to use conductive toner for development.

Furthermore, in order to keep the amount of developer on the sleeve constant, velvet was wound spirally around the sleeve surface without any gaps during development. The amount of developer is regulated by bringing a metal plate into contact with this velvet surface. Good images were obtained when the velvet was treated with conductive paint containing carbon.

The above was the result when the mixing ratio of conductive toner and insulating toner was 1:2, but when I tried changing this mixing ratio, the ratio was 1:1 to 1:2.
The range was good in terms of image quality and changes in the component ratio of the developing toner.

Furthermore, even in a state where the consumption rate of conductive toner is low, if a replenishing developer containing a large amount of insulating toner is used, it is possible to maintain a substantially constant mixed state of the developer.

The toner image thus obtained was electrostatically transferred to transfer paper using a transfer corona discharger. In this case, there is no blurring on the transfer material, which is the case when transferring images using only conventional conductive toner.
A transfer rate of 70% was obtained. Looking at the transfer rate of each component, the transfer rate of the insulating toner is 81%, while the transfer rate of the conductive toner is slightly worse at 46%. However, when compared with the transfer rate of 12% when an image made only of conductive toner was transferred under the same conditions, it can be seen that the transfer rate of conductive toner is significantly improved by the present invention. In an actual copying apparatus, untransferred toner is removed from the surface of the photoreceptor by a cleaning means, but the toner may be collected again into the developing device and reused.

In such usage, in order to prevent the proportion of conductive toner in the developer from increasing, the content rate of conductive toner in the replenishing developer must be reduced. In the above example, it is considered that the replenishing developer should be a mixture of conductive toner and insulating toner at a ratio of about 1:3.5.

Although the present invention has been described in detail above, the present invention is not limited to the above examples, and a toner coated with a non-magnetic material such as carbon can also be used as the conductive toner, or a toner coated with a non-magnetic material such as carbon may also be used. It is also possible to disperse them and use them in the form of magnetic toner, and various combinations of these can be considered.

In the present invention, when developing an electrostatic latent image with a developer, a developer consisting of a mixture of a conductive toner and an insulating toner is used to develop the electrostatic latent image. A developing method is provided in which a mixture of toners is deposited.

This eliminates the need to use a conventional carrier, and eliminates various problems that carrier/toner mixed developers had, such as uneven development due to carrier deterioration and changes in the carrier/toner mixture ratio over time. This not only solves problems such as insufficient toner concentration, but also eliminates the problems associated with using only conventional conductive toners, such as charge instability due to the conductivity of the toner image and the electrostatic transfer process. It solves the problem that it is unsuitable for use in direct copying electrophotography, and has the advantage of being able to form a developed image on a photosensitive plate that can be easily transferred to any transfer material. ing.

Claims (1)

[Claims] 1. A method of developing an electrostatic latent image with a developer to form a developed image electrostatically transferred to a transfer material, comprising: an insulating toner; a conductive toner containing a resin component and a conductive component; The developer layer is regulated to a thickness of 1 mm or less, and this developer layer is supplied to the electrostatic latent image to develop it. At this time, the above-mentioned insulating toner is charged and the electrostatic latent image is and causing the conductive toner to adhere to the electrostatic latent image with a charge induced by the electrostatic latent image, resulting in depositing a mixture of conductive toner and insulating toner on the electrostatic latent image. Characteristic development method. 2. The developing method according to claim 1, wherein the conductive toner has triiron tetroxide on its surface.