JPS60140277A - Developing method by electrophotographic method - Google Patents

Abstract

PURPOSE:To evade the rubbing of a brush of carriers against an image by mixing and charging electrostatically chargeble toner and magnetic carriers and movingd only the toner in the mixer on the surface of a developer supply roll to a toner developing roll. CONSTITUTION:The chargeble toner and magnetic carriers 5 are mixed and charged electrostatically by friction by a stirrer 7 and biased by a power source 15 between a developer supply roll 8 and the toner developing roll 9, and only the charged toner 4 is moved to the conductive surface 14 to form a toner layer 4a. The mixing of the toner 4 and carriers 5 charges the toner intensely and uniformly and the scooping to the roll 8 is facilitated by the magnetic attractive force of the carriers to form the magnetic brush excellently on the roll 8. Therefore, the toner layer 4a sticking uniformly on the surface of the roll 9 contacts a photosensitive layer 1 to form a sharp image without any brush mark while evading the rubbing of the magnetic carriers 5 against the image.

Description

[Detailed Description of the Invention] The present invention relates to a developing method in electrophotography,
More specifically, the present invention relates to a new developing method for forming images of good quality using non-magnetic electrostatic toner.

Magnetic brush development is widely used to develop electrostatic images in commercial electrophotography. A developing machine (a) consisting of a circumferential sleeve made of a magnetic material and a magnet inside the sleeve is used, a magnetic developer is supplied onto the sleeve to form a magnetic brush, and the thickness of the magnetic brush is adjusted by a cutting mechanism. The electrostatic image is developed by controlling the magnetic brush to a predetermined value by, for example, moving the magnetic brush to the position of the photosensitive layer, and rubbing the photosensitive layer containing the electrostatic image with the magnetic brush.

The magnetic developer is a two-component developer consisting of a mixture of a magnetic carrier and a fixing electrostatic powder (toner), and a magnetic material fine powder is dispersed in a fixing medium and formed into particles. 2 with a one-component (or carrierless) developer
Although there are several known types of developers, each of these developers is known to have its own advantages and disadvantages.

First, in a two-component developer, the toner is charged by friction between the magnetic carrier and the toner, and the toner is electrostatically held on the surface of the carrier to form a magnetic brush. Thus, 2
The component-based developer has good magnetic brush formation and good fluidity, and the darkness value of development is determined by the magnitude of the Coulomb force between the toner and the carrier and the Coulomb force between the toner and the electrostatic image. The image formed has the advantage of having less capri.

However, in the known developing method using a two-component developer, so-called brush marks in the form of fine white streaks are likely to appear in the formed image due to the rubbing between the brush of the magnetic carrier and the image, resulting in poor image quality. However, it is still not completely satisfactory.

On the other hand, with a one-component magnetic developer, since no magnetic carrier is used, there is no problem of Pushimer 2 generation, but in this case, it is the developer itself that forms the ears of the magnetic brush, and the dark value of the development is determined by the magnetic attraction force of the developer to the sleeve and the Coulomb force to the electrostatic image, and since the magnetic material is dispersed in the fixing resin in this developer, the magnetic attraction to the sleeve is determined by the Coulomb force of the developer to the sleeve. Related to the fact that the force is weaker than that of magnetic carriers, there is a problem that capri is more likely to occur during development. In order to solve this problem, in the usual development method, the length of the spike is shortened to prevent capri from occurring, but this tends to cause troubles such as poor spike formation and decreased fluidity of the developer.

Furthermore, since it contains a magnetic material, it is unsuitable due to limitations in coloring.

The present invention uses a combination of a non-magnetic visible toner and a magnetic carrier as a developer component, and when developing an electrostatic image, it is a developing method that can avoid rubbing between the brush of the magnetic carrier and the image. The purpose is to provide

Another object of the present invention is to effectively charge a non-magnetic electrostatic toner, and to faithfully adhere the toner to an electrostatic image without generating brush marks. To provide a developing method.

According to the present invention, there is provided a method for developing an electrostatic image on an electrophotographic photoreceptor with a charged non-magnetic electrostatic toner, the method comprising: developing an electrostatic image by mixing a non-magnetic electrostatic toner and a magnetic carrier; Charging the toner and forming a magnetic brush of the mixture on a first carrier surface, selectively transferring only the visible toner in the magnetic brush to a second carrier surface adjacent to the first carrier surface. transfer to form a layer of toner on a second carrier surface, and transfer the one layer of toner on the second carrier surface to the electrophotographic photoreceptor surface adjacent to the second carrier surface in accordance with the electrostatic image. Provided is a developing method characterized by:

According to the present invention, there is further provided a method for developing an electrostatic image on an electrophotographic photoreceptor with a charged non-magnetic electrostatic toner, the method comprising: mixing a non-magnetic electrostatic toner and a magnetic carrier; charging the electrostatic toner and forming a magnetic brush of the mixture on a first carrier surface, and selectively charging only the electrostatic toner in the magnetic brush onto this carrier surface adjacent to the first carrier surface. transfer to form a layer of toner on the second carrier surface, and transfer the second carrier surface and the electrophotographic photoreceptor to the surface of the electrophotographic photoreceptor that is close to the second carrier surface at a distance greater than the thickness of the one layer of toner. Under conditions where the toner vibrates or flies between the toner and the photoreceptor surface,
A developing method is provided, characterized in that a layer of toner on the second carrier surface is transferred in correspondence with the electrostatic image.

The present invention will be described in detail below based on specific examples shown in the accompanying drawings.

In FIG. 1 showing an example of a developing device used in the present invention,
A drum-shaped support 2 having an electrophotographic photosensitive layer 1 on its surface is rotatably mounted, and along the moving surface of the photosensitive layer 1, a developing device is provided as a whole. This developing device 6 includes a tank 6 containing a two-component developer consisting of a mixture of a non-magnetic electrostatic toner 4 and a magnetic carrier 5, and a developer stirring mechanism 7 provided within the tank.
α, 7h, consists of a developer supply roll 8 serving as a first carrier surface and a toner developing roll 9 serving as a second carrier surface.

The developer supply roll 8 consists of a circumferential sleeve 10 made of a non-magnetic material and a magnet 11 having multiple poles housed within the sleeve, at least one of which is rotatable about an axis. It is provided. The lower part of the developer supply roll 8 is immersed in the developer, and the upper part is provided in close proximity to the toner developing roll 9.Upstream of the toner developing roll 9, there are
Ear cutting board 12 for cutting the magnetic brush described below
However, a scraping plate 16 for scraping off the magnetic brush is also provided on the downstream side.

The toner developing roll 9 has a circumferential conductive surface 14 and is provided in a positional relationship close to both the developer supply roll 8 and the electrophotographic photosensitive layer 10 described above.

A bias voltage is applied between the sleeve 10 of the developer supply roll and the conductive surface 14 of the toner developer roll by a power source 15 to allow the toner 4 to move to the conductive surface 14 of the sleeve 10. ing.

The electrostatic toner 4 and the magnetic carrier 5 are stirred by a stirring mechanism 7α,
7h, the electrostatic toner 4 is triboelectrically charged, and the toner 4 is electrostatically held on the surface of the carrier 50. The carrier 5 on which the toner 4 is held is
A magnetic brush 16 is formed on the surface of the sleeve 100 by being attracted by the magnet 11, and rotates in a fixed direction, clockwise in the figure, by rotation of the sleeve or the magnet. After the magnetic brush 16 is cut into a predetermined length by the cutting plate 12, the magnetic brush 16 comes into contact with the surface of the toner developing row (v9). On this occasion,
Charged toner 4 is located between the sleeve 10 and the conductive surface 14.
A bias voltage is applied so that the charged toner 4 is attracted to the conductive surface 14 and held on the surface, whereby the charged toner 4 is separated from the magnetic carrier surface and transferred to the conductive surface 14.
Then, a toner layer 4α is formed.

The toner developing roll 9 also rotates in a fixed direction, counterclockwise in the figure, and the toner layer 4α on the conductive surface 14 comes into contact with the photosensitive layer 1, so that the charged toner particles are statically applied to the electrostatic image on the photosensitive layer 1. The toner image 4h is formed by electrical attraction.

On the other hand, the magnetic brush 16 remaining on the developer supply roll 8
The toner is scraped off into the tank 6 by the scraping plate 16, and the toner 4 and carrier 5 are mixed and a magnetic brush is formed on the roll 8. Also.

The toner image 4h is formed by the friction between the magnetic brush 16 on the developer supply roll 8 and the conductive surface 14 of the toner development roll 9.
An amount of toner is supplied to the conductive surface commensurate with the toner consumed in the formation of the conductive surface.

According to the present invention, similarly to a normal development method using a two-component developer, by mixing a different type of non-magnetic electrostatic toner and a magnetic carrier, toner charging can be achieved by mixing different types of non-magnetic electrostatic toner and a magnetic carrier. By using the magnetic attraction force of the magnetic carrier, the developer can be easily pumped up to the developer supply roll 8, and moreover, the formation of a magnetic brush on the roll 8 can be easily carried out. Very well done.

By rubbing this magnetic brush 16 on the surface of the toner developing roll, the strongly charged toner particles adhere to the surface of the developing roll to a uniform thickness, and one layer of toner 4α on the developing roll surface comes into contact with the photosensitive layer 1. By doing so, it is possible to form a clear toner image without generating brush marks while avoiding rubbing between the magnetic carrier and the image.

In the present invention, the non-magnetic electrostatic toner is a toner known per se, for example, a coloring agent and, if necessary, a charge control agent are blended into a high electrical resistance fixing resin, and mixed materials are pulverized. Toners adjusted to a range of 60 to 60 microns are used. As the magnetic carrier, iron powder carriers, ferrite carriers, etc., which are known per se, are used, and those having a particle size of 20 to 150 microns are particularly advantageously used.

The mixing ratio of toner and magnetic carrier is generally preferably in a weight ratio of 2=98 to 15:85.

The bias voltage applied between the surface of the toner development roll 9 and the surface of the developer replenishment roll 8 varies depending on the characteristics of the photosensitive layer and the characteristics of the toner, but it is preferable that the potential difference between the two is about 50 to 600 volts. . Further, it is desirable that the potential of the toner developing roll 9 has the same polarity as the charge of the electrostatic image on the photosensitive layer 1 and is in the range of blue to 3 of the potential of the electrostatic image from the viewpoint of preventing capri.

Generally speaking, it is desirable that the thickness of the toner layer 4α formed on the surface of the toner developing roll 9 be in the range of 50 to 600 microns. In order to control the thickness of this toner layer 4α to a constant value, a doctor blade for controlling the thickness of the toner layer can be provided upstream of the contact position with the photosensitive layer 1.

In a preferred embodiment of the invention, instead of bringing the toner layer 4α on the second carrier surface, i.e. the surface of the toner developer roll 9, into direct contact with the photosensitive layer 1, the surface 14 of the toner developer roll /l/9 and the photosensitive layer The thickness of each toner layer is set to be thicker than 4α between the two surfaces, and development is performed under conditions where the charged toner vibrates or flies between the two surfaces.

In FIG. 2 showing this embodiment, parts common to those in FIG. 1 are designated by common reference numerals.

The distance d between the surface of the toner developing roll 9 and the surface of the photosensitive layer 1 is set larger than the thickness do of one layer of toner 4α on the surface of the roll 9. Further, in order to cause the charged toner to be photographed or flown between these two surfaces, an AC power source 18 is connected in series with the DC power source 17 to the conductive surface 14 of the toner developing roll 9.
is connected.

By applying a bias voltage consisting of a direct current and an alternating current between the surface of the toner developing roll 9 and the photosensitive layer 1,
Charged toner particles in the toner layer 4α due to the alternating potential are
Vibration or flying occurs between the photosensitive layer 1 and low) L/9,
The electrostatic image on the surface of the photosensitive layer 1 is developed. AC power supply 18
The amplitude (V, 2) is preferably 1.5 to 6 times the voltage of the DC power supply 17.

In addition, as a method for developing the charged toner by causing it to vibrate or fly, in addition to applying an AC potential to the developing roll 9, for example, a screen electrode to which an AC voltage is applied is placed between the developing roll 9 and the photosensitive layer 1, It is also possible to image the charged toner particles on the surface of the developing roll 9 and make them into a so-called atomized state in the developing area for development.

[Brief explanation of drawings]

FIG. 1 shows an example of a visualization device used in the developing method of the present invention, and FIG. 2 is a diagram for explaining one embodiment of the developing method of the present invention. Reference number 1 is an electrophotographic photoreceptor, 6 is a developing device, 4 is electrostatic toner, 5 is a magnetic carrier, 8 is a developer supply roll,
9 indicates a toner developing roll. Figure 1 Figure 2

Claims (2)

[Claims] (1) A method of developing an electrostatic image on an electrophotographic photoreceptor with a charged non-magnetic electrostatic toner, the electrostatic toner being charged by mixing the non-magnetic electrostatic toner and a magnetic carrier. and,
forming a magnetic brush of the mixture on a first carrier surface, selectively transferring only the electrostatic toner in the magnetic brush to a second carrier surface close to the first carrier surface; A single layer of toner is formed on a second carrier surface, and the one layer of toner on the second carrier surface is transferred to the surface of the electrophotographic photoreceptor adjacent to the second carrier surface in accordance with an electrostatic image. development method. (2) A method of developing an electrostatic image on an electrophotographic photoreceptor with a charged non-magnetic electrostatic toner, the electrostatic toner being charged by mixing the non-magnetic electrostatic toner and a magnetic carrier. and,
forming a magnetic brush of the mixture on the first carrier surface (
- Selectively transfer only the electrostatic toner in the magnetic brush to a second carrier surface close to the first carrier surface to form a single layer of toner on the second carrier surface; on the surface of the electrophotographic photoreceptor that is close to the surface at a distance greater than the thickness of one layer of toner, under conditions where the toner vibrates or flies between the second carrier surface and the surface of the electrophotographic photoreceptor; A developing method characterized in that a layer of toner on a second carrier surface is transferred in correspondence with an electrostatic image.