JPS5932790B2 - Electrostatic latent image development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing an electrostatic latent image formed on a latent image carrier in an electrophotographic apparatus or the like.

Magnetic, uncharged toner is held magnetically and conveyed to a developing section to form a magnetic brush in the developing section, and the tip of the toner is brought into contact with the surface of a moving latent image carrier to form a magnetic brush on the surface. A developing method for developing an electrostatic latent image is known.

FIG. 1 shows a typical example of a developing device that implements such a developing method.

That is, in FIG. 1, reference numeral 1 indicates a photoreceptor as a latent image carrier, reference numeral 2 a developing device, reference numeral 3 a toner hopper, and reference numeral 4 a toner.

The photoreceptor 1 is formed into a drum shape and can be rotated in the direction of the arrow.The copying process from forming an electrostatic latent image to transferring a visible image and cleaning the photoreceptor is performed by rotating the photoreceptor 1 in the direction of the arrow. This is done by sequentially operating mechanisms placed around the rotation while rotating it.

The developing device 2 includes a sleeve 20 and a magnet (not shown). That is, the sleeve 20 is formed of a non-magnetic material into a hollow cylindrical shape, and is provided so as to be rotatable in the direction of the arrow, that is, counterclockwise, around a shaft 21 parallel to the rotation axis of the photoreceptor 1. A part of the photoreceptor 1 is close to the circumferential surface of the photoreceptor 1. This region where the sleeve 20 and the photoreceptor 1 are close to each other is called a developing section. The internal space of the sleeve 20 is designed to generate a magnetic field near the circumferential surface of the sleeve 20 sufficient to hold the toner on the circumferential surface, and to form a magnetic brush of the held toner in the developing section. A magnet (not shown) is fixedly magnetized and oriented to generate a magnetic field.

The toner 4 is stored in the hopper 3 and the sleeve 2
It is designed to be appropriately supplied to the circumferential surface of 0.

The toner 4 itself has magnetic properties and is not electrically charged.
It is a so-called one-component type. If the sleeve 20 is rotated in the direction of the arrow while supplying the toner 4, the supplied toner 4 is held on the circumferential surface of the sleeve 20, as shown in FIG. The magnetic brush is conveyed to the developing section by rotation, and forms a magnetic brush in the developing section, the tip of which comes into contact with the circumferential surface of the photoreceptor 1 .

Now, with such a developing device, good development can be achieved. When doing so, the following points must be kept in mind.

That is, firstly, a sufficient amount of toner must be conveyed by the sleeve 20 to the developing section in order to obtain sufficient image density in the visible image, and secondly, more toner must be conveyed to the developing section. The magnetic brush must rub the surface of the photoreceptor 1 so as to come into contact with the surface, thereby stirring the toner in the developing section. These points are
Both conditions are satisfied by increasing the rotational speed of the sleeve 20.

Development is based on electrical interaction between the electrostatic latent image and charges of opposite polarity to the charges that are generated in the toner by electrostatic induction or dielectric polarization caused by the action of an electric field formed by the charges that constitute the electrostatic latent image. It is done by twisting. During development, which of the electrostatic induction and dielectric polarization is dominant depends on the magnitude of the electrical resistance of the toner. That is, the electrical resistance of the toner is 1
011Ω? If it is below, electrostatic induction is dominant and the electrical resistance is 1012Ω? In the above toners, dielectric polarization is dominant.

By the way, the electrical resistance of toner is 1012Ω? When the above-mentioned method is used, the following problems occur in the above-mentioned development method. This point will be explained with reference to FIG. FIG. 2 shows the dependence of electrostatic induction and dielectric polarization on time when a constant electric field is applied to the toner used in the above development method.

That is, in FIG. 2, t on the horizontal axis represents the time during which the electric field acts, and Q on the vertical axis represents the induced charge for electrostatic induction.
For dielectric polarization, it represents the polarization charge.

In order to match both saturation values, the scale of the vertical axis is appropriately changed for the induced charge and the polarized charge. In Figure 2, curve 2-1 is for electrostatic induction, and curve 2-2 is for dielectric polarization.As is clear from this, the response to the electric field in dielectric polarization is compared to that in electrostatic induction. It's extremely slow.

Therefore, the electrical resistance is 1012Ω, which mainly uses dielectric polarization. When implementing the above-mentioned development method using the above toner, the amount of toner supplied to the developing section, the agitation of the toner in the developing section, and the contact time between a specific portion of the electrostatic latent image and the toner at the developing section. is an important factor for obtaining good visible images.

That is, if the above-mentioned contact time is not sufficient, sufficient polarization charge will not be generated in the toner, and the toner will not adhere to the photoreceptor. Based on this point, looking at the developing device shown in Figure 1, this developing device has an electrical resistance of 1012 Ω as toner? It turns out that it is not suitable when using the above. That is, in this device, since the moving directions of the photoreceptor 1 and the sleeve 20 in the developing section are opposite to each other, the moving speed of the toner 4 to a specific portion of the photoreceptor 1 is increased, and the above-mentioned contact time is shortened. This tendency becomes even more pronounced when the rotation speed of the sleeve 20 is increased to ensure a sufficient amount of toner supply.

The purpose of the present invention is to have an electrical resistance of 1012Ω? The purpose of the present invention is to solve such problems when performing development using the above toner.

The present invention will be explained below.

In order to make the explanation concrete, the explanation will be based on the apparatus shown in FIG. In the developing method according to the present invention, the above-mentioned problem is solved as follows. That is, the first step is to change the direction of rotation of the sleeve 20 from the counterclockwise direction shown in FIG. 1 to the clockwise direction.

That is, the direction of rotation of the sleeve 20 is determined so that the direction of movement of the surface of the sleeve 20 and the direction of movement of the circumferential surface of the photoreceptor 1 in the developing section are the same. In this way, the peripheral surface of the photoreceptor 1 in the developing section and the toner 4
The relative speed between the two is the difference in the moving speed of the two, so the contact time between the surface of the photoreceptor and the toner passing through the developing section is
This makes it possible to increase the size compared to conventional methods.
The above contact time can be maximized by making the moving speed of the toner 4 in the developing section equal to the moving speed of the surface of the photoreceptor 1. In this case, the toner 4 in the developing section Stirring is not performed. So the second
Second, the rotation speed of the sleeve 20 is determined so that the speed of movement of the surface of the sleeve 20 is greater than the speed of movement of the circumferential surface of the photoreceptor 1.

This also serves the purpose of ensuring a sufficient amount of toner 4 to be transported. However, if the rotation speed of the sleeve 20 becomes too high, not only will the contact time between the toner 4 and the photoreceptor 1 be shortened, but also the visible image formed on the circumferential surface of the photoreceptor 1 will be A problem arises in that it is disturbed by the rubbing of the brush. Therefore, thirdly, the ratio of the moving speed of the surface of the sleeve 20 and the moving speed of the circumferential surface of the photoreceptor 1 is determined as follows in the visible image:
The value is determined to be within an appropriate range so that neither insufficient image density nor image disturbance occurs.

This appropriate value range is determined depending on the type of latent image carrier, the potential of the electrostatic latent image, the moving speed of the surface of the latent image carrier, the magnitude of the electrical resistance of the toner, etc. It cannot be determined exactly.

Therefore, in reality, it is determined by experiment depending on each individual case. FIG. 3 shows an example of the results obtained from such an experiment.

That is, the vertical axis in FIG. 3 shows the image density of the visible image, and the horizontal axis shows the ratio of the moving speed Vs of the surface of the sleeper 20 to the moving speed Vp of the surface of the photoreceptor. The experiment is
A zinc oxide photoreceptor is used as a latent image carrier, the potential of the electrostatic latent image on the surface of the latent image carrier is -400V, and a toner with an electrical resistance of 1012 to 1013 Ω is used,
The photoreceptor surface was moved at a speed of 80 mm/Sec. In this case, the optimum value range of Vs/Vp is from 3 to 8. As described above, according to the present invention, when magnetic brush development is performed using a single-component magnetic toner having high electrical resistance, a good visible image can be easily obtained, and it can be easily carried out by effectively using conventional equipment. A method for developing a transparent electrostatic latent image can be provided.

It goes without saying that the present invention can be applied to any generally known shape or type of latent image carrier; however, the shape of the sleeve may also be a hollow cylinder as shown in FIG. It is not necessary to have one, and it can also be formed into a belt shape.

When the sleeve is formed into a belt shape, the contact time between the toner and the surface of the latent image carrier at the developing section can be reduced by aligning the shape of the sleeve along the surface of the latent image carrier at the developing section. Can be made larger.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing only the essential parts of an example of a conventionally known developing device using one-component magnetic toner, and FIGS. 2 and 3 are for explaining the present invention. This is a diagram. 1...Photoreceptor, 20...Sleeve, 4
······toner.

Claims (1)

[Claims] 1. Electric resistance is 10^1^2Ωc on the circumference of a rotatable sleeve surrounding a magnet fixed in a fixed position.
m or more and uncharged one-component magnetic toner is held by the magnetic force of the magnet, the sleeve is rotated to convey the held toner to a developing section, and in the developing section, the magnetic force of the magnet is forming a magnetic brush of the toner,
In a method of developing an electrostatic latent image formed on the surface by bringing the tip into contact with the surface of a moving latent image carrier, the direction of movement of the sleeve and the direction of movement of the surface of the latent image carrier are In the developing section, the direction of rotation of the sleeve is determined so that they are in the same direction, and the speed of movement of the surface of the sleeve is greater than the speed of movement of the surface of the latent image carrier. An electrostatic latent image developing method characterized in that the ratio of both moving speeds is determined to be within an appropriate range.