JPH0430600Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an image forming apparatus that reversely develops an electrostatic latent image.

[Prior art and its problems]

2. Description of the Related Art Image forming apparatuses are known that use an electrophotographic process in which an image is formed by charging, exposing, developing, and transferring a photoreceptor. In the above-described image forming apparatus, a reversal development process is widely used in which development is performed using a developer (magnetic toner) having the same polarity as the charged polarity of the photoreceptor. For example, using a photoconductor with negative (hereinafter referred to as -) polarity, a charger applies negative corona ions to uniformly charge the circumferential surface of the photoconductor, and imagewise exposure is applied to this, and the circumferential surface is After forming an electrostatic latent image, this electrostatic latent image is developed with negative toner, and a positive (hereinafter referred to as +) is created using a transfer device.
A toner image is formed on the paper by applying corona ions from the back side of the transfer paper to perform the transfer.

In the case of the reversal development shown in the above example, the potential distribution on the circumferential surface of the photoreceptor after the electrostatic latent image is formed is in the state shown in FIG. However, in the same figure, the vertical axis indicated by -V is
- Since a polar photoreceptor is used, the potential on the circumferential surface of the photoreceptor is lower as it goes higher; however, in this specification, as commonly used by those skilled in the art, it means that the higher the charging potential, the higher the charging potential. The potential is called high. In the figure, areas A and C where the surface potential of the photoreceptor is −V _L (e.g., approximately −50 V) indicate that the potential has decreased due to exposure, and the surface potential of the photoreceptor is −V _B (e.g., approximately −50 V). −300V) several tens of volts higher−
Regions B and D of V' (for example, about -350 V) are not exposed to light and have a high potential. Here, the potential -V _S indicates the uniform charging voltage level (for example, about -400V) on the photoreceptor by the above-mentioned charger, but regions B and D actually have a slight potential even if they are not exposed to light. It decays, and the voltage drops to the potential -V' as described above.

Then, by a developing device (developing roll) to which a potential of _-VB is applied, the - polarity toner adheres to areas A and C as shown in the figure. The retention force of the toner on the photoreceptor after the above-mentioned development and up to the transfer is caused by forces such as the mirror image force and van der Waals force of the toner. Further, since the Coulomb force between the toner and the photoconductor has negative polarity, they act as repulsive forces.

The mirror image force of the toner is a force due to the electric charge of the toner, and is only 1/10 ³ to 1/10 ⁴ of the Coulomb force or van der Waals force in normal development. Further, the van der Waals force is largely influenced by the particle size of the toner and the state of contact with the photoreceptor, so it cannot be expected to have much holding power.

Therefore, in the case of reversal development, the toner holding power of the photoreceptor decreases, causing development called toner scattering before transfer, causing problems such as toner scattering into the machine and deterioration of print quality due to toner scattering.

[Purpose of invention]

In view of the above-mentioned conventional drawbacks, the present invention has been developed in an image forming apparatus that reversely develops an electrostatic latent image.The present invention uses magnetic force to maintain the toner retention force on the photoreceptor from development to transfer during the image forming process, and prevents the toner from entering the machine. It is an object of the present invention to provide a toner scattering prevention device that can prevent toner scattering.

[Key points of the idea]

In order to achieve the above object, the present invention provides at least an image forming means for charging, exposing, and transferring on the circumferential surface of a photoreceptor, and magnetic toner is applied to an electrostatic latent image formed by exposure in the image forming means. In an image forming apparatus including a developing means for adhesion and reversal development, a magnet that attracts and holds magnetic toner on the photoreceptor at least in an area from a development position to a transfer position on a side opposite to the development means with respect to the photoreceptor. It is characterized by being provided with.

[Example of idea]

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of an image forming apparatus including a toner scattering prevention device according to the present invention.

In the figure, the interior of an image forming apparatus 1 includes an image forming section 2, a paper conveying section 3, and a toner scattering prevention section 4. The image forming section 2 includes a belt-shaped photoreceptor 5, a print head 6 for optically writing on the photoreceptor 5, a charger 7, a developer 8 containing magnetic toner, a transfer device 9, and a cleaner 10. It is made up of. The paper transport section 3 also includes a paper feed roller 1 for transporting the paper T from the paper cassette 11.
2, standby roll 13, fixing device 14, paper output tray 1
It consists of 5.

On the other hand, the toner scattering prevention section 4 is composed of a rubber magnet 16. Rubber magnet 16
is located between the developing device 8 and the transfer device 9, and is disposed at a position where it rubs against the inner circumferential surface of the photoreceptor 5. and,
The rubber magnet 16 is made of synthetic rubber or natural rubber impregnated with ferromagnetic material powder. Further, since the rubber magnet 16 contains rubber, it has elasticity and is configured so that even if it rubs against the inner peripheral surface of the photoreceptor 5, it will not damage the photoreceptor surface.

Further, the developing device 8 includes a developing container 8a and a developing roll 8.
b, a toner hopper 8c, and a toner supply roll 8d, and a developer container 8a stores magnetic toner 8e. The developing roll 8b is disposed at a position where it rubs against the photoconductor 5, and transfers the electrostatic latent image formed on the circumferential surface of the photoconductor 5 to the magnetic toner 8e, as will be described later.
Develop. Further, the magnetic toner stored in the toner hopper 8c is replenished by the toner supply roll 8d, and the magnetic toner 8e in the developer container 8a is replenished.
The amount of is controlled to be constant.

In the image forming apparatus including the toner scattering prevention device of this embodiment configured as described above, the image forming operation including the toner scattering prevention operation will be described below.

First, by the charge wire 7a in the charger 7,
- Polar corona discharge is performed to impart a - uniform charge to the photosensitive layer 5a. Next, arrow E on the photoreceptor 5
As the photoreceptor 5 is moved in the direction, the uniformly charged photoreceptor 5 is exposed to light by the print head 6. This exposure is performed, for example, using transmitted light from a liquid crystal light shutter that is driven to open and close in accordance with recorded data in the print head 6. Therefore, by this exposure, negative charges are discharged from the portions of the photoreceptor 5 that are irradiated with light in accordance with the recorded data, and an electrostatic latent image that is a distribution of residual charges is formed.

Next, the electrostatic latent image formed on the photoreceptor 5 rubs against the developing roll 8b, and the electrostatic latent image is developed with the magnetic toner 8e in the developing container 8a, thereby becoming a toner image.

At this time, the above-mentioned developing roll 8a is powered by a power source (not shown), and the potential is lower than the -potential of the above-mentioned residual charge.
A voltage higher than the potential of the portion that has lost its charge due to exposure is applied, and the above-mentioned electrostatic latent image is developed by the negative polarity magnetic toner 8e attached to the developing roll 8a.

The photoreceptor 5 that has been developed as described above (on which a toner image has been formed) further moves toward the transfer device 9 as the photoreceptor 5 moves in the direction of arrow E.

A rubber magnet 16 is disposed between the developing device 8 and the transfer device 9 at a position where it rubs against the photoreceptor 5 as described above, and a predetermined magnetic field is applied to the rubber magnet 16.
It is being created nearby.

Therefore, the photoreceptor 5 is transferred from the developing device 8 to the transfer device 9.
The magnetic toner 8 attached to the photoconductor 5 while moving to
A predetermined magnetic force acts on e. That is, the magnetic toner 8e attached to the outer peripheral surface of the photoreceptor 5 is affected by the magnetic force of the rubber magnet 16 that rubs against the inner peripheral surface of the photoreceptor 5, and the magnetic toner 8e is attracted to the rubber magnet 1.
Receives the force on the 6th side. For this reason, the magnetic toner 8e attached to the photoconductor 5 is held by magnetic force, and the scattering of the toner from the photoconductor 5, which is likely to occur due to the repulsive force due to the Coulomb force between the toner and the photoconductor, as described in the conventional example, is prevented. This can be prevented by the magnetic force mentioned above.

The above-mentioned Coulomb force F between toners is F = qe (q: electric charge per toner,
E: electric field), approximately 10 ^-4
It becomes dyn. Since this Coulomb force F acts as a repulsive force as described above, the magnetic toner 8e is transferred from the photoconductor 5.
In order to prevent (retain) the magnetic toner from scattering, a higher holding force is required, but it is weak to generate a magnetic force of about 10 ^-4 to 10 ^-3 dyn between the rubber magnet 16 and the magnetic toner 8e. It is also easily possible to use a magnetic rubber magnet 16.

Therefore, due to the magnetic force of the rubber magnet 16, the toner image on the photoreceptor 5 reaches the transfer device 9 without causing toner scattering. The toner image on the photoreceptor 5 is transferred from the transfer device 9 to the paper T fed from the paper feed cassette 11 via the paper feed roller 12 and the standby roll 13 in synchronization with the toner image. Transferred by corona discharge.
The paper T on which the toner has been transferred is discharged to a paper discharge tray 15 via a fixing device 14. On the other hand, residual toner on the photoreceptor 5 that has not been completely transferred by the transfer device 9 is removed by a cleaner 10, and a uniform charge is applied to the photoreceptor 5 by a charger 7 in preparation for re-exposure.

As described above, in the toner scattering prevention device of this embodiment, the photoconductor 5 is placed between the developing device 8 and the transfer device 9, where toner scattering is likely to occur, on the opposite side of the developing device 8.
A rubber magnet 16 that rubs against the photoreceptor 5 is provided, and the electrostatic latent image on the photoreceptor 5 is developed with magnetic toner to form a toner image made of the magnetic toner. After development, the magnetic force of the rubber magnet 16 This holds the magnetic toner on the photoreceptor 5 and prevents the toner from scattering.

In this embodiment, the negative polarity photoreceptor 5 is used to perform reversal development, but the same method can be used when reversal development is performed using a + polarity photoreceptor with + polarity toner. I can do it.

Furthermore, although the rubber magnet 16 is used in this embodiment, it is not limited to the rubber magnet 16, and any member that provides magnetic force to the magnetic toner can be used as long as it does not damage the inner circumferential surface of the photoreceptor 5.

Furthermore, the toner scattering prevention device of this embodiment can also be used in image forming apparatuses such as microfilm printers.

[Effect of idea]

As explained in detail above, according to the present invention, it is possible to prevent toner from scattering within the image forming apparatus, so that other members within the apparatus, such as the light exit port of the print head, the charger, and the charge line of the transfer device, can be prevented. It doesn't get dirty.

Furthermore, since the toner forming the image on the photoreceptor after development can be prevented from scattering, the quality of the printed image on the paper after transfer can be improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an image forming apparatus including the toner scattering prevention device of this embodiment, and FIG. 2 is a configuration diagram illustrating the potential distribution and toner adhesion state on the photoreceptor after development. DESCRIPTION OF SYMBOLS 1... Image forming device, 4... Toner scattering prevention part, 5... Photoreceptor, 8... Developing device, 8b... Developing roll, 8e... Magnetic toner, 16... Rubber magnet.

Claims (1)

[Scope of utility model registration request] An image comprising at least an image forming means for charging, exposing, and transferring arranged on the circumferential surface of a photoreceptor, and a developing means for adhering magnetic toner to an electrostatic latent image formed by exposure in the image forming means and performing reversal development. In the toner forming apparatus, a magnet for attracting and holding the magnetic toner on the photoreceptor is provided at least in an area from a development position to a transfer position on a side opposite to the developing means with respect to the photoreceptor. Shatterproof device.