JPH04328780A - Developing device - Google Patents

Abstract

PURPOSE:To prevent toner with a reverse polarity from being carried to a developing area and to execute clear development by impressing voltage with the same polarity as initial potential on an image carrier on a regulating member. CONSTITUTION:An adjusting blade 28 is made of conductive material on which the voltage can be impressed, for example, stainless steel, and electrically connected to the grid part 34 of a scorotron charger 30 which is set to electrostatically charge a photosensitive body 14 so that it may have -700V initial potential. When developer 24 passes the blade part 28, the toner with the positive polarity is brought into contact with the blade 28 by electrostatic force, and the charge electrostatically charged by such contact is lost by the injection of the charge, then the toner is carried to the developing area A after the negative charge is given. Therefore, the toner with the reverse polarity is prevented from being carried to the developing area A, so that the toner adhering to non-image part on a latent image is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, and more particularly to a developing device used in electrophotographic devices and the like, for developing an electrostatic latent image on a photoreceptor into a visible image.

0002

2. Description of the Related Art Conventionally, a two-component magnetic brush development method has been put to practical use as a developing device for developing an electrostatic latent image on an image carrier (photoreceptor) into a visible image. In the two-component magnetic brush development method, large-sized magnetic particles (carrier) and toner are mixed and stirred and triboelectrically charged, and then the toner and carrier, which adhere to each other by electrostatic force, are non-magnetic and cylindrical. A magnetic brush is formed on the shaped developing sleeve by the magnetic force of the magnet provided inside the sleeve. This magnetic brush is transported to the development area by the rotation of the sleeve, where it rubs against the electrostatic latent image on the photoreceptor, causing toner to adhere to the electrostatic latent image and developing it into a visible image. . According to this method, the toner is charged uniformly and the carrier functions as a developing electrode, so it is possible to obtain beautiful images with excellent reproducibility of fine lines.

However, the above development method has the following drawbacks. That is, in order to triboelectrically charge the toner uniformly, a stirring means is required to mix and stir the toner with the carrier. Also,
Regarding the mixing ratio of toner and carrier, if there is too much toner, the toner will not be charged sufficiently, resulting in uncharged toner, which will tend to adhere to the non-image area of the photoreceptor, causing the image to deteriorate. It gets dirty. On the other hand, if the amount of toner is too small, the image density will decrease and the carrier will overcome the restraining force due to the electrostatic force and adhere to the photoreceptor. Therefore, the mixing ratio of toner and carrier must be strictly controlled, which requires means for detecting the mixing ratio and means for replenishing toner. For these reasons, a two-component magnetic brush development system inevitably becomes larger and more complex.

[0004] In order to solve the above-mentioned drawbacks, a one-component magnetic toner development method that does not use a carrier has been proposed. FIG. 2A shows an example of a developing device using a one-component magnetic toner developing method. As shown in FIG. 2(A), the developing device 1
0 includes a magnetic toner 12, a non-magnetic and conductive developing sleeve 16 that supports the magnetic toner 12 on its surface and transports it to a developing area facing the photoreceptor 14, and a magnet 18 provided inside the developing sleeve 16. , an elastic blade 20 that is pressed against the developing sleeve 16 and charges the toner and regulates the layer pressure. The developing sleeve 16 is provided with a developing bias applying means 22 for applying a developing bias, and reversely develops the electrostatic latent image on the photoreceptor 14 into a visible image.

However, this one-component magnetic toner development method
In order to sufficiently charge the toner with the elastic blade 20, the thickness of the toner layer on the developing sleeve 16 must be made very thin, and as a result, toner tends to accumulate at the pressure contact portion between the elastic blade 20 and the developing sleeve 16. the result,
The toner sticks due to stress, resulting in toner clogging between the blade and the sleeve. This appears as white streaks on the developing sleeve 16 in the output image, detracting from the beauty of the image. Furthermore, in order to prevent this toner from sticking, if the pressing force of the elastic blade 20 is weakened, the developing sleeve 1
The toner layer on the toner layer 6 becomes thicker, and sufficient charging is not performed. As a result, toner adheres to non-image areas on the photoreceptor, staining the image.

[0006] Recently, a developing device has been put into practical use that uses a developer containing magnetic toner and a small amount of magnetic carrier, and carries the developer using a relatively rotating sleeve and a magnetic roll to carry out development. There is. An example of this is shown in FIG. 2(B). As shown in FIG. 2(B), the developing device 10 holds a developer 24 containing a mixture of magnetic toner and magnetic carrier, and includes a relatively rotatable developing sleeve 16 and a magnet roll 26.
It is composed of a regulating blade 28 and the like that regulates the height of spikes of developer on the developing sleeve 16. The developer 24 attached to the developing sleeve 16 by the magnetic force of the magnet roll 26 forms a magnetic brush, and is conveyed to the developing area while being rolled by the rotation of the developing sleeve 16 and the magnet roll 26 . At this time, the toner is triboelectrically charged between the toners and between the toner and the carrier or sleeve due to the rolling of the magnetic brush, and is given the charge necessary for development. Then, the electrostatic latent image on the photoreceptor 14 is developed into a visible image by the developer 24 conveyed to the development area. This developing method can realize a developing device with relatively excellent fine line reproducibility and high solid black density with a simple configuration.

[0007]

However, the developing device has the following drawbacks. That is, in the frictional charging that imparts the charge necessary for development to the toner, the frictional charging of the toners together is dominant, and as a result, so-called reverse polarity toner having a charge of the opposite polarity to a predetermined charge is generated. When this toner of opposite polarity is conveyed to the development area, it adheres to non-image areas on the photoreceptor, staining the image, and increasing toner consumption.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a developing device that can prevent toner of opposite polarity from being conveyed to the developing area and, as a result, can perform beautiful development. With the goal.

[0009]

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a developing device for developing an electrostatic latent image on an image carrier into a visible image using a developer. a developer transport device that transports the developer onto the image carrier while holding the developer;
A regulating member for regulating the layer thickness of the developer on the developer transporting device is provided, and a voltage of the same polarity as the initial potential on the image carrier is applied to the regulating member.

0010

[Function] According to the present invention, the initial potential of the image carrier (for example, -700
A voltage of the same polarity as V) is applied. That is, the same polarity voltage of, for example, -700V is applied to the regulating member and the image carrier. In this state, when the developer passes near the regulation member, the toner charged to the opposite polarity (for example, positive polarity) contacts the regulation member due to electrostatic force, and the charge charged to the opposite polarity is removed by charge injection. and is given a charge of the same polarity (negative in this case). Therefore, only toner having the same polarity as the initial potential of the carrier is transported to the development area.
Toner of opposite polarity is not transported.

[0011]

Embodiments Hereinafter, embodiments embodying the present invention will be described with reference to the drawings. This embodiment is a reversal development type developing device using a mixed developer of magnetic toner and magnetic carrier, and the initial charge polarity of the photoreceptor and the charge polarity of the toner are
This is a negative case.

As shown in FIG. 1(A), the developing device 10 includes:
A developer 24 containing a mixture of magnetic toner 12 and magnetic carrier 23 is stored inside. The magnetic toner 12 contains 100% of magnetic powder such as ferrite in a styrene-acrylic resin.
It is a powder with an average particle size of about 10 μm mixed with carbon black as a coloring agent.
Electron-accepting substances such as chlorinated paraffin and chlorinated polyester are externally added. The magnetic carrier is a ferrite spherical particle with an average particle size of about 50 μm. In addition, the mixing ratio of toner and carrier does not need to be as strict as in the two-component magnetic brush development method, and is 50 to 90 in terms of weight ratio.
% is maintained.

The developing device 10 includes a developing sleeve 16 that holds developer 24 on its surface and transports it to a developing area, and a magnet roll 26 that is supported within the developing sleeve 16 so as to be coaxial with the developing sleeve. There is. The developing sleeve 16
is made of a conductive material, such as an aluminum cylinder, so that a voltage can be applied, and its surface is coated with a substance that charges the toner to a predetermined polarity (in this case, negative polarity). is preferable, and silicone resin or the like is suitable as the corresponding substance. The magnet roll 26 has the function of magnetically adhering the developer 24 onto the developing sleeve 16 and transporting it, is magnetized with eight poles in the circumferential direction, and is supported rotatably relative to the developing sleeve 16.

The developing sleeve 16 and the regulating blade 28 are arranged with a predetermined interval (200 to 400 μm) maintained therebetween. The developer 24 deposited on the developing sleeve 16 passes through the gap to regulate the developer layer thickness, and then the photoreceptor 14 carrying the electrostatic latent image and the developing sleeve 16 face each other. The toner 12 is conveyed to the development area A where the toner 12 is attached to the electrostatic latent image by electrostatic force, and the latent image is developed into a visible image.

Developer 24 attached to developing sleeve 16
The spikes are formed by the magnetic force of the magnet roll 26. Then, due to the rotation of the magnet roll 26, the spikes repeatedly roll, and as a result of this repetition, the toner is negatively charged due to mutual friction between the toners or with the surface of the carrier and the sleeve. However, the frictional charging at this time is predominantly caused by toner particles, and therefore, positive polarity toner that is charged to a polarity opposite to the predetermined polarity is also generated. The charge of this reverse polarity toner is removed by charge injection when it comes into contact with a developing sleeve to which a voltage of the same polarity as the predetermined polarity of the toner is applied, but this is still not enough and a considerable amount of reverse polarity still remains. The toner is transported to the development area A and adheres to the non-image area of the electrostatic latent image, causing background fog.

[0016] Therefore, a configuration according to the gist of the present invention was adopted. That is, a negative voltage having the same polarity as a predetermined polarity is applied to the regulating blade 28 to quickly remove the charge of the toner having the opposite polarity. In this way, by injecting negative charges of a predetermined polarity into the toner, more beautiful development can be performed. FIG. 1(B) shows an example of applying a voltage to the regulating blade 28. The regulation blade 28 is made of a conductive material to which a voltage can be applied, such as stainless steel,
The regulating blade 28 sets the photoreceptor 14 to an initial potential of about -700.
Scorotron charger 30 set to be charged to V
It is electrically connected to the grid section 34 of.

[0017] The scorotron charger 30 has a power of about -5.5k.
The wire section 32 is made of tungsten and has a wire diameter of about 80 μm to which a high voltage of V is applied, and a grid section 34 and a case 36 are provided to face the photoreceptor 14 . Since the surface of the photoreceptor 14 is charged to approximately the same potential as the grid section 34, it is necessary to keep the potential of the grid section 34 constant.
By grounding through the constant voltage diode 37,
The potential of the grid portion 34 is kept constant. The rating of this voltage regulator diode 37 is selected to be the same as the initial potential value to be applied to the surface of the photoreceptor 14, and here, -700V
is selected.

Therefore, the grid portion 34 and the regulating blade 2
8 by electrical means, the regulation blade 28 is maintained at approximately -700V. Therefore, developer 2
When the toner 4 passes through the regulating blade section 28, the positive toner contacts the regulating blade 28 due to electrostatic force, loses the charge charged by this contact by charge injection, and is given a negative charge before moving to the development area. It will be transported to A. Therefore, it is possible to prevent the toner of opposite polarity from being conveyed to the development area A, so that the amount of toner adhering to the non-image area of the latent image can be reduced, and as a result, beautiful development can be performed.

Note that in this embodiment, the regulating blade 28 is electrically connected to the grid section 34 of the scorotron charger 30, but even if it is electrically connected to the developing sleeve 16, the regulating blade 28 is not connected to the photoreceptor 14. A voltage having the same polarity as the initial potential can be applied. Further, although this embodiment is an example of a developing method using negatively charged toner, positively charged toner may also be used, or regardless of whether the toner is magnetic or non-magnetic, Of course, the present invention can be applied to any reversal development method.

[0020]

As explained above, according to the present invention, on the upstream side of the development area, toner of opposite polarity has its charge removed, and after being given a charge of a predetermined polarity, it is transported to the development area. Therefore, good development with little background fogging can be achieved. Furthermore, since toner background fogging is reduced, toner consumption can be reduced and running costs can be reduced.

[Brief explanation of drawings]

FIG. 1 (A) is an overall configuration diagram of a developing device of the present invention;
B) is a perspective view of essential parts of the developing device.

FIG. 2(A) is a schematic diagram of a conventional two-component magnetic brush development method, and FIG. 2(B) is a schematic diagram of a conventional one-component magnetic toner development method.

[Explanation of symbols]

10... Developing device 12... Magnetic toner 14... Photoreceptor (image carrier) 16... Developing sleeve (developer transport device) 26... Magnet roll 28... Regulating blade (regulating member) 30... Scorotron charger (voltage application device) 32 ... Wire section 34 ... Grid section 36 ... Case 37 ... Constant voltage diode A ... Development area

Claims (1)

[Claims] 1. In a developing device that develops an electrostatic latent image on an image carrier into a visible image using a developer, the developer is conveyed onto the image carrier while holding the developer on the surface. A developing device comprising: a device; and a regulating member for regulating the layer thickness of the developer on the developer transport device, and a voltage having the same polarity as the initial potential on the image carrier is applied to the regulating member. Device.