JPH0336573A - Developing device - Google Patents

Abstract

PURPOSE:To uniformize the distribution of the electrostatically charged quantity of developer and to stably form a high-quality image by providing a covering layer containing at least one kind of resin on the surface of a magnetic roller. CONSTITUTION:In a developing device 7, the developer 8 being the component element of the developer is electrostatically charged and conveyed by the rotating cylindrical magnetic roller 9. In such case, the covering layer 16 containing at least one kind of resin is provided on the surface of the magnetic roller 9, that means, a developer conveying surface. Therefore, as to the developer 8 conveyed on the magnetic roller 9, the electrostatic charging to the developer 8 by the triboelectrification with the developer 8 is controlled by the resin like carrier being the component element of the two-component developer 8, so that the distribution of the electrostatically charged quantity of the developer 8 is uniformized. Thus, the high-quality image is stably formed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a magnetic brush developing device.

[Prior Art] A conventional developing device, known as a magnetic brush developing device, has a plurality of magnetic poles attached to the inside of a rotatable non-magnetic and conductive cylindrical developer conveying member, also called a developing sleeve. It has a magnetized cylindrical magnetic roller, holds the developer on the developer transport member by a magnetic field generated by the magnetic roller, and develops by rotating at least one of the magnetic roller and the developer transport member. It was used to transport the developer on the agent transport member. As is well known, examples of the developer include a one-component developer made up of only a developer and a two-component developer made up of a developer and a carrier.

In such a developing device, it is necessary to polish the outer diameter of the magnetic roller, to process the outer diameter of the developer conveying member, and to precisely arrange the magnetic roller with a small gap between the magnetic roller and the developer conveying member. This caused an increase in man-hours and costs. Furthermore, the developing device has many components such as a magnetic roller, a developer conveying member, and parts for supporting each component, making it impossible to reduce the size and weight of the developing device. Furthermore, if the number of magnetized poles of the magnetic roller is increased in order to reduce uneven development density due to the magnetic pole pitch of the magnetic roller that occurs in the image when the magnetic roller is rotated, sufficient leakage magnetic flux will be generated on the developer transport member. Therefore, it was not possible to secure a sufficient amount of developer to be transported.

[Problems to be Solved by the Invention] Therefore, the present applicant has devised a developing device that directly transports developer on the surface of a magnetic roller, as a developing device that solves these problems. However, due to various charging mechanisms such as frictional charging between the surface of the magnetic roller and the developer, frictional charging between the developer and the developer, and frictional charging between the developing device components such as the developer transport amount regulating member and the developer, As a result of the developer having a large difference in the amount of charge that each developer has, and furthermore having a broad charge amount distribution being conveyed on the magnetic roller, the resulting image is of very low quality. There's a problem.

The present invention is intended to solve these problems.The purpose of the present invention is to make the charge distribution of the developer uniform, and to create a simple structure that can stably form high-quality images. The company provides a developing device.

[Means for Solving the Problems] A developing device of the present invention includes a cylindrical magnetic roller magnetized with a plurality of magnetic poles, and a magnetic field generated by the magnetic roller causes the developer to be transferred to the magnetic roller. In the developing device that transports the developer by rotating the magnetic roller, the developing device is characterized in that a coating layer containing at least one type of resin is provided on the surface of the magnetic roller (developer transport surface). shall be. Further, the coating layer is characterized in that it contains a resin containing at least one of fluorine and silicon.

[Function] According to the above configuration of the present invention, by providing a coating layer containing at least one type of resin on the surface of the magnetic roller, the resin is applied to the developer conveyed on the magnetic roller. is a component of a two-component developer (for example, ferrite particles), and by controlling the charge of the developer by frictional charging with the developer, the charge amount distribution of the developer is made uniform, In turn, it becomes possible to stably form high-quality images.

Furthermore, since the coating layer contains a resin containing at least one of fluorine and silicon, the developer is prevented from being filmed (adhered or fused) to the surface of the magnetic roller. The surface can be stably kept clean for a long period of time, and high quality images can be stably formed for a long period of time.

Hereinafter, the present invention will be explained in detail with reference to Examples.

[Embodiment] FIG. 1 shows a cross-sectional schematic view of an image forming apparatus including a developing device in an embodiment of the present invention.

A latent image carrier 1 rotating in the direction indicated by A in the figure has a photoconductive layer 3 coated on a conductive support 2. After being charged to a potential of form an image.

The developing device 7 charges a developer 8, which is a component of the developer, and transports the developer 8 with a cylindrical magnetic roller 9 that rotates in the direction indicated by B in the figure. The developer 8 held by magnetic force on the magnetic roller 9 covered by the coating layer 16 containing at least one type of resin is regulated to an appropriate amount by the developer transport amount regulating member 10 and then transferred to the latent image carrier 1. The magnetic roller 9 is conveyed to the adjacent developing gap portion. The developer 8 has the most contact with the surface of the magnetic roller 9 until it is conveyed to the development gap, and therefore, when it adheres to the magnetic roller 9,
It is thought that frictional charging with the surface of the magnetic roller 9 during transport on the magnetic roller 9 makes the largest contribution to the charge amount (distribution) of the developer 8 at the time it reaches the development gap. By providing a coating layer 16 on the surface of the body roller 9, the charging property of the developer is controlled,
Moreover, it becomes possible to obtain a uniform charge amount distribution.

In the development gap portion, a bias voltage is applied to the developer 8 by a power supply 11 serving as a development bias voltage application means, and the developer 8 is applied to the latent image carrier 1 according to the electric potential of the electrostatic latent image on the latent image carrier 1. By adhering to the electrostatic latent image on the latent image carrier 1, the electrostatic latent image on the latent image carrier 1 is visualized.

The developer 8 (on which the electrostatic latent image has been developed) on the latent image carrier 1 is transferred onto the recording paper 13 by the transfer device 12, and is further fixed on the recording paper 13 by means such as pressure or heating, thereby creating a desired image. images can be obtained.

In this embodiment, as shown in FIG. 1, the rotational directions of the latent image carrier 1 and the magnetic roller 9 are shown as "man" and "B" in the figure, respectively, but this does not limit the present invention. .

Further, in this embodiment, as shown in FIG. 1, an example was shown in which the coating layer 16 completely or uniformly covers the surface of the magnetic roller 9, but this is not intended to limit the present invention. The thickness of the coating layer 16 may be non-uniform, the coating may be incomplete such that the magnet (the surface of the magnetic roller) is exposed, or the coating layer 16 may not be continuous but may have resin islands. A large number of them may be independently formed on the surface of the magnetic roller 9.

In addition, in the present invention, all known developers such as one-component magnetic brush developer and two-component magnetic brush developer can be used, and by appropriately selecting the resin constituting the coating layer 16, the developer can be It is possible to control the charging polarity of 8 to a desired polarity, whether positive or negative. In addition, in controlling the chargeability of the developer 8 using the coating layer 16, as described above, the coating layer 1
The selection of the resin constituting the developer 6 is important, but in a process using a one-component developer as the developer 8, if a charge control agent is mixed in the developer 8, the charging effect of the charge control agent can be maximized. In order to achieve this effect, it is desirable to use a resin that is equivalent in the charging series to the resin constituting the developer 8.
A charge control agent is mixed in the developer 8, but if the charge control agent does not provide sufficient charging or excessive charging occurs, the charging effect of the charge control agent on the resin constituting the developer 8. It is desirable to use a charge-based resin that reinforces or suppresses the electrification, and in the case where the present invention is particularly effective, in which the charge control agent is not mixed in the developer 8, the resin constituting the developer 8 is preferably used. It is desirable to use a charging series resin that can obtain the desired amount of charge.
Even in a process using a two-component developer as the developer 8, the resin constituting the coating layer 16 may be selected in the same manner.
From the viewpoint of making the charge amount distribution uniform, it is particularly desirable to use a resin in the same charging series as the carrier or the resin coating the carrier surface.

Further, as the magnetic material of the magnetic roller 9, known magnetic materials such as ferrite, alnico, manganese aluminum, and rare earth magnets can be used, but in particular, atomic number 5
8 to 71 (element symbol Ce% LU), at least one of the rare earth elements represented by Nd, Pr and Sm, Fe% Ni and C
It is desirable to use a rare earth magnet to which at least one of the 3D transfer metals represented by O is added.

Example 1 In this example, a sintered ferrite magnet was used as the magnetic roller 9, and as the coating layer 16, (many independent) island-shaped coating layers were formed of polyester resin.

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 5,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high temperature, and high quality, similar to the first sheet of printing.

Comparative Example 1 Images were continuously formed under the same conditions using an image forming apparatus with a developing device having the same configuration as in Example 1 except that the coating layer 16 was not provided on the surface of the magnetic roller 9. However, the obtained image was a low-quality image in which the image temperature was low and temperature unevenness was observed.

Example 2 In this example, a samarium cobalt extruded magnet was used as the magnetic roller 9, and as the coating layer 16,
A (multiple independent) island-like coating layer of polycarbonate resin was formed.

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 5,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high density, and high quality, similar to the first sheet of printing.

Comparative Example 2 Images were continuously formed under the same conditions using an image forming apparatus with a developing device having the same configuration as in Example 2, except that the coating layer 16 was not present on the surface of the magnetic roller 9. However, the obtained image was of low quality with low image density and density unevenness.

Example 3 In this example, a neodymium-iron sintered magnet was used as the magnetic roller 9, and a uniform (no exposed magnet) coating layer was formed of polyimide resin as the coating layer 16.

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 5,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high density, and high quality, similar to the first sheet of printing.

Comparative Example 3 Images were continuously formed under the same conditions using an image forming apparatus with a developing device having the same configuration as in Example 3 except that the coating layer 16 was not present on the surface of the magnetic roller 9. However, the obtained image was of low quality with low image density and density unevenness.

Example 4 In this example, a neodymium/iron sintered magnet was used as the magnetic roller 9, and a uniform coating layer (with no exposed magnet) was formed using silicone resin (organosilane resin) as the coating layer 16. .

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 50,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high density, and high quality, similar to the first printed sheet. Further, no filming due to the developer was observed on the surface of the magnetic roller 9.

Comparative Example 4 When images were formed continuously in the same manner as in Example 4 using an image forming apparatus with a developing device having the same configuration as in Example 3, the resulting images had low image density and were even A4 size. After continuously forming images equivalent to 30,000 sheets of paper, the resulting images became low-quality images with blurred brush marks and the like. Furthermore, filming due to the developer was observed on the surface of the magnetic roller 9.

Example 5 In this example, a praseodymium-iron cast magnet was used as the magnetic roller 9, and a polyurethane resin was used as the coating layer 16 to form a uniform coating layer (with no exposed magnet).

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 5,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high density, and high quality, similar to the first sheet of printing.

Comparative Example 5 Images were continuously formed under the same conditions using an image forming apparatus with a developing device having the same configuration as in Example 5 except that the coating layer 16 was not present on the surface of the magnetic roller 9. However, the obtained image was of low quality with low image density and density unevenness.

Example 6 In this example, a neodymium/iron sintered magnet was used as the magnetic roller 9, and a polyurethane resin in which tetrafluoroethylene resin particles were dispersed was used as the coating layer 16 to provide a uniform coating (no exposed magnet). formed a layer.

Using the image forming apparatus with the developing device configured as described above, A4
Images equivalent to 50,000 sheets of plain paper were successively formed, and the resulting images had high resolution, high temperature, and high quality, similar to the first printed sheet. Further, no filming due to the developer was observed on the surface of the magnetic roller 9.

Comparative Example 6 When images were formed continuously in the same manner as in Example 6 using an image forming apparatus with a developing device having the same configuration as in Example 5, the resulting images had low image density and were roughly A4 size. After continuously forming images equivalent to 30,000 sheets of plain paper, the resulting images became low-quality images with blurred brush marks and the like. Furthermore, filming due to the developer was observed on the surface of the magnetic roller 9.

Although the embodiments have been described above, the present invention is particularly effective when applied not only to the above embodiments but also to a wide range of image forming apparatuses such as electrophotographic recording apparatuses, such as page printers, facsimile machines, and copying machines.

[Effects of the Invention] As described above, the present invention includes a cylindrical magnetic roller magnetized with a plurality of magnetic poles, and uses a magnetic field generated by the magnetic roller to move the developer to the magnetic roller. In a developing device that transports the developer by rotating the magnetic roller, a coating layer containing at least one type of resin is provided on the surface of the magnetic roller (developer transport surface). With respect to the developer conveyed on the magnetic roller, the resin acts like a so-called carrier, which is a component of a two-component developer, by controlling the charging of the developer by frictional charging with the developer. It is possible to make the charge amount distribution uniform, and as a result, it is possible to stably form high-quality images. Furthermore, since the coating layer contains a resin containing at least one of fluorine and silicon, the developer is prevented from filming on the surface of the magnetic roller, and the surface of the magnetic roller is kept stable for a long period of time. This makes it possible to maintain high quality images stably for a longer period of time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional schematic diagram of an image forming apparatus including a developing device in a practical example of the present invention. Latent image carrier, developer, magnetic roller, developer transport amount regulating member, power supply coating layer

Claims (3)

[Claims] (1) It has a cylindrical magnetic roller magnetized with a plurality of magnetic poles, the developer is held on the magnetic roller by a magnetic field generated by the magnetic roller, and the magnetic roller is rotated. A developing device for transporting the developer, characterized in that a coating layer containing at least one type of resin is provided on the surface of the magnetic roller. (2) The developing device according to claim 1, wherein the coating layer contains a resin containing fluorine. (3) The developing device according to claim 1, wherein the coating layer contains a resin containing silicon.