JPS60130777A - dry developing device - Google Patents

Abstract

PURPOSE:To improve development efficiency by establishing an electric field between a developing roller and a supply roller and electrostatically charging toner forcibly, sticking the electrostatically charged toner on the outer circumferential surface of the developing roller, and rotating the developing roller closely to a photosensitive body and carrying out development. CONSTITUTION:The outer circumferential surface of the developing roller 30 contacts the outer circumferential surface of the photosensitive body 7, and the developing roller 30 rotates following up the rotating of the photosensitive body 7 in rolling contact to rotate at the same speed with and in the opposite direction to the photosensitive body 7. A coat layer 32 is made of the same material with the toner 4 so as to reduce the resistance of adhesion between the coat layer 32 and toner 4 when the both contact each other. The supply roller 40 is arranged at the entrance side of a storage chamber for the toner 4 so that its outer circumferential surface is put close to the outer circumference of the developing roller 30. A DC voltage having the polarity opposite to that of an electrostatic charge generated on the surface of the photosensitive body 7 is impressed to the supply roller 40 to establish an electric field having specific intensity between the rollers 40 and 30. A voltage impressing means 43 controls its electric field intensity freely. Thus, the development efficiency is improved greatly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing device used in an electrostatic photographic device such as a copying machine, or an electrostatic recording device such as a printer or facsimile, and in particular, it relates to a developing device for use in an electrostatic latent image formed on the surface of a photoreceptor. The present invention relates to a dry developing device that performs development using toner.

Conventionally, dry developing devices for developing electrostatic latent images formed on the surface of photoreceptors include those using two-component developers;
There are some that use component-based developers.

The former uses an insulating non-magnetic toner mainly made of resin and a colorant and carrier particles such as glass beads or iron powder, and by stirring and mixing the toner with the carrier particles, the toner has a polarity opposite to that of the electrostatic latent image. The toner is charged by friction and conveyed to the surface of the photoreceptor, and only the toner is attracted to the electrostatic latent image area and visualized.

In this type of development method, only toner is consumed sequentially each time development is performed, so in order to obtain appropriate image quality, the toner is regularly replenished to maintain a constant mixing ratio. It was necessary and inevitable that the developing device would become more complex and larger. Furthermore, since the carrier is used repeatedly over a long period of time, image quality deteriorates due to deterioration of the carrier, and the carrier itself needs to be replaced periodically. In particular, replacing the carrier requires removing and disassembling the developing device and cleaning the inside, making maintenance troublesome.

On the other hand, the development method using a -component developer has various advantages such as eliminating the above-mentioned drawbacks, making it possible to miniaturize the device and simplify maintenance, and various technologies have been proposed in recent years. There is.

For example, FIG. 1 shows a developing device that uses a high-resistance magnetic toner formed by uniformly dispersing magnetic powder in a resin/colorant, and performs development by conveying the toner toward the electrostatic latent image side using a magnetic brush. To briefly explain its structure, a magnet roller is made up of a cylindrical magnet assembly l having a large number of magnetic poles formed on its surface, and a conductive sleeve 2 arranged around the assembly l in a concentric circle shape. 3, a hopper 5 located above the roller 3 and replenishing the toner 4 onto the surface of the sleeve 2, and a frame 6 that surrounds these and is fixedly installed in the device. The conductive sleeve 1 and the conductive sleeve 2 are configured to rotate relative to each other, and the roller 3 is disposed close to the surface of the drum-shaped photoreceptor 7.

In the developing device having such a structure, the toner 4 (magnetic brush 4a) carried in the form of a spike on the conductive sleeve 2 by the magnetic attraction force of the magnet assembly 1 is moved between the magnet assembly 1 and the conductive sleeve 2. The magnetic brush 4a is conveyed to the photoreceptor 7 side by the relative rotation of the electrostatic latent image portion 7.
When IT approaches and contacts a, the conductive sleeve 2 imparts a charge of opposite polarity to the latent image charge to the toner 4, and as a result, the electrostatic latent of the photoconductor 7 is caused by the Coulomb force of the charge and the latent image charge. The toner 4 sticks to the image area 7a, and development is performed.

Therefore, in such a developing device, a forced toner charging method such as the Hiko-fri charging method of the above-mentioned two-component developing method is not adopted, but instead the toner is simply charged within the electric field formed between the conductive sleeve 2 and the electrostatic latent image portion 78. Since the toner 4 is charged with electricity, the developing efficiency inevitably becomes lower than that of the two-component developing method.

For this reason, in conventionally known developing devices, the opposing distance d between the conductive sleeve 2 and the photoreceptor 7 is narrowed, high frequency/heirth is applied to the magnetic brush 4a, and the resistance of the toner 4 is reduced. (A method of increasing the developing efficiency by controlling +rj is adopted, but in either method, the basic step is to charge the toner 4 between the conductive sleeve 2 and the photoreceptor 7. Since the basic structure is the same, it is impossible to achieve a significant improvement in developing efficiency, and the rubbing of 1 and 4 on the photoconductor 7 creates an image on the surface of the -H electrostatic latent image 7a. The adhered toner 4 may flow, or the toner 4 may adhere to the non-electrostatic latent image surface, causing image disturbances and fogging.Fourth, the facing distance d between the conductive sleeve 2 and the photoreceptor 7. It is extremely difficult to keep the image constant at all times, and also from an assembly point of view, and from this point of view as well, the image lacks stability.

In view of the drawbacks of the prior art, the present invention aims to significantly improve the developing efficiency 4, and also makes it possible to develop without rubbing the toner on the surface of the photoreceptor, thereby producing a clear image without any disturbance of the image. The object of the present invention is to provide a developing device capable of obtaining an image, and its characteristics are as follows. a conductive developing roller that rotates in contact with or in close proximity to the developing roller;
The present invention is configured such that an electric field is formed between the two rollers in conjunction with a supply roller that conveys the component toner toward the developing roller by magnetic force.

The present invention will be described in detail below based on the drawings.

FIG. 2 shows a schematic configuration of a copying machine to which an embodiment of the present invention is applied, in which 7 is a drum-shaped photoreceptor with a photoconductive layer on its surface, around which are a charging device 8, an exposure device 8, and a developing device. device 10
．． A transfer device 11, a cleaning device 12, and the like are arranged.

In such a copying machine, as is well known, when the photoreceptor 7 rotates clockwise in synchronization with the movement of the document table (not shown), a predetermined charge is first applied by the charging device 8, and then exposure is performed. An electrostatic latent image 7a corresponding to the original image on the original platen is formed on the surface of the photoreceptor 7 through sequential exposure by the device 9. This electrostatic latent image 7a is visualized as a toner image by a developing device 10, which will be described in detail later, and reaches a transfer device 11. In the transfer device 11, the toner image is transferred and carried on the transfer paper 13 fed from the paper feed device 14, and then the transfer paper 13 is separated from the photoreceptor 7 and fixed as a final image in the fixing device 15. On the other hand, the photoreceptor 7 to which the toner image has been transferred is prepared for the next copying after the remaining 1.sup.-4 is removed by a cleaning device 12.

Since these copying steps are already well known, detailed explanation will be omitted.

On the other hand, the toner 4 used in the copying machine is at least 1
A high-resistance magnetic toner with a volume resistivity of 0.01 gΩcm or more, containing appropriate ingredients such as styrene-acrylic resin, magnetite (magnetic powder), carbon black (coloring agent/competitive control agent), silica (additive), etc. After kneading and heating at a specific temperature, the powder is pulverized and classified to have an average particle size of 15 to 25 m.

3 to 4 show a developing device 10 according to an embodiment of the present invention used in an Mj copying machine, which includes a frame 20, a developing roller 30, a supply roller 40, a cleaning member 50, and a height regulating member 6O. It is configured.

The frame body 20 is disposed along the circumferential direction of the photoconductor 7 over almost the entire length of the photoconductor 7 in the longitudinal direction, and is connected to a cartridge mounting section 21 formed above and connected to the mounting section 21. ,
It consists of an l/ner storage chamber 22 which is open on the side facing the photoreceptor 7.

A toner replenishment cartridge 23 is removably installed in the car I/ridge installation part 21, and by peeling off the seal member 24 stuck to the bottom surface of the cartridge 23 using a peeling means (not shown), the inside of the cartridge 23 can be removed. 1.
The storage chamber 22 is configured so that the water flows down along the frame bottom plate 25 and is replenished into the storage chamber 22.

Inside the toner storage chamber 22, the developing roller 30, the supply roller 40, and the cleaning member 50 are arranged parallel to the rotation axis of the photoconductor 7, respectively, and a height regulating member 60 is disposed at the lower end 61 of the supply roller 40. are arranged close to the outer peripheral surface of the supply roller 40.

The developing roller 30 includes a rotating body 31 made of conductive rubber and a conductive coating layer 32 applied to the outer peripheral surface of the rotating body 31.
The developing roller 30 is disposed so that its outer circumferential surface is in contact with the outer circumferential surface of the photoreceptor 7, and the developing roller 30 rotates in contact with the rotation of the photoreceptor 7 via a gear (not shown), that is, the developing roller 30 The roller 3O has the same circumferential speed as the photoreceptor 7 and rotates in the opposite direction. By the way, the photoreceptor? The contact with the outer circumferential surface may be either contact or elastic pressure contact. And the rotating body 31 formed of the conductive rubber
A material having a volume resistivity value of 1E air resistance of 10"1 Ωcm or less, preferably in the range of 10! to 10900 m is used.

Further, since the developing roller 30 is grounded and is electrically conductive as described above, an electric field can be formed between it and the supply roller 40 as described later.

Next, to explain the coat layer 32 in detail, the material of the coat layer 32 is selected from the above 1. -4 is made of the same type of material>+, and in order to smoothly form the electric field, its volume resistivity is controlled to be 1011 Ωcm or less, preferably in the range of 10 to 10900 m, similarly to body 31. are doing.

Here, "the same kind as the toner 4" refers to the above-mentioned 1.
4. It refers to a material made of a composition material containing at least one of the following materials, such as resin, magnetic powder, colorant, resistance control agent, and additives.

In addition, in this example, the material # composing the above-mentioned 1 and S-4 is
H in magnetite, carbon black, etc. in 1.

Only the blending ratio of the anti-control agent was changed (increased) to control the Ja resistance value within the range of 109 to 109 Ωcm.

As the thickness of the coating layer 32 increases, the conductive resistance increases, which is not preferable for toner sticking and electric field formation, as will be described later.
Preferably, it is formed to have a thickness of about 3 to 5 times.

Further, the application of the coat 1/layer 32 absorbs the irregularities on the surface of the rotating body 31, which is made of a TTF conductive comb, and is applied to the developing roller 30.
The coating may be carried out so that the surface becomes a smooth surface, and the coating method may be spraying, brushing, dipping or other well-known coating methods.Furthermore, baking or baking may be applied to prevent peeling from the surface of the rotating body 31. It may also be cured by electron beam.

The upstream side of the developing roller 30 on the contact side of the photoreceptor 7, that is, I
- On the entrance side of the S-4 storage chamber, a supply roller 40 is arranged with its outer circumferential surface close to the outer circumferential surface of the developing roller 30.

The t'lk supply roller 40 includes a cylindrical magnet assembly 41 having a large number of magnetic poles formed on its surface, and is arranged in a circular shape around the assembly 41 and is made of a conductive non-magnetic material such as aluminum. By rotating the magnet assembly 41 and the conductive sleeve 42 relative to each other, the toner 4 (magnetic brush 4a) carried in the form of a spike on the conductive sleeve 42 is developed. It is configured so that it is conveyed to the roller 30 side. Here, "relatively rotating" means that the magnet assembly 41 and/or the conductive sleeve 42 are rotated, and a relative speed is generated between the magnet assembly 4I and the conductive sleeve 42. Next, to explain the configuration of the supply roller 40 in more detail, the supply roller 40 moves from a point near the supply roller 4O of the developing roller 30 (hereinafter referred to as the supply position) to a point of contact with the photoreceptor 7 (hereinafter referred to as the supply position). The circumferential length up to the developing position is α
) is arranged such that the length from the exposure point where the electrostatic latent image 7a is formed on the photoreceptor 7 to the development position is greater than β), and the facing distance between the supply roller 40 and the development roller 30 is It is set to about 0.3 mm.

A modulated AC or DC voltage applying means 43 is electrically connected to the supply roller 40, and a DC voltage having a polarity opposite to that of the electrostatic charge formed on the surface of the photoreceptor 7 by the voltage applying means 43 is electrically connected to the supply roller 40. is applied to the supply roller 40 to generate an electric field of a predetermined strength near the supply position between the conductive developing rollers 30. Further, since the voltage applying means 43 is configured to be able to control the voltage, both the rollers 30 and 40
The electric field strength between the two can be freely controlled. Further, a control circuit 4 is provided between the voltage applying means 43 and the roller 40.
4 is interposed therebetween, and the voltage applying means 43 is configured to be turned off at the same time or immediately after the exposure process by the exposure device 8 is completed.

Note that the voltage applying means 43 may be connected to the developing roller 30 side, contrary to this embodiment, but when a DC voltage is applied to the developing roller 30 side, the surface of the photoreceptor 7 and the developing roller 30 are connected.
For example, if a DC voltage with the opposite polarity to the electrostatic charge is applied, the background area where the electrostatic latent image 7a is not formed will also have a potential difference. )do. However, application of a moderate DC voltage may be helpful in removing fog.

The cleaning member 50 is located downstream of the developing position of the developing roller 3o, and is made of polyester, acrylic, rayon,
Conductive fibers such as carbon fiber rayon, nylon, and vinylon A are formed around a rotating shaft in the shape of a rotating plan, or the fibers are wound to form a rotating roller shape, and the outer peripheral surface of the fiber is formed into a rotating roller shape. It is arranged so as to be in contact with the surface of the developing roller 3o between the downstream side of the developing position with the photoreceptor 7 and the supplying position with the supply roller 40.

The cleaning member 50 controls its rotational direction and circumferential speed so that the toner 4 remaining on the developing roller 30 is not swept toward the photoreceptor 7 but only toward the supply roller 4O. It is set. Specifically, the developing roller 30 is configured to rotate in a direction opposite to the rotating direction of the developing roller 30, and its circumferential speed is greater than the circumferential speed of the developing roller 30.

The brush height regulating member 60 has a blade shape, and its tip is disposed close to the outer peripheral surface of the supply roller 40 on the upstream side of the supply position, so that the brush height of the magnetic brush 4a can be regulated to a predetermined height.

Next, the present invention having such a configuration will be explained in detail.

First, when the copying machine is started, the developing roller 30, the supply roller 40, and the cleaning member 50 rotate in predetermined rotational directions as the photoreceptor 7 rotates, and a DC voltage is applied to the supply roller 4O. , development is performed in the following order.

That is, first, the toner 4 staying in the storage chamber 22 is attracted to the conductive sleeve 4 by the magnetic attraction force of the magnet assembly 41.
After being supported in the form of an ear (magnetic brush 4a) on the magnetic brush 4a, it is conveyed to the developing roller 30 side by the relative rotation between the magnet assembly 41 and the conductive sleeve 42, and the magnetic brush 4a is While the height is regulated, only an appropriate amount of toner 4 is supplied between the developing rollers 30 by the supply position number ÷
approach.

Since a DC voltage of opposite polarity to the electrostatic charge is applied to the supply roller 4o, and the conductive developing roller 3o is grounded, an electric field corresponding to the DC voltage is created between the rollers 3o and 40. is formed, while since the rollers 30, 40 are rotating in opposite directions to each other, there is a considerable relative speed of rotation between the two rollers 30, 40, so that the paper guided to said supply position is S-4 is between both rollers 3o and 40.
- While being rubbed, a charge of opposite polarity to the electrostatic charge corresponding to the electric field strength formed between the two rollers 30 and 40 is applied, and a desired amount of toner 4 is charged and adhered to the entire outer peripheral surface of the developing roller 3o. do. The toner 4 stuck to the developing roller 3o is conveyed to the photoreceptor 7 side by the rotation of the roller 30 and guided to the developing position.

Note that the amount of toner adhered to the developing roller 3o, that is, the amount of toner conveyed to the developing position on the photoreceptor 7 side, can be freely controlled by a bar that changes the DC voltage applied to the supply roller 40. Therefore, depending on whether the electrostatic latent image formed on the surface of the photoreceptor 7 is an area image or a line image, and also when adjusting the copy density of the latent image area, the DC voltage can be changed manually or automatically. This makes it possible to easily adjust copy density and select development effects depending on the type of image area.

Next, since the toner 4 guided to the development position is charged with a polarity opposite to the electrostatic charge, it comes into contact with the electrostatic latent image 7a on the surface of the photoconductor 7, and is therefore attached to the electrostatic latent image 7a. It attaches by suction and a visible image is formed.

At this time, since the photoreceptor 7 and the developing roller 30 are rotating at the same circumferential speed while rolling in contact with each other, the toner 4 is transferred to the photoreceptor? It is possible to develop the image without rubbing, and therefore it is possible to obtain extremely clear images without image disturbances (shifts or blurring) caused by mechanical rubbing, which are the drawbacks of conventional one-component development methods. I can do it.

In particular, in this embodiment, since the surface layer of the developing roller 30 is formed of a conductive rubber-like rotating body 31 with the coating layer 32 in between, the developing roller 30 is pressed against the surface of the photoreceptor 7 (elastically The developing efficiency is further improved.

In addition, the development is performed using the supply roller 4 instead of applying an electric charge by mechanical friction as in the conventional one-component development system.
The toner 4, which is forcibly charged at the supply position between the developing roller 30 and the developing roller 30, is electrically attracted and attached to the electrostatic latent image area while being brought into rolling contact with the photoreceptor 7, so that the developing efficiency is extremely high. It gets expensive.

For example, in order to achieve a print density of 1°4 or higher, as indicated by the reflective optical density, in the conventional one-component development method, the surface potential of the photoreceptor 7 had to be set to 100OV or higher, but this method In the example, the surface potential of the photoreceptor 7 is set to 4.
Even when the voltage was lowered to 00V, it was possible to maintain a print density of 1.4 or higher.

Furthermore, in this embodiment, a low-resistance conductive coating layer 32 made of the same material as 1.S-4 is provided between the rotating body 31 of the developing roller 30 made of conductive rubber and the toner 4.
is present, 1f is created to reduce the surface energy between the surface of the developing roller 30 and the toner 4, and the toner 4
is easily transferred (adhered by suction) from the developing roller 30 to the photoreceptor 7, and the image clarity on the surface of the photoreceptor 7 is improved. Furthermore, the presence of the coating layer 32 can prevent the toner 4 from adhering to the surface of the developing roller 30, and the development conditions due to time-series resistance changes and/or irregularities on the surface of the developing roller 30 caused by the adhesion of the toner 4 can be prevented. It is possible to prevent destabilization and image unevenness.

The developing roller 30 that has passed the developing position further rotates and reaches the cleaning member 50. This cleaning member 5
Since the toner 0 rotates while being rubbed on the surface of the developing roller 30, the toner 4 remaining on the developing roller 30 is surely swept away to the supply roller 40 side. At this time, in this embodiment, the surface of the developing roller 30 is coated with a conductive coating layer 32 made of the same material as the toner 4.
Since the toner 4 is applied, it becomes easier to sweep off the toner 4.

Since the cleaning member 50 is disposed in contact with the surface of the developing roller 30 between the downstream side of the developing position and the supply position, the surface of the developing roller 30 is always kept in a clean state and the vehicle power is prepared for the next charging. As a result, the electric field strength between the supply roller 40 and the developing roller 30 is always constant, and even if charging is repeatedly performed between the two rollers 30 and 40, the amount of toner 4 adhering to the developing roller 30 remains constant. Stable image formation is possible without fluctuations.

Further, the cleaning member 50 sweeps off the toner 4 only on the supply roller 40 side without sweeping it on the photoreceptor 7 side, so that the toner 4 is swept off only on the side of the supply roller 40, so that the visible image area and the background on the surface of the photoreceptor 7 after development are removed. This prevents excess toner 4 from landing on the 411 area, and it is possible to prevent image distortion and the like.

Furthermore, since the cleaning member 50 is made of a conductive material, the -11 and -4 charges that are swept away can be removed, and no problems will occur during the next reuse.

From then on, development is performed while repeating the above operations.

At the end of the development, at the same time or immediately after the exposure process by the exposure device 8 is completed, the voltage application means 43 is turned off to stop applying the DC voltage to the supply roller 40 side, and both the rollers 30, 40 are turned off. The supply of toner 4 to the developing roller 30 is stopped by cutting off the electric field between them, and the developing roller 30 is rotated so that no toner other than toner 4 necessary for development is placed on the developing roller 30, and the exposure step After developing the rearmost electrostatic latent image 7a formed at the end point, the developed visible image is transferred onto the developing roller 30 before being transferred or performing the subsequent final process, that is, forming the final image. The last toner that was attached to the developing position, that is, the photoreceptor? The toner 4 passes through the contact position and is further swept away by the cleaning member 50 on the downstream side, and the machine is stopped in a state where no toner 4 is deposited on the surface of the developing roller 30.

In this embodiment, the circumferential length from the supply position of the developing roller 30 to the developing position where it contacts the photoreceptor 7 is α).
is configured so that the length from the exposure point where the electrostatic latent image 7a is formed on the photoconductor 7 to the development position is greater than β), so that the length β Before the end toner passes through the development position, the rearmost electrostatic latent image 7a formed at the end of the exposure process passes through the development position, and the above operation is smoothly achieved.

As described above, according to the present invention, the toner is forcibly charged by forming an electric field between the supply roller and the developing roller, the charged toner is attached to the outer peripheral surface of the developing roller, and the developing roller is connected to the photoreceptor. Since development is performed while rotating in contact or close proximity, development efficiency can be greatly improved.

In particular, the present invention completely eliminates the difficulty of setting the facing distance between the developing roller and the photoreceptor by rotating the developing roller while rolling it into contact with the photoreceptor, and also enables development at a low voltage. Furthermore, it is possible to eliminate blurring of the image, that is, to form an image at the same potential as the photoreceptor.

Furthermore, the present invention creates an electric field between the two rollers using a modulated alternating current or direct current voltage applied to one or both of the rollers. Copy density adjustment and image area (area image, line image) that could only be done by adjusting exposure t1
Development effects can be easily selected depending on the type of image.

Furthermore, since the developing efficiency of the present invention is improved as described above, it is possible to obtain a printing density higher than that of the conventional technology even if the surface potential of the photoreceptor is significantly lowered, and as a result, the photoconductive layer formed on the surface of the photoreceptor is It has various advantages such as being able to use various photoconductive semiconductors without being limited by the material used.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of a developing device using a conventionally known one-component toner. E? 'S2 to 4 show embodiments of the present invention, and the second
8 is a schematic explanatory diagram of a copying machine to which the developing device according to the present embodiment is applied, FIG. Engraving (no change in content) Fig. 1 Fig. 2 Fig. 3 Fig. 4 Procedural amendment closed-door format) March 2, 1980 Mr. Kazuo Wakasugi, Commissioner of the Japan Patent Office■, Indication of the case Patented in 1988 Application No. 2379ElB 2, Title of the invention Dry developing device 3, Relationship with the case of the person making the amendment Patent applicant address 52-11 Higashino Inoue-cho, Yamashina-ku, Kyoto-shi, Kyoto Name (Name) Kyocera Corporation 4, Agent 〒 104 廿552-2544 March 27, 1980 "Shipping date" 6. Drawings subject to amendment (engraving) 7. Contents of amendment as per attached sheet

Claims (1)

[Claims] A dry type developing device that develops an electrostatic latent image formed on the surface of a photoreceptor using a one-component toner includes a conductive developing roller that rotates in contact with or in close proximity to the photoreceptor, and a conductive developing roller located upstream of the developing roller. and a supply roller that conveys the component-based toner to the developing roller side by magnetic force, and is configured to form an electric field between the two rollers.