JPH071408B2 - One-component developing device - Google Patents

Description

The present invention relates to a one-component developing device, and more particularly to a one-component developing device capable of forcibly charging a toner to a desired polarity and a desired charge amount.

(Prior Art) A two-component developing device has been widely put into practical use as a developing device for visualizing an electrostatic latent image formed on an image forming member such as a photosensitive drum. This two-component developing device mixes and stirs a magnetic carrier such as iron powder and an insulating toner, and frictionally charges the carrier and the toner to charge the toner to a predetermined polarity and charge amount. However, since the toner and the carrier are mixed and stirred, there is a drawback that carrier deterioration easily occurs and the durability as a developer is limited. Further, it is necessary to control the toner density in order to maintain an appropriate image density, and there is a drawback that the structure of the developing device becomes complicated. As a method of solving these drawbacks, a one-component non-magnetic developing device which does not use a carrier is known and is disclosed in, for example, Japanese Patent Publication No. 60-7790. In this known developing device, a one-component non-magnetic toner is used as a developer, and the toner is directly supplied from a hopper through an opening at the bottom of the developing roller to a friction plate with a charging plate arranged on the front side of the developing position. The toner conveyed on the developing roller is charged to a predetermined polarity by using charging. That is, a charging plate made of Teflon, nylon, or the like is arranged close to the developing roller,
While the toner conveyed by the developing roller passes through the gap between the charging roller and the charging plate, the toner is charged to have a predetermined polarity and a predetermined charging amount by frictional charging generated between the toner and the charging plate. .

(Problems to be Solved by the Invention) In the above-described known developing device, since the toner on the developing roller is configured to charge the toner particles by frictional charging generated between the toner on the developing plate and the charging plate, There is a drawback that the charge amount is insufficient and it is difficult to form a uniformly charged toner layer. That is, when the multi-layered toner passes through the gap formed between the charging plate and the developing roller, some toner does not come into contact with the charging plate, and such toner becomes uncharged toner. When such uncharged toner or toner with poor charging is generated, a clear image is not formed and the image performance is significantly deteriorated.

Furthermore, in order to charge the toner by frictional charging,
It is necessary to appropriately select the resin and the charge control agent, which are the constituents of the toner, and the material for the charging plate, which has the drawback that the degree of freedom in designing the developer is significantly limited.

Therefore, the developing method for charging the toner by utilizing triboelectric charging must be said to have various drawbacks in terms of durability and image performance in both the two-component developing method and the one-component developing method. Therefore, an object of the present invention is to provide a one-component developing device capable of forcibly charging a toner to a desired polarity without utilizing triboelectric charging.

(Means for Solving the Problems) A one-component developing device according to the present invention includes a developing roller, a hopper that stores a one-component developer and supplies the one-component developer to the developing roller, and a developing roller that faces the developing roller. An electrode member and a discharge member having a porous insulating coating formed on at least a part of the outer peripheral surface of the electrode member, a support member for supporting the discharge member in an electrically insulated state, and the electrode A power supply device for applying a discharge voltage to the member, and the developer supplied to the developing roller is charged to a desired polarity by the discharge charge emitted from the surface of the electrode member through the holes of the porous insulating film. It is characterized in that it is configured to.

(Operation) FIG. 1 is a schematic view for explaining the toner charging principle of the one-component developing device according to the present invention. The toner layer 2 is formed on the counter electrode 1. The counter electrode 1 can be, for example, a developing roller, can be electrically grounded and biased to some positive or negative polarity. Discharge body 3 facing toner layer 2
To place. The discharge body 3 has an electrode member 4 and a porous insulating film 5 formed on the electrode member, and the discharge body 3 is supported by an insulating support member 6. On the surface of the electrode member 4 on which the porous insulating coating is formed, minute convex portions having a large curvature are uniformly formed so that discharge easily occurs. For example, if the electrode member 4 is made of a conductive rubber material impregnated with conductive particles such as carbon or metal powder, or conductive fibers, minute convex portions are formed on the surface without any special surface treatment. Therefore, it can be directly used as an electrode member. The porous insulating film can be made of an electrically insulating material such as polyester, polyvinyl chloride, polyethylene, or fluororesin. To form fine pores in the insulating film, for example, the above insulating material is used in various solvents. It can be simply constructed by dissolving it in the solution, depositing it on the electrode member and then volatilizing the solvent. Alternatively, a film can be formed by coating the surface of the electrode member with insulating fine particles as an electrostatic powder and heat treatment. The average pore diameter of the holes 5a formed in the porous insulating film 5 is such that the toner particles do not penetrate into the holes 5a even when the toner layer 2 contacts the surface of the insulating film, for example, the average particle size of the toner. Set to about 1/5 of the diameter. High-voltage power supply 7 that acts as a discharge voltage source on the electrode member 4.
Connect. The polarity of the high-voltage power supply is set to a positive polarity when the toner is positively charged, and a negative polarity when the toner is negatively charged. It is also possible to use a voltage source in which an AC voltage is superimposed on a DC voltage. When a discharge voltage of about 1 KV is applied from the high voltage power source 7 to the electrode member 4, an air discharge is generated between the electrode member 4 and the counter electrode 1, and the discharge charge generated on the surface of the electrode member 4 has a porous insulating property. It is emitted toward the counter electrode 1 through the holes 5a of the coating film 5. Therefore, the toner layer 2 is forcibly charged to the desired polarity by the discharge charge. In this case, if the toner layer 2 moves at a constant speed relative to the discharge body 3, the toner layer charged to a predetermined potential can be formed on the opposite charge. Therefore, if the counter electrode is a developing roller, a toner layer uniformly charged to a predetermined potential can be formed on the developing roller. Moreover, when the toner particles are charged, charges of opposite polarity are electrostatically induced on the side of the counter electrode (developing roller), so a Coulomb force is generated between the toner particles and the developing roller, and the Coulomb force develops the charged toner. Held on a roller. As a result, by rotating the developing roller, it is possible to transfer the toner amount having a predetermined charge amount to the developing position facing the photosensitive drum.

In the discharge body of the present invention, the distance between the electrode member and the counter electrode is the sum of the thickness of the intervening toner layer and the film thickness of the insulating film 5, so that the distance between the electrodes is a minute distance of, for example, about 200 μm. Becomes As a result, the discharge starting electrode can be set extremely low. Further, by forming the minute protrusions on the surface of the electrode member, it becomes possible to further lower the discharge starting voltage. Furthermore, since the surface of the electrode member where the discharge charge is generated is protected by the porous insulating film, even if it is brought into direct contact with the developer layer, the discharge is not adversely affected.

(Embodiment) FIG. 2 shows a constitution of a first embodiment of a one-component developing device according to the present invention, and FIG. 2a is a schematic sectional view taken along a plane orthogonal to an axis of a developing roller, 2b is a sectional view taken along a plane including the axes of the developing roller and the charging roller, and FIG. 2c is a schematic sectional view showing the relationship between the developing roller and the charging roller. A developing device is arranged so as to face the photosensitive drum 10 on which the electrostatic latent image is formed. The developing device has a hopper 11 in which a one-component developer is stored. The one-component developing device according to the present invention can be applied to both a magnetic one-component developer and a non-magnetic one-component developer, but in this example, a developing device for a non-magnetic one-component developer consisting only of insulating toner will be described. The developer in the hopper 11 is passed through the opening 11a of the hopper by the transport bar 12 rotating in the direction of the arrow a to the developing roller 1.
Transfer in 3 directions. The developing roller 13 is composed of a cylindrical conductive sleeve roller, and is rotated in the direction of arrow b by a driving device (not shown). The developing roller 13 is supported while being electrically insulated, and the developing bias 14 is connected. This developing bias is set equal to or slightly higher than the potential of the non-image portion of the photosensitive drum 10. A charging roller 15 is arranged so as to face the developing roller 13. This charging roller is formed by forming the above-mentioned discharge body into a roller shape.
As shown in FIG. 3, it is composed of a roller-shaped electrode member 15a and a porous insulating coating 15b formed on the outer peripheral surface of this electrode member. Then, both ends of the electrode member 15a are connected to the insulating bearings 16a and 16a.
It is rotatably supported by b and is rotated in the direction of arrow c by a driving device (not shown). Further, an electric brush is brought into contact with one end of the electrode member 15a and a high voltage power supply 17 for generating a discharge is connected. As shown in FIG. 2c, a gap Δd is formed between the developing roller 13 and the charging roller 15. This gap Δd corresponds to the thickness of the developer layer to be formed on the developing roller 13. The surface of the charging roller can be cleaned by bringing the blade 18 into contact with the outer peripheral surface of the charging roller 15. The developer supplied by the carrying bar 12 is transferred onto the developing roller via the guide plate 19 and passes through the charging position facing the charging roller 15 by the rotation of the developing roller. At the charging position where the charging roller 15 and the developing roller 13 face each other, discharge charge is discharged from the charging roller toward the developing roller, so that the developer on the developing roller is positively charged by the charge discharged from the charging roller. Will be. And
The charged developer is held on the surface of the developing roller by the Coulomb force generated between the developer and the charges of opposite polarities induced on the developing roller side, and is transferred to the developing position facing the photosensitive drum 10. Further, at the charging position, the outer periphery of the charging roller 15 moves in the opposite direction to the outer periphery of the developing roller 13, so that the developer layer 20 having a thickness substantially equal to the gap Δd is formed on the surface of the developing roller. Further, since the developer layer 20 on the developing roller moves relative to the charging roller, it is diffused at the charging position (smear effect), and even if a multi-layered toner layer is formed on the developing roller, the surface layer portion to the inner layer portion ( It is possible to form a substantially uniformly charged developer layer toward the side close to the surface of the developing roller). That is, the developer particles on the developing roller move relative to the discharge roller while rotating, and also move between the developer particles while changing their positions, so that they can be uniformly charged. The toner layer formed on the developing roller 13 is transferred to a developing device facing the photosensitive drum to develop the electrostatic latent image. in this case,
The toner layer 20 may be brought into contact with the photosensitive drum 10,
Alternatively, it is possible to perform jumping development separately from the surface of the photoconductor. As for the charge amount of the developer, the gap Δd between the developing roller and the charging roller, the diameter of the developing roller, and the number of revolutions of the developing roller are determined in advance, and the high-voltage power supply 17 corresponds to these factors.
It can be easily controlled by controlling the output value of.

FIG. 3 is a diagram showing the construction of the second embodiment of the one-component developing apparatus according to the present invention. The same members as the members used in FIG. 2 will be described with the same reference numerals. In this example, the plate-shaped discharge body described in FIG. 1 is used as the developer charging device. The developer in the hopper 11 is transferred to the developing roller 13 side by the first transport bar 12, and the second transport bar is further transferred.
It is transferred to the developing roller 13 by 30. Developing roller 13
A charging plate 31 having a plate-shaped discharge body is arranged on the lower side. The charging plate 31 has a plate-shaped electrode portion 31a and a porous insulating film 31b formed on the electrode member as shown in FIG. 3B, and the electrode member is supported by an insulating support member 31c. And, this support member 31c,
The insulating film 31b is fixed to the housing 32 so that it is lightly pressed against the surface of the developing roller. The developer transferred by the second transfer bar 30 is transferred by the rotational transfer force of the developing roller 13 and slips between the charging plate 31. At this time, the charge layer 31 is positively charged by the discharge charges emitted toward the developing roller 13, and a developer layer having a uniform thickness is formed on the surface of the developing roller. This developer layer is transferred to a developing position facing the photosensitive drum 10 to develop the electrostatic latent image formed on the photosensitive drum 10, and the remaining developer passes through a sheet member 33 for preventing toner outflow and a housing 32. Transferred inside. Then, the residual developer is scraped off by the scraper 34, the surface of the developing roller is cleaned, and new developer is supplied. Incidentally, in order to enhance the transfer force of the developing roller 13, the surface of the developing roller may be sandblasted to form a minute recess. Further, in this example, the charging plate is brought into pressure contact with the developing roller, but the charging plate may be mounted so that a minute gap is formed between the charging plate and the developing roller.

FIG. 4 is a diagram showing the construction of the third embodiment of the one-component developing apparatus according to the present invention. The same members as those used in FIGS. 2 and 3 are designated by the same reference numerals for description. Charging roller
The first conductive sleeve roller 40 corresponding to the first developing roller is rotatably arranged so as to be opposed to 15 by a minute gap, and is rotated in the arrow direction by a driving device (not shown). Electrically ground. The developer sent between the charging roller 15 and the first sleeve roller 40 by the carrying bar 30 is transferred to a position facing the charging roller 15 by the rotational force of the first sleeve roller 40. Then, the discharge charge discharged from the charging roller 15 is charged to a positive polarity to form a uniformly charged developer layer on the surface of the first sleeve roller. A second developing roller which faces the conductive sleeve roller 40 shown in FIG. 1 and corresponds to a second developing roller.
The conductive sleeve roller 41 is placed and rotated in the direction of the arrow by a driving device (not shown). This second conductive sleeve roller acts as a developing roller,
The bias source 42 biases the negative polarity. The positively charged developer layer formed on the first sleeve roller 40 is electrostatically charged to the second sleeve roller side by the electric field formed between the first sleeve roller and the second sleeve roller. Shift to the target. At this time, the insufficiently charged developer particles on the first sleeve roller 40 cannot move to the second sleeve roller side, so that the surface of the second sleeve roller (developing roller) is charged to a certain level or more. Only the developer migrates to form a uniformly charged developer layer.
Then, the electrostatic latent image formed on the photosensitive drum 10 is developed by the developer layer formed on the second sleeve roller 41.

The present invention is not limited to the above-described embodiments, but various modifications can be made. For example, in the above-mentioned embodiments, the one-component non-magnetic developer has been described as an example, but it is of course applicable to the one-component magnetic developer of the insulating layer.

In the above-described embodiment, the example in which one charging roller or one charging plate is arranged with respect to the developing roller has been described.
It is also possible to arrange two or more charging rollers in multiple stages.

Further, as the developing roller, various types of developing rollers such as a brush roller having a large number of conductive fibers formed on the outer peripheral surface thereof and a developing roller having a conductive rubber layer formed on the outer peripheral surface thereof can be used.

Further, in the above-described embodiment, the case of regular development (positive) has been described as an example, but it is of course applicable to the case of reversal development. In the case of reversal development, a charge having the same polarity as that of the electrostatic latent image is applied to the developer, and a bias equal to or slightly higher than the potential of the image area is applied to the developing roller.

(Effects of the Invention) The effects of the present invention described above are summarized as follows.

(1) A certain discharge body is used from an electrode member and a porous insulating film formed on at least a part of its outer periphery, and the developer is forcibly charged to a desired polarity by the discharge charge discharged from this discharge body. Since the constitution is adopted, a substantially uniformly charged developer layer can be formed on the developing roller.

(2) A porous insulating film is formed on the surface of the electrode member where the discharge charge is generated, and since the porous insulating film functions as a protective layer for the electrode member where the discharge charge is generated, the discharge body is developed. Even if it is placed in the housing, the discharge can be stably maintained.

[Brief description of drawings]

FIG. 1 is a schematic view showing the charging principle of the present invention, FIGS. 2a to 2c are schematic sectional views showing the constitution of a first embodiment of a one-component developing apparatus according to the present invention, and FIGS. 3a and 3b are shown. FIG. 4 is a schematic sectional view showing the constitution of the second embodiment of the one-component developing device according to the present invention, and FIG. 4 is a schematic sectional view showing the constitution of the third embodiment. 10 ... Photosensitive drum, 11 ... Hopper 12 ... Conveyor bar, 13 ... Developing roller 15 ... Charging roller, 15a ... Electrode member 15b ... Porous insulating film 17 ... High voltage power supply, 20 ... Development Agent layer

Claims (4)

[Claims] 1. A developing roller, a hopper for containing a one-component developer, and supplying the one-component developer to the developing roller,
A discharge body having a porous insulating film formed on at least a part of the outer peripheral surface of the electrode member and the electrode member, which is arranged to face the developing roller, and a support for supporting the discharge body in an electrically insulated state. A member and a power supply device for applying a discharge voltage to the electrode member, and a developer supplied onto the developing roller by discharge charges emitted from the surface of the electrode member through the holes of the porous insulating film. A one-component developing device, which is configured to be charged to a desired polarity. 2. The developing roller is a first developing roller,
A second developing roller is arranged so as to face the first developing roller, a potential difference is applied between the second developing roller and the first developing roller, and a charged developer formed on the first developing roller. The layer is moved to the side of the second developing roller, and the electrostatic latent image formed on the image forming member is visualized by the developer layer formed on the second developing roller. The one-component developing device according to claim 1. 3. The one-component developing device according to claim 1, wherein the discharge body is formed in a roller shape or a plate shape. 4. The one-component developing device according to claim 1, wherein the power supply device outputs a DC voltage or a voltage in which an AC voltage is superimposed on the DC voltage. .