JP2001318526A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a developing roller to fully utilize the developer transporting function and the electrostatic charging function of the developer and the discharge preventing function of developing bias, and to make the developing roller simple and inexpensive. SOLUTION: Ruggedness is formed by performing sand blasting treatment on a surface of the developing roller 4 to be in contact with a photoreceptor 2, and moreover the rugged surface of this developing roller 4 is anodized. Moreover, on the developing roller 4, the developing bias of DC current superimposed on AC current is applied. Thus, the developing roller 4 surely utilize the transporting function of the developer, the electrostatic charging function of the developer, and the static discharge preventive function of the developing bias, and moreover, the developing roller 4 can be formed from a metallic roller such as aluminum at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a developing device used for an image forming apparatus such as an electrostatic copying machine or a printer, and more particularly, to a developing roller which carries a developer and transports it to a latent image carrier. Belongs to the technical field of a contact developing type developing device that comes into contact with a latent image carrier.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrostatic copying machine or a printer, an electrostatic latent image carried on a latent image carrier such as a photoreceptor is developed by a developer of a developing device and then developed. Transfer the image on the latent image carrier to a recording medium such as paper,
Further, by fixing the transferred image transferred to the recording medium,
You get an image.

As a conventional developing device in such an image forming apparatus, there is a contact developing type developing device in which a developing roller that carries a developer and conveys the developer to a latent image carrier contacts the latent image carrier. In this contact developing type developing device, a charged one-component developer is conveyed by a developing roller toward a latent image carrier with which the developing roller comes into contact, and the one-component developer transfers the charged one-component developer onto the latent image carrier. The electrostatic latent image is developed. In this case, an aluminum or iron-based metal roller is used as the developing roller. In particular, an aluminum metal roller is often used because processing is easy and inexpensive.

[0004] By the way, the developing roller in the developing device has functions of transporting the developer, charging the developer,
Also, it is required to prevent the discharge of the developing bias. Therefore, in order to improve the transportability of the developer and the chargeability of the developer, conventionally, the surface of the metal roller is subjected to sandblasting to form irregularities, and the irregularities are subjected to metal plating such as nickel plating. Japanese Patent Application Publication No. 6-46331 proposes such a carrier roll (that is, a developing roller). According to the carrier roll disclosed in this official gazette, the uneven surface formed on the surface of the carrier roll can dynamically increase the developer transfer ability,
The transportability of the developer is improved. In addition, the contact area with the developer increases due to the uneven surface, so that the chargeability of the developer is improved. By performing metal plating on the uneven surface of the metal roller, the wear resistance of the uneven surface of the metal roller is improved.

Further, in order to prevent the discharge of the developing bias, a developing roller having a specific resistance set to a predetermined value has been conventionally proposed. For example, a conductive film is formed on the inner surface of a cylindrical rigid body having a specific resistance in the range of 10 ⁴ to 10 ¹² Ωcm, or a conductive film of 10 ⁷ Ωcm or less is formed on the inner surface of the resin. The carrier (that is, the developing roller) of the non-magnetic one-component toner coated with the conductive paint is a
No. 6226 has proposed this. Moreover, the specific resistance 1
0 ⁴ 10 ¹² semiconductive layer thickness which is formed of a ceramic such as alumina is 100~1000μm of [Omega] cm, the toner carrying member of a non-magnetic one-component toner formed on the surface (i.e. the developing roller) is No. 2,705,090 Has been proposed. According to the non-magnetic one-component toner carrier disclosed in these publications, since at least the surface has a predetermined resistance, discharge of the developing bias can be effectively prevented and image defects can be prevented. .

On the other hand, as disclosed in Japanese Patent Publication No. Hei 2-26226 and Japanese Patent No. 2705090, a conventional developing device uses a developing bias in which an AC voltage is superimposed on a DC voltage. In order to prevent the toner from adhering to the non-image portion of the latent image carrier (so-called fogging), to provide an appropriate edge effect, and to improve the gradation.

[0007]

However, in the case of the support roll disclosed in Japanese Patent Publication No. 464631/1994, a metal plating process is performed on the surface on which unevenness is formed by sandblasting. Due to this plating process, a plating material is applied on the uneven surface. For this reason, the sharp unevenness due to the sand blasting process is deformed by the plating material, and the protrusions, that is, the edges (ridgelines) of the borders between adjacent concaves are broken, and the unevenness becomes unclear. Therefore, even if sharp irregularities are formed by sandblasting and the abrasion resistance of the irregular surface is improved, the metal plating makes the irregularities unclear. However, there is a problem that the effect of improving the performance cannot be sufficiently and reliably obtained.

[0008] Further, in the carrier disclosed in Japanese Patent Publication No. Hei 2-26226, which is formed of a resin in which conductive powder is dispersed, since the conductive powder is dispersed, it is affected by the dispersion state. Therefore, it is difficult to make the surface of the carrier have uniform resistance, and there is a problem that density unevenness occurs in an image. Further, 100-100 made of ceramics disclosed in Japanese Patent No. 2705090.
In a toner carrier having a 0 μm semiconductive layer formed thereon, the semiconductive layer melts the ceramic particles by arc discharge,
Since this is formed by spraying it on the base material of the toner carrier, there is a problem that the production is troublesome and the cost is high.

In addition, it is desired that the developing roller has the three functions of the above-mentioned items (1) to (3) more reliably. Therefore, the technical matters described in the above-mentioned publications are combined. By these three
It is conceivable to provide the developing roller with two functions. However, when the developing roller is provided with the above-described three functions by combining the components described in the respective publications, there are the following problems.

[0010] That is, when it is attempted to combine the one described in Japanese Patent Publication No. 462631/1994 with the one described in Japanese Patent Publication No. 2-226226, the conductive powder described in Japanese Patent Publication No. 2-22626 is dispersed. The carrier formed of resin is not a metal carrier, and it is difficult to perform the process of forming unevenness by sandblasting and improving the wear resistance of the uneven surface described in JP-B-6-46331. . Therefore, Japanese Patent Publication No. 6-46331
Japanese Patent Publication No. 2-26226 cannot be combined with that described in Japanese Patent Publication No. 2-226226, and it is extremely difficult to provide the above three functions to the developing roller more reliably.

[0011] Further, when an attempt is made to combine the structure described in Japanese Patent Publication No. 6-46331 with the structure described in Japanese Patent No. 2705090, the uneven surface of the structure described in Japanese Patent Publication No. The semiconductor device described in Japanese Patent Application Laid-Open No. H11-216, will form a semiconductive layer made of ceramic melted by arc discharge. For this reason, similarly to the case where metal plating is applied to the uneven surface described in Japanese Patent Publication No. 6-46331, the edges (ridge lines) at the boundaries between adjacent concave portions are distorted and the unevenness becomes unclear. There's a problem. Therefore, Japanese Patent Publication No. 6-46331
It cannot be combined with the one described in Japanese Patent No. 2705090, and in this case as well, it is extremely difficult to make the above-mentioned three functions more reliably provided by the developing roller. Moreover, since the developing devices described in the above publications are all non-contact developing type developing devices, they are directly applied to a contact developing type developing device in which a developing roller contacts a latent image carrier. It is not possible.

The present invention has been made in view of such circumstances, and has as its object three functions: a developer transport function, a developer charging function, and a developing bias discharge preventing function.
It is an object of the present invention to provide a developing device of a contact developing type which is provided with a developing roller capable of more reliably performing the two functions, and which can easily and inexpensively form the developing roller.

[0013]

In order to solve this problem, according to the first aspect of the present invention, a developing roller for carrying a developer on a surface and transporting the developer to a latent image carrier is brought into contact with the latent image carrier. In the contact-developing type developing device provided, the developing roller is formed of a metal roller, and the metal roller has at least a surface formed by a sand blast process on a surface of a developer carrying region, and further has at least A feature of the present invention is that the uneven portion is subjected to an alumite treatment. The invention according to claim 2 is characterized in that a developing bias is applied to the developing roller, and the developing bias is formed by superimposing an alternating current on a direct current.

Further, according to a third aspect of the present invention, the potential of the developing bias is set to a potential side set in an image area of the latent image carrier from a potential set in a non-image area of the latent image carrier. The potential is not set on the opposite side of the potential set in the image area of the latent image carrier beyond the potential set in the non-image area of the latent image carrier. Further, the invention according to claim 4 is characterized in that the developer is a non-magnetic one-component toner in which an external additive having a predetermined hardness is attached to toner particles, and the hardness of the surface of the metal roller is the external additive. It is characterized by being set lower than the hardness of the agent. Furthermore,
The invention according to claim 5 is characterized in that the peripheral speed of the developing roller is set higher than the peripheral speed of the latent image carrier. Further, the invention according to claim 6 is characterized in that the sphericity of the particles of the developer is set to 0.9 to 1 as a practical sphericity of Wardel.

[0015]

In the developing device of the present invention having the above-described structure, at least the surface of the developer-carrying region of the metal roller constituting the developing roller is subjected to sandblasting to form an edge (ridge) at a boundary between adjacent concave portions. Are clearly formed. Then, an alumite treatment (anodizing treatment) is performed on the uneven portion of the metal roller, and an oxide film is formed on the surface of the uneven portion of the metal roller. At this time, most of the electrolysis reaction due to the alumite treatment penetrates from the surface of the metal roller to the inside, so that the thickness of the oxide film formed on the surface is small. For this reason, even if an oxide film is formed on the surface of the metal roller, the uneven shape due to the sandblasting process is not hindered by the oxide film, and the uneven shape after the alumite treatment is substantially maintained in the uneven shape due to the sandblasting process. Become so. That is, the edge (ridge line) at the boundary between the adjacent concave portions is clearly formed.
Therefore, the transport of the developer is further ensured by the edge (ridge line) effect in the uneven shape of the developing roller surface, and the transportability of the developer is improved.

Further, since the edges (ridges) in the uneven shape by the sandblasting process are maintained, the contact area of the developing roller with the developer particles increases.
As a result, the friction between the developing roller and the developer particles is sufficiently performed, and the developer particles are effectively frictionally charged. Therefore, the chargeability of the developer is improved.

Further, since the surface of the developing roller is hardened by the oxide film formed by the alumite treatment, both the wear resistance and the mechanical strength of the developing roller are improved. In that case, while making the aqueous solution of electrolysis in the alumite treatment a relatively low temperature and performing the treatment slowly,
The surface of the developing roller becomes even harder.

In addition, the oxide film has a cell structure including a thick porous layer having a large number of fine pores and a dense and very thin active layer. In this case, since the active layer has electric resistance, an electric resistance layer is formed by alumite treatment on the surface of the metal roller having a relatively low electric resistance, and the metal roller has a predetermined electric resistance. At this time, since the surface of the metal roller is uniformly alumite-treated, the electric resistance can be more uniformly obtained over the entire surface of the alumite-treated portion of the metal roller. This eliminates the need to use a special material having a predetermined electrical resistance in advance as a material for the developing roller.
It can be formed inexpensively and easily from a metal roller having a predetermined size and a uniform electric resistance.

In particular, in the second aspect of the present invention, a developing bias is applied to the developing roller. However, since the electric resistance layer is formed on the surface of the developing roller by alumite treatment, the developing roller is attached to the latent image carrier. Even if they are in contact, the discharge of the developing bias from the developing roller to the latent image carrier is effectively prevented.

Further, the developing bias applied to the developing roller is formed by superimposing alternating current on direct current. By appropriately controlling the alternating current, it is possible to prevent the discharge of the developing bias to the latent image carrier, and in addition to the above-described prevention of the discharging of the developing bias due to the electric resistance, the discharging of the developing bias is more effective. Will be prevented.
In particular, according to the third aspect of the present invention, the potential of the developing bias is set to be closer to the potential set in the image area of the latent image carrier than the potential set in the non-image area of the latent image carrier. Discharge of the developing bias from the developing roller to the latent image carrier is more effectively prevented, and the adhesion of the developer to the non-image area of the latent image carrier is suppressed, thereby preventing the developer from fogging. Is done.

Further, since the developing roller has a uniform electric resistance of a predetermined magnitude, it is possible to prevent the injection of excessive charges into the developer due to the developing bias. In particular, in a contact developing type developing device in which the developing roller contacts the latent image carrier as in the present invention, the pressure of the developer particles pinched between the latent image carrier and the developing roller increases. If the pressure is large, excess charge injection into the developer is promoted, and such uniform electric resistance prevents excess charge injection into the developer more effectively. Thus, in the developing device of the present invention, the developing roller more reliably has the three functions described above. Therefore, the developing device of the present invention can obtain a high-quality image free of image defects such as uneven density for a long period of time. Further, by superimposing the alternating current, an appropriate edge effect is given to the image, and a uniform intermediate color of the image is reproduced, and the gradation is improved.

Further, in the present invention, the hardness of the surface of the metal roller is set lower than the hardness of the external additive of the toner. As a result, the unevenness of the surface of the developing roller is slightly scraped or slightly chipped by the friction of the external additive of the toner, so that the adhesion of the toner to the developing roller is suppressed and the filming of the developing roller is prevented. In addition, a new edge (ridge line) in the unevenness is formed due to the lack of the unevenness.

Further, in the fifth aspect of the present invention, since the peripheral speed of the developing roller is set to be higher than the peripheral speed of the latent image carrier, the peripheral speed of the developing roller contacts the latent image carrier by a speed difference. The particles of the developer roll and rub, so that the developer is effectively recharged. As a result, the charge amount of the developer having a small charge amount increases, so that the developer adhered to the non-image area of the latent image carrier is reliably collected toward the developing roller and the image area of the latent image carrier is At the position where the developer should adhere to the original position,
The so-called image dust, which is a shift in the position where the developer is attached, is prevented.

Further, in the invention according to claim 6, the sphericity of the particles of the developer is 0.9 to less than the Wardell's practical sphericity.
Since it is set to 1, the developer particles are more reliably rolled and rubbed, and the developer is more effectively recharged. This ensures that the developer in the non-image area of the latent image carrier is recovered toward the developing roller in the same manner as in the case of the fifth aspect of the invention, and that the image in the image area of the latent image carrier is dusted. Is prevented, and a high-definition latent image on the latent image carrier is faithfully visualized. Since the porous layer has a large number of micropores, foreign matter is easily attached thereto and is easily corroded. Therefore, by performing a sealing treatment for sealing the large number of micropores, the porous layer is inactivated and the environmental stability is improved. Become like

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an example of an embodiment of the developing device of the present invention. As shown in FIG. 1, a developing device 1 of this example includes a photosensitive member 2 as a latent image carrier on which an electrostatic latent image is formed, and a toner 3 as a developer.
, A supply roller 5 for supplying toner 3 to the developing roller 4, and regulating the toner 3 supplied from the supply roller 5 and conveyed by the developing roller 4. A regulating member 6. The developing device 1 is a contact developing type developing device in which the developing roller 4 is in contact with the photoconductor 2, and the peripheral speed of the developing roller 4 is set to be higher than the peripheral speed of the photoconductor 2 (peripheral speed). Speed ratio = peripheral speed of developing roller 4 / peripheral speed of photoconductor 2> 1). The supply roller 5 having a conductive or insulating elastic body surface is in contact with the developing roller 4, and the regulating member 6 is constantly pressed against the developing roller 4 while being rotationally driven at a predetermined peripheral speed ratio. .

The developing roller 4 is composed of a metal roller made of aluminum, and at least the toner carrying area (toner transport area) of the surface of the metal roller is subjected to sandblasting. By this sandblasting process,
An uneven surface is formed on the surface of the metal roller. As shown in FIG. 2, the convex and concave portions, that is, the edges (ridge lines) 4b at the boundaries between the concave portions 4a adjacent to each other are clearly formed.

Further, alumite treatment is applied to the sand blasted portion of the metal roller. When the alumite treatment is performed on the surface of the metal roller as described above, a reaction of electrolysis permeates into the metal roller, so that a relatively thin oxide film is formed on the surface of the metal roller. Since the oxide film has a predetermined electric resistance and a predetermined hardness, the surface portion of the aluminum metal roller having an extremely low electric resistance has a predetermined electric resistance and a predetermined hardness. At this time, the aqueous solution of electrolysis in the alumite treatment is brought to a relatively low temperature, and by performing the treatment slowly,
The surface of the developing roller 4 can be further hardened.

As described above, even if the surface of the metal roller is subjected to an alumite treatment to form an oxide film, the oxide film is extremely thin, so that the uneven surface formed by sandblasting is impeded by the oxide film. Not changed, almost unchanged. Therefore, as shown in FIG. 3, the unevenness of the surface of the metal roller after the alumite treatment is almost the same as that of the sandblasting. Since the oxide film has a porous layer composed of a large number of fine pores, a sealing treatment for sealing the large number of the fine pores is performed to inactivate the porous layer, so that foreign substances are hardly adhered and hardly corroded. And environmental stability has been improved.

Further, as shown in FIG.
One developing roller 4 has a developing bag in the same manner as a conventional developing device.
The bias is applied. In that case, the developing device of this example
In 1, the DC of the DC power supply 7 and the AC of the AC power supply 8 are superimposed.
The applied developing bias is applied to the developing roller 4.
As shown in FIG. 4, the potential of the image portion of the photoconductor 2 is set to V_onTo
(In the illustrated example, ground, that is, 0 V), and
The potential of the non-image area is V_o(In the example shown, negative voltage)
The developing bias potential V of the developing roller 4 _dIs
Its maximum value V_dmaxIs the potential V of the image portion_onIs set equal to
And its minimum value V_dminIs the potential V of the non-image portion
_oIt is set larger. That is, the developing bias
Potential V_dIs the potential V of the non-image portion_oThe potential V of the image portion_on~ side
Is set to a predetermined value, and the potential V of the non-image portion is set to_oPainting beyond
Image portion potential V_onIs not set on the other side. This
The toner 3 particles on the developing roller 4
Adhering to the part is more effectively suppressed.

Further, the toner 3 used in the developing device 1 of this embodiment is formed as a non-magnetic one-component toner in which an external additive made of relatively hard silica is attached to toner base particles made of a relatively soft polyester resin. ing. In this case, the hardness (hardness) of the surface of the developing roller 4 is set lower than the hardness (hardness) of the external additive of the toner 3. More specifically, the hardness of the surface of the developing roller 4 is set to such a degree that the irregularities on the surface of the developing roller 4 are reduced to some extent but not excessively reduced with respect to the hardness of the external additive of the toner 3. .

In addition, the toner 3 has a particle sphericity of 0.9 to 1, which is the practical sphericity of Wadel, and
It is suitable for faithfully visualizing a high-definition latent image on the photoconductor 2. The practical spherical degree of Wardell of the toner 3 is represented by the ratio of the diameter of a circle having an area equal to the projected area of the particle in the projected image of the toner particle to the diameter of the smallest circle circumscribing the projected image of the particle. It is a numerical value.

The reason that the degree of sphericity of the toner 3 is suitable for faithful visualization of a high-definition latent image is proposed by the inventor of the present invention and has been filed by the present applicant. 9-
Since it is disclosed in Japanese Patent Publication No. 31544, it can be easily understood by referring to this publication. To put it simply, the reason is that the toner 3 on the developing roller 4 is developed by the photoreceptor in the developing operation by making the shape of the toner 3 approximate to a true sphere with a practical sphericality of 0.9 to 0.9-1. When the toner 3 adheres to the photosensitive member 2 according to its potential, the particles of the toner 3 easily form a densely packed adhesion layer on the photoreceptor 2, and faithfully and clearly reproduce the image contour portion of the latent image details. That is because The practical degree of sphericality of Wardell can be measured using an image processing apparatus equipped with an optical microscope (manufactured by Apionix Co.), and the measuring procedure is described in the above-mentioned JP-A-9-31544. The description is omitted because it can be easily understood by referring to this publication.

In the developing device 1 of this embodiment having such a configuration, the toner 3 supplied from the supply roller 5 onto the developing roller 4 is regulated by the developing roller 4 which rotates counterclockwise in FIG. 6 is conveyed. The amount of toner 3 that has reached the regulating member 6 is regulated by the regulating member 6 to be conveyed toward the photoconductor 2, and excess toner is returned to the supply roller 5. Further, the toner 3 that has passed through the regulating member 6 forms a thin toner layer 3 a having a predetermined thickness on the developing roller 4. The thinned toner 3 is conveyed toward the photoreceptor 2 by the developing roller 4, and the toner 3
As a result, the electrostatic latent image on the photoconductor 2 is developed, and a toner image is formed on the photoconductor 2.

According to the developing device 1 of this embodiment, it is possible to maintain the unevenness of the surface of the developing roller 4 after the alumite treatment to be substantially the same as the unevenness by sandblasting. That is, the unevenness after the alumite treatment can be a shape in which edges (ridges) are clearly formed.
Therefore, the toner 3 can be transported more reliably by the edge (ridge line) effect in the uneven shape of the surface of the developing roller 4, and the transportability of the toner 3 can be improved.

Further, since the edge (ridge line) in the uneven shape due to the sand blasting process is maintained, the contact area of the developing roller 4 with the toner 3 particles can be increased.
Thereby, the friction between the developing roller 4 and the particles of the toner 3 is sufficiently performed, and the particles of the toner 3 can be effectively frictionally charged. Therefore, the chargeability of the toner 3 can be improved. Further, since the surface of the developing roller 4 is hardened by the oxide film formed by the alumite treatment, both the wear resistance and the mechanical strength of the developing roller 4 can be improved.

Further, an oxide film formed by alumite treatment
Since the electric resistance layer is formed on the surface of the aluminum metal roller having a relatively low electric resistance, the metal roller can have a predetermined electric resistance. At this time, since the surface of the metal roller is uniformly alumite-treated, electric resistance can be obtained more uniformly over the entire surface of the alumite-treated portion of the metal roller. Accordingly, it is not necessary to use a special material having a predetermined electric resistance in advance as a material of the developing roller 4, so that the developing roller can be formed inexpensively and easily from a metal having a predetermined size and a uniform electric resistance. Become like

Further, since the developing roller 4 has a uniform electrical resistance of a predetermined magnitude, it is possible to prevent the injection of excessive charges into the toner 3 by the developing bias. In particular,
In the contact developing type developing device 1 in which the developing roller 4 comes into contact with the photosensitive member 2 as in this example, the photosensitive member 2 and the developing roller 4
The pressure of the particles of the toner 3 sandwiched between the toner and the toner becomes large. However, if this pressure is large, the injection of excess charge into the toner 3 is promoted. Effective injection of excessive charges into the toner 3 is effectively prevented. Thus, the developing roller 4 of the developing device 1 of this embodiment can more reliably have the three functions described above. Therefore, according to the developing device 1 of this example,
A high-quality image free from image defects such as uneven density can be obtained for a long period of time.

Further, since a developing bias in which an alternating current is superimposed on a direct current is applied to the developing roller 4, by appropriately controlling the developing bias, the discharging of the developing bias from the developing roller can be prevented. In particular, since the maximum potential of the developing bias is set lower than the potential set in the non-image area of the photoconductor, discharge of the developing bias can be more effectively prevented, and toner adheres to the non-image area of the photoconductor. Can be suppressed, and fogging of the toner can be prevented.

In addition, by superimposing an alternating current on a direct current, an appropriate edge effect can be imparted to the image, a uniform intermediate color of the image can be reproduced, and the gradation can be improved. Further, since the hardness of the surface of the developing roller 4 is set lower than the hardness of the external additive of the toner 3, the unevenness of the surface of the developing roller 4 is slightly removed by friction with the external additive of the toner 3. Alternatively, the developing roller 4
It is possible to reliably remove the toner 3 adhered to the surface. Accordingly, the adhesion of the toner 3 to the developing roller 4 can be suppressed to prevent filming of the developing roller 4, and a new uneven edge (ridge line) can be formed by lacking the unevenness. Become.

Further, since the peripheral speed of the developing roller 4 is set to be higher than the peripheral speed of the photosensitive member 2, the particles of the toner 3 roll due to the speed difference in the developing section where the developing roller 4 contacts the photosensitive member 2. By rubbing, the toner 3 can be effectively recharged. As a result, the charge amount of the toner having a small charge amount can be increased, so that the toner adhered to the non-image area of the photoconductor 2 can be reliably collected toward the developing roller 4 and the toner 3 can be collected in the image area of the photoconductor 2. The toner can be reliably adhered to the position where it should originally adhere, and the toner 3
So that the so-called image dust, which is a shift in the attachment position, can be prevented.

In addition, since the spherical degree of toner 3 is set to 0.9 to 1 as a practical spherical degree of Wardel and is closer to a true sphere, the particles of toner 3 roll more reliably. As a result, the toner 3 can be recharged even more effectively. As a result, the developer in the non-image area of the photoconductor 2 can be reliably collected toward the developing roller 4 in the same manner as described above, and image dust in the image area of the photoconductor 2 can be prevented. High-precision latent image can be faithfully visualized.

[0042]

As is clear from the above description, according to the developing apparatus of the present invention, the uneven shape of the surface of the developing roller after the alumite treatment is formed with the same clear edge (ridge line) as the uneven shape by the sandblasting process. It can be maintained in the uneven shape having. Therefore, the developer can be transported more reliably by the edge (ridge line) effect in the uneven shape of the surface of the developing roller, and the transportability of the developer can be improved.

Further, since the edge (ridge line) in the uneven shape by the sand blasting process can be maintained, the contact area of the developing roller with the developer particles can be increased. Thereby, friction between the developing roller and the developer particles can be sufficiently performed, and the developer particles can be effectively frictionally charged. Therefore, the chargeability of the developer can be improved.

Further, since the surface of the developing roller is hardened by the oxide film formed by the alumite treatment, both the wear resistance and the mechanical strength of the developing roller can be improved. Furthermore,
Since the electrical resistance layer is formed on the surface of the aluminum metal roller having a relatively small electrical resistance by an oxide film formed by alumite treatment, the metal roller can have a predetermined electrical resistance. At this time, since the surface of the metal roller can be alumite-treated uniformly, electric resistance can be obtained more uniformly over the entire alumite-treated portion of the metal roller. This eliminates the need to use a special material having a predetermined electric resistance in advance as a material of the developing roller, so that the developing roller can be formed inexpensively and easily from a metal having a predetermined size and a uniform electric resistance. become.

In particular, when a developing bias is applied to the developing roller, an electric resistance layer is formed on the surface of the developing roller by alumite treatment, so that even if the developing roller is in contact with the latent image carrier, the latent image can be transferred from the developing roller. The discharge of the developing bias to the carrier can be effectively prevented.

Since a developing bias in which alternating current is superimposed on direct current is applied to the developing roller, discharge of the developing bias from the developing roller can be prevented by appropriately controlling the developing bias. In particular, since the potential of the developing bias is set to be closer to the potential set in the image area of the latent image carrier than the potential set in the non-image area of the latent image carrier, The discharge of the development bias to the body can be more effectively prevented,
The developer can be prevented from adhering to the non-image area of the photoconductor,
Fogging of the developer can be prevented.

Further, since the developing roller has a uniform electric resistance of a predetermined magnitude, it is possible to prevent the injection of excessive charges into the developer due to the developing bias. In particular, in a contact developing type developing device in which the developing roller contacts the latent image carrier as in the present invention, the pressure of the developer particles pinched between the latent image carrier and the developing roller increases. If the pressure is large, excessive charge injection into the developer is promoted. Therefore, such uniform electric resistance can prevent the excessive charge injection into the developer more effectively.

Thus, the developing roller of the developing device of the present invention can more reliably have the above three functions. Therefore, according to the developing device of the present invention,
A high-quality image free from image defects such as uneven density can be obtained for a long period of time. Further, by superimposing an alternating current on a direct current, an appropriate edge effect can be given to the image, a uniform intermediate color of the image can be restricted, and the gradation can be improved.

Further, the hardness of the surface of the developing roller is set lower than the hardness of the external additive of the toner, so that the irregularities on the surface of the developing roller are slightly scraped off or slightly chipped by friction with the external additive of the toner. With this configuration, it is possible to prevent the toner from adhering to the developing roller and prevent filming of the developing roller, and to form a new edge (ridge line) in the unevenness by lacking the unevenness.

Further, according to the developing device of the present invention, since the peripheral speed of the developing roller is set to be higher than the peripheral speed of the latent image carrier, the speed difference in the developing section where the developing roller comes into contact with the latent image carrier is set. By rolling and rubbing the developer particles,
The toner can be effectively recharged. As a result, the charge amount of the toner having a small charge amount can be increased.
The toner adhering to the non-image area of the latent image carrier can be reliably collected toward the developing roller, and the toner can be surely adhered to the position where the toner should originally adhere in the image area of the latent image carrier. It is possible to prevent so-called image dust, which is a shift in the attachment position.

Further, since the spherical degree of the developer particles is set to 0.9-1 as the practical spherical degree of Wardel, the developer particles can be more reliably rolled and rubbed. As a result, the developer can be recharged more effectively. As a result, the developer in the non-image area of the latent image carrier can be reliably collected toward the developing roller in the same manner as in the case of the fifth aspect of the invention, and the image dust in the image area of the latent image carrier can be reduced. And a high-definition latent image on the latent image carrier can be faithfully visualized.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an example of an embodiment of a developing device of the present invention.

FIG. 2 is an enlarged view of a concavo-convex surface on a developing roller formed by sandblasting with a microscope.

FIG. 3 is an enlarged view of a concavo-convex surface on a developing roller after alumite processing by a microscope.

FIG. 4 is a diagram illustrating a developing bias applied to a developing roller, on which an alternating current is superimposed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Developing device, 2 ... Photoconductor (latent image carrier), 3 ... Toner (developer), 4 ... Developing roller, 5 ... Supply roller, 6 ... Regulatory member, 7 ... DC power supply, 8 ... AC power supply, V _on : the potential of the image portion of the photoconductor, V _o : the potential of the non-image portion of the photoconductor, V _d : the developing bias potential, V _dmax : the maximum value of the developing bias potential,
V _dmin : minimum value of the developing bias potential

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[Procedure amendment]

[Submission date] April 26, 2001 (2001.4.2
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

[0007]

However, in the case of the support roll disclosed in Japanese Patent Publication No. 464631/1994, a metal plating process is performed on the surface on which unevenness is formed by sandblasting. By this plating process, a plating material is applied on the uneven surface. For this reason, the sharp unevenness due to the sand blasting process is deformed by the plating material, and the protrusions, that is, the edges (ridgelines) of the borders between adjacent concaves are broken, and the unevenness becomes unclear. Therefore, even if sharp irregularities are formed by sandblasting and the abrasion resistance of the irregular surface is improved, the metal plating makes the irregularities unclear. However, there is a problem that the effect of improving the performance cannot be sufficiently and reliably obtained.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram schematically showing an example of an embodiment of the developing device of the present invention. As shown in FIG. 1, a developing device 1 of this example includes a photosensitive member 2 as a latent image carrier on which an electrostatic latent image is formed, and a toner 3 as a developer.
, A supply roller 5 for supplying toner 3 to the developing roller 4, and regulating the toner 3 supplied from the supply roller 5 and conveyed by the developing roller 4. A regulating member 6. The developing device 1 is a contact developing type developing device in which the developing roller 4 is in contact with the photoconductor 2, and the peripheral speed of the developing roller 4 is set to be higher than the peripheral speed of the photoconductor 2 (peripheral speed). Speed ratio = peripheral speed of developing roller 4 / peripheral speed of photoconductor 2> 1).

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 375 G03G 9/08 375 15/06 101 15/06 101 F term (Reference) 2H005 AA08 AA15 CB13 FA07 2H073 AA03 BA04 BA23 BA45 CA02 2H077 AC04 AD02 AD06 AD36 AE04 BA03 EA14 EA15 FA01 FA12

Claims (6)

[Claims] 1. A contact-developing type developing device in which a developing roller for carrying a developer on a surface thereof and transporting the developer to a latent image carrier is provided in contact with the latent image carrier. This metal roller, at least the surface of the developer carrying area is formed with irregularities by sandblasting,
A developing device, wherein at least an uneven portion is subjected to an alumite treatment. 2. The developing device according to claim 1, wherein a developing bias is applied to the developing roller, and the developing bias is formed by superimposing an alternating current on a direct current. 3. A potential of the developing bias is set to a potential side set in an image area of the latent image carrier from a potential set in a non-image area of the latent image carrier, and the potential of the latent image carrier is set. 3. The developing device according to claim 2, wherein the potential is not set on a side opposite to a potential set in an image area of the latent image carrier beyond a potential set in a non-image area. 4. The developer is a non-magnetic one-component toner in which an external additive having a predetermined hardness is attached to toner particles, and the hardness of the surface of the metal roller is lower than the hardness of the external additive. The developing device according to claim 1, wherein the setting is set. 5. The developing device according to claim 1, wherein a peripheral speed of said developing roller is set higher than a peripheral speed of said latent image carrier. 6. The developing device according to claim 1, wherein the spherical degree of the particles of the developer is set to 0.9 to 1 as a practical spherical degree of Wardell. .