JPH1124388A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable developing characteristic by performing binary development through the use of a developer carrier in which specific grains are dispersed in the front layer of a substrate made of a specific conductive material so as to expose at least a part of the specific grains to the surface of the front layer. SOLUTION: The substrate 3a of a developer carrier is made of a conductive material whose volume resistivity is <=10<5> Ω.cm and also binary development is performed by using the developer carrier in which grains 8 which are >=10<6> Ω.cm in the volume resistivity and <=20 μm in the grain diameter (a) are dispersed on the front layer of the substrate 3a, so as to expose at least a part of the grains 8 to the surface 3b of the front layer. Therefore, a developing electric field between a latent image on a photoreceptor drum and the developer carrier can be stressed. Thus, even if a developing potential is changed, the concentration of the developing electric field on an optical writing dot on the photoreceptor drum is mitigated. Further, the volume resistivity of the grains 8 dispersed on the front layer is increased to suppress the concentration and also a developer supplied from a developer supplying member is triboelectrified to increase the supply rate of the developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as a copying machine, a facsimile, a printer, and the like.
That is, the present invention relates to a developing device for performing a binary image forming process development of a method of developing an optically written dot on the photoreceptor by two values, that is, adhesion and non-adhesion of toner as a one-component developer.

[0002]

2. Description of the Related Art Conventionally, a developing device of this type includes a developing roller as a developer carrying member for carrying and transporting a toner as a one-component developer in a developing area facing a photoreceptor as a latent image carrying member. A doctor as a thin layer forming member for forming the toner carried on the developing roller into a uniform thin layer, a toner supplying roller as a developer supplying member for supplying toner to the developing roller, and the toner supplying roller. A toner container as a developer accommodating case for accommodating the supplied toner, a bias for forming an appropriate electric field in the developing area is applied to the developing roller, and a bias is applied between the developing roller and the photosensitive member in the developing area. By reciprocating the toner on the surface of the developing roller, the optical writing dots written on the photoreceptor by the optical writing means (not shown) can be attached or non-adhered. A developing device of the non-contact development is a binary imaging process developing method is known by the binary.

On the other hand, in a general ordinary developing method,
With the aim of providing a developing device capable of stably obtaining a uniform and sufficient image without developing a sleeve ghost or fading due to development regardless of a low-humidity and high-humidity environment. A developing device that develops the latent image by using a one-component developer carried on a developer carrier to form a visible image, wherein a resin coating layer containing at least crystalline graphite is formed on the surface of the developer carrier. A developing device characterized in that the surface of the developer carrying member is polished to expose crystalline graphite on the surface. ”(Japanese Patent Laid-Open No. 4-284).
No. 474 (hereinafter referred to as "known example 1").

[0004] In a general ordinary developing method,
For the purpose of providing a high toner chargeability, “a conductive roll having a conductive layer formed on the outer periphery of a shaft body, wherein the conductive layer is contained in a phenolic resin binder and contains a component (A): A phenolic resin cured powder having a particle size of 20 μm or less, and a conductive paint containing at least a component (A) of component (B): a polyfluorinated ethylene-based powder having a particle size of 20 μm or less, and a conductive metal oxide powder dispersed therein. The conductive roll is characterized in that it has been performed (Japanese Patent Application Laid-Open No. 4-284475 (hereinafter referred to as "known example 2")).

Further, in a general ordinary developing method,
Even when used for a long time, the wear resistance of the surface layer of the developer carrying member is maintained, the surface roughness of the stable film and the charge-imparting property of the toner are suppressed, the fusion of the toner to the carrier is suppressed, and the image density is reduced and the sleeve is reduced. For the purpose of providing a developer carrier in which ghosts are less likely to occur, `` In a developer carrier that carries a one-component developer for developing a latent image formed on an image carrier,
A developer carrier, wherein a coating layer containing at least conductive spherical particles and low surface energy spherical particles in a binder resin is provided on the surface of the developer carrier. (Japanese Patent Laid-Open No. 8-179616 (hereinafter referred to as "known example 3")).

[0006]

However, in the developing device of the conventional binary image forming process developing system, the binary developing is performed by a non-contact developing method using a one-component toner with respect to a threshold value of a constant potential of the photosensitive member. When the number of optical writing dots per unit length of the optical writing dots at the time of optical writing in the main scanning direction is 600 [dpi], for example, In the case of dense dots in which only two dots are available for writing, if the development potential is changed, the dot area of the visible image on the photoconductor changes.

That is, in the current developing device, the volume resistivity of the conductor of the developing roller is 10 ⁵ [Ω · c].
m] or less, and when the resolving power of the latent image formed on the photoconductor is increased, a sufficient developing electric field is not obtained. Therefore, when such dense dots are visualized, for example, Vpp = 1200 [V] and F (frequency) = 2 [k]
[Hz] of a sine wave is applied to the developing roller to emphasize the developing electric field and sufficiently develop the dense dots. Thus, the AC applied to the developing roller
By changing the bias condition to enhance the developing electric field, it becomes possible to sufficiently reproduce the visible image on the photoconductor with dense dots.

However, as described above, when the AC bias condition applied to the developing roller is changed in order to emphasize the developing electric field, for example, extra toner from around the portion corresponding to the latent image of the developing roller becomes Or the absolute amount of toner moving from the developing roller toward the latent image is insufficient, and the dot area of the visible image on the photoconductor varies. Specifically, when the developing potential is changed by ± 50 [V], the visualized dot area fluctuates by about 30%.

As a method of suppressing the development by the extra toner from around the portion corresponding to the latent image of the developing roller as described above, a dispersion developing method in which particles having different resistances are dispersed in a base of the developing roller is used. Attempts have been made to use rollers.

However, in the conventional dispersion type developing roller, even if the particles dispersed in the substrate have different resistances, the particles have a relatively large particle size of 50 [μm] or more.
For example, when a latent image having a relatively low potential such as a halftone image is developed, the pattern remains as a sleeve ghost, and an image having a uniform density cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to provide a stable and stable dot area of a visible image on a photoreceptor even when a development potential changes. An object of the present invention is to provide a developing device capable of obtaining a binary developing system.

The developing device of the "known example 1" has a different purpose from that of the present invention, and its developing system is not a binary image forming process developing system. When applied as it is, the resin coating layer containing crystalline graphite formed on the surface of the developer carrying member adversely affects the developing potential of the developing electric field, and the developing capability is likely to be reduced. .

Further, the conductive roller of the above-mentioned "known example 2" has a different purpose from that of the present invention. Further, since the conductive layer has a high toner charging property, the conductive roll is subjected to binary developing. When the toner is directly used as the developing roller in the system, the frictional charging characteristic with the toner is improved, so that the adhesive force of the toner to the developing roller is excessively increased, and there is a high possibility that the developing ability is reduced.

Further, the developer carrier of the above-mentioned "known example 3" has a different purpose from that of the present invention, and the coating layer of the developer carrier has to have a high resistance. And the developing ability is likely to be reduced. That is, in the developer carrier of “known example 3”,
Even if a relatively low potential development such as a binary development is to be performed, the photoreceptor potential, that is, the development potential must be increased from 200 V of the binary development to 500 V in order to perform saturated development because of a low γ.
V. In order to achieve this, it is necessary to increase the thickness of the photoreceptor. Therefore, a high-resolution image is obtained due to the effect of light diffusion during exposure due to the increase in the thickness of the photoreceptor. Can not be.

[0015]

In order to achieve the above object, the present invention is directed to a developer carrying member for carrying and transporting a one-component developer in a developing region facing a latent image carrying member; A thin layer forming member for forming the developer carried on the developer carrier into a uniform thin layer, a developer supply member for supplying the developer to the developer carrier, and a developer supply member for supplying the developer to the developer carrier. And a developer accommodating case for accommodating the developer, wherein the developing device carries out a binary development in accordance with a threshold value of the potential of the latent image carrier.
0 ⁵ [Ω · cm] below as to form a conductive material, the surface layer of the base body, a volume resistivity of 10 ⁶ [Ω · c
m] or more and particles having a particle size of 20 [μm] or less are dispersed such that at least a part of the particles is exposed on the surface of the surface layer. In this developing device, a volume resistivity of 10 ⁶ is formed on a surface layer of a substrate formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less.
[Ω · cm] or more and particles having a particle size of 20 [μm] or less,
Since the binary development is performed using the developer carrier dispersed so that at least a part thereof is exposed on the surface of the surface layer, the developing electric field between the latent image on the latent image carrier and the developing roller is enhanced. Is done. Further, even if the developing potential is changed, the concentration of the developing electric field on the optically written dots on the latent image carrier is reduced (the details will be described later). Further, by increasing the volume resistivity of the particles dispersed in the surface layer of the base of the developer carrying member, the concentration of the developing electric field on the optical writing dots on the latent image carrying member is further suppressed, and the developer supplying member The developer supply rate is improved by triboelectric charging with the developer supplied from the printer.

According to a second aspect of the present invention, there is provided a developer carrying member for carrying and transporting a one-component developer in a developing region opposed to a latent image carrying member, and the developer carried on the developer carrying member is uniformly formed. A thin layer forming member formed in a thin layer, a developer supply member for supplying a developer to the developer carrier, and a developer accommodating case for accommodating the developer supplied by the developer supply member,
In a developing device that performs binary development according to the potential threshold of the latent image carrier, irregularities are formed on the surface of the substrate of the developer carrier, and a volume resistivity of 10 ⁶ [ Ω · cm] or more and particles having a particle size of 20 [μm] or less are attached so that at least the tops of the projections on the substrate surface are exposed. In this developing device, particles having a volume resistivity of 10 ⁶ [Ω · cm] or more and a particle size of 20 [μm] or less are formed in the concave portion formed on the surface of the substrate of the developer carrying member. Since the binary development is performed using the developer carrier adhered so that at least the top of the projected portion is exposed, the developer carrying ability is improved by the effect of the surface roughness of the developer carrier. At the same time, the developing electric field is emphasized by the area ratio of the exposed portion of the substrate. Further, similarly to the developing device of the first aspect, even when the developing potential is changed, the concentration of the developing electric field on the optically written dots on the latent image carrier is reduced. Further, by increasing the volume resistivity of the particles attached to the concave portion of the base of the developer carrier, the concentration of the developing electric field on the optical writing dots on the latent image carrier is further suppressed, and the developer supply member The developer supply rate is improved by triboelectric charging with the developer supplied from the printer.

According to a third aspect of the present invention, there is provided a developer carrying member for carrying and transporting a one-component developer in a developing region opposed to a latent image carrying member, and a method of uniformly transferring the developer carried on the developer carrying member. A thin layer forming member formed in a thin layer, a developer supply member for supplying a developer to the developer carrier, and a developer accommodating case for accommodating the developer supplied by the developer supply member,
In a developing device for performing binary development in accordance with the threshold value of the potential of the latent image carrier, the base of the developer carrier is formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less. The surface of the substrate has a volume resistivity of 10 ⁶ [Ω]
Cm] or more and particles having a particle size of 20 [μm] or less are dispersed and attached. In this developing device, the surface of a substrate formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less has a volume resistivity of 10 ⁶ [Ω · cm] or more and a particle size of 20 [μm]. ] Since binary development is carried out using a developer carrier on which the following particles are dispersed and adhered, the unevenness of the substrate surface is not as steep as the unevenness of the substrate surface according to claim 2; Its surface shape is maintained for use. Further, similarly to the developing device of the first aspect, by increasing the volume resistivity of the particles dispersed and attached to the surface of the base of the developer carrying member, the concentration of the developing electric field on the optical writing dots on the latent image carrying member can be reduced. Further, while being suppressed, the developer supply rate is improved by frictionally charging with the developer supplied from the developer supply member.

According to a fourth aspect of the present invention, in the developing device according to the first aspect, the volume specific resistance of the particles dispersed in the surface layer of the base of the developer carrier is 10 ⁶ [Ω · cm] or more.
It is characterized by being less than ¹⁰ [Ω · cm].

According to a fifth aspect of the present invention, in the developing device of the second aspect, the volume specific resistance of the particles adhered to the concave portion on the substrate surface of the developer carrier is 10 ⁶ [Ω · cm] or more.
It is characterized by being less than ¹⁰ [Ω · cm].

According to a sixth aspect of the present invention, in the developing device of the third aspect, the volume specific resistance of the particles dispersed and adhered to the surface of the substrate of the developer carrier is 10 ⁶ [Ω · cm] or more.
It is characterized by being less than ¹⁰ [Ω · cm].

In the developing device according to any one of the fourth to sixth aspects, the volume specific resistance of the particles dispersed or attached to the surface layer or the surface of the developer carrier is 10 ⁶ [Ω · cm] or more.
^Since the range is less than ¹⁰ [Ω · cm], the increase in the dot area of the optically written dots on the latent image carrier when the development potential changes is suppressed, and the developer when the developer supply is repeated is repeated. Residual charge on the carrier is eliminated.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of a copying machine for performing a binary image forming process development will be described below. FIG. 4 is a schematic sectional view of a developing device of a copying machine that performs a binary image forming process development. The developing device includes a developing roller 3 as a developer carrying member that carries and conveys a toner 2 as a one-component developer in a developing area facing a photosensitive drum 1 as a latent image carrying member; A doctor 4 as a thin layer forming member for forming the toner 2 carried on the toner in a uniform thin layer, and the toner 2
Supply roller 5 as a developer supply member for supplying toner
And a toner container 6 serving as a developer accommodating case for accommodating the toner 2 supplied by the toner supply roller 5, and agitating the toner 2 accommodated in the toner container 6 toward the toner supply roller 5. And an agitator 7 for feeding.

The developing roller 3 is, as shown in FIG.
In the developing area A, the surface of the photosensitive drum 1 is
m], and is arranged so as to perform contact or non-contact development with the development gap Gp of [m]. In this developing device, as a method of maintaining the developing gap Gp at a predetermined distance, a disc-shaped spacer roller (not shown) having a radius larger than the radius of the developing roller 3 by a desired developing gap Gp is used. It is configured to be brought into contact with the surface outside the one latent image forming area. The developing roller 3 is applied with a voltage having good flying conditions for the toner by a bias power supply (not shown).

The toner supply roller 5 is provided with an elastic foam layer on the surface, and a large number of holes are formed on the surface of the elastic foam layer so that the toner can be held at least in the vicinity of the surface. I have.

The agitator 7 supplies the toner 2 in the developer container 3 to the surface of the toner supply roller 5 and
The toner 2 is agitated. However, if the toner can be supplied to the surface of the toner supply roller 5 by its own weight due to the shape of the developer container 3 and the fluidity of the toner, it may be omitted. good.

In the above configuration, the toner supply roller 5
The toner 2 inside the developer container 3 is supplied to the surface of the developer container 3 by the agitator 7. The toner 2 supplied to the toner supply roller 5 is conveyed toward a contact portion between the toner supply roller 5 and the developing roller 3 by rotating the toner supply roller 5 counterclockwise. In this contact portion, the toner is frictionally charged by the friction between the toner supply roller 5, the toner and the developing roller 3, and is supplied to the surface of the developing roller 3. The toner supplied to the surface of the developing roller 3 is thinned and frictionally charged by the doctor 4 as a layer thickness regulating plate, and adheres to the surface of the developing roller 3 with a desired charge amount and a desired layer thickness. Then, the developer is conveyed to a developing area A which is a portion facing the photosensitive drum 1 by the rotation of the developing roller 3.

In the developing area A, the toner on the surface of the developing roller 3 to which the bias for forming an appropriate electric field is applied reciprocates between the developing roller 3 and the photosensitive drum 1, and The electrostatic latent image formed on the surface of the drum 1 is visualized. Here, the reciprocating movement of the toner means that the toner reciprocates in both the image portion and the non-image portion on the developing roller 3 and the photosensitive drum 1, but strictly speaking, the toner reciprocates between the non-image portions. This also includes the case where the toner moves but does not return from the developing roller 3 side in the image portion, that is, the case where the toner moves only to the photosensitive drum 1 side while passing through the developing area A. Further, the remaining toner corresponding to the non-image portion remaining on the surface of the developing roller 3 without adhering to the surface of the photosensitive drum 1 when passing through the developing area A is removed from the surface of the developing roller 3 by the toner supply roller 5. It is scraped off mechanically and electrically. Also,
The electric charge on the developing roller 3 is also fixed by the frictional charging by the toner supply roller 5, and the surface of the developing roller 3 is initialized. (Hereinafter, margin)

By the way, in a developing apparatus for performing this type of binary image forming process development, as described above, 600 [dp
In the case of i), in the case of dense dots in which only two dots are available for writing one dot, if the development potential is changed, the dot area of the visible image on the photoconductor changes.

Therefore, in the developing device according to the present embodiment,
As shown in FIG. 1, the base 3a of the developing roller 3 is formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less, and a volume resistivity of 10 ⁵ [Ω · cm] is formed on the surface of the substrate 3a.
Particles 8 having a diameter of ⁶ [Ω · cm] or more and a particle diameter a of 20 [μm] or less were dispersed such that at least a part of the particles 8 was exposed on the surface 3b of the surface layer.

Here, the particle diameter a of the particles 8 is 16 [μm].
And a minimum dot diameter of 42.3 [μ] of 600 [dpi]
m]. Further, although the interval between the particles 8 depends on the degree of filling in the surface layer of the substrate 3a, it is preferable that adjacent particles do not completely contact each other. However, it is possible to make them as close as possible as long as a conductive path made of the conductive material of the base 3a can be secured.

The conductive material of the substrate 3a includes
A resin in which carbon and TiO ₂ particles are dispersed and mixed in a silicon-based resin may be used. As the particles 8 to be contained in the surface layer of the substrate 3a, it is preferable that the dispersion amount of carbon or TiO ₂ particles is reduced with respect to the material of the substrate 3a. In other words, by forming the particles 8 with a smaller amount of carbon or TiO ₂ particles dispersed in the material of the base 3a, the base 3a and the particles 8 are formed.
Physical properties are almost the same except for the volume resistivity.
Separation of the particles 8 due to repeated use of the developing roller 3 is less likely to occur, and the life of the developing roller 3 can be extended.

In the developing device having this configuration, the surface layer of the substrate 3a formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less has a volume resistivity of 10 ⁶ [Ω · c].
m] and particles 20 having a particle size of 20 [μm] or less are subjected to binary development using the developing roller 3 in which at least a part thereof is dispersed so as to be exposed at least partially on the surface of the surface layer. The developing electric field between the latent image on the developing roller 1 and the developing roller 3 can be enhanced.

That is, when particles 8 having a volume resistivity of 10 ⁶ [Ω · cm] or more are dispersed in the developing roller 3, the developing electric field due to the application of the developing bias is affected by the residual charge on the particles 8. Changes locally. As a result, the development of the negatively charged toner is promoted. This process is based on the fact that a charge is partially left on the particles 8 when the members (toner supply roller 5 and doctor 4) to which the voltage is applied come into contact with the particles 8.

That is, the toner supply roller 5 comes into contact with the developing roller 3, and the toner 2 sandwiched therebetween is contact-frictionally charged, and the voltage applied to each of the developing roller 3 and the toner supply roller 5 is reduced. The toner 2 is supplied to the developing roller 3 by the potential difference. At this time, in the region of the conductive material in which the volume resistivity of the developing roller 3 is 10 ⁶ [Ω · cm] or less, the developing bias (−20 in this example) is used.
0V) is applied, so there is no change. However, the particles 8 having a volume resistivity of 10 ⁶ [Ω · cm] or more of the developing roller 3 contact the members (toner supply roller 5 and doctor 4) to which the above-described voltage is applied. Charge is injected. Here, since the toner supply roller 5 and the doctor 4 use the negatively charged toner in the present configuration example with respect to the DC bias of the developing bias, the toner supply roller 5 and the doctor 4 are relatively further in the negative direction (-600 V in this example). . Therefore, negative charges remain on the particles 8. When the particles 8 face the photosensitive drum 1 in this state, the developing bias is emphasized and the developing ability is improved.

In the developing device having this configuration, the AC bias condition applied to the developing roller 3 is changed to
Even if the development potential is changed, the concentration of the development electric field on the optically written dots on the photosensitive drum 1 is reduced, so that the variation in the dot area of the visible image on the photosensitive drum 1 can be reduced.

That is, the presence of the particles 8 locally lowers the dielectric constant of the developing roller 3, thereby reducing the developing electric field. The concentration of the developing electric field on the optical writing dots is reduced.

That is, when a material having a high volume resistivity is present in an electric field, the electric field has an effect of weakening the electric field. For example, the electric field due to the photoconductor potential and the developing bias is shown below. E = (Vp−VB) / (dp / εp + dt / εt + dD
r / εDr + Air-Gap) dp: photoconductor thickness, εp: photoconductor relative dielectric constant, dt: toner layer thickness, εt: toner layer dielectric thickness, dDr: developing roller thickness, εDr: developing roller relative dielectric thickness, Air-Gap
p: Void Here, if the relative dielectric constant of the embedded dielectric particles is 3 with respect to the relative dielectric constant of 10 of the low-resistance developing roller material, the electric field E becomes small. However, it is considered that the electric field E depends on the content (volume ratio) of the dielectric particles. This allows
When the development potential (Vp-VB) is changed, the change in the electric field becomes small. This is the same as the decrease in the slope of γ, but in this case, dp: the effect is further increased in order to increase the thickness of the photoreceptor, and it is considered that this effect is smaller in this configuration example. Can be

Further, in the developing device having this configuration, by increasing the volume resistivity of the particles 8 dispersed in the surface layer of the base 3a of the developing roller 3, the developing electric field applied to the optically written dots on the photosensitive drum 1 is increased. Concentration can be further suppressed, and the toner 2 supplied from the toner supply roller 5 is frictionally charged, so that the supply rate of the toner 2 is improved and stable development characteristics can be obtained.

FIG. 2 shows the structure of another developing roller of the developing device according to the present embodiment. Developing roller 3 of this developing device
As shown in FIG. 2, the surface of the base 3a of the developing roller 3 is formed with irregularities and the concave 3c of the surface of the base 3a.
In addition, when the volume resistivity is 10 ⁶ [Ω · cm] or more and the particle size is 2
The resin 9 made of particles of 0 [μm] or less is poured and solidified so that at least the top of the projection 3d on the surface of the substrate 3a is exposed, and is adhered.

The conductive material of the base 3a of the developing roller 3 is the same as that of the developing roller occupied in FIG. 1, such as silicon resin, carbon and TiO ₂ particles dispersed and mixed, and , A metal or a metal oxide.

In the developing roller 3 of the illustrated developing device, the height b of the convex portion 3d of the surface 3b of the developing roller 3 is set to 20 [μm], and the concave portion 3c of the surface 3b of the developing roller 3 is formed.
The layer thickness c of the resin 9 attached to the substrate 3 was set to 15 [μm] to expose the top of the projection 3d on the surface of the base 3a.

As a result, the developer carrying ability is improved by the effect of the surface roughness of the developing roller 3, and the developing electric field is emphasized by the area ratio of the exposed portion of the base 3a. As in the case of the developing device shown in FIG. 1, even if the AC bias condition applied to the developing roller 3 is changed to change the developing potential, the concentration of the developing electric field on the optically written dots on the photosensitive drum 1 can be improved. Can be reduced, so that the variation in the dot area of the visible image on the photosensitive drum 1 can be reduced. Further, by increasing the volume specific resistance of the resin 9 attached to the concave portion 3c on the surface 3b of the developing roller 3, the concentration of the developing electric field on the optically written dots on the photosensitive drum 1 can be further suppressed, and the toner supply roller By frictionally charging the toner 2 supplied from the toner 5, the supply rate of the toner 2 is improved, and stable development characteristics can be obtained.

FIG. 3 shows the structure of still another developing roller of the developing device according to this embodiment. As shown in FIG. 3, the developing roller 3 of the developing device
It is formed of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less, and has a volume resistivity of 10 ⁶ [Ω · cm] or more and a particle size of 20 [μm] or less on the surface 3b of the substrate 3a. Are dispersed and attached.

Here, it is desirable that the diameter of the particles 10 dispersedly attached to the surface 3b of the substrate 3a is smaller than the width of one dot of 600 [dpi]. When the particles 10 are dispersed and attached to the surface 3b of the substrate 3a, it is not preferable that the particles 10 contact each other. When the particles 10 are dispersed and attached to the surface 3b of the substrate 3a, a masking member or the like is used. It is devised so that the particles 10 do not contact each other.

Under such conditions, the layer thickness d of the particles 10 dispersed and attached to the surface 3b of the developing roller 3 is 2 [μm].
Although the thickness is as follows, the unevenness on the surface of the base 3a
Does not become as steep as the irregularities on the surface of the substrate 3a shown in FIG.
Even when used for a long time, the surface shape can be maintained.

Further, similarly to the developing device shown in FIG. 1, by changing the AC bias condition applied to the developing roller 3,
Even if the development potential is changed, the concentration of the development electric field on the optically written dots on the photosensitive drum 1 is reduced, so that the variation in the dot area of the visible image on the photosensitive drum 1 can be reduced. Furthermore, by increasing the volume resistivity of the particles 10 dispersed and attached to the surface 3b of the developing roller 3, the concentration of the developing electric field on the optical writing dots on the photosensitive drum 1 can be further suppressed, and the toner supply roller 5
The toner 2 supplied from the toner is charged by friction, so that the supply rate of the toner 2 is improved, and stable development characteristics can be obtained.

The base 3 of the developing roller 3 shown in FIG.
2, the volume resistivity of the particles 8 dispersed in the surface layer of the developing roller 3 shown in FIG. 2, the volume resistivity of the particles 9 adhered to the concave portion 3c of the surface 3b of the base 3a of the developing roller 3 shown in FIG. Particles 1 dispersed and attached to surface 3b of substrate 3a
By setting the volume specific resistance of each of O to 0 ⁶ [Ω · cm] or more and less than 10 ¹⁰ [Ω · cm], the dot area of the optically written dots on the photosensitive drum 1 when the development potential is changed. In addition to suppressing the increase, the charge remaining on the developing roller 3 when the supply of the developer is repeated is eliminated, so that stable developing characteristics can be always obtained.

Here, the surface 3 of the base 3a of the developing roller 3
b has a volume resistivity of 10 ¹⁰
In the case of [Ω · cm] or more, the time constant of the material itself (time during which the retained charge [charge-up] is released)
Exceeds 0.25 sec.
When the 6 mm developing roller rotates at 100 mm / s and exceeds half a circumference, the residual charge affects the toner supply condition. Since this charge is "negative", it acts in the direction of reducing the toner supply property, and further reduces the developing electric field as is clear from the above description.

[0049]

According to the first aspect of the present invention, the surface layer of the substrate made of a conductive material having a volume resistivity of 10 ⁵ [Ω · cm] or less has a volume resistivity of 10 ⁶ [Ω · cm]. As described above, binary development is performed using a developer carrier in which particles having a particle size of 20 [μm] or less are dispersed such that at least a part thereof is exposed on the surface of the surface layer. The developing electric field between the latent image and the developer carrier can be enhanced. Also, even if the developing potential is changed by changing the AC bias condition applied to the developer carrier, the concentration of the developing electric field on the optically written dots on the latent image carrier is reduced. Variations in the dot area of the upper visualized image can be reduced. Further, by increasing the volume resistivity of the particles dispersed in the surface layer of the base of the developer carrier, the concentration of the developing electric field on the optical writing dots on the latent image carrier can be further suppressed, and the developer supply member By frictionally charging with the supplied developer, there is an excellent effect that the supply rate of the developer is improved and stable development characteristics can be obtained.

According to the second aspect of the present invention, the developer carrying ability is improved by the effect of the surface roughness of the developer carrying member, and the developing electric field is emphasized by the area ratio of the exposed portion of the base. Further, similarly to the developing device according to the first aspect, by changing the AC bias condition applied to the developer carrier,
Even if the development potential is changed, the concentration of the development electric field on the optically written dots on the latent image carrier is reduced, so that the variation in the dot area of the visible image on the latent image carrier can be reduced. Further, by increasing the volume resistivity of the particles dispersed in the surface layer of the base of the developer carrier, the concentration of the developing electric field on the optical writing dots on the latent image carrier can be further suppressed, and the developer supply member By frictionally charging with the supplied developer, there is an excellent effect that the supply rate of the developer is improved and stable development characteristics can be obtained.

According to the third aspect of the present invention, the unevenness of the substrate surface is not as steep as the unevenness of the substrate surface shown in FIG. 2, and the surface shape can be maintained even when used for a long time. Can be. Further, similarly to the developing device according to claim 1, even when the developing potential is changed by changing the AC bias condition applied to the developer carrier, the developing electric field to the optically written dots on the latent image carrier is changed. , The fluctuation of the dot area of the visible image on the latent image carrier can be reduced. Further, by increasing the volume resistivity of the particles dispersed in the surface layer of the base of the developer carrier, the concentration of the developing electric field on the optical writing dots on the latent image carrier can be further suppressed, and the developer supply member By supplying friction with the supplied developer, the supply rate of the developer is improved,
There is an excellent effect that stable development characteristics can be obtained.

According to the present invention, the increase in the dot area of the optically written dots on the latent image carrier when the development potential changes is suppressed, and the development when the developer supply is repeated is suppressed. There is an excellent effect that the residual charge on the agent carrier is eliminated and stable development characteristics can always be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a configuration of a surface portion of a developing roller of a developing device according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a configuration of a surface portion of another developing roller of the developing device according to the embodiment.

FIG. 3 is an explanatory diagram for explaining a configuration of a surface portion of still another developing roller of the developing device according to the embodiment.

FIG. 4 is a schematic sectional view of a main part of the developing device according to the embodiment.

[Explanation of symbols]

Reference Signs List 1 photosensitive drum 2 toner 3 developing roller 3a developing roller base 3b developing roller surface 3c developing roller surface concave portion 3d developing roller surface convex portion 4 doctor 5 toner supply roller 6 toner container 7 agitator 8 developing roller surface layer 9 Particles dispersed and adhered on the surface of the developing roller 10 Particles dispersed and adhered on the surface of the developing roller 10 Particles dispersed and adhered on the surface of the developing roller b Particles of the particles dispersed on the surface layer of the developing roller b Height c Layer thickness of resin adhered to the concave portion on the surface of the developing roller d Layer thickness of particles dispersedly adhered on the surface of the developing roller A Developing area

Claims (6)

[Claims] A developer carrying member for carrying and transporting a one-component developer in a developing region opposed to a latent image carrier, and a uniform thin layer of the developer carried on the developer carrying member. The latent image carrier, comprising: a thin layer forming member; a developer supply member for supplying a developer to the developer carrier; and a developer accommodating case for accommodating the developer supplied by the developer supply member. In the developing device for performing the binary development according to the threshold value of the potential of the developer, the base of the developer carrying member may be formed to have a volume resistivity of 10 ⁵ [Ω].
· Cm] or less, and particles having a volume resistivity of 10 ⁶ [Ω · cm] or more and a particle size of 20 [μm] or less are formed on the surface layer of the substrate, at least a part of the particles. Are dispersed so as to be exposed on the surface of the surface layer. 2. A developer carrier for carrying and transporting a one-component developer in a development area facing a latent image carrier, and a uniform thin layer of the developer carried on the developer carrier. The latent image carrier, comprising: a thin layer forming member; a developer supply member for supplying a developer to the developer carrier; and a developer accommodating case for accommodating the developer supplied by the developer supply member. In the developing device for performing the binary development in accordance with the threshold value of the electric potential of the developer carrier, the unevenness is formed on the surface of the substrate of the developer carrying member, and the volume resistivity is 10 ⁶ [Ω ·
cm] or more and particles having a particle diameter of 20 [μm] or less are attached such that at least the tops of the projections on the surface of the base are exposed. 3. A developer carrier for carrying and transporting a one-component developer in a development area facing a latent image carrier, and a uniform thin layer of the developer carried on the developer carrier. The latent image carrier, comprising: a thin layer forming member; a developer supply member for supplying a developer to the developer carrier; and a developer accommodating case for accommodating the developer supplied by the developer supply member. In the developing device for performing the binary development according to the threshold value of the potential of the developer, the base of the developer carrying member may be formed to have a volume resistivity of 10 ⁵ [Ω].
· Cm] or less, and particles having a volume resistivity of 10 ⁶ [Ω · cm] or more and a particle size of 20 [μm] or less dispersed and adhered to the surface of the substrate. Characteristic developing device. 4. The developing device according to claim 1, wherein the volume resistivity of the particles dispersed in the surface layer of the base of the developer carrier is 10 ⁶ [Ω · cm] or more and 10 ¹⁰ [Ω · c].
m]. 5. The developing device according to claim 2, wherein the volume resistivity of the particles adhered to the concave portion on the surface of the base of the developer carrier is 10 ⁶ [Ω · cm] or more and 10 ¹⁰ [Ω · cm].
cm]. 6. The developing device according to claim 3, wherein the volume specific resistance of the particles dispersed and attached to the surface of the base of the developer carrying member is 10 ⁶ [Ω · cm] or more and 10 ¹⁰ [Ω · cm].
cm].