JPH07114265A - Developing device - Google Patents

Abstract

PURPOSE:To obtain the uniform image of a sufficient image density without fogging and further, unevenness in a density by forming the surface of a devel oper carrier in a tooth shape, arranging a tooth-shaped projection so as to face a regulating member and specifying the average height of the projection. CONSTITUTION:This developing device is composed of the developer carrier supplying a developer 2 to latent image carrier and the regulating member putting the developer 2 on the developer carrier in a uniform thin layer. The developer carrier is constituted of at least an elastic body 5, its surface has the tooth shape and the tooth-shaped projection A is arranged so as to face the regulating member. The average height H1 of the tooth-shaped projection A of the surface of the elastic body is <=8mum. Moreover, it is preferable that a surface roughness Rmax in a pitch of the tooth shape on the surface of the elastic body is <=3mum and the pitch P of the tooth shape is <=50mum. Thus, a one-component developer is uniformly carried onto the developer carrier and uniformly electrified to always and stably supply the developer to the latent image carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for forming an image with a one-component developer, and more particularly to a developer carrier which constitutes the developing device.

[0002]

2. Description of the Related Art Conventionally, a developing device using a one-component developer, regardless of whether it is a magnetic or non-magnetic developer, forms a uniform thin layer of the developer on a developer carrying member by a regulating member such as an elastic blade. The developer is transported onto the latent image carrier,
It is visualized. In such a developing device, in order to faithfully visualize the electrostatic latent image, the developer must be uniformly charged and uniformly transported continuously. However, it is extremely difficult to satisfy these requirements, and various proposals have been made so far. Above all, many proposals for improvement have been made with respect to the developer carrying member related to the present invention.

For example, in Japanese Patent Laid-Open No. 2-242274, the direction of polishing the surface of the toner layer thickness regulating member and the toner carrier is regulated. However, with this method, the amount of toner conveyed is small, and it is difficult to obtain a predetermined image density.
Further, there is a problem that surface irregularities are likely to appear in an image, and it is difficult to form a clear image. In addition, JP-A-55
In -11070, only surface roughness is specified to form a developer layer having a uniform thickness. Further, JP-A-55-14
No. 0858 defines the relationship between the height of peaks on the surface of the magnetic developer supporting member and the average particle diameter of the developer, and the interval between peaks. Japanese Patent Laid-Open No. 3-8
In 4570, it is specified that the surface of the developer carrier is composed of a smooth convex portion and a concave portion having a fine rugged rough surface on the surface in relation to the average particle diameter of the developer. In JP-A-3-273271, the surface roughness Rz of the developer holding member and the volume average particle diameter of the developer are specified. Japanese Unexamined Patent Publication (Kokai) No. 4-80775 stipulates that the surface roughness of the developing roller should be equal to or smaller than the average particle diameter of the toner. As described above, the roughness of the surface of the developer carrier and the relationship between the surface of the developer carrier and the average particle diameter of the developer have been conventionally defined. All of these are intended to uniformly charge and uniformly convey the developer in the one-component developing method. However, by only defining the surface roughness and the average particle size of the developer, the following three points can be satisfied at the same time: preventing the developer from adhering to the non-printed part (hereinafter referred to as fog), ensuring sufficient image density, and uniformity of density (image unevenness). There is a problem that it is difficult to do. Also, JP-A-57-1
81569, JP-A-61-1769959, JP-A-2-2
59785, JP-A-3-249675, JP-A-3-27.
There are many applications for a multi-layered structure in which a coating layer is formed on the surface of a developer bearing member such as 3271. These are for the purpose of preventing the softening agent from seeping out from the elastic layer, uniform charging, and uniform conveyance. Further, in JP-A-1-38780, regarding the composition of the conductive layer, a hetero five-membered ring polymer is dispersed in a thermoplastic resin in order to improve humidity resistance and temperature characteristics. But,
Fogging and image unevenness are likely to occur in conventional coating layers,
In particular, there is a problem that the above-mentioned image deterioration remarkably occurs under high temperature and high humidity.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention solves the above-mentioned problems, and an object of the present invention is to develop a one-component developer when a developer carrier composed of an elastic body is used. Evenly conveyed and uniformly charged on the agent carrier, always supplying a stable developer to the latent image carrier, there is no fog and sufficient image density is satisfied, and there is no image density unevenness due to supply delay, It is an object of the present invention to provide a developing device that can always form a clear image having high resolution and excellent gradation reproducibility regardless of changes over time and environmental changes.

[0005]

A developing device according to the present invention comprises a developer carrying member for supplying a developer to a latent image carrying member, and a regulating member for uniformly thinning the developer on the developer carrying member. The developer carrying member is composed of at least an elastic member, the surface of the elastic member has a sawtooth shape, the sawtooth-shaped projections A are arranged so as to face the regulating member, and the projections on the elastic member surface are provided. The average height H1 of the portion A is 8 μm or less.

Further, the surface roughness Rmax within one pitch of the sawtooth shape of the elastic body is 3 μm or less.

Further, the sawtooth-shaped pitch P is 50 μm.
It is characterized by the above.

Further, the surface of the elastic body is formed of a member having at least a glass transition point of 50 ° C. or higher.

The present invention will be described in detail below with reference to examples.

[0010]

【Example】

(Embodiment 1) FIG. 1A shows the shape of the surface of the developer carrier of the present invention, and is a schematic cross-sectional view of the developer carrier. The surface of the elastic body 5 has a sawtooth shape as shown in the drawing, and the protrusion A rotates in the direction of arrow a so as to face the regulating member 9. In this example, urethane having a hardness of 45 (JIS A) was used as the elastic body. The resistance was 10 ⁶ Ωcm. The resistance was determined from the voltage when a developer support was placed on a flat plate electrode and a constant current of 1 μA was applied to both ends with a load of 500 g, totaling 1 kg. As the regulation member 9, a metal blade made of stainless steel and having a tip R having a thickness of 0.2 mm was used. The elastic body and the regulating member are not limited to those in this embodiment, and other materials can be used. For example, silicon as an elastic body, EPD
M (ethylene propylene diene rubber), NBR (nitrile butadiene rubber) or the like can be used. Further, rubber or the like other than metal can be used for the regulating member.

In this embodiment, as shown in FIG.
The average height H1 of the sawtooth-shaped projections A is 6 μm, H2 showing the surface roughness Rmax within a pitch is 2 μm, and the pitch P is 150 μm, so that the projections A are repeatedly formed at least over the entire image forming region. A developer carrier was prepared. The average height H1 of the protrusion A is a 10-point average value excluding the maximum and minimum values. The average height of the protrusions A and the surface roughness within 1 pitch were measured with a laser microscope (manufactured by Lasertec). The pitch P was measured with an optical microscope. In addition, another example of the sawtooth shape is shown in FIG.
And (d).

As described above, the saw-toothed shape of the present invention has a steep slope on the downstream side with respect to the ridgeline of the protrusion A as viewed from the rotation direction of the developer carrier, and a slope on the upstream side with respect to the slope on the downstream side. It has a gentle shape.

As the developer used for the developer carrier having the above surface shape, a negatively chargeable non-magnetic developer prepared by a pulverization method was used. The composition is polyester resin 8% by weight of carbon black as a colorant, charge control agent 3
wt% and wax 4 wt% are used, and silica surface-treated with silicone oil as an external additive is 0.8.
What was externally added wt% was used. The volume average particle size of the developer was 9.1 μm, and the number average particle size was 7.7 μm.
Further, although the developer as described above is used in this embodiment, the present invention is not limited to this.

A developing device using the developer carrier and the developer will be described. FIG. 2 shows an embodiment of the developing device of the present invention. The developing device 1 conveys and develops the developer 2, and the developer carrying member 3 that conveys the developer 2 has elastic bodies 5 arranged concentrically around the shaft 4. Further, the developer supply member 6 for supplying the developer 2 to the developer carrier 3 has a foam member 8 on the outer periphery of the shaft 7.
Are formed concentrically, and the developer 2 is supplied to the developer carrier 3 by the foaming member 8. At this time, the developer supply member 6 rotates in the same direction as the developer carrying member 3.
The developer carrier 3 supplied with the developer 2 presses the plate-shaped regulating member 9 made of stainless steel to charge the developer 2 to a negative polarity and at the same time thin the developer layer into an appropriate amount to form an electrostatic mirror image. The developer 2 is directly held on the developer carrier 3 by a force, and the developer carrier 3 is rotated to convey the thin layer developer 2. Next, when the developer 2 is conveyed to the developing unit where the latent image carrier 10 and the developer carrier 3 are in pressure contact with each other, the potential contrast of the latent image carrier 10 and the developing bias applying unit 11 form a developing electric field, and the development is performed. The developer 2 charged according to the electric field adheres to the latent image carrier 10 to visualize the electrostatic latent image.
At this time, the peripheral speed ratio between the latent image carrier 10 and the developer carrier 3 is 2
So that If the peripheral speed ratio is large, the load on the drive motor increases, which is not preferable. Further, although not shown, a transfer device such as a corona transfer device or a transfer roller was used to transfer the image with the developer onto the recording paper, and the developer was fixed onto the recording paper using heat or pressure to form an image. . As a result, an image formed by using the developing device of the present invention was able to form a clear high density image without image deterioration such as fog and black solid density unevenness. Further, even under a low temperature and low humidity environment of 10 ° C.-15% RH and under a high temperature and high humidity condition of 35 ° C.-65% RH, the above image deterioration was not observed at all, and a clear image could be formed. Furthermore, a clear image could always be stably formed even after performing durable printing on 30,000 sheets. The details of the results are shown in Table 1 together with the results of Comparative Example 1 described later.

Comparative Example 1 In this comparative example, the shape and orientation of the surface of the developer carrying member will be described. That is, FIG. 3 (a)
As shown in FIG. 3, the saw tooth shape on the surface of the developer carrying member is the regulating member 9.
On the other hand, the development was performed in the reverse order of Example 1. As a result, the amount of developer conveyed on the developer carrying member was reduced, and uneven density of black solid continuous printing occurred due to the delay in the supply of the developer, so that a good image could not be formed.
In addition, as shown in FIG. 3B, the surface is not a sawtooth shape,
A developer carrier having a concavo-convex surface shape that has been conventionally used was prepared and developed. Unlike the saw-toothed shape of the present invention, the conventional unevenness is such that the inclination of the unevenness has no directivity when viewed from the rotation direction of the developer carrying member. At this time, the average height of the convex portions, the surface roughness Rmax of one pitch, and the pitch were the same as those of the saw tooth-shaped developer carrying member of the first embodiment. As a result, as in the case where the saw-tooth shape is reversed, the developer carrying amount on the developer carrying member is smaller than that in the case of Example 1, and density unevenness in solid black continuous printing occurs. The results are shown in Table 1.

[0016]

[Table 1]

Black solid density upper end: 10 cm from A4 vertical upper part
10 point average value Black solid density lower end: 10 point average value from 10 cm below A4 vertical lower portion From this comparative example, it is understood that there is a large difference in developer transportability between the conventional uneven surface and the sawtooth shape. Further, it can be seen that even if the surface has a saw-tooth shape, the carry amount varies greatly depending on its directionality. It is considered that this is due to the mechanical carrying force at the protrusion A, and when viewed from the saw tooth-shaped developer carrier surface and the developer carrier rotating direction shown in FIG. It is preferable to move so that the surface of which the steep slope is facing the regulating member.

(Embodiment 2) In this embodiment, the surface shape of the present invention will be described in detail.

A developer carrier having the same composition as that of the developer carrier used in Example 1 but having a different sawtooth average height H1 was prepared, and the fog amount on the latent image carrier was determined. At this time, H2 showing the surface roughness Rmax of 1 pitch is 2 μm, and the pitch P is
Was 150 μm. The same developer as in Example 1 was used. The results are shown in Fig. 4. As is clear from the figure, the allowable amount of fog on the latent image carrier is 0.01 mg / c.
Since it is m ² or less, the average height H1 is preferably 8 μm or less. As described above, the height H1 of the protrusion is largely related to the fog of the developer. That is, if the height is too large, the fog that is considered to be caused by the poorly charged developer increases. Further, as the height is lowered, the developer carrying amount on the developer carrying member is reduced, but as is well known, the developing amount is increased by increasing the peripheral speed ratio of the developer carrying member to the latent image carrying member. Can be secured. However, if the peripheral speed ratio is set to 3 or more, the load of the starting motor increases and the image quality is deteriorated due to the jitter, which is not preferable. Therefore, the average height H1 of the protrusions A is more preferably in the range of 3 to 8 μm.

Next, a developer carrying member was prepared in which H2 showing the surface roughness Rmax of 1 pitch was changed, and similarly, the fog amount was obtained. As a result, as shown in FIG. 5, H2 was 3 μm.
If it exceeds, the fog amount remarkably increases, and the fog allowable value is 0.
It turns out that it exceeds 01 mg / cm ² . Therefore, the surface roughness Rmax for one pitch is preferably 3 μm or less. It is considered that this is because the developer on the fine particle size side enters the concave portion of the surface, becomes immobile, and is not sufficiently charged by contact or rolling friction on the surface of the developer.

Next, a developer carrier having a different pitch P was prepared, and the amount of fog was similarly obtained. Results are shown in FIG. As is clear from FIG. 6, when the pitch P is less than 50 μm, the fog amount exceeds the allowable value of 0.01 mg / cm ² . Therefore, the pitch P is preferably 50 μm or more. Further, when it is 300 μm or more, the carrying amount on the developer carrying member decreases, and the peripheral speed ratio must be increased in order to secure the developing amount as described above. Therefore, the pitch P is more preferably 50 to 300 μm. The reason for this is that if the distance between the pitches is small, the carrying force of the developer increases, but conversely, the frequency of contact of each developer with the surface of the developer carrying member decreases, and charging is not sufficiently performed. Further, if the pitch is too long, it is considered that the mechanical transport force by the protrusion A is reduced and the transport amount is reduced.

Example 3 An elastic body was formed by NBR in place of the developer carrying body made of the urethane material used in Example 1, and the surface of this elastic body was coated with a conductive urethane resin. The reason for coating is elastic NB
This is to prevent contamination of the photoconductor by R. The coating was performed by the dipping method. However, coating on the elastic layer is also possible by a spray method. The NB
The resistance of the developer carrying member made of an R elastic body is 5 × 10 ⁶ Ω
It was cm. Further, carbon black was used as the conductive agent for the conductive urethane resin so that the volume resistance was 10 ³ Ωcm or less. This is because when the volume resistance is 10 ³ Ωcm or less, uneven resistance due to poor dispersion of carbon black is eliminated and a uniform image can be formed. The conductive urethane resin layer had a thickness of 20 μm, and the surface of the developer carrying member after coating was the same as in Example 1. Further, the same developing device and developer as in Example 1 were used to form an image. Further, in this example, materials having different glass transition points of urethane resin were prepared, and image characteristics, particularly fog and density unevenness were evaluated. The results are shown in FIG. 7. Thus, when the glass transition point is less than 50 ° C.
Fog exceeds a permissible value under high temperature and high humidity of -65%, which is not preferable. Further, under high temperature and high humidity of 35 ° C.-65%, in the member having a glass transition point of less than 50 ° C., the transport amount on the developer carrying member was decreased, and uneven density was generated in solid black continuous printing. Therefore, the glass transition point is preferably 50 ° C. or higher in order to form a good image without fog and density unevenness in all environments.

The thickness of the coating layer is 5 to 50 μm.
m is preferred. If it is less than 5 μm, the influence of the base cannot be prevented. Further, when it is 50 μm or more, cracking and peeling of the coating layer occur, which is not preferable.

Example 4 In this example, the same NBR elastic body as in Example 3 was used, and the coating agent was changed to the nylon type to prepare a developer carrying body. Also in this example, a nylon material having a different glass transition point was prepared as in Example 3, and image formation was performed in the same manner as in Example 3.
As a result, the same result as in Example 3 was obtained. That is, also in this example, as in Example 3, the glass transition point was 50 ° C.
If the amount is less than the range, fog and uneven density occur under high temperature and high humidity, which is not preferable. Therefore, in the case of a nylon-based coating agent, it is preferable that the glass transition point is 50 ° C. or higher. The film thickness was the same as in Example 3.

Although the embodiments of the present invention have been described above, the present invention is not limited to these. Also,
The developing device of the present invention can be widely applied to copying machines, printers, facsimiles and the like.

[0026]

As described above, according to the present invention, the surface of the developer carrying member that conveys the one-component developer has a saw-tooth shape, the saw-tooth protrusions are arranged so as to face the regulating member, and The average height H1 of the sawtooth-shaped projections A on the body surface is 8μ
By setting m or less, it is possible to always form a uniform image without fog and having a sufficient image density and without density unevenness due to a delay in supply.

[Brief description of drawings]

FIG. 1A is a diagram showing a relationship between a cross-sectional outline view showing a surface shape of a developer carrier used in a developing device of the present invention and a regulating member, and FIG. 1B is a surface of the developer carrier of the present invention. Enlarged schematic sectional view showing the shape, (c) is an enlarged schematic sectional view showing the surface shape of another developer carrying member of the present invention, (d) is an enlarged schematic sectional view showing the surface shape of another developer carrying member of the present invention Schematic sectional view.

FIG. 2 is a schematic sectional view of a developing device used in an embodiment of the present invention.

FIG. 3A is a cross-sectional view showing the surface shape of the developer carrying member used in the comparative example of the present invention and a diagram showing the relationship between the regulating members, and FIG. 3B is a conventional technique used in the comparative example of the present invention. FIG. 6 is a diagram showing a relationship between a cross-sectional schematic view showing the uneven upper surface of FIG.

FIG. 4 is a diagram showing a relationship between the average height H1 of the saw-tooth shape of the present invention and the amount of fog on the photoconductor.

FIG. 5 is a sawtooth-shaped one-pitch surface roughness Rm of the present invention.
FIG. 4 is a diagram showing axH2 and the amount of fog on the photoconductor.

FIG. 6 is a diagram showing the relationship between the saw-toothed pitch P of the present invention and the amount of fog on the photoconductor.

FIG. 7 is a graph showing the relationship between the glass transition point of the coating layer of the present invention and the amount of fog on the photoconductor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Developing device 2 Developer 3 Developer carrier 4 Shaft 5 Elastic layer 6 Developer supply member 7 Shaft 8 Foaming member 9 Regulation member 10 Latent image carrier

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidenori Kim, 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Co., Ltd. (72) Inventor Shuhei Mori 3-35, Yamato, Suwa, Nagano Prefecture Seiko Epson Within the corporation

Claims (4)

[Claims] 1. A developing device comprising a developer carrier for supplying a developer to a latent image carrier and a regulating member for uniformly thinning the developer on the developer carrier, wherein the developer carrier is at least an elastic body. The surface of the elastic body has a sawtooth shape, the sawtooth-shaped protrusions are arranged so as to face the regulating member, and the average height H1 of the protrusions on the surface of the elastic body is 8 μm or less. A developing device characterized by the above. 2. The developing device according to claim 1, wherein a surface roughness Rmax within one pitch of the saw-tooth shape of the elastic body is 3 μm or less. 3. The developing device according to claim 1, wherein the saw tooth-shaped pitch P is 50 μm or more. 4. The developing device according to claim 1, wherein the surface of the elastic body is formed of a member having a glass transition point of 50 ° C. or higher.