JPH05210296A - Developing device - Google Patents

Abstract

PURPOSE:To prevent fogging of a texture part and thinning of vertical lines with the one-component developing device of a contact development system. CONSTITUTION:A developing roller 3 of the developing device is formed by providing a dielectric layer 3b on the surface of a base body roller 3a consisting of, for example, aluminum and inscribing spiral grooves 3c on the surface of this dielectric layer 3b. The grooves 3c may be formed over the entire width of the developing roller 3 or may be formed in the region in a transverse direction corresponding to the latent image forming region on a photosensitive body and the grooves 3c may not be formed at both ends facing the sealing members for preventing toner splashing, not shown in Fig. The grooves 3c within a range where the surface roughness R2 in the axial direction is larger than 5mum and smaller than 30mum. The width W of the grooves 3c is preferably smaller than 400mum for the ease of production, etc. These grooves may be so formed that smooth parts remain between the adjacent grooves 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, a printer, etc., and more specifically, a latent image carrier carrying a latent image carrying a one-component developer. The present invention relates to an improvement of a developer carrier in a developing device for developing the latent image on the latent image carrier by bringing the developer carrier into contact with the developer carrier.

[0002]

2. Description of the Related Art In recent years, a number of developing devices using a one-component developer have come into practical use due to the simplification and cost reduction of the developing device. This one-component developer does not include a carrier that functions as a developing electrode in the developing area and facilitates toner transportation. Therefore, a dielectric layer is provided on the surface of a developer carrier that carries a one-component developer to improve image quality, or the surface is roughened by sandblasting or sandpaper to improve the developer transporting power. Or
The surface shape is made uneven to function as an electrode. For example, JP-A-58-153973 discloses that
In order to form a stable image for a long period of time, it is necessary to make the surface of the developer carrier smooth and uneven. Is made of an elastic material and has a surface roughness of 6 s or more. In JP-A-59-126567, the surface of the developer carrying member is roughened to about 0.2 to 10 μm by sandblasting or sandpaper. To face
Japanese Unexamined Patent Publication No. 59-189374 discloses that a non-contact developing device using a non-magnetic toner is provided with irregularities on the surface of a developer carrier and the height of the peaks of the irregularities is defined as the average particle size of the developer used. 11/4 to 3 times the height of the peak, and the gap between the peaks is larger than the height of the peaks and smaller than the developing gap (the gap between the latent image carrier surface and the developer carrier surface).
No. 446461 discloses a sleeve-shaped developer carrier having a surface roughness which is 2 to 3 times the average particle size of the developer used, and a scraper for scraping off the developer adhering to the developer carrier. In Japanese Patent Publication No. 3-14191 and Japanese Patent Publication No. 3-14192, a developing device having an alumite treatment is applied to the surface of a one-component developer carrying member, and then sandblasting is performed by sandblasting with regular or irregular particles. Surface-developed developing devices have been proposed.

[0003]

A contact developing system for developing a latent image on a latent image bearing member by bringing a developer bearing member carrying a one-component developer into contact with the latent image bearing member having a latent image formed thereon. When a developer carrying member having a surface of a dielectric layer is used in the developing device of 1., if the dielectric surface has a protrusion of about several μm,
The electric field is concentrated there, and an abnormal image with white spots appears on the image. Therefore, it has been said that it is necessary to suppress the surface roughness of the dielectric layer to 5 μm or less in order to improve the image quality. However, when such a smooth surface is used, the charge of the developer becomes insufficient (see, for example, JP-A-59-126567 mentioned above), and the developer transport ability is weak, so that the background portion There is a problem that fogging is likely to occur. Further, there is a problem that a line latent image parallel to the moving direction of the latent image carrier is faintly developed finely, or is severely broken (hereinafter, this phenomenon is referred to as faint vertical line).

The present invention has been made in view of the above problems, and an object of the present invention is to provide a developing device of a contact developing type which can prevent fogging of the background portion and blurring of vertical lines. Is.

[0005]

In order to achieve the above-mentioned object, the invention of claim 1 brings a latent image carrier on which a latent image is formed into contact with a developer carrier carrying a one-component developer. In a developing device for developing a latent image on a latent image carrier, as a developer carrier, a spiral having a surface layer made of a dielectric material having a surface roughness in the axial direction of more than 5 μm and less than 30 μm. In the developing device of claim 1, the width of the groove in the axial direction is 4
It is characterized in that it is formed so as to have a diameter of not more than 00 μm, and the invention of claim 3 uses the one-component developer having a volume average particle diameter of not more than 10 μm in the developing device of claim 1. According to the invention of claim 4,
The developing device according to claim 1 is characterized in that the spiral groove is formed such that a smooth portion is interposed between adjacent grooves in the axial direction. 5. The developing device according to claim 4, wherein the width of the smooth portion in the axial direction is 150 .mu.m or less and the width of the groove in the axial direction is 400 .mu.m or less. According to a sixth aspect of the present invention, in the developing device according to the first, second, third, fourth or fifth aspect, the groove is formed only in the widthwise region corresponding to the latent image forming region on the latent image carrier. It is characterized by that.

[0006]

In the developing device of the present invention, a spiral groove having an axial surface roughness of more than 5 μm and less than 30 μm is formed on the surface layer made of the dielectric material of the developer carrier. Therefore, the developer can be properly charged, and the developer carrying member can exhibit sufficient developer transporting ability.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine (hereinafter referred to as a copying machine) which is an image forming apparatus will be described below. FIG. 4 is a schematic configuration diagram of the developing device according to the present embodiment. In the figure, reference numeral 1 denotes a belt-shaped photosensitive member (OPC) which is a latent image carrier, which is hung around a plurality of supporting rollers (1a, 1b, etc.) and rotationally driven in the arrow direction. In order to execute a well-known electrophotographic process on the moving path of the photoconductor 1, a uniform charging device, an optical system for forming an electrostatic latent image, a transfer device for transferring a toner image onto a transfer paper, which are not shown, A cleaning device for removing the residual toner on the photoconductor 1 after the transfer, a static eliminator for removing the residual charge on the photoconductor 1, and the like are provided. The developing device 2 of this embodiment is arranged so as to face the portion of the photoconductor 1 that is stretched between the pair of support rollers 1a and 1b.

The developing device 2 includes a developing roller 3 as a developer bearing member, a replenishing roller 4 for supplying toner to the surface of the developing roller 3, and a thin layer blade for forming a thin layer of toner on the surface of the developing roller 3. 5 and a destaticizing brush 6 for destaticizing the surface of the developing roller 3. A toner storage portion 7 is formed in a part of the casing of the developing device 2, and magnetic one-component toner is stored therein, for example. The developing device 2 is arranged so that the surface of the developing roller 3 is in contact with the surface of the photoconductor 1 through the toner layer, and performs contact development.

As shown in FIG. 1A, the developing roller 3 has a dielectric layer 3b formed on the surface of a base roller 3a made of, for example, aluminum, and the surface of the dielectric layer 3b is processed to be described later. It has a surface shape. As is well known, a magnetic material such as ferrite may be mixed in the dielectric layer 3b, and a magnetic pole pattern for attracting magnetic toner may be formed by magnetizing. The developing roller 3 is rotationally driven in the counterclockwise direction of the arrow by a driving unit (not shown), and a developing bias is applied by a power source unit (not shown). The replenishment roller 4 is provided in the toner storage portion 7
The toner is supplied to the surface of the developing roller 3 without being triboelectrically charged, and is rotationally driven in a counterclockwise direction by a driving unit (not shown). The roller 4 also has a function of removing the toner remaining on the surface of the developing roller 3 after passing through the developing area without adhering to the photoconductor 1. Instead of such a replenishing roller 4, a toner replenishing rotary bar that exhibits only a toner replenishing function may be used. The thinning blade 5 is arranged so that its tip end contacts the surface of the developing roller 3, and regulates the toner adhering to the surface of the developing roller 3 to a predetermined layer thickness. The toner on the developing roller 3 may be frictionally charged. The destaticizing brush 6 is for removing non-uniformly remaining charges on the surface of the developing roller 3 which has passed through the developing area. A roller-shaped or blade-shaped static eliminator may be used instead of the brush-shaped static eliminator.

Next, the surface shape of the dielectric layer 3b of the developing roller 3 will be described. As shown in FIGS. 1A and 1B, a spiral groove 3c is formed on the surface of the dielectric layer 3b of the developing roller 3 according to this embodiment. This groove 3c
1 may be formed over the entire width of the developing roller 3 as shown in FIG. 1A, or as shown in FIG. 2, at least in a widthwise area corresponding to the latent image forming area on the photoconductor 1. In addition, the groove 3c may not be formed at both end portions facing the seal member for preventing toner scattering, not shown. According to the latter, the sealing performance of the sealing member can be sufficiently exhibited.

The groove 3c has a surface roughness R _Z in the axial direction.
Is larger than 5 μm and smaller than 30 μm. In addition, the width W of the groove 3c in the axial direction (see FIG. 1B) is preferably smaller than 400 μm from the effect of preventing fogging of the background portion and blurring of vertical lines.

A specific example of the developing roller 3 will be described below. Volume resistivity 10 ¹² to 10 ¹³ Ω · cm, relative permittivity 1
A plurality of developing rollers 3 in which a dielectric layer 3b made of a dielectric material of 0 to 14 is formed so that the developing roller 3 has a diameter of 16 mm, and surface roughness of each developing roller 3 in the axial direction is provided. Grooves having different axial widths W of about 100 μm were formed within the range of R _Z of 5 to 40 μm. The images formed by using the developing rollers 3 in the developing device 2 were evaluated for fog in the background portion and vertical line blurring. As a result, as shown in Table 1 below, with respect to the surface roughness R _Z in the axial direction of 5 to 30 μm, fog and vertical line blurring of the background part do not occur (indicated by ◯ in the table) or allowed. It was within the range (△). (Hereafter, margin)

[Table 1]

In addition, the volume resistivity 10 ¹² to
A plurality of developing rollers 3 each having a dielectric layer 3b made of a dielectric material with a dielectric constant of 10 ¹³ Ω · cm and a relative dielectric constant of 10 to 14 and having a diameter of 16 mm are prepared. Grooves having different axial surface roughnesses R _Z of about 10 μm were formed on the surface, with axial widths W in the range of 50 to 500 μm. The images formed by using the developing rollers 3 in the developing device 2 were evaluated for fog in the background portion and vertical line blurring. As a result, as shown in Table 2 below, in the case where the width W in the axial direction is about 50 to 400 μm, the fog and vertical line blurring of the background part do not occur (indicated by ○ in the table) or an allowable range. It was the inside (△).

[Table 2]

The reason why the fogging of the background portion and the fogging of the vertical lines can be effectively prevented in the developing roller 3 described above is considered as follows. That is, it is considered that the unevenness of the spiral groove on the surface of the developing roller 3 improves the charging efficiency of the toner and the developer carrying ability as compared with the conventional developing roller having a smooth surface. As a result, the toner can be sufficiently rubbed and charged at the portion where the supply roller 4 or the thinning blade 5 and the surface of the developing roller 3 face each other. In addition, the toner once attached to the surface of the photoconductor 1 when the contact portion between the photoconductor 1 and the development roller 3 is considered to be one of the causes of the faint vertical line is pulled back to the surface of the development roller 3. It is considered that this phenomenon is suppressed because the electric field or mechanical blocking action is exerted by the unevenness due to the spiral groove on the surface.

In Tables 1 and 2, a plurality of different toners are selected, using the developing roller 3 which has obtained good results, and having different volume average particle diameters of 15 μm or less. When the image was evaluated by using the toner, as shown in Table 3 below, when the toner having the volume average particle diameter of 10 μm or less was used, the image quality was remarkably improved.

[Table 3]

In each of the specific examples described above, as shown in FIG. 1B, a spiral groove is formed so that adjacent grooves 3c are in contact with each other, but instead of this, FIG. ), The smooth portion 3d may be formed between the adjacent grooves 3c. Similar to each of the above specific examples, a dielectric layer 3b made of a dielectric having a volume resistivity of 10 ¹² to 10 ¹³ Ω · cm and a relative dielectric constant of 10 to 14 was formed so that the developing roller 3 had a diameter of 16 mm. A plurality of developing rollers 3 were prepared. The axial surface roughness R _Z is about 10 μm so that the axial widths F (see FIG. 3A) of the smooth portions on the surfaces of the developing rollers 3 are different from each other within the range of 50 to 200 μm. A groove having a width of about 80 μm in the axial direction was formed. The images formed by using the developing rollers 3 in the developing device 2 were evaluated for fog in the background portion and vertical line blurring. As a result, as shown in Table 4 below, when the width F of the smooth portion 3d in the axial direction is 150 μm or less, fog on the background portion and vertical line blurring do not occur (indicated by ○ in the table) or acceptable. It was within the range (△).

[Table 4] Even in the case where the grooves 3c and the smooth portions 3d alternately appear in the axial direction of the surface of the developing roller as in this example, the charging efficiency of the toner and the developer transporting ability are higher than those of the conventional developing roller having a smooth surface. As a result, the toner can be sufficiently rubbed and charged at the portion where the supply roller 4 or the thinning blade 5 and the surface of the developing roller 3 face each other. In addition, the toner once attached to the surface of the photoconductor 1 when the contact portion between the photoconductor 1 and the development roller 3 is considered to be one of the causes of the faint vertical line is pulled back to the surface of the development roller 3. This phenomenon is suppressed by the electric or mechanical blocking action of the spiral groove 3c on the surface and the unevenness of the smooth portion 3d.

In the example shown in FIG. 1 (b) or FIG. 3 (a), the groove 3c is formed so that the groove surface is rounded. However, instead of this, the groove 3c is formed as shown in FIG. 3 (b) or 3 (c). ),
The groove 3c may be formed such that the groove surfaces intersect at inclined planes at the deepest portion. Any other groove surface shape may be used.

Further, for example, when the inclination angle of the groove 3c with respect to the axial direction of the developing roller shown by α in FIGS. 3 (b) and 3 (c) is smaller to some extent, moire of the dot image is prevented and the image becomes uniform. It is advantageous in maintaining the sex. In particular, it is effective for preventing moire in a dot image such as a halftone of a digital image. Similar to each of the above specific examples, a dielectric layer 3b made of a dielectric material having a volume resistivity of 10 ¹² to 10 ¹³ Ω · cm and a relative dielectric constant of 10 to 14 is used.
Two developing rollers 3 formed so that
Then, on the surface of one developing roller 3, the inclination angle α
Is 89.8 ° and the width 220 in the axial direction is such that adjacent grooves 3c are in contact with each other as shown in FIG. 3 (b).
A groove 3c of μm was formed (this resulted in a simple threaded surface profile). In addition, on the surface of the other developing roller 3, the inclination angle α is 70 °, and
As shown in (b), a groove 3c having a width of 220 μm in the axial direction was formed so that the adjacent grooves 3c were in contact with each other. The images formed by using the developing rollers 3 in the developing device 2 were evaluated for fog, vertical line blurring and moire on the background. As a result, as shown in Table 5 below, moiré can be completely prevented by making the inclination angle α smaller to some extent than simply cutting the groove 3c in a threaded shape (in the table, ◯).
, Or within an allowable range (Δ).

[Table 5]

[0019]

According to the inventions of claims 1 to 6, the surface layer made of the dielectric material of the developer carrying member has a surface roughness of 5 μm in the axial direction.
By forming a spiral groove within a range larger than m and smaller than 30 μm, the developer can be charged well, and the developer carrier can exhibit sufficient developer transporting ability. As a result, there is an excellent effect that fog on the background and vertical line blurring can be prevented.

In particular, according to the developing device of the second aspect, the width of the groove is smaller than 400 μm, and the groove can be easily processed by using a lathe or the like. Therefore, the manufacturing cost of the development carrier is reduced. be able to.

Further, according to the developing device of claim 3, since the one-component developer having a volume average particle size of 10 μm or less is used,
It is possible to particularly well prevent fogging of the background portion and blurring of vertical lines.

Further, according to the developing device of the fourth aspect, since the spiral groove is formed such that the smooth portion is interposed between the grooves adjacent to each other in the axial direction, the adjacent grooves are in contact with each other. As compared with the case of forming the groove, the processing time for forming the groove can be shortened and the manufacturing cost can be reduced.

Further, according to the developing device of the sixth aspect, since the groove is not formed on the both end surfaces of the developer carrying member, the seal member of the seal member arranged facing the both end surfaces,
The sealing performance can be fully exerted.

[Brief description of drawings]

FIG. 1A is a perspective view of a developing roller according to an embodiment,
(B) is an enlarged view of the surface of the developing roller.

FIG. 2 is a perspective view of a developing roller according to a modified example.

3A to 3C are enlarged views of a surface of a developing roller according to another modification.

FIG. 4 is a front view showing a schematic configuration of a developing device according to an embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photoconductor, 2 Developing device 3 Developing roller, 3a Base roller 3b Dielectric layer, 3c Groove 3d Smooth part, 4 Replenishing roller 5 Thinning blade, 6 Static elimination brush 7 Toner accommodating part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Ota 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. A developing device for developing a latent image on a latent image bearing member by bringing a latent image bearing member bearing a one-component developer into contact with the latent image bearing member having a latent image formed thereon. A developing device, wherein a surface layer made of a dielectric material is provided with a spiral groove having a surface roughness in the axial direction of more than 5 μm and less than 30 μm. 2. The width of the groove in the axial direction is 400.
The developing device according to claim 1, wherein the developing device is formed so as to have a thickness of not more than μm. 3. The developing device according to claim 1, wherein a one-component developer having a volume average particle diameter of 10 μm or less is used. 4. The developing device according to claim 1, wherein the spiral groove is formed so that a smooth portion is interposed between adjacent grooves in the axial direction. 5. The width of the smooth portion in the axial direction is 1
5. The developing device according to claim 4, wherein the groove is formed to have a width of 50 μm or less and the width of the groove in the axial direction is 400 μm or less. 6. The developing device according to claim 1, wherein the groove is formed only in a widthwise area corresponding to a latent image forming area on the latent image carrier.