JPH0777867A - Developing roller for electrophotography - Google Patents

Abstract

PURPOSE:To provide a developing roller for electrophotography where developer carrying capacity is high and an abnormal image such as void, longitudinal line thinning, and also the gradation unevenness of stripe pattern or the like is hardly caused. CONSTITUTION:A dielectric part 10 has a projection line 11 whose cross section is trapezoidal, where regular surface ruggedness of a specified pitch in a roller shaft direction is formed, and which is extended in a nearly peripheral direction, and the pitch of ruggedness of the projection line 11 is set to be >=0.3mum to <=500mum. When it is assumed that the pitch of ruggedness of the projection line 11 is deltaf and the main scanning direction pitch of light irradiating a latent image carrier from the optical writing system of an electrophotographic device corresponding to the light emitting cycle of a light source is deltaL, the pitch deltaf of ruggedness of the projection line 11 is more preferably set out of the range of + or -15% of the pitch deltaL taking the main scanning direction pitch deltaL of the light as a reference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing roller provided in an electrophotographic image forming apparatus such as a copying machine, a facsimile machine or a printer, and more particularly, to a cylindrical dielectric part containing a one-component developer. The present invention relates to a developing roller for electrophotography, which is carried and conveyed to a latent image carrier, and is suitable for writing to the latent image carrier by coherent light such as laser light.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus for recording digital image information as an image, a latent image carrier composed of a photoconductor substrate is optically scanned by a laser beam modulated according to the digital image information. Then, a latent image is formed on the latent image carrier, and the developer is carried on the latent image carrier by a developing roller which is a developer carrier to carry out the development.
It is also known to perform processing such as transfer and fixing as needed. Further, a small and inexpensive He-Ne laser or semiconductor laser (usually having an emission wavelength of 650 to 820 nm) is widely used as a laser for optical writing.

When laser writing is performed using a photoreceptor substrate having a multi-layered light-receiving layer, the surface of the developing roller is roughened by sandblasting or sandpaper to enhance the developer transporting power, or its surface shape is uneven. By making it function as an electrode, an abnormal image is prevented from occurring. Specifically, in order to enable stable image formation for a long time, for example, the roller surface is made smooth and uneven (see JP-A-58-153973), and the roller surface of the contact developing system is made of an elastic material. And surface roughness of 6s
The above (see Japanese Patent Laid-Open No. 55-113073), the one in which the roller surface is roughened by sandblasting or sandpaper to have a surface roughness of about 0.2 μm to 10 μm (see Japanese Laid-Open Patent Publication No. 59-126567), and the developing used. A component provided with a sleeve-shaped developing roller having a surface roughness of 2 to 3 times the average particle size of the developer and a member for scraping off the developer adhering thereto (see Japanese Patent Laid-Open No. 3-44661), one component There has been proposed one in which a surface of a developing roller is subjected to an alumite treatment and then roughened by sandblasting using regular or irregular particles (see JP-A-3-14191 and JP-A-3-14192). There is.

[0004]

However, in the above-mentioned conventional electrophotographic developing roller, if there is a projection of several μm on the roller surface, the electric field is concentrated there and the developer is developed on the image. However, there is a problem that an abnormal image with white spots (hereinafter referred to as white spots) is likely to occur. Therefore, in order to improve the image quality, it is necessary to suppress the surface roughness of the roller to 5 μm or less. On the other hand, if such a smooth roller surface is used, the developer may be insufficiently charged (see the above-mentioned Japanese Patent Laid-Open Publication No. Sho. 59-126567), there is a problem that the so-called fog is likely to occur on the background portion due to a low developer transporting ability. Further, when developing a fine line latent image parallel to the moving direction of the latent image carrier (rotation of the photoconductor substrate), it becomes faint and thin, and in severe cases, it is cut off (hereinafter, this is caused by vertical line fading). That).

For the above problem (particularly vertical line blurring),
For example, it is conceivable to prevent the development by regularly arranging protrusions or spiral unevenness extending in the circumferential direction on the roller surface of the developing roller. If the tip is sharp, it is difficult for the developer to deposit, and therefore the developer tends to run out, and the latent image formed on the latent image carrier by the light emitted from the optical writing system in a predetermined cycle and the axial direction of the developing roller. Due to the interference phenomenon with the irregularities that are regularly arranged in the (longitudinal direction), the uneven density of stripes having a certain period with respect to the latent image parallel to the movement (rotation) direction of the latent image carrier (hereinafter, This is called pitch unevenness)
The problem remains that it is easy to occur. That is, due to this interference phenomenon, interference fringes as shown in FIG. 6 are likely to occur in a recorded image, and the image becomes difficult to see particularly when a halftone image having high gradation is formed.

The present invention has been made in view of such conventional problems, and by devising the surface irregularity shape, the developer carrying ability is high, and white spots, vertical line blurring, pitch unevenness and the like are caused. An object of the present invention is to provide an electrophotographic developing roller in which an abnormal image is unlikely to occur.

[0007]

To achieve the above object, the invention according to claim 1 comprises a conductive support and a cylindrical dielectric portion having at least one dielectric layer supported by the support. In the electrophotographic developing roller that conveys the developer carried on the dielectric part to the latent image carrier, the dielectric part comprises:
It has a protrusion with a trapezoidal cross section that extends in the substantially circumferential direction by forming regular surface irregularities having a predetermined pitch in the roller axial direction, and the irregularity forming pitch of the protrusion is 0.3 μm or more and 500 μm or less. It is characterized by that.

According to a second aspect of the present invention, the unevenness forming pitch of the protrusions is set to δ _f, and the latent image carrier is irradiated from the optical writing system of the electrophotographic apparatus in correspondence with the light emitting cycle of the light source. when the main scanning direction pitch of the light and [delta] _L, unevenness formation pitch [delta] _f of the protrusions is set to be out of the range of ± 5% of the pitch [delta] _L relative to the main scanning direction pitch [delta] _L of the light It is characterized by being. This is
As shown in the principle diagram in Fig. 2, the pitch difference between the main scanning direction pitch δ _{L of the} light irradiated on the latent image carrier corresponding to the light source emission period of the optical writing system and the surface unevenness pitch δ _f of the developing roller is The peak of the interference phenomenon that occurs as sensitivity unevenness based on
Since it appears for each pitch δ _m corresponding to a multiple value of the main scanning direction pitch δ _L of the light, by specifying the setting area of the uneven pitch, the pitch of the interference fringes caused by the interference phenomenon is not visible in the area. Means to do.

According to a third aspect of the present invention, the ridge has a trapezoidal cross section in which the ratio of the tip end width to the base end width is 0.2 or more and 1.0 or less, and the depth is larger than the tip end surface. A groove of 0.5 μm or more and 30 μm or less is formed, and a width of the tip end surface of the ridge in the roller axial direction is 0.1 μm or more and 200 μm or less.

The projection having a trapezoidal cross section preferably has a tip end surface that is spiral or similar to a projection that is continuous in the roller axial direction. The number of the projections is arbitrary and The ridges can form a dielectric portion having a multilayer structure. Also, the pitch of the interference fringes can be obtained by replacing the light emission period of the light source and the period (corresponding to the pitch) of the unevenness formed by the ridges with a sine function and synthesizing the two. The concavo-convex forming pitch δ _f is set within a setting area where the pitch becomes invisible. further,
The concavo-convex forming pitch δ _f is preferably set in consideration of the developing range in the roller axis direction and a multiple of the main scanning direction pitch δ _L of the light. It is because the peak of the interference is present for every multiple of the main scanning direction pitch [delta] _L of the light, the pitch [delta]
_L is because the setting range of very uneven formation pitch [delta] _f any value may exist. Further, the conductive support,
Including the journal portion, either one made of a single conductive material or one having a conductive layer portion provided on the main body made of a non-conductive material may be used. Further, the conductive support may be either integrally formed with the journal portion or attached separately.

[0011]

According to the first aspect of the present invention, the protrusions having a trapezoidal cross section extending substantially in the circumferential direction have a pitch of 0.3 in the roller axial direction.
Regular surface irregularities of not less than μm and not more than 500 μm are formed. Therefore, no protrusion for concentrating the electric field is formed on the roller surface, and the unevenness necessary for obtaining the developer carrying force is secured. In addition, since the ridge has a trapezoidal cross section and extends in the substantially circumferential direction, the developer is likely to be deposited on the tip end surface of the ridge, and the charge can be released radially. Therefore, it is possible to reduce the influence of the interference with the latent image carrier side due to the unevenness formed by the protrusions.

According to the second aspect of the invention, the ridge is used.
Pitch of irregularity formation δ_fIs the light emission cycle of the optical writing system
In the main scanning direction of the light emitted to the latent image carrier corresponding to
Chi δ _LIts pitch δ relative to_L± 5% range of
The interference fringes that are set outside
This is an area where J is not visible. Therefore, interference
The occurrence of abnormal images due to stripes is reliably prevented.

Further, in the invention described in claim 3, the effect of claim 1 becomes more remarkable by making the projection of trapezoidal cross section have a specific shape, the developer transporting ability is further improved, and white spots are generated. It is also possible to reliably prevent abnormal images such as vertical lines and faint lines.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 4 are views showing an embodiment of the electrophotographic developing roller according to the invention described in claims 1 to 3. FIG. First, the configuration will be described.

In FIG. 2, 10 is at least one dielectric layer supported by a conductive support (none of which is shown).
Is a cylindrical dielectric portion having. The dielectric portion 10 is charged by a known method in the electrophotographic apparatus, and when the conductive support rotates about its journal portion, the developer carried on the surface is provided in the electrophotographic apparatus. It is adapted to be conveyed to a photoreceptor substrate (latent image carrier). The structure of the electrophotographic apparatus itself is well known and will not be described in further detail.

The dielectric portion 10 has a ridge 11 having a trapezoidal cross section that forms regular surface irregularities having a predetermined pitch in the left-right direction (roller axis direction) in the figure. It has a spiral shape extending in the circumferential direction and has a concavo-convex forming pitch of 0.3 μm in a predetermined vertical section as shown in FIG.
It is not less than 500 μm. Specifically, the protrusion 11 has a ratio of the tip end width W to the base end width W _L of 0.2.
A groove 11b having a trapezoidal cross section of not less than 1.0 and not more than 1.0 and a depth DP of not less than 0.5 μm and not more than 30 μm with respect to its tip surface 11a is formed. The width W of the tip surface 11a in the roller axial direction is preferably 0.1 μm or more and 200 μm.
It is below.

Further, as shown in FIG. 1 (principle diagram of the invention described in claim 2), the concavo-convex forming pitch of the protrusions 11 is set to δ _f, and the light emission cycle of the laser light source from the optical writing system of the electrophotographic apparatus is set. Corresponding to the main scanning direction pitch of the laser light irradiating the photoreceptor substrate is δ _L , the unevenness forming pitch δ _f of the protrusions 11 is the main scanning direction pitch δ _{L of the} laser light.
It is more desirable to set it outside the range of ± 5% of the same pitch δ _L with respect to. This is as sensitivity unevenness based on the pitch difference between the main scanning direction pitch δ _{L of the} laser light applied to the photoconductor substrate corresponding to the light emitting period of the light source of the optical writing system and the surface unevenness pitch δ _f formed by the ridges 11. Since the peak of the interference phenomenon that appears appears in the main scanning direction pitch δ _L of the laser light and the places corresponding to multiples thereof, as shown in FIGS. This means that the uneven pitch δ _f is set, and this makes it possible to reduce the pitch (image pitch) δ _m of the interference fringes caused by the interference phenomenon to the invisible region.

When forming the ridges 11 on the dielectric portion 10, for example, the dielectric portion 10 is cut with a diamond bite or the like at a feed pitch (the feed amount of the cutting edge per one revolution) corresponding to the irregularity forming pitch δ _f. Then, after performing a cutting process of a substantially sinusoidal cross section as shown by a broken line in FIG. 2 so that the surface roughness is in the range of 1 to 50 μm, a projecting ridge having a spiral trapezoidal cross section is formed by a flat cutting tool. Forming 11. Alternatively,
On the contrary, a smooth outer peripheral surface of the dielectric part 10 is cut at a feed pitch corresponding to the unevenness forming pitch δ _f by a sword cutting tool having a sharp tip to form the ridge 11 together with the groove 11b.

In the electrophotographic developing roller of the present embodiment thus configured, the pitch 11 in the roller axial direction is not less than 0.3 μm and not more than 500 μm due to the protrusions 11 having a trapezoidal cross section extending in the substantially circumferential direction. Regular surface irregularities are formed. Therefore, no protrusion for concentrating the electric field is formed on the roller surface, and the unevenness necessary for obtaining the developer carrying force is secured. In addition, since the developer easily deposits on the tip end surface 11a of the ridge 11 and the charge can be easily released radially, an abnormal image due to interference fringes due to an interference phenomenon with the photoconductor substrate side is less likely to occur. Also, ridge 11
By a pitch [delta] _f the irregularities formed on the outside of the same pitch [delta] range of ± 5% of the _L which corresponds to the light source luminous frequency referenced to the main scanning direction pitch [delta] _L of laser light irradiated to the photoconductor substrate If set, the pitch Δ _{m of the} interference fringes caused by the interference phenomenon is reduced to an invisible region, and the occurrence of an abnormal image due to the interference fringes can be more reliably prevented. Furthermore, by making the cross-sectional shape of the ridge 11 have a specific size and shape, the above-mentioned action and effect are more remarkable.

<Test Results> Next, the comparison test results for this embodiment will be described with reference to Table 1. In this test, the dielectric part 10 has a linear protrusion with a trapezoidal cross section similar to the protrusion 11.
The developing rollers of the examples of the types and the developing rollers of the comparative examples of the four types having the linear protrusions of the sine wave shape in the dielectric portion were manufactured and performed. Each of the four types of developing roller has a diameter of 25 mm and a length of 3
As shown in Table 1, the unevenness forming pitch (cutting feed pitch) due to the protrusion is 20 mm. In the processing, the journal parts at both ends of the conductive support were supported on a lathe, and the feed rate per rotation (corresponding to the feed pitch) was changed as shown in Table 1 and cut with a diamond bite. Then, the necessary pieces were cut so as to have the cross-sectional shapes of the respective protrusions. When the surface roughness of each developing roller cut in this way was measured by a surface roughness measuring machine, a sinusoidal cross section as shown in FIG. 4 or a surface roughness as shown in FIG. 5 was obtained in the range of 0.3 to 30 μm. It was found to be a linear protrusion with a trapezoidal cross section. Then, these developing rollers were attached to an electrophotographic apparatus to perform image determination. In this electrophotographic apparatus, the main scanning direction pitch δ _L of the laser light with which the photoconductor substrate is irradiated corresponding to the light emission period of the light source is 0.0635 mm. Therefore, in this case, the unevenness forming pitch δ _f by the ridges 11 is 0.
0603 mm (60.3 μm)> δ _f or 0.06
It is more preferable that 67 mm <δ _f . (Below margin)

[0021]

[Table 1]

In the image determination, all vertical line blurring, which is a defective image, does not occur, and the uneven pitch image is 0.0635 mm in the main scanning direction pitch δ _L corresponding to the light source emission period.
It occurred in the comparative example having the sinusoidal linear protrusions having a cutting feed pitch (concavo-convex forming pitch) of 0.064 mm, and a defective image was obtained. However, in the case of the example product having the trapezoidal linear projections having the same cutting feed pitch, a practically no problem image was obtained, and the uneven pitch image was effectively prevented. Therefore, it can be seen that the interference action which occurs as sensitivity unevenness can be suppressed by making the cross section of the ridge a specific trapezoid.

[0023]

As described above, according to the invention of claim 1, the pitch in the roller axis direction is not less than 0.3 μm and not less than 500 μ due to the protrusion having the trapezoidal cross section extending substantially in the circumferential direction.
Since the regular surface irregularities of m or less are formed, it is possible to eliminate the protrusions that concentrate the electric field from the roller surface, and to secure the irregularities necessary to obtain the developer carrying force. It is possible to effectively suppress the interference phenomenon with the latent image carrier side due to the unevenness formed by the protrusions. as a result,
It is possible to provide an electrophotographic developing roller that has a high developer transporting ability and that is unlikely to cause abnormal images such as white spots and faint vertical lines.

According to the second aspect of the present invention, the pitch δ _f for forming the unevenness by the protrusions is set to the pitch δ in the main scanning direction of the light irradiating the latent image carrier corresponding to the light emitting period of the light source of the optical writing system. since the set outside the range of the pitch δ range of ± 5% of _L relative to the _L, the pitch of the interference fringes is expressed by the interference phenomenon and a region which can not be visible, the occurrence of abnormal images due to interference fringes It can be surely prevented.

According to the third aspect of the invention, the protrusion of the trapezoidal cross section has a specific shape, whereby the effect of the first aspect becomes more prominent, and the developer carrying ability is further improved. It is possible to more reliably prevent abnormal images such as white spots and vertical line blurring.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the principle of the invention according to claim 2.

FIG. 2 is a longitudinal sectional view of a dielectric portion showing an embodiment of the electrophotographic developing roller according to the invention described in claims 1 to 3.

FIG. 3 is a diagram showing the relationship between the main scanning direction pitch δ _{L of the} light irradiated on the latent image carrier and the image pitch δ _m corresponding to the light emission period of the light source of the optical writing system, and the ridges formed on the dielectric portion. 7 is a graph showing the relationship with the unevenness forming pitch Δ _f .

FIG. 4 is a diagram showing an example of a cross section of a linear protrusion having a sinusoidal shape used in a comparative test.

FIG. 5 is a diagram showing an example of a trapezoidal ridge cross section of an example used in a comparative test.

FIG. 6 is a schematic diagram of a pitch unevenness image.

[Explanation of symbols]

10 dielectric portion 11 the main ridge 11a tip surface 11b groove DP depth W End width W _L proximal width [delta] _f protrusion of the unevenness forming pitch [delta] _L light emitting period in the light to be irradiated on the latent image bearing member corresponding Scanning pitch δ _m Interference fringe pitch

Claims (3)

[Claims] 1. A conductive support and a cylindrical dielectric portion having at least one dielectric layer supported by the support,
In an electrophotographic developing roller that conveys a developer carried on the dielectric portion to a latent image carrier, the dielectric portion forms regular surface irregularities having a predetermined pitch in the roller axial direction to form a substantially circumferential direction. A developing roller for electrophotography, comprising an elongated protrusion having a trapezoidal cross section, and an unevenness forming pitch of the protrusion is 0.3 μm or more and 500 μm or less. 2. A pitch in the main scanning direction of light radiated from the optical writing system of the electrophotographic apparatus to the latent image carrier corresponding to the light source light emission cycle is defined as δ _f. when _{L, the} uneven formation pitch [delta] _f of the protrusion, characterized in that it is set outside the range of ± 5% of the pitch [delta] _L relative to the main scanning direction pitch [delta] _L of the light The developing roller for electrophotography according to claim 1. 3. The protrusion has a trapezoidal cross section in which a ratio of a tip end width to a base end width is 0.2 or more and 1.0 or less, and a depth of 0.5 μm or more and 30 μm with respect to the tip end surface.
A groove of m or less is formed, and the width of the tip end surface of the ridge in the roller axial direction is 0.1.
The developing roller for electrophotography according to claim 1, wherein the developing roller has a thickness of not less than μm and not more than 200 μm.