JPH1173006A - Semiconductive roll and developing device using thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductive roll to be used for a developing roll of an electronic photographic printer or the like which is excellent in the durability of printing and the environmental resistance, and by which a high-quality image can be obtained by having a toner with a stable suppying capacity. SOLUTION: An elastic semiconductive layer 2 whose surface has been finished to have a surface roughness Rz of 10 μm or less is provided to the circumference of a conductive shaft body 1. Ranging over the entire printing region on the circuference of the elastic semiconductive layer 2, grooves 3 of a width of 1 to 50 μm, a depth of 5 to 30 μm, and a pitch of 2 to 100 μm are spirally provided at a constant pitch in the circumferential direction of a roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductive roll used for a developing roll of a developing device for visualizing an electrostatic latent image formed on a latent image carrier with a frictionally charged toner, and a developing device using the same. Related to the device.

[0002]

2. Description of the Related Art A latent image on a photosensitive drum or the like is formed on a peripheral surface of a roll-shaped toner carrier having an elastic semiconductive layer formed around a conductive shaft by a triboelectric toner carried in a thin state. In a developing device for visualizing an electrostatic latent image formed on an image carrier, a semiconductive roll is used as a developing roll. The semiconductive roll is required to have conductivity, environmental resistance, low hardness, triboelectric charging, and the like. For this reason,
Made of urethane rubber, NBR, silicone rubber, etc.
As a conductivity imparting agent, there is a roll imparted with semiconductivity by adding an ion-conductive additive or an electron-conductive filler.

As a method of controlling the print density, Japanese Patent Application Laid-Open
Japanese Patent No. 44149 (conductive roller and an apparatus using the same) discloses that the vicinity of the center in the longitudinal direction of the developing roll is affected by pressure unevenness of a regulating member that regulates the thickness of the developing material layer on the surface of the developing roll in the contact developing device. In order to prevent the contact with the electrostatic latent image carrier from being stopped, the longitudinal direction of the conductive roll on the surface of the conductive roll in which the elastic layer having conductivity is formed on the outer periphery of the good conductive shaft is in the rotation direction of the conductive roll. It is disclosed that the print density unevenness is improved by forming minute grooves substantially along the groove.

As a method of improving image accuracy, Japanese Patent Application Laid-Open No. 8-328374 (Developing Roller for Image Forming Apparatus and Manufacturing Method Thereof) is disclosed in Japanese Patent Application Laid-Open No. H8-328374. The laser light output from the laser source is pulsed, and the pulsed laser light is shaped into a point beam linearly arranged at a predetermined pitch interval via an optical system, and the point beam is rotated to form an image. It is disclosed that the surface of a cylindrical member for an apparatus is irradiated to form concave portions having a predetermined pitch on the surface of the cylindrical member, thereby minimizing the uneven surface of the surface of an aluminum developing sleeve.

[0005]

The above-mentioned conventional semiconductive rolls using, for example, urethane rubber or NBR,
Since various process oils and liquid agents such as softeners are added for lower hardness, as a bleed prevention layer, protective layers of various resins including urethane coating and nylon coating are provided, Environmental resistance is not always satisfactory. In particular, if left for a long time in a high-temperature, high-humidity environment, in extreme cases, the resin component is hydrolyzed and adheres to the photosensitive drum, which is a latent image carrier. There was a problem that the charging characteristics of the semiconductive roll changed significantly.

Further, the conventional semiconductive roll has environmental dependence on the charging characteristics of the toner, has a broad charging amount distribution, and may cause background fouling (hereinafter referred to as fogging) due to an insufficient charging amount. On the other hand, a semiconductive roll using silicone rubber as a material has a very stable environment resistance to negatively charged toner and a very sharp charge distribution of the toner, but the print density becomes insufficient with the increase in speed. There was a problem.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an electrophotographic printer which is excellent in printing durability and environmental resistance, has a stable toner supply capability, and can obtain a high-quality image. And a developing device using the same.

[0008]

According to the present invention, there is provided a semiconductive roll comprising an elastic semiconductive body having a surface finished to a surface roughness Rz of 10 μm or less around a conductive shaft (hereinafter simply referred to as a shaft). A roll having a body layer (hereinafter, simply referred to as an elastic body layer), and a groove width of 1 to 50 μm and a groove depth of 5 to 30 μ in the circumferential direction of the roll over the entire printing area around the elastic semiconductive layer.
m, groove pitch is provided spirally at a constant pitch in the range of 2 to 100 μm. If the surface roughness before helical groove processing exceeds Rz = 10 μm, even if grooving is performed later, the shallow part of the groove and the extremely deep part will coexist, A uniform toner conveying force cannot be obtained. That is, unevenness in the thickness of the toner layer becomes large, and poor density of the print density easily occurs, which is not appropriate. Further, when Rz is smaller, since the toner has a sufficient toner conveying ability in the groove portion, even if the surface roughness of the elastic layer is smooth (Rz ≒ 0 μm).
There is no problem). The peripheral surface of this roll may be irradiated with ultraviolet rays or electron beams to perform a surface hardening treatment. This ultraviolet irradiation or electron beam irradiation may be performed before or after the grooving process of spirally forming grooves on the peripheral surface of the roll. Also, in order to improve the charging characteristics of the roll surface with respect to the toner,
It is preferable to apply a silane coupling agent on the peripheral surface of the roll to provide a silane coupling agent treatment layer. The semiconductive roll manufactured in this manner is suitably used as a developing roll of a developing device.

The shape of the groove is 1-50 μm in groove width and 5-5 in groove depth.
It is necessary that the pitch is 30 μm and the groove pitch is in the range of 2 to 100 μm, and grooves are provided spirally at a constant pitch along the axial length on the peripheral surface of the roll. If the width and depth of the groove are less than this range, they do not contribute to an increase in the amount of transported toner, and if they exceed this range, the amount of transported toner is excessively increased and fog is further increased. If the groove pitch is outside this range, the resolving power will be insufficient.
The range of the groove processing is a rubber portion corresponding to the entire printing area. No groove processing is performed on a portion outside the printing area, particularly on a portion at both ends of the semiconductive roll. The biggest reason is prevention of toner leakage. Normally, seal materials are arranged at both ends to prevent toner leakage.However, when the width and depth of the groove on the roll side of that portion is equal to or larger than the toner particle size, , The sealing effect cannot be expected, toner leakage is likely to occur, and the developing roll surface is liable to wear due to friction with the toner sealing member.
Groove processing further reduces wear resistance.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The semiconductive roll of the present invention and a developing apparatus using the same will be described in more detail with reference to FIGS. FIG. 1 is a perspective view schematically showing a semiconductive roll of the present invention. After a semiconductive silicone rubber layer 2 is formed around a shaft body 1, a large number of grooves 3 are circumferentially formed by grooving. It is provided spirally. FIG. 2 (a)
The semi-conductive roll shown in FIG. 1 is provided with a surface-cured silicone rubber layer 4 whose surface is accelerated by irradiating ultraviolet rays or electron beams. FIG. 2B shows a silane coupling agent-treated layer 5 provided by further applying a silane coupling agent thereon.

FIG. 3 schematically shows an electrophotographic printer as an example of a developing device using the semiconductive roll of the present invention as a developing roll. Inside the housing 11, a photosensitive drum 12, which is a latent image carrier, is provided.
After the charging roller 13 uniformly charges the surface of the photosensitive drum 12 to a negative polarity, the charging roller 13 irradiates LED light from the LED array 14 to form a latent image on the surface of the photosensitive drum 12. This latent image is visualized by toner carried on the surface of the developing roll 15,
The image is transferred to the recording paper 17 by the transfer roll 16. The developing roll 15 is uniformly charged by the friction charging blade 18,
The toner carried on the surface of the toner transport roll 19 is received. The toner is supplied from the toner supply device 20. Reference numeral 21 denotes a cleaning roll for removing residual toner adhering to the photosensitive drum 12.

The material used for the shaft body may be a conductive metal such as iron, aluminum, SUS, brass, or the like, a conductive resin in which a thermosetting resin is blended with carbon black or metal powder, or a thermoplastic resin. A material obtained by applying metal plating to the surface of an insulator such as a thermosetting resin to form a conductor may be used, and may be appropriately selected in consideration of workability, economy, and the like.

The silicone rubber layer as the elastic layer includes
A material obtained by blending silica, conductive powder and the like with a polyorganosiloxane and crosslinking with a vulcanizing agent is used. In particular,
As the polyorganosiloxane, for example, dimethylsilicone, methylvinylsilicone, methylphenylsilicone, etc., at least one of which is prepared by using fumed silica, precipitated silica, conductive filler, etc. A mixture kneaded with a vulcanizing agent such as hydrogen siloxane in the presence of a platinum catalyst is used.

The conductive filler includes conductive carbon black, metal powders such as nickel, aluminum and copper, metal oxides such as zinc oxide and tin oxide, and cores such as barium sulfate, titanium oxide and potassium titanate. A material coated with tin oxide may be used. The volume resistivity of the silicone rubber is 10 ¹ to 10 ⁹ Ω · cm. If the volume specific resistance is out of this range, problems such as generation of fog, reduction in transfer efficiency, and inconsistency in print density are likely to occur.

In molding, a shaft body and a silicone rubber composition are integrated and fractionated by using an extruder using a crosshead, and then subjected to primary vulcanization in a gear oven or an IR furnace (infrared heating furnace). Alternatively, a method of injecting a silicone rubber composition after setting a shaft in a mold and performing primary vulcanization at room temperature or under heating, or a method of simultaneously heating and compression molding a shaft and a silicone rubber composition in a mold Are used. After that, it is preferable to stabilize the physical properties by secondary vulcanization for a certain period of time by a heating means such as a gear oven.

The formed roll is finished to a surface roughness Rz of 10 μm or less by using a cylindrical grinder, a shot blaster, a sand blaster, a lapping machine, a buffing machine, etc., and then the YAG is rotated with the roll shaft as an axis. laser,
The grooves are spirally formed along the circumferential direction of the roll by using a laser processing machine such as an excimer laser or other general-purpose processing methods.

After the grooving, ultraviolet irradiation or electron beam irradiation is performed. By this irradiation treatment, the surface of the roll can be further hardened, and the abrasion resistance is improved. This irradiation with ultraviolet rays or electron beams may be performed before the grooves are provided.
This is because the improvement of the material strength required in the present invention is recognized whether the ultraviolet irradiation or the electron beam irradiation is performed before or after the groove processing. However, from the viewpoint of the penetration depth into the rubber surface, ultraviolet light penetrates only the outermost surface, and if groove processing is performed after irradiation, the inner surface of the groove is closer to the original material strength, so Preferably, ultraviolet irradiation should be performed after the groove processing. On the other hand, in the case of electron beam irradiation, since the penetration depth reaches several hundred μm, the material strength of the inner surface of the groove is improved regardless of whether the groove is formed before irradiation or after irradiation.

Furthermore, in order to control the charging characteristics of the roll, a silane coupling agent such as aminosilane may be applied to the surface of the roll using a pad. By applying the silane coupling agent, the charging characteristics of the toner can be controlled to an optimum state, and the printing characteristics can be further improved. The application method is not limited to this method, and an application method such as spray application, dipping, roll coating, or the like can be arbitrarily selected. Further, in order to accelerate drying of the silane coupling agent, heating can be performed at an appropriate temperature.

The shaft, which is also a support for the elastic layer, has one end grounded or a bias voltage applied thereto.
This is to obtain performance such as charging of the electrostatic latent image carrier, injection of charge into the toner, and development of the electrostatic latent image by transporting the toner to the electrostatic latent image carrier. The elastic layer functions as an electrode in the charging step and the developing step, and further functions as an electrode for contact charging to the toner and charge injection.
In the developing step, the toner is carried and conveyed on the surface of the semiconductive roll by the unevenness of the surface, van der Waals force, mirror image force, Coulomb force and the like.

The surface of the roll is irradiated with ultraviolet rays or electron beams to increase its surface hardness, improve its abrasion resistance, change little in irregularities even after a printing durability test, and extremely decrease the toner transporting ability. The toner is charged by friction between a triboelectric charging blade, a toner transport roll, and the surface of the developing roller which is a semiconductive roll, and a groove is formed on the surface of the developing roll in a circumferential direction. By forming the grooves spirally at a constant pitch by applying the toner, the toner layer can be formed to have a large and constant thickness over the entire peripheral surface of the developing roll. At the same time, the toner can smoothly flow in the groove, and the probability of the toner contacting the surface of the developing roll is increased, so that the charging characteristics of the toner can be controlled. As a result, the charge amount (average value) can be stabilized, and fog can be reduced. Fog is considered to occur when the absolute value of the charge amount is low, and the mechanism of the occurrence is such as the probability of toner contact with the developing roll and the ease with which charge is injected into the toner from the developing roll. It is believed to depend on.

Further, in order to control the charge amount of the toner,
By applying a compound having an atomic group containing an electron donating group or an electron accepting group such as a silane coupling agent to the surface of a roll, the charge amount distribution of the toner can be sharply charged to the required potential. As a result, the printing density is stable, and at the same time, a high-quality printed image free from fog can be obtained. In addition, the semiconductive roll of the present invention is excellent in environmental resistance to temperature and humidity because silicone rubber is used for the elastic layer.

[0022]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. Example 1 As a shaft, SUM22 was electroless nickel plated and had a diameter of 10
Using a shaft with a length of 250 mm and a length of 250 mm, apply silicone primer / Primer No. 16 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) to the peripheral surface of the shaft.
A baking treatment was performed at 50 ° C. for 10 minutes to produce a shaft. As conductive silicone rubber composition, 100 parts by weight of organic peroxide-reactive silicone raw rubber, KE-78VBS (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), carbon black and thermal black (trade name, manufactured by Asahi Carbon Co., Ltd.) 10 parts by weight, 25 parts by weight of fumed silica-based filler, Aerosil 200 (trade name, manufactured by Nippon Aerosil Co., Ltd.) were added and kneaded with a pressure kneader to prepare a conductive silicone rubber composition.

After adding 2.0 parts by weight of an organic peroxide-based vulcanizing agent, C-8 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.), to this silicone rubber composition, compression was performed with a cylindrical cavity having an inner diameter of 20 mm. It was set and filled together with the shaft body in the cavity of the molding die, and was subjected to vulcanization adhesive molding at 175 ° C. for 10 minutes. After that, secondary vulcanization is performed at 200 ° C for 7 hours in a gear oven, and the surface is polished by a cylindrical grinder. Rolls having a diameter of 18 mm, a rubber part length of 210 mm, and a surface roughness of 8.5 µm (Rz) are obtained. And Then, while rotating this roll around its axis, using a YAG laser processing machine, a spiral groove is formed in the circumferential direction of the roll with a width of 25 μm, a depth of 20 μm, and a pitch of 50 μm. Was made. Further, the surface of the semiconductive roll was irradiated with ultraviolet light from a low-pressure mercury lamp to improve printing durability.

Examples 2 to 4 Rolls were prepared in the same manner as in Example 1, and the width, depth,
The semiconductive rolls of Examples 2 to 4 were manufactured by changing the pitch.

Example 5 While rotating the semiconductive roll obtained in Example 1 around this shaft as a rotation axis, a bifunctional silane coupling agent γ-aminopropylmethyldiethoxysilane · KBE was used.
−902 (Shin-Etsu Chemical Co., Ltd., trade name) 10 parts by weight of toluene
The solvent diluted with 100 parts by weight was applied to the roll surface using a pad. Thereafter, the film was dried at 150 ° C. for 1 hour in a gear oven to produce a semiconductive roll.

Next, each of the manufactured semiconductive rolls is mounted on a commercially available electrophotographic printer using a negatively charged toner as a developing roll of a developing device for visualizing an electrostatic latent image.
Printing tests were performed under high temperature and high humidity, constant temperature and constant humidity, and low temperature and low humidity. The results are as shown in Table 1. All of the rolls of Examples 1 to 5 had high print density and no fog after initial printing under each environment and after printing 6000 sheets, and produced high quality printed images. Obtained. at the same time,
Microscopic observation of the surface of the developing roll revealed no abnormalities such as adhesion of the toner and deterioration of the roll material (see Table 1). The initial fog means the Macbeth density on a white background in a 5% duty image immediately after the start of the durability test, and the fog after durability means the Macbeth density on a white background after printing 6,000 sheets.

[0027]

[Table 1]

Comparative Example 1 As a comparative example, a semiconductive roll was manufactured in the same manner as in Example 1 except that a groove was formed on the roll surface and irradiation of ultraviolet rays was performed, and a printing test was performed in each of the above environments. It carried out similarly to Examples 1-5.

Comparative Example 2 A semiconductive roll was manufactured in the same manner as in Example 1 except for the formation of a groove on the roll surface, and a printing test was performed in each of the above environments in the same manner as in Examples 1 to 5. went. The printing test results of the developing rolls obtained in Comparative Examples 1 and 2 are as shown in Table 1 above, and all were inferior to the developing rolls of Examples 1 to 5.

The same result was obtained when an electron beam irradiation process was performed instead of the ultraviolet irradiation in the above embodiment, and the same result was obtained even when the irradiation process was performed before the groove forming process. Obtained. Further, the groove processing may be performed by a method such as wet polishing or buffing instead of laser processing.

The measurement method for each measurement item in Table 1 is as follows. Roll resistance: The roll before applying the silane coupling agent is placed on a gold-plated electrode that is 5 mm longer than the entire length of the rubber portion, and 500 g of a weight is placed on each end of the roll.
A voltage of 10 V was applied between the roll shaft (shaft) and the roll surface, and the resistance at this time was measured. Surface roughness: Ten points were measured in the circumferential direction of the roll before grooving using a universal roughness tester, and the average value was displayed.・ Fog: The produced semiconductive roll is incorporated as a developing roll into an electrophotographic printer, and black solid
The% duty / white background printing was repeated, and the Macbeth density of the white background portion of the 5% duty image was measured using a Macbeth densitometer. Print density: Both the initial print density and the post-durability print density were measured using a Macbeth densitometer at the Macbeth density of a black solid printed portion printed by the same method as for fog.

(Judgment of Pass / Fail) Fog: Both initial fog and post-durability fog having a Macbeth density of more than 0.015 in a white background are rejected (indicated by a symbol x). -Print density: Both the initial print density and the post-durability print density are unacceptable if the Macbeth density of the black solid print portion is less than 1.3. -Toner fixation: The roll surface after the durability test was observed with a microscope. If the toner fixation was observed, the roll was rejected.

[0033]

The semiconductive roll according to the present invention has grooves provided spirally at a constant pitch along the peripheral surface thereof. For this reason, the amount of toner sandwiched between the triboelectric charging blade and the developing roll increases, the toner can be carried thickly at a constant thickness, the toner charging characteristics are improved, and fog is reduced. . At the same time, since the rotation direction of the roll and the direction of the groove are provided at a certain angle, the toner can flow smoothly in the groove, and the contact probability of the toner on the developing roll surface is reduced. And the charging potential of the toner is stabilized. In addition, the surface of the elastic layer is increased in hardness by irradiation with ultraviolet rays or electron beams, has improved abrasion resistance, has a small change in unevenness even after a printing durability test, and has a very small decrease in toner conveyance force. The semiconductive roll having a surface coated with a silane coupling agent has a sharp charge amount distribution of the toner, has a stable print density, and can provide a high-quality printed image with less fog. This effect is more remarkable in a high-temperature and high-humidity environment. In addition, since the elastic layer is formed using silicone rubber as a base material, it is not hydrolyzed by moisture in the air, has excellent environmental resistance, does not adhere to the photosensitive drum, and does not adhere to the toner. As described above, the semiconductive roll of the present invention has excellent environmental resistance, stable printing durability, and extremely excellent printing characteristics.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing one embodiment of a semiconductive roll of the present invention.

2A is a cross-sectional view of the semiconductive roll shown in FIG. 1, and FIG. 2B is a cross-sectional view of a semiconductive roll showing another embodiment.

FIG. 3 is a schematic front view showing a layout of a developing device.

[Explanation of symbols]

 1. Shaft 2. 2. Semi-conductive silicone rubber layer Groove 4. 4. Surface-cured silicone rubber layer 10. Silane coupling agent treatment layer Housing 12. Photosensitive drum 13. Charging roll 14. LED array 15. Development roll 16. Transfer roll 17. Recording paper 18. Friction charging blade 19. Toner transport roll 20. Toner supply machine 21. Cleaning roll

Claims (2)

[Claims] (1) The surface around a conductive shaft body has a surface roughness Rz =
A roll having an elastic semiconductive layer finished to 10 μm or less, over the entire printing area around the elastic semiconductive layer, a groove width of 1 to 50 μm, a groove depth of 5 to 5 in the circumferential direction of the roll.
A semiconductive roll characterized in that grooves are spirally provided at a constant pitch in a range of 30 μm and a groove pitch of 2 to 100 μm. 2. A developing device using the semiconductive roll according to claim 1 as a developing roll.