JPH08185014A - Electrifying member and image forming device provided with the same - Google Patents

Abstract

PURPOSE: To provide an electrifying device whose electrifying noise is less and in which scrape on a photoreceptor is decreased, and an image forming device provided with the same electrifying device. CONSTITUTION: As to this electrifying member 10 which is arranged proximately to or in contact with a body to be electrified, and which performs electrifying processing on the body to be electrified by impressing electrifying voltage; the maximum diameter of the non-image area part of the member 10 is >=1.0010 times and <1.5000 times as large as that of an image area part. Furthermore, a distance between the member 10 and the body to be electrified becomes curvedly large toward the end of the electrifying member, the shape has a radius of curvature R, the radius of curvature R is 1mm<=10mm, and the electric resistance value of the non-image area of the member 10 is higher than that of the image area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact or proximity charging device used in an image forming apparatus such as electrophotography.

[0002]

2. Description of the Related Art For the sake of convenience, an explanation will be given by taking as an example a charging process of a photoconductor in an image forming apparatus such as an electrophotographic copying machine, a laser beam printer, an electrostatic recording apparatus or the like.

The image forming apparatus as described above includes a step of uniformly charging a charged body such as a photosensitive body as an image carrier or a derivative or a transfer material to a predetermined potential.

Conventionally, 5 to 10 kV has been used as the charging means.
A corona charging device for causing corona discharge by applying a high voltage to a wire having a thickness of 60 μm to 100 μm has been widely used.

However, the above corona charging device has
Due to various drawbacks, contact and proximity charging have been proposed as an alternative. In the contact and proximity charging, a charging member is brought into pressure contact with or close to the surface of the charged member and a voltage (DC voltage or a superimposed voltage of DC voltage and AC voltage) is applied to the charging member so that the surface of the charged member is predetermined. It is charged to the polarity and electric potential. Since such a contact and proximity charging device can use a lower applied voltage than the corona charging device, it has advantages such as less ozone generation.

Further, as a contact type charging member which has been put into practical use at present, a roller type member is generally used. In this case, for example, in this case, a conductive elastic layer and a resistance control are sequentially provided around a conductive cored bar. In many cases, it has a structure in which a layer and a surface layer are laminated, but at least a core metal and an elastic body are sufficient.

The material of the elastic body in this case is, for example, urethane, SBR, EVA, SBS, SEBS, SI.
S, TPO, EPDM, EPM, NBR, IR, BR,
There are resins and rubbers such as silicone rubber and epichlorohydrin rubber. Depending on the required resistance value, for example, carbon black, carbon fiber, metal oxides, metal powder, solid electrolyte such as perchloric acid, and conductivity of surfactants, etc. For example, there is a material added with a property imparting material.

Examples of materials for the resistance control body include polyamide, polyurethane, fluorine, polyvinyl alcohol,
There are resins and rubbers such as silicone, NBR, EPDM, CR, IR, BR, and hydrin rubber, and there are, for example,
There is a mixture of conductive or insulating fillers and additives.

The above-mentioned materials are used and the electric resistance value of the charging member is set to 1 × 10 ³ to 1 × 10 ¹⁰ Ω. It doesn't matter.

Cartridges in which a toner container, a developing machine and the like are integrated using these charging members are generally used. These cartridges are 3000 to 800.
It is common that the toner runs out when printing about 0 sheets and the cartridge life ends at that point.

[0011]

By the way, recently, due to environmental problems and increased load on the printer due to networking of computers, there is an increasing demand for higher speed printers and correspondingly higher cartridge durability.

However, when the speed of the cartridge utilizing the contact type or proximity type charging is increased, there are the following problems.

In order to charge the photoreceptor at a high speed,
It is necessary to increase the voltage because it is not charged to a predetermined potential unless the current is increased from the low speed one, and the frequency must be increased in the case where the alternating current is superposed. Therefore, in the case of contact charging, the vibration is transmitted to the photoconductor and the sound becomes loud.

As another problem in the case of speeding up, in a contact and proximity type charging device utilizing discharge in a minute gap, the charging member comes into contact with or comes close to the surface of the organic photoreceptor, so that the film of the organic photoreceptor is formed. If there is a thin portion, discharge is likely to concentrate because the resistance value of that portion is low.

As a result, the influence of the contact of the charging member or the discharge in the vicinity of the adjacent surface strongly acts on the organic photoconductor, degrading the surface of the photoconductor and causing local abrasion. These effects are likely to occur at the end of the charging member. This is because the organic photoconductor is mainly made by a coating method called dipping, so the starting part on one side of the organic photoconductor becomes thin,
This is because the end portion of the charging member hits the portion where the film thickness is thin, or the end portion approaches.

Further, when the speed of the printer is increased, it is necessary to increase the value of the current flowing through the charging member, and the local abrasion is increased.

Therefore, as disclosed in Japanese Unexamined Patent Publication No. 4-1574843, there has been proposed a device in which the end of the charging member has a high resistance in order to prevent the end leak. However, in this case, when the current value flowing through the charging member is low,
Although the effect is sufficient, when the current value is increased with the speedup of the printer, the discharge current is switched if only the non-image area is formed with a high resistance material close to insulation and the discharge current is reduced by one step. The discharge at the part may become strong,
The effect was sometimes insufficient.

Even if a resistor having a slightly higher resistance than that of the image area is used instead of a high-resistor in order to reduce the resistance difference in the portion where the discharge current is switched, the effect of suppressing the discharge from the end is reduced. Results in insufficient effect. Further, looking at the embodiment of the Japanese Patent Laid-Open No. 4-157483,
Since the end of the charging member is cut off vertically, if a material having a high coefficient of friction is brought into contact with a highly rigid drum while applying a load, kinking occurs when the end is loaded and the stress is recovered. Therefore, the end portion of the charging member may be rapidly returned in the rotating direction of the charging member, and the end portion may be rubbed against the photosensitive drum, which may cause an unpleasant sound.

Further, Japanese Patent Laid-Open No. 63-208877,
As disclosed in Japanese Patent Application Laid-Open No. 1-179959, there is also proposed a taper shape or an R shape at the end to weaken the electric field strength at the end. However, even in this case, when the current value flowing to the charging member is low, the effect is sufficient, but when the current value is increased, the discharge suppressing effect may be insufficient, or the charging noise suppressing effect may be insufficient. Can't be seen.

As another method, for example, there is a method of reducing the influence of the surface-deteriorated portion by increasing the thickness of the drum. If the thickness is increased, uneven thickness is likely to occur, which causes uneven density of an image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charging member that produces less charging noise and reduces abrasion of the photosensitive drum, and an image forming apparatus including the charging member.

[0022]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is arranged in the state of being close to or in contact with an object to be charged, and a charging voltage is applied to charge the object to be charged. In the member (10), the charging member (1
0) the maximum diameter of the non-image area portion is 1.0010 times or more and less than 1.5000 times the maximum diameter of the image area portion,
In addition, a shape in which the distance between the charging member (10) and the body to be charged increases curvedly toward the end of the charging member,
The shape thereof has a curvature R, R = 1 mm or more and less than 10 mm, and the electric resistance value of the non-image area of the charging member is higher than that of the image area.

Further, according to the present invention, in a charging member (10) which is arranged in the state of being close to or in contact with a member to be charged and which is charged with a charging voltage, the charging member (10) is charged with the charging member (10). The maximum diameter of the non-image area portion is 1.0010 times or more and less than 1.5000 times the maximum diameter of the image area portion, and the distance between the charging member and the body to be charged is linear toward the end of the charging member. Has a chamfered surface which becomes large, and the angle formed by the chamfered surface and the surface of the body to be charged contacting or approaching the charging member in the image area is 1
It is characterized in that it is 0 ° or more and less than 70 ° and that the electric resistance value of the non-image area of the charging member is higher than that of the image area.

In this case, the electric resistance value of the image area of the charging member (10) is 1 × 10 ³ to 1 × 10 ¹⁰ Ω, and the electric resistance value of the non-image area is 6 times higher than that of the image area. Is desirable.

According to the present invention, the electrostatic latent image is formed on the charged surface of the charged body uniformly charged by the charging member by the exposing means, and the toner is formed on the electrostatic latent image via the developing means. The charging member (10) is applied to an image forming apparatus in which a toner image is formed by adhering the toner to a transfer material, and the toner image is transferred to a transfer material by a transfer unit, and the member to be charged is an organic photoconductor. Is characterized by.

[0026]

Since the present invention is constructed as described above,
The vibration is suppressed by changing the end portion of the charging member (10), and the discharge amount of the non-image area is also reduced by increasing the resistance value of the non-image area of the charging member 6 times or more than that of the image area.

Since the chamfered surface or the R surface is formed by concentrating the discharge from the end portion of the charging member (10), the synergistic effect with the above causes the speedup of the printer and the accompanying high durability of the cartridge. It is possible to suppress an increase in charging noise, and also with respect to the durability of the body to be charged, by increasing the resistance value in the non-image area by 6 times or more and by providing a chamfered surface or an R surface, discharge at a portion where the discharge current is switched High durability is possible by preventing discharge from concentrating from the end while preventing it from becoming strong.

In addition, the non-image area has a high resistance,
Even when a load is applied to the end portion while applying a load, the chamfered surface or the R surface is formed at the end portion of the charging member to gradually reduce the peripheral speed of the outermost end portion so that the load escapes. Therefore, the unpleasant rubbing noise is prevented because the kink does not occur.

The reference numerals in parentheses are for checking the drawings and do not limit the structure of the present invention.

[0030]

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the maximum diameter b of the non-image area portion of the charging member 10 is set to 1.0010 times or more and less than 1.5000 times the maximum diameter a of the image area portion, and the end shape is R =. The resistance value in the non-image area of the charging member is set to be 1 mm or more and less than 10 mm and higher than that of the image area. For example, if the end of the elastic layer 2 of the charging member 10 is R = 1 mm or more and 10 m
After forming the layer 3 for adjusting the resistance to less than m, the layer 4 in which the electric resistance value of the non-image area is 10 times or more higher than that of the image area is set to 1.0010 times or more of the image area maximum diameter a and 1.50 or more.
It is formed with the maximum diameter b which is not 00 times. In addition, reference numeral 1 in the drawing
Is a cored bar.

Further, as shown in FIG. 2, the end portion of the elastic layer 2 of the charging member 10 is set to R = 1 mm or more and less than 10 mm to directly increase the electric resistance value of the non-image area 10 times or more than that of the image area. 4 is divided into a portion for forming the maximum diameter b of 1.0010 times or more and less than 1.5000 times the maximum diameter a of the image area and the layer 3 for adjusting the resistance.

Alternatively, as shown in FIG. 3, the end portion of the elastic layer 2 of the charging member 10 is set to be R = 1 mm or more and less than 10 mm, and the electric resistance value of the non-image area is 10 or less than that of the image area without forming the resistance control layer. After forming the layer 4 having a height more than twice as large as the large diameter b which is 1.0010 times or more and less than 1.5000 times the maximum diameter a of the image area, the layer 3 for adjusting the resistance is formed from thereabove as shown in FIG. There are ways to do it.

Further, as a processing method when the charging member 10 has an R shape, there are a method in which the R shape is previously attached to the mold at the time of molding, and a method in which the charging member 10 is scraped with a file after molding.

When the maximum diameter of the non-image area is less than 1.0010 times the maximum diameter of the image area, the pressure is almost the same as the pressure at the contact portion of the image area surface, so that it is difficult to obtain the effect of reducing the charging noise and the non-image area is not obtained. When the maximum diameter of 1 is more than 1.5000 times the maximum diameter of the image area, the effect of reducing the charging noise can be obtained, but the area of the discharge portion of the image area becomes unstable, and image unevenness easily occurs.

If the electric resistance value of the non-image area is less than 6 times the electric resistance value of the charging member, it is almost the same as the discharge state of the image area, so that it is difficult to obtain the effect of reducing the deterioration of the body to be charged. When the electric resistance value of the non-image area is 10,000 times or more the electric resistance value of the charging member, the discharge at the portion where the discharge current is switched may be strong, and the effect may be insufficient.

The electric resistance value described in the present invention is a value obtained by partially measuring between the support of the charging member and the surface in contact with or close to it, and is different from the volume resistivity.

Next, another embodiment will be described.

As shown in FIG. 5, the maximum diameter of the non-image area portion of the charging member 10 is changed to the maximum diameter of the image area portion 1.00.
10 times or more and less than 1.5000 times, the distance between the charging member and the member to be charged is gradually increased linearly toward the end at the end of the charging member, and the chamfered surface of the end is 10 ° or more and less than 70 °. In addition, the resistance value of the non-image area of the charging member is set higher than that of the image area. For example, after chamfering the edge of the elastic layer 2 at a chamfering angle of 10 ° or more and less than 70 ° and forming a layer 3 for adjusting the resistance, a layer 4 in which the electric resistance value of the non-image area is 10 times or more higher than that of the image area. Is formed with a maximum diameter b that is 1.0010 times or more and less than 1.5000 times the maximum diameter a of the image area.

Further, as shown in FIG. 6, after chamfering the end of the elastic layer 2 at a chamfering angle of 10 ° or more and less than 70 °,
Directly, the layer 4 whose electric resistance value in the non-image area is 10 times higher than that in the image area is 1.00 with respect to the maximum diameter a of the image area.
There is a method in which a portion formed to have a maximum diameter b of 10 times or more and less than 1.5000 times and a layer 3 for adjusting resistance are divided and separately coated.

Further, as shown in FIG. 7, after chamfering the end portion of the elastic layer 2 at a chamfering angle of 10 ° or more and less than 70 °, the electric resistance value of the non-image region is adjusted without forming the resistance control layer. A layer 4 which is 10 times or more higher than the image area maximum diameter a is formed to have a maximum diameter b of 1.0010 or more and less than 1.5000 times, and a layer 3 for adjusting resistance is formed thereon from above. There are ways to do it.

The chamfered surface described in the text means, as shown in FIG. 9, an arbitrary point 7 on the surface 5 where the charging member 10 and the member to be charged are in contact with or close to each other and the end surface 6 of the charging member. It is a surface 9 that connects arbitrary points 8, and the chamfer angle is also the angle α in FIG. 9.

As a processing method for chamfering the end portion of the charging member 10 at 10 ° or more and less than 70 °, a method of preliminarily forming a chamfered shape in a mold at the time of molding, a method of cutting with a cutter or the like after molding, etc. is there.

The chamfering angle of the end of the charging member 10 is 10 °.
If it is at least 70 °, the effect of the present invention can be obtained, but it is preferably at least 10 ° and at most 30 °. When the angle is 70 ° or more, the distance from the power supply portion such as a core bar to the discharge portion is less likely to be uniform, so that the effect of gradually reducing the discharge is lessened and the discharge easily concentrates on a part, and is less than 10 °. In this case, the effect of reducing the electric discharge is good, but the working is substantially difficult.

The elastic body 2 used in this embodiment may be sponge-like one, and in this case, the effect of the present invention is further enhanced.

As the resin of the paint used in this embodiment, for example, polyamide, polyurethane, fluorine, polyvinyl alcohol, silicone, NBR, EPDM, CR, IR,
Examples thereof include resins such as hydrin rubber and rubbers, and for example, insulating or conductive fillers or additives may be mixed therein.

According to the present embodiment, the charging member 10 manufactured can be used with either a DC voltage or a voltage applied with a superimposed voltage of a DC voltage and an AC voltage. Due to the cause of its occurrence, the charging noise reduction effect is observed only during contact-type body electrification when a superimposed voltage of DC voltage and AC voltage is applied. It is effective regardless of the applied DC voltage or the superimposed voltage of the DC voltage and the AC voltage.

As the member to be charged used in this embodiment, for example, an organic photosensitive layer is provided on a conductive support, and if necessary, an undercoat layer having a barrier function and an adhesive function therebetween. May be provided.

The features of such an organic photoreceptor are that it is often used as a member to be charged because of its high safety, good chargeability, good productivity, and low cost.
On the other hand, as shown below, since a resin is generally used as a binder, it is easily affected by a decrease in molecular weight due to discharge.

However, by using the charging member 10 of this embodiment, it is possible to realize high durability while taking advantage of the characteristics of the organic photoconductor.

As the conductive support for the member to be charged used in this embodiment, for example, the following ones can be used. (1) Aluminum, aluminum alloy, stainless steel,
Metals such as copper. (2) Formed by vapor-depositing or laminating a metal such as aluminum, palladium, rhodium, gold or platinum on the surface of a non-conductive support such as glass, resin or paper or the conductive support of (1) above. . (3) A layer of a conductive compound such as a conductive polymer, tin oxide or indium oxide is vapor-deposited or applied on the surface of a non-conductive support such as glass, resin or paper or the conductive support of the above (1). Formed by

As the material for forming the undercoat layer, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, methyl cellulose, casein, polyamide, glue, gelatin, etc. are usually used.

The organic photosensitive layer comprises a charge generating layer and a charge transporting layer, and a protective layer may be provided on the photosensitive layer for controlling charge injection, for example.

The charge-generating layer can be formed by dispersing the charge-generating substance in a suitable binder and coating this on a conductive support. Also, vapor deposition on a conductive support,
The thin film can also be formed by a dry method such as sputtering or CVD. Examples of the charge generating substance include the following substances. These charge generating substances may be used alone or in combination of two or more. (1) Azo pigments such as monoazo, bisazo and trisazo. (2) Indico pigments such as indico and thioindico. (3) Phthalocyanine-based pigments such as metal phthalocyanine and non-metal phthalocyanine. (4) Perylene-based pigments such as perylene anhydride and perylene imide. (5) Polycyclic quinone pigments such as anthraquinone and hydroquinone. (6) Squalilium dye. (7) Pyrylium salts and thiopyrylium salts. (8) Triphenylmethane dye.

The binder can be selected from a wide range of binder resins such as polycarbonate resin, polyester resin, polyacrylate resin, butyral resin, polystyrene resin, polyvinyl acetal resin, diallyl phthalate resin, acrylic resin, methacrylic resin, Examples include, but are not limited to, vinyl acetate resin, phenol resin, silicone resin, polysulfone resin, styrene-butadiene copolymer resin, alkyd resin, epoxy resin, urea resin, vinyl chloride-vinyl acetate copolymer resin, and the like. is not.

Further, these may be used alone or in combination as a homopolymer or a copolymer.

The resin contained in the charge generation layer was 8
It is preferably 0% by weight or less, more preferably 40% by weight or less.
The film thickness of the charge generation layer is 5 μm or less, especially 0.01 μm.
It is preferable that the thin film layer has a thickness of m to 2 μm. Various sensitizers may be further added to the charge generation layer.

The charge generation layer is formed by applying and drying a paint in which a charge transporting substance and a binder resin are dissolved in a desire agent. Examples of the charge transport material include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, and the like. Further, as the binder resin, those mentioned above can be used. For coating the organic photosensitive layer, any conventionally known method such as a dipping method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a beam coating method and a roll coating method can be used.

An organic photoconductor is prepared using such a material and used in a cartridge or the like. Hereinafter, an actual embodiment will be described. [Example 1 of embodiment] (Adjustment of compound for elastic layer) EPDM: 100 parts by weight, zinc oxide: 5 parts by weight, higher fatty acid: 1 part by weight, conductive carbon black: 5 parts by weight, paraffin oil: 1
0 parts by weight, sulfuric acid: 2 parts by weight, vulcanization accelerator MBT: 1 part by weight, vulcanization accelerator TMTD: 1.5 parts by weight, vulcanization accelerator Z
nMDC: 1.5 parts by weight were mixed for 20 minutes while cooling with a two-roll mill to prepare a compound. (Preparation of coating material for coating layer) Methylolated nylon: 100
Parts by weight, methanol: 420 parts by weight, toluene: 150
Nylon paint was prepared by mixing parts by weight. (Preparation of paint for coating both ends) Silicone resin: 100 parts by weight and toluene: 335 parts by weight were mixed to prepare a silicone paint. (Measuring Method of Charging Sound) The charging sound was measured in accordance with the item 6 of ISO 7779. (Packing of photoconductor) A packing of φ28.45, length 65 mm, and weight 120 g was inserted into a drum having a diameter of 30.0 mm and a length of 260.5 mm. (Measuring method of electric resistance of charging member) Under the conditions of temperature 22.5 ° C and humidity 55% RH, a thin film of good conductivity such as aluminum foil is cut into a width of 1 cm and a length of 10 cm and wound on the charging member. Then, a digital meguohm high tester (manufactured by HIOKI) is connected to both ends of the core metal and the thin film, a DC voltage of 250 V is applied, and the value after 10 seconds is read. (Preparation and Evaluation of Charging Member) First, the elastic layer compound was placed on a stainless steel core bar having a diameter of 6 mm at 150 ° C. for 1 hour.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. Next, the radius R =
After polishing to a state of 3.5 mm, the coating material for coating layer was applied by dipping, and then the coating material for coating both end portions was coated by 5 mm from the end portions. When the maximum diameter of the image area and the maximum diameter of the non-image area of this charging member were measured, the maximum diameter of the image area was 12.029 mm and the maximum diameter of the non-image area was 12.
149 mm, the maximum diameter of the non-image area portion is 1.0100 times the maximum diameter of the image area portion, and the electric resistance value (the resistance value is measured according to the electric resistance value of the charging member) of the image area is 1 × 10. ^The charging value is ⁶ Ω, the resistance value of the non-image area at both ends is 1 × 10 ⁹ Ω, the resistance value of the non-image area is 1000 times that of the image area portion, and the discharge from both ends is gradually reduced. Got

This charging member was transferred to the position of the primary charger of the laser beam printer (laserjet 4si manufactured by Hewlett Packard), and the DC voltage was -750.
V, AC voltage 2.0 kV (peak-to-peak voltage), frequency 6
It was 49 when superimposed charging was applied at 50 Hz and the charging noise was measured.
Fog is a level that does not matter and the fog is caused by the thin film thickness of the drum (the main cause is scraping due to discharge) on the image in high temperature and high humidity (32.5 ° C, 85% RH) environment. When a durability test was conducted until
After printing 000 sheets, slight fog was observed at the edge of the image.

When the drum abrasion amount at this time was measured, the initial drum film thickness was 40 μm at the center of the contact surface between the drum and the charging member and 32 μm at the drum portion in contact with the charging member bullet. However, the amount of abrasion at the center of the contact surface between the drum and the charging member is 16 μm, and the amount of abrasion at the drum part in contact with the end of the charging member is 16.5 μm, which is almost the same as the central portion and the contact surface of the charging roller. The entire area is averagely scraped, and the durability that the drum originally possesses is fully exploited, resulting in a durability that is three times that of the conventional one. [Embodiment 2] (Adjustment of compound for elastic layer) The rubber used is SBR.
Same as Embodiment 1 except that it is changed (Preparation of coating material for coating layer) Same as Embodiment 1 (Adjustment of coating material for both end coatings) Same as Embodiment 1 (stuffed with photoconductor) Embodiment 1 Same (preparation and evaluation of charging member) First, the above-mentioned compound for elastic layer was placed on a stainless steel core bar having a diameter of 6 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. Next, both ends of this roller are chamfered at 30 °, and after dip coating with a coating material for the coating layer, 5
The coating composition for coating both ends, which had been adjusted as described above, was applied in units of mm. When the maximum diameter of the image area and the maximum diameter of the non-image area of this charging member were measured, the maximum diameter of the image area was 12.1
13 mm, the maximum diameter of the non-image area is 12.295 mm, and the maximum diameter of the non-image area is 1.0 of the maximum diameter of the image area.
When the resistance value of this charging member was measured according to the electric resistance value of the charging member described above, the resistance value of the non-image area at both ends was 1 × 10 ^{6 in the} image area.
Ω, the area of the non-image area at both ends is 1 × 10 ⁹ Ω,
A charging member was obtained in which the resistance value of the non-image area was 1000 times that of the image area and the discharge from both ends was gradually reduced.

This charging member was attached to the position of the primary charger of the laser beam printer (laserjet 4si, manufactured by Hewlett Packard), and the DC voltage was -750.
V, AC voltage 2.0kV (peak-to-peak voltage), frequency 65
50d when the charging sound was measured by superimposing application at 0Hz.
b is the level at which the charging sound is not noticeable, and the image is fogging due to the thin film thickness of the drum (the main cause is scraping due to discharge) in a high temperature and high humidity (32.5 ° C., 85% RH) environment. It was 27,0 when the durability test was conducted until it occurred.
A slight fog was observed at the edge of the image after printing 00 sheets.

When the drum abrasion amount at this time was measured, the initial drum film thickness was 40 μm at the center of the contact surface between the drum and the charging member and 32 μm at the drum portion in contact with the end of the charging member. However, the amount of abrasion at the center of the contact surface between the drum and the charging member was 15.5 μm, and the amount of abrasion at the drum part in contact with the end of the charging member was 16.5 μm, which was not much different from that at the center. The entire contact surface has been averagely scraped, and the durability inherent in the drum has been fully brought out, resulting in 2.7 times longer durability than the conventional one. [Comparative Example 1] (Adjustment of compound for elastic layer) Same as embodiment 1 (Adjustment of coating material for coating layer) Same as embodiment 1 (stuffed with photoconductor) Same as embodiment 1 (Preparation of charging member) , Evaluation) First, the above-mentioned compound for the elastic layer was placed on a stainless steel core bar having a diameter of 6 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. Next, both ends of this roller were cut vertically, and a resistance adjusting paint was applied by dipping to obtain a charging member. When the maximum diameter of the image area and the maximum diameter of the non-image area of the roller at this time were measured, the maximum diameter of the image area was 1
Maximum diameter of non-image area is 11.964 m at 1.986 mm
m, the maximum diameter of the non-image area was 0.9982 times the maximum diameter of the image area, and the electric resistance value was 1 × 10 ⁶ Ω in both the image area and the non-image area.

This charging member was attached to the position of the primary charger of the laser beam printer (laserjet 4si, manufactured by Hewlett Packard), and the DC voltage was -750.
V, AC voltage 2.0kV (peak-to-peak voltage), frequency 65
It was 57d when the charging sound was measured by superimposing at 0Hz.
B is a level at which the charging noise is slightly large, and the image is fogged due to the thin film thickness of the drum (the main cause is scraping due to discharge) in a high temperature and high humidity (32.5 ° C., 85% RH) environment. When endurance test was performed until
Fog was observed at the edge of the image after printing 0 sheets.

When the amount of abrasion of the drum at this time was measured, the initial drum film thickness was 40 μm at the center of the contact surface between the drum and the charging member, and 32 at the portion in contact with the end of the charging member.
Although the abrasion amount of the central portion of the contact surface between the drum and the charging member is 8.0 μm, the resistance value of the non-image area of the charging member is in the drum portion in contact with the end portion of the charging member. Was less than 6 times the image area, or discharge concentration relaxation treatment was not performed, and discharge concentration was caused. Therefore, 16.5 μm was shaved early and it was not suitable for high durability. [Comparative Example 2] (Adjustment of compound for elastic layer) Same as embodiment 1 (Adjustment of coating material for coating layer) Same as embodiment 1 (stuffed with photoconductor) Same as embodiment 1 (Preparation of charging member) , Evaluation) First, the above-mentioned compound for the elastic layer was placed on a stainless steel core bar having a diameter of 6 mm at 150 ° C.
It was heated and vulcanized for 5 minutes to obtain a rubber roller having an elastic layer with a thickness of 3 mm. Next, the radius R =
It was cut into a state of 3.0 mm, and a resistance adjusting paint was applied by dipping to obtain a charging member.

This charging member was attached to the position of the primary charger of the laser beam printer (laserjet 4si, manufactured by Hewlett Packard), and the DC voltage was -750.
V, AC voltage 2.0kV (peak-to-peak voltage), frequency 65
58d when the charging noise was measured by superimposing application at 0Hz.
At B, the charging noise is a little loud and the level is high,
Durability test was carried out in the high humidity (32.5 ° C, 85% RH) environment until fogging occurred due to the thin film thickness of the drum (the main cause is scraping due to electric discharge). Fog was seen on.

When the drum abrasion amount at this time was measured, the initial drum film thickness was 40 μm at the center of the contact surface between the drum and the charging member and 32 μm at the drum portion in contact with the end of the charging member. However, the amount of abrasion of the central portion was 9.0 μm due to the contact between the drum and the charging member, but the resistance value of the non-image forming area of the charging member is the image area in the drum portion in contact with the end of the charging member. It was found that it was not suitable for high endurance because the discharge concentration was due to being less than 6 times the value of 1. Comparative Example 3 (Adjustment of compound for elastic layer) Same as embodiment 1 (Adjustment of paint for coating both ends) 40 parts by weight of urethane rubber,
60 parts by weight of THF were mixed to prepare a urethane rubber paint. (Packing with photoconductor) Same as in Embodiment 1 (Preparation and evaluation of charging member) A stainless steel core having a diameter of 6 mm was first coated with the above compound for elastic layer at 150 ° C. for 15 minutes.
It was heated and vulcanized for a minute to obtain a rubber roller having an elastic layer with a thickness of 3 mm. Next, both ends of this roller were cut vertically, dip-coated with the coating material for the coating layer, and then urethane rubber coating with a volume resistivity value of 1 × 10 ¹⁴ Ω · cm was applied by 5 mm from each end, and this electrification was performed. When the image area diameter and non-image area diameter of the member were measured, the image area diameter was 12.103 m.
m, the non-image area diameter is 12.124 mm, the non-image area diameter is 1.0017 times the image area diameter, the electric resistance value of the image area is 1 × 10 ⁶ Ω, and the resistance value of the non-image area at both ends is Was 1 × 10 ¹² Ω, and a charging member having an electric resistance value in the non-image area of 1,000,000 times that of the image area was obtained.

This charging member is a laser beam printer (laserjet 4si manufactured by Hewlett Packard)
Installed at the primary charger position, DC voltage -750V, AC voltage 2.0kV (peak-to-peak voltage), frequency 650Hz
It was 58 dB when the charging sound was measured by superimposing and charging, and the charging sound was at a level that was not noticeable, but because the end was cut vertically, the rubbing sound from the end was noticeable. The overall noise was uncomfortable.

High temperature and high humidity (32.5 ° C., 85% RH)
When an endurance test was performed in an environment until fogging occurred due to the thin film thickness of the drum, fogging was observed at the edge of the image after printing 14,000 sheets.

When the amount of abrasion of the drum at this time was measured, the initial drum film thickness was 40 μm at the center of the contact surface between the drum and the charging member, and the drum in contact with the edges of the image area of the charging member and the non-image area. The part had a thickness of 32.5 μm, but the amount of abrasion in the central part due to the contact between the drum and the charging member was 9.5.
However, the drum portion in contact with the image area of the charging member and the edge of the non-image area is a portion where the discharge current is switched when the electric resistance value of the non-image area is 10,000 times or more the electric resistance value of the charging member. It was found that the discharge was stronger and the scraping-reducing effect in the non-image area was reduced, but the discharge current was switched by 16.5 μm, which is not suitable for high durability.

[0071]

As described above, according to the present invention,
By reducing the amount of discharge at both ends of the charging member or mitigating the discharge concentration at low cost, it is possible to reduce the charging noise and reduce the concentration of local scraping of the drum portion that is the end of the charging member. In addition, it is possible to prevent unpleasant rubbing noise at the end of the charging member.

Therefore, since the abrasion of the drum is averaged, it is possible to obtain a life corresponding to the drum film thickness, and it is possible to obtain an image forming apparatus suitable for high speed and high durability.

[Brief description of drawings]

FIG. 1 is a sectional view of a first embodiment of a charging member according to the present invention.

FIG. 2 is a sectional view of a second embodiment of the charging member according to the present invention.

FIG. 3 is a sectional view of a charging member according to a third embodiment of the present invention during manufacture.

FIG. 4 is a sectional view of a completed product of the charging member shown in FIG.

FIG. 5 is a sectional view of a charging member according to a fourth embodiment of the present invention.

FIG. 6 is a sectional view of a charging member according to a fifth embodiment of the present invention.

FIG. 7 is a cross-sectional view of the charging member according to the sixth embodiment of the present invention during manufacture.

8 is a cross-sectional view of a completed product of the charging member shown in FIG.

FIG. 9 is an enlarged schematic view of chamfered portions at both ends of the charging member according to the present invention.

[Explanation of symbols]

 1 core metal 2 elastic layer 3 resistance adjustment layer 4 enlargement of diameter of non-image area 5 contact or close surface of charging member and non-charging body 6 end surface of charging member a image area maximum diameter b non-image area maximum diameter

Claims (4)

[Claims] 1. A charging member, which is disposed in proximity to or in contact with an object to be charged and which applies a charging voltage to charge the object to be charged, wherein a maximum diameter of a non-image area portion of the charging member is an image area. A shape that is 1.0010 times or more and less than 1.5000 times the maximum diameter of the portion, and that the distance between the charging member and the body to be charged increases curvilinearly toward the end of the charging member,
A charging member having a shape having a curvature R, R = 1 mm or more and less than 10 mm, and a non-image region of the charging member having an electric resistance value higher than that of the image region. 2. A charging member, which is disposed in the state of being close to or in contact with a member to be charged and which applies a charging voltage to charge the member to be charged, wherein a maximum diameter of a non-image region portion of the charging member is an image region. A chamfer having a chamfer that is 1.0010 times or more and less than 1.5000 times the maximum diameter of the portion and linearly increases as the distance between the charging member and the charged member increases toward the end of the charging member; The angle formed by the chamfered surface and the surface of the body to be charged that contacts or approaches the charging member in the image region is 10
A charging member, which is not less than 70 ° and is less than 70 °, and the electric resistance value of the non-image area of the charging member is higher than that of the image area. 3. The electric resistance value of the image area of the charging member is 1 × 10 ³ to 1 × 10 ¹⁰ Ω, and the electric resistance value of the non-image area is 6 times or more higher than that of the image area. The charging member according to claim 1 or 2. 4. An electrostatic latent image is formed on the charged surface of a charged body uniformly charged by the charging means by the exposing means, and toner is attached to the electrostatic latent image via the developing means. An image forming apparatus in which a toner image is formed and the toner image is transferred to a transfer material by a transfer means, wherein the charging means has the charging member according to any one of claims 1 to 3, and An image forming apparatus in which an object to be charged is an organic photoconductor.