JP2002006632A - Electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device where shaving or filming of a developing roll is not generated, with high uniformity and high image quality. SOLUTION: The device includes one component toner where an additive with a reverse polarity as the electrified polarity of a toner base is added to the toner base consisting of binding resin, charge controller and colorant, a developing roll, a contact member installed in contact with the developing roll and provided with a conductor in at least one part and a power source applying AC and DC voltage between the developing roll and the contact member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus used for a copying machine, a printer and the like.

[0002]

2. Description of the Related Art Various development methods have been proposed for an electrophotographic apparatus. In recent years, a one-component development method using only toner without using a carrier has been widely used. The one-component developing method is excellent in maintainability because there is no need to replace the carrier. Further, since there is no need to control the toner concentration in the developer, the size of the apparatus can be easily reduced.

However, on the other hand, it is necessary to charge the toner by using components of the developing device such as a developing roller and a blade. In order to stably charge the toner, it is necessary to constantly maintain these surface conditions. . However, in order to stably charge the toner, it is necessary to frictionally charge these members and the toner with a certain amount of force, and these members may be scraped over time and the filming of the toner on these members may occur. This has caused a problem in that a streak is formed on an image, and charging of the toner becomes unstable. In particular, the above problem was remarkable in contact development in which a photosensitive member and a developing roller were brought into contact with each other to perform development.

On the other hand, for example, Japanese Patent Application Laid-Open No. 2000-00
9129 proposes a method for preventing the developing roller from being scraped or filmed by incorporating a toner release material into the rubber composition of the developing roller. Also, JP
No. 01-015260 proposes a method for preventing filming by providing a rubber layer having high hardness on an elastic layer.

[0005]

However, the above configuration is not sufficient for the abrasion and filming of the developing roller, and the abrasion and filming occur on the surface of the developing roller after long-term use. There have been problems in that streaks and density unevenness occur on the image, and that charging of the toner becomes unstable and fogging occurs. This greatly depends on the composition of the toner used, and was particularly remarkable when a large amount of an external additive was added or when an external additive having a polarity opposite to that of the toner base was added. As a result of studying the cause of the problem of shaving and filming of the developing roller, the external additive released from the toner base accumulates on the surface of the developing roller, and this triggers the shaving and filming of the developing roller. It was speculated that ming had occurred. In particular, when a reverse polarity external additive is added, the released reverse polarity external additive receives an electric field force in a direction opposite to that of the toner base due to an electric field, and is easily separated from the toner base and accumulated on the surface of the developing roller. Therefore, it was considered that scraping and filming of the developing roller surface were further promoted.

Further, in the contact development, since the photosensitive member and the developing roller are always in contact with each other and rotate with a difference in peripheral speed, there is a problem that the surface of the photosensitive member is more easily scraped than in the non-contact development. On the other hand, Japanese Patent Laid-Open Nos.
No. 65137 proposes a method for reducing and improving the coefficient of friction of the photoreceptor surface by adding a silicone component to the photoreceptor surface layer. However, there is a problem that although the effect on the surface of the photoreceptor is initially obtained, the effect is not maintained over time.

Further, in the contact development, when printing is performed again after standing, when the toner is stopped between the photosensitive member and the developing roller, the toner is not sufficiently collected by the developing roller due to the electric field and remains on the photosensitive member. It is easy to be taken by the rotation of the photoreceptor. As a result, problems such as increased waste toner and contamination of the transfer member and the charging member have been observed.

An object of the present invention is to provide a high-quality electrophotographic apparatus in which the surface of the developing roller is hardly shaved or filmed. Another object of the present invention is to provide a high-quality electrophotographic apparatus in which the photoreceptor surface is less likely to be scraped. It is still another object of the present invention to provide a high-quality electrophotographic apparatus that does not waste toner and does not cause contamination of a charging member or a transfer member.

[0009]

In order to solve the above-mentioned problems, an electrophotographic apparatus according to the present invention comprises a toner base comprising at least a binder resin and a colorant, wherein at least the toner base has a charge polarity opposite to that of the toner base. A one-component toner externally added with an external additive, a developing roller that carries the one-component toner on its surface and rotates, and a contact member that is provided in contact with the developing roller and has a conductor at least in part. And a power supply for applying AC and DC voltages between the developing roller and the contact member. With this configuration, the external additive having the opposite polarity attached to the surface of the developing roller is removed by the electrostatic force due to the AC electric field and the collision of the toner oscillating due to the AC electric field, and the accumulation on the developing roller surface can be prevented. . Further, since the toner base and the opposite polarity external additive are disturbed by the alternating fluctuating electrostatic force due to the AC electric field, the distribution of the reverse polarity external additive on the surface of the toner base is made uniform, and the charging of the toner is stabilized.

It is preferable to use a one-component toner obtained by externally adding an external additive having the same polarity as the toner base in addition to an external additive having a polarity opposite to that of the toner base. By adding an external additive having the same polarity as the toner base, the electric field is partially concentrated on the toner surface, and the effect of holding the opposite polarity external additive on the toner base surface is increased. Further, the action of removing the external additive having the opposite polarity attached to the surface of the developing roller is enhanced. Further, since external additives having different polarities vibrate on the surface of the toner base by the action of the AC electric field, the external additives are uniformly dispersed on the surface of the toner base. As a result, the charge of the toner is made uniform, and the image is made uniform.

Preferably, the contact member is a photoreceptor which rotates in contact with the developing roller. By applying an AC voltage between the photoreceptor and the developing roller, the reverse polarity external additive floating from the toner base removed from the developing roller surface moves to the photoreceptor surface and is removed outside the developing device.
As a result, the floating external additive does not accumulate in the developing device, and the fog over time is reduced. In addition, the reciprocating movement of the toner between the photosensitive member and the developing roller enables development faithful to the electrostatic latent image.

The contact member is preferably a supply roller which rotates in contact with the developing roller and supplies toner to the surface of the developing roller. By applying an AC voltage between the supply roller and the developing roller, the effect of scraping off the toner on the developing roller is increased, and there is an effect of reducing sleeve ghost.

Preferably, the surface of the supply roller is formed of a porous material. By using a porous material, the electric field is concentrated and the action of removing the external additive having the opposite polarity attached to the surface of the developing roller is enhanced.

Preferably, the surface of the supply roller is formed with a brush. By using a brush, the electric field is concentrated, and the action of removing the reverse polarity external additive attached to the surface of the developing roller by mechanical scraping of the brush is enhanced.

It is preferable that the contact member is a layer forming blade which is provided in contact with the developing roller and forms a toner layer on the surface of the developing roller. By applying an AC voltage between the blade and the developing roller, toner adhered to the blade by the AC electric field can be removed, and toner sticking to the blade can be prevented.

The contact member is preferably a seal member provided in contact with the developing roller. By applying an AC voltage between the seal member and the developing roller, the effect of removing the toner on the developing roller by the AC electric field is enhanced, and there is an effect of preventing overcharging of the toner and reducing a sleeve ghost.

It is preferable that the surface of the seal member that contacts the developing roller contains a Teflon component. By containing the Teflon component, it is possible to prevent the toner from sticking to the sheet member due to the discharge when the AC is applied.

It is preferable to use a one-component toner composed of a toner base having a negative polarity and an external additive having a positive polarity. The negative polarity of the toner matrix makes it difficult for the peripheral members to discharge to the toner in an AC electric field.

It is preferable to use a one-component toner comprising a toner base having a negative polarity, an external additive A having a positive polarity, and an external additive B having a negative polarity. By adding an external additive having the same polarity as the toner base, the electric field is partially concentrated on the surface of the toner base, and the effect of holding the external additive of the opposite polarity on the surface of the toner base is increased. further,
Since the external additives having different polarities vibrate on the surface of the toner base by the action of the AC electric field, they are uniformly dispersed on the surface of the toner base. Thereby, the charge of the toner is made uniform, and the uniformity of the image is improved.

A toner base having a negative charge polarity and a BET specific surface area of 50 to 350 m ² due to nitrogen adsorption.
/ G, an external additive A having a positive charge polarity and a BET specific surface area by nitrogen adsorption of 5 to 150 m ² / g, and an external additive B having a negative charge polarity. It is preferable to use a one-component toner in which the ratio of the specific surface area of A to the specific surface area of the external additive B is 1: 1 to 70: 1. When the content is in the above range, the vibration of the external additive on the surface of the toner base by the AC electric field is promoted, and the effect of uniformly dispersing the external additive is enhanced. Thereby, the charge of the toner is made uniform, and the uniformity of the image is improved.

The toner further comprises a toner base having a negative charge polarity, an external additive A having a positive charge polarity, and an external additive B having a negative charge polarity. Agent B
It is preferable to use a one-component toner having a ratio of 50:50 to 95: 5. When the content is within the above range, the vibration of the external additive on the surface of the toner base by the AC electric field is promoted, and the effect of uniformly dispersing the external additive is enhanced. Thereby, the charge of the toner is made uniform, and the uniformity of the image is improved.

Further, it is preferable to use a one-component toner containing an external additive composed of one or more of alumina, titania and silica subjected to hydrophobic treatment. By including the above-mentioned external additive, the effect of dispersing the external additive on the surface of the toner base by the AC electric field is enhanced. Thereby, the charge of the toner is made uniform, and the uniformity of the image is improved.

It is preferable to use a one-component toner having a charge amount of the toner of −5 to −45 μC / g by a suction type Faraday cage method. By setting the charge amount of the toner to the above range, the toner is not scattered by the AC electric field, and the toner is vibrated actively by the AC electric field, so that the external additive having the opposite polarity attached to the developing roller surface can be effectively removed. Can be removed.

The binder resin is a polyester resin prepared by polycondensation of an alcohol and an acid. The polyester resin has at least a succinic acid monomer and a terephthalic acid monomer as an acid component. The value is 5-30 KOHmg /
g is preferable. By setting the settlement resin to the above-described composition, it is possible to prevent the external additive from being buried in the toner matrix due to the vibration of the toner in the AC electric field, and to suppress a change in the physical properties of the toner over time. In addition, good fixability can be obtained.

The binder resin is a polyester resin prepared by polycondensation of an alcohol and an acid. The polyester resin has at least a fumaric acid monomer and a terephthalic acid monomer as an acid component. The value is 5-30 KOHmg /
g is preferable. By setting the settlement resin to the above-described composition, it is possible to prevent the external additive from being buried in the toner matrix due to the vibration of the toner in the AC electric field, and to suppress a change in the physical properties of the toner over time. In addition, good fixability can be obtained.

It is preferable to use a toner containing a charge control agent comprising at least one of a metal salt of salicylic acid, a metal complex of salicylic acid and an organic boron compound. By using the charge control agent, transfer of charges from peripheral members is easily performed by vibration of the toner in an AC electric field,
The uniformity of toner charging is improved. This improves the homogeneity of the image.

When the chargeability of the toner matrix is negative,
It is preferable that the surface of the developing roller is made of silicone. By configuring the surface of the developing roller with silicone, the positively chargeable external additive, which is the external additive of the opposite polarity, adhering to the surface of the developing roller can be removed by frictional charging to prevent overcharging. Thereby, the external additive of the opposite polarity can be effectively removed in the AC electric field.

Further, the electrophotographic apparatus according to the present invention comprises a one-component toner, a developing roller which carries the one-component toner on the surface thereof and rotates, and a silicone component which is rotated in contact with the developing roller and is in a surface layer. And a power supply for applying AC and DC voltages between the developing roller and the photosensitive member. By applying an AC voltage between the photoreceptor and the developing roller, the silicone component on the photoreceptor surface is always kept high by the action of the AC electric field.

The electrophotographic apparatus according to the present invention further comprises a one-component toner, a rotatable photoreceptor, a developing roller which carries the one-component toner on a surface thereof and rotates while being in contact with the photoreceptor. And a power supply for applying AC and DC voltages between the developing roller and the photoconductor at the time of rotation start. By applying an AC voltage between the photoreceptor and the developing roller at the time of starting, the developing area becomes wider than when only the DC voltage is applied. Further, the toner is charged by the vibration of the toner due to the AC electric field. This makes it possible to completely collect the toner between the photosensitive member and the developing roller at the time of stop.

In addition, it is preferable that a DC voltage be applied between the photosensitive member and the developing roller at the end of rotation of the photosensitive member. By stopping the operation while the DC voltage is applied, the movement of the toner to the photoconductor is limited to the contact portion between the photoconductor and the developing roller. This makes it easier to collect the toner on the photoconductor at the next startup of the photoconductor.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophotographic apparatus according to one embodiment of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 is a schematic sectional view of an electrophotographic apparatus according to one embodiment of the present invention. FIG. 2 is an enlarged view near the developing section. Reference numeral 1 denotes a photoconductor of φ30 mm having a photoconductor on a hollow cylindrical conductive substrate, which rotates at a peripheral speed of 105 mm / s in the direction of the arrow. Reference numeral 2 denotes a charging roller having a diameter of 12 mm made of epichlorohydrin rubber, which is driven to rotate with respect to the photosensitive member 1 in the direction of the arrow. Charging roller 2
Is supplied with a DC voltage of -1 kV by the power supply 3,
The surface of the photoconductor 1 is uniformly charged to -450V. Reference numeral 4 denotes signal light corresponding to an image pattern, and an electrostatic latent image is formed on the photoconductor 1. Reference numeral 5 denotes a developing roller having a JIS-A hardness of 60 ° and made of silicone rubber and having a diameter of 18 mm.
Rotate at 8 mm / s. Φ14 mm on the developing roller 5
The toner 8 in the toner hopper 7 is supplied by a supply roller 6 made of urethane sponge, and a metal blade 9
And the toner layer is formed. The developing roller 5 is supplied with a DC voltage of -23 by the power source 11 during development.
0 V and an AC voltage of 500 Vpp (1 kHz) are applied. The supply roller 6 and the blade 9 were set to the same potential as the developing roller 5. Reference numeral 10 denotes a conductive sealing member made of Teflon in which carbon is dispersed and which is provided in contact with the developing roller 5. -80 V was applied to the seal member 10. 12 is φ1 made of conductive urethane sponge
A peripheral speed of 105 mm / s in the direction of the arrow with a 4 mm transfer roller
Spinning at. A power supply 13 applies a DC voltage of 700 V to the transfer roller 12. The toner image developed on the photoreceptor 1 is transferred by the transfer roller 12 to the paper conveyed in the direction of arrow 14 and then fixed by the fixing device 15 to obtain a final image. The transfer residual toner remaining on the photoconductor 1 is removed by the cleaner 16.

The toner used is obtained by externally adding positively charged hydrophobic silica and negatively charged hydrophobic silica to a toner base containing a polyester resin as a main component, a metal salicylate and a colorant dispersed therein. It is. In the present specification, the term “charge polarity” refers to a positive polarity when frictionally charged with iron powder, and a negative polarity when negatively charged.

In the electrophotographic apparatus having the above-described configuration, the surface of the developing roller was slightly scraped even after printing 10,000 sheets, and no filming occurred. And it was at a level having no problem on the image. In addition, high-quality images with high image homogeneity were obtained even after elapse of time.

The same experiment was conducted by changing the AC voltage applied to the developing roller, and the number of vertical streaks appearing on the image due to the scraping of the developing roller and the result of subjective evaluation of image uniformity are shown in Table 1. . The frequency was 1 kHz.
According to Table 1, the scraping of the developing roller and the image homogeneity largely depend on the amplitude of the AC voltage applied to the developing roller. The peak-to-peak effect begins to appear at 200 V or more, and at 400 V or more. was gotten. However, when the voltage is 1 kV or more, a partial discharge occurs between the photosensitive member and the developing roller, and the potential of the developing roller temporarily drops, causing a problem that white spots occur on an image. The frequency also depends on the process speed.
Good results were obtained at 3 kHz.

[0036]

[Table 1]

The material of the developing roller is not limited to silicone, but rubber materials such as urethane and NBR,
Resin, metal and the like may be used, and the same effect is obtained even when these are laminated.

Further, similar experiments were conducted by changing the type of developing roller, and the results of subjective evaluation of the number of vertical streaks appearing on the image due to scraping or filming of the developing roller and the image homogeneity were shown in Table 2. Shown in

The AC voltage applied to the developing roller has an amplitude of 1 kVpp and a frequency of 1 kHz. When silicone was used, the effect of applying an AC voltage on the scraping of the developing roller and the homogenization of the image was extremely high. This is considered to be due to the fact that silicone has a very strong positive charging property as a material. That is, it is considered that the positively chargeable external additive, which is the external additive of the opposite polarity, attached to the surface of the developing roller was neutralized by the disturbance caused by the AC electric field, and was easily removed. It is also considered that the opposite polarity external additive that was simultaneously charged was easily moved on the surface of the toner base by the AC electric field, and the uniformity of toner charging was improved.

[0040]

[Table 2]

Further, the one-component toner is not limited to the one of the present embodiment. For example, the same effect was obtained with polystyrene, styrene-acrylic copolymer and the like as the binder resin. As a result of repeated studies on the binder resin, it is a polyester resin obtained by polycondensation of an alcohol and an acid, and contains a succinic acid monomer and a terephthalic acid monomer, and has an acid value of 5 to 30 KOHmg / g. By using a polyester resin obtained by condensation polymerization of an alcohol and an acid and containing a phthalic acid monomer and a terephthalic acid monomer and having an acid value of 5 to 30 KOH mg / g, the fixing property is improved. Without sacrificing, it was possible to prevent the external additive from being buried in the toner matrix due to the vibration of the toner, and to maintain good image uniformity over time.

Similar effects were obtained with a salicylic acid metal complex compound, an organic boron compound, a nigrosine dye, a fatty acid metal salt, and the like as the charge control agent. In particular, by using a charge control agent comprising at least one of a metal salicylate, a metal salicylate complex compound, and an organic boron compound, remarkable improvement in image uniformity was observed. This is presumably because the use of the charge control agent facilitates the transfer of charges from peripheral members during the vibration of the toner in the AC electric field. Further, the charge polarity of the toner base is preferably one having negative chargeability. In the case of the negative chargeability, the occurrence of discharge from the peripheral members to the toner in the AC electric field was relatively small, and stable characteristics were obtained even in a high temperature and high humidity environment.

Further, as the external additive, alumina, titania, fatty acid metal salt or the like may be used in addition to silica.
Those obtained by subjecting them to a hydrophobic treatment may be used. In particular, the use of one or two or more of the hydrophobized alumina, titania and silica has a great effect on the uniformity of image quality. By using the above external additive,
It is considered that the effect of dispersing the external additive on the surface of the toner base by the AC electric field is high. The specific surface area of the external additive is 50 to 3 in terms of the BET value for the external additive A having a positive polarity.
The range of 50 m2 / g is desirable, and the range of 5-150 m2 / g is desirable for the external additive B of negative polarity. The ratio between the BET value of the positive external additive and the BET value of the negative external additive is preferably A: B = 1: 1 to 70: 1. If the BET value of the external additive A and the external additive B is smaller than the above value, the fluidity of the toner is deteriorated, and when the solid image is output, the toner is not sufficiently supplied and the trailing edge of the image is blurred. Was. On the other hand, when the value is larger than the above value, the image force between the external additive and the developing roller becomes strong, so that it cannot be sufficiently removed even by an AC electric field, and no effect is seen on the problem of shaving or filming of the developing roller. In addition, a phenomenon was also observed in which the external additive was buried in the toner matrix over time, so that the fluidity of the toner was reduced and the fog was increased. The ratio of the BET value of the external additive A having a positive polarity to the BET value of the external additive B having a negative polarity is 1
If it is smaller than this, most of the negative external additive will adhere to the positive external additive surface, and the BET value of the positive external additive A and the BET value of the negative external additive B If the ratio is greater than 70, on the contrary, many of the external additives of the negative polarity adhere to the surface of the external additive of the positive polarity, and the vibration of the external additives on the toner surface due to the AC electric field is inhibited, No improvement in the homogeneity of the image was observed by the application of the AC voltage.

Further, as for the additive amount of the external additive, the additive amount ratio of the external additive A having a positive polarity and the external additive B having a negative polarity is A: B.
= 50: 50 to 95: 5. If the amount of the external additive of the negative polarity was larger than that of the external additive of the positive polarity, fogging due to overcharging of the toner was likely to occur.
Further, by adding 5% or more of the negatively chargeable external additive, further improvement in image uniformity was observed.

Further, the charge amount of the toner is desirably 5 to 45 μC / g as an absolute value. 5
At μC / g or less, the vibration of the toner due to the AC electric field is small, so that the effect of removing the external additive having the opposite polarity attached to the developing roller was small, and no effect on the shaving of the developing roller was observed. Further, toner scattering easily occurred. 45
Above μC / g, the image force of the toner increases, so that the vibration of the toner due to the AC electric field also decreases, and the effect of removing the external additive having the opposite polarity attached to the developing roller decreases. No effect was seen.

In the present embodiment, the photosensitive member 1 has a drum shape. However, the present invention is not limited to this, and the photosensitive member 1 may have a belt shape. By making the photoreceptor 1 in a belt shape, the width of contact with the developing roller is widened, and the above effect by applying an AC voltage is improved.

The photoreceptor 1 is a laminated photoreceptor formed by forming a charge generation layer and a charge transport layer on a conductive substrate in this order, wherein silicone oil is contained in the charge transport layer, or The charge transport layer may be composed of a polycarbonate resin or a polyester resin containing a silicone component in the main chain or side chain. By including the silicone component in the charge transport layer, the photoreceptor 1 hardly scraped after printing 10,000 sheets. This is presumably because the action of the AC electric field keeps the silicone component on the photoreceptor surface high over time.

(Embodiment 2) FIG. 3 is an enlarged view of the vicinity of a developing section of an electrophotographic apparatus according to another embodiment of the present invention.
The configuration other than the vicinity of the developing unit is the same as that of FIG. The difference from the first embodiment is that the developing roller 5
A DC voltage of -230 V is applied from a power supply 11, and a DC voltage of −230 V and an AC voltage of 3
The point is that 00 Vpp (1 kHz) is applied. The used toner and process conditions are the same as in the first embodiment.

In the electrophotographic apparatus having the above-described structure, the surface of the developing roller was slightly scraped even after printing 10,000 sheets, and no filming occurred. Then, it was at a level having no problem on the image. In addition, high-quality images with high image homogeneity were obtained even after elapse of time. Further, the effect that the sleeve memory generated over time is improved was also observed. This is considered to be because applying an AC voltage between the supply roller and the developing roller increases the effect of scraping off the toner on the developing roller. It is desirable to use a porous material such as urethane sponge or a brush made of nylon fiber or the like as the supply roller 6. By making the surface material of the supply roller 6 a porous material or a brush, the contact area with the developing roller is reduced and the electric field is concentrated, so that the effect of removing the external additive of the opposite polarity accumulated on the surface of the developing roller 5 is improved. Get higher,
The effect of preventing the developing roller from being scraped was improved.

(Embodiment 3) FIG. 4 is an enlarged view of the vicinity of a developing section of an electrophotographic apparatus according to another embodiment of the present invention.
The configuration other than the vicinity of the developing unit is the same as that of FIG. The difference from the first embodiment is that the developing roller 5
The point is that a DC voltage of −230 V is applied from the power supply 11, and a DC voltage of −230 V and an AC voltage of 400 Vpp (1 kHz) are applied to the metal blade 9 by the power supply 18. The used toner and process conditions are the same as in the first embodiment.

In the electrophotographic apparatus having the above configuration, even after printing 10,000 sheets, the surface of the developing roller was slightly scraped, and no filming occurred. Then, it was at a level having no problem on the image. In addition, high-quality images with high image homogeneity were obtained even after elapse of time. Further, according to this configuration, not only the scraping of the developing roller but also the adhesion of toner to the blade 9 can be prevented at the same time, and the unevenness of layer formation due to the adhesion of toner to the blade 9 has been reduced. This is presumably because the effect of removing the toner attached to the blade by the AC electric field is high. The blade material is not limited to metal, and similar effects can be obtained as long as the material has conductivity, such as conductive rubber and conductive resin.

(Embodiment 4) FIG. 5 is an enlarged view of the vicinity of a developing section of an electrophotographic apparatus according to another embodiment of the present invention.
Except for the vicinity of the developing section, the configuration is the same as that of FIG. The difference from the first embodiment is that a DC voltage of −230 V is applied from the power supply 11 to the developing roller 5 during development, and a DC voltage of −230 V and an AC voltage of 300 Vpp (1 kHz) are applied to the seal member 10 from the power supply 11. It is a point.
The used toner and process conditions are the same as in the first embodiment.

In the electrophotographic apparatus having the above configuration, even after printing 10,000 sheets, the surface of the developing roller was slightly scraped, and no filming occurred. And it was at a level having no problem on the image. In addition, high-quality images with high image homogeneity were obtained even after elapse of time. Further, according to the present configuration, not only the scraping of the developing roller but also the sticking of the toner to the seal member 11 can be prevented at the same time, and the toner spill due to the toner sticking to the seal member 10 can be reduced. . The seal member 10 may be made of PET with carbon coated on the surface, or resin obtained by kneading a conductive agent such as carbon. Further, by including the Teflon component, the effect of preventing the toner from sticking to the seal member 10 became remarkable.

(Embodiment 5) FIG. 6 is a schematic sectional view of an electrophotographic apparatus according to an embodiment of the present invention. Reference numeral 1 denotes a photoconductor of φ30 mm having a photoconductor on a hollow cylindrical conductive substrate, which rotates at a peripheral speed of 105 mm / s in the direction of the arrow. Reference numeral 2 denotes a charging roller having a diameter of 12 mm made of epichlorohydrin rubber, which is driven to rotate with respect to the photosensitive member 1 in the direction of the arrow. The charging roller 2 has a DC voltage of -1 k
V is applied, and the surface of the photoconductor 1 is uniformly charged to -450V. Reference numeral 4 denotes signal light corresponding to an image pattern, and an electrostatic latent image is formed on the photoconductor 1. 5 is JIS-
A developing roller having a diameter of 18 mm and made of silicone rubber having an A hardness of 60 ° is pressed against the photosensitive member 1 with a force of 20 N, and rotates at a peripheral speed of 168 mm / s in the direction of the arrow. The toner 8 in the toner hopper 7 is supplied onto the developing roller 5 by a supply roller 6 made of urethane sponge having a diameter of 14 mm, and the layer is regulated by a metal blade 9 to form a thin toner layer. When the photoreceptor 1 is started, a DC voltage of +100 V and an AC voltage of 500
Vpp (1 kHz), and a DC voltage of −230 V and an AC voltage of 500 Vpp (1 kHz) by the power source 11 during development.
z) was applied. The supply roller 6 and the blade 9
Has the same potential as the developing roller 5. 10 is a developing roller 5
Is a conductive sealing member made of Teflon in which carbon is dispersed and is placed in contact with the sealing member. -80 V was applied to the seal member 10. Reference numeral 12 denotes a transfer roller having a diameter of 14 mm made of a conductive urethane sponge and rotating at a peripheral speed of 105 mm / s in the direction of the arrow. A power supply 13 applies a DC voltage of 700 V to the transfer roller 12. Photoconductor 1
The toner image developed above is transferred to the paper conveyed in the direction of arrow 14 by the transfer roller 12 and then fixed by the fixing device 15 to obtain a final image. The transfer residual toner remaining on the photoconductor 1 is recovered by the developing roller 5 again by the rotation of the photoconductor.

The toner used is obtained by externally adding negatively-charged hydrophobic silica to a toner base containing a polyester resin as a main component and a metal salicylate and a colorant dispersed therein.

In the electrophotographic apparatus having the above structure, even when printing is performed after leaving for several hours, the toner sandwiched between the photosensitive member and the developing roller at the time of stoppage is transferred from the photosensitive member surface to the developing roller by the AC electric field. Complete recovery was possible. As a result, even after printing 10,000 sheets, dirt on the charging roller and the transfer roller was reduced, and the level on the image was completely satisfactory.

In addition to the above configuration, by applying only a DC voltage to the developing roller 5 immediately after the photosensitive member is stopped after the development, the contamination of the charging roller and the transfer roller is further reduced.

(Comparative Example) FIG. 7 is a schematic sectional view of a conventional electrophotographic apparatus as a comparative example. Reference numeral 101 denotes a φ30 mm photoconductor having a photoconductor on a hollow cylindrical conductive substrate, and rotates at a peripheral speed of 105 mm / s in the direction of the arrow. 10
Reference numeral 2 denotes a charging roller made of epichlorohydrin rubber and having a diameter of 12 mm, which is driven to rotate with respect to the photoconductor 101 in the direction of the arrow. The charging roller 102 has a DC voltage minus
1 kV is applied and the surface of the photoreceptor 101 is
It is uniformly charged to 0V. Reference numeral 104 denotes signal light corresponding to an image pattern, and an electrostatic latent image is formed on the photoconductor 101. Reference numeral 105 denotes a developing roller made of silicone rubber having a JIS-A hardness of 60 ° and having a diameter of 18 mm, which is pressed against the photoreceptor 101 with a force of 20 N and has a peripheral speed of 168 mm in the direction of the arrow.
/ S. Supply roller 1 is on developing roller 105
At 06, the toner 108 in the toner hopper 107 is supplied, and the layer is regulated by the blade 109 to form a thin toner layer. A DC voltage of −230 V is applied to the developing roller 105 by the power supply 111 during development. 1
Reference numeral 12 denotes a transfer roller having a diameter of 14 mm made of a conductive urethane sponge and rotating at a peripheral speed of 105 mm / s in the direction of the arrow. A 700 V DC voltage is applied to the transfer roller 112 from a power supply 113. The toner image developed on the photoreceptor 101 is transferred to the paper conveyed in the direction of arrow 114 by the transfer roller 112, and then fixed by the fixing unit 115 to obtain a final image. Transfer residual toner remaining on the photoconductor 101 is removed by the cleaner 116.

In the present electrophotographic apparatus, when 10,000 sheets were printed, streak-like scraping occurred on the surface of the developing roller in the circumferential direction, and a portion corresponding to the streak appeared as a dark streak on the image. . In addition, the uniformity of the image is higher in Embodiments 1 to 5.
It was low from the beginning, and worsened after printing 10,000 sheets. When the developing roller 105 was formed of urethane rubber instead of silicone rubber, the toner filmed over the entire surface of the developing roller, and fogging occurred. In addition, the surface of the photosensitive member was scraped due to friction with the developing roller. Further, the transfer roller 112 gradually became dirty due to the toner take-out phenomenon at the time of starting the photosensitive member, and the transfer became unstable.

[0060]

As described above, the present invention relates to an electrophotographic apparatus using a one-component toner in which an external additive having a polarity opposite to that of the toner base is externally added to the toner base. By applying an AC or DC voltage between the electrophotographic apparatus and the member having the above, it is possible to obtain an electrophotographic apparatus with high homogeneity and high image quality, in which the surface of the developing roller is hardly shaved or filmed.

Further, according to the present invention, in contact development, abrasion of the surface of the photoreceptor is caused by applying an alternating current and a direct current voltage between the photoreceptor containing a silicone component in the surface layer and the photoreceptor and the developing roller. It is possible to obtain a high quality electrophotographic apparatus which is difficult to perform.

Further, the present invention provides a method for contact development,
By applying AC and DC voltages between the photoconductor and the developing roller at the time of starting the photoconductor, it is possible to obtain a high-quality electrophotographic apparatus that does not waste toner and does not cause contamination of the charging member or the transfer member. .

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrophotographic apparatus according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of the vicinity of a developing unit of the electrophotographic apparatus according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of the vicinity of a developing unit of an electrophotographic apparatus according to a second embodiment of the present invention.

FIG. 4 is an enlarged view of the vicinity of a developing unit of an electrophotographic apparatus according to a third embodiment of the present invention.

FIG. 5 is an enlarged view of the vicinity of a developing unit of an electrophotographic apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a schematic sectional view of an electrophotographic apparatus according to a fifth embodiment of the present invention.

FIG. 7 is a schematic sectional view of a conventional electrophotographic apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 5 Developing roller 6 Supply roller 8 Non-magnetic one-component toner 9 Blade 10 Seal member 11 Power supply

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 9/087 G03G 9/08 375 9/097 15/06 101 9/08 374 15/08 507L 375 9/08 331 15 / 06 101 344 346 (72) Inventor Yasuhito Yuasa 1006 Kadoma, Kazuma, Osaka Prefecture F term in Matsushita Electric Industrial Co., Ltd. 2H005 AA01 AA08 CA08 CA25 CB07 CB13 DA02 DA03 EA01 EA07 EA10 FA05 2H073 AA03 BA02 BA04 BA04 BA13 BA43 CA02 2H077 AA37 AB23 AC04 AC16 AD06 AD13 AD31 AD36 AE08 CA02 CA04 CA12 DB25 EA14 EA15 FA11 FA22 FA23 GA03

Claims (22)

[Claims] 1. A one-component toner obtained by externally adding a toner base comprising at least a binder resin and a colorant to an external additive having a polarity opposite to that of the toner base, and a surface of the one-component toner. A developing roller that carries and rotates
An electrophotographic apparatus comprising: a contact member provided in contact with the developing roller and having a conductor at least in part; and a power supply for applying an alternating current and a direct current voltage between the developing roller and the contact member. apparatus. 2. A one-component toner obtained by externally adding at least an external additive A having a charge polarity opposite to that of a toner base and an external additive B having a charge polarity same as that of the toner base. The electrophotographic apparatus according to claim 1, wherein 3. The electrophotographic apparatus according to claim 1, wherein the contact member is a photoreceptor that rotates in contact with the developing roller. 4. The electrophotographic apparatus according to claim 1, wherein the contact member is a supply roller that rotates in contact with the developing roller and supplies toner to the surface of the developing roller. 5. The electrophotographic apparatus according to claim 4, wherein the contact member is a supply roller whose surface is made of a porous material. 6. An electrophotographic apparatus according to claim 4, wherein said contact member is a supply roller having a surface made of a brush. 7. The electrophotographic apparatus according to claim 1, wherein the contact member is a layer forming blade which is provided in contact with the developing roller and forms a toner layer on the surface of the developing roller. 8. An electrophotographic apparatus according to claim 1, wherein said contact member is a seal member provided in contact with said developing roller. 9. The electrophotographic apparatus according to claim 8, wherein the contact member is a seal member containing a Teflon (registered trademark) component on a surface that contacts the developing roller. 10. The electrophotographic apparatus according to claim 1, wherein a one-component toner comprising a toner base having a negative charge polarity and an external additive having a positive polarity is used. 11. A one-component toner comprising a toner base having a negative charge polarity, an external additive A having a positive polarity, and an external additive B having a negative polarity. An electrophotographic apparatus according to the above. 12. A toner base having a negative charge polarity and a BET specific surface area of 50 to 350 m ² due to nitrogen adsorption.
/ G, an external additive A having a positive polarity of a charging polarity and an external additive B having a BET specific surface area of 5 to 150 m ² / g and a negative polarity of a charging polarity by nitrogen adsorption. Ratio of the specific surface area of the agent A to the specific surface area of the external additive B is 1: 1 to 70: 1
2. The method according to claim 1, wherein a one-component toner is used.
An electrophotographic apparatus according to the above. 13. An external additive A comprising: a toner base having a negative charging polarity; an external additive A having a positive charging polarity; and an external additive B having a negative charging polarity. 2. The electrophotographic apparatus according to claim 1, wherein a one-component toner in which the ratio of the additive amount of the external additive B is 50:50 to 95: 5 is used. 14. The electrophotography according to claim 1, wherein a one-component toner containing an external additive consisting of one or more of alumina, titania or silica subjected to hydrophobic treatment is used. apparatus. 15. The electrophotographic apparatus according to claim 1, wherein a one-component toner having a charge amount of -5 to -45 .mu.C / g by a suction type Faraday cage method is used. 16. The binder resin is a polyester resin prepared by polycondensation of an alcohol and an acid, and has at least a succinic acid monomer and a terephthalic acid monomer as an acid component. Acid value is 5-30 KOHmg / g
2. The method according to claim 1, wherein a one-component toner is used.
An electrophotographic apparatus according to the above. 17. The binder resin is a polyester resin prepared by polycondensation of an alcohol and an acid, and has at least a fumaric acid monomer and a terephthalic acid monomer as an acid component. Acid value is 5-30 KOHmg / g
2. The method according to claim 1, wherein a one-component toner is used.
The electrophotographic apparatus according to claim 1. 18. The electrophotographic apparatus according to claim 1, wherein a one-component toner containing a charge controlling agent comprising at least one of a metal salicylate, a metal salicylate complex compound and an organic boron compound is used. 19. An electrophotographic apparatus according to claim 1, further comprising a one-component toner having a negative polarity of a toner base and a developing roller made of silicone. 20. A one-component toner, a developing roller which carries the one-component toner on its surface and rotates, a photosensitive member which rotates in contact with the developing roller and contains a silicone component in a surface layer, and the developing roller An electrophotographic apparatus comprising: a power source for applying an AC and a DC voltage between the photoconductor and the photoconductor. 21. A one-component toner, a rotatable photoreceptor,
A developing roller that carries the one-component toner on its surface and rotates while being in contact with the photoconductor; and a power supply that applies an AC and DC voltage between the developing roller and the photoconductor when the photoconductor starts rotating. An electrophotographic apparatus, comprising: 22. An electrophotographic apparatus according to claim 21, further comprising a power supply for applying a DC voltage between said photosensitive member and said developing roller when rotation of said photosensitive member is completed.