JPH0876557A - Charge supplying device - Google Patents

Abstract

PURPOSE: To maintain wear resistance and release property for a long time and to obtain stable images. CONSTITUTION: A charging roller 2 as a charge supply member is disposed facing a photosensitive drum 1. The charging roller 2 consists of a hollow aluminum core metal 21 coated with a composite layer 22. The composite layer 22 contains fluoride particles and metal. At least a part of the composite layer 22 facing the image holding surface is specified to have >=130 deg. contact angle with pure water at 23 deg.C. By this method, wear resistance and release property can be maintained in a good state even when the device is used for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge supplying device for supplying charges to an image carrier in an image forming apparatus such as a copying machine or a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, a charge supplying member mounted on an image forming apparatus such as a copying machine, for example, a charging roller for charging a photosensitive member as an image carrier or a toner image on the photosensitive member is transferred onto paper or the like. A member made of a material having a good releasability is used for a transfer roller or the like for transferring to a material. That is, in order to prevent foreign matter such as toner and paper powder from adhering to the surface of these rotatable charge supply members, a material having high releasability, such as PTFE (polytetrafluoroethylene) or PVdF, is used.
A fluororesin such as (polyvinylidene fluoride) or PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) is used. These fluororesins are molded into a tube and coated on a conductive substrate, or fine powder of these fluororesins is dispersed in a resin solution of epoxy, phenol, urethane, acrylic, etc., and then sprayed or dipping. By applying it to a conductive substrate,
The surface of the charging roller and the transfer roller has good releasability.

[0003]

However, in the above-mentioned conventional charge supply member, a small amount of discharge product generated during charging or transfer (during charge supply) enters between the photosensitive member and the photosensitive member during rotation. Minute scratches and the like caused by rubbing with the toner, the external additive, and the amount of the filler in the paper powder gradually lower the releasability of the surface with the endurance. There is a risk that image defects such as unevenness, white streaks, and black streaks may occur on the image due to poor charging.
In particular, in a high-speed image forming apparatus such as a copying machine or a printer which is often used for long-term durability, image deterioration has been a problem. As a cause of this, although a fluorine resin is used for a part or all of the surface of the charge supply member, the conventional surface has been able to increase the fluorine atom concentration to about 20% at the maximum, so that the surface release It is considered that the durability is not sufficient, and that the surface resistance of the fluororesin is not high.

Generally, for the releasability or leak property of the solid surface, a method of dropping a liquid on the solid surface and measuring the contact angle is used. Room temperature 2 measured in this way
Taking the contact angle with pure water at 3 ° C as an example, the conventional fluororesin tube and the material in which fine particles of fluororesin are dispersed have a PFA tube of about 120 degrees, and a tube made only of resin is resistant to scratches and abrasion. It was weak, and streaks and the like were generated on the image even at a durability of about 5000 rpm, which was a practical problem. Further, in a material in which fine powder of fluororesin is dispersed, the durability and abrasion resistance can be improved to some extent by the resin of the binder, but on the other hand, the characteristics of the resin of the binder influence the releasability, and generally, the fluororesin is used. Since the releasability is lower than that of No. 3, toner and paper powder are likely to adhere, and the durability is still about 5000 rpm, and the image is uneven. Furthermore, in a semiconductive layer using a conventional fluororesin, the resistance value has less fluctuation than other polyamide resins, but in a fluororesin having resistance control of ion conductivity, it is easily affected by ambient humidity. In some cases, the resistance range was unusable due to durability.

Therefore, it is an object of the present invention to provide a charge supply member capable of exhibiting sufficient wear resistance and releasability over a long period of time.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and comprises a composite layer containing fluoride particles and a metal, and a conductive substrate coated with the composite layer. In a charge supply device having a configured charge supply member and supplying a charge to an image carrier by applying a voltage to the charge supply member, at least the surface of the image carrier in the composite layer is opposed to the surface. The portion is characterized in that the contact angle with respect to pure water is set to 130 degrees or more at 23 ° C.

Further, it has a charge supplying member composed of a composite layer containing tetrafluoroethylene particles and a metal, and a conductive substrate covered with the composite layer, and a voltage is applied to the charge supplying member. In the electric charge supply device for supplying electric charges to the image carrier by doing so, at least a portion of the composite layer facing the surface of the image carrier is set to have a contact angle to pure water of 130 degrees or more at 23 ° C. In addition, the volume resistivity of the applied voltage of 100 V is 1
It is characterized by being set to 0 ⁴ Ω · cm or more and 10 ¹³ Ω · cm or less.

In this case, the contact angle is 140 at 23 ° C.
It is further preferable that the volume resistivity of the applied voltage of 100 V is set to 10 ⁶ Ω · cm or more and 10 ¹² Ω · cm or less while being set to 10 ° C. or more.

[0009]

According to the above construction, by setting the contact angle and the low volume efficiency as described above, high releasability and wear resistance can be realized.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 1 schematically shows an image forming apparatus having a primary charging roller as a charge supply member according to the present invention.
The configuration and operation will be briefly described below.

The image forming apparatus includes a photosensitive drum 1 as an image carrier. The photosensitive drum 1 has a diameter of 10
An 8 mm amorphous silicon photosensitive member is used, and is rotationally driven in the direction of arrow R1 at a process speed (peripheral speed) of 500 mm / sec by a driving unit (not shown).

The surface of the photosensitive drum 1 is uniformly charged to a predetermined potential by a primary charging roller (charge supplying member) 2. The charging roller 2 is rotationally driven at a constant speed in the forward direction (direction of arrow R2) with respect to the photosensitive drum 1. Further, the charging roller 2 has a direct current 16
00V is applied, and as a result, about 600 at the developing unit position.
A dark area potential of V is obtained. In the sequence, the above voltage is applied only to the portion corresponding to the image area, and 800 V of DC is applied to the area other than the rotating image area. The surface of the charging roller 2 is, as shown in FIG.
The toner and the like adhering to the surface is removed by the charging roller cleaning member 23 made of a material such as urethane rubber or polyester. A composite layer 22 is formed on the surface of the charging roller 2, which will be described later.

The charged photosensitive drum 1 is subjected to image exposure to form an electrostatic latent image on its surface.

This electrostatic latent image is developed by the developing device 4. The developing device 12 has an aluminum developing sleeve 41 having a diameter of 20 mm. The developing sleeve 41 has a surface
The toner T, the layer pressure of which is regulated by the elastic rubber blade 42, is coated, and as the developing bias, a superimposed voltage in which a sine wave having a frequency of 2700 Hz and a peak-to-peak voltage of 1400 V and a direct current are superimposed is applied. As a result, toner is attached to the electrostatic latent image on the photosensitive drum 1 described above,
It is developed as a toner image. The toner T is a one-component magnetic toner obtained by adding 0.5% of silica as an external additive to a material of styrene-acrylic material having an average particle size of about 9 μm. Is -3 to 12 (μC / g), and the coating amount is 0.6 to 1.
It is 3 mg / cm ² .

The toner image on the photosensitive drum 1 is transferred onto the transfer material P by the transfer roller 6. A high voltage power source (not shown) is connected to the transfer roller 6, and a transfer voltage is applied. The transfer roller 6 maintains a distance between the transfer roller 6 and the photosensitive drum 1 at about 40 μm by abutting spacers (not shown) at both ends in the longitudinal direction against the surface of the photosensitive drum 1.

The transfer material P after the toner image transfer is carried by the conveying member 9
Is conveyed to the fixing device 10. The transfer material P is inserted into a nip portion formed by a fixing roller 10a having a heater 10c and a pressure roller 10b therein, and the toner image on the surface is heated and pressed to be fixed. The fixing roller 10a is made of a fluorocarbon resin (PTFE) having a surface layer of about 20 μm on a silicon rubber layer having a thickness of 0.25 mm.
Is coated by baking or the like, while the pressure roller 1
0b is a silicone rubber having a diameter of 60 mm and a thickness of 5 mm, which is coated with a fluororesin (PFA) tube having a thickness of 100 μm. The transfer material P after the toner image is fixed is discharged as a print to the outside of the main body of the image forming apparatus.

On the other hand, the photosensitive drum 1 after the toner image transfer is
The cleaning device 7 removes the residual toner on the surface, receives the sheet exposure 8, and then is used for image formation.

FIG. 2 shows an enlarged vertical sectional view of the primary charging roller 2 as a charge supplying member according to the present invention.

The charging roller 2 has a diameter of 20 mm and a thickness of 1.
After 5 mm of stainless steel hollow core bar 21 is plated with nickel of about 10 μm and further electrically plated, the surface of metal and T of about 10 to 15 μm is deposited.
The composite layer 22 with an FE (tetrafluoroethylene) oligomer is formed. The plating method of the composite layer 22 is to disperse a TFE oligomer having an average particle size of about 5 μm in a sulfamic acid solution using a fluorine-based surfactant, and use a nickel electrode as the anode and the hollow core metal 21 as the cathode to produce electricity. Plating. The plating thickness can be arbitrarily set by the set current and the energization time. As for the production of TFE, there is a method of cutting the molecular chain of PTFE at high temperature to increase the bond between carbon and fluorine. according to this,
It is possible to change the concentration of fluorine atoms on the surface after the formation of the complex by appropriately changing the conditions such as the temperature at which the molecular chain is cleaved. At least a portion of the composite layer 22 of the present embodiment facing the surface of the photosensitive drum 1 has a fluorine atom concentration of about 50%, a contact angle with pure water of about 160 degrees at 23 ° C., and a volume resistance. Rate is 100V
The applied voltage is about 10 ⁶ to 10 ⁷ Ω · cm.

FIG. 3 shows the relationship between the releasability and durability of the composite layer 22. As shown in the figure, the releasability (contact angle) was appropriately changed, and the relationship with the durable rotation speed at that time was examined by experiments. In the experiment, using the image forming apparatus shown in FIG. 1 described above, in an environment of room temperature of 23 ° C. and humidity of 60%,
A document having an image ratio of 4% was subjected to continuous paper feeding durability with A4 size 64-gram paper manufactured by Daishowa Paper Co., Ltd. under the condition of an appropriate density. The contact angle was changed by changing the ratio of the carbon-fluorine bond of TFE as described above. It should be noted that the contact angle is a value before endurance, and as an evaluation criterion of endurance rotation speed, an image is actually output under the developing condition that the original with a reflection density of 0.3 has an average reflection density of about 0.5. Then, the graininess was objectively evaluated by the Wiener spectrum, and the number of revolutions of the charging roller 2 until the grain size fell below a certain level was determined. As shown in FIG. 3, there is a correlation between the releasability of the initial surface and the durability, and it can be seen that the durability is gradually improved when the contact angle exceeds 130 degrees. From this, it is understood that the contact angle should be set to 130 degrees or more, and more preferably 140 degrees or more.

Further, when the charging resistance and the image evaluation were carried out by appropriately changing the volume resistance value of the composite layer 22, the volume resistivity at an applied voltage of 100 V was 10 ⁴ Ω · cm or more and 10 ¹³ Ω.
-Cm or less, more preferably 10 ⁶ Ω-cm or more and 10 ¹² Ω
・ A good image was obtained at cm or less. <Second Embodiment> FIG. 4 shows a second embodiment. In this example, the primary charging plate 20 is used as the charge supplying member instead of the primary charging roller 2. 10 μm on the surface of the photosensitive drum 1 side of a stainless steel substrate (conductive substrate) 21 having a thickness of 10 mm and a width of 50 mm in the rotating direction of the photosensitive drum 1.
After applying approximately nickel plating, it is further electroplated to obtain a TFE of about 10 to 15 μm on the surface.
Complex layer 2 with (tetrafluoroethylene) oligomer
2 is formed. The plating method for the surface layer was the same as in Example 1, except that a fluorine-based surface active agent was used and the average particle size was 5 μm.
About m of TFE oligomer is dispersed in a sulfamic acid solution, and the nickel electrode is used as the anode and the stainless steel substrate 21 is used as the cathode to perform electroplating. The composite layer 22 of this embodiment has a volume resistivity of 10 ⁶ to 10 ⁷ Ω when 100 V is applied.
・ It is about cm, and the concentration of fluorine atoms on the surface is about 50%.
The contact angle with pure water is around 160 degrees.

Spacers (not shown) at both ends of the charging plate 20 in the longitudinal direction are brought into contact with the photosensitive drum 1 to set the distance between the photosensitive drum 1 surface and the photosensitive drum 1 surface to about 40 μm. At the time of image formation, a voltage of DC 1600V is applied to the electrode portion of the charging plate 20 to obtain a dark portion potential of the photosensitive drum 1 of about 600V at the developing portion position. on the other hand,
At a timing between image formation, in order to return the toner and the paper powder that have adhered to the surface of the charging plate 20 and slipped from the cleaning device toward the photosensitive drum 1, a direct current of minus 600 V is applied. <Actual Sister Example 3> FIG. 5 shows the actual sister example 3. In this embodiment,
The transfer roller 6 is used as a charge supply member.

The transfer roller 6 shown in the figure has a diameter of 20 mm.
1 on a stainless steel hollow core 61 with a thickness of 1.5 mm
After the nickel plating of about 0 μm, it is further electrically plated to obtain a T of about 10 to 15 μm on the surface.
A composite layer 62 with an FE (tetrafluoroethylene) oligomer is formed. The surface layer is plated by using a fluorosurfactant to disperse a TFE oligomer having an average particle size of about 5 μm in a sulfamic acid solution, using a nickel electrode as the anode and the hollow core metal 61 as the cathode for electroplating. To do. The volume resistivity of the composite layer 62 of this example is 100.
It is about 10 ⁹ to 10 ¹⁰ Ω · cm when V is applied, and has a higher resistivity than the charging roller 2 of the first embodiment. The fluorine atom concentration on the surface of the composite layer 62 is about 50%, and the contact angle with pure water is about 160 degrees. The distance between the transfer roller 6 and the photosensitive drum 1 is set to 80 μm by abutting the spacers (not shown) at both ends of the non-sheet passing portion in the longitudinal direction against the surface of the photosensitive drum 1.
It is set to a degree. When the thickness of the transfer material P is large, the pressure applied to the transfer roller 6 is set so that the distance between the transfer roller 6 and the photosensitive drum 1 is increased according to the thickness so that the actual total pressure is 0. It is pressurized with a spring so that it is about 5N.
Further, when the transfer characteristics and the image evaluation were performed by changing the volume resistance value of the composite layer 62, the volume resistivity at an applied voltage of 100 V was 10 ⁴ Ω · cm or more and 10 ¹³ Ω · cm or less, and more preferably 10 ⁶ Good images were obtained at Ω · cm or more and 10 ¹² Ω · cm or less.

[0024]

As described above, according to the present invention,
In the charge supply device, at least a portion of the composite layer containing the fluorinated particles and the metal that faces the surface of the image carrier is set so that the contact angle with pure water is 130 degrees or more at 23 ° C. Even after long-term use, abrasion resistance and releasability can be maintained well, so that a stable image can be obtained over a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus in which a charging roller according to a first exemplary embodiment is mounted.

FIG. 2 is an enlarged vertical cross-sectional view showing the configuration of the charging roller according to the first exemplary embodiment.

FIG. 3 is a view showing a relationship between a contact angle of a charging roller and a durable rotation speed.

FIG. 4 is an enlarged vertical sectional view showing the configuration of a charging plate according to a second embodiment.

FIG. 5 is an enlarged vertical cross-sectional view showing the configuration of a transfer roller of Example 3.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 image carrier (photosensitive drum) 2 charge supply member (charging roller) 3 image exposure 4 developing device 6 charge supply member (transfer roller) 7 cleaning device 10 fixing device 20 charge supply member (charging plate) 21 hollow core metal, substrate 22 composite layer 23 charging roller cleaning member 61 hollow cored bar 62 composite layer P transfer material T toner

Claims (3)

[Claims] 1. A charge supply member comprising a composite layer containing fluoride particles and a metal, and a conductive substrate coated with the composite layer, and applying a voltage to the charge supply member. In the electric charge supply device for supplying electric charge to the image carrier by means of the above, at least a portion of the composite layer facing the surface of the image carrier has a contact angle of 1 ° C. with pure water of 1 ° C.
The charge supply device is characterized by being set to 30 degrees or more. 2. A charge supply member comprising a composite layer containing tetrafluoroethylene particles and a metal, and a conductive substrate coated with the composite layer, and a voltage is applied to the charge supply member. In the electric charge supply device for supplying electric charges to the image carrier by doing so, at least a portion of the composite layer facing the surface of the image carrier has a contact angle of 1 ° C. with pure water of 1 ° C.
It is set to 30 degrees or more and the applied voltage is 100V.
The electric charge supply device is characterized in that the volume resistivity of is set to 10 ⁴ Ω · cm or more and 10 ¹³ Ω · cm or less. 3. A charge supply member comprising a composite layer containing tetrafluoroethylene particles and a metal, and a conductive substrate coated with the composite layer, and a voltage is applied to the charge supply member. In the electric charge supply device for supplying electric charges to the image carrier by doing so, at least a portion of the composite layer facing the surface of the image carrier has a contact angle of 1 ° C. with pure water of 1 ° C.
It is set to 40 degrees or more and the applied voltage is 100V.
The electric charge supply device is characterized in that the volume resistivity of is set to 10 ⁶ Ω · cm or more and 10 ¹² Ω · cm or less.