JP2939458B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for visualizing an electrostatic latent image in an electrophotographic device or an electrostatic recording device, and more particularly to a developing device capable of obtaining a high-quality image.

[0002]

2. Description of the Related Art As one of development methods using a one-component developer, a pressure development method (Impression Development) is known. This method is characterized in that an electrostatic latent image is brought into contact with a toner particle or a toner carrier at a substantially zero relative peripheral speed (US Pat. Nos. 3,152,012 and 3,731,
146, JP-A-47-13088, JP-A-47-13089, etc.), and since there is no need for a magnetic material, the apparatus can be simplified and downsized, and the toner can be easily colored. have.

In the above-described pressure development method, development is performed by pressing or contacting a toner carrier with an electrostatic latent image.
It is necessary to use a developing roller having elasticity and conductivity. In particular, when the electrostatic latent image holder is a rigid body, it is an essential condition that the developing roller is made of an elastic body in order to avoid damaging the electrostatic latent image holder. In order to obtain a well-known developing electrode effect and a developing bias effect, it is preferable to provide a conductive layer on or near the surface of the developing roller and apply a bias voltage to the conductive layer as necessary.

As a specific example of the developing roller having such a configuration, an elastic layer such as foam rubber or polyurethane foam is provided on the surface of a metal roller base material, and a flexible conductive layer and a binder resin are used. There is a developing roller in which an outermost layer in which graphite particles are dispersed is sequentially coated (JP-A-47-13088). That is, the surface layer was formed by applying the above-mentioned graphite-binder resin mixture to a thin plate of aluminum-treated polyethylene terephthalate by using a horizontal coating device by about 20 minutes.
It was applied to a thickness of μm. However, in the above invention, a thin plate of polyethylene terephthalate coated with a graphite-binder resin mixture,
It does not specify how to cover the surface of the elastic layer. As a trial, when the thin plate was wound around the surface of the elastic layer to create a roller bonded and pressure-developed, the seam of the thin plate showed unique electrical characteristics,
A uniform toner layer could not be formed at the seam and its vicinity, and the seam of the thin film appeared remarkably in the image, resulting in an undesirable image.

On the other hand, the present inventors have moved the toner carrier at a speed higher than that of the electrostatic latent image holding member in the pressure development method, so that the quality of the developed image is higher than that of the developed image in the conventional pressure development. It was found that an image could be obtained.

That is, by rubbing the electrostatic latent image holding member with a toner holding member having a toner layer on the surface, the sharpness of a line image and the uniformity of a solid image can be improved, and the toner holding member can be slid. It has been found that by moving the image at a speed higher than that of the electrostatic latent image, a high-density solid image can be obtained while suppressing fog.

However, as described above, there has been a problem that it is difficult to obtain a high-quality image with a developing device using a conventional pressure developing method, particularly with a developing roller.

As a charging device for uniformly charging the surface of the electrostatic latent image holding member, a corona charging device, a brush charging device using a conductive brush, a roller charging device using a conductive rubber roller, and the like have been known. Have been.

The known corona charging device is the most widely used practically. However, since corona discharge is used, a large amount of discharge products such as ozone are generated, and these discharge the electrostatic latent image holding member. There is a drawback that the discharge products must be removed with an ozone filter or the like in order to cause deterioration or adverse effects on the human body. In addition, since a high voltage of about 5 kV is required as a corona voltage, there has been an inevitable problem of a power supply device, an increase in size and an increase in current capacity.

On the other hand, a contact charging device such as a brush charging device or a rubber roller charging device hardly generates a discharge product, and can use a relatively low voltage of about 500 V to 1000 V as a power supply voltage. However, it has the following disadvantages, which hinders full-scale practical use.

That is, the brush charging device applies a voltage to a brush made of a conductive fiber, and rubs the surface of the electrostatic latent image holding member to thereby charge the electrostatic latent image holding member. The charging target can be charged to a potential close to the above-mentioned applied voltage regardless of the shape of the brush or the roller-type rotary brush (Japanese Patent Application Laid-Open No. 58-72981). If you use it for a long time, the brushed state of the fiber changes and it falls down in a certain direction,
There is a problem that the charging ability is reduced.

Further, the roller-shaped rotating brush is generally less likely to cause the above-described hair loss phenomenon than the fixed type brush, but it is difficult to form a cylindrical flocking body, and a flocking cloth which is generally referred to as an extraordinary rare. Must be wound around the outer periphery of the roller, which inevitably causes a seam of the cloth, and the seam cannot be uniformly charged by the seam.

On the other hand, a roller charging device using a conductive rubber roller is a device in which a voltage is applied to the conductive rubber roller so as to come into contact with an electrostatic latent image holding roller and roll at the same surface speed as the roller. (JP-A-58-49960). This device can avoid the above-mentioned problem associated with the brush fibers, but has the problem that charging unevenness is more likely to occur than in the brush charging device.

That is, since the rubber surface generally has a large coefficient of friction, it is practically difficult to rub the surface of the electrostatic latent image holding member. Therefore, a spatial variation in the resistance value of the rubber roller may lead to uneven charging. Many. In addition, since the conductive rubber roller generally has high hardness, it is difficult to increase the nip width between the conductive rubber roller and the electrostatic latent image holding member, and it is easy to cause charging unevenness. Further, there is a problem that the toner adheres to the surface of the roller due to the plasticizer oozing out on the rubber surface, thereby lowering the charging ability.

[0015] All of these problems with the contact charging device lead to a reduction in image quality, and there has been a problem that it is difficult to obtain a high quality image with the conventional contact charging device.

[0016]

As described above, the pressure development method is a method capable of obtaining a high quality image, but it is difficult to obtain a high quality image with a conventional developing roller. There was a problem. In addition, the contact charging device has the advantage that almost no discharge products are generated, and the power supply device does not need to be large and has a large current capacity, but it is difficult to maintain the charging capability with the brush charging device. In the roller charging device, it is difficult to uniformly charge the electrostatic latent image holding member, so that there is a problem that it is difficult to obtain a high quality image in any case.

Therefore, taking advantage of the pressure development method,
In addition, in order to obtain a high quality image, there is a problem that a developing roller capable of forming a uniform toner layer must be obtained. Also, taking advantage of the contact charging method,
In addition, in order to obtain a high-quality image, there is a problem that a contact charging device that has a small reduction in charging ability even after long-term use and can suppress occurrence of charging unevenness has to be obtained.

The present invention has been made to solve the problems of the prior art, and has as its object to provide a developing device having a developing roller capable of forming a uniform toner layer using a pressure developing method. .

[0019]

According to the present invention, there is provided an image forming apparatus comprising: a resilient developing roller disposed so as to be in contact with an electrostatic latent image holding member;
Form a thin layer of non-magnetic toner on the surface of the developing roller
That blade and, a developing device having a means for rotating the developing roller at a faster peripheral speed than the electrostatic latent image holding member, the developing roller has a roller base with elasticity, of the roller base Has flexibility formed on the outer circumference
A conductive layer made of a seamless tube
The conductor layer is in direct contact with the electrostatic latent image holder.
Characterized by having a substantially smooth surface .

Examples of the roller base used in the present invention include those obtained by adhering a soft urethane foam having a foam cell number of 30 to 100 cells / 25 mm, a rubber sponge, or urethane rubber to the outer periphery of a metal shaft. Further, as the conductor layer, the outer surface of a seamless tube of polyester, polyethylene, polyethylene terephthalate or the like is coated with a polyester resin which is made conductive by dispersing conductive carbon, or the seamless tube is made of conductive carbon. Can be used, or a seamless tube in which an aluminum vapor deposition layer or a metal plating layer is formed on the outer surface can be used.

The developing roller can be obtained by inserting a roller base into a seamless tube. At this time, if a roller base having a high coefficient of friction on the surface is used, if the outer diameter of the roller base is equal to or larger than the inner diameter of the seamless tube, there is no need to bond the two with an adhesive or the like, which facilitates production. Become. Further, when using a heat-shrinkable tube having an inner diameter larger than the outer diameter of the roller base,
The tube can be easily brought into close contact with the surface of the roller base by the heat treatment, and can be more easily obtained. In the case where an extremely flexible material such as a flexible polyurethane foam is used as the roller base, or in a case where the seamless tube and the roller base are used under severe conditions against slippage, the two may be bonded to each other. preferable. In this case, first, a hot-melt adhesive is applied to the inside of the seamless tube and the outside of the roller base, and the roller base is inserted into the seamless tube in a state where the adhesive is solidified.
After that, it is effective to apply a heat treatment to surely bond the two.

In the present invention, the developing roller preferably satisfies the following conditions.

The electric resistance value of the conductive layer constituting the developing roller is preferably 10 ⁹ Ω · cm or less, particularly preferably 10 ⁶ Ω · cm or less. If the electric resistance value is too high, the effect as a developing electrode is lost, and particularly, the density of a solid image decreases, which is not preferable.

It is preferable that the rotational peripheral speed of the developing roller is 1.5 to 7.0 times the rotational peripheral speed of the photosensitive drum. If the rotational peripheral speed is lower than this range, the toner supply amount to the photoconductor drum will be insufficient and sufficient image density will not be obtained. Both of these are not preferred because tailing occurs.

The contact width between the developing roller and the photosensitive drum is preferably in the range of 0.3 to 0.6 mm. If the contact width is less than 0.3 mm, the toner particles in the developing nip will have insufficient rolling and slippage, and the effect of improving the sharpness of the image will not be sufficiently exhibited. on the other hand,
If it exceeds 6.0 mm, fogging occurs in the non-image area and trailing of the image occurs, which is not preferable.

In the present invention, bias leakage can be prevented by providing a resistance layer on the surface of the conductor layer of the seamless tube. Here, the bias leak refers to the following phenomenon.

That is, if a part of the photosensitive member is missing for some reason, a current flows between the conductive layer on the developing roller surface and the grounded photosensitive member base. Although this current is limited to a small value by the protection resistor, even if the current is small, a potential difference occurs across the protection resistor once the current flows, and the potential of the conductor layer becomes the ground potential or a potential close to this. Would. This phenomenon is called bias leak. In the case of reversal development, a bias leak causes a noticeable white streak in a solid image and significantly lowers the image quality. However, when a resistance layer is provided on the surface of the conductor layer, it is possible to prevent bias leakage from appearing remarkably in an image for the following reasons.

That is, if the resistance value of the resistance layer is sufficiently high, for example, 10 ¹³ Ω · cm or more, no bias leak occurs even if the photosensitive member base is exposed. On the other hand, when the resistance layer is, for example, about 10 ⁸ Ω · cm, a current flows in the height direction of the resistance layer, which may cause a bias leak. Therefore, the potential of the entire resistance layer does not decrease. Therefore, white spots having the same area as the defect of the photoreceptor may occur in the solid portion, but it is possible to prevent white stripes from appearing in other areas. In this way, the resistive layer has the effect of preventing the occurrence of significant defects in the image.

Although the electric resistance of the resistance layer should be determined in relation to the resistance of the protective resistor, it is generally higher than that of the conductor layer, preferably 10 ⁷ Ω · cm or more. In order to obtain the developing electrode effect, the thickness of the resistance layer is preferably set to 0.5 mm or less.

Further, in the present invention, a bias can be supplied from a metal shaft by using a seamless tube consisting only of a conductive resin layer and forming the roller base with an elastic conductor. With such a configuration, the grade does not necessarily have to be a conductor, and the range of choice of the blade material is greatly expanded. Further, a more reliable power supply can be performed as compared with a method in which power is supplied from the blade to the conductor layer via the toner layer.

In this case, bonding the seamless tube and the elastic roller is effective in preventing the tube from slipping, but it is preferable to use a conductive adhesive for bonding.

Further, the electric resistance value of the roller base is set to 10 ⁶ Ω ·
cm or less and using a seamless tube having a higher electric resistance value can prevent bias leak and obtain a good image.

In the present invention, since a developing roller having a seamless surface can be formed, a uniform toner layer can be formed, and a high-quality developed image can be obtained. In addition, by rotating the developing roller at a higher peripheral speed than the electrostatic latent image holding member, it is possible to supply an appropriate amount of toner to the electrostatic latent image holding member. Since the toner can be slid or rolled at the contact portion of the body, it is possible to obtain a very good image including a high-density and uniform solid image, a sharp line image, and a fog-free background.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described specifically and in detail by way of examples with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view schematically showing a main part of an embodiment of a developing device according to the present invention. In the developing device 1, the developing roller 2 rotates counterclockwise at a higher speed than the photosensitive drum 3 while being in contact with the photosensitive drum 3. The blade 4 as a toner layer forming means is made of a phosphor bronze plate having a thickness of 0.2 mm, and its free end is lightly pressed against the developing roller 2. The seal member 5 has a function of preventing the toner 7 in the toner container 6 from spilling to the outside, and at the same time, collecting the undeveloped toner on the surface of the developing roller 2 into the toner container without spilling. A sponge bonded with a 1 mm urethane rubber sheet was used. The toner supply roller 8 is made of a flexible polyurethane foam, and has a function of supplying toner to the surface of the development roller 2 by rotating while being in contact with the development roller 2. A developing bias voltage is applied to the blade 4 from a DC power supply 9 via a protective resistor 10.

In this embodiment, the contact width between the developing roller 2 and the photosensitive drum 3 is set to about 1 mm, and the rotational peripheral speed of the developing roller 2 is 188 mm / sec (4.0 times the rotational peripheral speed of the photosensitive drum 3).
And

In this embodiment, a case where the above-described developing device is applied to a so-called laser beam printer which forms a latent image by irradiating a laser beam onto the surface of a photoreceptor will be described. It is needless to say that the present invention can also be applied to a so-called copying apparatus of a type in which the image is formed on a photosensitive member. Although the photosensitive member is a negatively charged organic photoconductor, a selenium-based or amorphous silicon-based photosensitive member may be used.

FIG. 2 is a partial sectional view showing an embodiment of the developing roller according to the present invention.

The developing roller 11 includes a metal shaft 12
A polyurethane microcell foam layer 13 (trade name: ENDUR, manufactured by Inoue MTP Co., Ltd.), which is a roller substrate adhered to the outer periphery of the substrate, and covers the outer periphery of the developing member layer 13 (hereinafter, referred to as the roller substrate 13) And an 80 μm thick seamless polyester tube 15 having a 10 μm thick conductor layer 14 on the surface.

The conductor layer 14 is formed by immersing a seamless polyester tube 15 in a solution composed of a polyester resin, conductive carbon and a solvent, and has a volume resistance of 2 × 10 ³ Ω · cm. It is.

The inner diameter of the seamless polyester tube 15 is 20 mm, and a roller base 1 having an outer diameter of 20.5 mm is provided inside the tube.
By inserting No. 3, the adhesion between the seamless polyester tube 15 and the roller base 13 was improved, and the developing roller 11 free from slippage and displacement was produced.

When the developing roller 11 is mounted on the developing device shown in FIG. 1 and the developing roller 2 and the toner supply roller 8 are rotated by a driving device (not shown), the surface of the developing roller 2 A thin toner layer of about 0.5 mg / cm ² was formed.

At this time, the contact width of the developing roller 2 with respect to the photosensitive drum 3, that is, the developing nip is as described above.
1.0 mm. A developing bias having an output voltage of -300 V is applied to the blade 4 from a DC power supply 9 via a protective resistor 10 having an electric resistance value of 1 × 10 ⁸ Ω · cm.
The protection resistor 10 limits the current value to prevent or minimize the breakdown when a discharge breakdown is to occur between the conductive layer 14 on the surface of the developing roller 2 and the photosensitive member or the conductive base of the photosensitive member. With the goal. The electric resistance between the blade and the developing roller at the time of driving is determined by the potential difference between the two.
It was 2 × 10 ⁴ Ω at 100V.

As the toner, a negatively charged insulating one-component non-magnetic toner in which carbon black was dispersed in a polyester resin was used. The volume average particle size is 12.0 μm.

The toner layer thus formed on the surface of the developing roller 2 was sucked into the Faraday cage by air, and the charge amount of the toner was measured to be -8.2 μC / g. The toner particles mainly consist of the blade 4 and the developing roller 2
The toner is charged by friction with the toner supply roller 8.

Next, the developing device is operated, a negative charge is applied to the surface of the photosensitive drum 3 by a well-known corona charger, the surface potential is set to -550 V, and only the image portion is exposed by a laser beam. About -50V depending on the exposure
When a negatively charged toner was applied to the portion where the potential was attenuated by a well-known reversal developing method, a good reversal developed image was obtained.

When the DC power supply 9 is directly connected to the blade 4 without using the protective resistor 10, discharge breakdown occurs between the developing roller 2 and minute pinholes or electrically weak portions of the photosensitive layer. Then, a remarkable defect occurs in the photoconductor layer. For this reason, it is preferable to prevent discharge breakdown by using a protective resistor having an electric resistance value of 10 ⁶ Ω · cm to 10 ¹³ Ω · cm, preferably 10 ⁷ Ω · cm, or 10 ¹¹ Ω · cm. If the electric resistance value of the protective resistor is less than 10 ⁶ Ω · cm, the current limiting effect is insufficient, and if it exceeds 10 ¹³ Ω · cm, the effect of the developing bias is lost, which is inconvenient.

[0048]

[0049]

[0050]

[0051]

Embodiment 2 In this embodiment, a urethane conductive rubber sponge roller having an electric resistance value of 10 ³ Ω · cm was used as a roller substrate, and this roller substrate was formed by dispersing conductive carbon in polyester resin. Then, it was inserted inside the seamless polyester tube which was made conductive, thereby forming a developing roller. The electrical resistance of the conductive seamless polyester tube was 10 ⁵ Ω · cm.

In the developing device using the roller base, a developing bias can be supplied from a metal shaft.

When the reversal development of the latent image was performed under the same conditions as in Example 1 using the obtained developing roller, a good toner image was obtained.

In this embodiment, the conductive adhesive is obtained by mixing a synthetic resin such as an acrylic resin, an epoxy resin, a phenol resin, or a polyester resin with a metal powder or a carbon powder as a conductive substance to give an adhesive property. It is preferred to use agents. Also, by providing a resistance layer on the surface of the conductive tube, it is needless to say that bias leak can be prevented.

Next, the charging device will be described.

The charging device has an elastic conductive roller including an elastic roller base and a flexible conductive layer formed outside the roller base.

Examples of the above-mentioned roller base include those formed by adhering a soft urethane foam, rubber sponge or urethane rubber having a foam cell number of 30 to 100 cells / 25 mm to the outer periphery of a metal shaft. Further, as the conductor layer, the outer surface of a seamless tube of polyester, polyethylene, polyethylene terephthalate or the like is coated with a polyester resin which is made conductive by dispersing conductive carbon, or the seamless tube is made of conductive carbon. Can be used, or a seamless tube in which an aluminum vapor deposition layer or a metal plating layer is formed on the outer surface can be used.

The elastic conductive roller can be obtained by inserting the roller base into a seamless tube.
At this time, if a roller base having a high coefficient of friction on the surface is used, if the outer diameter of the roller base is equal to or larger than the inner diameter of the seamless tube, there is no need to bond the two with an adhesive or the like, which facilitates production. Become. Further, when a heat-shrinkable tube having an inner diameter larger than the outer diameter of the roller base is used, the tube can be easily brought into close contact with the surface of the roller base by a heat treatment, and can be more easily obtained.

When an extremely flexible material such as a flexible polyurethane foam is used as the roller base, or when it is used under severe conditions against slippage between the seamless tube and the roller base, a gap between the two is required. Adhering is preferred. In this case, first, a heat-soluble adhesive is applied to the inside of the seamless tube and the outside of the roller base, and the roller base is inserted into the seamless tube in a state where the adhesive is solidified. It is effective to use a method for securely bonding the two.

The electric resistance of the conductive layer of the elastic conductive roller is preferably 10 ⁶ to 10 ¹² Ω · cm. 10 ⁶ Ω
If it is less than cm, the photoconductor is destroyed by discharge and the charged potential is lowered by bias leak.
On the other hand, if it exceeds 10 ¹² Ω · cm, it is not preferable because it can hardly be charged. A particularly preferred range is from 10 ⁶ to 10 ⁸
Ω · cm. Of course, as long as the electrostatic latent image holding member is electrically strong and has few defects, a conductive layer of less than 10 ⁶ Ω · cm may be used.

The contact width between the elastic conductive roller and the electrostatic latent image holding member is preferably 0.3 to 8.0 mm.
If the contact width is less than 0.3 mm, charging unevenness occurs, which is not preferable. On the other hand, if it exceeds 8.0 mm, the rotational torque of the elastic conductive roller increases, which is not practically preferable.

Further, it is preferable that the rotational peripheral speed of the elastic conductive roller is higher than the rotational peripheral speed of the photosensitive member. Even when the rotation speed of the elastic conductive roller is lower than the rotation speed of the photoconductor, relatively uniform charging is possible.However, the higher the rotation speed of the elastic conductive roller is higher than the rotation speed of the photoconductor, the more uniform the charging. Since charging can be performed, it is more preferable to set the value quickly.

The surface roughness of the elastic conductive roller is 6 μm.
It is preferably not more than R _Z (JIS 10-point average roughness),
Exceeding this is not preferable because uneven charging occurs. The average value of the pitch of the surface irregularities is preferably 10 μm or less.

In the charging device configured as described above, the elastic layer and the conductive layer are separated from each other, and the elastic and conductive functions are independently given to each other. All the problems relating to the conductive rubber roller charging device can be solved. That is, since the conductive layer is not necessarily required to have flexibility and may be simply formed of a material having flexibility, for example, a conductive polyester film or the like can be used, and does not cause a chemical reaction with the toner. The choice of material becomes very easy. Further, if the surface of the latent image holding member is made of a material having a small friction coefficient, the surface of the latent image holding member can be rubbed, and the resistance unevenness of the conductive layer can be set so as not to appear directly as charging unevenness. . At the same time, since the roller base having elasticity is not necessarily required to be conductive, a foam such as a soft urethane foam, a rubber sponge, or the like can be used, and an extremely flexible conductive roller can be formed. Thus, it is possible to increase the nip width between the elastic conductive roller and the electrostatic latent image holding member, and it is possible to perform more uniform charging.

Accordingly, a contact charging device which can suppress the occurrence of charging unevenness with a small decrease in charging ability even after long-term use can be obtained, and a high-quality image can be obtained.

FIG. 3 is a sectional view of a main part showing a specific example of such a charging device.

In the contact charging device 20, the elastic conductive roller 22 that rotates while being in contact with the drum-shaped photoreceptor 21 as a holding member is a surface of a foamed elastic member 24 which is a roller base provided on the outer periphery of the metal shaft 23. Covered with a conductive seamless tube 25, and supported rotatably clockwise.

In this example, a foamed polymer material (trade name: ENDUR C-250-20) having a polyurethane microcell structure manufactured by Inoue MTP Co., Ltd. was used as the foamed elastic body 24. 20.5 mm. The conductive seamless tube 25 has an inner diameter of 20 mm and a thickness of 100 μm.
The thickness of the polyester resin layer made conductive by dispersing conductive carbon on the surface of the polyester tube
The one coated at 80 μm was used, and the volume resistivity of the surface conductor layer was 10 ⁷ Ω · cm. Elastic conductive roller 22
Is a method of forming the elastic foam 24 into a conductive seamless tube 2.
5 has been created by inserting it into.

An electrode member 26 made of a phosphor bronze plate having a thickness of 0.15 mm is pressed against the surface of the conductive seamless tube 25.
6, a predetermined voltage is applied to the conductive seamless tube 25. Further, a cleaning member 27 for cleaning toner particles attached to the surface is pressed against the conductive seamless tube 25. In this example, the cleaning member 27 is made of felt having a width of 10 mm and a thickness of 3 mm. The outer diameter of the metal shaft 23 is 6 mm, and is rotatably supported by a fixing member (not shown).

Using the contact charging device 20 and a negative band type photoconductor made of an organic photoconductor, a charging experiment was performed with a contact width between the elastic conductive roller 22 and 1 mm. The peripheral speed 80 mm / sec of the elastic conductive roller 22, the peripheral speed of the photosensitive drum as 47 mm / sec, where a negative voltage is applied to the electrode member, the photosensitive member exhibited charging characteristics as shown in FIG. 4. The variation of the photoconductor surface potential showed a small value of 20 V or less.

The elastic conductive roller 22 and the photosensitive member 2
When the apparatus was operated with a contact width of less than 0.3 mm during the period 1, charging unevenness of 50 V or more occurred, which was not preferable.

As another example, a conductive silicone rubber having a hardness of 35 degrees and a volume resistance of 10 ⁴ Ω · cm is used for the roller base, and a conductive silicone rubber having a volume resistance of 10 ⁷ Ω · cm An elastic conductive roller was formed by covering the polyester resin layer.

When a bias voltage was applied to the elastic conductive roller from a metal shaft and a charging experiment was performed, the same result as in the above example was obtained. In addition, even after long-term use, the toner did not adhere to the surface of the elastic conductive roller, and showed extremely good charging characteristics.

As described above, in the above-described charging device, the elasticity and the conductive function are separately provided to the roller base and the conductive layer, so that the resistance of the conductive layer can be easily adjusted and the variation of the electric resistance value can be reduced. It is possible to manufacture a small number of elastic conductive rollers with good reproducibility. For this reason,
Extremely uniform charging can be performed without causing deterioration of the electrostatic latent image holding member.

Further, since the elastic layer does not need to have conductivity, the range of material selection can be greatly expanded, and the elastic layer can be made of a material that is extremely flexible and has a small compression set. Therefore, a sufficient contact width between the elastic conductive roller and the electrostatic latent image holding member can be ensured, and the change with time can be minimized, so that uniform charging can be always performed.

Further, if the conductive layer is made of a material having a small coefficient of friction, it is possible to provide a speed difference between the elastic conductive roller and the electrostatic latent image holding member, thereby promoting uniform charging. You. At the same time, oil and plasticizer peculiar to the rubber material do not exude, and the surface is not contaminated by the toner. Further, it is easy to remove the toner attached to the roller surface.

[0078]

As described above, according to the present invention, it is possible to obtain a high quality image and obtain a one-component developing apparatus which can be manufactured by a simple process. In addition, since the appropriate range of the resistance value of the developing roller surface is clarified, a great effect can be obtained in practical use, such as a developing device capable of obtaining a good image can be manufactured with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing one embodiment of the present invention.

FIG. 2 is a partial sectional view showing one embodiment of a developing roller according to the present invention.

FIG. 3 is a sectional view of a main part showing an example of a charging device.

[4] characteristic diagram showing an example of charging characteristics by contact charging device shown in FIG.

[Explanation of symbols]

Reference Signs List 1 developing device 2, 11 developing roller 3, 21 electrostatic latent image holder 13, 24 roller base 14, 25 conductive layer 20 contact charging device 22 ... Elastic conductive roller

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Mitsucho Saito 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Research Institute Co., Ltd. (72) Inventor Shutsu Sato 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa In the Toshiba Research Institute, Inc. (72) Inventor Koji Endo 6-78 Minamicho, Mishima-shi, Shizuoka Prefecture Within the Technical Research Institute of Tokyo Electric Co., Ltd. (56) References JP-A-57-64762 (JP, A) JP-B-46-34080 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08

Claims (1)

(57) [Claims] 1. A developing roller having oppositely disposed resilient so as to be in contact with the electrostatic latent image holding member, the developing roller
A non-magnetic toner on the surface of the developing roller.
A blade for forming a thin layer comprising: a developing roller; and a unit configured to rotate the developing roller at a higher peripheral speed than the electrostatic latent image holding member. And a flexible seamless formed on the outer periphery of the roller base.
A conductor layer comprising a tube, and the conductor
The layer is substantially smooth in direct contact with the electrostatic latent image carrier.
A developing device having a smooth surface .