JP2763436B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus utilizing an electrophotographic system such as an electrophotographic printer, generally, a charging step for uniformly and uniformly charging the surface of an image bearing member, that is, a photosensitive drum, the photosensitive member, A latent image forming step of writing an electrostatic latent image on the drum, a developing step of developing the electrostatic latent image with a dry developer, that is, a toner, a transferring step of transferring the toner on the photosensitive drum to a transfer material, An image is formed by a fixing step of fixing the toner on the material and a cleaning step of cleaning the toner remaining on the photosensitive drum after the transfer step. Also, after the transfer step is completed and before the next charging step is started,
In some cases, a charge elimination step is provided to prevent the formation of an afterimage on the photosensitive drum. In the charging step and the transfer step, charging and transfer are generally performed by corona discharge.

However, when the corona discharge is used, harmful substances such as ozone are generated. For this reason, harmful substances are collected by filters, etc.
If the filter is used for a long time, the collection efficiency is reduced, or the filter needs to be replaced. Therefore, an ozone-free process has been proposed in which ozone is not generated by roller transfer (see IEICE Transactions '77 / 4 Vol.J60-C N0.4 P213-8).

In the roller type transfer, a transfer material is superimposed on a toner image formed on the surface of a photosensitive drum by development, and a transfer roller is pressed from above, and a voltage having a polarity opposite to that of the toner is applied to the transfer roller. I am trying to do it.
As a result, an electric field is generated in a gap between the transfer material and the upper layer of the toner image, and the toner is transferred to the transfer material by the electrostatic force of the electric field. Further, there is also provided a device in which charging is performed based on the same principle as that of the roller type transfer.

There is also provided a cleaningless process in which a cleaning step is omitted (Japan Hard-Cop).
y '89 Proceedings, P143-6). In the cleaning-less process, toner is applied by reverse development to the portion of the photosensitive drum on which the surface potential has been attenuated by exposure, and at the same time, the thin toner remaining on the unexposed portion is collected by the developing device. Is done. That is, the toner remaining on the photosensitive drum is charged in the charging step,
Due to the difference between the charged surface potential of the photosensitive drum and the developing bias, the toner is attracted to the developing device by electrostatic force.

The use of the above-mentioned cleaningless process makes it possible to reduce the size of the image forming apparatus and to collect the remaining toner in the developing step. Toner can be used.

[0007]

However, in the above-mentioned conventional image forming apparatus, in the case of the ozone-free process, a method of collecting the remaining toner by a cleaning blade is adopted, and it is necessary to process the collected toner. . In the case of a cleaningless process,
Since a method of performing corona discharge in the charging step and the transfer step is employed, harmful substances such as ozone are generated. Therefore, the generated harmful substances are collected by the filter, but the collection efficiency not only decreases gradually as the usage time of the image forming apparatus increases, but also maintenance and management for replacing the filter are required. It becomes necessary and the work becomes cumbersome.

Therefore, it is conceivable to combine both processes, but it is difficult for the following reasons. That is, in a process in which the ozone-free process and the cleaningless process are combined, the photosensitive drum comes into contact with the charging roller in a state where the toner remaining after the transfer remains attached. Then, at this time, the toner extremely easily moves from the photosensitive drum to the charging roller, and adheres to the charging roller like a thin toner layer formed on the developing roller.

Even in such a state, high quality printing can be performed by setting the electrophotographic process. In this case, the supply voltage to the charging roller is controlled by the dielectric layer of the photosensitive drum and the toner layer on the charging roller. Will be distributed to. As described above, when the toner adheres to the charging roller, the surface potential of the photosensitive drum decreases, and in an extreme case, the non-image portion is developed. When the amount of toner adhered is small, high-quality printing can be performed by balancing with the developing bias, etc., but even in this case, if the amount of adhered toner gradually increases due to continuous operation, charging becomes unstable. become.

Therefore, in a process in which the ozone-free process and the cleaningless process are combined, it is necessary to prevent toner from adhering to the charging roller in order to stabilize the surface potential of the photosensitive drum.
Even when the toner adheres, it is necessary to extremely reduce the amount of toner attached. The present invention solves the problems of the conventional image forming apparatus described above, suppresses the toner remaining on the surface of the image carrier from adhering to the charging roller, and forms a stable surface potential on the image carrier. It is an object of the present invention to provide an image forming apparatus capable of performing high-quality printing.

[0011]

For this purpose, in the image forming apparatus of the present invention, an image carrier, a charging roller for uniformly and uniformly charging the surface of the image carrier, and a charged image bearing member are provided. A latent image forming apparatus that forms an electrostatic latent image on the surface of a carrier, a developing apparatus that performs development by attaching a developer to the electrostatic latent image, and a transfer apparatus that transfers the developer to a transfer material. Have.

After the transfer by the transfer device is completed, the developing device applies a developing bias for collecting the developer remaining on the non-image portion of the image carrier, and the charging roller is made of a metal. A conductive shaft, and a single member coated on the conductive shaft and formed of a conductive material including silicone, and having a predetermined electric resistance between a surface of the conductive shaft and a surface of the charging roller. Consisting of an elastic layer.

[0013]

According to the present invention, as described above, in an image forming apparatus, an image carrier, a charging roller for uniformly and uniformly charging the surface of the image carrier, and a charged image carrier are provided. A latent image forming apparatus that forms an electrostatic latent image on the surface of a body, and a developing apparatus that performs development by attaching a developer to the electrostatic latent image,
A transfer device for transferring the developer to a transfer material.

The developing device applies a developing bias for recovering the developer remaining on the non-image portion of the image carrier after the transfer by the transfer device is completed, and the charging roller is made of a metal. A conductive shaft, and a single member coated on the conductive shaft and formed of a conductive material including silicone, and having a predetermined electric resistance between a surface of the conductive shaft and a surface of the charging roller. Consisting of an elastic layer. In this case, after the transfer by the transfer device is completed, the developer remaining on the surface of the image carrier comes into contact with the charging roller with the rotation of the image carrier, and the charging roller removes the conductive shaft and the silicone. Since it is made of an elastic layer formed of a conductive material, it reaches the developing area without adhering to the charging roller.

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic view of the image forming apparatus of the present invention. In the figure, reference numeral 1 denotes a photosensitive drum that rotates in the direction of arrow A. In this embodiment, the negative polarity OPC
(Organic photoreceptor), and the dielectric constant of the dielectric layer is ε _P = 3.5ε ₀ (ε ₀ = 8.855 × 10 ⁻¹² C / V
m: dielectric constant of vacuum), and the thickness is d _P = 20 μm. Reference numeral 2 denotes a charging roller made of a conductive rubber roller, which contacts the photosensitive drum 1 at a predetermined pressure and is driven. The above-mentioned charging roller 2 may receive power by a gear or the like without being rotated by being driven.

Although an electric resistance of about 10 ⁰ to 10 ⁹ Ω can be used, the lower limit is set to 10 to prevent a large current from flowing when a pinhole or the like occurs in the photosensitive drum 1. ^It is preferable to set it to about ⁴ Ω. If the electric resistance is too high, the surface potential of the photosensitive drum 1 tends to decrease, and it is difficult to obtain stability in manufacturing.
It is preferable to set it to about ⁰⁹ Ω.

The electric resistance referred to here is the electric resistance of the charging roller 2.
Of the surface of the photosensitive drum 1 (nip width x longitudinal direction)
Length) and the electrical resistance between the conductive shaft 2a.
The electric resistance is Ω · cm in consideration of the surface area of the charging roller 2.
^Two10 when the unit of ^Four-10⁹Ω · cm^TwoTosa
It is. 2b is for supplying a voltage to the conductive shaft 2a.
Power supply.

Reference numeral 3 denotes a latent image forming apparatus for writing an electrostatic latent image on the photosensitive drum 1. Although an LED array is used in this embodiment, a laser beam scanning device, a liquid crystal shutter array, or the like may be used instead. Reference numeral 4 denotes a developing roller serving as a toner carrier, which contacts the photosensitive drum 1 at a predetermined pressure and rotates in the direction of arrow B.

The electrical resistance 10 ^0-1 of the developing roller 4
0 but is set to about ⁹ Omega, the electric resistance is 10 in the present embodiment ⁶
Ω conductive rubber roller is used. The developer, that is, the toner on the developing roller 4 thinned to several tens μm by means (not shown) enters the developing area which is in contact with the photosensitive drum 1 with the rotation of the developing roller 4, and the development is stopped. Done. The toner has a charge having the same polarity as the charged polarity of the photosensitive drum 1, and the reversal development is performed. Reference numeral 4b denotes a power supply for supplying a voltage to the conductive shaft 4a.
Accordingly, an intermediate potential between the potential of the image portion and the potential of the non-image portion of the photosensitive drum 1 is applied to the developing roller 4 as a developing bias.

Reference numeral 5 denotes a transfer roller for transferring the toner image on the photosensitive drum 1 onto a transfer material 6 which is conveyed in the direction of arrow C by means not shown. The transfer roller 5 has a structure in which the transfer roller 5 comes into contact with the photosensitive drum 1 at a predetermined pressure and is driven. The transfer unit may use another method that substantially satisfies its performance. The electric resistance of the transfer roller 5 used in the present embodiment is defined in the same manner as in the case of the charging roller 2, and refers to the electric resistance between the contact portion of the surface of the transfer roller 5 with the photosensitive drum 1 and the conductive shaft 5a. 10 ⁰
The resistance is about 10 to 10 ⁹ Ω, and in this case, a resistance of 10 ⁸ Ω is used.

The transfer material 6 onto which the toner image has been transferred is separated from the photosensitive drum 1 and introduced into a fixing device (not shown).
After the fixing is completed, the sheet is discharged out of the apparatus as a printed matter.
5b is a power supply for supplying a voltage to the conductive shaft 5a.
The toner remaining on the photosensitive drum 1 after the transfer process is completed comes into contact with the charging roller 2 by the rotation of the photosensitive drum 1 in the direction of arrow A.
And reaches the developing area by the rotation of the photosensitive drum 1.

At this stage, the latent image forming device 3
Remaining in the image area where the electrostatic latent image was written
The toner is attached to the photoreceptor drum 1 and is renewed from above.
Is developed. On the other hand, toner remaining in the non-image area
Is mainly due to electrostatic force, that is, Coulomb force,
Will be recovered by Next, a method of manufacturing the charging roller 2 and
And the results of the printing test will be described. [Example 1] A conductive shaft 2a made of metal and having a diameter of 6 mm.
Is used as core metal and raw gum of silicone rubber (Toray Dow Corni
100 kg of SH841U (produced by Nippon Silicone Co., Ltd.)
Part, carbon black (DENKA BLACK manufactured by Denka Co., Ltd.)
10 parts by weight and a vulcanizing agent (Toray Dow Corning Silicone)
0.7 parts by weight of RC-4) manufactured by Tonen Co., Ltd.
The kneaded material is used as a rubber stock and the primary vulcanization is 170 °.
C, 200kgf / cm ^Two, 12 minutes, secondary vulcanization
At 200 ° C. for 10 hours. Then polishing
The diameter is φ12mm, the length of rubber elastic layer is 230mm, J
ISA hardness 35 °, electrical resistance 5 × 10^FiveΩ · cm^Two
Is obtained.

Using the charging roller 2, continuous printing was performed on 10,000 sheets of A4 size paper at a duty of 5%. The toner used was a styrene-acrylic copolymer. The toner did not substantially adhere to the charging roller 2 after the continuous printing, and the decrease in the surface potential of the photosensitive drum 1 at this time was 2% as compared with the initial value. From a comparison experiment with an image forming apparatus using a scorotron charger, a decrease in the surface potential is caused by repeated use of the photosensitive drum 1, not by adhesion of toner to the charging roller 2. It is confirmed that.

Further, high-quality printing can be performed even after continuous printing without the occurrence of solid black development in the non-image area or background fog. [Embodiment 2] A metal conductive shaft 2a having a diameter of 6 mm.
Is used as a core metal, 100 parts by weight of IPN alloy pellets of silicone rubber and thermoplastic urethane polymer (Rimplast PTUA102 manufactured by Petrarch System) are hot-melted, and carbon black (DENKA BLACK manufactured by Denka Co., Ltd.) is added to the melt. The rubber stock obtained by adding and kneading parts by weight is cooled. After that, polishing is performed and the diameter is φ
12 mm, the length of the rubber elastic layer is obtained 230 mm, JISA hardness of 40 °, the electric resistance of ⁵ × 10 5 Ω · cm ² charging roller 2. When continuous printing was performed in the same manner as in Example 1 using this, no toner adhered to the charging roller 2 and the decrease in the surface potential of the photosensitive drum 1 was 2% or less as compared with the initial value. .

In the non-image area, solid black development and background fog do not occur.
High quality printing can be performed.

Comparative Example 1 A metal conductive shaft 2a having a diameter of φ6 mm was used as a core metal.
Liquid polybutadiene rubber (PIP manufactured by Idemitsu Petrochemical Co., Ltd.)
-H) and 1 part of methylene diisocyanate (Dismodule W manufactured by Sumitomo Bayer Urethane Co., Ltd.)
2 parts by weight, dibutyltin dilaurate (Kyodo Yakuhin Co., Ltd.)
Of carbon black (DENKA BLACK manufactured by Denka Co., Ltd.) in an amount of 0.05 parts by weight as a rubber stock, and vulcanization was performed at 120 ° C. and 200 kgf /
cm ² for 1 hour, cure, then 70 ° C
After curing for 15 hours. Then, after polishing, the diameter is φ12 mm, the length of the rubber elastic layer is 230 mm, JIS
A hardness of 40 °, the electrical resistance obtain ⁵ × 10 5 Ω · cm ² urethane rubber of the charging roller 2.

Next, continuous printing was performed in the same manner as in Example 1 using the charging roller 2 of Comparative Examples 1 and 2.
When about 200 sheets of A4 size paper are printed on the charging roller 2 of Comparative Example 2, and when about 500 sheets of A4 size paper are printed on the charging roller 2 of Comparative Example 2, the charging roller 2 is placed on the non-image portion. , A solid black image and a background fog occurred. At this time, the charging roller 2 has a thickness of 10 to 20 μm.
Is formed like a thin toner layer formed on the developing roller 4 by the regulating blade.
Further, the surface potential of the photosensitive drum 1 after charging was reduced by about 30% as compared with the initial value.

In this case, as the absolute value of the voltage of the power supply 2b is increased, the solid black image and the background fog in the non-image portion gradually become inconspicuous, and finally normal printing is performed. . For this reason, when the toner significantly adheres to the charging roller 2, the voltage of the power supply 2b is distributed to the photosensitive drum 1 and the toner layer on the charging roller 2, and the surface potential of the photosensitive drum 1 is reduced. The toner adheres to the image area.

That is, in order to substantially produce the results described in the first and second embodiments, it is necessary to prevent the toner from adhering to the charging roller 2,
Alternatively, it is necessary to extremely reduce the amount of adhered toner. FIG. 2 is a schematic diagram of an image forming apparatus provided with a blade-type cleaning device.

As shown in FIG. 1, when a blade-type cleaning device 11 is provided opposite to the photosensitive drum 1 as in a conventional image forming apparatus, toner remaining on the surface of the photosensitive drum 1 is cleaned. It is removed by the device 11. Therefore, in each of Examples 1 and 2 and Comparative Examples 1 and 2, no toner adheres to the charging roller 2, and a good printing result can be obtained even when continuous printing of 10,000 sheets of A4 size paper is performed. Can be.

On the other hand, as in the present invention, the charging roller 2 is used in an image forming apparatus that combines an ozone-free process and a cleaningless process without a cleaning process after the transfer is completed and before the charging process is started. In this case, the charging roller 2 is formed of a conductive shaft made of metal and a conductive material containing silicone, which is coated on the conductive shaft, and is formed of a conductive material containing silicone. It consists of a single elastic layer, which makes the electrical resistance between them a predetermined value. In this case, a silicone rubber may be used as in the first embodiment, or a polymer alloy may be used as in the second embodiment. In any case, it is considered that the good releasability of the silicone suppresses the toner from adhering to the charging roller.

The present invention is not limited to the above embodiment, but can be variously modified based on the gist of the present invention, and these are not excluded from the scope of the present invention.

[0033]

As described above in detail, according to the present invention, in an image forming apparatus, an image carrier, a charging roller for uniformly and uniformly charging the surface of the image carrier, and
A latent image forming apparatus for forming an electrostatic latent image on the surface of a charged image carrier, a developing apparatus for applying a developer to the electrostatic latent image for development, and transferring the developer to a transfer material And a transfer device. The developing device applies a developing bias for collecting the developer remaining on the non-image portion of the image carrier after the transfer by the transfer device is completed, and the charging roller includes a metal conductive shaft. And a single elastic layer coated on the conductive shaft and formed of a conductive material including silicone, and having a predetermined value of electrical resistance between the surface of the conductive shaft and the surface of the charging roller. Consists of

In this case, the charging roller is a metal conductive shaft, and is coated on the conductive shaft.
It is made of a conductive material containing silicone, and is composed of a single elastic layer that makes the electric resistance between the surface of the conductive shaft and the surface of the charging roller a predetermined value. Adhesion of the developer remaining on the surface of the body to the charging roller is suppressed. As a result, a stable surface potential can be formed on the image carrier, and solid black development and background fog do not occur in the non-image portion, so that high-quality printing can be performed. .

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an image forming apparatus of the present invention.

FIG. 2 is a schematic diagram of an image forming apparatus provided with a blade-type cleaning device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor drum (image carrier) 2 charging roller 2 a conductive shaft 2 b power supply 3 latent image forming device 4 developing roller (developing device) 5 transfer roller (transfer device) 6 transfer material

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-42669 (JP, A) JP-A-54-156548 (JP, A) JP-A-4-34566 (JP, A) JP-A-58-58 194061 (JP, A) JP-A-60-19178 (JP, A) JP-A-56-132356 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/02 101 G03G 15/22 G03G 15/08 507

Claims (3)

(57) [Claims] And 1. A (a) image bearing member, to (b) said image and carrier charging roller Ru is uniformly and evenly charging the surface of, (c) charged canceller surface of the image bearing member a latent image forming device for forming an electrostatic latent image, (d) a developing device for performing development by attaching the developer to the electrostatic latent image, a transfer device you transferred to a transfer material (e) a the developer to have a door
Rutotomoni, (f) the developing device imparts a developing bias for collecting the developer remaining on the non-image portion of said image bearing member after transcription by the transcription device has been completed, (g) the charging roller Is a metal conductive shaft and
And is coated on the conductive shaft and includes silicone.
It is formed of a conductive material, a single of the electrical resistance between the surface and the surface of the charging roller of the conductive shaft to a predetermined value
An image forming apparatus comprising: an elastic layer . 2. The conductive material is a silicone rubber.
The image forming apparatus according to claim 1. 3. The conductive material comprises a silicone rubber and another
2. The method according to claim 1, wherein the material is formed by kneading the material.
Image forming apparatus.