JPH08220900A - Transfer roller for electrophotographic device and method for cleaning transfer roller - Google Patents

Abstract

PURPOSE: To make it possible to realize uniform and sure transferability regardless of various sizes (A3 size to postcard size) of recording papers. CONSTITUTION: An elastic roller part 52 of a transfer roller 5 consists of a urethane foam imparted with ion conductivity by incorporating a tetrabutyl ammonium salt therein. This urethane foam is so prepd. that the implantation of electric charges into the rear surface of the recording paper is made possible and that the urethane foam is brought into uniform and elastic contact with the recording paper. The tetrabutyl ammonium salt makes one kind of coordinate bond with the polar groups, such as ether groups and ester groups, in the urethane foam and is, therefore, dispersed uniformly at a molecular level into the elastic roller part 52. A uniform surface charge distribution is consequently obtd. and carriers (p), (n) maintain uniform contact with the recording paper in a large area when the nipping regions of a photosensitive drum and the transfer roller 5 are microscopically viewed and, therefore, transfer defects, such as black solid, drop-out and unequal transfer, hardly arise even in the case the recording of the postcard size is printed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer roller used in an image forming process of an electrophotographic apparatus and a cleaning method for the transfer roller.

[0002]

2. Description of the Related Art In electrophotographic devices such as laser printers,
A photosensitive drum is installed in an image forming section in the middle of the paper transport path, and a main charger, a writing device, a toner hopper, a developing roller, a transfer roller, a cleaning device, and the like are arranged around the photosensitive drum. Toner image formation on recording paper
The electrostatic latent image is formed on the surface of the photosensitive drum by the main charger and the writing device, and is developed by the toner hopper and the developing roller. The toner image obtained by the development is transferred from the photosensitive drum to the recording paper by the transfer roller. Transcribed. At the time of transfer, the recording paper is nipped between the photosensitive drum on which the toner image has been developed and the transfer roller pressed against the photosensitive drum, and at this time, the transfer bias having the opposite polarity to the toner image is applied to the transfer roller. By applying a voltage, a charge having the opposite polarity to the toner image is supplied to the back surface of the recording paper,
As a result, the toner image on the photosensitive drum is electrostatically attracted to the recording paper.

Therefore, the transfer roller is required to have conductivity. In this case, however, if the resistance value is too low, the transfer bias voltage cannot be maintained at a constant height, resulting in transfer failure. Therefore, as a conventional transfer roller, as described in JP-A-3-212672, a high resistance rubber elastic body (or foamed rubber elastic body) such as chloroprene rubber, silicone rubber, urethane rubber, EPDM, etc. Further, it is known that carbon black particles such as Ketjen black and acetylene black are dispersed to have semiconductivity.

[0004]

By the way, as shown in FIG. 5, the above-mentioned conventional transfer roller 101 has carbon black particles 10 in a polymer chain such as silicone or polyurethane.
2, 102, ... are entangled with each other to form carbon particles 102, 10
A chain of 2, ... (A kind of aggregation) is formed, and electrons move along this chain to obtain semiconductivity. Therefore, the dispersibility of the carbon black particles 102, 102, ... With respect to the rubber-like substance or the polymer substance is very poor.

This problem is caused when the transfer roller is short.
Although it can be ignored, it appears remarkably on a long transfer roller corresponding to A3 (297 mm × 420 mm). That is, in the case of a long transfer roller corresponding to A3, the dispersibility of carbon black particles is poor, so that the resistance value varies in the axial direction and the circumferential direction of the roller (the resistance value varies by about two digits). As a result, the charge density (current) supplied to the recording paper fluctuates, which causes uneven transfer as a whole, and often fails to obtain high-quality image.

As described above, the carbon particles dispersed in the roller axial direction are not only the conductive path between the roller shaft (metal shaft) and the roller surface, which is important in the transfer process because of the conductive mechanism. A conductive path is formed, and a current that flows in the axial direction inside the transfer roller or on the surface is generated, which is different from the direction of the required transfer bias.

Further, as shown in FIG. 6, when a small size recording paper (for example, a postcard) 103 is printed by using the transfer roller 101 corresponding to A3 size, the width of the recording paper 103 is smaller than that of A3 size paper. Therefore, there is an area where the photosensitive drum 104 and the transfer roller 101 are in direct contact with each other. At this time, in the conventional transfer roller 101,
The photosensitive drum 104 and the transfer roller 101 form the recording paper 10.
The photosensitive drum 1 is more than the area that is indirectly pressure-contacted through the photosensitive drum 1.
In the area where 04 and the transfer roller 101 are in direct contact, the resistance value is much smaller. Therefore, the transfer current is
It flows through a region where the transfer roller 101 and the photosensitive drum 104 are in direct contact with each other, and does not flow through a region where the toner 105, 105, ... There was also a problem that it would occur.

The present invention has been made in view of the above circumstances, and provides a transfer roller for an electrophotographic apparatus and a method for cleaning the transfer roller, which can realize uniform and reliable transferability regardless of the size of the recording paper. It is intended to be provided.

[0009]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a conductive cylindrical core material and a semiconductive roller portion provided around the cylindrical core material. The transfer roller of the electrophotographic apparatus, wherein the roller portion is formed by applying an ion conductive substance to an insulating elastic member.

According to a second aspect of the present invention, there is provided the transfer roller of the electrophotographic apparatus according to the first aspect, wherein the roller portion comprises an insulating elastic member, a quaternary ammonium salt, and an alkali metal peroxide. , An alkaline earth metal peroxide salt, or a quaternary phosphonium salt.

According to a third aspect of the present invention, there is provided the transfer roller of the electrophotographic apparatus according to the second aspect, wherein the roller portion is made of an insulating elastic member and is made of tetramethylammonium salt, tetraethylammonium salt, or tetraethylammonium salt. Propyl ammonium salt, tetrabutyl ammonium salt, lithium peroxide, barium peroxide, tetramethylphosphonium salt,
It is characterized by being provided with an ion conductive substance selected from a tetraethylphosphonium salt or a tetraphenylphosphonium salt.

Further, the invention according to claim 4 is based on claim 1,
The transfer roller of the electrophotographic apparatus according to 2 or 3, wherein the roller portion is adjusted to have a hardness of 35 ± 5 degrees under an Asker C sponge hardness meter.

Further, the invention according to claim 5 is based on claim 1,
2. The transfer roller of the electrophotographic apparatus according to 2, 3, or 4, wherein the transfer roller has an electric resistance of 1 to 2 × 10 ⁸ at room temperature and normal humidity between the cylindrical core member and the surface of the roller portion. Ω,
It is characterized in that the electric resistance at low temperature and low humidity is adjusted to 1 to 1.5 × ⁹ Ω, and the electric resistance at high temperature and high humidity is adjusted to 2 to 4 × 10 ⁷ Ω.

Further, in the invention according to claim 6, the recording paper is nipped and passed by the photosensitive drum or the photosensitive belt and the transfer roller, so that the toner image developed on the photosensitive drum or the photosensitive belt is transferred. In an electrophotographic apparatus for transferring onto a recording paper, a transfer bias voltage having a polarity opposite to that of the toner image developed on the photosensitive drum or the photosensitive belt is applied to the transfer roller under constant current control during paper passing. The toner image is transferred onto the recording paper by means of the above-mentioned method, and at the time of non-sheet passing, a cleaning bias voltage having the same polarity as that of the toner attached to the transfer roller is applied under constant voltage control so that the toner is transferred onto the photosensitive drum or the photosensitive drum. Characterized by returning to the belt.

[0015]

According to the present invention, in the roller portion, the ion conductive substance is applied to the insulating elastic member. The ionic species contained in the roller part form a kind of coordination bond with polar groups such as ether groups and ester groups of elastic members such as urethane foam, so that they are uniformly dispersed at the molecular level in the transfer roller (uniform. The dispersion is stable).
Therefore, a uniform surface charge distribution is obtained, and when the nip area (transfer area) between the photosensitive drum and the transfer roller is viewed microscopically, the carrier is in contact with the recording paper evenly over a large area. Even when printing a recording sheet of a size, transfer defects such as black solid white spots and uneven transfer are unlikely to occur.

Further, according to the fourth aspect of the present invention, since the transfer roller is provided with sufficient elasticity, the photosensitive drum and the transfer roller can cover the entire area of the transfer portion (of the recording paper even with a small pressure contact force to the photosensitive drum). The contact state is uniform over the width.

Further, in the structure of claim 5, the resistance value of the roller portion is 1 to 2 × at normal temperature and normal humidity (25 ° C., 50%).
10 ⁸ Ω, 1 to 1.5 × at low temperature and low humidity (10 ° C, 20%)
10 ⁹ Ω, 2-3x at high temperature and high humidity (32.5 ° C, 80%)
Since it was adjusted to 10 ⁷ Ω, a good direct transfer power can be obtained with a simple DC power supply without a complicated control circuit over a wide environmental range from low temperature and low humidity to high temperature and high humidity.

Further, according to the sixth aspect of the present invention, since the constant current control is performed during sheet passing (at the time of transfer), the resistance value of the transfer roller fluctuates due to environmental changes such as low temperature and low humidity and high temperature and high humidity. In the case or when the thickness of the recording paper is changed, the transfer current (injection current into the recording paper) required to obtain good transfer efficiency is secured. Further, when the resistance value of the transfer roller 5 is lowered due to high temperature and high humidity, the transfer bias voltage does not become high, and therefore black solid white spots due to localized minute discharge do not occur. On the other hand, since the constant voltage control is performed when the paper is not passed (at the time of non-transfer), a constant cleaning voltage can be secured even if the environment of temperature and humidity changes, so that good cleaning performance can always be maintained. In this case, there is no possibility that a high-voltage cleaning bias will be applied to the photosensitive drum, and pinholes or the like will not be generated on the surface. Even if the photosensitive drum has scratches or pinholes, there is no risk of overcurrent, so the scratches will not expand and the power supply will not be damaged.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a main part (image forming part) of a laser beam printer according to an embodiment of the present invention. The printer includes a transfer roller according to an embodiment of the present invention and the transfer roller. A roller cleaning method is used. First, a schematic configuration of the laser beam printer will be briefly described. The laser beam printer is arranged on the photosensitive drum 1 based on image information sent from a personal computer or the like, and a paper feed unit that separates the recording paper set in a tray (not shown) one by one and sends the paper to a paper transport path. An electrostatic latent image is formed, then this is developed, and the toner image transferred to the recording sheet and the image forming section that transfers the toner image obtained by the development to the recording sheet sent from the paper feeding section The outline is composed of a fixing unit for heat-pressure fixing.

As shown in FIG. 1, the image forming section is an OPC which exhibits the characteristics of an electrical insulator in a dark place and a good electrical conductor in a bright place.
A photosensitive drum 1 having an outer peripheral surface coated with (organic photoconductor) to form a photosensitive layer, a main charger 2, a writing device (exposure device) 3, and a developing device that are respectively arranged along the outer peripheral surface of the photosensitive drum 1. 4, a transfer roller 5, and a cleaning device 6. The main charger 2 is a scorotron charger, and the surface of the photosensitive drum 1 has a predetermined potential (for example,
It is uniformly charged to −850V. The writing device 3 includes a laser scanning optical system in which a semiconductor laser, a polygon mirror, an fθ lens, and the like are incorporated, and exposes the photosensitive surface of the photosensitive drum 1 uniformly charged by the main charger 2 based on image information. , An electrostatic latent image is formed on the surface of the photosensitive drum 1.

The developing device 4 comprises a toner hopper 41, a supply roller 42, a developing roller 43 and a toner regulating blade 44, and visualizes the electrostatic latent image formed on the photosensitive drum 1 by using the toner 7 as a developer. . The supply roller 42 and the developing roller 43 are rotationally driven in the directions indicated by the arrows by a rotational drive mechanism (not shown). The developing roller 43 is, for example, a metal roller made of stainless steel, aluminum, or the like, on the outer peripheral surface of which silicone is provided with conductivity,
An nitrile / butadiene copolymer, an elastic layer of urethane rubber or the like (rubber hardness of JIS A hardness meter of 30 to 40 degrees) is formed. A toner regulating blade 44 made of silicon resin or the like is in contact with the developing roller 43. The toner hopper 41 is a hollow container for storing the toner 7 (in this example, negatively-charged polyester non-magnetic toner, average particle diameter 10 μm), and a developing opening for supplying the toner 7 to the supply roller 41 on the front surface. 41a is bored. The toner 7 in the toner hopper 41 is stirred by the stirring member 41.
When it is agitated by a and discharged through the developing opening 41b, it is carried by the supply roller 42 and supplied to the developing roller 43. When the toner carried on the developing roller 43 passes between the developing roller 43 and the toner regulating blade 44, the toner is thinned and frictionally charged to a predetermined polarity (negative electrode in this example), After this, the photosensitive drum 1
It is carried to the portion opposite to and is brought into contact with the surface of the photosensitive drum 1.

The developing roller 43 has a predetermined developing bias voltage (-in this example,-) from a developing bias power source (not shown).
480 V) is applied, and as a result, the developing roller 4
In the contact between the toner carried on No. 3 and the photosensitive drum 1, the unexposed portion (charged portion, potential −850V) of the photosensitive drum 1 is caused by the electrostatic action between the electrostatic latent image, the developing bias voltage and the electric charge of the toner. Toner charged to the negative electrode does not adhere to
Toner adheres to the exposed portion (non-charged portion, -200V). In this way, a toner image corresponding to the electrostatic latent image is formed on the photosensitive drum 1.

The transfer roller 5 is arranged on the paper conveying path and in pressure contact with the photosensitive drum 1, and nips the conveyed recording paper 8 between the transfer roller 5 and the photosensitive drum 1,
It is passed between the transfer roller 5 and the photosensitive drum 1. At the time of sheet passing, a transfer bias constant current power supply (not shown) applies a transfer bias voltage (for example, +200 to +4000 V) having a polarity opposite to that of the toner image on the photosensitive drum 1 to the transfer roller 5. As a result, the toner image on the photosensitive drum 1 is transferred to the recording paper 8. On the other hand, when the paper is not passed (after the transfer of the toner image to the recording paper 8 is completed and before the next recording paper 8 is nipped), the cleaning bias constant voltage power source (not shown) performs cleaning with the same polarity as the toner. A bias voltage (for example, -1200 V) is applied to prevent the toner on the photosensitive drum 1 from being transferred to the transfer roller 5, and at the time of paper passing, the transfer roller 5
The toner attached to the photosensitive drum 1 is returned to the photosensitive drum 1. When the width of the recording paper is narrower than the width of the transfer roller 5 or the photosensitive drum 1, toner may adhere to the transfer roller 5. The cleaning device 6 is composed of a cleaning blade, a charge eliminating portion, and a waste toner accommodating portion. The cleaning device 6 scrapes off the toner remaining on the photosensitive drum 1 even after the transfer to clean the photosensitive surface and eliminate the charge on the photosensitive surface.

FIG. 2 is an enlarged sectional view and side view showing the structure of the transfer roller 5. The transfer roller 5 in this example is
A metal shaft 51 made of stainless steel, aluminum or the like, and an elastic roller portion 5 provided on the outer periphery of the metal shaft 51.
The elastic roller portion 52 has a diameter of 20 mm and a length of 300 mm so that A3 size recording paper can be used. In this example, the elastic roller portion 52
In this case, a urethane foam having ion conductivity by using a tetrabutylammonium salt (quaternary ammonium salt) is used, and this urethane foam applies a transfer bias voltage to the recording paper. It is possible,
In other words, it is prepared so that charges can be injected into the back surface of the recording paper 8 and the recording paper 8 can be uniformly elastically contacted. That is, the resistance value between the inner and outer peripheral surfaces of the elastic roller portion 52 is 1 to 2 × 10 at room temperature and normal humidity (25 ° C., 50%).
⁸ Omega, at low temperature and low humidity (10 ℃, 20%) 1~1.5 × 10 in
⁹ Omega, high temperature and high wet-(32.5 ℃, 80%) 2~3 × 10 in
The average foam diameter of urethane foam is ⁷ to
By setting the thickness to 250 μm, the hardness of the elastic roller portion 52 is adjusted to 35 ± 5 degrees by the Asker C sponge hardness meter.

The transfer roller 5 having the above-mentioned structure is a roller obtained by kneading urethane and various compounding agents (crosslinking agent, foaming agent, ion conductive agent (tetrabutylammonium salt) reinforcing agent, pigment, surfactant, softening agent). The composition of the roller part is adjusted, and then the composition of the roller part is supplied to an extruder and extruded around the metal shaft 51 at a predetermined melting temperature to cool it, followed by polishing to a desired size and smoothness. Get the ones.

In this example, urethane foam is used as the elastic roller portion 52, but other than this, any material can be used as long as it can be adjusted to the above physical properties range.
For example, silicone rubber, urethane rubber, EPDM (ethylene-propylene-diene-terpolymer), NBR
(Nitrile rubber), SBR (styrene-butadiene-rubber) polyisoprene, natural rubber, elastic rubber such as polybutadiene, polystyrene-based or polyolefin-based thermoplastic elastomer, acrylic resin, polyethylene,
Chlorinated polyethylene, polypropylene, polyimide, polystyrene, polyesteramide, polyvinyl chloride, ethylene-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, polyvinyl fluoride, polyvinylidene fluoride, styrene-acrylic copolymer, etc. A molecular material can be preferably used. The elastic roller portion is not limited to foam.

Similarly, as the ion conductive agent, in addition to the tetrabutylammonium salt, quaternary ammonium salts such as tetramethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, and alkali metal peroxides such as lithium peroxide. An alkaline earth metal peroxide such as barium peroxide, or a quaternary phosphonium salt such as a tetramethylphosphonium salt, a tetraethylphosphonium salt, or a tetraphenylphosphonium salt can be preferably used.

Next, the operation of this example will be described with reference to FIG. As described above, the control of the transfer bias voltage applied to the transfer roller 5 is performed when the recording paper 8 passes through the nip region between the photosensitive drum 1 and the transfer roller 5 (when the paper is passing or when transferring). Is different from when the next recording sheet 8 is nipped (when the sheet is not passed and when the sheet is not transferred). That is, at the time of sheet passing (at the time of transfer), as shown in (e) of the figure, under the constant current control by the transfer bias constant current power source, the bias voltage of the opposite polarity to the toner (+200 to +4).
000 V) is applied. On the other hand, when the paper is not passed (at the time of non-transfer), the cleaning roller 5 has the same polarity as the toner under the constant voltage control by the cleaning bias constant voltage power source in order to clean the transfer roller 5, as shown in FIG. The bias voltage (-1200V) of is applied.

Here, since constant current control is performed during sheet passing (during transfer), when the resistance value of the transfer roller 5 fluctuates due to environmental changes such as low temperature and low humidity, high temperature and high humidity, and the recording paper 8 is changed. Even when the thickness changes, the transfer current (current injected into the recording paper) required to obtain good transfer efficiency is secured. Therefore, the unfixed toner on the recording paper 8 after the transfer is transferred to the recording paper 8
Since the toner can be securely held in the fixing unit, the toner adheres to the heat roller in the fixing unit, and the toner adhered to the heat roller is transferred to the pressure roller, which causes a problem such as soiling the back surface of the recording paper conveyed later. Can be prevented. Further, when the resistance value of the transfer roller 5 is lowered due to high temperature and high humidity, the transfer bias voltage does not become high, and therefore black solid white spots due to localized minute discharge do not occur.

On the other hand, since the constant voltage control is performed when the paper is not passed (at the time of non-transfer), a constant cleaning voltage can be secured even when the environment of temperature and humidity changes, so that good cleaning performance can always be maintained. In this case, there is no possibility that a high-voltage cleaning bias will be applied to the photosensitive drum 1, and pinholes or the like will not be generated on the surface. Further, even if the photosensitive drum 1 already has a scratch or a pinhole, there is no risk of an overcurrent, so that the scratch or the like will not expand and the power source or the like will not be damaged. If the constant current control is performed, the photosensitive drum 1 and the transfer roller 5 come into direct contact with each other to lower the resistance value between them, so that a high-voltage bias is applied to the photosensitive drum 1 to cause a pinhole or the like on the surface of the photosensitive drum. Cause

Next, with the same transfer current and the same bias voltage, and under the environment of low temperature and low humidity to high temperature and high humidity, a laser beam printer employing a conventional transfer roller of carbon dispersion type and the transfer of this example. As a result of a comparison experiment using a laser beam printer employing the roller 5, an image without partial density unevenness (transfer unevenness) was obtained in one recording paper as compared with the conventional one. That is, when the transfer roller 5 of this example is used, a printing experiment is performed using A3 to A5 size paper and a postcard on the recording paper 8 at any of low temperature and low humidity, normal temperature and normal humidity, and high temperature and high humidity. As a result, it was possible to obtain transfer efficiencies of 85% or more for all recording papers 8 and image densities of 1.4 or more for solid black areas with a Macbeth densitometer. Also,
The characters and halftone images were free from distortion, crushing, and voids, and the print quality was good. Also, with respect to the solid black image, white spots were not seen and it was good.

When the pressure contact force of the transfer roller 5 with respect to the photosensitive drum 1 is set to a small value, specifically 300 g / cm ² , a sufficient nip width is provided between the photosensitive drum 1 and the transfer roller 5. It was possible to obtain good print quality without causing the toner once transferred onto the recording paper 8 to return to the photosensitive drum 1 and causing no distortion or hollow in the character or solid black image. Further, since the roller portion 52 (polyurethane foam) has a small average foam diameter of 200 to 250 μm, good transfer efficiency can be obtained even in a fine line drawing.

On the other hand, in the case of using the conventional transfer roller, the partial dispersion of the resistance in the transfer roller becomes remarkable when the temperature is low and the humidity is low. White spots and uneven density occurred. Further, even when A5 or a postcard is printed at room temperature and normal humidity, a current easily flows in the axial direction on the surface or inside of the transfer roller, and the transfer current is transferred to a portion where the photosensitive drum having a small resistance value and the transfer roller are in direct contact with each other. Many of them flowed, causing a decrease in concentration. Further, white spots, which are generated in a black solid image due to the application of a high-voltage transfer bias at low temperature and low humidity, were also generated at a lower voltage than when the transfer roller of the present invention was used.

When the transfer roller 5 of this example is compared with that of the conventional one, the ionic species contained in the elastic roller portion 52 are one type of polar groups such as ether groups and ester groups in the urethane foam. Transfer roller 5 in order to perform position coupling.
It is evenly dispersed at the molecular level in it (uniform dispersion is a stable state). Therefore, it is possible to easily prepare a roller having almost no variation in the resistance value in the axial direction and the circumferential direction, and to eliminate solid black spots due to the variation in the resistance value of the transfer roller 5. This is particularly noticeable when the environment is low temperature and low humidity and the resistance value is large.

Further, in the conventional case using carbon black, the carrier is an electron, whereas in the case using the ion conductive material, the carrier is an ionic species and has a large volume compared to the electron and is evenly distributed on the transfer roller 5. Since they are dispersed, a uniform surface charge distribution is obtained as shown in FIG. 4, and when the nip area (transfer area) between the photosensitive drum 1 and the transfer roller 5 is microscopically observed, the carriers p, n Is evenly contacted with the recording paper 8 over a large area, and therefore, even when the recording paper of the postcard size is printed, the transfer failure hardly occurs. Also, the electrons are localized,
Unlike the conventional carbon-dispersed type that flows in a concentrated manner, the discharge phenomenon is unlikely to occur, so in the past there is also a so-called white spot, which is a transfer omission caused by minute discharge between the transfer roller 5 and the recording paper 8, which tends to occur at low temperature and low humidity. hard.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific structure is not limited to this embodiment, and there are design changes and the like within the scope not departing from the gist of the present invention. Also included in the present invention. For example, the electrostatic latent image carrier (toner image carrier) is not limited to the photosensitive drum and may be a photosensitive belt. Further, the present invention is not limited to the laser beam printer, but can be applied to other electrophotographic apparatuses such as a printing machine, a copying machine and a facsimile machine. Also,
A release layer containing, for example, a fluororesin powder or a nylon resin powder may be provided on the surface of the elastic roller portion so that the toner particles can be easily released from the roller surface.

[0037]

As described above, according to the structure of the present invention, it is possible to obtain a transfer roller having almost no variation in the resistance value in the roller axial direction and the circumferential direction. For this reason,
Regardless of the size of the recording paper from A3 size to postcard size, it shows stable transferability of characters, lines, halftone dots, and black solid images, and good and stable print quality can be obtained. Also,
It is resistant to environmental changes, and it is possible to eliminate the characters peculiar to the transfer roller, omission of line images, and white spots due to minute discharge. Further, the bias voltage required for transfer is always obtained when passing through the recording paper. On the other hand, when the recording paper is not passed, good cleaning performance can always be ensured.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a main part (image forming part) of a laser beam printer according to an embodiment of the present invention.

2A and 2B are a cross-sectional view and a side view showing an enlarged configuration of a transfer roller of the embodiment.

FIG. 3 is a diagram for explaining an image forming process in the embodiment.

FIG. 4 is a schematic diagram for explaining a bias mechanism of the transfer roller.

FIG. 5 is a schematic diagram for explaining a conventional bias mechanism of a transfer roller.

FIG. 6 is a schematic diagram for explaining problems of a conventional transfer roller.

[Explanation of symbols]

 1 Photosensitive Drum 2 Main Charger 3 Writing Device (Exposure Device) 4 Developing Device 5 Transfer Roller 51 Metal Shaft (Cylindrical Core Material) 52 Elastic Roller Part (Roller Part) 7 Toner 8 Recording Paper

Claims (6)

[Claims] 1. A transfer roller of an electrophotographic apparatus, comprising a conductive cylindrical core material and a semiconductive roller portion provided around the cylindrical core material, wherein the roller portion is made of insulating elastic material. A transfer roller for an electrophotographic apparatus, wherein an ion conductive substance is applied to a member. 2. The roller portion is an insulating elastic member,
2. The electron according to claim 1, which is provided with an ion conductive substance selected from a quaternary ammonium salt, an alkali metal peroxide, an alkaline earth metal peroxide salt, or a quaternary phosphonium salt. Transfer roller for photographic equipment. 3. The roller portion is an insulating elastic member,
Ionic conductivity selected from tetramethylammonium salt, tetraethylammonium salt, tetrapropylammonium salt, tetrabutylammonium salt, lithium peroxide, barium peroxide, tetramethylphosphonium salt, tetraethylphosphonium salt, or tetraphenylphosphonium salt The transfer roller for an electrophotographic apparatus according to claim 2, wherein a substance is applied. 4. The transfer roller of an electrophotographic apparatus according to claim 1, wherein the roller portion is adjusted to have a hardness of 35 ± 5 degrees under an Asker C sponge hardness tester. . 5. The transfer roller has an electric resistance of 1 to 2 at room temperature and normal humidity between the cylindrical core member and the surface of the roller portion.
× 10 ⁸ Ω, electrical resistance at low temperature and low humidity is 1 to 1.5 × ⁹ Ω,
5. The transfer roller for an electrophotographic apparatus according to claim 1, 2, 3 or 4, wherein the electric resistance at high temperature and high humidity is adjusted to 2 to 4 × 10 ⁷ Ω. 6. An electrophotographic apparatus for transferring a toner image developed on the photosensitive drum or the photosensitive belt to the recording paper by niping the recording paper between the photosensitive drum or the photosensitive belt and the transfer roller and passing the recording paper. The transfer roller is applied with a transfer bias voltage having a polarity opposite to that of the toner image developed on the photosensitive drum or the photosensitive belt on the recording paper under constant current control during paper passing. On the other hand, while the transfer is not performed, under a constant voltage control, a cleaning bias voltage having the same polarity as the toner attached to the transfer roller is applied to return the toner to the photosensitive drum or the photosensitive belt. How to clean the rollers.