JPH0926687A - Electrostatic charging roller and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase of the cost of the device itself, the increase of a power source cost and the generation of a large amt. of ozone and to avert the deterioration of an electrostatic charging member and photoreceptor and further, pollution problems by specifying the content of the constituting material of the electrostatic charging roller consisting of a surface layer and an elastic layer having a constituting material. SOLUTION: The constituting material of the elastic layer 102 is incorporated into the surface layer 103 of the electrostatic charging roller 100 having the elastic layer 102 and the surface layer 103 covering the surface of the elastic layer 102. The content of the constituting material of the elastic layer 102 incorporated into the surface layer 103 is 5 to 60wt.% and the difference in the electric resistance values between the elastic layer 102 and the surface layer 103 is about <=10<3> Ω.cm. The surface layer 103 is formed of a high-polymer compd. consisting of at least polar synthetic resin and a nonadhesive resin. The high-polymer compd. is so formed on the elastic layer 102 that its film thickness attains about 10 to 100μm. As a result, the good electrostatic charge efficiency is obtd. and the uniform electrostatic charge is obtd. only by the impression of the DC voltage. The constitution is simplified when a thermistor detecting the temp. on the peripheral of the electrostatic charging roller 100 is built into a developing bias power source circuit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention employs a charging roller for charging a photosensitive member in a series of image forming processes, a method for manufacturing the charging roller, and an electrophotographic system such as a copying machine, a printer, a facsimile machine and the like. And an image forming apparatus using the charging roller and the charging device.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger has been widely used as a charging means for uniformly charging the entire surface of a photoreceptor. This corona discharger is effective as a means to uniformly charge the photoreceptor to a certain potential. Conversely, charging by corona discharge requires a high-voltage power supply, Ozone is generated. The generation of a large amount of ozone not only adversely affects the environment, but also causes the problem that the charging member and the photoconductor are deteriorated by the ozone.

[0003] As shown in FIG. 34, the charging roller 3400 is brought into contact with the photosensitive drum 3401 and is driven to rotate by the corona discharger to rotate the core 3 of the charging roller 3400.
A charging roller for charging the surface of the photosensitive drum 3401 by applying a voltage from a power supply 3403 to 402 has been put to practical use. A charging roller as the charging means is provided with a power supply 3403.
This has the advantage that the voltage can be reduced and the amount of ozone generated due to the charging process is small. In addition, there is an advantage that there is no electrostatic adsorption of dust due to the use of the corona electrode wire, and a high voltage power supply is not required.

[0004] However, there are drawbacks that charging unevenness is likely to occur, and that the charging potential fluctuates greatly due to environmental changes. At present, the uniformity of the charging is considerably inferior to the charging treatment using a corona discharger.

FIG. 35 shows a conventionally known charging device using a charging roller.
A core metal 3502c and a conductive rubber layer 35 are provided on the surface of a photoconductive drum 3501 in which a photoconductive layer 3501b is coated on the photoconductive layer 3501b.
Roller 3 having a surface layer 02b and a surface resistance layer 3502a
The charging roller 3502 is driven to rotate counterclockwise by the clockwise rotation of the photosensitive drum 3501. Photoconductor drum 350
A DC power supply 3503 is connected between the charging roller 3501 and the charging roller 3502, and an electrometer 3504 for measuring the charged position of the photoconductor drum 3501 is provided in proximity to the photosensitive drum 3501.

Here, three types of environments having different temperatures and humidities, for example, a high-temperature and high-humidity region with a temperature of 30 ° C. and a humidity of 90%, a normal temperature and normal humidity region with a temperature of 25 ° C. and a humidity of 52%, a temperature of 10 ° C., and a humidity A low-temperature and low-humidity region of 15% is set, and an applied voltage Va (-KV) and a corresponding charging potential Vs (-KV) in each region are set.
FIG. 36 shows the relationship with V).

When a constant voltage DC power supply is used as the high voltage power supply 3503 and the charging potential Vs is set to -800 V in a normal temperature and normal humidity range, as can be seen from FIG. 36, the applied voltage Va is substantially-. 1.5 KV. When the environment changes from this state and enters a high-temperature and high-humidity region, the charging potential Vs becomes approximately -90.
At 0 V and a low-temperature and low-humidity region, the voltage becomes approximately -600 V, and the fluctuation range reaches as much as 300 V, and there are various problems in practical use.

[0008] In fact, the present inventor has experienced that in a laser printer using a charging roller, an image in the early morning in winter is soiled. This is because the charging roller was left in a low temperature state at night and its electric resistance increased, so that the charging potential of the photosensitive drum was lowered by about 200 V compared to the room temperature and normal humidity range, and the background was stained by reversal development. I think that the.

In order to improve the charging uniformity, the "contact charging method" disclosed in Japanese Patent Application Laid-Open No. 63-149668 discloses a method in which a peak-to-peak voltage that is at least twice the charging start voltage (V _TH ) when a DC voltage is applied is applied. It is disclosed that by superimposing the AC voltage, the uniformity of charging can be considerably improved.

[0010] In addition, in order to solve the above-mentioned problems, conventional methods are disclosed in, for example, JP-A-56-132356 and JP-A-2-1-1.
An image forming apparatus and a charging device as disclosed in JP-A-56476 or JP-A-2-288174 have been proposed.

According to the first publication, a voltage is applied to a charging roller by a constant current type power supply so as to improve fluctuations in charging potential due to changes in environmental conditions. According to the publication, the voltage is applied to the charging roller by superimposing an AC voltage on a DC voltage.
The device in which stable charging is always performed irrespective of changes in the environment, and the device described in the third publication are intended to prevent environmental dependence by providing means for heating the charging roller.

[0012]

However, in the "contact charging method" of Japanese Patent Application Laid-Open No. 63-149668, the peak-to-peak voltage which is twice or more the charging start voltage (V _TH ) when a DC voltage is applied. To superimpose AC voltage
An AC power source is required separately from the DC power source, which leads to an increase in the cost of the apparatus itself. Further, a large amount of useless AC current that does not contribute to the charging position of the photoconductor is consumed, thereby increasing the power source cost. In addition, a large amount of ozone is generated, which results in deterioration of the charging member and the photoconductor, and furthermore, has a problem of developing pollution.

In Japanese Patent Application Laid-Open No. 56-132356, a constant current power supply is used, so that even if the electric resistance of the charging roller changes, the current is constant and the charging potential of the photosensitive member should be constant. However, there has been a problem that a change in leak current due to a change in environment, particularly humidity, cannot be ignored, a current contributing to charging of the photoreceptor changes, and charging unevenness occurs depending on a charged surface.

Further, in the device disclosed in Japanese Patent Application Laid-Open No. Hei 2-156476, charging unevenness is reduced, but there is a problem that the cost is increased since an AC power supply must be used. Further, in Japanese Patent Application Laid-Open No. 2-288174, provision of a means for heating the charging roller makes it possible to prevent an increase in the electrical resistance of the charging roller due to a decrease in the temperature of the environment. Since the entire roller is heated, there is a problem in that the apparatus becomes large-scale and the cost increases.

The present invention has been made in view of the above, and suppresses an increase in the cost of the apparatus itself, an increase in the cost of the power supply, and the generation of a large amount of ozone, and avoids the deterioration of the charging member and the photoreceptor and the pollution problem. This is the first object.

A second object is to always obtain a good image with a simple configuration irrespective of environmental changes.

[0017]

In order to achieve the above object, the present invention provides a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer. The present invention provides a charging roller containing a layer constituent material.

Further, in a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The charging roller has a content of the constituent material of the elastic layer contained in the surface layer of 5 to 60 wt%.

A charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The difference in electric resistance between the elastic layer and the surface layer is 10 ³ Ω.
It provides a charging roller having a size of not more than cm.

Further, the electric resistance value of the surface layer is larger than the electric resistance value of the elastic layer.

A charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The surface layer provides a charging roller formed of a polymer compound including at least polar synthetic rubber and non-adhesive resin.

In a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The surface layer has a polymer compound consisting of at least polar synthetic rubber and a non-adhesive resin and has a thickness of 10 to 10 on the elastic layer.
The present invention provides a charging roller formed to have a thickness of 100 μm.

A charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The surface layer has a higher resin content as it is closer to the surface,
The present invention provides a charging roller having a higher rubber content as it is closer to the elastic layer.

In a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The surface layer is provided with a method for manufacturing a charging roller, which is formed by dividing the surface layer into a plurality of times with a solution having a different blending ratio of rubber and a resin and applying the coating layer repeatedly.

The rubber is epichlorohydrin rubber, nitrile rubber, urethane rubber, acrylic rubber or chloropretan rubber.

The resin is fluororesin or silicon resin.

Further, in a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The elastic layer has a thickness of 2 to 10 mm, and provides a charging roller made of synthetic rubber having an electric resistance value of 10 ⁶ to 10 ¹⁰ Ω · cm.

An elastic layer is formed of epichlorohydrin rubber, and 100 parts of epichlorohydrin rubber solution (solid content: 2.5 wt%) and a solvent-soluble fluororesin solution (solid content: 10.8 wt% are formed on the elastic layer. ) A method of manufacturing a charging roller for coating 40 parts is provided.

Further, an elastic layer is molded from nitrile rubber, and a nitrile rubber solution (solid content: 2.
(5 wt%) 100 parts and solvent-soluble fluororesin solution (solid content: 10.8 wt%) 40 parts are applied.

Further, an elastic layer is formed of epichlorohydrin rubber, and an epichlorohydrin rubber solution (solid content: 2.5 wt%) and a solvent-soluble fluororesin solution (solid content: 10.8 wt%) are formed on the elastic layer. It is intended to provide a method for manufacturing a charging roller in which the mixing ratio is changed and the application is performed twice.

The first time was 100 parts of epichlorohydrin rubber solution / 20 parts of fluororesin solution (electrical resistance 2 × 1).
0 ⁹ Ω · cm) was applied, in which the second time is applied epichlorohydrin rubber solution 100 parts / fluorocarbon resin solution 60 parts (electric resistance ^{2 × 10 11 Ω · cm)} .

Further, an elastic layer is molded from urethane rubber, and a urethane rubber solution (solid content: 2.
(5 wt%) 100 parts, solvent-soluble silicone resin solution (solid content: 7.5 wt%) 50 parts, and carbon 2 parts are provided.

Further, an elastic layer is molded from chloroprene rubber, and 100 parts of the chloroprene rubber solution (solid content: 2.5 wt%) and a solvent-soluble silicone resin solution (solid content: 7.5 wt% are formed on the elastic layer. The present invention provides a method of manufacturing a charging roller that applies 50 parts and 2 parts of carbon.

Further, at least the photosensitive drum, a charging roller that comes into contact with the photosensitive drum and is driven to rotate, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and an exposing means. An image forming apparatus having a developing means for converting the latent image into a visible image, means for detecting the temperature around the charging roller, and at least the voltage applied to the charging roller and the developing means based on the detected temperature. And an image forming apparatus having means for controlling one of the bias voltages.

Further, at least the photosensitive drum, a charging roller which is in contact with the photosensitive drum and is driven to rotate, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and an exposing means formed by the exposing means. An image forming apparatus provided with a developing means for converting a latent image into a visible image, in which a thermistor for detecting a temperature around the charging roller is incorporated in a bias power supply circuit of the developing means. .

Further, at least a photosensitive drum, a charging roller which is rotated by being in contact with the photosensitive drum, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and an exposing means formed by the exposing means. Developing means for converting the latent image into a visible image, transfer means for transferring the visible image formed on the surface of the photosensitive drum by the developing means onto a sheet, and fixing means for thermally fixing the transferred transfer image An image forming apparatus including: an image forming apparatus that supplies heat generated from the fixing unit to the charging roller.

Further, at least a photosensitive drum, a charging roller which comes into contact with the photosensitive drum and is driven to rotate, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and an exposing means formed by the exposing means. Developing means for converting the latent image into a visible image, transfer means for transferring the visible image formed on the surface of the photosensitive drum by the developing means onto a sheet, and fixing means for thermally fixing the transferred transfer image An image forming apparatus including: an image forming apparatus that controls the surface temperature of the charging roller by supplying heat generated from the fixing unit to the charging roller.

Further, in a charging device of an image forming apparatus for applying a voltage to a charging roller which is rotated by being contacted with a photosensitive drum to uniformly charge the surface of the photosensitive member, the temperature around the charging roller is detected. To provide a charging device for an image forming apparatus in which a thermistor is incorporated in a DC voltage power supply circuit applied to the charging roller.

Further, a cleaning member is brought into sliding contact with the surface of the charging roller.

In a charging roller having at least two elastic layers and a surface layer covering the surface of the elastic layer,
The elastic layer is provided with a medium-resistance polar rubber, and the surface layer provides a charging roller in which a non-adhesive resin contains a constituent material of the elastic layer.

The non-adhesive resin is a fluorine resin.

Further, the present invention provides an image forming apparatus which applies a DC voltage to a charging roller having an elastic layer made of polar rubber having a medium resistance characteristic and uniformly charges the surface of the cleaned photoreceptor. is there.

The surface of the elastic layer is coated with a resin layer.

Further, a charging device for applying a DC voltage to a charging roller having an elastic layer made of polar rubber having a medium resistance characteristic to uniformly charge the surface of the photosensitive member, and a roller pressed against the back surface of the recording paper. Alternatively, the present invention provides an image forming apparatus including a transfer device that applies a DC voltage having a polarity opposite to the toner charging polarity on the photoconductor to the belt to transfer the belt.

Further, an image forming apparatus is provided in which a constant current type DC power source is connected to a charging roller having an elastic layer made of polar rubber having a medium resistance characteristic to uniformly charge the surface of a cleaned photoreceptor. To do.

The polar rubber may be epichlorohydrin rubber, nitrile rubber, urethane rubber, acrylic rubber,
It is chloropretan rubber.

Further, a dew condensation preventing heater is provided around the charging roller having an elastic layer made of epichlorohydrin rubber to keep the surface temperature of the charging roller at an appropriate temperature.

The suitable temperature is 10 ° C. or higher.

Further, the present invention provides an image forming apparatus having a charging roller having an elastic layer made of polar rubber (epichlorohydrin rubber) and a contact member that contacts the roller while the charging roller is rotating. .

Further, the contact member is a charging roller cleaning member, and the charging roller rotates in advance before the image forming process.

The surface of the charging roller is black.

Further, temperature detecting means is provided around the charging roller having an elastic layer composed of epichlorohydrin rubber, and a DC voltage output controlled on the basis of the temperature detected by the temperature detecting means is applied to the charging roller. The present invention provides an image forming apparatus that does.

[0053]

The charging roller according to the present invention has good charging efficiency,
Furthermore, uniform charging can be obtained only by applying a DC voltage.

The image forming apparatus and the charging device thereof according to the present invention are configured as described above to control the applied voltage of the charging roller and / or the bias voltage of the developing means based on the temperature around the charging roller. A stable image can be obtained regardless of changes in the environment. If a thermistor for detecting the temperature around the charging roller is incorporated in the developing bias power supply circuit, the configuration can be significantly simplified.

Further, if the heat generated from the fixing means can be supplied to the charging roller, the surface temperature of the charging roller can be raised without providing a separate heating means, so that the image temperature in a low temperature environment can be improved. It is possible to prevent quality deterioration. At this time, if the surface of the charging roller is blackened, the heat absorption rate is improved and the image can be stabilized in a short time.

Further, in the charging devices in these image forming apparatuses, the one in which the thermistor for detecting the temperature around the charging roller is incorporated in the DC voltage power supply circuit for applying to the charging roller reduces the charging unevenness and reduces the AC power supply. Since it does not use ozone, it produces less ozone and can be supplied at low cost. If the cleaning member is brought into sliding contact with the charging roller, the temperature of the charging roller is further increased by frictional heat in addition to the original cleaning effect. It can be hastened.

Further, by making the electric resistance value of the surface layer of the charging roller larger than the electric resistance value of the elastic layer, it is possible to avoid voltage concentration, spark discharge, dielectric breakdown, etc. in the pinhole.

Further, by coating the surface of the elastic layer with a resin layer, uneven charging can be prevented.

Further, since the charging roller has an elastic layer composed of polar rubber (epichlorohydrin rubber) and the contacting member that contacts the roller while the charging roller is rotating, the contacting member is Since the charging roller is a cleaning member, and the charging roller rotates in advance prior to the image forming process, the surface temperature value of the charging roller can be controlled by frictional heat.

Further, since the surface of the charging roller is black, the efficiency of absorbing radiant heat is improved.

[0061]

FIG. 1 is an explanatory view showing the structure of a general charging roller 100. In FIG.
Is an 8φ cored bar 101 and approximately 4 mm covering the cored bar 101
A conductive elastic layer 102 made of carbon-dispersed silicon rubber (10 ³ Ω · cm) and a surface layer 103 made of 50 μm nylon (10 ¹² Ω · cm) coating the surface of the elastic layer 102 It is configured. Note that, for example, the difference in electric resistance of 10 ³ Ω · cm or less means that the difference in common logarithm of the electric resistance (Ω · cm) is 3 or less.

Next, the charging roller shown in FIG.
The image forming apparatus is equipped with an image forming apparatus as a charging roller experimental apparatus described in (1), and its charging characteristics and charging uniformity are measured. The charging roller experimental device includes a drum-shaped photosensitive drum 201 using a photosensitive member, a charging roller 100 in contact with the surface of the photosensitive drum 201, and a photosensitive drum 201 charged by the charging roller 100. A developing unit 202 for attaching toner to an electrostatic latent image formed by performing an exposure process on the photosensitive drum 201 to form a visible image, and a toner image on a photosensitive drum 201 on a recording paper conveyed from a conveyance system (not shown). Charger 203 for transferring the recording paper and the charge of the recording paper after the transfer processing is completed, thereby removing the recording paper from the photosensitive drum 2.
01, a cleaning blade 205 for removing the residual toner on the photosensitive drum 201 after the transfer process is completed, a static elimination lamp 206 for erasing the residual charge on the photosensitive drum 201 after the completion of the transfer process, The power supply unit 207 applies a voltage to the charging roller 100.

Further, the developing section 202 is provided with a developing sleeve 202a for carrying toner to the photosensitive drum 201 and applying a developing bias for adjusting the amount of toner adhering to the photosensitive drum 201. Further, reference numeral 208 denotes an ozone monitor for monitoring ozone generated by the charging process of the charging roller 100, and reference numeral 209 denotes an electrometer for measuring a charged position on the surface of the photosensitive drum 201.

The operation of the above configuration will be described. The photosensitive drum 201 is rotated at a linear speed of vmm / sec by a drive system (not shown). The charging roller 100 applies a voltage from the power supply unit 207 to negatively charge the photosensitive drum 201, and then charges the photosensitive drum 2 after the charging process is completed.
In No. 01, an exposure process is performed, and the charge on the photosensitive drum 201 is erased (discharged) by the intensity of light to form an electrostatic latent image. The electrostatic latent image is reversely developed by the developing unit 202 to be visualized, and the toner image is transferred onto the recording paper conveyed from the conveyance system by the action of the transfer charger 203. The separation charger 204 separates the recording paper on which the transfer process has been completed from the photosensitive drum 201. After the transfer process, the toner remaining on the photosensitive drum 201 is scraped off by the cleaning blade 205, and the photosensitive drum 201 after the completion of the cleaning process is irradiated with light from the neutralization lamp 206 to erase residual charges. One process ends.

The result of the measurement by the electrometer 209 is shown in FIG.
(Charging characteristics) and FIG. 4 (Charge uniformity). That is, FIG. 3 shows the DC voltage V applied to the charging roller 100.
_a Charge potential V _S of the photosensitive drum 201 with respect to _a (−KV)
(-V) is shown. FIG. 4 shows the center of the photosensitive drum 201,
It is obtained by measuring the traveling direction of the variation of the charge potential V _S of the photosensitive drum 201 by a potential meter 209 installed in the developing unit just before position (charging uniformity). When the voltage applied to the charging roller 100 is DC (-1200 V), DC + AC
(DC: -600 V, AC: V _PP = 2.0 KV / f =
1.0 KHz), the variation width of the charged potential Vs is | V _{S (MAX)} −V _{S (MIN)} | = 80 V, whereas it is about 10 V.

Further, as shown in FIG. 5, the developing bias V _B (−550 V) is applied to the charged potential V _S (−600 V).
V, -600V, -650V)
Toner adheres to the lower developing bias V _B V _S moiety,
Uneven charging over the entire charging area appears. As a result, soiling appears at the roller cycle. This is determined to be charging unevenness due to non-uniformity of electrical characteristics in the roller layer.
It can be seen that the toner slightly adheres to the entire surface, and that uneven charging is small.

Further, in FIG. 6, the ozone (O ₃ ) concentration (ppm) is provided by providing a suction port of the ozone monitor 208 on the outlet side of the contact portion of the charging roller 100 / photosensitive drum 201 under the above voltage application conditions. Is measured. From this comparison, it can be seen that the amount of ozone generated has increased due to the AC current. As a result, in the charging process by the charging roller 100, generation of ozone can be suppressed unless only a DC voltage is applied, that is, an AC voltage is not superimposed (DC + AC).

As a result of further studying the charging unevenness of the charging roller 100 when a DC voltage is applied, the conductive elastic layer 102 is obtained.
Was found to be a dispersion of carbon and silicone rubber. This fact indicates that the conductive elastic layer 1
The experiment was conducted using a charging roller (nylon / epichlorohydrin rubber) in which 02 was replaced with epichlorohydrin rubber. That is, the charging unevenness of the charging roller 100 is due to the electrical non-uniformity of the conductive elastic layer 102 due to poor dispersion of carbon / silicone rubber, and the charging unevenness is eliminated by using non-dispersed epichlorohydrin rubber.

Next, since the environmental fluctuation rate of the surface layer 103 of nylon used for the charging roller 100 is large, the materials shown in FIG. 7 (a), (b),
The charging roller 100 of (c) was manufactured on a trial basis, and the charging characteristics and the uniformity of charging were evaluated. As a result, in order to obtain a uniform charge only by applying a DC voltage, the elastic layer (2 to 10 mm) of the charging roller 100 needs to be electrically uniform, and a non-dispersed low-resistance (epichlorohydrin) rubber is required. (A) in FIG. 7 is optimal, but the uniformity of charging is deteriorated in that the surface properties are poor.

In order to improve the surface property, a resin surface layer (30 μm) is provided as shown in FIG. 7 (b). However, since the fluororesin surface layer has a high resistance, the charging characteristic is improved. Deterioration and, at the same time, poor uniformity of charging. In order to improve the surface properties without deteriorating the charging characteristics, the surface layer (1
(0 to 100 μm) may be used as the dispersion of the low-resistance rubber and resin used for the elastic layer. This is (c) shown in FIG. More desirably, the closer to the surface of the surface layer, the higher the resin content, and the closer to the elastic layer, the higher the rubber content. This can be achieved by applying the surface layer in a plurality of times with solutions having different blend ratios of resin and rubber. Here, in addition to epichlorohydrin rubber, nitrile rubber, urethane rubber, acrylic rubber, chloropretan rubber, and the like are used as the elastic layer material. Fluororesin, silicon resin, and the like are most suitable as the surface layer material.

As described above, the electric characteristics (R, C) of the charging roller according to the present invention, which is intended to obtain uniform charging only by applying the DC voltage, and the conventional charging roller, which leaves the charging uniformity to AC superimposition. ) And the roller layer structure are greatly different. That is, the conventional AC superposition type comprises a conductive elastic layer (carbon dispersed rubber) and a surface (resistance) layer.
Since the layer functions as a capacitor, the capacitance C is large, and the effect on uniform charging by AC superposition is large.
On the other hand, in the DC voltage application type charging roller of the present invention, the roller layer acts as a resistor (the capacitance C is small).
Therefore, even if the AC superposition is performed, the charge uniformity is not significantly improved. Hereinafter, a specific embodiment of the present invention will be described with reference to FIG.
A detailed description will be given based on (a) to (e).

[Embodiment 1] In the first embodiment, an epichlorohydrin rubber is attached to a 6φ core metal 101 so that the roller outer diameter is 12φ, and an elastic layer 102 of the charging roller 100 is provided.
Was molded. The electric resistance of the elastic layer 102 is 3 × 10 ⁸ Ω
・ Cm. Next, 100 parts of epichlorohydrin rubber solution (solid content: 2.5 wt%) and 40 parts of solvent-soluble fluororesin solution (solid content: 10.8 wt%) were added to the elastic layer 102.
It is coated on the above so that the film thickness after drying may be 30 μm.
The electric resistance of the surface layer 103 is 3 × 10 ¹⁰ Ω · cm. Charging characteristics of the charging roller 100 is V _a (DC) -
V _S = -580V against 1200 V, the variation range of the charge potential V _S is 12V, charge uniformity is good.

[Embodiment 2] In the second embodiment, nitrile rubber (NBR) is attached on the core metal 101 of 8φ so that the roller outer diameter is 16φ, and the elastic layer 102 of the charging roller 100 is provided.
Was molded. The electric resistance of the elastic layer 102 is 8 × 10 ⁸ Ω
・ Cm. Next, a nitrile rubber solution (solid content: 2.
5 parts by weight (100 parts by weight) and 40 parts of a solvent-soluble fluororesin solution (solid content: 10.8% by weight) are applied on the elastic layer 102 so that the film thickness after drying is 50 μm. The electric resistance of the surface layer 103 is 8 × 10 ¹⁰ Ω · cm. Charging characteristics of the charging roller 100 is V _a (DC) -1200V
On the other hand, V _S = −570 V, the variation width of the charged potential V _S is 15 V, and the charging uniformity is as good as that of the first embodiment.

[Embodiment 3] In the third embodiment, an epichlorohydrin rubber is attached on a core metal 101 of 8φ so that the outer diameter of the roller is 16φ, and the elastic layer 102 of the charging roller 100 is provided.
Was molded. 2 on the elastic layer 102 by changing the mixing ratio of the epichlorohydrin rubber solution (solid content: 2.5 wt%) and the solvent-soluble fluororesin solution (solid content: 10.8 wt%).
It is applied so that the film thickness after drying is 30 μm each. The first time was 100 parts epichlorohydrin rubber solution / 20 parts fluororesin solution (electrical resistance 2 × 10 ⁹ Ω · c
m), and the second time is epichlorohydrin gum solution 1
00 parts / fluorine resin solution 60 parts (electrical resistance 2 × 10 ¹¹ Ω
· Cm). The surface of the charging roller 100 is smooth because the content of the fluororesin is large, and the charging characteristic is V _S = −580V with respect to V _a (DC) −1200V.
The variation width of the charging position V _S is 10 V, and the uniformity of charging is good.

[Embodiment 4] In the fourth embodiment, the elastic layer 102 of the charging roller 100 is molded by attaching urethane rubber so that the outer diameter of the roller is 12φ on the core metal 101 of 6φ. The electric resistance of the elastic layer 102 is 8 × 10 ⁹ Ω · cm. Next, urethane rubber solution (solid content: 2.5 wt
%) 100 parts, solvent-soluble silicone resin solution (solid content: 7.5 wt%) 50 parts, carbon 2 parts elastic layer 10
It is applied onto 2 so that the film thickness after drying is 40 μm. The electric resistance of this surface layer 103 is 2 × 10 ⁹ Ω · cm.
It is. The charging characteristic of the charging roller 100 is V _a (D
C) -1200 V vs. _S = -560 V, charged potential V
The variation width of _S is 18V, and the uniformity of charging is good.

[Embodiment 5] The fifth embodiment is the fourth embodiment.
Replacing the urethane rubber in the example with chloroprene rubber,
The fourth implementation except that the thickness of the surface 103 is 60 μm
It has the same configuration as the example. The charging characteristics of this charging roller 100
Sex is V_aV for (DC) -1200V _S= -590
V, electrostatic charge V_SVariation range is 15V, charging uniformity is
Good.

As described above, according to the charging roller of the present invention, since the polar synthetic rubber used for the elastic layer is the surface layer made of the blend of the non-adhesive resin, the charging roller surface is not deteriorated without deteriorating the charging characteristics. You can improve your sex. In addition, since the resin content is increased closer to the surface of the surface layer, the surface property is improved and the durability of the charging roller is improved. Further, since the elastic layer is made of a synthetic rubber (non-dispersed system) having an electric resistance value of 10 ⁶ to 10 ¹⁰ Ω · cm instead of a dispersed system of carbon or the like, the elastic layer is in contact with the pinhole portion of the photoconductor. Does not cause electrical breakdown.

[Sixth Embodiment] FIG. 9 is a block diagram showing a sixth embodiment of the present invention applied to an image forming apparatus such as a laser printer.

This image forming apparatus has, for example, a diameter of 60 mm.
A roller 15 of 15 mm in diameter is rotatably brought into contact with the surface of the photosensitive drum 901 of this type.
Is connected to a high-voltage power supply 903 '. This charging roller 9
02 is, for example, a core bar 902c having a diameter of 10 mm and a thickness of 5 mm.
And a surface resistance layer 902a having a thickness of 50 μm.

The reversal developing device 905 is the photosensitive drum 90.
A visible image is formed by attaching dry toner to the latent image written and irradiated with the laser beam L to the laser beam 1, and a bias voltage Vb is applied by a bias power supply 906. At least one of the bias power supply 906 and the high-voltage power supply 903 ′ is controlled by a thermistor 907 as means for detecting the temperature around the charging roller 902 via a central processing unit (CPU) 908.

Here, according to the experiment of the present invention, the linear velocity v of the surface of the photosensitive drum 901 is 120 mm / sec, the temperature T around the charging roller 902 detected by the thermistor 907 is 25 ° C., and the charging roller 902 is applied. Voltage Va =-
1.54 KV, charging voltage Vs of photosensitive drum 901 = −
An appropriate image could be obtained under the conditions of 800 V and the developing bias voltage Vb = -600 V.

In the above device, the CPU 908 is operated in an environment of, for example, T = 10 ° C., which corresponds to the start of use in the early morning of winter.
Under the conventional conditions in which the control of the high voltage power supply 903 'or the bias power supply 906 is not performed, Vs = 590V, and the background dirt occurs as shown in FIG.

When the control by the CPU 908 is performed under the same environmental conditions, first, the thermistor 907 causes T = 1.
0 ° C. is detected, the detection result is input to the CPU 908, and as shown in FIG.
b ′ = − 500 V, or as shown in FIG. 10C, the applied voltage Va ′ = − 1.
By controlling to 6KV (Vs' =-650V),
A good image without background stain was obtained.

In FIG. 11, the thermistor 907 is connected to the DC power supply circuit for the developing bias voltage Vb and the charging roller applied voltage Va.
Roller 9 when incorporated in DC power supply circuit
02, the temperature R of the thermistor 907,
FIG. 5 is a diagram showing TR-Vb characteristics and TR-Va characteristics showing the relationship with C power supply outputs Vb and Va.

[Embodiment 7] FIG. 12 shows the T shown in FIG.
FIG. 10 shows a seventh embodiment of the present invention in which the bias voltage Vb applied to the reversal developing device 905 in the sixth embodiment shown in FIG. 9 is controlled based on the −R-Vb characteristic diagram. , A thermistor 907 disposed around the charging roller 902 is incorporated in the developing bias DC power supply circuit 906 'so that an optimal developing bias voltage Vb is always applied in any environment, and a good image without background stain can be obtained. it can. Specifically, when T = 16 ° C., R =
A good image was obtained at 14 KΩ and Vb = −560V, and Vs at this time was −740V.

[Embodiment 8] Next, FIG. 13 shows a sixth graph shown in FIG. 9 based on the T-R-Va characteristic diagram shown in FIG.
8 shows an eighth embodiment of the present invention in which the applied voltage Va of the charging roller 902 in the above embodiment is controlled, and the thermistor 90 arranged around the charging roller 902 is shown.
7 is incorporated in the DC voltage power supply circuit 903 'so that the optimum applied voltage Va is always output under any environment, and the charging voltage Vs of the photosensitive drum 901 is kept substantially constant.

In the eighth embodiment, in addition to the above structure, the cleaning member 909 is brought into sliding contact with the charging roller 902 to clean the surface of the charging roller 902 and also to clean the surface even at low temperature. Member 9
The charging characteristics are improved by raising the temperature in a short time by the frictional heat generated by the friction with the friction coefficient 09. Actually, T = 12 ° C
, R = 16.5KΩ, Va = -1.65KV and Vs
= −760 V, and a good image could be obtained with Vb = −600 V constant.

[Embodiment 9] According to each of the above embodiments, a good image can be obtained in a considerably short time even when the environmental temperature is low, but FIG. 14 can further shorten the waiting time. 9 illustrates a ninth embodiment of the present invention.

Photosensitive drum 901, charging roller 902,
In an image forming apparatus including a reversal developing device 905, a transfer unit 910, a heat roller fixing unit 911, an exhaust fan 912, and a photosensitive drum cleaning unit 913, whether or not carbon is dispersed and mixed in the conductive rubber layer 902b of the charging roller 902; The surface of the charging roller is blackened by adding a small amount of carbon to the surface resistance layer 902a, for example, to improve the absorption of radiant heat.

The heat roller fixing device 9 is used prior to use.
At the same time when the fixing heater 11 is turned on, the photosensitive drum 901 and the charging roller 902 driven by the photosensitive drum 901 are rotated idlely, and the exhaust fan 912 is rotated in the reverse direction, so that the heat roller fixing device 9 is rotated.
11 is sent to the charging roller 902 to increase the surface temperature, and the temperature is detected by the thermistor 907. When the temperature reaches a predetermined temperature, the exhaust fan 912 is rotated in the exhaust direction to start image formation. To do it.

By doing so, even if the image forming apparatus is left in a low temperature state for a long time, it is possible to raise the surface temperature of the charging roller in an extremely short time and obtain a good image without background stain. become. The waiting time can be further reduced by using the developing bias control means and the charging roller applied voltage control means as shown in the seventh and eighth embodiments as needed in the ninth embodiment. It is possible.

Next, the charging unevenness of the conventional charging roller (having a resin overcoat layer on the surface of the conductive elastic layer) when a DC voltage is applied will be described. This uneven charging is due to the fact that the conductive elastic layer is a dispersion of carbon and silicon rubber. This was found as a result of an experiment using a charging roller in which the conductive elastic layer was replaced with epichlorohydrin rubber (an overcoat of resin on the epichlorohydrin rubber elastic layer). That is, the uneven charging of the conventional charging roller is due to the electrical non-uniformity of the conductive elastic layer due to poor dispersion of carbon / silicone rubber, and the use of non-dispersed epichlorohydrin rubber causes
The charging unevenness is eliminated.

FIG. 15 shows a charging roller capable of uniform charging only by applying a DC voltage, that is, without superimposing an AC voltage (DC + AC). In the drawing, the roller A is composed of a single layer of epichlorohydrin rubber (1 to 5 mm thick), and the roller B is composed of an epichlorohydrin rubber elastic layer (1 to 5 mm thick) and a fluororesin surface layer (1 to 10 μm). Similarly, roller C has an epichlorohydrin rubber elastic layer (1 to 1).
(5 mm thick) and a fluororesin / epichlorohydrin rubber dispersion layer (10 to 100 μm). In addition, a single layer (1 to 5 mm thick) of epichlorohydrin rubber may be used so that the fluororesin is intensively mixed with the surface of the single layer of epichlorohydrin rubber.

The thickness of the epichlorohydrin rubber layer is 1 to 5
When the thickness is 1 mm or less, the function as an elastic body is insufficient when the thickness is 1 mm or less, and when the thickness is 5 mm or more, the electric resistance becomes high, or when the external heating is performed by a heater, the thermal conductivity becomes poor (the resistance becomes low). It does not fall). In addition, FIG. 16 shows the experimental results regarding the thickness (1 to 5 mm) of the epichlorohydrin rubber layer.

Example 10 An elastic layer (thickness: 3 mm) of epichlorohydrin rubber was molded on a core metal 1501 of 8φ so that the roller outer diameter was 14φ. Next, 100 parts of epichlorohydrin rubber solution (solid content 2.5 wt%) and 40 parts of solvent-soluble fluororesin solution (solid content 10.8 wt%) 40
Part is applied onto the elastic layer so that the film thickness after drying is 30 μm. The charging roller (FIG. 15 (c)) has a charging characteristic of Vs = -720V with respect to Va = -1400V, a variation range of the charging potential Vs of 10V, and good charging uniformity.

When DC + AC is applied to the charging roller according to the prior art, even if the latent image potential remains on the photosensitive member or there is some residual toner on the photosensitive member, uniform charging is obtained by the AC superposition effect. However, in order to obtain uniform charging only by applying a DC voltage to the charging roller, in addition to using the charging roller of the present invention (non-dispersion type, epichlorohydrin type elastic roller), firstly, QL is used. It is indispensable to enter the charging step from the surface of the photoreceptor that has been subjected to pre-exposure, and secondly to enter the charging step from the surface of the photoreceptor on which the residual toner on the surface of the photoreceptor has been completely removed by a cleaning blade. In this case, the charging uniformity shown in FIG. 17 was obtained. As a comparative example, when QL is not used, the toner is added to the residual potential, resulting in non-uniform charging (FIG. 17). The image is transferred to the surface, and thereafter, charging unevenness occurs at the roller cycle (FIG. 17).

[Embodiment 11] In addition to the contact charging device of the above embodiment, the transfer device can change the conventional corona transfer to the contact transfer, thereby making it possible to drastically reduce the amount of ozone generated. 0 ₃ A comparison of concentration shown in FIG. 18. FIG. 19 shows an example of this image forming apparatus. Generally, in the case of a small-diameter photosensitive drum (or belt photosensitive member) 1901a to which the curvature separation method is applied for separating transfer paper, transfer by a roller 1902 (FIG. 19 (a)), and in the case of a drum 1901b of 50φ or more, by a belt 1903. Transfer (FIG. 19 (b)) is applied. In an image forming apparatus that performs roller charging / roller transfer only by applying a DC voltage, the amount of generated ozone is applied by superimposing AC on DC at 1/800 to 1000 times that of corona charging / corona transfer. It is 30 to 40 times smaller than that of an image forming apparatus of roller charging / roller transfer.

The outer diameter of the roller is 16 on the core metal 1501 of 8φ.
An elastic layer (thickness: 4 mm) of epichlorohydrin rubber was formed so as to have a diameter φ, and a charging roller (roller A in FIG. 15) was formed. The temperature / humidity dependence of the I-Va characteristic and the Vs-Va characteristic of the charging roller was measured using an experimental device shown in FIGS. 20 (a) and (b) (FIGS. 21 (a) and (b) /). 22
(A), (b)). Resistance R of epichlorohydrin rubber layer
(= Va / 2) has a large temperature dependency (FIG. 21A) and a small humidity dependency (FIG. 22A). Accordingly, the charging characteristics (charge potential Vs, charging uniformity) are greatly affected by the temperature (FIG. 21B), and at 10 ° C. or lower, Vs decreases and the uniformity deteriorates. However, the influence of humidity is not so large (FIGS. 22A and 22B). From the above experimental results, in order to always use the epichlorohydrin rubber elastic roller as the charging roller to uniformly and uniformly charge the photosensitive member, the roller temperature should be 10 ° C. or more. Second, it is necessary to detect the roller temperature with a thermistor and to perform output correction of the charging roller applied voltage with respect to the temperature fluctuation.

[Embodiment 12] In FIG. 23, a charging roller 2301 is an elastic roller of 4 mm thick epichlorohydrin rubber, and a dew condensation preventing heater (30 × 200 mm ² heat sink, 220 v, 1) is provided above the charging roller 2301.
8w) 2302 is installed, and in winter and at night,
It is configured so that the temperature inside the machine does not drop below 5 ° C when the heater is turned on. For this reason, the roller temperature is 10 ° C. or higher during image formation in winter and early morning.
By applying C, the charging property is good and a good image can be obtained.
Since the dew condensation preventing heater 2302 also prevents dew condensation on the optical system and the photoconductor drum 2303, it is possible to prevent the occurrence of an abnormal image.

[Embodiment 13] Referring to FIG. 24, a charging roller 2401 is a 3 mm thick epichlorohydrin rubber elastic roller having an overcoat layer of 1 to 3 μm thick made of fluororesin on the surface thereof, for cleaning the roller surface. When the roller is rotated while the cleaning member 2402 is pressed, the roller surface is cleaned and at the same time the roller surface temperature rises due to friction. By setting the surface temperature of the charging roller 2401 to 10 ° C. or higher by idle rotation of the drum prior to the image forming process in winter or early morning, the charging characteristics can be restored to a normal state. Note that the cleaning member 2402 of the charging roller 2401 may be always in contact with the roller, or may be pressed against the roller only when the photosensitive drum 2403 is idled prior to the image forming process, and may be in contact with the roller during the image forming process. It may be configured to be away from.

[Embodiment 14] FIG. 25 shows a roller charging device using a charging roller having the same structure as that shown in the tenth embodiment. From the temperature characteristics of the charging roller 2501, the roller surface temperature T ° C. and the thermistor resistance R (K
Ω) and the roller applied voltage Va (KV) are shown in FIG. The DC power supply 2502 of FIG.
A control circuit is incorporated that can obtain an applied voltage according to the roller temperature based on the V characteristic. When the roller charging device according to the present invention is used, even if the charging roller has temperature dependence, an applied voltage corresponding to the roller temperature is output, so that a constant charging position can be always obtained.

Next, the charging unevenness of the conventional charging roller (having a resin overcoat layer on the surface of the conductive elastic layer) when a DC voltage is applied will be described. This uneven charging is caused by the fact that the conductive elastic layer is a dispersion of synthetic rubber and carbon. This is the result of experiments using a conventional charging roller in which the conductive elastic layer (dispersed system of synthetic rubber and carbon) of the charging roller was replaced with urethane rubber containing no carbon or urethane rubber containing a small amount of alkali metal salt. ,found. That is, the uneven charging of the conventional charging roller is due to the electrical non-uniformity of the conductive elastic layer due to poor dispersion of carbon / synthetic rubber, and the uneven charging is eliminated by using non-dispersed urethane rubber. .

FIG. 27 shows a structure of a charging roller capable of uniform charging only by applying a DC voltage, that is, without superimposing an AC voltage (DC + AC). In the figure, a roller D is a core metal 2701 having a thickness of 1 to 5 mm of urethane rubber or an elastic layer 270 containing urethane rubber containing an alkali metal salt.
It consists of two. Roller E is the elastic layer 270 of roller D
2 having a surface layer 2703 made of a non-adhesive resin having a thickness of 1 to 30 μm. Here, the elastic layer 2702
Is a urethane rubber having an electric resistance of 10 ⁶ to 10 ¹⁰ Ω · cm irrespective of the dispersion of conductive particles such as carbon, or a urethane rubber containing an alkali metal salt. The whole is electrically uniform. Further, since urethane rubber has appropriate hardness and surface properties, the roller D has sufficient performance, but if a higher performance charging roller is required, it is made of a non-adhesive resin (for example, fluororesin, silicone resin). The roller E provided with the surface layer 2703 may be used.

[Embodiment 15] The elastic layer 2 of urethane rubber is formed on the core metal 2701 of 8φ so that the roller outer diameter is 14φ.
702 (thickness 3 mm) was molded (roller D). The electric resistance of the elastic layer of this charging roller is 3 × 10 ⁹ Ω · cm (temperature 20 ° C., humidity 50%). FIG. 28 shows a part of an image forming apparatus using the charging roller 2800. The photosensitive drum 2801 has a photosensitive layer thickness of 30 μm, and a power source 28
Reference numeral 03 is a DC voltage (Va), QL2804 is an LED, and cleaner 2805 is a blade cleaning unit for removing residual toner on the photoconductor 2801. The charging characteristics of the charging roller 2800 are such that Vs = −800 V with respect to Va = −1500 V, and the variation width of the charging potential Vs is about 15 V, so that charging uniformity is good.

DC + AC marking is applied to the charging roller which is a conventional technique.
In the case of addition, even if the photoconductor has a residual potential,
Even if there is some residual toner on the body, due to the AC superposition effect
Uniform charging was obtained, but only DC voltage was applied to the charging roller
In order to obtain uniform charging with the charging roller of the present invention,
(Urethane rubber regardless of containing conductive particles such as carbon
Rubber or urethane rubber with alkali metal salt added
Electrical resistance 10⁶-10 ^TenBand with elastic layer of Ω · cm
In addition to using electric roller), firstly, in QL
Entering the charging process from the exposed photoreceptor surface, the second
Then, clean the residual toner on the surface of the photoconductor with a cleaning blade.
It is essential to start the charging process from the photoconductor surface that has been completely removed
Condition. Under this condition, the charging of
Uniformity is obtained. As a comparative example, in the case without QL, the remaining
Since it is added to the residual potential, it becomes unevenly charged (FIG. 29).
), And if cleaning is not enough,
Residual toner is transferred to the roller surface when joining with the charging roller
After that, uneven charging occurs in the roller cycle (Fig.
29).

[Embodiment 16] An elastic layer 2 of urethane rubber is formed on a core metal 2701 of 8φ so that the roller outer diameter is 16φ.
702 (thickness 4 mm) was molded. Since this elastic layer contains 0.5 wt% of lithium perchlorate salt with respect to urethane rubber, its electric resistance is 3 × 10 ⁸ Ω · cm.
(Temperature 20 ° C., Humidity 50%). Next, a solvent-soluble fluororesin solution (solid content: 1
0.8 wt%) was applied so that the film thickness after drying would be 5 μm to form a surface layer 2703 (roller E). When the same experiment was performed by replacing the charging roller with the charging roller (roller D) shown in the fifteenth embodiment, substantially the same effect as in the above-described embodiment was obtained.

Urethane rubber is known to be a strong rubber-like elastic body having excellent low hardness, abrasion resistance, compressive strain resistance and the like among various synthetic rubbers, and has strength as an elastic layer of a charging roller. Although it is optimal from the standpoint of hardness and hardness, it had problems of high electrical resistance and large environmental fluctuations.

The resistance reduction of the urethane rubber can be achieved by molding the urethane rubber containing an alkali metal salt. Moreover, in this case, there is no variation in resistance as in the case of dispersion of conductive particles such as carbon, and the resistance can be reduced uniformly throughout the elastic layer (see JP-A-63-189876). Of the alkali metal salts, perhalogen oxyacid salts are most suitable. FIG. 30 shows the amount of lithium perchlorate added to urethane rubber and the value of its electrical resistance.

Next, measures against environmental changes in the electrical resistance of urethane rubber will be described. Using a roller D as a charging roller and a roller D ′ to which 0.05 wt% of lithium perchlorate is added, Vs in two kinds of environments (temperature 25 ° C., humidity 80% and temperature 15 ° C., humidity 30%) The -Va characteristic was measured by the experimental device shown in FIG.
(B) shows the result. The reason why the charging characteristics of both the rollers D and D ′ change under the above-mentioned environmental conditions is that the electric resistance of the charging roller changes depending on the environment.

In the experimental apparatus shown in FIG. 31, the measured current I is a power supply current for the applied voltage Va and at the same time a charging current for charging the photosensitive member to Vs. Therefore, if the current I can be kept constant even if the electric resistance of the roller changes, the photosensitive member charged potential Vs can be made constant.

In FIG. 33, roller D (solid line) and roller D '
(Dashed line) I-Vs at a temperature of 25 ° C. and a humidity of 50%,
It shows Vs-Va characteristics. Here, if a constant current DC power supply is used as the applied voltage power supply, D and D having different resistances can be used.
D ′ Regardless of the roller, the current I = 30 μ
The applied voltage fluctuates by ΔVa so that A becomes Vs = 8
00v is obtained. This method is applied to environmental variations in the electrical resistance of each roller.

[Embodiment 17] The rollers D and D ′ are shown in FIG.
The image forming apparatus shown in FIG. 8 has a constant current type DC power source at a temperature of 15 ° C., a humidity of 30%, a temperature of 25 ° C. and a humidity of 80%.
% Constant current I =
Vs = 800 ± 25 for photoconductor charging potential for 30 ± 1 μA
V. The use of a constant current power supply means that a constant charge is always supplied to the photoreceptor. Therefore, the absolute condition is that there is no residual potential on the photoreceptor surface before charging and the residual toner is removed. Become.

[0113]

As described above, according to the charging roller and the method of manufacturing the same according to the present invention, since the charging roller is constructed as described above, the charging efficiency is good and uniform charging can be obtained only by applying a DC voltage. It is possible to suppress an increase in the cost, an increase in the cost of the power supply, and a large amount of ozone, thereby avoiding the deterioration of the charging member and the photoconductor and the pollution problem.

Further, according to the image forming apparatus and the charging device thereof according to the present invention, the one in which at least one of the voltage applied to the charging roller and the developing bias voltage is controlled based on the temperature around the charging roller is a change in environment. Regardless of the situation, a stable image without background stains can always be obtained, and if a thermistor that detects the temperature around the charging roller is incorporated in the developing bias power supply circuit, the configuration of the image forming apparatus can be significantly simplified. .

Further, in the case where the heat generated from the fixing means can be supplied to the charging roller, heating means for the charging roller is separately provided to raise the surface temperature,
Image quality can be prevented from deteriorating in low-temperature environments.
In addition, when the surface of the charging roller is blackened, the heat absorption rate is improved, and the image can be stabilized in a shorter time.

Further, in the charging device, if a thermistor for detecting the temperature around the charging roller is incorporated in the DC voltage power supply circuit for applying the voltage to the charging roller, it becomes a constant voltage power supply with less charging unevenness and energization due to voltage fluctuation. Since there is no danger of damage and no AC power is used,
Ozone generation is low and it can be supplied at low cost.
When the cleaning member is brought into sliding contact with the charging roller, the temperature of the charging roller can be raised in a short time by frictional heat, which is particularly effective at the beginning of use in the early morning of winter.

[Brief description of drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a general charging roller.

FIG. 2 is an explanatory diagram showing a configuration of an experimental apparatus based on an electrophotographic process used for measuring characteristics of a charging roller.

3 is a graph showing the charge potential V _S of the photosensitive drum with respect to the roller applied DC voltage V _a.

4 is a graph showing the results of measurement of the variation in the traveling direction of the charge potential V _S of the photosensitive drum.

FIG. 5 is an explanatory diagram showing a pattern of uneven charging.

FIG. 6 is a graph showing a comparison of ozone concentrations.

FIG. 7 is a table comparing characteristics of three types of prototype rollers.

FIG. 8 is an explanatory diagram showing the configuration of each of the five embodiments.

FIG. 9 is an explanatory diagram illustrating a configuration of an image forming apparatus according to the present invention.

FIG. 10 is an explanatory diagram showing an improved state of an image as compared with a conventional example.

FIG. 11 is a graph showing a relationship among a charging roller surface temperature, a thermistor resistance, and a power supply output.

FIG. 12 is an explanatory diagram illustrating a configuration of an image forming apparatus according to the present invention (controlling a bias voltage applied to a reversal developing device).

FIG. 13 is an explanatory diagram illustrating a configuration of the image forming apparatus according to the present invention (controlling the voltage applied to the charging roller).

FIG. 14 is an explanatory diagram illustrating a configuration of an image forming apparatus according to the present invention.

FIG. 15 is an explanatory diagram showing a configuration of a charging roller (three types) according to the present invention.

FIG. 16 shows the thickness of epichlorohydrin rubber (1 to 5 m).
3 is a table showing the relationship between m) and charging uniformity / charging property.

FIG. 17 is a graph showing charging characteristics of the charging roller under each condition.

FIG. 18 is a table showing ozone concentration comparison values.

FIG. 19 is an explanatory view showing another configuration (contact charging device + contact transfer device) of the image forming apparatus according to the present invention.

FIG. 20 is an explanatory diagram showing a configuration of an experimental device used in the present invention.

FIG. 21 is a graph showing the temperature dependence of each characteristic in the charging roller according to the present invention.

FIG. 22 is a graph showing the humidity dependence of each characteristic of the charging roller according to the present invention.

FIG. 23 is an explanatory diagram showing another configuration (condensation prevention heater) of the image forming apparatus according to the present invention.

FIG. 24 is an explanatory diagram illustrating another configuration (cleaning member) of the image forming apparatus according to the invention.

FIG. 25 is an explanatory diagram showing another configuration (DC power supply with control circuit) of the image forming apparatus according to the present invention.

FIG. 26 shows the roller surface temperature T based on the temperature characteristics of the charging roller.
° C, thermistor resistance R (KΩ) and roller applied voltage Va
It is a graph which shows the relationship with (KV).

FIG. 27 is an explanatory view showing another configuration (two types) of the charging roller according to the present invention.

FIG. 28 is an explanatory diagram showing a configuration of an image forming apparatus using the charging roller according to the present invention.

FIG. 29 is a graph showing charging characteristics of the charging roller under each condition.

FIG. 30 is a table showing the amount of lithium perchlorate added to urethane rubber and the value of its electrical resistance.

FIG. 31 is an explanatory view showing the configuration of an experimental device for experimenting with the charging roller according to the present invention.

FIG. 32 is a graph showing measurement results of the experimental device shown in FIG. 31.

FIG. 33 is a graph showing IVs and Vs-Va characteristics of the charging roller according to the present invention at a temperature of 25 ° C. and a humidity of 50%.

FIG. 34 is an explanatory diagram showing a conventional method of using a charging roller.

FIG. 35 is an explanatory diagram showing a configuration of a charging device of a conventional image forming apparatus.

FIG. 36 is a graph showing a relationship between a voltage applied to a charging roller and a charging potential of a photosensitive drum in different environments in the related art.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 charging roller 101 cored bar 102 elastic layer 103 surface layer 208 ozone monitor 209 electrometer 902 charging roller 907 thermistor 908 CPU 909 cleaning member 912 exhaust fan 913 cleaning means 1902 transfer roller 1903 transfer belt 2301 charging roller 2302 anti-condensation roller 2401 charging roller 2402 Cleaning member 2501 Charging roller 2502 DC power supply

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] August 22, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 7

[Correction method] Change

[Correction contents]

FIG. 7 is a chart comparing the characteristics of three types of prototype rollers.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 16 shows the thickness of epichlorohydrin rubber (1 to 5 m).
3 is a chart showing the relationship between m) and charging uniformity / charging property.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 18 is a chart showing ozone concentration comparison values.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 30 is a chart showing the amount of lithium perchlorate salt added to urethane rubber and the value of its electrical resistance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Nakahara 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (6)

[Claims] 1. In a charging roller having at least an elastic layer and a surface layer covering the surface of the elastic layer, the content of the constituent material of the elastic layer contained in the surface layer is 5 or less.
Charging roller characterized in that the charging roller is -60 wt%. 2. A charging roller having two layers, at least an elastic layer and a surface layer covering the surface of the elastic layer, wherein the surface layer is formed of a polymer compound containing at least polar synthetic rubber and a non-adhesive resin. A charging roller characterized by the above. 3. A charging roller having two layers, at least an elastic layer and a surface layer covering the surface of the elastic layer, wherein the surface layer comprises a polymer compound containing at least polar synthetic rubber and a non-adhesive resin. Thickness 10-10 on elastic layer
The film is formed to have a thickness of 0 μm.
The charging roller described in 1. 4. A charging roller having at least an elastic layer and a surface layer covering the surface of the elastic layer, wherein the elastic layer has a thickness of 2 to 10 mm and an electric resistance value of 10 ⁶ to. A charging roller comprising a synthetic rubber of 10 ¹⁰ Ω · cm. 5. At least a photosensitive drum, a charging roller that comes into contact with the photosensitive drum and is driven to rotate, an exposing unit that exposes the surface of the photosensitive member charged by the charging roller, and an exposing unit. Developing means for converting the latent image into a visible image, transfer means for transferring the visible image formed on the surface of the photosensitive drum by the developing means onto a sheet, and fixing means for thermally fixing the transferred transfer image An image forming apparatus including: an image forming apparatus, wherein heat generated from the fixing unit is supplied to the charging roller. 6. A photosensitive drum, a charging roller which rotates in contact with the photosensitive drum and is driven by the photosensitive drum, an exposing means for exposing the surface of the photosensitive body charged by the charging roller, and an exposing means formed by the exposing means. Developing means for converting the latent image into a visible image, transfer means for transferring the visible image formed on the surface of the photosensitive drum by the developing means onto a sheet, and fixing means for thermally fixing the transferred transfer image An image forming apparatus including: an image forming apparatus, wherein the surface temperature of the charging roller is controlled by supplying heat generated from the fixing unit to the charging roller.