JPH09218566A - Image recording device - Google Patents

Abstract

(57) Abstract: An image forming process is applied to an image carrier by applying an image forming process including a step of uniformly charging the image carrier,
In an image forming apparatus in which an image carrier is repeatedly used for image formation, it is possible to solve the problem of image deletion due to discharge products, and to maintain high-quality recording for a long time even in a cleanerless system apparatus. SOLUTION: The means for uniformly charging the image carrier 1 is a charger 2 which is in contact with the image carrier and is applied with a voltage,
Use of the charger 2 and the image carrier 1 in which the charge amount of the image carrier 1 when a voltage equal to or lower than the minimum discharge start voltage is applied to the charger 2 is 80% or more of the applied voltage.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrophotographic photosensitive member.
An image is formed on an image carrier such as an electrostatic recording dielectric by applying an image forming process such as an electrophotographic method or an electrostatic recording method including a step of uniformly charging the image carrier. The body relates to an image recording apparatus (image forming apparatus) such as a copying machine or a printer, which is repeatedly used for image formation.

[0002]

2. Description of the Related Art For convenience, a transfer type electrophotographic copying machine,
An image recording device such as an LPB (laser beam printer) or a facsimile will be described as an example.

A transfer type electrophotographic image recording apparatus generally uses a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member. A) This rotating photosensitive drum is predetermined by a charging means. The polarity of
Charging step for uniformly charging to electric potential b) Image exposure is performed on the uniformly charged surface of the rotating photosensitive drum by exposure means (projection / image formation exposure means for original image, laser light scanning exposure means, etc.) to obtain exposure image information. Image exposure step for forming a corresponding electrostatic latent image c) Regular development of the formed electrostatic latent image with positive toner or negative toner charged by the developing means (toner adhesion to exposed dark areas of electrostatic latent image) or reversal development Development step of developing as a toner image by (adhering toner to the exposed bright portion of the electrostatic latent image) d) Transfer step of transferring the toner image from the photosensitive drum side to the recording material side as a transfer target member by a transfer means e) Photosensitization Fixing step of fixing the transferred toner image of the recording material separated from the drum onto the surface of the recording material f) Removal of the toner remaining on the surface of the photosensitive drum after the transfer of the toner image onto the recording material to remove the toner on the surface of the photosensitive drum To execute the image forming by a cleaning step of cleaning.

The cleaned photosensitive drum is repeatedly used for image formation.

In the above, as the image forming process means of a) to f), various methods and configurations are specifically known.

In recent years, such image recording apparatuses have been reduced in size, but there is a limit only in reducing the size of the image carrier and each image forming process means constituting the apparatus. Further, the toner remaining on the surface of the photosensitive drum after the transfer of the toner image to the recording material is removed by the cleaning step means to become waste toner, but this waste toner is preferably not in view of environmental protection.

Therefore, the charging process means and the developing process means are also used as the cleaning process means for the toner remaining on the surface of the photosensitive drum after the toner image is transferred, thereby eliminating the provision of the cleaning process means as a dedicated device. Image recording devices for cleanerless systems have also appeared.

This is because the charging process means is a charging device (contact charging member) which is in contact with the photosensitive drum and to which a voltage is applied, for example, a fur brush charging device (brush member of conductive fiber). The charging of the photosensitive drum is performed by the charging means, and the transfer residual toner that has adhered to the surface of the photosensitive drum in a certain pattern according to the transfer image from the transfer step means and is transferred to the charging portion is in contact with the photosensitive drum surface. The toner is diffused and unpatterned by the container, and at least a part of the toner is at least temporarily collected by the charger.

Then, diffused and non-patterned by the charger,
Further, it is the potential difference between the DC voltage applied to the developing device at the time of the development in the developing process by the developing process means (developing device) after the toner re-emitted from the charging device to the photosensitive drum and transferred to the developing portion and the surface potential of the photosensitive drum. The cleaning is carried out by the fog removal potential difference Vback (simultaneous development cleaning).

According to this, even without the cleaning step means as a dedicated device, the transfer residual toner is at least temporarily collected by the charging step means, and is collected by the developing step means to be used for the development after the next step. Therefore, waste toner can be eliminated. Further, since the cleaning process means as a dedicated device is not provided, there is a great advantage in terms of space, and the device can be significantly downsized.

[0011]

By the way, an image forming process including a step of uniformly charging the image bearing member is applied to the image bearing member to perform image formation, and the image bearing member repeats image formation. In the image forming apparatus used for the above, there is a problem that "image deletion" occurs as recording is performed and the quality of the recorded image is degraded.

The image deletion is a phenomenon in which the electrostatic latent image formed on the charged surface of the photosensitive drum loses its contrast and becomes blurred before it reaches the developing portion. When the latent image is blurred, the developed toner image also has low contrast, the image area is thickened, and small-sized characters and halftone dot images are crushed, degrading the image quality.

This is because the surface resistance of the photosensitive drum (including the surface resistance of the photosensitive drum) is lowered. Since the resistance in the surface direction of the photosensitive drum is reduced, the charge retention property is reduced, and the electrostatic latent image formed on the charged surface of the photosensitive drum loses contrast and blurs before the development portion is reached. .

The main cause of the reduction in surface resistance of the photosensitive drum is that discharge products such as active oxygen (ozone) generated by the discharge of the charging process means of the photosensitive drum adhere to the surface of the photosensitive drum, By changing the quality of the photosensitive drum surface. That is, since the discharge products such as active oxygen generated by the discharge of the charging process means of the photosensitive drum have a strong oxidizing power, the resin forming the photosensitive drum as the image carrier is oxidized or dirty. It sticks to the surface of the photosensitive drum together with (paper dust, toner, etc.) to make the surface of the photosensitive drum hydrophilic. When the surface of the photosensitive drum becomes more hydrophilic, dirt is further attracted and a vicious cycle is advanced to reduce the resistance in the vicinity of the surface of the photosensitive drum. This decrease in surface resistance of the photosensitive drum progresses as recording is performed, and image deletion occurs.

A corona charger, which is generally used as a charging process means for a photosensitive drum, is arranged such that the discharge opening is opposed to the photosensitive drum in a non-contact manner, and a high voltage is applied to the corona charger from the discharge opening. By exposing the surface of the photosensitive drum to the discharged discharge corona, the surface of the photosensitive drum is uniformly charged to a predetermined polarity and potential, and the generation of many discharge products causes the above-described image deletion to occur remarkably. .

Therefore, in the case of an image recording apparatus in which the toner remaining on the surface of the photosensitive drum after the toner image transfer is removed by a cleaning process means as a dedicated device, a cleaning member such as a blade contacting the photosensitive drum. To remove residual toner after transfer from the surface of the photosensitive drum, and at the same time to polish the surface of the photosensitive drum and gradually scrape the surface of the photosensitive drum, which reduces the resistance by discharge. Maintain sex
Measures are taken to prevent the occurrence of the image deletion phenomenon.

However, in the case of the image recording apparatus of the cleanerless system as described above, since there is no cleaning process means for scraping the surface of the photosensitive drum to renew the surface, the resistance in the surface direction of the photosensitive drum caused by the discharge products. There is a problem in that the deterioration progresses as recording is performed and image deletion occurs.

Further, even in the case of an image recording apparatus having a structure in which the toner remaining on the surface of the photosensitive drum after the toner image is transferred is removed by a cleaning process means as a dedicated device, the image carrier is an amorphous silicon photosensitive member. As described above, in the case of a material having a high hardness and difficult to be surface-polished, there is a problem in that the resistance reduction in the surface direction of the photosensitive drum due to the discharge products progresses as recording is performed and image deletion occurs.

An object of the present invention is to solve the problem of image deletion due to discharge products and to provide an image recording apparatus capable of maintaining high quality recording for a long period of time.

[0020]

SUMMARY OF THE INVENTION The present invention is an image recording apparatus having the following configuration.

(1) An image forming apparatus in which an image forming process including a step of uniformly charging the image bearing member is applied to the image bearing member to perform image formation, and the image bearing member is repeatedly used for image formation. In the above, the means for uniformly charging the image carrier is a charger that is in contact with the image carrier and a voltage is applied to the image carrier, and the image carrier when a voltage not higher than the minimum discharge start voltage is applied to the charger. An image recording apparatus using a charging device and an image carrier, the charging amount of which is 80% or more of the applied voltage.

(2) The potential difference of the image carrier before and after applying a voltage equal to or lower than the minimum discharge start voltage to the charger is 80% of the applied voltage.
The image recording apparatus described in (1) is characterized by using the charger and the image carrier as described above.

(3) The image recording apparatus as described in (1) or (2), wherein the voltage applied to the charger is a DC voltage.

(4) The image recording apparatus according to (1) or (2), wherein the voltage applied to the charger is a superimposed voltage of a DC voltage and an alternating voltage.

(5) The image bearing member is a photoconductive photoconductor, and the outermost layer of the photoconductor has a layer in which conductive fine particles are dispersed in a binder resin, and is charged to the electronic level of the outermost layer. The image recording apparatus described in any one of (1) to (4), characterized in that an electric charge is directly injected from a container to charge the surface of the photoconductor.

(6) The charger is a conductive fiber brush member, and the conductive fiber brush portion is in contact with the image bearing member (1) to (5). The image recording device described in 1.

(7) The charging device is a magnetic brush member in which conductive magnetic particles are magnetically restrained, and the magnetic brush portion is in contact with the image carrier (1) to (5).
The image recording apparatus according to any one of 1.

(8) The image recording apparatus described in any one of (1) to (7), wherein the charger is rotatable.

(9) An electrostatic latent image is formed on the uniformly charged surface of the image carrier by the charging device, the electrostatic latent image is visualized as a toner image by the toner charged by the developing device, and the toner image is covered. The image is formed by being transferred to the transfer member,
The image recording apparatus according to any one of (1) to (8), wherein the image carrier is repeatedly used for image formation.

(10) The image recording apparatus as described in (9), wherein the toner remaining on the image carrier after transfer is at least temporarily collected by a charger.

(11) The image recording apparatus according to (9), wherein the toner remaining on the image carrier after the transfer is collected by a developing device.

(12) The image bearing member is a photoconductive photosensitive member, and an electrostatic latent image is formed on the uniformly charged surface of the photosensitive member by a charging device by exposure (9) or (1
The image recording device according to 0).

(13) A photoconductive image carrier, a charger which contacts the image carrier and uniformly charges the image carrier by applying a voltage, and a uniformly charged surface of the image carrier. An exposure device that forms an electrostatic latent image by exposure to light, a developing device that visualizes the electrostatic latent image as a toner image with charged toner, and a transfer device that transfers the toner image from the image carrier side to the transfer target side. The toner remaining on the image carrier after transfer is at least temporarily collected by the charger and the image carrier is repeatedly used for image formation, and the voltage below the minimum discharge start voltage is applied to the charger. An image recording device using a charger and an image carrier, in which the potential difference between the image carrier before and after the application is 80% or more of the applied voltage.

(14) A photoconductive image carrier, a charger which contacts the image carrier and uniformly charges the image carrier by applying a superimposed voltage of a DC voltage and an alternating voltage, and the image carrier. An exposing device that forms an electrostatic latent image on the uniformly charged surface of the carrier by exposure, a developing device that visualizes the electrostatic latent image as a toner image with charged toner, and the toner image is transferred from the image carrier side. It has a transfer device for transferring to the member side, and the toner remaining on the image carrier after transfer is at least temporarily collected by the charger and the image carrier is repeatedly used for image formation, and the minimum discharge to the charger. An image recording apparatus using a charger and an image carrier, wherein a potential difference of the image carrier before and after applying a voltage equal to or lower than a start voltage is 80% or more of an applied voltage.

(15) The outermost surface layer of the image bearing member has a layer in which conductive fine particles are dispersed in a binder resin, and an electric charge is directly injected into the electronic level of the outermost surface layer from a charger to expose the surface of the image bearing member. The image recording apparatus according to (13) or (14), which is charged.

(16) One of (13) to (15), wherein the charger is a brush member made of a conductive fiber, and the conductive fiber brush portion is in contact with the image carrier. The image recording device described in 1.

(17) Any one of (13) to (15), wherein the charger is a magnetic brush member magnetically restraining conductive magnetic particles, and the magnetic brush portion is in contact with the image carrier. The image recording device as described in any one of the above.

(18) The image recording apparatus as described in any one of (13) to (17), wherein the charger is rotatable.

(19) The image recording apparatus as described in any one of (13) to (18), wherein the toner remaining on the image carrier after the transfer is collected by a developing device.

(20) The charging device is provided in a process cartridge detachably attached to the main body of the image recording apparatus together with at least the image carrier (1) to (1).
The image recording device according to any one of 9).

<Operation> a) In the contact charger which contacts the image carrier and applies a voltage to uniformly charge the image carrier, the charging mechanism is as follows: There are "charging due to corona discharge" and "charging due to charge injection" at the contact portion with the image carrier. Depending on the configuration of the charging device, the ratio of charging by corona discharge and charging by charge injection is greatly different.

In the present invention, attention is paid to the ratio of discharge and charge injection contributing to charging, and by using a charger and an image carrier in which charging by charge injection is dominant, discharge generation of active oxygen or the like generated by discharge is generated. This is to prevent deterioration of the image carrier (reduction of charge retention) due to an object, that is, to solve the problem of the image deletion phenomenon.

An important point in the present invention is not the constitution of each of the charger and the image carrier but the charge injection ability when the two are combined, and as a result of the study conducted by the present inventors, the discharge is theoretically performed. It is important that the image bearing member is charged to 80% or more of the applied voltage when a voltage that cannot occur in the contact charging device is applied to the contact charger. Since no discharge is generated even when the image carrier is charged, it is possible to prevent the resistance in the surface direction of the image carrier from lowering due to the generation of the discharge products and the resulting image deletion.

Here, the minimum discharge starting voltage means the minimum value of the discharge starting voltage according to the Paschen's law. It is approximately 325 V under normal temperature and normal humidity.

That is, without substantially using charging by discharge,
By charging the image carrier by injecting charge, deterioration such as low resistance of the image carrier caused by discharge products is prevented, and even in a cleanerless image recording apparatus, no image deletion occurs. It is possible to maintain high-quality image output for a long period of time. Further, by almost completely eliminating the discharge, it is also very effective in preventing the deterioration of other component parts / members of the apparatus due to the discharge products.

B) Regardless of whether the voltage applied to the contact charger is a DC voltage only or the alternating voltage is a superposed voltage, the image bearing member has a layer in which conductive fine particles are dispersed in a binder resin as the outermost layer. By directly injecting a charge from the contact charger to the electronic level of the outermost layer to charge the image bearing member, the image bearing member can be efficiently charged by the charge injection, and the charging by the discharge is substantially performed. The object of the present invention can be achieved with advantage.

C) Further, as the contact charger, a rotatable fur brush (brush member of conductive fiber) is used, and more preferably, a magnetic brush member in which conductive magnetic particles are magnetically restrained is used to efficiently inject charges. It is possible to achieve the object of the present invention in a more advantageous manner.

[0048]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 4) (1) Schematic configuration of an example of an image recording apparatus FIG. 1 is a schematic configuration diagram of an example of an image recording apparatus according to the present invention. The image recording apparatus of this example is a laser beam printer using a transfer type electrophotographic process, and is a cleanerless system apparatus in which a fur brush charger is used as a contact charger of an image carrier and simultaneous cleaning is performed by a developing device. is there.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (photosensitive drum) as an image bearing member. The photosensitive drum 1 is rotationally driven in the clockwise direction indicated by the arrow at a predetermined peripheral speed around the central support shaft, and in the course of the rotation, a fur brush charger 2 as a contact charger is used to obtain a negative polarity in the present example. Received a charging process like this.

Then, it is outputted from the exposure device 3 such as a laser scanner to the uniformly charged surface of the rotating photosensitive drum 1.
Scanning exposure L is performed by the laser light modulated corresponding to the image signal sent from the host device such as an image reading device (not shown) to the printer side, so that the surface of the rotary photosensitive drum 1 is scanned and exposed. The electrostatic latent image corresponding to is sequentially formed.

The electrostatic latent image formed on the surface of the rotating photosensitive drum 1 is successively developed as a toner image by the developing device 4 in the present embodiment by reversal development with negatively frictionally charged toner (negative toner).

On the other hand, a recording material (transfer material) P as a material to be transferred from a paper feeding mechanism portion (not shown) is a contact nip portion between the photosensitive drum 1 and the transfer roller 5 as a transfer process means at a predetermined control timing. By being fed to the transfer section T,
The toner image on the surface of the photosensitive drum 1 is transferred to the surface of the fed recording material P.

The recording material P which has received the transfer of the toner image through the transfer portion T is sequentially separated from the surface of the photosensitive drum 1 and conveyed to the fixing device 6, where it is subjected to heat fixing of the toner image to form an image-formed product (print). , Copy) is output.

After the toner image is transferred onto the recording material P, the surface of the rotary photosensitive drum 1 is repeatedly subjected to the image formation by the above-mentioned image formation cycle.

(2) Photosensitive drum 1 The photosensitive drum 1 as an image bearing member in this example is an OPC (organic photosensitive member) drum having a charge injection layer on its outermost surface, and the drum diameter is 30 mm and the lengthwise direction is 30 mm. The length is approximately 210 mm, and the rotational peripheral speed is 100 mm / sec.

FIG. 2 shows a model diagram of the layer structure of the photosensitive drum 1. That is, 11 is a conductive drum substrate, and this example is an aluminum drum substrate. This drum base 11
The undercoat layer 12 and the positive charge injection prevention layer 1 are sequentially formed on the outer peripheral surface of the
3, the charge generation layer 14 and the charge transport layer 15 are applied in an overlapping manner to form a general OPC photosensitive layer, and the charge injection layer 16 is applied to the outer peripheral surface of the layer. The charge injection layer 16 is the outermost layer of the photosensitive drum 1.

The charge injection layer 16 in this example comprises a photocurable acrylic resin, a SnO ₂ ultrafine particle 16a (diameter of about 0.03 μm), a lubricant such as tetrafluoroethylene resin (Teflon), a polymerization initiator, etc. Is mixed and dispersed, and after coating, a film is formed by a photo-curing method.

The resistance value of the charge injection layer 16 is 1 × 10.
^{The range of 9} to 1 × 10 ¹⁴ Ω · cm is suitable. This is because a resistance in this range is capable of injecting charges, and does not cause image deletion due to the charge injection layer, and neutralizes the counter charge of the charge transport layer 15 at the time of exposure to form a good charge injection layer having no residual potential. I was able to. Furthermore, considering the resistance fluctuation in use environment such as high temperature and high humidity or low temperature and low humidity, 1 x 1
A resistance value in the range of 0 ¹² to 1 × 10 ¹³ Ω · cm was used.
Further, the contact angle of water on the surface of the photosensitive drum was 90 degrees or more, and the contactability with the fur brush charger 2 as a contact charger was good.

(3) Fur brush charger 2 The fur brush charger 2 used in this example is a conductive core metal 2c.
The resistance-adjusted fiber 2a is attached to the outer peripheral surface of the conductive base cloth 2b.
It is a roller-type conductive fiber brush member prepared by fixing a pile cloth woven into the.

In this example, carbon black is dispersed in rayon, and a fiber having a thickness of 300 denier / 50 filaments whose resistance is adjusted to 5 × 10 ⁵ Ω · cm is used.
A pile cloth having a planting density of 155 pieces / mm ² and a fiber length of 5 mm was electrically fixed on the core metal 2c having a diameter of 6 mm.

The fur brush charger 2 is arranged such that the brush portion of the conductive fiber brush 2a is in contact with the surface of the photosensitive drum 1, and the fur brush charger 2 is in contact with the photosensitive drum 1 (charging portion). At a, the rotational speed is set to 200% in the opposite direction relative to the surface of the photosensitive drum, and the charging bias applying power source S is applied to the core metal 2c of the fur brush charger 2.
A direct current voltage of 1 to -700 V was applied.

As a result, in this embodiment, the surface of the rotary photosensitive drum 1 is uniformly charged by the contact charging / charge injection charging method to the same potential as the DC voltage -700 V applied to the fur brush charger 2. By subjecting the uniformly charged surface of the photosensitive drum 1 to image exposure L by the exposure device 3, the surface of the photosensitive drum corresponding to the bright portion of the exposure is selectively discharged or the potential is attenuated to correspond to the exposed image pattern. An electrostatic latent image is formed.

(4) Developing Device 4 The developing device 4 of this example is of the jumping developing system / reverse developing system, 4a is a developing sleeve of the developing device, and this developing sleeve 4a is between the photosensitive drum 1. 0.3 mm
Are opposed to each other with a gap of, and are rotationally driven in the counterclockwise direction indicated by an arrow at a predetermined peripheral speed, and the developer in the developing device 4 is applied to the peripheral surface in a thin layer by the blade member 4b. The developer application surface of the developing sleeve 4a faces the electrostatic latent image forming surface of the photosensitive drum 1.

S2 is a power source for applying a developing bias to the developing sleeve 4a. In this example, a DC voltage of -500V, a frequency of 2.0KHz, and a peak-to-peak voltage of 1.6k.
By applying a voltage in which an alternating (alternating) voltage of V is superposed, the developer thin layer on the developing sleeve 4a is negatively frictionally charged in the developing portion b, which is the opposing portion of the photosensitive drum 1 and the developing sleeve 4a. Toner (negative toner) is the photosensitive drum 1.
The electrostatic latent image on the surface of the photosensitive drum 1 is reversely developed by selectively adhering to the exposed bright portion of the electrostatic latent image on the surface by the electric field of the applied developing bias.

(5) Transfer Roller 5 The transfer roller 5 as the transfer step means of this embodiment is
A medium resistance foam layer 5a is formed on the outer periphery of the conductive core metal 5b,
The resistance value is 5 × 10 ⁸ Ω. The transfer roller 5 is disposed so as to contact the surface of the photosensitive drum 1 with a predetermined pressing force to form a transfer portion T, and rotates in the forward direction of the rotation of the photosensitive drum 1 at substantially the same peripheral speed as the photosensitive drum 1. Driven. Alternatively, it rotates following the rotation of the photosensitive drum 1.

S3 is a power supply for applying a transfer bias to the transfer roller 5. In this example, the recording material P is transferred to the transfer portion T.
By passing a DC voltage of +2.0 kV from the power source S3 to the transfer roller 5 while passing through,
The back surface of the transfer material P is positively charged with a polarity opposite to that of the toner of the toner image, and the toner image on the surface of the photosensitive drum 1 is recorded on the recording material P.
Are sequentially electrostatically transferred to the surface of.

The recording material P which has received the transfer of the toner image through the transfer portion T is sequentially separated from the surface of the photosensitive drum 1 and conveyed to the fixing device 6, where it is subjected to heat fixing of the toner image and output as an image formed product. To be done.

(6) Simultaneous development cleaning The transfer residual toner adheres on the photosensitive drum 1 after the transfer in a certain pattern according to the image. In the case of an image recording apparatus provided with a cleaning process means as a dedicated device, as the photosensitive drum 1 continues to rotate, the cleaning process means removes the transfer residual toner and the cleaned photosensitive drum surface reaches the charging portion a and is charged again. Although it is processed and repeatedly used for image formation, in the case of a cleanerless image recording apparatus, the transfer residual toner on the photosensitive drum 1 after transfer reaches the charging portion a as it is as the photosensitive drum 1 continues to rotate.

The untransferred toner on the photosensitive drum 1 which has reached the charging portion a is diffused by the fur brush charger 2 which is in contact with the surface of the photosensitive drum 1 to be non-patterned. The non-patterning of the transfer residual toner prevents the ghost image corresponding to the image pattern of the transfer residual toner from appearing on the recording material in the next transfer process. At the same time as the transfer residual toner is diffused and unpatterned, the fur brush charger 2 uniformly charges the surface of the rotary photosensitive drum 1 in a predetermined manner.

Further, the fur brush charger 2 takes in at least a part of the diffusion / non-patterned transfer residual toner into the fur brush and at least temporarily collects it. The transfer residual toner collected and collected at least temporarily by the fur brush charger 2 is then transferred to the photosensitive drum 1.
Is released on.

The transfer residual toner diffused and non-patterned by the fur brush charger 2 and the toner discharged from the fur brush charger 2 are continuously rotated.
To the developing portion b, and at the same time as the development of the electrostatic latent image on the photosensitive drum 1 side by the developing sleeve 4a of the developing device 4 during the subsequent development, the DC voltage of the developing bias voltage applied to the developing sleeve 4a and the photosensitive voltage are applied. The fog-removing potential difference Vback, which is the potential difference between the drum surface potentials, is collected on the developing sleeve side.

That is, the untransferred toner on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the developing device 4 by simultaneous cleaning.

In the image exposure unit between the charging unit a and the developing unit b, the transfer residual toner diffused and non-patterned on the rotary photosensitive drum 1 and the fur brush charger 2
Although there is toner released from the toner, the amount of toner is practically small and it does not substantially affect the formation of the electrostatic latent image by image exposure.

When the transfer residual toner amount increases due to an increase in the image ratio or the like, an operation of discharging the toner in the brush by applying an accelerating bias before or after printing or during non-recording during printing. Was done.

(7) Evaluation of charge injection capability and image flow in combination of various photosensitive drums and various contact chargers In the cleanerless printer as described above, the following A
The charge injection capability and the image deletion were evaluated in each of the cases of C to C.

A: Example 1 When the fur brush charger 2 was used as the contact charger, and the OPC photosensitive drum 1 having the charge injection layer 16 as the outermost layer as shown in FIG. 2 was used as the image carrier B; Comparative example 1 In the case where the fur brush charger 2 is used as the contact charger and the conventional OPC photosensitive drum without the charge injection layer 16 is used as the image carrier, the charge injection layer 16 is removed from the OPC photosensitive drum 1 in FIG. Comparative Example 2 A charging roller (roller charger) is used as a contact charger,
The image carrier is the charge injection layer 1 from the OPC photosensitive drum 1 of FIG.
Conventional OPC without the charge injection layer 16
When a photosensitive drum is used Here, the charging roller in the case of C is composed of a core metal having a diameter of 6 mm and an elastic resistance layer formed in a thickness of 3 mm, and the resistance of the charging roller is a total pressure of 1 kg on the metal drum. Then, a voltage of 100 V was applied between the core metal and the metal drum, and the measurement was 1 × 10 ⁶ Ω.

FIG. 3 is a diagram showing the difference in charging characteristics in each of the cases A to C. The horizontal axis shows the DC bias applied to the fur brush charger, which is a contact charger, or the charging roller, and the vertical axis shows the fur brush when the photosensitive drum and the far brush charger or the charging roller are rotated and the potential on the surface of the photosensitive drum becomes stable. A bias is applied to the charger or the charging roller, and the potential difference before and after the bias is shown.

A) In the contact charging, frictional charging occurs due to the contact between the photosensitive drum and the fur brush charger or the roller charger. Therefore, standardization is shown to evaluate the net charge amount when the bias is applied to the charger.

When the charging roller of the contact charger and the photosensitive drum without the charge injection layer 16 of Comparative Example 2 were used, the charging was recognized under the minimum discharge starting voltage at which discharge could not occur. No (potential convergence rate 0%), it was confirmed that there was almost no charging due to charge injection. Since the charging roller is in surface contact with the photosensitive drum and the contact point with the photosensitive drum is uneven, uniform charging is difficult.

Therefore, as shown in FIG. 3C, the photosensitive drum is charged to a desired potential by applying a bias to the charging roller above the discharge threshold. However, at this time, a large amount of discharge products are generated, which causes a problem of image deletion.

In other words, in order to prevent image deletion, it is necessary to carry out charging by direct injection of charges. In the charging by the charge injection, unlike the charging by the discharge, the contact part (charging part) a
Can only be charged in a narrow range. Therefore, it is important how to secure the contacts evenly and finely.

B) The fur brush charger as the contact charger and the charge injection layer 1 as the photosensitive drum of B of Comparative Example 1
In the case of using one without 6, the potential rises slightly to the photoconductor even at 325V (under 1 atmospheric pressure) which is the minimum discharge start voltage (Vmin) as shown in FIG. 3B. Therefore, the charging is performed by the charge injection.

However, in the case of B, Vmin
At, only about 30% of Vmin can be charged (potential convergence rate of 30%). Therefore, when the photosensitive drum potential of -700 V is actually required, the applied voltage of -950 V is required, and the charge obtained by the charge injection is about 30% at the most, and the remaining 70% is the local discharge. Since the charging is performed by, the discharge product accompanying the discharge is naturally generated, so that the image deletion occurs and the quality of the recorded image deteriorates.

C) In contrast to these comparative examples, in the case of the A of Example 1, which uses the fur brush charger as the contact charger and the charge injection layer 16 as the photosensitive drum, Thus, when Vmin is applied,
It can be seen that the charging is possible up to a potential of approximately Vmin, and the charging is achieved by the charge injection (potential convergence rate 80
%).

When printing was repeated in the printer in the case of A which is Example 1, it was possible to carry out image recording for a long period of time without image deletion.

From the correlation between the phenomenon of image flow and the potential convergence rate when Vmin is applied, if the potential convergence is up to 80%, the image is not deteriorated and a good recording apparatus can be constructed.
It has been confirmed that it is sufficient if it can be made within 80% even if they do not completely match.

D) Further, the results of the examination by the present inventors will be shown. In Comparative Example 1, the fiber resistance of the fur brush charger was set to 1
× was 10 ⁵ Ω · cm, the pair photosensitive drum relative velocity of the fur brush 300%. In this case, Comparative Example 3 was used to evaluate the potential convergence rate and the image deletion image.

In Example 1 and Comparative Examples 1 to 3, the image deletion was evaluated by evaluating the image after printing 5,000 sheets and judging from the amount of collapse of the checkered pattern image in the image.

In Comparative Example 3, the potential convergence rate of 70% was obtained, but in the evaluation of the image, the occurrence of image deletion was recognized.

Examples 2 and 3 relate to Examples 2 and 3 described later.

[0091]

[Table 1] e) In the above-mentioned configuration, only the DC voltage is applied as the bias applied to the fur brush charger as the contact charger or the charging roller, but an alternating voltage is applied to accelerate the non-patterning of the transfer residual toner and to improve the charging property. It is desirable to overlap. By applying an alternating voltage, a DC component potential is stably applied to the photosensitive drum.

Similar to FIG. 3, FIG. 4 shows the results of measuring the charging characteristics in the charging configurations of Example 1 (A) and Comparative Examples 1 (B) and 2 (C).

Here, in FIG. 4, in B or C, when a photosensitive drum potential of −700 V is required,
In order to fill the potential amount b in B and c in C, it is necessary to superimpose a high AC voltage having a peak-to-peak voltage that is at least twice the discharge start voltage, and discharge the drum for charging. For example, frequency 800Hz, peak-to-peak voltage 1.2k
Stable charging can be performed by superimposing the V sine wave.

On the other hand, in A, since the charging is sufficiently performed, it is possible to satisfy the non-patterning of the transfer residual toner and the charging property by applying a low AC voltage.

The charger and the photoconductor of this structure are AC biased.
Even in a system in which is superposed, discharge does not occur, so that defects such as image deletion can be eliminated and good image recording can be performed.

F) In the present embodiment, as the charge injection layer 16 of the photosensitive drum 1, a resistance-adjusted functional layer having excellent lubricity is added to improve the charge injection efficiency. It is considered that the same effect can be obtained by providing the surface layer of the photoconductor.

In addition, many inorganic compounds have excellent charge injection properties by themselves. For example, regardless of the crystal type, a metal semiconductor such as silicon or selenium shows relatively excellent charge injection characteristics.

G) In addition to the above-described structure, the same effect can be obtained in a structure in which the charging process also serves as the cleaning process, or in a structure in which the cleaning process is temporarily collected by the charging device and then passed through the drum and then collected by the developing device. .

As described above, in the image recording apparatus in which the charging device or the developing device also serves as the drum cleaning process, the charge injection is predominantly performed to solve the problem of the image deletion due to the discharge products. It is possible to maintain high-quality image recording for a long period of time.

Here, according to the result of the examination by the present inventors, Vm
It was confirmed that the object of the present invention can be sufficiently achieved when the charge amount in is 80% or more of the applied potential.

<Embodiment 2> (FIG. 5) In this embodiment, a magnetic brush charger 2A is used in place of the fur brush charger 2 as the contact charger in the printer of Embodiment 1 described above. The other device configurations are the same.

FIG. 5 shows a magnetic brush charger 2A used in this example.
The schematic configuration of is shown. The magnetic brush charger 2A of this example is a sleeve rotation type.

The magnetic brush charger 2A includes a magnet roll 2f fixedly supported and a magnet roll 2f.
A non-magnetic charging sleeve 2e, which is concentrically rotatably fitted around the outer circumference of f, and conductive magnetic particles formed on the outer peripheral surface of the charging sleeve 2e by being attracted and held by the magnetic force of a magnet roll 2f inside the charging sleeve. It is composed of a magnetic brush layer 2d of (conductive magnetic carrier).

The magnet roll 2f was prepared by magnetizing the magnetic roll at a uniform magnetic flux density of 0.08 (T).

The conductive magnetic particles constituting the magnetic brush layer 2d have an average particle size of 30 μm and a volume resistance of 1 × 10.
⁶ Ωcm ferrite particles with a saturation magnetization of 60 (A
・ M ² / kg) was used.

The average particle diameter of the conductive magnetic particles is indicated by the maximum chord length in the horizontal direction. The measuring method is determined by microscopically selecting 300 or more particles at random, measuring the diameters, and taking the arithmetic mean. It was

For measuring the magnetic characteristics of the conductive magnetic particles, a direct current magnetization BH characteristic automatic recording device BHH- manufactured by Riken Denshi Co., Ltd.
50 can be used. At this time, the diameter (inner diameter) 6.
A columnar container having a height of 5 mm and a height of 10 mm is filled with conductive magnetic particles under a load of about 2 g, and the saturation magnetization is measured from the BH curve while keeping the particles from moving in the container.

The resistance of conductive magnetic particles was measured by measuring the bottom area 22.
² g of the conductive magnetic particles were filled in a cylindrical container of 8 mm ² and pressurized, and a voltage of 100 V was applied from the top and bottom to calculate from the current flowing in this system and defined as normalized.

As the conductive magnetic particles, it is possible to use magnetic metal particles such as ferrite and magnetite, or particles obtained by fixing these magnetic particles with a resin. Resistance value is 1 ×
Those having a resistivity of 10 ⁶ to 10 ⁹ Ωcm are advantageous in terms of chargeability and pressure resistance against pinhole leak of the photosensitive drum. Also,
It is possible to improve the charging property by mixing and using a plurality of magnetic particles.

The magnetic brush charger 2A is arranged substantially in parallel with the photosensitive drum 1, and the end portion in the lengthwise direction is a spacer member so that the distance between the surface of the charging sleeve 2e and the surface of the photosensitive drum 1 is 0.5 mm. The magnetic brush layer 2d is disposed by abutting on the end surface of the photosensitive drum via (not shown).
Is formed in contact with the surface of the photosensitive drum 1 by forming a charging portion a having a predetermined width.

The charging sleeve 2e is rotationally driven in the charging portion a in the direction indicated by the arrow, which is the opposite direction to the rotational direction of the photosensitive drum 1, and accordingly, the magnetic brush layer 2d also rotates in the same direction so that the surface of the photosensitive drum 1 is rotated. Rub. Then, at the time of charging, a predetermined charging bias is applied to the charging sleeve 2e from the charging bias applying power source S1, so that the magnetic brush layer 2
Electric charges are injected into the photosensitive drum at the charging portion a through the conductive magnetic particles of d, and the surface of the photosensitive drum is finally charged to the same potential as the magnetic brush.

In this example, the photosensitive drum is the first embodiment.
Similarly to the above, as shown in FIG. 2, the charge injection layer 16 having a resistance adjusted and excellent in slipperiness is added to the surface of a general OPC photosensitive drum.

Since the magnetic brush charger 2A functions as an electrode that uniformly contacts the member to be charged (photosensitive drum), it is a charger excellent in charging by charge injection. Therefore, the charging due to the charge injection is dominant and the amount of discharge is extremely small, so that there is no reduction in image flow due to discharge products, and the apparatus of this configuration enables high-quality image recording for a long period of time.

In the constitution of this example, as shown in Table 1 as Example 2, the surface potential (convergence rate of potential) of the photosensitive drum at the time of applying the DC voltage of Vmin reached 96%, and the image deletion was evaluated sufficiently. was gotten.

<Third Embodiment> In this embodiment, in order to efficiently perform charge injection in the second embodiment, the contact property of the magnetic brush charger 2A is improved and a charge injection layer is used as a photosensitive drum. This is an example in which the image deterioration is improved by applying a photosensitive drum which is generally used in the past and which is not provided.

In this example, the average particle size of the conductive magnetic particles forming the magnetic brush layer of the magnetic brush charger is determined by the second embodiment.
The fineness was changed from 30 μm in Example 1 to 15 μm. As a result, the density of the contact points with the photosensitive drum surface in the charging section is high, and the magnetic brush structure is capable of uniformly contacting the photosensitive drum surface. The other characteristics of the conductive magnetic particles are the same as those of the conductive magnetic particles in the second embodiment. The photosensitive drum is a commonly used photosensitive drum that does not have a charge injection layer. The device configuration other than the above is the same.

In the configuration of this example, as shown in Table 1 as Example 3, the photosensitive drum surface potential (potential convergence rate) when Vmin DC voltage is applied reaches 85%, which is sufficient for image deletion evaluation. Results were obtained.

<Modifications, etc.> 1) The present invention is not limited to the device configurations of the first to third embodiments. For example, as a contact charger, a charging roller using conductive rubber or conductive sponge, It is also possible to use a charger that does not rotate even if it is a magnetic brush or a fur brush, and is applicable to all contact-type charging devices.

2) Regarding the photoconductor as the image bearing member,
It is desirable to have a low resistance layer with a surface resistance of 10 ⁹ to 10 ¹⁴ Ω · cm from the viewpoint of preventing charge generation and ozone generation. However, even for organic photoreceptors other than the above, contact charger contamination prevention is also possible. With respect to, a sufficient effect can be obtained.

3) Further, the image exposing means as the information writing means for the charged surface of the image carrier is limited to the laser scanning exposing means for forming a digital latent image as shown in the embodiment. Instead of ordinary analog image exposure or other light emitting element such as LED, a combination of a light emitting element such as a fluorescent lamp and a liquid crystal shutter can form an electrostatic latent image corresponding to image information. It doesn't matter if it is a thing.

The image carrier may be an electrostatic recording dielectric or the like. In this case, after the primary surface of the dielectric surface is uniformly charged to a predetermined polarity and potential, the target electrostatic latent image is selectively discharged by a discharging means such as a discharging needle head (multi-needle electrode head) or an electron gun. The image is written and formed.

4) As the developing method, other developing methods than those in the embodiment may be used. Preferably, the one-component contact development or the two-component contact development, in which the developer is developed in contact with the image bearing member, is effective in further enhancing the simultaneous toner recovery effect during development.

It is also effective to use polymerized toner (spherical toner) as the toner particles in the developer. In addition to the above-described one-component contact development and two-component contact development, one-component non-contact development and two-component non-contact development are also possible. A sufficient toner collecting effect can be obtained by other developing methods.

Of course, the regular developing method may be used.

5) As the transfer method, not only the roller transfer shown in the embodiment but also the blade transfer and other contact transfer charging methods, and further the transfer drum, transfer belt, intermediate transfer member, etc. It goes without saying that it is applicable not only to image formation but also to an image forming apparatus that forms a multicolor or full-color image by multiple transfer or the like.

6) As the waveform of the alternating voltage applied to the contact charger and the developing means, a sine wave, a rectangular wave, a triangular wave or the like can be appropriately used. Further, it may be a rectangular wave formed by periodically turning on / off the DC power supply. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

7) The contact charger may be provided in a process cartridge detachably attached to the main body of the image recording apparatus together with at least the image carrier.

8) Further, the electrophotographic photosensitive member as the image bearing member or the electrostatic recording dielectric member is made into a rotating belt type, and charging / charging
A toner image corresponding to the required image information is formed by means of the latent image forming / developing process, the toner image forming section is positioned on the reading display section for image display, and after the display, the toner image is transferred to a transfer material. There is also an image display device in which the image carrier is repeatedly removed from the surface of the image carrier without being used, and the image carrier is repeatedly used for forming a display image. The present invention is also effective in the case where such a toner image after display is cleaned and removed by the charging means and the developing means at the same time as the cleaning in the image display device to form a cleanerless system device.

9) The present invention is also effective in preventing the adverse effects of discharge products in an image recording apparatus in which the transfer residual toner on the surface of the image carrier after transfer is removed by a cleaning device as a dedicated device.

[0130]

As described above, according to the present invention, an electrophotographic system / electrostatic system including a step of uniformly charging an image carrier such as an electrophotographic photosensitive member / electrostatic recording dielectric is carried out. An image formed by a discharge product of an image recording apparatus (image forming apparatus) such as a copying machine or a printer that performs image formation by applying an image forming process such as an electric recording method, and the image carrier repeats image formation. It is possible to solve the problem of flow and maintain high-quality recording for a long time even in the image recording apparatus of the cleanerless system. Also, other adverse effects due to the discharge products can be eliminated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image recording apparatus according to a first embodiment.

FIG. 2 is a model diagram of the layer structure of a photosensitive drum.

FIG. 3 is a graph showing charging characteristics (No. 1)

FIG. 4 is a graph showing charging characteristics (No. 2)

[Fig. 5] Configuration model diagram of magnetic brush charger

[Explanation of symbols]

1 ・ ・ Image carrier (photosensitive drum), 2, 2A ・ ・ Contact charger (fur brush charger, magnetic brush charger), 3 ・ ・
Image exposure device, 4 ・ ・ Developing device, 5 ・ ・ Transfer roller, 6 ・ ・
Fixing device, S1 to S3 ... Biasing power supply, P ... Transferred member (recording material)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Mashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Jun Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non Inc. (72) Inventor Nobuyuki Ito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (20)

[Claims] 1. An image forming apparatus in which an image forming process including a step of uniformly charging the image carrier is applied to the image carrier to perform image formation, and the image carrier is repeatedly subjected to image formation. The means for uniformly charging the image carrier is a charger that is in contact with the image carrier and a voltage is applied to the image carrier, and the charge of the image carrier when the voltage below the minimum discharge start voltage is applied to the charger. An image recording apparatus comprising a charging device and an image carrier having a charge amount of 80% or more of an applied voltage. 2. The charger and the image carrier, wherein the potential difference of the image carrier before and after applying a voltage equal to or lower than the minimum discharge start voltage to the charger is 80% or more of the applied voltage. The image recording device described in 1. 3. The image recording apparatus according to claim 1, wherein the voltage applied to the charger is a DC voltage. 4. The image recording apparatus according to claim 1, wherein the voltage applied to the charger is a superimposed voltage of a DC voltage and an alternating voltage. 5. The image bearing member is a photoconductive photoconductor, and the outermost layer of the photoconductor has a layer in which conductive fine particles are dispersed in a binder resin, and a charger is provided at the electronic level of the outermost layer. 5. The image recording apparatus according to claim 1, wherein the surface of the photoconductor is charged by directly injecting a charge from the image recording apparatus. 6. The charging device according to claim 1, wherein the charging device is a brush member made of a conductive fiber, and the conductive fiber brush portion is in contact with the image carrier. Image recording device. 7. The charging device is a magnetic brush member magnetically restraining conductive magnetic particles, and the magnetic brush portion is in contact with the image carrier. The image recording device described in 1. 8. The image recording apparatus according to claim 1, wherein the charger is rotatable. 9. An electrostatic latent image is formed on a uniformly charged surface of an image carrier by a charging device, the electrostatic latent image is visualized as a toner image by toner charged by a developing device, and the toner image is transferred. 9. The image recording apparatus according to claim 1, wherein the image bearing member is repeatedly transferred to a member for image formation and the image carrier is repeatedly used for image formation. 10. The image recording apparatus according to claim 9, wherein the toner remaining on the image carrier after transfer is at least temporarily collected by a charger. 11. The image recording apparatus according to claim 9, wherein the toner remaining on the image carrier after transfer is collected by a developing device. 12. The image carrier is a photoconductive photoconductor,
11. The image recording apparatus according to claim 9, wherein an electrostatic latent image is formed on the uniformly charged surface of the photoconductor by a charging device by exposure. 13. A photoconductive image carrier, a charger which contacts the image carrier and uniformly charges the image carrier by applying a voltage, and a uniformly charged surface of the image carrier. An exposure device that forms an electrostatic latent image by exposure, a developing device that visualizes the electrostatic latent image as a toner image with charged toner, and a transfer device that transfers the toner image from the image carrier side to the transfer target side. The toner remaining on the image carrier after transfer is at least temporarily collected by the charger and the image carrier is repeatedly used for image formation, and a voltage not higher than the minimum discharge start voltage is applied to the charger. An image recording apparatus using a charger and an image carrier, in which the potential difference between the front and rear image carriers is 80% or more of the applied voltage. 14. A photoconductive image carrier, a charger which contacts the image carrier and uniformly charges the image carrier by applying a superimposed voltage of a DC voltage and an alternating voltage, and the image carrier. An exposing device that forms an electrostatic latent image on the uniformly charged surface of the body by exposure, a developing device that visualizes the electrostatic latent image as a toner image with charged toner, and the toner image from the image carrier side to the transfer target member. It has a transfer device for transferring to the side, and the toner remaining on the image carrier after transfer is at least temporarily collected by the charging device, and the image carrier is repeatedly used for image formation, and the minimum discharge starts on the charging device. An image recording apparatus using a charger and an image carrier, wherein a potential difference of the image carrier before and after applying a voltage equal to or lower than a voltage is 80% or more of an applied voltage. 15. An image carrier having a layer in which conductive fine particles are dispersed in a binder resin as the outermost layer, and a charge is directly injected into the electronic level of the outermost layer from a charger to charge the surface of the image carrier. The image recording device according to claim 13, wherein 16. The charging device according to claim 13, wherein the charging device is a brush member made of a conductive fiber, and the conductive fiber brush portion is in contact with the image carrier. Image recording device. 17. The charging device is a magnetic brush member magnetically restraining conductive magnetic particles, and the magnetic brush portion is in contact with the image carrier.
The image recording apparatus according to any one of 1. 18. The image recording apparatus according to claim 13, wherein the charger is rotatable. 19. The image recording apparatus according to claim 13, wherein the toner remaining on the image carrier after the transfer is collected by a developing device. 20. The image recording apparatus according to claim 1, wherein the charger is provided together with at least the image carrier in a process cartridge detachably mountable to the main body of the image recording apparatus.