JPH05346683A - Developer for forming image - Google Patents

Abstract

PURPOSE:To efficiently impart electric charges to a toner at the time of exposure as well as to ensure satisfactory transfer characteristics and to obtain a stable toner image. CONSTITUTION:A developer consisting of a toner and a carrier is brought into contact with the photoconductive layer 1c of a photosensitive drum with a transparent electrode 1b and the photoconductive layer 1c successively formed on the transparent substrate la, the photoconductive layer 1c is irradiated with light from the substrate 1a side in accordance with information to be recorded while impressing bias between the developer and the electrode 1b, and the toner is stuck on the irradiated part of the photoconductive layer 1c to form a toner image. The toner is made of high resistance resin particles and the carrier is made of particles of a magnetic substance having lower resistance than the toner.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming developer used in an image forming apparatus such as an electrophotographic machine.

[0002]

2. Description of the Related Art An electrophotographic process using a charger that uniformly charges the entire surface of a photosensitive member by corona discharge is well known. In such an electrophotographic process, an electrostatic latent image is formed on a uniformly charged surface of a photoreceptor by exposure according to recorded information. Next, a high resistance magnetic toner charged in the opposite polarity is brought into contact with the electrostatic latent image on the photoconductor to form a toner image.

At the end of the developing unit, the high-resistance magnetic toner is in contact with a non-magnetic conductive sleeve containing a magnet roller, and an image portion (non-exposed portion) on the photosensitive member on which an electrostatic latent image is formed. The electric field is applied between the conductive sleeve and the conductive sleeve to inject charges. The high-resistance magnetic toner injected with electric charges is conveyed while being held by the conductive sleeve as the magnet roller rotates, and adheres to the electrostatic latent image on the image portion to form a toner image.

[0004]

However, in the above-mentioned conventional structure, ozone is generated by the corona discharge type charger for sufficiently injecting the electric charge into the high resistance magnetic toner, whereby the charger and the photosensitive member are exposed. There is a problem that the body surface and the like deteriorate.

Further, since the non-exposed portion becomes an image portion, there is a problem that the image forming efficiency is extremely low in the case of an image forming apparatus that handles characters as an image such as a printer.

In order to solve these problems, Japanese Patent Publication No. 2-4900 discloses a transparent support, a transparent electrode,
The photoconductor is sequentially provided with a photoconductive layer, and the photoconductive layer is charged by bringing the charged conductive magnetic toner into contact with the surface of the photoconductive layer.

According to this method, since the corona discharge type charger is not required, the image forming apparatus can be downsized and simplified. In addition, since ozone is not generated, the life of the photoconductor is extended. Further, since the charged conductive magnetic toner adheres to the exposed portion of the photoconductive layer to form a toner image, the image forming efficiency is increased when characters are handled.

However, in this case, the charge is injected from the conductive sleeve to the conductive magnetic toner only when the conductive magnetic toner is in contact with the photoconductive layer and the photoconductive layer is exposed. Poor injection efficiency. Therefore, a new problem that a stable image is hard to obtain is brought about.

[0009]

In order to solve the above-mentioned problems, a developer for image formation according to the present invention is provided with a photoconductive material of a photoconductor in which a transparent electrode and a photoconductive layer are sequentially formed on a transparent support. A developer consisting of toner and carrier is brought into contact with the layer, and while applying a bias between the developer and the transparent electrode, the photoconductive layer is irradiated with light from the transparent support side of the photoconductor in accordance with the recorded information, and is irradiated with light. An image forming developer that forms a toner image by attaching toner to a portion on the photoconductive layer, wherein the toner is composed of high-resistive resin particles, and the carrier has a lower resistance than the toner. It is characterized by being composed of magnetic particles.

[0010]

According to the above construction, the developer consisting of toner and carrier is brought into contact with the photoconductive layer of the photoconductor in which the transparent electrode and the photoconductive layer are successively formed on the transparent support, and the space between the developer and the transparent electrode is brought into contact. While applying a bias to the photoconductor, the photoconductive layer is irradiated with light from the transparent support side of the photoconductor according to the recorded information, and toner is attached to the portion on the photoconductive layer that has been irradiated with light to form a toner image. A developer for use, wherein the toner is made of high resistance resin particles, and the carrier is
Since it is composed of magnetic particles having a resistance lower than that of the toner, good transfer characteristics can be obtained, and charge can be efficiently injected into the toner during exposure. As a result, a stable toner image can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.
The explanation is based on the following.

As shown in FIGS. 1 and 2, the image forming apparatus of the present embodiment comprises a cylindrical photosensitive drum 1 rotatably supported, and an exposure device provided inside the photosensitive drum 1. 7, a developing device 2, and a transfer / fixing belt 8.

As shown in FIG. 7, the photosensitive drum 1 has three
It has a layered structure in which a transparent electrode 1b and a photoconductive layer 1c are sequentially laminated on the outer cylindrical surface of a cylindrical transparent support 1a.

The material of the transparent electrode 1b is, for example, In ₂
O ₃ and SnO ₂ are used. Se, ZnO, CdS, amorphous Si, or the like is used as the material of the photoconductive layer 1c. Specifically, the photosensitive drum 1 is formed, for example, by forming an In ₂ O ₃ film having a thickness of 0.5 μm on the transparent support 1 a by sputtering and then forming an amorphous Si layer having a thickness of 3 μm. It is obtained by doing.

The exposure device 7 is composed of, for example, an LED head 58 (described later) in which a light-emitting diode array is combined with a short focus lens array, and a video signal generated according to character data or image data to be recorded. The light is emitted based on. The emitted light is
The photoconductive layer 1 passes through the transparent support 1a and the transparent electrode 1b.
converged to c.

The developing device 2 is provided near the light irradiation position from the exposure device 7 and close to the photosensitive drum 1.
A developer tank 3 that stores the developer, a stirring roller 4 that stirs the developer in the developer tank 3, and an opening 3 a of the developer tank 3.
And a cylindrical developing sleeve 5 provided on the.

The developer is a high-resistance toner T and a toner T.
It consists of a lower resistance carrier. Toner T is
It is obtained by crushing a resin such as a styrene-acrylic copolymer to an average particle size of 10 μm and adding carbon thereto. The resistance value is set to about 10 ¹² Ωcm by adjusting the amount of carbon. The carrier is made of flat iron powder having an average particle size of about 30 μm, and the resistance value is set to 10 ⁴ Ωcm. The developer is obtained by mixing the above-mentioned toner T and carrier in a ratio of 3: 7.

The developing sleeve 5 is made of a non-magnetic conductive member such as aluminum or martensitic stainless steel, and as shown in FIG.
Are rotatably supported by bearings 33, 33 provided in respective opposing walls of the. One end of the developing sleeve 5 penetrates the developer tank 3 through a bearing 33, and a gear 31 for rotationally driving the developing sleeve 5 in the B direction is fixed to the penetrating portion.

In the developing sleeve 5, a hollow cylindrical magnetic roller 5a is rotatably inserted. The magnetic roller 5a is made of a magnet arranged so that the magnetic poles are alternately reversed, and when the magnetic roller 5a rotates, the radial magnetic field of the magnetic roller 5a is reversed. Similar to the developing sleeve 5, one end of the magnetic roller 5a also penetrates the developer tank 3 through a bearing 33, and a gear 32 for rotationally driving the magnetic roller 5a in the -B direction is fixedly provided in the penetrating portion. There is.

As a result, the developer is the magnetic roller 5a.
It is held on the surface of the developing sleeve 5 by the magnetic force from, and forms the magnetic brush 5c. The magnetic brush 5c rotates in the B direction, which is the opposite direction to the rotating direction of the magnetic roller 5a, by the rotation of the developing sleeve 5 (see FIG. 7).

The rotation axis of the developing sleeve 5 is parallel to the rotation axis of the photosensitive drum 1, so that the magnetic brush 5c formed on the surface of the developing sleeve 5 contacts the surface of the photoconductive layer 1c. The developing sleeve 5 is arranged. In addition, a doctor blade 6 that limits the length of the magnetic brush 5c is provided near the opening 3a of the developer tank 3, whereby the amount of developer conveyed can be adjusted to a predetermined amount. ing.

On the upper surface of the above-mentioned photosensitive drum 1, a transfer roller 9 arranged above the photosensitive drum 1
An endless belt-shaped transfer / fixing belt 8 is pressed. The transfer / fixing belt 8 has a photosensitive drum 1 on its surface.
The high-resistance toner T transferred from is fixed on the transfer paper P and the tension roller 11 disposed below the left side of the heating device 10. A pressure roller 12 is arranged close to the heating device 10.

The transfer / fixing belt 8 is made of a film material mainly composed of a polyimide resin having excellent mechanical strength and high heat resistance. However, the material is not limited to this material as long as the surface on the side to which the high-resistance toner T is transferred has an insulating property.
A metal belt such as an electroformed nickel belt as a base material may be coated with fluorine. Also,
The surface may be rough so that the gloss of the image is appropriate. Considering thermal conductivity and mechanical strength, the thickness of the transfer / fixing belt 8 is preferably about 10 to 200 μm.

The heating device 10 heats and melts the high resistance toner T transferred onto the surface of the transfer / fixing belt 8. The heating is performed by a planar heating element 10 a provided on the upper surface of the heating device 10 so as to directly contact the surface of the transfer / fixing belt 8. The heating element 10a is composed of a ceramic heater in which a planar Mo-based heating element is printed on an alumina ceramic substrate and a glass coat layer is printed and laminated thereon.

In addition to the above, the image forming apparatus has a main motor 13 which is a drive source of a rotary drive system, a conveying section 14 which conveys the transfer sheet P to the heating device 10, and a delivery unit which ejects the transfer sheet P to the outside. A paper section 21 is provided. In this embodiment, a stepping motor is used as the main motor 13.

The transport unit 14 includes a pair of paper feed rollers 18
18, a pair of registration rollers 19 and 19, and conveyance guide plates 15 and 15. A paper feed actuator 16 is provided in front of the paper feed roller 18 (on the paper feed side), and a switch (not shown) for detecting whether or not the transfer paper P has been loaded into the transport unit 14 is turned on / off. OFF
It is supposed to do. In addition, in the upper part of the developer tank 3,
A sheet feeding solenoid 20 is provided to control the rotation of the registration roller 19. As a result, the timing at which the transfer paper P conveyed by the registration roller 19 reaches the position of the heating element 10a of the heating device 10 is controlled so that the toner image on the transfer / fixing belt 8 is fixed on the transfer paper P. It

The paper output section 21 has paper output guide plates 22 and 22 for guiding the output of paper and a pair of paper output rollers 25 and 25. A paper output actuator 23 is provided in front of the paper output guide plate 22 (on the side of the heating element 10a), and a switch (not shown) for detecting whether the transfer paper P has been output is turned on / off. It is like this.

The transfer / fixing belt 8 and the heating device 1
0 and the photosensitive drum 1 may be integrated into one unit.

Next, the control system of the image forming apparatus is shown in FIG.
It will be explained based on.

The control system has a printer engine control CPU 54, a ROM / RAM section 53, a controller interface 52, a driver group 55, an input interface 56, and a buffer / LED driver section 57, which are a data bus and an address bus. Are connected to each other via a bus 59a.
The controller interface 52 has a bus 59b.
A control CPU 51 is connected via.

The driver group 55 is the main motor 1
3, sheet feeding solenoid 20, and fixing semiconductor SSR
It has a plurality of dedicated drivers for driving the (solid-state relay) 61. A paper feed sensor 62, a paper output sensor 63, a fixing temperature sensor 64, and a toner sensor 65 are connected to the input interface 56. The LED head 58 is connected to the buffer / LED driver unit 57.

The fixing semiconductor SSR 61 turns ON / OFF the power supply to the heating element 10a based on the temperature detected by the fixing temperature sensor 64. Thereby, the heating element 10a
Is controlled to the optimum value. The toner sensor 65 is
The amount of toner T in the developer and the toner T on the photosensitive drum 1
To detect the amount of As a result, the toner T is replenished and the image density is stabilized.

The paper feed sensor 62 includes a switch for detecting the above-mentioned paper feed, the presence or absence of the transfer paper P, the size of the transfer paper P,
Alternatively, it is composed of a sensor group that detects a paper jam of the transfer paper P. The paper output sensor 63 includes a switch for detecting paper output described above and a sensor group that detects whether or not the transfer paper P is discharged without jamming.

The print / image information input from the external device is sent to the control CPU 51. The control CPU 51 determines the ROM / RA based on these information.
A bitmap corresponding to print data for at least one page (one transfer sheet P) is created in the RAM area of the M portion 53. When a user's printout instruction is received, a print start signal is output to the printer engine control CPU 54.

Printer engine control CPU 5
Reference numeral 4 supplies a video signal (a switching signal including a synchronization signal) corresponding to the bitmap to the buffer / LED driver unit 57. Buffer / LED driver part 5
7 drives the LED head 58 in response to the video signal to blink the light beam from the LED head 58.
Further, the printer engine control CPU 54
Based on various detection signals received from the input interface 56, a command corresponding to each image forming process or image forming condition is generated in accordance with a control program stored in the ROM area of the ROM / RAM unit 53, and the driver group 55 is generated. Output.

The control of the image forming apparatus by the control system in the above configuration will be described below with reference to FIGS. 5 and 6.

When the transfer paper P is fed, the leading end of the transfer paper P pushes up the paper feed actuator 16. When this is detected by the paper feed sensor 62, the printer engine control CPU 54 starts the rotational drive of the main motor 13.

The rotation of the main motor 13 is transmitted to the paper feed roller 18, and as the paper feed roller 18 rotates,
The transfer paper P is conveyed to the registration roller 19 along the upper surface of the developer tank 3. On the other hand, the rotation of the registration roller 19 is stopped by the sheet feeding solenoid 20. Therefore, the conveyance of the transfer paper P is stopped when the leading end of the transfer paper P reaches the registration roller 19. At this time, the paper feed roller 18 slips on the surface of the transfer paper P,
The surface of the paper feed roller 18 is processed so as to have a small frictional resistance.

When this state is detected by the paper feed sensor 62, as shown in step 1 of FIG. 5 (hereinafter referred to as S1), the printer engine control CPU 54
Becomes a standby state for receiving a print start signal from the control CPU 51.

When the print start signal is not sent within the predetermined time, the printer engine control CPU 54 temporarily stops the rotation of the main motor 13.

When a print start signal is sent (see FIG. 6).
(B)), printer engine control CPU 54
Detects the output of the paper feed sensor 62 at the rising edge of the print start signal (S2), as shown in FIG. Then, a drive start command for the main motor 13 is output to the driver group 55 (S3), and the rotation speed of the main motor 13 is gradually increased (S4). This can be realized, for example, by gradually increasing the frequency of the drive pulse supplied to the main motor 13 during the period t1 ((d) in the figure) in which the photosensitive drum 1 makes at least one rotation. The control system operates on the basis of the clock shown in FIG.

The rotation of the main motor 13 is transmitted to all the rotating parts except the above-mentioned registration roller 19 via a rotation transmission system. As a result, the rotational speeds of the photosensitive drum 1, the magnetic roller 5a, and the developing sleeve 5 gradually increase.

After gradually increasing the frequency of the drive pulse supplied to the main motor 13, it is determined whether the rotation speed of the main motor 13 has reached a predetermined value (S5). This determination may be made based on whether the frequency of the drive pulse has reached a predetermined value, or may be made based on whether a predetermined time t1 has elapsed. When the rotation speed of the main motor 13 reaches a predetermined value, the printer engine control CPU 54 outputs the print data stored as a bitmap in the RAM area of the ROM / RAM section 53 to a video signal as shown in FIG. As
A request signal for transfer to the buffer area of the buffer / LED driver unit 57 is output (S6).

When it is confirmed that the buffer / LED driver unit 57 has received the video signal ((f) in the figure) (S
7) The buffer / LED driver unit 57 drives the LED head 58 and blinks the light beam from the LED head 58 to expose the photosensitive drum 1 (S8). As a result, the print data is developed on the surface of the photosensitive drum 1 and a toner image is obtained.

When a voltage having a polarity opposite to the charge injected into the toner image is applied to the transfer roller 9, the transfer roller 9 transfers the toner image onto the surface of the transfer / fixing belt 8 which is pressed against the photosensitive drum 1.

Next, the printer engine control C
The PU 54 outputs to the driver group 55 a signal for turning on the paper feeding solenoid 20 ((g) in the figure). As a result, the rotation of the main motor 13 causes the registration roller 19 to rotate.
And the transfer paper P is conveyed to the heating device 10. The timing at which the above signals are output is such that the toner image on the transfer / fixing belt 8 and the transfer sheet P are
It is set so as to reach the pressure contact portion between the pressure roller 12 and the pressure roller 12 at the same time.

As the transfer / fixing belt 8 and the transfer paper P are conveyed while being superposed between the heating device 10 and the pressure roller 12, the transfer and fixing of the toner image on the transfer paper P are performed simultaneously. Be seen. The overheated toner T is more likely to adhere to the transfer paper P than to the surface of the transfer / fixing belt 8, so that the toner image is transferred / fixed to the transfer paper P.

The transfer paper P on which the toner image is transferred and fixed is
Push up the paper output actuator 23, and press the paper output roller 2
It is discharged to the outside by the rotation of 5. The output of the transfer sheet P is detected by the output sensor 63 (S9). When a paper jam occurs, a predetermined process such as error display is performed (S10).

Printer engine control CPU 5
No. 4 terminates energization of the heating element 10a of the heating device 10 and driving of the main motor 13 after a predetermined time has passed since both signals from the paper feed sensor 62 and the paper output sensor 63 are inactive. (S11).

In the above control of the image forming apparatus, the reason why the rotation speed of the main motor 13 is gradually increased is shown in FIG.
Or, it demonstrates based on FIG.

As shown in FIG. 7, the developer is conveyed in the direction B opposite to the direction A, which is the direction of rotation of the photosensitive drum 1, while forming the magnetic brush 5c on the surface of the developing sleeve 5. .. At this time, in the contact portion between the magnetic brush 5c and the photosensitive drum 1, the developing sleeve 5 and the transparent electrode 1b are connected.
By the voltage of several tens of V applied between and, electric charge is injected from the developing sleeve 5 to the photosensitive drum 1 through the developer. As a result, the surface of the photoconductor drum 1 is charged to substantially the same potential as the developing sleeve 5.

The time required to charge the surface of the photosensitive drum 1 to substantially the same potential as the developing sleeve 5 is slightly longer than when the image forming apparatus starts operating and when it continuously operates. Further, since the photosensitive drum 1 is pressed against the transfer / fixing belt 8 when the image forming apparatus is stopped, the photosensitive drum 1 is distorted, and the characteristics of the photosensitive drum 1 become non-uniform. Can also be considered.

Therefore, after the print start signal is received, the rotation speed of the main motor 13 is gradually increased during the period t1 in which the photosensitive drum 1 makes at least one revolution to uniformly charge the photosensitive drum 1 and The characteristics are made uniform.

Toner T is accumulated on the side of the contact between the magnetic brush 5c and the photoconductor drum 1 in the direction of rotation of the photoconductor drum 1. This is when the photoconductor drum 1 and the developing sleeve 5 start to rotate. If the photosensitive drum 1 drops due to abrupt acceleration or vibration, the charging efficiency of the photosensitive drum 1 and the gradation reproducibility of the toner image are deteriorated. The fall of the toner T can be prevented by gradually increasing the rotation speed of the main motor 13, so that the charging efficiency of the photosensitive drum 1 can be improved and the image quality immediately after the start of the operation can be stabilized.

When the developer contacts the photosensitive drum 1, the surface of the photosensitive drum 1 and the developing sleeve 5 become equipotential. Therefore, the electrostatic force does not work between the developer and the photosensitive drum 1. Therefore, the developer is held on the developing sleeve 5 by the magnetic force of the magnetic roller 5a and does not adhere to the photosensitive drum 1.

Next, as shown in FIG. 8, the magnetic brush 5c
In the area C near the contact portion between the photosensitive drum 1 and the photoconductor drum 1, the exposure device 7
In the region C, the photoconductive layer 1c and the transparent electrode 1b have almost the same potential when exposed to light. That is, area C
The potential of the surface of the photoconductor drum 1 corresponding to is lowered and a potential difference is generated between the surface of the photoconductor drum 1 and the developing sleeve 5.

As a result, the electrostatic force acting between the developing sleeve 5 and the area C on the surface of the photosensitive drum 1 or the Van der Waals force acting between the developing sleeve 5 and the developer is the magnetic force generated by the magnetic roller 5a. To overcome, the developer remains in the area C on the surface of the photosensitive drum 1 as shown in FIG. In this way, a toner image corresponding to the image pattern is formed on the surface of the photosensitive drum 1.

Since the carrier of magnetic particles is mixed in the developer of this embodiment, the transport efficiency is extremely high, and therefore the characteristics of the photosensitive drum 1 and the developer can be easily made uniform. .. Therefore, it is not always necessary to increase the rotation speed of the main motor 13 at the start of the operation of the image forming apparatus. However, when a stepping motor is used as the main motor 13, it is preferable to start the rotation gradually so as to prevent step-out.

According to the developer of this embodiment, since the high-resistance toner T is used, it is possible to form a higher density image on the transfer paper P than when the conductive toner is used.

In this embodiment, the transfer / fixing belt 8 having an insulating surface is pressed against the photosensitive drum 1 to transfer the toner image to the transfer / fixing belt 8 once.
Then, although the toner is transferred and fixed on the transfer paper P, it is also possible to directly transfer the high resistance toner T from the photosensitive drum 1 to the transfer paper P.

Further, in this embodiment, the magnetic roller 5a is used.
Disturbs the developer on the developing sleeve 5, and injects electric charge into the high-resistance toner T in the exposed area C to adhere the toner T onto the photosensitive drum 1, and yet to remove the unexposed area C. Since the toner T is removed together with the carrier by the magnetic roller 5a, a good image with less "fog" can be obtained.

[0062]

As described above, the image forming developer according to the present invention comprises a toner and a carrier in the photoconductive layer of a photoconductor in which a transparent electrode and a photoconductive layer are sequentially formed on a transparent support. While contacting the developer and applying a bias between the developer and the transparent electrode, the transparent support side of the photoconductor irradiates the photoconductive layer with light according to the recorded information, and the toner is applied to the part on the photoconductive layer where the light is irradiated. An image forming developer for forming a toner image by adhering, wherein the toner is composed of high resistance resin particles, and the carrier is composed of magnetic particles of lower resistance than the toner, Good transfer characteristics can be obtained, and charges can be efficiently injected into the toner during exposure. Thereby, there is an effect that a stable toner image can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an image forming apparatus of this embodiment.

FIG. 2 is an enlarged view of FIG.

FIG. 3 is an explanatory view showing an installed state of a developing sleeve and a magnetic roller of FIG.

FIG. 4 is a block diagram showing a schematic configuration of a control system for controlling the image forming apparatus of FIG.

5 is a flowchart for controlling the image forming apparatus by the control system of FIG.

6 is a timing chart showing the timing of control of the image forming apparatus by the control system of FIG.

FIG. 7 is an explanatory diagram showing a schematic configuration of a photosensitive drum of FIG.

FIG. 8 is an explanatory diagram showing a process in which a toner image is formed on the photosensitive drum of FIG.

9A and 9B are explanatory views showing a process in which a toner image is formed on the photosensitive drum of FIG.

[Explanation of symbols]

 1 Photoconductor Drum 1a Transparent Support 1b Transparent Electrode 1c Photoconductive Layer 2 Developing Device 3 Developer Tank 4 Stirring Roller 5 Developing Sleeve 5a Magnetic Roller 5c Magnetic Brush 7 Exposure Device 8 Transfer / Fixing Belt 9 Transfer Roller 10 Heating Device 10a Heat Generation Body 12 pressure roller

Claims (1)

[Claims] 1. A developer comprising a toner and a carrier is brought into contact with a photoconductive layer of a photoconductor having a transparent electrode and a photoconductive layer sequentially formed on a transparent support, and a bias is applied between the developer and the transparent electrode. However, it is a developer for image formation that forms a toner image by irradiating the photoconductive layer from the transparent support side of the photoconductor to the photoconductive layer according to the recorded information, and attaching the toner to the part on the photoconductive layer that has been irradiated with the light. The toner for forming an image is characterized in that the toner is composed of resin particles having a high resistance, and the carrier is composed of magnetic particles having a resistance lower than that of the toner.