JP3004063B2 - Color electrophotographic equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic apparatus, and more particularly, to a color electrophotographic apparatus in which a multicolor toner image is formed on a photoreceptor and then collectively transferred.

[0002]

2. Description of the Related Art In recent years, there has been a great demand for color printers such as full-color and multi-color printers, and apparatuses using an ink jet system or a bubble jet system have been announced. It has disadvantages such as many troubles of the nozzle after being left for a long time.
On the other hand, an apparatus using color electrophotography provides a color image relatively stably.

[0003] A conventionally known general color electrophotographic apparatus uses a magenta, cyan, yellow, and black toner and sequentially performs a series of charging, developing, transferring, and cleaning steps for each color. Is transferred to form a color image by printing each toner image on a transfer material. For example, the drum-shaped photoreceptor is charged using a corona charger, then irradiated with a magenta light image to form an electrostatic image, developed with magenta toner by a magnet brush, and then transferred onto a transfer material. Next, the photoconductor is cleaned, charged again, irradiated with a cyan light image to form an electrostatic image, developed with cyan toner, and transferred onto a transfer material carrying the magenta toner image transferred in the previous step. The transfer is performed synchronously so as to match. This process is performed for other colors in order to form a multicolor toner image on the transfer material. The order may be, for example, yellow, cyan, and magenta. The transfer material is then sent to a fixing device where the multicolor toner image is fixed on the transfer material to form a color copy.

[0004]

As described above, in the conventional color electrophotographic apparatus, it is necessary to repeat the steps of charging, developing, and transferring for each color, so that high-speed color copying or printing can be performed. It was difficult. In addition, it is necessary to transport the transfer material four times with precise timing in a state where the unfixed toner is adhered.
It requires a transport path length at least as long as the length of the transfer material, and is extremely large and expensive as an apparatus, and has the disadvantage that it is difficult to obtain a long color copy, such as the difficulty in precise timing described above.

Further, in the conventional apparatus, since the development is performed using a magnet brush, there is a problem such as mixing of toner between the developing units, and the unused developing units are separated from the photosensitive member surface. It requires a complicated mechanism.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a color electrophotographic apparatus capable of simplifying the configuration of the apparatus and achieving high speed.

[0007]

For this reason, a color electrophotographic apparatus according to the present invention comprises a photoreceptor having a light-transmitting conductive layer and a photoconductive layer disposed on a light-transmitting substrate in this order.
Connected to an optical substrate to form a dark potential in the photoconductive layer;
Irradiating a biasing device which applies a bias voltage to the so that the induced member arranged in contact with the <br/> photoconductive layer, a light image corresponding to different colors from the light-transparent substrate side,
The voltage applied to the bias device on the transparent substrate is substantially
A plurality of light image irradiating devices that form the same potential, and a plurality of developing devices that apply toner of a color corresponding to the color to the photoconductive layer side simultaneously with or after the light image irradiation by each light image irradiating device Wherein the developing device includes a conductive toner carrier biased to have a characteristic opposite to the charging characteristic of the toner, and a supply unit for supplying a thin toner layer on the toner carrier.

[0008]

In such a means, when the surface of the photosensitive member is brought into contact with the inducing member, electric charges are induced on the surface of the photosensitive layer, and thereafter, the light image corresponding to the first color is irradiated from the light transmitting body side .
Then, the portion of the photoreceptor surface irradiated with the light image rises substantially to the photoreceptor bias potential, and a potential difference is formed between the non-irradiated portion and an electrostatic image corresponding to the light image. The electrostatic image is then developed with a first color toner provided by a toner carrier.

Thereafter, the photoreceptor is similarly irradiated with the light image corresponding to the second color and forms a multicolor toner image on the developed photoreceptor, and then the multicolor toner image is formed on the transfer material. Is transferred in batch.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of a main part of a color electrophotographic apparatus according to the present invention. A charging section 2 for applying a charge to the surface of a photoreceptor 1 along a movement path of the photoreceptor 1 is optically separated on the photoreceptor. Exposure and development unit 3 for developing each of the developed light images and corresponding color toners for each color, and a transfer unit for transferring a multicolor toner image formed on photoconductor 1 by exposure and development unit 3 onto a transfer material 4, and a cleaning and erasing section 5 for cleaning the surface of the photoreceptor after transfer.

As shown in FIG. 2, the photoreceptor 1 has a structure in which a light-transmitting conductive layer 12 and a photoconductive layer 13 are sequentially arranged on a light-transmitting substrate 11, and is used in the form of a belt or a belt. Any of a drum shape may be used. The photoconductive layer 13 is made of OP
Any type of N-type or P-type optical semiconductor such as C, Se, ZnO, CdS, and a-Si is suitable for use. The photoreceptor 1 shown in FIG. 1 has a belt shape, uses an endless polyester film (trade name: Mylar) as a light-transmitting substrate 11, forms a light-transmitting electrode layer on both surfaces thereof, and further on one surface thereof. And a photoconductive layer 13 of an organic optical semiconductor (OPC) formed by doctor coating or spray coating. The belt-shaped photoconductor 1 is formed of an endless body having the photoconductive layer 13 side outside, and includes a plurality of guide rollers (three guide rollers are shown in the illustrated example).
It is movably stretched by 7, 8, and 9, and moves at a predetermined speed in the direction shown by arrow A with any rotation of the guide roller.

At least one of the guide rollers constitutes a conductive electrode roller 7, which is a conductive layer 1 of the photosensitive member 1.
2 and electrically connected to a bias power supply 10 to apply a predetermined bias to the conductive layer 12 of the photoconductor 1. The bias voltage is a DC voltage, a voltage obtained by superimposing an AC voltage on a DC voltage, or an AC voltage.

An inducing member 21 of the charging unit 2 is arranged in contact with the surface of the photosensitive member 1 so as to face the electrode roller 7.
(It is not necessary to be in strict contact, as the case may be.) In the illustrated example, the inducing member 21 is formed in the shape of a roller in which a layer 23 made of a conductive or semiconductive elastic rubber material is mounted on a conductive metal core 22 rotatably supported. It is pressed against the body surface and rotates forward (clockwise in FIG. 1) at the contact portion at a peripheral speed substantially equal to the peripheral speed of the photoreceptor. The layer 22 may be made of, for example, NBR or silicon rubber containing a conductive material, and most preferably has a volume resistance of 10 ³ to 10 ¹⁰ Ωcm ^3.
If a material with too high resistance is used, a high bias potential to the photoconductor must be required,
In addition, the repetitive characteristics of the photosensitive member for forming an electrostatic image are reduced.

The inducing member 21 may be provided with an insulating layer such as a synthetic resin on the outer peripheral surface of the layer 23 in some cases. Also,
Alternatively or similarly, an insulator layer may be provided on the surface of the photoreceptor, and these are not essential, but contribute to uniform charging of the photoreceptor depending on conditions. Further, the inducing member 21 may be in the form of a blade or a brush in addition to the roller shape as shown.

The core 22 is directly grounded or a rectifier such as a varistor, a constant voltage diode, or a diode (when the bias voltage applied to the photoreceptor is a voltage obtained by superimposing AC on DC or AC voltage). Indirectly grounded via In order to obtain a desired potential on the photoreceptor, an appropriate resistor may be interposed.

As described above, when the inducing member 21 comes into contact with the surface of the photosensitive member to which the bias voltage has been applied to the translucent conductive layer , electric charges are induced on the surface of the photosensitive member, and the surface of the photosensitive member becomes
It is charged to a value divided according to the impedance of the photoconductor 1, the impedance of the inducing member 21, and the impedance of the air layer between them.

The exposure / development unit 3 includes a light-transmitting substrate 11 of a photosensitive member.
A plurality of light image irradiating means, for example, LED arrays 31, 3 arranged in order along the moving direction of the photoconductor 1 on the side
2, 33, 34, and developing units 35, 36, 3 arranged in this order on the photoconductive layer 13 side of the photoconductor, that is, on the surface side of the photoconductor 1.
7, 38. The light image irradiating means is not limited to the LED array, but may be another digital light image irradiating means such as a laser. Each of the developing units 35, 36, 37, and 38 can apply toner to the photoconductor at the same time as or after (preferably immediately after) the position where the photoconductor receives the light image irradiation of the LED arrays 31, 32, 33, and 34, respectively. A developing cylinder, which will be described later, is located at the position. The operation and timing of light image irradiation of these LED arrays 31, 32, 33, and 34 are controlled by control means (not shown), and light images corresponding to magenta, cyan, yellow, and black are respectively transmitted to the light-transmitting substrate of the photosensitive member. Irradiate from 11 side. The developing units 35, 36, 37, and 38 respectively apply magenta, cyan, yellow, and black toners having polarities opposite to those of the electrostatic image to the photoconductor.

As described above, when the LED array 31 irradiates a light image, the surface potential (bright portion potential) of the light irradiating portion is changed to the light transmitting conductive layer 12 of the photosensitive member 1 as described above.
And a potential difference is formed between the bias potential and the potential of a portion not irradiated with light (dark portion potential).

The electrostatic image contrast is obtained by adding the bias potential applied to the light-transmitting conductive layer 11 of the photosensitive member, and the electrostatic image contrast becomes substantially equal to the bias potential at the saturation potential of the dark portion and the bright portion.

As described above, the bias applied to the light-transmitting conductive layer 12 of the photoreceptor 1 may be a voltage obtained by superimposing an alternating current on a direct current. In this case, the electrostatic latent image potential on the photoreceptor surface is different from the AC component. Amplitude at almost the same value. The center value of the dark surface potential of the oscillating surface potential differs depending on the peak value of the superimposed alternating current, and in an atmosphere of 1 atm, it becomes almost 0 V when it exceeds about 1400 Vp-p, and the light portion potential also decreases at a value equal to the amount of movement. . Below 1000 Vp-p, the dark area shown in FIG.
Although it is 00V, when the superimposed AC voltage is gradually increased, the voltage drops to about 0V in proportion to the value. This is important for the movement of the developer from the developing sleeve to the surface of the photoconductor at the time of development, and the development density can be adjusted by changing the peak value of the AC. In this case, the AC frequency is several hundred H
The range of z to 3 KHz is preferable, and if it is 3 KHz or more, the radiation noise increases, which is not preferable.

Since the developing devices 35, 36, 37, and 38 have substantially the same configuration, the developing device 35 will be described as an example with reference to FIG. The developing device 35 includes a conductive developing cylinder (toner carrier) 351 that rotates in a forward direction with respect to the moving direction of the photoconductor 1, and a non-magnetic member in which a magnet roll 352 is disposed for supplying toner to the developing cylinder 351. And a casing 354 for storing a developer composed of toner and carrier.

The developing cylinder 351 preferably has a relatively smooth surface, such as a nickel-plated iron material, a brass material, or a polished aluminum tube surface blasted with a mesh of 400 mesh or less. It is used, and there is no particular limitation on magnetic or non-magnetic. The developing cylinder 351 is electrically connected to a developing bias power supply 355 to apply a bias having a polarity opposite to the charging polarity of the toner, and a thin layer of magenta toner is formed on the surface thereof as described later. A DC bias potential of plus several hundred volts is applied as a developing bias, and the developing density is varied by changing the bias potential. For example, as a bias, about plus 100 with respect to the non-image area potential on the photoconductor.
A voltage of about V is applied.

The distance between the developing cylinder 351 and the surface of the photoreceptor 1 is optimally small as far as possible so that the toner layer carried on the developing cylinder 351 does not contact the surface of the photoreceptor. In the experiment, the interval was about 200μ ~
When the thickness is 300 μm, the best development is performed, but the interval is not limited to this because it is determined by the surface potential of the photoconductor, the development bias, the peripheral speed of the cylinder, the characteristics of the toner, and the like.

Incidentally, the peripheral speed of the developing cylinder 351 is preferably substantially equal to the moving speed of the photosensitive member 1, and when it is twice or more, the resolution tends to decrease.

In the casing 354, the toner is mixed with a charge accelerator (carrier) at a ratio of about 5 to 10% by weight, and is stirred by the sleeve 353. The toner density is detected by a known method, and toner consumed during use is replenished as needed in accordance with the detection result, and the density is controlled.

The toner in the casing 354 is, for example,
It is charged by stirring with a ferrite carrier of about 150 mesh. The charged toner is attracted to the developing cylinder 351 to which a bias having a polarity opposite to that of the toner is applied, and forms a uniform thin toner layer on the peripheral surface. It is desired that the toner used here has a large charge amount, for example, a toner having a charge amount of 20 microcoulombs or more is particularly preferable, and the toner has a property of being substantially reduced to a non-image portion potential after the toner adheres to an electrostatic image. Is optimal.

The supply of toner to the developing cylinder 351 is performed by a sleeve 353. The sleeve 353 attracts the toner onto the sleeve by the magnetic force of the magnet roll 352 while stirring the toner with the carrier, and the doctor blade 35
6, a predetermined developer layer is formed, and a developing cylinder 35 is formed.
1 to form a thin toner layer on the cylinder. After the toner is supplied to the developing cylinder 351, the developer is removed from the sleeve 353 by the scraping plate 357 and is stirred again.

FIG. 5 shows the latent image potential after development. In order to avoid overlapping with the toner of the next color, the potential at the portion where the toner is adhered is set to a potential that is not developed in the next step. It is preferable to have a charge approximately equal to

Such light image irradiation and development are controlled by LED circuits 31, 32, 33, and 3 controlled by a control circuit.
4, and magenta, cyan, yellow, and black are performed in that order by the developing units 35, 36, 37, and 38, and a multicolor toner image is formed on the photoconductor. The multi-color refers to a full color, a mono-color or a multi-color (two or more mono-colors).
ED arrays 31, 32, 33, 34 and developing device 35,
In the case of multicolor or monocolor, only light image irradiation and development corresponding to a required color need be performed. Preferably, in a multi-color or a mono-color, the developing unit not used is provided with a cylinder surface by, for example, turning off the bias of the developing cylinder 351 or switching the applied bias to a bias having the same polarity as the toner. It is preferable to prevent the toner from adhering to the photoconductor and not contribute to the development on the photoconductor.

The dot diameter of the light image by the LED array is 60
A micron or less is preferable, and a control circuit is obtained to scan the photoreceptor with a light image in the generatrix direction. When the dot diameter is large, not only the resolving power decreases but also the color reproduction decreases.

FIGS. 6 and 7 show an example of the flow of electrostatic image formation and development by image irradiation in the case of full color image formation. The LED arrays 31, 32, 33, and 34 perform raster scanning so that the light image of each LED array does not overlap with that of another LED array. That is, the digital light image corresponding to the first color is raster-scanned at predetermined intervals, a toner of the first color is applied simultaneously with or immediately after the irradiation of the light image, and development is performed. The digital light image corresponding to the first color is irradiated at a dot interval that does not overlap the dot of the digital light image of the first color. By performing the process for other colors, a multicolor toner image is formed on the photoconductor.

As described above, according to the present invention, various complementary colors can be produced by a combination of light image irradiation of the LED arrays 31, 32, 33, and 34. On the other hand, image formation similar to gravure printing is performed.

The multicolor toner image thus formed on the photoreceptor is transferred to a transfer material such as paper in the transfer section 4. Reference numeral 41 denotes a transfer corona charger having a conventionally known configuration, which applies a high voltage having a polarity opposite to the charge polarity of the toner from the back surface of the transfer material to transfer the toner image onto the transfer material. A transfer roller may be used instead of the transfer corona charger.

Reference numeral 42 denotes an AC neutralizing corona separator. The paper feed roller 43 operates so that the transfer material comes into contact with the surface of the photoconductor by registering with the toner image on the photoconductor at a controlled timing.

Next, the transfer material onto which the toner image has been transferred is conveyed to the fixing device 50 by the conveyance belt 44, where the toner image is fixed on the transfer material, and a clear color copy is obtained. The fixing device 50 holds a transfer material between a heating roller 51 and a pressure roller 52 having a heat source provided inside a roller having silicon rubber as a surface, and performs fixing by heat and pressure. The surface of the heating roller is coated with a silicone liquid to prevent the roller surface from being stained.

On the other hand, foreign matters such as toner remaining on the surface of the photoreceptor to some extent after transfer are cleaned by a cleaning means 51 such as a cleaning brush or a cleaning blade for the next repetitive use of the photoreceptor, and then cleaned. The surface of the photoconductor is erased by exposing the residual potential to a lamp 52 or the like. The illustrated example shows a configuration in which the erase exposure is performed from the front side of the photoconductor, but may be performed on the back side, that is, on the transparent substrate side. Thereafter, the photoreceptor is charged again by the induction roller and is used again and again.

[0037]Experimental example 1  In the apparatus having the configuration shown in FIG.
An experiment was carried out. Magenta and developing unit 3 in developing unit 35
6 for cyan, yellow for developing unit 37, and black for developing unit 38.
Each of the toners was used. The transparency of the belt-shaped photoconductor 1
Positive to light electrode 12 via electrode roller 7900VBa
When the bias is applied, the dark area potential is increased by about +5
The surface potential of 00 is induced by the induction roller 21,
After the light image is irradiated by the LED array 31, about plus 9
A surface potential of 00V was formed. This is only the developing unit 35
, And deactivate other LED arrays for development.
As a result, a magenta toner image
This is transferred to a transfer material, and then fixed.
A bright sepia image was obtained. Similarly, LED LED
Ray 32 only, LED array 33 only, LED array 3
When the light image irradiation was performed using only
, Yellow and black monocolor images were obtained.

Experimental Example 2 In the same configuration as in Experimental Example 1, electric charges are induced on the photosensitive member 1 moving at a speed of 40 mm / Sec, and the light image exposure of the LED array 31 is raster-scanned every other dot, and immediately thereafter. Developing is performed by the developing device 35 (lighting time for one ton of about 0.4 μsec, raster scan time for one line is 1.5 mSec). Next, when that part of the photoconductor moves to a position corresponding to the LED 32, 1 LE after the time difference
When the D array 32 is raster-scanned every other dot and then passed through the developing units 36, 37 and 38, the developing units 37 and 38 hardly develop, and the developing units 35 and 36
Thus, a toner image of a complementary color with the toner was obtained. In this toner image, the toner was somewhat crushed by fixing, and the toners were fused to each other, and a clear complementary color was reproduced.

EXPERIMENTAL EXAMPLE 3 The LED arrays 31, 32, 33, and 34 were the same as in Experimental Example 2.
Is controlled so as to form a time difference and irradiate a light image, and when the toner of each color is applied by the developing units 35, 36, 37, and 38, various multi-colors or full-colors are reproduced by a combination thereof, and a clear color image is formed. Obtained.

As described above, the light image irradiation controlled by the control unit circuit is sequentially performed, and the desired color image is obtained by developing with the necessary toner at the same time or immediately after the light image irradiation, and furthermore, the continuous color image can be continuously obtained. A color image of a scale can be obtained.

In the above experimental example, a belt-shaped photosensitive member was used. However, it is needless to say that an image can be formed by a similar method even if the photosensitive member is a drum-shaped member, and the developing devices 35, 36, 37, 38 The colors of the toner are not limited to the above order.

[0042]

As described above, according to the present invention, a color image is continuously obtained, and only one transfer is required. Therefore, not only can the apparatus be miniaturized, but also a large-size color image cannot be produced at low cost. However, the present invention has solved these problems.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a color electrophotographic apparatus according to the present invention.

FIG. 2 is a diagram illustrating charging of a photoconductor in the embodiment of FIG.

FIG. 3 is a diagram illustrating an example of a relationship between an exposure amount and a surface potential of a photoconductor.

FIG. 4 is a diagram illustrating an example of a developing unit.

FIG. 5 is a diagram showing a surface potential of a photoconductor after development.

FIG. 6 is a diagram illustrating a flow of a series of light image irradiation and development.

FIG. 7 is a diagram illustrating a flow of a series of light image irradiation and development.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor 2 charging unit 3 exposure and development unit 4 transfer unit 5 cleaning unit 10 bias power supply 11 translucent substrate 12 translucent conductive layer 13 photoconductive layer 21 inducing member 34 LED array 38 developing unit 351 developing cylinder 353 toner supply sleeve

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 13/01 G03G 15/01-15/01 117 G03G 13/02 G03G 15/02-15/02 103

Claims (1)

(57) [Claims] 1. A light-transmitting conductive layer on at least a light-transmitting substrate,
A photoconductor in which a photoconductive layer is disposed in order is in contact with the translucent substrate.
Are continued, and the biasing device to apply a bi <br/> Ass voltage so as to form a dark portion potential on the photoconductive layer, and the induced member arranged in contact with the photoconductive layer, the light-transparent substrate side Irradiate light images respectively corresponding to different colors from the transparent group.
Apply the same potential as the voltage applied to the bias device on the body
A plurality of light image irradiating devices to be formed, and a plurality of developing devices that apply a toner of a color corresponding to the color to the photoconductive layer side simultaneously or after the light image irradiation by each light image irradiating device, A color electrophotographic apparatus comprising: a developing device having a conductive toner carrier biased to a polarity opposite to a charging characteristic of a toner; and a supply unit for supplying a thin toner layer on the toner carrier.