JPH04356072A - Digital color electrophotographic copying device - Google Patents

Abstract

PURPOSE:To make a device compact and of high-speed operation by executing developing by giving the toner of a first color, executing the developing by irradiating a digital optical image corresponding to a second color at an interval that it is not overlapped with the dot of the digital optical image of the first color and successively executing such a process as for the other color. CONSTITUTION:An electrostatic charge part 2 which gives electric charge to the surface of a photosensitive body 1, an exposure and developing part 3 which executes the developing by the toner of the color corresponding to the optical image which is optically classified on the body 1 as for the respective colors or the like are provided. Then, a bias voltage is impressed on a translucent conductive layer and the electric charge is induced by bringing an induction member into contact with the surface of the body 1 at the same time. Next, a multicolor toner image is formed by irradiating the digital optical image corresponding to the respective different colors from a translucent substrate side and giving the toner of the color corresponding to the concerned color to a photoconductive layer side. The raster scanning of the digital optical image is executed every other prescribed dot and the digital optical image is irradiated so that the dots of the respective colors are not overlapped. The formed toner image on the photosensitive body 1 is transferred on a transfer material.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art] In recent years, the demand for color printers such as full-color and multi-color printers has been very large, and devices using inkjet methods, bubble jet methods, etc. have been announced, but they suffer from lack of clarity of color images and long print times. It has the disadvantage that there are many problems with the nozzle after it has been left for a long time. In contrast, devices using color electrophotography provide relatively stable color images.

Conventionally known general digital color electrophotographic devices use magenta, cyan, yellow, and black toners, and sequentially perform a series of charging, developing, transferring, and cleaning steps for each color. By multiple transfers, each toner image is printed on the transfer material to form a color image. For example, a drum-shaped photoreceptor is charged using a corona charger, then irradiated with a magenta light image to form a static image, developed with magenta toner, and then transferred onto a transfer material. The photoconductor is then cleaned, charged again, irradiated with a cyan light image to form a static image, developed with cyan toner, and placed on the transfer material that carries the magenta toner image transferred in the previous step. Transcription is performed synchronously to match. This step is repeated for other colors in order to form a multicolor toner image on the transfer material. For example, the order is
The order may be yellow, cyan, and magenta. The transfer material is then sent to a fusing device where the multicolored toner image is fused onto the transfer material to form a color copy.

0004

[Problems to be Solved by the Invention] As described above, in the conventional digital color electrophotographic apparatus, charging and
It is necessary to repeat the development and transfer steps, making it difficult to perform high-speed color copying or printing. Moreover, it is necessary to repeatedly transport the transfer material with unfixed toner attached four times at precise timing, and the transport mechanism requires a transport path length that is at least as long as the length of the transfer material, making the device extremely large. Moreover, it is not only expensive and expensive, but also has the disadvantage that it is difficult to obtain long color copies, such as the above-mentioned difficulty in precise timing.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a digital color electrophotographic apparatus which can be made compact and capable of increasing speed.

[0006]

[Means for Solving the Problems] Therefore, the digital color electrophotographic apparatus according to the present invention provides a photoreceptor in which a light-transmitting conductive layer and a photoconductive layer are sequentially disposed on a light-transmitting substrate. A bias voltage is applied to the conductive layer and a grounded induction member is brought into contact with the surface of the photoreceptor to induce an electric charge, and then a digital optical image corresponding to the first color is projected from the transparent substrate side at predetermined intervals. A toner of a first color is applied to the photoconductive layer side at the same time as or after the light image irradiation, and development is performed, and then a digital light image corresponding to a second color is converted into a digital light image of the first color. Irradiate from the transparent substrate side at dot intervals that do not overlap with the dots of the digital optical image, develop with a toner of a second color at the same time as or after the optical image irradiation, and perform this step sequentially for other colors. The method is characterized in that a multicolor toner image is formed on a photoreceptor and then transferred onto a transfer material.

Furthermore, the voltage applied to the transparent conductive layer may be a DC voltage, a voltage obtained by superimposing an AC voltage on a DC voltage, or an AC voltage. Furthermore, the present invention can be applied not only to full color but also to multicolor (monocolor of two or more colors).

[0008]

[Operation] In such means, when an inducing member is brought into contact with the surface of the photoreceptor, charges are induced on the surface of the photosensitive layer, and then, when a light image corresponding to the first color is irradiated from the transparent substrate side, The portion of the surface of the photoreceptor that is irradiated with the light image rises to approximately the photoreceptor bias potential, and a potential difference is formed between the portion of the surface of the photoreceptor and the portion that is not irradiated, and an electrostatic image corresponding to the light image is formed. This electrostatic image is then developed with a first color toner.

Thereafter, the photoreceptor is further irradiated with a light image corresponding to a second color in the same manner and a multicolor toner image is formed on the photoreceptor, which is developed, and then the multicolor toner image is transferred to a transfer material. All images are transferred to the top.

0010

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of the main parts of a digital color electrophotographic apparatus according to the present invention.
A charging section 2 for applying charge to the surface of the photoreceptor, an exposure and development section 3 that develops optically separated optical images on the photoreceptor and toners of the corresponding colors for each color; A transfer section 4 that transfers the multicolor toner image formed on the photoreceptor 1 onto a transfer material, and a cleaning and eraser section 5 that cleans the surface of the photoreceptor after the transfer are provided.

As particularly shown in FIG. 2, the photoreceptor 1 has a structure in which a light-transmitting conductive layer 12 and a photoconductive layer 13 are arranged in this order on a light-transmitting substrate 11, and has a belt-like or It may be in any shape of a drum. The photoconductive layer 13 is OP
Any type of optical semiconductor, N-type or P-type, such as C, Se, ZnO, CdS, a-Si, etc., 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 transparent substrate 11, has transparent electrode layers formed on both sides, and further has a transparent electrode layer on one side. A photoconductive layer 13 of an organic optical semiconductor (OPC) is formed by doctor coating or spray coating. The belt-shaped photoreceptor 1 is an endless body with the photoconductive layer 13 side facing outward, and includes a plurality of guide rollers (three guide rollers are shown in the illustrated example) 7.
, 8, and 9, and moves at a predetermined speed in the direction shown by arrow A as one of the guide rollers rotates.

At least one of the guide rollers constitutes a conductive electrode roller 7, which roller is connected to the conductive layer 1 of the photoreceptor 1.
2 and is electrically connected to a bias power supply 10 to apply a predetermined bias to the conductive layer 12 of the photoreceptor 1 . The bias voltage consists of either 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 section 2 is disposed facing the electrode roller 7 and in contact with the surface of the photoreceptor 1. (It doesn't necessarily have to be exact contact, depending on the case). In the illustrated example, the inducing member 21 has the shape of a roller having a rotatably supported conductive metal core 22 covered with a layer 23 made of a conductive or semiconductive elastic rubber material, and is photosensitive by applying appropriate pressure. The contact portion is pressed against the body surface and is moved in the forward direction (
(clockwise as seen in Figure 1). The layer 22 is made of, for example, N
It may be BR or silicone rubber containing a conductive material, and optimally the volume resistance is 103 to 1010 Ωc.
If a material with an extremely high resistance is used, a high bias potential must be applied to the photoreceptor, and furthermore, the repeatability of static image formation on the photoreceptor will deteriorate.

In the inducing member 21, an insulating layer made of synthetic resin or the like may be provided on the outer peripheral surface of the layer 23, depending on the case. Also,
Alternatively or similarly, an insulating layer may be provided on the surface of the photoreceptor, and although these are not essential, they contribute to uniform charging of the photoreceptor depending on the conditions. Further, the inducing member 21 may be in the shape of a blade or a brush other than the roller shape as shown.

The core 22 is directly grounded, or (if the bias voltage applied to the photoconductor is a voltage obtained by superimposing a direct current and an alternating current, or is an alternating current voltage), a rectifying means such as a varistor, a constant voltage diode, or a diode is used. is indirectly grounded through. Further, a suitable resistor may be interposed in order to obtain a desired potential on the photoreceptor.

In this manner, when the inducing member 21 comes into contact with the surface of the photoreceptor to which a bias voltage has been applied to the transparent conductive layer layer, charges are induced on the surface of the photoreceptor, and the surface of the photoreceptor is , the impedance of the inducing member 21 , and the impedance of the air layer between them. Next, the photoreceptor is sent to an exposure and development section 3.

The exposure and development section 3 is a light-transmitting substrate 11 of a photoreceptor.
A plurality of light image irradiation means, for example, LED arrays 31 and 32, are sequentially arranged along the moving direction of the photoreceptor 1 on the side.
, 33, 34, and developing devices 35, 36, 37 arranged in order on the photoconductive layer 13 side of the photoreceptor, that is, on the surface side of the photoreceptor 1.
, 38. The light image irradiation means is not limited to an LED array, but may be other digital light image irradiation means such as a laser. The developing devices 35, 36, 37, and 38 can apply toner to the photoreceptor at the same time or after (preferably immediately after) the position where the photoreceptor 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 this position. The operation and timing of light image irradiation of these LED arrays 31, 32, 33, and 34 are controlled by a control means (not shown), and each light image corresponding to magenta, cyan, yellow, and black is transmitted to a transparent substrate of a photoreceptor. Irradiate from the 11 side. Further, the developing units 35, 36, 37, and 38 are each
Magenta, cyan, yellow, and black toners with polarities opposite to those of the electrostatic image are applied to the photoreceptor.

When the LED array 31 now irradiates a light image in this way, the surface potential (bright area potential) of the light irradiated portion changes to the light-transmitting conductive layer 12 of the photoreceptor 1, as described above.
approaches the value of the bias potential applied to the area, and forms a potential difference between the potential of the area that is not irradiated with light (dark area potential). For example, when N-type OPC is used as the photoconductive layer 13 and a DC voltage of +1000V is applied to the transparent conductive layer 12 of the photoreceptor 1, the dark area potential is approximately +500V and the light area potential is approximately +100V. A static image is formed in which the bright area potential is higher than the dark area potential.

The static image contrast is obtained by adding the bias potential applied to the transparent conductive layer 11 of the photoreceptor, and at the saturation potential of the dark and bright areas, the static image contrast has a value almost equal to the bias potential.

Further, as described above, the bias applied to the transparent conductive layer 12 of the photoreceptor 1 may be a voltage obtained by superimposing an alternating current on a direct current, and in this case, the electrostatic latent image potential on the surface of the photoreceptor is different from the alternating current component. The amplitude is approximately the same value. The center value of the dark potential of the oscillating surface potential varies depending on the peak value of the superimposed alternating current, and in an atmosphere of 1 atm, when it exceeds about 1400 Vp-p, it becomes almost 0 V, and the bright potential also decreases by a value equal to the amount of movement. . Below 1000Vp-p, the dark area shown in FIG. 3 is approximately 500V, but as the alternating current superimposed voltage is gradually increased, it decreases to approximately 0V in proportion to the value. This is important for the movement of the developer from the developing sleeve to the surface of the photoreceptor at the time of development, and the developed density can be adjusted by changing the peak value of the alternating current. In this case, the frequency of the alternating current is preferably in the range of several hundred Hz to 3 KHz, and if it exceeds 3 KHz, the radiation noise will increase, which is not preferable.

Since the developing units 35, 36, 37, and 38 have substantially the same configuration, the developing unit 35 will be explained as an example with reference to FIG. 4. The developing device 35 includes a conductive developing cylinder (toner carrier) 351 that rotates in the forward direction of the movement direction of the photoreceptor 1, and a non-magnetic developing cylinder (toner carrier) that has a magnet roll 352 disposed inside to supply toner to the developing cylinder 351. It includes a toner supply sleeve 353 and a casing 354 for storing a developer consisting of toner and carrier.

The developing cylinder 351 preferably has a relatively smooth surface, and is made of iron material plated with nickel, brass material, or a polished aluminum tube whose surface is blasted to a particle size of 400 mesh or less. It does not matter whether it is magnetic or non-magnetic. The developing cylinder 351 is electrically connected to a developing bias power source 355 to apply a bias having a polarity opposite to the charged polarity of the toner, and a thin layer of magenta toner is formed on the surface of the developing cylinder 351 as described later. As a developing bias, a DC bias potential of plus several hundred volts is applied, and the developing density is varied by changing the bias potential. For example, as a bias, approximately +100
Apply a voltage of about V.

Optimally, the distance between the developing cylinder 351 and the surface of the photoreceptor 1 is such that the toner layer carried on the developing cylinder 351 does not touch the surface of the photoreceptor, and is as narrow as possible. In experiments, the distance was set to about 200μ~
The best development was achieved when the distance was 300 μm, but this distance is not limited to this, as it is determined by the surface potential of the photoreceptor, the developing bias, the circumferential speed of the cylinder, the characteristics of the toner, etc.

It is preferable that the circumferential speed of the developing cylinder 351 is approximately equal to the moving speed of the photoreceptor 1; if it is twice or more, the resolution tends to decrease.

The toner is mixed with a charging accelerator (carrier) at a weight ratio of about 5 to 10% in the casing 354 , and is stirred by the sleeve 353 . The toner concentration is detected by a known method, and the toner consumed during use is replenished as needed to control the concentration.

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 of polarity opposite to that of the toner is applied, forming a uniform thin layer of toner on the circumferential surface of the developing cylinder 351 . It is desired that the toner used here has a large charge amount, for example, one having a charge amount of 20 microcoulombs or more is particularly preferable, and a toner having a property that the potential decreases to approximately the non-image area potential after the toner adheres to the electromagnetic image. is optimal.

Toner is supplied to the developing cylinder 351 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 to form a predetermined developer layer, and the developing cylinder 35
1 to form a thin layer of toner on the cylinder. After toner has been supplied to the developing cylinder 351, the developer is removed from the sleeve 353 by a scraping plate 357 and stirred again.

FIG. 5 shows the latent image potential after development. In order to reliably avoid overlapping with the toner of the next color, for example, the toner used should be adjusted so that the potential at the part where the toner adheres is a potential that will not be developed in the next step. It is preferable to have a charge approximately equal to that of .

Such light image irradiation and development are performed by the LED arrays 31, 32, 33, 3 controlled by a control circuit.
4 and developing units 35, 36, 37, and 38, magenta, cyan, yellow, and black are processed in this order, and a multicolor toner image is formed on the photoreceptor. In addition, multicolor refers to full color, monocolor, or multicolor (monocolor of two or more colors), and in full color, all LE
D arrays 31, 32, 33, 34 and developing devices 35, 3
6, 37, and 38, and in the case of multi-color or mono-color, it is sufficient to perform only the light image irradiation and development corresponding to the required color. Preferably, in multi-color or mono-color, the developing device that is not used is removed by turning off the bias of the developing cylinder 351, or by 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 photoreceptor and to prevent it from contributing to development on the photoreceptor.

[0030] The dot diameter of the light image by the LED array is 60
Preferably, the diameter is less than a micron, and a control circuit is provided to perform optical image scanning on the photoreceptor in the generatrix direction. If the dot diameter is large, not only the resolution will be lowered but also the color reproduction will be lowered.

FIGS. 6 and 7 show an example of the flow of static image formation by image irradiation and development in the case of full-color image creation. The LED arrays 31, 32, 33, and 34 are raster scanned so that the dots of the light images produced by each do not overlap with the dots produced by other LED arrays. That is,
A digital light image corresponding to the first color is raster-scanned at predetermined intervals, a toner of the first color is applied at the same time or immediately after the light image irradiation, and development is performed, and then a digital light image corresponding to the second color is scanned. The digital light image obtained is irradiated at dot intervals that do not overlap with the dots of the digital light image of the first color, and development is performed with a toner of a second color at the same time as or immediately after the light image irradiation, and this step is sequentially performed. By performing this process for other colors, a multicolor toner image is formed on the photoreceptor.

As described above, according to the present invention, various complementary colors can be created by combining the 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 charging polarity of the toner from the back side of the transfer material to transfer a toner image onto the transfer material. A transfer roller may be used instead of the transfer corona charger.

Reference numeral 42 is an AC neutralizing corona separation device. The paper feed roller 43 operates at a controlled timing so that the transfer material registers with the toner image on the photoreceptor and contacts the surface of the photoreceptor.

Next, the transfer material onto which the toner image has been transferred is conveyed by the conveyor belt 44 to a fixing device 50, where the toner image is fixed onto the transfer material to obtain a clear color copy. The fixing device 50 holds the transfer material between a heating roller 51 and a pressure roller 52, each having a silicon rubber surface and a heat source provided inside the roller, and fixes the transfer material using heat and pressure. The heating roller surface is coated with silicone liquid to prevent the roller surface from getting dirty.

On the other hand, some foreign matter such as toner remaining on the surface of the photoreceptor after the transfer is cleaned by a cleaning means 51 such as a cleaning brush or a cleaning blade for the next repeated use of the photoreceptor. The residual potential on the surface of the photoreceptor is erased by exposure from a lamp or the like 52. In the illustrated example, the erase exposure is performed from the front side of the photoreceptor, but it may be performed from the back side, that is, the transparent substrate side. After this, the photoreceptor is charged again by the induction roller and used again.

Experimental Example 1 An experiment was conducted regarding the formation of a monochrome image using the apparatus having the configuration shown in FIG. Magenta in developer 35, developer 3
Cyan toner was used in the toner 6, yellow toner was used in the developer 37, and black toner was used in the developer 38. When a bias of +900 V is applied to the transparent electrode 12 of the belt-shaped photoreceptor 1 via the electrode roller 7, the dark area potential on the photoreceptor surface increases by approximately +5.
When a surface potential of 00 is induced by the induction roller 21 and then a light image is irradiated by the LED array 31, the potential increases to about +9.
A surface potential of 00V was created. When this was developed by energizing only the developing device 35 and deenergizing the other LED arrays, a magenta toner image was formed on the surface of the photoreceptor, which was transferred to a transfer material and then fixed. A clear sepia-toned image was obtained. Similarly, only the LED array 32, only the LED array 33, and only the LED array 34
When light images were irradiated using only cyan, yellow, and black monochrome images were obtained.

Experimental Example 2 In the same configuration as Experimental Example 1, the speed was 40 mm/Sec.
The LED array 3 induces charges on the moving photoreceptor 1.
The light image exposure of 1 is performed by raster scanning every other dot, and immediately thereafter, development is performed by the developing device 35 (one dot lighting time is about 0.4 μSec, the raster scan time of one line is 1.5 mSec), and then When that part of the photoconductor moves to the position corresponding to the LED 32, the LED array 32 is raster scanned every other bit after a time difference of one bit, and then the developing units 36, 37,
38, almost no development occurred in the developing devices 37 and 38, and a complementary color toner image was obtained using the toner of the developing devices 35 and 36. In this toner image, the toner was crushed to some extent by fixing, and the toners were fused with each other, so that clear complementary colors were reproduced.

Experimental Example 3 Similar to Experimental Example 2, LED arrays 31, 32, 33, 34
When the toner of each color is applied by the developing units 35, 36, 37, and 38, various multicolors or full colors can be reproduced depending on the combination, and a clear color image can be produced. Obtained.

As described above, by sequentially performing the light image irradiation controlled by the control unit circuit and developing with the necessary toner at the same time as or after the light image irradiation, a desired color image can be obtained, and moreover, a long image can be continuously produced. A color image can be obtained.

In the above experimental example, a belt-shaped photoreceptor was used, but it goes without saying that an image can be formed using a drum-shaped photoreceptor in the same manner. The toner colors are not limited to the above order.

[0041]

[Effects of the Invention] In this way, the present invention allows continuous color images to be obtained and only one transfer is required, which not only allows the device to be made more compact, but also allows large-sized color images to be produced at low cost, which was previously impossible. However, the present invention has solved these problems.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of a digital color electrophotographic apparatus according to the present invention.

FIG. 2 is a diagram illustrating charging of a photoreceptor in the embodiment of FIG. 1;

FIG. 3 is a diagram showing an example of the relationship between exposure amount and surface potential of a photoreceptor.

FIG. 4 is a diagram showing an example of a developing section.

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

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

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

[Explanation of symbols]

1 Photoreceptor 2 Charging section 3 Exposure and development section 4 Transfer section 5 Cleaning section 11 Transparent substrate 12 Transparent conductive layer 13 Photoconductive layer 15 Bias power supply 21 Induction members 31, 32, 33, 34 LED arrays 35, 36,
37, 38 Developing device 351 Developing cylinder 353 Toner supply sleeve.

Claims (7)

[Claims] [Claim 1] Applying a bias voltage to the light-transmitting conductive layer and bringing a grounded inducing member into contact with a photoreceptor having a light-transparent conductive layer and a photoconductive layer disposed in this order on a light-transparent substrate. A charge is induced on the surface of the photoreceptor, and then a digital optical image corresponding to the first color is raster-scanned at predetermined intervals from the transparent substrate side, and the photoconductive layer side is scanned at predetermined intervals at the same time as or after the light image irradiation. A toner of a first color is applied to the toner and developed, and then a digital optical image corresponding to a second color is applied to the transparent substrate side at dot intervals that do not overlap with dots of the digital optical image of the first color. At the same time as or after the irradiation of the light image, development is performed with toner of the second color, and this process is performed sequentially for other colors to form a multicolor toner image on the photoreceptor, and then on the transfer material. A digital color electrophotographic device characterized by transferring images to 2. Developing according to claim 1, wherein the development is performed using a toner having a charge approximately equal to the amount of charge on the surface of the photoreceptor.
The digital color electrophotographic device described. 3. The bias voltage applied to the transparent conductive layer is a positive DC voltage when the photoconductor is an N type, and a negative DC voltage when the photoconductor is a P type. The digital color electrophotographic device described. 4. The digital color electrophotographic apparatus according to claim 2, wherein the bias voltage applied to the light-transmitting conductive layer is a voltage obtained by superimposing an alternating current on a direct current, or an alternating current voltage. 5. The electrophotographic apparatus according to claim 1, wherein the inducing member is a conductive or semiconductive roller. 6. The photoreceptor surface and the dielectric member are in contact with each other via an insulator coated on the photoreceptor surface and/or the dielectric member surface.
The digital color electrophotographic device described. 7. A digital optical image corresponding to the first color is raster scanned onto the charged photoreceptor at predetermined intervals, and toner of the first color is applied at the same time as or after the irradiation of the optical image. Then, a digital light image corresponding to the second color is irradiated at dot intervals that do not overlap with the dots of the digital light image of the first color, and the second color is developed at the same time as or after the light image irradiation. 1. A digital color electrophotographic apparatus characterized in that a multicolor toner image is formed on a photoreceptor by performing development with a toner of 1, and sequentially performing this step for other colors, and then transferring the image onto a transfer material.