JPH035748B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image recording method such as copying a color image, and in particular, to a color image recording method such as copying a color image. This invention relates to a color image recording method in which toner images are superimposed.

[Prior art]

As the above-mentioned color image recording method, the methods described in Japanese Patent Laid-Open No. 56-144452, Japanese Patent Laid-Open No. 58-116553, and Japanese Patent Laid-open No. 58-116554 are known. In all of these recording methods, a photoconductive photosensitive layer on the surface of an image forming body is charged, and the charged surface is subjected to imagewise exposure to form a low-potential electrostatic image.
This is a method using a reversal development method in which dry toner (hereinafter simply referred to as toner) charged to the same polarity as that of the image forming member is attached to the electrostatic image. Since this method obtains a reversed image, it is not possible to make a positive color copy, and colorization is limited to techniques using dot exposure such as a printer. If you want to obtain a positive image when copying a normal original, the image will be reversed, making it difficult to take countermeasures. In addition, in this reversal development method, even if the potential of the photosensitive layer in the exposed area is low, the toner has the same polarity as the toner, so it is difficult for the toner to adhere to the electrostatic image, causing the toner to scatter inside the recording device. There is a problem that it is easy to get dirty.

[Purpose of the invention]

The present invention was made in order to solve the problems in the conventional color image recording method as described above, and it not only makes it possible to obtain a positive image or a negative image, but also allows development to be performed in the opposite direction to that of an electrostatic image. To provide a color image recording method that can employ a developing method in which toner charged to a polarity adheres by Coulomb attraction, thereby sufficiently adhering the toner to an electrostatic image and reducing toner scattering. It is something to do.

[Structure of the invention]

The present invention forms a first electrostatic image by performing primary charging, secondary charging, and image exposure on a photoreceptor having an insulating layer, and a first electrostatic image charged to a polarity different from that of the first electrostatic image. After developing the first electrostatic image with a first color dry toner to form a first toner image on the photoreceptor, primary charging, secondary charging, and image exposure are performed in the presence of the first toner image. to form a second electrostatic image having the same polarity as the first electrostatic image, and forming the second electrostatic image with a second color dry toner charged to the same polarity as the first color dry toner. or a photoconductor having an insulating layer. , a first electrostatic image is formed by performing primary charging, secondary charging, simultaneous image exposure, and uniform exposure, and a first color dry toner charged to a polarity different from the first electrostatic image is used. After developing the first electrostatic image to form a first toner image on the photoreceptor, primary charging, secondary charging simultaneous image exposure, and uniform exposure are carried out in the presence of the first toner image. to obtain a second electrostatic image of the same polarity as the first electrostatic image.
The second color dry toner is used to form an electric image and is charged to the same polarity as the first color dry toner.
A color image recording method, comprising: developing an electrostatic image to form a second toner image on the photoreceptor to form a plurality of color toner images on the photoreceptor;
Alternatively, a first electrostatic image is formed by performing primary charging, secondary charging, and image exposure on a photoreceptor having an insulating layer, and a first color is charged to a polarity different from that of the first electrostatic image. After developing the first electrostatic image with a dry toner to form a first toner image on the photoreceptor,
performing recharging and image exposure in the presence of the first toner image to form a second electrostatic image having the same polarity as the first electrostatic image, and forming a second electrostatic image having the same polarity as the first color dry toner; Developing the second electrostatic image with a charged dry toner of a second color to form a second toner image on the photoreceptor, forming a plurality of color toner images on the photoreceptor. The main feature lies in the color image recording method.

That is, the color image recording method of the present invention uses, as an image forming body, a photoreceptor having an insulating layer provided with a transparent insulating surface layer on a photoconductive photosensitive layer, and the photoreceptor is subjected to primary charging, secondary charging, and image exposure. Alternatively, an electrostatic image formed by performing primary charging, secondary charging, simultaneous image exposure, and uniform exposure is developed with toner charged to a polarity different from that of the electrostatic image, which is repeated multiple times, or the first electrostatic image is When formation is performed by primary charging, secondary charging, and image exposure, the second and subsequent electrostatic image formation is repeated by recharging and image exposure to create a color image consisting of overlapping toner images of multiple colors. This method solves the above-mentioned problems in the conventional color image recording method using the reversal development method described in Japanese Patent Laid-Open No. 56-144452 and the like.

〔Example〕

Hereinafter, with reference to the drawings, the present invention will be described in detail with reference to an example of a developing method in which toner charged to an opposite polarity is attached to an electrostatic image.

FIG. 1 is a schematic configuration diagram showing an example of a recording apparatus for carrying out the method of the present invention, FIG. 2 is a partial sectional view showing the configuration of an image forming body, and FIG. 3 is a diagram of a laser beam scanner for image exposure. 4 is a partial sectional view showing an example of a developing device; FIG. 5 is a charging state change diagram schematically showing an example of an electrostatic image formation process; FIG.
The figure shows a potential change chart of the surface portion of the image forming body shown in correspondence with FIG. 5, and FIGS. 7 to 11 are flowcharts for carrying out the method of the present invention, respectively.

In the recording apparatus shown in FIG. 1, 1 is a drum-shaped image forming body that rotates in the direction of the arrow;
As shown in Fig. 2, Se, CdS, and Si are deposited on a conductive substrate 1a made of aluminum, nickel, etc.
A transparent insulating surface layer 1c made of transparent resin or the like is provided on top of the photoconductive photosensitive layer 1b, which is in contact with a conductive substrate 1a.

2 is a primary charger consisting of a combination of a lamp 2a that irradiates the surface of the image forming body 1 and a corona discharger 2b;
3 is a secondary charger consisting of a corona discharger, and 4 is an image exposure device for each color of a color image. Here, if the photoconductive photosensitive layer 1b of the image forming body 1 has a semiconductor characteristic that exhibits a rectifying effect that allows charge to be injected from the substrate 1a, the primary charger 2 does not necessarily include the lamp 2a. No need to prepare. Further, the image exposure 4 for the drum-shaped image forming body 1 may be one in which slit exposure as in a normal electrophotographic copying machine is filtered for each color using a filter.
In order to record clear color images, it is preferable to use a laser beam scanner as shown in FIG.

The laser beam scanner in Figure 3 is He-Ne
A laser beam emitted from a laser 5 such as a laser is turned on and off by an acousto-optic modulator 6, deflected by a mirror scanner 7 consisting of an octahedral rotating polygon mirror, and passed through an imaging f-theta lens 8 to an image forming body 1. Image exposure 4 is formed by scanning the surface of the image at a constant speed. Note that 9 and 10 are mirrors, and 11 is a lens for enlarging the diameter of the beam incident on the imaging f-theta lens 8 in order to reduce the diameter of the beam on the image forming body 1. Third to form image exposure 4
If you use a laser beam scanner like the one shown in the figure,
As will be described later, electrostatic images can be formed in different colors, and therefore clear color images can be recorded. However, the image exposure 4 is not limited to the above-mentioned slit exposure or dot exposure using a laser beam; for example,
LEDs, CRTs, and liquid crystals may also be obtained using optical fiber transmission bodies. Further, in the case where the image forming body can take a flat state such as a belt shape, flash exposure can also be used.

12 to 15 in Figure 1 are yellow, magenta,
These developing devices use toners of different colors, such as cyan and black, as developers, and those having a structure as shown in FIG. 4 are preferably used for these developing devices.

In FIG. 4, 16 is a developing sleeve made of non-magnetic material such as aluminum or stainless steel;
7 is a magnet body provided inside the developing sleeve 16 and has a plurality of magnetic poles in the circumferential direction; 18 is a layer thickness regulating blade that regulates the thickness of the developer layer formed on the developing sleeve 16; 19 is a sleeve 16; a scraper blade that removes the developer layer after development from above;
20 is a stirring rotating body that stirs the developer in the developer reservoir 21; 22 is a toner hopper; 23 is a toner replenishment roller that supplies toner from the toner hopper 22 to the developer reservoir 21; and 24 is a protective resistor; This is a power source for applying a bias voltage such as a DC voltage or an oscillating voltage to the developing sleeve 16 via the developing sleeve 25 to form an electric field between the developing sleeve 16 and the image forming body 1 to control the movement of toner. The figure shows the developing sleeve 16 and the magnet body 1.
7 indicates that each rotates in the direction of the arrow, but even if the developing sleeve 16 is fixed, the magnet body 17 is fixed, or the developing sleeve 16 and the magnet body 17 are rotated in the same direction. It may be something that rotates. When the magnet body 17 is fixed, usually, in order to make the magnetic flux density of the magnetic pole facing the image forming body 1 larger than the magnetic flux density of other magnetic poles, the magnetization is strengthened or a magnetic pole of the same or different polarity is attached thereto. The two magnetic poles may be placed close to each other.

In the developing device as described above, the magnetic pole of the magnet body 17 is usually
It is magnetized to a magnetic flux density of 500 to 1500 Gauss,
The magnetic force attracts the developer in the developer reservoir 21 to the surface of the developing sleeve 16, and the thickness of the adsorbed developer is regulated by the layer thickness regulating blade 18 to form a developer layer. The developer layer is the image forming body 1
The surface of the developing sleeve 16 develops the electrostatic image on the image forming body 1 in the developing area facing the surface of the image forming body 1, and the remaining Scraper blade 19
The developer sleeve 16 is removed from the surface of the developer sleeve 16 and returned to the developer reservoir 21.
In the method of the present invention, as described later, a developer layer is formed on the developing sleeve 16 so as not to rub the surface of the image forming member 1, and the toner is flown from the developer layer to the image forming member 1. to adhere to the electrostatic image. This can easily be done under so-called non-contact jumping development conditions. FIG. 4 shows the state of development under such non-contact jumping development conditions. In particular, it is preferable for the second and subsequent development cycles to be performed under non-contact jumping development conditions, so that there is little risk that the previously adhered toner will be displaced or mixed into the subsequent developing device.

In addition, as a developer, non-magnetic toner is used, which does not require the toner to contain a black or brown magnetic material, and therefore can provide a toner with a clear color, and the charging of the toner can be easily controlled. It is preferable to use a so-called two-component developer consisting of a mixture of a magnetic carrier and a magnetic carrier. In particular, the magnetic carrier may be made of styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin,
Fine particles of ferromagnetic or paramagnetic substances such as triiron tetroxide, γ-ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloy, etc. are dispersed in a resin such as epoxy resin or polyester resin. The resistivity is made by coating the surface of these magnetic particles with the above-mentioned resin.
Preferably, the insulating carrier has a resistance of 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more. If this resistivity is low, when a bias voltage is applied to the developing sleeve 16, charges are injected into the carrier particles.
Problems arise in that carrier particles tend to adhere to the surface of the image forming body and that a sufficient bias voltage is not applied. In particular, if the carrier adheres to the image forming body 1, it will adversely affect the tone of the color image.

The resistivity is determined by placing the particles in a container with a cross-sectional area of 0.05 cm ² and tapping them, then applying a load of 1 Kg/cm ² to the packed particles between the electrode that also serves as the load body and the bottom electrode. This value is obtained by reading the current value when applying a voltage that generates an electric field of 1000 V/cm.

Furthermore, if the average particle size of the carrier is less than 5 μm, the magnetization will be too weak, and if it exceeds 50 μm, the image will be improved, breakdown or discharge will easily occur, and high voltage will not be able to be applied. is preferably 5 μm or more and 50 μm or less,
If necessary, a suitable amount of a flow agent such as hydrophobic silica may be added as an additive.

The toner preferably has an average particle size of 1 to 20 μm, and has an average charge amount of 3 to 300 μc/cm.
g, particularly preferably 10 to 100 μc/g. When the average particle size of toner is less than 1 μm, it becomes difficult to separate from the carrier, and when it exceeds 20 μm, the resolution of the image decreases.

When a developer made of a mixture of an insulating carrier and toner as described above is used, the bias voltage applied to the developing sleeve 16 is adjusted such that the toner sufficiently adheres to the electrostatic image and fog does not occur. Changes can be made easily. In addition,
In order to effectively control the toner by such a bias voltage, the toner may contain a magnetic material such as that used in a magnetic carrier to the extent that color clarity is not impaired.

The above is the structure of the developing device and developer preferably used in the method of the present invention, but the present invention is not limited thereto.
Nos. 55-18656 to 18659, No. 56-144452, No. 58-
Publications Nos. 116553 to 116554 and Japanese Patent Application Laid-Open Nos. 59-181362, 59-222847, and 59-
Developing devices and developers as described in Publications No. 222851-3 and No. 59-223467 may be used. In particular, it is preferable to use a two-component developer and develop under non-contact jumping development conditions.

A pre-transfer lamp 26 in FIG. 1 irradiates the surface of the image forming body 1 after repeated development and before transfer;
1 is a corona discharger that charges the toner before transfer; 27 is a transfer device consisting of a corona discharger; and 28 is a combination of one or both of a lamp 28a and a corona discharger 28b for irradiating the surface of the image forming body 1. A static eliminator 29 is a cleaning device that removes residual toner on the image forming body 1 by a cleaning blade 29a that moves toward and away from the surface of the image forming body 1; 30 is a toner image transferred to the recording body P; It is a fixing device that fixes.

In the recording device as described above, the primary charger 2
When the corona discharger 2b performs corona discharge while irradiating the surface of the image forming body 1 with the lamp 2a (as mentioned earlier, the lamp 2a may not be necessary), the image forming body 1 The surfaces of the photoconductive photosensitive layer 1b and the transparent insulating surface layer 1c are charged as shown in FIG. 5A. When the secondary charger 3 performs corona discharge on the surface of the charged image forming body 1, the charge on the surface of the transparent insulating surface layer 1c decreases because the photoconductive photosensitive image 1b is insulating. As a result, the charge on the image forming body 1 changes as shown in FIG. 5B. When image exposure light 4 is incident on the surface of this secondarily charged image forming body 1, the photoconductive photosensitive layer 1b in the exposed area PH
Since the surface charge of the image forming member 1 decreases and the original charge remains in the unexposed area DA, the charge of the image forming member 1 changes as shown in FIG. 5C. FIG. 6 shows changes in the surface potential of the image forming body 1 during this period.

The potentials in states A, B, and C in FIG. 6 correspond to the charged states in FIG. 5, A, B, and C, respectively. That is, the potential of the exposed area PH where the imagewise exposure light 4 is incident is the surface potential shown in C (PH) in FIG. C, which is almost the same as the surface potential shown by B in
(DA), an electrostatic image with a surface potential indicated by C(PH) was formed by image exposure 4 with respect to this background potential. This electrostatic image can be developed using toner that charges the exposed area PH to the opposite polarity to that of the latent image, as in a normal electrophotographic copying machine. The color development is performed using one of the color development devices 12 to 15 corresponding to the color development device. As a result, a toner image of the first color is formed on the surface of the image forming body 1.

The above-mentioned toner image forming surface of the image forming body 1 passes through the intermediate position from the developing device placed in an inactive state to the cleaning device 29 and returns to the primary charger 2.
When the position of the secondary charger 3 is reached, corona discharge is applied to that surface by the primary charger 2 and the secondary charger 3 as before, and when the surface reaches the incident position of the image exposure 4, This time, image exposure 4 for an image of a different color is applied. The electrostatic image thereby formed is developed as before by a corresponding developer. As a result, a second color toner image is formed on the surface of the image forming body 1, and by repeating the above process, a color image consisting of three or four color toner images superimposed is formed.

The present invention is not limited to this, and even if the previous charge is eliminated by the static eliminator 28 before the second and subsequent primary chargers and secondary charging, or the dark decay is compensated for the second and subsequent times. The image exposure 4 may be applied only by secondary charging. Especially when primary charging and secondary charging are performed again without removing the previous charge, or when only secondary charging is performed, the previous charge may be applied to the corona discharger of the primary charger 2 or the secondary charger 3. It is preferable to use a scorotron corona discharger, which can perform stable charging even at low temperatures. Performing primary charging and secondary charging each time an electrostatic image is formed is particularly suitable when gradation reproducibility is important or when image exposure 4 is slit exposure or flash exposure.
Furthermore, an NP or KIP method may be adopted in which after primary charging, image exposure is performed simultaneously with secondary charging, and then front exposure is performed to form an electrostatic image. In some of the methods described above, the electrostatic image potential can be controlled so that the exposed area PH and the non-exposed area DA have the same polarity or opposite polarity depending on the relative strength of the primary charging and the secondary charging. Considering the ease of development, it is preferable that the potentials of the exposed area and the non-exposed area are opposite in polarity.

The surface of image forming pair 1, which has been subjected to the final development, is
If necessary, the toner image is charged with a corona discharger 31 and further irradiated with a pre-transfer lamp 26, so that the color image can be easily transferred onto the recording medium P with a transfer device 27. The color image transferred to the recording medium P is fixed on the recording medium P by a fixing device 30. The surface of the image forming body 1 to which the color image has been transferred is neutralized by the static eliminator 28, and the cleaning blade 29a of the cleaning device 29, which had been separated until then, comes into contact with the surface, thereby removing any residual after the transfer. Toner is removed. When the surface portion of the image forming body 1 on which the color image has been formed passes through the cleaning device 29, the cleaning blade 29a is separated from the surface of the image forming body 1, thereby recording one color image. cycle ends.

FIG. 7 is a flowchart of changes in the surface potential of the image forming body, showing an example of the present invention in which static electricity removal, primary charging, secondary charging, and image exposure are performed each time to form an electrostatic image. This is a flowchart showing a change in potential on the surface of an image forming body showing an example of the present invention in which an electrostatic image is formed by performing subsequent charging and image exposure, and these are all flowcharts shown in the fifth figure.
As shown in FIG. 6, an example of electrostatic image formation by negative exposure is shown in which an electrostatic image is formed in the image exposure area and toner is adhered thereto. On the other hand, FIG. 9 shows that by changing the conditions of primary charging and secondary charging in the example of FIG.
This is a flowchart showing an example of electrostatic image formation by positive exposure according to the present invention, in which the PH becomes a background part and the unexposed part DA becomes an electrostatic image, to which toner is attached. . Also, the first
Figures 0 and 11 are flowcharts of changes in the surface potential of an image forming body, showing an example of the present invention using an electrostatic image forming process called NP or KIP process, and Figure 10 is a flowchart for positive exposure as in Figure 9. In this case, FIG. 11 shows the case of negative exposure like FIGS. 7 and 8. To briefly explain the examples shown in FIGS. 10 and 11, in FIG. 10, charges are applied to the photoconductive photosensitive layer 1b by primary charging to positively charge the image forming body 1, and then secondary charging is performed. At times, image exposure is also performed to form an ion image on the transparent insulating surface layer 1c to negatively charge the image forming body 1, and by exposing the entire surface to light, no image exposure is performed during secondary charging. The potential of the non-exposed area DA is generated to show a positive potential, forming an electrostatic image, and a charged toner of the opposite polarity is attached to the electrostatic image by development. , shows an example in which electrostatic image formation and development similar to those described above are repeated. Also, the 11th
The figure shows primary charging, in which the image forming body 1 was positively charged in the example of FIG. Non-exposed areas other than image exposure during secondary charging by positively charging and exposing the entire surface to light.
The potential of DA is set to the same negative potential as in the primary charging, and a toner of opposite polarity is attached by development to the electrostatic image of the positively charged portion exposed to image during the secondary charging. , an example in which static elimination (this may be omitted), electrostatic image formation and development similar to those described above are repeated.

Note that the above figures 7 to 11 all show up to the stage where the second development was performed, and the position of the second image exposure was shifted from that of the first image exposure. An example is shown. However, not only in the examples shown in Fig. 7 and Figs. 9 to 11 in which static electricity removal, primary charging, and secondary charging are repeated each time, but also in the example shown in Fig. 8, the amount of light for image exposure is adjusted as necessary. The subsequent image exposure is made incident on the previous image exposure position using means such as increasing the number of exposures.
An electrostatic image can also be formed there, and by development, toner of a different color from the previous one can be deposited in an overlapping manner. T in FIGS. 7 to 11,
T' indicates toners of different colors attached to the surface of the image forming member.

Furthermore, in any of the examples shown in FIGS. 7 to 11, each development is performed using a developer of opposite polarity to that of the electrostatic image, making it possible to record extremely clear color images. Excellent results were obtained in that there was little scattering of the agent, and by configuring the recording device as shown in Figure 1, the primary and secondary chargers involved in each electrostatic image formation, and the image There is also the advantage that the exposure and forming apparatus can also be used.

The examples shown in FIGS. 7 to 11 will be described in more detail below as Examples 1 to 5.

Example 1 (Example shown in FIG. 7) A recording apparatus as shown in FIG. 1 was used. However, the image forming body 1 was one in which a 10 μm thick transparent insulating layer was provided on a 10 μm thick α-Si photosensitive layer, and its peripheral speed was 180 mm/sec. The image forming body 1 was uniformly exposed to light using a primary charger 2 lamp 2a, and charged by a DC scorotron corona discharger 2b so that the surface potential of the image forming body 1 was +700V.
Next, a secondary charger 3 consisting of a scorotron corona discharger with an AC component increases the surface potential of the image forming body 1.
It was charged to 0V. On this charged surface, He−
Writing exposure was performed at a density of 16 dots/mm using a laser beam scanner using a Ne laser as shown in Figure 3, and the exposed area was
An electrostatic image with a PH potential of +300V was formed. This electrostatic image was developed using a developing device 12 as shown in FIG.

In the developing device 12, magnetite is contained in the resin.
The average particle size is 30μm and the magnetization is 50wt% dispersed.
30 emu/g, a carrier with a resistivity of 10 ¹⁴ Ωcm or more, and a nonmagnetic toner with an average particle size of 10 μm, which is made by adding 10 parts by weight of a benzidine derivative as a yellow pigment to a styrene-acrylic resin and other charge control agents. The ratio of agent to toner to carrier is
It was used under conditions of 20wt%. Further, the outer diameter of the developing sleeve 16 is 30 mm, its rotation speed is 100 rpm, the magnetic flux density of the N and S magnetic poles of the magnet body 17 is 900 Gauss,
The rotation speed is 1000 rpm, the thickness of the developer layer in the development area
0.7mm, gap between developing sleeve 16 and image forming body 1
0.8mm, and the developing sleeve 16 has a DC voltage of 100V.
Non-contact jumping development conditions were used in which a weight voltage of 500 Hz and 400 V AC voltage was applied.

Note that while the developing device 12 is developing the electrostatic image, the developing device 13 as shown in FIG.
~15 were kept undeveloped. This can be done by disconnecting the developing sleeve 16 from the power supply 24 and placing it in a floating state, or by grounding it, or by actively applying a DC bias voltage to the developing sleeve 16 with the same polarity as the electrostatic image, that is, the opposite polarity to the charging of the toner. Among these, it is preferable to apply a DC bias voltage. Since the developing units 13 to 15 are also assumed to perform development under the same non-contact jumping development conditions as the developing unit 12, the developer layer on the developing sleeve 16 does not need to be removed. This developing device 13 uses a developer in which the toner in the developer in the developing device 12 is changed to a toner containing polytungstophosphoric acid as a magenta pigment instead of a yellow pigment, and the developing device 14 also uses a cyan toner. A developer was used in which the toner contained a copper phthalocyanine derivative as a pigment, and a toner in which the toner contained carbon black as a black pigment was used in the developing device 15. Of course, color toners in which other pigments are dyes can also be used, and the order of developing colors can be appropriately determined so as to obtain clear color images. In particular, when the image exposure positions overlap, the order of developing colors must be carefully determined because it is greatly related to the clarity of the color image.

When the toner image forming surface of the image forming body 1 developed by the developing device 12 passes through the position of the corona discharger 31 and the pre-transfer lamp 26, which are placed in an inactive state, and reaches the position of the static eliminator 28. , the charge is removed from the toner image forming surface by a charge remover 28. This static elimination step can also be omitted. and a cleaning device 2 in which the toner image forming surface is also placed in an inactive state.
When it passes through position 9 and reaches the position of primary charger 2 and secondary charger 3 again, it is subjected to primary charging and secondary charging under the same conditions as before, and when it reaches the position where it receives image exposure 4. The writing exposure was performed under the same conditions as before, but this time for a magenta image. As a result, the electrostatic image formed in the same manner as before is transferred to the developing unit 13.
The film was developed under the same conditions as the developing device 12. The same procedure was repeated for the third and fourth times, and development was carried out using the developing devices 14 and 15, respectively.

This fourth development is performed, and 4
At the stage when color images began to be formed,
activating the corona discharger 31 and the pre-transfer lamp 26;
Thereby, the color image was easily transferred, transferred to the recording medium P by the transfer device 27, and fixed by the fixing device 30.

The image forming body 1 to which the color image has been transferred is provided with a static eliminator 28
When the residual toner is removed from the surface by contact with the cleaning blade 29a of the cleaning device 29, and the surface on which the color image has been formed passes through the cleaning device 29, the color image is completely recorded. One cycle process has been completed.

The color image recorded in the above manner was extremely clear, with no color mixing not only in areas where the color toners were loosely adhered to each other, but also in areas where they were closely adhered.

Example 2 (Example of FIG. 8) Same as in Example 1, except that image forming body 1
used a recording device in which a 20 μm thick transparent insulating layer was provided on a 30 μm thick CdS photosensitive layer. The image forming body 1 was charged to +1000V by the primary charger 2 while being uniformly exposed to light using the lamp 2a as in Example 1, and then charged to -100V by the secondary charger 3. Writing was performed on this charged surface using a laser beam scanner in the same manner as in Example 1. The potential of the electrostatic image thus obtained was +500V compared to -100V in the background. This electrostatic image is transferred to the developing sleeve 16 with a DC component of 50V and an AC component of 1.5KHz and 1000V.
Developing was carried out using the developing device 12 under the same conditions as in Example 1, except that a voltage of .

Then, when the surface of the image forming body 1 developed by the developing device 12 reaches the position of the secondary charger 3 again,
The image forming body 1 is charged again by the secondary charger 3 so that the surface potential becomes -100V, and the surface is exposed for writing for the second time under the same conditions as before except that the dot position is shifted using the same laser beam scanner. An electrostatic image was formed again, and the electrostatic image was developed using the developing device 13 using the same developer as in Example 1 under basically the same developing conditions as the developing device 12.

Furthermore, repeat charging and exposure in the same way as the second time.
The electrostatic image for the fourth time was developed using the developer 14, and the electrostatic image for the fourth time was similarly developed using the developer 15. in this case,
Each time of development, the amplitude, frequency, duty ratio, etc. of the DC bias component and AC component of the voltage applied to the developing sleeve 16 are adjusted in accordance with changes in the surface potential of the image forming body 1, development characteristics, and color reproduction conditions. I decided to change it.

After the fourth development was performed and a four-color image was formed on the image forming body 1, the color image recording operation was completed in the same manner as in Example 1.

The obtained recorded image is similar to that in Example 1,
It was extremely clear.

Example 3 (Example shown in FIG. 9) A recording apparatus similar to that in Example 1 was used.
The image forming body 1 was charged to -700V by the primary charger 2 while being uniformly exposed to light using the lamp 2a as in Example 1, and then charged to +300V by the secondary charger 3. This charged surface was subjected to slit exposure through a blue filter in an ordinary color copying machine. The background area corresponds to the exposed area PH.
In contrast to 50V, an electrostatic image corresponding to the unexposed area DA was obtained at a potential of +300V. This electrostatic image is transferred to a developing sleeve with DC component +50V and AC component 500Hz, 400V.
Developing was carried out using the developing device 12 under the same conditions as in Example 1, except that a voltage of . The second time, after activating the static eliminator 28 to eliminate static electricity (this static elimination step may be omitted), primary charging, secondary charging, and image exposure through a green filter are performed under the same conditions as the first time. Developing was carried out using the developing device 13 using the same developer as in Example 1 under the same developing conditions as the developing device 12. The third and fourth times are the same as the second time, but the exposure filters are changed to a red filter and a neutral filter, respectively.
Electrostatic images are repeatedly formed, and the developing devices 14 and 1 are used, respectively.
5 was developed. The developers in the developing units 14 and 15 are the same as in Example 1, and
Although this was hardly necessary in practice, the voltage conditions applied to the developing sleeve were changed in accordance with the potential change of the image forming member 1, the developing characteristics, and the color reproduction situation, as in Example 2. Then, the color image recording operation was completed in the same manner as in Example 1.

The recorded image obtained was extremely clear as in Example 1.

Example 4 (Example shown in FIG. 10) A recording apparatus similar to that in Example 1 was used.
While uniformly exposing the image forming body 1 with the lamp 2a, it was charged to +700V by the primary charger 2 in the same manner as in Example 1, and then charged to -100V by the secondary charger 3. At the time of charging, slit exposure was simultaneously performed through a blue filter in an ordinary color copying machine, and then uniform exposure was performed. As a result, an electrostatic image corresponding to the non-exposed DA was formed at a potential of +300 V against a background area of -100 V corresponding to the exposed area PH. This electrostatic image is transferred to the developing sleeve with a DC component of 0V.
Developing was carried out in Developing 12 under the same conditions as in Example 1, except that a voltage of 400 V and an AC component of 500 Hz was applied. 2
For the second time, after activating the static eliminator 28 to eliminate static electricity (this static elimination step may be omitted),
Primary charging, secondary charging, image exposure through a green filter, and uniform exposure were performed under the same conditions as in Example 1, and the developing conditions were the same as those of developing device 12 using developing device 13 using the same developer as in Example 1. Developed under the following conditions. The third and fourth times were carried out in the same manner as the second time, except that the image exposure filters were changed to a red filter and a neutral filter, respectively, and electrostatic images were repeatedly formed and developed using the developing devices 14 and 15, respectively. The developer in the developing units 14 and 15 is the same as in Example 1, and although it is hardly necessary in practice, the developer may be applied to the developing sleeve depending on the potential change of the image forming member 1, the developing characteristics, and the color reproduction. The same procedure as in Example 2 was carried out by changing the voltage conditions. Then, the color image recording operation was completed in the same manner as in Example 1.

The recorded image obtained was extremely clear as in Example 1.

Example 5 (Example shown in FIG. 11) A recording apparatus was used in the same manner as in Example 1.
A recording device as shown in FIG. 1 was used. however,
The image forming body 1 is formed on an α-Si photosensitive layer with a thickness of 10 μm.
A 10 μm transparent insulating layer was provided, and the circumferential speed was 180 mm/sec. As in Example 1, this image forming body 1 was charged to -700V by the primary charger 2 while being uniformly exposed to the lamp 2a, and then charged to +300V by the secondary charger 3. At the same time as this secondary charging, writing was performed using a laser beam scanner, and then uniform exposure was performed. As a result, for the background area -100V corresponding to the unexposed area DA,
An electrostatic image corresponding to the exposed area PH was formed at a potential of +300V. This electrostatic image is transferred to the developing sleeve as a direct current component.
Developing was carried out using the developing device 12 under the same conditions as in Example 1, except that a voltage of 50 V and AC components of 500 Hz and 400 V were applied. For the second time, after the static eliminator 28 was activated to remove static electricity, primary charging, secondary charging, image exposure, and uniform exposure were performed under the same conditions as for the first time, and development was performed using the same developer as in Example 1. Developing device 12 by container 13
Developed under the same conditions as . Repeat the same process as the second time for the third and fourth time, and use developer 1 for each time.
4.15. The developers in the developing units 14 and 15 are the same as in Example 1,
In addition, although it is hardly necessary in practice, the image forming body 1
Similarly to Example 2, the voltage conditions applied to the developing sleeve were changed depending on potential changes, developing performance, and color reproduction conditions. Then, the color image recording operation was completed in the same manner as in Example 1.

The recorded image obtained was extremely clear as in Example 1.

〔Effect of the invention〕

According to the present invention, the potential and polarity of an electrostatic image can be changed by the relative strength of the primary charger and the secondary charger, and positive or negative exposure can be easily performed. Furthermore, toner images can be easily overlapped by non-contact jumping development conditions. In particular, since the electrostatic image polarity and the toner are made to have different polarities, dry toner can easily adhere to the electrostatic image, and development conditions can be easily adjusted in response to changes in the potential of the image forming body, allowing for sufficient density. It can reproduce color images with excellent clarity, and there is little toner scattering. Furthermore, when the same charger or image exposure forming device is used for each electrostatic image formation, there is no registration problem and the recording apparatus can be made smaller and less expensive.

Note that in the present invention, the image forming body is mounted on a substrate like electrofax paper, and
It can also be applied to a device in which a color image formed thereon is fixed without being transferred. In this case, a pre-transfer lamp, a transfer device, and even a cleaning device are not required. Of course, the lamp 26 and the static eliminator 31 before transfer can be omitted even when transferring, and
In addition to corona transfer, the transfer may be bias roller transfer, adhesive transfer, direct pressure transfer, or transfer using an intermediate transfer member, and fixing is, of course, not limited to hot roller fixing.

Also, it is a great advantage that the polarity of the latent image potential between the image area and the non-image area can be reversed by balancing the strength of primary charging and secondary charging, but even if the polarity is the same, it is possible to change the developing bias conditions. Of course, it is also possible to develop the image by exposing it to the image. The potential at this time holds the relationship that is obtained by shifting the 0 potential upward or downward in FIGS. 7 to 11.
Similar development is possible by changing the developing bias accordingly.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an example of a recording apparatus for carrying out the method of the present invention, FIG. 2 is a partial sectional view showing the configuration of an image forming body, and FIG. 3 is a diagram of a laser beam scanner for image exposure. Figure 4 is a partial cross-sectional view showing an example of a developing device, Figure 5 is a charging state change diagram schematically showing an example of the electrostatic image formation process, Figure 6 corresponds to Figure 5. The potential change chart of the surface portion of the image forming body shown in FIG. DESCRIPTION OF SYMBOLS 1... Image forming body, 1a... Conductive substrate, 1b... Photoconductive photosensitive layer, 1c... Transparent insulating surface layer, 2... Primary charger, 2a... Lamp, 2b... Corona discharger, 3... Secondary charger, 4 ...image exposure, 5...laser, 6...acousto-optic modulator, 7...mirror scanner, 8...imaging f
-θ lens, 9, 10...mirror, 11...lens,
12-15...Developing device, 16...Developing sleeve, 17
... Magnet body, 18 ... Layer regulation blade, 19 ... Scraper blade, 20 ... Stirring rotor, 21 ... Developer reservoir, 22 ... Toner hopper, 23 ... Toner supply roller, 24 ... Power supply, 25 ... Protection resistor, 26 ... Before transfer Lamp, 27... Transfer device, 28... Static eliminator, 28
a... Lamp, 28b... Colon discharger, 29... Cleaning device, 29a... Cleaning blade,
30... Fixing device, 31... Corona discharger, P... Recording body, T, T'... Adhesive toner.

Claims (1)

[Scope of Claims] 1. A photoreceptor having an insulating layer is subjected to primary charging, secondary charging, and image exposure to form a first electrostatic image, and is charged to a polarity different from that of the first electrostatic image. After developing the first electrostatic image with a dry toner of a first color and forming a first toner image on the photoreceptor, primary charging and secondary charging are performed in the presence of the first toner image. Charging and image exposure are performed to form a second electrostatic image having the same polarity as the first electrostatic image, and the dry toner of the second color is charged to the same polarity as the first color dry toner. 1. A color image recording method, comprising: developing two electrostatic images to form a second toner image on the photoreceptor, thereby forming toner images of a plurality of colors on the photoreceptor. 2. A first electrostatic image is formed by performing primary charging, secondary charging, simultaneous image exposure, and uniform exposure on a photoreceptor having an insulating layer, and the photoreceptor is charged to a polarity different from that of the first electrostatic image. After developing the first electrostatic image with a first color dry toner to form a first toner image on the photoreceptor, primary charging and secondary charging are simultaneously performed in the presence of the first toner image. performing image exposure and uniform exposure to form a second electrostatic image having the same polarity as the first electrostatic image;
Developing the second electrostatic image with a second color dry toner charged to the same polarity as the first color dry toner to form a second toner image on the photoreceptor; A color image recording method characterized by forming toner images of multiple colors on. 3. A photoreceptor having an insulating layer is subjected to primary charging, secondary charging, and image exposure to form a first electrostatic image, and a first color charged to a polarity different from that of the first electrostatic image is formed. After developing the first electrostatic image with dry toner to form a first toner image on the photoconductor, recharging and image exposure are performed in the presence of the first toner image to form the first electrostatic image. forming a second electrostatic image having the same polarity as the first electrostatic image; developing the second electrostatic image with a second color dry toner charged to the same polarity as the first color dry toner; A color image recording method, comprising: forming a toner image of a plurality of colors on the photoconductor by forming a toner image of a plurality of colors on the photoconductor.