JPH03212663A - Color image forming device and its using method - Google Patents

Abstract

PURPOSE:To excellently secure the image quality of the color of three systems while effectively restraining the color mixture and the contaminative development of a reproduced image by using toner having a different polarity in the case of forming the image. CONSTITUTION:A negative latent image Zn where the potential of an image part is lower than that of a background part is formed on a latent image carrier 1 by a 1st latent image forming means 2. The latent image Zn is reversely developed with the 1st toner T1 (negative polarity) by a 1st developing means 3. Next, a positive latent image Zp where the potential of the image part is higher than that of the background part is formed by a 2nd latent image forming means 4. The latent image Zp is normally developed with the 2nd toner T2 (positive polarity) by a 2nd developing means 5. Next, an electrostatic recharging means 6 prevents the inversion of the polarity of the toner T1 and adjusts the potentials of the 1st and the 2nd toner images nearly equal. A positive latent image Zp where the potential of the image part is higher than that of the background part is formed by a 3rd latent image forming means 7. The latent image Zp is normally developed with the 3rd toner T3 (positive polarity) by a 3rd developing means 8. After arranging the polarities of the respective toner images by a pre-transfer processing means 9, the images are transferred on a recording sheet 11 en bloc by a transfer means 10.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color image forming apparatus such as a color printer or a color copying machine, and a method of using the same, and particularly relates to a color image forming apparatus such as a color printer or a color copying machine, and a method of using the same. , relates to an improvement in a color image recording device that transfers a plurality of color images onto a recording sheet at once, and a method for using the same.

[Conventional technology]

Taking a printer as an example of a conventional color image forming apparatus, in each rotation cycle of a photosensitive drum that rotates multiple times, a corresponding system of toner images is formed on the photosensitive drum, and the toner image is transferred to a transfer drum that rolls in contact with the photosensitive drum. For example, there is a so-called transfer drum method in which toner images of each system on a photosensitive drum are transferred onto a wound recording sheet in an overlapping manner for each rotation cycle, and a method using a plurality of image forming units (photosensitive drum, latent image forming unit, developing unit, etc.). The so-called tandem system is a so-called tandem system in which the toner images formed by each image forming unit are sequentially transferred onto a recording sheet that is conveyed along a predetermined direction by a sheet conveying device. Something called the above has already been proposed.

However, in the former type, the photosensitive drum must be rotated multiple times to form one color image, which poses problems such as the time it takes to form a color image, and the accuracy of the transfer position of each toner image. In order to improve the performance of the printer, the rotation of the photosensitive drum and transfer drum must be controlled with high precision, which poses the problem of complicating device control.

In addition, in the latter type, it is possible to shorten the color image forming time compared to the former type, but not only does the device itself become larger, but it is also difficult to control the rotation of the photosensitive drum of each image forming unit. In addition, conveyance control of the recording sheet must be performed with high precision, and there is a problem that device control becomes complicated (see Japanese Patent Laid-Open No. 174564/1983).

In order to solve this problem, a device has already been proposed in which multiple systems of toner images are formed on a photosensitive drum and then these toner images are transferred all at once to a recording sheet (Japanese Patent Laid-Open No. 58 -57139, 60-2476
(See Publication No. 50).

For example, as shown in FIG. 9, the photosensitive drum 100
A charger 10 for pre-charging the photosensitive drum 100 is placed around the
1. A first laser 102 for forming a first latent image; a first developer 10 of a developing bias type for developing the first latent image;
3. First recharger 104 that recharges the photosensitive drum 100
, a second laser 105 for forming a second latent image, and a second developing device 106 of a developing bias type for developing the second latent image.
, a second recharger 107 that recharges the photosensitive drum 100;
a third laser 108 for forming a third latent image; a third developing device 109 of a developing bias type for developing the third latent image;
A charger 110 that adjusts the potential level of each toner image on the photosensitive drum 100, a transfer device 111 that transfers all toner images on the photosensitive drum 100 to a recording channel 112, and a cleaner that removes residual toner on the photosensitive drum 100. 113 are arranged respectively.

In this type of image forming process, for example, as shown in FIG. In step b), forming a first negative latent image Zn whose potential is lower than the background potential, the negative latent image is formed with the first toner T1 while a predetermined developing bias VBI is applied to the first developing device 103. The Zn is reversely developed (step C), and then the photosensitive drum 100 is recharged by the first recharger 104 (step d). To form a second negative latent image Zn, in step e), only the second negative latent image Zn is reversely developed with the second toner T2 while a predetermined developing bias VB□ is applied to the second developing device 106. In step f), furthermore, the second recharger 10
After recharging the photosensitive drum 100 in step 7 (step g), a third laser 108 is used to form a third negative latent image Zn in which the potential of the image area is lower than the potential of the background area (step h), and the third development described above. With a predetermined developing bias VBI applied to the device 109, the third negative latent image Zn is formed using the third toner T3.
In step i), the charger 100 adjusts the potentials of the toner images of each system to be approximately equal (step j), and then the transfer device 112 transfers each toner image at once to the recording sheet 111 side. This is how it was done.

[Invention or problem to be solved]

However, in such an image forming process, when forming toner images of each system, the negative latent image is developed in reverse using toner of the same polarity. In the second and third development steps, a color mixing phenomenon in which each toner mixes with each other on the image tends to occur, and
When some of the toner from the developer toner image on the photosensitive drum 100 peels off and enters the next developing device, the mixed toner will accumulate in the developing device, and the triboelectric charging characteristics of the toner in the developing device will deteriorate. This not only accelerates the deterioration of the toner inside the developing device, but also changes the color tone of the toner inside the developing device, which causes a corresponding loss in the color quality of the reproduced image.

In addition, when reproducing a two-color image using this type of device, for example, two lasers 102, 105 and two developing devices 103, 106 are used to reproduce the two-color image. The image color is limited to the color of the toner in the developing device being used, and it is difficult to reproduce a customer's (custom) desired color image unless the toner in the developing device is replaced.

The present invention has been made in view of the above-mentioned problems, and satisfies the demands of increasing the color image forming speed and making the device more compact, while effectively suppressing color mixing and mixing phenomena in reproduced images. To provide a color image forming device that can maintain good three-system color image quality and efficiently reproduce two-color images including a customer's favorite color image, and a method for using the same. .

[Means to solve the problem]

That is, the color image forming apparatus according to the present invention has a first
As shown in Figure (a), there is a latent image carrier 1 carrying an electrostatic latent image, and a negative latent image Zn on which the image area potential is lower in absolute value than the background area potential. a first latent image forming means 2 for forming a first latent image; a first developing means 3 for reversing and developing a negative latent image Zn formed by the first latent image forming means 2 with a second toner T1; Arranged after the forming means 2,
A second latent image forming means 4 for forming a positive latent image Zp on the latent image carrier l, in which the image area potential is higher in absolute value than the background area potential.
and a positive latent image Z formed by this second latent image forming means 4.
a second developing means 5 which regularly develops p with a second toner under 2, and a recharging means which adjusts the potentials of the first toner image and the second toner image to be approximately equal while preventing polarity reversal of the first toner TI. 6, and a third latent image forming means 7 for forming a positive latent image Zp on the latent image carrier 1 recharged by the recharging means 6, the potential of the image area being higher in absolute value than the potential of the background area; A third developing means 8 for regularly developing the positive latent image Zp formed by the second latent image forming means 4 or the third latent image forming means 7 with a third toner T3; This apparatus is characterized by comprising a transfer pre-processing means 9 for aligning the polarity of each toner image, and a transfer means 10 for collectively transferring each toner image of uniform polarity onto a recording sheet 11.

In such an apparatus invention, the latent image carrier 1 includes:
The design may be changed as appropriate depending on the type of latent image forming means, such as using a photoreceptor when forming an electrostatic latent image using light and using a dielectric when forming an electrostatic latent image using ions.

Further, the structure of the latent image carrier 1 may be drum-shaped or belt-shaped, and the charging type may be positive or negative.

Further, the first latent image forming means 2, the second latent image forming means 4, and the third latent image forming means 7 include latent image writing means for forming an electrostatic latent image on the latent image carrier l. If it is necessary to charge the surface of the latent image carrier 1 in advance for writing an electrostatic latent image, it is necessary to configure the charging means to include a charging means.

In this case, the latent image writing means can be appropriately selected from an exposure lamp, an optical imaging system, a laser, an LED, a liquid crystal shutter, etc. in the case of a type using a light beam, or an appropriate one for a type using ions. The discharge head and the like can be selected as appropriate.

Furthermore, the developing method and type of developer for the first developing means 2, second developing means 5, and third developing means 7 may be selected as appropriate, but in consideration of developing efficiency, it is preferable to use a two-component developer. A magnetic brush development type is preferred. In this case, from the viewpoint of preventing disturbance of the toner image in the developing section in the second developing step and the third developing step,
For example, when adopting a magnetic brush development method using a two-component developer, a low-density developer carrier is used, a repulsive magnetic pole is provided at the development area of the developer carrier, and the developer Decrease the relative speed ratio between the carrier and the latent image carrier l (Japanese Patent Laid-Open Nos. 142363-1983 and 1999), etc.
-287581, Patent Application No. 168696/1983)
Therefore, it is preferable to use a soft magnetic brush using the developer, or it is preferable to use a non-contact developing method.

Furthermore, regarding the recharging means 6, the first toner T
1, the first toner T1,
The second toner bottom 2 may be recharged without changing its polarity, or when forming a three-system toner image, the second toner T1 may be recharged without reversing the polarity of the first toner T1. Recharging may be performed with the polarity of the lower 2 reversed.

Further, the design of the transfer pretreatment means 9 may be changed as appropriate as long as it at least aligns the polarity of each toner image on the latent image carrier 1, but considering the transfer efficiency of each toner image, for example, When the latent image carrier 1 is a photoconductor, an exposure process is performed simultaneously with the charging process or after the charging process, so that the latent image carrier l of each toner image area is
It is preferable to take measures to lower the potential of .

Also, regarding the transfer means 10, if the toner image on the latent image carrier 1 is transferred to the recording sheet 11 side, each toner image on the latent image carrier 1 is electrostatically transferred to the recording sheet 11 side. It is not limited to those that are transferred, but also includes those that are transferred to the recording sheet 11 side by a method such as thermal transfer.

Furthermore, in consideration of the lifespan of the developer, when a two-component developer having an insulating carrier is used as the developer of the first developing means 3, the toner image forming area in the second developing step must be accurately set. From the perspective of defining, Figure 1 (
As shown by the imaginary line in a), it is preferable to arrange a recharging means 12 before the second latent image forming means 4 and to reduce the electric potential of the first toner image in absolute value.

Further, the image forming process when obtaining three systems of color images using the above color image forming apparatus is shown in FIG. 1(b).
As shown, a negative latent image Zn is formed on the latent image carrier l by the first latent image forming means 2, and this negative latent image Zn is reversely developed by the first toner TI of the first developing means 3. In the first system toner image forming step AI, a positive latent image Zp is formed on the latent image carrier 1 by the second latent image forming means 4, and this positive latent image Zp is transferred to the second toner T2 of the second developing means 5. A second system toner image forming step A2 in which regular development is carried out by the recharging means 6, and the potentials of the first system toner image and the second system toner image are adjusted to be approximately equal while preventing polarity reversal of the first toner T1. After that, the third latent image forming means 7 forms a positive latent image Zp on the latent image carrier l, and the third developing means 8 regularly develops this positive latent image Zp with the third toner T3. Systemic toner image forming step A3
and a toner image transfer step A4 in which, after the polarities of the first to third system toner images are aligned in the transfer pretreatment means 9, the toner images are transferred all at once to the recording sheet 11 by the transfer means 10. It is characterized by the presence of

Furthermore, in the image forming process of obtaining two color images using the color image forming apparatus, as shown in FIG. A negative latent image Zn is formed, and this negative latent image Zn is transferred to the first developing means 3.
A first system toner image forming step B1 in which reversal development is performed using the first toner TI, and a positive latent image Zp is formed on the latent image carrier 1 by the second latent image forming means 4. After regular development with the second toner T2 other than black in the second developing means 5,
A second system toner image forming step B2 in which the third toner other than black toner T3 of the third developing means 8 is further superimposed and regularly developed, and the polarity of the first and second system toner images is adjusted in the transfer pretreatment means 9. The toner images are aligned and transferred to the recording sheet 11 by the transfer means 10.
The method is characterized in that it includes a toner image transfer step B3 in which the toner image is transferred all at once.

In the image forming process shown in FIG. 1(c), the same positive latent image zp is processed by the second developing means 5. It is necessary to adjust the third developing means 8 so that each toner can be developed in an overlapping manner, and if the second and third developing means 5 and 8 are of a developing bias type, for example, different developing biases may be used. is applied, the second toner T2. The degree of development of the third toner T3 may be adjusted.

[Effect]

When forming three systems of color images using the above color image forming apparatus, in the first system toner image forming step Al, the negative latent image Zn corresponding to the first image on the latent image carrier 1 is The positive latent image Zp corresponding to the second image on the latent image carrier 1 is developed normally with the second toner T2 in the second system toner image forming step A2, and the third system In the toner image forming step A3, the positive latent image Zp corresponding to the third image on the latent image carrier 1 is regularly developed with the third toner T3, and in the toner image transfer step A4, toner images of each system are recorded. The images are transferred all at once to the sea hll.

In such an image forming process, even if the first system toner image formed by the first toner Tl comes into contact with the second toner T2 and third toner T3 in the second and third development steps, the first toner TI and second and third toner T2. T3
Since the polarity is different from that of the second and third toners T2. T
3 will not be mixed with the first system toner image.

Moreover, the first toner T1 of the first system toner image is peeled off, and the second developing means 5. Even if the first toner T1 enters the nozzle of the third developing means 8, the first toner T1 will be replaced by the second toner T2 in the second developing means 5 or the third toner T in the third developing means 8.
3, the first toner T1 is easily discharged from each housing and does not accumulate inside the housing.

Further, when forming two systems of color images using the color image forming apparatus, in the first system toner image forming step Bl, a negative latent image Zn corresponding to the -th image on the latent image carrier 1 is formed. is reversely developed with the first toner T1, and in the second system toner image forming step B2, a positive latent image Zp corresponding to the second image on the latent image carrier 1 is normally developed with the second toner bottom 2. At the same time, it is further developed properly with the third toner T3,
In the toner image transfer step B3, the toner images of each system are transferred to the recording sheet 11 at once.

In such an image forming process, the second toner under the second toner is added to the first system toner image by the same effect as described above.
, the third toner T3 will not be mixed, and the first toner TI will not be mixed into the housings of the second developing means 5 and the third developing means 8.

Furthermore, in this image forming process, since the second system toner image is a superposition of the second toner bottom 2 and the third toner T3, the color of the second system toner image is different from that of the second toner bottom 2. Alternatively, the toner is adjusted to be different from the third toner T3.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

◎Basic configuration Figure 2 shows an embodiment in which the present invention is applied to a color printer.

In the figure, reference numeral 20 indicates a negatively charged type OPC (Orga
21 is a charging scorotron that charges the photosensitive drum 20 in advance; 22 is a first laser that forms a first negative latent image corresponding to the first image on the photosensitive drum 20; A first developer of a two-component magnetic brush development system that reversely develops one negative latent image with a first toner Tl (negative polarity); 24 a second positive latent image corresponding to a second image on the photosensitive drum 20; 25 is a second developer of a two-component magnetic brush development system that regularly develops the second positive latent image with the second toner (positive polarity) T2; 26 is the polarity of the first toner TI; A recharging scorotron 27 for recharging the surface of the photosensitive drum 20 by reversing the polarity of the second toner bottom 2 while preventing reversal;
28 is a third laser which forms a third positive latent image corresponding to the third image on the photosensitive drum 20, and 28 regularly develops the third or second positive latent image with, for example, a third toner (positive polarity). A third developer of a two-component magnetic brush development type; 29 a pre-transfer corotron for aligning the polarity of each toner image formed on the photosensitive drum 20 to, for example, negative polarity; 30 a pre-transfer corotron for charging the recording sheet 31; Record each toner image on sheet 3
A transfer corotron 32 performs electrostatic transfer to the photosensitive drum 20 at once, and a daytack corotron 32 removes static electricity from the recording sheet 31 on which each toner image has been transferred on the photosensitive drum 20 and peels the recording sheet 31 from the photosensitive drum 20. 33 is photosensitive drum 2
A cleaner 34 removes the residual toner on the photosensitive drum 20, and a discharge lamp 34 removes the residual charge on the photosensitive drum 20.

In this embodiment, the charging scorotron 21 and the recharging scorotron 26 are provided with a discharge wire 42 disposed within a shield 41 having a U-shaped cross section, and a control grid provided in an opening of the shield 41, as shown in FIG. 43, a discharge wire 42 and a control grid 43
A negative high voltage of a predetermined level is applied to each from a high voltage power supply 44 and 45.

In addition, in this embodiment, the second developing device 25.28
As shown in FIGS. 4 and 5, a developing roll 62 is disposed within a housing 61, and the developing roll 62 has seven poles (Nl to N4.
SL to S3) A magnet roll 64 with an asymmetrical magnetization configuration is fixedly provided, and the magnetic flux density of the main pole (repulsive magnetic pole made of N2 and N3) 65 is about 1200 Gauss, and the difference between its peak and valley is 50 to 200 Gauss. Furthermore, the magnetic flux density of the other magnetic pole 66 is set to about 800 Gauss.

Furthermore, as the developer in the second developing device 25 and the third developing device 28, a carrier in which magnetic powder is dispersed in a resin binder and has a density of 4 g/c& or less is used.

◎Operation of Apparatus Next, the operation of the color printer according to this embodiment in each image forming mode will be explained.

Note that the process speed of the photosensitive drum 20 in this example is 150 mm/see.

(1) Three-color image mode (see Figure 6) In this mode, it is difficult to use non-transparent black toner as the toner in the first and second developing units 23, 25.
A transparent yellow toner is used as the first toner T1 of the first developing device 23, a transparent magenta toner is used as the second toner bottom 2 of the second developing device 25, and a black toner is used as the third toner of the third developing device 28. is used.

■-Uniform electrical process (step a) The surface of the photosensitive drum 20 is uniformly charged to -600V.

■First exposure process (step b) A first negative latent image Zn whose image part potential is lower than the background part potential is formed by the first laser 22 (a pattern generator is used for the image signal, the same applies to each laser below). Form.

In this embodiment, the image portion potential is set to -100V, and the background portion potential is set to -600V.

(1) First developing step (Step C) The developing bias VB1 of the first developing device 23 is set to -450 V, and the negative latent image Zn is reversely developed with the first black toner T1 (negative polarity).

(2) Second exposure step (step d) The second laser 24 forms a second positive latent image zp in which the potential of the image area is higher than the potential of the background area. At this time, the first system toner image potential (1) is set to be smaller in absolute value than the background potential.

In this embodiment, the background potential is -250V, the image potential is -580V, and the first system toner image potential is V.

Set to about -130V.

■Second developing step (step e) The developing bias VB2 of the second developing device 25 is -400■, and the positive latent image Zp is transferred to the second yellow toner T2 (
Regularly develop with positive polarity).

In this case, since the first system toner image is held by the well-shaped potential pattern, the first system toner image is hardly destroyed, and the second toner bottom 2 is in the first system toner image. Moreover, the peeled toner T1 of the first system toner image is mixed with the second developing device 2.
It will not be mixed into 5.

■Recharging process (step f) By appropriately adjusting the voltage of the control grid 43 of the recharging scorotron 26 and the applied voltage of the discharge wire 42,
Without reversing the polarity of the first toner TI, the polarity of the second toner under 2 is reversed, and the surface potential of the photosensitive drum 20 is recharged to the initial charging level (approximately -600V).

(3) Third exposure step (step g) The third laser 27 forms a third positive latent image Zp in which the potential of the image portion is higher than the potential of the background portion. At this time, since each toner of the first system toner image and the second system toner image is a transparent toner, it is not possible to sufficiently reduce the potential of the photosensitive drum 20 corresponding to each toner image in absolute value in this exposure step. This is possible, and by appropriately adjusting the exposure amount, the first system toner image potential vT1 and the second system toner image potential VT2 are set to be slightly lower in absolute value than the background potential. In this example, the background potential is -150V and the image potential is -150V.
80■, 1st and 2nd system toner image potential VT1, VT2
Set to about -100V.

(3) Third developing step (step h) The developing bias VB3 of the third developing device 28 is set to -350 V, and the positive latent image Zp is regularly developed with the third black toner T3 (positive polarity).

In this case, since the first system toner image and the second system toner image are held together by the well-shaped potential pattern, the first system toner image and the second system toner image are almost never destroyed. Third toner T3 and first toner TI
, since the polarity is different from that of the second toner lower 2, the third toner T
3 is hardly mixed into the first system toner image and the second system toner image, and furthermore, the peeled toner of the first system toner image and the second system toner image does not mix into the third developing device 29. .

(2) Pre-transfer processing step (step i) A predetermined DC component voltage with an AC component superimposed is applied to the discharge wire of the pre-transfer corotron 29 to align the toner polarities of the toner images of each system to positive polarity.

[Phase] Transfer process When a predetermined DC component voltage with an AC component superimposed was applied to the discharge wire of the transfer corotron 31, the recording sheet 3
The toner images of each system on the photosensitive drum 20 were transferred at once to the second side, and three color images of yellow, macenta, and black were obtained.

(2) Two-color standard color image mode (see FIG. 7) In this mode and the two-color custom color image mode described below, for example, black toner is used as the first toner TI in the first developer 23, and black toner is used in the second developer. For example, a yellow toner is used as the second toner bottom 2 of 25, and a third toner T3 of the third developing device 28 is used.
For example, cyan toner is used.

(2) The charging process (step a) and the first exposure process (step b) are performed in the same manner as in the three-color image mode.

(1) First developing step (Step C) The developing bias VBI of the first developing device 23 is set to -450 V, and the negative latent image Zn is reversely developed with the first black toner Tl (negative polarity).

(2) Second exposure step (step d) The second laser 24 forms a second positive latent image Zp in which the potential of the image portion is higher than the potential of the background portion. At this time, the first system toner image potential V1 is set to be smaller in absolute value than the background potential.

In this example, the background potential is -250V, the image potential is -580V, and the first system toner image potential VT is -140V.
Set to a certain degree.

(2) Second developing step (step e) The developing bias VB2 of the second developing device 25 is set to -350 V, and the positive latent image Zp is regularly developed with the second yellow toner T2 (positive polarity).

In this case, since the first system toner image is held by the well-shaped potential pattern, the first system toner image is hardly destroyed, and the yellow toner T
2 is rarely mixed in the first system toner image (,
Moreover, the peeled toner of the first system toner image is transferred to the second developing device 2.
It will not be mixed into 5.

(2) Pre-transfer processing step (step f) A predetermined DC component voltage with an AC component superimposed is applied to the discharge wire of the pre-transfer corotron 29 to align the toner polarities of the toner images of each system to positive polarity.

■Transfer process When a predetermined DC component voltage with an AC component superimposed was applied to the discharge wire of the transfer corotron 30, the recording sheet 3
The toner images of each system on the photosensitive drum 20 were collectively transferred to the first side, and two color images of black and yellow were obtained.

Incidentally, instead of forming the second system toner image with the second laser 24 and the second developing device 25, the latent image formed with the second laser 45 or the third laser 2f is transferred to the cyan toner image of the third developing device 28. It is also possible to form a second system toner image by developing with color toner T3.

(3) Two-color custom color image mode (see Figure 8) This image forming mode forms a two-color image that includes a color that is different from the color of the toner being used and that can be selected arbitrarily by the customer to some extent (custom color). Image formation is performed through the following steps.

■-like charging process (step a), ■first exposure process (step b), ■first development process (step C), and ■second exposure process (step d) are the same as in the above two-color standard color image mode. It will be done.

(2) Second developing step (step e) The developing bias VB□ of the second developing device 25 is set to -450 V, and the positive latent image Zp is regularly developed with the second yellow toner T2 (positive polarity).

In this case, due to the same effect as described above, the first system toner image is hardly destroyed, yellow toner T2 is hardly mixed into the first system toner image, and moreover, the first system toner image is hardly destroyed. The peeled toner of the systematic toner image does not get mixed into the second developing device 25.

■Third developing process (step f) The developing bias Vaa of the third developing device 28 is changed to the second developing device 25.
The developing bias VB2 is set to 350 V, and the positive latent image Zp is changed to the third cyan toner T3 (positive polarity).
Regularly develop the image. Then, development is performed with the third toner T3 superimposed on the second toner bottom 2, and a second system toner image consisting of the second toner bottom 2 and the third toner T3 is formed.

In this case, due to the same effect as described above, the first system toner image is almost never destroyed, and the cyan toner T3 is almost never mixed into the first system toner image. Peeled toner of one system toner image does not get mixed into the third developing device 28.

■Pre-transfer treatment process (step h),■Transfer process is the above 2
It is carried out in the same way as the color specification color image mode, and the photosensitive drum 2
After each toner image on 0 was aligned in positive polarity, it was transferred all at once to a recording sheet 31, and a two-color image consisting of black, and green by overlapping yellow and cyan was obtained on recording sheet 1-31. .

〔Effect of the invention〕

As explained above, according to the color image forming apparatus according to claim 1, a system is adopted in which three or two systems of color images are transferred at once for recording sorting in one rotation cycle of the latent image carrier. Therefore, compared to the so-called transfer drum method or tandem method, it is possible to satisfy the basic requirements of making the device more compact, increasing the speed, and simplifying the alignment control. Since a three-system or two-system color image can be formed using this method, a color image with good image quality can be reliably obtained.

That is, according to the method of use according to claim 2.3.4,
To avoid mixing of the second and third toners in the first system toner image in the second development step and the third development step, the second development means,
Since it is possible to avoid mixing of the first toner into the third developing means, it is possible to prevent the color quality of the first system toner image from being deteriorated due to color mixture, and also to prevent the first toner from being mixed with the second and third developing means. In addition to effectively preventing early deterioration of the second and third toners due to the mixing of the first toner, it also prevents the color image from being damaged due to color changes in the second and third toners due to toner mixing. It can be prevented.

In addition, the applicant has proposed an image forming process that has the same effects as the image forming process of the present invention, in which a first positive latent image is first formed and developed properly, and then a second negative latent image is formed. The company provides a color image forming method (hereinafter referred to as positive, negative, negative method) in which a third negative latent image is formed and reversely developed.
Compared to negative and negative force systems, the present invention allows the initial charging potential of the latent image carrier to be set low even when forming three-system color images, thereby preventing damage such as pinholes. In addition to the advantages of being able to control the intermediate potential (non-image area potential), in the positive, negative, and negative methods described above, if the fringe electric field at the periphery of the first system toner image is quite large, recharging is possible. However, in the present invention, since there is no need to provide the above-mentioned recharging means, the device configuration is can be simplified.

Further, according to the method of using the color image forming apparatus according to claim 3.4, since the second system toner image is formed by overlapping the plurality of toners used, the color of the toner itself is different from the color of the toner used. It is possible to easily obtain two systems of color images including colors that can be arbitrarily selected to a certain extent with different customizations.

In particular, according to the method of using the color image forming apparatus according to claim 4, in a developing bias type apparatus, two toners can be reliably superimposed on the image area of the latent image when forming a custom color image. , can maintain good custom color image quality.

[Brief explanation of drawings]

FIG. 1(a) is an explanatory diagram showing an outline of a color image forming apparatus according to the present invention, FIGS. 1(b) and 1(c) are explanatory diagrams showing how to use the color image forming apparatus according to the present invention, and FIG. The figure is an explanatory diagram showing an embodiment in which the present invention is applied to a color printer, Fig. 3 is an explanatory diagram showing the configuration of a charging scorotron and a recharging scorotron, and Fig. 4 is an explanatory diagram showing the configuration of a charging scorotron and a recharging scorotron. FIG. 5 is an explanatory diagram showing the main parts of the configuration, FIG. 5 is an explanatory diagram showing the magnetic pole characteristics, FIG. 6 is an explanatory diagram showing the image forming process in three-color image mode, and FIG. 7 is an image in two-color standard color image mode. FIG. 8 is an explanatory diagram showing the image forming process in two-color custom color image mode. FIG. 9 is an explanatory diagram showing an example of a conventional color printer. FIG. 1O is an explanatory diagram showing the image forming process. FIG. [Explanation of symbols] ■...Latent image carrier 2...First latent image forming means 3...First developing means 4...Second latent image forming means 5...Second developing means 6 ... Recharging means 7 ... Third latent image forming means 8 ... Third developing means 9 ... Transfer pretreatment means 10 ... Transfer means 11 ... Recording sheet 2 Figure diagram

Claims (1)

[Scope of Claims] 1) A latent image carrier (1) on which an electrostatic latent image is carried, and a negative latent image on which the image area potential is lower in absolute value than the background area potential. a first latent image forming means (2) for forming an image (Zn); and a negative latent image (2) formed by the first latent image forming means (2).
A first developing means (3) for reversing developing Zn) with a first toner (T1), and a first developing means (3) disposed after the first latent image forming means (2), and disposed on the latent image carrier (1). a second latent image forming means (4) for forming a positive latent image (Zp) in which the image part potential is higher in absolute value than the background part potential; and a positive latent image formed by the second latent image forming means (4). image(
a second developing means (5) for regularly developing Zp) with a second toner (T2); A recharging means (6) for equal adjustment, and a latent image carrier (1) recharged by the recharging means (6).
), the third latent image forming means (7) forms a positive latent image (Zp) on which the image part potential is higher in absolute value than the background part potential, and the second latent image forming means (4) or the third latent image forming means The positive latent image (Zp) formed by the image forming means (7) is transferred to the third toner (
a third developing means (8) for regular development at T3); a transfer pre-processing means (9) for aligning the polarities of each toner image on the latent image carrier (1); A color image forming apparatus characterized by comprising a transfer means (10) for transferring data all at once onto a recording sheet (11). 2) When forming three systems of color images using the color image forming apparatus according to claim 1, the first latent image forming means (2) forms a negative latent image (Zn ), and this negative latent image (Zn) is reversely developed with the first toner (T1) of the first developing means (3), a first system toner image forming step (A1), and a second latent image forming means In (4), a positive latent image (Zp) is formed on the latent image carrier (1), and this positive latent image (Zp) is regularly developed with the second toner (T2) of the second developing means (5). A second system toner image forming step (A2) of forming a first system toner image and a second system toner image potential while preventing polarity reversal of the first toner (T1) using a recharging means (6). After equal adjustment, the third latent image forming means (7
) to form a positive latent image (Zp) on the latent image carrier (1), and develop this positive latent image (Zp) regularly with the third toner (T3) of the third developing means (8). After the three-system toner image forming step (A3) and the transfer pretreatment means (9) align the polarities of the first to third system toner images, the transfer means (10) transfers each toner image onto a recording sheet ( 11) A method for using a color image forming apparatus, comprising: (11) a toner image transfer step (A4) for transferring a toner image all at once; 3) When forming two systems of color images using the color image forming apparatus according to claim 1, the first latent image forming means (2) forms a negative latent image (Zn) on the latent image carrier (1). ), and this negative latent image (Zn) is reversely developed with the first toner (T1) of the first developing means (3), a first system toner image forming step (B1), and a second latent image forming means In step (4), a positive latent image (Zp) is formed on the latent image carrier (1), and this positive latent image (Zp) is transferred to a second toner other than black (T2) in the second developing means (5). After regular development, the third toner (other than black) in the third developing means (8) is
A second system toner image forming step (B2) in which the toner images of the first and second systems are further overlapped and regularly developed in T3), and the polarity of the first and second system toner images is aligned in the transfer pretreatment means (9), and the polarity of the first and second system toner images is aligned in the transfer means (10). A toner image transfer step (B) in which each toner image is transferred all at once to a recording sheet (11).
3) A method of using a color image forming apparatus comprising: 4) In the method according to claim 3, when the second developing means (5) and the third developing means (8) are of a developing bias type, the second toner ( T2), third toner (T3
) A method for using a color image forming apparatus, characterized in that the degree of development is adjusted.