JPH036501B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image forming method for forming a multi-image toner image in which a plurality of image toner images are superimposed on an image support, and relates to an image forming method for forming a multi-image toner image on an image support, and relates to an image forming method for forming a multi-image toner image in which a plurality of image toner images are superimposed on an image support. Used for facsimiles, transmission records, laser printers, etc.

[Prior art]

In general, in an image forming method that forms a plurality of toner images, for example, a color image forming method, the color density of the image area in the recorded image to be formed is high,
It is required that there is little fog in non-image areas, that the gradation is faithful to the original, and that the color balance is good. For example, JP-A-49-74034,
JP-A-49-127629 and JP-A-50-20730 disclose a method in which a reference patch is used to form a reference toner image on an image support, and the image quality of a color image is controlled by information from the reference toner image. The technology to do so is described. In such known techniques, for example, a color image is formed by the following method. That is, a reference patch is placed on the document table at a position that receives light from a light source before the document and the document, and the reference patch and the document are placed on a photoreceptor that has been uniformly charged in advance. The reflected light is imagewise exposed through, for example, a blue film to form a reference latent image and an image latent image. A developing device containing yellow toner then first develops the reference latent image to form a yellow reference toner image, and subsequently forms a yellow image toner image controlled by information from the reference toner image. This image toner image is transferred onto recording paper fed at the same timing from a paper feeding device. On the other hand, the photoreceptor is cleaned of the reference toner image and the residual toner image, and after the residual charge is erased, it is uniformly charged again and imagewise exposed through a green filter to form the reference latent image and the image. A latent image is formed. Next, the reference latent image is developed by the developing device containing magenta toner to form a magenta reference toner image in the same manner as before, and subsequently a magenta image toner image is formed under control based on information from the reference toner image. The magenta reference toner image is cleaned and removed, but this magenta toner image is superimposed and transferred onto the recording paper onto which the yellow toner image has already been transferred in the previous step. Similarly, the cyan image toner image is further transferred, and a multi-image toner image in which the three primary color toner images are superimposed is obtained on the recording paper. Next, this recording paper is separated from the transfer drum, fixed, and then discharged outside the machine.

This image forming method has the advantage of being able to provide a color image with improved image characteristics on the one hand, but on the other hand, (a) it requires a transfer drum to transfer the image to the recording paper each time the development of each color is completed. (2) The development process and transfer process are repeated many times, which may cause the toner images of each color to be misaligned and misaligned. There are problems such as formation of an unsightly color image.

Therefore, for example, in Japanese Patent Application Laid-open No. 56-144452, Japanese Patent Application No. 58-183152, and Japanese Patent Application No. 58-184381, a plurality of toner images are superimposed on an image support by a reversal development method or the like. A technique has been proposed in which the image is formed on a sheet of paper and then transferred onto recording paper at the same time. The typical image forming principle of the technique described below will be explained based on the flowchart of FIG.

In FIG. 3, S is, for example, a drum-shaped photoreceptor, E is a positive surface potential applied to the surface of the photoreceptor S, PH is an image exposed area of the photoreceptor S, and DA is an unexposed area of the photoreceptor S. , PUP is the increase in potential caused by the positively charged toner T adhering to the exposed area PH during the first development, and CUP is the increased potential caused by the second charging.
Indicates the increase in PH potential.

The photoreceptor S is uniformly charged by a scorotron charger or the like to give a constant positive surface potential E. This surface potential E decreases to a point where the potential of the exposed portion PH is close to zero by the first imagewise exposure. Here, by performing so-called reversal development in which development is performed by applying a positive bias in which the DC component is approximately close to the surface potential E of the unexposed area to the developing device, the positively charged toner T in the developing device is The toner particles then adhere to the exposed areas PH where the potential is low, and a first toner image (for example, a yellow toner image) is formed.
The area where the toner image is formed is positively charged toner T.
The potential increases by DUP due to the adhesion of
Next, a second charge is applied by the scorotron charger, and the potential is further increased by the amount of CPU to obtain a potential close to the surface potential E of the non-exposed area. Next, a second image exposure was performed on the surface of the photoreceptor S, which had obtained a substantially uniform surface potential E, to form an electrostatic charge image, and after a similar development operation, magenta toner T' was attached. A second toner image (e.g.
A magenta toner image) is obtained. By repeating the above process, a multiple toner image in which a third toner image (for example, a cyan toner image) is superimposed on the photoreceptor S is obtained. This multiple toner image is transferred onto recording paper, fixed by pressure or heat, and then discharged. On the other hand, the photoreceptor S after the transfer is cleaned by a cleaning device and prepared for the next image formation.

According to the above-described image forming principle, the transfer process is performed only once, and there are advantages such as eliminating problems such as an increase in the size of the apparatus, a long image forming time, and misalignment of the toner images. It is conceivable to add the technique using a reference toner image described in the above-mentioned Japanese Patent Laid-Open No. 74034/1983 to such an improved image forming method. However, in the case of a multi-image toner image formed by superimposing a plurality of image toner images on an image support, information on the reference toner image for each color as described in the above-mentioned Japanese Patent Application Laid-Open No. 74034/1983, etc. However, there is a problem in that desirable control of image characteristics cannot be achieved. That is, even if the image toner images of each color are controlled, the superimposed multiple image toner images are not controlled, resulting in a problem that a high quality color image cannot be obtained.
Further, in general, in a multicolor image forming apparatus, in order to form a plurality of toner images, image formation is often performed by rotating an image support by the number of toner images. In this case, the recording time required is several times that of a monochrome image forming apparatus, and the efficiency of multicolor image formation is extremely poor.

[Problems to be solved by the present invention]

The problem to be solved by the present invention is to improve the color balance, gradation, image quality, etc. of multicolor images in an image forming method in which a plurality of toner images are superimposed on an image support to form a multi-image toner image. and to improve multicolor image forming efficiency.

[Means to solve the problem]

The above-mentioned problem arises in an image forming method in which toner images of multiple colors are superimposed on an image support by repeating charging, exposure, and development. After forming toner images on the image support by repeating charging, exposure, and development, forming the image toner image based on information from the reference toner image,
Transferring the image toner image to a transfer material, and removing the reference toner image formed on the image support prior to formation of the image toner image from the image support without transferring it to the transfer material. This is achieved by an image forming method characterized by:

[Function] In the image forming method having the above structure, each reference toner image of the plurality of reference toner images and each corresponding image toner image may be alternately formed; however, in this method, , the image forming process becomes complicated, and the usable range of the image forming surface of the image support becomes narrow. Therefore, it is preferable to form an image toner image after forming a plurality of reference toner images. In this case, the information of the previously formed reference toner image is stored in the memory and cleaned by the cleaning device without being transferred to the recording paper, but in the process of cleaning, the image toner image is created based on the memory information. is formed and transferred onto recording paper. The plurality of reference toner images are formed by being superimposed on a drum-shaped or endless image support, for example, at the front of one revolution of the drum-shaped image support. Therefore, when the image toner image is transferred, the reference toner image has already been cleaned and removed. Therefore, when forming a toner image, the image forming surface of the image support can be fully utilized. Furthermore, there are cases where the longitudinal direction of the image to be formed is larger than the outer circumference of the drum, in which case the drum is rotated that much more to form the image. Therefore, in the above case, since the image support can be made smaller, the apparatus can be made more compact, and image formation can be performed with high efficiency.

In the image forming method of the present invention, a scorotron charger capable of imparting a stable and uniform charge to the image support is used, and the image exposure device is an output signal of an image sensor that scans an original, a transmission signal from another device, or a memory. A laser device that uses data stored in the image signal as an image signal, and is modulated or driven by the image signal.
OFT, liquid crystal shutter, LED, etc. are used. As the developing device, a developing device that performs reversal development based on the image forming principle shown in the flowchart of FIG. 3 and performs non-contact development at least from the second time onwards is preferably used. The non-contact developing method applies an alternating current bias to the developing device and causes the contained toner to fly toward the image support for development, and the developing operation can be turned on or off simply by turning on or off the alternating current bias.
off is controlled. Therefore, the development steps of the reference latent image and the image latent image are performed without being influenced by each other. Further, when the AC bias is turned off, it is preferable that only a DC bias in a direction that prevents the toner from flying is applied. Further, in order to turn off the developing operation, the developing device is separated from the image support, the entire developing device is grounded using a means for removing the developer layer from the sleeve surface, or it is floated. It may be a method.

There are various image forming modes for the reference toner image and the image toner image in the present invention, and typical examples will be explained with reference to the flowchart in FIG. 1 and the partial sectional view of the image forming apparatus in FIG. 2. The image support 1 in FIG. 1 is shown as a planar development of the drum-shaped image support 1 in FIG. 2, and the arrow indicates the direction of movement thereof.

First, a uniform positive charge is applied to the area A by the scorotron charger 5, and then image exposure L is performed based on the reference signal to form a reference latent image 4a, which is developed by the developing device 8 to yellow. A reference toner image 2a is formed. Next, recharging is performed by the scorotron charger 6, and image exposure L is performed based on the reference signal.
is applied to form a reference latent image 4b, and the developing device 9
The yellow reference toner image 2a is developed by
A reference toner image 2b is formed in which the magenta reference toner image is superimposed at a different position. Furthermore, after being similarly re-charged by the Scorotron charger 7 and developed by the developing device 10, the multiple reference toner image 2 is further superimposed with the cyan reference toner image.
c is formed in the area A, but the reference toner image 2c is subsequently cleaned and removed by a cleaning device. Following the formation of the reference toner image 2c, uniform positive charging is performed by the charger 5 based on the information of the reference toner images 2a to 2c and image exposure L is performed based on the image signal, and the developing device 8 performs uniform positive charging and image exposure L based on the image signal. After being developed, the yellow image toner image 3a becomes B.
Formed in the area of

Next, while the image toner image 3a is formed up to the area A, it is re-charged by the charger 6, subjected to image exposure L based on the image signal, and developed by the developing device 9 to form the yellow image toner image. An image toner image 3b is formed by superimposing a magenta image toner image on 3a. Similarly, after being re-charged by the charger 7 and developed by the developing device 10, the cyan image toner images are superimposed to form a multi-image toner image 3c, which is transferred to recording paper.

A multi-image toner image in the image forming mode described above is formed by one rotation of the image support.

[Examples] The present invention will be explained below using Examples, but the embodiments of the present invention are not limited thereto.

Embodiment 1 FIGS. 4 to 7 are diagrams for explaining this embodiment, in which FIG. 4 is a sectional view of main parts of a three-color image forming apparatus, FIG. 5 is a developing device, and FIG. 6 is a reference toner image. FIG. 7 shows the development mode of the image toner image.

In this embodiment, image formation is performed by the image forming apparatus shown in FIG. 4 based on the image forming mode shown in the flowchart of FIG. Reference numeral 11 denotes a drum-shaped selenium photoreceptor having a diameter of 240 mm and is rotated in the direction of the arrow at a circumferential speed of 120 mm/sec. A scorotron charger 12 uniformly charges the surface of the photoreceptor 11 to +600V (first charge). Next, the yellow reference signal is input to a known helium-neon laser device 13, and the laser beam L _Y modulated by the signal is irradiated onto the charged surface of the photoreceptor 11 (first image exposure is performed). A reference latent image is formed.
Thereafter, as shown in the development mode of FIG. 8, reversal development (first development) is performed by the development device 14, and
A yellow reference toner image (FIG. 1, 2a) to which yellow toner T is attached is formed.

Next, it is recharged by the scorotron charger 15 (second charging), and a reference latent image is formed by image exposure (second image exposure) of the laser beam L _M from the laser device 16 based on the magenta reference signal. Ru.
This is then subjected to reversal development (second development) by the developing device 17, and a magenta reference toner image with magenta toner T' attached at a different position is superimposed on the yellow reference toner image (FIG. 1 2b is formed). ).

Similarly, recharging by the charger 18, image exposure (third image exposure) of the laser beam L _C from the laser device 19 modulated by the cyan reference signal, and development device 2
After the reversal development (third development) with 0, a multiple reference toner image (FIG. 1 2c) in which cyan reference toner images are superimposed is formed (in the area of FIG. 1A). Subsequently, the reference toner images (FIGS. 1, 2a to 2)
c) Positive uniform charging by the charger 12 based on the information from c), image exposure L _Y based on the yellow image signal,
After development by the developing device 14, a yellow toner image (FIG. 1, 3a) is formed (in the area of FIG. 1B). On the other hand, the reference toner image 2c continues to be removed by the pre-cleaning static eliminator 28 of the cleaning device 27.
The cleaning blade 29 then cleans and removes it. While the yellow image toner image is formed (up to the area shown in FIG. 1A), the magenta image toner image is superimposed after being charged by the charger 15, image exposed L _M , and developed by the developing device 17. (FIG. 1 3b) is formed.
Subsequently, after being charged by the charger 18, subjected to image exposure L _C , and developed by the developing device 20, a multi-image toner image in which cyan image toner images are superimposed (FIG. 1, 3c) is obtained.
is formed. This toner image is transferred onto the recording paper P after being made easy to transfer using a pre-transfer charging device (not shown) or the like. That is, the recording paper P is fed from the paper feeding device 21 by the paper feeding roller 22 in synchronization with the image formation on the photoreceptor 11, and is transferred by the action of the transfer electrode 23. Developing modes by each developing device for forming the reference toner image and the image toner image are shown in FIGS. 6 and 7. That is, the reference toner images of each color are developed so as to be superimposed at different positions, and the toner images of each color are developed so as to be superposed both at the same position and at different positions.
Also, a recording paper P to which the image toner image 3c is transferred
is fixed by the heating roller 26 of the fixing device 25 and discharged.

Next, FIG. 5 shows the developing devices 15, 17, 20.
29 is a developing sleeve made of a non-magnetic material such as aluminum or stainless steel, 30 is a magnet body provided inside the developing sleeve 29 and has a plurality of magnetic poles in the circumferential direction, and 31 is a developing sleeve. 31 is a layer thickness regulating blade made of a magnetic or non-magnetic material that regulates the thickness of the developer layer formed on the developing sleeve 29; 32 is a scraper blade that removes the developed developer layer from above the developing sleeve 29; 34 is a developer a stirring rotary body 36 for stirring the developer in the reservoir 33;
35 is a toner hopper, and 35 has a recess on the surface into which the toner enters, and is connected from the toner hopper 36 to the developer reservoir 33.
A toner replenishing roller 37 applies a bias voltage including an oscillating voltage component in some cases to the developing sleeve 29 via a protective resistor 38, thereby controlling the movement of toner between the developing sleeve 29 and the photoreceptor 11. The figure shows that the developing sleeve 29 and the magnet 30 rotate in the directions of the arrows, but even if the developing sleeve 29 is fixed, the magnet The body 30 may be fixed, or the developing sleeve 29 and the magnet body 30 may rotate in the same direction. When the magnet body 30 is fixed, normally, in order to make the magnetic flux density of the magnetic pole facing the photoreceptor 11 larger than the magnetic flux density of other magnetic poles, the magnetization is strengthened or two of the same polarity or different polarity are attached thereto. In some cases, magnetic poles are placed close to each other.

In such a developing device, the magnetic pole of the magnet body 30 is usually
It is magnetized to a magnetic flux density of 500 to 1500 Gauss,
The developer in the developer reservoir 33 is attracted to the surface of the developing sleeve 29 by the magnetic force, and the thickness of the adsorbed developer is regulated by the layer thickness regulating blade 31 to form a developer layer. The developer layer is the photoreceptor 11
The surface of the developing sleeve 29 develops the latent image on the photoreceptor 11 in the development area E where it faces the surface of the photoreceptor 11, and the remaining image is removed. is removed from the surface of the developing sleeve 29 by the scraper blade 32 and returned to the developer reservoir 33. The development is repeated in order to superimpose the color toner images, and at least from the second development onwards, the toner attached to the photoconductor 11 in the previous development is not shifted in the subsequent development. In addition, it is preferable to use non-contact developing conditions.

In this embodiment, the reference latent image is developed using the vibration bias in the power supply 37 of the developing devices 14, 17, 20, etc. as a reference vibration bias, and a reference toner image is formed. This reference toner image is
For example, it is detected by optical means that measures reflection density using a pair of a light emitting element and a light receiving element. This detected information is compared with a memory stored in the CPU in advance, and an appropriate bias value is selected as the applied voltage when developing the image latent image.
Further, an appropriate value is selected from among the reference vibration bias values that vary according to a certain program, and is used as the bias value when developing the image latent image. Furthermore,
In comparison with the memory stored in the CPU, the charging potential to the photoreceptor 11 and/or the image exposure amount are controlled. In addition, 39 in FIG. 5 is a D/A converter,
40 is an A/D converter, and 41 is a photo sensor for measuring reflection density.

Next, in this embodiment, the power supply 37 (AC bias power supplies 37a, 37a ₂ , 37a ₃ and DC bias power supplies 37b ₁ , 37b ₂ , 37b ₃ in FIG. 3) has a voltage of 1.2KV at 2KHz when normally on. An alternating current bias and a direct current bias of +500V are applied, and these values are controlled to fluctuate based on information from the reference toner image. Also, the sleeve 29 has a diameter of 30mm and a diameter of 65r in the direction of the arrow.
pm, and the gap d between the developing area E and the photoreceptor 11 was 1000 μm. The gap between the sleeve 29 and the layer thickness regulating blade 31 is 300 μm, the formed developer layer is about 700 μm, and the magnetic flux density is N with a magnetic flux density of 900 Gauss.
The rotation speed in the direction of the arrow of the magnet body 30 having six S magnetic poles at equal intervals was 700 rpm.

As for the developer used in this embodiment, it is not necessary to include a black or brown magnetic material in the toner, and a toner with a clear color can be obtained, and the charging of the toner can be easily controlled. It is preferred to use a so-called two-component developer consisting of a mixture of a non-magnetic toner and a magnetic carrier. In particular, when magnetic carriers are used in resins such as styrene resins, vinyl resins, ethyl resins, rosin-modified resins, acrylic resins, polyamide resins, epoxy resins, and polyester resins, triiron tetroxide, γ-ferric oxide, and Products containing dispersed fine particles of ferromagnetic or paramagnetic materials such as chromium, manganese oxide, ferrite, manganese-copper alloy, or materials whose surfaces are coated with the above-mentioned resins. An insulating carrier having a resistivity of 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more is preferred. If this resistivity is low, when a bias voltage is applied to the developing sleeve 29, charges may be injected into the carrier particles, making it easier for the carrier particles to adhere to the surface of the photoreceptor 11, or if the bias voltage is not sufficiently applied. The problem arises that it is not done. In particular, if the carrier adheres to the photoreceptor 11, it will adversely affect the tone of the color image.

The resistivity was determined by placing the particles in a container with a cross-sectional area of 0.50 cm ² and tapping them, then applying a load of 1 kg/cm ² on the packed particles, and applying a load of 1 kg/cm 2 between the electrode that also served as the load and the bottom electrode. This value is obtained by reading the current value when a voltage is applied 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 not be improved, breakdown or discharge will easily occur, and high voltage will not be able to be applied. It is preferable that the diameter is 5 μm or more and 50 μm or less,
If necessary, a fluidizing agent such as hydrophobic silica may be appropriately 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 5 to 30 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 31 shown in FIG. This allows settings to be easily performed without fear of leaks. In addition, in order to more effectively control the development movement of toner by applying such a bias voltage, the toner may contain a magnetic material such as that used in magnetic carriers to the extent that color clarity is not impaired. Good too.

Of course, the present invention is not limited to the two-component developer, but can also be applied to a non-component developer using the one-component developer described in, for example, U.S. Pat. A contact development method can also be used. Also, JP-A-56-125753, JP-A-59-
Publications No. 42565, Japanese Patent Application 1986-97973, Japanese Patent Application 1987-
The methods described in the specifications of No. 231434 can also be used.

In this example, magnetite was added to the resin.
Average particle size 20μm with 50% dispersion content, magnetization
A carrier having a resistivity of 30 emu/g and a resistivity of 10 ¹⁴ Ωcm or more is used. The toner used is a styrene-acrylic resin with a benzidine derivative as a yellow pigment, rhodamine B as a magenta pigment, 10 parts by weight of a copper phthalocyanine pigment as a cyan pigment, and 2 parts by weight of a positive charge control agent with an average particle size of 10 μm. .

In this embodiment, a developer is used in which the content ratio of toner to the developer is adjusted to be 20% by weight.

In this embodiment, a method is adopted in which a reference toner image and an image toner image are formed using a reference signal and an image signal from the outside, and a method is adopted in which the image toner image is transferred while the reference toner image is removed. Therefore, various selections can be made in the formation position and formation method of the reference toner image, and almost the entire surface of the photoreceptor can be used when forming the image toner image.

Further, in this embodiment, since a multiple image toner image can be formed by one rotation of the photoreceptor, the image forming efficiency is improved to the same level as a black and white image.

Further, the reference toner image may be formed from an image signal, or may be formed from a signal from a document provided with a certain color density difference. Furthermore, the order in which the cyan, magenta, and yellow color toner images are formed may be arbitrarily changed depending on the situation.

〔Effect of the invention〕

As is clear from the above examples, in the present invention, a plurality of toner images are superimposed on an image support and transferred onto recording paper at once, so a transfer drum is not required. Since the toner image can be formed using almost the entire surface of the image support, the image support can be miniaturized.
The image forming apparatus can be made more compact. Further, since the image toner image is formed by one rotation of the image support, an image forming efficiency comparable to that of a black and white image can be obtained. Furthermore, since image formation is performed based on information from the reference toner image, a multicolor image with good image quality, gradation, and color balance can be obtained. Furthermore, when multiple toner images are superimposed on an image support, especially when a reversal development method and a non-contact development method are adopted,
Furthermore, in addition to clear images and reduced fatigue of the photoreceptor, there are many other effects such as the development operation when developing each latent image can be easily and rationally controlled without waste.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining the image forming mode of the present invention, FIG. 2 is a partial sectional view of an image forming apparatus for explaining the flowchart, and FIG. 3 is a flowchart for explaining the image forming mode of the present invention. A flowchart illustrating the imaging mode is shown. FIG. 4 is a sectional view of a main part of an image forming apparatus for explaining an embodiment, FIG. 5 is a sectional view of a developing device incorporated in the apparatus of FIG. 4, and FIG. 6 is a sectional view of a reference toner image of an embodiment. Flowchart for explaining development mode FIG. 7 shows a flowchart for explaining the development mode for the image toner image of the embodiment. 11... drum-shaped photoreceptor, 12, 15, 18...
...Scorotron charger, 13,16,19...Laser device, 14,17,20...Developing device, 23
...Transfer electrode, 24...Separation electrode, 29...Sleeve, 30...Magnet, 31...Regulation plate, E...
Development area, 37, 37a ₁ , 37a ₂ , 37a ₃ , 37
b ₁ , 37b ₂ , 37b ₃ ...Development bias, 39...
D/A converter, 40...A/D converter, 41...
Photo sensor, T, T'...Toner, D...Developer, L...Laser light, P...Recording paper, Y, M,
C...Yellow, magenta, cyan.

Claims (1)

[Scope of Claims] 1. An image forming method in which toner images of multiple colors are superimposed on an image support by repeating charging, exposure, and development, comprising: After forming a reference toner image on the image support by repeating charging, exposure, and development,
forming the image toner image based on information from the reference toner image and transferring the image toner image to a transfer material; and the reference formed on the image support prior to forming the image toner image. An image forming method characterized in that the toner image is removed from the image support without being transferred to a transfer material.