JPS61156067A - Multi-color image forming device - Google Patents

Abstract

PURPOSE:To make possible the formation of multi-color images having always good color reproducibility without being affected by a secular change and envi ronmental change by constituting a titled device in such a manner that a refer ence signal is determined by the image forming conditions at every image forma tion. CONSTITUTION:The recording conditions of a recorder are detected as the image forming conditions and the reference signal group for processing input image data is selected from the preliminarily prepd. groups according to the result of the detection. The recording conditions such as the surface potential of a photosensitive body, the quantity of light for image exposure, the toner concn. of a developer, a developing bias, the fluidity of the developer, the quan tity of the electrostatic charge of the toner, fixing temp., climatic temp. and humidity are important for recording characteristics. These conditions are detected by an electrometer, optical sensor, piezoelement and thermocouple and are fed to an image data processing part. The reference signal is set in the image data processing part.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a multicolor image forming apparatus, and more specifically, the present invention relates to a multicolor image forming apparatus that sequentially forms images of different colors on an image carrier based on image data. The present invention relates to an improved multicolor imaging device suitable for producing color images, such as electrostatic or electrophotographic recording.

B. Prior Art Conventionally, for example, to form a multicolor image by electrophotography,
The copying steps of charging, m-light, development, and transfer are repeated for each component color, so that toner images of each color are superimposed and transferred onto the copy paper. For example, blue and green obtained through color separation filters.

An electrostatic latent image is formed in each auxiliary step using decomposed light such as red, and developed with yellow, magenta, cyan, and if necessary black toner to form a toner image, and the toner image is laminated on recording paper. It is transferred to form a multiple image. However, in such a multicolor image forming method, it is necessary to transfer the image to a transfer body each time the development of each color is completed, which increases the size of the machine and takes a long time to form the image, and There are some drawbacks, such as the need to guarantee positional deviation accuracy.

Therefore, there is a multicolor image forming method that solves the above drawback by superimposing and developing multiple toner images on the same photoreceptor so that the transfer process only needs to be done once. This may cause problems such as disturbing the toner image obtained by development, or mixing the toner in the developer in the previous stage into the developer in the latter stage, disrupting the color balance of the multicolor image.

In order to avoid such inconveniences, a method is adopted in which a bias with an alternating current component superimposed is applied to the developing device during the second and subsequent development to cause the toner to fly onto the electrostatic latent image formed on the photosensitive surface. , a method of forming a multicolor image has been proposed. In this method, since the developer layer does not rub against the toner image formed by the supporting stage, no disturbance of the image occurs.

The principle of this image forming method will be explained below with reference to the flowchart shown in FIG. FIG. 26 shows changes in the interfacial potential of the photoreceptor, taking as an example the case where the charge polarity is positive. PH represents the exposed area of the photoreceptor, DA represents the unexposed area of the photoreceptor, and DUP represents the increase in potential caused by the positively charged toner T adhering to the exposed area PH during the first development.

The photoreceptor is Scorotron band 1! Uniform charging is applied by the device, resulting in a constant positive interfacial potential E as shown in (a). Next, first image exposure is applied using a laser, cathode ray tube, LED, etc. as a non-light source, and as shown in FIG. The thus formed latent image is developed by a developing device to which a positive bias approximately equal to the surface potential E of the unsawned portion is applied. As a result, as shown in (C), the positively charged toner T adheres to the exposed portion PH, which has a relatively low potential, and a first toner image T is formed. The area where this toner image T is formed has a potential of D due to the adhesion of the positively charged toner T.
Although only UP rises, it does not reach the same potential as the unexposed area DA. Next, the surface of the photoreceptor on which the first toner image has been formed is charged a second time by a charger, and as a result, the toner T
Regardless of the presence or absence of , a uniform surface potential E is obtained. This is shown in (di). A second image exposure is performed on the surface of this photoconductor to form an electrostatic latent image ((el), and similarly to (c), the toner T is positively charged with a different color. The toner image is developed and a second toner image is obtained.
Shown in f).

By repeating the above process, a multicolor toner image is obtained on the photoreceptor. A multicolor recorded image is obtained by transferring this onto recording paper and further fixing it by heating or applying pressure. In this case, the photoreceptor is cleaned of toner and charges remaining on the surface and used for the next multicolor image formation.

On the other hand, apart from this, there is also a method of fixing a toner image on a photoreceptor.

In the method explained in FIG. 26, it is desirable that at least the developing step (fl) be carried out without the developer layer coming into contact with the surface of the photoreceptor. It can be omitted. If such charging is not omitted and charging is repeated each time, a static elimination process may be included before charging. However, the exposure sources used for each image exposure may be the same or different. good.

In the multicolor image forming method, for example, yellow.

Toners of four colors, macenta, cyan, and black, are often superimposed on a photoreceptor for the following reason. According to the principle of the subtractive color method, a black image should be obtained by superimposing the three primary colors of yellow, magenta, and cyan, but the toners for the three primary colors that are put into practical use have ideal absorption wavelength ranges. However, due to misalignment of the toner images of the three primary colors, it is not only difficult to reproduce the clear black that is essential for letters and lines with only these three primary color toners, but also the density of the three primary colors is difficult to reproduce. tends to be in short supply.

Therefore, as described above, a multicolor image is formed using four colors, which are the three primary colors plus black.

As a method for forming a latent image for forming a multicolor image, in addition to electrophotography, static 1! A method of forming a latent image, a method of forming a magnetic latent image using a magnetic head, etc. can be used.

A recording device using this method is incorporated into a system whose block diagram is shown in FIG. 25, for example.
In this example, a document containing multicolor optical information is read by a reading device using a solid-state image sensor, and the image data is converted into data suitable for the recording device (hereinafter referred to as recording data) in an image processing section.

There are two ways to express various colors using the methods described above.

01 A method that does not directly overlap toners of different colors.

A method of layering toners of 00 different colors.

(2) is a method in which colors are reproduced in a pseudo manner on recording paper by distributing toners T, , T, on the image forming body without overlapping them, as shown in Figure n. (3) reproduces colors by superimposing toner of a different color on a toner image of a certain color and developing it.

However, in the case of electrophotography, for example, in case (2), the toner T that has been developed earlier is absorbed and does not reach the photosensitive layer of the image forming member, and a latent image is not completely formed. As shown in FIG.

In addition, in (■), it is necessary to precisely align the image exposure so that the toner images of each color do not overlap at the same position.
Figure 27 (% if the image exposure position is inaccurate like in
There is a tendency that the toner image T1 of the stage [1N] partially blocks the image exposure, and the amount of adhesion of the toner image T developed in the latter stage decreases as shown in FIG. 27 (Q). This shows that the recording characteristics differ depending on the spectral sensitivity of the formed body, the spectral characteristics of the light source for image exposure, the spectral transmittance characteristics of the toner, and the order of colors to be developed.

On the other hand, each of the above-mentioned latent formation methods is a method that allows for gradation expression depending on light intensity, but stable recording at high speed ζ
The problem is that this is not suitable. Furthermore, since the gradation expression by such a method is so-called multi-level, a large capacity of image data is required. Therefore, in order to perform high-speed and stable recording and to reduce the amount of image data, a method has been proposed in which each pixel of an input image is binarized to form image data that can express gradations in a pseudo manner. There is. For example, the #degree pattern method shown in FIG. 30 and the dither method shown in FIG. 31 are known.

The density pattern method shown in FIG. 30 is a method of converting one pixel of an input image having a gradation into a plurality of pixels having two gradations. la is an input image, 2a is a pixel 5a of the input image 13 having a typical density value of IJ
3a is an MxN standard concentration matrix for binarizing this sample, and 4a is a sample 2a that is binarized by comparison with the reference #degree matrix 38. This is the resulting pattern.

The dither method shown in the 31st factor is a method of converting one pixel with gradation of an input image into one pixel with binary gradation.

1b is an input image, 2b is an example of a specific MxN pixel matrix of the input image 1b, which is a sample for binarization processing, and 3b is an MX for binarizing this sample.
4b is a pattern obtained by binarizing the sample 2b by comparison with the reference density matrix 3b.

As described above, in the conventional multicolor image forming apparatus, data in the form of color separation of input color image information is
Recording is performed based on data that is binarized and compared with a reference signal read out from the memory. By the way, various recording conditions, such as electrophotography, include the Teiden horizontal position of the photoconductor, the amount of exposure, the toner concentration of the developer, the development bias, the amount of charge and fluidity of the toner, the order of color development, and the fixing temperature. Recording characteristics such as image density and resolution are affected by factors such as temperature, humidity, etc. The recording characteristics also vary depending on the color of the toner used. However, conventionally, image data has been binarized using the same reference signal in all cases without taking these influences into consideration.

Furthermore, input images require good color rendition during recording, such as photographs, images that require high color reproduction, such as character information, and strong reproducibility of specific colors. Conventionally, recorded data was uniformly formed.

For the above-mentioned reasons, the conventional technology has one disadvantage: (1) Recording characteristics differ for each color, so the balance of color reproduction is likely to be lost.

■Color reproducibility is inconsistent due to changes over time or environmental changes.

(2) Recorded data suitable for reproducing input image information cannot be obtained, and depending on the image, resolution, gradation reproducibility, sharpness, etc. may be insufficient.

There were problems such as:

OBJECT OF THE INVENTION The object of the present invention is to provide an apparatus that is not affected by changes over time or changes in the environment and can always form multicolor images with good color reproduction.

A second object of the present invention is to improve color reproduction by taking into account the color of toner.

A third object of the present invention is to perform color reproduction suitable for an input image.

21 Composition of the invention As a result of intensive research, the inventor discovered the following fact.

For example, various combinations can be considered for setting and arranging the density values of each element in the reference density matrix 3b shown in FIG. 31, but recording data is formed using this reference density matrix as a reference signal, The quality of the final multicolor image obtained by recording the Go stones depends on the combination of the density values of each of the above elements. Therefore, if we apply this fact, we can - Prepare multiple reference density maps with different combinations of density values for each element for the color components, and select from these IJ hooks to determine the state of the input image and other conditions. By selecting the reference #lf matrix according to the situation, and by applying OQ to each matrix element appropriately, the optimum reference signal is added, and as a result, a high-quality multicolor image is always obtained. can be obtained.

The present invention has been made based on the above considerations.

That is, the present invention converts input multicolor image data into recorded data by referring to a reference signal for each color component, and then forms a latent image on an image carrier based on this recorded data. In a multicolor image forming apparatus that sequentially performs the step of developing a latent image one color component at a time to form a multicolor image on a carrier, the reference signal is determined each time an image is formed according to the image forming conditions. The present invention relates to a multicolor image forming apparatus characterized in that it is configured to

The above-mentioned reference signal is not only determined using a matrix of a specific size as each element of the IJ box, but also all pixels of image data. This includes those that are applied uniformly to each pixel, and those that are determined individually for each pixel. Furthermore, these reference signals include not only those that binarize input image data, but also those that apply a plurality of reference data to one image data to obtain multi-level recording data.

The determination of the reference signal includes, for example, preparing a plurality of types of reference signals for one color and selecting from among them, as well as modifying and changing the prepared reference signal.

The embodiments of the present invention include, for example, the following three types of contents.

■ Various recording conditions, such as electrophotography, detect the first charge of the photoreceptor, exposure amount, toner concentration of the developer, development bias, charge amount and fluidity of the toner, fixing temperature, air temperature, humidity, etc. Then, the results are fed back to the setting of the reference signal for recording data formation.

■ Set a reference signal that matches the color and development order.

■ Set the reference signal passed through the input image information.

Ho,! ! ! Examples Hereinafter, the present invention will be specifically explained with reference to Examples.

FIG. 1 is a schematic diagram showing the structure of an example of a multicolor image forming apparatus according to the present invention.

This device includes an image reading section R, an image data processing section 37, an image memory 38. It is composed of a recording section P. According to this, a multicolor image is formed as follows.

The light emitted from the original multicolor image (original document fixed by the original document holder 32) 31 after receiving the light from the illumination light source 33 is as follows.
In FIG. 1, the CCD (Charge Couple
ed Devise) 36. CCD36
converts the intensity of light into an electrical signal while scanning the multicolor image of the original document 31, and processes this electrical signal in the image processing section 37 to obtain recording data. This is an image memo 1J3 if necessary
Recorded in 8. The laser control system 10 of the recording section P is controlled according to the recording data obtained in this way.

On the other hand, the surface of the photoreceptor 1 is uniformly charged by the scorotron charging electrode 2.

Image exposure from the laser optical system 10 is directed onto the photoreceptor 1 through the lens 3. In this way, an electrostatic latent image is formed. This latent image is developed by the developer HM A in which yellow toner is stored. The photoreceptor 1 on which the toner image has been formed is uniformly charged again by the scorotron charging electrode 2 and subjected to imagewise exposure. The electrostatic latent image that is formed is the image that contains the master toner! Developed by device B. As a result, a two-color toner image of yellow toner and magenta toner is formed on the photoreceptor 1. Thereafter, the cyan toner and the black toner are developed in a similar manner, and a four-color toner image is formed on the photoreceptor 1. The four-color toner image is transferred to the recording paper at the transfer pole 4 while the strip is charged by the pole 9. Recording paper Pa is separated from photoreceptor 1 by separation pole 5 and fixed by fixing device 6 . On the other hand, the photoreceptor l has a removal electrode 7
and is cleaned by the cleaning device 8.

Cleaning equipment fI! , 8 is a cleaning blade 81
and a fur brush 82. These are kept out of contact with the photoreceptor 1 during image formation, and when a multicolor image is formed on the photoreceptor 1, they come into contact with the photoreceptor 1 and scrape off the residual toner after transfer. After that, the cleaning blade 81 cleans the photoconductor 1.
The fur brush 82 separates from the photoreceptor 1 after a little delay. The fur brush 82 is the cleaning blade 8
When the photoreceptor 1 leaves the photoreceptor 1, the toner remaining on the photoreceptor 1 is removed.

In this multicolor image forming apparatus, one color is developed each time the photoreceptor 1 rotates, but each image exposure must start from the same position on the photoreceptor 1. Further, during the formation of scratches, the dusting device, each true pole other than the band pole 2, the paper, the paper conveyance, and the cleaning device 8, which are not used, do not act on the photoreceptor 1.

Incidentally, in the multicolor image forming apparatus shown in FIG. 1, the recording section P.

Alternatively, in addition to this, the image data processing section 37 can be used independently from other parts, and image data can be input from an external device to be used as a multicolor printer.

Each developer is, for example, the current iJ! In the case of device A, it has a configuration as shown in FIG. The basic convention is the same for B, C, and D. The developer De has the hunting roll 12 in the direction of arrow F,
By rotating the sleeve 11 in the direction of arrow G, it is conveyed in the direction of the arrow. The thickness of the developer De is regulated by the spike regulating blade 13 during the development. A stirring screw 14 is provided in the developer reservoir 19 to sufficiently stir the developer De, and when the developer De in the developer reservoir 19 is consumed, the toner supply roller 15 rotates. Possibly, the toner hopper 16
Toner T is replenished from. and a DC power supply 17 and an AC power supply 18 that apply a developing bias to the sleeve 11;
and a protection resistor R are connected in series. The sleeve 11 and the photoreceptor 1 are arranged facing each other with a distance d between them, and the toner is held in a non-contact state with respect to the photoreceptor 1 in the developing area E.

In order to obtain a desirable image, this non-contact state is essential, especially in the second and subsequent development.

The above-mentioned non-contact state refers to a state in which there is no potential difference between the sleeve 11 and the photoreceptor L (state U where no developing bias is applied), where they are placed facing each other with a distance d between them, and the developer layer thickness is This means that the gap d is set smaller than the gap d. By doing this, damage to the toner image already formed on the photoreceptor 1 during the second and subsequent development can be avoided, and the toner already attached on the photoreceptor 1 can be removed from the sleeve 11. It is possible to avoid the occurrence of color turbidity due to the toner going backwards and getting mixed into the subsequent developing device which stores toner of a different color than the toner of the pleura.

On the other hand, the developer used in the developing device of such an image forming apparatus includes a two-component developer composed of toner and a carrier, and a one-component developer composed only of toner.

Two-component developers require control of the amount of toner relative to carrier, but have the advantage that triboelectric charging of toner particles can be easily controlled. In addition, especially in a two-component developer composed of a magnetic carrier and a non-magnetic toner, it is not necessary to contain a large amount of black magnetic material in the toner particles, so it is possible to use color toner that does not become cloudy due to the magnetic material. It is possible to form clear color images.

In such a two-component developer, the toner composition usually consists of the following (1) to (6).

(II Thermoplastic resin (binder) 80-90wt
Examples: polystyrene, styrene-acrylic copolymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer, or mixtures thereof.

(2) Pigment (coloring agent) Work: Kuroni Carbon Black.

Cyan: Copper phthalocyanine, sulfonamide T15t
dye.

Yellow: 94 benzines.

Magenta: polytan dust phosphoric acid, rhodamine B lake, carmine 6B, etc.

(3) Charge control agent: Polymorphic toner Contains many 22-glosine-based electron-donating dyes.
1. In addition, naphthenic acids or higher fatty acids, alkoxylated amine alkylamides, chelates, pigments,
Fluorinated surfactant, quaternary ammonium salt.

Negative polarity toner: Electron-accepting organic complexes are effective, and others include chlorinated paraffin, chlorinated polyester, polyester with excess acid groups, and sulfonylamine of copper phthalocyanine.

(4) Examples of fluidizing agents: Typical examples are colloidal silica and hydrophobic silica.
Other products include silicone varnish, metal soap, and nonionic surfactants.

(5) Cleaning agent Something that prevents toner from filming on the photoreceptor.

Examples: Fatty acid gold salts, oxidized silicon acids with organic groups on the surface,
There are fluorine-based surfactants.

(6) Filler The purpose is to improve the surface gloss of l1kl images and reduce raw material costs.

Dog: Includes calcium carbonate, clay, talc, pigments, etc.

In addition to these materials, a magnetic material may be included to prevent fogging and toner scattering.

As magnetic powder, 0.1-1 μm triiron tetroxide, r-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder, etc. have been proposed, but at present, triiron tetroxide is the most popular. It is used in an amount of 5 to 70 wt% based on the toner. The resistance of toner varies considerably depending on the type and amount of magnetic powder, but in order to obtain sufficient resistance, the amount of magnetic material should be
The content is preferably 5 wt% or less. As a color toner, in order to maintain clear colors, the amount of magnetic material must be increased by 3.
It is desirable to reduce the content to 0 wt% or less.

Other resins suitable for pressure fixing toner include approximately 2o
Adhesive resins such as wax, polyolefins, ethylene-vinyl acetate copolymers, polyurethane, and rubber are selected so that they can be plastically deformed with a force of about ky/cm and adhere to paper. Capsule toners can also be used.

A toner can be made using the above-mentioned materials by a conventionally known manufacturing method.

In the present invention, in order to obtain a more preferable image, it is desirable that the average particle size of the toner particles is usually about 1 μm or less in view of the relationship with resolution.

In the present invention, there is no theoretical limit to the toner particle size, but it is usually 1 to 30 μm due to resolution, toner scattering, and transportation.
m8 degrees is preferably used.

In addition, in order to visualize delicate points and lines or increase gradation, magnetic carrier particles are particles consisting of magnetic particles and resin (for example, resin dispersion system of magnetic powder and resin, or mother particles coated with resin). ), which are more preferably spherical and have an average particle diameter of preferably 50 μm or less, particularly preferably 30 μm or less, and 5 μm or more.

In addition, we have solved the problem that charges are easily injected into carrier particles by bias voltage, which hinders good image formation, and carriers tend to adhere to the surface of the carrier, and the problem that bias voltage is no longer applied to the light beam. In order to prevent this from occurring, the carrier should have an insulating resistivity of 1♂Ω or more, preferably 1011Ωα or more, and more preferably 1014Ωα or more, and with these resistivities and a particle size as described above. good.

Such a finely divided carrier is produced by coating the surface of the magnetic body with the resin by using the above-mentioned magnetic substance and thermoplastic resin that can be used for toner, or by coating the particles with a resin containing fine magnetic particles dispersed therein. The obtained particles are then subjected to particle size selection using conventional means for selecting average particle size from public wholesalers.

In addition, in order to improve the agitation performance of the toner and carrier and the transportability of the developer, and also to improve the charge control performance of the toner and make it difficult for toner particles to aggregate with each other or between toner particles and carrier particles, the carrier is added. It is desirable to make it spherical. In order to produce spherical magnetic carrier particles, for resin-coated carrier particles, choose magnetic particles that are as spherical as possible and coat them with resin; for carrier particles that are dispersed in magnetic fine particles, use magnetic particles as much as possible. Methods such as forming dispersed resin particles using fine particles and then subjecting them to a spheroidizing treatment using hot air or hot water; or directly forming spherical dispersed resin particles by a spray drying method are employed.

In the image forming method of the present invention, U.S. Pat.
6-18659, JP-A-56-125753, and % Application No. 58-57446 using a one-two-component developer,
Japanese Patent Application No. 58-97973, Japanese Patent Application No. 59-4563,
% Application No. 1983-10699, Patent Application No. 58-238295
No. 58-238296, patent application No. 1987-107
The developing method shown in No. 00 or the like may be adopted.

In particular, according to the development method using a two-component developer disclosed in Japanese Patent Application No. 58-238296, in each development process during the above-mentioned multicolor image formation, the amplitude of the alternating current component of the development bias is changed to Vhc.
(V ), frequency ff wo f CHl), image carrier and developer! When the gap between the developer conveying body and the conveying member is d(W), 0.2≦vAC/(d−f) (('VAC/d) −1500)/f≦1.
It is desirable to satisfy 0.

In this way, by leaving the developing conditions such as AC bias and frequency, it is possible to avoid image distortion and color mixture.
High quality images can be obtained.

The reason for this will be explained below based on the results of experiments conducted by the inventor. The experimental conditions set are as follows.

A two-component developer consisting of a magnetic carrier and a non-magnetic toner is used as the developer. The magnetic carrier has an average particle size of 30/
Jm (average particle size is weight average particle size) or Omnico Alpha (manufactured by Bausch & Lomb) or Coal Counter (manufactured by Coulter).
), magnetization 50 emu7'g.

It is a spherical carrier in which fine ferrite particles are dispersed in a resin with a resistivity of 1oJ4Ω or more. The resistivity is determined by placing the particles in a container with a cross-sectional area of 0.0532, tapping them, and then applying a load of lk$F/am'' on the packed particles. 1000 between the load and the bottom surface' [pole] so that the thickness is
This is a problem that can be met by reading the current value when a voltage that produces an electric field of V/cm is applied.

The above toner has 90wt% thermoplastic resin and IQwt% pigment.
Add a small amount of charge control agent to the mixture and cross-mill it to obtain an average particle size of 10 μm.
m was used. The above carrier s as a developer
o wt%, and the above toner was mixed at a ratio of 20 wt% to prepare a developer. Note that the toner is positively charged due to friction with the carrier. Further, a toner image is formed on the photoreceptor in advance.

When experiments were conducted while changing the alternating current bias and the distance between the photoreceptor sleeves, the relationship between the amplitude EAC of the alternating current electric field strength and the frequency f was able to be sorted out, and the results shown in FIG. 3 were obtained. In FIG. 3, the area indicated by A is an area where uneven development is likely to occur, the area indicated by B is an area where the effect of the AC component does not appear, the area indicated by C is an area where toner backflow is likely to occur, D, E is a region where the effect of the alternating current component is limited and toner backflow does not occur, and E is a particularly preferable region.

This result shows that in order to develop the next (subsequent) toner image at an appropriate density without destroying the toner image formed by the pleura on the photoreceptor drum, the width of the alternating current electric field strength and its frequency are required. This indicates that there is a castle called Tsusho Kokujo.

To summarize the above experimental results, in each development process, the amplitude of the AC component of the development bias is changed to VAC (V) frequency and f (H
z), M When the gap between the optical drum and the sleeve is d (dragon), the above-mentioned condition 0.2 ≦VAC'/ (d' f ) ((VA
C/a) -1500)) 7 If development is performed under conditions that satisfy r≦1.0, subsequent development can be performed with the perfect density without disturbing the toner image already formed on the photoreceptor drum. can.

Among the above conditions, in order to obtain sufficient image density and not disturb the toner family formed by the auxiliary layer, 0.5≦VAC/ (d − f ) ((VAC/ d) −1500)) / f≦1.0
It is preferable to drain it. Furthermore, among these, especially o, s≦VAC/ (d − f) ((VAC/ d ) −1500)) / f ≦0
．． When 8 is satisfied, a clearer multicolor image without color turbidity can be obtained, and it is possible to prevent toners of different colors from getting mixed into the developing device even if the developing device is operated many times.

In order to prevent uneven development due to the alternating current component, the frequency of the alternating current component is set to 200 Hz or higher, and when a rotating magnetic roll is used as a means for supplying the developer to the photoreceptor, the alternating current component and the rotation of the magnetic roll In order to eliminate the effect of the so-called beat that occurs, the frequency of the AC component is set to 500H.
It has become clear that it is more desirable to set the value to z or more. The magnetic roll has a magnetic flux density of 500~ on the sleeve surface.
If you set it to 1500 Gauss, the number of poles should be 6 to 2.
It is better to set it to 0.

In the above experiment, since the developer is conveyed without contacting the image carrier (photoreceptor), it is necessary to make the toner fly to the latent image surface using an alternating current bias. However, due to the phase of the alternating current, an electric force from the developer toward the image carrier and an electric force in the opposite direction act on the toner particles between the image carrier and the developer.

Of these, the latter causes the toner on the image carrier to move to the developing device, causing toner of a different color to mix into the developing device. In order to prevent this situation and develop successive toner images on the photoreceptor at a constant density without destroying the toner image formed on the photoreceptor, as development is repeated (a) Toners with larger bands Im are sequentially used.

(Sequentially reduce the noise of the AC component of the cllS developing bias.

(/1, the frequency of the AC component of the developing bias is increased sequentially.

It is more preferable to employ these methods individually or in any combination.

That is, toner particles with a larger amount of charge are more easily affected by the electric field. Therefore, if highly charged toner particles adhere to the photoreceptor drum during initial development, they will
These toner particles may return to the sleeve. For this reason, the idea of using toner particles with a small electrical charge in the initial development is to prevent the toner particles from returning to the sleeve during development.
tol is a method in which the toner particles already attached to the photoreceptor drum are prevented from returning by decreasing the @order electric field strength as development is repeated (that is, the later stages of development). Specific methods for reducing the electric field strength include a method of lowering the voltage of the alternating current component by 1111 orders, and a method of widening the gap d between the photoreceptor and the sleeve in later stages of development. Also, the above (/
→ is a method in which toner particles already attached to the photoreceptor are prevented from returning to the developing device by sequentially increasing the frequency of the AC component as development is repeated.

It is effective to use these (A) and (C) alone, but for example, as development is repeated, toner band 1!
It is even more effective when used in combination, such as by sequentially increasing the amount and gradually decreasing the AC bias. When the above three methods are adopted, an appropriate image temperature or color balance can be maintained by adjusting the DC bias respectively.

Furthermore, in addition to the above-mentioned methods B) to e, the following methods can also be employed.

), move the unused developing device away from the image holder.

(E) Increase the toner supply amount by one order.

(f) The latent image potential contrast is gradually increased.

(g) The gap between the image carrier and the developer layer is gradually increased.

(g) Apply a bias to the unused developing device to prevent toner from being mixed in.

In addition to the above experiment, development may be carried out using a -component developer under the conditions shown in Japanese Patent Application No. 58-238295.

FIG. 4 is a block diagram of a system that selects and binarizes reference signals for processing input image data based on differences in developing colors or order as image forming conditions. Using the multicolor image forming apparatus shown in Fig. 1, when monochrome images of yellow, 7477M, cyan, C, and black were formed under appropriate common conditions, recording characteristics as shown in Fig. 6 were obtained. . In the system shown in FIG. 4, in order to control recording characteristics, a plurality of reference signal groups are prepared, and processing is performed using appropriate ones among them.

FIG. 6 shows the relationship among the input image density, the density of pixels at H level (that is, the pixels to be colored), and the recorded image density. The 6th country is input 1. This is the relationship between the fiI flaw density and the density of pixels at the H level, and each curve is the result of using a reference matrix (dither matrix) formed by the reference data group shown in FIG. $7
In the figure, the horizontal axis represents the density level, and the vertical bar represents the value of the reference data set in the reference matrix. (B) is when each standard data is set uniformly on the low concentration side, (Q is when each standard data is set on the high concentration side with respect to concentration) If p is set densely, p indicates a case where each reference data is set densely in the middle with respect to density, respectively, giving rise to the gradation reproducibility of the 7th national standard AS BS CS D.

Figure 6 tBl is the relationship between the density of pixels at H level and the recorded image density, and each curve is the reference map shown in Figure 8) IJ
This is the result of using a box. The numbers are concentration levels, with higher numbers indicating higher concentrations.

Note that (to) is arranged so that the dots are dispersed from each other, (Bl, (Q) is arranged so that the dots are concentrated, and (Q has a higher degree of concentration).

8th country, tel, (Q is the curve a in Figure 6 (a).

Give 5% C.

As a result of selection of these reference signals, the relationship between the input image density DO and the recorded image density Dp can be controlled as shown in FIG. is not limited to this.Furthermore, although the above-mentioned saku is a dither method, this technical idea can be applied directly to the density pattern method, etc.Also, for example, multi-value processing using standard data of Zfl class or higher The same applies to the case of forming image data.

FIG. 9 is a block diagram of a system using the multicolor image forming apparatus of FIG. 1 as a recording device, which detects the recording conditions of the recording device as image forming conditions and processes input image data according to the detected results. The reference signal group is selected from among those prepared in advance.

The recording conditions include the surface potential of the photoreceptor, the amount of light for image exposure,
The toner concentration of the developer, the development resistance, the amount of charge of the toner, the fluidity of the developer, the fixing temperature, the air temperature, the humidity, etc. are important for recording characteristics. These are detected by an optical sensor, a piezo element, a thermocouple, etc. as shown in Table 1, and sent to an image data processing section. The image data processing section sets the reference signal according to the flowchart shown in FIG.

(The following description continues on the next page.) FIG. 11 is a block diagram of a multicolor image forming apparatus system that selects a reference signal according to the type of input image as an image forming condition. In the system of Figure 11, the input IfIgI
It determines whether the data consists of text information, a gradation image, a monochrome image, or a color image, and performs binarization using a reference signal according to the results. A flowchart outlining the procedure is shown in FIG.

More detailed examples are shown below.

Example 1 In the multicolor image forming apparatus system shown in FIG. 4, input image data is input from a computer (not shown), and is binarized by a dither method in a first processing section. The recording section P of the multicolor image forming apparatus shown in FIG. 1 is used as a recording device. The reference signal matrix (dither matrix) is set as shown in FIG. 13 so as to be suitable for the following recording conditions.

In Figure 13, C, CB), (Cl, (Dl) are dither matrices for yellow, magenta, cyan, and black color information, respectively, and the numbers represent the #1 degree level from O to 63 lengths. be.

The recording conditions are shown in Table 2. FIG. 14 shows the spectral transmittance characteristics of the toner used.

*Only during development In this example, since the yellow dither matrix is of the dot-dispersion type, the flk degree is a little high, and it is balanced with the other colors due to the fact that it is first developed. The magenta dither matrix is dot-concentrated and has good tone reproducibility. The cyan dither matrix is also dot-concentrated, but the reference signal is densely distributed on the high-density side, so the density is slightly low and balance with other colors is maintained. Furthermore, black dithering) I7 is a dot type T&, but each reference signal is densely set to an intermediate density, creating image data with good contrast.

When various color images were recorded as described above,
Differences in development characteristics due to image forming conditions such as color and image forming order could be well corrected, color balance was good, and letters were clearly printed.

Example 2 In F1, the dither matrix related to black was changed as shown in FIG. 13(E). As a result, the density of the color image was high (clear recording was performed).

In the multicolor image forming apparatus system shown in FIG. 9, input image data is input from a CRT display (not shown) and is binarized using a dither method. As a recording device, section #1 P of the multicolor image forming apparatus shown in FIG. 2 is used.
The reference signal (DIZ) detects the recording conditions shown below and is set as shown in FIGS. 15 and 16 to suit the conditions. The other conditions are Example 1 and the inside ball. In Figures 15 and 16, the mouths represent yellow, magenta, cyan, and black dithered IJ boxes, respectively.
FIG. 5 shows each dither matrix when a high density recording state is determined, and FIG. 16 shows each dither matrix when a low density recording state is determined.

In this multicolor image forming apparatus system, about 11 reference toner images are provided on the non-transfer area of the photoreceptor, for example, the side edge, during image formation, and an LED (light emitting diode) as a light emitting element and a phototransistor as a light receiving element are used. , an optical sensor constituted by a filter reads the density of the reference toner image, and a detection circuit (none of which is shown) containing an arithmetic circuit compares the density of the reference toner image with the reference value, and determines the density of the reference toner image. If the base value is not reached, toner is replenished from the toner hopper. Furthermore, the surface potential 1 shown in FIG.
i21 measures the charging potential of the photoreceptor l, which is an image forming condition, and as a result, if the potential of the non-exposed area is low, it is determined that the recording state is low density, and if the potential of the non-exposed area is high, it is determined that the recording state is high density recording.

In FIG. 15, the yellow, magenta, and cyan dither matrices are of the dot-concentrated type, and only black is of the dot-distributed type. The former has excellent gradation reproducibility, and the latter has excellent maintenance of resolution. In the yellow dithered IJ, each reference signal is set to be low and dense, and the recording density is slightly higher than that of other colors. Furthermore, the black dither matrix is set to be dense with high density, and the recording density is slightly lower than that of other colors. Therefore, if a multicolor image is formed by superimposing toner images of yellow, magenta, cyan, and black on the photoreceptor in this order, each color will be well balanced.

On the other hand, in FIG. 16, the magenta and cyan dither matrices are of the dot-concentrated type, and the yellow and black dither matrices are of the dot-distributed type. Each reference signal of the dither matrix is set so that yellow and magenta are dense at low density, and the other signals are uniform. As a result, under the same conditions, higher image densities can be obtained for all colors than with the dithering (IJ) shown in FIG. 15. In this case as well, if a multicolor image is formed by overlapping toner images of yellow, magenta, cyan, and black on the photoreceptor in this order, the colors will be well balanced.

When color images were recorded using the dither matrices shown in Figs. 15 and 16, changes in the recording conditions due to changes in the image forming conditions such as the environment and changes over time of the device were compensated for by selecting an appropriate dither matrix. We were able to maintain constant reproducibility.

Example 4 In Example 3, the recorded image data is recorded using the dither matrix shown in FIG. 18 instead of that shown in FIG. 16. Each dither matrix in FIG. This has been changed by subtracting it.

In this case as well, if a multicolor image is formed by overlapping toner images of yellow, magenta, cyan, and black on the photoreceptor in this order, the colors will be well balanced.

The recorded images showed consistent color reproducibility despite changes in the environment and changes in the device over time.

Example 5 In Example 4, the amount of charge of toner in the developer, which is an image forming condition, was checked and the dither matrix could be changed accordingly. The charge and amount of toner is detected by a sensor 101 shown in FIG.

In FIG. 19, the toner on the sleeve is moved to a roller 102 by a developing bias, and a sensor 101 measures the surface potential according to the amount of charge on the toner.

The toner on the roller 102 is scraped off by the guide plate 103 and returned to the developer. As a result, when the toner charge amount is large, it is determined that the recording state is low density, and when the toner band *n is small, it is determined that the recording state is high density recording.

The enshrined memorial painting source always showed the same color reproducibility despite changes in the environment and changes in the equipment over time.

Example 6 In the multicolor image forming apparatus system shown in FIG. 11, input image data is input from an image memory (not shown) and is binarized by the dither method in the image data processing section.

The recording section P of the multicolor image forming apparatus shown in FIG. 1 is used as a recording device. Reference signal multiplex (dithering) I
The input image data (Jx) is determined as shown below and is selected from among those set as shown in FIG. 20 in accordance with Table 3 as appropriate for the input image data. Other conditions are the same as in Example 1.

In Table 3, symbols such as A and B are shown in Figure 20.
It corresponds to Bl etc. In Figure 20, only prisoners are decentralized, others are centralized, and rice fields have a particularly high degree of concentration.

(D performs simple binarization. Also, the reference signal is set so that the prisoner is dense at an intermediate density, and C
B+ and (C) are set to be uniform, and (mouth and field are set to be dense with high concentration.

Table 3 Note) A is recorded sharply and with good resolution, B, C and D are recorded with good wt tonality.

The input image data is processed by the IJ (IJ), and toners are applied to the photoreceptor in the order of yellow, magenta, cyan, and black according to the results as shown in Table 3.

- When images are superimposed to form a multicolor image, each color is well balanced.

The method of determining input image data is shown in the flowchart of FIG. The explanation will be based on this figure.

■ Compare each image data of yellow, magenta, cyan, and black with standard values and convert them into binary values.

■ Distinguish whether it is a line drawing or a gradation drawing from the black image data.

■ Count the number of pixels that reached H level by color by
Y them. , Mo, co%D0.

■ Determine whether there is a particularly large YoSMo%co. In the figure, P is a constant given in advance.

■ As a result of ■, if the difference between each is small, it is determined that it is a multicolor image, and depending on whether it is a line drawing or a gradation image, ■ In the case of a line drawing, a dither matrix is applied to any color, and the one shown in Figure 20 is applied to the gradation image. For pictures, [Bl, tc), β, and ■ are commonly used for yellow, magenta, cyan, and black.

(2) If the difference is large as a result of (2), it is determined that it is a monochromatic image, and (2) the dither matrix is applied to each color as shown in Table 3, depending on whether it is a line drawing or a gradation drawing.

Note that the determination of whether the drawing is a line drawing or a gradation drawing may be made using data of other colors. The determination method is based on the histogram of the input image data, the background level, etc.

When various multicolor images were formed under the above conditions, recorded images suitable for the type of input image data, which is one of the image forming conditions, could always be obtained.

Example 7 Similarly, in the system shown in FIG. 11, the multicolor image forming apparatus shown in FIG. 1 was used in the following cases. In other words, the input 1 data is obtained by reading the original with a CCD image sensor,
The determination method was performed as shown in FIG. Further, selection of a dither matrix based on the determination result is performed according to Table-4. Symbols such as A and B in Table-4 are in Example 6
Similarly, it corresponds to the prisoner in Figure 20, (Bl, etc.).

Shishi-4 The determination method shown in FIG. 22 will be explained below.

■ Read the original with a sensor dedicated to discrimination.

■ If the background area is large, it is determined to be a line drawing, and if it is small, it is determined to be a gradation drawing.

- In the case of line drawings, Fl is used as a dither matrix, that is, pure divalentization is performed.

■ Compare each image data of yellow, magenta, cyan, and black with standard values and convert them into binary values.

■ Count the number of pixels that reached H level by color by
Let these be Yo, Mo%co, and Do.

■ Determine whether there is a particularly large value among Yo and Mo%co. In the figure, P is a constant given in advance.

■ If the difference is large as a result of (■), it is determined that it is a multicolor image, and dithering (IJ) is applied to each color as shown in Table 4.

■ If the difference between the two results is small, it is determined that the image is a monochromatic image, and dithering (IJ) is applied to each color as shown in Table 4.

■ Process image data.

When various multicolor images were formed under the above conditions, recorded images suitable for the type of input image data could always be obtained.

Example 8 Similarly, in the multicolor image forming apparatus shown in FIG. 1, a dither matrix for binarizing input image data is created as shown in FIG.
Furthermore, the method for determining input image data was changed as shown in FIG. The other conditions are the same as for inferior 6.

In FIG. 23, only W is distributed and the others are centralized.
The reference signals are set so that the prisoner has an intermediate concentration, the prisoner has a low concentration, (q and (to) are uniform, and (E) has a high concentration and is dense. ,tQ,
CDI, ■ are yellow, magenta, cyan, respectively.
commonly used for black. When the input image data is processed using these dither matrices and the toner images are superimposed on the photoreceptor in the order of yellow, magenta cyan, and black according to the results to form a multicolor image, each color is well balanced.

The image discrimination method shown in FIG. 24 will be explained below. This is a method for determining whether each color is a line drawing or a gradation drawing.

(2) The dither matrix and four-color input image data shown in FIG. 23 are expressed using M and V.

■ - Create a histogram of color components.

■ Distinguish whether it is a line drawing or a gradation drawing.

■ Process the input image data using IJ (dithering) A for line drawings and dithering (corresponding to color) for gradation drawings.

■ Perform steps from ■ to ■ for each color component.

When various multicolor images were formed under the above conditions, recorded images suitable for the type of input image data could always be obtained.

As the recording device of the system shown in the above example, the one shown in FIG. 1 is used. However, the recording device is not limited to this. For example, a plurality of image forming sections each consisting of a charging electrode, an image exposure section, and a developing device are successively arranged around the photoreceptor, and the image forming section is arranged around the photoreceptor. It may also be one in which a multicolor image is formed all at once in one rotation. Furthermore, the method shown in Japanese Patent Application No. 58-183152 and the method shown in Japanese Patent Application No. 58-18
7001 #1 [Recording method 'formula, 59-1316
It is also possible to use a device using the No. 7 magnetic recording method or the like.

As described in detail of the invention, the multicolor image forming apparatus according to the invention includes:
Since it has the above-mentioned configuration, it is possible to always record high-quality recorded images with good resolution or gradation according to the original image without being affected by the condition of the original image or the environment, and without changing over time. I can do it.

[Brief explanation of drawings]

1 to 24 show embodiments of the present invention, in which FIG. 1 is a schematic diagram showing the structure of a multicolor image forming device, and FIG. 2 is an enlarged view showing the developing device portion of FIG. 1. 3 is a graph showing the density characteristics of a recorded image when the electric field strength and frequency are changed; FIGS. 4, 9, and 11 are block diagrams of the multicolor image forming apparatus; The figure is a graph showing the relationship between original image density and recorded image density for each color. Figure 6 is a reference matrix)
This is a graph showing the relationship between H level pixel density and recorded image density. ) indicate the relationship between the original image density and the recorded image density, respectively. Figure 7 (4), (Bl, G+, (Dl) are all graphs showing the reference signal setting method, Figure 8, Figure 13, Figure 15, Figure 16, and Figure 18 are all reference signal M) IJ Fuchs is shown, prisoner is yellow, (B) is magenta, (C) is cyan, 0 and [F]
) applies to black. 1O, 12, 21, 22, and 24 are flowcharts of flaw recording by the multicolor image forming apparatus;
Fig. 4 is a graph showing the spectral transmission characteristics of toner, Fig. 17 is a partially enlarged view showing an example in which a band mNN measurement sensor of a photoreceptor is installed in the multicolor image forming apparatus shown in Fig. 1, and Fig. 19 is a graph showing a second 20 and 2 are partially enlarged cross-sectional views showing an example in which a sensor for measuring toner band tt is arranged in the developing device shown in the figure.
All three figures show other reference signal matrices;
(Bl, (C), a%■, (the town has changed the concentration of dots) There is an IJ hook. Figures 25 to 31 show conventional examples, and Figure 25 shows the conventional example. Block diagram of multicolor image forming device, No. 26
Figures 1al, (b), (cl, tdl, (el, (fl) are diagrams showing changes in the Shishimen position of the photoreceptor drum during recording, 27th National, (Bl, (Q, Figure 4 and Figure 29 is a cross-sectional view showing the state of toner adhesion during image formation, Figure 30 is a diagram showing the step of binarizing an input image using the density pattern method, and Figure 31 is a diagram showing the step of binarizing an input image using the dither method. In addition, in the symbols shown in the drawing, l...... Photoreceptor 2...... Charging electrode A% B, C% D...Developing device 4...
......Transfer pole 5...Separation pole 6...Fuser 7...Removal electrode 8... ...Cleaning ring 10... Laser optical system &...
... Recording paper 11 ...... Toner transport sleeve 12 ...
......Magnetic roll 13......Ear stand blade, 17...
......DC power supply 18......AC power supply 21...Surface electrometer 31...Manuscript 36... ... CCD 37...1iII image data processing section 38.
......Image memory 101...Sensor 13%lb...Input images 2a, 2b...
・・・・・・Pixel Matori, Kuyu 3a13b...Song...
・Reference concentration matrix 4a, 4b...
This is a pixel waiting for a representative density in the bivalent pattern 5a ``'''''''la. Agent Patent Attorney Hiroshi Aisaka 0 F 2 3 [KH2) f 50th 70th (B) (C) (D). Figure 8 110 120 Wavelength (/rLgt) Figure 19 20 E] 220 230 240 250 27th 280 298 30th

Claims (1)

[Claims] 1. After converting the input multicolor image data into recording data by referring to a reference signal for each color component, a latent image is formed on the image carrier based on this recording data and this latent image is developed. In a multicolor image forming apparatus that sequentially performs steps for each color component to form a multicolor image on an image carrier, the reference signal is determined each time the image is formed according to the image forming conditions. A multicolor image forming device characterized by: