JPS63205672A - Method and device for forming image - Google Patents

Abstract

PURPOSE:To obtain an image which has a stable color tone, stable and sufficient density and sufficient resolving power without having fogging by measuring the surface potential at the prescribed point of an image carrying body and controlling at least either of a developing bias potential and voltage and/or current of an electrostatic charge electrode. CONSTITUTION:The surface potential at the prescribed point of the image carrying body 1 is measured by a sensor 15 and at least either of the developing bias potential and the voltage and/or current of the electrostatic charge electrode 2 are controlled in accordance with the measured potential in a method for forming the image by using the image carrying body contg. metallic phthalocyanine and/or nonmetallic phthalocyanine and subjecting the image carrying body 1 to stages including electrostatic charge and formation and development of the electrostatic image repeatedly several times. The developing conditions and/or the electrostatic charge potential can be thereby set always at the desired value and the image having the stable color tone and density is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an image forming method and apparatus, and particularly to a color image forming method and apparatus.

Prior Art Conventionally, as a color image recording method, Japanese Patent Application Laid-Open No. 56-144
The methods described in Japanese Patent Application Laid-open No. 452, Japanese Patent Application Laid-Open No. 58-116553 and Japanese Patent Application Laid-open No. 58-116554 are known.

The method described in JP-A-56-144452 is
After the surface of the photoreceptor as an image carrier is charged by a charger, an electrostatic image is formed on the charged surface by a first exposure means, and developed by a first developer, and then an electrostatic image is formed on the charged surface by a first developing device. An electrostatic image is formed by a second exposure means, which is developed by a second developing device, an electrostatic image is further formed by a third exposure means on the same charged surface, and the electrostatic image is developed by a third exposure means. This is a method of forming a colored toner composite image on an image carrier by developing with a developing device. JP-A-58-116553 and JP-A-58-116553
The method described in JP-A-116554 is substantially the same as that in JP-A-56-144452 in that the electrostatic image formation and development are performed using different devices each time. Therefore, the recording apparatus becomes large and costly, and it is difficult to control the exposure synchronization of each exposure means, which similarly causes color misregistration.

In order to solve these problems, Japanese Patent Application Laid-Open No. 60-767
No. 66 and JP-A No. 60-95456, by repeatedly forming electrostatic images on an image carrier using the same device, the recording device can be made smaller and less costly, and non-contact development using a two-component developer is proposed. This method prevents fogging, mixing and adhesion of different colored toners.

However, in such a color image forming process, in order to obtain an image with stable density and tone, it is necessary to keep the charging potential of the image carrier constant. However, in JP-A-60-76766 and JP-A-60-95456, it is described that a scorotron charger is used to provide stable charging; It was found that it is not easy to provide a constant charging potential multiple times using only a scorotron charger, and that the charging potential tends to fluctuate. In particular, when charging, electrostatic image formation, and development are repeated for each color in one color image forming process, the charging potential of the first color and the second color are
The charged potentials of different colors often differ. In addition, in such cases, in order to simplify the process, if the static elimination step between development and the next charging process is omitted,
The charging potential becomes even more likely to become unstable. For this reason, there is a drawback that the density of each color changes, and the color tone, which is important in color images in particular, becomes unstable.

Incidentally, in recent years, semiconductor lasers have been developed that are small, low cost, capable of direct modulation, and expected to be highly reliable. The oscillation wavelength of such a semiconductor laser is 7
50 nm or more, and is sensitive to light in such a long wavelength range, for example, Japanese Patent Application Laid-Open No. 58-10
No. 0134 describes a photoreceptor containing ε-type copper phthalocyanine, and JP-A-58-182639 describes a photoreceptor containing τ-type metal-free phthalocyanine. Photoreceptors using these metals or achromatic phthalocyanine are sensitive to the oscillation wavelength of semiconductor lasers, but they are not suitable for color image recording methods such as those disclosed in JP-A-60-76766 and JP-A-60-95456. When used as a carrier,
In particular, it has been found that the charging potential of the first color is low, the charging potential of the second and subsequent colors is relatively high, and the difference between the potentials of the first color and the second and subsequent colors tends to become large.

The reason for this is not clear, but phthalocyanine has many levels that act as traps for carriers, so when the second color and subsequent colors are charged, the traps are filled with carriers and the photosensitive layer becomes highly resistive. It is presumed that the charging ability is improved.

C.4 Objective of the Invention An object of the present invention is to provide a method and apparatus capable of obtaining an image with stable color tone, no capri, stable sufficient density, and sufficient resolution.

D0 Structure of the Invention That is, the present invention uses an image bearing member containing metal phthalocyanine and/or metal-free phthalocyanine, and performs a step including charging, electrostatic image formation, and development on the image bearing member. In the image forming method that is repeated multiple times, the surface potential of a predetermined portion of the image carrier is measured, and based on this, at least one of the development bias potential and the voltage and/or current of the charging electrode is controlled. The invention relates to an image forming method.

Further, the present invention provides image formation in which an image bearing member containing a metal phthalocyanine and/or a metal-free phthalocyanine is used, and a process including charging, electrostatic image formation, and development is repeated multiple times on the image bearing member. The apparatus is characterized in that a surface potential measuring sensor is disposed on the image carrier, and the surface potential measuring sensor is connected to at least one of the developing device and the charging electrode via a control section. An image forming apparatus is also provided.

In the present invention, the above-mentioned "development bias potential" particularly means the development potential applied to the development sleeve. In addition, the above-mentioned "voltage and/or current of the charged electrode" refers not only to the original electrode of the charged electrode, but also to the grid electrode if a grid electrode exists, and therefore applies to the original electrode of the charged electrode. It means the charging electrode voltage, the high-voltage power supply current flowing into the charging electrode, or the grid voltage.

This "voltage and/or current of the charging electrode" may be hereinafter referred to as "charging current of the image carrier".

E, Example Examples of the present invention will be described in detail below.

First, the image forming apparatus used in this example is shown in Figures 1 to 3.
This will be explained with a diagram.

In the apparatus shown in FIG. 1, 1 is a metal phthalocyanine and/or
or a drum-shaped image carrier having a photoreceptor surface layer of metal-free phthalocyanine and rotating in the direction of the arrow, 2 is the image carrier 1;
A charging device 4 uniformly charges the surface of a color image; 4 is an image exposure device for each color of a color image; 5 to 8 are sensors 15 for measuring surface potentials of yellow, magenta, cyan, and black; The value measured by the sensor 15 at each time is input to the control circuit section 19. This control circuit provides surface potential. The sensor 15 may be of a non-contact type and a vibration capacitance type, and the sensors 9 and 10 transfer a color image formed by superimposing a plurality of color toner images on the image carrier 1 to the recording medium P. A pre-transfer charger and a pre-transfer exposure lamp are provided as necessary to facilitate the transfer, 11 is a transfer device, and 12 is a fixing device for fixing the toner image transferred to the recording medium P. 13 is a static eliminator consisting of one or a combination of a static eliminator lamp and a corona discharger for static elimination; 14 is a static eliminator that comes into contact with the surface of the image carrier 1 after the color image has been transferred to remove residual toner on the surface; This is a cleaning device having a cleaning blade or a fur brush that separates from the surface of the image carrier 1 by the time the surface on which the first development has been performed reaches.

For image exposure 4, a laser beam scanner shown in FIG. 2 is used. In this system, a laser beam 20 emitted from a laser 21 such as a semiconductor laser is deflected by a mirror scanner 23 consisting of an octahedral rotating polygon mirror, and an r-θ lens 2 for imaging is used.
4 to form an image exposure 4 that scans the surface of the image carrier 1 at a constant speed.

Note that 25 and 26 are mirrors, and 27 is an imaging f-θ lens 24 to reduce the diameter of the beam on the image carrier 1.
This lens is used to expand the diameter of the beam that enters the beam. If a laser beam scanner as shown in FIG. 2 is used to form the image exposure 4, electrostatic images of different colors can be easily formed with shifts, and therefore clear color images can be recorded. However, the image exposure 4 is not limited to slit exposure or dot exposure using a laser beam, and may be obtained using, for example, an LED, a CRT, a liquid crystal, or an optical fiber transmission body.

In a recording apparatus in which the image carrier can take a flat state like a belt, the image exposure can also be flash exposure.

As the developing units 5 to 8, those having a structure as shown in FIG. 3 are preferably used. In FIG. 3, 31 is a developing sleeve made of a non-magnetic material such as aluminum or stainless steel, 32 is a magnet body provided inside the developing sleeve 31 and has a plurality of magnetic poles in the circumferential direction, and 33 is a developing sleeve. A layer thickness regulating blade 34 regulates the thickness of the developer layer formed on the developing sleeve 31, and a scraper blade 34 removes the developed developer layer from the developing sleeve 31. 3
5 is a stirring rotating body that stirs the developer in the developer reservoir 36;
37 is a toner hopper; 38 has a recess on the surface into which the toner enters; and a developer reservoir 36 from the toner hopper 37
A toner replenishing roller 39 applies a bias voltage including an oscillating voltage component in some cases to the developing sleeve 31' via a protective resistor 40, and supplies toner between the developing sleeve 31 and the image carrier 1. This is a power source for creating an electric field that controls movement. The protection resistor 40 and bias power supply 39 are connected to the control circuit 19 described above (see FIG. 1).
Built-in.

In addition, in the above, the second and subsequent development steps are
It is preferable to carry out this process without bringing the developer layer formed in the developing device into contact with the surface of the image carrier. Further, after the color image in which the toner images are superimposed on the image carrier is transferred, the image carrier is preferably cleaned by a cleaning device.

Further, in the present invention, in addition to transferring an image to a transfer body P such as a recording paper as described above, an intermediate transfer body used for a known adhesive transfer can also be employed as a transfer body.

Next, the composition of the developer used in this example will be explained.

This developer is a two-component system and consists of the following resin-coated carrier and toner, which are prepared as follows.

(Preparation of resin-coated carrier) The monomer composition ratio of styrene and methyl methacrylate is 3.
0:70 styrene-methyl methacrylate copolymer (Mn: 82,000, Mn: 25,000
, Tg: 110° C.) was dissolved in 300 mf of methyl ethyl ketone to prepare a coating liquid. Ferrite was coated with this coating liquid using a Subira coater (manufactured by Kaida Seiko Co., Ltd.),
Carrier A having a coating layer with a thickness of 1.0 μm was manufactured. The average particle size of this carrier A is 30μ, and the magnetization is 25em.
u/g, specific resistance is 10'4Ω-0m or more, ratio ff1
It was 5.2 g/cd.

In addition, vinylidene fluoride-tetrafluoroethylene copolymer r
VT-100J (manufactured by Daikin Industries, Ltd.) in acetone
Carrier B was prepared in the same manner as carrier A except that it was dissolved in 300 ml of methyl ethyl ketone (1:1).
I got it. This carrier B had an average particle size of 30 μm, magnetization of 25 emu/g, specific resistance of 10'Ω-1 or more, and specific gravity of 5.2 g/aj.

(Preparation of toner) 100 parts by weight of polyester resin, polypropylene 660
3 parts by weight of Carbon Black: Mogul L (manufactured by Cabot) were mixed in a Henschel mixer. After that, 1 roll with 3 rolls
After sufficiently kneading at a temperature of 40°C, let it cool and coarsely grind it, then grind it with a jet mill and classify it to obtain an average particle size of 10μ.
A "black toner" of m was obtained.

In place of the carbon black used in this black toner, yellow pigment, magenta pigment, and cyan pigment were used in the same manner as the black toner. ”
I got it.

(Preparation of developer) A developer was prepared using the carrier and toner so that the toner concentration was 12% by weight.

Using the developer thus obtained, an image was formed using the apparatus shown in FIG. As for the development method, an electrostatic image is formed by an electrostatic image forming method in which the exposed area becomes an electrostatic image with a lower potential than the background area, and the development process uses toner that charges the electrostatic image to the same polarity as the background area potential. This method (reversal development) is carried out by the adhesion of .

At the first time, charging is performed by the charging electrode 2, and the charged surface is subjected to color-specific image exposure 4 using a laser beam scanner as shown in Fig. 2.
was projected, and image exposure as shown in FIG. 1 was performed so that the potential of the electrostatic image area was approximately 0. The obtained electrostatic image is first developed by one of the developing devices 5 to 8, which uses a developer of a color toner corresponding to image exposure 4, and is then processed as it is (
(i.e., without transferring) the image carrier (or image forming body)
The surface of 1 is uniformly charged again by the charging electrode 2, and the charged surface is subjected to a second image exposure, and then a second development is performed, and in the same manner, the third and fourth electrostatic image formation and Development was repeated.

In this way, the color image formed on the image carrier was transferred to the recording medium P by the transfer device 11. With such a method, a color image can be easily obtained without color shift.

A semiconductor laser was used for the an light. The AC bias was 2 KHz and 1 kV.

What is extremely important in the above-mentioned image formation is that the surface potential of the photoreceptor is measured individually by the sensor 15 for each development, and the development bias potential (development This means that the development potential applied to the sleeve is measured. For example, when the surface potential is high in absolute value, a controlled bias potential is applied to the developing sleeve from the control circuit section 19 so as to increase the developing bias potential in absolute value. In this way, it is possible to reliably obtain a fog-free image of sufficient density in a phthalocyanine photoreceptor whose charging potential tends to increase each time it is charged.

FIG. 4 shows an image forming apparatus according to another embodiment of the present invention.

In the example shown in FIG. 4, the charger 2 is used as the original charger, while the photoreceptor is placed behind it before the charging process of the first color (that is, before the start of the original copying process). A preliminary charging electrode 16 for performing preliminary charging is provided, and a sensor 22 for measuring surface potential is provided between both charging electrodes.

The measured value of this sensor 22 is input to the control circuit section 2, and the control circuit section 28 then outputs the voltage and/or current of the charger 2 (specifically, the voltage of the charging electrode or the high voltage to the charging electrode). It controls the power outflow current or the scorotron grid voltage). That is, when the charging potential by the precharging electrode 16 is high, the sensor 22 detects this and controls the main charger 2 to lower the voltage or current (charging current of the photoreceptor), and conversely, the charging potential by the precharging electrode 16 is controlled to be low. When the charging potential is low, the voltage or current of the main charger 2 is increased.

However, in any case, due to the uniqueness of the photoreceptor being a phthalocyanine type, the surface potential of the photoreceptor increases each time the process is repeated, so from the second time onwards, the charging potential by the main charger 2 will be the same as the first charger. In terms of fog and density, it is desirable to make the exposure lower than the first exposure.

In addition, since preliminary charging is performed by the preliminary charging device 15 before the first charging, the previous history of the photoreceptor, which varies depending on the location, is kept constant, a constant charging potential is obtained, and an image with stable color tone and density is obtained. be able to.

FIG. 5 shows an image forming apparatus according to still another embodiment of the present invention.

According to this example, a sensor 29 for measuring the surface potential is disposed in front of the charger 2 and supplies a measured value of the surface potential of the photoreceptor to the control circuit section 30. In this case, in the photoreceptor 1, the surface potential of the non-image area (especially the surface potential immediately in front of the image area) is measured by the sensor 29, and based on this value, the amount of charge on the surface of the subsequent image area is determined. Control. Specifically, the voltage and/or current of the charging electrode 2 is controlled by the control circuit unit 30, and for example, when the surface potential is high, the charging electrode 2
However, since the photoreceptor 1 is made of phthalocyanine, it is desirable to control the surface potential from the second time onward to a relatively lower value.

Examples based on the present invention will be described below together with comparative examples, and they are shown together in FIGS. 6 to 8. However, FIG. 6 corresponds to the example in FIG. 1, FIG. 7 corresponds to the example in FIG. 4, and FIG. 8 corresponds to the example in FIG. 5.

Month 1.2 and 1.2 τ-type metal phthalocyanine Toyo Ink Co., Ltd.! ! Riyaε
When using an OPC (organic photoconductive substance) containing - type copper phthalocyanine (Nori Onol Blue manufactured by Toyo Ink Co., Ltd.), if the development potential for the second and subsequent colors is made the same as in Comparative Example 1.2, Fog appears on the first color. On the other hand,
If the development potential (DC development bias) for the second and subsequent colors is increased in accordance with the increase in the absolute value of the surface potential as in Example 1.2, images of sufficient density without fogging can be obtained for each Buddhist scripture.

Comparative example 1. ■ S e / T e photoconductor, a-3iGe photoconductor,
In particular, even if the development potential of the second and subsequent colors is made the same as that of the first color, there is no problem in this respect since the charging potentials of each color will be approximately equal.

However, Se/Te has insufficient sensitivity to a semiconductor laser and cannot obtain sufficient image density, and a-3iGe has insufficient charging ability and cannot obtain sufficient image density.

3.4.5.6.7.8 and 5.6.7 When the same phthalocyanine-containing OPC as in Example 1.2 was used, the charging conditions were not controlled as in Comparative Example 5.6.7. In this case, the charging potential of the first color is low, and the density of the first color is low. Moreover, the charging potential after the second color increases significantly,
Bad condition. In contrast, Examples 3.4, 5.6.7
．． 8, if the outflow current value or the voltage of the high-voltage power supply of the charging electrode or the grid voltage of the scorotron is controlled according to the surface potential of the photoreceptor [particularly, the sensitivity of the second color and subsequent colors is lower than that of the first color. If the current flowing into the body is set to be sufficiently small (i.e., the charging current of the photoreceptor is set to be
When the charge potentials are made smaller after the first color)], the charging potentials of the first to fourth colors become almost the same, and images with sufficient density, no fog, and good color tone were obtained for each Buddhist scripture.

In the NM-5E/TE photoconductor and the A-3iGe photoconductor, the charging potentials of each color are approximately equal even if charging conditions are not particularly set according to the surface potential.

However, Se/Te has insufficient sensitivity to a semiconductor laser and cannot obtain sufficient image density, and a-5iGe has insufficient charging ability and cannot obtain sufficient image density.

9.0.11.12.13.4 and 1O111, using the same phthalocyanine-containing OPC as in Example 1.2, when the charging conditions were not controlled as in Comparative Example 10.11.12, , the charging potential of the first color is low (, the first color
The color density becomes low, and the charging potential of the second and subsequent colors increases significantly, which is bad. In contrast, Example 9.
As shown in 10.11.12.13.14, if the outflow current value or the voltage of the high voltage power supply of the charging electrode or the grid voltage of the scorotron is controlled according to the surface potential of the non-image area [especially, the first color If the current flowing into the photoconductor is set to be sufficiently small for the second and subsequent colors (that is, the charging current of the photoconductor is made small for the second and subsequent colors)]
The charging potentials of the first to fourth colors were almost the same, and images with sufficient density, no fog, and good color tone were obtained for each Buddhist scripture.

In the comparative S e/Te photoconductor and the a-3i Ge photoconductor, the charging potentials of each color are approximately equal even if the charging conditions are not set according to the surface potential of the non-image area.

As described above, based on the present invention, Color II! i@!
By stabilizing the charging potential of a metal or metal-free phthalocyanine that has sufficient sensitivity to a semiconductor laser in a recording device, it is possible to obtain an image with stable color tone, sufficient density, and no fog.

Although the present invention has been illustrated above, the embodiments described above can be further modified based on the technical idea of the present invention.

For example, regarding the above-mentioned development potential, it is better to set the value for the second and subsequent times at least 30V higher in absolute value than that for the first time, and the sensor position should be placed immediately before each developing device. It is also preferable that the charging current of the photoreceptor described above is lower by 4% or more in absolute value than that of the first color for the second and subsequent colors.

Further, even after the second color, the value of the charging current may be changed each time, or it may be changed only partially and kept constant in other times.Also, when adjusting the grid voltage, the value of the charging current may be changed each time.
It is preferable that the grid voltage for subsequent colors is at least 30 V lower in absolute value than the first color; the above-mentioned control of the development potential and control of the voltage or current of the charging electrode may be performed at the same time; The type and content of the phthalocyanine used may be varied in accordance with known techniques, and the type of toner, arrangement of the developing device, operating order, etc. may also be varied.

(1) Functions and Effects of the Invention The present invention provides the above-mentioned effects (when the process is repeated multiple times on an image bearing member containing metal or metal-free phthalocyanine,
Since the surface potential of a predetermined location on the image carrier is measured and at least one of the development bias potential and the voltage and/or current of the charging electrode is controlled, the development conditions and/or charging potential can always be kept at the desired value. It can be set easily and images with stable color tone and density can be obtained. This effect can be obtained with good reproducibility because the sensor is connected to the developing device or the charging electrode via the control section.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, in which FIG. 1 is a schematic diagram of main parts of an image forming apparatus, FIG. 2 is a schematic diagram of a laser beam scanner, FIG. 3 is a sectional view of a developing device, and FIG. 5 are schematic diagrams of the main parts of other image forming apparatuses, and FIGS. 6, 7, and 8 are tables showing data for each side in comparison. In addition, in the symbols shown in the drawings, 1... Image carrier 2... Charger 4... Image exposure 5.6.7 .8...Developer 12...
. . . Fixing device 14 . . . Cleaning device 15.22.
29......Sensor 16...
・Preliminary charging electrode 19.28.30... Control circuit section.

Claims (1)

[Claims] 1. Using an image carrier containing metal phthalocyanine and/or metal-free phthalocyanine, repeating the steps including charging, electrostatic image formation, and development on the image carrier multiple times. In the image forming method, the surface potential of a predetermined portion of the image carrier is measured, and based on this, at least one of the development bias potential and the voltage and/or current of the charging electrode is controlled. Method. 2. An image forming apparatus that uses an image carrier containing metal phthalocyanine and/or metal-free phthalocyanine and repeats a process including charging, electrostatic image formation, and development multiple times on the image carrier, An image forming apparatus characterized in that a surface potential measuring sensor is disposed on the image carrier, and the surface potential measuring sensor is connected to at least one of a developing device and a charging electrode via a control section. .