JPS62159156A - Developing method - Google Patents

Abstract

PURPOSE:To improve development efficiency and to obtain uniform development performance by setting the amount of a developer carried to a development area within a range of 0.01-0.04g/cm<2>. CONSTITUTION:The amount of the development De is controlled by a pristling control blade 40 and a specific amount of the developer is carried and conveyed onto a sleeve 42 through the relative rotation between the sleeve 42 and a magnetic roll 43. In the development area E, the developer De whose amount is controlled faces an electromagnetic latent image on a photosensitive drum 9 without contact and the latent image is developed with toner as a result of the sum of latent image electric field developing bias magnetic force etc. Then, when the amount of the developer carried to the development area is specified with a range of 0.01-0.04g/cm<2>, the whole layer of the developer on a developer carrier becomes movable freely and has uniform and sufficient concentration without making a developing device complex nor large in size; and carrier sticking is not caused, and a visible image of good quality is obtained without any fogging.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a developing method, and more specifically, to a developing method for visualizing an electrostatic latent image formed on an image carrier in electrophotography. Regarding the method.

BACKGROUND OF THE INVENTION As a developing device used for the above-mentioned development, the following type of developing device is widely adopted because it is easy to downsize. That is, a magnetic brush of magnetic developer is formed on the surface of the developing sleeve as a developer conveying body by the action of a magnet located on the back side, and the magnetic developer is supplied to the developing area to carry an image under a developing bias. This method uses toner to adhere to an electrostatic latent image on the body.

In recent years, there has been a strong demand for faster copying speeds and higher density copies in electrophotographic copying devices, and as a result, it is necessary to move the image bearing member at high speed to develop the electrostatic latent image reliably in a short time. It is becoming desirable to do so. In addition, with the trend toward colorization of documents in offices and the like, the need for making color hard copies is increasing. Furthermore, in order to realize a color copying apparatus that is high-speed, high-resolution, and has good color reproducibility, it has become desirable to develop a suitable developing method.

In order to meet the demand for faster development, it is conceivable to use a developing device provided with a plurality of developing sleeves, but this increases the size of the developing device and loses the above-mentioned advantages.

Developers are broadly classified into one-component developers made of magnetic toner and two-component developers made of non-magnetic toner and magnetic carrier. Two-component developers are suitable for color copying because they do not require the toner to contain a black or brown magnetic material, can provide toner images with clear colors, and can easily control the charge of the toner. Further, in a color copying method in which toner images of a plurality of colors are formed on an image carrier (photoreceptor) in a superimposed manner, a developing method is preferably used first. Non-contact development involves applying alternating current and/or direct current bias to the developer conveying body to form an alternating electric field in the development area and causing the toner to fly, without causing the developer on the developer conveying body to come into contact with the image carrier. This is a method in which the electrostatic latent image is made to adhere to the electrostatic latent image.

An example of developing using a two-component developer using a non-contact development method or a near-contact development method is JP-A-56-144452.
, 57-139761, 59-67565, 5
9-91453, 59-121077, 59-1
54469 and 59-181362.

When performing color copying, unless sufficient development is performed with color toner, the resulting copies will have poor appearance and poor reproducibility. For this reason, in conventional color copying, a magnetic brush is rotated at high speed to perform development, but the torque of this rotation is large, the brush sweeps, and the density is not sufficient, making it unsatisfactory. The current situation is that we are not able to obtain copies of the image quality that we expect.

In the case of reversal development, in addition to the above problems, the non-image area (white background area), especially the non-image area around the image area (colored area), has charges of opposite polarity to the electrostatic charge on the photoreceptor. This poses a troublesome problem in that image quality deteriorates due to fogging and developer is wasted.

Object of the Invention The present invention provides high developing efficiency without increasing the size of the developing device, without rotating the magnetic brush at high speed and requiring excessive torque, and without causing fogging or sweeping. The object of the present invention is to provide a developing method that enables high-density development.

20 Process leading to the invention As a result of intensive research, the inventor has determined that the amount of developer conveyed to the developing area is within the range of 0.01 to 0.04 g/aJ. The entire developer layer can move freely on the top, and Tlg, t7111MtlJ<
California lmayi, eytv shoulder analysis-i1. ! E*薯%〆d
I have found that a captivation can be achieved by cutting off a man's butt and his neck. The present invention has been made based on the above findings.

If the amount of developer conveyed is less than 0.01 g/ci, the density of the visible image obtained will be insufficient;
n! If it exceeds the above range, the developer will also adhere to non-image areas (white background areas), causing fogging, and carrier adhesion will likely occur at the periphery of the image area, making it impossible to obtain a good-quality visible image.

E1 Structure of the Invention In other words, the present invention provides a developing method for non-contact development of an electrostatic latent image under an alternating electric field, in which the amount of developer conveyed to the developing area is reduced to 0.
．． The present invention relates to a developing method characterized in that reversal development is performed with an amount in the range of 0.01 to 0.04 g/cj.

EXAMPLES Before describing specific examples of the present invention, a non-contact developing method using a two-component developer, which is suitable for application to the present invention, will be explained.

Gap d between the image carrier and developer conveyor in the development area
(mm) (hereinafter sometimes simply referred to as gap d),
Voltage VAC and frequency j (H
It has become clear that even if the value of z) is determined alone, it is not possible to obtain an excellent image, and that these parameters are closely related to each other. Therefore, when an experiment was conducted using the apparatus, the results shown in FIGS. 2 and 3 were obtained. This developing device 11 includes a non-magnetic sleeve 4 which is a developer conveying body.
2 and the magnetic roll 43 rotate, the developer De
is conveyed in the direction of arrow B on the circumferential surface of the sleeve 42, and the developer De is supplied to the development area E. Note that the developer De is a two-component developer consisting of a magnetic carrier and a non-magnetic toner.
The carrier has an average particle size of 30 μm and a magnetization of 50 emu/
g, a resin-coated spherical carrier with a resistivity of 1014 Ω or more, and the resistivity of particles is 0.50
After tapping in a container with a cross-sectional area of CD,
This value is obtained by applying a load of 1 kg/cd on the packed particles and reading the current value when applying a voltage that generates a 1000 V 7-hole electric field between the load and the bottom electrode. The toner contains 90wt% of thermoplastic resin and pigment (
A small amount of a charge control agent was added to 10-t% of carbon black, which was kneaded and ground to give an average particle size of 10 μm.

The developer Da is placed in the sleeve 4 with the magnetic roll 43 in the direction of arrow A.
2 is rotated in the direction of arrow B, thereby being conveyed in the direction of arrow B. The thickness of the developer De is regulated by a spike regulating blade 40 during transportation. A stirring screw 41 is provided in the developer reservoir 47 to sufficiently stir the developer De, and when the toner in the developer reservoir 47 is consumed, the toner supply roller 39 rotates. As a result, toner T is replenished from the toner hoverer 38. An AC power source 46 is connected to a DC power source 45 between the sleeve 42 and the photoreceptor drum 9, which is an image carrier, so that a sufficient developing bias De is supplied to the photoreceptor drum 9 for development. are installed in series. R
is the protective resistance.

In FIG. 2, the gap d between the photosensitive drum 9 and the sleeve 42 is set to 1. Otxm, the developer layer thickness is 0.5 mm, the charging potential of the photoreceptor is 600V, the DC component of the developing bias is 200V, and the amplitude of the AC component and the exposed area on the photoreceptor drum 9 when the frequency of the AC component is set to lK11z. (The potential is OV) shows the relationship with the image density of the toner image formed. The amplitude EAC of the AC electric field strength is the value obtained by dividing the amplitude VA of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in FIG. 2 indicate that the average charge amount of the toner is 30 μC/g, respectively.
・These are the results when using those whose charge was controlled to 20 μC/g and 15 μC/g. For both of the three curves A and BSC, the effect of the AC component appears when the amplitude of the AC component of the electric field is 200 V/R or more.

Figure 3 shows that the frequency of the AC component of the developing bias is 2.5.
Kf(z) shows the change in image density when alternating current electric field strength Esc is changed under the same conditions as in the experiment shown in FIG.

According to this experimental example, when the amplitude EA of the AC electric field strength exceeded 500 V/arm, the image density became thicker.

As can be seen from the results in Figures 2 and 3, the image density changes greatly after a certain amplitude, and as seen from curves A, B, and C, the value of this certain amplitude changes depending on the toner concentration. This can be obtained without much dependence on the average charge amount. The reason may be as follows. In other words, in a two-component developer, the toner is charged by friction with the carrier and mutual friction between the toners, and the amount of charge on the toner is expected to be distributed over a wide range, and the toner with a large amount of charge is preferentially charged. It is thought that it will be developed. Even if the average charge amount is controlled using a charge control agent, the proportion occupied by toners with a large charge amount does not change significantly, and as a result, although changes in development characteristics can be seen, a large Conceivable.

Now, when we conducted experiments similar to those shown in Figs. 2 and 3 while changing the conditions, we were able to sort out the relationship between the amplitude Exc of the alternating current electric field strength and the frequency, and obtained the results shown in Fig. 4.

In FIG. 4, the areas marked with ■ are areas where uneven development is likely to occur, the areas marked with ■ are areas where the effect of the alternating current component does not appear, and the areas marked with ◎ are areas where toner tends to return toward the sleeve 42. , ■, and ■ are regions where the effect of the alternating current component appears and sufficient development density is obtained, and the already formed toner image is not destroyed, and [F] is a particularly preferable region.

In a region where the image density tends to increase with respect to the fluctuation of the AC electric field strength @E sc, for example, regarding the density curve A in Fig. 2,
In the region where the amplitude EAc of the AC electric field strength is 0.2 to 1.2 KV/dragon, the AC component of the developing bias acts to easily exceed the darkness value at which the toner flies from the sleeve, and the toner with a small charge amount However, it is attached to the photoreceptor drum 9 and subjected to development.

Therefore, as the amplitude of the AC field strength increases, the image density increases.

On the other hand, in the region where the image density is saturated with respect to the amplitude Esc of the alternating current electric field strength, the amplitude Esc of the alternating current electric field strength is
For regions where c is 1.2 KV/dragon or higher, this phenomenon can be explained as follows. That is, in this region, as the amplitude of the alternating current electric field strength increases, the toner vibrates strongly, and the clusters formed by toner aggregation become more likely to break, and only toner with a large charge is selectively applied to the photoreceptor drum 9. Toner particles that are attached and have a small charge are difficult to develop. Furthermore, even if toner with a small electric charge adheres to the -transformation photo drum 9, its mirror image force is weak, so it is likely to return to the sleeve 42 due to the alternating current bias.
Furthermore, the electric charge on the surface of the photoreceptor drum 9 leaks due to the amplitude of the electric field strength of the AC component being too large.
It is considered that the toner remains constant despite the increase in the amount of development.

The developing bias conditions suitable for the developing method of the present invention are that the amplitude of the AC component of the developing bias is VAI, (V), and the frequency is f.
(llz), the gap between the image bearing member and the developer transporting member is d
(fin), VAc/ (d − j ) is 0
．． It is preferable to set within the range of 4≦VAc/(d−j)≦1.2.

It is particularly preferable that the two-component developer used in the present invention is composed of a magnetic carrier as a carrier and a non-magnetic toner as a toner.

The composition of the toner is generally as follows.

(1) Thermoplastic resin: binder 80-90wt%
Examples: Polystyrene, styrene-acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer, etc. are often used as a mixture.

(2) Pigment: Coloring material 0-15t% Example: Black: Carpon black Blue: Copper phthalocyanine, sulfonamide dielectric dye φ Yellow: Benzine derivative Magenta: Polytungstophosphoric acid, Rhodamine B lake, Carmine 6B, etc. 3) Charge control agent 0 to 5 wt% Example Nibrass: Nigrosine type (electron donating property) Minus: Organic complex (electron accepting property) (4) Fluidizing agent example: Colloidal silica and hydrophobic silica are typical,
Other products include silicone face, metal soap, and nonionic surfactants.

(5) Cleaning agent Prevent toner filming on the photoreceptor.

Examples: fatty acid metal 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 images and reduce raw material costs.

Examples: 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, triiron tetroxide, γ-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder, etc. with a size of 0.1 to 1 μm have been proposed, but at present, triiron tetroxide is the most common. It is used in an amount of 0.5 to 75-1% 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 adjusted to 5.
5W It is preferable to make it 1% or less. In addition, in order to maintain clear colors as a color toner, the amount of magnetic material must be increased by 10%.
It is desirable to keep it below -1%. Especially 0.5~5wt
% is preferred.

Other resins suitable for pressure fixing toner include approximately 20
Adhesive resins such as wax, polyolefins, ethylene-vinyl acetate copolymers, polyurethane, and rubber are selected so that they can be plastically deformed and adhered to paper with a force of about kg/cm. Capsule toners can also be used.

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

In the structure of the present invention, in order to obtain a more preferable image, it is desirable that the average particle diameter of these toner particles is usually about 50 pm or less in view of the resolution. In this method, there is no theoretical limit to the toner particle size, but the resolution and
In view of toner scattering and transportation, a thickness of about 1 to 15 μm is usually preferably used.

In addition, in order to create delicate points, lines, or gradation ridges, magnetic carrier particles are particles made of magnetic particles and resin, such as a resin dispersion system of magnetic powder and resin, or resin-coated magnetic particles. More preferably, particles are spherical and have an average particle size of preferably 50 μm or less, particularly preferably 30 μm or more and 5 μm or more.

In addition, it does not cause problems such as charges being easily injected into carrier particles by a bias voltage and causing carriers to adhere to the surface of the image carrier, which would impede good image formation, and problems such as not being able to apply a sufficient bias voltage. Therefore, the resistivity of the carrier is 109ΩCm or more, preferably 10I3Ωcm or more, more preferably 1014Ωc
It is best to use insulating materials with a resistivity of m or more, and with these resistivities,
It is preferable that the particle size is as described above.

A method for manufacturing such a finely divided carrier is to use a magnetic material and a thermoplastic resin as described for toner, and coat the surface of the magnetic material with the resin, or coat the particles with a resin containing fine magnetic particles dispersed therein. It can be obtained by preparing particles and selecting the particle size using a conventionally known average particle size selection means.

The carrier is shaped into a spherical shape in order to improve the agitation performance of the toner and carrier and the transportability of the developer, as well as to improve the charge control performance of the toner and to make it difficult for toner particles to coagulate with each other or toner particles and carrier particles. However, for spherical magnetic carrier particles, resin-coated carrier particles should be selected as spherical as possible and coated with resin. It is manufactured by using fine particles of a magnetic material and performing a spheroidizing treatment with hot air or hot water after forming dispersed resin particles, or directly forming spherical dispersed resin particles by a spray drying method.

The amount of developer conveyed in the present invention will be explained.

In FIG. 1, the amount of developer De is regulated by a spike regulating blade 40, and a predetermined amount of developer is supported and conveyed on the sleeve 42 by relative rotation of the sleeve 42 and the magnetic roll 43. In the development area E, a regulated amount of developer De faces the electrostatic latent image on the photoreceptor drum 9 in a non-contact manner, and is developed with toner as a result of the sum of the latent image electric field development bias magnetic force.

Here, the developer conveyance amount ° is the development area E, and the sleeve 4
The unit surface area of 2 is the weight of the developer being transported. The amount of developer that can contribute to development weighs 0.25g.
In this case, the amount of developer 1M fed is 0.025g/clI
It is calculated as I.

FIG. 5 is a sectional view of the developing device used in the experiment described later.

In FIG. 5, 138 is a toner replenisher, 139 is a sponge roller, +41-1 and 141-2 are developer stirring members, 144 is a scraper, 142 is a developing sleeve, 14
3 is a magnetic roll, 140 is a spike regulating blade, R-2
is a resistor, 146 is an AC power supply, and 145 is a DC power supply.

The toner supplied from the toner replenisher 138 is sent to a developing section consisting of a developing sleeve 142 and a magnetic roll 143 by the action of a sponge roller 139 and stirring members 141-1 and 141-2. A layer of developer De made of toner and carrier is formed on the developing sleeve 142, the thickness of which is regulated to be constant by the buffing regulation blade 140, thereby developing the latent image formed on the surface of the photoreceptor drum 109. do. A scraper 144 scrapes off the developer on the surface of the sleeve 142 after development. Note that arrow a is the moving direction of the developer, and arrow s is the rotating direction of the magnetic roll. An AC power source 146 and a DC power source 145 are connected to the developing sleeve 142 via a resistor R-2.
A developing bias is applied between the sleeve 142 and the photosensitive drum 109.

The gap between the sleeve 142 and the earing regulation blade 140 (
Hereinafter, this will be referred to as the developer layer thickness regulation gap. ) g and the amount of developer conveyed across the development area, it was found that
The results shown in the figure were obtained.

The operating conditions of the developing device are as follows.

Sleeve φ24 Dragon Made of non-magnetic stainless steel without surface treatment Sleeve rotation speed 30 rpm...Magnetic roll NS alternating arrangement 10 pole magnetic roll rotation speed
80Orpm magnetic roll surface magnetic flux density
800 gauss developer carrier Resin-dispersed magnetic carrier, specific resistance ≧10'1Ω Mouth weight average particle size 20μm, magnetization 50emu/g (under magnetic flux density of 1000 gauss) Toner Weight based average particle size 11μm Fluidizer Hydrophobic Toner concentration 20v t% Toner concentration 20v t% Toner density regulating blade Non-magnetic blade From Figure 6, the developer layer thickness regulating gap g is 0.01 to
In the range of 0.065 mm, the relationship with the amount of developer conveyed is linear, and both are in a proportional relationship.

The rotation speed of the sleeve 142 is in the range of 10 to 300 rpm, and the rotation speed of the magnetic roll 143 is in the range of 100 to 1500 rpm.
When the same experiment as above was carried out by changing the range of , substantially the same results as those shown in FIG. 6 were obtained. From this, it can be understood that within the above conditions, the developer layer thickness regulation gap g is the main factor determining the amount of developer conveyed.

By changing the number of revolutions of the magnetic plate roll 143, the photoreceptor drum 1
The relationship between the surface potential of the image area (electrostatic latent image forming area) of No. 09 and the image density was determined.

The operating conditions are as follows.

1. Photosensitive drum a, photosensitive layer Se-based, linear velocity 150 mm/5ec2, surface potential a, charging potential +1000 V b1 image area potential +900 V C1 exposed area potential 10 OV 3, developer a, carrier magnetic powder dispersion System average particle size (weight basis) 20μm Specific resistance 10″Ω or more Magnetization Approx. 50emu/g (σ1000)σ100
0: Magnetized in a magnetic flux density of 1000 Gauss, )ner + MN Styrene/acrylic average particle size (weight basis) 11 μm 4. Developing device a, sleeve Made of non-magnetic stainless steel Rotated at 24 mm linear velocity 30 mm/sec Magnet 8-pole sleeve surface magnetic flux density 800 Gauss 100-1500 rpm + 11 rotations 5, development conditions a,! Gear pump closest to optical sleeve 0.9 lb
, regulation gap 0.3 Tsuru C0 development bias AC voltage (effective value) 1. OKV frequency
2KHz DC component +650v d, developer conveyance amount 0.024 g/cA The results are as shown in FIG.

When the magnetic roll was rotated at 100 to 1500 rpm, the image density reached nearly 1.0 or more from a surface potential difference of about 600 V between the image area and the non-image area, and a sufficient density was obtained at 800 V. The magnetic roll was fixed without rotating (
Orpm), the developer transport is unstable or insufficient,
This resulted in unevenness on the sleeve, uneven density, and low image density.

There was also a difference in the uniformity of the developed image between when the magnetic roll was rotated and when it was stopped. FIG. 8 shows an example of scanning an image area with a reflective darkening needle.

The scanning direction is perpendicular to the developing direction.

Kodamasu 1 The developer layer thickness regulation gap g was changed to change the amount of developer conveyed, and the relationship between the amount of developer conveyed and the image density was determined.

The operating conditions are that the rotation speed of the magnetic roll 143 is 80° rpm.
It is the same as in Experimental Example 1, except that it is kept constant.

The results are shown in FIG.

was there.

If the conveyance amount is less than 0.01 g/cd, the photosensitive drum 1
As the gap between the developer 09 and the sleeve 142 is narrowed, the density increases, but if it is too narrow, it becomes difficult to obtain the precision of the gap.Furthermore, it is not preferable because it causes unevenness in the general feeding of the developer.

When the conveyance amount exceeded 0.04 g/cj, fogging could be removed to some extent by widening the gap, but the density tended to decrease accordingly. Further, toner scattering increases, which is not preferable. Furthermore, carrier scattering and carrier adhesion become increasingly noticeable, which is not preferable.

The developing method of the present invention was first developed by the applicant in Japanese Patent Application Laid-Open No. 60/75.
Publication No. 850, Publication No. 60-76766 and Japanese Patent Application No. 1983
The method was applied to the color image recording method disclosed in No. 0-166549.

FIG. 10 shows a color image forming apparatus.

The resolved light is received by a line image sensor (such as a COD), converted into an electrical signal, and then converted into a digital signal.The color signal of the original obtained by a color separation circuit is sent to a semiconductor laser or LED.
This is a so-called digital color copying machine that forms an electrostatic latent image by writing on a photoreceptor with a writing device such as a liquid crystal head.

The development method was a reversal development method.

In FIG. 10, A is a reading unit, B is a writing unit, C is an image forming section, and D is a paper feeding section.

In the reading unit A, 201 is a platen glass, and an original 202 is placed on this platen glass 201. The document 202 is illuminated by fluorescent lights 205 and 206 provided on a carriage 4 that moves on a slide rail 203. The movable mirror unit 208 has a mirror 2.
09 and 209' are provided and move on the slide rail 203, and in combination with the first mirror 207 provided on the carriage 204, the original 20 is placed on the platen glass 201.
2 is led out to the lens reading unit 220.

The carriage 204 and the movable mirror unit 208 are driven by pulleys 211, 212, 213, and 214 driven by a stepping motor 210 through a wire 215.
They are driven in the same direction at speeds of 1 and 1/2, respectively.

Standard white plates 2 are installed on the back side of both ends of the platen glass 201.
06.207, and is configured so that a standard white signal can be obtained before the start of original reading scanning and after the end of scanning.

L/7 SA Take Unisoto 220 is lens 221
, a prism 222, a first reading board 224, a red channel (hereinafter referred to as R-ch) CCD 225, a second reading board 226, and a cyan channel (hereinafter referred to as C-ah) CCD 227.

The original light image transmitted by the first mirror 207, the mirror 209, and the mirror 209' is focused by the lens 221,
Guicroic mirror 2 provided within the prism 222
23 into an R-ch image and a C-ch image, and the R-ch CCD 225 is provided on the first reading board 224.
and C-chCC provided on the second reading board 226
The two light planes of D227 are imaged.

The fluorescent lamps 205 and 206 are commercially available warm white fluorescent lamps that are used as light sources when reading color originals to prevent emphasis or attenuation of specific colors. It is lit by 1lzO high-frequency radio waves and kept warm by a heater using a POSISTOR to maintain a constant temperature of the tube wall or to promote warm-up.

The image signals output from the R-ch CCD 225 and C-ch CCD 227 are subjected to signal processing in a signal processing section E, which will be described later. In the signal processing section E, a color signal separated according to the color of the toner, which will be described later, is outputted and inputted to the writing unit B.

The writing unit I-B is configured as shown in FIG.
A laser beam generated by a semiconductor laser 331 is rotated and scanned by a polygon mirror 332 rotated by a drive motor 330, and reflected 831 through an Fθ lens 333-1.
337, the optical path is bent and projected onto the surface of the photoreceptor drum 109 to form a bright line 339. 334 is an index sensor for detecting the start of beam scanning;
5.336 is a cylindrical lens for tilt angle correction. Reflecting mirrors 338a, 338b, and 338C form a beam scanning optical path and a beam detection optical path.

When scanning is started, the beam is directed to the index sensor 334.
is detected, and modulation of the beam by the first color signal is started. The modulated beam is transferred to the charger 2 in FIG.
The photosensitive drum 10 is uniformly charged in advance by 41.
9. Scan above. A latent image corresponding to the first color is formed on the drum surface by the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 109. This latent image is developed by a developing device 243 loaded with red toner, for example, to form a toner image on the drum surface. The obtained toner image, while being held on the drum surface, passes under a cleaning device 246 that is separated from the photosensitive drum surface and enters the next copy cycle. Photosensitive drum 10
9 is charged again by the charger 241.

Next, the second color signal output from the signal processing section E is input to the writing unit B, and is written on the drum surface in the same manner as the first color signal described above to form a latent image. The latent image is developed by a developer 244 loaded with toner of a second color, for example blue. This blue toner image is formed over the already formed red toner image.

A developing device 245 has black toner, and forms a black toner image on the drum surface based on a control signal generated by a signal processing section. AC and DC biases are applied to the sleeves of these developing devices 243, 244, and 245 to perform jumping development using two-component toner, and non-contact development is performed on the grounded photosensitive drum 109.

The superimposed image of the toner image based on the first color signal, the toner image based on the second color signal, and the toner image developed using the black toner thus developed is transferred to the paper feed section by the transfer pole 250. The image is transferred onto the recording paper 261 fed by the feeding belt 264 and the feeding roller 263. The transfer paper on which the toner image has been transferred is separated from the photoreceptor by a separation pole 251, and further conveyed to a fixing section 252 where it is fixed and a color hard copy is obtained.

A cleaning device 246 comes into contact with the photosensitive drum 240 after the transfer, and performs cleaning with a blade 247 to remove unnecessary toner from the drum surface. The roller 249 of the cleaning device is used to remove a small amount of toner left behind between the drum surface and the blade when the blade 247 leaves the drum surface in preparation for the next exposure and development after cleaning. While rotating in the opposite direction, the contact portion with the drum surface is rubbed and residual toner is collected.

Developing devices 243 and 24 of the color image forming apparatus shown in FIG.
4.245 has the structure shown in Figure 12, and has the following (i
), (ii), and (iii) have the same structure as the developing device shown in Fig. 5, and in Fig. 12, the same parts as in Fig. 5 are denoted by the same reference numerals. be.

(i) The direction of rotation of the sleeve 142 and magnetic roll 143 is opposite to that shown in FIG.

(ii) The position of the ear stand regulating blade 140-2 has been changed from that in FIG. 5 in accordance with the direction of rotation of the sleeve 142.

(iii) The position of the scraper 144-2 is changed from that in FIG. 5 to match the rotation direction of the sleeve 142,
Since it is buried in the developer De in the developer reservoir, it is a magnetic material. This is to remove the developer remaining on the sleeve 142 from the sleeve 142 and stir it together with the developer De.

The operating conditions for image formation are as follows.

Image forming conditions Image forming photosensitive layer OPC (organic photoconductive material) drum diameter
140 III Linear velocity 58mm/sec Surface potential charging potential (potential of non-image area during development) -650V exposed area potential
-10V image exposure conditions Light source Semiconductor laser wavelength 780±20nm Recording density
16dots/*n developing device sleeve made of non-magnetic stainless steel, 18 φ linear speed 2
Rotating magnet 8 poles at 0 dragon/sec, rotating magnetic flux density at 600 rpm
700 gauss (sleeve surface) Developer carrier Magnetic powder resin dispersion system, average particle size (weight basis) 20 μm Specific resistance 10'4 Ωam or more Magnetization approximately 50 emu / g (IIFI-) σ16 @
6: Magnetized toner red (R) in too Gauss magnetic flux density Average particle size (weight basis) 11 μm Average charge amount 10 μC/g (toner concentration 15-t%) Blue (B) Average particle size (weight basis $) 11 μm average charge amount 11 μC/g (toner concentration 15 wt%) Black (K) Average particle size (weight basis) 11 μm average charge amount 12 μC/g (I-toner concentration 15-L%) Development conditions Between photoreceptor and sleeve 1. 0 Discussion Developer layer thickness 0.2 to 0.8 degrees (at rest) (regulated by non-magnetic blade) (Common to the above) Developer conveyance amount (actual value) Red developer's 0.030 g/co! Blue 〃 ■ 0.025 g/cA black 〃@
l O,032g/cnT3 co-conveyed amount, for example, 0
．． 025 g/crA may be set.

Development bias A (R) DC-500V ACl, OKν (effective value) 2KIIzB (B) DC-500V
ACl, OKl effective value) 2KHzC(K) DC-
500V ACo, 8KV (effective value) 2KIIZ
Development order R-B-K Other process methods Transfer Corona transfer fixing Pressure cleaning with a heated roller Blade and cleaning roller An image with a sufficiently high density was obtained in this experimental example as well. Images produced with color toners such as red and blue also had good uniformity and high quality images.

The density of the black image area is 1.1 or more in reflection density (exposed area),
No fogging or toner scattering was observed in the obtained non-image.

In addition, the linear velocity of the photoreceptor was changed from 58-m/sec to 120-m/sec.
A sufficiently high concentration was obtained even when the speed was increased to am/sec 230 mm/sec.

In the apparatus shown in FIG. 10, the rotating polygon t of the laser writing section
In place of the M332c (see FIG. 11), a vibrating and rotating mirror unit (called a Gartno mirror) having a similar function can be used.

This writing unit B is configured as shown in FIG. 13, and a laser beam generated by a semiconductor laser 331 is vibrated and scanned by a galvanometer mirror 351 that is vibrated by a drive unit 352, and is reflected through a sin'θ lens 333-2. The optical path is bent by the mirror 337 and the photosensitive drum 109
projected onto the surface of The rest is the same as in FIG. 11.

FIG. 14 shows the principle of the mirror vibration mechanism 350, in which the operational amplifier OP is connected to the magnetic drive unit 3 via the position sensor 350b.
drive the magnetic drive section 350a in response to a position signal and an analog input signal from the amplifier AMP connected to the amplifier AMP;
A galvanometer mirror 351 fixed to the vibrator is caused to reciprocate by a specified amount by a current flowing through the coil.

FIG. 15 shows an overview of a color printer using the writing unit 350 shown in FIG. Other parts common to FIGS. 10 and 14 are designated by the same reference numerals.

(Comparative Experiment Example 1) The amount of developer conveyed was 0.05 g/cJ, 0.08 g/c
Two points of No. 11 were selected, and development was performed under the same conditions as in Experimental Example 1 above. As a result, fogging in non-image areas increased as the conveyance amount increased, carrier adhesion to image areas and toner scattering also became significant, and the level was not high enough to withstand long-term practical use.

(Comparative Experiment Example 2) The amount of developer conveyed was 0.007 g/cd, 0.005 g/c
Two points J were selected, and development was performed under the same conditions as in Experimental Example 1 above. As a result, the image density in a portion where the potential difference between the image area and the non-image area was 800 V decreased as the conveyance amount decreased. The highest concentrations were 0.95 and 0.70, respectively.

(Comparative Experiment Example 3) Carrier adhesion and capri occurred.

1. The photoconductor, developer, etc. used in the present invention are not limited to the above examples; for example, the photoconductor may be a photoconductor equipped with an amorphous silicon photoconductive layer, or the developer carrier may be a granular photoconductor. Various modifications can be made without departing from the spirit of the present invention, such as applying a resin coating to ferrite powder having a diameter of 10 to 40 μm.

As described in detail, since the present invention is applied to the development area, the following effects can be achieved.

The entire layer of developer can move freely on the developer transport body, and the Bg metal waste is reduced to 77%! Circulation employment/dismissal me% degree Iwao Yf
Fake I/Da charcoal is I/! rt, y As a result, it is possible to obtain a high-quality visible image with uniform and sufficient density, no carrier adhesion, and no fogging without complicating or increasing the size of the developing device. I can do it.

[Brief explanation of drawings]

The drawings all show embodiments of the present invention, and FIGS. 1, 5, and 12 are cross-sectional views of the developing device, and FIGS. 2 and 3 are cross-sectional views of the developing device when the AC bias voltage is changed. Figure 4 is a graph showing the image density characteristics when changing the electric field strength and AC bias frequency. Figure 6 is the relationship between the developer layer thickness regulation gap and the amount of developer conveyed. Figure 7 is a graph showing the relationship between image area potential and image density. Figure 8 is a graph showing image density changes in the direction perpendicular to the development direction. Figure 9 is a graph showing the relationship between the amount of developer conveyed and image density. Figure 10 is a schematic diagram of a color image forming apparatus, Figures 11 and 13 are schematic diagrams of a laser writing system, and Figure 14 is an example of the principle of driving the laser writing system mirror in Figure 13. FIG. 15 is a schematic diagram of a color printer using the laser writing system of FIG. 13. In addition, in the reference numerals shown in the drawings, 9.109......Photosensitive drum 40.14
0.140-2 ...... Ear stand regulation blade 41.141-
1.141-2・・・・・・Stirrer 42.142
......Developer transport body (sleeve) 43.1
43...Magnetic roll 44.144.14
4-2...Scraper 45.145...
......DC power supply 46.146...
・AC power supply 243.244.245...
Developing device De...Developer.

Claims (1)

[Claims] 1. In a developing method in which an electrostatic latent image is developed in a non-contact manner under an alternating electric field, the amount of developer conveyed to the developing area is set to 0.01 to 0.
A developing method characterized by performing reversal development with an amount in the range of 0.04 g/cm^2.