JPS61226768A - Method and device for multicolor image formation - Google Patents

Abstract

PURPOSE:To improve a transfer state and the conveyance of transfer materials by forming a multicolor toner image on an image formation body and conveying a transfer material while holding it electrostatically on a transfer means, and transferring the multicolor toner image on the image formation body to the transfer material and separating the transfer material from the transfer means. CONSTITUTION:A toner image forming process is repeated by rotating the image carrier once for each color in the order of yellow, magenta, cyan, and black to form a multicolor tone image by superposing toner images of the respective colors one over another. This multicolor toner image is charged electrostatically by a before-transfer charger 9 and made easy to transfer and then transferred by a transfer roll 50 to a transfer material P supplied by a paper feeding device 11, a paper feed roll 12, and a timing roll 13. The transfer material P to which the multicolor toner image is transferred is discharged by an AC charger 64 according to a timing chart and separated from the transfer roll 50. The image formation body 1 after the transfer operation is discharged by a before-cleaning discharger 7 and residual toner is cleaned by the blade 81 and fur brush 82 of a cleaning device 8. The separated transfer material P is conveyed by a fixing device 6 and heat-fixed by a heat roll.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method and apparatus for forming a multicolor toner image on an image forming body and transferring it to a transfer material to obtain a recorded image. It is used in fields such as electrophotography and electrostatic recording.

[Conventional technology]

Various methods of forming multicolor images as described above have been proposed in the past.

Conventional Example 1 One of them is to repeat the steps of charging, exposing, developing, and transferring for each color component to superimpose toner images of each color on recording paper. That is, an electrostatic latent image is formed according to color component data such as blue, green, and red, and yellow, magenta,
The image is developed with cyan or black toner, transferred to a transfer material such as recording paper or film for an over-the-top projector, and the above steps are performed for each color component to form a multicolor image on the transfer material.

Conventional Example 10 Problems However, with this method, (1) It is necessary to transfer the image onto the transfer material each time the development of each color is completed, which increases the size of the apparatus and increases the time required for image formation.

■ There are drawbacks such as the tendency for positional deviations to occur due to repeated movements.

Conventional Example 2 (Improvement of Conventional Example 1) A multicolor image forming method in which a plurality of toner images are superimposed and developed on the same image forming body such as a photoreceptor, and the transfer process is completed only once, thereby solving the above drawbacks. There is.

Conventional Example 20 Problems There are negative effects such as the toner image formed by the previous stage development being disturbed during the latter stage development, and the donor from the toner image developed in the former stage being mixed into the latter stage developer, disrupting the color balance. .

Conventional Example 3 (Improvement of Conventional Side 2) In the method of Conventional Example 2, a bias with an alternating current component superimposed is applied to the development IT during the second and subsequent development to reduce the electrostatic latent image formed on the image forming body. A method of forming a multicolor image by employing a method of making toner fly has been proposed. In this method, the developer layer does not rub the toner image formed up to the previous stage, so that image disturbance does not occur.

The principle of this multicolor image forming apparatus will be explained below with reference to the flowchart shown in FIG. FIG. 7 shows changes in the surface potential of the image forming body, which is a photoreceptor, and takes as an example the case where the charging polarity is positive. The pH is the exposed area of the image forming body, D
A indicates the unexposed area of the image forming member, and DUP indicates the increase in potential caused by the adhesion of positively charged toner to the pH of the exposed area during the first development.

(2) The image forming body is uniformly charged by a charger and has a constant positive surface potential E.

(2) First image exposure is applied using a laser, cathode ray tube, LED, or the like as an exposure source, and the potential of the pH of the exposed area decreases according to the amount of light.

(2) The electrostatic latent image thus formed is developed by a developing device to which a positive bias approximately equal to the surface potential E of the unexposed area is applied. As a result, the positively charged toner T adheres to the exposed area pH, which has a relatively low potential, and a first toner image is formed. In the area where this toner image is formed, the potential increases by DUP due to the adhesion of the positively charged toner T1, but normally it does not have the same potential as the unexposed area DA.

■ Next, the surface of the image forming body 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 , the surface potential E is uniform.

(2) A second image exposure is performed on the surface of this image forming body to form an electrostatic latent image.

(2) Similarly to 01 above, positively charged toner T of a different color from toner T1 is developed to obtain a second toner image.

By performing the above process multiple times, a multicolor toner image is obtained on the image forming body. A multicolor recorded image can be obtained by transferring this to a transfer material and further fixing it by heating or applying pressure. In this case, the toner and charges remaining on the surface of the image forming member are cleaned and used for the next multicolor image formation.

In the method illustrated in FIG. 7, at least the developing step (2) is carried out in such a way that the developer layer does not come into contact with the surface of the image forming member.

In the multicolor image forming method, a step of eliminating electricity from the surface of the image forming body can be provided before the second and subsequent charging. Furthermore, the exposure sources used for each image exposure may be the same or different.

In the multicolor image forming method, toners of four colors, for example, yellow, magenta, cyan, and black, are often superimposed on an image forming member for the following reason. According to the principle of the subtractive color method, a black image should be obtained by overlapping the three primary colors of yellow, magenta, and cyan, but the toner for the three primary colors used in actual eyebrows has an ideal absorption wavelength range. Not only is it difficult to reproduce the clear black required for characters and lines using only these three primary color toners, but also it is difficult to reproduce the clear black required for characters and lines due to the misalignment of toner images of the three primary colors. The concentration tends to be insufficient. Therefore, as described above, a multicolor image is formed using four colors, which are the three primary colors plus black.

In electrophotography, gas or semiconductor laser light, L11iD% CRT, liquid crystal, etc. are used as image exposure means.

In addition to the electrophotographic method described above, methods for forming latent images for forming multicolor images include a method in which an electrostatic latent image is formed by directly injecting charges onto the image forming body using a multi-needle electrode, and a method in which an electrostatic latent image is formed by directly injecting charges onto the image forming body using a multi-needle electrode. For example, a method of forming a magnetic latent image can be used.

FIG. 8(a) shows an example of a device that implements this method. In this device, a multicolor image is formed as follows. The surface of the image forming body 1 is uniformly charged by the charging electrode 2. Subsequently, the image forming body 1 is irradiated with image exposure light from the laser optical system IO. In this way, an electrostatic latent image is formed. This electrostatic latent image is developed by a developing device A containing yellow toner. Image forming body 1 on which a toner image is formed
is uniformly charged again by the charging electrode 2 and subjected to imagewise exposure. The formed electrostatic latent image is developed by a developing device flB containing magenta toner. As a result, a two-color toner image of yellow toner and magenta toner is formed on the image forming body 1. Similarly, cyan toner,
The black toner is superimposed and developed to form a four-color toner image on the image forming body 1.

The four-color toner image is charged by the charging electrode 9, while
After the charges on the image forming body are erased by an exposure lamp, they are transferred to a transfer material P by a transfer pole 4. The transfer material P is separated from the image forming body 1 by the separation pole 5 and fixed by the fixing device 6. On the other hand, the image forming body 1 is cleaned by the removing electrode 7 and the cleaning device 8.

The cleaning device 8 includes a cleaning blade 81 and a fur brush 82. These are kept out of contact with the image forming body 1 during image formation, and when a multicolor image is formed on the image forming body 1, they come into contact with the image forming body 1 and scrape off residual toner after transfer. Thereafter, the cleaning blade 81 separates from the image forming body 1, and a little later, the fur brush 82 separates from the image forming body 1. 7 A brush 82 is a cleaning blade 81
When the toner leaves the image forming body 1, it functions to remove the toner remaining on the image forming body 1.

The laser optical system IO is shown in FIG. 8(b). In the figure, 21
is a semiconductor laser oscillator, n is a rotating polygon mirror, n is fo
It's a lens.

In this multicolor image forming apparatus, one color is developed each time the image forming member 1 rotates once, but the application of a large alternating current voltage that contributes to development to developing devices that are not in use is stopped. Note that during image formation, none of the fItsi, paper feed, paper conveyance, and cleaning devices 8 other than the charging electrode 2 act on the image forming body 1.

Problems with Conventional Example 3 In the conventional methods described above, the corona transfer method is used as the transfer method. This includes: (1) The mechanism is simple; and (2) The image forming body 1 is not damaged.

(2) Toner adhering to the transfer means does not stain the back surface of the transfer material P.

There are advantages such as However, on the other hand, ■ the adhesion between the transfer material P and the image forming body 1 is incomplete, which tends to cause transfer unevenness, ■ the transfer characteristics tend to change due to the influence of the surrounding environment such as temperature and humidity, and ■ image formation. When the intermediate toner image passes the transfer position,
Toner adheres to the electrode, reducing transfer efficiency; ■ When multiple types of toner overlap in the same position, it is difficult to transfer the lower toner; ■ The position of the toner shifts or the toner scatters during transfer. , problems such as disrupting currency exchange remained unresolved.

Conventional Example 4 (Improvement of Conventional Example 3) In the multicolor image forming apparatus shown in FIG. 8(A), a roller or a belt is used instead of the transfer pole 4 in pressure contact with the image forming body, and the image is transferred to the pressure position. For example, there is an apparatus shown in FIG. 9 that transports a material P and transfers a toner image. In the roller section shown in the figure, an electric field is formed at the transfer position by applying a transfer bias or injecting charge by corona discharge, etc.
Methods are taken to increase transfer efficiency.

In FIG. 9, the transfer material P is supplied from the paper feeder 1 by the paper feed roller 12 and timing roller 13.
A transfer roller, which is rotatably fixed to the other end of a lever group rotating about a shaft 51, is pressed against the image forming body 1, and a bias is applied from a power source 14, The multicolor toner image on the image forming body 1 is transferred. Further, the transfer roller is brought into contact with or out of contact with the image forming body 1 by an eccentric roller that rotates eccentrically about a shaft 57.

[Problem that the invention seeks to solve]

In this transfer method, the transfer material P is conveyed to the transfer position, the toner image is transferred, and the transfer material P is transferred to the image forming body 1 and the transfer means such as the transfer roller. There is a problem in that a large space is required to separate the

That is, since the transfer material P cannot be held by the transfer means if it is bent significantly due to its stiffness, it must be carried into and out of the transfer position along a path as close to a straight line as possible.

[Means for solving problems]

(Objective of the Invention) The present invention solves the above-mentioned problems, and provides image formation in which the transfer state is good, the conveyance of the transfer material P is good, and the space from transfer to separation does not require a large amount of space. An object of the present invention is to provide a method and an apparatus thereof.

(Structure of the Invention) The present invention provides the following steps: (1) (a) A step of forming a multicolor toner image on an image forming body; a step of holding and transporting, (e)
a multicolor image forming method comprising the steps of: (d) separating the transfer material from the transfer means; means for forming a latent image on the image forming body; at least one developing means; means for applying an electric charge to the transfer material; and means for transferring the toner image from the image forming body to the transfer material while conveying the transfer material. The above-mentioned object is achieved by a multicolor image forming apparatus comprising a means for eliminating static electricity from a transfer material.

FIG. 1(A) shows an example of a multicolor image forming apparatus based on the present invention.

The difference from the conventional multicolor image forming apparatus shown in FIG. 8(A) is the transfer section. That is, this device operates as follows.

(1) The surface of the image forming body 1, which is a photoreceptor, is uniformly charged by the charging diameter 2.

(Laser optical system @! Exposure from 0 is irradiated onto the image forming body 1. As a result, an electrostatic latent image is formed.

(3) This electrostatic latent image is developed by a developing device A containing, for example, yellow toner.

(4) The image forming body 1 on which the toner image has been formed is neutralized by emitting light from the static eliminating lamp 3, and then uniformly charged again by the charging electrode 2 and subjected to imagewise exposure.

(5) The formed Wbi latent image is developed by a developing device B containing, for example, magenta toner. As a result, a two-color toner image of yellow toner and magenta toner is formed on the image forming body 1.

(6) Similarly, the cyan toner and the black toner are developed in a superimposed manner to form a four-color toner image on the image forming body 1.

(7) The four-color toner image is charged by the charging electrode 9, and the N? N is eliminated by the static elimination lamp 3.

(8) On the other hand, the transfer roller gloss remains at a position away from the image forming body 1 until the three-color toner image passes through the transfer position.

(9) Thereafter, a fourth color toner image is formed, and by the time the leading edge of the toner image reaches the transfer position, the transfer roller comes into contact with the image forming body 1 and begins driven rotation.

(The transfer material P is charged with the same polarity as the toner by the discharge electrode 8 and comes into close contact with the transfer roller. Thereafter, as the transfer roller rotates, the transfer material P is transferred between the image forming member 1 and the roller η. transported to.

(1)) A bias voltage having a polarity opposite to that of the toner on the image forming body 1 is applied to the transfer roller.

(12) The transfer material P is further conveyed as the image forming body 1 and the transfer roller rotate, and the transfer is completed.

Even after the transfer, the transfer material P remains in close contact with the transfer roller.

(13) The transfer material P is electrically neutralized by the pole 64, separated from the transfer roller, and the transferred toner particles are fixed by the fixing device 6. During separation, a separation tool or the like may be used as necessary.

(14) On the other hand, is image forming body 1 excluded? ! It is cleaned by the pole 7 and the cleaning device 8. The cleaning device 8 has a cleaning blade 81 and a fur brush 82. These are kept out of contact with the image forming body 1 during image formation, and when a multicolor image is formed on the image forming body 1, they come into contact with the image forming body 1 and scrape off residual toner after transfer. Thereafter, the cleaning plate '81 separates from the image forming body 1, and a little later, the fur brush 82 separates from the image forming body 1. The fur brush functions to remove toner remaining on the image forming body 1 when the cleaning blade 81 leaves the image forming body 1 .

(15) At the same time, the transfer roller mark separates from the image forming body 1.

In the above process, the transfer roller circle comes into contact with the image forming body 1 only after the third color toner image (generally one color before the multicolor toner image is completed) passes through the transfer position. A blade 57 is always pressed against the transfer roller, and as the roller rotates, it cleans its surface. Therefore, it is possible to prevent toner from adhering to the surface of the transfer roller father, and the back surface of the transfer material P is not stained.

Since the transfer material P is charged to the same polarity as the toner to be transferred before coming into contact with the transfer roller father, an electrostatic force acts between it and the transfer roller group, and the transfer material P comes into close contact with the roller father. Therefore, the transfer material P
can be easily bent along the transfer roller, and the conveyance path can be accommodated in a small space. On this occasion,
Due to the bias voltage applied to the transfer roller father, the toner on the image forming body 1 receives a force in the direction of the transfer material P, and the toner is transferred. After that, if the transfer material P is neutralized, no electrostatic force will act between it and the transfer roller father, so that the transfer material P will be immediately separated. As described above, the transfer means shown here has the effect that the overall size of the image forming apparatus can be significantly reduced compared to the case of the multicolor image forming apparatus shown in FIG. 9. Note that the transfer material P may be charged with the same polarity as the toner to be transferred. In this case, in order to bring the transfer material P into close contact with the transfer roller, it is desirable to apply a bias having a polarity opposite to that of the toner to the transfer roller group. The toner on the image forming body 1 is transferred to the transfer material P due to the charge held by the transfer material P.

Preferred conditions regarding the transfer roller include: ■ Image forming body 1
be in close contact with the object with a constant pressure.

■ Toner easily separates from the surface.

■ Easily generate a uniform and sufficiently large electric field in the transfer area.

Examples include. In order to satisfy this, (a)
The axis is a strong hollow cylinder made of aluminum or similar conductive metal (Sakaki), and around it is an elastic layer of conductive rubber such as silicone rubber, polyurethane rubber, or butyl rubber with a thickness of about 0.5 to 5XIg. put.

The resistivity of the conductive rubber is desirably 1010Ω or less, more preferably 10701Ω or less, in order to satisfy the above (2). The hardness is preferably JIS standard (K6301/doll). In addition, in order to prevent the applied bias voltage from spreading due to scratches on the image forming body 1 and from making it impossible to generate a sufficient electric field in the transfer section, ) A dielectric layer with a thickness of about 10 to 100 μm is placed thereon.

This is desirable. In any case, in order to maintain good adhesion to the image forming body 1, it is desirable that the surface roughness be 100 μm or less.

In addition, as the transfer means, a belt-shaped one can be used.

The bias voltage applied to the roller stamp during transfer depends on various conditions, but is usually set within the range of ±0.5 to 4 KV. In order to prevent the toner on the image forming member 1 from adhering to the transfer roller during non-transfer, it is effective to apply a bias of 800 V or less with the same polarity as the toner.

Furthermore, sufficient adhesion with the image forming body 1 can be obtained by setting the pressure when the transfer roller contacts the image forming body 1 in the range of 0.1 to 1.5 Kf/cJ.

An enlarged sectional view of the transfer section as described above is shown in FIG. 1(B). Here, the state in which the image forming member 1 is in contact is shown with a solid line, and the state in which it is not in contact is shown with a dotted line.

A lever group is arranged on the shaft 51 and supports the shaft 52. Further, the lever 55 receives a downward force from the spring 5. A tubular roller core 53 is rotatably arranged on the shaft 52 by means of a ball bearing. The transfer roller section is provided on the roller core 53. 8 rollers are supported by eccentric cams. The eccentric force bead is eccentrically rotated by a motor (not shown) rotating between its axes. Therefore, the distance between the rollers and the image forming body 1 changes due to the rotation of the eccentric force worm. Further, the surface of the transfer roller mark is cleaned by a blade 57. This blade 5
7 is always placed on the surface of the roller group. In addition, in the conveyance path of the transfer material P, there is a discharge 1! which applies an electric charge of the same polarity as the toner to be transferred to the transfer material P before it comes into contact with the transfer roller gloss. A gap is provided between the pole 63 and a neutralizing electrode for neutralizing the transfer material after transfer.

In the above example, it is desirable that the electric sweat 9 provided to apply to the toner on the image forming body 1 before transfer discharges with the same polarity as the charge that the toner had during development.
It is not limited to this. Alternatively, when the transfer roller is not in contact with the image forming body 1, a driving force may be applied from the outside to rotate it, and the blade 57 may clean the surface of the roller stamp.

Next, preferred development conditions in the present invention will be explained.

The four developing devices used in the multicolor image forming apparatus shown in FIG. 1(a) may be of the same or similar construction. As an example, a sectional view of the first developing device 1A is shown in FIG. Developer De
has a sleeve 42 and a magnetic roll 41 with 12 sweat numbers.
It is transported in the direction of the arrow by zero rotation. The developer De is formed into a developer layer with a constant thickness by the spike control blade 43 during transportation. In the developer reservoir 44, stirring spoons +J and -45 are provided to sufficiently stir the developer De. When the developer De in the developer reservoir is consumed, the toner supply v-r 46 rotates and the toner T is captured from the toner hopper 47. A power source 48 for applying a developing bias is connected to the sleeve 42 . Also, the sleeve 42,
The magnetic reel 41 and stirring screw 45 are driven by a motor 49 integrated with the developing device.

On the other hand, there are two types of developer: a two-component developer mainly composed of non-magnetic toner and a magnetic carrier, and a one-component developer composed only of magnetic toner, and either one may be used in the present invention. In particular, two-component developers require the control of the toner relative to the carrier; however, it is easy to control the charge of the toner, and there is no need to include a large amount of magnetic material in the toner, so there is no color smudging. Color toner can be made.
There are lessons such as:

A preferred example of a two-component developer as mentioned above is given below.

Thermoplastic resin (binder) 80-90 wt% Examples: polystyrene, styrene acrylic polymer, polyester, polyvinyl butyral, eho.

resin, polyamide resin, polyethylene, ethylene-vinyl acetate, etc., or a mixture of the above ■ Pigment (coloring agent) 0 to 15 wt% Example: Black carbon black Yellow: Benzidine derivative Magenta: Rhodamine B lake, Carmine 6B, etc. Cyan : Copper 7 thalocyanine, sulfonamide dielectric dye, etc.■ Charge control agent 0-5wt% Positive donor: Nigrosine-based electron-donating dye, alfoxylated amine, alkylamide, chelate, pigment, 4
Negative toners such as ammonium salts: Electron-accepting organic complexes, chlorinated paraffins, chlorinated polyesters, polyesters with excess acid groups,
Chlorinated steel phthalocyanine, etc. ■ Examples of fluidizing agents: colloidal silica, hydrophobic silica, silicon face, metal soap, nonionic surfactants, etc. ■ Cleaning agents (preventing toner filming on the image forming body) Examples: Fatty acid gold salt, oxidized silicon acid with organic groups on the surface,
Fluorine surfactants, etc. ■ Fillers (improves image surface gloss, reduces raw material costs) Examples: Calcium charcoal, clay, talc, pigments, etc. In addition to these materials, they also prevent fogging on the image surface and toner scattering. Therefore, magnetic powder may be included.

As such magnetic powder, trioxide needles with a particle size of 0.1 to 1, r-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder, etc. are used, and the content is 5 to 70 wt%. . The resistance of the toner varies greatly depending on the type and content of magnetic powder, but it is preferably 1080 or more, preferably 01
In order to obtain a sufficient fold of 20 or more, the amount of magnetic material should be 5
5wt% or less, 30wt to maintain even clearer colors
% or less.

In addition, wax,
Adhesive resins such as polyolefins, ethylene-vinyl acetate copolymers, polyurethanes, and rubbers are used.

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

In this apparatus, the toner particle size (weight average) is preferably about 50 μm or less in order to obtain a more preferable image.

The weight average particle size (hereinafter referred to as average particle size) is a value measured with a Coulter Counter (manufactured by Coulter Co., Ltd.).

In addition, the specific resistance of particles is determined by placing the particles in a container with a cross-sectional area of 0.50 d, tapping them, and then applying IK! on the packed particles. A load of 7/ffl is applied to make the thickness about 1 screen, and tO ~ 10 V/c! between the load and the bottom surface @i.
It is determined from the current value that flows when an electric field of n is generated.

As the carrier, basically those listed as the Ip constituent materials of the toner are used.

The carrier particles are mainly composed of magnetic particles and resin, and in order to improve resolution and p'P development, they are preferably spherical and have an average particle diameter of 5011 m J:
, below I, particularly preferably 5 tim or more and 30 μm below the edge.

Also, due to the bias voltage, charges are generated, causing carriers to adhere to the surface of the stool-carved body, or to form a latent image. The resistivity of the carrier is 10Ωα to prevent the load from disappearing.
The insulating material is preferably 100 min or more, more preferably 1O94 or more.

Such a carrier is produced by coating the surface of a magnetic material with a resin, or by dispersing and containing fine particles of a magnetic material in a resin, and sorting the obtained particles by a known method according to particle size.

Furthermore, when the carrier is to be made into a spherical shape, it is carried out as follows.

■Resin-coated carrier: Select spherical magnetic particles.

■ Magnetic Powder Dispersion Carrier After forming the dispersed resin, perform spheroidizing treatment using hot air or hot water, or directly form spherical dispersed resin by spray drying.

Next, the developing method will be explained.

In the present invention, it is desirable to use a non-contact development method in which the developer layer on the sleeve 42 does not rub against the surface of the image forming body for at least the second and subsequent development. In the non-contact developing method, when there is no developing bias between the image forming body 1 and the sleeve 42, the thickness of the developer layer in the developing area is smaller than the gap between the image forming body 1 and the sleeve 42. It is set so that In this case, the amplitude of the AC component of the developing bias applied to the sleeve 42 is vAo (v), and the frequency is r
(H2), the distance between the image forming body 1 and the sleeve 42 is d
(11m+), development with a -component developer is 0.2≦vAc//(d-f)≦1.6, and development with a two-component developer is 0.2≦VAc/(d-f) ( (VAC/d)-1500)/f≦1.0.

The above desirable conditions were determined for the following reasons. The present inventor conducted an experiment in which another toner image was superimposed on an image forming member 1 on which a toner image had been formed by non-contact development while changing conditions. FIG. 3 shows the results using a one-component developer. The diagram shows the frequency of the AC component on the horizontal axis and the amplitude (half between peaks) of the electric field (potential difference divided by distance) on the vertical axis. The area where uneven development is likely to occur is shown in ■, and the AC component is shown in the figure. (■) is an area where the toner image already formed on the image forming body is likely to be destroyed, and (C%) is an area where the toner image already formed on the image forming body is likely to be destroyed. These areas are difficult to develop, and 0 of them is particularly well developed.

Moreover, FIG. 4 shows the results using a two-component developer. The symbols in the figure represent the same meanings as in FIG. As the two-component developer, the preferred conditions described above were used.

As a result, the above-mentioned preferable development conditions were obtained, but in the case of a -component developer, 0.4≦vAc
The toner image will not be destroyed under the condition of /(d-f)≦1.2, and sufficient image density can be obtained under the condition of 0.6≦vAc/cd-f)≦1.0. It will be done. In addition, when using a two-component developer, the toner image will not be destroyed under the condition of 0.5≦■Ac/(d-f) ((VA(7/d)-1500)/f≦1.0. Furthermore, if 0.5≦vAc/(d−f) ((vAc/d) −1s o o )/f≦0.8 is satisfied, sufficient image density can be obtained.

〔Example〕

The present invention will now be explained in more detail with reference to Examples, but the embodiments of the present invention are not limited thereto.

1, 2, 5, and 6 are diagrams for explaining this embodiment. FIG. 5 is a block diagram showing the image forming system of this embodiment, and FIG. 6 is a diagram showing the image forming process. This is a time chart.

Further, Tables 1 and 2 show specific setting conditions necessary to achieve this embodiment.

First, the formation of a multicolor image in this embodiment is performed according to the image forming system shown in FIG. That is, the data obtained by the image data input section (FIG. 5 (a)) in which an image sensor scans the original image is transferred to the image data processing section (FIG. 5 (a)) including a computer.
Image data is created through arithmetic processing in (b)), which is temporarily stored in an image memory (FIG. 5 (c)), which is a magnetic disk. The image data is then taken out during recording and input into the laser optical system IO of the multicolor image forming apparatus of FIG. 1, which is the recording section (FIG. 5(d)).

In the description ν of the multicolor image forming apparatus, first, a scorotron charger 2 uniformly charges an image forming member 1 having a photoconductive photosensitive layer rotating in the direction of the arrow. Next, on the charging surface, a laser optical system IO having the configuration shown in FIG.
Image exposure obtained by modulating n data is performed,
An electrostatic latent image is formed.

This electrostatic latent image is developed by the reversal development method shown in FIG. 7 using the developing device shown in FIG. 2 containing the two-component developer to form a toner image. This image forming process is repeated by rotating the image forming member 1 four times for each color in the order of yellow, magenta, cyan, and black, thereby forming a multicolor toner image in which the toner images of each color are superimposed. After this multicolor toner image is charged by pre-transfer charging number 9 to be easily transferred, it is transferred to a paper feeder @11, a paper feed roll 12, and a timing roll 1.
The image is transferred onto the transfer material P supplied by the transfer roller 3 by a transfer roller having the configuration shown in FIG. 1(b). At this time, a transfer bias having a polarity opposite to that of the toner shown in Table 2 is applied to the transfer roll. Specific image forming conditions and transfer conditions that are highly recommended for the formation of multicolor toner images and roll transfer described above are shown in Table 1 (a), Table 1 (b), and Table 2 below. In the transfer conditions shown in Table 2, 3Wt types, &1, &2, and O3 are used as transfer rolls, and conditions are set for each of them.

Further, the configuration of the transfer roll is such that an elastic layer with a thickness of 1 mm is provided on the outer periphery of a core metal having a diameter of 28w1, and an insulator layer (dielectric layer) with a thickness of 50 um is further provided on the outer periphery.

Table 1 (A) Section I 11 (B) Table 2 The transfer material P to which the multicolor toner image has been transferred is shown in Table 6 below.
According to the timing chart in the figure, for example, the AC charger 6
4, the charge is removed and separated from the transfer roller father. On the other hand, after the transferred image forming body 1 is neutralized by the pre-cleaning static eliminator 7, residual toner is cleaned by the blade base and fur brush area of the cleaning device 8, and the image forming body 1 is prepared for the next image formation.

FIG. 6 shows the operation timings of charging, image exposure, development, transfer, and cleaning as the image forming body 1 rotates in the multicolor image forming process described above. In the same figure,
The transfer material P supplied from the paper feeder [11 is transferred t,=0
Two seconds ago, a positive charge is applied by the charger B, and the sheet is electrostatically attracted to the transfer roller and conveyed to the transfer section by the transfer roller. At the time of transfer, since a selenium photoreceptor is used as the image forming body 1 and a reversal development method is used, the toner is of positive polarity, so a negative transfer bias is applied to the transfer roller father.

Then, after the transfer, the negative transfer bias is released t! =
After 0.1 seconds, the charge on the transfer material P is removed by a negative DC charger 64, preferably an AC charger 64, and the transfer material P is separated from the transfer roller. This separated transfer material P is conveyed to the fixing device 6 and is heated and fixed by a heat roll.

As a result of the above, the size of the multicolor image forming apparatus according to this embodiment can be made smaller than that of the conventional apparatus by the size of the conveyance path for the transfer material P.

As a result of image formation, a multicolor toner image is transferred to the transfer material P in both cases.
It was transferred well and no separation defects occurred.

〔Effect of the invention〕

As explained above, the present invention uses a roller or a belt-like member that supports the transfer material and contacts the image forming member as a means for transferring the multicolor toner image formed on the image forming member. Since the transfer material is charged with the same polarity as the charge of the toner to be transferred before it comes into contact with the transfer means, the conveyance path can be easily bent, and the image forming apparatus can be miniaturized.

[Brief explanation of drawings]

FIG. 1(a) is a cross-sectional view of the main parts of the multicolor image forming apparatus of the present invention;
FIG. 1(b) is an enlarged sectional view of the transfer section, FIG. 2 is a sectional view of a developing device suitable for the present invention, and FIG. 3 is a graph showing preferable developing conditions when using a one-component developer in the present invention. FIG. 4 is a graph showing preferred development conditions when using a two-component developer, FIG. 5 is a block diagram showing an image forming system of the embodiment, and FIG. 6 is a timing chart of the image forming process of the embodiment. Also, Fig. 7 is a flowchart showing a general multicolor image forming process, and Fig. 8 (a) is a sectional view of main parts of a conventional multicolor image forming apparatus. FIG. 9 is a sectional view of a main part of another example of a conventional multicolor image forming apparatus. DESCRIPTION OF SYMBOLS 1... Image forming body, 2... Sufrotron charger 3... Exposure lamp, 6... Fixing device 7...
Pre-cleaning static eliminator, 8...Cleaning device, 81...Blade, hidden/
...Faplash, 9...Pre-transfer charger, 10.
... Laser optical system, 11... Paper feeding device, 12...
Paper feed roller, 13... Timing roller, 14...
Bias power supply, ga...laser oscillator, n...rotating polygon mirror, ku...fθ lens, 41...magnetic roll, 42...sleeve, 43...head-standing regulation blade, tsuki...・Developer reservoir, 45... Stirring screw, Tochi... Toner supply roller, 47... Toner hopper,
A, B, C, D...each developing device, L...image exposure,
Seki...Transfer roller, 51...Lever shaft,
52... Transfer roller shaft, Group... Roller core,
Masu...eccentric cam, group...lever, ah...
・Spring, enclosure... Eccentric camshaft, 57... Blade, field, 64... Charger. Applicant: Konishiroku Photo Industry Co., Ltd. Figure 1 (a) SuJ '2 Figure 2 (a) (b) (c)
(d) Figure 8 (b) Figure 8)

Claims (6)

[Claims] (1) (a) a step of forming a multicolor toner image on an image forming body; (b) a step of imparting an electric charge to a transfer material to electrostatically hold the transfer material in a transfer means and transporting the transfer material; ( A multicolor image forming method comprising the steps of: c) transferring the multicolor toner image on the image forming body to the transfer material; and (d) separating the transfer material from the transfer means. (2) The transfer means is a transfer roller, and after transferring the multicolor toner image on the image forming body to the transfer material, the transfer material is destaticized and separated from the transfer roller. Multicolor image forming method described in Section 1. (3) The multicolor image forming method according to claim 1 or 2, wherein the multicolor toner image is formed by overlapping each color toner image on the image forming body. (4) an image forming body, a means for forming a latent image on the image forming body, at least one developing means, a means for imparting an electric charge to a transfer material, and transferring from the image forming body while conveying the transfer material; A multicolor image forming apparatus comprising a means for transferring a toner image onto a material and a means for removing static from the transfer material. (5) The multicolor image forming apparatus according to claim 4, wherein the transfer means is a transfer roller, and the transfer roller is provided with a cleaning member that constantly cleans the surface of the transfer roller. (6) The multicolor image forming apparatus according to claim 4, wherein the multicolor toner image is formed by overlapping each color toner image on the image forming member.