JPH0685100B2 - Multicolor image forming device - Google Patents

Description

The present invention relates to an image forming method for forming a multicolor toner image on an image forming body and transferring it to a transfer material to obtain a recorded image, and an image forming method therefor. The apparatus is used in the fields of, for example, electrophotography and electrostatic recording.

[Prior Art] An important technique among the above-mentioned image forming methods is a method of forming a multicolor image.

Conventional Example 1 In order to form a multicolor image by electrophotography, the steps of charging, exposing, developing and transferring are repeated for each color component to superimpose the toner images of the respective colors on the recording paper. Ie blue,
An electrostatic latent image is formed according to color component data such as green and red,
Develop with a toner such as yellow, magenta, cyan, or black, transfer it to a transfer material, and perform the above steps for each color component, for example, a multicolor image on a transfer material such as recording paper or other overhead projector film. To form.

Problems of Conventional Example 1 It is necessary to transfer to a transfer material after each color development is completed, the apparatus becomes large and the image forming time becomes long.

 There are drawbacks such as misalignment due to repeated operation.

Conventional example 2 (improvement of conventional example 1) There is a multicolor image forming method for solving the above-mentioned drawbacks by superposing a plurality of toner images on the same image forming body such as a photoconductor and developing the same, and performing the transfer step only once. .

Problems of Conventional Example 2 There are problems such as disturbing the toner image formed by the former development at the time of the latter development, and mixing the toner from the toner image developed in the former stage with the developer of the latter stage to disturb the color balance. is there.

Conventional Example 3 (Improvement of Conventional Example 2) In the method of Conventional Example 2, a bias having an AC component superimposed is applied to the developing device during the second and subsequent developments to form an electrostatic latent image formed on the image forming body. The present inventors have proposed a method of forming a multicolor image by adopting a method of flying toner. In this method, the developer layer does not rub the toner image formed up to the previous stage, so that the image is not disturbed.

The principle of this multicolor image forming apparatus will be described below with reference to the flowchart of FIG. FIG. 7 shows changes in the surface potential of the image forming body, and takes the case where the charging polarity is positive as an example. pH is the exposed area of the image forming body, DA is the non-exposed area of the image forming body, and DUP is the amount of increase in potential caused by the electrostatic toner T ₁ adhering to the exposed area pH during the first development.

The image forming body is uniformly charged by the scorotron charger, and has a constant positive surface potential E as indicated by. Next, a first image exposure is performed using a laser, a cathode ray tube, an LED, etc. as an exposure source, and the potential of the exposed portion PH decreases according to the amount of light as shown in. 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 portion is applied. As a result, as shown in, the positively charged toner T ₁ has a relatively low potential
To form a _first toner image T ₁ . In the area where the toner image T ₁ is formed, the potential increases by DUP due to the adhesion of the positively charged toner T _1, but it does not become the same potential as the unexposed portion DA. Next, the surface of the image forming body on which the first toner image is formed is charged a second time by the charger, and as a result, a uniform surface potential E is obtained regardless of the presence or absence of the toner T ₁ . This is shown in. A second image exposure is performed on the surface of the image forming body to form an electrostatic latent image (), and the positively charged toner image T ₂ of a color different from that of the toner T ₁ is developed in the same manner as described above. A second toner image is obtained. This is shown in. By performing the above process a plurality of times, a multicolor toner image is obtained on the photoconductor. A multicolor recording image is obtained by transferring this onto recording paper and further fixing it by heating or pressurizing it. In this case, the toner and charges remaining on the surface of the image forming body are cleaned and used for the next multicolor image formation.

In the method described in FIG. 7, at least the developing step is performed so that the developer layer does not contact the surface of the image forming body.

In the multicolor image forming method, the second and subsequent charging can be omitted. The exposure sources used for each image exposure may be the same or different.

In the multicolor image forming method, for example, four color toners of yellow, magenta, cyan and black are often overlaid on the image forming body for the following reason. According to the principle of the subtractive color method, a black image should be obtained by superimposing the three primary colors of yellow, magenta, and cyan, but the toner for practical three primary colors has an ideal absorption wavelength range. Not only is it difficult to reproduce the clear black color required for characters and lines due to the positional deviation of the toner images of the three primary colors, but it is also difficult to reproduce the clear black required for characters and lines. It tends to run short. Therefore, as described above, a multicolor image is formed by the four colors obtained by adding black to the three primary colors.

In the electrophotographic method, laser light such as gas or semiconductor, LED, CRT, liquid crystal or the like is used as an image exposure means.

As a method of forming a latent image for forming a multicolor image, in addition to the electrophotographic method, a method of directly injecting charges onto an image forming body by a multi-needle electrode or the like to form an electrostatic latent image, or a magnetic A method of forming a magnetic latent image with a head can be used.

FIG. 8 shows an example of an apparatus that realizes this method. In this device, a multicolor image is formed as follows. The surface of the photoconductor 1 is uniformly charged by the scorotron band electrode 2.
Then, the image forming body 1 is irradiated with the image exposure L from the laser optical system 10. In this way, an electrostatic latent image is formed.
This electrostatic latent image is developed by the developing device A containing the yellow toner. Image forming body 1 on which a toner image is formed
Is again uniformly charged by the scorotron band electrode 2,
Receive image exposure L. The formed electrostatic latent image is developed by the developing device B 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. Thereafter, in the same manner, the cyan toner and the black toner are overlaid and developed to form a four-color toner image on the image forming body 1. The four-color toner image is charged by the belt electrode 9, while the charge on the image forming body 1 is erased by the exposure lamp 3 and then transferred to the transfer material P by the transfer pole 4. The transfer material P is separated from the image forming body 1 by the separating electrode 5, and is 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 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 contact the image forming body 1 and scrape off the transfer residual toner.
After that, the cleaning blade 81 separates from the image forming body 1, and the fur brush 82 separates from the image forming body 1 after a short delay. The fur brush 82 functions to remove the toner remaining on the image forming body 1 when the cleaning blade 81 separates from the image forming body 1.

The laser optical system 10 is shown in FIG. In the figure, 21 is a semiconductor laser oscillator, 22 is a rotary polygon mirror, and 23 is a θ lens.

In this multicolor image forming apparatus, each color of the image forming body 1 is developed one by one, but application of a large AC voltage that contributes to the development is stopped to the developing apparatus which is not used. During image formation, each electrode other than the strip electrode 2, paper feed, paper transport,
None of the cleaning devices 8 act on the image forming body 1.

Problems of Conventional Example 3 In the above conventional method, the corona transfer method is used as the transfer method.

This has the advantages that the mechanism is simple, the image forming body 1 is not damaged, and the toner attached to the transfer means does not stain the back surface of the transfer material P. However, the transfer material P and the image forming body are 1 is incompletely adhered, transfer unevenness is likely to occur, transfer characteristics are likely to change due to the influence of the surrounding environment such as temperature and humidity, and when the toner image during image formation passes the transfer position,
The toner adheres to the electrode 4 and the transfer efficiency is reduced. In a place where a plurality of types of toner are overlapped at the same position, it is difficult for the lower toner to be transferred. The position of the toner is displaced during the transfer, or the toner is scattered, There were problems such as disturbing the image, and these were unsolved.

Conventional Example 4 Instead of the transfer pole 4 in the multicolor image forming apparatus of FIG.
There is a method of transferring a toner image by transporting a transfer material P to a pressure contact position using a transfer unit that is pressed against the rotor or the belt image forming body 1. A transfer bias may be applied to these rollers or belts, or electric charges may be injected by corona discharge or the like to form an electric field at the transfer position to increase the transfer efficiency.

[Problems to be solved by the invention]

By using such transfer means, the problems in the case of using the corona discharge are improved, but, for example, a toner image that has already been formed adheres to the transfer means, and it stains the back surface of the transfer material P. Due to the difference in the linear velocity between the forming body 1 and the transfer means, the transfer material P may be wrinkled or the transferred image may be displaced. The transfer bias and the charge may be leaked from the scratches of the image forming body 1 to further increase the scratches. At the same time, there are some important problems to be solved such as lowering transfer efficiency.

[Means for solving problems]

(Object of the Invention) The present invention solves the above problems, has a good transfer state, does not stain the transfer material, and as a result, can always obtain a high quality recorded image. And its device.

(Structure of the Invention) The present invention relates to an image forming body having a photoconductive photosensitive layer, a charging unit for charging, an exposing unit for forming a latent image, and a plurality of developing units for forming a toner image by the latent image. Means and a transfer means capable of contacting and separating and rotating the multicolor toner image on the image forming body onto a transfer material, and charging, exposing on the image forming body by one rotation of the image forming body, By repeating one step consisting of developing for each rotation of the image forming body,
A multicolor image forming apparatus for forming a multicolor toner image by superimposing toner images on the image forming body, and transferring the multicolor toner images to a transfer material at a time, which is one step before the final step. The transfer unit does not contact the image forming body until the toner image passes the transfer position, and the final step is finished after the toner image one step before the final step has passed the transfer position. By the time the tip of the multicolor toner image reaches the transfer position,
The transfer means starts contact and rotation with the image forming body,
After the transfer means starts contacting and rotating with the image forming body, the transfer material is conveyed between the transfer means and the image forming body by the rotation of the sheet feeding means and the transfer means and the image forming body. The above object is achieved by a multicolor image forming apparatus including control means for controlling such that the multicolor toner images are collectively transferred from the image forming body to the transfer material.

[Work]

FIG. 1A shows an example of a multicolor image forming apparatus according to the present invention, and the same contents as those in FIG. 8 are designated by the same reference numerals.

The portion different from the conventional multicolor image forming apparatus of FIG. 8 is a transfer section, and the multicolor image forming apparatus of the present invention operates as follows.

(1) The image forming body 1 having a photoconductive photosensitive layer is a strip electrode 2
As a result, the surface is uniformly charged.

(2) The image exposure L from the laser optical system 10 is the image forming body 1.
It is illuminated above, resulting in the formation of an electrostatic latent image.

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

(4) The image forming body 1 on which the toner image is formed is subjected to the image exposure L after being uniformly charged by the strip electrode 2 again after the charge eliminating lamp 3 emits light to eliminate the charge.

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

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

(7) The four-color toner image is charged by the belt electrode 9, and the charge on the image forming body is erased by the charge eliminating lamp 3.

(8) On the other hand, the transfer roller 50 is located away from the image forming body 1 until the three color toner images pass through the transfer position.

(9) After that, a toner image of the fourth color is formed, and the leading end of the toner image comes into contact with the image forming body before reaching the transfer position. Here, the contact of the transfer roll 50 with the image forming body 1 is preferably t = 0.01 seconds to 1.0 seconds before the start of transfer.

(10) The transfer material P is conveyed between the image forming body 1 and the transfer roller 50 from the paper feeding device 11 by the paper feeding rotor 12 and the timing roller 13.

(11) A bias voltage is applied to the transfer roller 50.

(12) The transfer material P is conveyed as the image forming body 1 and the transfer roller 50 rotate, and the transfer is completed. Eccentric cam 54 here
The timing of contact of the transfer roll 50 with the image forming body 1 by the control unit 14 is controlled by the control unit 14 in relation to the timing roller 13 and the transfer bias.

(13) The transfer material P is separated from the image forming body 1 by a separation claw or the like and fixed by the fixing device 6.

(14) 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 has a cleaning blade 81 and a fur brush 82. These are not in contact with the image forming body 1 during image formation. When a multicolor image is formed on the photoconductor 1, the toner remains in contact with the image forming body 1 and scrapes the transfer residual toner.
Is separated from the image forming body 1, and the fur brush 82 is separated from the image forming body 1 with a slight delay. The fur brush 82 functions to remove the toner remaining on the image forming body 1 when the cleaning blade 81 separates from the image forming body 1.

(15) At the same time, the transfer roller 50 separates from the image forming body 1.

In the above process, since the transfer roller 50 comes into contact with the image forming body 1 after the toner image of the third color (generally, one color before the completion of the multicolor toner image) has passed the transfer position, the toner is transferred to the transfer roller 50. There is an effect that it is possible to prevent the back surface of the transfer material P from being contaminated due to the adherence of. It is desirable that the bias applied to the transfer roller 50 for the transfer is not applied until just before the transfer material P reaches the transfer position, and further, a bias having the same polarity as the charge of the toner is applied so that the toner does not adhere to the transfer material P during the non-transfer. It is effective to do.

A preferable condition of the transfer roller 50 is that the transfer roller 50 is in close contact with the image forming body 1 at a constant pressure.

 Toner easily separates from the surface.

A uniform and sufficiently large electric field can be easily generated in the transfer part.

And so on. To satisfy this, (a) a strong hollow cylinder made of aluminum or similar conductive metal is used as the axis, and (b) a silicon rubber layer with a thickness of 0.5-5 mm as an elastic layer around it. Place conductive rubber such as polyurethane rubber or butyl rubber.

Due to the above, the resistivity of the conductive rubber is 10 ¹⁰ Ωcm or less,
Further, it is desirable that it is 10 ⁷ Ωcm or less. Altitude is 20
It is desirable to be -80 degrees JIS standard (K6301 ・ A type).
Further, in order to prevent the applied bias voltage from leaking from scratches of the image forming body 1 to spread the scratches or prevent the sufficient electric field from being generated in the transfer portion, (c) A dielectric layer having a thickness of about 10 to 100 μm is placed thereon.

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

Further, in order to remove the toner adhering to the surface of the transfer roller 50, it is necessary to clean the surface of the roller 50 with a blade or a fur brush. These blades and fur brushes may be in contact with the surface of the transfer roller 50 at all times. In addition, a belt-shaped transfer means can be used as the transfer means.

The bias voltage applied to the roller 50 at the time of transfer depends on various conditions, but is usually set within a range of ± 0.5 to 4 KV. Further, if the pressure when the transfer roller 50 comes into contact with the image forming body 1 is set in the range of 0.1 to 1.5 kg / cm ² , sufficient adhesion can be obtained.

An enlarged cross-sectional view of the transfer portion as described above is shown in FIG. Here, the state in contact with the image forming body 1 is represented by a solid line,
The non-contact state is shown by a dotted line.

A lever 55 is arranged on the shaft 51 and supports the shaft 52. Further, the lever 55 receives a downward force by the spring 56. Axis 52
A tubular roller core 53 is rotatably arranged on the upper side by a ball bearing. The transfer roller 50 is a roller core 53.
It is provided above. The roller core 53 is supported by the eccentric cam 54. The eccentric cam 54 is eccentrically rotated by rotating its shaft 58 by a motor (not shown). Therefore, the rotation of the eccentric cam 54 changes the distance between the roller 50 and the image forming body 1. Further, the surface of the transfer roller 50 is cleaned by the blade 57. The blade 57 is always in contact with the surface of the roller 50.

Since the transfer roller 50 is rotatable, when it comes into contact with the rotating image forming body 1, it is driven to rotate.

Here, the features of the present invention are as follows. That is, the transfer roller 50 forms an image by the action of the eccentric cam 54 or the like after the toner image of one color before the completion of the multicolor toner image has passed the transfer position, and preferably immediately before the transfer of the multicolor toner image. Since it is brought into contact with the body 1, the transfer roller 50 does not damage the toner image and is not contaminated with toner. Therefore, the back surface of the transfer material is prevented from being contaminated.

Further, there is an effect such that the transfer material fed in time with the transfer is smoothly introduced into the transfer region by the transfer roller 50 which is rotating first.

Next, preferable developing conditions in the present invention will be described.

The four developing devices used in the multicolor image forming apparatus of FIG. 1 (a) may have the same or similar structure. As an example, a sectional view of the first developing device A is shown in FIG. The developer De is conveyed in the direction of the arrow by the rotation of the sleeve 42 and the magnetic roll 41 having 12 poles. The developer De becomes a developer layer having a constant layer thickness by the spike regulation blade 43 during conveyance. A stirring screw 45 is provided in the developer reservoir 44 in order to sufficiently stir the developer De. When the developer De in the developer reservoir 44 is consumed, the toner supply roller 46 rotates and the toner T is replenished from the toner hopper 47. A power source 48 for applying a developing bias is connected to the sleeve 42. In addition, sleeve 42, magnetic roll 41, stirring screw 45
Is driven by a motor 49 integrated with the developing device.

On the other hand, as the developer, there are a two-component developer mainly composed of a non-magnetic toner and a magnetic carrier, and a one-component developer composed only of a magnetic toner, and either one may be used in the present invention. In particular, a two-component developer requires management of the amount of toner with respect to the carrier, but since it is not necessary to add a large amount of a black magnetic material whose toner charge control is ready to the toner, it is possible to obtain a color toner with no color stain. , And so on.

Preferred constitutional examples of the above-mentioned two-component developer will be given.

Toner Thermoplastic resin (binder) 80-90wt% Example: polystyrene, styrene acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene vinyl acetate copolymer, etc., or a mixture of the above pigments (coloring Agent) 0-15wt% Example: Black: Carbon black Yellow: Benzidine derivative Magenta: Rhodamine B lake, Carmine 6B, etc. Cyan: Copper phthalocyanine, sulfonamide dielectric dye, etc. Charge control agent 0-5wt% Plus toner: Nigrosine electron donor Dyes, alkoxylated amines, alkylamides, chelates, pigments, 4
Mineral toner, etc. Minus toner: electron-accepting organic complex, chlorinated paraffin, chlorinated polyester, excess acid group polyester,
Chlorinated copper phthalocyanine, etc. Fluidizer Example: Colloidal silica, hydrophobic silica, silicon varnish, metal soap, nonionic surfactant, etc. Cleaning agent (prevents toner filming on the image forming body 1) Example: fatty acid metal Salt, silicon oxide having organic groups on the surface,
Fluorine-based surfactants and other fillers (improving image surface gloss and reducing raw material costs) Examples: calcium carbonate, clay, talc, pigments, etc. In addition to these materials, to prevent fogging and toner scattering on the image surface, Magnetic powder may be included. As such a magnetic powder, triiron tetraoxide having a particle diameter of 0.1 to 1 mm, r-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder or the like is used, and the content thereof is 5 to 70 wt%. Resistance of the toner on the type and content of the magnetic powder is greatly changed, but 10 ¹⁰
In order to obtain a sufficient resistance of Ωcm or more, preferably 10 ¹² Ωcm or more, it is desirable that the amount of the magnetic substance be 55 wt% or less, and in order to keep a clear color, it is 30 wt% or less.

Incidentally, as the resin suitable for the pressure fixing toner which is plastically deformed and fixed on the paper by a force of about 20 kg / cm, an adhesive resin such as wax, polyolefins, ethylene acetic acid, vinyl copolymer, polyurethane, rubber, etc. Used.

A toner can be produced by a conventionally known production method using the above materials.

In this apparatus, in order to obtain a more preferable image, the toner particle size (weight average) is preferably about 50 μm or less. Furthermore, to prevent toner scattering and improve transportability,
The range of 1 to 30 μm is preferable.

The weight average particle diameter is a value measured by a Coulter counter (manufactured by Coulter). In addition, the specific resistance of the particles is determined by placing the particles in a container having a cross-sectional area of 0.50 cm ² and tapping them, and applying a load of 1 kg / cm ³ on the packed particles to a thickness of about 1 mm, and the load and the bottom surface. 10 ² to 10 ⁵ V / c between electrodes
It can be calculated from the value of the current that flows when an electric field of m is generated.

Carrier Basically, the materials listed as the constituent materials of the toner are used.

The carrier particles are composed mainly of magnetic particles and a resin, and are preferably spherical in order to improve resolution and gradation reproducibility, and have a weight average particle diameter of 50 μm or less, particularly preferably 5 μm or more and 30 μm or less. Are preferred.

Further, in order to prevent the charge from being injected by the bias voltage to adhere to the surface of the image forming body 1 and the charge forming the latent image to disappear, the resistivity of the carrier is 10 ¹⁰ Ω.
cm or more, preferably 10 ¹² Ωcm or more, more preferably 10
Insulating material of ¹⁴ Ωcm or more is preferable.

Such a carrier is prepared by coating the surface of a magnetic material with a resin or by dispersing magnetic particles in a resin and selecting the obtained particles by a known particle size selecting means.

If the carrier is made spherical, the procedure is as follows.

Resin-coated carrier: Select spherical magnetic particles.

Magnetic powder dispersion carrier: Spherical treatment with hot air or hot water is performed after the dispersion resin is formed, or a spherical dispersion resin is directly formed by a spray dry method.

Next, the developing method will be described.

In the present invention, it is desirable to employ a non-contact developing method in which the developer layer on the sleeve 42 does not rub the surface of the image forming body 1 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 developer layer thickness in the developing area is smaller than the gap between the image forming body 1 and the sleeve 42. Is set. In this case, the amplitude of the AC component of the developing bias applied to the sleeve 42 is V _AC (V), and the frequency is f (H
z), when the distance between the image forming body 1 and the sleeve is d (mm), development with a one-component developer is 0.2≤V _AC /(df)≤1.6 Development with a two-component developer is 0.2≤V _{AC / (d · f) {} ( it is desirable to carry out under the condition that V _AC /d)-1500}/f≦1.0.

The above desirable conditions were obtained for the following reasons. The present inventor conducted an experiment for superimposing another toner image by non-contact development on the image forming body 1 on which the toner image is formed, while changing the conditions. FIG. 3 shows the results using a one-component developer. In the figure, the horizontal axis is the frequency of the AC component, and the vertical axis is the amplitude of the electric field (potential difference divided by distance) (half the peak), where is the area where uneven development is likely to occur, and AC is the AC component. Is an area where the effect of is not sufficient, is an area where destruction of the toner image already formed on the image forming body is likely to occur,
And are areas that are sufficiently developed and are less likely to cause destruction of the toner image that has already been formed, and those areas are particularly well developed.

Further, FIG. 4 shows the result of using the two-component developer. The symbols in the figure have the same meanings as in FIG. As the two-component developer, the one under the preferable conditions described above was used.

As a result of the above, the preferable developing conditions were obtained, but in the case of a one-component developer, the toner image is not destroyed under the condition of 0.4 ≦ V _AC /(d·f)≦1.2. None, and further, if 0.6 ≦ V _AC /(d·f)≦1.0 is satisfied, a sufficient image density can be obtained. When using a two-component developer, the toner image will not be destroyed under the condition of 0.5 ≦ V _AC / (d · f) {(V _AC /d)−1500}/f≦1.0. If 0.5 ≦ V _AC / (d · f) {(V _AC /d)−1500}/f≦0.8 is satisfied, a sufficient image density can be obtained.

〔Example〕

Hereinafter, the present invention will be specifically described with reference to examples, but the embodiments of the present invention are not limited thereto.

1, FIG. 2, FIG. 5, FIG. 6, and FIG. 9 are diagrams for explaining the present embodiment, FIG. 5 is a block diagram showing the image forming system of the present embodiment, and FIG. 6 is a timing chart of the image forming process of the present embodiment. Tables 1 to 4 show specific setting conditions required in this embodiment.

First, the formation of the multicolor image of this embodiment is performed according to the image forming system shown in FIG. That is, the data obtained by the image data input unit (FIG. 5 (a)) in which the image sensor scans the original image, and the image data processed by the image data processing unit (FIG. 5 (b)) equipped with a computer are processed. Is created and is once stored in the image memory (FIG. 5C) which is a magnetic desk. Next, the image memory is taken out at the time of recording and is input to the recording unit (FIG. 5 (d)), which is the multicolor image forming apparatus of FIG. 1 (a).

In the recording by the multicolor image forming apparatus, first, a scorotron charger 2 applies a uniform charge to an image forming body 1 having a photoconductive photosensitive layer that rotates in the arrow direction. Next, the charged surface is subjected to image exposure L obtained by modulating the laser device having the structure shown in FIG. 9 with the image data taken out from the image memory (FIG. 4C). , An electrostatic latent image is formed.

This electrostatic latent image is developed by the reversal development method by the developing device of FIG. 2 containing the two-component developer to form a toner image. The image forming process is repeated by rotating the image forming body 1 four times for each color in the order of yellow, magenta, cyan, and black to form a multicolor toner image in which the toner images of the respective colors are superposed. This multicolor toner image is charged by the pre-transfer charger 9 to facilitate transfer, and as shown in Table 4 below, the transfer roll 50 is brought into contact with the image forming body 1 and rotated before the start of transfer, The transfer material P supplied from the paper supply device 11 through the paper supply roller 12 and the timing roller 13 at the same timing as the image formation is transferred by the transfer roll 50 having the structure shown in FIG. Transfer is applied by applying a transfer bias in the range of −3 KV.

Specific image forming conditions, developers and developing conditions, and transfer conditions required for the formation and roll transfer of the multicolor toner image described above are shown in Tables 1 to 4 below.

Three kinds of transfer rolls 50, No. 1, No. 2 and No. 3, are prepared, and the conditions are set for each transfer roll in Table 4 above.

The structure of the transfer roll 50 is as follows, for example.
That is, a 1 mm thick elastic layer is provided on the outer circumference of a 28 mm diameter cored bar, and an insulating layer (dielectric layer) of 50 μm is further provided on the outer circumference thereof.

The transfer material P on which the multicolor toner image is transferred is a transfer roll 50.
And is fixed by heating by the fixing device 6. On the other hand, the image forming body 1 after transfer is destaticized by the pre-cleaning static eliminator 7, and then the residual toner is cleaned by the blade 81 and the fur brush 82 of the cleaning device 8 to prepare for the next image formation. FIG. 6 shows the operation timings of charging, image exposure L, development, transfer, and cleaning accompanying the rotation of the image forming body 1 in the above-described multicolor image forming process. The horizontal axis of FIG. 6 represents the number of revolutions of the image forming body 1 and the elapsed time second, and the vertical axis represents each step for image formation. Also, T in the figure
Is the time when the leading edge of the transfer material P comes into contact with the transfer roll 50 and the image forming body 1, which almost coincides with the start of transfer, and T ′ is the time when the transfer roll 50 and the image forming body 1 are in contact with each other. Is the time difference between the two. By the above image forming process, there was no transfer deviation and the like, and an extremely clear copy of a multicolor image was obtained.

〔The invention's effect〕

As described above, according to the present invention, as a means for transferring a multicolor toner image formed on an image forming body, an elastic member and an insulating member (dielectric body) are provided on the surface which is brought into contact with the image forming body while supporting the transfer material. Since the transfer means is in contact with the image forming body before transfer by using a roller or a belt-like member having a roller, the toner on the image forming body does not adhere to the transfer means and the back surface of the transfer material is soiled. Never.

The difference in linear velocity between the image forming body and the transfer means does not cause wrinkles or shifts in the image on the transfer material.

Bias and charges for transfer do not leak from scratches on the image forming body.

Since the toner image is transferred by adding a physical action and an electrical action, the transfer efficiency is high and a high quality recorded image can be obtained.

Since the transfer material is introduced after the image forming body and the transfer means come into contact with each other, the transfer means holds the transfer material and transfers the multicolor toner image to the transfer material all at once. As a result, the transfer timing of the transfer material can be easily adjusted, and the position of the transfer material held by the transfer means does not shift due to the contact / separation operation of the transfer means.

[Brief description of drawings]

FIG. 1 (a) is a sectional view showing a multicolor image forming apparatus according to the present invention, FIG. 1 (b) is an enlarged sectional view of a transfer portion, and FIG.
FIG. 3 is a cross-sectional view of the developing device used in the apparatus shown in FIG. 3, FIG. 3 is a graph showing conditions when developing with a one-component developer, and FIG. 4 is a graph showing development conditions with a two-component developer. FIG. 5 is a block diagram showing the image forming system, and FIG. 6 is a timing chart of the image forming process. Further, FIG. 7 is an image forming flowchart as a conventional technique, FIG. 8 is a sectional view of a multicolor image forming apparatus as a conventional technique, and FIG. 9 is a sectional view of a laser device. 1 ... Image forming member, 2 ... Scorotron charger, 3 ... Exposure lamp, 6 ... Fixing device, 7 ... Pre-cleaning static eliminator, 8 ... Cleaning device, 81 ... Blade, 82 ... Fabrush, 9-pre-transfer charger, 10-laser device, 11-paper feeding device, 12-paper feeding roller, 13-timing roller, 14-timing control device, 21-laser oscillator, 22 --- Rotating polygon mirror, 23 …… θ lens, A, B, C, D …… Developer, P …… Transfer material, 41 …… Magnetic roll, 42 …… Sleeve, 43 …… Brushing control blade, 44 …… Developer pool, 45 …… Stirring screw, 46 …… Toner supply roller, 47 …… Toner hopper, 48 …… Development bias, 50 …… Transfer roller, 51 …… Lever shaft, 52 …… Transfer roller shaft, 53 …… Roller core, 54 …… Eccentric cam, 55 …… Lever, 56 …… Spring, 57 …… Blade, 58 …… Eccentric cam shaft

 ─────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-56-25759 (JP, A) JP-A-59-104673 (JP, A) JP-A-60-33575 (JP, A) JP-A-50- 71341 (JP, A) JP-A-50-34543 (JP, A) Actually developed 55-113552 (JP, U)

Claims (1)

[Claims] 1. An image forming body having a photoconductive photosensitive layer, a charging means for charging, an exposing means for forming a latent image, a plurality of developing means for forming a toner image by the latent image, and the image. Since a multi-color toner image on a formed body is transferred to a transfer material, the transfer means can be moved in and out and rotated, and charging, exposure, and development are performed on the image formed body by one rotation of the image formed body. By repeating the above-described one step for each rotation of the image forming body, a toner image is superimposed on the image forming body to form a multicolor toner image, and the multicolor toner images are collectively used as a transfer material. In a multi-color image forming apparatus for transferring, the transfer unit does not contact the image forming body until the toner image before the final step passes through the transfer position. After the toner image has passed the transfer position, the final process is finished. By the time the leading edge of the multicolor toner image reaches the transfer position, the transfer means starts contacting and rotating with the image forming body, and after the transfer means starts contacting and rotating with the image forming body, paper feeding is performed. The transfer material is conveyed between the transfer means and the image forming body by the rotation of the means, the transfer means and the image forming body, and the multi-color toner image is collectively transferred from the image forming body to the transfer material. A multicolor image forming apparatus comprising a control unit for controlling transfer.