JPH0220882A - Image forming device - Google Patents

Abstract

PURPOSE:To stick transfer material to a belt side after transfer, to stabilize separation and to prevent the transfer material from being crinkled or a transfer image from shifting by bringing the transfer material into contact with an image forming body in almost flat state while said material is electrostatically held on a dielectric belt and transferring a toner image onto the transfer material. CONSTITUTION:A transfer belt 50 is away from the image forming body 1 until a three-color toner image passes by a transfer position. A paper feeding roller 12 and a timing roller 13 carry the transfer material to the transfer belt 50 from a paper feeder 11, and an electrifying means 65 imparts electric charges to the transfer belt 50, which comes into contact with the image forming body 1 in flat state. The rotation of the image forming body 1 and transfer rollers 59 and 60 carry the transfer material to complete transfer. Here, the timing of when an eccentric cam 61 prompts the transfer belt 50 to come into contact with the image forming body 1 is controlled in connection with the timing roller 13 and a transfer bias. Under a satisfactory transfer and a good separation condition, a high quality recorded image free of transfer shift can be obtained constantly and stably without damaging the image forming body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus that forms a multicolor toner image on an image forming member and transfers it to a transfer material to obtain a recorded image.
For example, it is used in fields such as electrophotography and electrostatic recording.

[Background of the invention]

Important technologies in the image forming apparatus mentioned above include:
There are methods for forming multicolor images.

Conventional Example 1 To form a multicolor image by electrophotography, the steps of charging, exposure, development, and transfer are repeated for each color component, and toner images of each color are superimposed on recording paper. i.e. blue,
Forms an electrostatic latent image according to color component data such as green and red,
Develop with yellow, magenta, cyan, or black toner, transfer this to a transfer material, and perform the above steps one color at a time to create a multicolor image on a transfer material such as recording paper or other overhead projector film. Form.

Conventional Example 2 (Improvement of Conventional Example 1) There is a multicolor image forming method that solves the above drawback by superimposing and developing multiple toner images on the same image forming body such as a photoreceptor so that only one transfer step is required. .

Conventional Example 3 (Improvement of Conventional Example 2) In the Conventional Example 2I75 method, a bias with a superimposed alternating current component is applied to the developing device during the second and subsequent development to apply toner to the electrostatic latent image formed on the image forming body. The present inventors have proposed a method of forming a multicolor image by employing a method of flying a color image. 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.

Problems with Conventional Example 3 Also in Conventional Example 3, which solved the problems of Conventional Examples 1 and 2,
As the transfer method, a corona transfer method is used.

This has the following advantages: ■ The mechanism is simple; ■ It does not damage the image forming body L; ■ The toner attached to the transfer means does not stain the back surface of the transfer material P. ■ Image formation The diameter of the drum is large and separation is difficult; ■ The adhesion between the transfer material P and the image forming body L is incomplete, which tends to cause uneven transfer; ■ The transfer characteristics are affected by the surrounding environment such as temperature and humidity. ■ When the toner image passes through the transfer position, the toner adheres to the transfer electrode, reducing transfer efficiency.■ When multiple types of toner overlap at the same position, it is difficult for the lower toner to transfer. ,■ Performing photostatic charge removal before transfer stabilizes the separation, but there are problems such as the toner being misaligned during transfer and the toner scattering, disturbing the image, which have not been resolved yet. .

Conventional Example 4 Instead of the transfer pole in the multicolor image forming apparatus of Conventional Example 3,
A method of transferring a toner image by conveying a transfer material to a pressure contact position using a transfer means in which a roller or a belt is pressed against an image forming body has been disclosed by the present applicant in Japanese Patent Laid-Open Nos. 61-226766 and 61.
This method has been proposed in Japanese Patent Nos. -226767 and 61-226768. In this proposal, the roller part directly hits the image forming body, and an electric field is formed at the transfer position by applying a transfer bias or applying a charge by corona discharge, etc., to increase transfer efficiency. .

[Problem that the invention seeks to solve]

In the present invention, it is necessary to improve the following problems in Conventional Example 4 with respect to a drum-shaped image forming member by improving the transfer means using a belt.

■ Stable separation by keeping the transfer material attached to the belt side even after transfer, and ■ Preventing the transfer material from wrinkling or misaligning the transferred image due to the difference in linear speed between the image forming body and the transfer means. ■ Prevent damage to the image forming body caused by strong pressure contact with the image forming body; ■ Prevent speed unevenness of the image forming body or transfer means when the transfer material P is caught in the image forming body. The present invention solves the above-mentioned problems, and prevents the image from being misaligned when superimposing the image. As a result, it is an object of the present invention to provide an image forming apparatus that can always stably obtain high-quality recorded images.

[Structure of the invention]

The present invention achieves the above object, and includes a rotating drum-shaped image forming member, a means for forming a latent image on the image forming member, and a method for developing the latent image multiple times to form a toner image. means for repeatedly forming a plurality of toner images on the image forming member;
An image forming apparatus comprising a transfer means for electrostatically holding a transfer material on a dielectric belt and contacting an image forming member in a substantially flat state to transfer the toner image onto the transfer material. It provides:

[Effect]

FIGS. 1(a) and 1(b) show an example of a multicolor image forming apparatus based on the present invention, and FIG. 1(b) shows paper conveyance using a belt with the toner transfer surface facing downward. It is meant to be transported,
Identical content is marked with the same asterisk. Paper conveyance as shown in FIG. 1(b) is a preferred form for a printer.

The image forming apparatus according to the present invention operates as follows.

(2) The surface of the image forming body 1 having a photoconductive photosensitive layer is uniformly charged by a charging electrode 2 of a scorotron.

(2) Image-wise exposure from the laser optical system IO is applied onto the image forming body 1, and as a result, an electrostatic latent image is formed.

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

■ The image forming body l on which the toner image has been formed is charged again with the charging electrode 2.
It is uniformly charged and subjected to imagewise exposure.

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

(2) Thereafter, the cyan toner and the black toner are developed in a layered manner in the same manner, and a four-color toner image is formed on the image forming member 1.

(2) The four-color toner image may be charged by the charging electrode 9, or may be omitted. Further, the charges on the image forming body can be erased using the charge eliminating lamp 3, but in the present invention, since separation is stabilized as will be explained later, it is preferable not to perform irradiation with the charge eliminating lamp 3. is preferred.

If this is used, the toner image on the image forming body will scatter,
This is because the quality of the transferred image tends to deteriorate.

(2) On the other hand, the transfer belt 50 remains at a position away from the image forming body 1 until the three-color toner image passes through the transfer position.

(2) The transfer material P is conveyed onto the transfer belt 50 from the paper feeder 11 by the paper feed roller 12 and the timing roller 13. When the transfer material P on the transfer belt 50 is conveyed, a charge is applied to the transfer belt 50 by the charging means 65.

(2) Thereafter, a fourth color toner image is formed, and before the leading edge of the toner image reaches the transfer position, the transfer material P has been conveyed onto the transfer belt 50 in advance.

■ Next, it comes into contact with the image, the forming body. Here, the transfer belt 50
The contact with the image forming member l is preferably carried out at t-0 before the start of transfer.
, 01 seconds to 1.0 seconds.

(2) The transfer material P is conveyed as the image forming body 1 and the transfer roller 50 rotate, and the transfer is completed. Here, the eccentric cam 61 or electromagnetic clutch 62 shown in FIG.
The timing of contact of the transfer belt 50 with the image forming body 1 is controlled by a control means in relation to the timing roller 13 and the transfer bias.

@ The transfer material P is separated from the image forming body 1 by curvature separation or separation using the elasticity of the transfer material P, and is fixed by the fixing device 6.

■ On the other hand, the image forming body l has a removing electrode 7 and a cleaning device 8.
Cleaned by. 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 photoreceptor I, they come into contact with the image forming body 1 and scrape off residual toner after transfer. After that, the cleaning blade 8
1 leaves the image forming body l, and a little later the fur brush 82
is separated from the image forming body 1. The fur brush 82 functions to remove toner remaining on the image forming body l when the cleaning blade 81 is separated from the image forming body l.

(2) At the same time, the transfer belt 50 separates from the image forming body l.

In the above process, the transfer belt 50 transfers the third color (
Generally, the toner image (one color before the completion of a multicolor toner image) comes into contact with the image forming member L after passing through the transfer position, so that the back surface of the transfer material P is prevented from becoming dirty due to toner adhering to the transfer belt 50. It has the effect of preventing It is desirable that the charge applied to the transfer belt 50 for transfer is not applied until just before the transfer material P reaches the transfer position, and furthermore, to prevent toner from adhering to the non-transfer area, the charge should be of the same polarity as the toner charge. Applying a charge is effective.

Preferable conditions for the transfer belt 50 are: (1) It should be in close contact with the image forming body 1 with a constant low 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 requirement, (a) a rubber belt or a similar belt-like member is used as a base, and (b) an elastic layer around it is made of silicone rubber, polyurethane rubber, butyl rubber, etc. with a thickness of about 0.5 to 5 mm. Place the conductive rubber.

The resistivity of the conductive rubber is desirably 10'' Ωcm or less, more preferably 10' Ωcm or less, for the above-mentioned (2).

The hardness is preferably 20 to 80 degrees JIS standard (K6301-A type). In addition, in order to prevent the applied bias voltage from leaking from scratches on the image forming body, widening the scratches, and making it impossible to generate a sufficient electric field in the transfer area, it is necessary to ) 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 20 μm or less.

Further, in order to remove toner adhering to the surface of the transfer belt 50, it is necessary to clean the surface of the belt 50 with an elastic rubber blade, a fur brush, or the like. These blades and fur brushes may be kept in constant contact with the surface of the transfer belt 50.

The charge applied to the belt 50 in the transfer area depends on various conditions, but the surface potential is usually set within the range of ±0.5 to 4 KV. Further, the pressure when the transfer belt 50 comes into contact with the image forming body 1 is 0. O1~1.5kg/cm2
If the contact length is set within the range of 0.5 to 5 cm, sufficient adhesion can be obtained.

As a dielectric belt suitable for such conditions, a special dielectric belt SDB (trade name) made by Yamauchi Rubber Industries Co., Ltd., which is composed of a conductive base and a dielectric layer, is preferably used. The dielectric belt becomes capable of attracting and transporting the transfer paper by applying an external voltage.

When the transfer paper is in close contact with this dielectric belt, it weighs 1 to 2 kg.
It has an adsorption force of /cm2.

The dielectric belt is charged by a charging brush or a corotron. 1.5KV to 2.0KV on the surface of the dielectric belt. OK
It is particularly preferred to provide an applied voltage of V, approximately 90%
After the toner on the image forming body 1 is transferred to the transfer material P with a transfer efficiency of
The above transcription is made.

FIG. 2(a) is an enlarged cross-sectional view of the transfer section as described above.

Shown in (b) and (c). Here, the state in which it is in contact with the image forming member 1 is shown by a solid line, and the state in which it is not in contact is shown by a dotted line.

2(a) and 2(b), the transfer belt 50 is moved to the roller 59.
The transfer belt 50 is rotated by the drive of the roller 60 stretched between the image forming bodies 1 and 60, and the roller 59 moves up and down.
It is designed to be in contact with or separate from. The rotating shaft 53 of the roller 59 is attached to a lever 54 that swings about the axis 52, and the lever 54 is urged by a spring member 56 in a direction in which the transfer belt 50 is moved away.

In FIG. 2(a), an eccentric cam 61 rotated by a motor (not shown) is used to bring the transfer bell 1-50 into contact with or separate from the image forming body l, and the rotation of the eccentric cam 61 resists the tension of the spring member 56. and push up the lever 54 to bring it into contact.

Also, in FIG. 2(b), the solenoid 6 is used instead of the eccentric cam 61.
2, by energizing the solenoid 62, the belt 50
is brought into contact with the image forming body l.

In addition, FIG. 2(C) shows a roller 60 whose axis is fixedly positioned.
．． The belt 50 is stretched between 63 and a tension roller 64 movable by a motor or solenoid that comes into contact with the inner surface of the belt 50. When the tension roller 64 moves to a protruding position, the belt 50
is in contact with the image forming member 1, and is otherwise spaced apart.

Here, the features of the present invention are as follows. That is, after the transfer belt 50 passes the transfer position of the toner image of one color before completing the multicolor toner image, and preferably immediately before the multicolor toner image is transferred, the image is formed by the action of the eccentric cam 61 or the like. Since the transfer belt 50 is brought into contact with the body 1 under low pressure and rotated, (1) the transfer belt 50 will not damage the toner image and will not be contaminated by the toner.

Therefore, the occurrence of stains on the back surface of the transfer material is also avoided.

(2) Furthermore, effects such as the transfer material fed at the same timing as the transfer are smoothly introduced into the transfer area and separated.

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

The four developing devices used in the multicolor image forming apparatus of FIG. 1(a) may be of the same or similar construction. 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 with a constant thickness by the spike control blade 43 made of a magnetic material during transportation. A stirring screw 45 is provided in the developer reservoir 44 to sufficiently stir the developer De. When the developer De in the developer reservoir 44 is consumed, the toner supply roller 46 rotates and toner T is replenished 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 roll 41. Stirring screw 4
5 is 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 toner, and either of them may be used in the present invention. In particular, two-component developers require control of the amount of toner relative to the carrier; however, ■ It is easy to control the charge of the toner. ■ There is no need to include a large amount of black magnetic material in the toner, so it is possible to produce color toner without color turbidity. There are advantages such as being able to

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

Toner■ Thermoplastic resin (binder) 80-9Qwt% Examples: polystyrene, styrene acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin,
Polyethylene, 'ethylene-vinyl acetate copolymer, etc., or a mixture of the above ■ Pigment (coloring agent) l -15wt% Example: Black carbon black Yellow: Benzidine derivative Magenta: Rhodamine h lake, Carmine 6B, etc. Cyan: Copper phthalocyanine, etc.■ Charge control agent 0-5wt% Positive donor: Nigrosine-based electron-donating dye, alkoxylated amine, alkylamide, chelate, pigment, quaternary ammonium salt, etc. Negative toner: Electron-accepting organic complex, chlorinated paraffin, chlorinated Polyester, polyester with excess acid groups, chlorinated steel phthalocyanine, etc. ■ Examples of fluidizing agents: colloidal silica, hydrophobic silica, silicone varnish, metallic soap, nonionic surfactants, etc. ■ Cleaning agents (on the image forming body 1 Prevent toner filming) Examples: fatty acid metal salts, silicic acids with organic groups on the surface,
In addition to these materials such as fluorine-based surfactants, magnetic powder may be included to prevent fogging on the image surface and toner scattering.

As such magnetic powder, triiron tetroxide, r-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder, etc. with a particle size of 0-1-1 mm are used.

Although there are differences depending on the type of magnetic powder, it is desirable to keep the amount of magnetic material at 3 Qwt% or less in order to maintain a clear color.

In addition, resins suitable for pressure fixing toners that are plastically deformed and fixed to paper with a force of about 20 kg/cm include waxes, polyolefins, ethylene acetic acid, vinyl copolymers,
Adhesive resins such as polyurethane and rubber are used.

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

In this apparatus, in order to obtain a more preferable image, it is desirable that the toner particle size (weight average) be about 20 μm or less. Further, in order to prevent toner scattering, improve transportability, and provide high image quality, a thickness in the range of 1 to 5 μm is preferable.

Note that the weight average particle diameter is a value measured with a Coulter Counter (manufactured by Coulter Co., Ltd.). In addition, the specific resistance of the particles is determined by placing the particles in a container with a cross-sectional area of 0.50 cm" and tapping the packed particles, then l kg / 0 m on the packed particles.
The thickness is about 1 mm by applying a load of 3 mm, and an electric field of 10 2 to IQ'V/cm is generated between the load and the bottom electrode, and the value of the current flowing at that time is determined.

Carrier The carrier particles are mainly composed of a magnetic material, 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 less.
A thickness of .mu.m or more and 30 .mu.m or less is preferable.

In addition, in order to prevent charges from being injected by the bias voltage and carriers from adhering to the surface of the image forming body and from dissipating charges that form a latent image, the resistivity of the carrier is set to 101.
An insulating material having an insulation value of 0 Ω·cm or more, preferably 10 12 Ω·cm or more, and more preferably 10'40·cm or more is preferable.

Such a carrier is made by coating the surface of a magnetic material with a resin, or by dispersing and containing fine magnetic particles in a resin, and selecting the resulting particles using a known particle size selection means.

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 dispersed carrier: After dispersing the magnetic material and resin, spherical particles are formed using hot air or hot water, or directly 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 l and the sleeve 42, the thickness of the developer layer in the developing area is smaller than the gap between the image forming body l 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 VAC (V), the frequency is f (H2), and the distance between the image forming body 1 and the sleeve is VAC (V).

When d (mm), development with -component developer is 0
．． 2≦VAC/ (d-r)≦1.6 Development with two-component developer is under the condition of 0.2≦VAC/ (ct, -r) ((VAc/d) -1500) /f≦1.0. It is preferable to do it below.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the embodiments of the present invention are not limited thereto.

1, 2, 3, 4, and 5 are diagrams for explaining this embodiment. FIG. 4 is a block diagram showing the image forming system of this embodiment, and FIG. 5 is a block diagram showing the image forming system of this embodiment. 3 is a timing chart of the image forming process of this embodiment. Further, Tables 1 to 4 show specific setting conditions necessary in this embodiment.

First, the formation of a multicolor image in this embodiment is performed according to the image forming system shown in FIG. In other words, the image data obtained by scanning the original image with the image sensor (Fig. 4 (a)) is processed by the image data processing part (Fig. 4 (b)) equipped with a computer. Create image data, which is −
The image is then stored in the image memory (FIG. 4(c)). The image memory is then taken out during recording and inputted into the multicolor image forming apparatus shown in FIG. 1(A), which is a recording section (FIG. 4(D)).

In recording by the multicolor image forming apparatus, first, a scorotron charger 2 uniformly charges an image forming member I having a photoconductive photosensitive layer rotating in the direction of the arrow. Next, a laser device is connected to the image memory (FIG. 4 (c)) on the charging surface.
An electrostatic latent image is formed by performing image exposure modulated by image data taken out from the image data.

This electrostatic latent image is developed by a reversal development method using the developing device shown in FIG. 3 containing the two-component developer to form a toner image. This image forming process is repeated by rotating the image forming body 1 once 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. This multicolor toner image is transferred to a pre-transfer charger 9
The transfer belt 50 is rotated from the start of transfer, as shown in Table 4 below, after being charged with electricity to facilitate transfer.
The transfer belt 50 having the configuration shown in FIG. A transfer charge having a polarity opposite to that of the toner, preferably in the range of 0.5 to 3 KV, is applied to transfer the toner.

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

Note that the transfer belt 50 has No., L, No., 2. N
Three types of transfer belts, 0 and 3, are available, and the conditions are set for each transfer belt in Table 4 above.

Further, the configuration of the transfer belt 50 is, for example, as follows. In other words, 0 on the outer periphery of the rubber belt containing conductive cloth as the base.
．． An elastic layer with a thickness of 5 mm is provided, and a 5 mm thick elastic layer is provided on the outer periphery.
The insulator layer (dielectric layer) of 0 μm is provided in Table 1, Table 2, Table 3, Table 4.
0 and is heated and fixed by the fixing device 6. on the other hand,
After the image forming body 1 after transfer is neutralized by the pre-cleaning static eliminator 7, residual toner is cleaned by the blade 81 and the fabric brush 82 of the cleaning device 8, and the image forming body 1 is prepared for the next image formation. The operation timings of charging, image exposure, development, transfer, and cleaning as the image forming body l rotates in the multicolor image forming process described above are shown in FIG.

In FIG. 5, the horizontal width indicates the number of rotations of the image forming body l and the elapsed time in seconds, and the vertical axis indicates each step for image formation.

Further, in the figure, T is the time when the leading edge of the transfer material P comes into contact with the transfer belt 50 and the image forming body l, which coincides with the start of the transfer, and T'' is the time when the leading edge of the transfer material P comes into contact with the transfer belt 50 and the image forming body l. The contact time is t, and t is the time difference between the two.The above-described image forming process produced a copy of an extremely clear multicolor image without any transfer deviation.

〔Effect of the invention〕

As explained above, the present invention provides a belt having an insulating member (dielectric material) on the surface that is brought into contact with the image forming body while supporting the transfer material as a means for transferring a multicolor toner image formed on the image forming body. Since the transfer means is brought into contact with the image forming body immediately before transfer, (1) the toner on the image forming body does not adhere to the transfer means, and the back surface of the transfer material is not stained.

(2) Wrinkling of the transfer material or misalignment of the image due to the difference in linear velocity between the image forming body and the transfer means does not occur.

■ Bias and charge for transfer do not leak due to scratches on the image forming body.

■ Since toner images are transferred using both physical and electrical effects, transfer efficiency is high and high-quality recorded images can be obtained.

There are effects such as

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1(a) and (b) are both sectional views showing a multicolor image forming apparatus according to the present invention, and FIGS. FIG. 3 is a cross-sectional view of the developing device used in the apparatus of FIG. 1, FIG. 4 is a block diagram showing the image forming system, and FIG. 5 is a timing chart of the image forming process. be. 1... Image forming body 2... Sufrotron charger 3... Static elimination lamp 6... Fixing device 7...
Pre-cleaning static eliminator 8...Cleaning device 81...Blade 82.
...Faplash 9...Pre-transfer charger 10...
・Laser device 11... Paper feeding device 12... Paper feeding roller 13... Timing rollers A, B,
C, D...Developer P...Transfer material 41...Magnetic roll 42
... Sleeve 43 ... Spilling regulation blade 44 ... Developer reservoir 45 ... Stirring screw 46 ... Toner supply roller 50 ... Transfer belt 59, 60. 63 ... Roller 53 ... Rotating shaft 54
...Lever 56...Spring member 6I...
・Eccentric cam 62...Solenoid 64...
tension roller

Claims (1)

[Claims] A rotating drum-shaped image forming body, means for forming a latent image on the image forming body, and developing the latent image to form a toner image are repeated multiple times to form a toner image on the image forming body. The present invention includes a means for forming an image, and a transfer means for contacting the image forming member in a substantially flat state while electrostatically holding the transfer material on a dielectric belt and transferring the toner image onto the transfer material. Characteristic image forming device.