JPH0720729A - Toner image transfer device - Google Patents

Abstract

PURPOSE:To satisfactorily transfer a toner image without imparing resolution. CONSTITUTION:The device visualizes an electrostatic latent image on a latent image carrier 1 by the use of liquid developer 3, and removes an excess of the liquid developer by means of a sqeeze roller 53, thereby transferring the toner image TI formed on the surface of the latent image carrier to transfer paper 29. The transfer device is provided with a transfer paper carry means 20 which carries the transfer paper 29 so that the surface of the transfer paper passes near the toner image with a minute transfer-gap between them in the prescribed transfer part where the latent image carrier 1 with the toner image TI on it passes, and transfer electric field acting means 22 and 23 which cause a transfer electric field for toner image transfer to act between the transfer paper 29 and latent image carrier surface in the transfer part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner image transfer device. INDUSTRIAL APPLICABILITY The present invention can be applied to various image forming apparatuses such as an optical copying machine, an optical printer, a facsimile apparatus, and the like that form an image by an electrostatic recording method.

[0002]

2. Description of the Related Art An electrostatic latent image formed on a latent image carrier such as a photoconductive photoconductor is developed with a "developer in which toner is dispersed in a dispersion medium", and after development, on the latent image carrier. A toner image transfer system for electrostatically transferring a "toner image" obtained on a latent image carrier by removing excess developer from a latent image carrier by a squeeze roller has been widely known.

The developer is present in the form of a thin liquid film on the surface of the latent image carrier after the excess developer is removed by the squeeze roller, and the toner particles are distributed in the liquid film according to the electrostatic latent image. Although the toner particles are electrically bound by the latent image charge, they are still mobile in the dispersion medium. Therefore, when the transfer paper is brought into close contact with the surface of the latent image carrier by electrostatic force during electrostatic transfer, the transferred toner image is easily crushed due to the pressure at the time of contact.

Recently, in an optical printer or a digital copying machine, an image having a very high resolution has been written by optical writing. However, the written electrostatic latent image is developed to obtain a toner image having a high resolution. However, there is a problem in that the resolution of the image recorded on the transfer paper becomes low due to "crushing" of the toner image at the time of transfer.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to effectively avoid crushing of a toner image and transfer the toner image satisfactorily without impairing the resolution. An object is to provide a toner image transfer device.

[0006]

The toner image transfer apparatus according to the present invention is capable of "developing an electrostatic latent image on a latent image bearing member with a developing solution and removing a residual developing solution with a squeeze roller. This is a device for transferring the "toner image formed on the surface of the carrier" onto a transfer paper.

A toner image transfer device according to a first aspect of the present invention has a transfer paper conveying means and a transfer electric field acting means. The “transfer paper conveying means” is configured so that the surface of the transfer paper passes through a predetermined transfer portion through which the latent image carrier having the toner image passes, with a minute transfer gap being close to the toner image.
It is a means for conveying the transfer paper. "Transfer electric field acting means"
Is means for applying a transfer electric field for transferring a toner image between the transfer paper and the surface of the latent image carrier in the transfer section.

The transfer sheet conveying means may be constructed such that the transfer sheet is electrostatically attracted to the outer peripheral surface of the belt and is conveyed by the rotation of the belt, or by two roller pairs. In the transfer portion, the transfer paper is conveyed while being stretched in the conveying direction ”(claim 2).

The transfer electric field acting means may be configured, for example, to "apply a voltage to the transfer paper conveying member in contact with the rear surface of the transfer paper", or to transfer the transfer paper conveyed by the above two pairs of rollers. It may be configured such that "corona discharge is applied to the back side of the transfer paper" (claim 2), or as in the embodiment described below, the surface of the transfer paper transport member in contact with the back surface of the transfer paper is charged. May be.

A toner image transfer device according to a third aspect of the present invention includes an intermediate transfer member, a transfer electric field forming means, and an electrostatic transfer means. The "intermediate transfer member" is formed in a rotating body, that is, a drum shape or a belt shape, at least the peripheral surface of which is dielectric, and at the predetermined first transfer portion through which the latent image carrier having the toner image passes, the peripheral surface is formed. Are circulated and rotated in close proximity to the toner image with a minute transfer gap. The "transfer electric field forming means" is means for forming a transfer electric field for transferring a toner image between the peripheral surface of the intermediate transfer member and the surface of the latent image carrier in the first transfer portion.

The "electrostatic transfer means" is means for electrostatically transferring the toner image transferred onto the intermediate transfer member onto the transfer paper at the second transfer portion. As the electrostatic transfer means, an appropriately known one such as a transfer charger or a transfer roller can be used.

In the toner image transfer device of the third aspect, the moving direction of the peripheral surface of the intermediate transfer member and the moving direction of the surface of the latent image carrier may be "opposite directions in the first transfer portion" ( Alternatively, the same orientation may be used in the first transfer portion (claim 5).

The "distance between the latent image carrier surface and the transfer paper surface" or the "distance between the latent image carrier surface and the peripheral surface of the intermediate transfer member" in the transfer section or the first transfer section is 400 μm or less,
It is preferably 100 μm or less.

[0014]

As described above, the state in which the toner image is formed on the latent image carrier is "the developer exists in the form of a very thin liquid film on the surface of the latent image carrier, and the toner particles are formed in this liquid film. Is distributed according to the electrostatic latent image. However, in the invention of claim 1, when the toner image is transferred to the transfer paper, in the invention of claim 3, the toner image is transferred to the intermediate transfer member. At this time, the toner image and the surface of the transfer paper, or the toner image and the peripheral surface of the intermediate transfer member are in non-contact with each other with a developing gap therebetween.

The developer film forming the toner image is developed when a transfer electric field is applied or formed between the surface of the latent image carrier and the transfer paper or between the surface of the latent image carrier and the peripheral surface of the intermediate transfer member. Polarization is generated in the thickness direction of the film, and the developer film rises toward the transfer paper by the electric force acting on the polarized charge and is transferred to the surface of the transfer paper. At that time, a considerable part of the dispersion medium forming the developer film remains on the surface of the latent image carrier.

[0016]

EXAMPLES Specific examples will be described below. FIG. 1 is a diagram for explaining one embodiment of the toner image transfer device according to the first aspect. In FIG. 1A, reference numeral 1 indicates
The "photoconductive photoconductor" as a latent image carrier is formed in a drum shape and rotates in the direction of the arrow, and has charging means and exposure means (not shown) such as an original image exposure method for irradiating an original optical image or writing by a light beam. Electrostatic latent image is formed by a developing device 50, and a toner image corresponding to the electrostatic latent image is formed by the developing device 50.

The main part of the developing device 50 is the developing roller 5
1, 52 and a squeeze roller 53, and the developer 3 in which the toner is dispersed in the dispersion medium is a contact portion between the developing roller 51 and the scraper 54, and a contact portion between the developing roller 52 and the scraper 55. It is supplied to the “liquid pool” formed in each by means of a supply means (not shown). The supplied developing solution 3 adheres to the peripheral surfaces of the developing rollers 51 and 52, and is brought to the developing section in accordance with the rotation of the developing rollers 51 and 52 to develop the electrostatic latent image on the photoconductor 1.

When the residual developing solution adhering to the surface of the photoconductor during development is removed from the surface of the photoconductor by the squeeze roller 53, a toner image TI is formed on the peripheral surface of the photoconductor 1.
The peripheral surfaces of the developing rollers 51, 52 and the squeeze roller 53 are cleaned by scrapers 54, 55, 56, respectively.

A transfer paper conveying means 20 is provided below the photoconductor 1. The transfer sheet transporting means 20 includes a drive pulley 2
0B, a pulley 20C, and a belt 20 wound around these
And the belt 20A is a drive pulley 20.
At the position of winding around B, it is close to the peripheral surface of the photoconductor 1 with a predetermined gap. This proximity portion is the “transfer portion”.

The belt 20A is formed of a dielectric film, has a metal film 28 formed on the inner peripheral surface thereof as shown in FIG. 1B, and the metal film 28 is grounded. The charger 22, the DC voltage power supply 23, and the metal film 28 constitute “transfer electric field acting means”, and the charger 22 corona-discharges by using the grounded metal film 28 as a counter electrode.
The outer peripheral surface of the belt 20A is uniformly charged with "reverse polarity to toner".

Transfer paper 29 onto which the toner image TI is transferred
(See FIG. 1B) is a cassette 32 shown in FIG.
The sheet is distributed by the sheet distributing roller 26, is conveyed by the conveying roller 25, and is sent out to the transfer section side by the registration roller 24 at the transfer timing. At this time, the transfer sheet conveying means 20 rotates counterclockwise while the surface of the belt 20A is uniformly charged.

The transfer paper 29 sent out by the registration rollers 24 is electrostatically adsorbed on the outer peripheral surface of the belt 20A by the electrostatic charge on the outer peripheral surface of the belt 20A, and is conveyed to the transfer portion by the rotation of the belt 20A. At the transfer portion, the surface of the transfer paper 29 being conveyed is close to the toner image on the photoconductor 1 with a minute transfer gap therebetween, and the toner image TI is transferred by the action of the transfer electric field due to the charge on the outer peripheral surface of the belt 20A. Paper 2
9 is transferred. Since the transfer is performed in a state where the transfer paper 29 and the surface of the photoconductor are not in contact with each other, “crush” does not occur in the transferred toner image.

The transfer paper 29 on which the toner image has been transferred is separated from the belt 20A by the separation claw 21, and the guide plate 2
7 is guided and discharged to the outside of the apparatus.

The embodiment schematically shown in FIG. 2 is one embodiment of the invention described in claim 2, and the transfer sheet conveying means is "two pairs of rollers", that is, the registration roller 24 and the conveying roller 3.
It is composed of 0s. The transfer paper 29 is a cassette 32.
The sheet is distributed by the sheet distributing roller 26, is conveyed by the conveying roller 25, and is fed to the transfer portion by the registration roller 24. When the leading end of the transfer paper 29 is sandwiched by the transport rollers 30, the transfer paper 29 is in a “tensioned” state at a predetermined distance from the photoconductor 1 due to the difference in transport speed between the rollers 24 and 30. Then, the surface of the transfer paper 29 comes close to the toner image on the surface of the photoconductor with a predetermined transfer gap, and passes through the transfer portion while being stretched in the transport direction.

At this time, the charger 33, which constitutes the "transfer electric field acting means" together with the DC voltage power supply 34, is corona-discharged, and the back side of the transfer paper 29 is charged to the opposite polarity to the toner. A transfer electric field acts on the transfer portion by the charge, and the toner image on the photoconductor 1 is transferred onto the transfer paper 29 in a non-contact manner.

FIG. 3 shows a modification of the embodiment of FIG. As shown in this example, the latent image carrier may be a belt photosensitive member 31 formed in an endless belt shape. If the latent image carrier is formed in a belt shape, "the degree of freedom in the layout of the apparatus" is large, which is convenient.

FIG. 4 schematically shows an embodiment according to claims 3 and 4. A drum-shaped intermediate transfer member 12 is arranged on the photoconductor 1 with a predetermined transfer gap therebetween, and is rotated clockwise. Photoconductor 1 and intermediate transfer member 1
The portion adjacent to 2 is the first transfer portion.

The intermediate transfer member 12 is formed by forming a smooth dielectric layer on the outer peripheral surface of a grounded conductive drum, and at the time of transfer, the transfer electric field forming means composed of a DC voltage power supply 14 and a charger 13 is used. It is charged to the opposite polarity to the toner image.

The charged peripheral surface of the intermediate transfer member 12 is the first
When passing through the transfer portion, a transfer electric field is formed in the first transfer portion, and the toner image on the photoconductor 1 is transferred onto the intermediate transfer member 12 in a non-contact manner. The transferred toner image is transferred to the charger 15 and the intermediate transfer member 12 of the “electrostatic transfer unit” composed of the DC voltage power supply 16 and the charger 15.
In the second transfer portion where and are opposed to each other, electrostatic transfer is performed on the transfer paper 29 by the electrostatic transfer means.

In the state where the toner image TI is transferred onto the intermediate transfer member 12, the toner component is substantially the majority and the dispersion medium component is small, so that the electrostatic transfer is performed in the second transfer portion. At this time, even if the transfer paper 29 is pressed against the toner image, the toner image is not crushed.

The peripheral surface of the intermediate transfer member 12 and the photoreceptor 1
Since the toner image TI moves in the opposite direction to each other in the first transfer portion, the toner image TI is transferred from the surface of the photoconductor 1 to the peripheral surface of the intermediate transfer member 12 in a state of “upside down”. Since it is transferred, the state when it is transferred onto the transfer paper 29 at the second transfer portion is the same as when it is directly transferred from the photoconductor 1 onto the transfer paper 29.

Contrary to the embodiment of FIG. 4, the intermediate transfer member 12
The rotation direction of may be "counterclockwise" (claim 5). In that case, the charging position by the transfer electric field forming means by the DC voltage power source 14 and the charger 13 is set as shown in FIG.
It may be arranged on the right side of the intermediate transfer member 12 in, and the “conveyance direction of the transfer paper 29” in the second transfer portion may be set in the opposite direction to the case of the example of FIG.

In this case, however, the toner image transferred onto the transfer paper 29 has a "mirror image" relationship with the state on the photoconductor 1, so that the toner image transferred onto the transfer paper 29 is shown. So that the electrostatic latent image formed on the photoconductor 1 is a mirror image of the electrostatic latent image formed in the case of the examples shown in FIGS.

In the embodiment shown in FIG. 4, the form of the intermediate transfer member is not limited to the drum form, but may be a belt form regardless of the rotation direction, and the latent image carrier may be a belt form. it can.

[0035]

As described above, according to the present invention, a novel toner image transfer device can be provided. Since this apparatus is configured as described above, even a toner image having a high resolution can be satisfactorily transferred without impairing the resolution.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of the invention according to claim 1;

FIG. 2 is a diagram for explaining another embodiment of the invention according to claim 2;

FIG. 3 is a diagram showing a modification of the embodiment of FIG.

FIG. 4 is a diagram for explaining one embodiment of the invention described in claims 3 and 4.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (latent image carrier) 3 Developer 20 Transfer paper transport member 22 Charger 23 DC voltage power supply 29 Transfer paper

Claims (5)

[Claims] 1. A toner image formed on the surface of a latent image carrier is transferred onto a transfer paper by visualizing an electrostatic latent image on the latent image carrier with a developer and removing excess developer with a squeeze roller. The transfer paper is such that the surface of the transfer paper passes through a predetermined transfer portion through which the latent image carrier having the toner image passes, with a minute transfer gap being close to the toner image. And a transfer electric field acting means for applying a transfer electric field for transferring a toner image between the transfer paper and the surface of the latent image carrier in the transfer section. Toner image transfer device. 2. The toner image transfer device according to claim 1, wherein the transfer paper transport means has two pairs of rollers for transporting the transfer paper while tensioning the transfer paper in the transport direction at the transfer portion. A toner image transfer apparatus, wherein the operating means has a charger for performing corona discharge on the back side of the transfer paper conveyed by the two pairs of rollers. 3. A toner image formed on the surface of a latent image carrier is transferred onto a transfer paper by visualizing an electrostatic latent image on the latent image carrier with a developer and removing excess developer with a squeeze roller. Which is formed on the rotating body and has at least a peripheral surface that is dielectric, and through which the latent image carrier having the toner image passes.
An intermediate transfer member that rotates circularly with the peripheral surface located close to the toner image with a minute transfer gap in the transfer section; and the peripheral surface of the intermediate transfer member and the latent image carrier in the first transfer section. Transfer electric field forming means for forming a transfer electric field for transferring a toner image between the surface and the surface, and electrostatic transfer for electrostatically transferring the toner image transferred on the intermediate transfer member onto the transfer paper at the second transfer portion. And a toner image transfer device. 4. The toner image transfer apparatus according to claim 3, wherein the moving direction of the peripheral surface of the intermediate transfer member and the moving direction of the surface of the latent image carrier are opposite to each other at the first transfer portion. Toner image transfer device. 5. The toner image transfer device according to claim 3, wherein the moving direction of the peripheral surface of the intermediate transfer member and the moving direction of the surface of the latent image carrier are the same in the first transfer portion. Toner image transfer device.