JPH0193776A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention provides a static image forming apparatus suitable for use in image forming apparatuses, particularly league printers that can obtain positive images from both positive and negative films. The present invention relates to an image forming apparatus that uses an electric transfer process.

(Prior art and problems to be solved) A microfilm is used as an original image, and this is enlarged and projected onto a charged photosensitive layer to form an electrostatic latent image, and then toner is supplied to the latent image to form a toner image, and this is further League printers configured to transfer onto a transfer material such as paper have been well known.

Among these types of printers, printers have already been proposed that have two modes, allowing a positive image to be obtained from either negative or positive film as an original image.

FIG. 2 is a side view schematically showing the configuration of an image forming portion of such a printer.

The surface photosensitive layer of an image bearing member (referred to as a photoreceptor) 1 which rotates in the direction of arrow A and extends perpendicularly to the plane of the paper is
Assume that the light image 3 is uniformly charged, for example, to a negative polarity, and a latent image is formed by projecting the optical image 3 obtained by a projection means (not shown) onto the surface.

Next, this latent image is transferred to a positive mode and a negative mode which are arranged so that one of them is selectively brought to an operating position close to the photoreceptor l by appropriate means such as cams 4a and 5a. The image is developed by one of the developing devices 4.5 (developing device 5 in the illustrated case), and then,
The developed toner image reaches a transfer site provided with a transfer separation charger 8 as the photoreceptor rotates.

This toner image comes into contact with a transfer material (not shown) supplied from a conveyance path 7 consisting of a pair of guide members 7a and 7b at the transfer site at the same timing, and is brought into contact with the transfer material by the action of a transfer charger. transcribed.

Next, the transfer material is separated from the photoreceptor by the separation action portion of the transfer separation charger 8 and conveyed to a fixing site (not shown) via the conveyance path 1O, and residual toner that does not contribute to the transfer and remains on the photoreceptor during transfer is It is removed by the cleaning device W19.

In such a configuration, since the above-mentioned guide members 7a and 7b forming the conveyance path, especially the upper surface of the guide member 7a, are located close to the photoreceptor, toner on the photoreceptor or floating in the device However, there is a risk that this may adhere to the guide member due to electrostatic adsorption force, fall onto the transferred transfer material, stain it, and cause deterioration of image quality. In those equipped with this, the charging polarity of the toner is both positive and negative, so
It has been difficult to eliminate the above-mentioned disadvantages by simple means such as grounding the guide member.

The present invention has been made in order to cope with the above-mentioned situation, and even in a printer equipped with both negative and positive development modes, it is possible to prevent toner from adhering to the guide member arranged close to the photoreceptor. It is an object of the present invention to provide a printer that actively prevents the occurrence of contamination and can obtain high-quality images without contaminating the transfer material.

(2) Structure of the invention (technical means for solving the problem, its effect) In order to achieve the above object, the present invention selectively uses toners charged with different polarities to convert negative film to positive film into positive film. In a printer that obtains images, a guide member that guides a transfer material to a photoreceptor is configured to apply a bias having the same polarity as the toner depending on the charged polarity of the toner used. be.

With this configuration, it is possible to actively prevent toner scattered from the photoreceptor and toner floating within the device from adhering to the guide member, thereby preventing deterioration of image quality.

(Description of the Embodiment) FIG. 1 is a schematic side view showing the printing mechanism part, showing an embodiment in which the present invention is applied to a printer similar to that shown in FIG. In the same way as
An electrostatic latent image formed on a rotating cylindrical photoreceptor 1 arrives at a development site equipped with a developer 4.5.

The developing device 4.5 is compatible with positive and negative films, in positive mode and negative mode.

It is assumed that the cams 4a and 5a are operated to bring one of the developing devices to an operating position close to the photoreceptor to develop the latent image.

In the illustrated case, it is assumed that the developing device 4 stores positively charged toner for positive mode, and the developing device 5 stores negatively charged toner for negative mode.

The toner image formed at the development site passes through a pre-transfer charger 6 arranged to improve transfer efficiency.
It reaches the position of the transfer separation charger 8.

At this position, the toner image is spread between the pair of guide plates 7a and 7b.
The toner image is transferred to the transfer material at the same timing as the transfer material (not shown) supplied by a guide member 7 consisting of a guide member 7 .

Next, this transfer material is separated from the photoreceptor and is conveyed to a fixing site (not shown) via a conveyance path IO.

The guide plates 7a and 7b are connected to a bias application circuit B equipped with a power source E.

As can be seen from the figure, the circuit is provided with a movable contact 11.12 and fixed contacts 13 to 16, the operation of which is determined by connecting the movable contact 19 to one of the fixed contacts 17.18. The bias is connected to the guide plate 7.
It will be applied to pins a and 7b.

In the case of FIG. 1, the print mode is a negative mode with the developing device 5 located close to the photoreceptor. In this case, negatively charged toner is deposited on the photoreceptor during development.

Therefore, in the circuit, contacts 11 and 13 are
It is also assumed that contacts 12 and 14 are connected, and furthermore, contacts 19 and 17 are connected.

As a result, a negative bias is applied to the guide plates 7a and 7b, so that the toner has the same polarity as the toner on the photoreceptor, and the toner that forms the toner image is electrostatically attracted to the guide plates, disturbing the image. It is possible to reliably prevent floating toner from being attached to the guide plate.

In the case of positive mode, contacts 11 and 15, contacts 12 and 1
It is easy to understand that by connecting the contact point 6 and the contact point 19 to the guide plate 18, a positive bias can be applied to the guide plates 7a and 7b to prevent the positively charged toner from adhering to the guide plates 7a and 7b.

In addition, to explain the switching of contacts 17, 18, and 19, in the case of negative mode, toner adheres to the part of the photoconductor that has no potential, so the adhesion force is lower than in the case of positive mode, in which toner adheres to the charged part. In other words, it is in a state where it is easy to be attracted to the guide plates 7a and 7b.

Of course, a high bias with the same polarity as the toner is advantageous in terms of preventing toner stains, but since the transfer charger placed nearby has the opposite polarity for each mode, it is difficult to transfer. A problem arises in which the charge that should be contributed leaks.

Considering these points, set the bias to -300 to -500v in negative mode and +1 in positive mode.
It can be set as appropriate in the range of 00V to +300V,
Good results were preferably obtained by setting the former to -400V and the latter to +200V.

Although the present invention has been described above with respect to a case where it is applied to a league printer, it goes without saying that the present invention is not limited to this and can also be applied to copying machines and the like.

(3) As described in detail, the present invention is configured to transfer a toner image formed on a photoreceptor to a transfer material conveyed via a transfer material guide member disposed close to the photoreceptor. In this case, it is possible to reliably prevent the guide member from adsorbing toner on the photoconductor or suctioning floating toner, so that the transfer material may be damaged due to dirt on the guide member or toner particles accumulated on the guide member falling off. It is possible to avoid deterioration of image quality even when contaminated with water, which greatly contributes to obtaining high-quality images.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of main parts showing the configuration of a printer to which the present invention is applied, and FIG. 2 is a side view showing the operation of a known printer. L... Photoreceptor, 4.5 fist... Developer, 7... Guide member, 8... φ transfer separation charger, B... φ bias circuit,
11.12.19...Movable contact, 13.14.15.
16.17.18φ...Fixed contact. Engraving of drawings Figure 1 Figure 2 < Kusho procedure amendment entry (method) % formula %: 1) Indication of case Japanese Patent Application No. 1982-250717: 2) Title of invention Image forming device: 3) Person making the amendment Relationship to the case Applicant address name Canon Co., Ltd. [4] Agent (6) Number of inventions increased by amendment 0 (7)
Target of correction Drawing

Claims (1)

[Scope of Claims] An image forming apparatus having two print modes for obtaining a positive image from a negative original image and a positive original image by selectively using two types of toners charged with different polarities to transfer a transfer material. An image forming apparatus comprising: means for applying a bias having the same polarity as the polarity of toner in a selected mode to a guide member that guides the toner to the site.