JPH01225978A - Image forming method - Google Patents

Abstract

PURPOSE:To enable forming an image in detail only when the image is reproduced by forming an electrostatic latent image on a latent image carrier corresponding to image information, producing an invisible image by means of developing insulating toner whose polarity is opposite to the electrostatic latent image and whose transparency is high, and fixing the toner after transferring it on a transfer material. CONSTITUTION:The electrostatic latent image is formed by exposing the image information 3 on a photosensitive drum 2 which is the image carrier electrostatically charged by an electrostatic charger 1. The highly transparent insulating toner 5 is brought into contact with the electrostatic latent image by a developing device 4 to form the invisible image, which is overlapped with a transfer sheet 6, and the toner 5 is transferred by a transfer electrostatic charger 7. Consecutively, the transfer sheet 6 is separated from the photosensitive drum 2, a transferred image only electrically lying on the transfer sheet 6 is fixed by a fixing device 8. Meanwhile, residual toner on the photosensitive drum 2 is cleaned by a cleaning device 9 and residual charges are eliminated by a destaticizing lamp 10. Thus, environment never cause coloring, so that image formation and image reproducing in detail can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an image forming method particularly suitable for creating so-called confidential documents that must be kept secret.

[Prior Art] Confidential documents are usually kept in strict storage to prevent information leakage. Also, when transporting, it is strictly sealed when it passes through the hands of a third party.

However, in either case, if you copy only the information without deforming (or altering) the document and leaving it in the same state as restored, the information can be removed without anyone knowing that the information has been extracted. This made it possible to spy on information. Therefore, if information cannot be obtained unless the document is altered, the alteration of the document makes it clear that an information extraction operation has been performed, thereby preventing information leakage.

As a means for obtaining information by altering a document, a grilling method (or a similar method) is conventionally known.

However, in the case of such conventional methods, chemical changes are used, so the environment (light, components in the atmosphere, etc.)
The problem is that it can be used only for pictures, etc., because it may develop color due to the influence of color, and it is difficult to reproduce fine details.

[Purpose] Therefore, the present invention aims to prevent images from being reproduced due to the influence of the environment.
The purpose of this invention is to provide an image forming method that allows images to be visualized in detail during image reproduction, so that it can be applied particularly to forming images of confidential documents to achieve remarkable effects. .

[Structure] In order to achieve the above object, the present invention forms an electrostatic latent image on a latent image carrier according to image information, and then converts the electrostatic latent image in the opposite direction to the electrostatic latent image. The image forming method involves developing a polar and highly transparent insulating toner to form an invisible image, and then transferring the invisible image to a transfer material and then fixing it.

The invisible copy obtained by the image forming method of the present invention is
It just looks like a blank sheet of paper. Therefore, a third party cannot know the contents unless it is visualized in a separate process.

Therefore, it is extremely effective when forming an image for a confidential document.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a copying machine as an example of an apparatus for carrying out the image forming method of the present invention.
is exposed to light to form an electrostatic latent image, and a developing device 4 is applied to the electrostatic latent image.
A highly transparent insulating toner 5 is brought into contact with the insulating toner 5 to form an invisible image, a transfer paper 6 is placed on top of the invisible image, and the toner 5 is transferred by a transfer charger 7. is separated from the photoreceptor drum 2, and the transfer image electrically placed on the transfer paper 6 is fixed by the fixing device 8 and ejected, while the photoreceptor after the transfer paper 6 is separated The residual toner on the drum 2 is cleaned by a cleaning device 9, and the residual charge on the photosensitive drum 2 is further erased by a static elimination lamp 10.

Toners used in copiers typically contain binders, pigments,
It is composed of a polarity control agent, and the binder is a resin, the pigment is carbon black in the case of black toner, and the polarity control agent is a dye. That is, toner is usually colored with a pigment and a polarity control agent. However, the toner 5 used in the present invention is a toner with high light transmittance, that is, high transparency. Here, toner 5 with high transparency can be considered as toner made only of binder, that is, resin. Generally, in order for a toner to have the function of developing an electrostatic latent image, it must have polarity controllability, so when the toner consists only of a resin, the resin must have polarity controllability. Phenolic resins are available as such resins, but they have the disadvantage that their properties vary greatly depending on the environment. However, since it has the highest transparency, if this difficulty is solved in the future, it will become the most useful toner 5 for use in the present invention, and will almost completely achieve the effects of the present invention, which will be described later. The next highly transparent toner 5 to be considered is a toner made of a binder and a polarity control agent (dye). Such a toner has lower transparency than a toner made only of the binder due to the dye used as a polarity control agent, but it has higher transparency than a normal toner containing a pigment, and also has the polarity controllability necessary for a toner. Since it is definitely provided by the dye, it can be used immediately.

Therefore, when the present invention is carried out using a copying machine having the above configuration using the highly transparent toner 5, the developing process by the developing device 4, the transferring process by the transfer charger 7, and the fixing process by the fixing device 8 are sequentially performed, and then the toner is discharged. The printed transfer paper 6 is
That is, the image of the obtained copy becomes an invisible image. Therefore, the image appears to be nothing more than a blank sheet of paper, and a third party cannot understand the image content. Moreover, since this invisible image is a toner image, it hardly develops color due to the influence of the environment.

In order to visualize the image of the invisible copy obtained in this manner, it is necessary to convert the invisible copy into a visible copy using a visualization device, which will be described later. Therefore, by forming a confidential document by invisiblely creating an image of information to be kept secret on the transfer paper 6, manipulation of the information can be prevented. In other words, if what is supposed to be an invisible copy is made visible, it becomes clear that such an operation was performed at an intermediate stage, making it impossible to extract only the information at an intermediate stage. Also, at this time,
If a seal is affixed to the visible copy, for example, if an operation such as ■invisible copy → ■visible copy → ■invisible copy is performed at an intermediate stage, the difference (presence or absence) between the stamps of ■ and ■ will be detected. This makes information handling operations at intermediate stages even more difficult.

The visualization device that visualizes the invisible copy is as shown in FIG. A conductive roller 13 is an ordinary colored toner (regardless of whether it is a one-component type or a two-component type). ) 16 is a developing device, and 14 is a fixing device.

Note that the charging polarity of the charger 11 is AC biased toward the positive side.

Now, when the transfer paper 6 used for invisible copying is fed between the charger 11 and the conductive roller 12, by appropriately selecting the AC potential and the positive potential of the charger 11, the toner 5 on the transfer paper 6 is is made positive and the parts other than the toner 5 are made to have almost zero potential, so that an electrostatic latent image is formed on the transfer paper 6, with the image area having a positive potential and the non-image area having almost zero potential. Next, colored toner 16 is brought into contact with this electrostatic latent image by a developing device 13 to create a visible image, and this visible image is further fixed by a fixing device 14, so that an invisible copy becomes a visible copy. The image is reproduced as

The image reproduced in this way is
Since the developing process and fixing process are similar to the copying process using a normal copying machine, a copy image with clear details can be obtained.

Next, FIG. 3 shows another example of a visualization device, in which a DC discharge type charging device is used instead of the charging device 11 in the same configuration as the visualization device shown in FIG. 2 above. 11', and a static eliminating brush 15 is provided on the back side of the transfer paper 6.

When such a system is adopted, the same effect as the visualization apparatus shown in FIG. 2 can be obtained without using AC. In addition, in the case of this method, if the poor charging property of the transfer paper 6 itself is utilized, the static elimination lamp 15 can be omitted.

In the above embodiments, a copying machine was exemplified as an apparatus for carrying out the image forming method of the present invention, but a printer, facsimile, etc. may also be used. Copies can be reproduced in detail in the same way as when they are exposed, so they can be used in addition to confidential documents, such as New Year's cards, and various other changes can be made without departing from the gist of the present invention. Of course you can get it.

[Effects] As described above, according to the image forming method of the present invention, highly transparent toner is used to form image information as an invisible image, so the obtained invisible copy is only a blank sheet of paper. In addition to being invisible, the image does not develop color due to environmental influences, and there is no risk of the image content becoming known to a third party. Therefore, when a confidential document is created by invisible copying, a remarkable effect is achieved in that information handling operations can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a copying machine showing an example of an apparatus for carrying out the image forming method of the present invention, and FIGS. 2 and 3 both show a visualization device for visualizing invisible copies. It is a schematic diagram. 2... Photosensitive drum, 3... Image information, 4... Developing device, 5... Toner, 6... Transfer paper, 7... Transfer charger, 8... Fixing device.

Claims (1)

[Claims] 1) Forming an electrostatic latent image on a latent image carrier according to image information,
Next, the electrostatic latent image is developed with highly transparent insulating toner having a polarity opposite to that of the electrostatic latent image to create an invisible image, and then the invisible image is transferred to a transfer material and then fixed. An image forming method characterized by: