JPH05127570A - Image forming device - Google Patents

Abstract

PURPOSE:To facilitate the formation of a secret image by means of the simple constitution. CONSTITUTION:The device is provided with a first developing unit 12 which selectively attaches first toner to the image formed on a photosensitive body 11 electrostatically, a second developing unit 13 which attaches second toner whose polarity is different from that of the first toner, to the image and transfer devices 14 and 15 which transfer the image, to which the first and second toners are attached, to a sheet. The first toner and the second toner are in the same color. The second toner is decolorized when receiving a beam of light with the specific wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine for forming an image by using a photoconductor.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus,
The electrostatic latent image on the photoconductor is developed by a plurality of developing devices,
2. Description of the Related Art There is known an image forming apparatus configured to superimpose images of a plurality of types or a plurality of colors on the same sheet.

[0003]

However, in such a conventional image forming apparatus, it is not easy to form a secret document or a secret image. The present invention has been made in consideration of such circumstances, and provides an image forming apparatus capable of easily forming a secret document or image by using a toner that is decolorized by a light beam having a specific wavelength. It is a thing.

[0004]

SUMMARY OF THE INVENTION According to the present invention, there is provided a first developing device for selectively adhering a first toner to a screen electrostatically formed on a photoconductor, and a polarity different from that of the first toner on the screen. A second developing device for adhering the second toner and a transfer device for transferring the screen on which the first and second toners are adhered onto a sheet are provided.
An image forming apparatus is provided in which the toner and the second toner have the same color, and the second toner is a toner that is decolorized when receiving a light beam having a specific wavelength.

[0005]

When the first toner adheres to the screen on the photoconductor by the first developing device, the second toner adheres to the area of the screen where the first toner does not adhere by the second developing device. Since the first toner and the second toner have the same color, the entire screen transferred to the paper has the same color, and the formed image cannot be discriminated. As a result, a secret image is formed. When the transferred paper is irradiated with light of a specific wavelength, the second toner is decolorized, so that only the image formed by the first toner appears.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. This does not limit the invention. FIG. 1 is a diagram showing the construction of a digital electrophotographic copying machine showing an embodiment of the present invention. In the figure,
Reference numeral 1 is a document table, 2 is a document cover, 3 is an exposure lamp for exposing a document, 4 is a CCD camera, and 5, 6 and 7 are mirrors for guiding image light from the document exposed by the exposure lamp 3 to the CCD camera 4. The mirrors 5 to 7 move so that the optical path length from the document to the CCD camera 4 becomes constant when the exposure lamp 4 moves in the direction of arrow A to scan the document. As a result, the image light from the document is transferred to the CCD camera 4
Read and converted into an electric signal.

Reference numeral 8 denotes a laser output device for emitting laser light modulated by the electric signal output from the CCD camera 4,
Reference numeral 9 denotes a polygon mirror. The polygon mirror 9 is rotated by a motor 9a to scan the laser beam from the laser output device 8 on the photosensitive drum 11 via the mirror 10.

Reference numeral 12 denotes a first developing device, 13 denotes a second developing device, and the second developing device 13 has a toner that is decolorized when receiving light of a specific wavelength (hereinafter referred to as a toner that disappears), for example, an organic boron. A toner using a cyanine dye reacted with an ammonium salt (which becomes colorless by absorbing light having a wavelength near 820 nm) is used.

Further, the first developing device 12 has toner that is not decolorized by light (hereinafter referred to as normal toner).
Is used, and the toner that disappears and the normal toner have the same color, and the polarities are set to be opposite to each other. Then, first toner is attached to the screen electrostatically formed on the photosensitive drum 11 by the laser light by the first developing device 12, and toner that is erased by the second developing device 13 is attached to the remaining portion. ..

Reference numeral 14 is a transfer charger for transferring the image developed by the first developing device 12 onto the paper, 15 is a transfer charger for transferring the image developed by the second developing device 13 onto the paper, and 16 is on the photosensitive drum 11. Is a cleaning unit for removing the remaining toner, and 17 is a main charger for uniformly charging the photosensitive drum 11.

Reference numerals 18 and 19 denote paper feed cassettes, 20 denotes a conveyance path for conveying paper from the paper feed cassette 18 or 19 to the photoconductor drum 11, and 21 denotes a conveyance path 20 for feeding the rotation of the photoconductor drum 11. A registration roller that determines the paper timing, and 22 is a registration switch that is provided near the registration roller 21 and that detects when the paper reaches the registration roller 21. Reference numeral 23 is a conveyor belt that conveys the transferred paper to the fixing roller 24, and 25 is a paper discharge roller that discharges the fixed paper.

FIG. 2 is a block diagram showing a control circuit of the electrophotographic copying machine shown in FIG. 1, where MC is a control unit containing a microcomputer, KB is a keyboard for inputting various copying conditions, and DP is various copying conditions. And a display section for displaying the copy status, M is an exposure lamp 3 for exposing the original document, and the original image is C
A reading unit for making the CD camera 4 read, JS is a jam detecting sensor for detecting a jam (paper jam), and PS1 is the registration roller 1 from the cassette 18 or 19 via the conveying unit 20.
PS2, a primary paper feed drive unit that drives primary paper feed systems up to 7
Is a secondary paper feed drive unit that drives the secondary paper feed system from the registration roller 17 to the paper discharge roller 21, and PS3 is the exposure lamp 3
And an optical system driving unit for driving an optical system such as mirrors 5 to 7.

The control unit MC includes a keyboard KB, a reading unit M,
The display unit DP, the laser output device 8, the main charger 17, the transfer chargers 14 and 15, the primary sheet feeding driving unit PS1, the secondary sheet feeding driving unit PS2, and the optical unit in response to outputs from the jam detection sensor JS and the registration switch 22 are received. The system drive unit PS3 is driven.

The operation in such a configuration will be described with reference to the flow chart shown in FIG. For example, when a manuscript having character information "A" as shown in FIG. 4 is placed on the manuscript table 1 and "encryption process" and "start" are entered on the keyboard KB (step 101), the character The information "A" is read by the reading unit M (step 102).

Next, the photosensitive drum 11 is uniformly charged by the main charger 17 (step 103), and the laser output device 8 outputs the image shown in FIG. 4 to the photosensitive drum 11 as an electrostatic latent image. (Step 104).
Then, the electrostatic latent image is developed by the developing devices 12 and 13 with the normal toner and the erasing toner (step 1).
05, 106). Since the normal toner and the erasing toner have different polarities from each other, the character "A" is developed with the normal toner and the other areas are developed with the erasing toner as shown in FIG.

Next, the primary paper feed, that is, the cassette 18
Alternatively, the sheet is fed from 19 to the registration roller 21 (step 107). At this time, if it is confirmed that no jam has occurred (step 108), the registration roller 21 is driven next and the paper is fed toward the photoconductor drum 11 (step 109), and no jam occurs. If it is confirmed (step 110), the transfer charger 14,
The toner image is transferred from the photoconductor drum 11 to the sheet by 15 (steps 111 and 112). The transferred sheet is fixed (step 113) and discharged (step 114).

In this way, on the paper, an image in which the character "A" in FIG. 4 is smeared with the disappearing toner of the same color as in FIG. 5, that is, the character information "A" in FIG. 4 is made unreadable. An image is obtained. When this secret image is irradiated with specific light, the image developed with the disappearing toner disappears, and the character image shown in FIG. 4 remains, so that it can be decoded.

If "encryption processing" is not input in step 101 of FIG. 3, normal copy processing is executed (step 115), and steps 108,
When the occurrence of a jam is confirmed at 110, the operation of each unit is stopped and the display unit DP performs "jam display" (steps 116 and 117).

[0019]

According to the present invention, a secret image can be easily created with a simple structure.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a control circuit of the embodiment.

FIG. 3 is a flowchart showing the operation of the embodiment.

FIG. 4 is an explanatory diagram showing a character image of a document.

FIG. 5 is an explanatory diagram showing an unreadable secret character image.

[Explanation of symbols]

 1 Document Placement Table 3 Exposure Lamp 4 CCD Camera 8 Laser Output Device 11 Photoreceptor Drum 12 Developing Device 13 Developing Device 14 Transfer Charger 15 Transfer Charger

Claims (1)

[Claims] 1. A first developing device that selectively attaches a first toner to a screen electrostatically formed on a photoconductor, and a second developer that attaches a second toner having a polarity different from that of the first toner to the screen. A developing device and a transfer device for transferring the screen on which the first and second toners are attached to a sheet, and the first toner and the second toner are the same color, and the second toner is decolorized when receiving a light beam of a specific wavelength. Image forming apparatus that is a toner that does.