JPH01188884A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from scattering, transferring defect, and reverse transferring to a photosensitive body by giving heat energy which is lower than normal fixing heat energy to a toner image transferred at a pre-stage by a temporary fixing device. CONSTITUTION:The temporary fixing device 2 which is provided between a transferring device 9 and a transferring device 10 by using a laser beam is constituted of a laser beam source 21 and a cylindrical lens 22. A CO2 laser beam source is used as the laser beam source 21. I.e., because the temporary fixing device 20 is of non-contact system, pressure is not applied to a copying sheet (a) and a toner image. In addition, since the arising heat energy is lower than normal fixing heat energy at the time of fixing, a toner image is fixed temporarily with weaker fixing power than normal fixing condition. After a toner image transferred on a copying sheet in the transferring part of the pre-stage is temporarily fixed it is repeatedly transferred in a transferring part at a post-stage. Thus, the scattering of toner powder, transferring defect, and reverse transferring to the photosensitive body are eliminated, and deterioration in image quality is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to an electrophotographic image forming apparatus, specifically a multicolor image forming apparatus that performs multiple transfer, in which a toner image after transfer is well fixed. The present invention relates to a device for obtaining high-quality copies.

[Conventional technology]

Conventionally, a color copying machine that performs multiple transfer is known, for example, as described in Japanese Patent Application Laid-Open No. 47-37434.

In this copying machine, transfer is performed multiple times corresponding to a plurality of colors onto one sheet of copy paper, and fixing is performed after all the transfers are completed.

In general, when multiple transfer is performed, the powder toner image transferred on the upstream side is further transferred on the downstream side, and finally fixed. .

Incidentally, the above-mentioned publication also proposes performing fixing in the middle of each transfer, but does not disclose any specific means for doing so.

On the other hand, as a fixing device for a copying machine, a fixing device using laser light has been proposed in Japanese Patent Laid-Open No. 59-95564.

This fixing device includes a laser light source 30 as shown in FIG.
A laser beam is emitted from a rotating polygon mirror 32 rotated by a motor 31, and the laser beam is transmitted through a correction lens 33 to scan the copy sheet a.

The toner image developed on the surface of the photoreceptor 34 is transferred to the copy paper a by discharge of the transfer corotron 35, and the copy paper a is conveyed in the direction of the arrow. And rotating polygon mirror 32
Since the copy paper a is rotating at a high speed, the copy paper a is repeatedly irradiated with laser light and becomes high in temperature, and the toner image on the copy paper a is melted and fixed by this thermal energy.

[Problem to be solved by the invention]

However, the conventional device described above has the following problems.

That is, when a toner image is transferred on top of a powder toner image transferred on the upstream side, as in a general color copying machine, the electrical repulsion between the toner particles causes the toner to scatter or cause transfer failure. Further, there is a problem in that the toner of a color transferred on the upstream side is reversely transferred onto the photoreceptor on the downstream side.

Furthermore, if fixing is performed for each transfer as proposed in Japanese Patent Application Laid-Open No. 47-37434, there is a problem that the apparatus becomes complicated. Here, it is possible to use the fixing device described in the above-mentioned Japanese Patent Application Laid-Open No. 59-95564 as a device that performs fixing after each transfer, but in this device, the toner image is melted by the thermal energy of the laser beam. There is a problem in that a large amount of thermal energy is required to fix the image on the copy paper.

Therefore, the present invention provides a temporary fixing device between a plurality of transfer sections to eliminate toner scattering, transfer defects, and reverse transfer to the photoreceptor during multiple transfers, and to prevent toner images on copy paper after transfer. The purpose is to ensure good fixation.

[Means to solve the problem]

In order to achieve the object, the image forming apparatus of the present invention has the following features:
In an image forming apparatus having a plurality of transfer devices that perform multiple transfers on a single sheet of copy paper, a thermal energy lower than that during normal fixing is applied to the toner image on the copy paper between the plurality of transfer devices. The present invention is characterized in that it is provided with a temporary attachment device that irradiates a laser beam that gives .

The temporary attachment device may be a device that irradiates a laser beam whose width is widened in a direction perpendicular to the conveying direction of the copy sheet.

[Effect]

In the image forming apparatus of the present invention, a temporary fixing device is provided between the plurality of transfer devices, and the temporary fixing device applies thermal energy lower than that during normal fixing to the toner image transferred in the previous stage. Therefore, the toner image is fused to the copy sheet to some extent.

Due to this temporary adhesion, there will be no toner scattering, transfer failure, or reverse transfer to the photoreceptor during the next transfer. Furthermore, since the thermal energy applied to the toner image is lower than that during normal fixing, the device for irradiating the laser beam can be downsized. By performing the main fixing after the final transfer, a good image can be obtained.

〔Example〕

Hereinafter, the features of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a side view of an image forming apparatus in an embodiment of the present invention. Note that in order to simplify the explanation, this embodiment is shown as a two-color color copying machine.

Laser beams 3 and 4 are emitted from the cyan laser scanner 1 and the magenta laser scanner 2, respectively. On the side to which the laser beams 3 and 4 are irradiated, a cyan image photoreceptor 5 and a magenta image photoreceptor 6 are arranged in parallel, respectively.

A cyan developing device 7 and a transfer device 9 are installed around the cyan image photoreceptor 50. Cleaning blade 11. A charger 13 is provided, and a magenta developer 8 is provided around the magenta photoreceptor 6.
．． Transfer device 10. Cleaning blade 12. Charger 1
4 is provided.

A paper transport device 5 for transporting the copy paper a is provided between the paper feed roller 17 and the fixing device 18, and transfers the copy paper a fed from the paper feed section 16 side to the transfer device 9.1.
0 to the fixing device 18.

The cyan image photoreceptor 5 and the magenta photoreceptor 6 are exposed to laser beams 3 and 4, respectively, to form electrostatic latent images. Next, the cyan developer 7 and the magenta developer 8
Accordingly, the cyan image photoconductor 5 and the magenta photoconductor 6
A cyan toner image and a magenta toner image are respectively formed on the wafer. Furthermore, the transfer device 9 and IO sequentially transfer the image onto the copy paper a.

In the transfer to the copy paper a, the transfer device 9 first transfers the cyan toner image to the copy paper a conveyed by the paper conveyance device 15, and then the transfer device 10 transfers the magenta toner image. .

Here, in this embodiment, the transfer device 9 and the transfer device 1 are
A temporary attachment device 20 using laser light is provided between 0 and 0.

The temporary attachment device 20 includes a laser beam R21 and a cylindrical lens 22, and a CO2 laser light source is used as the laser light source 21. As shown in FIG. 2, which is a front view of the temporary attachment device 20, the laser beam 23 from the laser light source 21 is directed by a cylindrical lens 22 in a direction perpendicular to the conveyance direction of the copy paper a (left-right direction in the figure). Copy paper a
The beam is expanded to a width wider than the width of , to form a fan-shaped beam of light, and is irradiated onto the copy sheet a after the cyan toner image has been transferred. In this embodiment, the size of the luminous flux of the fan-shaped laser beam 23 is 1 in the paper conveyance direction.
The width of the paper is 300 mm in the paper width direction.

The wavelength of the C02 laser beam is 10.6p, and as can be seen from FIG. 3, which shows the relationship between the wavelength of light and the absorption rate of each color toner, more than 95% of the Co2 laser beam is absorbed by the toner and copy paper.

By configuring the temporary attachment device 20 as described above, the laser beam 23 with high energy density is irradiated onto the copy paper a,
Relatively reducing the influence of thermal grazing from copy paper a,
The energy of the laser beam 23 can be efficiently used to raise the temperature. In other words, Rede light has a higher energy density than an infrared lamp or a xenon lamp, and since it takes an extremely short time to melt the toner, the amount of heat that flows out and escapes by thermal conduction during heating is small.

When the leading edge of the copy paper a to which the cyan toner image has been transferred by the transfer device 9 is detected by the paper detector 24 composed of a light emitting diode and a photodiode, the laser light source 21 starts emitting laser light 23. ing.

While the copy paper a is passing through, the laser light source 21 continues to irradiate the copy paper a with Rede light 23, and the cyan toner image on the copy paper a absorbs the laser light 23 and becomes high temperature, causing the toner to be thermally melted. do.

Here, since the temporary fixing device 20 is a non-contact type, no pressure is applied to the copy paper a and the toner image, and the heat energy generated by the conventional laser fixing device described above is 3.
000 to 4000 J/m', whereas the thermal energy generated by the temporary fixing device 20 is about 10 to 50 J/m''. It will stop being done.

The tentatively attached copy paper a is further conveyed and transferred to the transfer device 10.
The magenta toner image is transferred in an overlapping state with the cyan toner image. At this time, the cyan toner image is temporarily attached to the copy sheet a as described above. Therefore, the toner does not scatter, and since the cyan toner image has increased adhesion to the copy paper a, it is not reversely transferred to the magenta image layer photoreceptor 6.

When the trailing edge of the copy sheet a passes the temporary attachment device 20, a signal from the sheet detector 24 turns off the laser light source 21.

The toner image that has been transferred in the second color by the transfer device 10 is finally fixed by the main fixing device, for example, a fixing device 18 equipped with a heating roller and a pressure roller, and then transferred to the paper discharge section 1.
It is discharged at 9.

FIG. 4 is a side view of an image forming apparatus according to another embodiment of the present invention, and FIG. 5 is a front view of a temporary attachment device used in the image forming apparatus. In FIGS. 4 and 5, parts corresponding to those shown in FIGS. 1 and 2 are designated by the same reference numerals. In this embodiment, an auxiliary heater 25 is added to the temporary attachment device 20. By using this auxiliary heater 25 to supplementally heat the copy paper a and the toner from the back side of the copy paper a,
The capacity of the Rade light source 21 is being reduced.

In the above embodiment, a C02 laser beam was used as the laser beam, but as can be seen from FIG. 3, if the wavelength of the light is 5 JIM or more, the light absorption rate of the copy paper a is 8
5% or more, and the toner has a light absorption rate of about 95%, so other laser beams can be used as long as they have a wavelength of 5- or more.

Further, in the above description, a two-color copying machine of cyan and magenta was used as an example, but the same applies to a three-color or four-color copying machine. That is, after the transfer of each color toner image except for the final stage, the toner image is temporarily attached to the copy sheet a by irradiating the laser beam, and multiple transfer can be performed satisfactorily.

〔Effect of the invention〕

As explained above, according to the image forming apparatus of the present invention,
A temporary fixing device using Raded light is provided between the transfer units, and after the toner images transferred on the copy paper are temporarily attached in the former transfer unit, they are superimposed and transferred in the subsequent transfer unit. Therefore, toner powder scattering, transfer failure, and reverse transfer to the photoreceptor do not occur, so deterioration of image quality can be prevented and high-quality copies can be obtained in a color copying machine that performs multiple transfer. In addition, since the temporary attachment device uses laser light, temporary attachment can be performed without contact and does not stain the copy paper, and the laser beam is emitted so that the laser beam is only irradiated while the copy paper is passing through. Since it is easy to control on and off, there is no wasted energy consumption and the entire device does not become complicated.

[Brief explanation of the drawing]

FIG. 1 is a side view of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a front view of a temporary fixing device used in the image forming apparatus, and FIG. 3 is a diagram showing the wavelength of light and the absorption rate of each toner. FIG. 4 is a side view of an image forming apparatus according to another embodiment of the present invention, FIG. 5 is a front view of a temporary attachment device used in the image forming apparatus, and FIG. 6 is a graph showing the relationship between FIG. 2 is a perspective view of a fixing device using Rede light. 1 Laser scanner 2 for magenta: Laser scanner 3 for magenta 4: Laser light 5 Photoreceptor 6 for nijian image:
Photoreceptor for macenta image 7 Cyan developer 8: Magenta developer 9, 10: Transfer device 11, 12: Cleaning blade 13.14: Charger 15: Paper transport device 16
: Paper feed section 17: Paper feed roller 18: Fixing device 19: Paper discharge section 20: Temporary fixing device 21
: Laser light source 22 Nijilintorical lens 23: Laser light 24: Paper detector 25: Auxiliary heater 30: Laser light source 31: Motor
32: Rotating polygon mirror 33: Correction lens 34
: Photoreceptor 35 : Transfer corotron a : Copy paper Patent applicant Fuji Xerox Co., Ltd. Agent
Masu Kobori (and 2 others) No. 19 No. 2 Fig. 3 Fig. 0 0.5 1
5 10 wavelengths (p
m) Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. In an image forming apparatus having a plurality of transfer devices that perform multiple transfers on one sheet of copy paper, normal fixing is performed on the toner image on the copy paper between the plurality of transfer devices. 1. An image forming apparatus characterized by being provided with a temporary attachment device that irradiates a laser beam that provides thermal energy lower than the thermal energy of the image forming apparatus. 2. An image forming apparatus, wherein the temporary attachment device according to claim 1 is a device that irradiates a laser beam whose width is widened in a direction perpendicular to the conveying direction of the copy sheet.