JPH075738A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To provide a multicolor image forming device which can obtain a high-quality multicolor image by evenly transmitting the heat of a fixing part to a toner image and preventing the incomplete fused part of toner from being formed. CONSTITUTION:In the multicolor image forming device forming the multicolor image by superposing the toner of plural colors, a developing device housing the colorless transparent toner T is ruggedness of the multicolor image caused by the difference of the superposing frequency of the color toner Y, M and C is reduced by superposing the toner T on the rugged part of the multicolor image. Thus, since the fixing process is executed after the ruggedness of the multicolor image caused by the difference of the superposing frequency of the color toner Y, M and C is reduced, the heat of the fixing part is uniformly transmitted to the toner image without irregularities and the incomplete fused parts of the toner Y, M and C are prevented from being formed. As a result, the high-quality image is stably obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic multicolor image forming apparatus.

[0002]

2. Description of the Related Art A conventional example of such a multicolor image forming apparatus is shown in FIG.
Shown in.

That is, FIG. 6 is a vertical cross-sectional view of a conventional multicolor image forming apparatus. In the multicolor image forming apparatus, a sheet 102 fed from a sheet feeding section 101 has a leading end of a transfer drum 103. It is held by the gripper 103 f and held on the outer periphery of the transfer drum 103.

On the other hand, a latent image for each color is formed on the image carrier 1 of the drum cleaner cartridge C by the optical unit 107.

By the way, the developing device selecting mechanism is used for the image carrier 1.
A developing cartridge holding member 108 rotatable about an axis 110 parallel to the axis of
A pressure member 111 for pressing and positioning m, Dc, Dy, and Db in the developing unit toward the image carrier 1 of the drum cleaner cartridge C and a holding member 108 to rotate the developing cartridge Dm, It is composed of a control / drive mechanism for selectively moving Dc, Dy, Db, a drive mechanism for maintaining each developing cartridge Dm, Dc, Dy, Db in a specific posture.

Thus, the developed images formed by the developing device selection mechanism for each color are sequentially transferred to the paper 102 on the transfer drum 103, and a multicolor image is formed on the paper 102. Then, the paper 102 is separated from the transfer drum 103 and sent to the fixing unit 104, where the fixing unit 104 fixes the multicolor image, and the paper discharge unit 10
The sheet is discharged from the sheet 5 to the sheet discharge tray unit 106.

After the transfer process is completed, a toner layer as shown in FIG. 7 is formed on the sheet 102. In FIG. 7, M is magenta toner, C is cyan toner, Y is yellow toner, and B is black toner.

[0008]

However, when the sheet 102 on which the toner layer as shown in FIG. 7 is formed is fixed by the fixing unit 104, there are the following problems.

That is, as shown in FIG. 8, the toner layer is fixed to the sheet 102 by applying pressure and heat by the fixing roller 104g in the fixing unit 104. If the toner layers have unevenness due to the difference in Y, the heat of the fixing roller 104g is hard to be transferred to the toner portion at the bottom of the concave portion even if pressure is applied, and as shown in FIG. When the toner M is present, the magenta toner M is not sufficiently melted and remains as it is, as shown in (b) of FIG. This may cause deterioration of image quality such as poor transmission.

When the toner layers are piled up in multiple layers as shown in FIG. 10 (a), the end portion (outline portion) of the toner image is laterally moved by fixing as shown in FIG. 10 (b). It collapses and spreads, causing deterioration in image quality.

The present invention has been made in view of the above problems, and an object of the present invention is to uniformly transfer heat of a fixing portion to a toner image to prevent generation of an incompletely melted portion of the toner and a colored toner. It is an object of the present invention to provide a multicolor image forming apparatus capable of improving image quality by preventing the image end portion of the image from collapsing and spreading due to fixing.

[0012]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a multi-color image forming apparatus for forming a multi-color image by superposing toners of a plurality of colors, and a developing device containing a colorless transparent toner. It is characterized in that the fixing step is performed after the colorless and transparent toner is superposed on the uneven portion of the multicolor image to reduce the unevenness of the multicolor image due to the difference in the number of overlapping color toners.

Further, according to the present invention, the colorless and transparent toner layer is formed also on the image end portion (outline portion), or the colorless and transparent toner layer is formed on the lowermost layer of the printing medium to reduce the unevenness of the multicolor image. It is characterized by having done.

[0014]

According to the present invention, since the fixing step is carried out after the unevenness of the multicolor image due to the difference in the number of overlapping color toners is reduced, the heat of the fixing portion is uniformly transferred to the toner image, and Generation of incompletely fused portions is prevented, and high quality images can be stably obtained.

Further, according to the present invention, an image end portion (contour portion)
Also, since the layer of the colorless and transparent toner is formed, it is possible to prevent the edge portion of the image of the colored toner from collapsing and spreading, and it is possible to improve the image quality.

[0016]

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

<First Embodiment> FIG. 1 shows the overall structure of a multicolor image forming apparatus according to the present invention.

Paper 102 fed from the paper feed unit 101
Is held by the gripper 103 f of the transfer drum 103 on the outer periphery of the transfer drum 103.

On the other hand, the optical unit 107 forms a latent image of each color (yellow, magenta, cyan, black and transparent) on the image carrier 1 of the drum cleaner unit C.

The developing device selecting mechanism includes a developing cartridge holding member 108 rotatable about an axis 110 parallel to the axis of the image carrier 1 and developing cartridges Dy, Dm, D.
A pressing member 111 for pressing and positioning c, Db, and Dt in the developing unit toward the image carrier 1 of the drum cleaner cartridge C, and a holding member 108 are rotated to rotate the developing cartridges Dy, Dm, Dc, The control / driving mechanism for selectively moving Db and Dt and the driving mechanism for maintaining each developing cartridge Dy, Dm, Dc, Db, and Dt in a specific posture are included.

Then, the developed image developed into each color by the developing device selecting mechanism is transferred onto the paper 102 held on the transfer drum 103, and a multicolor image is formed on the paper 102. After that, the paper 102 is separated from the transfer drum 103 and sent to the fixing unit 104, where the fixing unit 104 fixes the multicolor image, and the paper discharge unit 105.
The sheet is discharged from the sheet discharge tray unit 106.

By the way, in this embodiment, after the color images of yellow, magenta, cyan and black are formed, the transparent toner T is positioned in the concave portion of the color image by the developing cartridge Dt provided with the transparent toner T as shown in FIG. Development and transfer are performed as described above. As a result, the unevenness of the toner image becomes small, and as shown in FIG. 3, the fixing roller 104g easily exerts pressure and heat uniformly on the toner layer, and the incomplete melting portion of the toner (Y, M, C, T) is generated. Generation is prevented and a high-quality multicolor image is stably obtained.

<Second Embodiment> As shown in FIG.
In the transfer process, first, a toner layer of the transparent toner T is formed, and then an image of each color toner Y, M, and C is developed and transferred onto the paper 102, so that the unevenness of the toner layer can be reduced as shown in the drawing. Similar to the first embodiment, a high quality multicolor image can be stably obtained.

Except for use in an OHT sheet in order to form a toner layer for improving unevenness on the lowermost layer,
Instead of the transparent toner T, white toner may be used.

<Third Embodiment> Further, as shown in FIG. 5, if a layer of the transparent toner T is formed at the image end portion (outline portion), the end portion of the colored toner image is spread by the fixing portion due to fixing. In this embodiment, it is possible to stably obtain a high-quality multicolor image as in the first embodiment.

In the above embodiment, the transparent toner T and the other toners Y, M, C and B form a single layer and have the same diameter for the sake of convenience of explanation.
Actually, one color is formed by several layers of toner. The thickness of the transparent toner layer is preferably 1 to 2 times that of the color toner layer in the first and second embodiments, and is preferably about twice that in the third embodiment.

[0027]

As is apparent from the above description, according to the present invention, in a multicolor image forming apparatus for forming a multicolor image by superposing toners of a plurality of colors, a developing device containing a colorless and transparent toner is provided. Since the colorless transparent toner is superposed on the uneven portion of the multicolor image to reduce the unevenness of the multicolor image due to the difference in the number of overlapping color toners, the fixing step is performed, so that the heat of the fixing unit is reduced. It is possible to prevent the occurrence of an incompletely melted portion of the toner by transmitting the toner to the toner image without unevenness, and to prevent the end portion of the image of the colored toner from collapsing and spreading due to fixing, so that a high quality image can be stably obtained.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a multicolor image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an overlapping state of toner layers after transfer in the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing an overlapping state of toner layers at the time of fixing in the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing an overlapping state of toner layers in a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an overlapping state of toner layers according to a third exemplary embodiment of the present invention.

FIG. 6 is a vertical cross-sectional view of a conventional multicolor image forming apparatus.

FIG. 7 is an explanatory diagram showing an overlapping state of toner layers after transfer in a conventional example.

FIG. 8 is an explanatory diagram showing an overlapping state of toner layers at the time of fixing in a conventional example.

FIG. 9A is an explanatory diagram showing a toner layer overlapping state after transfer in a conventional example, and FIG. 9B is an explanatory diagram showing a toner layer overlapping state after fixing.

FIG. 10A is an explanatory diagram showing an overlapping state of toner layers after transfer in a conventional example, and FIG. 10B is an explanatory diagram showing an overlapping state of toner layers after fixing.

[Explanation of symbols]

 1 image carrier 103 transfer drum Dy, Dm, Dc, Db developing cartridge Dt developing cartridge Y yellow toner M magenta toner C cyan toner B black toner T transparent toner

Claims (4)

[Claims] 1. A multicolor image forming apparatus for forming a multicolor image by superposing toners of a plurality of colors on each other, comprising a developing device for accommodating colorless and transparent toner, wherein the colorless and transparent toner is used for unevenness of the multicolor image. A multicolor image forming apparatus characterized in that a fixing step is performed after the unevenness of the multicolor image due to the difference in the number of overlapping color toners is reduced by superimposing it on the image forming section. 2. The multicolor image forming apparatus according to claim 1, wherein the layer of the colorless transparent toner is also formed on an image edge portion (outline portion). 3. The multicolor image forming apparatus according to claim 1, wherein the layer of the colorless transparent toner is formed on the bottom layer of the printing medium to reduce the unevenness of the multicolor image. 4. The multicolor image forming apparatus according to claim 1, wherein a white toner layer is formed on the lowermost layer of the printing medium to reduce the unevenness of the multicolor image.