JP2002214871A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device, in which an image of high quality where transferring of fogged toner in a non-image part is prevented, there is no soiling of the background or any scattering of characters. SOLUTION: In the image forming device, a toner image by transparent toner is formed on the non-image range, a toner image by color toner is formed on the image forming part, after the toner image by the transparent toner has been transferred to an intermediate transfer body and the toner image by the color toner is transferred to the intermediate transfer body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile, etc., in which a charging means, an image exposing means, a developing means and the like are arranged around an image forming body to form a toner image on the image forming body. And then transferring the toner image onto an adhesive intermediate transfer member to form an image, and particularly to an electrophotographic image forming apparatus using an adhesive intermediate transfer member to form an image with a transparent toner and a color toner. The present invention relates to an electrophotographic image forming apparatus for forming.

[0002]

2. Description of the Related Art Conventionally, as a method of forming a multi-color image, an image forming body of the same number as that of a required image and a charging means, an image exposing means and a developing means are provided around the image forming body. , The monochrome toner image formed on each image forming body,
An apparatus for superimposing a color image on an intermediate transfer member,
An apparatus that forms a color image superimposed on an image forming body by repeating charging, image exposure and development for each color by rotating one image forming body a plurality of times, and charging, image exposing and developing on one image forming body There is known an apparatus which transfers a toner image formed by an image forming method onto an intermediate transfer member, repeats the process for each color, and forms a color image superimposed on the intermediate transfer member.

[0003] In particular, an image forming body of the same number as that of a required color and an image forming process means such as a charging means, an image exposing means and a developing means are provided around the image forming body. A color image forming apparatus that superimposes a single-color toner image on an intermediate transfer member to form a color image has recently been used as a device that forms a good color image. Furthermore, as a device that reduces toner scattering and the like and forms a high-quality image, using a sticky intermediate transfer member, a single-color toner image formed on each image forming member is transferred to a sticky intermediate transfer member. 2. Description of the Related Art A color image forming apparatus that forms a color image by superimposing it on a body has been used to form a better color image.

[0004]

SUMMARY OF THE INVENTION However,
Image forming process means such as a charging means, an image exposing means, and a developing means can reduce toner scattering and the like to obtain a high-quality image, but the single-color toner image formed on each image forming body is adhered. When the image is transferred onto the intermediate transfer member having the fog, the fogging toner in the non-image area is also transferred, and a problem occurs in that background fouling occurs.

An object of the present invention is to provide an image forming apparatus which solves the above-mentioned problems, prevents transfer of fogging toner in a non-image area, and provides a high quality image free from background smear and character dust. Aim.

[0006]

An object of the present invention is to form an image by forming a toner image on an image forming body by charging, image exposure and reversal development, and then transferring the toner image onto an adhesive intermediate transfer body. Forming a toner image of a transparent toner in a non-image area, transferring the toner image of the transparent toner to the intermediate transfer member, and then forming a toner image of a color toner on an image forming unit; The image forming apparatus is characterized in that the toner image is transferred onto the intermediate transfer member.

[0007]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

An image forming process and each mechanism of an embodiment of the image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the image forming apparatus according to the present invention, FIG. 2 is a block diagram of an image processing system, and FIG. FIG. 3 is an enlarged cross-sectional view illustrating a thickness and a layer thickness of a transparent toner layer.

Referring to FIG. 1, the image forming apparatus of the present invention comprises:
It comprises an image reading section A, an image processing section B, an image forming section E and the like.

At the top of the image forming apparatus, there is provided a document table made of a transparent glass plate or the like, and a document placing section 111 composed of a document cover for covering the document D placed on the document table. Below and in the apparatus main body, there is provided an image reading unit A including a first mirror unit 112, a second mirror unit 113, a main lens 120, a color CCD 123, and the like. The first mirror unit 112 includes an exposure lamp 114 and a first mirror 115. The first mirror unit 112 is mounted in parallel with the document table and linearly movable in the horizontal direction of the drawing, and optically scans the entire surface of the document D. The second mirror unit 113 includes a second mirror 116 and a third mirror 117.
And the first so as to always maintain a predetermined optical path length.
It moves linearly in the same direction on both sides at half the speed of the mirror unit 112. Of course, the movement of the second mirror unit 113 is parallel to the platen similarly to the first mirror unit 112. The image of the document D on the document table illuminated by the exposure lamp 114 is
An image is formed on the color CCD 123 via the mirror 115, the second mirror 116, and the third mirror 117. When scanning is completed, the first mirror unit 112 and the second
The mirror unit 113 returns to the original position and waits for the next copy.

Image data of each color obtained by the color CCD 123 is subjected to image processing in an image processing section B, and laser writing is performed in an image forming section E described below as an image signal.

The image forming apparatus shown in FIG. 1 is a tandem type color image forming apparatus using an intermediate transfer member having an adhesive property as an image forming portion E, and has an adhesive transfer belt 14a which is an intermediate transfer member having an adhesive property. Are provided with five process units 10 including transparent (T), black (K), cyan (C), magenta (M), and yellow (Y).
0 is provided, and in each process unit 100, T, K, C, M, and Y toner images are formed on the photosensitive drum 10, and the toner images are superimposed and transferred on the adhesive transfer belt 14a. The transferred color toner images are collectively transferred and fixed onto recording paper as a transfer material, and are discharged outside the apparatus.

The five process units 100 all have a common structure, and only one of them will be described.

The photosensitive drum 10, which is an image forming member, is formed by forming a conductive layer and a photoconductive layer of an organic photosensitive layer (OPC) on the outer periphery of a cylindrical substrate. As a result, the conductive layer is rotated in the counterclockwise direction indicated by the arrow while being grounded.

Numeral 11 denotes a scorotron charger as charging means, which is attached to the photosensitive drum 10 in a direction perpendicular to the moving direction of the photosensitive drum 10 so as to face and be close to the photosensitive drum 10.
The photosensitive drum 1 is driven by corona discharge having the same polarity as the toner.
A uniform potential is given to 0.

Reference numeral 12 denotes K, C, M, and Y image exposures based on image data of an image section (image forming section), and a non-image area (an area of the non-image section excluding the image section) in accordance with an instruction from the control section. Alternatively, an exposure optical system that performs T image exposure in the entire area including the image portion and the non-image portion around the image portion, and a scanning optical system that performs scanning in parallel with the rotation axis of the photosensitive drum 10 using, for example, a polygon mirror. It is. Photoreceptor drum 1 uniformly charged
The latent image is formed by performing image exposure on the zero by the exposure optical system 12.

A developing device 13 containing a one-component developer composed of only negatively charged toner or a two-component developer composed of toner and carrier is provided on the periphery of the photosensitive drum 10 to hold the developer. Rotating developing roller 13
By a, the latent image on the photosensitive drum 10 is reversely developed in contact or non-contact.

Between the developing roller 13a and the photosensitive drum 10, a DC voltage V _DC or a DC voltage V _DC or an AC voltage V _DC is applied.
A developing bias voltage with _AC superimposed is applied. Since charging of the toner is a DC voltage V _DC of the same polarity (negative), do not adhere to the high V _H portion of the absolute value of the potential from the DC voltage V _DC,
The toner amount corresponding to the potential difference adheres to the portion of _VL where the absolute value of the potential is low, and the image is visualized (reversal development).

Transparent (T), black (K), cyan (C),
Magenta (M) and yellow (Y) process units
Adhesive intermediate transfer member 100 facing in parallel
The adhesive transfer belt 14a having a volume resistivity of 10^Ten-10
¹⁵Ω · cm, surface resistivity 10 ^Ten-10¹⁵Ω / □ endless base
Are modified polyimide, thermosetting polyimide
, Ethylene tetrafluoroethylene copolymer, polyolefin
Engineering of vinylidene disulfide, nylon alloy, etc.
Conductive material dispersed in plastic, thickness 0.1-1.
An adhesive layer on the outside of a 0 mm semiconductive film substrate
Silicon rubber or urethane with a thickness of about 5 to 50 μm
This is a seamless belt coated with rubber etc.
You. Adhesive transfer belt 14a is used for transfer / fixing
Roller 14f, driven roller 14e, tension roller 1
4k and stretched around the backup roller 14j
During image formation, an intermediate transfer member driving motor (not shown) is used.
The transfer / fixing roller 14f is rotated by the
At the transfer position for each color, the photosensitive drum is exposed by the primary transfer roller 14c.
The adhesive transfer belt 14a is pressed against the body drum 10 and
The transfer belt 14a is rotated in the direction indicated by the arrow in the figure.
The transfer / fixing roller 14f is outside the metal pipe (no symbol)
It is formed by providing a rubber roller layer (no symbol) on the peripheral surface.
Heating means is provided inside the transfer / fixing roller 14f.
Halogen lamp HLa is provided for transfer and fixing.
The roller 14f is heated.

A primary transfer roller 14c, which is a roller-like transfer means for each color including transparent, is provided to face the photosensitive drum 10 for each color with the adhesive transfer belt 14a interposed therebetween.
A transfer area (no symbol) for each color is formed between the adhesive transfer belt 14a and the photosensitive drum 10 for each color. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the primary transfer roller 14c for each color, and a transfer electric field is formed in a transfer area (no sign), thereby forming a photosensitive member for each color. Adhesive transfer belt 14 transfers toner image on drum 10
Transfer onto a.

The static eliminator 14m, which is a static elimination means for each color,
It is preferably constituted by a corona discharger, and removes electricity from the adhesive transfer belt 14a charged by the primary transfer roller 14c.

Upon start of image recording, a photosensitive drum driving motor (not shown) is started to rotate the photosensitive drum 10 of the transparent (T) process unit 100 in the direction shown by the arrow in FIG. The application of a potential to the T photoconductor drum 10 is started by the charging action.

After a potential is applied to the T photosensitive drum 10, a non-image area (a non-image area excluding an image area or a non-image area or a non-image area) is output by an electric signal output from a control unit described later by the T exposure optical system 12. Image exposure (image writing) of the entire area including the image area and the non-image area around the image area is started, and a static image corresponding to the non-image area by an electric signal from the control unit is formed on the surface of the photosensitive drum 10 at T. An electrostatic latent image is formed.

The latent image of T is a developing unit 1 for a transparent toner.
3, the reversal development is performed in a contact or non-contact state, and T
In accordance with the rotation of the photosensitive drum 10, a toner image of a non-image area (a non-image area excluding an image area or an entire area including an image area and its surrounding non-image area) is formed by the transparent toner of T. .

The non-image area formed of the transparent toner formed on the photosensitive drum 10 of the image forming body T by the above-described image forming process (the area of the non-image area excluding the image area or the non-image area of the image area and its surrounding area). The toner image of T in the whole area including the image portion) is 1 in T in the T transfer area (no sign).
The toner image is transferred onto the adhesive transfer belt 14a by the next transfer roller 14c.

Slightly behind the operation of the transparent (T) process unit 100, the black (K) process unit 100
Is rotated in the direction indicated by the arrow in FIG.
At the same time, the charging action of the K scorotron charger 11 causes K
Of the photosensitive drum 10 is started.

After a potential is applied to the K photosensitive drum 10, the K exposure optical system 12 synchronizes with the T toner image and performs image exposure using an electric signal corresponding to K image data of an image portion (image writing). Is started, and the photosensitive drum 10 of K is started.
An electrostatic latent image corresponding to the K image of the original image is formed on the surface of the image.

The K latent image is subjected to reversal development in a contact or non-contact state by a K developing unit 13, and a K toner image of an image portion is formed by K toner in accordance with the rotation of the K photosensitive drum 10. You.

The K of the image portion formed on the photosensitive drum 10 of K as the image forming body by the above image forming process.
In the K transfer area (no symbol), the K primary transfer roller 14c causes the non-image area (including the non-image area excluding the image area or the image area and the non-image area around the non-image area) by the K primary transfer roller 14c. (The entire area) is transferred onto the adhesive transfer belt 14a having the T toner image.

Next, the adhesive transfer belt 14a is synchronized with the C toner image, and corresponds to the C image data of the image area formed on the C photosensitive drum 10 by the cyan (C) process unit 100. The C toner image in the image area is transferred to the above-described non-image area (the area of the non-image area except for the image area or the image area and its surroundings) by the C primary transfer roller 14c in the C transfer area (no symbol). It is formed by superimposing on the K toner image on the adhesive transfer belt 14a having the T toner image of the entire area including the non-image portion).

By the same process, the superimposed toner images of T, K, and C are synchronized, and the image unit M of the image area formed on the photosensitive drum 10 of M by the magenta (M) process unit 100 is synchronized. When the M toner image in the image portion corresponding to the image data is
Of the non-image area (the non-image area excluding the image area or the entire area including the image area and the non-image area around the image area) on the adhesive transfer belt 14a having the toner image in the above-described primary transfer roller 14c. The toner images of K and C are superimposed on each other, are synchronized with the toner image of T and the superimposed toner images of K, C and M, and are processed by the yellow (Y) process unit 100 so that the Y photoreceptor is formed. The Y toner image of the image portion corresponding to the Y image data of the image portion formed on the drum 10 is transferred to the Y transfer area (no symbol).
Adhesive transfer belt 14a having a toner image of T in the above-described non-image area (the area of the non-image area excluding the image area or the entire area including the image area and the non-image area around it) by the primary transfer roller 14c The T of the non-image area (the area of the non-image area excluding the image area or the entire area including the image area and its surrounding non-image area), which is formed by being superimposed on the toner images of K, C, and M above. Transfer belt 14a having a toner image of
A superimposed color toner image of K, C, M and Y in the image area is formed on the top.

The transfer residual toner remaining on the peripheral surface of the photosensitive drum 10 for each color after the transfer is cleaned by a cleaning device 19 which is a cleaning means of the image forming body for each color.

The toner image of the non-image area of T on the adhesive transfer belt 14a (the area of the non-image area excluding the image area or the entire area including the image area and its surrounding non-image area), and the K and K of the image area In synchronization with the formation of the superposed color toner images of C, M, and Y, the sheet is fed from the sheet feeding cassette 15 serving as the transfer material storing means.
A recording paper P is provided via a timing roller 16 as a transfer material feeding means, facing a transfer / fixing roller 14f with an adhesive transfer belt 14a interposed therebetween, and a transfer roller P of a pressure roller 17b having a halogen lamp HLb therein. It is transported to the transfer area (no sign).

The pressure roller 17b is formed as a soft roller having a rubber roller layer (not numbered) having a low rubber hardness on the outer peripheral surface of a metal pipe (not numbered). A halogen lamp HLb is provided to heat the pressure roller 17b.

Preferably, the pressure of the pressure roller 17b to which a DC voltage having the opposite polarity to that of the toner is applied, and the heat and pressure of the transfer / fixing roller 14f and the pressure roller 17b cause the non-contact on the adhesive transfer belt 14a. The toner image of T in the image area (the area of the non-image area excluding the image area or the entire area including the image area and its surrounding non-image area) and the K, C, and M of the image area
After the superimposed color toner images of Y and Y are collectively transferred and fixed onto the recording paper P, they are discharged to a tray outside the apparatus through the discharge rollers 18. Y on the recording paper P
The color toner layers in the M, C, and K image areas and the non-image area around the color toner image (the area including the non-image area except the image area or the entire area including the image area and the non-image area around the image area) T
Is present.

The untransferred toner remaining on the peripheral surface of the adhesive transfer belt 14a after the transfer is transferred by a cleaning device 19a which is a cleaning means for the adhesive transfer belt provided opposite the driven roller 14e with the adhesive transfer belt 14a interposed therebetween. Will be cleaned.

As shown in FIG. 2, in the image processing section B of the present invention, the amplified analog signal (S1) of r, g, b of the image section (image forming section) obtained by the color CCD 123 is A The digital signal is converted into a digital signal of 8 to 10 bits for each pixel by the / D conversion (S2). Next, the light distribution characteristics are equalized by shading correction (S3), and the output luminance signal is subjected to complementary color conversion by density conversion (S4) and converted into 256-level density information. Further, a non-image region (a region of the non-image portion excluding the image portion or a region including the image portion and a non-image portion around the non-image portion) is determined (S71), and the non-image region is determined based on the determination of the non-image region. Image data creation with the non-image part is performed (S72). After setting the non-image area by discriminating the non-image area (the area of the non-image part excluding the image part or the area including the image part and its surrounding non-image part), the image data of the non-image part is subjected to multi-value processing. Is performed (S8B), and image exposure is performed by the T exposure optical system 12 (S9B). Color processing (S5) such as masking, UCR, and color correction is performed based on the image data of the image section (image forming section) obtained by the image data creation (S72). Masking is generally linear masking,
Alternatively, when performing advanced color correction, non-linear masking or masking using a look-up table is used.
In the UCR, an operation of removing the gray component from the three color components and replacing it with black (K) is performed, and a process of improving the reproducibility of the shadow portion and the character portion is performed. The image data of the image section (image forming section) is subjected to γ correction (S
6) is performed, and after the multi-value processing (S8A) is performed,
The image is output to the K, C, M, and Y exposure optical systems 12 (S9A), and K, C, M, and Y image exposure is performed.

As shown in FIG. 3A, the amount of adhesion (layer thickness) H _T of the transparent toner layer at the non-image portion where the color toner image does not exist on the adhesive transfer belt 14a, Amount (layer thickness) H of the color toner layer at the target pixel position where the color toner image exists in the portion (image forming portion)
The relationship with _C is preferably set as H _T = C (H _C = 0) H _T = 0 (H _C ≠ 0) H _C = h _Y + h _M + h _C + h _K. Where h _Y , h _M , h _C , h _K
Is the adhesion amount (layer thickness) of each of the Y, M, C, and K color toner images at the target pixel position. It is preferable that the thickness of the H _T as (layer thickness) is 5~15μm at maximum. The adhesion amount (layer thickness) H _T of the transparent toner layer is a constant value C where there is no adhesion amount H _C of the color toner (H _C = 0), and the maximum thickness may be 5 to 15 μm. preferable.

The arithmetic processing is performed in a circuit for determining a non-image area (a non-image area excluding an image area or an entire area including an image area and a non-image area around the image area) (S71).
To change the amount of T toner adhering to the non-image area, use T
Is performed by intensity modulation or pulse width modulation of the exposure optical system 12 described above.

As described above, by covering the non-image area except for the image forming section (image section) with the transparent toner, the transfer of the fogging toner in the non-image section when the adhesive intermediate transfer member is used is prevented. It is possible to provide an image forming apparatus capable of obtaining a high-quality image free from background dirt and having no dust.

Further, using the process described above with reference to FIG.
The entire area including the image portion and the non-image portion around the image portion is defined as a non-image region, and the non-image region is covered with transparent toner,
A superimposed color toner image of black (K), cyan (C), magenta (M), and yellow (Y) may be formed on the transparent toner image. When used, it is possible to provide an image forming apparatus in which transfer of fog toner in a non-image portion is prevented, and a high-quality image free from background smear and having no character dust can be obtained. In this case, as shown in FIG. 3B, the adhesion amount (layer thickness) of the transparent toner layer in the non-image area (the area including the image area and the surrounding non-image area) on the adhesive transfer belt 14a. H
And _T, the relationship between the deposition amount of the color toner layer (layer thickness) H _C at the target pixel position of the color toner image on the image forming portion (image _{portion), H T = C-k} · H C H C = it is preferable to set the _{h Y + h M + h C} + h K. C is a constant and h _Y ,
h _M , h _C , and h _K are adhesion amounts (layer thicknesses) of the Y, M, C, and K color toner images at the target pixel position. The k is a proportionality coefficient, H _T is varied by the adhesion amount H _C of the color toner (set) but is preferably set between 0.1 and 0.3. Since the amount of adhesion (layer thickness) H _T of the transparent toner layer changes with the amount of adhesion H _C of the color toner, the thickness is 5 to 5 in the absence of the color toner (that is, at H _C = 0). It is preferably 15 μm.

[0042]

According to the present invention, when an adhesive intermediate transfer member is used, the transfer of the fogging toner in the non-image area is prevented, and a high quality image free of background smear and having no dust is obtained. An image forming apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a block diagram of an image processing system.

FIG. 3 is an enlarged cross-sectional view showing a layer thickness of a color toner layer and a layer thickness of a transparent toner layer.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11 scorotron charger 12 exposure optical system 13 developing device 14a adhesive transfer belt 14c primary transfer roller 14f transfer / fixing roller 15 paper feed cassette 16 timing roller 17b pressure roller 100 process unit HLa, HLb halogen lamp P recording paper

Continued on the front page F-term (reference) 2H027 EA07 EB04 2H030 AB02 AD01 BB02 BB13 BB42 BB61 2H032 AA15 BA05 BA09

Claims (2)

[Claims] An image forming apparatus for forming a toner image on an image forming body by charging, image exposure and reversal development, and then transferring the toner image onto an adhesive intermediate transfer body, comprising: Is formed in a non-image area, a toner image of the transparent toner is transferred to the intermediate transfer body, and then a toner image of a color toner is formed on an image forming unit,
An image forming apparatus, wherein a toner image of the color toner is transferred onto the intermediate transfer member. 2. The image forming apparatus according to claim 1, wherein the adhesion amount of the transparent toner layer by the transparent toner is set by the adhesion amount of the color toner layer by the color toner.