JP2002108039A - Image forming device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of an image quality caused as a result when hue of a finished image is varied due to the color of a base such as the color of transfer material, to prevent deterioration of image quality by eliminating disorder of transfer condition due to ruggedness on a surface of the transfer material and to prevent turbidness in color and roughness due to mixture of white color toner image and a normal toner image provided on top of it. SOLUTION: In the image forming device provided with a multiple number of process parts 100 carrying out electrifying, image exposing and developing on an image carriers 10, one process part 100WT is provided with a developing device 13T containing transparent toner, and a developing device 13W containing white color toner and transferring is carried out after forming the toner image on the image carrier.

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 and an image forming method for forming an image using toner by electrophotography, and more particularly to an image forming apparatus and an image forming method using a white toner or a transparent toner. It is.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrophotographic method, an image forming body is uniformly charged by a charging means and then exposed to an image to form a latent image. The latent image portion is developed by the subsequent developing means to form a toner image. In a digital image forming apparatus, image exposure is performed by, for example, dots that have been subjected to pulse width modulation, and reversal development in which toner adheres to the dot portions is performed. The amount of toner adhering to the dot portion is determined by the area and potential state of the dot portion on the image forming body, the developing bias for the dot portion, the state of the charge of the toner, and the like.

A high-density image portion recorded on an image forming body by an image exposure means has a large number of dots per area,
The size of the dots is also large. On the other hand, the low-density image portion has a small number of dots per area and a small size of one dot. Thus, after development, the amount of toner adhered to the high density image portion on the image forming body is large, and the amount of toner adhered to the low density image portion is small. The difference in the density of the recorded image is expressed by the amount of toner adhering to the area of the image formed on the image forming body by development.

However, when the toner image formed on the image carrier is transferred to a transfer material, the adhesion between the image carrier surface and the toner acts strongly, and the transfer ratio of the toner at the interface is deteriorated.
There are various transfer materials, such as plain paper and resin paper, on which the toner image on the image forming body is transferred and finally becomes an image support. There are many cases. Particularly in a color image, color turbidity or the like due to coloring of the transfer material occurs. In addition, since the toner image has fine irregularities on the surface, irregular reflection of light occurs on the surface, lowering the image density range, and furthermore, the glossiness is insufficient and the image becomes rough as a whole.

Further, in a highlight portion where the amount of toner adhered is small, the above-mentioned adhesive force between the image bearing member surface and the toner acts strongly. Therefore, the transfer ratio of the toner at the interface deteriorates. As a result, it is difficult to say that the transfer is performed under constant conditions, and image deterioration occurs due to unevenness and roughness of the transfer of the toner image.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems.

An object of the present invention is to prevent the color tone of a finished image from being changed by the color of the base such as the color of the transfer material, thereby preventing the image quality from deteriorating, and causing the unevenness on the surface of the transfer material. Eliminates disturbances in transfer conditions, maintains gloss properly,
It is to prevent image quality from deteriorating.

Another object of the present invention is to prevent color turbidity and roughness caused by mixing a white toner image and a normal toner image provided thereon.

[0009]

The object of the present invention is achieved by adopting the following constitution.

[1] In an image forming apparatus having a plurality of process units for performing charging, image exposure, and development on an image forming body,
An image forming apparatus having a developing unit having a transparent toner and a developing unit having a white toner in one process unit, and forming and transferring a toner image on an image forming body.

[2] In an image forming method using an image forming apparatus having a plurality of process units for performing charging, image exposure, and development on an image forming body, a developing unit having a transparent toner in one process unit and a white toner are used. After forming a toner image on an image forming body using an image forming apparatus having a developing device having
An image forming method characterized by transferring.

[3] The image forming method according to [2], wherein only one of the developing device having a transparent toner and the developing device having a white toner is operated to form an image.

[4] The image forming method according to [2], wherein both the developing device having a transparent toner and the developing device having a white toner are operated to form an image.

[5] The image forming method according to [2], wherein the developing device having the transparent toner and the developing device having the white toner are operated to separately control the image forming areas.

[6] The image forming method according to [2], wherein an image is formed by operating a developing device having a transparent toner and a developing device having a white toner, and the amount of toner adhered is separately controlled.

[7] In an image forming apparatus having a plurality of process units for performing charging, image exposure, and development on an image forming body,
An image forming apparatus, comprising: a developing unit having a transparent toner and a developing unit having a white toner, and a process unit for forming an image by separately controlling an image forming area and a toner adhesion amount thereof is arranged in parallel. .

[8] In an image forming apparatus having a plurality of process sections for performing charging, image exposure and development on an image forming body and transferring the formed image to a transfer material, a developing device having a transparent toner and a white toner are used. An image forming apparatus, comprising: a process unit having a developing unit having a developing unit, wherein a transparent toner is used when a glossiness difference between a transfer material surface and a transparent toner image surface exceeds a specified value.

[0018]

[9] The image forming apparatus according to [8], wherein a transparent toner is used when the gloss difference is at least 15 ° or more.

[10] In an image forming apparatus having a plurality of process units for performing charging, image exposure and development on an image forming body and transferring an formed image to a transfer material, a developing device having a transparent toner and a white toner are used. An image forming apparatus, comprising: a process unit having a developing unit having a developing unit, wherein a white toner is used when a density difference between a transfer material surface and a white toner image surface exceeds a specified value.

[11] The image forming apparatus according to [10], wherein a white toner is used when the reflection density of the transfer material becomes at least 0.1 or more.

In the present invention, the normal toner image is a toner image for forming a normal image, and if it is a color image, it is yellow (Y), magenta (M), cyan (C) and black. This means at least one of the toner images of (K). Also, "corresponding to a normal toner image" means that it is in the same region as a normal toner image, and "to attach a certain amount of white toner or transparent toner" means "regardless of the amount of toner attached to the normal toner image." Means that a predetermined amount of toner (approximately constant amount) is added.

Since the glossiness of the color toner image surface is higher than that of the transfer material, if the difference in glossiness from the transfer material surface is large, an image having a strange feeling is obtained. The glossiness is preferably less than 15 °. Therefore, it is preferable to provide a transparent toner layer on the transfer material surface.

Further, if the transfer material surface is colored, light to be reflected on the transfer material surface (base surface) after passing through the toner image is:
Since the light is absorbed on this surface and does not reflect much, the background color is reflected or the image has a dull tint. When the coloring of the transfer material surface exceeds 0.1 in reflection density, there is a particular problem. Therefore, in order to whiten the transfer material surface with a white toner layer, and more preferably at the same time to make the gloss uniform, the transparent toner layer is formed. It is preferred to provide.

[0024]

First, an embodiment of the present invention will be described.

Any of the image forming apparatuses of the present invention decomposes image density information into light toner image data and dark toner image data, and uses image exposure based on light toner image data and light toner. An image forming apparatus that forms a light toner image by developing in all directions, forms a dark toner image by image exposure based on dark toner and development using dark toner, and forms an image by superimposing the light toner image. I do. Of course, the present invention is not limited to this mode, but is because it is a preferable configuration of the image forming apparatus.

(1) In this embodiment, as shown in the sectional structural views of FIGS. 1 and 2, an image is formed by superimposing light and dark toner images on an image forming body by repeating charging, image exposure and development. An image forming apparatus for forming an image by superimposing light and dark toner images of Y, M, C, and K colors in a tandem system, and is characterized by having a small size.

The color image forming apparatus shown in FIG. 1 is a tandem type color image forming apparatus using an intermediate transfer member, and a yellow (Y), magenta (M) ), Cyan (C) and black (K) are provided, and each process unit 100 forms Y, M, C, and K toner images using light and dark toners. Then, the toner image is superimposed and transferred on the transfer belt 14a,
The transferred color toner image is collectively transferred onto a recording sheet as a transfer material, fixed, and discharged outside the apparatus.

Since all four process units 100 have a common structure, only one of them will be described. The photoconductor drum 10 serving as an image forming body includes a photoconductor made of a light-transmitting conductive layer and an organic photoconductive layer (OPC) on the outer periphery of a cylindrical base formed of a transparent member such as glass or transparent acrylic resin. A layer is formed.

The photosensitive drum 10 is rotated in the counterclockwise direction indicated by an arrow with the light-transmitting conductive layer grounded by power from a driving source (not shown) or by the transfer belt 14a.

Numerals 11A and 11B denote scorotron chargers as charging means, which are mounted so as to face and close to the photosensitive drum 10 in a direction perpendicular to the moving direction of the photosensitive drum 10 and have the same polarity as the toner. A uniform potential is applied to the photosensitive drum 10 by the discharge.

The exposure optical systems 12 (L) and 12 (H)
Each is a linear exposure element (not shown) in which a plurality of LEDs (light emitting diodes) as light emitting elements for image exposure are arranged in an array in parallel with the axis of the photosensitive drum 10 and a selfoc as an equal-magnification imaging element. A lens (not shown) is configured as an exposure unit attached to a holder. Exposure optical systems 12 (L) and 12 (H) are attached to a cylindrical holding member and housed inside the base of the photosensitive drum 10. In addition, as the exposure element, a linear element in which a plurality of light emitting elements such as FL (phosphor emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used. Reference numeral 12 (L) denotes an image exposure unit that performs image exposure using image data for light toner, and 12 (H) denotes an image exposure unit that performs image exposure using image data for dark toner.

An exposure optical system 12 (L), which is an image exposure means for light toner, is provided with a scorotron charger 11 A and a developing device 13 containing light toner in the exposure position on the photosensitive drum 10.
Between (L) and the developing unit 13 (L), the photosensitive drum 10 is disposed inside the photosensitive drum 10 in a state provided on the upstream side in the rotation direction of the photosensitive drum 10. The exposure position of the exposure optical system 12 (H), which is an image exposure means for dark toner, on the photosensitive drum 10 is on the downstream side of the developing device 13 (H), and incorporates a scorotron charger 11 B and dark toner. Developing device 13
(H), the photosensitive drum 1 is provided on the upstream side in the rotation direction of the photosensitive drum 10 with respect to the developing device 13 (H).
0.

The developing device 13 (L) is a developing device which contains a one-component light toner or a two-component developer of a light toner and a magnetic carrier and performs reversal development by contact or non-contact. The developing device 13 (H) incorporates a one-component dark toner or a two-component developer of a dark toner and a magnetic carrier, which enables superposition development without destroying the toner image, and performs soft development or more preferably non-development. This is a developing device that performs reversal development by contact development.

In forming an image, the image data of each color of Y, M, C and K is divided into image data for light toner and image data for dark toner, which will be described in detail later. Image exposure is performed by the optical system 12 (L), and development with light toner is performed by the developing device 13 (L). The image data for the dark toner is subjected to image exposure by an exposure optical system 12 (H), and a developing device 13 (H).
As a result, development with dark toner is performed, and a toner image with dark toner is formed on the photosensitive drum 10 on the toner image with light toner. This toner image is transferred onto a transfer belt 14a described later at a transfer position. The transfer residual toner remaining on the drum after the transfer is cleaned by a cleaning device 19 that electrostatically collects the toner.

Process unit 1 for Y, M, C, K colors
The transfer belt 14a in which 00 is opposed in parallel has a volume resistivity of 10 ¹⁰ to 10 ¹⁵ Ω · cm and a surface resistivity of 10 ¹⁰ to 10 ¹⁵ Ω.
・ Cm ² endless belt, for example, modified polyimide,
Thermosetting polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, dispersed conductive material in engineering plastics such as nylon alloy, outside the semi-conductive film substrate of 0.1 to 1.0 mm thickness, preferably Thickness 5 as a toner filming prevention layer
This is a seamless belt having a two-layer structure and having a fluorine coating of about 50 μm. In addition, as the base of the transfer belt 14a, a semiconductive rubber belt having a thickness of 0.5 to 2.0 mm in which a conductive material is dispersed in silicon rubber or urethane rubber can be used. Transfer belt 14a
Is stretched in contact with a driving roller 14d, a driven roller 14e, a tension roller 14k, and a backup roller 14j. At the time of image formation, the driving roller 14d is rotated by a driving motor (not shown) to rotate the driving roller 14d. At the transfer position, the transfer belt 14a is pressed against the photosensitive drum 10 by the primary transfer device 14c, and the transfer belt 14a is rotated in the direction indicated by the arrow in the drawing.

A primary transfer unit 14c, which is a transfer roller for each color, is provided to face the photosensitive drum 10 for each color with the transfer belt 14a interposed therebetween, and the transfer belt 14a and the photosensitive body for each color are provided. A transfer area (no reference numeral) for each color is formed between the transfer area and the drum 10. Primary transfer unit 14 for each color
By applying a DC voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) to c, and forming a transfer electric field in the transfer area, the toner image on the photosensitive drum 10 for each color is transferred onto the transfer belt 14a. Transfer to

The static eliminator 14m, which is a static elimination means for each color,
Preferably, the primary transfer unit 1 is constituted by a corona discharger.
The transfer belt 14a charged by 4c is neutralized.

The process unit 1 of black (K) is started by starting a photoconductor drive motor (not shown) by starting image recording.
00 is rotated in the direction indicated by the arrow in the figure, and at the same time, the application of the potential to the K photoconductor drum 10 is started by the charging action of the K scorotron charger 11A.

After an electric potential is applied to the K photosensitive drum 10, an electric signal corresponding to the first color signal, that is, image data for the K light toner, is applied by the K light toner exposure optical system 12 (L). Is started, and an electrostatic latent image for light toner corresponding to the K image of the original image is formed on the surface of the K photosensitive drum 10.

The latent image for light toner is subjected to reversal development in a contact state by a developing device 13 (L) for light toner of K, and a toner image of light toner of K is formed in accordance with the rotation of the photosensitive drum 10 of K. It is formed. Then the scorotron charger 11
B and the exposure optical system 12 for the dark toner of K
(H), an electrostatic latent image for dark toner corresponding to the image of K is formed, and the developing device 13 (H) for dark toner forms the K latent image.
Is formed on the previously formed toner image of the light K toner.

The K toner image formed of the light and dark toners formed on the K photoreceptor drum 10 as the image forming body by the above-described image forming process is the first toner image in the K transfer area (no sign). The image is transferred onto the transfer belt 14a by a K primary transfer device 14c as a transfer unit.

Next, the transfer belt 14a is synchronized with the toner image of C, and the process unit 10 of cyan (C) is
0, the light color of C formed on the photosensitive drum 10 of C,
Toner image composed of dark toner is C transfer area (no sign)
, The primary transfer device 14c of C as the first transfer means
As a result, a toner image composed of light and dark toners C is superposed on the toner image composed of light and dark toners K.

By the same process, the image is synchronized with the K and C superimposed toner images, and is formed on the M photoconductor drum 10 by the magenta (M) process unit 100 using the third color signal. M corresponding to the image data of
In the M transfer area (no symbol), the M primary transfer unit 14c, which is the first transfer means, transfers the M toner images of the K and C toner images from above the K and C toner images. A toner image composed of light and dark toners is formed by being superimposed, synchronized with the superimposed toner images of K, C, and M.
The toner image formed of the light and dark toners of Y corresponding to the image data of Y based on the fourth color signal is formed on the photosensitive drum 10 of the first color in the Y transfer area (no sign). By the Y primary transfer device 14c, a toner image composed of light and dark toners of Y is superimposed on the K, C and M toner images, and the transfer belt 14a
A superimposed color toner image of K, C, M and Y is formed thereon.

In the image forming apparatus according to the present invention,
Further, a process unit 100 is added (this process unit is referred to as 100 WT). After an electric potential is applied to the photosensitive drum 10 to this process unit, image writing is started by an electrical signal corresponding to all image data by the exposure optical system 12 (W) for white toner of W, On the surface of the drum 10, an electrostatic latent image for white toner corresponding to all images of the original image is formed.

The white toner latent image is subjected to reversal development in a non-contact state by a white toner developing unit 13 (W), and the photosensitive drum 10 of the process unit 100WT is processed.
The toner image is formed by the white toner in accordance with the rotation of.

In one embodiment of the present invention, a white toner image is superimposed on the K, C, M, and Y toner images by the WT primary transfer device 14c as the first transfer means. Formed on the transfer belt 14a.
A superposed color toner image of Y and white is formed.

However, in another embodiment of the present invention, the charging by the scorotron charger 11B and the formation of the electrostatic latent image for the transparent toner corresponding to the entire image by the exposure optical system 12 (T) for the transparent toner are continued. The formed toner image is formed by the transparent toner developing unit 13 (T) so that the toner image of the transparent toner is superimposed on the previously formed toner image of the white toner by non-contact development, and then the process proceeds to the transfer step. .

The photosensitive drum 10 of the process unit 100WT which is an image forming body by the above image forming process
The toner image formed of white or further transparent toner formed on the WT transfer area (no sign)
Is transferred onto the transfer belt 14a by the WT primary transfer device 14c, which is a transfer unit of the WT.

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 means for cleaning the image forming body for each color.

Transfer from a paper feed cassette 15 as a transfer material storage means via a timing roller 16 as a transfer material feeding means in synchronism with the formation of the superimposed color toner on the transfer belt 14a and the white or further transparent toner image. The material (recording paper) P is a secondary transfer unit 14g as a second transfer unit
Is transferred to the transfer area (no sign), and a superimposed color toner image on the transfer belt 14a is transferred to the recording paper P by a secondary transfer unit 14g to which a DC voltage having a polarity opposite to that of the toner is applied.
It is transcribed all at once.

The recording paper P to which the color toner image and the white or further transparent toner image have been transferred is neutralized by a neutralizing electrode 16b which is a separating means composed of a saw-toothed electrode plate, is conveyed to a fixing device 17, and is fixed to a fixing roller 17a. The toner image on the recording paper P is fixed by applying heat and pressure between the recording paper P and the pressure roller 17b, and then discharged to a tray outside the apparatus.

The transfer residual toner remaining on the peripheral surface of the transfer belt 14a after the transfer is cleaned by a cleaning device 19a which is a transfer belt cleaning means provided opposite to the driven roller 14e across the transfer belt 14a. .

In this embodiment, Y, M,
Although the development using light and dark toners is performed for the four colors C, K, and C, the development is performed using only the dark toner for Y, M, and C, and the development using only the light and dark toners is performed only for K. Thus, the excellent effects of the present invention can be obtained.

As described above, the object of the present invention is to prevent the color tone of the finished image from being changed by the color of the base such as the color of the transfer material, thereby preventing the image quality from deteriorating. The image forming apparatus which is small in size and can easily perform color superposition, which can eliminate the disturbance of the transfer conditions caused by the above, adjust the glossiness, and prevent the image quality from deteriorating, has been described with reference to FIG.

FIG. 2 is a sectional view of an image forming apparatus showing another embodiment having the same effect. Although the process units 100 for forming Y, M, C, and K toner images using light and dark toners are arranged in parallel as in FIG. 1, in the present embodiment, an intermediate transfer member is used. The toner image is superimposed on the transfer material without any intervention. Only the differences from FIG. 1 will be described.
In synchronization with the toner image formation on
The recording paper P discharged from the printer is transported to the transport belt 14 via the timing roller 16.

Accordingly, since the white toner image or the transparent toner image formed by the process unit 100WT is first transferred onto the recording paper P, the process unit 100WT shifts to the right end in FIG. Also, the order of forming the white toner and the transparent toner image is reversed.

The transported recording paper P is charged to the same polarity as the toner by the paper charger 14m, and the rotating transport belt 1 is rotated.
4 and is transported in close contact with the process unit 10.
The toner images formed on 0WT, 100M, 100C, and 100K are transferred in a superimposed manner to form a color toner image.

The recording paper P carrying the color toner image is neutralized by the separation electrode 14n, separated from the transport belt 14 and transported to the fixing device 17, and after the color toner image on the recording paper P is fixed, the recording paper P is fixed. Discharge to an external tray.

In the embodiment shown in FIG.
For M and C, development using only the dark toner is performed, and only K is developed using the light and dark toner. Alternatively, Y is performed using only the dark toner, and K, C, and M are used as the light,
It is also possible to adopt a configuration in which development with dark toner is performed, and the excellent effects of the present invention can be achieved. Further, the present invention can also be applied to a monochrome image forming apparatus of K single color.

(2) In the present embodiment, as shown in the sectional configuration diagrams of FIGS. 3 and 4, charging, image exposure,
An image forming apparatus that forms a light toner image and a dark toner image by development and superimposes a light toner image and a dark toner image. In particular, Y, M, C,
K is an image forming apparatus that forms a color image by superimposing a color light toner image and a color dark toner image that are formed by superimposing the respective colors. It is a configuration suitable for

FIG. 3 shows an image forming apparatus for superimposing a light toner image and a dark toner image on an intermediate transfer member and transferring the superposed toner image on recording paper. This is an image forming apparatus in which a formed color image composed of a light toner and a color image composed of a dark toner are superimposed on a recording sheet. Members having the same functions as those already described in FIGS. 1 and 2 are denoted by the same reference numerals.

The color image forming apparatus shown in FIG. 3 includes a process unit 100L for forming a color image using light toner and a process unit 100L for forming a color image using dark toner on the peripheral portion of the transfer belt 14a. ,
A process unit 100H for forming a color image using dark toner is arranged in parallel. Since the process units 100L and 100H have a common structure,
The process unit 100L will be described. Y, M, C, and K are arranged from the upstream side in the rotation direction along the photosensitive drum 10.
Scorotron charger 1 as charging means for four colors
1. Four sets of an exposure optical system 12 (L) and a developing unit 13 (L) are provided. The photosensitive drum 10 whose peripheral surface has been cleaned by the cleaning device 19 is uniformly charged by the scorotron charger 11Y, and is further exposed to light toner by the exposure optical system 12 (L) Y based on Y image data for light toner. A latent electrostatic image of Y is formed, and a developing device 13 (L) Y containing a light toner forms a Y toner image with the light toner.

An M toner image of light toner is superimposed on the Y toner image of light toner by the scorotron charger 11M, the exposure optical system 12 (L) M, and the developing device 13 (L) M. Further, a scorotron charger 11C, an exposure optical system 12
(L) C, a C toner image of light toner is superposed by the developing unit 13 (L) C, and a scorotron charger 11K, an exposure optical system 12 (L) K, and a developing unit 13 are formed thereon.
(L) The K toner image of light toner is superimposed and formed by K.

Similarly, with respect to the process unit 100H, the Y, M, C,
A scorotron charger 11 for K4 color, an exposure optical system 12 (H) for exposing an image based on image data for dark toner, and a developing device 13 (H) containing dark toner, all of Y, M, C using dark toner. , K4 color toner images are superposed.

The color toner image formed of the light toner formed on the process unit 100L is transferred onto the transfer belt 14a by the primary transfer unit 14c, and is transferred to the transfer belt 14a.
The color toner image of the dark toner formed on the process unit 100H is transferred onto the color toner image of the light toner transferred thereon so as to overlap.

Next, in the present invention, a process unit 100WT is further added to this image forming apparatus as in FIG. Figure 2 shows the functions and roles of this process unit.
Is the same as After a potential is applied to the photosensitive drum 10, a scorotron charger 11 (W) for white toner of W is applied.
And an exposure optical system 12 (W) starts image writing by an electric signal corresponding to all image data, and an electrostatic latent image for white toner corresponding to all images of the original image on the surface of the photosensitive drum 10 Is formed.

The latent image for white toner is subjected to reversal development in a non-contact state by a developing unit 13 (W) for white toner, and the photosensitive drum 10 of the process unit 100WT.
The toner image is formed by the white toner in accordance with the rotation of.

In the present invention, the above K, K are transferred by the WT primary transfer device 14c as the first transfer means.
A white toner image is formed by superimposing on the C, M, and Y toner images, and a superimposed color toner image of K, C, M, Y, and white is formed on the transfer belt 14a.

However, in another embodiment of the present invention, charging by the scorotron charger 11 (T) and static electricity for the transparent toner corresponding to the entire image by the exposure optical system 12 (T) for the transparent toner are subsequently performed. After the electrostatic latent image is formed and the toner image of the transparent toner is formed on the previously formed white toner image by the transparent toner developing unit 13 (T), the process proceeds to the above-described transfer step. .

The photosensitive drum 10 of the process unit 100WT which is an image forming body by the above image forming process
The toner image formed of white or further transparent toner formed on the WT transfer area (no sign)
Is transferred onto the transfer belt 14a by the WT primary transfer device 14c, which is a transfer unit of the WT.

The color toner image superimposed and transferred on the transfer belt 14a is collectively transferred by a secondary transfer unit 14g onto a recording paper P fed through a timing roller 16, and is discharged by a discharging electrode 16b. Thereafter, the toner is fixed by the fixing device 17 and is discharged to the outside of the device.

FIG. 4 shows another embodiment in which a toner image is directly transferred to a recording sheet P without using an intermediate transfer member, so that a white toner or a transparent toner image is first transferred to the recording sheet P. . Therefore, as in FIG. 2, the process unit 100WT is located at the right end of the drawing.

The process unit 100H for forming a color toner image using a dark toner and the process unit 100L for forming a color toner image using a light toner are arranged in parallel with each other in the same manner as in FIG. . In forming an image, the process unit 10
The recording paper P discharged from the paper feed cassette is transported to the transport belt 14 via the timing roller 16 in synchronization with the formation of the toner image by the dark toner on 0H. Paper charger 1
4m, the recording paper P is conveyed in close contact with the conveyance belt 14, and a color toner image formed of the dark toner formed on the process unit 100H is transferred onto the recording paper P by the primary transfer device 1.
4c, and a color toner image of the light toner formed on the process unit 100L is synchronously transferred thereon in a superimposed manner. The recording paper P carrying the color toner image of the light and dark toners is neutralized by the separation electrode 14n, separated from the conveyor belt 14, conveyed to the fixing device 17, and discharged out of the device after being fixed.

The image forming apparatus shown in FIGS. 3 and 4 uses the process unit 100WT to change the tint of the finished image depending on the color of the base such as the color of the transfer material, and as a result, the image quality deteriorates. In addition, it is possible to prevent the transfer conditions from being disturbed due to the unevenness of the transfer material surface, thereby preventing the image quality from deteriorating.

(3) In this embodiment, Y, M,
The image density data for each of the colors C and K is divided into image density data for light toner and image density data for dark toner, and the image density data for light toner is the exposure optical system 1 for light toner.
By 2 (L), the image exposure data for the dark toner is subjected to image exposure on the photosensitive drum 10 by the exposure optical system 12 (H) for the dark toner.

FIG. 5 is a block diagram of the image processing system according to the present embodiment. An original image is read by an image reading means using a solid-state imaging device such as a CCD (F1). The amplified analog image signal output from the CCD is converted to an 8- to 10-bit digital signal by A / D conversion.
After the conversion, shading correction and subsequent image processing (1) such as color space conversion, logarithmic conversion, black generation, and color correction are performed. The image data may be read from the stored memory and subjected to the same processing.

The image data obtained in the image processing (1) is
By checking the density distribution of the data and the density difference between adjacent dots, it is possible to determine whether the original image is a halftone image such as a photograph or a picture or a character image such as a character or a line drawing. (F3).

The image data obtained in the image processing (1) is
The image data for light toner (F5A) and the image data for dark toner (F5B) are determined based on the determination result as to whether the image is a halftone image or a character image, or based on the specified output form (F3). Is created.

The decomposed image data for light and dark toners is subjected to γ correction for each toner (F6A, F6B),
MTF correction (F7A, F7B) and PWM modulation are performed (F
8A, F8B). In the PWM modulation, it is preferable to form large dots so as to improve dot reproduction in a highlight portion (low-density portion) and increase the recording unit. For example, the image data for light toner is subjected to two-pixel PWM in order to enhance the gradation, and the recording unit is increased. On the other hand, with respect to the image data for dark toner, since the emphasis is placed on the resolving power, this is performed with one pixel PWM. Note that intensity modulation may be used instead of PWM modulation.

The image data for the light toner after the PWM modulation is subjected to image exposure on the photosensitive drum 10 by the exposure optical system 12 (L) (F9A), and the image data for the dark toner after the PWM modulation is subjected to the exposure optical system. Image exposure on the photosensitive drum 10 is performed by the system 12 (H) (F9B).

It is preferable that these correction values are successively changed according to the image discrimination. That is, in the half tone, the form in which the γ correction is performed is used, the MTF correction is weakened, and the PWM recording unit is increased. On the other hand, for character images, it is preferable to make changes such as setting the γ correction higher, increasing the MTF correction, and reducing the PWM recording unit.

In the present invention, a transparent toner image and a white toner are formed in the same manner as in the color image forming process for modifying the base of the transfer material, and are formed on the same transfer material as the color toner image. In the area specified based on the area specification data, an arbitrary reforming level is realized.

Therefore, depending on the purpose, the designated area and whether to form only the transparent toner image, only the white toner image, or both of them are designated.

For example, after specifying the area, both the white toner and the transparent toner are applied to the base improvement section. To adjust the glossiness of an image, only the transparent toner is applied. Further, when the transfer material surface is colored and whitening is desired, only the white toner is adhered. When there are a plurality of these purposes, as shown in FIG. 6, different conditions are designated for different areas on the same screen.

In this case, the specific method of designating the image area is not particularly limited. For example, as shown in FIG. 7, the entire image forming area (or the size of the transfer paper) is displayed on a digitizer (tablet). Then, an area is designated using an electronic pen (touch pen) thereon, and the designated contents of each area, for example, whether to attach only the transparent toner or both the white toner and the transparent toner, are designated. The data is sent to the above-described FIG. 6F3 and used to generate white toner image data or transparent toner image.

In the image forming apparatus of the present invention, the process unit having the developing unit having the transparent toner and the developing unit having the white toner has one exposure optical system and is commonly used (FIG. 8A )) And a system in which the exposure optical system for the transparent toner and the exposure optical system for the white toner are separately provided.
Separate is preferred. As shown in FIG. 9A, even in a process section having one exposure optical system, it is possible to create both images by forming a two-level latent image and controlling the developing bias. However, it is necessary to strictly define the potential of the latent image and the development conditions, and even if it is performed, a white toner image and a transparent toner image cannot be freely formed on the same screen (FIG. 9). In (a), a region having only a transparent toner image cannot be formed). On the other hand, as shown in FIG. 8 (b), if there are separate exposure optical systems 12 (T) and 12 (W) for a white toner image and a transparent toner image, FIG.
As shown in (b), any image can be freely created.

As described above, it is preferable that the conditions can be set independently for the image data W for the white toner image and the image data T for the transparent toner image, and the amount of adhesion can be determined accordingly.

In the most frequent cases, the formation of the white toner layer and the mixing of the white toner layer with the normal color image toner to reduce the coloration of the transfer paper and the influence of the surface property on the color image will reduce the saturation. This is the formation of a transparent toner layer for suppressing the reduction. In this case, the white toner layer area and the transparent toner layer area coincide with each other and overlap with the area of the normal color image. Therefore, it is preferable to obtain the area from the normal color image data as follows.

In the image data W for the white toner image, the adhesion amounts T _K + T _Y + T _M + T _{C of} the respective color toners are obtained from the black component image signals K and the Y, M, and C image signals, and T _K + T _Y + T _M + T. _{When C} > 0, the adhesion amount T _W of the white toner is given by T _W = Z ₁ −α ₁ (T _K + T _Y + T _M + T _C ), and the image data of the white toner is formed in accordance therewith (Z ₁ is A predetermined constant, α _1, is a constant of 0.3 to 1.0).

As a result, a constant amount of toner is always adhered to the image area as shown in FIG. 10 (in this case, α ₁ is set to 1), thereby preventing the influence of surface irregularities and coloring of the transfer material, The layer thickness is constant in the entire image area. According to this method, it is more preferable to always adhere a fixed amount of white toner (that is, determine the amount of adhered white toner by setting T _W = Z ₁ ).

Similarly, in the image data T for a transparent toner image, the adhesion amount T _T of the transparent toner is given by T _T = Z ₂ −α ₂ (T _K + T _Y + T _M + T _C ) (Z ₂ is predetermined. constant, α ₂ is 0.3 to 1.0
Is determined by forming image data corresponding to this.

However, as for the amount of adhesion T _T of the transparent toner, the object of the present invention is to adjust the glossiness and to prevent the white toner layer from mixing with the normal toner layer, so that T _T = Z ₃ (Z ₃ is a predetermined constant) in some cases.

In the above equation, the adhesion condition of the white toner and the transparent toner and the threshold value for the adhesion amount of each color toner are set to 0 or more. It is preferable to control. Specifically, when the gloss difference between the transfer material surface and the transparent toner image surface becomes at least 15 ° or more, it is preferable to use the transparent toner. When the reflection density of the transfer material becomes at least 0.1 or more, it is preferable to use a white toner. As a result, it is possible to reduce the difference in glossiness between the transfer paper and the toner image, and to reduce the influence of the base color.

Further, it is preferable to control the amount of the white toner or the transparent toner to be changed according to the transfer paper as the base.

The area where the white toner or the transparent toner adheres may be the same as the image area, but may be one to two times larger than the image area.
It is preferable to form a white toner image or a transparent toner image by spreading dots. Further, the white toner and the transparent toner image may be formed only in the gradation image region by the above-described image determination, and the white toner image or the like may not be formed in the non-gradation region such as the character portion region.

By forming the transparent toner image on the white toner image as described above, it is possible to effectively prevent the white toner image and the other toner images from being mixed at the time of transfer or fixing and causing color turbidity. The effect can be expected. However, it goes without saying that in the embodiment of the present invention, either a white toner image or a transparent toner image suitable for the purpose of improvement may be provided.

Whatever the purpose of the invention is used,
The white toner can be produced in the same manner as the Y, M, and C toners, and the coloring agent is TiO ₂ , ZnO, M
A white pigment such as gO is used. Also, the transparent toner is
What is necessary is just to use what is usually used as a binder resin (also called a binder resin) of a toner, without adding a coloring agent.

The amount of the white toner image and the transparent toner image on the transfer material is not particularly limited. However, in order to uniformly cover the transfer paper, the toner layers of the white toner and the transparent toner are converted in terms of the toner resin amount. Preferably it is 0.3 to 2.0 layers, more preferably 0.5 to 1.0 layers.

[0099]

According to the present invention, the color of the finished image is prevented from being changed by the color of the base such as the color of the transfer material, and as a result, the image quality is prevented from deteriorating. Disturbance in transfer conditions can be eliminated, and image quality can be prevented from deteriorating.

Further, color turbidity and roughness due to mixing of a white toner image and a normal toner image provided thereon can be prevented by interposing a transparent toner image therebetween.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus according to an embodiment of a first invention.

FIG. 2 is a cross-sectional configuration diagram of the image forming apparatus according to the embodiment of the first invention.

FIG. 3 is a sectional configuration diagram of the image forming apparatus according to the embodiment of the first invention;

FIG. 4 is a cross-sectional configuration diagram of the image forming apparatus according to the embodiment of the first invention.

FIG. 5 is a block diagram of an image processing system.

FIG. 6 is an exemplary view for explaining that different conditions are designated in different areas on the same screen;

FIG. 7 is a view for explaining an area designation method.

FIG. 8 is a view for explaining installation of an exposure optical system for transparent toner and white toner.

FIG. 9 is a diagram illustrating installation of an exposure optical system for transparent toner and white toner.

FIG. 10 is a diagram illustrating that a constant amount of toner is always used in an image area.

[Explanation of symbols]

 Reference Signs List 10 photoconductor drum 11A, 11B scorotron charger 12 (L), 12 (H) exposure optical system 13 (L), 13 (H) developing device 14 transport belt 14a transfer belt 14c primary transfer device 14g secondary transfer device 15 Paper cassette 16 Timing roller 17 Fixing device 100Y (M, C, K) Process unit 100L (H) Process unit

Claims (11)

[Claims] 1. An image forming apparatus having a plurality of processing units for performing charging, image exposure, and development on an image forming body, wherein one processing unit includes a developing device having a transparent toner and a developing device having a white toner, An image forming apparatus, wherein a toner image is formed on an image forming body and then transferred. 2. An image forming method using an image forming apparatus having a plurality of process sections for performing charging, image exposure and development on an image forming body, wherein one process section includes a developing device having a transparent toner and a white toner. An image forming method, wherein a toner image is formed on an image forming body using an image forming apparatus having a developing device and then transferred. 3. The image forming method according to claim 2, wherein only one of the developing device having a transparent toner and the developing device having a white toner is operated to form an image. 4. The image forming method according to claim 2, wherein both the developing device having the transparent toner and the developing device having the white toner are operated to form an image. 5. The image forming method according to claim 2, wherein the developing device having the transparent toner and the developing device having the white toner are operated to separately control the image forming areas. 6. The image forming method according to claim 2, wherein a developing device having a transparent toner and a developing device having a white toner are operated to form an image, and the toner adhesion amount is separately controlled. 7. An image forming apparatus having a plurality of processing units for performing charging, image exposure, and development on an image forming body, comprising: a developing device having a transparent toner and a developing device having a white toner; An image forming apparatus, wherein processing units for forming an image by individually controlling the toner adhesion amount are arranged in parallel. 8. An image forming apparatus having a plurality of process units for performing charging, image exposure, and development on an image forming body and transferring a formed image to a transfer material, comprising a developing unit having a transparent toner and a white toner. Has a process section with a developing unit,
An image forming apparatus, wherein a transparent toner is used when a gloss difference between a transfer material surface and a transparent toner image surface exceeds a specified value. 9. The method according to claim 8, wherein a transparent toner is used when the gloss difference is at least 15 ° or more.
The image forming apparatus as described in the above. 10. An image forming apparatus having a plurality of process units for charging, exposing and developing an image on an image forming body and transferring a formed image to a transfer material, comprising a developing unit having a transparent toner and a white toner. An image forming apparatus, comprising: a process unit having a developing device, wherein a white toner is used when a density difference between a transfer material surface and a white toner image surface becomes a specified value or more. 11. The reflection density of the transfer material is at least 0.1.
11. The image forming apparatus according to claim 10, wherein a white toner is used in the above case.