JP2001318499A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device using toner of low and high density and for selecting how to use the toner of low and high density in accordance with an image. SOLUTION: An image data changing operation of changing the using ratio of the low-density toner to the high-density toner is performed by a means for dividing the image density data into image data for the low density toner and image data for the high density toner in accordance with the image or in accordance with the purpose while including the use of only the high density toner or the low density toner.

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 for forming an image using toner by electrophotography,
In particular, the present invention relates to an image forming apparatus that develops an image by using two types of toners of the same color, a light color toner and a dark color toner, and forms an image.

[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.

[0004]

However, it is difficult to form an image with good gradation with one type of toner. Particularly in a highlight portion (low-density portion), the attachment of a very small amount of toner per area is unstable due to the small size of the dot, so that image unevenness is likely to occur and it is difficult to obtain stable gradation. In the high-density portion, the toner is in an excessively toner-adhered state, and the image density is likely to be saturated, and the gradation property in a wide area is not obtained.

The present invention is applied to a monochrome or color image forming apparatus, and includes two kinds of toners of the same color, a light color and a dark color (for example, cyan (C), magenta (M), yellow (Y), An image forming apparatus that performs development using any one of black (K), and performs image density data processing in combination with the use of image data for light and dark toners, thereby obtaining light colors corresponding to images. It is a first object of the present invention to provide a small-sized image forming apparatus using dark toner, and an image forming apparatus capable of changing an image to a glossy, non-glossy, or OHP image according to the purpose. .

By performing the processing of the image density data in combination with the use of the image data for the light and dark toners, the continuity of the image quality and the continuity of the flatness from the low density portion to the high density portion are maintained. A second object is to provide an image forming apparatus excellent in transferability.

[0007] An image forming apparatus using light and dark toners, which is particularly suitable for a small-sized color printing apparatus, and selection of how to use light and dark toners according to an image. For example, only dark toner is selectively used for business documents. It is a third object to provide an image forming apparatus suitable for performing the above.

[0008]

A first object of the present invention is to provide an image forming apparatus which performs image exposure and development with light toner and image exposure and development with dark toner based on image data.
2. An image forming apparatus according to claim 1, wherein said means for decomposing the image density data into image data for light toner and image data for dark toner performs image data change for changing the usage ratio of light and dark toner. ) And an image forming apparatus that performs image exposure and development with light toner based on image data, and image exposure and development with dark toner, using light toner having higher gloss than dark toner, The means for decomposing the image data into the image data for dark toner is achieved by an image forming apparatus (invention of claim 2) wherein the image data is changed to change the glossiness of the output image.

A second object of the present invention is to provide an image forming apparatus which performs image exposure and development with light toner based on image data, and image exposure and development with dark toner based on image data. An image forming apparatus (invention of claim 6), wherein the means for decomposing into image data has light toner image data in a high density portion; and image exposure and development with light toner based on the image data. An image forming apparatus that performs image exposure and development with a dark toner and has light and dark toners on a transfer material, wherein the light toner is an upper layer of the dark toner on the transfer material. Invention 8) and an image forming apparatus that performs image exposure and development with light toner and image exposure and development with dark toner based on image data, and has light and dark toner on a transfer material. Large cities than glossiness of the dark toner and glossiness of the toner, the image forming apparatus characterized by having a light toner image data even in a high density portion (claim 1
0 invention).

A third object of the present invention is to provide an image forming apparatus for performing image exposure and development with light toner and image exposure and development with dark toner based on image data. An image forming apparatus for forming an image by superimposing light and dark toner images by repetition; developing with image exposure and light toner based on image data; and developing with image exposure and dark toner based on image data In an image forming apparatus that performs development, a light toner image and a dark toner image are formed on two image forming bodies by charging, image exposure, and development, respectively, and the light and dark toner images are overlapped. This is achieved by a forming apparatus (the invention of claim 13).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The image forming apparatus of the present invention has
The image density information is decomposed into light toner image data and dark toner image data, and a light toner image is formed by image exposure based on the light toner image data and development using the light toner. Is an image forming apparatus which forms a dark toner image by image exposure based on image formation and development using a dark toner, and forms an image by superimposing a light toner image. First, the structure of a preferable image forming apparatus will be described.

(1) In this embodiment, as shown in the cross-sectional 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 (invention of claim 12), in which light in Y, M, C, and K colors,
A color image forming apparatus for forming a color image by superimposing a dark toner image is characterized in that it has a small shape.

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 photoreceptor drum 10 as an image forming body includes a light-transmitting conductive layer and an organic photosensitive layer (OPC) on the outer periphery of a cylindrical base formed of a light-transmitting member such as glass or light-transmitting acrylic resin. Is formed.

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

Reference numerals 11A and 11B both denote scorotron chargers as charging means, which are 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, 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 11A and a developing device 13 having light toner built therein.
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 four colors of Y, M, C and K
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 device 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 member 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

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

A black (K) process unit 1 is started by starting a photosensitive member drive motor (not shown) when image recording is started.
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 a potential is applied to the K photosensitive drum 10, an electric signal corresponding to the first color signal, that is, the 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 superposed toner images of K and C, and is formed on the photosensitive drum 10 of M by the process unit 100 of magenta (M). 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). The Y primary transfer device 14c forms a toner image composed of Y light and dark toners on the K, C and M toner images in a superimposed manner, and the transfer belt 14a
A superimposed color toner image of K, C, M and Y is formed thereon.

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.

In synchronization with the formation of the superimposed color toner image on the transfer belt 14a, the recording paper P is transferred from the paper feed cassette 15 as the transfer material storage means via the timing roller 16 as the transfer material supply means to the second transfer. The superimposed color toner image on the transfer belt 14a is recorded by the secondary transfer device 14g, which is conveyed to a transfer area (no symbol) of the secondary transfer device 14g, which is a unit, and to which a DC voltage having a polarity opposite to that of the toner is applied. It is transferred onto the paper P at once.

The recording paper P on which the color toner image has been transferred is
The charge is removed by a charge removing electrode 16b, which is a separating means formed of a sawtooth electrode plate, conveyed to the fixing device 17, and heat and pressure are applied between the fixing roller 17a and the pressure roller 17b, so that the recording paper P After the toner image is fixed,
It is discharged to a tray outside the device.

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 the present embodiment, the process is such that the light toner adheres to the photosensitive drum 10 of the process unit 100, and then the dark toner adheres. Good transfer of dark toner is achieved. Even if light toner previously attached due to image exposure is scattered, it is not noticeable. The following effects are obtained: the effect is small even if the color mixture of the light toner is present in the developing device 13 (H) located on the downstream side.

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. In this case, the developing device is an image forming apparatus provided with five sets.

As described above, a small-sized image forming apparatus in which color reproduction is easily performed by widening a reproduction area using light and dark toners is shown in FIG.
Explained by. FIG. 2 is a cross-sectional configuration diagram of an image forming apparatus showing another embodiment having the same effect. Pale
Although the process units 100 for forming Y, M, C, and K toner images using dark toner are arranged in parallel with each other as in FIG. 1, in the present embodiment, an intermediate transfer member is used. Instead, the toner image is superimposed on the transfer material. Only the differences from FIG. 1 will be described. In the image formation, the recording paper P discharged from the paper feed cassette 15 is synchronized with the toner image formation on the process unit 100 by the timing roller 16.
Is transported to the transport belt 14 via the

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.
The toner image formed of the light and dark toners of Y formed on the process unit 100Y is transferred onto the recording paper P by the primary transfer unit 14c, and the process units 100M and 100C are transferred onto the toner image. , 100K, M, C, and K toner images formed of light and dark toners are transferred in an overlapping 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 conveyor belt 14 and conveyed to the fixing device 17, where the color toner image on 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 may be performed, and only K may be developed using the light and dark toner. Alternatively, Y may be developed using only the dark toner, and K, C and M may be developed using the light toner.
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 obtained. 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 in which a light toner image and a dark toner image are formed by development and the light and dark toner images are superimposed on each other, and in particular, Y, M, C, K is a color image forming apparatus that forms a color image by superimposing a color light toner image formed by superimposing the respective colors and a color dark toner image. It is a configuration suitable for

FIG. 3 shows an image forming apparatus in which a light toner image and a dark toner image are superimposed on an intermediate transfer member and then transferred onto recording paper. FIG. 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 on the peripheral portion of the transfer belt 14a and a process unit 100L for forming a color image using dark toner. ,
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 a scorotron charger 11M, an exposure optical system 12 (L) M, and a 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, for the process unit 100H, 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 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. Light transferred by being superimposed on the transfer belt 14a,
The color toner image by the dark toner is
The sheet is collectively transferred by a secondary transfer unit 14g onto a recording sheet P fed through the printer 6 and is discharged by a discharging electrode 16b. Thereafter, the sheet is fixed by a fixing device 17 and discharged to the outside of the device.

FIG. 4 shows another embodiment. As in FIG. 3, a process unit 100H for forming a color toner image using dark toner and a process unit 100L for forming a color toner image using light toner. Are arranged side by side facing the conveyor belt 14. In the image formation, the recording paper P discharged from the paper supply cassette is conveyed to the conveyance belt 14 via the timing roller 16 in synchronization with the formation of the toner image by the dark toner on the process unit 100H. The recording paper P is transported in close contact with the transport belt 14 by the paper charger 14m, and a color toner image formed by the dark toner formed on the process unit 100H is transferred onto the recording paper P by the primary transfer unit 14c. Process unit 100L synchronized with above
The color toner image of the light toner formed thereon is transferred in an overlapping 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 can obtain continuous high-quality images with gradation by using the process units 100L and 100H. The light and dark toners can be easily used according to the image or the purpose of use, for example, by forming an image only by using the image.

(3) In the present invention, Y, M, C, K
The image density data for each color is divided into image density data for light toner and image density data for dark toner. The image density data for light toner is
By (L), the image density 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 this 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 light and dark toner image data are 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 light-toner image data after the PWM modulation is subjected to image exposure on the photosensitive drum 10 by the exposure optical system 12 (L) (F9A), and the dark-toner image data after the PWM modulation is exposed to light. 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.

(4) For an image forming apparatus using a light toner and a dark toner, in order to obtain a sufficient effect according to the present invention, for example, the toner adhesion amount shown in FIG. It is desirable to have a relationship of concentration. The density difference between the light and dark toners is caused by the difference in the amount of the pigment contained in the toner particles. Further, the amount of toner adhered at the time of saturation depends on the toner particle size. For example, for a dark toner, the amount of toner adhering to white paper is 1 mg / c.
The recording density becomes saturated at about m ² . It is necessary that the saturated concentration value _Dmax (H) in the saturated state be 1.7 to 2.5. As shown in FIG. 6, the density value at the place where the saturation is substantially reached is defined as D _max (H). To be exact, the concentration gradually increases as shown by the broken line.

On the other hand, the density of the light toner does not reach a saturated state when the amount of toner attached to white paper is 1 mg / cm ² , for example. When the light toner has the same toner adhesion amount as the dark toner reaching the saturation density value, that is, the recording density D of the light toner when the dark toner concentration is saturated.
It is necessary that (L) is between 0.3 and 0.8.
The ratio between the recording density D _S (L) when a light toner having a toner adhesion amount of, for example, 0.5 mg / cm ² before the toner adhesion amount on the white paper reaches the saturation density value,
That is, the gradient ratio D of the recording density between the light toner and the dark toner
It is necessary to be between _{S (L) / D S (} H) = 0.2~0.5.

The recording density needs to have the above-described relationship between the dark toner and the light toner, but the toner particle diameter and the charge amount may be the same for the light and dark toners. preferable. For toner particle size,
Because both light and dark toners ensure image quality and developability,
It is preferable that the volume average particle size is between 3 and 10 μm, and even if there is a difference, it is ± 20% or less. The charge amount is between 5 and 30 .mu.C / g for both the light and dark toners. In particular, when the toner particle size is small, a high charge amount is required. Preferably, there is. By satisfying these conditions,
A similar γ characteristic can be obtained between the light and dark toners, and the design can be made so that the sum of the adhesion amounts of the light toner and the dark toner in the middle to high density areas is almost the same and the change in the recording density is linear. It will be easier.

Note that the gradation characteristics shown in FIG. 6 also change depending on the toner particle size and the contained coloring material. In the case of a small particle size toner, the toner may be saturated even with a smaller amount of adhesion of 0.5 mg / cm ² , but the saturation density and the slope ratio are important in designing a light toner and a dark toner.

(5) In this embodiment, in the image forming apparatus shown in FIGS. 1 to 4 using light and dark toners, for example, image data for light toner and image data for dark toner are converted from image density data. The decomposing means changes the image data to change the usage ratio of the light and dark toners (the invention of claim 1), and uses light toner having a higher gloss than the dark toner to convert the image density data. A means for decomposing into image data for light toner and image data for dark toner changes the image data to change the glossiness of the output image.
Is done.

That is, in the block diagram of the image processing system shown in FIG. 5, in the output mode (F3), the change of the image data using only the dark toner, the change of the image data to change the usage ratio of the light and dark toners, The change of the image data using only the light toner is selected.

In this embodiment, whether the output image is a business document, a high-quality image such as a photograph,
Depending on the output form, such as whether the image is a P image or the like, selection is made, or the expression area of the image is expanded according to the specified output form. FIG. 7 shows the decomposed image data of.

Change of image data using only dark toner Used for business documents. Since the light toner is not used, the reproducibility of low density is not good, but the reproducibility of non-glossy and high density portions such as characters is good. The amount of toner used is the smallest compared to the amount of toner used. If the image is compressed by binarization or the like, the amount of memory can be reduced, so that it is suitable for changing image data for a printer.

Change of Image Data to Change Usage Ratio of Light and Dark Toners Reproduction from low to high density is improved by using light and dark toners. By increasing the amount of the light toner used, uniformity of the surface gloss can be realized (FIG. 7). In particular, when a low-melting toner is used as the light toner, the glossiness can be improved.

Change of image data using only light toner Used for OHP and photographic images. In this case, since the dark toner is not used, the saturation density value is not high. However, since the light toner has a high translucency, a clear projected image can be obtained by using only the light toner as the OHP developer. Further, since the photographic image has a low image density and is faint, an image in which the gradation is emphasized can be obtained.

(6) In this embodiment, in the image forming apparatus shown in FIGS. 3 and 4 using light and dark toners, the image density data is decomposed into light toner image data and dark toner image data. The means for performing the operation includes the image data for the light toner even in the high-density area (the invention of claim 6), and the light toner becomes the upper layer of the dark toner on the transfer material (the invention of claim 8). The glossiness of the toner is set to be larger than the glossiness of the dark toner, and the image data for the light toner is included even in the high density portion.
Is done.

As already described with reference to FIG. 5, the image data obtained in the image processing (1) is a result of area discrimination as to whether the image is a halftone image or a character image, or a designated output. Based on the form (F3), image data (F5A) for light toner and image data (F5B) for dark toner are created. FIG. 8 is an explanatory view showing a state in which image data is decomposed into light and dark toner image data.
FIG. 8A shows image data for a light and dark toner when a halftone image is a character image, and FIG. 8B shows light and dark toner images depending on whether the image data is a halftone image or a character image.
This shows a state in which the composition ratio of the image data for dark toner is changed. That is, image data that uses a large amount of light toner is created for a halftone image, and image data that uses a large amount of dark toner is created for a character image in accordance with the area determination result.

In the present embodiment, the image data for the decomposed light toner in the high-density portion should be originally the image data indicated by the dotted line, but the image data for the dark toner is indicated by the solid line. The image data for light toner is provided in addition to the data, and the image data for light toner is created such that the adhesion ratio of the light toner is between 3% and 30% in the maximum density portion. In a high-density portion, even a light toner image having a light toner adhesion ratio in such a range can be used without affecting the printed image density because the color tone of the toner is light. It should be noted that the dark toner image data need not be created for the low density portion.

Since the light toner is present up to the high density portion, the continuity of the image quality is maintained. Since the light toner image always exists in the dark toner image portion, the flatness of the adhered toner is continuous and excellent. Transferability can be obtained.

Further, by setting the glossiness high by, for example, lowering the melting point of the light toner to be used as compared with the dark toner, gloss can be uniformly obtained over the entire printed image.

The above results have been obtained based on a number of experimental studies by the present inventor, and the images in which the light toner exists even in the high-density portion have been described with reference to FIGS. 3 and 4, for example. As shown in FIG. 9, the light toner is present in the upper layer of the dark toner on the recording paper as the transfer material by the image forming process, so that the uniform glossiness, the depth of the image, and the continuity of the image on the printed image are reduced. And the difference that the dark toner is superior to that existing in the upper layer of the light toner.

[0071]

According to the present invention, a small-sized image forming apparatus using light and dark toners corresponding to an image is provided.
Further, an image forming apparatus which can obtain an image according to a purpose such as glossy, non-glossy, or OHP image is provided.

According to the present invention, an image forming apparatus is provided in which continuity of image quality and continuity of flatness from a low density portion to a high density portion are maintained and transferability is excellent. became.

According to the twelfth and thirteenth aspects, an image forming apparatus suitable as a small-sized color printing apparatus and an image forming apparatus capable of selecting how to use light and dark toners according to an image are provided. Was.

[Brief description of the drawings]

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

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

FIG. 3 is a cross-sectional configuration diagram of the image forming apparatus according to the embodiment.

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

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

FIG. 6 is a graph showing a relationship between a toner adhesion amount and a print image density.

FIG. 7 is an explanatory diagram of an embodiment showing a state in which image data is decomposed.

FIG. 8 is an explanatory diagram of another embodiment showing a state in which image data is decomposed.

FIG. 9 is an explanatory diagram showing the state of toner adhesion.

[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 (13)

[Claims] 1. An image forming apparatus which performs image exposure and development with light toner based on image data and image exposure and development with dark toner based on image data, decomposes the image density data into image data for light toner and dark toner. An image forming apparatus configured to change image data for changing a usage ratio of light and dark toners. 2. An image forming apparatus which performs image exposure and development with light toner based on image data, and image exposure and development with dark toner, uses a light toner having a gloss higher than the dark toner, An image forming apparatus characterized in that the means for decomposing into image data for toner and image data for dark toner performs image data change for changing the glossiness of an output image. 3. The image forming apparatus according to claim 1, wherein the image data is changed to use only the dark toner. 4. The image forming apparatus according to claim 1, wherein the image data is changed to use only the light toner. 5. The image forming apparatus according to claim 1, wherein the image data is changed to change the usage ratio of the light and dark toners. 6. An image forming apparatus which performs image exposure and development with light toner based on image data and image exposure and development with dark toner, decomposes the image density data into light toner and dark toner image data. An image forming apparatus, wherein the image forming device has light toner image data in a high density portion. 7. The image forming apparatus according to claim 6, wherein the ratio of the amount of light toner adhering in the highest density portion is 3 to 30%. 8. An image forming apparatus which performs image exposure and development with light toner and image exposure and development with dark toner based on image data, and has light and dark toner on a transfer material.
An image forming apparatus, wherein a light toner forms an upper layer of a dark toner on a transfer material. 9. The image forming apparatus according to claim 8, wherein the ratio of the amount of light toner adhering in the highest density portion is 3 to 30%. 10. Performing image exposure and development with light toner and image exposure and development with dark toner based on image data,
In an image forming apparatus having light and dark toners on a transfer material, the gloss of the light toner is set to be larger than the gloss of the dark toner,
An image forming apparatus having image data for light toner even in a high density portion. 11. The image forming apparatus according to claim 10, wherein the ratio of the amount of light toner adhering in the highest density portion is 3 to 30%. 12. An image forming apparatus that performs image exposure and development with a light toner based on image data and image exposure and development with a dark toner, by repeating charging, image exposure and development on an image forming body. An image forming apparatus for forming an image by superimposing toner images. 13. An image forming apparatus that performs image exposure and development with light toner based on image data and image exposure and development with dark toner based on charging, image exposure and development on two image forming bodies. And a dark toner image, respectively, and superimpose the light and dark toner images.