JP2002229365A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device having a fixing device capable of shortening warming-up time by preventing irregular toner at the time of fixing, preventing the occurrence of irregularities in an image due to the spread caused by the crush of toner, and making the width of a nip part small. SOLUTION: In this image forming device, flat toner is used as the toner, and electric field making the flat toner act on the surface of transfer material in a flat state is formed, and the flat toner stuck in the flat state on the transfer material by a flattening part is fixed on the transfer material under a pressuring condition by a fixing means.

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 having a fixing device used for forming an image such as a copying machine, a printer, a facsimile, etc.
The present invention relates to an image forming apparatus that improves fixing performance.

[0002]

2. Description of the Related Art After forming a toner image on an image forming body using a spherical or irregular shaped toner produced by a usual pulverization method or polymerization method, an image to be transferred and fixed on a transfer material is formed. Forming device and superimposing the toner image on the image forming body, forming a superimposed color toner image on the image forming body, then transferring the color toner image on the transfer material at once,
The toner image formed on the image forming body is sequentially transferred to the intermediate transfer body using the image forming apparatus to be fixed or the toner whose color is changed for each image forming unit, and the superimposed color toner image is transferred to the intermediate transfer body. After forming on the surface, the color toner image on the intermediate transfer body is collectively transferred to the transfer material, and the image created by an image forming apparatus or the like has a large amount of toner consumption. It was difficult to get image quality. Further, since the toner consumption is large, the toner layer becomes thick and the transfer rate is deteriorated, so that a high-density image cannot be obtained. Further, toner scattering occurs and a good image cannot be obtained. In particular,
This problem is remarkable in the case of superposed color toner images, and the fixability is poor.

Until now, to obtain a print-like image, attempts have been made to reduce the toner consumption by reducing the particle size of the toner, eliminate irregularities on the surface, and obtain uniform gloss. As the particle size of the toner decreases, the covering power of the toner decreases, and sufficient image density cannot be obtained.
In addition, image forming processes such as development, transfer, and cleaning of the image forming body are difficult, and the image quality of a print-like image cannot be obtained by an electrophotographic image forming method. When the toner particle size is 2
When toner particles having a small particle size of about 3 μm are used, when the toner particles are inhaled, a disease such as pneumoconiosis may be caused, which is not preferable in terms of safety and health.

When a color image (25% printing rate) is formed by superposing color toners by electrophotography using a color toner having a spherical or irregular shape having a particle diameter of about 5 μm and having no worry about pneumoconiosis, etc. The toner consumption is about 90 mg per A-4 size print, and development, transfer,
In fixing, a thick toner layer is handled. For this reason, toner scattering occurs in the toner image, and irregularities occur on the image surface, so that the gloss difference between the toner-attached portion and the base portion increases, so that it is not possible to form print-like image quality at present.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the inventors of the present invention have proposed a method of thinning and flattening a toner image using a developer using a flat toner, particularly, a superposition of color toners. We are trying to make the image thinner and flatter,
When the toner is fixed under high pressure due to the disturbance of the flat toner (turbulence of the toner image) at the time of fixing (particularly, the superposed color toner image has a large toner layer because the toner layer becomes thick, and high pressure is required). It is necessary to increase the width of the nip portion due to the collapse of the toner and the spread of the toner image, and the spread of the collapse of the toner. Needs to be wide), which causes a problem that the warm-up time becomes long.

The present invention solves the above-mentioned problems, prevents toner disturbance during fixing, prevents occurrence of image disturbance due to spread of toner collapse, and makes it possible to reduce the width of a nip portion. It is an object of the present invention to provide an image forming apparatus having a fixing device for shortening a warm-up time.

[0007]

An object of the present invention is to form an electrostatic latent image on an image forming body, develop the electrostatic latent image with a developer containing a toner, and form a toner image on the image forming body. After forming the toner image, in an image forming apparatus that transfers the toner image onto a transfer material and fixes the toner image on the transfer material by a fixing device, the toner is flat toner, and the flat toner is fixed by the fixing unit. Forming an electric field acting on the surface of the transfer material in a flat state, and fixing flat toner adhered in a flat state on the transfer material in a flat portion to the transfer material under pressure. This is achieved by a device (first invention).

Another object of the present invention is to form an electrostatic latent image on an image forming body and develop the electrostatic latent image with a developer containing toner to form a toner image. After forming a color toner image to be superimposed on the image forming member by repeating the formation, the color toner image on the image forming member is collectively transferred onto a transfer material, and the color toner image on the transfer material is collectively transferred. In the image forming apparatus for fixing the toner by a fixing device, the toner is a flat toner, and the fixing unit forms an electric field that causes the flat toner to act on the surface of the transfer material in a flat state, and a flat portion on the transfer material. The second aspect of the present invention is achieved by an image forming apparatus (second invention), wherein the superimposed flat toner adhered in a flat state is fixed to the transfer material under pressure.

Another object of the present invention is to form an electrostatic latent image on an image forming body and develop the electrostatic latent image with a developer containing toner to form a toner image. A plurality of image forming units for forming the toner images thereon are arranged on an intermediate transfer body, and the toner images formed on the image forming bodies are sequentially transferred to the intermediate transfer body by using toner of different colors for each image forming unit. Transfer to the body, forming a superimposed color toner image on the intermediate transfer body, and then collectively transferring the color toner image on the intermediate transfer body onto a transfer material to form a color image on the transfer material. In an image forming apparatus for fixing a toner image by a fixing device, the toner is a flat toner,
The fixing means forms an electric field which acts on the surface of the transfer material in a flat state, and the superimposed flat toner adhered to the transfer material in a flat portion at the flat portion is fixed to the transfer material under pressure. This is achieved by an image forming apparatus (third invention).

[0010]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope. In the following description of each image forming apparatus and each fixing device in the embodiments, members having the same functions and structures are denoted by the same reference numerals or symbols.

First, examples of an image forming apparatus using flat toner as a developer will be described with reference to FIGS. FIG. 1 is a cross-sectional view of a color image forming apparatus showing a first example of an embodiment of an image forming apparatus using flat toner according to the present invention, and FIG. 2 is an image forming apparatus using flat toner according to the present invention. FIG. 3 is a sectional configuration diagram of a color image forming apparatus showing a second example of the embodiment of the apparatus, and FIG.
FIG. 4 is a cross-sectional configuration view of a color image forming apparatus showing a third example of an embodiment of an image forming apparatus using flat toner according to the present invention. FIG. FIG. 4 is a diagram illustrating a toner image.

According to FIG. 1 or FIG. 4, as shown in FIG. 1, a photosensitive drum 10a as an image forming body has a cylindrical shape formed of a light-transmitting member such as glass or a light-transmitting acrylic resin. A light-transmitting conductive layer and a photoconductor layer of an organic photosensitive layer (OPC) are formed on the outer periphery of the substrate.

The photoreceptor drum 10a is rotated clockwise as indicated by an arrow in FIG. 1 with the light-transmitting conductive layer grounded by power from a driving source (not shown).

In the present invention, the exposure beam for image exposure is
The photoconductor layer of the photoconductor drum 10a, which is the image forming point, only needs to have an exposure light amount of a wavelength that can provide an appropriate contrast with respect to the light attenuation characteristic (photocarrier generation) of the photoconductor layer. . Therefore, the light transmittance of the light-transmitting substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic of absorbing a certain amount of light when transmitting the exposure beam. . The point is that any suitable contrast can be provided. As a material of the light-transmitting substrate, an acrylic resin, particularly one obtained by polymerizing a methyl methacrylate monomer, is preferably used because of its excellent light-transmitting properties, strength, accuracy, surface properties, etc. Various translucent resins such as acryl, fluorine, polyester, polycarbonate, polyethylene terephthalate and the like used for the above can be used. Further, as long as it has a light-transmitting property with respect to the exposure light, it may be colored. As the light-transmitting conductive layer, indium tin oxide (I
TO), tin oxide, lead oxide, indium oxide, copper iodide, or a metal thin film of Au, Ag, Ni, Al, or the like that maintains light transmissivity. Reactive deposition method, various sputtering methods, various CV
D method, dip coating method, spray coating method and the like can be used.
Various organic photosensitive layers (OPC) can be used as the photoconductor layer.

The organic photosensitive layer serving as the photosensitive layer of the photoconductor layer includes a charge generation layer (CGL) mainly composed of a charge generation substance (CGM) and a charge transport layer (CTM) mainly composed of a charge transport substance (CTM). And CTL). An organic photosensitive layer having a two-layer structure has high durability as an organic photosensitive layer due to its thick CTL and is suitable for the present invention.
The organic photosensitive layer may have a single layer structure containing a charge generation material (CGM) and a charge transport material (CTM) in one layer. ,
Usually, a binder resin is contained.

A scorotron charger 11 as a charging unit described below and an exposure optical system 12 as an image writing unit
a, The developing device 13 as a developing unit is prepared for an image forming process for each color of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Are arranged in the order of Y, M, C, and K with respect to the rotation direction of the photosensitive drum 10a indicated by the arrow in FIG.

The scorotron charger 11 is mounted so as to face and be close to the photosensitive drum 10a in a direction (perpendicular to the plane of FIG. 1) orthogonal to the moving direction of the photosensitive drum 10a as an image forming body. The above-mentioned organic photoreceptor layer of the drum 10a is charged by a control grid (no sign) maintained at a predetermined potential and a corona discharge electrode having, for example, a discharge wire (no sign) as a corona discharge electrode and having the same polarity as the toner. The operation (in this embodiment, negative charging) is performed, and a uniform potential is applied to the photosensitive drum 10a. As the corona discharge electrode, a sawtooth electrode or a needle electrode may be used.

The exposure optical system 12a is a linear exposure element (not shown) in which a plurality of LEDs (light emitting diodes) as light emitting elements of image exposure light are arranged in an array in parallel with the axis of the photosensitive drum 10a. And a SELFOC lens (not shown) as an equal-magnification imaging element are configured as an exposure unit attached to a holder. An exposure optical system 12a for each color is provided on a cylindrical holder 20 as an exposure optical system holding member.
Is attached and housed inside the base of the photosensitive drum 10a. Other exposure elements include FL (phosphor emission),
A linear element in which a plurality of light emitting elements such as EL (electroluminescence) and PL (plasma discharge) are arranged in an array is used.

The exposure optical system 12a includes a photosensitive drum 10a.
The above exposure position is determined by the scorotron charger 11 and the developing device 1
In the state provided between the developing device 13 and the developing device 13 in the rotation direction upstream of the photosensitive drum 10a, the photosensitive drum 10a is disposed inside the photosensitive drum 10a.

The exposure optical system 12a performs image processing based on image data of each color sent from a separate computer (not shown) and stored in a memory, and then forms an image on a uniformly charged photosensitive drum 10a. After exposure, the photosensitive drum 10a
A latent image is formed thereon. The emission wavelength of the light-emitting element used in this embodiment is preferably in the range of 680 to 900 nm, which is generally high in the transmittance of the Y, M, and C toners. A shorter wavelength that does not sufficiently transmit light to the toner may be used.

The developing unit 13 contains a two-component (or one-component) developer of yellow (Y), magenta (M), cyan (C) or black (K) (a flat toner described in detail later). And a developing roller 13a which is a developer carrier formed of, for example, a cylindrical non-magnetic stainless steel or aluminum material having a thickness of 0.5 to 1 mm and an outer diameter of 15 to 25 mm, respectively. I have.

In the developing area, the developing roller 13a is kept out of contact with the photosensitive drum 10a by a contact roller (not shown) with a predetermined gap, for example, 100 to 1000 μm, to keep the developing roller 13a in the rotating direction of the photosensitive drum 10a. At the closest position, it rotates in the forward direction, and at the time of development, a DC voltage of the same polarity as the toner (in the present embodiment, a negative polarity) or a DC voltage is superimposed on the DC voltage with respect to the developing roller 13a. By applying the developing bias voltage, non-contact reversal development is performed on the exposed portion of the photosensitive drum 10a. At this time, the precision of the development interval needs to be about 20 μm or less in order to prevent image unevenness.

As described above, the developing device 13 is a photosensitive drum 10a formed by charging by the scorotron charger 11 and image exposure (image writing) by the exposure optical system 12a.
The upper electrostatic latent image is reversely developed in a non-contact state with toner having the same polarity as the charged polarity of the photoconductor drum 10a (in the present embodiment, the photoconductor drum is negatively charged and the toner has a negative polarity).

The photosensitive drum 10a is rotated clockwise as indicated by an arrow in FIG. 1 by starting an image forming body driving motor (not shown) at the start of image formation, and at the same time, the photosensitive drum 10 is charged by the charging action of the Y scorotron charger 11. Application of a potential to 10a is started. After a potential is applied to the photosensitive drum 10a, exposure (image writing) by a first color signal, that is, an electric signal corresponding to Y image data is started in the Y exposure optical system 12a, and the rotation of the photosensitive drum 10a is started. By scanning, an electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the photosensitive layer on the surface. This latent image is reversely developed by the Y developing device 13 in a non-contact state, and a toner image composed of yellow (Y) flat toner is formed on the photosensitive drum 10a.

Next, the photosensitive drum 10a is placed on the yellow (Y) toner image by the M scorotron charger 1.
A potential is applied by the charging action of M, and the exposure optical system M of M
Exposure (image writing) is performed by an electric signal corresponding to the second color signal 2a, that is, the image data of magenta (M), and the yellow (Y) of the yellow (Y) is developed by non-contact reversal development by the M developing unit 13 A toner image made of magenta (M) flat toner is superimposed on a toner image made of flat toner.

According to the same process, the C scorotron charger 11, the exposure optical system 12a, and the developing device 13 further form a toner image composed of cyan (C) flat toner corresponding to the third color signal. By the scorotron charger 11, the exposure optical system 12a, and the developing device 13, a toner image composed of black (K) flat toner corresponding to the fourth color signal is sequentially superimposed and formed, and the photosensitive drum 10a is formed.
Within one rotation, a superimposed color toner image composed of flat toner is formed on the peripheral surface.

As described above, in this embodiment, Y, M,
Photoconductor drum 10a by C and K exposure optical system 12a
The exposure of the organic photosensitive layer is performed through a transparent substrate from the inside of the photosensitive drum 10a. Therefore, the second,
Exposure of an image corresponding to the third and fourth color signals can form an electrostatic latent image without being shielded by the previously formed toner image, which is preferable. Exposure may be performed from outside.

On the other hand, recording paper P, which is mainly used as a transfer material (recording material), is sent out from a paper feed cassette 15 as a transfer material storage means by a feed roller (no code), and is fed by a feed roller (no code). The sheet is fed and conveyed to a timing roller 16 as a transfer material feeding unit.

The recording paper P is synchronized with the superimposed color toner image composed of flat toner carried on the photosensitive drum 10a by driving the timing roller 16, and a paper charger as a transfer material charging means is provided. Due to the charging of 150, it is attracted to the conveyor belt 14A and is fed to the transfer area (no symbol). The recording paper P closely transported by the transport belt 14A is transferred around the photosensitive drum 10a by a transfer unit 14C as a transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied in a transfer area. The superimposed color toner images made of flat toner on the surface are collectively transferred onto the recording paper P.

The recording paper P to which the superposed color toner image made of flat toner has been transferred is neutralized by a paper separation AC neutralizer 14h as a transfer material separating means, separated from the transport belt 14A, and transferred to the fixing device 17. Is conveyed.

The fixing device 17 includes a fixing roller 17a as a fixing roller member (a roller member provided on the surface of the transfer material having the toner image) for fixing the superimposed color toner image made of flat toner, and a fixing device. Roller 17a
And a pressure roller member 17b as a pressure roller member (a roller member provided on the surface of the transfer material not having the toner image).
Halogen lamp HLa, which is a heating means having a heating filament (no symbol) as a heat source,
Is provided.

The recording paper P is sandwiched by a nip portion N formed between the fixing roller 17a and the pressure roller 17b, and a superposed color of flat toner on the recording paper P is applied by applying heat and pressure. The toner image is fixed and the recording paper P
Is sent by a paper discharge roller 18 and discharged to a tray at the top of the apparatus.

The toner remaining on the peripheral surface of the photoconductor drum 10a after the transfer is cleaned by a photoconductor cleaning blade (not numbered) provided in a photoconductor cleaning device 19 as an image forming body cleaning means. The photosensitive drum 10a from which the residual toner has been removed is uniformly charged by the scorotron charger 11, and enters the next image forming cycle.

As described above, by using the flat toner, as shown in FIG.
4A, a superimposed color toner image without toner disturbance is formed, and the superimposed color toner image on the photosensitive drum 10a is transferred as shown in FIG. 4B. The recording layer P is also made thinner and flatter, and a superposed color toner image without toner disturbance is formed.

In the above-described image forming apparatus, color image formation has been described, but image formation of only a monochrome image can be performed.

According to FIG. 2 or FIG. 4, as shown in the sectional view of FIG. 2, a document table made of a transparent glass plate or the like, and a document placed on the document table There is a document placing portion 111 made up of a document cover or the like covering D. Below the document platen, in the apparatus main body, there are a first mirror unit 112, a second mirror unit 113, a main lens 120, a color CCD 123, and the like. An image reading unit A is provided. The first mirror unit 112 includes an exposure lamp 114 and a first mirror 115, and is attached in parallel with the document table so as to be linearly movable in the horizontal direction of the drawing, and optically scans the entire surface of the document D. The second mirror unit 113 integrally includes a second mirror 116 and a third mirror 117, and linearly moves in the same direction on the left and right at half the speed of the first mirror unit 112 so as to always maintain a predetermined optical path length. Of course, the movement of the second mirror unit 113 is parallel to the platen similarly to the first mirror unit 112. The image of the document D on the document table illuminated by the exposure lamp 114 is
5, an image is formed on the color CCD 123 via the second mirror 116 and the third mirror 117. When the scanning is completed, the first mirror unit 112 and the second mirror unit 113 return to their original positions, and wait for the next copy.

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

The image forming apparatus shown in FIG. 2 is a tandem-type color image forming apparatus using an intermediate transfer member as an image forming portion E, and a black (K) is formed on the peripheral edge of a transfer belt 14a as an intermediate transfer member. , Cyan (C), magenta (M)
Sets of four process units 1 composed of yellow and yellow (Y)
00 are provided in this order from the upstream side in the rotation direction of the transfer belt 14a.
K, C, M using the flat toner described in detail later
And the Y toner image are formed, the toner image composed of the flat toner is superimposed and transferred on the transfer belt 14a, and the transferred superimposed color toner image is collectively transferred onto a recording paper P as a transfer material. Then, the toner is fixed and discharged outside the apparatus.

Since the four process units 100 all have a common structure, only one of them will be described.

The photosensitive drum 10 serving as an image forming body has a conductive layer and an organic photosensitive layer (OPC) on the outer periphery of a cylindrical substrate.
Is formed.

The photosensitive drum 10 is rotated counterclockwise as indicated by an arrow with the conductive layer grounded by power from a drive source (not shown) or by the transfer belt 14a.

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

Reference numeral 12 denotes an exposure optical system as an image writing means for performing K, C, M, and Y image exposure based on image data.
Is a scanning optical system that performs scanning in parallel with the rotation axis. A latent image is formed by performing image exposure on the uniformly charged photoconductor drum 10 by the exposure optical system 12.

A developing device 13 containing a two-component developer composed of a negatively charged conductive toner and a magnetic carrier is provided on the periphery of the photosensitive drum 10, and a developer is held by incorporating a magnet body. Then, reversal development is performed by a developing roller 13a as a developer carrier that rotates.

The developer is a mixture of a carrier having a ferrite core as a core and an insulating resin coated around the core and a flat toner, which will be described in detail later.
The layer 3a is conveyed to the developing zone while being regulated to a layer thickness of 0.1 to 0.6 mm.

The gap between the developing roller 13a and the photosensitive drum 10 in the developing area is larger than the layer thickness of the developer by 0.2.
As 1.0 mm, applies an AC bias voltage obtained by superposing an AC voltage V _AC to a DC voltage V _DC between the developing roller 13a and the photosensitive drum 10. Since charging of the toner is a DC voltage V _DC of the same polarity (negative), flat toner given the opportunity to leave from the carrier by the AC voltage V _AC, the high V _H absolute value of the potential from the DC voltage V _DC The toner does not adhere to the portion, and the toner amount corresponding to the potential difference adheres to the portion of _VL where the absolute value of the potential is low, and the toner is visualized (a toner image composed of flat toner by reverse development is formed). A DC voltage V _DC is applied between the developing roller 13a and the photosensitive drum 10.
You may apply only. The development may be contact development. The toner image composed of the flat toner is transferred onto a transfer belt 14a described later at a transfer position. The transfer residual toner remaining on the photoconductor drum 10 after the transfer is cleaned by a photoconductor cleaning device 19 that electrostatically collects the toner.

The transfer belt 14a, in which four color process units 100 of K, C, M and Y face in parallel, has a volume resistivity of 10 ¹⁰ Ω · cm to 10 ¹⁵ Ω · cm and a surface resistivity of 10 ¹⁰
~10 ¹⁵ Ω / □ is an endless belt, for example modified polyimide, thermal curing polyimide, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, and dispersed with a conductive material engineering plastics nylon alloy, such as, 0.1 thickness It is a seamless belt having a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is preferably formed on the outside of a semiconductive film substrate having a thickness of 1.0 to 1.0 mm, preferably as a toner filming preventing layer. 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 1
Reference numeral 4a is stretched around a drive roller 14d, a driven roller 14e, a tension roller 14k, and a backup roller 14j. At the time of image formation, the drive roller 14d is rotated by a drive motor (not shown). In the transfer position, the transfer belt 14a is pressed against the photosensitive drum 10 by the primary transfer roller 14c as a first transfer unit, and the transfer belt 14a is rotated in the direction indicated by the arrow in the drawing.

The primary transfer roller 14c composed of a roller member as a first transfer unit for each color is provided on a transfer belt 14a.
Are provided to face the photosensitive drums 10 for each color, and a transfer area (no symbol) for each color is formed between the transfer belt 14a and the photosensitive drum 10 for each color. A DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the primary transfer roller 14c for each color, and a transfer electric field is formed in the transfer area. The toner image is transferred onto the transfer belt 14a.

The static eliminator 14m, which is a static eliminator for each color,
Preferably, the transfer belt 14a is constituted by a corona discharger, and charges the transfer belt 14a charged by the primary transfer roller 14c.

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

After a potential is applied to the K photosensitive drum 10, image writing is started by an electrical signal output from the control unit by the K exposure optical system 12, and the control unit is placed on the surface of the K photosensitive drum 10. An electrostatic latent image corresponding to the output image from is formed.

The K latent image is subjected to reversal development in a non-contact state by the K developing device 13 to form a toner image composed of the K flat toner by the K flat toner in accordance with the rotation of the K photosensitive drum 10. You.

The toner image composed of the K flat toner formed on the K photoreceptor drum 10 as the image forming body by the above-described image forming process is the primary transfer of K in the K transfer area (no sign). The image is transferred onto the transfer belt 14a by the roller 14c.

Slightly after the operation of the K process unit 100, the photosensitive drum 10 of the cyan (C) process unit 100 is rotated in the direction shown by the arrow in the drawing, and at the same time, the charging action of the C scorotron charger 11 is performed. As a result, the application of the potential to the C photoconductor drum 10 is started.

After the potential is applied to the photosensitive drum 10 of C, image writing by an electric signal corresponding to the image data of C is started by the exposure optical system 12 of C in synchronization with the toner image of K. An electrostatic latent image corresponding to the image C of the original image is formed on the surface of the photosensitive drum 10.

The C latent image is subjected to reversal development in a non-contact state by the C developing unit 13 to form a toner image composed of the C flat toner by the C flat toner according to the rotation of the C photosensitive drum 10. You.

The toner image formed of the C flat toner formed on the photosensitive drum 10 of the image forming body C by the above-described image forming process is subjected to the primary transfer of the C in the C transfer area (no sign). The toner image is transferred onto the transfer belt 14a on the toner image formed of the flat K toner by the roller 14c.

Next, the transfer belt 14a is synchronized with the M toner image, and the magenta (M) process unit 1
The toner image composed of the M flat toner corresponding to the M image data formed on the M photoconductor drum 10 by M.00 in the M transfer area (no symbol) by the M primary transfer roller 14c. Are superposed and formed on the superposed toner images made of the flat toners K and C.

By the same process, synchronization is achieved with the superposed toner image composed of K, C, and M flat toners.
The Y formed on the Y photoconductor drum 10 by the process unit 100 using the yellow (Y) flat toner
The toner image composed of the Y flat toner using the Y flat toner corresponding to the image data is transferred to the Y transfer area (no sign).
In the above, the Y primary transfer roller 14c is formed by being superimposed on the superposed toner images composed of the K, C, and M flat toners, and the K, C, M, and Y are formed on the transfer belt 14a. A superimposed color toner image made of flat toner is formed.

The untransferred toner remaining on the peripheral surface of the photosensitive drum 10 for each color after the transfer is cleaned by a photosensitive body cleaning device 19 as an image forming body cleaning unit for each color.

In synchronization with the formation of the superposed color toner image on the transfer belt 14a, the transfer material (recording material) is mainly transferred from a paper feed cassette 15 as a transfer material storage means via a timing roller 16 as a transfer material feeding means. The recording paper P used as the secondary transfer unit 14 is used as the second transfer unit.
g is transferred to the transfer area (no sign), and a superimposed color toner image composed of flat toner on the transfer belt 14a is formed on the recording paper P by the secondary transfer device 14g to which a DC voltage having a polarity opposite to that of the toner is applied. Are transferred collectively. A superposed color toner image composed of flat toners of K, C, M, and Y exists on the recording paper P.

The recording paper P on which the superposed color toner image made of flat toner has been transferred is neutralized by the neutralizing electrode 16b which is a separating means composed of a sawtooth electrode plate, and is conveyed to the fixing device 17.

The fixing device 17 includes a fixing roller 17a as a fixing roller member (a roller member provided on the surface of the transfer material having the toner image) for fixing the superposed color toner images made of flat toner, and a fixing device. Roller 17a
And a pressure roller member (a roller member provided on the surface of the transfer material on the side not having the toner image) pressure roller 17b. A halogen lamp HLa, which is a heating unit having a heating filament (no symbol) as a heat source, is provided in the center of the inside of the fixing roller 17a.

After heat and pressure are applied between the fixing roller 17a and the pressure roller 17b, a superimposed color toner image made of flat toner on the recording paper P is fixed, and then fed by the discharge roller 18. And discharged to the tray on top of the device.

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

By using the flat toner as described above, as shown in FIG.
A toner image without toner disturbance is formed thereon by thinning and flattening, and as shown in FIG. 4C, a transfer belt 14a on which the toner images on the photosensitive drum 10 of each color are transferred.
4A and 4B, a superimposed color toner image without toner disturbance is formed by thinning and flattening.
As shown in (B), the superposed color toner image on the transfer belt 14a is also thinned and flattened on the recording paper P to which the superimposed color toner image is transferred, so that the superimposed color toner image without toner disturbance is formed. You.

According to FIG. 3 or FIG. 4, the color image forming apparatus shown in FIG. 3 is a tandem type color image forming apparatus using an intermediate transfer member, and is provided at a peripheral portion of a transfer belt 14a as an intermediate transfer member. Is provided with four color image forming process units 100 including black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side in the rotation direction of the transfer belt 14a. K,
In the C, M, and Y process units 100, a superimposed toner image of flat toners of K, C, M, and Y is formed using a light toner made of flat toners and a dark toner made of flat toners, Each process unit 100
The toner image formed of the flat toner is superimposed and transferred on the transfer belt 14a.
A superimposed color toner image made of flat toner is formed on the transfer belt 4a, and the superimposed color toner image made of flat toner transferred onto the transfer belt 14a is collectively transferred onto a transfer material and fixed. It is configured to be discharged outside.

Since the four process units 100 of K, C, M and Y all have a common structure, only one of them will be described.

The process unit 100 includes the photosensitive drum 10 and the photosensitive drum 1 as viewed from the transfer position of the toner image.
From the upstream side in the rotation direction of 0, a photoconductor cleaning device 19 for cleaning the transfer residual toner on the photoconductor drum 10, and a scorotron charger 11 (L) for light toner for forming a light toner image. Exposure optical system 12 (L) for light toner, developing device 13 (L) for light toner composed of flat toner, scorotron charger 11 (H) for dark toner for forming a dark toner image, dark toner And a developing unit 13 (H) for dark toner composed of flat toner.

The photosensitive drum 10 serving as an image forming body has a photoconductive layer of a conductive layer and an organic photosensitive layer (OPC) formed on the outer periphery of a cylindrical base using, for example, an aluminum pipe or an acrylic resin pipe. Things.

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

Charging means for light toner (first charging means)
And a scorotron charger 11 (H) serving as a charging means (second charging means) for dark toner, respectively, in a direction orthogonal to the moving direction of the photosensitive drum 10. The photoconductor drum 10 is attached to face and close to the photoconductor drum 10, and gives a uniform potential to the photoconductor drum 10 by corona discharge having the same polarity as the toner.

The exposure optical system 12 (L), which is an image exposure means (first image exposure means) for light toner, and the exposure optical system 12 (L) which is an image exposure means (second image exposure means) for dark toner H)
Each uses a scanning optical system that performs scanning in parallel with the rotation axis of the photosensitive drum 10 using, for example, a polygon mirror. The exposure optical system 12 (L) uses external exposure,
First image writing (first image writing) using image data for light toner
Image writing means for performing image exposure
(H) is an image writing unit that writes a second image (second image exposure) using image data for dark toner using external exposure.

The developing device 13 (L), which is a developing means (first developing means) for light toner made of flat toner, contains a light toner developer made of flat toner, and contacts or non-contacts the first developer. Perform reversal development. The developing device 13 (H), which is a developing unit for dark toner composed of flat toner, incorporates a dark toner developer composed of flat toner and performs second reversal development by contact or non-contact development.

In forming an image, image data for each color is divided into light toner image data and dark toner image data. First, the light toner scorotron charger 11 (L) uniformly charges the image data. Photoreceptor drum 10
A first image exposure using light toner image data is performed by the exposure optical system 12 (L) to form a light toner latent image, and the light toner developing device 1 made of flat toner is formed.
The first development using light toner composed of flat toner is performed by the 3 (L) developing roller 13 a (L). Next, a scorotron charger 11 for dark toner is placed on the photosensitive drum 10 on which a light toner image made of flat toner is formed.
(H) performs the maximum charging, performs the second image exposure using the image data for the dark toner by the exposure optical system 12 (H), and forms a latent image of the dark toner. Developing roller 13 of developing unit 13 (H) for toner
According to a (H), the second development using the dark toner composed of the flat toner is performed, and the toner image composed of the dark toner composed of the flat toner is formed on the photosensitive drum 10 on the toner image composed of the light toner composed of the flat toner. Are formed on top of each other.
The light and dark toner images (superimposed toner images) made of the flat toner are transferred onto the transfer belt 14a at the transfer position of the first transfer unit.

The untransferred toner remaining on the photosensitive drum 10 after the transfer is cleaned by a photosensitive member cleaning device 19 that electrostatically collects the remaining toner.

The transfer belt 14a as an intermediate transfer member in which four process units 100 of K, C, M and Y face in parallel has a volume resistivity of 10 ¹⁰ to 10 ¹⁵ Ω · cm and a surface resistivity of 10 It is an endless belt of ¹⁰ to 10 ¹⁵ Ω / □,
For example, a modified polyimide, a thermosetting polyimide, an ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, a conductive material dispersed in an engineering plastic such as nylon alloy, the outside of a semiconductive film substrate having a thickness of 0.1 to 1.0 mm. Preferably, the seamless belt has a two-layer structure in which a fluorine coating having a thickness of 5 to 50 μm is applied as a toner filming preventing layer. In addition to the above, the transfer belt 14a has a thickness of 0.5 in which a conductive material is dispersed in silicon rubber or urethane rubber.
A semiconductive rubber belt of ~ 2.0 mm can also be used. The 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. During image formation, the transfer belt 14a is driven by a driving motor (not shown).
Are rotated, and the primary transfer roller 14 is moved at the transfer position for each color.
The transfer belt 14a is pressed against the photosensitive drum 10 by c, and the transfer belt 14a is rotated in the direction indicated by the arrow in the figure.

A primary transfer roller 14c, which is a roller member serving as a first transfer means of K, C, M and Y, is provided opposite to each photosensitive drum 10 with a transfer belt 14a interposed therebetween. Each transfer area (no symbol) is formed between the photoconductor drum 14a and each photoconductor drum 10. Each one
By applying a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) to the next transfer roller 14c and forming a transfer electric field in a transfer area (no sign),
Light and dark toner images made of flat toner on the C, M and Y photoconductor drums 10 are transferred onto the transfer belt 14a.

The static eliminator 14n, which is a static eliminator for each color,
Preferably, the transfer belt 14a is constituted by a corona discharger, and charges the transfer belt 14a charged by the primary transfer roller 14c.

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, a scorotron charger 11 for K light toner
The application of the potential to the K photoconductor drum 10 is started by the charging action (L).

After a potential is applied to the K photosensitive drum 10, the K light toner exposure optical system 12 (L) is used to control the electric charge corresponding to the K light toner image data of the first color signal. The first image exposure in the external exposure is started by the signal, 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 above-described latent image for light toner is subjected to first reversal development in a contact state by a developing unit 13 (L) for light toner composed of flat toner of K, and the rotation of the photosensitive drum 10 of K is performed. A toner image is formed by the light toner composed of the K flat toner. Subsequently, it corresponds to the charging by the scorotron charger 11 (H) for the K dark toner and the image data for the K dark toner of the first color signal by the exposure optical system 12 (H) for the K dark toner. The formation of an electrostatic latent image for dark toner corresponding to the K image by the second image exposure in the external exposure by an electric signal, and the developing unit 13 (H) for dark toner composed of K flat toner By the second development, a toner image of dark toner composed of K flat toner is formed on the previously formed toner image of light toner composed of K flat toner.

The K toner image formed of the light and dark toners using the flat toner (the superposed toner formed of the flat toner) is formed on the K photoreceptor drum 10 as the image forming body by the image forming process described above. Image) in the K transfer area (no sign), the K primary transfer roller 14
c, the image is transferred onto the transfer belt 14a.

Next, the transfer belt 14a is synchronized with the C toner image, and the cyan (C) process unit 10
0 corresponds to image data for C light and dark toners formed on the C photoreceptor drum 10 by the second color signal, and a toner image composed of C light and dark toners using flat toner, respectively. A superimposed toner image made of flat toner) is made of dark and light K toners using flat toner on the transfer belt 14a by the C primary transfer roller 14c in the C transfer area (no symbol). It is formed on a transfer belt 14a by superimposing on a toner image (an overlaid toner image made of flat toner).

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). Corresponding to image data for light and dark toners of M,
A toner image composed of dark toner (a superimposed toner image composed of flat toner) is transferred to the M primary transfer roller 14c in the M transfer area (no symbol) by the K primary and flat toner of the transfer belt 14a. Are formed on the transfer belt 14a from the top of the superimposed toner image, and are synchronized with the superposed toner image composed of flat toners of K, C, and M, and yellow (Y)
Y photosensitive drum 10 by the process unit 100
A toner image composed of Y light and dark toners using flat toner corresponding to the Y light and dark toner image data formed by the fourth color signal formed above (superimposed toner composed of flat toners) Image), Y transfer area (no sign)
, The Y primary transfer roller 14c is formed on the transfer belt 14a by superimposing the K, C, and M flat toners on the transfer belt 14a. A superimposed color toner image of K, C, M, and Y made of flat toner is formed on the top.

After transfer, the untransferred toner remaining on the peripheral surface of each photosensitive drum 10 is cleaned by a cleaning device 19 as each image forming body cleaning means.

In synchronization with the formation of the superposed color toner images on the transfer belt 14a, the transfer material (recording material) is mainly transferred from a paper feed cassette 15 as a transfer material storage means via a timing roller 16 as a transfer material feeding means. The recording paper P used as the secondary transfer unit 14 is used as the second transfer unit.
g is transferred to a transfer area (no sign), and a superimposed color toner image composed of flat toner on the transfer belt 14a is formed on the recording paper P by a secondary transfer device 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 superimposed color toner image made of flat toner has been transferred is neutralized by the neutralizing electrode 16b which is a separating means formed of a sawtooth electrode plate, and is conveyed to the fixing device 17.

The fixing device 17 includes a fixing roller 17a as a fixing roller member (a roller member provided on the surface of the transfer material having the toner image) for fixing the superimposed color toner image made of flat toner, and a fixing device. Roller 17a
And a pressure roller 17b as a pressure roller member (a roller member provided on the surface of the transfer material on the side not having the toner image). Fixing roller 17
a, a halogen lamp H serving as a heating means having a heating filament (no symbol) as a heating source.
La is provided.

After heat and pressure are applied between the fixing roller 17a and the pressure roller 17b, a superimposed color toner image composed of flat toner on the recording paper P is fixed, and then fed by the discharge roller 18. And discharged to the tray on top of the device.

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

As described above, by using the flat toner, as shown in FIG.
A toner image without toner disturbance is formed thereon by thinning and flattening, and as shown in FIG. 4C, a transfer belt 14a on which the toner images on the photosensitive drum 10 of each color are transferred.
4A and 4B, a superimposed color toner image without toner disturbance is formed by thinning and flattening.
As shown in (B), the superposed color toner image on the transfer belt 14a is also thinned and flattened on the recording paper P to which the superimposed color toner image is transferred, so that the superimposed color toner image without toner disturbance is formed. You.

Next, the flat toner used for forming a toner image in each of the above image forming apparatuses will be described with reference to FIG. 5 or FIG. 6 and FIG. FIG. 5 is a schematic diagram illustrating an example of the flat toner, and FIG. 6 is a cross-sectional view of a main part illustrating an example of an annular-type continuous wet stirring mill.

According to FIG. 5 or FIG. 4 described above, the flat toner (flat particles) used in the image forming apparatus of the present invention.
Is a spherical particle made by emulsion polymerization or suspension polymerization,
It can be manufactured by flattening with heat and external pressure.

The volume average particle diameter of the flat toner is 3 to 10 μm.
And more preferably 4 to 9 μm.

The flat toner preferably has a specific shape. That is, the long side (r ₁ ) of the average length of the flat toner
And the short side (r ₂ ) is 5 to 20 μm, and the average thickness (d) is 1 to
Preferably it is 5 μm. The ratio of the short side to the long side (r ₂ / r ₁ ) of the average length is preferably 0.6 to 1.0, and 0.8 to 1.0.
1.0 is more preferred. The ratio of the average thickness to the average short side length (d / r ₂ ) of the toner is preferably 0.1 to 0.5, and more preferably 0.2 to 0.4.

In fact, when such a flat toner is used, when a color image (printing rate 25%) is formed by each of the above-described image forming apparatuses, the toner consumption per A-4 size print is 20 to 40 mg. Even if the amount is extremely small, a high-density image without unevenness can be obtained, and a print-like image quality without toner scattering can be obtained.

The average length (r ₁ , r ₂ ) of the flat toner is 5 μm.
If it is less than m, there is a risk of suffering from diseases such as pneumoconiosis, which is not preferable in terms of safety and hygiene. If it exceeds 20 μm, developability is reduced, and faithful development cannot be performed, and the resolution is undesirably reduced.

The ratio of the long side to the short side of the average length of the flat toner (r
_{When the} ratio ( ₂ / r ₁ ) is less than 0.8, especially less than 0.6, the flat portion of the flat toner hardly adheres onto the image forming body, the toner layer becomes thicker, the toner consumption increases, and the transfer occurs. In addition, toner scattering and toner spread in the fixing process increase, which is not preferable.

If the average thickness (d) of the flat toner is less than 1 μm, the flat toner is crushed at the time of development, and ultrafine powder is generated, causing toner scattering and fogging. If it exceeds 5 μm, it is not preferable. Is difficult to develop in a layered form, and the toner layer becomes thicker, and the amount of consumed toner is increased.

If the ratio of the average thickness to the average short side length (d / r ₂ ) of the flat toner is 0.2 or less, particularly less than 0.1, the flat toner is crushed at the time of development, and ultrafine powder is generated. It is not preferable because it causes scattering and fogging. If it is more than 0.4, especially more than 0.5, the flat portion of the toner hardly adheres to the image forming body, the toner layer is hardly developed in a layer, and the toner layer becomes thick. This is not preferable because toner consumption increases. In addition, toner scattering and toner spread also increase in the transfer and fixing steps, which is not preferable.

By forming the flat toner into the above-described shape, as described above with reference to FIG. 4, when development is performed using the flat toner and a toner image is formed on an image forming body (photosensitive drum), The flat toner on the formed body is attached in a more layered manner with the flat portion of the flat toner facing the image forming body. Further, when the flat toner is transferred from the image forming body to the intermediate transfer body (transfer belt), the flat part of the flat toner adheres in a layer shape toward the intermediate transfer body. In particular, when using recording paper as a transfer material (recording material), the recording paper is composed of fibers,
Furthermore, since the surface has irregularities, the surface and the inside are electrically non-uniform, and the electrical characteristics change greatly due to humidity. Therefore, the image is transferred from the image forming body to the transfer material (recording paper) or from the intermediate transfer body At the time of transfer to a material (recording paper), the flat toner adhesion state tends to be disordered.

The surface charge state of the flat toner is substantially uniformly charged. For this reason, the Coulomb force between the image forming body and the flat portion of the flat toner is higher than that of the flat toner end portion. Is considered to be attached. In this way, the flat toner on the image forming body and on the intermediate transfer body is arranged in the horizontal direction with the edges thereof laid down, and the flat toners are easily overlapped with each other in flat layers, so that a stable toner image can be maintained even when moved. Conceivable. Particularly in color image formation, since the toner images of the respective colors are superimposed, it is necessary to superimpose the toner images of the respective colors in layers on flat surfaces and on an intermediate transfer member having a uniform electric characteristic. It is an important component for obtaining a good image. In this manner, it is preferable to superimpose toner images on an image forming body or an intermediate transfer body in a large number of times, and to reduce the number of times of transfer onto a transfer material (recording paper) having large surface irregularities and large changes in electrical characteristics. Become.

A toner having an insufficient flatness or an irregular toner has a flattened portion that cannot be laid down uniformly and is in a random adhesion state, and toner scattering and spread of a toner image in a transfer and fixing process become large. Was observed.

Even when flat toner is used, in the tandem system in which the toner is transferred onto a transfer material (recording paper) every time, toner scattering and toner spread in the transfer process were observed to a lesser extent than in the case of the irregular toner.

The toner having an insufficient flatness or an irregular toner has a shape deviating from the flat toner shape defined as described above. The toner is produced by a pulverization method or is not subjected to a flattening treatment by a polymerization method. The prepared toner and the like correspond.

Hereinafter, a method for producing flat toner (flat particles) will be specifically described. The flat toner used in the image forming apparatus of the present invention is prepared by suspending / fusing resin particles having a number average primary particle diameter of 10 to 500 nm produced by a suspension polymerization method or an emulsion polymerization method to produce secondary particles. Then, an organic solvent, a coagulant, a polymerization catalyst and the like are added to carry out polymerization, and the polymerization rate becomes 8
The spherical secondary particles (spherical toner) in the solution advanced to 0% are circulated through a pressurized bottleneck while being heated together with the solution to flatten the particle shape, and a polymerization catalyst is added to polymerize. To complete the process.

The salting out / fusing means that the resin fine particles produced in the polymerization step are salted out with an aggregating agent, excess dispersing agents, surfactants and the like are removed, and the size of the resin particles is reduced by heat fusion. Adjusting.

The flattening treatment may be performed after the polymerization is completed to 100%. However, the shape is more uniform if the flattening treatment is performed after the spheroidization is performed with the polymerization progressing to 80%. Is preferable.

The number-average primary particles are light scattering electrophoresis particle size analyzer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).
Can be measured.

The volume average particle size was measured using a Coulter counter TA.
-2 or Coulter Multisizer (manufactured by Coulter Inc.).

The salting-out / fusion may be performed by mixing the resin particles with a dispersion of a releasing agent or a coloring agent necessary for forming the toner, or by mixing the releasing agent or the coloring agent in the monomer. Number average primary particle size 1 prepared by a method such as emulsion polymerization after dispersing the components
It can be carried out by salting out / fusing resin particles of 0 to 500 nm.

That is, various constituent materials such as a colorant and, if necessary, a release agent, a charge control agent, and a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, a sand grinder, and an ultrasonic disperser are added. Various constituent materials are dissolved or dispersed in the polymerizable monomer by a machine or the like. The liquid in which the various constituent materials are dissolved or dispersed is dispersed in an oil medium having a desired size as a toner in an aqueous medium containing a dispersion stabilizer using a homomixer or a homogenizer. afterwards,
The mixture is transferred to a reactor equipped with a stirring mechanism having stirring blades, and heated so that the polymerization reaction proceeds up to 80% to form spherical particles (spherical toner). Thereafter, the heated bottle is circulated through a pressurized bottleneck to flatten the shape, and a polymerization catalyst is added to proceed with the polymerization, thereby completing the polymerization. After completion of the polymerization, the dispersion stabilizer is removed, filtered, washed, and dried to obtain the flat toner used in the image forming apparatus of the present invention.

Examples of the polymerizable monomer constituting the binder resin include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, and p-chlorostyrene. , 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene,
Styrenes such as p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, styrene derivatives, methacrylic acid Methyl, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, Methacrylate derivatives such as diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate,
Acrylate derivative such as isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc .; olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride Vinyl halides such as vinyl bromide, vinyl fluoride, vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl methyl ketone , Vinyl ethyl ketone, vinyl hexyl ketone, and other vinyl ketones, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, and other N-vinyl compounds, vinyl naphthalene, vinyl pyridine, and other vinyl compounds Acrylonitrile, methacrylonitrile, acrylic acid or methacrylic acid derivatives of acrylamide. Among them, vinyl monomers can be used alone or in combination.

Further, it is more preferable to use a polymerizable monomer constituting the resin in combination with one having an ionic dissociation group. For example, those having a substituent such as a carboxyl group, a sulfonic acid group, and a phosphate group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid,
Maleic acid, itaconic acid, cinnamic acid, fumaric acid, monoalkyl maleate, monoalkyl itaconate, styrenesulfonic acid, allylsulfosuccinic acid, 2-acrylamido-2-methylpropanesulfonic acid, acid phosphooxyethyl Methacrylate,
3-chloro-2-acid phosphooxypropyl methacrylate and the like.

Further, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate,
Polyfunctional vinyls such as neopentyl glycol diacrylate can be used to form a crosslinked resin.

These polymerizable monomers can be polymerized using a radical polymerization initiator. In this case, an oil-soluble polymerization initiator can be used in the suspension polymerization method. As the oil-soluble polymerization initiator, 2,2'-azobis- (2,2
4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'-azobis-4-
Azo or diazo polymerization initiators such as methoxy-2,4-dimethylvaleronitrile and azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide , Di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-
Examples include peroxide-based polymerization initiators such as (4,4-t-butylperoxycyclohexyl) propane and tris- (t-butylperoxy) triazine, and polymer initiators having a peroxide in a side chain. .

When the emulsion polymerization method is used, a water-soluble radical polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and salts thereof, and hydrogen peroxide.

Examples of dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, and calcium sulfate. , Barium sulfate,
Bentonite, silica, alumina and the like can be mentioned. Further, those generally used as surfactants such as polyvinyl alcohol, gelatin, methyl cellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as the dispersion stabilizer.

As the resin excellent in the present invention, a resin having a glass transition point of 20 to 90 ° C. is preferable and a softening point of 8
The thing of 0-220 ° C is preferred. The glass transition point is measured by a differential calorimetric analysis method, and the softening point can be measured by a Koka type flow tester. Furthermore, these resins have a number average molecular weight (Mn) of 10 as measured by gel permeation chromatography.
00 to 100000, weight average molecular weight (Mw) 200
Those having 0 to 1,000,000 are preferred. Further, as a molecular weight distribution, Mw / Mn is 1.5 to 100, particularly 1.8.
-70 are preferred.

The flat toner used in the image forming apparatus of the present invention contains at least a resin and a colorant, but may contain, if necessary, a releasing agent or a charge control agent which is a fixability improving agent. Can also be. Further, an external additive composed of inorganic fine particles or organic fine particles may be added to the particles of the flat toner mainly composed of the above-mentioned resin and colorant.

As the colorant used in the flat toner used in the image forming apparatus of the present invention, carbon black, dye, pigment and the like can be arbitrarily used.

As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black and the like can be used.

As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 1
22, C.I. I. Solvent Yellow 19, 44, 7
7, 79, 81, 82, 93, 98, 10
3, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 9
5 and the like, and a mixture thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122,
139, 144, 149, 166, 177,
178, 222, C.I. I. Pigment Orange 3
1, 43, C.I. I. Pigment Yellow 14, 1
7, 93, 94, 138, C.I. I. Pigment Green 7, C.I. I. Pigment Blue 15: 3, 60
Etc. can be used. The above dyes and pigments can be used alone or as a mixture. Although the number average primary particle size of the colorant varies depending on the type, it is generally 10 to 200 nm.
Is preferred.

As a method of adding a colorant, a method of adding a colorant at the stage of polymerizing a monomer and polymerizing it to obtain colored particles can be used. When the colorant is added at the stage of preparing the polymer, it is preferable to use the colorant after treating the surface with a coupling agent or the like so as not to inhibit the radical polymerizability.

Further, low molecular weight polypropylene (number average molecular weight = 1500 to 9000) or low molecular weight polyethylene as a fixing property improving agent may be added.

The charge control agents are also various known ones.
In addition, those that can be dispersed in water can be used. Specifically, nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines,
Quaternary ammonium salt compounds, azo-based metal complexes, salicylic acid metal salts or metal complexes thereof.

The particles of the charge control agent and the fixability improving agent have a number average primary particle diameter of 10 to 500 in a dispersed state.
It is preferable to set it to about nm.

The flattening of the spherical secondary particles formed by salting out / fusing can be performed by an annular type continuous wet stirring mill, a piston type high pressure homogenizer, an in-line screw pump, or the like.

Further, in the flat toner used in the image forming apparatus of the present invention, more effects can be exhibited by adding and using fine particles such as inorganic fine particles and organic fine particles as an external additive. It is presumed that the reason for this is that since the burying and desorption of the external additive can be effectively suppressed, the effect is remarkable.

As the inorganic fine particles, it is preferable to use inorganic oxide particles such as silica, titania and alumina.
Further, it is preferable that these inorganic fine particles have been subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent, or the like. The degree of the hydrophobic treatment is not particularly limited, but a methanol wettability of 40 to 95 is preferable. Methanol wettability is to evaluate the wettability to methanol. In this method, 0.2 g of the inorganic fine particles to be measured is weighed and added to 50 ml of distilled water placed in a 200 ml beaker. Methanol is slowly dropped from a buret whose tip is immersed in the liquid until the whole of the inorganic fine particles is wet while being slowly stirred. When the amount of methanol required to completely wet the inorganic fine particles is a (ml), the degree of hydrophobicity is calculated by the following equation.

Degree of hydrophobicity = (a / (a + 50)) × 100 The amount of the external additive added is 0.1 to 0.1 in the flat toner.
5.0 mass% is preferred, and more preferably 0.5-4.
0% by mass. Various external additives may be used in combination.

As shown in FIG. 6, an example of an annular type continuous wet stirring mill is a kind of a known mill, which is an annular (annular) stator 50 having a triangular cross section.
1, a rotor 502 having substantially the same shape rotates, and a narrow gap between the stator 501 and the rotor 502, that is, a crushing zone 503 is filled with a medium 504 and supplied to a mill. % Of the secondary particles (spherical toner) in the solution having undergone polymerization to a mechanical impact force together with the solution containing the secondary particles to flatten the shape of the secondary particles. The solution passes through the crushing zone 503 having a W-shaped cross section by a pump from a supply port 505 of the mill, is separated from a medium 504 by an upper cap separator 506, and is discharged from an outlet 507. The temperature of the solution during the flattening process is controlled by circulating hot water 508 through the stator and the rotor. The media 504 sequentially moves through the W-shaped pulverizing zone due to centrifugal force, and returns to the entrance and circulates again. Pressure on the particles is applied by the walls or media of the grinding zone by circulating through a pressurized bottleneck. As the medium, zircon, glass, steel or the like having a diameter of 0.5 to 3 mm is usually used.

The flattening temperature of the solution containing the secondary particles using such an annular continuous wet stirring mill is preferably −5 ° C. to + 40 ° C. of the glass transition point (Tg) of the resin of the secondary particles, and 0 ° C. To + 30 ° C, more preferably +10 to + 30 ° C. 5 than the glass transition point
If the treatment is performed at a temperature lower than or equal to ° C., the polymer particles are crushed, and it is difficult to perform the intended flattening, which is not preferable. On the other hand, when the treatment is performed at a temperature higher than the glass transition point by 40 ° C. or more, the secondary particles fuse with each other to form agglomerates, and the flattened polymer particles are again spheroidized by their surface tension. Therefore, flattening cannot be performed efficiently, which is not preferable.

The prevention of the disturbance of the flat toner on the transfer material at the time of fixing will be described with reference to FIGS.
FIG. 7 is a schematic sectional view of a fixing device common to each of the above-described image forming apparatuses, FIG. 8 is a diagram showing flat toner on a transfer material under an electric field, and FIG. FIG. 10 is a diagram illustrating a first example of the configuration, and FIG. 10 is a diagram illustrating a second example of another configuration of the fixing device.

According to FIG. 7 or FIG. 8, as shown in FIG. 7, the fixing device 17 provided in each image forming apparatus described above is provided.
A fixing roller 17a as a fixing roller member (a roller member provided on the surface of the transfer material having the toner image) for fixing the superimposed color toner image made of flat toner, and a fixing roller 17a facing the fixing roller 17a. And a pressure roller 17b as a pressure roller member (a roller member provided on the surface of the transfer material not having the toner image). At the center inside the fixing roller 17a, a halogen lamp HLa, which is a heating unit having a heating filament (no symbol) as a heat source, is provided, and heats the fixing roller 17a.

The fixing roller 17a has a cylindrical metal pipe 171a having a thickness of about 1 to 3 mm made of, for example, aluminum or stainless steel, and a silicon material formed on the outer peripheral surface of the metal pipe 171a. (Thickness) 2-5 mm thick, rubber hardness 10Hs-40Hs (JIS, A
Rubber roller layer 1 composed of a soft rubber layer having a rubber hardness)
72a are formed as soft soft rollers having an outer diameter of about 30 to 50 mm. Pressing roller 1
Reference numeral 7b denotes a cylindrical metal pipe 171b having a thickness of about 1 to 3 mm using, for example, an aluminum material or a stainless steel material, and a silicon material on the outer peripheral surface of the metal pipe 171a. ~ 5mm thick, rubber hardness 2
A rubber roller layer 172b made of a thin hard rubber layer having a thickness of 0Hs to 50Hs (JIS, A rubber hardness);
It is configured as a harder soft roller having an outer diameter of about 30 to 50 mm.

A nip portion N having the fixing roller 17a side in a convex shape is formed between the fixing roller 17a formed as a softer soft roller and the pressure roller 17b formed as a harder soft roller. The fixing of the toner image composed of the flat toner on the paper P is performed.

At the time of transfer, the transferred toner image composed of the flat toner is adhered on the recording paper P at the flat part, and the recording paper P is made thinner and flatter. The flat toner tends to stand up and is easily scattered at the entrance of the nip portion N during fixing. To prevent this, the fixing roller 1
7a, the polarity of the flat toner on the recording paper P is the same as that of the flat toner (the polarity of the flat toner used in the description of each of the above-described image forming apparatuses is minus), for example, -5.
An electric field E is formed between the fixing roller 17a and the pressing roller 17b by applying a fixing bias VTa composed of a negative polarity DC voltage of about 00 to -2000V and grounding (grounding) the pressing roller 17b. As shown in FIG. 8, the electric action of the electric field E causes the flat toner to be pressed onto the recording paper P with the flat portion, and the recording paper P is moved to the nip portion N without disturbing the flat toner.
To the recording paper P by heat and pressure (under pressure).
Fix the toner image composed of the upper flat toner (recording paper P
To be fixed).

That is, the electric field E is applied to press the toner against the recording paper P. By the electric field E, the flat toner lying in advance is more stabilized. By applying the electric field E, the flat toner moves to lie down (applies flat to the surface of the recording paper P).

As shown by a dashed line in FIG. 7, the polarity of the flat toner on the recording paper P is opposite to the polarity of the flat toner on the pressure roller 17b (used in the description of the above-described embodiments of the image forming apparatuses). The flat toner has a positive polarity (for example, a positive polarity). For example, a fixing bias VTb composed of a DC voltage having a positive polarity of about +500 to +2000 V is applied, and the fixing roller 17a is grounded (grounded).
a between the pressure roller 17a and the pressure roller 17b.
By pressing the flat toner onto the recording paper P with the flat portion by the electric action of, the recording paper P enters the nip portion N without causing the flat toner to be disturbed,
The toner image composed of the flat toner on the recording paper P may be fixed (fixed to the recording paper P) by heat and pressure (under pressure).

As described above, since the toner layer is thin at the time of fixing, the toner image is fixed under a high pressure (particularly, a superimposed color toner image has a large toner layer because the toner layer becomes thick, and the toner is greatly disturbed, and high pressure is required). Also, the toner does not collapse and spread, and no image disturbance occurs. Also, good fixing is achieved even when the width of the nip portion N is small. Since the width of the nip portion N can be reduced, the recording paper P does not need to take heat, and even if the heating from the pressure roller 17b side is insufficient, the fixing roller heated by the included halogen lamp HLa 17
The fixing of the toner image is made possible only by a. That is, the conventional toner layer requires a wide nip portion due to the thick layer thickness, and also requires heat from the pressure roller 17b. However, by thinning the toner layer with flat toner, the fixing roller 17a Only the fixing of the toner image can be performed, and the heating of the pressure roller 17b is not required. The heat contribution of the pressure roller 17b is reduced, and the heat insulation of the pressure roller 17b is increased, and the heat capacity can be reduced.

As described above, with the developer using the flat toner, the toner image can be thinned and flattened.
Disorder of the flat toner at the time of fixing (disorder of the toner image) is prevented, the spread of the toner collapse is prevented, and the occurrence of the image disorder is suppressed. Further, by preventing the spread of the toner collapse, the width of the nip portion can be reduced, and an image forming apparatus having a fixing device with a reduced warm-up time can be provided.

In particular, when forming a color toner image in the image forming apparatus shown in FIGS. 1 to 3, a developer using flat toner is used to reduce the thickness and flatness of a superimposed color toner image whose thickness is increased. In addition, since the layer thickness is large, the disturbance of the flat toner at the time of fixing (the disturbance of the toner image) in the superimposed color toner image requiring high pressure is prevented, and the layer thickness is reduced. The thickness of the nip portion is reduced by preventing the spread of toner collapse and the occurrence of image disturbance is suppressed, and the spread of the toner collapse is prevented by the increase of the layer thickness. (In the case of superimposed color toner images, the layer thickness is increased, so that the width of the nip portion, which needs to be wider, can be reduced), and the warm-up time can be reduced. Provide an image forming apparatus having a reduced fixing device is made possible.

As shown in FIG. 9, a halogen lamp HLa is provided inside, having the same configuration as described above with reference to FIG.
Metal Pipe 171a and Rubber Roller Layer 172 Outside It
a tension roller TRa, a tension roller TRb, and a tension roller Tb, which are formed of a hard roller using a metal member and are opposed to the fixing roller 17a.
The fixing device 17 </ b> A may be configured by providing a fixing belt 27 stretched over Rt. Fixing belt 27
Is a semiconductive film or a conductive belt-shaped member having a conductive nickel film formed on the surface of the film, and is capable of applying a voltage.

A nip portion N is formed between the fixing roller 17a and the fixing belt 27, and a toner image made of flat toner on the recording paper P is fixed.

In the same manner as described above with reference to FIG.
A bias voltage is applied between the fixing belt 27a and the fixing belt 27 to form an electric field E (see FIG. 7, not shown in FIG. 9), and the flat toner is recorded with a flat portion by the electric action of the electric field E. The recording paper P is caused to enter the nip portion N while pressing the recording paper P on the paper P so as not to disturb the flat toner, and the heat of the fixing roller 17a and the pressure due to the tension of the fixing belt 27 are applied (under pressure). Alternatively, a toner image made of flat toner on the recording paper P may be fixed (fixed to the recording paper P). As a result, the toner layer is thin at the time of fixing, so that even if the toner is fixed under a high pressure (especially a superimposed color toner image is thickened and the toner layer is thick, the toner disturbance is large and a high pressure is required), the toner remains It does not collapse and spread, and no image disturbance occurs. Nip part N
Good fixing is achieved even if the width is small. Since the width of the nip portion N can be reduced, the recording paper P does not need to take heat, and even if the heating from the fixing belt 27 side is insufficient, the fixing roller 17a heated by the included halogen lamp HLa. Only with this, it is possible to fix the toner image. That is, conventionally, a thick nip portion was required due to the thick layer of the toner layer, and heat from the fixing belt 27 was also required. However, by thinning the toner layer with flat toner,
It is possible to fix the toner image only by the fixing roller 17a, and it becomes unnecessary to heat the fixing belt 27. The heat contribution rate of the fixing belt 27 is reduced.

As described above, it is preferable to use the above-mentioned flat toner as the toner in which the bias application at the time of fixing is more effectively exerted.

The volume average particle diameter of the flat toner is 3 to 10 μm.
And more preferably 4 to 9 μm.

The flat toner preferably has a specific shape. That is, the long side (r ₁ ) of the average length of the flat toner
And the short side (r ₂ ) is 5 to 20 μm, and the average thickness (d) is 1 to
Preferably it is 5 μm. The ratio of the short side to the long side (r ₂ / r ₁ ) of the average length is preferably 0.6 to 1.0, and 0.8 to 1.0.
1.0 is more preferred. The ratio of the average thickness to the average short side length (d / r ₂ ) of the toner is preferably 0.1 to 0.5, and more preferably 0.2 to 0.4.

The average length (r ₁ , r ₂ ) of the flat toner is 5 μm.
If it is less than m, there is a risk of suffering from diseases such as pneumoconiosis, which is not preferable in terms of safety and hygiene. If it exceeds 20 μm, developability is reduced, and faithful development cannot be performed, and the resolution is undesirably reduced.

If the average thickness (d) of the flat toner is less than 1 μm, the flat toner is crushed at the time of development, and ultrafine powder is generated, causing toner scattering and fogging. Is difficult to develop in a layered form, and the toner layer becomes thicker, and the amount of consumed toner is increased.

If the ratio (d / r ₂ ) of the average thickness of the flat toner to the average short side length (d / r ₂ ) is less than 0.2, especially less than 0.1, the flat toner is crushed at the time of development, and ultrafine powder is generated. It is not preferable because it causes scattering and fogging. If it is more than 0.4, especially more than 0.5, the flat portion of the toner hardly adheres to the image forming body, the toner layer is hardly developed in a layer, and the toner layer becomes thick. This is not preferable because toner consumption increases. In addition, toner scattering and toner spread also increase in the transfer and fixing steps, which is not preferable.

As described above, with the developer using the flat toner, the toner image can be thinned and flattened.
Disturbance of the flat toner at the time of fixing (disorder of the toner image) is prevented, so that the spread of the toner collapse is prevented, the occurrence of the image disturbance is suppressed, and the spread of the toner collapse is prevented, so that the nip portion is prevented. Can be narrowed, and an image forming apparatus having a fixing device with a reduced warming-up time can be provided.

In particular, when forming a color toner image in the image forming apparatus shown in FIGS. 1 to 3, the developer using flat toner is used to reduce the thickness and flatness of the superposed color toner image. In addition, since the thickness is increased and the layer thickness is large, the disturbance of the flat toner at the time of fixing (the disturbance of the toner image) in the superimposed color toner image requiring high pressure is prevented. Since the layer thickness is large, the spread of the toner crush that spreads is prevented, and the occurrence of image disorder is suppressed. In addition, since the toner collapse is prevented from spreading due to the large layer thickness, the width of the nip portion can be reduced. (In the case of a superposed color toner image, the layer thickness is increased. The width of the nip portion, which needs to be wide, can be reduced), and an image forming apparatus having a fixing device with a reduced warm-up time can be provided.

As shown in FIG. 10, a halogen lamp HLa is provided inside, a metal pipe 171a and a thin wall having an outer thickness of about 0.5 to 1 mm and a rubber hardness of 40H are provided.
A fixing belt 27A is stretched around a fixing roller 17c composed of a hard rubber roller layer 172c of about s to 60Hs (JIS, A rubber hardness) and a first fixing roller 47a as a soft roller composed of a soft rubber layer. And a first fixing roller 47a sandwiching the fixing belt 27A.
The fixing device 17B may be configured by providing a second fixing roller 47b as a soft roller made of a hard rubber layer opposite to the fixing roller 17b. The fixing belt 27A is a semiconductive film or a conductive belt-shaped member having a conductive nickel film formed on the film surface, and is capable of applying a voltage.

A nip portion N is formed between the first fixing roller 47a as a softer soft roller and the second fixing roller 47b as a harder soft roller with the fixing belt 27A interposed therebetween, and passes through the guide plate PAa. A toner image composed of flat toner on the recording paper P entering the nip N is fixed.

As described above with reference to FIG. 7, a bias voltage is applied between the first fixing roller 47a and the second fixing roller 47b to generate an electric field E (see FIG. 7, not shown in FIG. 10). The flat paper is pressed against the recording paper P with the flat portion by the electric action of the electric field E, and the recording paper P is caused to enter the nip portion N without causing the flat toner to be disturbed. The heat of the fixing belt 27A heated by the roller 17c and the pressure of the first fixing roller 47a and the second fixing roller 47b (the first fixing roller 4a).
7a and the second fixing roller 47b under pressure), the recording paper P
Fix the toner image composed of the upper flat toner (recording paper P
May be fixed). As a result, the toner layer is thin at the time of fixing, so that even if the toner is fixed under a high pressure (especially a superimposed color toner image is thickened and the toner layer is thick, the toner disturbance is large and a high pressure is required), the toner remains It does not collapse and spread, and no image disturbance occurs. Also, good fixing is achieved even when the width of the nip portion N is small. Since the width of the nip portion N can be reduced, the recording paper P does not take heat, and even if the heating from the second fixing roller 47b side is insufficient, only the fixing belt 27A heated by the fixing roller 17c is used. To fix the toner image. That is, the conventional toner layer requires a wide nip due to the thick layer thickness, and also requires heat from the first fixing roller 47a or the second fixing roller 47b. However, the toner layer is thinned by the flat toner. By doing so, it is possible to fix the toner image only with the fixing belt 27A heated by the fixing roller 17c, and it becomes unnecessary to heat the first fixing roller 47a and / or the second fixing roller 47b. .
First fixing roller 47a and / or second fixing roller 47
b is intended to reduce the heat contribution rate.

As described above, it is preferable to use the above-mentioned flat toner as the toner in which the bias application at the time of fixing is more effectively exerted.

The volume average particle diameter of the flat toner is 3 to 10 μm.
And more preferably 4 to 9 μm.

The flat toner preferably has a specific shape. That is, the long side (r ₁ ) of the average length of the flat toner
And the short side (r ₂ ) is 5 to 20 μm, and the average thickness (d) is 1 to
Preferably it is 5 μm. The ratio of the short side to the long side (r ₂ / r ₁ ) of the average length is preferably 0.6 to 1.0, and 0.8 to 1.0.
1.0 is more preferred. The ratio of the average thickness to the average short side length (d / r ₂ ) of the toner is preferably 0.1 to 0.5, and more preferably 0.2 to 0.4.

The average length (r ₁ , r ₂ ) of the flat toner is 5 μm.
If it is less than m, there is a risk of suffering from diseases such as pneumoconiosis, which is not preferable in terms of safety and hygiene. If it exceeds 20 μm, developability is reduced, and faithful development cannot be performed, and the resolution is undesirably reduced.

If the average thickness (d) of the flat toner is less than 1 μm, the flat toner is crushed at the time of development, and ultrafine powder is generated, causing toner scattering and fogging. Is difficult to develop in a layered form, and the toner layer becomes thicker, and the amount of consumed toner is increased.

If the ratio of the average thickness to the average short side length (d / r ₂ ) of the flat toner is 0.2 or less, particularly less than 0.1, the flat toner is crushed at the time of development, and ultrafine powder is generated. It is not preferable because it causes scattering and fogging. If it is more than 0.4, especially more than 0.5, the flat portion of the toner hardly adheres to the image forming body, the toner layer is hardly developed in a layer, and the toner layer becomes thick. This is not preferable because toner consumption increases. In addition, toner scattering and toner spread also increase in the transfer and fixing steps, which is not preferable.

As described above, with the developer using the flat toner, the toner image can be thinned and flattened.
Disturbance of the flat toner at the time of fixing (disorder of the toner image) is prevented, so that the spread of the toner collapse is prevented, the occurrence of the image disturbance is suppressed, and the spread of the toner collapse is prevented, so that the nip portion is prevented. Can be narrowed, and an image forming apparatus having a fixing device with a reduced warming-up time can be provided.

In particular, when forming a color toner image in the image forming apparatus shown in FIGS. 1 to 3, a developer using a flat toner is used to reduce the thickness and flatness of a superposed color toner image whose thickness is increased. In addition, since the thickness is increased and the layer thickness is large, the disturbance of the flat toner at the time of fixing (the disturbance of the toner image) in the superimposed color toner image requiring high pressure is prevented. Since the layer thickness is large, the spread of the toner crush that spreads is prevented, and the occurrence of image disorder is suppressed. In addition, since the toner collapse is prevented from spreading due to the large layer thickness, the width of the nip portion can be reduced. (In the case of a superposed color toner image, the layer thickness is increased. The width of the nip portion, which needs to be wide, can be reduced), and an image forming apparatus having a fixing device with a reduced warm-up time can be provided.

[0167]

According to the first aspect of the present invention, the developer using the flat toner can reduce the thickness and the flatness of the toner image, and can reduce the disturbance of the flat toner at the time of fixing (the disturbance of the toner image). Is prevented, the spread of toner collapse is prevented,
The occurrence of image disturbance is suppressed. Further, by preventing the spread of the toner collapse, the width of the nip portion can be reduced, and an image forming apparatus having a fixing device with a reduced warm-up time can be provided.

According to the second or third aspect, the developer using the flat toner makes it possible to reduce the thickness and flatten the superimposed color toner image having a large layer thickness. Disorder of the flat toner at the time of fixing (disorder of the toner image) in a superposed color toner image requiring high pressure is prevented. Since the layer thickness is large, the spread of the toner crush that spreads is prevented, and the occurrence of image disorder is suppressed. In addition, since the toner collapse is prevented from spreading due to the large layer thickness, the width of the nip portion can be reduced. (In the case of a superposed color toner image, the layer thickness is increased. The width of the nip portion, which needs to be wide, can be reduced), and an image forming apparatus having a fixing device with a reduced warm-up time can be provided.

[Brief description of the drawings]

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

FIG. 2 is a sectional configuration diagram of a color image forming apparatus showing a second example of the embodiment of the image forming apparatus using flat toner according to the present invention.

FIG. 3 is a cross-sectional configuration diagram of a color image forming apparatus showing a third example of an embodiment of an image forming apparatus using flat toner according to the present invention.

FIG. 4 is a diagram illustrating a toner image formed of flat toner on an image forming body or an intermediate transfer body.

FIG. 5 is a schematic diagram illustrating an example of a flat toner.

FIG. 6 is a sectional view of a main part showing an example of an annular continuous wet stirring mill.

FIG. 7 is a schematic sectional view of a fixing device common to the above-described image forming apparatuses.

FIG. 8 is a diagram illustrating flat toner on a transfer material under an electric field.

FIG. 9 is a diagram illustrating a first example of another configuration of the fixing device.

FIG. 10 is a diagram illustrating a second example of another configuration of the fixing device.

[Explanation of symbols]

 10, 10a Photoreceptor drum 11, 11 (H), 11 (L) Scorotron charger 12, 12 (H), 12 (L), 12a Exposure optical system 13, 13 (H), 13 (L) Developer 14A Conveying belt 14a Transfer belt 14C Transfer device 14c Primary transfer roller 14g Secondary transfer device 15 Paper cassette 16 Timing roller 17, 17A, 17B Fixing device 17a, 17c Fixing roller 17b Pressure roller 27, 27A Fixing belt 47a First fixing Roller 47b Second fixing roller 100 Process unit E Electric field P Recording paper VTa, VTb Fixing bias

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/16 G03G 9/08 361 F term (Reference) 2H005 AA15 AA21 2H030 AB02 AD01 AD04 BB23 BB42 BB71 2H032 AA02 BA05 BA08 BA09 BA21 BA23 2H033 AA01 AA49 BA13 BA58 BB01 BB28

Claims (3)

[Claims] Forming an electrostatic latent image on an image forming member, developing the electrostatic latent image with a developer containing toner, forming a toner image on the image forming member, and then forming the toner image on the image forming member; An image forming apparatus that transfers the toner image onto a transfer material and fixes the toner image on the transfer material by a fixing device, wherein the toner is a flat toner, and the fixing unit causes the flat toner to be flat on a surface of the transfer material. An image forming apparatus, wherein an electric field to be applied is formed, and flat toner adhered to the transfer material in a flat state at a flat portion is fixed to the transfer material under pressure. 2. An image forming method comprising: forming an electrostatic latent image on an image forming body; developing the electrostatic latent image with a developer containing toner to form a toner image; After forming a superimposed color toner image on the image forming body, the color toner image on the image forming body is collectively transferred onto a transfer material, and the color toner image on the transfer material is fixed by a fixing device. In the image forming apparatus for fixing, the toner is flat toner, and the fixing unit forms an electric field that causes the flat toner to act on the surface of the transfer material in a flat state, and the flat portion is flat on the transfer material on the transfer material. An image forming apparatus, wherein the attached superimposed flat toner is fixed to the transfer material under pressure. 3. An electrostatic latent image is formed on an image forming body, and the electrostatic latent image is developed with a developer containing a toner to form a toner image, wherein the toner is formed on the image forming body. A plurality of image forming units for forming an image are arranged on the intermediate transfer body, and the toner images formed on the image forming body are sequentially transferred to the intermediate transfer body using toner of different colors for each image forming unit. Forming a superimposed color toner image on the intermediate transfer member, transferring the color toner image on the intermediate transfer member onto a transfer material at a time, and fixing the color toner image on the transfer material. In the image forming apparatus which is fixed by an apparatus, the toner is a flat toner, and the fixing unit forms an electric field acting on a surface of the transfer material in a flat state, and is attached to the transfer material in a flat state at a flat portion. Flat superimposed An image forming apparatus, wherein toner is fixed to the transfer material under pressure.