JPS6381493A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To faithfully transfer toner images without image disturbance to obtain a multicolor image free from color blur and character blur by forming multicolor toner images on a photosensitive body and turning the photosensitive body once more thereafter to only electrify all of the surface including toner images by an electrifier. CONSTITUTION:The image of a first color component (for example, red) is exposed and is developed with a corresponding toner (for example, cyan) to form a toner image on the surface of the photosensitive body. The photosensitive body passes a transfer electrode 50, a separating means, a cleaning means 46 without being subjected to functions of them and enters into the next copy cycle. Plural toner images of red, black, etc., are successively formed on the photosensitive body 40 in this manner to form multiple or multicolor toner images. The last toner image is formed on the photosensitive body, and the photosensitive body is turned once more to only electrify all of the surface, and thereafter, toner images are transferred to a recording paper 61 by the transfer electrode 50. Since potentials of respective toners are equalized to equalize transfer rates, color impurity and color blur or each color are eliminated to form the multicolor image of high density.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus using an electrophotographic method.

(Prior art) Multicolor image forming apparatuses include wire tod matrix recording method, ink jet recording method, thermal transfer recording method,
There are electrostatic recording methods, electrophotographic recording methods, etc. ? ! ! Although it is difficult to miniaturize the device because the secondary photographic recording method requires multiple developing devices that handle photoreceptors, powders, or liquids, it has the advantage of easily achieving a resolution of 16 dots (7 am) or higher and recording at high speed. There is. With other methods, it is difficult to stably obtain such high resolution.

There are various methods for recording multicolor images using electrophotography.
The method called full color process separates the original image into three colors: blue (B), green (G), and red (R), and exposes each color separately to a photoreceptor to produce yellow (Y) and magenta (M).
, cyan (C) (black, if necessary) development is performed, and toner images of one color are transferred onto a transfer paper in layers to obtain a full-color image. Furthermore, as an electrophotographic method for color hard copies, there is one disclosed, for example, in Japanese Patent Laid-Open No. 5G-144452. In this case, there are multiple exposure devices and developing devices for each color on the circumference of the photoreceptor, and by transferring the images onto recording paper at once, it is possible to obtain one multicolor hard copy per rotation of the photoreceptor. . Also, in the above example, the image is written using multiple exposures.
Examples in which this is performed using one laser exposure device are disclosed in Japanese Patent Application Laid-Open Nos. 60-75850 and 60-76766. However, in this case, the photoreceptor needs to be rotated multiple times. The above method performs color reproduction by separating the three primary colors (B%G%R) for image formation, but in contrast to this, there is a slightly special method that separates the colors into two colors and reads them. Several methods for obtaining signals have been disclosed. Examples include JP-A-56-162755 and JP-A-57-44825.

(Problems to be Solved by the Invention) In the electrophotographic multicolor image forming apparatus as described above, there are problems that have not been experienced with monochrome electrophotographic copying machines, and it is difficult to always produce stable multicolor images. It was difficult to obtain with good reproducibility. In the above-mentioned method in which multiple or multicolor toner images are formed on a photoreceptor and transferred at once, the transfer becomes extremely unstable, and good hard copies cannot be obtained in some cases. Therefore, it is necessary to solve such transfer problems and to obtain a stable transfer state so that good hard copies can be obtained with good reproducibility.

The purpose of the present invention is to solve the problem of Matsusha,
First, it is desirable to provide an image forming apparatus that can faithfully copy a multicolor toner image without image holes and produce a multicolor image without color bleeding or character bleeding. The purpose of Pt52 is to provide a multicolor image forming apparatus that can maintain a high copying rate of toner images of each color regardless of environmental changes and changes in paper quality, and can obtain high-density, vivid multicolor images. A third purpose is to provide a multicolor image forming apparatus with high feeding reliability by assisting the performance of electrostatic separation of recording paper from the photoreceptor.

(Means for solving the problem of point m) The object of the present invention is to provide a band Mlir1 for uniformly charging the surface of the photoreceptor along the surface of the photoreceptor that circulates, a position for writing an electrostatic latent image, and It is equipped with a plurality of developing devices for different color toners and an electrostatic transfer device, and the photoreceptor is rotated multiple times to repeat formation of an electrostatic latent image and development with different color toners multiple times to form a multicolor toner image. After that, the multicolor toner is formed on the photoreceptor, and then the photoreceptor is rotated again, and the entire surface including the toner image is charged by the charging device, and then the multicolor toner is transferred to the electrostatic transfer device without imagewise exposure. This cannot be achieved by a multicolor image forming device that transfers an image onto a recording paper at once to obtain a multicolor image.Furthermore, after the electrostatic transfer device, the static charge on the recording paper is removed by AC corona discharge. Good transfer and separation performance can be obtained by having an AC corona charge removal/separation device that separates the recording paper together with the toner image from the photoreceptor.

Next, the present invention will be explained, but the present invention is not limited thereto.

An example of an electrophotographic copying machine according to the present invention is shown in FIG. 1, where A is a reading unit and B is a writing unit. Along the moving surface of the photoreceptor, there are a charger 41, an image exposure section 37, and a developer 43, 44, 45, and a transfer pole 50.
A separation pole 51 is provided, and the recording paper separated there is fixed by a fixing unit 52. The remaining toner adhering to the photoreceptor is removed by the cleaning section 46.

In forming a multicolor image in the present invention, first, image exposure of a first color component (for example, red) is performed, and this is developed with a corresponding toner (for example, cyan) to form a toner image on the surface of the photoreceptor. Then, it passes through these processes without being subjected to transfer separation, cleaning, etc., and enters the next copy cycle. In this way, a plurality of toner images of red, black, etc. are sequentially superimposed on the photoreceptor to form a multiple or multicolor toner image.

Then, the final toner image is formed on the photoreceptor, and after it is made to circulate once more over the entire surface to perform charging, the toner image is transferred to the transfer pole.
)) The toner image is transferred to recording paper, separated from the photoreceptor by separation poles, and fixed, thereby producing a multicolor image copy on the recording paper.

8 like this! Considering the state of the toner layer potential in the structure, as shown in Figure Pt53, the relationship between the potential remaining in the toner layer (toner layer potential) and recharging shows that when charging is repeated, the toner potential rises to a certain level. Understand 0 In the figure, M/^ is a unit surface.

This is the amount of toner per product. For example, if toner is stacked in the order of black, red, and blue, black and red will be charged three times and two times, respectively, so the toner potential will be as shown in Figure 4. The potential of the layer, vt, indicates the potential of the toner layer. That is, the blue toner potential is different from the red and black toner potentials. However, the transfer rate is affected by the amount of charge on the toner. This relationship is the fifth
Shown in the figure.

In the figure, the vertical axis represents the toner transfer rate, and the horizontal axis represents the transfer current.

The method for measuring the transfer rate and transfer current will be described below.

Transfer rate measurement method: Form a constant batch toner image on a photoconductor, measure the amount of toner forming the primary image before transfer, and then measure the amount of toner remaining on the photoconductor after transfer. The amount Mr is measured to obtain the transfer rate R according to the following formula.

Incidentally, the toner mfl on the photoreceptor can be measured by a general method such as a dog test.

1! Using a soft pad with a known amount, the toner on the photoreceptor is sampled and the weight am can be determined by subtracting the known weight of the soft pad to obtain the amount of adhered toner ffl.

Generally speaking, when it comes to measuring transfer current values, a constant current power source that keeps the output current constant is the mainstream for high-voltage devices, due to the need for stability against environmental changes.

For this setting, in the development stage, a drum (dummy drum) in which the photosensitive layer, which is less affected by shape etc., is not shaped is mounted and the Tl flow value flowing into this dummy drum from the transfer power source through the transfer pole is measured. . This is called a dummy current, and the set value is determined from this optimum value. The transfer current shown on the horizontal axis of FIG. 5 is the value of the dummy current. The symbols in FIG. 5 are as follows. ○ and ・ are for the toner charge amount corresponding to the red toner at the above point, and Δ and Mu are for the blue toner band? This is the case for the tt amount. Also, O1Δ is when the environmental conditions are 30° C. and 80% RH, and Mu is when the environmental conditions are 10° C. and 20% RH. As can be seen from the figure, in the case of Δ and Mu, that is, blue toner that is not recharged, the transfer rate decreases as the transfer current increases, and the behavior is different from that of red and black toners, that is, when they are recharged. . However, as can be seen from FIG. 3, by recharging the blue toner, the toner potential can be raised to match the potential of other toners.

Therefore, by the method of the present invention in which the toner image is superimposed on the photoreceptor and then rotated one more time to perform charging, it was possible to equalize the potential of each toner and to equalize the transfer rate. Then, after transferring at the electrostatic transfer pole, the electrostatic charge on the recording paper is removed by AC corona discharge, which increases the transfer ability and separation ability, resulting in high resolution (good multicolor image copies with no character bleed could be obtained). .

As the photoreceptor of the multicolor image forming apparatus of the present invention, there are those using, for example, photoconductors such as selenium thread, organic compound type, 7 mol 7 as silicon type, titanium oxide type, zinc oxide type and the like. However, there are many types of compounds with various properties, and organic compounds are superior in the sense that they have an extremely wide range of choices. Among these, a desirable organic compound-based photosensitive material must be one that is particularly sensitive to a semiconductor laser and has sufficient color sensitivity in the red to infrared range. Specifically, for example, azo pigments described in JP-A-59-218447, or JP-A-59-219752,
JP-A-59-214034, JP-A-59-15585
No. 1, JP-A-59-155847, JP-A-55-5
9468 and JP-A No. 54-147839, a 7-thalocyanine compound or complex is used as a charge-generating substance, and a charge-transporting substance is used as a charge-transporting substance, for example, as described in JP-A-61-14642. It is better to use a triarylamine conductor such as For the actual production of photoreceptors, for example, JP-A-52-135736, JP-A-53-44028, JP-A-53-76036,
It is possible to manufacture a photoreceptor using the N configuration or manufacturing technology described in publications such as No. 53-58240 and JP-A-53-58240.

Developers used in multicolor image forming devices On the other hand, there are two types of developers used in such devices: two-component developers consisting of toner and carrier, and one-component developers consisting only of toner. .

A two-component developer has the advantage that the ratio of toner to carrier can be easily controlled. In addition, especially in a two-component developer composed of a magnetic carrier and a non-magnetic toner, there is no need to include a large amount of black magnetic material in the toner particles.
It has the advantage of being able to use color toners that are free from color turbidity caused by magnetic substances and forming clear color images.

It is particularly preferable that the two-component developer used in the present invention is composed of a magnetic carrier as a carrier and a non-magnetic toner as a toner.

It is preferable to use a carrier particle size having an average particle size of about 5 to 80 μs, and most preferably a carrier particle size of about 5 to 40 μs.
In addition, the toner particle size has a good average particle size of about 1 to 20 μm.
3-15 μl is most desirable.

Examples of these developers include, for example, Japanese Patent Application Laid-Open No. 53-83
No. 60, Patent Application No. 1982-129213, Patent Application No. 1987-1
No. 07452, Japanese Patent Application No. 59-134078, Japanese Patent Application No. 1983
It is described in Japanese Patent Application No. 9-125283, Japanese Patent Application No. 59-129215, Japanese Patent Application No. 59-129216, and Japanese Patent Application No. 129217.

As the binder resin for these developers, various thermoplastic resins can be used, including styrene resin, styrene-acrylic resin, styrene-butadiene It resin,
Examples include addition polymerization type resins such as acrylic resins, condensation polymerization type resins such as polyester resins and polyamide resins, and epoxy resins. The materials constituting the toner include (1) thermoplastic resin binder 80 to 90 wt% e.g. polystyrene, styrene acrylic polymer, polyester,
Polyvinyl butyl, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer, etc. or a mixture of the above <2>m Materials: Colorant 0-15wt% Example: Black: Carpon Black Cyan: Body 7 Taroshi 7 nin, sulfonamide derivative dye yellow: benone derivative magenta: rhodamine B lake, carmine 6[1, etc.

(3) Charge control agent 0 to 5 wt% Positive donor: Nigrosine-based electron-donating dye, alkoxylated amine, alkylamide chelate, pigment, quaternary ammonium salt, etc.

Negative toner Two-electron accepting organic complex, chlorinated paraffin, chlorinated polyester, polynystyl with excess acid groups. Chlorinated copper 7-talonanine, etc.

(4) Fluidization examples: coroiglusilica, hydrophobic silica, silicon face, metal soap, nonionic surfactants, etc.

(5) Cleaning agent (prevents toner filming on the photoreceptor) Examples: fatty acid metal salts, oxidized silicic acid with organic groups on the surface, fluorine surfactants, etc.

(6) Fillers (aimed at improving the surface gloss of images and reducing the amount of raw materials/materials used) Examples: calcium carbonate, clay, talc, pigments, etc.

In addition to these materials, a magnetic material may be included to prevent fogging and toner scattering.

As magnetic powder, 0.1 to 1 μl of triiron tetroxide, γ-M
Ferric oxide, chromium dioxide, nickel 7-elite, iron alloy powder, etc. are used, and are contained in an amount of 5 to 70 wt % based on the toner.

The resistance of the toner varies considerably depending on the type and amount of magnetic powder, but in order to obtain a sufficient resistance of 10"9cm1, preferably 1012Ωcx or more, it is preferable to keep the amount of magnetic material at 55wt% or less. In order to maintain clear colors, the amount of magnetic material is desirably 30 wt% or less, and particularly desirably 5% or less.

Resins suitable for pressure fixing toner that plastically deform and adhere to paper with a force of about 20 kg/c+i include wax,
Non-adhesive materials such as polyolefin neck, ethylene-vinyl acetate copolymer, polyurethane, rubber, etc. (fats, etc.) are selected.

Capsule toners can also be used.

A toner can be made using the above-mentioned materials by a conventionally known manufacturing method.

In the configuration of the present invention, in order to obtain a more preferable image, it is desirable that the toner particle diameter (average particle diameter in mm) be approximately 50 scans or less.

In the multicolor image forming apparatus of the present invention, there is no theoretical limit to the toner particle size, but from the viewpoint of resolution, toner scattering, and conveyance, it is usually preferably about 1 to 30 μl, but 3 to 15 μl.
Particularly preferred are those with a diameter of 1.1, and the ff1fi average particle diameter is a value measured with a Coulter Counter manufactured by Coulter.

Molecule%t? ! ! The poles are placed alongside the transfer electrodes.

The transfer wire is composed of a discharge wire, and the transfer wire applies a DC voltage, and the separation wire applies an AC voltage of several KV between the photoreceptor and the substrate.

(Example) Example 1 FIG. 1 shows the configuration of a multicolor image forming apparatus according to the present invention, and a multicolor image is formed in the following manner.

In FIG. 1, A is a reading unit, B is a writing unit, C is a developing unit, and D is a paper feeding section.

! (Mitori Units) In A, 1 is the platen plus,
Original 2 is placed on this platen glass 1 (original w4
2 is illuminated by fluorescent lamps 5 and 6 provided on a carriage 4 that moves on a slide rail 3. The movable mirror unit 8 is provided with mirrors 9 and 9', which move on the slide rail 3, and in combination with the first mirror 7 provided on the carriage 4 read the optical image of the document 2 on the platen glass 1 with the lens. Derived to unit 20.

The lens reading unit 20 includes a lens 21 and a prism 22.
, the first reading board 24, the red channel (hereinafter R-
cl+) CCD 25, lQ2 reading board 26,
Cyan channel (hereinafter referred to as C-cl+) CCD 2
Consists of 7. The original light image transmitted by the PISl mirror 7, mirror 9, and mirror 9' is focused by a lens 21, and divided into an R-ah image and a C-ch image by a guichroic mirror provided in a prism 22. , P
R-cl+ CC provided on the J1 reading board 24
D 25 and C- provided on the second reading board 26
The images are respectively formed on the light receiving surface of the ch CCD 27.

Said 11cb CCD 25 and C-ah CCD 2
The image signal output from 7 is sent to signal path Fi section E, which will be described later.
At the signal road J! I will be treated. Signal road J! In the first part E, a color signal separated according to the toner color, which will be described later, is outputted and inputted to the eight input unit B.

In the writing unit (13), a laser beam generated by a semiconductor laser is rotated and scanned by a polygon mirror 32 rotated by a drive motor 30, passes through an Fθ lens, has its optical path bent by a reflecting mirror 37, and is uniformly charged in advance by a charger 41. The charged photosensitive drum 40 is scanned. A latent image corresponding to the first color is formed on the drum surface by the main scanning by the laser beam and the W11 scanning by the rotation of the photosensitive drum 40. This latent image is developed by a developing device 44 loaded with red toner, for example, to form a toner image on the drum surface. The obtained toner image is separated from the photoreceptor drum surface while being held on the drum surface by the cleaning device i! 46 and enters the next copy cycle. The photosensitive drum 40 is charged again by the charger 41.

Next, the f52 color signal output from the signal foil 31 section E is input to the writing unit) B, and is written on the drum surface in the same manner as the first color signal, forming a latent image. be done. The latent image is developed by a developer 45 loaded with toner of a second color, for example blue. This blue toner image is formed on top of the previously formed red toner image.

A developing device 43 has black toner and forms a black toner image on the drum surface based on a control signal generated by a signal processing section. AC and DC biases are applied to the sleeves of these developing units 43, 44, and 45, and noyanming development is performed using two-component toner, and non-contact development is performed on the grounded photoreceptor drum 40. In this embodiment, the toner images are stacked in the order of black, red, and blue.

The superimposed toner images developed with black, red, and blue toners in this way are then made to revolve around the photosensitive drum once more and are recharged by the charger 41.
Next, the image is transferred by the @photographic pole 50 onto the recording paper 61 fed by the feeding belt 62 and feeding roller 63 of the paper feeding section. The transfer paper on which the toner image has been transferred is separated from the photoreceptor by a separation pole 51 using AC corona discharge, and is further conveyed to a fixing device 52 where it is fixed and a color hard copy is obtained.

A cleaning device 46 comes into contact with the photosensitive drum 40 after the transfer, and performs cleaning with a blade 471 to remove unnecessary toner from the drum surface.

The row 249 of the cleaning device is used to remove a small amount of toner left between the drum surface and the blade when the blade 47 is separated from the drum surface in preparation for the next exposure and development after cleaning. While rotating in the opposite direction, the contact portion with the drum surface is rubbed and residual toner is collected.

The image forming conditions in the multicolor image forming apparatus of this example were as follows.

l Image forming conditions (1) Image forming member Photoreceptor Organic photosensitive layer consisting of a charge generating substance 7 talocyanine compound and a charge transporting substance triarylamine derivative Drum diameter 1401 Linear speed
581/see Surface potential Charging potential (potential of non-image area during development) -650V exposure area potential -10V image exposure conditions Light source Semiconductor laser wave R780±20++@ Recording density 16doLs\I Developing device sleeve Non-magnetic stainless steel, 180m+aφ line Rotating magnet 8 poles at speed 20+++m/see, rotating magnetic flux density 70 at 600 rpm-
0 Gauss (sleeve surface) Developer carrier Magnetic powder resin dispersion system, average particle size (weight basis) 20 μm Specific resistance 10I4 Ωel11 or more Magnetization Approx. 50
eIau/g(σ1000)σ1°. o:1000. f
Magnetized toner red (R) in a magnetic flux density of 1.5 μm average particle size (weight basis) 11 μIfi average charge amount 10 μc/g (toner concentration 15 III%) Rhodamine B lake is dispersed.

Blue ([1) Average particle size (MFL standard) 11μ average charge amount 12μc/g (toner concentration 15-t%) Copper 7 talocyanine is dispersed.

Black (K) Average particle size (1! I! fi a fi
l 01 pm average charge amount 12 μc/g (toner concentration 15 wt%) Carbon black is dispersed.

Development conditions Between photoreceptor and sleeve 1, Omm Developer N thickness 0.2 to 0.8II+m (quiet) (regulated by non-magnetic blade) (common to the above) Development bias (black) DC-500VAC1, OKV<effective value)
2KHz (red) DC-500VAC1,0KV (
Effective value) 2KIlz(ff) DC-500V
ACO, 8KV (effective value) 2KHz transfer electrode D
a -4,5--5, OKV separation electrode frequency WL5
00IIz Output current (constant type) 350~450μ＾Gummy current value
80 to 100 .mu.^ According to this example, it was possible to obtain good copies without blurring of images and characters.

(Example 2) Example 1 was a multicolor image using three color toners, but mushroom (Y), magenta (M), cyan (C), black ( B) describes an example in which multicolor image numbers formed by overlapping four color toners are simultaneously transferred, and FIG. 2 shows the multicolor image numbers 7 & 8 of VC position!
One structure is shown. In this example as well, after forming a multicolor toner image on the photoreceptor according to the present invention, it is further recharged and
Good copies can be obtained by applying a method of removing the electric charge on the recording paper using C corona discharge.

(Effects of the Invention) As explained in detail in the Examples and clarified, in the multicolor image forming apparatus according to the present invention, which forms multicolor or multiple toner images on a photoreceptor and transfers them onto recording paper at once,
Color turbidity in each color without damaging the toner image,
It was possible to form a multicolor image with high density and no color bleeding. In addition, it is possible to form good character images with high resolution and no character bleed, and it also forms multicolor images that are always clear and have sufficient density even when the environment changes and the paper quality changes. It was possible to provide a multicolor image forming device with less curling and high feeding reliability.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the configuration of a multicolor image forming apparatus according to the present invention;
FIG. 2 is a schematic diagram showing the configuration of a multicolor image forming apparatus according to another embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the number of times of charging and the potential of the toner layer.
FIG. 4 shows the surface potential of each toner, and FIG. 5 shows the relationship between transfer rate and eaves current. A: Reading units) % B: 6 reading units, C
: Image forming section, D: Paper feeding section, 40: Photoreceptor, 51: Applicant of static eliminator separation device
Konishi Roku Photo Industry Co., Ltd. Figure 3 Figure 4 “Saisu Denni f!

Claims (2)

[Claims] (1) A charging device that uniformly charges the surface of the photoreceptor along the surface of the rotating photoreceptor, an electrostatic latent image writing device, multiple developing devices for different color toners, and one electrostatic transfer device. The photoreceptor is rotated multiple times to repeat formation of an electrostatic latent image and development with different color toners multiple times to form a multicolor toner image on the photoreceptor, and then rotated one more time. A multicolor image forming apparatus characterized in that the charging device performs only charging, and then an electrostatic transfer device transfers the multicolor toner image onto recording paper at once to obtain a multicolor image. (2) The invention further comprises an AC corona charge removal/separation device which removes the static charge on the recording paper by AC corona discharge after the electrostatic transfer device and separates the recording paper from the photoreceptor together with the toner image. 2. The multicolor image forming apparatus according to item 1.