JP2802847B2 - Color image forming equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a laser beam as an image exposure means and sequentially exposes a photosensitive member to an image to form a color toner image and obtain a color recording image. The present invention relates to an image forming apparatus. 2. Description of the Related Art Conventionally, in order to form a color image by, for example, electrophotography, a recording wound around a transfer body by repeating respective steps of charging, image exposure, development and transfer for each component color. Each color toner image sequentially superimposed on paper is obtained. That is, in order to form a color image using yellow, magenta, cyan, and black toners using light modulated by color information data from a color original,
The above steps are repeated four times to obtain a color toner image. However, in such a color image forming method, it is necessary to transfer the toner to a transfer member every time development with each color toner is completed, which increases the size of the apparatus, complicates the recording process, makes it difficult to align the image, and consumes it. There are problems such as a lot of time loss. Further, since each color toner image is transferred onto a recording sheet for each process, there is a problem that a transfer deviation occurs and a remarkable color image is formed. Therefore, yellow, yellow,
There is a color image forming method which solves the above-mentioned problem by superimposing and developing magenta and cyan toner images so that the transfer process is completed only once. Japanese Patent Application Laid-Open No. 58-143352 describes a configuration in which B, G, and R signals read by a reading device are modulated by respective semiconductor lasers to perform image exposure. On the other hand, the image forming process is characterized in that a step of repeating image exposure and development after charging is performed. Regarding this development, it is determined from the description that
In the development, saturated development is performed. For this reason, it is difficult to superimpose the three primary colors of yellow, magenta, and cyan at the same position, and it is similarly difficult to form the reproduction of black from the three primary colors. Semiconductor lasers have variations in output (emission wavelength, emission characteristics),
Further, the light emission characteristics are steep, and it is difficult to control the light amount of each laser, and the image quality becomes unstable. In addition, a highly accurate apparatus configuration for guaranteeing the resist including the parallelism between the lasers is also required. Also, because there is no recharging process,
There is a problem that the photoconductor has no sensitivity. Further, as pointed out in the above-mentioned publication, the area where the toner is adhered by the earlier development is hardly transmitted through the image exposure, and the surface potential does not decrease due to these. Therefore, the toner adheres in the later development. There is a problem that it is difficult to do. In this case, even if various color tones are expressed, the color balance is lost or a desired color image is not formed. As described above, in a multicolor image forming apparatus, gas laser light is often used as a light source for image exposure.However, since the laser light source conventionally uses a gas such as helium or neon, control of gas pressure is performed. However, it is pointed out that the light source device is difficult and the light source device becomes large and expensive. The laser beam L ₃ for image exposure is output from the laser beam exposure device 1 shown in FIG. In FIG. 2, for example, a signal 7 from a signal source 6 based on image information, facsimile, computer or the like is input to a driver 8, and the driver 8 uses an optical device such as an EOM (electro-optic modulator) or an AOM (acousto-optic modulator). modulator 5 is driven, the laser beam L ₃ from the light source 2 is modulated. The modulated laser beam L ₃ is
It is reflected by the reflecting surface of the polygon 9 rotating at a high speed, the laser beam L ₃ which is the reflected electrostatic image is irradiated to the photoconductor 12 that has been previously positively charged is formed. The lens 3 is a lens that converges the laser beam L ₃ to a diameter (for example, 50 to 300 μm) that can be modulated by the modulator 5, and the lens 4 is a collimating lens for obtaining a parallel laser beam L ₃ after modulation. , and the lens 10 is a fθ lens for imaging, 11 denotes a scan range of the laser beam L _3. As shown in FIG. 2, the laser light L ₃
To modulate is to require a device such as a driver 8 and the optical modulator 5, and the laser beam L ₃ is in an image forming is requested that the output constantly, consumption of the light source energy is enormous What is the source. On the other hand, semiconductor lasers have a problem of luminous efficiency due to manufacturing variations. Further, the light emission characteristics are steep as shown in FIG. 8, and it is necessary to control the light quantity individually. Particularly, in the case of forming a multi-color image, a large amount of image data is required, and in order to maintain color balance, a stable, high-speed and good exposure source capable of reproducing gradation is required. Therefore, a compact and low-cost laser light source capable of modulating light intensity corresponding to image data and a method of using the same are required. There is also a need for a compatible multicolor image forming apparatus. SUMMARY OF THE INVENTION The present invention has been proposed in view of the above circumstances, and an object of the present invention is to use a laser light source which is compact, low-cost and capable of high-speed modulation and is suitable for forming a multicolor image. An object of the present invention is to provide a color image forming apparatus. The object of the present invention is to provide a charging device, an image exposing device, and a developing device made of yellow, magenta, cyan, and black around a photoreceptor. The multi-color toner images laminated on the photoreceptor are overlapped and formed by repeating an image forming step of performing image exposure by the developing unit and developing by the developing unit for each color, and then transferring the multi-color toner image to a transfer material. In the color image forming apparatus, the image exposing means is a semiconductor laser, and the semiconductor laser performs an arithmetic processing on an input signal of a color image in the image forming process according to a toner image forming order, yellow, magenta, A color image forming apparatus, comprising: performing image exposure using a semiconductor laser beam that modulates exposure intensity for each color using color image data of cyan and black. Is achieved by In the present invention, using a high-performance semi-conductors laser light source, the semiconductor perform yellow and processing an input signal of a color image, magenta, cyan, and control by giving the color image data signal consisting of black It is characterized in that an intensity-modulated laser beam is oscillated, and an electrostatic latent image for each color is formed on a photoreceptor using the laser beam. An example of a color image forming process using such a laser beam will be described below with reference to FIGS. FIG. 1 is a flowchart illustrating a multicolor image forming process;
FIG. 5 shows an image exposure apparatus using a laser beam. In FIG. 1, E is a positive surface potential applied to the surface of the photoreceptor;
H is the image exposed portion of the photoreceptor, DA is the unexposed portion of the photoreceptor, Du
p indicates a rise in potential caused by the positively charged toner T adhering to the exposed portion PH in the first development, and Cup indicates a potential rise in the exposed portion PH caused by the second charging. The photoreceptor is uniformly charged by a scorotron charger or the like and given a constant positive surface potential E. The surface potential E is the first time the image exposure by the laser beam L ₃ in FIG. 2 to be described later, lowered to near the zero potential in the exposed portion PH. Here, so-called reversal development is performed in which a DC component is applied to the developing device by applying a positive bias that is substantially close to the surface potential E of the unexposed portion to attach toner to the exposed portion. As a result, the positively charged toner T in the developing device adheres to the exposed portion PH having a relatively low potential, and a first toner image (for example, a yellow toner image) is formed. In the area where the toner image is formed, the potential is increased by Dup because the positively charged toner T adheres. Next, a second charge is applied by a scorotron charger. The potential of the portion where the positively charged toner T adheres rises by Dup and becomes a potential close to the surface potential E of the non-exposed portion. Next, the laser light L is applied to the surface of the photoreceptor where a substantially uniform surface potential E is obtained.
The second image exposure by ₃ is performed to form an electrostatic image, and a second toner image (for example, a magenta toner image) is obtained through a similar developing operation. By repeating the above process, a multi-color toner image including a third toner image (for example, a cyan toner image) and a fourth toner image (for example, a black toner image) is formed on the photoreceptor. can get. By the image exposure process involving the charging,
The smoothing of the potential prevents color mixing of the toner and imparts photosensitivity to the photoreceptor. This multicolor toner image is collectively transferred to recording paper, fixed by pressure or heat, and discharged. On the other hand, the photoreceptor after the transfer is cleaned by the cleaning device to prepare for the next multicolor image formation. FIG. 5 shows an image forming apparatus for performing the above process. Using a laser device 32 as a first exposure source, a toner image of one color is formed by charging, image exposure, and development each time the photosensitive member rotates, and the Y, M, C, and BK toner images are formed by four rotations. After being superimposed on the photoreceptor, it is transferred. By the way, in a multicolor image forming apparatus,
It is important in this image forming process that the external image data is subjected to arithmetic processing and then input to the exposure system of the image forming apparatus. FIG. 3 shows an example of a block diagram of the arithmetic processing unit and the control system. External image data Yi (yellow), M
i (magenta), Ci (cyan), and BKi (black) are calculated by an arithmetic processing unit in accordance with the image forming order, development conditions, image exposure conditions, and the like, for example, in accordance with the present image process. Data Yo, Mo, Co, and Bo are formed and are used as output signals. The data is stored in the memory M
It is temporarily stored in y, Mm, Mc, and MB, but is output to the exposure system according to a command from the control unit. That is, by modulating the exposure intensity of the semiconductor laser on the basis of the image data Yo, Mo, Co, and Bo, the photoconductor is neutralized, whereby an appropriate electrostatic image is formed on the photoconductor. This electrostatic image is developed by a developing device driven at the same time. This arithmetic processing is an important step in the main image formation in which fluctuations in the photoconductor and development conditions directly affect the color balance in order to superimpose the toner image on the photoconductor. As the semiconductor laser light source, for example, a semiconductor device 20 composed of a gallium-aluminum-arsenic double heterostructure shown in FIG. 4 is used. Reference numeral 21 denotes an upper electrode, and reference numeral 25 denotes a lower electrode, to which the color-corrected data signal of FIG. 3 is input. 22 is P-AlzG
a (1-y) As upper cladding layer, 23 is nA
An active layer of lx.Ga (1-x) .As, 24 is n-
A lower cladding layer made of Aly.Ga (1-y) As; 25 a substrate made of n-GaAs; L an active layer;
23 shows laser light emitted from 23. However, X, Y, and Z take any value of 0 or 1. The light emission characteristics change sharply according to the applied current as shown in FIG. This characteristic varies from laser to laser and even from the emission wavelength. In this case, when a plurality of laser light sources are used, it is extremely difficult to form a desired potential latent image on the photoconductor. In this configuration, these problems are solved by performing image exposure using the same laser. This makes it possible to stabilize image exposure, that is, stabilize an image including color balance. The oscillation wavelength of the semiconductor laser light is relatively long at 700 to 830 nm, and a photosensitive member suitable for the semiconductor laser light is, for example, a charge generation layer (CGL).
And a function-separated type photoreceptor comprising a charge transport layer (CTL). That is, a Se deposition layer containing 10 to 40% by weight of tellurium as CGL, a resin dispersion layer of a photoconductive bisazo pigment or a trisazo pigment, a hydrogenated nitrogenated amorphous silicon deposition layer, a resin dispersion layer of a vanadyl phthalocyanine pigment, and the like are used. As the CTL, for example, polyvinyl carbazole, polyarylalkane-based aromatic amino compound, oxadiazole derivative, selenium vapor-deposited layer, or the like is used. The developer used to form the multicolor toner image of the present invention includes a two-component developer composed of a toner and a carrier and a one-component developer composed of only a toner. The two-component developer requires control of the amount of toner with respect to the carrier, but has the advantage that the triboelectric charging of the toner particles can be easily controlled. In particular, in the case of a two-component developer composed of a magnetic carrier and a non-magnetic toner, it is not necessary to include a large amount of a black magnetic substance in the toner particles. There is an advantage that a clear color image can be formed. It is particularly preferred that the two-component developer used in the present invention comprises a magnetic carrier as a carrier and a non-magnetic toner as a toner. The constitution of the toner is generally as follows. Thermoplastic resin: binder 80-90 wt
% Example: Polystyrene, styrene-acrylic polymer, polyester, polyvinyl butyral, epoxy resin, polyamide resin, polyethylene, ethylene-vinyl acetate copolymer and the like are often used in combination. Pigment: colorant 0 to 15 wt% Example: black: carbon black cyan: copper phthalocyanine, sulfonamide dielectric dye yellow: benzidine derivative magenta: rhodamine B lake, carmine 6R and the like. Charge control agent: 0 to 5% by weight Plus toner: Nigrosine-based electron-donating dye is large,
In addition, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, alkylamides, chelates, pigments, quaternary ammonium salts and the like. Negative Toner: An electron-accepting organic complex is effective. Outer chlorinated paraffins, chlorinated polyesters, polyesters having excess acid groups, chlorinated copper phthalocyanines and the like. Fluidizing agent examples: colloidal silica, hydrophobic silica are typical,
Other examples include silicon varnish, metal soap, and nonionic surfactant. The filming of the toner on the cleaning agent photoconductor is prevented. Examples: There are fatty acid metal salts, silicon oxide having organic groups on the surface, and fluorine-based surfactants. The purpose of the present invention is to improve the surface gloss of a filler image and to reduce raw material costs. Examples: Calcium carbonate, clay, talc, pigments and the like. In addition to these materials, a magnetic substance may be contained in order to prevent fogging and toner scattering. As the magnetic powder, ferric oxide of 0.1 to 1 μm, γ-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder and the like have been proposed. It is often used and contains 5 to 70% by weight based on the toner. Although the resistance of the toner varies considerably depending on the type and amount of the magnetic powder, the amount of the magnetic material is preferably set to 55 wt% or less in order to obtain a sufficient resistance. In order to maintain a clear color as a color toner, the amount of the magnetic material must be 30 watts.
It is desirable to set it to t% or less. Other resins suitable for the pressure fixing toner include wax, polyolefins, ethylene-vinyl acetate copolymer, polyurethane, rubber and the like so that the resin is plastically deformed with a force of about 20 kg / cm and adheres to paper. Adhesive resin and the like are selected. Capsule toner can also be used. Using the above-mentioned materials, a toner can be produced by a conventionally known production method. These cyan, magenta and yellow pigments have high transmittance to infrared light. Therefore, when charging and image exposure with a semiconductor laser are performed on the formed toner image, the toner image is transmitted and the photosensitive member can be neutralized, so that a latent image can be reliably formed. In the constitution of the present invention, in order to obtain a more preferable image, it is desirable that the particle diameter of the toner is usually about 50 μm or less from the relation with the resolving power. In the present invention, there is no principle limitation on the toner particle size, but usually 1 to 5 from the relation of resolution, toner scattering and conveyance.
Approximately 30 microns is preferably used. In this embodiment, a toner having a weight average particle diameter of 10 μm is used for all four colors. The magnetic carrier particles may be fine particles or lines composed of magnetic particles and a resin, for example, a resin dispersion system of a magnetic powder and a resin, or resin-coated magnetic particles in order to improve delicate points or lines. In addition, particles which are more preferably spherical and have a weight average particle size of preferably 50 μm or less, particularly preferably 30 μm or less and 5 μm or more are suitable. In this embodiment, the weight average particle size of all four colors is 30 μm.
Carrier particles were used. The weight average particle diameter of the toner and the carrier is a Coulter counter (manufactured by Coulter Inc.)
Was measured. In addition, the bias voltage makes it easy for charge to be injected into carrier particles, which hinders good image formation, and the carrier tends to adhere to the image support surface, and the bias voltage is not sufficiently applied. In order to prevent generation of the carrier, the resistivity of the carrier is 10 ⁸ cm or more, preferably 10 ¹² cm or more. It is more preferable that the insulating material has an insulating property of 10 ¹⁴ cm or more. In this embodiment, a resin dispersion type carrier having a magnetization of 500 e.mu and a specific resistance of 10 ¹⁴ cm or more was used. The specific resistance of the carrier is measured by the following measuring method. That is, after placing the particles in a container having a cross-sectional area of 0.50 cm ³ and tapping, a load of 1 kg / cm ² is applied on the packed particles, and 10 ² to ⁶ V / cm is applied between the load and the bottom electrode. It is determined by applying a voltage that generates an electric field, reading the value of the current flowing at that time, and performing a predetermined calculation. At this time, the thickness of the carrier particles is about 1 mm. The method for producing such a finely divided carrier is a method of coating the surface of a magnetic material with a resin using the magnetic material and the thermoplastic resin described for the toner, or dispersing and containing magnetic particles. , And the obtained particles are subjected to particle size selection by a conventionally known average particle size selection means. In order to improve the agitation property of the toner and the carrier and the transportability of the developer, and also to improve the charge control property of the toner so that toner particles and toner particles and carrier particles are hardly aggregated, the carrier is spherical. It is desirable that the spherical magnetic carrier particles are magnetically coated carrier particles, and the magnetic particles are selected as spherical as possible and subjected to a resin coating treatment. It can be obtained by using a magnetic fine particle to perform spheroidizing treatment with hot air or hot water after forming the dispersed resin particles, or by directly forming spherical dispersed resin particles by a spray drying method. An embodiment of the present invention will be described below in detail with reference to FIGS. 5, 6, 7, and 8, but the embodiment of the present invention is not limited thereto. FIG. 5 is a cross-sectional view of the color image forming apparatus of the present embodiment, FIG. 6 is a cross-sectional view of a laser light exposure apparatus,
7 shows a developing device, and FIG. 8 shows a current modulation characteristic. In FIG. 5, reference numeral 30 denotes a drum-shaped photosensitive member having a diameter of 120 mm.
A CGL in which selenium containing 1% by weight is deposited to a thickness of 1 μm and a CTL in which selenium is deposited to a thickness of 20 μm thereon;
It is rotated at a peripheral speed of 120 mm / sec in the direction of the arrow. Lk is a laser beam, which is output from the laser beam exposure device 32. The exposure apparatus
The structure of 32 is shown in FIG. 6, and the light source 50 has the gallium-arsenide-gallium-aluminum-arsenic double hetero (DH) structure shown in FIG. 4 and outputs 750 nm light at 15 mw. The output characteristic of the laser light source 50 is, as shown in (I), the output P with increasing current i (mA).
(Mw) slightly increases, but when the current value i reaches a predetermined value, laser oscillation occurs and the output increases rapidly. Thus, when the pulse current of (II) is charged, (II)
A sharp laser oscillation output as described above can be obtained. The laser light from the light source 50 shown in FIG. 6 passes through the reflection mirrors 54 and 55, is converted into parallel light by the collimator lens 51, is reflected by the polygon 52, and is irradiated on the photoreceptor 30 via the fθ lens 53. In FIG. 5, the photoreceptor 30 is charged to +600 V in advance by a charger 31 and then image-exposed to laser light Lky modulated by yellow data to form an electrostatic charge image. It is developed to form a first toner image (yellow toner image). The structure of the developing device 33 is shown in FIG. Benzidine derivative as the developer D is a coloring agent contained in this include nigrosine dye as a charge control agent, the weight average particle size 10 [mu] m, and more toner resistivity 10 ¹⁴ cm, distributed four-trioxide iron in the resin Made of
Weight average particle size 30 μm, magnetization 50 e.mu/g, specific resistance 10 ¹⁴
This is a two-component developer in which a carrier of not less than 1 cm is mixed at a weight ratio of 1: 9. In the developer D, a magnetic roll 56 having six poles is rotated in the direction of arrow F at a speed of 1000 rpm, and a sleep 57 having a diameter of 30 mm is rotated in the direction of arrow G at a peripheral speed of 120 mm / sec. As a result, the sheet is transported in the direction of arrow G.
A developer layer having a thickness of 0.5 mm is formed by the spike regulating blade 58 during the conveyance. In the developer reservoir 59, a stirring device 60 is provided for uniform mixing of the developer D, and when the amount of toner in the developer D is insufficient, the toner T is replenished from the hopper 62 via the supply roller 61 by a fixed amount. Is done. Next, the gap d between the sleep 56 and the photoreceptor 30 is set to 0.
During this time, a DC voltage of +500 V is applied from the power supply 63 to perform reversal development. Further, in order to vibrate the developer D in the development area E so that the development can be performed without contact with the photoconductor 30, the effective value is obtained from the power supply 64 at 2 KHz.
An AC bias of 1.2 KV is applied. The development area E
, The toner T is provided with a charge amount of 20 μc / g by frictional charging. Here, R is a protection resistor. In FIG. 5, the first toner image is not transferred to the recording paper P, and the photosensitive member 30 is again charged by +600 V by the scorotron charger 31. Next, the laser beam LkB modulated by the magenta data is irradiated, and the same as the first developing device 33, except that rhodamine B is used as a colorant of the toner on which the electrostatic charge image is formed. The image is developed by the second developing device 34 to form a second toner image. In the same manner as described above, the laser beam LkC modulated with cyan data and then the laser beam LkB modulated with black data are irradiated onto the photoreceptor 30 after uniform charging, and respective electrostatic charge images are formed. These electrostatic images are the same as those in the first developing device except that a developing agent in which the colorant in the toner is copper phthalocyanine is used. A third developing device 35 in which the developer is stored. The portion other than black is sequentially developed by a fourth developing device 36 in which a similar developer is stored to form a third toner image (cyan toner image).
And a fourth toner image (black toner image). Next, the stacked four-color toner images formed on the photoreceptor 30 are easily transferred by the operation of the static eliminator 37, and then transferred onto the recording paper P supplied from the paper feeding device 38. Is transcribed by the action of Here, 39 is a paper feed roller, and 40 is a guide plate. Next, the recording paper P is separated from the photoreceptor 30 by the separation electrode 42, transported by the guide 43 and the transport belt 44, carried into the fixing roller 45, heated and fixed, and discharged to the paper discharge tray 46. After the transfer is completed, the photosensitive member 30 is neutralized by a neutralizer 48 that has not been used during the formation of the toner image.
The blade 49 and the fur brush 65 of the cleaning device 47 were released while the toner remaining on the surface was being formed.
To be removed. In the color image forming apparatus of the present invention, after the image data from the multicolor original is subjected to the arithmetic processing by the arithmetic processing section as shown in FIG. 3, the laser light source shown in FIG.
Entered in 50. In the laser light source 50, the light source 50 is driven by the signal of the corrected image data as shown in FIG.
Is controlled, and the intensity P (mw) of the laser light oscillated from the light source 50 is modulated. When the intensity-modulated laser light Lk is irradiated onto the photoreceptor 30 which has been uniformly charged in advance, the amount of charge dissipated in accordance with the intensity of the laser light Lk is different. An electrostatic charge image having a gradation corresponding to the data signal is formed. Therefore, a multi-color toner image with gradation can be obtained by developing the electrostatic charge image with each color toner. As described above, according to the present invention, by adopting the above-described configuration, the color toner is exposed by performing the exposure on the toner image developed in the first stage and the development in the second stage. It is possible to correct a decrease in the amount of toner adhered in the later development, which is a problem when forming an image by superimposing it on a photoreceptor, and to obtain a multicolor image with excellent color balance and reproducibility. This is an excellent effect. [0054]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flowchart illustrating a process for forming a multicolor image. FIG. 2 is a sectional view showing a conventional image exposure system using a laser beam. FIG. 3 is a block diagram showing an image data arithmetic processing unit and a control system. FIG. 4 is a perspective view of a gallium / arsenic-based semiconductor laser device. FIG. 5 is a cross-sectional view of the color image forming apparatus according to the embodiment. FIG. 6 is a sectional view of an image exposure system using a semiconductor laser. FIG. 7 is a sectional view of a developing device used in the color image forming apparatus of FIG. FIG. 8 is a diagram illustrating a relationship between a signal current and a laser oscillation output. [Description of Signs] 20, 50 Laser light source 30 Photoconductor 31 Scorotron charger 32 Laser exposure device 33, 34, 35, 36 Developing device 37 Pre-transfer static eliminator 38 Paper feeder 41 Transfer electrode 42 Separation electrode 40, 43 Guide plate 44 Conveyor belt 45 Fixing device 47 Cleaning device 48 Static eliminator for removing residual charge 49 Blade 55 Reflecting mirror 51 Collimating lens 52 Polygon 53 fθ lens 56 Magnet body 57 Sleeve 63 DC bias 64 AC bias 65 Fur brush D Developer T Toner

Continuation of the front page (56) References JP-A-58-57139 (JP, A) JP-A-57-63565 (JP, A) JP-A-58-7661 (JP, A) JP-A-61-27565 (JP) JP-A-59-164568 (JP, A) JP-A-60-76766 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/44

Claims (1)

(57) [Claims] A charger around the photoreceptor, image exposure means, yellow,
Magenta, cyan, arranged developing means consisting of black, charged by the charger, an image exposure by the image exposure means, development by the developing unit, the on the photoreceptor by repeating the image forming process for each color for performing superposed multicolor bets toner images are stacked to form, then the color image forming apparatus for transferring to a transfer material the multi-color toner image, with the image exposure means is a semiconductor laser, the semiconductor laser is the image In the forming process, the input signal of the color image is
Yellow and arithmetic processing in accordance with the formation order, magenta, cyan, a color image forming apparatus which is characterized in that the image exposure by a semiconductor laser beam for modulating the exposure intensity for each color by using the color image data consisting of black .