JPH01126670A - Electrophotographic image producing method - Google Patents

Abstract

PURPOSE:To obtain a fine image with high definition and to make the device excellent in cleaning by executing the cleaning of a photosensitive body after developing operation by undefined particles is performed on the surface of the photosensitive body after transfer. CONSTITUTION:In a developing device 1, a main developing device 13, a transfer charger 16, a cleaning developing device 17 by using the undefined toner, a cleaning blade 18 and an eraser lamp 19 are provided on the circumference of the photosensitive drum 10. During one rotation of the photosensitive drum 10 in an arrow direction, a process such as electrification exposure development with globular toner transfer development with undefined toner-cleaning is executed. In such a case, two-component system developer including the undefined particles and carriers such as what is called the undefined toner which is not globular is used as the developer. Thus the fault in cleaning does not occur at all and the fine image with high definition can be obtained.

Description

[Detailed description of the invention]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method used in electrophotographic copying machines and printers using a one-component or two-component developer. 2. Description of the Related Art In order to obtain an image using an electrophotographic copying machine or printer, an electrostatic latent image is first formed on the surface of a photoreceptor, which is an image carrier. Next, the surface of the photoreceptor having this electrostatic latent image is developed using a developer, and the resulting toner image is transferred onto paper or the like. Developers used in such electrophotographic copying machines include a two-component developer mainly consisting of an insulating non-magnetic toner and a magnetic carrier, a one-component developer consisting only of an insulating magnetic toner containing a magnetic substance, Alternatively, there is a one-component developer using non-magnetic toner. Such toner usually comprises a thermoplastic resin, a colorant, a charge control agent, and, in the case of a magnetic toner, magnetic powder. In recent years, in such electrophotography, efforts have been made to reduce the diameter of toner for the purpose of achieving high definition images. However, such small-diameter particles have poor fluidity and also cause poor cleaning of the photoreceptor after development. Cleaning involves removing residual toner that has not been transferred to the paper from the surface of the photoreceptor with a blade made of rubber or the like, and if such cleaning is not sufficient, it will not be possible to form a good image the next time. Further, in order to stabilize the amount of charge and improve fluidity, it is also being considered to make the toner spherical in shape. However, such spherical particles also have the disadvantage of greatly deteriorating cleaning performance. Problems to be Solved by the Invention In order to solve this problem of poor leaning, it has been proposed to use a mixed toner consisting of a spherical toner and an amorphous toner with a smaller average particle size (Japanese Patent Application Laid-Open No. 5-11112).
9-102252). However, in such a proposal, the effects of the spherical toner, such as excellent high fluidity and precise latent image development characteristics, are diminished.
ゝ- The present invention provides an electrophotographic developing method that uses spherical toner to obtain high-definition, precise images and has excellent cleaning properties. In order to solve the problem, the present invention is characterized in that, in an electrophotographic development method using spherical toner, the surface of the photoreceptor is developed with irregularly shaped particles after transfer, and then the photoreceptor is cleaned. The present invention provides an electrophotographic image forming method. Next, the present invention will be explained in more detail with reference to Examples. FIG. 1 is a schematic sectional view showing a developing device for carrying out the image forming method of the present invention. In FIG. 1, the developing device l includes a main charger (11) around a photoreceptor drum (10).
, exposure device (12), main developing device using spherical toner (
13), a transfer charger (16), a cleaning developing device (17) using irregularly shaped toner, a cleaning blade (18), and an eraser lamp (19),
While the photosensitive drum (10) rotates once in the direction of the arrow, the following steps are performed: charging, exposure, development with spherical toner, transfer, development with amorphous toner, and cleaning. Therefore, the image forming process is performed according to the following steps (a) to (g). (a) The surface of the photosensitive drum (10) is uniformly charged with the main charger (11). (b) Next, the photoreceptor is exposed to a laser beam (12) or the like to form an electrostatic latent image. (c) Next, the main developing device (13) performs development. A two-component magnetic developer containing spherical toner and carrier is used as the developer. The spherical toner is transported from the hopper into the developing device, and is sufficiently mixed with the carrier by a stirring blade (20) to obtain a desired amount of charge. The spherical toner is carried by the ears of carrier on the developing sleeve (21), moves onto the electrostatic latent image on the photosensitive drum (10), and is developed. In addition,
A bias voltage may be applied to the developing sleeve (21) in consideration of the residual potential of the photoreceptor. (d) Transfer the obtained toner image to a charger (16)
is used to transfer and fix the image onto a recording medium such as paper. The paper is fed from the paper feed roller (22), and after being transferred, the paper is moved to the separation claw (23).
) is separated from the photoreceptor drum (10) and taken out to the outside of the apparatus by a conveyor belt (24). (e) Developing is performed by the cleaning developing device (17). A two-component developer containing amorphous particles such as non-spherical toner and a carrier is used as the developer. The amorphous particles are sufficiently mixed with the carrier by a stirring blade (25) in the developing device to obtain a desired amount of charge. The irregularly shaped particles are carried by the ears of carrier on the developing sleeve (26) and are developed by a bias voltage applied between the photoreceptor (10) and the developing sleeve (26). The bias voltage is appropriately selected depending on process conditions such as the characteristics of the photoreceptor and the charging characteristics of the amorphous particles. (f) The residual toner on the surface of the photoreceptor drum (10) is scraped off by the cleaning blade (18). (g) The surface potential of the photoreceptor is lowered to near OV by the eraser lamp (19), and the photoreceptor is subsequently charged and used for forming a latent image. The spherical toner used in the method of the present invention comprises a binder resin, a colorant, a charge control agent, a magnetic material, and other known toner components. In addition, the amorphous toner used as the amorphous particles may also be composed of the same components as the spherical toner. Further, the amorphous particles may be obtained by pulverizing only the binder resin without containing a colorant by an appropriate method. Spherical toner can be produced by a method in which irregularly shaped toner particles are scattered and treated with hot air to make them spherical, a spray drying method in which a resin solution in which toner components are dispersed and mixed is spray-dried, and a dispersion made of monomers in which toner components are dispersed and mixed. It can be produced by a method of performing suspension polymerization. The particle size of the spherical toner is preferably 3 to 20 μl. When the particle size is smaller than 3 μm, image density decreases. On the other hand, if it is larger than 20μ, the image quality will be poor. On the other hand, the irregularly shaped toner used in the method of the present invention is, for example, a conventionally known irregularly shaped toner obtained by sufficiently mixing the above-mentioned materials using a mixer or the like, and then melting and kneading them using an extrusion kneader. It may be. After cooling the obtained mixed material, it is finely pulverized and classified to obtain a toner having a predetermined particle size of 5 to 20 μm. Note that it is desirable that the average particle size of the irregularly shaped particles is smaller than the particle size of the spherical toner. Although toner with a particle size equal to or larger than spherical toner can be used, if irregular-shaped toner is inserted between the blade and the photoconductor, a smaller particle size of irregular-shaped toner will prevent the spherical toner from slipping through. can. Furthermore, it is preferable to use amorphous particles that are charged to the opposite polarity to the spherical toner because the remaining spherical toner and amorphous toner are electrostatically attracted to each other and become large particles that are easier to clean. Binder resins for these spherical and amorphous toners include conventionally known binder resins such as polystyrene, styrene-acrylic copolymers, polyesters, epoxy resins, polyolefin resins such as polyethylene and polypropylene, polyamide resins, maleic acid resins, and modified resins thereof. Examples include resin. These may be used alone or in combination of two or more. Further, as the coloring agent, carbon black, phthalocyanine-based organic pigments, xanthine-based organic pigments, dyes, etc. are used. If necessary, other known additives may be added, such as charge control agents such as nigrosine dyes and triphenylmethane dyes, silica, fluidizing agents such as titanium oxide and vinylidene fluoride, and mold release agents such as polypropylene and polyethylene. Good too. In addition, in the case of a one-component magnetic developer consisting only of toner,
Examples of magnetic materials that can be mixed into magnetic toner include metals such as iron, nickel, and cobalt; these metals and zinc;
Alloys or mixtures with metals such as antimony, aluminum, lead, tin, bismuth, beryllium, manganese, selenium, tungsten, zirconium, vanadium, etc., mixtures with metal oxides such as iron oxide, titanium oxide, magnesium oxide, etc., and ferromagnetic ferrite. , magnetite, and mixtures thereof. The particle size of these magnetic substances is 2 μl or less, preferably 1 μl or less as a primary particle. The blending ratio of the polymer and magnetic powder is 10 parts by weight of magnetic powder per 100 parts by weight of resin.
The amount is 0 to 900 parts by weight, preferably 200 to 800 parts by weight. Below, the present invention will be explained in more detail based on production examples, working examples, and comparative examples.

[Manufacture of spherical toner]

Production Example 1 Ingredients 11 parts by weight - Styrene 60 N-butyl methacrylate 35 Methacrylic acid.
5 The above acid components were sufficiently mixed using a sand stirrer to prepare a polymerizable composition. The composition was added to an aqueous gum arabic solution (concentration 3% by weight), and a stirrer (T,
Stir with a homogenizer (manufactured by Tokushu Kogyo Co., Ltd.) (30
The polymerization reaction was carried out at 60° C. for 6 hours at 00 rpm), and the temperature was further raised to 80° C. to carry out the polymerization reaction. After the reaction was completed, the reaction system was cooled, washed with water 5 to 6 times, filtered, and dried to obtain spherical particles. The average particle size of the obtained spherical particles was 10
．． 2 μl, the softening point (Tm) was 141'C, and the glass transition point (Ts) was 61°C. Production Example 2 Monodisperse spherical styrenic polymer obtained by seed polymerization method (average particle size of 7 μm, coefficient of variation of particle size within 10%,
Polymer particles (A) have a softening point of 128°C and a glass transition point of 54°C. 100 parts by weight of the polymer particles (A) and 5 parts by weight of carbon black (Mitsubishi Chemical Industries, Ltd. MA#8) were mixed and stirred at 1500 rpm for 5 minutes using a 101 Henschel mixer to coat the surface with carbon black. Polymer particles (B) were obtained. Next, 100 parts by weight of the polymer particles (B) and 2000 parts by weight of water in which 5 parts by weight of sodium polyacrylate were dissolved were mixed and stirred to obtain a system in which intermediate particles were dispersed in water. Then, styrene/n-butyl methacrylate/2,2,2. - 100 parts by weight of a monomer with a composition ratio of trifluoroethyl acrylate = 75/15/10 and 2 parts by weight of potassium persulfate as a polymerization initiator were added, the temperature of the system was raised to 80°C, and polymerization was carried out for 6 hours. , toner particles further having a resin coat layer on the polymer particles (B) were obtained. Toner particles have an average particle size of 1081
The coefficient of variation for one particle size was 11%.

[Production of amorphous toner for cleaning] Production example 3 [(+
) Chargeable toner] Ingredients Parts by weight Styrene-n-butyl meth 100 Acrylate resin (Softening point = 132°C, Glass transition point 26 Transition point power-Bon Black 5 (Mitsubishi Chemical Industries, Ltd., MA#8) Nigrosine Dye 3 (manufactured by Orient Chemical Co., Ltd., Bontron N-01) After thoroughly mixing the above materials in a ball mill, the dye 3 was heated to 140°C.
It was kneaded on the main roll. After cooling the kneaded material, feather
It was coarsely ground using a mill and further finely ground using a jet mill. Next, air classification was performed to obtain a fine powder with an average particle size of 8 μm. Production Example 4 ((-) Chargeable Toner) A toner was produced using the same method as Production Example 1 with the following composition. Acid value: 25. Hydroxy value: 38) Carbon black 5 (manufactured by Mitsubishi Chemical Industries, Ltd.) , MA#8)

[Manufacture of carrier]

Production example 5 Acid value 23. Hydroxyl value 40) Inorganic magnetic powder 500 (manufactured by Toda Kogyo Co., Ltd., EPT-1000) Carbon black
2 (manufactured by Mitsubishi Chemical Industries, Ltd., MA#8
) Thoroughly mix and grind the above materials using a Henschel mixer,
Next, the cylinder part is heated to 180°C, and the cylinder head part is heated to 170 degrees Celsius.
The mixture was melted and kneaded using an extrusion kneader set at ℃. After cooling, the kneaded material was finely pulverized using a jet mill, and then classified using a classifier to obtain a magnetic carrier having an average particle size of 55 μm. Production Example 6 Bisphenol type polyester resin (softening point 123°C;
Glass transition point: 65°C; AV, 21) in toluene solution (2
% solution) was adjusted. Next, core material ferrite F-25Q
HR (average particle size 50μ; electrical resistance 3.50X10'Ω
cl: 30°0 parts by weight (manufactured by Nippon Tetsuko Co., Ltd.) was sprayed using Spiller Coater 5P-40 (manufactured by Kaida Seiko Co., Ltd.) at a pressure of 3.5 kg/am and a spray amount of 40 g10+in.
The treatment was carried out for 120 minutes at a temperature of 50°C. A coated carrier (a) was obtained by removing aggregates from the obtained particles using a sieve (mesh size: 105 μl). 400 parts by weight of the coat carrier (a) and Fe-Zn
Ferrite fine particles MFP-2 (electrical resistance 5.21XI
4 parts by weight of O@Ωam (manufactured by TDK Corporation) was treated for 40 minutes at a rotational speed of 1100 Orp using Ongmill AM-20F (manufactured by Hosokawa Micron). Aggregates were removed from the obtained carrier particles using a sieve (sieve opening: 105 μR) to obtain a carrier. Example 1 Spherical toner (+ chargeability) obtained in Production Example 1 and Production Example 5
A developer having a toner mixing ratio of 8 wt % was obtained using the carrier obtained in step 1 and loaded into the main developing device. On the other hand, the carrier and the amorphous particles (+chargeable) obtained in Production Example 3 of Amorphous Particles for Cleaning were loaded into a developing device for cleaning, and copies were made using the electrophotographic copying device shown in FIG. Ta. The process conditions are as follows. System speed: 28 cm/sec Photoreceptor surface potential: -700 ■ Developing bias: -150 V Erase light amount: 10,001 ux As a result, an excellent image was obtained, and there were no cleaning defects at all. Example 2 Copying was carried out in the same manner as in Example 1 except that the spherical toner (+ chargeability) obtained in Production Example 2 was used. As a result, high-quality images were obtained, and no cleaning defects were observed. Example 3゜Spherical toner (+ chargeability) obtained in Production Example 2 and Production Example 6
A developer having a toner mixing ratio of 8 wt % was obtained using the carrier obtained in step 1 and loaded into the main developing device. On the other hand, the carrier and the amorphous particles (+chargeable) obtained in Production Example 3 of Amorphous Particles for Cleaning were loaded into a developing device for cleaning, and copies were made using the electrophotographic copying device shown in FIG. Ta. The process conditions are as follows. System speed 20 cm/see Photoreceptor surface potential -550v Developing bias -100V Erase light amount 10001ux As a result, excellent images were obtained and there were no cleaning defects. Example 4 Copying was carried out in the same manner as in Example 1 except that the system speed was 35 am/sec. As a result, excellent images were obtained, and no cleaning defects were observed. That is, according to the method of the present invention, excellent cleaning performance can be obtained regardless of the system speed, and stable, high-quality images without cleaning defects can be obtained even when using spherical toner. . Examples 5 to 8 In Examples 1 to 4, the amorphous toner obtained in Production Example 4 was used as the amorphous toner for cleaning, and the polarity of the developing bias for cleaning was reversed in the process conditions. Copying was carried out in the same manner as in 4. In all cases, excellent images were obtained, and no cleaning defects were observed. Example 9 The styrene-n-butyl methacrylate resin (softening point 13) used in Production Example 4 was used as amorphous particles for cleaning.
Copying was carried out in the same manner as in Example 1, except that a material (2° C.; glass transition point: 60° C.) was pulverized with a jet pulverizer to give an average particle size of 8 μm. As a result, excellent images were obtained, and there were no cleaning defects. Comparative Examples 1 to 4 Images were formed in exactly the same manner as Examples 1 to 4 except that the cleaning developing device 17 in FIG. 1 was removed. As a result, although the first copy image was excellent, poor cleaning occurred from the second copy.
The image quality deteriorated as the number of copies was increased. If a spherical toner is used without being equipped with a developing device for cleaning using amorphous particles as described above, poor cleaning will occur and a stable and excellent image cannot be obtained. Effects of the Invention According to the method of the present invention, high-definition, dense images can be obtained, and the cleaning properties of the photoreceptor are excellent.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an apparatus for carrying out the method of the invention. The main symbols in the figure are as follows. 1: developing device, 10: photosensitive drum, 13: main developing device, 17: developing device for cleaning, 18: cleaning blade. Patent applicant Minolta Camera Co., Ltd.

Claims (1)

[Claims] (1) An electrophotographic developing method using spherical toner, which is characterized in that after transfer, the surface of the photoreceptor is developed with irregularly shaped particles, and then the photoreceptor is cleaned.