JPH0458030B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of developing an electrostatic latent image with a dry developer, particularly a non-magnetic dry developer. Conventionally, various apparatuses have been proposed and put into practical use as dry developing systems. However, in any of the developing methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, the developing device has been constructed by forming a relatively thick layer. However, nowadays, there is a need to improve the clarity, resolution, etc. of developed images.
It is essential to develop a method for forming a thin layer of dry developer and an apparatus for the same. As a conventionally known method for forming a thin layer of dry developer, the method disclosed in Japanese Patent Application Laid-open No. 43037/1983 has been proposed and put into practical use. However, this concerned the formation of a thin layer of magnetic developer. Magnetic developers must have a magnetic substance added to them in order to have magnetism.
This is due to problems such as poor fixing properties when thermally fixing the developed image transferred to transfer paper, and poor color reproduction due to the color of the magnetic material (magnetic material is usually dark brown or black). Leads to. For this reason, methods for forming a thin layer of non-magnetic developer include a method in which soft bristles such as beaver hair are used as a cylindrical brush and the developer is adhered to the brush, and a method in which the surface is made of fibers such as velvet is used. A method has been proposed in which the developer is coated on the developing roller using a doctor blade or the like. However, when an elastic blade is used as a doctor blade for the above-mentioned fiber brush, it is possible to regulate the amount of developer, but uniform application is not achieved, and the fibers of the brush are simply rubbed by the fiber brush on the developing roller. Since no triboelectric charge is imparted to the developer present in between, there is a problem in that ghosts and the like are likely to occur. The present applicant has solved the above-mentioned problems of the prior art by forming a uniform thin layer of developer on the surface of the developer holding member and providing sufficient triboelectric charging to the developer holding member. Regarding the direction of movement of the surface, a method and apparatus have already been proposed in which a magnetic brush of magnetic particles is formed upstream of a magnetic particle restraining member, and a thin layer of non-magnetic developer is formed on the developer holding member by this magnetic brush. . (Special request 1982)
−71687). The thin layer of non-magnetic developer (toner) thus formed is disclosed in Japanese Patent Application Laid-open No. 54-43037 or No. 55-18656.
It can be suitably applied to the development of electrostatic images under the action of an alternating electric field by the so-called one-component jumping development method as disclosed in the above publication. The purpose of the present invention is to improve such a developing method, and in particular to provide a developing method that can obtain sufficient image density with small values of the frequency of the alternating electric field applied to the toner and the pp (peak-to-peak) voltage. It is about providing. According to research conducted by the present inventors, it has been found that it is extremely effective to use a toner containing a high dielectric constant substance in addition to a binder and a colorant in order to achieve the above-mentioned object. The developing method of the present invention is based on the above-mentioned knowledge, and more specifically, a latent image carrier that holds a latent image on its surface and a toner carrier that carries an insulating non-magnetic toner are fixed at a constant level in a developing section. a toner supply container having magnetic particles and an insulating non-magnetic toner having a binder, a colorant, and a high dielectric constant material having a dielectric constant of 10 or more is disposed on the surface of the toner carrier; A fixed magnet for forming a magnetic brush made of magnetic particles is disposed inside the toner carrier so as to be in contact with the toner carrier on the upstream side of the toner outlet of the toner supply container; At the same time, by circulating the magnetic particles in the toner supply container, the insulating non-magnetic toner is taken in and coated on the toner carrier, and the coated layer is regulated to a thickness thinner than the gap. The toner is transported to a developing section, and the latent image is developed in the developing section while applying an alternating electric field to the insulating nonmagnetic toner. The present invention will be explained in more detail below. In the following description, "%" and "parts" indicating quantitative ratios are as follows:
Unless otherwise specified, measurements are based on weight. As described above, the toner of the present invention contains a high dielectric constant material in addition to a colorant and a binder. Examples of high dielectric constant materials that can be used in the present invention include those having a relative dielectric constant of 10 or more. Specific examples include barium titanate, titanium oxide, magnesium titanate, and the like. These high dielectric substances are preferably used in the form of fine powder of about 0.01 to 1 μm in a ratio of 1 to 10 parts per 100 parts of the binder described below. As a binder, polystyrene, polyP-
Monopolymers of styrene and its substituted products such as chlorostyrene and polyvinyltoluene; styrene-p-
Chlorstyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer,
Styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer polymer,
Styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α
Methyl chlormethacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrenic copolymers such as indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene,
polypropylene, polyester, polyurethane,
Polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin,
Terpene resins, phenolic resins, aliphatic or alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, paraffin waxes, etc. can be used alone or in combination. All known colorants can be used, such as carbon black, nigrosine dye, lamp black, Sudan Black SM, First Yellow G, benzidine yellow, pigment yellow,
India First Orange, Irgazine Red, Paranitroaniline Red, Toluidine Red
Red, Carmine FB, Permanent Bordeaux
FRR, Pigment Orange R, Resol Red 2G, Lake Red C, Rhodamine FB, Rhodamine B Lake, Methyl Violet B Lake, Phthalocyanine Blue, Pigment Blue,
Brilliant Green B, Phthalocyanine Green, Oil Yellow GG, Zapon Fast Yellow CGG, Kayaset Y963, Kayaset YG,
Examples include Sumiplast Yellow GG, Zapon First Orange RR, Oil Scarlet, Sumiplast Orange G, Orazole Brown B, Zapon First Scarlet CG, Eisenspiron Red BEH, and Oil Pink OP. These colorants are used in amounts that give the toner the desired color tone, generally from 0.1 to 100 parts of binder.
Used in an amount of 5 parts. If necessary, a charge control agent and a fluidity modifier may be further added to the toner, and the charge control agent and fluidity modifier may be mixed (externally added) with the toner particles. good. Examples of the charge control agent include metal-containing dyes and nigrosine, and examples of the fluidity modifier include colloidal silica and fatty acid metal salts. Further, for the purpose of increasing the amount, fillers such as calcium carbonate and finely divided silica can be incorporated into the toner in an amount of 0.5 to 20 wt%. Furthermore, in order to prevent mutual aggregation of toner particles and improve their fluidity, a fluidity improver such as fine Teflon powder may be added, and this is for the purpose of improving mold releasability during hot roll fixing. It is also possible to add about 0.5 to 5 wt% of wax-like substances such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, carnauba wax, and Sasol wax. When manufacturing toner from each of the above components,
A method in which the constituent materials are thoroughly kneaded using a thermal kneader such as a hot roll, kneader, or extruder, and then mechanically crushed and classified; materials such as colorants and high dielectric constant substances are dispersed in a binder solution. Alternatively, a polymerization method in which a monomer that provides a binder resin is mixed with materials such as a colorant and a high dielectric constant substance to form an emulsified suspension, and then polymerized to obtain a magnetic toner. Toner manufacturing method, etc.
Each method can be applied, preferably when the particle size is 1
~30 μm toner is formed. Next, the developing method of the present invention using the above toner will be explained with reference to the drawings. The drawing is a schematic side sectional view of an example of a developing device including a toner thin layer forming section for carrying out the developing method of the present invention. Referring to the drawings, the cylindrical electrophotographic photoreceptor 1 includes:
Formed on a conductive substrate 1a such as A1, arrow a
move in the direction. A non-magnetic holding member 2 for holding toner is provided with a gap between the photoreceptor 1 and, in this embodiment, the holding member 12 has a cylindrical shape, but it may also have a web shape that moves endlessly. This also applies to the electrophotographic photoreceptor 1. Along with this movement of the photoreceptor 1, the toner holding member 2 is rotated in the direction of arrow b. In order to supply toner D to the toner holding member 2, a toner supply container 3 made of a non-magnetic material such as plastic or A1 is provided. The toner supply container acid has an opening near its lower part, and the toner holding member 2 is provided in the opening. Since a part of the toner holding member 2 is exposed to the outside through the opening, its surface moves from the inside of the toner supply container to the outside thereof,
Next, return to the same interior. The lower part 4 of the toner holding container 3 forms an enclosure so as to cover the lower part of the toner holding member 2, so that the toner does not leak to the outside. Further, a sealing member 5 is provided to further ensure prevention of toner leakage to the outside. A fixed magnetic field generating means for generating a fixed magnetic field is provided inside the toner holding member 2, that is,
A magnet 7 is fixedly provided. Therefore,
Only the toner holding member 2 rotates. This magnet 7
has N and S magnetic poles. A magnetic blade 6 made of a magnetic material is arranged near the top of the opening of the toner supply container 3 . A magnetic pole N of a magnet 7 is located on the opposite side of the magnetic blade 6 with the toner holding member 2 interposed therebetween. The position of the magnetic pole N is at an angle θ at a position upstream in the rotational direction of the toner holding member 2 from the position facing the magnetic blade 6.
(5 to 50 degrees) offset. Magnetic particles M (particle size: 30 to 200 μm, preferably 70 to 150 μm) are placed in the toner supply container of an apparatus having such a configuration.
When the toner holding member 2 is rotated with the mixture containing the non-magnetic toner D and the magnetic particles M
is due to the magnetic field and gravity of each magnetic pole,
While forming the magnetic brush 8, a circular motion is performed as shown by arrow c in the drawing. That is, near the outer surface of the toner holding member 2, the magnetic particles in the lower part of the toner supply container 3 are exposed to the magnetic field of the magnet 7 and the toner holding member 2.
Due to the rotational interaction of the toner, the toner rises along the outer circumference of the toner holding member 2, and at this time, the non-magnetic toner and the surface of the toner holding member 2 come into contact, and the non-magnetic toner in the base layer is electrostatically transferred to the toner holding member. 2 is coated on top. The particle size of the magnetic particles M is 30 to 200 μm, especially 70 μm.
The diameter is preferably 150 μm, and each magnetic particle may be made of magnetic material only or may be a combination of magnetic material and non-magnetic material. In this embodiment, the non-magnetic toner is charged by friction with the magnetic particles or the toner holding member 2, but preferably an oxide film or a resin or the like that is electrostatically at the same level as the non-magnetic toner is formed on the surface of the magnetic particles. By applying insulation treatment to reduce triboelectricity from the magnetic particles and allowing the toner holding member 2 to receive the necessary charge, it is possible to prevent the influence of deterioration of the magnetic particles and to prevent the toner from being applied to the toner holding member 2. Stabilize. The magnetic particles rise as the toner holding member 2 rotates, but due to the magnetic field formed between the magnetic blade 6 and the S pole of the magnet 7, they pass through the gap between the surface of the toner holding member 2 and the tip of the magnetic blade 6. be prevented from doing something. Therefore, the magnetic particles in this area are pushed by the magnetic particles sent one after another, rotate as shown in FIG. 2, and then fall slowly due to gravity. During this fall, it returns to the lower part of the toner supply container 3 while taking in the non-magnetic toner, and this process is repeated. On the other hand, since the triboelectrically charged toner is non-magnetic, it can pass through the toner holding member 2 without being restrained by the magnetic field that exists between the tip of the magnetic blade 6 and the surface of the toner holding member 2. The toner is uniformly and thinly coated on the surface by the action of the mirroring force, forming a thin layer 9 of toner on the surface of the toner holding member 2, and exits the container 3 to face the surface of the photoreceptor 1 for development. Ru. The developing method used here is JP-A-55-
The method described in Japanese Patent No. 18656 is preferred. An alternating voltage is applied between the electrophotographic photoreceptor 1 and the toner holding member 2 by a bias power supply 10 . The bias power source 10 may be a simple alternating current, but it is more preferable to have a direct current superimposed on an alternating current. In addition, in the above explanation of the principle, a magnetic blade made of a magnetic material such as iron is used as the regulating member, but a non-magnetic blade made of a non-magnetic material such as aluminum, copper, or resin or a non-magnetic blade made of a non-magnetic material such as resin or aluminum constituting the container is used. A magnetic wall can also be used as this regulating member. However, in this case, in order to prevent the magnetic particles from flowing out, it is necessary to make the gap between the sleeve and the regulating member even smaller than when using a magnetic blade. Further, when a magnetic blade is used, it is preferable in that a magnetic brush can be stably formed at the toner exit portion by the magnetic field between the blade and the magnetic pole. As described above, according to the present invention, by using a toner containing a high dielectric constant material, the frequency and pp (peak-to-peak) voltage of an alternating electric field applied to the toner can be improved in a so-called jumping development method by using a toner containing a high dielectric constant material. Provided is a developing method in which sufficient image density can be obtained with a small value. Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 Styrene-n-butyl meth 100 parts by weight Acrylate (70:30 copolymer) Nigrosine 1 Carbon black 5 Titanium oxide 10 Each of the above components was kneaded at 150°C with a hot roll, cooled, and coarsely ground with a speed mill. did. Next, it is finely pulverized with a diet mill and classified with an air classifier to obtain particles with a particle size of 5 to 20μ.
I got the toner. This toner was used in a Canon PC that had the developer configuration shown in the drawing and was modified so that a developer with a variable alternating electric field applied to the sleeve could be attached.
The minimum frequency of the alternating electric field and the difference in positive and negative peak values (p-p voltage) necessary to obtain an image density of 1.0 or more were determined using the -20 machine. Example 2 A toner was made in the same manner as in Example 1 except that barium titanate was used instead of titanium oxide in Example 1, and the alternation necessary to obtain an image density of 1.0 or higher was produced in the same manner. The lowest frequency of the electric field and the difference between positive and negative peak values were determined. Comparative Example A toner was made in the same manner as in Example 1, except that titanium oxide was not used in Example 1, and the minimum frequency, positive and negative values of the alternating electric field necessary to obtain an image density of 1.0 or higher were obtained in the same manner. The peak value difference was calculated. The measurement results of Examples 1 and 2 and Comparative Example are summarized in Table 1 below. 【table】

[Brief explanation of the drawing]

The drawing is a schematic side sectional view of an example of a developing device including a toner thin layer forming section for carrying out the developing method of the present invention. DESCRIPTION OF SYMBOLS 1... Electrophotographic photoreceptor, 2... Toner holding member, 3... Toner container, 7... Fixed magnetic field generating means, 6... Magnetic particle restraining member, 8... Magnetic brush, 9... Toner thin layer.

Claims (1)

[Claims] 1. A latent image carrier that holds a latent image on its surface and a toner carrier that carries an insulating non-magnetic toner are arranged with a certain gap in a developing section, and a binder, a colorant and A toner supply container having an insulating non-magnetic toner having a high dielectric constant material with a dielectric constant of 10 or more and magnetic particles is disposed on the surface of the toner carrier, and the toner is supported on the upstream side of the toner outlet of the toner supply container. A fixed magnet for forming a magnetic brush of magnetic particles in contact with the body is disposed inside the toner carrier, and as the toner carrier rotates, the magnetic particles are transferred into the toner supply container. The insulating non-magnetic toner is taken in and applied to the toner carrier by circulating the insulating non-magnetic toner, the applied layer is regulated to a thickness thinner than the gap and conveyed to a developing section, and the insulating non-magnetic toner is circulated in the developing section. A developing method characterized by developing a latent image while applying an alternating electric field to non-magnetic toner.