JPH0578831B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a developer for developing latent images in electrophotography, electrostatic recording, electrostatic printing, magnetic recording, and the like. More specifically, the present invention relates to an electrophotographic developer that is uniformly and strongly positively charged, visualizes a negative electrostatic charge image, and provides a high-quality image in a direct or indirect electrophotographic development method. [Summary of the Disclosure] This specification describes a positively charged magnetic developer used for direct or indirect electrophotographic development, in which the magnetic developer contains a magnetic toner, positively charged silicic acid fine powder, and a group a group of the periodic table. A technology that enables stable high image density to be obtained from the initial stage without fogging or scattering by containing oxide powder of elements belonging to This is to disclose. [Prior Art] Conventionally, electrophotography has been carried out using the following procedure. Charging of the photoconductive layer → photoimage exposure (latent image formation) → adhesion of toner (development) → transfer to paper, cloth, etc. → heating, pressure (fixing). There are many known developing methods for electrophotography, but they can be broadly classified into two-component developing methods and one-component developing methods. The former is a widely used method such as a cascade method or a magnetic brush method, and a two-component toner in which a toner and carrier particles are mixed is used for development. All of these methods are methods by which good images can be obtained relatively stably, but on the other hand, they have common problems associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier. In order to avoid such problems, various methods have been proposed that use a single-component developer that does not contain a carrier, but among these methods, many are superior to methods that use a developer made of magnetic toner particles. The MagneDry method (U.S. Pat. No. 3,909,258), which uses conductive magnetic toner, avoids the problems of the two-component development method, but because the toner is conductive, the developed image can be transferred to the final support material such as plain paper. The problem is that it is difficult to transfer electrostatically to In addition, electrostatic transfer is possible using high-resistance magnetic toner, and there is a development method that utilizes the dielectric polarization of this toner, but the development speed is inherently slow and the density on the developed surface cannot be obtained sufficiently. There are problems such as not being able to Another known method using this high-resistance magnetic toner is to charge the toner particles by friction with each other or with a sleeve, etc., but the number of times of contact between the toner particles and the friction member is small, and the friction The toner particles tend to be insufficiently charged, and the Coulomb force between the charged toner particles and the sleeve becomes strong and they tend to aggregate on the sleeve. The applicant previously proposed a new developing method that eliminates the above-mentioned problems in Japanese Patent Application Laid-Open No. 55-42141.
This is a jumping method in which an extremely thin layer of insulating magnetic toner is applied onto a sleeve, it is charged by friction, and developed by placing it very close to an electrostatic image under the action of a magnetic field, causing the toner to fly. be. This method increases the degree of contact between the sleeve and toner, enables good frictional charging for a one-component developer, supports the toner with magnetic force, and moves the magnet and toner relative to each other. This is because the toner particles are disaggregated from each other and are sufficiently rubbed against the sleeve, and background fog is prevented by developing the toner with the toner facing the electrostatic image without coming into contact with it. Therefore, excellent images can be obtained. However, even in this method, the amount of triboelectric charge that the toner particles have is significantly smaller than the amount of triboelectric charge that the toner particles have in normal two-component development. If a magnetic toner having only a weak charge is used in these methods, the image quality will be insufficient, such as low image density, scattering, blurring, and unevenness of the image. In particular, the initial image density is low, and several hundred copies are usually required to reach a constant density, and this instability in the rise is one of the major problems in one-component development. Furthermore, when the developing bias is lowered in order to increase the image density, problems such as background fog occur. Therefore, it was necessary to improve the triboelectric charge amount of the magnetic toner. As a means for this purpose, it is known to add silicic acid fine powder to a developer having negative chargeability, which improves image density and image quality, and provides images that are somewhat satisfactory. However, silicic acid fine powder generally has a strong negative charge, and good images cannot be obtained even if negatively charged silicic acid fine powder is added to a positively chargeable developer. Generally, a toner contains a charge control agent for the purpose of obtaining desired polarity and chargeability. Positive charge control agents include, for example, generally quaternary ammonium compounds and organic dyes, particularly basic dyes and their salts. Common positive charge control agents include benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium chloride, nigrosine base, nigrosine, safranin γ
and crystal violet. In particular, nigrosine base and nigrosine are often used as positive charge control agents. These are usually added to magnetite and a thermoplastic resin, heated, melted and dispersed, finely pulverized, and adjusted to an appropriate particle size as needed before use. [Problems to be Solved by the Invention] However, these dyes used as charge control agents have complex structures, inconsistent properties, and poor stability. In addition, it is easily decomposed or deteriorated due to decomposition during thermal kneading, mechanical impact, friction, changes in temperature and humidity conditions, etc., and tends to cause a phenomenon in which charge controllability is deteriorated. Therefore, when a toner containing these charge control agents is used in a copying machine for development, as the number of copies increases, the charge control agent decomposes or changes in quality, which may cause deterioration of the toner during durability. In addition, many positive charge control agents are hydrophilic,
Due to poor dispersion in these resins, the control agent is exposed on the toner surface when it is crushed after melt-kneading. Therefore, when using the toner under high humidity conditions,
Since these control agents are hydrophilic, there is a problem in that good quality images cannot be obtained. In this way, when a conventional positive charge control agent is used in toner, it can be applied to the surface of toner particles between toner particles, between toner and carrier, or between toner and toner carriers such as sleeves. The amount of charge generated varies, and problems such as development fog, toner scattering, and carrier contamination are likely to occur. When the toner is stored for a long period of time, it often deteriorates and becomes unusable due to the instability of the positive charge control agent used. Therefore, there is a method in which silicic acid fine powder, which is originally negatively charged, is modified to be positively charged and then added. For example, as described in Japanese Patent Publication No. 53-22447 and Japanese Patent Application Laid-open No. 58-185405, toners may contain silicic acid fine powder treated with aminosilane, or they may be treated with silicone oil having an amine in the side chain. A method of incorporating fine silicic acid powder has been attempted. By adding such positively charged silicic acid fine powder, it is possible to obtain clear, high-density images that are relatively fog-free, but it does not sufficiently solve the problems caused by tribocharging mentioned above. The current situation is that we have not yet reached this point. The present invention has been made in view of the above-mentioned problems of the prior art, and uses a positively charged magnetic developer that can stably obtain fog-free, clear, high-density images, especially without density fluctuations during initial startup. For the purpose of providing. [Means and effects for solving the problems] According to the present invention, a positively charged magnetic developer comprising a magnetic toner, positively charged silicic acid fine powder, and oxide powder of an element belonging to group a of the periodic table. agent is provided. The periodic table referred to here is based on the one described in Physical and Chemistry Dictionary (Iwanami Shoten, 3rd edition), page 1484. The positively charged silicic acid fine powder herein refers to one that has a charge amount of +5 μC/g or more with respect to the iron powder carrier.
In this charge amount measurement, first, the test substance (silicic acid fine powder) is mixed with an iron powder carrier having a particle size of 200/300 mesh at a ratio of 1:100.
Accurately weigh 1.5g. This was measured at _25cmH2 on a metal 400 mesh screen connected to an electrometer.
It is suctioned by the pressure of O, and the amount of charge per unit weight is determined from the sample substance separated and suctioned at that time and its amount of charge. In addition, in this specification, silicic acid fine powder includes anhydrous silicon dioxide (silica), aluminum silicate, sodium silicate, potassium silicate,
Refers to silicates such as magnesium silicate and zinc silicate. In addition, in this specification, two types of names, "magnetic developer" and "toner" are used for convenience, but "toner" is a part of "magnetic developer",
It consists of components selected from binder resins, magnetic substances, dyes, pigments, charge control agents, fluidity modifiers, lubricants, etc., and in addition, positively charged silicic acid fine powder and substances from the groups of the periodic table. ``Magnetic developer'' is made by adding oxides, carbon and other additives as needed.
That's what it means. The silicic acid fine powder used in the present invention is produced by a dry method or a wet method. The dry method is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, silicon tetrachloride is expressed by the following reaction formula. SiC ₄ +2H ₂ +O ₂ →SiO ₂ +4HC Also, during this process, a composite fine powder of silica and other metal oxides obtained by using other metal halide compounds such as aluminum chloride or titanium chloride together with silicon halide compounds. Also includes.
Silicic acid fine powder (silica) manufactured by dry method
Commercially available products include the following: AEROSIL (Japan Aerosil Co., Ltd.)
130 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Cab-O-SiL CABOT Co.
(Kyabot Co., Ltd.) M-5 MS-7 MS-75 HS-5 EH-5 Wacker HDK N 20 WACKER-CHEMIE
GMBH (Watker Hemie GMBH)
V15 N20E T30 T40 D-C Fine Silica Dow Corning Fransol Fransil There are various conventionally known wet methods. For example, decomposition of sodium silicate with acid, ammonia salts or alkali salts, a method of generating alkaline earth metal silicate from sodium silicate and then decomposing it with acid, and a method of converting sodium silicate solution to silicic acid using ion exchange resin. There are ways to do this. Commercially available silicic acid fine powders synthesized by a wet method include the following. Carplex Shionogi & Co. Nipsil Nippon Silica Toxil, Fine Seal Tokuyama Soda Vita Seal Takihi Silton, Silnetx Mizusawa Chemical Starsil Kamishima Chemical Himesil Ehime Pharmaceutical Cyroid Fuji Davison Chemical Hi-Sil Pittsburgh Plate Glass Co. Durosil ) Ultrasil Fiillstoff-Gesellschaft Marquart Manosil Hardman and Holden Hoesch Chemische Fabrik Hoesch K-G Sil-Stone −Stone) Stoner Rubber Co. Nalco Nalco Chem.Co. Quso Philadelphia Quartz Co. Santocell Monsanto Chemical Co. Imsil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch.K-G Calsil Fiillstoff-Gesellschaft Marquart Fortafil Imperial Chemical Industries Ltd (Imperial Chemical Industries) Microcal Joseph Crosfield & Sons Ltd. Manosil Hardman and Holden Vulkasil Farbenfabriken Bayer, A.-G. Albenfabriken Bayer) Tufknit Durham Chemicals Ltd. Silmos Shiraishi Kogyo Starex Kamishima Chemical Fricosil Taki Fertilizer Among the silicic acid fine powders above, the specific surface area due to nitrogen adsorption measured by the BET method is 30 m ² / g or more (especially 50
~400 m ² /g) gives good results. When these silicic acid fine powders are modified to be positively charged and incorporated into a developer, they exhibit charge controllability.
Examples of methods for modifying silicic acid fine powder to make it positively charged include a method of treating it with a silicone oil having an amine in its side chain, a method of treating it with an aminosilane, and the like. As the silicone oil having an amine in its side chain, a silicone oil containing a structural unit represented by the formula (1) is generally used.

[Chemical formula] (Here, R ₁ represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R ₂ represents an alkylene group or a phenylene group, and R ₃ and R ₄ represent hydrogen, an alkyl group, or an aryl group. However, The above-mentioned alkyl group, aryl group, alkoxy group, alkylene group, and phenylene group may contain an amine, or may have a substituent such as halogen within a range that does not impair chargeability.) Among these, As commercially available products, for example, those represented by the following structural formula can be preferably used.

[Chemical formula] (Here, R ₁ , R ₄ , R ₅ represent an alkyl group or an aryl group, R ₂ represents an alkylene group or a phenylene group, and R ₃ represents hydrogen, an alkyl group, or an aryl group.m, (n is an integer of 1 or more.) Specifically, the following are preferred, and one type or a mixture of two or more types may be used.

[Table] Note that the amine equivalent is the equivalent per amine (g/eqiv), which is the value obtained by dividing the molecular weight by the number of amines per molecule. Further, the viscosity at 25°C is preferably 5000 cps or less, particularly preferably 3000 cps or less. At 5000 cps or more, the dispersion into the silicic acid fine powder becomes insufficient, which tends to cause defective images such as fog. The above-mentioned treatment of fine silicic acid powder with silicone oil having an amine in its side chain can be carried out, for example, as follows. Vigorously stir the silicic acid fine powder while heating if necessary, and spray or vaporize the silicone oil or solution thereof having an amine in the side chain onto it, or
Alternatively, the treatment can be easily carried out by making silicic acid fine powder into a slurry and adding silicone oil having an amine in the side chain or a solution thereof while stirring the slurry. At this time, the amount of silicone oil having an amine in the side chain added is 0.2 to 70% by weight of the total amount of treated silicic acid fine powder.
It is preferable that the amount is 0.0001 to 10% by weight in the developer. In addition, aminosilane used for surface treatment of silicic acid fine powder is a so-called amino functional silane with the general formula: X _n SiY _o (X is an alkoxy group or a chloro atom, m is 1
an integer of ~3, Y is a hydrocarbon group having a primary to tertiary amino group, and n is an integer of 3 to 1. ), and the following compounds may be mentioned.

[Formula] H ₂ N-CONH-CH ₂ CH ₂ CH ₂ -Si- (OC ₂ H ₅ ) ₃ H ₂ N-CH ₂ CH ₂ CH ₂ Si (OCH ₂ CH ₃ ) ₃ H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ H ₂ NCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si
(0CH ₃ ) ₃ H ₅ C ₂ OCOCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ H ₅ C ₂ OCOCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂
Si(OCH ₃ ) ₃ H ₅ C ₂ OCOCH ₂ CH ₂ NHCH ₂ CH ₂ NHCH ₂ CH ₂
NHCH ₂ CH ₂ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ NH ₂ C ₆ H ₄ Si (OCH ₃ ) ₃ C ₆ H ₅ NHCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ or polyaminoalkyltrialkoxy Examples include silane, and these may be used alone or in a mixed yarn of two or more. The surface of the silicic acid fine powder can be treated with amino functional silane, for example, as follows. That is, the silicic acid fine powder is stirred and the above-mentioned aminosilane compound or its solution is sprayed or vaporized, or the silicic acid fine powder is made into a slurry and the aminosilane compound is mixed with the slurry while stirring. It can be easily treated by dropping the solution. The amount of aminosilane added is based on 100 parts by weight of silicic acid fine powder.
The amount is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight. Alternatively, as described in Japanese Patent Publication No. 54-16220, positively charged silicic acid fine powder may be obtained by reacting the silanol groups on the surface of the silicic acid fine powder with an organosilicon compound. Further, the silicic acid fine powder used in the present invention may be further treated with a conventionally known hydrophobizing agent as necessary, and a known method may be used for this treatment, such as reaction or physical treatment with the silicic acid fine powder. It is applied by chemical treatment with an adsorbing organosilicon compound. Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allyl phenyldichlorosilane, benzyldimethylchlorosilane. Silane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, Dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and having 2 to 12 siloxane units per molecule. Examples include dimethylpolysiloxane, which contains one Si-bonded hydroxyl group in each unit located at the end. These may be used alone or in a mixture of two or more. In this way, fine silicic acid powder whose surface has been treated with silicone oil or aminosilane having an amine in its side chain is kneaded and blended with the other components of the developer, such as a resin as a binder and a coloring agent, and then pulverized and classified. The required developer is obtained. Incidentally, the surface treatment of the silicic acid fine powder may be carried out during this developer preparation process. That is, in the process of kneading and blending the required silicic acid fine powder with a resin etc. as a binder, silicone oil or aminosilane having an amine in the side chain is added and the surface treatment of the silicic acid fine powder is carried out along with the kneading and blending. It's okay to get old. The applied amount of the silicic acid fine powder treated in this way is 0.01 to 20 parts by weight per 100 parts by weight of toner, and the effect is exhibited, and particularly preferably 0.05 to 5 parts by weight is used to achieve excellent stability. It exhibits positive chargeability. Examples of oxides of group a elements that can be used in the present invention include titanium oxide, zirconium oxide, and hafnium oxide. There are di-, tri-, and tetravalent titanium oxides, and titanium oxide (TiO) is obtained by reducing titanium oxide () with carbon or metal. Titanium oxide () is obtained by reducing titanium oxide () with a mixture of hydrogen and titanium chloride (). Titanium oxide () is
There are three types of transformation: rutile type, brookite type, and anatase type, and to produce it in the laboratory, the hydroxide is precipitated and separated from a titanium salt aqueous solution and then ignited. Rutile type can be obtained by baking at high temperature, and anatase type can be obtained by dissolving titanium oxide powder little by little in molten potassium hydrogen sulfate. When a tetravalent titanium halide is passed through a red-hot tube together with water vapor and carbon dioxide, an brookite type is obtained. Commercially available products for white pigments give satisfactory results. Zirconium oxide ZrO ₂ is obtained by heating zirconic acid or thermal decomposition of zirconium salt, and is commercially available in the form of white fine powder, with a purity of 95% or more as a first-class reagent. That's enough. Hafnium oxide HfO ₂ is a white crystal obtained by igniting hafnium hydroxide. It is desirable that these metal oxides be contained in an amount of 0.1 to 20% by weight, preferably 0.2 to 5% by weight, based on 100 parts by weight of the toner. Its particle size is 5μ
Below, it is desirable that it is preferably in the range of 0.01 to 3μ. All known binder resins can be used in the present invention, including monopolymers of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene:
Styrene-p-cross styrene 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, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethacrylic acid Methyl copolymer, styrene-acrylonitrile copolymer,
Styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, Styrenic copolymers such as styrene-maleic acid copolymers and styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resins , polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin,
Wax etc. can be used alone or in combination. When this binder resin contains a magnetic substance and is made into particles, the particle size is 5 to 5, which is the general toner particle size.
30μ is preferred. In addition, as the magnetic substance contained in the binder resin,
Ferromagnetic elements such as iron, cobalt, and nickel, and alloys and compounds containing these, such as magnetite, hematite, and ferrite, can be used as appropriate.
Its particle size is 100~800mμ, preferably 300~
500 mμ, 30 to 100 parts by weight of binder resin
The content is preferably 100 parts by weight, more preferably 40 to 80 parts by weight. In addition, the present invention will not be hindered in any way by adding (external addition) or containing (internal addition) a charge control agent, flow modifier, coloring agent, lubricant, etc. to the magnetic toner as necessary. In producing the magnetic toner of the present invention, the constituent materials are well kneaded using a heat kneader such as a heat roll, kneader, or extruder, and then mechanically pulverized.
A method obtained by classification can be applied. Further, in order to add and contain each of the above-mentioned inorganic powders into the magnetic toner, a known mixer such as a rotary container type mixer such as a V-type mixer or a turbula mixer, a ribbon type, a screw type, a rotary blade type, etc. Other fixed container mixers can be used as appropriate. Alternatively, a material such as magnetic powder is dispersed in a binder resin solution and then spray-dried.Alternatively, a predetermined material is mixed with the monomers that should constitute the binder resin, and then the emulsified suspension is obtained. Various methods can be applied, such as a polymerization method and a toner manufacturing method, in which a magnetic toner is obtained by polymerizing the magnetic toner. [Example] A more detailed explanation will be given below using Examples. Styrene-butyl acrylate copolymer (mole ratio 80/20, weight average molecular weight approximately 300,000) 100 parts by weight Magnetite (EPT-1000 manufactured by Toda Industries)
60 parts by weight Nigrosine dye (Nigrosine Base EX manufactured by Orient Chemical Industry Co., Ltd.) 2 parts by weight Low molecular weight polyethylene wax 4 parts by weight The above materials were mixed and melt-kneaded using a roll mill. After cooling, it is roughly pulverized using a hammer mill, and then finely pulverized using a jet pulverizer. Next, the particles were classified using an air classifier to obtain a magnetic toner having a particle size of approximately 5 to 30 μm. A magnetic developer was prepared by adding various positively charged silicic acid fine powders, oxides of group A elements, and others to the above magnetic toner. Example 1 100 parts by weight of silicic acid fine powder synthesized by a dry method (trade name Aerosil #130, specific surface area approximately 130 m ² /g; manufactured by Aerosil Co., Ltd.) was kept at 250°C with stirring to add amines to the side chains. silicone oil (KF857, viscosity 70cps at 25℃, amine equivalent
830, manufactured by Shin-Etsu Chemical) was sprayed and treated for 10 minutes. To 100 parts by weight of the magnetic toner, 0.4 parts by weight of the silicic acid fine powder treated with the silicone oil having an amine in the side chain and 2 parts by weight of titanium oxide (TiO ₂ , grade 1 reagent manufactured by Tokyo Kasei) were mixed. This was used as a magnetic developer. Example 2 Fine silicic acid powder (Aerosil) synthesized by dry method
OX-50, specific surface area approximately 50 m ² /g; manufactured by Aerosil) 100 parts by weight of silicone oil with amine in the side chain (KF393, viscosity at 25°C 60 cps,
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 1 part by weight (amine equivalent: 360, manufactured by Shin-Etsu Chemical) was used. Example 3 Silicic acid fine powder synthesized by dry method (Aerosil #200, specific surface area approximately 200 m ² /g; manufactured by Aerosil)
100 parts by weight of silicone oil with amine in the side chain (X-22-3801C, viscosity at 25℃
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 40 parts by weight (3500 cps, amine equivalent 3800, manufactured by Shin-Etsu Chemical) was used. Example 4 A silicone oil (X ^- 22- 3810B, viscosity
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 10 parts by weight (1300 cps, amine equivalent 1700, manufactured by Shin-Etsu Chemical) was used. Example 5 Silicic acid fine powder synthesized by dry method (Aerosil #380, specific surface area approximately 380 m ² /g; manufactured by Aerosil)
Magnetic development was carried out in almost the same manner as in Example 1, except that 100 parts by weight was treated with 40 parts by weight of silicone oil having an amine in the side chain (KF862, viscosity 750, amine equivalent 1900, manufactured by Shin-Etsu Chemical). obtained the drug. Example 6 Silicic acid fine powder synthesized by wet method (Nalco CD
-100, specific surface area approximately 120 m ² /g; manufactured by Nalco Chemical), 100 parts by weight of silicone oil having an amine in the side chain (SF8417, viscosity 1200 cps, amine equivalent
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 15 parts by weight of 3500 (manufactured by Toray Silicone) was used. Example 7 Silicic acid fine powder synthesized by dry method (Aerosil #200, specific surface area approximately 200 m ² /g; manufactured by Aerosil)
While stirring 100 parts by weight, a solution prepared by diluting 2 parts by weight of γ-aminopropyltriethoxysilane (A-1100, Nippon Unicar Co., Ltd.) with 20 parts by weight of 90% ethanol is added dropwise using a dropper. After adding 3
After stirring for a minute, the powdered liquid was transferred to a container and placed in a nitrogen gas atmosphere in a dryer.
Heat at 110°C for 1 hour to remove ethanol.
While stirring the obtained powder again, a solution prepared by diluting 4 parts by weight of hexamethyldisilazane with 16 parts by weight of hexane is dispersed in the same manner as described above, and the hexane is removed. The powder thus obtained is transferred to a flask equipped with a reflux condenser, a stirring tank, and a thermometer, and heated at 150° C. for 4 hours. A magnetic developer was obtained by externally adding and mixing 4 parts by weight of the silicic acid fine powder treated with the aminosilane and 2 parts by weight of titanium oxide (TiO ₂ , grade 1 reagent manufactured by Tokyo Kasei) to 100 parts by weight of the magnetic toner. . Example 8 Titanium oxide () instead of titanium oxide ()
A magnetic developer was obtained in the same manner as in Example 1 except that TiO (TiO, a first class reagent manufactured by Tokyo Kasei) was used. Example 9 A magnetic developer was obtained in the same manner as in Example 1, except that 0.5 part by weight of carbon (#40 manufactured by Mitsubishi Kasei) was also externally added and mixed. Example 10 A magnetic developer was obtained in the same manner as in Example 1, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 11 A magnetic developer was obtained in the same manner as in Example 2, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 12 A magnetic developer was obtained in the same manner as in Example 3, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added in place of 2 parts by weight of titanium oxide. Example 13 A magnetic developer was obtained in the same manner as in Example 4, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 14 A magnetic developer was obtained in the same manner as in Example 5, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 15 A magnetic developer was obtained in the same manner as in Example 6, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 16 A magnetic developer was obtained in the same manner as in Example 7, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Example 17 A magnetic developer was obtained in the same manner as in Example 9, except that 2 parts by weight of zirconium oxide (ZrO ₂ , grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) was externally added and mixed in place of 2 parts by weight of titanium oxide. Comparative Example 1 Negatively charged hydrophobic colloidal silica (Aerosil R972,
A magnetic developer was obtained by externally adding and mixing only 0.4 parts by weight (specific surface area: about 120 m ² /g, manufactured by Aerosil). Comparative Example 2 A magnetic developer was obtained in the same manner as in Example 1 except that titanium oxide was not externally added. Comparative Example 3 A magnetic developer was obtained in the same manner as in Example 2 except that titanium oxide was not externally added. Comparative Example 4 A magnetic developer was obtained in the same manner as in Example 3 except that titanium oxide was not externally added. Comparative Example 5 A magnetic developer was obtained in the same manner as in Example 4 except that titanium oxide was not externally added. Comparative Example 6 A magnetic developer was obtained in the same manner as in Example 5 except that titanium oxide was not externally added. Comparative Example 7 A magnetic developer was obtained in the same manner as in Example 6 except that titanium oxide was not externally added. Comparative Example 8 A magnetic developer was obtained in the same manner as in Example 7 except that titanium oxide was not externally added. Comparative Example 9 A magnetic developer was obtained in the same manner as in Example 9 except that titanium oxide was not externally added. Normal temperature and humidity (25℃, 60℃) for the above examples and comparative examples.
%RH), high temperature and high humidity (35℃, 85%RH), and low temperature and low humidity (15℃, 10%RH) in Table 1 (normal temperature and humidity) and Table 2 ( High temperature and high humidity, low temperature and low humidity). In the table, ○ is good, △
indicates somewhat poor quality, and × indicates poor quality. As for the development method, in Examples 9 and 17 and Comparative Example 9, a toner image was created by powder development using a magnetic brush method, and the toner image was transferred onto plain paper and fixed by heating. For other Examples and Comparative Examples, images were printed using a copying machine (NP-150Z, manufactured by Canon Inc.) using the jumping method.

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【table】

[Table] In each of the examples, the transferred images obtained were sufficiently dark from the first sheet, there was no fogging, and there was no toner scattering around the image, and a good image with high resolution was obtained. Further, transferred images were continuously created and durability was examined, and the transferred images after 30,000 sheets were completely comparable to the initial images. At that time, toner adheres to the surface of the photoreceptor,
So-called filming development, which is said to have an adverse effect on latent image formation, was not observed at all, and no problems were found in the cleaning process. In addition, the environmental conditions were high temperature and high humidity (35℃, 85%RH),
Even at low temperature and low humidity (15°C, 10% RH), we were able to obtain clear images almost as clear as at normal temperature and humidity, and the results were satisfactory. In Comparative Example 1, there was little fog at room temperature and humidity, but the image density was low at 0.42, the line drawings were scattered, and the solid black was noticeably rough. Regarding durability, the density decreased to 0.20 after 30,000 sheets. In addition, from around 10,000 sheets onwards, the toner material formed a thin, streak-like film on the surface of the photoreceptor, which began to appear as lines on the image (filming). Even under high temperature, high humidity, and low temperature and low humidity conditions, image density was low, and fogging, scattering, and roughness were noticeable. In Comparative Examples 2 to 9, the image density was relatively high compared to Comparative Example 1, but the rise was unstable and it took about 100 sheets to saturate to a constant density. In addition, there was a tendency for the density to decrease slightly under high temperature and high humidity conditions and after 30,000 sheets in the durability test. Also, filming started to appear around 10,000 sheets. [Effects of the Invention] As explained above, the magnetic developer of the present invention has the following effects:
It has stable and uniform positive chargeability, and enables faithful development and transfer of latent images. That is, there is no toner adhesion in the background area during development, that is, there is no fogging or toner scattering around the edges of the latent image, high image density is obtained, and halftone reproducibility is also good. Furthermore, there is no rise in image density and the image density is high from the beginning. In addition, the magnetic developer of the present invention maintains its initial characteristics even after long-term continuous or repeated use and long-term storage, does not cause filming development,
Good cleaning properties. It also reproduces stable images that are unaffected by changes in temperature and humidity.
It is a magnetic developer that does not cause scattering or transfer defects even in high humidity or low humidity.

Claims (1)

[Scope of Claims] 1. A positively charged magnetic developer containing at least a magnetic toner, positively charged silicic acid fine powder, and oxide powder of an element belonging to group a of the periodic table. 2. The developer according to claim 1, wherein a mixing ratio of the positively charged silicic acid fine powder is 0.01 to 20 parts by weight per 100 parts by weight of the magnetic toner. 3. The developer according to claim 1, wherein the mixing ratio of the oxide is 0.1 to 20 parts by weight per 100 parts by weight of the magnetic toner. 4. The developer according to claim 1, wherein the oxide has an average particle size of 0.01 to 5 μm. 5. The developer according to claim 1, wherein the magnetic toner has an average particle size of 5 to 30 μm.