JPH06103403B2 - Positively charged magnetic developer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a developer for developing a latent image in electrophotography, electrostatic recording, electrostatic printing, magnetic recording and the like. More specifically, it relates to a developer for electrophotography which is uniformly charged with a strong positive charge in a direct or indirect electrophotographic development method to visualize a negative electrostatic charge image and give a high quality image.

[Summary of Disclosure] The present specification describes a positively charged magnetic developer used for direct or indirect electrophotographic development, in which the magnetic toner, positively charged silicic acid fine powder, and Group IIIb of the periodic table are used. By containing an oxide powder of an element belonging to, stable high image density can be obtained from the beginning without fog or scattering.
Disclosed is a technique for reproducing a stable image that is not affected by changes over time and temperature and humidity.

[Prior Art] Conventionally, electrophotography has been performed in the following procedure.
Photoconductive layer charging → Photoimage exposure (latent image formation) → Toner adhesion (development) → Transfer to paper, cloth, etc. → Heating, pressure (fixing).

Although many developing methods for electrophotography are known, they are roughly classified into a two-component developing method and a one-component developing method. The former is a method that has been widely used as, for example, a cascade method or a magnetic brush method, and a two-component toner in which toner and carrier particles are mixed is used for development. All of these methods can obtain a good image relatively stably, but on the other hand, they have the common problems associated with a two-component developer, such as deterioration of the carrier and variation in the mixing ratio of the toner and the carrier.

In order to avoid such a problem, various methods using a one-component developer containing no carrier have been proposed, but among them, many methods are superior to the method using a developer composed of magnetic toner particles.

Magndry method using conductive magnetic toner (US Patent No.
No. 3,909,258) avoids the problems of the two-component developing method, but because the toner is conductive, it is difficult to electrostatically transfer the developed image to the final support member such as plain paper. I have a problem.

In addition, when a high resistance magnetic toner is used, electrostatic transfer is possible, and there is a developing method that uses the dielectric polarization of this toner, but the developing speed is essentially slow, and sufficient density on the developing surface is obtained. There are problems such as not being able to do so. Further, as another method using the high-resistance magnetic toner, a method of charging toner particles by friction between the toner particles or with a sleeve is known, but the number of contact between the toner particles and the friction member is small and the friction is small. There are problems that the charging is likely to be insufficient, and that the charged toner particles have an increased Coulomb force between them and tend to aggregate on the sleeve.

The applicant previously proposed a new developing method in JP-A-55-42141 which eliminates the above-mentioned problems. This is a jumping method in which an insulating magnetic toner is applied very thinly on a sleeve, which is triboelectrically charged, and is brought into close proximity to an electrostatic image under the action of a magnetic field to develop by flying the toner. is there. According to this method, the degree of contact between the sleeve and the toner is increased, good triboelectric charging is possible as a one-component developer, the toner is supported by a magnetic force, and the magnet and the toner are relatively moved. To prevent the toner particles from aggregating each other and to rub sufficiently against the sleeve, and to prevent the background fog by developing the toner by facing the electrostatic image without touching it. Is obtained. However, even in this method, the triboelectric charge amount of the toner particles is remarkably smaller than the triboelectric charge amount of the toner particles in the normal two-component development.

When a magnetic toner holding only a weak charge amount is used in such a method, the image quality becomes insufficient, such as low image density, scattering, bleeding, and image unevenness. In particular, the initial image density is low, and several hundred copies are usually required to reach a constant density, and this instability at the start-up is one of the major problems in the one-component system development. Further, when the developing bias is lowered to increase the image density, there is a problem such as background fog.

Therefore, it is necessary to improve the triboelectric charge amount of the magnetic toner. As a means for this, it is known to add fine powder of silicic acid to a developer having a negative charging property, and the image density and image quality are improved, and a satisfactory image is obtained to some extent. However, silicic acid fine powder is generally highly negatively charged, and a good image cannot be obtained even if negatively charged silicic acid fine powder is added to a positively chargeable developer.

Generally, the toner contains a charge control agent for the purpose of obtaining a desired chargeability of polarity and strength. Examples of the positive charge control agent generally include quaternary ammonium compounds and organic dyes, particularly basic dyes and salts thereof. Common positive charge control agents are benzyl dimethyl-hexadecyl ammonium chloride, decyl trimethyl ammonium chloride, nigrosine base, nigrosine, safranine 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 as charge control agents have a complicated structure, inconsistent properties, and poor stability. In addition, decomposition or deterioration is likely to occur due to decomposition during thermal kneading, mechanical shock, friction, changes in temperature / humidity conditions, etc., and a phenomenon in which charge controllability is deteriorated is likely to occur.

Therefore, when the toner using these charge control agents is developed in a copying machine and developed, the charge control agents may be decomposed or deteriorated as the number of times of copying increases, and the toner may deteriorate during durability.

Many of the positive charge control agents are hydrophilic, and the control agents are exposed on the surface of the toner when pulverized after melt-kneading due to poor dispersion in these resins. Therefore, when the toner is used under a high humidity condition, there is a problem that a high quality image cannot be obtained because these control agents are hydrophilic.

As described above, when the conventional positive charge control agent is used in the toner, the toner is used between the toner particles, or between the toner and the carrier, and between the toner carrier such as the toner and the sleeve.
The amount of electric charge generated on the surface of the toner particles 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 deteriorates due to instability of the positively chargeable control agent used, and often becomes unusable.

Therefore, there is a method of modifying the negatively charged silicic acid fine powder to a positively charged one and adding it. For example, Japanese Patent Publication No. Sho 53-22447,
A method of incorporating fine silica powder treated with aminosilane into a toner as described in JP-A-58-185405,
Further, a method of incorporating fine silicic acid powder treated with a silicone oil having an amine in a side chain has been tried.

By adding such positively charged silicic acid fine powder, it is possible to obtain a clear and high-concentration image relatively free from fog, but it sufficiently solves the above-mentioned problems caused by tribo-charging property. The current situation is that it has not reached this point.

The present invention has been made in view of the above-mentioned problems of the prior art, and is a positively chargeable magnetic developer capable of stably obtaining an image having no fog, a clear and high density, and in particular, no density fluctuation at the initial rising. For the purpose of provision.

[Means and Actions for Solving Problems] Specifically, according to the present invention, 100 parts by weight of positively chargeable magnetic toner, 0.05 to 5 parts by weight of positively chargeable silicic acid fine powder as independent particles, and independent Containing 0.1 to 20 parts by weight of an oxide powder of an element belonging to Group IIIb of the periodic table as the particles of, the content of the oxide fine powder is higher than the content of the positively charged silicic acid fine powder. The present invention relates to a characteristic positively chargeable magnetic developer.
In addition, the periodic table referred to here is a physics and chemistry dictionary (Iwanami Shoten,
3rd edition) P.1484.

Here, the positively chargeable silicic acid fine powder refers to one having a charge amount of +5 μC / g or more with the iron powder carrier. For this measurement of the amount of charge, first, 0.5 to 1.5 g of a substance (silicic acid fine powder) mixed with an iron powder carrier having a particle size of 200/300 mesh at a ratio of 1: 100 is precisely weighed. 25 cmH on a metal 400 mesh screen connected to an electrometer
_The amount of charge per unit weight can be obtained from the substance to be inspected and the amount of electric charge that was separated and aspirated at the pressure of ₂ O.

In the present specification, the silicic acid fine powder refers to anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate and zinc silicate. .

Further, in the present specification, two types of names, “magnetic developer” and “toner” are used for convenience, but “toner” is a part of “magnetic developer”, and a binder resin, Magnetic materials, dyes, pigments, charge control agents, flow modifiers, lubricants, and other components are selected, and positively charged silicic acid fine powder and oxides of Group IIIb of the periodic table are added to this. A material to which carbon and other additives are appropriately added as needed is called a "magnetic developer".

The silicic acid fine powder used in the present invention is manufactured by a dry method and a wet method. The dry method is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halogen compound. For example, silicon tetrachloride is represented by the following reaction formula.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl Also included in this process is a composite fine powder of silica and another metal oxide obtained by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound. To do. The commercially available silica fine powder (silica) produced by the dry method is as follows.

AEROSIL 130 (Japan Aerosil) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Cab-O-SiL M-5 CABOT Co. MS-7 MS-75 HS-5 EH-5 Wacker HDK N20 V15 WACKER-CHEMIE GMBH N20E (Wackel Hemier GMBH) T30 T40 DC Fine Silica (Fine silica) Dow Corning Fransol (Fransol) Fransil (Fransil) In addition, there are various conventionally known wet methods. . For example, a method of decomposing sodium silicate with an acid, an ammonia salt or an alkali salt, generating an alkaline earth metal silicate from sodium silicate, and then decomposing with an acid,
There is a method of converting sodium silicate solution into silicic acid using an ion exchange resin.

The following are commercially available products of fine silicic acid powder synthesized by the wet method.

Carplex Shionogi Pharmaceutical Nipseal Nippon Silica Tokseal, Fineseal Tokuyama Soda Vitaseal Takihi Shilton, Shirnex Mizusawa Chemical Starsil Kamijima Chemical Himedir Ehime Pharmaceutical Syloid Fuji Devison Chemical Hi-Sil Pittsburgh Plate Glass Co. (Pittsburgh Plate Glass) Durosil (Douro Seal) Ultrasil Fiulstoff-Gesellschaft Marquart Manosil (Manosir) Hardman and Holden Hoesch (Hesch) Chemische Fabrik Hoesch KG (Hemische Fabrikhesch) Sil- Stone (Sil-Stone) Stoner Rubber Co. (Stone rubber) Nalco (Nalco) Nalco Chem.Co. (Nalco Chemical) Quso (fucking) Philadelphia Quartz Co. (Philadel) Santocell Monsanto.Chemical Co. Imsil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch.KG Chemische Fabrik Heche Calsil-Fiillstoff Gesellschaft Marquart Fortafil Imperial Chemical Industries Ltd. (Chemicals) Microcal Joseph Crosfield & Sons Ltd. (Joseph Crossfield & Sons) Manosil (Hard) Man and Holden Vulkasil Farbenfabriken Bayer, A.-G. Tufknit Durham Chemicals Ltd. Chemicals) Of Shirumosu Shiraishi Kogyo Starex Kamijima chemical Furikoshiru multi wood fertilizer the fine silica powder, the range of specific surface area by nitrogen adsorption measured by BET method is 30 m ² / g or more (especially 50 to 400 m ² / g) Gives good results.

When these silicic acid fine powders are modified to be positively charged and contained in the developer, charge controllability is exhibited. As a method for modifying the silicic acid fine powders to be positively charged, an amine is included in the side chain. There are a method of treating with silicone oil and a method of treating with aminosilane.

As the silicone oil having an amine in its side chain, a silicone oil containing a constitutional unit represented by the formula (1) is generally used.

(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. Is an aryl group, an alkoxy group, an alkylene group, or a phenylene group may contain an amine, and may have a substituent such as a halogen within a range that does not impair chargeability.) Of these, commercially available For example, those represented by the following structural formulas can be preferably used.

(Here, R ₁ and R ₅ represent an alkyl group or an aryl group,
₂ represents an alkylene group or phenylene, R ₃ is hydrogen,
It represents an alkyl group or an aryl group. m and n are integers of 1 or more. ) Specifically, the following are preferable, and one type or a mixture of two or more types may be used.

The amine equivalent is the equivalent per amine (g / eq
In iv), the molecular weight is divided by the number of amines per molecule. The viscosity at 25 ° C is preferably 5000 cps or less, and particularly preferably 3000 cps or less. Above 5000cps,
Dispersion in fine silicic acid powder is insufficient, and it tends to cause defective images such as fog.

The above-mentioned treatment with the silicone oil having an amine in the side chain of the silicic acid fine powder can be performed, for example, as follows. The silicic acid fine powder is vigorously agitated while being heated if necessary, and the silicone oil having an amine in the side chain or a solution thereof is sprayed or vaporized and sprayed on this, or the silicic acid fine powder is slurried. It can be easily treated by adding a silicone oil having an amine to a side chain or a solution thereof while stirring. At this time, the addition amount of the silicone oil having an amine in the side chain is preferably 0.2 to 70% by weight and 0.0001 to 10% by weight of the total amount of the treated silicic acid fine powder in the developer.

The aminosilane used for the surface treatment of fine silicic acid powder is a so-called aminofunctional silane represented by the general formula: XmSiYn (X is an alkoxy group or chlorine atom, m is an integer of 1 to 3, Y is a primary to tertiary amino). A hydrocarbon group having a group, n
Is an integer of 3 to 1. ) And include the following compounds.

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 N 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 (OCH 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 and poly aminoalkyl trialkoxysilanes and the like, which one or You may use in a mixed system of 2 or more types.

The surface of the silicic acid fine powder surface can be treated with aminofunctional silane, for example, as follows. That is, the silicic acid fine powder is agitated, and the aminosilane compound or a solution thereof is sprayed or vaporized and sprayed on the silicic acid fine powder, or the silicic acid fine powder is slurried and the aminosilane compound It can be easily processed by dropping the solution. The amount of aminosilane added is 0.01 to 1 with respect to 100 parts by weight of fine silicic acid powder.
It is 0 part by weight, preferably 0.1 to 5 parts by weight.

Further, as described in JP-B-54-16220, a silanol group on the surface of the silicic acid fine powder may be reacted with an organosilicon compound to obtain a positively charged silicic acid fine powder.

Further, the silicic acid fine powder used in the present invention may be further treated with a conventionally known hydrophobizing agent, if necessary, and a known method may be used for the reaction or physical reaction with the silicic acid fine powder. It is provided by chemically treating with an adsorbing organosilicon compound or the like.

Examples of such organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allylphenyldichlorosilane, benzyldimethylchlorosilane, brommethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane,
Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, one for each terminally located unit Examples include dimethylpolysiloxane containing a hydroxyl group bonded to Si.
These are used alone or as a mixture of two or more.

Thus, silicic acid fine powder surface-treated with silicone oil or aminosilane having an amine in the side chain is kneaded with a resin or a colorant as a binder which is another constituent component of the developer, blended, and then pulverized and classified. The required developer is obtained. The surface treatment of the silicic acid fine powder may be performed in the developer adjusting process. That is, in the process of kneading and blending the required silicic acid fine powder with a resin as a binder, the silicone oil or amine silane having an amine in the side chain is added and mixed, and the surface treatment of the silicic acid fine powder is performed together with the blending. May be.

The applied amount of the silicic acid fine powder treated in this manner exhibits a positive chargeability with excellent stability when added in an amount of 0.05 to 5 parts by weight with respect to 100 parts by weight of the toner.

Examples of Group IIIb element oxides that can be preferably used in the present invention include boron oxide, aluminum oxide, gallium oxide, indium oxide, and thallium oxide. Among them, boron oxide includes diboron trioxide B ₂ O ₃ , and dioxide. Diboron B
₂ O ₂ , tetraboron trioxide B ₄ O ₃ .H ₂ O, tetraboron pentoxide B ₄ O _{5 and the} like can be mentioned. Diboron trioxide can be easily obtained by a known production method. It is a colorless glassy substance obtained by melting boric acid in a platinum crucible and dehydrating it (2H ₃ BO ₃ → B ₂ O ₃ + 3H ₂ O), and white fine powder is usually widely marketed. The purity of the first-class reagent is 95% or more, which is applicable to the present invention.

Further, as the aluminum oxide Al ₂ O ₃ , those generally commercially available as reagents and industrial ones can be preferably used. As a manufacturing method, it can be obtained by precipitating aluminum hydroxide from an aqueous solution of a soluble aluminum salt, filtering it, and igniting it. The method called the Bayer method is most widely used industrially, and the principle is that when bauxite is treated with sodium hydroxide, aluminum dissolves as an aluminate, but SiO ₂ , Fe ₂ O _{3 in} ore , TiO ₂
Will precipitate, so they can be separated. The sodium aluminate solution was hydrolyzed to precipitate Al (OH) _3, a is α-Al ₂ O ₃ having no hygroscopicity burn it obtained. In addition to the α-type alumina, various types of β-type and γ-type modifications are known, and any of them can be preferably used in the present invention.

These metal oxides are added in an amount of 0.1 to 20 per 100 parts by weight of toner.
It is desirable that the amount of this component be contained in an amount of 0.2 parts by weight, preferably 0.2-5 parts by weight. The particle size is 5 μ or less, preferably 0.01
It is desirable that the range is ˜3 μ.

As the binder resin used in the present invention, all known binder resins can be used. For example, a homopolymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, or a substitution product thereof; styrene-p-chloro. 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-methylmethacrylate copolymer, styrene-ethylmethacrylate copolymer, styrene-butylmethacrylate copolymer, styrene-α-chloromethylmethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl Ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid Copolymer, styrene Styrene copolymers such as maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester,
Polyurethane, epoxy resin, polyvinyl butyral,
Polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin,
Paraffin, wax and the like can be used alone or in combination.

The particle size when the binder resin contains a magnetic substance to form particles is preferably 5 to 30 μ which is a general toner particle size.

As the magnetic substance contained in the binder resin, ferromagnetic elements such as iron, cobalt and nickel and alloys and compounds containing them, such as magnetite, hematite and ferrite, can be appropriately used. The particle size is 100-800m
μ, preferably 300 to 500 mμ, and it is suitable to contain 30 to 100 parts by weight, more preferably 40 to 80 parts by weight with respect to 100 parts by weight of the binder resin.

In addition, a charge control agent, flow modifier,
Addition (external addition) or inclusion (internal addition) of colorants, lubricants, etc., as necessary, does not interfere with the present invention.

In the production of the magnetic toner of the present invention, a method in which the constituent materials are well kneaded by a heat kneader such as a hot roll, a kneader or an extruder, and then mechanically crushed and classified can be applied.

Further, when adding the inorganic powders to the magnetic toner, a known mixer, for example, a V-type mixer, a rotary container type mixer such as a turbula mixer, a ribbon type, a screw type, a rotary blade type, or other fixed type is used. A container-type mixer can be appropriately used.

Alternatively, a method in which a material such as magnetic powder is dispersed in a binder resin solution and then spray-dried, or a monomer to form the binder resin is mixed with a predetermined material, and then this emulsion suspension is prepared. Each method such as a polymerization method for obtaining a magnetic toner by polymerizing the above can be applied.

[Examples] The present invention will be described in more detail below with reference to Examples.

Styrene-butyl acrylate copolymer (molar ratio 80/2
0, weight average molecular weight about 300,000) 100 parts by weight Magnetite (EPT-1000 manufactured by Toda Kogyo) 60 parts by weight Nigrosine dye (Nigrosine base EX manufactured by Orient Chemical Industries) 2 parts by weight Low molecular weight polyethylene wax 4 parts by weight The above materials are mixed. Melt and knead with a roll mill. After cooling, coarse pulverization is performed with a hammer mill and then fine pulverization is performed with a jet pulverizer. Then, classification was performed using an air classifier to obtain a magnetic toner having a particle size of about 5 to 30 μm.

Various positively charged silicic acid fine powders, Group IIIb element oxides and others were added to the above magnetic toner to prepare a magnetic developer.

Example 1 Silica fine powder synthesized by a dry method (trade name Aerosil #
130, specific surface area of about 130 m ² / g; made by Aerosil Co., Ltd.) 100 parts by weight of silicone oil having an amine in a side chain by maintaining at 250 ° C. with stirring (KF857, viscosity at 25 ° C. 70 cps,
20 parts by weight of amine equivalent (830, manufactured by Shin-Etsu Chemical Co., Ltd.) was sprayed and treated for 10 minutes.

To 100 parts by weight of the magnetic toner, 0.4 parts by weight of fine silicic acid powder treated with a silicone oil having an amine in the above side chain and 2 parts by weight of diboron trioxide (B ₂ O ₃ , reagent grade 1 manufactured by Tokyo Kasei) are excluded. A magnetic developer was added and mixed.

Example 2 Silica fine powder synthesized by a dry method (Aerosil OX-50,
Specific surface area of about 50 m ² / g; Aerosil Co., Ltd.) 100 parts by weight treated with 1 part by weight of silicone oil (KF393, viscosity at 25 ° C. 60 cps, amine equivalent 360, manufactured by Shin-Etsu Chemical Co., Ltd.) having amine in the side chain is used. A magnetic developer was obtained in substantially the same manner as in Example 1 except for the above.

Example 3 Silica fine powder synthesized by a dry method (Aerosil # 200,
Specific surface area of about 200 m ² / g; Aerosil Co., Ltd.) Silicone oil having 100 parts by weight of amine in the side chain (X-22-3801C, 25 ° C)
Viscosity 3500 cps, amine equivalent 3800, manufactured by Shin-Etsu Chemical) 4
A magnetic developer was obtained in substantially the same manner as in Example 1 except that the one treated with 0 parts by weight was used.

Example 4 100 parts by weight of fine silicic acid powder synthesized by a wet method (Vulkazil C, specific surface area of about 80 m ² / g; manufactured by Farben Fabry Ken Bayer) was used as a silicone oil having an amine as a side chain (X-22-3810B, A magnetic developer was obtained in substantially the same manner as in Example 1 except that the product treated with 10 parts by weight of viscosity 1300 cps, amine equivalent 1700, manufactured by Shin-Etsu Chemical) was used.

Example 5 Silica fine powder synthesized by a dry method (Aerosil # 380,
Specific surface area of about 380 m ² / g; Aerosil Co., Ltd.) 100 parts by weight of silicone oil having amine in the side chain (KF862, viscosity 750,
A magnetic developer was obtained in substantially the same manner as in Example 1 except that the one treated with 40 parts by weight of amine equivalent 1900, manufactured by Shin-Etsu Chemical Co., Ltd. was used.

Example 6 100 parts by weight of fine silicic acid powder (Nalco CD-100, specific surface area of about 120 m ² / g; made by Nalco Chemical) synthesized by a wet method was used as a silicone oil (SF8417, viscosity 1200) having an amine in a side chain.
cps, amine equivalent 3500, manufactured by Toray Silicone) 15 parts by weight was used, and a magnetic developer was obtained in substantially the same manner as in Example 1.

Example 7 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 added and mixed.

Example 8 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 1 except that 2 parts by weight of Tokyo Kasei reagent grade 1) was externally added and mixed.

Example 9 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 2 except that 2 parts by weight of Tokyo Kasei reagent grade 1) was externally added and mixed.

Example 10 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 3 except that 2 parts by weight of Tokyo Kasei Reagent 1) was externally added and mixed.

Example 11 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 4 except that 2 parts by weight of Tokyo Kasei reagent grade 1) was externally added and mixed.

Example 12 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 5, except that 2 parts by weight of Tokyo Kasei reagent grade 1) was externally added and mixed.

Example 13 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 6 except that 2 parts by weight of Tokyo Kasei reagent grade 1) was externally added and mixed.

Example 14 Instead of 2 parts by weight of boron oxide, aluminum oxide (Al ₂ O
₃ , a magnetic developer was obtained in the same manner as in Example 8, except that 2 parts by weight of Tokyo Kasei Reagent Grade 1) was externally added and mixed.

Comparative Example 1 100 parts by weight of the same magnetic toner as in Example was added to negatively charged hydrophobic colloidal silica (Aerosil R972, specific surface area of about 120 m ² /
g, manufactured by Aerosil Co., Ltd.) and 0.4 parts by weight were externally added and mixed to obtain a magnetic developer.

Comparative Example 2 A magnetic developer was obtained in the same manner as in Example 1 except that boron oxide was not added externally.

Comparative Example 3 A magnetic developer was obtained in the same manner as in Example 2 except that boron oxide was not added externally.

Comparative Example 4 A magnetic developer was obtained in the same manner as in Example 3 except that boron oxide was not added externally.

Comparative Example 5 A magnetic developer was obtained in the same manner as in Example 4 except that boron oxide was not added externally.

Comparative Example 6 A magnetic developer was obtained in the same manner as in Example 5 except that boron oxide was not added externally.

Comparative Example 7 A magnetic developer was obtained in the same manner as in Example 6 except that boron oxide was not added externally.

Comparative Example 8 A magnetic developer was obtained in the same manner as in Example 7, except that boron oxide was not added externally.

Comparative Example 9 A magnetic developer was obtained in the same manner as in Example 8 except that boron oxide was not added externally.

Comparative Example 10 Silica fine powder synthesized by a dry method (Aerosil # 200,
Γ-aminopropyltriethoxysilane (A with a specific surface area of about 200 m ² / g; Aerosil Co., Ltd.) 100 parts by weight while stirring
-1100, Nippon Unicar) 2 parts by weight of 90% ethanol 20
The solution diluted with parts by weight is added dropwise with a dropper. After continuing the stirring for 3 minutes after the addition, transfer this powder liquid to a pad and put it in a dryer at 110 ° C in a nitrogen gas atmosphere.
Heat for 1 hour to remove ethanol. While stirring the obtained powder again, this time, hexamethyldisilazane 4
A solution prepared by diluting 16 parts by weight of hexane with parts by weight is dispersed by the same method as above to remove hexane. The powder thus obtained is transferred to a flask 1 equipped with a reflux condenser, a stirring tank and a thermometer, and heated at 150 ° C. for 4 hours.

To 100 parts by weight of the magnetic toner, 4 parts by weight of the silicic acid fine powder treated with the aminosilane and 2 parts by weight of diboron trioxide were externally added and mixed to obtain a magnetic developer.

No fog under normal temperature / normal humidity, high temperature / high humidity, low temperature / low humidity, no scattering, good fine line reproducibility, and good filming, but compared with other examples, images were better in each environment. The concentration was a little low.

Comparative Example 11 A magnetic developer was obtained in the same manner as in Comparative Example 10 except that 2 parts by weight of aluminum oxide (Al ₂ O ₃ , Reagent Grade 1 manufactured by Tokyo Kasei) was externally added and mixed instead of 2 parts by weight of diboron trioxide. It was

No fog under normal temperature / normal humidity, high temperature / high humidity, low temperature / low humidity, no scattering, good fine line reproducibility, and good filming, but compared with other examples, images were better in each environment. The concentration was a little low.

Comparative Example 12 Instead of the fine silicic acid powder and boron trioxide used in Example 1, fine powder of metal co-oxide of alumina and silica (containing about 1% by weight of alumina), trade name MOX80 (manufactured by Nippon Aerosil Co., Ltd.) ) A magnetic developer was obtained in the same manner as in Example 1 except that 2.4 parts by weight was used.

Fog, splattering, and fine line reproducibility under normal temperature and normal humidity, high temperature and high humidity, and low temperature and low humidity were good, but the image density was slightly lower in each environment compared to the other examples.
A slight amount of filming occurred on the surface of the photoconductor, and the effect of filming began to appear on the developed image from about 20,000 sheets.

Normal temperature and normal humidity (25 ° C., 60% RH) in the above Examples and Comparative Examples,
High temperature and high humidity (35 ℃, 85% RH), low temperature and low humidity (15 ℃, 10% RH)
The evaluation results of the images under various environmental conditions are shown in Table 1 (normal temperature and normal humidity) and Table 2 (high temperature and high humidity, low temperature and low humidity). In the table, ◯ means good, Δ means slightly bad, and × means bad.

As for the developing method, in Examples 8 and 16 and Comparative Example 9, powder development was performed by a magnetic brush method to form a toner image, which was transferred to plain paper and heat-fixed. In the other Examples and Comparative Examples, images were printed using a copying machine (NP-150Z, manufactured by Canon Inc.) equipped with an OPC photoconductor by the jumping method.

In each of the examples, it was stated that all of the obtained transferred images were sufficiently dark from the first sheet, no fog was observed, no toner was scattered around the image, and a high resolution was obtained.
In addition, I made continuous transfer images and checked the durability,
The transferred image after 30,000 sheets was also comparable to the initial image. At that time, so-called filming development, in which toner adheres to the surface of the photoconductor and adversely affects the latent image format, was not observed at all, and no problem was found in the cleaning step.

Also, even if the environmental conditions are high temperature and high humidity (35 ° C, 85% RH) and low temperature and low humidity (15 ° C, 10% RH), a clear image similar to that at normal temperature and normal humidity can be obtained, which is satisfactory. Results were obtained.

In Comparative Example 1, fog is small at room temperature and normal humidity, but the image density is
It was as low as 0.42, line drawings were scattered, and solid black was noticeable. Regarding the durability, the density decreased to 0.20 after 30,000 sheets. In addition, from around 10,000 sheets, the toner material formed a thin streak film on the surface of the photoconductor and appeared as lines on the image (filming). The image density was low even under conditions of high temperature and high humidity and low temperature and low humidity, and fog, splattering, and roughness were noticeable.

In Comparative Examples 2 to 9, the image density was relatively higher than that in Comparative Example 1, but the rise was unstable and about 100 sheets were required to saturate the image with a constant density. In addition, the density tended to decrease slightly under high temperature and high humidity conditions and after 30,000 sheets in the durability test. Also, filming began to appear from around 10,000 sheets.

[Advantages of the Invention] As described above, the magnetic developer of the present invention has stable and uniform positive charging property, and can perform development and transfer faithful to a latent image. That is, there is no adhesion of toner in the background area during development, that is, there is no fog or toner scattering around the edges of the latent image, high image density is obtained, and halftone reproducibility is good. Further, the image density does not rise and the image density is high from the beginning.

Further, the magnetic developer of the present invention maintains the initial characteristics even after long-term continuous or repeated use and long-term storage, does not cause a filming phenomenon, and has good cleaning properties. In addition, it is a magnetic developer that reproduces a stable image that is not affected by changes in temperature and humidity, and that does not scatter or lack of transfer even at high and low humidity.

Claims (3)

[Claims] 1. Positively chargeable magnetic toner 100 parts by weight, positively chargeable silicic acid fine powder 0.05 to 5 parts by weight as independent particles, and oxide powder 0.1 of an element belonging to Group IIIb of the periodic table as independent particles. The content of the oxide fine powder is higher than the content of the positively chargeable silicic acid fine powder. 2. The positively chargeable magnetic developer according to claim 1, wherein the oxide has an average particle size of 0.01 to 5 μm. 3. The average particle size of the positively chargeable magnetic toner is 5 to 5.
The positively chargeable magnetic developer according to claim 1, which has a size of 30 μm.