JPS6261065A - Magnetic developer - Google Patents

Abstract

PURPOSE:To obtain a high image density which is table from an initial period without fogging and splashing and to reproduce the stable image which is not affected by age and the change of temp. and humidity by incorporating magnetic toner, pulverous positive chargeability silicic acid powder and strontium oxide powder into a magnetic developer. CONSTITUTION:This positive chargeability magnetic developer consists of the magnetic toner, pulverous positive chargeability silicic acid powder and strontium oxide powder. The pulverous silicic powder is effective when said powder is used at 0.01-20pts.wt. per 100pts.wt. toner. Said powder exhibits the positive electrostatic chargeability having excellent stability when the powder is added to the toner more particularly preferably at 0.05-5pts.wt. The strontium oxide SrO to be used is the colorless cubic crystal powder obtd. by ignition of the hydroxide, carbonate or nitrate of strontium and the purity of the commercially marketed reagent is satisfactory if >=95%. These metallic oxides are incorporated into the developer at 0.1-20wt%, more preferably 0.2-5wt% per 100pts. wt. toner. The grain size thereof is preferably <=5mu, more preferably in a 0.01-3mu range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a developer for developing latent images in electrophotography, electrostatic recording, electrostatic printing, and magnetic recording. More specifically, in direct or indirect photographic development methods, is it possible to produce a uniform and strong positive charge? This invention relates to a developer for electrophotography, which visualizes negative electrostatic charge images and produces high-quality images.

[Summary of the Disclosure] Unspecified; Shichinansha≠# is a positively charged magnetic developer used in direct or indirect type r photographic development, in which the magnetic developer contains a magnetic toner, positively charged silicic acid fine powder, and oxidation. By containing strontium powder, it is possible to obtain stable high image density from the initial stage without fogging or flying dust, and discloses a technology for reproducing stable images that are not affected by changes in temperature or humidity over time. be.

[Conventional technology] Conventionally, electrophotography has been carried out in the following L order.

■Photoconductive layer? 17 electrons → ■ Light image exposure (latent image formation) → ■ Toner adhesion (development) → ■ Paper,! Transfer to 1st class→■Heating,
Pressure (fixing).

There are many known developing methods for electrophotography, which can be broadly classified into two-component developing methods and one-component developing methods. The former method is a widely used method such as 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 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 cannot be transferred to a final paper such as plain paper. The problem is that it is difficult to electrostatically transfer the image to a support member.

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 cap, 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 Laid-Open No. 55-42141. This is a jumping method in which an extremely thin layer of insulating magnetic toner is applied to the sleeve, and the toner is applied as a friction band, which is placed very close to the electrostatic image under the action of a magnetic field, causing the toner to fly and develop. be. According to this method, the degree of contact between the sleeve and the toner is increased, - water is used as a component developer that enables good frictional charging, the toner is supported by magnetic force, and the magnet and the toner are moved relative to each other. The bar disaggregates the toner particles and causes sufficient friction with the sleeve, and the toner is developed by facing the electrostatic image without coming into contact with it! Excellent images can be obtained by preventing soil blurring by adding 1 yen. However, even in this method, the amount of tripocharges that the toner particles have is significantly smaller than the amount of tripocharges 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 usually several hundred copies are required to reach a constant density, and this instability is one of the major problems in one-component development. Further, when the developing bias is lowered in order to increase the image density, there is a problem of blurring due to the background force.

Therefore, it was necessary to improve the amount of tripostatic charge of the magnetic toner. As a means for this purpose, it is known to add fine silicic acid powder to a developer having negative chargeability, and this improves image density and image quality, resulting in images that are somewhat satisfactory. However, silica fine powder generally has a strong negative charge, and good images cannot be obtained even if negatively charged fine silicic acid powder is added to a positively chargeable developer.

Generally, a toner contains a charge control agent for the purpose of obtaining desired polarity and strength of charge. 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 gamma 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 and melted and dispersed, and then finely pulverized and adjusted to an appropriate particle size as necessary 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 of the heat-kneaded soybean, mechanical impact, friction, changes in temperature and humidity conditions, etc., and the charge controllability is likely to be low.

Therefore, when toner using 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.

Furthermore, most of the positive charge control agents are hydrophilic, and due to poor dispersion in these resins, the control agent is exposed on the toner surface when the toner is crushed after melt-kneading. Therefore, when the toner is used under high humidity conditions, there is a problem in that good quality images cannot be obtained because these control agents are wood-philic.

In this way, when a conventional positive charge control agent is used in a toner, between toner particles, between a toner and a gear, or between a toner and a toner carrier such as a sleeve,
The amount of charge generated on the surface of toner particles varies, and problems such as development fog, toner scattering, and gear 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 added.
No. 47, JP-A No. 58-185405, there is a method of incorporating silicic acid fine powder treated with aminosilane into a toner, and a method of incorporating silicic acid fine powder treated with silicone oil having an amine in the side chain. Attempts have been made to incorporate

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 the above-mentioned tripostatic properties. 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, particularly without density fluctuations during initial startup. For the purpose of providing.

[Means for Solving the Problems and Effects 1] According to the present invention, a positively charged magnetic developer comprising a magnetic toner, positively charged silicic acid fine powder, and strontium oxide powder is provided.

The positively charged silicic acid fine powder herein refers to one that has a charge amount of +5.07 g or more with respect to the iron powder carrier.

To measure the amount of charge, first, the test substance (silicic acid fine powder) is
A mixture of an iron powder carrier having a particle size of 00/300 mesh at a ratio of 1:IOQ is 0.5 to 1.
Accurately weigh 5g. This is sucked at a pressure of 25 cmH2O with a metal 400 mesh screen L connected to an electrometer, and the amount of charge per unit weight is determined from the separated and sucked test substance and its charge amount.

In this specification, silicic acid fine powder refers to anhydrous silicon dioxide (silica), aluminum silicate, sodium silicate, potassium silicate, magnesium silicate,
Refers to silica F11 salts such as 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", and calculus resin, It consists of components selected from magnetic materials, dyes, pigments, charge control agents, flow modifiers, and lubricant caps, in addition to positively charged silicic acid fine powder, strontium oxide, and carbon and other substances as necessary. A developer to which appropriate additives are added is called a "magnetic developer."

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.

SiCβa + 2H2+ 07→SiO; + + 4
HCβ also includes a composite fine powder of silica and other metal oxides obtained by 19 in which another metal halide compound such as aluminum chloride or titanium chloride is used together with a silicon compound in this process. The following are reprinted products of fine silicic acid powder (silica) produced by the dry method.

AEROSIL 130 (] 1 piece Aerosil) 200 X50 T800 OX80 MOK! , 70 0K84 Cab-0-SiL (Chara Ozil) M
-5CABOT Co, (Cabot Co.)
MS-7s-5 H-5 Wacker HDK N 20
V15WACKEI? -C) JEMIIE GMBI
(N20E (Wackel Hemie GMB) 1 company) T30
0-CFine 5ilica (7 fin silica) Tau Corning Fransol Fransil (7 Ransil) In addition, there are various conventionally known wet methods. For example, decomposition of titrium 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,
There is a method of converting a sodium silicate solution into silicic acid using an ion exchange resin.

The following are reprints of fine silicic acid powder synthesized by the wet method.

Carplex Shionogi & Co. Nip Seal Nippon Silica Toxeal, Fine Seal Tokuyama T Tatsuvitaseal Taki Hijiruton, Silnex Mizusawa Kagaku Starsil
Kamishima Chemical Himezil
Ehime Pharmaceutical Thyroid Tomitodevison Chemical H
i-Sil Durosil Ultra
sil (Ultra Seal) Fillstoff-G
esellschaft Marquart Manosil Hardman and Ho1den
and Holden) Hoesch Sit-Stone Stone
r Rubber Co.

(Stoner rubber) Nalco (Nalco) Nalco Cbera, Go.

(Narco Chemical) Quso (shoes) Philadelphia Quartz Co.

(Philadelphia Quartz) Santocell (Santocell) Monsant
o Chemical Co.

(Monsanto Chemical) Imsil 111inois Minerals Co.

(Illinois Mineral) Calcium 5ilikat (Calcium Silicate) Che+5ische Fabrik Ho
esch, K-G Calsil Fiillstoff-Gesellschaft M
arquartF□rtafil (7*Lutafil)
Tmperial Chemical Industry
ies Ltd.

Microcal Manosil Hardman and Ho1den
and Holden) Vulkasil Farbenfabriker+ Bayer, A.
-G.

(Falpenfabriken Bayer) Tufkni
t (tough knit) Durham Chemicals Ltd.

(Durham Chemicals°) Silmos Shiraishi Kogyo Starex Shinshin Kagaku Fricocil
Among the fine silicic acid powders, those with a specific surface area due to nitrogen adsorption measured by the BET method in the range of 30II2/g or more (particularly 50 to 400m2/g) give good results.

When these fine silicic acid powders are modified to have a positive charge and are incorporated into a developer, charge controllability is exhibited. There are methods such as treatment with silicone oil and treatment with aminosilane.

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

-5i・0...(1) ■■ (Here, R1 represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R2 represents an alkylene group or a phenylene group, R:l, R4 represents hydrogen, an argyl group, or an aryl group. represents a group, provided that the above alkyl group, aryl group,
The alkoxy group, alkylene group, and phenylene group may contain an amine, or may have a substituent such as a halogen within a range that does not impair chargeability. ) Among these, among the published ones, those represented by the following structural formula, for example, can be preferably used.

(Here, R1, R4, and R5 represent an alkyl group or an aryl group, R2 represents an alkylene group or a phenylene group, and R3 represents hydrogen, an alkyl group, or an aryl group. m + n is an integer of 1 or more. ) Specifically, the following are preferred, and may be used singly or in a mixed system of two types.

5F8417 (manufactured by Torre Silicone) 1
200 3500KF393 (manufactured by Shin-Etsu Chemical) 80 360KF85
7 (manufactured by Shin-Etsu Chemical) 70
830KF860 (manufactured by Shin-Etsu Chemical)
250 7600KF8Eil
(Manufactured by Shin-Etsu Chemical) 3500
2000KF862 (manufactured by Shin-Etsu Chemical)
750 1900KF8e4 (manufactured by Shin-Etsu Chemical) 1700 380
0KF8B5 (manufactured by Shin-Etsu Chemical)
90 4400KF369 (manufactured by Etsu Kagakusha) 20 320KF3
83 (manufactured by Shin-Etsu Chemical) 20
320X-22-3880 (manufactured by Shin-Etsu Chemical)
90 8800X-22-380
0 (manufactured by Shin-Etsu Chemical) 2300 3
800-22-380IC: (manufactured by Shin-Etsu Chemical)
3500 3800・22-3810B
(Manufactured by Shin-Etsu Chemical Co., Ltd.) 1300 1
700 In addition, amine 5 star means T per amine.
ii: (g/eqiv), which is the molecular weight divided by the number of amines per molecule. In addition, the viscosity at 25°C is preferably 5000 cps or more, particularly 3000 cps.
PS or less is preferable. If the speed is less than 5,000 cps, the dispersion into the fine silicic acid powder becomes insufficient, which tends to cause poor images with fogging.

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. The fine silicic acid powder is vigorously stirred while being heated if necessary, and then the silicone oil having an amine in the side chain or its solution is sprayed or vaporized, or the fine silicic acid powder is slurried. The treatment can be easily carried out by adding a silicone oil having an amine in the side chain or a solution thereof while stirring the mixture. At this time, the addition amount of the silicone oil having amyl/ in the side chain is 0.2 to 70% by weight of the amount of treated silicic acid fine powder, and 0.00% to the developer.
It is preferable that the amount is 0.01 to 10% by weight.

In addition, the aminosilane used for surface treatment of silicic acid fine powder is a so-called aminofunctional silane, and has the general formula: ~Hydrocarbon group 1,1 having 7 tertiary amide groups
is an integer from 3 to 1. ) and include the following compounds.

CH3 H2N-CH2CH2NHCH2Glh CH2S i
-(QC:Hz)2H2N-C:0NH-CH2C
H2CH2-Si-(OC2H5hH2N-CH2CH
2CH2Si(OCH2CIhhH2NCH7CH2N
HCH2CH2CH25i (0CH3)3H1・NC
H2C1h CH2S i (OCH3)3)12 N
CH? CH2NHCH2CH2N)IGH2GH2C
H2S i (OCH3): l85G20COCH2C
H2NHC1hGlhGIhSi(OCH3)3H! ,
C/ CIC0CH2C1b NHCH7CH7NH
CIL7 CH2CH25i (OCH+) =H5
C7QC;0CH2GH2NHCH7CH2CH2:I
h CH2NHCH2CH2NHCH7CH2CH2S
i (QC:H:+)::Nl2 Ct, Hs
S i (OC:H+)3Cb)15NHcH2cH
/CH25i(QC:Hs):+ or polyaminoalkyltrialkoxysilane, and these may be used alone or in a mixed system of two types.

The surface of the fine silicic acid powder can be treated with aminofunctional 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 additive amount of aminosilane is 0.0 per 100 parts of silicic acid fine powder.
1-10 parts by weight, preferably o, i to 5 parts by weight.

Alternatively, as described in Japanese Patent Publication No. 18220/1982, positively charged silicic acid fine powder may be obtained by reacting the sitenol groups on the surface of the silicic acid fine powder with an organosilicon compound.

In addition, 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 adsorption with the silicic acid fine powder. Organic silicon is treated chemically with compounds to make it more attractive.

Examples of such organosilicon compounds are hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allyl phenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triocassylylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, Vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyljethoxysilane,
Hexamethyldisiloxane, 1,3-divinylte!・Ramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and a water alcohol bonded to Si with 2 to 12 siloxane centers per molecule and one each to the terminal center. There are dimethylpolysiloxane shades containing groups. These can be used alone or in a mixture of two types of devices.

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 crushed and classified. The required developer is obtained. Note that the surface treatment of the silicic acid fine powder mentioned above may be performed during this developer preparation process. That is, the required silicic acid fine powder is kneaded with resin as a binder,
In the step of blending, silicone oil or aminosilane having an amine in the side chain may be added and kneaded, and the silicic acid fine powder may be surface-treated in conjunction with blending.

The applied amount of the thus treated silicic acid fine powder is 0.01 to 20 parts by weight per 100 parts by weight of toner, and is particularly effective. It exhibits positive chargeability with excellent stability.

The strontium oxide SrO used in the present invention is a colorless cubic crystal powder obtained by igniting strontium hydroxide, carbonate, nitrate, etc. The purity of the commercially available reagent is 95% or more, and the purity of the commercially available reagent is 95% or more. This is sufficient for our purposes.

These metal oxides are 0 to 100 i of toner
．． The particle size is preferably 1 to 20% by weight, preferably 0.2 to 5% by weight.

It is desirable that the amount is 5 liters or less, preferably in the range of 0.01 to 3 liters.

As the binder resin used in the present invention, all known binder resins can be used, but for example, '1 combination of styrene and its substituted products such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene: styrene-p-chlorostyrene. Styrene type polymer, styrene-prohylene Jt, polymer, styrene-vinyl)/luene 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-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer Polymer, styrene-butadiene copolymer, styrene-imprene copolymer, styrene-
Styrenic copolymers such as acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; 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, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated puttyfin, paraffin , wax, etc. can be used alone or in combination.

When this binder resin contains a magnetic substance and is formed into particles, the particle size is preferably 5 to 30 l, which is the general toner particle size.

Also, as a 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 1
00-800mg, preferably 300-500mg
The content is preferably 30 to 100 parts by weight, more preferably 40 to 80 parts by weight, based on 100 parts by weight of the binder resin.

In addition, this magnetic toner contains a charge control agent, a flow modifier,
Colorants and lubricants can be added (externally added) or included (
(internal attachment) does not impede the present invention in any way.

In producing the magnetic toner of the present invention, a method can be applied in which the constituent materials are thoroughly kneaded using a hot kneader such as a hard roll, a kneader, or an extruder, followed by mechanical crushing and classification.

Further, in order to add and contain each of the above-mentioned inorganic powders into the magnetic toner, a known mixer can be used, such as a rotary container type mixer such as a V-type mixer, a tarpaulin mixer, a ribbon type, screw type, rotary blade type, or other fixed container. A mold mixer can be used as appropriate.

Alternatively, after dispersing a material such as magnetic powder in a binder resin solution and then spray-drying it, the emulsified suspension can be obtained by mixing a predetermined material with the monomers that should constitute the binder resin. 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] The present invention will be explained in more detail with reference to Examples below.

100 parts by weight (Nigrosine Base EX, manufactured by Orient Kagaku f Gyo) 2 parts by weight paper) 1 polyethylene wax 4 parts by weight The following materials were mixed and melted and kneaded in a roll mill. After cooling, it is coarsely pulverized using a hammer mill, and then finely pulverized using a jet pulverizer. Then, it is classified using a wind classifier to obtain particles with a particle size of approximately 5.
A magnetic torch of ~30μ was obtained.

1- Various positively charged silicic acid fine powders, strontium oxide, and others were added to the magnetic toner to prepare a magnetic developer.

Example 1 Silicic acid fine powder synthesized by dry method (trade name Aerosil 1)
1130. 100 parts by weight of silicone oil (specific surface area approximately 130 m + 2/g; manufactured by Aerosil Co., Ltd.) was kept at 250°C with stirring and mixed with silicone oil (KF85) having an amine in the side chain.
7. Viscosity 70 cps at 25°C, amine 5 stitches 8
30, Shin-Etsu Chemical) 20! If amounts were sprayed and treated for 10 minutes.

100 parts by weight of the magnetic toner was treated with the above-mentioned silicone oil having an amine in its side chain, and 0.0% of the Kff1i powder was added.
A magnetic developer was prepared by externally adding and mixing 4 parts by weight of strontium oxide (SrO, grade 1 reagent manufactured by Tokyo Kasei Co., Ltd.) and 2 parts by weight.

Example 2 Silicic acid fine powder synthesized by dry method (Aerosil 0X-5
0. Specific surface area approximately 50m? /g; manufactured by Aerosil) 1
00 parts by weight of silicone oil with amine in the side chain (
A magnetic developer was obtained in substantially the same manner as in Example 1, except that 1 part of KF393 (viscosity at 25° C., amine adhesion 360, manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

Example 3 Silicic acid fine powder synthesized by dry method (Aerosil 1120
0, specific surface area 20h2/g; manufactured by Aerosil) 10
0 parts by weight of silicone oil with amine in the side chain (X
-22-38010, viscosity at 25°C 3500 cp
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with amine 3800 (manufactured by Shin-Etsu Chemical Co., Ltd.) 40 was used.

Example 4 Silicic acid fine powder synthesized by a wet method (Purkasil C1 specific surface M PJ 80 m2 /g; manufactured by Falpenfabriken Bayer) 100 parts by weight of silicone oil having an amine in the side chain (X-22-3810B, A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer having a viscosity of 1300 cps and an amine fi 1700 (manufactured by Shin-Etsu Chemical Co., Ltd.) treated with an io layer was used.

Example 5 Silicic acid fine powder synthesized by dry method (Aerosil 1138
0, specific surface area 380 m2/g; manufactured by Aerosil) 1
00 parts by weight of silicone oil with amine in the side chain (
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 40 parts by weight of KF8G2, viscosity 750, Amine 5-1900 (manufactured by Shin-Etsu Chemical) was used.

Example 6 Kei m fine powder synthesized by wet method (Nalco co-too
, specific surface area 120+*2/g; manufactured by Narcogamical)
100 parts by weight of silicone oil having an amine in the side chain (SF8417, viscosity 1200 cps, amine 5
A magnetic developer was obtained in substantially the same manner as in Example 1, except that a developer treated with 15 parts by weight (manufactured by Toray Silicone Co., Ltd., 3500 A.D.) was used.

Example 7 Fine silicic acid powder synthesized by dry method (Aerosil Powder 200)
, specific surface area 200m2/g; manufactured by Aerosil) IQ
Q% While stirring 1 part of Es, add γ-aminopropyltrietogysilane (A-1100, Nippon Unicar Co., Ltd.)
A solution prepared by diluting 2 parts by weight with 20 parts by weight of 90% ethanol is added dropwise using a dropper. After stirring was continued for 3 minutes after the addition, the powder liquid was transferred to a vat and heated in a dryer at 110° C. in a nitrogen gas atmosphere for 1 hour to remove ethanol. While stirring the obtained powder again, 4 parts by weight of hexamethyldisilazane was added to 1 part by weight of hexane.
A solution diluted with 6 parts by weight is dispersed in a L-renma-like manner,
Remove hexane. The powder thus obtained was transferred to a one-piece flask equipped with a flow condenser, a stirring tank, and a thermometer.
50° (E Te 4 o'clock 1&'f JrJ Heat.

4 parts by weight of the silicic acid fine powder treated with the aminocythene and strontium oxide (S) are added to 100 parts by weight of the magnetic toner.
A magnetic developer was obtained by externally adding and mixing 2 parts by weight of rO (reagent grade 1 manufactured by Tokyo Kasei Co., Ltd.).

Example 8 A magnetic developer was obtained in the same manner as in Example 1, except that 0.5 part by weight of carbon (Mitsubishi Kasei 140) was also externally added and mixed.

Comparative Example 1 Only 0.4 parts by weight of negatively charged hydrophobic colloidal silica (Aerosil R372, specific surface area 120 m2/g, manufactured by Aerosil Co., Ltd.) was externally added to 100 parts by weight of the same magnetic toner as in Example, and magnetic development was performed. obtained the drug.

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

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

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

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

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

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

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

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

Normal temperature and humidity (25°C, 60% R
H), high temperature and high humidity (35°C, 185% RH), low temperature and low humidity (15°C, 10% RH), and Table 1 (normal temperature and humidity) and Table 2 (high temperature and humidity) High humidity, low temperature and low humidity). In the table, O indicates good, Δ indicates slightly poor, and × indicates poor.

As for the development method, in Example 8 and Comparative Example 9, powder was developed using a magnetic brush method to create a toner image, which was transferred to sweat paper and fixed by heating. For other Examples and Comparative Examples, copy fi (NP-15
02, manufactured by Canon ■) was used to eject both.

In each of the examples, the transferred images obtained were sufficiently clear from the first sheet +1, had no fogging, and had no toner scattering around the image, resulting in a good image with high resolution.

In addition, we created continuous transfer images and examined their 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 photoreceptor and adversely affects latent image formation, was not observed at all, and no problems were found during cleaning.

In addition, even if the environmental conditions are high temperature and high humidity (35°C, 85% RH) or low temperature and low humidity (15°C, 10% RH), clear images almost the same as those at normal temperature and humidity can be obtained, giving satisfactory results. The results were obtained.

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. Further, from around 10,000 sheets onwards, toner material formed a thin streak-like pattern on the surface of the photoreceptor and began to appear as lines on the image (filming).

Even under condition F of high temperature and high humidity, and low temperature and low humidity, the 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. Further, the density tended to decrease slightly under high temperature and high humidity conditions and when 30,000 sheets were printed in a durability test. Also, filming started to occur after around 10,000 copies.

[Effects of the Invention] As explained above, the magnetic developer of the present invention has a stable and uniform positive charging property, and enables development and transfer faithful to the latent image. 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, halftone reproducibility is good, and image density rises. Image density is high from the beginning.

Further, 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 a filming phenomenon, and has good cleaning properties. In addition, it is a magnetic developer that reproduces stable images that are unaffected by changes in temperature and humidity, and does not cause scattering or transfer failure even in high 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 strontium oxide powder. 2) The mixing ratio of the positively charged silicic acid fine powder is 1 for the magnetic toner.
The developer according to claim 1, wherein the amount is 0.01 to 20 parts by weight based on 0.00 parts by weight. 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.