JPH083652B2 - Developer - Google Patents

Description

The present invention relates to a developer used in electrophotography, electrostatic printing, and the like. More specifically, it relates to an insulating black developer containing a positively chargeable toner.

[Conventional technology]

Conventionally, as a method for developing a non-magnetic toner in an electrophotographic method, methods such as a cascade method and a powder cloud method are known, but in general, in the case of a non-magnetic toner, in order to efficiently convey the toner to a developing unit, A method of mixing with magnetic particles such as iron powder and ferrite powder is adopted.

As one example, mixing toner and magnetic particles,
A method of forming a magnetic brush and rubbing and developing an electrostatic charge image is widely known.

As still another developing method, a developer container that stores toner and magnetic particles for toner application, a toner carrier that conveys toner to a latent image carrier, and the toner carrier on the upstream side of the toner outlet of the developer container. A thin layer of toner is formed on the toner carrier by arranging a magnet that forms a magnetic brush made of magnetic particles for toner application that comes into contact with the body, and the toner carrier and the electrostatic image holding are more than the toner layer thickness. There is a method of developing an electrostatic image by setting a large gap with the body.

These methods require that a substantially non-magnetic toner be kept in a uniformly mixed state with magnetic particles or in a uniformly thin layer coating state on a carrier in a developing section, and that state is maintained. Electrostatic attraction and physical adhesion are the predominant forces to achieve. That is, it is necessary to precisely control the amount of electrostatic charge and the triboelectric charging ability of the toner.

As a developing method using a magnetic toner, there is known a developing method using an insulating magnetic toner, which the applicant of the present invention has previously proposed in JP-A-55-42141. This is developed by applying a very thin coating of insulating magnetic toner on the sleeve, triboelectrically charging it, facing it very closely to the electrostatic image under the action of a magnetic field, and flying the toner.
This is the jumping method. 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, it is known that the chargeability of the toner greatly affects the image. In particular, since there is no charge imparting member such as a carrier, the opportunity for toner contact and frictional charging is insufficient, and the electrostatic charge of the toner The amount of electric charge and triboelectrification capability need to be controlled more precisely.

However, it is quite difficult to uniformly control the charge amount of the toner and to stabilize the charge amount even after repeated copying over a long period of time or under a special environment of high temperature / high humidity / low temperature / low humidity. It is accompanied. Particularly in the case of positively chargeable insulating toner, it is very difficult to uniformly positively charge the components of the toner such as resin, pigment, fluidizing agent, abrasive, lubricant, etc., and uniform positive charge is possible. In a low temperature and low humidity, the toner tends to be charged, a good image cannot be displayed, and the cleaning failure of the residual toner on the photoconductor occurs.

[Problems to be solved by the invention]

An object of the present invention is to provide a positively chargeable toner that solves the above problems.

That is, an object of the present invention is to provide a toner having an ideal material structure as a positively chargeable insulating toner and exhibiting stable triboelectric chargeability even under a special environment of low temperature and low humidity.

[Means and Actions for Solving Problems]

That is, the feature of the present invention is at least a positively chargeable toner containing carbon black fine particles or black magnetic fine particles and a positively chargeable silicic acid fine powder, and the triboelectric charge amount T _{A of the} positively chargeable toner is T _A ≧ +20 μC / g, 1 ≦ T _A / T _B ≦ 3, preferably 1.2 ≦ T _A / T _B, where T _B is the triboelectric charge amount of the mixture of the positively chargeable toner and the silicic acid fine powder. ≤
2 in the insulating black developer.

The toner here means kneading, crushing, and classifying raw materials.
Alternatively, it refers to integrated particles obtained by melting / spraying (dispersion) granulation or polymerization granulation, and the form of the developer to be put into practical use by mixing the particles with a fluidizing agent / charge control agent thereafter. different.

As a result of earnest studies, the inventors of the present invention, as a fluidity improving agent or a charge control agent, are one of the major causes of the fluctuation of the charging ability after the developer has been copied for a long period of time or under the special environment of high temperature and high humidity and low temperature and low humidity. It was confirmed that there was a quantitative change of the silicic acid fine powder added to the toner; a qualitative change due to moisture absorption and drying. Further, the present inventors have examined the constitution relating to the charging between the toner and the silicic acid fine powder, and found that the toner has a large charging ability to some extent and the silicic acid fine powder rather plays a role of suppressing the charge. It was confirmed that the chargeability was stable as a whole, and it was found that satisfying the above conditions was extremely good as the material constitution of the positively chargeable developer.

Further, it is well known that an insulating toner that exhibits good chargeability under normal temperature and normal humidity causes charge deterioration under low temperature and low humidity, resulting in image deterioration. In addition, it has been found that it is extremely effective to incorporate carbon black fine particles, black magnetic fine particles, or both as an antistatic agent in the toner.

The toner of the present invention can be produced by including a conventionally known substance having a positive charging property, and particularly, a styrene-based copolymer containing 1 to 15% by weight of an amino acrylic monomer is used. Those containing more than the weight (%) have a large triboelectric charge amount and are most preferable. As the aminoacryl monomer, all known ones can be used, but generally, the one represented by the following structural formula is effective.

R ₁ is hydrogen or a methyl group or an ethyl group R ₂ is an alkylene group having 1 to 4 carbon atoms R ₃ , R ₄ is an alkyl group having 1 to ₄ carbon atoms As a constituent component other than aminoacryl of the above-mentioned copolymer, conventionally known Although all of the known monomers can be used, it is generally desirable to contain 70% by weight or more of styrene-acrylic comonomer. Examples of the styrene-based monomer include styrene, vinyltoluene, α-methylstyrene and the like, and examples of the acrylic-based monomer include acrylic acid and esters of methyl, ethyl, propyl, butyl and 2-ethylhexyl of acrylic acid, Methacrylic acid, methacrylic acid methyl, ethyl, propyl, butyl, 2-hexyl esters, and the like can be mentioned, respectively. As a method of polymerizing the copolymer, all conventionally known methods can be used, but a homogeneous system such as bulk polymerization or solution polymerization is particularly preferable.

As the silicic acid fine powder used in the present invention, all those in which the variation of the triboelectric charge amount due to the mixing with the toner satisfies the above conditions are used, but it is desirable that the toner charge is not disturbed as much as possible, and therefore it is The silicic acid fine powder having a positive charging property, for example, the silicic acid fine powder treated by coupling with an aminoalkylsilane compound or treated with a silicone oil having an amine in a side chain is most preferable from the viewpoint of environmental stability. As the matrix of fine silica powder,
Fine silicic acid powder produced by a dry method or a wet method can be used.

The dry method here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halogen compound.
For example, in a method utilizing a thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, the basic reaction formula is as follows.

SiCl ₄ + 2H ₂ + O ₂ → SiO ₂ + 4HCl Further, in this manufacturing process, by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound, a composite of silicic acid and another metal oxide can be obtained. It is also possible to obtain fine powders and these are included.

Examples of commercially available silicic acid fine powders produced by vapor phase oxidation of a silicon halogen compound used in the present invention include those commercially available under the following trade names.

AEROSIL 130 (Japan Aerosil Co., Ltd.) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL M-5 (CABOT Co. Co.) MS-7 MS-75 HS-5 EH-5 Wacker HDK N 20 V15 (WACKER-CHEMIEGMBH N20E T30 T40 D-C Fine Silica (Dow Corning Co.) Fransol (Fransil) On the other hand, the method for producing the silicic acid fine powder used in the present invention by a wet method includes various conventionally known methods. Applicable. For example, if sodium silicate is decomposed by an acid, and if it is shown by a general reaction formula (the reaction formula is abbreviated below), Na ₂ O ・ XSiO ₂ + HCl + H ₂ O → SiO ₂・ nH ₂ O + NaCl, other ammonium salts of sodium silicate or alkali Decomposition by salts, method of generating alkaline earth metal silicate from sodium silicate, then decomposing with acid to silicic acid, method of converting sodium silicate solution into silicic acid by ion exchange resin, natural silicic acid or There is a method of using silicate.

As the silicic acid fine powder referred to here, anhydrous silicon dioxide (silica) or any of silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be applied.

Examples of commercially available silicic acid fine powders synthesized by the wet method include those commercially available under the following trade names.

Carpretx Shionogi Nepseal Nippon Silica Tokseal, Huainseal Tokuyama Soda Vita Seal Taki Manure Shiruton, Shirunetsusu Mizusawa Chemical Starsil Kamijima Kagaku Himesir Ehime Pharmaceutical Syroid Fuji Debison Kagaku Hi-Sil (High Seal) Pittsburgh Plate Glass.Co. Fiillstoff-Gesellschaft Ultorasil (Ultraseal) Marquart (Manufacture) Manosil (Manosir) Hardes and Holden (Hoesch) Chemische Fabrik Hoesch S. Stone) Stoner Rubber Co. (Stoner rubber) Nalco (Nalco) Nalco Chem. Co. (Nalco chemical) Quso (fucking) Philadelphia Quartz Co. (Firade) Santocell Monsanto.Chemical Co. Immon Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch.KG Chemische Fabrik Hoesch.KG Gesellschaft Marquart Fortafil Imperial Chemical Industries.Ltd. (Imperial Chemical Industries) Microcal Joseph Crosufiels & Sons.Ltd. And Holden Vulkasil Farbenfabriken Bryer, A.-G. Tufknit Durham Chemicals.Ltd. Of arm Chemicals) Shirumosu Shiraishi Kogyo Sutaretsukusu Kamijima Chemical Furikoshiru multi wood fertilizer the silicon acid fine powder, the specific surface area by measuring nitrogen adsorption by the BET method is 30 m ² / g or more (especially 50 to 400 m ² / g)
Those in the range of give good results.

As the silicone oil having an amine in the side chain used for the treatment of the silicic acid fine powder, a silicone oil containing a structural unit represented by the formula (I) can be generally used.

(Here, R ₁ represents hydrogen, an alkyl group, an aryl group, or an alkoxy group, R ₂ represents an alkylene group, a phenylene group, and R ₃ and R ₄ represent hydrogen, an alkyl group, or an aryl group. The above alkyl group, aryl group, alkylene group and phenylene group may contain an amine, and may have a substituent such as halogen within a range not impairing the charging property.) A commercially available side chain The amine-containing silicone oil is preferably an amino-modified silicone oil represented by the following structural formula. that is (Here, R ₁ and R ₅ represent an alkyl group or an aryl group,
R ₂ represents an alkylene group, a phenylene group, or an alkyl group containing an amine, and R ₃ represents hydrogen, an alkyl group, or an aryl group. m and n are numbers of 1 or more. ) The silicone oils represented by the following are specifically preferable, and these may be used in one kind or in a mixed system of two or more kinds.

The amine equivalent is equivalent to one amine (g /
eqiv) is the value obtained by dividing the molecular weight by the number of amines per molecule.

The amount of the silicone oil having an amine in the side chain in the present invention is 0.2 to 70% of the total amount of the treated silicic acid fine powder.
It is preferable that the weight percent is 0.0001 to 10 weight percent in the developer. Further, the proper treatment amount of the silicone oil having an amine in the side chain is such that the weight part of the silicone oil is x with respect to 100 parts by weight of the fine silica powder before the treatment with the silicone oil. If the specific surface area of the fine powder is bm ² / g and the amine equivalent of the silicone oil having amine in the side chain is a,
When the relation of formula (II) is satisfied, particularly good results are given.

In the above formula, In the case of, the silicone oil having an amine in the side chain is in a large excess relative to the silicic acid fine powder, which may cause a problem such as leaching of the silicone oil having an amine in the side chain from the silicic acid fine powder. . Also, In this case, the chargeability is insufficient and it becomes difficult to achieve the object of the present invention.

On the other hand, 25 ° C of silicone oil having amine in the side chain
The viscosity is preferably 5000 cps or less, and particularly preferably 3000 cps or less. When the viscosity is 5000 cps or more, the silicone oil having an amine in the side chain is insufficiently dispersed in the silicic acid fine powder, which easily causes a defective image such as fog.

The above-mentioned treatment with the silicone oil having an amine on 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.

In particular, a method of spraying or vaporizing a silicone oil having an amine in the side chain or a solution thereof and spraying it onto the silicic acid fine powder is a preferable method from the viewpoint of processing uniformity. Further, it is preferable from the viewpoint of the charge stability of the treated silicic acid fine powder to cure and crosslink the silicone oil having the amine in the side chain on the silicic acid fine powder by heating after the treatment once. The best heating temperature is 270-350 ° C. If the temperature is lower than that, the triboelectric chargeability of the treated silica fine powder may be lowered, and the condition of the present invention may not be satisfied when externally added to the toner. Decomposes easily, making positive charging impossible.

In the present invention, one kind or a mixture of two or more kinds of the above-mentioned silicone oil having an amine in the side chain may be used.

Further, the applied amount of these treated silicic acid fine powders may be set so that the ratio of triboelectric charge amount T _A / T _B satisfies the above condition.
~ 3 parts by weight exerts an effect, particularly preferably 0.03
It shows positive chargeability with excellent stability when added up to 1.5 parts by weight.

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, Prommethyldimethylchlorosilane, α
-Chloroethylcoliclorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane,
Triorganosilyl mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane,
Dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule There is dimethylpolysiloxane having a Si-bonded hydroxyl group for each unit located at the terminal. These are used alone or as a mixture of two or more.

As the carbon black fine particles used in the present invention, all known particles can be used. For example, those manufactured by the channel black method, the fan net black method or the like can be used, but the particle size is 1 as primary particles.
It is preferably μ or less, more preferably 0.5 μ or less. or,
The specific surface area by the BET method is 50 to 1000 m ² / g, preferably 1
00 to 800 m ² / g is good.

The amount of carbon black fine particles added is preferably 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the total binder resin in the toner. If the addition amount exceeds this, it becomes difficult for the toner to retain the electrostatic charge, and if it is less than this, the blackness is deteriorated. As a method of adding to the toner, a method of uniformly dispersing in the binder resin, a method of mixing particles to the outside of the toner, and the like are possible, but from the viewpoint of coloring degree and charge stability, It is desirable to disperse.

As the black magnetic fine particles used in the present invention, all the conventionally known ones can be used, but in general, Fe ₃ O ₄ , MO.Fe ₂ O ₃ (M = Mg, Al, Si, Ca, Ti , V, Cr, Mn, Co, Ni, Cu, Zn, Sr, Y, Zr, Nb, Mo, Sn, Sb, Ba, W, Bi) Fine particles of ferrite are desirable. The particle size of the primary particles is 5 μm or less, preferably 3 μm or less. Further, the specific surface area by the BET method 2 to 10 m ² / g, more preferably 4 to 8 m ² / g is good.

The amount of the black magnetic fine particles added is 5 to 120 parts by weight, more preferably 100 parts by weight of the total binder resin in the toner.
10 to 100 parts by weight is good. If the addition amount exceeds this, it becomes difficult for the toner to retain the electrostatic charge, and if it is less than this, the blackness is deteriorated. As a method of adding to the toner, a method of uniformly dispersing in the binder resin, a method of mixing particles to the outside of the toner, and the like are possible, but from the viewpoint of coloring degree and charge stability, It is desirable to disperse.

In the present invention, it is possible to add other resins, polymers, etc. to the toner in addition to the above copolymers. Examples thereof include polystyrene, polystyrene / butadiene copolymers, styrene / acrylic copolymers and other styrene copolymers, polyethylene, polyethylene vinyl acetate copolymers,
Examples thereof include ethylene-based copolymers such as polyethylene vinyl alcohol copolymer, phenol-based resins, epoxy-based resins, allyl phthalate resins, polyamide resins, polyester resins, maleic acid-based resins and the like. In addition, the manufacturing method and the like of each resin is not particularly limited.

As the coloring material used in the toner of the present invention, conventionally known coloring materials such as carbon black, dyes and pigments can be used.

It is also possible to add other lubricants / abrasives to the toner.

It is also possible to implement the constitution of the present invention in the microcapsule toner by using the core material, the shell material, or both of them.

As an image forming method using the developer of the present invention, an electrostatic charge image formed on an electrostatic charge image support by an electrostatic charge image forming method such as an electrophotographic method, an electrostatic recording method, an electrostatic printing method, Develop with the developer. For example, in electrophotography, as shown in FIG. 2, a static charge is applied to the surface of a drum 1 made of a photoconductive photosensitive member rotated in the direction of an arrow by a charging mechanism 2 such as a corona charger, A light image of the original is projected onto the document by the exposure mechanism 3 to form an electrostatic charge image. This electrostatic charge image is developed by the developing device 4 filled with the above-mentioned developer to form a developer image.

As the developing method here, a method according to the characteristics of the developer is used, a magnetic brush developing method, a cascade developing method, a method using a conductive magnetic developer described in U.S. Pat.No. 3,909,258, Method using a high-resistance magnetic developer described in JP-A-53-31136, JP-A-54-42141
JP-A-55-18656 and the like, a fur brush developing method, a powder cloud method, an imprinting method and the like.

The developer image thus formed is transferred onto a transfer material such as transfer paper. In the example of FIG. 2, the developer image is electrostatically transferred to the transfer paper which is synchronously conveyed along the transfer paper path p indicated by the chain line by the action of the transfer discharger 5. As the transfer means, various means such as pressure transfer and thermal transfer can be used. Then, the transfer material which has received the transfer of the developer image is then conveyed to a fixing device and subjected to a fixing process by a contact heating fixing system using a heating roller, for example, whereby a visible image is formed.

On the other hand, the electrostatic charge image support that has undergone the transfer process is subjected to a cleaning process after being neutralized, if necessary, and then subjected to the next image forming process. In the example of FIG. 2, the static charge on the drum 1 is made to disappear by the action of the discharger 6 for static elimination, and in the figure, the cleaning mechanism 7 by the fur brush removes the developer particles remaining on the drum 1. It is removed and cleaning is performed. Here, the cleaning system is optional, but it is preferable to use the blade cleaning system or the fur brush cleaning system capable of surely achieving the required cleaning, and it is possible to sufficiently cope with high-speed image formation. .
The blade cleaning method is a method in which a scraping blade is provided so that its leading edge contacts the surface of the electrostatic image support to be moved for cleaning, and the structure is simple and energy is not required. A blade cleaning method is preferable as a combination with the toner of the present invention.

In particular, when an organic photoconductor (OPC) is used as a photoconductive photoconductor and the transfer residual developer is cleaned by a blade cleaning method, the developer of the present invention exhibits extremely good cleaning properties. This is because the fine powder of silicic acid has the same polarity as the toner and shows a weaker charging property than the toner, so that it does not adhere too strongly to the toner surface or is not too far away from the toner, and is dispersed with an appropriate adhesion force on the toner. Therefore, it is considered that it is possible to act as a lubricant or an abrasive, and to adjust the appropriate abrasiveness-sliding property between the OPC and the blade.

Next, a method of measuring the triboelectric charge amount in the present invention will be described.

 FIG. 1 is an explanatory diagram of a triboelectric charge amount measuring device.

Toner or toner-constituting fine particles for measuring the triboelectric charge amount in a metal measuring container 12 having a conductive screen 13 of 400 mesh (the size can be appropriately changed so that magnetic particles do not pass) at the bottom, and 200 to 300 Weight ratio of irregularly shaped iron powder with particle size between meshes (EFV200 / 300 made by Nippon Iron Powder, the surface is untreated and, like the toner carrier, has virtually no triboelectricity of its own)
Approximately 4 g of a 1: 9 mixture (developer) is put and a metal lid 14 is placed. At this time, the total weight of the measurement container 2 is weighed and set as W ₁ (g). Next, in the suction device 11 (at least the portion in contact with the measurement container 2 is an insulator), suction is performed from the suction port 17 and the air flow rate control valve 16 is adjusted to bring the pressure of the vacuum gauge 15 to 70 mmHg. In this state, sufficient suction (about 1 minute) is performed to remove the toner or the mixture of the toner and the fine powder of silicic acid by suction. The potential of the electrometer 19 at this time is V (volt). Here, 18 is a capacitor, and the capacity is C (μF). In addition, the total weight of the measuring container after suction is weighed and is W ₂ (g). This triboelectric charge amount T (μC / g) is calculated by the following equation.

However, the measurement conditions are 23 ° C and 50% RH.

〔Example〕

Specific examples will be described below. All parts and percentages are parts by weight.

Example 1 Styrene-butyl acrylate-100 parts Dimethylaminoethyl methacrylate copolymer (80: 15: 5) 10 parts of carbon black fine particles (primary particle size 15 mμ, BET surface area 400 m ² / g) were kneaded, crushed and classified. A toner having an average particle size of 9μ was obtained.
The triboelectric charge amount T _A was 30.1 μC / g.

On the other hand, 100 parts by weight of fine silicic acid powder (trade name, Aerosil # 130, specific surface area and 130 m ² / g, manufactured by Aerosil Co., Ltd.) synthesized by a dry method are stirred while silicone oil having an amine in a side chain (25 ° C. Viscosity at 70 cps, amine equivalent 8
30) 20 parts by weight was sprayed and treated for 10 minutes, and heat treatment at about 280 ° C. was performed for 20 minutes while continuing stirring.

To 100 parts by weight of the black toner, 0.4 parts by weight of fine silicic acid powder treated with the above silicone oil having an amine in the side chain was added. Triboelectric charge of the mixture T _B = 24.3 μC / g
And T _A / T _B = 1.2, which satisfies the condition of the present invention.

5 parts of a mixture of this toner and fine silica powder, and a particle size of 30
100 parts of irregular iron powder of 0 to 400 mesh is mixed, a developer is obtained, and an OPC photoconductor is charged and charged into a Canon NP-5000 copier which is resolved so as to form a negative latent image, When an image was produced, a clear image free of fog was obtained, and the image reflection density was 1.45. Furthermore, even when continuous copying of 10,000 sheets was carried out at a low temperature and low humidity of 15 ° C. and 10% RH, the image quality was not deteriorated at all, and there was no problem such as reduction in image density due to developer charge.

Further, when the cleaning method of the photosensitive member was carried out by the doctor blade cleaning method, the cleaning property was good.

Example 2 Styrene-butyl acrylate-70 parts Dimethylaminoethyl methacrylate copolymer (80: 12: 8) Styrene-butadiene copolymer 30 parts Carbon black fine particles 8 parts (Primary particle size 30 mμ, BET surface area 200 m ² / g) Was mixed, pulverized, and classified to obtain a toner having an average particle size of 11 μ (T _A = 42.6 μC / g).

When 0.8 part of the treated silicic acid fine powder of Example 1 was added to 100 parts of this toner, T _B = 24.8 μC / g and T _A / T _B = 1.7, which satisfied the conditions of the present invention.

Thereafter, when the same operation as in Example 1 was performed, the same good result was obtained.

Example 3 Styrene-diethylaminoethyl 60 parts Methacrylate copolymer (90:10) Styrene-butyl methacrylate 40 parts Copolymer (80:20) Magnetite fine particles 60 parts (primary particles 0.1 µ, BET surface area 6 m ² / g) When 100 parts of the toner having an average particle size of 12 μm (T _A = 22.4 μC / g) was added with 0.6 part of the treated silicic acid fine powder of Example 1, T _B = 13.9 μC / g, T _A / T _B = It became 1.6.

When the mixture of this toner and the fine powder of treated silicic acid was put into a NP-150Z copying machine manufactured by Canon Inc., the same good results as in Example 1 were obtained.

Example 4 Styrene -2-ethylhexyl acrylate 100 parts rate - dimethylaminoethyl meth acrylate copolymer (84: 12: 4) ZnO · Fe 2 O 3 fine particles 50 parts (primary particles 1 [mu], BET specific surface area of 4m ² / g) 5 When except for using parts carbon black fine particles (primary particles 10 [mu], BET surface area of 700m ² / g) having an average particle size of 10 [mu] consisting of toner (T _a = 25.0μC / g) was carried out in the same manner as in example 3, T _B = 14.2μ
C / g, T _A / T _B = 1.8, and the same good results as in Example 1 were obtained.

〔The invention's effect〕

By using the positively chargeable toner and the positively chargeable silicic acid fine powder based on the material structure of the present invention, a developer having a stable chargeability can be always obtained. In particular, the charging stability under low temperature and low humidity was excellent, and an extremely good image was exhibited.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a triboelectric charge amount measuring device according to the present invention. FIG. 2 is a schematic explanatory view of the structure of an electrophotographic copying machine which carries out the electrophotographic process. 1 ... Drum, 2 ... Charging mechanism, 3 ... Exposure mechanism, 4 ...
... Developer, 5 ... Transfer discharger, 6 ... Electrification discharger,
7 ... Cleaning mechanism, 11 ... Suction device, 12 ... Measuring container, 13 ... Conductive screen, 14 ... Metal lid, 15
…… Vacuum gauge, 16 …… Air flow control valve, 17 …… Suction port, 18 ……
Condenser, 19 ... Electrometer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuru Uchida 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Kobayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP 59-83171 (JP, A) JP 52-135739 (JP, A) JP 61-23160 (JP, A) JP 61-198251 (JP, A) JP-A-59-201063 (JP, A)

Claims (1)

[Claims] 1. A positively chargeable toner containing at least carbon black fine particles or black magnetic fine particles and a positively chargeable silicic acid fine powder, wherein the triboelectric charge amount T _{A of the} positively chargeable toner is T _A ≧ + 20 μC / g, and insulative black developing agent, characterized in that the triboelectric charge of a mixture of a positive charged toner and the fine silica powder in case of the T _B is _{1 ≦ T a / T B ≦} 3 .