JPH0736082B2 - Positively charged developer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a positively chargeable developer used in electrophotography, electrostatic printing, and the like. More specifically, it relates to a developer containing positively charged silicic acid fine powder and a positively charged toner.

[Prior Art] Conventionally, a method such as a cascade method or a powder cloud method is known as a developing method of a non-magnetic toner in an electrophotographic method, but generally, in order to efficiently convey the non-magnetic toner to a developing unit. A method of mixing with magnetic particles such as iron powder and ferrite powder is adopted.

As one example thereof, a method in which toner and magnetic particles are mixed, a magnetic brush is formed, and an electrostatic charge image is rubbed and developed is widely known.

As still another developing method, a developer container for storing toner and magnetic particles for toner application, a toner carrier for conveying the toner to the 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 disposing a magnet that forms a magnetic brush made of magnetic particles for toner application in contact with the toner carrier and the electrostatic image carrier. There is a method of developing an electrostatic image by setting a large gap between and.

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.

However, by uniformly controlling the charge amount of the toner,
Moreover, it is quite difficult to stabilize the charge amount even after repeated copying for a long period of time or in a special environment of high temperature / high humidity / low temperature / low humidity. Particularly in the case of positively chargeable toner, it is very difficult to uniformly positively charge the components of the toner such as resin, pigment, fluidizing agent, abrasive, lubricant, etc. It is not clear what the material composition involved should be.

[Problems to be Solved by the Invention] An object of the present invention is to provide a positively chargeable developer that solves the above problems.

That is, an object of the present invention is to have a positively chargeable toner having an ideal material structure as a positively chargeable toner and exhibiting stable triboelectric chargeability even after long-term use or under a special environment of high temperature / high humidity / low temperature / low humidity. To provide a developer.

[Means and Actions for Solving the Problems] That is, the present invention relates to 100 parts by weight of a positively chargeable toner containing a styrene-aminoacrylic copolymer containing an aminoacrylic component in an amount of 1 to 15% by weight as a binder resin. And 0.01 to 3 parts by weight of positively charged silicic acid fine powder, and the triboelectric charge amount T _{A of the} positively charged toner is T _A ≧ + 20 μC / g. The triboelectric charge amount of the positively charged toner is suppressed so that 1.2 ≦ T _A / T _B ≦ 3, where T _B is the triboelectric charge amount of the mixture of the conductive toner and the silicic acid fine powder, and T _B
Is 3.7 μC / g or more lower than T _A , and relates to a positively charged developer.

The toner referred to here is an integrated particle obtained by kneading, crushing, classifying, melting, spraying (dispersing) granulating, or polymerizing granulating the raw material, and the fluidizing agent and charge controlling agent after that. It is different from the form of the developer having an external additive that is put into practical use by mixing particles with.

As a result of earnest studies, the inventors of the present invention have found that a positively chargeable developer having a positively chargeable toner containing a styrene-aminoacrylic copolymer as a binder resin is used for a long period of time after copying, or at high temperature / high humidity / low temperature. One of the major causes of fluctuations in the charging ability in a special environment of low humidity is the quantitative change of fine silicic acid powder added to the toner as a fluidity improver or charge control agent; qualitative changes due to moisture absorption and drying. I was confirmed. Further, the inventors of the present invention have examined the configuration relating to the charging between the toner and the silicic acid fine powder. As a result, the toner has a large positive charging ability to some extent, and the positively chargeable silicic acid fine powder rather plays a role of suppressing the charge. It is the responsibility of the developer to confirm that the chargeability is stable as a whole and to satisfy the above-mentioned conditions, as shown in Examples below, as a material composition of the positively chargeable developer. I found it.

In the present invention, a styrene-aminoacrylic copolymer containing 1 to 15% by weight of an aminoacrylic component having excellent positive triboelectric charging characteristics is used as the binder resin. In particular, a binder resin component containing 50% by weight or more of the styrene-aminoacrylic copolymer has a large triboelectric charge amount, and thus is most preferable. As the amino acrylic monomer, conventionally 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 alkyl 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 copolymer, conventional Known monomers can be used, but generally,
It is preferable that the styrene-acrylic copolymer is contained in an amount of 70% by weight or more. 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 acrylic acid methyl.
Examples thereof include esters of ethyl, propyl, butyl, and 2-ethylhexyl, and esters of methacrylic acid and methacrylic acid, methyl, ethyl, propyl, butyl, and 2-hexyl, respectively. The polymerization method of the copolymer is
Although a conventionally known method can be used, a homogeneous system such as bulk polymerization or solution polymerization is particularly preferable.

As the positively chargeable silicic acid fine powder used in the present invention, 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 preferable that the charge of the positively chargeable toner is not disturbed. For example, fine silicic acid powder treated with a coupling treatment with an aminoalkylsilane compound or treated with a silicone oil having an amine in the side chain is preferable, and among them, fine silicic acid powder treated with a silicone oil having an amine in the side chain is preferable. The body is most preferable in terms of environmental stability. As the matrix of the fine silicic acid powder, fine silicic acid powder manufactured by a dry method or a wet method can be used.

The dry method referred to 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, for example, by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound, a fine composite powder of silica and another metal oxide is obtained. It is also possible to obtain and include them.

Examples of commercially available silica fine powder 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) 200 300 380 OX50 TT600 MOX80 MOX170 COK84 Ca-O-SiL M-5 (CABOT Co.) MS-7 MS-75 HS-5 EH-5 Wacker HDK N 20 V15 (WACKER-CHEMIE) GMBH) 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 is various conventionally known methods. Can be applied.
For example, if sodium silicate is decomposed by an acid, it can be expressed 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.

Carplex Shionogi Nepseal Nippon Silica Tokseal, Fineseal Tokuyama Soda Vita Seal Takiki Shilton, Shirnex Mizusawa Kagaku Starsil Kamijima Kagaku Himejiru Ehime Yakuhin Syroid Fuji-Dilson Hi-Sil (High Seal) Pittsburgh Plate Glass.Co. (Pittsburgh Plate Glass) Durosil Ultorasil Ultra seal Fiillstoff-Gesellschaft Marquart Manosil Hardman and Holden Hoesch Chemische Fabrik Hoesch K-G Hemisch Fabrich Hebrich Sil-Stone Stoner Rubber Co. Nalco Nalco Chem.Co. Nalco Chem. Quso Philadelphia Quartz Co. Ladelphia Quartz Santocell Monsanto.Chemical Co. Imsil Illinois Minerals Co. Calcium Silikat Chemische Fabrik Hoesch.K-G Calhem ) Fiillstoff-Gesellschaft Marquart Fortafil Imperial Chemical Industries.Ltd. (Imperial Chemicals, Industries) Microcal Joseph Crosfiels & Sons.Ltd. (Joseph Crossfield & Sons) Manosil Hardman and Holden Vultasil Farbenfabriken Bryer, A.-G. Tufknit Durham Chemicals.Lt d. (Doulham Chemicals) Silmos Shiraishi Kogyo Starlex Kamishima Chemical Phlycosyl Polywood Fertilizer Among the above silica fine powders, the comparison area by nitrogen adsorption measured by BET method is 30m ² / g or more (especially 50-400m ² / g ) Range gives 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 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,
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 the equivalent per amine (g / eq
In iv), the molecular weight is divided by the number of amines per molecule.

The treating amount of the silicone oil having amine in the side chain in the present invention is preferably 0.2 to 70% by weight and 0.0001 to 10% by weight in the developer, based on the total amount of the treated silicic acid fine powder. 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. When the specific surface area of the fine powder is bm ² / g and the amine equivalent of the silicone oil having an amine in the side chain is a, particularly good results are obtained when the relationship of the formula (II) is satisfied.

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, the viscosity of the silicone oil having an amine in the side chain at 25 ° C. is preferably 5000 cPs or less, and particularly preferably 3000 cPs or less. If the viscosity exceeds 5000 cPs, the silicone oil having an amine in the side chain is insufficiently dispersed in the silicic acid fine powder, which tends to cause a defective image 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.

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 is such that the triboelectric charge amount of the positively chargeable toner is reduced by 3.7 μC / g or more and the triboelectric charge amount ratio T _A / T _B satisfies the above condition. Although it may be set, generally 0.01 to 3 parts by weight per 100 parts by weight of the positively chargeable toner exerts an effect, and particularly preferably 0.03 to 1.5 parts by weight has excellent stability. It exhibits positive chargeability.

Further, the positively-charged 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 as the silicic acid fine powder. It is provided by chemically treating with an organic silicon compound that reacts or physically adsorbs.

Examples of such organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane,
Allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, toluorganosilylacrylate, 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.

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-styrene copolymers, styrene-styrene copolymers such as styrene-acrylic copolymers; polyethylene, polyethylene-vinyl acetate copolymers, polyethylene-vinyl alcohol copolymers such as ethylene-based copolymers. Copolymers: phenolic resins, epoxy resins, allyl phthalate resins, polyamide resins, polyester resins, maleic acid resins, etc. In addition, the manufacturing method and the like of each resin is not particularly limited.

As the coloring material used for the positively charged toner, 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 positively chargeable toner.

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

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

FIG. 3 is an explanatory diagram of a triboelectric charge amount measuring device.

In a metal measuring container 12 having a conductive screen 13 of 400 mesh at the bottom (which can be appropriately changed to a size through which magnetic particles do not pass), a toner or a toner constituent fine particle whose triboelectric charge is to be measured, and 200 to Weight ratio of irregular iron powder with particle size between 300 mesh (EFV200 / 300 made by Nippon Iron Powder, the surface is untreated, and at the same time as the toner carrier, there is virtually no triboelectricity)
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 air is sucked from the suction port 17
Adjust 16 to bring the pressure of vacuum gauge 15 to 70 mmHg. Suction is sufficiently performed in this state (for about 1 minute) to remove the toner or the mixture of the toner and fine silica powder 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.

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

Example 1 Styrene-butyl methacrylate-diethylaminoethyl methacrylate copolymer 95 parts (copolymerization ratio 80: 17: 3) Phthalocyanine pigment 5 parts The above materials were kneaded, ground and classified to give a positively charged toner having an average particle size of 7 μm. Obtained. The triboelectric charge amount T _A of the positively chargeable toner is
It was +35.3 μC / g.

On the other hand, silicic acid fine powder synthesized by the dry method (trade name Aerosil ^# 130, specific surface area of about 130 m ₂ / g, manufactured by Aerosil)
While stirring 100 parts of the mixture while maintaining the temperature at about 250 ° C., 20 parts of a silicone oil having a side chain of amine (viscosity 70 cPs at 25 ° C., amine equivalent 830) was sprayed and treated for 10 minutes.

100 parts of the blue positively chargeable toner and 0.8 part of positively chargeable silicic acid fine powder treated with a silicone oil having an amine in the above side chain were externally mixed. The resulting triboelectric charge T _B of the mixture + 22.6MyuC a / g, T _B than T _A 12.7μC / g low, T _A / T _B was 1.6.

6 parts of the mixture of the positively chargeable toner and fine powder of positively chargeable silicate and 100 parts of irregular iron powder having a particle size of 300 to 400 mesh are mixed to obtain a two-component developer to form a negative latent image. The image was put into a NP-5000 copier manufactured by Canon Inc. modified so that it could be formed, and an image was produced. As a result, a clear image without fog was obtained and the image reflection density was 1.41. Further, when the durability of the developer was examined to run 10,000 sheets, a clear image (image density 1.38) without fog similar to the initial stage was obtained. On the other hand, when images were similarly printed in a high temperature and high humidity environment (30 ° C., 90% RH), the image reflection density was 1.28, and an image free from problems such as fog was obtained. In addition, clear and fog-free images were obtained even in low-temperature and low-humidity environments (10 ° C, 10%).

Comparative Example 1 The silicic acid fine powder of Example 1 was added to the positively chargeable toner of Example 1.
When 3.5% was externally added and mixed, T _B of the mixture was 9.3 μC / g and T _A / T _B was 3.8, which did not satisfy the conditions in the present invention.

Using this toner, the same test as in Example 1 was carried out. As the number of copies increased, the image became severely fogged. In addition, under low-temperature and low-humidity environment, the density was thin.

Comparative Example 2 Styrene-butyl acrylate copolymer 95 parts (copolymerization ratio 80:20) Phthalocyanine pigment 5 parts Nigrosine (positive charge control agent) 2 parts Using the above materials, positively charging in the same manner as in Example 1. Toner was obtained. The triboelectric charge amount T _A of the obtained positively chargeable toner was +11 μC / g. Next, 100 parts by weight of the positively chargeable toner and 0.8 part by weight of the positively chargeable silicic acid fine powder prepared in Example 1 were externally added and mixed.

The resulting triboelectric charge T _B of the mixture is + 15 .mu.C / g, T _B
Was 4 μC / g higher than T _A , and T _A / T _B was about 0.73.

Using this mixture, an image development test was conducted in the same manner as in Example 1. As a result, an image reflection density of 1.33 was initially obtained, but when 10,000 sheets were used for durability, an image reflection density of 1.07 was obtained.
Fell to. Further, in the image output test under high temperature and high humidity environment, the image reflection density was 1.16, and under the environment of low temperature and low humidity, fog development occurred in the non-image area.

Example 2 FIG. 1 is another example of the embodiment. In the figure, 1 is an electrostatic image carrier, 2 is a toner carrier, 5 is a one-component developer,
43 is a developing device, 48 is a magnetic roller, 49 is its non-magnetic sleeve, 50 is a magnet, 52 is a magnetic brush, 53 is a one-component developer or a mixture of a developer and magnetic particles. Non-magnetic sleeve 49
The magnetic carrier is magnetically held on the top and made into a brush sleeve
By rotating 49, the toner or the developer 53 is drawn up by the carrier brush and applied on the toner carrier 2 by contact to form a uniform one-component developer layer 5. At that time, the magnetic particles are attracted to the magnetic roller 48 by the magnetic force.
Since it is held above, it does not move onto the toner carrier 2. Next, flight development is carried out from the toner carrier 2 onto the electrostatic image carrier 1. The gap between the magnetic roller 48 and the toner carrier 2 is such that the thickness of the one-component developer layer on the toner carrier 2 is 5 to 100 μm.
Adjust to about m. The gap between the toner carrier 2 and the electrostatic image carrier 1 may be made larger than the thickness of the one-component developer layer, and a developing bias voltage may be applied to the toner carrier 2.

Styrene-dimethylaminoethyl acrylate copolymer
93 parts (copolymerization ratio 99: 1) Rhodamine pigment 7 parts Average particle size 12 using the above materials in the same manner as in Example 1.
A positively chargeable toner having a size of μm was obtained. T _A of positively charged toner is +
It was 22.0 μC / g.

100 parts of this positively chargeable toner was mixed with 1.0 part of the positively chargeable silicic acid fine powder prepared in Example 1. T _B of the mixture is +1
A 8.3μC / g, from T _A 3.7μC / g low, T _A / T _B was 1.2.

Mixture of this positively chargeable toner and positively chargeable silica fine powder
10 parts and 100 parts of the iron powder carrier of Example 1 were mixed, and the gap between the toner carrier 2 and the magnetic roller 48 was set to about 2 mm, and the maximum thickness of the magnetic brush 52 was set to about 3 mm. It is put into the developing device shown in the figure, and the gap between the developing roller and the electrostatic image carrier is kept at 300 μm, and a toner layer of about 80 μm is formed on the developing roller, and the AC waveform has a frequency of 200 Hz and a peak voltage value of ± 450 V. When a DC component of -250 V was added and the peak voltage values of -700 V and +200 V were applied and development was performed with a Canon Copier PC-20, the same good results as in Example 1 were obtained.

Example 3 FIG. 2 is a diagram showing another example of the embodiment. In the figure, 1 is an electrostatic image carrier, 2 is a toner carrier, 3 is a hopper, 6 is a developing bias power source, 5 is a one-component developer, 50 is a fixed magnet, 52 is magnetic particles, and positively charged toner. Is a magnetic brush made of a mixture of a fine powder of positively charged silicic acid (silica externally added toner), and 58 is a blade for controlling toner thickness. The magnetic brush 52 formed on the toner carrier 2 is attached to the toner carrier 2.
Is circulated by rotating, and the silica externally added toner in the hopper 3 is taken in to coat the toner carrier 2 uniformly in a thin layer. Next, the toner carrier 2 and the electrostatic image carrier 1 are made to face each other with a gap larger than the toner layer thickness,
The upper toner 5 is fly-developed onto the electrostatic charge image on the electrostatic holder 1. The thickness of the toner layer is controlled by the size of the magnetic brush 52, that is, the carrier amount and the regulating blade 58. The gap between the electrostatic image carrier 1 and the toner carrier 2 may be set larger than the thickness of the toner layer, and a developing bias may be applied from the bias power source 6.

Here, 20 g of the mixture of the positively chargeable toner of Example 1 and the positively chargeable silicic acid fine powder was previously mixed with 20 g of the iron powder particles, and the mixture had a gap of about 25 between the regulating blade 58 and the toner carrier 2.
It is put in the developing device of FIG. 2 set to be 0 μm,
Keep the gap between the developing roller and the electrostatic image carrier at 300 μm,
A toner layer of about 80 μm is formed on the developing roller, and an AC waveform with a frequency of 200 Hz and a peak value of voltage ± 450 V is applied to the DC component.
When 250 V was applied and the peak voltage values of -700 V and +200 V were applied for development, good results were obtained.

Comparative Example 3 Styrene-butyl methacrylate copolymer 96 parts (copolymerization ratio 85:15) Nigrosine dye 2 parts Carbon black 4 parts Using the above materials, the average particle size was 10 μm in the same manner as in the example.
To obtain a positively chargeable toner. T _A of positively charged toner is +17.5
It was μC / g. 0.4 parts of negatively charged silicic acid fine powder with a specific surface area of about 90 m ² / g synthesized by the wet method on 100 parts of positively charged toner
When the parts were externally mixed, T _B of the mixture was +12.1 μC / g, and T _A / T _B was 1.4. Using this mixture, an image-forming test was conducted in the same manner as in Example 3. When a few tens of sheets were copied, the image was extremely thin, and this tendency was remarkable when the image was formed in a high-temperature and high-humidity environment. It was

[Advantages of the Invention] By using the positively chargeable toner and the positively chargeable silicic acid fine powder based on the material structure of the present invention, the charge of the developer is lowered and the image is deteriorated even after repeated copying for a long time. It became possible to always provide good images. Further, since the toner exhibits a stable charging ability even under a special environment of high temperature and high humidity and low temperature and low humidity, a stable image can be displayed against various environmental changes.

[Brief description of drawings]

1 and 2 are cross-sectional views showing different forms of the developing device used in the embodiment of the developing method according to the present invention. FIG. 3 is an explanatory diagram of a triboelectric charge amount measuring device according to the present invention. 1 ... Electrostatic image holder, 2 ... Toner carrier 3 ... Hopper 5 ... Toner or one-component developer 6 ... Development bias power supply, 11 ... Suction device 12 ... Measuring container, 13 ... Conductivity Screen 14 …… Metal lid, 15 …… Vacuum gauge 16 …… Air flow control valve, 17 …… Suction port 18 …… Condenser, 19 …… Electrometer 48 …… Magnetic roller, 49 …… Non-magnetic sleeve 50 ...... Permanent magnet, 52 ...... Magnetic brush 53 ...... Two-component developer in which toner or magnetic particles are mixed 58 ...... Regulator blade

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Claims (1)

[Claims] 1. A positively chargeable toner containing 100 parts by weight of a styrene-aminoacrylic copolymer containing 1 to 15% by weight of an aminoacrylic component as a binder resin, and 0.01 to 3 fine powder of positively charged silicic acid. And a triboelectric charge amount T _{A of the} positively chargeable toner is T _A ≧ + 20 μC / g, and a mixture of the positively chargeable toner and the fine silica powder is contained. When the triboelectric charge amount is T _B , the positively charged triboelectric charge amount is suppressed so that 1.2 ≦ T _A / T _B ≦ 3, and T _B
Is 3.7 μC / g or more lower than T _A , a positively charged developer.