JPH0764349A - One component magnetic developing and image forming method - Google Patents

Abstract

PURPOSE:To provide an one component magnetic developer capable of forming an image with high resolution and high precision reproducibility. CONSTITUTION:The one component magnet developer is obtained by adding a hydrophobic silicic acid fine powder into toner particles containing at least a binding resin, a magnetic powder and a black titanium oxide and is 4-10mum weight average particle diameter, contains 5-60 pts.wt. magnetic material and 0.2-20 pts.wt. black titanium oxide per 100 pts.wt. binding resin and is 100>=¦Qd¦>= 40muc/g in the absolute value ¦Qd¦ of two component tribo of the magnetic developer per that of iron powder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating magnetic developer used in electrophotography, electrostatic recording and the like, and an image forming method using the developer.

[0002]

2. Description of the Related Art Conventionally, a number of electrophotographic methods are known, but generally, a photoconductive material is used to form an electric latent image on a photoconductor by various means, and then the electrophotographic image is formed. The latent image is developed with a developer to make it a visible image, and if necessary, the developer image is transferred to a transfer material such as paper, and then the developer image is fixed on the transfer material by heat or pressure to make a copy. You get what you get.

In recent years, in addition to conventional copying machines, there have been many printers, facsimile machines, and the like using electrophotographic methods. Particularly in printers and facsimiles, a developing device using a one-component developer is often used because it is necessary to reduce the size of the copying device.

Unlike the two-component developing system, the one-component developing system does not use carrier particles such as glass beads or iron powder, so that the developing device itself can be made compact and lightweight.

Further, in the two-component developing system, since it is necessary to keep the toner concentration in the carrier constant, a device for detecting the toner concentration and supplying a required amount of toner is required. Therefore, also in this case, the developing device becomes large and heavy. Such a device is not necessary in the one-component developing system, and it is preferable because it can be made small and light. The one-component developer used in such a one-component developing system contains a relatively large amount of magnetic material in the toner.

Further, in the copying machine, there is always a demand for higher speed and stabilization. Especially for medium to high speed machines, the two-component developing method is the mainstream. This is because the stability of the copied image with respect to long-term use at high speed becomes more important than the problem of the size and weight of the developing device in such a large machine. Generally, the two-component developing type toner is colored with carbon black or the like, and the other components are mostly composed of a binder resin.

Therefore, the toner particles are light and have no force to adhere to the carrier particles other than the electrostatic force, so that the toner is scattered especially at high-speed development, and the optical lens, the original glass, the transport section, etc. are used for a long period of time. It may stain and impair the stability of the copied image. Therefore, a developer has been put into practical use in which the magnetic substance is contained in the toner to make the toner heavy and to adhere to the magnetic carrier particles not only by the electrostatic force but also by the magnetic force to prevent toner scattering. As described above, the toner containing the magnetic material is becoming more and more important.

Further, as for printer devices, LED and LBP printers have become the mainstream of the market these days, and the direction of technology is higher resolution, that is, 400, 600, 800 dpi instead of 240, 300 dpi in the past. There is. Therefore, the development method is required to have higher definition. Further, the functions of copiers are also becoming more sophisticated, and as a result, they are moving toward digitalization. In this direction, the method of forming an electrostatic charge image with a laser is the main method, so it is also advancing toward high resolution, and here too, as with printers, high resolution and high definition development methods are required. Japanese Patent Laid-Open No. 1-112253,
JP-A-2-284158 proposes a toner having a small particle size.

A magnetic developer in which black titanium oxide is externally added to the surface is proposed in JP-A-60-142354, but the resistance is too low, which is not preferable.

In addition, in recent years, from the viewpoint of environmental protection, the primary charging and transfer process using a charging roller is becoming the mainstream from the conventionally used primary charging and transfer process using corona discharge.

Specifically, a voltage is applied to a conductive roller, which is a charging member, and the roller is brought into contact with a photosensitive member, which is a member to be charged, to charge the surface of the photosensitive member to a predetermined potential. For example, in Japanese Examined Patent Publication No. 50-13661, a roller having a core metal coated with a dielectric made of nylon or polyurethane rubber enables application of a low voltage when the photosensitive paper is charged.

Further, in Japanese Patent Laid-Open No. 59-46664, an electrostatic charge image carrier that runs in an endless shape such as a rotating cylinder or an endless belt is used, and a transfer device to which a bias is applied is pressed against this. It has already been proposed to transfer the developer image on the side of the electrostatic image holder onto the transfer material by passing the transfer material between them.

However, in such a transfer method which does not use corona discharge, the transfer member is brought into contact with the photoconductor through the transfer material such as paper at the time of transfer, so that the developer image formed on the photoconductor is formed. When a toner image is transferred to a transfer material, a developer image is pressed against the transfer material, which causes a partial transfer failure, which is a problem of so-called void in transfer.

Further, in the charging method using the primary charging roller, a slight amount of the developer, which has passed through the cleaner, adheres to the charging roller and is pressed against the photoconductor, so that the fusion of the developer to the photoconductor is likely to occur. .

These problems are problems that must be solved in order to obtain the above-mentioned high resolution and high definition images.

[0016]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, the object of the present invention is to achieve high resolution and high definition reproducibility that is true to the original, true to the signal, that is, true to the latent image. To provide a magnetic developer and an image forming method, and to provide a magnetic developer and an image forming method in which there is no phenomenon of dropout during transfer even in a copying process which does not use corona charging, or these phenomena are suppressed. It is to provide a magnetic developer and an image forming method in which fusion of the developer to the photoconductor does not occur even when a large number of images are printed.

[0017]

Means and Actions for Solving the Problems The above-mentioned object is to provide a one-component magnetic developer obtained by adding fine particles of hydrophobic silicic acid to toner particles containing at least a binder resin, magnetic powder and black titanium oxide. The particle size is 4 to 10 μm, the amount of magnetic material is 5 to 60 parts by weight with respect to 100 parts by weight of the binder resin, and the amount of black titanium oxide is 0.2 to 20 parts by weight. When the value is | Qd |, 10
It has been found to be achieved by a one-component magnetic developer with 0 ≧ | Qd | ≧ 40 μc / g.

Further, in the image forming method in which the photosensitive member and the developer carrying member carrying the developer layer are opposed to each other for development,
While using the above developer as the developer, the developer carrier is coated with a resin layer containing conductive fine particles,
The absolute value of tribo by the suction method on the developer carrier is | Qm
When |, it is preferable that 15 ≧ | Qd | / | Qm | ≧ 2.5, and more preferably 14 ≧ | Qd | / | Qm | ≧ 3.5.

The method of measuring Qd and Qm in the present invention is shown in FIG.
This will be described with reference to the triboelectric charge amount measuring device.

Regarding the measurement of Qd, first, EFV200 / 300 (manufactured by Powder Tech Co., Ltd.) was used as a carrier, and a mixture of 9.5 g of carrier and 0.5 g of developer was placed in a polyethylene bottle having a capacity of 50 to 100 ml. 5
Shake by hand 0 times.

Then, in an environment of 23 ° C./60% relative humidity, 1.0 to 1.2 g of the above mixture was placed in a metal measuring container 22 having a 500 mesh screen 23 at the bottom,
Cover the lid 24 made of metal. At this time, the total weight of the measurement container 22 is weighed and designated as W1 (g). Next, in the suction device 21 (at least the portion in contact with the measurement container 22 is an insulator), suction is performed from the suction port 27, and the air volume control valve 26 is adjusted to set the pressure of the vacuum gauge 25 to 250 mmAq.

In this state, suction is performed for 1 minute to remove the developer by suction. The potential of the electrometer 29 at this time is V (volt). Here, 28 is a capacitor, and the capacitance is C (μF). The weight of the entire measurement container 22 after suction is weighed and is W2 (g). The triboelectric charge amount Qd (μc / g) of this developer is calculated by the following equation.

Qd = CV / (W1-W2) For the measurement of Qm, a measuring container having a cylindrical filter paper instead of the 500 mesh screen was used, and the metal lid 2 was used.
In place of 4, a metal suction port conforming to the shape of the surface of the developer carrier is attached, and the suction pressure is adjusted so that the developer layer on the surface of the developer carrier can be uniformly sucked without excess or deficiency. Aspirate. The developer weight sucked at this time is M (g), and is calculated by Qm = CV / M.

In the magnetic developer according to the present invention, the weight average particle diameter is 4 to 10 μm (preferably 4.5 to 9 μm), and the amount of magnetic material is 5 to 60 parts by weight per 100 parts by weight of the binder resin ( 15 to 45 parts by weight), black titanium oxide is 0.2 to 20 parts by weight (preferably 2 to 10 parts by weight), and Qd and Qm are 100 ≧ | Qd | ≧ 40 μc / g, 15 ≧ | Qd | / | Qm | ≧ 2.5 (preferably 14 ≧
The reason why high resolution and high definition are achieved by the magnetic developer having | Qd | / | Qm | ≧ 3.5) and the image forming method using the same, and the reason why it is effective against dropout in transfer Although not clear, in the present invention, an electrostatic latent image of the developer particles by an appropriate electrostatic cohesive force of the developer particles on the developer carrier and an appropriate adhesion force to the developer carrier. Faithful movement to the transfer material / magnetic developer / photoreceptor at the transfer site where the transfer material / magnetic developer / photoreceptor is electrostatically balanced. It seems to be due to things.

In the present invention, | Qd | is 100 μc / g
If it exceeds, the image density tends to be low in copying / printing, and | Qd | is less than 40 μc / g, | Qd |
/ | Qm | exceeds 15 or less than 2.5, the above
Since the relationship of No. 1 is broken, the development rate is lowered, and moreover, voids in transfer tend to occur.

Further, the above-mentioned effects obtained by using the magnetic developer of the present invention are as follows: a photosensitive member having a radius of curvature of 50 mm or less, a developer carrier having a radius of curvature of 20 mm or less, and a radius of curvature of 30 mm.
Particularly excellent performance is obtained in combination with the following transfer member. It is considered that this is due to the fact that the narrowing of both the development area and the transfer area increases the influence of the physical properties of the developer on the development and transfer.

When the amount of black titanium oxide contained in the magnetic developer of the present invention is less than 0.2 parts by weight with respect to 100 parts by weight of the binder resin, the developer melts onto the photosensitive member by continuous image formation on many sheets. Easy to wear.

This is because the toner according to the present invention having a small particle size and a small amount of magnetic material has a small polishing power for the photoconductor, and the polishing power is supplemented by black titanium oxide.

If the amount of black titanium oxide exceeds 20 parts by weight, | Qd | ≧ 40 μc / g cannot be maintained, and the voids in transfer are exacerbated.

Such black titanium oxide is obtained by reducing titanium dioxide which is a white pigment, and preferably has a Ti element content of 60 wt% or more and a specific resistance of 10 ⁷ Ω · cm or less.

The average particle size of the primary particles obtained from a transmission electron micrograph is preferably 0.03 to 0.2 μm in terms of dispersion in the developer.

When the amount of the magnetic material contained in the developer of the present invention is less than 5 parts by weight with respect to 100 parts by weight of the binder resin, the transportability is insufficient and unevenness occurs in the developer layer on the developer carrying member. It becomes uneven. Further, when the amount exceeds 60 parts by weight, voids in transfer are likely to occur.

Further, the weight average particle diameter of the developer of the present invention is 4
If it is less than μm, the agglomeration of the developer is remarkable and a problem occurs in handling. In addition, 100μ when exceeding 10μm
Reproduction of dot latent image or fine line of m or less is not sufficient.

The surface roughness of the developer carrier used in the present invention is 0.2 to 1.5 in terms of JIS center line average roughness (Ra).
It is preferably in the range of μm. When Ra is less than 0.2 μm, the charge amount Qm on the developer carrying member becomes high, and 15 ≧
| Qd | / | Qm | ≧ 2.5 cannot be satisfied, and the developability becomes insufficient. When Ra exceeds 1.5 μm, unevenness occurs in the developer coating layer on the developer carrying member, resulting in uneven density on the image.

As the conductive fine particles contained in the resin layer coating the surface of the developer carrier, carbon black, graphite, conductive metal oxides such as conductive zinc oxide and metal complex oxides are used alone or in combination. The above is preferably used. Further, as the resin in which the conductive fine particles are dispersed, a phenol resin, an epoxy resin, a polyamide resin, a polyester resin, a polycarbonate resin,
Known resins such as polyolefin resins, silicone resins, fluorine resins, styrene resins, and acrylic resins are used. A thermosetting resin is particularly preferable.

The developer of the present invention is preferably regulated by a member which is in contact with the developer carrier via the developer on the developer carrier, from the viewpoint of uniformly charging the developer.

The type of the binder resin used in the present invention is, for example, a homopolymer of styrene such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene and the like, or a substitution product thereof; styrene-p-chlorostyrene copolymerization. Coal, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene- Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrene-based copolymers such as indene copolymers Combined; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin , Polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin and the like can be used.

A crosslinked styrene copolymer is also a preferable binder resin.

Examples of the comonomer for the styrene monomer of the styrene type copolymer include acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate,
Didecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc. A monocarboxylic acid having a heavy bond or a substituted product thereof;
For example, a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate and the like, and its substitution products; for example, vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate and the like;
Ethylenic olefins such as ethylene, propylene, butylene, etc .; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, etc .; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, etc .; These vinyl monomers are used alone or in combination of two or more.

As the cross-linking agent, a compound having two or more polymerizable double bonds is mainly used. For example, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, etc .; for example, ethylene glycol diacrylate, Ethylene glycol dimethacrylate,
A carboxylic acid ester having two double bonds such as 1,3-butanediol dimethacrylate; a divinyl compound such as divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone; and a compound having three or more vinyl groups; Are used alone or as a mixture.

A colorant may be used in the toner according to the present invention if necessary.

As the colorant used in the present invention, carbon black, lamp black, iron black, ultramarine blue, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa yellow G, rhodamine 6
Conventionally known dyes and pigments such as G, chalco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triarylmethane dyes, monoazo dyes and disazo dyes may be used alone or in combination.

As the magnetic fine particles contained in the magnetic toner according to the present invention, a substance which is magnetized by being placed in a magnetic field is used. Powders of ferromagnetic metals such as iron, cobalt and nickel, or magnetite, γ Alloys and compounds such as —Fe ₂ O ₃ and ferrite can be used. The saturation magnetization σs of the magnetic substance is 20 to 100 emu / under 1 K oersted.
g, particularly 30 to 70 emu / g is preferable.

These magnetic fine particles are preferably magnetic powders having a BET specific surface area of 1 to ²⁰ m ² / g, particularly 2.5 to 12 m ² / g, and a Mohs hardness of 5 to 7 according to the nitrogen adsorption method.

In the developer of the present invention, it is preferable to use a charge control agent in the developer particles (internal addition) or to mix with the developer particles (external addition). The charge control agent makes it possible to optimally control the charge amount according to the developing system, and particularly in the present invention, it is possible to further stabilize the balance between the particle size distribution and the charge.

The following substances control the toner to be negatively charged.

Organic metal complexes and chelate compounds are effective, for example, monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Other examples include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol.

There are the following substances for controlling the toner to be positively charged.

For example, modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonic acid, tetrabutylammonium tetrafluoroborate, and phosphonium salts which are analogs thereof. Onium salts such as and lake pigments thereof, triphenylmethane dyes and lake pigments thereof, (as a laker, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid,
Ferricyanide, ferrocyanide, etc.) Metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; diorganotin borates such as dibutyltin borate, dioctyltin borate, dicyclohexyltin borate; These can be used alone or in combination of two or more. Among these,
Charge control agents such as nigrosine, quaternary ammonium salts and triphenylmethane pigments are particularly preferably used.

In addition, the general formula

[0051]

[Chemical 1]

Monomer of monomer represented by: A copolymer with a polymerizable monomer such as styrene, acrylic acid ester and methacrylic acid ester described above can be used as a positive charge control agent. In this case, these charge control agents also function as (all or part of) the binder resin.

The above charge control agent (which does not act as a binder resin) is preferably used in the form of fine particles. In this case, the number average particle size of this charge control agent is
Specifically, it is preferably 4 μm or less (further, 3 μm or less).

When internally added to the toner, such a charge control agent is preferably used in an amount of 0.1 to 20 parts by weight (more preferably 0.2 to 10 parts by weight) with respect to 100 parts by weight of the binder resin.

The developer of the present invention is used by adding a hydrophobized silicic acid fine powder, and the silicic acid fine powder is a so-called dry method produced by vapor phase oxidation of a silicon halogen compound. Both dry silica called fumed silica and so-called wet silica produced from water glass and the like can be used, but there are few silanol groups on the surface and inside the silica fine powder, and Na ₂ O, SO ₃
Dry silica having no production residue such as ^2- is preferable.

In the case of dry silica, it is possible to obtain a composite fine powder of silica and another metal oxide by using another metal halogen compound such as aluminum chloride or titanium chloride together with a silicon halogen compound in the manufacturing process. And includes them. The average particle size of the particles is preferably in the range of 0.001 to 2 μm, particularly preferably 0.002 to 2 μm.
It is preferable to use fine silica powder in the range of 0.2 μm. For the hydrophobizing treatment, conventionally known silane coupling agents, silicone oil and other hydrophobizing agents and methods are used.

The developer of the present invention may contain other additives, such as fixing aids (eg low molecular weight polyethylene), or metals such as tin oxide as a conductivity-imparting agent, as long as they have no substantial adverse effect. You may add an oxide etc.

The weight average particle diameter (D ₄ ) of the toner can be measured by various methods, but in the present invention, it was measured using a Coulter counter.

That is, a Coulter Counter TA-II type (manufactured by Coulter) is used as a measuring device, an interface (manufactured by Nikkaki) for outputting number distribution and volume distribution, and a PC-9801 personal computer (NE).
(Made by C) is connected, and a 1% NaCl aqueous solution is prepared by using primary sodium chloride as an electrolytic solution. As a measuring method, a surfactant, preferably an alkylbenzene sulfonate, as a dispersant was added to 100 to 150 ml of the electrolytic aqueous solution in an amount of 0.
Add 1 to 5 ml, and further add 2 to 20 mg of the measurement sample (about 30,000 to about 300,000 particles). The electrolytic solution in which the sample is suspended is dispersed by an ultrasonic disperser for about 1 to 3 minutes,
The Coulter Counter TA-II type was used to measure the particle size distribution of particles of 2 to 40 μm with a 100 μm aperture as an aperture,
The volume distribution and number distribution of 40 μm particles were calculated, and the weight-based weight average diameter (D ₄ ) obtained from the volume distribution (the median value of each channel was used as the representative value of the channels) was calculated.

In producing the toner according to the present invention,
Obtained by mechanically crushing and classifying the constituent materials after kneading the constituent materials well with a heat kneader such as a heat roll, kneader, or extruder, or by dispersing the material in a binder resin solution and then spray drying. Each method can be applied, such as a method, or a polymerization method in which a predetermined material is mixed with a monomer that constitutes a binder resin to form an emulsion suspension, and the mixture is polymerized to obtain a toner.

[0061]

EXAMPLES The present invention will be specifically described below with reference to production examples and examples, but this does not limit the present invention in any way.

All parts in the following formulations are parts by weight.

Production Example 1 Styrene-n-butyl acrylate copolymer 100 parts (copolymerization weight ratio 8: 2, Mw = 260,000) magnetic iron oxide 30 parts (BET value 6.5 m ² / g, σs = 65. 6 emu / g) Negative charge control agent (monoazo dye type iron complex) 2 parts Low molecular weight polypropylene (Mw = 6000) 3 parts Black titanium oxide (specific resistance 10 ⁴ Ω · cm, Ti content 66 wt%) 5 parts

The above mixture was melt-kneaded with a twin-screw extruder heated to 140 ° C., the kneaded product was cooled, coarsely pulverized with a hammer mill, and the coarsely pulverized product was finely pulverized with a jet mill. The ground material was subjected to air classification to obtain a negatively chargeable magnetic toner (I) having a weight average particle diameter (D ₄ ) of 7.0 μm.

Production Example 2 Styrene-2 ethylhexyl acrylate 100 parts-Maleic acid n-butyl half ester copolymer (copolymerization weight ratio 7: 2: 1, Mw = 220,000) Magnetic iron oxide 40 parts (BET value 6. 5 m ^{2 /} g, σs = 65.6 emu / g) Negative charge control agent (monoazo dye-based chromium complex) 0.5 part Low molecular weight polypropylene (Mw = 6000) 3 parts Black titanium oxide (specific resistance 10 ⁴ Ω · cm, Ti content 62 wt%) 5 parts

The above components were used in the same manner as in Production Example 1 to prepare a negatively chargeable magnetic toner (I) having a weight average particle diameter (D ₄ ) of 5.5 μm.
I) was obtained.

Production Example 3 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5, Mw = 290,000) Magnetic iron oxide 15 parts (BET value 5.5 m ² / g, σs = 98. 5 emu / g) Negative charge control agent (monoazo dye type iron complex) 1 part Low molecular weight polypropylene (Mw = 6000) 6 parts Carbon black 5 parts Black titanium oxide (specific resistance 10 ⁴ Ω · cm, Ti content 66 wt%) 10 parts Using the same components as in Production Example 1, a negatively chargeable magnetic toner (III) having a weight average particle diameter (D ₄ ) of 7.5 μm was obtained.

Production Example 4 Styrene-n-butyl acrylate copolymer 100 parts (copolymerization weight ratio 7.5: 2.5, Mw = 290,000) Magnetic iron oxide 50 parts (BET value 6.5 m ² / g, σs = 65.6 emu / g) Positive charge control agent (triphenylmethane lake pigment) 2 parts Aluminum stearate compound 1 part Black titanium oxide (specific resistance 10 ⁴ Ω · cm, Ti content 66 wt%) 5 parts Low molecular weight polypropylene (Mw) = 6000) 3 parts In the same manner as in Production Example 1, a positively chargeable magnetic toner (IV) having a weight average particle diameter (D ₄ ) of 8.5 μm was obtained.

Production Example 5 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5, Mw = 290,000) Magnetic iron oxide 65 parts (BET value 6.5 m ² / g, σs = 65. 6 emu / g) Negative charge control agent (monoazo iron complex) 0.5 part Low molecular weight polypropylene (Mw = 6000) 3 parts

The above components were used in the same manner as in Production Example 1 to prepare a negatively chargeable magnetic toner (V) having a weight average particle diameter (D ₄ ) of 7.5 μm.
Got

Production Example 6 Styrene-n-butyl acrylate 100 parts (copolymerization weight ratio 7.5: 2.5, Mw = 290,000) Magnetic iron oxide 65 parts (BET value 6.5 m ² / g, σs = 65. 6 emu / g) Negative charge control agent (monoazo iron complex) 0.5 part Low molecular weight polypropylene (Mw = 6000) 3 parts

The above components were used in the same manner as in Production Example 1 to prepare a negatively chargeable magnetic toner (V) having a weight average particle diameter (D ₄ ) of 12.0 μm.
I) was obtained.

Example 1 Negatively Chargeable Magnetic Toner (I) of Production Example 1 100 parts Hydrophobic silica fine powder 0.7 parts (hexamethyldisilazane treated BET value 200 m ² / g) The above mixture was mixed with a Henschel mixer. And mixed as a developer.

Further, as a developer carrying member, the layer thickness of the following constitution is about 7 μm, and the JIS center line average roughness (Ra) is 0.8 μm.
A resin sleeve was formed on an aluminum cylinder having a mirror surface and a diameter of 16φ to prepare a developing sleeve.

Phenolic resin 100 parts Graphite (particle size about 7 μm) 90 parts Carbon black 10 parts

An image forming apparatus (laser jet IIISi manufactured by Hewlett-Packard Co.) having a charging member in contact with a commercially available photoreceptor, a transfer member, and a developer regulating member in contact with a developer carrier, using the developer. In the image forming apparatus in which the developing sleeve of the developing device of No. 2 was replaced with the developing sleeve, 8000 sheets of continuous images were output in an environment of 23 ° C. and 65% RH. As a result, a good image as shown in FIG. 1 (a) was obtained in which there were no voids in the transfer and there was no scattering on the image. Even after 8000 sheets, white spots on a solid black image due to toner fusion on the photoconductor were not seen. Also, the resolution of a 1-dot latent image of 80 μm was sufficient. At this time, | Qd | = 55.3 μc / g, | Qd
| / | Qm | = 3.5.

Example 2 Negatively Chargeable Magnetic Toner (II) of Manufacturing Example 100 100 Parts Hydrophobic Silica Fine Powder 1.5 Parts (Polydimethylsiloxane-treated BET Value 250 m ² / g)

The above mixture was mixed with a Henschel mixer to obtain a developer. When an image was formed in the same manner as in Example 1 by using the developer, a good image without voids in the transfer and scattering of the developer was obtained. Even after 8000 sheets, white spots on a solid black image due to toner fusion on the photoconductor were not seen. Also, the resolution of a 1-dot latent image of 80 μm was sufficient. At this time, | Qd | = 70.9 μc / g,
| Qd | / | Qm | = 4.6.

Example 3 Negatively Chargeable Magnetic Toner (III) of Production Example 100 100 parts Hydrophobic silica fine powder 1.3 parts (Hexamethyldisilazane treated BET value 250 m ² / g)

The above mixture was mixed with a Henschel mixer to prepare a developer. When an image was formed in the same manner as in Example 1 by using the developer, a good image without voids in the transfer and scattering of the developer was obtained. Even after 8000 sheets, white spots on a solid black image due to toner fusion on the photoconductor were not seen. Further, the resolution of a 1-dot latent image of 80 μm was sufficient, although some scattering was seen around the dots. At this time, | Qd | = 80.4 μc / g, | Qd |
/|Qm|=7.4.

Example 4 Positively chargeable magnetic toner (IV) of Production Example 100 100 parts Hydrophobic silica fine powder 0.7 parts (amino-modified silicone oil treated BET value 200 m ² / g)

The above mixture was mixed with a Henschel mixer to obtain a developer. An image forming apparatus (FC33 manufactured by Canon Inc.) having a charging member in contact with a photoreceptor, a transfer member, and a toner regulating member in contact with a toner carrier is formed by using the developer.
At 0), continuous image output was performed on 8,000 sheets while replenishing the toner under the environment of 23 ° C. and 65% RH. As a result, a slight void in the transfer was recognized, but it was at a level where there was no practical problem. Even after 8000 sheets, black spots on a solid white image due to toner fusion on the photoconductor were not seen. Also, a good image without scattering was obtained. At this time, | Qd | = 53.5 μc / g, | Qd | /
| Qm | = 3.9.

Comparative Example 1 Negatively Chargeable Magnetic Toner (V) of Production Example 100 100 Parts Hydrophobic Silica Fine Powder 0.6 Parts (Hexamethyldisilazane Treated BET Value 200 m ² / g)

The above mixture was mixed with a Henschel mixer to obtain a developer. Image forming apparatus using the developer (laser jet IIISi manufactured by Hewlett Packard)
At 23 ° C. and 65% RH, continuous printing of 8,000 sheets was performed. As a result, a void in the transfer occurred as shown in FIG. Also, many white spots were found on the solid black image after 8000 sheets. Scattering was recognized in the development of a 1-dot latent image of 80 μm. At this time | Qd
| = 33.5 μc / g and | Qd | / | Qm | = 2.4.

Comparative Example 2 Negatively Chargeable Magnetic Toner (VI) of Production Example 100 100 parts Hydrophobic silica fine powder 0.4 parts (Hexamethyldisilazane treated BET value 200 m ² / g)

The above mixture was mixed with a Henschel mixer to obtain a developer. Image formation was performed in the same manner as in Example 1 using the developer. As a result, a void in the transfer occurred as shown in FIG. Also, many white spots were found on the solid black image after 8000 sheets. Further, in the development of a 1-dot latent image of 80 μm, the image was scattered without being resolved, and was not a dot. At this time | Qd |
= 13.5 μc / g and | Qd | / | Qm | = 2.2.

[0087]

As described above, according to the magnetic developer of the present invention, it is possible to obtain a high-quality image with high resolution and high-definition reproducibility, which is free from voids in transfer and scattering.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an image state.

FIG. 2 is an explanatory diagram of a triboelectric charge amount measuring device.

[Explanation of symbols]

 21 Suction Machine 22 Measuring Container 23 Screen 24 Lid 25 Vacuum Gauge 26 Air Volume Control Valve 27 Suction Port 28 Condenser 29 Electrometer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G03G 13/09 G03G 9/08 368 375

Claims (4)

[Claims] 1. A one-component magnetic developer comprising a toner particle containing at least a binder resin, magnetic powder and black titanium oxide, and a hydrophobic silica fine powder added thereto.
10 μm, the amount of magnetic material is 5 to 100 parts by weight of the binder resin.
60 parts by weight, the amount of black titanium oxide is 0.2 to 20 parts by weight, and when the absolute value of the two-component tribo with respect to the iron powder of the magnetic developer is | Qd |, 100 ≧ | Qd | ≧ 40 μc / g A one-component magnetic developer characterized in that 2. An image forming method in which a photoreceptor and a developer carrying member carrying a developer layer are opposed to each other for development, and the one-component magnetic developer according to claim 1 is used as the developer.
Further, when the developer carrier is covered with a resin layer containing conductive fine particles, and the absolute value of tribo by the suction method on the developer carrier is | Qm |, 15 ≧ | Qd | / | An image forming method, wherein Qm | ≧ 2.5. 3. The image forming apparatus according to claim 2, wherein a member for regulating the developer on the developer carrier is in contact with the developer carrier via the developer. Method. 4. A transfer member is brought into contact with the photosensitive member via a transfer material during transfer.
Or the image forming method according to item 3.