JPH0612462B2 - Insulating magnetic dry developer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an insulating magnetic dry developer for developing a latent image in electrophotography, electrostatic recording, electrostatic printing and the like. More specifically, in a developer for a direct or indirect electrophotographic developing method, a toner that is uniformly strongly and negatively charged, a negatively chargeable hydrophobic silica, and an insulating magnetic dry type having at least specific cerium oxide particles Regarding the developer.

BACKGROUND ART Conventionally, US Pat. No. 2,297,6 has been used for electrophotography.
91, JP-B-42-23910 (US Pat. No. 3,666,363), JP-B-43-24.
7448 (US Pat. No. 4,071,361)
As described in, etc., the photoconductive layer is uniformly charged, and a photoimage is exposed according to the original to eliminate the charge in the exposed portion to form a latent image. Development is performed by adhering a fine powder electrophotographic substance, so-called toner, on the obtained electrostatic latent image. The toner is attracted to the electrostatic latent image according to the magnitude of the amount of charge on the photoconductive layer to form a toner image having a shade. If necessary, this toner image is transferred onto a supporting surface such as paper or cloth, and is permanently fixed on the supporting surface by heating, pressing, a heating / pressing roller or the like. If it is desired to omit the toner image transfer step, the toner image can be fixed on the photoconductor layer. In addition to the fixing method described above, it is possible to use other means such as a solvent treatment or a top coating treatment.

A large number of developing methods in electrophotography are known, and are developing methods in which carrier particles and toner are mixed and used as a two-component developing agent, such as the cascade developing method described in US Pat. No. 2,618,552 and US Pat. The magnetic brush method described in the specification of 2,874,063 has been widely used. All of these methods are excellent methods in which a good image can be obtained relatively stably, but on the other hand, they have the common problems associated with two-component developers, such as carrier deterioration and fluctuations in the mixing ratio of toner and carrier. In order to avoid such a problem, various developing methods using a one-component developer containing no carrier rather than toner have been proposed. Among them, as a method of using a developer composed of magnetic toner particles, for example, US Pat. No. 3,909,258 proposes a method of developing using a magnetic toner having electrical conductivity. Has been done. In this, a conductive magnetic developer is supported on a cylindrical conductive toner carrier (sleeve) having magnetism inside, and is brought into contact with an electrostatic image for development.
At this time, a conductive path is formed between the surface of the recording body and the surface of the sleeve by the toner particles in the developing device, and the electric charges are introduced from the sleeve to the toner particles through the conductive path, and the coulomb between the image portion of the electrostatic image and The toner particles adhere to the image area by the force and are developed. This developing method using the conductive magnetic toner is an excellent method that avoids the problems associated with the conventional two-component developing method, but on the other hand, since the toner is conductive, the developed image is transferred from the recording medium to the final paper such as plain paper. However, there is a problem in that it is difficult to electrostatically transfer to a general support member.

Therefore, a method of developing a magnetic toner capable of electrostatic transfer having a high electric resistance of 10 Ωcm or more or an electric insulation property has been proposed. For example, U.S. Pat. No. 4,336,318 proposes a method of developing using a magnetic toner having an electrically insulating property. Also, British Patent 1,50
Japanese Patent No. 3,560 proposes a method of developing an electrostatic latent image with toner having a magnetic material exposed. In a developing method using an insulating magnetic developer containing no carrier particles, triboelectric charges are imparted to the toner particles by friction between the toner particles and the toner carrier (that is, the developing sleeve) and / or friction between the toner particles. ing. When the carrier-containing two-component developer is used, the toner particles can obtain sufficient triboelectric charge by frictional contact with the carrier which is remarkably large in quantity and stirring action by the carrier. Since it is difficult to obtain a triboelectric charge with a one-component developer as much as with a two-component developer, a charge control agent is usually contained in the toner particles.

Also, these one-component developers tend to agglomerate in the developing device because there are no carrier particles that also play the role of agitating the toner unlike two-component developers. It is added as an external additive. When the fluidizing agent is fine particles of silicon oxide, since the fine particles of silicon oxide themselves have negative chargeability, they can be an auxiliary agent for holding good negative charge to negatively charge toner. However, since the toner has a negative charge and the silicon oxide fine particles also have the same negative charge, electrostatic repulsion works, and it is difficult to impart the silicon oxide fine particles to the toner well. Therefore, especially in a copying machine. The low image density and the remarkable falling development of the image density were developed in the initial stage of the movement.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an insulating magnetic developer which eliminates the fall development of the image density which the conventional one-component developer containing a negatively chargeable insulating magnetic toner has.

A further object of the present invention is to provide an insulating magnetic developer capable of forming a copied image with high image density.

Further, an object of the present invention is to provide an insulating magnetic developer that is not easily affected by environmental changes.

A further object of the present invention is to provide an insulating magnetic developer in which a coating film that causes image deletion or image distortion is not easily formed on the surface of the latent image carrier.

SUMMARY OF THE INVENTION That is, the present invention relates to negatively charged insulating magnetic toner particles containing at least a binder resin, a magnetic substance and a zinc organic complex compound, and a volume average particle size of 1.0 to 4 μm up to 100 ° C. Has a heating loss of 0.5% by weight or less, a BET surface area of 15 m ² / g or less by a nitrogen gas adsorption method, and Ce
The present invention relates to an insulating magnetic dry developer comprising cerium oxide particles containing O ₂ as a main component and negatively charged hydrophobized silicon oxide fine particles.

In the present invention, the zinc organic complex compound is dispersed in the binder resin in order to improve the negative charge characteristic of the insulating magnetic toner. The zinc organic complex compound used in the present invention has negative charge controllability and includes, for example, a zinc complex salt type monoazo dye and a zinc complex of salicylic acid or alkylsalicylic acid, which are used alone or Used as a mixture of two or more species. Usually, considering the blocking property and the offset resistance, it is added in an amount of 0.1 to 10% by weight based on the binder resin.

Examples of the zinc organic complex compound include an acetylacetone zinc complex compound, an EDTA zinc complex compound, an anthranyl zinc complex compound, and a picolinate zinc complex compound.

The negatively chargeable insulating magnetic toner to which the zinc organic complex compound is added has improved tribo-charging property by rubbing, but on the other hand, it tends to exhibit cohesive property and lower fluidity. Hydrophobicized silicon oxide fine particles are added to the developer as an agent. The hydrophobically treated silicon oxide fine particles impart fluidity to the toner particles, assist negative chargeability, and also function as an abrasive in the cleaning step.

The hydrophobized silicon oxide fine particles used in the present invention are obtained by subjecting the silicic acid fine powder to a surface treatment with a silane coupling agent or silicone oil in order to obtain hydrophobic properties, and have excellent moisture resistance.

In the present invention, the hydrophobized silicon oxide particles to be used preferably have an arbitrary size of 2 by an electron microscope.
It is preferable to select 0 or more particles, measure the average particle diameter thereof, and have an order average particle diameter of 0.5 μ or less and a secondary average particle diameter of 3 μ or less. The method for producing silicon oxide fine particles includes a dry method and a wet method. In the case of the present invention, those produced by the dry method are preferable in terms of physical properties.

The hydrophobized silicon oxide fine particles preferably have a methanol hydrophobization degree of 40% measured by a methanol titration test.
The above hydrophobic silicon oxide fine particles are used. A typical example of the silicic acid fine powder to be hydrophobized is anhydrous silicon dioxide (silica). In addition, hydrophobized silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be applied. The hydrophobized silicon oxide fine particles are mixed in an amount of 0.01 to 3 parts by weight (preferably 0.1 to 2 parts by weight) based on 100 parts by weight of the magnetic toner.

Examples of the hydrophobizing agent (organosilicon compound) used for the surface hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, and allyldimethyl. Chlorsilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, organosilylmercaptan, trimethylsilylmercaptan, triorgano Silyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane , 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, each bonded to a single terminal Si unit. Dimethyl polysiloxane containing a hydroxyl group and the like. These are used in one kind or a mixture of two or more kinds. As these hydrophobized silicon oxide fine particles (hydrophobic silica), R97 manufactured by Aerosil Co., Ltd. is commercially available.
2, R-974, R-976, RY-130, RY-2
00, RY-300, R-812; T-34 manufactured by Tarco.
0, T-500 and the like.

Hydrophobization treatment When the hydrophobicity of the hydrophobic silica, which is fine particles of silicon oxide, is the hydrophobicity measured by the methanol titration test and the hydrophobicity is 40% or more, such a silica fine powder is used. The triboelectric charge of the developer contained is more sharp and shows a uniform negative chargeability, which is preferable. Here, the methanol titration test confirms the degree of hydrophobicity of the silica fine powder having the hydrophobicized surface. The "methanol titration test" defined in the present invention for evaluating the hydrophobicity of the treated silica fine powder is performed as follows. 0.2 g of the silica fine powder to be tested is added to 50 m of water in an Erlenmeyer flask having a capacity of 250 m. Methanol is titrated from the bath until the total amount of silica is wet. At this time, the solution in the flask is constantly stirred with a magnetic stirrer. The end point is observed by suspending the total amount of silica fines in the liquid and the degree of hydrophobization is expressed as the percentage of methanol in the liquid mixture of methanol and water when the end point is reached.

An insulating magnetic toner having an improved negative chargeability by the addition of a zinc organic complex compound has a strong tendency that the silicon oxide particles are hard to be imparted by electrostatic repulsion with the hydrophobically treated silicon oxide fine particles having negative chargeability. Therefore, in the present invention, specific cerium oxide particles are mixed with the developer as an additive for overcoming electrostatic repulsion of the hydrophobized silicon oxide fine particles and quickly imparting them to the toner.

In the present invention, the cerium oxide particles containing CeO2 as a main component (50% by weight or more), which constitutes one component of the developer, have a volume average particle diameter of 1.0 to 4.0 μm (preferably, measured with an Elzone counter). Is 1.5 to 3.5 μ), and the specific surface area by the BET method is 15 m ² / g or less,
72 in an environment with a temperature of 20 ° C and a relative humidity of 90% or more
Weight loss up to 100 ℃ after standing for 0.5 hour is 0.5wt
% Or less is used.

The volume average particle size measurement in the present invention is carried out by an Elzone counter using an orifice of 24 μm. The L-zone counter is similar to the Coulter counter in principle, but it has a large number of divided channels and uses a small-diameter orifice, so that
A fine particle size distribution in the range of about μm can be measured more accurately. Further, the measurement of the specific surface area by the BET method in the present invention is performed by using an automatic specific surface area measuring device, nitrogen gas (N ₂ ) is adsorbed on the powder sample, and the ratio of the changed gas amount and sample weight is used to determine the ratio. It is to determine the surface area.

In the present invention, the weight loss on heating up to 100 ° C. is measured by leaving about 50 mg after leaving the particles in a desiccator (temperature 20 ° C., relative humidity 90% or more) for which the humidity has been adjusted with a saturated ammonium chloride solution for 72 hours. For example, DTA-TG (manufactured by Rigaku Denki, differential type differential thermal balance) can be used as the sample without using the carrier gas.

Cerium oxide in the present invention has CeO2 as a main component and also functions as an abrasive. The cerium oxide particles are mixed in an amount of 0.1 to 5 parts by weight with respect to 100 parts by weight of the magnetic toner. If the content of CeO2 is 50% by weight or less, the ability as an abrasive in the cleaning step is reduced. Oxides of lanthanide elements such as praseodymium and lanthanum are contained in the cerium oxide particles due to the manufacturing raw material. For example, as commercially available products, Mirake T (manufactured by Mitsui Metal Industry Co., Ltd.), Mirake (manufactured by Mitsui Metal Industry Co., Ltd.), ROX M-1 (manufactured by Tohoku Metal Chemical Co., Ltd.), ROX M-3 (Tohoku Metal Chemical Co., Ltd.) Co., Ltd., etc.

The cerium oxide particles used in the present invention are the same as those described above.
It has a volume average particle size of ˜4 μ. Volume average particle size is 1
When the cerium oxide particles with a particle size of μ or less are used, the aggregating property of the cerium oxide particles is developed and the behavior as free particles is deteriorated, so that the stirring ability is deteriorated. When a cerium oxide particle size having a volume average particle size of 4 μ or more is used,
Since the particle size of the hydrophobized silicon oxide fine particles and the gap between them become large, the dissociation ability and stirring ability of the aggregates of the silica fine particles decrease. Therefore, the reduction of the initial image density and the ability to suppress falling development are reduced. Similarly, in the case of cerium oxide particles having a heating loss value and a BET specific surface area outside the ranges specified in the present invention, the fluidity and moisture resistance of the cerium oxide itself are poor, and the cerium oxide particles intended by the present invention are Work is reduced. The cerium oxide used in the present invention can be produced by firing at a temperature higher than the firing temperature of ordinary cerium oxide, pulverizing, and then classifying more strictly than before. By adding specific cerium oxide particles to a mixture of negatively chargeable insulating toner containing a zinc organic complex compound and hydrophobically treated silicon oxide particles, the hydrophobically treated silicon oxide fine particles show strong negative chargeability, With respect to the negatively chargeable insulating magnetic toner, not only the role as the fluidizing agent but also the role as the charge imparting agent is excellent. This is also inferred from the fact that when the hydrophobic silicon oxide fine particles are added to the developer, the concentration is remarkably increased as compared with the developer not added.

Further, even in the initial stage of development, the hydrophobized silicon oxide fine particles and the toner are sufficiently stirred, and the hydrophobized silicon oxide fine particles are well dispersed between the toner particles, and the charge is transferred to the toner. Be done enough. As a result, the initial concentration is improved and the fall is suppressed. When observed under a microscope, many agglomerates of toner and agglomerates of silicon oxide particles are found in the developer containing no cerium oxide particles, but such agglomerates are observed in the developer containing cerium oxide particles. None or very few. Further, it can be understood that the cerium oxide particles have a function as a microdisperser that disperses the silicon oxide fine powder satisfactorily in the toner because the latter exhibits extremely good fluidity between the two. In fact, from the observation of the surface with and without cerium oxide particles, the amount of silicon oxide particles adhering to the toner and the state of adhesion differ greatly, and in the case of a developer having cerium oxide particles, the morphology of the oxygen silicon fine powder present on the toner surface Are found to be extremely finely dispersed and evenly adhered to the toner surface, whereas in the developer containing no cerium oxide particles, silicon oxide fine particles are unevenly distributed in a part of the toner surface in a form close to aggregates. It is discovered.
Further, in a developer containing cerium oxide particles, cerium oxide particles in which silicon oxide fine particles are adhered around the cerium oxide particles are seen, so the cerium oxide particles loosen such aggregates of silicon oxide fine particles. It is presumed that the toner acts as a carrier of the fine particles of silicon oxide by being dispersed, and the toner has a role of supplying the fine particles of silicon oxide. Therefore, the cerium oxide particles act particularly on the negatively charged silicon oxide fine particles in the relation between the negatively charged toner and the negatively charged silicon oxide, and the aggregation thereof is released, and the negatively charged toner is rapidly transferred to the negatively charged hydrophobic oxide. It is considered that the chemical-treated silicon oxide fine particles are supplied. The cerium oxide particles selectively act on the silicon oxide fine particles rather than the toner, probably because the silicon oxide fine particles have a potentially higher negative charge capacity than the toner and at the same time the particles of the silicon oxide fine particles are It is presumed that the diameter is closer to cerium oxide particles than the toner.

Such an action generally causes the deterioration of the characteristics because the negatively charged toner and the negatively charged silicon oxide fine particles are easily separated and easily aggregated after leaving for a long period of time. The fine particles must be agitated and mixed, and if they have already been left in the developing device, they must wait until they are gradually recovered by the agitating device in the developing device. On the other hand, in the present invention, in the developer containing the specific cerium oxide particles, since the silicon oxide fine particles are rapidly supplied into the negatively-charged toner by the action of the stirring device and the cerium oxide particles as described above, almost no deterioration is caused. Is consistent with not being seen.

In order to promote the action of the cerium oxide particles on the negatively charged silicon oxide fine particles and to perform the function of the photoconductor as a polishing agent satisfactorily, it is desirable that the triboelectric charge of the cerium oxide particles themselves is low, and particularly negatively strongly charged. That is not preferable. The cerium oxide particles preferably have a triboelectric charging property of | Q | <1.5 when expressed by the triboelectric charge amount Q (μc / g). The amount of tribo charge is measured as follows.

FIG. 1 is an explanatory view of an apparatus for measuring the triboelectric charge amount of sample particles. First, about 4 g of a mixture (developer) of a sample particle carrier (200 to 300 mesh) in a weight ratio of 1: 9 is placed in a metal measuring container 2 having a screen 3 of 400 mesh at the bottom to measure triboelectric charge. Put the lid 4 made of metal. The weight of the measuring container 2 as a whole in this case Tsubori, and W 1 _(g). Next, in the suction device 1 (at least the part in contact with the measurement container 2 which is an insulator), suction is performed from the suction port 7 to adjust the air volume control valve 6 to adjust the pressure of the vacuum gauge 5 to 70 mm.
Hg. In this state, suction is sufficiently performed (for about 1 minute) to remove the sample particles by suction. The potential of the electrometer 9 at this time is V (volt). Here, 8 is a capacitor and the capacitance is C (μF). Further, the total weight of the measuring container after the suction and Tsubori W _{2 (g).} The triboelectric charge amount (μc / g) of this sample particle is calculated by the following formula.

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

In addition, the carrier (iron powder) used for the measurement is 200 to 30.
The carrier is 0 mesh, but in order to eliminate the error, the carrier is sufficiently sucked by a steam suction device, and the carrier passing through the 400 mesh screen is removed and then mixed with the sample particles.

As the binder resin of the toner used in the present invention, known resins can be used. For example, polystyrene, poly-p-chlorostyrene, homopolymers of styrene such as polyvinyltoluene, and substitution products thereof; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-
Vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, Styrene-methylmethacrylate copolymer, styrene-ethylmethacrylate copolymer, styrene-butylmethacrylate copolymer, styrene-α-chloromethylmethacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl Ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer,
Styrene-based copolymers such as styrene-maleic acid copolymers, styrene-maleic acid half ester copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, Polyethylene, polypropylene,
Polyester, polyurethane, epoxy resin, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin, Wax or the like can be used alone or in combination. Among them, styrene-based resins, styrene-acrylic acid ester-based resins, styrene-methacrylic acid ester-based resins and polyester resins are preferable in terms of developability and durability.

The particle size of the binder resin containing a magnetic substance and formed into particles as a magnetic toner is preferably 5 to 30 μm in volume average particle size. The negatively chargeable insulating toner according to the present invention has a triboelectric charge amount, and in order to have sufficient developing property and electrostatic transfer property, it is 10 ¹⁰ Ω · cm or more, preferably 10 ¹³ Ω · c.
It preferably has an electric resistance of m or more.

As the magnetic substance contained in the toner, ferromagnetic elements and alloys containing these, magnetite, hematite, iron such as ferrite, compounds such as cobalt and nickel manganese,
Other ferromagnetic alloys and the like can be appropriately used, and the particle size thereof is 100 to 800 mμ, preferably 300 to 500 mμ.
It is preferable to contain 30 to 100 parts by weight, more preferably 40 to 90 parts by weight, based on 100 parts by weight of the binder resin.

Further, in the magnetic toner according to the present invention, an anti-offset agent such as low-molecular weight polyethylene or low-molecular weight polypropylene is used for improving the offset resistance in an amount of 0.1 to 10 parts by weight (preferably 0.5-8
It is preferable to add (part by weight).

In producing the toner of the present invention, a heat roll, a kneader,
A method in which the constituent materials are well kneaded by a heat kneader such as an extruder and then mechanically pulverized and classified. Alternatively, a method in which a material such as magnetic powder is dispersed in a binder resin solution and then spray-dried, or an aqueous solution containing a dispersion stabilizer after mixing a predetermined material with a monomer that constitutes the binder resin is used. Each method such as a polymerization method and a toner production method in which a toner is obtained by polymerizing a monomer in a suspension prepared by adding it to a medium can be applied.

Recently, a microencapsulated toner or the like has been proposed for the purpose of separating the function of the toner, but the present invention can be applied by satisfying the requirements of the present invention.

Further, as a method of mixing the inorganic fine powder with the toner, a known mixer, for example, a V-type mixer, a rotary container type mixer such as a turbula mixer, a ribbon type, a screw type, a rotary blade type, or other fixed A container-type mixer can be used as appropriate.

Further, the three may be mixed at once at the time of mixing, or may be mixed in an order considering the properties of the toner. It is also possible to further mix the known fourth component. For example, polyfluoroethylene, polyvinylidene fluoride, fatty acid metal salts, various abrasives, and the like.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

Example 1 The mixture having the above formulation was melt-kneaded, cooled, and then ground and classified to obtain an insulating magnetic toner (electrical resistance value 10 ¹⁵ Ω · cm) having a particle size of 5 to 20 μ (volume average particle size of about 12 μ). To 100 parts by weight of the obtained insulating magnetic toner, 0.4 parts by weight of hydrophobic silica having a hydrophobicity of about 65 and an average primary particle size of 0.15 μ and Ce
Cerium oxide particles containing 80% by weight of O ₂ component (volume average particle diameter by LZONE COUNTER (manufactured by US Particle Data Co., Ltd.) 2.74μ, heating loss up to 100 ° C. after moisture absorption 0.14% by weight, nitrogen gas BE by measuring the specific surface area automatic measuring device type 2200 (manufactured by Shimadzu Corporation) by the adsorption method.
T specific surface area 3.6 m ² / g] 1 part by weight was mixed to prepare a developer.

This developer was applied to a commercially available plain paper copying machine (made by NP-400 Canon) and 500 images were continuously copied to obtain images, and the reflection density of the image was 1 as shown in the graph in the attached drawings.
1st sheet 1.38, 20th sheet 1.37, 50th sheet 1.37, 1
The 1.40th for the 00th sheet and the 1.40th for the 500th sheet, there is no drop in the image density in the initial copying, and the reflection density is stable at about 1.39 throughout the entire image, and there is no fog and an extremely clear image is obtained. It was The developer of the present invention has a high temperature and high humidity (32.
Even under the environment of 5 ° C. and 90%) and low temperature and low humidity (15 ° C. and 10%), the development characteristics were as good as those of normal temperature and normal humidity.

Examples 2 to 6 Each developer was prepared in the same manner as in Example 1 except that the cerium oxide particles shown in Table 1 below were used. The results of the image forming test conducted in the same manner as in Example 1 are shown in Table 2.

Example 7 A developer was prepared in the same manner as in Example 1 except that 0.4 part by weight of hydrophobic silica having a hydrophobicity of about 50 and an average primary particle size of 0.25 μ was used. The results of the image forming test are shown in Table 2.

Example 8 Styrene-2-methylpentyl methacrylate copolymer as a binder resin (copolymerization weight ratio 6: 4; Mw = 260.
000) A developer was prepared in the same manner as in Example 1 except that 100 parts by weight was used. The results of the image forming test are shown in Table 2.

Example 9 Styrene-n-butyl methacrylate maleic acid monobutyrate copolymer as a binder resin (copolymerization ratio 60: 3
5: 5; MW = 350.000) A developer was prepared in the same manner as in Example 1 except that 100 parts by weight was used. The results of the image forming test are shown in Table 2.

Example 10 A developer was prepared in the same manner as in Example, except that 2 parts by weight of alkylsalicylic acid Zn complex was used as the charge control agent. The results of the image forming test are shown in Table 2.

Comparative Example 1 100 parts by weight of the magnetic toner prepared in Example 1 was mixed with 0.4 part by weight of hydrophobic silica having a degree of hydrophobicity of about 65 and an average primary particle size of 0.15μ without adding cerium oxide particles. Then, a developer was prepared, and an image forming test was conducted in the same manner as in Example 1.

As shown in the graph in the attached drawing, the reflection density is 1.
The image density was low, and the trailing development was observed at the 13,20th sheet 1.03, the 50th sheet 0.8, the 100th sheet 0.91 and the 500th sheet 1.11.

Comparative Example 2 100 parts by weight of the magnetic toner prepared in Example 1 was used and 0.4 of non-hydrophobicized silica having a hydrophobicity of 0 and an average particle size of 0.25 μm was used.
Volume average particle diameter by weight part and L zone is 3.25μ,
Cerium oxide particles 1 containing 63.2% by weight of CeO ₂ having a weight loss of 2.3% by weight at 100 ° C. after moisture absorption and a BET specific surface area of 39.0 m ² / g (outside the specified range of the present invention). A developing agent was prepared by mixing with 1 part by weight. As is apparent from the graph shown in the attached drawings, the number of copies is 50 to 10
A remarkable fall phenomenon was observed at the time of 0 sheets.

Comparative Example 3 Volume average particle size by L zone 1.64μ, 1 after moisture absorption
Weight loss at heating at 00 ° C. of 1.08% by weight (outside the specified range of the present invention), specific surface area by BET method of 8.1 m ² / g C
A developer was prepared in the same manner as in Example 1 except that 1 part by weight of cerium oxide particles containing 53% by weight of eO ₂ was used. The test results are shown in Table 2.

Comparative Example 4 Volume average particle diameter by L zone 1.47μ, 1 after moisture absorption
Example except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO ₂ having a specific surface area of 18.1 m ² / g according to the BET method at a weight loss of 1.50% by weight at 00 ° C. was used. A developer was obtained in the same manner as in 1. The test results are shown in Table 2.

Comparative Example 5 Volume average particle diameter of 4.52μ by L zone, 1 after moisture absorption
Except that 1 part by weight of cerium oxide particles containing 0.18% by weight of heating at 00 ° C. and 51.8% by weight of CeO ₂ having a specific surface area of 1.8 m ² / g according to the BET method were used. A developer was prepared in the same manner as in Example 1. The test results are shown in Table 2.

Comparative Example 6 Volume average particle size by L zone 0.91μ, 1 after moisture absorption
Example except that 1 part by weight of cerium oxide particles containing 0.02% by weight of heating loss at 00 ° C. and 72.5% by weight of CeO ₂ having a specific surface area of 9.5 m ² / g by the BET method was used. A developer was prepared in the same manner as in 1. The test results are shown in Table 2.

Comparative Example 7 A developer was obtained in the same manner as in Example 1 except that 0.4 part by weight of non-hydrophobicized silica having a hydrophobicity of 0 and an average particle size of 0.15μ was used. The test results are shown in Table 2.

In Examples 2 to 10, there was substantially no initial fall of the image density, the reflection density was stable from the beginning to the end, and extremely clear images without fog were obtained. The initial fall of No. 2 is remarkable, and in any case from the initial stage to the 50th sheet, the reflection density is reduced by about 0.3 or more, and the fog is compared with the case of the embodiment of the present invention. Only conspicuous, unclear and poorly resolved image quality was obtained. From this, it is found that the effect of the developer of the present invention is very remarkable.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an apparatus for measuring the amount of tribo charge. FIG. 2 is a graph showing the relationship between the durable sheet number and the image reflection density for the developers of Example 1, Comparative Example 1 and Comparative Example 2. 1 ... Aspirator, 2 ... Measuring container, 3 ... Screen, 7
…… Suction port, 8 …… Condenser

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03G 9/08 375 6923-2H 101 (72) Inventor Yusuke Karami 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) Reference JP 61-236560 (JP, A) JP 60-32060 (JP, A) JP 52-30437 (JP, A) JP 53-127726 ( JP, A) Actually open 56-101150 (JP, U) Actually open 53-81127 (JP, U) Special public 43-27596 (JP, B1)

Claims (2)

[Claims] 1. A negatively chargeable insulating magnetic toner particle containing at least a binder resin, a magnetic substance and a zinc organic complex compound, and having a volume average particle diameter of 1.0 to 4.0 μm and heating to 100 ° C. Weight loss is 0.5 wt% or less, BET specific surface area by nitrogen gas adsorption method is 15 m ² / g or less, and C
An insulating magnetic dry developer comprising cerium oxide particles containing eO ₂ as a main component and negatively-charged hydrophobized silicon oxide particles. 2. A cerium oxide particle in an amount of 0.1 to 5 parts by weight and a hydrophobized silicon oxide fine particle in an amount of 0.01 to 3 parts by weight based on 100 parts by weight of a negatively chargeable insulating magnetic toner particle. The insulating magnetic dry developer according to item 1.