JPH06100843B2 - 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 development method, an insulating magnetic material containing at least a toner that is uniformly strongly and negatively charged, a negatively chargeable hydrophobic silica, and specific cerium oxide particles. It relates to a dry developer.

[Background technology]

Conventionally, electrophotographic methods have been described in US Pat. No. 2,297,691 and JP-B-42-23910 (US Pat. No. 3,666,363).
Specification), Japanese Patent Publication No. 43-24748 (US Pat. No. 40713)
No. 61), etc., the photoconductive layer is uniformly charged and exposed to a light image according to the original to eliminate the electric 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.

Many developing methods in electrophotography are known, and a cascade developing method described in US Pat. No. 2,618,552, which is a developing method in which carrier particles and toner are mixed and used as a two-component developer, and US Pat. No. 2,874,063. The magnetic brush method described in the specification 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 common problems associated with a two-component developer, such as deterioration of the carrier and variation in the mixing ratio of the toner and the carrier. In order to avoid such problems, various developing methods using a one-component developer containing no carrier made of 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. 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. On this occasion,
In the developing device, toner particles form a conductive path between the surface of the recording medium and the surface of the sleeve, and the electric charge is spilled from the sleeve to the toner particles through the conductive path. The particles adhere to the image area 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 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. Further, British Patent 1,503,560 proposes a method in which magnetic toners having exposed magnetic bodies are rubbed against each other to develop an electrostatic latent image with the charged toner. 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 a 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 the stirring action by the carrier. It is difficult to obtain a triboelectric charge with a one-component developer as much as with a two-component developer, so that it is 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 a good negative charge with respect to negatively chargeable 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. In the initial stage of the movement, the low image density and the remarkable fall phenomenon of the image density were exhibited.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an insulating magnetic developer that eliminates the phenomenon of image density falling, which has been associated with conventional one-component developers containing negatively charging insulating magnetic toner.

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.

Further, an 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.

[Means and Actions for Solving Problems]

That is, the present invention relates to negatively charged insulating magnetic toner particles containing at least a binder resin and a magnetic substance (excluding toner particles containing a chromium organic complex compound or a zinc organic complex compound), and a volume average particle size. Is 1.0 to 4.0 μm, the weight loss on heating up to 100 ° C. is 0.5% by weight or less, the BET specific surface area by the nitrogen gas adsorption method is 15 m ² / g or less, and cerium oxide particles containing CeO ₂ as a main component are used. The present invention relates to an insulating magnetic dry developer, characterized in that it has negatively charged hydrophobically treated silicon oxide fine particles.

Further, in the present invention, in order to improve and stabilize the negative chargeability of the insulating magnetic toner, it is preferable to disperse the metal-containing complex compound in the binder resin.

Further, in the present invention, the aggregation of the insulating magnetic toner is prevented,
For the purpose of improving the fluidity, hydrophobized silicon oxide fine particles are added to the developer as a fluidizing agent. Further, the hydrophobized 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 used are preferably optionally observed by an electron microscope.
It is preferable to select 20 or more particles, measure the average particle diameter thereof, and have a primary 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, but in the case of the present invention, those produced by the dry method are physically preferable.

As the hydrophobized silicon oxide fine particles, preferably used are hydrophobic silicon oxide fine particles having a methanol hydrophobicity of 40% or more measured by a methanol titration test. 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, trilugano Silyl acrylate, vinyl dimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and 2 to 12 siloxane units per molecule, each of which is bonded to a single terminal Si unit. There is dimethylpolysiloxane containing a hydroxyl group. These are used alone or as a mixture of two or more. These hydrophobized silicon oxide fine particles (hydrophobic silica)
As commercially available products, R972 and R-97 manufactured by Aerosil Co., Ltd.
4, R-976, RY-130, RY-200, RY-300, R812; T-340, T-500 and the like manufactured by Tarco.

Hydrophobized Silica fine powder when the hydrophobicity of hydrophobic silica, which is fine particles of silicon oxide, is 40% or more of the hydrophobicity measured by the methanol titration test. The triboelectric charge amount of the developer containing 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 fine silica powder to be tested is added to 50 ml of water in an Erlenmeyer flask having a volume of 250 ml. Methanol is titrated from the bath until the total amount of silica is wet. On this occasion,
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.

The negatively chargeable insulating magnetic toner has a strong tendency to be difficult to be imparted with the negatively chargeable silicon oxide particles due to electrostatic repulsion with the hydrophobically treated silicon oxide particles. This tendency is further reinforced by the addition of the negatively chargeable metal-containing organic compound in the insulating magnetic toner having the improved and stable negatively chargeability.

The negatively charged metal-containing organic compound is added in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin in consideration of blocking property and offset resistance. Various metal-containing organic compounds are exemplified below.

(A) Magnesium-containing organic compound: acetylacetone magnesium complex compound, EDTA magnesium complex compound, magnesium anthranilate complex compound, (b) Iron-containing organic compound: 8-oxyquinoline iron salt compound, acetylacetone iron complex compound, 4-methylphthalic acid iron complex compound , Iron dimethyldithiocarbamate, iron picolinate complex compounds, iron anthranilate complex compounds, ferric citrate, iron 4-chlorophthalate, iron 5-methylanthranilate complex compounds, (c) manganese-containing organic compounds anthranil Acid manganese complex compound, N-methyl-anthranilic acid manganese complex compound, 2-oxy-3-manganese naphthoate complex compound, acetylacetone manganese complex compound, (d) cobalt-containing organic compound cobalt organic complex compound, acetylacetone cobalt complex compound, EDTA Baltic complex compound, cobalt anthranilate complex compound, cobalt picolinate complex compound, cobalt organometallic salt, dimethyldithiothiocarbamic acid cobalt salt, 3-methyl-2-hydroxy-1-naphthoic acid cobalt salt, 4-chlorophthalic acid cobalt salt , 2-hydroxy-
m-toluic acid cobalt salt, citric acid cobalt salt, (e) nickel-containing organic compound acetylacetone nickel complex compound, dimethyldithiocarbamic acid nickel salt, picolinic acid nickel salt, 4-chlorophthalnickel salt, 3-methyl-2-hydroxy- 1-
Naphthoic acid nickel salt, EDTA nickel complex compound, therefore, in the present invention, specific cerium oxide particles are added as an additive for overcoming electrostatic repulsion of hydrophobically treated silicon oxide fine particles and rapidly imparting to toner. It is mixed with the developer.

In the present invention, the cerium oxide particles containing CeO ₂ as a main component (50 wt% or more), which is one of the constituents of the developer, have a volume average particle size of 1.0 to 4.0 measured with an Elzone counter.
μm (preferably 1.5-3.5 μ), specific surface area by BET method is 15 m ² / g or less, temperature 20 ° C., relative humidity
A material that has a weight loss on heating to 100 ° C of 0.5 wt% or less after being left for 72 hours in an environment of 90% or more is used.

The volume average particle size measurement in the present invention is performed by an L zone counter using an 24 μm orifice. The L-zone counter is similar to the Coulter counter in principle, but it has a large number of split channels and uses a small diameter orifice to reduce submicron to 5μ.
A fine particle size distribution in the range of about m can be measured more accurately. Further, the measurement of the specific surface area by the BET method in the present invention is carried out 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 gives 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 placing the particles in a desiccator prepared by adjusting a saturated ammonium chloride solution (temperature 20 ° C., relative humidity 90% or more) for 72 hours and then taking about 50 mg. 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 CeO ₂ 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.
When the content of CeO ₂ is 50% by weight or less, the ability as an abrasive in the cleaning step is reduced.

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 having a particle size of μ or less are used, the aggregating property of the cerium oxide particles is exhibited 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 distance between them become large, the dissociation ability and stirring ability of the aggregates of the silica fine particles are reduced. Therefore, the ability to suppress the initial image density and the falling phenomenon is reduced. Similarly, in the case of cerium oxide particles having a heating loss value and a BET specific surface area outside the range specified in the present invention, the fluidity and moisture resistance of cerium oxide itself are poor, and the cerium oxide particles of the present invention are intended. Work is reduced.

The specific cerium oxide particles used in the present invention are usually cerium oxide particles used as an abrasive for optical glass, and ultrafine silica added for the purpose of improving cohesion and precipitation preventive cleaning properties and silica sol. Less or
It is produced by removing coarse particles by using a non-mixed material, and by setting the firing temperature to a higher value than that produced as an ordinary abrasive material, pulverizing and classifying after firing.

By adding specific cerium oxide particles to a mixture of negatively charged insulating toner and hydrophobized silicon oxide particles, the hydrophobized silicon oxide fine particles show a strong negative charge, and the negatively charged insulating magnetic toner On the other hand, in addition to the role as a fluidizing agent, it also serves as a charge imparting agent. 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. Thereby, the improvement of the initial concentration and the suppression of the fall are achieved. 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 of favorably dispersing the silicon oxide fine powder in the toner because the latter exhibits extremely good fluidity between the two. In fact, from the observation of the toner surface depending on the presence or absence of cerium oxide particles, the amount of silicon oxide fine particles adhering to the toner and the adhesion state differ greatly, and in the developer having cerium oxide particles, the silicon oxide fine powder present on the toner surface It can be seen that the morphology is 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 an aggregate. Are found to exist. 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 particles are dispersed and behave as a carrier for the silicon oxide particles, and have a role of supplying the silicon oxide particles to the toner. Therefore, the cerium oxide particles act in particular on the negatively charged silicon oxide fine particles in the relationship between the negatively charged toner and the negatively charged silicon oxide fine particles to dissolve the agglomerates, and at the same time, the negatively charged toner and the rapidly negatively charged hydrophobic oxide particles can be treated. 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 when left for a long period of time. The fine particles must be agitated and mixed, and if the particles 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, the developer containing the specific cerium oxide particles is almost deteriorated because 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. The phenomenon of is consistent with not being seen.

In order to promote the action of the cerium oxide particles on the silicon oxide fine particles, it is desirable that the cerium oxide particles themselves have a low triboelectric charge, and it is not preferable that they are negatively charged. When this is shown by the triboelectric charge amount Q (μc / g), | Q | <1.5 is preferable.

This measuring method will be described below.

FIG. 1 is an illustration of an apparatus for measuring the triboelectric charge amount of toner or fine particles. First, in a metal measuring container 2 having a 400 mesh screen 3 at the bottom, a mixture (developer) of toner or fine particles and a carrier (200 to 300 mesh) having a weight ratio of 1: 9, whose tribo charge is to be measured, is approximately 1: 1. Put 4g and put a lid 4 made of metal. At this time, the total weight of the measurement container 2 is weighed and set as W ₁ (g). Next, in the suction device 1 (at least the portion in contact with the measurement container 2 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 toner or fine 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). In addition, the total weight of the measuring container after suction is weighed to obtain W ₂ (g). The triboelectric charge amount (μc / g) of the toner or fine particles is calculated by the following formula.

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

Also, the carrier (iron powder) used for the measurement is of 200 to 300 mesh, but in order to eliminate the error, the carrier is sufficiently sucked by the above suction device and the one passing through the screen of 400 mesh is removed before the toner or Mix with fine 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-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid Copolymer, styrene Maleic acid half ester copolymer, styrene - styrene copolymer and 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, phenyl resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin, wax, etc. Can be used alone or in combination.

The particle size of the binder resin containing a magnetic substance and granulated 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 an electrical resistance of 10 ¹⁰ Ω · cm or more, preferably 10 ¹³ Ω · cm or more in order to retain triboelectric charge and have sufficient developing property and electrostatic transfer property. It is preferable to have a value.

As the magnetic substance contained in the toner, ferromagnetic elements and alloys containing them, compounds such as magnetite, hematite, and ferrite such as iron, cobalt, nickel, alloys such as manganese, compounds and other ferromagnetic alloys are appropriately used. Can be used.

The particle size is 100 to 800 mμ, preferably 300 to 500 mμ, and 30 to 100 parts by weight, and more preferably 40 to 90 parts by weight is suitable for 100 parts by weight of the binder resin.

Further, in the magnetic toner according to the present invention, in order to improve the offset resistance, low molecular weight polyethylene, an anti-offset agent such as low molecular weight polypropylene is 0.1 to 10 parts by weight (preferably 0.5 to 10 parts by weight) with respect to 100 parts by weight of the binder resin. It is preferable to add 8 parts by weight).

In the production of the toner of the present invention, a method in which the constituent materials are well kneaded by a heat kneader such as a hot roll, a kneader or an extruder and then mechanically pulverized and classified.
Alternatively, after dispersing a material such as magnetic powder in the binder resin solution,
Each method such as a method obtained by spray-drying or a polymerization method in which a predetermined material is mixed with a monomer to form a binder resin and then the emulsion suspension is polymerized to obtain a toner is applied. I can.

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. Examples include poly (ethylene fluorinated), poly (vinyl fluorinated), 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 is melt-kneaded, cooled, pulverized, and classified to have a negatively charged insulating magnetic toner having a particle size of 5 to 20 μ (volume average particle size of about 12 μ) (electric resistance value 10 ¹⁵ Ω · cm; tribo value − 11 μc /
g) was obtained. To 100 parts by weight of the obtained insulating magnetic toner, 0.4 parts by weight of negatively charged hydrophobic silica (tribo value −110 μc / g) having a hydrophobicity of about 65 and an average primary particle size of 0.007 μ and 8 parts of CeO ₂ component are added.
Cerium oxide particles A containing 0% by weight (volume average particle diameter by L-zone counter (manufactured by US Particle Data Co., Ltd.) 2.74μ, heating loss up to 100 ° C after moisture absorption 0.14% by weight, specific surface area automatic by nitrogen gas adsorption method) A developer was prepared by mixing 1 part by weight of a BET specific surface area of 3.6 m ² / g] measured by a measuring device Model 2200 (manufactured by Shimadzu Corporation). The tribo value of the cerium oxide particles was -1 μc / g.

When this developer was applied to a commercially available plain paper copier (NP-400 Canon) and 500 continuous copies were made to obtain images,
Image reflection density is 1.21 for the first sheet, 1.17 for the 20th sheet, 1.2 for the 50th sheet
There is no drop in the image density in the 0th, 100th sheet 1.22, 500th sheet 1.18 and the initial copy, and the reflection density is about 1.2 throughout.
The image was stable, free from fog, and extremely clear. Further, the developer of the present invention has a high temperature and high humidity (32.5 ° C, 90%
%) And low temperature and low humidity (15 ° C, 10%) environment, the development characteristics were as good as 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 B to F 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 1.

Example 7 Example 1 except that 0.4 parts by weight of negatively charged hydrophobic silica having a degree of hydrophobicity of about 50 and an average primary particle size of 0.016μ are used.
A developer was prepared in the same manner as in. The results of the image forming test are shown in Table 2.

Example 8 Loading was carried out in the same manner as in Example 1 except that 100 parts by weight of a styrene-2-methylpropyl methacrylate copolymer (copolymerization weight ratio 7: 2; Mw = 243,000) was used as the binder resin. A current formulation with an electrically conductive toner was prepared. The results of the image forming test are shown in Table 2.

Example 9 Styrene-n-propyl acrylate-as a binder resin
Maleic acid monobutyrate copolymer (copolymerization ratio 65: 30: 5;
A developer was prepared in the same manner as in Example 1 except that 100 parts by weight of Mw = 390,000) 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 1 except that 2 parts by weight of Mg alkylsalicylic acid 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 without adding cerium oxide particles, a degree of hydrophobicity of about 65, and an average primary particle size of 0.007.
An image forming test was conducted in the same manner as in Example 1 by preparing a developer by mixing with 0.4 part by weight of negatively charged hydrophobic silica.

Reflection density 1.03 for the first sheet, 0.85 for the 20th sheet, 0.58 for the 50th sheet, 100
The image density was low at 0.65th sheet and 1.05th sheet at 500th sheet, and a falling phenomenon was observed.

Comparative Example 2 100 parts by weight of the magnetic toner prepared in Example 1 had 0.4 degree of hydrophobicity, 0.4 parts by weight of non-hydrophobicized silica having an average particle size of 0.016 μ, and a volume average particle size of 3.25 μ by L zone after moisture absorption.
Heat loss at 100 ℃ 2.3% by weight, BET specific surface area 39.0m
^A developer was prepared by mixing with 1 part by weight of cerium oxide particles containing 63.2% by weight of CeO ₂ of ² / g (outside the range of the present invention). At the time of 50 to 100 copies, a remarkable falling phenomenon was observed.

Comparative Example 3 Containing 53% by weight of CeO ₂ having a specific surface area of 8.1 m ² / g according to the BET method, with a volume average particle size of 1.64 μ by Ersol, heating after moisture absorption at 100 ° C. and a weight loss of 1.08% by weight (outside the range of the present invention). A developer was prepared in the same manner as in Example 1 except that 1 part by weight of cerium oxide particles was used. The test results are shown in Table 2.

Comparative Example 4 Volume average particle size by L zone 1.47μ, heat loss after moisture absorption at 100 ° C. 1.50% by weight, specific surface area by BET method 18.0 m ₂ / g
A developer was obtained in the same manner as in Example 1 except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO ₂ was used. The test results are shown in Table 2.

Comparative Example 5 1 part by weight of cerium oxide particles containing a volume average particle diameter of 4.52μ by L-zone, a heating loss at 100 ° C. after moisture absorption of 0.14% by weight, and a BET method of 51.8% by weight of CeO ₂ having a specific surface area of 1.8 m ² / g. A developer was prepared in the same manner as in Example 1 except that was used. The test results are shown in Table 2.

Comparative Example 6 1 part by weight of cerium oxide particles containing 0.91 μ in volume average particle size by L zone, 0.08 wt% by weight loss after heating at 100 ° C. after moisture absorption, and 72.5 wt% CeO ₂ having a specific surface area of 9.5 m ² / g by BET method. A developer was prepared in the same manner as in Example 1 except that was used. 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 0.007 μ was used. The test results are shown in Table 2.

Example 11 The mixture having the above formulation is melt-kneaded, cooled, pulverized, and classified to have a negatively charged insulating magnetic toner having a particle diameter of 5 to 20 μ (volume average particle diameter of about 12 μ) (electric resistance value 10 ¹⁵ Ω · cm, tribo value − 13 μc /
g) was obtained. To 100 parts by weight of the obtained insulating magnetic toner, 0.4 parts by weight of negatively charged hydrophobic silica (tribo value −110 μc / g) having a hydrophobicity of about 65 and an average primary particle size of 0.007 μ and 8 parts of CeO ₂ component are added.
Cerium oxide particles A containing 0% by weight (volume average particle diameter by L-zone counter (manufactured by US Particle Data Co., Ltd.) 2.74μ, heating loss up to 100 ° C after moisture absorption 0.14% by weight, specific surface area automatic by nitrogen gas adsorption method) A developer was prepared by mixing 1 part by weight of a BET specific surface area of 3.6 m ² / g] measured by a measuring device Model 2200 (manufactured by Shimadzu Corporation). The tribo value of the cerium oxide particles was -1 μc / g.

When this developer was applied to a commercially available plain paper copier (NP-400 Canon) and 500 continuous copies were made to obtain images,
Image reflection density is 1.24 for the first sheet, 1.20 for the 20th sheet, 1.2 for the 50th sheet
The first, 1.100th, 1.500th, 1.22th, 500th and 1.22th, there is no fall of the image density in the initial copy, and the reflection density is about 1.2 throughout.
The image was stable, free from fog, and extremely clear. Further, the developer of the present invention has a high temperature and high humidity (32.5 ° C, 90%
%) And low temperature and low humidity (15 ° C, 10%) environment, the development characteristics were as good as normal temperature and normal humidity.

Examples 12 to 16 Each developer was prepared in the same manner as in Example 11 except that the cerium oxide particles shown in Table 3 below were used. The results of the image forming test performed in the same manner as in Example 11 are shown in Table 4.

Example 17 Hydrophobic silica having a hydrophobicity of about 50 and an average primary particle size of 0.016 μ
A developer was prepared in the same manner as in Example 11 except that 0.4 part by weight was used. The results of the image forming test are shown in Table 4.

Example 18 Same as Example 11, except that 100 parts by weight of styrene-2-ethylpentyl methacrylate copolymer (copolymerization weight ratio 6: 4; Mw = 180,000) was used as the binder resin. The agent was prepared. The results of the image forming test are shown in Table 4.

Example 19 Styrene-n-propyl acrylate-as a binder resin
Maleic acid monobutyrate copolymer (copolymerization ratio 65: 30: 5;
A developer was prepared in the same manner as in Example 1 except that 100 parts by weight of Mw = 400,000) was used. The results of the image forming test are shown in Table 4.

Example 20 A developer was prepared in the same manner as in Example 11 except that 2 parts by weight of the alkyl salicylic acid Fe complex was used as the charge control agent. The results of the image forming test are shown in Table 4.

Comparative Example 8 100 parts by weight of the magnetic toner prepared in Example 11 without adding cerium oxide particles, a degree of hydrophobicity of about 65, and an average primary particle size of 0.007.
A developer was prepared by mixing with 0.4 part by weight of hydrophobic silica of μ, and an image forming test was conducted in the same manner as in Example 11.
Reflection density is 1.02 for the first sheet, 0.85 for the 20th sheet, 0.61 for the 50th sheet, 100
The image density was low at 0.63 for the first sheet and 0.98 for the 500th sheet, and a falling phenomenon was observed.

Comparative Example 9 100 parts by weight of the magnetic toner prepared in Example 11 was used, and 0.4 part by weight of non-hydrophobicized silica having an average particle size of 0.016 μ was used for 100 parts by weight of the magnetic toner.
2.3% weight loss on heating at 100 ° C, specific surface area by BET method 39.
63.2% by weight of CeO ₂ which is 0 m ² / g (outside the specified range of the present invention)
A developer was prepared by mixing 1 part by weight of the contained cerium oxide particles. At the time of 50 to 100 copies, a remarkable falling phenomenon was observed.

Comparative Example 10 Volume average particle diameter of Elsol 1.64μ, 100 ℃ after moisture absorption
Loss on heating at 1.08% by weight (outside the specified range of the present invention), BET
A developer was prepared in the same manner as in Example 11 except that 1 part by weight of cerium oxide particles containing 53% by weight of CeO ₂ having a specific surface area of 8.1 m ² / g according to the method was used. Fourth test result
Shown in the table.

Comparative Example 11 L-zone volume average particle size 1.47μ, 100 ° C after moisture absorption
Loss on heating at 1.50% by weight, specific surface area by BET method 18.0 m ² /
A developer was obtained in the same manner as in Example 11 except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO _{2 (} g) was used. The test results are shown in Table 4.

Comparative Example 12 L-zone volume average particle size 4.52μ, 100 ° C after moisture absorption
Loss on heating at 0.14% by weight, specific surface area by BET method 1.8 m ² / g
A developer was prepared in the same manner as in Example 11 except that 1 part by weight of cerium oxide particles containing 51.8% by weight of CeO ₂ was used. The test results are shown in Table 4.

Comparative Example 13 L-zone volume average particle size 0.91μ, 100 ° C after moisture absorption
Weight loss on heating at 0.08% by weight, BET specific surface area 9.5 m ² / g
A developer was prepared in the same manner as in Example 11 except that 1 part by weight of cerium oxide particles containing 72.5% by weight of CeO ₂ was used. The test results are shown in Table 4.

Comparative Example 14 A developer was obtained in the same manner as in Example 11 except that 0.4 part by weight of non-hydrophobicized silica having a hydrophobicity of 0 and an average particle size of 0.007 μ was used. The test results are shown in Table 4.

Example 21 The mixture having the above formulation is melt-kneaded, cooled, pulverized, and classified to have a negatively charged insulating magnetic toner having a particle size of 5 to 20 μ (volume average particle size of about 12 μ) (electric resistance value 10 ¹⁵ Ω · cm; tribo value − 9 μc /
g) was obtained. To 100 parts by weight of the obtained insulating magnetic toner, 0.4 parts by weight of negatively-charged hydrophobic silica having a hydrophobicity of about 65 and an average primary particle size of 0.007 μ (tribo value −110 μc / g) and 8 parts of CeO ₂ component are added.
Cerium oxide particles containing 0% by weight [volume average particle diameter by L-Zone Counter (manufactured by US Particle Data Co.) 2.74μ, loss on heating to 100 ° C. after moisture absorption 0.14% by weight,
A developer was prepared by mixing with 1 part by weight of BET specific surface area 3.6 m ₂ / g] measured by an automatic measurement device for specific surface area 2200 type (manufactured by Shimadzu Corporation) by nitrogen gas adsorption method. The tribo value of the cerium oxide particles was -1 μc / g.

When this developer was applied to a commercially available plain paper copier (NP-400 Canon) and 500 continuous copies were made to obtain images,
Image reflection density is 1.23 for the first sheet, 1.19 for the 20th sheet, 1.2 for the 50th sheet
There is no drop in the image density in the initial copying with 1.2 for the 100th sheet, 1.22 for the 500th sheet, and 1.20 for the 500th sheet.
The image was stable, free from fog, and extremely clear. Further, the developer of the present invention has a high temperature and high humidity (32.5 ° C, 90%
%) And low temperature and low humidity (15 ° C, 10%) environment, the development characteristics were as good as normal temperature and normal humidity.

Examples 22 to 26 Respective developers were prepared in the same manner as in Example 21, except that the cerium oxide particles B to F shown in Table 5 below were used. The results of the image forming test conducted in the same manner as in Example 21 are shown in Table 6.

Example 27 A hydrophobic silica having a degree of hydrophobicity of about 50 and an average primary particle size of 0.016μ was used.
A developer was prepared in the same manner as in Example 30, except that 0.4 part by weight was used. The results of the image forming test are shown in Table 2.

Example 28 A current preparation was prepared in the same manner as in Example 30 except that 100 parts by weight of a styrene-2-ethylhexyl acrylate copolymer (copolymerization ratio 8: 2; Mw = 180,000) was used as a binder resin. Was prepared. The results of the image forming test are shown in Table 8.

Example 29 Styrene-n-pentyl acrylate as a binder resin
Maleic acid monobutyrate copolymer (copolymerization ratio 70: 25: 5;
A developer was prepared in the same manner as in Example 21, except that 100 parts by weight of Mw = 380,000) was used. The results of the image forming test are shown in Table 6.

Example 30 A developer was prepared in the same manner as in Example 21 except that 2 parts by weight of the alkylsalicylic acid Mn complex was used as the charge control agent. The results of the image forming test are shown in Table 6.

Comparative Example 15 100 parts by weight of the magnetic toner prepared in Example 21 without adding cerium oxide particles, a hydrophobicity of about 65, and an average primary particle size of 0.007.
A developer was prepared by mixing with 0.4 part by weight of hydrophobic silica of μ, and an image forming test was conducted in the same manner as in Example 21.
Reflection density 1.08 for the first sheet, 0.87 for the 20th sheet, 0.62 for the 50th sheet, 100
The image density was low at 0.66th sheet and 0.98th sheet at 500th sheet, and a falling phenomenon was observed.

Comparative Example 16 100 parts by weight of the magnetic toner prepared in Example 21 was used, and 0.4 part by weight of non-hydrophobicized silica having an average particle size of 0.016 μ was used for 100 parts by weight of the magnetic toner.
2.3% weight loss on heating at 100 ° C, specific surface area by BET method 39.
63.2% by weight of CeO ₂ which is 0 m ² / g (outside the specified range of the present invention)
A developer was prepared by mixing 1 part by weight of the contained cerium oxide particles. At the time of 50 to 100 copies, a remarkable falling phenomenon was observed.

Comparative Example 17 Ersol-based volume average particle size of 1.64μ, 100 ° C after moisture absorption
Loss on heating at 1.08% by weight (outside the specified range of the present invention), BET
A developer was prepared in the same manner as in Example 21 except that 1 part by weight of cerium oxide particles containing 53% by weight of CeO ₂ having a specific surface area of 8.1 m ² / g according to the method was used. The test result is No. 6
Shown in the table.

Comparative Example 18 L-zone volume average particle size 1.47μ, 100 ° C after moisture absorption
Loss on heating at 1.50% by weight, specific surface area by BET method 18.0 m ² /
A developer was obtained in the same manner as in Example 21 except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO _{2 (} g) was used. The test results are shown in Table 6.

Comparative Example 19 L-zone volume average particle size 4.52μ, 100 ° C after moisture absorption
Loss on heating at 0.14% by weight, specific surface area by BET method 1.8 m ² / g
A developer was prepared in the same manner as in Example 21 except that 1 part by weight of cerium oxide particles containing 51.8% by weight of CeO ₂ was used. The test results are shown in Table 6.

Comparative Example 20 L-zone volume average particle size 0.91μ, 100 ° C after moisture absorption
A developer was prepared in the same manner as in Example 21 except that 1 part by weight of cerium oxide particles containing 72.5% by weight of CeO ₂ having a specific surface area of 9.5 m ² / g by BET method was used. Was prepared. The test results are shown in Table 6.

Comparative Example 21 A developer was obtained in the same manner as in Example 21 except that 0.4 part by weight of non-hydrophobicized silica having a hydrophobicity of 0 and an average particle diameter of 0.007 μm was used. The test results are shown in Table 6.

Example 31 The mixture of the above formulation is melt-kneaded, cooled and then pulverized and classified to have a negatively charged insulating magnetic toner having a particle size of 5 to 20 μ (volume average particle size of about 12 μ) (electric resistance value 10 ¹⁵ Ω · cm; tribo value −13 μc / g)
Got 100 parts by weight of the obtained insulating magnetic toner contains 0.4 parts by weight of hydrophobic silica (tribo value −110 μc / g) having a hydrophobicity of about 65 and an average primary particle size of 0.007 μ and 80% by weight of CeO ₂ component. Cerium oxide particles [Volume average particle size 2.74μ by L-Zone Counter (manufactured by US Particle Data Co., Ltd.),
0.14% by weight loss on heating to 100 ° C after moisture absorption, mixed with 1 part by weight of BET specific surface area 3.6m ² / g] measured by automatic surface area measuring device Model 2200 (manufactured by Shimadzu) by nitrogen gas adsorption method A developer was prepared. The tribo value of the cerium oxide particles was -1 μc / g.

When this developer was applied to a commercially available plain paper copier (NP-400 Canon) and 500 continuous copies were made to obtain images,
Image reflection density is 1.26 for the first sheet, 1.23 for the 20th sheet, 1.2 for the 50th sheet
The first, 1.25th, and 500th sheets, 1.26, and the image density does not fall in the initial copy, and the reflection density is approximately 1.24 throughout.
The image was stable, free from fog, and extremely clear. Further, the developer of the present invention has a high temperature and high humidity (32.5 ° C, 90%
%) And low temperature and low humidity (15 ° C, 10%) environment, the development characteristics were as good as normal temperature and normal humidity.

Examples 32-36 Respective developers were prepared in the same manner as in Example 31, except that the cerium oxide particles shown in Table 7 below were used. The results of the image forming test conducted in the same manner as in Example 31 are shown in Table 8.

Example 37 A hydrophobic silica having a degree of hydrophobicity of about 50 and an average primary particle size of 0.016μ was used.
A developer was prepared in the same manner as in Example 31 except that 0.4 part by weight was used.

The results of the image forming test are shown in Table 8.

Example 38 Development was carried out in the same manner as in Example 31 except that 100 parts by weight of a styrene-2-methylhexyl acrylate copolymer (copolymerization weight ratio 6: 3; Mw = 195,000) was used as a binder resin. The agent was prepared. The results of the image forming test are shown in Table 8.

Example 39 Styrene-n-methylmethacrylate-as a binder resin
Maleic acid monobutyrate copolymer (copolymerization ratio 70: 25: 5;
A developer was prepared in the same manner as in Example 31 except that 100 parts by weight of Mw = 390,000) was used. The results of the image forming test are shown in Table 8.

Example 40 A developer was prepared in the same manner as in Example 31 except that 2 parts by weight of the alkylsalicylic acid Co complex was used as the charge control agent. The results of the image forming test are shown in Table 8.

Comparative Example 22 100 parts by weight of the magnetic toner prepared in Example 31 without adding cerium oxide particles, a hydrophobicity of about 65, and an average primary particle size of 0.007.
A developer was prepared by mixing with 0.4 part by weight of hydrophobic silica of μ, and an image forming test was conducted in the same manner as in Example 31.
Reflection density 0.98 for the first sheet, 0.80 for the 20th sheet, 0.58 for the 50th sheet, 100
The image density was low at 0.57 for the 1st sheet and 1.02 for the 500th sheet, and a falling phenomenon was observed.

Comparative Example 23 100 parts by weight of the magnetic toner prepared in Example 31 was used, 0.4 part by weight of non-hydrophobicized silica having an average particle size of 0.016 μ and 0.4 part by weight of silica having an average particle size of 0.016 μ, and a volume average particle size of 3.25 μ by the L-zone.
2.3% weight loss on heating at 100 ° C, specific surface area by BET method 39.
63.2% by weight of CeO ₂ which is 0 m ² / g (outside the specified range of the present invention)
A developer was prepared by mixing 1 part by weight of the contained cerium oxide particles. At the time of 50 to 100 copies, a remarkable falling phenomenon was observed.

Comparative Example 24 Elsol volume average particle size 1.64μ, 100 ° C after moisture absorption
Loss on heating at 1.08% by weight (outside the specified range of the present invention), BET
A developer was obtained in the same manner as in Example 31 except that 1 part by weight of cerium oxide particles containing 53% by weight of CeO ₂ having a specific surface area of 8.1 m ² / g according to the method was used. The test results are shown in Table 8.

Comparative Example 25 L-zone volume average particle size 1.47μ, 100 ° C after moisture absorption
Loss on heating at 1.50% by weight, specific surface area by BET method 18.0 m ² /
A developer was obtained in the same manner as in Example 31 except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO _{2 (} g) was used. The test results are shown in Table 8.

Comparative Example 26 L-zone volume average particle diameter of 4.52μ, 100 ° C after moisture absorption
Loss on heating at 0.14% by weight, specific surface area by BET method 1.8 m ² / g
A developer was obtained in the same manner as in Example 31 except that 1 part by weight of cerium oxide particles containing 51.8% by weight of CeO ₂ was used. The test results are shown in Table 8.

Comparative Example 27 1 part by weight of cerium oxide particles containing 0.91μ in volume average particle size by L zone, 0.08% by weight loss by heating at 100 ° C. after moisture absorption, and 72.5% by weight CeO ₂ having a specific surface area of 9.5 m ² / g by BET method. A developer was prepared in the same manner as in Example 31 except that was used. The test results are shown in Table 8.

Comparative Example 28 A developer was obtained in the same manner as in Example 31 except that 0.4 part by weight of non-hydrophobicized silica having a hydrophobicity of 0 and an average particle diameter of 0.007 μm was used. The test results are shown in Table 8.

Example 41 The mixture having the above formulation is melt-kneaded, cooled, pulverized, and classified to have a negatively charged insulating magnetic toner having a particle size of 5 to 20 μ (volume average particle size of about 12 μ) (electric resistance value 10 ¹⁵ Ω · cm; tribo value − 8 μc /
g) was obtained. 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 0.007 μ (tribo value −110 μc / g) and 80% by weight of CeO ₂ component are added.
Cerium oxide particles contained [L-zone counter (manufactured by US Particle Data Corp.) volume average particle size 2.74
μ, heating loss up to 100 ° C after moisture absorption 0.14% by weight, mixed with 1 part by weight of BET specific surface area 3.6m ² / g] measured by automatic specific surface area measuring device Model 2200 (manufactured by Shimadzu) by nitrogen gas adsorption method To prepare a developer. The tribo value of the cerium oxide particles was -1 μc / g.

When this developer was applied to a commercially available plain paper copier (NP-400 Canon) and 500 continuous copies were made to obtain images,
Image reflection density is 1.42 for the first sheet, 1.40 for the 20th sheet, 1.4 for the 50th sheet
1.100th sheet 1.40, 500th sheet 1.44 and no drop in image density in the initial copy.
And stable, no fog and extremely clear images can be obtained. Further, the developer of the present invention has a high temperature and high humidity (32.5 ° C, 90%
%) And low temperature and low humidity (15 ° C, 10%) environment, the development characteristics were as good as normal temperature and normal humidity.

Examples 42-46 Respective developers were prepared in the same manner as in Example 41, except that the cerium oxide particles shown in Table 9 below were used. The results of the image forming test conducted in the same manner as in Example 41 are shown in Table 10.

Example 47 A hydrophobic silica having a hydrophobicity of about 50 and an average primary particle size of 0.016 μ
A developer was prepared as in Example 41, except that 0.4 part by weight was used. The results of the image forming test are shown in Table 10.

Example 48 A present agent was prepared in the same manner as in Example 41, except that 100 parts by weight of a styrene-butyl acrylate copolymer (copolymerization weight ratio 7: 2; Mw = 200,000) was used as a binder resin. did. The results of the image forming test are shown in Table 10.

Example 49 Styrene-n-butyl acrylate-maleic acid monobutyrate copolymer as a binder resin (copolymerization ratio 60: 35: 5; Mw
= 350,000) A developer was prepared in the same manner as in Example 41, except that 100 parts by weight was used. The results of the image forming test are shown in Table 10.

Example 50 A developer was prepared in the same manner as in Example 41, except that 2 parts by weight of the EDTA nickel complex was used as the charge control agent. The results of the image forming test are shown in Table 10.

Comparative Example 29 Without adding cerium oxide particles, 100 parts by weight of the magnetic toner prepared in Example 50, hydrophobicity of about 65, and average primary particle size of 0.15
A developer was prepared by mixing with 0.4 part by weight of hydrophobic silica of μ, and an image forming test was conducted in the same manner as in Example 41.
Reflection density 1.33 for the first sheet, 1.13 for the 20th sheet, 0.90, 100 for the 50th sheet
The image density was low at 0.89th sheet and 1.13th sheet at 500th sheet, and a falling phenomenon was observed.

Comparative Example 30 100 parts by weight of the magnetic toner prepared in Example 41 was used, 0.4 part by weight of non-hydrophobicized silica having an average particle size of 0.25 μ, 0.4 part by weight of silica having an average particle size of 0.25 μ, and a volume average particle size of 3.25 μ by L-zone, after moisture absorption.
2.3% weight loss on heating at 100 ° C, specific surface area by BET method 39.
63.2% by weight of CeO ₂ which is 0 m ² / g (outside the specified range of the present invention)
A developer was prepared by mixing 1 part by weight of the contained cerium oxide particles. At the time of 50 to 100 copies, a remarkable falling phenomenon was observed.

Comparative Example 31 Volume average particle diameter of 1.64μ by L-zone, heating after moisture absorption at 100 ° C. 1.08 wt% (outside of the specified range of the present invention), and 53 wt% of CeO ₂ having a specific surface area of 8.1 m ² / g by BET method Example except that 1 part by weight of cerium oxide particles to be used is used
A developer was obtained in the same manner as in 41. The test results are shown in Table 10.

Comparative Example 32 Volume average particle diameter by L zone 1.47μ, heat loss after moisture absorption at 100 ° C. 1.50% by weight, specific surface area by BET method 18.0 m ² / g
A developer was prepared in the same manner as in Example 41, except that 1 part by weight of cerium oxide particles containing 80% by weight of CeO ₂ was used. The test results are shown in Table 10.

Comparative Example 33 1 part by weight of cerium oxide particles containing 4.52μ by volume average particle diameter by L zone, 0.14% by weight loss by heating at 100 ° C. after moisture absorption, 51.8% by weight of CeO ₂ having a specific surface area of 18 m ² / g by the BET method. A developer was prepared in the same manner as in Example 41 except that it was used. The test results are shown in Table 10.

Comparative Example 34 L-zone volume average particle size 0.91μ, 100 ° C after moisture absorption
Weight loss on heating at 0.08% by weight, BET specific surface area 9.5 m ² / g
A developer was prepared in the same manner as in Example 41, except that 1 part by weight of cerium oxide particles containing 72.5% by weight of CeO ₂ was used. The test results are shown in Table 10.

Comparative Example 35 A developer was obtained in the same manner as in Example 41 except that 0.4 part by weight of non-hydrophobicized silica having a hydrophobicity and an average particle size of 0.007 μm was used. The test results are shown in Table 10.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing an apparatus for measuring the triboelectric charge amount of a toner or fine particle sample. 1 ... Suction machine 2 ... Measuring device 3 ... Conductive screen 4 ... Lid 5 ... Vacuum gauge 6 ... Wind force control valve 7 ... Suction port 8 ... Capacitor 9 ... Electrometer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keita Nozawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yusuke Karami 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (56) Reference JP-A-6-12462 (JP, A) JP-A-6-12461 (JP, A)

Claims (2)

[Claims] 1. A negatively chargeable insulating magnetic toner particle containing at least a binder resin and a magnetic material (excluding toner particles containing a chromium organic complex compound or a zinc organic complex compound), and a volume average particle size. Is 1.0 to 4.0 μm,
Heat loss up to 100 ℃ is 0.5 wt% or less, BET specific surface area by nitrogen gas adsorption method is 15 m ² / g or less and CeO ₂
An insulating magnetic dry developer comprising cerium oxide particles containing as a main component, and negatively-charged hydrophobized silicon oxide fine particles. 2. The cerium oxide particles in an amount of 0.1 to 5 parts by weight and the hydrophobized silicon oxide fine particles in an amount of 0.01 to 3 parts by weight per 100 parts by weight of the negatively chargeable insulating magnetic toner particles. Insulating magnetic dry developer.