JP3180158B2 - Electrostatic image developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developer applied to, for example, electrophotography, electrostatic recording, electrostatic printing, and the like.

[0002]

2. Description of the Related Art For example, as an electrostatic image developer for electrophotography, a technique of adding inorganic fine particles in order to improve the cleaning property has been known (Japanese Patent Application Laid-Open No. 60-32060;
No. 60-136752). However, the method of adding the inorganic fine particles has a problem that the photoreceptor itself is damaged and its durability is reduced due to a large polishing effect. On the other hand, a technique using organic fine particles as a cleaning aid has been proposed (see JP-A-53-84741 and JP-A-60-186851). However, these techniques are still insufficient in the effect of polishing the photoreceptor necessary for achieving good cleaning. For this reason, a phenomenon in which deposits such as toner accumulate on the surface of the photoconductor occurs, and problems such as a decrease in durability of the photoconductor occur. On the other hand, there has been proposed a technique using composite fine particles in which inorganic fine particles are fixed to the surface of resin fine particles having a diameter smaller than that of the colored particles and an average particle diameter of 0.05 to 3.0 μm (see JP-A-64-91143). . This technology is
The purpose is to maintain the surface of the photoreceptor in a good state by the polishing action of the composite fine particles and to improve the cleaning property.

[0003]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No.
In the developer disclosed in Japanese Patent No. 1143, since the composite fine particles are present in the colored particles in a free state, there is a problem that the chargeability of the colored particles is changed by frictional charging with the colored particles. That is, since the composite fine particles act as a carrier for the colored particles, so to speak, there is a problem that the charge amount of the colored particles is reduced depending on the chargeability of the composite fine particles, and the image density is reduced. In particular, in the developing method of forming a thin layer, there is a problem that the transportability of the developer is deteriorated due to the colored particles charged to the opposite polarity.

The present invention has been made in view of the above circumstances, and an object of the present invention is to control the triboelectric charging of composite fine particles to stabilize the charge amount of colored particles and reduce image density. Accordingly, an object of the present invention is to provide an electrostatic image developer having excellent transportability without inducing.

[0005]

In order to achieve the above objects, the electrostatic image developer of the present invention comprises a colored particle comprising at least a resin and a coloring agent, and the surface of the resin fine particle being uniformly covered. And a triboelectric charge amount H (Q / M) of the composite fine particles in an electrostatic image developer containing inorganic fine particles fixed to the colored particles and composite fine particles existing in a free state in the colored particles. The triboelectric charge amount T (Q
/ M) and the electrostatic image developer der consisting of one-component toner and satisfies the relation represented by the following formula and
You . Formula [T (Q / M)] × [H (Q / M)] < 0 Formula 20 ≧ | H (Q / M) |

[0006]

[Function] As a result of intensive studies conducted by the present inventors, colored particles were obtained.
By controlling the chargeability of the composite fine particles that are present in a free state, the charge amount of the colored particles can be improved, the image density can be improved, the generation of colored particles of the opposite polarity can be prevented, and stable The inventors have found that an image can be formed and completed the present invention. That is, the table of resin fine particles
Inorganic fine particles are fixed on the surface so as to cover the surface uniformly
Since the composite fine particles are constituted and the charged polarity of the composite fine particles and the colored particles is different, the composite fine particles exhibit a function as a so-called carrier with respect to the colored particles, and can increase the charge amount of the colored particles, and the image density can be increased. Is improved. Also,
Since the absolute value of the charge amount of the composite fine particles is 20 μC / g or less, the charge amount of the colored particles does not become excessive, and therefore, there is no possibility that the non-image area is developed, and the transportability of the colored particles increases with time. There is no danger of lowering.

Hereinafter, the present invention will be described specifically. In the present invention, the triboelectric charge amount H (Q / M) of the composite fine particles,
The developer is constituted by using the composite fine particles and the colored particles that satisfy the relationship represented by the above formula and the triboelectric charge amount T (Q / M) of the colored particles. The triboelectric charge amount H (Q /
M) and the triboelectric charge T (Q / M) of the colored particles were measured as follows. That is, iron powder "DSP-138" (made by Powder Tech) as a carrier
With colored particles and composite fine particles,
Weight percent, and mix at a temperature of 20 ° C and relative humidity.
Shake for 20 minutes using a shaker under 50% environmental conditions. Then, under the same environmental conditions, the charge amount generated by separating from the mesh by a so-called nitrogen gas flow, that is, the blow-off charge amount, is measured by a blow-off powder charge amount measuring apparatus “TB-200” (manufactured by Toshiba Chemical Corporation).

In the developing method of forming a thin layer, the colored particles are charged mainly by friction with the developing sleeve. Therefore, the actual amount of frictional charge is measured by the amount of charge generated by friction with the developing sleeve. Is preferred. However, in practice, the amount of frictional charge with the developing sleeve can be measured by performing air blowing from the developing sleeve itself. However, since the amount of generated charge itself becomes a very small value, a measurement error is large. Therefore, in the present invention, as described above, the frictional charge amount of the composite fine particles and the colored particles is defined by the frictional charge with a material similar to the surface of the developing sleeve, that is, with the iron powder. According to the iron powder, the triboelectric charge amount can be easily and reliably measured.

When the triboelectric charge amount H (Q / M) of the composite fine particles and the triboelectric charge amount T (Q / M) of the colored particles satisfy the above expression, the charge amount of the colored particles is improved, and the density is improved. Further, it is possible to obtain a stable image without fogging in which generation of colored particles having the opposite polarity is prevented. However, when the above formula is not satisfied, that is, when the charged polarity of the colored particles and the composite fine particles is the same, the charged amount of the colored particles decreases, and the image density decreases with time. Further, a phenomenon occurs in which the composite fine particles adhere to the surface of the developing sleeve according to the developing bias and contaminate the surface of the developing sleeve. For this reason, the effect of the bias is reduced, the phenomenon that the concentration is reduced occurs, and the colored particle layer becomes excessive, the photoreceptor is violently rubbed by the colored particles, and the colored particles adhere to the non-image area, so-called fog is formed. There are problems that occur. When the above expression is not satisfied, that is, the triboelectric charge amount H of the composite fine particles
If the absolute value of (Q / M) exceeds 20 μC / g, the amount of triboelectricity of the colored particles becomes excessive, causing a phenomenon that the non-image area is also developed, and so-called fog occurs. In addition, the transportability of the colored particles changes over time, and the transport amount on the developing sleeve becomes excessive. As a result, fog is further caused in the image.

The composite fine particles used in the present invention are obtained by fixing inorganic fine particles to the surface of resin fine particles.
The resin fine particles constituting the composite fine particles have an average particle diameter of 0.1 to 7 from the viewpoint of cleaning properties and triboelectric charging properties.
μm, particularly preferably 0.2 to 5 μm. The average particle size of the resin fine particles refers to the volume-based average particle size, and is a laser diffraction type particle size distribution analyzer “HELOS” equipped with a wet disperser (SYMPAT (SYMPAT)
EC). However, before measurement, several 10 mg of resin fine particles were dispersed in 50 ml of water together with a surfactant, and then an ultrasonic homogenizer (output 150 W)
Pre-dispersion was performed for 1 to 10 minutes while paying attention to re-aggregation due to heat generation.

[0011] As a resin material constituting the resin fine particles,
Various resins are used without any particular limitation. For example, styrene resin such as styrene, α-methylstyrene, divinylbenzene, etc., methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, acrylic resin such as butyl acrylate, styrene, α A copolymer of a styrene monomer such as methylstyrene and divinylbenzene with an acrylic monomer such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate and butyl acrylate; A styrene-acrylic copolymer,
Dimethylaminomethacrylate, diethylaminomethacrylate, nitrogen-containing resin containing vinylpyridine and the like, Teflon, fluorine-containing resin containing vinylidene fluoride and the like,
Polyolefins such as polypropylene and polyethylene,
Nylon resin, urethane resin, urea resin and the like can be mentioned.

Means for obtaining resin fine particles composed of the above resins include a method of synthesizing a monomer by a polymerization reaction such as emulsion polymerization or suspension polymerization using a monomer, or melting the resin itself by heat or the like. Examples thereof include a method of atomizing by spraying and a method of dispersing in water or the like to obtain a predetermined particle size. In the case where the resin fine particles are produced by a polymerization method, a so-called soap-free polymerization method is preferably used so that a surfactant or the like does not remain on the surface of the resin fine particles in order to stabilize the chargeability. A method of removing the suspension stabilizer may be used.

As the inorganic fine particles constituting the composite fine particles, those having an average primary particle diameter of 5 to 200 nm are preferable, and especially 10 to 100 nm, from the viewpoint of enhancing the cleaning property.
nm is preferred. In addition, the primary average particle diameter of the inorganic fine particles refers to a number average particle diameter measured by image analysis observed with a scanning electron microscope. As the inorganic material constituting the inorganic fine particles, various inorganic oxides, carbides, nitrides,
Borides and the like are preferably used. For example, silica, alumina, titania, zirconia, barium titanate, aluminum titanate, strontium titanate, magnesium titanate, calcium titanate, zinc oxide, chromium oxide, cerium oxide, antimony oxide, tungsten oxide, tin oxide, tellurium oxide , Manganese oxide, boron oxide, silicon carbide, boron carbide, titanium carbide, silicon nitride, titanium nitride, titanium nitride, boron nitride and the like.

In order to control the triboelectric charge H (Q / M) of the composite fine particles, the chargeability of these inorganic materials is important. As a method of controlling the chargeability, a method of controlling the chargeability by changing the material itself fixed to the surface of the resin fine particles is effective. That is, it is fundamental to select a material having a different charging polarity from the colored particles. Further, a method of combining materials having different charging properties and fixing them to the surface is also an effective method. The chargeability can also be changed by treating the surface of the inorganic fine particles with a surface treatment agent such as a titanium coupling agent, a silane coupling agent, a long-chain carboxylic acid, or a surfactant.

Examples of the titanium coupling agent include tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, and bis (dioctyl pyrophosphate) oxyacetate titanate. As a silane coupling agent,
γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoacetyl) aminopropylmethyldimethoxysilane, aminosilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-anilinopropyltrimethoxysilane, methyltrichlorosilane , Dimethyldichlorosilane, trimethylchlorosilane, and γ-glycidoxypropyltrimethoxysilane.

The long-chain carboxylic acids include undecylic acid,
Lauric acid, tridecylic acid, myristic acid, pentadecylic acid, stearic acid, palmitic acid, heptadecylic acid,
Long-chain carboxylic acids having 10 or more carbon atoms, such as arachinic acid, montanic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid. Examples of the surfactant include general surfactants such as a sorbitan surfactant, a sulfonic acid surfactant, a phosphoric acid surfactant, and a fluorine surfactant.

In the above-mentioned surface treatment, the inorganic fine particles treated with the material containing an amino group generally have positive charging properties, and the composite fine particles obtained by using these inorganic fine particles have positive charging properties. In general, inorganic fine particles treated with a material containing a halogen element such as fluorine exhibit negative chargeability. The chargeability of these materials can be determined by measuring the amount of triboelectric charge with the iron powder carrier. When treating the surface of the inorganic fine particles, it is preferable to mix the inorganic fine particles and the above-mentioned surface treating agent, disperse them in a solvent or the like, perform heating or the like, perform treatment for a predetermined time, and then perform filtration and drying.

It is also possible to treat the surface using an inorganic material in addition to the above-mentioned organic material. That is, the surface can be treated by treating a material such as alumina or iron oxide by a method such as anodic oxidation or plating. Further, it is also possible to adjust the charge amount by mixing two or more materials that adhere to the surface. That is, the charge amount may be adjusted by using an appropriate amount of a positively charged material and a negatively charged material. Further, the chargeability of the resin fine particles themselves may affect the chargeability of the composite fine particles. For example, in the case of nitrogen-containing resin fine particles exhibiting a large positive chargeability as resin fine particles, this chargeability affects the chargeability of the composite fine particles, and positive chargeable composite fine particles can be obtained. Also,
When a fluorine-based resin having a large negative chargeability is used, it is easy to obtain negatively chargeable composite fine particles.

As a method of fixing the inorganic fine particles to the surface of the resin fine particles, the resin fine particles and the inorganic fine particles are mixed, the inorganic fine particles are electrostatically adhered to the surface of the resin fine particles, and then mechanical energy is applied. A method of fixing inorganic fine particles to the surface of resin fine particles can be used. Examples of a method for electrostatically adhering the inorganic fine particles to the surface of the resin fine particles include a method in which the resin fine particles and the inorganic fine particles are put into a mixer such as a turbuler mixer, a Laedige mixer, a Henschel mixer or the like, and stirred. No.

As methods for applying mechanical energy, "Hybridizer" (manufactured by Nara Kikai Seisakusho), "Ongmill" (manufactured by Hosokawa Micron), and "Kryptron" (manufactured by Kawasaki Heavy Industries), which are improved impact-type pulverizers, are used. And the like. The degree of sticking changes depending on the magnitude of this mechanical energy, but this mechanical energy is
For example, it can be adjusted by the peripheral speed of the stirring blade, the stirring time, the product temperature at the time of processing, and the like.

The amount of the inorganic fine particles to be added to the fine resin particles may be an amount capable of uniformly covering the surface of the fine resin particles. Specifically, although it varies depending on the specific gravity of the inorganic fine particles, it is preferably 5 to 100 parts by weight, particularly preferably 5 to 80 parts by weight, per 100 parts by weight of the resin fine particles. For example, when the addition amount of the inorganic fine particles is too small, the surface of the composite fine particles becomes non-uniform, and the chargeability of the composite fine particles may change, making it difficult to obtain a desired charge amount. Since a large amount of resin is present in the resin, the polishing effect may be reduced. On the other hand, when the amount of addition of the inorganic fine particles is excessive, the amount of the inorganic fine particles becomes excessive with respect to the surface of the resin fine particles, free inorganic fine particles are generated, and the appropriate chargeability of the composite fine particles is changed, and the predetermined charge amount is changed. In some cases, it may be difficult to obtain the toner, and in addition, excessive inorganic fine particles may adhere to the photoreceptor, resulting in poor cleaning.

The amount of the composite fine particles added to the colored particles is as follows:
From the viewpoint of enhancing the cleaning property by the polishing effect, and not hindering the triboelectric charging property of the colored particles, the content of the colored particles is 0.1%.
It is preferably from 0.01 to 5% by weight, particularly preferably from 0.01 to 2% by weight. It is also possible to add a fluidity improver such as hydrophobic silica or a fatty acid metal salt before use. When adding and mixing, it is preferable that the compound be present in a free state, not in a state of being fixed to the colored particles. When mixing, it is preferable to use a turbular mixer, Henschel mixer or the like.

The colored particles contain a binder resin, a colorant, and other additives such as a charge control agent used as needed. The average particle size is usually 1 to 30 μm. Range. The charging polarity of the colored particles themselves is determined by the developing method. The chargeability of the colored particles can be controlled by the type and amount of the charge control agent, the combination with the resin, and the like. The binder resin constituting the colored particles is not particularly limited,
Conventionally known various resins are used. For example, polyester resin, styrene / acrylic resin and the like are typical examples. As a coloring agent constituting the colored particles,
There is no particular limitation, and various conventionally known coloring agents are used. Examples include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, and the like.

Other additives include charge control agents such as salicylic acid derivatives, and fixability improvers such as low molecular weight polyolefins. When a magnetic toner is obtained, magnetic particles are contained in the colored particles as an additive. As such magnetic particles, particles such as ferrite and magnetite having an average particle diameter of 0.1 to 2 μm are used. The amount of the magnetic particles added is usually 20 to 70% by weight of the colored particles excluding external additives such as composite fine particles.
Is the range.

Further, from the viewpoint of enhancing the fluidity of the toner,
In addition to the colored particles and the composite fine particles, inorganic fine particles may be further added from the outside to constitute the toner. As such inorganic fine particles, particularly, silica fine particles which have been subjected to a hydrophobic treatment with a silane coupling agent, a titanium coupling agent or the like are preferable.

Although the developer of the present invention can be used in combination with various conventionally known developing methods, it can be suitably used particularly for a thin layer forming type developing method. In order to form a thin layer, it is necessary to form a thin toner layer on the surface of the developing sleeve. Here, the thin layer refers to a toner layer of 20 to 500 μm in the development area. In order to form such a thin layer on the developing sleeve, it is necessary to regulate the toner to a height of about 20 to 500 μm when transporting the toner to the surface of the developing sleeve. In this case, a method using a magnetic blade capable of utilizing the magnetic force of the toner is preferable. There is also a toner layer regulating method of pressing a toner layer regulating rod against the surface of the developing sleeve. In this case, it is preferable to press the regulating rod against the surface of the developing sleeve by a magnetic force. Furthermore, a urethane blade, a phosphor bronze plate or the like can be brought into contact with the surface of the developing sleeve to form a thin layer. The gap between the surface of the developing sleeve and the surface of the photoconductor may be larger or smaller than the thickness of the toner layer. Further, the developing bias may be a DC component only.
C bias may be applied simultaneously.

[0027]

EXAMPLES Hereinafter, more specific examples will be described, but the present invention is not limited to these examples. In the following, “parts” means “parts by weight”.

Composite Fine Particles H-1 100 parts of resin fine particles composed of styrene / acrylic resin fine particles (average particle size = 1.8 μm) synthesized by an emulsion polymerization method and titanium oxide (primary average particle size = 15 nm) were treated with lauric acid. 17 parts of the inorganic fine particles subjected to the surface treatment were added, and these were mixed by a high-speed stirring device to electrostatically adhere the inorganic fine particles to the surface of the resin fine particles. Next, the mixture was transferred to a “Hybridizer” (manufactured by Nara Machinery Co., Ltd.), and a mechanical impact was applied to fix the inorganic fine particles on the surface of the resin fine particles to obtain composite fine particles H-1.

Composite Fine Particles H-2 Composite fine particles H-2 were prepared in the same manner as composite fine particles H-1, except that inorganic fine particles were obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with aluminum oxide. Fine particles H-2 were obtained.

Composite Fine Particles H-3 Composite fine particles H-1 were prepared in the same manner as composite fine particles H-1 except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with tetraoctyl titanate. Composite fine particles H-3 were obtained.

Composite Fine Particles H-4 Composite fine particles H-4 were obtained in the same manner as composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles made of aluminum oxide (primary average particle size = 20 nm). .

Composite Fine Particles H-5 Composite fine particles H-5 were prepared in the same manner as composite fine particles H-1, except that inorganic fine particles were obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with stearic acid. Fine particles H-5 were obtained.

Composite Fine Particles H-6 The same as the composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with stearic acid and aluminum oxide. Thus, composite fine particles H-6 were obtained.

Composite Fine Particles H-7 The same as the composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with lauric acid and aluminum oxide. Thus, composite fine particles H-7 were obtained.

Composite Fine Particles H-8 The same as the composite fine particles H-1 except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with stearic acid and iron oxide. Thus, composite fine particles H-8 were obtained.

Composite Fine Particles H-9 Composite fine particles H-9 were prepared in the same manner as composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with a fluorine surfactant. Thus, composite fine particles H-9 were obtained.

Composite Fine Particles H-10 Composite fine particles H-10 were prepared in the same manner as composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating titanium oxide (primary average particle size = 15 nm) with hexamethylsilazane. Composite fine particles H-10 were obtained.

Composite Fine Particles H-11 Composite fine particles H-11 were prepared in the same manner as composite fine particles H-1, except that the inorganic fine particles were changed to inorganic fine particles obtained by surface-treating aluminum oxide (primary average particle size = 15 nm) with lauric acid. Fine particles H-11 were obtained.

Composite Fine Particles H-12 Composite fine particles H-12 were prepared in the same manner as composite fine particles H-1, except that inorganic fine particles obtained by surface-treating zirconium oxide (primary average particle size = 15 nm) with lauric acid were used. Fine particles H-12 were obtained.

Composite Fine Particles H-13 In the composite fine particles H-1, the resin fine particles were mixed with nylon particles (average particle size = 2.5 μm) obtained by a suspension reaction in water.
m-13) to obtain composite fine particles H-13 in the same manner.

Composite Fine Particles H-14 Composite fine particles H-14 were obtained in the same manner as composite fine particles H-14, except that 1 part of hydrophobic silica whose surface was treated with a methyl group was further added.

Composite Fine Particle H-15 Composite fine particle H-15 was obtained in the same manner as composite fine particle H-1, except that the inorganic fine particles were changed to hydrophobic silica (primary average particle size = 12 nm).

Magnetic colored particles 1 100 parts of polyester resin and 50 magnetic powder (magnetite)
Part, and 1 part of a negatively chargeable charge control agent (salicylic acid derivative) are mixed, and the mixture is ground, crushed, and classified by an ordinary method.
Magnetic colored particles 1 having an average particle size of 11 μm were obtained.

Magnetic Colored Particles 2 Magnetic colored particles 2 having an average particle size of 11.3 μm were obtained in the same manner as in magnetic colored particles 1 except that the polyester resin was changed to styrene / acrylic resin.

Magnetic Colored Particles 3 In the magnetic colored particles 1, magnetic colored particles 3 having an average particle size of 11.2 μm were similarly prepared except that the negatively chargeable charge control agent was changed to a positively chargeable charge control agent (nigrosine dye). I got

Measurement of Charge Amount The charge amounts of the composite fine particles and the magnetic colored particles were measured as follows. Regarding the composite fine particles, one part of each composite fine particle was replaced with iron powder “DSP-138” (manufactured by Powder Tech).
Add to 100 parts, shaker "Yayoi type NewYS-3"
After shaking for 20 minutes at an angle of 45 ° and 200 revolutions / minute by Yayoi Co., Ltd., room temperature and normal humidity (20 ° C, 50% R)
The charge amount of the composite fine particles was measured by a blow-off method under the environmental condition of H). For magnetic colored particles, the addition amount is 3
The charge amount of the magnetic colored particles was measured in the same manner as described above, except that the above-mentioned parts were used. The measurement results are shown in Table 1 below.

[0047]

[Table 1]

Examples 1 to 13 and Comparative Examples 1 to 6 In a combination shown in Table 2 below, 100 parts of magnetic colored particles, 0.4 parts of hydrophobic silica, and 0.5 parts of composite fine particles were mixed, and a one-component toner was prepared. Thus, a developer according to the present invention and a comparative developer were obtained. However, in Table 2, "R-972" is a product name manufactured by Degussa.

[0049]

[Table 2]

Evaluation A laser printer "LP-3015" (Konica Corporation) equipped with an organic photoconductive photoreceptor and a developing device fixed to a magnet roller and employing a contact developing system applying an AC bias.
Was used for evaluation. As a means for forming a thin layer, a toner layer regulation system of a magnetic blade system was adopted, and the thickness of the toner layer was set to 150 μm. The developing device is a system in which a developing sleeve having a diameter of 25 mm and a four-pole magnet roller is provided inside, and the magnet roller is fixed and only the developing sleeve is rotated. The photoreceptor has negative polarity.
With respect to the developers obtained in Examples 1 to 12 and Comparative Examples 1 to 3 and 5, the photoconductor potential was -250 V under the condition of -500 V.
The DC bias was applied, further frequency 2 kHz, were evaluated by applying an AC bias voltage -50V _PP ~- 450V _PP. On the other hand, with respect to the developers obtained in Example 13 and Comparative Examples 4 and 6, under the condition of the photoconductor potential of -500 V,-
A DC bias of 40 V is applied, and a frequency of 2 kHz,
The evaluation was performed by applying an AC bias of a voltage of −240 V _PP to +160 V _PP . The gap between the developing sleeve and the surface of the photoconductor is 100 μm. The evaluation was carried out 20,000 times under normal temperature and normal humidity (20 ° C., 50% RH) printing conditions, and the change in density, developer transportability and fog were evaluated. The density was measured using a reflection density measuring device “RD-914” (manufactured by Macbeth). The above results are shown in Table 3 below.

[0051]

[Table 3]

As is clear from Table 3 above, according to the developer of the present invention, a stable image having a stable density and no fog can be obtained. On the other hand, the comparative developer has a large change in concentration, and also has a deposit on the developing sleeve. Fog also occurs and a stable image cannot be obtained.

[0053]

As described above in detail, according to the present invention, by controlling the triboelectric charging property of the composite fine particles, the charge amount of the colored particles is stabilized, and the transport of the composite particles is prevented without lowering the image density. An electrostatic image developer having excellent properties can be provided.

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-2962 (JP, A) JP-A-64-91143 (JP, A)

Claims (1)

(57) [Claims] 1. A composite particle comprising a colored particle comprising at least a resin and a colorant, and an inorganic fine particle fixed to the surface of the resin fine particle so as to uniformly cover the surface of the resin fine particle. Wherein the triboelectric charge amount H (Q / M) of the composite fine particles and the triboelectric charge amount T (Q / M) of the colored particles are represented by the following formula and From a one-component toner characterized by satisfying
The electrostatic image developer comprising. Formula [T (Q / M)] × [H (Q / M)] < 0 Formula 20 ≧ | H (Q / M) |