JP3148993B2 - 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 using organic fine particles as a cleaning aid has been proposed (Japanese Patent Application Laid-Open Nos. 53-84741 and 60-18).
No. 6851). 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 technique is intended 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, when the inorganic fine particles are not sufficiently fixed to the surface of the resin fine particles, the inorganic fine particles are released from the composite fine particles, and the inorganic fine particles are adhered to the photoreceptor, thereby causing a problem of poor cleaning. . Further, when the phenomenon that inorganic fine particles are released from the composite fine particles occurs, there is a problem that the chargeability of the developer is changed and the image density is lowered.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrostatic image developer excellent in cleaning property and charging stability by preventing release of inorganic fine particles. Is to do.

[0005]

Means for Solving the Problems To achieve the above object, the electrostatic image developer of the present invention comprises colored particles comprising at least a resin and a colorant, and inorganic fine particles fixed on the surface of the resin fine particles. In an electrostatic image developer containing the composite fine particles, the composite fine particles are represented by the formula described below.
The fixing rate of the inorganic fine particles to the surface of the resin fine particles is 25% or more and less than 100% as defined .

[0006]

As a result of extensive studies by the present inventors, it has been found that, in order to prevent the release of inorganic fine particles, the fixation rate of the inorganic fine particles to the surface of the resin fine particles is an important factor. The present invention has been completed by finding that the above-mentioned problems can be solved by specifying. That is, when the fixing ratio of the inorganic fine particles is 25% or more and less than 100%, the fixing of the inorganic fine particles to the surface of the resin fine particles becomes sufficient, and the release of the inorganic fine particles is prevented even when the number of times of image formation is large. Is done. Therefore,
No cleaning failure due to the adhesion of the inorganic fine particles to the photoreceptor does not occur, and the image density does not decrease due to the change in chargeability.

Hereinafter, the present invention will be described specifically. The composite fine particles used in the present invention are those in which inorganic fine particles are fixed on the surface of resin fine particles, and the fixing ratio of the inorganic fine particles to the surface of the resin fine particles is 25% or more and less than 100%. Here, the fixing rate is defined as the specific surface area of the resin fine particles Sa,
Assuming that the specific surface area of the inorganic fine particles is Sb, the specific surface area of the composite fine particles after the inorganic fine particles are fixed on the surface of the resin fine particles is Sh, and the addition ratio of the inorganic fine particles is x, the following formula 1 is defined. However, the specific surface area is "Flowsorb 23
00 "(manufactured by Shimadzu Corporation) and the nitrogen adsorption surface area was measured by the one-point method based on the BET specific surface area measurement method.

[0008]

(Equation 2)

It is necessary that the range of the fixation ratio is 25% or more and less than 100%, but it is particularly preferable that the ratio is 40% or more and 80% or less. When the fixing rate is in such a range, the release of the inorganic fine particles from the resin fine particles is sufficiently prevented. But,
When the fixing rate is less than 25%, the fixing of the inorganic fine particles to the surface of the resin fine particles becomes insufficient, and the inorganic fine particles present on the surface of the composite fine particles are easily released. Therefore, when an image is formed a number of times, the release of inorganic fine particles gradually increases, causing a cleaning defect that adheres to the surface of the photoreceptor to form spot-like stains (black spots). There is a problem that the image quality changes with time, causing a decrease in image density. The fixing rate can be adjusted by setting the fixing conditions in the fixing device.

The resin fine particles constituting the composite fine particles preferably have an average particle size of 0.1 to 7 μm, particularly preferably 0.2 to 7 μm, from the viewpoints of cleaning properties and triboelectric charging properties.
5 μm is preferred. Incidentally, the average particle size of the resin fine particles,
The volume-based average particle diameter is measured by a laser diffraction particle size distribution analyzer “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser. However, before the measurement, several 10 mg of the resin fine particles were dispersed in 50 ml of water together with a surfactant, and then, with an ultrasonic homogenizer (output 150 W), paying attention to reaggregation due to heat generation.
Pre-dispersion was performed for ~ 10 minutes.

[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, silicone 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.

The inorganic fine particles constituting the composite fine particles preferably have an average primary particle size of 5 to 1000 nm, particularly 10 to 500 nm, from the viewpoint of enhancing the cleaning property and the fixing property. Are 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 suitably 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.

As a method of fixing the inorganic fine particles on the surface of the resin fine particles, a method of mixing the resin fine particles and the inorganic fine particles, electrostatically adhering the inorganic fine particles to the surface of the resin fine particles, and then applying mechanical energy thereto. 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 a method of applying mechanical energy, "Hybridizer" (manufactured by Nara Machinery Co., Ltd.), "Ongmill" (manufactured by Hosokawa Micron), "Kryptron", which is an improved impact type pulverizer,
(Manufactured by Kawasaki Heavy Industries, Ltd.). The fixing rate changes depending on the magnitude of the mechanical energy. The mechanical energy can be adjusted by, for example, the peripheral speed of the stirring blade, the stirring time, the product temperature during the treatment, and the like.
In other words, by increasing the peripheral speed of the stirring blade, increasing the stirring time, increasing the product temperature during processing, and the like, the mechanical conditions are strict, so that the inorganic fine particles become embedded in the resin fine particles. The sticking rate can be defined by adjusting the degree of embedding.

The amount of the inorganic fine particles to be added to the resin fine particles may be an amount capable of uniformly covering the surface of the resin fine particles. Specifically, although it varies depending on the specific gravity of the inorganic fine particles, from the viewpoint of improving the polishing effect by the composite fine particles and preventing the release of the inorganic fine particles, it is preferably 5 to 100 parts by weight with respect to 100 parts by weight of the resin fine particles, particularly 5 to 80 parts by weight are preferred. For example, when the addition amount of the inorganic fine particles is too small,
Since the surface of the composite fine particles becomes non-uniform and many resin portions are present on the surface, the polishing effect is likely to be reduced.

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 toner, 0.01 to the colored particles.
To 5% by weight, particularly 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 required. The average particle size of the colored particles is usually 1 to 30 μm. Range. The binder resin constituting the colored particles is not particularly limited, and conventionally known various resins are used. For example, polyester resin, styrene / acrylic resin and the like are typical examples. The colorant constituting the colored particles is not particularly limited, and various conventionally known colorants are used. For example, 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.

Examples of 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. Such magnetic particles have an average particle size of 0.1 to
Particles of 2 μm such as ferrite and magnetite are used. The amount of the magnetic particles added is generally in the range of 20 to 70% by weight of the colored particles excluding external additives such as composite fine particles.

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.

The developer of the present invention may be a two-component developer composed of the above toner mixed with a carrier, or, when the toner is a magnetic toner, composed of only the magnetic toner. Or a one-component developer. As the carrier constituting the two-component developer, any of an uncoated carrier such as iron powder and a resin-coated carrier in which the surface of magnetic particles is coated with a resin can be used. The average particle size of the carrier is usually in the range of 30 to 150 μm.

The developer of the present invention can be used in combination with various conventionally known developing methods. Further, the developer of the present invention includes a selenium-based photoconductor, an organic photoconductive photoconductor (OP
It can be used in combination with various conventionally known photoconductors such as C photoconductor and amorphous silicon photoconductor (a-Si photoconductor).

[0022]

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”.

Example of Production of Composite Fine Particles Styrene / acrylic resin fine particles (average particle size = 1.5 μm) synthesized by an emulsion polymerization method are used as resin fine particles, and titanium oxide (primary average particle size = 20n) is used as inorganic fine particles.
m) using 100 parts of resin fine particles and 17 inorganic fine particles
Parts were added, and these were charged into a V-type mixer, sufficiently stirred, and the inorganic fine particles were electrostatically attached to the surfaces of the resin fine particles. The mixture is then "hybridized"
(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. At this time, by changing the mechanical energy and the processing time to be applied, as shown in Table 1 below, composite fine particles H having different fixing rates
-1 to H-8 were obtained.

On the other hand, as shown in Table 2 below, several types of styrene / acrylic resin fine particles having different average particle diameters were used as the resin fine particles, and aluminum oxide (primary average) was used as the inorganic fine particles. Particle size = 15 nm), and the inorganic fine particles were electrostatically attached to the surface of the resin fine particles in the same manner as above except that the blending amount of the inorganic fine particles with respect to 100 parts of the resin fine particles was changed as shown in Table 2 below. I let it. Then, using a “Hybridizer” (manufactured by Nara Machinery Co., Ltd.), a mechanical impact is applied with the same energy, that is, the same impact force and impact time, and the inorganic fine particles are fixed on the surface of the resin fine particles. As shown in Table 2, composite fine particles H-9 to H-13 having different fixing rates were obtained.

[0025]

[Table 1]

[0026]

[Table 2]

Examples 1 to 11 and Comparative Examples 1 and 2 100 parts of polyester resin and 50 magnetic powder (magnetite)
And 1 part of a charge control agent (salicylic acid derivative) were mixed, ground, crushed and classified by a usual method to obtain magnetic colored particles having an average particle diameter of 11 μm. The magnetic colored particles
To 100 parts, 0.4 part of hydrophobic silica and 0.7 part of composite fine particles in a combination shown in Table 3 below were added and mixed to obtain each one-component developer composed of one-component toner.

Examples 12 to 22 and Comparative Examples 3 to 4 100 parts of a polyester resin and 8 parts of carbon black were mixed, and the mixture was ground, crushed and classified by a conventional method to obtain a non-magnetic material having an average particle size of 10 μm. Colored particles were obtained. To 100 parts of the non-magnetic colored particles, 0.4 parts of hydrophobic silica and 0.7 parts of composite fine particles in a combination shown in Table 4 below were added and mixed to obtain each two-component toner. 100 parts of a resin-coated carrier obtained by coating a styrene / acrylic resin on ferrite particles having an average particle diameter of 80 μm and 4 parts of each two-component toner were mixed to obtain each two-component developer.

[0029]

[Table 3]

[0030]

[Table 4]

Each of the developers obtained in the above Examples and Comparative Examples was evaluated for chargeability, cleaning property, and developability as follows.

Charging property For the one-component developer, an iron powder carrier “DSP-13” is used.
8 "(manufactured by Powder Tech) and 3 parts of each one-component developer were mixed, and the charge amount was measured by a blow-off method. The results are shown in Table 5 below. For the two-component developer, the charge amount was measured by directly applying the blow-off method. The results are shown in Table 6 below. Shake at a temperature of 20
The measurement was performed under environmental conditions of 50 ° C. and a relative humidity of 50%, and the amount of charge was measured at 1 minute and 60 minutes after changing the shaking time from 1 minute to 60 minutes.

Cleaning Properties As for the one-component developer, a laser printer "LP" equipped with an organic photoconductive photoreceptor, a cleaning blade, and a developing device fixed to a magnet roller and adopting a contact developing system applying an AC bias is used. −3015 ”(Konica Corporation)
20,000 times in low-temperature, low-humidity environmental conditions at a temperature of 10 ° C and a relative humidity of 20%. The cleaning property was evaluated by The results are shown in Table 7 below. In Table 7, "black spots" refers to deposits having a diameter of 0.3 mm or more that are present on the surface of the photoreceptor. If the number of black dots is 15 or less, it is a practical level. As for the two-component developer, a digital copying machine “DC-8028” (manufactured by Konica Corporation) employing an organic photoconductive photoreceptor, a cleaning blade, and a non-contact developing method applying an AC bias.
The cleaning property was evaluated in the same manner as in the case of the one-component developer except that. The results are shown in Table 8 below.

Developability For the one-component developer, use the laser printer "LP-3015" used in the evaluation test of the cleaning property under the conditions of high temperature and high humidity of 30 ° C. and 80% relative humidity.
An actual printing test for forming an image continuously for 10,000 times was performed, and the change in image density was measured with a reflection densitometer “RD-914” (manufactured by Macbeth) to evaluate developability. The results are shown in Table 7 below. If the image density is 1.0 or more, it is a practical level. For the two-component developer, the digital copying machine "DC-8028" used in the cleaning test
The developability was evaluated in the same manner as in the case of the one-component developer, except that was used. The results are shown in Table 8 below.

[0035]

[Table 5]

[0036]

[Table 6]

[0037]

[Table 7]

[0038]

[Table 8]

From the above results, in the developer of the present invention, the stability of the charge amount over time is excellent, the occurrence of cleaning failure is small, and the decrease in image density is small compared to the comparative developer. It is clear that.

[0040]

As described in detail above, according to the present invention, the release of inorganic fine particles is sufficiently prevented, and an electrostatic image developer having excellent cleaning properties and charge stability can be obtained.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-91143 (JP, A) JP-A-63-294570 (JP, A) JP-A-1-250963 (JP, A) JP-A 61-294 273566 (JP, A) JP-A-2-55367 (JP, A) JP-A-3-20750 (JP, A) JP-A-2-149856 (JP, A)

Claims (1)

(57) [Claims] And 1. A least a resin and a colored particle comprising a colorant, in an electrostatic image developer inorganic fine particles on the surface of the resin particles comprising the composite fine particles comprising fixed, the composite fine particles, the following An electrostatic image developer characterized in that the fixation ratio of the inorganic fine particles to the surface of the resin fine particles is defined as 25% or more and less than 100% as defined by the following formula: (Equation 1) Here, Sa is the specific surface area of the resin fine particles, and Sb is the inorganic fine particles.
The specific surface area of the particles, Sh
The specific surface area of the composite fine particles after fixing, x is the
The specific surface area is determined by the BET specific surface area measurement method.
The nitrogen adsorption surface area was measured by the one-point method based on
You.