JPH04291352A - Electrostatic charge image developer - Google Patents

Abstract

PURPOSE:To prevent liberation of an inorganic particulate and to improve cleaning ability and stability of chargeability by containing a composite particulate having >=25% sticking ratio of the inorganic particulate to a surface of a resin particulate. CONSTITUTION:The composite particulate is made to stick the inorganic particulate on the surface of the resin particulate and sticking ratio of the inorganic particulate to the surface of the resin particulate is 25-100%. This range of sticking ratio is preferably 40-8O% to sufficiently prevent liberation of the inorganic particulate from the resin particulate. But in the case of >=25% of sticking ratio, sticking of the inorganic particulate becomes insufficient to easily liberate. When specific surface area of the resin particulate is Sa, specific surface area of the inorganic particulate is Sb, specific surface of the composite particulate after the inorganic particulate is stick on the surface of the resin particulate is Sh and additive ratio of the inorganic particulate is X, sticking ratio is expressed by the formula I.

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

BACKGROUND OF THE INVENTION 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 No. 84741/1983).
(See Publication No. 60-186851). However, these techniques are still insufficient in polishing the photoreceptor, which is necessary to achieve good cleaning. For this reason, a phenomenon occurs in which deposits such as toner are deposited on the surface of the photoreceptor, resulting in problems such as decreased durability of the photoreceptor. On the other hand, the average particle size is 0.05, which is smaller than the colored particles.
A technique using composite fine particles in which inorganic fine particles are fixed to the surface of resin fine particles of ~3.0 μm has been proposed (see Japanese Patent Application Laid-Open No. 64-91143). This technique maintains the surface of the photoreceptor in good condition through the abrasive action of composite fine particles and improves cleaning performance.

0003

[Problem to be solved by the invention] However, JP-A-64-
In the developer of Publication No. 91143, if the inorganic particles are insufficiently fixed to the surface of the resin particles, the inorganic particles will be released from the composite particles, and this will adhere to the photoreceptor, resulting in poor cleaning. . Further, when a phenomenon in which inorganic fine particles are released from composite fine particles occurs, there is a problem that the charging property of the developer changes, leading to a decrease in image density.

The present invention has been made based on the above-mentioned circumstances, and its object is to provide an electrostatic image developer with excellent cleaning properties and charging stability by preventing the release of inorganic fine particles. It's about doing.

[0005]

[Means for Solving the Problems] In order to achieve the above objects, the electrostatic image developer of the present invention includes colored particles consisting of at least a resin and a colorant, and inorganic fine particles fixed to the surface of the resin fine particles. An electrostatic image developer containing composite fine particles is characterized in that the composite fine particles have an adhesion rate of the inorganic fine particles to the surface of the resin fine particles of 25% or more and less than 100%.

[0006]

[Function] As a result of extensive research, the present inventors have found that the adhesion rate of inorganic particles to the surface of resin particles is an important factor in preventing the release of inorganic particles. The present invention was completed by discovering that the above-mentioned problems can be solved by specifying the above-mentioned characteristics. That is, the adhesion rate of inorganic fine particles is 25% or more 100
%, the inorganic fine particles are sufficiently fixed to the surface of the resin fine particles, and separation of the inorganic fine particles is prevented even when image formation is performed many times. Therefore, cleaning failures due to inorganic fine particles adhering to the photoreceptor do not occur, and image density does not decrease due to changes in chargeability.

The present invention will be explained in detail below. The composite fine particles used in the present invention are those in which inorganic fine particles are fixed to the surface of resin fine particles, and the adhesion rate of the inorganic fine particles to the surface of the resin fine particles is 25% or more and less than 100%. Here, the adhesion rate is defined as Sa, the specific surface area of the resin fine particles, Sb, the specific surface area of the inorganic fine particles, and S the specific surface area of the composite fine particles after fixing the inorganic fine particles to the surface of the resin fine particles.
h and the addition rate of inorganic fine particles is defined by the following equation 1. However, the specific surface area is determined by measuring the nitrogen adsorption surface area by a single point method using "Flowsorb 2300" (manufactured by Shimadzu Corporation) based on the BET specific surface area measurement method.

[0008]

[Math 1]

[0009] The range of this adhesion rate is 25% or more 100
It is necessary to be less than 40%, but especially 40% or more 80%
% or less is preferable. If the fixation rate is within this range,
The release of inorganic fine particles from resin fine particles is sufficiently prevented. However, when the adhesion rate is less than 25%, the adhesion 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 tend to be separated. Therefore, when images are formed many times, the release of inorganic fine particles gradually increases, causing cleaning failures in which they adhere to the surface of the photoreceptor and form dots (black spots).
Further, there is a problem in that the chargeability of the developer changes over time, causing a decrease in image density. The adhesion rate can be adjusted by setting the adhesion conditions in the adhesion device.

[0010] The fine resin particles constituting the composite fine particles preferably have an average particle diameter of 0.1 to 7 μm from the viewpoint of cleaning properties and triboelectric charging properties, particularly 0.1 to 7 μm.
．． 2 to 5 μm is preferable. Note that the average particle size of resin fine particles refers to the average particle size on a volume basis, and is measured using a laser diffraction particle size distribution measuring device "HELOS" equipped with a wet dispersion machine.
)” (manufactured by SYMPATEC). However, before the 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) was used.
Pretreatment was carried out to disperse the particles for 1 to 10 minutes while paying attention to reagglomeration due to heat generation.

[0011] As the resin material constituting the resin fine particles,
Various resins can be used without particular limitation. For example, styrene resins such as styrene, α-methylstyrene, divinylbenzene, acrylic resins such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, α - A copolymer of styrene monomers such as methylstyrene and divinylbenzene and acrylic monomers such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, and butyl acrylate. Certain styrene-acrylic copolymers, nitrogen-containing resins containing dimethylamino methacrylate, diethylamino methacrylate, vinylpyridine, etc., fluorine-containing resins containing Teflon, vinylidene fluoride, etc., polyolefins such as polypropylene, polyethylene, nylon resins, Examples include urethane resin, urea resin, and silicone resin.

[0012] Means for obtaining resin fine particles composed of the above resin include a method of synthesizing the resin by a polymerization reaction such as emulsion polymerization or suspension polymerization using monomers, and a method of melting the resin itself by heat or the like. Examples include a method of atomizing the particles by spraying, and a method of forming a predetermined particle size by dispersing in water. In addition, when producing resin fine particles by a polymerization method, a so-called soap-free polymerization method is preferably used in order to stabilize chargeability and prevent surfactants etc. from remaining on the surface of the resin fine particles. A method of removing the suspension stabilizer may also be used.

[0013] The inorganic fine particles constituting the composite fine particles preferably have an average particle size of 5 to 1000 nm as a primary average particle size, particularly 10 to 500 nm, from the viewpoint of improving cleaning performance and adhesion. Preferably. Note that the primary average particle size of the inorganic fine particles refers to the number average particle size observed with a scanning electron microscope and measured by image analysis. As the inorganic material constituting the inorganic fine particles, various inorganic oxides, carbides, nitrides, borides, etc. 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.

[0014] As a method for fixing inorganic fine particles to the surface of resin fine particles, the resin fine particles and inorganic fine particles are mixed, the inorganic fine particles are electrostatically attached to the surface of the resin fine particles, and then mechanical energy is applied. Examples include a method of fixing inorganic fine particles to the surface of resin fine particles. As a method for electrostatically adhering the inorganic fine particles to the surface of the resin fine particles, there is a method in which the resin fine particles and the inorganic fine particles are placed in a mixer such as a turbular mixer, Lodeige mixer, Henschel mixer, etc., and then stirred. Can be mentioned. Methods for applying mechanical energy include "Hybridizer" (manufactured by Nara Kikai Seisakusho), which is an improved impact crusher, "Ong Mill" (manufactured by Hosokawa Micron), and "Cryptron".
(manufactured by Kawasaki Heavy Industries, Ltd.) and the like. The fixation rate changes depending on the magnitude of this mechanical energy, and this mechanical energy can be adjusted by, for example, the circumferential speed of the stirring blade, stirring time, product temperature during processing, etc. In other words, by tightening mechanical conditions such as increasing the circumferential speed of the stirring blade, increasing the stirring time, and increasing the product temperature during processing, the inorganic fine particles become embedded in the resin fine particles. The fixation rate can be determined by adjusting the degree of embedding.

The amount of inorganic fine particles added to the resin fine particles may be any amount that can uniformly cover the surface of the resin fine particles. Specifically, it varies depending on the specific gravity of the inorganic fine particles, but from the viewpoint of improving the polishing effect of the composite fine particles and preventing the release of the inorganic fine particles, it is preferably 5 to 100 parts by weight based on 100 parts by weight of the resin fine particles, particularly. 5-80
Parts by weight are preferred. For example, if the amount of inorganic fine particles added is too small, the surface of the composite fine particles will be non-uniform and a large amount of resin will be present on the surface, which will likely reduce the polishing effect.

[0016] The amount of composite fine particles added to the colored particles is:
From the viewpoint of improving the cleaning performance due to the abrasive effect and not inhibiting the triboelectric charging properties of the toner, the coloring particles should be 0.
0.01 to 5% by weight is preferred, 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. When carrying out addition and mixing, it is preferable to exist in a free state rather than in a state fixed to colored particles. When mixing, it is preferable to use a turbular mixer, a Henschel mixer, or the like.

[0017] The colored particles contain a binder resin, a colorant, and other additives such as a charge control agent used as necessary, and the average particle size is usually 1 to 30 μm. range. The binder resin constituting the colored particles is not particularly limited, and various conventionally known resins can be used. Typical examples include polyester resin, styrene/acrylic resin, and the like. The coloring agent constituting the colored particles is not particularly limited, and various conventionally known coloring agents can be 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,
Examples include lamp black and rose bengal.

Examples of other additives include charge control agents such as salicylic acid derivatives and fixing property improvers such as low molecular weight polyolefins. Further, when obtaining a magnetic toner, magnetic particles are contained as an additive in the colored particles. Such magnetic particles have an average particle size of 0.
Particles of 1 to 2 μm such as ferrite and magnetite are used. The amount of magnetic particles added is usually 20 to 70% by weight of the colored particles excluding external additives such as composite fine particles.

[0019] Also, from the viewpoint of increasing the fluidity of the toner,
In addition to the colored particles and composite fine particles, inorganic fine particles may be added from the outside to form the toner. As such inorganic fine particles, silica fine particles which have been hydrophobized with a silane coupling agent, a titanium coupling agent, etc. are particularly 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, it may be composed only of the magnetic toner. Alternatively, a one-component developer may be used. As the carrier constituting the two-component developer, it is possible to use either an uncoated carrier such as iron powder or a resin-coated carrier in which the surface of magnetic particles is coated with a resin. The average particle size of the carrier is usually 30 to 150 μm.
is within the range of

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

[0022]

[Examples] More specific examples will be described below, but the present invention is not limited to these examples. In addition, in the following, "part" represents "part by weight".

Example of production of composite fine particles Styrene/acrylic resin fine particles (average particle size = 1.5 μm) synthesized by emulsion polymerization were used as resin particles, and titanium oxide (primary average particle size = 2) was used as inorganic fine particles.
0nm), add 17 parts of inorganic fine particles to 100 parts of resin fine particles, put them into a V-type mixer, stir thoroughly, and electrostatically attach the inorganic fine particles to the surface of the resin fine particles. I let it happen. Next, these mixtures were transferred to a "hybridizer" (manufactured by Nara Kikai Seisakusho), and a mechanical impact force was applied to fix the inorganic fine particles to the surface of the resin fine particles. By varying the mechanical energy applied at this time and the treatment time, composite fine particles H-1 to H-8 having different adhesion rates were obtained as shown in Table 1 below.

On the other hand, as shown in Table 2 below, several types of styrene/acrylic resin particles synthesized by emulsion polymerization and having different average particle sizes were used as the resin particles, and aluminum oxide (primary average) was used as the inorganic particles. Particle size=
15 nm), inorganic fine particles were electrostatically attached to the surface of resin fine particles in the same manner as described above, except that the amount of inorganic fine particles added to 100 parts of resin fine particles was changed as shown in Table 2 below. Next, "hybridizer" (
(manufactured by Nara Kikai Seisakusho) to apply a mechanical impact force with the same energy, that is, the same impact force and impact time,
Inorganic fine particles are fixed to the surface of resin fine particles to produce composite fine particles H-9 to H-13 with different fixing rates as shown in Table 2 below.
I got it.

[0025]

[Table 1]

[0026]

[Table 2]

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

Examples 12 to 22 and Comparative Examples 3 to 4 100 parts of polyester resin and 8 parts of carbon black were mixed, ground, crushed, and classified by a conventional method to form a non-magnetic material with an average particle size of 10 μm. Colored particles were obtained. 0.4 parts of hydrophobic silica per 100 parts of the non-magnetic colored particles
1 part and 0.7 part of composite fine particles in combinations shown in Table 4 below were added and mixed to obtain respective two-component toners. 100 parts of a resin-coated carrier made of ferrite particles with an average particle size of 80 μm coated with styrene/acrylic resin, and 2 parts each
Each two-component developer was obtained by mixing with 4 parts of component-based toner.

[0029]

[Table 3]

[0030]

[Table 4]

The charging properties, cleaning properties, and developing properties of the developers obtained in the above Examples and Comparative Examples were evaluated in the following manner.

Regarding the chargeable one-component developer, iron powder carrier "DSP-1
38'' (manufactured by Powder Tech Co., Ltd.) and 3 parts of each one-component developer were mixed, and the amount of charge was measured by a blow-off method. The results are shown in Table 5 below. As for the two-component developer, the amount of charge was measured by directly applying the blow-off method. The results are shown in Table 6 below. The shaking was performed under the environmental conditions of a temperature of 20°C and a relative humidity of 50%, and the shaking time was varied from 1 minute to 60 minutes.
The amount of charge after minutes was measured.

Regarding the cleanable one-component developer, the laser printer "LP" is equipped with an organic photoconductive photoreceptor, a cleaning blade, and a developing device fixed to a magnetic roller, and employs a contact development method that applies an alternating current bias. -3015” (Konica (
Co., Ltd.), we conducted a live-action test in which images were continuously formed 20,000 times in a low-temperature, low-humidity environment with a temperature of 10°C and relative humidity of 20%, and the surface of the photoreceptor was observed to identify any deposits. The cleaning performance was evaluated based on the presence or absence of. The results are shown in Table 7 below. In Table 7, "black spots" refer to deposits with a diameter of 0.3 mm or more existing on the surface of the photoreceptor. If the number of black spots is 15 or less, it is at a practical level. Regarding the two-component developer, the digital copying machine "DC-8028" uses an organic photoconductive photoreceptor, a cleaning blade, and a non-contact development method that applies AC bias.
The cleaning performance was evaluated in the same manner as in the case of the one-component developer, except that one-component developer (manufactured by Konica Corp.) was used. The results are shown in Table 8 below.

Regarding the developability one-component developer, using the laser printer "LP-3015" used in the cleaning performance evaluation test, it was We conducted a live-action test in which images were continuously formed 10,000 times, and the changes in image density were measured using a reflection densitometer "RD-911".
” (manufactured by Macbeth) to evaluate the developability. The results are shown in Table 7 below. Note that an image density of 1.0 or more is at a practical level. Regarding the two-component developer, the digital copying machine used in the cleaning evaluation test
The developability was evaluated in the same manner as in the case of the one-component developer except that "DC-8028" 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, the developer of the present invention has superior charge amount stability over time, less occurrence of cleaning defects, and less decrease in image density than the comparative developer. That is clear.

[0040]

As described above in detail, according to the present invention, it is possible to obtain an electrostatic image developer in which the release of inorganic fine particles is sufficiently prevented and the cleaning properties and charging stability are excellent.

Claims (1)

[Claims] 1. An electrostatic image developer comprising colored particles consisting of at least a resin and a colorant, and composite fine particles having inorganic fine particles fixed to the surface of the resin fine particles, wherein the composite fine particles are made of a resin. An electrostatic image developer characterized in that the adhesion rate of inorganic fine particles to the surface of the fine particles is 25% or more and less than 100%.