JPH096040A - Developer for developing electrostatic charge image - Google Patents

Abstract

PURPOSE: To stabilize the ability of a carrier to impart electric charges over a long period of time and to obtain a developer capable of stably giving a high density output image free from fogging and having high resolution over a long period of time. CONSTITUTION: This developer contains a carrier obtd. by forming polyolefin resin coating layers on the surfaces of core particles and a toner with inorg. fine particles and/or org. fine particles fixed on the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for developing electrostatic images (hereinafter also simply referred to as a developer) used in electrophotography, electrostatic photography, electrostatic printing and the like.

[0002]

2. Description of the Related Art Conventionally, a developer containing a carrier and a toner has been widely used in a copying machine utilizing an electrophotographic method. Further, in general, a carrier whose core particles are coated with a resin is often used as a carrier in order to impart durability as a developer and charge stability.

Polyolefin resin has been attracting attention as a resin for coating the surface of a carrier. Since the polyolefin resin itself has no polar group, it has excellent water repellency and releasability, and when used as a coating material for a carrier, its surface is less likely to be contaminated.

However, at present, when the polyolefin resin-coated carrier is applied to a conventional developer, sufficient performance has not been obtained yet. The reason is described below.

Conventionally, a toner used in a developer generally has inorganic / organic fine particles (so-called external additive fine particles) added to its surface for the purpose of imparting fluidity and adjusting a charge amount. The fine particles added to the surface of the toner have an important function for stabilizing the performance of the toner.

However, the polyolefin resin used as the carrier coating resin has a characteristic that it is more likely to be plastically deformed than conventional coating resins such as styrene resin and acrylic resin. On the other hand, styrene resins, acrylic resins, polyester resins and the like generally used as toner binder resins are less likely to be plastically deformed than polyolefin resins.

Therefore, during use as a developer, when the toner comes into contact with the toner, the external additive fine particles added and treated on the toner surface are taken up not on the toner surface but on the carrier coating resin surface. Cause The external additive fine particles once taken in are embedded in the carrier coating resin surface, and as the developer is continuously used,
The external additive fine particles will gradually accumulate on the carrier surface.

As a result, if the developer is used for a long period of time, the charging performance of the carrier will be significantly reduced. This problem is a characteristic problem found in the polyolefin resin-coated carrier of the present invention, which is not found in other conventionally known resin-coated carriers. The phenomenon of deterioration of the charging performance of the carrier extremely deteriorates the output image quality and is a serious problem in practical use.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to stabilize the carrier charge imparting ability for a long period of time, to obtain an output image having a high density and no fog and a high resolution, stably for a long period of time. Another object of the present invention is to provide a developer for developing an electrostatic charge image capable of achieving the above.

[0010]

The above object of the present invention is achieved by the following constitution.

1. In a developer for developing an electrostatic charge image, which comprises a carrier having a polyolefin resin coating layer formed on the surface of core particles and a toner, the toner is characterized in that inorganic particles and / or organic particles are immobilized on the surface. Developer for charge image development.

Hereinafter, the present invention will be described in detail.

The present invention is a proposal of a technique for solving the problem of a developer for developing an electrostatic image containing a carrier coated with a polyolefin resin.

First, a carrier having a polyolefin resin coating layer formed on the surface of magnetic particles is used as the carrier.

The core particles of the carrier that can be used in the present invention are preferably magnetic particles. Here, the magnetic particles mean substances that are strongly magnetized in that direction by a magnetic field, and specifically include iron, ferrite, magnetite, and other metals exhibiting ferromagnetism such as nickel and cobalt, or these metals. Known materials such as alloys or compounds can be used. The term “ferrite” as used herein is a general term for magnetic compounds containing iron and is not limited to spinel type.

The volume average particle diameter of the core particles is preferably 20 to 200 μm, more preferably 30 to 200 μm.
100 μm.

The amount of the polyolefin resin coated on the carrier that can be used in the present invention is preferably 1 wt% to 20 wt%, more preferably 2.5 wt% with respect to the core particles.
~ 8 wt%.

If the amount is less than 1 wt%, the advantages of the polyolefin resin may not be fully exhibited. On the other hand, if it is 20 wt% or more, the film becomes too thick and the carrier has a high resistance, and the image density may decrease depending on the developing conditions (potential, developing gap, etc.).

As the method for producing the carrier of the present invention, various generally known coating methods, for example, a method in which an olefin resin is dissolved in an appropriate solvent and spray-coated on the surface of magnetic particles, and the surface of magnetic particles is coated. Any of a method of attaching a polyolefin resin powder and mechanically fixing it while heating it to a temperature higher than the melting point of the resin material, a surface polymerization coating method described in JP-A-60-106808, or the like may be used. .

If necessary, after the resin coating, a treatment for applying mechanical stress for smoothing the carrier surface (hereinafter referred to as surface smoothing treatment) may be performed. Further, if the carrier is heated at the same time during the treatment, the surface smoothing treatment can be completed in a short time. In that case, good results can be obtained by setting the carrier temperature by heating within the range of the melting point of the coating resin ± 50 ° C.

By smoothing the carrier surface, the mechanical frictional force on the carrier surface can be reduced, so that the performance of the developer can be further stabilized.

Here, as the monomer constituting the polyolefin resin, specifically, known resin group hydrocarbon type monomers such as ethylene, propylene, butene, cyclopentene are preferable. Further, resins or copolymers obtained from other vinyl monomers can also be used. Further, these monomers may be used alone or in combination of two or more. Among these, preferably, a polyethylene resin containing ethylene as a monomer is used to obtain good performance.

If necessary, a conductive material may be added to the coating resin of the carrier used in the present invention. In this case, as the conductive material that can be introduced into the coating resin,
Known materials that can meet the purpose of adjusting the volume resistance can be used, and specifically, fine particles of metal such as iron, aluminum and nickel and fine particles such as carbon black, conductive titania, silicon carbide, tin oxide and magnetite are used. be able to. The average primary particle diameter is preferably within the range of 1/5000 to 1/50 with respect to the weight average particle diameter of the carrier.

As the toner used in the present invention,
Inorganic fine particles and / or organic fine particles (hereinafter, also referred to as an external additive) are immobilized on the surface thereof. here,
The state in which the external additive is immobilized is defined by the following method in the present invention.

First, the content of the external additive in the toner added with the external additive is determined. Next, 5 g of the toner is dispersed in 200 ml of water together with a surfactant. After applying ultrasonic waves with a homogenizer (ultrasonic disperser), a supernatant is separated from a precipitate (toner) by a centrifugal separator, and the supernatant is removed. Here, the external additive which is not fixed is removed together with the supernatant. After that, the toner as a precipitate is dried, and the content of the external additive is determined again. The external additive immobilization rate is calculated from the external additive content before and after the application of ultrasonic waves. As a result, a toner having an external additive fixing ratio of 75% or more and 100% or less is referred to as a “toner having an external additive fixed”.

The method for measuring the content of the external additive may be selected according to the characteristics of the external additive, and can be quantified by, for example, a wavelength dispersive X-ray spectrometer (WDX).

The ultrasonic wave application conditions are as follows.

Ultrasonic wave application device: Homogenizer US-150T (Nippon Seiki Seisakusho Co., Ltd.) Ultrasonic oscillator diameter: 20 mmφ Output current value: 100 μA Tuning value: 4 Ultrasonic wave application time: 30 sec Further, as a material that can be used as an external additive, Inorganic or metal oxide fine particles such as silicon oxide, titanium oxide, aluminum oxide, zinc oxide, zirconium oxide, magnesium oxide, copper oxide, tungsten oxide, and tin oxide, and inorganic particles such as boron nitride, titanium nitride, and silicon nitride. Fine particles of metal nitrides, fine particles of inorganic or metal carbides such as silicon carbide and boron carbide, fine particles of inorganic or metal fluorides such as zinc fluoride, carbon fluoride and zirconium fluoride, calcium carbonate, barium titanate Carbonic acid / titanium such as aluminum silicate and magnesium silicate / Silicate compound fine particles also can be used known materials such as organic particles such as acrylic particles, styrene particles, silicone particles. Also, one of these
The type may be selected and used, or two or more types may be used in combination. Furthermore, the surface of the external additive can be subjected to a hydrophobizing treatment, if necessary.

As the hydrophobizing agent capable of hydrophobizing, known agents can be used. In particular,
A silane coupling agent, a titanium coupling agent, an aluminate coupling agent, a zirco aluminum coupling agent, a silicone oil, etc. can be used.

As a result of examination, the average primary particle diameter of the external additive fixed on the toner surface is 0.005 μm to 0.005 μm.
Preferably it is 5 μm. Further, it is more preferably in the range of 0.01 μm to 0.3 μm. The average primary particle size of the external additive can be determined by observing with an electron microscope.

The amount of the external additive to be fixed on the toner surface varies depending on the kind of the external additive, but it is preferable to add the additive in an amount of about 0.01 to 10% by weight based on the toner. However, it is more preferable that the toner content is 0.05 to 5%.
The content is 5% by weight.

The shape of the external additive that can be used in the present invention does not necessarily have to be a perfect spherical shape, but may be a spherical shape, a flat plate shape, a spindle shape, a needle shape, or an indefinite shape.

Further, it is necessary to fix the above-mentioned external additives on the toner surface before use. As a method of fixing the toner on the toner surface, for example, after the toner and the external additive are mixed in advance and adhered to the toner surface, mechanical stress or mechanical The external additive can be fixed to the toner surface by applying thermal stress.

Specifically, as a mixer, a Henschel mixer (Mitsui Miike), a vertical granulator (Fuji Sangyo), a high speed mixer (Fukae Kogyo), a mechano mill (Okada Seiko), a new speed kneader (Okada Seiko), etc. Can be used. Further, as the surface modification device,
Hybridization system (Nara Machine Works),
Mechanofusion system (Hosokawa Micron), theta composer (Dokuju Kosakusho), etc. can be used.

As the toner of the present invention, a toner containing a binder resin and a colorant is used. The weight average particle diameter of the toner used in the present invention is preferably in the range of 1/3 to 1/30 of the weight average particle diameter of the carrier used.

Specific examples of the binder resin that can be used in the toner include styrenes such as styrene, chlorostyrene and vinylstyrene, vinyl acetates such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, and acrylic acid. Α- such as methyl, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, dodecyl methacrylate, phenyl methacrylate, etc.
Methylene aliphatic monocarboxylic acid esters, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether and other vinyl ethers, vinyl methyl ketone,
Examples thereof include vinyl ketones such as vinyl hexyl ketone and vinyl isopropyl ketone, and a polymer of one type of known monomers or a copolymer or a mixture of two or more types of monomers.

Of these, particularly preferred are polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyamide, Epoxy resin, silicone resin, modified rosin, paraffin, or the like, or a mixture of two or more thereof can be used.

As the coloring agent, carbon black such as furnace black, acetylene black and lamp black, nigrosine dye, aniline blue, calcoil blue, ultramarine blue, phthalocyanine blue, chrome yellow, quinoline yellow, malachite green oxalate. , Rose Bengal, and other known coloring agents can be used.

Further, the toner of the present invention may further contain a releasing agent, a charge control agent, a magnetic material, a lubricant, and a cleaning aid, if necessary.

Further, after fixing the external additive to the surface of the toner of the present invention, different kinds of external additives may be added and mixed if necessary.

As a method for producing the toner, a known method can be used. Specifically, the constituent materials are mixed, melted and kneaded, and then subjected to a cooling step, pulverization and classification to obtain a toner, and a pulverization method for obtaining a toner, or emulsion polymerization, suspension polymerization, etc. to obtain a toner. A polymerization method or the like can be used.

Further, the carrier and the toner are mixed to prepare the developer of the present invention. In that case, a conventionally known mixer can be used. However, it is preferable that the stress applied to the developer during mixing is small.

Specifically, a rotation type mixer such as a V-type mixer, a W-cone mixer or a rocking mixer can obtain better results than a stirring type mixer such as a Henschel mixer.

[0044]

Examples of the present invention will be described below. The present invention is not limited to the following embodiments.

[Production of Carrier 1] 500 ml of dehydrated hexane and 450 g of dried core particles (ferrite having a volume average particle diameter of 60 μm) are put in an autoclave and stirred.
Then, 2.0 mmol of Ziegler-Natta catalyst was added and stirred to support the catalyst on the surface of the magnetic particles.

Next, 0.50 g of carbon black (Keschen Black EC: Lion Akzo), which had been previously dried under reduced pressure, was added and further stirred.

Thereafter, the total pressure was adjusted to 6.0 kg / cm ² G, ethylene gas was continuously supplied at 90 ° C. and reacted for 45 minutes to polymerize ethylene on the surface of the core particles to coat the carbon black-containing polyethylene resin. I got carrier 1. The polyethylene resin coating amount of this carrier 1 was 4.0 wt%.

[Production of Carrier 2] The polyethylene resin-coated carrier 1 obtained in Production of Carrier 1 was put into a Henschel mixer, and the stirring blade peripheral speed was 10 m / s and 80 ° C.
The mixture was stirred under heating for 20 minutes. After that, the carrier 2 was obtained by passing through a sieve having an opening of 106 μm to remove aggregates.

[Manufacture 3 of Carrier] The polyethylene resin-coated carrier 1 obtained in Manufacture 1 of carrier was put into a Henschel mixer, and the peripheral speed of the stirring blade was 20 m / s, 100.
Mixing and stirring were performed for 20 minutes under heating at ℃. afterwards,
The carrier 3 was obtained by passing through a sieve having an opening of 106 μm to remove aggregates.

[Production of Colored Particles] 2 parts by weight of low molecular weight polypropylene (Viscole 660P: Sanyo Kasei) as a release agent and 100 parts by weight of styrene / acrylic resin, and carbon black (Black Pearl L: Cabot) 10 as a coloring agent. Parts by weight were mixed and melt-kneaded with a twin-screw kneader. Then, after cooling and coarse crushing steps, fine pulverization and air classification were carried out to obtain colored particles having a weight average particle diameter of 7.5 μm.

[Manufacture of Toner 1] 1.0 part by weight of hydrophobic silicon oxide fine particles (HDK-H2050EP: Wacker Chemical: average primary particle size 0.008 μm) was added to the above colored particles in a hybridization system NHS-1 type ( (Nara Machinery Co., Ltd.), external mixing is performed in the OM dither section, and the rotor rotation peripheral speed is 100 in the hybridizer section.
Immobilization treatment of the external additive fine particles was carried out for 3 minutes under the conditions of m / s and a set product temperature of 50 ° C. to obtain positively chargeable toner 1 used in the examples of the present invention. The immobilization rate of the hydrophobic silicon oxide fine particles used in this toner was 96%.

[Production of Toner 2] Fine particles of titanium oxide (IT-PC: Idemitsu Kosan: instead of hydrophobic fine particles of silicon oxide)
The external additive fine particles were fixed in the same manner as the toner 1 except that 3.0 parts by weight of the average primary particle diameter of 0.06 μm) was used to obtain a positively chargeable toner 2 used in the examples of the present invention. .
The immobilization rate of the hydrophobic titanium oxide fine particles used in this toner was 92%.

[Production of Toner 3] Hydrophobic aluminum oxide fine particles (RFY-
C: Nippon Aerosil: Average primary particle size of 0.013 μm) 2.
The external additive fine particles were fixed in the same manner as Toner 1 except that 0 part by weight was used to obtain Positively Chargeable Toner 3 used in the examples of the present invention. The immobilization rate of the hydrophobic aluminum oxide fine particles used in this toner was 94%.

[Production of Toner 4] Magnesium oxide fine particles (high-purity magnesia 1000A: Ube Chemical Industries, Ltd .: average primary particle size 0.1 μm) instead of the hydrophobic silicon oxide fine particles
The external additive fine particles were fixed in the same manner as Toner 1 except that 2.5 parts by weight was used to obtain Positively Chargeable Toner 4 used in the examples of the present invention. The fixing rate of the magnesium oxide fine particles used in this toner was 90%.

[Production of Toner 5] In the same manner as Toner 1, except that 5.0 parts by weight of silicone fine particles (Tospearl 103: Toshiba Silicone: average primary particle size 0.3 μm) are used in place of the hydrophobic silicon oxide fine particles. By fixing the external additive fine particles, a positively chargeable toner 5 used in the examples of the present invention was obtained. The fixing rate of the silicone fine particles used in this toner was 88%.

[Production of Toner 6] In addition to the above-mentioned positively chargeable toner 2, hydrophobic silicon oxide fine particles (HDK-H205) are further added.
0EP: Wacker Chemical: Average primary particle size 0.008μ
m) After adding 0.5 part by weight, a mixing treatment was carried out with a Henschel mixer to obtain a positively chargeable toner 6 used in the examples of the present invention. The fixing rate of the aluminum oxide fine particles used in this toner was 95%.

[Production of Toner 9] The external additive fine particles are fixed in the same manner as in Toner 1 except that the processing time in the hybridizer section of the hybridization system is changed to 1 minute. A positively chargeable toner 9 used for is obtained. The immobilization rate of the hydrophobic silicon oxide fine particles used in this toner was 68%.

[Production of Toner 10] Instead of using a hybridization system, a Henschel mixer (Mitsui Miike) was used to produce a stirring blade with a peripheral speed of 10 m / s and a preset product temperature of 5
The external additive fine particles are fixed in the same manner as Toner 1 except that the mixing treatment is performed at 0 ° C. for 10 minutes.
A positively chargeable toner 10 used in the examples of the present invention was obtained. The immobilization rate of the hydrophobic silicon oxide fine particles used in this toner was 26%.

[Preparation of Developer] The developers used in the examples of the present invention were prepared in the following combinations. In preparing the developer, each carrier and each toner were put into a V-type mixer so that the toner concentration in the developer was 6% by weight, and mixed for 20 minutes.

Developer Carrier Toner Fixing Treatment External Additive Fine Particle Type Average Primary Addition Amount Particle Size [μm] [wt%] Example 1 Developer 1 Carrier 1 Toner 1 Hydrophobic Silicon Oxide 0.008 1.0 Example 2 Developer 2 Carrier 1 Toner 2 Titanium Oxide 0.06 3.0 Example 3 Developer 3 Carrier 1 Toner 3 Hydrophobic Aluminum Oxide 0.013 2.0 Example 4 Developer 4 Carrier 1 Toner 4 Magnesium Oxide 1 2.5 Example 5 Developer 5 Carrier 1 Toner 5 Silicone Fine Particles 0.3 5.0 Example 6 Developer 6 Carrier 1 Toner 6 Titanium Oxide 0.06 1.0 Example 7 Developer 7 Carrier 2 Toner 1 Hydrophobic Silicon Oxide 0.008 3.0 Example 8 Developer 8 Carrier 3 Toner 2 Titanium Oxide 0.06 3.0 Comparative Example 1 Developer 9 Carrier 1 Toner 9 Hydrophobic Oxidation Containing 0.008 1.0 Comparative Example 2 developer 10 carrier 1 Toner 10 hydrophobic silicon oxide 0.008 1.0 [Performance Evaluation] The above developer 500g commercially available copying machine Ko
Nica U-Bix4155 (Konica)
20,000 sheets continuously in N environment (20 ° C, 50% RH), 30,000 sheets continuously in HH environment (30 ° C, 80% RH), 3 consecutive sheets in LL environment (10 ° C, 20% RH) In the NN environment, a total of 100,000 actual images were evaluated. The evaluation items and methods are shown below.

(Image Density) A solid image having an original density of 1.30 was copied and the relative reflection density of the output image with respect to a blank sheet was measured. The evaluation was performed twice on the initial and 100,000 sheets. A reflection densitometer RD-917 (Macbeth) was used for density measurement, and image density of 1.30 or more was judged to be good.

(Fog Density) A blank original was copied after 100,000 sheets were copied, and the relative reflection density of the output image with respect to the blank was measured. In addition, the reflection densitometer RD-9 was used for the density measurement.
17 (Macbeth) was used, and an image density of 0.005 or less was judged to be good.

(Resolution) A fine line image was copied, and the number of fine lines reproduced per 1 mm width of the output image was evaluated. It should be noted that the larger the number of reproduced fine lines, the higher the resolution, and the image was judged to be good. The evaluation was performed on the 100,000th copy image.

(Amount of charge of developer) The amount of charge is NN
In an environment (20 ° C., 50% RH), it was measured by a blow-off powder charge amount measuring device TB-200 (Toshiba Chemical). The measurement was performed twice on the first copy and at the end, and the smaller the difference between the charge amounts of the two, the better the judgment.

[0065]

[Table 1]

As is clear from the above results, the present invention is superior to the comparison.

[0067]

The developer for developing an electrostatic image according to the present invention comprises
As shown by the results of the examples, it is possible to prevent the incorporation of the toner external additive in the polyolefin resin-coated carrier, which has been a problem in the past, and to achieve long-term stabilization of the performance of the developer. As a result, it is possible to stably obtain an output image with high density and high density without fog on the image background portion for a long period of time.

Claims (1)

[Claims] 1. A developer for developing an electrostatic charge image, comprising a carrier having a polyolefin resin coating layer formed on the surface of core particles and a toner, wherein the toner has inorganic fine particles and / or organic fine particles immobilized on the surface thereof. A developer for developing an electrostatic charge image, which comprises: