JPH07230181A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To prevent initial low changeability of the developer comprising a toner having a fine silica powder added on the surface and a carrier covered with a fluororesin by specifying the water content of the silica powder. CONSTITUTION:The developer for developing an electrostatic charge image comprises the toner composed essentially of a binder resin and the colorant and covered on the surface with the fine silica powder needed to be reduced to a water content of <=0.21 weight% and the carrier of magnetic particles or particles having a magnetic powder dispersed into themselves. As the magnetic particles, Fe3O4, gamma-Fe2O3, and various kinds of ferrites can be used, and the toner may contain a charge controller, a cleaning aid, a fluidity promoter, and the like, and in addition, low molecular weight polypropylene or polyethylene, and an offset preventive agent, and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used in electrophotography, electrostatic recording, electrostatic printing, etc. (hereinafter, it relates to a developer for electrophotography.

[0002]

2. Description of the Related Art As a developer for developing an electrostatic charge image in electrophotography or the like, a toner and a carrier are used.
Component developers are often used. Various carriers are known as the carrier in the two-component developer, and representative examples thereof include a conductive carrier such as iron oxide powder and a coat-type insulating carrier. The conductive carrier is excellent in solid developability, but is inferior in fine line reproducibility, and has a defect such as a marked decrease in chargeability due to fusion or adhesion of the toner to the carrier surface, while The coated insulating carrier is excellent in terms of life, reproducibility of fine lines, etc., but has a drawback of poor solid reproducibility. For the purpose of improving these drawbacks, a magnetic powder dispersion type carrier having a small particle size in which magnetic powder fine particles are dispersed in a binder resin, that is, a so-called microtoning carrier has been proposed and put into practical use. Such a dispersed carrier has a low true specific gravity, high insulating property,
Due to its small particle size, magnetic brushes are also denser and more uniform than conventional carriers, have good density reproducibility, and there is no noise such as brush eyes due to magnetic brushes, and it is generally better to improve image quality. Are known.

On the other hand, regarding the toner, in order to improve the fluidity, the anti-caking property, the stability, the charging property, the cleaning property and the like and have the process compatibility, various inorganic and inorganic additives are used. It is known to add organic fine powder, and it has been proposed to use, for example, silica, titanium oxide, aluminum oxide, tin oxide or the like.
Further, a developer in which these toners are combined with the above magnetic powder-dispersed carrier is also proposed.
No. 0-136775 discloses a developer comprising a magnetic powder-dispersed carrier and a toner to which fine particles of titanium oxide / silica are attached, and JP-A No. 61-9661 discloses a magnetic powder-dispersed carrier and silica. A developer consisting of a toner to which fine powder is attached is described. Further, in recent years, further long life is desired, in order to reduce the non-electrostatic adhesion of the surface between the toner and the carrier, it has been proposed to use a carrier surface coated with a fluorine-containing resin,
The life of the developer is extended.

[0004]

However, when the carrier and the toner to which the silicon oxide fine powder is externally added are used in combination, there is a problem that fog and the like often occur due to initial low charge. . The reason why this phenomenon occurs is not clear, but it is considered as follows. That is, the silicon oxide fine powder used for external addition of toner has an insufficient degree of hydrophobicity and high cohesiveness,
It tends to be difficult for the water and the like adsorbed on the surface to escape. When the silicon oxide fine powder is externally added to the toner, mechanical shearing loosens the agglomeration of the silicon oxide fine powder, and a new surface of the silicon oxide fine powder containing water is formed on the toner surface to release the water. It is easy to be done. As a result, it is considered that the toner is mixed with the carrier, so that the charge is reduced. This phenomenon occurs remarkably in combination with a fluorine-containing carrier, and the charge tends to be saturated with the release of water in the silicon oxide fine powder.
Initial charge reduction occurs.

The present invention has been made to solve the above-mentioned problems in the prior art. That is, an object of the present invention is to provide a two-component electrophotographic developer for electrophotography, which does not cause a low initial charge, has a fast rising of charges of a toner and a carrier, and has a long life.

[0006]

The developer for electrostatic charge images of the present invention comprises a toner to which silicon oxide fine powder is externally added,
A carrier coated with a fluorine-containing resin, wherein the silicon oxide fine powder has a water content of 0.21% by weight or less. In the electrostatic image developer of the present invention,
The carrier is composed of magnetic particles, or
Those composed of magnetic powder-dispersed particles in which magnetic powder is dispersed in a binder resin are preferably used. Further, the fluorine content on the carrier surface is preferably 0.01 to 0.5 atom%.

The present invention will be described in detail below. The toner in the developer for electrostatic charge images of the present invention is composed mainly of a binder resin and a colorant. Examples of the binder resin used include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate. , Methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate,
Α-, such as dodecyl methacrylate and phenyl methacrylate
Homopolymers or copolymers of vinyl ethers such as methylene aliphatic monocarboxylic acid esters, vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone. Specific examples of the binder resin include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and styrene. Mention may be made of maleic anhydride copolymers, polyethylene, polypropylene and the like. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, wax and the like can be mentioned.

As the colorant to be used, any one can be used as long as it is usually used for toners such as color toners, and one of organic dyes, organic pigments and inorganic pigments can be used. Alternatively, more than that can be appropriately selected and used. For example, carbon black, lamp black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, rose bengal, C.I. I. Pigment Red 4
8: 1, C.I. I. Pigment Red 122, C.I. I.
Pigment Red 57: 1, C.I. I. Pigment Yellow 97, C.I. I. Pigment Yellow 12, C.I.
I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 3 can be used. In the present invention, the colorant content is preferably in the range of 4 to 15% by weight.

In addition to the above components, the toner may further contain a charge control agent, a cleaning aid, a fluidity accelerator, etc., if necessary. Further, other known components such as an offset preventive agent such as low molecular weight propylene, low molecular weight polyethylene and wax can be added to the toner. In particular, the weight average molecular weight is 500 to 5
000 low molecular weight polypropylene is preferred. further,
In order to produce the toner of the present invention, the above toner materials may be mixed using a Banbury mixer, a kneader coater, a CM mixer, an extruder or the like, melt-kneaded, and pulverized and classified, and the average particle diameter is 20 μm or less. ,
In particular, it is preferable that the particle size is 2 to 20 μm.

Silicon oxide fine powder is externally added to the surface of the toner particles, and the silicon oxide fine particles must have a water content of 0.21% by weight or less. When the water content is higher than 0.21% by weight, there is a problem in that the charge is initially lowered and fog occurs. The preferred water content is 0.17% by weight or less, particularly 0.10% by weight or less, and in this case, favorable results are obtained in terms of environmental resistance. In order to bring the water content into the above range, the silicon oxide may be dried, but it is preferably dried at a high temperature of 80 ° C. or higher, particularly 100 ° C. or higher. The water content is a value obtained by measuring the loss on drying after drying 100 g of silicon oxide at 105 ° C. for 12 hours. In the present invention, the particle size of the silicon oxide fine powder is preferably 3 μm or less, and particularly preferably 0.005 to 1.0 μm. More preferably, 0.001-0.02μ
The range is m. The silicon oxide fine particles can be attached to the surface of the toner particles by adding the silicon oxide fine particles to the toner particles and mixing them with, for example, a Henschel mixer. In that case, the compounding amount is preferably in the range of 0.05 to 5.0% by weight with respect to the total amount of the toner.

On the other hand, the carrier in the present invention is composed of magnetic particles or magnetic powder-dispersed particles whose surfaces are coated with a fluorine-containing resin. As magnetic particles,
Any known one can be used such as ferric tetroxide, γ-iron sesquioxide, various ferrites and the like. The particle size of the magnetic particles is generally set in the range of about 20 to 400 μm. Further, as the magnetic powder dispersion type particles,
The magnetic powder is dispersed in a resin, and the compounding amount of the magnetic powder is about 30 to 95% by weight, preferably 45 to 90% by weight based on the whole carrier. As the resin, all the resins exemplified as the binder resin for the toner particles can be used. Moreover, as the magnetic powder, fine particles of a commonly used ferromagnetic material can be used, and specific examples thereof include triiron tetraoxide, γ-iron sesquioxide, various ferrites, chromium oxide, and various fine metal powders. To be Further, a charge control agent or the like can be contained if necessary. The magnetic powder-dispersed carrier preferably has an average particle size of 20 to 150 μm and a volume resistivity of 10 ¹⁰ to 10 ¹⁵ Ωcm. The magnetic powder-dispersed carrier can be produced by kneading, pulverizing and classifying the above components, or by dissolving the above components in an appropriate solvent or liquefying by heating and producing by spray drying or the like.

In the present invention, the particle surfaces of these carriers are coated with a fluorine-containing resin. Examples of the fluorine-containing resin include perfluoroalkanes,
Perfluoroalkyl (meth) acrylate polymers and copolymers, vinylidene fluoride polymers and copolymers, etc. can be used. As the perfluoroalkyl (meth) acrylate polymer and copolymer, preferred are polymers and copolymers having a monomer represented by the following formula (I) as a constituent component.

[Chemical 1] (In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a fluorine atom, n represents an integer of 1 to 8, and m represents an integer of 1 to 19.)

Specifically, a polymer composed of the following monomer units can be mentioned.

[Chemical 2]

Examples of the component copolymerizable with the monomer represented by the above formula (I) include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate,
Butyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, glycidyl (meth) acrylate, amide (meth) acrylate, hydroxyethyl (meth) acrylate, styrene, ethylene, propylene, butylene Etc. can be mentioned. Further, a styrene resin, an epoxy resin, a silicone resin or the like can be used in combination with the fluorine-containing resin. When these resins are used in combination, the amount used is preferably in the range of up to 99.5% by weight of the fluorine-containing resin.

In the present invention, the resin has a coating layer having a thickness of 0.005 to 5 μm, more preferably 0.05 to 5 μm.
It is preferable that the coating is carried out in the range of 0.5 μm.
Further, the fluorine content of the carrier surface is 0.01 to 0.
A range of 5 atom% is preferable. The fluorine content is X
It is a value measured by a line photoelectron spectroscopy (KPS) method. If the fluorine content is less than 0.01 atom%, the covering effect will not occur, and if it is more than 0.5 atom%, the charge level will be lowered, the developer life will be shortened, and fog will occur. It may be easier.
As a coating method, a method of adding an organic solvent solution of a fluorine-containing resin to a carrier and mixing them can be carried out.

[0016]

The present invention will be described in more detail with reference to the following examples. However, the present invention is in no way limited by these examples. In the following description, all “parts” represent “parts by weight”. Example 1 (Toner) Styrene-n-butyl acrylate (80/20) copolymer 100 parts (Tg: 63 ° C., Mw: 300,000) Carbon black 6 parts Low molecular weight polypropylene (Viscole 660P, 5 parts Sanyo Chemical Co., Ltd.) Manufacture) The above components were melt-kneaded with a Banbury mixer.
After cooling, it was finely pulverized by a jet mill, and the finely pulverized product was classified by a classifier to obtain toner particles having an average particle diameter d50 of 11 μm. To 100 parts of the toner particles, 1 part of silicon oxide fine particles having an average primary particle diameter of 0.016 μm was added and dispersed and mixed using a Henschel mixer to prepare a toner having silicon oxide fine particles adhered to the surface. The silicon oxide fine powder used here had a water content of 0.24.
% By weight of silicon oxide fine particles (R972, manufactured by Nippon Aerosil Co., Ltd.) was dried at 50 ° C. for 1 hour to a water content of 0.21% by weight. (Carrier) Ferrite particles having an average particle size of 100 μm 100 parts Polymethyl methacrylate toluene solution 5 parts (equivalent to 1 part solids) Perfluorooctylethyl methacrylate toluene solution 1.5 parts (equivalent to 0.15 parts solids) The above components were coated using a rolling fluid coating device to obtain a carrier. The surface fluorine content is 1.0
It was atomic%. (Developer) To 100 parts of the above carrier, 3 parts of toner was added and mixed with a V blender to prepare a developer.

Example 2 (Toner) In Example 1, carbon black was replaced with a copper phthalocyanine pigment (CI Pigment Blue 15:
A toner was obtained in the same manner as in Example 1 except that silicon oxide fine powder having a water content of 0.15% by weight was used instead of 3). The silicon oxide fine powder used here was obtained by drying silicon oxide fine particles (R972, manufactured by Nippon Aerosil Co., Ltd.) having a water content of 0.24% by weight at 70 ° C. for 2 hours to give a water content of 0.15% by weight. It was something that was done. (Carrier) Magnetite 75 parts Polyethylene 25 parts The above components are melt mixed and the particle size is 80 μm by the spray cooling method.
m carrier particles were prepared. Carrier particles 100 parts Polymethylmethacrylate toluene solution 10 parts (equivalent to solid content 2 parts) Vinylidene fluoride resin acetone / methyl 3.0 parts Ethylketone solution (equivalent to solid content 0.3 parts) Roll the above components A coating treatment was performed using a fluidized coating device to obtain a carrier. The surface fluorine content is 1.0
It was atomic%. (Developer) 5 parts of toner was added to 100 parts of the above carrier and mixed by a V blender to prepare a developer.

Example 3 A developer was prepared in the same manner as in Example 2 except that silicon oxide fine powder having a water content of 0.21% by weight was used. Example 4 Average primary particle size 0.007 μm with water content of 0.25% by weight
Silicon oxide fine powder (R812, manufactured by Nippon Aerosil Co., Ltd.)
Was dried at 105 ° C. for 12 hours and allowed to stand at room temperature to have a water content of 0.08% by weight.
A developer was obtained in the same manner as in.

Comparative Example 1 A developer was prepared in the same manner as in Example 1 except that silicon oxide fine powder having a water content of 0.23% by weight was used. Comparative Example 2 A developer was prepared in the same manner as in Example 2 except that silicon oxide fine powder having a water content of 0.25% by weight was used.

Examples 1 to 4 and Comparative Examples 1 and 2
The image evaluation was performed on the developer (1) using a modified copying machine (Able 1301, manufactured by Fuji Xerox Co., Ltd.). The results obtained are shown in Table 1. The evaluation criteria for the initial image are as follows. O means an image with clear image quality without fog, and X means an image with background fog and poor reproducibility of line drawing.

[0021]

[Table 1] As is clear from the above results, the developer of the present invention has an excellent effect on fog at the initial stage of copying and has a long developer life.

[0022]

EFFECT OF THE INVENTION The electrostatic latent image developer of the present invention has an excellent effect that the charge is not initially lowered, the charge rises quickly, and the life is long. Therefore, according to the electrostatic latent image developer of the present invention, it is possible to initially obtain a copy image with excellent image quality without fog, and it is possible to maintain the excellent image quality for a long period of time.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eimi Takahashi 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A toner comprising a silicon oxide fine powder added externally and a carrier coated with a fluorine-containing resin, wherein the silicon oxide fine powder has a water content of 0.21% by weight or less. Electrophotographic developer.