JPH04248563A - Developer for electrostatic charge image - Google Patents

Abstract

PURPOSE:To provide the two-component developer which does not generate the deterioration in electrostatic chargeability based on carrier contamination, has a long developer life and imparts the images improved in the resistance to staining by rubbing. CONSTITUTION:This developer consists of a toner which contains coloring agents in a binder resin and contains polyethylene wax having >=120 deg.Cm.p. at 0.3 to 2.0wt.% of the total weight of the toner and a triphenyl methane deriv. as a charge control agent, and a coated carrier consisting of a magnetic core material coated with a vinyl fluorinated hydrocarbon resin.

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 used when an electrostatic image formed by electrophotography, electrostatic recording, etc. is developed with a two-component developer.

0002

[Prior Art] Developers used to develop electrostatic latent images formed on photoreceptors by electrophotography include two-component developers consisting of a mixture of toner and carrier, and toners consisting of magnetic toner and the like. There is also a one-component developer that is used alone. The two-component developer is provided with functions such as stirring/transporting/charging by the carrier. Therefore, since it is functionally separated as a developer, it has characteristics such as good controllability, and is currently widely used. In particular, when using a resin-coated carrier, charge controllability tends to be improved, and environmental dependence and stability over time tend to be improved. As a developing method, a cascade method and the like were used in the past, but the mainstream developing method currently used is a magnetic brush method using a magnetic roll as a developer transport carrier.

0003

[Problems to be Solved by the Invention] The biggest problem with the magnetic brush method is the deterioration of charging properties, which is thought to be mainly caused by carrier contamination by toner ingredients. In particular, in recent years, as demands regarding the fixing quality of toners have increased, low-molecular-weight polyethylene wax is often included for the purpose of improving the toner's release properties and the rubbing resistance of images. As a result, the tendency of carrier contamination by toner is becoming increasingly strong, leading to a problem of shortening the life of the developer. Furthermore, when toners are manufactured using conventional methods such as kneading and pulverization, low molecular weight components such as polyethylene wax tend to cause non-uniform composition in the toner during kneading or pulverization, which can lead to a decrease in chargeability. There is also the issue of contribution. By the way, polyethylene wax is
It has the characteristics of being highly effective in rubbing stain resistance, and the higher the crystallinity and melting point, the better the thin layer releasability. However, conversely, regarding carrier contamination, the more likely thin layer peeling occurs, the more carrier contamination tends to occur. In addition, during kneading, the viscosity tends to decrease at low temperatures, so it is compatible with the charge control agent that is mixed at the same time, and therefore, when carrier contamination with polyethylene wax occurs, the charge control agent that is contained in the toner at the same time. Carrier contamination is also likely to occur, which causes a problem in that, particularly in positively chargeable toners, a dramatic deterioration in chargeability is caused. The present invention has been made in view of the above problems.

Therefore, an object of the present invention is to provide an image which, when developed by a magnetic brush method, does not suffer from deterioration in chargeability due to carrier contamination, has a long developer life, and has improved scratch resistance. The object of the present invention is to provide a two-component developer that provides the following properties.

[0005]

[Means for Solving the Problems] The present inventors have developed a carrier in which the melting point of polyethylene wax is above a certain temperature, a specific charge control agent, and a coating layer that is resistant to contamination. By combining
The inventors have discovered that it is possible to achieve both fixed image quality and developer life, and have completed the present invention. The developer for electrostatic images of the present invention contains a colorant in the binder resin, and further has a melting point of 12
A toner containing polyethylene wax of 0° C. or higher in an amount of 0.3 to 2.0% by weight based on the total amount of the toner and a triphenylmethane derivative as a charge control agent, and a magnetic core material coated with a vinyl-based fluororesin. A coated carrier consisting of:

The present invention will be explained in detail below. The toner constituting the two-component developer of the present invention consists of a binder resin and a colorant dispersed therein as main components.

Various thermoplastic resins can be used as the binder resin. Specific examples include, as vinyl resins, styrenes such as styrene, p-chlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, and acrylic resins; α-Methylene aliphatic monocarboxylic acid esters such as lauryl acid, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate, and 2-ethylhexyl methacrylate; acrylonitrile, methacrylonitrile Vinyl nitriles such as; 2-vinylpyridine, 4
- Vinylpyridines such as vinylpyridine; Vinyl ethers such as vinyl methyl ether and vinyl isopropyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; Unsaturated carbonization of propylene, isoprene, butadiene, chloroprene, etc. A polymer or copolymer consisting of one or more monomers such as hydrogens and their halides, or
Examples of non-vinyl resins include rosin-modified phenol-formalin resins, epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and mixtures of these and the above-mentioned vinyl resins.

[0008] As the colorant, in addition to carbon black,
Various dyes and pigments can be used as long as they do not adversely affect chargeability.

[0009] The polyethylene wax used in the present invention has a melting point of 120°C or higher (measured by DSC).
It is necessary to use the following. If a toner with a melting point lower than 120° C. is used, the rubbing resistance of the image will decrease and the fixing quality will deteriorate. Further, the amount added needs to be in the range of 0.3 to 2.0% by weight based on the total amount of toner. If the amount added is less than 0.3% by weight, fixing quality will deteriorate, and if it is more than 2.0% by weight, carrier contamination will become severe.

Triphenylmethane derivatives that can be used in the present invention include those having the following structural formula.

[0011]

0012

These triphenylmethane derivatives tend to have low affinity with polyethylene, and therefore are difficult to form a homogeneous phase with polyethylene, making them difficult to become a source of carrier contamination. Furthermore, fine powder of metal oxide such as silica or alumina may be included as a fluidity improver.

The carrier used in the present invention is a known magnetic core material, such as metals such as iron, cobalt, nickel, and alloys thereof, Fe3 O4, γ-Fe2 O3
, metal oxides such as cobalt-added iron oxide, various ferrites such as Mn-Zn ferrite and Ni-Zn ferrite, magnetite, hematite, etc., and a core material whose surface is coated with a vinyl fluororesin can be used. The particle size of the core material is 30 to 200 μm, preferably 50 to 200 μm.
A thickness in the range of 120 μm can be used.

Examples of the vinyl fluororesin that coats the core material include monomers such as vinylidene fluoride, tetrafluoroethylene, monofluoroethylene, trifluoroethylene, hexafluoroethylene, trifluoromonochloroethylene, and fluoromethacrylate. Examples include monopolymers or copolymerizers. Coating methods include dip coating method, spray coating method, fluidized bed method, etc.
Various commonly used methods can be used.

In the present invention, triphenylmethane derivatives tend to have little affinity with polyethylene wax, and therefore are unlikely to become a source of carrier contamination. Furthermore, since a carrier coated with a vinyl fluororesin having a low surface energy is used in combination, the effect of preventing carrier contamination is further improved.

[0017]

[Example] Styrene-butyl acrylate copolymer (M
n = 8,000, Mw = 100,000), 6% by weight of carbon black (BPL, manufactured by Degussa) based on the total weight of the toner, and a triphenylmethane derivative represented by the following structural formula based on the total weight of the toner. 1%,

[0018]

[0019] and polyethylene wax were blended in the amounts listed in Table 1, mixed by kneading and pulverizing method, and the average particle size was 10.
A μm toner was prepared. On the other hand, 1% by weight of a dimethylformamide solution of vinylidene fluoride-tetrafluoroethylene copolymer (copolymerization molar ratio 80:20) was mixed with a ferrite carrier having an average particle size of 80 μm, and the mixture was coated with a fluidized bed. A coating layer was applied.

Developers were prepared by mixing the toner and carrier obtained as described above at a weight ratio of 3:97 (sample numbers 1 to 6). Using these developers, electrophotographic copying machines (FX5990 modified machine, Fuji Xerox (
(manufactured by Co., Ltd.), and the scratch resistance of the fixed image and developer life were tested.

For comparison, the same procedure was carried out except that the triphenylmethane pigment was changed to nigrosine (Bontron No. 4, manufactured by Orient Chemical Co., Ltd.) or a quaternary ammonium salt (Bontron P51, manufactured by Orient Chemical Co., Ltd.). Developers were prepared (sample numbers 7 to 10) and evaluated in the same manner.

The results are shown in Table 1. In Table 1, the rubbing resistance was evaluated by rubbing the fixed image with a cloth, and the degree of staining of the cloth was visually determined. The judgment criteria are as follows. ○...There is little dirt, ×...There is significant dirt. Further, the image quality after 104 sheets were continuously copied was determined by visual inspection of the degree of occurrence of background stains and low-density images. The judgment criteria are as follows. ○: The degree of occurrence of background stains and low density images is low; ×: Significant background stains or significant occurrence of low density images.

[0023]

[Table 1]

[0024]

[Effects of the Invention] Since the developer for electrostatic images of the present invention has the above-mentioned structure, carrier contamination is less likely to occur.Therefore, even when used for a long period of time, there is little deterioration in chargeability, and the life of the developer is significantly extended. become longer. In addition, the copy image formed is
It has good fixing quality with excellent scratch resistance.

Claims (1)

[Claims] 1. A coloring agent is contained in the binder resin, and 0.3 to 2.0% by weight of polyethylene wax having a melting point of 120° C. or higher based on the total amount of the toner is contained, and triphenyl is added as a charge control agent. a toner containing a methane derivative;
A developer for electrostatic images comprising a coated carrier made of a magnetic core material coated with a vinyl fluororesin.