JPH0815898A - Electrostatic charge image developer and image forming method - Google Patents

Abstract

PURPOSE:To provide a one-component electrostatic charge image developer and an image forming method using this developer by which the charge distribution of the toner is made uniform, ghost images are hardly produced and problems on the cleaning property of the toner such as deposition on a photoreceptor are not caused. CONSTITUTION:This one-component electrostatic charge image developer consists of toner particles containing a binder resin and a magnetic material and titanium oxide fine particles having 0.05 to 1.5mum average primary particle size mixed by 0.1 to 1.5wt.% of the toner particles. Among aggregates of titanium oxide made of titanium fine particles, the number of titanium oxide aggregates having >=20mum particle size is 0. When an image is to be developed, a thin layer of the one-component electrostatic charge image developer is formed on a developer carrier body to develop a latent image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a one-component electrostatic image developer and an image forming method using the same.

[0002]

2. Description of the Related Art Dry developing methods in various electrostatic copying methods which are currently in practical use are divided into a two-component toner developing method using a carrier such as toner and iron powder and a one-component toner developing method not using a carrier. Broadly divided. The one-component toner development method does not require an automatic density adjuster, etc., which is required for a two-component toner development method developing machine, so the developing machine becomes compact and there is no carrier contamination, so maintenance such as carrier replacement is required. Becomes unnecessary. Therefore, it has come to be used not only in low-speed compact copying machines and printers but also in medium-speed copying machines and printers, and further improvement in performance is expected. Generally, the one-component toner developing system does not use a carrier like the two-component toner developing system, so that the one-component electrostatic image developer lacks the charge imparting ability to the toner particles, and as a result, There is a problem that the charge distribution tends to be non-uniform, and a phenomenon (ghost phenomenon) in which the history of the image of the previous cycle appears in the next cycle is likely to occur particularly in a low temperature and low humidity environment. In response to this phenomenon, various attempts have been proposed to make the charge distribution uniform by adding an additive such as titanium oxide having a relatively low electric resistance to the toner particles. The cohesiveness is strong, and when they are used in an electrophotographic process, there arises a problem of causing a problem such as adhesion to a photoconductor. Therefore, under the present circumstances, a one-component electrostatic image developer satisfying all the above-mentioned characteristics has not yet been obtained.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. Therefore, an object of the present invention is to provide a one-component electrostatic charge image developer in which the charge distribution of toner particles is made uniform and the above-mentioned ghost phenomenon does not occur. Another object of the present invention is to provide a one-component electrostatic charge image developer which does not cause problems related to toner cleaning properties such as adhesion of a photoreceptor. Still another object of the present invention is to provide an image forming method using the above-mentioned one-component electrostatic image developer.

[0004]

As a result of various studies, the present inventors have made it possible to deposit a specific amount of titanium oxide particles having a specific particle size on the surface of magnetic toner particles, and further to make certain particles in the developer. The inventors have found that the above object can be achieved by substantially eliminating the aggregate of titanium oxide having a diameter or more, and have completed the present invention. That is, the magnetic one-component electrostatic image developer of the present invention contains toner particles containing a binder resin and a magnetic substance, and 0.1% of the toner particles.
~ 1.5 wt% average primary particle size 0.05-1.5 μm
And titanium oxide fine particles having, and
Among the titanium oxide agglomerates formed by the titanium oxide fine particles, the number of titanium oxide agglomerates having a particle size of 20 μm or more is 0. The image forming method of the present invention comprises a step of forming a latent image on a latent image carrier, and a step of performing development using a developer on the developer carrier, which comprises: Is formed by forming a thin layer of the above-mentioned one-component electrostatic image developer.

First, the one-component electrostatic image developer of the present invention will be described in detail. The toner particles, which are a constituent component of the one-component electrostatic image developer of the present invention, are composed of at least a binder resin and a magnetic material. As the magnetic material, any known magnetic material that has been generally used can be used. For example, metals such as iron, cobalt, nickel and their alloys, Fe ₃ O ₄ , γ-
Fe ₂ O ₃ , metal oxides such as cobalt-added iron oxide, Mn
Those formed of various ferrites such as Zn ferrite and NiZn ferrite are used. The particle size of these magnetic materials is generally in the range of 0.05 to 0.5 μm. Further, in the present invention, the content range of the magnetic material used is preferably 20 to 70% by weight, and more preferably 40 to 60% by weight. When the content of the magnetic substance is less than 20% by weight, it is difficult to control the charge amount. Especially in a low temperature and low humidity environment, the image density is lowered or uneven development occurs. It deteriorates and causes practical inconvenience.

A vinyl polymer can be used as the binder resin. Specifically, it is a homopolymer or copolymer of one or more vinyl monomers, and typical vinyl monomers include vinyl aromatic compounds such as styrene, p-chlorostyrene, and vinylnaphthalene, for example, ethylene and propylene. Ethylenically unsaturated monoolefins such as butylene and isobutylene, vinyl halide compounds such as vinyl chloride, vinyl bromide and vinyl fluoride, such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and vinyl formate. Vinyl esters such as vinyl stearate and vinyl caproate, for example, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate Ethylenic monocarboxylic acids such as phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate and the like, and their esters such as acrylonitrile, methacrylonitrile, acrylamide and other ethylenic monocarboxylic acid substitutions Body, for example, dimethyl maleate, diethyl maleate, dibutyl maleate, and other ethylenic dicarboxylic acids and their esters, for example, vinyl methyl ketone, vinyl hexyl ketone, vinyl ketones, such as methyl isopropenyl ketone, such as vinyl methyl ether, vinyl isobutyl. Vinyl ethers such as ether, vinyl ethyl ether, etc., for example,
Vinylidene halogen compounds such as vinylidene chloride and vinylidene chloride, for example, N-vinylpyrrole, N-vinylcarbazole, N-vinylindole,
Examples thereof include N-vinyl compounds such as N-vinylpyrrolidone. Furthermore, resins such as polyester may be used or used in combination.

Further, if necessary, a conventionally known release agent such as a polyolefin wax can be added for the purpose of improving the releasability of the toner. Further, in the one-component electrostatic charge developer of the present invention, various substances can be added for the purpose of charge control, electric resistance control and the like.
For example, fluorine-based surfactants, dyes such as azo or salicylic acid metal complexes, polymeric acids such as copolymers containing maleic acid as a monomer component, quaternary ammonium salts, azine dyes such as nigrosine, carbon black, etc. Can be added.

The titanium oxide fine particles, which is another component of the one-component electrostatic image developer of the present invention, has a specific resistance of 1
A toner having a particle size of 10 ^{7 to} 2 × 10 ⁸ Ωcm is used, and the toner having a primary particle diameter of 0.05 to 1.5 μm is contained in an amount of 0.1 to 1.5% by weight based on the toner particles. It is necessary. It is preferably added in the range of 0.3 to 1.2% by weight. When the primary particle diameter and the addition amount of titanium oxide fine particles deviate from the above ranges, the ghost phenomenon cannot be suppressed.

In the present invention, the titanium oxide fine particles to be added may form titanium oxide aggregates in the developer, but among the titanium oxide aggregates, the number of titanium oxide aggregates having a particle size of 20 μm or more is large. 0, that is, substantially no titanium oxide agglomerate having a particle size of 20 μm or more is required. When the number of titanium oxide agglomerates is not 0, adhesion to the photoconductor, that is, filming phenomenon is likely to occur.

The titanium oxide fine particles can be subjected to a crushing step at the time of production thereof to reduce the amount of aggregates of the titanium oxide fine particles, and the sieving residue with a 500 μm mesh can be reduced to 30% by weight or less. However, in the present invention, it is preferable to use the titanium oxide fine particles thus obtained. If the titanium oxide fine particles have a 500 μm mesh sieve residue of more than 30% by weight, it becomes difficult to prevent the toner particles from adhering to the photoreceptor.

Further, the one-component electrostatic image developer of the present invention is
Other inorganic fine powder such as silica for the purpose of improving the durability, fluidity or cleaning property of toner particles,
Organic fine powder of fatty acid or its derivative and metal salt,
A resin fine powder such as a fluorine resin, an acrylic resin or a styrene resin may be used in combination with the titanium fine particles.

Next, an image forming method using the above-mentioned one-component type electrostatic image developer of the present invention will be described. The image forming method of the present invention comprises a step of forming a latent image on a latent image carrier,
And a step of performing development using the developer on the developer carrier. The step of forming a latent image on the latent image carrier can be carried out by a conventionally known method. Further, as the latent image carrier, an electrophotographic photoreceptor and a dielectric can be used. For example, when an electrophotographic photosensitive member is used as the latent image carrier, the electrostatic latent image may be formed by uniform charging and image exposure. The formed electrostatic latent image is then developed in the step of developing with the developer on the developer carrying member. In the present invention, the above-mentioned one-component electrostatic charge image developer is supplied to form a thin layer on the developer-carrying member by, for example, a layer regulating member, and the one-component electrostatic charge image developer formed on the developer-carrying member is supplied. A thin layer of charge image developer is opposed to the latent image carrier. As a result, the toner particles of the one-component system electrostatic image developer charged by the layer regulation member fly and adhere to the electrostatic latent image on the latent image carrier to visualize the electrostatic latent image. .

[0013]

EXAMPLES The present invention will be described below with reference to examples.
In addition, the number of titanium oxide aggregates having a particle size of 20 μm or more in the developer in the examples is the number in one visual field of the SEM photograph at a magnification of 1000 times. The sieving residue of titanium oxide fine particles alone is a value measured by the following method. A value obtained by setting a sieve with an opening of 500 μm on an Octagon 200 vibrator (made by endecotts), placing 25 g of the sample on the sieve, and vibrating the scale 5 for 3 minutes, and dividing the remaining amount of the sieve by the total amount of the sample. (× 100) is a value obtained as a sieve residue (% by weight).

Example 1 Styrene-n-butyl acrylate copolymer 46% by weight (copolymerization ratio 82:12, Mw = 150,000) Magnetic substance (magnetite having a particle size of 0.2 μm) 50% by weight Negatively chargeable charge control agent (Azo-based Cr compound) 2% by weight Polyethylene wax (Mn = 3000) 2% by weight The above materials were powder-mixed by a Henschel mixer, and this was heat-kneaded for 15 minutes by a two-roll mill at a preset temperature of 160 ° C. The kneaded product was cooled, coarsely pulverized and then finely pulverized to obtain a pulverized product having a 50% volume average particle diameter D50 of 8.5 μm. This is further classified and finely cut to obtain D
A classified product of 50: 9.5 μm was obtained. 0.5% by weight of hydrophobic colloidal silica and 0.8% by weight of titanium oxide fine particles (primary diameter: 0.3 μm, sieve residue: 10% by weight) were added thereto, mixed with a Henschel mixer, and then sieved with a 105 μm mesh. Then, the coarse particles were removed to obtain a developer. Comparative Example 1 A developer was obtained in the same manner as in Example 1 except that titanium oxide having a sieve residue of 50% by weight (without a crushing step) was used in place of the titanium oxide fine particles used in Example 1. Comparative Example 2 A developer was obtained in the same manner as in Example 1 except that titanium oxide fine particles were not added.

With respect to the developers obtained in Example 1 and Comparative Examples 1 and 2, XP-1 manufactured by Fuji Xerox Co., Ltd. having a developing machine for forming a thin layer of the developing agent on a developing agent carrier.
A printing test was conducted using one printer in an environment of 10 ° C. and 15% RH. About the ghost phenomenon
Evaluation was made by the difference between the image density of the leading edge of the first solid black sheet and the image density of the central portion of the second solid black sheet immediately after continuous printing of the sheets. , The surface of the photoreceptor after printing 20,000 sheets was observed and evaluated. In the comprehensive evaluation, ⊚ means good, ○ means no practical problem, and x means practical problem.

[0016]

[Table 1]

[0017]

As described above, the magnetic one-component electrostatic charge image developer of the present invention contains toner particles containing a binder resin and a magnetic material, and 0.1 to 1.5 weight% of the toner particles. % Of titanium oxide agglomerates having a particle size of 20 μm or more among titanium oxide agglomerates containing titanium oxide fine particles having an average primary particle diameter of 0.05 to 1.5 μm. Is 0, the charge distribution of the toner becomes uniform, the ghost phenomenon, which has been a problem of the conventional magnetic toner, is improved, and the problems related to the toner cleaning property such as adhesion to the photoconductor can be improved.

Claims (5)

[Claims] 1. Toner particles containing a binder resin and a magnetic material, and titanium oxide having an average primary particle diameter of 0.05 to 1.5 μm of 0.1 to 1.5% by weight based on the toner particles. Of the titanium oxide agglomerates containing fine particles and formed by the fine particles of titanium oxide, the particle diameter is 20 μm.
A one-component electrostatic charge image developer characterized in that the number of titanium oxide aggregates of m or more is 0. 2. The amount of magnetic material is 20 to 7 with respect to the toner particles.
The one-component electrostatic image developer according to claim 1, which is 0% by weight. 3. The one-component electrostatic image developer according to claim 1, wherein the titanium oxide fine particles are titanium oxide fine particles having a 500 μm mesh sieve residue of 30% by weight or less. 4. The one-component electrostatic image developer according to claim 1, wherein the titanium oxide fine particles are crushed. 5. An image forming method, comprising: a step of forming a latent image on a latent image carrier, and a step of developing with a developer on the developer carrier, wherein the image is formed on the developer carrier. 1. An image forming method, comprising: forming a thin layer of the one-component electrostatic image developer described in 1 and performing development.