JPH0690540B2 - Electrophotographic developer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic developer.

(Prior Art) Conventionally, as a constituent material of a developer for developing an electrostatic latent image, inorganic oxides such as silica, alumina, and titania that have been hydrophobized or not hydrophobized for the purpose of fluidity imparting and cohesiveness prevention, etc.
It is known to externally add fine powders of sulfides and nitrides and adhere them to the surface of toner particles. These fine powders are generally used as fine particles having a particle size of 0.5 μm or less, especially 0.1 μm or less (Japanese Patent Publication No. 45-16219, JP-A-56).
-128956, 59-123849, 61-14845).
For example, in the negatively charged developer, silicon dioxide fine powder is used, and in the positively charged developer, for example, JP-A-61-61
-148454 silica treated with an iminosilane compound, silica treated with a silane coupling agent containing a special ammonium salt in the molecular structure described in JP-A-59-123849, alumina, It is known to use fine powder of metal oxide such as titania.

On the other hand, in JP-A-60-122958, in order to prevent the toner surface from being crushed during roll fixing, a particle diameter of 0.1-20
A toner containing particles of silicon carbide, silicon nitride, boron carbide, and zirconium oxide having a particle diameter of μm alone or in a mixture is disclosed.

(Problems to be Solved by the Invention) With respect to the developer using the fine powder having the particle diameter of 0.5 μm or less, the fine powder has a remarkable function as a fluidity improving agent. There is such a drawback. That is, when, for example, hydrophobic silica is externally mixed with the negatively charged developer, the toner charge amount tends to be too high and the image density tends to decrease in a low temperature and low humidity atmosphere. Further, in a high temperature and high humidity atmosphere, the toner charge amount is too low, which causes a problem such as image blurring and fogging.
On the other hand, in the case of the positively charged developer, not only when untreated silica is used, but also when silica treated with various treating agents, and metal oxide fine particles such as titania are externally added and mixed, any temperature and humidity environment Even below, a toner having a low charge amount and a reverse polarity is likely to be generated. In addition, in the case of a developer that is positively or negatively charged, in particular,
When repeatedly used, developability defects are conspicuous and image blurring, bleeding, fogging, etc. occur, and the product cannot be used. This is because such a developer has a significantly wide distribution of charge amount and contains a toner of opposite polarity.

On the other hand, the particle size of 0.1 disclosed in the above-mentioned JP-A-60-122958.
The developer using fine particles of ˜20 μm is silica,
It is possible to suppress the drawback of fine powder such as alumina and titania, that is, the development of environmental dependence of the charging property of the developer, but to improve the fluidity of the developer, which is the original purpose of adding fine particles. There is almost no contribution to this, and defective image density occurs, such as uneven density that is thought to be due to poor fluidity. In particular, in solid image reproduction, a hollow image occurs remarkably like a so-called edge effect. Further, even in the reproduction of the line image, the fine line becomes thin and only a very low quality image is obtained.

As described above, in the conventional technique, it was extremely difficult to achieve both the developability and the fluidity of the developer. In particular, it was almost impossible to reduce or eliminate the temperature-humidity dependency of developability.

The present invention has been made in view of such problems of the conventional technology.

Therefore, the object of the present invention is to overcome the disadvantages of the conventional externally treated and mixed silica, alumina, titania and the like mixed developer, to achieve both fluidity and developability,
Another object of the present invention is to provide an electrophotographic developer in which the temperature and humidity dependency of developability is extremely reduced.

Furthermore, an object of the present invention is to provide an electrophotographic developer having a high image quality and capable of withstanding repeated use while reducing the environmental dependency of developability.

(Means for Solving the Problems) As a result of intensive studies by the present inventors, the drawbacks of the above-described conventional electrophotographic developers are that the particle diameter of the fine particles externally added to the toner and the material constituting the fine particles are They found that the two were related, and completed the present invention. That is, it is composed of primary particles having an average particle size of 0.05 μm or less and 3 to 8 mol% of Y ₂
When zirconium oxide containing O ₃ is externally added and mixed to the toner, unlike silica, alumina, titania, etc., surprisingly, both the developability and the fluidity of the developer at the time of copying a large number of 400,000 sheets are obtained. The present invention has been completed by discovering that the temperature dependence of the developing property can be extremely reduced and the temperature dependence of the developing property can be extremely reduced.

Therefore, the electrophotographic developer of the present invention has an average particle size of 0.05.
fine particles of zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ , or 3 to 8 mol% of primary particles having an average particle size of 0.05 μm or less when mixed with a toner. Is characterized in that the zirconium oxide compound fine powder containing Y ₂ O ₃ is added to the toner, and the zirconium oxide compound fine particles are uniformly attached to the surface of the toner particles.

Hereinafter, the present invention will be described in detail.

The zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ used in the present invention is a stabilized or partially stabilized oxide containing 80 mol% or more of zirconium oxide and 3 to 8 mol% of Y ₂ O _3. A zirconium compound, for example, partially stabilized zirconia containing 3 mol% to 8 mol% Y ₂ O ₃ and stabilized zirconia, or some impurities therein.
Examples thereof include those containing MgO, CaO and the like, and any of these can be preferably used.

The zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ used in the present invention is composed of primary particles having an average particle size of 0.05 μm or less, or has an average particle size of 0.05 μm or less when mixed with a toner. It is necessary that the particles can be primary particles.

In the present invention, "when mixed with toner, 3 to 8 mol% of Y _{2 which} can become primary particles having an average particle size of 0.05 μm or less can be obtained.
Zirconium oxide compound fine powder containing O ₃ ] means that when mixed with a toner by a well-known mixing means, aggregated particles formed by aggregating primary particles of a zirconium oxide compound are easily disintegrated by well-known mixing means. It means a zirconium oxide compound fine powder containing ₃ to 8 mol% of Y ₂ O ₃ which is agglomerated to be primary particles.

In the present invention, as a mixing means used for mixing with the toner, means known in the art can be used. For example, Henschel mixer, Nauta mixer,
A ball mill, V-type mixer, turbula mixer, paint shaker, etc. can be used. In the present invention, a mixer of a type having a high-speed stirring blade inside and dispersing particles by a shearing force, such as a Henschel mixer, is suitable. Also, a mixer in which the container simply rotates, such as V
Even a mold mixer can be advantageously used if the steel balls enclose glass beads and the like and the crushing force by them is utilized.

Whether or not the zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ is crushed into primary particles can be observed with a scanning electron microscope. What percentage of the total particles of the zirconium oxide compound needs to be crushed into primary particles depends on the amount of addition or how many primary particles the aggregated particles remaining without crushing are composed. However, for example, when the aggregated particles remaining without being crushed consist of several primary particles, if it is a normal addition amount, about 50%
Should be primary particles. In other cases, about 90% or more may be primary particles.

The average particle size used in the present invention is a value obtained from a scanning electron micrograph. The average particle size of the fine particles can be measured as it is, but on the toner particles or on the carrier (carrier in the electrophotographic two-component developing method).
It is easier to measure the particles after they are attached to the particles. The projected image of the fine particles in the photograph has the diameter of a circle of the same area as the particle diameter of the fine particles, and the average of the particle diameters of arbitrary 30 fine particles gives the average particle diameter.

The zirconium oxide compound fine powder containing ₃ to 8 mol% of Y ₂ O ₃ used in the present invention may be hydrophobized or may not be hydrophobized as long as the above conditions are satisfied.

The amount of the fine powder of zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ depends on the weight of the toner, but in the case of non-magnetic toner, it is usually 0.1 to 100 parts by weight of the toner.
The amount is preferably 10 parts by weight, more preferably 1 to 5 parts by weight. If the addition amount is less than 0.1 parts by weight, there is no effect on improving the fluidity of the toner, and if it exceeds 10 parts by weight, the liberated zirconium oxide compound fine powder adheres to the carrier and other developing member. Or damage to the photoconductor may occur. Further, the magnetic toner containing a magnetic substance has a large specific gravity, but the addition amount may be determined by converting the addition amount in the above range according to the specific gravity.

The toner used in the present invention comprises a colorant and a binder resin, and may contain other known additives. As the colorant, dyes and pigments such as carbon black, cyan color, magenta color, yellow color and extender pigment can be used. As the binder resin, a conventionally known one can be used. For example, styrene, chlorostyrene,
Styrenes such as vinyl styrene: Monoolefins such as ethylene, propylene, butylene, isobutylene: Vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc. Vinyl esters: methyl acrylate, ethyl acrylate, butyl acrylate, acrylic Dodecyl acid, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, etc. α-methylene aliphatic monocarboxylic acid esters: vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, etc. Vinyl ether:
Examples thereof include homopolymers or copolymers of vinyl ketone and the like such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone. Particularly typical binder resins include polystyrene and styrene-alkyl acrylate copolymer. Examples thereof include a polymer, a styrene-alkyl methacrylate copolymer, a styrene-acrylonitrile copolymer, a styrene-butadiene copolymer, a styrene-maleic anhydride copolymer, polyethylene and polypropylene.

Furthermore, natural and synthetic waxes polyester, polyamide, epoxy resin, polycarbonate, polyurethane,
Silicone-based resin, fluorine-based resin, petroleum resin and the like can be used.

As the additive, for example, a magnetic material such as ferrite,
Charge control agents, conductivity control agents, metal oxides such as tin oxide, titanium oxide, silica, alumina, zinc oxide, extender pigments,
A reinforcing filler such as a fibrous substance, an antioxidant, a release agent and the like can be contained as necessary.

In the present invention, in addition to the zirconium oxide compound fine powder containing ₃ to 8 mol% of Y ₂ O ₃ described above, other external additives may be used in combination. As such an external additive, silica,
Examples thereof include carbon, alumina, titanium oxide, zinc oxide, resin powder, tin oxide, long chain fatty acid, and metal salt powder thereof.

The electrophotographic developer of the present invention is the same as the above toner, except that
Zirconium oxide compound fine powder containing mol% Y ₂ O ₃ and, if necessary, other external additives can be added and mixed by using the above-mentioned mixing means, thereby producing The zirconium oxide compound fine particles and an external additive added as necessary are in a state of being attached to the surface of the toner particles. The obtained electrophotographic developer may be blown with hot air to fix the zirconium oxide compound fine particles and other external additives to the surface of the toner particles.

The electrophotographic developer of the present invention is used as a one-component developer or a two-component developer.

(Examples) Next, the present invention will be described by examples.

Example 1 Toner composition Styrene / butyl acrylate (80/20) copolymer 100 parts Carbon black (trade name: # 4000 manufactured by Mitsubishi Kasei) 10 parts Low molecular weight polyethylene wax 5 parts Charge control agent 2 parts (trade name: (Bontron P-51, manufactured by Orient Chemical Co., Ltd.) The above components were well mixed with a blender and then kneaded with a kneader. The kneaded product was roughly pulverized with a film mill, pulverized with a fine pulverizer using a jet stream, and further classified with an air classifier to obtain a fine powder having a particle size of 5 to 20 μm. Next, 2 parts of zirconium oxide (trade name: NS-3Y, manufactured by Nippon Shokubai Co., Ltd.) containing 3 mol% of yttrium oxide in 100 parts of this fine powder and having an average particle diameter of 0.020 μm was mixed with Henschel mixer (Mitsui). Blade speed of 20m / sec with Miike Kakoki)
And mixed for 5 minutes to obtain an electrophotographic developer. The surface of the toner particles after mixing with zirconium oxide was observed by a scanning electron microscope, and it was found that zirconium oxide was uniformly dispersed in the state of primary particles on the surface of the toner particles.

This electrophotographic developer was put in a non-magnetic one-component developing device schematically shown in the drawing, and the charging property of toner particles and a copy test were carried out. In the drawings, 1 is an electrostatic latent image holder, 2 is a developing machine main body, 3 is a hopper, 4 is a developer, 5
Is a developing roll, 6 is a bias power source, 7 is a layer forming charging member, 8 is a power source, and 9 is an electrostatic latent image. The developing roll 5 is
The surface of the shaft is provided with a phenol resin of about 10 ¹⁰ Ω · cm, and the layer forming charging member 7 is silicon rubber. The above-mentioned developer is put in the popper 3, a substantially single-layer developer layer is formed by the layer forming charging member 7, and the charged developer on the developing roll is blown off to pass in a parallel electric field.
The charge amount was measured at the reach distance (for details, see Japanese Patent Laid-Open No.
-79958 publication. ). The charge amount is a value obtained by measuring the reaching distance of the developer and the particle size of the developer with an optical microscope and analyzing the image.

The developer of the present invention has a normal temperature / normal humidity, 35 ° C./85% RH, and 15
It can be seen that strong positive chargeability is exhibited in each environment of ℃ / 10% RH, and the variation of charge amount due to environment is small.
The toner charge amount distribution was narrow in any environment, and the amount of reverse polarity toner was small.

Furthermore, when the electrophotographic developer of the present invention was applied to a copying machine FX-2700 (manufactured by Fuji Xerox Co., Ltd.) modified machine and a copying operation was performed, the obtained image had a sufficiently high density in each of the above environments. There was no background fog, and there was no toner scattering around the image, and the resolution was high. As a result of continuously examining copy images using the above-mentioned developer, the image at 20,000 sheets was comparable to the initial image, and scratches on the photoconductor or defective cleaning occurred. There wasn't.

Example 2 Except that 4% of zirconium oxide fine powder (trade name: NS-8Y, manufactured by Nippon Shokubai Co., Ltd.) containing 8 mol% yttrium oxide as an external additive and having an average particle diameter of 0.013 μm was externally added. An electrophotographic developer was obtained in the same manner as in Example 1, the charge amount was measured, and then a copy test was performed.

The charge amount of the toner was stable in all three environments as shown in Table 1, and there were no problems in image density and its uniformity, background fogging, and toner scattering.

Further, the copying operation was performed up to 20,000 sheets while supplying the electrophotographic developer, but good images were obtained in all three environments. In addition, neither scratches on the photosensitive member nor defective cleaning occurred.

Example 3 An electrophotographic developer was obtained in the same manner as in Example 1 except that the mixing was carried out using a V blender at 30 rpm for 60 minutes.

When the surface of the toner particles after mixing was observed with a scanning electron microscope, it was found that zirconium oxide was uniformly dispersed in the state of primary particles on the surface of the toner particles.

The charge amount of the toner was stable in all three environments as shown in Table 1, and there were no problems in image density and its uniformity, background fogging, and toner scattering.

Further, the image was printed up to 20,000 sheets while supplying the electrophotographic developer, but good images were obtained in all three environments. In addition, neither scratches on the photosensitive member nor defective cleaning occurred.

Example 4 3 parts by weight of the electrophotographic developer of Example 1 and 100 parts by weight of 100 μ iron powder carrier coated with a fluorine-containing resin were mixed and stirred for 10 minutes to obtain a two-component developer. The charge amount at this time is 12.1
It was μc / g.

When a copy test was performed with Fuji Xerox 1075 using this electrophotographic developer, the obtained image had a density
In each of the above-mentioned environments, it was sufficiently high, there was no background fog, there was no toner scattering around the image, and the resolution was good and good. As a result of continuously examining copy images using the above electrophotographic developer, the images at 400,000 sheets were comparable to the initial images.

Example 5 A negatively chargeable electrophotographic developer was obtained in the same manner as in Example 1 except that 2 parts by weight of Bontron S-34 (manufactured by Orient Chemical Co.) was used as a charge control agent in place of Bontron P-51. It was

This electrophotographic developer was put in the non-magnetic one-component developing device shown in FIG. 1 and the toner chargeability and copy test were conducted.

This copy test was performed by modifying the Fuji Xerox FX-2300. In each environment, the negative charge of the electrophotographic developer is small, and the obtained image has a sufficiently high density, no voids, no background fog, and no toner scattering around the image. It was a good one. As a result of continuously examining copy images using the above electrophotographic developer, the images at 20,000 sheets were comparable to the initial images.

Example 6 3 parts by weight of the toner of Example 5 and 100 μ uncoated
100 parts by weight of m-ferrite carrier was mixed and stirred for 10 minutes to obtain a two-component developer. The charge amount at this time is -11.5 μc /
It was g.

Fuji Xerox FX-5870 using this electrophotographic developer
When a copy test was performed with, the obtained image had a sufficiently high density in each of the above-mentioned environments, no background fog, and no toner scatter around the image.
It was a good one with high resolution. As a result of continuously examining copy images using the above electrophotographic developer, the images at 400,000 sheets were comparable to the initial images.

Example 7 Styrene-acrylic resin (trade name: Priolite AC
L, manufactured by Goodyear) 100% by weight Charge control agent (trade name: Bontron P-51, manufactured by Orient Chemical Co., Ltd.) 2% by weight Low molecular weight polypropylene (trade name: Viscol 550P, manufactured by Sanyo Kasei Co., Ltd.) 5% by weight Magnetic powder (Brand name: Mapico Black BL-500, made by Titanium Industry Co., Ltd.) 40% by weight Carbon black (Brand name: Mogar L, made by Cabot Co., Ltd.) 2% by weight The above components are mixed, kneaded, crushed, classified, and averaged. Particle size 13 μm
A magnetic toner for one component was obtained.

Zirconium oxide containing 100 parts by weight of the above magnetic toner and 3 mol% Y ₂ O ₃ (trade name: NS-3Y, manufactured by Nippon Shokubai Co., Ltd.) 1.5
Part by weight was placed in a Henschel mixer and mixed for 5 minutes at a peripheral speed ratio of 20 mm / sec to obtain a developer.

When this electrophotographic developer was placed in a copying machine FX-2700 and a copy was taken, good image quality was obtained without deterioration in image density and fog even after copying 20,000 sheets at room temperature and normal humidity. When a copy was similarly made under the environment of 35 ° C / 85% and 15 ° C / 10%, good image quality could be obtained even after copying 20,000 sheets.

Comparative Example 1 A developer was obtained in the same manner as in Example 1 except that the zirconium oxide was not added externally, and a copy test was conducted. Ground cover,
The toner did not scatter, but the image density was low.

Comparative Example 2 Instead of zirconium oxide, the average particle diameter was 0.016 μm.
Silica fine powder (trade name: R972, manufactured by Nippon Aerosil Co., Ltd.)
A developer was obtained in the same manner as in Example 1 except that 0.5 part by weight of was added externally.

When the dispersed state of the external additive was observed with a scanning electron microscope, the external additive was uniformly dispersed in the form of primary particles.

Even in the initial stage, the toner charge amount was low, the charge amount distribution was wide, and the reverse polarity toner was large.

As a result of the copy test, the image density was high, but the background fog and toner scattering were severe.

Comparative Example 3 Instead of zirconium oxide (trade name: NS-3Y) containing 3 mol% Y ₂ O ₃ having an average particle diameter of 0.02 μm, an average particle diameter of 0.3 μm
An electrophotographic developer was obtained in the same manner as in Example 1 except that 2 parts by weight of zirconium oxide of m (trade name: TZ-3Y, manufactured by Toyo Soda Kogyo Co., Ltd.) was externally added. The particle size of the primary particles of zirconium oxide was 0.024 μm, but when the dispersed state of the external additive was observed by a scanning electron microscope, many aggregates of about 0.3 μm were observed.

As a result of the copy test, there were no background fog and toner scattering, but the image density was as low as 1.10 from the initial stage, a hollow image occurred, and many scratches were observed on the photoconductor at 20,000 sheets.

The evaluation results of each Example and Comparative Example are shown in Tables 1, 2 and 3.

(Effects of the Invention) The electrophotographic developer of the present invention has the zirconium oxide compound fine particles having an average particle size of 0.05 μm or less and containing ₃ to 8 mol% of Y ₂ O ₃ uniformly attached to the surface of the toner particles. Since there,
Even when copying as many as 400,000 sheets, both developability and fluidity can be achieved, and excellent developability and fluidity are exhibited. Also, the temperature and humidity dependence of the developability is extremely small. Therefore, even under repeated use under any environment, an image having excellent image quality without image defects such as hollow spots, thin lines, image blur, bleeding, and fog can be obtained.

[Brief description of drawings]

The drawings are explanatory views showing a schematic configuration of a non-magnetic one-component developing device in which the electrophotographic developer of the present invention is used. 1 ... Electrostatic latent image holder, 2 ... Developing machine main body, 3 ... Hopper, 4 ... Developer, 5 ... Developing roll, 6 ... Bias power supply, 7 ... Layer forming charging member, 8 ... … Power supply, 9… electrostatic latent image.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Ide Matsui 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture, Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Yukihiro Ishii 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Business In-house (56) Reference JP-A-60-243665 (JP, A)

Claims (1)

[Claims] 1. A zirconium oxide compound fine powder comprising primary particles having an average particle diameter of 0.05 μm or less and containing ₃ to 8 mol% of Y ₂ O ₃ , or an average particle diameter of 0.05 when mixed with a toner.
characterized in that fine particles of zirconium oxide compound containing ₃ to 8 mol% of Y ₂ O ₃ capable of forming primary particles of μm or less are added to the toner. An electrophotographic developer consisting of