JPH07113781B2 - Electrophotographic developer - Google Patents

Description

The present invention relates to an electrophotographic developer for developing an electrostatic charge image, and more particularly to an electrophotographic developer having improved transfer efficiency and excellent durability independent of environment. The present invention relates to a developer for electrophotography.

(Prior Art) Conventionally, as an electrophotographic method, various methods are described in US Pat. No. 2,297,691, Japanese Patent Publication No. 42-23910 and Japanese Patent Publication No. 43-24748, but generally, , A photoconductive substance is used to form an electric latent image on a photoconductor by various means, and then the latent image is developed with a toner, and a powder image is transferred to paper or the like as necessary. After that, it is fixed by heating or solvent vapor to obtain a copy.

As a method of visualizing an electrical latent image using toner,
For example, the magnetic brush method described in U.S. Pat.No. 2,874,063, the cascade developing method described in No. 2,618,552, and the powder cloud method described in No. 2,221,776 are known. ing.

As a developer, a resin such as polystyrene, styrene-butadiene copolymer, or polyester is used with a pigment or dye such as carbon black or phthalocyanine blue as a colorant, and after melt-kneading, a toner pulverized to 1 μm to 30 μm is used. Generally, glass beads, iron, nickel, and ferrite particles having an average particle diameter approximately equal to the toner particle diameter or up to 500 μm, or a mixture of these with a carrier coated with various resins are generally used. Has been.

When these developers are used, whether by the cascade method or the magnetic brush method, only the toner is released from the developer mixture and directly participates in the development. The efficiency of developing the electrostatic charge image and the efficiency of transferring the electrostatic image to paper are extremely important problems for the toner. Further, uniformity of charging, environmental dependency of image quality, and durability of developer are required. Therefore, attempts are often made to add a charge controller as an additive.

(Problems to be Solved by the Invention) However, the charging controller that has been conventionally used does not always satisfy the above-mentioned requirements, and it cannot be said that a desired result is obtained.

Therefore, an object of the present invention is to provide an electrophotographic developer that satisfies all of the properties required in the above conventional techniques.

That is, an object of the present invention is to provide an electrophotographic developer having improved transfer efficiency.

Another object of the present invention is to provide an electrophotographic developer having good developability, particularly a stable triboelectric charge property with a sharp charge distribution.

Another object of the present invention is to provide an electrophotographic developer that does not depend on the environment in terms of charge amount and image quality.

Still another object of the present invention is to provide an electrophotographic developer which is excellent in durability without deterioration of image quality and fog even in copying a large number of sheets.

Still another object of the present invention is to provide an electrophotographic developer that satisfies the above requirements and does not impair the color tone when using a color toner.

(Means and Actions for Solving Problems) As a result of earnest research, the inventors of the present invention have mixed toner particles and tin complex oxide fine particles to solve all of the above drawbacks. It was found that an agent was obtained, and the present invention was completed.

The electrophotographic developer of the present invention comprises toner particles and SnO ₂ · SnO.
It is characterized by containing tin oxide fine particles having an electric resistance of 10 ⁵ Ω · cm to 10 ⁸ Ω · cm.

In the present invention, the tin oxide fine particles are a multiple oxide composed of SnO ₂ and SnO, and their electric resistance is 10 ⁵ Ω.
-Cm to 10 ⁸ Ω-cm. When the electric resistance is lower than 10 ⁵ Ω · cm, the electric resistance of the developer becomes low, and the triboelectrification effect becomes weak, so that the transferability is lowered, the image density is lowered, and the fog is increased. On the other hand, when it is higher than 10 ⁸ Ω · cm, the edge effect is likely to occur and the triboelectric charge amount becomes too large, resulting in a decrease in image density and a decrease in transferability.

The average particle size is preferably 0.3 μm or less. The tin oxide fine particles give good results in a content of 0.1 to 5.0 parts by weight, more preferably 1.0 to 3.0 parts by weight, based on 100 parts by weight of the toner.

The electric resistance value of the tin oxide fine particles in the present invention is the diameter
Teflon cell 5.5cm, in simplified resistivity measuring device using a diameter 4.2 cm, an area 13.85Cm ² press ram, the hydraulic 35.5 kg / cm ² pressure (sample hand press takes pressure of 100 kg / cm ² ) Is measured.

The particle size of the tin oxide fine particles is determined by the natural sedimentation method and the centrifugal sedimentation method.

In the developer of the present invention, known toner particles are used as the toner particles mixed with the tin oxide fine particles. The binder resin used for the toner particles includes styrenes such as styrene, chlorostyrene and vinyl styrene, ethylene,
Propylene, butylene, isoprene and other monoolefins, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl acetate and other vinyl esters, methyl allylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, acrylic acid Phenyl,
Α-methylene aliphatic monocarboxylic acid ester such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, vinyl ether such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, vinyl methyl ketone, vinyl hexyl ketone, Homopolymers or copolymers of vinyl ketone and the like such as vinyl isopropenyl ketone can be exemplified, and particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, and styrene-alkyl methacrylate copolymer. Examples thereof include polymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, styrene-maleic anhydride copolymers, polyethylenes and polypropylenes.

Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin and waxes can be mentioned.

Further, as the colorant of the toner, carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rose bengal and the like can be illustrated as a typical example.

In the present invention, the binder resin and the colorant are not limited to those exemplified above.

In the present invention, the toner particles are smaller than about 30 μm,
Preferably, those having an average particle size of 3 to 20 μm can be used.

The developer of the present invention mixed with the tin oxide fine particles is used as a so-called two-component developer having a carrier and a toner. That is, first, the tin oxide fine particles and the toner particles are mixed, and then the carrier is mixed to obtain a developer.

As the carrier, particles having an average particle diameter of up to 500 μm, and various known materials such as iron, nickel, cobalt, iron oxide, ferrite, glass beads, and granular silicon can be used.

Further, the surface of these particles may be coated with a coating agent such as a fluorine resin, an acrylic resin, or a silicone resin.

The developer of the present invention can be used for developing an electrostatic latent image formed on a photoconductor or an electrostatic recording material. That is, selenium, zinc oxide, cadmium sulfide, inorganic photoconductive material such as amorphous silicon, a phthalocyanine pigment, a photoreceptor made of an organic photoconductive material such as a bisazo pigment, to form an electrostatic latent image electrophotographically, or The electrostatic latent image is formed on the electrostatic recording material having a dielectric material such as polyethylene terephthalate by a needle electrode or the like, and the developer of the present invention is applied to the electrostatic latent image by a developing method such as a magnetic brush method or a cascade method. To form a toner image. This toner image is transferred to a transfer material such as paper and then fixed to form a copy.
The toner remaining on the surface of the photoconductor or the like is cleaned. As a cleaning method, a blade method, a brush method,
Various methods such as a web method and a roll method can be used.

(Examples) Hereinafter, the present invention will be specifically described with reference to Examples.

Example 1 Styrene-n-butylmeth 89 parts by weight Acrylate copolymer Dimethylquinacridone red pigment 1 part by weight Copper phthalocyanine blue pigment 10 parts by weight After melt-kneading, finely pulverized and classified to obtain a blue toner having an average particle size of 11.0 μm. It was

Then, SnCl ₄ was dissolved in water with respect to 100 parts by weight of the toner, and the precipitate was collected and collected. Then, tin oxide fine powder represented by SnO ₂ · SnO having an average particle size of 0.2 μm (this fine powder was analyzed by X-ray diffraction analysis Metal tin was not observed, and the electrical resistivity was 4.1 × 10 ⁷ Ω · cm.) 1.0 part by weight, polyvinylidene fluoride powder 0.5 part by weight and colloidal silica powder 0.5 part by weight were mixed with a Henschel mixer, Toner was obtained.

Example 2 For the toner composition of Example 1, 62 parts by weight of a graft copolymer of propylene copolymer and styrene-n-butylmethacrylate copolymer and styrene-n were used instead of the styrene-n-butylmethacrylate copolymer. Example 1 except that 27 parts by weight of -butyl methacrylate cross-linked copolymer is used
A toner was obtained in the same manner as in.

Example 3 A toner was obtained in the same manner as in Example 1 except that 11 parts by weight of carbon black was used instead of the dimethylquinacridone red pigment and the copper phthalocyanine blue pigment in the toner composition of Example 1.

Comparative Example 1 A toner was obtained in the same manner as in Example 2 except that the tin oxide fine powder represented by SnO ₂ .SnO was not used.

Comparative Example 2 A toner was obtained in the same manner as in Example 3 except that the tin oxide fine powder represented by SnO ₂ .SnO was not used.

Comparative Test Toners of Examples 1 to 3 and Comparative Examples 1 and 2 were mixed with a carrier obtained by coating a styrene-n-butyl methacrylate copolymer on a ferrite core having an average particle size of 130 μm to prepare a developer. Then, a continuous copying test of 15,000 sheets was performed using a copying machine (Fuji Xerox 3870), and the results shown in the following table were obtained.

Note: Charge Spectrograph (Charge Spect) introduced on page 85 of the Journal of the Electrophotographic Society, Vol. 22, No. 1 (1983).
rograph) Example 4 Propylene polymer and 56 parts by weight Graft polymer of styrene-n-butylmethacrylate copolymer 36 parts by weight styrene-n-butylmethacrylate Crosslinked acrylate polymer Copper phthalocyanine blue pigment 7 parts by weight Dimethylquinacridone red pigment After 1 part by weight was melt-kneaded, finely pulverized and classified to obtain an average particle size of 11.0 μ
m blue toner was obtained.

Next, SnCl ₄ was dissolved in water with respect to 100 parts by weight of the blue toner, and the precipitate was collected and recovered. Then, tin oxide fine powder represented by SnO ₂ · SnO having an average particle size of 0.2 μm , Metal tin is not recognized, and the electrical resistivity is 4.1 × 10 ⁷ Ω
・ It was cm. ) Was mixed with 0.5 parts by weight of polyvinylidene fluoride powder and 0.5 parts by weight of colloidal silica powder with a Henschel mixer to obtain a blue toner.

Example 5 Propylene polymer and 53 parts by weight Graft polymer of styrene-n-butylmethacrylate copolymer 35 parts by weight of styrene-n-butylmethacrylate Acrylate cross-linked polymer Copper phthalocyanine blue pigment 1 part by weight Dimethylquinacridone red pigment 5 parts by weight Disazo A brown toner was obtained in the same manner as in Example 4 except that 6 parts by weight of the yellow pigment was used.

Comparative Example 3 A blue toner was obtained in the same manner as in Example 4, except that carbon black (REGAL 330R) was used in place of the tin oxide fine powder represented by SnO ₂ .SnO in Example 4.

Comparative Example 4 A blue toner was obtained in the same manner as in Example 3 except that the tin oxide fine powder represented by SnO ₂ .SnO in Example 4 was not used.

Comparative Example 5 A brown toner was obtained in the same manner as in Example 5, except that the tin oxide fine powder represented by SnO ₂ .SnO in Example 5 was not used.

Comparative Test Toners of Examples 4 to 5 and Comparative Examples 3 to 5 were respectively mixed with a carrier obtained by coating a styrene-n-butyl methacrylate copolymer on a ferrite core having an average particle size of 130 μm to prepare a developer. Then, a continuous copying test of 15,000 sheets was performed using a copying machine (Fuji Xerox 3870), and the results shown in the following table were obtained. From the result, the effect of the present invention was clarified.

Note) The charge distribution values in the above table are based on the method introduced on page 85 of the Electrophotographic Society, Vol. 22, No. 1, (1983).

(Effects of the Invention) The electrophotographic developer of the present invention contains tin oxide fine particles having an electric resistance of 10 ⁵ Ω · cm to 10 ⁸ Ω · cm, which is represented by SnO ₂ · SnO. As is clear from the comparison, the transfer efficiency is improved, and good developability, particularly stable triboelectricity with a sharp charge distribution is exhibited. Further, there is no environmental dependence on the amount of charge and image quality, and the durability is excellent, and the image quality and fog do not occur even when copying a large number of sheets. Furthermore, when the color toner is used, the color tone is not impaired.

Claims (3)

[Claims] 1. A developer for electrophotography, comprising toner particles and tin oxide fine particles having an electrical resistance of 10 ⁵ Ω · cm to 10 ⁸ Ω · cm represented by SnO ₂ · SnO. . 2. The electrophotographic developer according to claim 1, wherein the tin oxide fine particles have an average particle diameter of 0.3 μm or less. 3. The electrophotographic developer according to claim 1, wherein the amount of tin oxide fine particles added is 0.1 to 5.0 parts by weight based on the weight of the toner.