JPH081521B2 - Toner for electrostatic charge development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrostatic charge developing toner used in the fields of electrophotography and the like. More specifically, the present invention relates to a toner for electrostatic charge development, which is excellent in developability and transferability, has good cleaning properties on a photoconductor, and has little toner film formation on the photoconductor and gear rear surface.

<Prior Art and Problems> Carriers have been conventionally used as a developer for developing an electrostatic latent image formed by various means on a latent image holding surface of an electrophotographic photoreceptor such as zinc oxide or selenium. A two-component developer composed of toner and toner is used. The toner is usually fine colored particles obtained by dissolving and kneading a binder resin, a colorant and the like, and then finely pulverizing them.

When using these toner particles in a PPC (plain paper copier), the following characteristics are required.

(1) The toner particles have uniform triboelectrification properties and have stable triboelectrification characteristics over time when mixed with a carrier. When the triboelectrification characteristics are non-uniform or unstable, various image defects such as fog occur and a good copy image cannot be obtained.

(2) The rate at which the developed toner particles are effectively transferred to paper or the like, that is, the transfer efficiency is sufficiently high. When the transfer efficiency is low, the obtained image is likely to have unevenness and blurring.

(3) When the toner particles remaining on the photoconductor after the transfer are cleaned by the cleaning member, the adhered toner particles can be easily and completely removed. When the cleaning property is poor, the load on the cleaning member becomes large, and finally, the toner particles left unremoved on the photoconductor may contaminate the copy image.

(4) Deterioration due to toner film formation on the photoconductor and the carrier surface is small during repeated copying. When the toner film formation is large, in the photoconductor,
There is a serious inconvenience that the function is deteriorated and the frictional electrification is deteriorated in the carrier.

As an attempt to satisfy these required characteristics,
For example, a method of adding fine particles of SiO ₂ or the like to the outside of toner particles is known. However, in the case of this method, during repeated use, development such as falling off and scattering of SiO ₂ particles or slipping into the toner particles was observed, and various defects due to these, that is, the triboelectric chargeability of the toner was remarkable. There are problems such as fluctuations, image contamination due to deterioration of cleaning property, and deterioration of function due to gradual increase of toner film formation on the surface of the photoconductor and the carrier. Therefore, the toner cannot sufficiently satisfy the above-mentioned required characteristics.

<Means for Solving Problems> The inventors of the present invention have solved the problems of the conventional toners described above and have made earnest studies to obtain a toner satisfying various required characteristics. As a result, the triboelectric chargeability of each toner particle is improved. We found a toner for electrostatic charge development that is uniform and stable, yet has good transferability, and also has excellent cleaning performance on the photoconductor, with less toner film formation on the photoconductor and the carrier surface.
The present invention has been reached.

<Configuration of the Invention> In other words, the gist of the present invention, at least a binder resin, the toner for electrostatic charge development made of metal oxide particles added to the colorant and an outer surface, the metal oxide fine particles CoO-Al ₂ O _{3 , CuO-Cr 2 O 3,} ZnO-Fe 2 O 3, CuO-Fe 2 O 3
-Mn ₂ O ₃ and TiO ₂ -BaO-NiO, one or more kinds of composite metal oxide fine particles selected from the group, and having a saturation magnetization of 10 CGS emu / g or less. It exists in the toner for charge development.

 Hereinafter, the present invention will be described in detail.

As the binder resin component in the toner of the present invention, various known ones can be used. For example, styrene resin, epoxy resin, polyester resin and the like. A styrene resin is particularly preferable, and specific examples thereof include polystyrene, a styrene-acrylate copolymer, and a styrene-methacrylate copolymer. Further, these may be crosslinked with a crosslinking agent such as divinylbenzene. Weight average molecular weight is 1,000 to 500,000,
It is preferably selected from 10,000 to 300,000.

As the colorant, various known colorants can be used.
Examples thereof include inorganic pigments such as carbon black, dark blue, and titanium oxide; organic pigments such as azo and phthalocyanine; and dyes such as triphenylmethane and anthraquinone. These are contained in the toner in an amount necessary for obtaining a clear visible image, but usually 20 parts by weight or less, preferably 10 parts by weight or less, relative to 100 parts by weight of the resin.

In the toner of the present invention, the binder resin, the colorant, and the specific composite metal oxide fine particles are essential constituent components.

The composite metal oxide fine particles used in the present invention are Zn, Ni, B.
After uniformly mixing compounds of two or more metals selected from the group of metals consisting of a, Fe, Co, Al, Cu, Ti, Cr and Mn (for example, oxides, hydroxides, carbonates, etc.), It is obtained by firing and pulverizing at an appropriate temperature and time. Specifically, CoO-Al ₂ O ₃ (blue), CuO-Cr ₂ O ₃ (black), ZnO-Fe ₂ O ₃ (brown), CuO _{-Fe 2 O 3 -Mn 2 O 3} ( black), a TiO ₂ -BaO-NiO (yellow) and the like.

The average particle diameter of these composite metal oxide fine particles is 3 μm or less, preferably 0.01 to 2 μm.

The composite metal oxide fine particles are added to the outer surface of the toner,
The amount used is preferably 0.01 to 5% by weight, and more preferably 0.05 to 2% by weight, per unit weight of the toner.

Further, in general magnetic toners, various magnetic compounds are used in order to impart magnetic force to the toner, but the complex metal oxide fine particles used in the present invention are different in the purpose, and are low magnetic or nonmagnetic. The composite metal oxide fine particles of 4 give good results. Therefore, in the composite metal oxide fine particles according to the present invention, the saturation magnetization is 10 CGS em
It should be u / g or less, preferably 5 CGS emu / g or less. When the saturation magnetization is larger than the above range,
With repeated use, the attraction of the toner particles or the fine particles of the composite metal oxide on the surface of the toner particles becomes remarkable due to the magnetic force of the developer magnet interposing the carrier, and the intended purpose cannot be achieved.

The value of the saturation magnetization in the present invention is a commercially available B-H value.
This is the value obtained by converting the strength of magnetization measured under a magnetic field of 5K oersted using a tracer per 1 g of the object to be measured.

Since the composite metal oxide according to the present invention can be obtained in various color tones, it can be advantageously used in color toners.

Moreover, you may use together with 2 or more types of composite metal oxide fine particles as needed.

Furthermore, the surface of the composite metal oxide fine particles may be treated with an inorganic substance such as SiO ₂ or an organic substance such as a resin in order to improve the charging property and the dispersibility.

The electrostatic charge developing toner of the present invention may contain a known charge control agent, if necessary. Examples of the positively chargeable charge control agent include nigrosine dye, polyamine resin, amino group-containing styrene resin, quaternary ammonium salt and the like. Examples of the charge control agent having negative chargeability include complex salt azo dyes containing Cr, Fe, Co and the like. The amount used is preferably 10 parts by weight or less based on 100 parts by weight of the binder resin.

In addition, various internal or external additives such as a low molecular weight olefin polymer may be included as a constituent component of the electrostatic charge developing toner of the present invention in order to improve fixability. It should not be detrimental to the purpose of.

Further, as a method for producing a toner, the above components may be kneaded in a kneader or the like, cooled, pulverized and classified, and externally added by a stirrer or the like, if necessary. The average particle size of the toner is preferably 5 to 20 μm.

Carriers that form a developer by mixing with the electrostatic charge developing toner of the present invention include, for example, iron powder, ferrite powder,
Magnetite powder and the like can be mentioned, and any of them can be preferably used. Further, a so-called coating carrier coated with various resins or the like may be used for the purpose of improving durability during continuous use. The average particle size of the carrier is 10-
200 μm is preferable. The mixing weight ratio of the carrier and the toner is preferably 100: 1 to 10.

<Examples> Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist. In the examples, "part" is "part by weight".
Indicates. Further, the saturation magnetization of the composite metal oxide fine particles is a DC magnetization BH characteristic automatic recording device (manufactured by Riken Denshi Co., Ltd., model).
BHU-60, magnetic field 5K Elsted), and the charge amount of the developer was measured using a blow-off charge amount measuring device (manufactured by Toshiba Chemical Co., Model TB-200).

Example 1 and Comparative Example 1 A styrene / n-butyl acrylate copolymer resin having a weight average molecular weight of about 70,000 as a binder resin (monomer ratio 80/2
0), diamond black # 30 (manufactured by Mitsubishi Kasei Co., Ltd.) as a colorant, and a negatively chargeable Bontron S as a charge control agent.
Toner A shown in Table 1 below was obtained using -34 (complex azo dye containing Cr, manufactured by Orient Chemical Co., Ltd.).

To prepare the toner, toner raw materials were preliminarily mixed, kneaded by an extrusion type kneader, cooled and solidified, coarsely pulverized by a hammer mill, and further pulverized by a jet mill. Then, classification was performed by a zigzag classifier to obtain a toner A having an average particle size of 11.3 μm.

Next, CuO-Fe ₂ O to toner A ₃ -Mn ₂ O ₃ (composition ratio 30: 10: 6
0.3% by weight of the composite metal oxide fine particles having a particle size of 0 and an average particle size of about 0.05 μm) was added using a chemical mixer (Model H-85 manufactured by Centrifuge manufactured by Japan) to obtain a toner sample. The saturation magnetization of the composite metal oxide fine particles is 2.5C.
It was GS emu / g.

Next, 5 parts of this toner sample was mixed with 100 parts of iron powder carrier having an average particle size of about 70 μm to prepare a developer. The charge amount of the developer was −20 μC / g.

On the other hand, Toner A containing no fine particles of the composite metal oxide
A single developer was prepared exactly the same and compared to the developer according to the invention. The charge amount of the developer was −19 μC / g.

When a developer using these developers was used in a copying machine having selenium as a photoreceptor, and the images were transferred onto plain paper, clear images were obtained. However, when the performance was examined by further conducting a continuous transfer test, a decrease in image density and an increase in fog were observed from around 8,000 sheets with the developer containing toner A alone, and it was almost used after about 10,000 sheets. I couldn't stand it. At that time, the charge amount of the developer was as low as −14 μC / g. The transfer efficiency was about 80% before and after. In contrast, the developer containing the composite metal oxide fine particles of the present invention showed almost no change in image quality up to about 30,000 sheets, the developer charge amount was almost constant, and the transfer efficiency was 90% or more.

Observation of the state of formation of the toner film on each photoconductor revealed that the toner film alone did not form a toner film, whereas the toner containing the composite oxide fine particles did not show any formation. It was

Further, regarding the state of the toner film formed on the carrier surface in these developers, the toner film formed on each carrier surface was dissolved in an organic solvent and the weight thereof was measured. %, Whereas the developer containing the composite metal oxide fine particles of the present invention was as small as about 0.1% by weight.

Examples 2 and 3 Toner samples and developers were prepared in exactly the same manner as in Example 1 except that the toner A prepared in Example 1 was used and the composite metal oxide fine particles shown in Table 2 below were externally added. .

The charge amount of the developer containing CuO-Cr ₂ O ₃ particles is -20 μC /
The developer containing g and ZnO-Fe ₂ O ₃ had a concentration of -22 μC / g.

Next, using these developers, image forming and continuous copying tests were conducted in exactly the same manner as in Example 1.

As a result, good quality copies were obtained with no change in image quality for all the developers up to about 30,000 sheets, and the charge amount of the developers was almost constant. The transfer efficiency was 90% or more, which was favorable.

Further, no toner film was formed on the photoconductor, and the amount of toner film formed on the carrier surface was almost the same as in Example 1 and small.

Example 4 and Comparative Example 2 The same binder resin and colorant as used in Example 1 were used, and positively chargeable Bontron NO1 (Nigrosine dye manufactured by Orient Chemical Co., Ltd.) was used as a charge control agent. Toner B shown in Table 4 below was obtained.

The toner was prepared in exactly the same manner as in Example 1. The average particle size of Toner B was 13 μm.

Next, for toner B, TiO-BaO-NiO (composition ratio 50:
A toner sample was prepared by adding 0.5% by weight of composite metal oxide fine particles having a particle size of 40:10 and an average particle size of about 0.5 μm) in the same manner as in Example 1. The saturation magnetization of the composite metal oxide fine particles was 0 CGS emu / g, that is, a non-magnetic substance.

A developer was prepared by mixing 5 parts of this toner sample with 100 parts of a fluorine-based resin coating carrier having an average particle size of about 70 μm. The charge amount of the developer was 23 μC / g.

On the other hand, instead of the above composite metal oxide fine particles, for toner B, SiO ₂ fine powder R-972 (manufactured by Nippon Aerosil Co., Ltd.)
A developer containing 0.2% by weight was prepared in the same manner as a comparative sample. The charge amount of this developer was 18 μC / g.

When these developing agents were used for development with a copying machine using OPC (organic photoconductor) as a photoconductor and transferred to plain paper, clear images were obtained.

However, when the performance was examined by further conducting a continuous copying test, a developer containing fine-powder SiO ₂ showed image contamination due to a decrease in image density and poor cleaning from around 10,000 sheets. Almost no longer usable. At that time, the charge amount of the developer was 27 μC / g, which was much higher than the initial amount. In contrast, the developer containing the composite metal oxide fine particles of the present invention showed almost no change in image quality even after about 40,000 sheets, and no image contamination due to poor cleaning occurred. The developer charge at that time is also 25 μC / g
Was stable.

Further, when the amount of toner film generated on the carrier surface in these developers was examined, it was about 0.5% by weight in the developer containing fine powder SiO ₂ , whereas the composite metal oxide fine particles of the present invention were used. The amount of the developer contained was as small as about 0.1% by weight.

Example 5 Epoxy resin Epicoat 1007 (manufactured by Yuka Shell Co., Ltd.) as a resin, Hosta Palm Blue B3G (manufactured by Hoechst) as a colorant, and positively chargeable SAM-955 (manufactured by Sanyo Kasei Co., containing an amino group) as a charge control agent. (Styrene-based resin) and in the same manner as in Example 1 to give blue toner C shown in Table 5 below.
(Average particle size 15 μm) was obtained.

Next, for toner C, blue CoO-Al ₂ O ₃ fine powder (composition ratio 25:75, average particle size of about 0.5 μm, saturation magnetization of 0.3 CGS e
A toner sample was prepared by adding 1.0% by weight of mu / g) in exactly the same manner as in Example 1.

Thereafter, a developer was prepared in exactly the same manner as in Example 3, and an image was printed and a continuous copying test was conducted. The initial charge amount of the developer was 16 μC / g.

As a result, a clear blue copy was obtained from the initial stage to about 40,000 sheets, and the charge amount was stable at 18 μC / g. Further, the transfer efficiency was 90% or more, which was good, and almost no toner film was found on the surface of the photoreceptor or the carrier.

<Effects of the Invention> When the toner for electrostatic charge development of the present invention is used, a long-life developer with high quality image and less deterioration in performance over time can be obtained.

Continuation of front page (56) Reference JP-A-60-32060 (JP, A) JP-A-56-66856 (JP, A) JP-A-53-81127 (JP, A) JP-A-52-135739 (JP , A) JP-A-60-136752 (JP, A)

Claims (3)

[Claims] 1. A toner for electrostatic charge development comprising at least a binder resin, a colorant, and metal oxide fine particles added to the outer surface of the toner, wherein the metal oxide fine particles are CoO—Al ₂ O ₃ ,
_{CuO-Cr 2 O 3, ZnO} -Fe 2 O 3, CuO-Fe 2 O 3 -Mn 2 O 3 and TiO ₂
-BaO-NiO, one or more kinds of composite metal oxide fine particles selected from the group consisting of, and having a saturation magnetization of 10 CGS em
A toner for electrostatic charge development, which is u / g or less. 2. The average particle size of the composite metal oxide fine particles is 3 μm.
The toner for electrostatic charge development according to claim 1, wherein: 3. Composite metal oxide fine particles on the outer surface of the toner
The toner for electrostatic charge development according to claim 1, wherein the toner is added in the range of 0.01 to 5% by weight.