JPH11174721A - Electrophotographic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic developer capable of regulating the quantity of electric charges with fine metal oxide particles and having stable electrostatic charge characteristics even in continuous use over a long period of time. SOLUTION: The electrophotographic developer consists of toner particles contg. at least a bonding resin and a colorant and fine metal oxide particles added to the toner particles. The fine metal oxide particles have a compsn. represented by the formula Six Ay O(4x+yz)/2 [where A is a metallic element, (Z) is the valance of A and 1<=x/y<=25].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer used in copying machines, printers, and the like. More specifically, the charge amount is adjusted by fine metal oxide particles, and the charge characteristics are stable even during long-term continuous use. To an electrophotographic developer.

[0002]

2. Description of the Related Art Heretofore, the charge amount of an electrophotographic developer has been adjusted by a charge control agent such as nigrosine or a quaternary ammonium salt. However, as the technology of the post-treatment agent has advanced, it has become possible to adjust the charge amount using the post-treatment agent. Examples of the method include a method of adding two or more different post-processing agents and adjusting the ratio according to the addition ratio, and a method of adjusting the surface of the post-processing agent by applying a coupling treatment to the developer, and the like. Is mentioned. For example, Japanese Patent Publication No. 53-22447 discloses a positively chargeable developer containing metal oxide particles treated with aminosilane as a component of the developer.

[0003]

However, in the method using the surface modification of the post-treatment agent, the surface stability cannot be obtained, and the treated surface is deteriorated by continuous use for a long period of time. Also, there is a problem that the initial charging characteristics cannot be maintained due to deterioration. In addition, even when two or more different post-treatment agents are used, due to continuous use, only one type of post-treatment agent selectively separates from the surface of the toner particles, thereby deteriorating the charge balance. It was difficult to hold. If the charging stability is low, background fogging occurs in the copied image due to repeated copying, which is a problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrophotographic developer capable of adjusting a charge amount by metal oxide fine particles and having stable charge characteristics even when used continuously for a long period of time. With the goal.

[0005]

According to the present invention, there is provided an electrophotographic developer comprising toner particles containing at least a binder resin and a colorant, and metal oxide fine particles added to the toner particles. composition oxide fine formula Si _x A _y
O _{(4x + yz) / 2} (where A represents a metal element and z represents the valence of A), and x / y is 1 to 25, for electrophotography. Related to the developer.

In the present invention, instead of modifying only the surface of the metal oxide fine particles added to the toner particles,
By changing the composition of each metal oxide fine particle to be added to adjust the charge amount of the metal oxide fine particles themselves, and adding this to the toner particles, the charge stability of the electrophotographic developer can be improved. It was found that the chargeability was improved, that is, the initial charging characteristics were maintained even after long-term continuous use.

Hereinafter, the present invention will be described for the case where metal oxide fine particles are externally added to toner particles comprising at least a binder resin and a colorant, but the present invention is not limited to this. The metal oxide fine particles may be added (internally added) in the toner particle manufacturing process so as to be present inside the toner particles. In the present invention, it is desirable that the metal oxide fine particles are externally added to the toner particles because the effect of adjusting the charge amount is higher when the metal oxide fine particles are present near the surface of the toner particles. In the present specification, “external addition” means adding and mixing once obtained toner particles.

[0008] Metal oxide fine particles added in the present invention is represented by the composition formula _{Si x A y O (4x +} yz) / 2. In the formula, A represents a metal element, preferably represents aluminum, boron, titanium, zinc, vanadium or the like, and more preferably represents aluminum, boron or titanium. z represents the valence of the metal element A used. In the above composition formula, x / y is 1 to 25, preferably 1 to 20, and more preferably 1 to 10. x / y is less than 1,
If it exceeds 25, even if the metal oxide fine particles are added,
The charging stability of the obtained electrophotographic developer is not improved.

Examples of the metal oxide fine particles having x / y of 1 to 25 include metal oxide fine particles having the composition formula shown in Table 1 below. Table 1 shows the composition formulas in the case where A in the composition formula is aluminum (Al), boron (B) and titanium (Ti), and Al ₂ O ₃ , B ₂ O ₃ or TiO ₂ in each composition formula. Is exemplified.

[0010]

[Table 1]

The metal oxide fine particles used in the present invention have a work function of 4.0 to 5.0 eV. The work function refers to the minimum energy required to extract one electron from the crystal surface to just outside the surface. In the metal inorganic fine particles used in the present invention, the work function is a value closely related to the chargeability of the toner. That is, by controlling this, the chargeability of the metal oxide fine particles can be more easily adjusted, and further, the chargeability of the toner to which the metal oxide fine particles are added can be adjusted. If the work function is less than 4.0 eV or exceeds 5.0 eV, the charge stability of the electrophotographic developer may not be improved even when the metal oxide fine particles are added.

In the present invention, the specific surface area of the metal oxide fine particles is from 10 to 10 from the viewpoints of chargeability and fluidity of the toner.
It is desirably 400 m ² / g, preferably 40 to 200 m ² / g.

The method for producing the metal oxide fine particles of the present invention is not particularly limited as long as the one having the above composition formula can be produced, and examples thereof include a known production method by a gas phase method. The gas phase method is a method of producing metal oxide fine particles by subjecting a metal halide compound to a vapor phase oxidation at a high temperature. The gas phase method, together with a silicon halide compound, forms a halogen of a metal corresponding to A in the above composition formula. The metal oxide fine particles having the above composition can be produced by using the compound in various ratios.

The metal oxide fine particles produced in this manner usually contain impurities contained in the above-mentioned metal halide compounds. In the present invention, the impurities are within a range that does not adversely affect the effects of the present invention. If so, impurities may be contained, and preferably 10% by weight or less is desirable.

The metal oxide fine particles are added in an amount of 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the toner particles. 0.0
When the amount is less than 1 part by weight, there is no effect on the adjustment of the charge amount. On the other hand, when the amount exceeds 5 parts by weight, the transfer amount to the carrier increases, so that the durability performance deteriorates.

Further, in the present invention, the inorganic particles having an average primary particle diameter of 20 nm or less, preferably 6 to 18 nm, which is different from the metal oxide particles having the above composition, are externally added together to the toner particles to further improve the chargeability. Fluidity can be obtained. As the inorganic fine particles, known inorganic fine particles conventionally known as a fluidizing agent, for example, silica, alumina, boron oxide, titanium oxide, magnesium fluoride, silicon carbide, boron carbide, titanium carbide, zirconium carbide, nitrided Examples include boron, titanium nitride, zirconium nitride, magnetite, molybdenum disulfide, aluminum stearate, magnesium stearate, and zinc stearate, and preferably silica. In addition, it is desirable to use these inorganic fine particles after hydrophobizing them with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil, or the like from the viewpoint of environmental stability. The addition amount of the inorganic fine particles is 0.01 to 5 parts by weight, preferably 0.1 to 3 parts by weight, based on the total amount of the metal oxide fine particles and 100 parts by weight of the toner particles. desirable.

In the present invention, the metal oxide fine particles are externally added to toner particles. The toner particles used in the present invention are prepared by using a binder resin, a colorant and other desired additives as described below, by a kneading and pulverizing method, a suspension polymerization method, an emulsion polymerization method, an emulsion dispersion granulation method, and encapsulation. It can be produced by other known methods such as a method. Among these manufacturing methods, kneading and mixing are considered from the viewpoint of manufacturing cost and manufacturing stability.
It is preferable to employ a pulverization method.

For example, the kneading and pulverizing method includes a step of mixing toner particles such as a binder resin and a colorant with a mixer such as a Henschel mixer, a step of melting and kneading the mixture, and a step of cooling and kneading the kneaded material. And toner particles are produced by a step of classifying the obtained pulverized particles. The volume average particle diameter of the toner particles of the present invention is preferably adjusted to 4 to 10 μm, more preferably 6 to 9 μm, from the viewpoint of high definition reproducibility of an image.

As the binder resin used in the present invention, for example, polyester, polystyrene, styrene-
Acrylic resins, methacrylic resins, and derivatives and mixtures thereof can be used.

Examples of the colorant include the following pigments and dyes. Black pigments include carbon black,
Copper oxide, manganese dioxide, aniline black, activated carbon,
Ferrite, magnetite, etc. can be used. Examples of yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, banza yellow G, banza yellow 10
G, benzidine yellow G, benzidine yellow GR,
Quinoline Yellow Lake, Permanent Yellow NC
G, tartrazine rake and the like can be used.

Examples of the red pigment include red lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indaslen brilliant orange RK, benzidine orange G, indaslen brilliant orange GK, bengala, cadmium red, lead red, permanent Red 4R, Risor Red,
Pyrazolone red, watching red, lake red C, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake,
Brilliant Carmine 3B, permanent orange GT
R, Vulcan Fast Orange GG, Permanent Red F4RH, Permanent Carmine FB and the like can be used. Blue pigments include navy blue, cobalt blue, alkaline blue lake, Victoria blue lake,
Phthalocyanine blue or the like can be used. In addition, although the addition amount of these coloring agents is not particularly limited,
Usually, 1 to 20 parts by weight with respect to 100 parts by weight of the binder resin,
Preferably, the amount is 3 to 15 parts by weight.

Other desired additives to be added in addition to the binder resin and the colorant include a magnetic substance, a charge control agent, and an anti-offset agent. Specifically, the magnetic substance includes magnetite. , Γ-hematite or various ferrites.

The charge control agent is not particularly limited. Examples of the positive charge control agent include a nigrosine dye, a triphenylmethane compound, and a quaternary ammonium salt compound. ,
Examples thereof include a salicylic acid metal complex, a gold-containing azo dye, a calixarene compound, and a boron-containing compound. The addition amount is 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin.

The offset preventing agent is not particularly limited. For example, polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax, carnauba wax, sasol wax, rice wax, candelilla wax, jojoba Oil wax, beeswax and the like can be used. The amount of the wax to be added depends on the binder resin 100
0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, based on parts by weight

The developer of the present invention comprises adding the above metal oxide fine particles to toner particles comprising the above toner particle components,
It is obtained by mixing with a mixer such as a Henschel mixer. When the metal oxide fine particles are internally added to the toner particles, that is, when the metal oxide fine particles are added during the production process of the toner particles, the metal oxide fine particles are added in the first mixing step similarly to other toner particle components.

The developer of the present invention can be used in either a one-component developer using no carrier or a two-component developer used with a carrier. As the carrier used with the toner of the present invention, known carriers can be used, for example, iron powder, a carrier composed of magnetic particles such as ferrite, a coated carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, Alternatively, any of a binder-type carrier obtained by dispersing a magnetic fine powder in a binder resin can be used. Such a carrier has a volume average particle size of 15 to 100 μm, preferably 20 to 80 μm.
μm is preferred.

The developer obtained as described above can maintain the initial charging characteristics without deteriorating the charging characteristics even when used continuously for a long period of time. No good copy image can be provided. The present invention is described in more detail by the following examples.

[0028]

EXAMPLES (Production of toner particles) 100 parts by weight of a styrene-acrylic resin (Tm = 118 ° C., Tg = 68 ° C.), 8 parts by weight of carbon black (Mogal L: manufactured by Cabot Corporation),
3 parts by weight of low-molecular-weight polypropylene (Viscol 550P: manufactured by Sanyo Chemical Co., Ltd.) were thoroughly mixed with a Henschel mixer,
After kneading with a twin screw extruder, the mixture was cooled. The kneaded product was pulverized using a jet mill and classified by wind power to obtain toner particles having a volume average particle size of 9 μm.

Example 1 Metal oxide fine particles having a composition weight ratio of SiO ₂ / Al ₂ O ₃ = 70/30 were obtained from Kojundo Chemical Laboratory Co., Ltd. and analyzed by X-ray fluorescence. As a result, the composition was identified to be Si ₅ Al ₂ O ₁₃ . Specific surface area meter (MS-12: QUANTAC) of the metal oxide fine particles.
The specific surface area was measured by HROME Co., Ltd., and the work function was measured by a contact potentiometer (SSVII-10: manufactured by Kawaguchi Electric Co., Ltd.). The results are summarized in Table 2. The metal oxide fine particles are mixed with the toner particles 10 described above.
0.8 part by weight was added to 0 part by weight, followed by stirring with a mixer for 2 minutes to obtain a developer.

Example 2 Metal oxide fine particles having a composition weight ratio of SiO ₂ / TiO ₂ = 70/30 were obtained from Kojundo Chemical Laboratory Co., Ltd., and subjected to elemental analysis by fluorescent X-ray analysis. As a result, the composition ratio was identified to be Si ₄₁ Ti ₁₀ O ₁₀₂ . The specific surface area and work function of the metal oxide fine particles were measured in the same manner as in Example 1, and are shown in Table 2. Thereafter, a developer was obtained in the same manner as in Example 1.

Example 3 Metal oxide fine particles having a composition weight ratio of SiO ₂ / B ₂ O ₃ = 95/5 were obtained from Kojundo Chemical Laboratory Co., Ltd.
When subjected to elemental analysis by fluorescent X-ray analysis, the composition ratio was identified to be Si ₆₈ B ₁₀ O ₁₅₁ . The specific surface area and work function of the metal oxide fine particles were measured in the same manner as in Example 1, and are shown in Table 2. Thereafter, a developer was obtained in the same manner as in Example 1.

Example 4 Hydrophobic silica (R-9) was added to 100 parts by weight of the above toner particles together with 0.8 parts by weight of the metal oxide fine particles used in Example 1.
74: manufactured by Nippon Aerosil Co., Ltd., work function 4.89, specific surface area 179 m ² / g)
After stirring for a minute, a developer was obtained. The specific surface area and work function of the metal oxide fine particles were measured in the same manner as in Example 1, and are shown in Table 2.

Comparative Example 1 Hydrophobic silica (RA20) was added to 100 parts by weight of the toner particles.
(0H: manufactured by Nippon Aerosil Co., Ltd.) and stirred with a mixer for 2 minutes to obtain a developer. The specific surface area and work function of the inorganic fine particles were measured in the same manner as in Example 1, and are shown in Table 2.

Comparative Example 2 Hydrophobic silica (R-97) was added to 100 parts by weight of the toner particles.
4: 0.6 parts by weight of Nippon Aerosil Co., Ltd.) and 0.2 parts by weight of alumina fine particles (RX-C: Nippon Aerosil Co., Ltd.) were added, followed by stirring with a mixer for 2 minutes to obtain a developer. A mixture of these inorganic fine particles (weight ratio: SiO ₂ / Al ₂ O ₃ = 3)
The specific surface area and work function of (/) were measured in the same manner as in Example 1, and are shown in Table 2.

[0035]

[Table 2]

(Evaluation Method) A two-component developer was prepared by mixing the developers obtained in Examples and Comparative Examples with the carriers obtained as described below at a ratio of developer / carrier = 5/95. This developer was mounted on EP470Z (manufactured by Minolta), and a durability test of 10,000 sheets was performed at 23 ° C. and 45 RH% using a chart having a B / W ratio of 6%. Before and after the durability test, the amount of charge was measured and the toner fog on the background was visually ranked. The ranking is performed in accordance with the above, x is not practically usable, Δ or more is practically usable, ○ is desirable, and ◎ is more desirable. Table 3 shows the evaluation results and the measurement results.

Fog ◎: Fog did not occur in the image at all; 〇: Fog hardly occurred in the image; Δ: Fog slightly occurred in the image, but there was no practical problem; This caused a practical problem.

Measurement of Charge Amount was measured by a blow-off method.

[0039]

[Table 3]

(Example of Carrier Production) Polyester Resin
(NE-1110: manufactured by Kao Corporation) 100 parts by weight, inorganic magnetic powder
500 parts by weight (EPT-1000: manufactured by Toda Kogyo KK) and 2 parts by weight of carbon black (MA # 8: manufactured by Mitsubishi Chemical Corporation) are sufficiently pulverized and mixed by a Henschel mixer, and are melted and kneaded using an extruder. After cooling the material, coarsely pulverizing, finely pulverizing with a jet mill, further classifying with an air classifier,
A binder type magnetic carrier having an average particle size of 55 μm was obtained.

[0041]

The chargeability of the developer of the present invention can be adjusted by adding metal oxide fine particles, and the chargeability of the initial state can be maintained even after repeated use for a long period of time.
Furthermore, by using inorganic fine particles of 20 nm or less different from the metal oxide fine particles in combination with the developer of the present invention, problems such as background fog on copied images during repeated use over a long period of time can be more effectively reduced. Can be solved.

Claims (4)

[Claims] 1. An electrophotographic developer comprising toner particles containing at least a binder resin and a colorant, and metal oxide fine particles added to the toner particles, wherein the metal oxide fine particles have a composition formula of Si _x A _y O _{(4x + yz) / 2} (where A represents a metal element and z represents the valence of A), wherein x / y is 1 to 25. Photographic developer. 2. The electrophotographic developer according to claim 1, wherein the metal oxide fine particles are externally added to the toner particles. 3. A composition formula _{Si x A y O (4x +} yz) / 2 ( in the formula, A
Represents a metal element, and z represents a valence of A. Average primary particle diameter 20 nm different from the metal oxide fine particles represented by
The electrophotographic developer according to claim 1, wherein the following inorganic fine particles are further externally added. 4. A composition formula _{Si x A y O (4x +} yz) / 2 of A is Al
The electrophotographic developer according to claim 1, wherein: