JPH07104520A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain a developer ensuring high image quality and having a long service life as well as to improve flowability and to increase the rising speed of electrostatic charge by reducing the average particle diameter of an electric charge controlling agent and the average particle diameter of the primary particles of hydrophobic fine silica particles sprinkled on toner particles. CONSTITUTION:This toner consists of toner particles contg. a bonding resin and an electric charge controlling agent, and hydrophobic fine silica particles. The volume average particle diameter of the toner particles is <=8mum, the average particle diameter of the electric charge controlling agent is <=4mum and the average particle diameter of the primary particles of the fine silica particles is <=0.013mum. The electric charge controlling agent is uniformly dispersed because of using the <=4mum average particle diameter and the rising of electrostatic charge is not affected. The toner particles can be efficiently coated with the hydrophobic fine silica particles because of the <=0.013mum average particle diameter and the flowability can be improved. Since both flowability and electrostatic chargeability are ensured, the service life of this fine toner in a severe environment can be prolonged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in powder toner used in electrostatic photography, electrostatic printing, etc.
The present invention relates to an improvement for improving the copy life without the influence of a bad environment.

[0002]

2. Description of the Related Art An electrophotographic copying method is a system for obtaining a hard copy by forming an image by utilizing a photoconductive phenomenon, and the process includes charging, exposing, developing, transferring, fixing and cleaning steps. There is. Among them, in the developing process, the electrostatic latent image formed on the image support is electrostatically attracted with a toner having a polarity opposite to that of the electrostatic latent image, so that the latent image is visualized. Is. This development process is the process that most strongly affects the final copy image,
Therefore, the characteristics of the toner are one of the important factors along with the characteristics of the photoconductor that forms the electrostatic latent image.

The toner contains a fixing resin and a colorant as essential components, and various organic and inorganic materials such as a charge control agent, a conductivity control agent and a release agent are dispersed and mixed in the fixing resin as required. These are fine resin particles, and in the production, the above-mentioned toner materials are mixed, and the mixture is melt-kneaded to uniformly disperse various constituent materials, followed by cooling, crushing and classification to obtain toner particles. Since these toner particles are still insufficient in fluidity, it is widely practiced to sprinkle fine particles of silica or the like. As silica fine particles, hydrophobic silica is used to prevent deterioration of electrical characteristics due to the environment. Is commonly used.

By the way, recently, as the image quality is improved, the particle size of the toner is becoming smaller. That is, it is not necessary to say that the smaller the particle size of the toner is, the better the resolving power of the image and the reproducibility of the fine line. The problem occurs.

[0005]

First, there is a problem that the fluidity is lowered and the charging becomes unstable especially in a bad environment of low temperature and low humidity and high temperature and high humidity. In order to prevent this, silica fine particles are generally attached to the surface of the toner particles, but it is difficult to say that the improvement in fluidity alone is a fundamental improvement.

That is, if silica fine particles are used, it is possible to improve the fluidity without adversely affecting the process, but since the chargeability of the toner particles themselves has not been improved, the charge rises in a bad environment. However, toner is scattered or images are fogged when a continuous copy or a document having a large black portion ratio is copied. The present invention has been made in view of the above circumstances, and provides an electrophotographic toner having a high fluidity even with a small particle size toner, a fast rising speed of charging, and a stable charging property. The purpose is to do.

[0007]

According to the present invention, there is provided an electrophotographic toner comprising toner particles containing at least a fixing resin, a charge control agent, and hydrophobic silica fine particles,
The volume average particle diameter of the toner particles is 8 μm or less, the average particle diameter of the charge control agent is 4 μm or less, and the average particle diameter of the primary particles of the hydrophobic silica fine particles is 0.013 μm or less. A photographic toner is provided.

[0008]

The electrophotographic toner of the present invention is composed of toner particles having a volume average particle size of 8 μm or less, which are composed of a fixing resin and a charge control agent dispersed in the fixing resin, and hydrophobic silica fine particles. It is a remarkable feature that both the average particle diameters of and the average particle diameter of the primary particles of the hydrophobic silica fine particles are smaller than those generally used.

In the present specification, the average particle diameter of the primary particles of the charge control agent and the hydrophobic silica fine particles means the number average diameter determined by a scanning electron microscope. In the present invention, if the charge control agent is larger than 4 μm, it is difficult for the charge control agent itself to be crushed when the fixing resin and the colorant, the charge control agent and other toner compounding agents are mixed and adjusted in the production stage, and finally, This is because even if toner particles having a small particle size are obtained by kneading, pulverizing, and classifying, it is difficult for the toner particles to uniformly exist on the surface and inside of the toner particles, and the rise of charging is reduced. As a result, toner scattering and fog occur. However, by using the charge control agent having a thickness of 4 μm or less, the charge control agent can be uniformly dispersed, and these can be prevented.

As the charge control agent, any charge control agent known per se and having an average particle size of 4 μm or less, for example, Bontron S-44 (manufactured by Orient Chemical Co., Ltd.), nigrosine base (CI 50415), oil black ( CI
26150), oil-soluble dyes such as spirone black, metal-containing azo dyes, metal salts of naphthenic acid, metal salts of alkylsalicylic acid, fatty acids, soaps, resin acid soaps and the like.

Further, in the present invention, when the hydrophobic silica fine particles are larger than 0.013 μm, the fluidity is deteriorated particularly in a bad environment, and the small particle toner having a large specific surface area can be efficiently coated with the silica fine particles. Can not. But,
By using the hydrophobic silica fine particles having a particle size of 0.013 μm or less, the coating can be efficiently performed, and the fluidity can be improved.

The hydrophobic silica-based additive used in the present invention is
It is obtained by treating vapor-phase process silica, that is, fine silica obtained from a high-temperature (fire) hydrolysis process of silicon chloride, with silanes such as dimethyldichlorosilane and sealing the silanol on the surface with organosilane. More liquidity,
By making both of the charging properties compatible, it becomes possible to extend the life of the small particle size toner in a bad environment.

In the toner particles of the present invention, a binder resin is mixed with additives such as a colorant, a charge control agent and a release agent,
It is manufactured by granulating to a particle size of 8 μm or less. A styrene resin, an acrylic resin, a styrene-acrylic resin, a polyester resin, a polyurethane resin, a silicone resin, a polyamide, a modified rosin, or the like is used as the binder resin as the toner component.

As the colorant, a conventionally known colorant can be used. For example, particles having an average primary particle size of 40 to 60 nm, such as Mitsubishi Kasei Carbon Black # 25 (registered trademark), are suitable. Other colorants listed below can be preferably used. Black furnace black, channel black, gas black, oil black, carbon black such as acetylene black, lamp black, aniline black white zinc white, titanium oxide, antimony white, zinc sulfide red red iron oxide, cadmium red, red lead, mercury sulfide , Cadmium, Permanent Red 4R, Resor Red,
Pyrazolone red, watching red calcium salt,
Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B Orange Red Lead Yellow, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Indanthrene Brilliant Orange RK, Benzidine Orange G, Indanthrene Brilliant Orange GK Yellow Yellow Lead, Zinc Flower, Cadmium Yellow, Yellow Iron Oxide, Mineral Fast Yellow, Nickel Titanium Yellow, Navels Yellow, Naphthol Yellow S, Hansar Yellow G, Hansar Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake Green Chromium Green, Chromium Oxide, Pigme Togulin B, Malachite Green Lake, Final Yellow Green Blue Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partial Chloride, Farnest Sky Blue, Indanthrene Blue BC, Metal-free Phthalocyanine Blue Purple Manganese Purple, Fast Violet B, methyl violet lake extender pigments include, for example, perlite powder, barium carbonate,
Examples include clay, silica, white carbon, talc, and alumina white.

Examples of the conductive pigment include conductive carbon black and various metal powders such as aluminum powder. Examples of magnetic pigments include iron trioxide (magnetite iron black); iron sesquioxide (γ-Fe2O3), zinc iron oxide (ZnFe2O4), yttrium iron oxide (Y3Fe5O1).
2), iron cadmium oxide (CdFe2O4), iron oxide gatorium (Gd3Fe5O4), iron oxide copper (CuFe2O)
4), iron oxide lead (PbFe12O19), iron oxide nickel (NiFe2O4), iron oxide neodymium (NdFeO3),
Iron oxide barium (BaFe12O19), iron oxide magnesium (MgFe2O4), iron manganese oxide (MnFe2O)
4), various ferrites such as lanthanum iron oxide (LaFeO3); iron powder, cobalt powder, nickel powder and the like.

Examples of the photoconductive pigment include zinc oxide,
Examples thereof include selenium, cadmium sulfide, selenium, cadmium sulfide, and cadmium selenide. Manufacture of Toner A binder resin, a colorant, a charge control agent, a release agent and the like are mixed and stirred. The mixing and stirring should be carried out under the condition that a low load and a low shearing force are applied, and generally, it can be carried out by various mixing and stirring devices such as a conical blender, a ribbon blender, a V type blender, a Nauta mixer, a Henschel mixer and a ball mill. The mixing and stirring temperature is preferably lower than the glass transition point (Tg) of the binder resin. The required mixing / stirring time varies depending on the type of equipment and the input amount, but generally a range of 10 to 300 minutes is suitable.

The premix thus obtained is melt-kneaded by a conventional method, and the kneaded product is crushed and classified to obtain toner particles. The obtained toner particles are sprinkled with hydrophobic silica fine particles in the mixing stirrer to obtain the final electrophotographic toner. The electrophotographic toner of the present invention obtained by mixing and dispersing toner particles and hydrophobic silica fine particles in this manner is useful as both a one-component developer and a two-component developer. When used as one component, the toner particles containing the above-mentioned magnetic material and the hydrophobic silica fine particles are mixed and dispersed to obtain a developer. When used as a two-component developer,
An electrophotographic toner consisting of toner particles and hydrophobic silica fine particles is prepared by coating glass beads, oxidized or non-oxidized iron powder, uncoated carrier such as ferrite, or magnetic substance such as iron, nickel, cobalt and ferrite with an acrylic polymer. , A fluororesin-based polymer, polyester, a coated carrier coated with a polymer such as a modified silicone resin to obtain a developer. The carrier generally has a particle size of 30 to 500 μm. When a two-component developer is used, the toner concentration is preferably 2-15%.

[0018]

EXAMPLES Hereinafter, the electrophotographic toner of the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 (Component) Styrene-acrylic polymer 100 parts by weight carbon black 8.5 parts by weight Chromium complex salt dye (charge control agent) 1.5 parts by weight (Orient Chemical Co., Ltd. Bontron S-44 4 μm) Low molecular weight polypropylene (Release agent) 2.0 parts by weight The above components were melt-kneaded by a twin-screw extruder, pulverized by a jet mill, and air-classified by a classifier to obtain toner particles having an average particle size of 8 μm.

Hydrophobic silica fine particles (average particle diameter of primary particles: 0.012 μm, trade name “R-974” manufactured by Nippon Aerosil Co., Ltd., hereinafter simply “R974”) are added to the toner particles.
Was mixed and dispersed in a proportion of 0.3% by weight with respect to the total amount of toner to obtain a final electrophotographic toner. Furthermore, Table 2 shows the evaluation results of each item. <Example 2> The same procedure as in Example 1 was carried out except that the average particle size of the hydrophobic silica fine particles was changed to 0.008 μm and 0.2 part by weight was used. Comparative Example 1 The procedure of Example 1 was repeated, except that the average particle size of the charge control agent was changed to 6 μm. Comparative Example 2 The procedure of Example 1 was repeated, except that the average particle size of the hydrophobic silica fine particles was changed to 0.016 μm. Comparative Example 3 The procedure of Example 1 was repeated, except that the average particle size of the charge control agent was changed to 7 μm and the average particle size of the primary particles of the hydrophobic silica fine particles was changed to 0.016 μm. <Evaluation Test> With respect to the toner obtained in each of the examples and comparative examples, a ferrite carrier having an average particle diameter of 80 μm was mixed and uniformly mixed with stirring to prepare a two-component developer having a toner concentration of 3.5%. Next, using Mita Kogyo Co., Ltd. (trade name "DC-4585"), as shown in Table 1, environmental conditions were changed for each predetermined number of sheets, and a total of 20,000 copies were made. However, the original used for copying was an original having an area ratio of 15% of black portions including characters and black solid portions. And it evaluated according to the following test methods.

[0020]

[Table 1]

Each test method is as follows. (1) Image Density (ID) Measurement Using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.), the density of the black solid portion of the copied image after copying 20,000 sheets was measured. (2) Measurement of Fog Density (FD) Using the reflection densitometer, the density of the blank area of the copied image was measured to obtain the fog density. However, only H / H, which is relatively susceptible to fog, is measured. (3) Rise of charge amount 0.965 g of the carrier and 0.035 g of the toner are added to 3 liters.
20 bottles were mixed and stirred for 20 revolutions, and the total amount was measured by a blow-off charge amount measuring device manufactured by Toshiba Chemical Co., Ltd., and the charge amount in the process of rising of charge was obtained. However, only H / H is measured. (4) Fluidity 20 g of the toner is put into the drop amount tester 1 shown in FIG. 1, and the knurled metallic roller 2 (diameter 20 m
m, length 135 mm) was rotated for 5 minutes, and the toner drop amount under high temperature and high humidity was measured. Here, it is shown that the greater the toner drop amount, the better the fluidity. (5) Toner scattering The state inside the copying machine at the end of copying 20,000 sheets was visually judged and evaluated according to the following criteria.

◯: No toner scattering Δ: Slight toner scattering X: Toner scattering From the results of Table 2, in Examples 1 and 2, both rising of charging under high temperature and high humidity and toner fluidity were observed. Since it is good, it is possible to prevent fogging and toner scattering, and it is possible to obtain a high-quality image even in continuous copying or copying an original with a lot of black areas under a bad environment. I knew it was.

On the other hand, even if one of the average particle size of the charge control agent and the average particle size of the primary particles of the hydrophobic silica fine particles is missing as in Comparative Example 1.2.3, fog and toner scattering occur. Occurred. It is considered that this was caused by lack of fluidity or rising speed of charging.

[0024]

According to the present invention, even in a toner having a small particle diameter of 8 μm or less, both the average particle diameter of the charge control agent and the average particle diameter of the primary particles of the hydrophobic silica fine particles to be treated by dusting the toner particles are small. By doing so, it is possible to improve the fluidity and the rising speed of charging all at once, and there is an advantage that a high image quality and a long-life developer can be obtained by compounding appropriate amounts in accordance with an appropriate method.

[0025]

[Table 2]

[Procedure amendment]

[Submission date] September 20, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a diagram of a knurling type drop amount measuring device for measuring a drop amount of toner.

[Explanation of symbols] 1 Measuring device 2 Metal roller 3 Toner hopper 4 Motor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Yamamura 1-22 Tamatsukuri, Chuo-ku, Osaka Mita Industrial Co., Ltd. (72) Inventor Seijiro Ishimaru 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Takeshi Higuchi 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Co., Ltd. (72) Inventor Katsumi Okamoto 1-228 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Business

Claims (1)

[Claims] 1. An electrophotographic toner comprising at least a fixing resin, a toner particle containing a charge control agent, and hydrophobic silica fine particles, wherein the volume average particle diameter of the toner particle is 8 μm.
The average particle size of the charge control agent is 4 μm or less, and the average particle size of the primary particles of the hydrophobic silica fine particles is 0.0
An electrophotographic toner having a thickness of 13 μm or less.