JP3157037B2 - Electrophotographic toner and manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly, to an electrophotographic toner used for forming an image by applying a so-called Carlson process, such as an electrostatic copying machine or a laser beam printer. .

[0002]

2. Description of the Related Art 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. In the production, the above toner materials are mixed, melt-kneaded, and various constituent materials are uniformly dispersed, and then cooled, pulverized, and classified to obtain toner particles. In the development, it is desirable that the toner has good fluidity and stable characteristics such as chargeability, and in particular, it is required to improve fluidity and stabilize chargeability under a bad environment of low temperature, low humidity and high temperature and high humidity. You. Conventionally, in order to satisfy fluidity and chargeability, a method of applying a specific external additive to toner particles is often used.

[0003] Japanese Patent Application No. 3-43788 uses hydrophobic silica fine particles to prevent overcharging in a low-temperature and low-humidity environment and to prevent a decrease in charge amount in a high-temperature and high-humidity environment. In addition, by using hydrophobic alumina fine particles in combination, the fluidity and the chargeability are improved, and the fluidity and the charge stability in a bad environment are prevented from lowering.

[0004]

However, recently, as the image quality has been improved, the toner particle size has become smaller, and the fluidity and chargeability have been required to be more stable and uniform than ever. In particular, in continuous copying under the above-mentioned bad environment and when copying a document having a large ratio of black portions, toner is replenished one after another. Fog starts to occur.

The present invention has been made in view of the above circumstances, and has a high fluidity and a high chargeability even in the case of continuous copying under a bad environment and copying of a document having a large black portion ratio. It is an object of the present invention to provide an electrophotographic toner having a small particle diameter, which has a fast rising speed and a stable charging property, and a method for producing the same.

[0006]

According to the present invention, there is provided a method for producing a toner for electrophotography, wherein fine silica particles and fine alumina particles are coated on the surface of the toner particles. A first step of spraying the alumina fine particles;
And a third step of spraying fine silica particles having an average primary particle diameter smaller than that of the fine silica particles in the step.

[0007]

[0008]

The toner according to the production method of the present invention is characterized by using two types of hydrophobic silica fine particles having different average primary particle sizes and using alumina fine particles together. Such a configuration is based on the following theory.

The role of the silica fine particles is mainly to control the chargeability of the toner, to improve the fluidity of the toner, and to improve the dispersibility of alumina on the toner surface. In order to fulfill these roles, it is desirable that the silica fine particles uniformly adhere to the toner surface. In the case of a toner having a small particle diameter, the fluidity and the chargeability are much worse than those of a conventional toner, which is even more so. However, as the toner becomes smaller, it becomes more difficult to uniformly disperse the silica fine particles on the toner surface. Thus, the problem in the small particle size toner was solved by using two types of silica fine particles and sharing the role of each type.

[0010] That is, the chargeability of the toner is mainly controlled by the smaller silica fine particles, and the flowability of the toner and the dispersibility of alumina are mainly controlled by the larger silica fine particles. Of course, these roles are mainly, and both silica fine particles play the role of the other silica fine particles. In the present specification, the average particle diameter of the primary particles is determined as a number average diameter by an electrophotographic microscope.

In the present invention, it is important to use silica fine particles of 15 to 20 nm as the first hydrophobic silica fine particles. The first hydrophobic silica fine particles must fulfill the two roles of improving the dispersibility of the alumina fine particles and improving the fluidity of the toner. Therefore, if the average particle size of the primary particles of the first hydrophobic silica fine particles is too large, the dispersibility of the alumina fine particles deteriorates, and the fluidity and chargeability of the finally obtained toner also deteriorate. Conversely, when silica fine particles having a small average primary particle diameter are used, the chargeability of the final toner is too high, so that the image density decreases under low temperature and low humidity, and the first hydrophobic silica fine particles adhere. Because the fluidity of the subsequent toner is too good, the shearing force in the mixed layer decreases,
On the contrary, the effect of uniformly dispersing the alumina particles is reduced.

In the present invention, it is important that the average particle size of the primary particles of the second hydrophobic silica fine particles is smaller than that of the second hydrophobic silica fine particles, and is 13 nm or less. If the second hydrophobic silica fine particles have the same particle size or more than the first hydrophobic silica fine particles, the fluidity of the toner becomes insufficient, and the first and second silica fine particles are located in the gap between the alumina fine particles in the additive mixing step. It is not efficiently added externally. As a result, the silica fine particles are released from the toner during development and adhere to the photoconductor,
This causes black streaks and white streaks to appear in the image.

Alumina fine particles may be untreated, hydrophilic, or subjected to a hydrophobic treatment. Examples of the hydrophobic treatment include the following formula: C8F17SO2NE.
Examples include those treated with t (CH2) 3Si (OEt) 3 (where Et represents an ethyl group) and dimethyl silicone. The addition amount of the hydrophobic silica fine particles is 0.01 to 0.4% by weight, preferably 0.05 to 0.2% by weight, based on the total amount of the toner in the first hydrophobic silica fine particles.
The hydrophobic silica fine particles are 0.01 to
It is 0.5% by weight, preferably 0.05 to 0.3% by weight. When the amount of the first hydrophobic silica fine particles is larger than the above range, the charge amount of the finally obtained toner increases, the fluidity increases in the first step, the shear force in the mixed layer decreases, and Cannot uniformly disperse the alumina particles. On the other hand, when the amount is small, the fluidity is poor, so that the fluidity of the toner in the mixed layer is reduced, and the dispersibility of the alumina particles is reduced. Also,
When the added amount of the second hydrophobic silica fine particles is larger than the above range, similarly to the first hydrophobic silica fine particles, the charge amount of the finally obtained toner increases, and free silica particles are also generated.
On the other hand, when the amount is small, the fluidity cannot be improved.

The amount of the alumina fine particles is 0.01 to 0.5% by weight, preferably 0.05 to 0.5% by weight based on the total amount of the toner.
~ 0.3% by weight. When the addition amount is less than the above range, the rising performance of the charging is reduced, while when it is large, the image density is reduced and the scattering is caused due to the reduced charging amount.
In a method for producing an electrophotographic toner in which hydrophobic silica fine particles and alumina fine particles are coated on the surface of toner particles, a first step in which silica fine particles are coated, a second step in which alumina fine particles are coated, and a first step It is desirable to provide a method for producing an electrophotographic toner, comprising a third step of subjecting silica fine particles having an average primary particle diameter smaller than the fine particles to a spraying treatment.

The reason that the large silica is first dispersed on the toner surface is that large particles are more easily dispersed uniformly on the toner surface. Since silica and alumina have opposite polarities, the next dipping of alumina will electrically attract the alumina to the silica which is uniformly dispersed on the toner surface, and consequently the alumina will be uniformly dispersed on the toner surface. . The reason why the next small silica is applied is that the small silica adheres to the gap between the large silica and the alumina, so that it is difficult to peel off during development and the durability as a developer is improved.

The toner particles of the present invention contain additives such as a colorant, a charge control agent and a release agent in a binder resin.
It is manufactured by granulating to a particle size of 8 μm or less. As the binder resin, a styrene resin, an acrylic resin, a styrene-acryl resin, a polyester resin, a polyurethane resin, a silicon resin, a polyamide, a modified rosin, or the like is used.

As the colorant, a conventionally known colorant can be used. The following coloring agents can be suitably 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 Bengala, cadmium red, lead red, lead mercury sulfide , Cadmium, Permanent Red 4R, Risor 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 mouth lead, molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, Indanthrene Brilliant Orange GK Yellow Yellow lead, zinc white, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navels yellow, naphthol yellow S, Hanser yellow G, Hanser yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, permanent yellow NCG, tartrazine lake green chrome green, chromium oxide, pygme Togulin B, Malachite Green Lake, Final Yellow Green Blue Navy Blue, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Partially Chlorinated Phthalocyanine Blue, Furnest Sky Blue, Indanthrene Blue BC, Metal-Free Phthalocyanine Blue Purple Manganese Purple, First Violet B, methyl violet lake As extender pigments, for example, pearlite powder, barium carbonate,
Clay, silica, white carbon, talc, alumina white and the like.

Examples of the conductive pigment include various metal powders such as conductive carbon black and aluminum powder. Examples of the magnetic pigment include iron trioxide (magnetite iron black); iron sesquioxide (γ-Fe2 O3), zinc iron oxide (ZnFe2 O4), and yttrium iron oxide (Y3 Fe5 O1).
2), cadmium iron oxide (CdFe2 O4), gallium iron oxide (Gd3 Fe5 O4), copper iron oxide (CuFe2 O)
4) lead iron oxide (PbFe12 O19), nickel iron oxide (NiFe2 O4), iron neodymium oxide (NdFeO3),
Barium iron oxide (BaFe12 O19), iron magnesium oxide (MgFe2 O4), iron manganese oxide (MnFe2 O)
4) Various ferrites such as iron lanthanum oxide (LaFeO3); iron powder, cobalt powder, nickel powder and the like.

As the photoconductive pigment, for example, zinc oxide,
Selenium, cadmium sulfide, selenium, cadmium sulfide, cadmium selenide and the like can be mentioned. Examples of the release agent include any release agents known per se, for example, aliphatic resins such as aliphatic resins, aliphatic metal salts, higher fatty acids, fatty acid esters, and partially saponified products thereof. .
Among them, particularly low molecular weight (weight average molecular weight is 1000-1
0000) is effective. Specifically, for example, low molecular weight polypropylene, high molecular weight polyethylene,
One or a combination of two or more of paraffin wax, a low-molecular-weight olefin polymer composed of an olefin alone having 4 or more carbon atoms is suitable. In addition, for example, silicone oil, various waxes and the like can be used.

As the charge control agent, any charge control agent known per se, for example, nigrosine base (CI 504)
15), oil-soluble dyes such as oil black (CI 26150) and spiron black, metal-containing azo dyes, metal salts of naphthenic acids, metal salts of alkyl salicylic acids, fatty acids, soaps, and resin acid soaps. The hydrophobic silica-based additive used in the present invention is obtained by treating fumed silica, that is, fine silica obtained by a high-temperature (fire) hydrolysis method of silicon chloride, with a silane such as dimethyldichlorosilane, Obtained by blocking silanol with organosilane.

As described above, the electrophotographic toner of the present invention obtained by mixing and dispersing the toner particles, the first and second hydrophobic silica fine particles, and the alumina fine particles according to the above-described production method,
It is useful as both a one-component developer and a two-component developer. When used as a component, the toner particles containing the magnetic substance, the first and second hydrophobic silica fine particles, and the alumina fine particles are mixed and dispersed to form a developer. When used as a two-component developer, toner particles and the first and second
A mixture of hydrophobic silica fine particles and alumina fine particles can be used as a glass bead, an oxidized or unoxidized iron powder, an uncoated carrier such as ferrite, or a magnetic material such as iron, nickel, cobalt, or ferrite as an acrylic polymer or a fluororesin. It is mixed with a coated carrier coated with a polymer such as a system polymer, polyester, modified silicone resin or the like to form a developer. The carrier generally has a particle size of 30 to 500 μm. When a two-component developer is used, the toner concentration in the developer is preferably 2 to 15%.

[0022]

EXAMPLES Hereinafter, the electrophotographic toner and the production method of the present invention will be described in more detail with reference to Examples and Comparative Examples. Example 1 (Components) Styrene-acrylic polymer 100 parts by weight Carbon black 8.5 parts by weight Chromium complex dye (charge control agent) 1.5 parts by weight 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 diameter of 8 μm.

The toner particles are provided with first hydrophobic silica fine particles (average particle diameter of primary particles: 16 nm, trade name “R-972” manufactured by Nippon Aerosil Co., Ltd .; hereinafter simply referred to as “R972”), and second hydrophobic silica fine particles. Fine particles (average particle size of primary particles: 12 nm, trade name “R-97” manufactured by Nippon Aerosil Co., Ltd.)
4], hereinafter simply referred to as “R974”), and hydrophobic alumina fine particles (average particle diameter of primary particles 20 nm, trade name “RFY-C” manufactured by Nippon Aerosil Co., Ltd.), hereinafter simply “RFY-C”
C) is mixed with 0.1% by weight, 0.2% by weight, and 0.2% by weight of the first hydrophobic silica fine particles R972 as a first step with respect to the total amount of the toner, respectively. As a second step, hydrophobic alumina fine particles RFY-C were mixed and dispersed, and finally, as a third step, second hydrophobic silica fine particles R974 were mixed and dispersed to obtain a toner. Example 2 A toner was obtained in the same manner as in Example 1, except that the first hydrophobic silica fine particles had an average primary particle diameter of 19 nm. << Comparative Example 1 >> A toner was obtained in the same manner as in Example 1 except that the primary hydrophobic silica fine particles having an average primary particle size of 22 nm were used. << Comparative Example 2 >> A toner was obtained in the same manner as in Example 1 except that the second hydrophobic silica fine particles having an average primary particle diameter of 16 nm were used. << Comparative Example 3 >> A toner was obtained in the same manner as in Example 1 except that the primary hydrophobic silica fine particles having an average primary particle size of 14 nm were used. << Comparative Example 4 >> A toner was obtained in the same manner as in Example 1, except that the order of the step of mixing and dispersing the hydrophobic alumina fine particles and the second hydrophobic silica fine particles was reversed in the surface treatment step of the toner. That is, after mixing and dispersing the first hydrophobic silica fine particles in the first step, mixing and dispersing the second hydrophobic silica fine particles in the second step, and finally mixing and dispersing the hydrophobic alumina fine particles in the third step to obtain a toner. Was. << Comparative Example 5 >> In the surface treatment step of the toner, after mixing and dispersing the second hydrophobic silica fine particles as the first step, the second step was carried out.
A toner was obtained in the same manner as in Example 1, except that the first hydrophobic silica fine particles were mixed and dispersed as a step, and finally, the hydrophobic alumina fine particles were mixed and dispersed as a third step. << Comparative Example 6 >> In the toner surface treatment step, after the hydrophobic alumina fine particles were mixed and dispersed as the first step, the first hydrophobic silica fine particles were mixed and dispersed as the second step, and finally the second hydrophobic silica particle was mixed as the third step. A toner was obtained in the same manner as in Example 1, except that the silica fine particles were mixed and dispersed. << Comparative Example 7 >> In the surface treatment step of the toner, as the first step, after mixing and dispersing the second hydrophobic silica fine particles,
A toner was obtained in the same manner as in Example 1, except that hydrophobic alumina fine particles were mixed and dispersed as a step, and finally, first hydrophobic silica fine particles were mixed and dispersed as a third step. <Evaluation Test> A ferrite carrier having an average particle size of 60 μm was blended with each of the toners obtained in each of the examples and comparative examples, and uniformly mixed with stirring to produce a two-component developer having a toner concentration of 3.5%. Then, using Mita Kogyo Co., Ltd. (product name "DC-4585"), environmental conditions were changed for each predetermined number of copies, and a total of 20,000 copies were made. Image density, fog density, and charge amount under each environment The rise of charge, the fluidity of the toner and the presence or absence of toner scattering were examined. That is, the environmental conditions were changed for each predetermined number of copies in the order shown in Table 1, and the above test was performed after copying under each condition. Where N
The measured value at / N (normal temperature and normal humidity) is a value after copying 20,000 sheets.

[0024]

[Table 1]

Each test method is as follows. (1) Image Density (ID) Measurement The density of the black solid portion of the copied image was measured using a reflection densitometer (Model TC-6D manufactured by Tokyo Denshoku Co., Ltd.). (2) Measurement of fog density (FD) Using the reflection densitometer, the density of a blank portion of a copy image was measured to obtain a fog density. However, the measurement is made only for H / H in which fog is relatively likely to occur. (3) Charge Amount Measured with a blow-off charge amount meter manufactured by Toshiba Chemical Corporation. (4) Rise of charge amount 0.95 g of the carrier and 0.035 g of the toner are 3 m
The mixture was mixed and stirred 20 times with a 1 l bottle, and the whole amount was measured by the blow-off charge amount measuring device to determine the charge amount during the charging rise process. However, only H / H is measured. (5) Toner Scattering The state in the copying machine at the end of copying 20,000 sheets was visually determined, and evaluated according to the following criteria.

：: No toner scattering Δ: Slight toner scattering X: Toner scattering (6) Fluidity 20 g of toner was put into the drop amount tester 1 shown in FIG. 1 and knurled metal roller 2 (diameter 20m
m, length 135 mm) was rotated for 5 minutes, and the amount of drop at that time was examined. Here, it is shown that the larger the amount of the developer dropped, the better the fluidity. However, only H / H is measured.

[0027]

According to the present invention, there is provided a method for producing an electrophotographic toner in which hydrophobic silica fine particles and alumina fine particles are coated on the surface of toner particles.
A method for producing an electrophotographic toner, comprising: a second step of spraying alumina fine particles; and a third step of spraying fine silica particles having an average primary particle diameter smaller than that of the first silica particles in the first step. By using the manufactured toner, even in a bad environment, the fluidity is good, the rising speed of the charging is fast, and the stable charging property can be obtained.

[0028]

[0029]

[Table 2]

[0030]

[Table 3]

[Brief description of the drawings]

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

[Description of Signs] 1 Measuring machine 2 Metal roller 3 Toner hopper 4 Motor

Continuing from the front page (72) Inventor Katsumi Okamoto 1-2-2 Tamazo, Chuo-ku, Osaka City Examiner at Mita Industries Co., Ltd. Kanae Isogai (56) References JP-A-2-151187 (JP, A) JP-A Sho 62-196672 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. A method for producing a toner for electrophotography, in which hydrophobic silica fine particles and alumina fine particles are coated on the surface of toner particles, a first step in which silica fine particles are coated, and a second step in which alumina fine particles are coated. 3. A method for producing an electrophotographic toner, comprising: dipping a silica fine particle having an average primary particle diameter smaller than that of the silica fine particle in the first step.