JPH07104501A - Electrophotographic toner and its production - Google Patents

Abstract

PURPOSE:To obtain a fine toner having high flowability, a high rising speed of electrostatic charge and stable electrostatic chargeability by using toner particles having a specified average particle diameter and two kinds of hydrophobic fine silica particles different from each other in the average particle diameter of primary particles. CONSTITUTION:This toner consists of toner particles, hydrophobic fine silica particles and fine alumina particles. First hydrophobic fine silica particles having 15-20nm average particle diameter of the primary particles and second hydrophobic fine silica particles having <=13nm average particle diameter of the primary particles are mixed with fine alumina particles and dispersed on the surfaces of toner particles having <=8mum average particle diameter to obtain the objective toner. The electrostatic chargeability of the toner is controlled chiefly by the smaller fine silica particles and the flowability of the toner and the dispersibility of the fine alumina particles are improved chiefly by the larger fine silica particles. The actions of the 1st and 2nd fine silica particles overlap each other.

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 in image formation by applying a so-called Carlson process such as an electrostatic copying machine and a laser beam printer. .

[0002]

2. Description of the Related Art A 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-mentioned toner materials are mixed, melt-kneaded to uniformly disperse various constituent materials, and cooled, pulverized, and classified to obtain toner particles. At the time of development, it is desirable that the toner has good fluidity and stable properties such as chargeability, and is required to have improved fluidity and stability of chargeability particularly in a bad environment of low temperature and low humidity and high temperature and high humidity. It Conventionally, in order to satisfy fluidity and chargeability, a method of sprinkling a toner particle with a specific external additive is often used.

In Japanese Patent Application No. 3-43788, by using hydrophobized silica fine particles, it is possible to prevent overcharge in a low temperature and low humidity environment and to prevent a decrease in charge amount in a high temperature and high humidity environment. Further, by using the hydrophobic alumina fine particles together, the fluidity is improved and the stability of the charging property is improved, and the deterioration of the fluidity and the charging stability under a bad environment is prevented.

[0004]

However, with the recent trend toward higher image quality, the toner particle size has become smaller, and the fluidity and chargeability are required to be even more stable and uniform than before. In particular, when continuously copying under a bad environment or copying a document with a large black portion, toner is replenished one after another, and if the charging speed is not very fast, toner may scatter or the image Fog will occur.

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

[0006]

According to the present invention for solving the above problems, first hydrophobic silica fine particles having an average particle diameter of 8 μm or less and primary particles having an average particle diameter of 15 to 20 nm are used. Provided is an electrophotographic toner characterized in that second hydrophobic silica fine particles having an average primary particle diameter of 13 nm or less and alumina fine particles are mixed and dispersed on the toner surface.

Further, in the method for producing an electrophotographic toner, in which toner particles are sprinkled with hydrophobic silica fine particles and alumina fine particles, a first step of sprinkling silica fine particles;
A method for producing an electrophotographic toner comprising a second step of sprinkling alumina fine particles and a third step of sprinkling silica fine particles having primary particles having an average particle size smaller than that of the silica fine particles of the first step. Provided.

[0008]

The toner of the present invention is a toner particle having an average particle size of 8 μm or less, and it is remarkable that two kinds of hydrophobic silica fine particles having different primary particle average particle sizes are used and alumina fine particles are used in combination. It is a characteristic. The reason for having such a structure is as follows.

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 play these roles, it is desirable that the silica fine particles be uniformly attached to the toner surface. This is even more the case for small particle size toners, because their fluidity and chargeability are much worse than conventional toners. However, the smaller the toner particle size, the more difficult it becomes to uniformly disperse the silica fine particles on the toner surface. Therefore, the problem of the small particle size toner was solved by using two kinds of silica fine particles and sharing the role of each.

That is, the toner chargeability is controlled mainly by the smaller silica fine particles, and the fluidity of the toner and the dispersibility of alumina are mainly improved 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 primary particles is obtained 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 dual roles of improving the dispersibility of the alumina fine particles and, at the same time, 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 charging property of the finally obtained toner also deteriorate. On the other hand, when silica fine particles having a small average primary particle size are used, the final toner has too high chargeability, so that the image density decreases at low temperature and low humidity, and the first hydrophobic silica fine particle adheres. Since the fluidity of the toner after that is too good, the shearing force in the mixed layer decreases,
On the contrary, the effect of uniformly dispersing the alumina particles decreases.

In the present invention, it is important that the average particle diameter of the primary particles of the second hydrophobic silica fine particles is smaller than that of the second hydrophobic silica fine particles and 13 nm or less. If the second hydrophobic silica fine particles have a particle size equal to or larger than that of the first hydrophobic silica fine particles, the fluidity of the toner will be insufficient, and the first and second silica fine particles will form a gap between the alumina fine particles in the additive mixing step. Not efficiently added externally. As a result, during development, fine silica particles are released from the toner and adhere to the photoreceptor,
This may cause black streaks and white streaks to appear in the image.

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

The amount of fine alumina particles added is 0.01 to 0.5% by weight, preferably 0.05, based on the total amount of toner.
Is about 0.3% by weight. If the addition amount is less than the above range, the charging start-up performance is deteriorated, while if the addition amount is more than the above range, the image density is decreased and scattering occurs due to the decrease in the charging amount.
In a method for producing a toner for electrophotography in which the surface of toner particles is sprinkled with hydrophobic silica fine particles and alumina fine particles, a first step of sprinkling silica fine particles, a second step of sprinkling alumina fine particles, and a silica of the first step A method for producing an electrophotographic toner, which comprises a third step of sprinkling silica fine particles having a primary particle size smaller than that of the fine particles, is desirable.

The reason why the large silica particles are first dispersed on the toner surface is that larger particles are more likely to be uniformly dispersed on the toner surface. Since the polarities of silica and alumina are opposite to each other, by sprinkling the alumina next, the alumina is electrically attracted to the silica that is uniformly dispersed on the toner surface, and as a result, it is uniformly dispersed on the toner surface. . Next, the reason why the small silica is sprinkled is that the small silica adheres to the gaps between the large silica and the alumina and is less likely to be peeled off during development, and the durability as a developer is improved.

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. As the binder resin, styrene resin, acrylic resin, styrene-acrylic resin, polyester resin, polyurethane resin, silicone resin, polyamide, modified rosin or the like is used.

As the colorant, a conventionally known colorant can be used. The following colorants 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 conductive pigments 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. Examples of the release agent include any release agent known per se, for example, aliphatic resins, aliphatic metal salts, higher fatty acids, fatty acid esters or aliphatic compounds such as partially saponified products thereof. .
Among them, particularly low molecular weight (weight average molecular weight of 1000 to 1
0000) aliphatic resins are effective. Specifically, for example, low molecular weight polypropylene, high molecular weight polyethylene,
One kind or a combination of two or more kinds of paraffin wax, a low molecular weight olefin polymer composed of a simple olefin having 4 or more carbon atoms, and the like are suitable. In addition, for example, silicone oil and various waxes can be used.

The charge control agent may be any charge control agent known per se, for example, nigrosine base (CI 504).
15), 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 are used. The hydrophobic silica-based additive used in the present invention is a gas phase process silica, that is, fine silica obtained from a high temperature (fire) hydrolysis process of silicon chloride, is treated with silanes such as dimethyldichlorosilane, It is obtained by blocking silanol with an 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 by the above-mentioned manufacturing method,
It is useful as both a one-component developer and a two-component developer. When used as one component, the toner particles containing the magnetic material, the first and second hydrophobic silica fine particles, and the alumina fine particles are mixed and dispersed to obtain a developer. When used as a two-component developer, the toner particles and the first and second
Mix a mixture of hydrophobic silica fine particles and alumina fine particles with glass beads, oxidized or unoxidized iron powder, uncoated carrier such as ferrite, or magnetic substance such as iron, nickel, cobalt, ferrite, acrylic polymer, fluororesin A developer is prepared by mixing with a coated carrier coated with a polymer such as a system polymer, polyester, or modified silicone resin. 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 2-15%.

[0022]

EXAMPLES Hereinafter, the electrophotographic toner and the manufacturing method 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 Low molecular weight polypropylene (release agent) 2.0 parts by weight The above components were melt-kneaded with a twin-screw extruder, pulverized with a jet mill, and air-classified with a classifier to obtain toner particles having an average particle size of 8 μm.

The toner particles contained in the toner particles were first hydrophobic silica fine particles (average particle size 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 (average particle diameter 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 size of primary particles: 20 nm, trade name “RFY-C” manufactured by Nippon Aerosil Co., Ltd., hereinafter simply referred to as “RFY-”).
C ”) is mixed with 0.1% by weight, 0.2% by weight, and 0.2% by weight based on the total amount of the toner in the first step, and the first hydrophobic silica fine particles R972 are mixed and dispersed. 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 primary hydrophobic silica fine particles having an average primary particle diameter of 19 nm were used. <Comparative Example 1> A toner was obtained in the same manner as in Example 1 except that primary particles having an average particle size of 22 nm were used as the first hydrophobic silica fine particles. Comparative Example 2 A toner was obtained in the same manner as in Example 1 except that primary particles having an average particle size of 16 nm were used as the second hydrophobic silica fine particles. Comparative Example 3 A toner was obtained in the same manner as in Example 1 except that primary particles having an average particle size of 14 nm were used as the first hydrophobic silica particles. Comparative Example 4 A toner was obtained in the same manner as in Example 1 except that the order of the mixing and dispersing step of the hydrophobic alumina fine particles and the second hydrophobic silica fine particles was reversed in the toner surface treatment step. That is, the first hydrophobic silica fine particles are mixed and dispersed in the first step, the second hydrophobic silica fine particles are mixed and dispersed in the second step, and finally the hydrophobic alumina fine particles are mixed and dispersed in the third step to obtain a toner. It was << Comparative Example 5 >> In the toner surface treatment step, after the second hydrophobic silica fine particles are mixed and dispersed as the first step, the second step is performed.
A toner was obtained in the same manner as in Example 1 except that the first hydrophobic silica fine particles were mixed and dispersed in the step, and finally the hydrophobic alumina fine particles were mixed and dispersed in the third step. Comparative Example 6 In the toner surface treatment step, hydrophobic alumina fine particles are mixed and dispersed as the first step, first hydrophobic silica fine particles are mixed and dispersed as the second step, and finally the second hydrophobic step is performed as the third step. A toner was obtained in the same manner as in Example 1 except that the fine silica particles were mixed and dispersed. << Comparative Example 7 >> In the toner surface treatment step, the second step was performed after the second hydrophobic silica fine particles were mixed and dispersed as the first step.
A toner was obtained in the same manner as in Example 1 except that hydrophobic alumina fine particles were mixed and dispersed in the step, and finally the first hydrophobic silica fine particles were mixed and dispersed in the third step. <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 60 μm was mixed and uniformly mixed with stirring to prepare a two-component developer having a toner concentration of 3.5%. Then, using Mita Kogyo Co., Ltd. (trade name "DC-4585"), the environmental conditions were changed for each predetermined number of sheets to make a total of 20,000 copies, and the image density, fog density, and charge amount under each environment were copied. Then, the rise of charging, 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 conducted after copying under each condition. However, N
The measured value at / N (normal temperature and normal humidity) is after copying 20,000 sheets.

[0024]

[Table 1]

Each test method is as follows. (1) Measurement of Image Density (ID) The density of a black solid part of a copied image was measured using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.). (2) Fog Density (FD) Measurement 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) Charge amount Measured with a blow-off charge amount measuring device manufactured by Toshiba Chemical Co. (4) Rise of charge amount: 0.965 g of the carrier and 0.035 g of the toner for 3 m
The mixture was stirred and mixed in a 1-liter bottle for 20 revolutions, and the total amount was measured by the blow-off charge amount measuring device to obtain the charge amount in the rising process of charging. However, only H / H is measured. (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 scatter Δ: Slight toner scatter x: Toner scatter (6) Flowability 20 g of toner was charged 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 greater the amount of developer dropped, the better the fluidity. However, only H / H is measured.

[0027]

Toner particles having an average particle diameter of 8 μm or less, first hydrophobic silica fine particles having an average primary particle diameter of 15 to 20 nm and second secondary silica particles having an average primary particle diameter of 13 nm or less are used.
By mixing and dispersing the hydrophobic silica fine particles and the alumina fine particles on the toner surface, the fluidity is good, the rising speed of charging is fast, and stable charging property is obtained even under adverse environment.

Further, in the method for producing an electrophotographic toner in which toner particles are sprinkled with hydrophobic silica fine particles and alumina fine particles, a first step of sprinkling silica fine particles,
The above effect becomes more remarkable by the manufacturing method including the second step of sprinkling the alumina fine particles and the third step of sprinkling the silica fine particles having a smaller average primary particle size than the silica fine particles of the first step.

[0029]

[Table 2]

[0030]

[Table 3]

[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 Takeshi Higuchi 1-2-28 Tamatsukuri, Chuo-ku, Osaka Mita Industrial Co., Ltd. (72) Katsumi Okamoto 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Within Kogyo Co., Ltd.

Claims (2)

[Claims] 1. An electrophotographic toner comprising toner particles and hydrophobic silica fine particles and alumina fine particles, wherein the toner particles are fine particles having an average particle size of 8 μm or less, and the hydrophobic silica fine particles have an average primary particle size of 15 To 20 nm of the first hydrophobic silica fine particles and the average primary particle diameter of 13
An electrophotographic toner comprising second hydrophobic silica fine particles having a particle size of not more than nm. 2. A method for producing a toner for electrophotography, wherein a surface of toner particles is sprinkled with hydrophobic silica fine particles and alumina fine particles, a first step of sprinkling silica fine particles, and a second step of sprinkling alumina fine particles. A method for producing an electrophotographic toner, comprising a third step of sprinkling silica fine particles having a primary particle size smaller than that of the silica fine particles of the first step.