JPH0619190A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain high heat resistance and to prevent carrier contamination by specifying the acid value of a styrene-acryl copolymer as a binder resin and using silica fine powder and alumina fine powder which are treated to become hydrophobic as external additives for the toner particles. CONSTITUTION:This electrophotographic toner has <=8mum average particle size and contains a styrene-acryl copolymer having 7.5-30mg/g acid value. If the acid value is <7.5mg/g, enough resistance is not obtd., and the toner has low fluidity. Further, spent of the toner, fog or splashing of the toner is caused. If the acid value exceeds 30mg/g, heat resistance becomes too high and fixing property decreases. Thereby, the styrene-acryl copolymer with that range of the acid value is used as a binder of the toner, and silica fine powder and alumina fine powder which are treated to become hydrophobic are used as external additives of the toner.

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

[0002]

2. Description of the Related Art Conventionally, a magnetic brush developing method using a two-component developer containing a toner and a carrier forms an image in the following steps. (A) First, a developer containing an electrophotographic toner is held on the outer periphery of a developing sleeve having a magnetic pole inside to form a so-called magnetic brush.

(B) This magnetic brush is brought into sliding contact with a photosensitive member having an electrostatic latent image formed on the surface thereof, and the electrophotographic toner is electrostatically adhered to the electrostatic latent image to form a toner image. Make it visible. (C) The toner image is transferred from the surface of the photoconductor onto paper,
Further, the image is formed by fixing it on the paper with a fixing roller.

As the electrophotographic toner used for the image formation, a binder resin containing a colorant such as carbon black or a charge control agent and granulated into a predetermined particle size is used. . In such a conventional electrophotographic toner, the occurrence of so-called offset such as back stain and stain of the fixing roller, poor fixing of the toner image on the paper when the fixing temperature is low, and insufficient thermal characteristics are caused. Blocking that occurs occurs, toner firefly, and poor cleaning occur.

In order to eliminate such a problem, Japanese Patent Application No. 2-197369 proposes to solve the above problems by specifying a styrene-acrylic resin as a binder resin and specifying the molecular weight distribution of the styrene-acrylic resin, the styrene amount and the acid value. It is proposed to eliminate it.

[0006]

However, in recent years, high image quality has been demanded, and the particle size of toner has been reduced. Therefore, with the resin acid value specified in Japanese Patent Application No. 2-197369, when the toner has a small particle size, the amount of development is small, so the heat resistance is excessively improved and the fixability deteriorates. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrophotographic toner having excellent fixability, offset resistance, and environment resistance.

[0007]

According to the present invention for solving the above problems, a styrene-acrylic copolymer having an acid value of 7.5 to 30 mg / g as a binder resin is used. An electrophotographic toner having a central particle diameter of 8 μm or less is provided, which comprises mixing and dispersing hydrophobized silica fine powder and hydrophobized alumina fine powder into toner particles.

In the electrophotographic toner of the present invention having a median particle diameter of 8 μm or less, the acid value of the styrene-acrylic copolymer is limited to the range of 7.5 to 30 mg / g. If it is less than / g, the heat resistance is not sufficient and fusion occurs in the developing device, which hinders the flow of the developer. Further, toner spent is generated, resulting in fogging and toner scattering. On the other hand, when the acid value exceeds 30 mg / g, the heat resistance is excessively improved and the fixability is poor.

The acid value as used herein refers to the number of mg of potassium hydroxide (KOH) necessary to neutralize the free fatty acid contained in 1 g of the styrene-acrylic copolymer. In the present invention, it is preferable to use hydrophobically treated silica fine powder or hydrophobically treated alumina fine powder as an external additive for a toner using a styrene-acrylic copolymer within the range of the above acid value as a binder resin. Is another feature of. That is, the use of the hydrophobized alumina fine powder prevents overcharge in a low temperature and low humidity environment, and also prevents the decrease of the charge amount in a high temperature and high humidity environment because it is hydrophobized. be able to. Further, by using together with the silica fine powder which has been subjected to the hydrophobic treatment, the fluidity is improved and the blocking resistance in the developing device is improved.

The electrophotographic toner of the present invention will be described in detail below. In order to keep the acid value of the styrene-acrylic copolymer in the present invention within the above range, the amount ratio of acrylic acid ester and acrylic acid in the acrylic component in the copolymer is adjusted. As the silica fine powder in the present invention,
For example, silica fine powder whose surface is treated with a (poly) alkyl group, a (poly) alkylsilyl group, a (poly) alkylsilane, or a silicone oil can be used. In particular, there is silica fine powder whose surface is subjected to a hydrophobic treatment with (poly) alkylsilane, and the primary particle size is preferably 13 nm or less.

The amount of the silica fine powder subjected to the hydrophobic treatment added is 0.01 to 5% by weight, preferably 0.05 to 1% by weight, based on the total amount of the toner. When the amount added is more than the above range, the effect of preventing the increase of the charge amount under the low temperature and low humidity environment by using the alumina fine powder that has been subjected to the hydrophobic treatment is likely to be reduced. On the other hand, if the addition amount is less than the above range, the effect of externally adding the silica fine powder to improve the fluidity cannot be expected.

As the hydrophobized alumina fine powder, the triboelectric charge amount with toner particles is smaller than that of conventional toner additives (the triboelectric charge amount by the blow-off method is 0).
It is preferable that the high degree of hydrophobicity (the degree of hydrophobicity by the titration method of methanol is 50% or more) is maintained at a level of -30 μc / g). The hydrophobic treatment is performed by, for example, the formula: C8F17SO2NEt (CH
2) 3Si (OEt) 3 (wherein Et represents an ethyl group) and dimethyl silicone are treated. A particle size of 0.005 to 0.050 μm is suitable.

The amount of the hydrophobic alumina fine particles added is
The amount is 0.01 to 5% by weight, preferably 0.05 to 1% by weight, based on the total amount of toner. If the addition amount is less than the above range, it becomes difficult to prevent the increase in the charge amount under the low temperature and low humidity environment due to the silica fine powder. On the other hand, when the addition amount is larger than the above range, the charge amount decreases, and fog and toner scattering are likely to occur.

The toner particles in the present invention are blended with additives such as a binder resin, a colorant, a charge control agent, a release agent (anti-offset agent) and the like within the above-mentioned acid value range to prepare an appropriate particle size. It is manufactured by granulating. Examples of the colorant include various color pigments, extender pigments, conductive pigments, magnetic pigments, and photoelectric pigments. These may be used alone or in combination of two or more depending on the purpose.

The following are preferably used as the color pigment. Black Furnace Black. , Channel black, thermal, 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, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, brilliankamine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B orange red mouth Yellow lead, molybden orange, permanent orange GTR, pyrazolo 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, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, Quinoline yellow rake, permanent yellow NCG, tartrazine rake.

Green chrome green, chrome oxide, pigment green B,
Malachite Green Rake, Fanal Yellow Green G. Blue Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue Partial Chloride, Fast Sky Blue, Indanthrene Blue B
C.

Purple Manganese purple, fast violet B, methyl violet lake. As extender pigment, perlite powder, barium carbonate, clay, silica, white carbon, talc,
Alumina white and the like can be mentioned. Examples of the conductive pigment include conductive carbon black and aluminum powder.

As the magnetic material, various ferrites such as iron trioxide (Fe3O4), iron sesquioxide (γ-Fe2O3), zinc oxide (ZnFe2O4), yttrium iron oxide (Y3Fe5O13), cadmium iron oxide (CdFe2O4), Gatrinium oxide (Gd3Fe5O
4), iron oxide copper (CuFe2O4), iron oxide lead (PdFe12O19), iron neodymium oxide (NdFeO3), iron manganese oxide (MnFe2O4), iron oxide lanthanum (LaFeO3), iron powder, cobalt powder, nickel powder, etc. .

Examples of the photoconductive pigment include zinc oxide, selenium, cadmium sulfide, cadmium selenide and the like. The colorant is 1 to 30 with respect to 100 parts by weight of the binder resin.
It is used in a proportion of parts by weight, preferably 2 to 20 parts by weight. As the charge control agent, two types of charge control agents for positive charge control and negative charge control are used depending on the polarity of the toner.

Examples of the charge control agent of the positive charge control agent include organic compounds having a basic nitrogen atom, such as basic dyes, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and the like, which are surface-treated with the above compounds. Agents and the like. Examples of the charge control agent for controlling the negative charge include a compound containing a carboxy group (for example, metal chelate of alkylsalicylate), metal complex salt dye, fatty acid soap, metal salt of naphthenic acid and the like.

The charge control agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin. Examples of the release agent (anti-offset agent) include aliphatic hydrocarbons, aliphatic metal salts, higher aliphatics, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. Above all,
Aliphatic hydrocarbons having a weight average molecular weight of about 1,000 to 10,000 are preferable. Specifically, one or a combination of two or more of low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, a low molecular weight olefin polymer composed of olefin units having 4 or more carbon atoms is suitable.

The release agent is used in an amount of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin. The toner particles are obtained by uniformly preliminarily kneading the above components in a dry blender, a Henschel mixer, a ball mill, etc., and kneading the mixture with, for example, a Banbury mixer, a roll, a uniaxial or biaxial extrusion kneading device, etc. After being melt-kneaded uniformly using an apparatus, the obtained kneaded product is cooled and pulverized, and if necessary, classified, or in some cases, it may be manufactured by the bitter astringent method or the like.

The particle size of the toner particles is suitably 3 to 35 μm, preferably 5 to 25 μm, and in the case of small particle size toner, the particle size is about 4 to 10 μm. Thus, the toner for electrophotography of the present invention obtained by mixing and dispersing the toner particles using the binder resin having the defined acid value range, the hydrophobized silica fine powder, and the hydrophobized alumina fine powder is a one-component developer. It is also useful as both an agent and a two-component developer. When used as a one-component developer, the toner particles containing the magnetic material, the silica fine powder, and the alumina fine powder are mixed to prepare a developer. When used as a two-component developer, a mixture of toner particles and the silica fine powder, the alumina fine powder, glass beads or oxidized or unoxidized iron powder, uncoated carrier such as ferrite, or iron, nickel, A magnetic material such as cobalt or ferrite is mixed with a coated carrier coated with a polymer such as an acrylic polymer, a fluororesin polymer, or a polyester to obtain a developer. The carrier generally has a particle size of 50 to 200 μm. When a two-component developer is used, the toner concentration is preferably 2-15% by weight.

[0026]

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) (Blending amount) Styrene-acrylic copolymer (acid value 7.7) 85% by weight carbon black 10% by weight Offset preventive agent 3% by weight Chromium-containing dye 2% by weight The above components are biaxial. The mixture was melt-kneaded with a kneader and pulverized with a jet mill to obtain toner particles having an average particle size of 7.8 μm by air classification. Hydrophobized silica fine powder (trade name "Cabot TS-720" manufactured by Cabot Corporation) and hydrophobized alumina fine powder (trade name "R"
FT-S "manufactured by Nippon Aerosil Co., Ltd.) was mixed and dispersed at a ratio of 0.2% by weight and 0.3% by weight based on the total amount of the toner to obtain a toner. Example 2 A toner was obtained in the same manner as in Example 1 except that as the styrene-acrylic copolymer, the one having an oxidation of 28.9 was used instead of the one having an oxidation of 7.7. Comparative Example 1 Only 0.2% by weight of hydrophobic silica fine powder was used as the surface additive with respect to the total amount of the toner, and the binder resin was oxidized at 7.
A toner was obtained in the same manner as in Example 1 except that 0 mg / g of styrene-acrylic copolymer was used. Comparative Example 2 Only 0.2% by weight of hydrophobic silica fine powder was used as the surface additive with respect to the total amount of the toner, and the binder resin was oxidized to 3
A toner was obtained in the same manner as in Example 1 except that 0.3 mg / g of styrene-acrylic copolymer was used. <Evaluation Test> With respect to the toners obtained in each of the examples and comparative examples, a ferrite carrier having an average particle size of 80 μm was blended and uniformly stirred and mixed to prepare a two-component developer having a toner concentration of 4%. Then, using an electrophotographic copying machine (trade name "DC-1205") manufactured by Mita Industry Co., Ltd., 2
0000 sheets were printed and evaluated.

[0027]

[Table 1]

Each test method is as follows. (1) Measurement of image density It was measured using a reflection densitometer (TC-6D manufactured by Tokyo Denshoku Co., Ltd.). (2) Measurement of Fog Density Using the same reflection densitometer as described above, the density of the blank area of the copied image was measured to obtain the fog density.

(3) Toner Scattering The condition inside the copying machine and the surface of the copy were visually judged and evaluated according to the following criteria. ◯: No toner scattering Δ: Slight toner scattering X: Toner scattering (4) Spent ratio The developer after printing 20,000 sheets was washed with a surfactant to remove the toner and weighed 100 g. Then, the weighed carrier was washed with toluene to remove the spent toner adhering to the carrier. The carrier from which the spent toner was removed was dried and weighed (this is Ag).

[0030]

[Equation 1]

(5) Fixability The copy was rubbed with a weight, and it was visually judged whether the density of the copy was lowered by the rubbing. (6) Blocking resistance The inside of the developing device after printing 20,000 sheets was visually judged and evaluated according to the following criteria. ◯: No blocking (no toner fusion) Δ: Slight blocking X: Blocking From Table 1, in Examples 1 and 2, the spent ratio is low and the fixing property and blocking resistance are excellent, resulting in no fog. Good images have been obtained.

In Comparative Example 1, the spent rate is high, the chargeability of the developer is lowered, and fog and toner scattering occur. In Comparative Example 2, since the acid value is high, it is considered that the acid value is not sufficiently melted at the fixing temperature of the copying machine.

[0033]

In the electrophotographic toner of the present invention, the acid value of the styrene-acrylic copolymer, which is the binder resin contained in the toner main body, is specified, and the toner particles are hydrophobized as an external additive. Highly heat-resistant and can prevent toner carrier contamination by using the finely divided silica powder and the finely-divided alumina powder, resulting in improved fluidity, low-temperature low-humidity environment, and high-temperature high-humidity environment. Even under the condition, the charging property is stable, and there is an effect that fog and toner scattering do not occur.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoshitake Shimizu, 1-2-2 Tamatsukuri, Chuo-ku, Osaka City Mita Industrial Co., Ltd. (72) Seijiro Ishimaru 1-2-2 Tamatsukuri, Chuo-ku, Osaka No. Mita Industrial Co., Ltd.

Claims (1)

[Claims] 1. A binder resin having an acid value of 7.5 to 30 mg /
A central particle diameter characterized by using a styrene-acrylic copolymer in the range of g and mixing and dispersing hydrophobized silica fine powder and hydrophobized alumina fine powder in toner particles. Electrophotographic toner of 8 μm or less.