JPH07140698A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic toner attaining tight melt sticking to a fixing sheet even in ultrahigh-speed copying, excellent in anti-offsetting property, having stable fluidity and electrostatic chargeability and ensuring little spent toner in a two-component system. CONSTITUTION:In an electrophotographic toner consisting of toner particles contg. at least a bonding resin and a releasing agent and of an additive, a propylene-olefin copolymer is used as the releasing agent and fine hydrophobic silica particles having >=3 Si atoms in each surface group are used as the additive.

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 The 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. ing. Among them, in the fixing step, the developed toner image is directly fused on the photoconductive photoreceptor or electrostatic recording body having the electrostatic latent image, or the developed toner image is transferred onto the photoconductive photoreceptor or It is carried out by transferring from an electrostatic recording medium onto a transfer sheet such as paper and fusing it onto the transfer sheet. At that time, the fusion of the toner image is generally performed by heating, and as a heating method, a non-contact heating method using a heater and a pressure heating method using a heating roller are adopted.

Among them, the pressure-bonding heating method is a method in which a toner image surface of a sheet to be fixed is brought into pressure contact with a heating roller having a surface formed of a material having releasability for toner to perform fixing. The heat exchange is good and the toner can be fused continuously, which is effective for the electrophotographic copying method. However, in this method, since the fixing roller is in pressure contact with the toner image in a heat-melted state, a part of the toner image adheres and transfers to the surface of the fixing roller, and re-transfers onto the next sheet to be fixed. A so-called offset phenomenon that causes dirt is generated.

Therefore, conventionally, in order to prevent the toner from adhering to the surface of the fixing roller, a fluorine-based material having a good releasing property has been used for the fixing roller, or silicone oil has been applied to the surface. . Further, as the toner, the melt viscosity of the resin should be increased, or a method described in JP-A-49-652 is used.
In No. 31, a low-molecular-weight polypropylene excellent in releasability is contained as an offset preventive agent, and when the toner comes into contact with a heated roller, the low-molecular-weight polypropylene is liquefied and released on the toner surface to coat the surface of the fixing roller. By doing so, the toner is prevented from adhering to the surface of the fixing roller.

[0005]

However, with the recent increase in copying speed, the conveyance speed of the fixing sheet becomes extremely high and the fixing time becomes short, so that the toner is fused to the fixing sheet at a lower temperature. Is required. For that purpose, it is considered to use a low-viscosity fixing resin. However, if the fixing resin is made to have a low viscosity, an offset phenomenon occurs particularly in an environment of high temperature and high humidity, so that it is the current situation that the performance of the heating roller and the pressure roller must be relied upon. Further, if not only the resin but also the toner as a whole has a low viscosity, not only the fluidity of the toner is deteriorated particularly at high temperature and high humidity, but also the chargeability of the toner is deteriorated and toner scattering occurs. Furthermore, in the two-component developer, the pressure applied in the developing device increases the amount of toner (so-called spent toner) attached to the carrier, causing toner scattering and fog.

The object of the present invention has been made in view of the above circumstances, and even in ultra-high speed copying, the toner is firmly fused to the fixing sheet and is excellent in offset resistance.
It is an object of the present invention to provide an electrophotographic toner having stable fluidity and chargeability, and having less spent toner in a two-component system.

[0007]

According to the present invention, in an electrophotographic toner comprising toner particles containing at least a binder resin and a release agent and an external additive, propylene and an olefin are used as the release agent. Provided is an electrophotographic toner, which is characterized by using a copolymer and using hydrophobic silica fine particles having 3 or more surface group Si atoms as an external additive.

[0008]

The toner of the present invention is characterized by using a copolymer of propylene and an olefin as a releasing agent and using hydrophobic silica fine particles having 3 or more surface group Si as an external additive. Is. In the toner of the present invention, it is important to contain a copolymer of olefin and propylene as a release agent. That is, by copolymerizing olefin and propylene, the crystallinity is lowered and the softening point of the toner can be lowered as compared with the conventional low molecular weight polypropylene, so that the toner can be fused to the fixing sheet even at a low temperature. it can. Further, since the entire toner is made to have a low viscosity by the release agent itself, the fixing resin does not adhere to and transfer to the fixing roller, and the conventional offset resistance can be maintained.

Examples of the olefin constituting the copolymer of olefin and propylene include pentene, butene, propane and the like. The composition ratio of olefin and propylene is 5
0:50 to 99: 1, preferably 65:35 to 8
It is 5:15. In the toner of the present invention, it is also important to mix and disperse the hydrophobic silica fine particles having 3 or more surface group Si particles as the external additive in the toner particles. By mixing and dispersing silica particles with high hydrophobicity,
Since it is possible to prevent moisture from adsorbing to the toner at room temperature and normal humidity, especially at high temperature and high humidity, it is possible to improve fluidity and chargeability, and it is possible to suppress torque applied to the developer in the developing device. As a result, toner scattering, fog, and spent toner can be prevented.

The hydrophobic silica fine particles having a surface group of 3 or more Si atoms can be obtained by surface-treating the silica fine particles with dimethyldichlorosilane, polydimethylsiloxane or the like. The addition amount of the hydrophobic silica fine particles is 0.01 to 2% by weight, preferably 0.1% by weight based on the total amount of the toner.
It is from 05 to 1.0% by weight. If the addition amount is more than the above range, the charge amount of the toner finally obtained tends to be high, the image density is likely to be lowered, and the hydrophobic silica fine particles are easily released and adhered to the photoreceptor. This is because white lines and black lines may be generated. On the other hand, when the amount is small, the fluidity and the charging property tend to be lowered, and the spent toner tends to increase.

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 an appropriate particle size. 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, as in Printex L (registered trademark), the average particle size of primary particles is 40 to 60.
Particles of nm are preferred. 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 various metal powders such as conductive carbon black and 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. As the charge control agent, any charge control agent known per se, for example, 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. 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 performed under the condition that a low load and a low shearing force are applied, and in general, 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 can be used. 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 is generally in the range of 10 to 300 minutes.

The pre-mixture thus obtained is melt-kneaded by a conventional method, and the kneaded product is crushed and classified to obtain a 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 comprising toner particles and hydrophobic silica fine particles, glass beads or oxidized or unoxidized iron powder, an uncoated carrier such as ferrite, or iron, nickel, cobalt, A magnetic material such as ferrite is mixed with a coated carrier coated with a polymer such as an acrylic polymer, a fluororesin polymer, polyester, and a modified silicone resin to prepare a developer. The carrier generally has a particle size of 30 to 500 μm. When a two-component developer is used, the toner density is 2
It is preferably from 15 to 15%.

[0016]

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 Copolymer of butene and propylene (release agent) 2 0.0 parts by weight The above components are melt-kneaded by a twin-screw extruder, pulverized by a jet mill, and air-classified by a classifier to obtain an average particle size of 10 μm.
Toner particles were obtained.

Hydrophobic silica fine particles (polymethylsiloxane group, trade name "TS720" manufactured by Cabot Corporation, hereinafter simply "TS720") are mixed with the toner particles in an amount of 0.3% by weight based on the total amount of the toner. Dispersed to obtain the final toner. Example 2 A toner is obtained in the same manner as in Example 1 except that a copolymer of pentene and propylene is used as a release agent and hydrophobic silica fine particles having a polymethylsiloxane group as a surface group are used. It was Comparative Example 1 A toner was obtained in the same manner as in Example 1 except that low-molecular-weight polypropylene was used as a release agent and hydrophobic silica fine particles having a polymethylsiloxane group as a surface group were used. << Comparative Example 2 >> A toner was obtained in the same manner as in Example 1 except that a copolymer of butene and propylene was used as a release agent and hydrophobic silica fine particles having a dimethylsilane group as a surface group were 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 3.5%. Then, 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 sheets were copied,
The image density under a low temperature and low humidity environment, the fog density under a high temperature and high humidity environment, the charge amount, the fluidity of the toner, and the presence or absence of toner scattering at the end of the copying test were examined.

[0018]

[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) 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 (6) Fluidity 20 g of toner was charged into the drop amount tester 1 shown in FIG. 1 and knurled metallic 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. (7) Fixability Electrophotographic copying machine manufactured by Mita Industry Co., Ltd., model number DC-45
Using 85, the transfer paper on which a toner image is formed on a black solid document is passed through the paper and fixed in a low temperature and low humidity (10 ° C., 45%) environment, and the image density at that time is measured. Next, the fixed toner image is reciprocated 5 times by its own weight by using a fixing jig in which the bottom surface of mild steel (diameter 50 mm, weight 400 g) is fixed by double-sided tape. Then, the image density of the toner image was measured again, and the fixing ratio was obtained from the following equation.

[0021]

[Equation 1]

However, the image density was measured using the reflection densitometer. (8) Offset resistance Electrophotographic copying machine manufactured by Mita Industry Co., Ltd., model number DC-45
No. 85 was used to make 500 copies using the original document shown in FIG. 2 in a high temperature and high humidity environment. At that time, the offset phenomenon and stain of the non-image area were visually judged and evaluated according to the following evaluation criteria.

◯: No offset, stains, etc. X: Offset, stains, etc. (9) Spent rate Toner was removed by blowing the developer before and after copying 20,000 sheets under each of the above-mentioned environments, and each was manufactured by Horiba Ltd. The carbon content (% by weight) was measured with a carbon content analyzer (trade name: Carbon Analyzer) of. Then, the spent rate was calculated by the following formula.

[0024]

[Equation 2]

From the results shown in Table 2, in Examples 1 and 2, both the fixing rate and the offset resistance are good, and the fluidity, the charging property, the toner scattering, and the spent rate are also good. On the other hand, in the comparative example, either the fixing rate or the offset resistance is not satisfied, and the other fluidity, chargeability, toner scattering, and spent rate are not good.

[0026]

[Table 2]

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 7, 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.

FIG. 2 is an explanatory diagram of a document for evaluating the offset resistance of toner.

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

Front Page Continuation (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 Co., Ltd. In the company

Claims (1)

[Claims] 1. An electrophotographic toner comprising toner particles containing at least a binder resin and a release agent and an external additive, wherein a copolymer of propylene and olefin is used as the release agent, and the external additive is used. As a toner for electrophotography, a hydrophobic silica fine particle having a surface group of 3 or more Si is used.