JP2003167375A - Toner for two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner that has excellent fluidity and electrostatic chargeability, can be polished away if it films the surface of an organic photoconductor (OPC) without scratching the surface of the OPC even when the OPC is used as a photoconductor and does not cause unevenness in an image even in long- term copying. <P>SOLUTION: Hydrophobic silica (A) having ≤18 nm average primary particle diameter and hydrophobic silica (B) having 40-70 nm average primary particle diameter are stuck to the surfaces of toner particles having at least a bonding resin and a colorant at 15-50% coverage of the silica (A) on the surfaces of the toner particles and 25-65% coverage of the silica (B) on the surfaces of the toner particles (the total coverage does not exceed 100%). In terms of improving the environmental resistance of the toner, the hydrophobic silica (A) and the hydrophobic silica (B) are preferably surface-treated with a silicone oil or a silane coupling agent. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-component developer toner (hereinafter sometimes simply referred to as "toner"),
More specifically, the present invention relates to a toner for a two-component developer that develops a latent image formed on the surface of an organic photoconductor (hereinafter sometimes referred to as “OPC”).

[0002]

2. Description of the Related Art Methods for developing an electrostatic latent image formed on the surface of a photoconductor can be roughly classified into a one-component developing system and a two-component developing system. The one-component developing method is a method that uses only toner as a developer, and the two-component developing method is a method that uses a two-component developer composed of toner and carrier. The image quality is better than that of the one-component developing method, the colorization is possible, and the toner can be manufactured relatively inexpensively. Therefore, the two-component developing method has been widely used for high-speed machines.

Further, in order to meet the market demand for a smaller and lighter device, a so-called oilless fixing device in which no oil is applied to the fixing roller is being used in the fixing device. In order to maintain good fixability as in the past using this oilless fixing device, a binder resin with a relatively low melt viscosity is used as the binder resin for the toner, and more low-melting-point wax is added to the toner. Need to be included in.

However, when such a toner is used together with OPC, which is in great demand in recent years due to its excellent workability, environmental safety, and environmental resistance, it may cause friction between the OPC surface and the cleaning blade. The toner composition is released and melted and adhered to the OPC surface (so-called filming), the melted and adhered area increases as the number of copies increases, and eventually adheres to the outer periphery of the OPC in a band shape and appears as image unevenness on a copied image.

In order to prevent such a filming phenomenon, the abrasiveness of titanium oxide, alumina, magnetite or the like which has been conventionally added externally to toner particles in order to improve the fluidity and chargeability of the toner is also required. It is considered that the amount of the metal oxide contained therein may be externally added more than before, but since OPC has low hardness and wear resistance, the OPC surface is shaved more than necessary due to the metal oxide. For example, in the case of a drum-shaped OPC. There is a problem in that the scratches appear in the circumferential direction and appear as black streaks in the copied image.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such conventional problems, and an object of the present invention is to provide an OPC as a photoconductor while having excellent fluidity and chargeability. It is to provide a toner capable of polishing and removing filming on the OPC surface without damaging the OPC surface even when used.

[0007]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventor has used two kinds of hydrophobic silicas having different particle diameters, and mainly uses O 2 for hydrophobic silica having a large particle diameter.
The inventors have found that the polishing action of the PC surface should be mainly exerted on the hydrophobic silica having a small particle size to impart the toner fluidity and the chargeability, and thus the present invention has been completed. That is, the toner for two-component developer of the present invention is a toner used for a two-component developer for developing an electrostatic latent image formed on the surface of an organic photoreceptor, and a toner containing at least a binder resin and a colorant. The hydrophobic silica (A) having an average primary particle size of 18 nm or less and the hydrophobic silica (B) having an average primary particle size of 40 to 70 nm are attached to the surface of the particles to form the hydrophobic silica (A) and the hydrophobic silica. The coverage of silica (B) on the surface of toner particles is 15 to 50% and 25 to 65%, respectively (however, the total coverage does not exceed 100%).

The average primary particle size of the hydrophobic silica in the present invention was determined as follows. First, using a scanning electron microscope (“JSM-880” manufactured by JEOL Ltd.), an image of the toner surface magnified 120,000 times at an acceleration voltage of 10 kV is taken. This photograph was taken into a computer with a scanner, and 10 hydrophobic silicas were visually extracted from the image of the toner surface displayed on the computer screen,
Calculate the equivalent circle diameters with image analysis software (“Win ROOF” manufactured by Mitani Corporation). Then, it is determined whether the calculated standard deviation of the equivalent circle diameter is 1.5 nm or less, and 1.5 nm
If the value is larger than the average value, the hydrophobic silica that is most deviated from the average value is removed, and new hydrophobic silica is extracted and added. This operation is repeated until the standard deviation of the equivalent circle diameter becomes 1.5 nm or less. Similarly, the equivalent circle diameters were obtained for the five visual fields of the toner surface, and the average value thereof was used as the average primary particle diameter Rn of the hydrophobic silica.

The coverage of the hydrophobic silica was determined as follows. The hydrophobic silica having an average primary particle diameter Rn ± 4.5 nm is visually extracted from the toner surface image displayed on the computer screen to make marking. Then, the total cross-sectional area of the marked hydrophobic silica was calculated using the image analysis software, and the ratio of this total cross-sectional area to the toner surface was defined as the coverage.

From the viewpoint of improving the environment resistance of the toner, the hydrophobic silica (A) and the hydrophobic silica (B) are preferably surface-treated with silicone oil or a silane coupling agent.

From the viewpoint of effectively preventing offset in so-called oilless fixing and paper wrapping around the fixing roller without applying oil to the fixing roller of the fixing device, the toner binder resin is melted at 95 ° C. A viscosity of 1 × 10 ⁶ to 1 × 10 ⁷ P, a melt viscosity at 105 ° C. of 1 × 10 ⁵ to 1 × 10 ⁶ P, and a softening point of 90 to 140 ° C. are used. Is recommended. Further, in the glass transition temperature range of 70 to 90 ° C,
It is preferable that the toner particles further contain a releasing agent having an endothermic amount of 1.5 J / g or more.

The melt viscosity of the binder resin is
(“CFT-500” manufactured by Shimadzu Corp.)
Pore of chair (diameter 1 mm, length 1 mm), pressurization 20 kg /
cm ², 1 cm under the condition of temperature rising rate of 6 ° C / min³Sample of
Is measured by melting and flowing out, and the softening point of the binder resin is the same.
1 cm under conditions³Of the sample when melted and flowed out
The temperature is equivalent to half the height from the start point to the outflow end point.
It was Further, the glass transition temperature and the endothermic amount of the binder resin are
Differential Scanning Calorimeter (“DSC-200” Seiko Instruments Inc.)
10 mg as a reference using alumina)
Sample at a temperature rising rate of 10 ° C / min in the range of 25 to 200 ° C.
It is measured in the box.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Of the two types of hydrophobic silica having different particle diameters, which are attached to the surface of the toner particles, the hydrophobic silica (A) having the smaller particle diameter must have an average primary particle diameter of 18 nm or less. There is. This is because if the average primary particle size is larger than 18 nm, sufficient fluidity and chargeability cannot be imparted to the toner. The coverage of the hydrophobic silica (A) on the surface of the toner particles needs to be 15 to 50%. If the coverage is less than 15%, sufficient fluidity and chargeability cannot be imparted to the toner. On the other hand, if the coverage is greater than 50%, the hydrophobic silica (A) is detached from the toner particles and the carrier or photosensitivity is reduced. It may adhere to the surface of the body. A more preferable coverage is in the range of 20-40%.

The larger particle size of the hydrophobic silica (B) must have an average primary particle size in the range of 40 to 70 nm.
If the average primary particle size is smaller than 40 nm, the filming on the OPC surface cannot be sufficiently removed by polishing. On the other hand, if the average primary particle size is larger than 70 nm, the OPC surface is unnecessarily abraded to show black streaks in the copied image, and the hydrophobic silica (B) is detached from the toner particles to the carrier or photoreceptor surface. This is because they may adhere.

The coverage of the hydrophobic silica (B) on the surface of the toner particles needs to be 25 to 65%. If the coverage is less than 25%, sufficient polishing cannot be obtained,
The filming on the OPC surface cannot be removed by polishing. On the other hand,
This is because if the coverage is greater than 65%, the OPC surface may be unnecessarily abraded and may be detached from the hydrophobic silica (B) toner particles and adhere to the carrier or the photoreceptor surface. A more preferable coverage is in the range of 33 to 55%.

The two types of silica used in the present invention are limited to hydrophobic ones. Since silica fine particles are hydrophilic as they are, they absorb moisture in the air in a high temperature and high humidity environment and the amount of charge on the toner. And liquidity is reduced. The hydrophobization of silica is performed by applying or adhering a hydrophobizing agent to the surface of silica particles. As the hydrophobic treatment agent,
Examples thereof include silicone oil, a silane coupling agent, and other polymer compounds, and among them, silicone oil and a silane coupling agent are preferable. Further, the hydrophobicity of silica is preferably 80 or more in the methanol titration test.

Examples of usable silicone oils are straight silicone oils such as dimethyl silicone oil, methylphenyl silicone oil, and methyl hydrogen silicone oil; methacrylic acid modified silicone oil, epoxy modified silicone oil, fluorine modified silicone oil, polyether modified silicone oil. Examples thereof include modified silicone oils such as silicone oil and amino-modified silicone oil, and among them, dimethyl silicone oil is preferable.

Examples of the silane coupling agent include organoalkoxysilane, organochlorsilane, organosilazane, organodisilazane, organosilane and the like, among which organochlorsilane and organosilazane are preferred. After the surface treatment of the silica fine particles with the silane coupling agent, the surface treatment may be further performed with silicon oil.

Among the commercially available products, hydrophobic silica (A) is AEROSIL R972, R974, R202, R805, R812, RX2.
00, RY200 (above, Nippon Aerosil); WACHER HDK H
2000, H22050EP (above, Wacker Chemicals East Asia); Nipsil SS-10, SS-15, SS-20, SS-50, SS-60, S
S-100 (above, manufactured by Nippon Silica Industry Co., Ltd.) and the like can be mentioned. For hydrophobic silica (B), AEROSIL R809, RX50
(These are manufactured by Nippon Aerosil Co., Ltd.); Nipsil SS-40, SS-70, S
Examples include S-72F (above, manufactured by Nippon Silica Industry Co., Ltd.).

As a method of attaching the hydrophobic silica to the surface of the toner particles, a conventionally known method can be used.
For example, there is a method in which hydrophobic silica and toner particles are charged into a high-speed fluidized stirrer or a V-type mixer and stirred and mixed. By adjusting the mixing time and stirring speed, the coverage of the hydrophobic silica on the toner particle surface can be adjusted. Of course, the coverage can also be adjusted by the type and particle size of the hydrophobic silica and the amount of external addition. The two types of hydrophobic silica may be charged into the agitator / mixer at the same time, or may be charged with a time difference. From the viewpoint of uniformly dispersing and adhering the two types of hydrophobic silica to the surface of each toner particle, the hydrophobic silica (B) having a large particle size is first charged into a stirrer / mixer and then the hydrophobic silica having a small particle size is added. It is desirable to add (A). The degree of adhesion of hydrophobic silica to the surface of toner particles is
It may be simply attached, or a part of the hydrophobic silica may be embedded in the toner particle surface.

The toner particles used in the present invention may be those having at least a binder resin and a colorant. For example, a colorant is dispersed and mixed in the binder resin, and if necessary, a charge control agent or a release agent. The thing which added is mentioned.

Examples of the binder resin used here include thermoplastic resins and thermosetting resins of ineffective or initial condensation products. Specific examples thereof include vinyl aromatic resins such as polystyrene, styrene-acrylic copolymers, acrylic resins, polyvinyl acetal resins, polyester resins, epoxy resins, and phenol resins. Of these, polyester resins are more preferable because they have excellent low-temperature fixability and offset resistance.

Such a polyester resin is obtained mainly by polycondensation of polyhydric carboxylic acids and polyhydric alcohols. Examples of the polyhydric carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid and amber. Acid, 1,2,4-benzenetricarboxylic acid, 2,5,7
-Aromatic polyvalent carboxylic acids such as naphthalene tricarboxylic acid, 1,2,4-naphthalene tricarboxylic acid and pyromellitic acid; maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, malonic acid, azelaic acid, mesaconic acid , Aliphatic dicarboxylic acids such as citraconic acid and glutaconic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and methylmedic acid; anhydrides and lower alkyl esters of these carboxylic acids, and one or more of these may be mentioned. used.

The content of the trivalent or higher valent component depends on the degree of crosslinking, and the amount of addition may be adjusted to obtain the desired degree of crosslinking. Generally, the content of trivalent or higher components is 1
It is preferably 5 mol% or less.

On the other hand, the polyhydric alcohols used for the polyester resin include, for example, ethylene glycol,
Alkylene glycols such as 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-butenediol, neopentyl glycol, 1,5-pentane glycol and 1,6-hexane glycol Alkylene ether glycols such as diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol;
Alicyclic polyhydric alcohols such as 1,4-cyclohexanedimethanol and hydrogenated bisphenol A; bisphenols such as bisphenol A, bisphenol F and bisphenol S, and alkylene oxides of bisphenols, and one of these Alternatively, two or more kinds can be used in combination.

If desired, monocarboxylic acid or monoalcohol may be used for the purpose of adjusting the molecular weight or controlling the reaction. Examples of the monocarboxylic acid include benzoic acid, paraoxybenzoic acid, toluenecarboxylic acid, salicylic acid, acetic acid, propionic acid and stearic acid. As monoalcohol, benzyl alcohol,
Monoalcohols such as toluene-4-methanol and cyclohexanemethanol may be mentioned.

The polyester resin usable in the present invention is
It is manufactured by a usual method using these raw materials. For example, an alcohol component and an acid component are charged into a reaction vessel at a predetermined ratio, and the reaction is started at a temperature of 150 to 190 ° C. in the presence of a catalyst while blowing an inert gas such as nitrogen. By-produced low molecular weight compounds are continuously removed from the reaction system. Thereafter, the reaction temperature is further raised to 210 to 250 ° C. to accelerate the reaction, and the target polyester resin is obtained. The reaction can be carried out under any conditions of normal pressure, reduced pressure and increased pressure, but after the reaction rate reaches 50 to 90%, 200 mmH
It is preferable to carry out the reaction by reducing the pressure to g or less.

Examples of the catalyst include tin, titanium,
Metals such as antimony, manganese, nickel, zinc, lead, iron, magnesium, calcium and germanium; and these metals; and compounds containing these metals are mentioned.

The binder resin used in the present invention is 95 ° C.
Melt viscosity in the range of 1 × 10 ⁶ to 1 × 10 ⁷ P, 1
It is preferable that the melt viscosity at 05 ° C. is in the range of 1 × 10 ⁵ to 1 × 10 ⁶ P and the softening point is in the range of 90 to 140 ° C. This is because low temperature fixability can be realized without lowering offset resistance and blocking resistance only by having such thermal properties. Also, by using it together with a specific release agent described later, it is possible to prevent offset and paper wrapping around the fixing roller even in an apparatus using an oilless fixing device.

Examples of the releasing agent that can be used in the present invention include synthetic hydrocarbon waxes such as Fischer-Tropsch wax, polyethylene wax and polypropylene wax; plant waxes such as carnauba wax, rice wax, paraffin wax and sugar cane wax. , Or a combination of two or more of these. Of these, carnauba wax, rice wax, and paraffin wax are more preferable. The amount of the release agent added to the binder resin is 2 with respect to 100 parts by weight of the binder resin.
The range of -8 parts by weight is preferred.

Further, in order to effectively prevent offset in the oilless fixing device and paper wrapping around the fixing roller, the release agent used has a glass transition temperature of 70 to 90 ° C.
In the range of 1, the endothermic amount is preferably 1.5 J / g or more.

As the coloring agent contained in the binder resin,
For example, black pigments include carbon black such as acetylene black, orchid black, and aniline black; yellow pigments include yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, and naphthol yellow. S,
Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; as orange pigments, reddish yellow lead, molybden orange, permanent orange GTR, pyrazolone orange, vulcan orange, Induslen Brilliant Orange RK, Benzidine Orange G, Induslen Brilliant Orange GK; red pigments such as red iron oxide, cadmium red, red lead, mercury cadmium sulfide, permanent red 4R, resole red, pyrazolone red, watching red calcium salt, lake red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3
B: Purple pigment, manganese purple, fast violet B, methyl violet lake; Blue pigment, dark blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated compound,
Fast Sky Blue, Induslen Blue BC; as green pigments, chrome green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G; as white pigments, zinc white, titanium oxide, antimony white, zinc sulfide; white As the pigment, barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white and the like can be used. Such colorant is preferably used in an amount of 2 to 20 parts by weight, particularly 5 to 15 parts by weight, based on 100 parts by weight of the binder resin.

Other additives may be used in the toner of the present invention within a range that does not impair the effects of the present invention. Examples of such additives include charge control agents and surface treatment agents. As the charge control agent, conventionally known charge control agents can be used. For example, as the positively chargeable charge control agent, nigrosine dye, fatty acid-modified nigrosine dye, carboxyl group-containing fatty acid-modified nigrosine dye, quaternary ammonium salt, amine-based A compound, an organometallic compound, or the like can be used, and as the negatively chargeable charge control agent, a metal complex of oxycarboxylic acid, a metal complex of an azo compound, a metal complex salt dye, a salicylic acid derivative, or the like can be used. Examples of the surface treatment agent include inorganic fine powder such as alumina, titanium oxide, zinc oxide, magnesium oxide, calcium carbonate; organic fine powder such as polymethylmethacrylate; fatty acid metal salt such as zinc stearate. , And these 1 type, or 2 or more types can be used together.

The toner particles used in the present invention can be manufactured by a method known per se such as a pulverizing and classifying method, a melt granulating method, a spray granulating method, and a suspension / emulsion polymerization method. The pulverizing and classifying method can be preferably used in view of the above. The pulverizing and classifying method will be outlined below. First, a binder resin, a colorant and, if necessary, a toner composition such as a wax or a charge control agent are premixed with a Henschel mixer or a V-type mixer, and then melt-kneaded using a melt-kneading device such as a twin-screw extruder. . After cooling this melt-kneaded product, coarse pulverization / fine pulverization,
If necessary, the particles are then classified to obtain toner particles having a predetermined particle size distribution. The particle size of the toner particles is preferably in the range of 5 to 15 μm, particularly preferably in the range of 7 to 12 μm in terms of median diameter measured by “Coulter counter”. Then, as described above, two types of hydrophobic silica are externally added to the produced toner particles to obtain the toner of the present invention.

The toner of the present invention is used as a two-component developer. The carrier to be mixed with the toner of the present invention is not limited, and examples thereof include magnetic metals such as iron, nickel and cobalt and alloys thereof, or alloys containing rare earths, hematite, magnetite, manganese-zinc ferrite, nickel- Manufactured by sintering and atomizing magnetic material such as zinc-based ferrite, manganese-magnesium-based ferrite, soft ferrite such as lithium-based ferrite, iron-based oxide such as copper-zinc-based ferrite and a mixture thereof. It is possible to use magnetic particles and resin particles whose surfaces are coated with a resin. Further, a magnetic material dispersed resin can be used as the carrier. In this case, the above magnetic material can be used as the magnetic material, and examples of the binder resin include vinyl resin, polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, and polyether. Resins or mixtures thereof can be mentioned.

The particle size of the carrier is generally 20 to 200 μm, particularly 30 to 15 expressed by particle size by electron microscopy.
It is preferably 0 μm. In addition, the apparent density of the carrier is generally 2.4 to 3.0 g / although it varies depending on the composition and surface structure of the magnetic material when the magnetic material is the main component.
A range of cm ³ is preferred.

In the two-component developer comprising toner and carrier, the toner concentration is 1 to 20% by weight, preferably 3-1.
It is 5% by weight. When the toner concentration is less than 1% by weight, the image density becomes too thin, while when the toner concentration exceeds 20% by weight, toner scattering occurs in the developing device and the toner adheres to the inside of the machine and the background portion such as transfer paper. This is because there is a possibility that a malfunction may occur.

The organophotoreceptor used in the present invention may be either a single layer type or a laminated type. The single-layer type photoreceptor is a charge carrier transport material (“CTM”: Charge Carrier Transp).
charge carrier generation material (“CGM”: Charge Carrier Generation Material) in the photosensitive layer containing the ortMaterial).
Are dispersed as particles.
GM and CTM are charge carrier generation layers (“CG
L ": Charge Carrier Generation Layer) and charge carrier transport layer (" CTL ": Charge Carrier Transport Layer)
er) is separated and laminated. The shape of the organic photoreceptor is not particularly limited, and may be any shape such as a drum shape, a sheet shape, a belt shape, and a web shape.

Examples of CGM include phthalocyanine pigments, perylene pigments, anthanthrone pigments, azo pigments, squarylium pigments, azurenium pigments,
Examples include thiapyrylium pigments and cyanine pigments. Among these, the phthalocyanine-based pigment and the perylene-based pigment are more preferable in that the increase in residual potential due to repeated use can be suppressed to a small level. On the other hand, examples of the CTM include triphenylamine derivatives, hydrazone compounds, arylamine compounds, benzidine compounds, oxadiazole, oxazole and the like.

As the binder resin for CGM, formal resin, silicone resin, polyester resin, phenol resin, butyral resin, etc. are recommended from the viewpoints of adhesion with CGL and dispersion stability of the solution. The content of CGM is preferably in the range of 20 to 600 parts by weight with respect to 100 parts by weight of the binder resin.

On the other hand, as the CTL binder resin, polystyrene, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polycarbonate resin, polyester resin, silicone resin, (meth) acrylic resin, etc. Is recommended from the viewpoint of compatibility with CTM and durability. Among them, polycarbonate resin is more preferable from the viewpoint of dispersibility of CTM. The content of CTM is preferably in the range of 10 to 200 parts by weight with respect to 100 parts by weight of the binder resin.

FIG. 1 is a sectional view showing an example of an image forming apparatus using the toner of the present invention. The major feature of this image forming apparatus is that the toner is used as the toner used in the developing unit, the organic photoconductor is used as the photoconductor, and the oilless fixing device is used as the fixing unit.

The image forming apparatus of FIG. 1 is a tandem type full color image forming apparatus. A transfer belt 11 which is stretched between a pair of rollers 12 and 12 ′ and runs is disposed in the housing 10, and the transfer belt 1 is provided above the transfer belt 11.
1, a black image forming section B, a cyan image forming section C, a magenta image forming section M, and a yellow image forming section Y are arranged in this order from the upstream side in the rotational direction of 1. The transfer paper (not shown) conveyed from the paper feed cassette 13 provided in the lower part of the housing 10 moves on the transfer belt 11 from right to left in the drawing. During this time, the toner images of the respective colors formed by the respective image forming units are transferred onto the transfer paper. Then, the full-color toner image on the transfer paper is melted and fixed to the transfer paper by the fixing means 7, and then discharged above the housing 10.

Next, each image forming section will be described. Each image forming unit has a structure in which a charging unit 1, an exposing unit 2, a developing unit 3, and a cleaning unit 5 are arranged around the organic photosensitive drum 6, and the lower side of the organic photosensitive drum 6 is a transfer belt 11. Is facing.

To outline the image forming process in the image forming section, first, the surface of the organic photosensitive drum 6 is uniformly charged to the positive polarity by the charging means 1. Next, an electrostatic latent image is formed on the surface of the organic photoconductor drum 6 by the exposure means 2. Then, in the developing means 3, the toner is adhered to the electrostatic latent image by the developer layer formed on the developing sleeve 31 (shown in FIG. 2) and composed of the toner and the carrier to form a visible image. Next, in an area (transfer area) facing the transfer belt 11, a bias charge having a polarity opposite to the charging polarity of the toner is applied to the transfer roller (transfer means) 4 provided below the transfer belt 11 to perform transfer. The toner image on the organic photosensitive drum 6 is transferred onto a transfer paper (not shown) conveyed on the belt 11. Then, the toner not transferred on the organic photoconductor drum 6 is removed by the cleaning unit 5. Such image formation is also performed in each of the cyan, magenta, and yellow image forming units. Then, the full-color image formed on the transfer paper is melted and fixed on the transfer paper by applying heat and pressure in the fixing means 7 including the upper fixing roller 71 and the lower fixing roller 72.

FIG. 2 is a sectional view showing an example of the developing means 3. This developing device includes a developing sleeve 31 in which a magnet 31a is fixedly incorporated in a sleeve 31b, and a spiral stirring member 32.
A blade 33 that regulates the amount of developer conveyed to the developing unit and imparts triboelectric charge is disposed at a predetermined distance from the developing sleeve 31. Further, a toner hopper 34 is provided above the stirring member 32, and when the toner sensor 35 provided on the right side wall of the stirring member 32 detects that the toner amount in the developing device is insufficient, the replenishment roller 3 is provided.
6 rotates to supply the toner T from the toner hopper 34 to the developing device. The supplied toner is stirred and mixed with the carrier by the stirring member 32 and sequentially supplied to the developing sleeve 31. The developer supplied to the developing sleeve 31 is sent to the facing position (developing portion) of the organic photosensitive drum 6 by the counterclockwise rotation of the developing sleeve 31. At this time, the amount of the developer sent to the developing unit is controlled by the blade 33, and the toner is triboelectrically charged.
Although the magnet 31a built in the developing sleeve 31 used here is fixed and the cylindrical sleeve 31b rotates, the structure in which the built-in magnet 31a is rotated to fix the sleeve 31b, or Internal magnet 31a
The structure may be such that both the sleeve 31b and the sleeve 31b are rotated (the rotation direction may be the same direction or the opposite direction).

The method for developing the electrostatic latent image on the organic photosensitive drum 6 may be either a positive development method or a reversal development method,
Further, the developing method may be either a contact developing method in which the developer layer and the photosensitive member are in contact with each other or a jumping developing method in which both are not in contact with each other. The reversal development method is recommended from the viewpoint of obtaining a high quality image. In this case, the organic photoconductor drum is charged to the same polarity as the toner, and the charge of the latent image portion is removed by exposure. Then, in the developing unit, an alternating voltage in which a direct current and an alternating current are superposed is applied as a developing bias between the developing sleeve and the organic photoconductor drum to develop an electrostatic latent image on the organic photoconductor drum from which electric charge is removed. The toner in the agent is transferred and adhered to the electrostatic latent image to be visualized as a toner image.

FIG. 3 is a schematic sectional view showing an example of the fixing means 7. The fixing means 7 in this figure has a basic structure in which an upper fixing roller 71 and a lower fixing roller 72 are in contact with each other. The oil coating device, which is conventionally arranged on the outer periphery of the upper fixing roller 71, is not provided here. Upper / lower fixing roller 7
Both 1 and 72 have a structure in which rubber layers 712 and 722 are formed on the outer circumference of cylindrical cores 711 and 721, and heaters 713 and 723 are arranged at the centers of the cores 711 and 721, and the upper and lower parts are arranged. The thermistors 714 and 724 arranged so as to come into contact with the surfaces of the fixing rollers 71 and 72 are on / off controlled to a predetermined temperature. The set temperature is appropriately determined depending on the type of toner used, but generally 160 to
It is in the range of 210 ° C. On the outer periphery of the upper fixing roller 71,
A cleaning blade 715 for removing the adhered toner is provided, and a separation claw 716 for preventing paper wrapping is provided.

As described above, in the fixing means of FIG. 3, oil is not applied to the fixing roller, but the action of the specific binder resin and the specific release agent is added to the action of the hydrophobic silica adhering to the surface of the toner particles. Offset and winding of the transfer paper are effectively prevented. On the other hand, since the oil application mechanism is unnecessary, the size and weight of the device can be reduced and the manufacturing cost can be reduced.

[0050]

Example (Preparation of Toner and Developer) 100 parts by weight of polyester resin as binder resin, 5 parts by weight of colorant (cyan pigment), 3 parts by weight of charge control agent, and 5 parts by weight of paraffin wax. After charging and mixing in a Henschel mixer, the mixture was melt-kneaded with a twin-screw extruder, cooled with a drum flaker, and coarsely crushed with a hammer mill. Next, it was finely pulverized with a mechanical mill and classified using an air classifier to produce toner particles having a volume average particle size of 9.0 μm. A predetermined amount of hydrophobic silica (A) and hydrophobic silica (B) having an average primary particle size shown in Tables 1 and 2 was added to 100 parts by weight of the toner particles, and a high stirring mixer “Henschel Mixer” was used. The rotation speed and the stirring and mixing time were adjusted to prepare positively chargeable toners having the coverage of hydrophobic silica shown in Tables 1 and 2. The toners of Comparative Example 7 and Comparative Example 8 include
Alumina and titanium oxide were externally added instead of the hydrophobic silica (B). 5 parts by weight of the manufactured toner and 95 parts by weight of a ferrite carrier (manufactured by Powder Tech Co., Ltd.) were mixed to prepare a developer. Then, the following evaluation was performed on the prepared developer using “Creage 8331” manufactured by Kyocera Mita Co., Ltd., which is equipped with an organic photoconductor. The evaluation results are summarized in Tables 1 and 2.

(Measurement of Image Density and Fog Density) After printing 30,000 sheets in a single run using the above copying machine, a copied image was printed using a reflection densitometer (Model No. TC-6D manufactured by Tokyo Denshoku Co., Ltd.). The black solid area (image density) and the non-image area density (fog density) were measured. As for the evaluation criteria, in the case of the image density, 1.35 or more in the initial stage was evaluated as "○" after printing 100,000 sheets, and in the case of the fog density, less than 0.008 was evaluated as "○", and other than the above. I marked it as "x".

(Filming and Drum Damage) After printing 30,000 sheets in a single press using the above copying machine, it was visually observed whether filming and drum damage occurred on the organic photosensitive drum.

(Image unevenness) A halftone original was copied after printing 30,000 sheets by using the above copying machine and visually observed whether the copied image had image unevenness.

[0054]

[Table 1]

[0055]

[Table 2]

As is clear from Table 1, in the toners of Examples 1 to 5, the toner charge amount and the fluidity are maintained even after the single-shot printing of 30,000 sheets, so that the image density and the fog density are The evaluation criteria were satisfied, and filming and scratches did not occur on the drum, and image unevenness did not occur.

With the toner of Comparative Example 1 having a small coverage of the hydrophobic silica (B), filming occurred on the drum. On the other hand, in the toner of Comparative Example 2 having a large coverage of the hydrophobic silica (B), image unevenness occurred due to poor toner replenishment to the developing sleeve due to a decrease in toner fluidity. Further, with the toner of Comparative Example 3 in which the average primary particle size of the hydrophobic silica (B) was large, filming, drum scratches, and image unevenness occurred. On the other hand, with the toner of Comparative Example 4 in which the average primary particle size of the hydrophobic silica (B) was small, fog and filming occurred. In the toner of Comparative Example 5 having a small coverage of the hydrophobic silica (A), the toner charge amount and the fluidity were lowered, so that the image density was lowered and the image unevenness was generated after the single-press printing of 30,000 sheets. In the toner of Comparative Example 7 in which the coverage of the hydrophobic silica (A) was large, silica was desorbed from the surface of the toner particles, the toner charge amount was reduced, and fog occurred. Hydrophobic silica (B)
Filming, drum scratches, and image unevenness occurred in the toner of Comparative Example 8 in which alumina was used in place of and the toner of Comparative Example 9 in which titanium oxide was used in place of hydrophobic silica (B).

[0058]

In the toner for two-component developer of the present invention, hydrophobic silica (A) having an average primary particle size of 18 nm or less and hydrophobic silica having an average primary particle size of 40 to 70 nm are formed on the surface of the toner particles. (B) is adhered to the surface of the toner particles of the hydrophobic silica (A) and the hydrophobic silica (B) to be 15 to 50% and 25 to 65%, respectively (however, the total coverage is 100%). Since it does not exceed), it has excellent fluidity and chargeability, and even when OPC is used as a photoreceptor, filming on the OPC surface can be removed by polishing without damaging the OPC surface, and copying can be performed for a long time. However, image unevenness does not occur.

If the hydrophobic silica (A) and the hydrophobic silica (B) surface-treated with silicone oil or a silane coupling agent are used, the environment resistance of the toner can be further improved.

The binder resin of the toner has a melt viscosity at 95 ° C. of 1 × 10 ⁶ to 1 × 10 ⁷ P and a melt viscosity at 105 ° C. of 1 × 10 ⁵ to 1 × 10 ⁶ P. Use one having a softening point in the range of 90 to 140 ° C.,
Alternatively, when the toner particles further contain a releasing agent having a glass transition temperature in the range of 70 to 90 ° C. and an endothermic amount of 1.5 J / g or more, even when an oilless fixing device is used, the offset or fixing roller is applied. Wrapping of paper can be effectively prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of an image forming apparatus using the toner of the present invention.

FIG. 2 is a cross-sectional view of an image forming unit of the image forming apparatus in FIG.

3 is a sectional view of a fixing unit of the image forming apparatus of FIG.

[Explanation of symbols] 1 charging means 2 Exposure means 3 developing means 4 Transfer means 5 Cleaning means 6 Organic photoconductor drum 7 fixing means T toner 71 Upper fixing roller 72 Lower fixing roller

Claims (4)

[Claims] 1. A toner used as a two-component developer for developing an electrostatic latent image formed on the surface of an organic photoconductor, comprising an average primary surface on the surface of toner particles having at least a binder resin and a colorant. Toner particles of hydrophobic silica (A) and hydrophobic silica (B) in which hydrophobic silica (A) having a particle diameter of 18 nm or less and hydrophobic silica (B) having an average primary particle diameter of 40 to 70 nm are attached. A toner for a two-component developer, characterized in that the coverage on the surface is 15 to 50% and 25 to 65%, respectively (however, the total coverage does not exceed 100%). 2. The toner for a two-component developer according to claim 1, wherein the hydrophobic silica (A) and the hydrophobic silica (B) are surface-treated with silicone oil or a silane coupling agent. 3. The binder resin has a melt viscosity at 95 ° C. of 1 × 10 ⁶ to 1 × 10 ⁷ P and a melt viscosity at 105 ° C. of 1 × 10 ⁵ to 1 × 10 ⁶ P. ,
The toner for a two-component developer according to claim 1, wherein a toner having a softening point in the range of 90 to 140 ° C. is used. 4. The toner particles according to claim 1, wherein the toner particles further contain a releasing agent having a glass transition temperature of 70 to 90 ° C. and an endothermic amount of 1.5 J / g or more. Toner for two-component developer.