JP2008281643A - Electrostatic latent image developing toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cope with the problem of finding a toner superior in polishing of the surface of a photoreceptor and electrification characteristics for electrostatic latent image developing toner used in an image forming apparatus conducting development by a touch-down developing method and including the amorphous silicon (a-Si) photoreceptor. <P>SOLUTION: The electrostatic latent image developing toner includes toner particles of cylindrical bodies of diameters ϕ and lengths L obtained by cutting the product of the molten toner material extended by a spinning method in the form of cylindrical fibers into prescribed lengths, and has been added by ultra-fine titanium oxide of 1×10<SP>1</SP>to 1×10<SP>7</SP>Ωcm of a volume resistivity value and 10 to 100 nm of primary particle diameters as an external additive. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic latent image developing toner, and more particularly to an electrostatic latent image developing toner used in an image forming apparatus for developing an electrostatic latent image formed on an amorphous silicon (a-Si) photoreceptor. .

  In an image forming apparatus such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a composite machine of these using an electrophotographic method, an electrostatic recording method, an electrostatic printing method, etc., first, a latent image holder The surface of the latent image is uniformly charged by a charging unit, and then the surface of the latent image holding member is exposed by an exposing unit such as a semiconductor laser or a light emitting diode to form an electrostatic latent image, and then the electrostatic latent image is developed. The toner image is visualized by means. Next, the toner image is transferred directly to the surface of the printed material such as paper by a transfer means, or transferred to the surface of the intermediate transfer body and then re-transferred to the surface of the printed material such as paper. A series of image forming steps is executed by fixing by the fixing means.

There are roughly two types of development methods for developing an electrostatic latent image into a toner image, and there are two types, dry and wet. Currently, dry development methods are widely used.
Also, the dry development method is based on the type of toner used, and a development method using a magnetic toner in which magnetic powder is encapsulated in toner particles having a binder resin (a magnetic one-component development method or a magnetic two-component development method). Etc.) and development methods (nonmagnetic one-component development method or nonmagnetic two-component development method, etc.) using a nonmagnetic toner that does not enclose magnetic powder.

By the way, as one of non-magnetic two-component developing methods using non-magnetic toner, in recent years, a touch-down developing method has attracted attention in full-color image forming apparatuses.
The touchdown development system is a method in which a developer having nonmagnetic toner and a magnetic carrier is stirred, and a magnetic roller for forming a developer spike on the peripheral surface thereof is in contact with the developer spiked on the magnetic roller. And a developing roller for forming a thin layer of non-magnetic toner on the peripheral surface thereof, and the surface of the developing roller with respect to the surface of the photoconductor disposed at a predetermined interval with respect to the peripheral surface of the developing roller. In this method, a non-magnetic toner having a thin layer formed on the surface is caused to fly toward the surface of the photoconductor to develop an electrostatic latent image on the surface of the photoconductor. In this developing method, the voltage between the magnetic roller and the developing roller after the non-magnetic toner is ejected is changed, the toner thin layer is peeled off from the developing roller, and a new toner thin layer is prepared for the next development. Formed again.

  On the other hand, as a mechanical configuration of the image forming apparatus, a tandem system that uses a plurality of photoconductors corresponding to the color of toner, forms a color image in synchronization with the feeding of the transfer member, and superimposes colors on the transfer member Attention has been focused on increasing the speed of full-color image forming apparatuses. Although this method has the advantage of being excellent in high-speed performance, it is undeniable that the electrophotographic process members of each color must be arranged side by side, and there is a disadvantage of increasing the size.

  Therefore, as a countermeasure, a small tandem image forming apparatus has been proposed in which a compact image forming unit is arranged by narrowing the interval between the photoconductors. In a small tandem image forming apparatus, in order to minimize the size of the image forming unit in the width direction, it is advantageous to make the developing device a vertical type. That is, it is desirable in terms of layout that the developing device is arranged in the upper direction of the photosensitive member.

In that case, if a non-contact development method with a gap between the photoconductor and the developing roller is used, there is no carrier adhesion to the photoconductor, and the photoconductor is not damaged by the magnetic brush, enabling high image quality. It becomes. Against this background, in the small tandem image forming apparatus, the configuration of the touch-down development method is being widely adopted.
The present invention relates to such a small tandem image forming apparatus, and more particularly to an image forming apparatus employing a touch-down development method, particularly an image forming apparatus in which the photoconductor is an amorphous silicon (a-Si) photoconductor. It is an object of the present invention to provide an electrostatic latent image developing toner that can be used satisfactorily.

By the way, conventionally, toner has been produced by a pulverization method or a polymerization method.
In order to improve the long-term printing durability, titanium oxide is mainly externally added as a polishing agent to the toner surface as an abrasive to improve the long-term printing durability. As titanium oxide to be externally added, those having a primary particle size of 10 nm to 100 nm, which are generally called ultrafine particles, are known to have an effect on charging stability. However, ultrafine titanium oxide has no polishing effect, and in order to obtain the polishing effect, titanium oxide having a relatively large primary particle size (for example, primary particle size of 150 nm to 500 nm) is externally added. The externally added titanium oxide exhibits a polishing effect, but on the other hand, there is a problem that the charge amount of the toner is lowered and the development characteristics are adversely affected.

In addition, an inorganic oxide such as titanium oxide is treated with a hydrophobizing agent or a polar group is introduced so that the toner is not affected by environmental conditions such as humidity. For example, in order to introduce a polar group, a technique using titanium oxide treated with a silane coupling agent such as an aminosilane compound has been proposed (Patent Document 1 and Patent Document 2).
Further, there has been proposed an electrostatic latent image developer in which abrasive fine particles such as alumina and zirconia are fixed to the surface of toner particles and the ratio between the particle size of the toner particles and the particle size of the abrasive particles is controlled (patent) Reference 3). In the method described in Patent Document 3, an excellent polishing effect can be obtained on the surface of the photoreceptor, it is not necessary to incorporate a large system such as a cleaning brush, the apparatus can be miniaturized, and image flow and image density are uniform. This is effective against aging and fogging.
Japanese Patent Laid-Open No. 52-1357395 (refer to the claims) Japanese Patent Laid-Open No. 10-3177 (refer to the claims) Japanese Patent Laid-Open No. 5-181306 (refer to the claims)

However, the above-described prior art has the following problems.
In the prior arts disclosed in Patent Document 1 and Patent Document 2, the polishing ability with respect to the surface of the photosensitive drum is insufficient, and problems such as drum filming may occur.
On the other hand, although the conventional technique disclosed in Patent Document 3 can exhibit an appropriate polishing ability for the surface of the photoreceptor, the charging characteristics are unstable under both high temperature and high humidity conditions and low temperature and low humidity conditions. There was a problem.

The present invention has been made based on such a background. An electrostatic latent image developing toner suitable for a touch-down developing system, which can exhibit a polishing ability on the surface of a photoreceptor and has good charging stability. The main purpose is to provide.
The present invention also relates to an electrostatic latent image developing toner for use in an image forming apparatus having an amorphous silicon (a-Si) photoreceptor and adopting a touch-down developing method. It is another object of the present invention to provide a toner for developing an electrostatic latent image in which the particle shape of itself has a polishing ability and the charge stability is achieved by an external additive.

According to the first aspect of the present invention, the developer having the nonmagnetic toner and the magnetic carrier is agitated to contact the magnetic roller for forming the developer spike on the peripheral surface, and the developer spiked on the magnetic roller. A developing roller for forming a thin layer of non-magnetic toner on the peripheral surface, and an amorphous silicon (which is provided with a certain distance from the peripheral surface of the developing roller, on which an electrostatic latent image is formed) a-Si) a photosensitive member, and is used in an image forming apparatus that develops an electrostatic latent image on the surface of the photosensitive member with the non-magnetic toner by flying the non-magnetic toner formed on the peripheral surface of the developing roller to the surface of the photosensitive member. The electrostatic latent image developing toner is obtained by cutting a molten toner material that has been drawn into a cylindrical fiber by a spinning method into a predetermined length. Obtained by Wherein toner particles of the cylindrical body of diameter φ and length L, a and as an external additive, a primary particle diameter of 10 nm to 100 nm, volume resistivity of ^{1 × 10 1 ~1 × 10 7} Ω · cm Ultra An electrostatic latent image developing toner comprising fine particle titanium oxide.

  The toner for developing an electrostatic latent image of the present invention has a diameter φ and a length L obtained by cutting a molten toner raw material into a cylindrical fiber shape by a spinning method. Since the toner is obtained by externally adding ultrafine titanium oxide to cylindrical toner particles, the toner particles themselves are cylindrical and have edges as compared to conventional toner particles. With this edge, the surface of the photoconductor can be polished appropriately, toner does not adhere to the surface of the photoconductor, and image defects such as image flow do not occur at the same time. Therefore, in particular, in the touch-down development method, the electrostatic latent image developing toner having good image forming performance can be obtained.

  In this invention, it is not necessary to use titanium oxide having a relatively large primary particle size by entrusting the polishing effect to the shape of the toner particles, and ultrafine titanium oxide having a small primary particle size that is preferable in terms of charging characteristics is obtained. Can be used. As a result, it is possible to provide a toner for developing an electrostatic latent image that has good charging characteristics and exhibits an excellent effect on image stability over a long period of time.

Hereinafter, exemplary embodiments of the present invention will be described in detail by way of example.
The electrostatic latent image developing toner according to one embodiment of the present invention is a toner raw material,
80-90% resin (referred to as binder resin or binder resin)
3-8% pigment (colorant)
1-3% charge control agent (charge control agent)
3-8% mold release agent (wax)
A melt mixing step of melt-mixing the toner raw material obtained by premixing, a fiberizing step of extruding the molten toner raw material obtained in the melt-mixing step from the nozzle to form a fiber, and a fiber It is manufactured as columnar toner particles having a diameter φ = 4 to 9 μm, a length in the cylinder direction L = 4 to 13 μm, and L ≧ φ by a particle forming process in which the formed toner raw material is cut to produce columnar particles. In addition, the manufacturing method which has the above-mentioned melt mixing process and fiberization process is called a spinning method.

The above steps will be specifically described based on the apparatus configuration as follows.
<Melt mixing process and fiberizing process>
Referring to FIG. 1, in the melt mixing step and the fiberizing step, a uniaxial type having a premixing device (for example, Hosokawa Micron Co., Ltd .: Cyclomix) 7 and a rotating screw 15 as a kneading member inside with a hopper 1A. An extruder 1, a static mixer 2, and a flow channel structure 3 having a multistage distribution flow channel 3A branched from the outlet of the static mixer 2 are used. A gear pump 4 driven by a motor 5 is disposed between the outlet of the uniaxial extruder 1 and the inlet of the stationary mixer 2.

An extrusion nozzle 6 is provided at each channel outlet of the final stage of the distribution channel 3A. The uniaxial extruder 1, the static mixer 2, the flow path structure 3, and the gear pump 4 are not shown in the figure, but each of the toner raw materials has a temperature higher than the melting point of the binder resin, for example, about 130 ° C to 240 ° C. A heater is provided for heating to a low viscosity.
In the above apparatus configuration, when the toner raw material is put into the uniaxial extruder 1 from the hopper 1A, it is heated by the heater to be in a molten state, and is sent to the outlet side while being mixed. The melted mixture of toner raw materials fed from the uniaxial extruder 1 is mixed while flowing through the flow path in the static mixer 2 and the multistage distribution flow path 3A after the pressure and the amount of extrusion are adjusted by the gear pump 4. Is promoted, and each component of the toner raw material is uniformly and finely dispersed. Then, the molten toner material is extruded downward from the plurality of nozzles 6 in a fibrous form.

The plurality of fibrous bodies 12 pushed out from the nozzles 6 are stretched by hot air blown from a drawing air blowing device (not shown) and then rapidly cooled by cold air from a blower fan.
As the static mixer 2 in the above configuration, a known static mixer can be used. Specifically, as shown in FIG. 1, blades having curved surfaces twisted so as to form a spiral flow path. A structure in which a plurality (three in the example of FIG. 1) of the bodies 14 are provided while reversing the twisting angle of the spiral between adjacent ones along the flow direction of the toner raw material can be exemplified.

Next, as shown in FIG. 2, a large number of fibrous bodies 12 pushed out from the nozzles 6 are placed on the belt conveyor 11 and conveyed laterally, and are allowed to cool to room temperature in the middle of conveyance. A substantially linear fibrous body 12 having a viscosity becomes a one-layer assembly in which the fibers are arranged in the lateral direction, and reaches the fiber cutting device 8 in the next step.
As a means for conveying the fibrous body 12, in addition to the belt conveyor 11, a gas conveying means by an air flow having a constant flow velocity and a flow direction can be used.
<Particulation process>
As shown in FIG. 2, in the particle forming step, a fiber cutting device 8 is used to cut the fibrous body 12. The fiber cutting device 8 includes a fixed blade 9 extending in a direction perpendicular to the conveying direction of the fibrous body 12 conveyed on the belt conveyor 11, and a rotating blade 10 having a plurality of cutting blades 10a attached to a rotation shaft. The fibrous body 12 is continuously supplied between the cutting blade 10a of the rotary blade 10 and the edge 9a of the fixed blade 9 that are rotationally driven by a motor (not shown), and the cutting blade 10a and the fixed blade edge 9a The fibrous body 12 is sequentially cut by a shearing action that occurs between them, and columnar particles 13 are continuously formed.

Here, the cutting length of the fibrous body 12 (the length of the columnar particles 13) can be adjusted by the ratio of the conveying speed of the fibrous body 12 and the rotational speed of the rotary blade 10.
Next, the nonmagnetic toner will be described.
<Toner shape>
FIG. 3 shows a typical shape example of the toner particles. 3A is an enlarged perspective view of toner particles, B is an end surface shape of a cylinder, and C is a side shape of the cylinder. As shown in FIG. 3, the toner particles have a cylindrical body having a diameter φ and a length L. In this embodiment, a cylindrical body having no distortion is shown as the shape of the toner particles. However, some distortion occurs in the end face shape and the peripheral surface shape due to the manufacturing technology. The cylindrical body which has is also included.

As described above, φ and L are preferably within the conditions of φ = 4 to 9 μm, L = 4 to 13 μm, and L ≧ φ.
As an example, a cylindrical body having an average value of φ = 5 μm and L = 7 μm was produced.
When the toner particles are cylindrical as shown in FIG. 3, the boundary between the cylindrical peripheral surface and the end surface forms an edge, so that the toner particles themselves have an appropriate polishing action on the surface of the photoreceptor. It has become.

The non-magnetic toner formed as described above may be obtained by treating the toner particle surface with, for example, colloidal silica or hydrophobic silica for the purpose of maintaining the fluidity and storage stability.
<Description of Toner Component (Toner Raw Material)>
Binder resin (binder resin):
The type of the binder resin is not particularly limited. For example, polystyrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin. It is preferable to use a thermoplastic resin such as a polyamide resin, a polyurethane resin, a polyvinyl alcohol resin, a vinyl ether resin, an N-vinyl resin, or a styrene-butadiene resin.

  More specifically, the polystyrene resin may be a homopolymer of styrene or a copolymer with another copolymerizable monomer copolymerizable with styrene. As copolymerizable monomers, p-chlorostyrene; vinyl naphthalene; ethylene unsaturated monoolefins such as ethylene, propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride; vinyl acetate, propion Vinyl esters such as vinyl acrylate, vinyl benzoate, vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, acrylic (Meth) acrylic acid esters such as phenyl acid, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; Vinyl ethers such as nylmethyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidene, etc. N-vinyl compounds of These may be used alone or in combination of two or more with a styrene monomer.

  The polystyrene resin preferably has two mass average molecular weight peaks (referred to as a low molecular weight peak and a high molecular weight peak) in terms of its molecular weight. Specifically, the low molecular weight peak is in the range of 3,000 to 20,000, the other high molecular weight peak is in the range of 300,000 to 1,500,000, and Mw / Mn is 10 or more. Those are preferred. If the mass average molecular weight peak is within such a range, the toner can be easily fixed, and offset resistance can be improved.

The mass average molecular weight of the binder resin is determined by measuring the elution time from the column using a molecular weight measuring device (GPC) and comparing it with a calibration curve prepared in advance using a standard polystyrene resin. Can be sought.
Moreover, as the polyester resin, any resin obtained by condensation polymerization or co-condensation polymerization of an alcohol component and a carboxylic acid component can be used. The following are mentioned as a component used when synthesize | combining a polyester-type resin.

  First, as an alcohol component, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1, Diols such as 5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol; bisphenol A, hydrogenated bisphenol A, polyoxyethylene Bisphenols such as bisphenol A and polyoxypropylene bisphenol A; sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol Dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, Examples thereof include divalent or trivalent or higher alcohols such as trimethylolethane, trimethylolpropane, 1,3,5, -trihydroxymethylbenzene.

  As the carboxylic acid component, a divalent or trivalent carboxylic acid, an acid anhydride or a lower alkyl ester thereof is used. Maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, Terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, or n-butyl succinic acid, n-butenyl succinic acid, isobutyl succinic acid, isobutenyl succinic acid, n-octyl succinic acid, n Divalent carboxylic acids such as alkyl or alkenyl succinic acid such as octenyl succinic acid, n-dodecyl succinic acid, n-dodecenyl succinic acid, isododecyl succinic acid, isododecenyl succinic acid; 1,2,4-benzenetricarboxylic acid ( Trimellitic acid), 1,2,5-benzenetricarbo Acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2 -Methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empole trimer acid, etc. Examples are trivalent or higher carboxylic acids.

Moreover, it is preferable that the softening point of a polyester-type resin is 110-150 degreeC, More preferably, it is 120-140 degreeC.
The binder resin is preferably a thermoplastic resin from the viewpoint of good fixability, but the amount of cross-linked portion (gel amount) measured using a Soxhlet extractor is a value of 10% by mass or less, more preferably 0.8. If it is a value within the range of 1 to 10% by mass, a thermosetting resin may be used. By introducing a partially crosslinked structure in this way, it is possible to further improve the storage stability, form retention, and durability of the toner without deteriorating the fixability. Therefore, it is not necessary to use 100% by mass of the thermoplastic resin as the binder resin of the toner, and a crosslinking agent can be added or a part of the thermosetting resin can be used.

  Therefore, an epoxy resin, a cyanate resin, or the like can be used as the thermosetting resin. More specifically, one or more of bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, polyalkylene ether type epoxy resin, cycloaliphatic type epoxy resin, cyanate resin, etc. Combinations are listed.

  In the binder resin, in order to improve the dispersibility of the magnetic powder, a resin having at least one functional group selected from a hydroxyloxy (hydroxy acid) group, a carboxyl group, an amino group, and a glycidoxy (epoxy) group in the molecule. It is preferable to use it. In addition, it can be confirmed using an FT-IR apparatus whether it has these functional groups, and also can be quantified using a titration method.

  In the binder resin, the glass transition point (Tg) is preferably set to a value within the range of 55 to 70 ° C. When the glass transition point of the binder resin is less than 55 ° C., the obtained toners are fused with each other, and the storage stability tends to be lowered. On the other hand, when the glass transition point of the binder resin exceeds 70 ° C., the fixability of the toner tends to be poor. In addition, the glass transition point of binder resin can be calculated | required from the change point of specific heat using a differential scanning calorimeter (DSC).

Pigment (colorant):
Examples of colorants include black pigments such as acetylene black, lanblack, and aniline black; black pigments such as yellow lead, zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, and navel. S Yellow, Naphthol Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake; orange pigments such as reddish yellow lead, molybdenum orange, permanent orange GTR, Pyrazolone orange, Vulcan orange, Indanthrene brilliant orange RK, Benzidine orange G, Indanthrene brilliant orange GK; As red pigment, Bengala, Kadomi Mured, red lead, mercury cadmium sulfide, permanent red 4R, risor red, pyrazolone red, watching red calcium salt, lake red D, brilliant carmine 6B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; , Manganese Purple, Fast Violet B, Methyl Violet Lake; As Blue Pigment, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Metal-free Phthalocyanine Blue, Phthalocyanine Blue Partial Chlorides, Fast Sky Blue, Induslen Blue BC: As a green pigment, chromium green, chromium oxide, pigment green B, malachite green lake, fanal yellow green G; white As a pigment, zinc oxide, titanium oxide, antimony white, zinc sulfide, barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white can be used. Such a colorant is preferably used in an amount of 2 to 20 parts by weight, particularly 5 to 15 parts by weight per 100 parts by weight of the binder resin.

Charge control agent (charge control agent):
The type of the charge control agent is not particularly limited. For example, nigrosine, a quaternary ammonium salt compound, a resin type charge control agent in which an amine compound is bonded to a resin, and the like exhibit positive chargeability. Charge control agents can be used. When used for a color toner, a colorless or white one is preferable. It is preferably used in an amount of 0.5 to 10 parts by weight, particularly 1 to 5 parts by weight per 100 parts by weight of the binder resin.

Mold release agent (wax):
The wax is not particularly limited. For example, plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; Fischer-Tropsch having ester in the side chain ( In the following, synthetic hydrocarbon waxes such as wax, polyethylene wax, and polypropylene wax may be mentioned. Among these, from the viewpoint of dispersibility, use of FT wax or polyethylene wax having ester in the side chain is recommended.

The wax preferably has an endothermic main peak in a range of 70 to 120 ° C. in an endothermic curve obtained by a differential scanning calorimeter. This is because when the endothermic main peak is less than 70 ° C., toner blocking and hot offset may occur, and when the endothermic main peak exceeds 120 ° C., low temperature fixability may not be obtained.
Further, the addition amount of the wax is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin. If the addition amount of the wax is less than 0.1 parts by weight, it is difficult to obtain a sufficient effect of the wax. On the other hand, if the addition amount is more than 20 parts by weight, the anti-blocking property is lowered and the toner may be detached. is there.
<External additive>
In the nonmagnetic toner according to this embodiment, ultrafine titanium oxide is used as an external additive.

The primary particle size of the ultrafine titanium oxide is desirably 10 nm to 100 nm. If it is less than 10 nm, the primary particle diameter is too small and the toner surface is buried in the toner during the durability, and the effect of charging stability of the ultrafine titanium oxide cannot be exhibited. On the other hand, if the thickness exceeds 100 nm, the charge amount of the toner is reduced, and an image defect such as a reduction in image density is caused.
The volume resistivity of the ultrafine titanium oxide is 1 × 10 ¹ to 1 × 10 ⁷ Ω · cm, preferably 1 × 10 ² to 1 × 10 ⁶ Ω · cm. If it is less than 1 × 10 ¹ Ω · cm, it becomes impossible to impart sufficient chargeability to the toner, causing a decrease in image density. On the other hand, if it exceeds 1 × 10 ⁷ Ω · cm, the charge amount is too high, and the durability is also increased, resulting in a decrease in image density and deterioration in durability. Furthermore, excessive charge-up of the toner may cause discharge breakdown in the amorphous silicon (a-Si) photoreceptor and cause a black spot image.

The volume resistivity of the ultrafine titanium oxide can be adjusted by adjusting the amount of tin oxide and antimony in the conductor added to the titanium oxide surface.
The primary particle diameter of titanium oxide can be measured using a particle counter that employs a laser system.
Further, the volume resistivity value of the titanium oxide can be obtained at an applied voltage of DC 10 V by applying a load of 1 kg using an R8340A ULTRA HIGH RESISTANCE METER manufactured by ADVANTEST. <Magnetic carrier>
Next, a magnetic carrier in which the nonmagnetic toner according to this embodiment is mixed will be described.

Carrier, as the carrier core material, particles of iron, oxidized iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, etc., and particles of alloys of these materials with manganese, zinc, aluminum, etc., Particles such as iron-nickel alloy, iron-cobalt alloy, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, Ceramic particles such as lead zirconate and lithium niobate, particles of high dielectric constant materials such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt, resin carriers in which the above magnetic particles are dispersed in a resin, etc. Various conventionally known carrier cores can be used.
(Meth) acrylic polymer, styrene polymer, styrene- (meth) acrylic copolymer, olefin polymer (polyethylene, chlorinated polyethylene, polypropylene, etc.), polyvinyl chloride, poly Vinyl acetate, polycarbonate, cellulose resin, polyester resin, unsaturated polyester resin, polyamide resin, polyurethane resin, epoxy resin, silicone resin, fluororesin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, etc.), phenol resin Various conventionally known resins can be used for coating carriers such as xylene resin, diallyl phthalate resin, polyacetal resin, and amino resin. These may be used alone or in admixture of two or more.

The weight average particle diameter of the carrier is preferably in the range of 10 to 200 μm, particularly in the range of 30 to 150 μm.
The resin coating layer contains additives for adjusting the properties of the resin coating layer, such as silica, alumina, carbon black, fatty acid metal salt, silane coupling agent, titanate coupling agent, etc. It can also be made.

The film thickness of the resin coat layer may be about the same as that of the conventional one, and is not particularly limited. Specifically, the resin coat layer is expressed in terms of the coating amount on the carrier core material and is 0.01 to 10% by weight, particularly 0. The coating amount is preferably from 5 to 5% by weight.
The toner and the carrier can be mixed at an appropriate ratio and used in an image forming apparatus such as an electrostatic copying machine or a laser beam printer. The blending ratio of the electrophotographic carrier and the toner may be the same as in the past. In order to improve the fluidity of the developer, conventionally known external additives such as silica, alumina, tin oxide, titanium oxide, strontium oxide, and various resin powders can be blended.

Hereinafter, the present invention will be described in more detail based on examples.
Needless to say, the following description exemplifies the present invention, and the scope of the present invention is not limited to the following description without any particular reason.
<Synthesis of binder resin>
Put 300 parts by weight of xylene in a reaction vessel connected to a thermometer, a stirrer, a nitrogen introduction tube, and a reflux tube, and heat the reaction vessel while continuously introducing nitrogen from the nitrogen introduction tube to adjust the liquid temperature. While maintaining the temperature at 170 ° C., a solution of 845 parts by weight of styrene, 155 parts by weight of n-butyl acrylate, and 8.5 parts by weight of di-tert-butyl peroxide in 125 parts by weight of xylene was placed in The solution was added dropwise over a period of time. After completion of the addition, the mixture was further stirred at 170 ° C. for 1 hour, and then the solvent was removed to produce a styrene-n-butyl acrylate copolymer as a binder resin.
Styrene / acrylic resin 92 parts by weight Polyethylene wax 3 parts by weight Charge control agent 1 part by weight Colorant (carbon black) 4 parts by weight However, the total of styrene / acrylic resin, polyethylene wax, charge control agent, and colorant is 100% by weight. did.

  Styrene / acrylic resin synthesized under the above conditions, polyethylene wax (manufactured by 110P (Mitsui Chemicals Co., Ltd.)), charge control agent (P-51 (manufactured by Orient Chemical Co., Ltd.)), and carbon black (MA- Toner particles having a mean diameter of φ = 5 μm and a length L = 7 μm, obtained by stretching and cutting a toner component in a molten state from a mixture of 100 (manufactured by Mitsubishi Chemical Corporation) into a cylindrical fiber shape Got.

  Examples of the present invention were prepared by adding 1.0% of each titanium oxide shown in Table 1 and 1.5% of silica (RA-200H (manufactured by Nippon Aerosil Co., Ltd.)) to the particles and mixing them to adhere to the surface. The toner of the comparative example was prepared by mixing the obtained toner with a carrier and using it as a two-component developer, and the photosensitive drum of a Kyocera Mita color page printer (FS-C5016N) was made of amorphous silicon (a-Si) photosensitive. Using an evaluation machine modified to a body drum, the initial image characteristics, durability, and image flow were evaluated and measured. The results are shown in Table 2.

These evaluation methods are as follows.
(1) Image characteristics 10 parts by weight of the toner and 100 parts by weight of ferrite carrier are mixed to form a two-component developer, and the photosensitive drum of the Kyocera Mita color page printer (FS-C5016N) is amorphous silicon (a-Si). Image characteristics were evaluated using an evaluation machine modified to a photosensitive drum. As the ferrite carrier, a Cu—Zn ferrite carrier having an average particle diameter of 50 μm was used. Using the printer described above, an image evaluation pattern is printed at the initial time in a normal environment (20 ° C., 65% RH) to obtain an initial image. Thereafter, 50,000 sheets are continuously fed, and the image evaluation pattern is printed again. A solid image was measured using a Macbeth reflection densitometer [RD914 manufactured by Gretag Macbeth Co., Ltd.], and image characteristics were evaluated by visually observing the fog. An image density of 1.30 or higher was evaluated as acceptable, and an image density of less than 1.30 was evaluated as unacceptable. As for fogging, ○ was accepted, and other items were rejected. The evaluation results are shown in Table 2.

○: Good fogging.
Δ: Slight fogging occurs.
X: The fog is terrible.
(2) Image flow As described above, 5,000 sheets are continuously passed in a normal environment (20 ° C., 65% RH), and then left overnight in a high temperature and high humidity environment (33 ° C., 85% RH). Then, image evaluation was performed by printing an image evaluation pattern and visually observing the level of image flow. ○ was accepted and others were rejected.

○: Image flow is not observed, and it is clean and good.
Δ: Some image flow is recognized.
X: Considerable image flow is recognized.

It is the schematic which shows an example of the apparatus structure of the melt mixing process and fiberization process in a toner manufacturing process. It is the schematic which shows the apparatus structural example which performs the particle-ized process of a toner manufacturing process. FIG. 3 is an illustrative view showing a typical shape of toner particles according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Uniaxial extruder 2 Static mixer 3 Flow path structure 3A Distribution flow path 4 Gear pump 6 Pushing nozzle 7 Preliminary mixing device 8 Fiber cutting device 9 Fixed blade 9a Edge 10 Rotary blade 10a Cutting blade 12 Fibrous body 13 Columnar shape particle

Claims (1)

Stir the developer with non-magnetic toner and magnetic carrier to contact the magnetic roller for forming the developer spike on the peripheral surface and the developer spiked on the magnetic roller, thereby making the peripheral surface non-magnetic. A developing roller for forming a thin layer of toner, and an amorphous silicon (a-Si) photoreceptor provided on the surface of the developing roller at a certain distance from the peripheral surface of the developing roller, on which an electrostatic latent image is formed. A toner for developing an electrostatic latent image, which is used in an image forming apparatus for developing the electrostatic latent image on the surface of the photosensitive member with the non-magnetic toner by flying the non-magnetic toner formed on the peripheral surface of the developing roller to the surface of the photosensitive member Because
The electrostatic latent image developing toner has a diameter φ and a length L obtained by cutting a molten toner raw material into a cylindrical fiber shape by a spinning method. It contains cylindrical toner particles, and contains, as an external additive, ultrafine particle titanium oxide having a primary particle diameter of 10 nm to 100 nm and a volume resistivity of 1 × 10 ¹ to 1 × 10 ⁷ Ω · cm. An electrostatic latent image developing toner.

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