JP2005241769A - Carrier for color developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new carrier for a color developer, the carrier which has a resin coating layer free from a problem of charge-up because the resin has the conductivity almost in the same level as a coating layer compounded with a conventional conducting agent, in particular, which does not inhibit hue of a color toner as for forming a full-color image. <P>SOLUTION: The carrier for a color developer constitutes a two-component color developer with a color toner, and has a resin coating layer containing polyalkylene oxide expressed by formula (1) as a conducting agent on the surface of a core material. In formula (1), m is an integer ≥2 and n is an integer ≥1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a color developer carrier for forming a two-component color developer together with a color toner, which is particularly suitable for forming a full-color image.

  Cyan, magenta, and yellow are used in image forming apparatuses such as electrostatic copying machines, laser printers, plain paper facsimile machines, and multi-function machines having two or more of these functions that use so-called electrophotography. In general, a full color image is expressed by superimposing four color toners for developing an electrostatic latent image obtained by adding black to these three colors, or by adding black to these three colors.

  As for the development method of each color toner, as in the case of a normal single-color image forming apparatus, the toner is frictionally charged by mixing a two-component developer in which the toner and the carrier are mixed at a predetermined ratio. A so-called two-component development system in which toner is conveyed by a carrier and brought into contact with an electrostatic latent image on the surface of a photoreceptor is widely used. As a carrier for an ordinary monochromatic image forming apparatus, for example, a so-called coat type in which the surface of a core material such as magnetic particles is coated with a resin coating layer to prevent toner spent or the like is used. It is done.

  In addition, the coating layer of the coat-type carrier has a positive charge imparting property that positively charges the toner by frictional charging because the toner itself is negatively charged, particularly when the toner is positively charged. It is preferable to form by.

  However, the resin coating layer as it is has a resistance value that is too high and a positive charge imparting property that is too strong, so that the toner is likely to be charged up. If stirring is continued in the developing device of the apparatus for a long period of time, there is a risk that a density defect will occur in the formed image.

Therefore, for example, by adding a conductive agent such as carbon black, titanium oxide, or alumina, the resistance value of the coating layer is lowered, and the positive charge imparting property to the toner is weakened to reduce the charge (see Patent Document 1). ).
JP-A-8-286429

  However, since carbon black is black among the above, when it is used in an image forming apparatus for full-color image formation and stirred in the developing device of the apparatus for a long period of time, it falls off from the coating layer. When mixed in the toner, the hue of the toner is hindered, and there is a problem that a good full color image cannot be formed.

  Therefore, in Patent Document 1, the outermost surface of the coating layer is a layer containing a white conductive agent such as titanium oxide or alumina. According to such a configuration, since the conductive agent exposed on the surface is white, even if it drops off from the coating layer and enters the toner, the hue is not hindered.

  However, according to the study of the present inventor, a white conductive agent having high brightness inhibits the hue when mixed in cyan, magenta and yellow toners for full-color image formation. It has been found that a good full-color image cannot be formed yet.

  The object of the present invention is to provide a resin coating layer that does not cause charge-up problems because it has the same degree of conductivity as when a conventional conductive agent is blended, and inhibits the hue of color toners, particularly for full-color image formation. It is an object of the present invention to provide a novel carrier for a color developer that does not have a risk of occurrence.

  As a result of various studies on materials to be included in the coating layer, the present inventor has shown that the polyalkylene oxide represented by the chemical formula (1) can impart appropriate electrical conductivity to the coating layer to prevent charge-up of the toner. It has been found that a good full-color image can be formed without being dropped from the coating layer and mixed into the toner, unlike conventional conductive agents, because it is compatible with the resin forming the layer.

  Chemical formula (1):

（ｍは２以上の整数、ｎは１以上の整数）
ポリアルキレンオキシドは、化学式（１）のような構造を有する飽和直鎖炭素鎖の化合物で、外観は、重合度ｎ＝６００以下では液体、重合度ｎ＝１０００以上では固体である。一般的には、溶剤、洗浄剤、潤滑剤、合成中間体、医薬、医薬中間体、顔料、塗料、染料助剤、インキ、接着剤、可塑剤、等に使用される。

(M is an integer of 2 or more, n is an integer of 1 or more)
The polyalkylene oxide is a saturated straight-chain carbon chain compound having a structure as represented by the chemical formula (1), and the appearance is liquid when the polymerization degree is n = 600 or less and is solid when the polymerization degree is n = 1000 or more. Generally, it is used for solvents, detergents, lubricants, synthetic intermediates, pharmaceuticals, pharmaceutical intermediates, pigments, paints, dye assistants, inks, adhesives, plasticizers, and the like.

  Polyalkylene oxide is particularly known as a conductive polymer, and among them, polyethylene oxide has recently been used as a polymer electrolyte for lithium polymer batteries. This is because polyethylene oxide exhibits excellent ionic conductivity. This ionic conductivity is said to depend on polymer mobility rather than ion hopping. Therefore, when m = 2 in the chemical formula (1) (polyethylene oxide), it is presumed that the molecule is short and the mobility of the polymer is good, and the ion conductivity is particularly excellent. Further, it was found that polyalkylene oxide has a good negative chargeability because it has an oxygen atom in the molecule.

  That is, as described above, polyalkylene oxide, particularly polyethylene oxide, ensures good negative chargeability to ensure positive chargeability to the toner, and in order to exhibit good ionic conductivity, the aforementioned conductive agent ( Carbon black, titanium oxide, and the like), and the resistance value of the coating layer is lowered to prevent toner charge-up.

  Since the polyalkylene oxide is compatible with the binder resin forming the coating layer of the carrier and exhibits good ionic conductivity and negative chargeability, a carrier for a color developer containing the polyalkylene oxide in the coating layer is used. As with the case where a conventional conductive agent such as carbon black is blended while ensuring positive chargeability to the toner, it is provided with a resin coating layer that does not cause a charge-up problem, and is a color toner. Thus, a good color image can be formed.

  The present invention is described below.

[Carrier for color developer]
Examples of the resin forming the coating layer include (meth) acrylic resins, styrene resins, styrene- (meth) acrylic resins, olefin resins (polyethylene, chlorinated polyethylene, polypropylene, etc.), polyester resins (polyethylene terephthalate). Etc.), polycarbonate, unsaturated polyester resin, vinyl chloride resin, polyamide resin, polyurethane resin, epoxy resin, fluorine resin (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, tetrafluoroethylene) -Hexafluoroethylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.), silicone resins, phenol resins, xylene resins, diallyl phthalate resins, etc. Kill.

The polyalkylene oxide contained in the coating layer is a compound represented by the above chemical formula (1).
Chemical formula (1):

（ｍは２以上の整数、ｎは１以上の整数）
ポリアルキレンオキシドの重量平均分子量Ｍｗは１００〜５０００が好ましく、特に２００〜１０００が好ましい。上記範囲を下回ると、イオン伝導性が不足してトナーのチャージアップが発生し易くなる傾向があり、上記範囲を上回ると、被覆層を形成する結着樹脂との相溶性が悪化して、結着樹脂中で粒子状に分散する傾向となり、被覆層から脱落してカラートナーの色相を悪化させるおそれがある。

(M is an integer of 2 or more, n is an integer of 1 or more)
The weight average molecular weight Mw of the polyalkylene oxide is preferably from 100 to 5,000, particularly preferably from 200 to 1,000. Below the above range, the ionic conductivity tends to be insufficient and toner charge-up tends to occur. Above the above range, the compatibility with the binder resin forming the coating layer deteriorates, resulting in a binding. It tends to disperse in the form of particles in the resin, and may fall off the coating layer and deteriorate the hue of the color toner.

  In the chemical formula (1), m represents an integer of 2 or more, and polyethylene oxide in which m = 2 is most preferably used for the carrier of the present invention. As described above, this is probably because the polymer has high mobility and the highest ionic conductivity. Of course, the ionic conductivity of polypropylene oxide in which m = 3 and polybutylene oxide in which m = 4 is also large and suitable for use. When m ≧ 5, the polymer mobility tends to decrease and the ionic conductivity tends to decrease, and there is a concern that toner charge-up is likely to occur.

  In chemical formula (1), n represents a polymerization degree and represents an integer of 1 or more. Depending on the degree of polymerization n, it changes from liquid to solid, but the preferred state for the carrier of the present invention is liquid. This is presumably because the compatibility with the coating resin is improved. The preferable value of the degree of polymerization n depends on the value of m, but when m ≦ 4, the degree of polymerization n ≦ 50 is preferable.

  The content of polyethylene oxide in the coating layer is preferably 1 to 40 parts by weight, particularly 5 to 20 parts by weight, based on 100 parts by weight of the resin. Below the above range, the ion conductivity tends to be insufficient due to insufficient ion conductivity, and above the above range, the positive charge imparting property to the toner tends to become too strong, and the image density decreases. There is a risk of malfunction.

  Next, as the core material, for example, 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 of iron-nickel alloy, iron-cobalt alloy, etc., particles having a composite structure in which fine powders of the above various materials are dispersed in resin particles, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, oxidation Ceramic particles such as zirconium, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, lead zirconate, lithium niobate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, Rochelle salt, etc. Examples thereof include particles of a high dielectric constant material.

  Among them, iron-based particles such as iron oxide and reduced iron and ferrite particles are preferable. Examples of the ferrite particles include zinc-based ferrite, nickel-based ferrite, copper-based ferrite, nickel-zinc-based ferrite, lithium-based ferrite, and manganese-magnesium-based. Examples of the particles include ferrite, copper-magnesium ferrite, manganese-zinc ferrite, and manganese-copper-zinc ferrite.

  In order to form a coating layer on the surface of the core material, first, each component constituting the coating layer is dissolved or dispersed in an appropriate solvent to prepare a coating agent, which is applied to the surface of the core material, and then heated. The solvent may be dried and removed, and the resin may be cured. As a method for applying the coating agent, any of known methods such as a mechanical mixing method, a spray method, a dipping method, a fluidized bed method, and a rolling bed method can be employed.

  Examples of the solvent include aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as trichloroethylene and perchloroethylene, ketones such as acetone and methyl ethyl ketone, cyclic ethers such as tetrahydrofuran, methanol, ethanol, isopropanol, and the like. Of these alcohols, those capable of satisfactorily dissolving or dispersing the resin forming the coating layer may be selected and used.

  The particle diameter of the color developer carrier of the present invention thus formed may be appropriately selected according to the system of the image forming apparatus to be used, etc., but usually the volume-based average particle diameter is 35. It is preferably ˜100 μm, more preferably 40 to 65 μm.

[Color toner]
The color toner constituting the two-component color developer together with the color developer carrier of the present invention can be formed in a conventional manner.

  In other words, yellow, magenta, or cyan colorants, charge control agents, offset control agents, and other additives as necessary, are prepared in a fixing resin such as polyester produced by pulverization or classification. The toner particles having a dispersed structure can be surface-treated with an external additive such as silica to form a color toner. The volume-based average particle diameter of the color toner is 5 to 10 μm, preferably 6 to 8 μm.

  The toner concentration in the two-component color developer is preferably 2 to 15% by weight.

  The color developer carrier of the present invention is preferably used as a two-component color developer for a full-color image forming apparatus. As a result, it is possible to form a full-color image having a good hue while preventing the spent or charged up of the color toner. However, the color developer carrier of the present invention can be used together with a monocolor toner for a monochromatic image forming apparatus.

<Example>
Hereinafter, the present invention will be described based on examples and comparative examples.

Examples 1 and 2
(Preparation of coating agent for coating layer)
100 parts by weight of a silicone resin [Toray Dow Corning Silicone, SR-2411], 5 parts by weight of polyethylene oxide [Mw = 300] (Example 1), 15 parts by weight (Example 2) are dissolved in toluene. Thus, a coating agent for the coating layer was prepared.

[Examples 3 and 4]
Example 1 was used except that 5 parts by weight of polypropylene oxide [Mw = 400] (Example 3) and 5 parts by weight of polybutylene oxide [Mw = 500] (Example 4) were used instead of polyethylene oxide. The coating agent was adjusted.

(Manufacture of color developer carrier)
Ferrite core particles (powder tech, volume center particle size: 60 μm, saturation magnetization: 65 emu / g), coating device by fluidized bed method (Freund Sangyo, SPIR-A-FLOW “MINI”) By applying the coating agents of Examples 1 to 4 above, heating at 180 ° C. for 2 hours, drying and removing toluene, and forming a coating layer by curing the silicone resin, the volume-based center particle size Produced a carrier for color developer having a thickness of 60 μm. The coating amount of the coating layer was 5 parts by weight with respect to 100 parts by weight of the core material.
[Comparative Example 1]
A coating agent was prepared in the same manner as in Example 1 except that polyethylene oxide was not added, and a carrier for color developer was produced.
[Comparative Example 2]
A coating agent was prepared in the same manner as in Example 1 except that 5 parts by weight of carbon black (M4100 manufactured by Mitsubishi Chemical Corporation) was used instead of polyethylene oxide, and a carrier for color developer was produced.
[Comparative Example 3]
A coating agent was prepared in the same manner as in Example 1 except that 5 parts by weight of titanium oxide (MPT240 manufactured by Ishihara Sangyo Co., Ltd.) was used instead of polyethylene oxide, and a carrier for color developer was produced.

(Production of color toner)
[Synthesis of polyester resin]
A polyester resin for cyan toner particles was synthesized by the following synthesis scheme. 4.0 mol of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and 1.0 mol of polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane Then, 4.5 mol of terephthalic acid and 0.5 mol of trimellitic anhydride are placed in a reaction vessel together with 4 g of dibutyltin oxide, reacted at 230 ° C. for 8 hours in a nitrogen atmosphere, and separated from the reaction system. The polyester resin was synthesized by washing and drying.

[Manufacture of color toners]
100 parts by weight of the above polyester resin, 5 parts by weight of Pigment Yellow 154 [trade name Yellow H3G manufactured by Clariant Japan Co., Ltd.] as a yellow pigment, 5 parts by weight of charge control agent [FCA201PS manufactured by Fujikura Kasei Co., Ltd.], and polypropylene Add 2 parts by weight of wax (trade name Umex 100TS manufactured by Sanyo Chemical Co., Ltd.), thoroughly premix with a Henschel mixer, then melt knead using a twin-screw extrusion kneader and pulverize using a jet mill Thereafter, classification was performed using an air classifier to produce yellow toner particles having a volume-based center particle size of 8.0 ± 0.5 μm.

  0.5 parts by weight of silica (REA200HS manufactured by Nippon Aerosil Co., Ltd.) as an external additive is added to 100 parts by weight of the yellow toner particles and mixed with a Henschel mixer, so that the surface of the yellow toner particles is made of silica. A yellow toner was prepared by processing.

(Preparation of two-component color developer)
The yellow toner and the color developer carrier prepared in each of Examples and Comparative Examples were mixed by a ball mill to prepare a two-component color developer. The toner concentration was 6% by weight.

(Real machine test)
Using the above two-component color developer in a full-color laser printer (KM-C2630 manufactured by Kyocera Mita Corporation), a solid yellow image with a temperature of 23 ° C., a relative humidity of 65%, and a normal temperature and humidity environment. 1000 sheets were output continuously.

  Then, the solid image density and the blank fog density of the first and 1000th output images were measured using a Macbeth reflection densitometer (RD-918 manufactured by Gretag Macbeth).

  The solid portions of the first and 1000th images were measured using a spectrocolorimeter [CM-3700α manufactured by Minolta Co., Ltd.] to determine the lightness L *. The colorimetric conditions were light source: D65, field of view: 10 °.

(Charge amount measurement)
The charge amount Q / M [μC / g] of the toner in the two-component yellow developer at each time point before and after the continuous image output is measured using a QM meter (Model 210HS manufactured by TREK). And measured.

  The results are shown in Table 1.

表１より、被覆層にポリエチレンオキシドを含有させなかった比較例１は、連続画像出力によってトナーの帯電量が大きく上昇するとともに、画像濃度が著しく低下しており、トナーのチャージアップが発生していることがわかった。

From Table 1, in Comparative Example 1 in which polyethylene oxide was not contained in the coating layer, the charge amount of the toner was greatly increased by continuous image output, the image density was remarkably decreased, and the toner was charged up. I found out.

  Further, in Comparative Example 2 in which carbon black was contained in the coating layer, the lightness L * of the solid portion was greatly reduced by continuous image output, and the carbon black was dropped from the coating layer and mixed into the yellow toner. It was found that the hue of the yellow toner was hindered.

  On the other hand, in Comparative Example 3 in which titanium oxide was contained in the coating layer, the brightness L * of the solid portion was greatly increased by continuous image output, and the titanium oxide dropped from the coating layer and mixed into the yellow toner. As a result, it was found that the hue of the yellow toner was inhibited.

On the other hand, in each of the examples, it was found that the image density hardly changed even by continuous image output, and it was possible to reliably prevent the toner from being charged up. In each of the examples, it was found that the lightness L * of the solid portion was hardly changed by continuous image output, and the hue of the yellow toner was not inhibited.

Claims (2)

A carrier for a color developer for constituting a two-component color developer together with a color toner, wherein the surface of the core is coated with a coating layer of a resin containing a polyalkylene oxide represented by the chemical formula (1) as a conductive agent A color developer carrier characterized by the above.
Chemical formula (1):

(M is an integer of 2 or more, n is an integer of 1 or more) The color developer carrier according to claim 1, wherein the polyalkylene oxide is polyethylene oxide (m = 2).