JP2006011290A - Electrophotographic apparatus and development device and developing toner used for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic apparatus which is free of the occurrence of toner filming and satisfies both the signal level and the waveform specifications as described in ANSI X9.27. <P>SOLUTION: The electrophotographic apparatus is so configured that the relationships among the carrier-mixing ratio T (%) of toner in developer, the amount of electrostatic charge Q of the toner and the field intensity E (V/cm) of a bias voltage to be applied to a developing roll satisfy the Formulas (1) and (2): the formula (1) is expressed as Q/T>1.28 and the formula (2) is expressed as E≥8.0(V/cm). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic apparatus using a developing toner that visualizes an electrostatic charge latent image formed in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, and the like, and is particularly disposed in the developing device. An electrophotographic apparatus that visualizes a toner image on a photoreceptor with a developing roll, and more specifically, a magnetic ink symbol identification (Magnetic Ink Character) whose specifications are defined by ANSI (American National Standards Institute) X9.27 The present invention relates to an electrophotographic apparatus capable of obtaining an image suitable for characters (hereinafter abbreviated as MICR), a developing device used therefor, and a developing toner.

  The MICR system, for example, prints information such as bank name, amount, and account number on checks and bills with magnetic ink, and reads the information with a magnetic reader (MICR reader) when handling checks and bills in banking operations. The system is efficient. The use of an electrophotographic apparatus as a means for printing the above-described information has been studied.

  Among the above-mentioned printing or recording methods, for example, in electrophotography, the photoconductive photoreceptor is charged and exposed to form an electrostatic charge latent image on the photoreceptor, and this electrostatic charge latent image is then used as a binder for the resin. Development is performed with fine particle toner containing a colorant and the like, and the obtained toner image is transferred onto a recording paper and fixed to obtain a recorded image.

  In such an electrostatic image recording process, in particular, in order to always maintain a clear image quality and to continuously obtain MICR characters having the specifications described in ANSI X9.27, the toner image is developed by a developing device. The imaging process is important. If the characters are not imaged as specified, they will not be recognized by the magnetic reader (MICR reader) used to ensure security in banking operations, etc., which will interfere with banking operations and will be recognized reliably. For this purpose, the development process is the most important process.

  Conventionally, as a method for developing toner, a magnetic brush development method using a two-component developer composed of a toner capable of high-speed and high-quality development and a magnetic carrier is often used. In addition, as a toner for MICR, a magnetic material typified by magnetite is contained, the toner itself has magnetic characteristics, and a printed matter on which a special character toner image for MICR described in ANSI X9.27 is placed is used as a write head of a magnetic reader ( The toner character is magnetized) and the read head (reading the magnetized toner character) so that the MICR authentication system is not hindered.

  On the other hand, recently, with the development of information equipment, laser beam printers have been developed that use a laser beam for exposure of a photoconductive photoreceptor and reproduce a recorded image with dots by a modulation signal instructed by a computer. In particular, recent laser beam printers are required to produce images with higher image quality. Therefore, the diameter of the laser beam is narrowed down and the dot density is increased to 600 to 1200 dpi (dots / inch). Along with this, for the purpose of developing a fine electrostatic charge latent image, the toner and carrier particle sizes are also reduced, a small particle size toner having a volume average particle size of 10 μm or less and a small particle size toner having a weight average particle size of 100 μm or less. Application of particle size carriers is underway.

  However, the toner of a small particle size increases the cost of the toner because the yield in the pulverization and classification process is reduced during the production of the toner. These problems occur with small particle size toners, and it is usually difficult to put toners of less than 4 μm into practical use. Fine toner particles are cut with an average particle size of the toner in the range of 4 to 10 μm. The toner fluidity is increased by improving the formulation.

  On the other hand, as the toner particle size is reduced, the weight average particle size is reduced to 100 μm or less, the specific surface area of the carrier is increased, and the triboelectric chargeability with the toner is improved. However, if the carrier is less than 30 μm, the magnetic force of the carrier is reduced, and the carrier tends to adhere to the electrostatic charge image holding member by electrostatic attraction. Therefore, the average particle diameter of the carrier is classified into a range of 30 to 100 μm, and if necessary The surface is coated with resin.

  Due to the improvement in particle size distribution and the improvement in fluidity and chargeability, small particle size toners and developers have been put to practical use in copying machines, printers and the like. However, when printing with an actual machine, particularly when printing 10 pages or more per minute, the above-mentioned problems peculiar to the small-diameter toner occur, the life of the developer is reduced due to the carrier spent by the toner, and the photosensitivity by the toner. The lifetime of the photosensitive member is likely to decrease due to body filming.

  Even in a toner containing magnetite for MICR, the small particle size toner has a strong electrostatic attraction and the characteristic of filming is not changed because of its adhesion. Furthermore, in the case of MICR toner, in addition to general specifications such as image density and fogging, it is required to satisfy the signal level and wave form specifications described in ANSI X9.27 in order to ensure security in the nature of banking operations. Is done.

  Improvement as a magnetic toner containing magnetite and improvement as a magnetic reader system to increase the reliability of the MICR authentication system have been made in each field, but filming of magnetic toner containing magnetite has occurred. There are no examples of developing and improving toners that satisfy both the signal level and wave form specifications described in ANSI X9.27, and must be solved.

In addition, the following patent documents can be mentioned as this kind of well-known literature.
JP 07-271090 A JP-A-11-202544 JP 2000-03073 A Japanese Patent Laid-Open No. 05-281778 Japanese Patent Application Laid-Open No. 07-093477

  The problem to be solved by the present invention is to optimize the type and amount of the magnetic material as the composition and carbon black as the colorant, and to make the relationship between the toner concentration and the charge amount and the bias electric field strength during development appropriate. Thus, an object of the present invention is to provide an electrophotographic apparatus that does not cause toner filming and satisfies both the signal level and wave form specifications described in ANSI X9.27, a developing apparatus used therefor, and a developing toner.

In order to achieve the above object, the first means of the present invention is that a two-component developer consisting of a mixture of developing toner and carrier is loaded inside, and a developing roll is disposed opposite to the photosensitive member with a predetermined gap. Equipped with a developing device,
In the electrophotographic apparatus that conveys the developer to the photosensitive member facing portion, applies a bias voltage to the developing roll, and visualizes the electrostatic latent image formed on the photosensitive member with the developing toner.
The developing toner includes at least magnetic powder and carbon black, the magnetic powder includes surface-treated magnetite having a content of more than 20% by weight, and the carbon black has a content of not less than 0% by weight and less than 2% by weight. Have
Charge amount Q of the developing toner measured using a suction / blow type powder charge amount measuring device under the conditions of a suction pressure of −3.5 to 4.0 KPa and a blow pressure of 7.0 KPa after 3 minutes. The ratio Q / T between the absolute value μC / g of the toner charge amount and the developing toner concentration T (%) in the two-component developer exceeds 1.28,
The electric field intensity E by the bias voltage applied to the developing roll is set to 8.0 (kV / cm) or more.

  According to a second means of the present invention, in the first means, the magnetite is needle-shaped and surface-treated with a silane coupling agent.

  A third means of the present invention is characterized in that, in the second means, the weight average particle size of the developing toner is regulated in the range of 4 to 10 μm.

  According to a fourth means of the present invention, in the third means, the proportion of particles having a weight average particle diameter of less than 4 μm contained in the developing toner is regulated to 25% by number or less of the total number of toner particles. It is what.

  According to a fifth means of the present invention, in the first means, the carbon black content is 0% by weight, the developing toner concentration T is 5.0 to 6.9, and the Q / T is 1.28. In addition, the electric field intensity E is regulated to a range of 8.0 to 9.0 (kV / cm).

  According to a sixth means of the present invention, in the first to fifth means, the developing device includes a plurality of developing rolls, at least one of which rotates in the forward direction with respect to the traveling direction of the photoconductor. And at least one other is a reverse developing roll that rotates in the reverse direction with respect to the traveling direction of the photosensitive member, and the forward developing roll and the reverse developing roll have a predetermined gap. Are arranged opposite to each other.

  The present invention is configured as described above, and the electrophotographic developing toner imparts an appropriate amount of charge to a toner composed of an appropriate material and material ratio and is developed with an appropriate bias electric field strength. Therefore, filming does not occur and both the signal level and wave form specification described in ANSI X9.27 can be satisfied.

  Hereinafter, embodiments of the present invention will be described in detail. First, a schematic configuration of an electrophotographic apparatus according to the present invention will be described with reference to FIG.

  The surface of the drum-shaped photoconductor 1 is uniformly charged by the charging device 2, and an electrostatic latent image is formed on the photoconductor 1 by the optical device 8. The electrostatic latent image is visualized by the developing device 3 to form a toner image on the photoreceptor 1.

  The developing device 3 includes a reverse developing roll 11 that rotates in the reverse direction with respect to the moving direction (rotating direction) of the photosensitive member 1 and a rotating direction in the forward direction with respect to the moving direction (rotating direction) of the photosensitive member 1. It has a center feed type structure in which the directional developing roll 12 is disposed facing the direction developing roll 12. In addition, the developing device 3 includes a two-component developer 13 including a toner 9 and a carrier 10, which will be described later, a stirring member 14, a regulating member 15, and the like. Although FIG. 1 shows a case where one reverse developing roll 11 and one forward developing roll 12 are provided, the number of rolls installed can be increased as necessary.

  The toner image on the photosensitive member 1 is transferred onto the recording medium 4 by the transfer device 5, and the toner remaining on the photosensitive member 1 is removed cleanly by the cleaning device 7 equipped with a cleaning blade. It has a series of recording processes in which the transferred toner image is fixed by the fixing device 6 to obtain a recorded image.

The developing device of the present invention contains at least magnetic powder as a constituent, the carbon contained as a colorant has a content (rate) of less than 2% by weight, and the magnetic powder contains 20% of surface-treated magnetite. The developing device is arranged with a developing roll having a magnet roll inside facing the photoconductor while maintaining a predetermined gap, and the toner is a toner concentration that is a mixing ratio with the carrier Is conveyed to the photosensitive member facing portion in a developer state controlled within a predetermined range, and a bias voltage electric field is applied to the developing roll to visualize the toner image.
Carrier mixing ratio [toner concentration = (toner amount) / {(toner amount) + (carrier amount)} × 100] T (%) and toner charge amount Q (= absolute toner charge amount) The value μC / g) and the electric field intensity E (kV / cm) of the bias voltage applied to the developing roll satisfy the following expressions (1) and (2). .

Q / T> 1.28 (1)
E ≧ 8.0 (kV / cm) (2)
In the two-component development method in which the toner and carrier are mixed by the magnetic roll method, the toner is given a triboelectric charge necessary for development from the carrier during mixing and stirring with the carrier. Since the toner is frictionally charged on the carrier surface, a sufficient surface area is required for each toner. However, when the toner is in an overcrowded state on the carrier surface, the toner is not sufficiently frictionally charged, and so-called fogging is caused. It becomes. On the other hand, when the amount of toner is small, the charge amount is increased more than necessary and the toner density is low, so that a sufficient developing ability cannot be obtained. Therefore, it is important to maintain the image quality by controlling the toner density and the toner charge amount to appropriate values and applying a bias voltage electric field necessary for development.

  However, when the magnetic toner is used in the two-component developing method using the magnetic roll method, the toner has magnetic characteristics, so that the binding force on the carrier is stronger and the developing ability is lower than when the non-magnetic toner is used. On the other hand, (1) the toner density condition is set higher than that of the non-magnetic toner, and (2) the bias voltage electric field at the time of development is set higher to compensate for it by creating a low charge and excessive development state. However, it has been found that the toner charge distribution is uneven, and toner filming on the surface of the photoreceptor due to the toner having the opposite polarity is generated.

  In the present invention, focusing on the fact that it occurs at the time of low charging, unlike the filming by the highly charged particles by the external additive such as silica described in the conventional example, first, the toner is excessive and the low charge amount side. Since the amount of charge was shifted, the toner of reverse polarity was reduced to improve filming by increasing the amount of charge.

  However, the toner that is the subject of the present invention is a toner for MICR characters, and it is required that the filming is improved and the MICR specification is also satisfied. Therefore, of course, there is no filming, but at the same time, it is also necessary to satisfy general image quality items such as image density and fogging, and MICR specifications such as signal level and wave form as MICR characters. Attention was paid to the improvement of the development conditions.

  Each font of MICR characters has a line width standard and is required to be within the standard on the wave form. In the present invention, it has been found that when the charge amount is low with respect to the toner concentration, there is a tendency that many abnormalities of the wave form tend to occur. Therefore, the charge amount (absolute value of charge amount: Q) and the toner concentration (Tc) ratio : By setting Q / Tc to a value exceeding 1.28, the wave form abnormality was reduced, and it was possible to achieve a level that would not hinder banking operations. When the Q / Tc is 1.28 or less, the occurrence of abnormality in a wave form having a narrow line width increases.

  The main reason for lowering the charge amount of the toner is due to the phenomenon of lowering the resistance of the toner by the magnetite magnetic powder and the colorant carbon black. In the present invention, the addition amount and the processing of the magnetite magnetic material surface are changed. As a result, the resistance of the toner can be increased, and the charge amount can be increased. The smaller the magnetite magnetic substance content, the more uniform solid image quality can be reproduced. However, in order to ensure the MICR signal level within the standard, the content exceeds 20% by weight, particularly preferably about 25% by weight is stable. It is necessary to secure the MICR signal level. The upper limit value of the magnetite magnetic substance content is suitably about 30% by weight because the shape is needle-like and the magnetizing force is strong, and when the content is high, the image density decreases.

  The wave form abnormality of MICR characters is a phenomenon that occurs when the line width of MICR characters is narrower than the standard, and occurs when the content of magnetite magnetic material and carbon black is low compared to other toner materials. Tend to increase. This is an edge effect action of the fine line portion, and is the same as the thinning phenomenon of the fine line portion by the low-resistance toner and developer.

  In the present invention, it is necessary to make the MICR signal level within the specification, and the magnetite content cannot be reduced to 20% by weight or less. Therefore, the surface of the magnetite magnetic body is not reduced without reducing the content. By treating the coupling agent, the dispersion performance is improved, and by increasing the toner resistance, the edge effect can be applied to the fine line portion, and the wave form abnormality of MICR characters is reduced, and there is no problem in banking operations. done.

  Similarly, as the carbon black content increases, the toner resistance decreases, the edge effect becomes insufficient, and the line width of the thin line portion becomes narrow. Conversely, reducing the carbon black content increases the toner resistance, so the line width increases and the charge amount tends to increase. In the present invention, by setting the carbon black content to less than 2% by weight, preferably 0% by weight, it was possible to reduce the MICR character wave form abnormality to a level that does not hinder normal banking operations.

  First, it is important to improve the filming so that the MICR specification is not satisfied at the same time, but it is important to improve the image quality and the MICR specification as described above. Satisfied by controlling the amount of charge by realizing Q / Tc> 1.28 in combination with a carrier that has been surface-treated as a toner composition> 20% by weight, carbon black <2% by weight, and a carrier as a developer I was able to. As a result, in the present invention, since the charge amount could be managed, the toner of reverse polarity could be reduced and the filimming phenomenon could be eliminated.

  As described above, the MICR character wave form abnormality is caused by the narrowing of the character line width, but this increases the toner adhesion amount by changing the bias voltage condition applied to the developing roll during development, thereby increasing the line width. With this, it is possible to make the condition that the wave form abnormality does not occur. In the present invention, this can be achieved by applying an electric field of 8.0 kV / cm or more, and at the same time, the MICR signal level can be increased, contributing to an increase in the tolerance. In consideration of the relationship between the bias voltage and the photoreceptor potential, the upper limit value of the electric field strength due to the bias voltage applied to the developing roll is suitably 14 kV / cm, preferably 8 kV / cm in terms of the fog tolerance and the high-pressure life of the photoreceptor. It is in the range of ˜12 kV / cm.

  The toner charge amount is measured by various methods. In the present invention, the toner charge amount is measured using a suction / blow-type powder charge amount measuring device. TB-203 (manufactured by Kyocera Chemical Co., Ltd.) was used as a measuring device, and the charge amount of the toner was measured. The developer sample was taken from the magnetic roll of the developing device, weighed about 0.2 g on a 400 mesh wire net in the Faraday cage, measuring time 3.0 seconds, suction pressure −3.5 to 4.0 KPa, blow pressure. The value measured at 7.0 KPa after 3 minutes was used.

  The signal level and wave form characteristics of special characters for MICR were measured using MICR Qualifier GTX manufactured by RDM (located in Ontario, Canada). The MICR Qualifier GTX is a MICR character dedicated tool designed and manufactured based on ANSI X9.27, and is the most commonly used device as a MICR tool currently on the market.

  The above device is equipped with a write head (magnetization of toner characters) and a read head (reading magnetized toner characters), and printed matter on which MICR characters are printed is transported between both heads one by one. The magnetic properties are read. An analysis result is made for each MICR character written at a predetermined position, so that the signal level and the wave form can be determined whether or not the ANSI X9.27 specification is satisfied.

  There are two types of MICR character specifications, E13-B and CMC-7, which are used all over the world. In the case of Japan, E13-B is used in the US, Canada, UK, Australia and Asian countries. The toner examined in the present invention was also printed using character fonts (number fonts 0 to 9 and four special fonts, a total of 14 characters) conforming to the E13-B specification. The basic specification of the signal level of E13-B character font is the USA specification with the relative value stipulated in ANSI X9.27: 50-200%, but 80-200% in Canada and other countries In many cases, this specification is the strictest specification, so in the present invention, OK / NG determination was performed at a signal level of 80 to 200%.

  Waveform specifications are determined for each character with respect to the distance between peaks and troughs of signals generated when scanning character fonts (corresponding to the line width in the font), and it is determined according to ANSI X9.27 specifications. It is to check whether it is within the range.

  In the case of MICR Qualifier GTX made by RDM, the distance between the peaks and valleys of each signal level is calculated in detail, and the distance is larger or smaller than the specification, and misrecognition may occur depending on the MICR reader used in banking etc. If the distance is so large that there is a possibility of being displayed, “Visual Check (VC)” is indicated so that the analyst knows that there is a problem with the MICR characters.

  The polarity of the toner studied in the present invention is negative and will be described below with an absolute value, but the polarity is not limited to negative.

  The particle size of the toner is measured by various methods. In the present invention, the particle size of the toner is measured using a Coulter counter. The aperture was 100 μm, and the number distribution and volume distribution were measured using a Coulter counter TA-II type (Coulter). At this time, 50000 measurement samples were prepared by adding the measurement toner to the electrolytic solution to which the surfactant was added and dispersing the sample for 1 minute with an ultrasonic disperser.

  The weight average particle size of the toner is preferably 4 to 10 μm, and the proportion of particles less than 4 μm contained in the toner is preferably suppressed to 25% by number or less of the total number of toner particles. Further, by suppressing the ratio of less than 4 μm to 15% or less of the total number of toner particles, the durability is further improved.

  In a two-component developer, a carrier and several percent of toner are mixed, and the toner is charged by friction between the toner and the carrier. . Further, the fine particle toner having a particle size of less than 4 μm requires a large amount of heat energy as compared with a toner having a large particle diameter at the time of fixing (fogging) to a non-image portion and fixing, which is disadvantageous for low-temperature fixability. Accordingly, the ratio of less than 4 μm in the toner is preferably 25% by number or less of the total number of toner particles, preferably 15% by number or less of the total number of toner particles, and more preferably 10% by number or less.

  Specific examples of the fixing resin used in the toner of the present invention include the following resins in addition to the polyester resin described above.

  Styrene and its substituted homopolymers such as polystyrene, poly-p-chlorostyrene, polyvinyltoluene; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene -Acrylic acid ester copolymer, Styrene-methacrylic acid ester copolymer, Styrene-α-Chloromethyl methacrylate copolymer, Styrene-acrylonitrile copolymer, Styrene-vinyl methyl ether copolymer, Styrene-vinyl ethyl ether Styrene copolymers such as copolymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-acrylonitrile-indene copolymers; and polyvinyl chloride, phenol Resin, natural modified phenolic resin, natural resin modified male Examples thereof include inic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, chroman-indene resin, and petroleum resin.

  Of these, polyester resins or styrene copolymers are preferred. Further, a low hygroscopic resin obtained by graft copolymerizing styrene-acryl with the above-described polyester resin can also be used.

  The styrene polymer or styrene copolymer may be cross-linked or a mixed resin. In order to fix at low temperature and prevent high temperature offset, for example, in the case of styrene to (meth) acrylic resin, it is composed of a high molecular weight polymer and a low molecular weight polymer, the former being a toner offset resistance and the latter being a fixing strength. It is effective for securing.

  Further, in order to improve the compatibility between the fixing resin and the wax, the fixing resin may be prepared by a co-polymerization method in which the wax coexists in all or part of the synthesis process.

  In the method of making a fixing resin by a co-polymerization method in the presence of a wax, the vinyl copolymer includes, as its structural unit, a styrene monomer and / or a (meth) acrylate monomer, Other vinyl monomers can be included.

  By performing the co-polymerization in which the wax is present in the present invention in all or part of the synthesis, a vinyl copolymer in which the wax is uniformly dispersed can be obtained as at least a component thereof. The vinyl copolymer is mainly a monomer having two or more polymerizable double bonds, such as divinylbenzene, divinylnaphthalene, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, divinylaniline, divinyl It may be partially crosslinked with a crosslinking agent such as vinyl ether, divinyl sulfide, divinyl sulfone and the like.

  Specific examples of the styrene monomer as the structural unit of the vinyl polymer include orthomethyl styrene, metamethyl styrene, alphamethyl styrene, 2,4-dimethyl styrene and the like in addition to styrene.

  Specific examples of the acrylate ester or methacrylate ester monomer as the structural unit of the vinyl polymer include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, and acrylic acid n. -Octyl, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, methacryl In addition to acrylic acid or methacrylic acid alkyl esters such as stearyl acid, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, Examples include diethylaminoethyl tacrylate, 2-hydroxyethyl methacrylate, glycidyl methacrylate, bisglycidyl methacrylate, polyethylene glycol dimethacrylate, methacryloxyethyl phosphate, etc., ethyl acrylate, propyl acrylate, butyl acrylate, methacrylic acid Methyl, ethyl methacrylate, propyl methacrylate, butyl methacrylate and the like are particularly preferably used.

  Other vinyl monomers as a constituent unit of the vinyl polymer include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and α- or β-alkyl derivatives thereof, fumaric acid, maleic acid. Examples thereof include unsaturated dicarboxylic acids such as acids, citraconic acid and itaconic acid and monoester derivatives and diester derivatives thereof, succinic acid monoacryloyloxyethyl ester, succinic acid monomethacryloyloxyethyl ester, acrylonitrile, methacrylonitrile, acrylamide, etc. it can.

  In the toner of the present invention, the charge amount of the toner can be controlled to a desired value by blending (internal addition) or mixing (external addition) a charge control agent with the toner particles.

  Examples of the positive charge control agent for toner include modified products of nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonic acid, tetrabutylammonium tetrafluoroborate, and the like. Onium salts such as phosphonium salts and their lake pigments, triphenylmethane dyes and their lake pigments, metal salts of higher fatty acids; diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate , Diorganotin borates such as dioctyl tin borate and dicyclohexyl tin borate; these can be used alone or in combination of two or more. Among these, charge control agents such as nigrosine, quaternary ammonium salts, and triphenylmethane dye are particularly preferably used.

  As the negative charge control agent of the toner, an organic metal complex and a chelate compound are effective, and there are a monoazo metal complex, an acetylacetone metal complex, an aromatic hydroxycarboxylic acid, and an aromatic dicarboxylic acid type metal complex. Others include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives such as bisphenol.

  When these charge control agents are internally added to the toner, it is preferable to add 0.1 to 10% by weight based on the fixing resin.

  In the toner of the present invention, it is preferable to add silica fine powder or the like externally in order to improve developability, fluidity, charging stability and durability.

The silica fine powder or the like used in the present invention preferably has a specific surface area of 30 m ² / g or more by nitrogen adsorption as measured by the BET method, and is externally added in the range of 0.01 to 5% by weight with respect to the toner. Further, if necessary, the silica fine powder is hydrophobized with various treating agents such as organosilicon compounds, or various treating agents, or the chargeability is controlled. Since fluidity, durability, storage stability, and the like vary depending on the type of the treatment agent and the particle size of the silica fine powder, it is selected according to the purpose.

  Further, for example, a fluorine resin powder such as polytetrafluoroethylene, a lubricant powder such as a zinc stearate powder and a polyvinylidene fluoride powder, among which polyvinylidene fluoride is preferable.

  Alternatively, a polishing agent such as cerium oxide powder, silicon carbide powder, and strontium titanate powder, among which strontium titanate is preferable. Alternatively, fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder, and particularly hydrophobic ones are preferable. A small amount of an anti-aggregation agent, or a conductivity imparting agent such as carbon black powder, zinc oxide powder, antimony oxide powder or tin oxide powder, and white and black fine particles having opposite polarity can also be used in small amounts.

  In the present invention, magnetite is described as the magnetic material of the toner, but the present invention is not limited to this. In addition to magnetite, the magnetic material contained in the toner includes hematite, ferritic iron oxide, iron, cobalt, nickel and other metals such as aluminium, cobalt, copper, lead, magnesium, tin, zinc, antimony. , Alloys with metals such as calcium, manganese, selenium, titanium, tungsten, vanadium and mixtures thereof.

  In the present invention, the magnetite surface is treated with an epoxy silane coupling to increase the dispersibility, but the present invention is not limited to this. Other examples of the silane coupling treatment include a terminal double bond silane coupling treatment, a methyl group silane coupling treatment, and an amino group silane coupling treatment. Other surface treatment methods include titanate coupling agent treatment and aluminate coupling agent treatment.

  These magnetic materials preferably have an average particle diameter of 2 μm or less, preferably about 0.1 to 0.5 μm. The amount contained in the toner is preferably 0.1 to 200% by weight based on the fixing resin. In the present invention, it is particularly preferable to contain more than 20% by weight. The particle shape may take the form of an octahedron or a needle, but in the present invention, it is necessary to satisfy the MICR specification, so a needle-like magnetic material with strong magnetic properties and particularly good saturation magnetization properties is used. Is preferred.

  Since the toner of the present invention assumes black toner due to the characteristics of MICR toner, carbon black is used as a colorant. However, the present invention is not limited to this, and a combination of other colorants and carbon black, or carbon Other colorants other than black may be used. Therefore, other examples of the toner colorant include aniline black, acetylene black, naphthol yellow, Hansa yellow, rhodamine lake, alizarin lake, Bengala, phthalocyanine blue, and indanthrene blue as pigments. These are used in an amount necessary and sufficient to maintain the optical density of the fixed image, preferably 0.2 to 15% by weight based on the resin, and in the present invention, an amount of less than 2% by weight is particularly preferred.

  Further, a dye is used for the same purpose. For example, there are azo dyes, anthraquinone dyes, xanthene dyes, and methine dyes, and these are added in an amount of 0.2 to 15% by weight based on the resin.

  In order to produce the electrophotographic toner of the present invention, carnauba wax alone or a mixture ratio of carnauba wax and rice wax is prepared in the range of 1:10 to 10: 1, and a fixing resin, a charge control agent, A pigment or dye as a colorant, magnetic powder, and if necessary, an additive and a fixing resin in which wax is uniformly dispersed are combined and sufficiently mixed by a mixer such as a Henschel mixer or a super mixer. Thereafter, the mixture is melt-kneaded using a hot-melt kneader such as a hot roll, a kneader, or an extruder to sufficiently mix the materials, and then cooled and solidified to be finely pulverized and classified to obtain a toner.

  The pulverization method at this time includes a jet mill method in which toner is included in a high-speed air stream, the toner collides with an impact plate and pulverizes with the energy, an inter-particle collision method in which toner particles collide with each other in the air flow, and further at high speed. A mechanical pulverization method in which toner is supplied and pulverized between a rotated rotor and a narrow gap can be used.

  In the jet mill method and the interparticle method, the toner is pulverized by collision energy, so the shape of the pulverized toner particles is relatively sharp, but when using the mechanical pulverization method, the toner is pulverized while being rubbed between the gaps. In addition, the toner surface is easily spheroidized by the frictional heat generated at this time. In particular, in a toner with a target of reducing the particle size and fixing at a low temperature, the phenomenon that the toner melts and adheres to the collision plate at the time of pulverization as pointed out in JP-A-7-287413 does not occur. And a decrease in toner fluidity, which is a unique phenomenon when a low molecular weight wax is contained, can also be prevented. Therefore, it is preferable to use a mechanical grinding method for fine grinding.

  It can also be obtained by a so-called polymerization method in which a monomer is polymerized in the presence of a colorant, a charge control agent, a wax or the like when polymerized. Further, it can be obtained by a microencapsulation method.

  The produced toner can be further adhered and mixed with a desired additive as required by a mixer such as a Henschel mixer to obtain a toner to which the additive is externally added.

  As the carrier used in the present invention, known ones can be used. For example, a resin carrier in which iron powder, ferrite, magnetite, glass beads, and magnetic fine particles are dispersed in a binder resin can be used, and the carrier surface can be used. A coating layer can be provided. The charging characteristics, electrical resistance value, etc. of the carrier can be controlled by the binder resin, the chargeable fine particles and the coating layer.

  Examples of the binder resin used for the resin carrier include thermoplastic resins such as vinyl resins, polyester resins, polyamide resins, and polyolefin resins, and thermosetting resins such as phenol resins.

  Magnetic fine particles include spinel ferrite such as magnetite and gamma iron oxide, and magnetoplumbite type such as spinel ferrite and barium ferrite containing one or more metals other than iron (Mn, Ni, Zn, Mg, Cu, etc.) Ferrite, iron or alloy particles having an oxide layer on the surface can be used. The shape may be granular, spherical, or needle-shaped. In particular, when high magnetization is required, it is preferable to use ferromagnetic fine particles such as iron.

  In view of chemical stability, it is preferable to use magnetoplumbite type ferrite such as spinel ferrite and barium ferrite containing magnetite and gamma iron oxide. By selecting the type and content of the ferromagnetic fine particles, a resin carrier having a desired magnetization can be obtained. At this time, the magnetic property of the carrier is preferably 30 to 150 emu / g as the magnetization strength at 1000 oersted.

  Such a resin carrier is manufactured by spraying a melt-kneaded product of magnetic fine particles and an insulating binder resin with a spray dryer, or reacting and curing a monomer or prepolymer in an aqueous medium in the presence of the magnetic fine particles. A resin carrier in which magnetic fine particles are dispersed in a condensed binder can be produced.

  Chargeability can be controlled by fixing positively or negatively charged fine particles or conductive fine particles on the surface of the carrier or coating a resin.

  As the surface coating material, a silicone resin, an acrylic resin, an epoxy resin, a fluorine resin, or the like is used. Further, coating can be performed including positive or negatively charged fine particles or conductive fine particles.

  The mixing ratio of the toner of the present invention to the carrier is preferably 2 to 10% by weight as the toner concentration.

  Using the electrophotographic toner of the present invention, the latent electrostatic image formed on the electrostatic charge holding member is visualized, the visualized toner image is transferred onto a recording medium, and remains on the electrostatic charge holding member. In the electrostatic image recording process that cleans the toner image and fixes the toner image transferred onto the recording medium to obtain a recorded image, especially with regard to MICR character specifications and image quality, reading in a magnetic authentication system in banking business etc. In order to ensure the reliability of the performance, the relationship between the specifications of the magnetic powder, the change in the carbon amount, the toner concentration and the charge amount was optimized together with the developing bias electric field.

  Therefore, the image quality including the image density and the MICR signal level are controlled within the specifications, and the MICR wave form that is out of the standard is as low as possible without causing any trouble in performing normal banking operations from the viewpoint of improving reliability. Thus, an electrophotographic toner and an electrophotographic production apparatus without toner filming can be realized.

  The developing device used in the present invention is selected depending on the moving speed of the electrostatic charge holding member. However, in the case of a high-speed printer or the like in which the moving speed of the electrostatic charge holding member is fast, the development of one developing magnetic roll is not always sufficient. A plurality of development magnetic rolls are used, and development is performed by increasing the development area and extending the development time.

  When multiple development magnetic rolls are used, a higher development capability is obtained compared to a single development roll system, which not only improves the response to high-area image printing and print quality, The toner content can be reduced, and the rotation speed of the developing roll can be reduced, and the carrier spent by the toner due to the scattering of the toner and the reduction of the load on the developer can be prevented and the life of the developer can be extended. Furthermore, it becomes possible.

  Furthermore, in a developing system using a plurality of developing rolls, unidirectional development in which the developing roll rotates in the forward direction and the forward direction of the electrostatic charge holding member has a high developing ability, but the background fogging easily occurs and Chips and magnetic brush marks are likely to appear.

  On the other hand, unidirectional development in which the developing roll rotates in the direction opposite to the traveling direction of the electrostatic charge holding member has stable background because there is little background fogging and the magnetic brush has little blurring, although there is a chip at the rear end of the image area. Is obtained. However, since the reverse direction development has a small effective toner amount in contact with the electrostatic charge holding member, the development ability may be small. On the other hand, since the center feed method has both the above-described forward and reverse developing rolls, the disadvantages of both the above-described developing methods can be avoided.

  Such a developing system and the charge amount of the electrophotographic toner of the present invention (absolute value of charge amount: Q) to toner density (Tc) ratio (Q / Tc), and bias voltage applied to the developing roll during development By controlling the electric field, it is possible to stably supply toner and an image forming apparatus that have excellent image quality and satisfy the MICR specifications.

  Hereinafter, examples of the present invention are described below. However, the present invention is not limited to this.

(Composition Example 1)
(A) Polyester resin [weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)] 28.7% by weight
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mg KOH / g)] 43.0 wt%
(C) Ammonium salt of trivalent iron complex salt (charge control agent) 0.8% by weight
(D) Magnetic powder (epoxy silane coupling agent surface-treated magnetite: needle shape, particle size 0.6 μm, BTE 14.5 (m ² / g), Hc 27.7 (kA / m), σr 30.7 (Am ² / kg), σs 87.0 (Am ² / kg) 25.0% by weight
(E) Carnauba wax (carnauba wax: acid value is 10 mg KOH / g or less, melting point is 80 to 86 ° C., penetration at 25 ° C. is 1 or less) 2.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a biaxial kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.7 μm. Obtained.

  Further, two kinds of hydrophobic silica A (trade name: Aerosil R972, manufactured by Nippon Aerosil Co., Ltd.) 0.5% by weight and hydrophobic silica B (trade name: HDK H3004, manufactured by Clariant Japan Co., Ltd.) 0.3% by weight are added to the particles. Then, the mixture was stirred with a Henschel mixer to attach hydrophobic silica to the surface of the particles to obtain a toner for composition example 1. At this time, the average particle diameter of the toner was 8.7 μm, and the toner of 4 μm or less was 7.0% by number.

  The above toner was mixed with a magnetite carrier having an average particle diameter of 65 μm with the surface coating agent ratio and sintering temperature changed to adjust the charge amount so that the mixing ratio (toner concentration) was 5.0 to 6.9% by weight, As shown in FIG. 2, five types of development toners (Sample Nos. 1 to 5) having different toner concentrations and toner charge amounts were prepared.

  As shown in FIG. 1, the developing device has a center-feed type developing device in which the developing magnetic roll has a developing magnetic roll that rotates in the reverse direction and a developing magnetic roll that rotates in the forward and reverse directions of the electrostatic charge holding member. The development gap (distance between the OPC photoreceptor and the developing roll sleeve) is 0.5 mm, and the doctor gap [distance between the doctor plate (developer layer thickness regulating plate) and the developing roll sleeve] is 0.3 mm. An image was produced by reversal development.

  The printing conditions were the following three conditions using an electrophotographic laser beam printer with a printing speed of 92 sheets per minute (printing process speed 41.3 cm / sec) using OPC as a photoreceptor.

That is, the residual potential of the laser exposure part is -50V, the combination of the charging potential of the OPC photoreceptor and the development bias voltage is the development part contrast potential 150V,
(A) Charging potential -500 V, development bias voltage -350 V (electric field strength 7.0 kV / cm),
(B) Charging potential -550 V, development bias voltage -400 V (electric field strength 8.0 kV / cm),
(C) Charging potential -600 V, development bias voltage -450 V (electric field strength 9.0 kV / cm)
The images were created under the three conditions, and each sample was printed for 2000 pages, and then sampling for evaluation was performed under each condition.

  The evaluation results (MICR signal, VC occurrence rate, ID, filming, MICR evaluation, ID evaluation, comprehensive evaluation) of the printing test are shown in the Composition Example 1 column of FIG. In the evaluation column, “◯” indicates good, “Δ” indicates good, but there is anxiety in reliability, and “×” indicates that evaluated as poor.

  As is apparent from the evaluation results of FIG. Samples Nos. 1 to 4 except 5 have no filming, and a comprehensive evaluation including MICR signal and ID is good under the condition of developing electric field strength (E) ≧ 8.0 kV.

  Sample No. No. 5 has a lower charge amount (Q) than the toner concentration (Tc) and does not satisfy Q / Tc> 1.28. Therefore, the phenomenon that the line width standard of the MICR wave form is out of specification [this RDM's MICR Qualifier GTX used in the evaluation shows “Visual Check (abbreviated as VC)”. This is due to the relatively low charge. As a result, the repulsive force due to the charge is weakened. As a result, the distance between the carrier and the carrier in the developer becomes close, the developer ear becomes hard, and the scraping effect is improved. This phenomenon occurs as a result of the increase.

  Among sample Nos. 1 to 4, the carbon black content is 0% by weight, the toner concentration T is 5.0 to 6.9, and the Q / T is 1.28 to 2.61. In addition, when the electric field intensity E is regulated within the range of 8.0 to 9.0 (kV / cm), filming does not occur, and the MICR evaluation, ID evaluation, and comprehensive evaluation are all good.

(Composition Example 2)
(A) Polyester resin [weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)] 27.9 wt%
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mgKOH / g)] 41.8% by weight
(C) Carbon black 2.0% by weight
(D) Ammonium salt of trivalent iron complex salt (charge control agent) 0.8% by weight
(E) a magnetic powder (surface treatment-free magnetite: acicular shape, particle size ^{0.6μm, BTE16.0 (m 2 /g),Hc28.2(kA/m),σr32.0(Am 2} / kg), σs84.7 (Am ² / kg) 25.0% by weight
(F) Carnauba wax (carnauba wax: acid value of 10 mgKOH / g or less, melting point of 80 to 86 ° C., penetration at 25 ° C. of 1 or less) 2.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a biaxial kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.7 μm. Obtained. The particles were subjected to silica external addition in the same process as in Composition 1. The average particle diameter of the toner was 8.7 μm, and the toner having a particle size of 4 μm or less was 8.0% by number.

  The above toner was mixed with a carrier whose charge amount was adjusted by changing the surface coating agent ratio and sintering temperature so that the mixing ratio (toner concentration) was 6.0 to 8.0% by weight. The developed toners Nos. 6 and 7 were prepared, and the printing test was conducted under the same conditions as in Composition Example 1. The results are shown in the Composition Example 2 column of FIG.

  As is apparent from this result, sample No. Nos. 6 and 7 have filming and VC is often observed. Differences from Composition Example 1 are two points: (1) 2% by weight of carbon black is added, and (2) no surface treatment of magnetite is applied. That is, the filming phenomenon occurs when 2% by weight of carbon black is added.

  Since it does not occur in Composition Example 1 with 0% by weight of carbon black, it can be seen that the addition of carbon black is the cause of filming. In addition, since the magnetite used in composition 2 has no surface treatment, it has poor dispersibility as compared with composition example 1, resulting in a toner having a lower resistance, and is less likely to be charged, empty, and Q / Tc> 1. 28 cannot be satisfied, and VC increases.

(Composition Example 3)
(A) Polyester resin [weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)] 28.4% by weight
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mg KOH / g)] 42.3 wt%
(C) 1.0% by weight of carbon black
(D) Ammonium salt of trivalent iron complex salt (charge control agent) 0.8% by weight
(E) a magnetic powder (surface treatment-free magnetite: acicular shape, particle size ^{0.6μm, BTE16.0 (m 2 /g),Hc28.2(kA/m),σr32.0(Am 2} / kg), σs84.7 (Am ² / kg) 25.0% by weight
(F) Carnauba wax (carnauba wax: acid value of 10 mgKOH / g or less, melting point of 80 to 86 ° C., penetration at 25 ° C. of 1 or less) 2.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a biaxial kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.7 μm. Obtained. The particles were subjected to silica external addition in the same process as in Composition 1. The average particle diameter of the toner was 8.7 μm, and the toner having a particle size of 4 μm or less was 8.0% by number.

  The above toner was mixed with a carrier whose charge amount was adjusted by changing the surface coating agent ratio and the sintering temperature so that the mixing ratio (toner concentration) was 5.0 to 7.0% by weight. 8 and 9 developing toners were prepared, and the results of a printing test under the same conditions as in Composition Example 1 are shown in the Composition Example 3 column of FIG.

  As is apparent from this result, sample No. In Nos. 8 and 9, filming did not occur, VC generation was small, and almost the same results as in Composition Example 1 were obtained. The difference from Composition Example 2 is that “the amount of carbon black added is less than 2 wt.” As in Composition Example 1.

  Composition Example 4 As will be apparent from the following examples, the filming phenomenon occurs when 2% by weight of carbon black is added. Since it is not generated in Composition Example 1 and Composition Example 3 of 1% by weight of carbon black, it can be seen that the addition of 2% by weight of carbon black is the cause of filming.

(Composition Example 4)
(A) Polyester resin [weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)] 27.9 wt%
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mg KOH / g 41.8 wt%
(C) Carbon black 2.0% by weight
(D) Ammonium salt of trivalent iron complex salt (charge control agent) 0.8% by weight
(E) a magnetic powder (surface treatment-free magnetite: acicular shape, particle size ^{0.6μm, BTE16.0 (m 2 /g),Hc28.2(kA/m),σr32.0(Am 2} / kg), σs84.7 (Am ² / kg) 25.0% by weight
(F) Carnauba wax (carnauba wax: acid value is 10 mg KOH / g or less, melting point is 80 to 86 ° C., penetration at 25 ° C. is 1 or less) 1.0% by weight
(G) Rice wax (rice bran wax: acid value is 13 mg KOH / g or less, melting point is 78-82 ° C., penetration at 25 ° C. is 5) 1.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a twin screw kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.9 μm. Obtained. The particles were subjected to silica external addition in the same process as in Composition 1. The average particle size of the toner was 8.9 μm, and the toner having a particle size of 4 μm or less was 8.7% by number.

  In the same manner as the carrier used in Composition Example 2 above, the coating material ratio and the sintering temperature were changed, and the charge ratio was adjusted and the mixing ratio (toner concentration) was adjusted to 6.0 to 7.0% by weight. Sample No. 10 to 12 developing toners were prepared, and the results of performing a printing test under the same printing conditions as in Composition Example 1 are shown in the Composition Example 4 column of FIG.

  Sample No. 2 is the same as Composition Example 2 except that the added species of wax is different. As shown in FIG. 10, the same results as in Composition Example 2 were obtained. Sample No. Although 11 and 12 satisfy Q / Tc> 1.28, the amount of VC generated is large. The reason why the MICR wave foam deviates from the standard is due to insufficient tolerance due to lack of dispersibility due to the absence of magnetite surface treatment and the fact that the wax contains not only carnauba wax but also rice wax. This occurs because the toner adhesion characteristic is lower than that in FIG.

(Composition Example 5)
(A) Polyester resin [weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)] 24.7% by weight
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mg KOH / g)] 50.0% by weight
(C) Carbon black 2.0% by weight
(D) Ammonium salt of trivalent iron complex salt (charge control agent) 0.8% by weight
(E) magnetic powder Surface Treatment No magnetite: acicular shape, particle size ^{0.6μm, BTE16.0 (m 2 /g),Hc28.2(kA/m),σr32.0(Am 2} / kg), σs84.7 (Am ² / kg)] 20.0 wt%
(F) Carnauba wax (carnauba wax: acid value is 10 mg KOH / g or less, melting point is 80 to 86 ° C., penetration at 25 ° C. is 1 or less) 1.0% by weight
(G) Rice wax (rice bran wax: acid value is 13 mg KOH / g or less, melting point is 78-82 ° C., penetration at 25 ° C. is 5) 1.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a twin screw kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.9 μm. Obtained. The particles were subjected to silica external addition in the same process as in Composition 1. The average particle size of the toner was 8.9 μm, and the toner having a particle size of 4 μm or less was 8.7% by number.

  The above toner was mixed with a carrier whose charge amount was adjusted by changing the surface coating agent ratio and sintering temperature so that the mixing ratio (toner concentration) was 6.0 to 7.0% by weight. 13 and 14 developing toners were prepared, and the results of printing tests conducted under the same conditions as in Composition Example 1 are shown in the Composition Example 5 column of FIG.

  Sample No. As can be seen from the results shown in FIGS. 13 and 14, the toner resistance increases and the charge amount can be increased by reducing the amount of magnetic powder (from 25% by weight to 20% by weight), so that the occurrence of VC is relatively low. Is able to. However, the MICR signal level tends to decrease due to a decrease in magnetic powder, and it has not reached a level that makes a good judgment overall. In addition, since carbon black is added, filming occurs in the same manner and is NG.

(Composition Example 6)
(A) Polyester resin {weight average molecular weight Mw 5,700, number average molecular weight Mn 2,800, oxidation 8.6 (mg KOH / g)} 25.2% by weight
(B) Polyester resin [Mw 118,900, Mn 4, 900, oxidation 3.76 (mg KOH / g 51.3 wt%
(C) Ammonium salt of trivalent iron complex salt (charge control agent) 1.0% by weight
(D) the magnetic powder Surface Treatment No magnetite: acicular shape, particle size ^{0.6μm, BTE16.0 (m 2 /g),Hc28.2(kA/m),σr32.0(Am 2} / kg), σs84.7 (Am ² / kg)] 20.0 wt%
(E) Carnauba wax (carnauba wax: acid value is 10 mg KOH / g or less, melting point is 80 to 86 ° C., penetration at 25 ° C. is 1 or less) 1.0% by weight
(F) Rice wax (rice bran wax: acid value is 13 mgKOH / g or less, melting point is 78-82 ° C., penetration at 25 ° C. is 5) 1.5% by weight
The raw materials having the above composition are premixed with a super mixer, hot melt kneaded with a twin screw kneader, cooled and pulverized, and then classified with a dry air classifier to obtain particles having an average particle size of 8.8 μm. Obtained. The particles were subjected to external silica addition in the same process as in Composition 1. The average particle diameter of the toner was 8.8 μm, and the toner having a particle size of 4 μm or less was 8.6% by number.

  The above toner was mixed with the carrier used in Composition Example 5 so that the mixing ratio (toner concentration) was 5.0 to 6.0% by weight. 15 and 16 developing toners were prepared, and the results of performing a printing test under the same conditions as in Composition Example 1 are shown in the Composition Example 6 column of FIG.

  Sample No. As can be seen from the results shown in FIGS. 15 and 16, since the charge amount is increased as in Composition Example 5, the MICR signal level and VC generation rate show the same results as in Composition Example 4. It has become. However, since carbon black is not added, filming does not occur, and as described in the results of Composition Example 1, the cause of filming can be specified as carbon black.

  As described above, according to the embodiments described above, according to the present invention, an electrophotographic apparatus suitable for MICR character printing without filming can be provided.

1 is a schematic configuration diagram of an electrophotographic apparatus according to an embodiment of the present invention. FIG. 6 is a diagram illustrating printing evaluation in each toner composition example. FIG. 6 is a diagram illustrating printing evaluation in each toner composition example.

Explanation of symbols

  1: Photoconductor, 2: Charging device, 3: Developing device, 4: Recording medium, 5: Transfer device, 6: Fixing device, 7: Cleaning device, 8: Optical device, 9: Toner, 10: Carrier, 11: Reverse developing roll, 12: forward developing roll, 13: developer, 14: stirring member, 15: doctor plate.

Claims (13)

A developing device in which a two-component developer made of a mixture of developing toner and carrier is loaded therein, and a developing roll is disposed opposite to the photosensitive member with a predetermined gap,
In the electrophotographic apparatus that conveys the developer to the photosensitive member facing portion, applies a bias voltage to the developing roll, and visualizes the electrostatic latent image formed on the photosensitive member with the developing toner.
The developing toner includes at least magnetic powder and carbon black, the magnetic powder includes surface-treated magnetite having a content of more than 20% by weight, and the carbon black has a content of not less than 0% by weight and less than 2% by weight. Have
Charge amount Q of the developing toner measured using a suction / blow type powder charge amount measuring device under the conditions of a suction pressure of −3.5 to 4.0 KPa and a blow pressure of 7.0 KPa after 3 minutes. The ratio Q / T between the absolute value μC / g of the toner charge amount and the developing toner concentration T (%) in the two-component developer exceeds 1.28,
An electrophotographic apparatus, wherein an electric field intensity E due to a bias voltage applied to the developing roll is set to 8.0 (kV / cm) or more.   2. The electrophotographic apparatus according to claim 1, wherein the magnetite is needle-shaped and surface-treated with a silane coupling agent.   3. The electrophotographic apparatus according to claim 1, wherein a weight average particle diameter of the developing toner is regulated in a range of 4 to 10 [mu] m.   4. The electrophotographic apparatus according to claim 3, wherein a proportion of particles having a weight average particle diameter of less than 4 μm contained in the developing toner is regulated to 25% by number or less of the total number of toner particles. .   2. The electrophotographic apparatus according to claim 1, wherein the carbon black content is 0% by weight, the developing toner concentration T is 5.0 to 6.9, and the Q / T is 1.28 to 2.61. The electrophotographic apparatus is characterized in that the electric field intensity E is regulated within a range of 8.0 to 9.0 (kV / cm).   6. The electrophotographic apparatus according to claim 1, wherein the developing device includes a plurality of developing rolls, at least one of which rotates in a forward direction with respect to a traveling direction of the photoconductor. At least one of the forward developing rolls is a reverse developing roll that rotates in the reverse direction with respect to the traveling direction of the photoconductor, and the forward developing roll and the reverse developing roll have a predetermined gap. And an electrophotographic apparatus, wherein the electrophotographic apparatuses are arranged to face each other. A two-component developer made of a mixture of developing toner and carrier is loaded inside, and a developing roll is disposed opposite to the photosensitive member with a predetermined gap,
The developer is transported to the photosensitive member facing portion, a bias voltage is applied to the developing roll, and the electric field intensity E by the bias voltage is set to 8.0 (kV / cm) or more, and is formed on the photosensitive member. A developing device for an electrophotographic apparatus that visualizes an electrostatic latent image with the developing toner,
The developing toner includes at least magnetic powder and carbon black, the magnetic powder includes surface-treated magnetite having a content of more than 20% by weight, and the carbon black has a content of not less than 0% by weight and less than 2% by weight. Have
Charge amount Q of the developing toner measured using a suction / blow type powder charge amount measuring device under the conditions of a suction pressure of −3.5 to 4.0 KPa and a blow pressure of 7.0 KPa after 3 minutes. A developing device characterized in that a ratio Q / T between an absolute value of toner charge amount μC / g) and a developing toner concentration T (%) in the two-component developer exceeds 1.28.   8. The developing device according to claim 7, wherein a plurality of the developing rolls are provided, at least one of which is a forward developing roll that rotates in the forward direction with respect to the advancing direction of the photoreceptor, and at least one other developing roll. Is a reverse developing roll that rotates in the reverse direction with respect to the traveling direction of the photosensitive member, wherein the forward developing roll and the reverse developing roll are arranged to face each other with a predetermined gap. A developing device. A developing device in which a two-component developer made of a mixture of developing toner and carrier is loaded therein, and a developing roll is disposed opposite to the photosensitive member with a predetermined gap,
The developer is transported to the photosensitive member facing portion, a bias voltage is applied to the developing roll, and the electric field intensity E by the bias voltage is set to 8.0 (kV / cm) or more, and is formed on the photosensitive member. A developing toner for an electrophotographic apparatus that visualizes an electrostatic latent image with the developing toner,
The developing toner includes at least magnetic powder and carbon black, the magnetic powder includes surface-treated magnetite having a content of more than 20% by weight, and the carbon black has a content of not less than 0% by weight and less than 2% by weight. Have
Charge amount Q of the developing toner measured using a suction / blow type powder charge amount measuring device under the conditions of a suction pressure of −3.5 to 4.0 KPa and a blow pressure of 7.0 KPa after 3 minutes. A developing toner, wherein a ratio Q / T between an absolute value of toner charge amount μC / g) and a developing toner concentration T (%) in the two-component developer exceeds 1.28.   The developing toner according to claim 9, wherein the magnetite is needle-shaped and surface-treated with a silane coupling agent.   11. The developing toner according to claim 9, wherein a weight average particle diameter of the developing toner is regulated in a range of 4 to 10 [mu] m.   12. The developing toner according to claim 11, wherein the proportion of particles having a weight average particle size of less than 4 [mu] m contained in the developing toner is regulated to 25% by number or less of the total number of toner particles.   10. The developing toner according to claim 9, wherein the carbon black content is 0% by weight, the developing toner concentration T is 5.0 to 6.9, and the Q / T is 1.28 to 2.61. The developing toner is characterized in that the electric field intensity E is regulated within a range of 8.0 to 9.0 (kV / cm).

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