JP2005202114A - Full color image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full color image forming method in which a change of the charging ability of a carrier due to spent of a colorant onto the carrier is suppressed to stabilize charge in long-term continuous use and by which full color images of high image quality free of fog and cleaning defects are produced over a prolonged period of time. <P>SOLUTION: In the full color image forming method, at least a developer consisting of a magenta toner and a carrier, a developer consisting of a cyan toner and a carrier, and a developer consisting of a yellow toner and a carrier are used as a developer, wherein each toner has a weight average particle diameter of 3-7 μm and is prepared by externally adding at least a metal salt of a fatty acid, and the highest content of the metal salt of the fatty acid in the toner is 3-10 times the lowest content in the toner. The full color image forming method includes the steps of supplying the toners to an intermediate transfer member and carrying out recovery by blade cleaning. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a full-color image forming method for developing an electrostatic latent image formed by electrophotography or the like.

  Generally, in electrophotography, an electrostatic latent image of electrostatic charge is formed on a photoconductor containing a photoconductive substance by various means, and then this latent image is developed as a powder image with toner, and is applied to paper or the like as necessary. After the transfer, the film is heated and / or pressurized and fixed. As for the technology of hard copy using electrophotography, the development from black and white to full color is rapidly progressing, and the full color market is particularly expanding. Color image formation by full-color electrophotography generally reproduces all colors using three color toners of three primary colors, yellow, magenta, and cyan, or four color toners with black added thereto.

  In recent years, there has been an increasing demand for high image quality and high-speed output of full-color images, particularly for high image quality. For example, for high image quality, it has often been proposed to improve the image quality by reducing or rounding the average particle diameter of the toner. Although reducing the average particle size of the toner is an effective technique for improving image quality, the specific surface area increases as the particle size of the toner decreases, so the amount of charge per unit weight tends to increase. There is. If the charge amount is too high, the development amount is limited, and a problem that a desired density cannot be obtained occurs.

  Therefore, it is conceivable to reduce the amount of toner required to obtain the same density (coloring power) by increasing the content of the colorant. That is, by increasing the colorant content, a desired density can be ensured even if the development amount is limited by a small particle size toner. However, since the colorant itself is easily released from the toner particles due to the increase in the colorant, there is a problem that the charging stability of the toner is lowered. That is, the liberated colorant spends on the carrier and the charge imparting ability of the carrier changes, so that the toner charge amount fluctuates during printing and fog occurs. This problem also occurred when the toner particles were made into a core-shell structure type by a wet granulation method and the shell layer did not contain a colorant; it was difficult to form a shell layer that completely covered the core particles. Conceivable. Furthermore, the influence of the colorant on the toner chargeability differs depending on the type, and the increase in the amount of the colorant increases the influence on the toner chargeability. Therefore, when forming a full-color image, the charge amount for each color. There is a problem that adjustment and development conditions must be changed. For example, the amount of charge can be adjusted by the type of external additive and the addition ratio (for example, the ratio of silica to titanium). It becomes necessary to set cleaning conditions. In addition, if the charge amount is different, the conveyance amount is different under the same regulation condition, so that it is necessary to set a regulation condition (for example, setting of Db (distance between the regulation blade and the developing sleeve)) for each color.

  On the other hand, as a full-color image forming method, there is a method in which each color toner image sequentially formed on the photosensitive member is once superimposed on an intermediate transfer material, and finally the toner images on the intermediate transfer material are collectively transferred to transfer paper. It is common. In an image forming apparatus employing such a method, an edge of a urethane rubber is covered as a means for cleaning the adhered toner, such as an intermediate transfer member or a photosensitive member, until the next image forming cycle. A blade cleaning system that presses against a cleaning object and scrapes off the toner, a fur brush cleaning system that uses a bristle brush, and the like are employed. In particular, the blade cleaning method is mechanically simple and inexpensive, so it is widely used. However, when the blade is caught between the blade and the intermediate transfer member, blade chipping occurs. There is a problem that defective cleaning such as streaky wiping and filming occurs. In particular, it tends to occur at both ends where there are few images.

In order to prevent poor cleaning on the intermediate transfer member, a coating apparatus that applies a lubricity-imparting agent to the surface of the intermediate transfer member is disclosed (for example, Patent Document 1). The system of this apparatus is a system in which a lubricant is supplied by a brush roller provided at a relative position where the slipperiness-imparting agent is rubbed against the solidified coating material. It lacks stability.
JP 7-325490 A

  The present invention is aimed at establishing an image forming method that stably outputs a high-quality full-color image over a long period of time, and has been made in view of the above-described situation in the prior art.

  That is, according to the present invention, a change in carrier charging ability caused by spent (transfer) of a colorant to a carrier, which occurs when a two-component developer composed of a small particle size full color toner containing a colorant at a high concentration and a carrier is used. An object of the present invention is to provide a full-color image forming method that suppresses the above and stabilizes charging during long-term continuous use and outputs a high-quality full-color image over a long period of time.

  The present invention also provides a full-color image forming method for outputting a full-color image free of defective cleaning such as streaky wiping and filming over a long period of time without providing a special lubricant coating device for the intermediate transfer member. Objective.

The present invention includes a step of forming an electrostatic latent image on an electrostatic latent image carrier, a step of developing the electrostatic latent image on the electrostatic latent image carrier using a developer to form a toner image, and a toner A step of primary transfer of the image to the intermediate transfer member is performed for each toner color to form a full-color toner image on the intermediate transfer member, and the full-color toner image is secondarily transferred to the transfer member all at once, by heating and pressurizing. In the full color image forming method for fixing,
As a developer, at least a developer composed of a magenta toner and a carrier, a developer composed of a cyan toner and a carrier, and a developer composed of a yellow toner and a carrier are used.
Each toner has a weight average particle diameter of 3 to 7 μm, and at least a fatty acid metal salt is externally added.
The present invention relates to a full-color image forming method characterized in that there is a difference of 3 to 10 times between the toner having the largest content of the fatty acid metal salt and the toner having the smallest content.

The present invention also includes a step of blade cleaning the surface of the belt-shaped intermediate transfer member, and a step of supplying toner having the highest content of fatty acid metal salt to the intermediate transfer member and recovering it by blade cleaning. The present invention relates to a full-color image forming method.

According to the present invention, even when a two-component developer comprising a small particle size full-color toner containing a colorant at a high concentration and a carrier is used, the ratio of the amount of fatty acid metal salt added in each color within a specific range. By doing so, it is possible to suppress the change in the carrier charging ability and to stabilize the charging in the long-term continuous use. Therefore, a high-quality full color image can be output over a long period of time.
Further, in the intermediate transfer type full-color image forming method, particularly in the tandem type full-color image forming method, a step of blade cleaning the surface of the intermediate transfer member is employed, and any one of the toners constituting the developer, preferably Uses a process of supplying the toner with the highest content of fatty acid metal salt to the intermediate transfer member and recovering it by blade cleaning, so that there is no need to install a special lubricant coating device on the intermediate transfer member. It is possible to easily prevent poor cleaning such as leftover and filming at low cost over a long period of time.

  As the developer used in the full color image forming method of the present invention, a plurality of color developers capable of forming a full color image are used in combination. Hereinafter, a magenta developer composed of magenta toner and carrier, a cyan developer composed of cyan toner and carrier, a yellow developer composed of yellow toner and carrier, and a black developer composed of black toner and carrier are used in combination. However, the black developer is not always necessary. The magenta, cyan, yellow, and black developers will be described together unless otherwise specified, and when these developers are included and expressed, they are simply expressed as “developer”. Further, magenta, cyan, yellow, and black toner (particles) will be described together unless otherwise specified, and when including these toners, they are simply expressed as “toner (particles)”.

In the present invention, the toner contained in the developer is formed by externally adding an external additive to toner particles.
In the present specification, “external addition” means to be added so as to exist outside (surface) of toner particles obtained in advance, and the added fine particles are referred to as “external additive”. To do.

  In the present invention, the toner particles may be produced by any production method, for example, a pulverization dry method or a wet granulation method. From the viewpoint of effectively obtaining the effect of preventing the decrease in carrier charging ability, it is preferable to use toner particles having a relatively small particle size. When toner particles having a small particle diameter are used, the colorant tends to be spent on the carrier, so that the carrier charging ability is lowered. However, in the present invention, this is effectively suppressed.

  As a method for producing small-sized toner particles, a wet granulation method such as a suspension polymerization method, a dispersion polymerization method, a resin particle agglomeration method, or an emulsification dispersion method is preferable. By producing toner particles by such a method, it is possible to provide toner particles having a small particle size and a sharp particle size distribution at a low cost compared to the pulverization method. Among the wet granulation methods, the suspension polymerization method and the resin particle aggregation method are preferable, and the resin particle aggregation method is particularly preferable from the viewpoint of the degree of freedom in controlling the shape of the toner particles.

  The resin particle aggregation method is a method for producing toner particles by aggregating (salting out) / fusing particles in a particle dispersion in which particles containing at least resin particles are dispersed. As a method for adding toner constituents to toner particles, for example, agglomeration / fusion may be performed by mixing with a colorant which is a toner constituent at the time of agglomeration and, if necessary, a dispersion liquid such as an offset inhibitor or a charge control agent. And a method in which a toner component such as a colorant or an anti-offset agent is dispersed in a monomer constituting the resin particles and then polymerized to obtain resin particles. Preferably, resin particles, colorant particles, and offset preventive agent particles are aggregated / fused in an aqueous medium to obtain toner particles.

In the present specification, “aggregation” is used in a concept intended to simply attach at least a plurality of resin particles. By “aggregation”, so-called hetero-aggregated particles (group) are formed in which the constituent particles are in contact with each other, but no bonding due to melting of resin particles or the like is formed. A group of particles formed by such “aggregation” is referred to as “aggregated particles”.
"Fusion" is used in a concept that is intended to form a bond as a unit of use and handling by forming a bond due to melting of resin particles etc. in at least a part of the interface of the individual constituent particles in the aggregated particles And The particle group that has undergone such “fusion” is referred to as “fused particles”.

  At the time of agglomeration (salting out) / fusion of particles including at least resin particles, a method in which the agglomerated particles are once formed and then fused may be employed, or the agglomeration (salting out) may be progressed and simultaneously fused You may employ | adopt the method of performing wearing. In the former method, for example, a salting-out agent such as an alkali metal salt or an alkaline earth metal salt is added to the water in which at least resin particles, colorant particles, and offset inhibitor particles are dispersed, and then aggregated once. After the particles are formed, the fusion is performed by heating to a temperature higher than the glass transition point of the resin particles. In the latter method, for example, a salting-out agent having an alkali metal salt, an alkaline earth metal salt, or the like is added in water in which at least resin particles, colorant particles, and offset preventing agent particles are dispersed, and then the resin is added to the resin. By heating above the glass transition point of the particles, salting-out proceeds and fusion is performed at the same time. In either method, an organic solvent that is infinitely soluble in water may be added to the dispersion system, and a technique for effectively performing fusion by substantially lowering the glass point transition temperature of the resin particles may be used.

  In the former method, after the aggregation and before the fusing, or after the fusing, or in the latter method after the agglomeration / fusion, a resin layer is further added to provide a shell layer on the surface of the toner particles. Also good. Specifically, by adding further resin particles, the resin particles are adhered to the surface of the toner particles once obtained and fused by heating to form a shell layer. As the resin particles, the same resin particles that can constitute the toner particles can be used.

  Examples of alkali metal atoms of alkali metal salts and alkaline earth metal salts that are salting-out agents include metal atoms such as lithium, potassium, and sodium. Examples of alkaline earth metal atoms include magnesium, calcium, strontium, and barium. A metal atom is mentioned. Of these, metal atoms such as potassium, sodium, magnesium, calcium, and barium are preferable. In addition, examples of salts that form salts with these metal atoms include chlorine salts, bromine salts, iodine salts, carbonates, sulfates, and the like.

  The temperature for adding the salting-out agent needs to be at least the glass transition temperature of the resin particles. The reason for this is that if the temperature at which the salting-out agent is added is equal to or higher than the glass transition temperature of the resin particles, the aggregation (salting out) / fusion of the resin particles proceeds rapidly, but it is difficult to control the particle size. Thus, there arises a problem that large particles are generated. The range of the addition temperature may be not more than the glass transition temperature of the resin particles, but is generally 5 to 55 ° C, preferably 10 to 45 ° C. In particular, in the latter method, it is preferable to add a salting-out agent below the glass transition temperature of the resin particles, then raise the temperature as quickly as possible, and then heat the glass particles to a temperature higher than the glass transition temperature of the resin particles.

  Examples of the organic solvent infinitely soluble in water include methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, glycerin, acetone and the like, preferably methanol having 3 or less carbon atoms, ethanol, 1-propanol, The alcohol of 2-propanol is more preferable, and 2-propanol is more preferable.

  The resin particles for forming the toner particles are preferably those having an average particle size of 50 to 1000 nm. For this reason, it is preferable that the resin particles are prepared by an emulsion polymerization method in which fine particles are obtained.

  As the polymerizable monomer for preparing the resin particles, a radical polymerizable monomer is an essential constituent, and a crosslinking agent can be used as necessary. Moreover, you may contain the radical polymerizable monomer which has the following acidic groups, or the radical polymerizable monomer which has a basic group.

  The radical polymerizable monomer is not particularly limited, and a conventionally known radical polymerizable monomer can be used. For example, aromatic vinyl monomers, (meth) acrylic acid ester monomers, vinyl ester monomers, vinyl ether monomers, monoolefin monomers, diolefin monomers, halogenated Olefin monomers and the like can be used.

  Examples of the aromatic vinyl monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples thereof include styrene monomers such as 4-dimethylstyrene and 3,4-dichlorostyrene and derivatives thereof.

  Examples of (meth) acrylate monomers include, for example, methyl acrylate, ethyl acrylate, butyl acrylate, -2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, Examples thereof include butyl methacrylate, hexyl methacrylate, -2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate and the like.

Examples of vinyl ester monomers include vinyl acetate, vinyl propionate, vinyl benzoate, and the like.
Examples of vinyl ether monomers include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether, and the like.
Examples of the monoolefin monomer include ethylene, propylene, isobutylene, 1-butene, 1-pentene, 4-methyl-1-pentene, and the like.
Examples of the halogenated olefin monomer include vinyl chloride, vinylidene chloride, vinyl bromide and the like.

  Moreover, in order to improve the characteristics of the resin particles, a radical polymerizable crosslinking agent may be used as a crosslinking agent. Examples of the radical polymerizable crosslinking agent include two or more unsaturated bonds such as divinylbenzene, divinylnaphthalene, divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diaryl phthalate, butadiene, isoprene, chloroprene, etc. The thing which has. The radical polymerizable crosslinking agent is preferably used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the total radical polymerizable monomer.

  As the radical polymerizable monomer having an acidic group, for example, a carboxyl group- or sulfone group-containing monomer can be used.

Examples of the carboxylic acid group-containing monomer include acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, maleic acid monobutyl ester, maleic acid monooctyl ester and the like.
Examples of the sulfonic acid-containing monomer include styrene sulfonic acid, arylsulfosuccinic acid, octyl arylsulfosuccinate, and the like.
These may have a structure of an alkali metal salt such as sodium or potassium, or an alkaline earth metal salt such as calcium.

  As the radical polymerizable monomer having a basic group, for example, amine compounds such as primary amine, secondary amine, tertiary amine, quaternary ammonium salt and the like can be used.

  Examples of amine compounds include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, and quaternary ammonium salts of the above four compounds, 3-dimethylaminophenyl acrylate, 2-hydroxy-3-methacryl. Oxypropyltrimethylammonium salt, acrylamide, N-butylacrylamide, N, N-dibutylacrylamide, piperidylacrylamide, methacrylamide, N-butylmethacrylamide, N-octadecylacrylamide, vinylpyridine, vinylpyrrolidone, vinyl N-methylpyridinium chloride, Vinyl N-ethylpyridinium chloride, N, N-diarylmethylammonium chloride, N, N-diarylethylammonium And muclide.

  The radical polymerization initiator used for emulsion polymerization can be used as appropriate as long as it is water-soluble. Peroxide compounds such as potassium persulfate persulfate, ammonium persulfate, etc., 4,4′-azobis 4-cyanovaleric acid and salts thereof, 2,2′-azobis (2-amidinopropane) salt, etc. Etc. Further, the radical polymerization initiator can be combined with a reducing agent and used as a redox initiator, if necessary. By using a redox initiator, the polymerization activity is increased, the polymerization temperature can be lowered, and the polymerization time can be further shortened.

  The polymerization temperature may be any temperature as long as it is equal to or higher than the lowest radical generation temperature of the polymerization initiator, but is preferably in the range of 50 to 90 ° C. However, it is also possible to perform polymerization at room temperature or higher by using a polymerization initiator that starts at room temperature, for example, a combination of hydrogen peroxide and a reducing agent (ascorbic acid or the like).

  A surfactant is preferably used for the emulsion polymerization of the radically polymerizable monomer. Although it does not specifically limit as surfactant which can be used in this case, The following anionic or nonionic surfactant can be mentioned as a preferable thing.

  As an anionic surfactant, for example, sodium dodecyl benzene sulfonate sulfonate, sodium arylalkyl polyether sulfonate, etc., sodium sulfate dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc. Examples of the fatty acid salts include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate, calcium oleate and the like.

  Nonionic surfactants include, for example, polyethylene oxide, polypropylene oxide, a combination of polyethylene oxide and polypropylene oxide, alkylphenol polyethylene oxide, esters of higher fatty acids and polyethylene glycol, esters of higher fatty acids and polypropylene oxide, sorbitan esters, and the like. .

As the colorant, it is preferable to use an inorganic pigment or an organic pigment.
Examples of inorganic pigments used in the production of black toner particles include conventionally known black pigments and magnetic pigments. Examples of the black pigment include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black. Examples of magnetic pigments include magnetite and ferrite. These inorganic pigments can be used alone or in combination as required.

  A conventionally well-known organic pigment can be used as an organic pigment. Any organic pigment can be used, and specific organic pigments are listed below.

  Examples of magenta pigments used in the production of magenta toner particles include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, and CI Pigment Red 16. CI Pigment Red 48: 1, CI Pigment Red 53: 1, CI Pigment Red 57: 1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 222, and the like.

  Examples of yellow pigments used in the production of yellow toner particles include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, and CI Pigment Yellow 17. CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 94, CI Pigment Yellow 138, CI Pigment Yellow 180, and the like.

Examples of cyan pigments used in the production of cyan toner particles include CI Pigment Blue 15, CI Pigment Blue 15: 2, CI Pigment Blue 15: 3, CI Pigment Blue 16, CI Pigment Blue 60, CI Pigment Green 7, and the like. Is mentioned.
These organic pigments can be used alone or in combination as required.

  The addition amount of the colorant is not particularly limited, but in the present invention, it is preferable to add a relatively large amount of the colorant in order to obtain a fixed image having a desired density with a relatively small amount of toner. When the amount of the colorant increases, the colorant is released from the toner particles and spent on the carrier, so that the chargeability of the carrier generally decreases. However, in the present invention, even if a relatively large amount is added, the chargeability of the carrier is reduced. This is because the decrease can be effectively suppressed.

Specifically, in the present invention, the colorant is magenta, cyan, yellow, or black, for each of the toners, and a fixed solid image having a toner adhesion amount of 5 g / m ² or less, preferably 4 g / m ² or less, has the following density. Added in an amount to achieve
Magenta toner; image density 0.9 or more, especially 1.0 to 1.2; CM 2002 manufactured by Minolta, wavelength 530 nm, density = -log (reflected light amount / incident light amount), SCI mode;
Cyan toner; image density 0.9 or more, especially 1.0 to 1.2; Minolta CM2002, wavelength 610 nm, density = -log (reflected light quantity / incident light quantity), SCI mode;
Yellow toner; image density 0.9 or more, especially 1.0 to 1.2; Minolta CM2002, wavelength 450 nm, density = -log (reflected light quantity / incident light quantity), SCI mode; and black toner; image density 1.2 or more, especially 1.3 to 1.4; Macbeth Reflection densitometer RD-914.

Specifically, the amount of such a colorant added depends on the hiding power of the colorant (pigment) itself, and thus cannot be specified unconditionally. For example, the amount is as shown below;
Magenta Pigment-CI Pigment Red 57: 1 = 7-12% by weight, CI Pigment Red 122 = 9-14% by weight;
Yellow Pigment—CI Pigment Yellow 74 = 6-10 wt%, CI Pigment Yellow 180 = 10-12 wt%;
Cyan pigment-CI pigment blue 15: 3 = 5.5-9 wt%;
Black pigment—carbon black (Regal 330R; manufactured by Cabot) = 7 to 12% by weight.

  A color modifier surface modifier may be used to modify the colorant surface. A conventionally known material can be used as the surface modifier of the colorant. Specifically, a silane coupling agent, a titanium coupling agent, an aluminum coupling agent, or the like can be preferably used.

  Examples of the offset preventive agent include polyethylene wax, acid-modified polyethylene wax (oxidized polyethylene wax), polypropylene wax, acid-modified polypropylene wax (oxidized polypropylene wax), paraffin wax, microcrystalline wax, and carna. Uba wax, fatty acid ester wax and the like can be mentioned.

  The offset inhibitor particles can be added by various methods such as a method of adding resin particles at the emulsion polymerization stage, a method of adding them simultaneously with the resin particles in the aggregation (salting out) step, a method of adding directly to the finished toner, and the like. I can do it. As a preferred method, a method of adding an offset inhibitor at the stage of emulsion polymerization of the resin particles, and a method of adding an offset inhibitor at the same time as the resin particles in the aggregation (salting out) step and including them in the toner. Is mentioned.

  In addition to the above-described colorant and offset preventive agent, additives capable of imparting various functions may be added as toner constituents. Specific examples include charge control agents.

  These additives can be added by various methods such as a method of adding resin particles at the emulsion polymerization stage, a method of adding them simultaneously with resin particles in the aggregation (salting out) step, a method of adding directly to the finished toner, and the like. I can do it. Preferable methods include a method in which an additive is added at the stage of emulsion polymerization of the resin particles, and a method in which an additive is added simultaneously with the resin particles in the aggregation (salting out) step and included in the toner. It is done.

  The charge control agent used as the additive is a known substance, and it is preferable to use a substance that can be dispersed in water. Specific examples include metal salts of naphthenic acid or higher fatty acids, azo metal complexes, salicylic acid metal salts, or metal complexes thereof. The charge control agent preferably has a number average primary particle diameter of about 10 to 500 nm in a dispersed state.

  In the present invention, it is preferable to use a charge control agent-less toner that does not contain a charge control agent from the viewpoints of environmental properties and cost reduction of the toner.

  The toner particles in the aqueous medium obtained by aggregation / fusion are usually filtered and washed with washing water to remove impurities such as surfactants and salting-out agents adhering to the toner particles. . The filtration and washing machine used in this step is not particularly limited, and for example, a centrifuge, a Nutsche, a filter press or the like is used.

  The toner particles after filtration and washing are dried. The dryer used in this step is not particularly limited. For example, spray dryer, vacuum dryer, vacuum dryer, stationary shelf dryer, mobile shelf dryer, fluidized bed dryer, rotary dryer, stirring A type dryer or the like is used. The water content in 100 parts by weight of the toner particles after drying is preferably 5 parts by weight or less, but more preferably 2 parts by weight or less.

An external additive is externally added to the toner particles obtained by the above-described method to obtain a toner.
In the present invention, at least a fatty acid metal salt is used as an external additive. In a small particle size toner containing a colorant at a high concentration, the colorant generally spends on the carrier surface when the toner and the carrier are mixed. As a result, the charging ability of the carrier changes, and fogging or dust is generated. However, when magenta, cyan, yellow and black toners externally treated with fatty acid metal salts within the specified range as described later are used as a two-component developer, the fatty acid metal salts are effectively used in all the toners. Pent and change in chargeability of carriers can be suppressed. The fatty acid metal salt spent on the carrier makes it difficult for the colorant to adhere, and / or the positive component (fatty acid metal salt) counteracts the chargeability of the negative component (colorant). Since it acts as a counter component, it is considered that the charging stability can be secured with all toners even in long-term use.

Examples of fatty acid metal salts include general formulas;
C _n H _{2n + 1} COOH
(Wherein n represents 12 to 18, preferably 16 to 18), and a salt of a fatty acid and a metal.

  Examples of the fatty acid constituting such a salt include tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, and nonadecanoic acid. From the viewpoint of achieving the object of the present invention more effectively, heptadecyl acid, stearic acid, nonadecanoic acid, particularly stearic acid is preferred.

  The metal constituting the salt is not particularly limited as long as it can form a salt with the fatty acid, and examples thereof include calcium, zinc, magnesium, aluminum, and lithium. Calcium is preferable from the viewpoint of cost, safety, and reduction in elasticity (hardness) of the silicone rubber in a full color process.

  The fatty acid metal salt preferably has a melting point of about 100 to 150 ° C. from the viewpoint of heat resistance and lubricity. For example, calcium stearate, zinc stearate, magnesium stearate, etc. are preferably used. Furthermore, calcium stearate is preferable in terms of environmental safety. As calcium stearate, those produced by the direct method and those produced by the metathesis method are known, but those obtained by the direct method with less impure content are preferably pulverized and used after adjusting the particle size.

  Fatty acid metal salts are used in particulate form. The volume average particle diameter is usually 2 to 10 μm, particularly 4 to 8 μm.

The amount of fatty acid metal salt added must be adjusted according to the type of colorant, its charging characteristics, and the state of exposure to the surface of the toner particles. As a result of intensive research, the charging stability of all full-color developers used In order to secure the image quality and satisfy the electrophotographic characteristics, the following relationship was found:
When the weight average particle diameter of the toner is set to 3 to 7 μm, particularly when the maximum adhesion amount of each toner on the intermediate transfer member is set to 5.0 g / m ² or less, the content of the fatty acid metal salt is The content of the fatty acid metal salt of each toner is determined so that it is within a range of 3 to 10 times, preferably 5 to 10 times, with the most toner and the least toner.

  “Fatty acid metal salt content” means the amount (parts by weight) of fatty acid metal salt added to 100 parts by weight of toner particles in each toner. In the present invention, the ratio (X / Y) between the fatty acid metal salt content (X) of the toner having the largest content value and the fatty acid metal salt content (Y) of the smallest toner is within the above range. That's fine. If the ratio is too small or too large, the chargeability adjustment for each color toner is not performed effectively, and the charge stability of any of the toners used decreases. In particular, when the ratio is too small and the content of the toner having the largest fatty acid metal salt content is small, in order to prevent poor cleaning, the toner is transferred to the intermediate transfer member as described in detail later. In the step of supplying the toner to the toner and collecting it by blade cleaning, it is necessary to supply a large amount of toner, so that the toner consumption in the image forming method of the present invention increases. Since yellow pigments generally have a strong negative chargeability and a stronger tendency to reduce the chargeability of carriers, the toner having the largest content of fatty acid metal salt is usually a yellow toner.

Since the content of fatty acid metal salt depends on the charging characteristics of the colorant as described above, it cannot be specified unconditionally, but the content in each toner is when the toner particle size is 4.5 μm and the adhesion amount is 3.5 g / m ² Usually, it is determined to be within the specified range within the following range;
Magenta toner; 0.03 to 0.30 parts by weight, preferably 0.05 to 0.20 parts by weight;
Cyan toner; 0.05 to 0.35 parts by weight, preferably 0.08 to 0.25 parts by weight;
Yellow toner; 0.10 to 0.60 parts by weight, preferably 0.20 to 0.50 parts by weight; and Black toner; 0.05 to 0.35 parts by weight, preferably 0.08 to 0.25 parts by weight.

  In the present invention, in addition to the fatty acid metal salt, various organic / inorganic fine particles are preferably added as external additives from the viewpoints of imparting toner fluidity and improving cleaning properties. For example, various carbides such as silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, diamond carbon lactam, boron nitride, Various nitrides such as titanium nitride and zirconium nitride, borides such as zirconium boride, various oxides such as titanium oxide, calcium oxide, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, silica and colloidal silica, calcium titanate , Various titanate compounds such as magnesium titanate and strontium titanate, sulfides such as molybdenum disulfide, fluorides such as magnesium fluoride and fluorocarbon, various nonmagnetic inorganic fine particles such as talc and bentonite, alone or in combination for Rukoto can.

  Also, styrene, (meth) acrylic, benzoguanamine, melamine, Teflon (registered trademark) granulated by emulsion polymerization method, soap-free emulsion polymerization method, wet polymerization method such as non-aqueous dispersion polymerization method, gas phase method, etc. Various organic fine particles such as silicon, polyethylene, and polypropylene can also be used.

  Especially for inorganic fine particles such as silica, titanium oxide, alumina, zinc oxide, etc., from the viewpoint of environmental stability and heat-resistant storage stability, silane coupling agents, titanate coupling agents, silicone oil, silicone varnish, etc. have been used. Surface treatment is carried out by a known method using a treating agent such as a hydrophobizing agent, a fluorinated silane coupling agent, or a fluorinated silicone oil, a coupling agent having an amino group or a quaternary ammonium base, or a modified silicone oil. It is preferable.

  In the present invention, it is preferable to use silica and titanium oxide in combination from the viewpoint of more effectively achieving toner fluidity imparting and cleaning performance improvement.

  The total amount of inorganic fine particles, particularly silica and titanium oxide, is preferably adjusted to an appropriate amount according to the particle size (= specific surface area) of the toner, and is usually 0.05 to 5 parts by weight with respect to 100 parts by weight of the toner particles. The amount is preferably 0.1 to 3 parts by weight.

  In the present invention, it is preferable to further contain inorganic particles having a number average particle diameter of 80 to 1200 nm, preferably 80 to 1000 nm, more preferably 100 to 800 nm. By externally adding such large-diameter inorganic particles, a static layer composed of the inorganic particles is formed in the gap between the photosensitive member and the cleaning blade, preventing sludge of other external additives, silica, titanium oxide, etc. Therefore, image noise (BS (black spot)) on a copy image due to adhesion of the toner to the surface of the photoconductor can be suppressed, and appropriate photoconductor polishing can be performed. The large-diameter inorganic particles preferably have a hardness that can polish the surface of the photosensitive member. For example, silica, titanium oxide, amyrna, titanic acid compounds, silicon acid compounds, and sintered bodies thereof are used. It is preferable. In particular, strontium titanate particles are preferably used. The large-diameter inorganic particles may be used after being hydrophobized with a known silane coupling agent or silicone oil. The addition amount of the large-diameter inorganic particles is suitably 0.4 to 3.5 parts by weight, preferably 0.5 to 3.0 parts by weight, and more preferably 1.0 to 3.0 parts by weight with respect to 100 parts by weight of the toner particles.

  In the present invention, it is desirable that the external additive configurations of magenta, cyan, yellow and black toners are substantially the same except for the fatty acid metal salt added for charging stability. If the external additive composition is changed for each color, the developability / transferability of the toner changes for each color, and it becomes necessary to design development conditions and the like for each color. The structure of the external additives other than the fatty acid metal salt being substantially the same means that at least the type, preferably the type and particle size of the “external additive other than the fatty acid metal salt” are the same.

  The external addition process is achieved by adding and mixing an external additive to the toner particles. For the treatment, a known mixer such as a Henschel mixer (manufactured by Mitsui Miike Kogyo) or a super mixer (manufactured by Kawada Seisakusho) can be used.

  When other external additives are used in addition to the fatty acid metal salt, the external addition process is performed by a divided mixing method in which the external additive is added and mixed in multiple stages, and at least the fatty acid metal salt is added to the first stage. -It is preferable to mix. That is, at least a fatty acid metal salt and toner particles are mixed, and then other external additives are added and mixed. When the fatty acid metal salt is added and mixed in the first stage, the effect of improving the charging stability and the effect of improving the cleaning property can be obtained at the same time. Specifically, when the fatty acid metal salt is added and mixed in the first stage, the fatty acid metal salt adheres to the toner particles with an appropriate strength, and the remaining amount of the fatty acid metal salt is spent on the carrier while an appropriate amount of the fatty acid metal salt is spent on the carrier. It behaves with the particles and reaches the intermediate transfer member. The fatty acid metal salt on the toner particles reaching the intermediate transfer member is detached from the toner particles by nip stress at the nip (gap) between the intermediate transfer member and its cleaning blade, and imparts lubricity to the surface of the intermediate transfer member. Such an effect of imparting lubricity to the intermediate transfer member becomes prominent when a process of supplying toner to the intermediate transfer member and collecting it by blade cleaning is performed in order to prevent poor cleaning as will be described in detail later. .

The toner of the present invention in which the above external additive is externally added to toner particles is used as a two-component developer used together with a carrier.
Color toners other than black toner (magenta, cyan, yellow) are used as non-magnetic toners.
The black toner may be used as either a magnetic or nonmagnetic toner, but is preferably used as a nonmagnetic full color toner for a two-component developer.

  The toner of the present invention has a weight average particle diameter of 3 to 7 μm, preferably 4 to 6 μm. By using such a toner particle size, the number of toners necessary for image formation is secured, and the graininess necessary for a full-color image is secured. If it is less than 3 μm, the adhesion between the toners is too high due to an increase in the surface area of the toner, and aggregation during storage, replenishment, and development becomes a problem. If it exceeds 7 μm, the granularity (fine image) level required for a full-color image cannot be achieved.

  As the carrier constituting the developer together with the toner, those conventionally known as carriers for two-component developers can be used, for example, carriers made of magnetic particles such as iron, ferrite, magnetite, and such magnetic A resin-coated carrier obtained by coating body particles with a resin, or a binder-type carrier obtained by dispersing magnetic fine powder in a binder resin can be used. From the viewpoint of magnetic properties, electrical properties, and productivity, a resin-coated carrier is preferable.

  The carrier core (magnetic particles) used for the resin-coated carrier can be generally known, but the stress applied to the developer during mixing and stirring in the developing machine is reduced, and the coating layer is destroyed and the toner carrier Magnetic material with true specific gravity of 3 to 7 g / ml and weight average particle size (measured by Microtrac SRA MK-II (manufactured by Nikkiso Co., Ltd.)) of 20 to 60 μm to make it difficult to cause fusion to the surface. It is preferable to use particles, and ferrite particles, magnetite particles, and the like are preferably used.

  As the coating resin, generally known resins can be used. From the viewpoint of charging ability, ability to form a coating layer, etc., homopolymers / copolymers of esterified products of acrylic acid and / or methacrylic acid and alkyl alcohol, And a copolymer thereof with styrene is preferably used. A carrier using such a coating resin generally tends to have a reduced charging ability due to the spent of the colorant. However, in the present invention, even if such a carrier is used, a reduction in charging ability can be effectively prevented. In addition, it is preferable to use a resin-coated carrier using a silicone resin, a copolymer resin (graft resin) of an organopolysiloxane and a vinyl monomer, or a polyester resin. A carrier coated with a resin obtained by reacting an isocyanate with a copolymer resin of polysiloxane and a vinyl monomer is preferred from the viewpoints of durability, environmental stability and spent resistance. As the vinyl monomer, it is necessary to use a monomer having a substituent such as a hydroxyl group reactive with isocyanate.

  The resin-coated carrier needs to be sufficiently coated with the core material from the leak resistance, and is preferably a carrier having a coating amount of 1.0 to 5.0, preferably 2.0 to 4.0. The coating amount is the weight ratio of the resin to the entire resin-coated carrier.

  The coating method is not particularly limited as long as the resin can be coated on the core. For example, mechanical impact force or a dry method in which the resin is fixed using mechanical impact force and heat melting, or by dissolving the resin in a solvent. The wet method etc. which apply | coat and dry are mentioned. In the image forming method of the present invention, the non-contact thin layer development method is preferably employed as the development method from the viewpoint of high image quality. In such a development method, it is preferable that the resin-coated carrier has a thick resin film from the viewpoint of increasing the electric resistance of the carrier. However, in the wet method, since the resin is dissolved, a large amount of granulation occurs during coating, which is not suitable for thickening. Therefore, it is preferable to use a resin-coated carrier manufactured by a dry method. The dry method using mechanical impact force has a low carrier granulation rate (ratio of carrier particles sticking together) because no solvent is used, and there is no drying process, so that the production time can be shortened and uniform coating can be achieved. It also has merit. The resin-coated carrier having a thick film generally tends to have a reduced charging ability due to the spent of the colorant. However, even if such a carrier is used in the present invention, the reduction in the charging ability can be effectively prevented.

  The dry coating method using such mechanical impact force will be described in detail below. First, as a first step, magnetic particles and coated resin fine particles are mixed and stirred by a normal stirring device or the like, and the resin fine particles are uniformly attached to the surface of the magnetic particles by physical adhesion force or electrostatic adhesion force. About this process, you may carry out under non-heating, and you may carry out under the heating to such an extent that resin fine particles are slightly softened. As an apparatus for performing this process, various mixing and stirring apparatuses can be used, but an apparatus capable of continuously performing the second process described below is preferable. Subsequently, as the second step, the fine particles are applied to the surfaces of the magnetic particles by stirring the mixture obtained through the first step with strong stirring force under non-heating or heating and repeatedly applying impact force to the mixture. To obtain a coated carrier.

  Even when the second step is performed without heating, the temperature of the mixture may usually rise to 30 to 60 ° C. due to spontaneous heat generation due to friction of the mixture. When heating, 60-120 degreeC is still more preferable. When the heating temperature is excessive, fusion between carrier particles tends to occur.

  A dry coating method using a mechanical impact force will be described in detail with reference to FIG. 1 showing an example of a carrier coating apparatus. First, as the first step, magnetic particles and resin fine particles are charged into the mixing and stirring tank 9 from the raw material charging port 2 and mixed and stirred by rotating the horizontal rotating body 8 provided with the stirring blades 6 on the surface of the magnetic particles. It adheres uniformly by physical adhesion or electrostatic adhesion. About this process, you may carry out under non-heating, and you may carry out under the heating of the grade which resin fine particle softens slightly. Subsequently, as a second step, the jacket 4 is heated and stirred again by the stirring blade 6 and the horizontal rotating body 8 to fix the resin fine particles on the surface of the magnetic particles to obtain a coated carrier. 7 is a carrier outlet obtained. 1 is an upper lid, 5 is a thermometer, and 3 is a back filter.

  The toner / carrier weight ratio (toner / carrier) in the developer is preferably 3/100 to 20/100, although the optimum value varies depending on the particle size.

  In the full-color image forming method of the present invention, a step of forming an electrostatic latent image on the electrostatic latent image carrier, a toner image is developed by developing the electrostatic latent image on the electrostatic latent image carrier using a developer. A step of forming and a step of primary transfer of the toner image to the intermediate transfer member for each toner color to form a full-color toner image in which the toner images of the respective colors are superimposed on the intermediate transfer member; Full-color toner images are collectively transferred to a transfer member such as recording paper and fixed by heating and pressing. The full-color image forming method of the present invention will be described in detail with reference to FIG. 2 showing a full-color image forming apparatus that suitably employs the method.

  FIG. 2 is an overall configuration diagram of a tandem digital color printer (hereinafter simply referred to as “printer”) 10. In the printer 10, an automatic image density control technique is provided for controlling the image density at the time of image formation based on the image density of a reference toner image formed on the surface of an electrostatic latent image carrier such as a photosensitive drum. Yes. In such automatic density control, a reference toner image is formed on the electrostatic latent image carrier under predetermined development conditions, and the image density is detected by an optical sensor or the like. Then, based on the detected image density of the reference toner image, the toner supply amount to the developing device is adjusted, or the developing potential is changed by correcting the values of the grid potential VG and the developing bias potential VB. The image density at the time of image formation, that is, the toner supply amount to the electrostatic latent image carrier is controlled. Hereinafter, this automatic density control is called AIDC (Auto lmage Density Control 1).

The printer 10 is provided with an intermediate transfer belt 12 as an intermediate transfer member at a substantially central portion inside thereof. The intermediate transfer belt 12 is supported by the outer peripheral portions of the three rollers 14, 16, and 18 and is driven to rotate in the direction of arrow A. Further, the intermediate transfer belt 12 is made of conductive carbon particles dispersed in a resin such as polycarbonate or polyimide, and has a semiconductivity of about 10 ⁹ to 10 ¹¹ Ω · cm.

  Below the lower horizontal part of the intermediate transfer belt 12, there are four image forming units 20Y, 20M, 20C, and 20K corresponding to yellow (Y), magenta (M), cyan (C), and black (K), respectively. Are arranged side by side along the intermediate transfer belt 12.

  Each of the image forming units 20Y, 20M, 20C, and 20K has photosensitive drums 22Y, 22M, 22C, and 22K as electrostatic latent image carriers. Around the photosensitive drum 22Y, a charger 24Y that uniformly charges the surface of the photosensitive drum 22Y in order along the rotation direction, and a statically charged surface by exposing the uniformly charged surface of the photosensitive drum according to image data. A print head unit 26Y that forms an electrostatic latent image, a developing device 28Y that develops an electrostatic latent image formed on the surface of the photosensitive drum with yellow toner to form a toner image, and a photosensitive drum with the intermediate transfer belt 12 interposed therebetween A primary transfer roller 30Y that opposes 22Y and electrostatically attracts the toner image formed on the surface of the photoconductor drum to perform primary transfer onto the intermediate transfer belt 12, and collects toner remaining on the surface of the photoconductor drum after the primary transfer And a cleaner 32Y for cleaning.

  Similarly, around the photosensitive drum 22M, the electrostatic latent image formed on the surface of the charging drum 24M, the print head unit 26M, and the photosensitive drum is developed with magenta toner in order along the rotation direction. A developing unit 28M for image formation, a primary transfer roller 30M, and a cleaner 32M are disposed. Around the photosensitive drum 22C, a charger 24C, a print head unit 26C, and a static image formed on the surface of the photosensitive drum. A developing device 28C that develops an electrostatic latent image with cyan toner to form a toner image, a primary transfer roller 30C, and a cleaner 32C are arranged, and around the photosensitive drum 22K, a charger 24K and a print head unit 26K. And a developing device 28K that develops the electrostatic latent image formed on the surface of the photosensitive drum with black toner to form a toner image, a primary transfer roller 30K, and a cleaner 32K. The print head units 26Y, 26M, 26C, and 26K are composed of a large number of LEDs arranged in the main scanning direction parallel to the axial direction of the photosensitive drum.

Each developing device 28Y, 28M, 28C, 28K accommodates the two-component developer composed of the toner and the carrier, and the developer is disposed opposite to the photosensitive drums 22Y, 22M, 22C, 22K. The developer is transported by a developer transport member to a developing area between the developer transport member and the toner in the developer is supplied to the photosensitive drum for development. From the viewpoint of high image quality, each developing device is a non-contact type that performs development by supplying toner in the developer from the developer conveying member to the photosensitive drum in a state where the photosensitive drum and the developer conveying member are not in contact with each other. It is preferable to adopt a developing method. More preferably, a non-contact development method is employed in which development is performed by applying a vibrating electric field in the development region to supply toner in the developer from the developer conveying member to the photosensitive drum. More preferably, a thin layer developing system is employed in which the amount of developer transported to the development area by the developer transport member is set to 50 to 200 g / m ² .

  A secondary transfer roller 34 is pressed against a portion of the intermediate transfer belt 12 supported by the roller 18. A nip portion between the secondary transfer roller 34 and the intermediate transfer belt is a secondary transfer region 36. A transfer voltage is applied to the secondary transfer roller 34. As will be described later, the toner image formed on the intermediate transfer belt 12 by this transfer voltage is electrostatically attracted to a sheet as a transfer member conveyed to the secondary transfer region and is secondarily transferred. It has become.

  A cleaner (cleaning blade) 38 is in pressure contact with the portion of the intermediate transfer belt 12 supported by the roller 16. The cleaner 38 is for scraping and collecting the toner remaining on the intermediate transfer belt 12 after the secondary transfer into the waste toner box 40. The cleaner is also used when toner is supplied to the intermediate transfer belt and then recovered in order to prevent poor cleaning as will be described in detail later.

  In the lower part of the printer 10, a paper feed cassette 42 is detachably disposed. The sheets S as transfer members stacked and accommodated in the sheet cassette 42 are sent out one by one from the uppermost one to the conveyance path 46 by the rotation of the sheet feeding roller 44.

  The conveyance path 46 extends from the paper feed cassette 42 to the paper discharge tray 11 through the nip portion of the timing roller pair 48, the secondary transfer region 36, and the fixing unit 50.

  A paper feed sensor 52 is disposed in the vicinity of the timing roller pair 48. The paper feed sensor 52 is for detecting that the leading edge of the paper S sent out from the paper feed cassette 42 to the transport path 46 is nipped by the timing roller pair 48. When the leading edge of the paper S is detected by the paper feed sensor 52, the timing roller pair 48 temporarily stops its rotation, and then the paper S is transferred to the secondary transfer region 36 in synchronization with the toner image on the intermediate transfer belt 12. It is starting to send out.

  The fixing unit 50 is supported by a pair of rollers 56 and 58 and is driven to rotate in the direction of arrow B, and a fixing roller 62 that is pressed against the roller 56 via the fixing belt 60 and is driven to rotate in the direction of the arrow. The fixing region 64 is a nip portion between the fixing belt 60 and the fixing roller 62 through which the sheet on which the toner image has been secondarily transferred passes.

  Next, the operation of the printer 10 having the above configuration will be described. When an image signal is input from an external device (for example, a personal computer) to an image signal processing unit (not shown) of the printer 10, the image signal processing unit converts the image signal into yellow, cyan, magenta, and black. A signal is generated and transmitted to the LED drive circuit for the print head. This drive circuit performs exposure by causing the print head units 26Y, 26M, 26C, and 26K of the image forming units 20Y, 20M, 20C, and 20K to emit light based on the input digital signals. This exposure is performed with a time difference in the order of the print head units 26Y, 26M, 26C, and 26K. Thereby, electrostatic latent images for the respective colors are formed on the surfaces of the respective photosensitive drums 22Y, 22M, 22C, and 22K.

  The electrostatic latent images formed on the photosensitive drums 22Y, 22M, 22C, and 22K are developed by the developing devices 28Y, 28M, 28C, and 28K, respectively, and become toner images of the respective colors. The toner images of the respective colors are sequentially superposed and primarily transferred by the action of the primary transfer rollers 30Y, 30M, 30C, and 30K to form toner images.

  In this manner, the superimposed full-color toner image formed on the intermediate transfer belt 12 reaches the secondary transfer region 36 as the intermediate transfer belt 12 moves. In the secondary transfer region 36, the toner images superimposed on each other are collectively delivered to the sheet S fed from the sheet feeding cassette 42 to the conveyance path 46 and supplied by the timing roller pair 48 by the action of the secondary transfer roller 34. Secondary transferred. The toner remaining on the intermediate transfer belt 12 after the secondary transfer is collected by the cleaner 38.

  The sheet S on which the toner image has been secondarily transferred is sent to the fixing unit 50 through the conveyance path 46, where the toner image is fixed on the sheet S by passing through the fixing region 64. Then, the paper S is discharged to the paper discharge tray 11.

  In the printer of FIG. 2, the image forming units 20Y, 20M, 20C, and 20K are arranged on the lower side of the intermediate transfer belt. However, for example, the image forming unit may be arranged on the upper side of the intermediate transfer belt. Good. By disposing each image forming unit below the intermediate transfer belt, the distance from the primary transfer position to the secondary transfer position of the image forming unit K can be shortened. For this reason, the printer of FIG. 2 has the following advantages. The speed at which the first image is formed can be increased. When the image forming operation is interrupted due to a trouble such as a jam, the toner image formed on the intermediate transfer belt is reduced, and the amount of wasted toner can be reduced. It is easy to shorten the distance from the secondary transfer position to the fixing device, and it can be applied to small-size paper such as postcards.

  In the image forming method of the present invention, the toner is lubricated to the intermediate transfer member without providing a special lubricant application device to the intermediate transfer member by supplying the toner to the intermediate transfer member and collecting it by blade cleaning. Sex can be imparted. As a result, a full color image free from defective cleaning such as streaky wiping and filming can be provided over a long period of time. Specifically, for the purpose of bringing the toner into contact with the intermediate transfer member, not for the purpose of forming a fixed image, the toner is supplied to the surface of the intermediate transfer member, and the toner is collected by a cleaning blade. That is, after the latent image is formed on the photosensitive member, developed, and the primary transfer to the intermediate transfer member is performed in the same manner as a normal image forming operation, the secondary transfer output is turned off or the secondary transfer roller is separated. Then, the toner on the intermediate transfer member is collected in a waste toner box by a cleaning blade of the intermediate transfer member. At this time, the fatty acid metal salt is released from the toner particles by nip stress between the blade and the intermediate transfer member, and the released fatty acid metal salt is pressed against the surface of the intermediate transfer member, thereby providing lubricity.

The latent image formed on the photoreceptor when the toner is supplied to the intermediate transfer member is not particularly limited as long as it can impart lubricity to the intermediate transfer member, but is usually continuous over the entire length in the width direction on the intermediate transfer member. The image is such that toner is supplied, and is preferably an image on which a rectangular solid image having a toner adhesion amount of 0.5 to 2.0 g / m ² is formed on the intermediate transfer member with the width of one side as one side.

The process of supplying and collecting the toner to the intermediate transfer member may be performed at various timings. For example, it can be performed between images before, after, and during multi-copying.
Here, before image formation is before the first copy starts.
After image formation is after the copying operation is completed.
For example, when copying 100 sheets, the interval between images in multi-copying is between the 50th and 51st sheets.

  The toner supplied to the intermediate transfer member may be any toner among the toners contained in the developer used for image formation, but is preferably the toner having the highest content of fatty acid metal salt. is there. If the toner having the highest content of the fatty acid metal salt is supplied, the intermediate transfer member can be effectively lubricated with a small amount of toner, which is efficient.

  The amount of toner supplied to the intermediate transfer member is not particularly limited as long as the effect of imparting lubricity can be obtained. Usually, when the width of the intermediate transfer member is 230 mm, 0.001 to 0.01 g, preferably 0.003 to 0.007g of toner is supplied.

In the present invention, it is further preferable that the maximum adhesion amount of each toner on the intermediate transfer member is controlled to 5.0 g / m ² or less, particularly 3 to 5 g / m ² . By controlling in such a manner, in full-color image formation, scattering and voids in the transfer portion can be suppressed, and offset and separation failure in the fixing portion can be suppressed. Therefore, the speed of full-color image formation can be increased. Further, in the present invention, even when the maximum adhesion amount is reduced in this way, it is possible to effectively maintain good cleaning properties of the intermediate transfer member. The maximum adhesion amount of each toner on the intermediate transfer member can be controlled by adjusting development conditions (for example, development bias, exposure amount, etc.).

EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited by these.
<Preparation of resin particle dispersion>
A solution was prepared by mixing and dissolving 315 parts by weight of styrene, 85 parts by weight of n-butyl acrylate, 6 parts by weight of acrylic acid and 10 parts by weight of dodecanethiol. On the other hand, 6 parts by weight of a nonionic surfactant (Nonipol 400: manufactured by Kao Corporation) and 10 parts by weight of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Co., Ltd.) are dissolved in 550 parts by weight of ion-exchanged water. The above solution was added thereto, dispersed and emulsified in a flask, and 50 parts by weight of ion-exchanged water in which 4 parts by weight of ammonium persulfate was dissolved was added while slowly stirring and mixing for 10 minutes. Next, after sufficiently replacing the inside with nitrogen, the flask was heated to 70 ° C. in an oil bath while stirring, and emulsion polymerization was continued for 5 hours as it was, a resin having a center diameter of 171 nm, a glass transition point of 54 ° C., and Mw 34300. A dispersion containing particles was obtained.

<Preparation of colorant dispersion>
CI Pigment Blue 15-3 (Cyan Pigment) 5O parts by weight, Nonionic Surfactant (Nonipol 400: manufactured by Kao Corporation) 5 parts by weight and ion-exchanged water 345 parts by weight using a homogenizer (Ultra Turrax: manufactured by IKA) Dispersion for 10 minutes gave a cyan colorant dispersion containing cyan pigment particles.

The yellow colorant dispersion Y1 was changed in the same manner except that CI Pigment Blue 15-3 (cyan pigment) was changed to CI Pigment Yellow 74, and the yellow colorant dispersion Y2 was changed in the same manner except that CI Pigment Yellow 18O was changed. Respectively.
Magenta colorant dispersion M1 was changed in the same manner except that CI Pigment Blue 15-3 (cyan pigment) was changed to CI Pigment Red 57-1, and magenta colorant dispersion was similarly changed except that CI Pigment Red 122 was changed. Liquid M2 was obtained.
A black colorant dispersion was obtained in the same manner except that the CI pigment blue 15-3 (cyan pigment) was changed to carbon black (Regal 330R: manufactured by Cabot Corporation).

<Preparation of anti-offset agent dispersion>
Heat 50 parts by weight of paraffin wax (HNP0190: Nippon Seiwa Co., Ltd.), 5 parts by weight of a cationic surfactant (Sanisol B50: manufactured by Kao Susumu) and 200 parts by weight of ion exchange water to 95 ° C. After sufficiently dispersing with Lux T50 (manufactured by IKA), it was dispersed with a pressure discharge type homogenizer to obtain an anti-offset agent dispersion containing wax particles having a center diameter of 180 nm.

<Preparation of toner particles>
(Toner particle CA (cyan))
200 parts by weight of resin particle dispersion, 61.6 parts by weight of cyan colorant dispersion, 50 parts by weight of anti-offset agent dispersion and 1.23 parts by weight of polyaluminum chloride in a round stainless steel flask (Ultra Turrax T50: manufactured by IKA) The mixture was sufficiently mixed and dispersed in (3), and the agglomeration temperature was heated to 52 ° C. while stirring the flask in a heating oil bath. Thereafter, after maintaining at 52 ° C. for 60 minutes, 60 parts by weight of the resin particle dispersion was further added and gently stirred for 60 minutes.

  Then, after adjusting the pH of the system to 6.0 with a 0.5 mol / L sodium hydroxide aqueous solution, the stainless steel flask was sealed and heated to 97 ° C. while continuing to stir using a magnetic seal, The pH was adjusted to 4.0 and held for 6 hours. Then, after cooling and sufficiently washing with filtration and ion exchange water, solid-liquid separation was performed by Nutsche suction filtration. Further, it was dispersed again in 3 L of ion exchange water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. After this washing operation was repeated 5 times, solid-liquid separation was performed by Nutsche suction filtration. Then, vacuum drying was continued for 12 hours to obtain toner particles C-A having a volume average particle size of 4.5 μm and a circularity of 0.975.

(Toner particle CB (cyan))
Toner particles CB were obtained in the same manner as in the production method of toner particles CA, except that the amount of the colorant dispersion added was changed so that the content of the colorant in the toner particles was 6 parts by weight.

(Toner particle CC (cyan))
Toner particles CC were obtained in the same manner as in the production method of the toner particles CA, except that the holding time at 52 ° C. was adjusted so that the volume average particle diameter was 6.5 μm.

(Toner particle CD (cyan))
Toner particles CC were obtained in the same manner as in the production method of the toner particles CA, except that the holding time at 52 ° C. was adjusted so that the volume average particle diameter was 8.0 μm.

(Toner particle YA (yellow))
Toner particles other than using yellow colorant dispersion Y1 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 9 parts by weight Toner particles YA were obtained in the same manner as the CA production method.

(Toner particles YB (yellow))
Toner particles other than using yellow colorant dispersion Y1 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 7 parts by weight Toner particles YB were obtained in the same manner as the CA production method.

(Toner particles YC (yellow))
The yellow colorant dispersion Y1 was used instead of the cyan colorant dispersion, the holding time at 52 ° C. was adjusted so that the volume average particle size was 6.5 μm, and the colorant content in the toner particles Toner particles YC were obtained in the same manner as in the production method of toner particles CA, except that the amount of the colorant dispersion added was changed so that the amount was 9 parts by weight.

(Toner particle YD (yellow))
The yellow colorant dispersion Y1 was used in place of the cyan colorant dispersion, the holding time at 52 ° C. was adjusted so that the volume average particle size was 8.0 μm, and the colorant content in the toner particles A toner particle YD was obtained in the same manner as the production method of the toner particle CA, except that the amount of the colorant dispersion added was changed so that the amount of the toner was 9 parts by weight.

(Toner particle YE (yellow))
Toner particles other than using yellow colorant dispersion Y2 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 11 parts by weight Toner particles YE were obtained in the same manner as the CA production method.

(Toner particle MA (magenta))
Toner particles other than using magenta colorant dispersion M1 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 10.3 parts by weight. Toner particles MA were obtained in the same manner as the CA production method.

(Toner particle MB (magenta))
Toner particles other than using magenta colorant dispersion M1 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 8 parts by weight. In the same manner as in the CA production method, toner particles MB were obtained.

(Toner particle MC (magenta))
Magenta colorant dispersion M1 was used instead of cyan colorant dispersion, holding time at 52 ° C was adjusted so that the volume average particle size was 6.5 µm, and the colorant content in the toner particles Toner particles MC were obtained in the same manner as in the production method of the toner particles CA, except that the amount of the colorant dispersion added was changed so as to be 10.3 parts by weight.

(Toner particle MD (magenta))
Magenta colorant dispersion M1 was used instead of cyan colorant dispersion, holding time at 52 ° C. was adjusted so that the volume average particle size was 8.0 μm, and the colorant content in the toner particles A toner particle MD was obtained in the same manner as in the production method of the toner particle CA, except that the amount of the colorant dispersion added was changed so as to be 10.3 parts by weight.

(Toner particle ME (magenta))
Toner particles other than using magenta colorant dispersion M2 instead of cyan colorant dispersion and changing the amount of colorant dispersion added so that the colorant content in the toner particles is 11 parts by weight Toner particles ME were obtained in the same manner as the CA production method.

(Toner particle KA (black))
Toner particles CA, except that the black colorant dispersion was used instead of the cyan colorant dispersion, and the amount of colorant dispersion added was changed so that the colorant content in the toner particles was 10.3 parts by weight. Toner particles KA were obtained in the same manner as in the above production method.

(Toner particle KB (black))
Toner particles CA, except that the black colorant dispersion was used instead of the cyan colorant dispersion, and the colorant dispersion addition amount was changed so that the colorant content in the toner particles was 8 parts by weight. In the same manner as in the production method, toner particles KB were obtained.

(Toner particle KC (black))
The black colorant dispersion was used in place of the cyan colorant dispersion, the holding time at 52 ° C. was adjusted so that the volume average particle size was 6.5 μm, and the colorant content in the toner particles was Toner particles KC were obtained in the same manner as in the production method of toner particles CA, except that the amount of the colorant dispersion added was changed to 10.3 parts by weight.

(Toner particle KD (black))
The black colorant dispersion was used instead of the cyan colorant dispersion, the holding time at 52 ° C. was adjusted so that the volume average particle diameter was 8.0 μm, and the colorant content in the toner particles was Toner particles KD were obtained in the same manner as in the production method of toner particles CA, except that the amount of the colorant dispersion added was changed to 10.3 parts by weight.

<Preparation of toner>
The first to fourth external additives are added in the addition amount shown in Table 1 with respect to 100 parts by weight of the toner particles shown in Table 1, and mixed with a Henschel mixer, and the cyan toners C1 to C7 and the yellow toners Y1 to Y1 are mixed. Y7, magenta toners M1 to M7 and black toners K1 to K6 were obtained.
Specifically, fatty acid metal salt (calcium stearate) particles having a volume average particle size of 4 μm were used as the first component of the external additive. As the second component, titania particles having a number average particle diameter of 3 Onm were hydrophobized with isobutyltrimethoxysilane. The degree of hydrophobicity was 55%. As a third component, silica particles (# 130; manufactured by Nippon Aerosil Co., Ltd.) having a number average particle diameter of 16 nm were hydrophobized with HMDS (hexamethyldisilazane). The degree of hydrophobicity was 80%. As the fourth component, strontium titanate particles having a number average particle diameter of 300 nm were used.
In addition, the external additive is mixed in a "two-stage mixing method" in which toner particles are mixed with fatty acid metal salts and titania particles for 3 minutes, and then silica particles and strontium titanate are added and mixed for 6 minutes. went. After the external addition treatment, each toner was obtained by sieving with a vibrating screen.

In the table, “colorant content” is a converted value of the colorant content relative to 100 parts by weight of the resin particles in the toner particles.
“StCa” indicates calcium stearate.
“Titast” refers to strontium titanate.

<Preparation of carrier>
Copolymer fine particles of styrene (St) / methyl methacrylate (MMA) = 4/6 (weight ratio) 70g, specific gravity 5.0, weight average particle diameter 35μm, saturation magnetization when applying an external magnetic field of 1000 Oersted is 62emu / g After putting 1930 g of Cu-Zn ferrite particles in a high-speed stirring type mixer and mixing for 15 minutes at a product temperature of 30 ° C, the product temperature was set to 105 ° C and mechanical impact force was repeatedly applied for 30 minutes and cooled. Created Career A. The coat amount (Rc) of this carrier is 3.5% by weight.

<Preparation of developer>
When using a toner having a particle diameter of 4.5 μm: 376 g of the carrier and 24 g of toner were mixed for 15 minutes in each test environment using a V-type mixer to prepare a developer for a live-action test.
When using toner having a particle diameter of 6.5 μm: 368 g of the carrier and 32 g of toner were mixed for 15 minutes in each test environment using a V-type mixer to prepare a developer for a live-action test.
When using a toner having a particle diameter of 8.0 μm: 360 g of the carrier and 40 g of the toner were mixed for 15 minutes in each test environment using a V-type mixer to prepare a developer for a live-action test.

<Evaluation conditions>
Using a developer containing toner shown in Table 2, a real-time evaluation of 5% / 100,000 BW ratio colors was performed using a modified Minolta CF3102 machine as an image forming apparatus. The main modification points and main conditions of the equipment are as follows.

In the developing unit, a regulating blade is provided on the upstream side of the developing region where the developing sleeve and the photosensitive member face each other in the developer transport direction, with a spacing between the developing sleeve and a required distance. The carrying amount is restricted to 130 g / m ² . The remodeling machine adds a control sequence such that the toner of the designated color is supplied to the intermediate transfer belt at a rate of 5 mg / time once every 10 sheets and is collected by the cleaner unit. In Example 7, toner was not supplied to the intermediate transfer belt once every 10 sheets. In each example / comparative example, the distance between the regulating blade and the developing sleeve was not changed for each color.

(Volume average particle diameter: toner and fatty acid metal salt)
These particle sizes were measured using Coulter Multisizer II.
(Circularity: Toner)
Using FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.), the sample analysis amount was 0.3 μl, and the number of detected particles was 1500 to 5000.

(Charge stability)
○ When the fluctuation range of the charge amount after printing 100,000 sheets with respect to the initial charge amount is less than 10μC / g, ○ when the variation range is 10μC / g or more and less than 20μC / g, and the variation range is 2OμC Those rated at / g or more were evaluated as x. The results are shown in Table 2.

(Transfer belt cleanability)
After passing 100,000 sheets, image noise (left unclean streaks due to chipping, filming, etc.) due to cleaning of the transfer belt portion was confirmed. ◎ no image noise caused by cleaning, image noise caused by cleaning cannot be discerned with the naked eye but can be discriminated with a loupe ○, image noise caused by cleaning can be discerned with the naked eye, but allowed as an image Evaluation was made with Δ for a possible level, and image noise caused by cleaning with a naked eye, and with an unacceptable level as an image. The results are shown in Table 2.

(Image quality)
Full-page halftone image was output in printer mode. Evaluate the halftone texture of the obtained halftone image and reproduce the fine and uniform halftone image ◎, which can hardly be discerned with the naked eye, but slightly rough due to graininess when viewed with a loupe ○ The evaluation was evaluated as Δ when the roughness due to graininess was discernable with the naked eye but acceptable as an image, and when the roughness due to graininess was severe with the naked eye and appeared as a rough image. The results are shown in Table 2.

In the table, “attachment amount” is the maximum attachment amount of each toner on the intermediate transfer belt.
“Patch” means toner supplied to the intermediate transfer belt for improving the cleaning property. “Y” indicates yellow toner.

  As is apparent from the above results, it can be seen that the examples of the present invention are superior to the comparative examples in terms of the effects of the present invention. It can also be seen that cleaning performance is improved by supplying toner to the intermediate transfer belt and collecting it at the cleaner.

It is a schematic sectional drawing which shows an example of the carrier coating apparatus relevant to this invention. 1 is an overall configuration diagram illustrating an example of an image forming apparatus employing a full-color image forming method of the present invention.

Explanation of symbols

1: upper lid, 2: raw material inlet, 3: back filter, 4: jacket, 5: thermometer, 6: stirring blade, 7: outlet, 8: horizontal rotating body, 9: mixing tank, 10: printer , 12: Intermediate transfer belt, 20Y: Imaging unit, 20M: Imaging unit, 20C: Imaging unit, 20K: Imaging unit.

Claims (7)

Forming a latent electrostatic image on the latent electrostatic image bearing member, developing a latent electrostatic image on the latent electrostatic image bearing member using a developer to form a toner image, and intermediate transferring the toner image; A full-color image is formed by performing a primary transfer process on the body for each toner color, forming a full-color toner image on the intermediate transfer body, performing a secondary transfer of the full-color toner image collectively to a transfer member, and fixing by heating and pressing. In the forming method,
As a developer, at least a developer composed of a magenta toner and a carrier, a developer composed of a cyan toner and a carrier, and a developer composed of a yellow toner and a carrier are used.
Each toner has a weight average particle diameter of 3 to 7 μm, and at least a fatty acid metal salt is externally added.
A full-color image forming method characterized in that there is a difference of 3 to 10 times between the toner having the highest content and the lowest content of the fatty acid metal salt. 2. The method according to claim 1, further comprising a step of blade cleaning the surface of the belt-shaped intermediate transfer member, and a step of supplying the toner having the highest fatty acid metal salt content to the intermediate transfer member and collecting the toner by blade cleaning. Full color image forming method.   3. The full-color image forming method according to claim 1, wherein the toner having the largest content of fatty acid metal salt is a yellow toner.   The full-color image forming method according to claim 1, wherein the carrier is a carrier manufactured by a dry method.   The full-color image forming method according to claim 1, wherein the fatty acid metal salt is calcium stearate.   The full-color image forming method according to claim 1, wherein the toner is produced by a resin particle agglomeration method. 7. The toner according to claim 1, wherein fatty acid metal salt particles and inorganic fine particles are externally added to the toner particles by a divided mixing method, and the fatty acid metal salt particles are externally added in the first stage. The full-color image forming method according to any one of the above.

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