JP4853324B2 - Image forming method, image forming apparatus, and toner cartridge - Google Patents

Description

  The present invention relates to an image forming method, an image forming apparatus, and a toner cartridge.

In the image formation by the electrophotographic method, the solid portion, the halftone portion, and the line portion are expressed by changing the dot density. Furthermore, an invention has been made to improve density reproducibility in a halftone highlight region by using a light color toner having a reduced pigment density in the toner. This system has a configuration of an image forming apparatus that additionally includes at least one kind of light color developer in addition to the YMCK color dark color developer.
On the other hand, an image forming apparatus using a dark color toner and a light color toner has been proposed in order to achieve both a high-quality highlight image and a reduction in toner consumption (see, for example, Patent Document 1).
JP 2004-317712 A

  SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming method, an image forming apparatus, and a toner cartridge that suppresses the wear of a photoconductor, has less image defects (background fog), and has high gradation reproducibility in a highlight area. To do.

The above-mentioned subject is achieved by the following present invention.
That is, the present invention
<1> A charging step for charging the surface of the image carrier, an electrostatic latent image forming step for forming an electrostatic latent image according to image information on the charged surface of the image carrier, and formation on the surface of the image carrier Developing the obtained electrostatic latent image with a toner containing dark toner to obtain a toner image, and transferring the toner image formed on the surface of the image carrier onto the surface of a recording medium; A fixing step of fixing the toner image transferred to the surface of the recording medium, a cleaning step of cleaning the surface of the image carrier after transferring the toner image, and a light color toner of the same color as the dark toner. A light-color toner supply step for supplying to the surface of the holding body, wherein the dark-color toner and the light-color toner have a relationship represented by the following formulas (1) and (2).
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02

<2> an image carrier, a charging unit that charges the surface of the image carrier, an electrostatic latent image forming unit that forms an electrostatic latent image according to image information on the charged surface of the image carrier, Developing means for obtaining the toner image by developing the electrostatic latent image formed on the surface of the image carrier with a toner containing dark toner, and the toner image formed on the surface of the image carrier on the surface of the recording medium A transfer unit for transferring, a fixing unit for fixing the toner image transferred to the surface of the recording medium, a cleaning unit for cleaning the surface of the image carrier after transferring the toner image, and a color similar to the dark toner. A light-color toner supply means for supplying the light-color toner to the surface of the image holding member, and the dark-color toner and the light-color toner have a relationship represented by the following formulas (1) and (2): It is.
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02

<3> Removably attached to the image forming apparatus, containing at least toner to be supplied to developing means provided in the image forming apparatus, wherein the toner includes dark toner and light color toner of similar colors, The toner cartridge is characterized in that the dark color toner and the light color toner have a relationship of the following formulas (1) and (2).
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02

  The present invention can provide an image forming method, an image forming apparatus, and a toner cartridge that suppress wear of a photoconductor, have few image defects (background fog), and have high gradation reproducibility in a highlight area.

The image forming method of the present invention includes a charging step of charging the surface of the image carrier, an electrostatic latent image forming step of forming an electrostatic latent image according to image information on the charged surface of the image carrier, and the image Developing the electrostatic latent image formed on the surface of the holding body with a toner containing dark toner to obtain a toner image, and transferring the toner image formed on the surface of the image holding body to the surface of the recording medium A transfer step for fixing, a fixing step for fixing the toner image transferred to the surface of the recording medium, a cleaning step for cleaning the surface of the image carrier after transferring the toner image, and a color of the same color as the dark color toner. And a light color toner supply step for supplying light color toner to the surface of the image carrier, wherein the dark color toner and the light color toner have a relationship of the following formulas (1) and (2).
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02

  The image forming apparatus of the present invention also includes an image carrier, a charging unit that charges the surface of the image carrier, and an electrostatic latent image that forms an electrostatic latent image according to image information on the charged surface of the image carrier. A latent image forming unit; a developing unit that develops the electrostatic latent image formed on the surface of the image carrier with a toner containing dark toner; and a toner image that is formed on the surface of the image carrier. Transfer means for transferring the toner image to the surface of the recording medium; fixing means for fixing the toner image transferred to the surface of the recording medium; cleaning means for cleaning the surface of the image carrier after transferring the toner image; A light color toner supply means for supplying a light color toner of the same color as the dark color toner to the surface of the image carrier, and the dark color toner and the light color toner have a relationship of the formulas (1) and (2). It is characterized by.

First, the toner used in the image forming method and the image forming apparatus of the present invention will be described.
The toner used in the present invention includes a dark color toner and a light color toner of similar colors, and the dark color toner and the light color toner have the relationship of the above formulas (1) and (2).
As used herein, the dark toner and the light toner are toner having a high image density when the toner amount on the recording medium is the same, and the toner having a low image density is a light toner. As a specific dark toner, when J paper (manufactured by FujiXerox) is used as the recording medium, the toner has an image density of 1.2 or more when the toner amount on the recording medium is 0.5 g / m ^2. The image density is more preferably 1.5 or more. As the light color toner, when J paper (manufactured by FujiXerox) is used as the recording medium, the image density when the toner amount on the recording medium is 0.5 g / m ² is preferably less than 1.2. More preferably, it is less than 0.0.
In addition, the similar color here means a yellow color, a magenta color, and a cyan color when a color space is expressed using three primary colors (yellow, magenta, cyan) of object color and black toner. Means a black color, and is not limited to the same exact color expression value (for example, the value of L ^* a ^* b ^{* in} the case of the CIElab expression system, the value of XYZ in the XYZ color system) .

  The toner used in the present invention satisfies the relationship of the above formula (1). That is, the difference obtained by subtracting the volume average particle size of the light color toner from the volume average particle size of the dark color toner (hereinafter sometimes referred to as “the difference in volume average particle size of the toner according to the present invention”) is 0.8 μm or more and 1 .5 μm or less. When the difference in volume average particle diameter of the toner according to the present invention is less than 0.8 μm, the wear of the image carrier is promoted. On the other hand, when the difference in volume average particle diameter of the toner according to the present invention exceeds 1.5 μm, fogging that is noticeable as an image defect occurs. The difference in volume average particle size of the toner according to the present invention is preferably 0.9 μm or more and 1.4 μm or less, and more preferably 1.0 μm or more and 1.2 μm or less.

Here, the volume average particle diameter of the toner is measured for at least 5000 toners using the FPIA-2100 manufactured by Sysmex under the conditions of HPF mode (high resolution mode) and dilution factor of 1.0. Ask for.
Sysmex FPIA-2100 employs a method in which particles dispersed in water or the like are measured by a flow image analysis method. The suctioned particle suspension is guided to a flat sheath flow cell, and is flattened by the sheath liquid. Form in the sample stream. By irradiating the sample stream with strobe light, the passing particles are imaged as a still image by the CCD camera through the objective lens. The captured particle image is subjected to two-dimensional image processing, and the equivalent circle diameter is calculated from the projected area and the perimeter. The equivalent circle diameter is calculated as the equivalent circle diameter from the area of the two-dimensional image for each photographed particle. The particles thus photographed are subjected to image analysis and statistical processing to determine the volume average particle diameter.

  Further, the toner used in the present invention satisfies the relationship of the above formula (2). That is, the difference obtained by subtracting the average circularity of the dark toner from the average circularity of the light-colored toner (hereinafter sometimes referred to as “difference in the average circularity of the toner according to the present invention”) is 0.01 or more and 0.02 or less. It is. When the difference in the average circularity of the toner according to the present invention is less than 0.01, the wear of the image carrier is promoted. On the other hand, if the difference in the average circularity of the toner according to the present invention exceeds 0.02, fog that stands out as an image defect occurs. The difference in average circularity of the toner according to the present invention is preferably 0.012 or more and 0.018 or less, and more preferably 0.014 or more and 0.016 or less.

Here, the average circularity of the toner is determined in the HPF mode (high resolution mode) by using FPIA-2100 manufactured by Sysmex for at least 5000 toners, as in the measurement of the volume average particle diameter of the toner. It is determined by measuring under the condition of a dilution factor of 1.0.
The average circularity of the toner was obtained by the following equation for each photographed particle. Similarly to the case of the volume average particle diameter of the toner, each image analysis was performed and statistical processing was performed to obtain the average circularity.
Circularity = circle equivalent diameter perimeter / perimeter = [2 × (A × π) ^1/2 ] / PM
(In the above formula, A represents the projected area and PM represents the perimeter.)

  The individual toners used in the present invention are not particularly limited as long as they have the relations of the above formulas (1) and (2), and known toners can be used. Examples of the toner include a colored toner having a binder resin and a colorant.

  Binder resins include monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, phenyl acrylate, octyl acrylate, and methacrylic acid. Α-methylene aliphatic monocarboxylic esters such as methyl, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; vinyl methyl ketone, vinyl hexyl ketone, vinyl Homopolymers or copolymers of vinyl ketones such as isopropenyl ketone; Among these, particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polystyrene, polypropylene, and the like. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin and the like.

  The crystalline binder resin is not particularly limited as long as it is a crystalline resin, and specific examples include crystalline polyester resins and crystalline vinyl resins. The crystalline polyester resin is preferable from the viewpoints of the properties and chargeability and the adjustment of the melting point within a preferable range. An aliphatic crystalline polyester resin having an appropriate melting point is more preferable.

  Examples of the crystalline vinyl resin include amyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, and decyl (meth) acrylate. , Undecyl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, oleyl (meth) acrylate, behenyl (meth) acrylate, etc. And vinyl resins using long-chain alkyl and alkenyl (meth) acrylic acid esters. In this specification, the description “(meth) acryl” means that both “acryl” and “methacryl” are included.

  On the other hand, the crystalline polyester resin is synthesized from an acid (dicarboxylic acid) component and an alcohol (diol) component. In the present invention, the “acid-derived component” refers to an acid before synthesis of the polyester resin. The component part which was a component is pointed out, and "alcohol-derived component component" indicates the component part which was an alcohol component before the synthesis of the polyester resin. In the present invention, the “crystalline polyester resin” refers to a resin having a clear endothermic peak instead of a stepwise endothermic amount change in differential scanning calorimetry (DSC). In the case of a polymer obtained by copolymerizing other components with respect to the crystalline polyester main chain, when the other components are 50% by mass or less, this copolymer is also called crystalline polyester.

-Acid-derived components-
The acid-derived constituent component is preferably an aliphatic dicarboxylic acid, and particularly preferably a linear carboxylic acid. Examples of the linear carboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10- Decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecane Dicarboxylic acid, etc., or lower alkyl esters and acid anhydrides thereof. Among these, those having 6 to 10 carbon atoms are preferable from the viewpoint of crystal melting point and chargeability. In order to increase the crystallinity, these linear dicarboxylic acids are preferably used in an amount of 95 mol% or more, more preferably 98 mol% or more of the acid component.

  The other monomer is not particularly limited. For example, a conventionally known divalent or carboxylic acid which is a monomer component as described in Polymer Data Handbook: Basics (Science of Polymer Science: Bafukan). And divalent alcohol. Specific examples of these monomer components include divalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, and cyclohexanedicarboxylic acid. And dibasic acids such as these, anhydrides thereof, and lower alkyl esters thereof. These may be used individually by 1 type and may use 2 or more types together.

As the acid-derived constituent component, in addition to the above-mentioned aliphatic dicarboxylic acid-derived constituent component, a constituent component such as a dicarboxylic acid-derived constituent component having a sulfonic acid group is preferably included.
The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a coloring material such as a pigment. Further, when emulsifying or suspending the entire resin in water to produce toner mother particles into fine particles, if there are sulfonic acid groups, emulsification or suspension is possible without using a surfactant, as will be described later. . Examples of such a dicarboxylic acid having a sulfone group include, but are not limited to, 2-sulfoterephthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, and sulfosuccinic acid sodium salt. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, 5-sulfoisophthalic acid sodium salt is preferable in terms of cost. The content of the dicarboxylic acid having a sulfonic acid group is preferably 0.1 to 2.0 mol%, and more preferably 0.2 to 1.0 mol%. When the content is more than 2 mol%, the chargeability is deteriorated. In the present invention, “component mol%” refers to a percentage when each component (acid-derived component, alcohol-derived component) in the polyester resin is 1 unit (mol).

-Alcohol-derived components-
The alcohol component is preferably an aliphatic dialcohol, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-dodecanediol, 1,12-undecanediol, 1,13-tridecanediol, 1,14-tetradecanediol 1,18-octadecanediol, 1,20-eicosanediol, and the like. Among them, those having 6 to 10 carbon atoms are preferable from the viewpoint of crystal melting point and chargeability. In order to enhance crystallinity, these linear dialcohols are preferably used in an amount of 95 mol% or more, more preferably 98 mol% or more of the alcohol constituent.

  Other divalent dialcohols include, for example, bisphenol A, hydrogenated bisphenol A, ethylene oxide or (and) propylene oxide adducts of bisphenol A, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, Examples include propylene glycol, dipropylene glycol, 1,3-butanediol, and neopentyl glycol. These may be used individually by 1 type and may use 2 or more types together.

  If necessary, monovalent acids such as acetic acid and benzoic acid, monovalent alcohols such as cyclohexanol and benzyl alcohol, benzenetricarboxylic acid, and naphthalenetricarboxylic acid for the purpose of adjusting the acid value and hydroxyl value. Trivalent alcohols such as acids and the like, anhydrides thereof, lower alkyl esters thereof, glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol can also be used.

  The polyester resin can be used in any combination of the monomer components described above, for example, polycondensation (chemical doujin), polymer experiment (polycondensation and polyaddition: Kyoritsu Publishing) and polyester resin handbook (edited by Nikkan Kogyo Shimbun). And the like, and a transesterification method, a direct polycondensation method, and the like can be used alone or in combination. The molar ratio (acid component / alcohol component) when the acid component and the alcohol component are reacted varies depending on the reaction conditions and the like, so it cannot be generally stated, but in the case of direct polycondensation, usually about 1/1. In the case of the transesterification method, ethylene glycol, neopentyl glycol, cyclohexanedimethanol, etc. are often used in excess of monomers that can be distilled off under vacuum. The production of the polyester resin is usually performed at a polymerization temperature of 180 to 250 ° C., and the reaction system is subjected to a reaction while reducing the pressure in the reaction system as necessary to remove water and alcohol generated during the condensation. When the monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. In the polycondensation reaction, the dissolution auxiliary solvent is distilled off. If there is a monomer with poor compatibility in the copolymerization reaction, the monomer with poor compatibility and the monomer and the acid or alcohol to be polycondensed may be condensed in advance before polycondensation with the main component. .

  Catalysts that can be used in the production of the polyester resin include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, and metal compounds such as zinc, manganese, antimony, titanium, tin, zirconium, and germanium. , Phosphorous acid compounds, phosphoric acid compounds, amine compounds, etc., specifically, sodium acetate, sodium carbonate, lithium acetate, lithium carbonate, calcium acetate, calcium stearate, magnesium acetate, zinc acetate, stearic acid Zinc, zinc naphthenate, zinc chloride, manganese acetate, manganese naphthenate, titanium tetraethoxide, titanium tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, antimony trioxide, triphenylantimony, trib Ruantimony, tin formate, tin oxalate, tetraphenyltin, dibutyltin dichloride, dibutyltin oxide, diphenyltin oxide, zirconium tetrabutoxide, zirconium naphthenate, zirconyl carbonate, zirconyl acetate, zirconyl stearate, zirconyl octylate, germanium oxide, triphenyl Examples of the compound include phosphite, tris (2,4-di-t-butylphenyl) phosphite, ethyltriphenylphosphonium bromide, triethylamine, and triphenylamine. Among these, a tin-based catalyst and a titanium-based catalyst are preferable from the viewpoint of chargeability, and among them, dibutyltin oxide is preferably used.

  The melting point of the crystalline polyester resin of the present invention is 50 to 120 ° C, preferably 60 to 110 ° C. When the melting point is lower than 50 ° C., the storage stability of the toner and the storage stability of the toner image after fixing become a problem. On the other hand, when the temperature is higher than 120 ° C., sufficient low-temperature fixing cannot be obtained as compared with the conventional toner.

  In the present invention, the melting point of the crystalline polyester resin is measured according to JIS K when a differential scanning calorimeter (DSC) is used and measured from room temperature to 150 ° C. at a heating rate of 10 ° C. per minute. It can be obtained as the melting peak temperature of the input compensation differential scanning calorimetry shown in −7121. The crystalline resin may show a plurality of melting peaks, but in the present invention, the maximum peak is regarded as the melting point.

  The colorant is not particularly limited. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, deyupon oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, pigment blue 15: 3, and the like.

The content in the dark toner varies depending on the type of the colorant, but is preferably 3.0% by mass or more and 12.0% by mass or less. Specifically, when PB15: 3 is used as the colorant, the content is preferably 4.0% by mass or more and 7.0% by mass or less.
On the other hand, the content in the light color toner varies depending on the kind of the colorant, but is preferably 0.1% by mass or more and 6.0% by mass or less. Specifically, when PB15: 3 is used as the colorant, the content is preferably 0.2% by mass or more and 1.0% by mass or less.

  The dark color toner and the light color toner are similar colors, and it is preferable to use the same colorant. However, if the above-mentioned definition of the similar color is satisfied, the dark color toner and the light color toner may use different colorants. Well, in this case, as a combination of pigment types, when the content of the colorant in the toner is the same and the amount of toner on the recording medium is the same, the formula difference ΔE in CIElab expression is 30 or less, preferably 10 or less. The pigments can be combined so that

The toner used in the present invention may be used alone (one-component developer) or may be used as a two-component developer together with a carrier. In the case of a one-component developer, a toner containing magnetic metal fine particles is used.
For example, in the case of using a carrier, the carrier is not particularly limited, and examples thereof include known carriers. For example, resins described in JP-A Nos. 62-39879 and 56-11461 are disclosed. Known carriers such as a coated carrier can be used.
Specific examples of the carrier include the following resin-coated carriers. Examples of the carrier core particles include normal iron powder, ferrite, and magnetite molding, and the volume average particle size is in the range of about 30 to 200 μm.

  Examples of the coating resin for the resin-coated carrier include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, acrylic acid 2 -Α-methylene fatty acid monocarboxylic acids such as ethylhexyl, methyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; nitrogen-containing acrylics such as dimethylaminoethyl methacrylate; acrylonitrile, methacrylonitrile, etc. Vinyl nitriles; vinyl pyridines such as 2-vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl Homopolymers such as vinyl ketones such as ketones; olefins such as ethylene and propylene; vinyl-based fluorine-containing monomers such as vinylidene fluoride, tetrafluoroethylene and hexafluoroethylene; and copolymers composed of two or more types of monomers Furthermore, silicone resins containing methyl silicone, methyl phenyl silicone, etc., polyesters containing bisphenol, glycol, etc., epoxy resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, polycarbonate resins and the like can be mentioned. These resins may be used alone or in combination of two or more. The coating amount of the coating resin is preferably in the range of about 0.1 to 10 parts by mass and more preferably in the range of 0.5 to 3.0 parts by mass with respect to 100 parts by mass of the core particles.

For the production of the carrier, a heating kneader, a heating Henschel mixer, a UM mixer, or the like can be used. Depending on the amount of the coating resin, a heating fluidized rolling bed, a heating kiln, or the like can be used. .
The mixing ratio of the electrostatic latent image developing toner of the present invention and the carrier in the electrostatic latent image developer is not particularly limited and can be appropriately selected according to the purpose.

The image forming apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of an image forming apparatus according to the present invention, which shows a so-called tandem type image forming apparatus.
In FIG. 1, 21 is a main body housing, 22a to 22h are image forming engines, 23 is a belt module, 24 is a recording medium supply cassette, 25 is a recording medium conveyance path, 30 is each photosensitive unit, and 31 is a photosensitive drum (image). Holder), 32 is a charging device (charging means), 33 is each developing unit (developing means), 34 is a cleaning device (cleaning means), 35a to 35h are toner cartridges, 40 is an exposure unit, 41 is a unit case, 42 is a polygon mirror, 51 is a primary transfer device (transfer means), 52 is a secondary transfer device (transfer means), 53 is a belt cleaning device, 61 is a feed roll, 62 is a takeaway roll, 63 is a resist roll, and 66 is Fixing device (fixing means), 67 is a discharge roll, 68 is a discharge section, 71 is a manual feed device, and 72 is a feed roll. 73 double-sided recording unit, the guide rolls 74, the conveying path 76, 77 transport roll, 230 is an intermediate transfer belt, 231 and 232 tension roller, 521 is a secondary transfer roll, 531 denotes a cleaning blade.

  The tandem type image forming apparatus shown in FIG. 1 has eight types of developers (developers including dark color toners and light color toners of similar colors for black, yellow, magenta, and cyan in this example) in the main body housing 21. The image forming engines (specifically 22a to 22h) are arranged in the horizontal direction, and a belt module 23 including an intermediate transfer belt 230 that is circulated and conveyed along the arrangement direction of the respective image forming engines is disposed above the image forming engines. On the other hand, a recording medium supply cassette 24 that accommodates a recording medium (not shown) such as paper is disposed below the main body housing 21, and serves as a conveyance path for the recording medium from the recording medium supply cassette 24. The recording medium conveyance path 25 is arranged in the vertical direction.

In the tandem type image forming apparatus shown in FIG. 1, each image forming engine (22 a to 22 h) is, for example, for black (dark color, light color) and yellow (dark color, light color) sequentially from the upstream side in the circulation direction of the intermediate transfer belt 230. ), Magenta (dark color, light color), and cyan (dark color, light color) toner images (arrangement is not necessarily in this order). The unit 33 and one common exposure unit (electrostatic latent image forming means) 40 are provided.
Here, the photosensitive unit 30 includes, for example, a photosensitive drum (image carrier) 31, a charging device 32 that precharges the photosensitive drum 31, and a cleaning device (cleaning) that removes residual toner on the photosensitive drum 31. (Means) 34 is integrated into a sub-cartridge.

The developing unit 33 develops the electrostatic latent image exposed and formed by the exposure unit 40 on the charged photosensitive drum 31 with a corresponding color toner (for example, negative polarity in the present embodiment). For example, a process cartridge (so-called CRU: Customer Replaceable Unit) is configured by being integrated with a sub-cartridge including the photosensitive unit 30.
Of course, the photoconductor unit 30 may be separated from the developing unit 33 to form a single CRU. In FIG. 1, reference numerals 35a to 35h denote toner cartridges for replenishing each developing unit 33 with each color component toner (the toner used in the present invention described above) (toner replenishment path is not shown).

  On the other hand, the exposure unit 40 includes, for example, four semiconductor lasers (not shown), one polygon mirror 42, an imaging lens (not shown), and respective mirrors (corresponding to the respective photoreceptor units 30) in a unit case 41. (Not shown), the light from the semiconductor laser for each color component is deflected and scanned by the polygon mirror 42, and the light image is guided to the exposure point on the corresponding photosensitive drum 31 through the imaging lens and mirror. It is a thing.

  In the tandem type image forming apparatus shown in FIG. 1, the belt module 23 is formed by, for example, an intermediate transfer belt 230 spanned between a pair of tension rolls (one is a drive roll) 231, 232, and each photoconductor. A primary transfer device (primary transfer roll in this example) 51 is disposed on the back surface of the intermediate transfer belt 230 corresponding to the photosensitive drum 31 of the unit 30, and a voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer device 51. Is applied to electrostatically transfer the toner image on the photosensitive drum 31 to the intermediate transfer belt 230 side. Further, a secondary transfer device 52 is disposed at a portion corresponding to the tension roll 232 on the downstream side of the most downstream image forming engine 22d of the intermediate transfer belt 230, and the primary transfer image on the intermediate transfer belt 230 is recorded. Secondary transfer (collective transfer) is performed on the medium.

In the tandem type image forming apparatus shown in FIG. 1, the secondary transfer device 52 is disposed on the back surface side of the intermediate transfer belt 230 and the secondary transfer roll 521 disposed in pressure contact with the toner image holding surface side of the intermediate transfer belt 230. And a backup roll (also serving as a stretching roll 232 in FIG. 1) that constitutes a counter electrode of the secondary transfer roll 521. For example, the secondary transfer roll 521 is grounded, and a bias having the same polarity as the charging polarity of the toner is applied to the backup roll (stretching roll 232).
Furthermore, a belt cleaning device 53 is disposed on the upstream side of the most upstream image forming engine 22a of the intermediate transfer belt 230 so as to remove residual toner on the intermediate transfer belt 230.

  The recording medium supply cassette 24 is provided with a feed roll 61 for picking up the recording medium. A takeaway roll 62 for feeding the recording medium is disposed immediately after the feed roll 61, and a secondary transfer site is also provided. A registration roll (registration roll) 63 for supplying the recording medium to the secondary transfer portion at a predetermined timing is disposed in the recording medium conveyance path 25 positioned immediately before. On the other hand, a fixing device 66 is provided in the recording medium conveyance path 25 located on the downstream side of the secondary transfer site, and a discharge roll 67 for discharging the recording medium is provided on the downstream side of the fixing device 66. A discharge recording medium is accommodated in a discharge portion 68 formed in the upper portion of the housing 21.

Further, in the tandem type image forming apparatus shown in FIG. 1, a manual feeding device (MSI) 71 is provided on the side of the main body housing 21, and the recording medium on the manual feeding device 71 is a feed roll 72 and a takeaway. The roll 62 is sent out toward the recording medium conveyance path 25.
Furthermore, the main body housing 21 is provided with a double-sided recording unit 73. The double-sided recording unit 73 discharges the recording medium on which single-sided recording has been performed when the double-sided mode in which image recording is performed on both sides of the recording medium is selected. 67 is reversed and taken in by the guide roll 74 in front of the entrance, the recording medium is conveyed along the recording medium return conveyance path 76 by an appropriate number of conveyance rolls 77, and again toward the registration roll 63 side. And supply.

  In addition, the image forming apparatus of the present invention includes a light color toner supply unit. The light color toner supply means is used in a light color toner supply process to be described later. Even when the developing unit 33 is not used for forming a toner image, the light color toner supply means is supplied to the surface of the photosensitive drum 31. Function as. By making this light color toner supply means function, it is possible to suppress wear of the photosensitive drum 31 and reduce image defects (background fog) while maintaining gradation reproducibility in a high highlight area.

Next, the image forming method of the present invention will be described with reference to FIG.
First, in each image forming engine (22a to 22h), as the photosensitive drum 31 rotates, the surface of the photosensitive drum 31 is uniformly charged by the charging device 32 (charging process), and is uniformly charged by the exposure unit 40. An electrostatic latent image corresponding to image information of each color is formed on the surface of the photosensitive drum 31 (electrostatic latent image forming step), and the electrostatic latent image is formed on the surface of the photosensitive drum 31 on which the electrostatic latent image is formed. A toner image is formed (developed) by supplying the toner used in the present invention described above from the developing unit 33 according to the color information (developing step).

Next, the toner image formed on the photosensitive drum 31 is applied to the primary transfer device 51 by a power source (not shown) so that the toner image on the photosensitive drum 31 is reversed. It is electrostatically transferred to the intermediate transfer belt 230 side. Further, a primary transfer image on the intermediate transfer belt 230 is secondarily transferred (collectively transferred) to the recording medium by applying a voltage having a polarity opposite to the toner charging polarity to the secondary transfer device 52 from a power source (not shown). (Transfer process).
The recording medium having the toner image transferred onto the surface in this way passes through the fixing device 66, and the toner image is fixed on the surface of the recording medium (fixing step) to form an image.

  On the other hand, the surface of the photosensitive drum 31 on which the toner image is transferred to the intermediate transfer belt 230 is neutralized by irradiating light from a neutralizing lamp (not shown), and the toner remaining on the surface is further cleaned by the cleaning device 34. (Cleaning process).

  When an image is formed as described above, light text toner consumption is extremely reduced with respect to the amount of dark color toner used when continuously printing a text with a lot of line / solid portions. When the amount of toner consumption is small, the amount of toner supplied to the cleaning device 34 for the photosensitive drum 31 is reduced, the wear of the photosensitive drum 31 is promoted, and the life of the photosensitive drum 31 is shortened. That is, the life of the light-sensitive toner drum 31 that consumes less toner is shortened.

  Therefore, the image forming method of the present invention supplies light color toner to the surface of the photosensitive drum 31 even when it is not used to form a toner image (light color toner supply step). As a result, a fog on the photosensitive drum 31 is generated by the light color toner, and the toner is supplied to the cleaning device 34, and the supplied toner becomes a lubricant. As a result, the frictional force between the photosensitive drum 31 and the cleaning device 34 is reduced, and wear of the photosensitive drum 31 is suppressed. Further, since the density of the light color toner is low, even if the photosensitive member fog is positively generated, it does not stand out as an image defect.

In particular, since the image forming method of the present invention uses the dark color toner and the light color toner having the relationship of the above formulas (1) and (2) as described above, the gradation reproducibility in the high highlight region is improved. While maintaining, it is possible to suppress wear of the photosensitive drum 31 and reduce image defects (background fog).
The amount of light color toner supplied to the photosensitive drum 31 in the light color toner supply step varies depending on the density of the light color toner, but is preferably 4.0 g / m ² or more and 7.0 g / m ² or less.

Further, in the present invention, even when the light color toner is not used for the formation of the toner image, the light color toner developing process generates fog in the light color toner developing process as compared with the dark color toner developing process. Conditions that are easy to cause are preferable. Specifically, the distance between the light-colored toner developing sleeve and the light-colored toner photosensitive drum disposed in the light-colored toner developing unit is in the range of 100 to 500 μm, and the dark-colored toner developing sleeve and the dark-colored toner photosensitive It is preferable to set the distance smaller than the distance to the body drum. In the case of a two-component developer, the developer amount on the light-colored toner developing sleeve disposed in the light-colored toner developing unit is within the range of 300 to 600 g / m ² and is on the dark-colored toner developing sleeve. It is preferable to set a larger amount than the developer amount.

<Toner cartridge>
Next, the toner cartridge of the present invention will be described. The toner cartridge of the present invention is detachably attached to the image forming apparatus, and stores at least toner to be supplied to a developing unit provided in the image forming apparatus. ) And (2), a dark color toner and a light color toner.

  Accordingly, in the image forming apparatus having a configuration in which the toner cartridge can be attached and detached, the photosensitive drum is maintained while maintaining the gradation reproducibility in the high highlight region by using the toner cartridge containing the toner of the present invention. 31 wear can be suppressed.

  In addition, in an image forming apparatus having a configuration in which a toner cartridge can be attached and detached, a toner cartridge containing a dark toner and a light toner having the relationship of the above formulas (1) and (2) is used. While maintaining the gradation reproducibility of the light region, it is possible to suppress wear of the photosensitive drum 31 and reduce image defects (background fog).

The following description will be given with reference to examples and comparative examples. However, the present invention is not limited to the following examples and comparative examples. In the following examples, “part” means “part by mass” and “%” means “mass%” unless otherwise specified.
(Production of toner)
[Preparation of resin dispersion]
-Production of crystalline resin (1)-
In a three-necked flask, 100 parts of dimethyl decanoate, 75 parts of 1,9-nonanediol, and 0.08 part of dibutyltin oxide are reacted at 180 ° C. for 8 hours in a nitrogen atmosphere. During the reaction, generated water was removed out of the system. Thereafter, while gradually reducing the pressure, the temperature was raised to 230 ° C., and the reaction was performed for 7 hours, followed by cooling to obtain a crystalline resin (1). The weight average molecular weight of the crystalline resin (1) was 22500.

-Preparation of non-crystalline resin (2)-
In a three-necked flask, 123 parts of dimethyl terephthalate, 61 parts of dimethyl isophthalate, 157 parts of bisphenol A ethylene oxide adduct, 171 parts of bisphenol A propylene oxide adduct, 14 parts dodecenyl succinic acid, and 0.25 parts dibutyltin oxide are added under a nitrogen atmosphere. At 180 ° C. for 3 hours. During the reaction, generated water was removed out of the system. Thereafter, while gradually reducing the pressure, the temperature was raised to 240 ° C. and reacted for 2 hours, followed by cooling to obtain an amorphous resin (2). The weight average molecular weight of the amorphous resin (2) was 18,200.

-Preparation of resin dispersion (1)-
・ Crystalline resin (1): 10 parts ・ Amorphous resin (2): 94 parts ・ Methyl ethyl ketone: 40 parts ・ Isopropyl alcohol: 22 parts Heat the mixture to 60 ° C. with stirring. After the resin is dissolved, 28 parts of a 10% aqueous ammonia solution is added. Further, 400 parts of ion-exchanged water was gradually added to carry out phase inversion emulsification, and after removing the solvent, the solid concentration was adjusted to 25% to obtain a resin dispersion (1). The volume average diameter of the resin fine particles in the resin dispersion (1) was 124 nm. Furthermore, ion-exchanged water was added so that the solid content concentration in the dispersion was 10%.

-Preparation of resin dispersion (2)-
-Styrene: 316 parts-n-butyl acrylate: 84 parts-Acrylic acid: 6 parts-Dodecanethiol: 6 parts-Carbon tetrabromide: 4 parts Emulsifier in a flask in 6 parts of a non-ionic agent (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) and 10 parts of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) While being dispersed and slowly mixed for 20 minutes, 50 parts of ion-exchanged water having 4 parts of ammonium persulfate dissolved therein was added thereto. After carrying out nitrogen substitution, while stirring the inside of the flask, it was heated in an oil bath until the contents reached 83 ° C., and emulsion polymerization was continued for 7 hours. Moreover, ion-exchanged water was added so that the solid content concentration in the dispersion was 10%. As a result, a resin dispersion (2) was obtained in which resin particles having an average particle diameter of 225 nm, a glass transition temperature (Tg) of 54.0 ° C., and a weight average molecular weight of 33300 were dispersed.

-Preparation of resin dispersion (3)-
・ Styrene: 330 parts ・ n-butyl acrylate: 70 parts ・ Acrylic acid: 6 parts ・ Dodecanethiol: 5 parts ・ Carbon tetrabromide: 4 parts Emulsified in a flask in 6 parts of a non-ionic agent (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) and 10 parts of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) in 550 parts of ion-exchanged water. While being dispersed and slowly mixed for 20 minutes, 50 parts of ion-exchanged water having 4 parts of ammonium persulfate dissolved therein was added thereto. After carrying out nitrogen substitution, the inside of the flask was stirred and heated in an oil bath until the content reached 80 ° C., and emulsion polymerization was continued for 5 hours. Moreover, ion-exchanged water was added so that the solid content concentration in the dispersion was 10%. As a result, a resin dispersion (3) in which resin particles having an average particle diameter of 185 nm, a glass transition temperature (Tg) of 62.3 ° C., and a weight average molecular weight of 47200 was dispersed was obtained.

-Preparation of resin dispersion (4)-
・ Styrene: 290 parts ・ n-butyl acrylate: 110 parts ・ Acrylic acid: 6 parts ・ Dodecanethiol: 6 parts ・ Carbon tetrabromide: 4 parts Emulsified in a flask in 6 parts of a non-ionic agent (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) and 10 parts of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) in 550 parts of ion-exchanged water. While being dispersed and slowly mixed for 20 minutes, 50 parts of ion-exchanged water having 4 parts of ammonium persulfate dissolved therein was added thereto. After carrying out nitrogen substitution, the inside of the flask was stirred and heated in an oil bath until the content reached 80 ° C., and emulsion polymerization was continued for 5 hours. Moreover, ion-exchanged water was added so that the solid content concentration in the dispersion was 10%. As a result, a resin dispersion (4) was obtained in which resin particles having an average particle diameter of 125 nm, a glass transition temperature (Tg) of 48.1 ° C., and a weight average molecular weight of 32500 were dispersed.

-Preparation of colored dispersion (1)-
-Cyan pigment (CI Pigment Blue B15: 3): 70 parts-Nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.): 5 parts-Ion-exchanged water: 200 parts And then dispersed for 10 minutes using a homogenizer (Ultra Turrax T50: manufactured by IKA). Further, ion-exchanged water was added so that the solid content concentration in the dispersion was 10%, and a color dispersant (1) in which colorant (Cyan pigment) particles having an average particle diameter of 190 nm were dispersed was prepared.

-Preparation of colored dispersion (2)-
-Magenta pigment (CI Pigment Red 122): 70 parts-Nonionic surfactant (Nonipol 400: manufactured by Sanyo Kasei Co., Ltd.): 5 parts-Ion-exchanged water: 200 parts It melt | dissolved and it disperse | distributed for 10 minutes using the homogenizer (Ultra Tlux Luxe: the product made by IKA). Furthermore, ion-exchange water was added so that the solid content concentration in the dispersion was 10%, and a color dispersant (2) in which colorant (Magenta pigment) particles having an average particle size of 210 nm were dispersed was prepared.

-Preparation of colored dispersion (3)-
Magenta pigment was added to C.I. I. A colored dispersion liquid (3) was prepared in the same manner as the colored dispersion liquid (3) except that it was changed to Pigment Red 202.

-Preparation of release agent dispersion (1)-
Paraffin wax (HNP0190: manufactured by Nippon Seiwa Co., Ltd., melting point: 85 ° C.): 50 parts Cationic surfactant (Sanisol B50: manufactured by Kao Corporation): 5 parts Ion-exchanged water: 200 parts or more The components were dispersed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA) for 10 minutes, and then dispersed with a pressure discharge type homogenizer. Furthermore, ion-exchange water was added so that the solid content concentration in the dispersion was 10% to prepare a release agent dispersion (1) in which release agent particles having an average particle diameter of 160 nm were dispersed.

-Toner mother particles (1) Production of concentrated cyan toner mother particles-
Resin dispersion (2): 670 parts Colorant dispersion (1): 50 parts Mold release dispersion (1): 80 parts Cationic surfactant (Sanisol B50: manufactured by Kao Corporation): 1 .5 parts The above components were mixed and dispersed in a round stainless steel flask using Ultra Turrax T50 (manufactured by IKA), and the temperature was raised to 48 ° C. over 200 minutes while stirring the flask in an oil bath for heating. The temperature was further raised to 52 ° C. over 100 minutes. Add 300 parts of the resin dispersion (2) at 52 ° C., leave it for 15 minutes, add 3 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 96 ° C. with continued stirring and held at 96 ° C. for 4 hours. After cooling, it was filtered, washed thoroughly with ion-exchanged water, and dried to obtain toner mother particles (1) that are dark cyan toner mother particles.

-Toner mother particles (2) Production of light cyan toner mother particles-
-Resin dispersion (4) 714 parts-Colorant dispersion (1) 6 parts-Mold release dispersion (1) 80 parts-Cationic surfactant 1.5 parts (Sanisol B50: manufactured by Kao Corporation)
The above ingredients were mixed and dispersed in a round stainless steel flask with Ultra Turrax T50 (manufactured by IKA), and then heated to 45 ° C. over 180 minutes while stirring the flask in an oil bath for heating, and further 120 minutes. Over 45 ° C. Add 300 parts of the resin dispersion (2) at 45 ° C., leave it for 60 minutes, add 3 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 94 ° C. with continued stirring and held at 94 ° C. for 6 hours. After cooling, the mixture was filtered, sufficiently washed with ion exchange water, and dried to obtain toner mother particles (2) which are light cyan toner mother particles.

-Toner mother particles (3) Production of light cyan toner mother particles-
Resin dispersion (3): 714 parts Colorant dispersion (1): 6 parts Mold release dispersion (1): 80 parts Cationic surfactant: 1.5 parts (Sanisol B50: Kao Corporation ) Made)
After mixing and dispersing the above components in a round stainless steel flask using Ultra Tarrax T50 (manufactured by IKA), the temperature was raised to 54 ° C. over 100 minutes while stirring the flask in an oil bath for heating. The temperature was raised to 60 ° C. over 120 minutes. Add 300 parts of the resin dispersion (4) at 60 ° C., leave it for 30 minutes, add 4 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. The mixture was heated to 96 ° C. with continued stirring and held at 96 ° C. for 8 hours. After cooling, the mixture was filtered, washed thoroughly with ion-exchanged water, and dried to obtain toner mother particles (3) that were light cyan toner mother particles.

-Toner mother particles (4): Production of light cyan toner mother particles-
Resin dispersion (2): 714 parts Colorant dispersion (1): 6 parts Mold release dispersion (1): 80 parts Cationic surfactant: 1.5 parts (Sanisol B50: Kao Corporation ) Made)
The above components were mixed and dispersed in a round stainless steel flask using Ultra Turrax T50 (manufactured by IKA), then heated to 43 ° C. over 100 minutes while stirring the flask in a heating oil bath, and further 120 minutes. Over 45 ° C. Add 300 parts of the resin dispersion (4) at 45 ° C. and leave it for 10 minutes, then add 3 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 96 ° C. with continued stirring and held at 96 ° C. for 7 hours. After cooling, the mixture was filtered, sufficiently washed with ion exchange water, and dried to obtain toner mother particles (4) which are light cyan toner mother particles.

-Toner mother particles (5) Production of light cyan toner mother particles-
Resin dispersion (3): 714 parts Colorant dispersion (1): 6 parts Mold release dispersion (1): 80 parts Cationic surfactant: 1.5 parts (Sanisol B50: Kao Corporation ) Made)
The above components were mixed and dispersed in a round stainless steel flask using Ultra Turrax T50 (manufactured by IKA), then heated to 55 ° C. over 100 minutes while stirring the flask in a heating oil bath, and further 120 minutes. The temperature was raised to 58 ° C. At 58 ° C, add 300 parts of resin dispersion (3), leave it for 60 minutes, add 3 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 98 ° C. with continued stirring and held at 98 ° C. for 7 hours. After cooling, the mixture was filtered, sufficiently washed with ion exchange water, and dried to obtain toner mother particles (4) which are light cyan toner mother particles.

-Toner mother particles (6) Production of light cyan toner mother particles-
Resin dispersion (3): 714 parts Colorant dispersion (1): 6 parts Mold release dispersion (1): 80 parts Cationic surfactant: 1.5 parts (Sanisol B50: Kao Corporation ) Made)
The above components were mixed and dispersed in a round stainless steel flask using Ultra Turrax T50 (manufactured by IKA), and then heated to 48 ° C. over 100 minutes while stirring the flask in a heating oil bath, and further 120 minutes. The temperature was raised to 50 ° C. Add 300 parts of the resin dispersion (2) at 50 ° C., leave it for 30 minutes, add 4 parts of an anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 96 ° C. with continued stirring and held at 96 ° C. for 12 hours. After cooling, the mixture was filtered, sufficiently washed with ion exchange water, and dried to obtain toner mother particles (6) as light cyan toner mother particles.

-Toner mother particles (7) Production of light cyan toner mother particles-
Resin dispersion (4): 714 parts Colorant dispersion (1): 6 parts Mold release dispersion (1): 80 parts Cationic surfactant: 1.5 parts (Sanisol B50: Kao Corporation ) Made)
The above ingredients were mixed and dispersed in a round stainless steel flask with Ultra Turrax T50 (IKA), and then heated to 45 ° C. over 100 minutes while stirring the flask in a heating oil bath, and further 120 minutes. The temperature was raised to 47 ° C. Add 300 parts of the resin dispersion (2) at 47 ° C., leave it for 120 minutes, add 4 parts of anionic surfactant (Neogen RK, Daiichi Kogyo Seiyaku), seal the stainless steel flask, and seal the magnetic force. Used and heated to 94 ° C. with continued stirring and held at 94 ° C. for 4 hours. After cooling, the mixture was filtered, sufficiently washed with ion exchange water, and dried to obtain toner mother particles (7) which are light cyan toner mother particles.

-Toner base particles (8) Production of concentrated Magenta toner base particles-
-Resin dispersion (1): 680 parts-Colorant dispersion (2): 80 parts-Release agent dispersion (1): 80 parts-Cationic surfactant (manufactured by Kao Corporation: Sanisol B50): 1 .5 parts The above components are contained in a round stainless steel flask, 0.1N sulfuric acid is added to adjust the pH to 3.5, and the concentration of polyaluminum chloride as a flocculant is 10% by weight. 30 parts of an aqueous nitric acid solution was added. Thereafter, the mixture was dispersed at 30 ° C. using a homogenizer (manufactured by IKA, Ultra Turrax T50), and then heated to 45 ° C. in an oil bath for heating. After maintaining the obtained particle dispersion at 45 ° C. for 30 minutes, 260 parts of the resin dispersion (1) is gradually added and maintained for 1 hour, and 0.1 N sodium hydroxide is added to adjust the pH to 8. After adjusting to 5, the mixture was heated to 85 ° C. while continuing stirring, and held for 5 hours. Thereafter, it is cooled to 20 ° C. at a rate of 20 ° C./min, cooled, filtered, sufficiently washed with ion-exchanged water, and dried to obtain toner mother particles (8) that are concentrated Magenta toner mother particles. Obtained.

-Toner mother particles (9) Production of light Magenta toner mother particles-
Resin dispersion (1): 750 parts Colorant dispersion (2): 10 parts Release agent dispersion (1): 80 parts Cationic surfactant (manufactured by Kao Corporation: Sanizol B50): 1 .5 parts The above components are contained in a round stainless steel flask, 0.1N sulfuric acid is added to adjust the pH to 3.5, and the concentration of polyaluminum chloride as a flocculant is 10% by weight. 30 parts of an aqueous nitric acid solution was added. Thereafter, the mixture was dispersed at 30 ° C. using a homogenizer (manufactured by IKA, Ultra Turrax T50), and then heated to 43 ° C. in an oil bath for heating. After the obtained particle dispersion is kept at 43 ° C. for 40 minutes, 260 parts of the resin dispersion (1) is gradually added and kept for 1 hour, and 0.1 N sodium hydroxide is added to adjust the pH to 8. After adjusting to 5, the mixture was heated to 90 ° C. while continuing stirring, and held for 5 hours. Thereafter, it is cooled to 20 ° C. at a rate of 20 ° C./min, cooled, filtered, sufficiently washed with ion-exchanged water, and dried to obtain toner mother particles (9) that are light Magenta toner mother particles. Obtained.

-Toner mother particles (10) Production of light Magenta toner mother particles-
Resin dispersion (1): 750 parts Colorant dispersion (2): 5 parts Colorant dispersion (2): 5 parts Release agent dispersion (1): 80 parts Cationic surfactant ( Kao Co., Ltd .: Sanizol B50): 1.5 parts The above components were placed in a round stainless steel flask, and 0.1 N sulfuric acid was added to adjust the pH to 3.5. As a solution, 30 parts of an aqueous nitric acid solution having a polyaluminum chloride concentration of 10% by weight was added. Thereafter, the mixture was dispersed at 30 ° C. using a homogenizer (manufactured by IKA, Ultra Turrax T50), and then heated to 40 ° C. in an oil bath for heating. After the obtained particle dispersion is kept at 40 ° C. for 10 minutes, 260 parts of the resin dispersion (1) is gradually added and kept for 1 hour, and 0.1 N sodium hydroxide is added to adjust the pH to 8. After adjusting to 5, the mixture was heated to 85 ° C. while continuing stirring and held for 3 hours. Thereafter, it is cooled to 20 ° C. at a rate of 20 ° C./min, cooled, filtered, sufficiently washed with ion-exchanged water, and dried to obtain toner mother particles (10) that are light Magenta toner mother particles. Obtained.

(Carrier production)
Ferrite particles (volume average particle size: 50 μm): 100 parts Toluene: 14 parts Styrene-methyl methacrylate copolymer (component ratio: styrene / methyl methacrylate = 90/10, weight average molecular weight Mw = 80000): 2 parts Carbon black (R330: manufactured by Cabot Corporation): 0.2 part First, the above components except for ferrite particles are stirred with a stirrer for 10 minutes to prepare a dispersed coating solution, and then the coating solution, ferrite particles, Was put in a vacuum degassing type kneader (manufactured by Inoue Seisakusho), stirred at 60 ° C. for 30 minutes, further depressurized while warming, degassed, and dried to obtain a carrier.

(Development of developer)
To the toner base particles (1) to (10), 1.5 parts of commercially available fumed silica RX50 (manufactured by Nippon Aerosil Co., Ltd.) as an external additive is added to 100 parts of toner, and a Henschel mixer (manufactured by Mitsui Miike Seisakusho) is added. ) To obtain electrostatic image developing toners (1) to (10). Subsequently, 8 parts of each of these toners and 100 parts of the carrier were mixed to obtain two-component developers (1) to (10).

(Measurement of volume average particle diameter and average circularity)
The volume average particle diameter of each toner was measured by the method described above. For the purpose of eliminating measurement noise, the number particle size analysis range was set to 2.0 to 30.1 μm. The results are shown in Table 1.
Further, the average circularity of each toner was measured by the method described above. For the purpose of removing measurement noise, the circularity analysis range was set to a range of 0.40 to 1.00. The results are shown in Table 1.

Example 1
Developers (1) and (2) were incorporated into Docu Center-II4300 manufactured by Fuji Xerox, and the following background fogging and photoreceptor wear were evaluated.

[Evaluation of background fogging amount]
The background fogging amount was evaluated by using a machine such that the character image chart was on paper (J paper manufactured by Fuji Xerox Co.) and the developer (1) and (2) had a toner amount of 5.0 g / m ^2. Adjusted and output the image. Sensory evaluation was performed on the fog of the image portion of the output gradation chart, and it was graded into 10 levels from G1 to G10. The higher the numerical value here, the worse the fogging. The grade OK level was G4 or lower. The results are shown in Table 2.

[Evaluation of photoconductor wear]
Evaluation of photoconductor wear was performed by outputting 30,000 character image charts on paper in the same manner as the above background fogging evaluation, and evaluating the wear amount of the photoconductor on which light color toner and dark color toner are developed. The amount of wear of the photoconductor was measured by measuring the thin film of the photoconductor before and after the running test with an eddy current film thickness meter (Fisher Instruments MMS) and calculating the difference. The uniform film thickness portion was randomly measured at 20 locations, and the average value was taken as the film thickness of the photoreceptor. The level of the photoreceptor wear amount OK is 50 nm or less. The results are shown in Table 2.

(Example 2)
In Example 1, the background fogging amount and the photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (1) and (7). did. The results are shown in Table 2.

(Example 3)
In Example 1, the background fogging amount and the photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (8) and (9). did. The results are shown in Table 2.

Example 4
The background fogging amount and photoreceptor wear were evaluated in the same manner as in Example 1 except that Developers (1) and (2) were changed to Developers (8) and (10) in Example 1. did. The results are shown in Table 2.

(Comparative Example 1)
The background fogging amount and photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (1) and (3) in Example 1. did. The results are shown in Table 2.

(Comparative Example 2)
In Example 1, the background fogging amount and the photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (1) and (4). did. The results are shown in Table 2.

(Comparative Example 3)
The background fogging amount and photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (1) and (5) in Example 1. did. The results are shown in Table 2.

(Comparative Example 4)
In Example 1, the background fogging amount and the photoreceptor wear were evaluated in the same manner as in Example 1 except that the developers (1) and (2) were changed to the developers (1) and (6). did. The results are shown in Table 2.

  From Table 2, it can be seen that in Examples 1 to 4, both the background fogging amount and the photoreceptor wear are good.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

21 Main body housings 22a to 22d Image forming engine 23 Belt module 24 Recording medium supply cassette 25 Recording medium conveyance path 30 Photosensitive unit 31 Photoconductive drum 32 Charging device 33 Developing unit 34 Cleaning devices 35a to 35d Toner cartridge 40 Exposure unit 41 Unit case 42 Polygon Mirror 51 Primary Transfer Device 52 Secondary Transfer Device 53 Belt Cleaning Device 61 Feed Roll 62 Takeaway Roll 63 Registration Roll 66 Fixing Device 67 Discharge Roll 68 Discharge Unit 71 Manual Feed Device 72 Feed Roll 73 Double-Sided Recording Unit 74 Guide Roll 76 Conveying path 77 Conveying roll 230 Intermediate transfer belts 231 and 232 Stretching roll 521 Secondary transfer roll 531 Cleaning blade

Claims (3)

A charging step for charging the surface of the image carrier, an electrostatic latent image forming step for forming an electrostatic latent image corresponding to image information on the charged surface of the image carrier, and the above-mentioned formed on the surface of the image carrier. A developing step of developing the electrostatic latent image with toner containing dark color toner to obtain a toner image, a transfer step of transferring the toner image formed on the surface of the image carrier to the surface of the recording medium, and the recording medium A fixing step for fixing the toner image transferred to the surface; a cleaning step for cleaning the surface of the image carrier after the toner image is transferred; and a light color toner similar in color to the dark toner. A light color toner supply step, wherein the dark color toner and the light color toner have a relationship of the following formulas (1) and (2).
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02 An image carrier, a charging unit for charging the surface of the image carrier, an electrostatic latent image forming unit for forming an electrostatic latent image according to image information on the charged surface of the image carrier, and the image carrier Developing means for developing the electrostatic latent image formed on the surface with toner containing dark toner to obtain a toner image, and transfer for transferring the toner image formed on the surface of the image carrier to the surface of the recording medium Fixing means for fixing the toner image transferred to the surface of the recording medium, cleaning means for cleaning the surface of the image carrier after transferring the toner image, and a light color toner similar in color to the dark color toner A light color toner supply means for supplying the toner to the surface of the image carrier, wherein the dark color toner and the light color toner have a relationship of the following formulas (1) and (2).
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02 The image forming apparatus is detachably mounted and contains at least toner to be supplied to a developing unit provided in the image forming apparatus, and the toner includes similar color dark toner and light color toner, and the dark color A toner cartridge, wherein the toner and the light color toner have a relationship of the following formulas (1) and (2):
Formula (1)
0.8 μm ≦ Volume average particle diameter of dark toner−Volume average particle diameter of light toner ≦ 1.5 μm
Formula (2)
0.01 ≦ average circularity of light color toner−average circularity of dark color toner ≦ 0.02

Images