JP2012173520A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method for achieving images with higher quality by eliminating light resistance and abrasion resistance of high-quality images formed with an electrophotographic system without causing flicker in black character images, improving durability of the formed higher-quality images, and retaining the higher-quality images for a long period.SOLUTION: Provided is an image forming method for forming color images on an image support using chromatic color toner containing a binder resin and colorant. A clear toner layer is provided only on an image part formed on the image support with the chromatic color toner, and the clear toner layer is provided on at least one of chromatic color toner layers that form chromatic color toner images.

Description

  The present invention relates to an electrophotographic image forming method.

  2. Description of the Related Art In recent years, an image forming apparatus that forms an image by an electrophotographic method using an electrostatic charge image developing toner is widely used as a copying machine in an office or the like. In particular, an image forming apparatus capable of forming a high-quality color image at high speed is also referred to as a “digital printing machine” and is suitable for creating a document by printing variable information such as a direct mail or a billing statement. . Furthermore, it is widely used as an alternative to an offset printing press that has been mainly used for commercial printing because it does not require a printing plate.

  In particular, an image forming apparatus in which an image forming speed is increased includes an optional device (finisher) for performing processing on transfer paper on which an image has been formed, such as a staple function, a bookbinding function, and a punch punching function. ) Is often used attached.

  With the image forming apparatus provided with such optional equipment, it is possible to further improve the efficiency of work relating to image formation. However, especially those with high speed and high functionality need to be differentiated from competitors, and studies for this purpose are being actively conducted.

  In an image forming apparatus called a digital printing machine, since the formed image itself is a product, it has excellent color reproducibility and there is no fluctuation in image density in image formation from thousands to tens of thousands of times. In addition, image density stability capable of forming a large amount of images with stable image quality is required. Further, the formed image itself is required to have light resistance and scratch resistance.

  For example, although the color reproducibility is good, the light fastness that the color of the image changes over time, or the color spreads outside the image area when the image is rubbed There were chromatic toners that could not be used as toner due to poor scratch resistance.

  From the viewpoint of light resistance, a toner for developing an electrostatic charge image that includes a light resistance improver and an ultraviolet absorber as a toner forming material has been proposed (for example, Patent Document 1). According to the toner for image development, although the color reproducibility and the light resistance can be improved, the color reproducibility and the scratch resistance effect required together with these can not be expected.

JP 2008-52086 A

  The present invention has been made to solve the above problems.

  The object of the present invention is to achieve higher image quality by eliminating light resistance and scratch resistance of high-quality images formed by electrophotography without causing flickering of black character images, and durability of high-quality images after formation It is an object of the present invention to provide an image forming method that can maintain high image quality over a long period of time.

  As a result of extensive studies by the inventors of the present invention, it has been found that the object of the present invention can be achieved by adopting the following configuration.

(1)
An image forming method for forming a color image on an image support using a chromatic toner containing a binder resin and a colorant, wherein the image is cleared only on an image portion formed by the chromatic toner formed on the image support. An image forming method comprising: providing a clear toner layer on at least one of the chromatic color toner layers provided with a toner layer and forming a chromatic color toner image portion.

(2)
The image forming method according to (1), wherein the chromatic toner layer is at least one of a yellow toner layer and a magenta toner layer.

(3)
The image forming method according to (1), wherein the chromatic toner layer is a magenta toner layer.

(4)
The image forming method according to (1), wherein a dye is used as a colorant for the chromatic toner.

(5)
The image forming method according to any one of (1) to (4), wherein a chromatic toner layer is further provided on the clear toner layer.

(6)
6. The image forming method according to any one of (1) to (5), wherein an ultraviolet absorber is contained in the clear toner layer.

  The present invention increases the light resistance and scratch resistance of high-quality images formed by electrophotography without causing flickering of black character images, achieves higher image quality, and improves the durability of high-quality images after formation Thus, it is possible to provide an image forming method capable of maintaining high image quality over a long period of time.

FIG. 4 is a diagram for explaining an example of a laminated structure of color image layers according to the present invention. 1 is a cross-sectional view of an example of a color image forming apparatus according to the present invention.

  The present invention will be described below.

  The present invention is an image forming method for forming a color image on an image support using a chromatic toner (also simply referred to as a color toner) containing a binder resin and a colorant, which is formed on the image support. And a clear toner layer is provided on at least one of the chromatic color toner layers.

  Here, the chromatic color toner represents a colored toner excluding black toner and white toner, and is composed of toner particles containing a chromatic colorant and a binder resin. Specific examples include yellow toner, magenta toner, cyan toner, orange toner, and green toner.

  The clear toner in the present invention is a toner whose color is not recognized due to the action of light absorption or light scattering. The clear toner only needs to be substantially colorless and transparent. For example, it is a toner that does not contain a colorant such as a pigment or a dye, or a toner that contains a colorant such as a pigment or a dye that cannot recognize a color. In addition, a toner whose transparency is slightly lowered depending on the type and amount of the external additive is also included.

  In the present invention, a clear toner layer is provided on at least one of the chromatic color toner layers, thereby satisfying light resistance and scratch resistance.

  The reason for this is that the presence of the clear toner layer on the chromatic color toner layer makes it possible to reduce the light irradiation, improve the light resistance of the chromatic color toner, and The existence eliminates physical friction of the chromatic color toner layer directly, so that the abrasion resistance of the toner layer having a poor fixing rate can be improved.

  In addition, unlike the image forming method in which the clear toner layer is formed on the entire surface of the image, the present invention forms the clear toner layer only on the chromatic toner layer and does not form the clear toner layer on the black toner layer. By doing so, it is possible to obtain an effect of preventing the occurrence of character flickering caused by reflection by the clear toner when reading a text sentence or the like formed with black toner.

  In the embodiment of the present invention, the clear toner layer can be further improved in light resistance and fastness by further containing an ultraviolet absorber.

  The ultraviolet ray is absorbed before the color image reaches the color image, so that the color image is prevented from being irradiated with the ultraviolet ray, and the effect of suppressing the light deterioration due to the ultraviolet ray is expected to be extremely large. .

  In addition, according to the color image forming method using a color toner containing a dye in the colorant, the obtained color image should exhibit sufficient color reproducibility with sufficient transparency and saturation. In addition, the color printed matter obtained from the color image can have sufficient light durability even when used under light for a long period of time.

[Layer structure of color image]
As the image layer formation of the color image forming method of the present invention, various configurations can be considered. For example, yellow toner, magenta toner, and cyan toner, which are chromatic color toners, are preferably formed from the upper layer in the order of yellow toner layer, magenta toner layer, and cyan toner layer from the viewpoint of light transmittance. From the viewpoint of property, it is preferable to form the cyan toner layer, yellow toner layer, and magenta toner layer in this order from the upper layer.

  In addition, the clear toner layer can be formed to cover the upper layer of each of the chromatic color toner layers. However, from the viewpoint of the configuration of the apparatus, the clear toner layer may be formed at least above the yellow toner layer and the magenta toner layer. preferable. In particular, it is preferable to dispose a clear toner layer on the upper layer of a magenta toner layer that is easily visible as light resistance.

  It is also preferable to provide a clear toner layer between the chromatic toner layers. The reason is that in the case of a colorant such as a dye that is soluble in a resin, the color is mixed into the other color toner layer, causing color bleeding, and the color tone immediately after fixing and the time after fixing. Although there is a phenomenon that the color tone changes later, by providing a clear toner layer between the chromatic toner layers, color mixing between the colorants can be avoided, and color bleeding can be suppressed.

  For easy understanding of the image layer formation in the color image forming method, FIG.

  FIG. 1A shows an example in which a black toner image portion is provided with a single layer of black toner, and a chromatic color toner image portion is provided with a clear toner layer only on the upper layer of the yellow toner layer, which is the uppermost layer of the chromatic color toner layer.

  FIG. 1B shows an example in which the black toner image portion is provided with one layer of black toner, the chromatic toner image portion is provided with an upper layer of the yellow toner layer, and two clear toner layers on the upper layer of the magenta toner layer.

  FIG. 1C shows a black toner image portion having a black toner layer, and a chromatic toner image portion having a lower layer of a magenta toner layer, and a clear toner layer provided between the chromatic toner layers. Is an example.

[Color image forming method]
Such a color image forming method can be performed by, for example, a tandem color image forming apparatus having a configuration in which a plurality of sets of image forming units are provided along an intermediate belt as an intermediate transfer member.

  FIG. 2 is an explanatory sectional view showing an example of the configuration of an image forming apparatus that can be executed by the color image forming method of the present invention.

  This color image forming apparatus includes an endless belt-like intermediate transfer body (hereinafter referred to as “intermediate transfer belt”) 17 arranged in a stretched state by a plurality of support rollers 17a to 17d. Along the outer peripheral surface of the intermediate transfer belt 17, six toner image forming units 30CL1, 30Y for forming a clear toner image, a yellow toner image, a clear toner image, a magenta toner image, a cyan toner image, and a black toner image, respectively. 30CL2, 30M, 30C, and 30K are brought into contact with each of the photosensitive drums 10CL1, 10Y, 10CL2, 10M, 10C, and 10K, which are electrostatic latent image carriers, in the toner image forming units. However, they are arranged so as to be spaced apart so as to be circulated.

  The toner image forming unit 30Y relating to the yellow toner image is arranged so as to be arranged in order of operation with respect to the rotating direction of the photosensitive drum 10Y along the rotating photosensitive drum 10Y and the outer peripheral surface of the photosensitive drum 10Y. The charging unit 11Y, the exposure unit 12Y, the developing unit 13Y, the primary transfer unit 14Y, and the cleaning unit 20Y are provided.

  The primary transfer unit 14Y is pressed against the photosensitive drum 10Y via the intermediate transfer belt 17, and a primary transfer roller 141Y provided so as to form a primary transfer region (primary transfer nip portion), and the primary transfer roller 141Y. The transfer current supply means (not shown) is connected, and a transfer electric field is formed by supplying a predetermined transfer current to the primary transfer roller 141Y by the transfer current supply means. The yellow toner image formed on the photosensitive drum 10Y by the action of the electric field is primarily transferred onto the intermediate transfer belt 17.

  In each of the other toner image forming units 30CL1, 30CL2, 30M, 30C, and 30K, the developer includes a clear toner, a magenta toner, a cyan toner, and a black toner instead of the yellow toner. The toner image forming unit 30Y has the same configuration.

  A secondary transfer unit 14S is provided at a position downstream of the toner image forming unit arrangement region in the moving direction of the intermediate transfer belt 17 (indicated by an arrow in FIG. 2).

  The secondary transfer unit 14S is pressed by the backup roller 17d, which is one of the support rollers that support the intermediate transfer belt 17, via the intermediate transfer belt 17, so that a secondary transfer region (secondary transfer nip portion) is formed. The secondary transfer roller 141S is provided, and a transfer voltage application unit (not shown) connected to the secondary transfer roller 141S. The potential of the primary transfer toner image is formed by the transfer voltage application unit. A transfer electric field is formed by applying a secondary transfer bias voltage having a reverse polarity to the secondary transfer roller 141S, and the primary transfer toner image formed on the intermediate transfer belt 17 by the action of the transfer electric field is transferred to the transfer material P. Transcribed above.

  In FIG. 2, 18 is a fixing device for fixing the toner image on the transfer material P conveyed from the secondary transfer area. For example, a heating roller 181 having a heating source therein, and the heating roller 181 and the fixing device are fixed. The pressure roller 182 is provided in a pressure contact state so that a nip portion is formed.

  Reference numeral 20S denotes an intermediate transfer member cleaning means provided with a cleaning blade for removing untransferred toner on the intermediate transfer belt 17, and is provided at a position downstream of the secondary transfer region in the moving direction of the intermediate transfer belt 17. ing.

  In such a full-color image forming apparatus, first, for each color formed on the photosensitive drums 10CL1, 10Y, 10CL2, 10M, 10C, and 10K of the toner image forming units 30CL1, 30Y, 30CL2, 30M, 30C, and 30K. The toner images are sequentially transferred and superimposed on the intermediate transfer belt 17, and the toner image primarily transferred onto the intermediate transfer belt 17 is secondarily transferred onto the transfer material P by the secondary transfer unit 14S and fixed. A toner image is formed on the transfer material P by heating and pressing in the apparatus 18.

[Chromatic toner]
The chromatic toner (also simply referred to as toner) used in the color image forming method of the present invention represents a toner colored in a color other than black toner and white toner as described above, and contains a colorant and a binder resin. It consists of particles.

  Specific examples include yellow toner, magenta toner, cyan toner, orange toner, and green toner.

  The toner particles include a shell composed of core particles containing a binder resin and a colorant, and a shell layer-forming resin (hereinafter also referred to as “shell resin”) that substantially does not contain a colorant that covers the outer peripheral surface of the toner particles. It may be of a core-shell structure composed of layers. By configuring the toner particles as having a core-shell structure, high production stability and storage stability can be obtained for the toner particles.

  The core-shell structure may cover a part of the core particle. Further, a part of the shell resin constituting the shell layer may form a domain or the like in the core particle. Furthermore, the shell layer may have a multilayer structure of two or more layers made of resins having different compositions.

[Colorant]
As the colorant contained in the chromatic toner of the present invention, generally known dyes and pigments can be used, but as the colorant, from the viewpoint of color reproducibility and transparency of the obtained toner, It is particularly preferable to use a dye.

  The colorant for obtaining the toner of each color can be used alone or in combination of two or more for each color.

  Examples of yellow pigments for obtaining yellow toner include C.I. I. Pigment yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, and the like.

  Examples of yellow dyes include C.I. I. Solvent Yellow 2, C.I. I. Solvent Yellow 3, C.I. I. Solvent Yellow 5, C.I. I. Solvent Yellow 7, C.I. I. Solvent Yellow 8, C.I. I. Solvent Yellow 17, C.I. I. Solvent Yellow 24, C.I. I. Solvent Yellow 30, C.I. I. Solvent Yellow 31, C.I. I. Solvent Yellow 35, C.I. I. Solvent Yellow 44, C.I. I. Solvent Yellow 77, C.I. I. Solvent Yellow 79, C.I. I. Solvent Yellow 81, C.I. I. Solvent Yellow 82, C.I. I. Solvent Yellow 88, C.I. I. Solvent Yellow 89, C.I. I. Solvent Yellow 98, C.I. I. Solvent Yellow 102, C.I. I. Solvent Yellow 103, C.I. I. Solvent Yellow 104, C.I. I. Solvent Yellow 105, C.I. I. Solvent Yellow 111, C.I. I. Solvent Yellow 112, C.I. I. Solvent Yellow 114, C.I. I. Solvent yellow 162 etc. are mentioned.

  As a magenta pigment for obtaining a magenta toner, C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, and the like.

  Examples of the magenta dye include C.I. I. Solvent Red 1, C.I. I. Solvent Red 3, C.I. I. Solvent Red 14, C.I. I. Solvent Red 17, C.I. I. Solvent Red 18, C.I. I. Solvent Red 22, C.I. I. Solvent Red 23, C.I. I. Solvent Red 51, C.I. I. Solvent Red 53, C.I. I. Solvent Red 87, C.I. I. Solvent Red 111, C.I. I. Solvent Red 122, C.I. I. Solvent Red 127, C.I. I. Solvent Red 128, C.I. I. Solvent Red 131, C.I. I. Solvent Red 145, C.I. I. Solvent Red 146, C.I. I. Solvent Red 149, C.I. I. Solvent Red 150, C.I. I. Solvent Red 151, C.I. I. Solvent Red 152, C.I. I. Solvent Red 153, C.I. I. Solvent Red 154, C.I. I. Solvent Red 155, C.I. I. Solvent Red 156, C.I. I. Solvent Red 157, C.I. I. Solvent Red 164, C.I. I. Solvent Red 176, C.I. I. Solvent red 179, chelate dye, etc. are mentioned.

  Examples of pigments for obtaining cyan toner include C.I. I. Pigment blue 15: 3.

  Examples of cyan dyes include C.I. I. Solvent Blue 4, C.I. I. Solvent Blue 8, C.I. I. Solvent Blue 19, C.I. I. Solvent Blue 21, C.I. I. Solvent Blue 22, C.I. I. Solvent Blue 50, C.I. I. Solvent Blue 55, C.I. I. Solvent Blue 63, C.I. I. Solvent Blue 78, C.I. I. Solvent Blue 82, C.I. I. Solvent Blue 83, C.I. I. Solvent Blue 8, C.I. I. Solvent Blue 85, C.I. I. Solvent Blue 86, C.I. I. Solvent Blue 90, C.I. I. Solvent Blue 91, C.I. I. Solvent Blue 92, C.I. I. Solvent Blue 93, C.I. I. Solvent Blue 94, C.I. I. Solvent Blue 95, C.I. I. Solvent Blue 97, C.I. I. Solvent Blue 104, C.I. I. Solvent blue 136, silicon phthalocyanine, etc. are mentioned.

  The number average primary particle size of these colorants in the toner varies depending on the type of the colorant, but is preferably about 10 to 200 nm.

  The method of introducing the colorant as described above into the toner particles is not particularly limited. For example, in the case of production by an emulsion polymerization aggregation method described later, (1) the resin is mixed at the molecular level. A method of obtaining toner particles by preparing a dispersion of fine particles and aggregating the fine particles, or (2) producing fine particles composed solely of a colorant separately from fine particles obtained from a binder resin, and dispersing these particles Examples thereof include a method of obtaining toner particles by mixing the liquid and aggregating both fine particles.

  The fine particles in which the binder resin and the colorant are mixed at the molecular level are prepared by dissolving the colorant in advance in the polymerizable monomer to form the binder resin, and containing the colorant. Can be produced by polymerizing.

  The content of the colorant is preferably 1 to 10% by mass in the toner, and more preferably 2 to 8% by mass. When the content of the colorant is less than 1% by mass in the toner, the obtained toner may be insufficient in coloring power, while the content of the colorant exceeds 10% by mass in the toner. In some cases, the colorant is liberated or adhered to the carrier, which may affect the chargeability.

  As a colorant for obtaining a black toner which is a toner other than a chromatic color, various known ones such as carbon black, a magnetic material, a dye, and a pigment can be arbitrarily used.

[Binder resin]
As the binder resin contained in the toner used in the color image forming method of the present invention, when the toner is produced, for example, by a pulverization method or a dissolution suspension method, the binder resin contained in the toner is: In addition to those exemplified as the above-mentioned transparent thermoplastic resin, thermosetting resins such as epoxy resins, urea resins and phenol resins can also be mentioned. In particular, in order to improve transparency and color reproducibility of a superimposed image, styrene resins, acrylic resins, and polyester resins having high transparency, low melting properties, and high sharp melt properties are preferable. It is done. These can be used alone or in combination of two or more.

  In addition, when the toner is produced by, for example, suspension polymerization method, miniemulsion polymerization aggregation method, emulsion polymerization aggregation method, etc., the polymerizable monomer for obtaining the binder resin contained in the toner is In addition to those exemplified as the polymerizable monomer for obtaining the transparent thermoplastic resin, further, as the polymerizable monomer, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, Polyfunctional vinyls such as triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, and neopentyl glycol diacrylate can be used.

  When the toner particles have a core-shell structure, styrene-acrylic resins are preferable as the core binder resin and the shell resin, respectively.

  When the core binder resin is made of a copolymer, as a polymerizable monomer for obtaining the copolymer, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2- It is preferable that what can make the glass transition point temperature (Tg) of the copolymer obtained low, such as ethylhexyl methacrylate, is contained.

  The copolymerization ratio of such a polymerizable monomer is 8 to 80% by mass, preferably 9 to 70% by mass, based on the entire polymerizable monomer that should form the core binder resin.

  In addition to the specific examples given above, these polymerizable monomers may have acid anhydrides or vinyl carboxylic acid metal salt forms.

  Further, when the shell resin is made of a copolymer, the glass transition point of the obtained copolymer, such as styrene, methyl methacrylate, methacrylic acid, etc., as the polymerizable monomer for obtaining the copolymer It is preferable that what can make temperature (Tg) high can be included.

  The copolymer ratio of such a polymerizable monomer is 8 to 80% by mass, and preferably 9 to 20% by mass, based on the entire polymerizable monomer that should form the shell resin.

  In addition to the specific examples given above, these polymerizable monomers may have acid anhydrides or vinyl carboxylic acid metal salt forms.

  The binder resin constituting the toner used in the color image forming method of the present invention has a number average molecular weight (Mn) of 3,000 to 6,000, more preferably 3,500 to 5,500, and a weight average molecular weight (Mw). And the number average molecular weight (Mn) ratio Mw / Mn is 2.0 to 6.0, more preferably 2.5 to 5.5, and the glass transition temperature (Tg) is 50 to 70 ° C., more preferably 55 to 55 ° C. It is preferred that the temperature is 70 ° C. and the softening point temperature is 90 to 110 ° C., more preferably 90 to 105 ° C. The molecular weight, glass transition temperature (Tg), and softening point temperature of the binder resin are each measured by the same method as described above using the measurement sample as a toner.

〔wax〕
Various known waxes can be used as the release agent.

  Examples of the wax include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, and dialkyls such as distearyl ketone. Ketone wax, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanedioldi Ester waxes such as stearate, tristearyl trimellitic acid, distearyl maleate, ethylenediamine behenylamide, tristearyl trimellitic acid Such as amide-based waxes such as bromide and the like.

  It is preferable that content of a mold release agent is 0.1-30 mass parts with respect to 100 mass parts of binder resin, More preferably, it is 1-20 mass parts.

[External additive]
The above toner particles can constitute the toner used in the color image forming method of the present invention as they are. However, in order to improve fluidity, chargeability, cleaning properties, etc., the toner particles are so-called post-treatment agents. The toner according to the present invention may be configured by adding external additives such as a fluidizing agent and a cleaning aid.

  As the post-treatment agent, for example, inorganic oxide fine particles composed of silica fine particles, alumina fine particles, titanium oxide fine particles, etc., inorganic stearate compound fine particles such as aluminum stearate fine particles, zinc stearate fine particles, or strontium titanate, titanium Inorganic titanic acid compound fine particles such as zinc acid are listed. These can be used individually by 1 type or in combination of 2 or more types.

  These inorganic fine particles are preferably subjected to surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil or the like in order to improve heat-resistant storage stability and environmental stability.

  The total amount of these various external additives added is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner. In addition, various external additives may be used in combination.

[Toner manufacturing method (other than clear toner)]
Examples of the method for producing a toner other than the clear toner used in the color image forming method of the present invention include a kneading / pulverizing method, a suspension polymerization method, an emulsion polymerization method, an emulsion polymerization aggregation method, a miniemulsion polymerization aggregation method, and an encapsulation method. Other known methods and the like can be mentioned, but as a method for producing the toner, it is necessary to obtain a toner having a reduced particle size in order to achieve high image quality. From the viewpoint of production cost and production stability, it is preferable to use an emulsion polymerization aggregation method.

  In the emulsion polymerization aggregation method, a dispersion of fine particles (hereinafter referred to as “binder resin fine particles”) made of a binder resin produced by an emulsion polymerization method is used as a dispersion of toner particle constituents such as other colorant fine particles. While mixing, slowly agglomerating while balancing the repulsive force of the fine particle surface by pH adjustment and the agglomeration force by addition of an aggregating agent consisting of an electrolyte, and performing association while controlling the average particle size and particle size distribution, This is a method for producing toner particles by controlling the shape by fusing fine particles by heating and stirring.

  As a method for producing the toner, the binder resin fine particles formed when the emulsion polymerization aggregation method is used may be composed of two or more layers of binder resins having different compositions. A method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of the first resin particles prepared by the emulsion polymerization treatment (first-stage polymerization), and the system is polymerized (second-stage polymerization). Can be adopted.

  As a method for producing core-shell structured toner particles, as described in detail later, first, core binder resin fine particles and colorant fine particles are associated, aggregated, and fused to produce core particles. Next, shell resin fine particles to form a shell layer are added to the core particle dispersion, and the shell resin fine particles are aggregated and fused on the surface of the core particles to form a shell layer that covers the surface of the core particles. It can be obtained by forming.

  The shape of the core particles constituting the toner particles having the core-shell structure can be adjusted, for example, by controlling the heating temperature in the aggregation / fusion process, the heating temperature in the first aging process, and the heating time. In particular, by controlling the heating time in the first ripening step, the circularity of the associated particles can be adjusted with certainty.

  The core particles are obtained by, for example, dispersing a polymerizable monomer that forms a core binder resin that constitutes the core particles into an aqueous medium mechanically and dispersing the polymerizable monomer by a miniemulsion polymerization method. As described later, a salting-out / fusion method in which the core binder resin fine particles and the colorant fine particles formed through the step of polymerizing are salted out / fused is preferably used.

[Clear toner]
As described above, the clear toner is a toner whose color is not recognized due to light absorption or light scattering. From the viewpoint of transparency, the clear toner preferably does not contain wax and colorant.

  Moreover, it is preferable to contain a ultraviolet absorber from a viewpoint of light resistance improvement.

[Ultraviolet absorber]
Examples of the ultraviolet absorber contained in the clear toner used in the color image forming method of the present invention include an ultraviolet absorber composed of a benzotriazole compound, a triazine compound, a benzophenone compound, or a zoate compound. An ultraviolet absorber made of a benzotriazole-based compound is preferable.

(1) Benzotriazole-based compounds Examples of ultraviolet absorbers composed of benzotriazole-based compounds (hereinafter also referred to as “benzotriazole-based ultraviolet absorbers”) include 2- (2p-cresol, 2- (2H-benzotriazole). -2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert- Butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-pentylphenol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3 3-tetramethylbutyl) phenol, methyl-3- [3-t-butyl-5- (2H-benzotriazol-2-yl) -4-hydroxyphenyl] Condensation with propionate-polyethylene glycol (molecular weight about 300), 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol, 2- (2-hydroxy-5-tert-butylphenyl) ) -2H-benzotriazole, 2-ethylhexyl-3- [3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, 2- (2H-benzotriazole -2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -6- (1-methyl to 1-phenylethyl) -4 -(1,1,3,3-tetramethylptyl) phenol and the like.

  Specific examples of the benzotriazole-based ultraviolet absorber include those represented by the following formulas (UV-1) to (UV-10), and among these, in particular, the following formula (UV-7) ) To (UV-10) are preferable.

(2) Triazine-based compound As an ultraviolet absorber made of a triazine-based compound (hereinafter, also referred to as “triazine-based ultraviolet absorber”), for example, 2- (4,6-bis (2,4-dimethylphenyl)- 1,3,5-triazin-2-yl) -5-hydroxyphenyl, 2- (4,6-diphenyl-1,3,5-triazin-2-yl) -5-[(hexyl) oxy] phenol, 2- [4-[(2-hydroxy-3-dodecyloxypropyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2- [4-[(2-hydroxy-3- (2′-ethyl) hexyl) oxy] -2-hydroxyphenyl] -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine, 2,4- (2-hydroxy-4-butyloxyphenyl) -6- (2,4-bis-butyloxyphenyl) -1,3,5-triazine, 2- (2-hydroxy-4- [1-octyloxycarbonyl) Oxy] phenyl) -4,6-bis (4-phenyl) -1,3,5-triazine and the like.

  As a specific example of a triazine type ultraviolet absorber, what is represented by a following formula (UV-11) can be mentioned, for example.

(3) Benzophenone-based compounds Examples of ultraviolet absorbers composed of benzophenone-based compounds (hereinafter also referred to as “benzophenone-based ultraviolet absorbers”) include, for example, octabenzone, 2,4-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone. 2-hydroxy-4-n-octyloxybenzophenone and the like.

  Specific examples of the benzophenone-based ultraviolet absorber include those represented by the following formula (UV-12).

(4) Benzoate compound As an ultraviolet absorber made of a benzoate compound (hereinafter also referred to as "benzoate ultraviolet absorber"), for example, 2,4-di-tert-butylphenyl-3,5-di- and tert-butyl-4-hydroxybenzoate.

  Specific examples of the benzoate-based ultraviolet absorber include those represented by the following formula (UV-13).

  The method for introducing the ultraviolet absorber as described above into the particles constituting the transparent powder (hereinafter, also referred to as “transparent particles”) is not particularly limited, and is produced by, for example, an emulsion polymerization aggregation method described later. (1) A method of obtaining a transparent particle by preparing a dispersion of fine particles mixed with a thermoplastic binder resin at a molecular level and aggregating the fine particles, or (2) a thermoplastic binder. A method of obtaining transparent particles by preparing fine particles consisting of only an ultraviolet absorber separately from the resin fine particles, mixing these dispersions, and aggregating both fine particles is exemplified.

  The fine particles in which the thermoplastic binder resin and the ultraviolet absorber are mixed at the molecular level are prepared by dissolving the ultraviolet absorber in advance in the polymerizable monomer that should form the thermoplastic binder resin. It can produce by polymerizing the polymerizable monomer which it has.

  The content of the ultraviolet absorber is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass in the transparent powder. When the content of the ultraviolet absorber is within the above range, stable light resistance is exhibited over a long period of time. Moreover, there is practically no influence on the chargeability of the transparent powder due to the addition of the ultraviolet absorber.

[Fluorescent brightener]
The ultraviolet absorbent contained in the transparent powder used in the color image forming method of the present invention may contain a fluorescent brightening agent. A transparent powder containing such a fluorescent brightening agent emits fluorescence.

  Examples of the fluorescent brightening agent include organic fluorescent pigments represented by the following general formulas (I) to (III). These organic fluorescent pigments absorb ultraviolet rays and emit fluorescence having a fluorescence peak wavelength of 350 to 450 nm.

  Such a fluorescent whitening agent is such that the fluorescent whitening agent itself becomes colorless under visible light in at least a transparent powder. From such a viewpoint, the fluorescent whitening agent preferably emits fluorescence having a fluorescence peak wavelength of 350 to 400 nm, particularly preferably a fluorescence peak wavelength of 350 to 380 nm.

  Here, the fluorescence peak wavelength of the fluorescent whitening agent was measured by using a spectrophotometer “U-4000” (manufactured by Hitachi, Ltd.) and dissolving the fluorescent whitening agent in a soluble solvent such as dimethylformamide. is there.

  The compound represented by the general formula (I) is a benzoxazole derivative, and the compounds represented by the general formula (II) and the general formula (III) are a coumarin derivative and a naphthalimide derivative, respectively.

  As the optical brightener, it is preferable to use a benzoxazole derivative represented by the above general formula (I).

In the general formula (I), R ¹ and R ² each represent a hydrogen atom or an alkyl group. In the general formula (II), R ³ represents a hydrogen atom or a monovalent substituent (triazine ring, triazole). R ⁴ represents a hydrogen atom, an alkyl group, an alkoxy group, or an aryl group, and, in the general formula (III), R ⁵ represents a hydrogen atom. R ⁶ and R ⁷ each represent a hydrogen atom, an alkyl group, an alkoxy group or an acylamino group.

  Examples of the fluorescent whitening agent comprising the benzoxazole derivative represented by the general formula (I) include compounds represented by the following general formulas (IA) to (IC).

In the general formulas (IA) to (IC), R ⁸ and R ⁹ represent a hydrogen atom or an alkyl group.

  Specific examples of the compounds represented by the general formulas (I) to (III) include compounds represented by the following formulas (FL-1) to (FL-13).

  The content of the optical brightener is preferably 0.1 to 20% by mass, more preferably 1 to 10% by mass with respect to the transparent powder.

  In the transparent powder, when the content of the fluorescent whitening agent in the ultraviolet absorber exceeds 20% by mass, the obtained transparent powder has low fixability, and the fluorescent whitening agent in the transparent powder Concentration becomes excessively high, concentration quenching occurs mainly due to energy transfer between fluorescent brighteners rather than fluorescent light emission, and it becomes difficult to obtain sufficient fluorescent light emission.

[Production method of clear toner]
Examples of the method for producing the clear toner used in the color image forming method of the present invention include kneading / pulverization method, suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method, miniemulsion polymerization aggregation method, encapsulation method, and the like. Known methods and the like can be mentioned, but as a method for producing a transparent powder, an emulsion polymerization aggregation method is preferably used from the viewpoint of production cost and production stability.

  In the emulsion polymerization aggregation method, a dispersion of fine particles composed of a thermoplastic binder resin contained in a transparent powder produced by the emulsion polymerization method is mixed with a dispersion of fine particles composed of wax in some cases, and pH adjustment is performed. Aggregating slowly while balancing the repulsive force on the surface of the fine particles and the cohesive force due to the addition of an aggregating agent made of an electrolyte, and performing aggregation while controlling the average particle size and particle size distribution, and at the same time heating and stirring the fine particles This is a method for producing transparent particles by performing fusion bonding between them and performing shape control.

  As a method for producing the transparent powder, the fine particles formed when the emulsion polymerization aggregation method is used may have a structure of two or more layers made of binder resins having different compositions. A method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of the first resin particles prepared by the emulsion polymerization process (first stage polymerization) and the system is polymerized (second stage polymerization). Can be adopted.

  As the thermoplastic binder resin (hereinafter referred to as “transparent thermoplastic resin”) contained in the transparent powder used in the color image forming method of the present invention, the transparent powder is, for example, a pulverization method or a dissolution suspension method. For example, styrene resins, (meth) acrylic resins, styrene- (meth) acrylic copolymer resins, vinyl resins such as olefin resins, polyester resins as transparent thermoplastic resins. And various known thermoplastic resins such as polyamide resins, polycarbonate resins, polyethers, polyvinyl acetate resins, polysulfone resins, polyurethane resins, and the like. In particular, in order to improve transparency, styrene-based resins, acrylic resins, and polyester-based resins having high transparency, low melting properties, and high sharp melt properties are preferable. These can be used alone or in combination of two or more.

  In addition, when the transparent powder is produced by, for example, suspension polymerization, miniemulsion polymerization aggregation, emulsion polymerization aggregation, etc., as a polymerizable monomer for obtaining a transparent thermoplastic resin, for example, styrene, o -Methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, Styrene or styrene styrene derivatives such as pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methacryl Isopropyl acid, isobutyl methacrylate, t-butyl methacrylate, methacrylate Methacrylic acid ester derivatives such as n-octyl acid, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate, ethyl acrylate, acrylic acid Acrylic acid ester derivatives such as isopropyl, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate; ethylene, Olefins such as propylene and isobutylene; vinyl fluorides such as vinyl fluoride and vinylidene fluoride; vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate; Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl hexyl ketone; N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone; Examples thereof include vinyl compounds such as vinyl naphthalene and vinyl pyridine; vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These vinyl monomers can be used alone or in combination of two or more.

  Moreover, it is preferable to use combining what has an ionic dissociation group as a polymerizable monomer. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate Etc.

  The transparent thermoplastic resin preferably has a number average molecular weight (Mn) of 3,000 to 6,000, more preferably 3,500 to 5,500, and a ratio Mw of the weight average molecular weight (Mw) to the number average molecular weight (Mn). / Mn is 2.0 to 6.0, preferably 2.5 to 5.5, glass transition temperature (Tg) is 40 to 70 ° C, preferably 45 to 65 ° C, softening point temperature is 90 to 110 ° C, It is preferable that it is 90-105 degreeC.

  The molecular weight of the thermoplastic resin is measured by gel permeation chromatography (GPC). Specifically, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent. The sample was flowed at a flow rate of 0.2 ml / min, and the sample was dissolved in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition in which treatment was performed at room temperature using an ultrasonic disperser for 5 minutes, and then a membrane having a pore size of 0.2 μm. A sample solution is obtained by processing with a filter, and 10 μL of this sample solution is injected into the apparatus together with the above carrier solvent, detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample is monodispersed. It is calculated using a calibration curve measured using polystyrene standard particles. Ten polystyrenes were used for calibration curve measurement.

  The glass transition temperature (Tg) of the thermoplastic resin is measured using a differential scanning calorimeter “DSC-7” (manufactured by PerkinElmer) and a thermal analyzer controller “TAC7 / DX” (manufactured by PerkinElmer). Is. Specifically, 4.50 mg of transparent powder is enclosed in an aluminum pan “KITNO.0219-0041”, which is set in a sample holder of “DSC-7”, and an empty aluminum pan is used for reference measurement. Heat-cool-Heat temperature control is performed at a measurement temperature of 0 to 200 ° C. under measurement conditions of a temperature increase rate of 10 ° C./min and a temperature decrease rate of 10 ° C./min. Data on Heat is acquired, and the glass transition point is the intersection of the baseline extension before the rise of the first endothermic peak and the tangent line indicating the maximum slope between the rise of the first endothermic peak and the peak apex. It is shown as temperature (Tg). 1st. The heat was raised at 200 ° C. for 5 minutes.

  Moreover, the softening point temperature of a thermoplastic resin is measured as follows.

First, in an environment of 20 ° C. and 50% RH, 1.1 g of transparent powder was placed in a petri dish, leveled, and allowed to stand for 12 hours or more, and then 3820 kg / day using a molding machine “SSP-10A” (Shimadzu Corporation). Pressurize with a force of cm ² for 30 seconds to prepare a cylindrical molded sample with a diameter of 1 cm. Then, the molded sample is subjected to a flow tester “CFT-500D” (Shimadzu Corporation) in an environment of 24 ° C. and 50% RH. Manufactured by using a piston with a diameter of 1 cm from a hole (1 mm diameter × 1 mm) of a cylindrical die under the conditions of a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min. The offset method temperature T _offset measured by setting the offset value of 5 mm by the melt temperature measurement method of the temperature rising method is the softening point temperature of the thermoplastic resin. It is said.

[Particle size of toner particles]
The particle size of the toner used in the color image forming method of the present invention is preferably 4 to 10 μm, and more preferably 6 to 9 μm, for example, on a volume basis median diameter. When the toner production method is an emulsion aggregation method, the particle size should be controlled by the concentration of the aggregation agent (salting out agent) used, the timing of addition of the aggregation terminator, the temperature during aggregation, and the composition of the polymer. Can do.

  When the volume-based median diameter is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  The particle diameter of the toner is measured by the same method as described above using the measurement sample as the toner.

  The median diameter of the toner used for the color image forming method of the present invention on the volume basis is a computer system (Beckman Coulter) equipped with data processing software “Software V3.51” in Coulter Counter Multisizer 3 (manufactured by Beckman Coulter). Measured and calculated using a device connected to the product.

  As a measurement procedure, 0.02 g of toner is blended with 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the display density of the measuring instrument becomes 5% to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count is set to 25000, the aperture diameter is set to 100 μm, the frequency value is calculated by dividing the measurement range of 2.0 to 60 μm into 256, and the volume integrated fraction is 50 % Particle diameter is defined as a volume-based median diameter (volume D50% diameter).

[Average circularity of toner]
From the viewpoint of improving transfer efficiency, the toner used in the color image forming method of the present invention preferably has an average circularity represented by the following formula (T) of 0.930 to 1.000, more preferably 0.8. 950 to 0.995.

Formula (T): Average circularity = peripheral length of circle obtained from equivalent circle diameter / perimeter length of projected particle image [Developer]
The toner used in the color image forming method of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer. In the case where the toner according to the present invention is used as a two-component developer, the carrier may be a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. Magnetic particles can be used, and ferrite particles are particularly preferable. Further, as the carrier, a coat carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a binder type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.

  The coating resin constituting the coat carrier is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene-acrylic resins, silicone resins, ester resins, and fluorine resins. Moreover, it does not specifically limit as resin which comprises a resin dispersion type carrier, A well-known thing can be used, For example, a styrene-acrylic-type resin, a polyester resin, a fluororesin, a phenol resin etc. can be used.

  The volume-based median diameter of the carrier is preferably 20 to 100 μm, and more preferably 20 to 60 μm. The volume-based median diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

(Image support)
As the image support 13 used in the color image forming method of the present invention, coated paper such as plain paper, high quality paper, art paper or coated paper from thin paper to thick paper, commercially available Japanese paper and postcards are used. Various types of paper, plastic films for OHP, cloth, and the like can be mentioned, but the invention is not limited to these.

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following text, “part” means “part by mass”.

1. Preparation of “Clear Toners 1 to 4” Clear toners 1 to 6 having the configuration of the present invention were prepared by the following procedure.

(1) Preparation of “Clear Toner 1 (CL-1)” (a) Preparation of “Resin Fine Particle Dispersion 1” Anionic surfactant in a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device A surfactant aqueous solution was prepared by dissolving 7.08 parts by mass of (sodium dodecylbenzenesulfonate: SDS) in 2760 parts by mass of ion-exchanged water. While stirring the surfactant aqueous solution at a stirring speed of 230 rpm under a nitrogen stream, the temperature was raised to 80 ° C.

On the other hand, the following compound: Styrene 105 parts by mass n-butyl acrylate 42 parts by weight Methacrylic acid 11 parts by weight Paraffin wax “HNP-57 (manufactured by Nippon Seiwa Co., Ltd.)” 72 parts by weight is mixed, heated to 80 ° C. and dissolved. To prepare a mixed solution.

  Next, using the mechanical dispersion device having a circulation path, the mixed solution heated to 80 ° C. is put into the surfactant aqueous solution heated to 80 ° C., and mixed and dispersed. An emulsified particle dispersion having a uniform dispersed particle size was prepared.

Next, a solution in which 0.84 parts by mass of potassium persulfate (KPS) was dissolved in 200 parts by mass of ion-exchanged water was added, and the polymerization reaction was performed by heating and stirring at 80 ° C. for 3 hours. Subsequently, with the temperature maintained at 80 ° C., a solution prepared by dissolving 8.00 parts by mass of potassium persulfate (KPS) and 10.00 parts by mass of 2-chloroethanol in 240 parts by mass of ion-exchanged water was added and added. The following compound heated to 80 ° C. after 15 minutes: A mixed solution of 384 parts by mass of styrene, 140 parts by mass of n-butyl acrylate and 37 parts by mass of methacrylic acid was added dropwise over 120 minutes. After completion of dropping, the mixture was stirred at 80 ° C. for 60 minutes and then cooled to 40 ° C. to prepare “resin fine particle dispersion 1”. “Resin fine particles 1” constituting “resin particle dispersion 1” had a weight average molecular weight of 30,000.

(B) Preparation of “clear toner base particle 1” In a reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe, and a nitrogen introducing device,
"Resin fine particle dispersion 1" 1370 parts by mass (in terms of solid content)
2000 parts by mass of ion-exchanged water was added and stirred. After adjusting the temperature in the reaction vessel to 30 ° C., a 5 mol / liter aqueous sodium hydroxide solution was added to adjust the pH to 10.

  Next, an aqueous solution in which 35 parts by mass of magnesium chloride hexahydrate was dissolved in 35 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. The temperature was raised after standing for 3 minutes, and the temperature of the system was raised to 90 ° C. over 60 minutes, and the aggregation and fusion of the particles were continued while maintaining the temperature at 90 ° C. In this state, using “Coulter Counter Multisizer 3 (manufactured by Beckman Coulter)”, the particle size of the particles obtained by agglomeration and fusion was measured, and when the volume-based median diameter of the particles became 6.7 μm Then, an aqueous solution in which 150 parts by mass of sodium chloride was dissolved in 600 parts by mass of ion-exchanged water was added to stop particle aggregation.

  After the agglomeration is stopped, fusing is continued until the average circularity of the agglomerated particles becomes 0.965 by using “FPIA2100 (manufactured by Sysmex)” while stirring with heating at a liquid temperature of 98 ° C. as an aging treatment. Clear toner base particles 1 ”were formed.

  Thereafter, the liquid temperature was cooled to 30 ° C., the pH was adjusted to 2 using hydrochloric acid, and stirring was stopped. The “clear toner base particle dispersion 1” produced through the above steps is subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40 (manufactured by Matsumoto Kikai Co., Ltd.)” to obtain “clear toner base particle 1”. A wet cake was formed.

  This wet cake was washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the basket type centrifuge, and then transferred to “Flash Jet Dryer (manufactured by Seishin Enterprise Co., Ltd.)”. Then, a “clear toner base particle 1” was produced by performing a drying process until the water content became 0.5 mass%.

(C) External Addition Treatment “Clear Toner 1” is produced by adding the following external additive to the produced “clear toner base particle 1” and performing an external addition treatment with a Henschel mixer (Mitsui Miike Mining Co., Ltd.). did.

Silica treated with hexamethylsilazane (average primary particle size 12 nm)
1.0 part by mass n-octylsilane-treated titanium dioxide (average primary particle size 20 nm)
0.3 parts by mass The external addition process by the Henschel mixer is performed under the conditions of a peripheral speed of the stirring blade of 35 m / second, a processing temperature of 35 ° C., and a processing time of 15 minutes, and the median diameter on the volume basis is 6.5 μm. A clear toner was prepared.

(2) Preparation of “Clear Toners 2-6 (CL-2 to CL-6)” Although it was prepared in the same manner as Clear Toner 1, 5.5 g of the ultraviolet absorbent described in Table 1 was prepared when the resin fine particle dispersion 1 was prepared. By addition, clear toners 2 to 6 having a median diameter of 6.5 μm on a volume basis were obtained.

[Production of toner]
(Production example A of resin fine particles)
(1) First-stage polymerization In a reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device, 4 parts by mass of an anionic surfactant [X] represented by the following formula (X) is ion-exchanged water. The surfactant solution dissolved in 3040 parts by mass was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

Formula _{(X): C 10 H 21} (OCH 2 CH 2) SO 3 Na
To this surfactant solution, an initiator solution in which 10 parts by mass of a polymerization initiator (potassium persulfate: KPS) was dissolved in 400 parts by mass of ion-exchanged water was added, and the temperature was adjusted to 75 ° C.
Styrene 532 parts by mass n-butyl acrylate 200 parts by mass Methacrylic acid 68 parts by mass n-Octyl mercaptan 16.4 parts by mass A monomer mixture was dropped over 1 hour. Thereafter, this system was heated and stirred at 75 ° C. for 2 hours to conduct polymerization (first stage polymerization), thereby preparing resin fine particles [A1]. The resin fine particles [A1] had a weight average molecular weight (Mw) of 16,500.

(2) Second stage polymerization (formation of intermediate layer)
In a flask equipped with a stirrer,
Styrene 100 parts by weight n-butyl acrylate 62 parts by weight Methacrylic acid 12 parts by weight n-octyl mercaptan 2 parts by weight Paraffin wax “HNP-57 (manufactured by Nippon Seiwa Co., Ltd.)” 66 parts by weight is added and heated to 80 ° C. And dissolved to prepare a monomer solution.

  On the other hand, a surfactant solution in which 3 parts by mass of the anionic surfactant [X] represented by the above formula (X) is dissolved in 1560 parts by mass of ion-exchanged water is heated to 80 ° C. Then, 32.8 parts by mass of the dispersion of the resin fine particles [A1] was added in terms of solid content, and the wax was dissolved by a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. The monomer solution was mixed for 8 hours to prepare a dispersion in which fine particles having a particle diameter of 160 nm were emulsified and dispersed.

  Next, an initiator solution in which 6 parts by mass of potassium persulfate is dissolved in 200 parts by mass of ion-exchanged water is added to this dispersion, and this system is heated and stirred at 80 ° C. for 3 hours for polymerization (second stage polymerization). ) To prepare a dispersion of resin fine particles [A2]. The resin fine particles [A2] had a weight average molecular weight of 23,000.

(3) Third stage polymerization (formation of outer layer)
An initiator solution in which 5.45 parts by mass of potassium persulfate is dissolved in 220 parts by mass of ion-exchanged water is added to the dispersion of the resin fine particles [A2], and the temperature is 80 ° C.
Styrene 300 parts by mass n-butyl acrylate 120 parts by mass n-octyl mercaptan A monomer mixture consisting of 7 parts by mass was added dropwise over 1 hour. After completion of the dropping, the mixture was heated and stirred for 2 hours for polymerization (third stage polymerization), and then cooled to 25 ° C. to obtain a dispersion of resin fine particles [A]. The resin-based fine particles [A] had a volume-based median diameter of 125 nm, a weight average molecular weight (Mw) of 27,800, and a glass transition temperature (Tg) of 41 ° C.

[Preparation Example of Colorant Fine Particle Dispersion [y-1] (for Yellow Toner)]
27 parts by mass of sodium n-dodecyl sulfate was dissolved in 500 parts by mass of ion-exchanged water while stirring, and C.I. I. 30 parts by weight of Solvent Yellow 3 is gradually added, and then dispersed by using a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) to disperse fine colorant particles. Liquid [y-1] was prepared. The particle diameter of the colorant fine particles in this colorant fine particle dispersion [y-1] was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.). It was 98 nm.

[Preparation Example of Colorant Fine Particle Dispersion [y-2] to [y-4] (for Yellow Toner)]
In the preparation example [y-1] of the colorant fine particle dispersion, C.I. I. Instead of Solvent Yellow 3, C.I. I. Solvent Yellow 33, C.I. I. Solvent Yellow 14, C.I. I. Colorant fine particle dispersions [y-2] to [y-2] to [y] in which colorant fine particles each having a particle size of 98 nm in terms of volume-based median diameter are dispersed, except that 30 parts by mass of Pigment Yellow 74 were used. y-4] was prepared.

[Preparation Examples of Colorant Fine Particle Dispersion [m-1] to [m-4] (for Magenta Toner)]
In the preparation example [y-1] of the colorant fine particle dispersion, C.I. I. Instead of 30 parts by mass of Solvent Yellow 3, C.I. I. Pigment red 57: 1, C.I. I. Solvent Red 49, C.I. I. Solvent Red 156, C.I. I. Colorant fine particle dispersions [m-1] to [m] in which colorant fine particles having a particle diameter of 98 nm in terms of volume-based median diameter are dispersed in the same manner except that 30 parts by mass of Solvent Red 82 are used. -4] was prepared.

[Preparation Example of Colorant Fine Particle Dispersion [c-1] (for Cyan Toner)]
In the preparation example [y-1] of the colorant fine particle dispersion, C.I. I. Instead of 30 parts by mass of Solvent Yellow 3, C.I. I. Similarly, except that 10 parts by mass of Pigment Blue 15: 3 was used, a colorant fine particle dispersion [c-1] in which colorant fine particles having a particle diameter of 98 nm in terms of volume-based median diameter were dispersed was prepared. did.

[Preparation Example of Colorant Fine Particle Dispersion [k-1] (for Black Toner)]
In the preparation example [y-1] of the colorant fine particle dispersion, C.I. I. Colorant fine particle dispersion in which colorant fine particles having a particle diameter of 98 nm in volume-based median diameter are dispersed in the same manner except that 30 parts by mass of carbon black is used instead of 30 parts by mass of Solvent Yellow 3 Liquid [k-1] was prepared.

[Toner Production Example [Y-1]]
4 liters of resin fine particle dispersion [1] 1250 g, ion exchange water 2000 g, and colorant fine particle dispersion [y-1] 165 g equipped with a temperature sensor, a cooling tube, a nitrogen introducing device and a stirring device An association solution was prepared by stirring in a neck flask. After adjusting the internal temperature of this associating solution to 30 ° C., a 5 mol / L sodium hydroxide aqueous solution was added to adjust the pH to 10.0. Next, an aqueous solution in which 52.6 g of magnesium chloride hexahydrate was dissolved in 72 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, temperature increase was started, and the system was heated to 90 ° C. over 6 minutes (temperature increase rate = 10 ° C./min). In this state, the average particle size of the associated particles was measured with “Coulter Counter Multisizer 3” (manufactured by Beckman Coulter), and 115 g of sodium chloride was ionized when the volume-based median diameter reached 6.7 μm. An aqueous solution dissolved in 700 g of exchange water was added to stop the particle growth, and further, the fusion was continued by heating and stirring at a liquid temperature of 90 ° C. ± 2 ° C. for 6 hours. When the circularity of the associated particles was measured by “FPIA2100” (manufactured by Sysmex Corporation), the average circularity was 0.958.

  Next, the mixture was cooled to 30 ° C. under conditions of 6 ° C./min, the associated particles were filtered, washed repeatedly with ion exchange water at 45 ° C., and then dried with hot air at 40 ° C. to obtain toner base particles.

(External additive treatment)
To the toner base particles, 1% by mass of hydrophobic silica (number average primary particle size = 12 nm, hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobicity = 63) are 1 The mass% was added and mixed by “Henschel mixer” (manufactured by Mitsui Miike Chemical Co., Ltd.). Thereafter, coarse particles were removed using a sieve having an opening of 45 μm, and toner [Y-1] having a median diameter of 6.5 μm on a volume basis was produced.

[Production Example of Toners [Y-2] to [Y-4]]
In the toner production example [Y-1], except that the colorant fine particle dispersions [y-2] to [y-4] were used instead of the colorant fine particle dispersion [y-1]. Toners [Y-2] to [Y-4] were obtained. The volume-based median diameter of each toner was 6.5 μm, and the average circularity was 0.958.

[Production Examples of Toners [M-1] to [M-4]]
In the toner production example [Y-1], except that the colorant fine particle dispersions [m-1] to [m-4] were used instead of the colorant fine particle dispersion [y-1] Toners [M-2] to [M-4] were obtained. The volume-based median diameter of each toner was 6.5 μm, and the average circularity was 0.958.

[Production Example of Toner [C-1]]
In the toner production example [Y-1], the toner [C-1] is similarly obtained except that the colorant fine particle dispersion [c-1] is used instead of the colorant fine particle dispersion [y-1]. ] Was obtained. The volume-based median diameter of the toner was 6.5 μm, and the average circularity was 0.958.

[Production Example of Toner [K-1]]
In the toner production example [Y-1], the toner [K-1] is similarly used except that the colorant fine particle dispersion [k-1] is used instead of the colorant fine particle dispersion [y-1]. ] Was obtained. The volume-based median diameter of the toner was 6.5 μm, and the average circularity was 0.958.

(Preparation of developer)
[CL-1] to [CL-6], [Y-1] to [Y-4], [M-1] to [M-4], [C-1] and [K-1] Clear toners [CL-1] to [CL-1], which are two-component developers, are mixed with each toner in a volume-based median diameter 50 μm ferrite carrier coated with a silicone resin so that the toner concentration becomes 6% by mass. CL-6] and developers [K-1], [Y-1] to [Y-2], [M-1] to [M-2], and [C-1] were prepared.

[Examples 1 to 12, Comparative Examples 1 and 2]
A full-color multifunction peripheral “bizhub Pro C500” (manufactured by Konica Minolta Business Technologies) is used as shown in FIG. 2, and developers [CL-1] to [CL-6], [Y-1] to [Y -4], [M-1] to [M-4], [C-1], and [K-1] were performed in combinations shown in Table 2, and Examples 1 to 12 and Comparative Examples 1 to 2 were obtained.

The output chart includes a character image using black toner, a yellow toner adhesion amount 0.2 mg / cm ² , a magenta toner adhesion amount 0.2 mg / cm ^2, and a cyan toner adhesion amount 0.2 mg / cm ^2. A full color test image having a gray solid image portion of 10 cm × 10 cm was formed by superimposing the images.

  In Comparative Example 2, an image obtained by placing clear toner [CL-1] on the entire uppermost layer of the image support was used.

[Performance evaluation]
(1) Light resistance Using a “Xenon Weather Meter XL75” (manufactured by Suga Test Instruments Co., Ltd.) on a 10 cm × 10 cm gray solid image as an output chart, irradiation is performed for 480 hours under irradiation conditions of a xenon lamp of 70,000 lux. The reflection density of the gray solid image before and after was measured, and the rate of change was obtained. Evaluation was performed with a reflection density change rate of 80% or more as an acceptable level.

The reflection density is measured using a color reflection densitometer “X-Rite 404A” (manufactured by X-Rite), and the change rate (after irradiation) of the reflection density at the maximum absorption wavelength in the wavelength region 380 to 780 nm. Concentration / concentration before irradiation).
(2) Scratch resistance The image density was measured with a Macbeth reflection densitometer “RD-918” for the gray solid image portion. The image density was a relative density with respect to white paper. The measurement part is rubbed 14 times with a load of 22 g / cm ² using plain weave bleached cotton. After rubbing, the image density of the measurement part was measured, and the density ratio before and after rubbing was defined as the fixing rate.
Fixing rate (%) = {(Image density after rubbing) / (Image density before rubbing)} × 100
When the fixing rate is 90% or more, the color is not transferred to the peripheral portion of the image, and the acceptable level is obtained.
(3) Flickering property of black character image portion With respect to the black character image portion using black toner, the flickering state of the character was evaluated by visually observing the image portion by moving the image portion and changing the observation angle.
○: Flicker is not felt ×: Flicker is felt and characters are difficult to read A reflection image of the edge portion of the yellow image was photographed with an optical microscope, and after magnifying it 2000 times, the color blur of the edge portion was visually determined. The state was evaluated using the following as an index.

×: Color blur from other color toners is observed and dot collapse is obvious Δ: Other color toners are mixed, but dot blurring is not visually recognized and color blur cannot be judged ○: Other color on edge No toner is present

  Although all the examples in the present invention have excellent characteristics, it can be seen that Comparative Examples 1 and 2 outside the present invention have problems in any of the characteristics.

10CL1, 10Y, 10CL2, 10M, 10C, 10K Photosensitive drum 30CL1, 30Y, 30CL2, 30M, 30C, 30K Toner image forming unit 17 Intermediate transfer belt

Claims (6)

  An image forming method for forming a color image on an image support using a chromatic toner containing a binder resin and a colorant, wherein the image is cleared only on an image portion formed by the chromatic toner formed on the image support. An image forming method comprising: providing a clear toner layer on at least one of the chromatic color toner layers provided with a toner layer and forming a chromatic color toner image portion.   2. The image forming method according to claim 1, wherein the chromatic color toner layer is at least one of a yellow toner layer and a magenta toner layer.   2. The image forming method according to claim 1, wherein the chromatic toner layer is a magenta toner layer.   2. The image forming method according to claim 1, wherein a dye is used as a colorant of the chromatic toner.   The image forming method according to claim 1, further comprising a chromatic toner layer provided on the clear toner layer.   6. The image forming method according to claim 1, wherein an ultraviolet absorber is contained in the clear toner layer.

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