JP4618109B2 - Image forming method - Google Patents

Description

  The present invention relates to a full-color image forming method using a transparent toner.

  With the recent progress in digitization, full-color image formation using color toner has been realized, and electrophotographic image forming apparatuses have entered the printing industry where high resolution, wide color reproduction area, and high-speed print creation are required. It has become like this.

  The full-color image forming method is, for example, developing electrostatic latent images formed on a plurality of photoconductors with yellow, magenta, cyan, and black toners, and forming the toner images of the respective colors as intermediate transfer members or recordings. A color image is formed by superimposing on paper.

By the way, when a high-gloss toner image is formed with a full-color image, the gloss difference between the toner image and the transfer sheet that supports the image increases, and there is a tendency that it is difficult to obtain a full-color image that looks good. Accordingly, an image forming method having uniform gloss over the entire surface of the transfer sheet has been studied, and a transparent toner layer is formed on the entire surface of the transfer sheet to form a transparent resin layer to obtain a toner image having uniform gloss. A technique has been proposed (see, for example, Patent Document 1). In addition, the surface roughness of the fixing layer formed with a transparent toner (for example, see Patent Document 2), or an image in which a transparent resin layer is formed with a non-spherical transparent toner after an image is formed with a spherical colored toner. There was a forming method (for example, see Patent Document 3).
Japanese Patent Laid-Open No. 11-7174 JP 2001-305816 A JP 2002-236392 A

  However, Patent Documents 1 and 2 do not have a specific description relating to the physical properties of the color toner used for image formation, and attempts to reproduce based on the disclosed contents have not yielded good results. Further, what is disclosed in Patent Document 3 is a non-spherical shape that places importance on the cleaning property of the transparent toner, and when an image is formed based on the disclosed content, a space is formed between the transparent toner layer and the image. May occur and uniform glossiness may not be obtained.

  The present invention provides an image forming method capable of forming a full-color toner image having a uniform gloss over the entire surface of the transfer sheet and forming a good appearance by forming a transparent resin layer with a transparent toner on the toner image. The purpose is to provide.

It has been found that the above-described problems can be achieved by the configurations described below. That is,
1. In an image forming method of forming a transparent resin layer using a transparent toner on a full-color image formed using at least yellow, magenta, cyan, and black toners,
The average value of the shape factor of the transparent toner is X, the average value of the shape factor of yellow toner is Ay, the average value of the shape factor of magenta toner is Am, the average value of the shape factor of cyan toner is Ac, and the shape factor of black toner When the average value of A is Ak, | X-Ay |, | X-Am |, | X-Ac |, and | X-Ak |
The volume-based median diameter of the transparent toner is Dx, the volume-based median diameter of yellow toner is Dy, the volume-based median diameter of magenta toner is Dm, the volume-based median diameter of cyan toner is Dc, and the volume-based median diameter of black toner Image formation characterized in that the values of | Dx−Dy |, | Dx−Dm |, | Dx−Dc |, and | Dx−Dk | Method.
2. 2. The image forming method according to 1, wherein an average value of a shape factor of the transparent toner is 110 to 150.
3. 3. The image forming method according to 1 or 2, wherein the transparent toner contains a wax.

  In the present invention, when a transparent resin layer is formed on a toner image using a transparent toner, a full color toner image having a uniform gloss over the entire transfer sheet can be obtained. As a result, it has become possible to stably form a full-color image with good gloss and no uneven appearance.

  The present invention relates to an image forming method for forming a transparent resin layer using a transparent toner on a full-color image formed using yellow, magenta, cyan, and black toners.

  The inventor has paid attention to the fact that a space is generated between the transparent toner layer and the image when the image is formed by the technique disclosed in Patent Document 3. And it was estimated that uniform glossiness was expressed over the entire surface of the transfer sheet by improving the adhesion between the image layer formed of the color toner and the transparent resin layer. Therefore, when image formation is performed with the shape and particle size of the color toner and the transparent toner close to each other, no space is generated between the toner image and the transparent resin layer, and a full color image having uniform gloss can be obtained. I found out.

  The reason why uniform glossiness is manifested by making the particle size difference and the shape difference between the color toner and the transparent toner within a certain range is not clear, but probably the melting state of each toner becomes uniform at the time of fixing. Therefore, the images are in a similar state, and as a result, the adhesion between the toner images is improved, the adhesion is improved, and the glossiness is assumed to be uniform.

  Hereinafter, the toner used in the present invention will be described.

  In the image forming method according to the present invention, the color toner used for image formation and the transparent toner for forming the transparent resin layer have the same particle diameter and shape as described below.

  For the toner used in the image forming method according to the present invention, the average value of the shape factor of the transparent toner is X, the average value of the shape factor of the yellow toner is Ay, the average value of the shape factor of the magenta toner is Am, When the average value of the shape factor is Ac and the average value of the shape factor of the black toner is Ak, the values of | X-Ay |, | X-Am |, | X-Ac |, and | X-Ak | 20 or less. In the present invention, the smaller the difference between the average values of the shape factors of the transparent toner and the colored toner, the better.

  In the present invention, by setting the difference between the shape factor of the color toner and the shape factor of the transparent toner within the above range, the shapes of both toners are aligned and the adhesion between the toner image layer and the transparent resin layer is improved during image formation. As a result, it is estimated that the glossiness of the image is improved.

The “shape factor” of the toner used in the present invention is represented by the following formula and represents the degree of roundness of the toner particles. That is,
Shape factor = {[(maximum toner diameter / 2) ² × π] / (projected area of toner)} × 100
Here, the maximum diameter refers to the width of the particle that maximizes the interval between the parallel lines when the projected image of the toner particles on the plane is sandwiched between two parallel lines. The projected area is the area of an image obtained when toner particles are projected onto a plane.

  This shape factor is obtained by taking a photograph in which toner particles are magnified 2000 times with a scanning electron microscope, and then analyzing a photographic image using “SCANNING IMAGE ANALYZER” (manufactured by JEOL Ltd.) based on this photograph. Was measured. At this time, the shape factor of the present invention was measured by the above formula using 100 toner particles.

  The average value of the shape factor is a value obtained by dividing the sum of the shape factors calculated by measuring a plurality of toner particles by the number of toner particles used for the measurement.

  The average value of the shape factor of the transparent toner used in the present invention is preferably 110 to 150.

  Thus, by setting the average value of the shape factor of the transparent toner within the above range, a certain degree of irregularity is imparted, the adhesion between the particles is improved, and the adhesion between the particles is improved. The reason for this is not clear, but it is presumed that this is probably because the adhesion between the particles is improved by the increase in the contact point compared to the true sphere. On the other hand, if it exceeds 150, voids are likely to be generated between the toners, and the effect is estimated to be reduced.

  Further, the volume-based median diameter (volume D50% diameter) of the transparent toner used in the present invention is Dx, the volume-based median diameter of yellow toner is Dy, the volume-based median diameter of magenta toner is Dm, and the cyan toner is When the volume-based median diameter is Dc and the volume-based median diameter of black toner is Dk, the values of | Dx−Dy |, | Dx−Dm |, | Dx−Dc |, and | Dx−Dk | It is less than 0.5 μm. In the present invention, the smaller the difference in volume-based median diameter between the transparent toner and the colored toner, the better.

  In the present invention, by making the difference between the color toner particle size and the transparent toner particle size within the above range, the difference between the image roughness of the toner image portion and the roughness of the resin layer formed of the transparent resin layer is suppressed. As a result of maintaining the uniformity formed by the transparent resin layer, it is presumed that uniform glossiness is expressed on the transfer sheet.

  The volume-based median diameter (volume D50% diameter) is measured and calculated using a device in which a computer system for data processing (Beckman Coulter, Inc.) is connected to Coulter Multisizer III (Beckman Coulter, Inc.). Can do.

  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, Inc.) in a sample stand with a pipette until the measured concentration becomes 8%, and the measurement is performed with a measuring machine count set to 2500. The aperture diameter of the Coulter Multisizer was 50 μm.

  The “transparent toner” used in the present invention contains a colorant (color pigment, coloring dye, black carbon particles, black magnetic powder, etc.) as described later for the purpose of coloring by light absorption or light scattering. It is something that does not. The transparent toner used in the present invention is usually colorless and transparent, but the transparency may be slightly lowered depending on the type and amount of wax contained therein, but it is substantially colorless and transparent. . For example, it is preferable that the light transmittance is 95% or more when only the toner particles are melted to form a pellet having a thickness of 0.5 mm.

  Next, the resin constituting the toner used in the present invention will be described.

  Polymers obtained by polymerizing polymerizable monomers such as those described below may be used for transparent toners used in the present invention and resins usable for yellow, magenta, cyan, and black toners (colored toners). Is mentioned.

  The resin used in the toner contains a polymer obtained by polymerizing at least one polymerizable monomer as a constituent component. Examples of the polymerizable monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene Styrene or styrene derivatives such as pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, methyl methacrylate, ethyl methacrylate, N-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate , Methacrylate esters such as n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, Acrylate derivatives such as isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, and phenyl acrylate , Olefins such as ethylene, propylene, isobutylene, halogenated vinyls such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride, vinylidene fluoride, vinyl propionate, vinegar Vinyl esters such as vinyl acid vinyl 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 carbazole, N-vinyl indole, There are N-vinyl compounds such as N-vinylpyrrolidone, vinyl compounds such as vinylnaphthalene and vinylpyridine, and acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide. These vinyl monomers can be used alone or in combination.

  Moreover, it is also possible to use combining what has an ionic dissociation group as a polymerizable monomer which comprises resin. For example, those having a substituent such as carboxyl group, sulfonic acid group, phosphoric acid group, specifically, acrylic acid, methacrylic acid, maleic 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, 3-chloro-2-acid phosphooxypropyl methacrylate, and the like.

  Furthermore, polyfunctionality such as divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a crosslinkable resin by using a functional vinyl.

  The binder resin obtained by polymerizing the polymerizable monomer described above has a weight average molecular weight of 5,000 to 40,000 and a glass transition point of 55 ° C. to 75 ° C. from the viewpoint of increasing the fixing speed and lowering the fixing temperature. It is preferable that it is less than.

  The binder resin for transparent toner used in the present invention may be any resin as long as the resin itself is not colored, that is, it is substantially transparent. Can be used.

  Next, the wax that can be used for the toner used in the present invention will be described. Conventionally known waxes can be used for the toner according to the present invention. Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax, long-chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, and trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellit Ester waxes such as acid tristearyl and distearyl maleate, ethylenediamine dibehenyl amide, trimellitic acid tristearyl amide, etc. Such as amide waxes.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  In the present invention, the transparent toner preferably contains a wax. By including the wax in the transparent toner, the releasability of the image surface is improved, and minute image blur due to offset at the time of fixing is prevented, so that uniform gloss can be expressed more reliably. Further, since the layer to which the wax is added is formed on the uppermost layer of the transfer sheet, the release effect on the surface of the transfer sheet is improved, and the resistance to rubbing is enhanced. As a result, the formed full-color image can maintain high gloss over a long period of time.

  Next, a method for producing the toner used in the present invention will be described. The method for producing the toner used in the present invention is not particularly limited. From the viewpoint of reproducing a full-color pictorial image with high definition, the particle size and shape can be controlled during the production process. Possible polymerized toners are preferred.

Here, a method for producing a toner having an association step in which resin particles are aggregated to form particles, which is a typical production example of toner usable in the present invention, will be described. This toner comprises (1) a resin particle dispersion preparation step, (2) a colorant particle dispersion preparation step, (3) particle association step, (4) colored particle solid-liquid separation step, and (5) drying. It is produced through the steps of (6) external additive treatment step for colored particles. Hereinafter, a method for producing a toner having a particle associating step will be described based on the order of the above steps.
(1) Production Step of Resin Particle Dispersion The resin particles referred to here are those that function as a “binder resin” for toner. The resin particles are preferably obtained by emulsion polymerization of a radical polymerizable monomer, but it is also possible to use a resin obtained by dissolving a polyester resin or the like in a solvent and then removing the solvent appropriately to adjust the solvent concentration. Is possible. Examples of the radical polymerizable monomer include the aforementioned vinyl monomers.

  Moreover, generally used chain transfer agents can be used for the purpose of adjusting the molecular weight of the resin particles. Examples of the chain transfer agent include mercaptan compounds such as octyl mercaptan, dodecyl mercaptan, t-dodecyl mercaptan, n-octyl-3-mercaptopropionic acid ester, terpinolene, α-methylstyrene dimer, and the like.

  When the polymerization is performed using a radical polymerizable monomer, a surfactant is required to disperse the radical polymerizable monomer in an aqueous medium with oil droplets. The surfactant that can be used when preparing the resin particles constituting the toner used in the present invention is not particularly limited, but includes the following.

  For example, ionic surfactants include sulfonates (sodium dodecylbenzene sulfonate, sodium arylalkylpolyether sulfonate, etc.), sulfate esters (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.) ).

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, ester compounds of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide And ester compounds of polypropylene oxide and higher fatty acids, sorbitan esters, and the like.

  In order to contain the wax in the toner, it is preferable that the toner is contained in the resin particle by dissolving in the radical polymerizable monomer forming the resin particle and then proceeding with the polymerization. Further, by separately adjusting the wax dispersion and mixing it with the resin particle dispersion and the colorant dispersion in the association step described later, these particles can be incorporated into the colored particles by aggregating and associating.

  Here, a production example of the wax dispersion will be described. The wax dispersion is prepared by, for example, adding 8 parts of an anionic surfactant to 100 parts of pure water after heating the non-polar wax, polar wax, and nonionic surfactant to the melting point of the wax or higher and uniformly melting them. A warm one is prepared separately, and the aforementioned wax melt is charged into this. And the wax melt is disperse | distributed in a liquid by applying the liquid into which the wax melt was thrown for 30 minutes-2 hours with an ultrasonic disperser, and produces a wax dispersion liquid.

  Here, the mixing ratio of the nonpolar wax and the polar wax is 15: 1 to 50: 1 by mass ratio, and preferably 20: 1 to 45: 1.

The surfactant used for wax dispersion is preferably a combination of an ionic surfactant and a nonionic surfactant. Specific examples of the ionic surfactant and the nonionic surfactant used for the wax dispersion include the same ones as mentioned for dispersing the radical polymerizable monomer in oil droplets. Usable waxes include those described above.
(2) Colorant Dispersion Making Process Colorant particles can be prepared by dispersing a colorant in an aqueous medium. The dispersion of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in an aqueous medium.

  The disperser used for the dispersion treatment of the colorant is not particularly limited, but a mechanical disperser represented by “CLEAMIX (M Technique Co., Ltd.)”, an ultrasonic disperser, a mechanical disperser A pressure disperser such as a homogenizer, a manton gourin or a pressure type homogenizer, a medium disperser such as a sand grinder, a Getzman mill or a diamond fine mill can be used.

  Examples of the surfactant used for the colorant dispersion treatment include the same surfactants as those described above.

  As the colorant, carbon black, a magnetic material, a dye, a pigment, or the like can be arbitrarily used.

  Examples of the carbon black used as the black colorant include furnace black, channel black, acetylene black, thermal black, lamp black, and the like, and examples of the magnetic substance include magnetite and ferrite.

  Examples of magenta or red pigments include C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 154, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 238 and the like.

  Examples of orange or yellow pigments include C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, solvent yellow 162, and the like.

  Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. And CI Pigment Blue 66.

The number average primary particle size of the colorant particles varies depending on the type, but is preferably about 10 to 200 nm.
(3) Particle association step In this step, resin particles, colorant particles, and the like are associated to form colored particles and particles constituting transparent toner. That is, this is a step of forming colored particles by associating resin particles encapsulating wax and colorant particles, or associating resin particles, colorant particles, and wax particles.

  As an association method for associating resin particles, colorant particles and the like, particles are obtained by mixing a resin particle dispersion, a colorant dispersion, and a wax particle dispersion, and adding an aggregating agent (salting out agent) to the mixture. Is a method of meeting. In the case of producing a transparent toner, particles are formed by a process of associating resin particles encapsulating wax without using a colorant dispersion and a process of associating resin particles and wax particles.

  When particles are aggregated, these dispersions are mixed below the glass transition temperature of the resin particles, and while the particles are aggregated, the temperature is increased and the aggregated particles are fused (fused) and simultaneously aggregated. There is a way to proceed. In this method, since the fusion can proceed while growing the particles, the particle shape and the particle size distribution can be made uniform.

  From this point of view, in the particle associating step, aggregation and fusion are performed in parallel, and when the particles grow to a desired particle size, an aggregation terminator is added to stop the growth of the particles. In order to control the shape, it is preferable to use an association method called “salting out / fusion method” in which heating is continued.

  In the association step by the “salting out / fusion method”, a colorant dispersion (or wax particle dispersion as the case may be) is added to the dispersion of resin particles obtained by the polymerization step, and the resin particles and the colored particles are added. And salting out and fusing. The “aqueous medium” in the present invention refers to a material in which the main component (50% by mass or more) is water. Examples of components other than water include water-soluble organic solvents such as methanol, ethanol, isopropanol, butanol, and acetone.

  In the particle association step, a metal salt is preferably used as an aggregating agent, and a divalent or trivalent metal salt is particularly preferably used. Moreover, a monovalent metal salt can be used as the aggregation terminator for stopping the aggregation.

  Examples of monovalent metal salts include salts of alkali metals such as sodium, potassium and lithium. Examples of divalent metal salts include salts of alkaline earth metals such as calcium and magnesium, divalent manganese and copper. Salt. Further, examples of the trivalent metal salt include metal salts such as iron and aluminum.

Specific examples of the monovalent metal salt include sodium chloride, potassium chloride, lithium chloride and the like. Specific examples of the divalent metal salt include magnesium chloride, calcium chloride, calcium nitrate, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate and the like. Further, specific examples of the trivalent metal salt include aluminum chloride and iron chloride. These are appropriately selected.
(4) Solid-liquid separation step of colored particles The solid-liquid separation step includes a filtration process for filtering the colored particles from the dispersion of colored particles obtained in the above step, and a toner cake ( This is a step of performing a cleaning treatment to remove deposits such as a surfactant and a salting-out agent from an aggregate of wet colored particles agglomerated in a cake form. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, a filtration method using a filter press and the like, and are not particularly limited.
(5) Drying process The drying process is a process in which the toner cake obtained by the washing process in the solid-liquid separation process is dried to obtain powder-shaped colored particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like.

The water content of the dried colored particles is preferably 5% by mass or less, more preferably 2% by mass or less. In addition, although colored particles that have been dried may be granulated with weak interparticle attractive force, in this case, the granules may be crushed. As the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.
(6) External Addition Processing Step The external addition processing step is a step of adding an external additive (also referred to as an external additive) to the dried colored particles as necessary to obtain a toner that can be used for image formation. It is. Examples of the apparatus used for adding the external additive include various mixing apparatuses such as a turbuler mixer, a Henschel mixer, a nauter mixer, and a V-type mixer.

  By adding an external additive, improvement in fluidity, chargeability, improvement in cleaning properties, and the like are realized. The types of these external additives are not particularly limited, and various inorganic fine particles, organic fine particles, and lubricants can be used.

  A conventionally well-known thing can be used as an inorganic fine particle. Specifically, silica, titania, alumina, strontium titanate fine particles and the like can be preferably used. These inorganic fine particles may be hydrophobized if necessary. Specific examples of the silica fine particles include commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150, H- manufactured by Hoechst. 200, commercial products TS-720, TS-530, TS-610, H-5, MS-5 and the like manufactured by Cabot Corporation.

  As titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc. are mentioned.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd. and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  In addition, examples of the lubricant include salts of zinc stearate, aluminum, copper, magnesium, calcium, etc., zinc oleate, salts of manganese, iron, copper, magnesium, etc., zinc palmitate, copper, magnesium, calcium, etc. And salts of higher fatty acids such as zinc of linoleic acid, salts of zinc, calcium and the like, zinc of ricinoleic acid, salts of calcium and the like.

  The addition amount of these external additives and lubricants is preferably 0.1 to 10.0% by mass with respect to the whole toner. The external additive and the lubricant can be added using various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer.

  The average particle size of these inorganic fine particles and organic fine particles is preferably 5 to 1000 nm. When the average particle diameter is within this range, the occurrence of aggregation due to the external additive added to the toner surface is prevented, and there is no possibility that the glossiness is impaired.

  In the transparent toner, it is preferable to control the fluidity and chargeability of the toner in order to uniformly express high glossiness uniformly. From the viewpoint of controlling the fluidity and chargeability of the transparent toner, the surface of the transparent toner In addition, it is preferable to externally add inorganic fine particles or organic fine particles.

  Next, an image forming apparatus capable of performing the image forming method according to the present invention will be described. FIG. 1 is a schematic configuration diagram of a color image forming apparatus capable of performing the image forming method according to the present invention.

  The color image forming apparatus 1 is roughly classified into a document reading device 2 that reads an image of a color document, a color image read by the document reading device 2, and an image output based on image data transmitted from a personal computer (not shown). And an image output device 3 for performing the above.

  The image output device 3 includes a photosensitive drum 4 that is an image carrier on which an electrostatic latent image is formed, a charger 5 that uniformly charges the surface of the photosensitive drum 4, and a ROS 6 (Raster Output) that is an image exposure unit. Scanner), a developing device 7 that develops the electrostatic latent image formed on the photosensitive drum 4 to form a plurality of toner images, and an intermediate transfer that sequentially transfers the toner images formed on the photosensitive drum 4 A belt 8, a first transfer charger 9 that transfers a plurality of color toner images formed on the photosensitive drum 4 to the intermediate transfer belt 8, and a color toner image formed on the intermediate transfer belt 8 are charged. A charger 10, a transparent toner developing device 11 that develops transparent toner facing the intermediate transfer belt 8, and a color toner image and a transparent toner image on the intermediate transfer belt 8 are transferred onto a transfer sheet 12. And a fixing device 14 for fixing the toner image and the transparent toner image formed on the transfer sheet 12 to the transfer sheet 12.

  The document reading device 2 illuminates a document 15 placed on a platen glass (not shown) with an illumination lamp 16, and reflects a reflected light image from the document 15 with a color scanner 17 to a predetermined dot density (for example, 16 dots / mm).

  The reflected light image of the document 15 read by the document reading device 2 is sent to the image processing device 18 as, for example, three-color document reflectance data of red (R), green (G), and blue (B) (8 bits each). Sent. In the image processing device 18, predetermined image processing such as shading correction, color correction, gradation correction, sharpness correction, and the like is performed on the reflectance data of the document 15, and yellow (Y), magenta (M), It is converted into image data of four colors of cyan (C) and black (K). The image data that has been subjected to image processing by the image processing device 18 is sent to the ROS 6 as image data of four colors of yellow (Y), magenta (M), cyan (C), and black (K).

  As shown in FIG. 1, the ROS 6 modulates the laser diode 19 in accordance with the image data, and the laser diode 19 emits a laser beam LB modulated in accordance with the image data. The laser beam LB emitted from the laser diode 19 is deflected and scanned by a rotating polygon mirror (not shown) and scanned onto the photosensitive drum 4 as an image carrier through an optical system including an f · θ lens and a reflecting mirror. Exposed.

  The photosensitive drum 4 on which the laser beam LB is scanned and exposed by the ROS 6 is rotationally driven at a predetermined speed in the direction of the arrow by a driving unit (not shown). The surface of the photosensitive drum 4 is charged to a predetermined polarity and potential by a charger 5 in advance, and then converted into yellow (Y), magenta (M), cyan (C), and black (K) colors according to image data. Corresponding laser beams LB are sequentially exposed to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 4 is developed with development units 7Y, 7M, 7C, and 7K for yellow (Y), magenta (M), cyan (C), and black (K). The toner image T is developed by the device 7 to form a toner image T of a predetermined color.

  The developing device 7 visualizes an electrostatic latent image of a corresponding color formed on the photosensitive drum 4 with each color toner of yellow (Y), magenta (M), cyan (C), and black (K). Turn into.

  The toner images T of the respective colors sequentially formed on the photosensitive drum 4 are transferred in multiple by the first transfer corotron 9 onto the intermediate transfer belt 8 disposed under the photosensitive drum 4. The intermediate transfer belt 8 is stretched by fixing an end portion to a roll-shaped member (not shown), and is driven to rotate along the arrow direction at a movement speed substantially the same as the peripheral speed of the photosensitive drum 4.

  The color toner image T formed on the photosensitive drum 4 is transferred to the intermediate transfer belt 8, but it is necessary to have a semiconductive property. When the surface of the intermediate transfer belt 8 is uniformly charged to, for example, a surface potential of −500 V, the color toner image in the transfer corotron 9 is intermediately transferred by setting the potential half-life to 0.05 seconds to 1.0 seconds. The uniform transfer onto the belt 8 and the color toner image on the transfer charger 13 can be smoothly transferred onto the transfer sheet 12. Further, the surface potential of the intermediate transfer belt 8 is sufficiently attenuated while the intermediate transfer belt 8 moves from the charger 10 to the transparent toner developing device 11.

  The intermediate transfer belt 8 can have a potential half-life in the above range by dispersing conductive inorganic powder such as conductive carbon, conductive polymer such as polyaniline, etc. in a dielectric such as polyimide. . Here, the half-life time of the potential is that the back surface of the intermediate transfer belt 8 is first grounded and the surface is charged with a charging scorotron so that the initial potential becomes −500 V, and this is directly under the electrometer within 0.05 seconds. The voltage drop is measured by moving at, and is defined as the time (including the moving time of 0.05 seconds) when the potential becomes −250V.

  As the transfer unit 9, for example, an electric field is formed between the photosensitive drum 4 and the intermediate transfer belt 8 using a conductive or semiconductive roller, brush, film, rubber blade, or the like to which a voltage is applied. The back surface of the intermediate transfer belt 8 is corona charged with a means for transferring toner particles, a corotron using a corona discharge or a scorotron charger, and the charged toner particles are transferred.

  On the intermediate transfer belt 8, all four colors of yellow (Y), magenta (M), cyan (C), and black (K) formed on the photosensitive drum 4 according to the color of the image to be formed or A part of the toner image is transferred in a state where the toner images are sequentially superimposed by the transfer corotron 9.

  Further, the surface of the intermediate transfer belt 8 onto which all or a part of the toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K) are transferred in multiple layers is charged by a charger 10. Thus, for example, it is uniformly charged to a predetermined negative polarity potential. A backup roll 20 is disposed on the back surface of the intermediate transfer belt 8 facing the charger 10.

  The charger 10 for charging the color toner image formed on the intermediate transfer belt 8 uses, for example, a contact charger using a conductive or semiconductive roller, brush, film, rubber blade, or corona discharge. Examples of the charger include a corotron charger and a scorotron charger. However, from the viewpoint of not disturbing the color toner image T on the intermediate transfer belt 8, a non-contact type charging unit that uses a corotron charger or a scorotron charger using corona discharge is preferable.

  Further, the color toner image T charged to a predetermined polarity, for example, a negative polarity by the charger 10 and the surface of the intermediate transfer belt 8 are developed with the transparent toner by the transparent toner developing device 11. A backup roll 21 is disposed on the back surface of the intermediate transfer belt 8 facing the transparent toner developing device 11.

  As the transparent toner developing device 11 for developing the transparent toner facing the intermediate transfer belt 8, a two-component developing device and a one-component developing device can be used, but the color toner image T formed on the intermediate transfer belt 8 is not disturbed. In addition, a non-contact one-component developing device is preferable because of the need for full-color pictorial image formation.

  The color toner image T and the transparent resin layer 40 transferred onto the intermediate transfer belt 8 are transferred to a secondary transfer position at a predetermined timing on a transfer sheet 12 that supports the intermediate transfer belt 8 and a backup roll 22. The second transfer roll 13 that is in pressure contact with the backup roll 22 is transferred by the pressure contact force and electrostatic attraction force. The transfer sheet 12 is fed in a predetermined size from a sheet feeding cassette (not shown) disposed inside the color image forming apparatus 1. Then, the color toner image T and the transparent resin layer 40 are collectively transferred from the intermediate transfer belt 8 to the transfer sheet 12 by the backup roll 22 and the second transfer roll 13.

  A known transfer device can be used for the second transfer roll 13 that transfers the color toner image T and the transparent resin layer 40 on the intermediate transfer belt 8 onto the transfer sheet 12. For example, a means for forming an electric field between the intermediate transfer member 8 and the transfer sheet 12 using a pair of conductive or semiconductive rolls to which a voltage is applied, and transferring charged toner particles, the intermediate transfer member 8 A means for transferring the charged toner particles by corona charging the back surface of the intermediate transfer body 8 or the back surface of the transfer material 12 by providing a counter electrode on a corotron charger or a scorotron charger provided on the back surface or the back surface of the transfer sheet 12. Is mentioned.

  The transfer sheet 12 on which the color toner image T and the transparent resin layer 40 are transferred from the intermediate transfer belt 8 is separated from the intermediate transfer belt 8 and then conveyed to the fixing device 14. As the fixing device 14 for fixing the color toner image T and the transparent resin layer 40 formed on the transfer sheet 12 on the transfer sheet 12, for example, the toner is melted and deformed using a heating roll and a pressure roll and fixed. And a heated roll fixing device.

  Further, as shown in FIG. 1, the fixing belt 30 in contact with the color toner image T and the transparent resin layer 40 on the transfer sheet 12, and the color toner T and the transparent resin layer 40 on the transfer sheet 12 are brought into contact with the fixing belt 30. It is also possible to use a heating / pressurizing device 31 that heats and melts in a heated state and a fixing device that includes a cooling and peeling means 32 that cools the heated and melted toner image and peels the color toner image and the transparent resin layer from the fixing belt 30.

  The fixing belt 30 is formed in an endless belt shape using a polymer film such as polyimide. From the viewpoint of releasability, the surface of the fixing belt 30 is preferably covered with a silicon resin or a fluorine-based resin. Further, the fixing belt 30 preferably has a surface glossiness of 60 or more as measured by a 75 ° gloss meter from the viewpoint of smoothness.

  For example, as shown in FIG. 1, the heating and pressing device 31 includes a fixing belt 30, a color toner image T, and a transparent resin layer 40 between a pair of heating and pressing rolls 33 and 34 that are driven at a constant speed. And a sheet that is conveyed and heated and pressed while sandwiching the transfer sheet 12 on which is formed. One or both of the heating / pressurizing rolls 33 and 34 are heated to a temperature at which the surface thereof melts the color toner image T and the transparent resin layer 40 by a method such as providing a heat source 35 at the center. The rolls 33 and 34 are in pressure contact. It is also possible to provide a silicon rubber or fluororubber layer on the surfaces of the rolls 33 and 34, or to specify the length of the nip region to be heated and pressurized within a range of about 1 to 8 mm.

  As shown in FIG. 1, the fixing device 14 is configured to press the transfer sheet 12 having the color toner image T and the transparent resin layer 40 transferred on the surface thereof to the heating roll 33 and the heating roll 33 via the fixing belt 30. The color toner image T and the transparent resin layer 40 are introduced into the pressure contact portion (nip portion) 34 with the heating roll 33 side and passed through the pressure contact portion between the heating roll 33 and the pressure roll 34. Then, the color toner image T and the transparent resin layer 40 are heated and melted and fixed on the transfer sheet 12. The transfer sheet 12 on which the transparent resin layer 40 and the color toner image T are cooled and solidified is peeled off by the peeling roll 36 due to the rigidity of the sheet itself.

  Through the above steps, an image having the transparent resin layer 40 made of transparent toner is obtained even in a non-image area where the color toner image T does not exist on the transfer sheet 12.

  In the present invention, the difference in the average value of the shape factors of the yellow, magenta, cyan, and black toners used for forming the color toner image and the transparent toner used for forming the transparent resin layer and the difference in the volume-based median diameter are described above. By specifying in this range, a full-color image having a uniform gloss over the entire transfer sheet can be obtained. As a result, it has become possible to stably form a full-color image with good gloss and no uneven appearance.

Hereinafter, although an example is given and explained concretely, the embodiment of the present invention is not limited to this.
1. Production of Developer (Toner) (1) Production of Resin Particles s1 for Toner Shell A polymerizable monomer solution was prepared by mixing the following polymerizable monomers. That is,
Styrene 322.3g
n-Butyl acrylate 121.9g
Methacrylic acid 35.5g
n-octyl-3-mercaptopropionate 9.55 g
In a separable flask equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, 7.08 g of anionic surfactant C ₁₂ H ₂₅ OSO ₃ Na was dissolved in 3010 g of ion-exchanged water, and stirred at 230 rpm under a nitrogen stream. While stirring at a speed, the internal temperature was raised to 80 ° C. to prepare a surfactant solution.

An initiator solution in which 9.2 g of a polymerization initiator (potassium persulfate: KPS) is dissolved in 200 g of ion-exchanged water is added to the surfactant solution to bring the temperature to 75 ° C., and then the polymerizable monomer. The solution was added dropwise over 1 hour. After completion of the dropping, polymerization was carried out by heating and stirring at 75 ° C. for 2 hours to prepare toner shell resin particles. The obtained toner particles for toner shell were designated as “toner shell resin particles s1”.
(2) Preparation of Toner Base Resin Particle Dispersion 2 7.008 g of anionic surfactant C ₁₂ H ₂₅ OSO ₃ Na was ion exchanged into a separable flask equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introducing device. It was dissolved in 3010 g of water, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

  An initiator solution prepared by dissolving 9.2 g of a polymerization initiator (potassium persulfate: KPS) in 200 g of ion-exchanged water was added to the surfactant solution to bring the temperature to 75 ° C., and then 70.1 g of styrene, n A monomer mixture composed of 19.9 g of butyl acrylate and 10.9 g of methacrylic acid was added dropwise over 1 hour. After completion of the dropwise addition, the system was heated and stirred at 75 ° C. for 2 hours to carry out polymerization (first stage polymerization) to prepare “resin particle dispersion for toner base (2H)”.

  Next, 131.2 g of pentaerythritol tetrabehenate, 105.6 g of styrene, 30.0 g of n-butyl acrylate, 6.2 g of methacrylic acid and n-octyl-3-mercaptopropionic acid were added to a flask equipped with a stirrer. It added to the monomer liquid mixture which consists of 5.6 g of ester, heated at 90 degreeC, it was made to melt | dissolve, and the monomer solution was prepared.

Meanwhile, a surfactant solution in which 1.6 g of an anionic surfactant C ₁₂ H ₂₅ OSO ₃ Na is dissolved in 2700 g of ion-exchanged water is prepared in a flask equipped with a stirrer, and the internal temperature is raised to 98 ° C. 28 g of the above-mentioned “toner base resin particle dispersion (2H)” was added in terms of solid content.

  Next, in a surfactant solution containing “toner base resin particle dispersion (2H)” by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path, The monomer solution was mixed and dispersed over 8 hours to prepare an emulsion in which emulsion particles (oil droplets) having a uniform dispersed particle size were dispersed.

  Next, an initiator solution prepared by dissolving 5.1 g of a polymerization initiator (potassium persulfate: KPS) in 240 g of ion-exchanged water and 750 g of ion-exchanged water are added to this dispersion (emulsion). Polymerization (second stage polymerization) was performed by heating and stirring at 98 ° C. for 12 hours. By the second-stage polymerization, a dispersion (2HM) of composite resin particles obtained by coating the resin particle surfaces with a resin containing pentaerythritol tetrabehenate ester.

Further, an initiator solution in which 7.4 g of a polymerization initiator (potassium persulfate: KPS) was dissolved in 200 g of ion-exchanged water was added to a flask with a stirrer charged with the entire amount of the composite resin particle dispersion (2HM), and the temperature Was added dropwise over 1 hour with a monomer mixture of 300 g of styrene, 95 g of n-butyl acrylate, 15.3 g of methacrylic acid and 10.4 g of n-octyl-3-mercaptopropionic acid ester. Then, this system was heated and stirred at 80 ° C. for 2 hours to carry out polymerization (third stage polymerization). Thereafter, this system was cooled to 28 ° C. to prepare “toner base resin particle dispersion 2” composed of composite resin particles having a structure in which the surface of the composite resin particles was coated with resin.
(3) Preparation of Colorant Dispersion Liquid (Bk) Anionic surfactant C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ OSO ₃ Na 90 g was added to 1600 g of ion-exchanged water, dissolved and stirred into a solution of carbon black. (Regal 330R: Cabot Corp.) 400 g was gradually added. Next, a colorant dispersion (Bk) was prepared by performing a dispersion treatment using a mechanical disperser CLEARMIX (M Technique Co., Ltd.). The particle diameter of the colorant particles in this dispersion was measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.) and found to be 110 nm.
(4) Preparation of Colorant Dispersion Liquids (Y), (M), (C) In the preparation of the above colorant dispersion liquid (Bk), instead of carbon black (Regal 330R: manufactured by Cabot Corporation), C.I. I. A yellow colorant dispersion (Y) was prepared in the same procedure except that 380 g of Pigment Yellow 74 was used. Further, instead of the carbon black, C.I. I. A magenta colorant dispersion (M) was prepared in the same procedure except that 390 g of Pigment Red 122 was used. Further, instead of the carbon black, C.I. I. A cyan colorant dispersion (C) was prepared in the same procedure except that 375 g of Pigment Blue 15: 3 was used. When the particle diameter of the colorant particles in the obtained colorant dispersion was measured using the aforementioned electrophoretic light scattering photometer “ELS-800”, the colorant dispersion (Y) was 108 nm, and (M) was 112 nm. , (C) was 107 nm.
(5) Association step 439.2 g (solid content conversion) of toner base resin particle dispersion 2 for toner base, 900 g of ion-exchanged water, and 200 g of “colorant dispersion (Bk)” were mixed with a temperature sensor, a cooling pipe, a nitrogen introducing device, and stirring. It stirred in the reaction container (four necked flask) which attached the apparatus. After adjusting the temperature in the container to 30 ° C., a 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 11.0.

  Next, an aqueous solution in which 12.1 g of magnesium chloride hexahydrate was dissolved in 1000 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature of the system was raised to 90 ° C. over 60 minutes to grow the particle size and perform an association reaction. In this state, the particle size of the associated particles was measured with “Coulter Multisizer III (manufactured by Beckman Coulter)”. When the volume-based median diameter reached 6 μm, 40.2 g of sodium chloride was added to 1000 g of ion-exchanged water. The dissolved aqueous solution was added to stop particle growth. Subsequently, as the aging treatment, the liquid temperature was set at 98 ° C., and the mixture was heated and stirred for 6 hours to continue the fusion.

Further, 96 g of toner shell resin particles (s1) were added, and the mixture was heated and stirred for 3 hours to be fused to the surface of the associated particles. Thereafter, 40.2 g of sodium chloride was added, the mixture was cooled to 30 ° C. at a cooling rate of 8 ° C./min, hydrochloric acid was added to adjust the pH to 2.0, and stirring was stopped. The generated particles were filtered, repeatedly washed with ion exchange water at 45 ° C., and then dried with hot air at 40 ° C. to obtain “colored particles 1Bk”. The average value of the shape factor of the obtained “colored particles 1Bk” and the volume-based median diameter were values shown in Table 1 described later.
(6) Preparation of colored particles 2Bk and colored particles 3Bk In the associating step of the colored particles 1Bk, the sodium chloride aqueous solution was added in the same manner when the particle size of the associated particles reached 4 μm in volume-based median diameter. Colored particles 2Bk ”were produced. Similarly, the sodium chloride aqueous solution was added when the particle size of the associated particles reached 8 μm in terms of the volume-based median diameter, and the mixture was further heated and stirred for 9 hours at a liquid temperature of 98 ° C. Colored particles 3Bk ”were produced.
(7) Preparation of toners 1Bk to 3Bk The obtained “colored particles 1Bk”, “colored particles 2Bk”, and “colored particles 3Bk” were coated with hydrophobic silica having a number average primary particle size of 12 nm and a hydrophobization degree of 68. 1% by mass and a hydrophobic titanium oxide having a number average primary particle size of 20 nm and a hydrophobization degree of 63 are added so as to be 1.2% by mass. ~ 3Bk ".
(8) Preparation of Toners 1Y to 3Y, 1M to 3M, 1C to 3C In the preparation of “Toners 1Bk to 3Bk”, carbon black (Regal 330R: manufactured by Cabot) was used instead of C.I. I. “Yellow toners 1Y to 3Y” were used in the same manner except that Pigment Yellow 74 was used. I. “Magenta toner 1M to 3M” is replaced with C.I. I. “Cyan toners 1C to 3C” were prepared in the same procedure except that Pigment Blue 15: 3 was used.
(9) Preparation of transparent toners 1T to 3T In the association step performed with the colored particles 1Bk to 3Bk, the toner base resin particle dispersion 2 added to the reaction vessel is changed to 639.2 g (in terms of solid content) and colored. The association reaction was carried out in the same manner except that the reaction liquid was adjusted without adding the agent dispersion (Bk). In this state, the particle size of the associated particles was measured with “Coulter Counter TA-III (manufactured by Beckman Coulter)”. When the volume-based median diameter reached 6 μm, 40.2 g of sodium chloride was added to 1000 g of ion-exchanged water. An aqueous solution dissolved in the toner was added to stop the particle growth, and “transparent toners 1T to 3T” were prepared.
(10) Preparation of toners 4Bk to 4T In the associating step of the colored particles 1Bk, the temperature was increased to 90 ° C., which was performed after the addition of the magnesium chloride hexahydrate aqueous solution, and the association was performed. Similarly, toners 4Bk to 4T were prepared.
(11) Preparation of toners 5Bk to 5T and 6Bk to 6T In the associating step of the colored particles 1Bk, the temperature increase to 90 ° C. performed after addition of the aqueous solution of magnesium chloride hexahydrate was changed to 80 ° C. Toners 5Bk to 5T were prepared in the same manner as described above.

Further, in the production of toners 5Bk to 5T, “toners 6Bk to 6T” were produced in the same manner except that the sodium chloride aqueous solution was added when the particle size of the associated particles reached 8 μm in terms of the volume-based median diameter.
(12) Preparation of Toners 7Bk to 7T In the association step of the colored particles 2Bk, the temperature was raised to 90 ° C. after the addition of the magnesium chloride hexahydrate aqueous solution to 75 ° C. for association. Made “Toners 7Bk to 7T” in the same manner.
(13) Preparation of toners 8Bk to 8T In the association step of the colored particles 1Bk, the temperature was increased to 90 ° C. after the addition of the magnesium chloride hexahydrate solution to 70 ° C. Made “Toners 8Bk-8T” in the same manner.

  Further, in the production of “Toners 8Bk to 8T”, “Toners 9Bk to 9T” was similarly prepared except that the above-described sodium chloride aqueous solution was added when the particle size of the associated particles reached 4.0 μm in terms of the volume-based median diameter. Was made. Further, in the production of “Toners 8Bk to 8T”, “Toners 10Bk to 10T” was similarly prepared except that the above-described sodium chloride aqueous solution was added when the particle size of the associated particles reached 8.0 μm in terms of the volume-based median diameter. Was made.

  Table 1 shows the average value of the shape factor and the value of the volume-based median diameter of each toner produced.

(14) Preparation of Developer Each toner shown in Table 1 is mixed with a ferrite carrier having a volume average particle diameter of 60 μm coated with a silicone resin, so that the toner concentration becomes 8% with a V-type mixer for 20 minutes. By mixing, developers 1 (1Bk, 1Y, 1M, 1C, 1T) to 10 (10Bk, 10Y, 10M, 10C, 10T) were prepared. Then, as shown in Table 2, Examples 1 to 13 and Comparative Examples 1 to 5 were made by combining a developer of transparent toner and a developer of colored toner. Table 2 shows the difference in the average value of the shape factor of the toner and the difference in the particle size of the toner in these combinations.

2. Evaluation Experiment (1) Evaluation Apparatus Evaluation was performed using the full-color image forming apparatus shown in FIG. The fixing speed was 245 mm / sec (about 50 sheets / min (A4 plate, lateral feed)), and the heating roll surface temperature was 120 ° C.
(2) Evaluation Paper Non-glossy paper (64 g / m ² ) produced by the following procedure was used as the evaluation paper (recording paper).

After beating hardwood bleached kraft pulp (LBKP) to 480 ml of freeness (Canadian Standard Freeness, CSF), 0.2% by mass of synthetic sizing agent “SPS-300” (Arakawa Chemical Industries, Ltd.) per absolute dry pulp, sulfate band 1.0% by mass and 5% by mass of talc as an inorganic filler were added to adjust the stock, and this stock was used to make paper at 950 m / min on a Simhomer wet paper machine “BALMET” (manufactured by Sumitomo Heavy Industries). In a gate roll size press apparatus, a polyglycol type nonionic surfactant per solid content (polyvinyl alcohol “P-7000” (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)) having a solid content concentration of 5% by mass comprising polyvinyl alcohol and a penetrant Apply “Hi-Lube D550” (Daiichi Kogyo Seiyaku Seiyaku Co., Ltd., 15 ppm) to the front and back of the paper. The amount and 0.55 g / m ^2, was produced non-glossy paper having a basis weight of 64 g / m ² (the foam sheet). The glossiness of the obtained non-glossy paper was 6%.
(3) Evaluation <Measurement of Gloss Difference>
Gloss meter GM-26D (Murakami Color Research Laboratory) was used to measure the glossiness (gross) of the image, and the incident angle of light with respect to the image was set to 75 degrees. The evaluated images include a uniform cyan image with cyan image signals of 10%, 50%, and 100%, a process gray image in which color toner is developed with each of the cyan image signal, magenta image signal, and yellow image signal as 50%, and Four types of images were used consisting of a process black image in which color toner was developed with each of the cyan image signal, magenta image signal, and yellow image signal being 100%, and an image in which the color toner image signals were all 0%. Then, the maximum value of the difference in glossiness of these images was obtained and evaluated according to the following criteria.

A: Glossiness difference is less than 15 B: Glossiness difference is 15 or more and less than 30 X: Glossiness difference is 30 or more <Standard Glossiness>
The standard glossiness was measured with a gloss meter VGS-1D (manufactured by Nippon Denshoku Industries Co., Ltd.) at an incident angle of 75 ° in an image portion where 90% or more of the recording material was coated with toner.

  If the standard glossiness is 17 to 37, the photographic image has a three-dimensional effect due to moderate gloss, and the characters are easy to read.

A: Standard glossiness is 25 to 37
○: Standard glossiness is 17 to 25
X: Standard glossiness is less than 17 <Glossiness unevenness>
A print image for evaluation was formed on a photoconductor with a toner image of 5 cm × 2 cm on the transfer paper under the condition that the toner adhesion amount on the photoconductor is 0.4 mg / cm ² after development. It was created by transferring and heat fixing.

  This evaluation print image was visually observed by 10 panelists, and the following evaluation was performed.

◎: 0 to 1 people responded that they felt toner image unevenness ○: 2 to 4 people answered that toner image unevenness was worrisome ×: People who answered that toner image unevenness was worrisome More than 5 people.
<Fixability of halftone image>
C, M, Y, and Bk halftone images (toner adhesion amount 0.2 mg / cm ² ) were respectively output and evaluated by the ratio of the reflection density before and after rubbing 20 times with a load of 1 Pa.

A: 80% or more B: 70% or more and less than 80% X: less than 70% The results are shown in Table 3.

  As shown in Table 3 above, in Examples 1 to 13, good evaluation results were obtained for all differences in glossiness, standard glossiness, glossiness unevenness, etc., whereas in Comparative Examples 1 to 5, evaluation items were evaluated. Either of them was not achieved, and it was confirmed that the effect of the present invention was not achieved. As described above, it was confirmed that a color image having high gloss can be maintained over a long period of time by the image forming method according to the present invention.

  By the way, in this evaluation experiment, the fixing properties of the halftone images were all good, but this was because the transparent toner layer containing wax was formed on the uppermost layer of the image, resulting in resistance to rubbing. This is presumably due to the fact that Furthermore, in Examples 1 to 13, the fixability is further improved. By specifying the shape and size of the toner used for image formation, the occurrence of offset during fixing can be avoided, and the toner image This is presumably because the occurrence of minute image blur on the surface was prevented.

FIG. 2 is a schematic diagram of a color image forming apparatus in which a transparent toner can be mounted.

Explanation of symbols

1 Color image forming apparatus 4 Photosensitive drum (image carrier)
7 Developing device 8 Intermediate transfer belt (intermediate transfer member)
9 First transfer charger 10 Charger 11 Transparent toner developing device 12 Transfer sheet 13 Second transfer charger 14 Fixing device 40 Transparent resin layer T Color toner image

Claims (3)

In an image forming method of forming a transparent resin layer using a transparent toner on a full-color image formed using at least yellow, magenta, cyan, and black toners,
The average value of the shape factor of the transparent toner is X, the average value of the shape factor of yellow toner is Ay, the average value of the shape factor of magenta toner is Am, the average value of the shape factor of cyan toner is Ac, and the shape factor of black toner When the average value of A is Ak, | X-Ay |, | X-Am |, | X-Ac |, and | X-Ak |
The volume-based median diameter of the transparent toner is Dx, the volume-based median diameter of yellow toner is Dy, the volume-based median diameter of magenta toner is Dm, the volume-based median diameter of cyan toner is Dc, and the volume-based median diameter of black toner Image formation characterized in that the values of | Dx−Dy |, | Dx−Dm |, | Dx−Dc |, and | Dx−Dk | Method. 2. The image forming method according to claim 1, wherein an average value of a shape factor of the transparent toner is 110 to 150. The image forming method according to claim 1, wherein the transparent toner contains a wax.

Images