JP2007079406A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method for forming a favorable toner image having no image defect on a back face of a sheet upon carrying out double-side printing. <P>SOLUTION: When an image is formed on the back face of a transfer sheet, the toner image formed on the top face of the transfer sheet satisfies a relational formula (1). In formula (1), ρt represents the volume resistivity of the toner, dt is the toner layer thickness, ρw is the volume resistivity of a wax single material, dw is the wax layer thickness, ρt' is the volume resistivity of a peeled layer, and dt' is the thickness of the peeled layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method using a toner containing a wax.

  In recent years, in the field of electrophotographic image forming technology, color image formation using a plurality of color toners has been performed in addition to the conventional monochrome image formation. With the advancement of digital technology, for example, it becomes possible to reproduce a minute dot image at a level of 1200 dpi (dpi; number of dots per inch, 1 inch = 2.54 cm) using toner, thereby achieving high resolution. Entry into the printing industry, which requires rich color reproducibility and high-speed print production, has come to be considered.

  Thus, as one of the factors for obtaining a finished toner image that is inferior to that of a printed image, a so-called wax containing a polymerized toner whose particle size and shape can be controlled in the manufacturing process is incorporated. The presence of oilless toner is mentioned (for example, refer patent document 1).

  In addition, print production by printing has the advantage of creating a large amount of high-quality images, but it is not suitable for ordering small prints with a small number of prints, because it requires time and effort to create prints. Had a face. On the other hand, an electrophotographic image forming method can provide a user with a required number of printed materials on demand without causing a plate like printing, and accepts a small print request with a small number of orders. It is a system that is convenient for contractors with many cases. Then, development of an image forming apparatus capable of creating an on-demand print is in progress. For example, there is a technique for providing a user-friendly device by making it possible to set a cover sheet, an insert sheet, or the like in an output bundle of printed materials, and by reducing the size of the apparatus and the number of parts ( For example, see Patent Document 2).

In addition, toner designs suitable for on-demand print creation are being developed. For example, there is a toner in which the toner image obtained by double-sided printing has a specific range of the dynamic friction coefficient of the toner image or the area occupied by carbon or oxygen by ESCA surface analysis so as not to cause blocking or tacking (for example, (See Patent Document 3). Also, by providing a step of concentrating the resin particle dispersion during the toner manufacturing process, the performance of the toner is improved, odor generation at the time of heat fixing and odor adhesion to printed matter are eliminated, and it is equivalent to an offset print image There is a toner that can obtain a pictorial image (see, for example, Patent Document 4).
Japanese Patent Application Laid-Open No. 2002-214821 (see paragraph 0049, etc.) Japanese Patent Laying-Open No. 2005-15225 (see paragraph 0097 etc.) Japanese Patent Laying-Open No. 2004-157423 (see paragraph 0018) JP 2004-271484 A (see paragraph 0019 and the like)

  By the way, there are cases where images are formed on both sides of the paper, as represented by bookbinding products, and the toner has been improved so that a good toner image can be obtained even if images are formed on both sides. Yes.

  However, when double-sided printing is performed, if image formation on the back side is continued after image formation on the front side, image defects such as white stripes will occur on the back side, and image quality will be lower than that on the front side. There was a problem of decline.

  An object of the present invention is to provide an image forming method capable of forming a good toner image without causing image defects on the back side when image forming is performed on both sides of a sheet. In particular, it is an object of the present invention to provide an image forming method applicable to on-demand print creation that requires high image quality for double-sided printed matter.

  It has been confirmed that the above problem can be solved by the configuration described below.

(1)
An image forming method for forming a toner image on both sides of a transfer sheet using a toner containing wax,
An image forming method, wherein when an image is formed on the back side of the transfer sheet, a toner image formed on the front side of the transfer sheet has the following relational expression.

(Where ρt is the volume resistivity of the toner (Ω · cm), dt is the thickness of the toner layer (μm), ρw is the volume resistivity of the wax alone (Ω · cm), and dw is the thickness of the wax layer (μm). , Ρt ′ represents the volume resistivity (Ω · cm) of the peeled layer, and dt ′ represents the thickness (μm) of the peeled layer.)
(2)
The image forming method according to (1), wherein the volume resistivity of the toner or wax is calculated by applying a voltage to a sample prepared by applying pressure to the toner or wax. .

(3)
The toner image is formed on both sides of the transfer sheet via an intermediate transfer belt, and the volume resistivity of the toner is higher than the volume resistivity of the intermediate transfer belt. The image forming method according to (1) or (2).

  According to the present invention, when an image is formed on both sides of a transfer sheet, a good toner image can be formed without causing image defects such as white stripes on the back side. In particular, it is possible to provide an image forming method that can be applied to on-demand printing, which often requires high-quality double-sided printed matter.

  The present invention relates to an image forming method using a toner containing a wax. The inventor examined a mechanism in which an image defect occurs on the back side when double-sided printing is performed. Pay attention to the presence of the wax layer formed on the transfer sheet after the toner image is formed, and pay attention to the fact that the image-formed transfer sheet is conveyed in contact with a member such as a reverse path when performing double-sided printing. did.

  When the transfer sheet immediately after fixing comes into contact with the member through the reverse path, the inventor scrapes off the toner image composed of the wax layer and the toner layer on the transfer sheet, resulting in non-uniform thickness of the layer. It was presumed that the charge distribution on the side fluctuated and image defects occurred.

  Therefore, the present inventor has a method for preventing variation in the charge distribution on the back side even when the wax layer or toner layer formed on the transfer sheet comes into contact with the member and the film thickness becomes somewhat uneven. Thought. Then, by specifying the relationship between the volume resistivity of the toner used for image formation and the wax contained in the toner, and the relationship between the thickness of the toner layer and the wax layer, a good toner image without image defects can be formed. Was found.

  Hereinafter, the present invention will be described in detail.

  In the present invention, when performing double-sided printing that forms an image on both sides of a transfer sheet, if the toner image formed on the front surface satisfies the following relational expression, the image formed on the back side may include white stripes or the like. It has been found that image defects do not occur. That is,

  In the formula, ρt is the volume resistivity (Ω · cm) of the toner, dt is the thickness (μm) of the toner layer, ρw is the volume resistivity (Ω · cm) of the wax alone, dw is the thickness (μm) of the wax layer, ρt ′ represents the volume resistivity (Ω · cm) of the peeled layer, and dt ′ represents the thickness (μm) of the layer peeled by contact with the member in the inversion path.

  FIG. 1 is a schematic cross-sectional view showing the structure of a toner image formed on the front side of a transfer sheet when duplex printing is performed. FIG. 1A shows a toner image composed of a toner layer and a wax layer formed on the front surface of a transfer sheet by a fixing process after the toner image formed on the intermediate transfer belt is transferred onto the transfer sheet. Indicates. FIG. 1B shows the state of the toner image on the front surface of the transfer sheet after passing through the reverse path. As shown in FIG. 1B, when the transfer sheet on which the image is formed on the front surface is passed through the reversing path, a wax layer covering the surface of the toner image by contact of the transfer sheet with the reversing path member or The toner layer is partially scraped off. In the present invention, the layer pressure and volume resistivity of the toner layer and the wax layer constituting the toner image formed on the transfer sheet, and the layer thickness and volume resistivity of the peeled toner image region satisfy the above relationship. It has been found that stable image formation can be performed on the back side.

  The thicknesses of the toner layer, wax layer, and peeled layer shown in FIG. 1 can be measured by, for example, a transmission electron microscope (TEM). When these thicknesses are measured using a transmission electron microscope, the toner image is embedded in a room temperature curable epoxy resin together with the transfer sheet and cured, and then the resulting block is flaky using a microtome. A sample is cut out and loaded into a transmission electron microscope, and a cross-sectional form of the toner image on the transfer sheet is photographed. Moreover, at the time of sample preparation, it is also possible to perform a dyeing | staining process using ruthenium tetroxide and osmium tetroxide together as needed.

It is also possible to calculate from the amount of toner adhering to the transfer sheet. For example, when 15 g / m ^{2 of} toner adheres to the transfer sheet, the thickness of the toner layer after fixing is 20 μm, and the amount of toner adhering Is 10 g / m ² , the thickness of the toner layer is 15 μm. A method for calculating the toner layer after fixing from the toner adhesion amount is obtained by a known method.

Next, the volume resistivity of the toner and wax used in the present invention will be described. As shown in the following procedure, the volume resistivity of the toner and wax used in the present invention is measured with a measurement sample prepared by pressurizing the toner or wax to form a measurement sample and molding only with pressure without applying heat. Is done.
(1) A toner or wax is put into a pressure molding machine, and pressure is applied to produce a disk-shaped measurement sample having a diameter of 80 mm and a thickness of 2 mm.
(2) A sample prepared on the counter electrode is placed, and an HR probe (diameter 50 mm) conforming to JIS-K6911 is placed on the sample.
(3) The counter electrode and the probe are connected to a microammeter (using a digital ultrahigh resistance / microammeter “R8340A” (manufactured by Advantest)), and a voltage of 500 V is applied between the counter electrode and the probe. The measurement environment is a temperature of 23 ° C. and a humidity of 45%.

  The pressure molding machine is an apparatus that press-molds a powder sample such as toner or wax into a disk shape, and produces a high-density measurement sample.

  In FIG. 2, the external shape (a) and measurement state (b) of the measurement sample produced with the press molding machine are shown.

  The volume resistivity of the toner can be adjusted by the amount of external additive added.

  Next, FIG. 3 shows the structure of the toner used in the present invention. The toner shown in FIG. 3 has a so-called sea-island structure in which a wax phase exists as an isolated phase (island) in a continuous resin phase (sea). 3A and 3B are schematic views of a toner having a sea-island structure in which a wax phase is present in a continuous phase of a resin.

  The structure of the toner used in the present invention is confirmed by a cross-sectional photograph taken with a transmission electron microscope. That is, it is confirmed by transmission electron microscope (TEM) that the colorant phase having different luminance and the above-described wax phase are present in an island shape in the continuous phase (resin phase) of the resin.

  Examples of the transmission electron microscope apparatus for observing the toner structure include “LEM-2000 type (manufactured by Topcon Corporation)”.

  For example, the toner can be photographed with a transmission electron microscope after the toner is sufficiently dispersed in a room temperature curable epoxy resin, embedded and cured, and then dispersed in a styrene fine powder having a particle size of about 100 nm. Mold. At this time, if necessary, the obtained block can be dyed with ruthenium tetroxide or osmium tetroxide. After the pressure molding, a flaky sample is cut out using a microtome equipped with diamond teeth and loaded into a transmission electron microscope (TEM) to photograph a tomographic form of the toner.

  Next, the wax used for the toner used in the present invention will be described. The toner used in the present invention is a toner containing a wax. The wax is not particularly limited as long as it satisfies the above-described relational expression, and a known wax can be used.

  Specifically, polyolefin waxes such as polyethylene wax, polypropylene wax and polybutylene wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax and montan wax. , Trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate , Ester waxes such as tristearyl trimellitic acid and distearyl maleate, ethylenediamine dibehenyl amide, trimellitic acid Such as amide-based waxes such as stearyl amide.

  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 10% by mass to 30% by mass.

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

  The weight average molecular weight (Mw) of the resin constituting the toner used in the present invention is not particularly limited, and has the same weight average molecular weight (Mw) as the binder resin constituting the known toner. It is.

  The molecular weight of the resin constituting the toner used in the present invention can be measured using, for example, GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a solvent.

  In the method of measuring the molecular weight of a resin by GPC (gel permeation chromatography), first, a measurement sample is dissolved in tetrahydrofuran (THF) so as to have a concentration of 1 mg / ml. The dissolution condition is 5 minutes using an ultrasonic disperser at room temperature.

  Next, after processing with a membrane filter having a pore size of 0.2 μm, 10 μl of sample solution is injected into GPC.

  Examples of specific measurement conditions for GPC are shown below.

Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKguardcolumn + TSKgelSuperHZM-M3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: tetrahydrofuran (THF)
Flow rate: 0.2 ml / min
Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of the sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes for calibration curve measurement were used.

  Next, the size of the toner used in the present invention will be described. The toner used in the present invention preferably has a volume-based median diameter (volume D50% diameter) of 3 to 8 μm. The volume-based median diameter can be measured and calculated using a device in which a computer system for data processing (manufactured by Beckman Coulter) is connected to Coulter Multisizer III (manufactured by Beckman Coulter, Inc.).

  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 injected into a beaker containing ISOTON II (manufactured by Beckman Coulter, Inc.) in a sample stand with a pipette until a measurement concentration of 5 to 10% is reached, and the measuring machine count is set to 2500. To do. The aperture diameter of the Coulter Multisizer was 50 μm.

The softening point of the toner and wax used in the present invention can be calculated by measurement with a flow tester. Specifically, using a flow tester “CFT-500” (manufactured by Shimadzu Corporation), the diameter of the die pores is 1 mm, the length is 1 mm, the load is 20 kg / cm ² , the temperature rising rate is 6 ° C./min, and the temperature rising start temperature. A softening point is defined as a temperature corresponding to one half of the height from the outflow start point to the outflow end point when a 1 cm ³ sample is melted out under a condition of 50 ° C.

  Next, a method for producing the toner used in the present invention will be described.

  The toner containing the wax used in the present invention has a structure in which the wax is not exposed on the surface of the toner in order to develop stable charging performance, and the built-in wax can be efficiently leached out during fixing. Is preferred. That is, the toner having the structure as shown in FIG. 1A is preferable, and such a toner can be manufactured through a process of aggregating resin particles containing wax in an aqueous medium to form particles. Is possible.

As typical methods for agglomerating resin particles containing wax in an aqueous medium to form toner particles, the following two methods may be mentioned.
(1) A method of producing a toner through a step of polymerizing a polymerizable monomer in which wax is dissolved to form resin particles, and aggregating the formed resin particles in an aqueous medium.
(2) A method for producing a toner through a step of aggregating resin particles and wax particles in an aqueous medium.

  Hereinafter, a method for producing the toner used in the present invention will be further described.

  For example, as described in (1) above, the toner used in the present invention is obtained by dissolving or dispersing wax in a polymerizable monomer that forms a resin, and then mechanically dispersing fine particles in an aqueous medium. The polymerizable monomer is polymerized by the mini-emulsion polymerization method to form composite resin particles containing a wax. There is a method of forming toner by aggregating the formed composite resin particles and colorant particles. In this case, when the wax component is dissolved in the polymerizable monomer, the wax component may be dissolved and dissolved or melted and dissolved.

  Further, as described in (2) above, resin particles are formed by polymerizing a polymerizable monomer that is mechanically dispersed in an aqueous medium to form resin particles, and the formed resin particles, colorant particles, and wax particles. There is a method of forming a toner by agglomerating the toner.

  The method for producing resin particles will be further described with the method (1) as the main.

[Dissolution / dispersion process]
In this step, a wax compound is dissolved in the radical polymerizable monomer, and a radical polymerizable monomer solution in which the wax compound is mixed is prepared. In the method (2), a radical polymerizable monomer is prepared without containing wax.

[Polymerization process]
In a preferred example of this polymerization step, a radical polymerizable monomer solution is added to an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less, and mechanical energy is applied to form droplets. Then, a water-soluble radical polymerization initiator is added, and the polymerization reaction proceeds in the droplet. An oil-soluble polymerization initiator may be contained in the droplets. In such a polymerization process, mechanical energy is imparted and forcedly emulsified (formation of droplets) is essential. Examples of the mechanical energy applying means include means for applying strong stirring or ultrasonic vibration energy such as homomixer, ultrasonic wave, and manton gorin.

  By this polymerization step, in the case of (1), resin particles containing wax are obtained. In the case of (2), resin particles containing no wax are obtained. Here, the produced resin particles may be colored particles. The colored resin particles can be obtained by polymerizing a monomer composition containing a colorant. In addition, when using uncolored resin particles, the dispersion of the colorant particles is added to the dispersion of the resin particles in the aggregation / fusion process described later to melt the resin particles and the colorant particles. Color particles can be obtained by attaching.

  In the case of (2), the colored particles can be formed by adding the colored particle dispersion and the wax particle dispersion to the resin particle dispersion and fusing the resin particles with the colorant particles and the wax particles. It is.

[Aggregation / fusion process]
As a method of aggregation and fusion in the aggregation / fusion process, a salting out / fusion method using resin particles (colored or non-colored resin particles) obtained in the polymerization process is preferable. In the agglomeration / fusion step, fine particles of internal additives such as wax particles and charge control agents can be agglomerated and fused together with the resin particles and the colorant particles.

  The “aqueous medium” in the agglomeration / fusion step is one in which the main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

  The colorant particles can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. Examples thereof include a medium type disperser. Examples of the surfactant used include the same surfactants as those described above. The colorant (fine particles) may be surface-modified. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the molecular weight solution, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is separated by filtration, washed and filtered with the same solvent, and dried to obtain a colorant (pigment) treated with the surface modifier.

  Also, the wax particle dispersion can be prepared in the same procedure as the colorant particle dispersion.

  The salting out / fusing method, which is a preferred agglomeration and fusing method, is a salting out method comprising an alkali metal salt, an alkaline earth metal salt, a trivalent salt, or the like in water in which resin fine particles and colorant fine particles are present. An agent is added as a coagulant having a critical coagulation concentration or higher, and then salting-out proceeds by heating to a temperature above the glass transition point of the resin fine particles and above the melting peak temperature (° C.) of the mixture. At the same time, it is a process of fusing. Here, the alkali metal salt and alkaline earth metal salt which are salting-out agents include lithium, potassium, sodium and the like as the alkali metal, and examples of the alkaline earth metal include magnesium, calcium, strontium and barium. Preferably, potassium, sodium, magnesium, calcium, and barium are used.

  When agglomeration and fusion are performed by salting out / fusion, it is preferable to make the time allowed to stand after adding the salting-out agent as short as possible. The reason for this is not clear, but there are problems that the aggregation state of the particles fluctuates depending on the standing time after salting out, the particle size distribution becomes unstable, and the surface property of the fused toner fluctuates. appear. The temperature for adding the salting-out agent needs to be at least the glass transition temperature of the resin fine particles. The reason for this is that if the temperature at which the salting-out agent is added is equal to or higher than the glass transition temperature of the resin fine particles, the salting out / fusion of the resin fine particles proceeds rapidly, but the particle size cannot be controlled. There arises a problem that particles having a particle size are generated. Although the range of this addition temperature should just be below the glass transition temperature of resin, generally it is 5-55 degreeC, Preferably it is 10-45 degreeC.

  Further, the salting-out agent is added at a temperature not higher than the glass transition temperature of the resin fine particles, and then the temperature is raised as quickly as possible to a temperature not lower than the glass transition temperature of the resin fine particles and not lower than the melting peak temperature (° C.) of the mixture. Heat to. The time until this temperature rise is preferably less than 1 hour. Further, although it is necessary to quickly raise the temperature, the rate of temperature rise is preferably 0.25 ° C./min or more. The upper limit is not particularly clear, but if the temperature is increased instantaneously, salting out proceeds rapidly, so there is a problem that particle size control is difficult, and 5 ° C./min or less is preferable. By this fusing step, a dispersion of associated particles obtained by salting out / fusing resin fine particles and arbitrary fine particles is obtained.

[Shelling process]
In the shelling step, the resin particle dispersion for shell is added to the associated particle dispersion, the resin particles are aggregated and fused on the surface of the associated particles, and the surface of the associated particles are coated with the resin particles for shell to give colored particles. Form. As described above, by forming the shell, the colorant and the wax are not exposed on the surface of the colored particles, and good charging performance is imparted.

  Specifically, the dispersion resin of shell resin particles is added to the associated particle dispersion while maintaining the temperature in the above-described aggregation / fusion process, and the resin for shell is slowly added over several hours while continuing heating and stirring. The particles are coated on the associated particle surface to form colored particles. The heating and stirring time is preferably 1 hour to 7 hours, particularly preferably 3 hours to 5 hours. To stop the particle growth by adding a terminator such as sodium chloride when the colored particles have reached a predetermined particle size by shelling, and then fuse the resin particles for the shell adhered to the associated particles. Continue to stir for several hours. In the shelling step, a surface layer having a thickness of 10 to 500 nm is formed on the surface of the associated particles. In this way, resin particles can be fixed to the surface of the core particles to form a shell, and colored particles having a uniform shape can be formed.

  In the present invention, it is possible to produce a rounded toner having a uniform shape through the above-described steps.

[Cooling process]
This step is a step of cooling (rapid cooling) the dispersion of colored particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

[Solid-liquid separation and washing process]
In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the colored particles from the dispersion of colored particles cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (in a wet state) A cleaning treatment for removing deposits such as a surfactant and a salting-out agent from an aggregate obtained by agglomerating certain colored particles into a cake is performed. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

[Drying process]
In this step, the washed toner cake is dried to obtain dried 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, when the dried colored particles are aggregated by weak interparticle attractive force, the aggregate may be crushed. Here, 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.

[External process]
This step is a step of preparing a toner by mixing the dried colored particles with an external additive as necessary. As a mixing device for the external additive, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

  Next, the polymerizable monomer used for the toner usable in the present invention will be described. The resin constituting the toner that can be used in the present invention contains a polymer obtained by polymerizing at least one polymerizable monomer as a constituent component. Specifically, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2 , 4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, etc. Styrene or styrene derivatives, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacryl Lauryl acid, methacrylate , Methacrylate derivatives such as diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-acrylate -Octyl, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, acrylate derivatives, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide, fluoride Halogenated vinyls such as vinyl 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 methyl Vinyl ketones such as ketone, vinyl ethyl ketone, vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, vinyl compounds such as vinyl naphthalene, vinyl pyridine, acrylonitrile, methacrylo Examples thereof include vinyl monomers such as acrylic acid or methacrylic acid derivatives such as nitrile 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, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar 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 phosphooxy And propyl methacrylate.

  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.

  Next, the polymerization initiator, chain transfer agent, and surfactant that can be used in the toner production method used in the present invention will be described.

  The resin constituting the toner used in the present invention is produced by polymerizing the polymerizable monomer described above, and usable radical polymerization initiators include oil-soluble polymerization initiators and water-soluble polymerization initiators. Is mentioned.

  Oil-soluble polymerization initiators include 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile ), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile and other azo or diazo polymerization initiators, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, Cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4-t -Butylperoxycyclohexyl) propane, tris- (t- Chiruperuokishi) triazine and the like polymeric initiators having a side chain a peroxide-based polymerization initiator or a peroxide, such as.

  Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and salts thereof, and hydrogen peroxide.

  In addition, a dispersion stabilizer can be used to appropriately disperse the polymerizable monomer and the like in the reaction system. Dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate , Bentonite, silica, alumina and the like. Furthermore, those generally used as surfactants such as polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as the dispersion stabilizer.

  Moreover, it is also possible to use a generally used chain transfer agent for the purpose of adjusting the molecular weight of the resin. The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide and α-methyl. Styrene dimer or the like is used.

  In addition, in order to perform polymerization using a radical polymerizable monomer, it is necessary to disperse oil droplets in an aqueous medium using a surfactant. Although it does not specifically limit as surfactant which can be used in this case, The following ionic surfactant can be mentioned as an example of a suitable thing.

  Examples of the ionic surfactant include sulfonates (sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6 Sodium sulfonate, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sodium sulfonate, etc.), sulfuric acid Ester salts (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate) Beam, calcium oleate and the like).

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester Etc.

  Next, the colorant used for the toner used in the present invention will be described. As the colorant used in the toner used in the present invention, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. Specific colorants are shown below.

  Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red 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 the colorant for orange or yellow 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 the colorant 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.

  These colorants may be used alone or in combination of two or more as required. The addition amount of the colorant is set in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

  As the charge control agent, a known one that can be dispersed in water can be used. Specific examples include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, azo metal complexes, disalicylic acid metal salts, dibenzyl acid salts or metal complexes thereof.

  In addition, it is preferable that these charge control agents and waxes have a number average primary particle diameter of about 200 to 900 nm in a dispersed state.

  The toner used in the present invention may be prepared by a suspension polymerization method as disclosed in, for example, Japanese Patent Application Laid-Open No. 7-152198, in addition to the toner prepared through the above-described step of aggregating particles. Is possible. That is, a polymerizable monomer composition in which a colorant and a wax are dissolved and dispersed in a polymerizable monomer is put into an aqueous medium, and the polymerizable monomer composition is dispersed and stirred in the aqueous medium. In this method, toner is prepared by polymerization.

  The toner used in the present invention may be either a one-component developer or a two-component developer, but a non-magnetic one-component developer is particularly preferably used for forming a clear full-color pictorial image. Is done.

  Next, an image forming apparatus that can be used in the image forming method according to the present invention will be described. The image forming apparatus that can be used in the image forming method according to the present invention is not particularly limited, but a monochrome image forming apparatus that forms an image with a single color toner, or an intermediate transfer belt that transfers a toner image on an image carrier. A color image forming apparatus that sequentially transfers images to each other, and a plurality of image carriers for each color are arranged in series on the intermediate transfer member, and each color toner image formed on each image carrier is placed on the intermediate transfer member. Examples thereof include a tandem color image forming apparatus that transfers and forms an image.

  FIG. 3 is a cross-sectional configuration diagram showing a color image forming apparatus as an embodiment of the image forming apparatus of the present invention. Note that the image forming apparatus in FIG. 3 can perform so-called double-sided printing, which forms an image on both sides of the transfer sheet P.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, an endless belt-shaped intermediate transfer belt unit 7 as a transfer unit, and a transfer sheet P. An endless belt-shaped sheet feeding and conveying means 21 and a belt type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 1Y as a first image carrier, and the photoconductor 1Y. A charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, a primary transfer roller 5Y as a primary transfer unit, and a cleaning unit 6Y are arranged around the periphery. In addition, an image forming unit 10M that forms a magenta image as another different color toner image is a drum-shaped photoconductor 1M as a first image carrier, and is arranged around the photoconductor 1M. The charging unit 2M, the exposure unit 3M, the developing unit 4M, the primary transfer roller 5M as the primary transfer unit, and the cleaning unit 6M are included. In addition, an image forming unit 10C that forms a cyan image as another different color toner image includes a drum-shaped photoconductor 1C as a first image carrier, and around the photoconductor 1C. A charging unit 2C, an exposure unit 3C, a developing unit 4C, a primary transfer roller 5C as a primary transfer unit, and a cleaning unit 6C are disposed. In addition, an image forming unit 10K that forms a black image as one of other different color toner images is disposed around a drum-shaped photoconductor 1K as a first image carrier and the photoconductor 1K. A charging unit 2K, an exposure unit 3K, a developing unit 4K, a primary transfer roller 5K as a primary transfer unit, and a cleaning unit 6K.

  The endless belt-shaped intermediate transfer belt unit 7 includes an endless belt-shaped intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  The respective color images formed by the image forming units 10Y, 10M, 10C, and 10K are sequentially transferred onto the rotating endless belt-shaped intermediate transfer belt 70 by the primary transfer rollers 5Y, 5M, 5C, and 5K, and are combined. A colored image is formed. A transfer sheet P such as a sheet as a recording medium accommodated in the sheet feeding cassette 20 is fed by a sheet feeding / conveying means 21, passes through a plurality of intermediate rollers 22 A, 22 B, 22 C, 22 D, and a registration roller 23, and is secondary. It is conveyed to a secondary transfer roller 5A as a transfer means, and color images are collectively transferred onto the transfer sheet P. The transfer sheet P to which the color image has been transferred is fixed by the belt-type fixing device 24, is sandwiched between the discharge rollers 25, and is placed on the discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the transfer sheet P by the secondary transfer roller 5A, the residual toner is removed by the cleaning means 6A from the endless belt-shaped intermediate transfer belt 70 from which the transfer sheet P is separated by curvature.

  During the image forming process, the primary transfer roller 5K is always in pressure contact with the photoreceptor 1K. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5A comes into pressure contact with the endless belt-shaped intermediate transfer belt 70 only when the transfer sheet P passes through the secondary transfer roller 5A.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10K, and an endless belt-shaped intermediate transfer belt unit 7.

  The image forming units 10Y, 10M, 10C, and 10K are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer belt unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1K in the figure. The endless belt-shaped intermediate transfer belt unit 7 includes an endless belt-shaped intermediate transfer belt 70 that can be rotated by winding rollers 71, 72, 73, 74, and 76, primary transfer rollers 5Y, 5M, 5C, and 5K, and a cleaning unit. 6A.

  The image forming units 10Y, 10M, 10C, and 10K and the endless belt-shaped intermediate transfer belt unit 7 are integrally pulled out from the main body A by the drawer operation of the housing 8.

  In this manner, toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer belt 70, and are collectively applied to the transfer sheet P. The image is transferred and fixed by a belt-type fixing device 24 by pressing and heating. The photoreceptors 1Y, 1M, 1C, and 1K after transferring the toner image to the transfer sheet P are cleaned with the cleaning device 6A to remove the toner remaining on the photoreceptor, and then the above-described charging, exposure, and development cycle. The next image formation is performed.

  An example of the structure of the endless belt-shaped intermediate transfer belt 70 is shown in FIG. FIG. 5A shows a two-layer structure having a surface layer 701 and a base material layer 703. FIG. 5B shows an intermediate layer 704 on the base material layer 703 and a surface on the intermediate layer 704. A three-layer structure including the layer 701 is employed. FIG. 5C shows a four-layer structure having two intermediate layers 704 and 705 outside the base material layer 703 and a surface layer 701 outside the intermediate layer 705.

  The surface layer 701 preferably contains a binder resin having a low surface energy. By reducing the surface energy on the intermediate transfer belt 70, the separation of the toner image from the belt can be promoted. As a result, the transferability of the toner image from the intermediate transfer belt 70 to the transfer sheet P during the secondary transfer is promoted, and a high-quality toner image is obtained on the transfer sheet. Examples of the material having low surface energy include a fluorine-based material, a silicon-based material, or a material mainly composed of these materials, a fluorine resin powder, a silicon resin, and a material obtained by dispersing a silicone oil component.

  Next, the base material layer 703 avoids deformation of the belt due to a load applied to the intermediate transfer belt 70 such as elongation caused by tension generated by tension on the tension roll and contact with the cleaning blade, and affects the transfer portion. It is made of a material having rigidity that reduces Specifically, resin materials such as polyimide, polyester, polyether ether ketone, polyamide, polyphenylene sulfide, polycarbonate, polyvinylidene fluoride (PVDF), polyfluoroethylene-ethylene copolymer (ETFE), and the like are used as main raw materials. Resin material is mentioned. It is also possible to use a material obtained by blending the aforementioned resin material and elastic material. Examples of the elastic material include polyurethane, chlorinated polyisoprene, NBR, chloropyrene rubber, EPDM, hydrogenated polybutadiene, butyl rubber, and silicone rubber. These may be used alone or in combination of two or more.

  Among these, it is preferable to contain a polyimide resin. The polyimide resin is formed by heating polyamic acid that is a precursor of the polyimide resin. The polyamic acid can be obtained by dissolving tetracarboxylic dianhydride or an approximately equimolar mixture of its derivative and diamine in an organic polar solvent and reacting in a solution state.

Further, the volume resistivity of the intermediate transfer belt 70 is preferably lower than the volume resistivity of the toner used in the present invention. In this way, by making the volume resistivity of the intermediate transfer belt lower than the volume resistivity of the toner, the toner image formed on the intermediate transfer belt can be smoothly transferred onto the transfer sheet. Specifically, the volume resistivity of the intermediate transfer belt 70 is preferably 1 × 10 ⁸ to 1 × 10 ¹² Ω · cm.

  The volume resistivity of the intermediate transfer belt can be measured based on JIS K6991 by using a circular electrode (for example, HR probe of High Lester IP manufactured by Mitsubishi Yuka Co., Ltd.). For a specific method of measuring the volume resistivity, reference can be made to, for example, paragraph 0048 of JP-A-2001-242725 and the description of FIG.

  The image forming apparatus that can be used in the image forming method according to the present invention is preferably capable of so-called double-sided printing that forms an image on both sides of the transfer sheet P.

  When the duplex printing mode is selected and image formation is performed on the back surface of the transfer sheet P, predetermined image data is applied to the back surface of the transfer sheet P in the same manner as image formation performed on the front surface of the transfer sheet P. Forming a toner image based thereon; At this time, after the transfer sheet P on which the image fixing of the front surface has been completed is conveyed to the refeeding means 9 below by the sorting guide 27 and the rear end portion is nipped by the refeeding reverse roller 91, The transfer sheet P is reversed by reverse feeding. The reversed transfer sheet P is sent out to the refeed conveyance path 92, and the toner image formed on the photoreceptors 1Y, 1M, 1C, 1K and superimposed on the endless belt-shaped intermediate transfer belt 70 is transferred onto the transfer sheet P. Transfer and fix. In this way, toner images are formed on both sides of the transfer sheet P.

  The transfer sheet P used in the image forming method according to the present invention is a support for holding a toner image, and is usually called an image support, a transfer material, or transfer paper. Specific examples include plain paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, OHP plastic film, and various transfer sheets such as cloth. It is done.

  Further, in the image forming method according to the present invention, glossy coated paper and non-glossy paper, which are papers used for offset printing with many opportunities to output pictorial photo-like images, can be used.

  Glossy coated paper used for offset printing requires high hydrophilicity on the surface of the paper in order to promote wetting by dipping water used during printing. In addition, a glossy layer is formed by applying a resin emulsion such as wax or polyacrylamide having a melting point of 100 ° C. to 160 ° C. to the paper substrate so that fibers and fillers do not peel from the paper surface even when the paper is wet. Yes.

  The glossy coated paper produced by the cast method (a method of producing glossy coated paper by pressing the paper against the mirror-finished cylinder surface while the paint applied to the base paper is dry) A structure in which two or more layers are laminated is representative. Such glossy coated paper uses a cured product formed by irradiating an electron beam curable resin composition containing no pigment on the inner resin coating layer, and an electron containing pigment on the outer resin coating layer. A cured product formed by irradiating a beam-curable resin composition with an electron beam is used. Glossy coated paper has high surface whiteness and good cosmetic properties.

  On the other hand, non-glossy paper for offset printing, like glossy coated paper, requires high hydrophilicity on the paper surface in order to promote wetting by dipping water used during printing. In addition, a chemical called a paper strength agent that gives strength to paper is used so that fibers and fillers do not peel from the paper surface even when the paper is wet.

  As the paper strength agent, polyacrylamide is generally used, and there are anionic polyacrylamide, cationic polyacrylamide and amphoteric polyacrylamide depending on its ionicity. The main formulation of the paper strength agent is a single formulation in which cationic polyacrylamide or amphoteric polyacrylamide is added to the pulp slurry as a single product, or a combined formulation in which anionic polyacrylamide and cationic polyacrylamide are added to the pulp slurry, respectively. There is.

  In addition, the strength to break was improved by making paper using a vinyl monomer having an acrylamide monomer and an anionic group, and optionally a vinyl monomer having a cationic group copolymerized. There is also non-glossy paper.

  Furthermore, there are non-glossy papers coated with starch or polyvinyl alcohol as a paper strength agent. When polyvinyl alcohol is used as the paper strength agent, the content of polyvinyl alcohol in the coating solution is set to 50% by mass or more, and a penetrant such as a polyglycol type nonionic surfactant is added to 10 to 10,000 ppm. When the coating solution is used, a good non-glossy paper can be obtained.

The paper weighed is preferably 64 to 150 g / m ² .

Hereinafter, although an example is given and explained concretely, the embodiment of the present invention is not limited to this. In the following description, “part” and “%” all mean “part by mass of solid” and “% by mass of solid” unless otherwise specified.
1. Preparation of toner 1-1. Preparation of Toners 1 to 4 (1) Preparation of Toner Shell Resin Particles s1 The following polymerizable monomers were mixed to prepare a polymerizable monomer solution.

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 Liquid 1 A polymerizable monomer solution 11 was prepared by mixing the following polymerizable monomers.

72.1 g of styrene
n-Butyl acrylate 20.0g
Methacrylic acid 7.9g
In a separable flask equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction 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 under a nitrogen stream. While raising the internal temperature to 80 ° C., a surfactant solution was prepared.

To the surfactant solution, an initiator region in which 9.2 g of a polymerization initiator (potassium persulfate: KPS) was dissolved in 200 g of ion-exchanged water was added to a temperature of 75 ° C. Body solution 11 was added dropwise over 1 hour. After completion of the dropping, the reaction system was heated and stirred at 75 ° C. for 2 hours to perform polymerization (first stage polymerization) to obtain a dispersion of resin particles. This is designated as “toner base resin particles 1”.
(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 (K) was prepared by performing a dispersion treatment using a mechanical disperser CLEARMIX (manufactured by 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 Wax Dispersion 1 A wax dispersion having the following constitution was prepared and used as Wax Dispersion 1.

Wax (polyethylene wax, melting point 78 ° C.) 20 parts Nonionic surfactant (polyglycerin behenate ester) 0.7 part Ion-exchanged water 100 parts Anionic surfactant (sodium dodecyl sulfate) 0.35 part (5) Colored particles 1Bk Production (meeting process)
Toner base resin particle dispersion 1 420.7 g (solid content conversion), ion exchange water 900 g, “colorant dispersion liquid (Bk)” 200 g (solid content conversion), “wax dispersion 1” 110 g (solid content conversion) Were stirred in a reaction vessel (four-necked flask) equipped with a temperature sensor, a cooling tube, a nitrogen introducing device, and a stirring device. 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 system was heated to 90 ° C. over 60 minutes to grow the particle size and carry out an association reaction. 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 7 μm, 40.2 g of sodium chloride was added to 1000 g of ion-exchanged water. The aqueous solution dissolved in 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”.
(6) Preparation of Toner 1Bk The obtained “colored particle 1Bk” has 1% by mass of hydrophobic silica having a number average primary particle size of 12 nm and a hydrophobization degree of 68 nm, and a number average primary particle size of 20 nm. Then, hydrophobic titanium oxide having a hydrophobization degree of 63 was added so as to be 1.2% by mass and mixed by a Henschel mixer to obtain “Black Toner 1Bk”. The volume resistivity of the obtained toner was measured with the above-described measuring apparatus and found to be 1.0 × 10 ¹⁶ Ω · cm. Further, the volume resistivity of the used wax 1 was measured and found to be 5.0 × 10 ¹⁶ Ω · cm.
(7) Preparation of toners 1Y, 1M, and 1C In preparation of toner 1Bk, C.I. was used instead of carbon black (Regal 330R: manufactured by Cabot Corporation). I. Pigment Yellow 74 was used in the same procedure except that Yellow Yellow 1Y was replaced with C.I. I. Magenta Toner 1M was replaced with C.I. I. A cyan toner 1C was prepared in the same procedure except that Pigment Blue 15: 3 was used. The resulting toner had the same surface resistivity as that of toner 1Bk.
(8) Preparation of Toner 2 Toner 2 was prepared in the same procedure except that the amount of “wax dispersion 1” added in the association step was changed to 80 g when toner 1 was prepared. The volume resistivity of the produced toner is shown in Table 1 described later.
(9) Preparation of toners 3 and 4 When preparing toners 1 and 2, 2% by mass of hydrophobic silica having a number average primary particle size of 12 nm and a hydrophobicity of 68 and a number average primary particle size of 20 nm Toners 3 and 4 were prepared in the same procedure except that a hydrophobic acid value titanium having a hydrophobization degree of 63 was added to 2.4 mass%.
1-2. Preparation of Toners 5 to 10 (1) Preparation of Toner Shell Resin Particles s1 Shell resin particles s1 were prepared in the same procedure as in the toner 1 to 5 preparation steps described above. 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-mercaptopropion were added to a flask equipped with a stirrer. It added to the monomer liquid mixture which consists of 5.6 g of acid ester, heated at 90 degreeC, and 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 colored particles 5Bk (association step)
Toner base resin particle dispersion 2 439.2 g (converted to solid content), ion-exchanged water 900 g, “colorant dispersion (Bk)” 200 g, temperature sensor, cooling tube, nitrogen introducing device, stirring device attached reaction It stirred in the container (four necked flask). 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 system was heated to 90 ° C. over 60 minutes to grow the particle size and carry out an association reaction. 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. The aqueous solution dissolved in 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, washed repeatedly with ion exchange water at 45 ° C., and then dried with hot air at 40 ° C. to obtain “colored particles 5Bk”.
(4) Preparation of Toner 5Bk The obtained “colored particles 5Bk” had 1% by mass of hydrophobic silica having a number average primary particle size of 12 nm and a hydrophobization degree of 68 nm, and a number average primary particle size of 20 nm. Then, hydrophobic titanium oxide having a hydrophobization degree of 63 was added so as to be 1.2% by mass and mixed with a Henschel mixer to obtain “Black Toner 5Bk”. Properties of the obtained toner 5 such as volume resistivity are shown in Table 1 described later.
(5) Preparation of toners 5Y, 5M, and 5C In preparation of toner 5Bk, C.I. I. Pigment Yellow 74 was used in the same procedure except that Yellow Yellow 5Y was replaced with C.I. I. Magenta Toner 5M was replaced by C.I. with the same procedure except that Pigment Red 122 was used. I. A cyan toner 5C was prepared in the same procedure except that Pigment Blue 15: 3 was used. The obtained toners 5Y, 5M, and 5C had the same physical properties such as volume resistivity as the toner 5Bk.
(6) Preparation of toner 6 In the preparation of the toner base resin particle dispersion 2 of toner 6, the amount of pentaerythritol tetrabehenate added was changed to 109.8 g, and the toner base resin particles in the associating step were changed. Toner 6 was produced in the same procedure except that the amount of dispersion 2 added was changed to 427.2 g.
(9) Preparation of toners 7 and 8 In the preparation steps of toners 5 and 6, 2% by mass of hydrophobic silica having a number average primary particle diameter of 12 nm and a hydrophobization degree of 68, a number average primary particle diameter of 20 nm, Toners 7 and 8 were produced in the same procedure except that a hydrophobic acid value titanium having a degree of hydrophobicity of 63 was added so as to be 2.4% by mass.
1-3. Preparation of toners 9 to 12 (1) Preparation of toner 9 45 parts by mass of a 0.1 mol / liter Na ₃ PO ₄ aqueous solution was added to 292 parts by mass of ion-exchanged water, heated to 60 ° C., and then subjected to TK homopolymer. The mixture was stirred at 12,500 rpm using a mixer (made by Tokushu Kika Kogyo Co., Ltd.). To this, 68 parts by mass of a 1.0 mol / liter CaCl ₂ aqueous solution was gradually added to obtain a pH 6 aqueous medium containing a calcium phosphate compound.

  Next, a polymerizable monomer composition was prepared using a polymerizable monomer having the following composition.

Styrene 83 parts by mass n-butyl acrylate 32 parts by mass Carbon black (Regal 330R: manufactured by Cabot Corp.) 17 parts by mass Charge control agent (di-t-butyl salicylate) 5 parts by mass Divinylbenzene 1 part by mass After heating, 14 parts by weight of wax 2 (polyethylene wax) was added and sufficiently dissolved and dispersed to prepare a dispersion composition.

  In this dispersion composition, a mixture of 3.5 parts by mass of an organic peroxide initiator t-butyl peroxypivalate and 1.5 parts by mass of toluene was dissolved to obtain a polymerizable monomer composition. .

  This polymerizable monomer composition was put into the aqueous medium, and granulated for 10 minutes by stirring at a high speed with a high-speed rotary shear stirrer CLEARMIX (manufactured by M Technique Co., Ltd.). This was replaced with a paddle stirrer, and polymerization was continued at an internal temperature of 65 ° C. After 5 hours from the start of the polymerization reaction, 5 parts by mass of anhydrous sodium carbonate was added to the system, and then the polymerization temperature was raised to 80 ° C., and stirring was further continued for 5 hours to complete the polymerization. The pH of the suspension at the completion of the polymerization was 10.6. After cooling, solid-liquid separation is performed by filtration, washing with water, reslurry is performed, further dilute hydrochloric acid is added to dissolve the dispersant, solid-liquid separation, washing with water, filtration, and drying are performed again to obtain colored 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) were added to the obtained colored particles. 2% by mass was added and mixed with a Henschel mixer to prepare a toner 9Bk having a volume-based median diameter of 7.0 μm.

Instead of carbon black (Regal 330R: manufactured by Cabot Corporation) used in the production of the toner 9Bk, C.I. I. Pigment Yellow 74 is used to add toner 9Y to C.I. I. Pigment Red 122 is used to add toner 9M to C.I. I. Toner 9C was prepared using Pigment Blue 15: 3.
(2) Preparation of Toner 10 Toner 10 was prepared in the same procedure except that the addition amount of wax 2 was changed to 12 parts by mass in the preparation process of toner 9.
(3) Preparation of Toners 11 and 12 When the toners 9 and 10 were prepared, 2% by mass of hydrophobic silica having a number average primary particle size of 12 nm and a hydrophobization degree of 68 was obtained, and the number average primary particle size was 20 nm. Toners 11 and 12 were prepared in the same procedure except that a hydrophobic acid value titanium having a hydrophobization degree of 63 was added to 2.4 mass%. Table 1 shows the physical properties such as the volume resistance ratio of the toners 1 to 12 produced as described above.
3. Manufacture of carriers (Manufacture of ferrite core material)
After 18 mol% of MnO, 4 mol% of MgO and 78 mol% of Fe ₂ O ₃ were pulverized, mixed and dried in a wet ball mill for 2 hours, they were temporarily fired by holding at 900 ° C. for 2 hours. It grind | pulverized for time and was made into the slurry. A dispersant and a binder were added, granulated and dried with a spray dryer, and then subjected to main firing at 1200 ° C. for 3 hours to obtain ferrite core material particles having a resistance value of 4.3 × 10 ⁸ Ω · cm.
[Manufacture of resin for coating]
First, a cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5 /) was prepared by an emulsion polymerization method in which the concentration in an aqueous medium using sodium benzenesulfonate having an alkyl group having 12 carbon atoms as a surfactant was 0.3% by mass. 5), a volume average primary particle size of 0.1 μm, a weight average molecular weight (Mw) of 200,000, a number average molecular weight (Mn) of 91,000, Mw / Mn = 2.2, and a softening point temperature. Resin fine particles having (Tsp) 230 ° C. and glass transition temperature (Tg) 110 ° C. were obtained. The resin fine particles azeotroped with water in the emulsified state, and the residual monomer amount was 510 ppm.

Next, 100 parts by mass of ferrite core material particles and 2 parts by mass of the resin fine particles are put into a high-speed agitator / mixer equipped with stirring blades, stirred and mixed at 120 ° C. for 30 minutes, and the mechanical impact force is applied to the volume. A resin-coated carrier having an average particle size of 61 μm was obtained.
4). Production of Developer Each of the toners 1 to 12 described above was mixed with the carrier to prepare a developer of each color having a toner concentration of 6% by mass. Examples 1 to 6 and Comparative Examples 1 to 6 using developer sets 1 to 12 were prepared by combining the developers of each color as shown in Table 1. The configuration of each developer set is shown in Table 1 described later.

The values of dt, dw, dt ′ in the table are taken out immediately after the transfer sheet immediately after fixing the transfer sheet immediately after fixing the front surface of the transfer sheet at a predetermined number of sheets in an image forming apparatus described later. It was obtained from the transfer sheet obtained by electron microscope photography. The values of ρt, ρw, and ρt ′ in the table indicate that each toner and wax are subjected to pressure treatment by a pressure molding machine to prepare a disk-shaped measurement sample having a diameter of 80 mm and a thickness of 2 mm. Is set in the measuring apparatus shown in FIG. 3 and calculated.
5. Evaluation Experiment (1) Evaluation Device The produced developers 1 to 12 are mounted on the image forming apparatus (Konica Minolta 8050 (manufactured by Konica Minolta Business Technology)) shown in FIG. The images output on the 2000th and 5000th sheets were evaluated. Image formation is performed in a high-temperature and high-humidity environment (30 ° C., 80% RH), and the recording paper is a color recording paper “POD gloss coat” (manufactured by Oji Paper Co., Ltd.) 128 g / mm ² (A3 size) for on-demand printing. Using.

The original used for image formation is a character image (3 points, 5 points) with a pixel rate of 7%, a gray halftone image having a reflection density of 1.30, a solid white image, and a solid image using two-color toner. ^Two original images (A4 size) on which images (cyan toner and magenta toner are used and the toner adhesion amount is 15 g / m ² (the thickness of the toner layer after fixing is 20 μm)) are each equally divided into two. It was done using a sheet.

The fixing temperature of the image forming apparatus is set so that the surface temperature of the upper roller is 200 ° C. and the surface temperature of the lower roller is 180 ° C., and the volume resistivity of the intermediate transfer belt is 5.5 × 10 ¹¹ Ω · It was lower than the volume resistivity of the toner used as cm.
(2) Evaluation items <Generation of white stripes>
The gray halftone image formed on the back surface was visually observed to evaluate the occurrence of white stripes. The state was evaluated by ○, Δ, and ×. The white streaks were visually observed and evaluated under the following conditions.

◎: No white streaks appear on the image ○: Three or less white streaks appear on the image, but there is no practical problem ×: Four or more white streaks appear on the image, causing a practical problem Yes <Occupation of solid image part>
In the solid image portion formed on the back surface, the number of omissions having a major axis of 0.4 mm or more was counted and evaluated. The missing part was measured with a microscope with a video printer.

◎: White spot frequency of 0.4 mm or more: No occurrence of missing part ○: White spot frequency of 0.4 mm or more: One or more and less than 5 missing parts occurred, but no problem in practical use ×: 0.4 mm or more White spot frequency: There are 5 or more missing parts, and there is a problem in practical use.

<Missing text image>
The character image formed on the back surface was observed with a magnifying glass to evaluate the occurrence of omission on the character image.

◎: No omission ○: No omission occurred until the 2000th print, but a slight omission was observed on the 5000th image, but there was no practical problem. X: Occurrence occurred on the 2000th print, There are practical problems.

  The results are shown in Table 2.

  As is clear from the results in Table 2, in Examples 1 to 6 corresponding to the present invention, even when 5000 double-sided continuous printing is performed, the toner image formed on the back side has almost no white streaks or missing images. I couldn't. On the other hand, in the comparative example, white streaks and image omissions were noticeably observed, and the results were clearly different from the examples.

  Moreover, when a color human face image was printed every 1000 sheets and the finish was visually evaluated using a loupe, in Examples 1 to 6, a color image with a beautiful finish without omission on the back side was obtained. In the comparative example, it was confirmed that white streaks and image omission occurred on the image formed on the back surface from about the 1000th sheet without a loupe. Therefore, it has been confirmed that the present invention is applicable to on-demand print creation, which often requires high-quality double-sided printed matter.

  As described above, it was confirmed that good toner transfer was also exhibited on the back side when double-sided continuous printing was performed by the image forming method according to the present invention.

FIG. 3 is a schematic cross-sectional view showing the structure of a toner image formed on the front side of a transfer sheet. It is a schematic diagram which shows the structure of the toner which contains a wax. It is the schematic of the measuring apparatus which measures the surface resistivity of a toner and wax. 1 is a schematic diagram of an image forming apparatus capable of duplex printing. FIG. 3 is a schematic diagram illustrating a structure example of an endless belt-shaped intermediate transfer belt.

Explanation of symbols

1 1 (1Y, 1M, 1C, 1K) Photoconductor 2 (2Y, 2M, 2C, 2K) Charging means 3 (3Y, 3M, 3C, 3K) Exposure means 4 (4Y, 4M, 4C, 4K) Developing means 5 (5Y, 5M, 5C, 5K) Primary transfer means 6 (6Y, 6M, 6C, 6K) Cleaning means 7 Endless belt-like intermediate transfer belt unit 70 Endless belt-like intermediate transfer belt 701 Surface layer 703 Base material layer P Transfer sheet

Claims (3)

An image forming method for forming a toner image on both sides of a transfer sheet using a toner containing wax,
An image forming method, wherein when an image is formed on the back side of the transfer sheet, a toner image formed on the front side of the transfer sheet has the following relational expression.

(Where ρt is the volume resistivity of the toner (Ω · cm), dt is the thickness of the toner layer (μm), ρw is the volume resistivity of the wax alone (Ω · cm), and dw is the thickness of the wax layer (μm). , Ρt ′ represents the volume resistivity (Ω · cm) of the peeled layer, and dt ′ represents the thickness (μm) of the peeled layer.) 2. The image forming method according to claim 1, wherein the volume resistivity of the toner or wax is calculated by applying a voltage to a sample prepared by applying pressure to the toner or wax. The toner image is formed on both sides of the transfer sheet via an intermediate transfer belt, and the volume resistivity of the toner is higher than the volume resistivity of the intermediate transfer belt. The image forming method according to claim 1.

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